The Improvement of Resolution on the Ultrasonic Inspection Method

Several data processing techniques used in petroleum exploration are applied to ultrasonic data to enhance resolution and signal to noise ratio. First, in the case of a medium of low absorption characteristics, the effectiveness of a wavelet processing, a deconvolution filter and a CDP stack is demonstrated. Second, in the case of a medium of high absorption characteristics, an attenuation coefficient is estimated using the spectrum ratio method. Waveforms at an arbitrary depth can be synthesized by the estimated attenuation coefficient and the reflected wave at the reference depth. Wavelet processing, which utilizes the synthesized wavelets at each depth as the new basic wavelet including the absorption characteristics, greatly improves resolution. Finally, the wavelet processing, the migration processing and the synthetic acoustic impedance log are applied to the data from a phantom model which exhibits ultrasound responses similar to those in a human liver. The fluid-filled objects, 10 mm in diameter, are not only resolved, but the polarity and phase information in the reflected waves is also preserved through these processings. Consequently, it is concluded that pin-holes in metals or small size cysts or tumors in a human body are detectable by the enhancement of resolution of ultrasonic diagnosis

Coupled Simulation of Seismic Wave Propagation and Failure Phenomena by Use of an MPS Method

The failure of brittle materials, for example glasses and rock masses, is commonly observed to be discontinuous. It is, however, difficult to simulate these phenomena by use of conventional numerical simulation methods, for example the finite difference method or the finite element method, because of the presence of computational grids or elements artificially introduced before the simulation. It is, therefore, important for research on such discontinuous failures in science and engineering to analyze the phenomena seamlessly. This study deals with the coupled simulation of elastic wave propagation and failure phenomena by use of a moving particle semi-implicit (MPS) method. It is simple to model the objects of analysis because no grid or lattice structure is necessary. In addition, lack of a grid or lattice structure makes it simple to simulate large deformations and failure phenomena at the same time. We first compare analytical and MPS solutions by use of Lamb’s problem with different offset distances, material properties, and source frequencies. Our results show that analytical and numerical seismograms are in good agreement with each other for 20 particles in a minimum wavelength. Finally, we focus our attention on the Hopkinson effect as an example of failure induced by elastic wave propagation. In the application of the MPS, the algorithm is basically the same as in the previous calculation except for the introduction of a failure criterion. The failure criterion applied in this study is that particle connectivity must be disconnected when the distance between the particles exceeds a failure threshold. We applied the developed algorithm to a suspended specimen that was modeled as a long bar consisting of thousands of particles. A compressional wave in the bar is generated by an abrupt pressure change on one edge. The compressional wave propagates along the interior of the specimen and is visualized clearly. At the other end of the bar, the spalling of the bar is reproduced numerically, and a broken piece of the bar is formed and falls away from the main body of the bar. Consequently, these results show that the MPS method effectively reproduces wave propagation and failure phenomena at the same time

Suppression of insolation heating using paint admixed with silica spheres – An approach from infrared band electromagnetic scattering

The temperature of materials would be raised when the materials are exposed to the sunlight. Recently, it has been experimentally confirmed that such temperature rise may be restrained when coating the materials with paint admixed with fine silica spheres. Experimental consideration of this type of paint has been conducted, but how the paint controls the temperature rise has merely been clarified theoretically. The best diameter of the silica spheres to be admixed is not well understood, either. In this study, we hypothesized that the scattering of light would be attributed to restrain the temperature rise and tried to estimate the optimum size of the silica spheres. We confirmed that our hypothesis would be justified. In the calculation of the scattering intensity, the diameter of spheres in conjunction with the wavelength of incident lights would be the predominant parameter to the scattering effects. Our results might explain that our experimentally observed phenomenon is caused by the scattering of light, i.e., electromagnetic waves