• 한국환경복원기술학회지
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• 제14권3호
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• pp.57-69
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• 2011

This study examined the relationship between Phragmites australis' growth and sediment properties at mud tidal flat of Donggum-ri, Gilsang-myeon, Gangwha-gun, Incheon city. Field survey was carried out from May, 2010 to October, 2010. Water content, soil texture, electric conductivity and water table depth for sediment, density, height, dry weight and flowering for P. australis were examined at several plots from the starting point (the coastal embankment) to the end point of the two populations. The result was as follows. Firstly, the water table increased along distance from the embankment at one line (N-line) but was similar at the other line (S-line) in a P. asustralis population. Water tables were higher out of than within a P. australis population at two populations. Secondary, in N-line, the height and dry weight of P. australis decreased along the distance from embankment but, in S-line, those were similar in its population. P. australis' growth was dependent on electric conductivity at lower layer (water table level) rather than upper one (the surface). Thirdly, density of P. australis changed during growing season and was similar in a population, except for the end point of patch. In summary, the growth and distribution of P. australis were dependent on salt content of tidal flat's sediment (water table level) and this was affected by fresh water of the inland.

• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4499-4513
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• 2022

Spent fuel behavior of dry storage was simulated in a continuous state from steady-state operation by modifying FRAPCON-4.0 to incorporate spent fuel-specific fuel behavior models. Spent fuel behavior of a typical PWR was compared with that of NuScale Power Module (NPM^TM). Current PWR discharge burnup (60 MWd/kgU) gives a sufficient margin to the hoop stress limit of 90 MPa. Most hydrogen precipitation occurs in the first 50 years of dry storage, thereby no extra phenomenological safety factor is identified for extended dry storage up to 100 years. Regulation for spent fuel management can be significantly alleviated for LWR-based SMRs. Hydride embrittlement safety criterion is irrelevant to NuScale spent fuels; they have sufficiently lower plenum pressure and hydrogen contents compared to those of PWRs. Cladding creep out during dry storage reduces the subchannel area with burnup. The most deformed cladding outer diameter after 100 years of dry storage is found to be 9.64 mm for discharge burnup of 70 MWd/kgU. It may deteriorate heat transfer of dry storage by increasing flow resistance and decreasing the view factor of radiative heat transfer. Self-regulated by decreasing rod internal pressure with opening gap, cladding creep out closely reaches the saturated point after ~50 years of dry storage.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.189-194
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• 2001

A simultaneous visualization of the behavior of bubbles and dry spots has been carried out for pool boiling of R-1l3 on a horizontal heater. From video imaging and image processing analysis, the formation of bubbles and dry spots occurs simultaneously, and therefore they should be considered as a synchronized concept rather than independent identities. The dry spot density is equivalent to the active site density in the region before CHF. At CHF point, large dry areas due to the coalescence of neighboring dry areas cover the heater surface.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제45회 KOSCO SYMPOSIUM 초록집
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• pp.233-236
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• 2012

In order to estimate the efficiency of an evaporative heat exchanger having mini channel, the equations to calculate heat exchanger properties, those are air temperatures and water temperatures etc, are derived from the governing equations based on the Navier-Stokes equation, even though there are several assumptions to make problem simplify. There are three heat transfer zones at the mini channel heat exchanger depending on the water condition. So, there are three governing equations and solutions to calculate the properties. As a results of this study, the equations to calculate a saturation point and a dry point are derived to evaluate an evaporative heat exchanger having micro channel. It is supposed to predict the performance and evaluate a mini channel heat exchanger.

• 한국주거학회논문집
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• 제17권3호
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• pp.1-7
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• 2006

The aim of the research was to evaluate the characteristics of thermal environment and thermal comfort in the Dry Double floors Hydronic Ondol System. Physical indoor thermal environments (the floor surface temperature, the vertical temperature, etc.) and skin temperature have especially been measured. Physical features conditions, sensation, thermal comfort, humidity sensation, comfort of body were investigated for the survey. As a result, (1) During the operation of the boiler (12 hour), the average indoor temperature is appeared to be $21.6^{\circ}C$. The floor surface temperature showed peak value of $31.4{\sim}40.6^{\circ}C$ after 8hours 30minutes after the start-point of the heating. The vertical difference of temperature was turned out to be not uniform. (2) While the skin temperature showed a narrow distribution of temperature in the Dry Double floors Hydronic Ondol system. (3) The response to thermal comfort which people felt was satisfactory, and most of them felt dry during the test.

• 품질경영학회지
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• 제47권3호
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• pp.497-508
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• 2019

Purpose: The purpose of this study is to overcome limitations of conventional studies that to predict Baltic Dry Index (BDI). The study proposed applications of Artificial Neural Network (ANN) named Long Short-Term Memory (LSTM) to predict BDI. Methods: The BDI time-series prediction was carried out through eight variables related to the dry bulk market. The prediction was conducted in two steps. First, identifying the goodness of fitness for the BDI time-series of specific ANN models and determining the network structures to be used in the next step. While using ANN's generalization capability, the structures determined in the previous steps were used in the empirical prediction step, and the sliding-window method was applied to make a daily (one-day ahead) prediction. Results: At the empirical prediction step, it was possible to predict variable y(BDI time series) at point of time t by 8 variables (related to the dry bulk market) of x at point of time (t-1). LSTM, known to be good at learning over a long period of time, showed the best performance with higher predictive accuracy compared to Multi-Layer Perceptron (MLP) and Recurrent Neural Network (RNN). Conclusion: Applying this study to real business would require long-term predictions by applying more detailed forecasting techniques. I hope that the research can provide a point of reference in the dry bulk market, and furthermore in the decision-making and investment in the future of the shipping business as a whole.

• 무역학회지
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• 제47권5호
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• pp.21-37
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• 2022

Baltic Dry Index (BDI) is difficult to forecast because of the high volatility and complexity. To improve the BDI forecasting ability, this study apply Bayesian variable selection method with a large number of predictors. Our estimation results based on the BDI and all predictors from January 2000 to September 2021 indicate that the out-of-sample prediction ability of the ADL model with the variable selection is superior to that of the AR model in terms of point and density forecasting. We also find that critical predictors for the BDI change over forecasts horizon. The lagged BDI are being selected as an key predictor at all forecasts horizon, but commodity price, the clarksea index, and interest rates have additional information to predict BDI at mid-term horizon. This implies that time variations of predictors should be considered to predict the BDI.

• 한국습지학회지
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• 제10권2호
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• pp.105-114
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• 2008

급격한 도시화에 따른 불투수 면적과 인구의 증가로 인하여 많은 양의 오염물이 배출되고 있고, 이로 인하여 지역 하천의 수질이 심각한 위협을 받고 있다. 특히 강우시 지표면의 쌓인 다량의 오염물질은 오수관으로 유입된 후 월류되어 하천으로 유입되기 때문에 이에 대한 연구와 관리시스템의 마련이 시급하다. 이에 본 연구에서는 청주시를 대상으로 도시배수구역의 유출특성을 분석하고 이에 영향을 미치는 인자를 추출 및 분석할 수 있는 통계적 분석방법을 제시 것에 목적이 있다. 선행된 연구를 참고하여 강우강도, 선행건기일수, 강우량과 5개의 수질분석항목(CODcr, BOD, SS, TN, TP)과의 관계를 통계적인 방법으로 분석하였으며, 강우시 도시유출특성을 지배하는 인자에 대한 규명을 시도하였다.

• 한국대기환경학회지
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• 제17권1호
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• pp.51-56
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• 2001

This study was carried out to interpret mathematically hydraulic behaviour in packing tower which packed 50 mm plastic Hiflow-ring with a dimension of 300 mm wide and 1,400 mm high. In view of energy saving, the recent packing. 50 mm plastic Higlow-ring was superior to conventional packings because of low pressure drop in high loads. As relative error between numerically predicted and experimentally obtained values was less then 6% in the loading and flooding point, it found that therir results appeared to be adequate. Comparison of hose two values in both dry and wet packing conditions. relative errors amount to 3.96 and 5.6%, respectively. In order to evaluate the operating characteristics of packing, the type, size, and material for packings must be estimated in various system and loads. This study is able to calculated pressure drop, hold-up, gas and liquid loads using mathematical interpretation. For these calculation, the specific constants of each packings must be calculated first all. The method of mathematical interpretation in this study turned out to be superior to the existing methods because of reduced errors at loading and flooding point.

• Tribology and Lubricants
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• 제5권1호
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• pp.28-35
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• 1989

The wear tests of ceramic materials in dry rolling contact were carried out at room temperature to investigate their macroscopic wear characteristics. Both point contact and line cootact were adapted in the wear tests of them. Ceramic materials used in these tests were silicon nitride, silicon carbide, cermet of TiN and TiC, titania, and alumina. The wear test of the bearing steel was carried out to compare to the wear test results of the ceramic materials. The results showed that the wear rate of silicon nitride was smaller than any other ceramic materials and bearing steel. In the steady wear, the wear volume of ceramic materials increases linearly with the rolling distance. It was also found from the experimental results that fracture toughness and surface roughness dominate the wear process of ceramic materials in dry rolling contact.