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It has been reported recently that the A-bomb gamma ray spectra received by the colon of the average Japanese survivor of Hiroshima and Nagasaki may be experimentally simulated using a hospital-based Philips SL15 linear accelerator. The simulated A-bomb gamma radiation may be used in radiobiology experiments to determine, amongst other things, the biological effectiveness of the A-bomb gamma radiation. However, in that study, the electron beams from the linear accelerator were poorly defined and photon contamination was ignored. In the study reported here, a Varian Clinac 2100C linear accelerator has been used for the same purpose but with photon contamination included in better defined output electron beams. It is found that the A-bomb gamma radiation can still be matched to an acceptable degree (<10%). The cause of the slightly poorer fit was due mainly to the different ranges of energies available from the linear accelerators used. The absorbed dose received by model breasts was also estimated in this study for the same situations as in the previous study. The ratio of the breast to colon doses was found to be only (3.9 ± 4.0)% low compared with the expected values of 1.17 and 1.16 for Hiroshima and Nagasaki, respectively. These results provide further confirmation of the acceptability of the simple cylindrically symmetrical body models employed in these studies to represent the average Japanese survivor.

An electromechanical oscillator was developed to simulate both surface-wave-induced motions and subsurface currents for the evaluation of current meters or other sensors that are suspended beneath surface buoys used in oceanographic operations. The oscillator will permit evaluating the hydrodynamic characteristics and performance of sensors under simulated sea conditions at amplitudes up to 4 ft (1.2 m) peak-to-peak and at periods from 3 to 30 s. Mechanical and operational details are described for each of three modes of operation producing circular, vertical, and horizontal motions. Sample experimental results are presented to illustrate the quality of motion in all three modes. (Author)

Linear scaling of deep-water moorings is impractical and reliance must be made by designers on analytic models. To provide a broad data base applicable to model validation, five small-scale mooring line materials were selected for evaluation. The horizontal and vertical components of dynamic tension generated by vertical, sinusoidal motion of the upper end of the mooring line were measured. The experiments were made under conditions of current and no current. Data were reduced to force response ratios as a function of frequency of input, and observations of mooring line motions were made. These response ratios were found to depend on preload, current, bending stiffness and scope.

The David W. Taylor Naval Ship R+D Center has undertaken the development of equipment to make precise measurements of the strumming phenomena of various cables and to conduct experiments with a variety of cable models at various tensions in both uniform and non-uniform flow conditons. The equipment was fabricated and three cable models were evaluated under tension in a uniform flow. In-line and transverse displacements, static tension, static and dynamic lift, drag and tangential forces were measured. Data are presented in engineering units and non-dimensional coefficient form; time varying displacements are presented as phase spectra versus frequency. From these data, a wide variety of cable strum conditions can be compared with various analytical predictions of strumming effects and improvement in the development of analytical models can be made. (Author)

Unsteady hydrodynamic lift, moment, and drag on a two-dimensional NACA 16-209 hydrofoil are determined experimentally as functions of depth of submergence, forward speed, mean angle of attack, and frequency of oscillation in pure heave and pure pitch motions. Various theoretical and experimental results are compared with the experimental steady and unsteady load coefficients on the hydrofoil model. The comparisons include both finite and zero forward speed effects. Added-mass coefficients are obtained from the zero forward speed case. Theoretical and experimental results do not agree because of limitations in both the theories and experiments. (Author)