• The Journal of Korean Physical Therapy
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• 제29권4호
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• pp.164-168
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• 2017

Purpose: Functional electrical stimulation (FES) is a device that activates the sensorimotor cortex through electrodes attached to the surface of the skin. However, it is difficult to expect positive changes if the recipient is not attentive to the motion. To complement the perceived cognitive limitations of FES, we attempted to investigate the changes of sensorimotor cortex activity by simultaneously providing action observation with FES. Methods: Electroencephalogram was measured in 28 healthy volunteers. Relative band power over the sensorimotor cortex was analyzed and compared in three conditions: during rest, during FES alone, during action observation with FES. Results: The results showed significant differences in each relative band power. Relative alpha power and relative beta power were the lowest by application of FES combined with action observation, while the relative gamma power was the highest. Conclusion: These results suggest that combining FES with observation could be more effective than FES alone in neurorehabilitation.

• 한국안전학회지
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• 제24권3호
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• pp.71-78
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• 2009

During a learning process, a human being is assumed to experience knowledge-based behaviors, rule-based behaviors, and skill-based behaviors sequentially if Rasmussen was right. If any psycho-physiological symptom to those different levels can be obtained, it can be useful as a measure whether a human being is fully trained and has gotten a skill in his work. Therefore, this study aimed to draw relationships between human performance measures and psycho-physiological measures while committing a computer-simulated pointing task by utilizing the power spectrum technique of EEG data, especially with the ratio of relative beta-to-alpha band power. The result showed that, during correct responses, the ratio came to stabilize as all the performance data went stable. However, response time was not a simple linear function of task difficulty level only, but a joint function of task characteristics as well as behavior levels. Comparing relative band power ratios from errors and correct responses, activated states of one's brain could be explained, and characteristics of the task could understood. To tell that of pointing task, correlations around C3, C4, P3, P4 and 01, 02 area were significant and high in correct response cases whereas most correlation coefficients went down in error cases standing for imbalance of psycho-motor functions. Though task difficulty was the only one factor that could influence on relative band power ratio with statistical significance, it should be comprehended to mean a different way of expression indicating task characteristics since at least error-some situation could be explained with the help of relative band power ratio that absolute band power failed.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.101-111
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• 2023

Many spoofing detection studies have been conducted to cope with the most difficult types of deception among various disturbances of GPS, such as jamming, spoofing, and meaconing. In this paper, we propose a spoofing detection scheme based on elevation masked-relative received power between GPS L1 and L2 signals in a system using a multi-band array antenna. The proposed scheme focuses on enabling spoofing to be normally detected and minimizes the possibility of false detection in an environment where false alarms may occur due to pattern distortion among elements of an array antenna. The pattern distortion weakens the GPS signal strength at low elevation. It becomes confusing to detect a spoofing signal based on the relative power difference between GPS L1 and L2, especially when GPS L2 has weak signal strength. We propose design parameters for the relative power threshold including beamforming gain, the minimum received power difference between L1 and L2, and the patch antenna gain difference between L1 and L2. In addition, in order to eliminate the weak signal strength of GPS L2 in the spoofing detection process, we propose a rotation matrix that sets the elevation mask based on platform coordinates. Array antennas generally do not have high usefulness in commercial areas where receivers are operated alone, but are considered essential in military areas where GPS receivers are used together with signal processing for beamforming in the direction of GPS satellites. Through laboratory and live sky tests using the device under test, the proposed scheme with an elevation mask detects spoofing signals well and reduces the probability of false detection relative to that without the elevation mask.

• 한국안전학회지
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• 제25권3호
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• pp.123-130
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• 2010

Electroencephalogram(EEG) would be the most objective psychophysiological research technique on human errors though few research has been taken yet. This study aimed to get characteristics of human error while committing simple Odd-Ball tasks by utilizing the power spectrum technique of EEG data. Each experiment was composed of 3 tasks with different rules, and 8 young undergraduate students participated in this study as paid subjects. The result showed in the affirmative that subject and the interaction of subject and task factors were statistically significant on variation of $\alpha$ band power $P_{\alpha/(\alpha+\beta+\theta)}$ and $\beta$ band power $P_{\beta/(\alpha+\beta+\theta)}$, and that the former increasing in backward direction to Pz reflects compatibility whereas the latter increasing in forward direction to Fz reflects familiarity. Therefore it was coucluded that, since task 2 carried out in the present research requiring decoding process would be more difficult to human beings than the task merely requiring psychological recall process, task 1 and task 3 were classified into a homogenious group excluding task 2, and the ratio $\alpha$ band power to $\beta$ band power indicated enormous increase of $\alpha$ band power relative to $\beta$ band power in the cases of contra-lateral errors, especially in task 2.

• The Journal of Korean Physical Therapy
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• 제29권1호
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• pp.27-32
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• 2017

Purpose: Recent electrophysiological studies have shown that the sensorymotor cortex is activated during both actual action excuted by themselves and observation of action performed by other persons. Observation of action based on mirror neuron system can be used as a cognitive intervention to promote motor learning. The purpose of this study was to investigate the brain activity changes during action observation and action execution using EEG. Methods: Thirty healthy volunteers participated and were requested to perform hand action and to observe the video of hand action performed by another person. The EEG activity was evaluated by a method which segregated the time-locked for each condition. To compare the differences between action observation and execution, the Mu suppression and the relative band power were analysed. Results: The results showed significant mu suppression during the action observation and execution, but the differences between the two conditions were not observed. The relative band power showed a significant difference during the action observation and execution, but there were no differences between the two conditions. Conclusion: These results indicate that action execution and observation involve overlapping neural networks in the sensorymotor cortical areas, proposing positive changes on neurophysiology. We are expected to provide information related to the intervention of cognitive rehabilitation.

• Ocean Systems Engineering
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• 제2권4호
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• pp.297-314
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• 2012

Power-take-off through inner dynamic system inside a floating buoy is suggested. The power take-off system is characterized by mass, stiffness, and damping and generates power through the relative heave motion between the buoy and inner mass (magnet or amateur). A systematic hydrodynamic theory is developed for the suggested WEC and the developed theory is illustrated by a case study. A vertical truncated cylinder is selected as a buoy and the optimal condition of the inner dynamic system for maximum PTO (power take off) through double resonance for the given wave condition is systematically investigated. Through the case study, it is seen that the maximum power can actually be obtained at the optimal spring and damper condition, as predicted by the developed WEC theory. However, the band-width of high performance region is not necessarily the greatest at the optimal (maximum-power-take-off) condition, so it has to be taken into consideration in the actual design of the WEC.

• 수면정신생리
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• 제27권2호
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• pp.67-76
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• 2020

목 적 : 뇌가 성숙해감에따라, 비대칭과 편측성역시 기능적, 효율적인 관점에서 볼 때, 성숙과 더불어 정보처리를 효과적으로 하기 위한 과정이라 할 수 있다. 인지적 복잡성이 높아지는 시기인 6~9세와 14~17세 사이의 뇌의 변화를 휴지기 뇌파를 주파수 분석을 하여 알아 본다. 방 법 : 본 연구는 6~9세(n = 24)와 14~17세(n = 26)의 피험자들의 뇌파는 공개된 자료(Multimodal Resource for Studying Information Processing in the Developing Brain, MIPDB)를 분석하였고, 정신과적 질환이 있거나, 잡파가 심한 뇌파의 피험자는 제외하여 최종적으로 6~9세(n = 14)와 14~17세(n = 11)을 대상으로, EEGlab을 이용하여 뇌파를 분석하였고, 적어도 2분이상의 휴지기 뇌파 중 눈을 감은 상태의 뇌파를 이용하여 주파수 분석을 하였다. 뇌의 구역을 총 9구획으로 나눠서 주파수 분석을 하여, 주파수별 비대칭성과 편측성을 측정하였다. 결 과 : 전반적으로 서파의 파워는 나이가 어릴수록 높았으며, 이 현상은 절대파워와 상대파워에 상관없이 나타났다. 베타밴드의 상대파워는 좌우 편측성없이 14~17세 그룹이 높았다. 비대칭성의 경향은 휴지기 뇌파에서 세타밴드와 알파밴드의 상대파워에서만 두 그룹간의 차이가 관찰되었으며, 세타파는 왼쪽 전두엽 구획에서 14~17세군이 오른쪽 전두엽구획에 비해서 높게 측정되었고, 이 현상은 두정엽 구획으로 갈 수록 반대의 경향, 즉 두정엽 구획에서는 오른쪽 세타밴드파워가 왼쪽의 세타밴드파워에비해서 높게 측정되었다. 알파밴드의 상대파워는 두정엽구획에서 왼쪽의 파워가 오른쪽의 파워보다 높게 측정되었다. 편측성을 보이는 주파수는 알파밴드였으며, 절대파워와 상대파워 모두에서 왼쪽의 알파밴드파워가 오른쪽에 비해서 높게 나타났으며 그 차이가 통계적으로 유의미하였다. 결 론 : 6~9세의 피험자들에 비해서 14~17세의 피험자들은 성장기를 거치며 비교적 수준이 높은 인지기능 및 수행기능을 하게 되고, 이 기능과 관련하여 베타밴드와 알파밴드가 이 변화를 반영한다고 볼 수 있다.

• 전자공학회논문지D
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• 제34D권3호
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• pp.17-24
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• 1997

Broad-band RAM's (Radar absorbing materials) are designed by multi-layered lossy dielectrics. The depth, the relative permittivity and the loss tangent of each layer are optimized in order to meet the required reflective power over the specified frequency range using a genetic algorithm. The reflection coefficients are calculated by the continued fraction method. A new population model of the partial initialization method during iterations is applied for the multi-modal functions to enhance the performance of the genetic algorithm. The optimal RAN's are designed by setting the relative permittivity and the loss tangent of the dielectrics as a funtion of the frequency over 5~20GHz.

• 한국정보통신학회논문지
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• 제13권5호
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• pp.860-867
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• 2009

본 논문에서 는 X-band FMCW Radar용 Microstrip Array Patch Antenna를 설계하여 제작하였으며 적층 구조를 채택하여 대역폭 특성을 개선하였다. 배열 안테나는 비유전율 2.33인 기판에 설계하였고, 적층 패치는 비유전율 4.6인 기판을 사용하였다. 배열 안테나와 적층 패치 사이에는 일정한 간격을 유지하기 위하여 공기와 유전율이 비슷한 폼 (foam)을 삽입하였다. 배열 안테나 제작 결과 설계 주파수 9GHz에서 반 전력 빔 폭은 $10.6^{\circ}$, 이득은 18.70dBi, 대역폭은 1.25GHz의 특성을 얻었다. 배열 안테나에 적층 구조를 추가한 결과 반 전력 빔 폭은 $15.17^{\circ}$, 이득은 15.85dBi, 대역폭은 2GHz의 특성을 얻었고, 향후 X-Band FMCW Radar에 응용하기 위해서는 배열 안테나의 대역폭은 유지한 채 이득을 개선할 필요가 있다.

• 한국의류산업학회지
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• 제14권6호
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• pp.1010-1017
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• 2012

This study examined the clothing wearing comfort of elderly women by electroencephalogram (EEG) and electrocardiogram (ECG) analyses. This study utilized 7 elderly individuals aged 65 or more. Two kinds of clothing ensemble (control and prototype) were used as experimental clothing. The control consisted of a general clothing ensemble and the prototype consisted of clothing that added an extra gap. Subjects wore the control or prototype from 9:00 to 21:30 and EEG and ECG signals were measured in the last 30 minutes. The EEG analysis showed that relative band power of a and ${\alpha}$/high ${\beta}$ were higher when they wore the prototype rather than the control. The ECG analysis showed that absolute band power of HF was higher; however, absolute band power of LF and LF/HF was lower when they wore the prototype rather than the control. Subjects felt less stressful and more comfortable when they wore the prototype. The results demonstrate the necessity to develop clothing in consideration of the body changes in elderly women. It is significant that the assessment of wearing comfort was aided by the use of EEG and ECG analysis in the field of clothing and textiles.