Use of Warranties on Highway Projects: A Real Option Perspective

Since the introduction of warranty provisions in federal highway jobs, more and more state departments of transportation (DOTs) have considered the use of such provisions to protect their initial investment. This paper describes the pros and cons of warranty contracting in highway construction based on a survey of warranty practices in the United States. In particular, the need for state DOTs to buy a warranty for a well-built project is questioned. As an alternative, this paper introduces the warranty option, which gives the DOT the right to buy a warranty only if it becomes necessary at the end of construction. This option is exercised if the performance on site warrants it. This paper describes the mechanics of the warranty option and its advantages over the conventional warranty. A bid evaluation model is also developed for the warranty option approach.     

Contractor-Performed Quality Control: Is the Fox Guarding the Henhouse?

At the same time that state departments of transportation are allowing contractor-performed quality control, they are also concerned about using the contractor-reported data for acceptance and payment purposes. The question is, are we putting the fox in charge of guarding the chickens? To address this concern, a large number of asphalt and concrete projects in Kentucky were examined. The statistical analyses showed that for the most part there is no significant difference between the contractor-performed acceptance data and concomitant highway agency-performed verification data. This is obviously a very encouraging finding that is expected to enhance the level of trust between the contractors and highway agencies.     

Bioprocess applications of model-based estimation techniques

The last decade has seen the development of a number of approaches for estimating those variables which are difficult to measure on-line in industrial process situations. Whilst a range of techniques is available, a common element is the use of process knowledge in the form of a system model. In the case of bioprocess systems, although a large range of models has been presented in the literature, their use in estimation schemes on an industrial scale has been limited. A number of reasons can be identified for their low level of utilisation. Of particular significance is the uncertainty which exists in quantifying system performance and the process-model mismatch which inevitably results. The level of ‘pre-defined model’ uncertainty, together with the knowledge gained during the course of the fermentation, serves to dictate estimator structure. The paper considers a range of estimation strategies and contrasts, through industrial applications, their performance characteristics and utility.     

European intercomparison on electron spin resonance identification of irradiated foodstuffs

The results of a co-trial organized by the Community Bureau of Reference on the use of Electron Spin Resonance spectroscopy for the identification of irradiated food in 21 laboratories are presented. The trial was qualitative on beef and trout bones, sardine scales, pistachio nut shells, dried grapes, and papaya, and quantitative on poultry bones. There was no difficulty in identifying irradiated meat bones, dried grapes, and papaya. In the case of fish bones there is a need for further kinetic study on different species. Identification of irradiation in pistachio nuts is more complicated and additional research is needed before further trials. All laboratories were able to distinguish between chicken bones irradiated at 1 to 3 kGy or 7 to 10 kGy although there was a partial overlap between the results.     

调质状态下40Cr钢的焊接

在合理制定焊接工艺的基础上，采用R307珠光体耐热钢焊条成功地进行40Cr钢在调质状态下的焊接，解决了通常采用25—13型奥氏体焊条焊接出现的焊缝强度低、焊接接头性能差的问题。     

Improved Estimates for the Accuracy of Small Disjuncts

Learning systems often describe a target class as a disjunction of conjunctions of conditions. Recent work has noted that small disjuncts, i.e., those supported by few training examples, typically have poor predictive accuracy. One model of this accuracy is provided by the Bayes-Laplace formula based on the number of training examples covered by the disjunct and the number of them belonging to the target class. However, experiments show that small disjuncts associated with target classes of different relative frequencies tend to have different error rates. This note defines the context of a disjunct as the set of training examples that fail to satisfy at most one of its conditions. An empirical adaptation of the Bayes-Laplace formula is presented that also makes use of the relative frequency of the target class in this context. Trials are reported comparing the performance of the original formula and the adaptation in six learning tasks.     

最大似然反褶积软件包的研制与应用

本文简明地介绍最大似然反褶积的基本原理、软件包的研制过程和应用效果。 最大似然反褶积是美国80年代研究出的一种地震资料处理新方法,它有效地解决了传统褶积模型中无法进行信噪分离的矛盾。经松辽盆地实践证明,它可以求出高分辨率和高信噪比的反射系数、最小相位化子波、合成记录、相对层速度和绝对层速度。与国外的VELOG和SEISLOG处理软件的处理结果相比,分辨率和信噪比均有很大的提高。 在软件包的研制过程中,我们主要解决了数学模型复杂和运算速度慢的问题,使最大似然反褶积在CYBER-855S计算机上成为可实用的数字处理技术。 该项技术在大庆油田朝阳沟地区进行了初步应用,结果表明,对薄层地震响应的分辨能力有明显的提高。与井岩性柱状图对比,6m以上的砂层都可以分辨出来,并且对应得比较准确。有些3m的薄层也可以找到。 该软件包的研制成功并在地震资料处理中得到应用,这在国内是首创。     

Spectral estimation of video signals

Spectrum analyzers are ubiquitous in laboratory work concerning one dimensional signals. This is because linear operators are best examined in the frequency domain. Linear operators, such as linear filters, DCT coders, line shufflers, etc., dominate also the video systems scenario. Their frequency domain study is as appropriate and informative as it is in the case of their one-dimensional counterparts. This paper considers the problems associated with the introduction of two well-known spectral estimation techniques, the periodogram and AR estimates, to the context of television signals. The potential for application of spectral estimation to video problems is exemplified by a number of applications related to the fields of enhanced quality television and HDTV. Special attention is paid to the computational aspects, whose effective solution conditions the practical applicability of the proposed spectral estimation techniques.R. Rinaldo is currently at the Department of Electrical and Computer Engineering of the University of California, Berkeley.