排序方式： 共有76条查询结果，搜索用时 31 毫秒
51.
Quantifying aggregation and change in runoff source in accordance with catchment area increase in a forested headwater catchment 
下载免费PDF全文
下载免费PDF全文 There has been a great deal of research interest regarding changes in flow path/runoff source with increases in catchment area. However, there have been very few quantitative studies taking subscale variability and convergence of flow path/runoff source into account, especially in relation to headwater catchments. This study was performed to elucidate how the contributions and discharge rates of subsurface water (water in the soil layer) and groundwater (water in fractured bedrock) aggregate and change with catchment area increase, and to elucidate whether the spatial variability of the discharge rate of groundwater determines the spatial variability of stream discharge or groundwater contribution. The study area was a 5‐km2 forested headwater catchment in Japan. We measured stream discharge at 113 points and water chemistry at 159 points under base flow conditions. End‐member mixing analysis was used to separate stream water into subsurface water and groundwater. The contributions of both subsurface water and groundwater had large variability below 1 km2. The contribution of subsurface water decreased markedly, while that of groundwater increased markedly, with increases in catchment area. The specific discharge of subsurface water showed a large degree of variability and decreased with catchment area below 0.1 km2, becoming almost constant above 0.1 km2. The specific discharge of groundwater showed large variability below 1 km2 and increased with catchment area. These results indicated that the variabilities of stream discharge and groundwater contribution corresponded well with the variability of the discharge rate of groundwater. However, below 0.1 km2, it was necessary to consider variations in the discharge rates of both subsurface water and groundwater. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
52.
Application of an earthquake early warning system and a real-time strong motion monitoring system in emergency response in a high-rise building 总被引：1，自引：0，他引：1
Tomohiro Kubo Yoshiaki Hisada Masahiro Murakami Fusako Kosuge Kohei Hamano 《Soil Dynamics and Earthquake Engineering》2011
We apply a combination of earthquake early warning system (EEWS) and real-time strong motion monitoring system (RSMS) to emergency response for a high-rise building; The Kogakuin University has a 29-story high-rise building in Shinjuku Ward, Tokyo. The proposed strategy is based on the Plan, Do, Check, Action (PDCA) Cycle to brush up the systems and the users: in the “Plan” stage, we apply EEWS and RSMS to the building, where EEWS predicts not only short-period strong ground motions but also long-period ground motions [1]. The system is built into a building announcement system, an emergency elevator control system, and an email message system, which quickly send emails to the emergency response team. Meanwhile, RSMS provides information on seismic intensities at each floor of the building via the web browser in real time using the existing network in the building. In addition, the building response and structural damage can be estimated based on this information. The network system is impervious to the earthquake damage, because the network cable has extra length, there is, however, possible that a network system does not work due to power outage. Thus, we develop the network system that has uninterruptible power-supply system (UPS) and apply it to EEWS and RSMS. The high-rise building has the emergency call units to the security control center in the building on every floor. The emergency call line, however, will be busy promptly, because it is able to use only one line. Therefore, we installed IP telephone which uses the network system on main floors. UPS will work about 30 min after a major earthquake, it is supposed to be enough time for gathering the damage information about the building during initial response. In the “Do” stage, we prepare emergency response instruction manuals and educate the faculty members and students to carry out promptly emergency response. In the “Check” stage, the validity of the proposed systems are verified by carrying out an earthquake drill in an actual high-rise building. The earthquake drill confirmed that our proposed approach is valid. In the final “Action” stage, we improve these systems and emergency response manual and educate people in the building how to use effectively these systems. 相似文献
53.
Mauricio M. Perillo James L. Best Miwa Yokokawa Tomohiro Sekiguchi Tomohiro Takagawa Marcelo H. Garcia 《Sedimentology》2014,61(7):2063-2085
The development of bedforms under unidirectional, oscillatory and combined‐flows results from temporal changes in sediment transport, flow and morphological response. In such flows, the bedform characteristics (for example, height, wavelength and shape) change over time, from their initiation to equilibrium with the imposed conditions, even if the flow conditions remain unchanged. These variations in bedform morphology during development are reflected in the sedimentary structures preserved in the rock record. Hence, understanding the time and morphological development in which bedforms evolve to an equilibrium stage is critical for informed reconstruction of the ancient sedimentary record. This article presents results from a laboratory flume study on bedform development and equilibrium development time conducted under purely unidirectional, purely oscillatory and combined‐flow conditions, which aimed to test and extend an empirical model developed in past work solely for unidirectional ripples. The present results yield a unified model for bedform development and equilibrium under unidirectional, oscillatory and combined‐flows. The experimental results show that the processes of bedform genesis and growth are common to all types of flows, and can be characterized into four stages: (i) incipient bedforms; (ii) growing bedforms; (iii) stabilizing bedforms; and (iv) fully developed bedforms. Furthermore, the development path of bedform; growth exhibits the same general trend for different flow types (for example, unidirectional, oscillatory and combined‐flows), bedform size (for example, small versus large ripples), bedform shape (for example, symmetrical or rounded), bedform planform geometry (for example, two‐dimensional versus three‐dimensional), flow velocities and sediment grain sizes. The equilibrium time for a wide range of bed configurations was determined and found to be inversely proportional to the sediment transport flux occurring for that flow condition. 相似文献
54.
Kazuo Konagai Tomohiro Fujita Takaaki Ikeda Shigeki Takatsu 《Soil Dynamics and Earthquake Engineering》2009
The October 23, 2004, Mid-Niigata Earthquake jolted central Japan, causing serious damage in a mountainous region of Pliocene sedimentary rocks. Though aftershocks distribution showed a diffused pattern, it indicated that a blind-thrust fault having a NE–SW strike and inclined towards NW was the most causative. Tectonic deformation caused by this faulting was considered to be one of the causes of flooding that occurred about 8 months after the earthquake. Precise digital elevation models (DEMs) before and after the earthquake were obtained with stereoscopy for aerial photographs and laser imaging detection and ranging technology (LIDAR), respectively, and then compared to detect elevation changes and translations. Lastly, the changes of landforms due to landslides are excluded from the estimated deformations to obtain only the components of tectonic deformations of the ground surface. 相似文献
55.
Tomohiro?OhuchiEmail author Takaaki?Kawazoe Yuji?Higo Akio?Suzuki 《Contributions to Mineralogy and Petrology》2017,172(8):65
Deformation experiments on olivine aggregates were performed under hydrous conditions using a deformation-DIA apparatus combined with synchrotron in situ X-ray observations at pressures of 1.5–9.8 GPa, temperatures of 1223–1800 K, and strain rates ranging from 0.8 × 10?5 to 7.5 × 10?5 s?1. The pressure and strain rate dependencies of the plasticity of hydrous olivine may be described by an activation volume of 17 ± 6 cm3 mol?1 and a stress exponent of 3.2 ± 0.6 at temperatures of 1323–1423 K. A comparison between previous data sets and our results at a normalized temperature and a strain rate showed that the creep strength of hydrous olivine deformed at 1323–1423 K is much weaker than that for the dislocation creep of water-saturated olivine and is similar to that for diffusional creep and dislocation-accommodated grain boundary sliding, while dislocation microstructures showing the [001] slip or the [001](100) slip system were developed. At temperatures of 1633–1800 K, a much stronger pressure effect on creep strength was observed for olivine with an activation volume of 27 ± 7 cm3 mol?1 assuming a stress exponent of 3.5, water fugacity exponent of 1.2, and activation energy of 520 kJ mol?1 (i.e., power-law dislocation creep of hydrous olivine). Because of the weak pressure dependence of the rheology of hydrous olivine at lower temperatures, water weakening of olivine could be effective in the deeper and colder part of Earth’s upper mantle. 相似文献
56.
A test on a full‐scale model of a three‐storey steel moment frame was conducted, with the objectives of acquiring real information about the damage and serious strength deterioration of a steel moment frame under cyclic loading, studying the interaction between the structural frame and non‐structural elements, and examining the capacity of numerical analyses commonly used in seismic design to trace the real cyclic behaviour. The outline of the test structure and test program is presented, results on the overall behaviour are given, and correlation between the experimental results and the results of pre‐test and post‐test numerical analyses is discussed. Pushover analyses conducted prior to the test predicted the elastic stiffness and yield strength very reasonably. With proper adjustment of strain hardening after yielding and composite action, numerical analyses were able to accurately duplicate the cyclic behaviour of the test structure up to a drift angle of 1/25. The analyses could not trace the cyclic behaviour involving larger drifts in which serious strength deterioration occurred due to fracture of beams and anchor bolts and progress of column local buckling. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
57.
Primitive magmas provide critical information on mantle sources, but most Martian meteorites crystallized from fractionated melts. An olivine-phyric shergottite, Yamato 980459 (Y-980459), has been interpreted to represent a primary melt, because its olivine megacrysts have magnesian cores (Fo84-86) that appear to be in equilibrium with the Y-980459 whole-rock composition based on Fe-Mg partitioning. However, crystal size distribution (CSD) plots for Y-980459 olivines show a size gap, suggesting a cumulus origin for some megacrysts. Because melting experiments using the Y-980459 whole-rock composition have been used to infer the thermal structure and volatile contents of the Martian mantle, the interpretation that this rock is primitive should be scrutinized.We report major, minor and trace element compositions of Y-980459 olivines and compare them with results from melting experiments (both hydrous and anhydrous) and thermodynamic calculations. Cores of the olivine megacrysts have major and minor element contents identical to those of the most magnesian olivines from the experiments, but they differ slightly from those of thermodynamic calculations. This is probably because the Y-980459 whole-rock composition lies near the limit of the range of liquids used to calibrate these models. The megacryst cores (Fo80-85) exhibit minor and trace element (Mn-Ni-Co-Cr-V) characteristics distinct from other olivines (megacryst rims and groundmass olivines, Fo < 80), implying that the megacryst cores crystallized under more reduced conditions (∼IW + 1).Y-980459 contains pyroxenes with orthopyroxene cores mantled by pigeonite and augite. We also found some reversely zoned pyroxenes that have augite cores (low-Mg#) mantled by orthopyroxenes (high-Mg#), although they are uncommon. These reversely zoned pyroxenes are interpreted to have grown initially as atoll-like crystals with later crystallization filling in the hollow centers, implying disequilibrium crystallization at a moderate cooling rate (3-7 °C/h). The calculated REE pattern of a melt in equilibrium with normally zoned pyroxene is parallel to those of glass and the Y-980459 whole-rock as well as other depleted olivine-phyric shergottites, suggesting that Y-980459 was derived from a depleted mantle reservoir.Considering the CSD patterns of Y-980459 olivines, we propose that the olivine megacrysts are cumulus crystals which probably formed in a feeder conduit by continuous melt replenishment, and the parent melt composition was indistinguishable from the Y-980459 whole-rock with 0-2 wt% of H2O and 0-5 wt% of CO2. The final magma pulse entrained these cumulus olivines and then crystallized groundmass olivines and pyroxenes. Although Y-980459 contains small amounts of cumulus olivine (<∼6 vol%), we conclude that the Y-980459 whole-rock composition closely approximates a Martian primary melt composition. 相似文献
58.
Environmental conditions determining the timing of the lifetime maximum intensities of tropical cyclones (TCs) are investigated for the TCs over the western North Pacific during the period 2008-2017. The results show that the land controls the timings of the lifetime maximum intensities in 42% of the TCs over this basin, indicating that accurate track forecasts are beneficial for TC intensity forecasts. With respect to other TCs that are not affected by the land (i.e., Ocean-TCs), the timings of their lifetime maximum intensities are determined by multiple oceanic factors. In particular, interactions between TCs and cold-core eddies occur in a large proportion (nearly 60%) of Ocean-TCs at or shortly after the times of their lifetime maximum intensities, especially in strong TCs (categories 4 and 5), suggesting that a consideration of the above interactions is necessary for improving TC intensity forecasting skills. In addition, unfavorable oceanic heat content conditions become common as the latitude increases over 25°N, influencing half of the Ocean-TCs. Strong vertical wind shear contributes detrimentally to the atmospheric environment in 17% of the TCs over this basin, especially in moderate and weak TCs. In contrast, neither the maximum potential intensity nor the humidity in the middle level of the atmosphere plays dominant roles when TCs turn from their peak intensities to weakening. 相似文献
59.
Asobo Nkengmatia Elvis Asaah Tetsuya Yokoyama Hikaru Iwamori Festus Tongwa Aka Jules Tamen Takeshi Kuritani Tomohiro Usui Takeshi Hasegawa Eric Martial Fozing 《Chemie der Erde / Geochemistry》2022,82(2):125865
We report whole-rock geochemistry and Sr–Nd–Pb isotopic compositions of mafic dykes intruded in the Precambrian granito-gneissic basement complex, exposed at Nyos, Batibo, Dschang and Foumban on the Cameroon Line. The dykes are alkaline (Batibo), transitional (Foumban), and subalkaline (Nyos, Batibo and Dschang) with SiO2 of 45–54 wt% and MgO of 2–9 wt%, similar to dykes reported in other areas of the Cameroon Line (CL) and the Central Atlantic Magmatic Province (CAMP). The abundances of rare earth elements (REE) and the Primitive Mantle normalised patterns for the Nyos, Batibo and Dschang dykes are similar to those of MORB, indicating that the dykes formed at shallower depths by a higher degree of partial melting relative to the Foumban dykes and the alkaline lavas of the CL. The transitional basaltic dykes with steeper REE patterns have their sources at deeper levels in the lithospheric mantle, possibly the garnet-spinel transition zone and were generated by a lower degree partial melting of the lithospheric and plume components. The Nyos and Batibo subalkaline dykes show similar isotopic compositions with a spectrum extending from depleted (DMM-like) to enriched (EM1-like) mantle, indicating the similarity in their source components. The Dschang dykes show distinct isotopic characteristics with relatively unradiogenic Nd-Pb isotope compositions compared to the Batibo and Nyos dykes. The Foumban transitional dykes with characteristic wide ranges in Sr-Nd-Pb isotopic compositions reveal varying contributions from enriched mantle components (EM1 and EM2) in addition to its plume signature similar to those of CL lavas. The Nyos and Batibo dykes alongside other dykes on the CL have low TiO2 abundances (<2 wt%), negative PM-normalised Nb-anomalies, and moderately to strongly enriched REE patterns, and isotopic composition that overlaps with those of CAMP, suggesting a similar lithospheric origin. 相似文献
60.
Jun Hosoi Makoto Okada Tomohiro Gokan Kazuo Amano Andrew James Martin 《Island Arc》2015,24(3):288-300
It is well known that a counterclockwise rotation occurred in the Miocene in northeast Japan. However, the detailed timing and mechanism of the rotation has been debated. Moreover, there has been no research about the relationship between rotational tectonics and the evolution of sedimentary basins. We carried out paleomagnetic and rock magnetic analyses in Nishiwaga Town, Iwate Prefecture, northeast Japan, where the stratigraphy and sedimentary basin formation have previously been clarified. We found that there was a counterclockwise rotational movement of about 45° at about 15 Ma. From our results and previous studies on the tectonics and sedimentary basin development, we are able to ascertain the following tectonic history and sedimentary basin evolution in this area: (i) before the rotational movement, sandstone and mudstone were deposited in a tranquil environment with no volcanic activity coupled with slow tectonic subsidence; (ii) between 16.4–15.1 Ma and 14 Ma, a counterclockwise rotation occurred with rapid tectonic subsidence and continuous explosive volcanism; (iii) at about 14 Ma, the counterclockwise rotation ended and there was a reduction in both subsidence and volcanism. This result shows the impact that rotational tectonics can have on sedimentary basin formation. 相似文献