• Journal of Institute of Control, Robotics and Systems
• /
• v.5 no.2
• /
• pp.139-144
• /
• 1999

The present paper is concerned with the robust decentralized stabilization problem of large-scale systems with time delays in the interconnections using sliding mode control. Based on Lyapunov stability theorem and H$_{\infty}$ theory, an existence condition of the sliding mode and a robust decentralized sliding mode controller are newly derived for large-scale systems under mismatched uncertainties. Finally, a numerical example is given to verify the validity of the results developed in this paper.

• Journal of Korean Academy of Nursing
• /
• v.42 no.5
• /
• pp.730-737
• /
• 2012

Purpose: This study was done to identify the time interval to pressure ulcer and to determine the optimal time interval for position change depending on pressure ulcer risk in patients using foam mattress in intensive care units. Methods: The Braden scale score, occurrence of pressure ulcers and position change intervals were assessed with 56 patients admitted to an intensive care unit from April to November, 2011. The time to pressure ulcer occurrence by Braden scale risk group was analyzed with Kaplan-Meier survival analysis and log rank test. Then, the optimal time interval for position change was calculated with ROC curve. Results: The median time to pressure ulcer occurrence was 5 hours at mild or moderate risk, 3.5 hours at high risk and 3 hours at very high risk on the Braden scale. The optimal time interval for position change was 3 hours at mild and moderate risk, 2 hours at high and very high risk of Braden scale. Conclusion: When foam mattresses are used a slight extension of the time interval for position change can be considered for the patients with mild or moderate pressure ulcer risk but not for patients with high or very high pressure ulcer risk by Braden scale.

• Korean Journal of Child Studies
• /
• v.19 no.2
• /
• pp.35-47
• /
• 1998

Negative life events, self-esteem, perceived social support, and maladjustment were studied longitudinally among late elementary children. Subjects were 241 boys and girls for depression and 258 for antisocial behavior. The instruments were the Adolescent Perceived Events Scale, the Rosenberg Self-Esteem Scale, the Social Support Scale for Children, the Revised Korean Version of the Center for Epidemiologic Studies' Depression Scale, and the Antisocial Behavior Scale. The results showed that the way variables were reciprocally related to one another in patterns over a period of one year differed by internal and external adjustment. For depression, depression at Time 1 had effects on self-esteem, social support, and depression at Time 2. For antisocial behavior, negative life events at Time 1 influenced negative life events, self-esteem, social support, and antisocial behavior at Time 2. The findings were discussed in relation to the effects of negative life events, self-esteem, and perceived social support on maladjustment.

• Korean Journal of Computational Design and Engineering
• /
• v.19 no.3
• /
• pp.294-304
• /
• 2014

This paper presents a real-time rendering algorithm of large-scale geometric data using GLSL (OpenGL shading language). It details the VAO (vertex array object) and VBO(vertex buffer object) to be used for up-loading the large-scale point clouds and polygon meshes to a graphic video memory, and describes the shader program composed by a vertex shader and a fragment shader, which manipulates those large-scale data to be rendered by GPU. In addition, we explain the global rendering procedure that creates and runs the shader program with the VAO and VBO. Finally, a rendering performance will be measured with application examples, from which it will be demonstrated that the proposed algorithm enables a real-time rendering of large amount of geometric data, almost impossible to carry out by previous techniques.

• Journal of Positioning, Navigation, and Timing
• /
• v.10 no.3
• /
• pp.197-206
• /
• 2021

We compared two typical ensemble time scale algorithms; AT1 and Kalman filter. Four commercial atomic clocks composed of two hydrogen masers and two cesium atomic clocks provided measurement data to the algorithms. The allocation of relative weights to the clocks is important to generate a stable ensemble time. A 30 day-average-weight model, which was obtained from the average Allan variance of each clock, was applied to the AT1 algorithm. For the reduced Kalman filter (Kred) algorithm, we gave the same weights to the two hydrogen masers. We also compared the frequency stabilities of the outcome from the algorithms when the frequency offsets and/or the frequency drift offsets estimated by the algorithms were corrected or not corrected by the KRISS-made primary frequency standard, KRISS-F1. We found that the Kred algorithm is more effective to generate a stable ensemble time scale in the long-term, and the algorithm also generates much enhanced short-term stability when the frequency offset is used for the calculation of the Allan deviation instead of the phase offset.

• Journal of Korean Academy of Nursing
• /
• v.17 no.1
• /
• pp.33-43
• /
• 1987

This study was to explore the level of self-actualization of the students in Korea Air and Correspondence University. The study subjects consisted of 507 students who visited the counseling center for taking advices to several psychosocial problems due to distance education through nursing counseling. The self actualization of the subjects evaluated by the self-actualization Inventory standardized by Kim and Lee in Korea. It consisted of 130 two-choice comparative value and behavior judgements. The items also consisted of two basic scales: one is inner directed scale (107 items) and the other is time competence (23 items) which included eight subscales, each of which measures a conceptually important element of self-actualization. Analysis of finding was as follows: 1) The self-actualization mean score of the total subjects was characterized by normal value within normal range of scale. The highest subscale score was NC scale: the lowest scale was EX scale. 2) The mean score of time competence scale of female student was higher than male student's time competence scale. 3) There was no significant differences in self aclualization among 4 groups in age. 4) There was also no significant differences in self-actualization between the group taken one time nursing counseling and the group taken two more times nursing counseling. 5) The problems of Job, learning, personality and further study, significantly had effects on the score of self-actualization level.

• Communications for Statistical Applications and Methods
• /
• v.1 no.1
• /
• pp.1-1
• /
• 1994

• Journal of applied mathematics & informatics
• /
• v.11 no.1_2
• /
• pp.215-241
• /
• 2003

In this paper, solute transport in heterogeneous aquifers using a modified Fokker-Planck equation (MFPE) is investigated. This newly developed mathematical model is characterised with a time-, scale-dependent dispersivity. A two-dimensional finite volume quadrilateral mesh method (FVQMM) based on a quadrilateral background interpolation mesh is developed for analysing the model. The FVQMM transforms the coupled non-linear partial differential equations into a system of differential equations, which is solved using backward differentiation formulae of order one through five in order to advance the solution in time. Three examples are presented to demonstrate the model verification and utility. Henry's classic benchmark problem is used to show that the MFPE captures significant features of transport phenomena in heterogeneous porous media including enhanced transport of salt in the upper layer due to its parameters that represent the dependence of transport processes on scale and time. The time and scale effects are investigated. Numerical results are compared with published results on the some problems.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1166-1171
• /
• 2004

The combustion instability acts as a serious obstacle for the lean premixed combustion of gas turbine and even causes the fatal damage to the combustor and whole system. In this experiment, the pressure fluctuation is highly related to the stabilizing position of flame and fuel injection location. The fuel injection location is connected with the convection time of the fresh mixture, which is important time scale to refresh the mixtures near the flame stabilization location. The flame is extremely unstable when the alternative stabilization occurs and bulk mode frequency (${\sim}10Hz$) of pressure fluctuation is observed in this condition. It was found that the convection time scale of the fresh reactant coincided with the time scale of the bulk mode fluctuation. Hence this phenomenon results from the local equivalence ratio change caused by the pressure fluctuation induced by thermo-acoustic effects.

• The Journal of the Acoustical Society of Korea
• /
• v.31 no.7
• /
• pp.427-434
• /
• 2012

The overlap-add technique based on waveform similarity (WSOLA) method is known to be an efficient high-quality algorithm for time scaling of speech signal. The computational load of WSOLA is concentrated on the repeated normalized cross-correlation (NCC) calculation to evaluate the similarity between two signal waveforms. To reduce the computational complexity of WSOLA, this paper proposes a fast NCC computation method, in which NCC is obtained through pre-calculated sum tables to eliminate redundancy of repeated NCC calculations in the adjacent regions. While the denominator part of NCC has much redundancy irrespective of the time-scale factor, the numerator part of NCC has less redundancy and the amount of redundancy is dependent on both the time-scale factor and optimal shift value, thereby requiring more sophisticated algorithm for fast computation. The simulation results show that the proposed method reduces about 40%, 47% and 52% of the WSOLA execution time for the time-scale compression, 2 and 3 times time-scale expansions, respectively, while maintaining exactly the same speech quality of the conventional WSOLA.