• Korean Journal of Medicinal Crop Science
• /
• v.26 no.6
• /
• pp.447-454
• /
• 2018

Background: The leaf temperature ($T_{LEAF}$) is one of the most important physical parameters governing water and carbon flux, including evapotranspiration, photosynthesis and respiration. Cnidium officinale is one of the important folk medicines for counteracting a variety of diseases, and is particularly used as a traditional medicinal crop in the treatment of female genital inflammatory diseases. In this study, we developed a model to estimate $T_{Leaf}$ of Cnidium officinale Makino based on black globe temperature ($T_{BGT}$). Methods and Results: This study was performed from April to July 2018 in field characterized by a valley and alluvial fan topography. Databases of $T_{LEAF}$ were curated by infrared thermometry, along with meteorological instruments, including a thermometer, a pyranometer, and an anemometer. Linear regression analysis and Student's t-test were performed to evaluate the performance of the model and significance of the parameters. The correlation coefficient between observed $T_{LEAF}$ and calculated $T_{BGT}$ obtained using an equation, developed to predict $T_{LEAF}$ based on $T_{BGT}$ was very high ($r^2=0.9500$, p < 0.0001). There was a positive relationship between $T_{BGT}$ and solar radiation ($r^2=0.8556$, p < 0.0001), but a negative relationship between $T_{BGT}$ and wind speed ($r^2=0.9707$, p < 0.0001). These results imply that heat exchange in leaves seems to be mainly controlled by solar radiation and wind speed. The correlation coefficient between actual and estimated $T_{BGT}$ was 0.9710 (p < 0.0001). Conclusions: The developed model can be used to accurately estimate the $T_{Leaf}$ of Cnidium officinale Makino and has the potential to become a practical alternative to assessing cold and heat stress.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2000.01a
• /
• pp.63-64
• /
• 2000

The low-temperature Si oxidation kinetics by inductively coupled oxygen plasma has been studied. Linear rate constants had negative values when the oxide growth rate was described by linear-parabolic growth law. The analysis of transverse-optical mode frequencies and etch rates indicated that the density of surface oxide was lower than that of bulk oxide. The oxidation kinetics could be explained qualitatively by assuming a surface layer with larger diffusion coefficient and a bulk layer with smaller diffusion coefficient.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.387-390
• /
• 1999

Electron swarm parameterdthe drift velocity and longitudinal diffusion coefficienthn $SiH_4-Ar$ mixtures containing 0.5% and 5% monosilane were measured using over the range of E/N from 0.01 to 300 Td at room temperature. Electron swarm parameters in argon were drastically changed by adding a small amount of monosilane. The electron drift velocity in both mixtures showed unusual behaviour against E/N. It had negative slope in the medium range of E/N, yet the slope was not smooth but contained a small hump. The longitudinal diffusion coefficient also showed a corresponding feature in its dependence on E/N. A two-tern approximation of the Boltzmann equation analysis and Monte Carlo simulation have been used to study electron transport coefficients.

• Nuclear Engineering and Technology
• /
• v.53 no.7
• /
• pp.2133-2150
• /
• 2021

In this work, Esfahan light water subcritical reactor (ELWSCR) is analysed using experimental and theoretical diagnostic methods. Important neutronic parameters of the system such as prompt neutron lifetime, delayed neutron fraction, prompt neutron decay constant, negative reactivity of the core, fuel and moderator temperature coefficient of reactivity, and overall and local void coefficient of reactivity are estimated. Also, neutron flux distribution, reflector saving, water level effect, and lattice pitch of the core including operating point of the facility are studied in details. Theoretical results are calculated by MCNPX and measurements are performed utilizing zero power reactor noise method. Detailed descriptions of the results are explained in the text.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.12
• /
• pp.8306-8313
• /
• 2015

Open-type current sensors have been commonly used for DC motor controller, AC variable controller and Uninterruptible Power Supply. Recently they have begun to be used more widely, as the growth of renewable energy and smart-grid in power system. Considering most of the open-type current sensors are imported, developing the core technology needed to produce open-type current sensors is required. This paper describes the development and test results of open-type current sensors. Design of C type magnetic core, selection and test of a Hall sensor, design of current source circuit and signal conditioning circuit are described. 100A class DIP(Dual In-line Package) type and SMD(Surface Mount Devide) type open-type current sensors was made and tested. Test results show that the developed open-type current sensor satisfies the accuracy requirement of 2% and linearity requirement of 2% at 100 A of DC and AC current of 60Hz. Temperature compensation was carried out by using a temperature compensation circuit with NTC(Negative Temperature Coefficient) thermistor and the effect of the temperature compensation are described.

• Clean Technology
• /
• v.25 no.3
• /
• pp.238-244
• /
• 2019

In this study, the ignition characteristics of petroleum-based aviation fuel (Jet A-1), bio aviation fuel (Bio-6308), and blended aviation fuel (50:50, v:v) were analyzed in accordance with change of temperature and pressure. The ignition delay time of each aviation fuel was measured by combustion research unit (CRU) and the compositions of the fuels were analyzed by GC/MS and GC/FID for qualitative and quantitative results. From the results, it was confirmed that the ignition delay times of all aviation fuels were shortened with increasing temperature and pressure. In particular, the effect of temperature was larger than the effect of pressure. Also, the ignition delay time of Jet A-1 was the longest at all measurement conditions, and it was judged that this result is because of the structurally stable characteristics of the benzyl radical generated during the oxidation reaction of the aromatic compound (about 22.48%) in Jet A-1. Also, it was confirmed that Jet A-1 had no section where the degree of shortening of ignition delay time was decreased by increasing temperature, which was because the benzyl radical inhibits the response that can affect the negative temperature coefficient (NTC). The ignition characteristics of blended aviation fuel (50:50, v:v) showed a similar tendency to those of Jet A-1, rather than to those of Bio-6308, so that the blended aviation fuel (50:50, v:v) can be applied to the existing system without any change.

• Korean Journal of Materials Research
• /
• v.21 no.4
• /
• pp.192-195
• /
• 2011

The electro-deposition of compound semiconductors has been attracting more attention because of its ability to rapidly deposit nanostructured materials and thin films with controlled morphology, dimensions, and crystallinity in a costeffective manner (1). In particular, low band-gap $A_2B_3$-type chalcogenides, such as $Sb_2Te_3$ and $Bi_2Te_3$, have been extensively studied because of their potential applications in thermoelectric power generator and cooler and phase change memory. Thermoelectric $Sb_xTe_y$ films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containing different ratios of $TeO_2$ to $Sb_2O_3$. The stoichiometric $Sb_xTe_y$ films were obtained at an applied voltage of -0.15V vs. SCE using a solution consisting of 2.4 mM $TeO_2$, 0.8 mM $Sb_2O_3$, 33 mM tartaric acid, and 1M $HNO_3$. The stoichiometric $Sb_xTe_y$ films had the rhombohedral structure with a preferred orientation along the [015] direction. The films featured hole concentration and mobility of $5.8{\times}10^{18}/cm^3$ and $54.8\;cm^2/V{\cdot}s$, respectively. More negative applied potential yielded more Sb content in the deposited $Sb_xTe_y$ films. In addition, the hole concentration and mobility decreased with more negative deposition potential and finally showed insulating property, possibly due to more defect formation. The Seebeck coefficient of as-deposited $Sb_2Te_3$ thin film deposited at -0.15V vs. SCE at room temperature was approximately 118 ${\mu}V/K$ at room temperature, which is similar to bulk counterparts.

• Proceedings of the KIEE Conference
• /
• 1999.07d
• /
• pp.1855-1857
• /
• 1999

$Mn_{1-x}Fe_{2+x}O_4$, $Mg_{1-x}Fe_{2+x}O_4$ (x=0.0, 0.025, 0.1, 0.2) for negative temperature coefficient (NTC) thermistor were prepared by calcining at $800^{\circ}C$ and sintering from 1100 to $1250^{\circ}C$ with $50^{\circ}C$ intervals. The best linear property was obtained in the Mn-based sample sintered at $1200^{\circ}C$ with x=0.0 composition. Temperature coefficient of resistance, $\alpha$, was -3.0 %/$^{\circ}C$ in the Mg-based sample at $25^{\circ}C$. Thermistor parameter, B, was in the range of 2500 [K] $\sim$7400 [K]. The results show the possibility that Mn-Ni-Co based thermistor could be substituted by the composition used in this study.

• Journal of the Korean Ceramic Society
• /
• v.30 no.5
• /
• pp.381-388
• /
• 1993

Due to the anisotropy of thermal expansion, LAS system which has low thermal expansion property is hard to obtain a dense sintered body. Therefore, the thermal expansion coefficient and the mechanical strength were decreased. In this study, mullite, which has good mechanical properties in high temperature and comparatively low thmeral expansion coefficient, was taken as a additive in LAS system. And then, sintering, thermal, and mechanical properties were investigated. The results are follows; When mullite is added in eucryptite composition (Li2O.Al2O3.2SiO2) of LAS system, the creation of liquid phase results in the densification of sintered body and the specimen sintered at 136$0^{\circ}C$ for 2 hours shows optimum sintering condition. With the addition of mullite in eucryptite composition, mechanical strength is increased by the control of grain growth. Especially, flexual strength of EM0 specimen was about double value than the basic composition. Thermal expansion coefficients of EM0 and EM15 specimens sintered at 136$0^{\circ}C$ were -8.23$\times$10-6/$^{\circ}C$ and -4.90$\times$10-6/$^{\circ}C$ in the temperature range of RT.~80$0^{\circ}C$. As the mullite content are increased, negative thermal expansion ratios are decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.662-665
• /
• 2002

The microwave dielectric properties and the microstructures of $Tm_2O_3$-modified $BiNbO_4$ ceramics were investigated. $Bi_{(1-x)}Tm_xNbO_4$ ceramics combined with orthorhombic and triclinic phases were identified at sintering temperatures of $920{\sim}960^{\circ}C$. The apparent density decreased slightly with the increasing Tm content. Regardless of the Tm content the dielectric constant $(\varepsilon_r)$ of all compositions except x=0.1 in $Bi_{(1-x)}Tm_xNbO_4$ ceramics saturated at the range of 42~44. The $Q{\times}f_0$ values of 6,000-12,000(GHz) were obtained for all compositions when the sintering temperatures were in the range of $920{\sim}960^{\circ}C$. The temperature coefficient of the resonant frequency$(\tau_f)$ can be also adjusted with increasing the amount of the doped Tm from a positive value of $+15ppm/^{\circ}C$ to a negative value of $-20ppm/^{\circ}C$. The $Bi_{(1-x)}Tm_xNbO_4$ ceramics can be possibly applied to multilayer microwave devices with low processing temperatures.