• Title/Summary/Keyword: Critical-temperature switch

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Development of a Low-Power Standalone Heat Detector Using a Critical-Temperature Switch (임계온도스위치를 이용한 저전력 단독경보형 정온식 감지기 개발)

  • Jo, Sungwoo;Jung, Sun-Kyu;Son, Jimin;Kim, Hyun-Tak
    • Fire Science and Engineering
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    • v.33 no.4
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    • pp.70-76
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    • 2019
  • This paper reports development of a low-power standalone heat detector using a Critical-Temperature Switch. The Critical-Temperature Switch, which is a thermally sensitive and passive component whose resistance decreases significantly at 70 ℃ due to a metal-insulator transition, provides reliable temperature measurements. This digital-like behavior of the Critical-Temperature Switch can detect fires without a microcontroller, meaning that it can minimize the power consumption of the standalone heat detector. The experimental results showed that the standalone heat detector using the Critical-Temperature Switch complied with the Notification of the National Emergency Management Agency. Compared to conventional standalone heat detectors, only 70% of the power was consumed monitoring the fires.

Thermo- and Acid/base-induced Spectral Switching of a Poly(N-isopropylacrylamide) Copolymer Containing Benzopyran-based D-π-A type Dye Units

  • Lee, Eun-Mi;Gwon, Seon-Yeong;Ji, Byung-Chul;Kim, Sung-Hoon
    • Textile Coloration and Finishing
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    • v.22 no.3
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    • pp.181-186
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    • 2010
  • A thermoresponsive poly(NIPAM-co-dye) labeled with benzopyran-based D-$\pi$-A type dye was prepared by typical radical copolymerization. It can be also constructed a acid/base-induced molecular switch by modulation of intramolecular charge transfer with protonation/deprotonation. The lower critical solution temperature behavior was investigated by means of UV-vis spectroscopy which allows the measurement of the phase transition from $25^{\circ}C$ to $45^{\circ}C$ in aqueous DMSO solution. The morphology of the internal microstructure of the poly(NIPAM-co-dye) hydrogel was observed by scanning electron microscopy. The reversible switch could be obtained by thermal and acid/base stimuli.

Fabrication and test of heater triggered persistent current switch using coated conductor tapes (Coated conductor를 이용한 히터트리거 방식의 영구전류 스위치의 제작과 실험)

  • Kim, Young-Jae;Yang, Seong-Eun;Park, Dong-Keun;Ahn, Min-Cheol;Yoon, Yong-Soo;Ko, Tae-Huk
    • Proceedings of the KIEE Conference
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    • 2006.07d
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    • pp.2039-2040
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    • 2006
  • Persistent current switch (PCS) system in NMR, MRI, MAGLEV and SMES has many advantages, such as uniformity and durability of magnetic field and reducing a thermal loss, which enable many superconducting application to operate effectively. This paper deals with fabrication and test of heater trigger persistent current switch using coated conductor (CC) which has high n-index, critical current independency from external magnetic field and adaptable selectivity of stabilizer. PCS system consists of magnet power supply for energizing current to a magnet, heater, switch and magnet using coated conductor tape. Finite element method (FEM) is used to simulate thermal quench (switching) characteristic and design heater trigger. With FEM simulation, optimal length of heater is calculated by temperature and time analysis. Fabrication of PCS system and test of heater trigger characteristic were performed and compared with simulation result. This paper would be the foundation of researches of superconducting switching application.

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Characteristics of joint resistance with different kinds of HTS tapes for heater trigger switch

  • Lee, Jeyull;Park, Young Gun;Lee, Woo Seung;Jo, Hyun Chul;Yoon, Yong Soo;Ko, Tae Kuk
    • Progress in Superconductivity and Cryogenics
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    • v.16 no.1
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    • pp.32-35
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    • 2014
  • Recently, many researches on the system of superconducting power supply and superconducting magnetic energy storage (SMES) using high temperature superconducting (HTS) tapes has been progressed. Those kinds of superconducting devices use the heater trigger switches that have a control delay problem at moments of heating up and cooling down. One way to reduce the time delay is using a different HTS tape at trigger part. For example, HTS tape having lower critical temperature can reduce time delay of heating up and heating down stage for heater trigger operation. This paper deals with resistances joint with different kinds of HTS tapes which have different properties to verify usefulness of the suggested method. Three kinds of commercial HTS tapes with different specifications are selected as samples and two kinds of solders are used for comparison. Joint is performed with temperature and pressure controllable joint machine and the joint characteristics are analyzed under the repeatable conditions.

Preparation and Properties of Polymer PTC Composites for Process Safety (공정안전용 Polymer PTC 소재의 제조 및 특성)

  • 강영구;조명호
    • Journal of the Korean Society of Safety
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    • v.18 no.3
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    • pp.101-108
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    • 2003
  • Polymeric positive temperature coefficient(PTC) composites have been prepared by incorporating carbon black(CB) into high density polyethylene(HDPE), polyphenylene sulfide(PPS) and polybutylene terephthalate(PBT) matrices. A PTC effect was observed in the composite, caused by the large thermal expansion due to He consecutive melting of HDPE, PPS and PBT crystallites. This theory is based upon the premise that the PTC phenomenon is due to a critical separation distance between carbon particles in the polymer matrix at the higher temperature. The influence of PTC characteristics of the PPS/CB composite can be explained by DSC result. HDPE, one of prepared composition, exhibit the higher performance PTC behavior that decreaseing of negative temperature coefficient(NTC) effect and improved reproducibility by chemically crosslinking. Also, PBT/CB and PPS/CB composites exhibit the higher PTC peack temperature than HDPE/CB PTC composite, individually $200^{\circ}C$ and $230^{\circ}C$. These PTC composite put to good use in a number of safety application, such as self$.$controlled heater, over-current protectors, auto resettable switch, high temperature proctection sensor, etc.

Optical Bistability in Nonlinear Etalons Filled with NOA81 Optical Adhesive (NOA81 Optical Adhesive를 중간층으로 하는 비선형 Etalon에서 나타나는 광쌍안정현상에 대한 연구)

  • Kong, Hong-Jin;Hwang, Wol-Yon;Lee, Sang-Soo
    • Proceedings of the KIEE Conference
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    • 1987.11a
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    • pp.387-391
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    • 1987
  • We have observed the optical bistabilities at $5145{\AA}$ in nonlinear etalons filled with NOA8l optical adhesive which is cured with UV light under the temperature gradient of $7^{\circ}C/mm$ on the NOA81 layer surface. The critical switch-on irradiance and switch-on time are $17\;KW/cm^2$ and $350{\mu}sec$. respectively. The switching contrast of up to 8 observed in NOA81 etalons is higher than that of ZnS or ZnSe interference filter, and the thermo-optic coefficient (dn/ndT) of NOA81 is measured to be at least $-3.8{\times}10^{-4}/^{\circ}C$ which is larger in magnitude than that of ZnS or ZnSe.

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Characteristics Analysis of a Small Scale Persistent Current Switch System by using Coated Conductor (Coated Conductor를 이용한 소용량 영구전류스위치 시스템의 특성 해석)

  • Kim, Yeong-Sik;Yoon, Yong-Soo;Yang, Seong-Eun;Park, Dong-Keun;Ahn, Min-Cheol;Ko, Tae-Kuk
    • Progress in Superconductivity and Cryogenics
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    • v.9 no.1
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    • pp.47-52
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    • 2007
  • This paper presents characteristics analysis of persistent current switch(PCS) system on a small scale by using YBCO coated conductor(CC). A high temperature superconductor(HTS) PCS system mainly consists of a PCS, a HTS magnet load and a magnet power supply(MPS). To design the optimal heater triggering switch. the three-dimensional heat conduction model was analyzed by finite element method(FEM). The electrical equivalent model considering the n-value of CC was applied to analyze current decay during persistent current mode. In the experiment and simulation, the heater was applied with a current of 0.43A and the current was ramped up to 10A and 20A with 0.2A/s. Finally, experimental results of the HTS PCS system have been compared with the theoretical results. It has been concluded that flux creep can not influence the results because the operating current was 40% of critical current and optimal sequential operation of the PCS system is indispensable to enhance its performance.

Dynamics of a Globular Protein and Its Hydration Water Studied by Neutron Scattering and MD Simulations

  • Kim, Chan-Soo;Chu, Xiang-Qiang;Lagi, Marco;Chen, Sow-Hsin;Lee, Kwang-Ryeol
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.21-21
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    • 2011
  • A series of Quasi-Elastic Neutron Scattering (QENS) experiments helps us to understand the single-particle (hydrogen atom) dynamics of a globular protein and its hydration water and strong coupling between them. We also performed Molecular Dynamics (MD) simulations on a realistic model of the hydrated hen-egg Lysozyme powder having two proteins in the periodic box. We found the existence of a Fragile-to-Strong dynamic Crossover (FSC) phenomenon in hydration water around a protein occurring at TL=$225{\pm}5K$ by analyzing Intermediate Scattering Function (ISF). On lowering of the temperature toward FSC, the structure of hydration water makes a transition from predominantly the High Density Liquid (HDL) form, a more fluid state, to predominantly the Low Density Liquid (LDL) form, a less fluid state, derived from the existence of a liquid?liquid critical point at an elevated pressure. We showed experimentally and confirmed theoretically that this sudden switch in the mobility of the hydration water around a protein triggers the dynamic transition (so-called glass transition) of the protein, at a temperature TD=220 K. Mean Square Displacement (MSD) is the important factor to show that the FSC is the key to the strong coupling between a protein and its hydration water by suggesting TL${\fallingdotseq}$TD. MD simulations with TIP4P force field for water were performed to understand hydration level dependency of the FSC temperature. We added water molecules to increase hydration level of the protein hydration water, from 0.30, 0.45, 0.60 and 1.00 (1.00 is the bulk water). These confirm the existence of the FSC and the hydration level dependence of the FSC temperature: FSC temperature is decreased upon increasing hydration level. We compared the hydration water around Lysozyme, B-DNA and RNA. Similarity among those suggests that the FSC and this coupling be universal for globular proteins, biopolymers.

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Liquid Metal Enabled Thermo-Responsive Poly(N-isopropylacrylamide)Hydrogel for Reversible Electrical Switch (액체금속이 첨가된 온도 감응성 poly(N-isopropylacrylamide) 하이드로젤의 전기적 특성 변화 고찰)

  • Lim, Taehwan;Lee, Sohee;Yeo, Sang Young
    • Textile Coloration and Finishing
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    • v.34 no.3
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    • pp.207-216
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    • 2022
  • Hydrogels have gained considerable attention in various fields due to their easily transformative ability by different stimulation. In addition, metal-based conductive additives can enable the hydrogels to be conductive with dimension change. Although the development of the additives offered enhanced electrical properties to the hydrogels, correspondingly enhanced mechanical properties may limit the volume and electrical properties switching after stimulation. Here we prepared poly(N-isopropylacrylamide) (PNIPAM) thermo-responsive hydrogel that has a 32℃ of low critical solution temperature and added liquid metal particles (LMPs) as conductive additives, possessing soft and stretchable benefits. The LMPs enabled PNIPAM (PNIPAM/LMPs) hydrogels to be constricted over 32℃ with a high volume switching ratio of 15.2 when deswelled. Once the LMPs are spontaneously oxidized in hydrogel culture, the LMPs can release gallium ions into the hydrogel nature. The released gallium ions and oxidized LMPs enhanced the modulus of the PNIPAM/LMPs hydrogel, triggering high mechanical stability during repeated swelling/deswelling behavior. Lastly, highly constricted PNIPAM/LMPs hydrogel provided a 5x106 of electrical switching after deswelling, and the switching ratio was closely maintained after repeated swelling/deswelling transformation. This study opens up opportunities for hydrogel use requiring thermo-responsive and high electrical switching fields.

Theoretical Heat Flow Analysis and Vibration Characteristics During Transportation of PCS(Power Conversion System) for Reliability (전력변환장치 캐비넷에서의 내부발열 개선을 위한 열유동 분석 및 유통안전성 향상을 위한 진동특성 분석)

  • Joo, Minjung;Suh, Sang Uk;Oh, Jae Young;Jung, Hyun-Mo;Park, Jong-Min
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.28 no.2
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    • pp.143-149
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    • 2022
  • PCS needs to freely switch AC and DC to connect the battery, external AC loads and renewable energy in both directions for energy efficiency. Whenever converting happens, power loss inevitably occurs. Minimization of the power loss to save electricity and convert it for usage is a very critical function in PCS. PCS plays an important role in the ESS(Energy Storage System) but the importance of stabilizing semiconductors on PCB(Printed Circuit Board) should be empathized with a risk of failure such as a fire explosion. In this study, the temperature variation inside PCS was reviewed by cooling fan on top of PCS, and the vibration characteristics of PCS were analyzed during truck transportation for reliability of the product. In most cases, a cooling fan is mounted to control the inner temperature at the upper part of the PCS and components generating the heat placed on the internal aluminum cooling plate to apply the primary cooling and the secondary cooling system with inlet fans for the external air. Results of CFD showed slightly lack of circulating capacity but simulated temperatures were durable for components. The resonance points of PCS were various due to the complexity of components. Although they were less than 40 Hz which mostly occurs breakage, it was analyzed that the vibration displacement in the resonance frequency band was very insufficient. As a result of random-vibration simulation, the lower part was analyzed as the stress-concentrated point but no breakage was shown. The steel sheet could be stable for now, but for long-term domestic transportation, structural coupling may occur due to accumulation of fatigue strength. After the test completed, output voltage of the product had lost so that extra packaging such as bubble wrap should be considered.