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Study on Relationship between Design Parameters and Formability in Flexible Stretch Forming Process
서영호,김정,강범수 한국정밀공학회 2012 International Journal of Precision Engineering and Vol.13 No.10
In the present work, relationships between the design parameters and the quality of aluminum sheets formed by the flexible stretch forming process (FSFP) were studied. The punch size, objective curvature radius, and elastic pad thickness were selected as the design parameters. The forming quality was expressed as the shape error, which can be defined by error values at the sampling points. The analytical dataset used to obtain the relationships was collected by means of a series of the finite element (FE) simulations including elastic recovery analysis. The relationships were investigated by regression analysis and a neural network that incorporated a backpropagation training algorithm. The neural network model shows a higher capability of estimating the shape error than the regression model. The effects of primary design parameters selected by the regression analysis were investigated for the shape error. This shows that two types of shape error are affected by different parameters. In order to achieve an acceptable forming quality, the optimum combination of the design parameters must be determined. The predictive model based on the neural network approach provides insights into this procedure.
Development of Audio Frequency Vibration Microforming System
서영호,김병희,박찬진,이혜진,이낙규 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.
Many researchers have developed several microforming technologies such as micro deep drawing, micro press forming,microforging, and extrusion for creating precise micropatterns on the surface of metal substrates, but they have found it difficult to avoid elastic recovery, which results in low formability and degradation of surface roughness and accuracy of three-dimensional formed profiles. The audio frequency vibration microforming system (AFV forming system) developed in this study can dramatically enhance not only the formability of metal substrates but also the accuracy of three-dimensional formed surfaces, because fast micro tramping action over a microdeformed region minimizes elastic recovery and removes several defects that occur in conventional microforming. The developed AFV system is mainly composed of a vertical hydraulic cylinder for macro movement and a vibratory tool actuated by an optimally preloaded lead zirconate titanate (PZT) stack, punches, and some structural compartments. In order to design the system optimally and determine the optimal process modes and conditions, several FEM analyses and experiments were performed. The experimental results of varying vibration schemes and processing conditions yielded the optimal process conditions and proved the validity of the developed novel microforming system.
스테레오 비디오를 이용한 실시간 3차원 입체 변환 시스템
서영호,김동욱,최현준 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.10
본 논문에서는 스테레오 카메라를 이용하여 실시간으로 3차원 입체 영상을 재생할 수 있는 시스템을 구현하였 다. 전체 시스템은 스테레오 카메라, FPGA(field programmable gate array) 보드, 그리고 3차원입체 LCD로 구성 된다. 스테레오 카메라로는 두 개의 CMOS 영상 센서를 사용하였다. 비디오 데이터를 처리하는 FPGA는 Verilog-HDL(hardware description language)을 이용하여 설계하였고 다양한 해상도의 비디오를 실시간으로 처리 할 수 있다. 3차원 입체 영상을 구성은 side-by-side와 up-down 방식을 이용한다. FPGA로 입력된 두 개의 프레 임은 입체 영상으로 재생되기 위한 형태로 가공된 후에 SDRAM에 저장된다. 다음 프레임이 입력될 때 이전 프레 임은 LCD로 재생하기 위해 DA 변환기로 출력된다. 이러한 전체적인 파이프라인 동작을 통해서 실시간 동작이 가능하다. 제안한 시스템은 실제 하드웨어로 구현한 후에 정확한 동작이 수행됨을 검증하였다.
서영호,김장수,서성철,서원희,유영,송대진,정지태 대한소아청소년과학회 2014 Clinical and Experimental Pediatrics (CEP) Vol.57 No.4
Purpose: The prevalence of macrolide-resistant Mycoplasma pneumoniae (MRMP) has increasedworldwide. The aim of this study was to estimate the proportion of MRMP in a tertiary hospital in Korea,and to find potential laboratory markers that could be used to predict the efficacy of macrolides in childrenwith MRMP pneumonia. Methods: A total of 95 patients with M. pneumoniae pneumonia were enrolled in this study. Detectionof MRMP was based on the results of specific point mutations in domain V of the 23S rRNA gene. Themedical records of these patients were reviewed retrospectively and the clinical course and laboratorydata were compared. Results: The proportion of patients with MRMP was 51.6% and all MRMP isolates had the A2063G pointmutation. The MRMP group had longer hospital stay and febrile period after initiation of macrolides. The levels of serum C-reactive protein (CRP) and interleukin-18 in nasopharyngeal aspirate were significantlyhigher in patients who did not respond to macrolide treatment. CRP was the only significant factor inpredicting the efficacy of macrolides in patients with MRMP pneumonia. The area under the curve forCRP was 0.69 in receiver operating characteristic curve analysis, indicating reasonable discriminativepower, and the optimal cutoff value was 40.7 mg/L. Conclusion: The proportion of patients with MRMP was high, suggesting that the prevalence of MRMPis rising rapidly in Korea. Serum CRP could be a useful marker for predicting the efficacy of macrolidesand helping clinicians make better clinical decisions in children with MRMP pneumonia.
PVA/CNC 바이오소재 하이드로겔의 기계적 물성과 생체적합성 연구
서영호,조선미,한성수,오태환 한국섬유공학회 2023 한국섬유공학회지 Vol.60 No.5
In this study, PVA (polyvinyl alcohol) and CNC (cellulose nano-crystal) compositehydrogel was manufactured and the effect of CNC content less than 1 wt% was investigatedon the mechanical properties and cell viability. The CNC was utilized to enhance thecompressive stress of the PVA hydrogel. We have focused on a low content of CNC lessthan 1 wt% because CNC is very expensive to use as an additive. The fabrication of PVA/CNC hydrogels with CNC contents of 0.25, 0.50, and 0.75 wt% was done using solvent castingand freeze-thawing physical cross-linking method. The compressive strength of thePVA/CNC hydrogel with a CNC content of 0.75 wt% was improved up to 95% higher thanthat of pristine PVA. Furthermore, through MTT and DAPI staining experiments, PVA/CNChydrogels exhibited no toxicity and good cell viability due to the smooth proliferation ofcells.
제 1형 신경섬유종증에 합병된 모야모야병에서 신장동맥 협착을 동반한 고혈압
서영호,임형은,유기환,Seo, Young Ho,Yim, Hyung Eun,Yoo, Kee Hwan 대한소아신장학회 2013 Childhood kidney diseases Vol.17 No.2
신경섬유종은 드문 전신 질환으로 여러 장기를 침범하며 특히 다양한 크기의 혈관을 침범하여 혈관병을 발생시켜 대동맥 협착, 모야모야병, 신동맥 협착 등을 일으킨다. 이로 인하여 약 0.4-6.4%의 환자에서 고혈압 증상이 있으며 이의 원인으로 신혈관 협착이 가장 흔하다. 특히 약물에도 조절되지 않는 고혈압은 혈관 협착 등이 원인이 될 수 있기 때문에 도플러 초음파 검사나 전산화 혈관 조영술 등의 정밀 검사가 필요하다. 이에 대한 치료는 약물 치료, 피부경유 혈관경유혈관성형술, 수술적 치료 등의 병합 요법으로 이루어지며 재협착 발생률이 높기 때문에 주의 깊은 추적 관찰이 필요하다. 본 저자들은 제 1형 신경섬유종증에 합병된 모야모야병에서 신장동맥 협착을 동반한 고혈압을 진단받고 치료한 1례를 경험하였기에 보고하는 바이다. Neurofibromatosis type 1 (NF-1) is an autosomal dominant neurocutaneous disorder, which can affect different organs or systems of the body, including the cardiovascular system. One of the more serious aspects of the disease relates to arterial involvement. In particular, renal artery stenosis is one of the most common vascular abnormalities in patients with NF-1, and the manifestations vary, ranging from no symptoms to end-stage renal failure. Treatment usually consists of antihypertensive drugs, percutaneous transluminal angioplasty, or surgery. Other causes of hypertension should be ruled out and the patient followed up for close monitoring and proper management. We report a case of bilateral renal artery stenosis and hypertension in a patient with moyamoya disease associated with neurofibromatosis type 1. This report discusses the literature available on the current subject, its clinical features, diagnosis, and treatment.