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Investigation on the Pinch Point Position in Heat Exchangers

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Journal of Thermal Science 2016年第3期25卷 258-265页

作者： PAN Lisheng shi weixiu State Key Laboratory of High-temperature Gas Dynamics Institute of MechanicsChinese Academy of Sciences School of Environment and Energy Engineering Beijing University of Civil Engineering and Architecture

The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out by theoretical method. The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties. In most cases, the pinch point locates at the bubble point for the evaporator and the dew point for the condenser. However, the pinch point shills to the supercooled liquid state in the near critical conditions for the evaporator. Similarly, it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser. It even can shift to the working fluid entrance of the evaporator or the supereritical heater when the heat source fluid temperature is very high compared with the absorb- ing heat temperature. A wrong position for the pinch point may generate serious mistake. In brief, the pinch point should be founded by the itcrativc method in all conditions rather than taking for granted.

关键词： pinch point position heat exchanger heat transfer phase transition supercritical condition

Enhanced service stability and thermoelectric performance in Cu_(2)−δSebased composites

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Science China Materials 2024年第7期67卷 2369-2370页

作者： Pengfei Qiu Xun shi State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China

Thermoelectric(TE)materials can directly convert the industrial waste heat into useful electricity based on the Seebeck effect,providing a promising way to tackle the environmental pollution and global energy crisis[1].In the past several decades,many new high-performance TE materials have been discovered to enrich the TE *** them,Cu_(2)−δSe-based TE materials,which are in line with the“phonon-liquid electron-crystal”concept,have sparked widespread interest due to the high TE figure-of-merit(ZT)and the combination of elements that are nontoxic and earth-abundant[2].In 2012,Liu et al.[3]reported a ZT of 1.5 at 1000 K in the stoichiometric Cu_(2)*** alloying S at the Se-site,the ZT was enhanced to around 2.0 at 1000 K[4].Via incorporating carbon nanotubes,the ZT was further enhanced to 2.4 at 1000 K[5].Moreover,Yang et al.[6]and Zhou et al.[7]reported that the ZT of Cu_(2)Se/BiCuSeO composites can reach 2.7–2.8 around 1000 K.

关键词： composites BiCuSeO performance

Reconstruction and transmission of astronomical image based on compressed sensing

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Journal of Systems Engineering and Electronics 2016年第3期27卷 680-690页

作者： Xiaoping shi Jie Zhang Control and Simulation Center Harbin Institute of Technology

In the process of image transmission, the famous JPEG and JPEG-2000 compression methods need more transmission time as it is difficult for them to compress the image with a low compression rate. Recently the compressed sensing（CS） theory was proposed, which has earned great concern as it can compress an image with a low compression rate, meanwhile the original image can be perfectly reconstructed from only a few compressed data. The CS theory is used to transmit the high resolution astronomical image and build the simulation environment where there is communication between the satellite and the Earth. Number experimental results show that the CS theory can effectively reduce the image transmission and reconstruction time. Even with a very low compression rate, it still can recover a higher quality astronomical image than JPEG and JPEG-2000 compression methods.

关键词： transmission time compression rate compressed sensing(CS) high resolution astronomical image

AN ANISOTROPIC NONCONFORMING FINITE ELEMENT SCHEME WITH MOVING GRIDS FOR PARABOLIC INTEGRO-DIFFERENTIAL EQUATIONS

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Journal of Systems Science & Complexity 2011年第5期24卷 1020-1032页

作者： Dongyang shi Lin WANG Department of Mathematics Zhengzhou University Zhengzhou 450052 China Department of Basic Henan Mechanical and Electrical Engineering College Xinxiang 453002 China

A Crank-Nicolson scheme based on nonconforming finite element with moving grids is dis- cussed for a class of parabolic integro-differential equations under anisotropic meshes. The corresponding convergence analysis is presented and the error estimates are obtained by using the interpolation operator instead of the conventional elliptic projection which is an indispensable tool in the convergence analysis of traditional finite element methods in previous literature.

关键词： Anisotropic meshes error estimates moving grids nonconforming finite element parabolicintegro-differential equations

Application of a fourth-order relaxation scheme to hyperbolic systems of conservation laws

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Acta Mechanica Sinica 2006年第1期22卷 84-92页

作者： Jianzhong Chen Zhongke shi EO.Box615 Northwestern Polytechnical UniversityXi'an 710072 China

A fourth-order relaxation scheme is derived and applied to hyperbolic systems of conservation laws in one and two space dimensions. The scheme is based on a fourthorder central weighted essentially nonoscillatory （CWENO） reconstruction for one-dimensional cases, which is generalized to two-dimensional cases by the dimension-by-dimension approach. The large stability domain Runge-Kutta-type solver ROCK4 is used for time integration. The resulting method requires neither the use of Riemann solvers nor the computation of Jacobians and therefore it enjoys the main advantage of the relaxation schemes. The high accuracy and high-resolution properties of the present method are demonstrated in one- and two-dimensional numerical experiments.

关键词： Hyperbolic systems of conservation laws Relaxation schemes CWENO reconstruction

Impact of volcanism on the formation and hydrocarbon generation of organic-rich shale in the Jiyang Depression, Bohai Bay Basin, China

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Petroleum Science 2024年第3期21卷 1539-1551页

作者： Jia-Hong Gao Xin-Ping Liang Zhi-Jun Jin Quan-You Liu Chang-Rong Li Xiao-wei Huang Ju-Ye shi Peng Li State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Efficient Development Institute of EnergyPeking University Petroleum Exploration and Production Research Institute SINOPECBeijing100871 China School of Energy Resources China University of Geosciences Beijing100083 China

Globally,most organic-rich shales are deposited with volcanic ash *** ash,a source for many sedimentary basins,can affect the sedimentary water environment,alter the primary productivity,and preserve the organic matter(OM)through physical,chemical,and biological *** an increasing number of breakthroughs in shale oil exploration in the Bohai Bay Basin in recent years,less attention has been paid to the crucial role of volcanic impact especially its influence on the OM enrichment and hydrocarbon ***,we studied the petrology,mineralogy,and geochemical characteristics of the organic-rich shale in the upper submember of the fourth member(Es_(4)^(1))and the lower submember of the third member(Es_(3)^(3))of the Shahejie Formation,aiming to better understand the volcanic impact on organic-rich shale *** results show that total organic carbon is higher in the upper shale intervals rich in volcanic ash with enriched light rare earth elements and moderate Eu *** indicates that volcanism promoted OM formation before or after the *** positive correlation between Eu/Eu*and Post-Archean Australian Shale indicates hydrothermal activity before the volcanic *** plane graph of the hydrocarbon-generating intensity(S1+S2)suggests that the heat released by volcanism promoted hydrocarbon ***,the nutrients carried by volcanic ash promoted biological blooms during Es_(4)^(1 )and Es_(3)^(3) deposition,yielding a high primary *** blooms consume large amounts of oxygen and form anoxic environments conducive to the burial and preservation of ***,this study helps to further understand the organic-inorganic interactions caused by typical geological events and provides a guide for the next step of shale oil exploration and development in other lacustrine basins in China.

关键词： Volcanic ash Hydrocarbon generation Organic-rich shale Shahejie Formation Jiyang Depression

THE MORTAR ELEMENT METHOD FOR A NONLINEAR BIHARMONIC EQUATION

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Journal of Computational Mathematics 2005年第5期23卷 537-560页

作者： shi, ZC Xu, XJ CHINESE ACAD SCI

The mortar element method is a new domain decomposition method（DDM） with nonoverlapping subdomains. It can handle the situation where the mesh on different subdomains need not align across interfaces, and the matching of discretizations on adjacent subdomains is only enforced weakly. But until now there has been very little work for nonlinear PDEs. In this paper, we will present a mortar-type Morley element method for a nonlinear biharmonic equation which is related to the well-known Navier-Stokes equation. Optimal energy and H^1-norm estimates are obtained under a reasonable elliptic regularity assumption.

关键词： Mortar method Nonlinear biharmonic equation H^1-norm error Energy norm error

Box-constrained Total-variation Image Restoration with Automatic Parameter Estimation

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自动化学报 2014年第8期40卷 1804-1811页

作者： HE Chuan HU Chang-Hua ZHANG wei shi Biao Hi-Tech Institute of Xi'an Xi'an 710025 China

The box constraints in image restoration have been arousing great attention, since the pixels of a digital image can attain only a finite number of values in a given dynamic range. This paper studies the box-constrained total-variation (TV) image restoration problem with automatic regularization parameter estimation. By adopting the variable splitting technique and introducing some auxiliary variables, the box-constrained TV minimization problem is decomposed into a sequence of subproblems which are easier to solve. Then the alternating direction method (ADM) is adopted to solve the related subproblems. By means of Morozov's discrepancy principle, the regularization parameter can be updated adaptively in a closed form in each iteration. Image restoration experiments indicate that with our strategies, more accurate solutions are achieved, especially for image with high percentage of pixel values lying on the boundary of the given dynamic range.

关键词：图像复原参数估计变差图像恢复动态范围最小化问题正则化参数 tM图像

Applications of the isolated-check visual evoked potential in primary open angle glaucoma with or without high myopia

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International Journal of Ophthalmology(English edition) 2021年第5期14卷 704-713页

作者： Xia Wang Ruo-shi Li Ya-Hui wei Yuan Fang Tian Tian Mei Li ying-Zi Pan Department of Ophthalmology Peking University First HospitalBeijing 100034China

AIM:To explore the diagnostic performance of isolatedcheck visual evoked potential(ic VEP)for primary open angle glaucoma(POAG)in both highly myopic and nonhighly myopic populations and compare it with those of optical coherence tomography(OCT)and Heidelberg retinal tomography(HRT)***:A total of 126 participants were recruited,including 31 highly myopic participants with POAG(HM-POAG),36 non-highly myopic participants with POAG(NHM-POAG),25 highly myopic participants without POAG(HM)and 34 controls without high myopia(Normal).All the participants underwent a complete ophthalmic *** signal-to-noise ratio(SNR)was used to assess the ic *** qualitative and quantitative diagnostic performances of OCT,HRT and the ic VEP were analyzed and ***:Based on the criterion of SNR≤1,the diagnostic performance of the ic VEP in highly myopic subjects[area under the receiver operating characteristic curve(AUC)=0.862]was better than that in non-highly myopic subjects(AUC=0.789),and the SNR had fairly good *** distinguishing the HM-POAG and HM groups,the AUC of the SNR was not different from those of the OCT and HRT parameters(P>0.05)in either the qualitative or quantitative *** the qualitative analysis,the ic VEP showed good consistency with damage to the central 10°of the visual field(kappa=0.695-0.747,P<0.001).CONCLUSION:The ic VEP has the potential to discriminate individuals with and without POAG,especially in populations with high myopia.

关键词： primary openangle glaucoma high myopia isolated check visual evoked potential diagnosis