• Journal of Biosystems Engineering
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• v.21 no.3
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• pp.283-292
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• 1996

Automatic guidance of farm tractors would improve productivity by reducing operator fatigue and increasing machine performance. To control tractors within $\pm$5cm of the desired path, fuzzy and adaptive steering controllers were developed to evaluate their characteristics and performance. Two input variables were position and yaw errors, and a steering command was fed to tractor model as controller output. Trapezoidal membership functions were used in the fuzzy controller, and a minimum-variance adaptive controller was implemented into the 2-DOF discrete-time input-output model. For unit-step and composite paths, a dynamic tractor simulator was used to test the controllers developed. The results showed that both controllers could control the tractor within $\pm$5cm error from the defined path and the position error of tractor by fuzzy controller was the bigger of the two. Through simulations, the output of self-tuning adaptive controller was relatively smooth, but the fuzzy controller was very sensitive by the change of gain and the shape of membership functions. Contrarily, modeling procedure of the fuzzy controller was simple, but the adaptive controller had very complex procedure of design and showed that control performance was affected greatly by the order of its model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.963-968
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• 2009

This paper deals with shrink fit analysis of rotor by 2D cross-section, 2D axis-symmetry, and 3D FEM model. And this paper presents 2nd order approximation function of thermal expansion displacement by design variables (shape dimension, heating temperature, sleeve length, interference etc.), table of orthogonal array and RSM(response surface methodology). The possibility of the rotor with shrink fit is evaluated by thermal expansion displacement. If thermal expansion displacement is larger than interference, shrink fit enable to make the rotor. 2D axis-symmetry model and 3D model are more reasonable than 2D cross-section model, because stress and strain is different along length of shaft.

• International Journal of Reliability and Applications
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• v.15 no.2
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• pp.125-150
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• 2014

Accelerated life tests (ALTs) are extensively used to determine the reliability of a product in a short period of time. Test units are subject to elevated stresses which yield quick failures. ALT can be carried out using constant-stress, step-stress, progressive-stress, cyclic-stress or random-stress loading and their various combinations. An ALT with linearly increasing stress is ramp-stress test. Much of the previous work on planning ALTs has focused on constant-stress, step-stress, ramp-stress schemes and their various combinations where the stress is generally increased. This paper presents an optimal design of ramp soak-stress ALT model which is based on the principle of Thermal cycling. Thermal cycling involves applying high and low temperatures repeatedly over time. The optimal plan consists in finding out relevant experimental variables, namely, stress rates and stress rate change points, by minimizing variance of reliability function with pre-specified mission time under normal operating conditions. The Burr type XII life distribution and time-censored data have been used for the purpose. Burr type XII life distribution has been found appropriate for accelerated life testing experiments. The method developed has been explained using a numerical example and sensitivity analysis carried out.

• Korean Journal of Human Ecology
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• v.18 no.5
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• pp.1115-1122
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• 2009

The purpose of this research was to measure the effects of a health management program through a school homepage on Obese Female College Students. The subjects were confined to 70 Obese Female College students from S University, located in C area. They voluntarily participated in this study. The subjects were divided into two groups by the BMI (Body Mass Index) classification: overweight or obesity program group(PG, n=35), and overweight or obesity comparative group(CG, n=35). The results obtained are summarized as follows: First, compared with the CG, there was a significant decrease for waist circumference in PG, and a significant decrease for the variables such as fat mass, weight, %fat, and BMI in PG. Second, in the investigation of blood lipids change of PG, there was a significant decrease for TC, TG and HR-rest. On the other hand, there was a significant increase for HDL-C.

• The Journal of Information Systems
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• v.25 no.3
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• pp.1-30
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• 2016

Purpose The purpose of this study is to grasp the factors influencing domestic SNS users' privacy protection behavior and verify their relationship through self-efficacy and responsiveness. Thus, this study tries to suggest efficient and effective measures for SNS personal information protection. Design/methodology/approach To this end, with main variables of the protection motivation theory based on the assumption that when users are exposed to the threat to their health, they would have protection motivation and change their behavior of protecting their health, a research model was suggested. In addition, in order to empirically verify the research model, a survey was performed targeting general college students having the experience of using SNS. Findings As a result of the analysis, first, perceived effectiveness and self-efficacy had a positive effect on responsiveness. Second, perceived barrier had a positive effect on self-efficacy. Third, self-efficacy and responsiveness had a positive effect on privacy protection behavior. This study is expected to contribute to establishing an effective guideline for measures that could induce SNS users' privacy protection behavior.

• The Journal of Information Systems
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• v.29 no.3
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• pp.77-101
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• 2020

Purpose Internet only bank is one of the promising untact businesses which are rising in COVID-19 pandemic. Kakaobank and Kbank have been offering banking services since 2017 in Korea and WeBank and MYbank in China opened the services since 2015. It is necessary to examining determinants of customer loyalty beyond intention to use. The purpose of the present study is to analyze factors influencing customer loyalty and their determinants. A research model integrating the relationships among customer loyalty, service satisfaction, trust, and social influence, and their determinants was proposed. Design/methodology/approach Structural equation modelling for validating the research model was employed. 235 valid data were collected from users of Internet only bank in China. Nine latent variables grouped from 38 indicators were reliable and valid and nine hypotheses were tested by using SmartPLS. Findings All nine hypotheses were supported at significant levels of 0.001 and 0.01. Trust, service satisfaction, and social influence had influenced on customer loyalty. Trust not only affected customer loyalty directly, but also had influence on it indirectly through service satisfaction. Empathy and convenience are determinants of trust. Perceived expertise and dispositions believing acquaints had a positive influence on social influence, whereas users' anxiety for technology or change had a negative influence on social influence. Implications for academics and practitioners were suggested.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.209-216
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• 2020

In this paper, parametric structural analysis is presented utilizing the co-rotational(CR) shell analysis utilizing EDISON. CR shell analysis shows faster convergence than the commercial software, NASTRAN, does. The 1st natural frequency of the rear frame is obtained, which is close to that of the engine during high speed cruise. Three cases under two design variables are presented and analyzed. Gusset is shown to be more effective among those which feature the same weight change. The results presented in this paper will be applicable for further researches to improve the durability of a motorcycle rear frame.

• Research in Community and Public Health Nursing
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• v.21 no.3
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• pp.273-281
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• 2010

Purpose: This study was to explore the effects of breast cancer education for college students on their mother's breast cancer screening promotion. Methods: This study used a one-group pretest and posttest design. Data were collected from September to November, 2007 from a sample of 80 college students and their mothers using a survey questionnaire, which asked about demographic variables, concerns over health and breast cancer, communication, stage of change and attitude (pros and cons) related to breast cancer, and confidence in breast self-examination. The college students received education about breast cancer for 50 minutes and then they educated their mothers about breast cancer. Data were analyzed with descriptive statistics and paired t-test. Results: The mean age of the college students was 22.0 years, and that of their mothers 49.4 years with a range from 43 to 58 years. After receiving education on breast cancer, there were significant changes in the mean scores of concerns about health and breast cancer, communication, pros in mammography, and confidence in practicing breast self-examination. Conclusion: This study indicates that education on breast cancer to mothers through their college-age daughters is effective and can be utilized to promote breast cancer screening for women.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.6
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• pp.77-82
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• 2008

This paper presents a Reliability-Based Topology Optimization(RBTO) using the Evolutionary Structural Optimization(ESO). An actual design involves some uncertain conditions such as material property, operational load and dimensional variation. The Deterministic Topology Optimization(DTO) is obtained without considering the uncertainties related to the uncertainty parameters. However, the RBTO can consider the uncertainty variables because it has the probabilistic constraints. In order to determine whether the probabilistic constraints are satisfied or not, simulation techniques and approximation methods are developed. In this paper, the reliability index approach(RIA) is adopted to evaluate the probabilistic constraints. In order to apply the ESO method to the RBTO, sensitivity number is defined as the change in the reliability index due to the removal of the ith element. Numerical examples are presented to compare the DTO with the RBTO.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.123-126
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• 1995

Characteristics of control system design using Universal Learning Network (U.L.N.) are that a system to be controlled and a controller are both constructed by U.L.N. and that the controller is best tuned through learning. U.L.N has the same generalization ability as N.N.. So the controller constructed by U.L.N. is able to control the system in a favorable way under the condition different from the condition of the control system in learning stage. But stability can not be realized sufficiently. In this paper, we propose a robust control method using U.L.N. and second order derivatives of U.L.N.. The proposed method can realize better performance and robustness than the commonly used Neural Network. Robust control considered here is defined as follows. Even though initial values of node outputs change from those in learning, the control system is able to reduce its influence to other node outputs and can control the system in a preferable way as in the case of no variation. In order to realize such robust control, a new term concerning the variation is added to a usual criterion function. And parameter variables are adjusted so as to minimize the above mentioned criterion function using the second order derivatives of criterion function with respect to the parameters. Finally it is shown that the controller constricted by the proposed method works in an effective way through a simulation study of a nonlinear crane system.