• Corrosion Science and Technology
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• v.20 no.5
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• pp.231-241
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• 2021

The objective of this study was to evaluate total current under steady-state conditions for a material undergoing corrosion using the electrochemical frequency modulation (EFM) technique, taking into account the presence of solution resistance and double layer capacitance. The analysis involving linearization of the Tafel curve allowed for the estimation of corrosion parameters. Results showed that the output signal was dependent on fundamental frequencies and their multiples. In addition, the output signal almost manifested itself at frequencies that were sums of fundamental frequencies of the applied sinusoidal signal. The harmonics calculated showed a significant shift from the principal frequency of input signals. The investigation involved the influence of corrosion current and anode-to-cathode Tafel slope ratio on faradaic and non-faradaic currents (including the average and RMS). The model presented showed both qualitative and quantitative improvements over the previously developed EFM technique that ignored the influence of solution resistance and the double layer capacitance while assuming the applied DC potential corresponded to the corrosion potential of the corroding material.

• Journal of the Korea Society of Computer and Information
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• v.24 no.9
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• pp.77-82
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• 2019

Collaborative filtering is a popular technique for recommender systems and used in many practical commercial systems. Its basic principle is select similar neighbors of a current user and from their past preference information on items the system makes recommendations for the current user. One of the major problems inherent in this type of system is data sparsity of ratings. This is mainly caused from the underlying similarity measures which produce neighbors based on the ratings records. This paper handles this problem and suggests a new similarity measure. The proposed method takes users rating patterns into account for computing similarity, without just relying on the commonly rated items as in previous measures. Performance experiments of various existing measures are conducted and their performance is compared in terms of major performance metrics. As a result, the proposed measure reveals better or comparable achievements in all the metrics considered.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.1043-1050
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• 2022

Markov chains and Monte Carlo Simulation were applied to account for the probabilistic nature of pavement deterioration over time using data collected in the field. The primary purpose of this study was to evaluate pavement network performance of Western Australia (WA) by applying the existing pavement management tools relevant to WA road construction networks. Two approaches were used to analyze the pavement networks: evaluating current pavement performance data to assess WA State Road networks and predicting the future states using past and current pavement data. The Markov chains process and Monte Carlo Simulation methods were used to predicting future conditions. The results indicated that Markov chains and Monte Carlo Simulation prediction models perform well compared to pavement performance data from the last four decades. The results also revealed the impact of design, traffic demand, and climate and construction standards on urban pavement performance. This study recommends an appropriate and effective pavement engineering management system for proper pavement design and analysis, preliminary planning, future pavement maintenance and rehabilitation, service life, and sustainable pavement construction functionality.

• Progress in Superconductivity
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• v.3 no.1
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• pp.1-4
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• 2001

Interface-engineered junctions with $YbBa_2$$Cu_3$$O_{7}$ as the counter electrode were demonstrated. The junctions exhibited excellent Josephson characteristics with a Josephson critical current ($I_{c}$) ranging from 0.1 mA to 8 mA and a magnetic field modulation of the $I_{c}$ exceeding 80% at 4.2 K while maintaining complete c-axis orientation of the counter-electrode layer. The$ 1\sigma$ spreads in $I_{c}$ for junctions with an average $I_{c}$ of 1-2 mA were 5-8% for 16 junctions within a chip, and 9.3% for a 100-junction array. Our dI/dV measurements suggest that a theoretical approach taking into account both a highly transparent barrier and the proximity effect is required to fully understand the Junction characteristics.ristics.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.565-573
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• 2007

The effect of wave and current interactions on irregular wave transformation over a submerged elliptic shoal is investigated based on numerical simulations of the Vincent and Briggs experiment [Vincent, C.L., Briggs, M.J., 1989. Refraction-diffraction of irregular waves over a mound. Journal of Waterway, Port, Coastal and Ocean Engineering, 115(2), pp. 269-284]. The numerical simulations are conducted by a combination of REF/DIF S(a wave model) and SHORECIRC(a current model) and a time dependent phase-resolving wavecurrent model, FUNWAVE. In the simulations, the breaking-induced currents defocus waves behind the shoal and bring on a wave shadow zone that shows relatively low wave height distributions. The computed results of the combined model system agree better with the measurements than the computed results obtained by neglecting wave-current interaction do. In addition, the results of FUNWAVE show a good agreement with the measurements. The agreement indicates that it is necessary to take into account the effect of breaking-induced current on wave refraction when wave-breaking occurs over a submerged shoal.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.3
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• pp.15-30
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• 2004

In this paper, an analytical modeling for the dark and photo-current characteristics of a buried-gate short- channel GaAs MESFET is presented. The presented model shows that the increase of drain current under illumination is largely due to not the increase of photo-conductivity in the neutral region but the narrowing effect of the depletion layer width. The carrier density profile within the neutral region is derived from solving the carrier continuity equation one-dimensionally. In deriving the photo-generated current, we assume that the photo-current is compensated with the thermionic emission current at the gate-channel interface. Moreover, the two-dimensional Poisson's equation is solved by taking into account the drain-induced longitudinal field effect. In conclusion, the proposed model seems to provide a reasonable explanation for the dark and photo current characteristics in a unified manner.

• Korean Journal of Metals and Materials
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• v.56 no.12
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• pp.893-899
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• 2018

In the present study, we investigated the sulfur poisoning of the Ni anode in solid oxide fuel cells (SOFCs) as a function of operating conditions. Anode supported cells were fabricated, and sulfur poising tests were conducted as a function of current density, $H_2S$ concentration and humidity in the anode gas. The voltage drop was significant under the higher current density (${\sim}714mA/cm^2$) condition, while it was much reduced under the lower current density (${\sim}389mA/cm^2$) condition, at 100 ppm of $H_2S$. A secondary voltage drop, which occurred only at the high current density, was attributed to Ni oxidation in the anode. Thus, operation at high current density with high $H_2S$ concentration may lead to permanent deterioration in the anode. The effect of water content (10%) on the sulfur poisoning was also investigated through a constant current test (${\sim}500mA/cm^2$) at 10 ppm of $H_2S$. The cell operating with 10% wet anode gas showed a much smaller initial voltage drop, in comparison with a dry anode gas. The present study indicates that operating conditions, such as gas humidity and current density, should be carefully taken into account, especially when fuel cells are operated with $H_2S$ containing fuel.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.961-965
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• 1998

The rapid development of small-scale (1-10 MJ) Superconducting Magnetic Energy Storage Systems (SMES) can be explained by real perspective of practical implementation of these devices in electro power nets. However the serious problem of all high mechanically stressed superconducting coils-problem of training and degradation (decreasing) of operating current still exists. Moreover for SMES systems this problems is more dangerous because of pulsed origin of mechanical stresses-one of the major sources of local heat disturbances in superconducting coils. We investigated acoustic emission (AE) phenomenon on model and 0.5 MJ SMES coils taking into account close correlation of AE and local heat disturbances. Two-coils 0.5 MJ SMES system was developed, manufactured and tested at Russian Research Center in the frames of cooperation with Korean Electrical Engineering Company (KEPCO) [1]. The two-coil SMES operates with the stored energy transmitted between coils in the course of a single cycle with 2 seconds energy transfer time. Maximum operating current 1.55 kA corresponds to 0.5 MF in each coil. The Nb-Ti-based conductor was designed and used for SMES manufacturing. It represents transposed cable made of Nb-Ti strands in copper matrix, several cooper strands and several stainless steel strands. The coils are wound onto fiberglass cylindrical bobbins. To make AE event information more useful a real time instrumentation system was used. Two main measured and computer processed AE parameters were considered: the energy of AE events (E) and the accumulated energy of AE events (E ). Influence of current value in 0.5 MJ coils on E and E was studied. The sensors were installed onto the bobbin and the external surface of magnets. Three levels of initial current were examined: 600A, 1000A, 2450 A. An extraordinary strong dependence of the current level on E and E was observed. The specific features of AE from model coils, operated in sinusoidal vibration current changing mode were investigated. Three current frequency modes were examined: 0.012 Hz, 0.03 Hz and 0.12 Hz. In all modes maximum amplitude 1200 A was realized.

• Management & Information Systems Review
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• v.35 no.2
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• pp.83-97
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• 2016

The purpose of this study is to evaluate our system and consider how the tax rules on corporate reorganization and asset adjustment account can be improved. The scope of this study includes the Korean tax rules on corporate reorganizations, as well as key tax benefits provided by the Special Tax Treatment Control Act. In case of Korea, The relevant regulations and system of taxation respecting the merger has been made the rapid progress in several respects in this situation, there are capable of improvement. This paper suggests improve some problems on tax avoidance abusing incomplete tax law. First, the asset adjustment account is the difficulty that it needs to follow-up during this period of time, as well as the complexity of the accounting and tax adjustments on the practice. If it is permitted to succeed asset-liability as market value, the complexity of asset adjustment account in corporate tax accounting also disappear. Second, in case that controlling shareholders possess more than 20% of merged entity, they could not get the tax deferral until after the time of two years has elapsed. It needs to further alleviate the merged entity ratio than the present level. Finally, after the merger it will be to strengthen the surveillance provisions of five years from the current two years. In addition, continuity of shareholder's requirements and business requirements, it is also necessary to strengthen the requirements of the follow-up provided by a separate regulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.5
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• pp.812-817
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• 2018

Blockchain technology removes the central system and connects each block throughout every person. This paper proposes new method to exploit the blockchain feature to apply existing donation system. In the current system, the donator does not donate to poor neighbor which means donator must have to donate some donate organization. The donator does not recognize how the donation has been spent after donation. In this case, we can solve that problem by using the blockchain where the donator can watch how the money works and everyone can browse the account history. To make a virtual fundraising box based on blockchain technology, donator sends some money at virtual account and exchanges the money to crypto-currency. Donator can use crypto-currency which is donate to poor neighbor that poor neighbor can exchanges crypto-currency to the money. Through this proposed system, the donation is managed by secure and transparent blockchain system.