A review of physics-based models in prognostics: application to gears and bearings of rotating machinery

Health condition monitoring for rotating machinery has been developed for many years due to its potential to reduce the cost of the maintenance operations and increase availability. Covering aspects include sensors, signal processing, health assessment and decision-making. This article focuses on prognostics based on physics-based models. While the majority of the research in health condition monitoring focuses on data-driven techniques, physics-based techniques are particularly important if accuracy is a critical factor and testing is restricted. Moreover, the benefits of both approaches can be combined when data-driven and physics-based techniques are integrated. This article reviews the concept of physics-based models for prognostics. An overview of common failure modes of rotating machinery is provided along with the most relevant degradation mechanisms. The models available to represent these degradation mechanisms and their application for prognostics are discussed. Models that have not been applied to health condition monitoring, for example, wear due to metal–metal contact in hydrodynamic bearings, are also included due to its potential for health condition monitoring. The main contribution of this article is the identification of potential physics-based models for prognostics in rotating machinery

A taxonomy for emergency service station location problem

The emergency service station (ESS) location problem has been widely studied in the literature since 1970s. There has been a growing interest in the subject especially after 1990s. Various models with different objective functions and constraints have been proposed in the academic literature and efficient solution techniques have been developed to provide good solutions in reasonable times. However, there is not any study that systematically classifies different problem types and methodologies to address them. This paper presents a taxonomic framework for the ESS location problem using an operations research perspective. In this framework, we basically consider the type of the emergency, the objective function, constraints, model assumptions, modeling, and solution techniques. We also analyze a variety of papers related to the literature in order to demonstrate the effectiveness of the taxonomy and to get insights for possible research directions

ADVANCES IN DECISION ANALYSIS. EFFICIENT METHODS IN FINANCE

Decision analysis offer workable solutions in domain such as the environment, health and medicine, engineering and operations research and finance. In finance area we can observe a big variety of method and techniques for research fluctuates from economy and financial date. Most economic decisions are related to monetary variables. Since money has a capacity to connect the present and the future, conflicts among long�run and short�run economic goals and uncertainties of the future make economic decisions very complicated. In this paper we will introduce some models to show how monetary variables can be investigated real aspects of economic development. We discusses problems encountered in financial models, describes efficient method and show how to apply them to practical problems in financedecision analysis, mathematical modeling, dynamic models, money

Fast reliable interrogation of procedurally defined implicit surfaces using extended revised affine arithmetic.

Techniques based on interval and previous termaffine arithmetic next term and their modifications are shown to provide previous term reliable next term function range evaluation for the purposes of previous termsurface interrogation.next term In this paper we present a technique for the previous termreliable interrogation of implicit surfacesnext term using a modification of previous termaffine arithmeticnext term called previous term revised affine arithmetic.next term We extend the range of functions presented in previous termrevised affine arithmeticnext term by introducing previous termaffinenext term operations for arbitrary functions such as set-theoretic operations with R-functions, blending and conditional operators. The obtained previous termaffinenext term forms of arbitrary functions provide previous termfasternext term and tighter function range evaluation. Several case studies for operations using previous termaffinenext term forms are presented. The proposed techniques for previous termsurface interrogationnext term are tested using ray-previous termsurfacenext term intersection for ray-tracing and spatial cell enumeration for polygonisation. These applications with our extensions provide previous termfast and reliablenext term rendering of a wide range of arbitrary previous termprocedurally defined implicit surfacesnext term (including polynomial previous termsurfaces,next term constructive solids, pseudo-random objects, previous termprocedurally definednext term microstructures, and others). We compare the function range evaluation technique based on previous termextended revised affine arithmeticnext term with other previous termreliablenext term techniques based on interval and previous termaffine arithmeticnext term to show that our technique provides the previous termfastestnext term and tightest function range evaluation for previous termfast and reliable interrogation of procedurally defined implicit surfaces.next term Research Highlights The main contributions of this paper are as follows. ► The widening of the scope of previous termreliablenext term ray-tracing and spatial enumeration algorithms for previous termsurfacesnext term ranging from algebraic previous termsurfaces (definednext term by polynomials) to general previous termimplicit surfaces (definednext term by function evaluation procedures involving both previous termaffinenext term and non-previous termaffinenext term operations based on previous termrevised affine arithmetic)next term. ► The introduction of a technique for representing procedural models using special previous termaffinenext term forms (illustrated by case studies of previous termaffinenext term forms for set-theoretic operations in the form of R-functions, blending operations and conditional operations). ► The detailed derivation of special previous termaffinenext term forms for arbitrary operators

The cultural models in international business research: A bibliometric study of IB journals

Culture has been a widely researched topic in the International Business (IB) literature over the last decades. To better understand what culture actually means and its implication in firms? IB operations, several cultural models and taxonomies have been put forward. In this paper we seek to scrutinize the use of three well known cultural models - Hall?s (1976), Hofstede?s (1980a) and Trompenaars & Hampden-Turner?s (1993) - in the extant research. Using bibliometric techniques of the papers published in the top ranked IB journals, we performed a citation and co-citation analysis to find out the most influential model and to examine the possible linkages between models and to the issues being researched. We conclude that Hofstede?s (1980a) taxonomy is the most cited and his taxonomy has strong linkages to several streams of research. Nonetheless, we also find that there are noticeable differences on how research in different journals make use of the cultural models, probably reflecting not surprising disciplinary emphases.Cultural models, Hofstede, Trompenaars, Hall, bibliometric study

APPLICATION OF OPERATION RESEARCH TECHNIQUES AND THEIR EFFECTS ON FIRMS PERFORMANCE A STUDY OF MAY & BAKER PLC AND DE UNITED FOODS INDUTRIES LIMITED (DUFIL) OTA, OGUN STATE, NIGERIA

Application of Operations Research (OR) techniques is traceable to the era of the Second World War II. It has since then been found applicable in different works of life. In the light of the current economic downturn, Operation Research techniques has become more relevant and useful for business activities. The primary purpose of this study is to explore the applicability of Operation Research techniques as competitive tools for business performance in manufacturing firms. This study adopted a descriptive research design and draws its strength from Operation Research theories such as Linear Programming, Transportation Problem, Markov Chain, Game Theory, Queue Model as well as Forecasting Models. The population of the study was 550 as a result, the sample size determined is 220. A well-structured, self-administered questionnaire was used as the main tool for data collection and was administered to 220 respondents out of which 187 were retrieved and appropriately filled. The reliability of the research instrument was calculated and the value of the Cronbach Alpha test is greater than 0.7 thereby making the instrument reliable. Data were analyzed using the regression analysis and findings revealed that majority agreed to the claim that manufacturing firms apply OR techniques in their operations. The study concluded that OR techniques are significant tools for improving firm’s performance. Finally, this study is an academic springboard for other related studies in the field of Operations Research and recommends that operations research techniques should be employed by firms for optimization of business performance

Strategic Location and Dispatch Management of Assets in a Military Medical Evacuation Enterprise

This dissertation considers the importance of optimizing deployed military medical evacuation (MEDEVAC) systems and utilizes operations research techniques to develop models that allow military medical planners to analyze different strategies regarding the management of MEDEVAC assets in a deployed environment. For optimization models relating to selected subproblems of the MEDEVAC enterprise, the work herein leverages integer programming, multi-objective optimization, Markov decision processes, approximate dynamic programming, and machine learning, as appropriate, to identify relevant insights for aerial MEDEVAC operations

Environmental Impact Assessment, on the Operation of Conventional and More Electric Large Commercial Aircraft

Global aviation is growing exponentially and there is a great emphasis on trajectory optimization to reduce the overall environmental impact caused by aircraft. Many optimization techniques exist and are being studied for this purpose. The CLEAN SKY Joint Technology Initiative for aeronautics and Air transport, a European research activity run under the Seventh Framework program, is a collaborative initiative involving industry, research organizations and academia to introduce novel technologies to improve the environmental impact of aviation. As part of the overall research activities, "green" aircraft trajectories are addressed in the Systems for Green Operations (SGO) Integrated Technology Demonstrator. This paper studies the impact of large commercial aircraft trajectories optimized for different objectives applied to the on board systems. It establishes integrated systems models for both conventional and more electric secondary power systems and studies the impact of fuel, noise, time and emissions optimized trajectories on each configuration. It shows the significant change in the fuel burn due to systems operation and builds up the case as to why a detailed aircraft systems model is required within the optimization loop. Typically, the objective in trajectory optimization is to improve the mission performance of an aircraft or reduce the environmental impact. Hence parameters such as time, fuel burn, emissions and noise are key optimization objectives. In most instances, trajectory optimization is achieved by using models that represent such parameters. For example aircraft dynamics models to describe the flight performance, engine models to calculate the fuel burn, emissions and noise impact, etc. Such techniques have proved to achieve the necessary level of accuracy in trajectory optimization. This research enhances previous techniques by adding in the effect of systems power in the optimization process. A comparison is also made between conventional power systems and more electric architectures. In the conventional architecture, the environmental control system and the ice protection system are powered by engine bleed air while actuators and electrics are powered by engine shaft power off-takes. In the more electric architecture, bleed off take is eliminated and the environmental control system and ice protection system are also powered electrically through engine shaft power off takes