• The Journal of Advanced Prosthodontics
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• 제7권2호
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• pp.93-97
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• 2015

PURPOSE. Xerostomia can diminish the quality of life, leads to changes in normal chemical composition of saliva and oral microbiata, and increases the risk for opportunistic infections, such as Candida albicans. Various artificial salivas have been considered for patients with xerostomia. However, the knowledge on the antifungal and antiadhesive activity of artificial saliva substitutes is limited. The aim of the present study was to evaluate influence of two artificial salivas on the adhesion of Candida albicans to the polymethylmethacrylate disc specimens. MATERIALS AND METHODS. Two commercial artificial salivas (Saliva Orthana and Biotene Oral Balance Gel) were selected. 45 polymethylmethacrylate disc specimens were prepared and randomly allocated into 3 groups; Saliva Orthana, Biotene-Oral Balance gel and distilled water. Specimens were stored in the artificial saliva or in the sterile distilled water for 60 minutes at $37^{\circ}C$. Then they were exposed to yeast suspensions including Candida albicans. Yeast cells were counted using ${\times}40$ magnification under a light microscope and data were analysed. RESULTS. Analysis of data indicated statistically significant difference in adhesion of Candida albicans among all experimental groups (P=.000). Findings indicated that Saliva Orthana had higher adhesion scores than the Biotene Oral Balance gel and distilled water (P<.05). CONCLUSION. In comparison of Saliva Orthana, the use of Biotene Oral Balance Gel including lysozyme, lactoferrin and peroxidase may be an appropriate treatment method to prevent of adhesion of Candida albicans and related infections in patients with xerostomia.

• The Journal of Advanced Prosthodontics
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• 제4권4호
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• pp.187-191
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• 2012

PURPOSE. The aim of the present study was to assess the effect of ascorbic acid, ethanol and acetone on microtensile bond strength between fiber posts pre-treated with hydrogen peroxide and composite resin cores. MATERIALS AND METHODS. Twenty four fiber posts were pre-treated with 24% hydrogen peroxide and divided into 4 groups as follows: G1: no treatment, as control group; G2: treatment with10% ascorbic acid solution for 5 minutes; G3: treatment with 70% ethanol solution for 5 minutes; and G4: treatment with 70% acetone solution for 5 minutes. Each fiber post was surrounded by a cylinder-shaped polyglass matrix which was subsequently filled with composite resin. Two sections from each sample were selected for microtensile test at a crosshead with speed of 0.5 mm/min. Statistical analyses were performed using one-way ANOVA and a post hoc Tukey HSD test. Fractured surfaces were observed under a stereomicroscope at ${\times}20$ magnification. The fractured surfaces of the specimens were observed and evaluated under a SEM. RESULTS. Means of microtensile bond strength values (MPa) and standard deviations in the groups were as follows: G1: $9.70{\pm}0.81$; G2: $12.62{\pm}1.80$; G3: $16.60{\pm}1.93$; and G4: $21.24{\pm}1.95$. G4 and G1 had the highest and the lowest bond strength values, respectively. A greater bond strength value was seen in G3 compared to G2. There were significant differences between all the groups (P<.001). All the failures were of the adhesive mode. CONCLUSION. Application of antioxidant agents may increase microtensile bond strength between fiber posts treated with hydrogen peroxide and composite cores. Acetone increased bond strength more than ascorbic acid and ethanol.

• 태양에너지
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• 제11권3호
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• pp.62-73
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• 1991

본 연구는 주어진 기름노즐의 분무특성을 실험적으로 조사하고 아울러 적정 가동조건을 설정하기 위하여 수행하였다. 실험에 공시한 노즐은 Delalvan과 Hago(압력분무 Simplex 1.25GPH)로서 각종 압력하에서 분무 각 $60^{\circ}$와 $80^{\circ}$에 대하여 조사하고 분무특성을 기술함에 있어서는 사우터 평균입경의 개념을 사용하였다. 포집된 모든 분무입자는 고감도 필름을 사용하여 50배로 확대 촬영하고, 이들을 Nukiyama-Tanazawa의 분포함수를 도입하여 해석하였다. 결론적으로 $80^{\circ}$의 경우가 $60^{\circ}$의 경우보다 분무특성이 양호하며, 적정 가동조건은 분무압 $8kg/cm^2$ 부근에서 정착됨을 알 수 있었다.

• 한국태양에너지학회 논문집
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• 제40권5호
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• pp.23-34
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• 2020

Concentrator photovoltaic (CPV) system consists of high-quality complex optical elements, mechanical devices, and electronics components and can have the advantages of high integration and high-efficiency energy sources. III-V compound semiconductor cells have proven performance based on high reliability in the aerospace field, but have characteristics that require absolute support of the balance of systems (BOS) such as solar position trackers, receivers with heat sinks, and housing instruments. To determine the optimum parameters of secondary optical elements (SOEs) design for CPV systems, we designed three types of CPV modules, classified as non-SOEs type, reflective mirror type, and CPC lens type. We measured the I-V and P-V characteristics of the prototype CPV modules with the angle of inclination varying from 0° to 12° and with a 500-magnification Fresnel lens. The experimental results assumed misalignment of the solar position tracker or module design of pinpoint accuracy. As a result, at the 0° tilt angle, the CPC lens produced lower power due to the quartz transmittance ratio compared to that by other SOEs. However, for tilt angles greater than 3°, the CPC lens type module achieved high efficiency and stability. This study is expected to help design high-performance CPV systems.

• International Journal of Precision Engineering and Manufacturing
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• 제8권2호
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• pp.70-74
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• 2007

This paper describes the development of a nano-positioning system for nanoscale science and engineering. Conventional positioning systems, which can be expensive and complicated, require the use of laser interferometers or capacitive transducers to measure nanoscale displacements of the stage. In this study, a new self-displacement sensing (SDS) nano-stage was developed using mechanical magnification of its displacement signal. The SDS nano-stage measured the displacement of its movement using a position-sensitive photodiode (PSPD), a laser source, and a hinge-connected rotating mirror plate. A beam from a laser diode was focused onto the middle of the plate with the rotating mirror. The position variation of the reflected beam from the mirror rotation was then monitored by the PSPD. Finally, the PSPD measured the amplified displacement as opposed to the actual movement of the stage via an optical lever mechanism, providing the ability to more precisely control the nanoscale stage. The displacement amplification process was modeled by structural analysis. The simulation results of the amplification ratio showed that the distance variation between the PSPD and the mirror plate as well as the length L of the mirror plate could be used as the basic design parameters for a SDS nano-stage. The PSPD was originally designed for a total travel range of 30 to 60 mm, and the SDS nano-stage amplified that range by a factor of 15 to 25. Based on these results, a SDS nano-stage was fabricated using principle of displacement amplification.

• 대한치과기공학회지
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• 제38권4호
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• pp.255-262
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• 2016

Purpose: This study examined the effect of wettability of gypsum materials and rubber impression material on the marginal fitness of zirconia copings. Methods: Three commercially available gypsum materials(Fugirock EP, Snow Rock, Tuff Rock) and three zirconia blocks(iJAM Emerald, LUXEN Smile block, ICE Zirkon transluzent) were studied. The zirconia copings were fabricated by using dental CAD/CAM system. Contact angles on the impression materials were measured with contact angle measuring device. Silicone replica method was used to measure the marginal fitness and cutting was performed on the bucco-lingual and mesio-distal sides. It were observed with a stereomicroscope at °ø40 magnification. The data were statistically analyzed with One-way ANOVA. Results: Mean values of contact angles were $58.3{\pm}0.7^{\circ}$ for Tuff Rock, $77.5{\pm}0.5^{\circ}$ for Fugirock EP and $87.8{\pm}0.5^{\circ}$ for Snow Rock and the difference between them was statistically significant(p<0.05). The smallest values of marginal fitness for the JF groups were $30.7{\pm}3.0{\mu}m$ for bucco-lingual direction, $29.3{\pm}3.0{\mu}m$ for mesio-distal direction. One-way ANOVA showed statistically significant difference between groups for marginal fitness(p<0.05). Conclusion: Tuff rock gypsum material had superior wettability to others. The mean marginal fitness of the Tuff rock gypsum material group were significantly better than other groups. Thus they can be also expected to show clinically satisfactory marginal fitness.

• 대한치과보철학회지
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• 제44권2호
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• pp.147-156
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• 2006

Statement of problem: The high melting temperature and chemical reactivity of titanium necessitates casting machines different from those used in conventional casting. Despite the new developments in Ti casting systems , inadequate mold filling and internal porosity are frequently observed casting defects. Therefore, the study on the fabrication technique including sprue design to solve these casting defects is still necessary. Purpose: The purpose of this study was to evaluate the effect of sprue design and cross sectional area of sprue on the internal porosity. Materials and methods: 30 simulated cast three units titanium crowns were prepared. 5 cast crowns for each with different sprue design(sinlge sprue, double sprue and plate sprue) of two cross sectional areas (small and large cross sectional areas) were fabricated. The sections of titanium castings were photographed in a microscope at ${\times}100$ magnification to record internal porosities. Results and Conclusion: Within the limits of this study, the following conclusions were drawn: 1. There was a significantly lower in internal porosity of titanium castings for large cross sectional area of sprue group than the small group (P<.05) 2. There was no significant difference in internal porosity among sprue designs in similar cross sectional area of sprue (P>.05).

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.41-46
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• 2006

This paper describes a marine watch system on a ship, which is aided by an image processing method. The system detects other ships through a navigational image sequence to prevent oversights, and it measures their bearings to maintain their movements. The proposed method is described, the detection techniques and measurement of bearings techniques are derived, and the results have been reported. The image is divided into small regions on the basis of the brightness value and then labeled. Each region is considered as a template. A template is assumed to be a ship. Then, the template is compared with frames in the original image after a selected time. A moving vector of the regions is calculated using an Excel table. Ships are detected using the characteristics of the moving vector. The video camera captures 30 frames per second. We segmented one frame into approximately 5000 regions; from these, approximately 100 regions are presumed to be ships and considered to be templates. Each template was compared with frames captured at 0.33 s or 0.66 s. In order to improve the accuracy, this interval was changed on the basis of the magnification of the video camera. Ships’ bearings also need to be determined. The proposed method can measure the ships’ bearings on the basis of three parameters: (1) the course of the own ship, (2) arrangement between the camera and hull, and (3) coordinates of the ships detected from the image. The course of the own ship can be obtained by using a gyrocompass. The camera axis is calibrated along a particular direction using a stable position on a bridge. The field of view of the video camera is measured from the size of a known structure on the hull in the image. Thus, ships’ bearings can be calculated using these parameters.

• Restorative Dentistry and Endodontics
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• 제24권2호
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• pp.356-363
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• 1999

The purpose of this study was to compare the apical sealing effect of Microseal obturation technique with lateral condensation technique in 26 recently extracted single rooted teeth. The root canals were instrumented using step-back technique and obturated with laterally condensed gutta-percha or Microseal. Teeth were suspended in methylene blue dye for 2 days and then longitudinary splited. The apical microleakage and the adaptability of gutta-percha to the root canal wall were examined under a stereomicroscope at ${\times}20$ magnification. The results were as follows: 1. The mean leakage was 1.38${\pm}$1.18 mm for laterally condensed gutta-percha group, and 0.71${\pm}$0.57 mm for Microseal gutta-percha group. But there was no statistical difference between two groups. 2. In Microseal gutta-percha group, they showed no gap between the master cone and Microseal gutta-percha, and showed homogeneous mass. 3. In contrast, laterally condensed gutta-percha group showed some gaps not only between gutta-percha cones, but also between gutta-percha cones and the canal walls, and the gaps were filled with some sealer. And also this group showed some amout of sealer on the root canal walls, Within the limits of the results of this experiment, Microseal gutta-percha obturation technique demonstrated relatively favorable apical sealing effect and shorter obturation time. Thus, it is thought that this obturation technique is a acceptable method for clinical use but further studies on this matter should be conducted.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 추계학술대회
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• pp.356-359
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• 2017

교육부의 운영계획에 따라서 학교당 1~2개 교실에 전자칠판(IWB, Interactive White Board)이 보급되었다. 따라서, 두상투영기(OHP, Overhead Projector)와 스크린 대신에 실물화상기와 전자칠판이 그 역할을 대신하게 되었다. 하지만 촬상소자와 디스플레이 장치의 발전 속도를 따라가지 못하고, 활용도가 떨어지는 경우가 많았다. 본 연구에서는 스마트폰의 카메라를 이용하여 고해상도의 이미지를 획득할 수 있도록 연구한다. 획득한 고해상도의 이미지를 전자칠판이나 대형 TV로 무선 통신으로 지연시간 없이 전송할 수 있도록 와이기그(WiGig, Wireless Gigabit) 기술을 이용한다. 또한 스마트폰 카메라에 넓은 화각(FOV, Field of View)의 렌즈를 탑재하여 출시하는 것에 반하여, 현미경 렌즈를 이용하여 스마트폰으로 특정 부분을 400배까지 확대하여 관찰할 수 있도록 한다. 본 연구결과로 교육 및 연구 현장에서 실시간 400배 확대의 활성화 자료로서 사용될 것이다.