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단결정립 PZT 박막의 피로 및 정보 유지 특성에 관한 연구
이장식,주승기,Lee, Jang-Sik,Ju, Seung-Gi 대한전자공학회 2000 電子工學會論文誌-SD (Semiconductor and devices) Vol.37 No.5
PZT seed에 의해 형성된 단결정립 PZT 박막을 이용하여 Pt/PZT/Pt 구조에서의 피로(fatigue) 및 정보 유지(data retention) 특성에 관하여 연구하였다. 피로 특성의 경우 1㎒의 주파수에서 ±10V의 square wave를 인가하여 측정한 결과 2×10/sup 11/ cycle 동안 전혀 특성의 변화가 관찰되지 않았으며, 정보 유지 능력의 경우 상온에서 30000초 동안 기억 상태의 변화가 없었으며, 고온에서의 retention 측정으로 계산된 활성화 에너지로부터 구한 상온에서의 20% 잔류분극간 감소를 보이는 시간은 6.6×10/sup 7/ 년이었다. Fatigue and data retention characteristics of the Pt/PZT/Pt structure using single grain PZT thin films by PZT seeding method were investigated. In case of fatigue, there is no loss in switched polarization up to 2$\times$10$^{11}$ cycles using 1MHz square wave form at $\pm$10V and no data loss after 30000sec of memory retention at room temperature. From the activation energy measured at high temperatures, the time required 20% loss in remanent polarization is estimated to be 6.6$\times$10$^{7}$ years at room temperature.
효율적으로 방위각 이노베이션을 구하는 다중표적 방위각 추적 알고리즘
유창수,이장식,이균경,Ryu, Chang-Soo,Lee, Jang-Sik,Lee, Kyun-Kyung 대한전자공학회 2001 電子工學會論文誌-SC (System and control) Vol.38 No.6
최근에 Ryu 등은 추정된 신호부공간(signal subspace)으로부터 구한 방위각 이노베이션을 이용하여 다중표적의 방위각을 추적하는 알고리즘을 제안하였다. 이 알고리즘은 데이터를 연관시키면서 동시에 표적의 방위각을 구하기 때문에 기존의 추적 알고리즘과 달리 별도의 데이터연관 기법이 필요 없으며, 구조가 간단하다는 장점을 가지고 있다. 그러나 표적의 개수가 N일 때, 각 표적의 방위각 이노베이션을 구하기 위하여 차원이 (2N+1)${\times}$(2N+1)인 실행렬의 역행렬을 구하는 것이 필요하다. 본 논문에서는 표적의 조향벡터를 신호부공간에 투영할 때, 투영오차가 0이 된다는 사실로부터 방위각 이노베이션을 구하기 위한 새로운 선형 방정식을 제안하였다. 제안한 새로운 선형방정식은 Ryu의 알고리즘에서 사용하는 식과는 달리 한 개의 방위각 이노베이션만을 변수로 사용하기 때문에 역행렬을 구할 필요가 없고 효율적이다. Recently, Ryu et al. proposed a multiple target angle tracking algorithm using the angular innovation extracted from the estimated signal subspace. This algorithm obtains the angles of targets and associates data simultaneously. Therefore, it has a simple structure without data association problem. However it requires the calculation of the inverse of a real matrix with dimension (2N+1)${\times}$(2N+1) to obtain the angular innovations of N targets. In this paper, a new linear equation for angular innovation is proposed using the fact that the projection error is zero when the target steering vector is projected onto the signal subspace. As a result, the proposed algorithm dose not require the matrix inversion and is computationally efficient.
이두현,이장식,김용성,Lee, Doo-Hyun,Lee, Jang-Sik,Kim, Young-Seung 대한한방내과학회 2010 大韓韓方內科學會誌 Vol.31 No.3
Objective : In benign prostatic hyperplasia, dihydrotestosterone acts as a potent cellular androgen and promotes prostate growth. Inhibiting enzyme $5{\alpha}$-reductase that is involved in the conversion of testosterone to the active form dihydrotestosterone reduces this excessive prostate growth. The mechanism on benign prostatic hyperplasia is substantiating evidence to support the clinical value in the evaluation of therapeutic efficacy. In this study, we investigated the effects of Lygodium japonicum on cyto-pathological alterations and expression of $5{\alpha}$-reductase in the rat model of benign prostatic hyperplasia induced by castration and testosterone treatment. Methods : Sprague-Dawley rats were treated with testosterone after castration for induction of experimental benign prostatic hyperplasia, which is similar to human benign prostatic hyperplasia in histopathological profiles. Lygodium japonicum as an experimental specimen, and finasteride as a positive control, were administered orally. The prostates were evaluated by histopathological changes and testosterone levels. Also, the prostates were observed by hematological alterations of AST, ALT, ${\gamma}$-GTP, BUN and creatinine. Results : The rats treated with Lygodium japonicum showed a diminished range of luminal cell and duct epithelial cell damage. The stromal elements and connective tissue proliferation of Lygodium japonicum treated group as compared to the control group decreased. Conclusions : These findings suggest that Lygodium japonicum may protect the glandular epithelial cells. We concluded that Lygodium japonicum could be a useful remedy agent for treating the benign prostatic hyperplasia.
새로운 유사 원자층 증착 방법에 의한 산화막의 형성 및 터널링 자기 접합에의 응용
한신희,정원철,이장식,김병동,주승기 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.1
The tunneling barrier is crucial to the overall performance in magnetic tunnel junction. We have suggested a new formation method for the tunnel barrier, which has utilized pseudo atomic layer deposition with sputtering (PALDS). As is well known, all metallic thin films oxidize more or less under atmospheric conditions. With using this property of metallic thin films, we have prepared tunnel barrier by sputtering metallic thin film and exposing it to the oxygen ambience. From transmission electron microscopy (TEM) observation, the formed tunnel barrier has been confirmed to have clear and good interface between magnetic layers and tunnel barrier. From atomic force microscopy (AFM) observation, it has been also confirmed to have low surface roughness. The TMR MRAM cell manufactured using PALDS method has been shown to exhibit typical tunnel resistance of 86 KΩ·μm^2 and TMR ratio of about 40%. The 40% of MR is quite large. It is considered that this value is geometrically enhanced magnetoresistance due to the low junction resistance of MTJ.
PZT seed 에 의한 거대 단결정립 PZT 박막형성에 관한 연구
이병일,박정호,주승기,이장식,박응철 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.1
Selective nucleation and lateral growing method have been developed for high quality ferroelectric PZT(65/35) thin films using perovskite-phase PZT island seed. The PZT films on PZT seed island transformed into perovskite-phase at temperature as low as 540℃, which temperature is lower than 150℃ compared to that of the PZT thin films deposited on Pt films. The temperature difference enables the lateral growth without undesirable random nucleation. Maximum grain sizes of the perovskite-phase PZT films are determined by annealing temperature. The PZT thin films show leakage current density of 8×10^(-8) A/㎠, breakdown field of 1240 kV/㎝, saturation polarization of 42μC/㎠, and remanent polarization of 30μC/㎠, which values are maintained up to 2×10^11 cycles.