• Structural Engineering and Mechanics
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• 제81권6호
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• pp.769-780
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• 2022

This paper studies the dynamic behavior of laminated composite circular cylindrical shells interacting with a fluid. The mathematical formulation of the dynamic problem for an elastic body is developed based on the variational principle of virtual displacements and the relations of linear elasticity theory. The behavior of an ideal compressible fluid is described by the potential theory, the equations of which together with boundary conditions are transformed to a weak form. The hydrodynamic pressure exerted by the fluid on the internal surface of the shell is calculated according to the linearized Bernoulli equation. The numerical implementation of the mathematical formulation has been done using the semi-analytical finite element method. The influence of the ply angle and lay-up configurations of laminated composites on the natural vibration frequencies and the hydroelastic stability boundary have been analyzed for shells with different geometrical dimensions and under different kinematic boundary conditions set at their edges. It has been found that the optimal value of the ply angle depends on the level of filling of the shell with a fluid. The obtained results support the view that by choosing the optimal configuration of the layered composite material it is possible to change upwards or downwards the frequency and mode shape, as well as the critical velocity for stability loss over a wide range.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.523-527
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• 2022

The objective of this study is to simulate the flow in pipes with various boundary conditions. Free-pressure fluid model, is used in the pipe based on Navier-Stokes equation. The models are solved by using the numerical method. A problem called "stability of pipes" is used in order to compare frequency and critical fluid velocity. When the initial conditions of problem satisfied the instability conditions, the free-pressure model could accurately predict discontinuities in the solution field. Employing nonlinear strains-displacements, stress-strain energy method the governing equations were derived using Hamilton's principal. Differential quadrature method (DQM) is used for obtaining the frequency and critical fluid velocity. The results of this paper are analyzed by hyperbolic numerical method. Results show that the level of numerical diffusion in the solution field and the range of well-posedness are two important criteria for selecting the two-fluid models. The solutions for predicting the flow variables is approximately equal to the two-pressure model 2. Therefore, the predicted pressure changes profile in the two-pressure model is more consistent with actual physics. Therefore, in numerical modeling of gas-liquid two-phase flows in the vertical pipe, the present model can be applied.

• Tuberculosis and Respiratory Diseases
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• 제48권5호
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• pp.781-787
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• 2000

연구배경 : 1972년 Light's criteria가 나온 이후 흉막액의 여출액과 삼출액의 감별에 이 방법이 주로 이용되어 왔으나 그 이후 여러 논문에서 많은 예의 오류가 나타나 여러 가지 흉막액의 감별율 위한 방법들, 즉 흉막액 cholesterol값, cholesterol값의 흉막액 및 혈청에서의 비용, 흉막액 및 혈청에서의 알부민 구배율, alkaline phosphatase값 등에 대한 연구가 있어왔으나 Light's criteria보다 더 나은 분류 방법이라고 밝혀진 것이 없었다. 이에 저자들은 흉막액 cholinesterase와 흉막액 및 혈청 cholinesterase값의 비율이 삼출액과 여출액에 대한 감별의 유용성을 알아보고자 본 연구를 시행하였다. 방법 : 흉막액 원인의 구분이 가능했던 43명의 환자를 대상으로 흉막액을 추출하여 Light's criteria, 흉막액 cholesterol값, 흉막액 및 혈청 cholesterol값의 비율, 흉막액으로 cholinesterase값, 흉막액 및 혈청 cholinesterase값의 비율 등을 측정하여 비교하였다. 결과 : 흉막액 원인의 구분이 가능했던 43명의 환자에서 33명이 삼출액, 10명이 여출액으로 분류되었다. 흉막액 cholinesterase값의 평균은 여출액이 335.0 U/L, 삼출액이 1,928.1 U/L(p=0.002) 이었고 2명(4.7%)에서 검사의 오류를 보였으며 흉막액과 혈청에서의 cholinesterase값의 비율의 평균은 여출액이 0.15, 삼출액이 0.56(p=0.002)이었고 1명(2.3%)에서 검사 오류를 보였다. 흉막액 cholesterol값의 평균은 여출액이 22.7 mg/dL, 삼출액이 86.1 mg/dL(p=0.002)이었고 1명(2.3%)에서 검사의 오류를 보였으며, 흉막액 및 혈청 cholesterol값의 비율에서의 평균은 여출액이 0.17. 삼출액이 0.73(p=0.002)이었고 1명(2.3%)에서 검사의 오류를 보였다. Light's criteria에서는 43례중 4례 (9.3%)에서 검사의 오류를 나타냈다. 결론 : 여출액과 삼출액의 감별 진단에 있어서 흉막액 및 혈청 cholinesterase비율이 유용할 것으로 사료되며 더불어 Light's criteria를 비롯한 다른 기준들과 병용 검사시 진단 율을 더 올릴 수 있을 것으로 사료된다.

• Interaction and multiscale mechanics
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• 제2권1호
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• pp.45-68
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• 2009

An aim of the study is to develop an efficient numerical simulation technique that can handle the two-scale analysis of fluid permeation filters fabricated by the partial sintering technique of small spherical ceramics. A solid-fluid mixture homogenization method is introduced to predict the mechanical characters such as rigidity and permeability of the porous ceramic filters from the micro-scale geometry and configuration of partially-sintered particles. An extended finite element (X-FE) discretization technique based on the enriched interpolations of respective characteristic functions at fluid-solid interfaces is proposed for the non-interface-fitted mesh solution of the micro-scale analysis that needs non-slip condition at the interface between solid and fluid phases of the unit cell. The homogenization and localization performances of the proposed method are shown in a typical two-dimensional benchmark problem whose model has a hole in center. Three-dimensional applications to the body-centered cubic (BCC) and face-centered cubic (FCC) unit cell models are also shown in the paper. The 3D application is prepared toward the computer-aided optimal design of ceramic filters. The accuracy and stability of the X-FEM based method are comparable to those of the standard interface-fitted FEM, and are superior to those of the voxel type FEM that is often used in such complex micro geometry cases.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제40권5호
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• pp.220-224
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• 2014

Objectives: This study aimed to assess and compare the levels of interleukin-1beta (IL-$1{\beta}$) and interleukin-6 (IL-6) in the crevicular fluid around healthy implants, implants with peri-implantitis, and healthy teeth. Materials and Methods: This study evaluated 16 dental implants in 8 patients (4 males and 4 females). These patients had at least one healthy implant and one implant with peri-implantitis next to healthy teeth. The crevicular fluid was collected using absorbent cones and transferred to the laboratory. Specimens were evaluated by ELISA for interleukin levels. Data were analyzed using repeated measures ANOVA and Bonferroni tests (P<0.05). Results: Levels of IL-$1{\beta}$ in the crevicular fluid around implants with peri-implantitis were significantly higher than around healthy implants (P=0.002); the latter was significantly higher than around healthy teeth (P=0.015). A significant difference was found in the level of IL-6 in the crevicular fluid around implants with peri-implantitis and healthy implants (P=0.049) and also between implants with peri-implantitis and healthy teeth (P<0.001). Conclusion: Within the limitations of this study, significant differences exist in the levels of IL-$1{\beta}$ and IL-6 in the crevicular fluid of implants with peri-implantitis, healthy implants, and healthy teeth. More studies with larger sample sizes in different populations are necessary.

• The Korean Journal of Physiology
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• 제11권1호
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• pp.21-26
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• 1977

Many cases have been reported that a post spinal headache can be relieved immediately by an epidural injection of saline; and autologous blood also has recently been used successfully instead of saline. The changes of the cerebrospinal fluid pressure in 40 cases were observed in the present study in support of the concept; that a continuous leakage in association with hypovolemia and hypotension of the cerebrospinal fluid is the primary cause of a post spinal headache. Subarachnoid pressure increased immediately with saline injection into the lumber epidural space. A spinal needle was inserted into the subarachnoid space at the level of $L2{\sim}3$ and opening pressure of the cerebrospinal fluid was read. An epidural Tuohy needle was insertad at the$L3{\sim}4$ and 25m1 of saline was injected into the epidural space and the cerebrospinal fluid pressure was read in the sitting position. $\underline{Sitting\;Position:}$ Mean pressure after injection $555{\pm}(110.9)mm\;H_2O$, Pressure rise rise (%) 51.3%, Mean opening pressure $366{\pm}(52.2)mm\;H_{2}O$, $\underline{Lateral\;position:}$ Mean pressure after injection $308{\pm}(70.8)mm\;H_{2}O$, Pressure(%) 86.7%, Mean opening pressure $165{\pm}(42.6)mm\;H_{2}O$. These pressure changes responded almost simultaneously as saline was injected. This pressure rise of 51.3% in the sitting position and 86.7% in the lateral position are clinically very significant. Therefore, it is most possible that the immediate relieve of post, spinal headache by injection of fluid into the epidural space is simultaneous with the increase of the cerebrospinal fluid pressure.

• Tuberculosis and Respiratory Diseases
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• 제67권5호
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• pp.402-408
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• 2009

Background: Pre-B-cell colony enhancing factor (PBEF) has been suggested as a novel biomarker in sepsis and acute lung injury. We measured the PBEF in bronchoalveolar lavage (BAL) fluid of acute critically ill patients with lung infiltrates in order to evaluate the clinical utility of measuring PBEF in BAL fluid. Methods: BAL fluid was collected by bronchoscope from 185 adult patients with lung infiltrates. An enzyme-linked immunosorbent assay was then performed on the collected fluids to measure the PBEF. Results: Mean patient age was 59.9 ${\pm}$14.5 years and 63.8% of patients were males. The mean concentration of PBEF in BAL fluid was 17.5 ${\pm}$88.3 ng/mL, and patients with more than 9 ng/mL of PBEF concentration (n=26, 14.1%) had higher Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores on the BAL exam day. However, there were no significant differences in clinical characteristics between survivors and non-survivors. In patients with leukocytosis (n=93) seen on the BAL exam day, the linear regression analysis revealed a significant, positive relationship between PBEF and APACHE II ($r^2$=0.06), SOFA score ($r^2$=0.08), Clinical Pulmonary Infection Score ($r^2$=0.05), and plateau pressure in patients on ventilators ($r^2$=0.07) (p<0.05, respectively). In addition, multivariate regression analysis with PBEF as a dependent variable showed that the plateau pressure ($r^2$=0.177, p<0.05) was correlated positively with PBEF. Conclusion: The PBEF level in the BAL fluid may be a useful, new biomarker for predicting the severity of illness and ventilator-induced lung injury in critically ill patients with lung infiltates and leukocytosis.

• 대한본초학회지
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• 제28권6호
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• pp.95-100
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• 2013

Objectives : The purpose of this study was to investigate antiaging and antioxidant effects on cultured human skin fibroblast with supercritical fluid extracts of Dendropanax morbifera, Corni fructus and Lycii Fructus. Methods : Supercritical fluid extraction (SFE) technique was applied to extract from three medicinal plants including stem of Dendropanax morbifera, Corni fructus and Lycii Fructus. Antioxidant activity of extract was evaluated by two different assays as 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and super oxide dismutase (SOD) like activities. These extracts were tested for cell viability on HS68 skin fibroblast by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. We investigated the effects of Ultraviolet-B irradiation on cytotoxicity, type 1 collagen, elastin level and oxidative damage in cultured human skin fibroblast (HS68). Recently, many studies have reported that elastin is also involved in inhibiting or repairing wrinkle formation, although collagen is a major factor in the skin wrinkle formation. Results : The extracts obtained dose-dependently increased the scavenging activity on DPPH radical scavenging activity and SOD like activity. The supercritical fluid extracts of complex herbal medicine showed low cytotoxicity as more than 100% cell viability in 100ppm/ml concentration. HS68 fibroblasts were survived 70% at $120mJ/cm^2$ UVB irradiation and treated tumor necrosis factor (TNF)-alpha. The levels of aging factors and cytotoxicity were decreased by supercritical fluid extract of complex herbal medicine. Conclusions : These results suggest that supercritical fluid extracts may have value as the potential antioxidant and antiaging medicinal plant.

• 한국발생생물학회지:발생과생식
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• 제16권2호
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• pp.95-100
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• 2012

Bisphenol A(BPA)는 약한 estrogen 활성도를 보이는 화학물질로서 착상 전 배아나 태아에 영향을 미쳐, 출생 후 그들의 신체발달에 변화를 초래한다고 알려져 있다. 본 연구는 인체에서 임신 중기에 양수 내 BPA 농도를 측정하였으며, 측정된 농도에 따라 임신결과에 영향을 미치는지 여부를 알아보고자 하였다. 임신 15주에서 20주 사이에 유전학적 적응증으로 양수천자 검사를 시행 받았던 120명의 임신부 양수를 연구대상으로 ELISA 방법으로 농도를 측정하였다. 양수천자의 가장 많은 적응증은 35세 이상의 고령 임신부였다. BPA는 모든 양수에서 검출이 가능하였으며, 그 농도는 최저치 0.89 ng/mL부터 최고치 37.13 ng/mL까지의 분포를 보였고, 평균치는 7.24 ng/mL이었다. 양수 내 BPA 농도가 여러 임신결과들과 관련성이 있는지를 알아보기 위해 임신부 나이 35세 이상 대 미만, 남자 태아 대 여자 태아, 분만 당시 재태 연령 37주 이상 대 미만, 출생 당시 신생아 체중 2.5 kg 이상 대 미만으로 각각 나누어, 두 군간에 농도를 비교한 결과, 통계학적으로 유의한 차이는 없었다. 본 연구는 한국인 임신부를 대상으로 최초로 양수 내 BPA 농도에 관한 보고이다. 본 연구결과 BPA 농도는 임신부 나이나 태아성별에 따라 차이를 보이지 않았으며, 조산이나 저체중아의 발생과도 관련이 없음을 알 수 있었다. 향후 산전 BPA 노출이 배발생에 영향을 미치는지에 대한 연구가 필요하다고 사료된다.

• 한국컴퓨터그래픽스학회논문지
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• 제19권3호
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• pp.1-11
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• 2013

FLIP 기반의 유체 시뮬레이션은 품질에 대비 높은 효율을 자랑하기 때문에 Visual Effect(VFX)산업에 널리 사용되고 있다. FLIP 기술에서는 바다와 같은 대규모의 물을 시뮬레이션 할 때 시각적으로 중요하지 않은 물의 안쪽까지도 파티클을 할당해야 하기 때문에 보이는 파티클보다 보이지 않는 파티클의 개수가 훨씬 많은 경우에는 시뮬레이션 작업의 효율성이 떨어진다. 본 논문에서는 이러한 단점을 보완하기 위하여 레벨셋 (Level Set)과 Fluid Implicit Particle(FLIP) 기반의 유체 시뮬레이션 기법을 혼합(hybrid)한 효율적인 유체 시뮬레이션 기법을 제안한다. 파티클들을 물의 안쪽 표면 근처의 얇은 층에만 배치함으로써 사용되는 파티클의 갯수를 줄여서 결과적으로 시뮬레이션의 효율성을 크게 높일 수 있었다. 또한 [1]의 표면 재구성 기법과 moving least squares(MLS) [2] 기법을 결합한 새로운 유체 표면 재구성 기법을 적용하여 FLIP을 통해 격자(Grid) 기반 시뮬레이션에서 발생하는 수치적 소실을 줄이고 동시에 유체의 부드러운 표면을 유지할 수 있다. 본 논문의 혼합 시뮬레이션 기술은 높은 품질의 유체 시뮬레이션을 효율적으로 수행하여 다양한 규모의 유체를 표현할 수 있었다.