• Journal of Korea Water Resources Association
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• v.55 no.2
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• pp.147-157
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• 2022

The backward-facing step (BFS) is a benchmark geometry for analyzing flow separation occurred at the edge and resulting development of shear layer and recirculation zone that are occupied by turbulent flow. It is important to accurately reproduce and analyze the mean flow and turbulence statistics of such flows to design physically stable and performance assurance structure. We carried out 3D RANS computations with widely used, two representative turbulence models, k-ω SST and RNG k-ε, to reproduce BFS flow at the Reynolds number of 23,000 and the Froude number of 0.22. The performance of RANS computations is evaluated by comparing numerical results with an experimental measurement. Both RANS computations with two turbulence models appear to reasonably well reproduce mean flow in the shear layer and recirculation zone, while RNG k-ε computation results in about 5% larger velocity between the outer edge of boundary layer and the free surface above the recirculation zone than k-ω SST computation and experiment. Both turbulence models underestimate the shear stress distribution experimentally observed just downstream of the sharp edge of BFS, while shear stresses computed in the boundary layer downstream of reattachment point are agree reasonably well with experimental measurement. RNG k-ε modeling reproduces better shear stress distribution along the bottom boundary layer, but overestimates shear shear stress in the approaching boundary layer and above the bottom boundary layer downstream of the BFS.

• Korean Journal of Psychosomatic Medicine
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• v.15 no.2
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• pp.93-99
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• 2007

Object : This study aimed to investigate the characteristics of delirium in liver transplanted patients in a hospital in Korea. Method : We reviewed the medical records of 29 liver transplanted patients who were confirmed as delirium by psychiatrists with DSM-IV-TR diagnostic criteria. We estimated the correlation between delirium and clinical conditions of liver transplantations. Result : Post-operative delirium duration was significantly correlated with frequency of hepatic encephalopathy, pre-operative mental status, and stay of intensive care unit. Conclusion : Although there were many limitations of this study, it seemed that pre-operative hepatic encephalopathy affected post liver transplantation delirium.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.301-302
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• 2015

본 연구는 출혈성 뇌졸중 환자의 배뇨장애 관련요인을 파악하기 위한 후향적 연구로서 환자의 나이와 출혈 부위는 배뇨장애와 관련성이 없었으며 출혈량이 많을수록, 입원기간이 길수록, 유치도뇨 기간이 길수록 GCS점수가 낮을수록 배뇨장애가 있는 것으로 나타났으나 배뇨장애에 영향을 미치는 요인으로는 유치도뇨 유지기간만이 유의하였으며, 유치도뇨 기간이 1일씩 늘어날 때마다 배뇨장애가 발생할 확률은 1.18배씩 늘어나는 것으로 나타났다.

• Journal of Dental Rehabilitation and Applied Science
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• v.25 no.3
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• pp.267-277
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• 2009

Recently implant supported single crown is the popular treatment option to replace a single missing tooth. The purpose of this retrospective study was to analyze and evaluate the survival of implants with the $TiUnite^{TM}$ surface for single tooth replacement. From September 2002 to December 2006, 269 TiUniteTM surfaced implants were used in single tooth replacements at the Institute of Oral Health Science, Samsung Medical Center. Twenty one cases were excluded because of neighbor implants, missing records & short follow up period. Among 248 implants, the 129 implants (52.0%) were inserted in the maxilla and 119 (48.0%) in the mandible. One hundred implants placement (40.3%) were combined with guided bone regeneration, and 36 implants placement (14.5%) were combined with sinus bone augmentation. Mean observation period was $26.0{\pm}11.8$ months after implant placement. Twelve implants were recorded as failures, rendering a single implant survival rate of 95.2% over the observation period. Among failed 12 implants, 10 implants placed in the maxilla. The survival rate in the maxilla was 92.2% and in the mandible was 98.3%. The use of $TiUnite^{TM}$ surfaced single implant placement showed high survival rate for short time period.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.4
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• pp.425-436
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• 2021

The aim of this study was to provide pathological information of pediatric oral lesions by retrospectively analyzing oral biopsy results from pediatric patients at the Seoul National University Dental Hospital. Biopsy results of all oral lesions from pediatric patients, aged 0 - 16 years, were collected from the files of the Department of Oral Pathology, Seoul National University Dental Hospital from January 2000 to April 2020. The patients were divided into 3 age groups: 0 - 5, 6 - 11 and 12 - 16 years. All oral lesions were classified into three main categories: inflammatory and reactive, tumor or tumor-like and cystic lesions. Among the total of 2928 biopsy specimens, tumor or tumor-like lesions(35.66%) were the most common, followed by inflammatory and reactive lesions(34.29%) and cystic lesions(30.05%). Regardless of the categories used in this study, odontoma was the most frequently found lesion, mucocele and dentigerous cyst being the next common. This study was the first retrospective review of pediatric oral pathology in Korea, and the results from this study may assist in providing informative insight into the pediatric oral pathology for pediatric dentists.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.363-368
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• 2020

Background: Intraoperative and postoperative ocular complications are rare. We retrospectively investigated the abnormal ocular findings in patients who underwent arthroscopic shoulder surgery. Methods: The records were investigated of patients who underwent shoulder arthroscopic surgery at our hospital between January 2018 and March 2019. Ocular complications were confirmed by review of medical records. We performed logistic regression analysis to defined the main factors associated with ocular complications. Results: The overall prevalence of postoperative ocular complications was 8.5% (18/211). A significant association was found between anti-adhesion barrier agent and ocular complications (p=0.020). Conclusions: Anti-adhesion barrier agent used during surgery may be the cause of postoperative ocular complication.

• Journal of the korean academy of Pediatric Dentistry
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• v.42 no.3
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• pp.249-256
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• 2015

Restorative dental materials have advanced rapidly, with improved physical properties that improve survival rates. Accordingly, various materials can be selected. Amalgam, composite resin, glass-ionomer cement, and preformed stainless steel crowns have all been used widely for the restoration of dental caries in primary molars. The various dental materials used to treat proximal caries in the primary molars have distinct advantages and disadvantages. However, few studies have examined their survival rates. This retrospective study examined the 2-year survival rates of more than 700 class II restorations of proximal caries in primary molars clinically and radiologically according to the type of restoration. The study results should help in the selection of class II restorations for molars, one of the biggest concerns of pediatric dentists.

• Journal of Aerospace System Engineering
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• v.13 no.6
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• pp.9-16
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• 2019

The experiment on the liquid jet in crossflow in supersonic BFS (backward-facing step) flow was conducted to investigate the mixing characteristics. The working fluids are nitrogen and water. The shadow graph technique was used to visualize the flow field. Images captured by the high-speed camera were applied to analyze the flow phenomena. The liquid jet was injected at the re-circulation zone created by the supersonic jet flow. Experimental conditions are defined based on the pressure of the nitrogen gas chamber and pressurized liquid tank. In respective cases, the penetration depth of liquid jet and location of the Mach disc were observed to be proportional to the momentum ratio of gas and liquid jets.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.363-367
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• 2016

A test section of a supersonic wind tunnel was designed for the analysis of flow characteristics over a backward-facing step with Mach 1.0 slot injection in a supersonic flow of Mach 2.5. The cavity flow of a high-speed vehicle is very complex at supersonic speed, so it is necessary to do experiments using supersonic wind tunnels to verify numerical analysis methods. The previous 2D symmetrical nozzle was replaced with an asymmetrical nozzle. The inviscid nozzle contour was designed using Method of Characteristics (MOC), and the boundary layer thickness correction was reflected by experimental data from the wind tunnel. The results were compared with a CFD analysis. The PID control system was changed to be based on the change of tank pressure. This improved the control efficiency, and the run times of supersonic flow increased by about 1 second. The flow characteristics over a backward facing step with slot injection were visualized by a Schlieren device. This equipment will be used for an experimental study of the film cooling effectiveness over a cavity with various velocities, mass flows, and temperatures.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.237-243
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• 2017

This study evaluated the applicability of computer-aided diagnosis by retrospective analysis of GLCM algorithm based on cytopathological diagnosis of normal and malignant nodules in thyroid ultrasound images. In the experiment, the recognition rate and ROC curve of thyroid malignant nodule were analyzed using 6 parameters of GLCM algorithm. Experimental results showed 97% energy, 93% contrast, 92% correlation, 92% homogeneity, 100% entropy and 100% variance. Statistical analysis showed that the area under the curve of each parameter was more than 0.947 (p = 0.001) in the ROC curve, which was significant in the recognition of thyroid malignant nodules. In the GLCM, the cut-off value of each parameter can be used to predict the disease through analysis of quantitative computer-aided diagnosis.