检索结果-南通市图书馆

Diffraction of SH-waves by topographic features in a layered transversely isotropic half-space

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2017年第1期16卷 11-22页

作者： ba Zhenning Liang Jianwen Zhang Yanju Department of Civil Engineering Tianjin University Tianjin 300072 China Key Laboratory of Coast Civil Structure Safety ( Tianjin University) Ministry of Education Tianjin 300072 China

Abstract： The scattering of plane SH-waves by topographic features in a layered transversely isotropic （TI） half-space is investigated by using an indirect boundary element method （IBEM）. Firstly, the anti-plane dynamic stiffness matrix of the layered TI half-space is established and the free fields are solved by using the direct stiffness method. Then, Green＇s functions are derived for uniformly distributed loads acting on an inclined line in a layered TI half-space and the scattered fields are constructed with the deduced Green＇s functions. Finally, the free fields are added to the scattered ones to obtain the global dynamic responses. The method is verified by comparing results with the published isotropic ones. Both the steady-state and transient dynamic responses are evaluated and discussed. Numerical results in the frequency domain show that surface motions for the TI media can be significantly different from those for the isotropic case, which are strongly dependent on the anisotropy property, incident angle and incident frequency. Results in the time domain show that the material anisotropy has important effects on the maximum duration and maximum amplitudes of the time histories.

关键词： wave scattering and diffraction Green's function transversely isotropic SH-waves indirect boundaryelement method

P-wave velocity prediction in porous medium with liquid-pocket patchy saturation

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2015年第11期36卷 1427-1440页

作者： Jiawei LIU Weitao SUN Jing ba Zhou Pei-Yuan Center for Applied Mathematics Tsinghua University Department of Computational Geophysics Xi'an Jiaotong University

It becomes increasingly clear that non-uniform distribution of immiscible fluids in porous rock is particularly relevant to seismic wave dispersion. White proposed a patchy saturation model in 1975, in which spherical gas pockets were located at the center of a liquid saturated cube. For an extremely light and compressible inner gas, the physical properties can be approximated by a vacuum with White＇s model. The model successfully analyzes the dispersion phenomena of a P-wave velocity in gas-water- saturated rocks. In the case of liquid pocket saturation, e.g., an oil-pocket surrounded by a water saturated host matrix, the light fluid-pocket assumption is doubtful, and few works have been reported in White＇s framework. In this work, Poisson＇s ratio, the bulk modulus, and the effective density of a dual-liquid saturated medium are formulated for the heterogeneous porous rocks containing liquid-pockets. The analysis of the difference between the newly derived bulk modulus and that of White＇s model shows that the effects of liquid-pocket saturation do not disappear unless the porosity approaches zero. The inner pocket fluid can no longer be ignored. The improvements of the P-wave velocity predictions are illustrated with two examples taken from experiments, i.e., the P-wave velocity in the sandstone saturated by oil and brine and the P-wave velocity for heavy oils and stones at different temperatures.

关键词： White's model porous medium P-wave dispersion liquid pocket

In-plane dynamic Green's functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic half-space

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2018年第2期17卷 293-309页

作者： ba Zhenning Kang Zeqing Liang Jianwen Department of Civil Engineering Tianjin UniversityTianjin 300072China Key Laboratory of Coast Civil Structure Safety(Tianjin University) Tianjin 300072China

The dynamic stiffness method combined with the Fourier transform is utilized to derive the in-plane Green’s functions for inclined and uniformly distributed loads in a multi-layered transversely isotropic（TI）*** loaded layer is fixed to obtain solutions restricted in it and the corresponding reactions forces,which are then applied to the total system with the opposite *** adding solutions restricted in the loaded layer to solutions from the reaction forces,the global solutions in the wavenumber domain are obtained,and the dynamic Green’s functions in the space domain are recovered by the inverse Fourier *** presented formulations can be reduced to the isotropic case developed by Wolf（1985）,and are further verified by comparisons with existing solutions in a uniform isotropic as well as a layered TI halfspace subjected to horizontally distributed loads which are special cases of the more general problem *** deduced Green’s functions,in conjunction with boundary element methods,will lead to significant advances in the investigation of a variety of wave scattering,wave radiation and soil-structure interaction problems in a layered TI *** numerical results are given to investigate the influence of material anisotropy,frequency of excitation,inclination angle and layered on the responses of displacement and stress,and some conclusions are drawn.

关键词： Green's functions transversely isotropic medium multi-layered half-space stiffness method dynamic response

Effect of mineral admixtures and repeated loading on chloride migration through concrete

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第9期11卷 683-690页

作者： Wu-man ZHANG Heng-jing ba School of Transportation Science and Engineering Beihang University Beijing 100191 China School of Civil Engineering Harbin Institute of Technology Harbin 150006 China

The effect of fly ash (FA) and ground granulated blast furnace slag (GGBFS) on chloride migration through concrete subjected to repeated loading was examined. Portland cement was replaced by three percentages (20%, 30%, and 40%) of mineral admixtures. Five repeated loadings were applied to concrete specimens using a WHY series fully automatic testing machine. The maximum loadings were 40% and 80% of the axial cylinder compressive strength (f′c). Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured. The results showed that the replacement percentages of mineral admixtures, the curing time and repeated loading had a significant effect on chloride migration through concrete. The transport number of chloride through concrete cured for 28 d increased with increasing FA replacement and markedly decreased with extension of the curing time. 20% and 30% GGBFS replacement decreased the transport number of chloride through concrete, but 40% GGBFS replacement increased the transport number. Five repeated loadings at 40% or 80% f′c increased the transport number of chloride for all mixes.

关键词： Concrete Fly ash (FA) Ground granulated blast furnace slag (GGBFS) Chloride migration Repeated loading

Water-stable ZIF-300/Ultrason? mixed-matrix membranes for selective CO_2 capture from humid post combustion flue gas

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2018年第5期26卷 1012-1021页

作者： Muhammad Sarfraz M. ba-Shammakh Department of Polymer and Process Engineering University of Engineering and Technology Lahore 54890 Pakistan Department of Chemical Engineering King Fahd University of Petroleum and Minerals Dhahran 31261 Saudi Arabia

Water stable mixed-matrix membranes(MMMs) were developed to help control the global warming by capturing and sequestrating carbon dioxide(CO_2) from post-combustion flue gas originated from burning of fossil *** of different compositions were prepared by doping glassy polymer Ultrason? S 6010(US) with nanocrystals of zeolitic imidazolate frameworks(ZIF-300) in varying degrees. Solution-casting technique was used to fabricate various MMMs to optimize their CO_2 capturing performance from both dry and wet gases. The prepared composite membranes indicated enhanced filler-polymer interfacial adhesion, consistent distribution of nanofiller, and thermally established matrix configuration. CO_2 permeability of the membranes was enhanced as demonstrated by gas sorption and permeation experiments performed under both dry and wet conditions. As compared to neat Ultrason? membrane, CO_2 permeability of the composite membrane doped with 40 wt% ZIF-300 nanocrystals was increased by four times without disturbing CO_2/N_2 ideal selectivity. In contrast to majority of previously reported membranes, key features of the fabricated MMMs include their structural stability under humid conditions coupled with better and unaffected gas separation performance.

关键词： Hydrophobic MMMs ZIF-300 Gas permeation CO2 capture Permselectivity

Scattering and diffraction of plane SH-waves by periodically distributed canyons

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2016年第2期15卷 325-339页

作者： ba Zhenning Liang Jianwen Zhang Yanju Department of Civil Engineering Tianjin University Key Laboratory of Coast Civil Structure Safety (Tianjin University) Ministry of Education

A new method is presented to study the scattering and diffraction of plane SH-waves by periodically distributed canyons in a layered half-space. This method uses the indirect boundary element method combined with Green＇s functions of uniformly distributed loads acting on periodically distributed inclined lines. The periodicity feature of the canyons is exploited to limit the discretization effort to a single canyon, which avoids errors induced by the truncation of the infinite boundary, and the computational complexity and the demand on memory can be significantly reduced. Furthermore, the total wave fields are decomposed into the free field and scattered field in the process of calculation, which means that the method has definite physical meaning. The implementation of the method is described in detail and its accuracy is verified. Parametric studies are performed in the frequency domain by taking periodically distributed canyons of semi-circular and semi-elliptic cross-sections as examples. Numerical results show that the dynamic responses of periodically distributed canyons can be quite different from those for a single canyon and significant dynamic interactions exist between the canyons.

关键词： periodically layered uniformly verified decomposed truncation elliptic discretization scattered circular

Spatial analysis and structure of a cross-timber stand in the TallGrass Prairie Preserve (Pawhuska, Oklahoma)

在线全文

学校读者我要写书评

暂无评论

Journal of Forestry Research 2013年第1期24卷 47-52页

作者： José Ramón arévalo Departamento de Ecología Facultad de BiologíaUniversidad de La LagunaLa Laguna 38206Spain

I analyzed the spatial distribution and structure of trees in a cross timber forest in the Tallgrass Prairie Preserve （Pawhuska, Oklahoma, USA）. I mapped and measured diameter of all stems, saplings （〉1.5 m tall） and dead trees in a 4-ha plot. The stand was dominated by Quercus stellata and Q. marilandica. In total, I mapped 7,636 trees, consisting of 6,785 Q. stellata, 846 Q. marilandica, 2 Celtis occidentalis, 1 Fraxinus pensilvanica and 2 Prunus americana. For saplings, I mapped 54 Q. stellata and 21 Q. marilandica. The size class distribution of the two dominant species did not differ. The dominant mortality class was “standing dead”, while I only found saplings less than 2 m tall. The spatial distribution of the species indicated segregation in the use of the environment, generating a clumped univariate distribution of stems of the same species within radii of 30 m, but repulsion outside 30 m. This segregation can be explained by the different ecological requirements of each species.

关键词： conservation point pattern analysis Quercus stellata Q.marilandica size class distribution

Acupuncture Enhances Chances of Pregnancy in Unexplained Infertile Patients Who Undergo A Blastocyst Transfer in A Fresh-Cycle

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Integrative Medicine 2019年第4期25卷 298-302页

作者： Hakan ?oksüer Mert ula barut Murat BozkurT Elif Agacayak Sibel Sak Mustafa Demir Eray Cal?skan Diyarlife IVF Center Department of Obstetrics and Gynecology Harran University School of Medicine Department of Obstetrics and Gynecology bahcesehir University Department of Obstetrics and GynecologyVM Medikalpark Pendik Hospital Dicle University School of Medicine Department of Obstetrics and Gynecology bahcesehir University Department of Obstetrics and Gynecology

Objective: To analyze the effects of acupuncture on in vitro fertilization patients with unexplained ***: We retrospectively analyzed the charts of a total of 302 cycles performed in 273 patients attending Assisted Reproductive Technology(arT) Centre from August 2013 to August *** the study period,embryo transfer with acupuncture(Acupuncture group,46 cases) and without acupuncture(Control group,42 cases) were *** to embryo transfer,the following points were used in the acupuncture group: Neiguan(CX 6),Diji(SP 8),Taichong(Liv 3),baihui(Gv 20),and Guilai(S 29).These sessions were carried out two times before and after embryo transfer in a single *** addition,auricular acupuncture was also performed at ear points,including ear point 55(Shenmen),ear point 58(Zhigong),ear point 22(Neifenmi)and ear point 34(Naodian).The biochemical pregnancy rate and clinical pregnancy rate after transplantation were compared between two ***: The clinical pregnancy rate in the acupuncture group was higher than that in the control group [60.9%(28/46) vs.33.3%(14/42),respectively,P<0.05].Likewise,the live birth rate in the acupuncture group was also higher than that in the control group [71.7%(33/46) vs.31.0%(12/42),P<0.01).Conclusion: Administration of acupuncture on the day of embryo transfer dramatically improved fertility results in women who underwent in vitro fertilization/intra-cytoplasm sperm injection for reproduction.

关键词： acupuncture assisted reproduction embryo transfer pregnancy rate

Regularity of Structural Superplasticity of Hypoeutectoid Steel

在线全文

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2005年第4期12卷 60-62页

作者： YANGYun-lin WENJiu-ba HenanUniversityofScienceandTechnology Henan471003China

The curve of the relation between fracture elongation and temperature for unltrafine grained low alloy hypoeutectoid steels generally shows that three peaks occur at temperatures just below A_ c1, between A_ c1 and A_ c3, and just above A_ c3, When these steels are subjected to superplastic tensile test at different temperatures, the value of the last one is the lowest and the other two peaks are different one from another depending on components, microstructures and deformation conditions of the steels.

关键词： hypoeutectoid steel structural superplasticity superplastic temperature