• 한국전자파학회논문지
• /
• 제25권10호
• /
• pp.1087-1094
• /
• 2014

본 연구에서는 유전체의 산란 특성 분석을 위해 이용되는 CFIE(Combined Field Integral Equation) 모멘트법의 계산효율을 높이기 위해 임피던스 경계면 조건을 적용시킨 수치해석 기법과 그 적용 범위에 대한 분석결과를 제시한다. 임피던스 경계면의 적용은 유전체의 등가 표면 전류(Js)와 등가 표면 자류(Ms)를 하나의 전류 또는 자류 성분으로 표현할 수 있으며, 임피던스 경계면 조건을 적용해 계산효율을 높인 수치해석 기법의 정확도는 기존의 CFIE 모멘트법과 이론값(Mie-series 해법, Small Perturbation 산란모델)을 이용하여 비교/분석하였다. 임피던스 경계면 조건을 적용한 수치해석 기법의 적용 범위 상대유전율 허수부 12 이상에서 1 dB 이내의 계산 편차를 확인하였다.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
• /
• pp.416-418
• /
• 2008

Dye-sensitized solar cell using transparent conducting oxide as electrode has large resistance such as surface resistance, charge transportation impedance in counter electrode and electrolyte, impedance between each interface. Among that resistances, surface resistance of transparent conducting oxide is relatively large. So the change of transparency has a large effect on internal resistance of dye-sensitized solar cell. Consequently, that change cause to increase or decrease the conversion efficiency. We tried to reduce the surface resistance by laser-scribing. The active area is seperated from total transparent conducting oxide by Nd:YAG laser-scribing. As a result, we achieved the improvement of efficiency about 7% and 11% in case of $0.25cm^2$ and $1.00cm^2$ dye-sensitized solar cells.

• 제어로봇시스템학회논문지
• /
• 제17권2호
• /
• pp.171-175
• /
• 2011

In this paper, I have developed a high-speed and high-resolution measuring device in order to check the performance of drycell. The system is developed for the drycell manufacturing plant. Measuring time is one of key factors to inference on the production speed. So the developed system is designed to generate the classified result up to 1200ea/min. In the other words, each product can be classified within 25ms. There have been many studies to estimate both state of charge as well as state of health, such as OCV (Open Circuit Voltage), SC (Short Circuit) and measuring impedance with frequency pulse. But those methods take a few second due to surface discharge. To overcome the phenomenon, I developed the method to engage the reverse current to two electrodes of battery. As a result, I could achieve to measure the indigenous capacity without the problem of surface discharge.

• 한국수소및신에너지학회논문집
• /
• 제7권1호
• /
• pp.39-44
• /
• 1996

The discharge capacity of V-Ti-Ni(V-rich) metal hydride electrode during the charge-discharge cycling was investigated in KOH electrolyte. All electrodes were degraded within 25 cycles. To investigate the cause of the degradation phenomena impedance measurements were performed by using E.I.S(electrochemical impedance spectroscopy). The surfaces of the degraded electrodes were examined by Auger electron spectroscopy (AES). It was observed that all electrodes were covered with oxygen from the surface to the bulk, titanium was enriched near surface, and vanadium was dissolved from the surface to the bulk.

• International Journal of Computer Science & Network Security
• /
• 제23권1호
• /
• pp.120-124
• /
• 2023

Strong surface waves among collinearly arranged patch antenna arrays pose unwanted inter element coupling particularly when high permittivity dielectric materials are used. In order to avert those waves, a novel Defected Ground Structure (DGS) is carved out systematically between two E-plane patch antenna elements. The introduced low profile μ shaped structure consequently improves impedance bandwidth and reflection coefficient by suppressing surface waves considerably. Parametric simulation results are analyzed and discussed.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2023년도 가을학술발표대회논문집
• /
• pp.151-152
• /
• 2023

Lightweight aggregates has a dry specific gravity of 2.0 or less, which is lower than natural aggregates. Lightweght aggregate is efficient for weight reduction but has low compressive strength. In this study, EIS(electrochemical Impedance Spectroscopy) was used to confirm the ITZ(Interfacial Transition Zone) between the lightweight aggregate and cement paste according to the coated of blast furnace slag powder. As a result of EIS measurement, the correlation between ITZ characteristics and compressive strength was determined. The phase angle of EIS was different depending on the blast furnace slag powder coated of the lightweight aggregate. The surface-cotead lightweight aggregate was improved and the ITZ was strengthened.

• Corrosion Science and Technology
• /
• 제13권5호
• /
• pp.170-177
• /
• 2014

Polyurethane coating was designed to give a hydrophobic property on its surface by modifying it with hydroxyl terminated polydimethylsiloxane and then effects of surface hydrophobic tendency, water transport behavior and hence corrosion protectiveness of the modified polyurethane coating were examined using FT-IR/ATR spectroscopy, contact angle measurement and electrochemical impedance test. As results, the surface of polyurethane coating was changed from hydrophilic to hydrophobic property due primarily to a phase separation tendency between polyurethane and modifier by the modification. The phase separation tendency is more appreciable when modified by polydimethylsiloxane with higher content. Water transport behavior of the modified polyurethane coating decreased more in that with higher hydrophobic surface property. The decrease in the impedance modulus ${\mid}Z{\mid}$ at low frequency region in immersion test for polyurethane coatings was associated with the water transport behavior and surface hydrophobic properties of modified polyurethane coatings. The corrosion protectiveness of the modified polyurethane coated carbon steel generally increased with an increase in the modifier content, confirming that corrosion protectiveness of the modified polyurethane coating is well agreed with its water transport behavior.

• Carbon letters
• /
• 제12권3호
• /
• pp.180-183
• /
• 2011

Li metal is accepted as a good counter electrode for electrochemical impedance spectroscopy (EIS) as the active material in Li-ion and Li-ion polymer batteries. We examined the existence of signal noise from a Li-metal counter quantitatively as a preliminary study. We suggest an electrochemical cell with one switchable electrode to obtain the exact impedance signal of active materials. To verify the effectiveness of the switchable electrode, EIS measurements of the solid electrolyte interphase (SEI) before severe $Li^+$ intercalation to SFG6 graphite (at > ca. 0.25 V vs. Li/$Li^+$) were taken. As a result, the EIS spectra without the signal of Li metal were obtained and analyzed successfully for the following parameters i) $Li^+$ conduction in the electrolyte, ii) the geometric resistance and constant phase element of the electrode (insensitive to the voltage), iii) the interfacial behavior of the SEI related to the $Li^+$ transfer and residence throughout the near-surface (sensitive to voltage), and iv) the term reflecting the differential limiting capacitance of $Li^+$ in the graphite lattice.

• 소음진동
• /
• 제6권3호
• /
• pp.297-303
• /
• 1996

The general approach using sine series expansions was represented to evaluate the radiation loading from a vibrating surface on a simply supported cylinder. In this paper, the fluid-loading coefficients (radiation impedance) for a submerged finite cylindrical shell with an arbitrary end condition are defined and evaluated. The vibrations of cylindrical shell are expressed by using cosine series expansions to analyze the radiation impedance for a finite cylindrical shell. It is possible to represent the displacements at both ends of cylindrical shell in comparison with sine series. The direct and cross modal components of fluid-loading coefficients are shown and the validity of cosine series expansions are verified from the results of numerical computations. This approach and results are directly applicable in the analysis of sound radiation from subemerged finite cylindrical shell with arbitrary end conditions.

• 소음진동
• /
• 제7권5호
• /
• pp.781-787
• /
• 1997

A new method is presented to determine two fundamental acoustic quantities of sound-absorbing materials such as characteristic impedance and propagation constant. In this study, the surface acoustic impedances of sound-absorbing materials are measured using the impedance tube and the anechoic chamber to determine the above acoustic quantities. The measured results are given for two typical sound-absorbing materials(glass wool and urethane foam) int the frequency range between 150 and 1, 600 Hz. The results are verified by other two known methods, which are Smith & Parrott method and Utsuno et al. method. The absorption coefficients calculated from the empirical models(Miki model for glass wool and Jung model for urethane foam) and two quantities by present method are in good agreement with the measured values.