• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.117-117
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• 2016

The natural hydrologic regime is intimately tied to the structure and function of stream and riparian ecosystems. Consequently, understanding the nature and extent of perturbations to the hydrologic regime, stemming from episodic-to-seasonal and longer-term climatic variations, as well as anthropogenic influences is an important starting point for developing an improved understanding of the coupled human-environmental systems. Herein, we pursued to explicate sensitivity of ecologically relevant flow metrics to climate variability and extremes in the five major river basins, Korea.

• Journal of the Korean earth science society
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• v.40 no.5
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• pp.476-486
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• 2019

This study examines the controlling role of synoptic disturbances on $PM_{10}$ spring variability in the Korean Peninsula by using empirical orthogonal function (EOF) and back trajectory analyses. Three leading EOF modes are identified, and a lead-lag analysis suggests that $PM_{10}$ variabilities be closely related to the synoptic weather systems. The first EOF shows the spatially homogeneous distribution of $PM_{10}$, which is influenced by travelling anticyclonic disturbance with negative precipitation and descending motion. The second and third modes exhibit the dipole structures of $PM_{10}$, being associated with propagating cyclones. Furthermore, the back-trajectory analysis suggests that the transport of pollutants by anomalous winds associated with synoptic disturbances also contribute to the altered $PM_{10}$ concentration. Hence, a substantial synoptic control should be considered in order to fully understand the $PM_{10}$ spatiotemporal variability.

• Speech Sciences
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• v.12 no.4
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• pp.17-29
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• 2005

Time-frequency representation reveals some useful information about instantaneous frequency, instantaneous bandwidth and boundary of each AM-FM component of a speech signal. In many cases, the instantaneous frequency of each component is not constant. The variability of instantaneous frequency causes degradation of resolution in time-frequency representation. This paper presents a method of adaptively adjusting the transform kernel for preventing degradation of resolution due to time-varying instantaneous frequency. The transform kernel is the form of frequency modulated function. The modulation function in the transform kernel is determined by the estimate of instantaneous frequency which is approximated by first order polynomial at each time instance. Also, the window function is modulated by the estimated instantaneous. frequency for mitigation of fringing. effect. In the proposed method, not only the transform kernel but also the shape and the length of. the window function are adaptively adjusted by the instantaneous frequency of a speech signal.

• Journal of Mechanical Science and Technology
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• v.20 no.10
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• pp.1662-1669
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• 2006

Since randomness and uncertainties of design parameters are inherent, the robust design has gained an ever increasing importance in mechanical engineering. The robustness is assessed by the measure of performance variability around mean value, which is called as standard deviation. Hence, constraints in robust optimization problem can be approached as probability constraints in reliability based optimization. Then, the FOSM (first order second moment) method or the AFOSM (advanced first order second moment) method can be used to calculate the mean values and the standard deviations of functions describing constraints and object. Among two methods, AFOSM method has some advantage over FOSM method in evaluation of probability. Nevertheless, it is difficult to obtain the mean value and the standard deviation of objective function using AFOSM method, because it requires that the mean value of function is always positive. This paper presented a special technique to overcome this weakness of AFOSM method. The mean value and the standard deviation of objective function by the proposed method are reliable as shown in examples compared with results by FOSM method.

• Journal of Oriental Neuropsychiatry
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• v.13 no.1
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• pp.19-37
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• 2002

Objectives : This study sought to define autonomic functional difference on heart rate variability between headache patients and normal subjects Methods : We determined, heart rate variability of 52 headache patients and 30 normal subjects by means of three time domain measures: Mean PR(mean pulse rate), SDNN(standard deviation of all normal R-R intervals), RMSSD(the square root of the mean of sum of the squares of differences between adjacent normal R-R intervals), and five frequency domain measures: TP(total power), VLF(very low frequency), LF(low frequency), HF(high frequency). Results : 1) RMSSD, TP, HF, HF Norm of HRV decreased with aging and LF Norm, LF/HF increased with aging in headache patients. 2) There was no significant differences between migraine and tention headache in any standard index of HRV, whereas, HRV of total headache patients were smaller than those of normal subjects. 3) In the gender comparison, SDNN, RMSSD, HF of tention headache patients were the smallest and then migraine patients, normal subjects in order with man, whereas, LF Norm, LF/HF of normal subjects were the smallest with man. RMSSD of migraine patients were the smallest and then tention headache patients, normal subjects in order with women. 4) In the term of history of headache patients, SDNN, RMSSD were getting lower as long term. 5) There was no significant differences of HRV in physical symptom of headache patients. Conclusions : All of these results show that standard index of HRV of headache patients were significantly different with normal subjects.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.1
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• pp.63-68
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• 2014

PURPOSE: The purpose of this study was to examine the position changes with tilt table on autonomic nervous system using heart rate variability analysis. METHODS: Fourty healthy adult males volunteered in this study. The low frequency, high frequency and low frequency/high frequency ratio and mean heart rate, standard deviation of all normal R-R intervals, root mean square of successive differences, heart rate variability index were measured at the tilt table angle of $0^{\circ}$, $45^{\circ}$ and $90^{\circ}$ with pulsoximeter. Data were analyzed one-way ANOVA and LSD post hoc test. RESULTS: The mean heart rate, low frequency and low frequency/high frequency ratio increased significantly at higher angle of tilt table(p<.05). The root mean square of successive differences, heart rate variability index decreased significantly at lower angle of tilt table(p<.05). The standard deviation of all normal R-R intervals, high frequency decreased at higher angle of tilt table did not show significant difference. CONCLUSION: The symphathetic activity increased significantly at higher angle of tilt table. The parasymphathetic activity decreased at higher angle of tilt table, but the difference were not significant. The autonomic adaptation, balance and heart rate variability decreased significantly at higher angle of tilt table. Based on these results, in the treatment of patients with a change in posture precedence should be carefully treated. Further studies are necessary to determine the most safety and effective methods.

• Atmosphere
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• v.24 no.1
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• pp.29-38
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• 2014

A characteristic of snowfall and minimum temperature variability in South Korea with respect to the variability of Arctic Oscillation (AO) was investigated. The climatic snowfall regions of South Korea based on daily new fresh snowfall data of 59 Korea Meteorological Administration (KMA) stations data corresponding to the sign of AO index during December to February 1979~2011 were classified. Especially, the differences between snowfalls of eastern regions and that of western regions in South Korea were seen by each mean 1000hPa geopotential height fields, which is one of physical structure, for the selected cases over the East Asia including the Korean Peninsula. Daily minimum temperature variability of 59 KMA station data and daily AO index during the same period were investigated using Cyclo-stationary empirical orthogonal function (CSEOF) analysis. The first CSEOF of wintertime daily AO index and that of minimum temperature of 59 KMA stations explain 33% and 66% of total variability, respectively. Correlation between principal component time series corresponding to the first CSEOF of AO index and that of temperature at the period of 1990s is over about -0.7 when that of AO index leads about 40 days.

• The Journal of Pediatrics of Korean Medicine
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• v.25 no.3
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• pp.77-84
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• 2011

Objectives: This study was performed to investigate the effect of hot spring therapy on children weight, body composition and heart rate variability. Methods: The study was carried out from 30 children who visited the spa from August 1, 2011 to August 31, 2011. We measured the change of weight, body composition, and heart rate variability after hot spring therapy for an hour per day. Results: The subject was consisted of 13 boys and 17 girls. This study revealed that their weight got lost from a hot spring therapy, which was statistically significant. Their body mass index(BMI) was decreased in from a hot spring therapy, which was not statistically significant. Total body water, muscle, protein, and mineral were decreased from a hot spring therapy, which was statistically significant. We measured HRV(heart rate variability) before and after the hot spring therapy. The mean HRT was increased, which was statistically insignificant. SDNN(standard deviation of the NN interval) and RMSSD(square root of the mean of the sum of the square of differences) were not different before and after the hot spring therapy. ln TP was decreased insignificantly. ln VLF was not affected before and after hot spring therapy. ln LF and ln HF was decreased, LF norm was increased, and HF norm was decreased, which were not statistically significant. Also, LF/HF ratio was increased insignificantly. Conclusions: From these results, we concluded that the weight, total body water, muscle, protein, and mineral got lost from the hot spring therapy. However, the HRV was not affected from the hot spring therapy.

• Journal of Korean Medicine for Obesity Research
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• v.8 no.1
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• pp.63-70
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• 2008

Objectives Obesity is the major risk factor of the heart disease and the metabolic disease. The autonomic nervous system is a key contributor in the regulation of energy balance, so the blunted activity may contribute to the maintenance of the obese state. So we evaluated the function of the autonomic nervous system in young overweight and obese women with heart rate variability. Methods The subjects were 26 overweight and obese young women(BMI〉$23kg/m^2$) and 25 lean women who visited Kangnam Kyunghee hospital for obesity management from March 2006 to April 2008. Bioimpedance Analysis (BIA), short-term spectral analysis of heart rate variability (HRV) were performed. Results HRV of obese young group was lower than the lean young group, but there is no statistical significance. BMI had significantly a negative correlation with Low Frequency(LF) of HRV. LF power is mediated by sympathetic nervous system activity. These results indicate a decrease of sympathetic modulation in overweight and obese young women. Conclusions Overweight and obese young women have decreased sympathetic nervous system activity. In clinical practice, an assessement of HRV would be noninvasive and sensitive methods for sympathetic nervous system of young overweight and obese women.

• Anxiety and mood
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• v.2 no.2
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• pp.101-107
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• 2006

Object : Since autonomic nerve system dysfunction was known as the mechanism of panic disorder, many researchers used heart rate variability (HRV) as means of measuring autonomic nerve function of patients with panic disorder. We aimed to examine the effect of paroxetine medication for 3 months on symptom improvement and change of heart rate variability of the patients with panic disorder. Methods : The subjects were patients with panic disorder who visited the psychiatric outpatient clinic of Samsung Medical Center in Seoul. We included panic disorder patients who were aged from 20 to 50 and in normal BMI range (from 18 to 30) to minimize the effect of age and weight on HRV data. We excluded the patients with EKG abnormalities, hypertension or other major psychiatric disorders. They took 20-40 mg paroxetine medication a day for 3 months. Alprazolam was used only during the first month to control the acute panic symptoms and was tapered off after that. We measured the acute panic inventory (API), Hamilton rating scale for anxiety and depression (HAM-A & HAM-D), Spielberger state-trait anxiety inventory (STAIS, STAIT), and Beck depression inventory (BDI) in order to assess clinical improvement of the patients. And we measured time and frequency domain HRV in the resting, standing and cognitive stress states to assess the change of HRV. All measurements were done before and after paroxetine treatment. Result : After paroxetine medication, patients showed significant improvement in all psychiatric scales. In time domain of HRV, standard deviations of all R-R intervals (SDNN) were significantly increased in all states. In frequency domain of HRV, the ratio of high frequency to total power (HF/TP) in the standing state was significantly increased. Conclusion : After 3 months paroxetine medication, panic disorder patients showed significant clinical improvement and change in HRV data such as SDNN in all states and HF/TP ratio in the standing state. This result suggests that paroxetine medication is effective for the improvement of autonomic nerve system dysfunction in panic disorder patients.