• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.391-398
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• 2004

The propagation mechanism of a detonation pressure with fully coupled charge is clarified and the blasting pressure propagated in rock mass is derived from the application of shock wave theory. Probabilistic distribution is obtained by using explosion tests on emulsion and rock property tests on granite in Seoul and then the probabilistic distribution of the blasting pressure is derived from their properties. The probabilistic distributions of explosive properties and rock properties show a normal distribution so that the blasting pressure propagated in rock can be also regarded as a normal distribution. Parametric analysis was performed to pinpoint the most influential parameter that affects the blasting pressure and it was found that the detonation velocity is the most sensitive parameter. Moreover, uncertainty analysis was performed to figure out the effect of each parameter uncertainty on the uncertainty of blasting pressure. Its result showed that uncertainty of natural rock properties constitutes the main portion of blasting pressure uncertainty rather than that of explosive properties.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1273-1281
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• 2003

The present study is mainly motivated to investigate the vaporization, auto-ignition, and combustion of liquid fuel spray injected into high pressure environment. The unsteady, multi-dimensional models were used for realistic simulation of spray as well as prediction of accurate ignition delay time. The Separated Flow (SF) model which considers the finite rate of transport between liquid and gas phases was employed to represent the interactions between spray and gas field. Among the SF models, the Discrete Droplet Model (DDM) which simulates the spray using finite number of representative samples of discrete droplets was adopted. The Eulerian-Lagrangian formulation was used to analyze the two-phase interactions. In order to predict an evaporation rate of droplet in high pressure environment, the high pressure vaporization model was applied using thermodynamic equilibrium and phase equilibrium at droplet surface. The high pressure effect as well as high temperature effect was considered in the calculation of liquid and gas properties. In case of vaporization, an interaction between droplets was studied through the simulation of spray. The interaction is shown up differently whether the ambient gas field is at normal pressure or high pressure. Also, the characteristics of spray behavior in high pressure environment were investigated through the comparison with normal ambient pressure case. In both cases, the spray behaviors are simulated through the distributions of temperature and reaction rate in gas field.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 춘계학술대회논문집
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• pp.140-143
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• 1997

The present study is concerned with the hydrostatic extrusion process of copper-clad aluminium bar to investigate the basic flow characteristics. Considering the bonding mechanism of bi-metal contact surface as cold pressure welding, the normal pressure and the contact surface expansion are selected as process parameters governing the bonding condition. The critical pressure required for the bonding at the interface is obtained by solving a "local extrusion" using a slip line meyhod. A viscoplastic finite element method is used to analyze the steady state extrusion process. The boundary profile of bi-metal rod is predicted by tracking a particle path adjacent to interface surface. The variations of contact surface area and the normal pressure along the interface profile are predicted and compared to those by experiments.

• 대한한방내과학회지
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• 제18권2호
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• pp.160-166
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• 1997

To evaluate the effect of acupuncture on the hypertension, the study was done by acupuncture on bilateral Inyong(ST9) with rats which are normal and acutely increased hypertensive. The results are as follows: 1. Under the normal condition, the acupuncture on bilateral Inyong caused a quick drop of mean arterial pressure(MAP), but heart rate(HR) was not changed significantly. 2. To increase the blood pressure, acutely epinephrine was administered and it caused a increase in both MAP and HR. With acupuncture, the MAP was decreased while HR did not show a significant change. In conclusion, the acupuncture was somewhat effective in lowering the mean arterial pressure in the rat.

• 대한인간공학회지
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• 제33권2호
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• pp.143-153
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• 2014

Objective: The aim of this study is to investigate the effects of trunk-forearm supported sitting on trunk flexion angle, trunk extensor fatigue and seat contact pressure. Background: The relationship between sitting posture and musculoskeletal disorders of the trunk extensor fatigue and seat contact pressure has been documented. The trunk-forearm support type ergonomic chair was devised from the fact that trunk-forearm support has been reported to reduce trunk extensor activity and discomfort. Method: Using three different sitting postures, upright ($P_1$), trunk-forearm supported ($P_2$) and normal sitting ($P_3$), six healthy subjects participated in the study. Motion capture system was used to collect head and trunk flexion angle, and surface electromyography (sEMG) was used to collect myoelectric signal of upper trapezius, lower trapezius, erector spinae, multifidus, and pressure mat system was used to measure seat contact pressure. Results: When trunk and forearm were supported by the ergonomic chair, higher head flexion angle showed upright > trunk-forearm supported > normal in order, and muscle fatigue showed less than upright and normal sitting. Mean seat contact pressure decreased 19% than upright sitting. But muscle fatigue was not affected by each condition. Conclusion: Trunk-forearm supported sitting of the ergonomic chair showed positive effect in respect of trunk and head flexion angle, trunk extensor fatigue, seat contact pressure. To acquire comprehensive understanding of the effectiveness of the ergonomic chair, further studies such as anatomical effects from measurement of external applied loading effect to the body from interface pressure analysis are required. Application: The results of the publishing trend analysis might help physiological effects of trunk-forearm support type chair.

• 한국보건간호학회지
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• 제17권1호
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• pp.144-152
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• 2003

The purpose of this study is to identify the prevalence rate of hypertension and diabetes a in the urban communities and to provide the basic data for development of health promot The subjects of this study were 526 people over the age of 20, living in Seoul. Data for this collected from June 19, 2001 to September 25, 2001. The results of this study are as follows: 1. The subject group is comprised of males, $57.4\%$ and females, $42.6\%$. Their ages range from 20 to 89, and the weights from 40 to 94 kilograms. 2. In the systolic blood pressure, $36.1\%$ showed high, $56.5\%$ normal. and $7.4\%$ low. In the diastolic blood pressure, $50.5\%$ showed high, $48.9\%$ normal, and $1.7\%$. low. In the blood glucose, $70.3\%$ showed normal. $27.9\%$ high, and $1.7\%$. low. 3. There was a significant difference in the mean(SD) of the systolic blood pressure by age(p=.017) and weight(p=.005). Another significant difference was found in the mean (SD) of the diastolic blood pressure by age(p=.006) and weight(p=.007). There was a significant difference in the mean(SD) of the blood glucose by sex and age(p=.001). 4. There were significant correlations between the blood pressure and the blood glucose and the sex, age and weight. 5. The multiple regression analysis showed that the age and weight explained $9.9\%$ of the systolic blood pressure, that the weight and age explained $7.1\%$ of the diastolic blood pressure, and that the age and systolic blood pressure explained $7.0\%$ of blood glucose. The results were useful in developing health promotion programs. This study suggests that a further study be needed.

• 소성∙가공
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• 제11권1호
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• pp.69-74
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• 2002

In addition to lightweight and moldable characteristics, polymeric foams possess an excellent energy absorbing capability that can be utilize for a wide range of commercial applications, especially in the crashworthiness of the automobiles. The purpose of the present study is to develop experimental methodology to characterize the pressure dependent yield behavior of the energy absorbing polymeric foams. For the compression test in a triaxial stress sate, a specially designed device was placed in a hydraulic press to produce and control oil pressure. For the test material, the polyurethane foams of two different densities were used. The displacement of the specimen, the load subjected to the specimen, and oil pressure applied to the specimen were measured and controlled. Stress strain curves and yield stresses for the four different oil pressure were obtained. It was found from the present experiments that the polyurethane foams exhibited significant increases in yield stress with applied pressure or mean normal stress. Based on this observation, a yield criteria which included the effect of the stress invariant were established for the polymeric foams. The obtained experimental constants which constituted the pressure-dependent yield criterion were verified.

• 대한후두음성언어의학회지
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• 제10권1호
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• pp.50-57
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• 1999

A study to get the data of normal stop consonants production as preliminary study for cleft palate patients was performed. Normal Korean native 21 speakers were pronounced $VCV(V=/a/,C=/P/,/{P^1}/,/P^h/,/t/,/{t^1}/,/{t^h}/,/k/,/{k^1}/,/{k^h}/)$ syllables with natural speech rate and intensity. With intrapharyngeal pressure waveforms by pressure sensor in oropharyngeal cavity, amplitude and time duration of intrapharyngeal pressure were analyzed, and with acoustic waveforms and spectrograms, closure duration and VOT were analyzed. As results, the highest amplitude of intrapharyngeal pressure showed in alveolars and heavily aspirated consonants. Velars and unaspirated consonants were higher than bilabials and slightly aspirated ones each, in intrapharyngeal pressure. Bilabilas, alveolars and velars showed similar rise time of intrapharyngeal pressure build-up, but in decay time and total duration time, bilabials were slightly shorter than alveolars and velars, with no statistic significance. In the aspects of tensity, unaspirated consonants showed the longest rise time, heavily aspirated, the second, and slightly aspirated consonants, the shortest, which were also seen in decay time and total duration time. In closure duration, slightly aspirated consonants had the shortest closure duration, and the heavily aspirated ones, the second, and unaspirated consonants showed the longest. In VOT, heavily aspirated consonants showed the longest, slightly aspirated ones, the second and unaspirated ones showed the shortest.

• Clinical and Experimental Pediatrics
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• 제57권9호
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• pp.403-409
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• 2014

Purpose: Although high morning blood pressure (BP) is known to be associated with the onset of cardiovascular events in adults, data on its effects in children with hypertension are limited. Our retrospective study aimed to define the clinical characteristics of children with morning hypertension (MH) and to determine its associated factors. Methods: We reviewed 31 consecutive patients with hypertension, confirmed by the ambulatory blood pressure monitoring (ABPM). We divided these patients into 2 groups: the MH group (n=21, 67.7%), morning BP above the 95th percentile for age and height (2 hours on average after waking up) and the normal morning BP group (n=10, 32.3%). We compared the clinical manifestations, laboratory results, and echocardiographic findings including left ventricular hypertrophy (LVH) between the groups. Results: The early/atrial (E/A) mitral flow velocity ratio in the MH group was significantly lower than that in the normal morning BP group. In addition, LV mass was higher in the MH group than in the normal morning BP group, although the difference was not statistically significant. The age at the time of hypertension diagnosis was significantly higher in the MH group than in the normal morning BP group (P =0.003). The incidence of hyperuricemia was significantly higher in the MH group than in the normal morning BP group. Conclusion: Older patients and those with hyperuricemia are at higher risk for MH. The rise in BP in the morning is an important factor influencing the development of abnormal relaxation, as assessed by echocardiography. Clinical trials with longer follow-up periods and larger sample sizes are needed to clarify the clinical significance of MH.

• 한국항공우주학회지
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• 제32권8호
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• pp.64-71
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• 2004

측 추력(Lateral Jet)을 이용하여 자세를 제어하는 미사일 주위의 초음속 유동장 해석을 위하여 삼차원 Navier-Stokes 코드 (AADL3D)를 개발하고, 이를 이용한 수치해석 연구를 수행하였다. 분출 제트 압력, 분출 마하수 등을 포함하는 제트의 유동특성이 미사일에 미치는 수직력 및 피칭모멘트에 대한 영향을 알아보기 위한 사례연구를 수행하였으며, 공력 해석 결과 제트의 분출 압력과 분출 마하수 변화에 따른 서로 다른 수직력과 모멘트 변화 양상 및 그 원인을 확인할 수 있었다. 또한 대부분의 수직력 손실과 피칭모멘트 발생은 노즐 후방의 저압영역에 의한 것이며, 동일한 제트 추력일지라도 분출 마하수가 큰 경우가 분출 압력이 큰 경우보다 모멘트 발생 최소화에 유리함을 확인하였다.