This report presents low-pressure chemical vapor deposition (LPCVD) Si 3 N 4 waveguide (WG) technology that does not require high-temperature annealing to eliminate residual hydrogen. A uniform refractive index of LPCVD Si 3 N 4 for the core was obtained through batch processing. A comparison of films produced by LPCVD and plasma-enhanced chemical vapor deposition (PECVD) techniques revealed that the LPCVD films resulted in significantly lower hydrogen contamination, measuring only 1.6 atomic percent-an order of magnitude smaller than found in the PECVD films. A propagation loss as low as 0.63 dB cm −1 was demonstrated for LPCVD Si 3 N 4 WGs. This value was approximately consistent with the simulated scattering loss due to line edge roughness, which was 0.44 dB cm −1 .
We present a comprehensive multi-parametric analysis of Lithosphere– Atmosphere–Ionosphere Coupling (LAIC) processes associated with the M = 8.8 earthquake that struck offshore Kamchatka, Russia, on 30 July 2025 (29 July 2015; 23:24:52 UTC). Thermal observations revealed coherent pre-seismic irregularities in near-surface air temperature, relative humidity, and atmospheric chemical potential (ACP), with maximum intensification occurring 1–2 days before the event, followed by rapid co-seismic dissipation and post-seismic recovery. Acoustic channel analysis revealed considerable enhancements in atmospheric gravity wave (AGW) potential energy, as computed from ERA5 reanalysis datasets, 3–5 days prior to the earthquake, with a co-seismic peak and weaker post-seismic irregularities at higher altitudes. Electromagnetic signatures manifested in both lower and upper ionospheric layers. Very-Low-Frequency (VLF) sub-ionospheric propagation from the NPM transmitter, continuously monitored at the PTK (Petropavlovsk-Kamchatsky) station in Kamchatka, Russia, exhibited both positive and negative deviations in amplitude and phase during the preparatory phase. VLF amplitude exhibited wavelike deviations consistent with AGW periods, peaking one day prior to the earthquake. Ionospheric Vertical Total electron content (VTEC) showed coherent pre-seismic maxima 2–3 days before the main shock. Together, these thermal, acoustic, and electromagnetic observations strongly suggest a consistent pre-seismic build-up, co-seismic dissipation, and post-seismic recovery, providing a robust multi-channel imprint of the Kamchatka earthquake and highlighting the importance of integrated multi-parameter approaches for understanding earthquake preparatory dynamics.
Understanding the role of aggregates in the compressive strength of brittle composites is crucial for optimizing construction material usage. In this study, we employed the rigid-body-spring-network model validated with experimental data. Through uniaxial compression loading tests on concrete, considering Young's modulus and compressive strength of the coarse aggregate as variables, we elucidated how the coarse aggregate's physical properties influence concrete's compressive strength, illustrated using a straightforward diagram. When the coarse aggregate's Young's modulus is lower than the mortar's, the stress transfer path within the mortar bends and cracks more rapidly, significantly lowering strength. Conversely, if the coarse aggregate's Young's modulus exceeds that of the mortar, stress becomes concentrated in the aggregate, and the crack of the coarse aggregate governs the failure of concrete.
