e-book A Bibliographic Guide to Resources in Scientific Computing, 1945-1975

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From the beginning, however, old English-language dictionaries formed the core of the Cordell collection, and this catalog documents the comprehensive nature of these holdings. The collection aims at completeness, with every variant copy of interest included. The format of the entries consists of seven basic parts: main entry, title, publication statement, collation, notes, provenance, and references.

A subject index is provided for those interested in dictionaries for particular topics. Libraries Unlimited. Need Help? Try our Search Tips. Award Winner. Although these generalizations have been valid, it does not mean that they will always apply. It is being noticed today, for instance, that some persons in professional occupations who have been among those with the least children now seem to be favoring larger families; the same is true of some high-income groups. The trend of urban migration out to the suburbs and dormitory towns seems also to encourage larger families in these "fringe" areas.

Anticipating the numbers and characteristics of future population is very difficult. Since the planner is unable to fully foresee and therefore to predict future world social and economic conditions, he can only project what he thinks will happen to present trends in the future. He must make assumptions about the future, assumptions which may be outmoded or invalidated in a rapidly changing industrial society.

A Bibliographic Guide to Resources in Scientific Computing, 1945-1975

For the practising planner today there is another obstacle. The population analyst has generally been concerned with forecasting the future populations of whole countries, and diverse national trends tend to cancel out each other in the largeness of the figures. However, projection of population in small areas, such as county or city is a more difficult task, because an error in projection may not be balanced by another unforeseen event or influential factor, and because an error in projection may result in a variation important when compared to the small local total although not important when compared to a national total.

In addition, in- and out-migration for the local area must be projected; this is no easy task. This is especially true for populations of large cities where the major element of population change has been migration. This is also especially true of certain sections of the country — some West Coast communities have doubled or trebled their populations in less than a decade. In spite of all the obstacles, none of which can be under-estimated, and all of which seem to announce the foolhardiness of any attempt, population projections must be made expertly enough so that the planner can perform his function planning for the future population of his area.

There are two major groups of projection methods which may be labelled mathematical and analytic. The mathematical methods, used in the early attempts to project population, involve the charting of past and present population data, the determination of "trends" and the projection of these present population trends into the future. There are two types of mathematical projection: arithmetic and geometric. Arithmetic projection assumes the continuation of the amount of population change observed in what is defined as the base period, the period from which the projection is started, through successive equal intervals of time.

Arithmetic projection, since it has been employed during periods of population increase, has generally been used to show population growth in fixed amounts. For example, it may be found that City X 3 increased by 20, people every 10 years since when its population was , Using the arithmetic method of population projection, — might be assumed as a base period.

Thus 20, people would be added for every future decade.

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The population of City X would be expected to be , in the year This method has not been used often in planning reports, perhaps because it has been found in the past to under-estimate population growth. The geometric projection method has been much more popular. It looks at population changes in terms of percentage changes rather than numerical changes. For a simple comparative example, in City X the population , is 60 percent greater than that in Thus, by a simple trend projection, it would be expected to be 60 percent greater in than it was in , or , Most geometric projections are, however, plotted over decade intervals where trends are derived from analysis of the changes between decades.

In the above example, there was an increase of 20 percent in as compared to , an increase of Thus the base period for analyzing trends is as important as the method of projecting future populations, whether viewed in arithmetic or proportional terms. One method which has been used to determine the rate of geometric population growth may be described as the "let's see how other cities who were our size once grew, and average out and project their experiences for our city" method.

Another approach is to examine projections for future population of the country, or the state, which have been prepared by another agency or to directly forecast population for these larger areas and to assign a parallel proportionate population for the smaller area. For example, the present population of a state might be six million, and the city's population might be one half million, or one-twelfth of the state's total population.

A forecast might have been made indicating the state's future population would be eight million. This method would assume the city's share would be one-twelfth or roughly , persons. A major criticism of the method of deriving local figures from projected figures for larger areas is that the assumed relationship between a particular city and other cities, the nation or the state may exist, but may also vanish overnight, since no attempt has been made to discover the reasons for the relationship. Usually, comparison of actual population with that estimated via geometric projection reveals that the estimate was much too large.

A study of Oakland and Berkeley, California, done in , made two predictions for San Francisco's population in One prophesized a population of , and the other 1,, San Francisco's actual population in was , Two estimates made in for Cedar Rapids, Iowa for ranged between 74,—80, while the actual population in was only 62, A Decatur, Illinois, study expected 85, by and , people by , but in the city had only 59, On the other hand, the Master Plan for Rockland County and Ramapo, New York, had over-estimated population by only 5 percent, and a Memphis, Tennessee, study which assumed a 25 percent increase per decade, estimated its population at ,, while its population had actually climbed to , that year.

In general, however, over-estimates are more frequent.

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If only some of these almost fantastic local population forecasts made in the past were added together, the result might have anticipated a population for the United States of close to a billion. A major defect of the geometric method that of assuming a constant proportional change was supposedly eliminated by the logistic S shaped curve developed by Raymond Pearl.

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This geometric projection assumes that the percentage of growth will increase for a while, then decrease and finally in the dim future stabilize itself. A city, by analyzing its growth pattern, would simply have to find its present location on the S curve whether increasing or decreasing and then follow the type of trend Pearl and his associates worked out for New York City. The advantage in using mathematical methods is that they are easy to compute, and that they sometimes have "worked.

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The fact that these methods have sometimes been successful when used for very short periods of projection is perhaps due to the fact that this country has enjoyed a fairly stable rate of population increase. It is generally felt today that this period is coming to an end, and mathematical methods are no longer acceptable.

Perhaps the best uses to which the mathematical methods may be put are as checks on analytical methods. The second group of projection methods has been labelled "analytic," because emphasis is placed on why population numbers and characteristics change. This method involves discovery of the factors that influence present and past population increase and decrease.

On the basis of assumptions concerning the future of these factors, and of other factors that are just emerging in the community, projections of fertility, mortality and migration trends are made. The main concern, therefore, is on analysis of the factors that influence population changes rather than on determination and projection of trends.

The analytical approach is generally associated with the work of P. Whelpton and Warren S.

Thompson who used it in their estimates of future populations for the United States for the U. Bureau of the Census. From this analysis they concluded that no single estimate could be made for the year of projection ; they therefore made three separate assumptions for a high, medium and low fertility and mortality rate and added migration assumptions to these.

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A population figure for the year was computed. They then carefully plotted interpolated a population curve from the year to the year , being careful to adjust the slope of the curve or rate of change to empirical data based on their knowledge of trends. See Appendix A for illustration.


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That, briefly, is the analytic method for forecasting national populations. It is our purpose in the rest of the report, to discuss how this method can be adapted for the needs of the planner concerned with smaller local areas. This method has already been used in some cases. See the Bibliography in Appendix B. The procedure used for the analytical method, as mentioned briefly above, is threefold: 1 to study present population trends, — the rate of decrease or increase of numbers of persons; the age and sex composition of the population; the fertility, mortality and migration patterns etc.

The emphasis of the procedure is on the assumptions made, and on the factors which make these assumptions reasonable. The essence of the method is to constantly ask questions: Why do we have so many old people in our city? Will they remain?

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  8. And how will that affect the future population? Or, why has the ratio of urban and rural population in our county resembled the national figure for the last fifty years?