• 한국환경복원기술학회지
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• 제19권2호
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• pp.83-93
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• 2016

This study purposed to examine the water retention capacity of floor litter in deciduous forests. Water holding capacity(WHC) and interception storage capacity of Alnus hirsuta Turcz. ex Rupr., Quercus acutissima, Quercus mongolica litters were experimentally estimated. Physical characteristics of litters were also obtained to understand the relationships between water-retention capacity and litter characteristics. Experiments showed that WHC increases with specific volume of litter, varying 244.4% to 416.8% of its dry mass. Interception storage have estimated with rainfall simulation experiments. Maximum interception storage ($C_{max}$) and minimum interception storage ($C_{min}$) of litters were 220% and 138% of dry mass in Alnus hirsuta Turcz. ex Rupr., 218% and 137% in Quercus acutissima, and 240% and 156% in Quercus mongolica. Both $C_{max}$ and $C_{min}$ increased linearly with litter mass, and the values of $C_{min}$ in broadleaf litters have also linear relation to leaf area.

• 분석과학
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• 제32권6호
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• pp.225-232
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• 2019

Traceability establishment in chemical measurements is a like a linkage established through an unbroken chain from the measured results to the international system (SI) of units. The primary process for traceability establishment is the purity assignment of a target material to be measured. In this study, we studied the purity assignment of 17α-hydroxyprogesterone (17-OHP). The presence of 17-OHP is indicative of congenital adrenal hyperplasia (CAH) and it builds up due to the deficiency of 21-hydroxylase and 11β-hydroxylase enzyme in the human blood. The purity assignment of 17-OHP was performed by the mass balance method, in which the impurities are categorized into four classes: total related structural impurities, water, residual organic solvents, and nonvolatiles/inorganics. The total related structural impurities were characterized by HPLC-UV; water content was determined by Karl-Fisher coulometer; and the total residual solvents and nonvolatiles/inorganics were determined by TGA. The purity of 17-OHP from a commercial manufacturer was calculated as 993.30 mg/g, and the expanded uncertainty was 0.58 mg/g. The proposed method was validated by uncertainty evaluation and comparing with the actual value of purity.

• Journal of Microbiology and Biotechnology
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• 제26권7호
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• pp.1216-1223
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• 2016

The aim of this study was to isolate antioxidant peptides from an enzymatic hydrolysate of Spirulina platensis. A novel antioxidant peptide was obtained by ultrafiltration, gel filtration chromatography, and reverse-phase high-performance liquid chromatography, with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay used to measure the antioxidant activity, and the sequence was determined to be Pro-Asn-Asn (343.15 Da) by electrospray ionization tandem mass spectrometry. This peptide was synthesized to confirm its antioxidant properties, and it exhibited 81.44 ± 0.43% DPPH scavenging activity at 100 μg/ml, which was similar to that of glutathione (82.63 ± 0.56%). Furthermore, the superoxide anion and hydroxyl free-radical scavenging activities and the SOD activity of the peptide were 47.84 ± 0.49%, 54.01 ± 0.82%, and 12.55 ± 0.75%, respectively, at 10 mg/ml. These results indicate that S. platensis is a good source of antioxidant peptides, and that its hydrolysate may have important applications in the pharmaceutical and food industries.

• International Journal of Contents
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• 제4권2호
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• pp.7-12
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• 2008

In this paper, we present a real-time physical simulation model of water surfaces with a novel method to represent the water mass flow in full three dimensions. In a physical simulation model, the state of the water surfaces is represented by a set of physical values, including height, velocity, and the gradient. The evolution of the velocity field in previous works is handled by a velocity solver based on the Navier-Stokes equations, which occurs as a result of the unevenness of the velocity propagation. In this paper, we integrate the principle of the mass conservation in a fluid of equilateral density to upgrade the height field from the unevenness, which in mathematical terms can be represented by the divergence operator. Thus the model generates waves induced by horizontal velocity, offering a simulation that puts forces added in all direction into account when calculating the values for height and velocity for the next frame. Other effects such as reflection off the boundaries, and interactions with floating objects are involved in our method. The implementation of our method demonstrates to run with fast speed scalable to real-time rates even for large simulation domains. Therefore, our model is appropriate for a real-time and large scale water surface simulation into which the animator wishes to visualize the global fluid flow as a main emphasis.

• 대한화학회지
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• 제57권4호
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• pp.507-514
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• 2013

이 연구에서는 시각장애를 가진 초등학생의 용해 개념 특성을 조사하였다. 서울시 소재 시각장애 초등학교 5학년 학생 4명(3명은 전맹, 1명은 저시력)을 대상으로 용해 현상, 용액의 균일성, 용해 시 질량의 보존, 그리고 용해 시 부피의 변화에 대하여 반구조화된 인터뷰를 실시하였다. 모든 인터뷰 상황은 녹화되었고 그 자료를 전사한 뒤 분석하였다. 인터뷰를 분석한 결과, 시각장애 학생들은 용해 현상, 용해의 균일성, 용해 시 질량의 보존에 대해서는 잘 알고 있었지만, 용해 시 부피변화에 대해서는 제대로 설명하지 못하였다. 전반적으로는 같은 학년의 일반 학생과 비슷한 양상을 보였지만, 용해의 균일성에 대해서는 오히려 더 바르게 알고 있었다. 그러나 이들의 설명 수준은 현상적 경험에 기초한 피상적 수준에 불과했다. 일부 시각장애 학생은 입자 수준의 설명을 시도하기도 하였다. 이러한 결과에 기초하여 교육학적 함의를 논의하였다.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1700-1716
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• 1996

The two-dimensional, unsteady, laminar conservation equations for mass, momentum, energy and species transport in the gas phase and mass, momentum and energy in the liquid phase are solved simultaneously in spherical coordinates in order to study heating and vaporization of a droplet entrained in the oscillating flow. The numerical solution gives the velocity and temperature distribution in both gas and liquid phase as a function of time. When the gas flow oscillates around an vaporizing droplet, the liquid flow circulates in the clockwise or counterclockwise direction and the temperature distribution in the liquid phase changes its shapes, depending on the gas fow direction. When the gas flow changes its direction of circulating liquid flow is opposite to the gas flow, forming two vortex circulating in the opposite direction. During the heating period, the difference in the maximum and minimum temperature is large, followed by the almost uniform temperature slightly below the boiling temperature. The mass and heat transfer from the droplet depend on the droplet temperature, droplet diameter and the magnitude of relative velocity, giving the droplet lifetime different from the d$^{2}$-law.

• 보존과학회지
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• 제31권3호
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• pp.299-308
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• 2015

본 연구는 1996년 천안시 유량동에서 출토된 분홍색 단령의 염료 동정을 통해 조선시대에 사용된 적색 염료를 실증하기 위한 것이다. 이를 위해 유물에 사용된 염료를 추출하고 이것을 당시 염색에 사용되었을 것으로 추정되는 적색계 염료(홍화, 소목, 꼭두서니)에서 추출한 염료와 함께 고성능액체크로마토그래피분석을 실시하였다. 그 결과 유물에서 추출한 염료와 홍화염색포의 추출 염료는 같은 시간대인 17.5분에서 피크가 나타났다. 이때 자외/가시선 분광 분석 결과는 두 시료 모두 519nm에서 최대흡수파장이 나타나 기존 홍화의 홍색소 분석 결과와 같은 것으로 조사되었다. 또한 negative ion mode에서 질량분석을 실시한 결과 유물과 홍화 염색포에서 추출한 염료 시료는 carthamin의 분자량인 910을 나타내는 m/z 909에서 같은 시간대의 피크가 확인되었다. 이와 같은 결과로 이 분홍 단령 직물을 염색하는데 사용된 염재는 홍화인 것으로 동정되었다.

• Membrane and Water Treatment
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• 제7권4호
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• pp.297-311
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• 2016

Modeling and simulation of air humidification by hollow fiber membrane contactors are investigated in the current study. A computational fluid dynamic model was developed by solving the k-epsilon turbulence 2D Navier-Stokes equations as well as mass conservation equations for steady-state conditions in membrane contactors. Finite element method is used for the study of the air humidification under different operating conditions, with a focus on the humidity density, total mass transfer flux and velocity field. There has been good agreement between simulation results and experimental data obtained from literature. It is found that the enhancement of air stream decreases the outlet humidity from 0.392 to 0.340 (module 1) and from 0.467 to 0.337 (module 2). The results also indicated that there has been an increase in air velocity in the narrow space of shell side compared with air velocity wide space of shell side. Also, irregular arrangement has lower dead zones than regular arrangement which leads to higher water flux.

• 한국수소및신에너지학회논문집
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• 제24권5호
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• pp.401-412
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• 2013

The paper is to study on the simulation of the micro/macroscale thermo-electrochemical model of a single cell of anode-supported SOFC with direct internal reforming. The coupled heat and mass transport, electrochemical and reforming reactions, and fluid flow were simultaneously simulated based on mass, energy, charge conservation. The micro/macroscale model first calculates the detailed electrochemical and direct internal reforming processes in porous electrodes based on the comprehensive microscale model and then solve the macroscale processes such as heat and mass transport, and fluid flow in SOFCs with assumption of fully-developed flow in gas channel. The simulation results evaluate the overall performance by analyzing distributions of mole fraction, current density, temperature and microstructural design in co/counter flow configurations.

• 대한토목학회논문집
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• 제12권2호
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• pp.21-33
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• 1992

충격하중을 받는 구조물은 초고압에서 부터 저압까지 다양한 압력을 짧은 시간에 경험하게 된다. 따라서 이들 구조물을 해석하기 위해서는 실제 물체의 재료특성을 표현할 수 있는 구성 법칙(constitutive law)이 필요하게 된다. 본 연구에서는 압력 부종속모델(pressure independent model)인 Von-Mises 모델과 압력 종속모델(pressure dependent model)인 Drucker-Prager 모델을 사용하여 충격과 폭발 현상시 발생하는 응력파의 전파과정(propagation process)을 재료특성에 따라 비교 분석하였다. 응력파의 전파과정을 연구하기 위한 지배 방정식(governing equation)으로서는 물체에 종속되어 있는 라그란지안 좌표계(lagrangian coordinate system)로 표현된 운동량과 질량보존(conservation of momentum and mass)법칙을 사용하였으며 또한 충격전면(shock front)에 연속성을 부여하기 위해 인공점성(artificial viscosity)을 운동량 보존식에 첨가하였다. 주요 방정식을 풀기 위한 수치해석법으로는 시간과 공간 좌표계로 구성된 유한차분법(finite difference method)을 사용하였으며 소성변형률을 구하기 위한 소성이론으로서는 Associated normality flow rule을 사용하였다.