• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.93-95
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• 2005

케이블 변압기용 케이블에는 반도전층이 설치되며 권선의 각 턴에 대하여 외측 반도전층을 접지함으로써 권선에 과다 전계가 인가되는 것을 억제하는 역할을 한다. 케이블 변압기는 케이블의 반도전층의 저항률에 따라 전계분포 및 전력손실이 다른 특성을 나타낸다. 반도전층의 저항률이 매우 높을 경우 각 턴에 인가되는 전계에 의해 각 턴의 접지 사이에 높은 전계가 인가되고, 저항률이 매우 낮을 경우 반도전층에서 높은 전력 손실을 야기하여 변압기의 전체 효율을 감소시키게 된다. 따라서 반도전층의 저항률을 적절히 선정함으로써 전체 변압기의 절연특성과 효율을 최적화 할 필요가 있다. 본 연구에서는 유한요소법과 진화전략을 적용하여 케이블 변압기용 케이블의 반도전층 최적화를 수행한다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.147-155
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• 2002

To find the safety and serviceability of bridges, it must consider the behaviour of structural member and evaluation of the exact resistance of the member subjected to external loads. To evaluate the behaviour and the resistance of the structural member, it must measure the strains and displacements of the structures. Usually we use the strain gauge to measure the strains. When, the bridge is long span and high pier, the setting of strain gauge is very difficult and not economic. It is not recommendable for the use of strain gauge, when the structural member has many cracks and moisture. Thus, to make up for this demerits, the algorithm of strain analysis by measured displacements data is proposed.

• Geophysics and Geophysical Exploration
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• v.13 no.4
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• pp.378-387
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• 2010

We present the results of laboratory measurement of porosity and electrical resistivity for the samples collected near marine hydrothermal deposit to provide fundamental perspective of physical properties for future electromagnetic survey. The rock cores are sampled from the host rock, pumice, hydrothermal altered zone, and chimney. These samples are featured as easily brittle, rough surface with large pores, having components easily solvable in the water. We suggest systematic approach for measuring weights, volumes of core samples to calculate density and porosity. Measurements reveal that the resistivities of black host rock, gray host rock, pumice and chimney are 102, 39, 11, 0.1 ohm-m, respectively, when the core samples are saturated with saline water of $32,000\;{\mu}S$/cm (0.5 ohm-m) at temperature of $2.5^{\circ}C$ and these correspond to the factors of 5 for sea water, 110 for pumice and 390~1020 for host rocks with respect to the resistivity of chimney. We also confirm that resistivity of rock samples saturated with water decrease with temperature linearly over the temperature range of $20{\sim}80^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1568-1569
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• 2011

최근 기후변화로 인해 낙뢰의 발생빈도가 크게 증가하고 있으며 이에 따라 피뢰시스템의 중요성이 부각되고 있다. 피뢰시스템의 원활한 기능을 수행하기 위해 접지시스템의 성능이 보장되어야 하며, 접지전극은 뇌격전류를 안전하게 대지로 방류시켜야 한다. 본 논문에서는 피뢰시스템에서 가장 흔하게 사용되는 수직접지전극을 대상으로 서지전류가 인가되었을 때 접지전극이 묻힌 대지저항률, 접지전극의 길이, 서지 전류의 파두시간 등에 따른 규약접지임피던스를 측정하고 그 특성을 분석하였다. 그 결과 대지저항률이 높은 토양과 접지전극의 길이가 짧은 경우 접지임피던스가 감소하는 용량성 특성이 지배적으로 나타나며, 대지저항률이 작고 접지전극의 길이가 긴 경우 접지임피던스가 증가하는 유도성 특성이 지배적으로 나타났다. 따라서 피뢰시스템을 위한 접지시스템 설계 시 대지저항률 및 접지전극의 길이를 고려하여 유도성 특성을 최소화 할 수 있도록 설계해야 한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.114-121
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• 2010

This paper deals with the frequency-dependent grounding impedances of counterpoises relevant to the soil resistivity, the length of counterpoises and the feeding point of test current. The grounding impedances of counterpoises buried in one-layered and two-layered soils were measured and analyzed in the frequency range from 1[kHz] to 10[MHz]. As a result, the frequency-dependent grounding impedances strongly depend on the soil resistivity, and the grounding impedances within the frequency of several tens [kHz] are capacitive behavior in high soil resistivity. When injecting the ground current to the end of counterpoise buried in soil with high resistivity, the grounding impedances in high frequency are increased.

• Geophysics and Geophysical Exploration
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• v.18 no.3
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• pp.105-114
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• 2015

A long-term resistivity monitoring system has been developed for saturated cores in room temperature and humidity condition. A 3-channel water-pump continuously drops the water onto the top of saturated core sample surrounded by shrinkable tube as well as on the paper filters of the electrodes at both sides of the core sample, by which one can monitor the resistivity changes with maintaining full saturation of the rock core for a week or longer. Monitoring the resistivity changes has been performed with 3 kinds of rock samples including biotite gneiss, andesitic tuff, and shale for 9 days using the system. Consequently, it is proposed two hypothesis that conversion speed of temperature coefficient has close relation to the thermal properties of the rock sample and that the ratio of resistance between dry and saturated conditions for a rock sample can be related to the effective porosity of the sample. The ratio between dry and saturated resistance for the three rock types are 48, 705, and 2, while effective porosity was 3.7%, 3.3%, and 13.0%, respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.5
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• pp.74-79
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• 2005

In this paper the earth structures of four cities are analysed on the basis of the measured soil resistivity and the characteristics of a grounding system is examined. As a result it is revealed that the soil resistivity has an effect on touch voltage and step voltage, which are directly related to safety, as well as ground resistance.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.65-70
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• 2005

A low resistivity zone is found in many places such as a fractured fault zone, weathered zone and aquifer. The electrical resistivity is influenced mainly by pore fluid as well as the clay mineral types and contents, Hence, it is very important to understand the relationship between the electrical resistivity and clay contents associated with the low resistivity zone for geotechnical applications such as civil engineering. This study examines the characteristics of clay mineral types and contents to electrical resistivity through sample measurements, and proposes an expression relating the resistivity and clay content. The electrical resistivity is measured for an artificial agar specimen with clay minerals instead of a natural rock. The clay minerals used are Kaolinite and Montmorillonite. Montmorillonite shows remarkably lower resistivity than Kaolinite, although its clay content is fewer than that of Kaolinite. Also, the proposed expression shows a good correlation coefficient as high as 0.89 or more in all clay minerals.

• Journal of the Korean Geotechnical Society
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• v.25 no.2
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• pp.45-54
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• 2009

The electrical characteristics of soils have been used for investigating soil properties. The purpose of this study is the development and application of the electrical resistivity cone probe (ERCP) for the evelation of the porosity in the field with high precision. The shape of the probe tip is a cone shape to minimize the disturbance during penetration. In addition, the four terminal pair configuration is adopted to minimize the electrical interference. The electrical resistances are continuously measured during penetration of the ERCP using penetration rigs with 0.33 mm/sec penetration rate at Incheon and Busan sites. With the measured resistance profile and electrical resisivity of electrolyte of undisturbed samples, soil porosity profiles are obtained by using Archie's law. The empirical coefficients for the Archie's law are obtained based on the electrolyte extracted from the undisturbed samples. The estimated porosity profiles show similar trends to those of in-situ penetration tests such as SPT, CPT, and DMT. This study suggests that the ERCP may be an effective tool for the porosity estimation in the field with minimum disturbance.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.1 no.1
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• pp.107-114
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• 1998

Purpose: The purpose of our study is to provide useful information for me-asurement methods of childhood obesity and to provide clinical significance of bioelectrical impedance analysis. Methods: We measured height, weight, waist to hip ratio, skinfold thickness and bioelectrical impedance from 206 elementary students in Kwangju from May to July 1997. Results: In males; 1) There were statistically high correlations between tri-ceps skinfold thickness and body mass index (BMI), percentage of body fat (%BF), weight, Rohler index (RI), total fat weight (TFW), waist to hip (W/H) ratio, height, lean body mass (LBM) (all, p<0.001). 2) There were statistically high correlations between subscapular skinfold thickness and BMI, RI, weig-ht, %BF, TBW (all, p<0.001). 3) There were statistically high correlations between %BF and BMI, triceps skinfold thickness, RI, TFW, subscapular skinfold thickness, weight (all, p<0.001). In females; 4) There were statistically high correlations between triceps skinfold thickness and BMI, weight, LBM, height, %BF (all, p<0.001). 5) There were statistically significant correlations between subscapular skinfold thickness and BMI, weight, LBM, RI, height. 6) There were statistically high correlations between percentage of body fat and BMI, RI, triceps skinfold thickness. The percentage of body fat according to the bioelectrical impedance analysis highly correlated with that calculated by skinfold thickness in males (r＝0.57, p<0.01) and in females (r＝0.30, p<0.01). Conclusion: The results of our study suggests that bioelectrical impedance analysis is a useful method of estimating body fat in the childhood obesity.