• 대한치과교정학회지
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• 제24권3호
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• pp.631-648
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• 1994

The purpose of this study was to investigate the effects of different types of orthodontic force on the root resorption and repair in rat molar. 77 rats were divided into three groups; The control group was not equiped with orthodontic appliance between incisor and first molar. The experimental group was subdivided into closed coil spring subgroup and elastic chain subgroup by the application methods of orthodontic force. Initial orthodontic force between incisor and first molar was 100g. Experimental period was 8 weeks; for 4 weeks the appliance was acting and for another 4 weeks, removed. Root resorption and repair in the root of first molar was examined by light microscope for histologic changes and by inductively coupled plasma spectroscopy(ICP) for quantitative changes. The results were as follows: 1. In the closed coil spring subgroup odontoclasts and root resolution were appeared one week earlier. 2. One week after orthodontic force was eliminated the repair response in the resorptive lacuna was seen in both subgroups. Delayed resorption was seen on the periphery of resorptive lacunae whereas reparative response was seen in the center of lacunae. A new resorption was seen one week after orthodontic force was eliminated. Root contour was partially restored by repairing of resorbed root. 3. The weight ratios of calcium and phosphorous to the sample were decreased during resorptive process but increased during repair process in both the orthodontic groups, but not more than the control group. 4. By different types of orthodontic force (closed coil spring or elastic chain) resorption process was affected but repair process was not.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권1호
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• pp.84-93
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• 2001

An electromagnetic micro x-y stage for probe-based data storage (PDS) has been fabricated. The x-y stage consists of a silicon body inside which planar copper coils are embedded, a glass substrate bonded to the silicon body, and eight permanent magnets. The dimensions of flexures and copper coils were determined to yield $100{\;}\mu\textrm{m}$ in x and y directions under 50 mA of supplied current and to have 440 Hz of natural frequency. For the application to PDS devices, electromagnetic stage should have flat top surface for the prevention of its interference with multi-probe array, and have coils with low resistance for low power consumption. In order to satisfy these design criteria, conducting planar copper coils have been electroplated within silicon trenches which have high aspect ratio ($5{\;}\mu\textrm{m}$in width and $30{\;}\mu\textrm{m}$in depth). Silicon flexures with a height of $250{\;}\mu\textrm{m}$ were fabricated by using inductively coupled plasma reactive ion etching (ICP-RIE). The characteristics of a fabricated electromagnetic stage were measured by using laser doppler vibrometer (LDV) and dynamic signal analyzer (DSA). The DC gain was $0.16{\;}\mu\textrm{m}/mA$ and the maximum displacement was $42{\;}\mu\textrm{m}$ at a current of 180 mA. The measured natural frequency of the lowest mode was 325 Hz. Compared with the designed values, the lower natural frequency and DC gain of the fabricated device are due to the reverse-tapered ICP-RIE process and the incomplete assembly of the upper-sided permanent magnets for LDV measurements.

• 대한전자공학회논문지SD
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• 제45권11호
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• pp.8-12
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• 2008

AC PDP에 사용되는 ITO 전극의 공정시간을 단축시키고 생산성을 향상시키기 위해서 Nd:$YVO_4$ laser를 사용하여 ITO 전극 패턴을 하였다. ITO etchant를 사용하여 ITO 전극패턴을 형성한 샘플과 비교해서 laser를 사용하여 제작한 샘플은 ITO 라인 끝 부분에 shoulder와 물결무늬가 형성되었다. shoulder와 물결무늬의 제거를 위해서 laser의 펄스반복율과 스캔 속도에 변화를 주었다. 또한 shoulder와 물결무늬를 갖는 ITO 전극이 PDP에 주는 영향을 알아보기 위해서 방전특성분석을 하였다. 실험결과 40 kHz와 500 mm/s를 기본 조건으로 결정하였다. 본 실험을 통하여 레이저를 이용한 PDP용 ITO 전극막의 직접 패터닝 가능성을 확인할 수 있었다.

• Advances in aircraft and spacecraft science
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• 제4권6호
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• pp.729-744
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• 2017

This investigation highlights rationale of electrically conductive nano adhesives for its essential application for Electromagnetic Interference (EMI) Shielding in satellites and Lightning Strike Protection in aircrafts. Carbon Nano Fibres (CNF) were functionalized by electroless process using Tollen's reagent and by Plasma Enhanced Chemical Vapour Deposition (PECVD) process by depositing silver on CNF. Different weight percentage of CNF and silver coated CNF were reinforced into the epoxy resin hardener system. Scanning Electron Microscopy (SEM) micrographs clearly show the presence of CNF in the epoxy matrix, thus giving enough evidence to show that dispersion is uniform. Transmission Electron Microscopy (TEM) studies reveal that there is uniform deposition of silver on CNF resulting in significant improvement in interfacial adhesion with epoxy matrix. There is a considerable increase in thermal stability of the conductive nano adhesive demonstrated by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Four probe conductivity meters clearly shows a substantial increase in the electrical conductivity of silver coated CNF-epoxy composite compared to non-coated CNF-epoxy composite. Tensile test results clearly show that there is a significant increase in the tensile strength of silver coated CNF-composites compared to non-coated CNF-epoxy composites. Consequently, this technology is highly desirable for satellites and EMI Shielding and will open a new dimension in space research.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권2호
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• pp.95-102
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• 2001

Hafnium oxide thin films for gate dielectric were deposited at $300^{\circ}C$ on p-type Si (100) substrates by plasma enhanced chemical vapor deposition (PECVD) and annealed in $O_2$ and $N_2$ ambient at various temperatures. The effect of hydrogen treatment in 4% $H_2$ at $350^{\circ}C$ for 30 min on the electrical properties of $HfO_2$for gate dielectric was investigated. The flat-band voltage shifts of $HfO_2$capacitors annealed in $O_2$ambient are larger than those in $N_2$ambient because samples annealed in high oxygen partial pressure produces the effective negative charges in films. The oxygen loss in $HfO_2$films was expected in forming gas annealed samples and decreased the excessive oxygen contents in films as-deposited and annealed in $O_2$ or $N_2$ambient. The CET of films after hydrogen forming gas anneal almost did not vary compared with that before hydrogen gas anneal. Hysteresis of $HfO_2$films abruptly decreased by hydrogen forming gas anneal because hysteresis in C-V characteristics depends on the bulk effect rather than $HfO_2$/Si interface. The lower trap densities of films annealed in $O_2$ambient than those in $N_2$were due to the composition of interfacial layer becoming closer to $SiO_2$with increasing oxygen partial pressure. Hydrogen forming gas anneal at $350^{\circ}C$ for samples annealed at various temperatures in $O_2$and $N_2$ambient plays critical role in decreasing interface trap densities at the Si/$SiO_2$ interface. However, effect of forming gas anneal was almost disappeared for samples annealed at high temperature (about $800^{\circ}C$) in $O_2$ or $N_2$ambient.

• Molecular & Cellular Toxicology
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• 제3권4호
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• pp.273-281
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• 2007

Ceramide is involved in cell death as a lipid mediator of stress responses. In this study, we developed an improved method of ceramide quantification based on added synthetic ceramide and thin layer chromatography (TLC) separation, and applied to biological samples. Lipids were extracted from samples spiked with N-oleoyl-D-erythro-sphingosine ($C_{17}$ ceramide) as an internal standard. Ceramide was resolved by TLC, complexed with fatty-acidfree bovine serum albumin (BSA), and deacylated by ceramidase (CDase). The released sphingosine was derivatized with o-phthalaldehyde (OPA) and measured by high performance liquid chromatography (HPLC). The limit of detection for ceramide was about 1-2 pmol and the lower limit of quantification was 5 pmol. Ceramide recovery was approximately 86-93%. Ceramide concentrations were determined in biological samples including cultured cells, mouse tissues, and mouse and human plasma. TLC separation of ceramide provides HPLC chromatogram with a clean background without any interfering peaks and the enhanced solubility of ceramide by BSAceramide complex leads to the increased deacylation of ceramide. The use of an internal standard for the determination of ceramide concentration in these samples provides an accurate and reproducible analytical method, and this method can be applicable to diverse biological samples.

• 한국축산식품학회지
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• 제34권1호
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• pp.106-114
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• 2014

Folic acid, one of the B group of vitamins, is an essential substance for maintaining the functions of the nervous system, and is also known to decrease the level of homocysteine in plasma. Homocysteine influences the lowering of the cognitive function in humans, and especially in elderly people. In order to determine the strains with a strong capacity to produce folic acid, 190 bacteria were isolated from various kinds of jeotgal and chungkuk-jang. In our test experiment, JA71 was found to contain $9.03{\mu}g/mL$ of folic acid after 24 h of incubation in an MRS broth. This showed that JA71 has the highest folic acid production ability compared to the other lactic acid bacteria that were isolated. JA71 was identified as Lactobacillus plantarum by the result of API carbohydrate fermentation pattern and 16s rDNA sequence. JA71 was investigated for its physiological characteristics. The optimum growth temperature of JA71 was $37^{\circ}C$, and the cultures took 12 h to reach pH 4.4. JA71 proved more sensitive to bacitracin when compared with fifteen different antibiotics, and showed most resistance to neomycin and vancomycin. Moreover, it was comparatively tolerant of bile juice and acid, and displayed resistance to Escherichia coli, Salmonella Typhimurium, and Staphylococcus aureus with restraint rates of 60.4%, 96.7%, and 76.2%, respectively. These results demonstrate that JA71 could be an excellent strain for application to functional products.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2011년도 추계학술발표대회
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• pp.40.2-40.2
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• 2011

초경합금은 경도가 높은 재료를 말하며 일반적으로는 탄화텅스텐(WC)계 재료를 말한다. 국내 현재 초경합금 동향은 반도체 산업, 내마모성 공구, 절삭공구, 금형 등 많은 분야에 사용되어지고 있다. 또한 최근 들어 FSW (Friction Stir Welding, FSW)기술이 발전함에 따라 접합기술개발이 다양화되면서 FSW Tool의 고성능의 초경 재료가 요구되어지며 장수명의 Tool개발이 되어야 한다. 국내에서는 초경 합금 재료로 사용되어지고 있는 텅스텐 카바이드(WC)와 코발트(Co)를 이용하여 많은 연구가 진행되었다. 본 실험에서는 텅스텐 카바이드와 코발트 및 몰르브덴 카바이드를 혼합하여 소결체를 제조하였다. 실험에 사용된 텅스텐 카바이드는 높은 경도를 가지고 강한 취성을 나타내며, 소결에 어려운 단점이 있다. 이러한 단점을 코발트와 몰리브덴 카바이드를 첨가하여 소결온도를 낮춰주는 역할과 액상 소결시 텅스텐카바이드 입자사이에 침투하여 액상소결에 의한 치밀화가 가능하게 해주며 인성이 향상되어 고인성 재료를 만들 수 있었다. 본 실험에서는 합성과 치밀화가 동시에 진행되는 SPS (Spark Plasma Sintering:SPS) 장비를 이용하여 실험을 진행하였다. 이 방법은 방전플라즈마 소결 공법으로, 기존의 연소법과 열간 가압기술(Hot-press, HIP)을 결합한 방식으로 단 시간, 단일공정으로 치밀한 소결체를 얻을 수 있는 장점이 있다. 본 연구에서는 $WC-5Mo_2C$-5wt%Co 소결체 제조를 위해 원소 분말을 Horizontal ball milling 혼합하였다. 균일하게 혼합된 분말을 흑연다이에 충진하여 펄스전류와 기계적 압력을 동시에 가하여 $WC-5Mo_2C-5Co$ 복합재료를 제조하고 소결체의 밀도, 순도, 상변태, 미세조직 등을 분석 및 평가하였다. SPS공정 조건은 고진공하에서 $1,200^{\circ}C$-60MPa, 펄스비 12:1 조건으로 수행하였으며, 얻어진 $WC-5Mo_2C-5Co$ 소결체의 상대 밀도는 98%이상 이였다. 또한, 결정립 크기는 약 400 nm였으며, 경도는 $2,453kg/mm^2$를 나타내었다.

• 대한장애인치과학회지
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• 제4권1호
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• pp.7-11
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• 2008

치과의사는 혈우병 환자의 치료 시 주의사항에 대해 잘 알고 있어야 한다. 혈우병 환자의 내원 시 소아과 의사 및 혈우재단 등 전문가에게 의뢰하여 환자의 상태에 대한 자문을 얻어야 하고, 치과 치료 시 적절한 계획 하에 최소의 침습적인 치료가 행해지도록 노력해야 하며, 응급 상황을 대비하여 지혈방법을 습득해야 한다. 또 환자와 보호자에게 평소 구강 관리의 중요성을 일깨워 침습적 치과 치료의 빈도를 줄일 수 있도록 해야 한다.

• 한국균학회지
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• 제30권2호
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• pp.131-135
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• 2002

표고버섯 균사체가 항당뇨 효과에 미치는 영향을 검토하기 위해 당뇨가 유발된 흰쥐에 표고버섯 균사체을 7일간 급여시킨 후 혈장 glucose, total cholesterol, triglyceride 및 ALT, AST 활성을 관찰하였고, 표고버섯 균사체 생장의 최적 배양 조건을 조사하였다. 균사체 생장을 위한 최적의 pH와 온도는 5와 $30^{\circ}C$로 나타났으며, 발효조배양시에는 최대 균사체 생장(8.13g/l)이 진탕배양일 때보다 6일 단축되었다. Hypoglycemic 효과에서 혈장 glucose는 당뇨 유발군에서 표고버섯 균사체 급여군이 대조군보다 23.0%가 유의하게 감소하였으며, 혈장 total cholesterol과 triglyceride는 20.3%와 27.1%로 낮게 나타났다. 또한 혈장 ALT와 AST 활성은 당뇨 대조군에 비해 표고버섯 균사체 급여군이 29.6%와 34.3% 낮은 활성을 보였다.