• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.381-384
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• 2000

Relationships between biochemical phenomena and hemodynamics on human endothelial cells are very important to study the mechanism of atherosclerotic formation and development. The objective of this study is to investigate the flow phenomena around the endothelial cell model by the PIV experiment. The microscopic images of endothelial cells were acquired by a CCD camera to fabricate the shape of endothelial cell. The cell models were fabricated by using a photoforming process. Two consecutive particle images were captured by the CCD camera for the image processing. Conifer powder as the tracing particles was added to water to visualize the flow field. The cross-correlation method was applied fer the image processing of the flow visualization. Pressure and wall shear stress variations on the surfaces of the endothelial cells were calculated to investigate the effects of hemodynamic forces on the morphological changes.

• KSBB Journal
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• 제27권3호
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• pp.186-194
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• 2012

Various human host cell lines, which are more effective than the other original human cell lines, have been developed and used. Highly efficient human cell line can be obtained from the fusion between human embryonic kidney 293 (HEK293) and human Burkitt's lymphoma cells (Namalwa). Fused cell line has the advantages of both cell lines such as the high transfection efficacy of HEK293 cells and the constitutive expression of Epstein-Barr virus (EBV) genome which is related with high expression of target protein and anti-apoptotic growth of Namalwa cells. In this study, characterization of two original cell lines was performed by using design of experiment (DOE) considering cell maintenance, media development, optimization of culture condition, and scale-up. The formation of aggregates was apparent with high glutamine concentration at more than 6 mM. Supplementation of hydrolysates showed positive effects on the growth performances of HEK293 cells. On the contrary, Namalwa cells showed negative results. It was confirmed that Namalwa cells were more sensitive to lower temperature at $35^{\circ}C$ and hyperosmotic condition over 260 mOsm/kg. In addition, both cell lines showed limited growth in 3-L bioreactor due to shear stress.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1505-1509
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• 2004

The suspension of hardened red blood cells (RBCs) differs from the suspension of normal RBCs with respect to their rheological behavior. The deformability of normal and hardened RBCs (obtained by heating blood at $49^{\circ}C$ or by incubating RBCs in a solution of hydrogen peroxide) was measured with a slit diffractometer and RBC suspension viscosity was measured with a rotational viscometer. The peroxide-treated RBCs showed a significant decrease of the deformability and their suspension viscosity increased over a range of shear rates. The suspension viscosity of the heated RBCs, however, where the deformability is even lower than that of the peroxide-treated RBCs, was slightly higher than that of the normal RBC suspension in the high shear rates. The present study found that not all rigid cells cause an increase of blood viscosity at high shear rate, and therefore that decreased membrane deformability is not predictive of high-shear blood viscosity.

• 대한의용생체공학회:의공학회지
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• 제31권2호
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• pp.99-105
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• 2010

In order to obtain velocity profile of blood flow with high spatial resolution, a micro PIV technique consisted of a fluorescent microscope, double-pulsed YAG laser, cooled CCD camera was applied to in-vitro blood flow experiment through a micro round tube of a diameter $100{\mu}m$. Velocity distributions of blood flow for rabbit were obtained. The viscosity profiles for shear rate were found at flowing condition. To provide hemorheological characteristics of blood flow, the viscosities for shear rate were evaluated. The viscosity of blood also steeply increase by decreasing shear rate resulting in Non-Newtonian flow, especially in low shear rate region caused by RBC rheological properties. The results show typical characteristics of Non-Newtonian characteristics from the results of velocity profile and viscosity for blood flow. From the inflection points, cell free layer and two-phase flow consisted with plasma and suspensions including RBCs can be separated.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.71-77
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• 2008

Microstructural changes may arise due to the particle vanishing, fluid diffusion, heating, etc. This study focuses on the changes in small-strain shear stiffness in k0 loading produced by local straining in particular system made of sand-salt mixtures. Local strains were induced by dissolution of salt particles. Experiments were carried out in a conventional oedometer cell equipped with bender elements. Axial displacement and shear wave signals are recorded at each loading stage and during saturation process. Experimental data showed that microstructural changes due to particle vanishing were clearly captured by using shear wave measurement. Saturation of sand-salt mixture at a larger axial stress did not always create a more condense soil at the end of loading stage. Sand-salt mixture is useful for laboratory test on controlled artificial specimen.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제27권1호
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• pp.9-15
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• 2005

The objective of this study is screening the shear stress related proteins in chondrocytes using twodimensional electrophresis and MALDI-TOF. C-28/I2 cell line were grown. The fluid-induced shear stress(FISS) was applied using a cone viscometer at a rotational velocity of 80rpm for periods of 12 hours. Control cultures were tested under identical conditions without mechanical load application. Collected samples were used for the two-dimensional electrophoresis and MALDI-TOF. The identified proteins were calcyclin, RPE-spondin, interleukin-2, extracellular signal regulated kinase (ERK), lamin B2, porA protein, and RET-ELE1 protein. All of them showed a decreased expression. In conclusion, seven proteins were identified as a shear stress related proteins in chondrocytes. As the destruction of articular cartilage is one of main pathogenesis of TMJ internal derangement, this study will give useful information for the understanding of the molecular aspect of TMJ disease.

• 대한기계학회논문집B
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• 제30권11호
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• pp.1027-1034
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• 2006

In order to investigate flow characteristics of chicken blood in a micro tube of 100$\mu$m in diameter, in-vitro experiments were carried out using a micro-PIV technique. The micro-PIV system consists of a microscope, 2-head Nd:YAG laser, 12 bit cooled CCD camera and a delay generator. Chicken blood with 40% hematocrit was supplied into a micro tube using a syringe pump. The blood flow shows clearly the cell free layer near the tube wall and its thickness is increased with increasing the flow speed. The hemorheological characteristics of chicken blood, including shear rate and shear stress were estimated from the PIV velocity field data obtained. Since the aggregation index of chicken blood is less than 50% of human blood, non-Newtonian flow characteristics of chicken blood are smaller than those of human blood. As the flow rate increases, the degree of flatness in the velocity profile at the center region is decreased and the parabola-shaped shear stress distribution becomes to have a linear profile. Under the same flow rate, chicken blood shows higher shear stress, compared with human blood.

• International Journal of Vascular Biomedical Engineering
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• 제3권2호
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• pp.1-9
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• 2005

Flow-induced dilation of blood vessel is the result of a series of bioreaction in vascular endothelial cells(VEC). Shear stress change by blood flow in human artery or vein is sensed by the mechanoreceptor and responsible for such a chain reaction. The inositol(1,4,5)-triphophate($IP_3$) is produced in the first stage to elevate permeability of the intercellular membrane to calcium ions by which the cytosolic calcium concentration is consequently increased. This intracellular calcium transient triggers synthesis of EDRF and prostacyclin. The mathematical model of this VEC calcium dynamics is reproduced from the literature. We then use the Computational Fluid Dynamics(CFD) technique to investigate the blood stream dictating the VEC calcium dynamics. The pulsatile blood flow in a stenosed blood vessel is considered here as a part of study on thrombogenesis. We calculate the pulsating shear stress (thus its temporal change) distributed over the stenosed artery that is implemented to the VEC calcium dynamics model. It has been found that the pulsatile shear stress induces larger intracellular $Ca^{2+}$ transient plus much higher amount of EDRF and prostacyclin release in comparison with the steady shear stress case. It is concluded that pulsatility of the physiological shear stress is important to keep the vasodilation function in the stenosed part of the blood vessel.

• 대한환경공학회지
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• 제33권3호
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• pp.191-195
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• 2011

본 연구의 목적은 낮은 전단흐름조건에서 편모 운동성이 박테리아의 거동 특성에 미치는 영향을 파악하는데 있다. 대다수의 미생물은 편모를 이용하여 수용액 내에서 운동할 수 있는 능력을 가지고 있으며, 이러한 운동성은 수계나 수처리 시스템에서 미생물의 거동에 있어서 중요한 역할을 한다. 그러나 현재까지 병원성 미생물의 이동 현상과 관련된 연구에서 편모에 의한 운동성은 거의 고려되지 않고 있는 실정이다. 본 연구에서는 미세유체장치를 이용하여 전단흐름이 낮은 조건에서 E. coli의 거동 특성을 파악하고자 하였다. 실험을 통하여 유속이 작은 경우에 E. coli는 포물선의 형태의 궤적들을 그리며 이동하는 것을 알 수 있었으며, 벽면 근처에서는 상류로 헤엄쳐 올라간다는 것을 파악하였다. 또한 유속과 종횡비(aspect ratio)에 따른 궤적의 변화를 분석하였는데, 유속이 작을수록 포물선 형태의 궤적을 그리게 되며, 길이가 짧을수록 보다 작은 회전 반경을 그리며 운동하는 것을 관찰할 수 있었다.

• Advances in nano research
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• 제13권3호
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• pp.297-312
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• 2022

Coughing and breath shortness are common symptoms of nano (small) cell lung cancer. Smoking is main factor in causing such cancers. The cancer cells form on the soft tissues of lung. Deformation behavior and wave vibration of lung affected when cancer cells exist. Therefore, in the current work, phase velocity behavior of the small cell lung cancer as a main part of the body via an exact size-dependent theory is presented. Regarding this problem, displacement fields of small cell lung cancer are obtained using first-order shear deformation theory with five parameters. Besides, the size-dependent small cell lung cancer is modeled via nonlocal stress/strain gradient theory (NSGT). An analytical method is applied for solving the governing equations of the small cell lung cancer structure. The novelty of the current study is the consideration of the five-parameter of displacement for curved panel, and porosity as well as NSGT are employed and solved using the analytical method. For more verification, the outcomes of this reports are compared with the predictions of deep neural network (DNN) with adaptive optimization method. A thorough parametric investigation is conducted on the effect of NSGT parameters, porosity and geometry on the phase velocity behavior of the small cell lung cancer structure.