Development of real-time pseudo dynamic testing

This paper presents a study for the development of a system capable of performing real-time pseudo dynamic testing. The system combines the basics of the pseudo dynamic test with a dynamic actuator, a digital displacement transducer and a digital servo-mechanism. The digital servo-mechanism has been introduced to ensure accurate displacement and velocity control, in which digital feedback control with a time interval of 2 msec has been performed continuously during actuator motion. Using the system, pseudo dynamic tests under sinusoidal and earthquake ground motion are carried out for a structure having a viscous damper, demonstrating that a perfectly real-time pseudo dynamic test can be achieved by incorporating the modified central difference method into an extra buffer operation of the digital servo-mechanism. The responses solved by the pseudo dynamic tests are compared with the responses of the test structure as well as those obtained from post-numerical analysis, and it is found that the real-time pseudo dynamic test conducted in this study is accurate.     

Dynamic behaviour of pile foundations in homogeneous and non-homogeneous media

A three-dimensional formulation based on Green's functions of cylindrical loads in layered semi-infinite media is employed to investigate the dynamic behaviour of piles in homogeneous and non-homogeneous half spaces. The pile-soil-pile interaction taking place in pile groups is incorporated in the model. The results presented in this paper include the dynamic stiffnesses and dampings of single piles as well as those of representative 2 × 2 and 4 × 4 square pile groups in the soil media considered in this study. In addition, the distribution of forces applied on the pile cap among the individual piles in a group is investigated.     

日本岛根县石见银矿区英安质火山岩中的黑云母矿物学特征及其K-Ar和40Ar-39Ar年代学研究

以显微镜、X射线衍射仪和电子探针等方法,对日本岛根县石见银矿区所产英安质火山岩中的黑云母进行了详细的研究．观察到部分黑云母经受了不同程度的热液蚀变作用。根据对未蚀变、或仅受到轻微蚀变作用的黑云母所进行的^40Ar-^39Ar同位素年龄测定,它们主要为第四纪产物。但是,从经受强热液蚀变作用的黑云母所获得的^40Ar-^39Ar同位素结果表明,后期的高温热液活动可以破坏晶体中的原始K—Ar同位素平衡,使得其。^40Ar-^39Ar同位素年龄与高于从未蚀变矿物所获得的结果,从而产生严重的年代失真。所以,对来自热液蚀变带的样品需要进行详细的矿物学研究。估计对黑云母的原始KAr同位素体系产生破坏的热扰动临界温度可能在200℃左右。     

Stability field of knorringite Mg3Cr2Si3O12 at high pressure and its implication to the occurrence of Cr-rich pyrope in the upper mantle

The stability field of knorringite (Mg₃Cr₂Si₃O₁₂) is studied experimentally. Knorringite is stable at pressures above 10.5 GPa at 1200°C and 11.8 GPa at 1400°C. Below these pressures, knorringite decomposes to enstatite + eskolaite. A phase diagram of the pyrope-knorringite system is described based on the available experimental data. The solubility of the knorringite molecule in pyrope is essentially dependent only on pressure, and the Cr/Cr+Al value of garnet is considered to be an indicator of the minimum pressure of equilibration. Consideration of the genesis of Cr-rich pyrope and other peridotitic inclusions in diamonds indicates that the fractionation process should have taken place, at least at depths to ca. 240 km, to give rise to the Cr-rich complement of Cr-poor upper mantle materials such as undepleted lherzolite. The knorringite-rich peridotitic suite in diamond will be identified with this complement, which may be the material constituting the deep upper mantle.     

Inequality of eddy transfer coefficients for vertical transport of sensible and latent heats during advective inversions

Similarity of transport of water vapour and sensible heat was investigated within an advective inversion layer by measuring eddy fluxes together with gradients of temperature and humidity. The experimental site was a field of rice, grown under flood irrigation, which was situated in a semi-arid region. The fetch was about 300 m and local stabilities (z/L) over the rice ranged from 0 to 0.1. Results were expressed as the ratio of eddy transfer coefficients for sensible heat (K _H) and water vapour (K _w). Near neutral stability, K _H/K_W approached 1, but the ratio decreased to about 0.65 with increasing stability. Existing theory predicts the result qualitatively but accounts for only about one fifth of the decrease in K _H/K_W with stability.     

Measurements of carbon dioxide in the Seto Inland Sea of Japan

The carbon dioxide in seawater (pCO₂) was measured in the Seto Inland Sea of Japan using newly developed equilibrator instrument designed to be free from the correction for addition or extraction of the carbon dioxide from carrier gas. The temperature dependence of pCO₂ was about 4.5%pCO₂/°C for a single seawater sample which was processed as free from biological activity and change in total carbon dioxide content during an experiment. The decrease in pCO₂ during daylight hours due to the photosynthetic fixation was about 30% of the daily mean of pCO₂ during warm months and about 15% during cold months. The effect of carbon dioxide exchange between air and seawater on pCO₂ was about 0.6 ppm in August and about 0.1 ppm in March. This is negligible small compared with the daily oscillation of carbon dioxide in seawater.     

Intrusion of less saline shelf water into the Kuroshio subsurface layer in the East China Sea

The possible origin and cause of the less saline shelf water detected in the Kuroshio subsurface layer around the shelf edge of the East China Sea are investigated using observational results obtained in May 1998–2001 in conjunction with a dataset archived by Japan Oceanographic Data Center and a numerical model. The observations show that subsurface intrusions of less saline water are always detected in May in layers above 24.5σθ isopycnal surface, and that salinity inversions (i.e., areas in which the less saline water lies beneath the saline water) are detected around the trough of the Kuroshio frontal eddy (or wave). Analyses of the archived dataset reveal that the isopycnal surface of 24.5σθ is the deepest layer of the Kuroshio pycnocline outcropping to the sea surface on the shallow shelf in early spring. Outcropping isopycnals above 24.5σθ encounter a less saline water plume originating from the Changjiang, especially in the western East China Sea. Thereafter, the less saline water moves along isopycnal layers and reaches the Kuroshio front around the shelf edge. Numerical models demonstrate that, when the frontal wave captures the less saline water, the shelf water takes the form of a salinity inversion in the trough because isohalines in the frontal wave have a phase lag between the upper and lower layers in consequence of the baroclinic instability.     

Symmetropy of earthquake patterns: asymmetry and rotation in a disordered seismic source

We demonstrate that the idea of symmetropy can be used for quantification of earthquake patterns. The symmetropy can be considered as a measure of asymmetry. A pattern is richer in asymmetry when the symmetropy is smaller. The specific results of its applications are obtained as follows. In a discrete model of a seismic source with self-organized criticality, the spatial patterns of earthquakes during critical states and sub-critical states are distinguished by the behaviour of the symmetropy: sub-critical patterns show that the symmetropy is approximately a constant but this has various values during critical states. The critical patterns show asymmetric property without any asymmetric force from the outside and without asymmetric intracellular rule. We show that the emergence of asymmetric patterns is a generic feature of dynamic ruptures in our model. Such a generic asymmetry results from the model which is an inherently discrete system consisting of finite-sized cells. These cells may represent geometrical disordered fault zones. We further discuss rotational motions that generate seismic rotational waves. In micromorphic continuum theory, such rotations are attributed to dynamic ruptures in disordered systems. We note that the concept of disorder in this theory is expressed by a set of finite-sized microstructures and is consistent with the concept of disorder modelled in the present study. Thus, we suggest that the spatially asymmetric patterns of earthquakes might be related to the rotational motions, because both come from dynamic ruptures in a discrete fault zone without a well-defined continuum limit.     

Concentrations of 222 Rn, Its Short-Lived Daughters And 212 Pb And Their Ratios Under Complex Atmospheric Conditions And Topography

Atmospheric activity concentrations of ²¹²Pb and short-lived ²²²Rndaughters, together with meteorological elements, have been observed continuously atthree sites at Kamisaibara Village in Japan. In addition, atmospheric activity concentrationof ²²²Rn, equilibrium-equivalent concentration of ²²²Rn and conditionsof the lower atmosphere were observed for three intensive observation periods at Akawase,one of the three sites in Kamisaibara Village. The equilibrium-equivalent concentration of²²²Rn is almost the same as the atmospheric activity concentration of short-lived²²²Rn daughters.The activity concentrations of ²¹²Pb and the short-lived ²²²Rn daughtersand their ratio were low in the daytime owing to convective mixing, and high at nightowing to the surface-based inversion during periods of no precipitation. Their variationshave several patterns corresponding to the scale of the drainage wind or weak mixing.Mechanical mixing due to strong winds through both day and night during the first andsecond observation periods made the atmospheric activity concentrations of ²¹²Pb and the short-lived ²²²Rn daughters continuously low. However, their ratios werecontinuously high during the first period yet continuously low during the second period.This difference can be explained by the effect ofextraction of ²²⁰Rn and ²²²Rndue to strong winds and snow cover. There were also cases in which the ratio of theatmospheric activity concentration of ²¹²Pb to that of the short-lived ²²²Rndaughters at night was equal to or less than the ratio in the daytime. Thisinverse trend, asin the periods of no precipitation mentioned above, is considered to be due to near-neutralconditions on these nights.We find a difference in the ratio of the equilibrium-equivalent concentration of²²²Rn (the activity concentration of short-lived ²²²Rn daughters) tothe activity concentration of ²²²Rn during the first observation period and thatduring the second. The difference can be explained by snow cover on the ground. Wealso find differences among the ratios of the activity concentration of the short-lived²²²Rn daughters to that of ²²²Rn during the three observation periods.These differences can be explained by the submergence of paddy fields.