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  • 122801.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    An adhesion model for wheel-rail contact at the micro level using measured 3d surfaces2012Ingår i: 9th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems, CM 2012, Southwest Jiaotong University , 2012, s. 550-562Konferensbidrag (Refereegranskat)
    Abstract [en]

    Railway vehicles require a certain level of wheel-rail adhesion for efficient, reliable, and economical operation. A comprehensive wheel-rail contact model is useful for optimizing the adhesion, to simulatevehicle running conditions and to predict wear and rolling contact fatigue. A new contact model using measured 3D surfaces has been developed, comprising normal contact, rolling-sliding contact, flash temperature, and local friction coefficient models. This model can predict the local contact pressure, including the plasticity, local flash temperature, local tangential stress, local friction coefficient, and global adhesion coefficient. The influence of surface topography, creep, and speed on the adhesion coefficient, real contact area, and contact temperature is discussed. Results indicate that, due to increased contact area, the adhesion coefficient decreases with increased surface roughness, although the change is small. Furthermore, increasing speed reduces the adhesion coefficient due to the increasing contact temperature.

  • 122802.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Maskinelement.
    An adhesion model for wheel-rail contact at the micro level using measured 3d surfaces2014Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 314, nr 1-2, s. 162-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Railway vehicles require a certain level of wheel-rail adhesion for efficient, reliable, and economical operation. A comprehensive wheel-rail contact model is useful for optimizing the adhesion, to simulate vehicle running conditions and to predict wear and rolling contact fatigue. A new contact model using measured 3D surfaces has been developed, comprising normal contact, rolling-sliding contact, flash temperature, and local friction coefficient models. This model can predict the local contact pressure, including the plasticity, local flash temperature, local tangential stress, local friction coefficient, and global adhesion coefficient. The influence of surface topography, creep, and speed on the adhesion coefficient, real contact area, and contact temperature is discussed. Results indicate that, due to increased contact area, the adhesion coefficient decreases with increased surface roughness, although the change is small. Furthermore, increasing speed reduces the adhesion coefficient due to the increasing contact temperature.

  • 122803.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Chen, Hur
    Friction Between Wheel and Rail: A Pin-On-Disc Study of Environmental Conditions and Iron Oxides2013Ingår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 52, nr 2, s. 327-339Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The coefficient of friction between railway wheels and rails is crucial to railway operation and maintenance. Since the wheel-rail system is an open system, environmental conditions, such as humidity and temperature, affect the friction coefficient. Pin-on-disc testing was conducted to study the influence of environmental conditions and iron oxides on the coefficient of friction between the wheel and rail. The iron oxides were pre-created in a climate chamber. The surfaces of the tested samples were analysed using X-ray diffraction, scanning electron/focused ion beam microscopy, and Raman spectroscopy. Results indicate that the coefficient of friction decreases with increasing relative humidity (RH) up to a saturation level. Above this level, the coefficient of friction remains low and stable even when the RH increases. In particular, when the temperature is low, a small increase in the amount of water (i.e., absolute humidity) in the air can significantly reduce the coefficient of friction. At high humidity levels, a water molecule film can keep the generated haematite on the surfaces, counterbalancing the effect of rising humidity.

  • 122804.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Nilsson, R.
    Stockholm public transport AB, Stockholm, Sweden.
    A field test study of leaf contamination on railhead surfaces2014Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 228, nr 1, s. 71-84Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Leaves on railway tracks affect the level of adhesion between the wheel and rail, especially in autumn. When crushed by wheels, leaves form a tarnished, low level of adhesion layer that sticks to the railhead and often requires mechanical removal. A Stockholm local traffic track with a long history of adhesion problems was subjected to field tests on railhead contamination. On five occasions under different conditions, spaced over a year, the friction coefficient was measured using a tribometer and samples of the rail were taken. The techniques of electron spectroscopy for chemical analysis and glow discharge optical emission spectrometry were conducted to determine the composition of the top layer of rail contaminants and hardness was measured using the nano-indentation technique. The tarnished layer contains much higher contents of calcium, carbon and nitrogen than do leaf residue layers and uncontaminated samples. These high element contents are generated from the leaf material, which chemically reacts with the bulk material. The hardness of the tarnished layer is one-fifth that of the non-tarnished layer of the same running band. A chemical reaction occurs from the surface to a depth of several microns. The thickness of the friction-reducing oxide layer can be used to predict the friction coefficient and extent of leaf contamination.

  • 122805.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Persson, Karin
    Institute for Surface Chemistry, Life Science and Chemical Industries Section, Stockholm, Sweden.
    Investigation of factors influencing wheel-rail adhesion using a mini-traction machine2012Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 292/293, s. 218-231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adhesion in the wheel-rail contact is a key factor determining stable running conditions and safety during train driving and braking. This paper presents an experiment performed in a mini-traction machine to simulate the problems of low adhesion in the wheel-rail contact. Tests were conducted under dry conditions and using water or oil as lubricants to study the influence of surface roughness on the adhesion coefficient. The results indicate that the adhesion coefficient can be reduced to as low as 0.02 for smooth surfaces lubricated with water. For rougher contact surfaces, the water-lubricated tests indicate a higher adhesion coefficient than do oil-lubricated ones, but also a clear dependence on water temperature. The oil-lubricated tests indicate a very slight dependence of the adhesion coefficient on variation in rolling speed, temperature, and surface roughness.

  • 122806.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Söderberg, Anders
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Adhesion modeling in the wheel-rail contact under dry and lubricated conditions using measured 3D surfaces2013Ingår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 61, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Adhesion between wheels and rails plays an essential role in the safe, efficient, and reliable operation of a railway network. Particularly under lubricated conditions, which can be a natural lubricant as water and an applied lubricant as rail oil, trains can experience adhesion loss. This paper presents an adhesion model constructed using the measured 3D wheel-rail surfaces. The numerical model comprises of three parts: a normally loaded contact model; an interfacial fluid model; and a rolling-sliding contact model. Simulation examples use the numerical model to investigate how water or oil contamination might affect wheel-rail adhesion in contacts with different surface roughness levels. Simulation indicates that adhesion peaks are almost at the same creep on different surfaces. The fluid load capacity is inversely proportional to the adhesion coefficient, both of which are clearly dependent on vehicle speed. Oil reduces adhesion coefficient more than water does. The adhesion coefficient on the low roughness surfaces is higher than that on the generated smooth surfaces under oil-lubricated conditions while it is the opposite for water-lubricated contact.

  • 122807.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Sundh, Jon
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    A tribological view of wheel-rail wear maps2013Ingår i: The international Journal of railway technology, ISSN 2049-5358, E-ISSN 2053-602X, Vol. 2, nr 3, s. 79-91Artikel i tidskrift (Refereegranskat)
  • 122808.
    Zhu, Yingming
    et al.
    Sichuan Univ, Inst New Energy & Low Carbon Technol, Chengdu 610065, Sichuan, Peoples R China..
    Wang, Fu
    Ningbo Univ, Fac Maritime & Transportat, Ningbo 315211, Zhejiang, Peoples R China.;Ningbo RX New Mat Tech Co Ltd, Ningbo 315200, Zhejiang, Peoples R China..
    Yan, Jinyue
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Energiprocesser. Sichuan Univ, Inst New Energy & Low Carbon Technol, Chengdu 610065, Sichuan, Peoples R China..
    The Potential of Distributed Energy Resources in Building Sustainable Campus: The Case of Sichuan University2018Ingår i: RENEWABLE ENERGY INTEGRATION WITH MINI/MICROGRID / [ed] Yan, J Wang, C Yu, J Jia, H Wu, J Xu, T Zhang, Y, ELSEVIER SCIENCE BV , 2018, s. 582-585Konferensbidrag (Refereegranskat)
    Abstract [en]

    Distributed energy resources systems are decentralized, modular and more flexible technologies. These systems can comprise multiple generation and storage components. Sichuan University (SCU) has joined Global Urban Development program, and takes part in Sustainability Tracking, Assessment & Rating System, aims at a sustainable campus. So we investigated the potential of distributed energy resources, e.g. solar power, that can be used in SCU. Firstly, we build 4 micro-grids with a total 156 Kw PV capacities to collect the power generation data. The total roof area of SCU Jiangan campus is 165701 m(2), and the estimated installed capacity is 8.3MW-11.6MW. Based on this data, 33% similar to 46% power cost can be covered by PV power generation.

  • 122809. Zhu, Yinian
    et al.
    Shum, Ping
    Nanyang Techbological University, Singapore.
    Bay, Hui-Wen
    Yan, Min
    Nanyang Techbological University, Singapore.
    Yu, Xia
    Hu, Juanjuan
    Hao, Jianzhong
    Lu, Chao
    Strain-insensitive and high-temperature long-period gratings inscribed in photonic crystal fiber2005Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 30, nr 4, s. 367-369Artikel i tidskrift (Refereegranskat)
  • 122810.
    zhu, yue
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.).
    Applying lean philosophy to the redesign of service delivery process: A case study in the telecommunication industry2012Självständigt arbete på avancerad nivå (masterexamen), 80 poäng / 120 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Lean is an umbrella term for a powerful combination of techniques to maximize customer value by minimizing waste and achieving continuous flow through a sustainable culture of continuous improvement. The term ―lean is used in the U.S. for what was originally created as the "Toyota Production System" by the Japanese carmaker. It is so fashionable since it was born that it’s been widely used in the manufacturing industry during the past decades all over the world. No matter in the opinion of insiders or outsiders, this is a magical word stands for discovering and eliminating discreet wastes, reducing resources requirement and time demand for production, making the manufacturing process efficient and cost effective and eventually building the sustainable competitive advantage of the organization.

    There’s already a world of books discussing the implementations. But as for the service delivery process, especially within the telecom industry, there’s no qualitative research carried out to check the validation of lean tool yet. Most researchers still remain on the theoretical level, arguing and debating on the applicability. The objective of this research is to fill in this research niche, check the possibility of using lean tool, naming VSM, to study and redesign the service delivery process in a qualitative way. The research question comes to how to apply the tool in a qualitative way and exam the both sides of the coin.

    The author investigated on the service delivery process performance in the Business-As-Usual projects and the key performance indicators of the case company business unit to find out any inconsistencies. One of the powerful lean tools - VSM is used step by step, node by node to identify existing discreet wastes. Based on the lean philosophy and literature reviews, potential possible improvements are proposed to eliminate the wastes, afterwards an ideal new VSM is created, with which it is able to dramatically reduce the resources required to seize customer value, satisfy the same amount of customer demand, increase customer satisfaction, make the company focusing on continuous improvement, and in the end move the company to a higher position in the field with stronger competence to win more market share.

    This research work is conducted as a single case study under the lean philosophy by collecting and studying qualitative data using various semi-structured interviews and archival data analysis. Six applicable solutions to lead the organization lean is proposed, and based on which, a brand new Optimization Focus Matrix is introduced to have a broader applicability. Possible benefit, difficulties in implementation and potential risks are also presented. The thesis ends with conclusion, answer to the research questions and discussion on the thesis limitation & future research direction.

  • 122811.
    Zhu, Yunyi
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Numerisk analys, NA.
    Epitope Mapping using Local Alignment Features2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Our immune system uses antibodies to neutralize pathogens such as bacteria and viruses. Antibodies bind to parts of foreign proteins with high efficiency and specificity. We call such parts epitopes. The identification of epitopes, namely epitope mapping, may contribute to various immunological applications such as vaccine design, antibody production and immunological diagnosis.

    Therefore, a fast and reliable method that can predict epitopes from the whole proteome is highly desirable.

     

    In this work we have developed a computational method that predicts epitopes based on sequence information. We focus on using local alignment to extract features from peptides and classifying them using Support Vector Machine. We also propose two approaches to optimize the features. Results show that our method can reliably predict epitopes and significantly outperforms some most commonly used tools.

     

  • 122812. Zhu, Z.
    et al.
    Höglund, Lars
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Larsson, H.
    Reed, R. C.
    Isolation of optimal compositions of single crystal superalloys by mapping of a material's genome2015Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 90, s. 330-343Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The multicomponent composition space pertinent to the single crystal nickel-based superalloys is mapped and searched, using computational modelling. A resolution of 0.1 wt.% for the alloying elements is assumed, consistent with manufacturing practice. Databases are constructed of alloy compositions which are predicted to be of promising microstructural architecture: e.g. equal fractions of the γ and γ′ phases. These may be regarded as maps - one might term them genomes - of this class of structural alloy. By combining the databases with additional composition-dependent property models, it is demonstrated that compositions can be identified which - subject to the accuracy and limitations of the sub-models - are likely to prove optimal, e.g. on the basis of their creep resistance, density and cost. The methods circumvent the need for the traditional empirically-driven approaches to alloy design.

  • 122813. Zhu, Z.
    et al.
    Zhou, Y. J.
    Kang, M. -K
    Krivoruchko, A.
    Buijs, N. A.
    Nielsen, Jens
    KTH, Centra, Science for Life Laboratory, SciLifeLab. Chalmers University of Technology, Technical University of Denmark.
    Enabling the synthesis of medium chain alkanes and 1-alkenes in yeast2017Ingår i: Metabolic engineering, ISSN 1096-7176, E-ISSN 1096-7184, Vol. 44, s. 81-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microbial synthesis of medium chain aliphatic hydrocarbons, attractive drop-in molecules to gasoline and jet fuels, is a promising way to reduce our reliance on petroleum-based fuels. In this study, we enabled the synthesis of straight chain hydrocarbons (C7–C13) by yeast Saccharomyces cerevisiae through engineering fatty acid synthases to control the chain length of fatty acids and introducing heterologous pathways for alkane or 1-alkene synthesis. We carried out enzyme engineering/screening of the fatty aldehyde deformylating oxygenase (ADO), and compartmentalization of the alkane biosynthesis pathway into peroxisomes to improve alkane production. The two-step synthesis of alkanes was found to be inefficient due to the formation of alcohols derived from aldehyde intermediates. Alternatively, the drain of aldehyde intermediates could be circumvented by introducing a one-step decarboxylation of fatty acids to 1-alkenes, which could be synthesized at a level of 3 mg/L, 25-fold higher than that of alkanes produced via aldehydes.

  • 122814. Zhu, Zhi-Shuang
    et al.
    Liao, Hua
    Cao, Huai-Shu
    Wang, Lu
    Wei, Yi-Ming
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    The differences of carbon intensity reduction rate across 89 countries in recent three decades2014Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 113, nr SI, s. 808-815Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the recent decades, most countries' CO2 intensity has decreased, but their decline rates are significantly different. Based on the data set of 89 countries from 1980 to 2008, this paper tries to quantitatively investigate the potential reasons for their differences, and discusses the possibility for developing countries to maintain a high carbon intensity reduction rate in the future as before. The econometric analysis implicate that (1) the decline rate of CO2 intensity in countries with high initial carbon intensity will be higher, which means CO2 intensity across the world has a significant convergence trend; and (2) keeping fast and steady economic growth can significantly help CO2 intensity decline, yet total carbon dioxide emissions will grow dramatically. Therefore, with the two objectives of intensity reduction and total amount control, carbon abatement policies need to weigh one against another. The results are robust to the initial year selection and country classification.

  • 122815. Zhu, Zhiwei
    et al.
    Zhou, Yongjin J.
    Krivoruchko, Anastasia
    Grininger, Martin
    Zhao, Zongbao K.
    Nielsen, Jens
    Expanding the product portfolio of fungal type I fatty acid synthases2017Ingår i: Nature Chemical Biology, ISSN 1552-4450, E-ISSN 1552-4469, Vol. 13, nr 4, s. 360-362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fungal type I fatty acid synthases (FASs) are mega-enzymes with two separated, identical compartments, in which the acyl carrier protein (ACP) domains shuttle substrates to catalytically active sites embedded in the chamber wall. We devised synthetic FASs by integrating heterologous enzymes into the reaction chambers and demonstrated their capability to convert acyl-ACP or acyl-CoA from canonical fatty acid biosynthesis to short/ medium-chain fatty acids and methyl ketones.

  • 122816. Zhuang, C.
    et al.
    Marquez, Juan C.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Medicinska sensorer, signaler och system. Shanghai Jiao Tong University, China.
    Qu, H. E.
    He, X.
    Lan, N.
    A neuromuscular electrical stimulation strategy based on muscle synergy for stroke rehabilitation2015Ingår i: International IEEE/EMBS Conference on Neural Engineering, NER, IEEE Computer Society, 2015, s. 816-819Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent experiments have suggested that the central nervous system (CNS) makes use of muscle synergies as a neural strategy to simplify the control of a variety of movements by using a single pattern of neural command signal. This nature of muscle coordination could have great significance in the treatment and rehabilitation of upper limb impairments for hemiparetic patients post stroke. The use of neuromuscular electrical stimulation (NMES) for neural prosthetics or therapeutic applications has been demonstrated as a promising clinical intervention for stroke patients to recover motor function of the upper extremity. However, the existing NMES systems do not provide control methods for the patient to achieve an individualized and functional rehabilitation training. In this research work, muscle synergies from the flexionextension elbow antagonistic muscles were studied. Using motion information and EMG signals, muscle synergies were extracted using non-negative matrix factorization (NMF) method. Reconstructed signals obtained from the muscle synergies were then applied to the virtual arm (VA) model to test a synergy based NMES strategy. Results show close resemblance to the original elbow trajectory of normal movements and thus the feasibility to control movements in stroke patients for rehabilitation.

  • 122817. Zhuang, F.
    et al.
    Shen, Jianqi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Ye, J.
    Controlling the photonic bandgap structures via manipulation of refractive index of electromagnetically induced transparency vapor2007Ingår i: Wuli xuebao, ISSN 1000-3290, Vol. 56, nr 1, s. 541-545Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new application of coherent manipulation of EIT (electromagnetically induced transparency) medium is suggested. A two-dimensional photonic crystal with a triangle lattice of elliptic air cylinders, which are filled with the EIT atomic vapor, in the KAs background material is designed. By manipulating the refractive index of the EIT vapor via the external control field, one can obtain the controllable bandgap structure that is sensitive to the variations of external conditions (e.g. the intensity of the control field) . It is shown that a large complete bandgap of about 0.0503ωe in the region of high normalized frequency could be achieved by choosing the specific parameters such as the spontaneous decay rate, dephasing rate, Rabi frequency of control light, atomic number density as well as elliptic geometric parameters.

  • 122818. Zhuang, F.
    et al.
    Wu, L.
    He, Sailing
    KTH, Tidigare Institutioner                               , Teoretisk elektroteknik.
    A two-dimensional photonic crystal with six large bandgaps formed by a hexagonal lattice of anisotropic cylinders2002Ingår i: Chinese Physics (Beijing), ISSN 1009-1963, E-ISSN 1741-4199, Vol. 11, nr 8, s. 834-838Artikel i tidskrift (Refereegranskat)
  • 122819. Zhuang, F.
    et al.
    Wu, L.
    He, Sailing
    Band structures of two-dimensional photonic crystals with regular polygon cylinders calculated by linear operations2002Ingår i: Wuli xuebao, ISSN 1000-3290, Vol. 51, nr 12, s. 2865-2870Artikel i tidskrift (Refereegranskat)
  • 122820. Zhuang, F.
    et al.
    Wu, L.
    Xiao, S. S.
    He, Sailing
    KTH, Tidigare Institutioner                               , Teoretisk elektroteknik.
    Band structure of a two-dimensional photonic crystal with a triangular lattice of anisotropic elliptic cylinders2002Ingår i: Chinese Physics Letters, ISSN 0256-307X, E-ISSN 1741-3540, Vol. 19, nr 1, s. 73-75Artikel i tidskrift (Refereegranskat)
  • 122821.
    Zhuang, Hao
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Performance Evaluation of Virtualization in Cloud Data Center2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Amazon Elastic Compute Cloud (EC2) har antagits av ett stort antal små och medelstora företag (SMB), t.ex. foursquare, Monster World, och Netflix, för att ge olika typer av tjänster. Det finns en del tidigare arbeten i den aktuella litteraturen som undersöker variationen och oförutsägbarheten av molntjänster. Dessa arbetenhar visat intressanta iakttagelser om molnerbjudanden, men de har misslyckats med att avslöja den underliggande kärnan hos de olika utseendena för molntjänster.

    I denna avhandling tittade vi på de underliggande schemaläggningsmekanismerna och maskinvarukonfigurationer i Amazon EC2, och undersökte deras inverkan på resultatet för de virtuella maskiners instanser som körs ovanpå. Närmare bestämt är det flera fall med standard- och hög-CPU instanser som omfattas att belysa uppgradering av hårdvara och utbyte av Amazon EC2. Stora instanser från standardfamiljen är valda för att genomföra en fokusanalys. För att bättre förstå olika beteenden av de olika instanserna har lokala kluster miljöer inrättas, dessa klustermiljöer består av två Intel Xeonservrar och har inrättats med hjälp av olika schemaläggningsalgoritmer.

    Genom en serie benchmarkmätningar observerade vi följande slutsatser: (1) Amazon använder mycket diversifierad hårdvara för att tillhandahållandet olika instanser. Från de olika instans-sub-typernas perspektiv leder hårdvarumångfald till betydande prestationsvariation som kan nå upp till 30%. (2) Två olika schemaläggningsmekanismer observerades, en liknande Simple Earliest Deadline Fist(SEDF) schemaläggare, medan den andra mer liknar Credit-schemaläggaren i Xenhypervisor. Dessa två schemaläggningsmekanismer ger även upphov till variationer i prestanda. (3) Genom att tillämpa en enkel "trial-and-failure" strategi för val av instans, är kostnadsbesparande förvånansvärt stor. Med tanke på fördelning av snabba och långsamma instanser kan kostnadsbesparingen uppgå till 30%, vilket är attraktivt för små och medelstora företag som använder Amazon EC2 plattform.

  • 122822.
    Zhuang, Qingyuan
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Parametric Study on the Aeroelastic Stability of Rotor Seals2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Labyrinth seals are widely used in rotating machinery and have been shown to experience aeroelastic instabilities. The rapid development of computational fluid dynamics now provides a high fidelity approach for predicting the aeroelastic behavior of labyrinth seals in three dimension and exhibits great potential within industrial application, especially during the detailed design stages. In the current publication a time-marching unsteady Reynolds- averaged Navier-Stokes solver was employed to study the various historically identified parameters that have essential influence on the stability of labyrinth seals. Advances in understanding of the related aeroelastic (flutter) phenomenon were achieved based on extensive yet economical numerical analysis of a simplified seal model. Further, application of the same methodology to several realistic gas turbine labyrinth seal designs confirmed the perceived knowledge and received agreements from experimental indications. Abbott’s criteria in describing the labyrinth seal aeroelastic behaviors were reaffirmed and further developed. 

  • 122823. Zhuang, Zanyong
    et al.
    Chen, Hong
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Lin, Zhang
    Dang, Zhi
    Mn2O3 hollow spheres synthesized based on an ion-exchange strategy from amorphous calcium carbonate for highly efficient trace-level uranyl extraction2016Ingår i: ENVIRONMENTAL SCIENCE-NANO, ISSN 2051-8153, Vol. 3, nr 6, s. 1254-1258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Well-defined hierarchical hollow spheres constructed from Mn2O3 quantum dots were prepared via an ion-exchange strategy starting from small-sized amorphous calcium carbonate. They show outstanding capability to extract trace-level uranyl from field water.

  • 122824. Zhukavin, R. Kh
    et al.
    Kovalevsky, K. A.
    Orlov, M. L.
    Tsyplenkov, V. V.
    Bekin, N. A.
    Yablonskiy, A. N.
    Yunin, P. A.
    Pavlov, S. G.
    Abrosimov, N. V.
    Huebers, H. -W
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Shastin, V. N.
    Terahertz-range spontaneous emission under the optical excitation of donors in uniaxially stressed bulk silicon and SiGe/Si heterostructures2015Ingår i: Semiconductors (Woodbury, N.Y.), ISSN 1063-7826, E-ISSN 1090-6479, Vol. 49, nr 1, s. 13-18Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The results of measurements of the total terahertz-range photoluminescence of Group-V donors (phosphorus, antimony, bismuth, arsenic) in bulk silicon and SiGe/Si heterostructures depending on the excitation intensity are presented. The signal of bulk silicon was also measured as a function of uniaxial stress. The results of measurement of the dependence of the spontaneous emission intensity on the uniaxial stress is in rather good agreement with theoretical calculations of the relaxation times of excited states of donors in bulk silicon. Comparative measurements of the spontaneous emission from various strained heterostructures showed that the photoluminescence signal is caused by donor-doped silicon regions.

  • 122825. Zhukovskii, Y. F.
    et al.
    Kotomin, E. A.
    Herschend, B.
    Hermansson, Kersti
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Jacobs, P. W. M.
    The adhesion properties of the Ag/alpha-Al2O3(0001) interface: an ab initio study2002Ingår i: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 513, nr 2, s. 343-358Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ab initio computer simulations of the atomic and electronic structure of the Ag/alpha-Al2O3(0 0 0 1) (corundum) interface have been performed for a periodic two-dimensional slab model using the Hartree-Fock method and a posteriori electron correlation corrections. We have considered both Al- and O-terminated corundum substrate surfaces. The dependence of the adhesion energy on the interfacial distance has been analyzed for the two most favorable Ag adsorption positions over corundum and for two different metal coverages (a 1/3 monolayer (NIL) of the Ag(l 1 1) crystallographic plane and a full Ag(I 1 1) monolayer). The two different terminations (Al- and O-) give rise to qualitatively different results. The former case corresponds to the most stable termination of the pure corundum (0 0 0 1) substrate where small adhesion energies per Ag atom (0.15-0.25 eV for I ML and 0.40-0.55 eV for 1/3 NIL) are accompanied by minor interfacial charge transfer, indicating physisorption, which may be explained by a weak atomic polarization. In contrast, for O-terminated corundum, substantial adhesion energies (3-5 eV per Ag atom at I ML coverage and 6-11 eV for 1/3 ML) combined with noticeable charge transfer from silver atoms towards the substrate (0.5e to 0.9e) are clear indications of a strong interfacial ion bonding. For both terminations, the observed difference in Ag adhesion energies for 1/3 NIL and I NIL coverages arises from a transition from directed Ag-O bonding towards a more delocalized electron density distribution in the complete monolayer. The results of our calculations are compared with available experimental studies and theoretical simulations for various Me/Al2O3 interfaces.

  • 122826. Zhuo, S.
    et al.
    Shokri-Ghadikolaei, Hossein
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Wang, Z.
    Adaptive congestion control in cognitive industrial wireless sensor networks2015Ingår i: Proceeding - 2015 IEEE International Conference on Industrial Informatics, INDIN 2015, IEEE conference proceedings, 2015, s. 900-907Konferensbidrag (Refereegranskat)
    Abstract [en]

    Strict quality of service requirements of industrial applications, challenged by harsh environments and huge interference especially in multi-vendor sites, demand incorporation of cognition in industrial wireless sensor networks (IWSNs). In this paper, a distributed protocol of light complexity for congestion regulation in cognitive IWSNs is proposed to improve the channel utilization while ensuring predetermined performance for specific devices, called primary devices. By sensing the congestion level of a channel with local measurements, a novel congestion control protocol is proposed by which every device decides whether it should continue operating on the channel, or vacate it in case of saturation. Such a protocol dynamically changes the congestion level based on variations of non-stationary wireless environment as well as traffic demands of the devices. The proposed protocol is implemented on STM32W108 chips that offer IEEE 802.15.4 standard communications. Experimental results confirm substantial performance enhancement compared to the original standard, while imposing almost no signaling/computational overhead. In particular, channel utilization is increased by 56% with fairness and delay guarantees. The presented results provide useful insights on low-complexity adaptive congestion control mechanism in IWSNs.

  • 122827.
    Ziadi, Ahmed
    KTH, Skolan för datavetenskap och kommunikation (CSC).
    Facebook som komplement till modersmålsundervisning2014Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Facebook är Sverige mest använda sociala medium. Användaren kan enkelt dela det senaste från sin vardag, sina åsikter samt kommunicera med sina bekanta. Enligt den senaste mätningen från Stiftelsen för internetinfrastruktur, spenderar en tredjedel av unga i åldersgruppen 12-15 år sin internettid på sociala medier, varav 63 % av dem besöker Facebook dagligen.

    I denna studie undersöktes hur Facebook kan användas som komplement till modersmålsundervisningen. Studien utfördes genom en enkätundersökning samt en testgrupp som har kompletterats med semistrukturerade intervjuer.

    Undersökningen gav positiva resultat gentemot användningen av Facebook vid modersmålsundervisningen. Genom användningen av Facebook, kunde elever öva sitt skriv- och diskussionsförmåga utanför klassrummet. Undersökningen visade även att kommunikationen mellan elever och lärare förbättrades genom att eleverna hade möjlighet till lektionsundervisning utanför klassrummet. En annan observation var att elever, som har växt upp i Sverige var mer positiva till användningen av Facebook än sina klasskamrater som har växt upp i andra länder.

  • 122828.
    Ziakouli, Marina
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Urbana och regionala studier.
    Fagerberg, Erika
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Arkitektur, Stadsbyggnad.
    RIN♀EBY - Exploring feminist design tools2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This project aims on exploring ways to redefine the relationship of gender and space through urban design. Gender inequalities expressed in spatial manners have been theorized by feminist geography, an approach to human geography. Having a good understanding of this theoretical context will provide the tools to tackle distantiation, spatial separation, constraint and the limited spatial opportunities women experience in public places. Using Rinkeby square as the canvas for this exploration, the effort will be put on mapping the uses of the square through observation, quantitative research, as well as interviews with local organisations, shops and authorities close to the square. An inventory of the architectural features of the square will be made along with a site analysis focusing on the questions of effects on equality. Furthermore existing female networks and societies in the area will be contacted seeking possible collaborations for a later project work, workshops or events. Finally, as a result of the initial investigations, this project intends to explore how a physical intervention would affect these questions at Rinkeby square. It is the working hypothesis of this project that any project in order to be successful would need to be based on a deeper understanding of the challenges surrounding female presence on the square, and be tied into the already existing networks for women. This project therefore hopes to establish contact with existing female networks such as (D)Järva Kvinnor, Café Respekt and Tensta-Hjulsta Kvinnocenter, amongst others.

  • 122829. Zibar, Darko
    et al.
    Caballero, Antonio
    Yu, Xianbin
    Pang, Xiaodan
    RISE ACREO AB; Technical University of Denmark.
    Dogadaev, Anton K
    Monroy, I Tafur
    Hybrid optical fibre-wireless links at the 75–110 GHz band supporting 100 Gbps transmission capacities2011Ingår i: 2011 IEEE International Topical Meeting on Microwave Photonics - Jointly Held with the 2011 Asia-Pacific Microwave Photonics Conference, MWP/APMP 2011, 2011, s. 445-449, artikel-id 6088767Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a photonic generation and down-conversion method for realizing a 40Gbps wireless link at the 75-110 GHz band exploiting the recent advances in photonic coherent detection technologies and digital signal processing. Furthermore, we analyze the capacities of hybrid optical fiber-wireless links at the 75-110GHz band, and propose several approaches to overcome the challenges towards 100Gbps wireless capacity.

  • 122830. Zibar, Darko
    et al.
    Sambaraju, Rakesh
    Caballero, Antonio
    Herrera, Javier
    Westergren, Urban
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik, Fotonik.
    Walber, Achim
    Jensen, Jesper Beevense
    Marti, Javier
    Monroy, Idelfonso Tafur
    High-Capacity Wireless Signal Generation and Demodulation in 75-to 110-GHz Band Employing All-Optical OFDM2011Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 23, nr 12, s. 810-812Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a radio-frequency (RF) and bit-rate scalable technique for multigigabit wireless signal generation based on all-optical orthogonal frequency-division multiplexing (OFDM) and photonic up-conversion. Coherent detection supported by digital signal processing is used for signal demodulation and data recovery. In order to demonstrate the RF frequency scalability and bit-rate transparency, the system is tested at 60 GHz and in the 75- to 110-GHz band at the baud rates of 5 and 10 Gbaud. In terms of the bit rate, the proposed system is experimentally tested up to 40 Gb/s for wireless signal generation and demodulation. The wireless transmission is not considered in this letter. Additionally, a novel digital carrier phase/frequency recovery structure is employed to enable robust phase and frequency tracking between the beating lasers.

  • 122831.
    Zichi, Julien
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    NbTiN for improved superconducting detectors2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The physics of single photons is fascinating, by manipulating them we can observe and probe quantum effects. Doing so requires the fabrication and utilization of single photon sources, of which many types have been developed including quantum dots, trapped atoms and ions, and color centers. On the other end of the experiments, single photon detectors play a role of utmost importance, and while several types of detectors exist, superconducting nanowire single photon detectors are now the state-of-the-art technology. By offering near unity detection efficiency from the ultra-violet to the mid-infrared light spectrum, with negligible noise and excellent time resolution, they made possible many experiments that were previously technologically unfeasible. The same appealing characteristics have found a use in applications outside of the quantum optics framework, with notably light detection and ranging, biomedical imaging or CMOS circuits testing.In this thesis a controlled growth method for tailoring the characteristics of niobium titanium nitride in the framework of superconducting nanowire single photon detectors was developed. Reactive co-sputter deposition of niobium titanium nitride was shown to be a versatile method, both in terms of the degree of control over the material composition, and in the choice of substrates that it allows. Unity internal detection efficiency of detectors at telecom wavelengths was achieved by optimizing the niobium content in the material. The influence of lattice matching on the critical temperatures of films deposited at room temperature was investigated. The fabrication of superconducting nanowire single photon detectors on aluminum nitride-on-sapphire, on lithium niobate nano-waveguides, on gallium arsenide, and the integration on SiN waveguides was achieved. The material was used to fabricate detectors with optimized response for any linear polarization of the incoming photons by using a fractal architecture. Another method was proposed to achieve the same results by encapsulating meandering detectors in a high index dielectric material, resulting in a decrease of the permittivity mismatch between the nanowire material and its surrounding and therefore optimizing the efficiency for both orthogonal linear polarizations.Finally, detectors were fabricated from films developed in this work, and were operated to enable the implementation of polarization-based entanglement distribution in optical fibers in a real-conditions scenario, over a record distance of 96 km. This paves the way for the development of quantum communication networks using existing optical fiber links.

  • 122832.
    Zichi, Julien
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Chang, Chang
    Steinhauer, Stephan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    von Fieandt, Kristina
    Los, Johannes W. N.
    Visser, Gijs
    Kalhor, Nima
    Lettner, Thomas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Elshaari, Ali W.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Esmaeil Zadeh, Iman
    Zwiller, Val
    NbxTi1-xN low timing jitter single-photon detectors with unity internal detection efficiency at 1550 nmManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The requirements in quantum optics experiments for high single photon detectionefficiency, low timing jitter, low dark count rate and short dead time have been fulfilled withthe development of superconducting nanowire single photon detectors. Although they offer adetection efficiency above 90%, achieving a high time resolution in devices made ofamorphous materials is a challenge, particularly at temperatures above 0.8 K. Devices madefrom niobium nitride and niobium titanium nitride allow to reach the best timing jitter, but inturn have stronger requirements in terms of film quality to achieve a high efficiency. Here wetake advantage of the flexibility of reactive co-sputter deposition to tailor the composition ofNbxTi1-xN superconducting films, and show that a Nb fraction of x = 0.62 allows for thefabrication of detectors from films as thick as 9 nm and covering an active area of 20 μm,with a wide detection saturation plateau at telecom wavelengths and in particular at 1550 nm.This is a signature of an internal detection efficiency saturation, achieved while maintainingthe high time resolution associated with NbTiN and operation at 2.5K. With our optimizedrecipe, we reliably fabricated detectors with high critical current densities reaching asaturation plateau at 1550 nm with 80% system detection efficiency, and with a FWHMtiming jitter as low as 19.47 ps.

  • 122833.
    Zichi, Julien
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Gyger, Samuel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Baghban, Mohammad Amin
    Elshaari, Ali W.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Gallo, Katia
    Zwiller, Val
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    An NbTiN superconducting single photon detector implemented on a LiNbO3 nano-waveguide at telecom wavelength2019Ingår i: Poster session T.Po2, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fiber-coupled superconducting nanowire single photon detectors are a ubiquitous tool for quantum optics experiments as they offer near unity detection efficiency over a broad wavelength range, low dark count rate, excellent time resolution and high saturation rate. Nevertheless, advancing quantum optics experiments and applications beyond the few-photon limit requires large scale integrated systems of quantum sources and detectors. In recent years there has been a tremendous progress with integrating single photon detectors with a variety of photonic platforms. This includes attempts on ion-diffused waveguides in LiNbO3, a non-linear and electro-optic material with widespread use for signal processing, frequency conversion, and quantum optics devices. However the realization of superconducting detectors on single mode waveguides remains elusive. Here we present an NbTiN superconducting single photon detector integrated directly on a LiNbO3 single mode nanophotonic waveguide at telecom wavelength, with a high critical current density and a dark count rate of 3 mHz at 99% of its critical current.

  • 122834.
    Zichi, Julien
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Yang, Lily
    Gyger, Samuel
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Lettner, Thomas
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Errando-Herranz, Carlos
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Mikro- och nanosystemteknik.
    Jöns, Klaus D.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Baghban, Mohammad Amin
    Gallo, Katia
    Steinhauer, Stephan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Zwiller, Val
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Kvant- och biofotonik.
    Heterogeneous integration of NbTiN by universal room temperature depositionManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Being the Nb-based compound with the highest known critical temperature, NbTiN is of particular interest for many applications. It is used in Josephson junctions for single flux quantum logic gates, as a superconducting electrode to contact semiconductor devices, and one important use is in superconducting nanowire single photon detectors. These detectors are the ideal candidate for on-chip integration in photonic circuits, offering near-unity detection efficiency, low noise and excellent time resolution, therefore it is desirable to implement them on a wide variety of platforms. However, it remains a challenge to deposit the superconducting material with a process suitable for heterogeneous integration, as the most widespread material, NbN, is associated with a deposition at a high temperature. Taking advantage of the possibility to deposit superconducting NbTiN with various stoichiometries by co-sputter deposition at room temperature, we demonstrate growth on six different substrates – silicon dioxide, silicon nitride, gallium arsenide, lithium niobate, [Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] or PMN-PT, and aluminum nitride – in the same deposition run, and show that all the films exhibit superconducting properties with similar critical temperatures. We fabricated waveguide-compatible superconducting nanowire single photon detectors on five substrates, report short dead times for all devices with a narrow spread of performances, and discuss their different photon detection saturation behavior. Our method simplifies the fabrication of superconducting devices on a wide range of materials.

  • 122835.
    Zickerman, Linnéa
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Arkitektur.
    Cirkushallen i Alby: Balans2012Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Mitt kandidatprojekt är ett förslag till en Cirkushall i Alby där Cirkus Cirkör verkar. Projektet handlar om att skapa och forma en identitet till en stadsdel, exponera en verksamhet och att forma en byggnad efter de behov en cirkusverksamhet efterfrågar. 

  • 122836.
    Zickerman, Linnéa
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Arkitektur.
    Vetenskapen: - En Forskningsstation i Tarfala2016Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Utan att forskarna riktigt kunde förklara varför stod det helt klart under 1900-talets första hälft att isarna blev mindre. På hela norra halvklotet blev glaciärerna allt mindre och denna storlekförändring sattes i samband med den temperaturökning som skett under samma tid. Glaciärerna krympte och man sökte den exakta kopplingen mellan klimatets förändring och smältande glaciärer. Professor Ahlman, glaciolog vid Stockholms universitet beslutade att Storglaciären i Tarfaladalen var platsen där mätningar skulle ske och sedan 1946 har Stockholms Universitet bedrivit verksamhet vid Tarfala Forskningsstation. Stationen fungerar som en plattform för glaciologer och används kontinuerligt av forskare och studentgrupper från SU men även av internationella forskare och studenter. Mätstudierna som utförs i Tarfala är betydelsefullt underlag för glaciologiska och klimatologiska studier, såväl nationellt som internationellt. Verksamheten och forskningsgruppen har med åren vuxit och är idag i stort behov av en större och mer komplex byggnad för att kunna bedriva forskning på världsledande nivå. I mitt examensarbete har jag undersökt platsen, vinden och forskningsverksamheten.

  • 122837.
    Zickert, Gustav
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematik (Avd.).
    Furstenberg's conjecture and measure rigidity for some classes of non-abelian affine actions on tori2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    1967 bevisade Furstenberg att mängden {2n3mα(mod 1) | n, m ∈N} är tät i cirkeln för alla irrationella tal α. Furstenberg ligger även bakom följande berömda förmodan: de enda ergodiska måtten påcirkeln som är invarianta under både x 􏰀—> 2x och x 􏰀—> 3x är Lebesguemåttet och mått med ändligt stöd. I det här examensarbetet behandlar vi Furstenbergs sats, Furstenbergs förmodan och Rudolphs sats. Vi följer Matheus presentation av Avilas idéer för ett bevis av en svag variant av Rudolphs sats och vi bevisar att en måttbevarande semigruppverkan under vissa antaganden kan utökas till en semigruppverkan av en större semigrupp. Med hjälp av detta resultat erhåller vi begränsningar av mängden av mått invarianta under vissa klasser av icke-abelska affina verkningar påtorusen. Vi studerar även allmänna egenskaper hos affina abelska och icke-abelska verkningar och vi visar att satser analoga med Furstenbergs sats håller för affina verkningar påcirkeln.

  • 122838.
    Zickert, Gustav
    KTH, Skolan för teknikvetenskap (SCI).
    On Algebraic Numbers and Quadratic Extensions2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Abstract.

    In this thesis some basic properties of algebraic el-

    ements, integral elements and extensions of rings and elds are

    investigated. Special focus is given to quadratic extensions. It is

    assumed that the reader is familiar with some elementary concepts

    from abstract algebra, such as the denitions of rings and elds.

    The rst section covers the basics of algebraic elements and in-

    tegral elements and serves as a foundation for the rest of the thesis.

    In section two and three some theory of Unique Factorization Do-

    mains and Euclidean Domains is developed. The concepts and

    results from these two sections are used in section four and ve,

    which treat Quadratic Extensions and certain Ring Extensions of

    the integers.

  • 122839.
    Zickert, Gustav
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematik (Avd.).
    Maretzke, Simon
    Univ Gottingen, Inst Numer & Appl Math, Gottingen, Germany..
    Cryogenic electron tomography reconstructions from phaseless data2018Ingår i: Inverse Problems, ISSN 0266-5611, E-ISSN 1361-6420, Vol. 34, nr 12, artikel-id 124001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We perform three-dimensional (3D) reconstructions from simulated and real cryogenic electron tomography (cryo-ET) data. Our reconstructions are based on a nonlinear and phaseless forward model very reminiscent of a commonly used model for phase contrast x-ray tomography.

  • 122840. Zieba, A.
    et al.
    Ponten, F.
    Uhlén, Mathias
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Landegren, U.
    In situ protein detection with enhanced specificity using DNA-conjugated antibodies and proximity ligation2018Ingår i: Modern Pathology, ISSN 0893-3952, E-ISSN 1530-0285, Vol. 31, nr 2, s. 253-263Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Antibodies are important tools in anatomical pathology and research, but the quality of in situ protein detection by immunohistochemistry greatly depends on the choice of antibodies and the abundance of the targeted proteins. Many antibodies used in scientific research do not meet requirements for specificity and sensitivity. Accordingly, methods that improve antibody performance and produce quantitative data can greatly advance both scientific investigations and clinical diagnostics based on protein expression and in situ localization. We demonstrate here protocols for antibody labeling that allow specific protein detection in tissues via bright-field in situ proximity ligation assays, where each protein molecule must be recognized by two antibodies. We further demonstrate that single polyclonal antibodies or purified serum preparations can be used for these dual recognition assays. The requirement for protein recognition by pairs of antibody conjugates can significantly improve specificity of protein detection over single-binder assays.

  • 122841.
    Zieba, Agata
    et al.
    Uppsala Univ, Dept Immunol Genet & Pathol, Sci Life Lab, S-75185 Uppsala, Sweden..
    Sjöstedt, Evelina
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Olovsson, Matts
    Uppsala Univ, Dept Womens & Childrens Hlth, S-75185 Uppsala, Sweden..
    Fagerberg, Linn
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Hallström, Björn M.
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Oskarsson, Linda
    Uppsala Univ, Dept Immunol Genet & Pathol, Sci Life Lab, S-75185 Uppsala, Sweden..
    Edlund, Karolina
    Uppsala Univ, Dept Immunol Genet & Pathol, Sci Life Lab, S-75185 Uppsala, Sweden..
    Tolf, Anna
    Uppsala Univ, Dept Immunol Genet & Pathol, Sci Life Lab, S-75185 Uppsala, Sweden..
    Uhlén, Mathias
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Ponten, Fredrik
    Uppsala Univ, Dept Immunol Genet & Pathol, Sci Life Lab, S-75185 Uppsala, Sweden..
    The Human Endometrium-Specific Proteome Defined by Transcriptomics and Antibody-Based Profiling2015Ingår i: Omics, ISSN 1536-2310, E-ISSN 1557-8100, Vol. 19, nr 11, s. 659-668Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The human uterus includes the complex endometrial mucosa, the endometrium that undergoes dynamic, hormone-dependent alterations throughout the life of fertile females. Here we have combined a genome-wide transcriptomics analysis with immunohistochemistry-based protein profiling to analyze gene expression patterns in the normal endometrium. Human endometrial tissues from five women were used for deep sequencing (RNA-Seq). The mRNA and protein expression data from the endometrium were compared to 31 (RNA) and 44 (protein) other normal tissue types, to identify genes with elevated expression in the endometrium and to localize the expression of corresponding proteins at a cellular resolution. Based on the expression levels of transcripts, we could classify all putative human protein coding genes into categories defined by expression patterns and found altogether 101 genes that showed an elevated pattern of expression in the endometrium, with only four genes showing more than five-fold higher expression levels in the endometrium compared to other tissues. In conclusion, our analysis based on transcriptomics and antibody-based protein profiling reports here comprehensive lists of genes with elevated expression levels in the endometrium, providing important starting points for a better molecular understanding of human reproductive biology and disease.

  • 122842.
    Ziegenhagen, Stephanie
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Matematik (Avd.).
    En-cohomology with coefficients as functor cohomology2016Ingår i: Algebraic and Geometric Topology, ISSN 1472-2747, E-ISSN 1472-2739, Vol. 16, nr 5, s. 2981-3004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Building on work of Livernet and Richter, we prove that En -homology and En - cohomology of a commutative algebra with coefficients in a symmetric bimodule can be interpreted as functor homology and cohomology. Furthermore, we show that the associated Yoneda algebra is trivial.

  • 122843. Zielińska, J. A.
    et al.
    Zukauskas, A.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Canalias, Carlota
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Noyan, M. A.
    Mitchell, M. W.
    Fully-resonant, tunable, monolithic frequency conversion as a coherent UVA source2017Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, nr 2, s. 1142-1150Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate a monolithic frequency converter incorporating up to four tuning degrees of freedom, three temperature and one strain, allowing resonance of pump and generated wavelengths simultaneous with optimal phase-matching. With a Rb-doped periodically-poled potassium titanyl phosphate (KTP) implementation, we demonstrate efficient continuous-wave second harmonic generation from 795 to 397, with low-power efficiency of 72% and high-power slope efficiency of 4.5%. The measured performance shows good agreement with theoretical modeling of the device. We measure optical bistability effects, and show how they can be used to improve the stability of the output against pump frequency and amplitude variations. 

  • 122844. Zientkiewicz, Jacek K.
    et al.
    Lach, Zbigniew T.
    Grabiec, Piotr
    Driessen, Alfred
    Jaskorzynska, Bozena
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Kvantelektronik och -optik, QEO (flyttad till SCI 2011-07-01).
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik (Stängd 20120101), Kvantelektronik och -optik, QEO (flyttad till SCI 2011-07-01).
    A roadmap to a technological platform for integrating nanophotonic structures with micromechanical systems in silicon-on-insulator2005Ingår i: Integrated Optics: Theory and Applications / [ed] Pustelny T., Lambeck P.V., Gorecki C., SPIE - International Society for Optical Engineering, 2005, s. 59560H-Konferensbidrag (Refereegranskat)
    Abstract [en]

    On the foundation of joint experience acquired by several research centres there was defined the roadmap to the desired single technological platform for fabrication of a specific class of photonic integrated circuits, which are controlled by mechanical means. In the paper the challenges of fabrication of such photonic circuits are discussed. The main arguments in favour of the Silicon-on-Insulator materials system as the basis for the platform are presented. Options for the mechanics-to-optics arrangement, materials and processes are described and illustrated with the current achievements from the authors' labs. In the roadmap the preference is given to the vertical arrangement in which, the mechanical part is stacked above the waveguiding layer. A flexible trimming routine is designed to complement the process flow if the technologies developed cannot provide the required reproducibility.

  • 122845. Zierkiewicz, W.
    et al.
    Privalov, Timofei
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    A computational study of oxidation of ruthenium porphyrins via ORuIV and (ORuO)-O-VI species2006Ingår i: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, nr 15, s. 1867-1874Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An unrestricted density functional theory (UDFT) was applied to study the oxidation of ruthenium porphyrins, [RuP], via an interaction with molecular oxygen. The important role of dimeric [ RuP] complexes, i.e. [RuP]-O-2-[RuP], in the oxidation mechanism and particular in the cleavage of O-O bond of molecular oxygen has been studied. Geometries and relative Gibbs free energies of the intermediate Ru-complexes, i.e. dimeric oxo-Ru-porphyrins and O2RuII-(or O-2(-) Ru-III)-, ORuIV- and (ORuO)-O-VI-porphyrins, were evaluated along the proposed reaction pathway. The detailed thermodynamic data of the oxidation reaction [(RuP)-P-II] -> O[(RuP)-P-IV] -> O[(RuP)-P-VI]O and important aspects of the vibrational spectra of an oxo-[RuP] has been presented.

  • 122846. Zierkiewicz, W.
    et al.
    Privalov, Timofei
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    A theoretical study of the essential role of DMSO as a solvent/ligand in the Pd(OAc)(2)/DMSO catalyst system for aerobic oxidation2005Ingår i: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 24, nr 24, s. 6019-6028Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dimethyl sulfoxide (DMSO) has unique properties as an aprotic, polar solvent. The oxygen atom in DMSO can interact with positive charges and thus stabilize metal cation. The sulfur atom, although somewhat positively charged, does not interact with negative charges effectively. Also, two methyl groups surround the sulfur atom and influence binding properties of DMSO. These features of DMSO are addressed in the present computational study of the Pd(AcO)(2)/DMSO-catalyzed aerobic oxidation system. Mechanistic and computational details are provided. The step-by-step Gibbs energy of reaction was calculated using the electronic energy at the B3LYP density functional level with thermal functions calculated at the same level of theory. The solvent was modeled using the polarized medium (PCM) with additional DMSO molecules in the second coordination sphere of the complexes studied. The overall reaction pathway was divided into several steps in accord with available experimental data. All steps, including the first deprotonation and the beta-hydride elimination transition states, were elucidated in good detail. Coordination and reorganization of DMSO in Pd(II)(AcO)(2)/DMSO and Pd(0)/(DMSO)(n) complexes has been studied to provide realistic data about coordination of DMSO with hard (O) versus soft (S) ligand donor atoms. The P-hydride elimination transition state was identified computationally to give an estimation of the activation energy of the alcohol oxidation reaction. Therefore, we suggest that the rate-determining step is related to the alcohol part of the reaction cycle.

  • 122847.
    Ziethén, Andreas
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Analys av QoS i mellanvaran Meteor2008Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Detta examensarbete har utförts i samarbete med ENEA. Delar av emonstrationsplattformen SHAPE som ENEA har utvecklat för DySCAS-projektet har använts i implementationsdelen av detta examensarbete. Målet med examensarbetet var att utvärdera hur mellanvaran Meteor, som är en släkting till DySCAS, bör hantera QoS och att designa en Quality of Service-manager för Meteor som har stöd för hårda realtidskrav. Examensarbetet hade även som delmål att kravställa den QoSM som skulle designas från ett QoS-perspektiv. Specifikt skulle de krav identifieras som var nödvändiga för att garantera att applikationer som körs på mellanvaran har stöd för hårda realtidskrav. Slutligen skulle examensarbetet utreda vilka andra mellanvaror med stöd för hårda realtidskrav som existerade. I examensarbetet har den tidigarenämnda QoSM designats och delvis implementerats. En applikationsmodell av en typisk Med Tech-produkt användes för att härleda kraven på QoSM. Existerande mellanvaror som HADES och ARMADA analyserades också för att identifiera nödvändiga krav på Meteor. Dessa krav användes för att designa en QoSM. Den resulterande QoSM har stöd för hårda realtidskrav och hög bandbreddskommunikation samtidigt. Dess huvudfunktion är en schemaläggare av nätverkstrafik på en Ethernetbus. Schemaläggningsalgoritmen är utbytbar men endast en algoritm har implementerats under examensarbetet. Den implementerade algoritmen är prioritetsbaserad. Intressanta områden för framtida arbete identifierades så som vidareutveckling av QoSM med olika QoS-nivåer, andra schemaläggningsalgoritmer och koppling av schemaläggning till schemaläggning av resurser utöver nätverket.

  • 122848. Zietz, Burkhard
    et al.
    Gabrielsson, Erik
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Johansson, Viktor
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    El-Zohry, Ahmed M.
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Tillämpad fysikalisk kemi.
    Photoisomerization of the cyanoacrylic acid acceptor group - a potential problem for organic dyes in solar cells2014Ingår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, nr 6, s. 2251-2255Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Organic solar cell dyes containing the most common anchoring group, cyanoacrylic acid, are shown to be photolabile and undergo photoisomerization. This may have significant consequences for dye-sensitized solar cells, as isomerisation competes with electron injection and leads to modifications of the dye and surface arrangement.

  • 122849. Zika-Viktorsson, A.
    et al.
    Ritzén, Sofia
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Integrerad produktutveckling.
    Project competence in product development2005Ingår i: Research in Engineering Design, ISSN 0934-9839, E-ISSN 1435-6066, Vol. 15, nr 4, s. 193-200Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents and discusses the individual competence particularly required to work in project-organized product development. Individual competence encompasses the knowledge, skills and abilities to deal with issues related to organizational, social and technological factors involved in projects. The purpose has been to explore the competence required for project members at the operational level, and to explore the conditions for developing such competence. The study is based on a qualitative approach, with interviews as the tool for data collection. The study group comprised 54 respondents working in RTD departments within five large Swedish manufacturing companies. The findings reveal the need for project co-workers to be skilled in both practical and psychosocial aspects of co-ordination, time planning and control. The findings of the study demonstrate the importance of being able to cope with prescribed as well as unpredictable processes. They also indicate the effect of time on experience transfer.

  • 122850.
    Zika-Viktorsson, Annika
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Integrerad produktutveckling.
    Interorganisatorisk samverkan kring samhällsutmaningar och digitala lösningar: En studie av programmet Digital Demo Stockholm2018Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Interorganisatorisk samverkan enligt trippelhelixmodellen är ett sätt att möta komplexa samhällsutmaningar och att lösa problem. Komplexiteten i problemen ställer krav på samverkan mellan behovsägare och experter samt med de som har de resurser som krävs för att lösningar ska förverkligas. Rapporten presenterar en studie av interorganisatorisk samverkan i programmet Digital Demo Stockholm (DDS). Det är ett program som genomförs av KTH tillsammans med partners från näringsliv och offentlig sektor och som arbetar för att möta samhällsutmaningar i Stockholmsregionen. Inom programmet bedrivs forsknings- och innovationsprojekt som tar fram digitala lösningar och demonstratorer. Programmet bygger på långsiktigt partnerskap mellan Stockholms stad, Stockholms Läns Landsting, KTH, ABB, Ericsson, Skanska, Scania, Vattenfall och Telia. På sikt ska programmet leda till ett samhälle som är hållbart och attraktivt och att Stockholm år 2040 är ”världens smartaste stad”. Resultaten baseras på intervjuer med initiativtagare till programmet och projektledare för demoprojekten samt på enkäter till medarbetare i demoprojekten och ledamöter i programmets rådsfunktioner. Studien är kvalitativ och alla utsagor och svar har analyserats med en kvalitativ ansats. Frågorna i studien rör deltagarnas inställning till programmet och till arbetet på den övergripande programnivån liksom i demoprojekten. Studien undersöker och beskriver deltagares uppfattning om DDS. Syftet har inte varit att utvärdera programmets olika delar utan att med en explorativ ansats beskriva vad som uppfattas som viktiga försättningar för samverkan. En viktig förutsättning är det engagemang som präglat arbetet i programmet och som delvis har en koppling till möjligheten att arbeta för samhällsnytta och organisatoriska innovationer. En annan är ett ledarskap som är agilt, entreprenöriellt och sammanhållande. De krav som ställs på att driva ett initiativ som DDS liknar de som ”start-up-verksamheter” ställer på drift och ledning. För att komma framåt krävs anpassning samtidigt med stora mått av uthållighet, en mångfald av kompetenser och utveckling på programmets samtliga nivåer.

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