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Träfflista för sökning "WFRF:(Ma Tianyu) "

Sökning: WFRF:(Ma Tianyu)

  • Resultat 1-9 av 9
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  • Fan, Peng, et al. (författare)
  • Scatter and crosstalk corrections for (99m)Tc/(123)I dual-radionuclide imaging using a CZT SPECT system with pinhole collimators.
  • 2015
  • Ingår i: Medical Physics. - : American Association of Physicists in Medicine. - 0094-2405. ; 42:12, s. 6895-6911
  • Tidskriftsartikel (refereegranskat)abstract
    • The energy spectrum for a cadmium zinc telluride (CZT) detector has a low energy tail due to incomplete charge collection and intercrystal scattering. Due to these solid-state detector effects, scatter would be overestimated if the conventional triple-energy window (TEW) method is used for scatter and crosstalk corrections in CZT-based imaging systems. The objective of this work is to develop a scatter and crosstalk correction method for (99m)Tc/(123)I dual-radionuclide imaging for a CZT-based dedicated cardiac SPECT system with pinhole collimators (GE Discovery NM 530c/570c).
  • Hu, Xing, et al. (författare)
  • Dynamic Channel Slot Allocation Scheme and Performance Analysis of Cyclic Quorum Multichannel MAC Protocol
  • 2017
  • Ingår i: Mathematical problems in engineering (Print). - : HINDAWI LTD. - 1024-123X .- 1563-5147.
  • Tidskriftsartikel (refereegranskat)abstract
    • In high diversity node situation, multichannel MAC protocol can improve the frequency efficiency, owing to fewer collisions compared with single-channel MAC protocol. And the performance of cyclic quorum-based multichannel (CQM) MAC protocol is outstanding. Based on cyclic quorum system and channel slot allocation, it can avoid the bottleneck that others suffered from and can be easily realized with only one transceiver. To obtain the accurate performance of CQMMAC protocol, a Markov chain model, which combines the channel-hopping strategy of CQM protocol and IEEE 802.11 distributed coordination function (DCF), is proposed. The results of numerical analysis show that the optimal performance of CQM protocol can be obtained in saturation bound situation. And then we obtain the saturation bound of CQM system by bird swarm algorithm. In addition, to improve the performance of CQM protocol in unsaturation situation, a dynamic channel slot allocation of CQM(DCQM) protocol is proposed, based on wavelet neural network. Finally, the performance of CQM protocol and DCQM protocol is simulated by Qualnet platform. And the simulation results show that the analytic and simulation results match very well; the DCQM performs better in unsaturation situation.
  • Hu, Xing, et al. (författare)
  • Performance analysis and saturation bound research of cyclic-quorum multichannel MAC protocol based on Markov chain model
  • 2017
  • Tidskriftsartikel (refereegranskat)abstract
    • In high diversity node situation, single-channel MAC protocols suffer from many collisions. To solve this problem, the research of multichannel MAC protocol has become a hotspot. And the cyclic quorum-based multichannel (CQM) MAC protocol outperformed others owing to its high frequency utilization. In addition, it can avoid the bottleneck that others suffered from and can be easily realized with only one transceiver. To obtain the accurate performance of CQM MAC protocol, a Markov chain model, which combines the channel hopping strategy of CQM protocol and IEEE 802.11 distributed coordination function (DCF), is proposed. The metrics (throughput and average packet transmission delay) are calculated in performance analysis, with respect to node number, packet rate, channel slot length and channel number. The results of numerical analysis show that the optimal performance of CQM protocol can be obtained in saturation bound situation. And then we obtain the saturation bound of CQM system by bird swarm algorithm (BSA). Finally, the Markov chain model and saturation bound are verified by Qualnet platform. And the simulation results show that the analytic and simulation results match very well.
  • Huang, Tianyu, et al. (författare)
  • 2D autoregressive model-based dynamic correlated massive MU-MIMO channel simulator
  • 2017
  • Ingår i: Electronics Letters. - : INST ENGINEERING TECHNOLOGY-IET. - 0013-5194 .- 1350-911X. ; 53:17
  • Tidskriftsartikel (refereegranskat)abstract
    • To design a dynamic correlated channel simulator which can precisely depict the space-time correlation properties and be suitable for the massive multi-user multiple-input multiple-output (MU-MIMO) system, a 2D autoregressive (2D AR) model-based method is proposed. Specifically, by exploiting stationarity in space-time domain, the authors use 2D AR method to create the space-time channel matrices of every user separately. In this way, the space-time dimension of the simulated channel can be modified flexibly without rebuilding the 2D AR model, and spatial correlation matrix with excessively big size is not necessary to guarantee the accuracy of the proposed simulator, making it suitable for massive MU-MIMO system. Simulation results verify the advantages of the proposed simulator.
  • Kristanl, Matej, et al. (författare)
  • The Seventh Visual Object Tracking VOT2019 Challenge Results
  • 2019
  • Konferensbidrag (refereegranskat)abstract
    • The Visual Object Tracking challenge VOT2019 is the seventh annual tracker benchmarking activity organized by the VOT initiative. Results of 81 trackers are presented; many are state-of-the-art trackers published at major computer vision conferences or in journals in the recent years. The evaluation included the standard VOT and other popular methodologies for short-term tracking analysis as well as the standard VOT methodology for long-term tracking analysis. The VOT2019 challenge was composed of five challenges focusing on different tracking domains: (i) VOT-ST2019 challenge focused on short-term tracking in RGB, (ii) VOT-RT2019 challenge focused on "real-time" short-term tracking in RGB, (iii) VOT-LT2019 focused on long-term tracking namely coping with target disappearance and reappearance. Two new challenges have been introduced: (iv) VOT-RGBT2019 challenge focused on short-term tracking in RGB and thermal imagery and (v) VOT-RGBD2019 challenge focused on long-term tracking in RGB and depth imagery. The VOT-ST2019, VOT-RT2019 and VOT-LT2019 datasets were refreshed while new datasets were introduced for VOT-RGBT2019 and VOT-RGBD2019. The VOT toolkit has been updated to support both standard short-term, long-term tracking and tracking with multi-channel imagery. Performance of the tested trackers typically by far exceeds standard baselines. The source code for most of the trackers is publicly available from the VOT page. The dataset, the evaluation kit and the results are publicly available at the challenge website(1).
  • Li, Danqin, et al. (författare)
  • n-Doping of photoactive layer in binary organic solar cells realizes over 18.3% efficiency
  • 2022
  • Ingår i: Nano Energy. - : ELSEVIER. - 2211-2855 .- 2211-3282. ; 96
  • Tidskriftsartikel (refereegranskat)abstract
    • Electronic doping of conjugated semiconductor plays a critical role in the fabrication of high efficiency organic optoelectronic devices. Here, we report an organic solar cell (OSC) by doping n-type DMBI-BDZC into one host binary bulk heterojunction (BHJ) photoactive layer comprised of a polymer donor PM6 and a nonfullerene acceptor Y6. The resulting champion device yields a significantly improved power conversion efficiency from 17.17% to 18.33% with an impressive fill factor of 80.20%. It is found that the electrically doped photoactive layer exhibits enhanced and balanced charge carrier mobilities, more effective exciton dissociation, longer carrier lifetime, and suppressed charge recombination with smaller energy loss. The dopant molecule DMBIBDZC also act as a surface morphology modifier of the photoactive layer with enhanced charge transport. This work demonstrates that manipulation of charge transport via adding a low concentration dopant into photoactive layer is a promising approach for further improvement of BHJ OSC performance.
  • Xiong, Shaobing, et al. (författare)
  • Defect passivation by nontoxic biomaterial yields 21% efficiency perovskite solar cells
  • 2021
  • Ingår i: Journal of Energy Challenges and Mechanics. - : ELSEVIER. - 2095-4956 .- 2056-9386. ; 55, s. 265-271
  • Tidskriftsartikel (refereegranskat)abstract
    • Defect passivation is one of the most important strategies to boost both the efficiency and stability of perovskite solar cells (PSCs). Here, nontoxic and sustainable forest-based biomaterial, betulin, is first introduced into perovskites. The experiments and calculations reveal that betulin can effectively passivate the uncoordinated lead ions in perovskites via sharing the lone pair electrons of hydroxyl group, promoting charge transport. As a result, the power conversion efficiencies of the p-i-n planar PSCs remarkably increase from 19.14% to 21.15%, with the improvement of other parameters. The hydrogen bonds of betulin lock methylamine and halogen ions along the grain boundaries and on the film surface and thus suppress ion migration, further stabilizing perovskite crystal structures. These positive effects enable the PSCs to maintain 90% of the initial efficiency after 30 days in ambient air with 60%+/- 5% relative humidity, 75% after 300 h aging at 85 degrees C, and 55% after 250 h light soaking, respectively. This work opens a new pathway for using nontoxic and low-cost biomaterials from forest to make highly efficient and stable PSCs. (C) 2020 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.
  • Yang, Jianming, et al. (författare)
  • Energetics and Energy Loss in 2D Ruddlesden-Popper Perovskite Solar Cells
  • 2020
  • Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840.
  • Tidskriftsartikel (refereegranskat)abstract
    • 2D Ruddlesden-Popper perovskites (RPPs) are emerging as potential challengers to their 3D counterpart due to superior stability and competitive efficiency. However, the fundamental questions on energetics of the 2D RPPs are not well understood. Here, the energetics at (PEA)(2)(MA)(n)-1PbnI3n+1/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) interfaces with varying n values of 1, 3, 5, 40, and infinity are systematically investigated. It is found that n-n junctions form at the 2D RPP interfaces (n = 3, 5, and 40), instead of p-n junctions in the pure 2D and 3D scenarios (n = 1 and infinity). The potential gradient across phenethylammonium iodide ligands that significantly decreases surface work function, promotes separation of the photogenerated charge carriers with electron transferring from perovskite crystal to ligand at the interface, reducing charge recombination, which contributes to the smallest energy loss and the highest open-circuit voltage (V-oc) in the perovskite solar cells (PSCs) based on the 2D RPP (n = 5)/PCBM. The mechanism is further verified by inserting a thin 2D RPP capping layer between pure 3D perovskite and PCBM in PSCs, causing the V-oc to evidently increase by 94 mV. Capacitance-voltage measurements with Mott-Schottky analysis demonstrate that such V-oc improvement is attributed to the enhanced potential at the interface.
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  • Resultat 1-9 av 9

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