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A Note on Solutions for Asymptotically Linear Elliptic Systems

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Acta Mathematicae Applicatae Sinica 2008年第3期24卷 511-522页

作者： Lei-ga Zhao Department of Mathematics Beijing University of Chemical Technology 100029 Beijing China Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China Department of Mathematics Yunnan Normal University Kunming 650092 China

In this paper, we are concerned with the elliptic system of{ -△u＋V（x）u=g（x,v）, x∈R^N, -△v＋V（x）v=f（x,u）, x∈R^N, where V（x） is a continuous potential well, f, g are continuous and asymptotically linear as t→∞. The existence of a positive solution and ground state solution are established via variational methods.

关键词： Elliptic system ground state solution variational methods concentration-compactness principle

A building-based data capture and data mining technique for air quality assessment

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Frontiers of Environmental Science & Engineering 2011年第4期5卷 543-551页

作者： Ni SHENG U wa TANG Faculty of Management and Administration Macao University of Science and TechnologyMacaoChina Department of Civil and Environmental Engineering University of MacaoMacaoChina Dirccao dos Servicos de Proteccao Ambiental MacaoChina

Recently,a building-based air quality model system which can predict air quality in front of individual buildings along both sides of a road has been *** the Macao Peninsula as a case study,this paper shows the advantages of building-based model system in data capture and data *** with the traditional grid-based model systems with input/output spatial resolutions of 1-2 km,the building-based approach can extract the street configuration and traffic data building by building and therefore,can capture the complex spatial variation of traffic emission,urban geometry,and air *** non-homogeneous distribution of air pollution in the Macao Peninsula was modeled in a highspatial resolution of 319 receptors·km^(-2).The spatial relationship among air quality,traffic flow,and urban geometry in the historic urban area is *** study shows that the building-based approach may open an innovative methodology in data mining of urban spatial data for environmental *** results are particularly useful to urban planners when they need to consider the influences of urban form on street environment.

关键词： traffic air pollution spatial distribution high resolution geographic information system

Failure behavior of soil-rock mixture slopes based on centrifuge model test

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Journal of Mountain Science 2019年第8期16卷 1928-1942页

作者： waNG Teng ZHANG ga State Key Laboratory of Hydroscience and Engineering Tsinghua University

The stability of soil-rock mixtures(SRMs) that widely distributed in slopes is of significant concern for slope safety evaluation and disaster prevention. The failure behavior of SRM slopes under surface loading conditions was investigated through a series of centrifuge model tests considering various volumetric gravel contents. The displacement field of the slope was determined with image-based displacement system to observe the deformation of the soil and the movement of the block during loading in the tests. The test results showed that the ultimate bearing capacity and the stiffness of SRM slopes increased evidently when the volumetric block content exceeded a threshold value. Moreover, there were more evident slips around the blocks in the SRM slope. The microscopic analysis of the block motion showed that the rotation of the blocks could aggravate the deformation localization to facilitate the development of the slip surface. The high correlation between the rotation of the key blocks and the slope failure indicated that the blocks became the dominant load-bearing medium that influenced the slope failure. The blocks in the sliding body formed a chain to bear the load and change the displacement distribution of the adjacent matrix sand through the block rotation.

关键词： Soil rock mixture Slope stability Slope failure Centrifuge model test

Application of Shear wave Elastography and Contrast-Enhanced Ultrasound in Transrectal Prostate Biopsy

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Current Medical Science 2022年第2期42卷 447-452页

作者： gao-wa SHAREN Jun ZHANG Department of Ultrasound Affiliated Hospital of Inner Mongolia Medical UniversityHohhot010050China Department of Urology Affiliated Hospital of Inner Mongolia Medical UniversityHohhot010050China

Objective To explore the clinical value of ultrasound shear wave elastography(SWE)and contrast-enhanced ultrasound(CEUS)in transrectal prostate *** A total of 54 patients(average age:67.79±12.01 years)in the experimental group underwent transrectal prostate biopsy under the guidance of SWE,while 46 patients(average age:69.22±11.54 years)in the control group underwent transrectal prostate biopsy guided by *** There were a total of 451 needles,with an average of 8.35±1.67 needles per patient in the experimental group,and a total of 462 needles,with an average of 10.04±1.33 needles per patient in the control *** difference in puncture times between the two groups was statistically significant(Pwas no significant difference in the positive detection rate,sensitivity or specificity between the two groups(P>0.05),but there was a significant difference in the diagnostic accuracy between the two groups(Pwas 0.752(S.E.=0.072,95%CI=0.611-0.894,P=0.007),and the best cutoff value was 47.005 *** In summary,both SWE-and CEUS-guided transrectal prostate biopsy can help find the focus and guide the puncture,and improve the positive detection rate.

关键词： prostate puncture ultrasonic shear wave elastography contrast-enhanced ultrasound biopsy analysis

Advances in photothermal conversion of carbon dioxide to solar fuels

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Journal of Energy Chemistry 2023年第8期83卷 62-78,I0004页

作者： wa.ga. Yinwen Li Dequan Xiao Ding Ma College of Bioscience and Resources Environment Beijing University of AgricultureBeijing 102206China College of Chemistry and Molecular Engineering and College of Engineering Peking UniversityBeijing 100871China Center for Integrative Materials Discovery Department of Chemistry and Chemical and Biomedical EngineeringUniversity of New HavenWest HavenCT 06516USA

Converting carbon dioxide(CO_(2)) into useful fuels or chemical feedstocks is important for achieving peak carbon emission and carbon ***,photothermal catalysis has been extensively studied and applied due to its advantages over traditional heat-driven *** this review,we focus on photothermal catalysis of thermodynamically uphill reactions that convert CO_(2)into value-added *** first introduce the fundamentals of photothermal catalysis for CO_(2)reduction,including the definition and classification of photothermal catalysis,followed by their photothermal conversion *** structure design of different types of photothermal catalysts is *** superior performance of photothermal catalytic conversion of CO_(2)is illustrated and discussed,including improved CO_(2)activation,tunable selectivity towards different solar fuel products,and resistance to sintering and ***,the perspectives and challenges in this cutting-edge field are presented with the aim of advancing understanding of the underlying mechanisms and inspiring rational design of photothermal catalysts for highly efficient solar-to-fuel conversion.

关键词： Solarenergy Photothermal catalysis CO_(2)reduction Catalyst design Performance improvement

Nanostructured Catalyst for Fischer-Tropsch Synthesis

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Chinese Journal of Chemistry 2018年第9期36卷 798-808页

作者： wa.ga. Qingshan Zhu Ding Ma College of Chemistry and Molecular Engineering and College of Engineering Peking University Beijing 100871 China Fritz-Haber-Institut der Max-Planck-Gesellschaft Faradayweg 4-6 D-14195 Berlin Germany

Fischer-Tropsch synthesis （FTS） is a heterogeneous catalytic process for the production of fuels or chemicals from synthesis gas （CO ＋ H2）, which can be derived from nonpetroleum feedstocks such as natural gas, coal, or biomass. Co, Ru, Fe and Ni are all active in FTS, but only cheaper Fe and Co based catalysts are used in industry because the price of Ru is relatively high. However, the industrial Fe- and Co-based FTS catalysts normally work at a relatively high temperature range of 493--623 K in order to get a reasonable space time yield. Moreover, the product selectivity of FTS is governed by the law of polymerization, i.e., a so-called Anderson-Schulz-FIory distribution holds, which restricts its industrial application. In this account, we highlight some of our progress toward the design/fabrication of nanostructured Fe, Co and Ru catalysts to improve FTS activity at the low temperature and to change the product selectivity and confine the product distribution into a certain range.

关键词： catalyst Fischer-Tropsch synthesis nanostructure

Centrifuge model tests on pile-reinforced slopes subjected to drawdown

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1290-1300页

作者： Sujia Liu Fangyue Luo ga Zhang State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing100084China

Piles are generally an effective way to reduce the risk of slope ***,previous approaches for slope stability analysis did not consider the effect of the piles coupled with the decrease of the water level(drawdown).In this study,a series of centrifuge model tests was performed to understand the deformation and failure characteristics of slopes reinforced with various pile *** the centrifuge model tests,the pile-reinforced slopes exhibited two typical failure modes under drawdown conditions:across-pile failure and through-pile *** the through-pile slope failure,a discontinuous slip surface was observed,implying that the assumption of the slip surface in previous stability analysis methods was *** test results showed that drawdown led to instability of the piles in cohesive soil,as the saturated cohesive soil failed to provide sufficient constraint for *** slope exhibited progressive failure,from top to bottom,during *** deformation of the piles was reduced by increasing the embedment depth and row number of *** addition,the deformation of soils outside the piles was influenced by the piles and showed a similar distribution shape as the piles,and the similarity degree weakened as the distance from the piles *** study also found that the failure mechanism of unreinforced and pile-reinforced slopes induced by drawdown could be described by coupling between the deformation localization and local failure,and it revealed that pile-reinforced slopes could reduce slope deformation localization during drawdown.

关键词： Slope Pile Drawdown Failure Reinforcement Centrifuge model test

Simplified method for analyzing soil slope deformation under cyclic loading

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 1967-1976页

作者： ga Zhang Yaliang wang Fangyue Luo State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing100084China

Reasonable assessment of slope deformation under cyclic loading is of great significance for securing the safety of slopes. The observations of centrifuge model tests are analyzed on the slope deformation behavior under cyclic loading conditions. The potential slip surface is the key for slope failure and follows two rules:(i) the relative horizontal displacement along the potential slip surface is invariable at an elevation, and(ii) the soil along the slip surface exhibits the same degradation pattern. These rules are effective regardless of the location of the potential slip surface throughout the entire deformation process of a homogeneous slope, ranging from the initial deformation stage to the failure process and to the post-failure stage. A new, simplified method is proposed by deriving the displacement compatibility equation and unified degradation equation according to the fundamental rules. The method has few parameters that can be determined through traditional element tests. The predictions from the proposed method agree with the centrifuge test results with vertical loading and shaking table loading. This result confirms that the proposed method is effective in predicting the full deformation process of slopes under different cyclic loading conditions.

关键词： Soil slope Cyclic load Deformation Centrifuge model test Slice method

On n-Widths of a Sobolev Function Class in Orlicz Spaces

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Acta Mathematica Sinica,English Series 2015年第9期31卷 1475-1486页

作者： Xiao Li waNG ga Ridi WU College of Statistics and Mathematics Inner Mongolia University of Finance and Economics College of Mathematics Science Inner Mongolia Normal University

This paper considers the problem of n-widths of a Sobolev function class Ωr∞ determined by Pr（D） = DσПlj=1 （D2 - tj2I） in Orlicz spaces. The relationship between the extreme value problem and width theory is revealed by using the methods of functional analysis. Particularly, as σ = 0 or σ = 1, the exact values of Kolmogorov＇s widths, Gelfand＇s widths, and linear widths are obtained respectively, and the related extremal subspaces and optimal linear operators are given.

关键词： n-width extremal subspace optimal linear operator Orlicz space