• Journal of Wetlands Research
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• v.14 no.1
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• pp.139-146
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• 2012

Stream ecosystems carry out significant functions such as water purification, especially denitrification. However, rapid landuse change since industrialization has altered ecological functions of streams. In this study, we aimed to investigate denitrification rates and their determinant factors in streams with different landuse patterns, and how denitrification rates vary with microtopology within streams. Ten fifth streams of each landuse were selected, and each stream was divided into four microtopological sites within streams - riparian zone, subsoil, and both head and tail parts of sand bars. In situ denitrification rates and physicochemical properties of soil were examined. Denitrification rates of agricultural, urban, and forest streams were $289.62{\pm}70.69$, $157.01{\pm}37.06$, $31.38{\pm}18.65mg$ $N_2O-N\;m^{-2}\;d^{-1}$ respectively. There were no significant differences in denitrification rates depending on microtopology, but the rates in riparian zone were the highest, and the rates in the head parts of sandbars were lower than those of tail parts. The determinant factors for denitrification rates included water temperature, silt and clay contents of soil, inorganic nitrogen, and organic carbon, and these factors all showed positive correlations with denitrification rates. Through this study, we find that landuse pattern in watershed region affects denitrification rates that is one of considerable functions of streams. In addition, estimation of denitrification rates taking into account for microtopology would contribute to developing ecological management and restoration strategy of streams.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.4 no.4
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• pp.1-11
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• 2001

This study was carried out to analyze the characteristics of forest environmental and stream morphological factors by using the quantification theory(I) for evaluation of the watershed stability. Present annual mean sediment yield of erosion control dams were investigated in 167 sites of erosion control dam constructed during 1986 to 1999 in Gyeongbuk. The results obtained from this study were summarized as follows; According to the coefficients of partial correlation, each factor affecting to sediment was shown in order of gravel contents, number of first streams order, number of total streams, length of total streams, forest type, length of main stream, parent rock, stand age, soil texture, stream order, slope gradient, soil depth and aspect. Descriptions of class I were as follow; Igneous rock of parent rock, hardwood stands of forest type, less than 20 year of stand age, less than 30cm of soil depth, sandy clay loam of soil texture, more than 41% of gravel contents, south~east of aspect, 2,501~3,500m of length of main stream, 21~25 of number of total streams, 5,501~10,000m of length of total streams, 3 or more than 4 of stream order, more than 16 of number of first stream orders and more than $31^{\circ}$ of slope gradient. Descriptions of class II were as follow; Metamorphic rock of parent rock, coniferous stands of forest type, more than 25 year of stand age, 31~40cm of soil depth, silt loam of soil texture, 11~20% of gravel contents, north~west of aspect, 2,501~3,500m of length of main stream, 16~20 of number of total streams, 3,501~5,500m of length of total streams, 3 of stream order, 11~15 of number of first stream orders and more than $31^{\circ}$ of slope gradient. Descriptions of class III were as follow; Sedimentary rock of parent rock, mixed stands of forest type, more than 25 year of stand age, more than 51cm of soil depth, silty clay loam of soil texture, less than 10% of gravel contents, south~west of aspect, less than 500m of length of main stream, less than 5 of number of total streams, less than 1,000m of length of total streams, less than 1 of stream order, less than 2 of number of first stream orders and less than $25^{\circ}$ of slope gradient. The prediction method of suitable site for erosion control dam divided into class I, II, and III for the convenience of use. The score of class I evaluated as a very unstable area was more than 8.4494. A score of class II was 8.4493 to 6.0452, it was evaluated as a moderate stable area, and class III was less than 6.0541, it was evaluated as a very stable area.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.89-104
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• 2001

The Chonju and Samchun streams are passing though Chonju city and several contamination sources are located along these streams. The Samchun stream joins the Chonju stream in the Gosapyeong waste disposal site and the Chonju stream finally joins to the Mankyeong River. The objectives of this study are to determine the state and sources of contamination for heavy metals and anions in the Chonju and Samchun streams and to evaluate the effect of these streams on the contamination of the Mankyeong River. In order to select sampling locations, a stratified random sampling method was used. These streams was divided into several parts according to the expected contamination state, and samples were selected randomly from these parts. Generally, the water qualities of these streams were generally below the Drinking Water Level at the time of sampling in various heavy metals and anions. However, the levels of AI, Fe, $NH_{3}-N,Cl^{-}$, Cl- in these streams could be higher during dry season due to continuous inputs from various contamination sources. This study identified several contamination sources for these streams; two waste disposal sites along these streams for Fe, Mn, AI, Zn and $Cl^{-}$, the Chonju Waste Water Treatment Plant for Zn, Mn, $Cl^{-}$, $SO_{4}S$, $NO_{2}N$, and $NH_{3}-N$ and the untreated sewages for AI, Zn, Mn, $Cl^{-}$, $SO_{4}S$, $NH_{3}-N$ and $PO_{4}^{2-}$. This study also revealed that the Chonju stream itself is an important contamination source for Fe, Mn, $Cl^{-}$ and $SO_{4}S$ in the Mankyung River.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.2
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• pp.93-107
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• 2008

Recently, there have been many projects regarding restoration of streams to recover their environmental and ecological functions. For the restoration of streams, it is valuable academically and economically to evaluate the ecological condition of streams and build a plan and an object for restoring streams based on that. On the other hand, one of the methods to figure out the ecological condition of streams is to evaluate the hydromorphological structure of stream. In this study we have developed a field survey system using the stream assessment methode of LAWA (Laenderarbeitsgemeinschaft Wasser in Germany) that can assess the hydromorphological structure of small and medium streams. In addition, we constructed a GIS-based stream assesment system which can support auto mapping system and report writing, using the survey results. These systems are aimed to help people in the area of restoring streams perceive the natural and ecological condition of streams in the process of making plans and managing the projects, and they also try to help in collecting raw data to determine an ideal potential model to which an existing stream should be turned.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.260-265
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• 2007

This study was carried out to complement water quality standards and to establish new concept for water quality standards reflecting current state of water quality in small streams. By this purpose, discriminant analysis was performed and Water Quality Level Model (WQLM) was developed using the data such as EC, BOD, $COD_{Mn}$, SS, T-N, T-P, $NH_3-N$ in 224 agricultural streams. To give water quality level for water quality parameters, it divided into 20% respectively in the order of excellent water quality. On the basis of the lowest water quality level, water quality level of small streams is granted. As a result of it, number of stream corresponding to Level I was no, Level II was 2 streams, Level III was 22 streams, Level IV was 70 streams, and Level V was 130 streams. Average of water quality in each level was the highest in Level V. EC, SS, and T-N of 7 parameters were selected in variance concerned water quality level. By standardized canonical discriminant function coefficient, EC of three variances was the highest in 0.625 at the discriminant power. The next was T-N (0.509), SS (0.414). By discriminant function for water quality level, Level II was equal to $-2.973+19.376{\times}(EC)+0.647{\times}(T-N)+0.009{\times}(SS)$, Level III was equal to $-3.288+19.190{\times}(EC)+0.733{\times}(T-N)+0.041{\times}(SS)$, Level IV was equal to $-4.462+27.097{\times}(EC)+0.792{\times}(T-N)+0.053{\times}(SS)$, and Level V was equal to $-9.117+40.040{\times}(EC)+1.305{\times}(T-N)+0.111{\times}(SS)$. As a result of test at real agricultural watershed of Jeongan and Euidang in Gongju city, the fitness of WQLM was high to 88.78%. But, to get accomplished water quality assessment more exactly in agricultural streams, we had to concentrate and get vast data, and WQLM was modified and complemented continually.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4307-4325
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• 2016

With the aim of solving the problems of long processing times, high memory consumption and low event throughput in the current processing approaches in out-of-order RFID event streams, an efficient complex event processing method based on INFA-HTS (Improved Nondeterministic Finite Automaton-Hash Table Structure) is presented in this paper. The contribution of this paper lies in the fact that we use INFA and HTS to successfully realize the detection of complex events for out-of-order RFID event streams. Specifically, in our scheme, to detect the disorder of out-of-order event streams, we expand the traditional NFA model into a new INFA model to capture the related RFID primitive events from the out-of-order event stream. To high-efficiently manage the large intermediate capturing results, we use the HTS to store and process them. As a result, these problems in the existing methods can be effectively solved by our scheme. The simulation results of our experiments show that our proposed method in this paper outperforms some of the current general processing approaches used to process out-of-order RFID event streams.

• Korean Journal of Environmental Biology
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• v.21 no.3
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• pp.223-233
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• 2003

This paper introduces a study on the development of environment assessment technique and biodiversity management system for stream ecosystems and their application to Korean streams. Based on comprehensive field investigations from a series of streams of Bukhangang (North Han River) system as well as on long-term field survey and bibliographic data from streams throughout South Korea, schemes for environmental and biodiversity research of stream ecosystems aye reviewed; types of major environmental damages in Korean streams are classified; a rapid assessment technique for nature quality of stream ecosystems is presented; and a list of environmental and biotic factors for the use of GIS-based biodiversity management system in stream ecosystems is provided. The biodiveysity management system, which is based on ArcView and GEUS programs, is applied to Gapyeong Creek, a typical mid-size stream in Korea.

• Journal of Computing Science and Engineering
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• v.3 no.1
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• pp.27-58
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• 2009

Aggregation join queries are an important class of queries over data streams. These queries involve both join and aggregation operations, with window-based joins followed by an aggregation on the join output. All existing research address join query optimization and aggregation query optimization as separate problems. We observe that, by putting them within the same scope of query optimization, more efficient query execution plans are possible through more versatile query transformations. The enabling idea is to perform aggregation before join so that the join execution time may be reduced. There has been some research done on such query transformations in relational databases, but none has been done in data streams. Doing it in data streams brings new challenges due to the incremental and continuous arrival of tuples. These challenges are addressed in this paper. Specifically, we first present a query processing model geared to facilitate query transformations and propose a query transformation rule specialized to work with streams. The rule is simple and yet covers all possible cases of transformation. Then we present a generic query processing algorithm that works with all alternative query execution plans possible with the transformation, and develop the cost formulas of the query execution plans. Based on the processing algorithm, we validate the rule theoretically by proving the equivalence of query execution plans. Finally, through extensive experiments, we validate the cost formulas and study the performances of alternative query execution plans.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.8
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• pp.34-40
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• 1992

This paper shows a new relational formula of multiplexing gain versus variable input bit rates useful for designing Nx1 ATM(Asynchronous Transfer Mode) multiplexer which mixes several asynchronous bit streams with different transmission rates. The relation between multiplexing gain and input bit stream speeds is derived from the occupied mean lenght(the width per unit time) of cells and the occupation probability of the number of cells at an arbitrary instant when the rates of the periodic cell strams change randomly. And the relation between multiplexing gain and variable bit rates from different number of input bit streams is analyzed accordingly. Under the condition of unlimited multiplexing speed, the more number of input bit streams increases, the bigger the multiplexing gain becomes. While for the case which restricts the multiplexing speed to a limited value, the multiplexing gain becomes smaller contrarily as the number of input bit streams continues too invrease beyond a boundary value. It is shown that for designing an ATM multiplexer according to the latter case, the combination of input bit streams should be determined such as its total bit rate is lower thean, but most apprpaximate to, the multiplexed output speed. Also the general formula evaluating the most significant parameters which should be needed to design the multiplexer is derived.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10C
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• pp.975-982
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• 2009

In this paper, we propose a novel mixing algorithm for multiple video streams, which can guarantee low complexity and low end-to-end delay. In the propose algorithm, we change the syntax bitstream in the compressed domain. And we mix the H.264/AVC video streams by coded slice unit. The syntax bitstream for a mixing changes according to the arrangement of videos streams in which it organizes the mixing screen layout. Experimental results show more than 4 video streams could be mixed at high speed. Moreover, it could display in the player which it supports the standard H.264/AVC without the picture quality loss.