Turbulence measurements in high-speed flows by resonant fluoresence

Both mean flow and turbulence measurements were investigated using the resonant Doppler velocimeter in a Mach 3.2 nitrogen flow. Data are presented showing velocity, temperature and pressure measured point by point across the flow field. This data is compared with conventional pitot and temperature surveys. Turbulence was induced by a small metal tab in the flow and observed by both hot wire and RDV techniques. Photographs of the flow field demonstrate the utility of the RDV for quantitative flow field visualization

Equivalent linearization for fatigue life estimates of a nonlinear structure

An analysis is presented of the suitability of the method of equivalent linearization for estimating the fatigue life of a nonlinear structure. Comparisons are made of the fatigue life of a nonlinear plate as predicted using conventional equivalent linearization and three other more accurate methods. The excitation of the plate is assumed to be Gaussian white noise and the plate response is modeled using a single resonant mode. The methods used for comparison consist of numerical simulation, a probabalistic formulation, and a modification of equivalent linearization which avoids the usual assumption that the response process is Gaussian. Remarkably close agreement is obtained between all four methods, even for cases where the response is significantly linear

The SIMRAND methodology: Theory and application for the simulation of research and development projects

A research and development (R&D) project often involves a number of decisions that must be made concerning which subset of systems or tasks are to be undertaken to achieve the goal of the R&D project. To help in this decision making, SIMRAND (SIMulation of Research ANd Development Projects) is a methodology for the selection of the optimal subset of systems or tasks to be undertaken on an R&D project. Using alternative networks, the SIMRAND methodology models the alternative subsets of systems or tasks under consideration. Each path through an alternative network represents one way of satisfying the project goals. Equations are developed that relate the system or task variables to the measure of reference. Uncertainty is incorporated by treating the variables of the equations probabilistically as random variables, with cumulative distribution functions assessed by technical experts. Analytical techniques of probability theory are used to reduce the complexity of the alternative networks. Cardinal utility functions over the measure of preference are assessed for the decision makers. A run of the SIMRAND Computer I Program combines, in a Monte Carlo simulation model, the network structure, the equations, the cumulative distribution functions, and the utility functions

Introduction to SIMRAND: Simulation of research and development project

SIMRAND: SIMulation of Research ANd Development Projects is a methodology developed to aid the engineering and management decision process in the selection of the optimal set of systems or tasks to be funded on a research and development project. A project may have a set of systems or tasks under consideration for which the total cost exceeds the allocated budget. Other factors such as personnel and facilities may also enter as constraints. Thus the project's management must select, from among the complete set of systems or tasks under consideration, a partial set that satisfies all project constraints. The SIMRAND methodology uses analytical techniques and probability theory, decision analysis of management science, and computer simulation, in the selection of this optimal partial set. The SIMRAND methodology is truly a management tool. It initially specifies the information that must be generated by the engineers, thus providing information for the management direction of the engineers, and it ranks the alternatives according to the preferences of the decision makers

A contemporary view of systems engineering

The concept of a 'system' is defined, and the 'systems approach' is discussed. Four contemporary examples of the systems approach are presented: an operations research project, the planning-programming-budgeting system, an information processing system, and aerospace programs

Structural perfection in poorly lattice matched heterostructures

Continuum elastic theory is applied to the formation of misfit dislocations and point defects in strained layer structures. Explicit calculations of the energies of misfit dislocations in the double‐ and single‐kink geometries yield line tensions below which strained films are stable with respect to defect formation. Our results yield a mismatch‐dependent stability limit which, in the double kink case, differs from the Matthews–Blakeslee model by a geometrical factor and by the addition of a stress term associated with climb of the misfit dislocation. While our calculations yield equilibrium stability limits which may not correspond to observed critical thicknesses, the calculated stresses may be applied to descriptions of the kinetics of strain relief in films grown beyond these limits. Last, calculations of strain‐related contributions to the free energy of formation of point defects suggest a contribution │ΔG_(strain)│ ≃0.25 eV for a 5% lattice mismatch. This suggests a means of suppressing or enhancing the formation of vacancies or interstitials in semiconductors favoring these defects

Oceanic wave measurement system

An oceanic wave measured system is disclosed wherein wave height is sensed by a barometer mounted on a buoy. The distance between the trough and crest of a wave is monitored by sequentially detecting positive and negative peaks of the output of the barometer and by combining (adding) each set of two successive half cycle peaks. The timing of this measurement is achieved by detecting the period of a half cycle of wave motion

Photocatalytic generation of hydrogen from water

A concept designed to overcome the problems encountered when using photodissociation for the generation of hydrogen is discussed. The problems limiting the efficiency of photodissociation of water are the separation of the photolysis products and the high energy photons necessary for the reaction. It is shown that the dissociation energy of a large number of molecules is catalytically reduced when these molecules are in intimate contact with the surface of certain metals. It is proposed to develop a surface which will take advantage of this catalytic shift in dissociation energies to reduce the photon energy required to produce hydrogen. This same catalytic surface can be used to separate the reaction products if it is made so that one of the dissociations products is soluble in the metal and others are not. This condition is met by many metal systems such as platinum group metals which have been used commercially to separate hydrogen from other gases and liquids