THE VARIATIONAL PRINCIPLES FOR PYROELECTRIC MEDIA

The pyroelectric medium is an important material in the application of smart materials and structures. It is necessary to systematically discuss ail kinds of variational principles which play a very significant role in the fundamental theory of mechanics and numerical analysis method. This paper firstly gives the quasi-static and the dynamic variational principles,then the principles for eigen problems. As a simple example, the principle was finally applied to derive the fundamental, equations for an anisotropic piezoelectric plate.

CONSIDER SAINT-VENANT'S PRINCIPLE BY MEANS OF CHAIN MODEL

A precise background theory of computational mechanics is formed. Saint_Venant's principle is discussed in chain model by means of this precise theory. The classical continued fraction is developed into operator continued fraction to be the constrictive formulation of the chain model. The decay of effect of a self_equilibrated system of forces in chain model is decided by the convergence of operator continued fraction, so the reasonable part of Saint_Venant's principle is described as the convergence of operator continued fraction. In case of divergence the effect of a self_equilibrated system of forces may be non_zero at even infinite distant sections, so Saint_Venant's principle is not a common principle.

Analytical solution to mapping rail deformation under bridge transverse deformation using energy variational principle

The track geometry is a critical factor that affects the running safety and riding comfort of trains moving on a high-speed railway bridge.This study addresses the mapping relationship between the track deformation and lateral deformations of bridges.Equilibrium equations and natural boundary conditions of the track-bridge system are established based on the energy variational principle,and an analytical solution is derived for the track deformation accounting for lateral bridge deformations.A five-span simply-supported bridge with continuous welded rail has been selected as the case study.The mapping rail deformations are compared to the finite element results,and both results agree well with each other,validating the analytical method proposed in this paper.The influence factors on the mapping rail deformation are further evaluated.Results show that the mapping rail deformation is consistent with the girder displacement at the area that is away from the girder ends when the flexural stiffness ratio between the track and the bridge girder is low.The interlayer stiffness has a significant effect on the mapping rail deformation when the track flexural stiffness is of a high value.

ON THE GENERALIZATION OF MAXIMUM MODULUS PRINCIPLE

We give the sufficient conditions of Retaining Region Theorem and Maximum Modulus principle, The results of this paper are generatizations of rele rant results in [1,2].

全口径环形抛光的光学元件面形误差影响因素及其控制

全口径环形抛光是加工大口径平面光学元件的关键技术之一,其瓶颈问题是元件面形的高效高精度控制。通过研究元件面形的影响因素及其控制方法从而提升其确定性控制水平。围绕影响面形误差的运动速度、抛光盘表面形状误差和钝化状态等关键工艺因素,建立基于运动轨迹有效弧长的环形抛光运动学模型,揭示了抛光盘表面开槽槽型对面形误差的影响规律;提出了采用位移传感器以螺旋路径扫描抛光盘表面并通过插值算法生成其形状误差的方法,建立基于小工具的子口径修正方法,实现了抛光盘形状误差的在位定量修正;提出抛光盘表面钝化状态的监测方法,研究了抛光盘表面钝化状态对面形误差的影响规律。结果表明:抛光盘表面开槽采用环形槽时元件表面容易产生环带特征,采用径向槽、方形槽和螺旋槽时元件表面较为匀滑;通过在位定量检测和修正抛光盘形状误差,可显著提升元件的面形精度;随着抛光盘表面的逐渐钝化,元件面形逐渐恶化。在研制的5 m直径大口径环形抛光机床上加工800 mm×400 mm×100 mm平面元件的面形PV值优于λ/6(λ=632.8 nm),提升了元件的面形控制效率和精度。

专业课程思政实施效果考核评价指标研究

大学教育是素质教育,归根到底是培养“人”,培养学生的责任意识、敢于担当、具有完善的人格、服务国家、服务社会和自主判断能力。2020年教育部印发《高等学校课程思政建设指导纲要》,让所有高校、所有教师、所有课程都承担育人责任。在课程思政全面实施后,建立课程思政实施效果考核评价指标成为“评价学生在每一门课程中的思政成绩,促进学生在大学期间素质教育的达成”的关键。针对专业课程思政实施效果,从学生和教学评价两方面建立考评指标,一方面从评价学生课程思政成绩的角度,定量、定性地在形成性考核、诊断性评价和终结性评价,以线、线下混合式教学过程多元化考量,促进学生素质教育的达成;另一方面从评价专业课程教学效果上,包括教学设计、思政案例、课堂评教、学生思政考题和调查问卷等多维度细化考核指标,形成“评价—诊断—反馈—改进”的循环过程。以卫星导航定位原理与应用课程思政教学为例,分析所建课程思政实施效果评价指标的有效性,通过反馈改进,循序渐进地提高课程思政育人成效。

中华文明连续性的突出表现、内在机理和意义价值

中华文明不同于“有古而无今”和“虽新而不古”的文明的地方在于它是“亘古亘今”“亦新亦旧”的文明类型。中华文明的连续性既借助并依托人种民族的连续性、国土疆域的连续性、语言文字的连续性表现出来,也体现在道统价值的连续性、治统或大一统的连续性、学统或思想文化传统的连续性等方面。中华文明之所以具有突出的连续性是与中华民族的精神气质、价值追求以及所创造的中华优秀传统文化、中华传统美德、中国哲学品质等密切联系在一起的,“旧邦新命”是中华文明独特的国性基质和价值特质。“新故相资而新其故”“新故相推,日生不滞”在中华文明体系中占有极其重要的地位,也正因为如此,使得中华文明发展起了一种“继往圣”“开来学”的文明精神,并赋予中华文化一种由古及今的发展机理。中华文明的连续性具有深刻而高远的意义和价值,它不仅是我们坚定文化自信、走好中国道路的力量源泉,是我们建设中华民族现代文明的价值支撑,而且也是构建人类文明新形态的精神动能,丰富并发展着世界文明的范式、类型和谱系。

工程教育专业认证背景下“自动控制原理”课程教学方法探索

自动控制原理是控制学科的核心基础课程,在自动化等专业的课程体系中起着极为重要的作用。针对目前课程中存在的课程内容多、难度大,学生基础与需求不统一,课程内容缺乏实践和创新等问题,文章从工程教育专业认证背景出发,结合新时代、新环境和新工科理念,从多层次立体教学、改善教学方法、改革课程设计和加强反馈迭代等方面,对自动控制原理课程教学方法进行了探索性改革。

分数阶Fourier变换的测不准原理

该文参考Fourier变换的性质研究了离散分数阶Fourier变换的测不准原理以及连续分数阶Fourier变换在Lebesgue测度下的测不准原理,使得分数阶Fourier变换的测不准原理性质更一般化.

钢混组合连续梁的设计方案分析

钢混组合梁由型钢和混凝土共同受力,具备较强的抗弯性、抗扭性、跨越性,是当前桥梁设计重点方向。文中以天祝县达隆路大桥项目为例,提出了3×28 m工字钢混组合连续梁的设计方案,以供参考。

“连行诗”命名的合理性研究——以陈东东的《七十二名》(组诗)为中心

不论是中国的古诗词还是自外国传入的现代诗,分行作为显性的外部特征,一直都是构成诗歌的重要条件与标准。陈东东提出“连行诗”的这一概念冲击了大众对于诗歌秩序的认知,将诗歌文体的定义重新聚焦于内容本身。在表现方式上,“连行诗”纠正了诗歌鉴赏对于形式的过分依赖,打破了旧有的分行标准,给予诗歌新的表达自由;在审美层面,“连行诗”纠正了过分私我化的表达趋势,强调日常的主体思索与精神表达,推动了检视原则的变更;在文体本身的定义中,“连行诗”的命名引出了诗歌的独特性与情感内核,缓和了变更引发的焦虑。在各个层面的质疑之下,“连行诗”作为形式本身已具备了诗性的意义。

多次盗窃中“次”的行政不法与刑事不法之衔接判断

多次盗窃系行刑交叉立法范式,其正当性基础在于将客观立场与主观立场相结合的社会危害性理论。将犯罪停止形态融入次目的计量时,需注意仅有未遂形态的行政不法行为符合要求,中止与预备形态无需计量;基于未遂形态行政不法的纳入,应当承认多次盗窃的整体亦存有未遂停止形态。将连续犯理论融入次目的计量时,在兼具形式数罪、实质一罪的场域,次目的计量应坚持一罪立场;在连续犯的具体认定时应坚持限缩立场。将禁止重复评价原则融入次目的计量时,禁止重复评价原则系罪刑均衡原则的当然要求;但该原则并不等同于禁止二次评价,基于评价的非彻底性及全面性要求,存有法律明文规定的,仍可进行评价。

基于CDIO模式的“DSP原理及应用”课程教学改革——以湖北理工学院为例

针对传统教学方式下“DSP原理及应用”课程培养的学生解决复杂工程问题的能力较差、课程目标达成度低的问题,以工程教育专业认证的核心理念为指导思想,以课程目标为依据,开展了基于CDIO模式的项目式教学改革,具体探究了以学生为中心的课程教学模式,明确了项目实施的流程,设计了各项目包含的课程内容,制定了以成果为导向的课程目标达成度评价方式。实践证明,这些改革措施有效地提高了课程目标达成度,培养了学生分析和解决实际工程问题的能力,对相关课程的教学改革提供的有价值的参考。

消防应急照明和疏散指示系统工程验收常见问题

总结工程验收中发现的消防应急照明和疏散指示系统设计的常见问题,包括未正确应用最短路径疏散原则和避险原则、疏散标志灯被遮挡、消防应急灯具的持续工作时间不满足规范要求等;指出线缆及保护管的选择错误、消防应急照明灯具无3CF认证等施工相关的问题;对与建筑及装饰专业、智能化专业、水专业、暖通专业的配合提出建议。

The Loeb Algebras of Absolutely Continuous Measure

It is proved that if μ and v be finite measures on a measurable space (X, S) and v is absolutely continuous with respect to v, then it is holds that L(* S, * μ) L(* S, *v), while L(*S, *μ) and L(*S, V) are the Loeb algebras with respect to measure spaces (X, S,μ) and (X,S,v).

HOMOTOPY CONTINUATION ALGORITHM FOR STRUCTURAL DAMAGE IDENTIFICATION

A new method is put forward for structural damage identification based on the homotopy continuation algorithm. A numerical example is presented to verify the method. The beams with different damage locations and different damage extents are identified by this method. The numerical examples have proved that this new method is capable of easy convergence, which is not sensitive to the initial iterative values. It is effective for accurately identifying multiple damages. By incorporating the finite element method into the homotopy continuation algorithm, the damage identifying ability of the new method can be greatly enhanced.

Maintenance Management Research of a Large-span Continuous Rigid Frame Bridge Based on Reliability Assessment by Using Strain Monitored Data

When the bridge components needing maintenance are the world problem at present,and the health monitoring system is considered to be a very help­ful tool for solving this problem.In this paper,a large number of strain data acquired from the structural health monitoring system(SHMS)installed on a continuous rigid frame bridge are adopted to do reliability assessment.Firstly,a calculation method of punctiform time-dependent reliability is proposed based on the basic reliability theory,and introduced how to cal­culate reliability of the bridge by using the stress data transformed from the strain data.Secondly,combined with“Three Sigma”principle and the basic pressure safety reserve requirement,the critical load effects distribu­tion function of the bridge is defined,and then the maintenance reliability threshold for controlling the unfavorable load state which appears in the early operation stage of this type bridge is suggested,and then the combi­nation of bridge maintenance management and health monitoring system is realized.Finally,the transformed stress distribution certifies that the load effects of concrete bridges practically have a normal distribution;as for the concrete continuous rigid frame bridge with C50 strength grade concrete,the retrofit reliability threshold should be valued at 6.13.The methodology suggested in this article can help bridge engineers do effective maintenance of bridges,which can effectively extend the service life of the bridge and bring better economic and social benefits.

一维六方准晶双材料界面共线裂纹的反平面问题

基于复变函数理论,利用Schwarz解析延拓原理,研究一维六方准晶双材料界面共线裂纹的反平面问题,获得了几个典型问题及相应应力强度因子的封闭解.结果表明,当趋于裂纹尖端路径选在双材料界面上时,双材料界面裂纹应力强度因子大小与材料参数无关,仅与裂纹尺寸及裂纹所受外载荷大小有关且成正比,即应力强度因子随着裂纹尺寸和外载荷的增大而增大.

“程序设计基础”课程实验教学改革的探索

文章突破了传统实验教学在时间和空间维度的限制,通过精细化实验内容,引入多元协作实验平台,对西南交通大学非计算机专业的“程序设计基础”课程进行了实验改革。其中,详细阐述了以“1+2+2+4”的模式实现精细化实验内容与多元化协作的实验平台。该实验教学改革有效地激发了学生的学习兴趣,提高了实验教学的质量和效果,在西南交通大学本科教学中取得了良好的示范作用。