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  • 122901.
    Yang, Xi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Migration resistant glucose esters as bioplasticizers for polylactide2015Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 132, nr 18, artikkel-id 41928Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Environmental and sustainability issues have catalyzed efforts to replace traditional polymer additives with biobased alternatives. Glucose pentaacetate (GPA) and sucrose octaacetate (SOA) as model commercial saccharide esters and three synthesized glucose hexanoate esters (GHs) were evaluated as bioplasticizers for polylactide (PLA). For the GHs different reaction times were utilized to reach plasticizers with different number of hexanoate groups to establish how the degree of substitution influences miscibility and migration resistance of the plasticizers. The synthesized GHs, GPA, and SOA all showed good miscibility with PLA. Largest improvements in strain at break were observed for the PLA films containing GH plasticizers. These films also exhibited simultaneous increase in stress at break as compared to plain PLA. The GH plasticizers had low tendency to migrate during aging in water and this migration resistance increased with increasing degree of substitution. The GHs are, thus, promising plasticizer alternatives for bioplastics as they also retain the biodegradable nature of these biobased materials.

  • 122902.
    Yang, Xi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Microwave-Assisted Reaction in Green Solvents Recycles PHB to Functional Chemicals2014Inngår i: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 2, nr 9, s. 2198-2203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient microwave-assisted process for chemical recycling of poly(3-hydroxybutyrate) (PHB) in green solvents was demonstrated. Previously, PHB has been thermally recycled to crotonic acid and unsaturated oligomers. Our aim was to utilize green solvents (water, methanol, and ethanol) under alkaline conditions to achieve fast hydrolysis and monomeric or oligomeric degradation products with carboxyl and hydroxyl or methoxy or ethoxy end groups. Preliminary screening confirmed that the most efficient degradation process was obtained in alkaline methanol. In addition, sample amount, sodium hydroxide concentration, and degradation time all influenced the degradation process and final degree of degradation. Comparison with pure thermal degradation clearly demonstrated the effectiveness of the microwave-assisted process as the time and temperature needed for complete degradation was significantly reduced. Several characterization techniques were utilized for mapping the degradation processes and resulting degradation products. After optimization of the process, complete degradation of PHB to monomeric degradation products (3-hydroxybutanoic acid, 3-methoxybutanoic acid, and crotonic acid) was reached after only 20 min of microwave heating at 110 degrees C. Functional chemicals for synthesis or modification of biopolymers are thus obtainable from microwave-assisted degradation of PHB in green solvents. This offers new possibilities for retaining the material value of PHB via chemical recycling.

  • 122903.
    Yang, Xi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Xu, Huan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hakkarainen, Minna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Poly(lactide)-g-poly(butylene succinate-co-adipate) with High Crystallization Capacity and Migration Resistance2016Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 9, nr 5, artikkel-id 313Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Plasticized polylactide (PLA) with increased crystallization ability and prolonged life-span in practical applications due to the minimal plasticizer migration was prepared. Branched plasticized PLA was successfully obtained by coupling poly(butylene succinate-co-adipate) (PBSA) to crotonic acid (CA) functionalized PLA. The plasticization behavior of PBSA coupled PLA (PLA-CA-PBSA) and its counterpart PBSA blended PLA (PLA/PBSA) were fully elucidated. For both PLA-CA-PBSA and PLA/PBSA, a decrease of Tg to around room temperature and an increase in the elongation at break of PLA from 14% to 165% and 460%, respectively, were determined. The crystallinity was increased from 2.1% to 8.4% for PLA/PBSA and even more, to 10.6%, for PLA-CA-PBSA. Due to the inherent poor miscibility between the PBSA and PLA, phase separation occurred in the blend, while PLA-CA-PBSA showed no phase separation which, together with the higher crystallinity, led to better oxygen barrier properties compared to neat PLA and PLA/PBSA. A higher resistance to migration during hydrolytic degradation for the PLA-CA-PBSA compared to the PLA/PBSA indicated that the plasticization effect of PBSA in the coupled material would be retained for a longer time period.

  • 122904.
    Yang, Xiaobin
    KTH, Skolan för industriell teknik och management (ITM), Tillämpad maskinteknik (KTH Södertälje).
    Market estimates in China for Swedish health food using stochastic approach2011Independent thesis Advanced level (degree of Master (Two Years)), 10 poäng / 15 hpOppgave
  • 122905.
    Yang, Xiaofan
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Enterprise’ E-invoicing Adoption in China2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis is an empirical investigation project that has been carried out in cooperation with Trustweaver AB. The purpose is to identify the key factors that influence the adoption of electronic invoicing in Chinese enterprises. A background study on global e-invoicing adoption and current e-invoicing development in China is conducted. A research model integrated by the diffusion of innovation theory, the technology, organization, and environment framework and Iacovou et al. (1995) model is postulated.The research model consists of three constructs which are technological context, organizational context and environmental and external context. Key factors that are analyzed in the research are perceived benefits and barriers, leader’s attitude, technology and financial readiness, top management support, partner and competitive pressure, government pressure, and regulatory concern. Based on the research model and the theoretical basis for each of the explanatory variables, nine hypotheses stating the relationships between the key factors and enterprises’ e-invoicing adoption intention are proposed.An online survey has been conducted and 72 responses have been collected from management of Chinese enterprises. Descriptive statistics and paired-samples T test are used to describe the values distribution and test the difference between the variables. Factor analysis and reliability test are performed to evaluate the validity of variables and assess the stability of constructs. Linear regression analysis is employed in order to examine six proposed hypotheses, i.e. the relationships between technological and organizational characteristics and enterprises’ adoption of e-invoicing.The results generally offer support for the research model and eight of the hypotheses hold while one rejects. Analysis has shown that perceived barriers, management attitude and support, technology and financial readiness are the determinant factors of e-invoicing adoption. Results also indicate that environmental and external factors strongly influence enterprises’ adoption decision, whereby government pressure and policy support have the most significant effect. The findings could be taken account to improve e-invoicing diffusion in China. Some strategies are developed in the study to promote enterprises’ adoption of e-invoicing.

  • 122906.
    Yang, Xiaohu
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Energiprocesser. Institute of the Building Environment & Sustainability Technology, School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China; School of Sustainable Development of Society and Technology, Mälardalen University, 721 23 Västerås, Sweden.
    Bai, Q.
    Guo, Z.
    Niu, Z.
    Yang, C.
    Jin, L.
    Lu, T. J.
    Yan, J.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Energiprocesser. School of Sustainable Development of Society and Technology, Mälardalen University, 721 23 Västerås, Sweden.
    Comparison of direct numerical simulation with volume-averaged method on composite phase change materials for thermal energy storage2018Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 229, s. 700-714Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Melting heat transfer in open-cell metal foams embedded in phase-change materials (PCMS) predicted by the volume-averaged method (VAM) was systematically compared with that calculated using direct numerical simulation (DNS), with particular attention placed upon the contribution of natural convection in the melt region to overall phase change heat transfer. The two-temperature model based on the assumption of local thermal non-equilibrium was employed to account for the large difference of thermal conductivity between metallic ligaments and PCM (paraffin). The Forchheimer extended Darcy model was employed to describe the additional flow resistance induced by metal foam. For the DNS, a geometric model of metal foam based on tetrakaidehedron cells was reconstructed. The DNS results demonstrated significant temperature difference between ligament surface and PCM, thus confirming the feasibility of local thermal non-equilibrium employed in VAM simulations. Relative to the DNS results, the VAM combined with the two-temperature model could satisfactorily predict transient solid-liquid interface evolution and local temperature distribution, although pore-scale features of phase change were lost. The presence of natural convection affected significantly the melting front shape, temperature distribution and full melting. The contribution of natural convection to overall phase change heat transfer should be qualitatively and quantitatively given sufficient consideration from both macroscopic (VAM) and microscopic (DNS) point of views. Besides, practical significance and economic prospective using metal foam in TES unit for WHR system to provide residential heating or hot water is discussed and analyzed.

  • 122907.
    Yang, Xiaohu
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Energiprocesser. Xi'an Jiaotong University, Xi'an, China.
    Bai, Q.
    Zhang, Q.
    Hu, W.
    Jin, L.
    Yan, Jinyue
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Energiprocesser. Mälardalen University (MDH), Västerås, Sweden.
    Thermal and economic analysis of charging and discharging characteristics of composite phase change materials for cold storage2018Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 225, s. 585-599Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study conducted both experimental and numerical investigations on the solidification behavior in a metal foam composite phase change material (PCM) for cold storage. Volume-average-method was adopted with the help of Forchheimer-Darcy equation to model the fluid flow through porous media. Experimental measurements were performed to validate the analytical model and the numerical method, with good agreement achieved. Local thermal equilibrium and non-equilibrium states were justified numerically and experimentally. Effect of pore morphological parameters (porosity and pore density) upon the solidification features of composite PCM were investigated. For the appliance of composite PCM to cold storage, techno-economic characteristics was also assessed. Results demonstrated that the full solidification time for metal foams with a porosity of 0.93 and 0.97 can be saved 87.5% and 76.7% respectively compared with pure water. It indicated that porosity of metal foam played a dominant role in heat transfer enhancement; while pore density seemed to have little influence on phase change behavior according to the results. Local natural convection in the unsolidified phase caused a remarkable promotion of the interface evolution, and the full solidification time with natural convection considered can be saved by 14.3% compared with pure conduction for the case with the same porosity of 0.97. The economic analyses indicated that using composite PCM was profitable with a short payback period less than 2 years.

  • 122908.
    Yang, Xiaohu
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser. Xi'an Jiaotong University, China; Mälardalen University, Sweden.
    Lu, Z.
    Bai, Q.
    Zhang, Q.
    Jin, L.
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser. Mälardalen University, Sweden.
    Thermal performance of a shell-and-tube latent heat thermal energy storage unit: Role of annular fins2017Inngår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 202, s. 558-570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study conducts numerical investigations on melting process in a shell-and-tube latent heat thermal energy storage (LHTES) unit with annular fins. Commercial grade paraffin is employed as the phase change material (PCM) and water serves as the heat transfer fluid (HTF). Finite-volume-method (FVM) based numerical simulations are performed to investigate the effects of fin number, height and thickness on the phase change process. Particular attention is made to justify the contribution of local natural convection to the overall phase change process. Results demonstrate that the full melting time could be maximally reduced by 65% by inserting annular fins into PCM. For maximizing thermal performance, an optimal group fin parameter (fin number N = 31, thickness t/l = 0.0248 and interval l/L = 0.0313) is recommended for the present study.

  • 122909.
    Yang, Xiaotian
    KTH, Tidigare Institutioner                               , Kemi.
    Interfacing spectrophotometry to process liquors applications to kraft pulping2002Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    This thesis summarizes the outcome of work performed withthe objective to contribute to the knowledge and development ofthe kraft cooking process using spectrophotometricinterfaces.

    In kraft cooking, it is desirable to maximize the removal oflignin in the cook without loss of pulp strength. Theselectivity can be improved by exchanging some of the hydrogensulfide ion in the white liquor for polysulfides. Paper Ipresents a spectrophotometric method for in-line monitoring ofthe electrochemical production of polysulfide using anATR-probe for the UV-Vis range. A linear relation existsbetween the ATR-probe response and the concentration ofabsorbing species. Thus the process can be followed by simplemonitoring of a few wavelengths.

    A spectrophotometric monitoring system using a durableNafion ionomer membrane interface for continuous on-linemeasurement of sulfide and dissolved lignin during kraftcooking has previously been developed by our group. In paperII, the permeation of low molecular weight anions from liquorshaving high ionic strengths through a membrane in Na+ form hasbeen studied. A general relation between penetration and ionsize approximated by molecular weight has been established. Thepenetration of different anions can be explained as a diffusionthrough the winding membrane channels. Further the differentanions transport independently without being interfered by thesample matrix.

    In light of this validation, we applied the membraneinterface to the determination of anthraquinone-2-sulfonate(AQ-S) in alkaline pulping liquor. In paper III, a simple andrapid spectrophotometric method was developed and implementedon real samples. Interferences from other compounds penetratingthe membrane were minimized by reduction of the penetrated AQ-Sand measurement at 520 nm. This method is quick and can be usedon-line. Further, we extended the method to determination ofanthraquinone (AQ) in pulping liquor (paper IV). Although AQ isregarded as insoluble, it was found that the apparentsolubility of AQ in alkaline solutions increases considerablyin the presence of lignin, reaching 0.14 g/L at 90 oC. Thismakes the calibration of AQ possible. Time-resolvedmeasurements of dissolved AQ in 3 kraft-AQ pulping processeswere performed.

    The results show that the membrane has great potential aspart of a selective interface in applications where theconcentrations of small anions are to be monitored in mediawith high ionic strength.

    Keywords: Kraft cooking, On-line, Sulfide, Lignin,Polysulfide excess sulfur, Anthraquinone-2-Sulfonate (AQ-S),Anthraquinone (AQ), Nafion Membrane, UV-Vis, ATR-probe,Spectrophotometric.

  • 122910. Yang, Xiaoxia
    et al.
    Dong, Hairong
    Wang, Qianling
    Chen, Yao
    Hu, Xiaoming
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.), Optimeringslära och systemteori.
    Guided crowd dynamics via modified social force model2014Inngår i: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 411, s. 63-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pedestrian dynamics is of great theoretical significance for strategy design of emergency evacuation. Modification of pedestrian dynamics based on the social force model is presented to better reflect pedestrians' behavioral characteristics in emergency. Specifically, the modified model can be used for guided crowd dynamics in large-scale public places such as subway stations and stadiums. This guided crowd model is validated by explicitly comparing its density-speed and density-flow diagrams with fundamental diagrams. Some social phenomena such as gathering, balance and conflicts are clearly observed in simulation, which further illustrate the effectiveness of the proposed modeling method. Also, time delay for pedestrians with time-dependent desired velocities is observed and explained using the established model in this paper. Furthermore, this guided crowd model is applied to the simulation system of Beijing South Railway Station for predictive evacuation experiments.

  • 122911.
    Yang, Xiaoyong
    et al.
    Southwest Univ Sci & Technol, Stale Key Lab Environm Friendly Energy Mat, Natl Collaborat Innovat Ctr Nucl Waste & Environ, Mianyang 621010, Sichuan, Peoples R China.;Uppsala Univ, Condensed Matter Theory Grp, Mat Theory Div, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Banerjee, Amitava
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Uppsala Univ, Condensed Matter Theory Grp, Mat Theory Div, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden..
    Probing the active sites of newly predicted stable Janus scandium dichalcogenides for photocatalytic water-splitting2019Inngår i: Catalysis Science & Technology, ISSN 2044-4753, E-ISSN 2044-4761, Vol. 9, nr 18, s. 4981-4989Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Janus structures of transition metal dichalcogenides with intrinsic dipoles have recently drawn attention as efficient candidates in the class of non-precious metal photocatalysts for water splitting. Here, we have proposed Janus ScXY (X/Y = S, Se, or Te, X not equal Y) monolayers as promising catalysts for the hydrogen evolution reaction (HER). We have thoroughly investigated the structural stabilities of the ScXY monolayers, as a primary step to understand the splitting mechanism more accurately. It has been observed that Janus ScSSe and ScSeTe monolayers are dynamically, thermally and mechanically stable, whereas the ScSTe monolayer is dynamically unstable. Moreover, based on hybrid functional (HSE06) calculations, these stable ScSSe and ScSeTe monolayers are semiconductors with direct band gaps of 1.810 and 0.921 eV, respectively. Considering spin-orbit coupling on top of the HSE06 calculations results in an insignificant change in the band gaps. The steady optical responses of Janus ScSSe and ScSeTe, respectively, in the visible and near IR spectra demonstrate their photocatalytic activities in the respective regions. Interestingly, we have observed excellent performance shown by the ScSeTe monolayer, where both surfaces are catalytically active, and maintain close to thermoneutral conditions with near-zero adsorption free energy at different H* coverages. Comparatively, the ScSSe monolayer shows poor performance for the HER due to strong bonds with the adsorbed hydrogen. Also, it has been confirmed that even the application of +/- 2% strain on the ScSSe monolayer does not enhance its HER activity. Our theoretical predictions demonstrate that out of all the Janus ScXY monolayers studied here, ScSeTe is the most active catalyst for the HER to efficiently split water, which certainly could make it worth performing further experimental investigations.

  • 122912.
    Yang, Xiaoyong
    et al.
    Southwest Univ Sci & Technol, Natl Collaborat Innovat Ctr Nucl Waste & Environm, Mianyang 621010, Sichuan, Peoples R China.;Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, Mat Them Div, Box 516, S-75120 Uppsala, Sweden..
    Singh, Deobrat
    Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, Mat Them Div, Box 516, S-75120 Uppsala, Sweden..
    Xu, Zhitong
    Southwest Univ Sci & Technol, Natl Collaborat Innovat Ctr Nucl Waste & Environm, Mianyang 621010, Sichuan, Peoples R China..
    Wang, Ziwei
    Southwest Univ Sci & Technol, Natl Collaborat Innovat Ctr Nucl Waste & Environm, Mianyang 621010, Sichuan, Peoples R China..
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Uppsala Univ, Dept Phys & Astron, Condensed Matter Theory Grp, Mat Them Div, Box 516, S-75120 Uppsala, Sweden..
    An emerging Janus MoSeTe material for potential applications in optoelectronic devices2019Inngår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 7, nr 39, s. 12312-12320Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Motivated by the extraordinary physical and chemical properties of Janus transition-metal dichalcogenides (TMDs) due to the change of the crystal field originating from their asymmetry structures, the electronic and optical properties of the MoSeTe monolayer in 2H and 1T phases are systematically studied by first-principles calculations, and a detailed comparison with the parental MoSe2 and MoTe2 monolayer is made. It is found that 2H-MoSeTe exhibits a direct bandgap of 1.859 eV and an indirect band gap of 0.391 eV in the 1T phase, resulting in a different way to interact with sunlight. Besides, the obtained results show that the SOC has little effects on the band gaps. The calculated optical properties show a significant red shift from the MoSe2 to MoSeTe to MoTe2 monolayer. However, a blue shift is observed from the in-plane to out-of-plane direction. Moreover, both electron-electron and electron-hole correlation effects are considered for obtaining the optical spectra of systems by G(0)W(0) and G(0)W(0) + BSE approaches. Besides, the absorption coefficient value reaches up to 1 x 10(6) cm(-1) in both phases, implying the high efficiency in the utilization of solar energy for the MoSeTe monolayer. Additionally, the 1T-MoSeTe monolayer is a good hot mirror material in that its maximum reflectivity could reach up to 51% in the infrared region. Additionally, the average optical absorbance of the Janus MoSeTe monolayer in the visible light region is calculated to be about 2% and the corresponding average transmittance is around 80%. More importantly, the difference in the optical response for the two side surfaces is considered in our work due to the intrinsic asymmetric structure of Janus MoSeTe. These results not only predict the great potential application of Janus MoSeTe in optoelectronics-electronic devices, but may enable the discovery of new optical science and the realization of various light emissions, detection, modulation and manipulation functions of specific frequencies.

  • 122913. Yang, Xiaoyu
    et al.
    Wang, Lihui
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion. University of Skövde.
    VR-Assisted Assembly Planning2009Inngår i: Proceedings of the 3rd International Swedish Production Symposium, 2009, s. 423-428Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we present an intelligent assembly planning and training system combining virtual reality (VR) and motion tracking technologies. The development conceptual prototype for assembly planning and training enables individuals to interact with virtual environment in real time. It extends the new technologies of motion tracking and integrates them with virtual environment technologies to create real-time virtual work cell simulations in which workers may be immersed with hands-on experiences. The experimental results to date are presented to demonstrate the contributions of human skills in achieving intelligent assembly planning.

  • 122914. Yang, Xichuan
    et al.
    Jiang, Xiao
    Zhao, Changzhi
    Chen, Ruikui
    Qin, Peng
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Donor-acceptor molecules containing thiophene chromophore: synthesis, spectroscopic study and electrogenerated chemiluminescence2006Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 47, nr 28, s. 4961-4964Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Donor-acceptor molecules containing thiophene chromophore with remarkably large Stokes shift (> 210 nm) have been found to exhibit strong and stable ECL emission via the singlet excited state without the addition of any co-reactant or a second compound.

  • 122915. Yang, Xichuan
    et al.
    Wang, Lei
    Li, Shifeng
    Cheng, Ming
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    A new type of organic sensitizers with pyridine-N-oxide as the anchoring group for dye-sensitized solar cells2013Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 3, nr 33, s. 13677-13680Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A series of organic dyes with alkaline pyridine-N-oxide as the electron acceptor and anchoring group have been synthesized and applied in dye-sensitized solar cells. Photoelectrical data show a good coordination between pyridine-N-oxide and TiO2 films, which effectively guarantee the injection and adsorption of the dye molecules. With the simple WL102 dye, the best photon-to-electron conversion efficiency of 3.72% and an excellent IPCE value about 95% have been achieved under optimized conditions.

  • 122916.
    Yang, Xichuan
    et al.
    Dalian Univ Technol, State Key Lab Fine Chem, Linggong Rd 2, Dalian 116024, Liaoning, Peoples R China..
    Wang, Weihan
    Dalian Univ Technol, State Key Lab Fine Chem, Linggong Rd 2, Dalian 116024, Liaoning, Peoples R China..
    Zhang, Yanyun
    Dalian Univ Technol, State Key Lab Fine Chem, Linggong Rd 2, Dalian 116024, Liaoning, Peoples R China..
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi.
    Improving the power conversion efficiency of solid state dye sensitized solar cells with a N-oxoammonium salt: 2,2,6,6-Tetramethyl-1-oxopiperidinebromide2018Inngår i: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 170, s. 1001-1008Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    P-type doping is a rational strategy for the enhancement of hole transporting properties of the organic semiconductors as well as the device performance of organic photo-electric devices. We originally introduce a stable and solution processed p-type dopant based on N-oxoammonium salts termed 2,2,6,6-tetramethyl-1-oxopiperidinebromide salt (TEMPO-Br) for 2,2',7,7'-tetrakis(N, N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (Spiro-OMeTAD) based solid state dye sensitized solar cells (ssDSC). By introducing TEMPO-Br doped Spiro-OMeTAD and a commercialized D-pi-A sensitizer into ssDSCs, a promising device performance of 6.83% is achieved under simulated AM 1.5G solar irradiation (100 mW cm(-2)), which is significantly better than the control devices ( similar to 1.7 times). The doping effect of TEMPO-Br on the photophysical and electrochemical properties of Spiro-OMeTAD, solid state device performance, cationic dye regeneration kinetics and preliminary long-term stability have been systematically investigated. This work indicates a potential application of N-oxoammonium salts as chemical P-type dopants for triphenylamine based hole transporting materials in solid state photo-electric devices.

  • 122917. Yang, Xichuan
    et al.
    Zhao, Jianghua
    Wang, Lei
    Tian, Jie
    Sun, Licheng
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för kemivetenskap (CHE), Centra, Molekylär elektronik, CMD.
    Phenothiazine derivatives-based D-pi-A and D-A-pi-A organic dyes for dye-sensitized solar cells2014Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, nr 46, s. 24377-24383Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    D-pi-A and D-A-pi-A-structured organic dyes represent different developmental directions of photosensitizers in dye-sensitized solar cells (DSSCs). In this work, two phenothiazine derivatives-based D-pi-A and D-A-pi-A-structured organic dyes have been synthesized and applied in DSSCs. The physical and electrochemical properties of both dyes have been investigated systematically. The results show that the D-A-pi-A-structured dye exhibits a broader spectrum response but lower molar coefficient of extinction when compared to the D-pi-A-structured dye. Regarding photovoltaic performance, the D-pi-A-structured dye yields a higher efficiency (h) of 7.5% with a higher short-circuit current density (J(sc)) of 16.36 mA cm(-2) and open-circuit voltage (V-oc) of 706 mV than that of the D-A-pi-A-structured dye. Incident photon-to-electron conversion efficiency (IPCE) studies and impedance analysis also support these results. These results demonstrate that the phenothiazine derivatives-based D-pi-A-structured organic dyes can compete with, and even exceed, D-A-pi-A-structured organic dyes under the same test conditions.

  • 122918.
    Yang, Xifeng
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Fu, Kai
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Fu, Ying
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi (stängd 20110512).
    Strain effect in determining the geometric shape of self-assembled quantum dot2009Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 42, nr 125414Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The geometric shape of a self-assembled quantum dot (QD) formed by the strain-induced Stranski-Krastanov mode has been studied as a function of strain energy by the short-range valence-force-field approach. It has been shown by dynamic bond relaxation through strain energy minimization that for the most commonly used InAs QD in GaAs and InP matrices and Ge QD in Si matrix, a pyramidal shape is energy favoured over an hemispherical shape when the QD is not capped due to the lattice relaxation at the QD surface. When the QD becomes totally embedded in the background material, the elastic strain energy of a hemispherical InAs QD is minimal. The results agree with experimental observations. We further studied the coupling of strain fields of QDs in adjacent QD layers which shows that QDs in multiply stacked QD layers can be aligned along the layer growth direction in order to minimize the strain energy.

  • 122919.
    Yang, Xifeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Liu, Y. S.
    Fu, Ying
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Cellens fysik.
    Optical absorptions in AlxGa1-xAs/GaAs quantum well for solar energy application2012Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, nr 5, s. 054314-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the optical transitions among localized and extended states in quantum solar cells based on AlxGa1-xAs/GaAs quantum well (QW). The absorption coefficients of localized-to-localized, ground localized-to-extended, and extended-to-localized transitions are enhanced obviously as the size of the QW decreases. When the wave functions of incident electrons and holes spread along different sides of the structure, the absorption coefficient of extended-to-extended states becomes non-zero value when the QW is inserted. This process has a main contribution to the photocurrents. In addition, our studies also show these optical transitions have different sensitivities to the Fermi levels. Therefore, optical absorptions in AlxGa1-xAs/GaAs solar cells can be optimized by the sizes of QW and Fermi levels.

  • 122920.
    YANG, XINYI
    KTH, Skolan för industriell teknik och management (ITM).
    Chip Breaking Optimization During Turning Shoulder2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 122921.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. 2Centre for Optical and Electromagnetic Research (COER), State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, 310058 Hangzhou, China.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    A 1.57 μm fiber source for CO2 Scheimpflug DIAL2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A 1.3 W, narrow linewidth source at 1.57 μm for Scheimpflug DIAL was developed. Itwas tunable from 1570.859 nm to 1573.068 nm with a 2.9 MHz linewidth, and used for CO2measurements.

  • 122922.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Larsson, Jim
    Lund Univ, Dept Phys, Solvegatan 14, S-22346 Lund, Sweden..
    Bood, Joakim
    Lund Univ, Dept Phys, Solvegatan 14, S-22346 Lund, Sweden..
    Brydegaard, Mikkel
    Lund Univ, Dept Phys, Solvegatan 14, S-22346 Lund, Sweden.;Norsk Elektro Optikk AS, Prost Stabels Vei 22, N-2019 Skedsmokorset, Norway..
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    1.57 mu m fiber source for atmospheric CO2 continuous-wave differential absorption lidar2019Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, nr 7, s. 10304-10310Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present an efficient fiber source designed for continuous-wave differential absorption light detection and ranging (CW DIAL) of atmospheric CO2-concentration. It has a linewidth of 3 MHz, a tuning range of 2 nm over the CO2 absorption peaks at 1.572 mu m, and an output power of 1.3 W limited by available pump power. Results from the initial CW DIAL testing are also presented and discussed. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

  • 122923.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Larsson, Jim
    Xu, Can
    Brydegaard, Mikkel
    Bood, Joakim
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik.
    A 1.57 µm fiber source for atmospheric CO2 continuous-wave differential absorption lidar2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a simple turn-key fiber amplifier system which allows for a narrow wavelength tunability with a stable level of output power.  This system was used in continuous-wave differential absorption light detection and ranging (CW-DIAL) [1] to measure the atmospheric CO2-concentration in Lund. Preliminary experimental results are also presented.

  • 122924.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Centre for Optical and Electromagnetic Research (COER), State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou, 310058, China.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Magrulis, Walter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Department of Fiber Optics, RISE Acreo, Kista, 164 40, Sweden.
    Fröjdh, Krister
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Continuously tunable, narrow-linewidth laser based on a semiconductor optical amplifier and a linearly chirped fiber Bragg grating2019Inngår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 27, nr 10, s. 14213-14220Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe a simple, narrow-linewidth, tunable fiber-based laser with a high degree of tuning accuracy. A polarization independent semiconductor optical amplifier (SOA) is used as the gain medium in a unidirectional fiber ring cavity with a circulator connected to a 6-meter long chirped fiber Bragg grating (CFBG). The laser wavelength is chosen by setting the modulation frequency of the SOA the same as the harmonics of the fundamental repetition rate of the light reflected at a specific point on the CFBG. Careful management of the drive current and pulse width helps to generate laser light of narrow linewidth (less than 0.03 nm) with low power variation (1.46 dB) over a tuning range of 40 nm.

  • 122925.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Zhejiang Univ, State Key Lab Modern Opt Instrumentat, COER, Hangzhou 310058, Zhejiang, Peoples R China..
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Margulis, Walter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. RISE Acreo, Dept Fiber Opt, S-16440 Kista, Sweden..
    Frojdh, Krister
    Proxim AB, Skalholtsgatan 10, SE-16440 Kista, Sweden..
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Rapid and Continuously Tunable Narrow Linewidth Fiber Source Based on a SOA and a Linearly Chirped Fiber Bragg Grating2019Inngår i: 2019 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), IEEE , 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We demonstrate a tunable narrow-linewidth laser based on a semiconductor optical amplifier and a linearly chirped FBG. High tuning resolution and small power variation over 40 nm tuning range were achieved by optimizing the drive current.

  • 122926.
    Yang, Xiong
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. Zhejiang Univ, State Key Lab Modern Opt Instrumentat, COER, Hangzhou 310058, Zhejiang, Peoples R China.
    Lindberg, Robert
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Margulis, Walter
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik. RISE Acreo, Dept Fiber Opt, S-16440 Kista, Sweden.
    Fröjdh, Krister
    Proxim AB, Skalholtsgatan 10, SE-16440 Kista, Sweden.
    Laurell, Fredrik
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Laserfysik.
    Rapid and continuously tunable narrow linewidth fiber source based on a SOA and a linearly chirped fiber Bragg grating2019Inngår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We demonstrate a tunable narrow-linewidth laser based on a semiconductor optical amplifier and a linearly chirped FBG. High tuning resolution and small power variation over 40 nm tuning range were achieved by optimizing the drive current.

  • 122927.
    Yang, Xuan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH Royal institute of technology.
    Eco-friendly Holocellulose Materials for Mechanical Performance and Optical Transmittance2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Cellulosic materials can be sustainable replacements for fossil-based plastics; yet for some applications improvements are needed for mechanical properties, optical transmittance and eco-friendly characteristics. In this thesis, holocellulose materials are investigated for this purpose, and processing-structure-property relationships are discussed. Molded fibers, without added polymer binder, is of particular interest for semi-structural applications, where facile recycling is possible with highly preserved fiber properties.

    Mild delignification is carried out to obtain ramie fibers, spruce holocellulose fibers and holocellulose nanofibrils. The chemical composition, molar mass, crystallinity, fiber length/width, and single fiber strength are measured. Fibers and fibrils show well-preserved native structure. Using water-based hot-pressing, fibers and fibrils are processed into different fiber network materials, including paper structures of 50% porosity, high density molded fibers, and high density nanopaper films. Biocomposites are obtained through methyl methacrylate impregnation and polymerization with molded fibers as reinforcing networks. Fiber orientation is quantified using 2D X-ray diffraction, mechanical properties are determined by tensile testing, and optical properties are measured by transmittance/haze tests in an integrating sphere. Holocellulose materials show much superior mechanical properties and optical transmittance to comparable materials based on industrially available kraft fiber grades. Strong effects from micro-, nano- and molecular scale structures are observed and discussed.

    The colloidal stability, redispersibility, and surface modification of holocellulose nanofibrils, as well as recycling and 3D-shaping performance of paper-like structures are investigated. Eco-friendly characteristics include high fiber yield, reduced need for chemical modification and excellent recycling performance with reduced embodied energy in the final material. The enhanced performance of holocellulose materials, compared with materials from kraft fibers, are related to the effects of well-preserved cellulose and hemicellulose structures, as well as structural homogeneity at both molecular, nanofibril and fiber length scales.

    Fulltekst tilgjengelig fra 2020-11-19 09:42
  • 122928.
    Yang, Xuan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Oriented all-cellulose film based on ramie fiber with high mechanical property and transparency2017Inngår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Artikkel i tidsskrift (Annet vitenskapelig)
  • 122929.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH Royal institute of technology.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Recycling without Fiber Degradation: Strong Paper Structures for 3D Forming Based on Nanostructurally Tailored Wood Holocellulose FibersManuskript (preprint) (Annet vitenskapelig)
  • 122930.
    Yang, Xuan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Water-Based Approach to High-Strength All-Cellulose Material with Optical Transparency2018Inngår i: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 6, nr 1, s. 501-510Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    All-cellulose composites are usually prepared by a partial cellulose dissolution approach, using of ionic liquids or organic solvents. Here, an all-cellulose film based on moist ramie fibers was prepared by hot-pressing. The original ramie fiber was degummed, alkali treated, aligned, and mounted into a specially designed mold. The wet ramie fiber "cake" was pressed into a transparent film. The structure, mechanical properties, moisture sorption, and optical properties of the films were investigated using scanning electron microscopy (SEM), X-ray diffraction, tensile tests, gravimetric method, and integrating sphere devices. The all-cellulose films showed an ultimate strength of 620 MPa and a Young's modulus of 39.7 GPa with low moisture sorption and optical transmittance of 85%. These eco-friendly all-cellulose films are of interest for laminated composites, as coatings and in photonics applications.

  • 122931.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berthold, Fredrik
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    High-Density Molded Cellulose Fibers and Transparent Biocomposites Based on Oriented Holocellulose2019Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, nr 10, s. 10310-10319Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ecofriendly materials based on well-preserved and nanostructured wood cellulose fibers are investigated for the purpose of load-bearing applications, where optical transmittance may be advantageous. Wood fibers are subjected to mild delignification, flow orientation, and hot-pressing to form an oriented material of low porosity. The biopolymer composition of the fibers is determined. Their morphology is studied by scanning electron microscopy, cellulose orientation is quantified by X-ray diffraction, and the effect of beating is investigated. Hot-pressed networks are impregnated by a methyl methacrylate monomer and polymerized to form thermoplastic wood fiber/poly(methyl methacrylate) biocomposites. Tensile tests are performed, as well as optical transmittance measurements. Structure-property relationships are discussed. High-density molded fibers from holocellulose have mechanical properties comparable with nanocellulose materials and are recyclable. The thermoplastic matrix biocomposites showed superior mechanical properties (Young's modulus of 20 GPa and ultimate strength of 310 MPa) at a fiber volume fraction of 52%, with high optical transmittance of 90%. The study presents a scalable approach for strong, stiff, and transparent molded fibers/biocomposites.Ecofriendly materials based on well-preserved and nanostructured wood cellulose fibers are investigated for the purpose of load-bearing applications, where optical transmittance may be advantageous. Wood fibers are subjected to mild delignification, flow orientation, and hot-pressing to form an oriented material of low porosity. The biopolymer composition of the fibers is determined. Their morphology is studied by scanning electron microscopy, cellulose orientation is quantified by X-ray diffraction, and the effect of beating is investigated. Hot-pressed networks are impregnated by a methyl methacrylate monomer and polymerized to form thermoplastic wood fiber/poly(methyl methacrylate) biocomposites. Tensile tests are performed, as well as optical transmittance measurements. Structure-property relationships are discussed. High-density molded fibers from holocellulose have mechanical properties comparable with nanocellulose materials and are recyclable. The thermoplastic matrix biocomposites showed superior mechanical properties (Young's modulus of 20 GPa and ultimate strength of 310 MPa) at a fiber volume fraction of 52%, with high optical transmittance of 90%. The study presents a scalable approach for strong, stiff, and transparent molded fibers/biocomposites.

  • 122932.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berthold, Fredrik
    RISE Res Inst Sweden, Master Samuelsgatan 60, SE-11121 Stockholm, Sweden..
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Preserving Cellulose Structure: Delignified Wood Fibers for Paper Structures of High Strength and Transparency2018Inngår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 19, nr 7, s. 3020-3029Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To expand the use of renewable materials, paper products with superior mechanical and optical properties are needed. Although beating, bleaching, and additives are known to improve industrially produced Kraft pulp papers, properties are limited by the quality of the fibers. While the use of nanocellulose has been shown to significantly increase paper properties, the current cost associated with their production has limited their industrial relevance. Here, using a simple mild peracetic acid (PAA) delignification process on spruce, we produce hemicellulose-rich holocellulose fibers (28.8 wt %) with high intrinsic strength (1200 MPa for fibers with microfibrillar angle smaller than 10 degrees). We show that PAA treatment causes less cellulose/hemicellulose degradation and better preserves cellulose nanostructure in comparison to conventional Kraft pulping. High-density holocellulose papers with superior mechanical properties (Young's modulus of 18 GPa and ultimate strength of 195 MPa) are manufactured using a water-based hot-pressing process, without the use of beating or additives. We propose that the preserved hemicelluloses act as "glue" in the interfiber region, improving both mechanical and optical properties of papers. Holocellulose fibers may be affordable and applicable candidates for making special paper/composites where high mechanical performance and/or optical transmittance are of interest.

  • 122933.
    Yang, Xuan
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Reid, Michael S.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Olsén, Peter
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Centra, Wallenberg Wood Science Center. KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Eco-Friendly Cellulose Nanofibrils Designed by Nature: Effects from Preserving Native StateManuskript (preprint) (Annet vitenskapelig)
  • 122934. Yang, Y.
    et al.
    Chen, Jiajia
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS, Optical Network Laboratory (ON Lab).
    Network performance analysis of an AWG-based passive optical interconnect for datacenters2014Inngår i: Optics InfoBase Conference Papers, OSA - The Optical Society , 2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    AWG-based passive optical interconnects (POIs) are considered a high-capacity and energy-efficient solution for datacenter networks. We concentrate on a cascaded AWG-based POI and analyze network performance to gain insights on efficiency of such an architecture.

  • 122935. Yang, Y.
    et al.
    Dimarogonas, Dimos V.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Reglerteknik.
    Hu, X.
    Opinion consensus under external influences2018Inngår i: Systems & control letters (Print), ISSN 0167-6911, E-ISSN 1872-7956, Vol. 119, s. 23-30Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    As a means to regulate the continuous-time bounded confidence opinion dynamics, an exo-system to the original Hegselmann–Krause model is added. Some analysis is made about the properties of the combined system. Two theorems are provided in this article in terms of sufficient conditions of the exo-system that can guarantee opinion consensus for any initial conditions. Two more corollaries are given to describe the resulting synchronized opinions. 

  • 122936. Yang, Y.
    et al.
    Gao, R. X.
    Fan, Z.
    Wang, J.
    Wang, Lihui
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Cloud-based prognosis: Perspective and challenge2014Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Comprehensive acquisition, distribution, and utilization of information about machine equipment and/or processes across spatial boundaries for improved productivity and decision have increasingly become the hallmark of advanced manufacturing. The emergence of cloud computing has created ample opportunities to achieve this goal. This paper presents a review of the state-of-the-art of prognosis technique for manufacturing and its future development motivated by the cloud infrastructure. Prevailing methods of prognosis are summarized, and their respective performance is comparatively evaluated. Basic principles and recent advances in cloud computing, as well as its application to cloud manufacturing, are introduced. Based on the survey, the concept of cloud-based prognosis is proposed, and its architecture as well as associated challenges are discussed.

  • 122937. Yang, Y.
    et al.
    Günther, D.
    Wuhrer, S.
    Brunton, A.
    Ivrissimtzis, I.
    Seidel, H. -P
    Weinkauf, Tino
    Max Planck Institute for Informatics, Saarbrücken, Germany.
    Correspondences of Persistent Feature Points on Near-Isometric Surfaces2012Inngår i: Proceedings of the Fifth Workshop on Non-Rigid Shape Analysis and Deformable Image Alignment (NORDIA) in Proceedings of ECCV 2012 and its Workshops, Springer Berlin/Heidelberg, 2012, s. 102-112Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a full pipeline for finding corresponding points between two surfaces based on conceptually simple and computationally efficient components. Our pipeline begins with robust and stable extraction of feature points from the surfaces. We then find a set of near isometric correspondences between the feature points by solving an optimization problem using established components. The performance is evaluated on a large number of 3D models from the following perspectives: robustness w.r.t. isometric deformation, robustness w.r.t. noise and incomplete surfaces, partial matching, and anisometric deformation.

  • 122938. Yang, Y.
    et al.
    Heijungs, R.
    Brandao, Miguel
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik.
    Hybrid life cycle assessment (LCA) does not necessarily yield more accurate results than process-based LCA2017Inngår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 150, s. 237-242Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybrid life cycle assessment (LCA), through combining input-output (IO) models and process-based LCA for a complete system boundary, is widely recognized as a more accurate approach than process-based LCA with an incomplete system boundary. Without a complete process model for verification, however, the performance of hybrid LCA remains unclear. Here, using a counterexample we show that hybrid LCA does not necessarily provide more accurate results than process-based LCA, simply because the aggregation of heterogeneous processes in IO models may introduce more errors. In so doing, we prove that only when IO-based LCA and process-based LCA have the same level of detail would they yield the same results. Whether hybrid LCA provides more accurate estimates depends on whether the IO model introduced serves as an adequate proxy for the missing products as opposed to if they were estimated by a complete process model. The use of a highly-aggregated IO model runs the risk of overestimation, and could result in a larger relative error than the truncation error resulting from an incomplete process model. Our study seeks to provide a balanced view of hybrid LCA, and our findings offer important insights for future hybrid LCA studies to improve the accuracy and realm of applicability of the approach.

  • 122939.
    Yang, Y.
    et al.
    KTH.
    Jafri, Syed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Stathis, Dimitrios
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    MTP-caffe: Memory, timing, and power aware tool for mapping CNNs to GPUs2017Inngår i: ACM International Conference Proceeding Series, Association for Computing Machinery (ACM), 2017, s. 31-36Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In the recent past, the Convolutional Neural Networks (CNNs) have attracted intense research. The high processing requirements (of CNNs) and the availability of efficient mapping tools have made GPUs a popular CNN accelerator. To extract the maximum performance, the mapping tools transform the unsupported convolutions to GPU supported matrix multiplications. However, this transformation incurs significant memory overheads (3-5X). Furthermore, since the tool is unaware of the GPU architecture, even after the transformation the performance and power is sub-optimal. To tackle this problem we present MTP-Caffe that complements Caffe by making it memory, timing, and power aware. It analyses the CNN structure and the GPU architecture to convert a CNN into smaller parts, tailored for GPU resources. Simulation results reveal that MTP-Caffe not only eliminates the additional memory overheads but also provides up to 21% speedup and up to 23.5% less power.

  • 122940. Yang, Y.
    et al.
    Pesavento, M.
    Chatzinotas, S.
    Ottersten, Björn
    Interdisciplinary Centre for Security, Reliability and Trust University of Luxembourg, Luxembourg City, L-1855, Luxembourg.
    Energy Efficiency Optimization in MIMO Interference Channels: A Successive Pseudoconvex Approximation Approach2019Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 67, nr 15, s. 4107-4121Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we consider the (global and sum) energy efficiency optimization problem in downlink multi-input multi-output multi-cell systems, where all users suffer from multi-user interference. This is a challenging problem due to several reasons: First, it is a nonconvex fractional programming problem; second, the transmission rate functions are characterized by (complex-valued) transmit covariance matrices; and third the processing-related power consumption may depend on the transmission rate. We tackle this problem by the successive pseudoconvex approximation approach, and we argue that pseudoconvex optimization plays a fundamental role in designing novel iterative algorithms, not only because every locally optimal point of a pseudoconvex optimization problem is also globally optimal but also because a descent direction is easily obtained from every optimal point of a pseudoconvex optimization problem. The proposed algorithms have the following advantages: First, fast convergence as the structure of the original optimization problem is preserved as much as possible in the approximate problem solved in each iteration; second, easy implementation as each approximate problem is suitable for parallel computation and its solution has a closed-form expression; and third, guaranteed convergence to a stationary point or a Karush-Kuhn-Tucker point. The advantages of the proposed algorithm are also illustrated numerically.

  • 122941. Yang, Y.
    et al.
    Pesavento, M.
    Chatzinotas, S.
    Ottersten, Björn
    University of Luxembourg.
    Successive Convex Approximation Algorithms for Sparse Signal Estimation With Nonconvex Regularizations2018Inngår i: IEEE Journal on Selected Topics in Signal Processing, ISSN 1932-4553, E-ISSN 1941-0484, Vol. 12, nr 6, s. 1286-1302Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we propose a successive convex approximation framework for sparse optimization where the nonsmooth regularization function in the objective function is nonconvex and it can be written as the difference of two convex functions. The proposed framework is based on a nontrivial combination of the majorization-minimization framework and the successive convex approximation framework proposed in literature for a convex regularization function. The proposed framework has several attractive features, namely, first, flexibility, as different choices of the approximate function lead to different types of algorithms; second, fast convergence, as the problem structure can be better exploited by a proper choice of the approximate function and the stepsize is calculated by the line search; third, low complexity, as the approximate function is convex and the line search scheme is carried out over a differentiable function; fourth, guaranteed convergence to a stationary point. We demonstrate these features by two example applications in subspace learning, namely the network anomaly detection problem and the sparse subspace clustering problem. Customizing the proposed framework by adopting the best-response type approximation, we obtain soft-thresholding with exact line search algorithms for which all elements of the unknown parameter are updated in parallel according to closed-form expressions. The attractive features of the proposed algorithms are illustrated numerically.

  • 122942. Yang, Y.
    et al.
    Welch, G. F.
    Sundberg, Johan
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Musikakustik.
    Himonides, E.
    Pedagogical strategies for ensuring the continued survival of China´s musical folksong heritage:: A case study2007Inngår i: Proceedings of APSMER 2007, 6th Asia-Pacific Society for Music Education Research, 2007, s. 37-38Konferansepaper (Fagfellevurdert)
  • 122943. Yang, Y.
    et al.
    Zhang, Yang
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Campana, P. E.
    Yan, Jerry
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Energiprocesser. Mälardalen University, Sweden.
    Peak-shaving and profit-sharing model by Aggregators in residential buildings with PV- a case study in Eskilstuna, Sweden2017Inngår i: Proceedings of the 9th International Conference on Applied Energy, Elsevier, 2017, Vol. 142, s. 3182-3193Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Nowadays, photovoltaic (PV) system combined with energy storage systems is playing increasing significant role in residential buildings in Sweden. At the same time it brings reliability problems because of the intermittency of electricity production and exceptionally distributed reservoir which is followed by the peak-valley electricity prices and power grid fluctuations. There is an increasing need for new business model and economic paradigm for a third party aggregator to bridge the gap between Power Grid and end-users. Providing the valuable electricity services at scale and breaking regulatory arbitrage, aggregators help to deliver desired levels of residents' engagements, value-added services and feasible level of unbundling of electricity market. This paper analyzes how the aggregators grab the indisputable business opportunity to interact between residents and Power Grid from the perspective of physical electricity flows and benefits share of peak-shaving. We employ a real case in Eskilstuna in Sweden to design new business model and validate using data. And the result indicates the compatibility of the aggregator service and its business model. It further sheds light on the pricing model of generated electricity by PV system, and benefits share ratio design.

  • 122944.
    Yang, Yang
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Equilibrium phase relationships in the CaO-MgO-SiO2-Cr2O3 slags2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 122945.
    Yang, Yang
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Harmonic Losses in Windings of Inverter-Fed High-Speed PM Motors2015Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This master thesis focuses on the estimation of losses in windings of a high-speed PermanentMagnet (PM) motor. The PM motor studied in this thesis is applied to a nut-runner systemwith specic characteristics such as operating at a high speed (30000 rpm), relatively smallsize and being slot-less. Previously published analytical models for calculation the losses inwindings are discussed in the literature study along with related background theory. Finiteelement method (FEM) 2D is applied in the simulations using FLUX v12. Simulations beginwith several conductors and bundles. Meanwhile, the analytical estimation of those caseswas carried out. The comparisons between results from both sources are discussed. Beforefurther investigations, the way of connection of bundles and conductors and the applicationof symmetrical conditions for following simulations are discussed. Furthermore, the wholewindings with a iron ring and the rotor are simulated step by step in FLUX. Eect of ironmaterial, lamination thickness and base value are investigated. Finally, losses in windingswith various situations are calculated and compared at 10 kHz and 20 kHz.

  • 122946.
    Yang, Yang
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Investigation of vanadium-containing oxide systems: CALPHAD and experiments2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Fundamental studies on thermodynamic properties of vanadium-containing oxides systems are essential to understand practical vanadium metallurgical process. The CALPHAD technique is here applied to the thermodynamic modelling of the V-O, Ca-V-O and Ti-V-O systems. The compound energy formalism is used for all the solution phases. All optimization processes and calculations are performed using the Thermo-Calc software package. The present work attempts to develop a self-consistent thermodynamic database of all phases in the studied systems. The obtained datasets can be used to calculate thermodynamic properties, stable as well as metastable phase equilibria and driving forces for oxidation etc.

    Steelmaking slag is an important secondary source for vanadium extraction. The phase relationships and vanadium distribution in the CaO-SiO2-MgO-V2O3-Al2O3 synthetic slags, whose compositions were chosen based on the relevance to the steel producers, are also studied. Phase equilibria in the temperature range of 1773 to 1823 K at oxygen partial pressure of 10-10 bar and 0.21 bar were characterized.

    An investigation of the volatilization of vanadium oxide was also carried out in the present work. Isothermal evaporation of vanadium pentoxide in the temperature range between 1723 and 1873 K was investigated by Thermogravimetric Analysis under different oxygen partial pressures, viz. oxygen, air or CO2. The Arrhenius activation energy for the evaporation reaction in various atmospheres was calculated from the experimental results. A mathematical model was developed to describe the kinetics of the evaporation process. Evaporation coefficients and enthalpies in various atmospheres were also estimated. The present results may have some implications in recovering vanadium from different vanadium-bearing sources.

  • 122947.
    Yang, Yang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Mao, Huahai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Chen, Hai-Lin
    Thermo-Calc Software AB, Norra Stationsgatan 93, 113 64 Stockholm, Sweden..
    An assessment of the Ti-V-O systemArtikkel i tidsskrift (Annet vitenskapelig)
  • 122948.
    Yang, Yang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Mao, Huahai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    An assessment of the Ca-V-O system2017Inngår i: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, s. 29-40Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Ca-V-O system is studied with an emphasis on the following oxide sub-systems: CaO-V2O5, CaO-V2O3, V2O5-CaV2O5 and CaO-V2O5-VO2. The aim of the present assessment is to obtain a thermodynamic description of the Ca-V-O system. The compound energy formalism was used to describe the liquid by applying the ionic two-sublattice model and the β-bronze phase CaxV2O5 (0.17≤x≤0.33) using a three-sublattice model. Phase equilibria and thermodynamic properties were critically evaluated using the CALPHAD approach and a consistent set of thermodynamic model parameters was obtained. Satisfactory agreement between calculated and experimental values is achieved.

  • 122949.
    Yang, Yang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Thermo-Calc Software AB, Sweden.
    Mao, Huahai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Thermo-Calc Software AB, Sweden.
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Thermo-Calc Software AB, Sweden.
    An assessment of the Ti-V-O system2017Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 722, s. 365-374Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Ti-V-O system has been assessed using the CALPHAD method based on recent assessments of its binary systems. The present work focuses on the following oxide sub-systems: V2O3-TiO2, VO2-TiO2, V2O5-TiO2 and V2O3-Ti2O3-TiO2. The liquid phase was described by the ionic liquid model while the solid solution oxide phases were modeled using a two-sublattice model within the framework of the compound energy formalism. The available experimental data were critically evaluated and a consistent set of thermodynamic model parameters was obtained. Satisfactory agreement between calculated and experimental information especially of the stability, solubility and phase relations of various oxide phases is achieved. Reliable predictions of oxygen solubility in Ti-V alloys can be made using the present thermodynamic descriptions.

  • 122950.
    Yang, Yang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Mao, Huahai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering. Thermo-Calc Software AB, Norra Stationsgatan 93, Stockholm, Sweden.
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Thermodynamic assessment of the V-O system2015Inngår i: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 51, s. 144-160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The V-O system was thermodynamically assessed using the CALPHAD method. The available experimental data on thermodynamic and thermochemical properties as well as phase diagram information were critically examined and a self-consistent set of thermodynamic parameters was obtained. In total 20 phases were included in this binary system. Five among them were treated as solid solution phases within the framework of the compound energy formalism. The halite phase was modeled as (V,V+2,V+3,Va)<inf>1</inf>(O-2,Va)<inf>1</inf> covering the solubility of both V and O. Thermodynamic descriptions of two different models for the corundum phase are presented, one of which is more complex to correctly take the defect mechanisms into account. The liquid phase was described by the ionic two-sublattice model with the formula (V+2)<inf>P</inf>(O-2,Va-Q, VO<inf>1.5</inf>,VO<inf>2</inf>, VO<inf>2.5</inf>)<inf>Q</inf>. The stoichiometric Magnéli phases V<inf>n</inf>O<inf>2n-1</inf> (n is an integer between 4 and 8) were modeled as (V+3)<inf>2</inf>(V+4)<inf>n-2</inf>(O-2)<inf>2n-1</inf>. Using the present thermodynamic description reliable experimental phase diagram, thermodynamic and thermochemical data were well reproduced.

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