检索结果-南通市图书馆

Analytical solution of ground-borne vibration due to a spatially periodic harmonic moving load in a tunnel embedded in layered soil

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第7期24卷 637-652页

作者： lihui XU Meng MA Key Laboratory of Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China School of Civil Engineering Beijing Jiaotong UniversityBeijing 100044China

In this study,we propose a novel coupled periodic tunnel–soil analytical model for predicting ground-borne vibrations caused by vibration sources in *** problem of a multilayered soil overlying a semi-infinite half-space was solved using the transfer matrix *** account for the interactions between the soil layer and tunnel structure,the transformation characteristics between cylindrical waves and plane waves were considered and used to convert the corresponding wave potentials into forms in terms of the Cartesian or cylindrical coordinate *** induced ground-borne vibration was obtained analytically by applying a spatially periodic harmonic moving load to the tunnel *** accuracy and efficiency of the proposed model were verified by comparing the results under a moving constant and harmonic load with those from previous ***,the response characteristics under a spatially periodic harmonic moving load were identified,and the effects of a wide range of factors on the responses were systematically *** numerical results showed that moving and Doppler effects can be caused by a spatially periodic harmonic moving *** critical frequency and frequency bandwidth of the response are affected by the load type,frequency,velocity,and wavenumber in one periodicity *** the tunnel depth is an efficient way to reduce ground-borne *** effect of vibration amplification on the free surface should be considered to avoid excessive vibration levels that disturb residents.

关键词： Coupled tunnel-soil model Spatially periodic load Transfer matrix method Wave transformation Parametric analysis

来源：

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

DFT calculation analysis of oxygen reduction activity and stability of bimetallic catalysts with Pt-segregated surface

引用

Science China Chemistry 2015年第4期58卷 586-592页

作者： lihui Ou Shengli Chen College of Chemistry and Molecular Sciences Wuhan University College of Chemistry and Chemical Engineering Hunan University of Arts and Science

The stability and oxygen reduction reaction （ORR） activity of the Pt-segregated surface in various Pt-M alloys （M： transition metals） are investigated through systematic DFT calculations on the thermodynamic （alloy formation energy and Pt surface segregation energy）, surface chemical property （oxygen binding energy） and electronic （d-band center） properties. Factors af- fecting these properties, such as the atomic radii and surface energy of M and the electronic ligand interaction between Pt and M are analyzed as a function of outmost d electron numbers of M. It is shown that the electronic ligand interaction plays de- termining role in the alloy formation energy of various Pt-M alloys; the formation of Pt-segregated surface in Pt-M alloys is faw）red when alloying metals have higher surface energy and smaller radii than Pt; the oxygen binding energy on the Pt-segregated surface in Pt-M alloys varies approximately linearly with the d-band center of surface Pt atoms; the lattice strain and electronic ligand effects are simply additive in Pt-M alloys; the stain effect in Pt-M alloys nearly linearly affects the d-band center of the Pt-segregated surface in Pt-M alloys; transition metals with less than 10 d electrons mostly exhibit electron ligand effects which result in downshift of the d-band center of the segregated surface Pt atoms, while those with ten d electrons exhibit electron ligand effect upshifting the d-band center of the segregated Pt atoms.

关键词： oxygen reduction reaction bimetallic catalysts Pt-segregated surface DFT calculation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

An Arbitrary Polygonal Stress Hybrid Element for Structural Dynamic Response Analysis

引用

Acta Mechanica Solida Sinica 2023年第5期36卷 692-701页

作者： Xin Zeng Ran Guo lihui Wang Faculty of Civil Engineering and Mechanics Kunming University of Science and TechnologyKunming 650000China

This paper constructs a new two-dimensional arbitrary polygonal stress hybrid dynamic(APSHD)element for structural dynamic response ***,the energy function is established based on Hamilton's ***,the finite element time-space discrete format is constructed using the generalized variational principle and the direct integration ***,an explicit polynomial form of the combined stress solution is give,and its derivation process is shown in *** completing the theoretical construction,the numerical calculation program of the APSHD element is written in Fortran,and samples are *** show that the APSHD element performs well in accuracy and ***,it is insensitive to mesh distortion and has low dependence on selecting time steps.

关键词： Stress hybrid element method Arbitrary polygonal element Dynamic response analysis Polynomial stress function solution

来源：

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

CNC FLEXIBLE GENERATING SPECIFIC GEAR TOOTH PROFILE BASED ON STANDARD INVOLUTE GEAR HOB

引用

Chinese Journal of Mechanical Engineering 2004年第3期17卷 377-380页

作者： FengXianying lihui AiXing SchoolofMechanicalEngineering ShandongUniversityJinan250061China

A new method named orthogonal two-way link-shift here has been *** on the method and a standard involute gear hob, a specific gear tooth profile (including anarbitrary gear tooth profile and a modified involute gear tooth profile) can be generated on aCNC(computer numerical control) bobbing machine. Computer simulation has been carried out, and theresults prove that the method is right and practicable. So, the fabrication costs can be greatlydecreased than before. The new method has momentous significance to realize gear's optimizedmodification under different work conditions.

关键词： Specific gear tooth profile Orthogonal two-way link-shift method CNCflexible generation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Study on Fe-Based Coating Produced by Plasma Surface Metallurgy

引用

材料热处理学报 2004年第05B期25卷 952-955页

作者： lihui-qi LIUBang-wu lihui-dong ZHANGLi-min LIMin SUNYu-zong ShandongUniversityofScienceandTechnology TaianChina BeijingUniversityofScienceandTechnology BeijingChina

In the paper, plasma surface metallurgy was performed using Fe-based powder on steel substrate. The microstructure and microhardness of the coating have been analyzed. On the base of orthogonal comparison tests, influences of many factors on the cracking sensibility of plasma metallurgy coating have also been studied. The results indicate that substrate and its surface condition, processing parameters and components of plasma metallurgy coating have great effects on cracking sensibility of plasma metallurgy coating. Through changing these factors, it is possible to reduce cracks and promote the applications of this technology.

关键词：等离子表面冶金显微结构显微硬度裂纹灵敏度铁涂层

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Extracting outer function part from Hardy space function

引用

Science China Mathematics 2017年第11期60卷 2321-2336页

作者： TAN lihui QIAN Tao School of Applied Mathematics Guangdong University of Technology Faculty of Science and Technology University of Macao

Any analytic signal fa(e^(it)) can be written as a product of its minimum-phase signal part(the outer function part) and its all-phase signal part(the inner function part). Due to the importance of such decomposition, Kumarasan and Rao(1999), implementing the idea of the Szeg?o limit theorem(see below),proposed an algorithm to obtain approximations of the minimum-phase signal of a polynomial analytic signal fa(e^(it)) = e^(iN0t)M∑k=0a_k^(eikt),(0.1)where a_0≠ 0, a_M≠ 0. Their method involves minimizing the energy E(f_a, h_1, h_2,..., h_H) =1/(2π)∫_0^(2π)|1+H∑k=1h_k^(eikt)|~2|fa(e^(it))|~2dt(0.2) with the undetermined complex numbers hk's by the least mean square error method. In the limiting procedure H →∞, one obtains approximate solutions of the minimum-phase signal. What is achieved in the present paper is two-fold. On one hand, we rigorously prove that, if fa(e^(it)) is a polynomial analytic signal as given in(0.1),then for any integer H≥M, and with |fa(e^(it))|~2 in the integrand part of(0.2) being replaced with 1/|fa(e^(it))|~2,the exact solution of the minimum-phase signal of fa(e^(it)) can be extracted out. On the other hand, we show that the Fourier system e^(ikt) used in the above process may be replaced with the Takenaka-Malmquist(TM) system, r_k(e^(it)) :=((1-|α_k|~2e^(it))/(1-α_ke^(it))^(1/2)∏_(j=1)^(k-1)(e^(it)-α_j/(1-α_je^(it))^(1/2), k = 1, 2,..., r_0(e^(it)) = 1, i.e., the least mean square error method based on the TM system can also be used to extract out approximate solutions of minimum-phase signals for any functions f_a in the Hardy space. The advantage of the TM system method is that the parameters α_1,..., α_n,...determining the system can be adaptively selected in order to increase computational efficiency. In particular,adopting the n-best rational(Blaschke form) approximation selection for the n-tuple {α_1,..., α_n}, n≥N, where N is the degree of the given rational analytic signal, the minimum-phase part of a rational analytic signal can b

关键词： complex Hardy space analytic signal Nevanlinna decomposition inner and outer functions minimum-phase signal all-phase signal Takenaka-Malmquist system

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Fabrication and oxidation resistance of mullite/yttrium silicate multilayer coatings on C/SiC composites

引用

Journal of Advanced Ceramics 2017年第4期6卷 360-367页

作者： Qingsong MA lihui CAI Science and Technology on Advanced Ceramic Fibers&Composites Laboratory National University of Defense TechnologyChangsha 410073China

A tri-layer coating of mullite/Y_(2)Si_(2)O_(7)/(70wt%Y_(2)Si_(2)O_(7)+30wt%Y_(2)SiO_(5))was prepared on carbon fiber reinforced silicon carbide(C/SiC)composite substrate through dip-coating route for the sake of improving oxidation resistance of C/SiC *** Al_(2)O_(3)-SiO_(2) sol with high solid content was selected as raw material for mullite,and a slurry of Y_(2)O_(3) powder filled silicone resin was used to synthesize yttrium *** microstructure,phase composition,and oxidation resistance of the coating were *** as-fabricated coating shows high density and favorable bonding to C/SiC *** oxidation at 1400 and 1500℃for 30 min under static air,the flexural strengths of coated C/SiC composite were both increased by~30%.The desirable thermal stability and the further densification are responsible for excellent oxidation *** the additional help of compatible thermal expansion coefficients among substrate and sub-layers in coating,the coated composite retained 111.2%of original flexural strength after 12 times of thermal shock in air from 1400℃ to room *** carbothermal reaction at 1600℃ between free carbon in C/SiC substrate and rich SiO_(2) in mullite resulted in severe frothing and desquamation of coating and obvious degradation in oxidation resistance.

关键词： oxidation resistance thermal shock resistance coatings mullite yttrium silicate C/SiC composites

来源：

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

R^2 Correction and Its Implication of Present Cosmic Accelerating Behavior

引用

Communications in Theoretical Physics 2004年第1期41卷 157-160页

作者： lihui XUJian-Jun DepartmentofPhysics FudanUniversityShanghai200433China DepartmentofPhysics FudanUniversityShanghai200433ChinaEmail：phylihui@***

In this work we show an model of the universe in which certain quadratic correction is considered. Our results indicate that the R2 term can act as the present impetus of cosmic acceleration, but there may be a future collapsing universe with this component damped. This model can also tolerate a negative cosmological constant ?, although there seems to be no need for a non-vanishing one. In our simplification, this curvature component has a stationary equation of state, which is similar to radiation. Unlike other dark energy models, this 'missing' energy has a negative density. Some details and effects on cold dark matter and Λ-relevant model have been discussed in the frame of curvature-squared gravity theories.

关键词： cosmic acceleration curvature-squared dark energy

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Responses of chlorophyll fluorescence and nitrogen level of Leymus chinensis seedling to changes of soil moisture and temperature

引用

Journal of Environmental Sciences 2004年第4期16卷 666-669页

作者： XUZhen-zhu ZHOUGuang-sheng lihui LaboratoryofQuantitativeVegetationEcology InstituteofBotanyChineseAcademyofSciencesBeijing100093China

Controlled experiment of Leymus chinensis seedlings grown in the environmental growth chambers at 3 soil moisture levels and 3 temperature levels was conducted in order to improve the understanding how leaf photosynthetic parameters will respond to climatic change. The results indicated that soil drought and high temperature decreased the photochemical efficiency of photosystem(F v/F m), the overall photochemical quantum yield of PSII(yield), the coefficient of photochemical fluorescence quenching(q\-P), but increased the coefficient of non-photochemical fluorescence quenching(q\-N). Severe soil drought would decrease F v/F m and yield by 3.12% and 37.04% under 26℃ condition, respectively, and 6.60% and 73.33% under 32℃ condition, respectively, suggesting that higher temperature may enhance the negative effects of soil drought. All the soil drought treatments resulted in the decline in leaf nitrogen content. There was no significant effect of temperature on leaf nitrogen level, but higher temperature significantly reduced the root nitrogen content and the ratio of root nitrogen to leaf nitrogen, indicating the different strategies of adaptation to soil drought and temperature. It was also implied that higher temperature would enhance the effect of soil drought on leaf photosynthetic capacity, decrease the adaptability of Leymus chinensis to drought.

关键词： chlorophyll fluorescence nitrogen level Leymus chinensis soil moisture soil temperature

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Imaging surface structure of purple membrane partly dissolved by CHAPS with atomic force microscope

引用

Chinese Science Bulletin 2003年第6期48卷 573-576页

作者： lihui CHENDeliang 等 StateKeyLaboratoryofMagnetism InstituteofPhysicsCenterofCondenseMatterPhysicsChineseAcademyofSciencesBeijing100080China InstituteofBiophysics ChineseAcademyofSciencesBeijing

Atomic force microscope was employed to study the surface structure of purple membrane (PM) using contact mode in liquid. The surface structures of native PM and PM partly dissolved by detergent CHAPS were com- pared. Results show that 6 mmol/L CHAPS could induce some cracks and holes in PM. While Bateriorhodopsin (BR) was still presented as trimers in the two-dimensional hex- agonal structure. We assume that it was caused by the inter- action between CHAPS micellar and PM. Both absorption spectra and flash photolysis kinetic spectra indicated that BR抯 biochemical functions have been changed.

关键词：嗜盐细菌紫色细胞膜 CHAPS 洗涤剂表面结构原子力显微镜

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：