• 대한안전경영과학회지
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• 제16권4호
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• pp.305-311
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• 2014

Recently, though it was developed several services using the context-awareness technology of IoT, there exist also obstacles for high quality service. Specifically it is short the study for uncertainty of context-awareness. This study focused on understanding the effect of frequency interference among several environmental factors for location determination to increase precision of location determination. It was found that frequency interference between devices using 2.4Ghz frequency effect on the location determination precision. It was resulted that frequency interference increase the error of location determination precision. Then, we confirmed that it was required the suitable compensation method corresponding to frequency interference.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.170-177
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• 2014

This paper presents a new method of classification of the induction machine faults using Time Frequency Representation, Particle Swarm Optimization and artificial neural network. The essence of the feature extraction is to project from faulty machine to a low size signal time-frequency representation (TFR), which is deliberately designed for maximizing the separability between classes, a distinct TFR is designed for each class. The feature vectors size is optimized using Particle Swarm Optimization method (PSO). The classifier is designed using an artificial neural network. This method allows an accurate classification independently of load level. The introduction of the PSO in the classification procedure has given good results using the reduced size of the feature vectors obtained by the optimization process. These results are validated on a 5.5-kW induction motor test bench.

• 대한의용생체공학회:의공학회지
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• 제38권4호
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• pp.211-217
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• 2017

During the emergency situation such as cardiac arrest, cardiopulmonary resuscitation(CPR) is the most important treatment to maintain patient's blood circulation. Since the quality of CPR can not be easily measured or evaluated by the eye, an assistive device with an accelerometer can help to assess the pressure depth of CPR. In this study, we propose a single frequency analysis method to reduce the error of the accelerometer by extracting only one frequency component from the Fourier transform process. To verify the effectiveness of the single frequency analysis, acceleration data at CPR conditions were measured at a sampling rate of 50 / sec using a wristband equipped with an acceleration sensor. Then, We compared the existing distance estimation method and the single frequency analysis method using the measured data. The amplitude value proportional to the compression depth was obtained by applying the single frequency analysis method.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.198-201
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• 1997

The new system for identification of organic vapours and analysis method of mechanism between organic vapours and sensitive materials were attempted using the resonant resistance and resonant frequency of Quartz Crystal Analyzer (Q. C. A.). The resonant resistance shift means rheological changes in sensitive LB films occurred by the adsorption of organic vapours, while the resonant frequency shift represent the mass of organic vapour loaded in or on the sensitive LB films. It is thought that we can obtain more accurate response mechanism of organic vapour using the resonant frequency and resonant resistance diagram. The polymeric sensitive material were quantitively depositied using the LB method. In the experimental results, the adsorption behavior of organic vapour response can be decided by two type ; surface adsorption and penetration into sensitive material. Organic vapours had different positions in the Frequency-Resistance (F-R) diagram as to the kinds and concentrations of organic vapours. Thus F-R diagram can be applied to the development of one channel gas sensing system using the Quartz Crystal Analyzer.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1375-1384
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• 2014

Flashover of power transmission line insulators is a major threat to the reliable operation of power system. This paper deals with the flashover prediction of polymeric insulators used in power transmission line applications using the novel condition monitoring technique developed by PD signal time-frequency map and neural network technique. Laboratory experiments on polymeric insulators were carried out as per IEC 60507 under AC voltage, at different humidity and contamination levels using NaCl as a contaminant. Partial discharge signals were acquired using advanced ultra wide band detection system. Salient features from the Time-Frequency map and PRPD pattern at different pollution levels were extracted. The flashover prediction of polymeric insulators was automated using artificial neural network (ANN) with back propagation algorithm (BPA). From the results, it can be speculated that PD signal feature extraction along with back propagation classification is a well suited technique to predict flashover of polymeric insulators.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.83-85
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• 2007

In this paper is described frequency control of Induction Heating System for using the resonant high-frequency inverter. To follow in output temperature and frequency in order to change, it controls a system and it confirms the electric change of induction heating system.

• 한국항행학회논문지
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• 제14권1호
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• pp.20-26
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• 2010

본 논문에서는 PHEMT 소자를 이용하여 100mW급 중전력 주파수 3체배기를 설계하였다. 이 주파수 3체배기는 목적하는 주파수 7.2 GHz를 얻기 위하여 2.4 GHz 입력주파수를 정수 체배하여, 3차 고조파를 발생시키는 비선형 소자를 이용하였다. 이 3체배기는 로드-풀 시뮬레이션을 이용하여 설계하였고 출력단에서 기본파와 2차 고조파를 억압하기 위하여 노치필터를 이용하였다. 설계된 3체배기는 출력전력이 21 dBm, 체배 이득이 6 dB이며 기본파는 약 20 dBc, 2차고조파는 약 30 dBc의 고조파억압특성을 나타내었다.

• 대한후두음성언어의학회지
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• 제9권1호
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• pp.11-16
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• 1998

Background and Objectives : Electrolarynx has been used as one of the methods of rehabilitation for the laryngectomees. Previous electrolarynx could not alter frequency and intensity simultaneously. This institute developed an electrolarynx named "Evada" using FSR(force sensing resistor) sensor, which can control the frequency(and/or intensity) simultaneously. This study was performed for the normal control and laryngectomees with three types of electrolarynx (Evada, Servox-inton, Nu-vois) to reveal functional characteristics of Evada Materials and Methods : five laryngectomees and five normal adults were made to express there sentences(discriptive sentence, "You stay here" ; question sentence, "You stay here？" ; exclamation sentence, "You!! stay here!"), using three types of electrolarynx. Frequency change and intensity change from first and last vowel was calculated in three sentences and analyzed statistically by paired T-test. Results : The frequency change in the question sentence and exclamation sentence was more prominent in Evada than in Servox-inton and Nu-vois. The intensity change in the question sentence and exclamation sentence was also more prominent in Evada than in Servox-inton and Nu-vois. Conclusions : Evada could control frequency and intensity simultaneously and control degree of frequency(and/or intensity) according to the pressing force into the button. Evada could adjust continuously frequency and intensity during conversation. So, Evada is better in producing intonation and contrastive stress than Nu-vois and Servox-inton.

• Journal of Biosystems Engineering
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• 제26권2호
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• pp.105-114
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• 2001

Modulus of elasticity, modulus of rigidity, damping ratio, and natural frequency of three varieties of boxthorn (Lycium chinense Mill) (Cheongyang #2, Cheongyang gugija, and Cheongyang native) branches were analyzed. Modulus of elasticity and modulus of elasticity and modulus of rigidity of the boxthorn branch was determined using standard formula after simple beam bending and torsion test, respectively, using an universal testing machine. Damping ratio and natural frequency of branches were determined using a system consisted of an accelerometer, a PC equipped with A/D converter, and a software for data analysis. Relationship between the elastic modulus and branch diameter in overall varieties and branch types showed a good correlation (r -0.81). There was, however, no correlation between torsional rigidity and branch diameter. The internal damping results were highly variable and the overall range of the damping ratio of the boxthorn branch was 0.014-0.087, which indicated that the branch was a lightly damped structure. The natural frequency of the boxthorn branch was in the range of 89-363 rad/s for the overall varieties and branch types. A good correlation (r 0.82) existed between the natural frequency and branch diameter in overall varieties and branch type.

• 한국산업융합학회 논문집
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• 제5권3호
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• pp.179-186
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• 2002

This paper proposed LC resonant current fed high frequency inverter for high frequency induction heating using leakage inductance of transformer and, its described operating principle. The analysis of circuit presented by using normalized parameter in considering leakage inductance of transformer and, discussed characteristic evaluation of inverter circuit in detail. The proposed inverter is operating ZVS to reduce turn-on and turn-off loss of switching devices so, raised an efficiency. And, the experimental apparatus was made on base characteristic evaluation of theoretical analysis to discuss possibility on high frequency source and confirmed a rightfulness theoretical analysis. A result of study, the proposed inverter is higher utilizing factor using on leakage inductance of transformer and show possibility, which is application on high frequency power system.