Transient noise ("glitches") in gravitational wave detectors can mimic or obscure true signals, significantly reducing detection sensitivity. Identifying and excluding glitch-contaminated data segments is therefore crucial for enhancing the performance of gravitational-wave searches. We perform a noise analysis of the KAGRA data obtained during the O3GK observation. Our analysis is performed with hierarchical veto (Hveto) which identifies noises based on the statistical time correlation between the main channel and the auxiliary channels. A total of 2531 noises were vetoed by 28 auxiliary channels with the configuration (i.e. signal-to-noise threshold set to 8) that we chose for Hveto. We identify vetoed events as glitches on the spectrogram via visual examination after plotting them with Q-transformation. By referring to the Gravity Spy project, we categorize 2354 glitches into 6 types: blip, helix, scratchy, and scattered light, which correspond to those listed in Gravity Spy, and dot and line, which are not found in the Gravity Spy classification and are thus named based on their spectrogram morphology in the KAGRA data. The remaining 177 glitches are determined not to belong to any of these six types. We show how the KAGRA glitch types are related to each subsystem of KAGRA. To investigate the possible correlation between the main channel and the round winner-an auxiliary channel statistically associated with the main channel for vetoing purposes-we visually examine the similarity or difference in the glitch pattern on the spectrogram. We compare the qualitative correlation found through visual examination with coherence, which is known to provide quantitative measurement for the correlation between the main channel and each auxiliary channel. Our comprehensive noise analysis will help improve the data quality of KAGRA by being applied to future KAGRA observation data.
Citizens use a variety of infrastructure. The majority of these are managed by municipalities. Therefore, in order for citizens to continue living safely and comfortably, proper maintenance of municipal infrastructure is essential. However, compared to the nation and prefectures, progress in inspections and measures for infrastructure managed by municipalities is lagging behind. This study extracted the true issues and needs of municipalities regarding the maintenance of road bridges, which cannot be picked up by a top-down system. In other words, professors from universities and technical colleges in the Hokuriku region visited 53 municipalities and conducted interviews to understand the real voices of staffs. As a result, it can be summarized nine major issues and needs for the management of many short-span reinforced concrete bridges.
Titanium (Ti)-zirconia (ZrO2) bonded materials have been developed as biomaterials with superior hardness, excellent wear resistance, and robust mechanical properties. However, it is crucial to investigate the Ti/ZrO2 interfacial microstructure and suppress the formation of Kirkendall voids caused by elemental diffusion at the bonding interface. This study aims to investigate the effect of oxidation treatment on suppressing elemental diffusion at the interface between pure Ti and ZrO2. Prior to sintering, the titanium surface was oxidized by supplying oxygen gas at a rate of 10 liters/min at 800, 900, and 1000°C for different periods of time. It was studied the effect of the temperature and the holding times during the oxidation treatment of Ti substrate. The Ti/ZrO2 sintered bonds were prepared using the spark plasma sintering process. The microstructures at the bonding interface were observed using SEM. The oxidized titanium surface was analyzed using X-ray diffraction, and elemental diffusion behavior was assessed through EDS analysis. The results demonstrated that elemental diffusion at the interface can be effectively suppressed when oxidation is carried out at temperatures above 900°C for extended periods.
The purpose of this study is to evaluate the compressive strength of sintered titanium porous materials and their composites with biopolymers. The sintered porous material exhibits a network morphology due to the contact between particles connected in three dimensions. Titanium alloy powder (Ti6Al4V) was used as the raw material, and the powder was sintered using the spark plasma sintering process at a temperature of 750°C. Three types of biopolymers—polylactic acid, chitosan, and a chitosan derivative—were impregnated into the porosities of the sintered porous materials to produce the composites. To predict the compressive proof stress, the Gibson-Ashby formula was modified for these materials. This prediction of compressive strength is based on relative density in relation to porosity and relative compression strength measured experimentally. Compression tests were performed, and the proof stress was calculated. All experimental data were represented by prediction-fitting curves derived from the modified equation. The compressive strength characteristics of the porous Ti6Al4V alloys were clarified, and measurements of bending strength and tensile strength were conducted. The results were compared with the strength characteristics of bone, suggesting the potential applicability of the material as an implant.
