基于多维性能极限状态的概率地震需求分析

基于概率地震需求分析(PSDA),分别采用增量动力和非线性时程分析,得到某框架结构的最大层间漂移比和最大加速度响应,通过定义多维性能极限状态的性能水准,计算该结构的多维地震易损性,联合地震动危险性曲线,建立了年平均超越概率的三重积分公式,采用梯形法求得50年内地震需求(漂移)危险性曲线。在此基础上,进行了同时考虑性能极限状态的随机性和相关性对结构需求危险性的敏感性分析。在性能极限状态不确定性中选择适当的变异系数(cidrcpfa)及相互作用因子NID R,能够使年平均超越概率增加;相比单一极限状态,考虑二维极限状态的年平均超越概率也将提高。研究结果表明,所提方法可描述对多维响应参数敏感的结构破坏行为,可获得设计基准期内更加符合实际的结构需求危险性曲线,为震后损失估计提供可靠的理论依据。     

Design and performance analysis of code families for multi-dimensional optical CDMA

A code design algorithm for application in multi-dimensional optical code division multiple access (MD-OCDMA) for asynchronous optical fibre communication is proposed. Two-dimensional (2D) wavelength-time or space-time OCDMA and three-dimensional (3D) space-wavelength-time OCDMA are subsets of MD-OCDMA. Some applications and the performance analysis of the algorithm in 2D multipulse per row codes and 3D multipulse per plane codes are shown. In the applications discussed, this design ensures a maximum cross-correlation of '1' between any two codes. The performance metrics studied are the probability of error due to multiple-access interference for different numbers of active users and optimum temporal length for different values of cardinality. The performance analysis shows that the proposed 2D design offers very low probability of error due to multiple-access interference at lower cardinality when compared with other 2D designs using equivalent code dimension. A comparison of the proposed 3D design with an existing 3D design shows better performance at lower cardinality. The 3D designs show better performance when compared with the 2D designs.     

The role of editorial material in bibliometric research performance assessments

In this study, the possibilities to extend the basis for research performance exercises with editorial material are explored. While this document type has been traditionally not considered as an important type of scientific communication in research performance assessment procedures, there is a perception from researchers that editorial materials should be considered as relevant document types as important sources for the dissemination of scientific knowledge. In a number of these cases, some of the mentioned editorial materials are actually ‘highly cited’. This lead to a thorough scrutiny of editorials or editorial material over the period 1992–2001, for all citation indexes of Thomson Scientific. The relevance of editorial materials through three quantitative bibliometric characteristics of scientific publications, namely page length, number of references, and the number of received citations, are thoroughly analyzed.     

Quantitative assessments of performance and robustness of maintenance policies for stochastically deteriorating production systems

Over the last few decades, many efforts have been invested in improving the economic performances of maintenance policies for stochastically deteriorating production systems. However, with the development of complex production systems, maintenance managers are interested not only in cost saving, but also in how to trustworthily plan and allocate the required maintenance budget. In this context, the robustness of maintenance policies which is related to the maintenance cost variability from a renewal cycle to another plays a pivotal role. This research deals with a quantitative approach to jointly assess the economic performance and robustness of some representatives of two most well-known classes of maintenance policies: time-based and condition-based maintenance. To this end, we first propose a new cost criterion which combines the long-run expected cost rate and standard deviation of maintenance cost per renewal cycle. Then, we develop and compare the associated mathematical cost models of the considered maintenance policies on the basis of the Gamma degradation process and the theory of stochastic renewal processes. The comparison results under different situations of maintenance costs and system characteristics show that the optimal configuration of maintenance policies gives the best compromise between the performance and robustness, and is mostly affected by the system downtime. Under this aspect, the condition-based maintenance remains more profitable than the time-based maintenance. Still, maintenance managers could implement condition-based maintenance policies that efficiently control the downtime to maximise the maintenance effectiveness of production systems from both performance and robustness viewpoints.     

Rasch techniques for detecting bias in performance assessments: an example comparing the performance of native and non-native speakers on a test of academic English

The use of common tasks and rating procedures when assessing the communicative skills of students from highly diverse linguistic and cultural backgrounds poses particular measurement challenges, which have thus far received little research attention. If assessment tasks or criteria are found to function differentially for particular subpopulations within a test candidature with the same or a similar level of criterion ability, then the test is open to charges of bias in favour of one or other group. While there have been numerous studies involving dichotomous language test items (see e.g. Chen and Henning, 1985 and more recently Elder, 1996) few studies have considered the issue of bias in relation to performance based tasks which are assessed subjectively, via analytic and holistic rating scales. The paper demonstrates how Rasch analytic procedures can be applied to the investigation of item bias or differential item functioning (DIF) in both dichotomous and scalar items on a test of English for academic purposes. The data were gathered from a pilot English language test administered to a representative sample of undergraduate students (N= 139) enrolled in their first year of study at an English-medium university. The sample included native speakers of English who had completed up to 12 years of secondary schooling in their first language (L1) and immigrant students, mainly from Asian language backgrounds, with varying degrees of prior English language instruction and exposure. The purpose of the test was to diagnose the academic English needs of incoming undergraduates so that additional support could be offered to those deemed at risk of failure in their university study. Some of the tasks included in the assessment procedure involved objectively-scored items (measuring vocabulary knowledge, text-editing skills and reading and listening comprehension) whereas others (i.e. a report and an argumentative writing task) were subjectively-scored. The study models a methodology for estimating bias with both dichotomous and scalar items using the programs Quest (Adams and Khoo, 1993) for the former and ConQuest (Wu, Adams and Wilson, 1998) for the latter. It also offers answers to the practical questions of whether a common set of assessment criteria can, in an academic context such as this one, be meaningfully applied to all subgroups within the candidature and whether analytic criteria are more susceptible to biased ratings than holistic ones. Implications for test fairness and test validity are discussed.     

Supportability of composite airframes: An integrated logistic viewpoint

The aim of this paper is to highlight supportability of composite aircraft structure from an integrated logistic support point of view. Under this view, availability and life cycle costs become important parameters to assess the supportability of a system. Good supportability will be achieved by close cooperation between engineering and logistic disciplines and by performing a comprehensive reliability and maintainability programme. As an important element of supportability, repair procedures for composite material known to date do not yet adequately consider the logistic interests of the aircraft users.     

Three-dimensional finite-element beam propagation method: assessments and developments

In recent years the finite-element method (FEM) has been widely applied to three-dimensional beam propagation analysis, and several FEM propagators have been presented. Up to now, as far as we know, an exhaustive, deep, and comparative analysis of these formulations and of the related algorithms has never been presented. We critically analyze and numerically compare, to our knowledge for the first time, different vectorial, semivectorial, and scalar formulations in order to check their performances, point out weaknesses, and suggest future developments. The results obtained highlight once more the inadequacy of scalar approaches in dealing with actual photonics devices and suggest vector formulations worthy of further development and future research.     

Simulation of multi-dimensional non-gaussian non-stationary random fields

This paper presents a method for simulating multi-dimensional stochastic processes. The target process is specified by its marginal density function which can vary along the indexing set, and by its two point correlation function, which need not be stationary. The polynomial chaos expansion is used to match the marginal densities while the Karhunen–Loève representation is used to fine tune the match of the correlation function. The resulting representation of the process is in the form of a polynomial chaos expansion, which can be readily realized.     

Optical investigations of multi-dimensional ZnO hybrid structures

The authors report on the optical properties of multi-dimensional ZnO hybrid structures, consisting of film (2D)/nanorods (1D)/sapphire substrate (2D), grown by metalorganic chemical vapor deposition (MOCVD). Photoluminescence investigations reveal that the sample with top layer grown at a decreased growth temperature of 240 °C and increased reactor pressure of 5 Torr exhibits superior emission properties. The presence of strong E₂^high optical phonon mode at 438.5 cm^− 1 in the visible micro-Raman spectra demonstrates the wurtzite nature of ZnO. Although the ultraviolet Raman scattering measurements of the hybrid structures reveal the presence of in-plane tensile stress in the top ZnO layer, the sample with the improved emission performance shows the release of tensile stress.     

Waves in microstructured solids: a unified viewpoint of modeling

The basic ideas for describing the dispersive wave motion in microstructured solids are discussed in the one-dimensional setting because then the differences between various microstructure models are clearly visible. An overview of models demonstrates a variety of approaches, but the consistent structure of the theory is best considered from the unified viewpoint of internal variables. It is shown that the unification of microstructure models can be achieved using the concept of dual internal variables.     

Chemical reactivity assessments in R&D

The evaluation of reactive chemical hazards at the pilot and manufacturing scale, using laboratory testing, is increasingly used and has been well documented. However, reactive chemical hazard evaluation at the R&D scale presents special challenges. The typical hazard testing program requires a significant amount of sample, often takes time (>3 days) to complete, and is can be quite costly. On the other hand, the synthesis of new molecules in the R&D environment often produces only a few grams, occurs quickly (<2 days), may only happen once and many synthetic reactions may be carried out before a suitable candidate for scale-up will be found. However, with each new synthesis there is the risk of injury, possibly serious or fatal, caused by unexpected and maybe violent reactivity. While it may not be possible at the R&D stage of product development to define the critical limits of temperature, pressure, concentration, and safe dosing rates of processes it is possible to identify the potential hazards of the planned synthesis. This paper describes a staged approach for chemical reactivity hazard evaluation and assessment applicable to an R&D environment. We will describe these initial phases of the R&D hazard evaluation process that rely on only data that can be obtained from the open literature. We will also indicate how the need for additional assessments can be determined from this initial hazard review.     

SPAD array module for multi-dimensional photon timing applications

Multi-dimensional time correlated single-photon counting has reached a prominent position among analytical techniques employed in the medical and biological fields. The development of instruments able to perform temporal and spectral fluorescence analysis (sFLIM) at the same time is limited by the performance of single-photon detectors, since currently available arrays cannot simultaneously satisfy all the requirements. To face this rising quest, a fully-parallel eight-channel module, based on a monolithic single-photon avalanche diode (SPAD) array with great temporal resolution, high photon detection efficiency and low dark count rate, has been designed and fabricated. The system relies on a novel architecture of the single pixel, based on the integration of the timing pick-up circuit next to the photodetector, making the negative effects of electrical and optical crosstalk on photon timing performance negligible. To this end, the custom technological process used to fabricate the SPAD has been modified, allowing the integration of MOS transistors without impairing the structure and the performance of the detector. The single channel is complemented by an external active quenching circuit, fabricated in a standard CMOS technology, that ensures high maximum counting rate (>5?MHz) and low after-pulsing (<2%). Finally, the output timing signals are read and conditioned by proper CMOS electronics. The complete system shows a very good temporal resolution of about 45?ps (FWHM).     

Assessing structural vulnerability against earthquakes using multi-dimensional fragility surfaces: A Bayesian framework

The present paper advocates a probabilistic framework for assessing structural vulnerability against earthquakes. This is justified by the significant randomness that characterizes not only the earthquake excitation (amplitude, frequency content, duration), but also the structural system itself (i.e. stochastic variations in the material properties). Performance predictions can readily be summarized in the form of fragility curves which express the probability of exceeding various damage levels (from minor to collapse) with respect to a metric of the earthquake intensity. In this paper, a Bayesian framework is proposed for the derivation of fragility curves which can produce estimates irrespective of the amount of data available. It is particularly flexible when combined with Markov Chain Monte Carlo (MCMC) techniques and can efficiently provide credible intervals for the estimates. Furthermore, a general procedure based on logistic regression is illustrated that can lead in a principled manner to the derivation of fragility surfaces which express the probability of exceeding a damage level with respect to several measures of the earthquake load and can thus produce more accurate predictions. The methodologies presented are illustrated using data generated from computational simulations for a structure on top of a saturated sand deposit which is susceptible to liquefaction.     

Architectural complexity and contradiction: a fuzzy set-theoretic basis and viewpoint

In this paper, the authors examine an essential problem of contemporary architecture, namely, that of complexity and contradiction. The complex and contradictory architecture considered here is that which is based on the richness and ambiguity of modern experience as well as on the perpetual imprecision and fuzziness of human experience. Such an architecture is a valid one which evokes many levels of meaning and combinations of focus, and whose space and elements become readable and workable in many ways at a single instance.The concept of a ‘fuzzy structure’ is developed for the purpose of analysis and synthesis of architectural complexities and contradictions. It is then shown in passing that, under appropriate semantics, the fuzzy algebra of Kandel and the fuzzy system of Zimmermann are ‘components’ — and hence special interpretative realizations — of the fuzzy structure.     

A multi-dimensional constitutive model for shape memory alloys

This paper presents a multi-dimensional thermomechanical constitutive model for shape memory alloys (SMAs). This constitutive relation is based upon a combination of both micromechanics and macromechanics. The martensite fraction is introduced as a variable in this model to reflect the martensitic transformation that determines the unique characteristics of shape memory alloys. This constitutive relation can be used to study the complex behavior associated with 2-D and 3-D SMA structures. A simple example using this constitutive model is also presented, which reveals a new and interesting phenomenon of 3-D SMA structures.     

Integrating ecosystem services in Swedish environmental assessments: an empirical analysis

Given the growing number of policies and laws that encourage inclusion of ecosystem services (ES) in processes, we have investigated environmental impact assessments (EIA) and strategic environmental assessments (SEA) conducted in Sweden in order to analyse whether ES may be integrated to enhance and improve environmental assessment of today. Representative Swedish environmental projects were reviewed. Three cases with different geographic and environmental settings were selected to allow us to study consideration of a wide range of different ES. We investigated the processes and discussions taking place using documentation from the cases. We formalized and labelled the expected impacts into an ES framework. Summarizing each case, we described conformities and divergences in explicit and implicit prioritizations between the actors. We discussed the benefits of integrating ES into current practices and possible improvements in the processes and methodologies. When ES could be integrated into EIAs and SEAs more aspects would be visualized and a larger stakeholder engagement stimulated leading to improved support for decision-making.     

Prior assessments for bands of probability measures: Empirical bayes analysis

Summary A useful non-parametric class of priors is formed as those probability measures which lie between an upper and a lower measure and it is called a Wand of probability measures Lavine (1991), Moreno and Pericchi (1991), Wasserman and Kadane (1992). This class allows considerable freedom in tail behaviour as long as the upper and lower measures have different tails. This property is inherited from the class of Interval of measures DeRobertis and Hartigan (1981), from which the Band of probability measures class is obtained by restricting attention to those measures that integrate to one, Although the analysis of this restricted class is somewhat more involved, the restriction is quite natural and may lead to robustness in situations in which the larger class is not robust. In fact, it is a generalization of the class implicitly considered by Edwards, Lindman and Savage (1963) in “Precise Measurement Theory”. An empirical analysis is performed with the two classes above. That is, we choose within a class of priors that measure which maximizes the probability of the actual data Good (1983). This “optimal” measure is used in this robust Bayesian context to assess the band of probability measures.