Language and tool support for event refinement structures in Event-B

Event-B is a formal method for modelling and verifying the consistency of chains of model refinements. The event refinement structure (ERS) approach augments Event-B with a graphical notation which is capable of explicit representation of control flows and refinement relationships. In previous work, the ERS approach has been evaluated manually in the development of two large case studies, a multimedia protocol and a spacecraft sub-system. The evaluation results helped us to extend the ERS constructors, to develop a systematic definition of ERS, and to develop a tool supporting ERS. We propose the ERS language which systematically defines the semantics of the ERS graphical notation including the constructors. The ERS tool supports automatic construction of the Event-B models in terms of control flows and refinement relationships. In this paper we outline the systematic definition of ERS including the presentation of constructors, the tool that supports it and evaluate the contribution that ERS and its tool make. Also we present how the systematic definition of ERS and the corresponding tool can ensure a consistent encoding of the ERS diagrams in the Event-B models

Test-Cost Modeling and Optimal Test-Flow Selection of 3D-Stacked ICs

Three-dimensional (3D) integration is an attractive technology platform for next-generation ICs. Despite the benefits offered by 3D integration, test cost remains a major concern, and analysis and tools are needed to understand test flows and minimize test cost.We propose a generic cost model to account for various test costs involved in 3D integration and present a formal representation of the solution space to minimize the overall cost. We present an algorithm based on A*—a best-first search technique—to obtain an optimal solution. An approximation algorithm with provable bounds on optimality is proposed to further reduce the search space. In contrast to prior work, which is based on explicit enumeration of test flows, we adopt a formal optimization approach, which allows us to select an effective test flow by systematically exploring an exponentially large number of candidate test flows. Experimental results highlight the effectiveness of the proposed method. Adopting a formal approach to solving the cost-minimization problem provides useful insights that cannot be derived via selective enumeration of a smaller number of candidate test flows.This research was supported in part by the National Science Foundation under grant no. CCF-1017391, the Semiconductor Research Corporation under contract no. 2118, a grant from Intel Corporation, and a gift from Cisco Systems through the Silicon Valley Community Foundation

Pricing firms on the basis of fundamentals

Determining the right or fair price of a stock is one of the oldest problems in finance. Business mergers and acquisitions rely on this information, but only in the last several decades have formal models been developed to address the question. This article focuses on fundamental valuation, a technique that determines the right price by forecasting cash flows from a stock market investment and calculating what that income is worth. ; The author first provides an overview of the literature and an illustration of commonly used fundamental valuation techniques based on relative valuation and the Gordon growth model and then discusses a valuation approach he developed in 2001. His work incorporates the proceeds from share liquidation into the cash flows that are used to value the firm, accounting for the reduction in future growth of cash flows from this liquidation of shares. The author demonstrates these methods by applying them to pricing BellSouth shares, the S&P 500 index, and some new-economy stocks. The discussion also looks at prices and estimated fundamental values during severe market turndowns. ; Pricing BellSouth using sales and sales growth is consistent with its dramatic rise and recent decline in price, the author finds; this method is also appropriate for a small group of high-growth stocks. Fundamental models, however, have more trouble explaining the price movements of the overall market. The author concludes that algorithmic valuation techniques provide, at best, a rough starting point for firm valuation.Asset pricing

Developing a Formal Navy Knowledge Management Process

Prepared for: Chief of Naval Operations, N1Organization tacit and explicit knowledge are required for high performance, and it is imperative for such knowledge to be managed to ensure that it flows rapidly, reliably and energetically. The Navy N1 organization has yet to develop a formal process for knowledge management (KM). This places N1 in a position of competitive disadvantage, particularly as thousands of people change jobs every day, often taking their hard earned job knowledge out the door with them and leaving their replacements with the need to learn such knowledge anew. Building upon initial efforts to engage with industry and conceptualize a Navy KM strategy, the research described in this study employs a combination of Congruence Model analysis, Knowledge Flow Theory, and qualitative methods to outline an approach for embedding a formal Navy KM process. This work involves surveying best tools and practices in the industry, government and nonprofit sectors, augmented by in depth field research to examine two specific Navy organizations in detail. Results are highly promising, and they serve to illuminate a path toward improving Navy knowledge flows as well as continued research along these lines.Chief of Naval Operations, N1Chief of Naval Operations, N1.Approved for public release; distribution is unlimited

Impurity in a granular gas under nonlinear Couette flow

We study in this work the transport properties of an impurity immersed in a granular gas under stationary nonlinear Couette flow. The starting point is a kinetic model for low-density granular mixtures recently proposed by the authors [Vega Reyes F et al. 2007 Phys. Rev. E 75 061306]. Two routes have been considered. First, a hydrodynamic or normal solution is found by exploiting a formal mapping between the kinetic equations for the gas particles and for the impurity. We show that the transport properties of the impurity are characterized by the ratio between the temperatures of the impurity and gas particles and by five generalized transport coefficients: three related to the momentum flux (a nonlinear shear viscosity and two normal stress differences) and two related to the heat flux (a nonlinear thermal conductivity and a cross coefficient measuring a component of the heat flux orthogonal to the thermal gradient). Second, by means of a Monte Carlo simulation method we numerically solve the kinetic equations and show that our hydrodynamic solution is valid in the bulk of the fluid when realistic boundary conditions are used. Furthermore, the hydrodynamic solution applies to arbitrarily (inside the continuum regime) large values of the shear rate, of the inelasticity, and of the rest of parameters of the system. Preliminary simulation results of the true Boltzmann description show the reliability of the nonlinear hydrodynamic solution of the kinetic model. This shows again the validity of a hydrodynamic description for granular flows, even under extreme conditions, beyond the Navier-Stokes domain.Comment: 23 pages, 11 figures; v2: Preliminary DSMC results from the Boltzmann equation included, Fig. 11 is ne