• Journal of the Korean Operations Research and Management Science Society
• /
• v.31 no.1
• /
• pp.105-115
• /
• 2006

In this paper, we investigate the problem of minimizing average inventory costs subject to a fill rate constraint in a two-stage serial inventory model with a normally distributed demand. Fill rate is the fraction of demand that is satisfied immediately from on-hand inventory. We first find the lower bounds of base-stock levels in each node by using the exact base-stock level that satisfies a fill rate in a single node model proposed by Sobel. And then, we extensively analyze the system and show that the cost function is convex. Using such convexity and some other useful properties, we can easily find optimal base-stock levels numerically.

• Environmental and Resource Economics Review
• /
• v.11 no.4
• /
• pp.633-657
• /
• 2002

This study presents a demand modelling for landfill gas, which is used as alternative energy source for district cooling business. By analyzing the cost minimizing behavior of producer facing with three alternative energy sources such as electricity, cooling heat water, and gas, a demand function for landfill gas is derived from the optimal operating time of gas fired production facility, and estimated using unpublished data, which are associated with Seoul city's development plan for Sang-am area. The estimation results repeals that Seoul City could supply the land-fill gas of 13.76 million cubic meters each year at the price of about 16 won per cubic meters. However, if the investment costs associated with installation of gas collecting facilities are treated as sunk costs, annual amount of gas supplied is expected to increase to 14.22 million cubic meters at a lower unit price of 14.76 won.

• Proceedings of the KOR-KST Conference
• /
• 2000.02a
• /
• pp.89-115
• /
• 2000

Traffic signal setting policies and traffic assignment procedures are mutually dependent. The combined signal control and traffic assignment problem deals with this interaction. With the total travel time minimization objective, gradient based local search methods are implemented. Deterministic user equilibrium is the selected user route choice rule, Webster's delay curve is the link performance function, and green time per cycle ratios are decision variables. Three implemented solution codes resulting in six variations include intersections operating under multiphase operation with overlapping traffic movements. For reference, the iterative approach is also coded and all codes are tested in four example networks at five demand levels. The results show the numerical gradient estimation procedure performs best although the simplified local searches show reducing the large network computational burden. Demand level as well as network size affects the relative performance of the local and iterative approaches. As demand level becomes higher, (1) in the small network, the local search tends to outperform the iterative search and (2) in the large network, vice versa.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.15 no.8
• /
• pp.2783-2804
• /
• 2021

In the network function virtualization environment, dynamic changes in network traffic will lead to the dynamic changes of service function chain resource demand, which entails timely dynamic adjustment of service function chain resource configuration. At present, most researches solve this problem through virtual network function migration and link rerouting, and there exist some problems such as long service interruption time, excessive network operation cost and high penalty. This paper proposes a dynamic adjustment method of service function chain resource configuration for the dynamic changes of network traffic. First, a dynamic adjustment request of service function chain is generated according to the prediction of network traffic. Second, a dynamic adjustment strategy of service function chain resource configuration is determined according to substrate network resources. Finally, the resource configuration of a service function chain is pre-adjusted according to the dynamic adjustment strategy. Virtual network functions combination and virtual machine reusing are fully considered in this process. The experimental results show that this method can reduce the influence of service function chain resource configuration dynamic adjustment on quality of service, reduce network operation cost and improve the revenue of service providers.

• Journal of the Korea Convergence Society
• /
• v.9 no.8
• /
• pp.319-330
• /
• 2018

The aim of this study was to identify the relationship of caregiving appraisal and family function among senile dementia patients' families using in-home services for the Long-Term Care Insurance(LTCI). The participants were 121 family caregivers of senile dementia patients using in-home services for the LTCI. The participants' mean age was $53.80{\pm}10.86years$, all middle-aged women(75.2%). When negative cognition's burden and neutral one's demand in their caregiving appraisal were low and positive cognition's satisfaction and mastery in their caregiving appraisal were high, emotional function in their family function was high. There is a need to develop nursing interventions for strengthening positive cognition's satisfaction and decreasing neutral one's demand in their caregiving appraisal to improve emotional function and communication of senile dementia patients' families.

• Environmental and Resource Economics Review
• /
• v.17 no.3
• /
• pp.1-29
• /
• 2008

The goal of this study is to analyze the effects of the second energy tax reform of the transportation sector in Korea. For this purpose, we estimated the elasticities of energy demand(for gasoline, diesel and LPG) by using the ARDL(Auto-Regressive Distributed Lag) Model during the period of 1997 and 2005. We have the empirical results that the demand for diesel would decrease as much as of 382 million barrel per year and the demand for LPG would increase as much as of 20 million barrel per year since 2007. The second energy tax reform would also result in the decrease of 27,346 ton of air pollutants and 0.96 million ton of carbon dioxide per year. This shows that the second energy tax reform would have achieved its own policy goals by reducing energy demand and improving the quality of environment.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.39 no.1
• /
• pp.25-30
• /
• 2016

It is critical to forecast the maximum daily and monthly demand for power with as little error as possible for our industry and national economy. In general, long-term forecasting of power demand has been studied from both the consumer's perspective and an econometrics model in the form of a generalized linear model with predictors. Time series techniques are used for short-term forecasting with no predictors as predictors must be predicted prior to forecasting response variables and containing estimation errors during this process is inevitable. In previous researches, seasonal exponential smoothing method, SARMA (Seasonal Auto Regressive Moving Average) with consideration to weekly pattern Neuron-Fuzzy model, SVR (Support Vector Regression) model with predictors explored through machine learning, and K-means clustering technique in the various approaches have been applied to short-term power supply forecasting. In this paper, SARMA and intervention model are fitted to forecast the maximum power load daily, weekly, and monthly by using the empirical data from 2011 through 2013. $ARMA(2,\;1,\;2)(1,\;1,\;1)_7$ and $ARMA(0,\;1,\;1)(1,\;1,\;0)_{12}$ are fitted respectively to the daily and monthly power demand, but the weekly power demand is not fitted by AREA because of unit root series. In our fitted intervention model, the factors of long holidays, summer and winter are significant in the form of indicator function. The SARMA with MAPE (Mean Absolute Percentage Error) of 2.45% and intervention model with MAPE of 2.44% are more efficient than the present seasonal exponential smoothing with MAPE of about 4%. Although the dynamic repression model with the predictors of humidity, temperature, and seasonal dummies was applied to foretaste the daily power demand, it lead to a high MAPE of 3.5% even though it has estimation error of predictors.

• 제어로봇시스템학회:학술대회논문집
• /
• 1993.10b
• /
• pp.224-229
• /
• 1993

The robot has spread remarkably, is used not only in manufacturing but also in various other fields, and is becoming more popular in everyday life. At the same time, the functional demands for all manner of robots have been diversified. Education regarding robots has been developing in the computer, mechanism, sensor and artificial intelligence fields. Technical education which integrates all of the above is necessary and in great demand. We have developed an educational robot so that it can be used in education in fields including structure, sensory and brain function and can also organically integrate those.

• 제어로봇시스템학회:학술대회논문집
• /
• 1993.10a
• /
• pp.456-459
• /
• 1993

CADET is used to analyze the performance of the missile. Miss distance is calculated for a given lateral fin force saturation level due to the aerodynamic characteristics, target acceleration, and glint and fading noises which is assumed as Gaussian noises. As .alpha.-.betha. filter is studied to attenuate the noises, the results are compared with those of without filter. For the easy simulation, the transfer function of a discrete .alpha.-.betha. filter is converted into the continuous model. Simulation results show that the results of CADET simulation is similar to those of Monte-Carlo simulation. Moreover CADET is the better in computing time demand.

• Journal of the Korean housing association
• /
• v.6 no.2
• /
• pp.205-212
• /
• 1995

The objective of this study were to determine new air conditioning's selling possibility and discriminate it's market in Pusan and Daegu. The data were collected by using questionnaire. On the basis of the findings. These are follwing conclusions : Come to think of using rates of air conditioning. Function of air conditioning in house is not satisfied nowadays. Residents prefer it's function of cooling plus heating to only cooling in order to use a air conditioning in winter and the turning point of the season. And the air conditioning should be furnished economy, environment, convenience, amenity, safety.