• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.5
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• pp.334-341
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• 2011

In the present study, optimal heat supply algorithm which minimize the heat loss through the distribution pipe line in group energy apartment was developed. Variation of heating load of group energy apartment building in accord with the outdoor air temperature was predicted by the heating load-outdoor temperature correlation. Supply water temperature and mass flow rate were controlled to minimize the heat loss through distribution pipe line. District heating apartment building located in Hwaseong city, which has 1,473 households, was selected as the object building for testing the present heat supply a1gorithm. Compared to the previous heat supply system, 10.4% heat loss reduction can be accomplished by employing the present method.

• Journal of computational fluids engineering
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• v.21 no.3
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• pp.64-70
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• 2016

Multiple solutions in natural convection of water with Pr=7 between two horizontal plates with small magnitude non-uniform temperature distribution in the upper plate is numerically investigated. The dimensionless temperature of upper plate is ${\theta}={\epsilon}sinkx$. Two upright cells are formed over one wave length in the conduction-dominated regime of small Rayleigh number. However, multicellular convection occurs above a critical Rayleigh number for small wave number. When k = 1.5, dual solutions are found and a transition of $6{\rightarrow}4$ eddy flow occurs with decrease of Rayleigh number. When k = 0.75, two, three, four and five multiple solutions are observed. Transitions of $14{\rightarrow}12$, $12{\rightarrow}10$, $10{\rightarrow}8$ and $6{\rightarrow}8$ eddy flow occur with decrease of Rayleigh number.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.6
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• pp.339-347
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• 2017

The objectives of this study were to analyze ecological characteristics of fish compositions and estimate the optimal ecological flow using the physical habitat simulation system (PHABSIM) in Wonju stream and Boseong river. We sampled fishes using two gears such as casting net and kicknet to determine fish distribution and also measured flow velocity, water depth, bed material at the point where fish collected. Total number of species and individuals sampled were 20 and 2,104, respectively and dominant species was Zacco platypus (39.7%) and subdominant species was Z. koreanus (RA: 15.8%) in Wonju stream. In Boseong river, collected fishes were 1,638 individuals, 28 species. Dominant and sub-dominant species was Z. platypus (RA: 22.0%) and Microphysogobio yaluensis (RA: 17.2%), respectively. For calculating habitat suitability index (HSI), we selected Z. platypus as representative fish species and analyzed water depth and flow velocity. Water depth and flow velocity were 0.2-0.6 m, 0.1-0.3 m/s, respectively in Wonju stream and 0.3-0.6 m, 0-0.3 m/s, respectively in Boseong river. According to the analysis of ecological flow simulation, optimal flow was 1.1 cms and 0.3 cms in Wonju stream and 0.4cms, 2.2cms in Boseong river at up and down stream respectively. WUA (Weighted Usable Area) was 9.5%, 26.6% in Wonju stream and 34.8%, 53.3% in Boseong river at up and down stream respectively.

• Journal of Energy Engineering
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• v.22 no.2
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• pp.226-236
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• 2013

The heat distribution and internal flow from the efficiency of actual reformer and specification variation, using the computer simulation and experiment about the steam methane reforming reaction which uses the high temperature reformer. Reaction model from steam refoemer uses the steam response model developed by Xu & Froment.As result we supposed the chemical react Steam Reforming(SR), Water Gas Shift(WGS), and Direct Steam Reforming(DSR) from the inner high temperature reformer dominates the response has dissimilar response. According to result of steam methane reforming reaction exam using high temperature reformer, we figured out when Steam Carbon Ratio(SCR) increase, number of hydrogen yield increases but methane decreases. When comparing and examining between design with one inlet and two inlet, result came out one inlet design is more outstanding at thermal distribution and internal flow, hydrogen yield in one inlet design than two inlet design.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.274-284
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• 2019

The control architectures of Chuan Suo (CS) deep submergence rescue vehicle are introduced. The hardware and software architectures are also discussed. The hardware part adopts a distributed control system composed of surface and underwater nodes. A computer is used as a surface control machine. Underwater equipment is based on a multi-board-embedded industrial computer with PC104 BUS, which contains IO, A/D, D/A, eight-channel serial, and power boards. The hardware and software parts complete data transmission through optical fibers. The software part involves an IPC of embedded Vxworks real-time operating system, upon which the operation of I/O, A/D, and D/A boards and serial ports is based on; this setup improves the real-time manipulation. The information flow is controlled by the software part, and the thrust distribution is introduced. A submergence vehicle heeling control method based on ballast water tank regulation is introduced to meet the special heeling requirements of the submergence rescue vehicle during docking. Finally, the feasibility and reliability of the entire system are verified by a pool test.

• Journal of Korea Water Resources Association
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• v.46 no.10
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• pp.1005-1016
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• 2013

The objective of this study was to evaluate spatio-temporal water shortage distribution in the Sapgyo catchment considering both permitted and non-permitted water rights obtained from the total water right survey conducted in 2010. The results showed that the agricultural water accounted for 98% of the total water uses with 83% being the non-permitted agricultural water uses. During the 11-year (2001~2011) simulation period, water shortage was shown only in the upper Gokgyo stream sub-catchment with the highest water stress from April to May in 2009, particularly because of the large demand for rice cultivation associated with low precipitation. As water shortage was not expected to happen when the permitted water rights were not considered, it was concluded that a proper management of non-permitted water rights would be urgent.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.63-70
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• 2011

In the present study, we developed optimal heat supply algorithm which minimizes the heat loss through the distribution pipe line in group energy apartment. Heating load variation of group energy apartment building in accordance with outdoor air temperature was predicted by the correlation obtained from calorimeter measurements of whole households of apartment building. Supply water temperature and mass flow rate were conjugately controlled to minimize the heat loss rate through distribution pipe line. Group heating apartment located in Hwaseong city, Korea, which has 1,473 households divided in 4 regions, was selected as the object apartment for verifying the present heat supply control algorithm. Compared to the original heat supply system, 10.4% heat loss rate reduction can be accomplished by employing the present control algorithm.

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.10-25
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• 2018

This study was conducted to estimate the habitat suitability of 17 benthic macroinvertebrate taxa in the Hwayang stream. Habitat Suitability Index (HSI) of benthic macroinvertebrates from the Hwayang stream was developed based on three physical habitat factors which include current velocity, water depth, and the substrate. The Weibull model was used as a probability density function to analyze the distribution of individual abundance by physical factors. The number of species and the total individual abundance increased along with the increase in current velocity. By means of Canonical Correspondence Analysis (CCA), the relative importance of each factor was determined in the following order: current velocity, water depth, and the mean diameter. The results depicted that, the most influential factor in the growth of benthic macroinvertebrates in the Hwavang system was current velocity. After comparing the analyzed results from the Hwayang stream with the resukts from the Gapyeong stream, the integrated HSI was drawn. The results indicated that current velocity and substrate had similar distributions of HSI in the two streams. This was due to the addition of unmeasured data from previous surveys, or the fact that benthic macroinvertebrates adapted to deeper waters in the Hwayang Stream. Most taxa showed a clear preference for a fast current velocity, deep water depth and coarse substrate except Baetiella, Epeorus, (mayflies), and Hydropsyche (caddisfly).

• Journal of Korea Water Resources Association
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• v.51 no.8
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• pp.703-711
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• 2018

Water distribution system (WDS) pipe bursts are caused from excessive pressure, pipe aging, and ground shift from temperature change and earthquake. Prompt detection of and response to the failure event help prevent large-scale service interruption and catastrophic sinkhole generation. To that end, this study proposes a improved Western Electric Company (WECO) method to improve the detection effectiveness and efficiency of the original WECO method. The original WECO method is an univariate Statistical Process Control (SPC) technique used for identifying any non-random patterns in system output data. The improved WECO method multiples a threshold modifier (w) to each threshold of WECO sub-rules in order to control the sensitivity of anomaly detection in a water distribution network of interest. The Austin network was used to demonstrated the proposed method in which normal random and abnormal pipe flow data were generated. The best w value was identified from a sensitivity analysis, and the impact of measurement frequency (dt = 5, 10, 15 min etc.) was also investigated. The proposed method was compared to the original WECO method with respect to detection probability, false alarm rate, and averaged detection time. Finally, this study provides a set of guidelines on the use of the WECO method for real-life WDS pipe burst detection.

• Journal of computational fluids engineering
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• v.14 no.1
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• pp.24-34
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• 2009

The equilibrium molecular-dynamic simulations have been performed to estimate the properties of the three kinds of fluids confined between two plates that are separated by 1.086 nm; included in the statical properties are the density distribution and the static structure, and the autocorrelation velocity function in the dynamic property. Three kinds of fluids considered in this study are the Lennard-Jones fluid, water and aqueous sodium-chloride solution. The water molecules are modeled by using the SPC/E model and the ions by the charged Lennard-Jones particle model. To treat the water molecules, we combined the quaternion coordinates with Euler angles. We also proposed a plausible algorithm to assign the initial position and direction of molecules. The influence of polarization of water molecules as well as the presence of ions in the solution on the properties will be addressed in this study. In addition, we performed the non-equilibrium molecular-dynamic simulation to compute the flow velocity for the case with the gravitational force acting on molecules.