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Optimization Study on a Single-cylinder Compressed Air Engine

Chinese Journal of Mechanical Engineering 2015年第6期28卷 1285-1292页

作者： YU Qihui CAI Maolin SHI Yan xu Qiyue School of Automation Science and Electrical Engineering Beihang University

The current research of compressed air engine（CAE） mainly focused on simulations and system integrations. However, energy efficiency and output torque of the CAE is limited, which restricts its application and popularization. In this paper, the working principles of CAE are briefly introduced. To set a foundation for the study on the optimization of the CAE, the basic mathematical model of working processes is set up. A pressure-compensated valve which can reduce the inertia force of the valve is proposed. To verify the mathematical model, the prototype with the newly designed pressure-compensated intake valve is built and the experiment is carried out, simulation and experimental results of the CAE are conducted, and pressures inside the cylinder and output torque of the CAE are obtained. Orthogonal design and grey relation analysis are utilized to optimize structural parameters. The experimental and optimized results show that, first of all, pressure inside the cylinder has the same changing tendency in both simulation curve and experimental curve. Secondly, the highest average output torque is obtained at the highest intake pressure and the lowest rotate speed. Thirdly, the optimization of the single-cylinder CAE can improve the working efficiency from an original 21.95% to 50.1%, an overall increase of 28.15%, and the average output torque increases also increases from 22.047 5 N · m to 22.439 N · m. This research designs a single-cylinder CAE with pressure-compensated intake valve, and proposes a structural parameters design method which improves the single-cylinder CAE performance.

关键词： single-cylinder compressed air engine experimental study mathematical model orthogonal design grey relation analysis

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Magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering(MPEOD) of activated sludge： Role and behavior of moisture and organics

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Journal of Environmental Sciences 2018年第12期30卷 147-158页

作者： Xinxin Guo xu Qian Yili Wang Huaili Zheng College of Environmental Science and Engineering Beijing Key Lab for Source Control Technology of Water Pollution Beijing Forestry University Beijing 100083 China Water Resource Development Research Center of Taihu Basin Authority Shanghai 200434 China Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment State Ministry of Education Chongqing University Chongqing 400045 China

In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electrical compression（MMPC–DG–MC–EC） stages was established to study the distribution and migration of water, extracellular polymeric substances（EPS）, and other organic matter in the activated sludge（AS） matrix at each *** showed that the MPEOD process could attain 53.52% water content（WC） in dewatered AS with bound water（BW） and free water（FW） reduction rates of 82.97% and 99.67%,respectively. The coagulation and time-delayed magnetic field effects of magnetic microparticles（MMPs） along the MMPC–DG–MC stages initiated the transformation of partial BW to FW in AS. EC had a coupling driving effect of electro-osmosis and pressure on BW, and the changes in pH and temperature at EC stage induced the aggregation of AS flocs and the release of partial BW. Additionally, MMPs dosing further improved the dewatering performance of AS by acting as skeleton builders to provide water passages. Meanwhile, MMPs could disintegrate sludge cells and EPS fractions, thereby reducing tryptophan-like protein and byproduct-like material concentrations in LB-EPS as well as protein/polysaccharide ratio in AS matrix, which could improve AS filterability. At EC stage, the former four Ex/Em regions of fluorescence regional integration analysis for EPS were obviously reduced, especially the protein-like substances in LB-and TB-EPS, which contributed to improvement of AS dewaterability.

关键词： Activated sludge Magnetic micro-particle Pressurized vertical electro-osmotic dewatering Water distribution Extracellular polymeric substance Fluorescence regional integration analysis

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Temporally Consistent Depth Map Prediction Using Deep Convolutional Neural Network and Spatial-Temporal Conditional Random Field

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Journal of Computer Science & Technology 2017年第3期32卷 443-456页

作者： xu-Ran Zhao xun Wang Qi-Chao Chen School of Computer and Information Engineering Zhejiang Gongshang University Hangzhou 310018 China

Deep convolutional neural networks （DCNNs） based methods recently keep setting new records on the tasks of predicting depth maps from monocular images. When dealing with video-based applications such as 2D （2-dimensional） to 3D （3-dimensional） video conversion, however, these approaches tend to produce temporally inconsistent depth maps, since their CNN models are optimized over single frames. In this paper, we address this problem by introducing a novel spatial-temporal conditional random fields （CRF） model into the DCNN architecture, which is able to enforce temporal consistency between depth map estimations over consecutive video frames. In our approach, temporally consistent superpixel （TSP） is first applied to an image sequence to establish the correspondence of targets in consecutive frames. A DCNN is then used to regress the depth value of each temporal superpixel, followed by a spatial-temporal CRF layer to model the relationship of the estimated depths in both spatial and temporal domains. The parameters in both DCNN and CRF models are jointly optimized with back propagation. Experimental results show that our approach not only is able to significantly enhance the temporal consistency of estimated depth maps over existing single-frame-based approaches, but also improves the depth estimation accuracy in terms of various evaluation metrics.

关键词： depth estimation temporal consistency convolutional neural network conditional random fields

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Deep oxidation in propane oxidative dehydrogenation to propene over V_2O_5/γ-Al_2O_3 studied by in-situ DRIFTS

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Journal of Natural Gas Chemistry 2009年第3期18卷 359-364页

作者： Yunbing He Hongbing Ji Jianhua xu Lefu Wang School of Chemistry and Chemical Engineering South China University of Technology Guangzhou 510640 Guangdong China

In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150-250℃ with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.

关键词： propane propene oxidative dehydrogenation in-situ DRIFTS deep oxidation

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Study on Aerodynamic Design Optimization of Turbomachinery Blades

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Journal of Thermal Science 2005年第4期14卷 298-304,320页

作者： Naixing CHEN Hongwu ZHANG Weiguang HUANG Yanji xu Institute of Engineering Thermophysics Chinese Academy of Sciences EO. Box 2706 Beijing 100080China

This paper describes the study on aerodynamics design optimization of turbomachinery blading developed by the authors at the Institute of Engineering Thermophysics, Chinese Academy of Sciences, during the recent few years. The present paper describes the aspects mainly on how to use a rapid approach of profiling a 3D blading and of grid generation for computation, a fast and accurate viscous computation method and an appropriate optimization methodology_ including a blade parameterization algorithm to optimize tm-bomachinery blading aerodynamically. Any blade configuration can be expressed by three curves, they are the camber lines, the thickness distributions and the radial stacking line, and then the blade geometry can be easily parameterized by a number of parameters with three polynomials. A gradient-based parameterization analytical method and a response surface method were applied herein for blade optimization. It was found that the optimization process provides reliable design for turbomachinery with reasonable computing time.

关键词： aerodynamic design optimization response surface method blade parameterization 3D aerodynamics of turbomachinery.

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Power-efficient dual-edge implicit pulse-triggered flip-flop with an embedded clock-gating scheme

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Frontiers of Information Technology & Electronic Engineering 2016年第9期17卷 962-972页

作者： Liang GENG Ji-zhong SHEN Cong-yuan xu College of Information Science & Electronic Engineering Zhejiang University

A novel dual-edge implicit pulse-triggered flip-flop with an embedded clock-gating scheme(DIFF-CGS) is proposed, which employs a transmission-gate-logic(TGL) based clock-gating scheme in the pulse generation stage. This scheme conditionally disables the inverter chain when the input data are kept unchanged, so redundant transitions of delayed clock signals and internal nodes of the latch are all eliminated, leading to low power efficiency. Based on SMIC 65 nm technology, extensive post-layout simulation results show that the proposed DIFF-CGS gains an improvement of 41.39% to 56.21% in terms of power consumption, compared with its counterparts at 10% data-switching activity. Also, full-swing operations in both implicit pulse generation and the static latch improve the robustness of the design. Thus, DIFF-CGS is suitable for low-power applications in very-large-scale integration(VLSI) designs with low data-switching activities.

关键词： Low power Flip-flop Implicit Clock-gating scheme Dual-edge

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Peering into the Milky Way by FAST:Ⅲ.Magnetic fields in the Galactic halo and farther spiral arms revealed by the Faraday effect of faint pulsars

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Science China(Physics,Mechanics & Astronomy) 2022年第12期65卷 39-54页

作者： Jun xu JinLin Han PengFei Wang Yi Yan National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy University of Chinese Academy of SciencesBeijing 100049China

The Five-hundred-meter Aperture Spherical radio Telescope(FAST)is the most sensitive radio telescope for pulsar *** make polarimetric measurements of a large number of faint and distant pulsars using the *** present the new measurements of Faraday rotation for 134 faint pulsars in the Galactic *** improvements are also made for some basic pulsar parameters for 15 of *** analyse the newly determined rotation measures(RMs)for the Galactic magnetic fields by using these 134 halo pulsars,together with previously available RMs for pulsars and extragalactic radio sources and also the newly determined RMs for another 311 faint pulsars which are either newly discovered in the project of the Galactic Plane Pulsar Snapshot(GPPS)survey or previously known pulsars without *** RM tomographic analysis in the first Galactic quadrant gives roughly the same field strength of around 2μG for the large-scale toroidal halo magnetic *** scale height of the halo magnetic fields is found to be at least 2.7±0.3 *** RM differentiation of a large number of pulsars in the Galactic disk in the Galactic longitude range of 26°

关键词： magnetic fields interstellar medium pulsars

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AN ACCURATE BINOMIAL MODEL FOR PRICING AMERICAN ASIAN OPTION

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Journal of Systems Science & Complexity 2014年第5期27卷 993-1007页

作者： LIU Jian WU Weixing xu Jingfeng ZHAO Haijian School of Insurance Central University of Finance and Economics Research Center for Applied Finance School of Banking and FinanceUniversity of International Business and Economics China Institute for Actuarial Science Central University of Finance and Economics Bosera Asset Management Co. Ltd.

This paper presents simple and fast algorithms for computing very tight upper and lower bounds on the prices of American Asian options in the binomial *** authors choose two types sets of the actual arithmetic average prices,instead of the simulated values in other existing models,as the representative average prices at each node of the binomial *** approach simplifies effectively the computation and reduces the error caused by the linear *** results show that the approach produces accurate upper and lower bounds compared to the other existing methods based on the binomial tree.

关键词： Asian option binomial tree option pricing

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Propagation behavior of SH waves in a piezomagnetic substrate with an orthorhombic piezoelectric layer

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Applied Mathematics and Mechanics(English Edition) 2018年第2期39卷 207-218页

作者： Yanping KONG Ruomeng TIAN Jie xu Jinxi LIU Department of Engineering Mechanics Shijiazhuang Tiedao University Department of Civil Engineering Shijiazhuang Tiedao University Sifang College State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering Mechanics

The dispersion behavior of the shear horizontal （SH） waves in the coupled structure consisting of a piezomagnetic substrate and an orthorhombic piezoelectric layer is investigated with different cut orientations. The surface of the piezoelectric layer is mechanically free, electrically shorted, or open, while the surface of the piezomagnetic substrate is mechanically free, magnetically open, or shorted. The dispersion relations are derived for four electromagnetic boundary conditions. The dispersion characteristics are graphically illustrated for the layered structure with the PMN-PT layer perfectly bonded on the CoFe2O4 substrate. The effects of the PMN-PT cut orientations, the electromagnetic boundary conditions, and the thickness ratio of the layer to the substrate on the dispersion behavior are analyzed and discussed in detail. The results show that, （i） the effect of the cut orientation on the dispersion curves is very obvious, （ii） the electrical boundary conditions of the PMN-PT layer dominate the propagation feature of the SH waves, and （iii） the thickness ratio has a significant effect on the phase velocity when the wave number is small. The results of the present paper can provide valuable theoretical references to the applications of piezoelectric/piezomagnectic structure in acoustic wave devices.

关键词： orthorhombic piezoelectric material PMN-PT single crystal piezomagneticmaterial shear horizontal (SH) wave dispersion relation

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Corrosion Properties of Light-weight and High-strength 2195 Al-Li Alloy

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Chinese Journal of Aeronautics 2011年第5期24卷 681-686页

作者： xu Yue WANG Xiaojing YAN Zhaotong LI Jiaxue School of Chemistry and Environment Beihang University Beijing 100191 China Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics Mianyang 621900 China

The intergranular corrosion and exfoliation corrosion of 2195 Al-Li alloy treated by multi-step heating-rate controlled aging （MSRC） are studied. The corrosion features of 2195 Al-Li alloys which are respectively treated by high-temperature nucleation MSRC （H-M） and low-temperature nucleation MSRC （L-M） are contrasted. And the corrosion mechanism of 2195 A1-Li alloy is also discussed from the viewpoint of microstructure （types, distribution, etc.） of the strengthening phase. The results show that 2195 A1-Li alloy after H-M is more susceptible to intergranular corrosion and exfoliation corrosion than that of alloy after L-M. The degree of intergranular corrosion increases with the increase of predeformation amount and the surface parallel to the rolling direction is more prone to exfoliation corrosion. The main reason of intergranular corrosion and exfoliation corrosion is the formation of corrosion galvanic couples among T1 phase, θ＇ phase and grain boundary precipitate-free zones （PFZ）.

关键词： 2195 Al-Li alloy corrosion resistance alloys multi-step heating-rate controlled aging intergranular corrosion exfo-liation corrosion corrosion mechanism

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