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        • KCI등재

          알루미늄 기반 Oxide/Metal/Oxide 구조의 투명전극 적용성 기초 연구

          김대균,최두호,Kim, Daekyun,Choi, Dooho 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.7

          In this study, oxide/metal/oxide-type transparent electrodes based on Al and ZnO were investigated. Thin films of these materials were sputter-deposited at room temperature. To evaluate the thickness dependence of the oxide layers, the top and bottom ZnO layers were varied in the range of 5~80 nm and 2.5~20 nm, respectively. When the thicknesses of the top and bottom ZnO layers were fixed at 30 nm and 2.5 nm, a maximum transmitance of 66% and sheet resistance of $16.5{\Omega}/{\square}$ were achieved, which is significantly improved compared with the Al layer without top and bottom ZnO layers showing a maximum transmitance of 44.3% and sheet resistance of $44{\Omega}/{\square}$.

        • KCI등재
        • KCI등재

          옥수수 부산물과 토끼 분변의 이화학적 성분특성 및 퇴비 제조조건

          김대균,김진영,이원석,김혜형,서명훈,박인태,현준기,유가영 한국환경영향평가학회 2018 환경영향평가 Vol.27 No.6

          This study was conducted to suggest a sustainable farming practice for resource recycling in vegetable gardens of North Korea. In North Korea, farmers are allowed to own private vegetable gardens less than 100 m2. However, usage of fertilizers in private vegetable gardens is very limited due to economic sanctions by UN security council. If North and South Korea initiated the cooperative action in the near future, agricultural sector would be the highest priority cooperation area. Considering the current North Korean situation in agriculture, we would like to suggest a method for producing organic fertilizer manure. For raw materials for producing manure, we selected corn byproduct, which is the most abundant material, and rabbits’ feces, which are easily obtained from individual private farms in North Korea. As we cannot get corn byproducts and rabbits’ feces from North Korea, we prepared samples of corn byproducts and rabbits; feces from many places in South Korea. After statistical analysis of variance, there was no significant difference in the T-N contents of corn byproducts from Gyeonggi, Gangwon, Chungnam, Chungbuk, Jeollabuk and Gyeongsangnam-dos, which indicates that the fertilizing quality of corn byproducts does not vary significantly in the spatial scale of South. Korea. In this sense, if we use corn samples from Gyeonggi province, they would not be very different from those of North Korean regions. Physicochemical properties of rabbits’ feces were different between those eating feed grains and those eating plants only. Hence, we used rabbits’ feces of the rabbits from Yeonchun area, which were fed by plants only. Using three different mixing ratios of corn byproducts and rabbits’ feces, composting was conducted for 60 days. The mixing ratio of 1:1 produced the manure with % T-N of 1.98% and OM/N ratio of 31.7 after 30 days of composting, which is comparable to the quality of commercial manure. 북한의 텃밭에서는 비료사용이 매우 제한적이므로 남북한 농업분야 협력사업의 하나로 텃밭 부산물을 이용한 퇴비 제조방법의 제안은 실용적 가치가 있다. 본 연구는 북한의 실정을 고려하여 토끼 분변과 옥수수 부산물이 가장 얻기 쉬운 원재료 물질로 판단하고 이를 이용한 퇴비 제조 방법을 제안하고자 하였다. 북한의 시료를 구하기는 불가능한 일이기 때문에 남한의 여러 지역에서 옥수수 부산물 시료를 구하여 이들의 이화학적 성질을 분석하였다. 분석 결과, 주요 비료 성분인 질소의 경우 남한 정도의 공간 규모에서 유의한 차이가 없었으므로 경기도 지역의 옥수수 부산물을 퇴비화 재료로 활용하였다. 토끼 분변도여러 지역에서 수집 분석하였는데 이를 풀만을 급이한 중국 단동의 분변 시료와 비교하였다. 이 결과 사료를 먹은 토끼 분변의 질소 함량은 풀을 먹인 토끼 분변에 비해 유의하게 낮았다. 북한 상황을 고려할 때텃밭에서 키우는 토끼는 사료가 아닌 풀을 급이할 확률이 크지만 재료의 가용성으로 인해 경기도 연천에서 토끼의 분변을 확보하여 퇴비화 재료로 활용하였다. 퇴비화 과정은 토끼 분변과 옥수수 부산물의 혼합비를 1:1, 1:2, 1:3 로 각각 처리하여 60일 동안 진행하였다. 그 결과 1:1 혼합비를 통해 제조된 퇴비는 부숙 완료 후 총 질소 함량은 1.98%이었고 유기물/질소 비도 31.7에 달하여 시판되고 있는 상업용 퇴비와질적으로 차이가 없음을 확인하였다.

        • KCI등재후보
        • KCI등재

          마그네트론 스퍼터링법으로 제조된 ZnO/Cu/ZnO 유연 투명전극 성능 최적화 연구

          김대균,이태형,최두호 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.12

          With the expanding development of flexible optoelectronic devices, the need for high-performance (i.e., high conductivity, high transmittance and flexibility) transparent conductive electrodes has grown. In this study, the critical role of thickness for each of the layers in ZnO/Cu/ZnO transparent conductive electrodes (TCE) for optoelectronic devices has been investigated. The Ag layer deposited on the bottom ZnO exhibited sheet resistance lower than 10 Ω/Sq. at a Ag thickness of 8 nm. It was then fixed with a top and bottom ZnO layer, whose thicknesses were independently varied to achieve the optimized transmittance of visible light. The variation in thickness of the top and bottom ZnO layers, which serve as anti-reflection layers as well as anti-oxidation layers, resulted in a significant modulation of the transmittance behavior. In particular, the relatively low transmittance in the wavelength range of 400-500 nm was shown to be strongly affected, requiring further thickness optimization. The optimized thicknesses for the top and bottom ZnO layers were found to be 30 and 40 nm, respectively, with the corresponding average visible light transmittance of 85% and peak transmittance of 95%. According to the Haccke figure of merit, the value for the optimized ZnO/ Ag/ZnO electrode was 0.021, which surpasses the reported values of Cu-based electrodes.

        • NLL과 GMM을 중심으로 한 확산모형 추정법 비교

          김대균,이윤동 서강대학교 경영연구소 2011 서강경영논총 Vol.22 No.1

          Black and Scholes (1973)의 연구 이후로 확산과정을 이용한 모형화 방법은 금융공학에서 중요 한 역할을 수행해 왔다. 현대 금융이론에서 다양한 형태의 확산모형이 제안되었고 실제 적용되어 +왔다. 확산모형을 이용하여 금융자료를 분석하기 위하여는 확산모형의 모수에 대한 추정이 필 수적이다. 이를 위하여 많은 연구자들이 다양한 추정방법을 제안하고 그 성질을 연구해 왔다. 본 연구에서는 제안된 추정방법 중 가장 현실에서 많이 사용되는 오일러 근사법, 일반화 적률법 (GMM) 그리고 신국소선형화 방법 (NLL)을 중심으로 그 추정방법들에 대한 통계적 성질을 살펴 보게 된다. 모의실험 연구를 통하여 살펴본 바에 의하면 NLL과 오일러 방법이, 그 적용방법의 단순성 때문에 확산모형의 추정방법으로 매우 자주 사용되어 오는 GNIM에 비하여 훨씬 좋은 성 질을 가지고 있음을 알 수 있었다. 본 연구에서 비교해 본 바에 의하면 특히 확산계수에 대한 모 수의 추정이 필요한 모형에서 GNIM의 성능은 급격히 저하되는 현상을 살펴볼 수 있었다. Since the famous research of Black and Scholes (1973), modeling methods using diffusion processes have performed principal roles in financial engineering. In modern financial theories, various types of diffusion processes were suggested and applied in real situations. To analyze financial data by using diffusion process models, estimation of model parameters is an indispensible step. Many estimation methods were suggested and their properties were investigated by many researchers. This paper reviews the statistical properties of the three estimation methods, Euler approximation method, New Local Linearization (NLL) method, and Generalized Methods of Moment (GMM), which are known as the most practical methods. From the simulation study, we found the NLL and Euler methods performed much better than GMM, GMM is know as the most popular method in estimating the parameters of diffusion model, because of its simplicity. However this paper shows the performance of 0MM is poorer than the simple Euler approximation method or the NLL method, and even the performance is extremely poor especially when the parameters in diffusion coefficient are to be estimated.

        • KCI등재

          결과에 대한 지식의 상대적 빈도와 지연간격 유형이 운동학습에 미치는 영향 비교

          김대균,차승규,김범규,안수경,김종만 한국전문물리치료학회 1997 한국전문물리치료학회지 Vol.4 No.1

          '스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 7시까지 원문보기가 가능합니다.

          Several studies have evaluated the effects of types of relative frequency and delay interval of knowledge of results(KR) on motor skill learning independently. The purpose of this study was to determine more effective types of KR relative frequency and KR delay interval for motor learning. Forty-six healthy subjects (15 female, 31 male) with no previous experience with this experiment participated. The subjects ranged in age from 20 to 29 years (mean=23.9, SD=0.474). All subjects were assigned to one of four groups: a high-instant group, a high-delay group, a low-instant group, and a low-delay group. During the acquisition phase, subjects practiced movements to a target (400 mm) with either a high (83%) or low (33%) KR relative frequency, and with either an instantaneous or delayed (after 8s) KR. Four groups were evaluated on retention (after 3min and 24hr) and transfer (450 mm) tests. The major findings were as follows: (1) there were no between-group differences in acquisition and short-term retention (p>0.05, (2) a low (33%) KR relative frequency during practice was as effective for learning as measured by both long-tenn retention and transfer tests, compared with high (83%) KR practice conditions (p<0.05), (3) delayed (8s) KR enhanced learning as measured by both long-term retention and transfer tests, compared with instantaneous KR practice conditions (p<0.05), and (4) there were no interactions between KR relative frequency and KR delay interval during acquisition, retention, and transfer phases. The results suggest that relatively less frequent and delayed KR are more effective types for motor learning than more frequent and instantaneous KR.ㅂ

        • KCI등재

          Spontaneous Intracranial and Spinal Subdural Hematoma: A Case Report

          김대균,조용수,왕희선,김석원 대한신경손상학회 2019 Korean Journal of Neurotrauma Vol.15 No.2

          Spinal subdural hematoma (SDH) is rarely reported, and their simultaneous occurrence with intracranial SDH is even more rare. A 67-year-old male patient with a history of posterolateral fusion to treat an L2 burst fracture came to our outpatient clinic due to an inability to walk by himself over the previous 3 weeks. A neurological examination revealed that the patient was alert with occasional confusion and slight motor weakness in the lower extremities. Brain and lumbar spine magnetic resonance imaging (MRI) was then performed. A brain MRI revealed a large subacute SDH along the right cerebral convexity and falx cerebri with midline shifting, and a spine MRI revealed a right side-predominant subacute SDH extending from L4 to S1. For treatment, burr hole trephination of the intracranial SDH and fluoroscopy-guided lumbar puncture of the spinal SDH were performed and resulted in a favorable outcome. This is a report of a rare case of spontaneous intracranial and lumbar spine SDH. We include a review of the current literature and a discussion of the pathogenesis of this condition in this report

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