• Journal of Korean Society of Transportation
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• v.23 no.7 s.85
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• pp.7-15
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• 2005

The objective of this study is to estimate highway trip demand functions in Korea. In order to estimate them, I propose various socio-economic variables that affect the highway trip demand functions. I use the unit root test for each variable and the cointegration test to and the relationships among variables. Finally, I use the vector error correction model, to get the highway trip demand functions. The implication which I derive from the estimation is that real GDP and highway tolls have positive and negative effects, respectively. on the highway trip demand.

• Journal of the Korean Home Economics Association
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• v.48 no.8
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• pp.13-26
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• 2010

This study tested the path model with regard to how certain variables (control attribution, demand-control-support of activity, and control strategy) affected the elderly workers' subjective well-being(swb). In the path model, the exogenous variables were internal and external control attribution. We used demand-control-support of activity, and primary and secondary control strategies as mediating variables. The endogenous variable was each elderly worker's swb. Study participants were 205 elders participating in an "education activity". We used descriptive statistical analysis, Pearson's correlation and hierarchical multiple regression to examine data collected from structured interviews with the participants. Path analysis revealed the followings: First, secondary control strategy was the strongest predictor of participants' swb but internal control attribution, demand of activity, and support of activity also positively affected participants' swb. Second, internal control attribution indirectly affected the participants' swb. Finally primary control strategy negatively affected on the participants' swb.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.639-645
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• 2007

In this study, an estimation of call demand for the internet telephony was carried out using the monthly time-series data from June 2001 to December 2004. In the estimation, the call traffic was assumed to be explained by tariff of the internet telephony service, tariff of fixed and wireless services, income, quality of service, and lagged traffic variable. The traffic is assumed to follow the partial adjustment mechanism. The estimation result shows that the call traffic demand is elastic to the tariff of the service while it is inelastic to the change of income. The qualisty of service is regarded as an important factor of demand. Also there appeared the call demand is adjusting to the change of explanatory variables with some lags.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.10 no.16
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• pp.143-147
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• 1987

Safety stocks constitute one of the major means of dealing with the uncertainties associated with variation in demand and lead time. Adeguate safety facilitate production activities and help to assure customers if good service on the other hand, carrying safety storks ties up working capital on goods that sit idle. The major problem of safety stocks management thus of consists of trying to achieve an optimal balance between the other carrying cost and the costs of stock shortage. Therefore, this study aims to find safety stock level of the fixed reorder quantity system and the fixed reorder cycle system of minimizing total cost when both demand and lead time are variable. (The distribution of demand and lead time is a mere assumption that follows the normal distribution) The results can be summarized as follows. i) Safety factor on the safety stock is determined by carrying cost and the costs of stock shortage: An optimal safety stick=the costs of stork shortage($C_s$) (the carrying cost($C_h$)+the costs of stock storage($C_s$). ii) The safety stock level of the fixed reorder quantity system is ($a{\;}_p\sqrt{L}{\sigma}$) under uncertainties. iii) The safety stock level of the fixed reorder cycle system is ($a{\;}_p\sqrt{R+L{\sigma}}$) under uncertain demand and constant lead time. ($a{\;}_p\sqrt{L{\sigma}_d{\;^2+{\mu}^2L{\sigma}^2}$) under demand and lead time uncertainties.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.4
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• pp.1-11
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• 2016

The purpose of this study is to analyze the effect of public transit accessibility on the Carsharing use demand. By utilizing the rental historical DB of Greencar which is operated in Suwon city and public transit GIS DB, the use demand models for Carsharing by rental offices are built and analyzed in accordance with public transit accessibility. The result indicates 73% of walking as a majority, 3% cycling, and 20% using buses and urban railways to access Carsharing rental offices. The goodness of fit of Carsharing use models reflecting accessibility to buses and railways is verified as 0.818 which proves that public transit accessibility is a significant variable. Therefore, it is verified that installing Carsharing rental offices where public transit transfer is convenient can possibly increase the use demand. Especially, while accessibility to buses is verified as a significant variable out of other public transit means, the accessibility to urban railways is verified as not significant. This suggests that a variety of complementary policies such as transfer discount policy and one-way transfer return policy are necessary in between urban railways and Carsharing in order to promote mutual use demand in accordance with the other public transit means. This study result is yet the basic research on Carsharing, however it is expected to contribute to improvement of transfer demand in between different public transit means.

• The Journal of Fisheries Business Administration
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• v.29 no.2
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• pp.97-110
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• 1998

This paper tries to estimate Korea's import demand function for fisheries using cointegration analysis. The estimation function consists of one dependent variable-import quantity of fisheries(FTIW) and two independent variables-relative price(RP) between importable and domestic products and real income(GDP). As it has been empirically found out that almost all of time series of macro-variables such as GDP, price index are nonstationary, existing studies which ignore this fact need to be reexamined. Conventional econometric method can not analyze nonstationary time series in level. To perform the analysis, time series should be differenciated until stationarity is guaranteed. Unfortunately, the difference method removes the long run element of data, and so leads to difficulties of interpretation. But according to new developed econometric theory, cointegration approach could solve these problems. Therefore this paper proceeds the estimation on the basis of cointegration analysis, because the quartly variables from 1988 to 1997 used in the model is found out to be nonstationary. The estimation results show that all of the variables are statistically significant. Therefore Korea's import demand for fisheries has been strongly affected by the variation of real income and the relative price.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.289-291
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• 2000

In a competitive electricity power market, the price of electricity changes instantly, that of conventional market is predetermined and hardly changes. In such a new environment, customers' behaviors change instantly according to the changing electricity prices. If we develop a electricity load model that well describes the behavior of electricity consumers, we can utilize that model in forecasting the amount of future load, solving the load flow problem and finding the weak point of the system. In this paper new electricity model that considers the price of electricity and power factor of the load is presented. While conventional load model, which is demand function of electricity, uses the price of real and reactive power as the independent variable of the demand function. this new load model uses price of real power and penalty factor according to the power factor for the calculation of amount of electricity demand.

• Journal of Korean Institute of Industrial Engineers
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• v.31 no.3
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• pp.228-239
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• 2005

In this paper, we propose a new conceptual HVRPCR(Heterogeneous Fleet Vehicle Routing Problem with Customer Restriction) model including additional restrictions that are consisted of loadage limit and possible visit number of demand post in HVRP. We propose HVRPCR algorithm using the heuristic in order to solve speedily because VRP is NP-Hard and need many solution time. The proposed model is simulated with changing demand post location, demand weight, loading and possible visit number limitation. Results of the computational experiment are provided along with some analysis like travel cost reduction rate.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.46-52
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• 2013

Economic properties of an integrated wind power plant (WPP) and the demand response (DR) programs in the sample electricity market are studied. Time of use (TOU) and direct load control (DLC) are two of the DR programs that are applied in the system. The influences of these methods and the incentive payments by market operator's (MOs) with variable elasticity are studied. It is observed that DR with TOU and DLC programs together yields better revenue and energy saving for MOs.

• Journal of Society of Preventive Korean Medicine
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• v.8 no.2
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• pp.1-12
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• 2004

This paper estimated the demand and supply of physicians for oriental medicine for the period of $2009{\sim}2019$. Two equation models were used in the estimation of manpower. In 2004, the total number of physicians of oriental medicine was amounted to 13,662 registered and 10,532 available in clinical practice, respectively. According to estimates in the study, overall excess supply of physician manpower in oriental medicine was expected in the period, such as $5,300{\sim}5,700$ persons in 2009 and $900{\sim}1,700$ persons in 2019. However, the excess supply would be mitigated after 2019 mainly due to an increase in demand for oriental medical services. Specially, opening medical service market to overseas could be an exogenous variable in physician supply. An alternative manpower policy for oriental medical doctors is needed in a way of controlling oversupply.