关于内有限的无限单群

主要对内有限的无限单群进行了研究,得到了:若非交换的内有限群含有对合,则非单群;而且内有限的无限单群是内可解的.在此基础上得到了:内有限的无限单群分别为内幂零、内交换、内循环的充分必要条件.

内有限环的结构

给出了内有限环的结构：Ｒ为内有限环，当且仅当Ｒ为内有限域。

关于内有限群的性质

研究了非交换的内有限单群,得到了非交换的内有限群的一些特殊性质.特别得到了:设G是由a和a′生成的非交换的内有限群,且G是类正规的,则a和a′都不是对合.

关于内有限环

本文提出了内有限环的概念,解决了内有限环的存在性,证明了内有限环的一个性质,给出了一类无限环是内有限环的充分必要条件。

代数注记两则

给出了内域环的两个等价条件 ,完全刻划了内有限维k

用Loeb测度构造正则及τ－光滑Borel测度

设（Ｘ，Ｔ）是Ｔ２空间，Ｔ１是拓扑Ｔ的基，Ａ是＊Ｘ上的内代数，ν是Ａ上的内测度，本文用无穷小方法证明了：在ｋ－饱和的非标准模型中，若Ｘ是正则空间，且对每一Ｔ∈Ｔ１，＊Ｔ∈Ａ，则对Ｘ的每一Ｂｏｒｅｌ集Ｂ，ｓｔ－１（Ｂ）∈Ｌｕ（Ａ）∩ｎｓ（＊Ｘ），且νｓｔ－１｜Ｆ（Ｘ）是τ－光滑Ｂｏｒｅｌ测度，νｓｔ－１｜Ｆ（Ｘ）是Ｒａｄｏｎ测度；若对每一Ｔ∈Ｔ，＊Ｔ∈Ａ，并且对每一Ｔ∈Ｔ及每一ε∈Ｒ＋，有闭集ＣＴ，使Ｌ（ν）（＊Ｔ－＊Ｃ）＜ε，则对每一Ｂｏｒｅｌ集Ｂ，ｓｔ－１（Ｂ）∈Ｌ（ν，Ａ）∩ｎｓ（＊Ｘ）且νｓｔ－１｜Ｆ（Ｘ）是正则τ－光滑Ｂｏｒｅｌ测度．

Loeb乘积空间及Keisler′s Fubini定理

在非标准多饱和模型下,研究了Loeb乘积空间及Keisler′s Fubini定理.首先,应用Loeb构造方法分别构造了Loeb乘积空间L(Y1×Y2)和乘积Loeb空间L(Y1)×L(Y2),并得到了L(A1)×L(A2)L(A1×A2).其次,A∈L(A1×A2),证明了如果(ν1×ν2)L(A)=0,则对于几乎所有的y1∈Y1,截口Ay1是L(A2)-可测的.最后,在Loeb乘积空间上证明了Keisler′s Fubini定理.

Numerical study of fatigue damage of asphalt concrete using cohesive zone model

In order to investigate the fatigue behavior of asphalt concrete, a new numerical approach based on a bi-linear cohesive zone model （CZM） is developed. Integrated with the CZM, a fatigue damage evolution model is established to indicate the gradual degradation of cohesive properties of asphalt concrete under cyclic loading. Then the model is implemented in the finite element software ABAQUS through a user-defined subroutine. Based on the proposed model, an indirect tensile fatigue test is finally simulated. The fatigue lives obtained through numerical analysis show good agreement with laboratory results. Fatigue damage accumulates in a nonlinear manner during the cyclic loading process and damage initiation phase is the major part of fatigue failure. As the stress ratio increases, the time of the steady damage growth stage decreases significantly. It is found that the proposed fatigue damage evolution model can serve as an accurate and efficient tool for the prediction of fatigue damage of asphalt concrete.

Improved hybrid iterative optimization method for seismic full waveform inversion

In full waveform inversion （FWI）, Hessian information of the misfit function is of vital importance for accelerating the convergence of the inversion; however, it usually is not feasible to directly calculate the Hessian matrix and its inverse. Although the limited memory Broyden-Fletcher-Goldfarb-Shanno （L-BFGS） or Hessian-free inexact Newton （HFN） methods are able to use approximate Hessian information, the information they collect is limited. The two methods can be interlaced because they are able to provide Hessian information for each other; however, the performance of the hybrid iterative method is dependent on the effective switch between the two methods. We have designed a new scheme to realize the dynamic switch between the two methods based on the decrease ratio （DR） of the misfit function （objective function）, and we propose a modified hybrid iterative optimization method. In the new scheme, we compare the DR of the two methods for a given computational cost, and choose the method with a faster DR. Using these steps, the modified method always implements the most efficient method. The results of Marmousi and overthrust model testings indicate that the convergence with our modified method is significantly faster than that in the L-BFGS method with no loss of inversion quality. Moreover, our modified outperforms the enriched method by a little speedup of the convergence. It also exhibits better efficiency than the HFN method.

华文漪回国

华文漪对领导同志三鞠躬,道:“我是来请罪的。”她是一位由新中国培养起来的昆剧演员,曾经是国内有限的数位最佳闺门旦之一。7年前赴美演出滞留未归。今番“绿卡”在手,但她魂牵梦绕昆剧艺术,回国参演后留下一片感慨。

对传主的心理记述必须有充分的史实依据

从已出版的新编志书看,其中有关传主心理历程方面的记述尚不充分,已经记述了的,其史料依据又显得不足或有记述者“想为然”的痕迹。 我们必须清醒地意识到,修志绝不是写小说。小说中的心理活动可以虚构,只要符合“艺术真实”的规律就可以了,而志传是在写历史,记述传主的心理活动必须有充分的史实依据,必须记述确实发生过的历史过程,这种心理活动必须“无一事无出处”,必须建立在已有史料的基础之上,必须在史料的基础上去揣摩传主的心理,必须在真实史料的框架内有限度地做一些合理的。

养花施肥须知

盆花依靠花盆内有限的土壤维持生活,要想枝繁叶茂,就要施肥,但施用不当往往会使植株受损。因此,施肥要注意:

Finite Element Analysis of Internal Gear in High-Speed Planetary Gear Units

The stress and the elastic deflection of internal ring gear in high-speed spur planetary gear units are investigated. A rim thickness parameter is defined as the flexibility of internal ring gear. Six evenly spaced linear springs are used to describe the fitting status between internal ring gear and the gearcase. The finite element model of the whole internal ring gear is established by means of Pro/E and ANSYS. The loads on meshing teeth of internal ring gear are applied according to the contact ratio and the load-sharing coefficient. With the finite element analysis (FEA), the influences of flexibility and fitting status on the stress and elastic deflection of internal ring gear are predicted. The simulation reveals that the principal stress and deflection increase with the decrease of rim thickness of internal ring gear. Moreover, larger spring stiffness helps to reduce the stress and deflection of internal ring gear. Therefore, the flexibility of internal ring gear must be considered during the design of high-speed planetary gear transmissions.

A numerical study of fracture initiation under different loads during hydraulic fracturing

The fracture initiation behavior for hydraulic fracturing treatments highlighted the necessity of proposing fracture criteria that precisely predict the fracture initiation type and location during the hydraulic fracturing process.In the present study,a Mohr-Coulomb criterion with a tensile cut-off is incorporated into the finite element code to determine the fracture initiation type and location during the hydraulic fracturing process.This fracture criterion considers the effect of fracture inclination angle,the internal friction angle and the loading conditions on the distribution of stress field around the fracture tip.The results indicate that the internal friction angle resists the shear fracture initiation.Moreover,as the internal friction angle increases,greater external loads are required to maintain the hydraulic fracture extension.Due to the increased pressure of the injected water,the tensile fracture ultimately determines the fracture initiation type.However,the shear fracture preferentially occurs as the stress anisotropy coefficient increases.Both the maximum tensile stress and equivalent maximum shear stress decrease as the stress anisotropy coefficient increases,which indicates that the greater the stress anisotropy coefficient,the higher the external loading required to propagate a new fracture.The numerical results obtained in this paper provide theoretical supports for establishing basis on investigating of the hydraulic fracturing characteristics under different conditions.

Forward modeling and inversion of tensor CSAMT in 3D anisotropic media

Tensor controlled-source audio-frequency magnetotellurics （CSAMT） can yield information about electric and magnetic fields owing to its multi-transmitter configuration compared with the common scalar CSAMT. The most current theories, numerical simulations, and inversion of tensor CSAMT are based on far-field measurements and the assumption that underground media have isotropic resistivity. We adopt a three-dimensional （3D） staggered-grid finite difference numerical simulation method to analyze the resistivity in axial anisotropic and isotropic media. We further adopt the limited-memory Broyden- Fletcher-Goldfarb-Shanno （LBFGS） method to perform 3D tensor CSAMT axial anisotropic inversion. The inversion results suggest that when the underground structure is anisotropic, the isotropic inversion will introduce errors to the interpretation.

Improved Adaptive Random Convolutional Network Coding Algorithm

To address the issue of field size in random network coding, we propose an Improved Adaptive Random Convolutional Network Coding (IARCNC) algorithm to considerably reduce the amount of occupied memory. The operation of IARCNC is similar to that of Adaptive Random Convolutional Network Coding (ARCNC), with the coefficients of local encoding kernels chosen uniformly at random over a small finite field. The difference is that the length of the local encoding kernels at the nodes used by IARCNC is constrained by the depth; meanwhile, increases until all the related sink nodes can be decoded. This restriction can make the code length distribution more reasonable. Therefore, IARCNC retains the advantages of ARCNC, such as a small decoding delay and partial adaptation to an unknown topology without an early estimation of the field size. In addition, it has its own advantage, that is, a higher reduction in memory use. The simulation and the example show the effectiveness of the proposed algorithm.

Experimental investigation of friction coefficient in tube hydroforming

The friction coefficient between tube and die in guide zone of tube hydroforming was obtained. In hydroforming, the tube is expanded by an internal pressure against the tool wall. By pushing the tube through tool, a friction force at the contact surface between the tube and the tool occurs. In guiding zone, the friction coefficients between tube and die can be estimated from the measured axial feeding forces. In expansion zone, the friction coefficients between tube and die can be evaluated from the measured geometries of expanded tubes and FE analysis.

Liquid holdup measurement with double helix capacitance sensor in horizontal oil-water two-phase flow pipes

This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.

Phase Field Simulation of Intragranular Microvoids Evolution Due to Surface Diffusion in Stress Field

Based on the bulk free energy density and the degenerate mobility constructed by the quartic double-well potential function,a phase field model is established to simulate the evolution of intragranular microvoids due to surface diffusion in a stress field.The corresponding phase field governing equations are derived.The evolution of elliptical microvoids with different stressesΛ,aspect ratiosβand linewidths hˉis calculated using the mesh adaptation finite element method and the reliability of the procedure is verified.The results show that there exist critical values of the stressΛc,the aspect ratioβc and the linewidth hˉc of intragranular microvoids under equivalent biaxial tensile stress.When Λ≥Λ_(c),β≥β_(c) or h≤h_(c),the elliptical microvoids are instable with an extending crack tip.WhenΛ<Λ_(c),β<β_(c) or hˉ>h_(c),the elliptical microvoids gradually cylindricalize and remain a stable shape.The instability time decreases with increasing the stress or the aspect ratio,while increases with increasing the linewidth.In addition,for the interconnects containing two elliptical voids not far apart,the stress will promote the merging of the voids.

Coupled analysis of engine noise and interior noise of an automobile

The coupled model of a four-cylinder internal combustion engine and a dash panel was constructed to analyze the relationship between the engine noise and interior noise of an automobile. Finite element analysis, flexible multi-body dynamics, and boundary element analysis were integrated to obtain the tetrahedron-element models, structural vibration response, and radiated noise,respectively. The accuracy of the finite-element model of the engine was validated by modal analysis via single-input multi-output technology, while the dash panel was validated by sound transmission loss experiment. The block was optimized to reduce the radiated acoustic power from the engine surface. The acoustic transfer path between the engine cabin and passenger compartment was then established. The coupled analysis results reveal that the interior noise is optimized due to the engine noise reduction.