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Z源双向DC-DC变换器及其移相直通控制策略 被引量:21
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作者 赵彪 于庆广 王立雯 《中国电机工程学报》 EI CSCD 北大核心 2011年第9期43-49,共7页
提出一种适合于宽电压调节的新型Z源双向DC-DC变换器。该变换器主要由Z源网络、传统双向DC-DC电路和部分状态控制管组成,变压器两侧电路完全对称,电路上没有高低侧之分,电源为电压源或电流源均可,并且电路可以承受桥臂直通,可靠性高。... 提出一种适合于宽电压调节的新型Z源双向DC-DC变换器。该变换器主要由Z源网络、传统双向DC-DC电路和部分状态控制管组成,变压器两侧电路完全对称,电路上没有高低侧之分,电源为电压源或电流源均可,并且电路可以承受桥臂直通,可靠性高。该电路的电压调节既可以通过阻抗网络,也可以通过变压器来实现,具有较宽的电压调节范围,同时通过开关管的控制还可使阻抗网络工作在滤波状态。该文介绍和分析了变换器的拓扑结构与工作原理,给出了一种移相直通控制策略,通过移相角和直通角的调节可以实现电压调节范围由0变化到无穷大。通过仿真和实验验证了理论分析的正确性。 展开更多
关键词 Z源逆变器 双向直流变换器 移相控制 直通角
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Joint Non-Orthogonal Multiple Access (NOMA) & Walsh-Hadamard Transform: Enhancing the Receiver Performance 被引量:2
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作者 Muhammad Rehan Usman Arsla Khan +1 位作者 Muhammad Arslan Usman Soo young Shin 《China Communications》 SCIE CSCD 2018年第9期160-177,共18页
Non-orthogonal multiple access(NOMA) is a new access method to achieve high performance gains in terms of capacity and throughput, so it is currently under consideration as one of the candidates for fifth generation(5... Non-orthogonal multiple access(NOMA) is a new access method to achieve high performance gains in terms of capacity and throughput, so it is currently under consideration as one of the candidates for fifth generation(5 G) technologies. NOMA utilizes power domain in order to superimpose signals of multiple users in a single transmitted signal. This creates a lot of interference at the receive side. Although the use of successive interference cancellation(SIC) technique reduces the interference, but to further improve the receiver performance, in this paper, we have proposed a joint Walsh-Hadamard transform(WHT) and NOMA approach for achieving better performance gains than the conventional NOMA. WHT is a well-known code used in communication systems and is used as an orthogonal variable spreading factor(OVSF) in communication systems. Application of WHT to NOMA results in low bit error rate(BER) and high throughput performance for both low and high channel gain users. Further, it also reduces peak to average power ratio(PAPR) of the user signal. The results are discussed in terms of comparison between the conventionalNOMA and the proposed technique, which shows that it offers high performance gains in terms of low BER at different SNR levels, reduced PAPR, high user throughput performance and better spectral efficiency. 展开更多
关键词 Bit error rate (BER) non-orthogonal multiple access (NOMA) orthogonal frequency division multiplexing (OFDM) peak to average power ratio (PAPR) successive interference cancellation (SIC) throughput and Walsh-Hadamard transform (WHT).
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Abrasion characteristic analyses of solid-liquid two-phase centrifugal pump 被引量:23
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作者 LI Yi ZHU Zuchao +1 位作者 HE Zhaohui HE Weiqiang 《Journal of Thermal Science》 SCIE EI CAS CSCD 2011年第3期283-287,共5页
Based on the solid-liquid two-phase mixture transportation test, the renormalization group (RNG) k-e turbulent model was utilized to simulate the solid-liquid two-phase turbulent flow in a centrifugal pump. By compari... Based on the solid-liquid two-phase mixture transportation test, the renormalization group (RNG) k-e turbulent model was utilized to simulate the solid-liquid two-phase turbulent flow in a centrifugal pump. By comparing the simulated and experimental results, inner flow features were revealed to improve the abrasion characteristic of the solid-liquid two-phase centrifugal pump. The influence of the solid phase on centrifugal pump abrasive performance is small when the particle volume fraction is less than 2.5%. The aggregation degree of the solid particles is enhanced as the particle diameter increases from 0.1 to 1 mm; however, the mixture density on the pressure side is reduced when the particle diameter increases to 1 mm for the impact of inertia. The wear on the hub is most severe for the shear stress on this position; it is also the largest. The wear characteristic is affected greatly by the parameters of the solid phase. The wear chracteristic can be optimized by decreasing the blade outlet angle. In the modified design, the blade angle is different, whereas the other geometric dimensions remain the same. The improved pump is simulated to contrast with the original pump. The results show that the values of mixture density and shear stress both decrease. The wear condition of the blade is improved to a certain extent. 展开更多
关键词 SOLID-LIQUID centrifugal pump numerical simulation abrasive experiment
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