Transient flexural vibrations of a timoshenko column supported by an elastic half-space

Transient flexural vibrations of an elastic column supported by an elastic half-space are investigated analytically under the condition that an arbitrarily shaped free-field lateral acceleration is given as an input. Applying the Timoshenko theory to the column and making use of Laplace transformations with respect to time and numerical inverse Laplace transformations, the time histories of the column free end acceleration are presented. Numerical results obtained from the Timoshenko theory are compared with those of a previous paper¹ (applying the Bernoulli-Euler theory to the column), and the effects of column slenderness and foundation stiffness on the transient flexural vibrations of the column are clarified.     

Short‐term temporal variation in gelatinous zooplankton populations over 48 hours in a coral reef at Redang Island,Malaysia

Gelatinous zooplankton abundance and species composition were investigated at 3‐h intervals for a 48‐h period at a fringing reef in Malaysia. A total of 20 gelatinous zooplankton species were observed; the community was dominated by the calycophoran siphonophore Diphyes chamissonis (79.9%), followed by the trachymedusdae Aglaura hemistoma (5.6%) and Liriope tetraphylla (4.8%). The gelatinous zooplankton were not collected in the water column during most of the daytime hours (1200, 1500 and 1800 h) but were common during the night. However, an abrupt peak in abundance was found at 0900 h on the second day. The times of appearance at night were different depending on the species, and the number of species was also different depending on the hour of sampling. Sampling at 3‐h intervals over a 48‐h period revealed that the temporal variation (or sampling availability) was large in this study. Careful consideration should be given to the sampling variability in handling the gelatinous zooplankton samples in coral reef areas.     

Subassemblage cyclic loading test of RC frame with buckling restrained braces in zigzag configuration

A new buckling restrained braced frame system is proposed for reinforced concrete building structures, which is featured by the zigzag configuration of the braces and the corresponding connection details. The connection details tend to separate the vertical and horizontal components of force imposed by the braces to be resisted by independent structural components to make the behavior of the connection easier to estimate and control. The performance of the brace connection details was evaluated through cyclic load testing on 1/2‐scale subassemblies of the proposed system, each of which consisted of a reinforced concrete part and a set of buckling restrained braces. To simplify the test control, the specimens were rotated 90° in the test and were loaded by two displacement controlled actuators. The test results show that the normal and the shear resistance of the gusset plate connection are essentially independent of each other. However, the rotation of the gusset plate with respect to the beam‐to‐column joint may result in nonuniform force distribution of the anchor bolts, the primary resistance for tensile force. At the same time, such rotation may also subject the concrete corbels, the primary shear resistance, to unfavorable tensile force. In addition, it is also confirmed that the buckling restrained braces performed well in the proposed system. Copyright © 2012 John Wiley & Sons, Ltd.     

Carbon isotopic thermometry calibrated by dolomite-calcite solvus temperatures

The temperature dependence of carbon isotopic fractionations between calcite and graphite, and between dolomite and graphite are calibrated by the calcite-dolomite solvus geothermometry using marbles collected from the contact metamorphic aureole in the Kasuga area, central Japan. The carbon isotopic fractionations (Δ¹³C_Cc-Gr and Δ¹³C_DoGr) systematically decrease with increasing metamorphic temperature. The concordant relationships between the fractionations and solvus temperatures are approximately linear with T^?2 over the temperature range. 400° to 680°C: Δ¹³C_CcGr (%.) = 5.6 × 10⁶ × T^?2 (K) ? 2.4 Δ¹³C_DoGr (%.) = 5.9 × 10⁶ × T^?2 (K) ? 1.9 These systematic relationships between fractionation and temperature suggest that carbon isotopic equilibria between carbonates and graphite were attained in many cases. The equation for the calcite-graphite system has a slope steeper than Bottinga's (1969) results. It is, however, in good agreement with that of Valley and O'Neil (1981) in the temperature range from 600° to 800°C.Because of the relatively high sensitivity to temperature, these isotopic geothermometers are useful for determining the temperatures in moderate- to high-grade metamorphosed carbonate rocks.     

Study on the fate of petroleum-derived polycyclic aromatic hydrocarbons (PAHs) and the effect of chemical dispersant using an enclosed ecosystem,mesocosm

Polycyclic Aromatic Hydrocarbons (PAHs) are one of the components found in oil and are of interest because some are toxic. We studied the environmental fate of PAHs and the effects of chemical dispersants using experimental 500 l mesocosm tanks that mimic natural ecosystems. The tanks were filled with seawater spiked with the water-soluble fraction of heavy residual oil. Water samples and settling particles in the tanks were collected periodically and 38 PAH compounds were analyzed by gas chromatography-mass spectrometry (GC-MS). Low molecular weight (LMW) PAHs with less than three benzene rings disappeared rapidly, mostly within 2 days. On the other hand, high molecular weight (HMW) PAHs with more than four benzene rings remained in the water column for a longer time, up to 9 days. Also, significant portions (10-94%) of HMW PAHs settled to the bottom and were caught in the sediment trap. The addition of chemical dispersant accelerated dissolution and biodegradation of PAHs, especially HMW PAHs. The dispersant amplified the amounts of PAHs found in the water column. The amplification was the greater for the more hydrophobic PAHs, with an enrichment factor of up to six times. The increased PAHs resulting from dispersant use overwhelmed the normal degradation and, as a result, higher concentrations of PAHs were observed in water column throughout the experimental period. We conclude that the addition of the dispersant could increase the concentration of water column PAHs and thus increase the exposure and potential toxicity for organisms in the natural environment. By making more hydrocarbon material available to the water column, the application of dispersant reduced the settling of PAHs. For the tank with dispersant, only 6% of chrysene initially introduced was detected in the sediment trap whereas 70% was found in the trap in the tank without dispersant.