High-order maximum-principle-preserving and positivity-preserving weighted compact nonlinear schemes for hyperbolic conservation laws

In this paper,the maximum-principle-preserving(MPP)and positivitypreserving(PP)flux limiting technique will be generalized to a class of high-order weighted compact nonlinear schemes(WCNSs)for scalar conservation laws and the compressible Euler systems in both one and two dimensions.The main idea of the present method is to rewrite the scheme in a conservative form,and then define the local limiting parameters via case-by-case discussion.Smooth test problems are presented to demonstrate that the proposed MPP/PP WCNSs incorporating a third-order Runge-Kutta method can attain the desired order of accuracy.Other test problems with strong shocks and high pressure and density ratios are also conducted to testify the performance of the schemes.

Connection between the Principles of Thermodynamics and the Conservation Laws: Physical Meaning of the Principles of Thermodynamics

It has been shown that the first principle of thermodynamics follows from the conservation laws for energy and linear momentum. And the second principle of thermodynamics follows from the first principle of thermodynamics under realization of the integrating factor (namely, temperature) and is a conservation law. The significance of the first principle of thermodynamics consists in the fact that it specifies the thermodynamic system state, which depends on interaction between conservation laws and is non-equilibrium due to a non-commutativity of conservation laws. The realization of the second principle of thermodynamics points to a transition of the thermodynamic system state into a locally-equilibrium state. Phase transitions are examples of such transitions.

Spatio-temporal variation of water conservation and its impact factors on the southern slope of Qilian Mountains

The ecology of Qilian Mountains has been seriously threatened by uncontrolled grazing and wasteland reclamation. This study examined the ecological changes on the southern slope of Qilian Mountains in China from the perspective of water conservation by classifying different clusters of water conservation functional areas to efficiently use limited human resources to tackle the water conservation protection problem. In this study, we used Integrate Valuation of Ecosystem Services and Tradeoffs(InVEST) model to estimate water conservation and analyzed the factors that influence the function. The results of this study include:(1) from 2000 to 2015, the water conservation of the southern slope of Qilian Mountains generally showed an increasing trend, and the total water conservation in 2015 increased by 42.18% compared with that in 2000.(2) Rainfall, fractional vegetation cover(FVC), and evapotranspiration have the most significant influence on the water conservation of the study area. Among them, water conservation is positively correlated with rainfall and FVC(P<0.05) and negatively correlated with evapotranspiration(P<0.05).(3) The importance level of water conservation functional areas gradually increases from northwest to southeast, and the region surrounding Menyuan Hui Autonomous County in the southeast of the southern slope of Qilian Mountains is the core water conservation functional area. And(4) the study area was divided into five clusters(Cluster Ⅰ–Cluster Ⅴ) of water conservation, with the areas of Clusters Ⅰ through Ⅴ accounting for 0.58%, 13.74%, 41.23%, 32.43%, and 12.01% of the whole study area, respectively.

THE CONSERVATION LAW OF NONHOLONOMIC SYSTEM OF SECOND-ORDER NON-CHETAVE'S TYPE IN EVENT SPACE

The conservation law of nonholonomic system of second-order non-Chataev's type in event space is studied The Jourdain's principle in event space is presented. The invariant condition of the Jourdain's principle under infinitesimal transformation is given by introducing Jourdain's generators in event space. Then the conservation law of the system in event space is obtained under certain conditions. Finally a calculating example is given.

THE CONSERVATION LAW OF SECOND-ORDER NON-HOLONOMIC SYSTEM OF NON-CHETAEV'S TYPE

The conservation law of second_order nonholonomic system of non_Chetaev's type was studied by means of the Jourdain's principle. The invariant condition of Jourdain's principle under infinitesimal transformation is given by introducing Jourdain's generators. Then the conservation law of the system is obtained under certain conditions. Finally a calculating example is given.

土壤侵蚀原理课程思政建设与思考

在课程思政建设背景下,以专业课程思政建设、改革与人才培养质量提升为目的,分析土壤侵蚀原理课程思政建设的价值,确立土壤侵蚀原理课程思政建设的原则与目标,探讨土壤侵蚀原理课程思政建设的内容、建设环节与方式等,并提出对土壤侵蚀原理课程思政建设的思考。以期推动土壤侵蚀原理课程思政建设与改革的同时,促进水土保持与荒漠化防治专业知识传授、学生能力培养和思政教育全面协同发展。

基于磁各向异性的管壁应力集中区域检测方法

针对应力集中导致管壁发生屈服失效的问题,提出了利用磁各向异性检测管壁应力集中区域的方法。从能量角度出发,研究了应力导致管壁产生磁各向异性的机理,建立了管壁当量应力与磁各向异性探头输出电压信号的数学模型,通过计算管壁的当量应力判断其是否发生屈服失效,搭建了应力检测实验平台。实验结果表明,应力会导致管壁产生磁各向异性,磁各向异性检测方法能够检测出管壁当量应力的变化趋势和主应力方向所在延长线的角度,进而判断管壁是否产生应力集中区域。

Several Fundamental Theorems and Conservative Integrals in Quasicrystal Elasticity Theory

Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were applied in the derivation. Results and Conclusion The principle of virtual work, Betti's reciprocal theorem and the uniqueness theorem of quasicrystal elasticity theory are proud, and some conservative integrals in quasicrystal elasticty theory are obtained.

A Theoretical Analysis of the Acceleration and the Angular Momentum of the Universe

The loss of Baryonic Matter through Black Holes from our spatial 3-D Universe into its 4th dimension as Dark Matter, is used along with the Conservation of Angular Momentum Principle to prove theoretically the accelerated expansion of the 3-D Universe, as has already been confirmed experimentally being awarded the 2011 Nobel Prize in Physics. Theoretical calculations can estimate further to indicate the true nature of the acceleration;that the outward acceleration is due to the rotation of the Universe caused by Dark Energy from the Void, that the acceleration is non-linear, initially increasing from zero for the short period of about a Million years at a constant rate, and then leveling off non-linearly over extended time before the outward acceleration begins to decrease in a non-linear fashion until it is matched by the gravitational attraction of the matter content of 4D Space and the virtual matter in 3-D Vacuum Space. m = m(4D) + m(Virtual). The rotation of our 3D Universe will become constant once all 3D matter has entered 4D space. As the 3-D Universe tries to expand further it will be pulled inward by its gravitational attraction and will then keep on oscillating about a final radius rf while it also keeps on oscillating at right angles to the radius rf around final angular velocity ωf, until it becomes part of the 4-D Universe. The constant value of the Angular Momentum of our Universe is L = .

历史文化街区保护原则的重新审视与组团式发展初探

过去20年,历史文化街区的保护利用已构建效果显著的理论体系与实践方法,但模式僵化、资源不均等系列问题也日渐凸显,故基于体系背景与实际需求的新模式探索迫在眉睫。研究首先追根溯源,重新解读了国内外历史文化街区保护的背景及原则,整理出动态性、整体性、应用性的核心保护理念。其次,基于科技创新与现代化治理背景,提出与之契合的组团式发展模式,探索宏观的组团理念在中微观层面的实践应用。最后,以哈尔滨历史文化街区为例,进行视域空间、路网结构、功能要素三方面的对比论证。研究表明,组团式发展能够协调空间分布矛盾,实现空间引流与文化互补,具有平衡城市资源的潜力。

基于质量守恒的缆索计算理论与找形解析算法

旨在解决既有缆索计算理论的基本假定不合理问题,基于质量守恒原则推导了精细化缆索计算理论;根据拉格朗日坐标建立了考虑缆索截面变形后受拉刚度变化的改进弹性悬链线计算理论。研究结果表明,精细化缆索计算理论与改进的分段悬链线计算理论具有等价性;自重下跨度为888m的缆索找形计算案例中,精细化缆索计算理论与悬链线方程理论的缆力及高程差值分别为61.5kN和-158.7mm,与弹性悬链线理论计算差值对应分别为1.9kN和0.5mm;受外载下跨度为1038m缆索找形计算案例中,推导的精细化缆索计算理论与悬链线方程理论缆力差值分别为77.8kN,与弹性悬链线理论无应力长度计算差值控制为1.0mm。精细化缆索单元计算理论及缆索找形算法可作为缆索承载结构体系一种完备的精细化计算理论与方法。

秸秆粉碎还田机工作原理与功能优化方向

在农业可持续发展理念的推广应用下,传统农业生产秸秆资源浪费问题得到了多途径的解决方案,有效避免了资源浪费和环境污染问题。秸秆粉碎还田机作为田间秸秆高效处理粉碎设备,成为近年来农业生产应用广泛的新型设备。该文总结并介绍了现阶段农业生产应用的秸秆粉碎还田机的总体结构特征和各部件工作原理,结合农业生产需求分析了秸秆粉碎还田机产品升级和功能优化的主要方向,并对未来应用价值进行了展望。

论广义相对论性波动力学

通过对Dirac方程推导过程的分析,当存在势场时,描述粒子体系的波动方程不能同时满足Dirac方程及Klein-Gordon方程,方程是否满足Lorentz不变性由等价原理决定。在此基础上,给出广义相对论性波动方程,并根据等价原理确定矩阵函数的具体表达式。作为现有理论的补充,详细论述了守恒量。

水利工程施工过程中防渗技术分析

总结了防渗技术的作用及防渗技术选择原则,分析了高压喷射灌浆、劈裂灌浆、防渗墙(混凝土或搅拌桩)、复合土工膜等防渗技术在水利工程的应用要点。最后,以某水库大坝为研究对象,分析了其防渗方案的施工要点,并以透水率为评价指标,评价了大坝的防渗效果。

乡村振兴背景下传统村落民宿改造设计研究

随着乡村振兴与旅游业蓬勃发展之际,乡村民宿作为承载产业转型和文化传承的重要标志,日益受到瞩目。本文以山东省烟台市西河阳古村落为例,对当地的建筑空间和民俗文化进行调研,分析了西河阳村古建筑的形制和村落情况,并采用拓展与交融的视角,提出对传统村落民宿改造设计的构建策略和保护原则,总结出回归乡村本源,融合现代设计理念,以此对西河阳村乡村民宿发展提出可行性策略。

螺旋卸煤机在散货码头中的应用分析

螺旋卸煤机是一种常见的散货码头装卸设备,具有高效、可靠、节能等优势。通过分析螺旋卸煤机在散货码头作业中的应用情况,包括工作原理、优势和限制,提出相关改进建议,旨在提高散货码头的作业效率,实现可持续发展。

A CLASS OF EXPLICIT FORWARD TIME-DIFFERENCE SQUARE CONSERVATIVE SCHEMES

In the present paper, a class of explicit forward time-difference schemes are established from a geometric view with strict analytical deductions. This class includes the schemes with a constant time interval and with adjustable time intervals, which is proved to be effective and remarkably time-saving in numerical tests and applications.

The Lie symmetries and Noether conserved quantities of discrete non-conservative mechanical systems

This paper investigates the Lie symmetries and Noether conserved quantities of discrete non-conservative mechanical systems. The variational principle of discrete mechanics, from which discrete motion equations of systems are deduced, is generalized to the case of including the time variational. The requirement for an invariant group transformation is defined to be the Lie symmetry and the criterion when the Noether conserved quantities may be obtained from Lie symmetries is also presented. An example is discussed for applications of the results.

FORM INVARIANCE AND NOETHER SYMMETRICAL CONSERVED QUANTITY OF RELATIVISTIC BIRKHOFFIAN SYSTEMS

A form invariance of the relativistic Birkhoffian system is studied, and the conserved quantities of the system are obtained. Under the infinitesimal transformation of groups, the definition and criteria of the form invariance of the system were given. In view of the invariance of relativistic Pfaff_Birkhoff_ D'Alembert principle under the infinitesimal transformation of groups, the theory of Noether symmetries of the relativistic Birkhoffian system were constructed. The relation between the form invariance and the Noether symmetry is studied, and the results show that the form invariance can also lead to the Noether symmetrical conserved quantity of the relativistic Birkhoffian system under certain conditions.

基于能量守恒框架下的波动力学理论研究

基于波动力学的基本概念,提出了在能量守恒框架下建立波动力学方程的新思路与方法.首先,回顾了用牛顿第二定律推导波动力学方程,同时回顾并分析了利用Hamilton变分原理,推导了在连续介质中的Lagrange方程、Hamilton正则方程,以及相应的波动力学方程;其次,在能量守恒的框架下,建立了连续介质的Lagrange方程、Hamilton正则方程和波动力学方程,并证明其结果与利用经典力学推导的结果的一致性,特别地,澄清了用Hamilton变分原理建立保守系统下连续介质的Lagrange方程和Hamilton正则方程时在边界条件应用时的一些模糊认识.在能量守恒框架下建立一系列动力学方程,为我们在不涉及泛函求极值的变分原理等基础上刻画和表述复杂介质中波动现象的演化规律提供了另一种途径,也深入探讨了最小作用原理的物理本质.最后,在能量守恒的框架下给出了建立黏弹性介质中的波动力学微分方程的应用.