Verification and validation of Bayesian knowledge-bases

Knowledge-base V&V primarily addresses the question: “Does my knowledge-base contain the right answer and can I arrive at it?” One of the main goals of our work is to properly encapsulate the knowledge representation and allow the expert to work with manageable-sized chunks of the knowledge-base. This work develops a new methodology for the verification and validation of Bayesian knowledge-bases that assists in constructing and testing such knowledge-bases. Assistance takes the form of ensuring that the knowledge is syntactically correct, correcting “imperfect” knowledge, and also identifying when the current knowledge-base is insufficient as well as suggesting ways to resolve this insufficiency. The basis of our approach is the use of probabilistic network models of knowledge. This provides a framework for formally defining and working on the problems of uncertainty in the knowledge-base.

In this paper, we examine the project which is concerned with assisting a human expert to build knowledge-based systems under uncertainty. We focus on how verification and validation are currently achieved in .     

Stochastic neural networks

The first purpose of this paper is to present a class of algorithms for finding the global minimum of a continuous-variable function defined on a hypercube. These algorithms, based on both diffusion processes and simulated annealing, are implementable as analog integrated circuits. Such circuits can be viewed as generalizations of neural networks of the Hopfield type, and are called diffusion machines.Our second objective is to show that learning in these networks can be achieved by a set of three interconnected diffusion machines: one that learns, one to model the desired behavior, and one to compute the weight changes.This research was supported in part by U.S. Army Research Office Grant DAAL03-89-K-0128.     

Temporal Bayesian Knowledge Bases – Reasoning about uncertainty with temporal constraints

Time is ubiquitous. Accounting for time and its interaction with change is crucial to modeling the dynamic world, especially in domains whose study of data is sensitive to time such as in medical diagnosis, financial investment, and natural language processing, to name a few. We present a framework that incorporates both uncertainty and time in its reasoning scheme. It is based on an existing knowledge representation called Bayesian Knowledge Bases. It provides a graphical representation of knowledge, time and uncertainty, and enables probabilistic and temporal inferencing. The reasoning scheme is probabilistically sound and the fusion of temporal fragments is well defined. We will discuss some properties of this framework and introduce algorithms to ensure groundedness during the construction of the model. The framework has been applied to both artificial and real world scenarios.     

An Analysis of Chorioretinal Thermal Response to Intense Light Exposure

An analytical expression has been obtained for the transient temperature distribution produced when the retina is irradiated by a high-intensity light source. The following factors are included in the analysis: (1) structurally the fundus consists of layers of material which have different physical properties, (2) absorption of energy from the light beam follows the Beer-Lambert law, (3) energy is absorbed in the sclera as well as in the pigment epithelium and choroid, (4) heat is removed from the fundus by blood circulating through the capillaries of the choroid, and (5) intensity of the light source may vary with time. Computed values indicate that absorption of energy in the sclera and removal of heat by convection are both important for longer irradiation times, which agrees with recent experimental observations. The asymptotic response to a train of pulses is presented also.     

组合了电源控制、用户输入功能的单刀单掷按钮开关

本设计实例介绍了对某种旧设计的增强措施(参考资料1)。图1中的电路使用常开型单刀单掷按钮开关S1,它代替了原始设计要求的单刀双掷开关。您可以使用膜片开关来大大简化该器件的工业设计并增强它的人机控制特性。另外,该电路消除了流过未动作开关的电流,由此略微减少了工作模式中的泄漏电流。     

Using a pseudo-stochastic approach for multiple-parts scheduling on an unreliable machine

In this paper we follow previous “pseudo-stochastic” approaches that solve stochastic control problems by using deterministic optimal control methods. In a similar manner to the certainty equivalence principle, the suggested model maximizes a given profit function of the expected system outcome. However, unlike the certainty equivalence principle, we model the expected influences of all future events (including those that are expected beyond the planning horizon), as encapsulated by their density functions and not only by their mean values. The model is applied to the optimal scheduling of multiple part-types on a single machine that is subject to random failures and repairs. The objective of the scheduler is to maximize the profit function of the produced multiple-part mix. A numerical study is performed to evaluate the suggested pseudo-stochastic solutions under various conditions. These solutions are compared to a profit upper bound of the stochastic optimal control solutions.     

Balanced timed regular expressions

Several classes of regular expressions for timed languages accepted by timed automata have been suggested in the literature. In this article we introduce balanced timed regular expressions with colored parentheses which are equivalent to timed automata, and, differently from existing definitions, do not refer to clock values, and do not use additional operations such as intersection and renaming.     

Seismic Performance and Deformation of Levees: Four Case Studies

During the 1989 Loma Prieta earthquake the Pajaro River levees near Watsonville, Calif., spread laterally at multiple locations. Four of these locations are discussed in this paper. At one location, an industrial facility was also damaged and a dispute arose as to whether lateral spreading of the adjacent levee was the cause. Stability analyses were made of the industrial site for conditions before, during, and after the earthquake. To confirm the findings, analyses were also made of three other nearby locations where the actual deformation was documented and the subsurface conditions are well defined. The calculated levee deformations at the four locations are quite consistent with the observed movements (up to 60 cm). This experience provides increased confidence in the methods of analysis described, for the characterized subsurface conditions, and the range of ground motions experienced. Additional analyses made using the more recently developed multilinear regression lateral-spreading model (e.g., Youd et al. in 1999) yielded inconsistent results.     

Windows 2000 security: A postmortem analysis

Introduction

After initially releasing Windows 2000 (W2K) in February 2000, Microsoft touted it as a secure operating system, one that was far improved over its predecessor, Windows NT(WNT). Yet even before Microsoft released W2K the software giant announced that it would release Service Pack 1 (SP1) for this operating system. The information security community immediately wondered whether the claims about the much improved security in W2K were true; many events and findings since then have reinforced this doubt. After a reign of three years as Microsoft's flagship operating system, last year Microsoft rolled out its newest server operating system, Windows Server 2003 (WS2003), signaling the end of an era for the W2K operating system. Windows XP (WXP) had already supplanted W2K Professional as the newest workstation operating system several years before. This is not to say that nobody uses W2K any more—to the contrary. But as W2K continues to increasingly take a proverbial back seat to newer Microsoft operating systems, now is a good time to take a retroactive look at W2K from a security viewpoint. Was it a success from a security perspective? What were its major failings and why? This paper addresses these issues.