• Proceedings of the KSME Conference
• /
• 2002.08a
• /
• pp.811-814
• /
• 2002

Using a mathematical theory, we show that the optimality condition of a turbulent diffuser with maximum pressure recovery at the exit is zero shear stress along the wall. The optimal diffuser shape is designed through iterative procedures by using the $k-{\varepsilon}-{\nu}^{2}-f$ turbulence model for flow simulation. The Reynolds number based on the bulk mean velocity and the channel height at the diffuser entrance is 18,000. We also perform large eddy simulation to validate the shape design results and investigate the flow characteristics near the zero-skin friction wall. Results from large eddy simulation show that the skin friction is slightly higher than zero but is still very small as compared to that of the flat plate boundary layer flow Although the time-averaged wall shear stress is slightly above zero along the diffuser wall, instantaneous flow reversals occur intermittently. The streamwise mein velocity shows an asymptotic behavior of the half-power-law near the wall where the skin friction is close to zero.

• Korean Journal of Cleft Lip And Palate
• /
• v.14 no.1_2
• /
• pp.37-44
• /
• 2011

Amniotic fluid is a complex and biological reservoir that provides mechanical cushioning and has many nutrients required for fetal growth and development. During our main research works about the fetal surgery of congenital facial defects, we reviewed several recent articles about the effectiveness and composition of amniotic fluid. Among these review processes, amniotic fluid, as the convenient medium to store sking grafts, was focused especially for its growth factors and rich nutrients, and we summarized some experimental investigations of skin grafts stored in amniotic fluid in rats. We reviewed mainly the article, "Turhan-haktanir N. et al. Histological assessment of skin grafts in amniotic fluid and saline. J Plast Surg Hand Surg 2010;44:226-30."

• Journal of Korean Society of Steel Construction
• /
• v.20 no.4
• /
• pp.505-517
• /
• 2008

A numerical analysis method was studied to predict the nonlinear behavior of slender double skin composite walls. For convenience in numerical analysis, the model for the double skin composite wall was developed as a macroscopic model that can predict nonlinear behavior with relatively simplified models. For the wall showing flexure-dominant behavior, a multiple layer model was used. Each layer was modeled with composite elements of concrete and steel plate. An X-type truss model was used for coupling beams showing shear-dominant behavior. To describe the cyclic behavior of concrete and steel elements, simplified cyclic models for the materials were proposed. The proposed analysis model was applied to isolated walls and coupled walls with rectangular or T-shaped cross-sections. The analytical results were compared with existing test results.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.3
• /
• pp.421-435
• /
• 2017

Recently, due to the saturation of ground structures and the overpopulation of pipeline facilities requires to development of underground structures as an alternative to ground structures. Thus, mechanized tunnel construction of the shield TBM method has been increasing in order to prevent vibration and noise problems in construction of the NATM tunnel for the urban infrastructure construction. Tunnel construction plan for the tunnel line should be formed in a sharp curve to avoid building foundation and underground structures and it is inevitable to develop a shield TBM technology that suits the sharp curve tunnel construction. Therefore, this study is about the structural stability technology of the articulation jack, shield jack and skin plate for the shield TBM thrust in case of the mechanized tunnel construction that is a straight and sharp curve line. The construction case study and shield TBM operation principle are examined and analyzed by the theoretical approach. The torque of the cutter head, the thrust of the articulation jack and the shield jack, the amount of over cutting for curve is important respectively in shield TBM construction of straight and sharp curve line. In addition, it is very important to secure the stability of the skin plate structure to ensure the safety of the inside worker. This study examines the general structure and construction of the equipment, experimental simulation was carried out through numerical analysis to examine the main factors and structural stability of the skin plate structure. The structural stability of the skin plate was evaluated and optimizes the shape by comparing the loads of the articulation jack by selecting the virtual soil to be applied in a straight and sharp curve line construction. Since the present structure and operation method of the shield TBM type in domestic constructions are very similar, this study will help to develop the localized shield TBM technology for the new equipment and the vulnerability and stability review.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.2
• /
• pp.289-301
• /
• 2008

Double skin composite (DSC) wall is a structural wall that is filed with concrete between two steel plate skins connected by tie bars. This type of wall was developed to enhance the structural performance of wall, to reduce wall thickness, and to enhance constructibility, eliminating the use of formwork and re-bars. In this study, cyclic tests were performed to investigate the inelastic behavior and earthquake resistance of isolated and coupled DSC walls with rectangular and T-shapedcross-sections. The DSC walls showed stable cyclic behaviors, exhibiting excellent energy dissipation capacity. The te st specimens failed by the tensile fracture of welded joints at the wall base and coupling beam and by the severe local buckling of the steel plate. The deformation capacity of the walls varied with the connection details at the wall base and their cross-sectional shapes. The specimens with well-detailed connections at the wall base showed relatively god deformation capacity ranging from 2.0% to 3.7% drift ratio. The load-carrying capacities of the isolated and coupled wall specimens were evaluated considering their inelastic behavior. The results were compared with the test results.

• Journal of Korean Foot and Ankle Society
• /
• v.13 no.2
• /
• pp.162-168
• /
• 2009

Purpose: To evaluate the efficiency of the minimally invasive percutaneous plate osteosynthesis (MIPPO) with locking compression plate (LCP) for distal tibial metaphyseal intra-articular fracture compared with extra-articular fracture. Materials and Methods: From February 2006 to June 2008, 21 patients with distal tibia metaphyseal intra-articular fracture and 20 patients with extra-articular fracture were treated operatively by MIPPO technique with LCP and followed for at least one year. In the group with intra-articular fracture, mean age was 48.85 years old and a mean follow-up was 15 months. In the other group with extra-articular fracture, mean age was 52.35 years old and a mean follow-up was 14.5 months. The type of fracture was evaluated using the AO/OTA classification and open-fractures were according to the Gustilo-And gron classification. Radiologic evaluation with fracture healing and tibial alignment, clinical evaluation with Olerud and Molander ankle score and restriction of motion were done for treatment. Results: According to AO/OTA classification, There were 21 type A, 15 type B, 5 type C. Average union time of the intra-articular fracture (type B, C) was 18.7 weeks. Average union time of the extra-articular fracture (type A) was 17.1 weeks. All fractures were healed without malunion. There were no difference of mean restriction angle between intra-articular fracture (ankle dorsiflexion was 3.57 degree, plantar-flexion was 5.95 degree) and extra-articular fracture (ankle dorsiflexion was 3 degree, plantar-flexion was 3.75 degree). There were no difference of Olerud and Molander ankle score between them as a mean score of intra-articular and extra-articular was 89.25, 91.25 each other. As a complication, there were 3 case of skin necrosis, 8 case of discomfortable skin tenting by plate and 1 superficial infection, but could be healed by conservative care. Conclusion: MIPPO technique, combined articular reduction, with LCP of distal tibial metaphyseal fracture was a good method with high functional recovery.

• Journal of Pharmacopuncture
• /
• v.16 no.2
• /
• pp.46-54
• /
• 2013

Objective: This study was undertaken to isolate a fibrin(ogen)olytic enzyme from the snake venom of Gloydius blomhoffii siniticus and to investigate the enzymatic characteristics and hemorrhagic activity of the isolated enzyme as a potential pharmacopuncture agent. Methods: The fibrinolytic enzyme was isolated by using chromatography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and fibrin plate assay. The characteristics of the enzyme were determined by using fibrin plate assay, protein hydrolysis analysis, and hemorrhage assay. Its amino acid composition was determined. Results: The fibrin(ogen)olytic enzyme with the molecular weight of 27 kDa (FE-27kDa) isolated from G. b. siniticus venom consisted of two heterogenous disulfide bond-linked polypeptides with the molecular weights of 15 kDa and 18 kDa. When more than $20{\mu}g$ of FE-27kDa was applied on the fibrin plate, fibrinolysis zone was formed as indicating its fibrinolytic activity. The fibrinolytic activity was inhibited completely by phenylmethanesulfonylfluoride (PMSF) and ethylenediaminetetraacetic acid (EDTA) and partially by thiothreitol and cysteine. Metal ions such as $Hg^{2+}$ and $Fe^{2+}$ inhibited the fibrinolytic activity completely, but $Mn^{2+}$ did not. FE-27kDa preferentially hydrolyzed ${\alpha}$-chain of fibrinogen and slowly hydrolyzed ${\beta}$-chain, but did not hydrolyze ${\gamma}$-chain. High-molecular-weight polypeptides of gelatin were hydrolyzed partially into polypeptides with molecular weights of more than 45 kDa. A dosage of more than $10{\mu}g$ of FE-27kDa per mouse was required to induce hemorrhage beneath the skin. Conclusion: FE-27kDa was a serine proteinase consisting of two heterogeneous polypeptides, hydrolyzed fibrin, fibrinogen, and gelatin, and caused hemorrhage beneath the skin of mouse. This study suggests that the potential of FE-27kDa as pharmacopuncture agent should be limited due to low fibrinolytic activity and a possible side effect of hemorrhage.

• Structural Engineering and Mechanics
• /
• v.68 no.3
• /
• pp.325-334
• /
• 2018

The Nonlinear dynamic response of a sandwich plate subjected to the low velocity impact is theoretically and experimentally investigated. The Hertz law between the impactor and the plate is taken into account. Using the Extended High Order Sandwich Panel Theory (EHSAPT) and the Ritz energy method, the governing equations are derived. The skins follow the Third order shear deformation theory (TSDT) that has hitherto not reported in conventional EHSAPT. Besides, the three dimensional elasticity is used for the core. The nonlinear Von Karman relations for strains of skins and the core are adopted. Time domain solution of such equations is extracted by means of the well-known fourth-order Runge-Kutta method. The effects of core-to-skin thickness ratio, initial velocity of the impactor, the impactor mass and position of the impactor are studied in detail. It is found that these parameters play significant role in the impact force and dynamic response of the sandwich plate. Finally, some low velocity impact tests have been carried out by Drop Hammer Testing Machine. The results are compared with experimental data acquired by impact testing on sandwich plates as well as the results of finite element simulation.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.2
• /
• pp.414-423
• /
• 1994

The planar laminar impingement jet with a confinement plate has been studied numerically. Discretzing the convection term with the QUICKER scheme, the full Navier-Stokes equations for fluid flow were solved using the well known SIMPLER algorithm. The flow characteristics with Reynolds number and jet exit velocity profile effects on it were considered for H=3, Re=200 - 2000. Results show that vortical flow forms in turn along the confinement and impingement plates as the Reynolds number increases and such a complicated flow pattern has never been reported prior. The jet exit velocity profile is shown to do an important role in determining the position of vortex flow and its size as well as in stagnation and wall jet flow region. Parabolic jet exit profile results in peak of skin friction 1.4-1.6 times greater than that of uniform profile. The channel height effects are also studied and shown to have an effect on flow pattern similar to that of Reynolds number. Also shown is that effects of the jet exit velocity profile becomes less significant over a certain channel height.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.20 no.4
• /
• pp.333-354
• /
• 2016

The present investigation deals, heat and mass transfer characteristics with the effect of slip on the hydromagnetic pulsatile flow through a parallel plate channel filled with saturated porous medium. Based on the pulsatile flow nature, exact solution of the governing equations for the fluid velocity, temperature and concentration are obtained by using two term perturbation technique subject to physically appropriate boundary conditions. The expressions of skin friction, Nusselt number and Sherwood number are also derived. The numerical values of the fluid velocity, temperature and concentration are displayed graphically whereas those of shear stress, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. By increasing the slip parameter at the cold wall the velocity increases whereas the effect is totally reversed in the case of shear stress at the cold wall.