• IE interfaces
• /
• v.14 no.2
• /
• pp.190-197
• /
• 2001

Growth curves including Logistic and Gompertz functions are widely used in forecasting the market demand. To estimated the parameters of those functions, we use the non-linear least square method. However, it is difficult to set up the starting points for each parameter. If a wrong starting point is selected, the result reveals the local optimum or does not converge to a certain value. The purpose of this paper is to resolve the problem of selecting a starting point. Especially, rescaling the market data using the national economic index make it possible to figure out the range of parameters and to utilize the grid search method. Applications to some real data are also included.

• Journal of Applied Reliability
• /
• v.18 no.2
• /
• pp.104-113
• /
• 2018

Purpose: This paper proposes the non-periodic preventive maintenance policy based on the level of cumulative hazard intensity. We aim to construct a cost-effectiveness on the proposed model with relaxing the constraint on reliability. Methods: We use the level of cumulative hazard intensity as a condition variable, instead of reliability. Such a level of cumulative hazard intensity can derive the reliability which decreases as the frequency of preventive maintenance action increases. We also model the imperfect preventive maintenance action using the proportional age setback model. Conclusion: We provide a numerical example to illustrate the proposed model. We also analyze how the parameters of our model affect the optimal preventive maintenance policy. The results show that as long as high reliability is guaranteed, the inefficient preventive maintenance action is performed reducing the system operation time. Moreover, the optimal value of the proposed model is sensitive to changes in preventive maintenance cost and replacement cost.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.12 no.1
• /
• pp.13-27
• /
• 1994

Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printablility of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular weight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.12 no.1
• /
• pp.145-157
• /
• 1994

Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printability of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular \veight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.11
• /
• pp.1608-1614
• /
• 2014

Power demand forecasting is an important factor of the peak management. This paper deals with the 15 minutes ahead load forecasting problem in a DC urban railway system. Since supplied power lines to trains are connected with parallel, the load characteristics are too complex and highly non-linear. The main idea of the proposed method for the 15 minutes ahead prediction is to use the daily load similarity accounting for the load nonlinearity. An Euclidean norm with weighted factors including loads of the neighbor substation is used for the similar load selection. The prediction value is determinated by the sum of the similar load and the correction value. The correction has applied the neural network model. The feasibility of the proposed method is exemplified through some simulations applied to the actual load data of Incheon subway system.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.11a
• /
• pp.301-305
• /
• 1996

$\mu$ theory can handle the parametric uncertainty and produces more non-conservative controller than H$_{\infty}$ control theory. However an existing solution of the theory, D-K iteration, creates a controller of huge order and cannot handle the real or mixed real-complex perturbation sets. In this paper, we use genetic algorithms to solve these problems of the D-K iteration method. The Youla parameterization is used to obtain all stabilizing controllers and the genetic algorithms determines the values of the state feedback gain, the observer gain, and Q parameter to minimize $\mu$, the structured singular value, of given system. From an example, we show that this method produces lower order controller which controls a real parameter-perturbed plant than D-K iteration method.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.17 no.11
• /
• pp.3145-3162
• /
• 2023

As an important technology of the internetwork, wireless sensor network technique plays an important role in indoor localization. Non-line-of-sight (NLOS) problem has a large effect on indoor location accuracy. A location algorithm based on improved particle filter and directional probabilistic data association (IPF-DPDA) for WSN is proposed to solve NLOS issue in this paper. Firstly, the improved particle filter is proposed to reduce error of measuring distance. Then the hypothesis test is used to detect whether measurements are in LOS situations or NLOS situations for N different groups. When there are measurements in the validation gate, the corresponding association probabilities are applied to weight retained position estimate to gain final location estimation. We have improved the traditional data association and added directional information on the original basis. If the validation gate has no measured value, we make use of the Kalman prediction value to renew. Finally, simulation and experimental results show that compared with existing methods, the IPF-DPDA performance better.

• Journal of Service Research and Studies
• /
• v.14 no.2
• /
• pp.101-116
• /
• 2024

As the spread of smartphones has become more common and the utilization rate has increased, the mobile shopping market is also growing and expectations for related industries are also increasing. Mobile shopping apps are converging with various industries such as fashion, beauty, and lifestyle, and competition among companies to increase the number of users is intensifying with the activation of non-face-to-face. Accordingly, in this study, a study on the perceived value and intention to use mobile shopping apps was conducted based on a VAM. In order to test the hypothesis of this study, a questionnaire was conducted on 266 people who had used a mobile shopping app and it was used for analysis. Looking at the results, it was confirmed that both usefulness and enjoyment among the perceived benefit of mobile shopping apps have a positive (+) effect on the perceived value. However, it was found that the technicality and perceived risk among the perceived sacrifices of mobile shopping apps did not significantly affect the perceived value. Finally, it was confirmed that the perceived value of the mobile shopping app had a positive (+) effect on the intention to use. Through this study, we would like to examine the factors that can affect perceived value and usage intention in the mobile shopping app industry, which is increasingly competitive among companies along with the rapid growth of mobile technology and market, and suggest practical implications for related companies and officials to establish efficient strategies to further increase mobile shopping app users.

• Journal of the Korean Society of School Health
• /
• v.18 no.2
• /
• pp.133-140
• /
• 2005

Purpose： This study estimated the prevalence of smoking among male and female school employees. This study also correlated key indicators of health with the number of cigarettes consumed per day by the male smokers. The indicators of health included health behavior, blood pressure (mmHg), BMI (kg/m2), diabetes, total cholesterol, GOT, GPT and GTP. Methods： Subjects included 2,640 male and 2,747 female employees working at elementary, middle, and high schools who received a physical check-up at the Seoul School Health Center in 2002. Data was obtained from the physical examinations, questionnaires, and laboratory results. Results： 39.7% of males and 0.4% of females were current smokers. 60% of the male smokers consumed between 10 and 19 cigarettes per day, and39.6% of male smokers had been smoking between 10 and 19 years. Smokers who consumed more than one pack per day had a relatively higher BMI than the non-smokers (24.7 24.1, respectively). However, smokers had lower blood pressure than non-smokers. The mean systolic and diastolic blood pressure of current-smokers were 128.2 and 82.8, respectively, while the values among non-smokers were 129 and 84.5, respectively. The proportion of current smokers with severe obesity (over BMI 30) was 5.0%. This was considerably higher than the 1.3% of severely obese non-smokers. Current-smokers also had mean and abnormal rate of fasting blood glucose, total cholesterol, GOT, GPT, and GTP that were higherthan those of non-smokers. The frequency of red meat consumption, alcohol use, perceived incidents of stress were alsomore frequent in current-smokers than in non-smokers. Exercise frequency was also lower among smokers. In multiple regression after adjusting all possible confounding factors including age, BMI, diet, and drink, the parameter value of fasting blood glucose, cholesterol, GOT, GPT, and GTP increased relative to the level of cigarette consumption. Conclusion： Among school employees, health behavior, and general health status including BMI, total cholesterol, GOT, GPT, GTP, and fasting blood glucose were worse in smokers than in non-smoker.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.607-610
• /
• 2005

If cement can be manufactured with industrial byproducts such as granulated blast furnace slag(GBFS), phosphogypsum(PG), and waste lime(WL) instead of clinker as its counterproposal, there would be many advantages, including maximum use of these industrial byproducts for high value-added resources, conservation of natural resources and energy by omitting the use of clinker, minimized environmental pollution problems caused by $CO_2$ discharge, and reduction of the production cost. This research investigates the chemical resistance of NSC mortar added PG and WL to GBFS as sulfate and alkali activators. The result of experiment of chemical resistance, showed that NSC is very excellent in acid resistance and seawater resistanc. Such a reasons are that the hydrate like CSH gel and ettringite formed dense pore structure of NSC matrix.