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[en] The utilization of neutron activation technique for various non-destructive studies is of ever increasing demand. This paper discusses the potential for prompt gamma neutron computerized tomography. This may provide a foundation for the development of a non-destructive system which can quantitate the elemental content of an object's substructure

[en] The amount of radiation exposure to passengers and crew members of aircraft was determined. Data were gathered from 15 pilots. They were issued film dosimeters sensitive to different ranges of energies. Research is discussed on the various results from altitude and latitude changes, solar cycle fluctuation, and nuclear testing. The exposures received are related to other fields that have radiation problems and then compared with previous research on high altitude aircraft

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[en] In neutron radiography, as in other forms of NDE, it is sometimes desirable to observe dynamic events. This need has generated increased interest in real-time neutron radiography systems. As in other forms of radiography, a standard method for measuring the image forming capability of real-time systems is necessary in order to compare the various methods and systems used. A technique which has been used extensively in general photography and has been applied in the characterization of several screen-film combinations used in conventional neutron radiography is to determine the imaging system's modulation transfer function (MTF). This gives a graphical representation of the system's spatial resolution capabilities and was therefore chosen as the method for evaluation of the real-time neutron radiography facility at the University of Missouri Research Reactor (MURR). The method used was to image a knife-edge, differentiate the edge gradient to obtain the line spread function (LSF) to obtain the system MTF. A Gd foil was used for the knife-edge on several neutron converter screens and was imaged by a low-light level ISIT camera. The video signal was then digitized and presented to a PDP-11/05 microcomputer for the numerical calculations

[en] Various numerical techniques were investigated and compared for the computer simulation of the pure advection problem par. deltaN/par. deltat + U par. deltaN/par. deltax = 0 given an initial condition on a periodic lattice. Graphical comparison of the analytical and numerical solutions exhibits the inadequacy of explicit finite difference methods for late time solutions. Investigation of implicit finite difference schemes demonstrated improved accuracy; however, the increased CPU time requirement was large. Equivalent accuracy and considerably improved computational advantage was exhibited for late time solutions using the ASH exponential operator method (spatial finite differencing), which solves the matrix equation dX/dt = A X , X(t) = exp(At)X(0). Additionally, when the pure advection problem operator spectrum was approximated by Chebyschev polynomials, the ASH method exhibited improved accuracy at even later times. Although a matrix inversion is required in addition to the matrix operations of the ASH solution method, late time solutions are obtained rapidly and accurately for more than 25 periods of a pulse propagating through a periodic system

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No abstract available

[en] The problem of the motion of a sphere under temperature gradient is considered in the framework of the kinetic theory of gases. Numerical results for thermophoresis are compared with available experimental data. The effect of particle-gas thermal conductivity on the thermal force is discussed in some detail

[en] The present analysis accounts for radiant and convective heat transfer for a transparent fluid flowing in a short tube with prescribed wall heat flux. The heat flux distribution used was of sine shape with maximum at the middle of the tube. Such a solution is the approximate one for axial power in a nuclear reactor. The solutions for the tube wall and gas bulk temperatures were obtained by successive substitutions for the wall and gas balance energy equations. The results show a decrease of 30% for the maximum wall temperature using black surface (e = 1). In this same case, the increasing in the gas temperature shows a decrease of 58%