Showing papers by "Naval Postgraduate School published in 1982"

Smooth Interpolation of Scattered Data by Local Thin Plate Splines

Abstract: An algorithm and the corresponding computer program for solution of the scattered data interpolation problem is described. Given points ( x k , y k , f k ), k = 1,…, N a locally defined function F ( x , y ) which has the property F ( x k , y k ) = f k , k = 1,…, N is constructed. The algorithm is based on a weighted sum of locally defined thin plate splines, and yields an interpolation function which is differentiable. The program is available from the author.

Pool Boiling Heat Transfer From Enhanced Surfaces to Dielectric Fluids

Abstract: Pool boiling heat-transfer measurements were made using a 15.8 mm o.d. plain copper tube and three copper enhanced surfaces: a Union Carbide High Flux surface, a Hitachi Thermoexcell-E surface and a Wieland Gewa-T surface. The dielectric fluids were Freon-113 and Fluorinert FC-72, a perfluorinated organic compound manufactured to cool electronic equipment. Data were taken at atmospheric pressure, and at heat fluxes from 100 W/m/sup 2/ to 200,000 W/m/sup 2/. Prior to operation, each test surface was subjected to one of three aging procedures to observe the effect of surface past history upon boiling incipience. For Freon-113 the enhanced surfaces showed a two to tenfold increase in the heat-transfer coefficient when compared to a plain tube, whereas for FC-72 an increase of two to five was measured. The High Flux surface gave the best performance over the range of heat fluxes. The Gewa-T surface did not show as much of an enhancement at low fluxes as the other two surfaces, but at high fluxes its performance improved. In fact, it was the only surface tested which delayed the onset of film boiling with FC-72. The degree of superheat required to activate the enhanced surfaces was sensitive to both past history ofmore » the surface and to fluid properties.« less

Short-Term Planetary-Scale Interactions over the Tropics and Midlatitudes during Northern Winter. Part I: Contrasts between Active and Inactive Periods

Abstract: Objectively analyzed 200 mb winds of four winters are used to study the short-term (several days) teleconnections between planetary-scale circulation components over the monsoon region. The composited structures suggest that during very actively northeasterly monsoon (surge) periods, the midlatitude and tropical circulation components vary in a coherent way. The jet streak and local Hadley circulation over East Asia, the divergent flow over the maritime continent, and the equatorial Walker circulations over the Pacific and Indian Oceans all strengthen steadily, while the secondary jet streak over West Asia weakens. During inactive (break) periods the midlatitude circulation components all exhibit reversed changes, while the variations in the tropics are less coherent, although still showing reversed tendencies. The results basically verify the short-term teleconnection model proposed by Chang and Lau (1980), but more complex processes in the acceleration of the midlatitude jet streaks are indicated. In addition, the contrast between the very active and break monsoon periods suggests the relative importance of tropical versus midlatitudinal forcings in different regions of the monsoon circulation.

Structural Optimization-Past, Present, and Future

Abstract: ' Introduction T concept of optimization is intrinsically tied to natural phenomena as well as to the human desire to excel. Sir George Cayley (1773-1857) measured the shape of a trout and noted, without mathematical proof, that the trout was ideally proportioned to minimize flow resistance. Theodore von Kdrmdn observed that this is precisely the shape of a lowdrag airfoil. Oliver Wendell Holmes (1809-1894), in his classic verse, "The Deacon's Masterpiece; or, The Wonderful OneHoss Shay," recorded man's desire to produce a uniformly strong, durable product. In this case it was the structural design of a shay to last a hundred years. Perhaps the first analytical work in structural optimization was by Maxwell in 1869, followed by the better-known work of Michell in 1904. These works provided theoretical lower bounds on the weight of trusses, and, although highly idealized, offer considerable insight into the structural optimization problem and the design process. The 1940s and early 1950s saw development of component optimization in such works as Shanley's Weight-Strength Analysis of Aircraft Structures. Also during this period, availability of the digital computer led to application of linear programming techniques to plastic design of frames, for example, the work of Heyman. This early numerical work is particularly significant in that it used mathematical programming techniques developed in the operations research community to solve structural design problems. Schmit in 1960 was the first to offer a comprehensive statement of the use of mathematical programming techniques to solve the nonlinear-inequality-constrained problem of designing elastic structures under a multiplicity of loading conditions. This work is significant, not only in that it ushered in an era of structural optimization, but also because it offered a new philosophy of engineering design which is only now beginning to be broadly applied. In Ref. 9 Schmit provides an excellent historical review of the development of this concept. Although this discussion will emphasize numerical design techniques, it is important to note that there has been an extensive amount of research in analytical methods of design. That work, although sometimes lacking the practicality of being applied to realistic structures, is nonetheless of fundamental importance because it provides insight into the design problem and because it often provides theoretical lower bounds against which more practical designs may be judged. References 10 and 11 provide an extensive review of the state-of-the-art in analytical design techniques. It is the use of numerical techniques in structural optimization that is emphasized here. The purpose is not to offer a tutorial on optimization or a comprehensive literature survey, although such works are referenced. Rather, it is to look briefly at the short history of modern structural optimization and assess the state-of-the-art from a somewhat more philosophical viewpoint. In this way we may begin to understand the ramifications of this fascinating approach to design. By learning what is now possible and what is not now possible, we may encourage the use of these techniques by practicing designers as well as identify research and development needs of the future.

Channels that Cooperatively Service a Data Stream and Voice Messages

Abstract: This paper presents an analysis of the performance of a special type of voice data queueing system. The system consists of an integrated circuit-and packet-switched multiplexer resembling that found in the SENET network. A fluid-flow approximation for the data component is introduced to ease study of the voice loss rate and data packet waiting times. In this paper it is shown that very long data queues are possible, with the mean data queue length being proportional to the ratio of the holding time for voice to the holding time for data. The equilibrium distribution is determined, and aspects of the transient behavior are characterized. The question of how much bandwidth to reserve for exclusive use of data and how much to share between voice and data is addressed.

Values and objects in programming languages

Abstract: : The terms value-oriented and object-oriented are used to describe both programming languages and programming styles. This paper will describe the differences between values and objects and to show that their proper discrimination can be a valuable aid to conquering program complexity. The first section will show that values amount to timeless abstractions for which the concepts of updating, sharing and instantiation have no meaning. The second section will show that objects exist in time and, hence, can be created, destroyed, copied, shared and updated. The third section shows that proper discrimination of these concepts in programming languages will clarify problems such as the role of state in functional programming. The paper concludes by demonstrating the use of the value/object distinction as a tool for program organization. (Author)

Thermally Driven Motions in an Equatorial β-Plane: Hadley and Walker Circulations During the Winter Monsoon

Abstract: The linearized shallow-water equatorial β-plane equation was solved for a subset of approximate solutions applicable to thermally driven large-scale tropical circulation. In particular, the heat-induced monsoon circulations during Southeast Asian northeasterly cold surges are investigated. It was demonstrated that the response of the tropical atmosphere to a localized heat source consists of forced Rossby waves propagating westward and Kelvin waves eastward along the equator away from the region of forcing. In general, for any source/sink distribution, the heat-induced motion can have the characteristics of a Walker-type (ν = 0 at the equator) or a Hadley-type (u = 0 at the equator) response or a combination of both, depending on the latitudinal location of the forcing. Away from the equator, a forcing corresponding to the sudden imposition of mass at the lower layer, or equivalently in our model a rapid cooling of the lower troposphere, produces a sudden local surface pressure rise and strong an...

Propositions on Military Deception

Abstract: The concept 'lying' encompasses that of 'cover'. To lie is also to withhold information, but it is something more as well: a liar acts to deflect his victim away from the truth, and thus lying highlights deception's positive side. Liars create and perpetrate falsities and seek to fasten a victim's attention to them. In the narrow sense, to lie simply means making an untrue statement, but in a broader sense it can also involve manipulating the context surrounding the statement in order to enhance its veracity.3 This is what we mean by artifice, an important element of nearly all strategic deceptions.

Derived Preconditions and Their Use in Program Synthesis

Abstract: In this paper we pose and begin to explore a deductive problem more general than that of finding a proof that a given goal formula logically follows from a given set of hypotheses. The problem is most simply stated in the propositional calculus: given a goal A and hypothesis H we wish to find a formula P, called a precondition, such that A logically follows from P ∧ H. A precondition provides any additional conditions under which A can be shown to follow from H. A slightly more complex definition of preconditions in a first-order theory is given and used throughout the paper. A formal system based on natural deduction is presented in which preconditions can be derived. A number of examples are then given which show how derived preconditions are used in a program synthesis method we are developing. These uses include theorem proving, formula simplification, simple code generation, the completion of partial specifications for a subalgorithm, and other tasks of a deductive nature.

Meteorological Models For Optical Properties In The Marine Atmospheric Boundary Layer

Abstract: Observational experiments on turbulent intensities and aerosol distributions in the marine boundary layer (MBL) have been performed over several years. Observations have been made with ship-mounted and airplane-mounted sensors. Objectives have been to relate optical properties to meteorological descriptions which utilize scaling laws for the MBL. The approach has been to incorporate* in the descriptions the surface fluxes of momentum, heat, and moisture, the processes at the inversion and the profiles within the intervening convectively mixed layer. We have found that the optical turbulence parameter Cn2 can be readily estimated using measured mean values of wind, temperature, and humidity with recent bulk formulas to derive the surface fluxes. These estimates appear to be more reliable than values obtained from direct (but difficult to perform) turbulence measurements. The model for obtain-ing the estimates was evaluated on the basis of optical Cn2 values with good agreement. Good comparisons have been observed between extinction values obtained from transmission measurements and those obtained from calculations on measured aerosol distributions. Existing empirical formulations which related the latter to wind speed and relative humidity appear to be inadequate except for climatological purposes. This is because other influences on equilibrium aerosol distribution are not included. Reformulation of these expressions is being performed to include the height of the inversion (mixing volume) and surface fluxes (aerosol generation and transport).

Modeling Real DASD Configurations

Abstract: In this paper we survey modeling of Direct Access Storage Devices (DASD) from the point of view of a practitioner attempting to model a real, running system. Our example is DASD subsystems for IBM MVS systems. We examine the features of DASD configurations and the components of DASD service and response times, indicating the important features for performance management. We then treat the incorporation of real performance data in such models and the resulting problems which arise.

The Development of Economical Rotating Heat Pipes

Abstract: In this experiment, a rotating heat pipe was constructed with a single evaporator section but with several commercially available cylindrical condenser sections. Tests were made with cylinders having smooth walls, straight axial fins, spiralled fins, and helical corrugations. Heat transfer measurements were taken at rotational speeds of 700, 1400 and 2800 RPM using distilled water, ethyl alcohol and Freon-113 as working fluids. Results show that the commercially available cylinders can be used effectively in place of more costly condensers manufactured with tapered walls. A comparison of heat transfer performance is provided.

Job perceptions when working with data, people and things

Abstract: In a national probability sample of the adult working population in the United States, 1515 Americans participated in a structured interview. This survey provided data on individual job perceptions and occupational characteristics. Occupational information was coded using the skill codes employed by the Department of Labor's Dictionary of Occupational Titles: the Data, People, and Thing hierarchies originally developed by Fine (1968). Analysis of the data indicates that perceived job characteristics are correlated with the level of data-oriented and people-oriented skills used in the job. Further, task characteristics such as autonomy and variety correlate more highly with the skill codes than do role characteristics such as conflict and ambiguity. Results also suggest that task characteristics are linearly related to data- and people-oriented skills; but non-linearly related to thing-oriented skills. Based on these results, it is concluded that the type and level of skill used on the job contribute significantly to employee work experiences.

On patrolling a channel

Abstract: A simple formula is found to be just as accurate as a complicated one for estimating the probability of detection achievable by an ingenious searcher patrolling a channel or barrier. The difference between “detection” and “closure” is emphasized in an extension.

Rapid solidification effects in martensitic Cu-Zn-AI Alloys

Abstract: The effects of rapid solidification on martensitic transformations were studied in Cu-Zn-AI samples prepared by the method of melt-spinning, with an estimated cooling rate of about 106 K per second near the freezing point. A diffusionless solidification reaction L → β occurs, and a very fine-grained β structure is obtained, with highly structured grain boundaries. The average β grain diameter (∼5 µm) is about two orders of magnitude smaller than that obtained by conventional solid state solution and quench treatment. The β:β grain boundaries contain extraordinary features such as large steps, and the matrix dislocation density is abnormally high. The Ms temperature is depressed significantly in as-melt-spun ribbon material, but as the martensitic transformation is cycled, it shifts upward in temperature and obtains a more narrow hysteresis loop. The martensite has the usual 9R structure (ABCBCACAB stacking) found in bulk alloys, and while the morphology is similar to that in bulk alloys, it is finer in scale. It is suggested that the β → 9R transformation is affected through the combined influence of rapid solidification on parent β grain size, disorder, β:β grain boundary structure, internal stresses, and dislocation substructure. Shape memory behavior is qualitatively similar in the rapidly solidified alloys.

A Mixed Exponential Time Series Model

Abstract: The simple model NMEAR 1 is described for a stationary dependent sequence of random variables which have a mixed exponential marginal distribution; the model is a first-order stochastic difference equation with random coefficients and is first-order Markovian. It should be broadly applicable for stochastic modelling in operations analysis. In particular, it provides a model for simulating interarrival times in queuing systems when these random variables are overdispersed relative to an exponential random variable, and moreover are positively correlated. The model also has capability to model a variable which may be zero, but which otherwise is exponentially distributed. Such variables are found as waiting times in queuing models. Because of the random linearity of the process, it is easily extended to the modelling of cross-coupled sequences of interarrival and service times. The model can also be extended quite simply to a mixed exponential process with mixed pth order autoregressive and qth order moving average correlation structure, NMEAR p, q, so that non-Markovian dependence can be handled.

Oscillating supersonic/hypersonic wings at high incidence

Abstract: An approximate analytic method is developed for predicting the aerodynamic stability of oscillating supersonic/hypersonic flat wings at a mean angle of attack. It uses the known exact unsteady unified supersonic/hypersonic flow solution for a two-dimensional flat plate plus the strip theory approximation to obtain the formulas for the stability derivatives. They are applicable for wings of arbitrary planform shape at arbitrary angles of attack provided the shock wave is attached to the leading edge of the wing. Good agreement is obtained with existing theories in various special cases. The formulas for stability derivatives given here become exact in the Newtonian limit.

Numerical Optimization of Circulation Control Airfoils

Abstract: A numerical procedure for optimizing circulation control airfoils, which consists of the coupling of an optimization scheme with a viscous-potent ial flow analysis for blowing jet, is presented. Without losing the generality of the methodology, special attention is given to optimizing the blunt trailing edge, which has a direct bearing on the jet deflection characteristics. The desired airfoil is defined by a combination of three baseline shapes: cambered ellipse, cambered ellipse with drooped trailing edge, and cambered ellipse with spiraled trailing edge. The coefficients of these shapes are used as design variables in the optimization process. Under the constraints of lift augmentation and lift-to-drag ratios, the optimal airfoils are found to lie between those of the cambered ellipse and the drooped trailing edge, toward the latter as the angle of attack increases. Results agree qualitatively with the available experimental data.

Sequential testing for selection

Abstract: In sequential testing for selection, an applicant for school or work responds via a computer terminal to one item at a time until an acceptance or rejection decision can be made with a preset probability of error. The test statistic, as a function of item difficulties for standardization subgroups scoring within successive quantiles of the criterion, is an approximation of a Waldian probability ratio that should improve as the number of quantiles increases. Monte carlo simulation of 1,000 first-year college students under 96 different testing conditions indicated that a quantile number as low as four could yield observed error rates that are close to their nominal values with mean test lengths between 5 and 47. Application to real data, for which interpolative estimation of the quantile item difficulties was necessary, produced, with quantile numbers of four and five, even more accurate observed error rates than the monte carlo studies did. Truncation at 70 items narrowed the range of mean test lengths fo...

Average Competence, Variability in Individual Competence, and Accuracy of Statistically Pooled Group Decisions

Abstract: We correct propositions advanced by Sattler in 1966 on the accuracy of group judgments as a function of the mean competence and distribution of competence of group members. We provide the special distributions which, for fixed total group competence, minimize/maximize group majority rule accuracy. We also show how group majority competence can be above/below that of group mean competence.

Experimental Investigation of Oscillating Subsonic Jets

Abstract: Steady two-dimensional jet flows have attracted the interest of many investigators because of their fundamental and practical importance. Much of the currently available information has been summarized by Harsha [5.45], Rajaratnam [5.46], and Everitt and Robins [5.47]. Significant interest in unsteady-jet-flow effects first was sparked by the development of the pulse-jet engine, especially when Bertin [5.48] and Lockwood [5.49] noted the favorable effect of pulsating jet flow on secondary-flow entrainment. Lockwood [5.49] also identified the generation of ring vortices in pulsing flow, a phenomenon later verified more clearly by Curtet and Girard [5.50]. Further investigations of pulsating jet flows were performed by Johnson and Yang [5.51], Didelle et al. [5.52], Binder and Favre-Marinet [5.53], Crow and Champagne [5.13] and, most recently, Bremhorst and Harch [5.54] and Bremhorst and Watson [5.55]. A different type of unsteady jet flow is produced by time-varying jet deflection, either by mechanical oscillation of the jet nozzle or by fluidic jet actuation. The flow patterns produced by a mechanically oscillated jet exhausting into a secondary flow recently were measured in some detail by Simmons et al. [5.56], whereas fluidic jet nozzles were developed and investigated by Viets [5.57, 5.58].

Generation of some First-Order Autoregressive Markovian Sequences of Positive Random Variables with Given Marginal Distributions

Abstract: Methods for simulating dependent sequences of continuous positivevalued random variables with exponential, uniform, Gamma, and mixed exponential marginal distributions are given. In most cases the sequences are first-order, linear autoregressive, Markovian processes. A very broad two-parameter family of this type, GNEAR(l), with exponential marginals and both positive and negative correlation is defined and its transformation to a similar multiplicative process with uniform marginals is given. It is shown that for a subclass of this two-parameter family extension to mixed exponential marginals is possible, giving a model of broad applicability for analyzing data and modelling stochastic systems, although negative correlation is more difficult to obtain than in the exponential case. Finally, two schemes for autoregressive sequences with Gamma distributed marginals are outlined. Efficient simulation of some of these schemes is discussed.

Performance Evaluation of Voice/Data Queueing Systems

Abstract: The behavior of voice/data queueing systems is presented. Several methods of analysis are reviewed including matrix geometric methods of Neuts, fluid flow approximations, and diffusion approximations. The methods are applied to the case of a TASI system for voice. The diffusion approximation is also applied to a system with a nonexponential service distribution.