• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.6 no.4
• /
• pp.344-353
• /
• 1994

This study numerically analyzed the dynamic characteristics of the frequency response on the pneumatic transmission line with load impedances. The pressure transfer function is represented by the distributed parameter line model. To validate the mathematical approximations of Bessel function ratios, the results of frequency response in a blocked line were compared with those obtained by the Infinite-product, Brown's and Square-root approximations. Special emphasis was given to the frequency response characteristics on the pneumatic transmission line with load impedances. Computations were carried out for the wide range of parameters in terms of load capacitance ratio and load resistance ratio. The present results indicated that the theoretical model is capable of accurately predicting the frequency response characteristics for any configuration of a fluid transmission line.

• International Journal of Precision Engineering and Manufacturing
• /
• v.9 no.2
• /
• pp.39-43
• /
• 2008

Atmospheric pressure plasma polishing (APPP) is a noncontact precision machining technology that uses low temperature plasma chemical reactions to perform atom-scale material removal. APPP is a complicated process, which is affected by many factors. Through a preliminary theoretical analysis and simulation, we confirmed that some of the key factors are the radio frequency (RF) power, the working distance, and the gas ratio. We studied the influence of the RF power and gas ratio on the removal rate using atomic emission spectroscopy, and determined the removal profiles in actual operation using a commercial form talysurf. The experimental results agreed closely with the theoretical simulations and confirmed the effect of the working distance. Finally, we determined the element compositions of the machined surfaces under different gas ratios using X-ray photoelectron spectroscopy to study the influence of the gas ratio in more detail. We achieved a surface roughness of Ra 0.6 nm on silicon wafers with a peak removal rate of approximately 32 $mm^{3}$/min.

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.1145-1148
• /
• 1998

New capacitance modeling and transient analysis for multi-layer interconnects with shielding effect are presented. The upper layer capacitances with under-layer shielding lines are represented by introducing a filling factor η which can be defined as the ratio of upper-layer line length to the total under-layer line width. The upper-layer effective self capacitances considering two extreme cases which the underlayer metals are assumed as a ground or as a Vdd are modeled. The signal transient analysis with shielding effect model is performed.

• Carbon letters
• /
• v.15 no.3
• /
• pp.210-213
• /
• 2014

Nitrogen-doped microporous carbons were prepared using a polyvinylidene fluoride/melamine mixture. The electrochemical performance of the nitrogen-doped microporous carbons after being subjected to different carbonization conditions was investigated. The nitrogen to carbon ratio and specific surface area decreased with an increase in the carbonization temperature. However, the maximum specific capacitance of 208 F/g was obtained at a carbonization temperature of $800^{\circ}C$ because it produced the highest microporosity.

• Journal of Biomedical Engineering Research
• /
• v.13 no.3
• /
• pp.201-208
• /
• 1992

In the indirect optical bio-telemetry, high frequency response and low minimum detectable optical power can be achieved by using photodiode with small light receiving area which minimizes junction capacitance. But, on the other hand, S/N ratio becomes low because the optical signal current is small. To solve such a problem, we attach plato-convex lens in front of photo diode, The results of comput- er simulation and experiments suggest promotion of light receiving efficiency and possibility of multi- telemetry system through directivity of convex lens in one room.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1986.04a
• /
• pp.206-210
• /
• 1986

Double Ion Implantation methods are used to improve the stiffness os carrier profiles, and then the analytical solutions to Poisson`s equation are derived with summation of each carrier profile. Numerical analyses are done using profer boudary conditions and the results show that the improvement of voltage-dependent-capacitance ratio (C(!)/C(25)) is obtained up to B.6. The third ion implantation is for the enhancement of the Schottky barrier height.

• 전기의세계
• /
• v.28 no.1
• /
• pp.53-58
• /
• 1979

In the microwave heating system, a ferroresonant transformer is used to regulate the magnetron power fluctuation. For the simplification, nonlinear characteristics of the transformer and the magnetron are idealized to be piecewise linear. Dipped peak shape of the magnetron current is explained qualitatively by considering the fundamental and third harmonic frequency components in the circuit. Design equations providing the values of the leakage inductance, turn ratio of the transformer and the capacitance are derived analytically by cosnidering the fundamental frequency component only. The ferroresonant transformer is designed to obtain a required regulation and high input power factor from the derived design equations, and analytical calculations are compared with experimental measurements.

• Applied Chemistry for Engineering
• /
• v.24 no.2
• /
• pp.201-207
• /
• 2013

In this study, the surface of a phenol based activated carbon (AC) used as an electrode in an electric double layer capacitor was modified via boric acid treatment for the capacitance investigation. The effect of boric acid treatment on electrochemical performance was also investigated. The AC surface functional groups ratio of quinone-like (O=C) which is electrochemical active functional groups was increased after the boric acid treatment. And, boric acid treated AC showed an increase in the specific surface area, total pore volume, and micropore volume. In case of optimum boric acid treated AC, its specific capacitance increased by 20% in comparison to that of untreated AC. These results demonstrate that a boric acid treated carbon surface-based electric double layer capacitor electrode effectively enhances specific capacitance.

• Journal of IKEEE
• /
• v.18 no.1
• /
• pp.31-36
• /
• 2014

In this paper, self-resonant characteristics of transformers were analyzed in accordance with changes of characteristics regarding to the stray capacitance, the volume of winding and the winding ratio were organized by formulas. Generally, the stray capacitance is considered as an unnecessary factor in processing transformers design as well as one of the inherent characteristics. In particular, these characteristics can be appeared clearly in the high frequency driving and Electrical resonance occurs in transformer, according to coupling with a magnetic factor at a particular frequency. In the case of high-voltage output applications, such as medical equipments, It is required to output high-voltage gain. Therefor, If Self-Resonant Characteristic is applied to High-Voltage transformer design, Not only the transformer and circuit but also related the system size can be reduced. So we propose it as one of additional high voltage transformer design methods.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.7 no.2
• /
• pp.33-42
• /
• 1970

This report is concerned with the fahrication with the falricationof silicon VVC diode by the double diffusion planer technique. At first, some design charts for VVC diode were derived by considering the voltage-capacitance relations, the critical field intensity at the metallurgical junction, and the cut-off frequency of the diode. These charts enables the fabrication engineers to design VVC diode easily without going into the sophisticated design theory. We started with a 2.5 ohm-cm n-type epitaxial silicon wafer. The phosphorous was diffused by POCl3 impurity source. Then boron diffusion followed make hyperabrupt p-n junction by BN source. The maximum to minimum capacitance ratio of the diode as a tuning diode for a TV tuner made in these experiments was 4:1. Measured electrical characteristics of the sample diodes showed in good agreement with the theoretical expectations. Slicing and polishing technique of the silicon wafer and diffusion technique of the impurity atoms, which were employed in our study, are also stated briefly in this report.