• Journal of Positioning, Navigation, and Timing
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• 제8권2호
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• pp.69-77
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• 2019

This study introduces MATLAB Graphical User Interface (GUI)-based software to monitor ionospheric disturbances. This software detects ionospheric disturbances using Global Positioning System (GPS) and Global Navigation Satellite System (GLONASS) measurements, and estimates a location of the disturbance source through the detected disturbance. In addition, this software includes a sky plot making function and frequency analysis function through wavelet transform. To evaluate the performance of the developed software, data of 2011 Tohoku earthquake in Japan were analyzed by using the software. The analysis results verified that the ionospheric disturbances were detected through GPS and GLONASS measurements, and the location of the disturbance source was estimated through the detected disturbance.

• Kyungpook Mathematical Journal
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• 제61권2호
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• pp.353-369
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• 2021

In this paper, we examine and analyze the concept of different non-integer chaotic systems with external disturbances, uncertainties, and input non-linearities. We consider both drive and response systems with external bounded disturbances and uncertainties. We also consider non-linear control inputs. For synchronization, we introduce the adaptive sliding mode technique, in which we establish the stability of the controlled system by a control which estimates uncertainties and disturbances, and then applies a suitable sliding surface to control them. We use computer simulations to established the efficacy and adeptness of the prospective scheme.

• 전기전자학회논문지
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• 제13권1호
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• pp.11-18
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• 2009

In this paper, the stability of second order uncertain systems with regulation of PID type controllers is analyzed by using Lyapunov second method for the first time in the time domain. The property of the stability of PID regulation servo systems is revealed in sense of Lyapunov, i.e., bounded stability due to the disturbances and uncertainties. By means of the results of this stability analysis, the maximum norm bound of the error from the output without variation of the uncertainties and disturbances is determined as a function of the gains of the PID control, which make it enable to analyze the effect resulted from the variations of the disturbances and uncertainties using this norm bound for given PID gains. Using the relationship of the error from the output without variation of the uncertainties and disturbances and the PID gain with maximum bounds of the disturbances and uncertainties, the robust gain design rule is suggested so that the error from the output without the variation of the disturbances and uncertainties can be guaranteed by the prescribed specifications as the advantages of this study. The usefulness of the proposed algorithm is verified through an illustrative example.

• 기본간호학회지
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• 제12권2호
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• pp.247-254
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• 2005

Purpose: This study was done to examine the sleep pattern of ICU patients, as well as characteristics of, and factors related to sleep disturbances, and state anxiety. It was done to provide the basic data fur effective nursing interventions to improve quality of sleep for these patients. Methods: The participants were 104 patients who were admitted to the surgical ICU in a hospital in Seoul. To measure sleep patterns, the Verran and Snyder-Halpern Sleep Scale and the Sleeping Scale developed by Oh et al.(1998) were used. Characteristics of sleep disturbances were measured using the Sleep characteristics scale developed by Park(1999). To measure factors related to sleep disturbances, thirty items developed by Oh(1998) were used. Results: There was no statistically significant difference in the sleep patterns according to the general characteristics of the patients. The characteristics of sleep disturbances showed statistically significant differences in general and specific characteristics of sleep patterns but there was no statistically significant difference according to the general characteristics of the patients. There were significant negative correlations between factors related to sleep disturbances and general and specific characteristics of sleep patterns but there were no statistically significant difference according to the general characteristics of the patients. Conclusion: The results showed that the majority of patients staying in the surgical ICU experienced sleep disturbances and that the physical factor was the major factor of sleep disturbances.

• 국제지역연구
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• 제15권1호
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• pp.31-58
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• 2011

본 논문의 목적은 양 대국에서 발생하는 실물교란과 화폐교란이 양 대국 경제에 미치는 영향을 분석하고, 이를 통해서 양 대국 중 일국에서 실시하는 재정정책과 통화정책이 자국과 해외에 어떤 영향을 미치는지 알아보는데 있다. 또한 양 대국에서 결정되는 임금연동지수에 의해서 양 대국에서 발생하는 실물교란과 화폐교란이 자국과 해외에 어떤 영향을 미치는지도 알아보았다. 이를 위해 양 대국 경제모형을 구성하고 우선 이론적으로 분석하였다. 이론적 분석을 토대로 일본과 미국을 대상으로 실증분석을 하여, 일본과 미국에서 발생하는 실물교란과 화폐교란이 양국경제에 미치는 영향을 분석하였다. 또한 일본과 미국에서 결정되는 임금연동지수에 의해서 양국에서 발생하는 실물교란과 화폐교란이 양국경제에 미치는 영향을 분석하였다. 실증분석결과에 의하면 미국이 일본에서 발생하는 경제교란에 의해서 영향을 받는 것보다는 일본이 미국에서 발생하는 경제교란에 의해서 더 커다란 영향을 받는 것으로 나타났다. 결국 해외의 경제정책이 일국경제에 미치는 파급효과는 미국보다는 일본의 경우에 더 큰 것으로 나타나, 일본이 해외경제충격에 더 취약한 것으로 나타났다.

• 한국항행학회논문지
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• 제22권6호
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• pp.616-622
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• 2018

규모가 큰 지진에 의해 발생한 에너지는 전리층까지 도달하여 교란을 발생시킨다. GNSS (global navigation satellite system) 위성의 신호의 전리층 지연을 분석하면 해당 교란을 검출할 수 있다. 지진에 의한 교란 검출에는 주로 band-pass filter가 사용되는데, 교란의 주파수에 맞는 주파수 대역 설정이 중요하다. 따라서 본 논문에선 GNSS 신호를 통해 지진에 의한 전리층 교란의 주파수를 분석하였다. 전리층 교란의 주파수 분석은 반송파의 geometry free combination으로 산출한 전리층 지연을 1 mHz high-pass filter로 처리한 후, fast Fourier transform을 통해 수행했다. 교란의 주파수 분석결과 초기 교란의 주파수는 4.5 mHz~11 mHz의 범위를 가지며, 5.7 mHz가 대표 주파수이다. 후속 교란의 경우 6 mHz~10 mHz의 주파수 대역을 가지며, 7.3 mHz가 대표 주파수로 관찰되었다.

• 전기학회논문지
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• 제63권7호
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• pp.976-986
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• 2014

In this paper, the problem of reliable control of linear systems with time-varying delays, randomly occurring disturbances, and actuator failures is investigated. It is assumed that actuator failures occur when disturbances affect to the systems. Firstly, by using a suitable Lyapunov-Krasovskii functional and some recent techniques such as Wirtinger-based integral inequality and reciprocally convex approach, stabilization criterion for nominal systems with time-varying delays is derived. Secondly, the proposed method is extended to the reliable $H_{\infty}$ controller design for linear dynamic systems with time-varying delays, randomly occurring disturbances, and actuator failures. Since nonlinear matrix inequalities (NLMIs) are involved in proposed results, the cone complementarity algorithm will be introduced. Finally, two numerical examples are included to show the effectiveness of the proposed criteria.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.200-214
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• 2016

This paper investigates the problem of stability analysis and robust H_∞ controller for time-delayed systems with parameter uncertainties and stochastic disturbances. It is assumed parameter uncertainties are norm bounded and mean and variance for disturbances of them are known. Firstly, by constructing a newly augmented Lyapunov-Krasovskii functional, a stability criterion for nominal systems with time-varying delays is derived in terms of linear matrix inequalities (LMIs). Secondly, based on the result of stability analysis, a new controller design method is proposed for the nominal form of the systems. Finally, the proposed method is extended to the problem of robust H_∞ controller design for a time-delayed system with parameter uncertainties and stochastic disturbances. To show the validity and effectiveness of the presented criteria, three examples are included.

• Journal of Welding and Joining
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• 제33권6호
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• pp.13-20
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• 2015

Many automotive companies are endeavoring to improve the quality of resistance spot welding by updating body-in-white (BIW) production line with adaptive control spot welding system to compensate the process disturbances such as gap, electrode wear, oxidized surfaces, poor fit up and adhesive etc. Most of the commercial adaptive weld controllers require proper "Initial Welding Schedule" or "Reference weld" to achieve compensation in welding parameters during real time welding. In this study, the compensation of a commercial adaptive weld controller had been observed and analyzed thoroughly for various process disturbances to find optimal initial welding schedule. It was observed that 90 percent of the expulsion current in constant current control as reference welding schedule conferred the maximum button diameter in adaptive control welding. Finally, effects of each disturbance in combined field disturbances system with adaptive control had also been confirmed with the design of experiment (DOE) by minitab(R)16 for combined disturbances situation and suitability of optimum initial weld current had also established with real body part validation test.

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.364-370
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• 2005

The active magnetic bearing (AMB) systems mounted in moving vehicles are exposed to the disturbances due to the base motion, often leading to malfunction or damage as well as inaccurate positioning of the systems. Thus, in the controller design of such AMB systems, robustness to base disturbances becomes an essential requirement. In this study, effective control schemes are proposed for the homo-polar AMB system, which uses permanent magnets for generation of bias magnetic flux, when it is subject to base motion, and its control performance is experimentally evaluated. The base motion of AMB system is modeled as the dynamic disturbances in the gravity and base excitation forces. To effectively compensate for the disturbances, the angle feed-forward controller based on the inverse dynamic model and the acceleration feed-forward controller based on the normalized filtered-X LMS algorithm are proposed. The performance test of the prototype AMB system is carried out, when the system is mounted on rate table. The experimental results show that the performance of the proposed controllers for the AMB system is satisfactory in compensating for the disturbances due to the base motion.