• Journal of Korea Society of Industrial Information Systems
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• v.20 no.6
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• pp.37-46
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• 2015

The wireless electrocardiographic monitoring system(WDMS) is designed to be long term monitoring for the early detection of cardiac disorders. The current version of the WDMS can identify two types of cardiac rhythms in real-time, such as atrial fibrillation(AF) and normal sinus rhythm(NSR), which are very important to track cardiac-rhythm disorders. In this study, we proposed the analysis method to discriminate the characteristics statistically evaluated in both time and frequency domains between AF and NSR using various parameters in the heart rate variability(HRV). And we applied various ECG detection methods (e.g., difference operation method) and compared the results with those of the discrete wavelet transform(DWT) method. From the statistically results, we found that the parameters such as STD RR, STD HR, RMSSD, NN50, pNN50, RR Trian, and TNN(p<0.05) are significantly different between the AF and NSR patients in time domain. On the other hand, the frequency domain analysis results showed a significant difference in VLF power($ms^2$), LF power($ms^2$), HF power($ms^2$), VLF(%), LF(%), and HF(%). In particular, the parameters such as STD RR, RMSSD, NN50, pNN50, VLF power, LF power and HF power were considered as the most useful parameters in both AF and NSR patient groups. Our proposed method can be efficiently applied to early detection of abnormal conditions and prevent the such abnormals from becoming serious.

• Journal of Power Electronics
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• v.14 no.3
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• pp.444-457
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• 2014

This paper presents the design and realization of a digital PV simulator with a Push-Pull Forward (PPF) circuit based on the principle of modular hardware and configurable software. A PPF circuit is chosen as the main circuit to restrain the magnetic biasing of the core for a DC-DC converter and to reduce the spike of the turn-off voltage across every switch. Control and I/O interface based on a personal computer (PC) and multifunction data acquisition card, can conveniently achieve the data acquisition and configuration of the control algorithm and interface due to the abundant software resources of computers. In addition, the control program developed in Matlab/Simulink can conveniently construct and adjust both the models and parameters. It can also run in real-time under the external mode of Simulink by loading the modules of the Real-Time Windows Target. The mathematic models of the Push-Pull Forward circuit and the digital PV simulator are established in this paper by the state-space averaging method. The pole-zero cancellation technique is employed and then its controller parameters are systematically designed based on the performance analysis of the root loci of the closed current loop with $k_i$ and $R_L$ as variables. A fuzzy PI controller based on the Takagi-Sugeno fuzzy model is applied to regulate the controller parameters self-adaptively according to the change of $R_L$ and the operating point of the PV simulator to match the controller parameters with $R_L$. The stationary and dynamic performances of the PV simulator are tested by experiments, and the experimental results show that the PV simulator has the merits of a wide effective working range, high steady-state accuracy and good dynamic performances.

• Journal of Convergence for Information Technology
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• v.11 no.10
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• pp.10-19
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• 2021

In this paper, we tried to derive characteristic parameters that reflect mental fatigue through EEG measurement and analysis. For this purpose, mental fatigue was induced through a resting state with eyes closed and performing subtraction operations in mental arithmetic for 30 minutes. Five subjects participated in the experiment, and all subjects were right-handed male students in university, with an average age of 25.5 years. Spectral analysis was performed on the EEG collected at the beginning and the end of the experiment to derive feature parameters reflecting mental fatigue. As a result of the analysis, the absolute power of the alpha band in the occipital lobe and the temporal lobe increased as the mental fatigue increased, while the relative power decreased. Also, the difference in power between resting state and task state showed that the relative power was larger than the absolute power. These results indicate that alpha relative power in the occipital lobe and temporal lobe is a feature parameter reflecting mental fatigue. The results of this study can be utilized as feature parameters for the development of an automated system for mental fatigue determination such as fatigue and drowsiness while driving.

• Journal of Power Electronics
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• v.17 no.1
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• pp.305-313
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• 2017

A novel interference isolation method is proposed by using several designed coils in capacitive power transfer systems as isolation impedances. For each designed coil, its stray parameters such as the inter-turn capacitance, coil resistance and capacitance between the coil and the core, etc. are taken into account. An equivalent circuit model of the designed coil is established. According to this equivalent circuit, the impedance characteristic of the coil is calculated. In addition, the maximum impedance point and the corresponding excitation frequency of the coil are obtained. Based on this analysis, six designed coils are adopted to isolate the interference from power delivery. The proposed method is verified through experiments with a power carrier frequency of 1MHz and a data carrier frequency of 8.7MHz. The power and data are transferred parrallelly with a data carrier attenuation lower than -5dB and a power attenuation on the sensing resistor higher than -45dB.

• Journal of Power Electronics
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• v.6 no.1
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• pp.18-28
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• 2006

The Electric Power Subsystem (EPS) is one of the most critical systems on any satellite because nearly every subsystem requires power. This makes the choice of power systems the most important task facing satellite designers. The main purpose of the Satellite EPS is to provide continuous, regulated and conditioned power to all the satellite subsystems. It has to withstand radiation, thermal cycling and vacuums in hostile space environments, as well as subsystem degradation over time. The EPS power characteristics are determined by both the parameters of the system itself and by the satellite orbit. After satellite separation from the launch vehicle (LV) to its orbit, in almost all situations, the satellite subsystems (attitude determination and control, communication and onboard computer and data handling (OBC&DH)), take their needed power from a storage battery (SB) and solar arrays (SA) besides the consumed power in the EPS management device. At this point (separation point, detumbling mode), the satellite's angular motion is high and the orientation of the solar arrays, with respect to the Sun, will change in a non-uniform way, so the amount of power generated by the solar arrays will be affected. The objective of this research is to select satellite EPS component types, to estimate solar array illumination parameters and to determine the efficiency of solar arrays during both detumbling and normal operation modes.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.453-457
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• 2008

We studied on the dependency of parameters which those were used to design a ballast of ICP light source. These parameters were derived from Barkhausen criterion equation about the oscillating condition of ballast. Comparing with a change of turns, we can suggest that a change of l is suitable to control a $I_p$ of an ICP light source. According to the Z-l equation, we can find an optimum rating power of ICP light sources corresponding to l.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.12
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• pp.2179-2189
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• 2010

This paper deals with analytical techniques for performance evaluation of small scaled wind power generator with outer permanent magnet rotor. In part (1), using transfer relations theorem, magnetic field distribution characteristics by PM and armature reaction field are derived. Moreover, electrical parameters such as back-EMF, inductance and resistance are calculated from the obtained field characteristic equations. The proposed analytical techniques are validated by nonlinear finite element method using commercial software 'Maxwell' and performance experiments of the manufactured generator. In part (2), generating characteristics analysis such as constant speed characteristics and constant resistive load characteristics, and performance evaluation according to variation of wind speed will be accomplished using the derived electrical parameters.

• KIEE International Transactions on Power Engineering
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• v.2A no.3
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• pp.109-113
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• 2002

This paper addresses the issue of parameter error identification and estimation in electric power systems. Parameter error identification and estimation is carried out as a part of the state estimation. A two stage estimation procedure is used to detect and identify parameter errors. Suspected parameters are identified by the WLAV state estimator in the first stage. A new WLAV state estimator adding suspected system parameters in the state vector is used to estimate the exact values of parameters. Supporting examples are given by using the IEEE 14 bus system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05b
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• pp.41-45
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• 2005

In this paper, parameters of electron temperature and density for the mercury-free lighting-source were measured to diagnosis and analyze in Xe based inductively coupled plasma(ICP). In results at several dependences of 20~100 mTorr Xenon pressure, 50~200W RF power and horizontal distribution were especially mentioned. When Xe pressure was 20mTorr and RF power was 200W, the electron temperature and density were respectively 3.58eV and $3.56{\times}10^{12}cm^{-3}$. The key parameters of Xe based ICP depended on Xe pressure more than RF power that could be verified. A high electron temperature and low electron density with a suitable Xe pressure are indispensible parameters for Xe based ICP lighting-source.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.1-17
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• 1997

The results of a restricted numerical simulation for the color gradients within globular clusters have been presented. The standard luminosity function of M3 and Salperter's initial mass functions were used to generate model clusters as a fundamental population. Color gradients with the sample clusters for both King and power law cusp models of surface brightness distributions are discussed in the case of using the standard luminosity function. The dependence of color gradients on several parameters for the simulations with Salpter's initial mass functions, such as slope of initial mass functions, cluster ages, metallicities, concentration parameters of King model, and slopes of power law, are also discussed. No significant radial color gradients are shown to the sample clusters which are regenerated by a random number generation technique with various parameters in both of King and power law cusp models of surface brightness distributions. Dynamical mass segregation and stellar evolution of horizontal branch stars and blue stragglers should be included for the general case of model simulations to show the observed radial color gradients within globular clusters.