FEM을 이용한 선삭가공 절삭조건의 영향 분석

임세환,송춘삼,홍석관,강정진,김주현 한국공작기계학회 2007 한국공작기계학회 추계학술대회논문집 Vol.2007 No.-

A plane strain finite element model is developed to simulate turning with continuous chip formation using adaptive remeshing during the thermal-mechanical coupled analysis. Comparisons between the experimental and simulation results for cutting forces are performed to validate FE analysis results. Influences of machining parameters such as depth of cut, cutting speed and feed rate on cuting force and shear angle are analyzed by Taguchi method. The more depth of cut and feed rate result in the increase of cutting forces, but the rates of increase are decrease due to the larger shear angle. As the cutting speed increases, von Mises stress of workpiece near the tool tip decreases because the strength of specimen decreases at high temperature above 500℃. This thermal effect on cutting force is negligible because the affected area is very localized and the average values of von Mises stress in the shear plane are the same among the diverse cutting parameters.

흰쥐에서 사염화탄소에 의해 유도된 간 상해에 미치는 키토산 올리고당의 영향

이영돈,박승림,강소영,김세재,박지권,고영환 제주대학교 생명과학연구소 1999 제주생명과학연구 Vol.2 No.-

Chitosan is the deacetylated product of chitin. Chitosan and its derivatives have many properties that make them attractive for a wide variety of health applications. We reported recently that water soluble chitooligosaccharides have hepatoprotective effect on ethanol induced liver injury in the mouse. The current study examined the effect of water soluble chitooligosaccharides on CC1₄-induced liver injury in rats. Male Sprague-Dawley rats were orally treated with CC1₄without or with administration of 5% chitooligosaccharides. After 5 weeks after CC1₄treatment, the histological sections and the expression of mRNA of interleukin-12(IL-12), hepatocyte growth factor(HGF), and tumor necrosis factor(TNF- ) were examined. The liver section of rats supplemented with chitooligosaccharides showed attenuated effects of the necrosis, steatosis, cirrhosis compared with those of non-supplemented rats. The level of TNF- mRNA in CC1₄-treated rats were higher than those in the rats supplemented with chitooligosaccharides, while the levels of IL-12 and HGF mRNA were higher in the rats supplemented with chitooligosaccharides than those of in CC1₄-treated rats. These findings suggested that water soluble chitooligosaccharides may have a hepatoprotective activity against CCl₄-induced liver injury in rats.

Controlled synthesis of (hk1) preferentially oriented Sb2Se3 rod arrays by co-evaporation for photovoltaic applications

Park, Si-Nae,Kim, Se-Yun,Lee, Sang-Ju,Sung, Shi-Joon,Yang, Kee-Jeong,Kang, Jin-Kyu,Kim, Dae-Hwan Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.45

<P>In this paper, we propose that the microstructural control of (<I>hk</I>1) preferentially oriented Sb2Se3 films from flat films to rod arrays can improve their photovoltaic efficiency by maximizing the carrier transport characteristics. We found that, during co-evaporation, there is a narrow substrate temperature window where the Sb2Se3 rod array can be formed with an (<I>hk</I>1) preferred orientation, thus maximizing the carrier transport characteristics. The substrate-temperature-dependent morphology of the Sb2Se3 films can be explained by nucleation and growth theory and the terrace-ledge-kink model. Dramatic changes in the (<I>hk</I>0) and (<I>hk</I>1) texture coefficients occur at 315 °C, and the critical temperature for obtaining the (<I>hk</I>1) preferentially oriented Sb2Se3 film is a substrate temperature of 315 °C. On the basis of the observed variation in the film microstructure and texture coefficient, the optimum Sb2Se3 rod array having an (<I>hk</I>1) preferred orientation is formed in a narrow range of substrate temperatures. As a result, we obtained an optimized Sb2Se3 thin-film rod array that shows effective carrier transportation. Further, the optimum fill factor, short circuit current, open circuit voltage, and efficiency of the Sb2Se3 device were observed in the Sb2Se3 rod array having an (<I>hk</I>1) preferred orientation, and the enhanced carrier transport characteristics are the main reason for the improved device properties. These results show that controlling the microstructure of Sb2Se3 allows improvements in the efficiency of (<I>hk</I>1) preferentially oriented Sb2Se3 films.</P>

Assessment of mechanical property and rabbit calvarial bone regeneration of kagome-structure scaffold using biocompatible synthetic polymer

Se-Hwan Lee(이세환),Kang-gon Lee(이강곤),Myoung Wha Hong(홍명화),Jaeyeon Lee(이재연),Young Sang Cho(조용상),Hoon-Jin Jeong(정훈진),Kang-Sik Lee(이강식),Youngdoo Park(박용두),Sang-Hyug Park(박상혁),Young Yul Kim(김영률),Bu-Kyu Lee( 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

Fibrous network of highly integrated carbon nanotubes/MoO3 composite bundles anchored with MoO3 nanoplates for superior lithium ion battery anodes

Se Hwan Oh,Seong Mi Park,Dong-Won Kang,Yun Chan Kang,Jung Sang Cho 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.83 No.-

Fibrous network of highly-integrated CNTs/MoO3 composite bundle in which CNTs anchored with MoO3nanoplates was prepared by electrospinning process and subsequent simple heat-treatment. Byperforming the pre-acid-treatments of both CNTs and PAN, dipole-dipole interactions and hydrogenbonding between CNTs and PAN could form MoO2(acac)2-PAN-CNTs complex in a solution, which allowsfor the formation of a stable jet during electrospinning. Notably, by selectively removing PAN in as-spunfibers during heat-treatment, a highly integrated CNTs/MoO3 bundle network anchored with MoO3nanoplates was obtained. This unique CNTs/MoO3 percolation network makes it possible to achieve asuperior lithium ion storage performance by improving electrical conductivity and structure stability. Thus, the unique nanostructure has high discharge capacities of 972 mA h g 1 after 100 cycles at 1.0 A g 1and 905 mA h g 1 after 800 long-term cycles at 2.0 A g 1, when applied as anode materials for lithium-ionbatteries. The discharge capacities of 980, 920, 819, 742, 599, 484, and 374 mA h g 1 were observed atcurrent densities of 0.5, 1.0, 2.0, 3.0, 5.0, 7.0, and 10.0 A g 1, respectively.

위와 대장 관상선종의 크기와 부위에 따른 Cyclooxygenase-2 (COX-2) 발현

김세환 ( Se Hwan Kim ),이종협 ( Jong Hyup Lee ),강경희 ( Kyung Hee Kang ),박지현 ( Jee Hyun Park ),박창근 ( Chang Keun Park ),조창민 ( Chang Min Cho ),권영오 ( Young Oh Kweon ),김성국 ( Sung Kook Kim ),최용환 ( Yong Hwan Choi ) 대한소화기학회 2004 대한소화기학회지 Vol.44 No.4

Background/Aims: Recent studies have shown that cyclooxygenase-2 (COX-2) may be involved in the process of invasion, growth and apoptosis in colorectal carcinoma and in the growth and tumorigenesis in familial adenomatous polyposis. This study was conduct

Void and secondary phase formation mechanisms of CZTSSe using Sn/Cu/Zn/Mo stacked elemental precursors

Kim, Se-Yun,Son, Dae-Ho,Kim, Young-Ill,Kim, Seung-Hyun,Kim, Sammi,Ahn, Kwangseok,Sung, Shi-Joon,Hwang, Dae-Kue,Yang, Kee-Jeong,Kang, Jin-Kyu,Kim, Dae-Hwan Elsevier 2019 Nano energy Vol.59 No.-

<P><B>Abstract</B></P> <P>In recent years, Cu<SUB>2</SUB>ZnSn(S<SUB>1-x</SUB>Se<SUB>x</SUB>)<SUB>4</SUB> (CZTSSe) prepared by a two-step process using metal precursors has been reported to exhibit a relatively high power conversion efficiency, and a high efficiency of 12.5% by two-step process contained via sputtering method was recently confirmed by our group. In this study, we proposed formation mechanisms for the CZTSSe double layer, voids and ZnSSe layer, which were observed in the CZTSSe using metal precursor. Due to the persistent dezincification from the metal precursors and preferential reaction between the Zn and chalcogens such as S and Se, almost all Zn is consumed to form the ZnSSe layer; as a result, large voids are produced first under the ZnSSe layer. Cu<SUB>2</SUB>Se and SnSe are grown on the ZnSSe layer via migration of the Cu and Sn through the grain boundaries of the ZnSSe layer. Thus, additional small voids are expected to form due to the mass transfer of Cu and Sn. Because of the preferentially formed ZnSSe layer and the chalcogenation of Cu and Sn after the mass transfer, a CZTSSe double layer can be formed, and ZnSSe can exist between these CZTSSe layers. Finally, we propose a method based on the formation mechanism to control the voids and secondary phases, which affect the fill factor and output current.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The new formation mechanisms of the voids, ZnSSe layer and CZTSSe double layer that were observed in the sister sample of 12.5% of CZTSSe cell. </LI> <LI> Large voids are produced under the ZnSSe layer due to the persistent dezincification and preferential reaction between the Zn and chalcogens. </LI> <LI> Additional small voids are expected to form due to the migration of Cu and Sn from under the ZnSSe layer to above ZnSSe layer. </LI> <LI> Due to the preferentially formed ZnSSe layer and Cu and Sn migration, ZnSSe secondary phase exists between the CZTSSe double layers. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The new formation mechanisms of the voids, ZnSSe layer and CZTSSe double layer that were observed in the sister sample of 12.5% of CZTSSe cell.</P> <P>[DISPLAY OMISSION]</P>

On - Site Diagnostic Device Based on Immuno - Separation of Proteins

Paek, Se Hwan,Cho, Joung Hwan,Kang, Moon Sik,Min, Nam Ki 한국화학공학회 2001 Korean Journal of Chemical Engineering Vol.18 No.2

A membrane immuno-chromatographic system that selectively separates plasma lipoproteins and generates a signal in proportion to the concentration of cholesterol (HDL-C) within high-density lipoprotein (HDL) was investigated as a point-of-care device for the prognosis of coronary heart disease. The system consists of three functional membrane strip pads connected in a sequence for: (from the bottom) immuno-separation based on biotinstreptavidin reaction, catalytic conversion of cholesterol to hydrogen peroxide, and production of a signal. For immunochromatography, a monoclonal antibody, specific to apolipoprotein B100 that is present on the surfaces of low-density lipoproteins (LDL) and very low-density lipoproteins (VLDL), with a high binding constant (5×10^ L/mol) was raised and chemically conjugated to streptavidin. The conjugate was first reacted with lipoprotein particles, and this mixture was absorbed by the capillary action into the biotin pad of the system. After being transferred by medium, immunocapture of LDL and VLDL particles onto the biotin pad took place, and in situ generation of a signal in proportion to HDL-C consecutively occurred. The capture was selective as well as effective (minimum 90% of LDL and VLDL in clinical concentration ranges), and the detection limit of HDL-C was far lower than 20 mg/dL. To construct a userfriendly device, we are currently investigating the automation of such processes of reactions and separation by adapting a liquid flow-controlling technology that programs the times for the immune reaction and separation. My group further pursues an interdisciplinary study to develop a micro system employing semiconductor-based technologies that will eventually enable the handling of sub-micro liter volume of body fluid as a specimen.

Evaluation of mechanical strength and bone regeneration ability of 3D printed kagome-structure scaffold using rabbit calvarial defect model

Lee, Se-Hwan,Lee, Kang-Gon,Hwang, Jong-Hyun,Cho, Yong Sang,Lee, Kang-Sik,Jeong, Hun-Jin,Park, Sang-Hyug,Park, Yongdoo,Cho, Young-Sam,Lee, Bu-Kyu Elsevier 2019 Materials Science and Engineering C Vol.98 No.-

<P><B>Abstract</B></P> <P>In clinical conditions, the reconstructions performed in the complex and three-dimensional bone defects in the craniomaxillofacial (CMF) area are often limited in facial esthetics and jaw function. Furthermore, to regenerate a bone defect in the CMF area, the used scaffold should have unique features such as different mechanical strength or physical property suitable for complex shape and function of the CMF bones. Therefore, a three-dimensional synthetic scaffold with a patient-customized structure and mechanical properties is more suitable for the regeneration. In this study, the customized kagome-structure scaffold with complex morphology was assessed in vivo. The customized 3D kagome-structure model for the defect region was designed according to data using 3D computed tomography. The kagome-structure scaffold and the conventional grid-structure scaffold (as a control group) were fabricated using a 3D printer with a precision extruding deposition head using poly(ε-caprolactone) (PCL). The two types of 3D printed scaffolds were implanted in the 8-shaped defect model on the rabbit calvarium. To evaluate the osteoconductivity of the implanted scaffolds, new bone formation, hematoxylin and eosin staining, immunohistochemistry, and Masson's trichrome staining were evaluated for 16 weeks after implantation of the scaffolds. To assess the mechanical robustness and stability of the kagome-structure scaffold, numerical analysis considering the ‘elastic-perfectly plastic’ material properties and deformation under self-contact condition was performed by finite element analysis. As a result, the kagome-structure scaffold fabricated using 3D printing technology showed excellent mechanical robustness and enhanced osteoconductivity than the control group. Therefore, the 3D printed kagome-structure scaffold can be a better option for bone regeneration in complex and large defects than the conventional grid-type 3D printed scaffold.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The customized PCL kagome-structure scaffold was successfully fabricated by a precision extruding deposition head. </LI> <LI> The superior mechanical robustness of the kagome-structure scaffold has been demonstrated by realistic numerical analysis. </LI> <LI> The fabricated kagome-structure scaffold was showed excellent osteoconductivity and fitting ability. </LI> <LI> The kagome-structure scaffold can be suitably applied for esthetic and functional reconstruction in complex bony defects. </LI> </UL> </P>

레이저 스캐닝 및 정상파를 이용한 평판 구조물의 손상탐지

강세혁(Se Hyeok Kang),전준영(Jun Young Jeon),김두환(Du Hwan Kim),박규해(Gyuhae Park),강토(To Kang),한순우(Soon Woo Han) 대한기계학회 2017 大韓機械學會論文集A Vol.41 No.5

본 연구에서는 레이저 스캐닝 및 단일 주파수 정상파 가진과 파수 분석을 통해 구조물의 손상을 탐지하는 기법을 개발하였다. 구조물에 부착된 압전소자를 통해 단일 주파수로 가진하고, 이때 발생한 구조물의 정상상태 응답을 레이저 도플러 속도계와 거울 방향조절 장치를 통해 측정하였다. 구조물의 결함을 탐지하기 위해 정상상태 응답에서 파수 필터링을 이용한 손상 탐지 기법을 개발 및 적용하였다. 부식결함이 발생한 알루미늄 평판과 층간 분리가 발생한 복합재료 구조물에 대한 손상 탐지를 수행하여 손상의 위치와 크기를 정확히 파악할 수 있었다. This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.