• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.35-40
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• 2011

An experimental study of the flame response in a turbulent premixed combustor has been conducted in order to investigate mechanisms for combustion instabilities in a lean premixed gas turbine combustor. A lab-scale combustor and mixing section system were fabricated to measure the flame transfer function. Measurements are made of the velocity fluctuation in the nozzle using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results show that the flame transfer functions are greatly dependent on the modulation frequency as well as operating conditions such as equivalence ratio. Flame dynamics can be generalized as a function of Strouhal number which is a ratio of flame length to modulation wave length.

• Physical Therapy Rehabilitation Science
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• v.12 no.2
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• pp.201-205
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• 2023

Objective: Resistance exercise is a necessary element to improve quality of life, and measurement and evaluation of muscle strength provide important information for prescription and management of rehabilitation and exercise programs. This study analyzed the correlation between direct and indirect 1RM for isokinetic maximum torque of the knee joint in order to provide useful information in the field of exercise programs. In addition, the flexion-extension ratio and the difference in left-right deviation were verified. Design: A cross-sectional study Methods: The subjects of this study were 33 healthy adult men and women without medical problems who participated in the health exercise class program at S University in Seoul. The correlation between isokinetic maximum torque and direct and indirect 1RM was analyzed, and a dependent t-test was performed to analyze the flexion-extension ratio and left-right deviation. Results: There was a high correlation between the isokinetic maximum torque and direct and indirect 1RM, and no statistically significant difference was shown between the test methods in the analysis of the flexion-extension ratio and left-right deviation. Conclusions: Isokinetic muscle function measuring equipment is expensive, so it is difficult to use it in local exercise rehabilitation and training sites. Through this study, it was found that direct and indirect 1RM isokinetic maximum torque showed a high correlation, and there was no difference in evaluating muscle function such as flexion-extension ratio and left-right deviation. Therefore, it is considered that the muscle function evaluation using 1RM in general field can be usefully utilized.

• The Journal of Internal Korean Medicine
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• v.29 no.3
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• pp.621-628
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• 2008

Objectives : The aim of this study was to investigate changes of gastric vagal nerve activity and pyloric valve function after execution of combination treatments of both electroacupuncture at Zusanli(ST36) and manual acupuncture at other acupoints in patient with functional dyspepsia. Methods : Bowel sounds of 49 patients (18 male, 31 female) were recorded and their % of bowel sound (%BS) and ratio of dominant frequency (DF) were analyzed. Postprandial %BS was used to indicate the gastric vagal activity after eating. Ratio of postprandial/fasting dominant frequency was used to present the degree of pyloric valve function. According to values of %BS and DF ratio, each patient was classified into normal or abnormal (<6 %BS, hypoactivity: <1 DF ratio, dysfunction) group. For 2 weeks, patients received a treatment consisting of both electroacupuncture stimulation at Zusanli (ST36) and acupuncture at other meridian points. Variation of parameters shifting normal to abnormal or abnormal to normal was observed, and total cure rate was calculated. Results : Total cure rate of %BS was 16%, and that of DF was 37%. Patients who improved to normal value from abnormal or aggravated to abnormal level showed both significant difference in both vagal nerve hypoactivity and pyloric valve dysfunction, respectively. Conclusions : Analysis of bowel sound might be useful to evaluate both gastric vagal nerve activity and pyloric valve function. Combination effects of Zusanli (ST36) electroacupuncture and manual acupuncture of other acupoints showed a bidirectional effect in which their activity and function were in general improved. sometimes from aggravated to abnormal level.

• Journal of Society of Preventive Korean Medicine
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• v.14 no.2
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• pp.105-120
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• 2010

Objectives : This study aims to evaluate the effects of expiration-to-inspiration time ratio (E/I-ratio) on heart rate, which represents cardiac autonomic function, and cold-heat in the healthy people. Methods : 49 healthy young volunteers(male : female = 32 : 17) were recruited in the study. The participants completed the questionnaire for yin-yang pattern identification and then we measured the chest plethysmogram for respiration signal and the electrocardiogram for NN intervals during different E/I-ratio from 1 to 2. We compared heart rate variability including RMS-SD, VLF, LF and HF, and the trend-cycle factors decomposed from NN interval data by time series analysis among the respective E/I-ratio. We also confirmed the difference on the trend-cycle factors according to the score of the questionnaire for cold and heat pattern identification. Results : There were differences on the trend-cycle factors from NN interval data, but no significant difference on heart rate variability, among the respective E/I-ratio. We also found significant relationship between the trend-cycle factors and the heat pattern identification scores. Conclusions : The results indicate that cardiac autonomic function can be modulated by the E/I-ratio and the modulation will be slower and more tendencious than respiratory sinus arrhythmia.

• Communications for Statistical Applications and Methods
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• v.31 no.1
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• pp.65-85
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• 2024

The tail probability of a function of a multivariate random variable is not easy to estimate by the crude Monte Carlo simulation. When the occurrence of the function value over a threshold is rare, the accurate estimation of the corresponding probability requires a huge number of samples. When the explicit form of the cumulative distribution function of each component of the variable is known, the inverse transform likelihood ratio method is directly applicable scheme to estimate the tail probability efficiently. The method is a type of the importance sampling and its efficiency depends on the selection of the importance sampling distribution. When the cumulative distribution of the multivariate random variable is represented by a copula and its marginal distributions, we develop an iterative algorithm to find the optimal importance sampling distribution, and show the convergence of the algorithm. The performance of the proposed scheme is compared with the crude Monte Carlo simulation numerically.

• Journal of Chest Surgery
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• v.25 no.11
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• pp.1169-1179
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• 1992

To determine the period and degree of full recovery of postoperative pulmonary function, the author performed seiral pulmonry function test with spirometry at preoperative period and 1st, 2nd, 3rd, 4th, 6th and 8th postoperative week in 64 patients who underwent chest surgery form 1990. 1. to 1990. 8. at Dep. of Thoracic & Cardiovascular surgery, Pusan National University Hospitcal, Pusan, Korea 28 patients underwent lung resection[Group A], 14 patients mediastinal and other thoracic surgery[Group B], and 22 patients heart surgery with cardiopulmonary bypass[Group C]. Al of them recovered normally and discharged without any complications. Their serial changes of pulmonary function test were compaired and its results was as follows; l. Over all mean recovery time of restrictive ventilatory function tests[ie, VC, ERV, IC, FEF1, FVC, FEF200-1200, MVV] were 4th & 6th postoperative week, and that of obstructive ventilatory function tests[ie., EFE25-75%, Vmax50] were 2nd postoperative week. 2. In patient who underwent lung resection surgery[Group A], FEF1 recovered in 4th~6th postoperative week and its ratio to preoperative value was 70% in pneumonectomy, and 75% in lobectomy. FVC recovered in 4th~6th postoperative week and its ratio to preoperative value was 65% in pneumonectomy, and 80% in lobectomy. MVV was recovered in 4th~8th postoperative week and recovery ratio was 80%, FEF200-1200 was recovered at 4th~6th postoperative week and its recovery ratio was 70%, FEF25-75% and Vmax50 was recovered in 2nd~4th postoperative week and recovered nearly to preoperative level. 3. In patient who underwent mediastinal and other thoracic surgery[Group B], FEV1 and FVC and recovered in 4th~6th postoperative week and the recovery ratio of FVC in blebectomy was 90%. MVV reached preoperative level in 4th~8th postoperative week. FEF200-1200, FEF25-75% and Vmax50 were recovered in 2nd~4th postoperative week and the recovery of FEF25-75% and Vmax50 in blebectomy was prominant. 4. In patient who underwent heart surgery[Group C], FEV1 and FVC were recovered in 4th~6th postoperative week. The recover ratio of FEF25-75% and Vmax50 was delaied to 6th~8th postoperative week From the above results we concluded that the recovery time of posoperative restrictive ventilatory disorder was 4th postoperative week and pulmonary complication would possibly occure during that period. So more intensive observations will be needed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.6
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• pp.727-737
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• 2010

Together with the Young's modulus the Poisson's ratio is another independent material parameter that governs the behavior of a structural system. Therefore, it is meaningful to evaluate separately the influence of the parameter on the random response of the structural system. To this end, a formulation dealing with the spatial randomness in the Poisson's ratio in laminated composite plates is proposed. The main idea of the paper is to transform the fraction form of the constitutive coefficients into the expanded form in an ascending order of the stochastic field function. To validate the adequacy of the formulation, a square plate is chosen and the computation results are compared with those obtained using conventional Monte Carlo simulation. It is observed that the results show good agreement with those by the Monte Carlo simulation(MCS).

• The Korean Journal of Health Service Management
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• v.4 no.1
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• pp.87-97
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• 2010

The study analyzed the cash flow and external funding in focusing on the relationship of the two factors in Korean hospitals and some changes in the relationship. The results analyzing this study were summarized as follows: First, the discriminant function of new external funds was generally the ratio of cash flow from operating activities to sales, the ratio of cash flow from investment activities to sales, the ratio of cash flow from financing activities to sales in order. The prediction rate of total discriminant function was more than 92%. Second, in case of Korean hospitals, it was known that the ratio of cash flow from operating activities to sales, particularly the net income to sales was the biggest influencing factor on the decision to external funding.

• Journal of the Korean Home Economics Association
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• v.40 no.3
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• pp.83-97
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• 2002

This study estimates the consumption needs of preretired households through target replacement ratio approach. Based on the Life Cycle Model, this study used the household expenditure function to derive the target replacement ratio appropriate for each household. The target replacement ratio is estimated using the 1996 National Survey of family Income and Expenditure by National Statistical Office. The estimated target replacement ratio was 82.4% for married couple households, and 85.1% for single households. Total retirement consumption needs during entire retirement period was 161,620,000 won for married couple households, and 50,532,039 won for single households.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.735-740
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• 2003

In this study, a numerical optimization to find the optimal shape of streamwise periodic ribs mounted on both of the principal walls is performed to enhance turbulent heat transfer in a rectangular channel. The optimization is based on Navier-Stokes analysis of flow and heat transfer with $k-{\varepsilon}$ turbulence model and is implemented using response surface method. The width-to-height ratio of a rib, rib height-to-channel height ratio, rib pitch to rib height ratio and distance between opposite ribs to rib height ratio are chosen as design variables. The object function is defined as a function of heat transfer coefficient and friction drag coefficient with weighting factor. Optimum shapes of the rib have been investigated for the range of 0.0 to 0.1 of weighting factor.