Creep characteristics of frozen soils     

K. Takegawa  A. Nakazawa  K. Ryokai  S. Akagawa 《Engineering Geology》1979,13(1-4):197-205

  相似文献   

Measurements of wave normal direction of whistler mode signals in the ionosphere by means of the Rocket-Doppler technique     

Iwane Kimura  Tetsuo Tomimoto  Kenji Hiraishi 《Planetary and Space Science》1973,21(4):671-682

Wave normal directions of VLF signals propagating through the ionosphere can be determined by measuring Doppler frequency shift of the signals by means of rocket borne receivers. Two rockets were launched to detect the NWC signal of 22.3 kHz which was transmitted from Australia and propagated on two completely different paths, one being propagated through the Earth-ionosphere waveguide and up to the rocket, the other propagated down to the rocket by the whistler mode directly from the source in the opposite hemisphere. The wave normal directions of the latter mode were almost vertically downward in the ionosphere in the northern hemisphere, although substantial error was involved in the determination of the wave normal direction for a part of the upgoing flight of the rockets, due to the relative geometry of the directions of the rocket flight and the geomagnetic field. The effect of the horizontal gradients of the ionosphere on the above results were found to be not significant. From the experimental results it is concluded that field aligned ducts stretching down to the rocket altitudes did not exist, at least, during the rocket flights.  相似文献   

Phase transformations in the earth's mantle and subducting slabs: Implications for their compositions, seismic velocity and density structures and dynamics   总被引：3，自引：0，他引：3  

Tetsuo  Irifune 《Island Arc》1993,2(2):55-71

Abstract Phase transformations in model mantle compositions and those in subducting slabs have been reviewed to a depth of 800 km on the basis of recent high-pressure experimental data. Seismic velocity and density profiles in these compositions have also been calculated using these and other mineral physics data. The nature of the seismic velocity and density profiles calculated for a pyrolite composition was found to generally agree with those determined by seismic observations (e.g. PREM). The locations of the seismic discontinuities at 400 and 670 km correspond almost exactly to the depths where the transformations of the olivine component to denser phases take place. Moreover, the steep gradients in the seismic velocity/density profiles observed between these depths are qualitatively consistent with those expected from the successive transformations in the complementary pyroxene-garnet component in the pyrolite composition. Further, the calculated seismic velocity and density values agree well with those observed in the upper mantle and mantle transition region within the uncertainties attached to these calculations and observations. Pyrolite or peridotite compositions are thus most likely to represent the composition of the mantle above 670 km depth, although some degrees of chemical heterogeneity may exist in the transition region. The observed sharp discontinuous increases of seismic velocities and density at this depth may be attributed either to the phase transformation to a perovskite-bearing assemblage in pyrolite or to chemical composition changes. Density profiles in subducted slabs have been calculated along adequate geotherms assuming that the slabs are composed of the former oceanic crust underlain by a thicker harzburgitic layer. It is shown that the former oceanic crust is substantially less dense than the surrounding pyrolite mantle at depths below 670 km, while it is denser than pyrolite in the upper mantle and the transition region. The subducted former oceanic crust may be trapped in this region, forming a geochemically enriched layer at the upper mantle-lower mantle boundary. Thick and cool slabs may penetrate into the lower mantle, but the chemically derived buoyancy may result in strong deformation and formation of megalith structures around the 670 km seismic discontinuity. These structures are consistent with those detected by recent seismic tomography studies for subduction zones.  相似文献   

Dust ring formation due to ice sublimation of radially drifting dust particles under the Poynting-Robertson effect in debris disks     

Hiroshi Kobayashi  Sei-ichiro Watanabe  Tetsuo Yamamoto 《Icarus》2008,195(2):871-881

In a disk with a low optical depth, dust particles drift radially inward by the Poynting-Robertson (P-R) drag rather than are blown out by stellar radiation pressure following destructive collisions. We investigate the radial distribution of icy dust composed of pure ice and refractory materials in dust-debris disks taking into account the P-R drag and ice sublimation. We find that icy dust particles form a dust ring by their pile-ups at the edge of their sublimation zone, where they sublime substantially at the temperature 100-110 K. The distance of the dust ring is 20-35 AU from the central star with its luminosity L_??30L_⊙ and 65(L_?/100L_⊙)^1/2 AU for L_??30L_⊙, where L_⊙ is the solar luminosity. The effective optical depth is enhanced by a factor of 2 for L_??100L_⊙ and more than 10 for L_??100L_⊙. The optical depth of the outer icy dust disk exceeds that of the inner disk filled with refractory particles, namely, the residue of ice sublimation, which are further subjected to the P-R effect. As a result, an inner hole is formed inside the sublimation zone together with a dust ring along the outer edge of the hole.  相似文献   

Sedimentary facies of Carboniferous–Permian mid-oceanic carbonates in the Changning–Menglian Belt, West Yunnan, Southwest China: Origin and depositional process     

Tsutomu  Nakazawa  Katsumi  Ueno    Xiangdong  Wang 《Island Arc》2009,18(1):94-107

Huge carbonate rock bodies ranging in age from the Visean (Middle Mississippian/Early Carboniferous) to the Changhsingian (Lopingian/Late Permian) overlie a basaltic basement in the Changning–Menglian Belt, West Yunnan, Southwest China. These carbonates lack intercalations of terrigenous siliciclastic material throughout. These lines of evidence indicate that they formed upon an isolated and continuously subsiding mid-oceanic island (or plateau), probably of hotspot origin. The carbonates are grouped into a shallow-water carbonate platform facies regime observed in the Yutangzhai section and a relatively deep-water carbonate slope facies regime typically represented in the Longdong section. These two facies regimes developed contemporaneously as parts of a carbonate depositional system on and around a mid-oceanic volcanic edifice. The carbonate platform is subdivided into four facies, including platform-margin, shoal, lagoon, and peritidal facies. Along the measured Yutangzhai section of the platform facies regime, the vertical facies succession from the platform-margin facies into inner-platform facies such as the shoal and lagoon facies is recognized. This facies succession is explained as resulting from the progradation of the carbonate platform. Worm tubes occur as a main reef builder in platform-margin facies of the Mississippian. Their occurrence as major constituents in a high-wave-energy reef is peculiar to Carboniferous reef distributions of the world. The occurrences of other reef- and/or mound-building organisms and peritidal dolo-mudstone are almost consistent in timing with those of Panthalassan counterparts such as the Akiyoshi and Omi limestones of Japan, and probably exhibit the worldwide trend.  相似文献   

河西绿洲区春小麦蒸腾蒸散的变化研究   总被引：4，自引：0，他引：4  

王亚军  谢忠奎  小林哲夫  兰念军 《中国沙漠》1999,19(3):272-275

在甘肃张掖绿洲区利用浮力称重式蒸散仪对春小麦蒸散量进行了测定,对蒸散量的日变化和季节变化特征进行了论述。研究结果表明:小麦田的日蒸散量在白天12:00~16:00达到最大,夜间20:00~08:00最小甚至呈负值。灌溉前后蒸腾强度出现峰值的时间有所变化。但灌溉以后,蒸腾与蒸散量均呈增大趋势。日蒸散量随着净辐射的增加而加大。在小麦不同的生育阶段,蒸散量有所不同,小麦拔节以前较小,拔节以后开始增大,灌浆期达到最大,接近成熟时逐渐降低。  相似文献   

Temporal variations of surface oceanic and atmospheric CO2 fugacity and total dissolved inorganic carbon in the northwestern North Pacific     

Tomonori Watai  Masaaki Kikuchi  Takakiyo Nakazawa 《Journal of Oceanography》1998,54(4):323-336

In order to examine temporal variations of the surface oceanic and atmospheric fCO₂ and the DIC concentration, we analyzed air and seawater samples collected during the period May 1992–June 1996 in the northwestern North Pacific, about 30 km off the coast of the main island of Japan. The atmospheric CO₂ concentration has increased secularly at a rate of 1.9 ppmv yr⁻¹, and it showed a clear seasonal cycle with a maximum in spring and a minimum late in summer, produced mainly by seasonally-dependent terrestrial biospheric activities. DIC also showed a prominent seasonal cycle in the surface ocean; the minimum and maximum values of the cycle appeared in early fall and in early spring, respectively, due primarily to the seasonally-dependent activities of marine biota and partly to the vertical mixing of seawater and the coastal upwelling. The oceanic fCO₂ values were almost always lower than those of the atmospheric fCO₂, suggesting that this area of the ocean acts as a sink for atmospheric CO₂. Values varied seasonally, mainly reflecting seasonal changes of SST and DIC, with a secular increase at a rate of 3.7 μatm yr⁻¹. The average values of the annual net CO₂ flux between the ocean and the atmosphere calculated by using the different bulk equations ranged between −0.8 and −1.7 mol m⁻²yr⁻¹, and its magnitude was enhanced and reduced late in spring and mid-summer, respectively, due mainly to the seasonally varying oceanic fCO₂.  相似文献   

Clockwise phase propagation of semi-diurnal tides in the Gulf of Thailand   总被引：2，自引：0，他引：2  

Tetsuo Yanagi  Toshiyuki Takao 《Journal of Oceanography》1998,54(2):143-150

The phase of semi-diurnal tides (M₂ and S₂) propagates clockwise in the central part of the Gulf of Thailand, although that of the diurnal tides (K₁, O₁ and P₁) is counterclock-wise. The mechanism of clockwise phase propagation of semi-diurnal tides at the Gulf of Thailand in the northern hemisphere is examined using a simple numerical model. The natural oscillation period of the whole Gulf of Thailand is near the semi-diurnal period and the direction of its phase propagation is clockwise, mainly due to the propagation direction of the large amplitude part of the incoming semi-diurnal tidal wave from the South China Sea. A simplified basin model with bottom slope and Coriolis force well reproduces the co-tidal and co-range charts of M₂ tide in the Gulf of Thailand.  相似文献   

P–V–T equation of state of Ca₃Al₂Si₃O₁₂ grossular garnet     

Steeve Gréaux  Yoshio Kono  Norimasa Nishiyama  Takehiro Kunimoto  Kouhei Wada  Tetsuo Irifune 《Physics and Chemistry of Minerals》2011,38(2):85-94

The thermoelastic parameters of synthetic Ca₃Al₂Si₃O₁₂ grossular garnet were examined in situ at high-pressure and high-temperature by energy dispersive X-ray diffraction, using a Kawai-type multi-anvil press apparatus coupled with synchrotron radiation. Measurements have been conducted at pressures up to 20 GPa and temperatures up to 1,650 K: this P, T range covered the entire high-P, T stability field of grossular garnet. The analysis of room temperature data yielded V _0,300 = 1,664 ± 2 ?³ and K ₀ = 166 ± 3 GPa for K^￠₀ K^{\prime}_{0} fixed to 4.0. Fitting of our P–V–T data by means of the high-temperature third order Birch–Murnaghan or the Mie–Grüneisen–Debye thermal equations of state, gives the thermoelastic parameters: (∂K _0,T /∂T) _P  = −0.019 ± 0.001 GPa K⁻¹ and α _0,T  = 2.62 ± 0.23 × 10⁻⁵ K⁻¹, or γ ₀ = 1.21 for fixed values q ₀ = 1.0 and θ ₀ = 823 (Isaak et al. Phys Chem Min19:106–120, 1992). From the comparison of fits from two different approaches, we propose to constrain the bulk modulus of grossular garnet and its pressure derivative to K _T0 = 166 GPa and K^￠_T0 K^{\prime}_{T0}  = 4.03–4.35. Present results are compared with previously determined thermoelastic properties of grossular-rich garnets.  相似文献   

Evolution of induced fabric in a strain space multiple mechanism model for granular materials     

Susumu Iai  Tetsuo Tobita  Osamu Ozutsumi 《国际地质力学数值与分析法杂志》2013,37(10):1326-1336

The strain space multiple mechanism model idealizes the behavior of granular materials based on a multitude of virtual simple shear mechanisms oriented in arbitrary directions. Within this modeling framework, the virtual simple shear stress is defined as a quantity that depends on the contact distribution function as well as the normal and tangential components of inter‐particle contact forces, which evolve independently during the loading process. In other terms, the virtual simple shear stress is an intermediate quantity in the upscaling process from the microscopic level (characterized by the contact distribution and inter‐particle contact forces). The stress space fabric (i.e. the orientation distribution of the virtual simple shear stress) produces macroscopic stress through the tensorial average. Thus, the stress space fabric characterizes the fundamental and higher modes of anisotropy induced in granular materials. Comparing an induced fabric associated with the biaxial shear of plane granular assemblies obtained via a simulation using Discrete Element Method to the strain space multiple mechanism model suggests that the strain space multiple mechanism model has the capability to capture the essential features in the evolution of an induced fabric in granular materials. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献