Polarization measurements using the Bragg crystal spectrometers on Hinotori     

Kyo Akita  Katsuo Tanaka  Tetsuya Watanabe 《Solar physics》1983,86(1-2):101-105

The two Bragg crystal spectrometers on board Hinotori provide a new technique for measuring linear polarization of the soft X-ray line emission from solar flares. The results of the measurements of large (X class) flares are given in this paper, and the polarization degree averaged over the soft X-ray maximum phases is estimated to be less than 4%.  相似文献   

Accurate Isotopic and Concentration Analyses of Small Amounts of Pb Using Isotope Dilution Coupled with the Double Spike Technique   总被引：1，自引：0，他引：1  

Takeshi Kuritani  Tomohiro Usui    Tetsuya Yokoyama  Eizo Nakamura 《Geostandards and Geoanalytical Research》2006,30(3):209-220

A new method has been developed for the simultaneous determination of Pb abundance and Pb isotopic composition with high precision and accuracy for small test portion masses by thermal ionisation mass spectrometry. In this method, a ²⁰⁵pb-²⁰⁴pb double spike is added to samples prior to the chemical separation of Pb, and the isotopic composition of the spike-sample mixture is determined rigorously by the double spike technique using a ²⁰⁷Pb-²⁰⁴Pb spike. The isotopic composition and concentration of Pb in the sample are then obtained by utilising the principle of isotope dilution. Using this technique, replicate determinations of Pb from NIST SRM 981 and GSJ JP-1 (peridotite; 0.07 μg g⁻¹ Pb) were performed. The measured concentration and isotopic data were identical, within uncertainty, to published data or to data that were determined independently in this study. The application of this method to U-Pb dating and the determination of the "initial" Pb isotopic composition was also tested. Lead isotopic compositions and the concentrations of Pb, Th and U were determined for a single batch of samples, through the addition of ²⁰⁵pb-²⁰⁴pb, ²³⁰Th and ²³⁵U spikes to samples prior to chemical separation. Also in these experiments, we confirmed that this routine gives accurate data for Pb, Th and U concentrations and Pb isotopic compositions.  相似文献   

Effect of the development of notches and tension cracks on instability of limestone coastal cliffs in the Ryukyus, Japan   总被引：1，自引：0，他引：1  

Tetsuya Kogure  Hisashi Aoki  Akira Maekado  Takashi Hirose  Yukinori Matsukura 《Geomorphology》2006,80(3-4):236-244

Notches cut by waves are currently developing at the base of vertical coastal limestone cliffs in Okinawa, Japan. The cliff height varies from 3.0–22.1 m, and the maximum notch depth is 8.8 m. Many rectangular or cubic blocks, which appear to have originated from cliff failures, are found on platforms in front of the cliffs. On the flat top surface of the cliff, tension cracks often run parallel to the cliff face. The vertical face of the cliffs displays small undulations but no sliding striation, suggesting that cliff failures have been caused by toppling rather than by shearing or sliding. We use slope stability analysis to determine the critical condition for toppling failure. Physical and mechanical properties of the cliff material were first obtained from laboratory tests. The results indicate that the strength of limestone shows a scale effect, such that the strength decreases with increasing size of the test specimens. Based on this result, we estimated the strength of a rock mass corresponding to the size of the coastal cliff. Cliff stability was then analyzed using a cantilever beam model. Comparison of the stability analysis and the dimension of fallen blocks indicates that toppling failure is strongly associated with the development of notches and tension cracks.  相似文献   

Nonlinear sloshing in a floating‐roofed oil storage tank under long‐period seismic ground motion     

Tetsuya Matsui  Takashi Nagaya 《地震工程与结构动力学》2013,42(7):973-991

A hybrid analytical and FEM is proposed to investigate the nonlinear sloshing in a floating‐roofed oil storage tank under long‐period seismic ground motion. The tank is composed of a rigid cylindrical wall and a flat bottom, whereas the floating roof is treated as an elastic plate undergoing large deflection. The contained liquid is assumed to be inviscid and incompressible, and the flow is assumed to be irrotational. The method of analysis is based on representation of the liquid motion by superposing the analytical modes that satisfy the Laplace equation and the rigid wall and bottom boundary conditions. The FEM is then applied to solve the remaining kinematic and dynamic boundary conditions at the moving liquid surface coupled with the nonlinear equation of motion of the floating roof. This requires only the discretization of the liquid surface and the floating roof into finite elements, thus leading to a computationally efficient and accurate method compared with full numerical analysis. As numerical examples to illustrate the applicability of the proposed method, two oil storage tanks with single‐deck type floating roofs damaged during the 2003 Tokachioki earthquake are studied. It is shown that the nonlinear oscillation modes with the circumferential wave numbers 0, 2 and 3 caused by the finite liquid surface elevation as well as the membrane action due to large deflection of the deck produce excessively large stresses in the pontoon, which may cause the catastrophic failure of pontoon followed by the submergence of the roof. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

In situ X-ray diffraction measurements of the <Emphasis Type="Italic">fcc</Emphasis>–<Emphasis Type="Italic">hcp</Emphasis> phase transition boundary of an Fe–Ni alloy in an internally heated diamond anvil cell     

Tetsuya?KomabayashiEmail author  Kei?Hirose  Yasuo?Ohishi 《Physics and Chemistry of Minerals》2012,39(4):329-338

The phase transition boundary between the face-centered cubic (fcc) structure and hexagonal close-packed (hcp) structure in an Fe–Ni alloy was determined at pressures from 25 to 107 GPa by using an internally resistive-heated diamond anvil cell (DAC), combined with in situ synchrotron X-ray diffraction measurements. The fcc–hcp phase transition boundary in Fe–9.7 wt% Ni is located at slightly lower temperatures than that in pure Fe, confirming the previous understanding that the addition of Ni expands the stability field of the fcc phase. The dP/dT slope of the boundary was determined to be 0.0426 GPa/K, which is slightly larger than that of pure Fe. The pressure interval of the two-phase region is about 6 GPa at a constant temperature, implying that the previous estimates by laser-heated DAC experiments of 10–20 GPa were overestimated. The two-phase region of fcc + hcp would be limited to a pressure of about 120 GPa even in Fe–15 wt%Ni, excluding the possibility of the existence of the fcc phase in the inner core if the simple linear extrapolation of the two-phase region is applied. The pressure and temperature dependences of the c/a axial ratio of the hcp phase in Fe–9.7 wt% Ni are generally consistent with those in pure Fe, suggesting that Ni has minor effects on the c/a ratio.  相似文献   

Application of an impact plate – Bedload transport measuring system for high-speed flows     

Takahiro Koshiba  Christian Auel  Daizo Tsutsumi  Sameh A. Kantoush  Tetsuya Sumi 《国际泥沙研究》2018,33(1):35-46

To achieve the sustainable use of dams, the development of methods for sediment management in reservoirs is required. One such method includes the use of Sediment Bypass Tunnels (SBTs) to divert sediment around a dam, thereby preventing sedimentation in the reservoir. However, SBTs are prone to severe invert abrasion caused by the high sediment flux. Therefore, it is necessary to establish a measurement system of the sediment transport rate in these tunnels. One system to measure sediment transport in rivers is the Swiss plate geophone, which can register plate vibrations caused by particle impact. In Japan, the Japanese pipe microphone is used, and sediment transport is measured based on the sound emitted by the particle impact. In this study an attempt was made to optimize the advantages of both systems by fixing a microphone and an acceleration sensor to a steel plate. The results of calibration experiments with this new system are presented and compared with the existing methods. It was found that the acceleration sensor can detect sediment particles larger than 2 mm in diameter. Moreover, a new parameter, referred to as the detection rate, was introduced to describe the correlation between the actual amount of sediment and the registered output. Finally, two parameters - the saturation rate and hit rate - are introduced and exhibit strong correlation with the detection rate.  相似文献   

Formal education and disaster response of children: evidence from coastal villages in Indonesia     

Shoji  Masahiro  Takafuji  Yoko  Harada  Tetsuya 《Natural Hazards》2020,103(2):2183-2205

Natural Hazards - Although children are exposed to a high mortality risk during disasters, what determines their disaster response, especially during earthquakes, remains largely unexplored. The...  相似文献   

Geochemistry and Sm‐Nd chronology of a Stannern‐group eucrite,Northwest Africa 7188     

Saya Kagami  Makiko K. Haba  Tetsuya Yokoyama  Tomohiro Usui  Richard C. Greenwood 《Meteoritics & planetary science》2019,54(11):2710-2728

We report the results of a detailed study of the basaltic eucrite Northwest Africa (NWA) 7188, including its mineralogical and bulk geochemical characteristics, oxygen isotopic composition, and ^147,146Sm‐^143,142Nd mineral isochron ages. The texture and chemical composition of pyroxene and plagioclase demonstrate that NWA 7188 is a monomict eucrite with a metamorphic grade of type 4. The oxygen isotopic composition and the Fe/Mn ratios of pyroxene confirmed that NWA 7188 belongs to the howardite–eucrite–diogenite meteorite suite, generally considered to originate from asteroid 4 Vesta. Whole‐rock TiO₂, La, and Hf concentrations and a CI chondrite‐normalized rare earth element pattern are in good agreement with those of representative Stannern‐group eucrites. The ^147,146Sm‐^143,142Nd isochrons for NWA 7188 yielded ages of 4582 ± 190 and 4554 +17/?19 Ma, respectively. The closure temperature of the Sm‐Nd system for different fractions of NWA 7188 was estimated to be >865 °C, suggesting that the Sm‐Nd decay system has either been resistant to reheating at ~800 °C during the global metamorphism or only partially reset. Therefore, the ¹⁴⁶Sm‐¹⁴²Nd age of NWA 7188 corresponds to the period of initial crystallization of basaltic magmas and/or global metamorphism on the parent body, and is unlikely to reflect Sm‐Nd disturbance by late reheating and impact events. In either case, NWA 7188 is a rare Stannern‐group eucrite that preserves the chronological information regarding the initial crustal evolution of Vesta.  相似文献   

High‐resolution national land use scenarios under a shrinking population in Japan     

Haruka Ohashi  Keita Fukasawa  Toshinori Ariga  Tetsuya Matsui  Yasuaki Hijioka 《Transactions in GIS》2019,23(4):786-804

In sharp contrast with the global trend in population growth, certain developed countries are expected to experience rapid national population declines. Considering future land use scenarios that include depopulation is necessary to evaluate changes in ecosystem services that affect human well‐being and to facilitate comprehensive strategies for balancing rural and urban development. In this study, we applied a population‐projection‐assimilated predictive land use modeling (PPAP‐LM) approach, in which a spatially explicit population projection was incorporated as a predictor in a land use model. To analyze the effects of future population distributions on land use, we developed models for five land use types and generated projections for two scenarios (centralization and decentralization) under a shrinking population in Japan during 2015–2050. Our results suggested that population centralization promotes the compaction of built‐up areas and the expansion of forest and wastelands, while population decentralization contributes to the maintenance of a mixture of forest and cultivated land.  相似文献   

Optimization of causative factors using logistic regression and artificial neural network models for landslide susceptibility assessment in Ujung Loe Watershed,South Sulawesi Indonesia     

Andang Suryana SOMA  Tetsuya KUBOTA  Hideaki MIZUNO 《山地科学学报》2019,(2)

Landslide susceptibility maps(LSMs) play a vital role in assisting land use planning and risk mitigation. This study aims to optimize causative factors using logistic regression(LR) and an artificial neural network(ANN) to produce a LSM. The LSM is produced with 11 causative factors and then optimized using forward-stepwise LR(FSLR), ANN, and their combination(FSLR-ANN) until eight causative factors were found for each method. The ANN method produced superior validation results compared with LR. The ROC values for the training data set ranges between 0.8 and 0.9. On the other hand, validation with the percentage of landslide fall into LSM class high and very high, ANN method was higher(92.59%) than LR(82.12%). FSLR-ANN with nine causative factors gave the best validation results with respect to area under curve(AUC) values, and validation with the percentage of landslide fall into LSM class high and very high. In conclusion, ANN was found to be better than LR when producing LSMs. The best Optimization was combination of FSLR-ANN with nine causative factors and AUC success rate 0.847, predictive rate 0.844 and validation with landslide fall into high and very high class with 91.30%. It is an encouraging preliminary model towards a systematic introduction of FSLR-ANN model for optimization causative factors in landslide susceptibility assessment in the mountainous area of Ujung Loe Watershed.  相似文献