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1.
以政策弹性的二维分析框架为基础,运用文本定量分析法,以中央及27个省、自治区、直辖市的“双减”政策文本为研究对象,发现地方政府“双减”政策刚性有余,略高于中央的比例,在课后服务和作业设计管理上弹性空间较大,政策刚性呈现由东北和东部区域向中西部递减的趋势,部分地方政府政策的有限弹性表现出色。应通过问责与监管方式增强政策的刚性,通过地方政府互相学习机制增强政策的弹性,并把握好刚性与弹性之间的平衡关系。 相似文献
2.
碰撞问题是高中物理中的典型问题,其中一维弹性碰撞问题一直是高考的热点,这类问题所涉及的数学运算往往比较麻烦,但是若能够活用一维弹性碰撞的二级结论,特别是掌握其推导方法,将大大提高解题的速度. 相似文献
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4.
郭军 《新课程学习(社会综合)》2013,(12):65-65
减压 阴茎勃起就是阴茎充血的过程,只有血管弹性好,阴茎才能正常的充血勃起。压力过大是中年男人“性福”的最大致命伤,长期处在压力之下,使体内肾上腺素分泌增加,造成血管收缩。因此平时要保持心情豁达,精神愉快,及时自我缓解压力,避免因精神压力造成性能力的下降。 相似文献
5.
刚性管理是一种以工作为中心,强调规章制度的管理模式;柔性管理是针对刚性管理的弊端提出的"以人为管理中心"的一种改革思路.两者都是以效率为中心的管理价值观为指导.但由刚转柔,简单的刚柔结合观点不过是一种非此即彼、亦此亦彼或非此非彼的简单思维模式的反映.崔德明先生的专著<高职院校教师弹性管理研究>提出了超越刚性与弹性的一种新的教师管理模式--弹性管理.教师弹性管理本质是以师为本,因师而治.它既是一种管理观念,也是一种管理模式和方法.高职院校要进行教师弹性管理,需要观念、制度和实践模式的全面创新. 相似文献
6.
基于MATCONT的电力系统电压稳定分岔及控制仿真试验 总被引：1，自引：0，他引：1
介绍了电力系统ODE模型中引起电压失稳的常见分岔类型及分岔控制的基本概念;运用基于Matlab的数值分岔分析软件MATCONT对一个经典单机—动态负荷系统进行了分岔分析,验证了PQ动态负荷模型系统存在着鞍结分岔(SNB)现象,而RL动态负荷模型系统并无分岔现象产生.为延迟PQ动态负荷模型系统的鞍结分岔点,在原系统中引入了线性状态反馈控制和SVC控制两种分岔控制方法.MATCONT仿真结果显示,这两种控制方法均能够有效延迟鞍结分岔,从而提高系统的电压稳定性,并可通过选择合理的反馈控制器增益及SVC增益获得理想的分岔控制效果. 相似文献
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廖红梅 《中学课程辅导(初三版)》2003,(7):42-42
动能、重力势能、弹性势能都具有两个特性:储存性和相对性.了解这两个特性,对机械能的掌握理解具有一定的帮助. 一储存性“物体能够做功,它就具有能量.”、“能够做功不一定非要做出来,它可以储存在那里。”物体的动能可以储存在它的速度中,如果物体的速度不变,它的动能就不变,它也不对 相似文献
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宋玉娥 《北京工业职业技术学院学报》2008,7(4):6-10
研究了各向同性不可压超弹性材料球体在表面均匀拉伸死载荷作用下的空穴分岔问题,得到了描述球体内部的空穴生成和增长的空穴分岔方程,证明了空穴分岔方程的平凡解支上存在唯一的分岔点,并给出了分岔的辨别条件;利用奇点理论给出了空穴分岔方程在分岔点的等价正规形,并利用最小势能原理讨论了空穴分岔方程的稳定性。 相似文献
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李玉叶 《赤峰学院学报(自然科学版)》2014,(13):3-6
本文研究了确定的和随机的INa,p+IK神经元模型中的超临界霍普夫(Hopf)分岔附近的动力学行为,随机模型中靠近Hopf分岔点的随机节律被认为是整数倍节律模式;还研究了相应于分岔点附近的随机自共振机制.结果不仅揭示了超临界Hopf分岔点附近的神经放电的统计特征和动力学机制,还给出了实用于现实神经系统中Hopf分岔的判断指标. 相似文献
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沈之菲 《思想理论教育(上半月综合版)》2010,(11)
"弹性研究的关键在于一个人的精神恢复能力,即一个人怎样恢复到承受压力之前的状态.也就是说,一个有弹性的人在困难中仍然具有适应力和竞争力.恢复并不是说一个人不能受伤,而是说在不利处境下,一个有弹性的人能够首先面对,适应压力,不被击垮,然后振作恢复." 相似文献
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It has been shown that thin-walled hyperelastic tubes could bulge under inflation. In this paper we investigate the possibility of bulging for thin-walled tubes composed of plastoelastic/viscoelastic materials. A general bifurcation condition is derived by near-critical post-bifurcation analysis, which can degenerate into an existing special one for hyperelastic tubes. It is demonstrated that the linearly elastic and plastoelastic tubes can bulge under inflation, but viscoelastic tubes cannot bulge unless the value of inflating pressure is just equal to the one of the critical pressure for the corresponding elastic tubes. 相似文献
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In this paper,a dynamic model on a rigid rotor-sliding bearing system with a SFD is established.The stability and bifurcation behaviors of the system are studied,on The basis of the differential equations of fluid momentum and mass continuity,the distribution pressure function is derived by taking oil film inertia force into consideration.Damping force, clearance excitation force,interference force of different frequencies and static load are also considered in the model,Finally,the governing equations of the stability and bifurcation behaviors of the system are solved by Floquet theory,Simulation of dynamic model shows that the rigid rotor-sliding bearing system can maintain stability and exhibit a Hopt bifurcation phenomenon in a certain range. 相似文献
13.
卢义玉 《重庆大学学报(英文版)》2003,2(1)
~~00002RKRSr= (6) If 0tKt=, Eqs. (2),(3) and (4) change into the following equation that is applied to simulations using the MathCAD software. ddd(,,)dd1dxyygxyzzttt=== (7) where 11251(,,)()(1)gxyzABCyxaaaa=++-+, 2132131145678222124531678831(1),23(1)[(1sin],[3cos()] AyyByxxyxzCxyxyxyxzggaaaaaaaaaaaaagaaaa-------=--=++---+=+-- (8) 5g00pK6g0p… 相似文献
14.
This paper proposes a theoretical method using finite element analysis （FEA） to calculate the plastic collapse loads of pressure vessels under internal pressure, and compares the analytical methods according to three criteria stated in the ASME Boiler Pressure Vessel Code. First, a finite element technique using the arc-length algorithm and the restart analysis is developed to conduct the plastic collapse analysis of vessels, which includes the material and geometry non-linear properties of vessels. Second, as the mechanical properties of vessels are assumed to be elastic-perfectly plastic, the limit load analysis is performed by employing the Newton-Raphson algorithm, while the limit pressure of vessels is obtained by the twice-elastic-slope method and the tangent intersection method respectively to avoid excessive deformation. Finally, the elastic stress analysis under working pressure is conducted and the stress strength of vessels is checked by sorting the stress results. The results are compared with those obtained by experiments and other existing models. This work provides a reference for the selection of the failure criteria and the calculation of the plastic collapse load. 相似文献
15.
轴对称压力容器弹塑性与强度分析 总被引：1，自引：0，他引：1
本文应用第一、第三强度理论对轴对称压力容器圆筒和半圆球部分进行弹塑性力学分析,得到各自弹性和塑性极限应力,将其与压力容器规范中径分析结果作对比分析。此外,本文还分析了径比对压力容器结构设计和强度的影响。 相似文献
16.
Strain growth is a phenomenon observed in containment vessels subjected to internal blast loading. The elastic response of the vessel may become larger in a later stage compared to its response during the initial stage. The dynamic responses of infinitely long cylindrical containment vessels subjected to uniformly-distributed internal blast loading are studied using LS-DYNA. The development of bending modes and the interaction between the breathing mode and bending modes are observed. The methodology developed for dynamic elastic buckling analysis is employed to study the strain growth phenomenon in explosion containment vessels. It is shown that the dynamic instable vibration of a containment vessel is the basic mechanism of strain growth. 相似文献
17.
基于Matlab仿真软件,考虑弹性水击对水轮机调节系统的影响,建立弹性水击水轮机微分代数模型,并与调速器和发电机共同构成水轮机调节系统非线性模型。在此基础上运用非线性动力学分叉理论对PID调速器参数进行Hopf分叉行为研究,得出PID参数三维分叉曲面、二维分叉曲线及稳定域,并通过对时域图、相轨迹图等的综合分析,得到取不同调速器参数时系统的非线性动力学特性,为机组PID参数选择提供理论依据。最后通过系统仿真得出,在小扰动下线性模型和非线性模型均能适用,在大扰动下非线性模型能更真实地反映机组动态特性。 相似文献
18.
Cun-jian MIAO Jin-yang ZHENG Xiao-zhe GAO Ze HUANG A-bin GUO Du-yi YE Li MA 《浙江大学学报(A卷英文版)》2013,14(1):31-37
Cold-stretched pressure vessels from austenitic stainless steels(ASS) are widely used for storage and transportation of liquefied gases,and have such advantages as thin wall and light weight.Fatigue is an important concern in these pressure vessels,which are subjected to alternative loads.Even though several codes and standards have guidelines on these pressure vessels,there are no relevant design methods on fatigue failure.To understand the fatigue properties of ASS 1.4301(equivalents include UNS S30400 and AISI 304) in solution-annealed(SA) and cold-stretched conditions(9% strain level) and the response of fatigue properties to cold stretching(CS),low-cycle fatigue(LCF) tests were performed at room temperature,with total strain amplitudes ranging from -.4% to -.8%.Martensite transformations were measured during the tests.Comparisons on cyclic stress response,cyclic stress-strain behavior,and fatigue life were carried out between SA and CS materials.Results show that CS reduces the initial hardening stage,but prolongs the softening period in the cyclic stress response.Martensite transformation helps form a stable regime and subsequent secondary hardening.The stresses of monotonic and cyclic stress-strain curves are improved by CS,which leads to a lower plastic strain and a much higher elastic strain.The fatigue resistance of the CS material is better than that of the SA material,which is approximately 1?03 to 2?04 cycles.The S-N curve of the ASME standard for ASS is compared with the fatigue data and is justified to be suitable for the fatigue design of cold-stretched pressure vessels.However,considering the CS material has a better fatigue resistance,the S-N curve will be more conservative.The present study would be helpful in making full use of the advantages of CS to develop a new S-N curve for fatigue design of cold-stretched pressure vessels. 相似文献
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在刚性承台下桩筏基础变分计算方法的基础上，采用弹性薄板单元，引进弹性承台，给出了计算方法并考虑了承台刚度变化对复合桩基工作性状的影响。应用本方法对一工程算例进行计算分析，结果表明承台刚度的变化对桩土分担比有显著影响。 相似文献
20.
Rotor systems supported by angular contact ball bearings are complicated due to nonlinear Hertzian contact force. In this paper, nonlinear bearing forces of ball bearing under five-dimensional loads are given, and 5-DOF dynamic equations of a rigid rotor ball bearing system are established. Continuation-shooting algorithm for periodic solutions of the nonlinear non-autonomous dynamic system and Floquet multipliers of the system are used. Furthermore, the bifurcation and stability of the periodic motion of the system in different parametric domains are also studied. Results show that the bifurcation and stability of period-1 motion vary with structural parameters and operating parameters of the rigid rotor ball bearing system. Avoidance of unbalanced force and bending moment, appropriate initial contact angle, axial load and damping factor help enhance the unstable rotating speed of period-1 motion. 相似文献