摘要:

AbstractPathbreaking logistics research over the next 10 years will focus on systems problems. Whereas past research generally has taken a “bottom‐up” approach, future investigations are likely to pursue a “top‐down” philosophy. Specifically, attention will concentrate on diagnosis of systems' improvement potentials; easy‐to‐use analytic approaches, inherently approximative, will be devised for quickly ascertaining whether a complex operating system can be substantially and effectively improved. Theories to assist in overall systems design, particularly the setting of boundaries and buffers among systems components, will be developed. At the same time, techniques for accurately forecasting future systems performance will be investigated.Underlying such research will be efforts to gain better understanding of management information requirements, including approaches for monitoring systems performance and providing early warning detection of systems degradation Improved management information systems will have to be coupled with appropriate design of managerial organizations and assignment of decision making responsibilities. Important avenues of research will he development of robust approaches, that is, both mathematical techniques and organizational approaches that are not too adversely affected by limited data, a changing environment, and human frailly.Finally, critical research will be directed at the implementation process, especially the interaction among initiation, design, testing and ultimate adoptionThis prognosis will explore the above themes in the context of large‐scale, complex systems. The decision areas will encompass inventory replenishment, multiechelon hierarchies for stockage and maintenance, procurement, transportation, scheduling, facilities planning, budgeting, reliability and per

ISSN:0028-1441    

DOI:10.1002/nav.3800260302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractTotal time on test (TTT) plots provide a useful graphical method for tentative identification of failure distribution models. Identification is based on properties of the TTT transform. New properties of the TTT transform distribution are obtained. These results are useful to the user of TTT plots. Although IFR (DFR) distributions are particularly easy to identify from TTT plots, the user must exercise caution relative to identification of IFR A (DFRA) distributions.

ISSN:0028-1441    

DOI:10.1002/nav.3800260303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractA simple and relatively efficient method for simulating one‐dimensional and two‐dimensional nonhomogeneous Poisson processes is presented The method is applicable for any rate function and is based on controlled deletion of points in a Poisson process whose rate function dominates the given rate function In its simplest implementation, the method obviates the need for numerical integration of the rate function, for ordering of points, and for generation of Poisson varia

ISSN:0028-1441    

DOI:10.1002/nav.3800260304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThis paper characterizes the structure of optimal strategies for a replacement problem for two special cases of observation quality. It is shown that when the state of the system is either completely observed or completely unobserved at every decision epoch by the controller, reasonable assumptions are sufficient for the existence of optimal replacement strategies composed of policies having a generalized, control‐limit form. These structural results are of particular interest since the optimal cost functions for the two special cases represent bounds on the optimal cost function for the general partially observed case, significant computational simplification can result for the two special cases due to their optimal strategy structure, and optimal strategies possessing a control‐limit structure do not necessarily exist for the general partially observed c

ISSN:0028-1441    

DOI:10.1002/nav.3800260305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe present paper presents an algorithm for the exact determination of survival distributions in crossing mine fields. The model under consideration considers clusters of mines, scattered at random in the field around specified aim points. The scatter distributions of the various clusters are assumed to be known The encounter process allows for a possible detection and destruction of the mines, for inactivation of the mines and for the possibility that an activated mine will not destroy the object. Recursive formulae for the determination of the survival probabilities of each object (tank) in a column ofncrossing at the same path are given. The distribution of the number of survivors out ofnobjects in a column is also determined. Numerical examples are given.

ISSN:0028-1441    

DOI:10.1002/nav.3800260306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractFor eachn.,X1(n),X2(n), …,Xn(n) are IID, with common pdffn(x).y1(n)<…

ISSN:0028-1441    

DOI:10.1002/nav.3800260307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThis exposition presents two algorithms for linear programs which allow a value change in more than one nonbasic variable at each iteration. The computational formulae are developed and errors which have appeared in the literature are noted. One algorithm is a multiple basis exchange procedure while the second is a feasible direction method. There remain many computational challenges in the area of linear programming and we hope that this investigation will encourage additional work in the directions indicated in this exposition.

ISSN:0028-1441    

DOI:10.1002/nav.3800260308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractA process control scheme is developed in which decisions as to the frequency of sampling are made based upon the choice of an Average Outgoing Quality Limit. The scheme utilizes plotted points on a U‐control chart for defects and the theory of runs to determine when to switch among Reduced, Normal, Tightened, and 100 percent inspection. The scheme is formulated as a semi‐Markov process to derive steady stale equations for the probabilities of being in Reduced, Normal, Tightened, or 100 percent inspection and for Average Outgoing Quality and Average Fraction Inspected. The resulting system and the computer programs used to derive it are discus

ISSN:0028-1441    

DOI:10.1002/nav.3800260309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThis paper considers a single server queueing system that alternates stochastically between two states: operational and failed. When operational, the system functions as anM/Ek/1 queue. When the system is failed, no service takes place but customers continue to arrive according to a Poisson process; however, the arrival rate is different from that when the system is operational. The durations of the operating and failed periods are exponential with mean 1/cβ and Erlang with mean 1/cβ, respectively. Generating functions are used to derive the steady‐state quantitiesLandW, both of which, when viewed as functions ofc, decrease at a rate inversely proportional to c2. The paper includes an analysis of several special and extreme cases and an application to a production‐storage s

ISSN:0028-1441    

DOI:10.1002/nav.3800260310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY

摘要:

AbstractThe determination of steady‐state characteristics in systems of tandem queues has been left to computer simulation because of the lack of exact solutions in all but the simplest newtorks. In this paper, several methods developed for approximating the average waiting time in single‐server queues are extended to systems of queues in series. Three methods, due to Fraker, Page, and Marchal, are compared along with results gathered through GPSS simulation. Various queueing networks with Erlangian service distributions are investiga

ISSN:0028-1441    

DOI:10.1002/nav.3800260311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1979

数据来源: WILEY