Japan Coast Guard Academy

Efficiency of optical beats in a chaotically oscillating laser is confirmed comparing that of free running CW laser using a highly efficient plasmonic photomixer. Ultra-stability of optical beats with laser chaos continues down to the laser threshold level. The output power is also estimated using conventional bowtie antenna. The great potential of chaotically oscillating lasers is verified for THz systems.

Triple junctions between fundamental tectonic units are where different compositions and magmatic processes interact. We investigated the intersection of a spreading center with an island arc within the Philippine Sea Plate, i.e. an arc-ridge-arc triple junction, using a combination of submersible sampling and shipboard geophysics. We use Ar Ar dating, elemental concentrations and Sr-Nd-Pb radiogenic isotope ratios to constrain the structure, age and origin of magmatism as spreading interacted with the arc. Between 33 and 31 Ma the tip of the West Philippine Basin spreading center was in the back-arc west of the Kyushu-Palau arc. Spreading volcanism had mantle-like Ce/Pb and Th/Ce indicating a lack of slab flux. Radiogenic isotopes form a trajectory towards low 143 Nd/ 144 Nd and high 20x Pb/ 204 Pb, but extend to Δ 208 Pb/ 204 Pb > 85 which corresponds to an EM-2-like mantle component rather than pelagic sediment input from the slab. The final stage of spreading-related activity occurred between 31 and 28.5 Ma when the spreading axis rotated from NW-SE to E -W and propagated eastwards into the arc. It resulted in magmatism contemporaneous with the adjacent frontal arc. This final magmatism extended the radiogenic isotopic trajectories observed in the earlier spreading towards less radiogenic Pb and higher 143 Nd/ 144 Nd, i.e. towards MORB from the EM-2 component. However, during the final stage magmatism La/Sm, Nb/Zr increased while Pb and Sr isotopes became progressively more radiogenic, demonstrating a progressive decrease in the degree of partial melting and preferential tapping of the EM-2 component. This change in melt generation and composition appears a common process at the end of spreading. • Magmatism at arc-ridge-arc triple junction in the Philippine Sea Plate was studied. • CBF Rift spreading center intersected KPR arc, caused overlapping MORB magmatism. • Interaction between a volcanic arc and a spreading centre caused excess magmatism. • Spreading center at wanning stage preferentially consumes more enriched mantle.

Abstract Identifying the frictionally locked area of a plate boundary is an important geodetic issue in mitigating earthquake disasters. However, recent long-term geodetic observations have revealed that actual geodetic data contain transient behaviors due to slow slip events or changes in slip deficit rates. Therefore, the use of a snapshot of temporally averaged geodetic data is far insufficient to understand the accurate frictional state. This problem is particularly serious at sub-seafloor plate boundaries, where continuous or periodic geodetic observations for a long time are rarely realized. Here, we evaluated long-term slip deficit rate variations in the Nankai Trough, the only area in the world for which high-density data on horizontal and vertical components have been accumulated via seafloor observations with a sufficient frequency on the decadal scale. Consequently, we constrained the constantly locked areas and found that it was limited mainly to a depth of 10 – 20 km, with slip deficit rate changes occurring throughout the entire shallow side adjacent to the locked area.

We solve an open problem posed by Thamrongthanyalak on the definable Banach fixed point property. Lipschitz curve selection is a key to our solution. In addition, we show a definable version of the Caristi fixed point theorem.

Low cost, compact, highly efficient, and highly stable THz wave using chaotically oscillating laser diode is investigated. Compared it to conventional continuous wave multi-mode semiconductor laser excitation system, about ten times output radio frequency power is increased because of chaotic supremacy.

Although the traditional fire detectors on ships are stable, they have problems such as delay, non-visualisation, and a single detector with a In the target detection algorithm, the YOLOv5 algorithm has advantages in real-time detection, visualisation, and scope. improve accuracy and reduce weight, a real-time detection method for flame and smoke based on the improved YOLOv5 algorithm is proposed. First, a data set of fire and smoke with the background of the YOLOv5 algorithm is proposed. Fire and smoke with the background of the enclosed space of the ship was produced through software simulation, so that the trained model was more targeted to the fire and smoke of the ship. Targeted to the fire and smoke of the ship, and then the YOLOv5 feature extraction network was replaced with PP-LCNet to reduce the model size and speed up the detection speed. And adjust the position of the attention mechanism SE module in the PP-LCNet network to improve the feature extraction ability of the feature extraction network. Finally, EIOU is used as the new bounding box loss function in the loss function part to further increase the accuracy and the experimental results show that the accuracy of the improved model is 0.820, which is 0.4% higher than that of the original YOLOv5 model. The experimental results show that the accuracy of the improved model is 0.820, which is 0.4% higher than that of the original YOLOv5 model. The de-tection speed of the improved model is 77 frames per second, and the model size is only 10.9MB. To enhance detection accuracy and processing speed while meeting lightweight requirements.

When a landslide occurs, the person who discovers it will likely report the disaster; however, a person who receives this report will likely need someone on site to check, since the reporter may have misread the information. This allows third parties to make use of the confirmed information. Facilitating such mechanisms for reporting, confirming, and utilizing disaster information is considered to be necessary for sharing details about one. In this paper, we proposed and analyzed an agent-based model that incorporates disaster behavior into the model of Toriumi et al. The reporting of a disaster refers to submitting articles, the confirmation of the information by another person refers to commenting on the articles, and utilizing the information refers to comments responding to the aforementioned comment using the framework of meta-reward games, based on the prisoner’s dilemma game. We then analyze the costs and rewards to encourage cooperation in several social networks. It is found that reducing the cost of commenting (conforming) encourages the submission of information. The properties of the results do not depend on network structure, which is novel and unexpected, and it is expected that the properties of real social networks will be predictable.

This study examines the degradation of acoustic waveforms in the seafloor crustal movement observation network called Seafloor Geodetic Observation – Array (SGO-A) operated by the Japan Coast Guard using Global Navigation Satellite System - Acoustics combination (GNSS-A) technology. Recently, it was found that the 10 kHz carrier wave used was distorted, resulting in a loss of accuracy. Misidentification of carrier waves due to distortion occurs on a scale of several to 20 cm and significantly hinders centimeter-level observations of vertical positioning. In this study, conducted in an experimental tank, the transmitted waveforms were investigated using the Phase-Only Correlation (POC) method with equipment similar to that used for actual observations. The results suggested that the waveform degradation was mainly due to the superposition of multiple reference waves. In order to evaluate the cause of the carrier wave degradation, a grid-search-like method was used to reproduce the degraded carrier wave. It was shown that the degradation of the carrier wave was not only caused by the hardware structure, but mainly by the internal electrical circuit. These findings suggest the need to examine waveform degradation phenomenon in detail with each equipment and other conditions to determine accurate round-trip times.

Abstract We define a discrete closure operator for definably complete locally o‐minimal structures . The pair of the underlying set of and the discrete closure operator forms a pregeometry. We define the rank of a definable set over a set of parameters using this fact and call it ‐dimension. A definable set X is of dimension equal to the ‐dimension of X. The structure is simultaneously a first‐order topological structure. The dimension rank of a set definable in the first‐order topological structure also coincides with its dimension.