An early warning system is essential for spotting suspicious or unknown ships approaching important facilities located at the coast. For this reason, we have developed a buoy equipped with a marine surveillance system.
In this paper, we focused our attention on a difference value between Fast Fourier transform and linear prediction methods to enable early detection of underwater sounds from an approaching boat and observed and analyzed underwater sounds from several ships. Results showed that this maritime surveillance system is highly effective in monitoring underwater sounds. We expect that the system will be useful in detecting the presence of dubious ships or poaching boats through underwater sound detection.
Surface texturing has been considered as one of the approaches for application of sliding contact elements. Surface texturing can generate hydrodynamic pressure to provide load capacity and improve tribological characteristics. In addition, surface texturing works as an oil reservoir to hold lubricating oil, and has the effect of collecting wear debris. The lubrication characteristics of sliding surfaces vary by the shape and size of surface texturing, but the exact effect of such elements on these lubrication characteristics has not been fully understood. The purpose of this study is to elucidate the real effects of surface texturing applied on parallel surfaces and to obtain optimum design guidelines of surface texturing. Authors conducted a numerical analysis of the solution of Reynolds equation using a finite element method to assess the effect of surface texturing. The analysis has been performed under two different conditions, one with constant oil film thickness and the other with constant load capacity. The results of the analysis showed that the optimum design of surface texturing to decrease coefficient of friction varies depending on the conditions. In the case of constant oil film thickness, the optimum design of surface texturing was as follows. As for dimples, the area ratio 50% led to the smallest coefficient of friction and the ratio of depth 0.0001 showed the largest load capacity. As for grooves, the area ratio 70% resulted in the smallest coefficient of friction while the ratio of grooves 0.00006 showed the largest load capacity. In the case of constant load capacity, the dimples area ratio 60% and the groove area ratio 70% showed the largest oil film thickness and the smallest coefficient of friction. The larger the ratio of depth got, the smaller the coefficient of friction became.
An electrostatic precipitator (ESP) has such advantages as high collection efficiency of high concentration particles and low pressure loss. However, it can cause the re-entrainment phenomenon, and the hole-type ESP is considered to suppress this phenomenon. The authors developed a parallel-plate hole-type ESP after investigating the characteristics of collection efficiency with the hole-type electrode having a double-cylinder. In this study, the authors examined the right conditions for particle collection and electrode configuration. In the case of large particles, the collection efficiency decreased when the discharge current increased. However, with respect to the particle size of 300nm or less, the greater collection efficiency was achieved when the discharge current increased. The collection efficiency was improved by moving the position of the needle electrode toward the ESP outlet. The collection efficiency also reached the highest point when the hole diameter was 5mm.