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1.
Standard finite element approaches are still ineffective in handling extreme material deformation, such as cases of large deformations and moving discontinuities due to severe mesh distortion. Among meshfree methods developed to overcome the ineffectiveness, Reproducing Kernel Particle Method (RKPM) has demonstrated its great suitability for structural analysis. This paper presents applications of RKPM in elasto-plastic problems after a review of meshfree methods and an introduction to RKPM. A slope stability problem in geotechnical engineering is analyzed as an illustrative case. The corresponding numerical simulations are carried out on an SGI Onyx3900 supercomputer. Comparison of the RKPM and the FEM under identical conditions showed that the RKPM is more suitable for problems where there exists extremely large strain such as in the case of slope sliding. 相似文献
2.
汤雁 《天津大学学报(英文版)》2004,10(3):225-228
The subject of the work is to propose a series of papers about adaptive finite element methods based on optimal error control estimate. This paper is the third part in a series of papers on adaptive finite element methods based on optimal error estimates for linear elliptic problems on the concave comer domains. In the preceding two papers (part 1 : Adaptive finite element method based on optimal error estimate for linear elliptic problems on concave comer domain; part 2:Adaptive finite element method based on optimal error estimate for linear elliptic problems on nonconvex polygonal domains), we presented adaptive finite element methods based on the energy norm and the maximum norm. In this paper, an important result is presented and analyzed. The algorithm for error control in the energy norm and maximum norm in part 1 and part 2 in this series of papers is based on this result. 相似文献
3.
Several fundamental problems in hydrophobic force measurements using atomic force microscope （AFM） are discussed in this paper. A novel method for colloid probe preparation based on chemical etching technology is proposed, which is specially fit for the unique demands of hydrophobic force measurements by AFM. The features of three different approaches for determining spring constants of rectangular cantilevers, including geometric dimension, Cleveland and Sader methods are compared. The influences of the sizes of the colloids on the measurements of the hydrophobic force curves are investigated. Our experimental results showed that by selecting colloid probe with proper spring constant and tip size, the hydrophobic force and the complete hydrophobic interaction force curve can be measured by using AFM. 相似文献
4.
In the practice of English Language Teaching, speaking can be the most difficult part for many learners, especially in China. This paper firstly reveals the necessity of giving more freedom and tolerance on speaking classes, based on the nature of teaching as well as speaking. Then there is more exploration for the Chinese ELT (English Language Teaching) approaches, explaining the difficulties from the aspects of Chinese culture and philosophy. Afterwards implications are showed on how to give a supportive class in different circumstances, such as dealing with silence, error correction and L1 (native language) interferences. 相似文献
5.
稳健图像Hash研究进展 总被引：3，自引：0，他引：3
The easy generation, storage, transmission and reproduction of digital images have caused serious abuse and security problems. Assurance of the rightful ownership, integrity, and authenticity is a major concern to the academia as well as the industry. On the other hand, efficient search of the huge amount of images has become a great challenge. Image hashing is a technique suitable for use in image authentication and content based image retrieval （CBIR）. In this article, we review some representative image hashing techniques proposed in the recent years, with emphases on how to meet the conflicting requirements of perceptual robustness and security. Following a brief introduction to some earlier methods, we focus on a typical two-stage structure and some geometric-distortion resilient techniques. We then introduce two image hashing approaches developed in our own research, and reveal security problems in some existing methods due to the absence of secret keys in certain stage of the image feature extraction, or availability of a large quantity of images, keys, or the hash function to the adversary. More research efforts are needed in developing truly robust and secure image hashing techniques. 相似文献
6.
There are several approaches to data collection, such as questionnaires, interviews, observations, focus groups and so on. This essay will look at two specific methods, interviews and questionnaires. It will involve individual strengths and weaknesses at first and then have a brief clarification of'why'and'when'to use. Finally, this essay will list out some problems that researchers might face during the process. 相似文献
7.
Synthesis of acetals and ketals catalyzed by tungstosilicic acid supported on active carbon 总被引：3，自引：0，他引：3
INTRODUCTION Acetals and ketals are among the most importantperfume materials and industrial materials of organicsynthesis. There are now many methods to synthesizethem. The H2SO4 conventionally used as catalyst infactories (Li and Fan, 1981) causes many problems,such as erosion of equipment, difficulty for af-ter-treatment, low quality of the products, etc. Withthe use of anhydrous copper sulfate (Hanzlik andLeinwetter, 1978), molecular sieve (Wang and Qian,1993), montmorillonite… 相似文献
8.
The challenges of writing itself and lack of appropriate teaching methodology demotivate EFL （English as a Foreign Language） learners in some Chinese universities to write more, especially as the only incentive for students to write is the compulsory tests. The main objectives of this article are： （1） to discuss the background of the EFL learners in Chinese tertiary education and then to elaborate on their needs and problems for EFL writing; （2） to review the existing approaches to teaching writing; and （3） to propose and justify an integrated model on the basis of these approaches for teaching EFL writing in the Chinese context. 相似文献
9.
Multi-attribute decision-making approach dealing with uncertain linguistic assessment information 总被引：1，自引：0，他引：1
Gu Jing Zhou Zongfang 《东南大学学报》2008,(Z1)
An approach is presented to deal with a multi-attribute decision-making problem in which the attribute weights are unknown and the attribute values take the form of uncertain linguistic variables. First, a linguistic assessment standard is set up to deal with the uncertain linguistic attributes, and the operation laws of uncertain linguistic variables and the uncertain linguistic weighting average(ULWA)operator are introduced. Then a ranking formula of uncertain linguistic variables based on expectation-variance is proposed. As for the case without weight information, a goal program based on a warp function is constructed to determine the attribute weights, and the ULWA operator is utilized to aggregate the assessment information of uncertain linguistic variables, and the corresponding alternatives are ranked by a formula based on expectation-variance. Finally, a numerical example is given, and the results demonstrate that it is much easier and faster for the ranking method based on expectation-variance when compared to the existing methods. 相似文献
10.
ESP,namely English for Specific Purposes,has become an integral part of English teaching in higher education.How ever,the majority of research on approaches in ESP teaching is focused on one specific method,which fails to generalize the de velopment of ESP teaching in China.In this thesis,recent Chinese research on approaches and methods in ESP teaching is re viewed,including those in established framework and an innovative one.The advantages and limitations of each methods are ana lyzed and the possible suggestions are made with a view to promoting the research on approaches and methods in ESP teaching in a more all-round way. 相似文献
11.
针对麦克斯韦方程中的电导率参数反演问题,构造一种具有大范围收敛的正则化共轭斜量反演算法,即将用于求解非线性问题大范围收敛的同伦法、求解大规模优化问题的共轭斜量法与求解不适定问题的Tikhonov正则化方法有机结合,得到解决麦克斯韦方程反演问题大范围收敛的数值方法,以求解电导率参数反演问题,解决了求解过程中局部陷入极小值的困惑。实验结果表明此算法是有效的,可以应用于其他类型的参数识别问题。 相似文献
12.
As a basic mathematical structure,the system of inequalities over symmetric cones and its solution can provide an effective method for solving the startup problem of interior point method which is used to solve many optimization problems.In this paper,a non-interior continuation algorithm is proposed for solving the system of inequalities under the order induced by a symmetric cone.It is shown that the proposed algorithm is globally convergent and well-defined.Moreover,it can start from any point and only needs to solve one system of linear equations at most at each iteration.Under suitable assumptions,global linear and local quadratic convergence is established with Euclidean Jordan algebras.Numerical results indicate that the algorithm is efficient.The systems of random linear inequalities were tested over the second-order cones with sizes of 10,100,,1 000 respectively and the problems of each size were generated randomly for 10 times.The average iterative numbers show that the proposed algorithm can generate a solution at one step for solving the given linear class of problems with random initializations.It seems possible that the continuation algorithm can solve larger scale systems of linear inequalities over the secondorder cones quickly.Moreover,a system of nonlinear inequalities was also tested over Cartesian product of two simple second-order cones,and numerical results indicate that the proposed algorithm can deal with the nonlinear cases. 相似文献
13.
In this paper, a new method named as the gradually descent method was proposed to solve the discrete global optimization problem. With the aid of an auxiliary function, this method enables to convert the problem of finding one discrete minimizer of the objective function f to that of finding another at each cycle. The auxiliary function can ensure that a point, except a prescribed point, is not its integer stationary point if the value of objective function at the point is greater than the scalar which is chosen properly. This property leads to a better minimizer of f found more easily by some classical local search methods. The computational results show that this algorithm is quite efficient and reliable for solving nonlinear integer programming problems. 相似文献
14.
在初中化学学习中,物质鉴别类的题目是考试中的热点与难点。提高学生解决这类题目的能力,对学生化学素养的培养有重要作用。文章从物质鉴别例题出发,为学生提出一些解题思路和技巧,以提升学生的解题速度,培养学生良好的化学推理思维。 相似文献
15.
本文提出了一种新的求解结构动力响应的仿真算法。算法原理基于求解状态方程的增广矩阵法。该算法能够给出精度今人十分满意的计算结果。 相似文献
16.
随着科学的发展,产生出了不同的专业。每个专业由于侧重点不同,从而具有不同的特色。信息与计算科学专业是以将数学应用于解决工程问题为研究方向,具有和数学专业明显的不同。因此,对该专业的定积分与微元法的教学必须要与数学专业的形式定义有所区别,也应与其他工科专业的过于粗糙有所不同,而应该充分凸显该专业既注重形式定义的重要,也要突出内在解决实际问题的本质的特色。本文从解决实际问题的方法出发,对定积分与微元法进行比较分析,探讨适合于该专业的关于这两个定义的教学方法,旨在指出该专业所要求的教学特色,以提高专业教学质量。 相似文献
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18.
针对局部灰度特征方法在高噪声图像中定位精度低的问题,提出改进局部灰度特征方法并用于工件亚像素边缘检测。首先,使用改进的Canny算子代替基于一阶导数的梯度算子,以便更精确地提取粗边缘;然后在采集到的像素窗口两侧建立子图像,代替单个窗口特征以修改边缘上下两侧强度值,再将新构造的子图像中间列像素进行加权,加速图像迭代复原速度;最后,通过所有新生成的子图像局部灰度特征重新计算亚像素位置,进一步提高检测精度。实验结果表明,在无外加噪声和加入1.00%、5.00%的噪声标准偏差图像中,RMS误差明显降低,亚像素坐标数与定位精度明显提高。 相似文献
19.
井下无定向导线测量 总被引：1，自引：0，他引：1
杨家文 《淮南职业技术学院学报》2004,4(3):25-26
在巷道延伸测量中，经常会遇到测量控制点被破坏，剩下的点又彼此不通视的情况，为了节省作业时间，不影响生产，应用井下无定向导线测量，可以恢复该段导线；该法是把两已知控制点看着是定向时两垂球线连接点，在两控制点间按所设计的精度进行相应等级的导线联测，并用两井几何定向的井下连接导线解算方法进行计算，使原来按一般导线测量方法不能解决的点位坐标问题得以解决。 相似文献
20.
In the conventional differential quadrature (DQ) method the functional values along a mesh line are used toapproximate derivatives and its application is limited to regular regions. In this paper, a local differential quadrature (LDQ)method was developed by using irregular distributed nodes, where any spatial derivative at a nodal point is approximatedby a linear weighted sum of the functional values of nodes in the local physical domain. The weighting coefficients in thenew approach are determined by the quadrature rule with the aid of nodal interpolation. Since the proposed method directlyapproximates the derivative, it can be consistently well applied to linear and nonlinear problems and the mesh-free feature isstill kept. Numerical examples are provided to validate the LDQ method. 相似文献