• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.142-149
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• 1997

This paper applied one of the well-known optimal control theory, namely, linear quadratic regulator(LQR), to the station-keeping maneuvers(SKM) for a geostationary satellite. The boundary conditions to transfer the system with a good accuracy at a terminal time were based upon the predicted orbital data which are created due to the Earth's non-uniform mass distribution's effect during 14 days and due to luni-solar effect during 28 days. Through the linearization of the nonlinear system equation with respect to reference orbit and the numerical integration of Riccati equation, the optimal trajectories and the corresponding control law have been obtained by using LQR. From the comparison of ${\Delta}V$ obtained by LQR with the ${\Delta}V$ obtained anatically by geometric method, Station Keeping Maneuvers(SKM) via LQR may provide comparable results to a real system. Furthermore it will demonstrate the possibility in fuel optimization and life extension of geostationary satellite.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.1
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• pp.107-116
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• 1984

In order to obtain an information for the improvement of wives' meal management especially in dual-income families, the survey was carried out through questionaires to 159 married women teachers(employed wives: EW) and 157 housewives(HW) in Daejeon city, from the Sep. 20 to 30, 1983. Most of the two groups' wives did not plan menu(74.7 %), and considered taste firstly when meal preparation and food buying. In EW, time was more considered than the other points for meal preparation and cookbook was more used than other sources of cooking methods, while in HW, cost, and, the mass media (p<0.01). Among 6 convenience foods, sausage, ham were used more frequently in EW and instant noo-dles and fried fish cake, in EW. Both the two groups' dietary pattern of three meals was similar, but much more of the EW(56.1 %) purchased foods for between meals rather than prepared at home in comparision with the HW. Almost all the HW prepared three meals themselves but the EW did not so. In the EW, husband and mother-in-law often assisted with meal-related activities, but in the HE, daughters (p<0.01) . HE spent more time on meal-related activities than do EW (Hw: 4.1 hrs/day, Ew·: 3.2 hrs/day) . The preparation time for supper was longest among three meals. As the problems of meal management, both the two groups' wives pointed 'too much time' (43.1 %), 'lack of nutrition knowledge '(42.8 %), but EW' husbands, 'no variety of cooking method'(42.8 %), while HW' husbands, 'lack of nutrition knowledge'(34.3 %).

• Journal of the Society of Cosmetic Scientists of Korea
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• v.29 no.2 s.43
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• pp.131-147
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• 2003

In the 21st century, the development of cosmetics is led to pursue the high functionality of cosmetics with excellent effectiveness and safety. As Cosmetic Act took effect in 2000, functional cosmetics is provided in the law. As a result, the research and development of functional cosmetics has continually increased, and the number of patent applications in functional cosmetics has also rapidly increased as a plan for preoccupying in the functional cosmetics age. Now, the cosmetic industry has a great interest in developing anti-wrinkle cosmetics among functional cosmetics, because women's desire for having young resilient skin has increased since Korea entered an aging society thanks to the advanced medical technology. The patent application trends of anti-wrinkle cosmetics at home since 2000 particularly show the rapid increase in the applications in natural plant extracts. It may be because Korean consumers preference of vegetable cosmetics has resulted in the development of raw materials based on the traditional medicine. As for the existing preparation such as Retinoid or Ascorbic acid, the patent application itself will be an essential technical element in the future because patent applications are filed in the field of a preparation of cosmetics for stabilizing ingredients, reducing skin irritability or promoting absorbance, and in the field of cosmetic formulation technology. As there are many studies on the causes of skin wrinkles, it is expected that new raw materials of cosmetics can be developed due to new mechanisms, and that the number of patent applications in new technologies will increase due to a change in the thought of cosmetics accompanied by the integration of cosmetics with biotechnology using Genetic Engineering, including the practical application of the medicine previously used far treating skin diseases to an anti-wrinkle agent and the mass production of active ingredients of cosmetics.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.625-630
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• 2018

The electrostatic interactions were investigated between the zirconia and the 11-Mercaptoundecylphosphoric-acid layer formed on gold surfaces for their complex structures. For the investigation, the atomic force microscope was used to measure the surface forces between the surfaces as a function of the salt concentration and pH value. The forces were analyzed with the Derjaguin-Landau-Verwey-Overbeek theory to estimate the potential and charge density of the surfaces for each condition. The concentration dependence of the surface properties, found from the measurement at pH 4 and 8, was consistent with the prediction from the law of mass action. The pH dependence was explained with the ionizable groups on the surface. It was found that the 11-Mercaptoundecylphosphoric-acid layer had higher values for the surface charge densities and potentials than the zirconia surfaces at pH 4 and 8, which may be attributed to the ionized-functional-groups of the layer.

• Child Health Nursing Research
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• v.2 no.2
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• pp.35-44
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• 1996

The purpose of this study was to examine the knowledge and attitude of breast feeding and to explore the predictive variables for the intention of breast feeding of mothers. One hundred and thirty-five mothers who delivered at the D University hospital during the period of May to June in 1996 comprised the sample. Data were collected by questionnaire methods before discharge at the hospital. Data were analyzed using percent, 1-test, and logistic regression. The results were as follows : 1. During their pregnancy, majority of mothers (74.8%) got the breast feeding information. Information sources were book (34.5%), family and relatives(32.4%), mass media(24.3%), and professionals such as nurses and doctors (8.8% ). The frequently reported sources of most encouragement for breast feeding were mother in law(20.7%) and baby's father (11.1% ). 2. The mean score of the items of Knowledge and Attitude toward Breast Feeding Scale were 42.56 (SD=5.47) and 39.07(SD=5.15) , representing positive attitude toward breast feeding. The correlation between knowledge and attitude score was significant(r 〓.54, p<.001). Knowledge of breast feeding were significantly different between breast feeding intention group (including partial breast feeding) and artificial feeding intention group(t=2.79, p<.01) 3. Logistic regression analysis revealed that feeding method in the hospital, delivery type, knowledge toward breast feeding, disease related to pregnancy, complication related to delivery, and educational level of mother were predictives of the intention of breast feeding. 4. The most frequently rated reasons for the plan for mixed feeding were concern about insufficient milk (37.9%) and work(27.6%), The major reasons for plan for artificial milk feeding were having premature baby(25.9%) and maternal health problems including infection(14.8% ) and drug use due to chronic illness (14.8%). From the result of the study, it is recommended to develop supportive nursing intervention strategy to promote breast-feeding intention and practice. The intervention could be more effective to begin early in pregnancy and include teaching for breast feeding skills as well as information provision for positive attitude formation.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.13 no.3
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• pp.43-60
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• 2005

In september 2004, a new pilot certificate scheme referred to as Sport Pilot Certificate was declared official and standardized in the US. The designation of Light-sport aircraft and the details of the relevant pilot certificate policy was announced out of the perception that a new regulation is required to be applied whereby the limitations on the manufacturing process enhancements and current aviation rules are considered the triggering factors. US Federal Aviation Regulation retains a comprehensive range of airworthiness certificates and aircrafts are managed systematically in accordance with FAR 21, 103. The airworthiness are further segregated into sub categories, which allows differentiated management. Korean Aviation Law classify aircraft into five different categories and powered air vehicle that weighs more than 150kg(19liters fuel capacity) for one seat, 225kg for two seats(38liters fuel capacity) while the systems that fall under a specific mass threshold level are known as ultralight vehicle. The research discusses the policy of the sport pilot certificate and the light-sport aircraft ratings announced official by the Federal Aviation Administration in an intuitive fashion with the analysis of the operations providing the evidence as to the viability of adopting the policy in local grounds. Based on the findings, the report discusses the case for introducing the light-sport aircraft and make recommendation on a strategy of applying the policy in Korea with respect to the pilot certificates, safety agenda, and the written test for the pilot certificate, and operating efficiency.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.405-413
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• 2006

In general mechanical servo systems, friction deteriorates the performance of controllers by its nonlinear characteristics. Especially, friction phenomenon causes steady-state tracking errors and limit cycles in position and velocity control systems, even though gains of controllers are tuned well in linear system model. Even if sensor is used higher accuracy level, it is difficult to improve tracking performance of the position to the same level with a general control method such as PID type. Therefore, many friction models were proposed and compensation methods have been researched actively. In this paper, we consider that the variation of mover's mass is various by loading and unloading. The normal force variation occurs by it an other parameters. Therefore, the proposed control system is composed of main position controller and a friction compensator. A parameter estimator for a nonlinear friction model is designed by adaptive control law and adaptive backstepping control method.

• Journal of Navigation and Port Research
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• v.31 no.1 s.117
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• pp.55-64
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• 2007

In general mechanical servo systems, friction deteriorates the performance of controllers by its nonlinear characteristics. Especially, friction phenomenon causes steady-state tracking errors and limit cycles in position and velocity control systems, even though gains of controllers are tuned well in linear system model. Even if sensor is used higher accuracy level, it is difficult to improve tracking performance of the position to the same level with a general control method such as PID type. Therefore, many friction models were proposed and compensation methods have been researched actively. In this paper, we consider that the variation of mover's mass is various by loading and unloading. The normal force variation occurs by it and other parameters. Therefore, the proposed control system is composed of main position controller and a friction compensator. A parameter estimator for a nonlinear friction model is designed by adaptive control law and adaptive backstepping control method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2189-2194
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• 2009

The automatic hot gas by-pass technique is applied to control the capacity of refrigeration and air-conditioning system when operating at part load. In the scheme, the hot gas from the compressor is extracted and injected into the outlet of an evaporator through a hot gas by-pass valve. Thus, In this paper, the hot gas by-pass scheme for CO2 is discussed and analyzed on the basis of mass and energy conservation law. A comparative study of the schemes is performed in terms of the coefficiency of performance (COP) and cooling capacity. The operating parameters considered in this study include compressor efficiency, superheating degree, outlet temperature of gas cooler and evaporating temperature in the R744 vapor compression cycle. The main results were summarized as follows : the superheating degree, outlet temperature and evaporating temperature of R744 vapor compression refrigeration system have an effect on the cooling capacity and COP of this system. With a thorough grasp of these effect, it is necessary to design the compression refrigeration cycle using R744.

• Journal of the Korea Society of Computer and Information
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• v.18 no.12
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• pp.207-215
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• 2013

The general opinion about the notion of cyberbullying hasn't existed yet, but in related laws it is defined as the entire behavior causing the counterpart to suffer the pain by continuously and repeatedly psychologic offending toward specific students with information and telecommunication products such as the Internet and mobile phones, and spreading the private information or false facts related with specific students. Recently a number of accidents related with abuse of cyberbullying are being broadcast on a variety of mass media, and the argument about the severity and countermeasures against cyberbullying is moving onward. This study has a purpose as suggesting the practical alternatives to prevent cyberbullying victim of middle school students by arguing cyberbullying of middle school students and analyzing the relationship between the general features such as victimized experience and frequency and the emotional behaviors according to victimized experience. As the result of this study, cyberbullying victimized experience has a significant effect on the emotional behavior such as depression, aggression, and academic stress. As political implication, this study suggests the practical alternatives to prevent cyberbullying of middle school students based on the analysis result.