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Sung Kim,Yong-In Kim,Jin-Hyuk Kim,Young-Seok Choi 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6
In this study, the shape of a mixed-flow pump impeller and its flow characteristics as a function of the specific speed are studied to improve its suction performance and efficiency. The shapes of mixed-flow pump impellers show a trend based on the specific speed. To construct the optimum database, a mixed-flow pump impeller with a specified specific speed is optimally designed using computational fluid dynamics (CFD) and design of experiment (DOE). The design variables of the impeller are defined in the meridional plane and vane plane development for impeller. By analyzing the trends of different mixed-flow pump impeller shapes, the optimized shape that satisfies the design specification can be designed easily. The trend exhibited by the design variables depending on the specific speed is analyzed using the shape of the optimally designed mixed-flow pump impeller. The shape of the mixed-flow pump impeller, as per the required design specification, is designed using the trends of the design variables based on the specific speed. The performance of the designed model is verified using CFD and experimental test.
Sang Hyun Lee,Su Hong Eom,Mun-Seok Jang,Eung Hyuk Lee 한국재활복지공학회 2018 한국재활복지공학회 학술대회논문집 Vol.2018 No.11
Transfemoral prosthesis is an assistive device that enables gait of below-knee amputees. Transfemoral prosthesis are largely divided into active powered and passive types depending on the control method. Currently, active powered transfemoral prosthesis support various gait environments by improving the disadvantages of transfemoral prosthesis. Active powered transfemoral prosthesis estimate the gait environment and conditions through the acquired gait information by measuring the motion state of the knee joint through inertia sensors and the ground reaction force through a load cell. However, these advanced active powered transfemoral prosthesis still have functional limitations in reacting to dangerous situations. Therefore, this study classifies collision types using inertia sensors which arc effective for estimating the motion and impulse among the sensors mounted in existing active powered transfemoral prosthesis, which can be used in prosthetic systems. Furthermore, to change the response method depending on the impulse, the dangerous situations in the event of a collision were classified through an extended support vector machine (SVM). Experiments were conducted with 5 persons of 70 ㎏ and 10 persons of 80 ㎏, and the dangerous situations were classified in accordance with each collision type.
Sung Cheol Park,Sangjun Park,Do-Hyung Lee,Jinew Seo,Jae Hyuk Yang,Min-Seok Kang,Yunjin Nam,Seung Woo Suh 대한정형외과학회 2024 Clinics in Orthopedic Surgery Vol.16 No.1
Background: The lumbosacral (LS) junction has a higher nonunion rate than other lumbar segments, especially in long-level fusion. Nonunion at L5–S1 would result in low back pain, spinal imbalance, and poor surgical outcomes. Although anterior column support at L5–S1 has been recommended to prevent nonunion in long-level LS fusion, fusion length requiring additional spinopelvic fixation (SPF) in LS fusion with anterior column support at L5–S1 has not been evaluated thoroughly. This study aimed to determine the number of fused levels requiring SPF in LS fusion with anterior column support at L5–S1 by assessing the interbody fusion status using computed tomography (CT) depending on the fusion length. Methods: Patients who underwent instrumented LS fusion with L5–S1 interbody fusion without additional augmentation and CT > 1 year postoperatively were included. The fusion rates were assessed based on the number of fused segments. Patients were divided into two groups depending on the L5–S1 interbody fusion status: those with union vs. those with nonunion. Binary logistic regression analyses were performed to identify risk factors for LS junctional nonunion. Results: Fusion rates of L5–S1 interbody fusion were 94.9%, 90.3%, 80.0%, 50.0%, 52.6%, and 43.5% for fusion of 1, 2, 3, 4, 5, and ≥ 6 levels, respectively. The number of spinal levels fused ≥ 4 (p < 0.001), low preoperative bone mineral density (BMD; adjusted odds ratio [aOR], 0.667; p = 0.035), and postoperative pelvic incidence (PI) – lumbar lordosis (LL) mismatch (aOR, 1.034; p = 0.040) were identified as significant risk factors for nonunion of L5–S1 interbody fusion according to the multivariate logistic regression analysis. Conclusions: Exhibiting ≥ 4 fused spinal levels, low preoperative BMD, and large postoperative PI–LL mismatch were identified as independent risk factors for nonunion of anterior column support at L5–S1 in LS fusion without additional fixation. Therefore, SPF should be considered in LS fusion extending to or above L2 to prevent LS junctional nonunion.
( Sang Soo Lee ),( Sook Hyang Jeong ),( Mun Hyuk Seong ),( Eun Sun Jang ),( Jin Wook Kim ),( Young Seok Kim ),( Youn Jae Lee ),( In Hee Kim ),( Si Hyun Bae ),( Han Chu Lee ),( Mee Kyung Kee ),( Sung S 대한간학회 2013 춘·추계 학술대회 (KASL) Vol.2013 No.1
Background: The natural history of hepatitis C virus (HCV)- related cirrhosis has been poorly investigated in hepatitis B virus virus (HBV) endemic area. The aim of this study was to investigate the outcome of HCV-related cirrhosis, and to search for the predictive factors related to poor outcome in Korea. Methods: A prospective, multicenter cohort study was conducted in which 233 patients with HCV-related cirrhosis were enrolled at six university hospitals in Korea from Jan 2007 to Jun 2012, and followed for mean duration of 26 months. Baseline clinical characteristics were collected from the subjects, and the clinical outcomes were defined as development of hepatocellular carcinoma (HCC) and liver transplantation or death. Results: During observation period of 26.5 ± 18.5 months (mean ± SD), HCC developed in 27 patients (12.1%), and mortality in 15 (6.7%) patients. The 5-year cumulative HCC incidence was 34.0%, and the cumulative overall mortality or transplantation at 5 years was 11.8%. At univariate analysis, age > 65 year (P=0.020), absence of anti-HBs (P=0.002), serum albumin level < 3.5 g/dL (P=0.003), and alpha-fetoprotein level > 20 ng/ml (P=0.027) were associated with an increased risk of HCC development. Multivariate analysis showed that serum albumin level < 3.5 g/dL was the independent factor for HCC development (HR 0.195, P=0.001). The independent factors for mortality or transplantation were age > 65 year (HR 3.898, P=0.040), lower serum hemoglobin level (HR 0.547 per 1 g/dL, P=0.001), and presence of ascites (HR 1.974, P=0.010). Conclusions: We found that the cumulative incidence of HCC from HCV-related cirrhosis seems to be high in Korea, similar to that of Japan. Poor liver function represented as serum albumin level or ascites was an independent factor for poor outcomes. Further study on the role of age and past infection of HBV in the HCV-related hepatocarcinogenesis is warranted.