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  • 124151.
    Xiong, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Kong, Y.
    Du, Y.
    Liu, Z. K.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Sun, W. H.
    Thermodynamic investigation of the galvanizing systems, I: Refinement of the thermodynamic description for the Fe-Zn system2009In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 33, no 2, p. 433-440Article in journal (Refereed)
    Abstract [en]

    The thermodynamic description for the Fe-Zn system was updated using CALPHAD approach. A set of self-consistent thermodynamic model parameters for this system was obtained by considering the available experimental data. Compared with the previous thermodynamic modeling, the present assessment with fewer parameters shows not only a better agreement with the experiments but also sounder physical meaning. The present CALPHAD modeling coupled with the ab initio calculations were used to predict the enthalpies of formation of the solid phases in the Fe-Zn system.

  • 124152.
    Xiong, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Chen, Qing
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Du, Yong
    Phase Equilibria and Thermodynamic Properties in the Fe-Cr System2010In: Critical reviews in solid state and materials sciences, ISSN 1040-8436, E-ISSN 1547-6561, Vol. 35, no 2, p. 125-152Article, review/survey (Refereed)
    Abstract [en]

    Phase equilibria and thermodynamic properties in the Fe-Cr system have been reviewed comprehensively based on experimental information and available computer simulations in different scales. The evaluated phase equilibria show significant differences from the currently accepted thermodynamic description by CALPHAD (calculation of phase diagram) approach. The thermodynamic properties of the Fe-Cr system, such as heat capacity, enthalpy, and activity, have been evaluated in reported experiments. The experiments on phase separation in the Fe-Cr system have also been critically reviewed with a focus on spinodal decomposition. The reported data are concentrated in the temperature range from 673 to 823 K. In addition, there is a transition region between spinodal decomposition and nucleation regimes within the composition limit from 24 to 36.3 at.% Cr and the temperature range between 700 and 830 K. In view of the importance of magnetism in the Fe-Cr system, some inadequacies of the currently used thermodynamic description are pointed out in addition to some problems with the current magnetic model. Remaining issues on the thermodynamics of the Fe-Cr system have been elaborated for future refinement of the thermodynamic description of the Fe-Cr system. According to the present review, the melting temperature of Cr is recommended to be about 2136 K, which is 44 K lower than the value adopted in the research community on thermodynamics, such as the Scientific Group Thermodata Europe.

  • 124153. Xiong, Wei
    et al.
    Xu, Honghui
    Du, Yong
    Thermodynamic investigation of the galvanizing systems, II: Thermodynamic evaluation of the Ni-Zn system2011In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 35, no 3, p. 276-283Article in journal (Refereed)
    Abstract [en]

    The Ni-Zn system is reassessed using the CALPHAD approach. An order-disorder transition model is adopted to describe the intermetallic phase with an ordered bcc_132 structure. A set of self-consistent thermodynamic parameters of the Ni-Zn system is obtained based on the available experimental information. The present modeling shows good agreement with the experimental data and predicts the thermodynamic properties of the Ni-Zn alloys reasonably, which indicates the importance of the CALPHAD technique to study galvanizing systems. The present thermodynamic description of the Ni-Zn system is in the framework for constructing a comprehensive thermodynamic database to design the process of galvanizing.

  • 124154.
    Xiong, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Zhang, Hualei
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Vitos, Levente
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Magnetic phase diagram of the Fe-Ni system2011In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 59, no 2, p. 521-530Article in journal (Refereed)
    Abstract [en]

    Magnetic phase diagrams of body-centered cubic and face-centered cubic Fe-Ni alloys were constructed using available experimental data and ab initio calculations. The results show that significant improvements in the "standard" diagrams (handbooks and CALPHAD databases) are required. The present work demonstrates that the CALPHAD magnetic model is not sophisticated enough to describe the Fe-Ni system. In addition, a new thermodynamic description of the lattice stability for pure Ni is urgently needed, since the recommended magnetic properties for CALPHAD modeling are distinct from the experimental and ab initio results. This work indicates that the construction of magnetic phase diagrams is indispensable during the phase transformation study of magnetic systems. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  • 124155.
    Xiong, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Zhou, Jing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    An Effective Method to Estimate Composition Amplitude of Spinodal Decomposition for Atom Probe Tomography Validated by Phase Field SimulationsManuscript (preprint) (Other academic)
    Abstract [en]

    Reasonable evaluation of composition amplitude in spinodal decomposition is a challenge to microanalysis of atom probe tomography, especially at early stages when phase separation is not prominent. This impedes quantitative analysis of spinodal structure in atom probe tomography as well as comparison with simulated results from phase field simulations. We hereby report an effective method to estimate the composition amplitude by constructing an amplitude density spectrum. This method can sensitively determine the composition amplitude at early stages. In particular, it substantially bridges experimental and simulation techniques comprising both discrete and continuum data in the study of spinodal decomposition. Moreover, it was found that the commonly adopted Langer-Bar-on-Miller method for atom probe analysis underestimates the composition amplitude of spinodal decomposition. Case studies have been performed on the Fe-Cr binary alloys.

  • 124156.
    Xiong, Wenjun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Carlsson, Per
    Lagerström, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Re-using Enterprise Architecture Repositories for Agile Threat Modeling2019In: 2019 IEEE 23rd International Enterprise Distributed Object Computing Workshop (EDOCW), Paris, France: Institute of Electrical and Electronics Engineers (IEEE), 2019Conference paper (Refereed)
    Abstract [en]

    Digitization has increased exposure and opened up for more cyber threats and attacks. To proactively handle this issue, enterprise modeling needs to include threat management during the design phase that considers antagonists, attack vectors, and damage domains. Agile methods are commonly adopted to efficiently develop and manage software and systems. This paper proposes to use an enterprise architecture repository to analyze not only shipped components but the overall architecture, to improve the traditional designs represented by legacy systems in the situated IT-landscape. It shows how the hidden structure method (with Design Structure Matrices) can be used to evaluate the enterprise architecture, and how it can contribute to agile development. Our case study uses an architectural descriptive language called ArchiMate for architecture modeling and shows how to predict the ripple effect in a damaging domain if an attacker's malicious components are operating within the network.

  • 124157.
    Xiong, Wenjun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Güsever, Melek
    KTH.
    Kaya, Koray Mustafa
    KTH.
    Lagerström, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    A Study of Security Vulnerabilities and Software Weaknesses in Vehicles2019In: Secure IT Systems: 24th Nordic Conference, NordSec 2019, Aalborg, Denmark, November 18–20, 2019, Proceedings, Aalborg, Denmark, 2019, Vol. 11875, p. 204-218Conference paper (Refereed)
    Abstract [en]

    In this paper, we conduct an empirical study with the purpose of identifying common security vulnerabilities discovered in vehicles. The vulnerability information is gathered for 60 vehicle OEMs (Original Equipment Manufacturers) and common vehicle components from the National Vulnerability Database (NVD). Each vulnerability (CVE) is analyzed with respect to its software weakness type (CWE) and severity score (CVSS). 44 unique CVEs were found in NVD and analyzed. The analysis results show that about 50% of the vulnerabilities fall into the medium severity category, and the three most common software weaknesses reported are protection mechanism failure, buffer errors, and information disclosure.

  • 124158.
    Xiong, Wenjun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Krantz, Fredrik
    Lagerström, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering.
    Threat modeling and attack simulations of connected vehicles: a research outlook2019Conference paper (Refereed)
  • 124159.
    Xiong, Wenjun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Lagerström, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Threat modeling – A systematic literature review2019In: Computers & security (Print), ISSN 0167-4048, E-ISSN 1872-6208, Vol. 84, p. 53-69Article, review/survey (Refereed)
    Abstract [en]

    Cyber security is attracting worldwide attention. With attacks being more and more common and often successful, no one is spared today. Threat modeling is proposed as a solution for secure application development and system security evaluations. Its aim is to be more proactive and make it more difficult for attackers to accomplish their malicious intents. However, threat modeling is a domain that lacks common ground. What is threat modeling, and what is the state-of-the-art work in this field? To answer these questions, this article presents a review of threat modeling based on systematic queries in four leading scientific databases. This is the first systematic literature review on threat modeling to the best of our knowledge. 176 articles were assessed, and 54 of them were selected for further analysis. We identified three separate clusters: (1) articles making a contribution to threat modeling, e.g., introducing a new method, (2) articles using an existing threat modeling approach, and (3) introductory articles presenting work related to the threat modeling process. The three clusters were analyzed in terms of a set of criteria, for instance: Is the threat modeling approach graphical or formal? Is it focused on a specific attack type and application? Is the contribution validated empirically or theoretically? We observe from the results that, most threat modeling work remains to be done manually, and there is limited assurance of their validations. The results can be used for researchers and practitioners who want to know the state-of-the-art threat modeling methods, and future research directions are discussed.

  • 124160.
    Xiong, Wenjun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Lagerström, Robert
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Threat Modeling of Connected Vehicles: A privacy analysis and extension of vehicleLang2019In: 2019 International Conference on Cyber Situational Awareness, Data Analytics And Assessment (Cyber SA), Oxford, United Kingdom, United Kingdom: Institute of Electrical and Electronics Engineers (IEEE), 2019Conference paper (Refereed)
    Abstract [en]

    Modern vehicles contain more than a hundred Electronic Control Units (ECUs) that communicate over different in-vehicle networks. These ECUs are often connected to the Internet, which makes them vulnerable to various cyber attacks. Besides, large amounts of data are generated and communicated through vehicular networks, and some of them are sensitive for the vehicle drivers. Previously, a threat modeling language named vehicleLang was proposed for security analysis of vehicles, however, privacy issues of the vehicular data have not been thoroughly addressed. To fill the gap, this paper proposes a privacy-focused enhancement of vehicleLang, and the suggested privacy extension is evaluated by threat modeling with test cases running through the Meta Attack Language (MAL) compiler.

  • 124161. Xiong, Xiangming
    et al.
    Tao, Jianjun
    Chen, Shiyi
    Brandt, Luca
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Turbulent bands in plane-Poiseuille flow at moderate Reynolds numbers2015In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 27, no 4, article id 041702Article in journal (Refereed)
    Abstract [en]

    In this letter, we show via numerical simulations that the typical flow structures appearing in transitional channel flows at moderate Reynolds numbers are not spots but isolated turbulent bands, which have much longer lifetimes than the spots. Localized perturbations can evolve into isolated turbulent bands by continuously growing obliquely when the Reynolds number is larger than 660. However, interactions with other bands and local perturbations cause band breaking and decay. The competition between the band extension and breaking does not lead to a sustained turbulence until Re becomes larger than about 1000. Above this critical value, the bands split, providing an effective mechanism for turbulence spreading.

  • 124162.
    Xiong, Xuelin
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    SCTP and Diameter Parameters for High Availability in LTE Roaming2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today mobile network operators utilize IP Packet exchange (IPX) carriers to interconnect their networks with other operators. Mobile network operators are free to choose one IPX carrier for their data traffic and another for their control traffic. This thesis examines the case of control traffic, specifically Stream Control Transmission Protocol (SCTP) carrying Diameter protocol traffic arising from users roaming from their home Long Term Evolution (LTE) network to another operator’s LTE network.

    The thesis project aims to identify a set of SCTP parameter configurations that can provide improved application/service level availability between two Diameter nodes in different network connectivity environments, specifically for IPX carriers who are Diameter service providers. These service providers provide Diameter connectivity for their customers who are mobile network operators. These mobile network operators in turn provide LTE roaming services to their customers.

    Unfortunately, applying the ‘One size fits all’ configuration recommendations given in the SCTP documentation is unsuitable for different network environments. In addition, the amount of Diameter signaling traffic is growing at a very rapid rate. Therefore, it is valuable to identify suitable parameter selection criteria for Diameter service providers to ensure 100% Diameter connectivity reliability for their customers. In this thesis project, author investigated how tuning SCTP parameter values affect Diameter message transmission in terms of Round Trip Delay and identified its determining parameters for packet loss recovery performance. Both IPX carriers and mobile network operators may use these values as reference when attempting to ensure high availability of Diameter transmissions under reliable, semi reliable, and unreliable network transport conditions.

  • 124163.
    Xiong, Yi
    KTH, School of Computer Science and Communication (CSC).
    Impact Factors of Business Service Sourcing Control System Design – A Comparative analysis in media and non-media industry in China.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In advanced economics, service sector accounts for two-third in GDP. Recent academic studies also acknowledge that business activities for service are significantly different from those for physical goods, due to service intangibility, heterogeneity, simultaneity, and perishability characteristics. So does it for service sourcing, in particular. However, little is still known about how service buyers source from their suppliers, which control pattern is used per phase in the sourcing process, and particularly, which factors are linked with the choice of control pattern, especially for the recently booming developed digital media industry. This paper addresses this gap as follows: (1) by examining in detail the buyers behavioral evidence in service sourcing process from selected cases to get general understanding regarding the control pattern used in sourcing process per phase; (2) by comparing the value of potential linked factors with the control choice in different sourcing phase to identify actual linked factors (i.e., asset specificities, frequency/size, nature of relationship and risks associated with service) and to develop propositions regarding their impact on the specific choice of control pattern; (3) by doing a comparative analysis between media industry and non-media industry to extract some useful business insights and to generate business intelligence for best practices. This study contributes to theory development on control issue within service sourcing context. It also offers a further possibility for researchers to design a systematic business service sourcing control system for media industry or even for broader industries.

    Key Words: Business Service, Service Sourcing Process, Management Control System, Transaction Cost Economics, Business Interaction Model, Media Industry.

  • 124164.
    Xiong, Ziyi
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Socio-economic Impact of Fiber to the Home in Sweden2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Fiber-to-the-Home (FTTH) has been talked about since the introduction of fiberin the 1970s. It is nowadays shaping up to be the foundation of our newdigital society, bringing economic prosperity and a multitude of business,social, and entertainment opportunities to its users. The increased consumerdemand for high-speed network accessibility is being taken more and moreseriously and a fiber-based network is able to cope with these growing demandsdue to its wide bandwidth and reliability. Today there is a practical need forquantitative analysis regarding the socio-economic impacts of fiber-basedaccess networks. This analysis could be used as an indicator/reference for allthe stakeholder entities as they consider future investments anddevelopments. Sweden is a suitable target country for this analysis since ithas adopted fiber for some years and the benefits that FTTH has brought seemto already be tangible.

    The primary value of this thesis lies ininvestigation of its quantified evidence of the socio-economic impacts of FTTHdeployment in Sweden. This has been achieved based on data from the SwedishPost and Telecommunications Authority (PTS), Statistics Sweden (SCB), previousrelated studies, and information collected on-line from operators involved inthe fiber market, along with empirical analysis based on multivariateregression models.

    The results of the study show that fiber penetrationhas had a significant impact on the population’s evolution, specially the netamount of migration into a municipality, which indicates the attractiveness ofmunicipalities per se. It is therefore reasonable to suggest that localgovernment and local authorities take fiber deployment into consideration, ifthey want to attract people to stay for further local development. The studyalso analyzed the competition in fiber-based open networks and the prices ofsubscribing for 10/10 Mbps symmetrical Internet Service. Study findingsrevealed that networks with multiple competing service providers have a widerrange of services and a lower price: the more ISPs competing in a fibernetwork, the lower consumer prices. Specifically, for each new serviceprovider present in the network, there will be 5 SEK per month decrease of theaverage price of the Internet services, and an approximately 7 SEK per monthreduction in the lowest price.

    Nevertheless, a number of socio-economicimpacts remain unquantifiable as of the current time and due to the limitedavailable data. It is recommended to incorporate more socio-economic effectsin future research in order to draw a more complete picture for all theinterested sectors, and to supplement the data with recent figures for 2012and 2013.

  • 124165.
    Xirouchakis, Michail
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Traffic Load Predictions Using Machine Learning: Scale your Appliances a priori2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Layer 4-7 network functions (NF), such as Firewall or NAPT, have traditionally been implemented in specialized hardware with little to no programmability and extensibility. The scientific community has focused on realizing this functionality in software running on commodity servers instead. Despite the many advancements over the years (e.g., network I/O accelerations), software-based NFs are still unable to guarantee some key service-level objectives (e.g., bounded latency) for the customer due to their reactive approach to workload changes.

    This thesis argues that Machine Learning techniques can be utilized to forecast how traffic patterns change over time. A network orchestrator can then use this information to allocate resources (network, compute, memory) in a timely fashion and more precisely. To this end, we have developed Mantis, a control plane network application which (i) monitors all forwarding devices (e.g., Firewalls) to generate performance-related metrics and (ii) applies predictors (moving average, autoregression, wavelets, etc.) to predict future values for these metrics. Choosing the appropriate forecasting technique for each traffic workload is a challenging task. This is why we developed several different predictors. Moreover, each predictor has several configuration parameters which can all be set by the administrator during runtime.

    In order to evaluate the predictive capabilities of Mantis, we set up a test-bed, consisting of the state-of-the-art network controller Metron [16], a NAPT NF realized in FastClick [6] and two hosts. While the source host was replaying real-world internet traces (provided by CAIDA [33]), our Mantis application was performing predictions in real time, using a rolling window for training. Visual inspection of the results indicates that all our predictors have good accuracy, excluding (i) the beginning of the trace where models are still being initialized and (ii) instances of abrupt change. Moreover, applying the discrete wavelet transform before we perform predictions can improve the accuracy further.

  • 124166. Xiu, L.
    et al.
    Svensson, V.
    Johansson, E.
    Ek, A.
    Marcus, C.
    Ekstedt, M.
    KTH, School of Technology and Health (STH).
    Bedtime eating and sleep disturbances among 2 years old children2016In: Journal of Sleep Research, ISSN 0962-1105, E-ISSN 1365-2869, Vol. 25, p. 326-327Article in journal (Other academic)
  • 124167.
    Xu, Annie
    KTH, School of Industrial Engineering and Management (ITM).
    Integration of an ERP system: A case study on integration challenges with Microsoft Dynamics AX2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Historically, system integration of ERP system and other existing IT systems within an

    organization has always been a complex challenge, both technically and organizationally. In

    many cases, the budget for system integration corresponds 30-40% of the whole IT budget.

    Since system integration accounts for a large part of the cost during acquisitions and

    implementation of an ERP system, companies are interested in the challenges that exist during

    system integration, to simplify the integration process and hence reduce the costs. To

    understand the challenges, a case study at Company X has been performed. The ERP system

    investigated in the case study is Microsoft Dynamics AX.

    The purpose with this study is to investigate challenges that exist in large organizations during

    system integration of ERP system and other IT systems that exist in the organization and

    thereby understand how integration can be developed in a more efficient way.

    The study entails an extensive literature study and two rounds of data collection through

    qualitative interviews.

    The results showed that the challenges that exist at Company X are mainly organizational.

    Technical challenges coexist but they have a much less significant impact than the

    organizational challenges. This can be explained by that there has been a heavier focus on

    solving the technical related problems and maybe to some extent neglected the impact

    organizational problems can have on system integration. Possible actions includes central

    strategy concerning how to work with Dynamics AX, it’s growth and future initiatives,

    policies and framework regarding working methods, increased authority and decision rights to

    the group working with AX as well as minimize customizations and own development.

  • 124168.
    Xu, Annie
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Management.
    Integration of an ERP System:: a case study onintegration challenges with Microsoft Dynamics AX2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Historically, system integration of ERP system and other existing IT systems within anorganization has always been a complex challenge, both technically and organizationally. Inmany cases, the budget for system integration corresponds 30-40% of the whole IT budget.Since system integration accounts for a large part of the cost during acquisitions andimplementation of an ERP system, companies are interested in the challenges that exist duringsystem integration, to simplify the integration process and hence reduce the costs. Tounderstand the challenges, a case study at Company X has been performed. The ERP systeminvestigated in the case study is Microsoft Dynamics AX.The purpose with this study is to investigate challenges that exist in large organizations duringsystem integration of ERP system and other IT systems that exist in the organization andthereby understand how integration can be developed in a more efficient way.The study entails an extensive literature study and two rounds of data collection throughqualitative interviews.The results showed that the challenges that exist at Company X are mainly organizational.Technical challenges coexist but they have a much less significant impact than theorganizational challenges. This can be explained by that there has been a heavier focus onsolving the technical related problems and maybe to some extent neglected the impactorganizational problems can have on system integration. Possible actions includes centralstrategy concerning how to work with Dynamics AX, it’s growth and future initiatives,policies and framework regarding working methods, increased authority and decision rights tothe group working with AX as well as minimize customizations and own development.

  • 124169.
    Xu, Annie
    KTH, School of Industrial Engineering and Management (ITM).
    Integration of an ERP System: a case study onintegration challenges with Microsoft Dynamics AX2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 124170.
    Xu, Bo
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Climate change mitigation in China2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    China has been experiencing great economic development and fast urbanisation since its reforms and opening-up policy in 1978. However, these changes are reliant on consumption of primary energy, especially coal, characterised by high pollution and low efficiency. China’s greenhouse gas (GHG) emissions, with carbon dioxide (CO2) being the most significant contributor, have also been increasing rapidly in the past three decades. Responding to both domestic challenges and international pressure regarding energy, climate change and environment, the Chinese government has made a point of addressing climate change since the early 2000s. This thesis provides a comprehensive analysis of China’s CO2 emissions and policy instruments for mitigating climate change.

    In the analysis, China’s CO2 emissions in recent decades were reviewed and the Environmental Kuznets Curve (EKC) hypothesis examined. Using the mostly frequently studied macroeconomic factors and time-series data for the period of 1980-2008, the existence of an EKC relationship between CO2 per capita and GDP per capita was verified. However, China’s CO2 emissions will continue to grow over coming decades and the turning point in overall CO2 emissions will appear in 2078 according to a crude projection. More importantly, CO2 emissions will not spontaneously decrease if China continues to develop its economy without mitigating climate change. On the other hand, CO2 emissions could start to decrease if substantial efforts are made.

    China’s present mitigation target, i.e. to reduce CO2 emissions per unit of GDP by 40-45% by 2020 compared with the 2005 level, was then evaluated. Three business-as-usual (BAU) scenarios were developed and compared with the level of emissions according to the mitigation target. The calculations indicated that decreasing the CO2 intensity of GDP by 40-45% by 2020 is a challenging but hopeful target.

    To study the policy instruments for climate change mitigation in China, domestic measures and parts of international cooperation adopted by the Chinese government were reviewed and analysed. Domestic measures consist of administration, regulatory and economic instruments, while China’s participation in international agreements on mitigating climate change is mainly by supplying certified emission reductions (CERs) to industrialised countries under the Clean Development Mechanism (CDM). The most well-known instruments, i.e. taxes and emissions trading, are both at a critical stage of discussion before final implementation. Given the necessity for hybrid policies, it is important to optimise the combination of different policy instruments used in a given situation.

    The Durban Climate Change Conference in 2011 made a breakthrough decision that the second commitment period under the Kyoto Protocol would begin on 1 January 2013 and emissions limitation or reduction objectives for industrialised countries in the second period were quantified. China was also required to make more substantial commitments on limiting its emissions. The Chinese government announced at the Durban Conference that China will focus on the current mitigation target regarding CO2 intensity of GDP by 2020 and will conditionally accept a world-wide legal agreement on climate change thereafter. However, there will be no easy way ahead for China.

  • 124171.
    Xu, Bo
    KTH, Superseded Departments, Biotechnology.
    Metabolic responses of<I>Pseudomonas stutzeri</I>and<I>Escherichia coli</I>subjected to starvation and surplus of carbon/energy substrates in bioreactors1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Transient nitrite accumulation during anaerobicdenitrification is a widespread phenomenon for manydenitrifying bacteria includingPseudomonasstutzeri. Nitrate starvation caused the degradation ofthe second denitrifying enzyme nitrite reductase (NiR) inP.stutzeri. A relationship exists between the nitratestarvation time (0-24 hr) and the lost NiR activity, whichaccounts for the varying degrees of nitrite accumulation(0-100%). When nitrate was re-supplied, the cell synthesizednew NiR and thus its activity was restored. A possible releaseof gaseous intermediates (nitric oxide and nitrous oxide) underthese conditions was examined by detecting the NOaqusing an ISO-NO sensor. No significant amount ofNOaqwas found. An integrated nitrate over-flow model,which included both conventional enzymatic kinetics and dynamicenzyme degradation/re-synthesis, was developed and used tosimulate the variable degrees of transient nitrite accumulationbyP.stutzeri.

    Another metabolic over-flow phenomenon, the aerobic acetateformation inEscherichiacolibatch and fed-batch culture, was also investigatedand modeled. Acetate inhibited the specific growth rate in anon-competitive manner. In the presence of growth-limitingglucose, the cell co-utilized previously formed acetate. Adynamic glucose over-flow model, which described the differentintracellular carbon flows and included the inhibitory effectsof acetate on substrate and oxygen uptake, is presented. Thismodel accurately describes cell growth, respiration, acetateformation and re-consumption during batch cultures, thetransitions of batch to fed-batch and the fed-batchcultures.

    Metabolic and stress response to hypothetical oxygendeficient zones in a large-scale fed-batch cultivation wasinvestigated. By using a scale-down two-compartment reactor,typical mixed-acid products such as D-lactate, formate andacetate were produced at high rates in the high glucoseconcentration zone (PFR reactor). All D-lactate, almost allacetate and 90% of formate produced in the PFR werere-assimilated by the glucose-limited and oxygen-sufficientcells in the STR. The steadily accumulating formate wassuggested to be an indicator of local oxygen depletion in anaerobic fed-batch process. The commonly observed loweredbiomass yield in large scale reactors, as compared to that of alab scale reactor, is suggested to be at least partly due tothe repeated production and re-assimilation of mixed-acidproducts. Under these heterogeneous conditions, also mRNAlevels of four stress genes (clpB,dnaK,uspA andproU) and three genes responding to oxygen limitationand/or glucose excess (pfl,frd, andackA) were investigated. In the STR reactor, theproU mRNA level was high when glucose uptake rate washigh; theackA mRNA level correlated with the production andconsumption phases of acetate. When batch glucose and acetatewere completely consumed,proU andackA mRNA levels dropped to zero. In the PFR reactor,the mRNA levels of genes that respond to glucose excess (ackA), to oxygen limitation (ackA,pfl) and to heat shock (dnaK andclpB) were significantly elevated within seconds. In thelarge-scale reactor, the level of stress mRNAs was, in mostcases, highest in the middle and lowest at the bottom of thefermentor. It is suggested that also these stress responsescontribute to a reduced biomass yield in large scaleprocesses.

    Key words:Pseudomonasstutzeri,Escherichiacoli, denitrification, over-flow metabolism, batch,fed-batch, aerobic, anaerobic, glucose, acetate, mathematicalmodel, simulation, scale-down, concentration gradients,mixed-acid fermentation, mRNA, stress genes.

  • 124172.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Bi, Dongqin
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Graetzel, Michael
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Dalian University of Technology (DUT), China.
    A low-cost spiro[fluorene-9,9 '-xanthene]-based hole transport material for highly efficient solid-state dye-sensitized solar cells and perovskite solar cells2016In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 3, p. 873-877Article in journal (Refereed)
    Abstract [en]

    A low-cost spiro[fluorene-9,9'-xanthene] (SFX) based organic hole transport material (HTM) termed X60 was designed and synthesized using a two-step synthetic route. Devices with X60 as HTM showed high power conversion efficiencies (PCEs) amounting to 7.30% in solid-state dye-sensitized solar cells (ssDSCs) and 19.84% in perovskite solar cells (PSCs), under 100 mW cm(-2) AM1.5G solar illumination. To the best of our knowledge, this is the first example of an easily synthesized spiro-structured HTM that shows comparable performance with respect to the well-known HTM Spiro-OMeTAD in both ssDSCs and PSCs. Furthermore, the facile synthesis of X60 from commercially available starting materials makes this HTM very promising for large-scale industrial production in the future.

  • 124173.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Gabrielsson, Erik
    Safdari, Majid
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    Gardner, James M.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    1,1,2,2-Tetrachloroethane (TeCA) as a Solvent Additive for Organic Hole Transport Materials and Its Application in Highly Efficient Solid-State Dye-Sensitized Solar Cells2015In: Advanced Energy Materials, ISSN 1614-6832, Vol. 5, no 10, article id 1402340Article in journal (Refereed)
    Abstract [en]

    A low-cost, chlorinated hydrocarbon solvent, 1,1,2,2-tetrachloroethane (TeCA), is used as an effective additive for the triarylamine-based organic hole-transport material, Spiro-OMeTAD, which is successfully applied in highly efficient solid-state dye-sensitized solar cells. A record power conversion efficiency of 7.7% is obtained by using the donor (D)-π-acceptor (A)-dye, LEG4, in combination with the new method of TeCA-doping of the hole-transporting material Spiro-OMeTAD.

  • 124174.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Gustafsson, Mats
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, Lund, Sweden..
    Shi, Shuai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Ying, Zhinong
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, Lund, Sweden..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Upper Bound Study of 5G RF EMF Exposure2018In: 2018 IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING, IEEE , 2018, p. 397-398Conference paper (Refereed)
    Abstract [en]

    Power density emitted by 5G user equipment should not exceed the power density limits set by compliance guidelines. When the amplitude of each port of millimeter-wave array antennas is uniform, the power density maximization problem can be relaxed to a semi-definite program. In this paper, the effect of sampling widths is considered for the maximum power density calculation. The results show that when the sampling distance is less than a half wavelength, the sampling rate should be higher than the Nyquist rate.

  • 124175.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Gustafsson, Mats
    Lund Univ, Dept Elect & Informat Technol, SE-22100 Lund, Sweden..
    Shi, Shuai
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Zhao, Kun
    Sony Mobile Commun AB, Res & Technol, Network Technol Lab, SE-22188 Lund, Sweden..
    Ying, Zhinong
    Sony Mobile Commun AB, Res & Technol, Network Technol Lab, SE-22188 Lund, Sweden..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Radio Frequency Exposure Compliance of Multiple Antennas for Cellular Equipment Based on Semidefinite Relaxation2019In: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187X, Vol. 61, no 2, p. 327-336Article in journal (Refereed)
    Abstract [en]

    Human exposure to radio frequency (RF) electromagnetic fields should not exceed the exposure limits set by the relevant regulatory guidelines. In this paper, we provide approaches to determine upper bounds of maximum exposure from multiple antennas. When the total transmitted power is fixed, the maximum exposure can be determined by an eigenvalue decomposition. If an individual antenna has additional power constraint, the exposure maximization problem can be relaxed to a semidefinite program. Two case studies are given to demonstrate the approaches to the maximum exposure of cellular equipment using multiple antennas. The methods and the obtained results provide valuable insights into RF compliance procedures of cellular equipment.

  • 124176.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Helander, Jakob
    Ericsson, Andreas
    Ying, Zhinong
    He, Sailing
    Gustafsson, Mats
    Sjoberg, Daniel
    Investigation of Planar Near-Field Measurement of Millimeter-Wave Antenna for 5G Application2016In: 2016 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP), IEEE , 2016, p. 600-601Conference paper (Refereed)
    Abstract [en]

    The requirement of higher data rates and the emergence of new wireless device demands in future 5G communication put millimeter-wave frequencies in focus. To investigate electromagnetic-filed exposure at such frequencies for 5G cellular phone application, a planar near-field antenna measurement system is established. A tapered open-ended rectangular waveguide was used as the probe antenna, and a patch array antenna operating at 28 GHz was used as antenna under test. The distribution of power density above the antenna surface was calculated based on the measured data and the plane wave expansion method.

  • 124177.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Huang, Jing
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    AgTFSI as p-Type Dopant for Efficient and Stable Solid-State Dye-Sensitized and Perovskite Solar Cells2014In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, no 12, p. 3252-3256Article in journal (Refereed)
    Abstract [en]

    A silver-based organic salt, silver bis(trifluoromethane-sulfonyl) imide (AgTFSI), was employed as an effective p-type dopant for the triarylamine-based organic hole-transport material Spiro-MeOTAD, which has been successfully applied in solid-state dye-sensitized solar cells (ssDSCs) and perovskite solar cells (PSCs). The power conversion efficiencies (PCEs) of AgTFSI-doped devices improved by 20%, as compared to the device based on the commonly used oxygen doping both for ssDSCs and PSCs. Moreover, the solid-state dye-sensitized devices exposed to AgTFSI as dopant showed considerably better stability than those of oxygen doped, qualifying this p-type dopant as a promising alterative for the preparation of highly efficient as well as stable ssDSCs and PSCs for the future.

  • 124178.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Scialacqua, L.
    Scannavini, A.
    Foged, L. J.
    Ying, Z.
    Bolin, T.
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Antenna diagnosis and power density calculation of 5G millimeter-wave mobile terminal using inverse source technique2018In: 12th European Conference on Antennas and Propagation (EuCAP 2018), Institution of Engineering and Technology, 2018, no CP741Conference paper (Refereed)
    Abstract [en]

    Millimeter-wave antennas may suffer from stronger effects of surface waves in 5G mobile terminals. In this paper, printed 28 GHz antennas are implemented in a mobile handset mock-up. The influence of surface waves is examined by the reconstructed equivalent currents obtained through the inverse source technique. The obtained equivalent currents are reused for the power density calculation for the purpose of millimeter-wave exposure assessment. The results provide valuable insight into 5G millimeter-wave mobile antenna design and measurement.

  • 124179.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Sheibani, Esmaeil
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Zhang, Jinbao
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Uppsala University, Sweden.
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Dalian University of Technology (DUT)Dalian, China .
    Carbazole-Based Hole-Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells and Perovskite Solar Cells2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 38, p. 6629-6634Article in journal (Refereed)
    Abstract [en]

    (Graph Presented) Two carbazole-based small molecule hole-transport materials (HTMs) are synthesized and investigated in solid-state dye-sensitized solar cells (ssDSCs) and perovskite solar cells (PSCs). The HTM X51-based devices exhibit high power conversion efficiencies (PCEs) of 6.0% and 9.8% in ssDSCs and PSCs, respectively. These results are superior or comparable to those of 5.5% and 10.2%, respectively, obtained for the analogous cells using the state-of-the-art HTM Spiro-OMeTAD.

  • 124180.
    Xu, Bo
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Sun, Qie
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Wennersten, Ronald
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    Brandt, Nils
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Industrial Ecology.
    An Analysis of China's Carbon Dioxide Mitigation Target2014In: Sustainable Development, ISSN 0968-0802, E-ISSN 1099-1719, Vol. 22, no 2, p. 113-121Article in journal (Refereed)
    Abstract [en]

    The Chinese government has announced a national mitigation target towards sustainable development of reducing carbon dioxide (CO2) emissions per unit GDP (CO2/GDP) by 40-45% by 2020 compared with the 2005 level. This paper analyses China's CO2 strategic mitigation target and suggests possible ways to reduce CO2/GDP. The mitigation target of reducing CO2 intensity in terms of GDP is ambitious and would greatly reduce CO2 emissions compared with business as usual (BAU) in China. However, it would not prevent an increase in absolute CO2 emissions and therefore a more ambitious target, e.g. a larger reduction goal for CO2/GDP, is still needed. Promoting energy structure by more ambitious economic instruments to increase the proportion of renewable energy and replace coal consumption with oil and gas, and improving energy efficiency by applied advanced technologies, are both necessary measures. Special attention should be given to improving technologies in the manufacturing sector owing to its high energy consumption and low energy use efficiency.

  • 124181.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Bi, Dongqin
    Gabrielsson, Erik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Efficient solid state dye-sensitized solar cells based on an oligomer hole transport material and an organic dye2013In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 46, p. 14467-14470Article in journal (Refereed)
    Abstract [en]

    A low-cost and easily-synthesized organic hole transport material (HTM) X3 bearing triphenylamine units and an organic dye was utilized for solid state dye sensitized solar cells (ssDSCs), which have achieved the power conversion efficiencies of 5.8% and 7.1% under 1 sun and 0.46 sun, respectively, outperforming the ssDSC based on Spiro-OMeTAD 5.4% (1 sun) and 6.4% (0.46 sun).

  • 124182.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. Uppsala University, Sweden.
    Lin, Lili
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Shandong Normal University, China.
    Qian, Deping
    Chen, Hong
    Zhang, Jinbao
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhang, Fengling
    Hagfeldt, Anders
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Integrated Design of Organic Hole Transport Materials for Efficient Solid-State Dye-Sensitized Solar Cells2015In: Advanced Energy Materials, ISSN 1614-6832, Vol. 5, no 3, article id 1401185Article in journal (Refereed)
    Abstract [en]

    A series of triphenylamine-based small molecule organic hole transport materials (HTMs) with low crystallinity and high hole mobility are systematically investigated in solid-state dye-sensitized solar cells (ssDSCs). By using the organic dye LEG4 as a photosensitizer, devices with X3 and X35 as the HTMs exhibit desirable power conversion efficiencies (PCEs) of 5.8% and 5.5%, respectively. These values are slightly higher than the PCE of 5.4% obtained by using the state-of-the-art HTM Spiro-OMeTAD. Meanwhile, transient photovoltage decay measurement is used to gain insight into the complex influences of the HTMs on the performance of devices. The results demonstrate that smaller HTMs induce faster electron recombination in the devices and suggest that the size of a HTM plays a crucial role in device performance, which is reported for the first time.

  • 124183.
    Xu, Bo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Wennersten, Ronald
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Brandt, Nils
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    A Comparison of Instruments for Chinese Greenhouse Gases Mitigation2009In: In Transitions toward Sustainability: 2009 ISIE Conference. June 21-24, 2009, Lisbon, Portugal., 2009Conference paper (Refereed)
  • 124184.
    Xu, Bo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Wennersten, Ronald
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Brandt, Nils
    KTH, School of Industrial Engineering and Management (ITM), Industrial Ecology.
    Sun, Qie
    A projected turning point in China's CO2 emissions - an Environmental Kuznets Curve analysis2012In: International Journal of Global Warming (IJGW), ISSN 1758-2083, E-ISSN 1758-2091, Vol. 4, no 3-4, p. 317-329Article in journal (Refereed)
    Abstract [en]

    This paper examines the possible existence fan Environmental Kuznets Curve (EKC) relationship between China's carbon dioxide (CO2) emissions per capita (CO2/capita) and GDP per capita (GDP/capita) during the period 1980-2008. The timing of the turning point in China's CO2/capita can be further estimated if an EKC relationship exists. In regression results, a natural logarithm-quadratic relationship was found between CO2/capita and GDP/capita, which supports the EKC hypothesis. However, China's CO2 emissions are still on a growing track until around 2078 in empirical analysis. More importantly, CO2 emissions will not spontaneously decrease if China continues to develop its economy without adopting instruments for mitigating climate change. China's wealth gap and China's role in international trade are discussed as two possible factors to affect EKC hypothesis. Therefore, reduction in domestic income inequality and negotiations to allocate responsibilities between China and developed countries for CO2 emissions associated with China's exports arc suggested as further efforts.

  • 124185.
    Xu, Bo
    et al.
    Uppsala Univ, Angstrom Lab, Dept Chem, Phys Chem, S-75120 Uppsala, Sweden..
    Wrede, Sina
    Uppsala Univ, Angstrom Lab, Dept Chem, Phys Chem, S-75120 Uppsala, Sweden..
    Curtze, Allison
    Ohio State Univ, Dept Chem & Biochem, 100 West 18th Ave, Columbus, OH 43210 USA..
    Tian, Lei
    Uppsala Univ, Angstrom Lab, Dept Chem, Phys Chem, S-75120 Uppsala, Sweden..
    Pati, Palas Baran
    Uppsala Univ, Angstrom Lab, Dept Chem, Phys Chem, S-75120 Uppsala, Sweden..
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry. KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, S-10044 Stockholm, Sweden..
    Wu, Yiying
    Ohio State Univ, Dept Chem & Biochem, 100 West 18th Ave, Columbus, OH 43210 USA..
    Tian, Haining
    Uppsala Univ, Angstrom Lab, Dept Chem, Phys Chem, S-75120 Uppsala, Sweden..
    An Indacenodithieno[3,2-b]thiophene-Based Organic Dye for Solid-State p-Type Dye-Sensitized Solar Cells2019In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 12, no 14, p. 3243-3248Article in journal (Refereed)
    Abstract [en]

    An indacenodithieno[3,2-b]thiophene (IDTT) unit is used as a linker moiety to design a new p-type dye-TIP-for solid-state p-type dye-sensitized solar cells. Solar cells based on the TIP dye offered an efficiency of 0.18 % with an open-circuit photovoltage of 550 mV and a short-circuit photocurrent density of 0.86 mA cm(-2), which is better than those of two reference dyes, PB6 and BH4. Charge lifetime experiments reveal that the IDTT linker-based TIP dye significantly suppresses charge recombination losses in the devices.

  • 124186.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Ying, Z.
    Gustafsson, M.
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Effective beam-scanning efficiency of millimeter-wave subarrays for 5G user equipment application2018In: IET Conference Publications, Institution of Engineering and Technology , 2018, no CP741Conference paper (Refereed)
    Abstract [en]

    The forthcoming 5G communication system is expected to adopt millimeter-wave bands in order to satisfy the ever-growing traffic explosion. The coverage efficiency was proposed in earlier works to evaluate the beam-scanning capability and coverage performance of array antennas implemented in 5G user equipment. However, when multi-subarray configurations are introduced into user equipment, the coverage efficiency fails to reflect the coverage performance of each subarray under the influence of housing. In this paper, we use the effective beam-scanning efficiency to evaluate the coverage performance of a subarray covered by a superstrate. The results provide valuable insight into 5G mobile antenna design.

  • 124187.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hu, Jun
    Investigation of Probe Distortion in 28GHz Near-field Antenna Measurement for 5G Communication Application2016In: 2016 PROGRESS IN ELECTROMAGNETICS RESEARCH SYMPOSIUM (PIERS), 2016, p. 106-106Conference paper (Refereed)
  • 124188.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. Ericsson AB, Ericsson Res, SE-16480 Stockholm, Sweden..
    Ying, Zhinong
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, SE-22188 Lund, Sweden..
    Scialacqua, Lucia
    Microwave Vis Italy, I-00040 Pomezia, Italy..
    Scannavini, Alessandro
    Microwave Vis Italy, I-00040 Pomezia, Italy..
    Foged, Lars Jacob
    Microwave Vis Italy, I-00040 Pomezia, Italy..
    Bolin, Thomas
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, SE-22188 Lund, Sweden..
    Zhao, Kun
    Sony Mobile Commun AB, Network Technol Lab Res & Technol, SE-22188 Lund, Sweden.;Aalborg Univ, Dept Elect Syst, Antennas Propagat & Radio Networking Sect, DK-9220 Aalborg, Denmark..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China.
    Gustafsson, Mats
    Lund Univ, Dept Elect & Informat Technol, SE-22100 Lund, Sweden..
    Radiation Performance Analysis of 28 GHz Antennas Integrated in 5G Mobile Terminal Housing2018In: IEEE Access, E-ISSN 2169-3536, Vol. 6, p. 48088-48101Article in journal (Refereed)
    Abstract [en]

    Radiation from printed millimeter-wave antennas integrated in mobile terminals is affected by surface currents on chassis, guided waves trapped in dielectric layers, superstrates, and the user's hand, making mobile antenna design for 5G communication challenging. In this paper, four canonical types of printed 28-GHz antenna elements are integrated in a 5G mobile terminal mock-up. Different kinds of terminal housing effects are examined separately, and the terminal housing effects are also diagnosed through equivalent currents by using the inverse source technique. To account for the terminal housing effects on a beam-scanning antenna subarray, we propose the effective beam-scanning efficiency to evaluate its coverage performance. This paper presents the detailed analysis, results, and new concepts regarding the terminal housing effects, and thereby provides valuable insight into the practical 5G mobile antenna design and radiation performance characterization.

  • 124189.
    Xu, Bo
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. University of Washington, United States.
    Zhang, J.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Wang, Linqin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Ruan, C.
    Li, Yuanyuan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Boschloo, G.
    Johansson, E. M. J.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, A.
    Jen, A. K. -Y
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Tailor-Making Low-Cost Spiro[fluorene-9,9′-xanthene]-Based 3D Oligomers for Perovskite Solar Cells2017In: Chem, ISSN 2451-9308, Vol. 2, no 5, p. 676-687Article in journal (Refereed)
    Abstract [en]

    The power-conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have increased rapidly from about 4% to 22% during the past few years. One of the major challenges for further improvement of the efficiency of PSCs is the lack of sufficiently good hole transport materials (HTMs) to efficiently scavenge the photogenerated holes and aid the transport of the holes to the counter-electrode in the PSCs. In this study, we tailor-made two low-cost spiro[fluorene-9,9′-xanthene] (SFX)-based 3D oligomers, termed X54 and X55, by using a one-pot synthesis approach for PSCs. One of the HTMs, X55, gives a much deeper HOMO level and a higher hole mobility and conductivity than the state-of-the-art HTM, Spiro-OMeTAD. PSC devices based on X55 as the HTM show a very impressive PCE of 20.8% under 100 mW·cm−2 AM1.5G solar illumination, which is much higher than the PCE of the reference devices based on Spiro-OMeTAD (18.8%) and X54 (13.6%) under the same conditions.

  • 124190.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    RF EMF Exposure of Beam-Steering Slot Array in 5G User Equipment at 15 GHz2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 177-178Conference paper (Refereed)
    Abstract [en]

    Above 6 GHz or 10 GHz, the radio frequency (RF) electro-magnetic field (EMF) exposure of user equipment (UE) is evaluated in terms of free space power density. The RF EMF exposure compliance of the fifth-generation (5G) UE with an 8 x 1 beam-steering slot array is analyzed in this paper. The maximum exposure (ME) and corresponding maximum permissible radiated power (MPRP) are calculated for different regulatory guidelines. The results give a good estimation on the range of compliance distance and MPRP of 5G UE, and provide the insight for the future RF EMF exposure compliance for the 5G communication. More results and comparisons of different sorts of arrays will be presented in the conference.

  • 124191.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ying, Zhinong
    Understandings of Maximum Spatially-Averaged Power Density in 5G RF EMF Exposure Study2017In: 2017 INTERNATIONAL WORKSHOP ON ANTENNA TECHNOLOGY: SMALL ANTENNAS, INNOVATIVE STRUCTURES, AND APPLICATIONS (IWAT), IEEE , 2017, p. 115-117Conference paper (Refereed)
    Abstract [en]

    In the millimeter-wave (mmW) frequency band, radio frequency electromagnetic field (RF EMF) exposure is evaluated in terms of free space power density rather than the localized specific absorption rate (SAR) used in current cellular communications. In this study, we investigated RF EMF exposure of user equipment (UE) mock-ups employing a patch array operating at 15 GHz. Different understandings of maximum spatially-averaged power density to comply with different regulatory requirements are studied. Based on free space power density, the maximum permissible transmitted power (MPTP) of UE is calculated to compare the influence of different understandings. The analysis and results suggest that there is 1-2.6 dB MPTP difference for the ICNIRP limits and 0.1-1 dB MPTP difference for the proposed FCC limits depending on the varying compliance distance.

  • 124192.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Thors, Björn
    Colombi, Davide
    Lundberg, Oscar
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Power Density Measurements at 15 GHz for RF EMF Compliance Assessments of 5G User Equipment2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 12, p. 6584-6595Article in journal (Refereed)
    Abstract [en]

    In this paper, different measurement schemes are studied in order to investigate the possibilities and limitations of scalar-and vector-based measurement systems for radio frequency electromagnetic fields compliance assessments of fifth generation mobile communication user equipment (UE). Two UE antenna array designs, transmitting at 15 GHz and employing patch and notch antenna elements, are considered for different phase excitations. Using free space power density as the exposure metric, the maximum permissible transmitted power of UE, compliant with the maximum permissible exposure limits specified by the U.S. Federal Communications Commission (FCC) and the basic restrictions of the International Commission on Non-Ionizing Radiation Protection, is determined. The accuracy of different measurement schemes is assessed using numerical simulation. Verifying measurements is carried out in a semiane-choic chamber. The results indicate that, for UE employing array antennas and intended to be used in immediate vicinity of the human body, scalar measurement systems used in combination with straightforward field combination techniques will lead to overly conservative results. A more accurate and less conservative approach for these products is to conduct separate measurements for different excitations in order to span the space of possible excitations. This will result in a more complicated measurement setup and increase the measurement time, which points to a need for very fast measurement systems.

  • 124193.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Zhao, Kun
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. SONY Mobile Communications AB, Sweden.
    Ying, Z.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hu, J.
    Investigation of surface waves suppression on 5G handset devices at 15 GHz2016In: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, article id 7481336Conference paper (Refereed)
    Abstract [en]

    The challenge of surface wave excitation and propagation to millimeter-wave (mm-wave) antennas of future fifth-generation (5G) cellular system is addressed in this paper. This paper presents three different schemes by simulation, including mushroom-like electromagnetic band-gap (EBG) structures, cross-shaped resonant structures and T-shaped wave trap structures, to suppress surface wave propagation in handset devices at 15 GHz. We also investigate the positional influence of EBG structures on the radiation patterns of two slot array antennas on a mock-up. The measurement results suggest that gain, sidelobe level and radiation efficiency are all increased when the EBG structures are placed close to the radiating element.

  • 124194.
    Xu, Bo
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Zhao, Kun
    Sony Mobile Commun, Network Technol Lab, Res & Technol, SE-22188 Lund, Sweden.;Aalborg Univ, Dept Elect Syst, Antennas Propagat & Radio Networking Sect, DK-9220 Aalborg, Denmark..
    Ying, Zhinong
    Sony Mobile Commun, Network Technol Lab, Res & Technol, SE-22188 Lund, Sweden..
    Sjoberg, Daniel
    Lund Univ, Dept Elect & Informat Technol, SE-22100 Lund, Sweden..
    He, Wang
    Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering. Zhejiang Univ, Ctr Opt & Electromagnet Res, Hangzhou 310058, Zhejiang, Peoples R China..
    Analysis of Impacts of Expected RF EMF Exposure Restrictions on Peak EIRP of 5G User Equipment at 28 GHz and 39 GHz Bands2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 20996-21005Article in journal (Refereed)
    Abstract [en]

    Above 6 GHz, radio frequency (RF) electromagnetic field (EMF) exposure from the mobile communication user equipment (UE) should be assessed in terms of incident power density, rather than specific absorption rate as below 6 GHz. Such regulatory RF EMF restrictions will constrain the transmit power of the UE and its peak equivalent isotropically radiated power (EIRP). This paper provides an analysis of the peak EIRP levels of UE containing code-book-based beamforming arrays at 28 GHz and 39 GHz. Different types of antenna elements, incremental element spacing, 4- and 8-element array configurations, and realistic housing integration are considered. The analysis and results show that in realistic housing integration, the 3GPP requirements on minimum peak EIRP can be generally met under the expected RF EMF exposure restrictions.

  • 124195. Xu, Can T.
    et al.
    Zhan, Qiuqiang
    Liu, Haichun
    Somesfalean, Gabriel
    Qian, Jun
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Andersson-Engels, Stefan
    Upconverting nanoparticles for pre-clinical diffuse optical imaging, microscopy and sensing: Current trends and future challenges2013In: Laser and Photonics Reviews, ISSN 1863-8880, Vol. 7, no 5, p. 663-697Article, review/survey (Refereed)
    Abstract [en]

    Upconverting nanoparticles (UCNPs) are a class of recently developed luminescent biomarkers that - in several aspects - are superior to organic dyes and quantum dots. UCNPs can emit spectrally narrow anti-Stokes shifted light with quantum yields which greatly exceed those of two-photon dyes for fluence rates relevant for deep tissue imaging. Compared with conventionally used Stokes-shifting fluorophores, UCNP-based imaging systems can acquire completely autofluorescence-free data with superb contrast. For diffuse optical imaging, the multiphoton process involved in the upconversion process can be used to obtain images with unprecedented resolution. These unique properties make UCNPs extremely attractive in the field of biophotonics. UCNPs have already been applied in microscopy, small-animal imaging, multi-modal imaging, highly sensitive bioassays, temperature sensing and photodynamic therapy. In this review, the current state-of-the-art UCNPs and their applications for diffuse imaging, microscopy and sensing targeted towards solving essential biological issues are discussed.

  • 124196.
    Xu, Chen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    EU Energy Situations and Supply Security2008Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Energy supply security is a hot topic today. It highly influences energy market, national security and also residents’ daily lives. However, due to different aims and study strategies, definitions of energy supply security are different. In this report, it is defined as stable energy supply processes that result from good infrastructure, delivery of energy sources, carriers and services, which are sturdily controlled by effective energy policies. Prices of energy supply system

    are also maintained on a reasonable level over a continuous period thanks to the efficient crises assessment and management.

    In order to make a comprehensive research, energy situation has been deeply investigated on worldwide, EU and Swedish levels, respectively. Results from these investments obviously certify that due to the big amount of populations, there are significant imbalances between energy supply and demands in developing countries. To make things better, these imbalances don’t exist in developed world, like EU Members including Sweden because of applications of advanced technologies and wide utilizations of renewable energy carriers. Oppositely, greenhouse gases emission is a severe problem in the world, which gives rise to temperature increasing year by year! Besides the global warming, some other factors also bring about uncertainties to energy supply security, so that efficient policies are necessary in order improve the recent

    situations and to create a secure atmosphere for energy supply, such as

    Directive 98/30/EC for natural gas supply security, Directive 2003/55/EC for integration and compatibility of the energy regulation and Directive 2003/54/EC, the first policy that regulates EU electricity market as well as IEM Directive, which is the improvement of Directive 2003/54/EC, etc.

    Although several policies aiming at creation of competitive energy markets and achieving energy supply security, vulnerabilities still exist in EU energy supply system, such as limited primary energy sources and high dependence on nuclear powers, energy network capacity inadequacy, high voltage electricity transmission, etc. Concerning Swedish energy supply system, extreme low temperatures in winter, drilling technologies and high economic budgets for heat sources from underground, hurricanes, thunderstorms to wind turbines and man-made disruptions are all potential vulnerabilities. Regarding these negative aspects, recommendations are given on four different levels, which are global, EU, Swedish and individual perspectives. Specific suggestions to achieve energy supply security include independence of different energy supplies, to enhance international cooperation, periodic assessments and inspections for energy facilities, population control, to keep original energy policies updated, to enhance abilities to resist abnormal weather conditions, to develop heat pump technologies and try to use energy in efficient ways, etc.

  • 124197. Xu, Chen
    et al.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Liotta, Roberto
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wyss, Ramon
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Wang, S. M.
    Xu, F. R.
    Jiang, D. X.
    Molecular structure of highly excited resonant states in Mg-24 and the corresponding Be-8+O-16 and C-12+C-12 decays2010In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 81, no 5, p. 054319-Article in journal (Refereed)
    Abstract [en]

    Exotic Be-8 and C-12 decays from high-lying resonances in Mg-24 are analyzed in terms of a cluster model. The calculated quantities agree well with the corresponding experimental data. It is found that the calculated decay widths are very sensitive to the angular momentum carried by the outgoing cluster. It is shown that this property makes cluster decay a powerful tool to determine the spin as well as the molecular structures of the resonances.

  • 124198.
    Xu, Cheng
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    A Segmented Silicon Strip Detector for Photon-Counting Spectral Computed Tomography2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Spectral computed tomography with energy-resolving detectors has a potential to improve the detectability of images and correspondingly reduce the radiation dose to patients by extracting and properly using the energy information in the broad x-ray spectrum. A silicon photon-counting detector has been developed for spectral CT and it has successfully solved the problem of high photon flux in clinical CT applications by adopting the segmented detector structure and operating the detector in edge-on geometry. The detector was evaluated by both the simulation and measurements.

    The effects of energy loss and charge sharing on the energy response of this segmented silicon strip detector with different pixel sizes were investigated by Monte Carlo simulation and a comparison to pixelated CdTe detectors is presented. The validity of spherical approximations of initial charge cloud shape in silicon detectors was evaluated and a more accurate statistical model has been proposed.

    A photon-counting energy-resolving application specific integrated circuit (ASIC) developed for spectral CT was characterized extensively by electrical pulses, pulsed laser and real x-ray photons from both the synchrotron and an x-ray tube. It has been demonstrated that the ASIC performs as designed. A noise level of 1.09 keV RMS has been measured and a threshold dispersion of 0.89 keV RMS has been determined. The count rate performance of the ASIC in terms of count loss and energy resolution was evaluated by real x-rays and promising results have been obtained.

    The segmented silicon strip detector was evaluated using synchrotron radiation. An energy resolution of 16.1% has been determined with 22 keV photons in the lowest flux limit, which deteriorates to 21.5% at an input count rate of 100 Mcps mm−2. The fraction of charge shared events has been estimated and found to be 11.1% for 22 keV and 15.3% for 30 keV. A lower fraction of charge shared events and an improved energy resolution can be expected by applying a higher bias voltage to the detector.

  • 124199.
    Xu, Cheng
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Chen, Han
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Persson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Karlsson, Staffan
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Svensson, Christer
    Bornefalk, Hans
    KTH, School of Engineering Sciences (SCI), Physics, Physics of Medical Imaging.
    Energy resolution of a segmented silicon strip detector for photon-counting spectral CT2013In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 715, p. 11-17Article in journal (Refereed)
    Abstract [en]

    We investigated the energy resolution of a segmented silicon strip detector for photon-counting spectral computed tomography (CT). The detector response to different monochromatic photon energies and various photon fluxes was characterized at the Elettra synchrotron. An RMS energy resolution of 1.50 keV has been demonstrated for 22 keV photons at zero flux, and it deteriorated as a function of input count rate at a rate of 5.13 eV mm2 /Mcps. The charge sharing effect has been evaluated. The results show that around 11.1% of the interacting photons experience charge sharing for 22 keV photons and 15.3% for 30 keV.

  • 124200.
    Xu, Cheng
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Danielsson, Mats
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Bornefalk, Hans
    KTH, School of Engineering Sciences (SCI), Physics, Medical Imaging.
    Evaluation of Energy Loss and Charge Sharing in Cadmium Telluride Detectors for Photon-Counting Computed Tomography2011In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 58, no 3, p. 614-625Article in journal (Refereed)
    Abstract [en]

    We present estimates of energy loss and charge sharing for a pixelated cadmium telluride (CdTe) detector used for photon-counting spectral computed tomography (CT). In a photon-counting pixelated CdTe detector, several physical effects lead to detected events with reduced energies, including Compton scattering, fluorescence emission, charge diffusion, trapping of charge carriers and slow-hole-motion-induced incomplete charge collection. Charge sharing is the result of the lost energy being collected by adjacent pixels. We simulated the photon transport and the charge-collection process with a Monte Carlo-based simulation and evaluated these effects on the detector performance. The trapping effect and poor hole collection have been studied together using an analytical model. We also investigated the detector response under the influence of only the fluorescence effect. We conclude that the charge sharing effects should be taken into account when the pixel is smaller than 1 mm(2). A straightforward way to decrease the double counting of X-rays from events with charge sharing is to increase the electronic threshold. However, increasing the threshold comes at the cost of losing low-energy events, which is undesirable, at least in applications such as pediatric imaging.

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