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351.
The interaction of a tunnel-soil-building system due to trains is investigated by a substructure technnique. The soil medium is assumed to be a viscoelastic halfspace. The method of wave function expansion is used to construct the displacement fields in terms of potentials. The total soil-structure interaction problem is decomposed into a foundation radiation problem and a tunnel radiation problem. The impedance matrices for the corresponding substructure problems are obtained using a collocation technique. The steady state response of buildings for a given tunnel-foundation geometry is determined using the impedance matrix. Hence, the response of the building to train loading at different speeds is evaluated and compared with allowable vibration limits. 相似文献
352.
In this study, the ability of macroalgae Gracilaria sp. of removing eutrophication factors and toxic heavy metals Al, Cr, and Zn in a closed cultivation system is reported.
The results show that the concentration of the three heavy metals decreased significantly during the experimental period in
an algal biomass dependent manner. The biofiltration capacity of the alga for Al, Cr, and Zn is 10.1%–72.6%, 52.5%–83.4% and
36.5%–91.7%, respectively. Using more materials resulted in stronger heavy metal removal. Additionally, the concentration
of chl-a, TN, TP and DIN of water samples from aquariums involving large, medium, and small algal biomass cultivation increased first
and then decreased during the experiment. COD value of all three groups decreased with time and displayed algal biomass dependency:
more algae resulting in a greater COD value than those of less biomass. Furthermore, changes in COD reflect an obvious organic
particles deprivation process of algae. This is the first report on heavy metal removal effect by Gracilaria species. The results suggest that macroalgae can be used as a biofilter for the treatment of nutrient-enriched or heavy-metal
polluted water, to which an appropriate time range should be carefully determined. 相似文献
353.
354.
Su-Cheng Pai Sen Jan Tung-Yuan Ho Jin-Yuan Liu Ken-Sheng Chu Wen-Huei Lee Cheng-Yun Wang Ping-Yi Huang Hung-Yu Hsu Yiing-Jang Yang 《Journal of Oceanography》2017,73(6):711-723
Significant variations of phosphate and silicate concentrations have been observed in seawater from selected industrial pipelines at intake depths between 400 and 710 m off the Hualien coast, eastern Taiwan, revealing a strong vertical movement of water mass in this intermediate layer. An intensive monitoring experiment was carried out, in which pipeline seawater from three land-based pumping stations and seawater collected by a research vessel were obtained and analyzed in parallel during a 2-day observation period. The results showed clearly that the changes of nutrient concentrations in both pipeline and shipboard samples followed a semidiurnal cycle. The maximum vertical displacement occurred in the 300–800 m layer with a scale as surprisingly large as 100 m, when compared with that observed in other areas. The tidal cycles for different layers may not synchronize with surface tide or each other. Empirical equations have been implemented between nutrient concentrations and temperature for the Hualien off-shore area. The equation can be used to check temperature variation of the intermediate water by measuring either phosphate or silicate in pipeline seawater. 相似文献
355.
Evaluating the performance of a physically based model for landslide prediction was conducted in this study. The model was developed based on the basis of the infinite slope instability analysis and TOPMODEL for saturated water level estimation, which enabled to predict the location and time of occurrence of shallow landslides. Field data from 2008 to 2013 in two areas vulnerable to landslide in Taiwan were collected to test the applicability of the model for landslide prediction. Three indexes including the probability of detection (POD), false alarm ratio (FAR), and threat score (TS) were adopted to assess the advantages and disadvantages of the model. The results indicated that the POD for the landslide prediction by using the proposed model was 1.00, the FAR was lower than 0.25, and the overall TS value was higher than 0.75. It is promising to apply the proposed model for landslide early warnings to reduce the loss of life and property. 相似文献
356.
Yeon Moon Choo Gwan Seon Yun Tai Ho Choo Yong Been Kwon Su Yong Sim 《Environmental Earth Sciences》2017,76(17):616
In fluid mechanics, the shear stress is calculated from the frictional force caused by viscosity and fluctuating velocity. Shear stress equations are used widely because of their simplicity. On the other hand, they have a critical limitation of requiring an energy gradient, which is generally difficult to estimate in practice. In particular, measuring the shear stress and velocity gradient on the boundary layer is difficult. The point velocity throughout the entire cross section is needed to calculate the velocity gradient. This study proposes the shear stress distribution equations for laminar flow based on entropy theory using the mean velocity and entropy coefficient. The proposed equations were compared with the measured shear stress distribution using Nikuradse’s data. The results revealed a correlation coefficient of approximately 0.99, indicating that the proposed method fits the Nikuradse’s data. Therefore, the shear stress distribution can be estimated easily and accurately using the proposed equations, which can be used in future for the management and design of a water pipeline. 相似文献
357.
Man Jae Kwon Ju Yeon Lee Yun Ho Hwang Soo-kyung Jeon Jung-Seok Yang Seong-Taek Yun Seunghak Lee 《Environmental Earth Sciences》2017,76(23):802
We investigated the source of heavy metals in soils at a site in South Korea, where a ground transportation of zinc-concentrates (ZnS, sphalerite) occurs daily. Seventy soil samples were collected at the site and analyzed for residual concentrations of heavy metals, as well as their chemical and mineralogical properties. Enrichment factor was calculated based on local geochemical background level of metals in soils and confirmed the contamination of soils in the area by an anthropogenic source. The concentration data were also subjected to a Pearson correlation analysis to determine the possible influences of anthropogenic sources and identify the primary source. A slight negative correlation between heavy metals and Al, and a weak correlation between heavy metals and Fe implied that the heavy metals originated from anthropogenic inputs rather than a geogenic source. A strong positive linear correlation between Zn and other heavy metals (i.e., As, Cd, Cu, Pb, r ≥ 0.96, p ≤ 0.001) suggested the influence of a single anthropogenic source of zinc-concentrates containing all of these heavy metals. Zinc-concentrate oxidation and leaching experiments, which mimicked physical and chemical weathering in the environment, indicated that zinc-concentrate could be transformed to zinc oxides and release Cd and Pb upon precipitation. The findings in this study provide an insight into the fate of the Zn that the original form of zinc-concentrate would not remain in the soil after long-term weathering, which should be considered when source of heavy metals is identified. 相似文献
358.
Aerosol retrieval algorithms for the MODerate Resolution Imaging Spectroradiometer (MODIS) have been developed to estimate aerosol and microphysical properties of the atmosphere, which help to address aerosol climatic issues at global scale. However, higher spatial resolution aerosol products for urban areas have not been well researched mainly due to the difficulty of differentiating aerosols from bright surfaces in urban areas. Here, a new aerosol retrieval algorithm using the MODIS 500 m resolution image... 相似文献
359.
In this paper, we use multi-satellite remote sensing data and Regional Ocean Model System (ROMS) to examine the physical and biological responses to Typhoon Nakri during a period from 1 to 8 June 2008 in the western North Pacific. From satellite observations, we find remarkable surface cooling (∼5 °C) and distinct phytoplankton enhancement after Nakri passage. It is interesting to note that in contrast to the well-documented rightward bias of the surface cooling response, the maximum biological response to Nakri occurred on the left of the Nakri’s track rather than the right side, where the most distinct cooling response occurred. To reveal the dynamic mechanism for this unusual phenomenon, we have done numerical experiments with and without the influence of preexisting cyclonic circulation and previous typhoon. The results from simulations show that both the physical and biological responses to Nakri are greatly affected by the preexisting cyclonic circulations. The discrepancy between the locations of maximum physical and biological responses mainly results from the advanced uplift and current advection of nutrient fields by previous typhoon Rammasun, which passed through the area about two weeks before Nakri. 相似文献
360.
Phytoplankton community reorganization driven by eutrophication and warming in Lake Biwa 总被引:1,自引:0,他引:1
Chih Hao Hsieh Kanako Ishikawa Yoichiro Sakai Toshiyuki Ishikawa Satoshi Ichise Yoshimasa Yamamoto Ting Chun Kuo Ho Dong Park Norio Yamamura Michio Kumagai 《Aquatic Sciences - Research Across Boundaries》2010,72(4):467-483
We compiled and analyzed long-term data, including chemical, physical and phytoplankton community data, for the Lake Biwa
ecosystem from 1962 to 2003. Analyses on environmental data indicate that Lake Biwa had experienced intensified eutrophication
(according to total phosphorus concentration) in the late 1960s and returned to a less eutrophic status around 1985, and then
exhibited rapid warming and thus increased water column stability since 1990. Total phytoplankton cell volume largely followed
the trend of total phosphorus concentration, albeit short-term fluctuations existed. However, phytoplankton community shifted
dramatically in response to those changes of environmental states. These shifts were cause by changes in trophic status driven
by phosphorus loadings and physical properties in the water column driven by warming. Moreover, most phytoplankton species
did not show a strong linear correlation with environmental variables, suggesting nonlinear transitions among different states. 相似文献