Integrated scheduling of rake and stockyard management with ship berthing: a block based evolutionary algorithm

An integrated problem of optimising the operations at a commercial bulk material port terminal is studied in this paper. We simultaneously optimise the stockyard operations and rake schedule for outbound cargo, in conjunction with the arriving vessels and the status of the stockyards at the port. A mixed integer linear programming model for the problem is developed while incorporating the inherent complexities of the integrated model. To solve the real-life instances, two heuristic methods are proposed specifically for the considered problem. Firstly, genetic algorithm coupled with a greedy heuristic and later, block-based evolutionary algorithm (BBEA) is employed. After applying both techniques, we obtain the optimised schedule for loading of rakes and allotment of stockyard space for vessels as well as rakes at the terminal. Finally, we test the results of both models in three traffic scenarios between themselves and with real-life data from a port situated along the Eastern coast of India. The study resulted in significant reduction of turnaround time for rakes at the port terminal, which in turn lead to monetary savings. The model also automates the day to day operational decision-making at the port.     

Effect of cutting speed and tool rake angle on the fatigue life of 2024-T351 aluminium alloy

Ring-shaped specimens of 2054-T351 aluminium alloy were machined orthogonally on a lathe equipped with a quick-stop device at cutting speeds of 0.5–1.5 m s^?1 with tools having positive rake angles in the range 10–30°. The machined specimens were then fatigued at a selected stress and the resulting fatigue lives were compared with that of the virgin material. The surfaces of the specimens were examined using optical and scanning electron microscopy.The fatigue life of the machined specimens was found to increase with increasing cutting speed or tool rake angle. The fatigue life of the specimens machined at higher cutting speeds was higher than that of the virgin material, due to the presence of compressive residual stresses in the surface layers. At lower cutting speeds the surface damage was so severe that, in spite of the presence of compressive residual stresses in the surface layers, the fatigue life of the machined specimens was lower than that of the virgin material.     

Uniform version of the modified theory of physical optics based boundary diffraction wave theory

The potential function of the modified theory of physical optics based boundary diffraction wave theory is made uniform by using the principles of the uniform theory of diffraction. The line integration of this new function along the edge contour gives the uniform diffracted fields which are finite for the transition regions of the diffraction geometry. The method is applied to the diffraction problem by the edge of a curved surface.     

Elasticity theory with response function for deformation gradient in terms of stress

A formulation of elasticity theory is presented, for which a response function is taken for the deformation gradient in terms of the stress. The issue of the response function being multi-valued is discussed. The objectivity, the theory of hyperelasticity, internally constrained materials, and material symmetry are studied.     

Evaluation of the Green function for 3-D wave-body interactions in a channel

This study deals with a 3-D boundary-value problem that arises when free-surface waves interact with a stationary body or body system in a channel or wave tank of rectangular cross-section. A consistent asymptotic analysis and an efficient numerical solution is presented of the Green function that satisfies the linear free- surface condition and the non-penetration condition on the channel bottom and the sidewalls. The formulation is based on the open-sea Green function and the complete series of images is evaluated accurately based on the asymptotic analysis. It is demonstrated that the Green function has a square-root singular behavior due to the sidewalls when the wave frequency approaches one of the resonant frequencies. The numerical results for the Green function presented in this paper are believed to have an absolute accuracy of 10^–5.     

Wave propagation in anisotropic plates using trigonometric shear deformation theory

In this article, wave propagation in anisotropic rectangular plates based on trigonometric shear deformation theory is studied. To the best of the authors' knowledge, it is the first time that this type of trigonometric plate theory is being used for investigating bulk waves in anisotropic plates. This type of trigonometric theory has only four unknowns but it can model thick plates. To study the accuracy of the present formulations, the authors' results are compared with other papers available in open literature for isotropic plates. Moreover, the influences of different parameters, such as wave number and thickness on the results, are investigated.     

Design and construction of a dynamometer to evaluate the influence of cutting tool rake angle on cutting forces

In this study, the influence of cutting tool rake angle on the cutting forces developed during turning operation was evaluated. For this purpose, a dynamometer was designed and constructed to measure cutting forces. In this dynamometer design, measurement of the cutting tool deflection under the cutting forces was aimed using two beam type load cells located suitably according to the cutting tool. In order to examine the influence of rake angle, turning tests were carried out on AISI 1040 steel workpiece using eight different rake angles. The turning tests at each rake angle were conducted at five different cutting speeds while depth of cut and feed rate were kept constant. The results showed that cutting forces decreased with increasing the rake angle.     

Floquet-Bloch理论在频散曲线计算中的应用

实现了一种基于波有限元方法计算无限大平面波导中弹性波频散曲线的方法。该方法在有限尺度计算单元两边添加Floquet-Bloch周期性边界条件来近似模拟无限大弹性平面波导,利用有限元Comsol Multiphysics软件计算波导中弹性波频散曲线,并讨论了有限尺度单元长宽之比与计算频段的关系。计算结果与谱方法计算结果对比,吻合很好,验证了方法的有效性。该方法回避了复杂特殊函数计算以及超越方程求解的困难,具有建模和计算简单的优点,并可推广至其它复杂弹性波导频散曲线的计算。     

A higher-order polynomial shear deformation theory for geometrically nonlinear free vibration response of laminated composite plate

In this paper, a nonlinear analysis for large amplitude free vibration of laminated composite plates is developed using higher-order shear deformation theory. The effect of all higher-order terms arising from nonlinear strain-displacement relations are included in the formulation and present plate theory exhibits traction-free surface of the laminated plate in von-Karman sense. A finite element procedure considering a C° continuous isoparametric nine-node rectangular element is implemented for nonlinear model. The accuracy of the theory is validated with some available theory for different aspect ratio, modular ratio, number of layers, ply orientations, etc. through some numerical examples.     

A new variational theory for linear field problems and its application to electrostatics

Abstract

A new theory, based on the concept of formally adjoint operator, is proposed to construct a variational formulation for a linear field problem, interior or exterior, with Dirichlet, Neumann, and continuity conditions. When our result is applied to the interface problem, a useful variational expression, which competes with integral equation formulation in its capability of reducing the problem dimensionality, can be obtained. The usefulness of this novel theory is demonstrated through its application to electrostatics. Three examples are also included to confirm its validity.     

TiN薄膜光学性质与色散分析的第一性原理研究

为研究氮气流量对TiN薄膜光学性能的影响,本文利用反应磁控溅射技术,在不同氮气分压下制备了氮化钛薄膜.采用第一性原理方法计算了氮化钛的态密度和光学常数,详细分析了氮化钛的电子态密度以及介电函数的色散关系,得出了适合氮化钛的Drude-3Lorentz色散模型;采用此模型拟合了椭圆偏振光谱仪测试出的薄膜介电函数谱.结果表明:随着氮分压的降低,薄膜的等离子体共振频率向高能方向移动,金属性增强,薄膜中的晶格缺陷增多,晶界散射和缺陷吸收作用增强,可见光区的透射率下降.     

工程科学领域的发展与现代物理学

从工程科学发展的角度探讨了相对论、量子理论和宏观物理学之间的关系,它们之间的矛盾和共同点,以及如何在共同的发展中寻找建立更加深刻的物理理论的可能途经。     

Investigation of the scattering of harmonic elastic antiplane shear waves by a finite crack using the non-local theory

In this paper, the scattering of harmonic antiplane shear waves by a finite crack is studied using the non-local theory. The Fourier transform is applied and a mixed boundary value problem is formulated. Then a set of dual integral equations is solved using the Schmidt method instead of the first or the second integral equation method. Contrary to the classical elasticity solution, it is found that no stress singularity is presented at the crack tip. The non- local dynamic elastic solutions yield a finite hoop stress at the crack tip, thus allowing for a fracture criterion based on the maximum dynamic stress hypothesis. The finite hoop stress at the crack tip depends on the crack length. This revised version was published online in July 2006 with corrections to the Cover Date.     

各向异性弹性层中SH波传播的边界元方法

本文利用坐标变换下的映象法求出了底部为刚性边界的各向异性弹性层中SH波传播问题的格林函数,并由此建立了求解分层介质问题的边界元方法。文中给出了在稳态线荷载作用下带有圆孔的弹性层中反应的计算实例。     

关于值分布论中一个著名猜测的推广

运用Nevanlinna的亚纯函数理论方法，研究了超越亚纯函数的值分布理论，获得了如下的结论：设f为超越亚纯函数，c为f的不恒等于0的的小函数，则当n≥3时，f^n f’-c有无穷多个零点；若附加条件厂只有有限多个级≤2的零点，则对一切正整数n，f^n f’-c都有无穷多个零点．因而对Chiang Y M的问题作出了部分回答．     

Scholte波波速和孔隙度关系的建立及实验验证

随着声学技术的快速发展,界面波在无损检测及环境参数反演领域的应用越来越广泛,但是目前理论与实践之间还存在一些差距,首先对基于Biot理论的流体饱和多孔介质声传播特性的理论进行了仿真分析,然后运用势函数结合多孔介质固体-流体边界条件建立了两半无限空间流-固界面Scholte波理论模型,最后对这一理论模型进行了实验验证。仿真结果表明:声波频率对各种波速几乎没有影响,但各种波速随孔隙度的变化较大;通过实验验证:Scholte波波速理论值与实际测量值之间的相对误差不超过0.24%。     

Numerical study of the influence of particle-cracking to the damage of MMC by the incremental damage theory

Based on the incremental damage theory, the influences of particle-cracking damage and its residue strengthening capacity on the stress–strain response of particle reinforced (metal matrix composite) MMC under uniaxial tension are carefully investigated in this paper. Two kinds of models are adopted in the numerical calculation to predict the damage evolution of MMC, one is modeling the broken particles as voids and the other is considering the remaining load carrying capacity of the damaged particles. Special emphasis is placed on the detailed comparison between the results predicted by the two models under different parameters such as the aspect ratio, volume fraction of particle and the elastic–plasticity properties of matrix. The damage process of MMC and the development of stress in the particles are predicted by two models and carefully analyzed.     

Bending analysis of functionally graded sectorial plates using Levinson plate theory

Based on the Levinson plate theory (LPT) and the first-order shear deformation plate theory (FST), the bending analysis of functionally graded (FG) thick circular sector plates is presented. The LPT solutions of FG sectorial plates are first expressed in terms of the solutions of the classical plate theory (CPT) for homogeneous sectorial plates and then presented using a direct method. It is assumed that the non-homogeneous mechanical properties of plate, graded through the thickness, are described by a power function of the thickness coordinate. The results are given in closed-form solutions and verified with the known data in the literature.     

The value of nonlinear control theory in investigating the underlying dynamics and resilience of a grocery supply chain

In an empirical context, a method to use nonlinear control theory in the dynamic analysis of supply chain resilience is developed and tested. The method utilises block diagram development, transfer function formulation, describing function representation of nonlinearities and simulation. Using both ‘shock’ or step response and ‘filter’ or frequency response lenses, a system dynamics model is created to analyse the resilience performance of a distribution centre replenishment system at a large grocery retailer. Potential risks for the retailer’s resilience performance include the possibility of a mismatch between supply and demand, as well as serving the store inefficiently and causing on-shelf stock-outs. Thus, resilience is determined by investigating the dynamic behaviour of stock and shipment responses. The method allows insights into the nonlinear system control structures that would not be evident using simulation alone, including a better understanding of the influence of control parameters on dynamic behaviour, the identification of inventory offsets potentially leading to ‘drift’, the impact of nonlinearities on supply chain performance and the minimisation of simulation experiments.