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Superconvergence and asymptotic expansions for linear finite element approximations on criss-cross mesh

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Science China Mathematics 2004年第Z1期47卷 136-145页

作者： HUANG Yunqing SHU Shi YU Haiyuan Department of Mathematics Xiangtan University Xiangtan 411105 China Department of Mathematics Xiangtan University Xiangtan 411105 China Department of Mathematics Xiangtan University Xiangtan 411105 China

In this paper, we discuss the error estimation of the linear finite element solution on criss-cross mesh. Using space orthogonal decomposition techniques, we obtain an asymptotic expansion and superconvergence results of the finite element solution. We first prove that the asymptotic expansion has different forms on the two kinds of nodes and then derive a high accuracy combination formula of the approximate derivatives.

关键词： criss-cross mesh, linear finite element, superconvergence.

Application of binary optical element to infrared hyperspectral detection

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Science China(Technological Sciences) 2003年第6期46卷 654-660页

作者：孙强于斌刘玉玲卢振武陈波王肇圻母国光 State Key Lab of Applied Optics Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Changchun 130022 China Institute of Modern Optics Nankai University The Key Laboratory of Opt-electronic Information Science and Technology MOE Tianjin 300071 China

Binary optical element (BOE) is applied to infrared hyperspectral detector. A new type of infrared hyperspectral detecting image system is designed based on the characteristics of abun-dant color-dispersion of BOE, and an example of combining refractive-diffractive zoom optical sys-tem with Cassegrain system is presented. The system not only has simple structure, long back-working distance and few requirements for material but also can increase the image resolu-tion, abilities of accepting ray energy and registration. Consequently, by adding an appropriate stare array detector to the system, the detecting precision can be raised.

关键词： binary optical element, hyperspectral detection, zoom optical system.

Special hybrid stress element for stress analyses around circular cutouts in laminated composites

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Science China(Technological Sciences) 2001年第5期44卷 531-541页

作者：田宗漱赵奉东田铮 Department of Mechanics Graduate School Chinese Academy of Sciences Beijing 100080 China

A 3-dimensional hybrid stress element with a traction-free cylindrical surface based on amodified complementary energy principle has been derived for efficient and accurate analysis of stressconcentration around circular cutouts in thin to thick laminated composites. New expressions of sixstress components are developed by using three stress-functions in cylindrical co-ordinates, so that thehomogeneous equilibrium equations, the interlayer surface transverse-stresses and the traction-freeboundary condition on the cylindrical surface are satisfied exactly, while the interelement traction conti-nuity has been relaxed via the Lagrange multiplier method. Transverse-shear deformation effects areincorporated in each layer with displacement continuity enforced along interlayer surface. Selected ex-amples are used to demonstrate the efficiency and accuracy of the present special element.

关键词： laminated composites, circular cutouts, special hybrid stress element, 3-dimensional stress analysis.

ON MORTAR-TYPE TRUNC element METHOD FOR PLATE BENDING PROBOEM

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Numerical Mathematics A Journal of Chinese Universities(English Series) 2002年第2期11卷 235-240页

作者： Liu Qing(刘庆) Li Likang(李立康) Mathematics Department Fudan University Shanghai 200433 PRC Mathematics Department Fudan University Shanghai 200433 PRC

Wepresnet a brief introduction of applying the idea of mortar method to locally nonconforming TRUNC element for solving plate bending problem. At the interfaces, three mortar conditions, one for the value of solution in pointwise way, the other two for the normal and tangential derivatives of the solution in projection way, are provided to secure the global convergence. Afte some detailed analysis, we obtain that its error estimates in both energy norm and discrete H1 norm are optimal for u*∈H3(Ω)∩H2 0(Ω).

关键词： plate bending problem, TRUNC element, mortar method.

In situ zircon Hf isotopic, U-Pb age and trace element study of monzonite xenoliths from Pingquan and Fuxin basalts: Tracking the thermal events of 169 Ma and 107 Ma in Yanliao area

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Science China Earth Sciences 2004年第Z2期47卷 39-52页

作者： ZHENG Jianping ZHANG Ruisheng YU Chunmei TANG Huayun ZHANG Pei Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China Faculty of Earth Sciences China University of Geosciences Wuhan 430074 China

K-Ar ages of the Mesozoic (92-100 Ma) Fuxin alkalic basalts (western Liaoning Province) and the Tertiary (23-45 Ma) Pingquan alkalic basalts (eastern Hebei Province), and the results of in situ zircon U-Pb dating, Hf isotope and the trace elements from three monzonite xenoliths carried in the alkalic basalts are reported. The crust-mantle interaction occurring in the Yanshan intracontinental orogenic belt is also discussed. Fuxin zircons show highly uniform U-Pb age ((1693) Ma). More than 95% Pingquan zircons display the age of (107?0) Ma except two are 2491 Ma and 513 Ma respectively. Zircons with the ages of (169?) Ma have eHf close to zero. eHf of the zircons with the ages of (10710) Ma are mainly at -11.5--16.3, showing the crustal derivation. Fuxin zircons contain low Nb, Ta, Sr, Th, U contents, low and narrow Hf model ages (0.87-1.00 Ga), which reflect that the source materials of the monzonite xenoliths are young to Pingquan (focus at (1.280.08) Ga). High contents of the incompatible elements, and wide range of Hf model ages (0.89-2.56 Ga) in Pingquan zircons suggest a more complex source and the highly crustal maturity in their petrogenesis. Comprehensive information including the published data indicates that J3-K1 is the key period of the deep processes and shallow tectonic reverse in the Yanliao area. However, the processes were highly heterogeneous in spatial and in temporal.

关键词： zircon, in situ analysis, Hf isotope, U-Pb age, trace element, thermal events, Yanliao area.

Implementing wavelet transform with SAW elements

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Science China(Technological Sciences) 2003年第6期46卷 627-638页

作者：卢文科朱长纯刘君华刘清洪 Institute of Vaccum Microelectronics & Microelectromechanical System School of Electronics and Information Engineering Xi'an Jiaotong University Xi'an 710049 China

In the design of the finger-overlap envelope according to the envelope of wavelet func-tion, it is concluded that the pulse-response function of the interdigital transducer (IDT) for surface acoustic wave (SAW) is identical to the wavelet function. SAW type of the wavelet-transform ele-ment is manufactured. A new method of using two wavelet-transform elements to manufacture the reconstruction element of the wavelet transform is proposed. The sources of the element error are analyzed, and the methods for reducing the error are put forward. SAW type of the wavelet trans-formation element and its reconstruction element have the following three characteristics: (i) the implementing methods of the wavelet transform element and its reconstruction element are simple, and free of complicated mathematical algorithms of the wavelet transform; (ii) because one of SAW element is fast, the response velocities of SAW type of the wavelet transform element and its reconstruction element are also fast; (iii) the costs of the wavelet transform element and its recon-struction element are low, so the elements may be manufactured in a large quantity.

关键词： wavelet transform element, reconstruction element, surface acoustic wave(SAW), interdigital transducer (IDT).

Impact of hillslope vegetation restoration on gully erosion induced sediment yield

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Science China Earth Sciences 2006年第2期49卷 176-192页

作者： CHEN Hao CAI Qiangguo Key Laboratory of Water Cycle and Related Land Surface Processes Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China Key Laboratory of Water Cycle and Related Land Surface Processes Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China

Facing the eco-environmental construction on the Loess Plateau, especially the vegeta-tion restoration in the semiarid areas, as well as the dam system engineering construction that is about to start, how can the vegetation restoration gain the optimum ecological benefits following the improvement of the preservation rates of trees and grass on the basis of guaranteeing water storage and silt trapping effects? What techniques should be taken to restore vegetation? These questions critical to environmental management on the Loess Plateau have to be settled urgently. According to the different macroscopic spatial distribution patterns of forest and grass on the Loess Plateau, this paper analyzes the macroscopic hillslope and gully management relationship in the middle Yellow River and weight of natural and human factors in erosion-induced sediment yield in the context of environmental background of the major silt producing areas. In light of the current status of the inte-grated management of small watersheds and soil and water conservation measure arrangement schemes of hillslopes and gullies on the Loess Plateau, this paper discusses the impact of vegetation restoration on gully erosion induced sediment yield and the effect of vegetation caused sediment re-duction. Studies indicate that there exists an erosional environmental background related to the natural and human activities in the sediment yield peak values of the sandy and coarse sandy areas in the middle Yellow River, sediment yield modulus is closely related to the synthetic effect of environ-mental elements, and the rainstorms, reclamation rate and forest coverage are the main factors af-fecting sediment yield modulus in the sandy and coarse sandy areas. The key to control soil erosion in the sandy and coarse sandy areas is the conversion of farmland into forestland and grassland, the reduction of reclamation rate and the increase of tree and grass vegetation. Small catchment man-agement should adhere to t

关键词： relationship between hillslope and gully erosion control, vegetation restoration, natural and human environmental element, Loess Plateau.

Comprehensive geochemical identification of highly evolved marine carbonate rocks as hydrocarbon-source rocks as exemplified by the Ordos Basin

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Science China Earth Sciences 2006年第4期49卷 384-396页

作者： Tenger Key Laboratory of Gas Geochemistry Lanzhou Institute of Geology Chinese Academy of Sciences

This study reversed the developing environments of hydrocarbon-source rocksin the Ordos Basin and evaluated carbonate rocks as hydrocarbon-source rocks and their distributionson account of the fact that China''s marine carbonate rocks as hydrocarbon-source rocks arecharacterized by intensive thermal evolution and relatively low abundance of organic matter, bytaking the Lower Paleozoic of the Ordos Basin for example and in light of the calculated enrichmentcoefficients of trace elements, the REE distribution patterns, the mathematical statistics analysisof elements and carbon isotopes and their three-dimensional diagrammatization in combination withthe necessary organic parameters. As for the Ordos Basin, TOC=0.2% is an important boundary *** have shown that in the strata where TOC is greater than 0.2%, Ba is highly enriched withpositive δ^(13)C_(carb) shifts and δ^(13)C_(org) less than -28per thousand, reflecting a thighpaleo-productivity, high burial amounts of organic matter, relatively good hydrocarbon-generatingpotentiality and intensive REE fractionation. All these indicated that the settlement rates are lowand the geological conditions are good for the preservation of organic matter, hence favoring thedevelopment of hydrocarbon-source rocks. The Klimory and Wulalik formations show certainregularities in those aspects and, therefore, they can be regarded as the potential effectivehydrocarbon-source rocks. In the strata where total TOC is less than 0.2%, the contents of Ba arelow, δ^(13)C_(carb) values are mostly negative, and δ^(13)C_(org) values range from -24perthousand—-28per thousand, demonstrating low burial amounts of organic matter, poor potentialitiesof hydrocarbon generation, weak REE fractionation and rapid settlement rates. These facts showedthat most of the hydrocarbon-source rocks were formed in shallow-water, high-energy oxidizingenvironments, thus un-favoring the development of hydrocarbon-source rocks. It is feasible to makeuse of the

关键词： effective hydrocarbon-source rock, sedimentary environment, trace element, stable isotope, identification index.

Thresholds of geographic environmental elements in sediment yield of drainage basins

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Science China Earth Sciences 2005年第2期48卷 230-240页

作者： CHEN Hao, ZHOU Jinxing, CAI Qiangguo, LU Zhongchen & LI Zhongyan Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China Institute of Forestry Science, Chinese Academy of Forestry Science, Beijing 100091, China Research Center for Eco-Environment Sciences, Chinese Academy of Sciences, Beijing 100085, China Computing Institute of Science and Engineering, North China Electric Power University, Beijing 102206, China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing China Institute of Forestry Science Chinese Academy of Forestry Science Beijing China Research Center for Eco-Environment Sciences Chinese Academy of Sciences Beijing China Computing Institute of Science and Engineering North China Electric Power University Beijing China

Threshold of environmental elements in drainage basin sediment yield refers to, under effect of climate, underlying surface and human activity, a turning point of abrupt changes in drainage sediment yield related to environmental element characteristics. Previous studies on threshold of sediment yield of relevant drainage basins were mainly concentrated on impact of natural zones with a few researches on impact of other environmental elements. Particularly studies on compound environmental element threshold in drainage basin sediment yield remain blank today. Studies indicate that sediment yield in drainage basins is affected by compound interactions and complex actions. Based on single element analysis, the present paper gives quantitatively compound threshold of environmental elements affecting sediment yield of the drainage basin between Hekouzhen and Tongguan in the middle Yellow River by the method of multi-variant, polynomial formula regression analysis.

关键词： middle Yellow River, environmental element, sediment, sediment delivery mudule, threshold.