Exploring the transferability of safety performance functions

Safety performance functions (SPFs), by predicting the number of crashes on roadway facilities, have been a vital tool in the highway safety area. The SPFs are typically applied for identifying hot spots in network screening and evaluating the effectiveness of road safety countermeasures. The Highway Safety Manual (HSM) provides a series of SPFs for several crash types by various roadway facilities. The SPFs, provided in the HSM, were developed using data from multiple states. In regions without local jurisdiction based SPFs it is common practice to adopt national SPFs for crash prediction. There has been little research to examine the viability of such national level models for local jurisdictions. Towards understanding the influence of SPF transferability, we examine the rural divided multilane highway models from Florida, Ohio, and California. Traffic, roadway geometry and crash data from the three states are employed to estimate single-state SPFs, two-state SPFs and three-state SPFs. The SPFs are estimated using the negative binomial model formulation for several crash types and severities. To evaluate transferability of models, we estimate a transfer index that allows us to understand which models transfer adequately to other regions. The results indicate that models from Florida and California seem to be more transferable compared to models from Ohio. More importantly, we observe that the transfer index increases when we used pooled data (from two or three states). Finally, to assist in model transferability, we propose a Modified Empirical Bayes (MEB) measure that provides segment specific calibration factors for transferring SPFs to local jurisdictions. The proposed measure is shown to outperform the HSM calibration factor for transferring SPFs.     

Theoretical advances in artificial immune systems

Artificial immune systems (AIS) constitute a relatively new area of bio-inspired computing. Biological models of the natural immune system, in particular the theories of clonal selection, immune networks and negative selection, have provided the inspiration for AIS algorithms. Moreover, such algorithms have been successfully employed in a wide variety of different application areas. However, despite these practical successes, until recently there has been a dearth of theory to justify their use. In this paper, the existing theoretical work on AIS is reviewed. After the presentation of a simple example of each of the three main types of AIS algorithm (that is, clonal selection, immune network and negative selection algorithms respectively), details of the theoretical analysis for each of these types are given. Some of the future challenges in this area are also highlighted.     

Variational Image Restoration and Decomposition with Curvelet Shrinkage

The curvelet is more suitable for image processing than the wavelet and able to represent smooth and edge parts of image with sparsity. Based on this, we present a new model for image restoration and decomposition via curvelet shrinkage. The new model can be seen as a modification of Daubechies-Teschke’s model. By replacing the B _p,q ^β term by a G _p,q ^β term, and writing the problem in a curvelet framework, we obtain elegant curvelet shrinkage schemes. Furthermore, the model allows us to incorporate general bounded linear blur operators into the problem. Various numerical results on denoising, deblurring and decomposition of images are presented and they show that the model is valid.

Dialectic decision support systems: System design and empirical evaluation

Many complex and unstructured decisions are hindered by a lack of clear understanding of various underlying assumptions and perspectives involved in the decision process. At present, the traditional decision support systems (DSS) pay little attention to the elicitation of underlying assumptions and perspectives in dealing with complex issues. We argue that the Socratic dialectic inquiry is an effective method for dealing with unstructured problems that are complex and require the involvement of different perspectives in DSS. In this paper, we propose a design for Dialectic Decision Support Systems (DDSS), in which dialectical processes are integrated with traditional DSS in order to provide support for individual decision makers. We then formulate a conceptual model for identifying factors that contribute to the efficacy of DDSS in comparison to traditional DSS. The empirical test of the model supports the superior efficacy of the DDSS and identifies factors that contribute to it. The contributions of this research are in generating support for stimulating critical thinking, dealing with complex decision issues and identifying creative solutions.     

引入人工免疫理论的入侵检测

由于计算机的安全问题与生物免疫系统具有惊人的相似性，特别是在网络入侵检测上，因此就产生了一个有意义的研究领域：引入人工免疫理论的入侵检测机制研究：首先介绍了入侵检测的概念和地位，然后在分析传统IDS缺陷的基础上，提出了在入侵检测中引入人工免疫理论：接着从AIS的生物原型入手，综述其仿生机理及其在计算机技术领域的应用，并介绍了阴性选择算法。然后通过局部修改portsentry，引入了人工免疫机制，并进行了仿真实验。     

南钢转炉实现“负能”炼钢的探讨

通过分析转炉工序能耗，了解回收二次能源在炼钢工序中的重要性。介绍了南钢65t转炉蒸汽、煤气回收利用的工艺流程及实现蒸汽、煤气回收利用所开展的一些工作，探讨了南钢转炉实现“负能”炼钢的途径。     

A Formal Definition of Time in LOTOS

Enhanced Timed-LOTOS, denoted ET-LOTOS, is an extension of LOTOS that allows the modelling of real-time behaviours. It covers all the aspects of full LOTOS, including data types, it supports both a dense and a discrete time domain and can manipulate time values as any other data values. A tutorial on ET-LOTOS, showing many application examples, has already been published [LéL97]. The present paper adds to it by providing an in-depth presentation of its theoretical aspects. The complete semantics is given and explained, and its properties are studied. In particular, we prove that the semantics is consistent and that strong bisimulation is a congruence. This requires to deal carefully with the presence of negative premises in the operational semantics, which are necessary to express urgency. ET-LOTOS is also shown to be a conservative extension of LOTOS for guarded processes, and is the basis of the timed extension of LOTOS currently developed by ISO [ISO98]. To our knowledge, this is the first in-depth study of a language that combines data types and real-time behaviours. Received May 1997 / Accepted in revised form October 1998     

实数向量型阴性选择算法的改进

通过对实数向量型阴性选择算法的分析,提出了检测器空间覆盖率的概念,用它作为估计检测器数量的一项理论依据,将这个估计值引入到实数向量型阴性选择算法中,控制检测器的生成,同时对检测器采取了新的变异操作.实验表明,这一改进在保证算法检出率的同时,又可降低误报率.     

Do too many cooks spoil the broth? Using the number of developers to enhance defect prediction models

Fault prediction by negative binomial regression models is shown to be effective for four large production software systems from industry. A model developed originally with data from systems with regularly scheduled releases was successfully adapted to a system without releases to identify 20% of that system’s files that contained 75% of the faults. A model with a pre-specified set of variables derived from earlier research was applied to three additional systems, and proved capable of identifying averages of 81, 94 and 76% of the faults in those systems. A primary focus of this paper is to investigate the impact on predictive accuracy of using data about the number of developers who access individual code units. For each system, including the cumulative number of developers who had previously modified a file yielded no more than a modest improvement in predictive accuracy. We conclude that while many factors can “spoil the broth” (lead to the release of software with too many defects), the number of developers is not a major influence.

14CrlMoR钢136 mm特厚板极限低温冲击韧性

为探究14Cr1MoR钢特厚板的低温冲击性能,对钢厂生产的136 mm厚14Cr1MoR钢板分别进行了交货状态(正火+回火)和长时模焊后的0～-30℃低温冲击试验,并借助金相显微镜对交货状态下和长时模焊后的全厚度组织、晶粒度和夹杂物进行了统计分析。结果表明:14Cr1MoR钢特厚板的极限冲击温度为-30℃,交货状态和长时模焊板厚1/2处-30℃冲击功分布为150～173 J和19.5～97 J。金相组织研究表明,影响钢板长时模焊后低温冲击性能下降的主要原因为碳化物在晶内和晶界处聚集长大,并趋向于球化,使基体韧性和晶界处性能大为弱化.从而导致冲击功明显下降。