• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.163-170
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• 2011

Natural stream disasters due to a localized torrential and flash flood has occurring in a small stream especially un-implemented small stream. The survey results during ten years from 2001 to 2010 show that the small stream implementation projects (SSIPs) expenses is increasing with the damages is generally decreasing with variableness in which SSIPs is contributing to disaster prevention in a small stream. This study develop guideline for the selection of SSIPs to support high risk stream at first and save the small streams located on the mountainous area, prevention area and agricultural area which streams have no implementation effects. Developed sub items in guideline are evaluated by stream data collected from 212 small streams where it is proved that sub distance of each item are well arranged by normal distribution. This SSIPs is useful for selecting high risk small stream at first to maximize disaster risk reduction with minimum SSIPs expenses. Also, this SSIPs is used for leading to save small stream on the upstream to minimize flood damages on the down stream with selection a SSIP purchasing agricultural land for preparing flood plane.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.285-288
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• 2008

The Present Study describes the numerical investigations concerning a fuel(Hydrogen), inert gas (Nitrogen) or supersonic air stream issued between each other. The basic flow configuration consists of a plane, double shear/mixing layer flow. For the numerical solution, a fully conservative unsteady $2^{nd}$ order time accurate sub-iteration method and a $2^{nd}$ order Total Variation Diminishing(TVD) scheme are used with the finite volume method(FVM). The results are consist of three categories ; single shear layer consist of fuel and supersonic air stream, inert gas stream issued between supersonic air and fuel stream, fuel gas stream issued between supersonic air and fuel stream. The numerical calculations has been carried out in case of 1,2, and 4mm thickness of center stream. The width of total gas stream is 4cm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.6973-6979
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• 2014

To mitigate global warming and climate change, many countries are investing massively on the development of CCS technology, which is assumed to be the key technology to reduce $CO_2$ emissions. CCS technology is comprised of the capture, transport, and storage processes. During the capture process, impurities other than $CO_2$ are inevitably flowed into the $CO_2$ stream. In the present study, corrosion characteristics of a phosphate coated tube for $CO_2$ transportation was investigated with a $CO_2$ stream composed of $CO_2$, $H_2O$, $SO_2$, and $NO_2$. The test specimen was a phosphate coated steel tube, which was filled with $CO_2$ stream with the impurities mentioned above. SEM-EDS analysis is conducted to investigate the corrosion behavior. The results showed that although the H2O concentration did not exceed the solubility limit, corrosion occurred in the specimen, which has an inflow of $SO_2$ or $NO_2$. This suggests that the $SO_2$, $NO_2$ and $H_2O$ concentration should be strictly controlled. These results suggest that the $SO_2$ and $NO_2$ concentration should be controlled below 175ppm and 65ppm, respectively.

• Journal of the Chungcheong Mathematical Society
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• v.29 no.4
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• pp.573-584
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• 2016

Invertible transformations over n-bit words are essential ingredients in many cryptographic constructions. Such invertible transformations are usually represented as a composition of simpler operations such as linear functions, S-P networks, Feistel structures and T-functions. Among them T-functions are probably invertible transformations and are very useful in stream ciphers. In this paper we will characterize a secure trinomial on ${\mathbb{Z}}_{2^n}$ which generates an n-bit word sequence without consecutive elements of period $2^n$.

• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.317-322
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• 2011

• Journal of The Korean Society of Agricultural Engineers
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• v.51 no.5
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• pp.69-78
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• 2009

In order to improve water quality of upper watershed of Paldang reservoir, it is necessary to evaluate non-point source pollution loads and identify critical watershed pollution sources. A GIS based Soil and Water Assessment Tool was applied to evaluate model application and reliability, estimate NPS pollution load, identify critical watershed by NPS pollution sources, and suggest various best management practices for Kyongan Stream watershed. Yearly NPS pollution loads were estimated 30.0% SS, 60.1% TN and 35.4% TP, respectably. The watershed pollution load is mainly decided by precipitation condition and SS and nutrients load have a significant regression relationship. Based on 10-year average yearly NPS pollution load, critical sub-watersheds were identified. The No. 5 and 17 which have lots of relatively intensive agricultural fields and scattered industrial area were vary critical sub-watersheds and under more intensive pollution load. In order to control critical watershed, watershed best management practices such as scientific fertilizer, contour farming and parallel terrace, transferring the sloppy farmland to grass or forest and constructing a buffer zone, and constructing wetlands and retention ponds will be applied. Overall the SWAT model can be efficiently used for identification of critical sub-watersheds in order to develop a priority watershed management plan to reduce water pollutions.

• Journal of the Korean earth science society
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• v.45 no.1
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• pp.72-84
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• 2024

Recently, the vulnerability of water resources has been increasing owing to climate change, highlighting the importance of groundwater. In particular, the Nakdong River Basin, located in the southern part of Korea, experiences frequent water scarcity phenomena, such as droughts. This study analyzed the hydrogeological characteristics of the study area by examining groundwater and stream water in the Gwangrye Stream, downstream of the Nakdong River Basin, in August and October 2023. Therefore, we collected samples from 54 groundwater wells and five streams for water quality analysis. The results of the field tests indicated an increasing trend in electrical conductivity from upstream to downstream in the study area. Laboratory analyses confirmed that the concentration of Na increased from upstream to downstream more than that of Ca. In conclusion, both stream water and groundwater were influenced by anthropogenic contamination. These changes were closely related to land use in the study area. The upstream areas are primarily composed of forests, whereas the downstream areas are composed of industrial complexes, wastewater treatment facilities, and agricultural areas, which are likely to affect both stream water and groundwater.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.2977-2997
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• 2018

In big data era, fresh data grows rapidly every day. More than 30,000 gigabytes of data are created every second and the rate is accelerating. Many organizations rely heavily on real time streaming, while big data stream computing helps them spot opportunities and risks from real time big data. Storm, one of the most common online stream computing platforms, has been used for big data stream computing, with response time ranging from milliseconds to sub-seconds. The performance of Storm plays a crucial role in different application scenarios, however, few studies were conducted to evaluate the performance of Storm. In this paper, we investigate the performance of Storm under different application scenarios. Our experimental results show that throughput and latency of Storm are greatly affected by the number of instances of each vertex in task topology, and the number of available resources in data center. The fault-tolerant mechanism of Storm works well in most big data stream computing environments. As a result, it is suggested that a dynamic topology, an elastic scheduling framework, and a memory based fault-tolerant mechanism are necessary for providing high throughput and low latency services on Storm platform.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.247-252
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• 2003

In this paper, we made four types of metal particle $Al_2$O$_3$ barrier reactors with and without dielectric of BaTiO$_3$ between metal particle and $Al_2$O$_3$ barrier to investigate NOx removal characteristic and the effect of dielectric on Nox removal. And Nox removal rate is measured when sludge pellets are put at down stream of plasma reactor. Nox removal rate in the reactor with $Al_2$O$_3$ barrier is much better than that in the reactor without $Al_2$O$_3$ barrier, Nox removal rate is not so good in metal particle-Al$_2$O$_3$ barrier reactor with BaTiO$_3$ between metal particle and $Al_2$O$_3$ barrier, however, Nox removal rate is about 40% in metal particle-Al$_2$O$_3$ barrier reactor with TiO$_2$. The most of NO is conversed to NO$_2$ in these kind of reactor. When sludge pellets are put at down stream of plasma reactor, Nox removal rate is greatly improved up to 90%. It indicates that sludge pellets have great effect on the NO$_2$ removal and the improvement of Nox removal rate, however, dielectric materials between metal particle and $Al_2$O$_3$ barrier have not effect. Organic materials included in sludge may react with NO$_2$ and ozone so that Nox removal rate is greatly improved.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.1
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• pp.39-48
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• 2008

This study was carried out to investigate the characteristics of the pollutant discharge from non-point source and to estimate the unit loads of the pollutant discharge from the upper watershed of Seomjin Dam during rainy season. The upper watershed of Seomjin Dam is located in the middle of Jeonbuk province is formed two tributaries mainly. A sub-branch stream of those tributaries is Imsil stream of which flow rate is about 13% of the main stream of Seomjin reservoir normally. On the basis of measurement result in this study, the water quality of Imsil stream was fluctuated highly and the quantity of measured pollutant discharge was higher than the value calculated with the proportion of flow rate during dry season. On the contrary, during rainy season the mean values of flow rate and water quality were higher than the quartile according to the statistical analysis. That means rainfall can influence strongly on the water quality of the upper watershed of Seomjin reservoir. Among the several criteria of water quality, SS discharge was most sensitive to the flow rate variation of stream, which was fluctuated in proportion of rainfall, basically. It was evaluated the event mean concentration (EMC) of non-point source pollutants depending on rainfall events as well. Though the pollutant discharge unit of Imsil stream was lower than the main stream of Seomjin reservoir, the EMC value of Imsil stream was higher than the main stream of Seomjin reservoir.