• 한국재료학회지
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• 제21권12호
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• pp.639-643
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• 2011

Zinc oxide as an optoelectronic device material was studied to utilize its wide band gap of 3.37 eV and high exciton biding energy of 60 meV. Using anti-site nitrogen to generate p-type zinc oxide has shown a deep acceptor level and low solubility. To increase the nitrogen solubility in zinc oxide, group 13 elements (aluminum, gallium, and indium) was co-added to nitrogen. The effect of aluminum on nitrogen solubility in a $3{\times}3{\times}2$ zinc oxide super cell containing 72 atoms was investigated using density functional theory with hybrid functionals of Heyd, Scuseria, and Ernzerhof (HSE). Aluminum and nitrogen were substituted for zinc and oxygen sites in the super cell, respectively. The band gap of the undoped super cell was calculated to be 3.36 eV from the density of states, and was in good agreement with the experimentally obtained value. Formation energies of a nitrogen molecule and nitric oxide in the zinc oxide super cell in zinc-rich conditions were lower than those in oxygen-rich conditions. When the number of nitrogen molecules near the aluminum increased from one to four in the super cell, their formation energies decreased to approach the valence band maximum to some degree. However, the acceptor level of nitrogen in zinc oxide with the co-incorporation of aluminum was still deep.

• 보존과학회지
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• 제36권3호
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• pp.162-177
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• 2020

부여 관북리 유적에서 시행된 동 생산 및 제련과정을 살펴보기 위하여 '나'지구, '라'지구 출토동 생산 부산물(동 슬래그 및 동 도가니) 11점의 과학적 분석을 시행하였다. 분석방법은 파장분산형 X-선 형광 분석, X-선 회절 분석, 금속 현미경 관찰, 주사 전자현미경-에너지 분산형 X-선 분석기, 전계방출 전자탐침미량분석기, 라만 마이크로분광분석법을 사용하였다. 분석결과 관북리 동 슬래그에서는 주로 도가니 슬래그 및 정련 슬래그에서 전형적인 특징으로 나타나는 규산염 광물, Magnetite, Fayalite, Delafossite 등이 검출되었다. 또한 관북리 동 슬래그는 외형 및 미세조직의 양상의 특성에 따라 1. 유리질 바탕 기지 + Cu prill, 2. 유리질 바탕 기지 + Cu prill + Magnetite, 3. 규산염 광물 바탕 기지 + Cu prill, 4. 결정질(Delafossite, Magnetite)/유리질(비정질) 바탕 기지 + Cu prill, 5. Magnetite + Fayalite, 6. 청동합금 슬래그로 분류되었다. 미세조직 내에는 SiO₂, Al₂O₃, CaO, SO₄ P₂O₅, Ag₂O, Sb₂O₃ 등의 불순물이 잔재되어 있으며, 일부는 주석과 납이 합금되어 있는 것을 확인하였다. 이와 같은 결과를 통해 부여 관북리 유적에서는 동 생산과정 중 배소와 제련을 거친 동 중간생성물의 정련과 불순물이 함유된 동-주석, 또는 동-주석-납의 합금정련을 시행하였다고 판단된다.

• 대한치과교정학회지
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• 제51권5호
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• pp.313-320
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• 2021

Objective: The purpose of this study was to evaluate the effects of chewing gum and low-level laser therapy in alleviating orthodontic pain induced by the initial archwire. Methods: Patients with 3-6 mm maxillary crowding who planned to receive non-extraction orthodontic treatment were recruited for the study. Sixty-three participants (33 females and 30 males) were randomly allocated into three groups: laser, chewing gum, and control. In the laser group, a gallium aluminum arsenide (GaAlAs) diode laser with a wavelength of 820 nm was used to apply a single dose immediately after orthodontic treatment began. In the chewing gum group, sugar-free gum was chewed three times for 20 minutes-immediately after starting treatment, and at the twenty-fourth and forty-eighth hours of treatment. Pain perception was measured using a visual analog scale at the second, sixth, and twenty-fourth hours, and on the second, third, and seventh days. Results: There were no statistically significant differences between the groups at any measured time point (p > 0.05). The highest pain scores were detected at the twenty-fourth hour of treatment in all groups. Conclusions: Within the limitations of the study, we could not detect whether low-level laser therapy and chewing gum had any clinically significant effect on orthodontic pain. Different results may be obtained with a higher number of participants or using lasers with different wavelengths and specifications. Although the study had a sufficient number of participants according to statistical analysis, higher number of participants could have provided more definitive outcomes.

• 대한전자공학회논문지SD
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• 제45권7호
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• pp.37-43
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• 2008

본 논문에서는 전하 펌프 방법 (Charge Pumping Method, CPM)를 이용하여 서로 다른 질화막 층을 가지는 N-Channel SANOS (Silicon-$Al_2O_3$-Nitride-Oxide-Silicon) Flash Memory Cell 트랜지스터의 트랩 특성을 규명하였다. SANOS Flash Memory에서 계면 및 질화막 트랩의 중요성은 널리 알려져 있지만 소자에 직접 적용 가능하면서 정화하고 용이한 트랩 분석 방법은 미흡하다고 할 수 있다. 기존에 알려진 분석 방법 중 전하 펌프 방법은 측정 및 분석이 간단하면서 트랜지스터에 직접 적용이 가능하여 MOSFET에 널리 사용되어왔으며 최근에는 MONOS/SONOS 구조에도 적용되고 있지만 아직까지는 Silicon 기판과 tunneling oxide와의 계면에 존재하는 트랩 및 tunneling oxide가 얇은 구조에서의 질화막 벌크 트랩 추출 결과만이 보고되어 있다. 이에 본 연구에서는 Trapping Layer (질화막)가 다른 SONOS 트랜지스터에 전하 펌프 방법을 적용하여 Si 기판/Tunneling Oxide 계면 트랩 및 질화막 트랩을 분리하여 평가하였으며 추출된 결과의 정확성 및 유용성을 확인하고자 트랜지스터의 전기적 특성 및 메모리 특성과의 상관 관계를 분석하고 Simulation을 통해 확인하였다. 분석 결과 계면 트랩의 경우 트랩 밀도가 높고 trap의 capture cross section이 큰 소자의 경우 전자이동도, subthreshold slop, leakage current 등의 트랜지스터의 일반적인 특성 열화가 나타났다. 계면 트랩은 특히 Memory 특성 중 Program/Erase (P/E) speed에 영향을 미치는 것으로 나타났는데 이는 계면결함이 많은 소자의 경우 같은 P/E 조건에서 더 많은 전하가 계면결함에 포획됨으로써 trapping layer로의 carrier 이동이 억제되기 때문으로 판단되며 simulation을 통해서도 동일한 결과를 확인하였다. 하지만 data retention의 경우 계면 트랩보다 charge trapping layer인 질화막 트랩 특성에 의해 더 크게 영향을 받는 것으로 나타났다. 이는 P/E cycling 횟수에 따른 data retention 특성 열화 측정 결과에서도 일관되게 확인할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.5-5
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• 2009

Thin-film-transistors (TFTs) that can be prepared at low temperatures have attracted much attention because of the great potential for transparent and flexible electronics. One of the mainstreams in this field is the use of organic semiconductors such as pentacene. But device performance of the organic TFTs is still limited due to low field-effect mobility and rapid degradation after exposing to air. Alternative approach is the use of amorphous oxide semiconductors as a channel. Amorphous oxide semiconductors (AOSs) based TFTs showed the fast technological development, because AOS films can be fabricated at room temperature and exhibit the possibility in application like flexible display, electronic paper, and larges solar cells. Among the various AOSs, a-IGZO has lots of advantages because it has high channel mobility, uniform surface roughness and good transparency. [1] The high mobility is attributed to the overlap of spherical s-orbital of the heavy post-transition metal cations. This study demonstrated the effect of the variation in channel thickness from 30nm to 200nm on the TFT device performance. When the thickness was increased, turn-on voltage and subthreshold swing was decreased. The a-IGZO channels and source/drain metals were deposited with shadow mask. The a-IGZO channel layer was deposited on $SiO_2$/p-Si substrates by RF magnetron sputtering, where RF power is 150W. And working pressure is 3m Torr, at $O_2/Ar$ (2/28 sccm) atmosphere. The electrodes were formed with electron-beam evaporated Ti (30 nm) and Au (70 nm) bilayer. Finally, Al (150nm) as a gate metal was thermal-evaporated. TFT devices were heat-treated in a furnace at 250 $^{\circ}C$ and nitrogen atmosphere for 1hour. The electrical properties of the TFTs were measured using a probe-station. The TFT with channel thickness of 150nm exhibits a good subthreshold swing (SS) of 0.72 V/decade and on-off ratio of $1{\times}10^8$. The field effect mobility and threshold voltage were evaluated as 7.2 and 8 V, respectively.

• Advances in pediatric surgery
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• 제19권2호
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• pp.81-89
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• 2013

The purposes of this study was to describe the clinical correlation of mass size and gestational age, prognostic factors in sacrococcygeal teratoma (SCT) at a tertiary pediatric surgery, University of Ulsan College of Medicine and Asan Medical Center (AMC), Seoul, Korea. Fifty five patients admitted to the AMC with a SCT between May 1989 and April 2013 were included in this retrospective review. Mean follow up was 861 days. Mean maternal age at delivery was $30{\pm}2.7$ year, mean gestational age (GA) was $36.9{\pm}3.6$ wks, and preterm delivery was 21.8%. Birth body weight was $3182{\pm}644$ g and male vs. female ratio was 1:2.05. We can't find significant difference between Caesarean section and maternal age at delivery (p =0.817). But, caesarean section was favored by gestational age (p = 0.002), larger tumor size (p =0.029) or higher tumor weight fraction rate to birth body weight (p =0.024). Type I was 13, II 21, III 17, and IV 3 according to Altman et al. classification. The tumor component was predominantly cystic(> 50%) in 73.1 %. And the majority histological classification of tumors were mature teratoma (70.3%). The motality rate was 5.5%. Three patients expired because of postpartum bleeding, post-op bleeding related complication such as DIC. SCT recurred in four patients. The interval between first and second operation was $206.2{\pm}111.0$ d (range 53~325 d). In two patients, serum AFP levels were elevated at a regular checkup without any symptom, and subsequent imaging studies revealed SCT. The most common cause of death was bleeding and bleeding related complication. So Caesarean section and active peripartum and perioperative management will be needed for huge solid SCT. In the case of Yolk sac tumor or huge immature teratoma, possibility of recurrence have to be always considered, so follow up by serial AFP and MRI is important for SCT management.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제38권
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• pp.48.1-48.8
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• 2016

Background: This study investigates the effect of alendronate-treated osteoblasts, as well as the effect of low-level laser therapy (LLLT) on the alendronate-treated osteoblasts. Bisphosphonate decreases the osteoblastic activity. Various treatment modalities are used to enhance the bisphosphonate-treated osteoblasts; however, there were no cell culture studies conducted using a low-level laser. Methods: Human fetal osteoblastic (hFOB 1.19) cells were treated with $50{\mu}M$ alendronate. Then, they were irradiated with a $1.2J/cm^2$ low-level Ga-Al-As laser (${\lambda}=808{\pm}3nm$, 80 mW, and 80 mA; spot size, $1 cm^2$; NDLux, Seoul, Korea). The cell survivability was measured with the MTT assay. The three cytokines of osteoblasts, receptor activator of nuclear factor ${\kappa}B$ ligand (RANKL), osteoprotegerin (OPG), and macrophage colony-stimulating factor (M-CSF) were analyzed. Results: In the cells treated with alendronate at concentrations of $50{\mu}M$ and higher, cell survivability significantly decreased after 48 h (p < 0.05). After the applications of low-level laser on alendronate-treated cells, cell survivability significantly increased at 72 h (p < 0.05). The expressions of OPG, RANKL, and M-CSF have decreased via the alendronate. The RANKL and M-CSF expressions have increased, but the OPG was not significantly affected by the LLLT. Conclusions: The LLLT does not affect the OPG expression in the hFOB cell line, but it may increase the RANKL and M-CSF expressions, thereby resulting in positive effects on osteoclastogenesis and bone remodeling.

• The Korean Journal of Pain
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• 제3권2호
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• pp.139-143
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• 1990

대상포진성 신경통 환자의 통증을 조정하기 위한 목적으로 본원 통증치료실을 내원한 환자 26명을 대상으로 저출력 레이저 치료를 시행한 결과는 아래와 같다. 1) 통증완화 효과에 대한 평가로서 LLLT는 통증환자에게 비침습적이고 안전하게 시행할 수 있었다. 2) 저출력 레이저 조사후 VAS의 변화는 치료전 $7.57{\pm}1.81$, 5회후 $4.01{\pm}2.01$ 10회후 $3.28{\pm}1.85$ 15회후 $2.82{\pm}1.95$이었다(p<0.01). 3) 15회의 LLLT후 VAS의 개선율은 63%였다. 4) 가장 현저한 VAS의 개선율은 1회 LLLT후의 24%였고 VAS의 개선율은 7회 LLLT후에 나타났다. 5) 대상포진후 신경통으로의 이환은 60세 이상군에서 나타난 1명(3.8%)이었다. 60세 이하 군에서 VAS의 변화는 치료전 $7.67{\pm}2.31$, 5회후 $3.42{\pm}1.77$, 10회후 $2.88{\pm}1.33$, 15회후 $2.22{\pm}1.63$이었으며 VAS의 개선율은 각각 55%, 62%, 71%였다. 60세 이상 군에서는 VAS의 변화는 치료전 $7.49{\pm}1.44$, 5회후 $4.51{\pm}2.20$, 10회후 $3.76{\pm}2.38$, 15회후 $3.47{\pm}2.32$이고 VAS의 개선율은 각각 40%, 50%, 54%로 유의한 차이가 없었다(p>0.05). 7) LLLT중이나 후에 특이한 합병증은 없었다. 이상에서 볼 때 대상포진성 신경통 환자에서 LLLT는 초기에 통증을 조절할 뿐만 아니라 대상포진후 신경통으로의 이환을 줄이며 환자의 전신상태와 비교적 무관하게 치료를 적용할 수 있는 방법으로 사료된다.