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  • 124301.
    Yu, Zu
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Vlachopoulos, Nick
    Physical Chemistry, Uppsala University.
    Hagfeldt, Anders
    Physical Chemistry, Uppsala University.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Incompletely Solvated Ionic Liquids as Electrolyte Solvents for Highly Stable Dye-Sensitized Solar CellsArticle in journal (Other academic)
    Abstract [en]

    Ionic liquids have been intensively investigated as alternative stable electrolyte solvents for dye-sensitized solar cells (DSCs). A highest overall conversion efficiency of over 8% has been achieved using ionic-liquid-based electrolyte in combination with an iodide/triiodide redox couple. However, the relatively high viscosities of ionic liquids require higher iodine concentration in the electrolyte due to mass-transport limitations of the triiodide ions. The higher iodine concentration significantly reduces the photovoltaic performance, which normally are lower than those using organic solvent-based electrolytes. Here, the concept of incompletely solvated ionic liquids (ISILs) is introduced and represents a conceptually new type of electrolyte solvents for DSCs. It is found that the photovoltaic performance of ISIL-based electrolytes can rival that of organic solvent-based electrolytes. Furthermore, the vapor pressures of ISILs are found be considerably lower than that for pure organic solvent. Stability tests show that ISIL-based electrolytes provide highly stable DSCs under light-soaking conditions. Thus, ISIL-based electrolytes offer a new platform to develop more efficient and stable DSC devices of relevance to future large-scale applications.

  • 124302. Yuan, C.
    et al.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Recent shell-model studies of light and medium-mass nuclei2014In: He Jishu/Nuclear Techniques, ISSN 0253-3219, Vol. 37, no 10, article id 100503Article in journal (Refereed)
    Abstract [en]

    Background: Nuclear shell model is widely applied in the studies of light and medium-mass nuclei. The ground and excited state energies, electromagnetic properties and β decay properties of these nuclei can be well understood by solving many body Schrödinger equation with effective shell-model Hamiltonian in the model space. Purpose: The aim is to introduce the framework of shell model and its application in nuclei. Methods: The nuclear shell model is used to study properties of selected nuclei. Results: In psd region, a new effective shell-model Hamiltonian is introduced. The neutron drip-line of C, N, and O isotopes can be given with such Hamiltonian. The nuclei around A=20 with weakly bound proton are investigated through a modified shell model Hamiltonian. N=Z nucleus is good for studying the effect of proton-neutron pair. 46V and 50Mn have both T=0 and 1 rotational band. 92Pd can be understood under a spin alignment isoscalar scheme of proton-neutron pair. Mirror nuclei around N=Z in fp region can be used for the investigation of charge symmetry breaking effect of nuclear force. Conclusion: Nuclear shell model is proper and useful for the description of light and medium-mass nuclei.

  • 124303.
    Yuan, C.
    et al.
    Peking University.
    Qi, Chong
    Peking University.
    Xu, F.
    Peking Unversity.
    Shell-model studies of the N=14 and 16 shell closures in neutron-rich nuclei2009In: Chinese Physics C, High Energy Physics & Nuclear Physics, ISSN 1674-1137, E-ISSN 0899-9996, Vol. 33, p. 55-57Article in journal (Refereed)
  • 124304. Yuan, C. X.
    et al.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Xu, F. R.
    Shell evolution in neutron-rich carbon isotopes: Unexpected enhanced role of neutron-neutron correlation2012In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 883, p. 25-34Article in journal (Refereed)
    Abstract [en]

    Full shell-model diagonalization has been performed to study the structure of neutron-rich nuclei around C-20. We investigate in detail the roles played by the different monopole components of the effective interaction in the evolution of the N = 14 shell in C, N and O isotopes. It is found that the relevant neutron neutron monopole terms, V-d5/2d5/2(nn) and V-s1/2s1/2(nn) contribute significantly to the reduction of the N = 14 shell gap in C and N isotopes in comparison with that in O isotopes. The origin of this unexpectedly large effect, which is comparable with (sometimes even larger than) that caused by the proton neutron interaction, is related to the enhanced configuration mixing in those nuclei due to many-body correlations. Such a scheme is also supported by the large B(E2) value in the nucleus C-20 which has been measured recently.

  • 124305. Yuan, C. X.
    et al.
    Xu, F. R.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Configuration mixing effects in neutron-rich carbon isotopes2013In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 420, no 1Article in journal (Refereed)
    Abstract [en]

    Shell model calculations are done to study the structure of neutron-rich carbon isotopes. For both even-A and odd-A neutron-rich carbon isotopes, the energy levels are strongly affected by the configuration mixing of valence neutrons. The calculated energy levels in the nucleus 17C are significantly improved compared with experimental values when the model space of the three valence neutrons is enlarged from pure v(0d5/2) 3 configuration to full sd space. We also investigate the configuration mixing effect on the B(E2) values in even-even nuclei 16-20C.

  • 124306. Yuan, Cenxi
    et al.
    Qi, Chong
    KTH, School of Engineering Sciences (SCI), Physics, Nuclear Physics.
    Xu, Furong
    Suzuki, Toshio
    Otsuka, Takaharu
    Mirror energy difference and the structure of loosely bound proton-rich nuclei around A=202014In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490X, Vol. 89, no 4, p. 044327-Article in journal (Refereed)
    Abstract [en]

    The properties of loosely bound proton-rich nuclei around A = 20 are investigated within the framework of the nuclear shell model. In these nuclei, the strength of the effective interactions involving the loosely bound proton s(1/2) orbit is significantly reduced in comparison with that of those in their mirror nuclei. We evaluate the reduction of the effective interaction by calculating the monopole-based-universal interaction (V-MU) in the Woods-Saxon basis. The shell-model Hamiltonian in the sd shell, such as USD, can thus be modified to reproduce the binding energies and energy levels of the weakly bound proton-rich nuclei around A = 20. The effect of the reduction of the effective interaction on the structure and decay properties of these nuclei is also discussed.

  • 124307.
    Yuan, Chunze
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Development of Nanoparticle Sensitized Solar Cells2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, I have been working with the development of nanoparticle sensitized solar cells. In the subarea of quantum dot sensitized solar cells (QDSCs), I have investigated type-II quantum dots (QDs), quantum rods (QRs) and alloy QDs, and developed novel redox couples as electrolytes. I have also proposed upconversion nanoparticles as energy relay materials for dye-sensitized solar cells (DSCs).

    Colloidal ZnSe/CdS type-II QDs were applied for QDSCs for the first time. The interesting features of those refer to that their photoelectrons and photoholes are located on the different parts of the dot, namely in the CdS shell and in the ZnSe core, respectively. That spatial separation between photoelectrons and photoholes can so effectively enhance the charge extraction efficiency, thus facilitating the electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to a high photon to current conversion efficiency. Furthermore, a comparison between the photovoltaic performance of ZnSe/CdS and CdS/ZnSe QDSCs shows that the electron distribution is important for the electron injection of the QDs.

    Colloidal CdS/CdSe QRs were applied to quantum rod-sensitized solar cells (QRSCs). They showed a higher electron injection efficiency than the analogous QDSCs. It is concluded that reduction of the carrier confinement dimensions of the nanoparticles can improve the electron injection efficiency of the nanoparticle sensitized solar cells.

    Two types of organic electrolytes based on the redox couples of McMT-/BMT (OS1) and TMTU/TMTU-TFO (OS2) were used for the QDSCs. By reducing the charge recombination between the electrolyte and the counter electrode, the fill factor and the photovoltage of these QDSCs were significantly improved, resulting in a higher efficiency for the studied solar cells than that with a commonly used inorganic electrolyte.

    Ternary-alloy PbxCd1-xS QDs used as photosensitizers for QDSCs were found to improve the photocurrent compared to the corresponding CdS and PbS QDs. By considering the effect of different ratios of Pb to Cd in thePbxCd1-xS QDs on the photovoltaic performance it was discovered that the photocurrent increases and the photovoltage decreases with the increase of the ratio in a certain range.

    Upconversion (UC) nanoparticles provide a strategy to develop panchromatic solar cells. Three types of UC nanoparticles employed by DSCs were confirmed to work as energy relay materials for effectively extending the light-harvesting spectrum to the near-infrared (NIR) region. They were also found to play a role as scattering centers to enhance the photovoltaic performance of the solar cells.

  • 124308.
    Yuan, Chunze
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    The Study of II-VI Semiconductor Nanocrystals Sensitized Solar Cells2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Semiconductor nanocrystals, also referred to as quantum dots (QDs), have been the focus of great scientific and technological efforts in solar cells, as a result of their advantages of low-cost, photostability, high molar extinction coefficients and size-dependent optical properties. Due to the multi-electron generation effect, the theoretically maximum efficiency of quantum dots-sensitized solar cells (QDSCs) is as high as 44%, which is much higher than that of dye-sensitized solar cells (DSCs). Thus QDSCs have a clear potential to overtake the efficiency of all other kinds of solar cells.

    In recent years, the efficiency of QDSCs has been improved very quickly to around 5%. It is however still much lower than that of DSCs. The low efficiency is mostly caused by the high electron loss between electrolyte and electrodes and the lack of an efficient electrolyte. In this thesis, we have been working to enhance the performance of QDSCs with II-VI group nanocrystals by increasing the electron injection efficiency from QDs to TiO2 and developing new redox couples in electrolyte.

    To increase the electron injection, firstly, colloidal ZnSe/CdS type-II QDs were synthesized and applied for QDSCs for the first time, whose photoelectron and photohole are located on CdS shell and ZnSe core, respectively. The spatial separation between photoelectron and photohole can effectively enhance the charge extraction efficiency, facilitating electron injection, and also effectively expand the absorption spectrum. All these characteristics contribute to the high photon to current conversion efficiency. Furthermore, a comparison between the performances of ZnSe/CdS and CdS/ZnSe QDs shows that the electron distribution is important for the electron injection of the QDs in QDSCs. Secondly, colloidal CdS/CdSe quantum rods (QRs) were applied to a quantum rod-sensitized solar cell (QRSCs) that showed a higher electron injection efficiency than analogous QDSCs. It is concluded that reducing the carrier confinement dimensions of nanocrystals can improve electron injection efficiency of nanocrystal sensitized solar cells.

    In this thesis, two types of organic electrolytes based McMT-/BMT and TMTU/TMTU-TFO were used for QDSCs. By reducing the charge recombination between the electrolyte and counter electrode, fill factor (FF) of these QDSCs was significantly improved. At the same time, the photovoltages of the QDSCs were remarkably increased. As a result, the overall conversion efficiency of QDSCs based on the new electrolytes was much higher than that with a commonly used inorganic electrolyte.

    In addition, CdS QDSCs on NiO photoelectrode were studied which shows a n-type photovoltaic performance. This performance is attributed to the formation of a thin Cd metal film before CdS QDs formation on NiO. Since the CB edge of CdS sits between the Fermi level and the CB edge of Cd metal, a much strong electron transfer between Cd and CdS QD is obtained, resulting in the observed n-type photovoltaic performance of these CdS/NiO QDSCs.

  • 124309.
    Yuan, Chunze
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Chen, Guanying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. University of Buffalo, United States; Harbin Institute of Technology, China .
    Li, Lin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Damasco, Jossana A.
    Ning, Zhijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xing, Hui
    Zhang, Tianmu
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zeng, Hao
    Cartwright, Alexander N.
    Prasad, Paras N.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Simultaneous Multiple Wavelength Upconversion in a Core-Shell Nanoparticle for Enhanced Near Infrared Light Harvesting in a Dye-Sensitized Solar Cell2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 20, p. 18018-18025Article in journal (Refereed)
    Abstract [en]

    The efficiency of most photovoltaic devices is severely limited by near-infrared (NIR) transmission losses. To alleviate this limitation, a new type of colloidal upconversion nanoparticles (UCNPs), hexagonal core-shell-structured beta-NaYbF4:Er3+(2%)/NaYF4:Nd3+(30%), is developed and explored in this work as an NIR energy relay material for dye-sensitized solar cells (DSSCs). These UCNPs are able to harvest light energy in multiple NIR regions, and subsequently convert the absorbed energy into visible light where the DSSCs strongly absorb. The NIR-insensitive DSSCs show compelling photocurrent increases through binary upconversion under NIR light illumination either at 785 or 980 nm, substantiating efficient energy relay by these UCNPs. The overall conversion efficiency of the DSSCs was improved with the introduction of UCNPs under simulated AM 1.5 solar irradiation.

  • 124310.
    Yuan, Chunze
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Chen, Guanying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, Lin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Damasco, Jossana
    Ning, Zhijun
    Xing, Hui
    Zhang, Tianmu
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zeng, Hao
    Prasad, Paras N.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Effective Dual-NIR-Wavelength Energy Relay of Colloidal Upconversion Nanocrystals for Dye-sensitized Solar CellsManuscript (preprint) (Other academic)
  • 124311.
    Yuan, Chunze
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Chen, Guanying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Prasad, Paras N.
    Ohulchanskyy, Tymish Y.
    Ning, Zhijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Tian, Haining
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Use of colloidal upconversion nanocrystals for energy relay solar cell light harvesting in the near-infrared region2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 33, p. 16709-16713Article in journal (Refereed)
    Abstract [en]

    Colloidal upconversion (UC) nanocrystals were explored as energy relay materials for dye-sensitized solar cells for the first time. The utilization of colloidal UC nanocrystals was found to significantly enhance the upconversion efficiency and improve the photocurrent of the cells for low infrared irradiation intensity. In addition, it was found that UC nanocrystals of small size favor infiltration into a TiO2 film and bring higher relay efficiency. Finally, we found that UC nanocrystals can serve as a scattering material to increase the light absorption capability of the cells and increase the overall photocurrent of the cells under simulated sunlight irradiation.

  • 124312.
    Yuan, Chunze
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, Lin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Huang, Jing
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ning, Zhijun
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Improving the Photocurrent in Quantum-Dot-Sensitized Solar Cells by Employing Alloy PbxCd1-xS Quantum Dots as Photosensitizers2016In: NANOMATERIALS, ISSN 2079-4991, Vol. 6, no 6, article id UNSP 97Article in journal (Refereed)
    Abstract [en]

    Ternary alloy PbxCd1-xS quantum dots (QDs) were explored as photosensitizers for quantum-dot-sensitized solar cells (QDSCs). Alloy PbxCd1-xS QDs (Pb0.54Cd0.46S, Pb0.31Cd0.69S, and Pb0.24Cd0.76S) were found to substantially improve the photocurrent of the solar cells compared to the single CdS or PbS QDs. Moreover, it was found that the photocurrent increases and the photovoltage decreases when the ratio of Pb in PbxCd1-xS is increased. Without surface protecting layer deposition, the highest short-circuit current density reaches 20 mA/cm(2) under simulated AM 1.5 illumination (100 mW/cm(2)). After an additional CdS coating layer was deposited onto the PbxCd1-xS electrode, the photovoltaic performance further improved, with a photocurrent of 22.6 mA/cm(2) and an efficiency of 3.2%.

  • 124313.
    Yuan, Chunze
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, Lin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ning, Zhijun
    Huang, Jing
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    A Strategy to Improve Photocurrent in Quantum Dot Sensitized Solar Cells by Employing Alloy PbxCd1-xS QDs as PhotosensitizersManuscript (preprint) (Other academic)
  • 124314.
    Yuan, Chunze
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, Lin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ning, Zhijun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fu, Ying
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Study of CdS quantum dot solar cells directly deposited on p-type NiO photoelectrodesManuscript (preprint) (Other academic)
  • 124315. Yuan, D. J.
    et al.
    Cuartero, M.
    Crespo, Gaston A.
    Bakker, E.
    Voltammetric Thin-Layer lonophore-Based Films: Part 1. Experimental Evidence and Numerical Simulations2017In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 89, no 1, p. 586-594Article in journal (Refereed)
  • 124316. Yuan, D. J.
    et al.
    Cuartero, M.
    Crespo, Gaston A.
    Bakkert, E.
    Voltammetric Thin-Layer Ionophore-Based Films: Part 2. Semi-Empirical Treatment2017In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 89, no 1, p. 595-602Article in journal (Refereed)
  • 124317. Yuan, Dajing
    et al.
    Anthis, Alexandre H. C.
    Afshar, Majid Ghahraman
    Pankratova, Nadezda
    Cuartero, Maria
    Crespo, Gaston A.
    Bakker, Eric
    All-Solid-State Potentiometric Sensors with a Multiwalled Carbon Nanotube Inner Transducing Layer for Anion Detection in Environmental Samples2015In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 87, no 17, p. 8640-8645Article in journal (Refereed)
  • 124318. Yuan, H.
    et al.
    Furdek, Marija
    KTH, School of Information and Communication Technology (ICT).
    Muhammad, Ajmal
    KTH, School of Information and Communication Technology (ICT).
    Saljoghei, A.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT).
    Zervas, G.
    Space-division multiplexing in data center networks: On multi-core fiber solutions and crosstalk-suppressed resource allocation2018In: Journal of Optical Communications and Networking, ISSN 1943-0620, E-ISSN 1943-0639, Vol. 10, no 4, p. 272-288Article in journal (Refereed)
    Abstract [en]

    The rapid growth of traffic inside data centers caused by the increasing adoption of cloud services necessitates a scalable and cost-efficient networking infrastructure. Space-division multiplexing (SDM) is considered as a promising solution to overcome the optical network capacity crunch and support cost-effective network capacity scaling. Multi-core fiber (MCF) is regarded as the most feasible and efficient way to realize SDM networks, and its deployment inside data centers seems very likely as the issue of inter-core crosstalk (XT) is not severe over short link spans (<1 km) compared to that in long-haul transmission. However, XT can still have a considerable effect in MCF over short distances,which can limit the transmission reach and in turn the data center's size. XT can be further reduced by bi-directional transmission of optical signals in adjacent MCF cores. This paper evaluates the benefits of MCF-based SDM solutions in terms of maximizing the capacity and spatial efficiency of data center networks. To this end, we present an analytical model for XT in bi-directional normal step-index and trench-assisted MCFs and propose corresponding XT-aware core prioritization schemes. We further develop XT-aware spectrum resource allocation strategies aimed at relieving the complexity of online XT computation. These strategies divide the available spectrum into disjoint bands and incrementally add them to the pool of accessible resources based on the network conditions. Several combinations of core mapping and spectrum resource allocation algorithms are investigated for eight types of homogeneous MCFs comprising 7-61 cores, three different multiplexing schemes, and three data center network topologies with two traffic scenarios. Extensive simulation results showthat combining bi-directional transmission in dense core fibers with tailored resource allocation schemes significantly increases the network capacity. Moreover, a multiplexing scheme that combines SDM and WDM can achieve up to 33 times higher link spatial efficiency and up to 300 times greater capacity compared to a WDM solution.

  • 124319.
    Yuan, Han
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Joglekar, Virinchi
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Design and Implementation of an Active Horse Gait Simulator2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This project aims to design and prototype an active horse gait simulator device. The main objective is to train horse riders and give them the feeling of riding a real horse. The mechanical structure as well as the control of this device have been designed, implemented and tested. A background study of horse gaits, and of the trot, which is the gait to be recreated by the active chair, was performed. It includes an analysis of these gaits and a study of how best to recreate these motions in a simplied manner, reducing the level of mechanical complexity from that of a real horse to a simpler mechanical machine. The mechanical structure has been modelled as a lumped two mass system for the purpose of performing the design of a high level controller which commands the Siemens SINAMICS S120 AC drive system to drive the mechanical structure. The high level controller was designed in Matlab/Simulink environment on the basis of an Integral Backstepping control approach and automatically implemented on a dSPACE DS1104 R&D Controller Board. An electronics board was designed to integrate the eletronics hardware systemand a simple physical HMI was also designed in support of the interaction with the device. The prototype device was tested to determine its performance in terms of accuracy and precision by comparing it with the simulation results. It was observed to be controlled to an acceptable performance by the designed controller. Testing with real riders showed that the motion of a horse's trot had been well recreated by this prototype device.

  • 124320. Yuan, J.
    et al.
    Zhu, Bin
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Shah, R. K.
    Sundén, B.
    Modeling and analysis of A bio-fuelled ceramic fuel cell stack2004In: Fuel Cell Science, Engineering and Technology - 2004, 2004, p. 453-459Conference paper (Refereed)
    Abstract [en]

    Recent development in the advanced ceramic fuel cell (CFC), working at intermediate temperature 600-700°C, brings up feasibility and new opportunity to employ renewable fuels with this innovative technology. It may offer a better solution concerning environment, natural resources and development of our civil society. Moreover, direct oxidation of hydrocarbon fuels at intermediate temperature possesses great advantage in avoiding complex and expensive external reforming process. This paper presents modeling and analysis of an inter-mediate temperature CFC stack. The model is a general one to evaluate the stack performance for the purpose of optimal design and/or configuration based on the specified electrical power or fuel supply rate, except that the Tafel coefficients are adjusted and/or obtained to match experimental data. The energy and gas flow data obtained from the investigation can be further used to identify the heat exchanger network configurations and optimal operating conditions using process integration techniques. The model can be applied as a stand alone one, or implemented into an overall energy system modeling for the purpose of system study.

  • 124321.
    Yuan, Jing
    KTH, School of Engineering Sciences (SCI), Physics.
    LBM simulation of bubble behavior and CHF prediction of pool boiling in narrow channels under different body forces2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 124322. Yuan, K.
    et al.
    Yu, Y.
    Lu, X.
    Ji, X.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    A new technology for spraying advanced low-temperature (300∼600 °C) Solid oxide fuel cells2017In: Proceedings of the International Thermal Spray Conference, ASM International , 2017, p. 132-137Conference paper (Refereed)
    Abstract [en]

    Solid oxide fuel cell (SOFC) has been developed for a hundred year and met a great challenge on material design and marketing. In recent years, new SOFC materials are dug up to achieve high energy-output performance at lower working temperature (300∼600 °C), namely low-temperature SOFC (LTSOFC). In this study, Ni-Co-Al-Li oxide (NCAL) was used for making dense, thin and uniform coatings on grooved bipolar electrode substrate for LTSOFC. Low-pressure plasma spray (LPPS) technology was applied to manufacture the NCAL coatings. The performance of a fuel cell package using the coated bipolars was tested between 350 and 600 °C, showing 6∼8 W power output with 4 single fuel cells (active area of 25 cm2). The LPPS technology is believed to be one of the ultimate ways for manufacturing the thin film/coatings for SOFC applications in future. 

  • 124323.
    Yuan, Ling
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Economics.
    Intra-industry trade between Sweden and middle income countries2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 124324.
    Yuan, Luyao
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering.
    Sustainability Aspects of ICT in Agriculture and Food Systems2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis project aims to explore ICT solutions in agriculture and food systems, and to analyze their sustainability aspects. As a result, a comprehensive picture of existing and coming ICT solutions along the food chain is presented based on extensive literature review. Their enabled impacts are qualitatively analyzed for selected aspects of food security and environmental sustainability. Moreover, a few of ICT enabled solutions’ GHG emissions reduction potentials in agricultural and land use sector in the year 2030 are estimated quantitatively, ranging from 9 Mt to 31 Mt, depending on assumptions (6 to 50 Mt after sensitivity analysis). These results, which cannot be seen as a representation of the overall ICT potential to enable emission reductions in agriculture and the food chain, are discussed in light of earlier suggested overall ICT potentials in this area. Moreover, limitations and uncertainties of the study are further clarified. Overall, the qualitative analysis identifies a high number of solutions for ICT in the agriculture and food systems with an assumed potential to promote sustainable development. However, due to the lack of published quality data for these solutions, the predicted sustainability potential cannot be accurately estimated. 

  • 124325. Yuan, Q.
    et al.
    Lembono, T. S.
    Chen, I. -M
    Landén, Simon Nelson
    KTH, School of Industrial Engineering and Management (ITM).
    Malmgren, Victor
    KTH, School of Industrial Engineering and Management (ITM).
    Automatic robot taping with force feedback2017In: 2017 IEEE International Conference on Robotics and Automation (ICRA), Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1821-1826, article id 7989215Conference paper (Refereed)
    Abstract [en]

    In surface treatment processes like plasma spraying and spray painting of workpieces, protecting the uninvolved surface by applying masking tape is a common process. Due to the operation complexity for different geometries, such taping tasks depend on a lot of manual works, which is tedious and tiring. This paper introduces an automatic agile robotic system and the corresponding algorithm to do the surface taping. The automatic taping system consists of a 3D scanner for workpiece 3D model reconstruction, a taping end-effector which is mounted on a robot manipulator to handle the taping task, and a rotating platform that is used to hold the workpiece. The surface covering method and the taping path planning algorithms using the scanned model are introduced. With the implementation of the compliance mechanism, the force feedback and the tape cutting mechanism, the system is able to tape flat, cylindrical, freeform, and grooved surfaces. Experiments conducted on taping an engine inner liner shows that the surface can be covered with uniform taping overlap and very little wrinkle. The proposed system is a useful taping package for industrial applications such as workpiece repairing and surface protection, where surface treatments are involved.

  • 124326.
    Yuan, Qiantailang
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH).
    The Performance of the Depth Camera in Capturing Human Body Motion for Biomechanical Analysis2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Three-dimensional human movement tracking has long been an important topic in medical and engineering field. Complex camera systems such as Vicon can be used to retrieve very precise motion data. However, the system is more commercial-oriented with a high cost. Besides, it would also be tedious and cumbersome to wear the special markers and suits for tracking. Therefore, there's an urgent need to investigate a cost-effective and markless tool for motion tracking.

    Microsoft Kinect provides a promising solution with a vast variety of libraries, allowing quick development of 3-D spatial modeling and analysis such as moving skeleton possible. For example, the kinematics of the joints such as acceleration, velocity, and angle changes can be deduced from the spatial position information acquired by the camera. In order to validate whether the Kinect system is sufficient for the analysis in practice, a micro-controller platform Arduino along with Intel® Curie™ IMU (Inertial Measurement Unit) module is developed. In particular, the velocity and Euler angels of joint movements, as well as head orientations are measured and compared between the two systems. In this paper, the goal is to present (i) the use of Kinect Depth sensor for data acquisition, (ii) post-processing with the retrieved data, (iii) validation of the Kinect camera.

    Results show that the RMS error of the velocity tracking ranges from 1.78% to 23.34%, presenting a good agreement of measurement between the two systems. Moreover, the relative error of the angle tracking is between 4.0% and 24.3%. The results of the head orientations tracking are hard to perform a mathematical analysis due to the noise and invalid data from the camera caused by the loss of tracking. Overall, the accuracy of joint movement tracked by the Kinect camera, particularly velocity, is proved to be acceptable and the depth camera has been found to be an effective tool for kinematic measurement as a cost-effective option. A platform and workflow are now established, thus making future work regarding validation and application possible when the advanced hardware is available.

  • 124327. Yuan, Qilong
    et al.
    Chen, I-Ming
    Lembono, Teguh Santoso
    Landén, Simon Nelson
    KTH, School of Industrial Engineering and Management (ITM).
    Malmgren, Victor
    KTH, School of Industrial Engineering and Management (ITM).
    Strategy for robot motion and path planning in robot taping2016In: FRONTIERS OF MECHANICAL ENGINEERING, ISSN 2095-0233, Vol. 11, no 2, p. 195-203Article in journal (Refereed)
    Abstract [en]

    Covering objects with masking tapes is a common process for surface protection in processes like spray painting, plasma spraying, shot peening, etc. Manual taping is tedious and takes a lot of effort of the workers. The taping process is a special process which requires correct surface covering strategy and proper attachment of the masking tape for an efficient surface protection. We have introduced an automatic robot taping system consisting of a robot manipulator, a rotating platform, a 3D scanner and specially designed taping end- effectors. This paper mainly talks about the surface covering strategies for different classes of geometries. The methods and corresponding taping tools are introduced for taping of following classes of surfaces: Cylindrical/ extended surfaces, freeform surfaces with no grooves, surfaces with grooves, and rotational symmetrical surfaces. A collision avoidance algorithm is introduced for the robot taping manipulation. With further improvements on segmenting surfaces of taping parts and tape cutting mechanisms, such taping solution with the taping tool and the taping methodology can be combined as a very useful and practical taping package to assist humans in this tedious and time costly work.

  • 124328.
    Yuan, Qilong
    et al.
    Foshan Univ, Sch Electromech Engn, Foshan, Peoples R China..
    Chen, I-Ming
    Nanyang Technol Univ, Sch Mech & Aerosp Engn, Singapore, Singapore..
    Lembono, Teguh Santoso
    Singapore Univ Technol & Design, Engn Prod Dev, Singapore, Singapore..
    Nelson Landén, Simon
    KTH, School of Industrial Engineering and Management (ITM).
    Malmgren, Victor
    KTH, School of Industrial Engineering and Management (ITM).
    Automatic robot taping system with compliant force control2018In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 94, no 9-12, p. 4105-4113Article in journal (Refereed)
    Abstract [en]

    In surface treatment processes like plasma spraying and spray painting of workpieces, protecting the uninvolved surface by applying masking tape is a common process. Due to the operation complexity for different geometries, such taping tasks depend on a lot of manual works, which is tedious and tiring. This paper introduces an automatic agile robotic system and the corresponding algorithm to do the surface taping. The automatic taping system consists of a 3D scanner for workpiece 3D model reconstruction, a taping end-effector which is mounted on a robot manipulator to handle the taping task, and a rotating platform that is used to hold the workpiece. The surface covering method and the taping path planning algorithms using the scanned model are introduced. With the implementation of the compliance mechanism, the force feedback and the tape-cutting mechanism, the system is able to tape flat, cylindrical, freeform, and grooved surfaces. Experiments conducted on taping an engine inner liner shows that the surface can be covered with uniform taping overlap and very little wrinkle. The proposed system is a useful taping package for industrial applications such as workpiece repairing and surface protection, where surface treatments are involved.

  • 124329. Yuan, S.
    et al.
    Zhang, H.
    Wang, P.
    Ling, L.
    Tu, L.
    Lu, H.
    Wang, J.
    Zhan, Y.
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Centres, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. Fudan University, Shanghai, China.
    High-gain broadband organolead trihalide perovskite photodetector based on a bipolar heterojunction phototransistor2018In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 57, p. 7-13Article in journal (Refereed)
    Abstract [en]

    Both a favorable material and designed structure are essential for a high-performance photodetector. For the excellent physical properties of organolead trihalide perovskites, with CH3NH3PbI3 films serving as a base layer, a bipolar heterojunction phototransistor-type perovskite photodetector is proposed. Benefiting from this bipolar heterojunction structure, which is characterized by high gain and low work voltage, an optimized device exhibits high performance with a photoresponsivity of 125 AW−1 and an external efficiency of 3.62 × 104% at 427 nm with a low work voltage of 0.7 V. Additionally, such phototransistors have a broad photoresponsivity from 360 to 820 nm. These results demonstrate that the bipolar heterojunction phototransistor, which is widely used in inorganic materials, is a promising structure for organolead trihalide perovskite optoelectronic devices, paving a new way for developing high-performance photodetectors.

  • 124330.
    Yuan, Sijian
    et al.
    Fudan Univ, Ctr Micronano Syst, State Key Lab ASIC & Syst, SIST, Shanghai 200433, Peoples R China..
    Wang, Jiao
    Fudan Univ, Ctr Micronano Syst, State Key Lab ASIC & Syst, SIST, Shanghai 200433, Peoples R China..
    Yang, Kunlong
    KTH, School of Electrical Engineering and Computer Science (EECS). IPack VINN Excellence Ctr, Royal Inst Technol KTH, S-16440 Stockholm, Sweden..
    Wang, Pengfei
    Fudan Univ, Ctr Micronano Syst, State Key Lab ASIC & Syst, SIST, Shanghai 200433, Peoples R China..
    Zhang, Xin
    Fudan Univ, Ctr Micronano Syst, State Key Lab ASIC & Syst, SIST, Shanghai 200433, Peoples R China..
    Zhan, Yiqiang
    Fudan Univ, Ctr Micronano Syst, State Key Lab ASIC & Syst, SIST, Shanghai 200433, Peoples R China..
    Zheng, Li-rong
    KTH. Fudan Univ, Ctr Micronano Syst, State Key Lab ASIC & Syst, SIST, Shanghai 200433, Peoples R China.;IPack VINN Excellence Ctr, Royal Inst Technol KTH, S-16440 Stockholm, Sweden..
    High efficiency MAPbI(3-x)Cl(x) perovskite solar cell via interfacial passivation2018In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 10, no 40, p. 18909-18914Article in journal (Refereed)
    Abstract [en]

    The trap states at the interface between perovskite and charge-transport layer have a great influence on the performance of perovskite solar cells. Here, a high efficiency MAPbI(3-x)Cl(x) perovskite solar cell has been demonstrated, by introducing a thin layer of LiF or PbF2 between the SnO2/perovskite. Improved charge collection and reduced interfacial charge recombination are realized, leading to remarkable rises of both open-circuit voltage (V-oc) and short-circuit current (J(sc)). This successful interfacial passivation paved a new way to fabricate high performance perovskite solar cells with large V-oc.

  • 124331.
    Yuan, Weihao
    et al.
    Hong Kong Univ Sci & Technol, ECE, Robot Inst, Hong Kong, Peoples R China..
    Hang, Kaiyu
    Yale Univ, Mech Engn & Mat Sci, New Haven, CT USA..
    Kragic, Danica
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS. KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL.
    Wang, Michael Y.
    Hong Kong Univ Sci & Technol, ECE, Robot Inst, Hong Kong, Peoples R China..
    Stork, Johannes A.
    Orebro Univ, Ctr Appl Autonomous Sensor Syst, Orebro, Sweden..
    End-to-end nonprehensile rearrangement with deep reinforcement learning and simulation-to-reality transfer2019In: Robotics and Autonomous Systems, ISSN 0921-8890, E-ISSN 1872-793X, Vol. 119, p. 119-134Article in journal (Refereed)
    Abstract [en]

    Nonprehensile rearrangement is the problem of controlling a robot to interact with objects through pushing actions in order to reconfigure the objects into a predefined goal pose. In this work, we rearrange one object at a time in an environment with obstacles using an end-to-end policy that maps raw pixels as visual input to control actions without any form of engineered feature extraction. To reduce the amount of training data that needs to be collected using a real robot, we propose a simulation-to-reality transfer approach. In the first step, we model the nonprehensile rearrangement task in simulation and use deep reinforcement learning to learn a suitable rearrangement policy, which requires in the order of hundreds of thousands of example actions for training. Thereafter, we collect a small dataset of only 70 episodes of real-world actions as supervised examples for adapting the learned rearrangement policy to real-world input data. In this process, we make use of newly proposed strategies for improving the reinforcement learning process, such as heuristic exploration and the curation of a balanced set of experiences. We evaluate our method in both simulation and real setting using a Baxter robot to show that the proposed approach can effectively improve the training process in simulation, as well as efficiently adapt the learned policy to the real world application, even when the camera pose is different from simulation. Additionally, we show that the learned system not only can provide adaptive behavior to handle unforeseen events during executions, such as distraction objects, sudden changes in positions of the objects, and obstacles, but also can deal with obstacle shapes that were not present in the training process.

  • 124332.
    Yuan, Weihao
    et al.
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Peoples R China..
    Hang, Kaiyu
    Yale Univ, Dept Mech Engn & Mat Sci, New Haven, CT USA..
    Song, Haoran
    Hong Kong Univ Sci & Technol, Dept Mech & Aerosp Engn, Hong Kong, Peoples R China..
    Kragic, Danica
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS.
    Wang, Michael Y.
    Hong Kong Univ Sci & Technol, Dept Elect & Comp Engn, Hong Kong, Peoples R China.;Hong Kong Univ Sci & Technol, Dept Mech & Aerosp Engn, Hong Kong, Peoples R China..
    Stork, Johannes A.
    Örebro Univ, Ctr Appl Autonomous Sensor Syst, Örebro, Sweden.
    Reinforcement Learning in Topology-based Representation for Human Body Movement with Whole Arm Manipulation2019In: 2019 International Conference on Robotics and Automation (ICRA) / [ed] Howard, A Althoefer, K Arai, F Arrichiello, F Caputo, B Castellanos, J Hauser, K Isler, V Kim, J Liu, H Oh, P Santos, V Scaramuzza, D Ude, A Voyles, R Yamane, K Okamura, A, Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 2153-2160Conference paper (Refereed)
    Abstract [en]

    Moving a human body or a large and bulky object may require the strength of whole arm manipulation (WAM). This type of manipulation places the load on the robot's arms and relies on global properties of the interaction to succeed-rather than local contacts such as grasping or non-prehensile pushing. In this paper, we learn to generate motions that enable WAM for holding and transporting of humans in certain rescue or patient care scenarios. We model the task as a reinforcement learning problem in order to provide a robot behavior that can directly respond to external perturbation and human motion. For this, we represent global properties of the robot-human interaction with topology-based coordinates that are computed from arm and torso positions. These coordinates also allow transferring the learned policy to other body shapes and sizes. For training and evaluation, we simulate a dynamic sea rescue scenario and show in quantitative experiments that the policy can solve unseen scenarios with differently-shaped humans, floating humans, or with perception noise. Our qualitative experiments show the subsequent transporting after holding is achieved and we demonstrate that the policy can be directly transferred to a real world setting.

  • 124333.
    Yuan, Weihao
    et al.
    Hong Kong Univ Sci & Technol, Hong Kong, Hong Kong, Peoples R China.;HKUST Robot Inst, Hong Kong, Hong Kong, Peoples R China.;Dept Elect & Comp Engn, Hong Kong, Hong Kong, Peoples R China..
    Stork, Johannes A.
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS.
    Kragic, Danica
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for Autonomous Systems, CAS.
    Wang, Michael Y.
    Hong Kong Univ Sci & Technol, Hong Kong, Hong Kong, Peoples R China.;HKUST Robot Inst, Hong Kong, Hong Kong, Peoples R China.;Dept Mech & Aerosp Engn, Hong Kong, Hong Kong, Peoples R China..
    Hang, Kaiyu
    Hong Kong Univ Sci & Technol, Hong Kong, Hong Kong, Peoples R China.;HKUST Robot Inst, Hong Kong, Hong Kong, Peoples R China.;Dept Comp Sci & Engn, Hong Kong, Hong Kong, Peoples R China.;HKUST Inst Adv Study, Hong Kong, Hong Kong, Peoples R China..
    Rearrangement with Nonprehensile Manipulation Using Deep Reinforcement Learning2018In: 2018 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), IEEE Computer Society, 2018, p. 270-277Conference paper (Refereed)
    Abstract [en]

    Rearranging objects on a tabletop surface by means of nonprehensile manipulation is a task which requires skillful interaction with the physical world. Usually, this is achieved by precisely modeling physical properties of the objects, robot, and the environment for explicit planning. In contrast, as explicitly modeling the physical environment is not always feasible and involves various uncertainties, we learn a nonprehensile rearrangement strategy with deep reinforcement learning based on only visual feedback. For this, we model the task with rewards and train a deep Q-network. Our potential field-based heuristic exploration strategy reduces the amount of collisions which lead to suboptimal outcomes and we actively balance the training set to avoid bias towards poor examples. Our training process leads to quicker learning and better performance on the task as compared to uniform exploration and standard experience replay. We demonstrate empirical evidence from simulation that our method leads to a success rate of 85%, show that our system can cope with sudden changes of the environment, and compare our performance with human level performance.

  • 124334.
    Yuan, Xiaolong
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wideband Sigma-Delta Modulators2010Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Sigma-delta modulators (SDM) have come up as an attractive candidatefor analog-to-digital conversion in single chip front ends thanks to the continuousimproving performance. The major disadvantage is the limited bandwidthdue to the need of oversampling. Therefore, extending these convertersto broadband applications requires lowering the oversampling ratio (OSR) inorder. The aim of this thesis is the investigation on the topology and structureof sigma-delta modulators suitable for wideband applications, e.g. wireline orwireless communication system applications having a digital baseband aboutone to ten MHz.It has recently become very popular to feedforward the input signal inwideband sigma-delta modulators, so that the integrators only process quantizationerrors. The advantage being that the actual signal is not distorted byopamp and integrator nonlinearities. An improved feedforward 2-2 cascadedstructure is presented based on unity-gain signal transfer function (STF). Theimproved signal-to-noise-ratio (SNR) is obtained by optimizing zero placementof the noise transfer function (NTF) and adopting multi-bit quantizer.The proposed structure has low distortion across the entire input range.In high order single loop continuous-time (CT) sigma-delta modulator, excessloop delay may cause instability. Previous techniques in compensation ofinternal quantizer and feedback DAC delay are studied especially for the feedforwardstructure. Two alternative low power feedforward continuous-timesigma-delta modulators with excess loop delay compensation are proposed.Simulation based CT modulator synthesis from discrete time topologies isadopted to obtain the loop filter coefficients. Design examples are given toillustrate the proposed structure and synthesis methodology.Continuous time quadrature bandpass sigma-delta modulators (QBSDM)efficiently realize asymmetric noise-shaping due to its complex filtering embeddedin the loops. The effect of different feedback waveforms inside themodulator on the NTF of quadrature sigma-delta modulators is presented.An observation is made that a complex NTF can be realized by implementingthe loop as a cascade of complex integrators with a SCR feedback digital-toanalogconverter (DAC), which is desirable for its lower sensitivity to loopmismatch. The QBSDM design for different bandpass center frequencies relativeto the sampling frequency is illustrated.The last part of the thesis is devoted to the design of a wideband reconfigurablesigma-delta pipelined modulator, which consists of a 2-1-1 cascadedmodulator and a pipelined analog-to-digital convertor (ADC) as a multi-bitquantizer in the last stage. It is scalable for different bandwidth/resolutionapplication. The detail design is presented from system to circuit level. Theprototype chip is fabricated in TSMC 0.25um process and measured on thetest bench. The measurement results show that a SNR over 60dB is obtainedwith a sampling frequency of 70 MHz and an OSR of ten.

  • 124335.
    Yuan, Xiaolong
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS. Zhejiang University, China .
    Signell, S.
    Wu, Xiaobo
    KTH, School of Information and Communication Technology (ICT), Electronic, Computer and Software Systems, ECS.
    Single amplifier sigma delta modulator with input feedforward2006Conference paper (Refereed)
    Abstract [en]

    It has recently become very popular to feedforward the input signal in wideband delta-sigma modulators, so that the integrators only process quantization errors. The advantage is that the actual signal is not distorted by op-amp and integrator nonlinearities. The paper applies this technique to single amplifier based sigma delta modulator in both analog and digital way. Their characteristic has been analyzed and simulation results are given which show the improved performance.

  • 124336.
    Yuan, Xiaolong
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    Tan, Nianxiong
    Signell, Svante
    KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Communication Systems, CoS.
    On low power design of feedforward continuous-time sigma delta modulators with excess loop delay2008In: PROCEEDINGS OF 2008 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS, 2008, p. 1882-1885Conference paper (Refereed)
    Abstract [en]

    In high order single loop continuous-time (CT) sigma delta modulators, excess loop delay may cause instability. In this paper, previous techniques in compensation of internal quantizer and feedback DAC delays are studied especially for the feedforward structure. Two alternative low power feedforward continuous-time sigma delta modulators with excess loop delay compensation are proposed. Simulation based CT synthesis from discrete time topologies is adopted to obtain the loop filter coefficients. Design examples are given to illustrate the proposed structure and the synthesis methodology.

  • 124337.
    Yuan, Xiaolong
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Wu, X.
    Signell, S.
    Continuous-time quadrature bandpass sigma delta modulators with different feedback DAC2008In: IEEE Int. Conf. Circuits Syst. Commun., ICCSC, 2008, p. 580-583Conference paper (Refereed)
    Abstract [en]

    Continuous time (CT) quadrature bandpass sigma delta modulators (QBSDM) are widely used in wireless receivers recently due to its inherent anti-aliasing filtering and complex filtering embedded in the loops to efficiently realize asymmetric noise-shaping. The complex noise-transfer-function (NTF) can be realized with complex coefficients or by implementing the loop as a cascade of complex integrators with only real coefficients, which is desirable due to its lower sensitivity to loop mismatch. In this paper, we will study the effect of different feedback waveforms inside the modulator on the NTF of quadrature sigma delta modulators. Complex NTF design is discussed for different bandpass center frequencies relative to the sampling frequency.

  • 124338. Yuan, Xiaoming
    et al.
    Zhang, Lijun
    Du, Yong
    Xiong, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Tang, Ying
    Wang, Aijun
    Liu, Shuhong
    A new approach to establish both stable and metastable phase equilibria for fcc ordered/disordered phase transition: application to the Al-Ni and Ni-Si systems2012In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 135, no 1, p. 94-105Article in journal (Refereed)
    Abstract [en]

    Both two-sublattice (2SL) and four-sublattice (4SL) models in the framework of the compound energy formalism can be used to describe the fcc ordered/disordered transitions. When transferring the parameters of 2SL disregarding the metastable ordered states into those of 4SL, inconsistence in either stable or metastable phase diagrams could appear, as detected in both Al-Ni and Ni-Si systems. To avoid such a kind of drawback, this behavior was analyzed and investigated in the Ni-Si and Al-Ni systems with the aid of first principle calculations. Furthermore, a new approach considering both the stable and metastable fcc ordered phase equilibria deduced from the first principles calculations was proposed to perform a reliable thermodynamic modeling for the fcc ordered/disordered transition. The Ni-Si system was then thermodynamically assessed using the presently proposed approach. The good agreement between the calculation and experiments demonstrates the reliability of the proposed approach. It is expected that the approach is valid for other systems showing complex ordered/disordered transitions.

  • 124339.
    Yuan, Yunxia
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Atmosphere density measurements using GPS data from rigid falling spheres2017In: Atmospheric Measurement Techniques Discussions, ISSN 1867-8610, E-ISSN 1867-8610Article in journal (Refereed)
    Abstract [en]

    Atmospheric density profiles in the stratosphere and mesosphere are determined by means of low cost Global Positioning System (GPS) receivers on in situ rigid falling spheres released from a sounding rocket. Values below an altitude of 80 km are obtained. Aerodynamic drag relates atmospheric densities to other variables such as velocities of spheres, drag coefficients,and reference area. The densities are reconstructed by iterative solution. The calculated density is reasonably accurate,with deviation within 10% with respect to the European Centre for Medium-range Weather Forecasts ( ECMWF) reference value. The atmospheric temperature and wind profiles are obtained as well, and compared to independent data.

  • 124340.
    Yuan, Yunxia
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Royal Institute of Technology KTH.
    Attitude and Trajectory Estimation for Small Suborbital Payloads2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sounding rockets and small suborbital payloads provide a means for research in situ of the atmosphere and ionosphere. The trajectory and the attitude of the payload are critical for the evaluation of the scientific measurements and experiments. The trajectory refers the location of the measurement, while the attitude determines the orientation of the sensors.

    This thesis covers methods of trajectory and attitude reconstruction implemented in several experiments with small suborbital payloads carried out by the Department of Space and Plasma Physics in 2012--2016.

    The problem of trajectory reconstruction based on raw GPS data was studied for small suborbital payloads. It was formulated as a global least squares optimization problem. The method was applied to flight data of two suborbital payloads of the RAIN REXUS experiment. Positions and velocities were obtained with high accuracy.

    Based on the trajectory reconstruction technique, atmospheric densities, temperatures, and horizontal wind speeds below 80 km were obtained using rigid free falling spheres of the LEEWAVES experiment. Comparison with independent data indicates that the results are reliable for densities below 70 km, temperatures below 50 km, and wind speeds below 45 km.

    Attitude reconstruction of suborbital payloads from yaw-pitch-roll Euler angles was studied. The Euler angles were established by two methods: a global optimization method and an Unscented Kalman Filter (UKF) technique. The comparison of the results shows that the global optimization method provides a more accurate fit to the observations than the UKF.

    Improving the results of the falling sphere experiments requires understanding of the attitude motion of the sphere. An analytical consideration was developed for a free falling and axisymmetric sphere under aerodynamic torques. The motion can generally be defined as a superposition of precession and nutation. These motion phenomena were modeled numerically and compared to flight data.

  • 124341.
    Yuan, Yunxia
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Schlatter, Nicola
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    RECONSTRUCTION OF ATTITUDE DYNAMICS OF FREE FALLING UNITS2015In: EUROPEAN ROCKET AND BALLOON: PROGRAMMES AND RELATED RESEARCH, 2015, p. 107-113Conference paper (Refereed)
    Abstract [en]

    Attitude reconstruction of a free falling sphere for the experiment Multiple Spheres for Characterization of Atmosphere Temperatures (MUSCAT) is studied in this paper. The attitude dynamics is modeled through Euler's rotational equations of motion. To estimate uncertain parameters in this model such as the matrix of inertia and the lever arm for the dynamic pressure with respect to the center of mass, the dynamics reconstruction can be formulated as an optimization problem. The goal is to minimize the deviation between the measurements and the propagation from the system equations. This approach was tested against a couple of flight data sets which correspond to different periods of time. The result is very reasonable compared to the laboratory test. The estimate can be improved further through allowing drag coefficients variable and taking advantage of measurements from a magnetometer in numerical calculation.

  • 124342.
    Yuan, Yunxia
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Linden, Erik
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Post-flight trajectory reconstruction of suborbital free-flyers using GPS raw dataIn: Journal of Geodetic Science, ISSN 2081-9919, E-ISSN 2081-9943Article in journal (Other academic)
    Abstract [en]

    This paper describes the reconstruction of postflight trajectories of suborbital free flying units by using logged GPS raw data. We took the reconstruction as a global least squares optimization problem, using both the pseudo-range and Doppler observables, and solved it by using the trust-region-reflective algorithm, which enabled navigational solutions of high accuracy. The code tracking was implemented with a large number of correlators and least squares curve fitting, in order to improve the precision of the code start times, while a more conventional phased lock loop was used for Doppler tracking.We proposed a weighting scheme to account for fast signal strength variation due to free-flier fast rotation, and a penalty for jerk to achieve a smooth solution. We applied these methods to flight data of two suborbital free flying units launched on REXUS 12 sounding rocket, reconstructing the trajectory, receiver clock error and wind up rates. The trajectory exhibits a parabola with the apogee around 80 km, and the velocity profile shows the details of payload wobbling. The wind up rates obtained match the measurements from onboard angular rate sensors.

  • 124343.
    Yuan, Yunxia
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Ivchenko, Mykola
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Precession and nutation of a free flying and axi-symmetric sphere2017In: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030Article in journal (Other academic)
    Abstract [en]

    Attitude motion of small suborbital probes is closely related to scientic measurements performed on these probes. Attitude dynamics of a free ying and axi-symmetric sphere is studied in this paper. The sphere is exposed to aerodynamic torques due to the deviation between the center of mass and the geometric center. For some system parameters and initial motion conditions, the attitude motion can be thought of as regular precession, as well as superposition of precession and nutation. These motion phenomena were modeled and some physical quantities were formulated to describe them. For regular precession to occur, the aerodynamic torque must be perpendicular to the total angular momentum, and the angular momentum of non-precession must be aligned with the axis of symmetry. For superposition motion, the aerodynamic torque must be perpendicular to the total angular momentum,and the angular momentum of non-precession must not be aligned with the axis of symmetry. Numerical simulations verify these analysis. Eventually, these models are used to analyze flight data.

  • 124344.
    Yuan, Yunxia
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Tibert, Gunnar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Ivchenko, Nickolay
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Attitude reconstruction of suborbital small spacecrafts using a global optimization method2017In: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030Article in journal (Other academic)
    Abstract [en]

    Attitude motion of suborbital payloads is closely related to the quality of scientic measurements. In this paper, attitude reconstruction of suborbital payloads in terms of yaw-pitch-roll Euler angle is studied, according to measurements of magnetic fields from a magnetometer and angular velocities from a gyro sensor. To avoid complex dynamical modelling, the kinematic equations were used. The Euler angles were established by using an global optimization method. Moreover, the Euler angles were estimated by employing Unscented Kalman Filter (UKF) technique. The comparison of the optimized results to the ones from the UKF shows that the global optimization method provides higher accuracy than the UKF.

  • 124345.
    Yuan, Zhao
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Convex Optimal Power Flow Based on Second-Order Cone Programming: Models, Algorithms and Applications2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optimal power flow (OPF) is the fundamental mathematical model to optimally operate the power system. Improving the solution quality of OPF can help the power industry save billions of dollars annually. Past decades have witnessed enormous research efforts on OPF since J. Carpentier proposed the fully formulated alternating current OPF (ACOPF) model which is nonconvex. This thesis proposes three convex OPF models (SOC-ACOPF) based on second-order cone programming (SOCP) and McCormick envelope. The underlying idea of the proposed SOC-ACOPF models is to drop assumptions of the original SOC-ACOPF model by convex relaxation and approximation methods. A heuristic algorithm to recover feasible OPF solution from the relaxed solution of the proposed SOC-ACOPF models is developed. The quality of solutions with respect to global optimum is evaluated using MATPOWER and LINDOGLOBAL. A computational comparison with other SOC-ACOPF models in the literature is also conducted. The numerical results show robust performance of the proposed SOC-ACOPF models and the feasible solution recovery algorithm. We then propose to speed up solving large-scale SOC-ACOPF problem by decomposition and parallelization. We use spectral factorization to partition large power network to multiple subnetworks connected by tie-lines. A modified Benders decomposition algorithm (M-BDA) is proposed to solve the SOC-ACOPF problem iteratively. Taking the total power output of each subnetwork as the complicating variable, we formulate the SOC-ACOPF problem of tie-lines as the master problem and the SOC-ACOPF problems of the subnetworks as the subproblems in the proposed M-BDA. The feasibility of the proposed M-BDA is analytically proved. A GAMS grid computing framework is designed to compute the formulated subproblems in parallel. The numerical results show that the proposed M-BDA can solve large-scale SOC-ACOPF problem efficiently. Accelerated M-BDA by parallel computing converges within few iterations.Finally, various applications of our SOC-ACOPF models and M-BDA including distribution locational marginal pricing (DLMP), wind power integration and ultra-large-scale power network or super grid operation are demonstrated.

  • 124346.
    Yuan, Zhao
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    A Distributed Economic Dispatch Mechanism to Implement Distribution Locational Marginal Pricing2018In: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    We address the challenges of power flow computation and network operator coordination to implement distribution locational marginal pricing (DLMP) in this paper. Compared with other dynamic pricing schemes, DLMP can give clearer economic signals regarding distributed energy resources (DERs) investment, demand side response, congestion management and network reinforcement. Without neglecting the power loss of distribution network, the second-order cone AC optimal power flow (SOPF) model is used here to calculate DLMP. A distributed economic dispatch mechanism based on the modified Benders decomposition and distributed generation cost (DGC) is proposed to reduce the dispatch complexity in facing high penetration of DERs. The key contribution is that we take the tie-line power flow as the complicating variable to formulate the modified Benders decomposition algorithm. The concept of DGC is proposed to reallocate the global dispatch cost to economically incentivize the regional network operators for coordination. The distributed economic dispatch mechanism is implemented in GAMS grid computing platform. Numerical results show that SOPF can give accurate power flow and DLMP results. The fast convergence of the proposed distributed dispatch is guaranteed by the convexity of the SOPF model and efficient grid computing technique.

  • 124347.
    Yuan, Zhao
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    A Hierarchical Dispatch Structure for Distribution Network Pricing2015In: 2015 IEEE 15TH INTERNATIONAL CONFERENCE ON ENVIRONMENT AND ELECTRICAL ENGINEERING (IEEE EEEIC 2015), IEEE , 2015, p. 1631-1636Conference paper (Refereed)
    Abstract [en]

    This paper presents a hierarchical dispatch structure for efficient distribution network pricing. The dispatch coordination problem in the context of hierarchical network operators are addressed. We formulate decentralized generation dispatch into a bilevel optimization problem in which main network operator and the connected distribution network operator optimize their costs in two levels. By using Karush-Kuhn-Tucker conditions and Fortuny-Amat McCarl linearization, the bilevel optimization problem is reduced into a mixed-integer linear programming (MILP) problem. Equivalence between proposed hierarchical dispatch and centralized dispatch is proved. The model is solved in GAMS platform. IEEE 14-bus meshed network and IEEE 13-node radial network are connected to be an illustrative example offering numerical dispatch results. Three scenarios representing distributed generation (DGs) successive development stages are analyzed. Hierarchical dispatch achieves same results as traditional centralized dispatch in the three considered scenarios. Distribution network nodal prices are obtained. Intrinsic advantages of the proposed hierarchical dispatch are to reduce the dispatch complexity with increasing DGs penetration and provide distribution locational marginal prices (DLMP).

  • 124348.
    Yuan, Zhao
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    A Max-Affine Approximation Model to Solve Power Flow Problem with Controllable Accuracy2018In: Proceedings - 2018 IEEE PES Innovative Smart Grid Technologies Conference Europe, ISGT-Europe 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, article id 8571864Conference paper (Refereed)
    Abstract [en]

    This paper proposes a max-affine power flow (MAPF) model to solve the power flow (PF) problem based on linear approximation. Both active and reactive power loss variables in the original power flow equations are approximated by multiple sets of affine functions. The derivations of the proposed MAPF model are based on the branch flow equations which have been validated in the literature. The problem of solving PF equations is then equivalently reformulated in an linear optimization model. The proposed MAPF model works by minimizing the approximation error in the objective function of the formulated optimization model while satisfying all the power flow equations serving as the constraints of the formulated optimization model. Since the proposed MAPF model is linear, it is advantageous in that the accuracy of the approximation is controllable by the number of affine functions. The fast convergence and accuracy of the proposed MAPF model are proved by numerical results for various IEEE test cases. A comparison with DC power flow (DCPF) results using AC power flow (ACPF) as the benchmark shows that the accuracy of MAPF is better especially in power distribution networks where power loss is un-neglectable due to larger resistance to reactance (R/X) ratio of the power lines. The proposed MAPF model is applicable for both radial and mesh power networks.

  • 124349.
    Yuan, Zhao
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    A Modified Benders Decomposition Algorithm to Solve Second-Order Cone AC Optimal Power Flow2019In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 10, no 2, p. 1713-1724Article in journal (Refereed)
    Abstract [en]

    This paper proposes to speed up solving large-scale second-order cone ac optimal power flow (SOC-ACOPF) problem by decomposition and parallelization. First, we use spectral factorization to partition large power network to multiple subnetworks connected by tie-lines. Then a modified Benders decomposition algorithm (M-BDA) is proposed to solve the SOC-ACOPF problem iteratively. Taking the total power output of each subnetwork as the complicating variable, we formulate the SOC-ACOPF problem of tie-lines as the master problem and the SOC-ACOPF problems of the subnetworks as the subproblems in the proposed M-BDA. The feasibility and optimality (preserving the original optimal solution of the SOC-ACOPF model) of the proposed M-BDA are analytically and numerically proved. A GAMS grid computing framework is designed to compute the formulated subproblems of M-BDA in parallel. The numerical results show that the proposed M-BDA can solve large-scale SOC-ACOPF problem efficiently. Accelerated M-BDA by parallel computing converges within few iterations. The computational efficiency (reducing computation CPU time and computer RAM requirement) can be improved by increasing the number of partitioned subnetworks.

  • 124350.
    Yuan, Zhao
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Implementing zonal pricing in distribution network: The concept of pricing equivalence2016In: IEEE Power and Energy Society General Meeting, IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    Distribution locational marginal pricing (DLMP) is critical market mechanism to boost services from distributed energy resources (DER). This paper propose to design zonal pricing in distribution network according to the concept of pricing equivalence (PE). The rules of the zonal pricing are derived. We prove that equivalent load shift from demand response can be achieved by zonal pricing if pricing equivalence is deployed. Convex AC optimal power flow (OPF) is used to calculate zonal prices. The benefits of convex AC OPF are more accurate energy pricing and global optimization target. The responsive load with passive load controllers are modeled and solved in GAMS platform. Different zonal pricing approaches (PE, reference node and average of nodal prices) are compared. IEEE 14-bus network and two IEEE 13-node networks are connected to be an illustrative test case offering numerical results. The results show that zonal pricing designed according to PE can achieve the same load shift effects and quite close consumer payments as nodal pricing. PE outperform other zonal pricing approaches prominently in congested network situations.

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