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  • 123951.
    Zhang, Ai-bing
    et al.
    KTH, School of Biotechnology (BIO), Gene Technology.
    Sikes, D. S.
    Muster, C.
    Li, S. Q.
    Inferring species membership using DNA sequences with back-propagation neural networks2008In: Systematic Biology, ISSN 1063-5157, E-ISSN 1076-836X, Vol. 57, no 2, p. 202-215Article in journal (Refereed)
    Abstract [en]

    DNA barcoding as a method for species identification is rapidly increasing in popularity. However, there are still relatively few rigorous methodological tests of DNA barcoding. Current distance-based methods are frequently criticized for treating the nearest neighbor as the closest relative via a raw similarity score, lacking an objective set of criteria to delineate taxa, or for being incongruent with classical character-based taxonomy. Here, we propose an artificial intelligence-based approachinferring species membership via DNA barcoding with back-propagation neural networks (named BP-based species identification)as a new advance to the spectrum of available methods. We demonstrate the value of this approach with simulated data sets representing different levels of sequence variation under coalescent simulations with various evolutionary models, as well as with two empirical data sets of COI sequences from East Asian ground beetles (Carabidae) and Costa Rican skipper butterflies. With a 630-to 690-bp fragment of the COI gene, we identified 97.50% of 80 unknown sequences of ground beetles, 95.63%, 96.10%, and 100% of 275, 205, and 9 unknown sequences of the neotropical skipper butterfly to their correct species, respectively. Our simulation studies indicate that the success rates of species identification depend on the divergence of sequences, the length of sequences, and the number of reference sequences. Particularly in cases involving incomplete lineage sorting, this new BP-based method appears to be superior to commonly used methods for DNA-based species identification.

  • 123952.
    Zhang, Anda
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Mathematical Statistics.
    Analys av bostadsrättspriset i Stockholms innerstad: En multipel linjär regression2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this study a multiple linear regression was carried out in the interest of analysing a number of variables effect on the final prices of apartments in Stockholm’s inner districts. The result may be employed to predict and observe percentage changes on the final price of apartments in Stockholm in the future. Five models were constructed after which they were analysed and compared. The construction of these models were supported by data from the real estate agency Erik Olsson. The result of this study displays that living space have the highest positive influence on the final prices. Among all the inner city districts, Östermalm is the district that contributes the most to the final price growth. All five models had a coefficient of determination between 89%-94%.

  • 123953.
    Zhang, Anda
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    Optimal Path Smoothing using Clothoids for Autonomous Vehicles in the Quarry Environment2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Autonomous vehicles are a rapidly growing field and will play an important role in future society. The introduction of autonomous machines in the quarry environment increases safety in the hazardous working conditions and reduces the risk of accidents caused by human error. By making the machine electric and autonomous it will also improve the fuel efficiency and reduces carbon emission.

    The results of this thesis are developed within the electric site project which is lead by Volvo Construction Equipment in Eskilstuna, Sweden. The goal is to transform the quarry and aggregates with the help of the introduction of electric hybrid autonomous machines which is predicted to result in reduced carbon emission by up to 95% .This thesis address the problem of path planning noisy curvatures of the paths that are calculated using coordinates recorded from a manual driven vehicle. This makes the control algorithm for the autonomous vehicle hard to implement. The purpose in this thesis is to develop a procedure to describe paths and smooth those so the curvature becomes smooth and drivable for an autonomous load carrier.

    To smooth the paths, we use the concept of clothoids which are curves with linear varying curvature. Clothoids are widely used in road design because of its smoothness properties. We solve the smoothing problem by formulating it as an optimization problem where we minimize the number of clothoid segments to avoid unnecessary noisy curvature variations. The results are successful and we are able to produce feasible paths for two test tracks Volvo Construction Equipment uses. We also create a Graphical User Interface in MATLAB to facilitate the creation of the clothoid-based paths from recorded GPS coordinates

  • 123954. Zhang, Andy Zhenzhong
    et al.
    Reshanov, Sergey A.
    Schöner, Adolf
    Kaplan, Wlodek
    Kwietniewski, N.
    Lim, Jang-Kwon
    Bakowski, Mietek
    Planarization of epitaxial SiC trench structures by plasma ion etchingManuscript (preprint) (Other academic)
  • 123955.
    Zhang, Andy Zhenzhong
    et al.
    Acreo, Sweden .
    Wang, Qin
    Karlsson, Stefan
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101). Kista Photonics Resarch Center, Sweden.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101). Kista Photonics Resarch Center, Sweden.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101). Kista Photonics Resarch Center, Sweden.
    Fonjallaz, Pierre-Yves
    Almqvist, Susanne
    Chacinski, Marek
    KTH, School of Information and Communication Technology (ICT), Material Physics (Closed 20120101).
    Thylen, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics (Closed 20120101), Photonics (Closed 20120101). Kista Photonics Resarch Center, Sweden.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Honecker, Joerg
    Steffan, Andreas
    Fabrication of an electro-absorption transceiver with a monolithically integrated optical amplifier for fiber transmission of 40-60 GHz radio signals2011In: Semiconductor Science and Technology, ISSN 0268-1242, E-ISSN 1361-6641, Vol. 26, no 1, p. 014042-Article in journal (Refereed)
    Abstract [en]

    We report on the fabrication of a monolithically integrated semiconductor optical amplifier (SOA) and a reflective electro-absorption transceiver (EAT) for 40-60 GHz radio-over-fiber applications. The EAT can either function as a transmitter (reflective modulator) or as a receiver (photodetector) depending on operation mode. The SOA and the EAT sections are based on different InGaAsP multiple quantum-well active layers connected by a butt joint. Benzocyclobutene is used to reduce the capacitance beside the ridge mesa. Devices are designed to have a peaked response at the operating frequency through the design of microwave waveguides on top of the devices. The packaged device exhibits at 0.1 mW optical input power an amplified DC responsivity of 18.5 mA mW(-1) and a modulation efficiency of 0.67 mW V-1. The estimated radio frequency loss at 40 GHz of an optical link consisting of two SOA-EAT devices was 23 dB using an unmodulated optical input carrier to the transmitter of 0.94 mW.

  • 123956. Zhang, B.
    et al.
    Berg, Lars-Erik
    KTH, Superseded Departments, Physics.
    Hansson, T.
    Wavepacket dynamics and predissociation of the D-1 Pi(u) state of Rb-22000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 325, no 06-maj, p. 577-583Article in journal (Refereed)
    Abstract [en]

    We present the first experimental investigation of the real-time dynamics of predissociation in a diatomic molecule involving more than two electronic states - the predissociation of the D(1)Pi(u) state of Rb-2. Our results show that the state is strongly predissociated, tau approximate to 5 ps, above a sharp energy threshold. We propose that mainly the (1)(3)Delta(u) state causes the fast predissociation and that the fine-structure components of the products are mixed by coupling among molecular states at large internuclear distances. Furthermore, an outward-inward asymmetry of the wavepacket signal is attributed to autoionisation of the wavepacket evolving in the probe (Rydberg) state.

  • 123957. Zhang, B.
    et al.
    Kreitz, Gunnar
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Isaksson, Marcus
    Ubillos, Javier
    Urdaneta, G.
    Pouwelse, J. A.
    Epema, D.
    Understanding user behavior in Spotify2013In: 2013 Proceedings - IEEE INFOCOM, 2013, p. 220-224Conference paper (Refereed)
    Abstract [en]

    Spotify is a peer-assisted music streaming service that has gained worldwide popularity in the past few years. Until now, little has been published about user behavior in such services. In this paper, we study the user behavior in Spotify by analyzing a massive dataset collected between 2010 and 2011. Firstly, we investigate the system dynamics including session arrival patterns, playback arrival patterns, and daily variation of session length. Secondly, we analyze individual user behavior on both multiple and single devices. Our analysis reveals the favorite times of day for Spotify users. We also show the correlations between both the length and the downtime of successive user sessions on single devices. In particular, we conduct the first analysis of the device-switching behavior of a massive user base.

  • 123958. Zhang, B.
    et al.
    Tornmalm, Johan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Widengren, Jerker
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
    Vakifahmetoglu-Norberg, H.
    Norberg, E.
    Characterization of the role of the Malate dehydrogenases to lung tumor cell survival2017In: Journal of Cancer, ISSN 1837-9664, E-ISSN 1837-9664, Vol. 8, no 11, article id 19373Article in journal (Refereed)
    Abstract [en]

    Cellular compartmentalization of biochemical processes in eukaryotic cells is critical for many functions including shuttling of reducing equivalents across membranes. Although coordination of metabolic flux between different organelles is vital for cell physiology, its impact on tumor cell survival is not well understood. By using an integrative approach, we have dissected the role of the key metabolic enzymes Malate dehydrogenases (MDH1 and MDH2) to the survival of Nonsmall Cell Lung Carcinomas. Here, we report that while both the MDH1 (cytosolic) and the MDH2 (mitochondrial) enzymes display elevated levels in patients compared to normal counterparts, only high expression of MDH1 is associated with poor prognosis. We further show that the MDH1 enzymatic activity is significantly higher in NSCLC cells than that of MDH2. Accordingly, genetic depletion of MDH1 leads to significantly higher toxicity than depletion of MDH2. These findings provide molecular insights into the metabolic characteristics of the malate isoenzymes and mark MDH1 as a potential therapeutic target in these tumors.

  • 123959. Zhang, B.
    et al.
    Wu, X.
    Li, F.
    Yu, F.
    Wang, Y.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    In Situ Formation of Efficient Cobalt-Based Water Oxidation Catalysts from Co2+-Containing Tungstate and Molybdate Solutions2015In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 10, no 10, p. 2228-2233Article in journal (Refereed)
    Abstract [en]

    Replacing rare and expensive noble-metal catalysts with inexpensive and earth-abundant ones is of great importance to split water either electrochemically or photoelectrochemically. In this study, two amorphous cobalt oxide catalysts (Co-W film and Co-Mo film) with high activity for electrocatalytic water oxidation were prepared by fast, simple electrodeposition from aqueous solutions of Na<inf>2</inf>WO<inf>4</inf> and Na<inf>2</inf>MoO<inf>4</inf> containing Co2+. In solutions of Na<inf>2</inf>WO<inf>4</inf> and Na<inf>2</inf>MoO<inf>4</inf>, sustained anodic current densities up to 1.45 and 0.95mA cm-2 were obtained for Co-W film at 1.87V versus a reversible hydrogen electrode (RHE) and Co-Mo film on fluorine-doped tin oxide (FTO) substrates at 1.85V versus RHE. For the Co-W film, a much higher current density of 4.5mA cm-2 was acquired by using a stainless-steel mesh as the electrode substrate. Significantly, in long-term electrolysis for 13h, the Co-W film exhibited improved stability in cobalt-free buffer solution in comparison with the previously reported Co-Pi film.

  • 123960.
    Zhang, Baorui
    KTH, School of Engineering Sciences (SCI), Physics.
    Preliminary Neutronic and Thermal-Safety Analysis for CFETR HCCB-TBM2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 123961.
    Zhang, Biaobiao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Chen, Hong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Daniel, Quentin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Philippe, Bertrand
    Yu, Fengshou
    Valvo, Mario
    Li, Yuanyuan
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Ambre, Ram B.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Zhang, Peili
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Li, Fei
    Rensmo, Håkan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Defective and "c-Disordered" Hortensia-like Layered MnOx as an Efficient Electrocatalyst for Water Oxidation at Neutral pH2017In: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 7, no 9, p. 6311-6322Article in journal (Refereed)
    Abstract [en]

    The development of a highly active manganese-based water oxidation catalyst in the design of an ideal artificial photosynthetic device operating under neutral pH conditions remains a great challenge, due to the instability of pivotal Mn3+ intermediates. We report here defective and "c-disordered" layered manganese oxides (MnOx-300) formed on a fluorine-doped tin oxide electrode by constant anodic potential deposition and subsequent annealing, with a catalytic onset (0.25 mA/cm(2)) at an overpotential (eta) of 280 mV and a benchmark catalytic current density of 1.0 mA/cm(2) at an overpotential (eta) of 330 mV under neutral pH (1 M potassium phosphate). Steady current density above 8.2 mA/cm(2) was obtained during the electrolysis at 1.4 V versus the normal hydrogen electrode for 20 h. Insightful studies showed that the main contributing factors for the observed high activity of MnOx-300 are (i) a defective and randomly stacked layered structure, (ii) an increased degree of Jahn-Teller distorted Mn3+ in the MnO6 octahedral sheets, (iii) effective stabilization of Mn3+, (iv) a high surface area, and (v) improved electrical conductivity. These results demonstrate that manganese oxides as structural and functional models of an oxygen-evolving complex (OEC) in photosystem II are promising catalysts for water oxidation in addition to Ni/Co-based oxides/hydroxides.

  • 123962.
    Zhang, Biaobiao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Daniel, Quentin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Cheng, Ming
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fan, Lizhou
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    Temperature dependence of electrocatalytic water oxidation: a triple device model with a photothermal collector and photovoltaic cell coupled to an electrolyzer2017In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 198, p. 169-179Article in journal (Refereed)
    Abstract [en]

    A water oxidation electrocatalyst with high activity is essential for promoting the overall efficiency of an integrated water splitting device. Herein, by investigating the prominent temperature dependence of electrocatalytic water oxidation catalyzed by first row transition metal oxides, we present how to elevate the operating temperature of the electrolyzer as an effective and universal method to improve its electrocatalytic performance. Consequently, a triple device model combining a photothermal collector with a photovoltaic (PV) cell coupled to a water splitting device is proposed to realize the comprehensive and efficient utilization of solar energy: solar heat + PV + electrolyzer.

  • 123963. Zhang, Biaobiao
    et al.
    Li, Fei
    Yu, Fengshou
    Cui, Honghua
    Zhou, Xu
    Li, Hua
    Wang, Yong
    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.
    Homogeneous Oxidation of Water by Iron Complexes with Macrocyclic Ligands2014In: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 9, no 6, p. 1515-1518Article in journal (Refereed)
    Abstract [en]

    The activity of eleven separated iron complexes and nine in situ-generated iron complexes towards catalytic water oxidation have been examined in aqueous solutions with Ce(NH4)(2)(NO3)(6) as the oxidant. Two iron complexes bearing tridentate and tetradentate macrocyclic ligands were found to be novel water oxidation catalysts. The one with tetradentate ligand exhibited a promising activity with a turnover number of 65 for oxygen evolution.

  • 123964. Zhang, Biaobiao
    et al.
    Li, Fei
    Yu, Fengshou
    Wang, Xiaohong
    Zhou, Xu
    Li, Hua
    Jiang, Yi
    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.
    Electrochemical and Photoelectrochemical Water Oxidation by Supported Cobalt-Oxo Cubanes2014In: ACS Catalysis, ISSN 2155-5435, Vol. 4, no 3, p. 804-809Article in journal (Refereed)
    Abstract [en]

    Cobalt-oxo cubane clusters were immobilized on a Nafion film-coated fluorine-doped tin oxide (FTO) electrode and an alpha-Fe2O3 photoanode as surface catalysts for water oxidation. The performance of electrochemical water splitting indicated that these earth-abundant metal complexes retain their homogeneous reactivity on the electrode. Furthermore, efficient visible light-driven water oxidation was realized by coupling a molecular electrocatalyst with an inorganic semiconductor as a noble metal-free photoanode, showing a stability significantly improved with respect to that of the homogeneous system.

  • 123965. Zhang, Biaobiao
    et al.
    Li, Fei
    Zhang, Rong
    Ma, Chengbing
    Chen, Lin
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. Dalian University of Technology (DUT), China.
    Characterization of a trinuclear ruthenium species in catalytic water oxidation by Ru(bda)(pic)(2) in neutral media2016In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 52, no 55, p. 8619-8622Article in journal (Refereed)
    Abstract [en]

    A Ru-III-O-Ru-IV-O-Ru-III type trinuclear species was crystallographically characterized in water oxidation by Ru(bda)(pic)(2) (H(2)bda = 2,2'-bipyridine- 6,60-dicarboxylic acid; pic = 4-picoline) under neutral conditions. The formation of a ruthenium trimer due to the reaction of Ru-IV QO with Ru-II-OH2 was fully confirmed by chemical, electrochemical and photochemical methods. Since the oxidation of the trimer was proposed to lead to catalyst decomposition, the photocatalytic water oxidation activity was rationally improved by the suppression of the formation of the trimer.

  • 123966.
    Zhang, Biaobiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Li, Yuanyuan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Valvo, M.
    Fan, Lizhou
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Daniel, Quentin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Zhang, Peili
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Wang, Linqin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Electrocatalytic Water Oxidation Promoted by 3 D Nanoarchitectured Turbostratic Δ-MnOx on Carbon Nanotubes2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 22, p. 4472-4478Article in journal (Refereed)
    Abstract [en]

    The development of manganese-based water oxidation electrocatalysts is desirable for the production of solar fuels, as manganese is earth-abundant, inexpensive, non-toxic, and has been employed by the Photosystem II in nature for a billion years. Herein, we directly constructed a 3 D nanoarchitectured turbostratic δ-MnOx on carbon nanotube-modified nickel foam (MnOx/CNT/NF) by electrodeposition and a subsequent annealing process. The MnOx/CNT/NF electrode gives a benchmark catalytic current density (10 mA cm−2) at an overpotential (η) of 270 mV under alkaline conditions. A steady current density of 19 mA cm−2 is obtained during electrolysis at 1.53 V for 1.0 h. To the best of our knowledge, this work represents the most efficient manganese-oxide-based water oxidation electrode and demonstrates that manganese oxides, as a structural and functional model of oxygen-evolving complex (OEC) in Photosystem II, can also become comparable to those of most Ni- and Co-based catalysts.

  • 123967.
    Zhang, Biaobiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Sun, Licheng
    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, Organic chemistry. Dalian Univ Technol.
    Across the Board: Licheng Sun on the Mechanism of O-O Bond Formation in Photosystem II2019In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 12, no 14, p. 3401-3404Article in journal (Refereed)
    Abstract [en]

    In this series of articles, the board members of ChemSusChem discuss recent research articles that they consider of exceptional quality and importance for sustainability. This entry features Prof. L. Sun, who proposes a special mechanism for O-O bond formation in photosystem II with involvement of an Mn-VII-oxo species induced by charge- and structural rearrangements. In this viewpoint, Proton transfer is involved in changes of the first coordination spheres around the Mn-VII-oxo site on the dangling Mn4 with de- and re-coordination of carboxylates (Glu333 and Asp170).

  • 123968.
    Zhang, Biaobiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Artificial photosynthesis: opportunities and challenges of molecular catalysts2019In: Chemical Society Reviews, ISSN 0306-0012, E-ISSN 1460-4744, Vol. 48, no 7, p. 2216-2264Article, review/survey (Refereed)
    Abstract [en]

    Molecular catalysis plays an essential role in both natural and artificial photosynthesis (AP). However, the field of molecular catalysis for AP has gradually declined in recent years because of doubt about the long-term stability of molecular-catalyst-based devices. This review summarizes the development history of molecular-catalyst-based AP, including the fundamentals of AP, molecular catalysts for water oxidation, proton reduction and CO2 reduction, and molecular-catalyst-based AP devices, and it provides an analysis of the advantages, challenges, and stability of molecular catalysts. With this review, we aim to highlight the following points: (i) an investigation on molecular catalysis is one of the most promising ways to obtain atom-efficient catalysts with outstanding intrinsic activities; (ii) effective heterogenization of molecular catalysts is currently the primary challenge for the application of molecular catalysis in AP devices; (iii) development of molecular catalysts is a promising way to solve the problems of catalysis involved in practical solar fuel production. In molecular-catalysis-based AP, much has been attained, but more challenges remain with regard to long-term stability and heterogenization techniques.

  • 123969.
    Zhang, Biaobiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Ru-bda: Unique Molecular Water-Oxidation Catalysts with Distortion Induced Open Site and Negatively Charged Ligands2019In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 141, no 14, p. 5565-5580Article, review/survey (Refereed)
    Abstract [en]

    A water-oxidation catalyst with high intrinsic activity is the foundation for developing any type of water-splitting device. To celebrate its 10 years anniversary, in this Perspective we focus on the state-of-the-art molecular water-oxidation catalysts (MWOCs), the Ru-bda series (bda = 2,2'-bipyridine-6,6'-dicarboxylate), to offer strategies for the design and synthesis of more advanced MWOCs. The O-O bond formation mechanisms, derivatives, applications, and reasons behind the outstanding catalytic activities of Ru-bda catalysts are summarized and discussed. The excellent performance of the Ru-bda catalyst is owing to its unique structural features: the distortion induced 7-coordination and the carboxylate ligands with coordination flexibility, proton transfer function as well as small steric hindrance. Inspired by the Ru-bda catalysts, we emphasize that the introduction of negatively charged groups, such as the carboxylate group, into ligands is an effective strategy to lower the onset potential of MWOCs. Moreover, distortion of the regular configuration of a transition metal complex by ligand design to generate a wide open site as the catalytic site for binding the substrate as an extra-coordination is proposed as a new concept for the design of efficient molecular catalysts. These inspirations can be expected to play a great role in not only water oxidation catalysis but also other small molecule activation and conversion reactions involving artificial photosynthesis, such as CO2 reduction and N-2 fixation reactions.

  • 123970.
    Zhang, Biaobiao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Sun, Licheng
    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.
    Why nature chose the Mn4CaO5 cluster as water-splitting catalyst in photosystem II: a new hypothesis for the mechanism of O-O bond formation2018In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 47, no 41, p. 14381-14387Article, review/survey (Refereed)
    Abstract [en]

    Resolving the questions, namely, the selection of Mn by nature to build the oxygen-evolving complex (OEC) and the presence of a cubic Mn3CaO4 structure in OEC coupled with an additional dangling Mn (Mn4) via mu-O atom are not only important to uncover the secret of water oxidation in nature, but also essential to achieve a blueprint for developing advanced water-oxidation catalysts for artificial photosynthesis. Based on the important experimental results reported so far in the literature and on our own findings, we propose a new hypothesis for the water oxidation mechanism in OEC. In this new hypothesis, we propose for the first time, a complete catalytic cycle involving a charge-rearrangement-induced Mn-VII-dioxo species on the dangling Mn4 during the S-3 -> S-4 transition. Moreover, the O-O bond is formed within this Mn-VII-dioxo site, which is totally different from that discussed in other existing proposals.

  • 123971. Zhang, Biaobiao
    et al.
    Zhan, Shaoqi
    Liu, Tianqi
    Wang, Linqin
    Inge, A. Ken
    Duan, Lele
    Timmer, Brian J.J.
    Kravchenko, Oleksandr
    Li, Fei
    Ahlquist, Mårten S. G.
    Sun, Licheng
    Modifying Ru-bda Backbone with Steric Hindrance and Hydrophilicity: Influence of Secondary Coordination Environments on Water-Oxidation MechanismIn: Article in journal (Other academic)
    Abstract [en]

    Understanding the seven coordination and O-O coupling pathway of the distinguished Ru-bda catalysts is essential for the development of next generation efficient water-oxidation catalysts based on earth-abundant metals. This work reports the synthesis, characterization and catalytic properties of a monomeric ruthenium catalyst Ru-bnda (H2bnda = 2,2'-bi(nicotinic acid)-6,6'-dicarboxylic acid) featuring steric hindrance and enhanced hydrophilicity on the backbone. Combining experimental evidence with systematic density functional theory calculations on the Ru-bnda and related catalysts Ru-bda, Ru-pda and Ru-biqa, we emphasized that seven coordination clearly determines presence of RuV=O with high spin density on the ORuV=O atom, i.e. oxo with radical properties, which is one of the necessary conditions for reacting through the O-O coupling pathway. However, an additional factor to make the condition sufficient is the favorable intermolecular face-to-face interaction for the generation of the pre-reactive [RuV=O...O=RuV], which is significantly influenced by the secondary coordination environments. This work provides a new understanding of the structure-activity relationship of water-oxidation catalysts and their potential to adopt I2M pathway for O-O bond formation.

  • 123972.
    Zhang, Bo
    KTH, Superseded Departments, Physics.
    Experimental studies of molecular quantum dynamics2000Licentiate thesis, comprehensive summary (Other scientific)
  • 123973.
    Zhang, Bo
    KTH, Superseded Departments, Physics.
    Experimental Studies of Quantum Dynamics and Coherent Control in Homonuclear Alkali Diatomic Molecules2002Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The main theme covered in this thesis is experimentalstudies of quantum dynamics and coherent control in homonuclearalkali diatomic molecules by ultrafast laser spectroscopy iththe implementation of pump-probe techniques.

    A series of experiments have been performed on the Rb2molecules in a molecular beam as well as in a thermal oven. Thereal-time molecular quantum dynamics of the predissociatingelectronically excited D(3)1Πu state of Rb2, which couples to/intersects several otherneighbouring states, is investigated using wavepackets. Thepredissociation of the D state, explored by this wavepacketmethod, arises from two independent states, the (4)3Σu+and (1)3u, for which the second corresponds to a much fasterdecay channel above a sharp energy threshold around 430 nm. Thelifetime of the D state above the energy threshold is obtained,τ ≈ 5 ps, by measuring the decay time of thewavepacket in a thermal oven. Further experimentalinvestigation performed in a molecular beam together withquantum calculations of wavepacket dynamics on the D state haveexplored new probe channels of wavepacket evolution: theD′(3)1Σu+ channel, which exhibits vibrational motionin a shelf state and the (4)3Σu+ channel, where direct build-up of thewavefunction is observed due to its spin-orbit oupling to the Dstate.

    The real-time quantum dynamics of wavepackets confined totwo bound states, A1Σu+(0u+) and b3Πu(0u+), have been studied by experiment andcalculations. It is shown that these two states are fullycoupled by spin-orbit interaction, characterised by itsintermediate strength. The intermediate character of thedynamics is established by complicated wavepacket oscillationatterns and a value of 75 cm-1is estimated for the coupling strength at thestate crossing.

    The experiments on the Li2molecule are performed by coherent control ofrovibrational molecular wavepackets. First, the Deutsch-Jozsaalgorithm is experimentally demonstrated for three-qubitfunctions using a pure coherent superposition of Li2rovibrational eigenstates. The function’scharacter, either constant or balanced, is evaluated by firstimprinting the function, using a phase-tailored femtosecond(fs) pulse, on a coherent superposition of the molecularstates, and then projecting the superposition onto an ionicfinal state using a second fs pulse at a specific delay time.Furthermore, an amplitude-tailored fs pulse is used to exciteselected rovibrational eigenstates and collision induceddephasing of the wavepacket signal, due to Li2-Ar collisions, is studied experimentally. Theintensities of quantum beats decaying with the delay time aremeasured under various pressures and the collisional crosssections are calculated for each well-defined rovibrationalquantum beat, which set the upper limitsfor ure dephasingcross sections.

    Keywords:Ultrafast laser spectroscopy, pump-probetechnique, predissociation, wavepacket, pin-orbit interaction,coherent control, (pure) dephasing

  • 123974.
    Zhang, Bo
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Location Based Pre-caching and Network Coding in Smart Content Distribution2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Since the boom of the smart phones, there is a huge amount of applicationsthat deal with data located in the cloud. This fact can makethese applications unavailable when the network is inaccessible due tocoverage or congestion. A solution to these problems have been designedand developed for the Android OS in this master thesis. The approachis the application of location-based pre-caching, downloading the contentof an application before the user enters in the zone where the applicationmay use this content. Network coding has also been introduced in orderto reduce the amount of data sent over the wireless networks. A cachingscheme is introduced in binary network coding and applied to the problemof retransmission in wireless broadcast network. A binary network codingalgorithm is designed which could asymptotically approach the efficiency of linear network coding with a much lower decoding complexity. 

  • 123975.
    Zhang, Bo
    et al.
    Dalian Univ Technol, Inst Energy Sci & Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Hou, Jungang
    Dalian Univ Technol, Inst Energy Sci & Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Wu, Yunzhen
    Dalian Univ Technol, Inst Energy Sci & Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Cao, Shuyan
    Dalian Univ Technol, Inst Energy Sci & Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Li, Zhuwei
    Dalian Univ Technol, Inst Energy Sci & Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Nie, Xiaowa
    Dalian Univ Technol, Inst Energy Sci & Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Gao, Zhanming
    Dalian Univ Technol, Inst Energy Sci & Technol, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Dalian 116024, Peoples R China..
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. Dalian Univ Technol, Inst Energy Sci & Technol, DUT .
    Tailoring Active Sites in Mesoporous Defect-Rich NC/V-o-WON Heterostructure Array for Superior Electrocatalytic Hydrogen Evolution2019In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 9, no 12, article id 1803693Article in journal (Refereed)
    Abstract [en]

    Tailoring active sites in earth-abundant non-noble metal electrocatalysts are required toward widespread applications in sustainable energy fields. Herein, an integrated mesoporous heterostructure array is reported by a hydrogenation/nitridation-induced in situ growth strategy. Highly conductive oxygen-vacancies-rich tungsten oxynitride (V-o-WON) nanorod array acts as the backbone encapsulated by ultrathin nitrogen-doped carbon (NC) nanolayers, forming high-quality shell/core NC/V-o-WON heterostructures. Density functional theory calculations reveal that defect-rich heterostructure arrays not only enhance the conductivity and modulate electronic structure but also promote the adsorption and dissociation of reactants and offer substantial potential sites. As expected, porous NC/V-o-WON array exhibits a small overpotential of 16 mV at the current density of 10 mA cm(-2) and a low Tafel slope of 33 mV per decade in alkaline media, accompanied by negligible loss upon a large current density over 100 h. Benefiting from outstanding electrocatalytic hydrogen evolution reaction performance and stability, this defective heterostructure could serve as a prominent alternative electrocatalyst for renewable energy applications.

  • 123976. Zhang, Bo
    et al.
    Käll, Lukas
    KTH, School of Biotechnology (BIO), Gene Technology.
    Zubarev, Roman A.
    DeMix-Q: Quantification-Centered Data Processing Workflow2016In: Molecular & cellular proteomics (online), ISSN 1535-9476, E-ISSN 1535-9484, Vol. 15, no 4, p. 1467-1478Article in journal (Refereed)
    Abstract [en]

    For historical reasons, most proteomics workflows focus on MS/MS identification but consider quantification as the end point of a comparative study. The stochastic data-dependent MS/MS acquisition (DDA) gives low reproducibility of peptide identifications from one run to another, which inevitably results in problems with missing values when quantifying the same peptide across a series of label-free experiments. However, the signal from the molecular ion is almost always present among the MS1 spectra. Contrary to what is frequently claimed, missing values do not have to be an intrinsic problem of DDA approaches that perform quantification at the MS1 level. The challenge is to perform sound peptide identity propagation across multiple high-resolution LC-MS/MS experiments, from runs with MS/MS-based identifications to runs where such information is absent. Here, we present a new analytical workflow DeMix-Q (https://github.com/userbz/DeMix-Q), which performs such propagation that recovers missing values reliably by using a novel scoring scheme for quality control. Compared with traditional workflows for DDA as well as previous DIA studies, DeMix-Q achieves deeper proteome coverage, fewer missing values, and lower quantification variance on a benchmark dataset. This quantification-centered workflow also enables flexible and robust proteome characterization based on covariation of peptide abundances.

  • 123977.
    Zhang, Bo
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Li, Yuxin
    KTH, School of Industrial Engineering and Management (ITM).
    The Adaptation of Lean Methodology in Swedish Cultures - the innovation approaches to Lean Manufacturing2017Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
  • 123978.
    Zhang, Bo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Marketing and Entrepreneurship.
    Li, Yuxin
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial Marketing and Entrepreneurship.
    The Adaptation of Lean Methodology in Swedish Cultures: the innovation approaches to Lean Manufacturing2017Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Japanese automobile manufacturer invented Lean Production or Toyota Production System (TPS) which has been introduced and implemented in Swedish manufacturers for around 20 years (Dabhilkar, et al., 2005). Many studies discussed how it creates success in optimizing production process and quality. However, many researches show that the gap between culture become the main barrier in the process of realizing ‘true’ lean manufacturing. So, what problems has been brought out because of cultural difference in the process of implementing the lean method in Swedish industry and how to eliminate them?The adaptation of lean method will have influences on the culture of a company. The purpose of this paper is to find out the problems which brought out by the cultural difference and a set of general approaches and principles which can be used for Swedish cultures to adapt and implement lean methodologies successfully and effectively.

  • 123979. Zhang, Bo
    et al.
    Pirmoradian, Mohammad
    Zubarev, Roman
    Käll, Lukas
    KTH, School of Biotechnology (BIO), Gene Technology. KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Covariation of Peptide Abundances Accurately Reflects Protein Concentration Differences2017In: Molecular & Cellular Proteomics, ISSN 1535-9476, E-ISSN 1535-9484, Vol. 16, no 5, p. 936-948Article in journal (Refereed)
    Abstract [en]

    Most implementations of mass spectrometry-based proteomics involve enzymatic digestion of proteins, expanding the analysis to multiple proteolytic peptides for each protein. Currently, there is no consensus of how to summarize peptides' abundances to protein concentrations, and such efforts are complicated by the fact that error control normally is applied to the identification process, and do not directly control errors linking peptide abundance measures to protein concentration. Peptides resulting from suboptimal digestion or being partially modified are not representative of the protein concentration. Without a mechanism to remove such unrepresentative peptides, their abundance adversely impacts the estimation of their protein's concentration. Here, we present a relative quantification approach, Diffacto, that applies factor analysis to extract the covariation of peptides' abundances. The method enables a weighted geometrical average summarization and automatic elimination of incoherent peptides. We demonstrate, based on a set of controlled label-free experiments using standard mixtures of proteins, that the covariation structure extracted by the factor analysis accurately reflects protein concentrations. In the 1% peptide-spectrum match-level FDR data set, as many as 11% of the peptides have abundance differences incoherent with the other peptides attributed to the same protein. If not controlled, such contradicting peptide abundance have a severe impact on protein quantifications. When adding the quantities of each protein's three most abundant peptides, we note as many as 14% of the proteins being estimated as having a negative correlation with their actual concentration differences between samples. Diffacto reduced the amount of such obviously incorrectly quantified proteins to 1.6%. Furthermore, by analyzing clinical data sets from two breast cancer studies, our method revealed the persistent proteomic signatures linked to three subtypes of breast cancer. We conclude that Diffacto can facilitate the interpretation and enhance the utility of most types of proteomics data.

  • 123980. Zhang, C.
    et al.
    Kjellström, Hedvig
    KTH, School of Computer Science and Communication (CSC), Robotics, perception and learning, RPL.
    Mandt, S.
    Determinantal point processes for mini-batch diversification2017In: Uncertainty in Artificial Intelligence - Proceedings of the 33rd Conference, UAI 2017, AUAI Press Corvallis , 2017Conference paper (Refereed)
    Abstract [en]

    We study a mini-batch diversification scheme for stochastic gradient descent (SGD). While classical SGD relies on uniformly sampling data points to form a mini-batch, we propose a non-uniform sampling scheme based on the Determinantal Point Process (DPP). The DPP relies on a similarity measure between data points and gives low probabilities to mini-batches which contain redundant data, and higher probabilities to mini-batches with more diverse data. This simultaneously balances the data and leads to stochastic gradients with lower variance. We term this approach Diversified Mini-Batch SGD (DM-SGD). We show that regular SGD and a biased version of stratified sampling emerge as special cases. Furthermore, DM-SGD generalizes stratified sampling to cases where no discrete features exist to bin the data into groups. We show experimentally that our method results more interpretable and diverse features in unsupervised setups, and in better classification accuracies in supervised setups.

  • 123981.
    Zhang, Cevin
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Health Informatics and Logistics.
    Sebastiaan, Meijer
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems.
    A Simulation Game of Patient Transportation2019In: Neo-Simulation and Gaming Toward Active Learning / [ed] Ryoju Hamada;Songsri Soranastaporn; Hidehiko Kanegae; Pongchai Dumrongrojwatthana; Settachai Chaisanit; Paola Rizzi; Vinod Dumblekar, Springer, 2019, 1, p. 53-66Chapter in book (Refereed)
    Abstract [en]

    The handling of patients is a complex process. The training and education of patient transportation workers are meant to ensure efficiency and health outcomes. A simulation game, joined by personnel with working experience or prospective professionals in the healthcare system, is a life-like medium for improving decision makings in non-rational operation management. However, few examples are known in regard to synthesizing complex systems, such as clinical facilities, into healthcare simulation games. In order to fill this gap, this work proposes the adopt theory and reports the development of a simulation game that reconciles patient handling with the support of different types of simulation techniques. The simulation game has a physical entity simulator as its back-end and a panel of command and control for each player as its front end. The physical entity simulator is based on the interactions of mobile agents. Agent-based modeling targets the correct level of representation of the operative environment. The simulation game is tested with managers who have more than 10-years of working experience with patient flow management in pediatric care. Reflections from players indicate that modeling and abstraction using an agent model is an efficient synthesis of complex systems. The theory, methods, and results of this study are expected to contribute to the development of simulation games that can be applied in health service provision, in general, and in patient transportation, in particular.

  • 123982.
    Zhang, Changyang
    KTH, School of Information and Communication Technology (ICT).
    Energy Ecient Cellular System Design with QoS Assurance2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Results from the smart-phones' ubiquitous Internet access and diverse multimedia applications, there has been an explosion in mobile data communication, this incredible increase will necessitate continual high energy consumption and leads to more CO2 emissions. It is crucial to develop more energy-efficient systems because of the potential harmful effects to the environment caused by CO2 emissions. It is also significant for the cellular network operators, since the electricity bills are a considerable portion of their Operational Expenditure (OPEX).

    The power consumption at base stations accounts around 60-80% of the total power consumption in a cellular network [1, 2]. Potential energy savings can be expected by implementing BSs sleeping mode, according to the traffic demands and user activity factors.

    There are many performance trade-offs in optimizing BSs sleeping modes [3]. One of them is the trade-off between service delay and power consumption of cellular networks. In this thesis, the service delay is considered as a measure of Quality of Service (QoS) user experiences.

    Based on the conception of cell wilting and dynamic base stations switching, BS sleep switching algorithms are developed while the QoS of User Equipments (UEs) is guaranteed in the meantime. The switching algorithms are decentralized which means no central controller is needed. The BSs can make the switching decisions based on the feedback from UEs and its neighboring BSs. Furthermore, the implementation of the proposed algorithms is also comprehensively described at the protocol level.

    An urban micro BSs network is built and used as the simulation scenario. Simulations are done with the help of the rudimentary network emulator (RUNE), a network simulator tool developed by Ericsson in MATLAB environment.

    Simulation results show that up to 62% of power consumption can be saved by implementing the QoS guaranteed BS switching algorithms. Furthermore, comparisons show that the QoS guaranteed BS switching algorithms have higher performance in terms of power consumption savings and QoS to the transitional BS switching algorithms.

    Many factors inuence the performance of BS switching algorithms. The analysis of the performance is challenging because the required parameters for analysis are dynamically changing during the switching processes. In this thesis, we develop a rough analysis, which gives an insight into some key factors affecting the performance.

    It shows that high system traffic load results in high power consumption and poor system performance. Either a very small or very large cell radius also leads to high power consumption and poor system performance for different reasons. In addition, choosing different values of the switching threshold affects the system performance in different ways.

  • 123983. Zhang, Chao
    et al.
    Osorio, Carolina
    Flötteröd, Gunnar
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Efficient calibration techniques for large-scale traffic simulators2017In: Transportation Research Part B: Methodological, ISSN 0191-2615, E-ISSN 1879-2367, Vol. 97, p. 214-239Article in journal (Refereed)
    Abstract [en]

    Road transportation simulators are increasingly used by transportation stakeholders around the world for the analysis of intricate transportation systems. Model calibration is a crucial prerequisite for transportation simulators to reliably reproduce and predict traffic conditions. This paper considers the calibration of transportation simulators. The methodology is suitable for a broad family of simulators. Its use is illustrated with stochastic and computationally costly simulators. The calibration problem is formulated as a simulation based optimization (SO) problem. We propose a metamodel approach. The analytical meta model combines information from the simulator with information from an analytical differentiable and tractable network model that relates the calibration parameters to the simulation-based objective function. The proposed algorithm is validated by considering synthetic experiments on a toy network. It is then used to address a calibration problem with real data for a large-scale network: the Berlin metropolitan network with over 24300 links and 11300 nodes. The performance of the proposed approach is compared to a traditional benchmark method. The proposed approach significantly improves the computational efficiency of the calibration algorithm with an average reduction in simulation runtime until convergence of more than 80%. The results illustrate the scalability of the approach and its suitability for the calibration of large-scale computationally inefficient network simulators. (C) 2016 Elsevier Ltd. All rights reserved.

  • 123984. Zhang, Chao-Zhi
    et al.
    Cao, Hui
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Guo, Zhao-Bing
    NONLINEAR OPTICAL PROPERTIES OF NOVEL AND EFFECTIVE H-SHAPED CHROMOPHORES CONTAINING THREE PARALLEL AND NON-CONJUGATED D-pi-A UNITS2011In: Journal of nonlinear optical physics and materials, ISSN 0218-8635, Vol. 20, no 3, p. 327-339Article in journal (Refereed)
    Abstract [en]

    H-shaped chromophores containing three parallel non-conjugated D-pi-A units are effective chromophores with high hyperpolarizability and good optical transparency. The semi-empirical methods ZINDO, AM1, MNDO and PM3 were employed to study the effect of strength of acceptors and donors, and steric repulsion between substituents on static first hyperpolarizabilities (beta(0)) and enhancements of beta(0) of the H-shaped chromophores. The results show that the H-shaped chromophore would exhibit the largest beta(0) and/or the largest enhancement of beta(0) of the chromophore when combination of a donor (D) and an acceptor (A) in a D-pi-A unit is suitable.

  • 123985. Zhang, Chao-Zhi
    et al.
    Cao, Hui
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Guo, Zhao-Bing
    Theoretical study of macroscopic optical nonlinearities of "parallel connection" chromophores containing PNA units2013In: Journal of nonlinear optical physics and materials, ISSN 0218-8635, Vol. 22, no 2, p. 1350014-Article in journal (Refereed)
    Abstract [en]

    The semi-empirical method ZINDO was employed to study relationship between macroscopic optical nonlinear parameter mu beta/MW (where mu is the dipole moment, beta is the first hyperpolarizability, and MW is molecular weight) and the number of parallel non-conjugated D-pi-A units in a chromophore. The computational results show that macroscopic optical nonlinear parameter mu beta/MW value increases remarkably from 1.64 to 2.53 with increasing the number of parallel and non-conjugated p-Nitroaniline (PNA) units in a chromophore from 1 to 3. Then the mu beta/MW value decreases rapidly from 2.53 to 0.43 with increasing the number of PNA units in a chromophore from 3 to 5. It suggests that design of chromophores containing two or three parallel non-conjugated D-pi-A units would be an effective strategy for increasing the first hyperpolarizability and macroscopic optical nonlinearity of designed NLO materials.

  • 123986.
    Zhang, Charlie Jianzhong
    et al.
    Univ Wisconsin, Madison, WI 53706 USA..
    Ma, Jianglei
    Huawei Canada R Ctr, Markham, ON, Canada..
    Li, Geoffrey Ye
    Georgia Tech, Atlanta, GA 30332 USA..
    Kishiyama, Yoshihisa
    Hokkaido Univ, Sapporo, Hokkaido, Japan..
    Parkvall, Stefan
    KTH. Ericsson Res, Kista, Sweden.
    Liu, Guangyi
    China Mobile Res Inst, Wireless & Device Dept, Beijing, Peoples R China..
    Kim, Young-Han
    Univ Calif San Diego, Dept Elect & Comp Engn, La Jolla, CA 92093 USA..
    Key Technology for 5G New Radio2018In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 56, no 3, p. 10-11Article in journal (Refereed)
  • 123987. Zhang, Charlie Jianzhong
    et al.
    Ma, Jianglei
    Li, Geoffrey Ye
    Georgia Tech, Sch ECE, Atlanta, GA USA..
    Yu, Wei
    Univ Toronto, Toronto, ON, Canada..
    Jindal, Nihar
    Univ Calif Berkeley, Elet Engn Comp Sci, Berkeley, CA USA..
    Kishiyama, Yoshihisa
    NTT DoCoMo, INC, Toyota, Japan..
    Parkvall, Stefan
    KTH. Royal Inst Technol, Stockholm, Sweden..
    New Waveforms for 5G Networks2016In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 54, no 11, p. 64-65Article in journal (Other academic)
  • 123988.
    Zhang, Chen
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    An empirical evaluation of an on-street parking pricing scheme: A case study in Stockholm inner city2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The congestion of on-street parking places in the core of metropolitan areas has attracted

    considerable attention in recent years. Low fares may result with an over consumption of

    this public good and result with a wide range of negative impacts such as the reduction of

    accessibility, deteriorating of the local air quality, extra vehicle miles travelled and increased

    traffic jams. Parking pricing is hence an important and common urban planning problem.

    However, a methodology framework for evaluating the impacts of on-street parking pricing

    is still lacking. The impact of pricing needs to be explored systematically and empirically.

    The principle aim of this thesis is to develop a systematic approach for evaluating the

    impacts of on-street parking pricing and attain concrete knowledge from the application of

    the proposed method for a case study. The project will utilize ticketing machine data and

    combine it with car floating and parking supply data. The method used in this work has the

    potential to be applied to various urban areas that utilize a similar ticketing machine system.

    The outputs of the case study function for supporting future design of on-street parking

    pricing in Stockholm. Results show that the on-street parking demand is relatively inelastic

    as a response to pricing change. The estimated own-price elasticity ranges from -0,17 to -

    0,29; and the cross price-elasticity is estimated to range from 0,13 to 0,20, for different

    street types and time-of-day periods. Raising the price leads to a significant reduction in the

    average parking duration, which contributes to a parking congestion relief. Moreover, the

    results indicate that the pricing policy affects trip scheduling and yield a more balanced

    utilization of the available parking supply through the day.

  • 123989.
    Zhang, Chen
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Health Informatics and Logistics.
    Grandits, Thomas
    KTH, School of Technology and Health (STH).
    Härenstam, Karin
    Karolinska Institutet.
    Hauge, Jannicke
    KTH, School of Industrial Engineering and Management (ITM).
    Meijer, Sebastiaan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Health Informatics and Logistics.
    A systematic literature review of simulation models for non-technical skill training in healthcare logistics2018In: Advances in Simulation, ISSN 2059-0628, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Resource allocation in patient care relies heavily on individual judgements of healthcare professionals. Such professionals perform coordinating functions by managing the timing and execution of a multitude of care processes for multiple patients. Based on advances in simulation, new technologies that could be used for establishing realistic representations have been developed. These simulations can be used to facilitate understanding of various situations, coordination training and education in logistics, decision-making processes, and design aspects of the healthcare system. However, no study in the literature has synthesized the types of simulations models available for non-technical skills training and coordination of care. A systematic literature review, following the PRISMA guidelines, was performed to identify simulation models that could be used for training individuals in operative logistical coordination that occurs on a daily basis. This article reviewed papers of simulation in healthcare logistics presented in the Web of Science Core Collections, ACM digital library, and JSTOR databases. We conducted a screening process to gather relevant papers as the knowledge foundation of our literature study. The screening process involved a query-based identification of papers and an assessment of relevance and quality. Two hundred ninety-four papers met the inclusion criteria. The review showed that different types of simulation models can be used for constructing scenarios for addressing different types of problems, primarily for training and education sessions. The papers identified were classified according to their utilized paradigm and focus areas. (1) Discrete-event simulation in single-category and single-unit scenarios formed the most dominant approach to developing healthcare simulations and dominated all other categories by a large margin. (2) As we approached a systems perspective (cross-departmental and cross-institutional), discrete-event simulation became less popular and is complemented by system dynamics or hybrid modeling. (3) Agent-based simulations and participatory simulations have increased in absolute terms, but the share of these modeling techniques among all simulations in this field remains low. An extensive study analyzing the literature on simulation in healthcare logistics indicates a growth in the number of examples demonstrating how simulation can be used in healthcare settings. Results show that the majority of studies create situations in which non-technical skills of managers, coordinators, and decision makers can be trained. However, more system-level and complex system-based approaches are limited and use methods other than discrete-event simulation.

  • 123990.
    Zhang, Chen
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering, Health Care Logistics.
    Hanchi, Hamza
    KTH, School of Technology and Health (STH), Health Systems Engineering, Health Care Logistics.
    Meijer, Sebastiaan
    KTH, School of Technology and Health (STH), Health Systems Engineering, Health Care Logistics.
    Evaluating the Effect of Centralized Administration on Health Care Performances Using Discrete-Event Simulation2017In: 2017 PORTLAND INTERNATIONAL CONFERENCE ON MANAGEMENT OF ENGINEERING AND TECHNOLOGY (PICMET) / [ed] Kocaoglu, DF Anderson, TR Daim, TU Kozanoglu, DC Niwa, K Perman, G Steenhuis, HJ, IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    Patient flow management is increasingly motivated by the request to improve system performance. The improvements on local departments are expected with minimal negative effects on the upstream and downstream departments which are integral parts of the care pathway. Although it is widely debated that hospital buildings are expensively constructed and operated, we observe a lack of efforts on the logistical efficiency of care provision within facilities in hospitals, especially in developing areas. This askes for more research attentions towards the knowledge gap between health care supply and demand. Our work presented a simulation-based approach to study the impact of centralized administrative works by evaluating waiting times of services and resource utilizations. A discrete-event simulation (DES) model was constructed in reference to a hospital complex in Jiangsu, China. The results showed that the centralized administration benefited patients regarding a reduced total length of stay and waiting times of administration; however, reorganizing administration also influenced waiting times of medical services and resource utilizations of different types of facilities. Neglecting administration in care pathway might yield to unclear knowledge of their impacts. This article can also support the inclusion of simulation in the strategic planning phase of health care projects.

  • 123991.
    Zhang, Chen
    et al.
    KTH, School of Technology and Health (STH), Health Systems Engineering, Health Care Logistics.
    Hanchi, Hamza
    KTH, School of Technology and Health (STH), Health Systems Engineering, Health Care Logistics.
    Meijer, Sebastiaan
    KTH, School of Technology and Health (STH), Health Systems Engineering, Health Care Logistics.
    Identifying Influential Factors of Patient Length of Stay In a Surgery Center: a Simulation Modelling Approach2017Conference paper (Refereed)
  • 123992.
    Zhang, Chencheng
    KTH, School of Information and Communication Technology (ICT).
    TLM-RTL Equivalence Automated Verification Method and Tool Evaluation: Performed in Ericsson AB2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Raising the abstraction level, from Register Transfer Level (RTL) to Transaction Level

    Model (TLM), accelerates the design and simulation speed for Application Specific

    Integrated Circuit (ASIC) design in modern industry.

    TLM can be used for reference model for RTL in verification process. TLM can also be

    used in High Level Synthesis (HLS) as the original model for RTL implementation. With

    the development of design automation tools for HLS by big Electronic Design Automation

    (EDA) vendors in recent years, it is now possible to generate RTL code from TLM directly

    by these fully automated industry commercial tools.

    When it comes up to automated ASIC design, the functional consistency between TLM and

    RTL is the top task of the verification. Several methodologies are developed or under

    development in both industry and research area. Some automated verification tools may

    help to greatly reduce the verification effort.

    This thesis report has proposed a flow for verifying the functional equivalence between

    TLM/SystemC/C code against its corresponding RTL code. The RTL code is the result of

    automated HLS from TLM. One commercial tool based on sequential equivalence

    checking (SEC) has been evaluated and its limitations have been assessed. The way to

    overcome those limitations by complementary verification methods has been scrutinized.

  • 123993.
    Zhang, Chenda
    et al.
    KTH, School of Engineering Sciences (SCI).
    Dowling, Gustav
    KTH, School of Engineering Sciences (SCI).
    Förbättring av kvaliten på "adversarial examples" i ljuddomänen2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this study is to create targeted adversarial examples for an audio classifier without access to the neural networks internal structure. Previous work in this domain has shown white box attacks that generate adversarial examples with very high measures of similarity and more noisy adversarial examples generated by black box attacks. By using an algorithm that iteratively applies noise to the audio file and selects the best candidates based on the output layer of the neural network we have managed to create new audio that is 98\% similar to the original but manages to fool the speech to text audio classifier. By evaluating the generated candidates based on different measures of similarity between the proposed candidate and the original audio file we managed to create high quality black box audio adversarial examples using genetic algorithms.

  • 123994.
    Zhang, Cheng
    East China University of Science and Technology, China; Chalmers University of Technology,Sweden.
    Logical transformation of genome-scale metabolic models for gene level applications and analysis2015In: Bioinformatics, ISSN 1367-4803, E-ISSN 1367-4811, Vol. 31, no 14, p. 2324-2331Article in journal (Refereed)
    Abstract [en]

    Motivation: In recent years, genome-scale metabolic models (GEMs) have played important roles in areas like systems biology and bioinformatics. However, because of the complexity of genereaction associations, GEMs often have limitations in gene level analysis and related applications. Hence, the existing methods were mainly focused on applications and analysis of reactions and metabolites. Results: Here, we propose a framework named logic transformation of model (LTM) that is able to simplify the gene-reaction associations and enables integration with other developed methods for gene level applications. We show that the transformed GEMs have increased reaction and metabolite number as well as degree of freedom in flux balance analysis, but the gene-reaction associations and the main features of flux distributions remain constant. In addition, we develop two methods, OptGeneKnock and FastGeneSL by combining LTM with previously developed reaction-based methods. We show that the FastGeneSL outperforms exhaustive search. Finally, we demonstrate the use of the developed methods in two different case studies. We could design fast genetic intervention strategies for targeted overproduction of biochemicals and identify double and triple synthetic lethal gene sets for inhibition of hepatocellular carcinoma tumor growth through the use of OptGeneKnock and FastGeneSL, respectively.

  • 123995.
    Zhang, Cheng
    KTH, School of Computer Science and Communication (CSC).
    Object Detection in Natural Images.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis work is aiming for detecting and localizing different classes of objects in natural images. Algorithm which start from object detection with Implicit Shape model (ISM), then with patch based class segmentation verifies hypothesis with MDL principle are used. This algorithm is able to achieve a high detection rate on both rigid and articulated objects. The thesis also proposes a novel multi-class ISM based on training joint codebook which benefits from sharing features. Experiments have verified that multi-class ISM can reach the same level of detection accuracy as the original ISM while being considerably more efficient. To further improve the computation efficiency, Information Gain(IG) integrated with word frequency criteria has been combined to select codebook entries. Evaluation shows that decreasing 60% of the codebook size would only lead to less than 5% loss in detection accuracy. To further improve the performance, saliency detection can be applied on test images on certain datasets. This has also been shown by the experiments.

  • 123996.
    Zhang, Cheng
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Structured Representation Using Latent Variable Models2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Over the past two centuries the industrial revolution automated a great part of work that involved human muscles. Recently, since the beginning of the 21st century, the focus has shifted towards automating work that is involving our brain to further improve our lives. This is accomplished by establishing human-level intelligence through machines, which lead to the growth of the field of artificial intelligence. Machine learning is a core component of artificial intelligence. While artificial intelligence focuses on constructing an entire intelligence system, machine learning focuses on the learning ability and the ability to further use the learned knowledge for different tasks. This thesis targets the field of machine learning, especially structured representation learning, which is key for various machine learning approaches.

    Humans sense the environment, extract information and make action decisions based on abstracted information. Similarly, machines receive data, abstract information from data through models and make decisions about the unknown through inference. Thus, models provide a mechanism for machines to abstract information. This commonly involves learning useful representations which are desirably compact, interpretable and useful for different tasks. In this thesis, the contribution relates to the design of efficient representation models with latent variables. To make the models useful, efficient inference algorithms are derived to fit the models to data. We apply our models to various applications from different domains, namely E-health, robotics, text mining, computer vision and recommendation systems.

    The main contribution of this thesis relates to advancing latent variable models and deriving associated inference schemes for representation learning. This is pursued in three different directions. Firstly, through supervised models, where better representations can be learned knowing the tasks, corresponding to situated knowledge of humans. Secondly, through structured representation models, with which different structures, such as factorized ones, are used for latent variable models to form more efficient representations. Finally, through non-parametric models, where the representation is determined completely by the data. Specifically, we propose several new models combining supervised learning and factorized representation as well as a further model combining non-parametric modeling and supervised approaches. Evaluations show that these new models provide generally more efficient representations and a higher degree of interpretability.

    Moreover, this thesis contributes by applying these proposed models in different practical scenarios, demonstrating that these models can provide efficient latent representations. Experimental results show that our models improve the performance for classical tasks, such as image classification and annotations, robotic scene and action understanding. Most notably, one of our models is applied to a novel problem in E-health, namely diagnostic prediction using discomfort drawings. Experimental investigation show here that our model can achieve significant results in automatic diagnosing and provides profound understanding of typical symptoms. This motivates novel decision support systems for healthcare personnel.

  • 123997.
    Zhang, Cheng
    et al.
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Aldrees, Mohammed
    Arif, Muhammad
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Li, Xiangyu
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Mardinoglu, Adil
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Aziz, Mohammad Azhar
    Elucidating the Reprograming of Colorectal Cancer Metabolism Using Genome-Scale Metabolic Modeling2019In: Frontiers in Oncology, ISSN 2234-943X, E-ISSN 2234-943X, Vol. 9, article id 681Article in journal (Refereed)
    Abstract [en]

    Colorectal cancer is the third most incidental cancer worldwide, and the response rate of current treatment for colorectal cancer is very low. Genome-scale metabolic models (GEMs) are systems biology platforms, and they had been used to assist researchers in understanding the metabolic alterations in different types of cancer. Here, we reconstructed a generic colorectal cancer GEM by merging 374 personalized GEMs from the Human Pathology Atlas and used it as a platform for systematic investigation of the difference between tumor and normal samples. The reconstructed model revealed the metabolic reprogramming in glutathione as well as the arginine and proline metabolism in response to tumor occurrence. In addition, six genes including ODC1, SMS, SRM, RRM2, SMOX, and SAT1 associated with arginine and proline metabolism were found to be key players in this metabolic alteration. We also investigated these genes in independent colorectal cancer patients and cell lines and found that many of these genes showed elevated level in colorectal cancer and exhibited adverse effect in patients. Therefore, these genes could be promising therapeutic targets for treatment of a specific colon cancer patient group.

  • 123998.
    Zhang, Cheng
    et al.
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Bidkhori, Gholamreza
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Benfeitas, Rui
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Lee, Sunjae
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Arif, Muhammad
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Systems Biology.
    Uhlen, Mathias
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Protein Science, Systems Biology.
    Mardinoglu, Adil
    KTH, Centres, Science for Life Laboratory, SciLifeLab.
    ESS: A Tool for Genome-Scale Quantification of Essentiality Score for Reaction/Genes in Constraint-Based Modeling2018In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 1355Article in journal (Refereed)
    Abstract [en]

    Genome-scale metabolic models (GEMs) are comprehensive descriptions of cell metabolism and have been extensively used to understand biological responses in health and disease. One such application is in determining metabolic adaptation to the absence of a gene or reaction, i.e., essentiality analysis. However, current methods do not permit efficiently and accurately quantifying reaction/gene essentiality. Here, we present Essentiality Score Simulator (ESS), a tool for quantification of gene/reaction essentialities in GEMs. ESS quantifies and scores essentiality of each reaction/gene and their combinations based on the stoichiometric balance using synthetic lethal analysis. This method provides an option to weight metabolic models which currently rely mostly on topologic parameters, and is potentially useful to investigate the metabolic pathway differences between different organisms, cells, tissues, and/or diseases. We benchmarked the proposed method against multiple network topology parameters, and observed that our method displayed higher accuracy based on experimental evidence. In addition, we demonstrated its application in the wild-type and ldh knock-out E. coli core model, as well as two human cell lines, and revealed the changes of essentiality in metabolic pathways based on the reactions essentiality score. ESS is available without any limitation at https://sourceforge.net/projects/essentiality-score-simulator.

  • 123999.
    Zhang, Cheng
    et al.
    Microsoft Res, Cambridge CB1 2FB, England..
    Butepage, Judith
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL.
    Kjellström, Hedvig
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL.
    Mandt, Stephan
    Advances in Variational Inference2019In: IEEE Transaction on Pattern Analysis and Machine Intelligence, ISSN 0162-8828, E-ISSN 1939-3539, Vol. 41, no 8, p. 2008-2026Article in journal (Refereed)
    Abstract [en]

    Many modern unsupervised or semi-supervised machine learning algorithms rely on Bayesian probabilistic models. These models are usually intractable and thus require approximate inference. Variational inference (VI) lets us approximate a high-dimensional Bayesian posterior with a simpler variational distribution by solving an optimization problem. This approach has been successfully applied to various models and large-scale applications. In this review, we give an overview of recent trends in variational inference. We first introduce standard mean field variational inference, then review recent advances focusing on the following aspects: (a) scalable VI, which includes stochastic approximations, (b) generic VI, which extends the applicability of VI to a large class of otherwise intractable models, such as non-conjugate models, mean field approximation or with atypical divergences, and (d) amortized VI, which implements the inference over local latent variables with inference networks. Finally, we provide a summary of promising future research directions.

  • 124000.
    Zhang, Cheng
    et al.
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Ek, Carl Henrik
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Damianou, Andreas
    The University of Sheffield.
    Kjellström, Hedvig
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Factorized Topic Models2013Conference paper (Refereed)
    Abstract [en]

    In this paper we present a modification to a latent topic model, which makes themodel exploit supervision to produce a factorized representation of the observeddata. The structured parameterization separately encodes variance that is sharedbetween classes from variance that is private to each class by the introduction of anew prior over the topic space. The approach allows for a more efficient inferenceand provides an intuitive interpretation of the data in terms of an informative signaltogether with structured noise. The factorized representation is shown to enhanceinference performance for image, text, and video classification.

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