• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.651-662
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• 2022

The electrochemical impedance spectroscopy(EIS) method was used to evaluate the concrete deterioration process related to chloride-induced steel corrosion with various corrosion levels(initiation, rust propagation and acceleration periods). The impressed current technique, with four total current levels of 0C, 13C, 65C and 130C, was used to accelerate steel corrosion in concrete cylinder samples with w/c ratio of 0.4, 0.5, and 0.6, immersed in a 0.5M NaCl solution. A series of EIS measurements was performed to monitor concrete deterioration during the accelerated corrosion test in this study. Some critical parameters of the equivalent circuit were obtained through the EIS analysis. It was observed that the charge transfer resistance(R_c) dropped sharply as the impressed current increased from 0C to 13C, indicating a value of approximately 10kΩcm². However, the sensitivity of R_c significantly decreased when the impressed current was further increased from 13C to 130C after corrosion of steel had been initiated. Meanwhile, the double-layer capacitance value(C_dl) linearly increased from 50×10^-6μF/cm² to 250×10^-6μF/cm² as the impressed current in creased from 0C to 130C. The results in this study showed that monitoring C_dl is an effective measurement parameter for evaluating the progress of internal concrete damages(de-bonding between steel and concrete, micro-cracks, and surface-breaking cracks) induced by steel corrosion. The findings of this study provide a fundamental basis for developing an embedded sensor and signal interpretation method for monitoring concrete deterioration due to steel corrosion at various corrosion levels.

• Journal of the Korean Chemical Society
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• v.14 no.4
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• pp.327-332
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• 1970

A simple and convenient device for deflection-type direct reading the variations in electrolytic conductance is described and applied to the analysis of sulfur by combustion-$H_2O_2$ oxidation method. The apparatus consisted of a high resistance-ratio bridge in which the other adjacent arms are the differential cells. By adopting unusually high a-c voltage source for the bridge excitation, the a-c method for unbalanced bridge is established, decreased sensitivity owing to reduced bridge factor, 0.01, is overcome and also the absolute sensitivity and linearity are greatly improved. Over 50% variations in impedance of the balanced cell, within 1% deviation from the linearity can be attained with a volt (rms)order of output which was detected directly with VTVM without further amplification. Analysis of the bridge shows that these useful features are natural result of the constant current character of the high source impedance generator and the performance of the device agreed with the theoretical predictions. A standard procedure for the rapid analysis of sulfur using the bridge is also given, the analytical accuracy was approximately 1%. A determination takes not more than 5 minutes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.445-446
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• 2012

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.89.1-89
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• 1998

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.195-201
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• 1999

The repassivation characteristics of Fe-Cr steels in deaerated 0.1 M $Na_2SO_4$ solution have been investigated with the variation of Cr content, applied potential and Cl- concentration. In the absence of chloride ion, abrading electrode test showed that, slope -n, of log i=k -n log t, a parameter of repassivation rate, approached to -1, regardless of Cr content but as Cr content increased, repassivation current density decreases with increasing Cr content. A.C. Impedance spectroscopy showed that the charge transfer resistance of passive film became higher as Cr content and applied potential increased. However, in the presence of chloride ion, it was observed that chloride ion suppressed the passive film formation, whose effect became greater with increasing applied potential.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.12
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• pp.36-42
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• 1993

By the variational method, the coplanar waveguide(C.P.W) shielded by two conducting plates has been analyzed. The particular potential solution has been obtained for the boundary conditions in C.P.W. The characteristic impedance and the effective dielectric constant in C.P.W. have been obtained by the variational method using the potential function and the assumed basis function for charge distributions. To consider the effect of the conducting plate in C.P.W. two cases, with and without the top plate, have been analyzed and compared respectively.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.99-104
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• 2024

In this study, a carbon coated hollow silicon (HSi/C) composite material was prepared for anode material of high-capacity lithiun-ion battery. Hollow silica (HSiO₂) was synthesized by the Stöber method with CTAB (N-Cetyltrimethylammonium bromide). The HSi/C anode composite was manufactured by carbon coating after magnesiothermic reduction of HSiO₂. The physical and electrochemical characteristics of the prepared anode materials were investigated based on CTAB amount. In the FE-SEM analysis, it was found that the HSiO₂ particle size increased as CTAB amount decreased, but shell thickness decreased. The HSi/C composites exhibited high initial discharge capacities of 1866.7, 2164.5 and 2188.6 mAh/g with various CTAB ratios (0.5, 1.0, 1.5), respectively. After 100 cycles of charge-discharge, 0.5-HSi/C demonstrated a high reversible capacity of 1171.3 mAh/g and a capacity retention of 70.9%. Electrochemical impedance spectroscopy (EIS) was employed to analyze the impedance characteristics, and it revealed that 0.5-HSi/C showed more stable resistance characteristics than HSi/C composites with other CTAB amount over 20 cycles.

• Journal of Sensor Science and Technology
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• v.26 no.5
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• pp.306-313
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• 2017

An early detection of infiltration in veins is essential to minimize the injuries caused during infusion therapy, which is one of the most important tasks for nurses in clinical settings. We report that bioelectrical impedance analysis is useful in the early detection of infiltration at puncture sites. When infiltration was intentionally induced in the vein of a rabbit's ear, impedance parameters showed significant difference before and after infiltration. In particular, the relative resistance at 20 kHz in the vein of rabbit's ear reduced largely at infiltration, decreased slowly, and then stayed at a constant value. This indicates that the vein in the ear of the rabbit is small, and hence the infiltrated intravenous (IV) solution no longer accumulates after 3 minutes of infiltration. However, when infiltration was induced in the vein of a human's forearm, the relative resistance at 20 kHz decreased gradually over time. In the $R-X_c$ graph, the positions in infiltration induced in the rabbit's ear rapidly shifted before and after infiltration whereas the positions in infiltration induced in the human's forearm changed gradually during infiltration. Our findings suggest that bioelectrical impedance analysis is an effective method to detect the infiltration early in a noninvasive and quantitative manners.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.11 no.1
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• pp.82-104
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• 2007

Purpose: We performed this study to examine the effect of controlled respiration on cardiovascular system in healthy adult subjects using impedance cardiography and photoplethysmography. Materials and Methods: This study had performed on 74 subjects, which were healthy men and women without a experience of respiration practice. Using the instruments for impedance cardiography and photoplethysmography, parameters of each subject had been measured after each controlled respirations which were natural respiration, controlled natural respiration (I:E=1.1.6), longer inspiration(I:E=3:3), and longer expiration(I:E=2:4). The measured parameters of impedance cardiography and photoplethysmography were processed statistically by one-way repeated ANOVA. Results: 1. HR and CI of impedance cardiography were decreased significantly during controlled respiration comparing with the result of basal state(the state of enough break). There was no significant difference among the results of controlled respiration. 2. PEP of impedance cardiography had no significant difference among the result of basal state and the results of controlled respiration(p=0.059). 3. VI of impedance cardiography had significant differences among the result of basal state and the results of controlled respiration, and decreased continuously through the controlled respiration. 4. b/a of photoplethysmography had no significant difference among the result of basal state and the results of controlled respiration(p=0.554). 5. c/a of photoplethysmography were decreased significantly during controlled respiration comparing with the result of basal state. There was no significant difference among the results of controlled respiration. 6. d/a of photoplethysmography had significant differences among the results of the controlled respiration decreasing continuously through the controlled respiration and had no significant difference between the result of basal state and the result of natural respiration. 7. AGI of photoplethysmography had significant differences among the result of basal state and the results of the controlled respiration increasing continuously through the controlled respiration. Conclusion: We had examined the effects of controlled respirations on cardiovascular system in multiple points of view. The effects of controlled respirations on cardiovascular system can't be explained in a simple way, as the cardiovascular system is controlled by many factors. Therefore, more physiological parameters must be measured in the future study on the effect of the controlled respiration on human cardiovascular system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.918-921
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• 2005

According to the mechanical-electrical coupling characteristics and the electrical Impedance property of resistor-inductor-capacitor(RLC) series resonant circuit, the mechanical impedance analysis of a bimorph piezoceramic patch shunted with a series RLC resonant circuit is conducted. The displacement transfer function of a cantilever beam bonded with a piezoelectric shunt damping module is deduced in the case of single mode vibration of the beam. By the use of vibration damping theory of tuned mass damper system, the parameter optimization of piezoelectric shunt damping system is performed. The optimal resonant state of the shunting circuit can be obtained when the resister and conductor are optimally adjusted. Test results show that the vibration control effect as well improved with optimized piezoelectric shunt system.