• 한국의학물리학회지:의학물리
• /
• 제4권2호
• /
• pp.49-58
• /
• 1993

열자극 과정의 수치해석적인 방법을 이용하여 열자극 세기곡선의 kinetic order, 활성화 에너지, 이탈 진동수 그리고 초기 트랩 밀도를 구하기 위하여 혼합된 열자극 세기곡선으로 분해하였고, 비선형 최소 자승법으로 분해된 열자극 곡선 세기와 측정된 세기의 차이를 최소화시켰다. 감마선 선량계로 사용되고 있는 $\alpha$-Al$_2$ $O_3$ 에감마선을 조사시킨 후 ,300K～600K의 온도 구간에서 측정된 $\alpha$-Al$_2$ $O_3$의 열자극 발광 세기곡선은 정점 온도가 381K, 415K, 441K, 460K, 488K 그리고 506K인 6개의 독립된 열자극 발광세기곡선으로 분해되었으며, 381K의 정점온도를 갖는 분해된 열자극 발광 세기곡선의 kinetic order, 활성화 에너지 그리고 이탈 진동수는 각각 1, 1.12eV 그리고 6.79X$10^{12}$sec$^{-1}$로써, 이 결과는 다른 측정법에 의한 값과 유사하였다.

• Structural Engineering and Mechanics
• /
• 제39권6호
• /
• pp.861-875
• /
• 2011

The aim of the present article is to study the micropolar thermoelastic interactions in an infinite Kelvin-Voigt type viscoelastic thermally conducting plate. The coupled dynamic thermoelasticity and generalized theories of thermoelasticity, namely, Lord and Shulman's and Green and Lindsay's are employed by assuming the mechanical behaviour as dynamic to study the problem. The model has been simplified by using Helmholtz decomposition technique and the resulting equations have been solved by using variable separable method to obtain the secular equations in isolated mathematical conditions for homogeneous isotropic micropolar thermo-viscoelastic plate for symmetric and skew-symmetric wave modes. The dispersion curves, attenuation coefficients, amplitudes of stresses and temperature distribution for symmetric and skew-symmetric modes are computed numerically and presented graphically for a magnesium crystal.

• Structural Engineering and Mechanics
• /
• 제14권3호
• /
• pp.365-380
• /
• 2002

Following a series of experiments on isolated low-rise RC shear walls with openings, a theoretical study on the backbone curve of a perforated shear wall shows that there are some important observations from experimental results that make clear a semi-empirical formula of the backbone curve of a perforated wall. Critical shear zones can be depicted from the configuration of shear walls with openings. Different factors, including the size and location of shear wall openings, the wall's height/width ratio, horizontal and vertical steel bar ratios, and location and amount of diagonal steel bars are involved in the derivation of the backbone curve. Bending and shear effects are also considered in the paper. In addition, a comparison of load and displacement for solid and perforated shear walls is discussed. Generally, the comparison between experimental curves and computed backbone curves is favorable.

• 미생물학회지
• /
• 제10권1호
• /
• pp.1-8
• /
• 1972

This experiment was carried out to investigate the physiological characteristics of isolated bacteria, Ferrobacillus ferooxidans from copper mine water in Korea. The results obtained were as follows ; 1. The optimum pH range for the growth of these bacteria was 2.0-3.0 and optimum temperature was $20^{\circ}C$-$30^{\circ}C$. 2. The oxidation curves of ferrous iron to the ferric iron ran parallel with the growth curves. 3. The optimum nitrogen concentration was 400-800 ppm and the minimal flow rate of air for the maximal growth of the bactria was 70 ml air/min./200ml medium. 4. The growth of these bacteria was inhibited by the absence of ferrous iron and by the addition of sulfur. 5. Ferrous iron at a concentration of 9000 ppm, appeared to be optimum for the most rapid growth of Ferrobacillus ferrooxidans.

• 생약학회지
• /
• 제51권2호
• /
• pp.139-145
• /
• 2020

The leaves of Diospyros kaki Thunb. were used to treat heart disease and hypotension in traditionally East Asia. The purpose of this study is to simultaneously quantitiative analyze the content of flavonoids in leaves of D. kaki. The isolated flavonoids from the leaves of D. kaki, and the structure of the isolated flavonoids were analyzed based on ¹H and ¹³C NMR spectrum compared to literature data. Simultaneous quantitative analysis of the isolated flavonoids was validated using high performance liquid chromatography (HPLC). Results showed that the calibration curves of the flavonoid compounds were confirmed that they have a large linearity with a correlation coefficient (R²) of 0.99. In the intra-day and inter-day analysis, accuracy and precision of five compounds were measured that accuracy was 94.39 to 114.47% and precision was less than 3.00%. Content analysis showed hyperoside (1.30 ± 0.09%), astragalin (0.81 ± 0.06%), trifoline (1.58 ± 0.07%), quercetin (0.13 ± 0.02%) and kaempferol (1.33 ± 0.25%).

• 한국세라믹학회지
• /
• 제41권1호
• /
• pp.19-23
• /
• 2004

The Hertzian indentation contact damage behavior of porous alumina with controlled pore shape was investigated by experiments. Porous alumina ceramics containing well-defined pore shape, size and distribution were prepared by incorporation of fugitive spherical starch. Porous alumina with isolated pore structure was prepared with porosity range up to 30%. The indentation stress-strain curves of porous alumina were constructed. Elastic modulus and yield stress can be obtained from the stress-strain relationship. Impulse excitation method for the measurement of elastic modulus was also conducted as well as Hertzian indentation and was confirmed as a useful tool to evaluate the elasticity of highly porous ceramics. Elastic modulus of the inter-connected pore structure is more sensitive to porosity than that of the isolated pore structure. When the specimen had isolated pore structure, higher yield point was obtained than it had inter-connected pore structure. This study proposed that the elastic modiulus of porous ceramics is strongly related to not only porosity, but also the structure of pore.

• Smart Structures and Systems
• /
• 제23권3호
• /
• pp.227-242
• /
• 2019

Seismic isolation systems employ structural control that protect both buildings and vibration-sensitive contents from destructive effects of earthquakes. Structural control is divided into three main groups: passive, active, and semi-active. Among them, semi-active isolation systems, which can reduce floor displacements and accelerations concurrently, has gained importance in recent years since they don't require large power or pose stability problems like active ones. However, their seismic performance may vary depending on the variations that may be observed in the mechanical properties of semi-active devices and/or seismic isolators. Uncertainties relating to isolators can arise from variations in geometry, boundary conditions, material behavior, or temperature, or aging whereas those relating to semi-active control devices can be due to thermal changes, inefficiencies in calibrations, manufacturing errors, etc. For a more realistic evaluation of the seismic behavior of semi-active isolated buildings, such uncertainties must be taken into account. Here, the probabilistic behavior of semi-active isolated buildings under historical pulse-like near-fault earthquakes is evaluated in terms of their performance in preserving structural integrity and protecting vibration-sensitive contents considering aforementioned uncertainties via Monte-Carlo simulations of 3-story and 9-story semi-active isolated benchmark buildings. The results are presented in the form of fragility curves and probability of failure profiles.

• 한국지진공학회논문집
• /
• 제19권5호
• /
• pp.207-217
• /
• 2015

In order to increase seismic performance of nuclear power plant (NPP) in strong seismic zone, lead-rubber bearing (LRB) can be applied to seismic isolation system of NPP structures. Simple equivalent linear model as structural analysis model of LRB is more widely used in initial design process of LRB than a bilinear model. Seismic responses for seismically isolated NPP containment structures subjected to earthquakes categorized into 5 different soil-site classes are calculated by both of the equivalent linear- and bilinear- LRB models and compared each others. It can be observed that the maximum displacements of LRB and shear forces of containment in the case of the equivalent linear LRB model are larger than those in the case of bilinear LRB model. From the seismic fragility curves of NPP containment structures isolated by LRB, it can be observed that seismic fragility in the case of equivalent linear LRB model are about 5~30 % larger than those in the case of bilinear LRB model.

• Nuclear Engineering and Technology
• /
• 제46권5호
• /
• pp.699-706
• /
• 2014

The probabilistic seismic performance of a standard Korean nuclear power plant (NPP) with an idealized isolation is investigated in the present work. A probabilistic seismic hazard analysis (PSHA) of the Wolsong site on the Korean peninsula is performed by considering peak ground acceleration (PGA) as an earthquake intensity measure. A procedure is reported on the categorization and selection of two sets of ground motions of the Tohoku earthquake, i.e. long-period and common as Set A and Set B respectively, for the nonlinear time history response analysis of the base-isolated NPP. Limit state values as multiples of the displacement responses of the NPP base isolation are considered for the fragility estimation. The seismic risk of the NPP is further assessed by incorporation of the rate of frequency exceedance and conditional failure probability curves. Furthermore, this framework attempts to show the unacceptable performance of the isolated NPP in terms of the probabilistic distribution and annual probability of limit states. The comparative results for long and common ground motions are discussed to contribute to the future safety of nuclear facilities against drastic events like Tohoku.

• Journal of Microbiology and Biotechnology
• /
• 제32권8호
• /
• pp.976-981
• /
• 2022

Phenanthrenes are bioactive phenolic compounds found in genus Dioscorea, in which they are distributed more in peel than in flesh. Recent studies on phenanthrenes from Dioscorea sp. peels have revealed the potential for valuable biomaterials. Herein, an analytical method using high-performance liquid chromatography (HPLC) for quantitation of bioactive phenanthrenes was developed and validated. The calibration curves were obtained using the phenanthrenes (1-3) previously isolated from Dioscorea batatas concentrations in the range of 0.625-20.00 ㎍/ml with a satisfactory coefficient of determination (R²) of 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) values of the isolated phenanthrenes ranged from 0.78-0.89 and 2.38-2.71 ㎍/ml, respectively. The intraday and interday precision ranged from 0.25-7.58%. The recoveries of the isolated phenanthrenes were from 95 to 100% at concentrations of 1.25, 2.5, and 5.0 ㎍/ml. Additionally, phenanthrenes (1-3) were found in all investigated peel extracts. Hence, the developed method was encouraging for the quantitative analysis of phenanthrenes in genus Dioscorea.