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김규원,박영일,박근 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.6
Topology optimization is a shape optimization method connected with finite element (FE) analysis, and has recently received increasing attention owing to rapid evolution of additive manufacturing (AM). In this study, an automotive knuckle part was developed by combining kinetic analysis, FE structural analysis, and topology optimization. A kinetic analysis based on a multibody dynamics simulation was performed to calculate reaction forces during a given driving course. Structural FE analyses were conducted to evaluate structural safety by applying the calculated reaction forces as boundary conditions. Topology optimization was then carried out to improve the stiffness and structural safety of the knuckle. Further structural FE analyses were performed to compare the structural efficiency of the optimized design where the stiffness increased more than 2.5 times in comparison with the original design. The optimized knuckle pairs were then manufactured by a metal AM process using AlSi10Mg powders, and were assembled to the other suspension components successfully. A formula-style electric car was then built by assembling the developed knuckle, and a number of driving tests showed that the knuckle ensured adequate structural stiffness and safety.
Hepatitis associated with Mycoplasma pneumoniae infection in Korean children: a prospective study
김규원,성재진,차한,Eell Ryoo,조혜경,선용한,조강호,손동우,전인상,김윤미 대한소아청소년과학회 2015 Clinical and Experimental Pediatrics (CEP) Vol.58 No.6
Purpose: Mycoplasma pneumoniae (MP) infection is a major cause of respiratory infection in school-aged children. Extrapulmonary manifestations of MP infection are common, but liver involvement has been rarely reported. The aim of this study was to determine the clinical characteristics of MP-associated hepatitis. Methods: This prospective study included 1,044 pediatric patients with MP infection diagnosed serologically with MP IgM at one medical center from January 2006 to December 2012. Eighty of these patients had elevated levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT), each greater than 50 IU/L, without any other specific liver disorder and were compared with the 964 children without liver disorders. Results: In total, 7.7% of patients with MP infection had a diagnosis of hepatitis, especially in fall and winter. The ratio of male to female patients was 1.7:1, and the mean age of the patients was 5 years and 5 months. The most common symptoms were cough, fever, and sputum. Anorexia was the most common gastrointestinal symptom, followed by nausea/vomiting, diarrhea, and abdominal pain. Mean levels of AST and ALT were 100.65 IU/L and 118.73 IU/L, respectively. Serum AST/ALT level was normalized within 7.5 days on average without complications. The mean duration of hospitalization (11.3 days) was longer for children with hepatitis than for those without hepatitis (P=0.034). Conclusion: MP-associated hepatitis is not uncommon and has a relatively good prognosis. Therefore, clinicians should be concerned about liver involvement in MP infection but avoid further unnecessary evaluation of hepatitis associated with MP.