Long-Term Variations of Potential Temperature and Dissolved Oxygen of the Japan Sea Proper Water

Observed potential temperatures and concentrations of dissolved oxygen are analyzed to elucidate their variations during the period from 1958 to 1996 at Stn. P (37°43′ N, 134°43′ E) and from 1965 to 1996 at Stn. H (40°30′ N, 137°40′ E) in the Japan Sea. At Stn. P, increases of the potential temperature for the period are found below 800 m depth with the largest value of 0.16 ± 0.09°C per century at 800 m depth. At Stn. H, the potential temperature increased below 500 m depth. The increase rate has the largest value of 0.50 ± 0.18°C per century at 500 m depth and it is 0.30 ± 0.09°C per century at 800 m depth. The concentrations of dissolved oxygen increased around 800 m depth at Stn. P. At Stn. H, they increased above 800 m depth. On the other hand, they decreased below 1200 m depth at both stations. The layer of the dissolved oxygen minimum has deepened in these decades. These features appearing in the distributions of temperature and dissolved oxygen are successively simulated by a vertical one-dimensional advection-diffusion model including consumption of dissolved oxygen and termination of the deep water supply. These results suggest that the supply of the Japan Sea Proper Water into the deep layer, which is cold and rich in dissolved oxygen, has been decreasing for the last four decades. This revised version was published online in August 2006 with corrections to the Cover Date.     

Metamorphic condition of a regional metamorphic complex in the Omuta district in northern Kyushu,southwest Japan

A high‐temperature (T) metamorphic complex occurs in the Omuta district, northern Kyushu, Japan. Three metamorphic zones are defined based on pelitic mineral assemblage, i.e. chlorite–biotite zone, muscovite–andalusite zone and sillimanite–K‐feldspar zone with ascending metamorphic grade from north to south. Two isograds trend approximately east–west, which is oblique to the boundary between the metamorphic complex and the Tamana Granodiorite located on the southeast. The metamorphic condition of two pelitic rocks that occur in the muscovite–andalusite zone and sillimanite–K‐feldspar zone are estimated as 510 ±30 °C, 300 ±60 MPa and 720 ±30 °C, 620 ±60 MPa, respectively. Thermodynamic consideration reveals that use of the same geothermobarometer enables precise determination of the difference in pressure between the samples as 320 ±10 MPa. This indicates that the pelitic samples were metamorphosed at different depth by 11–12 km that is significantly larger than the geographic distance of 6.8 km between the sample localities. This also suggests that crustal thinning took place after the high‐T metamorphism. The high‐T metamorphic complex is, therefore, not of static contact metamorphism but of dynamic regional metamorphism. The present result combined with petrological and chronological similarities implies that this complex suffered the regional Ryoke metamorphism.     

Mechanical properties and stress–dilatancy relationships of unsaturated soil under various cyclic loading conditions

Acta Geotechnica - Most studies investigating the effect of cyclic loading on soil properties have been conducted for saturated soils. Embankments such as fill dams, roads and railways are usually...     

台风过境期间辽河口滨海湿地水动力特征的数值模拟研究

本研究基于FVCOM环流模型,耦合ECMWF背景风场和Jelesnianski台风经验模型形成合成风场,对9711台风“温妮”过境辽河口区域的水动力进行模拟研究。模型通过在动量方程、湍流方程中加入附加源项来表达盐沼植被对水动力的阻碍作用。使用研究区域实测的潮位、流速、流向等数据对水动力模型进行验证,模拟结果与实测数据吻合较好。结果表明：潮滩盐沼植被对台风过境期间的潮位变化无明显影响,但对流速具有显著的衰减作用,且芦苇对潮流的衰减作用大于盐地碱蓬植被,芦苇区的速度最大衰减率达81.43%。此外,台风路径变化对辽河口湿地海域的增减水及流速影响较大,台风强度越强,局部区域造成的风暴潮增水和流速也相应越大。     

Investigating the vibration properties of integrated ceiling systems considering interactions with surrounding equipment

Studies on recent earthquakes highlighted that buildings with minimal structural damage still suffer from extensive damage and failure of nonstructural components. The dropping and damage of suspended ceiling systems, which typically consist of acceleration-sensitive nonstructural elements, resulted in lengthy functional disruptions and extended recovery time. This article experimentally and analytically examined the vibration properties of an integrated ceiling system considering the interactions with surrounding electrical equipment. The theoretical stiffness and corresponding frequency of electrical equipment were initially derived and then verified by subsequent vibration tests and numerical analyses. The seismic performance of the air conditioner (AC) was evaluated with different installment configurations based on design spectra and floor response spectra. Vibration tests of the suspended integrated ceiling system considering the interactions with surrounding equipment showed that the inclusion of peripheral constraints increased the first horizontal vibration frequency of the ceiling system by a factor of approximately 6. The natural frequencies of all components in the integrated ceiling system were almost identical, which was attributed to the coupled behavior between the ceiling panels and surrounding equipment, emphasizing the effect of interactions between adjacent components during dynamic analysis. Based on the above experimental investigation, an associated numerical model of the integrated ceiling system was created. Finally, corresponding parametric studies that included the interactions with surrounding equipment, reinforcing braces of ACs and strengthening members at the rise-up location between two elevations were performed.     

错列不等直径双圆柱绕流特性数值研究

为研究低亚临界雷诺数Re情况下错列角度θ对不等直径双柱体绕流特性的影响,利用Fluent软件模拟了Re为3 900、间距比G/D为2.0、直径比D/d为0.5、θ=0°~180°之间9种角度的绕流过程,得到了流场涡量图、斯特鲁哈数St_1和St_2、平均阻力系数C_(d1)和C_(d2)以及平均升力系数C_(l1)和C_(l2)。研究结果表明,随着θ的从小到大,St_1先增大后减小,且在θ=30°和180°时有两个值,St_2在θ=120°~150°时明显小于其它角度;C_(d1)和C_(d2)的整体趋势都是先增大后减小,C_(l1)在θ=150°时取得极大值,C_(l2)在θ=30°时取得极小值。θ=0°时,两柱后方有单一涡脱落形态;θ=30°时,小柱后方有稳定漩涡脱落产生,大柱后方涡脱落受到干扰,且大柱有两个涡脱落频率;θ=45°~90°时,在间隙流的作用下,两柱后方均有漩涡脱落,尾流中有两列涡街;θ=120°~180°时,大柱后有稳定漩涡脱落,小柱涡脱落受到抑制。研究结果可为相关海洋工程设计提供参考。     

Metabolism and chemical composition of pelagic decapod shrimps: synthesis toward a global bathymetric model

Respiration, ammonia excretion and chemical composition data [water content, ash, carbon (C), nitrogen (N) and C:N ratios] of 16–43 pelagic decapods from epipelagic through abyssopelagic zones of the world’s oceans were compiled. For respiration, the independent variables including body dry mass, habitat temperature and sampling depth were all significant predictors of the empirical regression model, whereas the former two variables were significant predictors of the theoretical regression model. For ammonia excretion, body dry mass and habitat temperature were significant predictors of both regression models. Overall, these variables accounted for 68–87 % of the variance in the data. Atomic O:N ratios (respiration:ammonia excretion) ranged from 9.1 to 91 (median 16.4), and no appreciable effects of the three variables were detected. Body composition components were not significantly affected by the three variables, except positive effects of habitat temperature on ash and negative effects of sampling depth on N composition. As judged by C:N ratios, protein was considered to be the major organic component of most pelagic decapods. Some pelagic decapods from >500 m depth exhibited high C:N ratios (8.6–10.2), suggesting a deposition of lipids in the body. Comparison of the present results with global bathymetric models of euphausiids and mysids revealed great similarities among these pelagic crustacean taxa characterized by common behavioral and morphological features such as active swimming, developed compound eyes and respiratory gill organ.     

Instability processes of mesoscale features in the Kuroshio Extension reproduced through assimilation of altimeter data into a quasi-geostrophic model using the variational method

The Kuroshio, one of the most energetic western boundary currents in the world, shows variations in its mesoscale features and recirculation gyres, providing an excellent test case of interactions between the mesoscale field and Kuroshio Extension (KE) states. A three-layer quasi-geostrophic model was used to reconstruct flow fields continuous in time and the horizontal plane from the TOPEX/POSEIDON altimeter data based on the variational method. Compared with the solutions obtained by the nudging method, the present results proved that the variational solution was closer to the real field. In the assimilation period, 1993–1997, the baroclinic instability index (BII) was defined to be the phase shift from the uppermost layer to the lowest layer with mesoscale features. In the first half of the assimilation period, the KE took the transition from the elongated to contracted states, in which BII decreased gradually, as a consequence of the KE state shift. In the second half period, BII increased in the downstream region just west of the Shatsky Rise, in which baroclinic instability contributed to the final stage of the contracted state, and was followed by rapidly weakened instability as a trigger of the opposite transition from the contracted to elongated states. The wind-driven recirculation gyre played an active role on the KE transition in the first half period, although not in the second half.     

Evidence of the restricted gene flow within a small spatial scale in the Japanese common intertidal goby Chaenogobius annularis

Elucidating the scale of gene flow among populations is an important challenge for understanding the ecological dynamics and local adaptation of marine organisms. We assessed whether gene flow is restricted even at a small spatial scale in the Japanese common intertidal goby Chaenogobius annularis, using highly polymorphic DNA markers, involving the mitochondrial DNA (mtDNA) control region and 15 microsatellite DNA (msDNA), because past ecological studies have suggested low dispersal ability for rocky intertidal fishes. We found significant heterogeneities between four neighboring local populations by both mtDNA and msDNA analyses. In addition, no genetic heterogeneity was detected by either method across generations within a population; it was considered that such genetic differentiation is retained across generations and that the gene flow of this species is restricted to within a radius of a few kilometers. This is the first report showing a clear genetic subdivision in rocky intertidal fish.