• Advances in nano research
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• 제1권3호
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• pp.171-182
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• 2013

The alternating current (AC) conductivity in semiconductor crystals with an open-core screw dislocation is studied in the current work. The screw dislocation in crystalline media results in an effective potential field which affects the electronic transport properties of the system. Therefore, from a technological view point, it is interesting to investigate properties of AC conductivity at frequencies of a few terahertz. To quantify the screw-induced potential effect, we calculated the AC conductivity of dislocated crystals using the Kubo formula. The conductivity showed peaks within the terahertz frequency region, where the amplitude of the AC conductivity was large enough to be measured in experiments. The measurable conductivity peaks did not arise in dislocation-free crystals threaded by a magnetic flux tube. These results imply different conductivity mechanisms in crystals with a screw dislocation than those threaded by a magnetic flux tube, despite the apparent similarity in their electronic eigenstates.

• Bulletin of the Korean Chemical Society
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• 제30권7호
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• pp.1543-1546
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• 2009

Temperature and frequency dependent AC conductivity behavior has been studied for the chemically synthesized polyaniline-polymannuronate (PANI-PM) composites. The temperature (300 - 500 K) and frequency (100 - $10^6$ Hz) dependent AC conductivity suggests evidence for the transport mechanism in PANI-PM composites. The frequency dependence of AC conductivity has been investigated by the power law. The frequency exponent (s) is determined, and the data suggest that s decreases with temperature. The variation of s with temperature suggests that AC conduction is due to the correlated barrier hopping.

• 대한전자공학회논문지
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• 제12권2호
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• pp.18-23
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• 1975

As-Te.Si-Ge 유리질 반도체의 직류 펀도도는 실온에서 3x10-7Ω-1cm-1∼1.5x10-8Ω-1cm-1이었고 각 시료의 온도 인화에 따른 전도특성은 상전이 온도(Tg) 이하에서 o=ooexp(-△E/kT)로 표시할 수 있었다. 또한 실온에서 각 시료의 교류 전도도의 주파수 의존도는 거의 같았으며 직류 전도도에 비해 상당치 높게 나타나서 o(w)=oo+Awn으로 표시할 수 있었다. 200KHz 경우에 교류 펀도도는 295。K∼473。K에서 온도에 무관하고 200Hz 경우에는 433。K에서 부터 심하게 증가하였다. 각 시fy는 기억스위칭 현상은 없었고 문지받스위칭 현상만 관찰할 수 있었다. The dc conductivity, ac conductivity and switching effect of As·Te-Si·Ge have beon investigated. The dc conductivity ranged from 3x10-7Ω-1cm-1∼1.5x10-8Ω-1cm-1 at room temperature and was found to be expressed by o=ooexp(-△E/kT) below the phase transition temperature Tg. The ac conductivity was much higher than dc conductivity and this result is consistent to experimental formula o(w)=oo+Awn. In the temperature range of 298。K∼147。K, the ac conductivity was independent of temperature at 200KHs. At lower frequencies the ac conductivity increased strong1y with temperature. Also, it has been found that all samples showed a threshold switching, but not a memory switching.

• 한국재료학회지
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• 제20권3호
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• pp.161-166
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• 2010

The ac, dc conductivity and dielectric properties of $DyCoO_3$ were reported in the temperature range of 77 - 300K and in the frequency range of 20 Hz - 100 kHz. It was observed that at low temperature, ac conductivity is much higher than dc conductivity and the hopping carrier between localized states near the Fermi level was the dominant loss mechanism. A comparison of the measured ac conductivity $\sigma(\omega)$ was made with some of the models of hopping conductivity of the proposed earlier in the literature. It was observed that in $DyCoO_3$ the measured ac conductivity, over the entire frequency and temperature region, can be explained reasonably well by assuming two contributions $\sigma_1(\omega)$ and $\sigma_2(\omega)$ to the measured $\sigma(\omega)$. The first, $\sigma_1(\omega)$, which dominates at low temperature, may be due to impurity conduction in a small polaron; the second, $\sigma_2(\omega)$, which dominates at higher temperatures, depending on the frequency of measurements, may be due to the hopping of a small polaron and is reasonable for the dielectric relaxation peak.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.599-600
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• 2005

The measurement method of electrical conductivity of the metal use a generally DC technique. Traceability to national standards in many countries is achieved using DC measurement technique and recently it's interested in AC technique. As a results for AC technique, the properties of electrical conductivity of non-ferrous and ferrous metals is decreasing at low frequency level.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.234-237
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• 1996

The amorphous chalogenide semiconductors are new material in semiconductor physics. Their properties, especially electronic and optical properties are main motives for device application. Amorphous As$_{10}$Ge$_{15}$ Te$_{75}$material has the stable ac conductivity at high frequency and the dc memory switching property. At higher frequency than 10MHz, ac conductivity of As$_{10}$Ge$_{15}$ Te$_{75}$ thin film is much higher than below frequency and independent of temperature and frequency. If the dc voltages are applied between edges of thin film, one can see the dc memory switching phenomenon, in other words the dc conductivity increases quite a few of magnitude after the threshold voltage is applied. Using the stable ac conductivity at high frequency and the increase of conductivity after dc memory switching, As$_{10}$Ge$_{15}$ Te$_{75}$thin film is considered as new material for microwave switch devices.vices.es.vices.

• Journal of Electrochemical Science and Technology
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• 제8권4호
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• pp.338-343
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• 2017

Activated carbon has lower electrical conductivity and reliability than other carbonaceous materials because of the oxygen functional groups that form during the activation process. This problem can be overcome by doping the material with heteroatoms to reduce the number of oxygen functional groups. In the present study, N, F co-doped activated carbon (AC-NF) was successfully prepared by a microwave-assisted hydrothermal method, utilizing commercial activated carbon (AC-R) as the precursor and ammonium tetrafluoroborate as the single source for the co-doping of N and F. AC-NF showed improved electrical conductivity ($3.8\;S\;cm^{-1}$) with N and F contents of 0.6 and 0.1 at%, respectively. The introduction of N and F improved the performance of the pertinent supercapacitor: AC-NF exhibited an improved rate capability at current densities of $0.5-50mA\;cm^{-2}$. The rate capability was higher compared to that of raw activated carbon because N and F codoping increased the electrical conductivity of AC-NF. The developed method for the co-doping of N and F using a single source is cost-effective and yields AC-NF with excellent electrochemical properties; thus, it has promising applications in the commercialization of energy storage devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.300-302
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• 1996

Using the AC and DC methods we have studied th electrical properties of ZnO added TiO$_2$. The electrical conductivity of ZnO added TiO$_2$ was nearly unchanged with increasing the content of ZnO. Ac conductivity and conductance as a function of Frequency showed the similar trends. The impedance, admittance, and modulus spectrums were consistent with the results of DC conductivity.

• 전기학회논문지P
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• 제56권4호
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• pp.157-160
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• 2007

The van der Pauw technique is one of the popular methods for determining the conductivity of flat metal samples. Traceability of the national standard for the conductivity has been achieved by direct current measurement techniques in national measurement institutes of many countries. But recently, alternative current measurement techniques for determining the conductivity of flat metal samples is also interested. In this study, we measured the conductivity of non-ferrous and ferrous flat metals at alternative current using van der Pauw technique. As measurement results, the conductivities of the samples were decreased according to increasing the test frequency even though the decreasing ratio was different.

• 대한수의학회지
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• 제24권1호
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• pp.91-98
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• 1984

A total of 466 foremilk from dairy farms in Chonnam district was examined for the subclinical mastitis over a period of one year, using a method of the electrical conductivities(EC); absolute conductivity(AC) and differential conductivity(DC) and quarter difference value(QD), in relation to the California mastitis test(CMT) and the direct somatic cell count(DSCC). The compatibility and efficiency rating between the EC values and the other screening tests was conducted. Obtained results are summarized as follows. 1. A linear relationship was found between the EC values and the CMT scores and direct somatic cell counts and it was found that electrical conductivity measurements were comparable with other screening tests for diagnosing animals with mastitis. 2. Compatibilities between the EC and CMT were 70.4% in AC, 74.6% in DC and 70.7% in QD, and that of the EC and DSCC were 53.0% in AC, 63.1% in DC and 53.2% in QD. On the other hand, relative efficiency ratings of Postle's equation between EC and CMT were 37.3% in AC, 26.5% in DC and 13.6% in QD, and that of the EC and DSCC were 33.1% in AC, 20.2% in DC and 11.9% in QD. 3. In the foremilk samples collected from damaged quarters determined by EC, the false positive rate wart higher than the false negative rate, and consequently tests of EC produced lower compatibility or efficiency rating scores. These tendencies suggested that any factors other than the mastitic condition influencing the EC values might be existed.