• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.8
• /
• pp.3925-3932
• /
• 2013

Emotion is closely related to the life of human, so has effect on many parts such as concentration, learning ability, etc. and makes to have different behavior patterns. The purpose of this paper is to extract important features based on physiological signals to recognize negative emotion. In this paper, after acquisition of electrocardiography(ECG), electroencephalography(EEG), skin temperature(SKT) and galvanic skin response(GSR) measurements based on physiological signals, we designed an accurate and fast algorithm using combination of linear discriminant analysis(LDA) and genetic algorithm(GA), then we selected important features. As a result, the accuracy of the algorithm is up to 96.4% and selected features are Mean, root mean square successive difference(RMSSD), NN intervals differing more than 50ms(NN50) of heart rate variability(HRV), ${\sigma}$ and ${\alpha}$ frequency power of EEG from frontal region, ${\alpha}$, ${\beta}$, and ${\gamma}$ frequency power of EEG from central region, and mean and standard deviation of SKT. Therefore, the features play an important role to recognize negative emotion.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.4
• /
• pp.393-400
• /
• 2014

In this study, an automatic transmission was developed for a bicycle. This transmission uses the pedal rpm and riding speed information for efficient riding. This transmission was installed on a bicycle using an internally geared hub. The automatic transmission was developed for a beginner to ride with proper gear changes. Indoor ride tests were performed to assess the performance of this transmission. Here, a 'beginner' is defined as a bicycle rider who can maintain a riding power of ~150W with a maximum heart rate of ~80%. Furthermore, 'ride with proper gear change' means that the rider could ride the bicycle while maintaining an efficient pedal rpm by the automatic transmission. One expert and four beginners participated in the ride test. The expert was chosen for the comparison with the beginners. To minimize environmental disturbances, the ride test was performed indoors. In this test, two types of gear changes manual and automatic were tested on two types of roads a road with a gradual incline of 0-3% and a road that simulates the bicycle road along the Han river in Seoul. The results of the ride tests show that the algorithm applied for the automatic transmission helps beginners to ride the bicycle efficiently.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.1
• /
• pp.418-425
• /
• 2013

In this study, the three scents effects on subjects due to EEG type, and it researched to find optimal scent to increase their amenity and productivity. EEG and HRV were compared and analyzed in the environmental test room by classifying subjects into two type: A and B. The condition of the environmental test room was in temperature 31[$^{\circ}C$], relative humidity 50[RH%], air current speed 0.02[m/s] and illuminance 1000[lux] with setting up three different scents which are Rosemary, Jasmine and Hazelnut. The result of this study, at Jasmine scent for A and B type, relative ${\alpha}$ wave, SEF50, $\frac{SMR}{\theta}$ and SDNN were revitalized, and ${\alpha}$ wave asymmetry index, HRT, stress index and fatigue degree were decreased. It was found that favorite scent of A and B type is same as Jasmine scent, but A type was more sensitive than B type about scent. Therefore Jasmine scent is very effective to increase amenity, productivity and concentration, and to decrease stress and fatigue degree.

• Sleep Medicine and Psychophysiology
• /
• v.25 no.1
• /
• pp.15-20
• /
• 2018

Objectives: This study was designed to assess the change of heart rate variability (HRV) at resting, upright, and psychological stress states in depressive disorder patients. Methods: HRV was measured at resting, upright, and psychological stress states in 62 depressive disorder patients. We used visual analogue scale (VAS) score to assess tension and stress severity. Beck depression inventory (BDI) and state trait anxiety inventories I and II (STAI-I and II) were used to assess depression and anxiety severity, respectively. Differences between HRV indices and VAS score were evaluated using paired t-tests. Gender difference analysis was conducted with ANCOVA. Results: SDNN (standard deviation of normal to normal intervals), LF/HF (low frequency/high frequency), and VLF (very low frequency) were significantly increased, while NN50 and pNN50 were significantly decreased in the upright position compared to resting state. SDNN, RMSSD (root mean square of the differences of successive normal to normal intervals), and VLF were significantly increased, while pNN50 was significantly decreased in the psychological stress state compared to resting state. SDNN, NN50, and pNN50 were significantly lower in an upright position compared to a state of psychological stress, and LF, HF, and LF/HF showed no significant differences Conclusion: The LF/HF ratio was significantly increased after physical stress in depressive disorder. However, the LF/HF ratio was not significantly increased after psychological stress, and the change in LF/HF ratio after physical stress and psychological stress did not significantly differ from each other. Significant increase in SDNN, NN50, and pNN50 in an upright posture compared to psychological stress suggests that depressive patients react more sensitively to physical stress than psychological stress.

• Sleep Medicine and Psychophysiology
• /
• v.9 no.1
• /
• pp.24-33
• /
• 2002

Objectives: Nasal continuous positive airway pressure (CPAP) corrected elevated blood pressure (BP) in some studies of obstructive sleep apnea syndrome (OSAS) but not in others. Such inconsistent results in previous studies might be due to differences in factors influencing the effects of CPAP on BP. The factors referred to include BP monitoring techniques, the characteristics of subjects, and method of CPAP application. Therefore, we evaluated the effects of one night CPAP application on BP and heart rate (HR) reactivity using non-invasive beat-to-beat BP measurement in normotensive and hypertensive subjects with OSAS. Methods: Finger arterial BP and oxygen saturation monitoring with nocturnal polysomnography were performed on 10 OSAS patients (mean age $52.2{\pm}12.4\;years$; 9 males, 1 female; respiratory disturbance index (RDI)>5) for one baseline night and another CPAP night. Beat-to-beat measurement of BP and HR was done with finger arterial BP monitor ($Finapres^{(R)}$) and mean arterial oxygen saturation ($SaO_2$) was also measured at 2-second intervals for both nights. We compared the mean values of cardiovascular and respiratory variables between baseline and CPAP nights using Wilcoxon signed ranks test. Delta ($\Delta$) BP, defined as the subtracted value of CPAP night BP from baseline night BP, was correlated with age, body mass index (BMI), baseline night values of BP, BP variability, HR, HR variability, mean $SaO_2$ and respiratory disturbance index (RDI), and CPAP night values of TWT% (total wake time%) and CPAP pressure, using Spearman's correlation. Results: 1) Although increase of mean $SaO_2$ (p<.01) and decrease of RDI (p<.01) were observed on the CPAP night, there were no significant differences in other variables between two nights. 2) However, delta BP tended to increase or decease depending on BP values of the baseline night and age. Delta systolic BP and baseline systolic BP showed a significant positive correlation (p<.01), but delta diastolic BP and baseline diastolic BP did not show a significant correlation except for a positive correlation in wake stage (p<.01). Delta diastolic BP and age showed a significant negative correlation (p<.05) during all stages except for REM stage, but delta systolic BP and age did not. 3) Delta systolic and diastolic BPs did not significantly correlate with other factors, such as BMI, baseline night values of BP variability, HR, HR variability, mean SaO2 and RDI, and CPAP night values of TWT% and CPAP pressure, except for a positive correlation of delta diastolic pressure and TWT% of CPAP night (p<.01). Conclusions: We observed that systolic BP and diastolic BP tended to decrease, increase or remain still in accordance with the systolic BP level of baseline night and aging. We suggest that BP reactivity by CPAP be dealt with as a complex phenomenon rather than a simple undifferentiated BP decrease.

• Korean Journal of Biological Psychiatry
• /
• v.15 no.4
• /
• pp.275-287
• /
• 2008

Depression and coronary artery disease are both highly prevalent diseases. Many previous studies suggest that depression is a common comorbid condition in patients with coronary artery disease and has a significant negative impact on the onset, course, and prognosis of coronary artery disease. However, the exact mechanisms that underlie the association between these two diseases remain unclear. Pathophysiologic mechanisms that may explain the effect of depression on coronary artery disease include hypercoagulability, hypothalamus-pituitary-adrenal axis and autonomic nervous system dysregulation, altered inflammatory response. On the contrary, pathophysiologic mechanisms in coronary artery disease that affect depression are less well known. It is also suggested that both diseases may share a common genetic vulnerability. The authors reviewed the literature on the pathophysiologic relationships of depression and coronary heart disease.

• Journal of Korean Society of Forest Science
• /
• v.103 no.1
• /
• pp.129-136
• /
• 2014

This study aims to investigate the effect of frequency of using forest environment on workers' stress. Workers in medical and counseling industry, which is recently known to require heavy emotional burden and thus cause a lot of stress and burnout syndrome, participated in the study. We classified 370 subjects, who were working at medical and counseling service institutions in Seoul metropolitan area, into two groups according to frequency of using forest environment by conducting a screening survey. 69 subjects submitted written consent and were recruited for either forest therapy program or control-group test; the "high" group (n=27) at the high frequency of using forest environment and the "low" group (n=42) at the low level. We measured the level of stress by using psychosocial indicators such as Worker's Stress Response Inventory (WSRI), Recovery Experience Questionnaire (REQ), and Maslach Burnout Inventory-General Survey (MBI-GS) and biological ones such as heart rate variability (HRV), cortisol, and Natural Killer cell (NK cell). The results suggested that the level of stress differed by frequency. The "high" group showed significantly low scores in the depression and work sub-scale and the total score of WSRI, emotional exhaustion, professional efficacy and total score of MBI-GS, and high scores in the total score of REQ. Similar tendencies were observed in the most of other indicators of psychosocial measures. Regarding the biological indicators, the "high" group showed the highest SDNN, RMSSD and TP measures of HRV and NK Cell activity and the low cortisol, although the statistical power did not reach the significant level. Our results suggest that the subjects who use forest environment frequently show favorable stress level both psychologically and biologically.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.6
• /
• pp.70-80
• /
• 2016

This study was conducted to investigate the effects of an integrated recreation program on mood states, flexibility, and stress of elderly women. The integrated recreation program was applied to dance as a physical activity and songs and art as emotional activities in consideration of the characteristics of the elderly activities. The subjects were 50 elderly women aged 65 years or older who reside in K-do. The examination period was December 2 in 2014 to February 17 in 2015, during which time mood states, flexibilities, density of the salivary cortisol, variations in heartbeats, and stress were measured. The integrated recreation program had positive effects on mood, flexibility and stress reduction in elderly women. Based on these results, the integrated recreation program is considered to increase mood states and flexibility of elderly women while lowering stress. Therefore, the integrated recreation program developed in this study not only helps the physical and mental health of elderly women, but can also be widely utilized as a health promotion program for the elderly.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.10a
• /
• pp.324-326
• /
• 2011

Measuring a biosignal during sleep is an important part of diagnosis and treatment of sleep disorder and also used to determine the general quality of sleep. As in current polysomnography, Contact method, which requires the attachment of electrodes to the skin, is the typical method to measure a biosignal during sleep. The procedure of this test is often considered to be inconvenient and tiresome because it requires attaching the device to the skin for each observation, and also limits free movement throughout the test. For this reason, the research on the acquiring the biosignal information without any attachment of a fixture on the skin is being conducted actively these days. In this study, it is suggested to check the heart rate per minute and the presence of breathing by placing a Piezo, which is a film type of pressure sensor, on the bed.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.10
• /
• pp.202-208
• /
• 2012

Fetal heart rate monitoring is important information to assess fetal well-being. Non-invasive fetal ECG (electrocardiography) can be derived from maternal abdominal signal. And various promising signal processing methods have been introduced to extract fetal ECG from mother's composite abdominal signal. However, non-invasive fetal ECG monitoring still has not been widely used in clinical practice due to insufficient reliable measurement and difficulty of signal processing. In application of signal processing method to extract fetal ECG, it might be lower signal to noise ratio due to time varying white Gaussian noise. In this paper, time varying Kalman smoother is proposed to remove white noise in fetal ECG and its feasibility is confirmed. Wiener process was set as Kalman system model and covariance matrix was modified according to white Gaussian noise level. Modified error covariance matrix changed Kalman gain and degree of smoothness. Optimal covariance matrix according to various amplitude in Gaussian white noise was extracted by 5 channel fetal ECG model, and feasibility of proposed method could be confirmed.