Showing papers by "Naval Postgraduate School published in 1970"

Optimal interdiction of a supply network

Abstract: Under certain conditions, the re-supply capability of a combatant force may be limited by the characteristics of the transportation network over which supplies must flow. Interdiction by an opposing force may be used to reduce the capacity of that network. The effects of such efforts vary for differing missions and targets. With only a limited total budget available, the interdictor must decide which targets to hit, and with how much effort. An algorithm is presented for determining the optimum interdiction plan for minimizing network flow capacity when the minimum capacity on an arc is positive and the cost of interdiction is a linear function of arc capacity reduction.

A Branch Search Algorithm for the Knapsack Problem

Abstract: This paper presents an algorithm for the solution of the knapsack problem. The method involves searching the nodes of a tree along a single branch at a time. The algorithm eliminates the computational drawbacks inherent in the usual branch and bound schemes.

Variation op longshore current across the surf zone

Abstract: The wave-induced longshore current variation across the surf zone is described for a simplified model The basic assumptions are that the conditions are steady, the bottom contours are straight and parallel but allow for an arbitrary bottom profile, the waves are adequately described by linear theory, and that spilling breakers exist across the surf zone Conservation equations of mass, momentum, and energy, separated into the steady and unsteady components, are used to describe second order-wave-induced phenomena of shoaling waves approaching at an angle to the beach An expression for the longshore current is developed, based on the alongshore component of excess momentum flux due to the presence of unsteady wave motion Wave set-down and set-up have been included in the formulation Emphasis in the analysis is placed on formulating usable predictive equations for engineering practice Comparison with experimental results from the laboratory and field show that if the assumed conditions are approximately fulfilled, the predicted results compare quite favorably.

Rigid body motions in curved finite elements

Abstract: D functions used to construct the stiffness matrix of a finite element should possess the following properties. 1) Infinitesimal rigid body motions should be accurately represented. If this requirement is not met the conditions of equilibrium of the element are not satisfied.*• 2) The displacement functions should contain all the lower terms of a complete set of functions. This requirement insures monotonic convergence by mesh size reduction. 3) A minimum degree of interelement continuity must be maintained between adjacent elements. This minimum degree of compatibility must insure a perfect match for the inplane and the out of plane components of displacement. Also for the out of plane component, slopes tangent and normal to all common edges of two adjacent elements must match. This requirement then insures convergence to an exact result by mesh size reduction. The importance of the last two requirements is firmly established; however, the first requirement has been shown to be problem dependent. If the structure to be analyzed is so constrained that no element of the structure is ever going to undergo any rigid body motion, then obviously this requirement can be violated. For example, axisymmetric elements acted upon by axisymmetric loads need to have only one rigid body mode: a rigid translation parallel to the axis of symmetry. For this particular type of element a truncated cone as used by Grafton and Strome always includes a rigid body motion parallel to the longitudinal axis. However, if the axisymmetric element is to have curvature in the longitudinal direction, then all the rigid body modes are absent. Jones and Strome recognized such a deficiency and reintroduced a longitudinal translation in their element. Later, Stricklin et al. reported on a similar improved element but omitted the longitudinal rigid body motion altogether. This last element is capable of handling asymmetric loading, therefore it is not difficult to imagine a loading in which many elements would have to undergo considerable transverse motion; a cantilevered structure would lead to such a situation. Haisler and Stricklin studied the influence of longitudinal translation and observed that such a rigid motion is recuperated by mesh size reduction. For elements of rectangular aspects, Bogner, Fox, and Schmit developed a systematic method for constructing acceptable displacement fields. However, for curved cylindrical elements, only two rigid body modes are accounted for. The same authors reported on a (48 X 48) stiffness matrix and mentioned that an eigenvalue analysis of such a matrix indicated that rigid body motions were adequately represented. However, as pointed out in our study of curved cylindrical elements, rigid body motions cannot be represented by independent displacement components. In the same reference, the importance of these rigid body motions is clearly illustrated in several examples. However, the inclusion of rigid body motions was done at the expense of rigorous interelement compatibility. This compromise resulted in a significant improvement in the behavior of the element. In this paper we develop a method to include rigid body motions without comprising deformational compatibility. The method is general and can be applied without difficulties to any element, curved or flat. The improvements of a curved cylindrical element are illustrated with one example.

Stagnation Temperature and Molecular Weight Effects in Jet Interaction

Abstract: The purpose of this study was to investigate the effect of injectant stagnation temperature and molecular weight variation on the flowfield generated from secondary injection of a gas normal to a supersonic stream. Experiments were conducted at a primary stream Mach number of 2.80 in the Naval Postgraduate School supersonic wind tunnel. Experimental data have been correlated with various theories, showing both agreement and disagreement. Data presented include penetration of secondary jet into primary flow and shock shape as correlated with the second-order blast wave theory. Jet momentum, not jet mass, was found to be the main determinant of the observed jet effects.

A Constant-Work Model for Student Attendance and Enrollment

Abstract: This paper develops a model of undergraduate student attendance that relies on five parameters, one of these being a parameter of total work, w, required to complete the degree. An enrollment forecasting method consistent with these attendance patterns is developed and compared with data for the period 1961-1966 and a cohort of 2,126 and 3,298 freshmen entering in the Fall semesters of 1955 and 1960, respectively. Under the assumptions of the model, the probability of graduation is shown to be the wth power of the conditional probability of successful completion of a unit of work, given that a student drops out or attends and successfully completes a unit of work.

The Religious Manager

Abstract: Managers' choice of goals, their rating of subordinates, and various organizational and biographical data were related to the managers' Religion Value score as measured by judging religious terms a...

Estimation of Stationary Stochastic Regression Parameters

Abstract: This article considers repeated regression experiments wherein the regression parameters vary according to a stationary stochastic process with known covariance structure. Expressions are derived for best linear estimators and predictors of linear functions of the regression parameters.

An investigation of the acceleration induced burning rate increase of nonmetallized composite propellants

Abstract: A model is developed which correlates the experimentally observed burning rates of composite nonmetallized propellants subjected to acceleration fields normal to the burning surface. The model attributes the increased burning rates to additional energy transfer to the propellant surface from the combustion of ammonium perchlorate particles retained on the propellant surface by the acceleration forces. A method for predicting, with limited experimental data, the burning rate of a propellant as a function of pressure and acceleration is described.

A Generalized Upper Bounding Method for Doubly Coupled Linear Programs

Abstract: : The algorithm proposed is an extension of the generalized upper bounding method for problems without coupling columns. It produces the same sequence of extreme point solutions as the primal simplex method, and hence has the desirable convergence properties of that algorithm. However, the operations within each simplex iteration are organized to take maximal advantage of problem structure.

Operational definitions of inventory record accuracy

Abstract: An inventory stock record is in error when the information on the stock record is not in agreement with the actual physical situation. We address the questions of what is meant by inventory record accuracy as reported in the literature and what should be meant by this term, in the context of the inventory record accuracy problem defined by the Naval Supply Systems Command. The need for, and suggestions of, operational definitions of error measures are demonstrated in terms of the reporting of accuracy statistics, the formulation of inventory record accuracy goals, and the determination of corrective measures.

CALORIMETRIC INVESTIGATION OF THE ANTIFERROMAGNETIC TRANSITION IN NiCl2. 6H2O

Abstract: Measurements of the heat capacity of NiCl2·6H2O were made in the vicinity of the antiferromagnetic transition using calorimetric techniques of sufficient resolution so that the observed behavior was intrinsic to the samples studied. Two crystals of different origins were investigated in zero field, and one crystal was investigated with external fields applied parallel to the easy axis. The temperature of the heat-capacity maximum Tmax differed by approximately 3 mK between the two crystals, but the heat-capacity anomalies of each were best described with the same value of TN, 5.348 K. This value of TN was 9 and 12 mK above the temperatures at which the maximum heat capacity occurred. The data implied critical exponents of 0.20 ± 0.03 above the transition and 0.00 ± 0.01 below. An analysis of the data in terms of the imaginary temperature described the rounding of the calorimetric anomaly which occurred below Tmax. The analysis yielded best values for the imaginary part of the temperature comparable to the shift between TN and Tmax. The application of an external field caused a slow monotonic decrease in the amplitude and an increase in the width of the calorimetric anomaly. The width could be described by Δ^2=Δ0^2+aH, suggesting that the broadening of the transition could be described by two independent mechanisms, one intrinsic to the sample and the second field dependent. The shift of the Tmax with field was proportional to H^2.

A Dual-Mode Routing Algorithm for an Autonomous Roving Vehicle

Abstract: A dual-mode algorithm for routing an unmanned autonomous roving vehicle designed to explore the uncertain terrain of other planets is presented. The algorithm consists of a global mode, which uses dynamic programming and terrain information available from photo reconnaissance data to determine a nominal optimal path, and a local mode, which routes the vehicle around obstacles whose presence, location, and extent are not known in advance. Gaussian probability density functions are used to simulate terrain for examples that illustrate the performance of the algorithm.

On the Distribution of a Difference of Two Scaled Chi-Square Random Variables

Abstract: by tending to make the animals remain in the protected area, the number of surviving animals is increased from 263 to 784. It can be noted that since the death rate, is between P21 and P31, i.e. 0.1 < death rate, <0.5 and the birth rate is bounded by M22 and M33, i.e. birth rate equals 0.1, extinction is inevitable. Any efforts to reduce the death rate or to increase the birth rate would change the transition matrix. Further reduction in death rates may be feasible by increased enforcement or patrols, increased hunting license fees, etc. By way of further example, another transition matrix P could be defined as P = .5 .2 .3

A Class of General Reliability Growth Prediction Models

Abstract: In structuring reliability growth prediction models as Markov chains it is seen that the computation of the reliability after n trials and possible associated repairs R, may be accomplished with any of several different methods. This paper considers a class of models that accommodates variations in several important factors, such as the interdependences of assignable cause failure modes, inclusion of an inherent failure mode, the repair policy, and the distribution of initial states of the system.

A digital computer study of the buckling of shallow spherical caps and truncated hemispheres

Abstract: A study of the buckling of thin shells was conducted using a digital computer program for the geometrically nonlinear analysis of arbitrarily loaded shells of revolution The objective was an evaluation of the program's applicability to bifurcation buckling and imperfection sensitivity analysis Clamped spherical caps under pressure loading and clamped truncated hemispheres under axial tension were investigated Buckling loads were determined for axisymmetric and nearly axisymmetric loads and are compared with previously published analytical results based on geometric imperfections

A Problem in Geometrical Probability

Abstract: (1970). A Problem in Geometrical Probability. Mathematics Magazine: Vol. 43, No. 5, pp. 237-244.

Analytic Functions whose Real Parts are Bounded Below

Abstract: The first three theorems of this paper are generalizations of some classical results. We first establish these theorems: The next two sections contain some applications of the first three theorems. The final section begins with a generalization of Theorem 2. In that section, we will also consider functions which map the unit disk into an annular region. Some of the results given here are contained in [10].

A note on the nature of optimality in the discrete Kalman filter

Abstract: A derivation is presented in which it is shown that the optimal gain sequence of the discrete Kalman filter minimizes not only the trace of the estimation covariance matrix, but any linear combination of the main diagonal elements of that matrix.

The measured energy loss of high energy electrons in copper and lead

Abstract: The energy distributions of electrons of about 53, 75 and 93 MeV have been measured before and after passing through copper absorber of thickness up to 5.726 g/cm2 and lead absorbers of thickness up to 2.825 g/cm2. Earlier data for aluminum absorbers are reviewed. The electrons were accelerated by the LINAC of the Naval Postgraduate School. The most probable energy losses agree with the theory of Blunck and Westphal for all thicknesses; the half widths agree except for large thicknesses, where they are smaller than theoretical values for lead, in agreement for copper, and larger for aluminum. Large numbers of electrons of energy less than 30 MeV are observed in the distributions of transmitted electrons, particularly for thick absorbers and higher values of atomic number. These are apparently the result of multiple processes in the absorbers.

Swell and storm characteristics from coastal wave records

Abstract: Manual analysis of strip-chart records from a conventional wave sensor at Monterey, California was found to yield a linear frequency shift associated with each arriving swell tram, from which the origin time and travel distance of the swell could be computed The use of surface weather maps allows identification of the source, and thereby yields an accurate determination of the deep-water arrival direction of the swell for use on the local coast The wave records are analyzed for the frequency of the individual waves composing wave groups, f , consistency of the results obtained indicates that f is equivalent to the frequency of maximum energy density f , obtained by spectral analysis Five swell sets studied were found to max J f J originate in North Pacific storms advancing toward Monterey The seas in the fetch were fully arisen at the time of computed swell origin, and the surface to geostrophic wind ratio was 0 83 The dominant swell emerged from the fetch at a time when its group velocity equalled the velocity of the fetch toward Monterey.

Superconductive energy storage with a flux pump

Abstract: On a eprouve une bobine de stockage d'energie de 8000 amperes 3000 joules chargee par une pompe a flux a redresseur pleine-onde. l'appareil a 1 m de haut et a un diametre de 33 cm et un poids de 60 kg. Toutes les parties sont concues pour un courant de 16000 A au moins. On discute la limite de 8000 A par rapport au comportement electrique et thermique des elements de commutation de la pompe. On donne les details de la construction de la pompe et de la bobine et l'on examine l'efficacite de pompage et de stockage.

A program for the nonlinear static and dynamic analysis of arbitrarily loaded shells of revolution

Abstract: Computer program for geometrical nonlinear static and dynamic structural analysis of arbitrarily loaded shells of revolution

Elliptical Evaporation Tanks with Vertical Base and Cover Plates

Abstract: I t seems worthwhile to report on a unique, economical, and effective design of evaporation tanks. Such tanks have been in continuous use for fifteen years at Michelson Laboratory, producing research quality evaporated films. Briefly, each tank consists of a 83.8 cm × 50.8 cm × 1.9 cm vertical stainless steel (316) base plate and a 83.8 cm × 50.8 cm × 2.5 cm vertical Pittsburgh Duplate two-ply laminated glass cover plate (four-ply laminates are unsatisfactory), separated by an 20.3-cm wide stainless steel elliptical hoop having a 76.2-cm major axis and an 45.7-cm minor axis, as shown in Fig. 1. The steel fins welded on the sides provide additional support to the ellipse. The base and cover plate seals are provided by L-shaped neoprene gaskets which are commercially available for 61.0-cm bell jars. When considerable heating of the substrates is required, Viton L-shaped gaskets are substituted for the neoprene gaskets. Figure 2 shows two tanks separated by approximately 71.1 cm to provide the necessary space for a forepump, diffusion pump, valves, and piping to evacuate either tank. A single set of instruments and power supplies is used for both tanks of such a dual arrangement, which provides for additional economies of construction and maintenance. Such a dual arrangement requires a minimum laboratory space of 50.8 cm × 121.9 cm × 152.4 cm and provides for routine evaporations at pressures in the vicinity of 10–10 Torr. The large ratio of base plate area to evacuated volume in the elliptical evaporation tank provides the following advantages over conventional glass bell jars: (1) shorter pumping time, (2) larger source-to-substrate distance, (3) larger internal area for the attachment of measuring and control devices, (4) larger window area for observation during an evaporation, and (5) greater flexibility of internal arrangement of component parts for general experimental work. When a 45.7-cm coating distance is used Fig. 1. Front view of elliptical evaporation tank.

Generalisation of parameter methods and D decomposition

Abstract: The parameter methods, namely the parameter-plane and the parameter-matrix formulations, were developed to solve high-order multiloop distributed-parameter problems that were too tedious to be solved using the usual classical techniques. Essentially, the methods give graphical plots relating two design parameters and the zeros of the characteristic equation. The paper summarises the solution for several previously obtained cases relating the parameters and coefficients, and generalises the relationship to a completely unrestricted case, using well known function-minimisation methods, such as the conjugate-gradient technique. Moreover, a useful comparison to the generalised D decomposition method is made.