• 폴리머
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• 제25권3호
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• pp.367-374
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• 2001

여러 가지 탄소함유가스로부터 Ni 및 Ni-Cu의 합금촉매를 사용하는 화학증착반응에 의해 제조한 나노탄소섬유를 충전재로 하고, poly(vinylidene fluoride) (PVDF)를 매트릭스로 이용하여 복합재를 제조하여 전자파 차폐성능을 조사해보았다. 전자파 차폐용 충전재의 중요한 물성치인 나노탄소섬유의 전기전도도는 10000psi 압력에서 4.2∼22.4S/cm 사이에 분포하였다. 나노탄소섬유/PVDF 복합재의 전기전도도는 0.22∼2.46 S/cm 사이에 값을 보였고, 전자파 차폐성능은 2∼13 dB 범위를 나타내었다. 나노탄소섬유의 전기전도도는 열처리 온도와 시간의 증가에 따라 높아지지만, 얻어지는 복합재의 전기전도도는 초기에 급속한 증가 후 일정해지는 경향을 나타내었다. 복합재의 전자파 차폐성능은 열처리 온도와 시간의 증가에 따라 증가하다가 감소하였고, 복합재의 전기전도도에 비례하였다. 열처리가 진행됨에 따라 나노탄소섬유의 비표면적이 감소하였으며, 전자파 차폐성능에 충전재의 전기전도도 외에 비표면적이 중요한 변수임을 알 수 있었다.

• 폴리머
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• 제37권5호
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• pp.638-641
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• 2013

유연 열전소자를 제조하기 위한 열전재료로서, graphite nanosheet(GNS)와 poly(vinylidene fluoride) (PVDF)를 복합화하여 GNS/PVDF 복합체를 제조하였다. GNS의 함량에 따른 전기전도도, 열전도도, 지벡상수를 측정하여 열전성능을 확인하였다. GNS의 함량이 10에서 70 wt%로 증가하면서 전기전도도는 389에서 1512 S/m로 향상되는 결과를 보였다. 복합체의 전기전도도가 크게 증가하는 반면에 지벡 상수는 26.7에서 31.2 ${\mu}V/K$로 큰 변화를 보이지 않았으며, 열전도도 역시 0.24 W/m K를 유지하면서 변화를 보이지 않았다. 고분자와의 복합화를 통하여 GNS 자체의 높은 열전도도를 낮춤으로써 향상된 열전성능을 갖는 열전재료를 제조할 수 있었다.

• 대한소아치과학회지
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• 제24권2호
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• pp.436-448
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• 1997

Topical fluoride application for children is a widely performed procedure in the field of Pediatric Dentistry for its dental caries prevention effects. However, it is recently recognized as having some unwanted effects on several esthetic restorative materials as it roughens the surfaces of the restorative materials. In order to evaluate the surface changes in esthetic restorative materials, the author immersed composite resin, glass ionomer cement, and resin-modified glass ionomer cement specimens in various topical fluoride agents and measured the weight loss and also, examined the specimens under the scanning electron microscope. The followings are the results : 1. All the specimens immersed in APF gel for 4 minutes showed statistically significant weight loss. (paired t-test, P<0.05). 2. There was no statistically significant weight loss for the resin-modified glass ionomer cement and composite resin groups immersed in sodium fluoride solution (paired t-test, P>0.05). 3. When the glass ionomer cement group was immersed in APF gel for 1 and 4 minutes, there was a statistically significant weight loss compare to other esthetic restorative materials (ANOVA, P<0.05). 4. In the resin-modified glass ionomer cement group and the composite resin group, weight loss in the APF gel 4 minutes immersion group was greater than the 1 minute immersion group, and it was statistically significant (ANOVA, P<0.05). 5. When the specimens were examined under scanning electron microscope, the surface changes were greatest in the order of glass ionomer cement, resin-modified glass ionomer cement, composite resin and also in the order of APF gel 4 minute immersion group, 1 minute immersion group, sodium fluoride immersion group, and control group.

• 한국전기전자재료학회논문지
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• 제21권10호
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• pp.923-929
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• 2008

On the piezoelectric polymer, PVDF (poly vinylidene fluoride), the transparent conducting oxide (TCO) electrode material thin film was deposited by roll to roll sputtering process mentioned as a mass product-friendly process for display application. The deposition method for ITO Indium Tin Oxides) as our TCO was DC magnetron sputtering optimized for polymer substrate with the low process temperature. As a result, a high transparent and good conductive ITO/PVDF film was prepared. During the process, especially, the gas mixture ratio of Ar and Oxygen was concluded as an important factor for determining the film's physical properties. There were the optimum ranges for process conditions of mixture gas ratio for ITO/PVDF From these results, the doping mechanism between the oxygen atom and the metal element, Indium or Tin was highly influenced by oxygen partial pressure condition during the deposition process at ambient temperature, which gives the conductivity to oxide electrode, as generally accepted. With our studies, the process windows of TCO for display and other application can be expected.

• International Journal of Clinical Preventive Dentistry
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• 제14권4호
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• pp.209-215
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• 2018

In recent years, the numbers of the orthodontic dental patients have been rapidly increased in adolescent or young adult aged generation. It has been well known that it would be very hard to control the oral hygiene cares for orthodontic applied dental patient because of the complexity of the appliance. So the caries prevalence of the orthodontic dental patients would be higher than non-appliance persons, and it might be easy to cause the dental caries especially on the labial or buccal surface of the tooth through equipping the fixed type appliance with a long period, even though the alignment of the teeth would be arranged well. So, the massive preventive program for preventive dentistry should be needed for the dental patients for orthodontic treatment, in order to protect the dental caries and the periodontal disease for them. But, lots of the dentists or dental hygienists sometimes neglect of this point for preventive dental cares orthodontic dental patients, or do not know the importance and how to manage the skill for the preventive dental works in clinical. In this article, it will be introduced the basic theories and skills for preventive cares as tooth-brushing instruction, fluoride topical application and pit and fissure sealant, scaling and professional mechanical tooth cleansing and the diet control, for the dental patients with the fixed type of the orthodontic appliance, in case by case.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.76-79
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• 2000

The 3$\mu\textrm{m}$-thick PVDF (Polyvinyiidene fluoride) thin film have been prepared using physical vapor deposition with electric field, and its FT-IR specrum, dielectric property and electric conduction phenomenon have been investigated. Since the characteristic peaks ate detected at 509.45 and 1273.6〔cm〕 in the FT-IR spectrum, we are confirmed that the ${\beta}$ -phase is dominant in the PVDF thin film. In the results of dielectric properties, the PVDF thin film shows anomalous dispersion, i.e. gradual decrease of dielectric constant with increase of frequency, and also that the dielectric absorption point changes from 200Hz to 7000Hz with increasing temperature of thin film, which is consistent with the Debye's theory. The activation energy (ΔH) obtained from temperature dependence of dielectric loss is 21.64 ㎉/㏖. We confirm that the electric conduction mechanism of PVDF thin film is dominated by ionic conduction by investigating the dependence of the leakage current of the thin film on the temperature and the electric field.

• 한국광학회지
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• 제15권3호
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• pp.222-228
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• 2004

측면 연마 광섬유를 이용하여 가변 광 감쇠기를 실험적으로 구현하였다. 오버레이 물질로는 poly(vinylidene fluoride)와 poly (methyl methacrylate) 고분자 혼합체를 사용하였다. 혼합고분자의 온도를 변화시켜 오버레이의 굴절률을 조절하였고, 그로 인한 소산장 결합정도를 변화시켜 광섬유로부터 추출되는 광량을 조절하였다. 삽입손실은 0.1 ㏈ 이하였으며 30㏈이상의 감쇠를 실현하였다.

• 유변학
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• 제3권2호
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• pp.156-165
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• 1991

폴리비닐리덴플루오라이드 바이모프 외팔보(poly(vinylidene fluoride) bimorph cantilever beam)의 진동을 기술하는 수학적 모형을 세우고 실험으로 그모형의 타당성을 고 찰하였다. 여러 전압의 교류전류에 대해 여러 길이의 외팔보의 주파수응답을 측정하였고 여 러 전압의 직류전류에 대해 여러 길이의 외팔보의 처짐을 측정하였다. 실험으로부터 이 외 팔보의 진동은 점성감쇠보다는 구조감쇠로 기술하는 것이 더 타덩하고 외팔보가 전기장에 대해 damping factor가 일정해야 하나 각각의 normal mode에 대해 다른 damping factor로 수정하여 계산한이론치가 실험과 더 일치하였다. 공명주파수의 공명진폭을 예측할수 있고 넓은 입력주파수 영역에 대한 외팔보의 응답을 기술 할수 있으며 진동하는 외팔보는 모든위 치에서의 진폭을 기술할수 있다는 점에서 여기서의 모형은 Toda와 Smits의 모형들보다 우 수하다고 볼수 있다.

• 대한치과의사협회지
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• 제48권6호
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• pp.443-453
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• 2010

We examined progress in oral health of Korean 5 year olds children and dental public health infrastructure since the National Health Promotion Plan 2010 Oral Health Objectives were issued. We summarize trends in the prevalence of dental caries and trends in national public oral health program activities and budget. The Oral Health Objectives were achieved in 2006. Oral health in Korean preschool children improved considerably by improving of lifestyle and consumption of fluoride containing toothpaste. Although the number of public oral health center and the budget of oral health education were increased, the impact of public oral health program for preschool children was not influential. New oral health program for infants such as fluoride varnish application and strengthening of existing public oral health program should be performed for continuing improvement of oral health in Korea.

• 한국토양비료학회지
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• 제14권3호
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• pp.163-168
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• 1981

농작물(農作物)에 대(對)한 불화수소(弗化水素)가스의 피해(被害)를 경감(輕減)시키기 위(爲)하여 피해경감제(被害輕減劑)로서 소석회(消石灰) 규회석(硅灰石)을 토양(土壤)에 증시(增施)하여 수도(水稻)를 재배(裁培)하고 $0.05g/m^3$ 및 $0.10g/m^3$의 불화수소(弗化水素)가스를 1시간(時間)씩 접촉(接觸)한후(后) 수량감소정도(收量減少程度), 피해엽율(被害葉率), 식물체중(植物體中)의 불소함량(弗素含量) 및 규산함량(珪酸含量)을 조사(調査)한 결과(結果)는 다음과 같다. 1. 소석회(消石灰) 및 규회석시용량(硅灰石施用量)에 따른 불화수소(弗化水素)가스에 의(依)한 피해경감효과(被害輕減效果)는 석회(石灰) 중화량(中和量)+150kg/10a이 가장 좋았고, 규회석(硅灰石)은 150kg/10a 시용(施用)이 가장 효과(效果)가 좋았다. 2. 식물체중(植物體中) 불소함량(弗素含量)과 피해엽율(被害葉率)이 증가(增加)함에 따라 피해(被害)가 증가(增加)되었다. 3. 가스접촉(接觸) 식물체중(植物體中) 불소함량(弗素含量)이 많았던 구(區)에서 수확기(收穫期) 식물체중(植物體中) 규산함량(珪酸含量)이 많았다. 4. 시용량(施用量) 증가(增加)에 따라서 토양중(土壤中) 가용성(可溶性) 규산함량(珪酸含量)이 增加하였고 식물체중(植物體中) 규산함량(珪酸含量)도 증가(增加)하는 경향(傾向)이었다.