Generation of U and P Singularities in Partially Coherent Beams Using Intensity Control Holographic Modal Wavefront Sensor

Xinyu Peng,Dong Ye,Guo Zheng Zhao,Qi Zhao,Minmin Song 한국광학회 2017 Current Optics and Photonics Vol.1 No.2

It is shown that polarization singularities of a new type, namely U and P singularities, arise at thetransverse cross section of a partially coherent beam, instead of the common singularities such as C pointsand L lines in a completely coherent vector field. A relationship between the two kind of singularitieswith respect to intensity is proposed. We also present a setup that can generate the new singularities, andany desired distribution of degree of polarization, using intensity control.

Feasibility of Three-Dimensional Balanced Steady-State Free Precession Cine Magnetic Resonance Imaging Combined with an Image Denoising Technique to Evaluate Cardiac Function in Children with Repaired Tetralogy of Fallot

Peng YaFeng,Su XinYu,Hu LiWei,Wang Qian,Ouyang RongZhen,Sun AiMin,Guo Chen,Yao XiaoFen,Zhang Yong,Wang LiJia,Zhong YuMin 대한영상의학회 2021 Korean Journal of Radiology Vol.22 No.9

Objective: To investigate the feasibility of cine three-dimensional (3D) balanced steady-state free precession (b-SSFP) imaging combined with a non-local means (NLM) algorithm for image denoising in evaluating cardiac function in children with repaired tetralogy of Fallot (rTOF). Materials and Methods: Thirty-five patients with rTOF (mean age, 12 years; range, 7–18 years) were enrolled to undergo cardiac cine image acquisition, including two-dimensional (2D) b-SSFP, 3D b-SSFP, and 3D b-SSFP combined with NLM. End-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), and ejection fraction (EF) of the two ventricles were measured and indexed by body surface index. Acquisition time and image quality were recorded and compared among the three imaging sequences. Results: 3D b-SSFP with denoising vs. 2D b-SSFP had high correlation coefficients for EDV, ESV, SV, and EF of the left (0.959– 0.991; p < 0.001) as well as right (0.755–0.965; p < 0.001) ventricular metrics. The image acquisition time ± standard deviation (SD) was 25.1 ± 2.4 seconds for 3D b-SSFP compared with 277.6 ± 0.7 seconds for 2D b-SSFP, indicating a significantly shorter time with the 3D than the 2D sequence (p < 0.001). Image quality score was better with 3D b-SSFP combined with denoising than with 3D b-SSFP (mean ± SD, 3.8 ± 0.6 vs. 3.5 ± 0.6; p = 0.005). Signal-to-noise ratios for blood and myocardium as well as contrast between blood and myocardium were higher for 3D b-SSFP combined with denoising than for 3D b-SSFP (p < 0.05 for all but septal myocardium). Conclusion: The 3D b-SSFP sequence can significantly reduce acquisition time compared to the 2D b-SSFP sequence for cine imaging in the evaluation of ventricular function in children with rTOF, and its quality can be further improved by combining it with an NLM denoising method.

Opportunistic Routing for Bandwidth-Sensitive Traffic in Wireless Networks with Lossy Links

Peng Zhao,Xinyu Yang 한국통신학회 2016 Journal of communications and networks Vol.18 No.5

Opportunistic routing (OR) has been proposed as a vi-able approach to improve the performance of wireless multihopnetworks with lossy links. However, the exponential growth ofthe bandwidth-sensitivemobile traffic (e.g.,mobile video streamingand online gaming) poses a great challenge to the performance ofOR in term of bandwidth guarantee. To solve this problem, a novelmechanism is proposed to opportunistically forwarding data pack-ets and provide bandwidth guarantee for the bandwidth-sensitivetraffic. The proposal exploits the broadcast characteristic of wire-less transmission and reduces the negative effect of wireless lossylinks. First, the expected available bandwidth (EAB) and the ex-pected transmission cost (ETC) under OR are estimated basedon the local available bandwidth, link delivery probability, for-warding candidates, and prioritization policy. Then, the policiesfor determining and prioritizing the forwarding candidates is de-vised by considering the bandwidth and transmission cost. Finally,bandwidth-aware routing algorithm is proposed to opportunisti-cally delivery data packets; meanwhile, admission control is ap-plied to admit or reject traffic flows for bandwidth guarantee. Ex-tensive simulation results show that our proposal consistently out-performs other existing opportunistic routing schemes in providingperformance guarantee.

Voltage balance evaluation strategy for DC-port faults in centralized aircraft ground power unit based on three-level neutral point clamped cascaded converter

Peng, Xu,Yu, Le,Gong, Kaiyue,Liu, Xiaohan,Yang, Guolong,Xu, Jiangjun,Zhou, Chao,Gao, Lixia,Zhu, Xinyu The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.8

An aircraft ground power unit (GPU) can replace the auxiliary power unit (APU) in an aircraft while the aircraft is parked at an airport. Therefore, the problems associated with the oil consumption and air pollution of the APU are solved. However, the GPU is faced with challenges in terms of utilization, power quality, and fault tolerance. Thus, a novel centralized aircraft GPU based on a three-level neutral point clamped cascaded converter (3LNPC-CC) is introduced in this paper to improve utilization and power quality. Furthermore, an evaluation voltage balance strategy is proposed for the DC-port fault tolerance of the 3LNPC-CC. In addition, both the modulation of the phase shift pulse width modulation (PSPWM) and the control of the double closed loop are used in the 3LNPC-CC. A simulation platform including the control, modulation, and fault tolerance of the system is established to verify the feasibility and performance of the proposed GPU. In particular, it is used to evaluate the voltage balance strategy for DC-port faults. Moreover, a prototype of the GPU and relevant experiments are completed to verify the correctness and feasibility of the system and the strategy.

Negative sequence control for DC voltage balancing in three‑phase cascaded H‑bridge rectifiers considering DC‑port failures

Xinyu Zhu,Xiao Liang,Kaiyue Gong,Xu Peng,Jun Cai,Xiaohan Liu,Chao Zhou,Siqi An,Chao Wu,Pengcheng Han 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.12

As a vital component of power electronic transformers (PET), the reliability of a cascaded H-bridge rectifier (CHBR) is essential. Therefore, in this paper, a DC-port voltage balance strategy considering DC-port failure is researched to ensure the stable operation of a CHBR. However, if the DC-port voltage balance strategy is adopted to realize the single-phase balance of a CHBR, the three-phase currents become unbalanced. This paper uses a negative sequence control (NSC) strategy that is conducive to balancing DC-port voltage to achieve three-phase current balance. For the DC-port voltage balance, the matrix generation modulation (MGM) algorithm is proposed. In addition, the DC-port voltage balance boundary is analyzed to determine the range of the DC-port voltage balance in the CHBR. A 3-module cascading topology is adopted to demonstrate the MGM algorithm and the NSC strategy. Through experiments, results show the correctness and feasibility of the proposed strategy.

Capacitors Energy Strategy Based Cascaded H-Bridge Converter for DC Port Failures

Peng, Xu,Liu, Xiaohan,Yang, Guolong,Liu, Xijun,Gao, Lixia,Zhu, Xinyu The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

In this paper, a capacitors energy strategy based Cascaded H-bridge Converter (CHBC) for steady DC link voltage is proposed, which allow the CHBC to work while DC power fails. The topology of the CHBC is analyzed to construct the proposed strategy. The capacitors energy strategy is deduced based on the principle that the DC link voltage should be steady, the switch state should be smooth and the switch frequency should be normal. Experiments based on a three-module prototype, including static experiment, start experiment and step change experiment, proves the correctness of the strategy. They also verified the excellent fault tolerance ability and good dynamic performance of the proposed strategy.

Finite-time Sliding Mode Fault-tolerant Control for Networked Control Systems With Intermittent Fault Under Event-triggered Scheme

Xinyu Guan,Yanyan Hu,Zengwang Jin,Kaixiang Peng 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.10

This paper is focused on the finite-time sliding mode fault-tolerant control problem for a class of discrete networked control systems with intermittent fault and time-varying delay under the event-triggered scheme. The intermittent fault is described as a randomly occurring fault obeying a Bernoulli distribution. The event-triggered mechanism is introduced to determine the transmission of signal, which can conserve communication resources and reduce network burdens. By means of the sliding mode observer method, a linear sliding mode function is constructed by employing the estimated state and fault information. Based on Lyapunov stability theory, sufficient criteria are derived, which can ensure the closed-loop system is finite-time bounded with pre-specified H∞ performance requirement satisfied. Then, the event-triggered observer-based sliding mode fault-tolerant controller is established to force the system state trajectories onto a pre-set sliding mode region. Afterward, the solvability of the non-convex problem is studied by testifying the feasibility of a minimization problem. Finally, a practice simulation result is provided to illustrate the effectiveness of the proposed theoretical results.

Hexahedral Mesh Quality Improvement with Geometric Constraints

Wei Peng,Xinyu Mei,Kun Shao,ChenXin Song,Xinguang Wu 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.12

Hexahedral mesh is of great value in the analysis of mechanical structure, and the mesh quality has an important impact on the efficiency and accuracy of the analysis. This paper presents a quality improvement method for hexahedral meshes, which consists of node classification, geometric constraints based single hexahedron regularization and local hexahedral mesh stitching. The nodes are divided into different types and the corresponding geometric constraints are established in single hexahedron regularization to keep the geometric shapes of original mesh. In contrast to the global optimization strategies, we perform the hexahedral mesh stitching operation within a few local regions surrounding elements with undesired quality, which can effectively improve the quality of the mesh with less consuming time. Several mesh quality improvements for hexahedral meshes generated by a variety of methods are introduced to demonstrate the effectiveness of our method.

Opportunistic Routing for Bandwidth-Sensitive Traffic in Wireless Networks with Lossy Links

Zhao, Peng,Yang, Xinyu The Korea Institute of Information and Commucation 2016 Journal of communications and networks Vol.18 No.5

Opportunistic routing (OR) has been proposed as a viable approach to improve the performance of wireless multihop networks with lossy links. However, the exponential growth of the bandwidth-sensitive mobile traffic (e.g., mobile video streaming and online gaming) poses a great challenge to the performance of OR in term of bandwidth guarantee. To solve this problem, a novel mechanism is proposed to opportunistically forwarding data packets and provide bandwidth guarantee for the bandwidth-sensitive traffic. The proposal exploits the broadcast characteristic of wireless transmission and reduces the negative effect of wireless lossy links. First, the expected available bandwidth (EAB) and the expected transmission cost (ETC) under OR are estimated based on the local available bandwidth, link delivery probability, forwarding candidates, and prioritization policy. Then, the policies for determining and prioritizing the forwarding candidates is devised by considering the bandwidth and transmission cost. Finally, bandwidth-aware routing algorithm is proposed to opportunistically delivery data packets; meanwhile, admission control is applied to admit or reject traffic flows for bandwidth guarantee. Extensive simulation results show that our proposal consistently outperforms other existing opportunistic routing schemes in providing performance guarantee.

Capacitors Energy Strategy Based Cascaded H-Bridge Converter for DC Port Failures

Xu Peng,Xiaohan Liu,Guolong Yang,Xijun Liu,Lixia Gao,Xinyu Zhu 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.5

In this paper, a capacitors energy strategy based Cascaded H-bridge Converter (CHBC) for steady DC link voltage is proposed, which allow the CHBC to work while DC power fails. The topology of the CHBC is analyzed to construct the proposed strategy. The capacitors energy strategy is deduced based on the principle that the DC link voltage should be steady, the switch state should be smooth and the switch frequency should be normal. Experiments based on a three-module prototype, including static experiment, start experiment and step change experiment, proves the correctness of the strategy. They also verified the excellent fault tolerance ability and good dynamic performance of the proposed strategy.