Frankia EuIKl 균주에서 nif-유전자의 배열과 nifW, nifZ, nifB, nifU, nifS의 염기 서열

학위논문(석사)--서울대학교 대학원 :생물학과,1996.Maste

Empirical study and forecasting on relationship between macroeconomic variables and the stock price index : VECM application

학위논문 (석사)-- 서울대학교 대학원 : 경제학부, 2011.2. 김영식.Maste

A Digital Control Method for Photovoltaic Module Based Power Conditioning System

학위논문 (석사)-- 서울대학교 대학원 : 전기. 컴퓨터공학부, 2011.2. 조보형.Maste

거시경제 변수와 주가 간 관계 실증분석 및 예측 : VECM 적용

학위논문(석사) --서울대학교 대학원 :경제학부,2011.2.Maste

Meniscus-Guided Three-Dimensional Writing of Organic Nanostructures

DoctorOrganic electronics increasingly impacts our everyday life with a variety of smart electronic devices. This blossoming domain could greatly profit from effective ways to fabricate conducting or semiconducting organic nanowires. Specifically, the three-dimensional (3D) and individual integration of each nanowire is essential for many new device concepts such as stretchable electronic devices and nano-bioprobe devices, but so far this was not possible. Typical methods for fabricating the nanowires such as soft lithography, dip-pen lithography, and electrospinning are still limited to 2D in-plane patterning of low-aspect ratio.In this work, we developed 3D writing method of organic nanostructures based on nanoscale meniscus-guided growth using a micropipette. To investigate the material growth dynamics, we performed real-time observation using x-ray microradiography. First, we demonstrated 3D conjugated polymer nanowire arrays fabricated by meniscus-guided polymerization in air. The wire radius is accuratelly controlled down to ~ 50 nm by modifying pulling speed of the micropipette. We specifically produced arrays of different types of freestanding nanocomponents: straight wires, complex-shape wires, branches and bridges. The technique individually controlled the electrical transport properties of each nanocomponent. The tests included the fabrication of real devices: nano-arches operating as individually addressable photo-switches. Our demonstration is an important step for organic electronic integration with high density and enhanced freedom in circuit design.Second, we demonstrated highly stretchable active electronic devices by using meniscus-guided 3D writing of organic conjugated polymers. Specifically, our method produced 3D microarches with > 270 % stretchability and no deterioration of the electrical characteristics. Then, we integrated the microarches into electrochemical transistors and photo-switches operating under extreme stretching condition. The impact of these successful tests goes well beyond these specific devices and opens the way to many different classes of stretchable microdevices based on organic materials.Lastly, we demonstrated the patterning of 3D polypyrrole (PPy) microcontainers using meniscus-guided bubble templates. Using real-time x-ray microradiography, we investigated the 3D microcontainer growth in electropolymerization of PPy on bubbles. We revealed the existence of a “deformation force” at the three-phase boundary between gas (bubble), liquid (electrolyte), and solid (PPy). As the deformation force increases, the microcontainer shape gradually changes from spherical to elliptical and then to cylindrical. From above investigation, we demonstrated patterned microcontainers with controlled shapes and site-specific positioning. This work suggests a simple but effective approach to modulate the 3D microstructure shapes in many cases of template-free method

Drawbar Pull Estimation in Agricultural Tractor Tires on Asphalt Road Surface using Magic Formula

Agricultural tractors drive and operate both off-road and on-road. Tire road interaction significantly affects the –tractive performance of a tractor, which is difficult to predict numerically. Many empirical models have beendeveloped to predict the tractive performance of tractors using the cone index, which can be measured throughsimple tests. However, a magic formula model that can determine the tractive performance without a cone indexcan be used instead of traditional empirical models as the cone index cannot be measured on asphalt roads. Theaim of this study was to predict the tractive performance of a tractor using the magic formula tire model. Thetraction force of the tires on an asphalt road was measured using an agricultural tractor. The dynamic wheelload was calculated to derive the coefficients of the traction slip curve using the measured static wheel load and –drawbar pull of the tractor. Curve fitting was performed to fit the experimental data using the magic formula. The parameters of the magic formula tire model were well identified, and the model successfully determined thecoefficient of traction of the tractor.N

Determination of Design Loads of Maize Harvester Using Actual Working Load

농업기계는 다양한 환경과 작물을 대상으로 작업을 수행하기 때문에 농업기계의 설계와 개발은 실 작업 부하를 고려하여 수행되어야 한다. 따라서 본 연구에서는 식용 옥수수 수확기의 실 작업 부하를 계측하기 위해 식용 옥수수 수확 시험을 수행하였다. 또한, 계측된 부하 데이터를이용하여 수확기 내 기어박스 요소들의 강도 및 수명을 평가하기 위한 부하 스펙트럼을 구축하였다. 부하 스펙트럼은 기어박스의 구성요소 중기어와 베어링에 적용 가능한 하중 지속 분포와 기어와 베어링을 제외한 축, 하우징, 캐리어 등에 적용 가능한 부하 스펙트럼으로 나누어 구축하였다. 본 연구를 통해 구축된 하중 지속 분포 및 부하 스펙트럼은 식용 옥수수 수확기의 기어박스 강도 및 수명 평가뿐만 아니라, 기어박스의 설계하중으로도 활용이 가능할 것으로 보인다.N