The efficiency of direct integration methods in elastic contact-impact problems

A comparison of direct integration methods is madeand their efficiency is investigated for impact problems.New-mark,Wilson-θ,Central Difference and Houbolt Methodsare used as direct integration methods.Impact analysisincludes that of elastic and large deformation based uponupdated Lagrangian including buckling check.The resultsshow that the direct integration methods give differentresults in different contact-impact cases.

Development of Non-Dissipative Direct Time Integration Method for Structural Dynamics Application

A direct time integration scheme based on Gauss-Legendre quadrature is proposed to solve problems in linear structural dynamics.The proposed method is a oneparameter non-dissipative scheme.Improved stability,accuracy,and dispersion characteristics are achieved using appropriate values of the parameter.The proposed scheme has second-order accuracy with and without physical damping.Moreover,its stability,accuracy,and dispersion are analyzed.In addition,its performance is demonstrated by the two-dimensional scalar wave problem,the single-degree-of-freedom problem,two degrees-of-freedom spring system,and beam with boundary constraints.The wave propagation problem is solved in the high frequency wave regime to demonstrate the advantage of the proposed scheme.When the proposed scheme is applied to solve the wave problem,more accurate solutions than those of other methods are obtained by using the appropriate value of the parameter.For the single-degree-offreedom system,two degrees-of-freedom system,and the time responses of beam,the proposed scheme can be used effectively owing to its high accuracy and lower computational cost.

The Zero-gap Directional Coupler Integrated on SOI for 1.3μm Operation

SOI zero-gap directional couplers are studied by using large cross-section single-mode rib waveguide theory and dual-mode interference principle in silicon direct bonding SOI by back-polishing. And they are fabricated by using KOH anistropic etching. The insertion loss is measured to 4.81 dB, and the crosstalk is below —18.6 dB at a wavelength of 1.3μm.

RETRACTED: Disintegration of Group Representations on Direct Integrals of Banach Spaces

Short Retraction Notice? The paper does not meet the standards of "Advances in Pure Mathematics".? This article has been retracted to straighten the academic record. In making this decision the Editorial Board follows COPE's Retraction Guidelines. The aim is to promote the circulation of scientific research by offering an ideal research publication platform with due consideration of internationally accepted standards on publication ethics. The Editorial Board would like to extend its sincere apologies for any inconvenience this retraction may have caused.? Editor guiding this retraction: Editorial Board (EIC of APM).? Please see the article page for more details. The full retraction notice in PDF is preceding the original paper which is marked "RETRACTED".

Structural Reliability Analysis Based on Support Vector Machine and Dual Neural Network Direct Integration Method

Aiming at the reliability analysis of small sample data or implicit structural function,a novel structural reliability analysis model based on support vector machine(SVM)and neural network direct integration method(DNN)is proposed.Firstly,SVM with good small sample learning ability is used to train small sample data,fit structural performance functions and establish regular integration regions.Secondly,DNN is approximated the integral function to achieve multiple integration in the integration region.Finally,structural reliability was obtained by DNN.Numerical examples are investigated to demonstrate the effectiveness of the present method,which provides a feasible way for the structural reliability analysis.

OPTIMIZATION OF ADAPTIVE DIRECT METHOD FOR APPROXIMATE SOLUTION OF INTEGRAL EQUATIONS OF SEVERAL VARIABLES

This paper determines the exact error order on optimization of adaptive direct methods of approximate solution of the class of Fredholm integral equations of the second kind with kernel belonging to the anisotropic Sobolev classes, and also gives an optimal algorithm.

Radar-Communication Integration Based on MSK-LFM Spread Spectrum Signal

At present, with the progress and innovation of technology, the radar communication dual function wave has become a hot research at home and abroad. Excellent integrated waveform can make full use resources of combat platform, reduce the size of equipment, and realize the actual functionality of the reality of the battle-field without affecting the radar communication func-tion. The MSK-LFM dual-function wave is a typical representative;it is based on LFM, through the MSK modulation to achieve the integration function. This paper proposes a scheme of combining the spread spectrum technology with the MSK-LFM waveform based on the previous literature. The simulation results show that the waveform envelope is more stable and the energy is more concentrated. With the introduction of spread-spectrum technology, the new waveform ambiguity function graph is much closer to the thumbtack than the traditional MSK-LFM waveform.

Direct method of finding first integral of two-dimensional autonomous systems in polar coordinates

A direct method to find the first integral for two-dimensional autonomous system in polar coordinates is suggested. It is shown that if the equation of motion expressed by differential 1-forms for a given autonomous Hamiltonian system is multiplied by a set of multiplicative functions, then the general expression of the first integral can be obtained, An example is given to illustrate the application of the results.

A PREDICT-CORRECT NUMERICAL INTEGRATION SCHEME FOR SOLVING NONLINEAR DYNAMIC EQUATIONS

A new numerical integration scheme incorporating a predict-correct algorithm for solving the nonlinear dynamic systems was proposed in this paper. A nonlinear dynamic system governed by the equation v = F（v, t） was transformed into the form as v = Hv ＋ f（v, t）. The nonlinear part f（v, t） was then expanded by Taylor series and only the first-order term retained in the polynomial. Utilizing the theory of linear differential equation and the precise time-integration method, an exact solution for linearizing equation was obtained. In order to find the solution of the original system, a third-order interpolation polynomial of v was used and an equivalent nonlinear ordinary differential equation was regenerated. With a predicted solution as an initial value and an iteration scheme, a corrected result was achieved. Since the error caused by linearization could be eliminated in the correction process, the accuracy of calculation was improved greatly. Three engineering scenarios were used to assess the accuracy and reliability of the proposed method and the results were satisfactory.

THE INTEGRATION OF ALGEBROIDAL FUNCTIONS

In this paper, we introduce the integration of algebroidal functions on Riemann surfaces for the first time. Some properties of integration are obtained. By giving the defi- nition of residues and integral function element, we obtain the condition that the integral is independent of path. At last, we prove that the integral of an irreducible algebroidal function is also an irreducible algebroidal function if all the residues at critical points are zeros.

SPATIAL－TEMPORAL DISCRETE COORDINATION OF FEM AND DIRECT INTEGRAL METHOD FOR TRANSIENT DYNAMIC PROBLEMS

In this paper, the coordination of spatial-temporal discrets of FEM and direct integral method is investigates.By analyzing the numespatial-temporal discrete,the principle of balancing the principle of balancing the energy error induced by spatialdiscrete and the energy error induced by temporal discrete is presented, and the prioriprocess and adaptive method for the coordination of spatial discerand temporal discrete is obtained.

ON DIRECT METHOD OF SOLUTION FOR A CLASS OF SINGULAR INTEGRAL EQUATIONS

In this article, by introducing characteristic singular integral operator and associate singular integral equations （SIEs）, the authors discuss the direct method of solution for a class of singular integral equations with certain analytic inputs. They obtain both the conditions of solvability and the solutions in closed form. It is noteworthy that the method is different from the classical one that is due to Lu.

AXISYMMETRIC BENDING OF TWO-DIRECTIONAL FUNCTIONALLY GRADED CIRCULAR AND ANNULAR PLATES

Assuming the material properties varying with an exponential law both in the thick- ness and radial directions, axisymmetric bending of two-directional functionally graded circular and annular plates is studied using the semi-analytical numerical method in this paper. The deflections and stresses of the plates are presented. Numerical results show the well accuracy and convergence of the method. Compared with the finite element method, the semi-analytical nu- merical method is with great advantage in the computational efficiency. Moreover, study on ax- isymmetric bending of two-directional functionally graded annular plate shows that such plates have better performance than those made of isotropic homogeneous materials or one-directional functionally graded materials. Two-directional functionally graded material is a potential alternative to the one-directional functionally graded material. And the integrated design of materials and structures can really be achieved in two-directional functionally graded materials.

A Straightforward Direct Traction Boundary Integral Method for Two-Dimensional Crack Problems Simulation of Linear Elastic Materials

This paper presents a direct traction boundary integral equation method(DTBIEM)for two-dimensional crack problems of materials.The traction boundary integral equation was collocated on both the external boundary and either side of the crack surfaces.The displacements and tractions were used as unknowns on the external boundary,while the relative crack opening displacement(RCOD)was chosen as unknowns on either side of crack surfaces to keep the single-domain merit.Only one side of the crack surfaces was concerned and needed to be discretized,thus the proposed method resulted in a smaller system of algebraic equations compared with the dual boundary element method(DBEM).A new set of crack-tip shape functions was constructed to represent the strain field singularity exactly,and the SIFs were evaluated by the extrapolation of the RCOD.Numerical examples for both straight and curved cracks are given to validate the accuracy and efficiency of the presented method.

Microstructure Development of Directionally Solidified Nb-Ti-Si Based Ultrahigh Temperature Alloy

Integrally directional solidification of an Nb-Ti-Si based ultrahigh temperature alloy was performed in an ultrahigh temperature and high thermal gradient furnace with the use of ceramic crucibles. The microstructural evolution with the withdrawing rate increasing during directional solidification was revealed. The integrally directionally solidified microstructure was composed of couple grown lamellar (Nbss+(Nb,X)5Si3) eutectic colonies and a few hexagonally cross-sectioned (Nb,X)5Si3 columns (X represents Ti and Hf elements). All the directionally solidified microstructure was straightly aligned along the longitudinal axis of the specimens. With increasing of the withdrawing rate, the average diameter of the eutectic cells and inter lamella spacings in the eutectic cell decreased. The near-planar solid/liquid interface appeared when the withdrawing rate was 1μm/s, and the cellular solid/liquid interface formed when the withdrawing rate was 5 μm/s.

不平衡电网下无刷双馈风电系统的虚拟同步发电机控制

无刷双馈发电机(brushless doubly-fed reluctance generator,BDFG)在风力发电领域有着广阔的应用前景。基于虚拟同步发电机(virtual synchronous generator,VSG)的无刷双馈风电系统具有一定的电网频率支撑能力,但在电网电压不平衡工况下运行性能较差。提出了一种不平衡电网工况下无刷双馈风电系统的虚拟同步发电机策略,来降低不平衡的电网电压对BDFG系统的影响;其核心思想为使用原有BDFG-VSG来控制正序分量,在功率绕组正向同步旋转坐标系下使用基于降阶广义积分器(reduced order generalized integrator,ROGI)的直接谐振控制调节负序分量。详细分析了电网电压不平衡对BDFG各电量的影响,据此提出了5种可供选择的优化目标,最后通过仿真验证了该策略的有效性。所提出的策略可抑制不平衡电网工况下BDFG的各电量中的负序分量或二倍频分量,无需计算负序电流的参考值,对电网具有友好性。

智媒时代应用型高校导播课程教学改革策略研究

智媒时代对传媒类人才培养提出了更高的要求。导播课程作为应用型高校传媒类专业的核心课程,应本着“以学生为中心”的教学理念,从教学模式、教育场景、课程建设等方面切入,紧跟行业一线,鼓励自主学习,推动产教融合,体现地域特色,着力培养掌握全媒体视听节目制作能力的复合型、应用型人才,与行业发展、岗位需求同频共振。

新文科赋意下的艺术教育: 意涵审思、实践逻辑与革新路向

新文科赋意下的艺术教育在“新技术”外部诱因与“新国情”内部动因的双重作用下促生了意涵新变。在准确把握其意涵变化的基础上,艺术教育的实践逻辑当因势而新,即实现价值引领与艺术审美核心把持的动态统整,秉持“跨学科”视野促生全域教学资源流动整合新样态。革新路向需从跨学科导向下的艺术课程与教学生态重塑、锚定科技与人文双向会通的艺术教育立场、构建“三元共融”的艺术教育考核评价体系三个方面展开探究,为时下新文科建设的实践探索提供来自艺术学科的创新注解。

供应链部分整合对再制造产品渠道策略的影响分析

再制造的研究主要聚焦于集中和分散的供应链,但在现实商业实践中部分整合的供应链十分常见。本文分别在无供应链整合、供应链部分前向整合(PFI)和供应链部分后向整合(PBI)三种情况下探讨了再制造产品的销售渠道策略选择问题。研究发现,在无供应链整合和PFI下,直销再制造产品对于制造商而言总是占优策略,但不利于零售商,因而造成制造商赢零售商输(win-lose)的局面。在PBI下,直销再制造产品并不一定是制造商的占优策略,此时根据零售商持有股份的大小可能会出现制造商赢零售商输、双赢、制造商输零售商赢三种结果。当制造商直销再制造产品时,相较于无整合情形,在一定条件下PFI可以形成制造商赢零售商赢(win-win)的双赢局面,而PBI总是造成制造商输零售商赢(lose-win)的局面。从对环境的影响来看,由制造商直销再制造产品比零售商销售更环保,而此时不进行供应链部分整合是最环保的。

职普融通政策的变迁历程、演进逻辑与发展路向

职普融通既是我国教育结构优化和教育体系完善的关键内容,也是推进教育高质量发展的重要举措。运用历史制度主义分析范式,以职普融通政策文本为基础,分析发现:职普融通政策经历前期渗透、探索推进、体系构建和深化发展四个时期;制度环境、社会需求和文化观念等构成职普融通政策变迁的深层结构;受退出成本、学习效应、协调效应和适应性预期影响,职普融通政策变迁体现出强劲的路径依赖特征,同时存在以重大事件为表现形式的“关键节点”。故政策制定者在推进职普融通政策创新时,需要完善配套政策体系,提升政策治理能力;健全多元主体参与机制,形成协同推进动力;优化政策实施环境,强化政策执行效力。