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우수한 압전 특성과 고온 상전이 온도를 가지는 BiAlO3 를 첨가한 BiFeO3-BaTiO3 세라믹
조형래,이명환,김다정,최해인,김원정,정성수,송태권 한국물리학회 2021 새물리 Vol.71 No.3
[1 - x]Bi1:03(Fe0:99Al0:01)O3-xBaTiO3 (x = 0.30, 0.33, 0.35, and 0.40) lead-free piezoelectric ceramics were prepared through a conventional solid-state reaction method followed by a waterquenching process. A single perovskite structure without any impurity or secondary phase was confirmed for all compositions. The crystal phase, phase transition, microstructure, dielectric, ferroelectric, and piezoelectric properties were investigated. The temperature-dependent dielectric losses (tan ) were found to decrease dramatically to 100 – 200 ◦C and then increased sharply at higher temperatures for x = 0.30, 0.33, and 0.35. The ferroelectric properties improved with increasing measurement temperatures and the highest value of 2Pr = 80.2 C/cm2 was observed at x = 0.33 at 100 ◦C. It was found that the best piezoelectric charge sensor coefficient (d33) was 323 pC/N and the Curie temperature (TC) was 452 ◦C for x = 0.33. The best piezoelectric actuator coefficient (d 33) was 515 pm/V and the TC was 344 ◦C for x = 0.40. These results showed that Al-doped BF-BT ceramics have great potential for were in high-temperature lead-free piezoelectric sensor and actuator applications. [1 - x]Bi1:03(Fe0:99Al0:01)O3-xBaTiO3 (x = 0.30, 0.33, 0.35, 그리고 0.40)의 고용체에 1 mol%의BiAlO3 를 첨가물로 사용하여 일반적인 고상반응법을 이용하여 소결한 후 물을 이용한 급속냉각법으로압전 세라믹을 제작하였다. 각 조성의 결정구조, 상전이, 미세구조, 유전, 강유전 및 압전특성을 조사하였다. 모든 조성에서 불순물 혹은 이차상 없이 단일 페로브스카이트 구조의 상을 가졌다. x = 0.30, 0.33, 0.35 조성에서 측정 온도에 따라 유전손실 (tan ) 값이 100 - 200 ◦C에서 급격히 감소되고 다시 증가되었다. 강유전 이력곡선 측정결과 100 ◦C에서 x = 0.33 조성이 가장 높은 잔류분극 2Pr = 80.2 C/cm2 을가졌다. x = 0.33 조성은 가장 높은 정압전 상수d33 = 323 pC/N와 452 ◦C의 상전이 온도(TC)를 가졌다. 또한, x = 0.40 조성에서 가장 높은 역압전 상수 d 33 = 515 pm/V와 TC = 344 ◦C의 값을 가지는 것을확인하였다. 이 결과로부터 Al을 첨가물로 사용한 비납계 압전체 BF-BT는 고온용 센서 및 액추에이터소자로 활용될 수 있는 가능성이 높다는 것을 보였다.
조형래,Chang Gyeong Ha 한국지질과학협의회 2013 Geosciences Journal Vol.17 No.4
In-situ thermal recovery of bitumen requires a detailed understanding of the subsurface stratal architecture of oil-sands deposits. In the present study, 455 well-logs and 10 drilled cores acquired at Christina Lake (Township 76–77, Range 6W4), northeastern Alberta, Canada are examined to reveal the stratigraphic architecture of the oil-sands deposits of the Early Cretaceous McMurray Formation, focusing on the lower fluvial succession overlying unconformably Paleozoic limestone. The lower McMurray succession comprises 3 major lithologic units of thick sand,interbedded sand/mud, and thick mud, which represent main fluvial channels, proximal floodplains with crevasse splays close to the main channels, and distal floodplains, respectively. Spatial correlation of well-log data shows the stratigraphic architecture of the succession and the paleotopography of the underlying unconformity surface. Thick channel sand bodies forming good bitumen reservoirs occur mainly along the axis of a paleovalley with minor intercalation of fine-grained floodplain deposits, which is ascribed to frequent interconnection of channel bodies resulting from slow increase of accommodation space during lowstand and the limitation of channel locations to the narrow axial part of the paleovalley during the early stage of valley-filling. The channel bodies tend to decrease in thickness and proportion toward the valley margin and upsection at the expanse of increase in proportion of fine-grained deposits. This overall stratigraphic architecture is in agreement with the sequence stratigraphic model. The succession,however, locally displays significantly different architectures from the model, controlled by the paleotopography. The recessed areas between topographic highs on the valley margins are dominated by fine-grained floodplain deposits, because those areas were not suitable for being occupied by channels.
수직적으로 차별화된 제품시장 내에서 유통업체의 다자간 협상전략에 관한 연구
조형래,이민호,임상규 한국산업경영시스템학회 2015 한국산업경영시스템학회지 Vol.38 No.2
In this paper, we study the bargaining strategy of a distributor who sells vertically differentiated, i.e. high and low brand products. We derive and analyze the equilibrium solutions for both simultaneous and sequential bargaining games among the distributor, the high brand product manufacturer and the low brand product manufacturer. The result shows that the optimal bargaining strategy for the distributor heavily depends on the relative quality and price level of the low brand product comparing to those of the high brand product. It is also shown that, for more bargaining profit, the distributor has strong motivation to prefer a low brand product which has lower quality level per unit price.
Tension Pneumocelhalus after Transsphenoidal Surgery: Report of Two Cases
조형래,홍용길,한영민 대한신경외과학회 2004 Journal of Korean neurosurgical society Vol.35 No.5
Tension pneumocephalus is an uncommon complication of transsphenoidal surgery. This rare complication may be caused by an external lumbar subarachnoid drainage (ELD) which is placed for the treatment of a cerebrospinal fluid (CSF) fistula. Most of the tension pneumocephalus which cause severe neurologic deterioration in itself require surgical treatment. However, the pneumocephalus may be resolved after removal of the spinal subarachnoid catheter in some cases. We report two cases of tension pneumocephalus which developed after transsphenoidal surgery for the pituitary adenoma and craniopharyngioma, and fully recovered with conservative treatment.