If the from a rigid curved surface hits other panels, or the inside of a concave panel has other specular reflection points, discrete reflections among these multiple reflections change their transfer functions very much. It is already shown that multiple reflections of a geometrical wave and boundary waves are separately calculated between rigid plane panels. An impulse response from a rigid curved panel resembles that of a rigid plane panel. A discrete reflection around the specular reflection point of the first panel is replaced by an equivalent image point source and the second reflection between rigid curved panels is estimated by the of it. The multiple reflections inside a rigid concave panel with large curvature and the contribution of wide area around the specular reflection point can be also approximately calculated by the equivalent image point source from the strength of the . These calculated results are compared with measured ones in the time and frequency domains.

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The sound reflection coefficient of a given material, which is measured from a sufficiently large plane of it for spherical wave incidence, has been used previously to predict the for plane, convex or concave, finite size panels covered with that material. The of such a panel can be treated as two separate waves. One is the wave from the specular reflection point and the other is a boundary wave comprised of components from the lined point sources at each edge. Here, multiple reflections between two plane panels covered with materials having reflection coefficients that may be different are approximately calculated from such separate waves as in the same treatment of rigid plane panels.

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The author fabricated a plain type thermal radiation detector with evaporating gold-black as the surface absorbent attached to a thermoelectric detector. The spectral responsivity of the thermal radiation detector under different evaporating conditions was investigated and the best condition for the highest degree of spectral responsivity is reported. The relative spectral responsivity of the thermal radiation detector with gold-black absorber against the thickness of the gold-black was explained with proposed plain type models. In the proposed plain type models, incident radiant energy is absorbed near the surface and transmitted through the gold-black absorber as heat. There were two kinds of the proposed plain type models, one was called the lumped constant model and the other was called the distribution constant model. Each model has two types. The best proposed model to fit the measured results was the distribution constant model 2, which contained reflection at the interface of the absorber and the PVDF pyroelectric film. To attain a very sensitive thermal radiation detector with constant spectral responsivity, which is constant within ±1% over a measured wavelength region, conical cavity type detectors were fabricated. Experimental samples were made to study the dependence of the effective reflectance of a conical cavity type thermal radiation detector on reflectance of the absorbent on the cone and the cone apex. The decrease in the effective reflectance for a conical cavity type was explained using a proposed conical cavity type model, which contains the , and the second repeated mutual reflections.

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The practical calculations of the first reflections from elements comprising the boundaries of an auditorium (such as a rigid plane panel, a rigid curved panel, and a panel having reflection coefficient other than unity) have reported. Multiple reflections between two rigid plane panels, two rigid convex panels, two plane panels with reflection coefficients different from unity, and those inside a rigid concave panel have also reported, based on the calculation of the . In this report, Terai's boundary integralequation is transformed by the successive substitution where early terms correspond to the early reflections. For each term, the equivalent result reported previously is applied. Finally, the calculated pulse response of the early reflections in a scale model auditorium, which is the convolution of the calculated impulse response and the direct sound simultaneously obtained, is compared with the measured result. It is shown that the sum of the reflections in a several orders correspond well to the measured early reflections and that the details of the formation of the sound field can be discussed on this method.

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This paper describes a new approximate calculation of interreflection in a room containing fixtures. In the conventional calculation for interior lighting which is based on luminous flux transfer, the number of calculated form factors and hence the computation time increases with the number of surface elements. For this evaluation, the illuminance of each surface in the room calculated vary in fixture type, fixture height, and fixture reflectance. We present results that the approximate values have strikingly good agreements with the exact values for the average illuminance and illuminance distribution of all surfaces, and the computation time is much shorter.

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An extended energy integral equation method has been developed for precise predictions of noise propagation in and around a multi-room building surrounded by other buildings. In this method, all energy flows between boundary elements of the calculation model are obtained by solving equations considering multiple reflections, multiple diffractions and sound transmission. In order to improve the precision of the method, the calculation of first reflections is separated from the calculation of multiple reflections, and the first reflections are calculated by the approximated method derived from the wave theory. This method is applied to the calculation of sounds transmitted through small openings. Predictions using these methods corresponded well with measurements from actual sound fields.

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Curved rigid boundaries are often used in an auditorium, composing a part of the early reflections and it is therefore very important to know their sound reflections. If a curved rigid panel is replaced by tangential plane partitions, the diffracted formula under Kirchhoff's boundary conditions is applicable to them in order to calculate the of the panel. When the interreflection on the surface is neglected and a panel is divided into partitions to be able to apply Fraunhofer's diffraction formula, the sound reflection of a curved rigid panel is approximated by the sum of their first reflections. Transfer function and impulse response of the panel are thus calculated. Calculated values for a few kinds of curved rigid panels are compared with measured values. They show good agreement. When the curvature of a panel is changed, the sound reflection is compared by calculation. The sound reflection of an actual curved rigid lateral wall is estimated by this method and compared with the measurement. They also agree well. For the periodically curved panel, it is shown that this approximation of calculation gives useful information.

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The purpose of this technique is to estimate the lubrication condition in ball bearing with the variation of ultrasonic echo height reflected from a contact surface of an outer ring and a ball. A part of ultrasonic wave sent from a probe attached on a bearing housing is transmitted to the outer ring of ball bearing through a boundary surface of the outer ring and the bearing housing, and arrives at a boundary surface contacting with the ball, and reflects from there. This reflection echo height is used for an evaluation of insufficient supply of oil in ball bearing. When sufficient oil is supplied to an inlet of contact surface between the outer ring and the ball, the echo height which continued decrease as the ball approaches a sound axis of ultrasonic probe is increased locally. However, degree of its increase becomes lower when oil supply is insufficient, and does not appear at all with running out of oil. Also the time lag between bottom of valley in echo height variation curve and the sound axis of ultrasonic probe decreases gradually as supply of oil becomes insufficient, and becomes zero with running out of oil from a contact surface. This evaluation method has a potential which can evaluate the insufficient supply of oil in the ball bearing by two indexes above.

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In the WG for the study of technical requirement for UWB in the UWB Radio System Committee of MIC, the interference of 24GHz UWB radars toward the Earth Exploiting Satellite Service (EESS) has been studied. This study is based on the ITU recommendations and includes Japan inherent conditions. They are car density, building density and building height. As an area under study, the area (306[m2]) with highest population densities in Tokyo metropolitan is chosen. It is assumed that the satellite and radiometer are GCOM-W1and AMSR2, respectively. Results tell: the worst case, excluding the building reflection loss and having high activity factor, has the margin of 1.2 [dB] for the diffusion rate of the vehicles with UWB radar = 0.1% and the apportion = 1%, and another case including the reflection loss and low activity factor has that of 6.4[dB].

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The early reflections in the sound field of an auditorium have important roles in the impulse response and transfer function. The practical calculations are already shown for the first reflections from the boundaries and compared with measured reflections in good agreement. In this paper, the estimation of the multiple reflections between rigid plane panels is treated, based on these. When a panel is small, or the distance between a point source or a receiving point and the panel is large, the multiple reflection of a boundary wave cannot be neglected compared with that of a geometrical wave. Because the of a rigid plane panel has separate geometrical wave and boundary waves, the multiple reflections between them are obtained by those of each wave. Since a boundary wave is explained as the contribution of lined point sources with directivity on an edge, its multiple reflection is calculated as their geometrical reflection and their boundary waves of a reflecting panel. This calculation method is applied to two rigid plane panels which have a broad angle in between, and two which are in parallel. The calculated results are compared, in the time and frequency domains, with measured values in good agreement.

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The ultrasonic pulse-echo method is applied to measure thickness in a liquid film. To prevent a piezoelectric element cracking under high temperature conditions, the maximum frequency of sound is limited. On the other hand, the required thickness resolution is about 0.05mm to detect whether or not dryout has occurred. An ultrasonic transducer frequency of 5MHz is selected to satisfy both frequency and resolution requirements for air-water experiments. The changing liquid film thickness on a stainless steel plate is simultaneously measured with the ultrasonic transducer and a laser displacement sensor. The two types of results show good agreement within the range from 0.06 to 0.22mm. Next, the air-water annular flow in the small vertical square pipe is measured using the pulse-echo method. A liquid film sensor based on the electrical conductance method is also used for results comparison. The most frequently observed thickness measured by the two methods is almost the same based on comparison of the measurement histograms. To estimate the resolution of the pulse-echo method, the pulse intensities of multiple reflections in the liquid film are simulated. The results show that a liquid film thickness of 0.03mm can be measured even if the ultrasonic frequency is less than 5MHz.

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A new lighting calculation algorithm was developed. It is composed of three method, namely, the luminous flux transfer method, the virtual image method, and the ray tracing. The luminous flux transfer method is used for luminance calculation in an anisotropic diffuse reflecting interior. The image method treats the from mirrored surfaces, and the ray tracing treats the second and after reflections from mirrored surfaces. After lighting calculation, rendering calculation makes the image of luminance distribution by ray tracing.

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Plane electromagnetic waves are assumed to be incident normally on an ocean surface, overlying a sea floor of uniform slope. Berdichevskii's method of images is used to extend the computations of surface fields for a basement with non-zero conductivity, at sites remote from the coastline. The vertical magnetic field is enhanced over shallower depths while the horizontal electric field shows a transition from the polarization behaviour on the landward side of a continental shore to that on the seaward side. The fields are computed for slopes of 3° and 10° and compared with those over an ocean with a horizontal floor. The calculations are applied to three sets of measurements on iceislands in the Arctic Ocean; no disagreement is found, although quantitative explanation cannot be made owing to the difficulties of controlling the experimental conditions, or of simulating them precisely in a mathematical analysis.

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Laser processing using axisymmetrically polarized beams, such as radially and azimuthally polarized beams, was simulated to investigate influence of beam polarization from a point of view of behavior of light. A numerical simulator based on a ray-tracing method was developed to calculate drilling holes and digging grooves including influence of multiple beam reflection of polarized light. Simulation results showed that, even in digging grooves, the absorbed energy of reflected light was greater than that of incident light at the , especially in the case of the circularly polarized beam. Reflected rays of light of the radially and circularly polarized beams contributed to making grooves deep. Reflected rays of the azimuthally polarized beam contributed to broadening the groove.

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In a small tokamak, the visible light emission is observed and used to investigate plasmas' behavior with a fast visible camera. However, the reflected light causes a systemic error in measuring visible light emitted from the plasma. In this paper, we managed to overcome the reflection effect with the ray-tracing technique which is utilized in a synthetic diagnostic platform of the small tokamak device PHiX at Tokyo Institute of Technology using Raysect and CHERAB python libraries. We successfully evaluated the amount of reflected light and obtained tomographic reconstruction images from simulated and experimental data with the Tikhonov-Phillips regularization and the L-curve method to choose an optimal regularization parameter. We also proposed to project the contour of a reconstruction image onto a camera image to validate tomography results.

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A magnetosonic shock wave propagating obliquely to an external magnetic field can repeatedly accelerate thermal ions if θ₀≈45°, where θ₀ is the angle between the wave normal and the external magnetic field. The ion energy gains in this process are theoretically analyzed, and an expression for the maximum energy is derived. This theory is verified using a two-dimensional, electromagnetic particle code. Furthermore, whistler wave instabilities generated by the accelerated ions are studied. The simulation demonstrates that whistler waves are excited in both the upstream and downstream regions, but that the whistler waves in these two regions have different frequencies and wavenumbers. It is shown that the characteristics of these waves can be explained by linear theory.

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