Polar Varieties, Real Equation Solving and Data-Structures: The hypersurface case

In this paper we apply for the first time a new method for multivariate equation solving which was developed in \cite{gh1}, \cite{gh2}, \cite{gh3} for complex root determination to the {\em real} case. Our main result concerns the problem of finding at least one representative point for each connected component of a real compact and smooth hypersurface. The basic algorithm of \cite{gh1}, \cite{gh2}, \cite{gh3} yields a new method for symbolically solving zero-dimensional polynomial equation systems over the complex numbers. One feature of central importance of this algorithm is the use of a problem--adapted data type represented by the data structures arithmetic network and straight-line program (arithmetic circuit). The algorithm finds the complex solutions of any affine zero-dimensional equation system in non-uniform sequential time that is {\em polynomial} in the length of the input (given in straight--line program representation) and an adequately defined {\em geometric degree of the equation system}. Replacing the notion of geometric degree of the given polynomial equation system by a suitably defined {\em real (or complex) degree} of certain polar varieties associated to the input equation of the real hypersurface under consideration, we are able to find for each connected component of the hypersurface a representative point (this point will be given in a suitable encoding). The input equation is supposed to be given by a straight-line program and the (sequential time) complexity of the algorithm is polynomial in the input length and the degree of the polar varieties mentioned above.Comment: Late

MODERNIZING SYSTEM DEVELOPMENT: REQUIREMENTS-BASED, MODEL-DRIVEN DESIGN, IMPLEMENTATION, AND TEST

International audienceWith no end in sight, mechatronic system complexity continues to increase, worsening the challenges that have already plagued systems designers for years. Incomplete or volatile requirements, poorly specified and managed interfaces, integration testing finding problems at the very last stages of a program, development and analysis in disconnected domains, multi-domain expertise in short supply, and coordinating work and status across multi-level supply chains-these are all problems commonly discussed among systems developers. These challenges are further compounded in highly regulated domains, such as aerospace, automotive, and medical, where the end system must also be proven safe and conform to pertinent policy. In this paper, we discuss the root causes of system design challenges, and how the industry is responding with more effective design methods, tools, and collaboration mechanisms

A system perspective on warranty problems within a supply chain

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, February 2005 [first author]; and, (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, February 2006 [second author].Includes bibliographical references (p. 111-113).Warranty is important financially to American manufacturers, especially automotive companies. Carmakers and suppliers must work aggressively to improve their warranty management approach as warranty cost often equals or exceeds their investment in engineering. This thesis focuses on studying warranty management in a supply chain from a systems perspective. Warranty data in the automotive industry, focused upon a "Tier one" supplier, is analyzed to obtain general warranty trends and typical failure types. Following the data analysis and hypothesis formation, a sequential series of surveys and interviews within the supplier are conducted in attempt to determine the root causes of warranty failures. A major finding of the study is the lack of a cross-company and long-term approach for dealing with warranty. Other root causes (though not as deeply imbedded as that noted first) include the lack of design discipline, design knowledge, and resources in the product development process. In addition, unclear accountability, poor communication, and lack of a supplier management process delay the warranty resolution process. Furthermore, the culture and mindset in an organization is a critical element in effective warranty management. A reactive warranty firefighting mindset is inadequate to attack the significant warranty issues. Based upon solving the root causes found in the research, the thesis provides five specific recommendations. These recommendations appear likely to be useful to a wide variety of automotive companies as well as manufacturers in other industries.by Wei Shen and Wangquan (Winston) Cheng.S.M

Numerical Modeling Of Incomplete Combustion In A Liquid Chemical Rocket Engine

Chemical rocket engines require very accurate modeling of chemical combustion to be optimized and safely developed. One may solve for chemical equilibrium by using the thermodynamic technique of minimizing the free energy of the system subject to mass-balance constraints. This is computationally accomplished by using Lagrange multipliers to constrain the system and using Newton’s method for multivariate root finding to identify free-energy minima within the constraints. In a manner suitable for a mathematical audience loosely familiar with chemistry, we will introduce the chemical problem which produces the constrained optimization problem Gordon and McBride seek to solve. We provide an overview of the concept of Lagrange multipliers and how they are used to transform constrained optimization problems into simpler unconstrained optimization problems, for both singly- and multiply-constrained systems. Further, we build upon the familiar Newton’s method for single-variate root finding to explain how Newton’s method for multivariate rootfinding works. From these concepts and first thermodynamic principles, we derive a model of the chemical problem which may be solved by numerical methods. We present this algorithm which will solve for the equilibrium state of arbitrary incomplete combustion problems and demonstrate it as an operational Python program. We evaluate its accuracy and capability by comparing it to the algorithm of Gordon and McBride, which has been made publicly available as the program NASA Chemical Equilibrium with Applications (CEA)

Assessment Report 2012 Grupo Miguel, El Salvador AA0000000158

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.FLA_2012_Grupo_Miguel_AR_El_Salvador_AA0000000158.pdf: 20 downloads, before Oct. 1, 2020

Assessment Report 2012 Adidas Group, Guatemala AA0000000030

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.FLA_2012_AdidasGroup_AR_Guatemala_AA0000000030.pdf: 71 downloads, before Oct. 1, 2020

Assessment Report 2012 Nike, USA AA0000000017

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.FLA_2012_Nike_AR_USA_AA0000000017.pdf: 57 downloads, before Oct. 1, 2020

Assessment Report 2013 Brooklyn Mfg. Ltda. de C.V., El Salvador AA0000000308

This document is part of a digital collection provided by the Martin P. Catherwood Library, ILR School, Cornell University, pertaining to the effects of globalization on the workplace worldwide. Special emphasis is placed on labor rights, working conditions, labor market changes, and union organizing.FLA_2013_Brooklyn_Mfg_Ltda_de_CV_AR_El_Salvador_AA0000000308.pdf: 21 downloads, before Oct. 1, 2020