• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제16회 학술발표회 논문개요집
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• pp.33-33
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• 1998

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.279-280
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• 2007

• 구강회복응용과학지
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• 제36권1호
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• pp.1-11
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• 2020

목적: 본 연구의 목적은 polyetherketoneketone (PEKK)의 표면 처리 방식에 따른 세가지 종류의 임시 보철물 제작용 레진과의 전단결합강도를 비교하는 것이다. 연구 재료 및 방법: 60개의 PEKK 시편을 110 ㎛의 산화알루미늄 입자(Cobra, Renfert GmbH, Hilzinge, Germany)로 분사 처리하고 시편에 Visio.link (Bredent, Senden, Germany)를 도포하지 않은 군(U)과 도포한 군(P)으로 30개씩 나누었다. 이후 한 변이 3.2 mm인 정사각형의 모양으로 polymethylmethacrylate (PMMA), polyethylmethacrylate (PEMA), bis-acryl composite resin을 PEKK에 각각 20개씩 접착하여 총 6개의 군(UM, UE, UC, PM, PE, PC)으로 분류하였다. 완성된 시편은 37℃의 증류수에 24시간 보관하였다. 만능재료시험기의 크로스헤드의 속도를 2 mm/min로 설정하고 전단결합강도를 측정하였다. 각 군간의 전단결합강도 값의 유의차를 확인하기 위하여 일원배치분산분석(one-way ANOVA)과 Tukey HSD test를 시행하였다. 결과:UM, UE군은 UC군과 유의한 전단결합강도의 차이를 나타내었다(P < 0.05). PC군이 UC군보다 높은 전단결합강도를 나타내었다(P < 0.05). 결론: 임상적으로 PEKK에 PMMA와 PEMA를 접착하는 경우에 Visio.link의 적용이 필요하지 않으나, bis-acryl composite resin을 접착하는 경우에는 Visio.link의 적용이 추천된다.

• 대한기계학회논문집
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• 제18권5호
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• pp.1288-1300
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• 1994

Mathematical modeling and numerical calculation on the flow and thermal characteristics induced by fire in a partial enclosure are performed. The solution procedures include the Shvab-Zeldovich approximation for the physical transport equations, low Reynolds number k-.epsilon. model for the turbulent fluid flow and Discrete Ordinate method(DOM) to calculate the radiative heat transfer. PMMA(Polymethylmethacrylate) is adopted as a solid fuel. Two different cases are considered : combustions with and without gas radiation occuring in a open cavity for variable pyrolyzing location of PMMA. When the fire source is located at the left-wall, the flow region of flame gas is limited at the left-wall and ceiling and recirculation region of inlet gas is formulated at neat the floor. In case of neglecting the radiative heat transfer, more large flame size and higher temperature is predicted. It is essential to consider the radiative heat transfer for analysis of fire phenomenon.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1000-1003
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• 1996

Nonlinear unified predictive control(UPC) algorithm was applied to the temperature control of a batch polymerization reactor for polymethylmethacrylate(PMMA). Before the polymerization reaction is initiated, the parameters of the process model are determined by the recursive least squares(RLS) method. During the reaction, nonlinearities due to generation of heat of reaction and variation of heat transfer coefficients are predicted through the nonlinear model developed. These nonlinearities are added to the process output from the linear process model. And then, the predicted process output is used to calculate the control output sequence. The performance of nonlinear control algorithm was verified by simulation and compared with that of the linear unified predictive control algorithm. In the experiment of a batch PMMA polymerization, nonlinear unified predictive control was implemented to regulate the temperature of the reactor, and the validity of the nonlinear model was verified through the experimental results. The performance of the nonlinear controller turned out to be superior to that of the linear controller for tracking abrupt changes in setpoint.

• 대한방사선기술학회지:방사선기술과학
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• 제42권6호
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• pp.455-460
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• 2019

This study compared the radiation transmission and image quality of polymethylmethacrylate (PMMA), polycarbonate (PC), and carbon, which are common components of the compression plates currently used during breast imaging. In addition to measuring the transmitted dose and the intensity without the use of a compression paddle, the four different compression paddles were evaluated according to the material and thickness of each paddle. Radiation transmittance, maximum intensity, and plot profile type w ere all evaluated for each material, and for each factor evaluated the follow ing order w as noted, from best to w orst: carbon 4 mm, PMMA 3 mm, PMMA 4 mm, and PC 4 mm. It is necessary to study a variety of materials and thicknesses in order to find the optimal combination of material and thickness, because not only does the material have a large influence in reducing the radiation exposure during mammography, but the thickness of the compression plate also has a great influence.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.655-656
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• 2005

In the future, plastic based system will play a crucial role in modem life, for examples, transparent display or disposable electronics and so on. In this paper, we introduced a new method to fabricate the metal line on the plastic substrate. Metal lines were fabricated by hot embossing and CMP process on PMMA (polymethylmethacrylate) substrates. A Si mold was made by wet etching process and a PMMA wafer was cut off from I mm thick PMMA sheet. A 100 nm thick Al was deposited on PMMA wafers. The Al deposited PMMA wafer and the Si mold carefully sandwiched which was directly imprinted by hot embossing. After imprinting process, a residual Al layer was removed by CMP process. Finally, we found the entire process may be very useful to fabricate the metal line on plastic substrates.

• 대한치과기공학회지
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• 제41권3호
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• pp.203-209
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• 2019

Purpose: The purpose of this study was to investigate the mechanical properties of polymer prosthetic and restorative materials for dental CAD/CAM using two test method; surface characteristics and shear bond strength. Methods: Commercialized CAD/CAM polymer blanks were investigated; One kinds of PMMA, and one PEKK blanks. A total of 20 PMMA and PEKK specimens were prepared, and each group was divided into 10 specimens. Average surface roughness was observed under surface profilometer. The contact angle was measured with a surface electrooptics. The bond strength was evaluated by a universal testing machine at a crosshead speed of 5mm/min. The data were statistically analyzed using independent t-test and Fisher's exact test(P<0.05). Results: The PMMA and PEKK group showed a significant difference in the shear bond strength with the composite resin(P<0.05). The surface roughness of the PEKK group was higher than that of the PMMA group. The fracture mode were observed in PEKK groups with 50% showing adhesive remnant index score. Conclusion: PEEK is used as substructure material and composite veneering material is applied. PEKK resins will contribute to the development of successful products that will provide structural and aesthetic satisfaction.

• 대한화학회지
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• 제33권4호
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• pp.431-435
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• 1989

완전히 불순물을 제거한 투명한 polymethylmethacrylate(PMMA)의 prerod를 제조하여 연속 열연신하여 얻은 플라스틱 섬유의 연신온도($T_d$)에 따른 굴절율, 굴절율분포, 복굴절율 및 전송손실율을 측정하였다. $T_d$가 높을수록 다소 낮은 굴절율을 보였으나, 섬유의 중심에서 주변으로 감에 따른 굴절율분포는 오히려 낮은 $T_d$에서가 현저했고, 높은 $T_d$에서는 주변에서만 급격한 굴절율의 강하를 보였다. 또한 $T_d$가 220$^{\circ}C$ 미만에서는 복굴절을 ${\Delta}$n = $5{sim}6{\times}10^{-4}$을 보이고 그 보다 높은 온도의 $T_d$에서는 이러한 현상이 나타나지 않았다. Attenuation은 높은 $T_d$일수록 낮은 값을 보였다.

• Journal of Korean Neurosurgical Society
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• 제46권4호
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• pp.305-311
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• 2009

Objective : The purpose of this study was to determine the efficacy, radiological findings, clinical outcomes and complications in patients with lumbar stenosis and osteoporosis after the use of polymethylmethacrylate (PMMA) augmentation of a cannulated pedicle screw. Methods : Thirty-seven patients with degenerative spinal stenosis and osteoporosis (T-score < -2.5) underwent lumbar fusion using the Dream Technology Pedicle Screw ($DTPS^{TM}$, Dream Spine Total Solutions, Dream STS, Seoul. Korea) between 2005 and 2007. The clinical outcomes were evaluated by using the visual analog scale (VAS) and the Prolo scale. Radiologic findings were documented through computed tomography (CT) and plain films. Results : Thirty-seven patients were evaluated and included, 2 males and 35 females with an average bone mineral density (BMD) of $0.47g/cm^2$. The average age of the patients was 68.7 (range, 57-88). The preoperative VAS for low back and leg pain ($7.87{\pm}0.95$ and $8.82{\pm}0.83$) were higher as compared with postoperative VAS ($2.30{\pm}1.61$ and $1.42{\pm}0.73$) with statistical significance (p = 0.006, p = 0.003). According to the Prolo scale, 11, 22, one and three patients were in excellent, good, fair and poor conditions, respectively. The average amount of the injected cement per one cannulated screw was $1.83{\pm}0.11\;mL$. Conclusion : The results show favorable outcome both clinically and radiographically for 37 patients who underwent lumbar fusion using $DTPS^{TM}$ and PMMA. Based on the results, the use of this surgical method can be a safe and effective option for the operation on the osteoporotic spine.