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  • 122751. Zhu, M-Y
    et al.
    Jones, T
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Modelling study of slag foaming by chemical reactio2001Ingår i: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, s. 51-56Artikel i tidskrift (Refereegranskat)
  • 122752.
    Zhu, Ning
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Design, Fabrication and Characterization of Planar Lightwave Circuits Based on Silicon Nanowire Platform2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Optical devices based on Planar Lightwave Circuit (PLC) technology have well been studied due to their inherited advantages from Integrated Circuits (IC), such as: small size, high reliability, mass production and potential integration with microelectronics. Among all the materials, silicon nanowire platform gains more and more interest. The large refractive index difference between core and cladding allows tremendous reduction of the component size. This thesis studies theoretically and experimentally some integrated optical devices based on silicon nanophotonic platform, including echelle grating demultiplexers and photonic crystals.

    Some of the numerical methods are introduced first. Scalar integral diffraction method is efficient for calculating the diffraction efficiency of gratings. Beam propagation method and finite-difference time-domain method are also introduced, for simulating the light propagation along the devices.

    The fabrication technology and characterization methods are described. The fabrication steps involve: plasma assisted film deposition, E-beam lithography, RIE-etching. All these steps are proceeded under cleanroom environment. The characterization is mainly based on two methods: end-fire coupling and vertical grating coupling. The grating coupler is more efficient compared with the butt-coupling between fiber and nanowires, but is worse solution for final packaging.

    Two types of components have been realized and characterized with the above technology. The echelle grating demultiplexer is one of the key components in WDM networks. A method for increasing the diffraction efficiency based on total internal reflection is applied, and a significant improvement of the diffraction efficiency of more than 3dB is achieved. A novel cross-order echelle grating-based triplexer, a bidirectional transceiver for application in the Passive Optical Networks (PON), has been designed and fabricated, which can multi/demultiplex three channels located at 1310nm, 1490nm and 1550nm. Polarization dependence issue of echelle grating demultiplexers has been studied. Two polarization compensation schemes have been proposed, which are for the first time polarization insensitive designs of echelle grating demultiplexers based on silicon nanowire platform.

    Photonic crystal devices are also addressed in the thesis. There has been little research on the photonic crystal cavity based on pillar type. A silicon pillar type photonic crystal cavity has been fabricated with the measured Q value as high as about 104, and with an extremely high sensitivity for the changing of the background material or the effective diameter of the pillars. This kind of structure has the advantage on sensing applications compared to the air-hole type structure.

  • 122753.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Dai, Daoxin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    A hybrid modeling for the theoretical analysis of reflections in a multimode-interference coupler based on silicon-on-insulator nanowires2008Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 281, nr 11, s. 3099-3104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A hybrid method combining the three-dimensional (3D) beam propagation method (BPM) and a 3D finite-difference time-domain (FDTD) method is presented for the simulation of multimode-interference (MMI) couplers based on silicon-on-insulator (SOI) nanowires. This hybrid method makes it possible to have a robust analysis for the reflection properties while avoiding a time-consumed computation with a simplex 3D-FDTD simulation. The reflected power is sensitive to both the length and the width of the MMI coupler and thus one should choose the optimal values for good self-imaging. Furthermore, the reflection could be reduced by introducing tapers between the MMI section and the access waveguides.

  • 122754.
    Zhu, Ning
    et al.
    E China Univ Sci & Technol, Key Lab Adv Mat, Shanghai 200237, Peoples R China.;E China Univ Sci & Technol, Inst Fine Chem, Shanghai 200237, Peoples R China..
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wang, Yuan
    Chinese Acad Sci, Key Lab Photochem Convers & Optoelect Mat, Tech Inst Phys & Chem, Beijing 100190, Peoples R China..
    Ma, Xiang
    E China Univ Sci & Technol, Key Lab Adv Mat, Shanghai 200237, Peoples R China.;E China Univ Sci & Technol, Inst Fine Chem, Shanghai 200237, Peoples R China..
    Photo-responsive chiral cyclic molecular switches based on stiff stilbene2016Ingår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 125, s. 259-265Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two novel photo-responsive chiral cyclic molecular switches constituted of stiff stilbene and binaphthyl moieties connected through alkyl chains of different length were fabricated. The cyclization synthetic strategy employed herein made it convenient to obtain the pure Z isomers rather than Z/E isomer mixtures. The detailed photo-switching behaviors of target compounds were studied by the UV-Vis absorption and circular dichroism spectra in dichloromethane. The twist angles of the binaphthyl of the switches were able to be reversibly modulated by Z/E isomerization of stiff stilbene unit under alternative UV light stimuli and influenced by the length of alkyl chain to some extent.

  • 122755.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Cross-Order Echelle Grating Triplexer Based on Amorphous Silicon Nanowire Platform2008Ingår i: 2008 7TH INTERNATIONAL CONFERENCE ON THE OPTICAL INTERNET (COIN), NEW YORK: IEEE , 2008, s. 37-38Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present fabrication and measurement results of an ultracompact silicon-on-insulator-based echelle-grating triplexer, which uses different diffraction orders to cover a large spectral range from 1.3 mu m to 1.5 mu m, with a footprint of 150 mu m x 200 mu m.

  • 122756.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Design of a polarization-insensitive echelle grating demultiplexer based on silicon nanophotonic wires2008Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 20, nr 9-12, s. 860-862Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A polarization-insensitive design of an echelle grating (or etched diffraction grating) demultiplexer based on silicon nanowires is proposed in the present letter, by introducing a polarization compensation area in its free propagation region. The polarization-dependent wavelength shift of the present device has been compensated at the whole spectral range. For a design with nine channels and 10-nm channel spacing, when the wavelength shift at the central channel 1550 nm is. completely compensated, the wavelength shifts of the two edge channels are only 0.14 and 0.15 nm, which are acceptable.

  • 122757.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Etched diffraction grating demultiplexers based on amorphous silicon nanowire platform2008Ingår i: 2008 Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, AOE 2008, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present some theoretical and experimental results of Etched Diffraction Grating demultiplexer based on amorphous silicon nanowire platform, including issues with polarization sensitivity, diffraction efficiency and an application to triplexer.

  • 122758.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES).
    Total internal reflection type echelle grating demultiplexer based on amorphous silicon nanowire platform2008Ingår i: Proceedings of SPIE - The International Society for Optical Engineering, Hangzhou, 2008, Vol. 7134Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we present measurement results of an ultracompact echelle-grating demultiplexer based on silicon-on-insulator nanowire platform, in which we introduced a total internal reflection design of the grating facets to improve the diffraction efficiency. An average increase of the diffraction efficiency with 3.7dB is observed for the 3 channels compared to a normal design.

  • 122759.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Experimental demonstration of a cross-order echelle grating triplexer based on an amorphous silicon nanowire platform2009Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, nr 3, s. 383-385Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the design, fabrication, and characterization of an ultracompact silicon-on-insulator-based echelle grating triplexer. It is based on the cross-order design, which utilizes different diffraction orders to cover a large spectral range from 1.3 to 1.5 mu m with three channels located at 1310, 1490, and 1550 nm and with a footprint of 150 mu m X 130 mu m.

  • 122760.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wang, Zhechao
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Bragg grating-assisted optical triplexer using two silicon nanowire-based directional couplers2009Ingår i: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009, s. 5377094-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A triplexer based on silicon nanophotonic wire structure consisting of two Bragg grating-assisted directional couplers is proposed. The device has low loss, low crosstalk, and a footprint of only 210 x40 μm, The 1-dB bandwidth for the three channels located at 1310, 1490 and 1550 nm are 110, 20, and 20 nm, respectively.

  • 122761.
    Zhu, Rui
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Gidofalvi, Gyözö
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    GPS-based Crowd Sourced Intelligent Traffic Information Hub2013Ingår i: Proceedings of the 26th International Cartographic Conference / [ed] Manfred F. Buchroithner, ICC International Cartographic Association , 2013, s. 669-670Konferensbidrag (Refereegranskat)
    Abstract [en]

    Congestion is a major problem in most metropolitan areas and given the increasing rate of urbanization it is likely to be an even more serious problem in the rapidly expanding mega cities. Some well know negative effects of congestion include: 1) the economic losses and quality of life degradation that result from the increased and unpredictable travel times, 2) the increased level of carbon footprint that vehicles idling in congestions leave behind, and 3) the increased number of traffic accidents that are direct results of the stress and fatigue of drivers that are stuck in congestion.

    One possible method to combat congestion is provide intelligent traffic management systems that can in a timely manner inform drivers about current or predicted traffic congestion that is relevant to them on their journeys. This this extent, the present paper proposes a scalable, grid-based intelligent traffic information hub that facilitates the manual definition and/or automatic detection of abnormal traffic condition events, e.g., accidents or congestion, and in advance informs drivers about events that will likely be relevant to them on their journey, thereby allowing the divers or their onboard navigation units to alter their paths as needed.

    The proposed system achieves the above described functionality through the following methodology. The system, without loss of generality, adopts a grid-based discretization of space, which by changing the resolution of the grid allows the system to scale in terms of it computation cost and the geographical level of detail of traffic information that it manages. The system derives traffic information from the continuous stream of grid-based position and speed reports that it receives from the vehicles. In particular, the system in an online fashion 1) summarizes Current (grid-based) Traffic Flow Statistics (CTFS), i.e., it records for each grid cell g from each neighboring grid cell n, the mean and standard deviation of the speeds of the vehicles that are currently located in g and have entered g from n; and 2) efficiently incorporates the CTFS into compressed Historical (grid-based) Traffic Flow Statistics (HTFS) using incremental statistics. Simultaneously, using a sliding window model, the system also 1) maintains the Recent (grid-based) Trajectories (RT) of the vehicles; 2) extracts Recent (gridbased) Mobility Statistics (RMS), i.e., it records for each destination grid cell d, for each neighboring grid cell n of g, and for each possible source grid cell s, the number of vehicles that (i) are currently in d, (ii) have entered d from n, and (iii) have a RT that has passed through s; and 3) efficiently incorporates the RMS into compressed Historical (grid-based) Mobility Statistics (HMS) using incremental statistics. To capture the temporal variability in traffic flow and mobility patterns at different scales, the system through temporal domain projections maintains day-of-week and hour-ofday based aggregations of HTFS and RMS. Then, the system classifies a grid cell g to be congested from the direction of a neighboring grid cell n if the current mean speed of vehicles that entered the grid cell g from the direction of n is below the normal according to the temporally relevant HFS. Finally, based on the temporally relevant HMS, the system sends out congestion notifications to vehicles that are likely to be effected in the future part of their journey by these congestions, i.e., the system sends out a congestion notification (g,n) to a vehicle v that is currently located in some grid cell s from which the likelihood of v moving to g through n within the prediction horizon is above a user-defined threshold.

    Extensive empirical evaluations on large sets of realistically simulated trajectories of vehicles illustrate that the above described methodology and its simple SQL-based implementation in a relational database system is scalable and effective. In particular, the execution time of- and the space used by the system scales linearly with the input size (number of concurrently moving vehicles) and the method’s mutually dependent parameters (grid resolution r and RT length l) that jointly define a spatio-temporal resolution. Within the area of a large city (40km by 40km), assuming a 60km/h average vehicle speed, the system, running on a single personal computer, can manage the described congestion detection and one-minute-ahead notification tasks within real-time requirements for 15 thousand and 2.5 million concurrently moving vehicles for spatio-temporal resolutions (r=62.5m, l=17) and (r=4km,l=2), respectively. Finally, the proposed method, for all spatio-temporal resolutions and prediction horizons, significantly outperforms in terms of notification accuracy the grid-based baseline method, which sends non-directional congestion notifications based on the recent linear movement tendencies of vehicles. 

  • 122762.
    Zhu Ryberg, Yingzhi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Wood Hydrolysate for Renewable Products2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

     

    Förnyelsebar biomassa har använts under lång tid för olika ändamål, från mat till industriprodukter. En stor familj av heteropolysackarider är hemicellulosa som har visat en potential i många applikationer, t. ex, inom medicin, jordbruket och förpackning industrin. För att utvinna renad hemicellulosa, krävs komplicerade processer, vilket är opraktiskt och för kostsant för många industriella tillämpningar. I detta arbete har vi använt ett hydrolysat som utvinns utan omfattande upprening från en flytande sidoström i massaindustrin. Detta barrveds hydrolysat är rikt på hemicellulosan, O-acetylerad galactoglucomannan (AcGGM) och innehåller även en del lignin.

    Filmer och beläggningar skapades genom blandning av detta hydrolysat med två andra polysackarider samkomponenter; karboximetylcellulosa (CMC) och kitosan. Olika formuleringar med varierade koncentrationer och kompositioner utvecklades. Dessutom framställdes motsvarande formuleringar av AcGGM. Filmerna och beläggningarna analyserades med avseende på mekaniska egenskaper, kemisk struktur, vattenånga- och syrebarriäregenskaper. Kitosan, som samkomponent, förbättrade de mekaniska egenskaperna bäst medan CMC gav bäst syrebarriäregenskaper vid såväl 50% som 80% relativ fuktighet. Hydrolysat-baserade filmer hade betydligt lägre syrepermeabilitet (OP) än AcGGM-baserade filmer. För att förstå varför mindre renat hydrolysat gav bättre syrebarriäregenskaper än upprenad AcGGM, utvecklades en kombinerat teoretisk-analytisk modell. Beräkningar baserade på Hansens löslighetsparametersteori (HSP) visade att det finns starka interaktioner mellan lignin och hemicellulosorna i hydrolysatet, och även att CMC var mer kompatibel med hydrolysat/AcGGM än kitosan, vilket ger en starkare affinitet mellan komponenterna och en mer kompakt molekylstuktur, och därmed mindre fri volym i matrisen. Denna tolkning verifieras av positron annihilation lifetime spectra (PALS), som visar att hydrolysat-baserade filmer har en mindre fri volym (hålstorlek) och högre homogenitet än AcGGM-baserade filmer. Även termiska analyser och FTIR verifierade inflytandet och arten av dessa interaktioner.

  • 122763.
    Zhu Ryberg, Yingzhi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Wood hydrolysates- New concepts in renewable material design2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Hydrolysat är processvätskor från träindustrin. Istället för komplicerade utvinningsprocesser av ren hemicellulosa från processvätskor, används här det oförädlade hydrolysatet, som innehåller till största delen hemicellulosa och en del lignin. Den här avhandlingen beskriver hur vi framgångsrikt utvecklade detta hydrolysat till syrgasbarriärfilmer och bestrykningar som kan användas till matförpackningar samt hur modellering av strukturerna och interaktionerna mellan hydrolysatets komponenter kan förutsäga deras prestanda som barriärmaterial.

    Fristående filmer och bestrykningar skapades från blandningar av vedhydrolysat och en samkomponent: antingen kitosan eller karboximetylcellulosa (CMC). Filmerna hade utmärkta syrgasbarriäregenskaper som till och med var bättre än filmer beredda av motsvarande renade hemicellulosa. Hansens löslighetsparametersteori (HSP) påvisade och kvantifierade interaktioner mellan molekylerna i både hydrolysat och hydrolysat-baserade blandningar vilket ger en förståelse för de goda barriäregenskaperna. Vår hypotes var att dessa starka interaktioner ökade affiniteten i matrisen vilket leder till tät molekylär packning och därmed bra syrgasbarriäregenskaper. Med Positron annihiliation lifetime spectroscopy (PALS) uppmättes de fria volymerna i de hydrolysat-baserade matriserna. HSP resultaten, storlek och fördelning av fri volym, samt termisk analys, verifierade hypotesen väl.

    HSP-modellen användes sedan för att prediktera kompositionen hos syrgasbarriärbestrykningar från hydrolysat-baserade blandningar. Genom att använda HSP-modellen, kan interaktionerna mellan olika hydrolysat och CMC beräknas och interaktionerna i matrisen utvärderas. De fria volymerna uppmätta med PALS, syrepermeabilitet (OP)-resultaten var generellt överensstämmande med förutsägelserna från HSP-modellen, vilket visar potentialen för HSP- modellen som verktyg i formuleringen av barriärbestrykningarr för matförpackningar.

    För att utveckla en industriellt realistisk och effektiv process för produktion av hydrolysat-baserade bestrykningar provades flera angreppssätt. Först gjordes bestrykningar manuellt från hydrolysat-baserade blandningar och dessa hade utmärkta syrebarriäregenskaper. Sedan utvecklades en spraytorkningsbeläggningsteknik (SPD) som en reproducerbar, effektiv bestrykningsprocess för hydrolysat utan tillsatser eller andra samkomponenter. Dessutom förbättrade töjbarheten hos bestrykningarna genom tvärbindning med glyoxal vilket i sin tur förbättrade kvalitet och syrgasbariäregenskaperna för bestrykningen. SEM integrerat med en dragprovutrustning gjorde det möjligt att i realtid observeraytan av bestrykningen under deformationsprocessen. Detta gjorde det möjligt att studera de mekaniska egenskaperna för beläggningarna utan inverkan av substratet.

  • 122764.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Conceptual approach to renewable barrier film design based on wood hydrolysate2011Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, nr 4, s. 1355-1362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biomass is converted to oxygen barriers through a conceptually unconventional approach involving the preservation of the biomass native interactions and macromolecular components and enhancing the effect by created interactions With a co-component. A combined calculation/assessment model is elaborated to understand, quantify, and predict which compositions that provide an intermolecular affinity high enough to mediate the molecular packing needed to create a functioning barrier. The biomass used is a wood hydrolysate, a polysaccharide-rich but not highly refined mixture where a fair amount of the native intermolecular and intramolecular hernicelluloses-lignin interactions are purposely preserved, resulting in barriers with very low oxygen permeabilities (OP) both at 50 and 80% relative humidity and, considerably lower OPs than coatings based on the corresponding highly purified spruce hemicellulose, O-acetyl galactoglucomannan (AcGGM). The component interactions and, mutual affinities effectively mediate an immobilization of the chain segments in a dense disordered structure, modeled through the Hansen's solubility parameter concept and quantified on the nanolength scale by positron annihilation lifetime spectrum (PALS).

  • 122765.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Innovative Approaches for Converting a Wood Hydrolysate to High-Quality Barrier Coatings2013Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 16, s. 7748-7757Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An advanced approach for the efficient and controllable production of softwood hydrolysate-based coatings with excellent oxygen-barrier performance is presented. An innovative conversion of the spray-drying technique into a coating applicator process allowed for a fast and efficient coating process requiring solely aqueous solutions of softwood hydrolysate, even without additives. Compared to analogous coatings prepared by manual application, the spray-drying produced coatings were more homogeneous and smooth, and they adhered more strongly to the substrate. The addition of glyoxal to the aqueous softwood hydrolysate solutions prior to coating formation allowed for hemicellulose cross-linking, which improved both the mechanical integrity and the oxygen-barrier performance of the coatings. A real-time scanning electron microscopy imaging assessment of the tensile deformation of the coatings allowed for a deeper understanding of the ability of the coating layer itself to withstand stress as well as the coating-to-substrate adhesion.

  • 122766.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Retrostructural model to predict biomass formulations for barrier performance2012Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, nr 8, s. 2570-2577Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Barrier performance and retrostructural modeling of the macromolecular components demonstrate new design principles for film formulations based on renewable wood hydrolysates. Hardwood hydrolysates, which contain a fair share of lignin coexisting with poly- and oligosaccharides, offer excellent oxygen-barrier performance. A Hansen solubility parameter (HSP) model has been developed to convert the complex hydrolysate structural compositions into relevant matrix oxygen-permeability data allowing a systematic prediction of how the biomass should be formulated to generate an efficient barrier. HSP modeling suggests that the molecular packing ability plays a key role in the barrier performance. The actual size and distribution of free volume holes in the matrices were quantified in the subnanometer scale with Positron annihilation lifetime spectroscopy (PALS) verifying the affinity-driven assembly of macromolecular segments in a densely packed morphology and regulating the diffusion of small permeants through the matrix. The model is general and can be adapted to determine the macromolecular affinities of any hydrolysate biomass based on chemical composition.

  • 122767.
    Zhu, Shanying
    et al.
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Chen, Cailian
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Xu, Jinming
    Arizona State Univ, Ira A Fulton Sch Engn, Tempe, AZ 85281 USA..
    Guan, Xinping
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Xie, Lihua
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Mitigating Quantization Effects on Distributed Sensor Fusion: A Least Squares Approach2018Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 66, nr 13, s. 3459-3474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we consider the problem of sensor fusion over networks with asymmetric links, where the common goal is linear parameter estimation. For the scenario of bandwidth-constrained networks, existing literature shows that nonvanishing errors always occur, which depend on the quantization scheme. To tackle this challenging issue, we introduce the notion of virtual measurements and propose a distributed solution LS-DSFS, which is a combination of a quantized consensus algorithm and the least squares approach. We provide detailed analysis of the LS-DSFS on its performance in terms of unbiasedness and mean square property. Analytical results show that the LS-DSFS is effective in smearing out the quantization errors, and achieving the minimum mean square error (MSE) among the existing centralized and distributed algorithms. Moreover, we characterize its rate of convergence in the mean square sense and that of the mean sequence. More importantly, we find that the LS-DSFS outperforms the centralized approaches within a moderate number of iterations in terms of MSE, and will always consume less energy and achieve more balanced energy expenditure as the number of nodes in the network grows. Simulation results are presented to validate theoretical findings and highlight the improvements over existing algorithms.

  • 122768.
    Zhu, Shaoling
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Experimental Study on Low Power Wireless Sensor Network Protocols with Native IP Connectivity for BuildingA utomation2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The recent development of wired and wireless communication technologiesmake building automation the next battlefield of the Internet of Things. Multiplestandards have been drafted to accommodate the complex environmentand minimize the resource consumption of wireless sensor networks. This MasterThesis presents a thorough experimental evaluation with the latest Contikinetwork stack and TI CC2650 platform of network performance indicators,including signal coverage, round trip time, packet delivery ratio and powerconsumption. The Master Thesis also provides a comparison of the networkprotocols for low power operations, the existing operating systems for wirelesssensor networks, and the chips that operate on various network protocols. Theresults show that CC2650 is a promising competitor for future development inthe market of building automation.

  • 122769.
    Zhu, Wanning
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Multipoint Relay flooding: Network coding improvements2009Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Network coding is a new research area with potential to reduce network resources. With network coding, intermediate nodes forward packets that are linear combinations of previously received packets.

    The type of networks we consider are vehicle mounted mobile tactical radio networks. Tactical communication may be required in areas where pre-deployed base stations are unavailable. Mobile ad hoc networks satisfy this requirement. Due to low antenna heights, network resources are scarce inmobile networks without base stations. Broadcast traffic, which disseminates information network-wide, is very important in tactical mobile networks. Multipoint relay flooding is a well-known technique for efficient distribution of broadcast traffic. It is therefore interesting to evaluate how much network coding can reduce the number of transmissions in a mobile ad hoc network. In this thesis we show that it is possible to further reduce the number of transmissions for Multipoints Relay flooding by using network coding. However, this improvement is largely theoretical - there has been no effort to evaluate this approach in practice.

  • 122770. Zhu, Weizhen
    et al.
    Theliander, Hans
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers, Sweden.
    Precipitation of Lignin from Softwood Black Liquor: An Investigation of the Equilibrium and Molecular Properties of Lignin2015Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, nr 1, s. 1696-1714Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Extracting lignin from black liquor is an attractive option in modern pulp mills as a unit process for a combined biorefinery. The lignin obtained can be utilized as solid fuel or other high-value added products. The precipitation equilibrium of kraft lignin from softwood black liquor was studied in this work. It was found that with decreasing pH and temperature, or increasing ion strength, the solid yield increases. Moreover, precipitated softwood kraft lignin has a higher molecular weight and contains lower amounts of carbohydrates and phenolic groups than lignin precipitated from mixed hardwood/softwood black liquor. The content of methoxyl groups in softwood kraft lignin was found to decrease with increasing precipitation yield. An empirical model for estimating the precipitation yield of lignin was proposed and evaluated.

  • 122771.
    Zhu, Weizhen
    et al.
    Chalmers, Sweden.
    Westman, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers, Sweden.
    Theliander, Hans
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers, Sweden.
    Lignin separation from kraft black liquor by combined ultrafiltration and precipitation: a study of solubility of lignin with different molecular properties2016Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 31, nr 2, s. 270-278Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lignin from wood is by far the largest source of bio-based aromatic raw material. Today a vast amount of lignin is processes and incinerated in kraft pulp mills around the world. One possible option to utilize the energy surplus in a modern kraft pulp mill is to extract lignin from black liquor. Precipitation of lignin is one important step in an extraction process. This study investigates how the molecular size and functional groups of lignin influenced the precipitation yield. Cross-flow filtration was applied to fractionate lignin with different molecular weights from a black liquor, precipitation studies was made on the different fractions. The precipitated lignin was characterized by GPC, HPAEC-PAD and NMR analysis. The results show that it was possible to obtain a more homogenous lignin by fractionation using cross-flow filtration. It was found that the molecular properties of kraft lignin, i.e. molecular weight and functional groups, influenced the yield of lignin precipitation: at the same precipitation condition, lignin fraction with higher molecular weight has higher precipitation yield. Lignin fraction with lower molecular weight contains less amount of carbohydrates and methoxyl groups but higher amount of phenolic groups.

  • 122772. Zhu, Weizhen
    et al.
    Westman, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    Theliander, Hans
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. Chalmers University of Technology, Sweden.
    The molecular properties and carbohydrate content of lignins precipitated from black liquor2015Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, nr 2, s. 143-152Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Precipitation and utilization of lignin from black liquor (BL) offers many promising advantages to modern kraft pulp mills. A novel process, known as "LignoBoost", has recently been introduced as a process for separating lignin from BL; it results in lignins with a low ash and high dry solid content. There is a lack of knowledge regarding the influences of process parameters on the behavior of lignin in the precipitation step. In this study, the yield of precipitated lignin and its average molecular weight (MWt) and carbohydrate content were the focus. Nuclear magnetic resonance (NMR) analysis showed that the lignin yield increased at lower pH and temperatures or when the ion strength of BL was elevated. High yield lignins contained more low MWt components and such lignins have more phenolic OH and methoxy groups. Xylan content of the lignins decreased with decreasing pH and increasing temperature, but glucomannan content was virtually unaffected by the conditions of precipitation.

  • 122773. Zhu, X.
    et al.
    Shen, Y.
    Chen, X.
    Hu, Yue O. O.
    KTH, Skolan för bioteknologi (BIO), Genteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Xiang, H.
    Tao, J.
    Ling, Y.
    Biodegradation mechanism of microcystin-LR by a novel isolate of Rhizobium sp. TH and the evolutionary origin of the mlrA gene2016Ingår i: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 115, s. 17-25Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The frequent presence of microcystin (MC) in eutrophic water bodies worldwide poses a serious threat to ecosystems. Biodegradation has been extensively investigated as a main pathway for MC attenuation, and an mlr-dependent mechanism of MC degradation have been elucidated in detail. However, the evolutionary origin and the distribution of mlr genes in MC-degrading bacteria is poorly understood. In this study, a novel Rhizobium sp. TH, which is the first α-proteobacterial MC-degrading bacterium other than Sphingomonadales, was isolated. Strain TH degraded MC via the mlr-dependent mechanism with a first-order rate constant of 0.18–0.29 h−1 under near-natural conditions. The partial length mlr gene cluster was sequenced, and the function of its key gene, mlrA, was verified by heterologous expression in Escherichia coli. Phylogenetic analyses show that the mlrA gene initially arose in α-proteobacteria by vertical evolution, and the two strains from β- and γ-proteobacteria acquired it by horizontal gene transfer. Therefore, the mlrA gene mainly exists in α-proteobacteria but is seldom present in other bacteria. A pair of primers matching well with mlrA sequences reported so far were designed and could be used to determine the MC-degrading mechanism for novel isolates or to screen for MC-degrading ability among environmental samples.

  • 122774. Zhu, X.
    et al.
    Zou, Rongfeng
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Sun, P.
    Wang, Q.
    Wu, J.
    A supramolecular peptide polymer from hydrogen-bond and coordination-driven self-assembly2018Ingår i: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 9, nr 1, s. 69-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A terpyridine- and guanine-functionalized peptide was developed that could form different morphologies by self-assembly or coordination with Fe2+ in dimethyl sulfoxide. The self-assembly of the peptide is attributed to the G-quartet formation of a guanine moiety and intermolecular terpyridine π-π stacking. Upon the addition of Fe2+, a Fe2+-(terpyridine)2 complex is formed that turns the square-planar self-assembly to a three-dimensional self-assembly. As a consequence, a variety of interesting morphologies and chemical properties were observed. The self-assembled polymers were studied by nuclear magnetic resonance spectroscopy, ultraviolet-visible and fluorescence spectroscopy, viscosity measurement, circular dichroism, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, and atomic force microscopy. This external stimuli driven self-assembly of a peptide may be further applied to drug delivery applications. 

  • 122775.
    Zhu, Xiaoqian
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Coordinated MIMO Precoder EvaluationBased on Measurement in IndoorEnvironment2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In this thesis, we investigate the performance of the coordinated MIMO precoders, using measured channels in indoorvenvironment. Instead of simulated radio propagationvconditions, measured channels are used to evaluate the precoder performance for real-world channels. Our measurement campaign includes several scenarios such as femtocell and “heterogeneous” networks. The study results illustrate that the precoders could reduce the interference significantly and support a high system throughput especially over high SNR where interference is dominant.

    Degree of freedom (DoF) is defined as the maximum number of data stream that could independently coordinate to be transmitted interference-free. Theoretically, the precoders could support 1 DoF per user, while DoF of uncoordinated transmission is 0 per user. Interference Alignment(IA) study arises from information theory of DoF in the interference channel (IC). Three precoding algorithms are investigated to align the interference: maximum sum rate, maxSINR and minWLI. Considering the distributed precoder methods, “maxSINR” always performs better than “minWLI”. Since it tries to maximize the user’s SINR instead of only repressing the interference as “minWLI” does. While “maximum sum rate” is not good at finding an IA like solution that scales well at high SNR. However “maximum sum rate” converges faster than “maxSINR” and “minWLI”.

    Our study about IA feasibility shows that precoding jointly over two subcarriers, using so called frequency extensions, allows 4 users to communicate interference-freeover a 2 × 2 MIMO IC. Without frequency extensions, only 3 users can communicate interference-free.

  • 122776. Zhu, Xuncheng
    et al.
    Ding, Zhizhong
    Punyal, Oscar
    Gross, James
    Design and Implementation of Baseband Algorithms for OFDM-based Wireless Communication Systems2011Ingår i: 7th International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM), 2011, IEEE conference proceedings, 2011, s. 1-5Konferensbidrag (Refereegranskat)
    Abstract [en]

    Orthogonal frequency-division multiplexing (OFDM) is an appropriate solution to combat inter-symbol interference (ISI) caused by multi-path propagation in wireless communications. OFDM-based wireless communication systems become more and more popular and the base-band algorithm is one of the significant parts of the systems. In this paper, we present the design and implementation of base-band algorithms for OFDM-based wireless communication systems. The results show that the designed algorithms are effective for implementation of the system.

  • 122777. Zhu, Y.
    et al.
    Cheng, D.
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Synchronization of a class of networked passive systems with switching topology2007Ingår i: Proceedings of the 46th IEEE Conference on Decision and Control, 2007, s. 2271-2276Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers the output synchronization of a class of networked agents. Each agent is a passive system. Local information, used by each agent to adjust its movement, forms a network with switching adjacent topology. First, we consider the asymptotic stability of nonlinear time-varying switched systems by using multiple Lyapunov function. An extended Lyapunov-like Lemma for switched systems is obtained. Then the result is applied to the output synchronization of a class of networked passive systems with switching topology. A pretty fair sufficient condition is presented.

  • 122778. Zhu, Y.
    et al.
    Engström, P. G.
    Tellgren-Roth, C.
    Baudo, C. D.
    Kennell, J. C.
    Sun, S.
    Billmyre, R. B.
    Schröder, M. S.
    Andersson, A.
    Holm, T.
    Sigurgeirsson, Benjamin
    KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Wu, G.
    Sankaranarayanan, S. R.
    Siddharthan, R.
    Sanyal, K.
    Lundeberg, Joakim
    KTH, Skolan för bioteknologi (BIO), Genteknologi. KTH, Centra, Science for Life Laboratory, SciLifeLab.
    Nystedt, B.
    Boekhout, T.
    Dawson, T.L., Jr.
    Heitman, J.
    Scheynius, A.
    Lehtiö, J.
    Proteogenomics produces comprehensive and highly accurate protein-coding gene annotation in a complete genome assembly of Malassezia sympodialis2017Ingår i: Nucleic Acids Research, ISSN 0305-1048, E-ISSN 1362-4962, Vol. 45, nr 5, s. 2629-2643Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Complete and accurate genome assembly and annotation is a crucial foundation for comparative and functional genomics. Despite this, few complete eukaryotic genomes are available, and genome annotation remains a major challenge. Here, we present a complete genome assembly of the skin commensal yeast Malassezia sympodialis and demonstrate how proteogenomics can substantially improve gene annotation. Through long-read DNA sequencing, we obtained a gap-free genome assembly for M. sympodialis (ATCC 42132), comprising eight nuclear and one mitochondrial chromosome. We also sequenced and assembled four M. sympodialis clinical isolates, and showed their value for understanding Malassezia reproduction by confirming four alternative allele combinations at the two mating-type loci. Importantly, we demonstrated how proteomics data could be readily integrated with transcriptomics data in standard annotation tools. This increased the number of annotated protein-coding genes by 14% (from 3612 to 4113), compared to using transcriptomics evidence alone. Manual curation further increased the number of protein-coding genes by 9% (to 4493). All of these genes have RNA-seq evidence and 87% were confirmed by proteomics. The M. sympodialis genome assembly and annotation presented here is at a quality yet achieved only for a few eukaryotic organisms, and constitutes an important reference for future host-microbe interaction studies.

  • 122779. Zhu, Y.
    et al.
    Hjalmarsson, Håkan
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    The Box-Jenkins Steiglitz-McBride algorithm2016Ingår i: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 65, s. 170-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An algorithm for identification of single-input single-output Box-Jenkins models is presented. It consists of four steps: firstly a high order ARX model is estimated; secondly, the input-output data is filtered with the inverse of the estimated disturbance model; thirdly, the filtered data is used in the Steiglitz-McBride method to recover the system dynamics; in the final step, the noise model is recovered by estimating an ARMA model from the residuals of the third step. The relationship to other identification methods, in particular the refined instrumental-variable method, are elaborated upon. A Monte Carlo simulation study with an oscillatory system is presented and these results are complemented with an industrial case study. The algorithm can easily be generalized to multi-input single-output models with common denominator.

  • 122780. Zhu, Y.
    et al.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Wang, W.
    Chen, X.
    On the iron oxides between railway wheels and rails using laboratory tests2015Ingår i: CM 2015 - 10th International Conference on Contact Mechanics of Wheel / Rail Systems, International Conference on Contact Mechanics of Wheel , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The contact between railway wheels and rails is influenced by various contaminants. Iron oxides present on both wheel and rail surfaces which constantly affects the wheel?rail adhesion and wear. The paper summarizes some laboratory work investigating the iron oxides between the wheel and rai contact which were previous performed in the authors’ group. A comparison of the contact conditions and application regarding the test rig (pin-on-disc and twin-disc) is also given. The influence of iron oxides on the coefficient of friction, adhesion coefficient and wear rate is presented and discussed. Results indicate iron oxides greatly influence the tribological behavior particularly under the wet condition. The author aims to highlight the importance of the iron oxides which may provide some hints to explain the difference between laboratory tests and field measurements. However, a quantitative study is needed based on controlled environmental conditions due to the complexity and fast transition of iron oxides.

  • 122781. Zhu, Y.
    et al.
    Wu, F.
    Xiong, Q.
    Lu, Zhonghai
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Xie, C.
    ALARM: A Location-Aware Redistribution Method to Improve 3D FG NAND Flash Reliability2017Ingår i: 2017 IEEE International Conference on Networking, Architecture, and Storage, NAS 2017 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, artikel-id 8026841Konferensbidrag (Refereegranskat)
    Abstract [en]

    3D NAND flash memory is enjoying an increasing popularity as it dramatically increases the bit density, presenting a grand opportunity to satisfy the growing demand on the storage capacity. However, this vertically stacked structure also introduces more serious read disturb problems compared with planar flash devices. Characterization results show that the read disturb errors on 3D floating gate (FG) MLC NAND flash chips exhibit a large discrepancy on the locations and types of pages, implying that pages should not be treated equally when designing migration schemes. This paper makes a thorough observation on read access characteristics by analyzing contemporary workloads collected from a wide range of applications with various read ratios. Based on the characterization results, we build a read disturb error model and propose a location-aware redistribution method (ALARM) that utilizes the intrinsic characteristics of the 3D floating gate NAND flash and redistributes read-hot pages to locations inducing less read disturb errors to improve its reliability. We implement the read disturb error model and our proposed design on an event-driven simulator, and the experimental results show that ALARM can reduce the maximum and average raw bit error rates (RBERs) by up to 99.49% and 91.80% with an operation overhead of 0.70%.

  • 122782.
    Zhu, Yafeng
    KTH, Skolan för bioteknologi (BIO).
    Identification and visualization of splice variants in shotgun proteomics data by Alternative Splicing Database2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    It has been shown in many studies that alternative splicing plays an important role in functional regulation and is associated with many neurological disorders and cancers. Current methods to detect splice variants are computational prediction by ESTs clustering and experimental approaches such as RNA probe microarray. These methods are only focusing on the the RNA level. But due to post transcriptional modification on pre-mRNA molecules, there is a weak correlation between mRNA abundance and protein expressin. Therefore, it is important to find evidence of these functioinally important splice variants at the protein level. Shotgun proteomics has become a favorable tool to do large scale identification of proteins. Recently, a tool called Protein Quantification and Peptide Quality Control (PQPQ) was develope to enhance information output from shotgun proteomics data and to detect protein variants. Here, we present a downstream program, SpliceView, a tool for analyzing and visualizing the output from PQPQ for finding splice variants. Proteomics data of A431 cell line was used to exemplify available functions of SpliceView.

  • 122783.
    Zhu, Yaoxuan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Huang, Xiaoting
    IMPROVEMENT OF COMPACTED GRAPHITE IRON DRILLING OPERATIONS WITH CUSTOMIZED CUTTING FLUID2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Inom bilindustrin används ofta kompaktgrafitjärn eftersom det har hög hållfasthet. Att bearbeta kompaktgrafitjärn är utmanade främst pga att det krävs hög temperatur och mycket kraft för att skära/borra materialet. I den här avhandlingen undersöks hur olika skärvätskor påverkar bearbetning av kompaktgrafitjärn under borrning. Skärvätskor där proportionerna mellan den alkaliska delen och oljedelen har anpassats, jämfördes mot traditionella emulsionsvätskor. Oljan i den kundanpassade skärvätskan kan hjälpa till att minska friktionskraften i bearbetningsoperationen. Fasförslitningsmätningen visade att det inte finns någon signifikant skillnad mellan skärvätskorna. Tryckraftsmätningarna visade emellertid att det kundanpassade skärvätskorna effektivt kunde reducera skärkraften med nästan 20%. Genom att använda de anpassade skärvätskorna kan man köra med högre mattningshastighet, reducera cykeltiden eller använda samma processparametrar men med mindre energianvändning.

  • 122784.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Adhesion in the wheel-rail contact2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    To attract more customers and compete with other modes of transportation, railway transport needs to ensure safety, punctuality, high comfort, and low cost; wheel–rail adhesion, i.e., the transmitted tangential force in the longitudinal direction during driving and braking, plays an important role in all these aspects. Adhesion needs to be kept at a certain level for railway operation and maintenance. However, wheel−rail contact is an open system contact. Different contaminants can present between the wheel and rail surfaces, forming a third-body layer that affects the adhesion. Prediction of wheel–rail adhesion is important for railway operations and research into vehicle dynamics; however, this prediction is difficult because of the presence of contaminants.

    This thesis deals with wheel–rail adhesion from a tribological perspective. The five appended papers discuss wheel–rail adhesion in terms of dry conditions, lubricated conditions, leaf contamination, iron oxides, and environmental conditions. The research methodologies used are numerical modelling, scaled laboratory experiments, and field tests. The research objective is to understand the mechanisms of the adhesion loss phenomenon. 

    A numerical model was developed to predict wheel–rail adhesion based on real measured 3D surfaces. Computer simulation indicates that surface topography has a larger impact on lubricated than on dry contacts. Plastic deformation in asperities is found to be very important in the model. Ball-on-disc tests indicate that water can give an extremely low adhesion coefficient on smooth surfaces, possibly due to surface oxidation. Investigation of lubricated contacts at low speed indicates that oil reduces the adhesion coefficient by carrying a normal load, while adhesion loss due to water depends on the surface topography, water temperature, and surface oxidation. A field investigation indicates that leaves reduce the friction coefficient because of the chemical reaction between leaves and bulk materials. The thickness of the surface oxide layer was found to be an essential factor determining adhesion reduction. Pin-on-disc experiments found a transition in the friction coefficient with regard to the relative humidity, due to a trade-off between the water molecule film and the hematite on the surface. 

  • 122785.
    Zhu, Yi
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Adhesion in the wheel-rail contact under contaminated conditions2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Railway vehicles require a certain level of adhesion between wheel and rail to operate efficiently, reliably, and economically. Different levels of adhesion are needed depending on the vehicle running conditions. In the wheel tread–railhead contact, the dominant problem is low adhesion, as low adhesion on the railhead negatively affects railway operation: on one hand, the vehicle will lose traction resulting in delay when driving on low-adhesion tracks; on the other hand, low adhesion during deceleration will extend the braking distance, which is a safety issue.

    This thesis examines the influence of several contaminants, i.e., water, oil, and leaves, on the adhesion in the wheel tread–railhead contact. This study will improve our knowledge of the low-adhesion mechanism and of how various contaminants influence adhesion. The thesis consists of a summary overview of the topic and three appended papers (AC).

    Papers A and B focus mainly on water and oil contamination examined using two methods, numerical simulation and lab testing. In paper A, real measured wheel and rail surfaces, low- and high-roughness surfaces, along with generated smooth surfaces are used as input to the numerical model for predicting the adhesion coefficient. Water-lubricated, oil-lubricated, and dry contacts are simulated in the model. In the research reported in paper B, scaled testing using a mini traction machine (MTM) was carried out to simulate the wheel–rail contact under lubricated conditions. Two types of disc surfaces of different roughnesses were run at different contact pressures and temperatures. A stylus machine and atomic force microscopy (AFM) were used to measure the surface topography. A study of leaf contamination on the railhead surface, based on field testing, is presented in paper C. Railhead surface samples were cut and the friction coefficient was measured on five occasions over the course of a year. Electron spectroscopy for chemical analysis (ESCA) and glow discharge optical emission spectrometry (GD-OES) were used to detect the chemical composition of the leaf-contamination layer on the railhead surface.

    The main conclusion of the thesis is that different contaminants reduce the adhesion coefficient in different ways. Oil reduces the adhesion coefficient by carrying the normal force due to its high viscosity. Water can reduce the adhesion coefficient to different degrees depending on the surface topography and water temperature. The mixture of an oxide layer and water contamination may have an essential impact. A leaf-formed blackish layer causes low adhesion by means of a chemical reaction between the leaves and bulk material. The thickness of the friction-reducing oxide layer predicts the friction coefficient and the extent of leaf contamination.

  • 122786.
    Zhu, Yi
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE).
    Extracting masts of overhead supply and street lights from point cloud2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Regelbunden inspektion och dokumentation för järnvägstillgångar är nödvändig för att övervaka trafikmiljön. Mobil Laser Scanning (MLS) gör det möjligt att samla in mycket exakt geografisk information om järnvägsmiljöer i form av punktmoln och en automatisk metod för att extrahera intresserade objekt från punktmoln är nödvändigt för att undvika för mycket manuellt arbete.

    I det här projektet samlades punktmoln längs en järnväg i Saltsjöbanan av MLS och bearbetades för att extrahera intresserade objekt från den. Huvudsyftet med projektet är att utveckla ett arbetsflöde för automatisk utvinning av kontaktledningsstolpar och gatubelysningsstolpar från studieområdet.

    Forskare har nyligen föreslagit olika metoder för objektutvinning som baseras på modell, form, semantisk och maskininlärning. I detta arbete har flera olika metoder för objektutvinning undersökts och slutligen valdes Support Vector Machine (SVM) för klassificering. Ett antal tillgängliga programvaror har utvärderats. TerraScan och CloudCompare valdes för förbehandling, och huvuddelen gjordes i MATLAB.

    Den föreslagna metoden består av 4 steg: förbehandling, voxelisering och segmentering, funktionen beräkning, klassificering och validering. Metoden beräknar funktioner för att beskriva varje objekt segmenterat från punktmoln och lär ut från de manuellt klassificerade objekten för att träna en klassificerare.

    Studieområdet delades in i träningsdata och validering av data. SVM-klassificeraren utbildades med träningsdata och utvärderades genom att validera data.

    I klassificeringen klassificerades 90,84% av kontaktledningsstolparna och 67,65% av belysningsstolparna korrekt. Det fanns vissa förluster av objekt under förbehandling och segmentering. Inkluderat förlusten i förbehandling och segmentering upptäcktes 87,5% av kontaktledningsstolparna och 53,49% av belysningsstolparna korrekt. Det något sämre resultatet vid detektion av belysningsstolpar beror på att dessa är placerade i en svårare miljö med närhet till andra objekt och inte minst vegitation. Att automatiskt detektera objekt i sådan miljö baserat på enbart laserdata är svårt vilket medförde en relativt låg noggrannhet.

  • 122787.
    Zhu, Yi
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi. Zhejiang University, The State Key Lab of Fluid Power Transmission and Control, China .
    Lyu, Yezhe
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Olofsson, Ulf
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.), Tribologi.
    Mapping the friction between railway wheels and rails focusing on environmental conditions2015Ingår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 324, s. 122-128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The coefficient of friction between railway wheels and rails is crucial to the railway adhesion, further greatly affecting railway operation and maintenance. Since the wheel-rail system is an open system, the coefficient of It is significantly influenced not only by various types of contaminants but also by environmental conditions. This paper conducted a set of pin-on-disc tests measuring the coefficient of friction focusing on the influence of environmental conditions (relative humidity and temperature). In addition, influences of iron oxides, leaves and glycol/water mixtures on the coefficient of friction were also studied. The friction results are shown in the form of friction maps. Results indicate that it oxides on the surfaces can prevent the samples from large friction reduction particularly at the low temperature. The friction mechanism is also discussed with the help of scanning electron microscopy photos. On the other hand, effects of leaves in reducing the coefficient of friction become limited with the presence of the glycol/water mixture.

  • 122788.
    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.

  • 122789.
    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.

  • 122790.
    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.

  • 122791.
    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.

  • 122792.
    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.

  • 122793.
    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.

  • 122794.
    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)
  • 122795.
    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.

  • 122796. 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)
  • 122797.
    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.

  • 122798.
    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.

     

  • 122799. 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.

  • 122800. 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.

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