关于镁合金中长周期有序结构的研究综述

系统地介绍了6H、10H、14H、18R、24R型LPSO结构的原子堆垛和RE、Zn的占位特点,探讨了LPSO结构的形成条件和形成机制,分析了含LPSO结构相合金的组织演变过程并概述了组织演变方面最新的研究成果,总结了含LPSO结构相镁合金的室温和高温性能的研究现状,最后对该类合金未来的研究方向进行了展望。     

不同缓冲材料的堆码包装振动特性分析

目的 研究物流运输中采用不同缓冲材料的堆码包装件的振动特性。方法 以缓冲材料聚乙烯泡沫(EPE)和聚苯乙烯泡沫(EPS)为研究对象,采用三维建模软件SoildWorks和有限元仿真软件Workbench建立有限元模型进行模态与谐响应分析,结合扫频振动试验和随机振动试验对各层堆码件的振动响应特性进行分析。结果 2类包装件共振频率处的第一激励能量都大于第二激励能量,振动幅值随层数增加而升高。EPE包装件第一和第二共振频率的激励能量占比分别为35.7%和3%,EPS包装件第一和第二共振频率的激励能量占比分别为26.8%和16.8%。EPE包装件共振区域主要分布于15～40 Hz,而EPS包装件共振频率区域分布于15～40 Hz和60～80 Hz。三层堆码件的中上层包装件受第一共振频率控制,EPS材料的底层包装件受多个共振频率影响,EPE材料的底层包装件受到第二共振频率控制。结论 经过循环载荷作用后的EPE的吸振缓冲性能优于EPS的。通过试验与有限元仿真数据绘制了相应的防振性能曲线,同时验证了有限元仿真的可靠性。这为堆码产品选择不同缓冲材料组合提供了的理论指导。     

Construction and programming of an autonomous focus stacker

Focus stacking is a technique of photomacrography and photomicrography that produces images of small three-dimensional subjects with an arbitrarily high depth of field, unencumbered by diffraction, by combining the in-focus portions of a stack of images of the subject recorded at different focal planes. Software packages are available for postprocessing an image stack into the final image, but the stack images are normally shot either with (typically expensive) automated equipment or by a manual, time-consuming, and error-prone procedures. This paper discusses the construction of an autonomous stacker with inexpensive preassembled electronics and a moderate amount of mechanical construction, and its C++ software.     

虚拟弧齿锥齿轮齿面可控性椭球抛物面误差的叠加新方法

为了研究弧齿锥齿轮测量精度稳定性及不同程序测量误差的问题,提出了一种对虚拟弧齿锥齿轮进行可控误差叠加的方法.分析虚拟弧齿锥齿轮建立时产生的误差,在虚拟工件上叠加可控的椭球抛物面误差,调用OpenGL图形库中的函数将叠加误差后的效果进行直观对比.研究结果表明:对虚拟弧齿锥齿轮进行误差可控的叠加,得到了齿面误差可控的虚拟弧齿锥齿轮.     

一种基于模糊评判的水平叠加方法

以信号的模式识别为基础,应用模糊评判的方法,通过道集叠加得到标准道,对道集内的各道进行模糊评判,剔除评判结果最差的道,再次进行叠加、评判、剔除,直到达到要求的评判结果或规定的最大剔除道数.模拟试验表明,通过模糊评判方法得到的叠加记录的效果明显优于直接叠加.     

Geometry and Stacking Sequence Effect on Composite Spinnaker Pole's Stiffness: Experimental and Numerical Analysis

Composite materials are widely employed in sailing sports, a possible application is for the mast pole or other sail poles. In the paper the attention is focused on the spinnaker poles mechanical performances; in particular the focus is on axial and ring compressive properties of three different carbon fibre/epoxy resin spinnaker poles, to investigate both the diameter and stacking sequence effect on the mechanical performance of the structure. Starting from the stacking sequence used in the production of a particular spinnaker pole, the effect of a lamina at 0° in the middle of wall thickness is investigated with the purpose to obtain a more stiff structure. Moreover to test the proposed stacking sequence on different size products, a prototype with lower diameter is realized. To properly evaluate axial and ring stiffness, axial compression test and ring stiffness one are performed. Then a numerical model is developed to support the design of the finished product: A simple and versatile numerical analysis (FEA with software ANSYS), by simulating ring stiffness and pull-direction compression tests, is carried out in elastic regime. Such model should be suitable for designing and/or verifying the mechanical performance of pole structures, even though differing from those above described, for materials, geometry and stacking sequence.     

Optimum weight design of fiber composite plates in flexure based on a two level strategy

This paper offers a method for weight optimization of multilayer fiber composite plates under the action of lateral loadings. The objective is to design a fiber composite plate of minimum thickness which can sustain multiple static loadings applied normal to its surface without exhibiting failure based on Tsai-Hill criterion in any of its layers. In this investigation, fiber orientation angles are treated as discrete variables, which can vary only by pre-assigned increments, while thicknesses of layers are treated as continuous variables. The optimization procedure is based on a two stage strategy; in the first of which only the fiber orientation angles for the layers are treated as variables, and in the second, only the layer thicknesses. A powerful criterion based on a load factor has been defined to find the best angle for a new layer in the first stage, and the method of center points has been used for thickness optimization in the second stage. After any angle and thickness optimization has been done, a new layer is added to the thickness and the procedure is repeated for other new layers. The end of the two stage procedure is signaled whenever the thickness of the new layer in the optimization process approaches zero; meaning that no new layers would improve the set of layers already found. In this way at the end of the optimization procedure the plate thickness would be made of a minimum number of layers whose fibers are optimally oriented, and whose thicknesses are minimal. A poor choice of layers in the stack produce near zero thickness for the respective layer, and are thus deleted from the set. A repeat process is performed after each cycle, to modify layer angles in order to compensate for errors due to approximations involved. The priorities exercised in the choice of new layers for inclusion in the set and exclusion of all the un-necessary ones, allow an optimal state of stacking sequence to be achieved. Several examples are given to demonstrate the operation of the algorithm.     

Advanced methods for container stacking

In this paper, we study stacking policies for containers at an automated container terminal. It is motivated by the increasing pressure on terminal performance put forward by the increase in the size of container ships. We consider several variants of category stacking, where containers can be exchanged during the loading process. The categories facilitate both stacking and online optimization of stowage. We also consider workload variations for the stacking cranes.