• International Journal of Aeronautical and Space Sciences
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• v.14 no.3
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• pp.256-263
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• 2013

The saturation of the actuator impairs the response performance of the near space interceptor control system. A control system based on the properties of linear tracking system is designed for this problem. The properties are that the maximum value of the pseudo-Lyapunov function of the linear tracking control system do not present at the initial state but at the steady state, based on which the bounded stability problem is converted into linear tracking problem. The pseudo-Lyapunov function of the linear tracking system contain the input variables; the amplitude and frequency of the input variables affect the stability of the nonlinear control system. Designate expected closed-loop poles area for different input commands and obtain a controller which is function of input variables. The coupling between variables and linear matrices make the control system design problem non-convex. The non-convex problem is converted into a convex LMI according to the Shur complement lemma and iterative algorithm. Finally the simulation shows that the designed optimal control system is quick and accurate; the rationality of the presented design techniques is validated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.4
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• pp.354-362
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• 2000

Optimal supervisory control strategy for the set points of controlled variables in the central cooling system has been studied by computer simulation. A quadratic linear regression equation for predicting the total cooling system power in terms of the controlled and uncontrolled variables was developed using simulated data collected under different values of controlled and uncontrolled variables. The optimal set temperatures such as supply air temperature, chilled water temperature, and condenser water temperature, are determined such that energy consumption is minimized as uncontrolled variables, load, ambient wet bulb temperature, and sensible heat ratio, are changed. The chilled water loop pump and cooling tower fan speeds are controlled by the PID controller such that the supply air and condenser water set temperatures reach the set points designated by the optimal supervisory controller. The influences of the controlled variables on the total system and component power consumption was determined. It is possible to minimize total energy consumption by selecting the optimal set temperatures through the trade-off among the component powers. The total system power is minimized at lower supply, higher chilled water, and lower condenser water set temperature conditions.

• Human Ecology Research
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• v.53 no.6
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• pp.641-654
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• 2015

This study identifies and tracks changes gender differences in adolescent users' problematic online behavior. This study used Korea Youth Panel Survey (KYPS), which has tracked respondents over 7 years, with self-control theory and social learning theory applied as a theoretical framework. The model included individual-level variables such as self-control and respondent's experience of problematic behavior (offline), as well as socialization variables such as the number close friends who engaged in problematic offline behavior, parent-child relationships, and parental monitoring. Dependent variables included problematic online behavior, unauthorized ID use (ID theft) and cyberbullying (cursing/insulting someone in a chat room or on a bulletin board). Control variables consisted of academic performance, time spent on a computer, monthly household income, and father's educational attainment. Random and fixed effects models were performed by gender. Results supported self-control theory even for the within-level analysis (fixed effects models) regardless of gender, while social learning theory was partially supported. Only peer effects were found significant (except for unauthorized ID use) among girls. Year dummy variables showed significant negative associations; however, academic performance and time spent using computers were significant in some models. Father's educational attainment and monthly household income were found insignificant, even in the random effects models. We also discuss implications and suggestions for future research and policy makers.

• Journal of muscle and joint health
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• v.16 no.2
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• pp.116-124
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• 2009

Purpose: The purpose of this study was to examine the effects of a Tai Chi exercise program on physical function and physiological variables in patients with degenerative arthritis. Methods: The study utilized a nonequivalent control group with pretest-posttest design. Data collection was done with the elders from two welfare institutions in C-city between July I and September 22, 2007. The participants were assigned either to an experimental group (n=24) or to a control group (n=22). The experimental group participated in Tai Chi exercise for 60 minutes per session, twice a week for 12 weeks and the control group received the education about arthritis for 3 weeks. Results: Except for $VO_2max$, weight, and body fat rate, the elders in the experimental group showed significant improvement in physical function (grip strength, flexibility, balance), and physiological variables (BP) compared to the control group. Conclusion: The results suggest that Tai Chi exercise would partially improve physical function, and physiological variables. Further studies are needed to determine the effects on physical fitness and physiological variables after Tai Chi exercise in this population.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.5
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• pp.375-380
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• 2021

Internal control is important for monitoring operations of organizations. In order to achieve the quality of internal control, organizations need to recognize different perspectives in which the components of internal control play a decisive role. Internal control is a process designed by the manager and it is applied within the organization to provide reasonable assurance of the reliability of financial information and to comply with policies, procedures, rules, regulations and laws. The article uses the ordinary least squares method and the seven-point Likert scale to test the variables affecting the quality of internal control in 18 Vietnamese listed banks. The article surveyed 179 leaders of listed banks. The results show that there are three variables out of a total of five variables that positively affect the quality of internal control, including the control environment, control activities, and monitoring. Accordingly, the managers of Vietnamese listed banks need to pay attention to building a corporate culture environment, improve the quality of control activities, and periodically and regularly conduct the monitoring. It contributes to improving the quality of internal control and is also an opportunity to increase economic benefits for Vietnamese listed banks in the context of international economic integration.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.537-541
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• 2003

In order to control the missiles by aerodynamics, control surfaces sometime called fins are used. Deflection angles of these fins are the right control variables of the aerodynamics, but aerodynamicists prefer to use analytic variables called aileron, elevator and rudder instead of these physical variables, because these three analytic variables dominantly influence on the roll, pitch and yaw channels of the missile maneuver, respectively, and each can be assumed a linear combination of four fin deflection angles. On that basis, roll, pitch and yaw autopilots for controlling the attitudes or lateral acceleration of the missile are designed, and as a consequence outputs of each autopilot are aileron, elevator and rudder commands, respectively. In the existing fin control scheme for the typical tail-fin controlled cruciform missiles, firstly these outputs are distributed to four fin defection commands, and after that four fins are actuated by fin controllers so that their deflections follow the commands. This paper shows that performance of such control schemes can be degraded significantly when fin actuators have certain physical constraints such as slew rate, voltage or current limit, uncertainty of actuator dynamics, and so on, and propose a new control scheme which alleviates such problems. This scheme can be widely applied to various fin actuation systems. But in this paper, for convenience, tail-fin controlled cruciform missile is taken as an example, and it is shown that a proposed control scheme gives better performance than the existing one.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.23-23
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• 2000

In this paper, we proposed the problems of robust stability and 개bust H$_{\infty}$ control of discrete time-delay linear st.stems with Frobenius norm-bounded uncertainties. The existence condition and the design method of robust H$_{\infty}$ state feedback control]or are given. Through some changes of variables and Schur complement, the obtained sufficient condition can be rewritten as an LMI(linear matrix inequality) form in terms of all variables.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.8
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• pp.555-565
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• 2020

This study examines the determinant factors affecting young people in preparing entrepreneurship in Indonesia. This study involved several variables, including the need for achievement, risk perception, locus of control, entrepreneurial attitude to predict entrepreneurial intention, and preparation for entrepreneurship among young people. The approach utilized in this study was a quantitative research design using a survey model. The participants of this study were recruited from young people in East Java, Indonesia. Structural equation modeling with Partial Least Square (SEM-PLS) was implemented to test the hypotheses and the relationships between variables. The findings of this research showed that the attitudes toward entrepreneurship and entrepreneurial intention of young people in Indonesia are determined by several variables such as the need for achievement, risk perception, and locus of control. The correlation between variables showed one positive direction in which all independent variables can influence dependent variables. Additionally, the result of this study confirms a robust relationship between the attitude toward entrepreneurship and preparing for entrepreneurship among young people. Lastly, this study showed a positive correlation between entrepreneurial intention and preparation for entrepreneurship. This study suggests that government institutions and universities need to be concerned about entrepreneurial programs to promote young entrepreneurs.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.3
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• pp.166-171
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• 2005

With development of the database, there are too many data on process variables and the manufacturing process for the traditional statistical process control methods to identify the process variables related with assignable causes. Data mining is useful in this situation and provides variety of approaches for improving the process. In this paper, we applied control charts to monitor the process and if assignable causes are detected, then we applied the SVM technique and the sequence pattern analysis to find out the process variables suspected. These techniques made possible to predict the behavior of process variables. We illustrated our proposed methods with real manufacturing process data.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1104-1110
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• 2012

The inverted pendulum system is a common, interesting control problem that involves many basic elements of control theory. In the early, controls of stabilization for the inverted pendulum system were used classical methods like PD, PID controller. In recently, however, control methods based on modern and intelligent control theory are widely applied. The fuzzy logic controller which is often used in nonlinear control is a little too hard to design due to increasing fuzzy rules rapidly if the given system like inverted pendulum has many state variables. Also, in case the state variables are divided into two parts, two fuzzy controllers are needed in the control system. In this paper, the authors propose FCSC(Fuzzy Controller based on State variables Combination) that reorganized into two new signals depending on the physical meaning of the four state variables of the inverted pendulum system. The proposed method is applied to the inverted pendulum system and simulations are accomplished to illustrate the control performance.