• Journal of Korean Society of Environmental Engineers
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• v.31 no.8
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• pp.635-640
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• 2009

After 1960s, in accordance with getting bigger in changing range of annual rain precipitation, those dams were built in order to prevent any drought and flood through the regulation of flux. In case of such dam, when it reaches to some definite pondage, for its regulation of water volume, numerous volume of water in the reservoir should be discharged by opening the floodgate, at this time a severe damage can be occurred to those lives and properties of the residents and tourists at the river or riverside. Accordingly, despite the sounding alarm broadcasting for prevention and notice such damage could be clearly travelled to those people without influence by the discharging noise or other neighboring environmental factor, since it was only empirically installed without any peculiar research until now, the alarm broadcasting could not effectively travel, and the travelling distance also could not known correctly. On such point of view, this Study has ever grasped the characteristics by frequencies and its sound pressure level about the discharge noise and the alarm broadcasting of Daechung Dam, one of multipurpose dams through the measurement and analysis by distances, and based on this, also has ever presupposed the proper location of additional alarm broadcasting spot using a simulation program named Cadna-A.

• Journal of Broadcast Engineering
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• v.3 no.1
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• pp.69-84
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• 1998

In digital broadcasting, services such as digital satellite TV, cable TV and digital terrestrial TV, several video programs are compressed by MPEG-2, and then simultaneously transmitted over a conventional CBR (Constant Bit Rate) broadcasting channel. In this paper, we propose a joint quality control scheme to be able to accurately control the relative picture quality among the video programs, which is achieved by simdt;,nL'Ously controlling the video encoders to generate the VBR (Variable Bit Rate) compressed video streams. Our quality control scheme can prevent the video buffer overflow and underflow by total target bit allocation process, and also exactly control the relative picture quality in terms of PSNR (Peak Signal to Noise Ratio) between some programs requiring higher picture quality and others by rate-distortion modification. Furthermore we present a rate-distortion estimation method for MPEG-2 video, which is base of our joint quality control, and verify its performance by experiments. The most attractive features of this estimation method are as follows: 1) computational complexity is low because main operation for the estimation is to calculate the histogram of OCT coefficients into quantizer; 2) estimation results are very accurate enough to be applied to the practical MPEG-2 video coding applications. Simulation results show that the proposed joint quality control scheme accurately controls the relative picture quality among the video progran1s transmitted over a single channel as well as provides more consistent and higher picture quality than independent coding scheme that encodes each program independently.

• The Journal of Industrial Distribution & Business
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• v.9 no.10
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• pp.73-82
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• 2018

Purpose - Unstable vegetable prices have been one of the major concerns in Korean agricultural and food marketing system. The Korean government has implemented a number of policy instruments, including government purchasing programs in order to alleviate fluctuations in vegetable prices. The economic impact of policy instruments has been assessed based on the average monthly price change rate before and after the implementation of the policy. However, this approach failed to provide a net impact of policy measures on price stabilization in the vegetable markets, as policy impacts could not be successfully distinguished from other effects on price changes in the vegetable market. The purpose of this study is to evaluate the net impact of the government purchasing program on the price volatility of dried red pepper which is considered one of the major vegetables in Korea. Research design, data, and methodology - This study develops a monthly dynamic partial equilibrium model of Korean dried red pepper market. Behavioral equations in the model were estimated by OLS and synthetic method based on the annual and monthly time series data from 1993 to 2015. The model is first simulated to yield actual dried red pepper market conditions in 2015 as a baseline and then compared it to the scenario assuming that there were no government purchases of dried red pepper in 2015. Results - According to the ex-post scenario analysis using the developed model, without the government procurements in 2015, the average monthly price change rate and the value of coefficient of variation of dried red pepper in 2015 would be respectably 7.9 percent and 0.10. It is relatively higher than the actual average monthly price change rate and the value of coefficient of variation of dried red pepper in 2015 which were respectively 1.7 percent and 0.06. Conclusions - The ex-post simulation results in this study shows that if there were no government purchases of dried red pepper in 2015, the dried red pepper market would have had much higher volatile price movements. The results of this study would provide useful information for future price stabilization policy of vegetable markets in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.15-20
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• 2018

The objective of this study is to numerically investigate the thermal characteristics of an automobile exhaust-based heat exchanger for automotive thermoelectric power generation with various exhaust gas mass flow rates and temperatures. The heat exchanger for automotive thermoelectric power generation has a square-type pin installed inside, so the maximum amount of heat can be transferred to the thermoelectric element from the heat energy coming from the automobile exhaust gas. The exhaust gas mass flow rate changed from 0.01, to 0.02, to 0.03 kg/s, and the exhaust gas temperature changed from 400, to 450, to 500, to 550, to $600^{\circ}C$, respectively. A numerical simulation was conducted by using the commercial program ANSYS CFX v17.0. Consequently, the exhaust gas pressure difference between the inlet and the outlet of the heat exchanger is determined according to the flow rate of the exhaust gas. When the mass flow rate of the exhaust gas increased, the pressure difference between the inlet and the outlet of the heat exchanger increased, but the exhaust gas pressure difference between the inlet of the heat exchanger and the outlet did not vary with the exhaust gas temperature. Therefore, in order to obtain the maximum surface temperature from the heat exchanger, the exhaust gas mass flow rate should be lower, and the exhaust gas temperature should be higher.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7287-7291
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• 2014

A CDTA (current differencing transconductance amplifier) is an active building block for current mode analog signal processing with the advantages of high linearity and a wide frequency bandwidth. In addition, it can generate a stable voltage because all the differencing input current flows to the grounded devices. In this paper, a new small signal equivalent circuit is proposed to analyze a CDTA. The proposed small signal equivalent circuit provides greater precision in analyzing the magnitude and frequency response than its previous counterparts because it considers the parasitic components of the input, internal and output terminal. In addition, observations of the changes made in various devices, such as the resistor (Rz) confirmed that those devices heavily influence the characteristics of CDTA. The designed parameters of the proposed small signal equivalent circuit of the CDTA provides convenience and accuracy in the further design of analog integrated circuits. For verification purposes, a 2.5 MHz low pass filter was designed on the HSPICE simulation program using the proposed small signal equivalent circuit of CDTA.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.15 no.4
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• pp.369-380
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• 2017

In order to manage the uncertainty about the evaluation and analysis of the human intrusion scenario of the Gyeongju Low and Intermediate Level Radioactive Waste(LILW) disposal facility, the calculation result by the GENII code was assessed using the RESRAD code, which was developed to evaluate the radiation effects of contaminated soil. The post-drilling scenario was selected as a human intrusion scenario into the near-surface disposal facility to analyze the uncertainty of the modeling by identifying any limitations in the simulation of each code and comparing the evaluation results under the same input data conditions. The results revealed a difference in the migration of some nuclides between the codes, but confirmed that the dose trends at the end of the post-closure control period were similar for all exposure pathways. Based on the results of the dose evaluation predicted by RESRAD, sensitivity analysis on the input factors was performed and major input factors were derived. The uncertainty of the modeling results and the input factors were analyzed and the reliability of the safety evaluation results was confirmed. The results of this study can be applied to the implementation 'Safety Case Program' for the Gyeongju LILW disposal facility.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.8
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• pp.860-865
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• 2006

The characteristics of flow field and turbulent mixing efficiency of SS in non-aerated contacting reactor are critical design parameters directly affecting on the efficiency of the overall process of wastewater treatment system. To this end, in this study numerical fluid dynamic calculation has been made to investigate the flow field and concentration distribution of SS in terms of specification(shape and dimension) of impeller and other operating conditions. As the first step, the performance of the computer program developed was successfully evaluated by the comparison of the typical flow field with the type of impeller with that appeared in open literature. Further, a series of parametric investigations are made in terms of interesting parameters such as the type and dimension of impeller, location, and number of impeller, etc. A number of useful conclusions obtained by numerical calculation are the superiority of mixing efficiency of pitched type than the flat one together with the visible increase of the overall mixing effect by the employment of the larger impeller and increase of the impeller number, etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.1
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• pp.52-57
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• 2009

In this study, a simulation program has been developed to predict the performance of energy recovery ventilators fur various indoor and outdoor conditions. In order to get a fundamental data about domestic air condition, the heat recovery ventilator is selected with the product of the wind quantity $250m^3/h$ Japanese M companies which are satisfied at High Efficiency Certification Standards. At the case on which the heat recovery ventilator is established, heating load decreases by 69.1% and cooling load decreases by 59.4% in Seoul, and heating load decreases by 66.4% and cooling load decreases by 59.6% in Pusan. The maximum humidification load of winter or summer time with $0.737{\ell}/h$ or $1.008{\ell}/h$ occurred in March from Kangnung or August from Mokpo respectively. In Southern part region and East Sea of winter time, the condensation or frost on exhaust side dose not occurred on exhaust side, but the area of that outside is occurred. Therefore, the preventive measure from the area except a southern part region and the east coast area must be considered, in order to condense or frost not to occur on exhaustion side in winter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.373-381
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• 2017

Kyeonggi Provincial Government is considering double decker bus service to solve the problem of heavy rush hour traffic. However, the height-to-width ratio is more than 1.16 times larger than that of a general high-speed single decker bus, and the center of gravity is higher. This could cause driving stability problems, such as turnover and breakaway from the lane, especially under strong side-wind conditions at high speed. In this numerical study, the driving characteristics of a model double decker bus were reviewed under side-wind and superelevation conditions at high driving speed. The rolling, pitching, and yawing moment of the model bus were calculated with CFD numerical simulation, and the results were compared to the recovery angular moments of the model bus to evaluate the dynamic stability under given driving conditions. As the model vehicle moves on a straight level road, it is stable under any side-wind conditions. However, on a curved road under side-wind conditions, it could reach unstable conditions dynamically. There is a chance that the bus will turn over when it moves on a curved road with a radius of gyration less than 100 m under side-wind (15 m/s). However, there is a very small chance of breakaway from the lane under any driving conditions.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.1
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• pp.10-20
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• 2010

In recent studies, $PM_{2.5}$ has been reported to be more harmful to human health than $PM_{10}$ because it penetrates more deeply into the lung. We estimated $PM_{2.5}$ related health benefits in Seoul from implementing the World Health Organization (WHO)'s guidelines (annual average $10{\mu}g/m^3$, 24-hour average $25{\mu}g/m^3$) and U.S. Environmental Protection Agency (EPA)'s National Ambient Air Quality Standard (annual average $15{\mu}g/m^3$, 24-hour average $35{\mu}g/m^3$). U.S. EPA's Environmental Benefits Mapping and Analysis Program was utilized for the analysis. It was predicted that the attainment of the WHO annual guideline and U.S. EPA's annual standard, relative to the concentration in 2006, would result in reduction of 2,333~2,895 premature deaths and 1,703~2,121 premature deaths, respectively. If the WHO and EPA's daily standard for $PM_{2.5}$ are attained, 1,211~1,394 and 1,012~1,165 premature deaths could be avoided, respectively. Sensitivity analyses indicated that the estimates were robust regardless of air quality simulation methods for attaining the $PM_{2.5}$ goals. This study provides a quantitative approach to evaluate health risks from air pollution as well as to assess the potential health benefits of improving atmospheric $PM_{2.5}$ concentration. Even considering the intrinsic limitations and uncertainties of the analysis, it is an important information to rationalize the enforcement of $PM_{2.5}$ management policies and measures in Seoul, Korea.