• Journal of Korean Society on Water Environment
• /
• v.25 no.3
• /
• pp.394-403
• /
• 2009

A total of 52 sampling sites were selected in the stream network of the upper Paldang watershed (e.g. Kyonan, Gapyeong, Jojong, Chengmi, Bockha, Yanghwa and Heuk streams). Over the time period of April 2007-February 2008, 1820 samples were collected and analyzed for physico-chemical variables of the upper watershed in order to investigate spatio-temporal water quality variation in particular the relationship with land use. Although temporal variations of water quality in each stream were similar and were significantly influenced by flow, spatial variations in each stream varied as physico-chemical characteristics of upper watershed. As a result of regression analysis, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Nitrogen (T-N), and Total phosphorus (T-P) concentration were the most significantly and positively associated with people population density. It is necessary to manage not only water quality but also land use of upper watershed and flow flux.

• Animal cells and systems
• /
• v.15 no.3
• /
• pp.235-241
• /
• 2011

To examine variation in trophic pathways and the characteristics of food webs from organic matters to aquatic insects, we used stable isotopes to study an intermittent stream system of the Inukami River, Japan. The aquatic insects, including Glossosoma spp., Chironominae spp., Stenelmis spp., Rhyacophilla nigrocephala, and Hexatoma spp., were characterized by different feeding strategies. The ${\delta}^{13}C$ values for these species indicated that Glossosoma spp. graze upon periphyton; Chironominae and Stenelmis spp. mainly feed on benthic particulate organic matter, and R. nigrocephala and Hexatoma spp., which were identified as predators, feed upon Glossosoma, Stenelmis, and/or Chironominae spp. This suggests that the trophic position of consumers at each station may be determined by the trophic position of basal food sources in situ. For trophic pathways, the ${\delta}^{13}C$ values for both organic matter and aquatic insects tended to gradually decrease, whilst the ${\delta}^{15}N$ values increased from the upper reach to the lower reaches, relative to the physicochemical and geographical conditions. These parameters indirectly influence the flow of energy from organic matter to consumers within food web in an intermittent stream system.

• Nuclear Engineering and Technology
• /
• v.53 no.3
• /
• pp.715-731
• /
• 2021

Uncertainties are calculated for pressurized water reactor (PWR) spent nuclear fuel (SNF) characteristics. The deterministic code STREAM is currently being used as an SNF analysis tool to obtain isotopic inventory, radioactivity, decay heat, neutron and gamma source strengths. The SNF analysis capability of STREAM was recently validated. However, the uncertainty analysis is yet to be conducted. To estimate the uncertainty due to nuclear data, STREAM is used to perturb nuclear cross section (XS) and resonance integral (RI) libraries produced by NJOY99. The perturbation of XS and RI involves the stochastic sampling of ENDF/B-VII.1 covariance data. To estimate the uncertainty due to modeling parameters (fuel design and irradiation history), surrogate models are built based on polynomial chaos expansion (PCE) and variance-based sensitivity indices (i.e., Sobol' indices) are employed to perform global sensitivity analysis (GSA). The calculation results indicate that uncertainty of SNF due to modeling parameters are also very important and as a result can contribute significantly to the difference of uncertainties due to nuclear data and modeling parameters. In addition, the surrogate model offers a computationally efficient approach with significantly reduced computation time, to accurately evaluate uncertainties of SNF integral characteristics.

• Water for future
• /
• v.21 no.3
• /
• pp.223-226
• /
• 1988

• Journal of Environmental Science International
• /
• v.11 no.4
• /
• pp.309-317
• /
• 2002

In this study, water protection reservoir is selected as the target which is located at the estuary of Taehwa river to analyze and examine the effects of hydraulic structure on river environment. This study examined the water quality variation characteristics among many effects of hydraulic structure on river environment before and after removal of the sediment protection reservoir when low flow is yielded. This study aims at the definition of factors which cause the change of ecological environment of river due to the effects of the sediment protection reservoir, and the proposal of the direction of environmental friendly river space development through the comparison of stream variation conditions(depth, velocity, and etc.) and riverbed variation characteristics with ecological depth condition of Taehwa-river's channel for each representative species of fish and examination those. Firstly, from the examination result of water quality when low flow is yielded before and after removal of the sediment protection reservoir for problems about water quality of river due to flow amount decrease in river, it is found that DO decreases about 0.78~0.86ppm at the lower stream of Myeongchon-gyo, and BOD decreases about 0.06~0.24ppm from right upper stream to the direction of estuary when the sediment protection reservoir is removed. It is known from the above that there is some improvement of water quality from the lower stream of Taehwa-gyo to the estuary in case of removal the sediment protection reservoir. Nextly, it is thought that the effects on ecosystem due to water depth and draw down in channel is not serious on the basis of the examination of water quality analysis result according to removal of sediment protection reservoir and hydraulic depths for reservation of ecosystem, these are 10~40cm for breeding season, 10~50cm for fry period, and 10~100cm for adult period of the representative species of fish in Korea.

• Journal of Environmental Impact Assessment
• /
• v.20 no.1
• /
• pp.1-11
• /
• 2011

This study was carried out to suggest the baseline data necessary for vegetation restoration at riverine wetland within stream corridor. We used the prevalence index for wetland assessment by applying the method of weighted averages with index values based on five hydrophyte indicator status as defined by estimated probability occurred in wetland. We selected near nature and urbanized reach of Gap and Yanghwa streams as experimental site. Although two sites have some different disturbance and characteristics of watershed, they showed that similarity of vegetation community including three dominant species - Salix koreensis, Phragmites communis, Miscanthus sacchariflorus - was very high. But in case of Yanghwa stream, various kinds of emergent plants along wetted condition were distinctly occurred, resulted from difference of hydrological regime and substrate, etc. Degree of naturalness of vegetation at the sampled areas indicated that near nature area of Gap stream and all area of Yanghwa stream were fitted as riverine wetland, while urbanized area of Gap stream has changed into upland condition. In conclusion assessment system using prevalence index would be considered an effective method for evaluating of natural states of riverine wetland, but further integrated consideration of physical, hydrological, and biological factors of stream process, and also with considering the difference between those qualitative data of vegetation community.

• Korean Journal of Ecology and Environment
• /
• v.50 no.3
• /
• pp.325-336
• /
• 2017

The ecosystem in the Gwangju Stream has taken a wide range of disturbance such as the discharging water of sewage treatment plant, the lake water and the river water from different water system over the past decade. This study was figured out some significant influence factors by analyzing the relationship between biotic and abiotic factors in the urban stream. Abiotic components included 15 water quality variables which were measured in five sampling sites along the stream from October 2014 to July 2015, whereas the benthic macroinvertebrates found in those sites were used to estimate various biotic indices representing the ecological status of the community. The results of correlation analyses indicated that abiotic factors by human activities affected on the inhabitation of benthic macroinvertebrates more than biotic factors. The results of cluster analyses and ANOVA tests also showed that biotic and abiotic characteristics were clearly different in season. The main influence factors of cluster analysis by sites were $NH_3-N$, EPT(I) and DO. It was considered that more various statistical analyses would be necessary to find some different relationships and influence factors between biotic and abiotic variables in the urban stream.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.32 no.2
• /
• pp.102-119
• /
• 2004

This study investigates the relation between the location of a habitat and the ecological connections according to the habitat type in the riparian zone at the Bokha stream. Stream habitat is classified into nine types for the aquatic insects and fish. For vegetation and birds, habitat is classified into five types of medium-scale streams, including both physical and chemical streams are analyzed accordingly. The major results of this study are as follows: 1) A pool connected to the main stream has a certain water depth (about 80 cm) and is disturbed at least 5 to 6 times a year. Although the pool has a somewhat bad water quality, it provides a habitat for various types of young fish. 2) A meander riffle is about 15 cm deep, the flow velocity in the region is about 75 cm/s. This region does not have large structures to which aquatic insects can attach, so it cannot be used as a spawning ground. 3) A rock type pool is about 60 cm deep, the flow velocity in the meander riffle is about 25 cm/s. In this region, many aquatic insects attached to large structures appear. Due to various riparian vegetation, the rock type pool is used as a habitat for aquatic insects. 4) A pool which is only connected to the main stream during floods has a bad water quality. Despite of its relatively small size, it has a high population density of aquatic insects. faculty.

• Journal of the Institute of Convergence Signal Processing
• /
• v.3 no.1
• /
• pp.21-26
• /
• 2002

Video stream invoke a variety of traffic with the structure of compression algorithm and image complexity. Thus, it is difficult to allocate the resource on the both sides of sender and receiver, and playout on the Internet such as a packet switched network. Thus, in this paper we proposed video stream smoothing using multistream for the effective transmission of video stream. This method specifies the type of LDU(logical data unit) according to the type of original stream, and then makes a large number of streams as a fixed size, and transfers them. So, the proposed method can reduce the buffering time which occurs during the process of the smoothing and prefetch be robust to the jitter on network, as well. Consequently, it has the effective transmission characteristics of fully utilizing the clients bandwidth.

• Journal of ILASS-Korea
• /
• v.8 no.2
• /
• pp.7-15
• /
• 2003

The effects of fuel density and fuel viscosity on spray characteristics were investigated under two different gas turbine fuels and various fuel supply pressure conditions through measurement of SMD, number density and volume flux by using PDPA system in dual orifice injector for gas turbine engines. In this study, we found out that the droplet size and spray structure are strongly depend on fuel density for dual orifice injector. The spray characteristics of high density fuel in dual orifice injector are similar with the characteristics of low density fuel in single orifice injector. The shear region between primary main fuel stream and secondary main fuel stream is examined in low density fuel condition but not exist in high density fuel condition, then this shear region is very important in quality of gas turbine spray. There are worth consideration for the effect of fuel density on spray characteristics in frontal device design to improve combustion efficiency.