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排序方式: 共有251条查询结果,搜索用时 15 毫秒
111.
Jeong-a ParkSeok-jin Hong Ik KimJi-yong Lee Tak Hur 《Resources, Conservation and Recycling》2011,55(4):456-462
Material flow analysis (MFA) is an evaluation technique that systematically identifies the flows and stocks of materials within predefined spatial and temporal boundaries. In this paper, the steel resources in Korea are investigated using dynamic MFA. Iron ore and steel scrap are added as raw material components during the production processes of steel, which is then used in a variety of product groups such as construction products, transportation equipment, machinery/metal products, electrical/electronic devices, and other products through fabrication and manufacturing processes. When such product groups are discarded, they are either recycled or landfilled. With consideration for the lifetimes of various product groups in conjunction with steel resource flows in Korea, dynamic MFA is conducted on the flows of steel stock change and annual scrap generation. By 2020, these two flows are expected to increase by as much as 40% and 30%, respectively, compared to 2008, with transportation equipment, in particular, envisaged to experience high growth. At the current recycling rate, however, it will be hard to meet future scrap demand. According to the scenario analysis, 100% of this future scrap demand can be supplied domestically if the recycling rate is increased to over 70% for all product groups, except construction products and transportation equipment, which already have high recycling rates. By 2020, the reduction in scrap importation costs is projected to offer a financial gain of 2.3 billion dollars. 相似文献
112.
Experimental results obtained to date indicate electrokinetic extraction is viable in removing organic and inorganic contaminants
from fine-grained soils. However, electrochemical reactions and soil-contaminant interactions that occur simultaneously may
enhance or reduce the removal efficiency of the hazardous waste site remediation process. Many sites worldwide are contaminated
by lead and its compounds, resulting in lead poisoning. It is difficult to remove lead from fine-grained soil because of the
existence of a great variety of lead complexes and their pH-dependent and reversible physicochemical properties. The feasibility
of electrokinetic extraction of lead from kaolinites is investigated theoretically, numerically, and experimentally in this
study. This is the first paper of two companion papers presenting the theoretical and numerical modeling of the transport
of lead species, and electrochemical reactions and soil-contaminant interactions occurring during the electrokinetic extraction
process. The comparison between simulation results and experimental results is presented in the second paper. 相似文献
113.
On the heating environment in street canyon 总被引:1,自引:1,他引:0
This study investigates the impact of building aspect ratio (building-height-to-street-canyon-width-ratio), wind speed and
surface and air-temperature difference (Δθs−a) on the heating environment within street canyon. The Reynolds-averaged Navier-Stokes (RANS) and energy transport equations
were solved with Renormalization group (RNG) theory version of k-e{\varepsilon} turbulence model. The validation process demonstrated that the model could be trusted for simulating air-temperature and
velocity trends. The temperature and velocity patterns were discussed in idealized street canyons of different aspect ratios
(0.5–2.0) with varying ambient wind speeds (0.5–1.5 m/s) and Δθs−a (2–8 K). Results show that air-temperatures are directly proportional to bulk Richardson number (R
b
) for all but ground heating situation. Conversely, air-temperatures increase significantly across the street canyon with
a decrease in ambient wind speed; however, the impact of Δθs−a was negligible. Clearly, ambient wind speed decreases significantly as it passes over higher AR street canyons. Notably,
air-temperatures were the highest when the windward wall was heated and the least during ground heating. Conversely, air-temperatures
were lower along the windward side but higher within the street canyon when the windward wall was heated. 相似文献
114.
Wanxia Gai Stephanie C. Y. Yu W. T. Charlotte Chan Wenlei Peng So Ling Lau Tak Y. Leung Peiyong Jiang K. C. Allen Chan Y. M. Dennis Lo 《黑龙江环境通报》2023,43(11):1385-1393
Objective
Long cell-free DNA (cfDNA) can be found in the plasma of pregnant women and cancer patients. We investigated if droplet digital PCR (ddPCR) can analyze such molecules for diagnostic purposes using preeclampsia as a model.Method
Plasma samples from ten preeclamptic and sixteen normal pregnancies were analyzed. Two ddPCR assays targeting a single-copy gene, VCP, and one ddPCR assay targeting LINE-1 repetitive regions were used to measure the percentages of long cfDNA >533, 1001, and 170 bp, respectively. The LINE-1 assay was developed as guided by in silico PCR analyses to better differentiate preeclamptic and normal pregnancies.Results
Preeclamptic patients had a significantly lower median percentage of long cfDNA than healthy pregnant controls, as determined by the LINE-1 170 bp assay (28.9% vs. 35.1%, p < 0.0001) and the VCP 533 bp assay (6.6% vs. 8.7%, p = 0.014). The LINE-1 assay provided a better differentiation than the VCP 533 bp assay (area under ROC curves, 0.94 vs. 0.79).Conclusion
ddPCR is a cost-effective approach for unlocking diagnostic information carried by long cfDNA in plasma and may have applications for the detection of preeclampsia. Further longitudinal studies with larger cohorts are required to assess the clinical utility of this test. 相似文献115.
Mu Yunsong Shao Meichen Zhong Buqing Zhao Yiqun Leung Kenneth M. Y. Giesy John P. Ma Jin Wu Fengchang Zeng Fangang 《Environmental science and pollution research international》2021,28(28):37051-37059
Environmental Science and Pollution Research - The coronavirus disease 2019 (COVID-19) pandemic has brought unprecedented public health, and social and economic challenges. It remains unclear... 相似文献
116.
Chelsey Walden-Schreiner Sebastian Dario Rossi Agustina Barros Catherine Pickering Yu-Fai Leung 《Ambio》2018,47(7):781-793
Managing protected areas effectively requires information about patterns of visitor use, but these data are often limited. We explore how geotagged photos on Flickr, a popular photo-sharing social-media site, can generate hotspot maps and distribution models of temporal and spatial patterns of use in two mountain-protected areas of high conservation value. In Aconcagua Provincial Park (Argentina), two routes to the summit of Aconcagua were used in summer, but most visitors stayed close to the main road, using formal and informal walking trails and the Visitor Centre, while in winter, there was very limited visitation. In Kosciuszko National Park (Australia), alpine walking trails were popular in summer, but in winter, most visitors stayed in the lower altitude ski resorts and ski trails. Results demonstrate the usefulness of social-media data alone as well as a complement for visitor monitoring, providing spatial and temporal information for site-specific and park-level management of visitors and potential impacts in conservation areas. 相似文献
117.
Kim YS Jeong CS Seong GT Han IS Lee YS 《Journal of environmental biology / Academy of Environmental Biology, India》2010,31(5):687-693
The diurnal vertical migration of Cochlodinium polykrikoides (C. polykrikoides), which caused a red tide in the Korean coastal waters of the East Sea/Sea of Japan in September 2003, was examined by determining the time-dependent changes in the density of living cells in relation to the depth of the water column. The ascent of this species into the surface layer (depth of water 2 m) occurred during 1400-1500. The descent started at 1600 and a high distribution rate (86%) at 15-20 m was observed at 0300. During the ascent, the cells were widely distributed at each depth level from 0600 hr and at 0800-1100, the cells were primarily distributed in the middle layer (0-6 m). The concentration of dissolved inorganic nitrogen was generally < or = 2.86 micromol l(-1), but at 1400-1500, the concentration in the surface layer reduced to < or = 0.14 micromol l(-1). Moreover, the concentration gradually increased as the depth increased to > or = 5 m. These results showed that the nutrient-consumption rate associated with the proliferation of C. polykrikoides during a red tide is more influenced by the inorganic-nitrogen resources ratherthan the inorganic-phosphorus compounds. 相似文献
118.
Wai-Chuen Ng F. C. C. Leung Solomon T. C. Chak G. Slingsby Gray A. Williams 《Marine Biology》2010,157(2):325-337
Variations in the relative contributions of gene flow and spatial and temporal variation in recruitment are considered the
major determinants of population genetic structure in marine organisms. Such variation can be assessed through repeated measures
of the genetic structure of a species over time. To test the relative importance of these two phenomena, temporal variation
in genetic composition was measured in the limpet Cellana grata, among four annual cohorts over 10 years at four rocky shores in Hong Kong. A total of 408 limpets, comprising individuals
from 1998, 1999, 2006 and 2007 cohorts were screened for genetic variation using five microsatellite loci. Minor but significant
genetic differentiation was detected among samples from the 1998/1999 collection (F
ST = 0.0023), but there was no significant differentiation among the 2006/2007 collection (F
ST = 0.0008). Partitioning of genetic variation among shores was also significant in 1998/1999 but not in the 2006/2007 collection,
although there was no correlation between genetic and geographic distances. There was no significant difference between collections
made in 1998/1999 and 2006/2007. This lack of clear structure implies a high level of gene flow, but differentiation with
time may be the result of stochastic recruitment variation among shores. Estimates of effective population size were not high
(599, 95% C.L. 352–11397), suggesting the potential susceptibility of the populations to genetic drift, although a significant
bottleneck effect was not detected. These findings indicate that genetic structuring between populations of C. grata in space and time may result from spatio-temporal variation in recruitment, but the potential development of biologically
significant differentiation is suppressed by a lack of consistency in recruitment variability and high connectivity among
shores. 相似文献
119.
As far as the impact of air pollutants on human health being is concerned, ozone (O3) is one of the most pollutant sources, and, in particular, the ground level ozone is responsible for a variety of adverse effects on both human being and plant life. To protect the population from such adverse health effects, early information and precautions about the high ozone level need to be ascertained. In this study, statistical characteristics of ground level ozone is analyzed according to field monitoring data in mixed residential, commercial and industrial areas, e.g., Tsuen Wan area in Hong Kong. The study deals with the characteristics of hourly and daily mean ozone levels under different climatic conditions such as temperature, solar radiation (SR), wind speed (WS), and other pollutant concentration levels. The study aims to investigate the importance of meteorological factors and their impact on relevant pollutant concentration levels from a chemical aspect. Further, reasons for the spatial and temporal variation of ozone levels are discussed. All these results will provide a physical basis for accurately predicting ozone concentration in similar research. 相似文献
120.
Nature and fate of Hudson Bay permafrost 总被引:4,自引:0,他引:4
Two aspects of the permafrost of the Hudson Bay region are examined. The first is the climatological conditions that support
permafrost especially along the southwestern shore of Hudson Bay. The second is the fate of the permafrost using recent climate
change scenarios. The continuous permafrost along the shores of southwestern Hudson Bay is examined from a climatological
perspective. Two hypotheses are explored to explain the presence of continuous permafrost in this region in spite of the relatively
"warm" local climate. Possible errors in the calculation of thawing degree days and the asymmetries in frozen and unfrozen
soil thermal conductivities are successively examined. Only the second hypothesis is likely to explain the presence of permafrost
in southwestern Hudson Bay. Sophisticated climate models are used to assess the potential change in permafrost distribution
in the Hudson Bay region. Nine simulations using three different versions of the Canadian Centre of Climate Modelling and
Analysis (CCCma) general circulation model are used to project permafrost distribution. Two surface temperature thresholds,
–5 and –10 °C, are used to diagnose permafrost grid points. All simulations, including those that include reduction of CO2 emissions, showed at least a 50% reduction of permafrost by 2100 using these temperature thresholds.
Electronic Publication 相似文献