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최동수 ( Dongsoo Choi ),박석호 ( Seokho Park ),김진세 ( Jinse Kim ),김용훈 ( Yonghun Kim ),이수장 ( Sujang Lee ),박천완 ( Cheonwan Park ),최승렬 ( Seung Ryul Choi ),최인덕 ( Induck Choi ) 한국농업기계학회 2017 한국농업기계학회 학술발표논문집 Vol.22 No.2
일반현미의 낮은 식미와 소화율을 보완하고 기존의 영양성분을 유지하는 과피층 제거 현미에 대한 수요가 증가하고 있다. 현미의 과피층 1%를 벗겨내면 밥을 지었을 때 거칠지 않고 부드러운 맛이 난다. 하지만 과피층을 벗겨내면 일반현미에 비하여 미질의 변화가 빨라 유통기한이 짧아지는 문제가 있으므로 이를 방지할 수 있도록 과피층 제거된 현미의 저장 기간 중에 품질변이 평가 및 품질 저하를 방지할 수 있는 포장방법에 대한 연구가 요구되고 있는 실정이다. 본 연구에서는 가공현미의 품질변화를 억제하기 위해서는 산소와 수분 투과성이 낮은 포장재로 포장을 하여야 하기 때문에 적합한 포장재 선정을 위하여 국내에서 사용되는 쌀 포장재 물성을 조사한 결과 재질은 나이론/폴리에틸렌/선형저밀도폴리에틸렌의 복합재질로 두께가 0.124~0.149 mm로 산소투과도 33.97~66.78 cc/m<sup>2</sup> · day, 투습도 2.18~4.46 g/m<sup>2</sup> · day로 산소투과도 및 투습도 두 가지 모두 좋은 특성을 보였다. 품종이 백진주인 가공된 현미를 산소투과도가 33.97, 투습도가 2.72인 포장재를 사용하여 대기, 진공, 기체치환(N<sub>2</sub>, N<sub>2</sub>+CO<sub>2</sub>) 조건으로 포장한 후 저장온도(10, 20, 30°C)에 따른 저장기간 중 품질변화를 조사하였다. 초기 지방산가는 72.9 mg KOH/100g로 30일차 지방산가 변화는 10°C에서 146.7±12.3, 20°C에서 200.8±6.9, 30°C에서 240.4±16.5로 온도에 따라 가공현미 품질변화에 크게 영향을 주었다. 대기조건 포장의 경우 포장 내 기체변화를 살펴본 결과, O<sub>2</sub>는 온도가 높을수록 호흡속도에 의해 급격히 감소하는 경향을 보였다. 진공 및 기체치환 포장방법에 따른 지방산가 변화에 크게 영향을 미치지 않았다. 이는 포장 내 산소가 존재하여 영향을 미친 것으로 판단되었다. 포장 내 산소흡착제 및 흡습제와 같은 충진재를 넣어 잔존산소를 제거하여 지방산가 변화에 미치는 영향에 대해 조사가 추가적으로 필요할 것으로 판단되었다.
Dongsoo Choi,Maenghyo Cho,Hyungi Kim 한국항공우주학회 2008 International Journal of Aeronautical and Space Sc Vol.9 No.1
The dynamic response analysis for large structures using finite element method requires a large amount of computational resources. This paper presents an efficient vibration analysis procedure by combining node-based substructuring reduction method with a response analysis scheme for structures with undamped, proportional or nonproportional damping. The iterative form of substructuring reduction scheme is derived to reduce the full eigenproblem and to calculate the dynamic responses. In calculating the time response, direct integration scheme is used because it can be applied directly to the reduced model. Especially for the non proportional damping matrix, the transformation matrices defined in the displacement space are used to reduce the system. The efficiency and the effectiveness of the present method are demonstrated through the numerical examples.
Choi, Su-Yeon,Han, Kihoon,Cutforth, Tyler,Chung, Woosuk,Park, Haram,Lee, Dongsoo,Kim, Ryunhee,Kim, Myeong-Heui,Choi, Yeeun,Shen, Kang,Kim, Eunjoon Frontiers Media S.A. 2015 Frontiers in cellular neuroscience Vol.9 No.-
<P>Synaptic adhesion molecules regulate diverse aspects of neuronal synapse development, including synapse specificity, formation, and maturation. Neph2, also known as Kirrel3, is an immunoglobulin superfamily adhesion molecule implicated in intellectual disability, neurocognitive delay associated with Jacobsen syndrome, and autism spectrum disorders. We here report mice lacking Neph2 (<I>Neph2<SUP>-/-</SUP></I> mice) display moderate hyperactivity in a familiar, but not novel, environment and defective novel object recognition with normal performances in Morris water maze spatial learning and memory, contextual fear conditioning and extinction, and pattern separation tests. These mice also show normal levels of anxiety-like behaviors, social interaction, and repetitive behaviors. At the synapse level, <I>Neph2<SUP>-/-</SUP></I> dentate gyrus granule cells exhibit unaltered dendritic spine density and spontaneous excitatory synaptic transmission. These results suggest that Neph2 is important for normal locomotor activity and object recognition memory.</P>
A Class-C Type Wideband Current-Reused VCO With Two-Step Automatic Amplitude Calibration Loop
Choi, Jin-Wook,Choi, Seung-Won,Kim, InSeong,Lee, DongSoo,Park, HyungGu,Pu, YoungGun,Lee, Kang-Yoon The Institute of Electronics and Information Engin 2015 Journal of semiconductor technology and science Vol.15 No.5
This paper presents a wideband Current-Reused Voltage Controlled Oscillator (VCO) with 2-Step Automatic Amplitude Calibration (AAC). Tuning range of the proposed VCO is from 1.95 GHz to 3.15 GHz. The mismatch of differential voltage is within 0.6 %. At 2.423 GHz, the phase noise is -116.3 dBc/Hz at the 1 MHz offset frequency with the current consumption of 2.6 mA. The VCO is implemented $0.13{\mu}m$ CMOS technology. The layout size is $720{\times}580{\mu}m^2$.
Analysis of Input Filter Interactions in Switching Power Converters
Choi, Byungcho,Kim, Dongsoo,Lee, Donggyu,Choi, Seungwon,Sun, Jian Institute of Electrical and Electronics Engineers 2007 IEEE transactions on power electronics Vol.22 No.2
<P>This paper presents the theoretical and practical details involved with the small-signal analysis of switching power converters under a strong influence of input filter interaction. A boost dc-to-dc converter controlled by voltage-mode control and the same boost converter controlled by current-mode control are used as illustrative examples. The theoretical predictions of this paper are supported by experimental results and computer simulations</P>
Dongsoo Choi,Hyungi Kim,조맹효 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.2
An accelerated substructuring reduction procedure for the iterated improved reduced system (IIRS) method is proposed. The iterated IIRS method can be combined with a substructuring scheme to provide an efficient methodology for large-scale eigenvalue problems. Not only can it reduce eigenvalue analysis errors through successive iterations, but the accuracy of the eigenanalysis is not sensitive to the selected master degrees of freedom. In practical structural eigenproblems, reducing the number of iterations can save a great deal of computation cost. The present substructuring technique modifies the iterative form of the transformation matrices in each substructure to achieve faster convergence. Applications of the present method to two numerical examples demonstrate that the proposed method can obtain lower eigensolutions of structures more accurately and efficiently, as compared with those of the current substructuring technique.
Choi, Pyungho,Kim, Dongsoo,Kim, Sangsub,Kim, Hyunwoo,Choi, Byoungdeog American Scientific Publishers 2016 Journal of Nanoscience and Nanotechnology Vol.16 No.10
<P>In this study, we characterized the interface and oxide charge generation in p-MOSFETs under negative bias temperature stress (NBTS). Thin (2.5 nm) and thick (6 nm) gate oxide MOSFETs were utilized to induce direct and Fowler-Nordheim (FN) tunneling, respectively. The threshold voltage and subthreshold swing in the thick oxide MOSFET was more significantly affected by NBTS than that of the thin oxide MOSFETs. The direct-current current-voltage (DCIV) method was implemented to investigate changes in trapped charges at the SiO2/Si interface. The change in oxide charges in the SiO2 bulk was obtained from the midgap voltage shift. The interface and oxide charges are predominantly affected by FN tunneling with less impact from direct tunneling, because of not only the hole-induced impact ionization at the SiO2/Si interface, but also the larger number of broken hydrogen atoms from the Si-H bonds, which are induced by the high applied gate bias. We conclude that devices' electrical performance can be significantly degraded when the MOSFETs are predominantly affected by FN tunneling rather than by direct tunneling under NBTS.</P>
최동수(Dongsoo Choi),김현기(Hyungi Kim),조맹효(Maenghyo Cho) 대한기계학회 2007 大韓機械學會論文集A Vol.31 No.2
An iterated improved reduced system (IIRS) procedure combined with sub-structuring scheme for nonclassically damped structural systems is presented. For dynamic analysis of such systems, complex eigenproperties are required to incorporate properly the nonclassical damping effect. In complex structural systems, the equations of motion are written in the state space form. Thus, the number of degrees of freedom of the new equations of motion and the size of the associated eigenvalue problem required to obtain the complex eigenvalues and eigenvectors are doubled. Iterated IRS method is an efficient reduction technique because the eigenproperties obtained in each iteration step improve the condensation matrix in the next iteration step. However, although this reduction technique reduces the size of problem drastically, it is not efficient to apply this technique to a single domain finite element model with degrees of freedom over several thousands. Therefore, for a practical application of the reduction method, accompanying sub-structuring scheme is necessary. In the present study, iterated IRS method combined with sub-structuring scheme for nonclssically damped structures is developed. Numerical examples demonstrate the convergence and the efficiency of a newly developed scheme.
전산유체/전산구조 연계 방법을 사용한 항공기 날개의 정적 공탄성 해석
최동수(Dongsoo Choi),전상욱(Sangook Jun),김병곤(Byung-Kon Kim),박수현(Soohyun Park),조맹효(Maenghyo Cho),이동호(Dong-Ho Lee),이경태(Kyung-Tae Lee),전승문(Seung-Moon Jun) 한국항공우주학회 2007 韓國航空宇宙學會誌 Vol.35 No.4
전산유체와 전산구조 연계 방법을 사용하여 하부에 외부 장착물이 부착된 초음속 비행체의 날개에 대한 정적 공탄성 해석을 수행하였다. 전산유체와 전산구조의 연계를 위하여 두 개의 사상 알고리즘, 즉 압력 사상 알고리즘과 변위 사상 알고리즘이 사용되었다. 공력해석은 날개주위의 유동장을 구하기 위하여 비정렬 3차원 오일러 방정식을 이용하였고 구조변위를 구하기 위하여 유한요소해석 프로그램을 사용하였다. 연계 절차는 특정 수렴조건을 만족할 때까지 반복 수행되며, 전형적인 초음속 비행체 날개에 대한 정적 공탄성 해석을 수행하여 수렴된 날개 형상을 얻었다. A static aeroelastic analysis for supersonic aircraft wing equipped with external store under the wing lower surface is performed using computational fluid dynamics (CFO) and computational structural technology(CST) coupling methodology. Two mapping algorithms, which are the pressure mapping algorithm and the displacement mapping algorithm, are used for CFD/CST coupling. A three-dimensional unstructured Euler code and finite element analysis program are used to calculate the flow properties and the structural displacements, respectively. The coupling procedure is repeated in an iterative manner until a specified convergence criterion is satisfied. Static aeroelastic analysis for a typical supersonic flight wing is performed and final converged wing configuration is obtained after several iterations.