• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.89-98
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• 1987

Analyzed by using finite element method was 2-dimensional pollutant transtport phenomenon considering longitudinal and lateral direction in river. The Galerkin's finite element method based on linear interpolation is used and triangle is adopted as an element. In a number of model test attempts it has been demonstrated that the results calculated by the model are in good agreement with analytical solutions in a simplified channel where there is a known solution available. Actual application of the model is attempted along the 9km reach of the Han River considering the influx of the Tan Cheon and the Joongryang Cheon. The resultant 2-dimensional BOD concentrations profile in the reach is exhibiting more realistically the field situations than conventional 1-dimensional models are.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.389-394
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• 1997

The distribution of impurity included in benzene layer crystal was explored in layer crystallization of cyclohexane and benzene mixtures. The influence of crystal growth rate on crystal purity was investigated. All experimental results for bezene-cyclohexane system obtained in layer crystallizer have been evaluated with the criterion of Wintermantel. The purity of crystal decreases with increasing degree of subcooling, decreasing feed concentration and increasing crystal growth rate. The crystal growth rate was a key parameter to determine the inclusion of impurity in crystals. The results obtained from runs performed at increasing crystallization time(i.e. crystal thickness) have clearly shown that migration of inclusions within crystal layer to the melt, leading to the removal of impurity occurs. The diffusion of impurity which takes place during the crystallization from the beginning, enhances a further purification of the crystal layer if that underwent a thermal gradient after growth of the layer crystal stops.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.905-910
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• 2014

The steel grating discussed in this study is a drain cover that enhances the rigidity of the steel frame using an inclined inflow tract for wastewater, facilitates smooth drainage, and prevents the escape of bad smell from the drain. Recently, the urban problem of bad smell in sewerage lines has been hindering the improvement of living standards. Moreover, the frequent failure of existing products deters bad smell prevention measures and results in administrative power and budget wastage. The pressure to reduce budgets propels the increased demand for functional steel grating. Thus, this study focused on optimizing the design parameters of a steel grating by simultaneously considering its rigidity and drainage efficiency.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.548-554
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• 1985

This research is to find a means of reducing diesel engine combustion noise with none or minimum sacrifice of engine performance by investigating the influence of Cylinder Pressure Level(CPL). For this purpose, modified Wiebe's combustion function, considering the heat release curve as a combustion of both premixed and diffusive combustion portion, was exclusively used to obtain the indicator diagram and computer coeds were developed for the numerical analysis. Following are the results of this research. (1) CPL increases almostly with lag of ignition timing increasing .alpha. and decreasing. theta.$_{d}$, but at the crank angle with the maximal efficiency, CPL is independent of .alpha. and .theta.$_{d}$ with constant value of 200 dB especially at the low frequency. (2) For the constant ignition timing, the effects of .alpha. and .theta.$_{d}$ on CPL were the most significant at the frequency of about 1KHz and 300Hz respectively. (3) For the constant value of .alpha. and .theta.$_{d}$, CPL increases linearly with load but thermal efficiency increase very rapidly with maximum value of load Q$_{T}$=30-40 MJ/Kmol, then starts to decrease slowly. (4) The most effective way of reducing combustion noise without sacrificing thermal efficiency, is to decrease .alpha.. In the case of constant .alpha., there always exists a optimum value of .theta.$_{d}$ with respect to the various compression ratio.o..atio.o..

• Atmosphere
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• v.25 no.4
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• pp.685-692
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• 2015

In this study, the effects of trees on flow and scalar dispersion in an urban street canyon were investigated using a computational fluid dynamics (CFD) model. For this, we implemented the drag terms of trees to the CFD model, and compared the CFD-simulated results to the wind-tunnel results. For comparison, we considered the same building configuration as the wind-tunnel experiment. The trees were located at the center of street canyon with the aspect ratio (defined as the ratio of the street width to the building height) of 1. First, the flow characteristics were analyzed in the tree-free and high-density tree cases and the results showed that the CFD model reproduced well the flow pattern of the wind-tunnel experiment and reflected the drag effect of trees in the street canyon. Then, the dispersion characteristics of scalar pollutants were investigated for the tree-free, low-density tree and medium-density tree cases. In the tree-free case, the nondimensionalized concentration distribution simulated by the CFD model was quite similar to that in the wind-tunnel experiment in magnitude and pattern. The correlation coefficients between the measured and simulated concentrations are more than 0.9 in all the cases. As the tree density increased, nondimensionalized concentration increased (decreased) near the wall of the upwind (downwind) building, which resulted from the decrease in wind speed case by the drag effect of trees. However, the CFD model underestimated (overestimated) the concentration near the wall of upwind (downwind) building.

• Journal of Digital Convergence
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• v.15 no.3
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• pp.65-75
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• 2017

Agricultural sector in Korea faces the threat of aging farmers and many other difficulties. Because agriculture is a very less-competitive industry in Korea and many solutions to improve the competitiveness of Korean agriculture should be studied. The advent of Internet of things(IoT) technology makes possible many new industries and business models in the current society. The adoption of this new technology in agriculture can bring about innovations in agricultural production and distribution as $6^{th}$ industry. This paper summarizes the opportunities in IoT and smart farm. The major benefits and obstacles in introducing smart farms are reviewed and the cases of two successful smart farms in Korea are analyzed. Through these case studies, we can recognize the current status and future strategies in Korean smart farms.

• Fire Science and Engineering
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• v.30 no.3
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• pp.48-54
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• 2016

Pilotis are support columns that lift a building above the ground. Thus, they can elevate the lowest floor to the secondfloor level and, in Korea, are used to leav a parking area below multifamily housing. However, if there is a fire in the piloti area, the cars and main entrance door are wrapped in flames. Due to the inflammability of the materials, the combustion of the cars and insulation at the ceiling of the pilotis, having a high heat release rate, can quickly destroy the front entrance of the building and spread heat, flames and a poisonous gas to the stairs and elevator pit. Therefore, the fire can quickly spread to the whole building, putting the lives of the residents in danger. This study was an in-depth accidental case study of the "Uijeongbu Fire Accident" that killed 5 residents and injured 139 others. The study identified the relationships between the fire at the piloti structure of multifamily housing and the vulnerability of this structure and its inherent weaknesses.

• Journal of Korea Water Resources Association
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• v.31 no.1
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• pp.85-93
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• 1998

This study is to analyze and predict the contaminant transport based on the hydrauli characteristics using 2-dimensional finite element model. The dynamic wate quality model. RMA-4. is used to predict the contaminant transport using the hydrulic characteristics obtained from RMA-2v model. The study region is from downstream of Cham-sil weir to upstream of Shin-Kok weir. From the results of contaminant transport analysis. it is shown that the variations of discharge and velocity give quite large effect to the transport and dispersion of contaminant material. and that the water qualities of Joong-Rang and Tan streams play an important role to the downstream also. when the incidental contaminant accident occurs and contaminant material moves to the downstream. it is resulted the decreasing of the maximum COD and the increasing of the duration time to be affected by contaminant. Finally. 2-dimensional analysis is required in the case of large river like Han River. since the large difference of contaminant concentration has been investigated in the left and right bank.

• Analytical Science and Technology
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• v.10 no.6
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• pp.418-426
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• 1997

Dewatered digested sewage sludge were heated with microwave and their drying characteristics were investigated on the effect of their surface area, shape, diameter and thickness. The drying characteristics of identical samples in a conventional drying oven were studied. In conventional drying, constant rate period was not found and moisture was evaporated with capillary action. Moisture in the sludge was a bound water and free water was not exist. In microwave drying, the falling rate period was divided into two zones. In falling rate drying period, moisture movement occured by diffusion. The evaporation surface area was a significant variable, the greater heating surface area promoted water removal rate over wide region of water content. Drying rate was slow and constant rate drying period was found in wide moisture content region with increasing diameter. Drying characteristics appeared differently in various shape. In microwave heating, first of all temperature of sludge center was increased and was the highest. Temperature in the constant rate drying period was remained constantly at $80{\sim}100^{\circ}C$.

• Korean Journal of Construction Engineering and Management
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• v.13 no.1
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• pp.87-94
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• 2012

The apartment reconstruction projects have the proper functions such as residential environment improvement and the new housing allocation system; however, intention of the projects are distorted by the combination of factors, like failure of relocation of the original occupants and income redistribution, speculation in real estate, sharp rise in housing price, disputation between various interested parties, inadequate system and etc and it makes the projects unable to go well. Disputations and litigations are due to spread of the small conflict. As a result of the problems, it could not going smoothly and that lead to increase or stop the period and cost. This study is to estimate the period and cost using the conflict index so as to prevent and solve the problem which is among the conflict in the reverse functions. The conflict index has estimated focus on the conflict impact and the period and cost has been estimated using an variable independent including the conflict index. Also, estimated the conflict index and estimate of the period and cost are able to succeed with a minimum of disputation and money.