• Korean Journal of Materials Research
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• v.18 no.9
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• pp.475-481
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• 2008

Positive temperature coefficient of resistivity (PTCR) characteristics of (1-x)$BaTiO_3-x(Bi_{0.5}K_{0.5})TiO_3$ ceramics doped with $Nb_2O_5$ were investigated in order to develop the Pb-free PTC thermistor available at high temperatures of > $120^{\circ}C$. The PTCR characteristics appearing in the ($B_{i0.5}K_{i0.5})TiO_3$ (< 5 mol%) incorporated $BaTiO_3$ ceramics, which might be mainly due to $Bi^{+3}$ ions substituting for $Ba^{+2}$ sites. The 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics showed good PTCR characteristics of a low resistivity at room temperature (${\rho}_r$) of $31{\Omega}{\cdot}cm$ a high ${\rho}_{max}/{\rho}_{min}$ ratio of $5.38{\times}10^3$, and a high resistivity temperature factor (${\alpha}$) of $17.8%/^{\circ}C$. The addition of $Nb_2O_5$ to 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics further improved the PTCR characteristics. Especially, 0.025 mol% $Nb_2O_5$ doped 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics exhibited a significantly increased ${\rho}_{max}/{\rho}_{min}$ ratio of $8.7{\times}10^3$ and a high ${\alpha}$ of $18.6%/^{\circ}C$, along with a high $T_c$ of $148^{\circ}C$ despite a slightly increased ${\rho}_r$ of $31{\Omega}{\cdot}cm$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.929-935
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• 2010

$(1-x)BaTiO_3-x(Bi_{0.5}Na_{0.5})TiO_3$ ($0.01{\leq}x{\leq}0.10$) ceramics were fabricated with muffled sintering by a modified synthesis process. Their positive temperature coefficient of resistivity (PTCR) characteristics were investigated systematically. All specimen showed a perovskite structure with a tetragonal symmetry. Both the lattice parameter of a and c axes were slightly decreased with increasing $(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) content. Grain growth was achieved when the incorporated BNT was increased to 6 mol% and the inhibition of grain growth is considered to be due to the appearance of Ba vacancy ($V^{"}_{Ba}$) in the $(1-x)BaTiO_3-x(Bi_{0.5}Na_{0.5})TiO_3$ ($0.08{\leq}x$). With 4 mol% BNT addition, room temperature resistivity decreased to $48 \Omega{\cdot}cm$ and a resistivity jump ($\rho_{max}/\rho_{min}$) was as high as $1.1{\times}10^4$, respectively. Curie temperature was also increased to $171^{\circ}C$ with increasing BNT content.

• Journal of the Korean Applied Science and Technology
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• v.35 no.1
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• pp.89-98
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• 2018

The purpose of this study was to compare the foot plantar pressure and temperature changes of the developed combat boots with functional impact absorption and ventilation insole. A total of 11 male subjects(age: $21.8{\pm}2.2yrs$, height: $174.3{\pm}3.6cm$, weight: $71.6{\pm}8.6kg$, foot length: $261.0{\pm}1.0mm$) were recruited to compare the foot plantar pressure and temperature changes of the three types of combat boots: Combat boots A (generalized combat boots), Combat boots B (developed combat boots with ventilation function), Combat boots C (Application of ventilation function and impact absorption insole to combat boots B). Pedar-X and a portable thermistor temperature sensor were used to measure the foot plantar pressure parameters and the internal temperature of the combat boots, respectively. One-way ANOVA was used to compare the results of plantar pressure and temperature changes. The results were as follows: First, in the foot plantar pressure parameters, combat boots C showed the significant lower maximum foot plantar pressure in the right/left rear foot compared with combat boots A and average foot plantar pressure in the left foot compared with combat boots B. Second, after 40 minutes from the start of walking, the developed combat boots B and C showed the significant lower temperature than the general combat boots A.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.35-36
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• 2008

PTC thermistor are characterized by an increase in the electrical resistance with temperature. The PTC materials of middle Curie point were produced or that of high Curie point (above $200^{\circ}C$), it was determined that compositional modifications of $Pb^{2+}$ for $Ba^{2+}$ produce change sin the Curie point to higher temperature. PTC ceramic materials with the Curie point above $120^{\circ}C$ were prepared by adding $PbTiO_3$, PbO or $Pb_3O_4$ into $BaTiO_3$. Thereby, adding $Pb^{2+}$ into $BaTiO_3$-based PTC material to improve Tc was studied broadly, however, weal know that PbO was poisonous and prone to volatilize, then to pollute the circumstance and hurt to people, so we should dope other innocuous additives instead of lead to increase Tc of composite PTC material. In order to prepare lead-free $BaTiO_3$-based PTC with middle Curie point, the incorporation on $Bi_{1/2}K_{1/2}TiO_3$ into $BaTiO_3$-based ceramics was investigated on samples containing 0, 1, 2, 3, 4, and 50mol% of $Bi_{1/2}K_{1/2}TiO_3$. $Bi_{1/2}K_{1/2}TiO_3$ was compounded as standby material by conventional solid-state reaction technique. The starting materials were $Bi_2O_3$, $K_2CO_3$, $BaCO_3$ and $TiO_2$ powder, and using solid-state reaction method, too. The microstructures of samples were investigated by SEM, DSC, XRD and dielectric properties. Phase composition and lattice parameters were investigated by X-ray diffraction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.32-32
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• 2008

Microstructure and positive temperature coefficient of resistivity (PTCR) characteristics of $0.9BaTiO_3-0.1(Bi_{0.5}Na_{0.5})TiO_3$ [BaBiNT] ceramics doped with $Nb_2O_5$ were investigated in order to develop the Pb-free high Curie temperature ($T_c$)(>$160^{\circ}C$) PTC thermistor. The BaBiNT ceramics showed a tetragonal perovskite structure, irrespective of the added amount of $Nb_2O_5$. They also have a homogeneous microstructure. The resistivity of BaBiNT ceramics was gradually decreased by doping $Nb_2O_5$, which might be due to $Nb^{+5}$ ions substituting for $Ti^{+4}$ sites. The PTCR characteristics of BaBiNT ceramics appeared when the amount of doped $Nb_2O_5$ exceeded 0.0025mol%. Moreover, the abrupt grain growth was observed for the 0.03mol% $Nb_2O_5$added BaBiNT ceramics. It showed an especially high $T_c$ of approximately $172^{\circ}C$ and good PTCR characteristics of a high $\rho_{max}/\rho_{min}$ ratio ($2.96\times10^3$), a high resistivity temperature factor (11.40/$^{\circ}C$) along with a relatively low resistivity ($3.5\times10^4\Omega{\cdot}cm$).

• Fire Science and Engineering
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• v.24 no.6
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• pp.61-68
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• 2010

In this paper, a research and development result for the implementation of single station fixed temperature detector for residential fire prevention is described. The detector was developed for the certification in Japanese market because of very low domestic market situation. It is in the situation that there is no other regulation especially for residential detectors in Korea, Japanese case has been reviewed. Investigation of domestic legal circumstances and a comparative study for the test standard owned by KFI (Korea Institute of Fire Industry & Technology) and JFEII (Japan Fire Equipment Inspection Institute) respectively are also indicated. The detector alarms with a buzzer and an indicating LED. In the implementation ultra low power MCU(Micro Controller Unit) is applied to control the sleeping state and the monitoring state properly with low current consumption. To sense the temperature fast response thermistor is adopted in the design of fixed temperature residential detector. Automatic test function and alarm stop function are also considered in the design. The major factors which influence to current consumption are explained for the purpose of design reference. Main electronics circuit parts related to it's characteristics of the detector are described. It is explained that the measured current and experimental result of the battery discharge can be met over 10 years operation.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.1
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• pp.1-9
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• 2000

Vertical temperature distributions in muddy intertidal sediments near the Jebu Island on the west coast of Korea were obtained during the period of ebb tide which occurred in day time. The observations of mud temperature were made with thermistor embedded probe at 2cm interval for 18cm-layer of sediment for five different months of the year. Temporal changes in the vertical profile of the sediment temperature are strongly depend on the air temperature, the previous time of flood tide and the time of ebb tide. Heat exchanges in the surface layer (0-2 cm) in terms of magnitude and direction are greater than and opposite to those in the deeper sediment layer (8-12 cm), respectively and do not show any significant seasonal variations. In general, the surface layer gains heat while the deeper layer loses the heat. By using the 1-D diffusion equation temporal vertical profiles of the sediment temperature were obtained and were compared with the observed ones. The results show that in the sediment layer below 4 cm-depth the heat transport is predominantly by molecular diffusion. The average magnitude of heat flux into the sediment layer (0-18 cm) during the ebb tide when the mudflats were exposed in the middle of the day were between 4.1 and $28.9\;W/m^2$.

• Journal of the Society of Disaster Information
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• v.11 no.2
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• pp.203-209
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• 2015

The heat detector detects heat in the fire and is an important core element of the automatic fire alarm system used generally for every fire prevention objects. The heat detector is distinguished in spot type and spread type and in spot type, there are differential and thermistor types. These heat detectors give a great influence on the loss of people and property according to the sensitivity of response such as operation time and operation temperature in actual fire and in overseas people apply it for the development of products that can be operated in the early stage of fire including certification, quality management, and comparison standard by introducing response time index through the theory of heat balance that considers the heat loss and ventilation tests. In Korea, the response time index is introduced and used in the head of sprinkler products, but it is not applied to the heat detector at present. It is necessary to introduce the response time index that shows the sensitivity of response of the heat detector the installation standard for the heat detector that the response time index is applied should be different according to the fire weight, danger degree of fire, and shape of buildings. Through this study, it tries to help reduce lives and property of people through the swift warning by installing detectors suitable for the building structure.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.8
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• pp.386-396
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• 2006

We implemented the Drug-Pad Moxibustion Method in order to improve the conventional moxibustion therapy. This method is aimed to eliminate burning wounds and smoke, which are the defects of conventional moxibustion therapy. And we performed to verify the efficiency by comparing the Drug-Pad Moxibustion Method with the conventional Indirect Moxibustion Therapy. We measured the body heat and the lasting time of blood circulation improvement using thermography. The moxibustion therapy has two kinds of effects: The formers are pharmacological effects of the Moxa's vasodilators and antioxidants. The latters are thermal effects which cause improvement of the blood circulation. To remove the demerits without omission of above therapeutic effects, we extracted the vasodilators and antioxidant compounds from the Moxa-$CH_2Cl_2$ fraction Moxa-EtOAc and composed the moxibustion kit with $(Ba_{0.8}\;Sr_{0.2})_{0.996}\;Y_{0.004}\;TiO_2+0.5_{WT}\;SiO_2%$ Positive Temperature Coefficients Thermistor. The experimental demonstrations have been made by the stimulating the spot which is CV4(Kwan-Won), CV8(Shin-Guel), CV12(Jung-Wan) acupuncture points of the conception vessel meridian(CV). And stimulating time was one hour. We divided the subjects into 5 groups such as no stimulation group, conventional Indirect Moxibustion group, only Drug-Pad stimulation group, only heat stimulation group, and Drug-Pad Moxibustion group. In the different cases, we have measured the body heat in pre-stimulation, just after stimulation, 2 hours after, and 4 hours after. The body heats of the group who were stimulated by the Drug-Pad Moxibustion Method were increased by over the $2^{\circ}C$. And the body heats of the group who were stimulated by the Indirect Moxibustion Method were increased by average the $1^{\circ}C$. We have evaluated that the Drug-Pad Moxibustion Method is improvement on the conventional Indirect Moxibustion Method by the heat-increasing rate is 200% and the lasting time is 150% with the body heat of the abdominal region. In the conclusions, We have implemented the Drug-Pad Moxibustion Method and evaluated the efficiency of the Drug-Pad Moxibustion Method comparing with the conventional Indirect Moxibustion Method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.57-58
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• 2008

PTC thermistor are characterized by an increase in the electrical resistance with temperature. The PTC materials of middle Curie point were produced or that of high Curie point (above $200^{\circ}C$), it was determined that compositional modifications of $Pb^{2+}$ for $Ba^{2+}$ produce change sin the Curie point to higher temperature. PTC ceramic materials with the Curie point above $120^{\circ}C$ were prepared by adding $PbTiO_3$, PbO or $Pb_3O_4$ into $BaTiO_3$. Thereby, adding $Pb^{2+}$ into $BaTiO_3$-based PTC material to improve Tc was studied broadly, however, weal know that PbO was poisonous and prone to volatilize, then to pollute the circumstance and hurt to people, so we should dope other innocuous additives instead of lead to increase Tc of composite PTC material. In order to prepare lead-free $BaTiO_3$-based PTC with middle Curie point, the incorporation on $Bi_{1/2}Na_{1/2}TiO_3$ into $BaTiO_3$-based ceramics was investigated on samples containing 0, 1, 2, 3, 4, and 50mol% of $Bi_{1/2}Na_{1/2}TiO_3$. $Bi_{1/2}Na_{1/2}TiO_3$ was compounded as standby material by conventional solid-state reaction technique. The starting materials were $Bi_{1/2}Na_{1/2}TiO_3$, $BaCO_3$, $TiO_2$ and $Y_2O_3$ powder, and using solid-state reaction method, too. The microstructures of samples were investigated by SEM, DSC, XRD and dielectric properties. Phase composition and lattice parameters were investigated by X-ray diffraction.