渐开线齿轮齿廓的简便绘制

介绍了利用电子图板(EB)快速绘制齿轮齿廓的简便方法,该绘制方法充分利用了电子图板的公式曲线功能,使比较困难的手工绘制变得简单、实用,解决了传统手工绘制误差较大、精度不高的问题。利用此方法还可进行给出齿廓公式的各种齿廓曲线的绘制,如圆弧齿廓、摆线齿廓等。     

An Optimal Strategy for Capacity Expansion

A mathematical model is developed for determining the optimal sequence of expansions for a processing industry. The demand for the output is increasing over time at a geometric rate. The economic objective is minimization of the present worth of the total system cost to meet this growing demand. The cost includes the expenditure for development and operation of local plants and the cost of importing products when the supply from these plants is not adequate to meet the demand.

For illustrative purposes the model is applied to find the expansion strategy for the primary aluminum industry in Argentina.     

On The Park-Thuesen Index and the Value of Earlier Uncertainty Resolution

In practice, engineering economic analysis involves uncertainty about future cash flows. To deal quantitatively with imprecision or uncertainty, fuzzy set theory is primarily concerned with vagueness in human thoughts and perceptions. As an alternative to conventional cash flow models where cash flows are defined as either crisp numbers or risky probability distributions, we propose an engineering economic decision model in which the uncertain cash flows and discount rates are specified as triangular fuzzy numbers. The present worth formulation of this fuzzy cash flow model is derived. The result of the present worth is also a fuzzy number with nonlinear membership function. The present worth can be approximated by a triangular fuzzy number. Deviation between exact present worth and its approximate form is examined. Finally, the fuzzy project selection is performed by applying different dominance rules. To demonstrate the application of the fuzzy present worth function, a comprehensive numerical example is presented.     

A Comprehensive Comparison and Critique of Discounting Indices Proposed For Capital Investment Evaluation

In the traditional literature of engineering and managerial economics, a variety of different and not generally consistent indices have been proposed for deciding whether a given capital investment project should be undertaken. Using mathematical programming, it is shown herein that in an unconstrained situation under certainty, with complete freedom to borrow or lend at one rate of interest, the present worth index and its equivalents are correct while indices inconsistent with present worth are wrong. However, in the presence of further constraints, e.g., on allowed borrowing or on available scarce material, even the present worth index is unsatisfactory, and, in general, a complete mathematical programming solution is required.     

AN EXCESS INVENTORY MODEL OF DETERIORATING ITEMS TAKING ACCOUNT OF PRESENT VALUE

In this study, both deterioration and present value are considered to derive an economic time supply when there is excess inventory. An excess inventory model is developed for a deterministic perpetual inventory system. Our goal in this research is to maximize the net benefit during the infinite planning horizon. Numerical examples are provided lo illustrate the theory, ft is demonstrated that the percentage of extra net benefit when present value is considered is at least 24%. The percentage of the extra net benefit when deterioration is considered is over 16%. When both present value and deterioration are considered, the net benefit increase is over 50%. Thus the consideration of present value and deterioration is significant.     

天然气甲烷值的计算方法及其标准化

天然气用作发动机燃料时，其抗爆性是一项重要指标。目前国外表示天然气抗爆性的方法甚多，但广泛应用的只有两个方法，即甲烷值(MN)法和辛烷值(MON)法。两者均以天然气的组成为计算依据，故相互间可建立换算的关联式。根据国内外的研究现状，提出了天然气甲烷值计算方法标准化的建议。     

Land Leverage: Decomposing Home Price Dynamics

This article demonstrates the importance of separating the bundled good of housing into land and improvements, arguing that changes in a property's overall value will depend critically on how much of its total value is contained in the land, a proportion we call land leverage. The importance of this deconstruction is demonstrated by highlighting how land leverage helps to explain variation in house price appreciation in Wichita, Kansas. Noting that land leverage should be relevant for many real estate issues and policies, we highlight four specific areas where consideration of land leverage could significantly improve our understanding of real estate markets.

Land is the only thing in the world that amounts to anything … for 'tis the only thing in this world that lasts, and don't you be forgetting it!'Tis the only thing worth working for, worth fighting for—worth dying for.
Gerald O'Hara in Gone with the Wind ¹

     

THE CUTOFF BENEFIT-COST RATIO SHOULD EXCEED ONE

The engineering economics textbook rule of accepting all projects with a benefit-cost ratio in excess of one worth fails to consider the bias introduced from there being typically more poor projects than good projects. Bayesian statistics provides an analytical solution to the problem of combining prior information with an engineer's estimates. With all distributions normal, the posterior mean (to be used for decision making) becomes a weighted average of the prior mean, and the mean derived from the engineer's estimates, A simple formula provides the optimal cut-off benefit-cost ratio. This value typically exceeds the textbook's unity cut-off benefit-cost ratio.     

A Review of: “ECONOMIC ANALYSIS FOR HIGHWAYS” By Robley Winfrey International Textbook Company 1969 923pp. $17.50

Five of the seven factors in most common use for compound interest calculations involve a uniform series of payments (or receipts). These interest factors, for use when interest is compounded at discrete points in time, are commonly referred to as the uniform series present worth factor, the uniform series compound amount factor, the capital recovery factor, the sinking fund factor and the uniform series gradient conversion factor. The proper use of these five factors requires that the period of time between the compoundings of interest coincide with the period of time between the uniform payments. If the interest is compounded more frequently (assume by an integer number of times) than the payments, then the best way to apply the compound interest factors is to determine the effective interest rate between payments. If interest is compounded less frequently than the payments (assume there are an integer number of payment periods within each compounding period), the correct solution procedure is not well known. Three methods are discussed for solving problems when interest is compounded less frequently than payments are made. It is argued that the method proposed in this note is better than the other two methods in popular use from both a theoretical and practical standpoint.     

The limitations of market-based regulation of the electronic communications sector

The European Union has recently implemented a system of regulation for the sector based on principles of competition law. The regulatory framework includes 18 markets where Regulatory Authorities should consider imposing ex ante obligations on dominant players. The paper explores the economic methodology being employed in particular to define market boundaries and concludes that the sector is too unstable for this approach to provide predictability and encourage long-term investment. In particular, emerging infrastructures and services can easily be captured while legacy networks remain subject to perpetual regulation. There are significant costs of excessive regulation and alternative approaches may be better.     

A Review of: “Risk Assessment and Decision Making in Business and Industry: A Practical Guide” By Glenn Roller CRC Press,Boca Raton,Florida, 1999, 239 pp. ISBN 0-8493-0268-4. List: $31.96”

The article surveys contributions to the literature covering the field of probabilistic discounted cash flow (DCF) analysis of individual capital investments from the earliest contributions of the 1960s to today. Such analysis includes the methods of present worth (net present value), annual worth, future worth, internal rate of return, payback period, and benefit:cost ratio. The history and development of the probabilistic case is traced, listing the main assumptions made and any restrictions to applications. The survey will be found useful by those engaged in risk management and decisions associated with investments and budgeting having uncertain outcomes.     

Strategies for deveIopment projects: an empirical study*

This paper summarizes results from a study of strategy choices and outcomes in one government laboratory over a fifteen-year time period. Several considerations associated with the effectiveness of a parallel strategy are presented and discussed. These include different types of uncertainty encountered in a given problem and their effect on the rate of learning. Contrary to observations in other studies, the present results suggest that the rate of learning is often slow and may not be facilitated by the use of many parallel approaches in only early project stages. In many instances major uncertainties are not reduced until the product is evaluated in the operational environment.     

NOTE ON “EQUIVALENCE OF CASH FLOWS WHEN COMPOUNDING OCCURS LESS FREQUENTLY THAN THE CASH FLOWS”

The present worth (PW) and future worth (FW) decision criteria are to be found in virtually all current engineering economy textbooks. Although the relationships between the internal rate of return (IRR) criterion and PW has been widely discussed in the literature, there remains some misunderstanding as to similar relationships between PW and FW. Of particular importance is the interest rates at which PW and FW are maximized. It is shown here that the maximizing rates are not necessarily equal. This leads to the seemingly peculiar result that a change in the discount rate may decrease the PW while at the same time increasing the FW, or vice versa. Numerical, mathematical and intuitive arguments are presented.     

Why drug prices will go lower

The industry's days of gargantuan earnings are gone forever. Why? Managed-care outfits are demanding price breaks, and generics are proving tough competitors.     

Project Balances as Division Coefficients and Implications for Rate of Return Analysis

Project balances are shown to be the coefficients resulting from division of the future worth polynomial by a simple monomial and are used in representations of the future worth polynomial and its derivative. Those representations are used to provide elementary proofs for some rate of return analysis results making use of our project balance framework. We develop a convenient method to determine the existence of a root of multiplicity from the derivative of the future worth polynomial using project balances. This article incorporates a useful, unified collection of results that previously have been dispersed throughout the literature that should be of interest to technical economic analysts.     

Some evidence on the accuracy of forecasts in R & D projects

In recent years many formal attempts, e.g. Baker & Pound, (1964), have been made to help R & D management assess the worth of R & D projects and select those most worthy of inclusion in the R & D programme. Most of these attempts are based on financial appraisals of a project's worth and require estimates of the costs and likely revenues that will result from the adoption of a given project. It is clear, therefore, that the validity of any measure of a worth for a project is dependent upon the accuracy of the estimates of cost and revenue associated with that project. Unfortunately the limited amount of evidence so far presented suggests, in particular, that cost estimates are extremely inaccurate.
In this paper, therefore, we try to add some further evidence on forecast accuracy for a number of industrial R & D projects. We begin with a short review of the existing literature evidence and continue with an analysis of the past effectiveness of R & D work and, in particular, of forecast accuracy.     

A Comparison of Fuzzy Set and Probabilistic Paradigms for Ranking Vague Economic Investment Information Using a Present Worth Criterion

This article introduces an approach for comparing the fuzzy set and probabilistic paradigms for ranking vague economic investment information when a present worth criterion is used. Comparisons are made between the two paradigms by forming a ratio of fuzzy ranking value to probabilistic ranking value for a set of tested economic decision conditions (vague cash flows and interest rates). A multivariable analysis of the comparison ratios indicates the dominance or spread required in the expected present worths of competing alternatives to guarantee consistent decision ranking among the paradigms. Results of the research suggest that probabilistic methods will not rank vague economic investment information the same as fuzzy set methods. As a result, decision makers who use probabilistic methods to model vagueness in human thought (the condition for which fuzzy theory was developed) may obtain rankings inconsistent with those obtained via the fuzzy models. In such cases, if decisions are based on project rankings, then different choices or recommendations are likely.     

Analogies of Cash Flow Concepts

Several different procedures for the implementation of the internal rate of return criterion are presented in the literature on investment projects evaluation. Taking the net present worth criterion as a basis for comparison, a survey of some of the suggested procedures and a critique of their theoretical basis are presented. It is showed that, although leading to a proper evaluaticn, they are internally inconsistent in the sense of incorporating modifications that may not really be necessary. To circumvent this possibility, we are going to suggest a conceptual algorithm that should be implemented if we are concerned with the formal application of the internal rate of return criterion.     

影响固井作业安全的水泥浆因素及其标准化工作对策

从分析几个典型的固井作业事故事例出发,指出了影响固井作业安全的各种水泥浆因素,具体包括实验室与现场配方材料的一致性问题、混配均匀性问题、油井水泥及外加剂材质问题及水泥浆配方设计问题。从完善标准化工作的角度提出了通过加强水泥浆技术管理工作以防范固井作业事故的一系列可行措施。     

The perils of high-growth markets

The conventional wisdom that businesses should invest in growth markets is based upon the assumptions that, in the early phase of a growth market, share gains are easier and worth more, the experience curve will lead to advantage, price pressure will be low, needed access to the technology will result and future entries will be deterred. These assumptions are examined and six major types of growth market risks are discussed. Finally, conditions which should be present if an early entry into a growth market is attempted are identified.