BaSnO$_{3}$를 첨가한 GdBa$_{2}$Cu$_{3}$O$_{7-x}$ 박막의 두께에 따른 임계전류밀도와 BaSnO$_{3}$ 결정 성장의 상관관계

전현규,강병원 한국물리학회 2016 New Physics: Sae Mulli Vol.66 No.6

We investigated the thickness dependence of the critical current density of 4 wt.% BaSnO$_{3}$ (BSO)-added GdBa$_{2}$Cu$_{3}$O$_{7-x}$ (GdBCO) thin films. BSO-added GdBCO films with thicknesses ranging from 0.2 $\mu$m to 1.0 $\mu$m were deposited by using a pulsed laser deposition (PLD) technique. The surface and the cross-sectioned morphologies, the crystal structures and the critical current densities of each film were analyzed. In most superconducting films, the critical current density decreased with increasing thickness of the films. On the contrary, the critical current densities of the BSO-added GdBCO films increased with increasing thickness up to 0.8 $\mu$m and then decreased. The growth of crystalline BSO inside the superconducting matrix also showed the same behavior with thickness, suggesting a close correlation between the growth of crystalline BSO and the thickness dependence of the critical current density of GdBCO. Based on the analysis, we discussed an optimal thickness for the BSO-added GdBCO superconducting film. BaSnO$_{3}$ (BSO)를 4 wt.% 첨가시킨 GdBa$_{2}$Cu$_{3}$O$_{7-x}$ (GdBCO) 초전도 박막의 두께변화에 따른 임계전류밀도를 연구하였다. Pulsed laser deposition (PLD) system을 이용하여 0.2 $\mu$m 부터 1.0 $\mu$m까지 두께를 변화시킨 초전도 박막을 증착하고 표면 및 단면 구조, 결정 구조, 그리고 임계전류밀도를 각각 분석하였다. 두께가 증가할수록 임계전류밀도가 감소하는 보통의 경향과는 달리 BSO를 첨가시킨 GdBCO 박막의 임계전류밀도는 두께가 증가함에 따라 0.8 $\mu$m까지 증가하다가 그 이상의 두께에서 감소하는 경향을 보였는데 BSO 결정 성장도 두께에 따라 같은 경향을 보였다. 이는 BSO 결정 성장이 임계전류밀도의 두께 의존성에 깊은 상관관계가 있음을 나타낸다. 두께에 따른 BSO의 성장과 임계전류밀도 변화를 통해 BSO가 첨가된 GdBCO 초전도 박막의 적정 두께에 대해 논의하였다.

순수한 GdBCO와 BSO가 첨가된 GdBCO 박막의 나노구조 비교

이재기,D. H. Tran,강병원 한국물리학회 2015 새물리 Vol.65 No.5

The nanostructure formation of pulsed-laser-deposited GdBa2Cu3O7−d(GdBCO) films with the addition of BaSnO3(BSO) was investigated. Pure and 2wt.% BaSnO3 (BSO)-added GdBCO films with film thicknesses ranging from 0.2 μm to 1.5 μm were deposited on SrTiO3 (STO) substrates by using a pulsed-laser deposition technique. In order to examine the microstructural evolution inside the thick films, we employed a sequential ion-milling process on and scanning electron microscope analyses of to 1.0-μm-thick pure and BSO-added GdBCO films. For the pure GdBCO films, perpendicularly-connected a-axis-oriented grains developed at 0.6 μm and persisted to the top surface of the 1.0-μm-thick film. For the BSO-added GdBCO films, a new feature of two-dimensional meandering grain boundaries was consistently observed from the very thin film to the thickest film, but the number of a-axis-oriented grains was significantly reduced. The difference between the two types of nanostructures as possible flux-pinning centers is discussed. 펄스레이저 증착법 (pulsed laser deposition, PLD)으로 성장시킨 BaSnO3(BSO)가 첨가된 GdBa2Cu3O7-x (GdBCO) 박막과 내부에 형성된 나노구조에 대해 조사하였다. SrTiO3(STO) 기판위에 순수한 GdBCO 와 2 wt.% BSO가 첨가된 GdBCO 박막의 두께를 0.2μm에서 1.5 μm까지 변화시키면서 증착하였다. 두꺼운 박막 내부 미세구조를 확인하기 위해 순수한 GdBCO와 BSO가 첨가된 GdBCO 박막에 ion-milling 과 주사 전자 현미경 (scanning electron microscope, SEM) 분석을 연속적으로 시행하였다. 순수한 GdBCO 박막의 경우 수직으로 연결된 a-축 방향 (a-axis oriented)의 낱알들이 0.6 μm 에서부터 1.0 μm까지 표면에 지속적으로 성장하였다. BSO가 첨가된 GdBCO 박막에서는 1.5 μm의 두께까지 a-축 방향의 알갱이들의 성장이 크게 감소한 반면, 새로운 특징으로 구불구불한 2차원 형태의 낱알 경계가 두께를 가로질러 지속적으로 관찰되었다. 이러한 두 가지 형태의 나노 구조의 자속 꽂음 중심 (flux pinning center)으로써의 가능성에 대하여 논의하였다.

임상적 병기 I-II 자궁내막암 환자의 병기설정 수술시 양측 난관난소절제술 유무에 따른 예후의 비교

한찬희 ( Chan Hee Han ),임시연 ( Si Yeon Lim ),국일영 ( Ill Young Kook ),이근호 ( Keun Ho Lee ),남궁성은 ( Sung Eun Namkoong ),박종섭 ( Jong Sup Park ),박태철 ( Tae Chul Park ) 대한산부인과학회 2007 Obstetrics & Gynecology Science Vol.50 No.2

Objective: The aim of this study is to verify the clinical outcome of staging surgery with and (or) without bilateral salpingo-oophorectomy (BSO) in clinical stage I-II endometrial cancer patients. Methods: We reviewed the medical records of 178 surgically treated patients in clinical stage I-II endometrial cancer between January 1994 and December 2004. Overall survival (OS) and disease free survival (DFS) were analyzed by using data gathered from the National Statistics Office. The clinical outcome was compared between patients who underwent hysterectomy with and without BSO. Results: One hundred sixty patients were in clinical stage I, and 18 patients were in clinical stage II. Most of the cases showed endometrioid (93.8%) in histology and G1 (56.1%) in differentiation. BSO was performed in 142 patients. Surgico-pathological features of two group are not different but the group without BSO were younger (40.7 vs. 55.8 years old) and less myometrial invasion than the group with BSO. After mean 39.27 months follow up, we found no difference in OS and DFS between the two groups with BSO and without BSO. No factors except stage were significantly related with OS and DFS by multivariate Cox regression analysis. The rate of pelvic and paraaortic lymph node metastasis was not different between two groups. Conclusion: The retrospective data in the study reveals that staging surgery with and without BSO does not affect OS and DFS in clinical stage I-II endometrial cancer patients. In limited cases, such as young women, omitting BSO can be considered carefully.

Effect of BSO addition on Cu-O bond of GdBa₂Cu₃O_7-x films with varying thickness probed by extended x-ray absorption fine structure

Jeon, H.K.,Lee, J.K.,Yang, D.S.,Kang, W.N.,Kang, B. The Korea Institute of Applied Superconductivity a 2016 한국초전도저온공학회논문지 Vol.18 No.4

We investigated the relation between the Cu-O bond length and the superconducting properties of $BaSnO_3$ (BSO)-added $GdBa_2Cu_3O_{7-x}$ (GdBCO) thin films by using extended x-ray absorption fine structure (EXAFS) spectroscopy. 4 wt.% $BaSnO_3$ (BSO) added $GdBa_2Cu_3O_{7-x}$ (GdBCO) thin films with varying thickness from $0.2{\mu}m$ to $1.0{\mu}m$ were fabricated by using pulsed laser deposition (PLD) method. The transition temperature ($T_c$) and the residual resistance ratio (RRR) of the GdBCO films increased with increasing thickness up to $0.8{\mu}m$, where the crystalline BSO has the highest peak intensity, and then decreased. This uncommon behaviors of $T_c$ and RRR are likely to be created by the addition of BSO, which may change the ordering of GdBCO atomic bonds. Analysis from the Cu K-edge EXAFS spectroscopy showed an interesting thickness dependence of ordering behavior of BSO-added GdBCO films. It is noticeable that the ordering of Cu-O bond and the transition temperature are found to show opposite behaviors in the thickness dependence. Based on these results, the growth of BSO seemingly have evident effect on the alteration of the local structure of GdBCO film.

Effect of double pinning mechanism in BSO-added GdBa₂Cu₃O_7-x thin films

Oh, J.Y.,Jeon, H.K.,Lee, J.M.,Kang, W.N.,Kang, B. The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.3

We investigated the effect of self-assembled BSO nano-defects as pinning centers in BSO-added GdBCO films when the thicknesses of films were varied. 3.5 vol. % BSO-added GdBCO films with varying thicknesses from 200 nm to 1000 nm were deposited on $SrTiO_3$ (STO) substrate by using pulsed laser deposition (PLD) process. For the films with thicknesses of 400 nm and 600 nm, 'anomaly shoulders' in $J_c-H$ characteristic curves were observed near the matching field. The anomaly shoulders appeared in the field dependence of $J_c$ may be attributed to the existence of double pinning mechanisms in thin films. The fit to the pinning force density as a function of reduced field h ($H/H_{irr}$) using the Dew-Hughes' scaling law shows that both the 400 nm- and the 600 nm-thick films have double pinning mechanisms while the other films have a single pinning mechanism. These results indicate that the self-assembled property of BSO result in different role as pinning centers with different thickness.

Block-based Self-organizing TDMA for Reliable VDES in SANETs

이솔비,Jung-Hyok Kwon,김부영,심우성,김동완,김의직 한국인터넷정보학회 2024 KSII Transactions on Internet and Information Syst Vol.18 No.2

This paper proposes a block-based self-organizing time-division multiple access (BSO-TDMA) protocol for very high frequency (VHF) data exchange system (VDES) in shipborne ad-hoc networks (SANETs). The BSO-TDMA reduces the collisions caused by the simultaneous transmission of automatic identification system (AIS) messages by uniformly allocating channel resources using a block-wise frame. For this purpose, the BSO-TDMA includes two functional operations: (1) frame configuration and (2) slot allocation. The first operation consists of block division and block selection. A frame is divided into multiple blocks, each consisting of fixed-size subblocks, by using the reporting interval (RI) of the ship. Then, the ship selects one of the subblocks within a block by considering the number of occupied slots for each subblock. The second operation allocates the slots within the selected subblock for transmitting AIS messages. First, one of the unoccupied slots within the selected subblock is allocated for the periodic transmission of position reports. Next, to transmit various types of AIS messages, an unoccupied slot is randomly selected from candidate slots located around the previously allocated slot. Experimental simulations are conducted to evaluate the performance of BSO-TDMA. The results show that BSO-TDMA has better performance than that of the existing SOTDMA.

The flux pinning properties of BaSnO₃-added GdBa₂Cu₃O_7-_δ films with varying growth conditions

Lee, J.K.,Oh, J.Y.,Lee, J.M.,Kang, W.N.,Kang, B. The Korea Institute of Applied Superconductivity a 2017 한국초전도저온공학회논문지 Vol.19 No.3

Addition of $BaSnO_3$ (BSO) to $GdBa_2Cu_3O_{7-{\delta}}$ (GdBCO) is reported to enhance the flux pinning property of GdBCO thick films. To investigate the effect of growth condition on the pinning properties, 700 nm-thick BSO-added GdBCO films deposited with varying temperatures and growth rates were prepared by using a pulsed laser deposition method. As the deposition temperature increases, the critical current density and the pinning force density show an improved field dependence up to $750^{\circ}C$ due to the increase in the formation of the a-axis growth and the BSO nanostructures. The films deposited at higher temperatures show degraded surfaces and as a result, degraded pinning behaviors. For the change in growth rate, the critical current density and the pinning force increase as the repetition rate increase at low magnetic fields, but this behavior is reversed in high magnetic fields. These results indicate that the film growth conditions significantly affect the formation of BSO nanostructures and the pinning properties of BSO-added GdBCO films.

Scaling of pinning forces in BaSnO₃-added GdBa₂Cu₃O_7-x superconducting thin films

Kang, B.,Tran, D.H.,Kang, W.N. Elsevier Sequoia 2017 THIN SOLID FILMS - Vol.624 No.-

We have investigated the flux pinning force F<SUB>p</SUB> in pure and 2wt.% BaSnO<SUB>3</SUB> (BSO)-added GdBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-x</SUB> (GdBCO) superconducting films. Both pure and BSO-added GdBCO films with the thicknesses varying from 0.2μm to 1.5μm were prepared by using a pulsed laser deposition (PLD) technique. As BSO is added to the GdBCO films, two changes were observed in the field dependence of the pinning forces. First, the magnitude of the pinning force was greatly enhanced at each corresponding thickness. Second, the pinning forces exhibited an interesting plateau-like behavior. As a result, a universal scaling law of the pinning forces can be applied to the BSO-added GdBCO films which accounts for all variation in thickness. These results suggest an existence of an extra pinning mechanism through the film thickness which is induced by the formation of the BSO nanostructures. PACS numbers: 74.25.Sv 74.25.Qt 74.62.Dh 74.72.Jt

Effect of double pinning mechanism in BSO-added GdBa2Cu3O7-x thin films

J. Y. Oh,H. K. Jeon,J. M. Lee,W. N. Kang,B. Kang 한국초전도저온학회 (구 한국초전도저온공학회) 2017 한국초전도저온공학회논문지 Vol.19 No.3

결정질 실리콘 태양전지의 광열화 현상 분석 및 평가에 관한 연구

김수민(Soo Min Kim),김영도(Youngdo Kim),박성은(Sungene Park),이해석(Hae-seok Lee),김동환(Donghwan Kim) 한국신재생에너지학회 2013 한국신재생에너지학회 학술대회논문집 Vol.2013 No.11