Knowledge that Transforms

Book Review —Jay W. Forrester, Urban Dynamics, The MIT Press, Cambridge, Mass., 1969, 285 pages, $12.50—reviewed by Walter Helly.

Book Reviews —Phillip M. Morse, Library Effectiveness: A Systems Approach, M.I.T. Press, Cambridge, Massachusetts, 1968, 207 pages, $10.00 and Jeffrey A. Raffel and Robert Shishko, Systematic Analysis of University Libraries: An Application of Cost-Benefit Analysis to the M.I.T. Libraries, M.I.T. Press, Cambridge, Massachusetts, 1969, 107 pages, $6.95—reviewed by F. F. Leimkuhler.

If every element from a source of identical particles has to perform a certain fixed success-run Markov chain with n + 2 states, and if the particles are put into the initial state one at a time, they act independently and reach the absorbing state n + 2 after n + 2 steps or they return to the source. This sequence of simultaneous success-run chains can be analysed by using a “basic” Markov chain with 2 n different states that is studied in great detail. Among others, we derive the transition matrix and the stationary distribution. It further turns out that, for m ≧ n the basic Markov chain already behaves in a stationary way , so that it is easy to find the distribution of the number of absorbed particles at a certain instant, as well as the number of particles that return to the source. The proofs of the main theorems are based on mathematical induction and matrix methods.

This paper models satellite communications systems by means of bipartite graphs. It assumes stochastic inputs and time delay is the factor of interest. The paper formulates the model and describes the routing and digital transmission schemes, assuming the network links to be synchronized. Messages may be transmitted only in the synchronized time slots, on a first-come first-served basis. The queuing problem is discussed for the single branch and for the satellite network cases, and approximate solutions are obtained for the case of satellites with finite memories.

Foreword to the issue devoted to space applications.

Book Reviews —J. W. Cohen, The Single Server Queue, Wiley-Interscience, New York, N. Y., 1969, 671 pages, $35.00—reviewed by Václav E. Beneš; —Joseph A. Panico, Queuing Theory: A Study of Waiting Lines for Business, Economics and Science. Prentice-Hall, 1969, 214 pages, $7.95—reviewed by N. U. Prabhu.

This study concerns itself with one aspect of possible post-Apollo space activity—a program of astronomical research on the moon that culminates in the establishment of a lunar observatory. A mathematical model is utilized to analyze the logistics implications of conducting such an astronomical research program. The nature of the research equipment needed for the accomplishment of the program is outlined. Superposition of this research program upon a basic, long-term, lunar-base operations plan tentatively indicates that it could be feasible to conduct such a program of research during the 1970's and 1980's well within the constraints imposed by the logistics of presently planned spacecraft, boosters, and launching facilities. In an earlier study, a mathematical model was described that can be used to evaluate various aspects of the logistics supply support of space operations. The present study utilizes this model to investigate the implications of superimposing a set of demanding scientific requirements on an existing space base support plan. First, a scenario is developed for a lunar astronomical research program in sufficient detail to fulfill the input requirements of the model. The resulting scientific requirements are described in terms of the equipment and instrumentation desired in a temporal sequence of gradually increasing demands that culminates in the establishment of an astronomical observatory on the moon. These requirements then are superimposed on a supply-support system that provides for the establishment and operation of a manned lunar base over an eight-year period. Detailed input parameters consider such aspects as capacities of launch vehicles and spacecraft, earliest and latest delivery times for various supply and scientific modules, etc. The numerical results from two computer runs determine the necessary delivery schedules and provide an indication of the logistic cost of the postulated mission. For the specific astronomical example investigated, the results indicate that a lunar astronomical research program that culminates in the construction of a lunar-based observatory is logistically feasible. Further, such an observatory with sizable equipment could be established—without any unrealistic logistic requirements—within the next decades rather than during the next century. However, these numerical results are of secondary significance at this time. The primary importance of the study is the demonstration of a technique that permits the quantitative comparison of the logistical aspects of alternative space missions where many interrelated input parameters can be examined in parametric fashion to determine the sensitivity of the system to each.

Work-measurement techniques generally are based upon the objective categorization of work activity. Several troublesome characteristics arise when applying the concept to professional people: antagonisms may develop between the observer and the professional being observed, and the importance of the qualitative aspect of the activity may say that the reason for doing something is as important as the fact that it is being done. This paper describes a project where these issues were faced in a constructive way by using subjective appraisal on the part of the professional being observed without unduly jeopardizing the principles of systematic scientific investigation.