Brass alloy blending problem from quality and cost perspectives: A multi-objective optimization approach

WOS:000595657400032Brass alloy is a composition of copper and zinc and it also includes lead, iron, tin, aluminum, nickel, antimony if necessary. One of the basic problems in brass casting is to determine which pure and scrap materials will be mixed at what quantities; this problem is known as the blending problem. The ingredient ratios of pure materials are exactly known, however they are expensive. The scrap materials are cheaper than the pure ones with varying ingredient ratios. Stochastic mathematical models aiming to minimize blend cost have been developed in the literature. In the solutions of these models, some of the ingredient ratios exactly equal to the specification limits. Because of the variation, some of them may violate the specification limits and cause quality problems in the actual blends. There is only one study in the literature to solve the quality problem by maximizing the process capability index. However, the blend cost increases when the process capability index maximized. In this study, a multiobjective stochastic mathematical model, which aims both to minimize blend cost and to maximize process capability index, has been developed. The developed model has been converted to a deterministic non-linear counterpart by using chance-constrained programming. Then, fuzzy programming is used to transform the multiobjective model into a single objective one. A solution procedure has been proposed to use it effectively in real life applications. The developed model and solution procedure have been tested by the data supplied from a brass factory. The solution of the numerical example has shown that the developed model and solution procedure can be used successfully in real life applications

Energy efficiency for reducing carbon footprint in historic buildings: Comparing case in the UK and Malaysia

Climate changes seem to be one of the controversial conflicts for people in today's world and reducing carbon dioxide emissions, which are one of the main reasons for climate changes, will be an appropriate solution for this alien. Buildings are one of the main resources for producing carbon dioxide emissions. For instance, around 40 percent of all carbon dioxide emission in the UK comes from buildings and so buildings especially heritage buildings need to improve their performance to contribute carbon reduction. The main aim of this research is to identify some acceptable and convenient ways for reducing carbon dioxide emissions in heritage buildings for controlling climate changes to some extent. In this paper, a desktop study was conducted to review the techniques and technologies to help us for reducing carbon dioxide emissions in heritage buildings. In this paper, the importance of heritage buildings and their elements such as wall, roof, window, door, floor has discussed and the main reasons for increasing energy consumption and carbon dioxide emissions have mentioned. In continuing, principles, risks, materials, methods, techniques and technologies for controlling energy loss of historic building elements have expressed. The results indicate that manufactured and transport of building materials will produce a large amount of carbon emissions and so the continued use of historic and heritage buildings can be an accommodative solution for this issue. For instance, in England in 2000 these processes accounted for more than 10 percent of the UK carbon dioxide emissions. It proves that conservation of heritage buildings is important not only for significant value of these buildings, but also for reduction of carbon dioxide emissions. All the methods, techniques and technologies which have discussed in this paper are correspondent solution for the goal of reduction carbon dioxide emissions that produce through the life-cycle of historic buildings

A decision support system for income-producing real estate development feasibility analysis and alternative assessment

The purpose of this study is to design, develop, and evaluate a prototype scenarioassisted decision support system (DSS) for use in venture and alternative assessment during the predevelopment stage of income-producing real estate development. This research examines theoretical underpinnings and associated advancements related to income-producing real estate development and decision support systems. Particular emphasis was placed on synthesis of relating disciplines?? models and advancements that support design and development of the decision support system. The result of the system design and development are embodied in a prototype scenario-assisted decision support system for income-producing real estate development (DSSVenture). The design and development of the program are documented in this dissertation. Following the design and development stage, the validation of DSSVenture??s data and logic models was conducted based on two case studies from well-known real estate development publications. The system was then tested on a group of graduate students who enrolled in an advanced real estate development course at Texas A&M University to examine whether its facilitation objective had been achieved. Since this research hypothesized that the decision support system would facilitate developers?? decision making during predevelopment stage of income-producing real estate development, three operational variables were tested, namely number of alternatives examined, time to reach decisions, and coefficient of projected net present value variations. The testing results indicate that DSSVenture system significantly enhances comprehensiveness of the decision context by increasing the number of alternatives for developers. Since the use of the system significantly reduces developers?? time to reach decisions, the efficiency of decision making is improved. Finally, the results of the study confirm that the use of DSSVenture system substantially diminishes variation of profit projection among decision makers. Therefore, the facilitation objective is achieved

Aplicación de un modelo de programación lineal para la minimización del costo de uso de ingredientes en una planta de fundición de estaño

El trabajo de investigación desarrollado se centra en construir un modelo matemático que conduzca la minimización general del costo de uso de ingredientes de una empresa de fundición de estaño, de manera que permita una administración eficiente de recursos durante un horizonte de planificación determinado. Para la realización de la tesis, se ha tomado como modelo genérico el propuesto por Kim y Lewis (1987), el cual fue adaptado a la realidad presentada, y, como fuente principal, la guía proporcionada por la misma empresa, así como información para poder trabajar con el modelo matemático. En cuanto a la problemática que sustenta el presente trabajo de investigación, se tiene que proviene de la dolencia de las técnicas de programación de producción en fundición actuales, las cuales no toman en cuenta el efecto que puede tener el trabajo en un lote sobre el trabajo en otro lote, lo cual, como consecuencia, no permite la mejor toma de decisiones para el largo plazo. Es así que la propuesta de mejora se compuso de un modelo matemático que permite la gestión de recursos y hace frente al aspecto señalado en el párrafo anterior. Luego de diseñar el modelo matemático y ejecutarlo, tras confrontar los resultados económicos conseguidos con los resultados de las operaciones actuales, se identifica un ahorro a favor de S/.3,314,964.22 anuales; además, se alcanza el mismo objetivo de producción de estaño con una menor cantidad de toneladas de carga total (un ahorro de 23% en el uso del horno); y, finalmente, el contenido de contaminantes para el metal crudo según la combinación de ingredientes de nuestro modelo matemático es menor, lo cual implicaría menores costos por concepto de menor uso de ingredientes químicos, menor energía involucrada, y menor tiempo de procesamiento para la remoción de contaminantes en la etapa siguiente, relacionada con la refinación. Es importante indicar que, para adaptaciones del modelo matemático en otras aplicaciones, y para obtener el mejor aprovechamiento del mismo, es indispensable contar con la participación del Gerente de área, quien deberá desplegar en detalle las formulaciones matemáticas y adaptarlas según el proceso particular que se realice, de acuerdo con su experiencia, para conseguir los mejores resultados.Tesi

Computer aided decision support system for the selection of subcontractors in building refurbishment works

Ph.DDOCTOR OF PHILOSOPH

Sistema de informação para a avaliação e monitorização da qualidade de vida em campi universitários

Doutoramento em Engenharia Civil, ramo de Planeamento TerritorialApós um período de crescimento continuado no que concerne a instalações, é agora consensual que as Universidades portuguesas caminham para um ciclo de estabilização e consolidação. Por não se vislumbrar grande sentido em aumentar a oferta face à procura, deverá nascer um processo onde o acréscimo de dimensão deverá dar lugar ao acréscimo de qualidade. A qualidade dos projectos de ensino e investigação passa também pela qualidade dos espaços onde estes se desenvolvem, quer sejam os edifícios, quer sejam os espaços exteriores dos campi. Os utentes, sejam estudantes, docentes, funcionários ou visitantes, para além das necessidades óbvias associadas à sua actividade específica, aspiram a um ambiente saudável, seguro, a níveis de mobilidade e acessibilidade aceitáveis, etc. Em suma, aspiram a um campus com qualidade de vida. Por outro lado, assume-se que os campi universitários podem ser equiparados a espaços urbanos. Este pressuposto advém das características, forma, dimensão e organização que estes assumem. Esta faceta de cariz urbano é muitas vezes realçada pela sua localização, situando-se em zonas urbanas ou, por vezes, inserindo-se como parte integrante da cidade. Neste enquadramento, o presente trabalho apresenta um modelo de avaliação da qualidade de vida em campi universitários que se baseia em abordagens para espaços urbanos. Os seus aspectos essenciais são implementados no sentido de poder conduzir à construção de um sistema de informação que permita acompanhar a evolução da qualidade de vida, bem como avaliar intervenções futuras através da elaboração de cenários. Para além da descrição da estrutura global, são igualmente alvo de atenção a forma de guardar os dados, a inclusão de modelos, a interface com o utilizador e a disponibilização de nova informação. Como aplicação prática, foi desenvolvido um sistema de informação para o Campus de Gualtar da Universidade do Minho. Este sistema opera em duas vertentes: uma informativa, aberta a toda comunidade, permitindo a qualquer utilizador vislumbrar qual a evolução da qualidade de vida no campus; e outra de apoio à decisão, principalmente no planeamento e gestão das infra-estruturas, apelando à participação da comunidade universitária através de avaliações individuais de forma a gerar avaliações globais.Nowadays, after a continuous growing of edifications, there is a consensus about the fact that Portuguese Universities are incoming in a cycle of stabilization and consolidation. Since the demand tends to be satisfied, a new process shall emerge where the physical expansion will be substituted by a quality increase. Teaching and research activities quality in Universities are somehow related to the quality of the spaces where they take place, either when considering the buildings facilities, either when taking into consideration the campus landscape. The University Campus users, besides the obvious needs associated to their specific activities, aspire to an healthy and secure environment with appropriated and well located facilities, good mobility and accessibility levels, etc. So, they aspire to a University Campus with quality of life. Due to their characteristics, form, dimension and organization, university campi are considered as urban spaces. This aspect is often enhanced by its location in urban areas or even merged in the city. In this context, a model for the evaluation of the quality of life based on concepts for urban spaces is proposed. Its essential aspects are discussed with the aim to produce an information system as a tool to evaluate the quality of life evolution and to assess future interventions using scenarios. The idealized global structure, the way that data can be kept, the inclusion of models, the user interface importance and the presentation of new information are focused. As a case study, an information system was developed for the Gualtar Campus of the University of Minho, located in Braga, Portugal. The system embodies two main functions: to inform, allowing any user to know how has evolved the quality of life on campus; to be a decision support tool, mainly in facilities planning and management, taking advantages of users participation through individual evaluations for the production of global evaluations