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김동학,전민정 한국공업화학회 2000 응용화학 Vol.4 No.2
We investigated the forming process and the properties of a semi-rigid polyurethane foam which was applicable to the instrument panel of a car. For the purpose of studying the free foaming process, we made a visual mold not only to see the foaming process but also to measure the temperature of the foam with reaction time. The effects of process variables such as the ratio of reactants(polyol : isocyante), the mixing speed, and the wall temperature on the growth and density of the foam were analysed to form the useful processing guideline.
김동학,박준석 경원전문대학 1997 論文集 Vol.19 No.1
We can obtain a good method for understanding the essence and technique of Taekwondo through the comparative research on the common and different properties between Taekwondo and Taekkyun. I suggest some insufficiencies should be refilled and that Taekwondo and Taekkyun should be developed as Korean traditional martial arts and identifled itself according to each other through more researches later. I think that such a comparative analytic researches are necessary in order to spread Taekwondo all over the world and to establish the identity of Taekwondo as Korean traditional martial art and that such researches should be made on the point of view that those concepts on Taekwondo and Taekkyun are not the exclusive but the interdependent ones theoretically.
김동학,임대영,박준원,김창오,정해양,최석호 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.2
We investigated the effect of thermal annealing on the memory properties of metal-oxide-highk-oxide-silicon (MOHOS)-type structures using high-k La₂O₃ as a charge-trapping layer. When a MOHOS memory capacitor underwent rapid thermal annealing (RTA), the memory window reached a maximum at an intermediate RTA temperature and then decreased with increasing annealing temperature. The oxide stack also broke down more easily with increasing RTA temperature. X-ray photoelectron spectroscopy and transmission electron microscopy revealed that high-temperature annealing led to the diffusion of La and the formation of crystalline lanthanum silicate, resulting in a smaller breakdown field and an increased leakage current. Our experimental result indicates that the MOHOS memory can be optimized near an RTA temperature of 600 C. On the other hand, laser spike annealing (LSA), with its high peak temperature and fast heating/cooling led to a good memory property by suppressing silicate formation while creating high-density charge trapping defects in the La₂O₃layer. Our results show that LSA can be an alternative choice for MOHOS memory devices when a high-temperature annealing process is needed for device applications.
Optical Second-harmonic Generation in Few-layer MoSe2
김동학,임대영 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.5
We show that optical second-harmonic generation (SHG) from few-layer MoSe2 can sensitivelyprobe external symmetry perturbations such as chemical doping. The SHGs from few-layer MoSe2are enhanced after AuCl3 chemical doping, especially more so for the thicker MoSe2 samples. Thisenhancement is due to an electric-field-induced SHG contribution originating from the charge transferbetween the adsorbed chemical dopants and the MoSe2. By using this sensitivity, we demonstratean in-situ monitoring of the thermal desorption of adsorbed chemical dopants. Moreover, we findthat the SHG generated from monolayer MoSe2 is counter-circularly polarized for a circularlypolarizedfundamental beam due to the three-fold rotational symmetry of MoSe2. Our work showsthat SHG can probe not only the symmetry properties of atomically-thin 2D semiconductors, butalso the external symmetry perturbations on them.
차광처리가 벌개미취와 구절초의 생장 및 생리적 특성에 미치는 영향
김동학,김영은,김상준,Kim, Dong-Hak,Kim, Young-Eun,Kim, Sang-Jun 한국환경복원기술학회 2022 한국환경복원기술학회지 Vol.25 No.4
본 연구에서는 차광처리가 벌개미취와 구절초의 생리적 반응에 미치는 영향을 조사하기 위해, 대조구(0%)와 3개의 서로 다른 차광처리구(50%, 75%, 95%)를 설치하고 엽록소 함량, 생장 및 광합성 특성을 조사하였다. 벌개미취와 구절초 모두 차광수준이 높아질수록 낮은 광도에 적응하기 위해 광합성에 대한 빛의 흡수 효율이 높은 잎이 형성되었다. 또한 차광수준이 높아질수록 낮은 광도에서 광합성을 수행하기 위해 암호흡속도의 저하와 광보상점의 감소가 나타났고, 광합성 효율을 높이기 위해 엽록소 함량과 순양자수율이 증가하였다. 광합성 속도는 대조구에서 가장 높았고 차광수준이 높아질수록 저하하였다. 대조구에서는 강광에 의한 수분손실을 막기 위해 기공전도도와 증산속도가 감소하였다. 50% 차광처리구의 기공전도도와 증산속도는 대조구에 비해 높았으나, 75%와 95% 차광처리구에서는 더 낮게 나타나 광합성 효율이 떨어지는 것으로 나타났다. 수분이용효율 또한 광합성속도와 유사한 경향으로 나타났고, 차광수준에 따라서 저하하는 것으로 나타났다. 벌개미취는 전천광보다 낮은 광 조건에서 생육할 시 광합성 능력이 저하하는 것으로 보이며, 구절초의 경우 50% 차광처리까지는 광합성에 큰 영향을 끼치지 않는 것으로 판단된다. 벌개미취와 구절초는 광을 제한하여 차광 상태를 지속하게 되면 생육에 불리할 것으로 판단된다. 이러한 벌개미취와 구절초의 생육특성은 상층임관이 존재하지 않은 DMZ 불모지와 같은 환경에 도입시키기 적합할 것으로 판단된다. This study was conducted to investigate the chlorophyll content, photosynthetic characteristics, and growth characteristics of Aster koraiensis and Dendranthema zawadskii var. latiloba according to shading treatment. A. koraiensis and D. zawadskii grew in four different shading treatment plots (0%, 50%, 75% and 95% of full sunlight) for experiments. It was found that as the shading level increased, the total chlorophyll content increased and dark respiration decreased in both A. koraiensis and D. zawadskii, indicating that A. koraiensis and D. zawadskii increase the utilization efficiency for photosynthesis under low light conditions. In addition, as the shading level increased, the net apparent quantum yield increased, resulting in the highest in the 95% shading plot, but the highest photosynthetic rate, water use efficiency, and leaf mass per area (LMA) were shown in the control group than in the shading treatments. The results showed that A. koraiensis and D. zawadskii are heliophytes showing plasticity to light, and if the light is restricted to continue to shade, it may be detrimental to growth. For healthy growth, it is considered suitable to grow A. koraiensis under full light conditions, and D. zawadskii under the light condition that blocks 0-50% of full sunlight.
Excitonic Valley Polarization and Coherence in Few-layer MoS2
김동학,신민주,임대영 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.5
We study the excitonic valley polarization and coherence in few-layer MoS2 by using circularandlinear-polarization-resolved photoluminescence. The valley polarization is largest in monolayerMoS2 and decreases with increasing number of layers or temperature. Contrary to the valleypolarization, the linear polarization is negligibly small in monolayer MoS2 and increases with increasingnumber of layers or temperature. The temperature-dependent valley depolarization canbe explained by the exciton center-of-mass momentum-dependent electron-hole exchange interaction. The valley decoherence in few-layer MoS2 is much faster than the valley depolarization at lowtemperature and is steady against increasing temperature or photoexcitation intensity, indicatingthat the decoherence process does not involve phonon or carrier-carrier scattering. The dominantvalley decoherence has a pure dephasing origin and cannot be explained by the valley-depolarizinge-h exchange interaction.