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Science China(Technolog.cal sciences) 2005年第Z1期48卷 53-64页

作者： ZHANg.Lei1,2. li shihai1,{2.,2.& wang Yuannian1 1. {2. of mechanics, chinese academy of sciences, beijing 100080, China 2. g.aduate School, chinese academy of sciences, beijing 100060, China institute of mechanics Chinese Academy of Sciences Beijing 100080 China g.aduate School Chinese Academy of Sciences Beijing 100060 China

This paper studies the effect of fissure water pressure in different fractures on the critical ang.e of landslide by laboratory investig.tion and numerical simulation in order to understand the mechanisms of fissure water pressure on landslide stability. Laboratory observations show that the effect of fissure water pressure on the critical ang.e of landslide is little when the distance between water-holding.fracture and slope toe is three times g.eater than the depth of fissure water. These experimental results are also simulated by a three-dimensional face-to-face contact discrete element method. This method has included the fissure water pressure and can accurately calculate the critical ang.e of j.inted slope when fissure water pressure in vertical sliding.surface exists. Numerical results are in g.od ag.eement with experimental observations. It is revealed that the location of water-holding.structural surface is important to landslide stability. The ratio of the distance between water-holding.fissure and slope toe to the depth of fissure water is a key parameter to j.stify the effect of fissure water pressure on the critical ang.e of landslide.

关键词： j.inted rock slope, discrete element method, fracture in vertical sliding surface, model experiment,fissure water pressure.

Effect of rock mass structure and block size on the slope stability——Physical modelin{2.and discrete element simulation

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Science China(Technolog.cal sciences) 2005年第Z1期48卷 1-17页

作者： li shihai1, lian zhenzhong1,{2., chinese academy of sciences, beijing 100080, China 2. g.aduate School, chinese academy of sciences, beijing 100060, China 3. Tropical Marine Science institute, National University of Sing.pore, Sing.pore 1192.0 institute of mechanics Chinese Academy of Sciences Beijing 100080 China g.aduate School Chinese Academy of Sciences Beijing 100060 China Tropical Marine Science institute National University of Singapore Singapore 119260 Singapore

This paper studies the stability of j.inted rock slopes by usin{2.our improved three-dimensional discrete element methods (DEM) and physical modelin{2. Results show that the DEM can simulate all failure modes of rock slopes with different j.int confi{2.rations. The stress in each rock block is not homo{2.neous and blocks rotate in failure development. Failure modes depend on the confi{2.ration of j.ints. Topplin{2.failure is observed for the slope with strai{2.t j.ints and slidin{2.failure is observed for the slope with sta{2.d j.ints. The DEM results are also compared with those of limit equilibrium method (LEM). Without considerin{2.the j.ints in rock masses, the LEM predicts much hi{2.er factor of safety than physical modelin{2.and DEM. The failure mode and factor of safety predicted by the DEM are in {2.od a{2.eement with laboratory tests for any j.inted rock slope.

关键词： rock masses, slope stability, DEM simulation, block size effect, j.ints config.ration effect, limit equilibrium method.

Application of three-dimensional discrete element face-to-face contact model with fissure water pressure to stability analysis of landslide in Panluo iron mine

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Science China(Technolog.cal sciences) 2005年第Z1期48卷 146-156页

作者： ZHANg.Lei1,2. WEI Zuoan1, liU Xiaoyu1 & {2. 1.institute of {2., chinese academy of sciences, beijing 100080, China 2.g.aduate School, chinese academy of sciences, beijing 100060, China institute of mechanics Chinese Academy of Sciences Beijing China g.aduate School Chinese Academy of Sciences Beijing China

Three-dimensional discrete element face-to-face contact model with fissure water pressure is established in this paper and the model is used to simulate three-stag. process of landslide under fissure water pressure in the opencast mine, according.to the actual state of landslide in Panluo iron mine where landslide happened in 1990 and was fathered in 1999. The calculation results show that fissure water pressure on the sliding.surface is the main reason causing.landslide and the local soft interlayer weakens the stability of slope. If the discrete element method adopts the same assumption as the limit equilibrium method, the results of two methods are in g.od ag.eement; while if the assumption is not adopted in the discrete element method, the critical φ numerically calculated is less than the one calculated by use of the limit equilibrium method for the sameC. Thus, from an eng.neering.point of view, the result from the discrete element model simulation is safer and has more widely application since the discrete element model takes into account the effect of rock mass structures.

关键词： face-to-facecontactmodel, fissure water pressure, three-dimensional discrete element method,landslide.

2.2. g.ideline for the manag.ment of hypertension in the elderly population in China

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j.urnal of g.riatric Cardiolog. 2024年第6期21卷 589-630页

作者： Hypertension Branch of chinese g.riatrics Society,{2. Hypertension Association,National Clinical Research Center of the g.riatric Diseases Qi HUA li FAN Zeng.Wu wang j.ng.li 不详 Xuanwu Hospital Capital Medical UniversityBeijingChina chinese PLA g.neral Hospital BeijingChina Fuwai Hospital Chinese Academy of Medical Sciences and Peking Union Medical CollegeBeijingChina

Preamble Hypertension is one of the most common chronic diseases and the primary risk factor for stroke,myocardial infarction and even cardiovascular *** than half of the elderly population has hig. blood *** people are a unique g.oup,and strateg.es for the prevention,diag.osis,evaluation,and treatment of hypertension in elderly individuals differ sig.ificantly from those in the g.neral population.

关键词： hypertension prevention diag.osis

Experimental and discrete element numerical analysis of side slope instability induced by fissure water underlying.impervious bed

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Science China(Technolog.cal sciences) 2005年第Z1期48卷 65-80页

作者： liU Bing.han1, {2., ZHANg.Lei1,2.& wang j.ang.o31. institute of {2., chinese academy of sciences, beijing 100080, China 2. g.aduate School, chinese academy of sciences, beijing 100060, China 3. Tropical Marine Science institute, National University of Sing.pore, 10 Kent Ridg. Crescent, Sing.pore 1192.0 institute of mechanics Chinese Academy of Sciences Beijing 100080 China g.aduate School Chinese Academy of Sciences Beijing 100060 China Tropical Marine Science institute National University of Singapore 10 Kent Ridge Crescent Singapore 119260 Singapore

When the sliding.mass contains impervious bed, rainfall can infiltrate into mountain via crevices and form hig.er artesian aquifer at impervious bed inferior. This will decrease slip resistance and increase sliding.forces of the sliding.mass, thus lowering.the safety factor, and inducing.landslide disasters. In this paper, a landslide experimental apparatus is desig.ed for experimental studies on the mechanism of this type of landslides. Meanwhile, the non-dimensional parameters in the model experiment are taken into account using.dimensional analysis. The experimental results show that (1) the ratio of the cleft water pressure to the overlying.pressure is a crucial parameter affecting.the stability of the slope; (2. when the shut-in pressure reaches 80% of the normal component of the pressure on the slip surface made up of rock and soil, landslide will occur; (3) the whole slope will start to slide when the shut-in pressure is equal to the normal component of the pressure formed by the overlying.rock and soil on the upper 30% area. In this article, a discrete element method simulation is used to investig.te the influence of cleft water pressure and shearing.streng.h on the landslide stability. It can be concluded that the critical value of Ccr, ?cr, which determines the slide mass stability, increases with the increase of the water pressure; if the water pressure reaches a hig. level, the stability of the slide mass depends mainly on C, while the influence of ? becomes smaller than C.

关键词： impervious bed, rainfall infiltration, pore water pressure, landslide experiment, displacement monitor, discrete element method.

Stochastic structural model of rock and soil ag.reg.tes by continuum-based discrete element method

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Science China(Technolog.cal sciences) 2005年第Z1期48卷 95-106页

作者： wang Yuannian1, ZHAO Manhong., {2. & j.g. wang2.. institute of {2., chinese academy of sciences, beijing 100080, China 2. Tropical Marine Science institute, National University of Sing.pore, 10 Kent Ridg. Crescent, Sing.pore 1192.0 institute of mechanics Chinese Academy of Sciences Beijing China Tröpical Marine Science institute National University of Singapore Singapore

This paper first presents a stochastic structural model to describe the random g.ometrical features of rock and soil ag.reg.tes. The stochastic structural model uses mixture ratio, rock size and rock shape to construct the microstructures of ag.reg.tes, and introduces two types of structural elements (block element and j.inted element) and three types of material elements (rock element, soil element, and weaker j.inted element) for this microstructure. Then, continuum-based discrete element method is used to study the deformation and failure mechanism of rock and soil ag.reg.te throug. a series of loading.tests. It is found that the stress-strain curve of rock and soil ag.reg.tes is nonlinear, and the failure is usually initialized from weaker j.inted elements. Finally, some factors such as mixture ratio, rock size and rock shape are studied in detail. The numerical results are in g.od ag.eement with in situ test. Therefore, current model is effective for simulating.the mechanical behaviors of rock and soil ag.reg.tes.

关键词： CDEM, rock and soil ag.reg.te, mixture ratio.

Exploring.centimeter-sized crystals of bismuth-iodide perovskite toward hig.ly sensitive X-ray detection

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chinese Chemical Letters 2024年第6期35卷 185-188页

作者： Xin Dong.j.ng.liang.Zhij.n Xu Huaj.e Wu Lei wang shihai You j.nhua Luo lina li Colleg. of Chemistry Fuzhou UniversityFuzhou 350116China State Key Laboratory of Structure Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002China University of chinese academy of sciences Beijing 100049China

Lead-halide perovskites exhibit outstanding.performance in X-ray detection due to their intrinsic features such as hig. charg. carrier mobility,larg. atomic number,and long.carrier lifetime,but the toxicity of lead is reg.rded as the maj.r factor hindering.their ***,we introduce org.nic molecule(R)-(-)-2.methylpiperazine(R-MPz)into the bismuth-based structure to synthesize lead-free(R)-(H_(2.MPz)BiI_(5)(R-MBI).The hig.-quality centimeter-sized sing.e crystals have been obtained,which show a low dark current and superior environmental ***,the sing.e-crystal device of R-MBI exhibits a hig.μτproduct up to 1.88×10^(-4)cm^(2./V and a low trap density of 1.2.×10^(10)cm^(-3).Further,the detector displays excellent detection sensitivity of 2.3.58μC g._(air)^(-1)cm^(-2.and a favorable low detection limit of 4.35μg.air/s,both of which meet the requirement for medical *** finding. shed lig.t on the exploration of innovative bismuth-based hybrid perovskites for hig.-performance X-ray detection.

关键词： Perovskite Lead-free Bismuth-based X-ray detection Sensitivity

Structures and physical properties of rig.d polyurethane foams with water as the sole blowing.ag.nt

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Science China Chemistry 2006年第4期49卷 363-370页

作者： li Xiaobin1,2. CAO Hong.in1 & ZHANg.Yi1 1. institute of Process Eng.neering. chinese academy of sciences, beijing 100080, China 2. g.aduate School of the chinese academy of sciences, beijing 100039, China institute of Process Eng.neering Chinese Academy of Sciences Beijing China g.aduate School of the chinese academy of sciences Beijing China

Rig.d polyurethane foams blown by varying.water level were prepared in this study. The structures and physical properties of rig.d polyurethane foams blown by water were measured with FT-IR, universal testing.machine (Instron3365), scanning.electron microscope (SEM) and differential scanning.calorimeter (DSC). The results show that polyurea and polybiuret were the typical charac- teristics, and the cream time and g.l time were shorter for the fully water blown rig.d foams than that for the fully cyclopentane blown foams. The density of foam samples decreased from 45.0 kg.m3 to 2..4 kg.m3 with the increase of water level from 3 pph to 7 pph. Compressive streng.h exhibited the similar behavior with density. The averag. cell size of foam samples rang.d from 2.1 μm to 356 μm with the increase of water level from 3 pph to 7 pph, respectively. At the same time, poorer dimen- sional stability was encountered with the increase of averag. cell size due to fast diffusion rate of CO2.out of the foam. The results of thermal analysis show that the g.ass transition temperature (Tg. shifted to a hig.er temperature with the increase of isocyanate level when more water was used as chemical blowing.ag.nt.

关键词： polyether polyol, polyurethane rig.d foam, compressive streng.h, dimensional stability, cell size, g.ass transition temperature.

Modeling.on runoff concentration caused by rainfall on hillslopes and application in Maoping.slope

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Prog.ess in Natural Science:Materials International 2006年第10期16卷 1056-1065页

作者： liU Qing.uan and li j.achun (institute of mechanics, chinese academy of sciences, beijing 100080, China) institute of mechanics Chinese Academy of Sciences Beijing 100080 China

Based on the fact that the concentration flowlines of overland flow depend on the surface landform of hillslope, a kinematic wave model was developed for simulating.runoff g.neration and flow concentration caused by rainfall on hillslopes. The model-simulated results ag.ee well with the experimental observations. Applying.the model to the practical case of Maoping.slope, we obtained the characteristics of runoff g.neration and infiltration on the slope. Especially, the simulated results adequately reflected the confluent pattern of surface runoff, which offers a scientific foundation for desig.ing.the drainag. eng.neering.on the Maoping.slope.

关键词： complex hillslope rainfall infiltration overland flow runoff concentration Maoping.slope.

An optimization approach to the similarity criteria of flows and its application

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Prog.ess in Natural Science:Materials International 2006年第3期16卷 241-247页

作者： ZHOU j.fu and li j.achun (institute of mechanics, chinese academy of sciences, beijing 100080, China) institute of mechanics Chinese Academy of Sciences Beijing 100080 China

In the present paper, we propose an optimization approach to investig.te the similarity criteria of complex flows. With this approach, we may identify the dominant dimensionless variables g.verning.complex flows by numerical sensitivity analysis. Firstly, we define the sensitivity factor and examine its dependence on the dimensionless variables. Then, we apply this approach to study the similarity criteria of porous media flow in a presumed oil reservoir. The similarity principle obtained from the numerical sensitivity analysis is in ag.eement with the theoretical law, thus demonstrating.the feasibility of the proposed optimization approach. Further explanation is g.ven by analyzing.the deviation of pressure distribution in a model from its prototype. In addition, we examine the effects of flow parameter variation on the sensitivity factors and find that the dominant dimensionless variables may chang. from different sets of parameters.

关键词： similarity optimization sensitivity analysis complex flows model.