Heat capacity anomalies at incommensurate-normal transition of åkermanite solid solution (Ca,Sr)2(Mg,Co, Zn,Fe)Si2O7     

K. Iishi  T. Mizota  K. Fujino  Y. Furukawa 《Physics and Chemistry of Minerals》1991,17(8):720-725

The heat capacity of åkermanite solid solutions was measured by a small scale adiabatic calorimeter near the incommensurate-normal (I-N) transition. The heat capacity anomalies caused by the I-N transition show the type characteristic behavior implying the presence of dynamical fluctuations. The heat capacity anomalies were observed over the whole range of the åkermanite solid solutions Ca₂Mg_1-xCo_xSi₂O₇ and Ca₂Mg_1-x-Zn_xSi₂O₂. With increase of Co or Zn atoms, the transition temperature, T_i, rises linearly from ca. 83° C to 220° C and to 130° C, respectively. In the system Ca₂CoSi₂O₇-Ca₂FeSi₂O₇ and Ca₂MgSi₂O₇-Ca₂-FeSi₂O₇ electronic microscopy revealed that the temperature of the heat capacity anomaly decreases with increasing Fe content, whereas the T_i rises. This unusual behavior is ascribed to the microdomains observed in high resolution lattice images.  相似文献   

Present environment of Dam Lake Sambe,southwestern Japan: a geochemical study of bottom sediments     

Mst. Hawa Bibi  Faruque Ahmed  Hiroaki Ishiga  Takashi Asaeda  Takeshi Fujino 《Environmental Earth Sciences》2010,60(3):655-670

Geochemical analyses of lakebed and core sediments from Lake Sambe on the outskirts of Oda City in Shimane prefecture in southwestern Japan were carried out in order to assess the water quality and the concentration and distribution patterns of sixteen elements. The lake water showed a stratified condition with respect to dissolved O₂, and As, Fe, and Mn concentrations in the bottom layers which increased in the summer. The chemical composition of the sediments, as measured by X-ray fluorescence, included major and trace elements (P, Ca, Sc, Ti, V, Cr, Fe, Ni, Cu, Zn, As, Sr, Zr, Pb, and Th), and total sulfur (TS). Elevated values of As, Zn, V, Fe, P, and TS were present in several layers of the upper cores (from 0 to 5 cm) and other surface sediments. Increases in the abundances of these metals in lake sediments are probably related to the reducing condition of the sediments, fine-grained organic rich sediments, and post-depositional diagenetic remobilization. Moreover, correlations between the concentrations of trace metals and iron in the sediments suggest their adsorption onto Fe (oxy)hydroxides, whereas correlations with sulfur indicate that they were precipitated as Fe-sulfides. The average abundances of As, Pb, Zn, and Cu exceeded the lowest effect level and Interim Sediment Quality Guideline values that the New York State Department of Environmental Conservation and the Canadian Council of Ministers of the Environment determined to have moderate impact on aquatic organisms. In addition, concentrations of As and Zn exceeded the Coastal Ocean Sediment Database threshold value, indicating potentially toxic levels. Therefore, the presence of trace metals in the lake sediments may result in adverse effects on biota health.  相似文献   

Identification of soil–structure interaction effect in base-isolated bridges from earthquake records     

M. T. A. Chaudhary  M. Ab  Y. Fujino 《Soil Dynamics and Earthquake Engineering》2001,21(8):713-725

Identification of system parameters with the help of records made on base-isolated bridge during earthquakes provides an excellent opportunity to study the performance of the various components of such bridge systems. Using a two-stage system identification methodology for non-classically damped systems, modal and structural parameters of four base-isolated bridges are reliably identified using acceleration data recorded during 18 earthquakes. Physical stiffness of reinforced concrete columns, dynamic properties of soil and foundation impedance are found by available theoretical models in conjunction with pertinent information from the recorded accelerographs. Soil–structure interaction (SSI) effect in these bridges is examined by comparing the identified and physical stiffness of the sub-structure components. It is found that SSI is relatively pronounced in bridges founded in weaker soils and is more strongly related to the ratio of pier flexural stiffness and horizontal foundation stiffness than soil shear modulus, G_s, alone. However, substantial reduction in G_s is observed for moderate seismic excitation and this effect should be taken into account while computing foundation impedance.  相似文献   

The properties of tuned liquid dampers using a TMD analogy     

L. M. Sun  Y. Fujino  P. Chaiseri  B. M. Pacheco 《地震工程与结构动力学》1995,24(7):967-976

Liquid motions in shallow Tuned Liquid Dampers (TLDs) with rectangular, circular, and annular tanks, subject to harmonic base excitation, are measured experimentally. Using a Single-Degree-of-Freedom (SDOF) Tuned Mass Damper (TMD) analogy, equivalent mass, stiffness and damping of the TLD are calibrated from the experimental results. These parameters are functions of the TLD base amplitude. Some important properties of the TLD are discussed on the basis of these results.  相似文献   

Design formulas for tuned mass dampers based on A perturbation technique     

Yozo Fujino  Masato Ab 《地震工程与结构动力学》1993,22(10):833-854

Modal properties of tuned mass damper (TMD)-structure two-degree-of-freedom (2DOF) linear systems are studied employing a perturbation technique. Using the perturbation solutions, formulas relevant to designing the TMD for various types of loading are obtained; they are expressed as a function of mass ratio, tuning ratio, damping ratio of the TMD and damping ratio of the structure. Equivalent additional dampings of the structure due to the TMD are derived for random and harmonic forces. Matched expressions of equivalent damping, which are valid for detuned, i.e. non-optimal, conditions are also presented. The stability boundary of TMD-structure systems subject to linear self-excited forces is derived in a closed form. Using the perturbation solutions, procedures for optimizing the TMD parameters for various types of loading are explained and the optimal values are derived. The formulas obtained in this study can be used with good accuracy for mass ratios less than 0.02.  相似文献   

High temperature creep of single crystal gadolinium gallium garnet     

Zichao Wang  Shun-ichiro Karato  Kiyoshi Fujino 《Physics and Chemistry of Minerals》1996,23(2):73-80

High temperature creep of single crystal gadolinium gallium garnet (GGG) was studied in the temperature range of 1723–1853 K (0.86–0.94 T_m, T_m: melting temperature) and strain rate from 9 · 10^?7 s^?1 to 2 · 10^?5 s^?1. The compression tests were made along the 〈100〉 and 〈111〉 orientations. We have performed both constant strain-rate and stress-dip tests. For the 〈100〉 orientation, deformation occurs via the 〈111〉 slip systems. For the 〈111〉 orientation, both the 〈100〉 {010} and the 〈111〉 slip systems can be activated. GGG garnet is very strong under these conditions: σ/μ=(1–3)×10^?3 (σ: creep strength, μ: shear modulus). The creep behavior is characterized by a power law with stress exponent n=2.9–3.3 and high activation energies E^*=612–743 kJ/mol (E^*～45×RT_m, at zero stress which decrease with the increase of stress). Stress-dip tests suggest a small internal stress (σ_i/σ～0.62; σ_i: internal stress, σ: applied stress) compared to other materials. These results suggest that the high creep strength of GGG is mainly due to difficulty of dislocation glide rather than dislocation climb.  相似文献   

Oblique and near collision subduction, Sagami and Suruga Troughs —preliminary results of the French-Japanese 1984 Kaiko cruise, Leg 2     

Kazuaki Nakamura  Vincent Renard  Jacques Angelier  Jacques Azema  Jacques Bourgois  Christine Deplus  Kantaro Fujioka  Yozo Hamano  Philippe Huchon  Hajimu Kinoshita  Pierre Labaume  Yujiro Ogawa  Tetsuzo Seno  Akira Takeuchi  Manabu Tanahashi  Akinori Uchiyama  Jean-Louis Vigneresse 《Earth and Planetary Science Letters》1987,83(1-4)

Leg 2 of the French-Japanese 1984 Kaiko cruise has surveyed the Suruga and the Sagami Troughs, which lie on both sides of the northwestward moving and colliding Izu-Bonin Ridge, the northernmost part of the Philippine Sea plate. The transition from the Nankai Trough to the Suruga Trough is characterized by northward decrease in width of the accretionary prism, in good agreement with the increasing obliquity between the through axis and the direction of the convergence, as the strike of the convergent boundary changes from ENE-NNE to south-north. South of the area, the southern margin of the Zenisu Ridge shows contractional deformations. This supports the interpretation made by the team of Leg 1 who studied the western extension of the area we studied, that it is an intra-oceanic thrusting of the ridge over the Shikoku Basin. In the Sagami Trough, where the relative motion is highly oblique to the plate boundary, active subduction is mostly confined in the east-west trending portions of the trough located south of the Boso Peninsula and along the lower Boso Canyon, near the TTT triple junction. In between, the present motion is mainly right-lateral along the northwest trending Boso escarpment. However, an inactive but recent (Pliocene to lower Pleistocene) accretionary prism exists south of the Boso escarpment, which suggests that the relative motion was more northerly than at present before about 1 Ma ago.  相似文献   

Evaluation of the non-hydrostatic stress produced in a multi-anvil high pressure apparatus     

Jun-ichi Ando  Tetsuo Irifune  Toru Takeshita  Kiyoshi Fujino 《Physics and Chemistry of Minerals》1997,24(2):139-148

Olivine single crystals have been deformed under high confining pressure (P=5?GPa) and temperature (T=1400?°C) conditions in a multi-anvil high pressure apparatus. NaCl, diamond and NaCl+diamond (2:1 by volume) powders were encapsulated along with the olivine single crystals in order to produce a range of stress states. The change of the non-hydrostatic stress transmitted to the olivine samples, enclosed within these three different media, during heating has been evaluated by observation of dislocation microstructure and density. A higher differential stress can be generated with diamond powder (0.1?GPa) than with NaCl powder (0.02?GPa). Although an intermediate differential stress between 0.1?GPa and 0.02?GPa had been expected to be generated using NaCl+diamond powder, the generation of non-hydrostatic stress in the olivine sample was unsuccessful. This may be caused by the fact that compaction (or sintering) proceeded in the capsule throughout the experiments. The most important finding of these experiments is that a constant non-hydrostatic stress can be applied to a sample under very high pressure and temperature conditions within the multi-anvil high pressure apparatus for the duration of the experiment. This approach is therefore suitable for investigating the steady-state rheological properties of mantle minerals at near-mantle conditions.  相似文献   

The influence of the brightness of the asteroidal dust bands on the gegenschein     

Tadashi Mukai  Masanori Fujino  Ryosuke Nakamura  Fumihiko Usui 《Icarus》2003,162(2):337-343

The position and shape of the Gegenschein’s maximum brightness provide information on the structure of the interplanetary dust cloud. We show that the asteroidal dust bands, extended near the anti-solar point, play an important role in determining both the position of the maximum brightness and the shape of the Gegenschein. After removing the asteroidal dust bands from an observation of the Gegenschein on November 2, 1997, it was found that the maximum brightness point shifted −0.4° in ecliptic latitude, i.e., to the south of the ecliptic plane, at an ecliptic longitude of 180°, in contrast to a latitude value of +0.1° when the dust bands were included. Furthermore, the part of the Gegenschein to the south of the ecliptic plane was brighter than the northern part at the time of observation. Referring to the cloud model of T. Kelsall et al. (1998, Astrophy. J. 508, 44-73), it can be estimated that the ascending node of the symmetry plane of the dust cloud is 57°^−3°_+7° when its inclination is 2.03° ? 0.50°.  相似文献   

Redeposition of volcaniclastic sediments by a tsunami 4600 years ago at Kushima City,south-eastern Kyushu,Japan     

Masaki Yamada  Shigehiro Fujino  Takashi Chiba  Kazuhisa Goto  James Goff 《Sedimentology》2020,67(3):1354-1372

The Hyuga-nada Sea, south-eastern Kyushu, Japan, is located between a strong (Nankai Trough) and a weak interplate coupling zone (Ryukyu Trench). Over the past 400 years this area has only experienced Magnitude 7·5 earthquakes or smaller and associated small-scale tsunamis. However, this short historical record most likely does not include the full range of high magnitude, low frequency giant earthquakes that might have occurred in the region. Thus, it is still unclear whether giant earthquakes and their associated tsunamis have occurred in this region. This paper reports on a prehistoric tsunami deposit discovered in a coastal lowland in south-eastern Kyushu facing the Hyuga-nada Sea. There is a reddish-brown pumiceous layer preserved in a non-marine, organic-rich mud sequence obtained from onshore sediment cores. This layer is recognized as the ca 4600 year old Kirishima-Miike tephra (that is now placed around 4500 years ago) sourced from Mount Kirishima, southern Kyushu. Another whitish pumiceous layer is evident below the Kirishima-Miike tephra in almost all of the sediment cores. A relatively high percentage of marine and brackish diatoms is recorded within this lower pumiceous layer (but not in the surrounding muds or in the overlying Kirishima-Miike tephra), indicating a marine or beach sediment source. Plant material obtained from organic-rich mud immediately below the event layer was dated to ca 4430 to 4710 cal yr bp , providing a limiting-maximum age for this marine incursion event. The presence of marine diatoms below the event layer is probably explained by pre-seismic subsidence. An absence of the resting spore of the planktonic brackish diatom Cheatoceros and the appearance of the freshwater diatom Eunotia serra immediately above the event layer probably represents a marked change to a relatively low-salinity environment. Assuming that there were no significant local geomorphological changes, such as drainage obstruction caused by formation of a new barrier spit, it is considered that co-seismic or immediate post-seismic uplift are the most likely explanations for this notable environmental change. Based on the crustal movements noted before and after the marine incursion, this event is interpreted here as an earthquake-generated tsunami. Moreover, because of these notable seismic crustal movements the tsunamigenic earthquake probably occurred immediately offshore of the study site.  相似文献