• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.4
• /
• pp.153-160
• /
• 2001

In order to analyze the degradation process of epoxy/glass fiber for outdoor condition, FRP laminate was exposed to high temperature. Then, the degradation process was evaluated by comparing contact angle, surface potential, surface resistivity, and XPS. The experimental results showed that the amount of weight loss, contact angle, surface potential and surface resistivity increased up to 200 $^{\circ}C$ as a function of temperature. These phenomena show the existence of hydrophobic surface. With the change to the hydrophobic surface and the electrical potential and resistivity on FRP surface increased. In XPS to analyze surface chemical structures, the increased hydrophobicity in thermal increase of unsaturated double bond in carbon chains. Aslo, thermal treatment caused the discoloration on the point of treated surface. These phenomena were attributed to the generations of ether group.

• Journal of the Korean institute of surface engineering
• /
• v.44 no.6
• /
• pp.264-268
• /
• 2011

The Molybedenium thin film is generally used on back contact material of CIGS solar cell due to low electrical resistivity and stable thermal expansion coefficient. The Mo thin films deposited on si wafer by the magnetron sputtering method. The research focused on the variation of electrical resistivity of films which deposited with various working pressure at the target power of 2.0 kW(8.4 W/). The lowest resistivity of Mo thin film showed $9.0{\mu}O$-cm at pressure of 1.5 mTorr. However, working pressure increasing up to 50 mTorr, resistivities were highly increased. The results showed that the conductivity of Mo films depended on growing structures and defects in deposition process. Surface morphology, porosity, grain size, oxidation, and bonding structures were analysed by SEM, AFM, spectroscopic ellipsometry (SE), XRD, and XPS.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.10a
• /
• pp.1318-1327
• /
• 2008

Geotechnical sites in urban areas may have embedded structures such as utility lines and underground concrete structures, which cause difficulties in site investigation. This study is a preliminary research to establish knowledge base for developing an optimal technique for site investigation in urban areas. Surface-wave method and resistivity survey, which are frequently adopted for non-destructive site-investigation for geotechnical sites, were investigated to characterize effects of adjacent structures. In case of surface wave method, patterns of wave propagation were investigated for typical sets of multi-layered geotechnical profiles by numerical simulation based on forward modeling theory and field experiments for small-size model tests and real-scale tests in the field. In case of resistivity survey, 3-D finite element analyses and field tests were performed to investigate effects of adjacent concrete structures. These theoretical and experimental researches for surface-wave method and resistivity survey resulted in establishing physical criteria to cause interference of adjacent structures in site investigation at urban areas.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1987-1989
• /
• 2000

In this paper, electric field distribution of dielectric sphere considering surface or volume resistivity is analysed by the use of rotational symmetric charge simulation method. We applied three methods such as ${\alpha},{\beta}$ modified $\beta$ method to check electric field calculation error. We find f method and modified $\beta$ method are suitable to simulate volume and surface resistivity respectively.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.241-244
• /
• 2007

Cement-grouts are injected into limestone cavities beneath the road in the project area, in order to improve strength and reduce permeability; the extent to which grout has penetrated in cavities need to be monitored in order to determined effectiveness of cement-grout. Geophysical approaches, offer great potential for monitoring the grout injection process in a fast and cost-effective way as well as showing whether the grout has successfully achieved the target. This paper presents the ability of surface electrical resistivity to investigate the verification of the grout placement. In order to image the cement-grout, time-lapse surface electrical resistivity surveys were conducted to compare electrical resistivity images before and after injection. Cement-grout was imaged as anomalies exhibiting low resistivity than the surrounding rocks. In accordance with field monitoring, laboratory study was also designed to monitor the resistivity changes of cement-grout specimens with time-lapse. Time-lapse laboratory measurements indicated that electrical methods are good tool to identify the grouted zone. Pre-and post grouting electrical images showed significant changes in subsurface resistivity at grouted zone. The study showed that electrical resistivity imaging technology can be a useful tool for detecting and evaluating changes in subsurface resistivity due to the injection of the grout.

• Carbon letters
• /
• v.16 no.2
• /
• pp.86-92
• /
• 2015

Multi-walled carbon nanotube (MWCNT)/polycarbonate (PC) nanocomposite was prepared by direct melt mixing to investigate the effect of the shear rate on the surface resistivity of the nanocomposites. In this study, an experiment was carried out to observe the shear induced orientation of the MWCNT in the polymer matrix using a very simple melt flow indexer with various loads. The compression-molded, should be eliminated. MWCNT/PC nanocomposite sample exhibited lower percolation thresholds (at 0.8 vol%) and higher electrical conductivity values than those of samples extruded by capillary and injection molding. Shear induced orientation of MWCNT was observed via scanning electron microscopy, in the direction of flow in a PC matrix during the extrusion process. The surface resistivity rose with increasing shear rate, because of the breakdown of the network junctions between MWCNTs. For real applications such as injection molding and the extrusion process, the amount of the MWCNT in the composite should be carefully selected to adjust the electrical conductivity.

• Geomechanics and Engineering
• /
• v.29 no.3
• /
• pp.301-310
• /
• 2022

Accurate prediction of mixed ground conditions ahead of a tunnel face is of vital importance for safe excavation using tunnel boring machines (TBMs). Previous studies have primarily focused on electrical resistivity surveys from the ground surface for geotechnical investigation. In this study, an FE (finite element) numerical model was developed to simulate electrical resistivity surveys for the prediction of risky mixed ground conditions in front of a tunnel face. The proposed FE model is validated by comparing with the apparent electrical resistivity values obtained from the analytical solution corresponding to a vertical fault on the ground surface (i.e., a simplified model). A series of parametric studies was performed with the FE model to analyze the effect of geological and sensor geometric conditions on the electrical resistivity survey. The parametric study revealed that the interface slope between two different ground formations affects the electrical resistivity measurements during TBM excavation. In addition, a large difference in electrical resistivity between two different ground formations represented the dramatic effect of the mixed ground conditions on the electrical resistivity values. The parametric studies of the electrode array showed that the proper selection of the electrode spacing and the location of the electrode array on the tunnel face of TBM is very important. Thus, it is concluded that the developed FE numerical model can successfully predict the presence of a mixed ground zone, which enables optimal management of potential risks.

• Korean Journal of Materials Research
• /
• v.23 no.6
• /
• pp.322-328
• /
• 2013

The relationship the between electrical properties and surface roughness (Ra) of a wet-etched silicon wafer were studied. Ra was measured by an alpha-step process and atomic force microscopy (AFM) while varying the measuring range $10{\times}10$, $40{\times}40$, and $1000{\times}1000{\mu}m$. The resistivity was measured by assessing the surface resistance using a four-point probe method. The relationship between the resistivity and Ra was explained in terms of the surface roughness. The minimum error value between the experimental and theoretical resistivities was 4.23% when the Ra was in a range of $10{\times}10{\mu}m$ according to AFM measurement. The maximum error value was 14.09% when the Ra was in a range of $40{\times}40{\mu}m$ according to AFM measurement. Thus, the resistivity could be estimated when the Ra was in a narrow range.

• Journal of the Korean institute of surface engineering
• /
• v.30 no.6
• /
• pp.374-381
• /
• 1997

We have studied the effect of the interface between tungsten silicide and polysilicon the silicide reaction. The results showed that the cleaning of the silicon surface prior to the deposition of tungsten silicide affected the interface properties, thereby leading to the difference in the resistivity and surface morhpology of tungsten silicide. Compared with HF cleaning, the use of SCl cleaning yielded higher resistivity of tungsten silicide at the low anneal temperature (up to $900^{\circ}C$). However, furtherature to $1000^{\circ}C$ reduced the resistivity significantly, similar to that obtained with HF cleaning. It was also observed that the annealing of WSix/HF-cleaned poly-si allowed the formation of bucking weve (partially decohesion area) on the surface. In contrast, the use of SCl celaning did not produce the buckling waves on the surface. Also the presence of 200$\AA$ -thick TiW between tungsten silicide and HF-cleaned poly-Si effectively prevented the formation of the waves. However, high-temperature annealing of WSix/200A-TiW/Poly-Si allowed the excess silicon in tungsten silicide to precipitate inside the silcide, causing the slight increase of the resistivity after annealing at $1050^{\circ}C$.

• Geophysics and Geophysical Exploration
• /
• v.13 no.4
• /
• pp.370-377
• /
• 2010

In this study, we investigated the current saturation which forces the apparent resistivity to converge when the conductivity contrast between the anomalous body and background medium is greater than a specific value. Analizing theoretical and numerical solutions for some simple models, we studied the behavior of the surface charge, and how the surface charge cause the current saturation and finally lead to the convergence of the apparent resistivity in the resistivity method. As a consequence of above analysis, we verified that the current saturation makes the apparent resistivity converge to a specific value and the magnitude of the apparent resistivity anomaly be less than that of the ideal conductor or insulator in the resistivity method. In general, current saturation is considered to occur when the conductivity contrast becomes larger than 100.