A survey of the machine interference problem

This paper surveys the research published on the machine interference problem since the 1985 review by Stecke & Aronson. After introducing the basic model, we discuss the literature along several dimensions. We then note how research has evolved since the 1985 review, including a trend towards the modelling of stochastic (rather than deterministic) systems and the corresponding use of more advanced queuing methods for analysis. We conclude with some suggestions for areas holding particular promise for future studies.Natural Sciences and Engineering Research Council (NSERC) Discovery Grant 238294-200

Advanced electrostatic ion thruster for space propulsion

The suitability of the baseline 30 cm thruster for future space missions was examined. Preliminary design concepts for several advanced thrusters were developed to assess the potential practical difficulties of a new design. Useful methodologies were produced for assessing both planetary and earth orbit missions. Payload performance as a function of propulsion system technology level and cost sensitivity to propulsion system technology level are among the topics assessed. A 50 cm diameter thruster designed to operate with a beam voltage of about 2400 V is suggested to satisfy most of the requirements of future space missions

A systems engineering analysis of energy economy options for the DDG-51 class of U.S. Naval ships

The SECNAV has identified an ambitious set of goals for the Navy's energy programs. The authors addressed DoN energy surety, economy, and ecology goals, scoped the problem to focus on the economy aspect of the DoN's energy goal, and further bounded the analysis to energy economy of the DDG-51 class of surface combatants which appeared to be an area with potentially high return on investment. The team determined that if energy was conserved or better utilized then the triad of SECNAV goals for energy surety, economy and ecology was positively addressed. This report documents a method to assess energy consumption that could be used to make trade-offs for current and future ships. Eight subsystems, along with fuel type, were researched for alternative solutions, with eight of nine subsystem alternatives resulting as "more cost effective." By implementing the optimal recommendations from our team findings and using the fully burdened cost of fuel, we estimate that the DDG-51 program could save $1 .9M per year per ship. For a fleet of 50 ships, this translates to a savings of$9 50M over ten years.http://archive.org/details/asystemsengineer109456950Approved for public release; distribution is unlimited

Implementación de un plan de mantenimiento preventivo para mejorar la disponibilidad de bombas sumergibles Empresa EICM Engineering Group, Arequipa-2021

Para el estudio se considera como objetivo principal implementar un plan de mantenimiento preventivo para las bombas sumergibles Gorman Rupp de la empresa EICM Engineering S.A.C., con el fin de incrementar la disponibilidad de las mismas. Para lo cual esta investigación tomó un enfoque cuantitativo de alcance aplicativo y diseño pre experimental. Tomando como población y muestra las 31 bombas de tipo sumergibles con las que cuenta la empresa minera para el bombeo de aguas ácidas en su proceso de lixiviación. El instrumento de recolección de información utilizado fueron las fichas de observación. Se realizó las pruebas de hipótesis con la prueba T de student de medias relacionadas. Los resultados hallados fueron el aumento de horas de mantenimiento cumplidas de acuerdo a lo programado de 72.74% a 89.58%, y el cumplimiento de número de actividades programadas de 67.96% a 89.99%. Mejorando así la disponibilidad de las bombas de 90% a 94%, a través de una mejora de la confiabilidad de 227.33 horas a 324 horas de trabajo continuo y una disminución de la mantenibilidad de 26.44 a 21.39 horas de mantenimiento. Finalizando que, el plan de mantenimiento preventivo mejoró significativamente la disponibilidad del conjunto de bombas

Some stochastic problems in reliability and inventory

An attempt is made in this thesis to study some stochastic models of both reliability and inventory systems with reference to the following aspects: (i) the confidence limits with the introduction of common-cause failures. (ii) the Erlangian repair time distributions. (iii) the product interactions and demand interactions. (iv) the products are perishable. This thesis contains six chapters. Chaper 1 is introductory in nature and gives a review of the literature and the techniques used in the analysis of reliability systems. Chapter 2 is a study of component common-cause failure systems. Such failures may greatly reduce the reliability indices. Two models of such systems (series and parallel) have been studied in this chapter. The expressions such as, reliability, availability and expected number of repairs have been obtained. The confidence limits for the steady state availability of these two systems have also been obtained. A numerical example illustrates the results. A 100 (1 - a) % confidence limit for the steady state availability of a two unit hot and warm standby system has been studied, when the failure of an online unit is constant and the repair time of a failed unit is Erlangian. The general introduction of various inventory systems and the techniques used in the analysis of such systems have been explained in chapter 4. Chapter 5 provides two models of two component continuous review inventory systems. Here we assume that demand occurs according to a poisson process and that a demand can be satisfied only if both the components are available in inventory. Back-orders are not permitted. The two components are bought from outside suppliers and are replenished according to (s, S) policy. In model 1 we assume that the lead-time of the components follow an exponential distribution. By identifying the inventory level as a Markov process, a system of difference-differential equations at any time and the steady-state for the state of inventory level are obtained. Tn model 2 we assume that the lead-time distribution of one product is arbitrary and the other is exponential. Identifying the underlying process as a semi-regenerative process we find the stationary distribution of the inventory level. For both these models, we find out the performance measures such as the mean stationary rate of the number of lost demands, the demands satisfied and the reorders made. Numerical examples for the two models are also considered. Chaper 6 is devoted to the study of a two perishable product inventory model in which the products are substitutable. The perishable rates of product 1 and product 2 are two different constants. Demand for product 1 and product 2 follow two independent Poisson processes. For replenishment of product 1 (s, S) ordering policy is followed and the associated lead-time is arbitrary. Replenishment of product 2 is instantaneous. A demand for product 1 which occurs during its stock-out period can be substituted by product 2 with some probability. Expressions are derived for the stationary distribution of the inventor}' level by identifying the underlying stochastic process as a semi-regenerative process. An expression for the expected profit rate is obtained. A numerical illustration is provided and an optimal reordering level maximising the profit rate is also studied. To sum up, this thesis is an effort to improve the state the of art of (i) complex reliability systems and their estimation study (ii) muitiproduct inventory systems. The salient features of the thesis are: (i) Analysis of a two-component reliability system with common-cause failures. (ii) Estimation study of a complex system in which the repair time for both hot standby and warm standby systems are assumed to be Eriangian. (iii) A multi-product continuous review inventory system with product interaction, with a (s, S) policy. (iv) Introduction of the concept of substitutability for products. (v) Derivation of expressions for various statistical measures. (vi) Effective use of the regeneration point technique in deriving various measures for both reliability and inventory systems. (vii) Illustration of the various results by extensive numerical work. (vii) Consideration of relevant optimization problems.Mathematical SciencesPhD (Statistics

Reliability Abstracts and Technical Reviews January-December 1967

No abstract availabl

Cumulative index to NASA Tech Briefs, 1963-1967

Cumulative index to NASA survey on technology utilization of aerospace research outpu

Research reports: The 1980 NASA/ASEE Summer Faculty Fellowship Program

The Summer Faculty Fellowship Research Program objectives are: to further the professional knowledge of qualified engineering and science faculty members; to stimulate an exchange of ideas between participants and NASA; to enrich and refresh the research and teaching activities of participants and institutions; and to contribute to the research objectives at the NASA centers. The Faculty Fellows engaged in research projects commensurate with their interests and background and worked in collaboration with a NASA/MSFC colleague

Human Factors Certification of Advanced Aviation Technologies

Proceedings of the Human Factors Certification of Advanced Aviation Technologies Conference held at the Chateau de Bonas, near Toulouse, France, 19-23 July 1993