• Water for future
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• v.24 no.2
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• pp.109-119
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• 1991

The river-bed variation and the sediment transport in an alluvial stream are very complicated physical phenomena, especially in a stream where the dam construction prevents the supply of earth and sand from upper tributaries Therefore, the mathematical modeling is needed to establish. The purpose of this study is to apply river-bed variation to the Han River downstream by the conception of gradually varied unsteady flow instead of that of steady flow in order to decrease errors. For the variation and forecast of river-bed, the numerical analysis has been made in this study by way of discharge variation and river-bed variation. In conclusion, the numerical analysis shows that river-bed variation, sediment transport , and their forecast have similarity to natural phenomena and that river-bed variation is greatly affected in sediment transport by discharge variation and retention time(duration). Therefore, the errors of numerical analysis can be reduced by the application of flood data instead of continuous discharge data.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.4
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• pp.247-252
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• 2013

Korea gas corporation (KOGAS) is responsible for the whole sale of natural gas in the domestic market. It is important to forecast the daily demand of city gas for supply and demand control, and delivery management. Since there is the autoregressive characteristic in the daily gas demand, we introduce a modified autoregressive model as the first step. The daily gas demand also has a close connection with the outdoor temperature. Accordingly, our second proposed model is a temperature-based model. Those two models, however, do not meet the requirement for forecasting performances. To produce acceptable forecasting performances, we develop a weighted average model which compounds the autoregressive model and the temperature model. To examine our proposed methods, the forecasting results are provided. We confirm that our method can forecast the daily city gas demand accurately with reasonable performances.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.5
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• pp.345-354
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• 2021

With the evolution of containerization and globalization of supply chains, aspects of port functions have made the transition from the sea to the inland region that forms the dry port. To explore the relationship between dry ports and regional economic development, this study uses a gravity model and forecast model to analyze 1,040 observations in 104 cities (22 dry port cities) along the Yangtze River Economic Belt (YREB) from 2008 to 2017. The model includes economic variables, logistics variables, foreign relations variables, and human capital variables. It was found that the dry port is positively correlated with trade volume. Compared with a city without a dry port, the trade volume of a city with a dry port will increase 0.099 times. It can be concluded that a dry port is crucial for the economic development of the YREB. It was also found that per capita GDP as an economic variable, road area and rail number as logistics variables, and foreign relation variables are positively correlated with trade volume, while the human capital variable has no significant effect on trade volume. In addition, governmental policy implications are addressed from the aspects of dry port and industry cluster caused by foreign investment.

• Korean Journal of Agricultural Science
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• v.45 no.4
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• pp.859-870
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• 2018

Dried red peppers are a staple agricultural product used in Korean cuisine and as such, are an important aspect of agricultural producers' income. Correctly forecasting both their supply and demand situations and price is very important in terms of the producers' income and consumer price stability. The primary objective of this study was to compare the performance of time series forecasting models for dried red peppers in Korea. In this study, three models (an autoregressive model with exogenous variables [ARX], AR-exponential generalized autoregressive conditional heteroscedasticity [EGARCH], and ARX-EGARCH) are presented for forecasting the wholesale price of dried red peppers. As a result of the analysis, it was shown that the ARX model and ARX-EGARCH model, each of which adopt both the rolling window and the adding approach and use the agricultural cooperatives price as the exogenous variable, showed a better forecasting performance compared to the autoregressive model (AR)-EGARCH model. Based on the estimation methods and results, there was no significant difference in the accuracy of the estimation between the rolling window and adding approach. In the case of dried red peppers, there is limitation in building the price forecasting models with a market-structured approach. In this regard, estimating a forecasting model using only price data and identifying the forecast performance can be expected to complement the current pricing forecast model which relies on market shipments.

• Korean Journal of Construction Engineering and Management
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• v.3 no.3 s.11
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• pp.58-65
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• 2002

University graduates from construction-related departments are undergoing serious difficulties in getting a job as construction companies are reluctant to employ new personnel due to the depression in the construction industry which has been downscaled in both domestic and overseas markets. In the situation is like this, statistics show that the percentage of employment among the university graduates is less than $25\%$, the unemployment problem in the construction sector has started to demand urgent countermeasures. This report anticipated demand and supply for technical man power in the field of construction in between 2002-2008. For preparation of an effectiveness of supply and demand plan on over-supplied in construction technical man power, this suggested expansion of SOC investment, induced into IT field of unemployed construction manpower, enlargement of overseas construction manpower And this considered an elastic operation of curriculum related to construction, and arranged an excess supply and demand of construction technical manpower, which has been considered to education that will meet with demand of enterprise, etc. on both side of quantity and quality simultaneously.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.4
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• pp.398-404
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• 2010

Purpose: Concerns had been voiced about an oversupply of optometrists in Korea. So, this study aimed to forecast the supply and demand for opticians for policy implications. Methods: Baseline Projection model combined with demographic method was adopted as the supply forecasting method and so was a ratio method using the number of physician and population using weight of healthcare utilization. Results: Under the 'physician to optician ratio', there would be a surplus of 83~700 opticians in 2010 and an undersupply of 15 to surplus of 6,118 opticians in 2025. Under the 'population to optician ratio', there would be a surplus of 1,055 opticians in 2010 and surplus of 9,376 opticians in 2025. Conclusions: We concluded that there would be oversupply for opticians until 2025, although the shortage and surplus of opticians might depend on the ratio's criteria. Hence, policies would need to be developed that could solve the imbalance in requirements and supply for opticians.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.373-377
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• 2006

By prosperous condition of construction economy in the early 90s in korea, we needed a lot of the qualified professional engineers(PE) to manage the construction site. In order to meet the high demand of P.E., government has established the admitted engineer system(AES) which is given to admitted engineer who do not take the written exam but have equivalent working experience in 1995. However, since 2000, while professional engineer's shortage has been resolved, the opposite situation has occurred that is serious over-supply of construction engineers. Thus, government announced that will abolish the admitted engineer systems as recognized existent admitted engineers. However, Professional Engineers institution is insisting that must not recognize existent admitted engineer. From this point of view, it is critical to make the supply-demand forecast systems as a derivative approach of system dynamics also, that is useful in comparing the argument between government and Professional Engineers institution. This paper describes about qualified engineer's supply change by admitted engineer system abrogation and suggests the idea to regulate the supply and demand with the improvement of the regal system.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.5
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• pp.855-866
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• 2023

With the rapid advancement and sophistication of defense weapon systems, the government, military, and the defense industry have conducted various innovative attempts to improve the efficiency of post-logistics support(PLS). The Ministry of Defense has mandated RAM-C(Reliability, Availability, and Maintainability-Cost) analysis as a requirement according to revised Total Life Cycle System Management Code of Practice in May 2022. Especially, for the project budget forecast of new PBL(Performance Based Logistics) business contacts, RAM-C is recognized as an obligatory factor. However, relevant entities have not officially provided guidelines or manuals for RAM-C analysis, and each defense contractor conducts RAM-C analysis with different standards and methods to win PBL-related business contract. Hence, this study aims to contribute to the generalization of the analysis procedure by presenting a cost analysis case based on RAM-C for the supply of military depot maintenance PBL project. This study presents formulas and procedures to determine requirements of military depot maintenance PBL project for repair parts supply. Moreover, a sensitivity analysis was conducted to find the optimal cost/utilization ratio. During the process, a correlation was found between supply delay and total cost of ownership as well as between cost variability and utilization rate. The analysis results are expected to provide an important basis for the conceptualization of the cost analysis for the supply of military depot maintenance PBL project and are capable of proposing the optimal utilization rate in relation to cost.

• Journal of Service Research and Studies
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• v.6 no.4
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• pp.75-85
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• 2016

Coal can be divided into thermal coal and coking coal. The price of thermal coal is basically affected by demand and supply. However, many other factors with regard to economic condition such as exchange rate, economy growth rate also make an influence on the price. This study is targeted to develop a forecast model for thermal coal price by using System Dynamics Method. System dynamics provides results that better reflect the real world by employing an inter-dependent system of variables. This study found out that 8 factors have important influence on the thermal coal price. Most of the data of the variables were acquired from the Bloomberg Database. The period extends to 2 years and 4 months, from May of 2011 to August of 2013. The causal relations among the variables were acquired by regression analysis

• Journal of Korea Port Economic Association
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• v.33 no.1
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• pp.75-87
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• 2017

The purpose of this study is to utilize the system dynamics to carry out a medium and long-term forecasting analysis of the bunker price. In order to secure accurate bunker price forecast, a quantitative analysis was established based on the casual loop diagram between various variables that affects bunker price. Based on various configuration variables such as crude oil price which affects crude oil consumption & production, GDP and exchange rate which influences economic changes and freight rate which is decided by supply and demand in shipping and logistic market were used in accordance with System Dynamics to forecast bunker price and then objectivity was verified through MAPEs. Based on the result of this study, bunker price is expected to rise until 2029 compared to 2016 but it will not be near the surge sighted in 2012. This study holds value in two ways. First, it supports shipping companies to efficiently manage its fleet, offering comprehensive bunker price risk management by presenting structural relationship between various variables affecting bunker price. Second, rational result derived from bunker price forecast by utilizing dynamic casual loop between various variables.