• Journal of People, Plants, and Environment
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• v.22 no.3
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• pp.309-319
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• 2019

This study was conducted to investigate the effects of watching a virtual reality (VR) forest video on stress reduction in adults. Experiments were performed in an artificial climate chamber where temperature, humidity and illumination were controlled. To cause stress in subjects, the subjects were asked to multiply two digit numbers by one digit numbers for two minutes. The subjects then watched a VR forest video for five minutes. During the experiment, the heart rate variability (HRV) and heart rate (HR) of subjects were continuously measured for evaluating their physiological state. After measuring the baseline and watching a VR forest video, their psychological state was evaluated using the profile of mood state (POMS), semantic differential (SD) method, and positive affect and negative affect schedule (PANAS). The results of physiological evaluation after watching a VR forest video showed a decrease in the stress index and HR, an increase in the activity of the parasympathetic nervous system, and the standard deviation of normal to normal RR intervals (SDNN). The results of psychological assessment confirmed that watching a VR forest video induced "comfort", "natural", and "soothed" feelings in subjects. In addition, watching a VR forest video decreased "tension-anxiety (T-A)", "depression-dejection (D)", "anger-hostility (A-H)", "fatigue (F)", "total mood disturbance (TMD)", and increased "vigor (V)" compared to the base line, and decreased "negative affect" and increased "positive affect." These results indicate that watching a VR forest video decreases adults' stress index, stabilizes physiological state, and has a positive impact on psychological state. The findings of this study can serve as a basis for providing forest welfare services to people in the blind spots of forest welfare, and can lay a foundation for the adoption of VR, one of the technologies of the fourth industrial revolution in forestry.

• Journal of Korean Medicine Rehabilitation
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• v.33 no.4
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• pp.167-184
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• 2023

Objectives This study was designed to assess the effectiveness of ultrasound therapy at the ST11 for regulation of sympathetic hyperactivity. Methods Forty healthy adult subjects were assigned to experimental group and control group. After taking mental stress, ultrasound therapy was applied at the ST11 in experimental group and sham-ultrasound therapy was applied in control group. The evaluation of sympathetic activity was measured by blood pressure, pulse rate, and heart rate variability at 3 times (Time 1: before the stress stimulation, Time 2: after the stress stimulation, Time 3: after the intervention). The primary end point was consisted of normalized (norm) low frequency (LF)/high frequency (HF) ratio, LF (norm), HF (norm). The secondary end point was consisted of systolic blood pressure, diastolic blood pressure, pulse rate, mean heart rate, standard deviation of NN intervals, root mean square of the successive differences, total power (log). Results After the stress stimulation, all subjects showed sympathetic hyperactivity. After the intervention, the experimental group showed lower sympathetic activity than the control group. Comparing the Time 3 and Time 1, the experimental group showed no significantly differences in sympathetic activity while the control group showed higher sympathetic activity in Time 3 than Time 1. Comparing the Time 3 and Time 2, the experimental group showed lower sympathetic activity in Time 3 than Time 2 while the control group showed higher sympathetic activity in Time 3 than Time 2. Conclusions We suggest that the ultrasound therapy at ST11 can decrease sympathetic activity in sympathetic hyperactivity condition.

• Journal of the Korean Applied Science and Technology
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• v.40 no.4
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• pp.674-684
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• 2023

The purpose of this study was to investigate the effect of acute listening to music on the cardiovascular reactivity to sympathoexcitation. In this crossover design study, 15 healthy adults(23.1±1.94(yrs) were randomized to either (1)acute listen to the subject's preferred music for 30 minutes and (2)sat as a time control by an experiment coordinator. After completing each trial, the cold pressor test(CPT) was conducted. Heart rate(HR) and blood pressure(BP) were measured for 4 times at baseline, during and after the CPT. Heart rate variability(HRV) were measured for 3 times at baseline, prior and after the CPT. HR and BP increased during the CPT in both trial and returned to baseline after CPT(time effect, p < .001). After CPT, brachial systolic BP reactivity to the CPT was attenuated in listening to music trial compared to control trial(p = . 008). As a result of heart rate variability(HRV), the difference values between the baseline and prior to the CPT showed a significant increase in standard deviation of the NN intervals(SDNN), total power(TP) and high frequency(HF) only in the music trial (p = .001, p = .002, p = .011). The difference value between prior to and after the CPT did not show significance. But compared with the control trial, the music trial was confirmed that SDNN, TP and HF were more activated. Therefore, listening to music alleviated anxiety and tension before the CPT, and it is estimated that it had a favorable effect on stability after the CPT. This findings showed that listening to music may have a positive effect on brachial systolic BP and HRV to sympathoexcitation.

• Journal of Korea Water Resources Association
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• v.32 no.1
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• pp.3-13
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• 1999

In this study, an alternative spatial analysis method against conventional methods such as Thiessen method, Inverse Distance method, and Kriging method, named Spatial-Analysis Neural-Network (SANN) is presented. It is based on neural network modeling and provides a nonparametric mean estimator and also estimators of high order statistics such as standard deviation and skewness. In addition, it provides a decision-making tool including an estimator of posterior probability that a spatial variable at a given point will belong to various classes representing the severity of the problem of interest and a Bayesian classifier to define the boundaries of subregions belonging to the classes. In this paper, the SANN is implemented to be used for analyzing a mean annual precipitation filed and classifying the field into dry, normal, and wet subregions. For an example, the whole area of South Korea with 39 precipitation sites is applied. Then, several useful results related with the spatial variability of mean annual precipitation on South Korea were obtained such as interpolated field, standard deviation field, and probability maps. In addition, the whole South Korea was classified with dry, normal, and wet regions.

• Knowledge Management Research
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• v.19 no.2
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• pp.151-162
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• 2018

Response surface methodology (RSM) is one of popular tools to support a systematic improvement of quality of design in the product and process development stages. It consists of statistical modeling and optimization tools. RSM can be viewed as a knowledge management tool in that it systemizes knowledge about a manufacturing process through a big data analysis on products and processes. The conventional RSM aims to optimize the mean of a response, whereas dual-response surface optimization (DRSO), a special case of RSM, considers not only the mean of a response but also its variability or standard deviation for optimization. Recently, a posterior preference articulation approach receives attention in the DRSO literature. The posterior approach first seeks all (or most) of the nondominated solutions with no articulation of a decision maker (DM)'s preference. The DM then selects the best one from the set of nondominated solutions a posteriori. This method has a strength that the DM can understand the trade-off between the mean and standard deviation well by looking around the nondominated solutions. A posterior method has been proposed for DRSO. It employs an interval selection strategy for the selection step. This strategy has a limitation increasing inefficiency and complexity due to too many iterations when handling a great number (e.g., thousands ~ tens of thousands) of nondominated solutions. In this paper, a TOPSIS-based method is proposed to support a simple and efficient selection of the most preferred solution. The proposed method is illustrated through a typical DRSO problem and compared with the existing posterior method.

• The korean journal of orthodontics
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• v.39 no.5
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• pp.300-309
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• 2009

Objective: The purpose of this study was to evaluate the correlation between menton deviation and dental compensation in facial asymmetry. Methods: Tooth axis and distance of first molar and canine to the reference plane were investigated by cone-beam computerized tomography. The subjects consisted of 50 patients with asymmetric mandibles (male 21, female 29, mean age 24.3 years). Control groups were also assessed (male 11, female 9, mean age 25.6 years). Nine measurements (5 linear measurements and 4 angular measurements) were measured in order to evaluate the correlation between menton deviation and the linear and angular difference of first molar and canine in the deviated and none-deviated sides using the defined MPR images. The differences between deviated and non-deviated side, according to menton deviation, were statistically analyzed using stepwise multiple regression analysis. Results: From the result, Menton deviation was negatively correlated with mandibular first molar's angular measurement (${\Delta\angle}LM6$-Mn plane (dev.-ndev.)) and positively with maxillary fist molar's angular measurement (${\Delta\angle}UM6$-FH plane (dev.-ndev.)) (p < 0.01). Two angular measurements (${\Delta\angle}LM6$-Mn plane (dev.-ndev.), ${\Delta\angle}UM6$-FH plane (dev.-ndev.)) explained the variability in menton deviation with a significant $r^2$ value of 0.589. Conclusions: This study suggests that the tooth axis of upper and lower first molars leans towards the deviated side of Menton when there is mandibular asymmetry with Menton deviation.

• Journal of Life Science
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• v.19 no.2
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• pp.271-276
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• 2009

The Purpose of this study was to examine the effects of boxing aerobic training on resting heart rate variability (HRV) in females. The subjects for this study were performed 16 female college students that aged 19-23. The subjects were divided into two groups; boxing aerobic exercise group (9 students) and control group (7 students). Boxing aerobic training program was performed three times a week for twelve weeks with $VO_{2max}$ 60-80% exercise intensity. The results of this study were following; 1. Mean HRT (mean heart rate) had no signigicant difference among the groups and exercise time. 2. SDNN (standard deviation of the normal to normal interval) had no significant difference among the group and exercise time. 3. RMS-SD (square root of the mean squared differences of successive normal to normal interval) had no significant difference among the groups and exercise time. 4. TP (total power) had no significant difference among the groups and exercise time. 5. LF (low frequency) had no significant difference among the groups and exercise time. 6. HF (high frequency) had no significant difference among the groups and exercise time. 7. LF/HF (low frequence/high frequency ratio) had no significant difference among the groups and exercise time. 8. VLF (very low frequency) had no significant difference among the groups and exercise time.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.4
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• pp.300-307
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• 2009

The transport of landfill leachate in the subsurface formations of unlined landfill sites is considered. The impacts of hydrogeological and chemical heterogeneities on the leachate transport are assessed by examining the results from a series of Monte-Carlo simulations. The landfill system simulated in this study is hypothetically represented with three levels of spatial variability for the hydrogeological and chemical parameter; (1) homogeneous hydraulic conductivity (K) and distribution coefficient ($K_d$), (2) K heterogeneity only, and (3) combined heterogeneities of K and $K_d$. To calculate the transport of leachate through negatively-correlated random hypothetical K-$K_d$ fields generated using geostatistical input parameters, a saturated flow model is linked with a contaminant transport model. Point statistic values such as mean, standard deviation, and coefficient of variation of the concentration were obtained from 100 Monte-Carlo trials. Results of point statistics show that the heterogeneities of K and $K_d$ in the landfill site prove to be an important parameter in controlling leachate concentrations. Consideration of combined K and $K_d$ heterogeneities results in enhancing the variability of contaminant transport. The variability in the leachate concentration for different realizations also increases as the distance between source and monitoring well increase.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.42 no.3 s.303
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• pp.47-52
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• 2005

Obstructive Sleep Apnea (OSA) is a representative symptom of sleep disorder caused by the obstruction of upper airway. Because OSA causes not only excessive daytime sleepiness and fatigue, hypertension and arrhythmia but also cardiac arrest and sudden death during sleep in the severe case, it is very important to detect the occurrence and the frequency of OSA. OSA is usually diagnosed through the laboratory-based Polysomnography (PSG) which is uncomfortable and expensive. Therefore researches to improve the disadvantages of PSG are needed and studies for the detection of OSA using only one or two parameters are being made as alternatives to PSG. In this paper, we developed an algorithm for the detection of OSA based on Heart Rate Variability (HRV). The proposed method is applied to the ECG data sets provided from PhysioNet which consist of learning set and training set. We extracted features for the detection of OSA such as average and standard deviation of 1 minute R-R interval, power spectrum of R-R interval and S-peak amplitude from data sets. These features are applied to the input of neural network. As a result, we obtained sensitivity of $89.66\%$ and specificity of $95.25\%$. It shows that the features suggested in this study are useful to detect OSA.

• Science of Emotion and Sensibility
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• v.21 no.1
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• pp.71-82
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• 2018

Stress involves changes in behavior, autonomic function and the secretion of hormones. Autonomic nervous system (ANS) contributes to physiological adaptive process in short durations. In particular, heart rate variability (HRV) analysis is commonly used as a quantitative marker depicting the ANS activity related to mental stress. The aim of this study is to investigate correlations between psychological responses to stress and HRV indices induced by the cognitive stressor. Thirty-three participants rated their mental and physical symptoms occurred during the past two weeks on Stress Response Inventory (SRI), which is composed of seven stress factors that may influence the status of mental stress levels. Then, they underwent the psychophysiological procedures, which are collected electrocardiogram (ECG) signals during a cognitive stress task. HRV indices, the standard deviation of R-R interval (SDNN), root mean square of successive R-R interval difference (RMSSD) and low frequency (LF)/high frequency (HF) ratio were extracted from ECG signals. Physiological responses were calculated stress responses by subtracting mean of the baseline from the mean of recovery. Stress factors such as tension, aggression, depression, fatigue, and frustration were positively correlated to HRV indices. In particular, aggression had significant positive correlations to SDNN, RMSSD and LF/HF ratio. Increased aggressive responses to stress correlated with the increases of all HRV indices. This means the increased autonomic coactivation. Additionally, tension, depression, fatigue, and frustration were positively associated with RMSSD reflecting increases in parasympathetic activation. The autonomic coactivation may represent an integrated response to specific cognitive reactions such as the orienting response.