首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 125 毫秒
1.
Comprehensive tests on Hangzhou intact soft clay were performed, which were used to obtain the soils’ critical response to undrained dynamic stress paths under different combinations of principal stress orientation. The different combinations included cyclic principal stress rotation (CPSR for short), cyclic shear with abrupt change of principal stress orientation (CAPSO for short) and cyclic shear with fixed principal stress orientation (CFPSO for short). On one side, under all these stress paths, samples have obvious strain inflection points and shear bands, and the excess pore water pressure is far from the level of initial effective confining pressure at failure. Stress paths of major principal stress orientation (α) alternating from negative and positive have quite different influence on soil’s properties with those in which α is kept negative or positive. On the other side, due to the soil’s strongly initial anisotropy, samples under double-amplitudes CPSR and CAPSO (or single-amplitude CPSR and CFPSO) have similar properties on dynamic shear strength and pore water pressure development tendency when α is kept within ±45°, while have quite different properties when α oversteps ±45°.  相似文献   

2.
裤子是我们现代人穿用的一种服装类型,不管是西方还是东方,裤装的发展与演变都有着悠久的历史,又因各自文化的不同,呈现出较大的差别。文章概述中西裤装发展的不同历程与特点,由此分析中西裤装的特色及文化差异。  相似文献   

3.
微波遥感的发展与应用   总被引:2,自引:0,他引:2  
微波遥感作为遥感技术的一个分支,是20世纪70年代发展起来的一门年轻的学科.着重以我国微波遥感发展的历程为例,回顾了三十多年来微波遥感领域学术与技术的迅速发展,比较分析了微波遥感对于可见光和红外遥感有着不可比拟的优越性,因而在海洋、冰雪、大气、测绘、农业、灾害监测等方面都有着广泛的应用.同时提出了目前我国在微波遥感领域存在的若干不足并指出了今后的研究方向.  相似文献   

4.
在梯度胶片制作系统的设计中,为了完成制胶系统上位机数据计算、图形显示、系统管理软件的设计,采用Matlab函数根据采样数据合出步进电机进给控制曲线,结合VB将曲线和数据显示在人机交互界面上,将所计算的参数提供给下位控制系统,系统通过曲线插补计算对步进电机进行控制来完成胶片制作.经实践检验,这种方法所设计的监控程序功能完善、界面良好、操作方便.  相似文献   

5.
胶原修饰反应的专一性   总被引:1,自引:0,他引:1  
对胶原修饰反应的专一性进行研究,有助于进一步研究皮革的鞣制机理.本文采用亚硝酸钠法、丁二酮法分别研究了氨基、胍基修饰反应的专一性,并通过氨基酸分析等方法,获得了专一性数据.结果显示,去氨基反应中,赖氨酸的去除率达到91%,精氨酸损失仅为4.1%,表明去氨基反应专一性较强;而在去胍基反应中,精氨酸的去除率约为83%,但是组氨酸、赖氨酸和酪氨酸的损失都在20%以上,表明去胍基反应专一性不强,但操作过程相对简单,蛋白质结构损伤不大.  相似文献   

6.
探讨了以亚麻油、丙三醇、苯酐为原料制备油改性醇酸树脂的方法及催化剂对合成工艺性能的影响.  相似文献   

7.
基于EPS格式条形码的图形识别   总被引:1,自引:0,他引:1  
由于EPS格式为矢量类文件,无分辨率可言,很难利用数字图像处理技术来识别。针对EPS格式条形码识别过程中存在诸如受黑墨扩展因素造成了条码的条和空的比例不符,无法准确识别出正确的条码等问题,提出了一种基于二进制法解析EPS格式条形码,并对其进行识别,判断条码的准确度,这样可以提前检测出EPS格式条码的错误。对不同放大系数的条形码进行分析,从而避免生成胶片和印刷时的误差和浪费。实验结果证明效果显著。  相似文献   

8.
校报是高校的“机关报”,起着宣传学校办学思想,弘扬主弦律的重要作用。随着数字化媒体的高速发展和有力冲击,校报怎样办出特色,让大家喜闻乐见,值得我们深思。本文就如何更好地发挥校报的舆论导向功能,如何使校报突出个性化作探讨。  相似文献   

9.
我国加入世贸组织之后,国民经济发展面临着新的机遇和挑战,同时,与经济发展密切相连的金融财税领域也迎来了新的挑战.文中总结了涉税案件移送司法机关处理中存在的问题,并就今后的研究重点和发展方向提出了一些建议,为税务行政执法与司法处理的衔接奠定坚实基础.  相似文献   

10.
为解决推进剂的脱湿问题合成出了3-烯丙基-5,5-二甲基海因(ADMH),并将其与甲基丙烯酸β-羟乙酯和丙烯腈两种单体进行反应物配比不同的共聚,得到3个共聚物键合剂.将其应用到NEPE推进剂的某个配方中,进行了力学性能测试.试验结果表明,ADMH可有效提高推进剂在常温、高温和低温时的最大抗拉强度、最大延伸率和断裂延伸率;3个聚合物键合剂可大幅度提高最大抗拉强度,但对延伸率的提高还有待研究.  相似文献   

11.
The influences of soil dilatancy angle on three-dimensional (3D) seismic stability of locally-loaded slopes in nonassociated flow rule materials were investigated using a new rotational collapse mechanism and quasi-static coefficient concept. Extended Bishop method and Boussinesq theorem were employed to establish the stress distribution along the rupture surfaces that are required to obtain the rate of internal energy dissipation for the nonassociated flow rule materials in rotational collapse mechanisms. Good agreement was observed by comparing the current results with those obtained using the translational or rotational mechanisms and numerical finite difference method. The results indicate that the seismic stability of slopes reduces by decreasing the dilatancy angle for nonassociated flow rule materials. The amount of the mentioned decrease is more significant in the case of mild slopes in frictional soils. A nearly infinite slope under local loading, whether its critical failure surface is 2D or 3D, not only depends on the magnitude of the external load, but also depends on the dilatancy angle of soil and the coefficient of seismic load.  相似文献   

12.
The robustly asymptotical stability problem for discrete-time nonlinear systems with time-delay was investigated. Positive definite matrix are constructed through Lyapunov functional. With the identity transform, property of matrix inverse and S-procedure, a new sufficient condition independent of the size of time-delay for robust stability of discrete-time nonlinear systems with time-delay is established. With Schur complement, another equivalent sufficient condition for robust stability of discrete-time nonlinear systems with time-delay is given. Finally, a sufficient condition dependent on the size of time-delay for robust stability of discrete-time nonlinear systems with time-delay is obtained. A unified approach is used to cast the robust stability problem into a convex optimization involving linear matrix inequalities. Foundation item: Project (60425310) supported by the National Natural Science Foundation of China; project (2001AA4422200) supported by the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of the Ministry of Education of China  相似文献   

13.
Estimation of compaction grouting pressure in strain softening soils   总被引:3,自引:2,他引:1  
A new method was proposed to predict the limited compaction grouting pressure for the soft soils. Theoretical basis of the method considered the conical shear failure above the grout bulb. Using the Mohr-Coulomb yield criterion as the initial yield function, the limited compaction grouting pressure was determined, according to the softening elastic-plastic model based on the conventional triaxial compression tests to simulate the strain softening soils. The small strain in the elastic zone and large stain in the plastic zone and the rational yield function for the strain softening phase stage, the analytical solutions to the compaction grouting pressure were presented. The results indicate reasonable agreement and show a good potential of the proposed method for rationally optimizing the design of compaction grouting operations. Foundation item: Project (200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China; Project (09JJ1008) supported by Hunan Provincial Natural Science Foundation of China  相似文献   

14.
In order to determine the slip plane of slope directly by the calculation results of strength reduction method, and analyze the influential factors of slope stability, a numerical model was established in plane strain mode by FLAC3D for homogeneous soil slope, whose parameters were reduced until the slope reached the critical state. Then FISH program was used to get the location data of slip plane from displacement contour lines. Furthermore, the method to determine multiple slip planes was also proposed by setting different heights of elastic areas. The influential factors for the stability were analyzed, including cohesion, internal friction angle, and tensile strength. The calculation results show that with the increase of cohesion, failure mode of slope changes from shallow slipping to the deep slipping, while inclination of slip plane becomes slower and slipping volume becomes larger; with the increase of friction angle, failure mode of slope changes from deep slipping to shallow slipping, while slip plane becomes steeper and upper border of slip plane comes closer to the vertex of slope; the safety factor increases little and slip plane goes far away from vertex of slope with the increase of tensile strength. Foundation item: Project(20060533071) supported by the Doctoral Program Foundation of Higher Education of China; Project (20060400264) supported by China Postdoctoral Science Foundation; Project (50774093) supported by the National Natural Science Foundation of China; Project (1343-74236000014) supported by Graduate Student Innovation Foundation of Hunan Province, China  相似文献   

15.
The stability and nonlinear dynamic behavior of drilling shaft system in copper stave deep hole drilling were analyzed. The effects of the fluctuation of the cutting force, the mass eccentricity and the hydrodynamic forces of cutting fluid could be taken into consideration in the model of drilling shaft system. Based on the isoparametric finite element method, the variational form of Reynolds equation in hydrodynamic fluid was used to calculate nonlinear hydrodynamic forces and their Jacobian matrices simultaneously. In the stability analysis, a new shooting method for rapidly determining the periodic orbit of the nonlinear drilling shaft system and its period was presented by rebuilding the traditional shooting method and changing the time scale. Through the combination of theories with experiment, the correctness and effectiveness of the above methods are verified by using the Floquet theory. The results show that the mass eccentricity can inhibit the whirling motion of drilling shaft to some extent. Foundation item: Project(2007CB707706) supported by the Major State Basic Research Development Program of China; Projects(2007E213, 2007E203) supported by the Natural Science Foundation of Shaanxi Province, China  相似文献   

16.
There exist three problems in the calculation of lateral vibration of the train-track time-variant system at home and abroad and the method to solve them is presented. Spatially coupling vibration analysis model of train-track time-variant system is put forward. Each vehicle is modeled as a multi-body system with 26 degrees of freedom and the action of coupler is also considered. The track structure is modeled as an assembly of track elements with 30 degrees of freedom, then the spatially coupling vibration matrix equation of the train-track time-variant system is established on the basis of the principle of total potential energy with stationary value and the "set-in-right-position" rule. The track vertical geometric irregularity is considered as the excitation source of the vertical vibration of the system, and the hunting wave of car bogie frame is taken as the excitation source of lateral vibration of the system. The spatially coupling vibration matrix equation of the system is solved by Wilson-θ d  相似文献   

17.
A robust decentralized H∞ control problem was considered for uncertain multi-channel discrete-time systems with time-delay. The uncertainties were assumed to be time-invariant, norm-bounded, and exist in the system, the time-delay and the output matrices. Dynamic output feedback was focused on. A sufficient condition for the multi-channel uncertain discrete time-delay system to be robustly stabilizable with a specified disturbance attenuation level was derived based on the theorem of Lyapunov stability theory. By setting the Lyapunov matrix as block diagonal appropriately according to the desired order of the controller, the problem was reduced to a linear matrix inequality (LMI) which is sufficient to existence condition but much more tractable. An example was given to show the efficiency of this method.  相似文献   

18.
To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into intrinsic mode functions using the empirical mode decomposition approach. Based on the empirical mode decomposition results, the energy of each intrinsic mode function was extracted, and the vortex energy ratio was proposed to analyze how the perturbation in the flow affected the measurement performance of the vortex flowmeter. The relationship between the vortex energy ratio of the signal and the flow condition was established. The results show that the vortex energy ratio is sensitive to the flow condition and ideal for the characterization of the vortex flowmeter signal. Moreover, the vortex energy ratio under normal flow condition is greater than 80%, which can be adopted as an indicator to diagnose the state of a vortex flowmeter. Foundation item: Project(200801346) supported by the China Postdoctoral Science Foundation; Project(2008RS4022) supported by the Hunan Postdoctoral Scientific Program; Project(2008) supported by the Postdoctoral Science Foundation of Central South University  相似文献   

19.
By taking cross-wind forces acting on trains into consideration, a dynamic analysis method of the cross-wind and high-speed train and slab track system was proposed on the basis of the analysis theory of spatial vibration of high-speed train and slab track system. The corresponding computer program was written by FORTRAN language. The dynamic responses of the high-speed train and slab track under cross-wind action were calculated. Meanwhile, the effects of the cross-wind on the dynamic responses of the system were also analyzed. The results show that the cross-wind has a significant influence on the lateral and vertical displacement responses of the car body, load reduction factor and overturning factor. For example, the maximum lateral displacement responses of the car body of the first trailer with and without cross-wind forces are 32.10 and 1.60 mm, respectively. The maximum vertical displacement responses of the car body of the first trailer with and without cross-wind forces are 6.60 and 3.29 mm, respectively. The maximum wheel load reduction factors of the first trailer with and without cross-wind forces are 0.43 and 0.22, respectively. The maximum overturning factors of the first trailer with and without cross-wind forces are 0.28 and 0.08, respectively. The cross-wind affects the derailment factor and lateral Sperling factor of the moving train to a certain extent. However, the lateral and vertical displacement responses of rails with the cross-wind are almost the same as those without the cross-wind. The method presented and the corresponding computer program can be used to calculate the interaction between trains and track in cross-wind. Foundation item: Project (2007CB714706) supported by the Major State Basic Research and Development Program of China; Project (50678176) supported by the National Natural Science Foundation of China; Project (NCET-07-0866) supported by the New Century Excellent Talents in University  相似文献   

20.
The effects of quality and content of fly ash on the early-age cracking behavior of high-flowing concrete (HFC) were investigated. The early-age cracking behavior of the HFC was analyzed by combining the tests of evaporation capacity and electrical resistivity of the HFC. In these tests, a modified flat-type specimen was adopted. The results show that the HFC will have a lower evaporation capacity when it is mixed with fine fly ash, while it will have a higher evaporation capacity when grade III fly ash is used as mineral admixture. And the electrical resistivity rate of HFC reduces with the increase of the content of fly ash. A nonlinear relationship exists between the cracking time of HFC and the minimum electrical resistivity. The early-age cracking behavior of HFC with fly ash can be enhanced by appropriately increasing the fine particle content and MgO, K2O, and SO3 contents of fly ash. The optimal content of fly ash, which makes a satisfied early-age cracking behavior of HFC, is obtained. And when the content of fly ash exceeds a critical value, the early-age cracking behavior of HFC will rapidly decrease. Foundation item: Project(50478003) supported by the National Natural Science Foundation of China; Project(2002F007) supported by the Natural Science Foundation of Fujian Province, China  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号