• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.542-548
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• 2001

A robust, accurate, broad-band, alternating current sensor using fiber-optics is being developed as a part of optical over current protection relay system. The sensor uses the Faraday effect in optical fiber and polarimetric measurements tc sense electrical current. The current sensing coil consists of a length of twisted optical fiber and Faraday rotator mirror to suppress the linear birefringence effect. Due to its single-ended closed path structure, it can not only be easily installed to the target with great isolation from other fields in the vicinity, but the sensitivity can be increased by using multiple turns. This paper reports on the theoretical backgrounds of the sensor design and the preliminary experimental results.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.271-281
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• 2013

Freeze-thaw experiments were conducted to evaluate changes in surface roughness and physical properties in samples of granite from Ilgwang and Imki mines, Korea. The temperature range in the experiments was $-20^{\circ}C$ to $40^{\circ}C$, based on typical summer and winter temperatures in Korea, and the surface was observed every 20 cycles. One cycle comprised 1 hour of heating or cooling of the samples and 1 hour during which the target temperature was maintained. With increasing repetitions of the freeze-thaw experiment, porosity increased by 0.05%-0.15% in the two samples and the dry weight increased, whereas the volume of the soil and saturation weight decreased. Observations by confocal laser scanning microscope (CLSM) revealed that line and surface roughness parameters showed a tendency to increase and decrease, respectively, with elapsed time. Changes in surface roughness were apparent on the CLSM images.

• Journal of the Korean Vacuum Society
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• v.14 no.4
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• pp.222-228
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• 2005

Undoped GaN epitaxial layer was grown on c-plane sapphire substrate by a two-step growth with metalorganic chemical vapor deposition(MOCVD). We have investigated the effects of the variation of final growth temperature on surface morphology, roughness, crystal quality, optical property, and electrical property In a horizontal MOCVD reactor, the film was grown at 300 Tow low-pressure with a fixed nucleation temperature of $500^{\circ}C$, varing the final growth temperature from $850\~1050^{\circ}C$ . The undoped GaN epilayers were characterized by atomic force microscopy, high-resolution x-ray diffractometer, photoluminescence, and Hall effect measurement.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.143-148
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• 1999

Magnetic properties and crystallographic properties of $Cu_{1-x}Ge_{1-y}Fe_{x+y}O_3$ system were studied by using x-ray diffraction, superconducting quantum interference device (SQUID) and Mossbauer spectroscopy. All the samples have orthorhombic structure and the lattice constants some decreased as the substituted iron contents increasing. The spin-Peierls (SP) transition temperature of our samples are about 12.5 K and these temperatures lowered as increasing substituted iron contents. The Mossbauer spectra consisted with two Zeeman sextets and one doublet due to $Fe^{3+}$ ions. The jump up of magnetic hyperfine field of 2nd Zeeman sextet and the increasing of the values of quadrapole splitting and isomer shift of doublet below SP transition temperature could be interpreted with the variation of the superexchange interaction, the symmetry of lattice sites and the covalency of bonds due to the atomic displacements.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.2
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• pp.149-156
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• 1999

An experimental simulation on the flow in Czochralski melt using a cold model was carried out to obtain the velocities of fluid flow which affects the oxygen concentration of Czochralski crystal growing system. Low melting point Woods metal with similar Pr number to the silicon melt was adopted as a working fluid. Local flow velocities at numerous positions in the melt were simulataneously measured in three dimension using incorporated magnet probe. The measured velocity field showed a non-axisymmetric pattern dominated by natural convection. The analysis on the correlation between data set of temperatures simultaneously measured at two melt positions showed that the values of correlation coefficients were smaller than those of previous study on the small size of silicon melt and these phenomena are believed to occur because turbulent behavior becomes stronger in large size of the melt.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.433-440
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• 1999

To develop Korean-style hot sauce using red pepper powder and/or Kochujang, its physiochemical and microbiological characteristics were investigated during storage at 20 and $30^{\circ}C$ for 56 days. The capsanthin contents and the value of surface color decreased during storage, but pH and titratable acidity were not changed. The sensory quality showed a decreased tendency during storage. Among the microorganisms, viable cell count decreased, but yeast, lactic acid bacteria and E. coli were not detected during storage. From the correlationship between sensory color and capsanthin content, the shelf-lives of hot sauce were predicted to be 221.7 days at $20^{\circ}C$, and 85.3 days at $30^{\circ}C$. While they were 230.0 days at $20^{\circ}C$ and 70.0 days at $30^{\circ}C$ in case of using Kochujang, hot sauce using both materials showed shelf-lives of 204.0 days at $20^{\circ}C$, 67.3 days at $30^{\circ}C$, respectively.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.08a
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• pp.79-79
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• 2020

본 연구는 새싹인삼(Panax ginseng sprout) 재배용으로 이용하기 위한 묘삼(종삼)의 장기 저온저장 시 저장온도가 묘삼의 새싹인삼으로의 생장과 품질에 미치는 영향을 조사하여 묘삼의 저장에 적합한 온도를 구명하고자 수행하였다. 2년생 묘삼을 50 ㎛ LDPE 필름에 100g씩 넣어 포장하였고 온도 0, -2, -4℃에서 10개월 동안 저장하면서 2개월 마다 꺼내어 5℃ 저장고로 이동하여 5~7일 온도순화처리를 거친 후 실험을 실시하였다. 1차 육안조사로 묘삼의 부패율과 2차 생육조사로 묘삼을 재식 후 새싹인삼으로 재배 후 생장 상태와 품질을 조사한 결과 저장 4개월 이후 묘삼의 생육조사 시 새싹인삼의 생장과 품질이 묘삼의 저장온도에 따라 유의적인 차이를 보였다. 즉, 저장 4개월 된 묘삼의 건전한 새싹인삼으로의 생장은 0℃ 저장 묘삼에서 58.3%, -2℃ 저장 묘삼에서 72.1%, -4℃ 저장 묘삼에서 37.2%로 조사되었고, 저장 8개월 된 묘삼은 0℃ 저장 묘삼에서 9.7%, -2℃ 저장 묘삼에서 54.3%, -4℃ 저장 묘삼에서 6.9%로 조사되었다. 특히 0℃ 저장 묘삼은 저장 2개월에 출아가 진행되었고 저장기간이 지날수록 출아된 싹이 동해의 피해를 받는 것으로 조사되었다. 묘삼의 생육특성인 엽장, 엽폭, 경장, 근장을 측정한 결과 -2℃에 저장된 묘삼의 엽폭과 경장의 길이가 유의적으로 긴 것으로 조사되어 새싹인삼 재배를 위한 묘삼의 적정 저장온도는 -2℃로 설정하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.579-580
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• 2017

Recently, as safety accidents by reagents increase in laboratories, systems are being developed to safely manage reagents. The existing system monitoring and manages the reagent through the web page, but the internal environment change of the reagent cabinet is considered or the remote monitoring and control function is insufficient. In order to solve this problem, this paper predicts the deterioration of the reagent loaded in the reagent cabinet. And we propose a system that can monitoring and control remotely. It predicts the deterioration of the reagent through the temperature attached to the inside of the reagent cabinet, the value measured by the humidity sensor and the validity period of the reagent, and sends a alert message to the manager. The manager monitoring and controls the reagent cabinet through the application. By predicting the deterioration of the reagents and remotely managing the reagents cabinet it is thought that safety accidents can be reduced.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.431-438
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• 2022

In functional materials, in situ experimental techniques as a function of external stimulus (e.g., electric field, magnetic field, light, etc.) or changes in ambient environments (e.g., temperature, humidity, pressure, etc.) are highly essential for analyzing how the physical properties of target materials are activated/evolved by the given stimulation. In particular, in situ electric-field-dependent X-ray diffraction (XRD) measurements have been extensively utilized for understanding the underlying mechanisms of the emerging electromechanical responses to external electric field in various ferroelectric, piezoelectric, and electrostrictive materials. This tutorial article briefly introduces basic principles/key concepts of in situ electric-field-dependent XRD analysis using a lab-scale XRD machine. We anticipate that the in situ XRD method provides a practical tool to systematically identify/monitor a structural modification of various electromechanical materials driven by applying an external electric field.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.721-727
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• 2010

The spontaneous ignition of coal stockpile causes serious safety and economic problems. Such spontaneous ignition occurs in coal stockpile when the rate of heat released by the oxidation of coal is greater than the rate of heat lost to the surroundings. In this study, a two-dimensional unsteady model is adopted for studying spontaneous ignition and the numerical results are compared with experimental results. The numerical results are in a good agreement with the experimental ones. Depending on the porosity, the internal maximum temperature, pressure, and oxygen mass fraction during spontaneous ignition are investigated. On the basis of the numerical results, the transient temperature variations for several shapes of coal stockpiles are analyzed. Further, the physical mechanisms of hot-spot formation and spontaneous ignition are analyzed.