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The dynamic change of pore structure for low-rank coal under refined upgrading pretreatment temperatures

Petroleum Science 2021年第2期18卷 430-443页

作者： Teng Li cai-Fang wu Zi-Wei Wang College of Petroleum Engineering Xi’an Shiyou UniversityXi’an710065ShaanxiChina Shandong Key Laboratory of Depositional Mineralization and Sedimentary Mineral Shandong University of Science and TechnologyQingdao266590ShandongChina Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil and Gas Reservoirs Xi’an Shiyou UniversityXi’an710065ShaanxiChina School of Resources and Geosciences China University of Mining and TechnologyXuzhou221008JiangsuChina

Pore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank *** this study,three low-rank coal samples were collected from the Xishanyao Formation,Santanghu Basin,and low-temperature liquid-nitrogen adsorption(LP-N2A)measurements were taken under various pretreatment *** to the continuous loss of water and volatile matter in low-rank coal,the total pore volume assumes a three-step profile with knee temperatures of 150°C and 240°***,the ash in the coal can protect the coal *** collapse mainly occurs for mesopores with aperture smaller than 20 *** with apertures smaller than 5 nm exhibit a continuous decrease in pore volume,whereas the pore volume of mesopores with apertures ranging from 5 to 10 nm increases at lower pretreatment temperatures(<150°C)followed by a faint *** for mesopores with apertures larger than 10 nm,the pore volume increases significantly when the pretreatment temperature reaches 300°*** pore structure of low-rank coal features a significant heating effect,the pretreatment temperature should not exceed 150°C when the LP-N2A is used to evaluate the pore structure of low-rank coal to effectively evaluate the reservoir characteristics of low-rank coal.

关键词： Low-rank coal Low-temperature liquid-nitrogen adsorption Pore structure Refined upgrading temperatures Heating effect

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Effect of reduction pretreatment process on evolution of micro-porosity in 42CrMo billet

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Journal of Iron and Steel Research International 2021年第4期28卷 413-423页

作者： Zhen Ning Wei Yu Hong-qiang Liu Qing-wu cai Collaborative Innovation Centre of Steel Technology University of Science and Technology BeijingBeijing 100083China HBIS Group Co. Ltd.Shijiazhuang 050000HebeiChina

Reduction pretreatment(RP)process,which is implemented after the billet is completely solidified,is an alternative process to further improve billet *** element method and experiment were used to investigate the effect of the RP process on the internal quality of 42CrMo *** ultrasonic testing technology was used to study the influence of the RP process on the *** a three-dimensional finite element model,the mechanism of the RP process on the porosity closure was *** experimental results show that the RP process eliminates the macro-porosities of the billet *** number of micro-porosities in the billets is effectively reduced,and the increase in deformation contributes to the reduction in *** with isothermal rolling,the RP process leads to a larger equivalent strain and hydrostatic integration in the billet center because of the temperature gradient,and the effect of the temperature gradient is greater with the increase in *** closure effect of micro-porosity is related not only to the stress state,but also to the distribution of *** increase in three-dimensional compressive stress is beneficial to the porosity *** the micro-porosities distributed densely,excessive stress could induce micro-porosity coalescence,which has the risk of inducing cracks.

关键词： Reduction pretreatment Temperature gradient Large deformation Micro-porosity Ultrasonic testing

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Effect of the lenticles on moisture migration in capillary zone of tailings dam

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International Journal of Minerals,Metallurgy and Materials 2020年第8期27卷 1036-1045页

作者： Di Liu Min-jie Lian cai-wu Lu Wen Zhang College of Materials Science and Engineering Xi’an University of Architecture and TechnologyXi’an 710055China Institute of Mining System Engineering Xi’an University of Architecture and TechnologyXi’an 710055China Sinosteel Mining Co. Ltd.Beijing 100080China School of Resource Engineering Xi’an University of Architecture and TechnologyXi’an 710055China

Small-particle interlayers(lenticles)show some characteristic hydraulic properties and can affect the movement of unsaturated *** this study,we developed a novel online capillary-water-absorption monitoring device and conducted three groups of comparison tests to simulate lenticle positions and thicknesses with respect to the capillary *** results show that the characteristic wetting front exhibits a fast rise in the early stage,a slow rise in the middle stage,and stability in the later *** motion of the capillary water in the lenticle is mainly transversal,with the upward curve being"flat,"and the longer is"flat,"the longer is the time needed for the water to *** interlayer can form a capillary stagnation zone with moisture content close to *** high interlayer may form a discontinuous corrugated capillary ***,when the wetting front reaches the"coarse-grain(lower)-fine-grain(upper)"interface,the"anti-capillary barrier effect"results in more moisture in the upper ***,when the wetting front of the capillary water reaches the"fine-grain(upper)-coarse-grain(lower)"interface,the"capillary barrier effect"causes the moisture content of the upper tailings to decreases sharply because of the horizontal movement of the water in the fine *** is clear that the presence of lenticles can retard the rise of capillary water by storing water.

关键词： tailings lenticle moisture migration capillary retarding effect microcosmic mechanism

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Magnetic properties and crystallization kinetics of Zn_(0.5) Ni_(0.5) Fe_2O_4

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Rare Metals 2011年第6期30卷 621-626页

作者： wu Wenwei cai Jinchao wu Xuehang LI Yongni LIAO Sen School of Chemistry and Chemical Engineering Guangxi University Nanning 530004 P.R. China

Precursor of nanocrystalline ***2O4 was obtained by grinding mixture of ZnSO4.7H2O, NiSO4.6H2O, FeSO4.7H2O, and Na2CO3.10H2O under the condition of suffactant polyethylene glycol （PEG）-400 being present at room temperature, washing the mixture with water to remove soluble inorganic salts and drying it at 373 K. The spinel Zn0.5Ni0.5Fe2O4 was obtained via calcining precursor above 773 K. The precursor and its calcined products were characterized by differential scanning calorimetry （DSC）, Fourier transform infrared （FF-IR）, X-ray diffraction （XRD）, and vibrating sample magnetometer （VSM）. The result showed that ***204 obtained at 1073 K had a saturation magnetization of 74 ***-1. Kinetics of the crystallization process of Zn0.5Ni0.5Fe2O4 was studied using DSC technique, and kinetic parameters were determined by Kissinger equation and Moynihan et al. equation. The value of the activation energy associated with the crystallization process of Zr0.5Ni0.5Fe2O4 is 220.89 kJ-mol-1. The average value of the Avrami exponent, n, is equal to 1.59±0.13, which suggests that crystallization process of Zn0.5Ni0.5Fe2O4 is the random nucleation and growth of nuclei reaction.

关键词： magnetic material Zn0.5Ni0.5Fe2O4 non-isothermal kinetics crystallization process solid-state reaction at low heat

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Effect of Nb on Austenite Recrystallization in High Temperature Deformation Process

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Journal of Iron and Steel Research International 2010年第8期17卷 39-44页

作者： JIAO Duo-tian cai Qing-wu wu Hui-bin REN Yi National Engineering Research Center for Advanced Rolling Technology University of Science and Technology BeijingBeijing 100083China Angang Technology Center Anshan 114001LiaoningChina

By analyzing the stepped test pieces with optical microscope,the influence of the technological parameters including rolling temperature and reduction on the austenite recrystallization fraction of steel with Nb content of 0.08% deformed at high temperature processing was studied,and the deformed austenite recrystallization figures of the test steel were *** result indicates that when the reduction is 60%,the critical temperature of complete recrystallization is 1070 ℃ and the borderline temperature of non-recrystallization is 900 ℃.In contrast with general HSLA steel,the recrystallization and non-recrystallization temperatures are respectively 120 ℃ and 100 ℃ higher than those of ordinary HSLA,so the steel with high content of Nb has better hot processing performance because Nb has great function of holding back recrystallization.

关键词： austenite recrystallization technological parameter niobium

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Facial expression feature extraction using hybrid PCA and LBP

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The Journal of China Universities of Posts and Telecommunications 2013年第2期20卷 120-124页

作者： LUO Yuan wu cai-ming ZHANG Yi School of Optoelectronic Engineering Chongqing University of Posts and Telecommunications School of Automation Chongqing University of Posts and Telecommunications

In order to recognize facial expression accurately, the paper proposed a hybrid method of principal component analysis （PCA） and local binary pattern （LBP）. Firstly, the method of eight eyes segmentation was introduced to extract the effective area of facial expression image, which can reduce some useless information to subsequent feature extraction. Then PCA extracted the global grayscale feature of the whole facial expression image and reduced the data size at the same time. And LBP extracted local neighbor texture feature of the mouth area, which contributes most to facial expression recognition. Fusing the global and local feature will be more effective for facial expression recognition. Finally, support vector machine （SVM） used the fusion feature to complete facial expression recognition. Experiment results show that, the method proposed in this paper can classify different expressions more effectively and can get higher recognition rate than the traditional recognition methods.

关键词： facial expression recognition PCA LBP eight eyes segmentation SVM

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Study of the relationship between the content of the rare earth element Eu in rice plants and in Nilaparvata lugens （Hemiptera： Delphacidae）

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Insect Science 2012年第1期19卷 13-20页

作者： Min Yang Jin-cai wu Hai-Nan Gu School of Plant Protection Yangzhou UniversityYangzhouChina Indooroopilly Science Centre Department of Primary Industries and FisheriesQueensland 4068Australia

The current study investigated changes in the content of the rare earth element Europium （Eu） in roots, shoots and leaves of rice plants and in Nilaparvata lugens Stal （Hemiptera： Delphacidae） using an Eu marker and hydroponic culture. The results showed that N. lugens infestation significantly reduced Eu content in roots, shoots and leaves of two rice varieties, Shenyou 1 and Xieyou 963. The Eu content in roots, shoots and leaves of the susceptible variety, Shenyou 1, was significantly higher than that in the resistant variety, Xieyou 963. The Eu content ofN. lugens fed on Shenyou 1 was significantly higher than of those fed on Xieyou 963. In addition, the Eu level was elevated at a higher density ofN. lugens infestation. Eu content in the bodies ofN. lugens was related to their weight and honeydew excretion, with a significant positive correlation. Thus, Eu content in the bodies ofN. lugens can be considered an index of the amount of phloem sap taken in by N. lugens because the amount of honeydew excretion is proportional to the amount of phloem sap consumed. The ratios of Eu content in N. lugens to that in roots, shoots and leaves of rice plants were elevated at a higher N. lugens infestation density. That ratio was maximal in leaves, was intermediate in shoots and was minimal in roots. There was no significant difference in ratios between the two plant varieties. An Eu marker may be useful in the screening of resistant varieties and in the study of the mechanisms of resistance.

关键词： markers Nilaparvata lugens rare earth element Eu rice

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Panel data models with cross-sectional dependence: a selective review

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Applied Mathematics(A Journal of Chinese Universities) 2016年第2期31卷 127-147页

作者： XU Qiu-hua cai Zong-wu FANG Ying The Wang Yanan Institute for Studies in Economics MOE Key Laboratory of Econometrics (Xiamen University)Fujian Provincial Key Laboratory of Statistical ScienceXiamen University Department of Economics University of Kansas

In this review, we highlight some recent methodological and theoretical develop- ments in estimation and testing of large panel data models with cross-sectional dependence. The paper begins with a discussion of issues of cross-sectional dependence, and introduces the concepts of weak and strong cross-sectional dependence. Then, the main attention is primarily paid to spatial and factor approaches for modeling cross-sectional dependence for both linear and nonlinear （nonparametric and semiparametric） panel data models. Finally, we conclude with some speculations on future research directions.

关键词： Panel data models Cross-sectional dependence Spatial dependence Interactive fixed effects,Common factors.

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A new test on the conditional capital asset pricing model

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Applied Mathematics(A Journal of Chinese Universities) 2015年第2期30卷 163-186页

作者： LI Xia-fei cai Zong-wu REN Yu Wang Yanan Institute for Studies in Economics The MOE Key Lab of Econometrics and Fujian Key Lab of Statistical Sciences Xiamen University Department of Economics University of Kansas

Testing the validity of the conditional capital asset pricing model （CAPM） is a puzzle in the finance literature. Lewellen and Nagel[14] find that the variation in betas and in the equity premium would have to be implausibly large to explain important asset-pricing anomalies. Unfortunately, they do not provide a rigorous test statistic. Based on a simulation study, the method proposed in Lewellen and Nagel[14] tends to reject the null too frequently. We develop a new test procedure and derive its limiting distribution under the null hypothesis. Also, we provide a Bootstrap approach to the testing procedure to gain a good finite sample performance. Both simulations and empirical studies show that our test is necessary for making correct inferences with the conditional CAPM.

关键词： Asset pricing model bootstrap test conditional CAPM large sample theory

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Econometric modeling of risk measures: A selective review of the recent literature

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Applied Mathematics(A Journal of Chinese Universities) 2019年第2期34卷 205-228页

作者： TIAN Ding-shi cai Zong-wu FANG Ying Wang Yanan Institute for Studies in Economics Department of StatisticsSchool of EconomicsMinistry of Education Key Laboratory of Econometrics and Fujian Key Laboratory of Statistical ScienceXiamen UniversityXiamenFujian 361005China Department of Economics University of KansasLawrenceKS 66045USA

Since the financial crisis in 2008, the risk measures which are the core of risk management, have received increasing attention among economists and practitioners. In this review, the concentration is on recent developments in the estimation of the most popular risk measures, namely, value at risk (VaR), expected shortfall (ES), and expectile. After introducing the concept of risk measures, the focus is on discussion and comparison of their econometric modeling. Then, parametric and nonparametric estimations of tail dependence are investigated. Finally, we conclude with insights into future research directions.

关键词： Expectile Expected Shortfall Network Risk Nonparametric Estimation Tail Dependence Value at Risk

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