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101.
Application of the ALE technique for underwater explosion analysis of a submarine liquefied oxygen tank 总被引:1,自引:0,他引:1
The design of submarines has continually evolved to improve survivability. Explosions may induce local damage as well as global collapse to a submarine. Therefore, it is important to realistically estimate the possible damage conditions due to underwater explosions in the design stage. The present study applied the Arbitrary Lagrangian–Eulerian (ALE) technique, a fluid–structure interaction approach, to simulate an underwater explosion and investigate the survival capability of a damaged submarine liquefied oxygen tank. The Lagrangian–Eulerian coupling algorithm, the equations of state for explosives and seawater, and the simple calculation method for explosive loading were also reviewed. It is shown that underwater explosion analysis using the ALE technique can accurately evaluate structural damage after attack. This procedure could be applied quantitatively to real structural design. 相似文献
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Restrictions on the use of tributyltin (TBT) in aquaculture and on boats in coastal regions, except for ocean-going vessels, have been in place in Japan since 1990 due to the strong toxic effects of TBT on marine organisms. However, TBT pollution along the Japanese coasts has been reported after this legislation was enacted. In order to elucidate the present status of contamination by butyltin (BT) compounds, we measured the levels of BTs [monobutyltin (MBT), dibutyltin (DBT) and TBT] in seawater and Caprella spp. samples obtained from the western part of Seto Inland Sea, Uwa Sea and Uranouchi Bay in western Japan during March to September, 2001. Butyltins were detected in more than 90% of the seawater samples (n = 59), with average concentrations of 8.2 ± 9.2 (SD) ng MBT L−1, 3.3 ± 3.0 ng DBT L−1 and 9.0 ± 7.0 ng TBT L−1. Among 41 stations situated on coastal lines, a sufficient number of Caprella organisms for chemical analysis could be collected from only 16 stations. The butyltin concentrations in seawater and Caprella samples from Uwa Sea and Uranouchi Bay, in which the dominant industry in both waters is aquaculture, showed significantly higher than or no significant differences from those samples from the western part of Seto Inland Sea, a major heavy-industry area in Japan. As the TBT concentration in seawater increased, the number of Caprella organisms collected decreased. The mean TBT concentration among the seawater samples was above the estimated lowest observable effect concentration (LOEC) that reduces the survival rate of Caprella danilevskii. Thus, the present study indicates that TBT is still a potential ecological hazard to the survival of marine invertebrates inhabiting coasts along western Japan, even 11 years after the partial ban on TBT usage was implemented. 相似文献
105.
Summary This paper presents a trend coefficient as a characteristic index with which to investigate the 1951–1998 secular trend variation
(STV) of northern 500-hPa height on a seasonal basis. Evidence suggests that low (high) latitude 500 hPa geopotential height
displays a remarkably positive (negative) trend; the positive anomaly of the height is maintained over NW Africa, the western
Mediterranean Sea and North Africa, mid-Pacific at lower latitudes, Lake Baikal and area to the east and NW North America;
the height drops significantly over the Aleutians and North Pacific, the area to the south of the Greenland and NE North America
and the sector to the north of the Arabian Sea. Further, analysis of abrupt change shows that the 500-hPa circulations experience
noticeable sudden change twice, once around the early 1960s and again in 1976, during which period the height exhibits great
differences between the Pacific and Atlantic. In the first period it drops (rises) over the mid-Atlantic at lower latitudes
(NW Africa); in the second period the height rises (drops) over the mid-Pacific at lower latitudes and Lake Baikal (the North
Pacific). Statistical tests indicate that in the 1976 case the low-latitude positive abrupt change is even more noticeable
compared to the negative of the North Pacific, thus representing a large-scale jumping event of the northern 500-hPa height.
Received April 9, 1999/Revised October 15, 1999 相似文献
106.
A series of laboratory experiments and numerical simulations are conducted to explore the characteristics of mixtures composed of sand and rubber particles of the same median diameter. The mixtures are prepared with different volumetric sand fractions (sf = Vsand/Vtotal). The experiment focuses on assessing the strain level on the characteristics of the mixture with the volume fraction of each component. Numerical simulations using the discrete element method are performed to obtain insight into the microscale behavior and internal mechanism of the mixtures. The experimental results show that the behavior of the mixtures is dependent on the relative sand and rubber particles composition with variation in the strain levels. The numerical simulation reveals the effect of the soft rubber particle inclusion in the mixture on the micromechanical parameters. In low sand fraction mixtures, a high shear stress along the contact is mobilized, and the stress state is driven to a more anisotropic condition because of the relatively high particle friction angle of the rubber. The rubber particles play different roles with the strain level in the mixture, including increasing the coordination number and controlling plasticity of the mixture in a small strain, preventing buckling of the force chain in an intermediate strain, and leading to contractive behavior in a large strain. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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108.
Sungkyun SHIN Young Min NOH Kwonho LEE Hanlim LEE Detlef MLLER Y.J.KIM Kwanchul KIM Dongho SHIN 《大气科学进展》2014,31(6):1417-1426
The vertical distribution of single scattering albedos (SSAs) of Asian dust mixed with pollutants was derived using the multi-wavelength Raman lidar observation system at Gwangju (35.10°N,126.53°E).Vertical profiles of both backscatter and extinction coefficients for dust and non-dust aerosols were extracted from a mixed Asian dust plume using the depolarization ratio from lidar observations.Vertical profiles of backscatter and extinction coefficients of non-dust particles were input into an inversion algorithm to retrieve the SSAs of non-dust aerosols.Atmospheric aerosol layers at different heights had different light-absorbing characteristics.The SSAs of non-dust particles at each height varied with aerosol type,which was either urban/industrial pollutants from China transported over long distances at high altitude,or regional/local pollutants from the Korean peninsula.Taking advantage of independent profiles of SSAs of non-dust particles,vertical profiles of SSAs of Asian dust mixed with pollutants were estimated for the first time,with a new approach suggested in this study using an empirical determination of the SSA of pure dust.The SSAs of the Asian dust-pollutants mixture within the planetary boundary layer (PBL) were in the range 0.88-0.91,while the values above the PBL were in the range 0.76-0.87,with a very low mean value of 0.76 ± 0.05.The total mixed dust plume SSAs in each aerosol layer were integrated over height for comparison with results from the Aerosol Robotics Network (AERONET) measurements.Values of SSA retrieved from lidar observations of 0.92 ± 0.01 were in good agreement with the results from AERONET measurements. 相似文献
109.
Sun-Yong Ha Hyong-Min Joo Sung-Ho Kang In-Young Ahn Kyung-Hoon Shin 《Journal of Oceanography》2014,70(1):1-10
We investigated the effects of ultraviolet-B (UV-B) radiation on the natural phytoplankton assemblage in Marine Cove on King George Island, Antarctica, in December 2005. The amount of newly synthesized phytoplankton polyunsaturated fatty acids (PUFAs) was lower with exposure to full irradiation (PAR+UV-A+UV-B) than without such exposure (exposed instead to PAR+UV-A radiation) in an in situ incubation under the light conditions in two different types of incubation bottles: quartz bottles transmitting all light wavelengths including UV-B and polycarbonate bottles with no UV-B transmission and 20 % reduced PAR compared to the quartz bottle. However, the amount of newly synthesized saturated fatty acids was greater with than without UV-B radiation. Thus, UV-B radiation may have a significant influence on fatty acid synthesis in phytoplankton. In particular, the production of eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] was reduced during incubation under the natural solar radiation including UV-B. To understand the indirect influence of UV-B on herbivores (the secondary producer), we conducted feeding experiments with amphipods fed in situ on the natural phytoplankton assemblage. The amphipods fed on the phytoplankton with the low PUFA values also exhibited a low PUFA accumulation rate, which could negatively affect their growth, development, and reproduction. Consequently, the diminished rate of essential fatty acid synthesis [especially 20:5(n-3) and 22:6(n-3)] in primary producers caused by UV-B exposure could affect the structure and function of the Antarctic marine ecosystem. 相似文献
110.
G. Bala Ken Caldeira Rama Nemani Long Cao George Ban-Weiss Ho-Jeong Shin 《Climate Dynamics》2011,37(5-6):915-931
Recent studies have shown that changes in solar radiation affect the hydrological cycle more strongly than equivalent CO2 changes for the same change in global mean surface temperature. Thus, solar radiation management ??geoengineering?? proposals to completely offset global mean temperature increases by reducing the amount of absorbed sunlight might be expected to slow the global water cycle and reduce runoff over land. However, proposed countering of global warming by increasing the albedo of marine clouds would reduce surface solar radiation only over the oceans. Here, for an idealized scenario, we analyze the response of temperature and the hydrological cycle to increased reflection by clouds over the ocean using an atmospheric general circulation model coupled to a mixed layer ocean model. When cloud droplets are reduced in size over all oceans uniformly to offset the temperature increase from a doubling of atmospheric CO2, the global-mean precipitation and evaporation decreases by about 1.3% but runoff over land increases by 7.5% primarily due to increases over tropical land. In the model, more reflective marine clouds cool the atmospheric column over ocean. The result is a sinking motion over oceans and upward motion over land. We attribute the increased runoff over land to this increased upward motion over land when marine clouds are made more reflective. Our results suggest that, in contrast to other proposals to increase planetary albedo, offsetting mean global warming by reducing marine cloud droplet size does not necessarily lead to a drying, on average, of the continents. However, we note that the changes in precipitation, evaporation and P-E are dominated by small but significant areas, and given the highly idealized nature of this study, a more thorough and broader assessment would be required for proposals of altering marine cloud properties on a large scale. 相似文献