• Fire Science and Engineering
• /
• v.21 no.4
• /
• pp.65-71
• /
• 2007

This paper is studied on a protective control system for electrical fire and electrical faults by using electrical and thermal characteristics of PTC thermistor. The PTC thermistor has characteristic or positive resistivity temperature coefficient according to the temperature variation, which is construction of a regular square and cube demarcation with $BaTiO_3$ Ceramics of positive temperature coefficient. Also PTC thermistor shows the phenomenon which is rapidly increased in the resistivity if the temperature is increased over Curie temperature point. This paper is proposed on a protective control system used PTC thermistor which is protected from electrical fire due to electric short circuit faults or overload faults. Some experimental results of the proposed electric safety control apparatus are confirmed to the validity of the analytical results.

• Proceedings of the KIEE Conference
• /
• 2001.11a
• /
• pp.140-145
• /
• 2001

In order to apply for silane crosslinking process to PTC products, especially. self-regulating heater, silane crosslinked samples were compared with radiation crosslinked sample in terms of PTC characteristic and PTC stability. Silane crosslinked samples have lower PTC intensity than radiation crosslinked sample. It can be explained that multiple networks of silane crosslink restrict the movement of molecules in the composite as the sample is heating. As a result of heat cycles at $140^{\circ}C$, the changes of volume resistivity and PTC intensity for radiation crosslinked sample were higher than those of silane crosslinked samples. Whereas, in the case of heat cycles at $85^{\circ}C$, which is limiting temperature for self-regulating heater, both silane and radiation crosslinked samples show stable results without pronounce changes of resistivity up to five cycles.

• Human Ecology Research
• /
• v.57 no.3
• /
• pp.383-393
• /
• 2019

This study examined the association among practical teaching competence (PTC) and teaching efficacy (TE), and explored the mediation effects of theoretical teaching competence (TTC) between the PTC and TE of Practical Arts (Technology and Home Economics Education) teachers. Data were collected from the 301 survey responses completed by elementary, middle, and high school teachers. All teachers showed high levels of PTC, TTC, and TE. Elementary school teachers perceived higher PTC than middle and high school teachers. PTC, TTC, TE showed significant effect in regards to teacher's age and teaching career. Using multiple regression analysis, this study found that TTC fully mediated PTC and TE of elementary school teachers. For middle and high school teachers, there was a partial mediation effect of TTC in the relationship between PTC and TE. This study suggests that teacher education programs should develop a program that can enhance teaching efficacy by cultivating TTC and support teachers who want to strengthen competence, and more practical opportunities to practice teaching.

• Journal of the Korean Ceramic Society
• /
• v.46 no.3
• /
• pp.330-335
• /
• 2009

We investigated the effects of the re-oxidation temperature and time on the positive temperature coefficient (PTC) of resistivity characteristics of Sm-doped $BaTiO_3$ sintered at $1200{\sim}1260^{\circ}C$ for 2 h in a reducing atmosphere (3% $H_2/N_2$), followed by re-oxidization processes in air, in which re-oxidization temperature and time were $600{\sim}1000^{\circ}C$ and $1{\sim}10$h, respectively. The result reveals that Smdoped (Ba,Ca)$TiO_3$ ceramics fired in a reducing atmosphere exhibit low PTC characteristics, whereas the sample re-oxidized at $800^{\circ}C$ for 1 h in air exhibit pronounced PTC characteristics. The room-temperature resistivity and jumping characteristics of resistivity (${\rho}_{max}/{\rho}25^{\circ}C$) decrease with Sm contents. The PTC characteristics with reoxidization time at $800^{\circ}C$ have improved about $2{\sim}3$ orders of magnitude whereas differed according to the sintering temperature. The 0.7 at% Sm-doped (Ba,Ca)$TiO_3$ samples reveal the best PTC characteristics in the present range of formula and processes.

• Journal of Sensor Science and Technology
• /
• v.3 no.3
• /
• pp.3-8
• /
• 1994

Flow sensor was fabricated with PTC thermistor usually operating as thermostats. The PTC thermistor was manufactured with $(Ba_{0.7}Sr_{0.3})TiO_{3}$ powder and its resistivity as a function of flow velocity was investigated. The resistivity changed from 4.45 $k{\Omega}{\cdot}cm$ to 3.95 $k{\Omega}{\cdot}cm$ as flow velocity varied 0 cm/s to 5 cm/s The sensitivities of the PTC thermistor were -204 (${\Omega}{\cdot}cm$)/(cm/s) and -24 (${\Omega}{\cdot}cm$)/(cm/s) at the flow velocity of 1 cm/s and 5 cm/s, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.1
• /
• pp.147-155
• /
• 1999

In this work, the defrosting characteristics of PTC heating sheet used as a defrosting heat source of fin-tube heat exchanger in a refrigerator have been experimentally compared with those of conventional electric heater. It is found that the characteristics of water draining rate with defrosting time show smoothly oscillating pattern when PTC heating sheet is used, and the drained water is completely melted. The defrosting efficiency of the PTC heating sheet is about 75%, which represents about 25% higher than that of the electric heater. A reduction of defrosting time and an increase of defrosting efficiency may be obtained by improving the arrangement of heating elements of the heating sheet. It is shown that the defrosting time of PTC heating sheet increases linearly with the amount of frost, however the defrosting efficiency is nearly constant. In the application to the refrigerating system, one should notice the fact that the defrosting performance of PTC heating sheet may be defraded due to the repeated operations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.06a
• /
• pp.305-306
• /
• 2006

자동차의 난방 열원은 HVAC(Heating, Ventilating & Air Conditioning)에 내장되어 있는 히터코어 (Heater Core) 에서 공급하게 되며, 이 히터코어는 엔진에서 가열된 냉각수 열원을 이용하게 된다. 그러나 최근 디젤 엔진의 경우 연소효율의 개선과 CEGR(Cooled Exhaust Gas Recirculation) 시스템의 적용으로 냉각부하가 증가하여 냉각수가 가지는 가용 열원이 기종보다 약 30~40% 정도 저하되고 있다. 따라서 디젤 자동차 및 하이브리드용 자동차의 난방 보조 히터의 국산화 개발이 시급해진 상황이며 초정밀, 고효율 보조 히터의 개발이 요구되고 있다. 현재 적용되고 있는 보조 히터 중에서 PTC 히터는 PTC 소자의 발열을 이용하여 공기를 직접 가열하기 때문에 추가적인 연료소비가 없고 소형 및 저가라는 장점이 있다. PTC 세라믹 소자는 $BaTiO_3$를 모체로 하며, 이의 특성 항상 및 제어를 위해서는 적절한 dopant를 선택하여 균일하게 doping 해야 한다. 지금까지 dopant에 따른 구성 요소 및 역할은 비교적 잘 알려져 있다. 하지만, 자동차용으로 사용되기 위해서는 12V의 저전압에서 동작해야 하며, 또한 소자의 두께가 얇아지게 됨에 따라서 발생하는 전기적 short와 같은 문제점들을 해결하여야 한다. 따라서 본 연구에서는 PTC 세라믹 소자에서 도펀트 종류와 양 조절을 통한 저저항을 확보하고, PTC 세라믹 소자의 박막화를 달성하고자 하였다.

• Journal of the Korean institute of surface engineering
• /
• v.56 no.1
• /
• pp.40-54
• /
• 2023

In this work, we synthesized a novel electrochemical sensing materials based on tetracarboxylic copper phthalocyanine (TcCuPtc) conjugated PANI (TcCuPtc@PANI). The synthesized materials were employed to modify the screen-printed carbon electrode (SPCE) for the selective sensing of 4-nitrophenol. The TcCuPtc was conjugated with conducting polymer of PANI through the electrostatic interaction and π-π electron conjugation, the polymer film of PANI to inhibit the leakage of TcCuPtc from the surface of the electrode. The prepared TcCuPtc@PANI were characterized and confirmed by scanning electron microscopy (SEM) with EDX, ATR-IR, UV-vis absorption spectroscopy, cyclic voltammetry, and differential pulse voltammetry techniques. The prepared TcCuPtc@PANI/SPCE showed an excellent electrocatalytic sensing of 4-NP in the linear concentrations from 3 to 500 nM with a LOD of 0.03 nM and a sensitivity of 8.8294 ㎂/nM cm^-2. However, the prepared TcCuPtc@PANI/SPCE showed selective sensing of 4-NP in the presence of other interfering species. The practical applicability of the TcCuPtc@PANI/SPCE was employed for the sensing of 4-NP in different water samples by standard addition method and showed satisfactory recovery results.

• Asian Pacific Journal of Cancer Prevention
• /
• v.16 no.9
• /
• pp.3875-3879
• /
• 2015

Background: The neutrophil/lymphocyte ratio (NLR) is a simple index of systemic inflammatory response, and has been shown to be a prognostic indicator in some types of cancer. Inflammation has been implicated in the initiation and progression of thyroid cancer. The aim of this study was to examine the relationship of NLR with papillary thyroid cancer (PTC) and different benign thyroid pathologies like multinodular goiter (MNG) and lymphocytic thyroiditis (LT). Materials and Methods: We retrospectively evaluated the neutrophil, lymphocyte counts and NLR calculated from these parameters of 232 patients with histologically confirmed as multinodular goiter (group MNG) (n=70), lymphocytic thyroiditis (group LT) (n=97), LT with PTC (group LT-PTC) (n=25) and PTC (group PTC) (n=40). The optimal cut-off value for NLR was determined. Results: NLR level was significantly higher in groups LT-PTC and PTC as compared to groups MNG and LT (p<0.05). NLR of LT subgroups according to TSH levels were not different (p>0.05). When we grouped the patients as benign and malignant according to PTC presence, the optimum NLR cut-off point obtained from ROC analysis was 1.91 (sensitivity 89.0% and specificity 54.5%). Conclusions: Since NLR was significantly elevated in group LT-PTC and group PTC, NLR value may give an opinion as a potential marker in differentiation of benign and malign thyroid disorders. For this purpose a cut-off value of 1.91 for NLR may be accepted.

• Journal of the Microelectronics and Packaging Society
• /
• v.15 no.1
• /
• pp.51-58
• /
• 2008

This paper is studied on a prevention system for electrical fire and electrical faults by using electrical temperature characteristic of PTC thermistor. The PTC thermistor has characteristic of positive resistivity temperature coefficient according to the temperature variation, which is construction of a regular square and cube demarcation with $BaTiO_3$ ceramics of positive temperature coefficient. Also PTC shows the phenomenon which is rapidly increased in the resistivity if the temperature is increased over Curie temperature point. This paper is proposed on a protective control system used with temperature sensor of PTC thermistor. The proposed prevention system will prevent electrical fires due to electric short circuit faults or overload faults. And the prevention system will solve the problems that circuit breakers to be commonly used at existing are happened frequently electrical fires and electrical disasters due to incapable operation, weak reliability and low speed response. Some experimental results of the proposed apparatus are confirmed to the validity of the analytical results.