检索结果-南通市图书馆

A note on near-field site amplification effects of ground motion from a radially inhomogeneous valley

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4期17卷 707-718页

作者： zhang Ning Gao Yufeng Wu Yongxin zhang fei Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai University College of Civil and Transportation Engineering Hohai University

To improve the understanding of the near-field soil and topographic amplification effects, an analytical solution by the authors for the scattering of plane SH waves by a radially inhomogeneous semi-cylindrical valley is extended to the case of a line source of cylindrical SH waves. Upon confirmation of its accuracy with past exact solutions for a homogeneous and an inhomogeneous semi-cylindrical valley under far-field plane SH waves, the extended solution is used to calculate the ground motion amplification factors for both the homogeneous and inhomogeneous valleys subjected to near-field waves. A comprehensive parametric study is conducted with respect to the location of the wave source, the dimensionless frequency of the incident waves, and the inhomogeneity degree of the covering soil layer. It is found that more amplifications and reductions of ground motions will occur within a certain range in and around the valley as the sources are located further. Consistent with the far-field case, it is confirmed that an increase of the degree of inhomogeneity of the covering soil layer generally amplifies the ground motions significantly.

关键词： elastic SH-waves wave scattering and diffraction ground motion amplification valley canyon

Redshift drift constraints on holographic dark energy

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2017年第3期60卷 80-86页

作者： Dong-Ze He Jing-fei zhang Xin zhang Department of Physics College of Sciences Northeastern University Center for High Energy Physics Peking University

The Sandage-Loeb （SL） test is a promising method for probing dark energy because it measures the redshift drift in the spectra of Lyman-o： forest of distant quasars, covering the ＂redshift desert＂ of 2 ≤ z ≤ 5, which is not covered by existing cosmological observations. Therefore, it could provide an important supplement to current cosmological observations. In this paper, we explore the impact of SL test on the precision of cosmological constraints for two typical holographic dark energy models, i.e., the original holographic dark energy （HDE） model and the Ricci holographic dark energy （RDE） model. To avoid data inconsistency, we use the best-fit models based on current combined observational data as the fiducial models to simulate 30 mock SL test data. The results show that SL test can effectively break the existing strong degeneracy between the present-day matter density Ωm0 and the Hubble constant 1-1o in other cosmological observations. For the considered two typical dark energy models, not only can a 30-year observation of SL test improve the constraint precision of Ωm0 and h dramatically, but can also enhance the constraint precision of the model parameters c and α significantly.

关键词： redshift drift Sandage-Loeb test holographic dark energy Ricci dark energy cosmological constraints

Inflation model selection revisited after a 1.91% measurement of the Hubble constant

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2020年第9期63卷 35-36页

作者： Rui-Yun Guo Jing-fei zhang Xin zhang Department of Physics College of SciencesXi’an Technological UniversityXi'an 710021China Department of Physics College of SciencesNortheastern UniversityShenyang 110819China

The recent local measurement of the Hubble constant based on the distance-ladder method has reached a 1.91%precision[1],but this result is in tension with the early-universe measurements at the more than 4σlevel,brin... 详细信息

关键词： cosmology. universe constant

RESEARCH ON IMPROVED CUT-OFF NEGATIVE PRESSURE METHOD FOR UNSTEADY SEEPAGE FLOW WITH FREE SURFACE

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2005年第5期17卷 521-531页

作者： zhang Qian-fei WANG Yan-ming Shanghai Municipal Engineering Design Institute Shanghai 200092 China

The cut-off negative pressure method is one of effective approaches to solve the seepage flow with free surface. According to the characteristics of this method, however, it has been found out that the deficiency of the algorithms is to easily cause inaccurate simulation in the vicinity of free surface owing to the penalty function with only one controlling penalty parameter. Therefore, an improved cut-off pressure method was presented by constructing penalty function with two controlling penalty parameters. The improved algorithms were illustrated to be able to improve the simulation accuracy and raise the convergence speed through considering the effects of the partially saturated or unsaturated elements more reasonably and calculating the nodal external forces more accurately. Finally, the improved cut-off negative pressure method was applied to the simulation of unsteady seepage flow with free surface, and the corresponding program codes were developed with validation of some cases.

关键词： free surface unsteady seepage flow finite element method improved cut-off negative pressure method

血栓弹力图在危重症创伤出血临床输血指导及凝血功能检测的应用价值

在线全文

学校读者我要写书评

暂无评论

罕少疾病杂志 2025年第1期32卷 164-166页

作者：张琼姚静张燕飞郑州市第二人民医院河南郑州450006

目的探究在临床危重症患者输血以及凝血功能检测用应用血栓弹力图(TEG)的价值。方法选取2021年1月至2023年1月在本院就诊的危重症创伤出血患者104例,随机分为对照组和观察组,各52例。对照组依据常规凝血指标指导输血,观察组则依据TEG... 详细信息

目的探究在临床危重症患者输血以及凝血功能检测用应用血栓弹力图(TEG)的价值。方法选取2021年1月至2023年1月在本院就诊的危重症创伤出血患者104例,随机分为对照组和观察组,各52例。对照组依据常规凝血指标指导输血,观察组则依据TEG结果来指导输血,比较两组凝血功能指标以及用血量的差异性,并对观察组输血前后TEG相关指标进行记录,分析TEG相关指标与凝血常规指标的关系。结果输血前,两组的凝血四项和PLT比较无统计学差异(P>0.05);输血后,观察组PT、APTT、TT均低于对照组(P0.05)。输血后,观察组患者的R值、K值均较输血前降低,MA值、Angle角以及CI值均较输血前升高(P0.05)。R值与APTT呈正相关(r=0.328,P=0.036<0.05),K值与PLT呈负相关(r=-0.389,P=0.001<0.05),Angle角与FIB、PLT均呈正相关(r=0.328、0.475,P=0.029、0.000<0.05),MA值与FIB、PLT均呈正相关(r=0.337、0.460,P=0.016、0.000<0.05),CI值与与FIB、PLT均呈正相关(r=0.235、0.348,P=0.020、0.014<0.05)。结论 TEG在临床危重症创伤出血患者输血治疗中具有较高的指导价值,且可以发现并改善患者凝血异常情况,TEG相关指标与凝常规凝血指标具有一定的关联性,在临床中的应用价值较高。

关键词：血栓弹力.图常规凝血功能检测危重症创伤出血临床输血

维普期刊数据库博看期刊

Constraints on brane inflation after Planck 2015: Impacts of the latest local measurement of the Hubble constant

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2019年第3期62卷 41-48页

作者： Rui-Yun Guo Lei zhang Jing-fei zhang Xin zhang Department of Physics College of Sciences Northeastern University Center for High Energy Physics Peking University

We investigate the observational constraints on three typical brane inflation models by considering the latest local measurement of the Hubble constant in the global fit. We also employ other observational data, including the Planck 2015 CMB data, the BICEP2/Keck Array B-mode data, and the baryon acoustic oscillations data, in our analysis. Previous studies have shown that the addition of the latest local H_0 measurement favors a larger spectral index, and can exert a significant influence on the model selection of inflation. In this work, we investigate its impacts on the status of brane inflation models. We find that, when the direct H_0 measurement is considered, the prototype model of brane inflation is still in good agreement with the current observational data within the 2σ level range. For the KKLMMT model, the consideration of the H_0 measurement allows the range of the parameter β to be amplified to O(10^(-2)), which slightly alleviates the fine-tuning problem. For the IR DBI model, the addition of the H_0 measurement does not provide a better fit. These results show that the consideration of the new H_0 prior can exert a considerable influence on the brane inflation models. At last, we show that, when β≤1.1, the equilateral non-Gaussianity in the IR DBI inflation model is compatible with the current CMB data at the 1σ level.

关键词： brane inflation inflationary cosmology observational constraints

Microstructural evolution and mechanical properties of Ni-45Ti-5Al-2Nb-1Mo alloy subjected to different heat treatments

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2023年第8期42卷 2774-2780页

作者： Xiao-Yun Song Yan Li fei zhang State Key Laboratory of Nonferrous Metals and Processes GRIMAT Engineering Institute Co.LtdBeijing 101407China School of Materials Science and Engineering Beihang UniversityBeijing 100191China

The effects of solution and aging heat treatment on microstructural evolution and room temperature tensile properties for as-forged Ni-45Ti-5Al-2Nb-1Mo alloy were investigated through scanning electron microscopy(SEM),transmission electron microscopy(TEM)and tensile *** results show that the microstructure of solution-treated alloy comprises NiTi matrix,Ti_(2)Ni and(Nb,Ti)ss *** aging treatment at 700℃for 6 and100 h,the distribution of Ti_(2)Ni and(Nb,Ti)ss precipitates increases in *** new type of precipitate is observed in the specimen aged at 700℃.After aging at800℃for 100 h,numerous nanosized Ni_(2)TiAl phases are precipitated within the *** and aging treatments improve the tensile properties at room *** strength and ductility are improved after solution treatment at 1100℃plus aging treatment at 800℃for 6 h or 700℃for 100 *** aging time prolonging to 100 h at 800℃,the precipitation of fine Ni2TiAl particles leads to the improvement in tensile strength and deterioration of elongation.

关键词： NiTi-Al-based alloy Intermetallics Microstructure Mechanical properties Heat treatment

Recent Advances in Lead Chemisorption for Perovskite Solar Cells

在线全文

学校读者我要写书评

暂无评论

Transactions of Tianjin University 2022年第5期28卷 341-357页

作者： Pengfei Wu fei zhang School of Chemical Engineering and Technology Tianjin UniversityTianjin 300072China Collaborative Innovation Center of Chemical Science and Engineering(Tianjin) Tianjin 300072China

Lead toxicity in perovskite materials,which have hazardous effects on the environment and the human body,has drawn considerable attention to emerging photovoltaic technology perovskite solar *** the capability of other strategies to prevent lead leakage,chemisorption is another efficient approach to block Pb leaching by employing Pb absorbents in/out of device *** review discusses lead toxicity and summarizes the recent research about chemisorption strategies by their functions:additives,the hole-transporting layers,interfacial modifiers,and encapsulation ***,the basic guidelines and challenges for designing novel Pb-ads orbing materials and encapsulation structures are presented.

关键词： Pb toxicity Pb leakage Pb-adsorbing materials Encapsulation layer

How does a strong surrounding magnetic field influence the evolution of a supernova remnant?

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2019年第9期19卷 21-28页

作者： Dan Wu Meng-fei zhang College of Information Science and Technology Beijing Normal UniversityBeijing100875China University of Chinese Academy of Sciences Beijing100049China Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing100101China

We simulate the evolution of supernova remnants(SNRs) in a strong magnetic field. Usually,supernovae explode in a normal interstellar medium with magnetic field of no more than 50 μG, which has been well studied. However, the surrounding magnetic field will be much stronger in some situations, such as in a galactic center. Therefore, we try to explore these situations. The simulations show that a strong magnetic field of 1 mG will align the motion of ejecta in a way similar to a jet. The ejecta propagating perpendicularly to the magnetic field will be reflected and generate a strong reverse shock. When the reverse shock converges in the explosion center, it will more or less flow along the central magnetic field. Finally,most of the ejecta will propagate parallel to the magnetic field.

关键词： ISM:supernova remnants ISM:magnetic fields magnetohydrodynamics