Model of low spatial frequency diffractive elements recorded in photopolymers during and after recording

Photopolymer are appealing materials for diffractive elements recording. Two of their properties when they are illuminated are useful for this goal: the relief surface changes and the refractive index modifications. In this paper we use a 2-dimensional model, based on direct parameter measurements, for predicting the refractive index distributions during and after illumination. We have analyzed different recording spatial frequencies for photopolymers based on PVA/Acrylamide. This model was successfully applied to different photopolymer compositions with different values of monomer diffusion and polymerization rates.     

Study of the effect of defects on the fatigue behaviour and the fracture toughness for low carbon steel (API 5L grade B) gas transmission pipelines

The use of low carbon steel pipes in gas transmission pipelines and network gas pipes has increased. API 5L grade B (American Petroleum Institute) pipes are welded and inspected according to the BGC/PS code (British Gas Standard). Since root undercut and lack of penetration are common defects, the acceptance and nonacceptance of these defects based on the BGC/PS/P2 code of butt welded pipes are evaluated. Pipes are welded with different degrees of root undercut and lack of penetration defects and are X-rayed. The defects are categorized based on both X-ray films and final crack area. Specimens are cut and fatigue precracked at different periods depending on the initial defect size. An equivalent crack length is calculated based on Paris' law for each defect size in the fatigue crack propagation. The crack opening displacement technique, J-integral method based on Begley and Landes and the residual strength method have been used to determine the fracture toughness. The results have been compared to the parent material and the initial defect size to evaluate the restrictions of the BGC/PS/P2 code.

The equivalent crack length results showed that the depth of lack of penetration welding defect should be taken into consideration for both API and BGC codes since this depth has a significant effect on the equivalent crack length.

The application of the Begley and Landes approach is shown to be suitable since it permits the use of specimens of different initial crack lengths. The technique is applied here for cracks of different shapes. The results are close and can be used as comparative results between different categories and the parent material since the conditions of specimen dimensions are not valid as restricted by Begley and Landes. Critical crack opening displacement is calculated which gives reliable results for different categories. Crack opening displacement technique based on the British Standard requires different specimens with the same initial crack length, which is not satisfied. The residual strength method based on ASTM gives reliable results for the different categories of defects.

The depth of lack of penetration welding defect should be taken into consideration for both API and BGC codes. The BGC code should specify an allowable depth for the root undercut welding defects.     

圆柱壳非圆大开孔的应力集中研究

本文以薄圆柱壳大开孔应力集中问题的理论解为基础,利用保角映射方法对圆柱壳非圆大开孔的应力集中问题进行研究。在给出映射函数的基础上,对承受不同外部载荷下开椭圆大孔圆柱壳孔边应力集中系数进行了数值计算,并与相应的圆柱壳小开孔理论解进行了比较。结果表明：大开孔解答更具有合理性。     

Optimal compensation rules for integrated services

Research on service compensation is rare. In this article we examine different compensation rules for integrated services (IS) which are produced jointly by a service provider and his client. Examples are consulting, advertising or management training. We distinguish three different compensation rules and compare them with joint profit maximization where both, service provider and client act as one organizational unit. The compensation rules are (1) the input based compensation (IBC) characterized by a compensation that is based on work hours or work days, (2) the sales based compensation (SBC) with the compensation based on client’s sales and (3) the profit based compensation (PBC) with compensation based on client’s profits. We can show that under reasonable, realistic conditions the IBC (surprisingly) leads to better results for the service provider and for the client as compared to the PBC and the SBC.     

On fuzzy and probabilistic control charts

In this article, different procedures of constructing control charts for linguistic data, based on fuzzy and probability theory, are discussed. Three sets of membership functions, with different degrees of fuzziness, are proposed for fuzzy approaches. A comparison between fuzzy and probability approaches, based on the Average Run Length and samples under control, is conducted for real data. Contrary to the conclusions of Raz and Wang (1990b) the choice of degree of fuzziness affected the sensitivity of control charts.     

Light‐Driven ZnO Brush‐Shaped Self‐Propelled Micromachines for Nitroaromatic Explosives Decomposition

Self‐propelled micromachines have recently attracted lots of attention for environmental remediation. Developing a large‐scale but template‐free fabrication of self‐propelled rod/tubular micro/nanomotors is very crucial but still challenging. Here, a new strategy based on vertically aligned ZnO arrays is employed for the large‐scale and template‐free fabrication of self‐propelled ZnO‐based micromotors with H₂O₂‐free light‐driven propulsion ability. Brush‐shaped ZnO‐based micromotors with different diameters and lengths are fully studied, which present a fast response to multicycles UV light on/off switches with different interval times (2/5 s) in pure water and slow directional motion in aqueous hydrogen peroxide solution in the absence of UV light. Light‐induced electrophoretic and self‐diffusiophoretic effects are responsible for these two different self‐motion behaviors under different conditions, respectively. In addition, the pH of the media and the presence of H₂O₂ show important effects on the motion behavior and microstructure of the ZnO‐based micromotors. Finally, these novel ZnO‐based brush‐shaped micromotors are demonstrated in a proof‐of‐concept study on nitroaromatic explosive degradation, i.e., picric acid. This work opens a completely new avenue for the template‐free fabrication of brush‐shaped light‐responsive micromotors on a large scale based on vertically aligned ZnO arrays.     

典型格构式结构风荷载及风致响应规范比较

对国内外四种常见格构式结构荷载规范中风荷载计算方法、关键参数取值等进行详细对比分析,以典型500 kV单回路酒杯型输电塔为例,将规范计算所得风荷载与风洞测力试验所测风荷载进行比较,计算结构的风致响应。对比分析发现,相同条件下（50年重现期）不同规范对同一输电塔结构的等效风荷载存在一定差异。随节段高度增加,我国规范GB50545的等效静力风荷载偏大。据规范计算所得风致响应值与据测力风洞试验计算结果吻合较好。由于我国规范未考虑重现期对线路影响,随线路安全等级提高,其等效静力风荷载可能会不安全。     

A Comparison of Various Patterns of Three‐Dimensional Strain Rosettes

Abstract: The strain tensor, principal strains and precision of the estimates of these values are derived for a range of different layouts of three‐dimensional strain rosettes. These values are based on the Monte Carlo technique applied to experimental work which was carried out on transducers tested in different laboratories. The estimates of precision are determined theoretically and compared with results based on experimental findings. A new design of a miniature tri‐rectangular tetrahedral rosette was manufactured and tested. Results suggest that this transducer does not perform as well as the rectangular patterns.     

噪声和振动信号的谐波小波时频表示

谐波小波变换的时频表示方法应用于持续时间、带宽和采样率差别很大的多种目标的噪声和振动信号处理当中,将其结果与基于STFT方法的结果进行了比对,并给出了其在不同应用场合的参数。结果表明,谐波小波方法用于信号的时频表示,具有很好的灵活性和突出的性能优点,有较好的应用前景。     

Optimum design of helically wound composite pressure vessels

The optimum design of dome shapes in helically wound composite pressure vessels which have been used as rocket motor cases, etc. is discussed, as a first step, based on the membrane stress theory. Some methods for determining the optimum dome shapes are proposed based on the two different kinds of criteria. One is based on the failure criteria of composite materials, and the simple formulae for determining the dome shapes are derived. The other is based on the performance factor for a rocket motor case, and the dome shape is analyzed by using mathematical optimization techniques. The dome shapes obtained are compared with the isotensoid dome shape derived from the netting analysis.     

Choosing a reliability inspection plan for interval censored data

ABSTRACT

Reliability test plans are important for producing precise and accurate assessment of reliability characteristics. This article explores different strategies for choosing between possible inspection plans for interval-censored data given a fixed testing timeframe and budget. A new general cost structure is proposed for guiding precise quantification of total cost in inspection test plan. Multiple summaries of reliability are considered and compared as the criteria for choosing the best plans using an easily adaptable method. Different cost structures and representative true underlying reliability curves demonstrate how to assess different strategies given the logistical constraints and nature of the problem. Results show several general patterns exist across a wide variety of scenarios. Given the fixed total cost, plans that inspect more units with less frequency based on equally spaced time points are favored due to the ease of implementation and consistent good performance across a large number of case study scenarios. Plans with inspection times chosen based on equally spaced probabilities offer improved reliability estimates for the shape of the distribution, mean lifetime, and failure time for a small fraction of population only for applications with high infant mortality rates. This article uses a Monte Carlo simulation-based approach in addition to the commonly used approach based on the asymptotic variance and offers comparison and recommendation for different applications with different objectives. In addition, the article outlines a variety of different reliability metrics to use as criteria for optimization, presents a general method for evaluating different alternatives, as well as provides case study results for different common scenarios.     

Advection approaches for single- and multi-material arbitrary Lagrangian–Eulerian finite element procedures

The essential feature in arbitrary Lagrangian–Eulerian (ALE) based finite element approaches is the additional requirement to consider flow effects of the materials and the solution variables through the computational domain. These flow effects are commonly known as advective effects. The present paper examines different advection strategies for the application of the ALE finite element method in a finite deformation solid mechanics framework, where especially micromechanical problems are referred to. The global solution algorithm is based on the well-known fractional step method that provides an operator splitting approach for the solution of the coupled ALE equations. Distinguishing the so-called single-material and the multi-material ALE method, different advection schemes based on volume- and material-associated advection procedures are required. For the latter case, the material interfaces are not resolved explicitly by the finite element mesh. Instead a volume-of-fluid interface tracking approach in terms of the volume fractions of the different material phases is applied.     

Corrosion rate of steel in concrete: evaluation of confinement techniques for on-site corrosion rate measurements

Earlier on-site investigations and laboratory studies have shown that varying corrosion rates are obtained when different commercially available instruments are used. The different confinement techniques, rather than the different electrochemical techniques used in the instruments, are considered to be the main reason for the discrepancies. This paper presents a method for the quantitative assessment of confinement techniques. The assessment is based on monitoring the operation of the corrosion rate instrument and following the current distribution between the electrode assembly on the concrete surface and a segmented reinforcement bar embedded in the concrete. The applicability of the method was demonstrated for two commercially available corrosion rate instruments based on different confinement techniques. The method provided an explanation of the differences in performance of the two instruments. Correlated measurements of linear polarisation resistance and macro-cell currents allowed the determination of calibration factors. Both instruments overestimated the corrosion rate of passive reinforcement, but underestimated the corrosion rate of reinforcement with intense localised corrosion.     

Development of solar cooling load factors for fenestration in Thailand

Abstract

This article describes the development of solar cooling load factors (SCL) for calculating cooling load from the fenestration part of the building envelopes in Thailand using Bangkok weather data. The Bangkok weather data are selected from 12 years of data collected by the meteorological department. Two sets of weather data are chosen based on dry bulb temperature of 0.4% annual cumulative frequency of occurrence and based on dry bulb temperature of 0.4% hourly cumulative frequency of occurrence and solar radiation obtained from the ASHRAE mathematical model. The building parameters that have effects on the room thermal response are studied. 288 different room types were checked. The values of amplitude and delay based on solar weighting factors are analyzed. Then, rooms with similar thermal response are grouped together and represented by a single point for the group. Each group is defined as a single zone type. Four different zone types are established. For each set of weather data, the values of solar cooling load factors for each zone type are developed.     

Branch and bound methods for scheduling problems with multiprocessor tasks on dedicated processors

Branch and bound methods for the scheduling problem with multiprocessor tasks on dedicated processors and arbitrary precedences are presented. The methods are based on different representations of feasible schedules. Computational results show that the methods surpass each other on different types of problems with multiprocessor tasks.Supported by the Deutsche Forschungsgemeinschaft, Project JoPTAG     

隐马尔可夫模型在舰船噪声目标识别中的应用

将Mel频率倒谱作为特征参数,实现了基于连续型隐马尔可夫模型的舰船辐射噪声目标识别。对五艘不同类别舰船的辐射噪声建立模型,并进行了识别实验。模型的状态数和高斯混合数分别确定为1和3,五艘舰船的平均识别率达到91．6％。利用两艘不同类型舰船的噪声分析了舰船的工况对识别结果的影响。     

Traceability of measurement results at different levels of metrological work

Features are considered of measurement result traceability at different levels of metrological work, that are based on existing international guides, standards and recommendations for metrology.     

Development of a Net Shape Manufacturing Method for Ventilated Brake Discs in Single Piece Design

Carbon fibre reinforced ceramic matrix composites (CMC), originally developed for lightweight heat shields of spacecraft, are used for high performance brake discs in sports cars from different manufacturers. In contrast to the CMC materials for space applications, based on woven fabrics and costly manufacturing methods, these low cost friction materials are produced by liquid silicon infiltration of porous Carbon/Carbon (C/C) preforms, based on short fibre reinforced CFRP green bodies manufactured via warm press technique. In this work, different manufacturing methods for ventilated CMC brake discs are compared to each other, and the development of a new technology for the manufacture of single piece C/C‐SiC brake discs in net shape technique is presented.     

Voxel‐based meshing and unit‐cell analysis of textile composites

Unit‐cell homogenization techniques are frequently used together with the finite element method to compute effective mechanical properties for a wide range of different composites and heterogeneous materials systems. For systems with very complicated material arrangements, mesh generation can be a considerable obstacle to usage of these techniques. In this work, pixel‐based (2D) and voxel‐based (3D) meshing concepts borrowed from image processing are thus developed and employed to construct the finite element models used in computing the micro‐scale stress and strain fields in the composite. The potential advantage of these techniques is that generation of unit‐cell models can be automated, thus requiring far less human time than traditional finite element models. Essential ideas and algorithms for implementation of proposed techniques are presented. In addition, a new error estimator based on sensitivity of virtual strain energy to mesh refinement is presented and applied. The computational costs and rate of convergence for the proposed methods are presented for three different mesh‐refinement algorithms: uniform refinement; selective refinement based on material boundary resolution; and adaptive refinement based on error estimation. Copyright © 2003 John Wiley & Sons, Ltd.     

Minimization of the effect of temperature on thin-film nano- and microelectromechanical systems and pressure sensors based on them

Methods for minimizing the effect of temperature on thin-film nano- and microelectromechanical systems and pressure sensors based on them are summarized. Properties are provided and different methods are described. Conclusions are derived from analyzing the methods about requirements for their comprehensive use.