• Journal of computational fluids engineering
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• v.16 no.4
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• pp.39-46
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• 2011

A numerical study of a turbulent natural convection in an enclosure with the lattice Boltzmann method (LBM) is presented. The primary emphasis of the present study is placed on investigation of accuracy and numerical stability of the LBM for the turbulent natural convection flow. A HYBRID method in which the thermal equation is solved by the conventional Reynolds averaged Navier-Stokes equation method while the conservation of mass and momentum equations are resolved by the LBM is employed in the present study. The elliptic-relaxation model is employed for the turbulence model and the turbulent heat fluxes are treated by the algebraic flux model. All the governing equations are discretized on a cell-centered, non-uniform grid using the finite-volume method. The convection terms are treated by a second-order central-difference scheme with the deferred correction way to ensure accuracy and stability of solutions. The present LBM is applied to the prediction of a turbulent natural convection in a rectangular cavity and the computed results are compared with the experimental data commonly used for the validation of turbulence models and those by the conventional finite-volume method. It is shown that the LBM with the present HYBRID thermal model predicts the mean velocity components and turbulent quantities which are as good as those by the conventional finite-volume method. It is also found that the accuracy and stability of the solution is significantly affected by the treatment of the convection term, especially near the wall.

• Journal of Chest Surgery
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• v.53 no.6
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• pp.381-386
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• 2020

Background: Behçet disease is a chronic inflammatory disorder with a varying etiology. Herein, we report the involvement of peripheral veins in Behçet disease and discuss the treatment thereof. Methods: Thirty-four patients with venous involvement in vasculo-Behçet disease were retrospectively analyzed over 15 years. We reviewed the clinical manifestations, treatment choices, and complications of these patients. Results: Deep vein thrombosis (DVT) was observed in 24 patients (70.59%) and varicose veins in 19 (52.94%). Immunosuppressive treatment was administered to all patients due to the pathological feature of vein wall inflammation. In patients with DVT, anticoagulation therapy was also used, but post-thrombotic syndrome was observed in all patients along with chronic luminal changes. Eleven patients with isolated varicose veins underwent surgery; although symptoms and lesions recurred in half of these patients, no cases of secondary DVT occurred. Conclusion: When DVT was diagnosed in patients with Behçet disease, there was no cure for the lesions. Ultrasonographic abnormalities were observed in all patients, and post-thrombotic syndrome remained to varying degrees. In cases of isolated varicose veins in patients with Behçet disease, DVT did not occur after surgical treatment. If the activity of Behçet disease is controlled, surgical correction of varicose veins is preferable.

• The Korean Journal of Pain
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• v.19 no.1
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• pp.56-62
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• 2006

Background: Balloon kyphoplasty is the new technique that helps to decrease the pain and improve mobility as well as restore the vertebral body height and kyphotic curve in fractured vertebrae. We evaluated the outcome of balloon kyphoplasty in the reduction of vertebral body height, kyphotic curve and clinical improvement in the patients with painful vertebral compression fractures. Methods: From July 2002 to February 2005, 84 levels of vertebral compression fractures in 66 patients were treated with balloon kyphoplasty. The assessment criteria were the changes over time in visual analogue scale (VAS) and mobility score. We evaluated the vertebral body height and kyphotic curve at preoperative 1 day and postoperative 1 day. Results: Procedures were performed in 66 patients with a total of 84 affected vertebral bodies. The anterior wall height was restored in 74 / 84 (88%) levels with a mean increment of 2.9 mm, and the mid-vertebral body height was restored in 79 / 84 (94%) levels with a mean increment of 4.2 mm. Kyphosis correction was achieved in 60 / 84 (71.4%) from 10.1 degrees to 7.5 degrees. Pain intensity reduced by 60% in one day after operation and by 75-85% in later time. Mobility scores of all patients were improved immediately after the procedure. Cement leakage occurred in 3 levels but there was no clinical problem. Conclusions: Kyphoplasty is an efficient and safe treatment of painful vertebral compression fracture in pain relief, mobility improvement, and reduction of deformity.

• KIEAE Journal
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• v.13 no.6
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• pp.121-128
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• 2013

This study attempted to explore the MC design methods of modular construction using discontinuous double module grids and further, the design methods of walls. Modular construction is generally characterized with multiple units called modules with a module dimension of 3M(300mm) appearing in the form of double grids. The discontinuous double grids including correction values and gap values occurs inevitably in the modular construction where units are joined horizontally. Therefore, it is desirable to carry out the MC design taking into account these discontinuous double grids. In this study, the MC design was applied to the plane of wooden houses in modular construction, going through a process of setting the size of pillars and inside dimensions, of determining the dimension of discontinuous double grids that occur during the assembly of units, and of setting the dimension of outer walls in conjunction with the derived dimensions. The dimension of outer walls was applied differently depending on the range of regional use by analyzing the energy performance with the materials used. Consequently, the materials and components of factory-produced buildings can be used directly without processing, and the suitability of the outer wall design can be pre-determined by previewing the calculation of the cross-sectional configuration and heat transmission coefficients of outer walls in modular construction, allowing to be used as a decision-making tool of design.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.4
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• pp.159-166
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• 2017

The position of autonomous driving vehicle is basically acquired through the global positioning system (GPS). However, GPS signals cannot be received in tunnels. Due to this limitation, localization of autonomous driving vehicles can be made through sensors mounted on them. In particular, a 3D Light Detection and Ranging (LIDAR) system is used for longitudinal position error correction. Few feature points and structures that can be used for localization of vehicles are available in tunnels. Since lanes in the road are normally marked by solid line, it cannot be used to recognize a longitudinal position. In addition, only a small number of structures that are separated from the tunnel walls such as sign boards or jet fans are available. Thus, it is necessary to extract usable information from tunnels to recognize a longitudinal position. In this paper, fire hydrants and evacuation guide lights attached at both sides of tunnel walls were used to recognize a longitudinal position. These structures have highly distinctive reflectivity from the surrounding walls, which can be distinguished using LIDAR reflectivity data. Furthermore, reflectivity information of tunnel walls was fused with the road surface reflectivity map to generate a synthetic reflectivity map. When the synthetic reflectivity map was used, localization of vehicles was able through correlation matching with the local maps generated from the current LIDAR data. The experiments were conducted at an expressway including Maseong Tunnel (approximately 1.5 km long). The experiment results showed that the root mean square (RMS) position errors in lateral and longitudinal directions were 0.19 m and 0.35 m, respectively, exhibiting precise localization accuracy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.4013-4026
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• 1996

A numerical simulation has been carried out for the jet impinging on a flat plate and a semi-circular concave surface. In this computation finite volume method was employed to solve the full Navier-Stokes equation based on a non-orthogonal coordinate with non staggered variable arrangement. The standard k-.epsilon. turbulent model and low Reynolds number k-.epsilon. model(Launder-Sharmar model) with Yap's correction were adapted. The accuracy of the numerical calculations were compared with various experimental data reported in the literature and showed good predictions of centerline velocity decay, wall pressure distribution and skin friction. For the jet impingement on a semi-circular concave surface, potential core length was calculated for two different nozzle(round edged nozzle and rectangular edged nozzle) to consider effects of the nozzle shape. The result showed that round edged nozzle had longer potential core length than rectangular edged nozzle for the same condition. Heat transfer rate along the concave surface with constant heat flux was calculated for various nozzle exit to surface distance(H/B) in the condition of same jet velocity. The maximum local Nusselt number at the stagnation point occurred at H/B = 8 where the centerline turbulent intensity had maximum value. The predicted Nusselt number showed good agreement with the experimental data at the stagnation point. However heat transfer predictions along the downstream were underestimated. This results suggest that the improved turbulence modeling is required.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.5
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• pp.335-344
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• 2011

A curvilinear non-hydrostatic free surface model is developed to investigate nonlinear wave interactions in a circular channel. The proposed model solves the unsteady Navier-Stokes equations in a three-dimensional domain with a pressure correction method, which is one of fractional step methods. A hybrid staggered-grid layout in the vertical direction is implemented, which renders relatively simple resulting pressure equation as well as free surface closure. Numerical accuracy with respect to wave nonlinearity is tested against the fifth-order Stokes solution in a two-dimensional numerical wave tank. Numerical applications center on the evolution of nonlinear waves including diffraction and reflection affected by the curvature of side wall in a circular channel comparing with linear waves. Except for a highly nonlinear bichrmatic wave, the model's results are in good agreement with superimposed analytical solution that neglects nonlinear effects. Through the numerical simulation of the highly nonlinear bichramatic wave, the model shows its capability to investigate the evolution of nonlinear wave groups in a circular channel.

• The Journal of Internal Korean Medicine
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• v.29 no.1
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• pp.67-79
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• 2008

Backgrounds & Objectives : The aims of this study were to observe how morphology was changed and whether gastric motility was impaired in streptozotocin(STZ)-induced diabetic rats(DR), and whether Yijin-tang(YJT) was able to restore their impaired gastric motility. Methods : We investigated the change of body weight, feed intake and blood glucose between normal rats (NR) and DR for 12 weeks after induction of diabetes. At the time of 12 weeks after induction of diabetes, gastric surface area, gastric slow wave and gastric emptying rate were measured. Results : Decreased body weight, increased feed intake and increased gastric surface area were observed in DR, compared with NR. The percentage of normogastria decreased but that of bradygastria increased in DR, compared with NR. YJT 90mg/kg had no effect on the correction of gastric slow wave. YJT 90mg/kg and 270mg/kg had a significant effect on improvement of gastric emptying, more than normal saline (NS) in both NR and DR but the gastric emptying rate of DR was significantly lower than that of NR when YJT 90mg/kg and YJT 270mg/kg were administered. Conclusions : We can expect that administration of YJT would be effective on the improvement of gastric emptying and upper gastrointestinal symptoms as a juvantia.

• Archives of Plastic Surgery
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• v.32 no.6
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• pp.710-716
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• 2005

A total of 21 patients were operated. Via a columellar labial incision, the upper lateral cartilages were separated from the septum. A submucous resection of the septal cartilage was carried out. After rasping the convex lateral nasal wall of the unaffected side, a low-to-low lateral nasal osteotomy was conducted. Along the deviated dorsal line at the bony vault passing the submucous tunnel, a paramedian nasal osteotomy was performed. The convex side of the nasal bone flap was contoured by rasping. The convex side of the "T"-shaped dorsal septum was trimmed. A total direct septal extension graft of the septal cartilage was done and the alar cartilages were suspended to it. The postoperative results were evaluated by photogrammetric analysis processed by a "neon glow" filter in Adobe Photoshop. The distance from the nasal midline to the most deflective point at 5 levels was measured, and the proportion indices were obtained in regard to intercanthal distance. The results revealed improvement in all levels (p < 0.05), although not perfect. In summary, this technique can result in a clinically good-looking in spite of a slight deflection that still exists

• Journal of Chest Surgery
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• v.39 no.11 s.268
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• pp.868-871
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• 2006

Nuss operation as a method for correction of pectus excavatum is safe and satisfactory, but its complication presents pneumothorax, displaced bar, wound infection, pericarditis, pleural effusion, hemothorax, cardiac injury etc. We report a rare case of acute ascending aortic rupture after displaced and adhered Nuss bar removal. The patient was a 30-years old man who received Nuss operation 3 years ago. Nuss bar was removed without resistance but massively bled at both operation wound, so immediately femoro-femoral CPB and median sternotomy was done and repaired proximal aortic arch under deep hypothermic total circulatory arrest. The patient was discharged without complication at postoperative 13 day.