• Elastomers and Composites
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• 제38권1호
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• pp.51-56
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• 2003

Cloud-point and bubble-point data to $170^{\circ}C$ and 50 bar are presented for four different solvents, normal pentane. n-hexane, n-heptane, and n-octane with poly(ethylene-co-42 wt% octene) ($PEO_{42}$) copolymer. The pressure-concentration isotherms measured for $PEO_{42}$ - normal pentane have maximums at around 5 wt% of the copolymer concentrations in the solution. $PEO_{42}$- normal pentane system exhibits LCST-type phase behavior at temperatures greater than $130^{\circ}C$. Below $120^{\circ}C$, bubble-point type transitions are observed. However, the binary mixtures for $PEO_{42}$ in n-hexane, n-heptane, and n-octane have only bubble-point type transitions at the pressure-temperature region investigated in this study. The single-phase region of PEO - alkane mixtures increases with the molecular size of alkane solvent due to the increasing dispersion interactions between PEO and the alkane.

• Journal of Mechanical Science and Technology
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• 제14권1호
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• pp.93-102
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• 2000

The objective of the present study is to investigate the pressure-strain correlation terms of the Reynolds stress models for the three dimensional turbulent boundary layer in a $30^{\circ}$ bend tunnel. The numerical results obtained by models of Launder, Reece and Rodi (LRR) , Fu and Speziale, Sarkar and Gatski (SSG) for the pressure-strain correlation terms are compared against experimental data and the calculated results from the standard k-${\varepsilon}$ model. The governing equations are discretized by the finite volume method and SIMPLE algorithm is used to calculate the pressure field. The results show that the models of LRR and SSG predict the anisotropy of turbulent structure better than the standard k-${\varepsilon}$ model. Also, the results obtained from the LRR and SSG models are in better agreement with the experimental data than those of the Fu and standard k-${\varepsilon}$ models with regard to turbulent normal stresses. Nevertheless, LRR and SSG models do not effectively predict pressure-strain redistribution terms in the inner layer because the pressure-strain terms are based on the locally homogeneous approximation. Therefore, to give better predictions of the pressure-strain terms, non-local effects should be considered.

• 농촌의학ㆍ지역보건
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• 제30권1호
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• pp.29-38
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• 2005

전북지역의 김제시의 2개 초등학교 4-6학년 학부모 434명을 대상으로 2003년 11월 20일부터 2003년 11월 30일까지 10일간 자기 기입식 방법으로 설문조사한 결과는 다음과 같다. 첫째, 고혈압 관련 지식의 정답률은 77.4%-94.5%로서 비교적 높게 나타났으며 이중 고혈압에 대한 혈압수치의 정답률이 77.4%로서 제일 낮았다. 그러나 비만인 사람이 고혈압에 더 걸리기 쉽다는 응답의 정답률이 94.5%로서 높은 지식을 나타냈다. 둘째, 혈압측정을 실천했는지를 분석한 결과 아버지 측정율이 53.7%인 반면 어머니의 측정율은 54.8%로서 높지 않게 나타났다. 셋째, 측정한 학부모들의 자기혈압을 알고 있는지 분석한 결과 알고 있다는 인지율이 아버지는 84.1%, 어머니는 91.1%로서 비교적 잘 알고 있었으며 이들이 작성한 자기 혈압 수치를 혈압 분류기준에 따라 분석한 결과 아버지들의 고혈압 전단계(120-139mmHg/80-89mmHg) 비율이 12.2% 및 고혈압(140/90mmHg)이 28.6%로 나타났다, 반면 어미니들의 고혈압 전 단계 비율이 7.7% 및 18.2%로 나타났다. 이와 같은 연구 결과를 기초로 다음과 같은 결론 및 제안을 하고자 한다. 첫째, 고혈압의 예방 및 관리를 위하여 지역 사회 대상 접근 방법이 기존의 보건의료기관에서 내소자를 중심으로 개인 대상 접근 방법보다 더 중요함을 시사하므로 적극적인 홍보가 실시되어야 한다. 둘째, 지역주민이 갖고 있는 고혈압관련지식 수준은 비교적 높은데 이러한 지식을 생활하면서 실천 하는 능력을 향상시키는 것이 매우 중요하다. 그러므로 지역사회 고혈압 예방 및 관리에서 학교라는 지역 사회시설과 감수성이 높고 교육효과가 크다고 증명된 초등학생들을 적극 활용하는 것이 중요하므로 초등학교에 고혈압 예방교육이 실시되어야 한다.

• Journal of Korean Neurosurgical Society
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• 제46권4호
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• pp.370-377
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• 2009

Objective : There is no definite adjustment protocol for patients shunted with programmable valves. Therefore, we attempted to find an appropriate method to adjust the valve, initial valve-opening pressure, adjustment scale, adjustment time interval, and final valve-opening pressure of a programmable valve. Methods : Seventy patients with hydrocephalus of various etiologies were shunted with programmable shunting devices (Micro Valve with $RICKHAM^{(R)}$ Reservoir). The most common initial diseases were subarachnoid hemorrhage (SAH) and head trauma. Sixty-six patients had a communicating type of hydrocephalus, and 4 had an obstructive type of hydrocephalus. Fifty-one patients had normal pressure-type hydrocephalus and 19 patients had high pressure-type hydrocephalus. We set the initial valve pressure to $10-30\;mmH_2O$, which is lower than the preoperative lumbar tapping pressure or the intraoperative ventricular tapping pressure, conducted brain computerized tomographic (CT) scans every 2 to 3 weeks, correlated results with clinical symptoms, and reset valve-opening pressures. Results : Initial valve-opening pressures varied from 30 to $180\;mmH_2O$ (mean, $102{\pm}27.5\;mmH_2O$). In high pressure-type hydrocephalus patients, we have set the initial valve-opening pressure from 100 to $180\;mmH_2O$. We decreased the valve-opening pressure $20-30\;mmH_2O$ at every 2- or 3-week interval, until hydrocephalus-related symptoms improved and the size of the ventricle was normalized. There were 154 adjustments in 81 operations (mean, 1.9 times). In 19 high pressure-type patients, final valve-opening pressures were $30-160\;mmH_2O$, and 16 (84%) patients' symptoms had nearly improved completely. However, in 51 normal pressure-type patients, only 31 (61%) had improved. Surprisingly, in 22 of the 31 normal pressure-type improved patients, final valve-opening pressures were $30\;mmH_2O$ (16 patients) and $40\;mmH_2O$ (6 patients). Furthermore, when final valve-opening pressures were adjusted to $30\;mmH_2O$, 14 patients symptom was improved just at the point. There were 18 (22%) major complications : 7 subdural hygroma, 6 shunt obstructions, and 5 shunt infections. Conclusion : In normal pressure-type hydrocephalus, most patients improved when the final valve-opening pressure was $30\;mmH_2O$. We suggest that all normal pressure-type hydrocephalus patients be shunted with programmable valves, and their initial valve-opening pressures set to $10-30\;mmH_2O$ below their preoperative cerebrospinal fluid (CSF) pressures. If final valve-opening pressures are lowered in 20 or $30\;mmH_2O$ scale at 2- or 3-week intervals, reaching a final pressure of $30\;mmH_2O$, we believe that there is a low risk of overdrainage syndromes.

• 소성∙가공
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• 제12권1호
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• pp.11-17
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• 2003

For metal forming analysis, upper-bound solution is a practical method because the solution is overestimated. However it is not easy to determine the stresses on dies by using upper-bound solution. In this study, new scheme to calculate the stresses on dies based on upper bound solution is proposed. In the velocity fields, imaginary velocity is adapted to analyze the normal pressure on die surfaces. To verify the proposed scheme. plane strain drawing has been considered. The stresses on dies obtained by the proposed scheme are compared with the results of rigid plastic FEM and the experimental results. In the experiments, pressure film is used to measure the normal pressure on dies.

• 대한기계학회논문집
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• 제19권8호
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• pp.1989-1998
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• 1995

Characteristics of the flame propagation for normal and abnormal combustion in hydrogen premixture in a cylindrical constant-volume combustion chamber are studied numerically. A detailed hydrogen oxidation kinetic mechanism, mixture transport properties and a model describing spark ignition process are used. The calculated pressure-time history of the stable deflagration wave propagation agrees well with the experiment. The ignition of the premixture in the unburned gas, initiated by the hot spot, causes a transition from deflagration to detonation under some initial temperature and pressure. Under the initial conditions with high temperature and pressure, excessive ignition energy initiates a strong blast wave and a detonation wave that follows. The chemical reaction in the detonation wave is much more vigorous than that in the deflagration wave and the peak pressure in the detonation wave is much higher than the equilibrium value.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.17-20
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• 2000

Polymeric foams are excellent energy absorber and have found a wide range of applications especially in the automotive industry. The purpose of the present study is to develop experimental and theoretical methodology to characterize the pressure dependent yield behavior of polymeric foams. For the compression test in a triaxial stress sate a specially designed device was placed in a press machine to produce and control oil pressure. From the experiment results it was observed that the size of Mother circles is changed with mean normal stress in contrast to general metal. Then the Coulomb-Mohr criterion was applied to the data.

• 대한기계학회논문집B
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• 제27권7호
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• pp.877-882
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• 2003

The main objective of the present study is to analyze the heat transfer characteristics in the vacuum carburizing furnace. Local temperatures are measured at different locations in the self-fabricated furnace for various operating conditions using K-type thermocouples. In addition, the present study simulates the fluid flows and heat transfer in the vacuum carburizing furnace using a commercial package (Fluent V. 6.0), and compares the predictions of local temperatures with experimental data. The temperature and flow fields are predicted. It is found that the time taken for reaching the steady-state temperature under the vacuum pressure is shorter than that under the normal pressure condition. It means that the carburizing furnace under vacuum pressure condition is capable of saving the required energy more efficiently than the furnace under the normal pressure condition. Furthermore, the temperature variations predicted by the numerical simulations are in good agreement with experimental data.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.193-199
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• 1999

In the 3-Dimensional contact of the smooth spheres, the effects of friction on the contact area and the distribution of contact pressure was studied numerically. The contact area and pressure distribution was evaluated for the only normal load and for the case of a normal load in the presence of a tangential traction. To do this work, the technique of simple discretization using the load . displacement relationship for a uniformly distributed load of a rectangular patch was used.

• 대한수학회지
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• 제32권4호
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• pp.761-773
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• 1995

The nonlinear boundary value problem $$ y" = f(x, y, y') = -\frac{x}{3}y' - \frac{y^2}{g(x)}, 0 < x < 1, $$ $$ (1.1) y'(0) = 0, and either (H) : y(1) = \lambda > 0 $$ $$ or (S) : y'(1) + (1 - \upsilon)y(1) = 0, 1 - \upsilon > 0, $$ $$g \in C[0, 1], k \leq g(x) \leq K on [0, 1] for some k, K > 0 $$ arises in the nonlinear circular membrane under normal pressure [2, 3]., 3].