Optimum inspection policy for a protective device

Almost all machines install a protective device to protect against unexpected internal or external shocks. Such a device should be inspected often to check whether it is working. A machine with a protective device which is inspected at predetermined ‘check times’ is considered. Using the usual calculus method of probability, two expected costs are derived. When the failure time of the device is exponential, optimum checking intervals to minimize the expected costs are obtained and numerical examples are given.     

Optimum laminate design for strength and stiffness

A method is presented for minimum weight optimum design of symmetric fibre-composite laminates subject to multiple in-plane loading conditions which takes into account membrane stiffness requirements and strength limitations. The problem is cast as a non-linear mathematical programming problem in which the thicknesses of material placed at preassigned orientation angles are treated as the only design variables. The non-linear programming formulation is transformed into a sequence of linear programs employing an adaptation of the method of inscribed hyperspheres in which only critical and near critical constraints are considered at each stage in the procedure. Example applications illustrate that the method presented offers an efficient and practical optimum design procedure for the fundamental and recurring problem treated.     

Required length of guardrails before hazards

One way to protect against impacts during run-off-road accidents with infrastructure is the use of guardrails. However, real-world accidents indicate that vehicles can leave the road and end up behind the guardrail. These vehicles have no possibility of returning to the lane. Vehicles often end up behind the guardrail because the length of the guardrails installed before hazards is too short; this can lead to a collision with a shielded hazard. To identify the basic speed for determining the necessary length of guardrails, we analyzed the speed at which vehicles leave the roadway from the ZEDATU (Zentrale Datenbank Tödlicher Unfälle) real-world accidents database.The required length of guardrail was considered the length that reduces vehicle speed at a maximum theoretically possible deceleration of 0.3 g behind the barrier based on real-world road departure speed. To determine the desired length of a guardrail ahead of a hazard, we developed a relationship between guardrail length and the speed at which vehicles depart the roadway. If the initial elements are flared away from the carriageway, the required length will be reduced by up to an additional 30% The ZEDATU database analysis showed that extending the current length of guardrails to the evaluated required length would reduce the number of fatalities among occupants of vehicles striking bridge abutments by approximately eight percent.     

Decision aid for allocation of transportation funds to guardrails

We address the need for allocation of resources to run-off-road and fixed-object hazards on immense secondary road systems. In Virginia, there are 95,000km of roadway with uncharacterized hazards in need of guardrail upgrade, installation, or related warning signs or other protection. A decision aid is developed to assist the planner in guardrail resource allocation by accounting for the potential crash severities, traffic exposures, costs of treatment, and other factors. A premise is that no single benefit-cost ratio or selection criterion applies across all localities. The decision aid enables the planner to interpret the variety of benefits and costs in their own units, emphasizing the needs and preferences of individual localities. The paper describes: (1) archiving and comparison of protected and unprotected hazards; (2) regional screening of hazardous corridors and (3) multicriteria benefit-cost analyses of guardrail sites. A case study of guardrail selection is presented.     

耳麦的优化与改良设计

耳麦是现代生活中不可缺少的工具,设计品质优良的耳麦具有重要的意义.本文从市场调查开始,结合产品人性化设计的研究,将耳麦设计的构思过程、细节设计及基本结构表达完全展现,研究内容涉及形态理论、色彩理论以及基本的结构设计.最后设计制作出充分体现人性化思想的耳麦产品.     

Required length of guardrails before hazards

One way to protect against impacts during run-off-road accidents with infrastructure is the use of guardrails. However, real-world accidents indicate that vehicles can leave the road and end up behind the guardrail. These vehicles have no possibility of returning to the lane. Vehicles often end up behind the guardrail because the length of the guardrails installed before hazards is too short; this can lead to a collision with a shielded hazard. To identify the basic speed for determining the necessary length of guardrails, we analyzed the speed at which vehicles leave the roadway from the ZEDATU (Zentrale Datenbank Tödlicher Unfälle) real-world accidents database.The required length of guardrail was considered the length that reduces vehicle speed at a maximum theoretically possible deceleration of 0.3 g behind the barrier based on real-world road departure speed. To determine the desired length of a guardrail ahead of a hazard, we developed a relationship between guardrail length and the speed at which vehicles depart the roadway. If the initial elements are flared away from the carriageway, the required length will be reduced by up to an additional 30% The ZEDATU database analysis showed that extending the current length of guardrails to the evaluated required length would reduce the number of fatalities among occupants of vehicles striking bridge abutments by approximately eight percent.     

Optimum design of composite laminates for frequency constraints

A method for minimum thickness multilayer rectangular composite laminates is presented which is based on a layerwise optimization procedure under natural frequency limitations. In this method, all types of boundary conditions and their combinations can be taken into account. Analysis is based on the Ritz approximations, and no limitations exist on the number of layers that can be considered or the plate’s aspect ratio. Coupling of flexural and torsional stiffness terms need not be zero in any of the cases. Optimization constraints can be either limits on the fundamental frequency or separation between two natural frequencies. Hybrid combination of layers is also made possible in order to enhance the laminate economy, and a short cut procedure is recommended to save total computational efforts.

Examples are offered that illustrate the method’s capabilities, and the results are verified by comparison to some published ones.     

Optimum design of hypertatic structures

The task of optimum design of structures is one that involves non-linear Programming. This is particularly the case when deflection as well as stress limitation are imposed as design criteria. In this paper a Fundamental approach is presented for the minimum weight design of statically indeterminate elastic structure subject to non-linear deflection and stress constrains. The matrix force method is adopted to formulate the problem. The constraints thus derived prove to have separable variables and therefore can be linearized in a piecewise manner. The computation aspects concerning the restricted entry in to the simplex tableau are briefly discussed and illustrative examples are given to verify the validity of the proposed method.     

Optimum design considerations for dual conductor bubble devices

A design for dual conductor, current-access bubble devices with 8-μm periods has been optimized with a numerical calculation method for bubble motion in a propagating magnetic field, generated around hole patterns in conductor layers. Magnetic bias field distributions are calculated for an oval hole chain in the conductor layers. Bubble motion equations are obtained with analytical field distribution functions approximating the calculated field distributions. Minimum drive current density Jminfor normal bubble propagation is determined by a solution to the equations. The hole shape has been optimized by the minimization of the drive power Pmin, the product of Jminand conductor resistance, which is calculated from current distributions around the hole pattern. Optimum layer thickness have also been obtained for 8-μm period bubble devices. Both registration tolerance between the two conductor layers and bubble skew effects have been studied semiquantitatively on the basis of the equations of motion. The numerical calculation method developed here is found to be a highly effective means to optimize pattern design for smaller period devices.     

滴点测定仪温度测试系统的优化设计

该文阐述了滴点测定仪温度测试系统的优化设计原理、方法及试验对比,研究证明:优化设计后的滴点测定仪温度测试系统用于替代玻璃温度计显示温度,其在玻璃液体温度计准确度的基础上,其分辨力和准确度有较大提高和改善,并实现了模拟显示到数字显示和记录的转变,便于计量确认,进一步提高了试验准确性和可靠性.     

非标准托盘尺寸的优化设计

针对某行业产品包装中标准托盘包装的利用率低的情况，提出非标准托盘的尺寸设计问题，并运用SQL数据库的运算功能实现了非标准托盘尺寸的优化设计。     

Optimum design of concrete cable-stayed bridges

The design of cable-stayed bridges involves a significant number of design variables and design objectives. The concrete cable-stayed bridge optimization is formulated here as a multi-objective optimization problem with objectives of minimum cost, minimum deflections and minimum stresses. A numerical method is developed to obtain the optimum design of such structures. This numerical method includes: structural analysis, sensitivity analysis and optimization. The structural analysis accounts for all the relevant effects (concrete time-dependent effects, construction stages and geometrical nonlinear effects). The structural response to changes in the design variables is achieved by a discrete direct sensitivity analysis procedure, and an entropy-based approach was used for structural optimization. The features and applicability of the proposed method are demonstrated by numerical examples concerning the optimization of a real-sized concrete cable-stayed bridge.     

Optimum design of structures by accounting for the manufacturing process

A mathematical statement of the problem of optimum design of structures by accounting for the manufacturing process, called a problem of bioptimum design, is examined. It is shown that solution of this problem reduces to successive solution of the problem of optimum design and optimization of the manufacturing process. To this end, a special minimizing sequence has been constructed. A problem of bioptimum design of hydraulic cylinders is discussed as an example. Four manufacturing process alternatives, including the following finishing operations, are presented: machining, autofretting with internal pressure; shaping on a mandrel; drawing with thinning. As the solution of the problem showed, drawing is the most effective process from the viewpoint of strength of hydraulic cylinders. It provides for a favorable residual stress field and best strengthening of the cylinder material.Translated from Problemy Prochnosti, No. 5, pp. 64–68, May, 1991.     

Optimum structural design with stability constraints

This paper presents an optimization method based on optimality criterion for minimum weight of structures with stability requirements. A recurrence relation is derived and the method is explained in the context of the displacement method of finite element analysis. The incipient buckling of the structure is determined by a linear eigenvalue solution. The method is programmed for trusses and frames. Illustrative problems are given to show the applicability of the method of design of structures with a large number of design variables.     

碳化硅反射镜轻量化结构优化设计

本文根据某型号碳化硅主反射镜的设计要求,对比了扇形、三角形、六边形轻量化孔对镜体静态、动态性能的影响,选择了综合性能较好的三角形轻量化结构方案,利用有限元方法进行参数建模,将对镜体力学性能和质量影响较大的镜体厚度、面板厚度、筋厚度等结构参数作为设计变量,运用零阶优化方法对镜体结构进行优化设计,得到了轻量化程度高、镜面变形误差完全满足设计要求的碳化硅反射镜体。