• 한국토양비료학회지
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• 제43권4호
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• pp.415-423
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• 2010

포어 네트웍 모델들 (Pore network model)은 토양 공극의 구조를 조사할 때 유용한 도구들이다. 이런 모델들은 삼차원 이미지들에서 공극의 구조와 관련된 양적 정보를 제공한다. 이 연구는 포어 네트웍 모델을 이용하여 공극의 구조와 수리학적 특성들을 양적으로 측정하였다. 연구목표는 큰 크기의 이미지에서 공극의 구조에 관한 양적 정보를얻기 위해 포어 네트웍 모델을 적용하고, 토양수분특성과 수리 전도도를 삼차원 이미지로부터 계산하고 이 값들은 실험을 통해 얻어진 실험값들과 결합하여 토양의 수리적 특성을 분석하는 것이었다. 토양 시료들은 발티모아 도시 중심에 있는발티모어 과학센터에 위치한 실험부지에서 채취되었다. 불교란 원주형 시료들이 채취되었고, 22 ${\mu}m$ 의 해상도로 x선 단층 촬영되었다. 포어 네트웍은 중심축 변형에 의해 공극에서 축출되었고 이를 바탕으로 공극 구조가 계산되었다. 토양수분특성과 불포화 수리 전도도 값들은 토양 이미지에서 계산 되었다. 토양 밀도, 토양수분특성과 불포화 수리 전도도들은 3 토양 시료들로부터 실험을 통해 구하였다. 삼차원 이미지 분석은 토양 공극의 특성들을, 예를 들어 공극 부피, 길이, 굴곡도, 가장 정확히 분석하였다. 이런 정확한 분석은 토양 내 수문학적 정보를 정확히 산출할 수 있게 하였다. 계산된 값과 실험을 통한 실험치의 결합은 공극에 대한 더 광범한 범위를 분석할 수 있게 하였다. 이 연구를 통해 이미지에서 계산되고 측정된 수문학적 자료들은 토양 내대기공과 소기공을 모두 다 설명해 줄 수 있는 방법이라는 것이 밝혀졌다.

• Restorative Dentistry and Endodontics
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• 제29권1호
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• pp.66-72
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• 2004

All-in-one adhesives were recently developed for reducing the technique sensitivity and chair time, but lots of concerns were made on bondability, longevity, and microleakage. The object of this study was to evaluate microleakage and marginal quality of all-in-one adhesives using electrochemical method and SEM analysis quantitatively. After making Class V cavities, they were bulk filled with Heliomolar(#A1 after surface treatment with three adhesives: Adper Prompt (Group A), One up bond F (Group O), Xeno III (Group X) Electrical conductivity (microamphere, ${\mu}A$) was checked two times: before and after cavity filling. Percentage of leaky margin was estimated from SEM image (${\times}1,000$). The data were statistically analysed: ANOVA and Paired T test for electrical conductivity, Kruskal-Wallis and Mann-Whitney test for marginal quality, Spearman s rho test for checking of relationships between 2 methods. The result were as follows: 1. There was no difference in microleakage between adhesive systems and every specimen showed some of microleakage after filling. 2. Microleakage was reduced about 70% with composite resin filling. 3. Marginal quality was the best in group A. decreasing among groups in the following order: group O, followed by group X. There were significant differences between group A and group X (p=0.015), and between group 0 and group X (p=0.019). 4. There was no relationship between the microleakage measured by electrochemical method and marginal quality measured by SEM analysis. Within the results of this study, there was no difference in microleakage among groups by electrical conductivity. However, significant difference in marginal quality was seen among groups. It was believed that these dissimilar results might be induced because of their own characteristics. Analysis of microleakage needs various methods for accuracy.

• 한국환경농학회:학술대회논문집
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• 한국환경농학회 2011년도 30주년 정기총회 및 국제심포지엄
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• pp.207-222
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• 2011

Relationships between soil saturated hydraulic conductivity ($K_s$) and porosity (${\phi}$) have been developed over many years; however, use of these relationships for evaluating rain-induced seals is limited mainly because of difficulties in estimating seal pore-size characteristics. The objectives of this study were to evaluate the $K_s$ of soil surface seals over a range of thicknesses, where seal thickness was determined using a High-Resolution-Computed-Tomography (HRCT) scanner, and to investigate relationships between $K_s$ and ${\phi}$ of developing seals in samples with equivalent diameters (e.d.) ${\geq}15\;{\mu}m$. A Mexico silt loam soil was packed to a bulk density (${\rho}_b$) of $1.1\;Mg\;m^{-3}$ in cylinders 160-mm i.d. by 160-mm long and subjected to $61-mm\;h^{-1}$ simulated rainfall having a kinetic energy (KE) of $25\;J\;m^{-2}\;min^{-1}$ for 7.5, 15, 30, and 60 min to create a range in seal development. Thicknesses of the seal layers were determined by analysis of HRCT images of seals. The $K_s$ values of the seals were estimated using an effective $K_s$ value ($K_{s-eff}$). The $K_s-{\phi}$ relationship was described by a Kozeny and Carmen equation, $K_s=B{\phi}^n$; where B and n are empirical constants and n = 31. This approach explained 86% of the variation between $K_s$ and ${\phi}$ within the soil seals. Knowledge of surface seal information and hydraulic conductivity can provide useful information to use in management of sites prone to sealing formation.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권1호
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• pp.44-50
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• 2005

In the present study, the characteristics of upward bubble flow were experimentally investigated in a liquid bath. An electro-conductivity probe was used to measure local volume fraction and bubble frequency. Since the gas was concentrated at the near the nozzle, the flow parameters were high near the nozzle. In general their axial and radial values tended to decrease with increasing distance. For visualization of flow characteristics, a Particle Image Velocimetry (PIV) and a thermo-vision camera were used in the present study. The experimental results showed that heat transfer from bubble surface to water was largely completed within z = 10 mm from the nozzle, and then the temperature of bubble surface reached that of water rapidly. Due to the centrifugal force, the flow was more developed near the wall than at bubble-water plume. Vortex flow in the bottom region was relatively weaker than that in the upper region.

• Computers and Concrete
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• 제18권3호
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• pp.319-336
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• 2016

In this study, both two- and three-dimensional (2D and 3D) finite-volume-based models were developed to analyze the heat transfer mechanisms through the porous structures of cellular concretes under steady-state heat transfer conditions and to investigate the differences between the 2D and 3D modeling results. The 2D and 3D reconstructed pore networks were generated from the microstructural information measured by 3D images captured by X-ray computerized tomography (X-CT). The computed effective thermal conductivities based on the 2D and 3D calculations performed on the reconstructed porous structures were found to be nearly identical to those evaluated from the 2D cross-sectional images and the 3D X-CT images, respectively. In addition, the 3D computed effective thermal conductivity was found to agree better with the measured values, in comparison with the 2D reconstruction and real cross-sectional images. Finally, the thermal conductivities computed for different reconstructed porous 3D structures of cellular concretes were compared with those obtained from 2D computations performed on 2D reconstructed structures. This comparison revealed the differences between 2D and 3D image-based modeling. A correlation was thus derived between the results of the 3D and 2D models.

• Nuclear Engineering and Technology
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• 제46권1호
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• pp.109-116
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• 2014

An electrical resistance tomography (ERT) technique combining the particle swarm optimization (PSO) algorithm with the Gauss-Newton method is applied to the visualization of two-phase flows. In the ERT, the electrical conductivity distribution, namely the conductivity values of pixels (numerical meshes) comprising the domain in the context of a numerical image reconstruction algorithm, is estimated with the known injected currents through the electrodes attached on the domain boundary and the measured potentials on those electrodes. In spite of many favorable characteristics of ERT such as no radiation, low cost, and high temporal resolution compared to other tomography techniques, one of the major drawbacks of ERT is low spatial resolution due to the inherent ill-posedness of conventional image reconstruction algorithms. In fact, the number of known data is much less than that of the unknowns (meshes). Recalling that binary mixtures like two-phase flows consist of only two substances with distinct electrical conductivities, this work adopts the PSO algorithm for mesh grouping to reduce the number of unknowns. In order to verify the enhanced performance of the proposed method, several numerical tests are performed. The comparison between the proposed algorithm and conventional Gauss-Newton method shows significant improvements in the quality of reconstructed images.

• 한국세라믹학회지
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• 제37권5호
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• pp.479-490
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• 2000

The microstructure of Ni-YSZ composite as an anode of SOFC was investigated as a function of Ni content(10-70 vol%) in order to examine the correlation between microstructural-and electrical property. Image analysis based on quantitative microscopy theory was performed to quantify the microstructural property. We could get the informations about the size and distribution, contiguity and interfacial area of each phase or between the phases from the image analysis. According to the image analysis, contiguity between the same phae was mainly dependent on the amount of the phase while the contiguity between different phases was additionally influenced by the microstructural changes, especailly by the coarsening of the Ni phase. The whole length of pores perimeter was increased as Ni content increased, which indicated the overall microstructural evolution was mostly related with the coarsening of Ni phase. Ni-Ni interfacial area was also gradually increased as Ni content increased but controlled by pore phase at low Ni content region and by YSZ phase at intermediate Ni content region. These quantified microstructural properties were used to characterize the electrical properties of Ni-YSZ composite.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.327-330
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• 2000

The scanning Maxwell-stress microscopy (SMM) is a dynamic noncontact electric force microscopy that allows simultaneous access to the electrical properties of molecular system such as surface potential, surface charge, dielectric constant and conductivity along with the topography. The Scanning near-field optical / atomic force microscopy (SNOAM) is a new tool for surface imaging which was introduced as one application of the atomic force microscope (AFM). Operated with non-contact forces between the optical fiber and sample as well as equipped with the piezoscanners, the instrument reports on surface topology without damaging or modifying the surface for measuring of optical characteristic in the films. We report our recent results of its application to nanoscopic study of domain structures and electrical functionality in organic thin films by SMM. Furthermore, we have illustrated the SNOAM image in obtaining the merocyanine dye films as well as the optical image.

• 한국표면공학회지
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• 제55권6호
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• pp.398-402
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• 2022

Vacuum Insulation Panel (VIP) is an high energy efficient insulation system that facilitate slim but high insulation performance, based on based on a porous core material evacuated and encapsulated in a multi-barrier envelope. Although VIP has been on the market for decades now, it wasn't until recently that efforts have been initiated to propose a standard on aging testing. One of the issues regarding VIP is its durability and aging due to pressure and moisture dependent increase of the initial low thermal conductivity with time. It is hard to visually determine at an early stage. Recently, a method of analyzing the damage on the a material surface by applying image processing technology has been widely used. These techniques provide fast and accurate data with a non-destructive way. In this study, the surface VIP images were analyzed using the Harris corner detection algorithm. As a result, 171,333 corner points in the normal packaging were detected, whereas 32,895 of the defective packaging, which were less than the normal packaging. were detected. These results are considered to provide meaningful information for the determination of VIP condition.

• 농업과학연구
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• 제39권3호
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• pp.407-412
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• 2012

Soil texture has an important influence on agriculture such as crop selection, movement of nutrient and water, soil electrical conductivity, and crop growth. Conventionally, soil texture has been determined in the laboratory using pipette and hydrometer methods requiring significant amount of time, labor, and cost. Recently, in-situ soil texture classification systems using optical diffuse reflectometry or mechanical resistance have been reported, especially for precision agriculture that needs more data than conventional agriculture. This paper is a part of overall research to develop an in-situ soil texture classification system using image processing. Issues investigated in this study were effects of sensor travel speed and light source and intensity on image quality. When travel speed of image sensor increased from 0 to 10 mm/s, travel distance and number of pixel were increased to 3.30 mm and 9.4, respectively. This travel distances were not negligible even at a speed of 2 mm/s (i.e., 0.66 mm and 1.4), and image degradation was significant. Tests for effects of illumination intensity showed that 7 to 11 Lux seemed a good condition minimizing shade and reflection. When soil water content increased, illumination intensity should be greater to compensate decrease in brightness. Results of the paper would be useful for construction, test, and application of the sensor.