• Journal of Biosystems Engineering
• /
• 제15권1호
• /
• pp.44-51
• /
• 1990

Four models in current use for cereal grain drying, equilibrium model, Morey model, partial differential equation model and simplified partial differential equation model, were modified to be suitable for natural air drying of barley. The predicted by the four models and experimental results were compared. Three models except equilibrium model predicted moisture comtent and grain temperature very well. But equilibrium model overpredicted moisture content and grain temperature of bottom layer. The degree of prediction of the four models for relative humidities of exhaust air didn't differ much from one another and equally the four models predicted relative humidity statisfatorily. Morey model took much shorter computing time than any other models. Therefore, considering the degree of prediction and computing time Morey model was the most suitable for natural air drying of barley.

• 수산경영론집
• /
• 제47권4호
• /
• pp.65-75
• /
• 2016

The purpose of this study was to analyze the production and marketing control effects of aqua-cultured flounder required for stable income growth of aqua-cultured household. We analyzed the supply and demand structure of cultured flounder using the partial equilibrium model approach. And we estimated the optimal yield of cultured flounder and analyzed the effect of marketing control through constructed model. The main results of this study are summarized as follows. First, the fitness and predictive power of the estimated model showed that the RMSPE and MAPE values were less than 5% and Theil's inequality coefficient was very close to 0 rather than 1. It was evaluated that the prediction ability of the aqua-cultured flounder supply and demand model by dynamic simulation was excellent. Second, dynamic simulation based on policy simulation was conducted to analyze the price increase effect of production and shipment control of cultured flounder. As a result, if the annual production volume is reduced by 1%, 5%, and 10% among 32,852~37,520 tons, it is analyzed that the price increase effect is from 1.2% to 12.5%. Finally, this study suggests that the production and marketing control can increase the price of aqua-cultured flounder in the market. In this paper, we propose a policy implementation of the total supply system instead of conclusions.

• 한국산림과학회지
• /
• 제97권4호
• /
• pp.458-466
• /
• 2008

본 연구는 장기 밤수급 예측과 국내외 시장여건 변화가 국내 밤시장에 미치는 영향을 분석하기 위하여 수행되었다. 이를 위해 본 연구에서는 생밤시장과 깐밤시장을 상호 수직적으로 연결하는 부분균형모델을 개발하였다. 개발된 모델의 내생변수에 대한 예측능력을 측정하기 위하여 1990년부터 2003년까지 사후예측을 실시하였다. 전반적으로 신규재배면적 및 폐기면적을 제외하고는 모든 내생변수들에 대한 모델의 예측오차가 낮았다. 수급예측 결과 국내 생밤생산량은 2005년에 76,447톤에서 2020년에는 76,286톤으로 약간 감소할 것으로 예측되었으며, 일본으로 수출되는 깐밤의 양은 지속적으로 감소할 것으로 예측되었다.

• 농업과학연구
• /
• 제50권4호
• /
• pp.629-643
• /
• 2023

The purpose of this study was to examine the effectiveness and efficiency of a policy by comparing and analyzing the impact of the rice market isolation system and production adjustment system (strategic crops direct payment system that induces the cultivation of other crops instead of rice) on rice supply, rice price, and government's financial expenditure. To achieve this purpose, a rice supply and demand forecasting and policy simulation model was developed in this study using a partial equilibrium model limited to a single item (rice), a dynamic equation model system, and a structural equation system that reflects the casual relationship between variables with economic theory. The rice policy analysis model used a recursive model and not a simultaneous equation model. The policy is distinct from that of previous studies, in which changes in government's policy affected the price of rice during harvest and the lean season before the next harvest, and price changes affected the supply and demand of rice according to the modeling, that is, a more specific policy effect analysis. The analysis showed that the market isolation system increased government's financial expenditure compared to the production adjustment system, suggesting low policy financial efficiency, low policy effectiveness on target, and increased harvest price. In particular, the market isolation system temporarily increased the price during harvest season but decreased the price during the lean season due to an increase in ending stock caused by increased production and government stock. Therefore, a decrease in price during the lean season may decrease annual farm-gate prices, and the reverse seasonal amplitude is expected to intensify.

• 한국철도학회논문집
• /
• 제5권1호
• /
• pp.10-17
• /
• 2002

In this study, we have developed the static and dynamic simulation program of a high speed current collection system. The catenary wire is modeled to discrete masses connected by massless strings and the pantograph is replaced with 3 d.o.f equivalent models that are composed of masses, springs and dampers. We derived partial differential equations of motion from the equivalent model and developed the simulation program. Then, we calculated the static equilibrium state of the overhead catenary and the dynamic behaviors of the high speed current collection system. The analysis results were compared with the results of GASENDO software developed at RTRI in Japan.

• 한국산학기술학회논문지
• /
• 제15권5호
• /
• pp.2689-2694
• /
• 2014

이 연구는 한 중 FTA 체결에 따른 오미자의 시장 파급영향을 계측 분석하여, 2014-2018년 동안의 중장기 수급의 변화를 검토한 내용을 담고 있다. 오미자에 대한 한 중 FTA 체결의 구체적인 내용을 알 수 없는 상황에서, 실현가능한 오미자 시장개방 상황을 시나리오로 구성하여 수급모형에 도입하고, 현재 중국산 오미자의 수입상황을 반영하여 분석하였다. 오미자에 대한 중장기 수급 및 가격 전망을 위해 오미자 개별 품목에 대한 별도의 부분균형모형을 구축하였고, 모형내 각 방정식들은 계량경제학 방법을 이용하여 추정하였다. 분석결과, 관세율이 현행 8%에서 2014년부터 2018년까지 단계적으로 철폐될 경우, 재배면적은 2018년 3,370ha으로 다소 감소하고, 소비량은 2018년 12,040.8톤으로 증가하는 것으로 전망되고, 생산액이 5년간(2014-2018)누적으로 약 98억원 수준 감소하는 것으로 추정되었다.

• 한국산학기술학회논문지
• /
• 제22권4호
• /
• pp.108-114
• /
• 2021

풋귤은 노지온주 감귤의 미숙과로 최근 카로티노이드, 펙틴, 비타민 C 등이 다량 함유되어 있어 건강증진에 도움이 된다는 것이 알려지면서 수요가 증대되고 있다. 제주지역에서 2월에서 녹색이다가 3-4월 노란색으로 착색되는 재래종 청귤품종과는 구분된다. 이 연구는 노지감귤 미숙과인 풋귤의 수요증대가 노지감귤 산업에 미치는 영향을 분석하였다. 분석을 위해 1989-2017년 노지감귤 수급자료를 이용하여 노지감귤 부분 수급모형을 구축하였다. 수급모형은 노지감귤 부분에 대한 수급균형모형으로 풋귤 수요확대에 따른 파급영향 계측을 위해 동태 축차적인 구조로 구성하였다. 구축된 수급모형에 대한 수급 예측력 검토를 시행하였고, 최종 모형을 이용하여 2018-2030년에 대한 풋귤 수요확대에 따른 파급영향을 시뮬레이션하였다. 시뮬레이션 분석결과, 풋귤 수요확대에 따라 노지감귤 재배면적이 초기에는 2022년까지 생산부문에 대한 영향에 큰 변화가 없으나 2023년 18ha, 2025년 52ha, 2030년 142ha의 재배면적이 증대되고, 2021-2030년 연평균 약 77.5억원의 조수입이 증대되는 효과가 있는 것으로 계측되었다.

• 대한기계학회논문집B
• /
• 제33권2호
• /
• pp.69-78
• /
• 2009

Cavitating flow simulation is of practical importance for many hydraulic engineering systems, such as pump, turbine, nozzle, injector, etc. In the present work, a solver for cavitating flow has been developed and applied to simulate the flows past axisymmetric cylinders. Governing equations are the two-phase Navier-Stokes equations, comprised of continuity equation of liquid and vapor phase. The momentum equation is in the mixture phase. The solver employed an implicit, dual time, preconditioned algorithm in curvilinear coordinates. Computations were carried out for three axisymmetric cylinders: hemispherical, ogive, and caliber-0 forebody shape. Then, the present calculations were compared with experiments and other numerical results to validate the present solver. Also, the code has shown its capability to accurately simulate the re-entrant jet phenomena and ventilated cavitation. Hence, it has been found that the present numerical code has successfully accounted for cavitating flows past axisymmetric cylinders.

• Computers and Concrete
• /
• 제27권4호
• /
• pp.385-393
• /
• 2021

Reinforcement corrosion is the main cause of the durability failure of reinforced concrete (RC) structure. In this paper, a three-dimensional (3D) numerical model of macro-cell corrosion is established to reveal the corrosion mechanisms of steel reinforcement in RC structure. Modified Direct Iteration Method (MDIM) is employed to solve the system of partial differential equations for reinforcement corrosion. Through the sensitivity analysis of electrochemical parameters, it is found that the average corrosion current density is more sensitive to the change of cathodic Tafel slope and anodic equilibrium potential, compared with the other electrochemical parameters. Furthermore, both the anode-to-cathode (A/C) ratio and the anodic length have significant influences on the average corrosion current density, especially when A/C ratio is less than 0.5 and anodic length is less than 35 mm. More importantly, it is demonstrated that the corrosion rate of semi-circumferential corrosion is much larger than that of circumferential corrosion for the same A/C ratio value. The simulation results can give a unique insight into understanding the detailed electrochemical corrosion processes of steel reinforcement in RC structure for application in service life prediction of RC structures in actual civil engineer.

• 산경연구논집
• /
• 제9권10호
• /
• pp.73-82
• /
• 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.