• Journal of the Korean Ceramic Society
• /
• v.40 no.11
• /
• pp.1073-1077
• /
• 2003

The Sn $O_2$-based gas sensors can detect inflammable and toxic gases of low concentration by the modulation of surface resistance, but they lack in selectivity on the whole. To give selectivity to the Sn $O_2$-based gas sensors, studies on the sensing mechanism, selective gas sensing materials and signal processing techniques are demanded. Ethanol (C$_2$ $H_{5}$OH) and acetonitrile ($CH_3$CN) were confirmed to undergo catalytic oxidation on Sn $O_2$ by gas chromatography. PdCl$_2$-doped Sn $O_2$ showed excellent sensitivity to ethanol and acetonitrile, while La$_2$ $O_3$-doped Sn $O_2$ showed excellent sensitivity to ethanol, but poor sensitivity to acetonitrile. Using these two sensors and pattern recognition, the selectivity to acetonitrile is greatly enhanced. The minimum detection level of acetonitrile was 15 ppm in air and 20 to 100 ppm when exposed to interfering gases together with acetonitrile.

• Biomolecules & Therapeutics
• /
• v.16 no.1
• /
• pp.1-8
• /
• 2008

Mitochondria are important sensor of apoptosis. $H_2O_2-induced$ cell death rate was enhanced by serum deprivation. In this study, we investigated whether serum deprivation using 0.5 or 3 % FBS induces apoptotic cell death through mitochondrial enzyme activation as compared to 10 % FBS. Apoptotic cell death was observed by chromosome condensation and the increase of sub-G0/G1 population. Serum deprivation reduced cell growth rate, which was confirmed by the decrease of S-phase population in cell cycle. Serum deprivation significantly increased caspase-9 activity and cytochrome c release from mitochondria into cytosol. Serum deprivation-induced mitochondrial changes were also indicated by the increase of ROS production and the activation of mitochondrial enzyme, succinate dehydrogenase. Mitochondrial enzyme activity increased by serum deprivation was reduced by the treatment with rotenone, mitochondrial electron transport inhibitor. In conclusion, serum deprivation induced mitochondrial apoptotic cell death through the elevation of mitochondrial changes such as ROS production, cytochrome c release and caspase-9 activation. It suggests that drug sensitivity could be enhanced by the increase of mitochondrial enzyme activity in serum-deprived condition.

• Proceedings of the KIEE Conference
• /
• 2008.10b
• /
• pp.123-124
• /
• 2008

본 논문에서 설계한 온도센서는 $0.l8{\mu}m$ CMOS 공정으로 $-55^{\circ}C{\sim}125^{\circ}C$의 온도 범위에서 ${\pm}0.1^{\circ}C$의 정확도를 갖는다. 이 센서는 parasitic PNP 트랜지스터로 온도 변화에 따른 전압을 추출하고 시그마-델타 변조기를 이용하여 디지털 온도 값을 얻기 위한 비트스트림을 생성한다. 또한, 이상적이지 않은 요소로 인해 발생할 수 있는 에러를 $0.01^{\circ}C$ 레벨로 감소시키기 위해 DEM(Dynamic Element Matching)과 2차 시그마-델타 변조기를 이용하였고, Bandgap Reference 회로로 온도 변화에 상관없이 일정한 bias 전압을 생성한다. 설계된 온도센서의 면적은 PAD를 포함하여 $0.98mm{\times}0.92mm$이고, 1.8V 단일 전원에서 동작한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.04b
• /
• pp.1-2
• /
• 2008

Thick films of Carbon fiber were prepared by a heating element of plan shape made in Darin co.. We have investigated surface morphology of the specimen depending on second heat-treatment temperatures. X-ray diffraction patterns of Carbon fiber thick films show that the specimen heat treated below $600^{\circ}C$ was an amorphous phase and the one heat treated above $1100^{\circ}C$ forms a poly-crystallization. Scanning electron microscope(SEM) image of Carbon fiber thick films of the specimen heat treated in between 900 and $1100^{\circ}C$ shows a grain growth. At $1100^{\circ}C$, the specimen stops grain-growing and becomes a poly-crystallization.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.33.1-33.1
• /
• 2018

pH is expressed mathematically as $pH=-{\log}[H^+]$, is a measure of the hydrogen ion concentration, [$H^+$] to specify the acidity or basicity of an aqueous solution. The pH scale usually ranges from 0 to 14. Every aqueous solution can be measured to determine its pH value. The pH values below 7.0 express the acidity, above 7.0 are alkalinity and pH 7.0 is a neutral solution. The solution pH can be determined by indicator or by measurement using pH sensor, which measuring the voltage generated between a glass electrode and a reference electrode according to the Nernst Equation. The pH value of solutions depends on the temperature and the activity of contained ions. In nickel electroless plating process, the controlled pH value in some limited ranges are extremely important to achieve optimal deposition rate, phosphorus content as well as solution stability. Basically, nickel electroless plating solution contains of $Ni^{2+}ions$, reducing agent, buffer and complexing agents. The plating processes are normally carried out at $82-92^{\circ}C$. However, the change of its pH values with temperatures does not follow any rule. Thus, the purpose of study is to understand the relationship between pH and temperature of some based solutions and electroless nickel plating solutions. The change of pH with changing temperatures is explained by view of the thermal dynamic and the practical measurements.

• Korean Journal of Medicinal Crop Science
• /
• v.22 no.5
• /
• pp.398-404
• /
• 2014

Salt stress is one of the major abiotic stresses affecting the yield of ginseng (Panax ginseng C. A. Meyer). The objective of this study was to identify bio-marker, which is early responsive in salt stress in ginseng, using proteomics approach. Ginseng plants were exposed to 5 ds/m salt concentration and samples were harvested at 0, 6, 12 and 18 hours after exposure. Total proteins were extracted from ginseng leaves treated with salt stress using Mg/NP-40 buffer and were separated on high resolution 2-DE. Approximately $1003{\pm}240$ (0 h), $992{\pm}166$ (6 h), $1051{\pm}51$ (12 h) and $990{\pm}160$ (18 h) spots were detected in colloidal CBB stained 2D maps. Among these, 8 spots were differentially expressed and were identified by using MALDI-TOF/TOF MS or/and LC-MS/MS. Ethylene response sensor-1 (spot GL 1), nucleotide binding protein (spot GL 2), carbonic anhydrase-1 (spot GL 3), thylakoid lumenal 17.9 kDa protein (spot GL 4) and Chlorophyll a/b binding protein (spot GL 5, GL 6) were up-regulated at the 12 and 18 hour, while RuBisCO activase B (spot GL 7) and DNA helicase (spot GL 8) were down-regulated. Thus, we suggest that these proteins might participate in the early response to salt stress in ginseng leaves.

• Journal of Sensor Science and Technology
• /
• v.10 no.4
• /
• pp.222-231
• /
• 2001

The material properties of $SnO_2$ were investigated as a function of the amount of $Fe_2O_3$, the partial pressure of oxygen, the concentration of CO gas, and temperature. $Fe_2O_3$-doped $SnO_2$ thick films were prepared by the screen printing technique on alumina substrate. The specimens sintered at $700^{\circ}C$ for 6 hours showed little difference of the grain size and narrow distribution with the content of $Fe_2O_3$. The electrical conductance of undoped $SnO_2$ is high at low firing temperature and at low partial pressure of oxygen. The electrical conductance of $Fe_2O_3-$-doped $SnO_2$ is increased with measurement temperature, but decreased with the content of $Fe_2O_3$. The dependence of oxygen partial pressure is decreased with dopant addition. The highest sensitivity and the good properties of response speed and repeatability for CO gas were observed on the specimen with 0.1 mol% $Fe_2O_3$ at $350^{\circ}C$.

• Journal of Sensor Science and Technology
• /
• v.3 no.1
• /
• pp.40-45
• /
• 1994

$112^{\circ}$ rot. x-cut $LiTaO_{3}$ wafer was used as the substrate of SAW gas sensor. Dual delay line SAW device with IDTs which consist of the reference delay line and the sensing delay line was fabricated using photolithigraphy. Each IDTs had 10 finger pairs and finger spacing is 10 microns. One delay line channel is the reference, while the second is the sensing channel with Pb-phthalocyanine film in the propagation path. Pb-phthalocyanine film which is p-type organic semiconductor was evaporated in $10^{-5}$ torr vacuum using shadow mask selectively. Dual delay line oscillator was constructed by using the rf amplifier and AGC. Frequency of the IDTs had the range of $87{\sim}$89 MHz oscillation frequency. Oscillation frequency shifts were investigated as a function of the temperature and the concentration of $NO_{2}$ gas.

• Korean Journal of Food Science and Technology
• /
• v.31 no.1
• /
• pp.1-6
• /
• 1999

A piezoelectric (PZ) biosensor system detecting Salmonella spp. was developed. The system consisted of an oscillator, a frequency counter and an antibody-immobilized quartz crystal. An anti-Salmonella antibody was immobilized on one gold. surface of the quartz crystal with protein A. Salmonella detection was made by measuring resonant frequency shift owing to a mass change by specific binding of microbial cells to the gold surface of the PZ crystal. The PZ antibody sensor was operated optimally at 0.1M phosphate buffer, pH 7.2 and $35^{\circ}C$. The sensor was quite specific to Salmonella spp. The obtained frequency shift was correlated with the Salmonella concentration in the range of $10^5{\sim}10^6\;CFU/mL$. The frequency shift increased further by addition of polystyrene beads. The Salmonella detection which is indicated by a steady-state microbial adsorption to the quartz crystal was accomplished within 50min.

• Proceedings of the KIEE Conference
• /
• 1999.07e
• /
• pp.2447-2449
• /
• 1999

This paper presents a distributed temperature sensor which uses a multimode optical fiber. The temperature distribution is derived from the intensity of the Raman back scattering light. Testing the sensors on measurement length of 2km of this system shows good temperature characteristics of the heated/cooled section. These performance will useful to design such as monitoring abnormal temperature rise of electric facilities.