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Effect of blade sweep on inlet flow in axial compressor cascades

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Chinese Journal of Aeronautics 2015年第1期28卷 103-111页

作者： Chang Hao Zhu Fang Jin donghai Gui Xingmin School of Energy and Power Engineering Beihang University Gas Turbine technology Institute Shanghai Electric Power Generation R&D Center

This paper presents comparative numerical studies to investigate the effects of blade sweep on inlet flow in axial compressor cascades. A series of swept and straight cascades was modeled in order to obtain a general understanding of the inlet flow field that is induced by sweep.A computational fluid dynamics（CFd） package was used to simulate the cascades and obtain the required three-dimensional（3d） flow parameters. A circumferentially averaged method was introduced which provided the circumferential fluctuation（CF） terms in the momentum equation.A program for data reduction was conducted to obtain a circumferentially averaged flow *** influences of the inlet flow fields of the cascades were studied and spanwise distributions of each term in the momentum equation were analyzed. The results indicate that blade sweep does affect inlet radial equilibrium. The characteristic of radial fluid transfer is changed and thus influencing the axial velocity distributions. The inlet flow field varies mainly due to the combined effect of the radial pressure gradient and the CF component. The axial velocity varies consistently with the incidence variation induced by the sweep, as observed in the previous literature. In addition, factors that might influence the radial equilibrium such as blade camber angles, solidity and the effect of the distance from the leading edge are also taken into consideration and comparatively analyzed.

关键词： compressor blade inlet sweep axial radial straight averaged momentum consistently

Pressure swing adsorption/membrane hybrid processes for hydrogen purification with a high recovery

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Frontiers of Chemical Science and Engineering 2016年第2期10卷 255-264页

作者： Baojun Li Gaohong He Xiaobin Jiang Yan dai Xuehua ruan State Key Laboratory of Fine Chemicals R&D Center of Membrane Science and Technology School of Chemical Engineering Dalian University of Technology Dalian 116012 China

Hydrogen was recovered and purified from coal gasification-produced syngas using two kinds of hybrid processes： a pressure swing adsorption （PSA）- membrane system （a PSA unit followed by a membrane separation unit） and a membrane-PSA system （a mem- brane separation unit followed by a PSA unit）. The PSA operational parameters were adjusted to control the product purity and the membrane operational parameters were adjusted to control the hydrogen recovery so that both a pure hydrogen product （〉 99.9%） and a high recovery （〉 90%） were obtained simultaneously. The hybrid hydrogen purification processes were simulated using HYSYS and the processes were evaluated in terms of hydrogen product purity and hydrogen recovery. For comparison, a PSA process and a membrane separation process were also used individually for hydrogen purifica- tion. Neither process alone produced high purity hydrogen with a high recovery. The PSA-membrane hybrid process produced hydrogen that was 99.98% pure with a recovery of 91.71%, whereas the membrane-PSA hybrid process produced hydrogen that was 99.99% pure with a recovery of 91.71%. The PSA-membrane hybrid process achieved higher total H2 recoveries than the membrane-PSA hybrid process under the same H2 recovery of membrane separation unit. Meanwhile, the membrane-PSA hybrid process achieved a higher total H2 recovery （97.06%） than PSA-membrane hybrid process （94.35%） at the same H2 concentration of PSA feed gas （62.57%）.

关键词： hydrogen purification PSA membrane separation hybrid process

Influence of growth conditions on the V-defects in InGaN/GaN MQWs

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Journal of Semiconductors 2011年第10期32卷 17-21页

作者：纪攀峰刘乃鑫魏学成刘喆路红喜王军喜李晋闽 Semiconductor Lighting r&d center Institute of SemiconductorsChinese Academy of Sciences

The influence of the growth temperature,TMIn/TEGa andⅤ/Ⅲratio on the V-defects of InGaN/GaN multi-quantum wells（MQWs） has been investigated and *** the TMIn flow increases from 180 to 200 sccm,the density of V-defects increases from 2.72×10^（18） to 5.24×10^（18） cm^（-2）,and the V-defect width and depth increase *** density also increases with the growth *** densities are 2.05×10~8,2.72×10^（18） and 4.23×10~8 cm^（-2）,corresponding to a growth temperature of 748,753 and 758℃*** the NH_3 flows are 5000,6600 and 8000 sccm,the densities of the V-defects of these samples are 6.34×10^（18）,2.72×10^（18） and 4.13×10^（18） cm^（-2）,respectively.A properⅤ/Ⅲratio is needed to achieve step flow growth *** get the best quality of InGaN/GaN MQWs at a growth temperature of 753℃TMIn flow at 180 sccm,NH_3 flow at 6600 sccm,a flatter surface and less V-defects *** depths of these V-defects are from 10 to 30 nm,and the widths are from 100 to 200 *** order to suppress the influence of V-defects on reverse current and electro-static discharge of LEds,it is essential to grow thicker p-GaN to fill the V-defects.

关键词： V-defect density width depth TMIn/TEGa NH_3 temperature

Improvement of the efficiency droop of GaN-LEds using an AlGaN/GaN superlattice insertion layer

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Journal of Semiconductors 2011年第11期32卷 65-68页

作者：纪攀峰刘乃鑫魏同波刘喆路红喜王军喜李晋闽 Semiconductor Lighting r&d center Institute of SemiconductorsChinese Academy of Sciences

With an n-A1GaN （4 nm）/GaN （4 nm） superlattice （SL） inserted between an n-GaN and an InGaN/GaN multiquantum well active layer, the efficiency droop of GaN-based LEds has been improved. When the injection current is lower than 100 mA, the lumen efficiency of the LEd with an n-AlGaN/GaN SL is relatively small compared to that without an n-AlGaN/GaN SL. However, as the injection current increases more than 100 mA, the lumen efficiency of the LEd with an n-A1GaN/GaN SL surpasses that of an LEd without an n-AlGaN/GaN SL. The wall plug efficiency of an LEd has the same trend as lumen efficiency. The improvement of the efficiency droop of LEds with n-AIGaN/GaN SLs can be attributed to a decrease in electron leakage due to the enhanced current spreading ability and electron blocking effect at high current densities. The reverse current of LEds at -5 V reverse voltage decreases from 0.2568029 to 0.0070543 μA, and the electro-static discharge （ESd） pass yield of an LEd at human body mode （HBM）-ESd impulses of 2000 V increases from 60% to 90%.

关键词： n-AlGaN/GaN superlattices wall plug efficiency droop reverse current

MOCVd epitaxy of InAlN on different templates

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Journal of Semiconductors 2011年第9期32卷 24-28页

作者：贠利君魏同波闫建昌刘喆王军喜李晋闽 r&d center for Semiconductor Lighting Institute of SemiconductorsChinese Academy of Sciences

InAlN epilayers were grown on high quality GaN and A1N templates with the same growth parameters. Measurement results showed that two samples had the same In content of～16%,while the crystal quality and surface topography of the InAlN epilayer grown on the AlN template,with 282.3＂（002） full width at half maximum （FWHM） of rocking curve,313.5＂（102） FWHM,surface roughness of 0.39 nm and V-pit density of 2.8×10~8 cm^（-2）,were better than that of the InAlN epilayer grown on the GaN template,309.3＂,339.1＂,0.593 nm and 4.2×10~8 cm^（-2）.A primary conclusion was proposed that both the crystal quality and the surface topography of the InAlN epilayer grown on the AlN template were better than that of the InAlN epilayer grown on the GaN template. Therefore,the AlN template was a better choice than the GaN template for getting high quality InAlN epilayers.

关键词： InAlN epilayer template crystal quality surface topography

Secure Power and Subcarrier Auction in Uplink Fullduplex Cellular Networks

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China Communications 2015年第S1期12卷 157-165页

作者： LI Mingliang GUO Yunfei HUANG Kaizhi GUO Fei National digital Switching System Engineering & Technological r&d center

We consider a cellular network with a full-duplex base station, multiple uplink users and an eavesdropper. The full-duplex base station transmits jamming signals to degrade the eavesdropper channel when receiving secure multi-user signals. To maximize the secrecy rate of uplink communications, we propose a distributed ascending-clock auction(ACA) algorithm to allocate subcarriers and jamming power. Specifically, the impact of the self-interference of the full-duplex base station on the secrecy rate is considered. The proposed algorithm consists of two parts. Firstly, subcarriers and the jamming power are respectively priced by the base station. Secondly, users select the subcarrier and the jamming power based on the price. Moreover, the convergence of the proposed auction algorithm is mathematically proved. Simulation results show that the proposed auction algorithm is more beneficial to improve the uplink secrecy performance compared to traditional auction algorithms.

关键词： uplink auction physical layer security full-duplex self-interference

Light extraction efficiency enhancement of GaN-based light emitting diodes by a ZnO current spreading layer

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Journal of Semiconductors 2009年第9期30卷 29-32页

作者：杨华王晓峰阮军李志聪伊晓燕段垚曾一平王国宏 r&d center for Semiconductor Lighting Institute of SemiconductorsChinese Academy of Sciences

Gallium nitride （GaN） based light emitting diodes （LEds） with a thick and high quality ZnO film as a current spreading layer grown by metal-source vapor phase epitaxy （MVPE） are fabricated successfully. Compared with GaN-based LEds employing a Ni/Au or an indium tin oxide transparent current spreading layer, these LEds show an enhancement of the external quantum efficiency of 93% and 35% at a forward current of 20 mA, respectively. The full width at half maximum of the ZnO （002） ω-scan rocking curve is 93 arcsec, which corresponds to a high crystal quality of the ZnO film. Optical microscopy and atomic force microscopy are used to observe the surface morphology of the ZnO film, and many regular hexagonal features are found. A spectrophotometer is used to study the different absorption properties between the ZnO film and the indium tin oxide film of the GaN LEd. The mechanisms of the extraction quantum efficiency increase and the series resistance change of the GaN-based LEds with ZnO transparent current spreading layers are analyzed.

关键词： GaN LEd ZnO extraction efficiency transparent electrode

domain-Oriented Software defined Computing Architecture

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China Communications 2019年第6期16卷 162-172页

作者： Ping Lv Qinrang Liu Hongchang Chen Ting Chen National digital Switching System Engineering and Technical r&d center

With the introduction of software defined hardware by dArPA Electronics resurgence Initiative,software definition will be the basic attribute of information *** from boundary certainty and algorithm aggregation of domain applications,domain-oriented computing architecture has become the technical direction that considers the high flexibility and efficiency of information *** at the characteristics of data-intensive computing in different scenarios such as Internet of Things(IoT),big data,artificial intelligence(AI),this paper presents a domain-oriented software defined computing architecture,discusses the hierarchical interconnection structure,hybrid granularity computing element and its computational kernel extraction method,finally proves the flexibility and high efficiency of this architecture by experimental comparison.

关键词： software defined hardware software defined computing architecture hierarchical interconnection mixed-granular computing element

An Aware-Scheduling Security Architecture with Priority-Equal Multi-Controller for SdN

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China Communications 2017年第9期14卷 144-154页

作者： Chao Qi Jiangxing Wu Guozhen Cheng Jianjian Ai Shuo Zhao National digital Switching System Engineering & Technological r&d center

Current SdN controllers suffer from a series of potential attacks. For example, malicious flow rules may lead to system disorder by introducing unexpected flow entries. In this paper, we propose Mcad-SA, an aware decision-making security architecture with multiple controllers, which could coordinate heterogeneous controllers internally as a "big" controller. This architecture includes an additional plane, the scheduling plane, which consists of transponder, sensor, decider and scheduler. Meanwhile it achieves the functions of communicating, supervising and scheduling between data and control plane. In this framework, we adopt the vote results from the majority of controllers to determine valid flow rules distributed to switches. Besides, an aware dynamic scheduling(AdS) mechanism is devised in scheduler to intensify security of Mcad-SA further. Combined with perception, AdS takes advantage of heterogeneity and redundancy of controllers to enable the control plane operate in a dynamic, reliable and unsteady state, which results in significant difficulty of probing systems and executing attacks. Simulation results demonstrate the proposed methods indicate better security resilience over traditional architectures as they have lower failure probability when facing attacks.

关键词： multi-controller security architec-ture aware scheduling