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        검색결과 91

        81.
        2012.06 KCI 등재 서비스 종료(열람 제한)
        Emission rates of biogenic hydrocarbon emitted from broad-leaved trees grown at Jeju Island were estimated using a dynamic enclosure method. Leaf temperature, PAR and relative humidity were monitored during the sampling time. The emission rates of isoprene and monoterpene were measured for five plants(Carpinus laxiflora, Quercus serrata, Styrax japonicus, Quercus acutissima, Quercus crispula) during the sampling period at the Halla mountain sites. Among five tree species, the highest isoprene emission rate of 10.60 ㎍ gdw-1hr-1 was observed for Quercus serrata. The seasonal emission rates were the highest during summer and the emission of isoprene was highly affected by light and temperature variations. The highest emission rate of isoprene was occurred between 13:00 and 14:00, but isoprene was not emitted in nighttime because of the absence of light.
        82.
        2010.05 KCI 등재 서비스 종료(열람 제한)
        Emission rate of monoterpene and isoprene was measured in five commonly growing tree species of conifers(Pinus thunbergii, Abies koreana, Cryptomeria japonica, Pinus densiflora, Chamaecyparis obtusa) at the Halla mountain sites. Dynamic flow enclosure technique was used and gas samples were collected into Tenax tube. The highest and lowest hourly emission rate was observed in Abies koreana (1.86 ㎍/gdw/hr) and Chamaecyparis obtusa (0.52 ㎍/gdw/hr), respectively. The major species of monoterpene from pine trees were α-pinene, β-pinene, β-phellandrene, myrcene. Particularly, d-limonene was abundant in Abies koreana but α-pinene, d 3 -carene and sabinene was in Cryptomeria japonica. Emission rates of isoprene show less significant than those of monoterpene. And also seasonal emission rates of monoterpene were dependent on environmental factors such as temperature.
        83.
        2009.09 KCI 등재 서비스 종료(열람 제한)
        This study was conducted to investigate the productivity of Hanwoo steers by feeding self-product organic rice straw and concentrates(conventional, T1 and organic T2). Sixteen Hanwoo steers(8 months on the average) were randomly assigned to two treatment groups. Feeding trail was carried out in 2 treatment(8 heads/ treatment) by Hanwoo steers for 600 days form 8 to 28 months in age. The range of average daily gains of T1 and T2 were 0.76 to 0.77㎏ in the growing stage, 0.93 to 0.90㎏ in the first fattening stage, 0.99 to 0.84㎏ in the middle fattening stage, and 0.59 to 0.64㎏ in the latter fattening, respectively, and the gains for overall period was higher in T1 than in T2. Concentrates and total digestive nutrients(TDN)(T1) intakes per unit of kg gains were higher than T2 without significant difference. In carcass characteristics, the carcass weight in T1 were higher about 5% than in T2. According to the above results, it may be concluded that dry matter(DM) intakes, crude protein(CP) and TDN contents of feedstuff between treatments was no significant difference. but marbling in T2 score was higher than in T1 about 20%. There were no significant differences rib-eye area, back fat thickness and fat color(p>0.05).
        84.
        2009.08 KCI 등재 서비스 종료(열람 제한)
        Suppressing residual vibrations of flexible materials cheaply is an important issue to increase productivity of automated factory using wafer or glass handling robots. In this paper, we present Linux/RTAI-based implementation of input shaping control for reducing residual vibrations of a mechanical system. Experimental results show that residual vibrations of the mechanical system are reduced up to 82% at a point-to-point linear motion.
        85.
        2007.12 KCI 등재 서비스 종료(열람 제한)
        Long-term trends and distribution patterns of water quality were investigated in the Asan coastal areas of Yellow Sea, Korea from 1975 to 2005. Water samples were collected at 3 stations and physicochemical parameters were analyzed including water temperature, salinity, suspended solids (SS), chemical oxygen demand (COD), dissolved oxygen (DO) and nutrients. Spatial distribution patterns were not clear among stations but the seasonal variations were distinct except COD, SS and nitrate. The trend analysis by principal component analysis (PCA) during twenty years revealed the significant variations in water quality in the study area. Annual water qualities were clearly discriminated into 4 clusters by PCA; year cluster 1988-1991, 1994-1997, and 1992-1993/1998- 2005. By this multi-variate analysis we can summarize the annual trends as the followings; salinity, suspended solids and dissolved oxygen tended to increase from late 1980's, increased pH and COD from 1992, and decreased salinity and increased nitrogen and COD from 1990 due to the runoff frow agricultural lands causing eutrophication.
        86.
        2007.12 KCI 등재 서비스 종료(열람 제한)
        To find proper water quality management strategy for oxygen consumption organic matters in Jinhae bay, the physical process and net supply/decomposition in terms of COD was estimated by three-dimensional eco-hydrodynamic modeling. The estimation results of physical process in terms of COD showed that transportation of COD was dominant in loading area from land to sea, while accumulation of COD was dominant in middle~bottom level. In case of surface level, the net supply rate of COD was 0~60 mg/m2/day. The net decomposition rate of COD was 0~-0.05 mg/m2/day(-5~-10 m, in depth) to 2 level, and -0.05~-0.20 mg/m2/day(10 m ~) to bottom level. These results indicate that the biological decomposition and physical accumulation of COD are occurred for the most part of Jinhae Bay bottom. The variation of net supply or net decomposition rate of COD as reducing land based input loading is also remarkable. Therefore, it is important to consider both allochthonous and autochthonous oxygen demanding organic matters to improve the water quality of Jinhae Bay.
        87.
        2007.08 KCI 등재 서비스 종료(열람 제한)
        The three-dimensional eco-hydrodynamic model was applied to estimate the autochthonous COD caused by production of phytoplankton in Jinhae Bay. A residual current was simulated, using a hydrodynamic model, to have a sightly complicated pattern in the inner part of the bay, ranging from 0.001 to 5 cm/s. In the outer part of the bay, the simulated current flowed out to the south sea with a southward flow at a maximum of 25 cm/s. The results of the ecological model simulation of COD levels showed high concentrations, exceeding 4 mg/L, in the inner bay of Masan, an area of wastewater discharge, and lower levels, approaching less than 1 mg/L, closer to the outer part of the bay. The simulation results of Autochthonous COD by two methods using ecological modeling, showed high ratio over 70% of total COD. Therefore, it is more important to consider nutrients than organic matters in the region for control COD standard.
        88.
        2007.05 KCI 등재 서비스 종료(열람 제한)
        The mechanism of water pollution in Lake Shihwa, one of highly eutrophicated artificial lakes in Korea, has been studied using a numerical 3D physical-biochemical coupled model. In this study, the model was applied to estimate the contribution of land-based pollutant load to water quality of heavily polluted Lake Shihwa. The chemical oxygen demand(COD) was adopted as an index of the lake water quality, and the spatial distribution of an average COD concentration during the summer from 1999 to 2000 was simulated by the model. The simulated COD showed a good agreement with the observed data. According to reproducibility of COD, the highest levels between 8 and 9 mg/L were shown at the inner site of the lake with inflow of many rivers and ditches, while the lowest was found to be about 5 mg/L at the southwestern site near to dike gate. In the prediction of water quality of Lake Shihwa, COD showed still higher levels than 3 mg/L in case of reduction of 95% for land-based pollutant load. This suggests that the curtailment of land-based pollutant load is not only sufficient but the improvement of sediment quality or the increase of seawater exchange should be considered together to improve a water quality in Lake Shihwa.
        89.
        2006.05 KCI 등재 서비스 종료(열람 제한)
        Long-term trends and distribution patterns of water quality were investigated in the Cheonsu Bay of Korea from 1983 to 2004. Water samples were collected at 4 stations and physicochemical parameters were analyzed including water temperature, salinity, suspended solids (SS), chemical oxygen demand (COD), dissolved oxygen (DO) and nutrients. Spatial distribution patterns were not clear between stations but the seasonal variations were distinctive except COD, SS and nitrate. Twenty two year long-term trend analysis by PCA revealed the significant changes in water quality in the study area. Water quality during 1980's and early 1990's showed high SS, low nutrients and low COD which increased during the mid and late 1990's and early 2000's. Overall water quality in the Cheonsu Bay indicated the increase in nutrients and COD concentration.
        90.
        2001.08 KCI 등재 서비스 종료(열람 제한)
        In an attempt to evaluate the possibility of producing an organic fertilizer using sediments from coastal farming areas, the chemical composition, bacteriological quality and heavy metals in the sediments alkalized by quicklime and magnesium hydroxide were analyzed. The optimum reaction was obtained from the following conditions : a 1:4 mixture of dry sediment to food wastes and the addition of 30% quicklime to the mixture. According to the classification standard for compost constituent by Higgins, all composts had a low or intermediate grade in T-N and K2O content, a low grade in P2O5 and a high grade in CaO and MgO content. Stabilization by quicklime and magnesium hydroxide is likely to inhibit the bacterial decomposition of organic matter and the activity of pathogenic organisms. Raising the pH of stabilized sediments to 12 for 2 hours(PSRP criteria of EPA) allowed 99.99% of the coliform group, fecal group and viable cell count to be reduced. The results suggested that the crude fertilizer produced by alkaline stabilization method was innoxious and thereby the sediments from coastal farming areas could be used as organic fertilizer.
        91.
        2000.10 KCI 등재 서비스 종료(열람 제한)
        It is very important to interprete and simulate the variation of phytoplankton maximum region for the prediction and control of red tide. This study was composed of two parts, first, the hydrodynamic simulation such as residual current and salinity diffusion, and second, the ecological simulation such as phytoplankton distribution according to freshwater discharge and pollutant loads. Without the Nakdong river discharge, residual current was stagnated in inner side of this estuary, and surface distribution of salinity was over 25psu. On the contrary, with summer mean discharge, freshwater stretched very far outward and some waters flowed into Chinhae Bay through the Kadok channel, and low salinity extended over coastal sea and salinity front occurred. From the result of contributed physical process to phytoplankton biomass, the accumulation was occurred at the west part of this estuary and the Kadok channel with the Nakdong river discharge. When more increased input discharge, the accumulation band was transported to outer side of this estuary. The frequently outbreak of red tide in this area is caused by accumulation of physical processes. The phytoplankton maximum region located inner side of this estuary without the Nakdong river discharge and with mean discharge of winter, but it was moved to outer side when mean discharge of the Nakdong river was increased. The variation of input concentration from the land loads was not largely influenced on phytoplankton biomass and location of maximum region. When discharge was increased, phytoplankton maximum region was transferred to inner side of the Kadok channel. On the other hand, when discharge was decreased, phytoplankton maximum region was transferred to inner side of this estuary and chlorophyll a contents increased to over 20㎍/L. Therefore, if any other conditions are favorable for growth of phytoplankton, decrease of discharge causes to increase of possibility of red tide outbreak.
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