Accurately computing the optical pathlength difference for a michelson interferometer with minimal knowledge of the source spectrum

Astrometric measurements using stellar interferometry rely on precise measurement of the central white light fringe to accurately obtain the optical pathlength difference of incoming starlight to the two arms of the interferometer. One standard approach to stellar interferometry uses a channeled spectrum to determine phases at a number of different wavelengths that are then converted to the pathlength delay. When throughput is low these channels are broadened to improve the signal-to-noise ratio. Ultimately the ability to use monochromatic models and algorithms in each of the channels to extract phase becomes problematic and knowledge of the spectrum must be incorporated to achieve the accuracies required of the astrometric measurements. To accomplish this an optimization problem is posed to estimate simultaneously the pathlength delay and spectrum of the source. Moreover, the nature of the parameterization of the spectrum that is introduced circumvents the need to solve directly for these parameters so that the optimization problem reduces to a scalar problem in just the pathlength delay variable. A number of examples are given to show the robustness of the approach.     

体积补偿式正压漏孔校准方法改进分析

针对被校漏孔接头种类繁多,接头漏气难以避免且其值测量不方便的问题。采用两种方式进行修正:一方面利用进退活塞得到两个修正的体积系数,推导出接头漏气和漏孔漏率引起的差压变化之比的测试方法,用以修正接头漏气的影响;另一方面通过粘滞流公式推导出微小压力差下气体漏率与压力差近似成正比。通过调整校准室的压力,利用差分的原理减少漏气对校准结果的影响。两种修正方式的采取,解决了常规漏孔接头漏气难以原位测量或减小到可以忽略的问题,降低了对被校漏孔接头的要求,提升了体积补偿法的测量准确度和工作效率,同时将校准下限延伸到10^-7Pa·m³/s。     

基于分析软件“CiteSpace”的声景研究英文文献知识图谱分析

国外关于声景的探索经历了数十年的发展,对其进行系统梳理与总结对于中国声景研究具有重要的借鉴价值。文章以"Web of Science"核心数据库中近20年的相关英文文献作为研究对象,依托科学计量分析软件CiteSpace的知识图谱绘制功能,展现国外声景研究的学科及期刊分布特征、理论基础与研究热点。研究发现,国外声景研究呈现出明显的多学科特征。在研究热点上,从接续Schafer的理念、关注人类对声景的感知,到兼顾生物圈中非人类生物对声景的响应,再到以"格局-过程"为指导关注区域层面的声景生态特征与演变机制,是国外声景研究的主要发展脉络。声景研究框架的拓展使国外声景研究得以越来越全面和科学地解释和理解声景现象,并为声景实践的开展奠定了良好的基础。不足之处在于研究内容有待深化、研究学科有待融合、声景标准化建设有待加强、声景普及有待提高,而这也是国内声景研究实现跨越发展需要积极补足的方面。     

Development of an interactive simulation system for the determination of the pressure–time relationship during the filling in a low pressure casting process

An interactive computer simulation system has been developed in this study to aid the determination of the pressure–time relationship during the filling of a low pressure casting to eliminate filling-related defects while maintaining its productivity. The pressure required to fill a casting in a low pressure casting process can be separated into two stages. The first stage is to exert pressure to force the molten metal to rise in the riser tube up to the gate of the casting die, which varies from casting to casting due to the drop of the level of the molten metal in the furnace, whilst the second stage is to add an additional pressure to push the molten metal into the die cavity in a way that will not cause much turbulence and have the proper filling pattern to avoid the entrapment of gas while maintaining productivity.One of the major efforts in this study is to modify the filling simulation system with the capability to directly predict the occurrence of gas porosity developed earlier to interactively determine the proper gate velocity for each and every part of the casting. The pressure required to fill the die cavity can then be obtained from the simulations.The operation principles and the interactive analysis system developed are then tested on an automotive wheel made by the low pressure casting process to demonstrate how the system can aid in determining the proper pressure–time relations, the p–t curve, required to produce a sound casting without sacrificing productivity.     

Anti-plane transient fracture analysis of the functionally gradient elastic bi-material weak/infinitesimal-discontinuous interface

The mechanical model was established for the Dirac-type anti-plane transient fracture problem of the weak-discontinuous interface between two FGMs half-planes. Integral transform was adopted to derive Cauchy singular integral equation and Erdogan’s allocation method was used to calculate transient stress intensity factors numerically. The numerical solutions of the weak-discontinuous case were contrasted with those of the infinitesimal-discontinuous one. Two possible effective methods to diminish the peak values of transient stress intensity factors are discussed. One is to reduce the weak-discontinuity of the interface, i.e., to make the ratio of the two non-homogeneity parameters be close to 1.0 and to avoid the case that the signs of the two non-homogeneity parameters are different. Another is to make a compromise between the weak-discontinuity and the all-continuity, i.e., to make FGMs interface infinitesimal-discontinuous. Simple method was suggested for the realization of the infinitesimal-discontinuity of FGMs interface. From the strong-discontinuous interface to the weak- discontinuous one, and then to the infinitesimal-discontinuous one, this is a law and trend of the development of composite interfaces. To design and manufacture infinitesimal-discontinuous interfaces may be a brand-new effective approach to enhance the reliability of composite structures, and the first rank infinitesimal-discontinuity is enough to improve the mechanical performances of composites notably.     

Risk analysis in safety reports required by the Seveso Directive

The Seveso Directive of the EC requires the operators of certain industrial installations deemed to present a ‘major hazard’ to produce and submit to the appropriate National Regulatory Authority a report (notification) giving information relevant to the safety of the installation. In particular, information has to be given with regard to the quantity and nature of dangerous substances handled, the circumstances under which a major accident might occur and the measures to prevent such accidents and to mitigate their consequences. In effect, this requires some form of risk analysis to be carried out. The laws introduced by Member States have specified to greater and lesser extents how that should be done, in particular the extent to which the consequences and likelihood of possible accidents should be quantified. That, together with the general view of industry that there are real limitations as to how far meaningful quantification of those aspects is possible, has resulted in some differences in the style of reports prepared.When considering the question of risk analysis it is important to recognise that it comprises a number of elements from the identification of causes of possible accidents, through evaluation of their consequences and likelihood to, in the limit, an evaluation of the risk of harm to people. In general, industry takes the view that the identification stage, which is largely qualitative, is the most important and is necessary for the preparation of a safety report. It is also generally accepted that some evaluation of the consequence of possible accidents in quantitative terms is necessary to indicate that management appreciates the potential for harm. But that has to take account of the uncertainties in the analysis procedure. Such uncertainties also limit the extent to which a meaningful quantification can be made of the probability or likelihood of accidents and, even more so, of the probability of harm to people. Hence, industry is largely opposed to the general use of those elements of quantified risk analysis (QRA) in a safety case for reasons discussed by CEFIC in its position paper ‘CEFIC Views on the Quantitative Assessment of Risks from Installations in the Chemical Industry’.     

Methodology of using delay-time analysis for a manufacturing industry

This paper has been written to give a methodology of applying delay-time analysis to a maintenance and inspection department. The aim is to reduce downtime of plant items and/or reducing maintenance and inspection costs, taking into account the possible environmental impact of a failure in terms of cost, both to the company and the environment. The paper also attempts to give a subjective measure of the consequences of such a failure in terms of cost to the environment, in monetary value to the company and the damaging effect to the company image.     

Scope methodology for safety

The EXTENDED Assessment/Certification task of the ESPRIT project SCOPE is intended to address those issues of Software Assessment/Certification which are not directly covered by its BASIC Assessment/Certification Model. That is it aims to cover some aspects of ‘Fitness of Purpose’ of software products, but, being mindful of the advice emanating from the Legal Study, will not claim to cover all aspects. This may readily be appreciated too, by appreciating the plethora of techniques which are already available to, say, the safety community. The aim is to assess the impact of these techniques upon the SCOPE BASIC model, and to recomment adjustments if necessary.We intend to introduce some of those problems and techniques which may be of relevance to the extended certification task of SCOPE, though it should be borne in mind that the project ultimately has to demonstrate the feasibility of its approach to certification, and that it is not its purpose to develop new tools but rather to investigate, adapt and integrate existing tools to demonstrate the viability of the proposed approach. In the Appendix we introduce a new relativistic software reliability model.This paper is not intended to be complete, it is meant to provoke discussion and reports on progress so far.     

A dynamometer table with a small inertia

Summary The dynamometers type DOS-1, which have a small inertia, are subject to variations in their readings according to the conditions of their use.The combination of the effects due to the displacement of the point of application of the resultant force within the lengths of the table, and the variation in the relations among the components of the force may lead to measurement errors up to 50% and more. In order to avoid considerable measurement errors it is necessary to keep, during measurements, the point of application of the resultant force within the limits of a portion of the table in its middle and amounting to 0.1–0.15 of its length.If the above requirements are adhered to, the calibration of the dynamometer can be carried out by the simplest of means, namely by applying one force only in the longitudinal direction. The dynamometer errors in this case will amount to ±4% of the measured value.     

Monte Carlo simulation of creep failure in a 0°/90° plain weave SiC/SiC composite lamina

A Monte Carlo model of the effects of fiber creep in a 0°/90° plain weave ceramic-grade Nicalon reinforced SiC composite has been developed. Creep degradation of fibers was predicted to result in stress dependent premature failure of woven ceramic matrix composites, and that premature failure was modeled using a power-law. A power-law exponent of 3.1 ± 0.1 was predicted. The power-law exponent was predicted to be independent of initial crack size for crack length to specimen width ratios of 0.02, 0.10, 0.25, and 0.50. The power-law exponent was also predicted to be independent of the matrix to fiber strength ratio for ratios from 0.25 to 1.0. Premature failure in the 90° (transverse) tows resulted in premature failure of the composite for low values of the matrix to fiber strength ratio (less than 0.75), and decreased creep life was predicted for decreased matrix to fiber strength ratio. For a matrix to fiber strength ratio of 1.0, the creep life of the woven composite was predicted to be equivalent to a unidirectional composite. At small initial crack lengths, a 10% improvement in the creep life was predicted for a reduction in the matrix to fiber strength ratio from 1.0 to 0.75. This improvement was related to the formation of microcracks in the 90° tows and shielding of the macrocrack tip from accelerated creep damage. This improvement in the predicted creep life at a matrix to fiber strength ratio of 0.75 was predicted to be independent of applied stress. However, improvement of the creep life was not predicted to occur for larger values of initial crack length.     

Simultaneous design of a product family and its related supply chain using a Tabu Search algorithm

Product family design is currently facing a multitude of challenges, the main problem stemming from the diversity offered to consumers. To design a product family, designers have to define an efficient bill of materials which ensures product assembly within a predefined length of time in order to satisfy the synchronised delivery principle. In addition, the modules used to assemble the finished products have to be competitive in terms of logistical costs. The ability to anticipate the constraints associated with the production process and with transportation is consequently of great interest. In this paper, we focus on the process of identifying a set of modules to be used in the assembly of the finished product. The objective is to define the bill of materials for each product from the modules belonging to that set, and to assign these modules to distant facilities where they will be manufactured and then shipped to a nearby facility for final assembly within a specific time. We use a set partitioning formulations to represent the problem, and solve it by adapting a Tabu Search algorithm in which the assembly process and the supply chain design are considered at the same time.     

Efficient structural computations with parameters uncertainty for composite applications

The aim of this paper is to propose a methodology in order to take into account the influence of uncertain data in structural calculations. To attain this goal, an approximation of the responses as a function of the uncertain data response called surface method (RSM) is proposed. In order to decrease the number of identification points necessary for the RSM, a progressive strategy is proposed. Error indicators are also used in order to increase the confidence. This strategy is applied to a laminate plate subjected to bending tests. The results are compared to Monte-Carlo simulations (considered as a reference). The method proposed in the present work permits to estimate correctly the whole response and is very simple to use (pre- and post-processing). This method is applied to asses the robustness of the point-stress method used to predict the rupture of perforated plates.     

Control of mechanical deformation of a laminate by electrical load to piezoelectric actuator considering the effects of damping and transverse shear

In this paper, we treat the control of dynamic deformation of a laminate by applying electrical load to piezoelectric actuators. Dynamic behavior of the laminate is analyzed considering the effect of damping due to interlaminar shear and the effect of transverse shear. The analytical model is a rectangular laminate composed of fiber-reinforced laminae and piezoelectric layers. The model is assumed to be a symmetric cross-ply laminate with all edges simply supported and to be subjected to unavoidable mechanical load and to electrical loads to piezoelectric actuators. Behavior of the laminate is analyzed based on the first-order shear deformation theory. The effect of damping due to interlaminar shear is incorporated into our analysis by introducing the interlaminar shear stresses which satisfy the Newton’s law of viscosity. The following quantities are obtained: (1) natural frequencies of the laminate, (2) weight functions for the deflection and rotations and (3) transient deflection due to loads varying arbitrarily with time. Moreover, the methods to control the deflection due to mechanical load by applying electrical voltage to the piezoelectric actuator are shown.     

案例知识的产品造型设计方法研究

目的为设计出符合消费者感性需求的产品,适应大规模定制的生产模式,缩短产品开发周期并方便企业后期的产品迭代,提出了一种应用已有产品案例进行产品快速设计的方法。方法以对象设计知识分类理论为基础,融入了消费者感性意象这一特征,建立了案例造型知识库模型,并由此模型指导案例各特征知识的获取,由此建立案例造型知识库。结论依据设计需求,应用案例造型知识库进行案例的检索、匹配、推理、变异,完成对四阀饮料机的方案设计,验证方法的可行性与高效性。     

Alternative approach for defining the particle population requirements for static image analysis based particle characterization methods

For image based particle characterisation approaches one of the most common discussion points is determining the number of particles required to have statistical confidence that the measurement is able to adequately describe the distribution of the sample. This topic becomes significantly more challenging when applied to the extraction of single component size distributions from multi-component samples.The aim of this work was to propose a means to accurately assess the particle number requirements using a method specific approach. The method applies a sub-sampling method to the original imaged dataset in order to provide an understanding of the impact of sub-sampling on the ability to accurately reproduce the original distribution.The method was applied to understand the particle number requirements for two batches of theophylline anhydrous with varied particle size distributions, using the input size distribution to guide the requirements for the subsequent multi-component samples of both materials.The results demonstrate the utility of the method to determine the appropriate number of particles required to recreate the size distributions. Whilst the minimum number of particles required to be sampled can be estimated, how those particles are sampled can also affect the validity of the measurement and must be taken into consideration.     

A comparative study of a vitreous biological composition suitable for coating steel prostheses

A correlation between composition and quality of a biological glass used as a bioglaze and an industrial glaze for sheet-steel coating was carried out. Apart from the extremely different conditions, particularly relative to the temperature for application of the coating to the metallic substrate, it was noted that the compositions are not very much different; this led us to think that the doping of the vitreous system with substances favouring the bonding of glaze to support (according what has been suggested by enamellists) is trustworthy in this case too. Some hypotheses relative to the role of nickel and the fluidity of the vitreous system were made to explain the observations, and to suggest the best way to improve the adhesion of metal to glaze.     

On the strength of discontinuous silicon carbide reinforced aluminum composites

The incorporation of dSiC into aluminum matrices results in substantial improvements in yield strength relative to the matrix material, but little change in the proportional limit. The Orowan strengthening mechanism was shown to be insufficient to account for the increase in yield strength of the composite. An increased dislocation density of the matrix due to a difference in the thermal expansion of the SiC and the matrix does predict an increase in composite strength, but is unable to explain why the proportional limit of the composite remains similar to that of the matrix or why the strength of the SiCw/6061Al is anisotropic. The conventional shear lag theory predicts yield strength values that are less than those observed. This is particularly so for the SiCp/Al composites, where the yield strength of the composite is predicted to be equal to that of the matrix independent of SiC volume fraction. If, however, the shear lag theory is modified to take into account the tensile transfer of load, the predicted composite strength is of sufficient magnitude to explain the strengthening effect of both the SiC whisker and platelet material. In addition, the modified shear lag theory can be used to rationalize why the proportional limit of the composite is similar to that of the matrix.     

Application of structural analysis to the mechanical behaviour of the cornea.

Structural engineering analysis tools have been used to improve the understanding of the biomechanical behaviour of the cornea. The research is a multi-disciplinary collaboration between structural engineers, mathematical and numerical analysts, ophthalmologists and clinicians. Mathematical shell analysis and nonlinear finite-element modelling have been used in conjunction with laboratory experiments to study the behaviour of the cornea under different loading states and to provide improved predictions of the mechanical response to disease and injury. The initial study involved laboratory tests and mathematical back analysis to determine the corneal material properties and topography. These data were then used to facilitate the construction of accurate finite-element models that are able to reliably trace the performance of cornea upon exposure to disease, injury or elevated intra-ocular pressure. The models are being adapted to study the response to keratoconus (a disease causing loss of corneal tissue) and to tonometry procedures, which are used to measure the intra-ocular pressure. This paper introduces these efforts as examples of the application of structural engineering analysis tools and shows their potential in the field of corneal biomechanics.     

United states regulations for siting LNG terminals: problems and potential

The regulations being applied to liquefied natural gas (LNG) import terminal siting in the United States are reviewed. There are no requirements for exclusion zones to protect the public from LNG spills onto water. Serious problems with current practices used to determine exclusion zones on the land-based part of the facility are identified. Many of the questions that are considered relate to the use of computational fluid dynamic (CFD) models, which appear to offer the best potential for realistic modeling to determine vapor cloud exclusion zones that result from LNG spills into impounded areas with or without dispersion in the presence of other obstacles to the wind flow. Failure to use CFD models, which are already approved by the regulation, and continued use of practices which have been demonstrated to be in error, raises important questions of credibility as well as denies the applicant full use of scientific tools that are available to optimize the design of such facilities so as to best provide for safety of the public.     

Contribution of the fill to the static behaviour of arched masonry structures: theoretical formulation

In the paper, one presents the theoretical set-up of an original formulation aimed at accounting for the contribution of the fill to the structural strength of masonry vaults and arches and at providing an evaluation about its skill of cooperating to stress absorption with the main vaulted resisting structure. Usually the action of components ordinarily regarded as non-structural members is often neglected in static analyses. Actually, it is a common practice to assume a number of elements of vaulted or arched constructions, such as the fill and the buttress, as completely unable to exert any structural action, rather than trying to evaluate their contribution; therefore, those are usually assumed to be a dead weight, unable to contribute to the bearing capacity of the vault. Starting from the consideration that the fill is somehow subject to some pre-compression because of the permanent load, an approach is proposed where the fill is considered to be able to provide a partial absorption of the variable loads with a reduced load transmission onto the main structural members. The procedure leads to more realistic evaluations about the safety assessment of vaulted structures, which are in major agreement with their real behaviour.