• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.277.2-277.2
• /
• 2016

현재 화합물 반도체 나노구조는 광학적, 전기적 특성을 기반으로 하는 단전자 트랜지스터, 적외선 검출기, 레이저, 태양전지와 같은 분야에 응용하기 위한 많은 연구가 진행되고 있다. 특히 양자점은 3차원으로 구속되어 있는 상태 밀도를 갖고 있어 레이저 응용 시 낮은 문턱 전류 밀도, 높은 이득, 높은 열적 안정성을 기대되고 있지만 양자점의 운반자 수집과 열적 안정성의 한계가 여전히 존재한다. 이러한 문제를 해결하기 위해 다양한 방법이 연구되고 있으며, 그 중 단층 양자점에 비해 운반자 수집과 열적 안정성이 뛰어난 다층 양자점이 결합된 구조에 대한 연구가 활발히 이루어지고, 다층으로 성장된 양자점 구조는 양자점의 크기 분포 조절이 용이하고 양자점 층간의 전기적 결합력이 강한 특성이 있다. 본 연구에서는 분자 선속 에피 성장법(Molecular Beam Epitaxy; MBE)과 원자 층 교대 성장법(Atomic Layer Epitaxy; ALE)으로 CdTe/ZnTe 다층 양자점을 ZnTe 장벽층의 두께를 변화하면서 성장 후 광학적 특성을 연구하였다. 저온 광루미네센스 측정(Photoluminescence; PL)을 통하여 ZnTe 장벽층 두께가 증가할수록 양자점의 PL 피크가 높은 에너지로 이동함을 알 수 있었는데, 이는 ZnTe 장벽층의 두께가 증가할수록 양자점 층간의 결합력이 감소하면서 양자점의 크기가 작아졌기 때문이다. 그리고 ZnTe 장벽층의 두께가 증가할수록 PL 세기가 커지는 것을 알 수 있었는데, 이는 ZnTe 장벽층의 두께가 증가할수록 더 많은 운반자가 양자점으로 구속되기 때문이다. 또한 온도 의존 광루미네센스 측정 결과 ZnTe 장벽층의 두께가 증가할수록 열적 활성화 에너지가 커지는 것을 관찰하였고, 시분해 광루미네센스 측정을 통해 ZnTe 장벽층의 두께에 따른 운반자 동역학에 대해 연구하였다. 이와 같은 결과 CdTe/ZnTe 다층 양자점 구조에서 장벽층의 두께에 따른 광학적 특성에 대해 이해 할 수 있었다.

• Journal of the Korean earth science society
• /
• v.31 no.1
• /
• pp.88-94
• /
• 2010

A simple laboratory device and methodology are developed for deep understanding of the western boundary current (WBC). The apparatus consists of a rotating (count-clockwise) rectangular tank with a sloping bottom in order to simulate the beta effect, the variation of the Coriolis parameter with latitude. We also used a clockwise rotating disk at the surface water to mimic the wind stress forcing in mid-latitude oceans. Four experiments were carried out using some combination of a bottom type and a rotation of the tank. Experiment with the beta effect clearly demonstrated the WBClike flow as well as the Sverdrup interior. However, the water in a tank gave rise to an inertial motion under the influence of a constant Coriolis force alone. We also discussed a stiffening of the rotating fluid on the basis of the Taylor-Proudman effect. We believe that the apparatus and methods developed in this study help to understand the WBC due to the beta effect.

• Composites Research
• /
• v.27 no.2
• /
• pp.66-71
• /
• 2014

This study carried out finite element vibration analysis of pole structures made of GFRP, which is based on the micro-mechanical approach for different fiber-volume fractions. The finite element (FE) models for composite structures using multi-scale approaches described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the effect of the material combination. The FE model is used for studying free vibrations of laminated composite poles for various fiber-volume fractions. In particular, new results reported in this paper are focused on the significant effects of the fiber-volume fraction for various parameters, such as fiber angles, layup sequences, and length-thickness ratios. It may be concluded from this study that the combination effect of fiber and matrix, largely governing the dynamic characteristics of composite structures, should not be neglected and thus the optimal combination could be used to design such civil structures for better dynamic performance.

• Korean Journal of Veterinary Research
• /
• v.37 no.4
• /
• pp.765-772
• /
• 1997

제주지역 돼지에서 각종 전염성 질병 원인체에 대한 항체를 조사하여 그간 전염성 병원체에 대한 역학조사가 미진하였던 부분을 보완하여 질병의 분포를 파악하고자 1995년부터 1996년에 걸쳐 제주도 전역에서 돼지의 혈청을 채취하여 각종 병원체에 대한 항체 분포율을 조사하였다. 본 연구에서 검사한 돼지 혈청 시료에서는 돼지 오제스키병 바이러스에 대한 항체는 전혀 검출되지 않았다. 돼지 콜레라바이러스에 대한 항체는 기대 수준 이하로 낮아 백신접종이 원활히 수행되고 있지 않음을 시사하였으며 특히 농장에 따라 항체 보유돈과 항체 음성돈이 혼재하는 농장과 항체가 전혀 검출되지 않는 농장 등 돼지 콜레라 방역의 사각지대가 존재할 가능성이 있음을 보여주었다. 유 사산 원인체인 돼지 파보바이러스 및 뇌심근염에 대한 항체가가 다양하게 나타나 일부 문제가 있을 것으로 사료되었다. 돼지 생식기호흡기증후군(PRRS) 바이러스에 대한 항체 분포율은 내륙 보다 다소 낮게 나타났고, 돼지 influenza virus, 위축성 비염, 흉막 폐염 등 각종 세균성 질환에 대한 항체수준도 다양하게 나타났다. 본 혈청학적인 연구결과는 제주지역에서의 양돈방역 정책수립 및 질병방제의 기초자료로 유용하게 이용될 것으로 사료된다.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.6
• /
• pp.33-51
• /
• 2013

This paper introduces the improvement of connection method for segment in tunnel lining system using prestressed steel cable and presents the results of real-scale tests. It conducted a study about the applicability and mechanical behaviour analysis of the new method that connects segment tunnel lining using prestressed steel cable by real-scale test. Through the research, it was found that the new method has stronger connection than conventional assembling methods. Also, the new method can be expected to have integrated behavior and stability increase of shield tunnel lining. It is considered that the new method is much more effective than conventional assembling methods.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.9
• /
• pp.766-774
• /
• 2017

When a plume flow exhausted from a lunar lander descent engine impinges on the lunar surface, regolith particles on the lunar surface will be dispersed due to a plume-surface interaction. If the dispersed particles collide with the lunar lander, some adverse effects such as a performance degradation can be caused. Thus, this study tried to predict the plume flow behaviors using the CFD methods. A nozzle inside region was analyzed by a continuum flow model based on the Navier-Stokes equations while the plume behaviors of the outside nozzle was performed by comparing and analyzing the individual results using the continuum flow model and the DSMC method. As a result, it was possible to establish an optimum procedure of the plume analysis for the lunar lander descent engine in the vacuum condition. In the future, it is expected to utilize the present results for the development of the Korean lunar lander.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.5
• /
• pp.869-886
• /
• 2018

Rockbolt is one of the most common supports used to reinforce discontinuous rock during underground excavation. Extra drain pipes are installed to improve excavation workability and the anchorage of rockbolts in water bearing ground. The drain pipe is effective in improving the workability by providing drainage path, but it is difficult to expect the reinforcement effect, increasing disturbance of the discontinuous rock mass and the construction cost. To solve this problem, dual purpose rockbolt (DPR) has been developed for the reinforcement of rock and the drainage of ground water. DPR was able to improve the mechanical and hydraulic stability of the rocks quickly and economically. Two kinds of DPRs using FRP (Fiber Reinforced Plastic) and steel were investigated for the mechanical and hydraulic performance. Also, the workability and stability of DPR were analyzed.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.6
• /
• pp.466-473
• /
• 2011

The buoyancy and initial momentum fluxes make near-field dominated by buoyant jet when thermal discharge releases underwater. In order to estimate prediction capabilities of those near-field phenomena, non-hydrostatic RANS applied CFD(Computational Fluid Dynamic) model was used. Condition of model was composed based on past laboratory experiments. Numerical simulations carried out for the horizontal buoyant jet in the stagnant flow and vertical buoyant jet into crossflow. The results of simulation are compared with the terms of trajectory and dilution rate of laboratory experiments and analytic model(CorJET) results. CFD model showed a good agreement with them. CFD model can be appropriate for assessment of submerged thermal discharge effect because CFD model can resolve the limitations of near-field analytic model and far-field quasi 3D hydrodynamic model. The accuracy and capability of the CFD model is reviewed in this study. If the computational efficiency get improved, CFD model can be widely applied for simulation of transport and diffusion of submerged thermal discharge.

• Tunnel and Underground Space
• /
• v.25 no.2
• /
• pp.144-154
• /
• 2015

Mechanical energy is accumulated in the object when stress is exerted on rock specimens, and the failure is occurred when the stress is larger than critical stress. The accumulated energy is emitted as various forms including physical deformation, light, heat and sound. Uniaxial compression strength test and point load strength test were carried out in low temperature environment, and thermal variation of rock specimens were observed and analyzed quantitatively using thermal infrared camera images. Temperature of failure plane was increased just before the failure because of concentration of stress, and was rapidly increased at the moment of the failure because of the emission of thermal energy. The variations of temperature were larger in diorite and basalt specimens which were strong and fresh than in tuff specimens which were weak and weathered. This study can be applied to prevent disasters in rock slope, tunnel and mine in cold regions and to analyze satellite image for predicting earthquake in cold regions.

• The Journal of the Korea Contents Association
• /
• v.16 no.12
• /
• pp.327-345
• /
• 2016

The purpose of this study was to carry out cognitive movement therapy program for children with affective and behavioral disorder based on neuro science, psychology, motor learning, muscle physiology, biomechanics, human motion analysis, movement control and to quantify characteristic of expression and gestures according to change of facial expression by emotional change. We could observe problematic expression of children with affective disorder, and could estimate the efficiency of application of movement therapy program by the face expression change of children with affective disorder. And it could be expected to accumulate data for early detection and therapy process of development disorder applying converged measurement and analytic method for human development by quantification of emotion and behavior therapy analysis, kinematic analysis. Therefore, the result of this study could be extendedly applied to the disabled, the elderly and the sick as well as children.