A generic, collaborative framework for internal constraint solving

Esta tesis propone un esquema genérico y cooperativo para CLP(Interval(X)) donde X es cualquier dominio de computación con estructura de retículo. El esquema, que está basado en la teoría de retículos, es un enfoque general para la satisfacción y op-timización de restricciones de intervalo así como para la cooperación de resolutores de intervalo definidos sobre dominios de computación con estructura de retículos, independientemente de la cardinalidad de estos. Nuestra propuesta asegura un enfoque transparente sobre el cual las restricciones, los dominios de computación y los mecanismos de propagación y cooperación, definidos entre las variables restringidas, pueden ser fácilmente especificados a nivel del usuario. La parte principal de la tesis presenta una especificación formal de este esquema.Los principales resultados conseguidos en esta tesis son los siguientes:Una comparativa global de la eficiencia y algunos aspectos de la expresividad de ocho sistemas de restricciones. Esta comparativa, realizada sobre el dominio finito y el dominio Booleano, muestra diferencias principales entre los sistemas de restricciones existentes.Para formalizar el marco de satisfacción de restricciones para CLP(Interval(X))hemos descrito el proceso global de resolución de restricciones de intervalo sobre cualquier retículo, separando claramente los procesos de propagación y división (ramificación) de intervalos. Una de las ventajas de nuestra propuesta es que la monótona de las restricciones esta implícitamente definida en la teoría. Además, declaramos un conjunto de propiedades interesantes que, bajo ciertas condiciones, son satisfechas por cualquier instancia del esquema genérico. Mas aún, mostramos que muchos sistemas de restricciones actualmente existentes satisfacen estas condiciones y, además, proporcionamos indicaciones sobre como extender el sistema mediante la especificación de otras instancias interesantes y novedosas. Nuestro esquema para CLP(Interval(X)) permite la cooperación de resolutores de manera que la información puede ⁰uir entre diferentes dominios de computación.Además, es posible combinar distintas instancias del esquema: por ejemplo, instancias bien conocidas tales como CLP(Interval(<)), CLP(Interval(Integer)),CLP(Interval(Set)), CLP(Interval(Bool)), y otras novedosas que son el resultado de la generación de nuevos dominios de computación definidos por el usuario, o incluso que surgen de la combinación de dominios ya existentes como puede ser CLP(Interval(X1 £ : : : £ Xn)). Por lo tanto, X puede ser instanciado a cualquier conjunto de dominios de computación con estructura de retículo de forma que su correspondiente instancia CLP(Interval(X)) permite una amplia flexibilidad en la definición de dominios en X (probablemente definidos por el usuario) y en la interaccion entre estos dominios.Mediante la implementacion de un prototipo, demostramos que un unico sistema,que este basado en nuestro esquema para CLP(Interval(X)), puede proporcionarsoporte para la satisfaccion y la optimizacion de restricciones as como para la cooperacion de resolutores sobre un conjunto conteniendo multiples dominios decomputacion. Ademas, el sistema sigue un novedoso enfoque transparente sujeto a una doble perspectiva ya que el usuario puede definir no solo nuevas restricciones y su mecanismo de propagacion, sino tambien nuevos dominios sobre los cuales nuevas restricciones pueden ser resueltas as como el mecanismo de cooperacion entre todos los dominios de computación (ya sean definidos por el usuario o predefinidos por el sistema).En nuestra opinión, esta tesis apunta nuevas y potenciales direcciones de investigación dentro de la comunidad de las restricciones de intervalo.Para alcanzar los resultados expuestos, hemos seguido los siguientes pasos (1) la elección de un enfoque adecuado sobre el cual construir los fundamentos teóricos de nuestro esquema genérico; (2) la construcción de un marco teórico genérico (que llamaremos el marco básico) para la propagación de restricciones de intervalo sobre cualquier retículo; (3) la integración, en el marco básico, de una técnica novedosa que facilita la cooperación de resolutores y que surge de la definición, sobre múltiples dominios, de operadores de restricciones y (4) la extensión del marco resultante para la resolución y optimización completa de las restricciones de intervalo.Finalmente presentamos clp(L), un lenguaje de programación lógica de restricciones de intervalo que posibilita la resolución de restricciones sobre cualquier conjunto de retículos y que esta implementado a partir de las ideas formalizadas en el marco teórico. Describimos una primera implementación de este lenguaje y desarrollamos algunos ejemplos de como usarla. Este prototipo demuestra que nuestro esquema para CLP(Interval(X)) puede ser implementado en un sistema único que, como consecuencia, proporciona, bajo un enfoque transparente sobre dominios y restricciones, cooperación de resolutores así como satisfacción y optimización completa de restricciones sobre diferentes dominios de computación

Flight Mechanics/Estimation Theory Symposium, 1994

This conference publication includes 41 papers and abstracts presented at the Flight Mechanics/Estimation Theory Symposium on May 17-19, 1994. Sponsored by the Flight Dynamics Division of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

The impact of the Johannesburg Stock Exchange's alternative exchange on listed firm's performance and entrepreneurship

This study’s primary objective is to determine the impact that the JSE’s AltX has on listed firm’s performance and the level of entrepreneurship in South Africa. Its secondary objective was to quantitatively determine whether there exists a link between increased capitalisation of the AltX and the expansionary drive of listed firms, as well as to ascertain the impact that the listing requirements of the AltX has on the broad-based black economic empowerment (B-BBEE) score performance of listed firms. In order to achieve the methodological objectives of this study, mixed methods was used to measure this phenomenon which led to the development of an integrated model for the JSE’s AltX listed firms, as well as for intending small and medium enterprises (SMEs) that might want to list. Accordingly, the researcher employed pragmatic research paradigm and conducted two types of analysis. Firstly, quantitative analysis which is based on primary and secondary data was conducted followed by a qualitative analysis based on a qualitative semi-structured case study. It was found that the JSE's AltX positively impacts on the performance of listed firms and the level of entrepreneurship in South Africa. Most especially as increased capitalisation levels was positively linked with the expansionary drive of these registered firms. And that the listing requirements of the AltX had a net positive effect on the B-BBEE score performance of these companies. Practically, by virtue of being listed many SMEs would generate enough capital and buzz to facilitate their expansion. This study also contributes to new knowledge by recommending that the JSE's AltX develop a custom-made business-friendly targeted listing procedure. Just as policy makers are encouraged to create a one-stop-shop investment portal which would streamline the activities of government agencies for the benefit of Small, Medium and Micro-Enterprises (SMMEs) in South Africa. The researcher proposes that future research would extend beyond South Africa, across the SADC, Africa or even across continents. Besides, a 3-level multi-level modelling (MLM) equation testing procedure was conducted to test the efficacy of firm listing, using IBM SPSS Statistics version 27 statistical software package. Quantitative analysis, comprising: quantitative analysis of primary data from survey questionnaire (investigated whether location or sector impacts on firm performance), and quantitative analysis of secondary data (determined if the number of both SMMEs and the JSE's AltX listed companies impacts on firm performance and the level of entrepreneurship in South Africa). Using participants' sample from sixty JSE's AltX listed firms who were either CEOs/directors/top management team members, and ten interviewees (i.e. for the qualitative analysis, comprising: qualitative analysis of primary data from semi-structured case study), this study's triangulated findings and conclusions became more valid and reliable. Evidence provided by the ensuing econometric analysis suggests that: Firstly, firms that are listed on the JSE’s AltX were more likely to perform better than their unlisted peers (i.e. both formal and informal SMMEs). Thus, this helped listed firms to improve their company’s performance, corporate profile, loan amount and profits, as well as assisted in securing a major investor for the firm. Besides, it was observed that the variation in the dataset occurred within sectors between the JSE's AltX variable parameters at Level 1. This positively impacted on the AltX market capitalisation, total number of employed personnel, foreign assets, as well as the total equity and liabilities of the JSE's AltX listed firms. Secondly, listing on the JSE’s AltX was found to be positively associated with the level of entrepreneurship in South Africa. There was evidence that listing boosted the level of creativity and innovation in South Africa, as well as encouraged entrepreneurial risk taking, and also increased business confidence levels. Furthermore, it was observed that the variation in the dataset occurred within sectors between the JSE's AltX variable parameters at Level 1. Likewise, the turnover, AltX market capitalisation, the total investments and loans, as well as the earnings yield of the JSE's AltX listed firms were positively linked with the level of entrepreneurship in South Africa. Thirdly, the rising share capitalisation of listed firms on the AltX was linked to an increased likelihood for company expansion. In addition, listing led to international firm exposure and industry position consolidation. However, the corporate bonds and equities sold by these listed firms on the AltX did not guaranty the long-term sustainability of their business. Also, it was observed that the variation in the dataset occurred within sectors between the JSE's AltX variable parameters at Level 1. Correspondingly, the qualitative case analysis indicated that listing on the AltX led to a high yield but with lower multiples, higher return on equity, joint ventures and acquisitions, share ownership dilution, debt reduction, more capital disbursement and risk diversification, and it also led to firm growth and economic development, which was good. Fourthly, higher compliance requirements for listing on the AltX, increased the likelihood that there would be improvements in quoted B-BBEE performance score. Equally, the implementation of good governance systems like the B-BBEE by listed firms made them more attractive to stakeholders. On the other hand, when the B-BBEE score of these listed firms becomes the regressand, listing had an undesirable effect on their value added, patents and trademarks in relation to company performance. This study therefore opens-up a new vista for examining the performance of listed firms in South Africa, which is a significant contribution to new knowledge.Business ManagementD. Phil. (Management Studies (Entrepreneurship)

ICRISAT Annual Report 1978 - 1979

This sixth Annual Report cover s research by ICRISAT for the crop year beginning 1 June 1978 and ending 31 May 1979. It includes wor k done at ICRISAT Center near Hyderabad, India, at substat ions on the campuses of agricultural universities in four dif ferent climatic regions of India, and at national and international research facilities in the nine countries of Africa, Latin America, and the Middle East where ICRISAT scientists are posted. Detailed reporting of the extensive activities of ICRISAT' s many research support units is beyond the scope of this volume, but a comprehensive coverage of ICRISAT ' score research programs is included. For easier management of material, the year's activities are, in general, reported unit by unit under individual research programs; however, it should be borne in mind that most research at . ICRISAT is highly interdisciplinary and the scientists work in teams. Their work is reported in more detail in individual program publications, which usually are available from the particular research program