Genetic algorithm approach to a production ordering problem in an assembly process with constant use of parts

An optimal production scheduling problem for an assembly process with buffers at the input and output sides of a machine is dealt with. The problem has two kinds of constraints. One constraint is that the buffers' capacity is limited. The other constraint is that the cycle time of the worker is constant without waiting time. An optimal production ordering is determined, subject to these constraints, in such a way that the rate of use of parts to produce each product should be as constant as possible. A procedure to apply the genetic algorithm to this problem is shown. The operations of reproduction, crossover and mutation are presented. It is observed from numerical results that the genetic algorithm gives a better suboptimal solution than the greedy method.     

Kinetics of Hydration of Monocaldum Aluminate

Hydration of CaAl₂O₄ (CA) was studied by calorimetry, analysis of the liquid phase, measurement of the combined water, and electron microscopy. During the induction period, the solution remains almost unchanged and is equilibrated temporarily with both superficially intrusion-hydrated CA particles and Al(OH)₃ gel formed by dissociation of Al(OH)₄^– ions, the solubility of the Al(OH)₃ gel being 10^–4.24 molkg^–1 at 25°C, while the intrusion-hydrated layer on the CA particles grows following a nearly linear law to reach a critical thickness (∼3 nm at 10° to 20°C, or 12 nm at 30°C). At this point destruction of the layer occurs, nuclei of hydrous compounds are generated, and the induction period terminates. Subsequent reaction proceeds in accordance with the rate equation of Schiller based on the dissolution-crystallization mechanism.     

Formation and microwave dielectric properties of Sr(Ga0.5Ta0.5)O3-based complex perovskites

The Sr(Ga0.5Ta0.5)O3-based perovskites with O2- and/or Sr2+ vacancies were formed by changing the A-site and/or B-site cation ratios. The Sr-deficient perovskites with a limited composition of Sr0.86(Ga0.36Ta0.64)O3 could be obtained, whereas oxygen vacancies were hardly created. The B′-site Ga3+ cation could be replaced with large Sc3+, In3+, Y3+, Nd3+ and La3+. The crystal symmetry of the complex perovskites changed from cubic (B′=Ga3+, Sc3+, In3+) to tetragonal (B′=La3+) through rhombohedral (B′=Y3+, Nd3+). The dielectric permittivities of these ceramics indicated no distinct dependence on the B′-site cation species. The temperature coefficient of permittivity might be associated with the symmetry change of the perovskite phases. Higher microwave Qf values, >Qf=38 000 GHz, were obtained for our complex perovskite ceramics, except with B′=La3+. This revised version was published online in July 2006 with corrections to the Cover Date.     

勒·柯布西耶绘画中空间观念的转向:纯粹主义前后

本文回溯了勒·柯布西耶在纯粹主义运动(1918—1925年)前后,其绘画中空间观念所经历的转向。彼时的让纳雷以绘画作为实验工具,发展了他对于空间的理解。本文把勒·柯布西耶在纯粹主义前后的绘画探索分为四个阶段,通过比较四个阶段的作品,指出勒·柯布西耶的空间观念经历了由注重写实与透视,到关注对象平面中的几何与秩序,再到用透明的块面相互叠加来营造深度感,最后转为对于大自然、人体等有机形式的探索,揭示出其不同绘画题材背后隐藏着的形式逻辑的必然联系。     

用ESCA分析等离子体处理了的氟树脂表面

用微波炉产生的微波对氟树脂进行等离子体处理,用ESCA作了表面分析。处理后的试样在533eV处出现O_(1S)的一大峰,在292eV～285eV间出现C_(1S)的连续宽谱带。氧的导入量随着处理时容器内气压(P)的降低而增大,可见随着P的降低处理的效果增大。为了得到深度方向的分布,采用了氩离子剥蚀法和掠射法。随着剥蚀的进行,由等离子体处理所导入的氧急剧减少。用掠射法测定了刚经过处理的FEP和处理后放置了70小时后的FEP的深度分布。刚处理后的试样,氧量随出射角(θ)的减少(即随分析深度的减小)而增大,氟量则减小。相反,处理后放置70小时,在15°<θ<60°的范围内,氟量增加,氧量减少。这是因为低表面自由能的含氟键段移动到表面上所致。由深度方向的分布的结果可以推断,等离子体处理的效果达到了ESCA在θ=90°的分析深度的一半左右。     

纳米Pt膜的晶粒尺寸及其对热导率的影响

采用电子束-物理气相沉积法（EB-PVD）制备了6个厚度为15-62nm的铂薄膜，研究了纳米薄膜的晶粒尺寸及其对热导率的影响规律．当薄膜厚度小于30nm时，晶粒平均尺寸接近于薄膜的厚度；晶粒尺寸随着薄膜厚度的增加而增大并趋于定值；当薄膜厚度大于30nm时，晶粒尺寸约为20nm．受薄膜的表面和内部晶界的综合影响，铂纳米薄膜的热导率大大低于体材料的值，并且纳米薄膜的热导率随着薄膜厚度的增加而增大并趋于一个低于体材料热导率的值．     

Evaluation of Fracture Toughness for Ceramic Materials by a Single-Edge-Precracked-Beam Method

As a substitute for the fatigue-cracked-beam method prescribed in ASTM E399 A2, a recently devised precracking method was applied to the evaluation of fracture toughness of ceramic materials. Straight-through precracks proved to be easily introduced into rectangular beams of several ceramic materials. This method gives K_ic values almost identical with those of the fatigue-cracked-beam method. The K_ic values are almost constant over wide ranges of the pop-in precrack length and the loading rate of the three-point bend test. The test can be easily performed even at elevated temperatures although its validity should be further examined.     

A simulation study on autonomous decentralized mechanism in fish behaviour model

The behaviour of a fish school is considered an interesting phenomenon because a fish school behaves differently in various situations. The paper considers a fish school as an autonomous decentralized system and constructs a mathematical model for the autonomous decentralized mechanism. Simulation results show that, by varying the quantity of information exchange among members in school, the present model describes fish behaviour not only for a school with fixed configuration but also for that with variable form. Furthermore, a remarkable difference in fish trajectory is found between the two schools.     

A METHOD FOR DETERMINING THE IMPACT FORCE IN CRASH TESTING

A method for measuring the impact force in crash testing is developed. In this method, a mass is made to collide with the object being tested and the instantaneous value of the impact force is measured as the inertial force acting on the mass. To realise linear motion with sufficiently small friction acting on the mass, a pneumatic linear bearing is used, and the velocity and acceleration of the mass, the moving part of the bearing, are measured using an optical interferometer. The relative combined standard uncertainty in determining the impact force in a three-point bending test is estimated to be 0.5×10⁻²(0.5%) of the maximum value of the impact force.