Spectroscopic properties of Cr-doped and Cr,Li-doped synthetic forsterite crystals

Cr-droped and Cr,Li-doped forsterite crystals were grown and their optical properties were investigated. It was shown that when only Cr is doped, Cr³⁺ is substituted at the site of low crystal field, and the energy level ²E lie above the ⁴T₂ level, while ⁴T₂ is just above ²E when Cr and Li are codoped. The difference was rationalized by a deformation of the Cr substituted site with the introduction of Li.     

Impacts of the South China Sea Throughflow on seasonal and interannual variations of the Indonesian Throughflow

Impacts of the South China Sea Throughflow (SCST) on seasonal and interannual variations of the Indonesian Throughflow are studied by comparing outputs from ocean general circulation model (OGCM) experiments with and without the SCST. The observed subsurface maximum in the southward flow through the Makassar Strait is simulated only when the SCST, which is driven by the large-scale wind, is allowed in the model. The mean volume and heat transport by the Makassar Strait Throughflow are reduced by 1.7 Sv and 0.19 PW, respectively, by the existence of the SCST in the model. The difference is particularly remarkable during boreal winter when the SCST reaches its seasonal maximum. Furthermore, the SCST is strengthened during El Niño, leading to the weakening in the southward volume and heat transport through the Makassar Strait by 0.37 Sv and 0.05 PW, respectively. These findings from the OGCM experiments suggest that the SCST may play an important role in climate variability of the Indo-Pacific Ocean.     

A stochastic model of earthquake occurrence and the accompanying horizontal land deformation

A large-scale earthquake is believed to be associated with a release of strain energy accumulated in the crust, probably by the motion of upper-mantle lithosphere. Such an earthquake mechanism is well simulated by a belt-conveyer model proposed by Utsu (1972). The probability of earthquake occurrence can be estimated on the assumption that the motion of a slider on the belt-conveyer is mathematically formulated as a Markov process.In the probabilistic expressions, the results of Mogi's (1962) rock-fracture experiments are applied to the hazard-rate function of earthquake occurrence. The hazard-rate function has two coefficients, A and B, to be determined by the experiments. It is concluded that, when B is small, a number of small-scale earthquakes occur in the early time after the accumulation of crustal strain energy starts, but that the accumulated strain energy changes catastrophically into a single large-scale earthquake, when B is large.     

A catalytic oxidation method for the determination of total nitrogen dissolved in seawater

A detailed examination of a high-temperature catalytic oxidation method for liquid samples in the analysis of total nitrogen dissolved in seawater is reported. The nitrogenous compounds in liquid samples are oxidized on a platinum catalyzer at 680°C under oxygen atmosphere and the generated NO₂ is absorbed into a chromogenic reagent, followed by a spectrophotometric determination. The results of this method are much higher than those of wet oxidation methods. Molecular size dependency of the results clearly indicates that the above discrepancy is caused by the low oxidation capacity of the wet oxidation method against high-polymer organic matter dissolved in seawater. The results revealed that the concentration of total nitrogen in seawater is nearly constant from surface to bottom, ranging from 30 to 40 μM 1^?1, which organic nitrogen concentration higher in the surface layer, and a rapid decrease with depth. An examination of molecular size distribution indicates that the concentration of high-polymer organic nitrogen decreases rapidly from surface to deeper layers, with molecular sizes ranging from 5 × 10³ to 3 × 10⁴. Because of the well-defined principle of the oxidation process, its reliability, ease of sample handling and of analytical procedure on board or in the land laboratory, the present method is much more suitable for the marine analytical chemistry of total and organic nitrogen than the other previous methods.     

Damage to buildings and structures due to recent devastating wind hazards in East Asia

Extreme wind events such as typhoons and tornadoes can cause devastating damage to structures and huge losses to human societies. This paper introduces recent devastating wind-related disasters in East Asia, including disasters in Japan, the Philippines and China, from 2013 to 2016. In particular, it describes several post-disaster investigations including those on Typhoon Haiyan in 2013 in the Philippines; typhoon Mujigae and two typhoon-associated tornadoes in October, 2015, in Guangdong, China; and a tornado in June, 2016 in Yancheng, China. Meteorological features, damage details and failure mechanisms of structures, factors related to damage generation and spread, scales to evaluate storms, estimations of tornado wind speeds and so on are discussed, with the aim of mitigating future wind-related disasters and to create safer and sustainable societies. Lessons derived from aerodynamic effects, cladding and component performances, debris impacts, building arrangements, fatigue effects, construction methods, etc. together with suggestions for wind-resistant design of buildings are given.     

High-Reflectivity Coatings for a Vacuum Ultraviolet Spectropolarimeter

Precise polarization measurements in the vacuum ultraviolet (VUV) region are expected to be a new tool for inferring the magnetic fields in the upper atmosphere of the Sun. High-reflectivity coatings are key elements to achieving high-throughput optics for precise polarization measurements. We fabricated three types of high-reflectivity coatings for a solar spectropolarimeter in the hydrogen Lyman-\(\upalpha \) (Ly\(\upalpha \); 121.567 nm) region and evaluated their performance. The first high-reflectivity mirror coating offers a reflectivity of more than 80 % in Ly\(\upalpha \) optics. The second is a reflective narrow-band filter coating that has a peak reflectivity of 57 % in Ly\(\upalpha \), whereas its reflectivity in the visible light range is lower than 1/10 of the peak reflectivity (\(\sim 5~\%\) on average). This coating can be used to easily realize a visible light rejection system, which is indispensable for a solar telescope, while maintaining high throughput in the Ly\(\upalpha \) line. The third is a high-efficiency reflective polarizing coating that almost exclusively reflects an s-polarized beam at its Brewster angle of 68° with a reflectivity of 55 %. This coating achieves both high polarizing power and high throughput. These coatings contributed to the high-throughput solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which was launched on 3 September, 2015.     

Analysis of the appearance and disappearance of point objects over time

The appearance and disappearance of immovable points are important spatiotemporal events in geographical information science. They represent phenomena such as the birth and death of trees in forests, construction and destruction of buildings in cities and openings and closures of shops and restaurants. This paper proposes a new method for analyzing the appearance and disappearance of points. The method helps analysts capture the overall picture and regional variation of event pattern and detecting significant local patterns. Four measures are defined that indicate the intensity of spatial and temporal patterns of events. The measures are visualized as grid maps. A statistical test is used to evaluate the significance of the measures to extract the regions of significant patterns. The proposed method is applied in an analysis of shops and restaurants in Shibuya, Tokyo. Technical soundness of the method is discussed along with empirical findings.     

Electromagnetic anomalies associated with 1995 Kobe earthquake

Occurrences of anomalous electro-magnetic phenomena at varied frequency ranges, covering ELF to VHF, have been reported in relation to the 17 January 1995 Kobe earthquake (M7.2), by several independent research groups. Prominent pre-seismic peaks, which could have been emitted from the focal area, were observed on 9-10 January in ELF, VLF, LF and HF ranges. Whether these changes were truly related to the earthquake is not certain, because atmospheric (thunderbolt discharge) activities also peaked on 9-10 January. The nomalous changes were markedly enhanced toward the catastrophe in agreement with many reports on unusual radio/TV noise. Anomalous transmission of man-made electromagnetic waves in VLF and VHF ranges was also detected from a few days before the earthquake, indicating the possibility that the ionosphere above the focal zone was disturbed at the final stage of the earthquake preparation process.     

Comparative Measurements Of Co2flux Over A Forest Using Closed-Path And Open-Path Co2analysers

An eddy covariance system using a closed-path CO₂analyser was constructed for long-term CO₂flux measurements above a forest, and its total frequency response was valuated experimentally. The amplitude and phase responses of the system wereexamined through a preliminary test, in which a prescribed pattern of CO₂fluctuation was input to the system. The result showed that the amplitude of the output from the system was attenuated as frequency increased, with a half-power frequency of 0.3 Hz. The phase was delayed by the air sampling through a long tube, but the delay in phase decreased asfrequency increased. We then presented a new technique for the correction of flux loss due to the inadequate system response for the eddy covariance measurements of CO₂ flux. Using the present system and the correction technique, diurnal variations in CO₂ flux were measured over a temperate deciduous forest on three days in 1997. The results were compared with the CO₂fluxes measured with a fast response open-path gas analyser. The CO₂fluxes from the closed-path system agreed with those from the open-path system after the Webb, Pearman and Leuning correction was made for the latter. In the present test over a forest, the contribution of the frequency-response correction to the CO₂fluxes was small and its averaged percentage was only 3%in the daytime. However, the percentage would likely increase, if the system were applied to a shorter vegetation site where high frequency components are more important. The comparison confirmed that we can obtain correct measurements of CO₂flux using the present closed-path system and the correction technique.