• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.11a
• /
• pp.418-421
• /
• 2003

Today, much terminologies such as noise spectrum, Sharpness, contrast, MTF had been defined for Image quality revaluation of radiation Image. Since development of Xeroradiography In the 1970s, Digital radiation detector that use amorphous selenium was developed. The aim of this research is to analyze physical phenomenon of digital radiation detector that use amorphous selenium. Result of Monte Carlo simulations on amorphous selenium based on physical properties(creation of electron-hole pairs) by induced x-ray are described. From the simulation, intrinsic point spread function(PSF) was found and used to observe modulation transfer function(MTF). We investigated how PSF and MTF changed with various x-ray energy. This result can be used to design digital x-ray detector based on a-Se.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1038-1040
• /
• 2005

This paper describes the optimal design, construction and performance evaluation of voltage divider used in high power testing laboratory for voltage measuring system. These dividers, which are of R, C, R&C type voltage dividers, the voltage to be measured range from voltage to several ten kilovolts, the frequency of the signals has a bandwidth from DC to megaHertz Measuring transient voltage and currents in the high voltage power laboratory is generally accompanied by electromagnetic interface and induced noise. above all, the measuring capabilities of voltage measuring system are dependent upon short response time and it must be as free as possible of inductive effects. In this paper presents both characteristic of voltage divider and design of voltage measuring system.

• Journal of Photoscience
• /
• v.2 no.1
• /
• pp.19-25
• /
• 1995

Picosecond time-resolved and static protein fluorescence spectra and absorption spectra of octopus rhodopsin, a photorecepting protein, are measured and compared with those of bacteriorhodopsin, a photon-induced proton pumping protein, to understand the protein conformations and functions of octopus rhodopsin and its deprotonated photocycle intermediate. The bluer and weaker absorption of retinal indicates that octopus rhodopsin is better in thermal noise suppression but less efficient in light harvesting than bacteriorhodopsin. The protein fluorescence of octopus rhodopsin shows the characteristic of Trp only and the uantum efficiency and lifetime variations may result primarily from variations in the coupling strength with the retinal. The stronger intensity by four times and larger red shift by 12 nm of fluorescence suggest that octopus rhodopsin has more open and looser structure compared with bacteriorhodopsin. Fluorescence decay profiles reveal two decay components of 300 ps (60%) and 2 ns (40%). The deprotonation of protonated Schiff's base increases the shorter decay time to 500 ps and enhances the fluorescence intensity by 20%. The fluorescence and its decay time from Trp residues near retinal are influenced more by the deprotonation. The increase of fluorescence intimates that protein structure becomes loosened and relaxed further by the deprotonation of protonated Schiff's base. The driving force of sequential changes initiated by absorption of a photon is too exhausted after the deprotonation to return the intermediate to the ground state of the begun rhodopsin form.

• Journal of KSNVE
• /
• v.9 no.2
• /
• pp.324-330
• /
• 1999

With the increase of track density, high rotational speed and the compatibility for various media such as CD-ROM, CD-R/RW, DVD-ROM/RAM/RW etc. in optical disk drive, the effective anti-vibration design is so crucial for robust operaton. Especailly when the drive is self-excited by unbalanced disk, internal sled base vibration and its external transmission to the case bring about so severe problem. Generally these two consideration points the practical anti-vibration design process to control thses two conflictive properties using finite element analysis. As an example of the design process, Duro 25 and 40 visco-elastic rubber mount was selected and analyzed. The stiffness obtained from FEM rubber model was well matched with the experiments. Also it was confirmed that the internal and external vibration induced from unbalanced disk have good agreement with experimental results. The proposed design process is adopted to the slim-type optical disk drive.

• Structural Engineering and Mechanics
• /
• v.73 no.4
• /
• pp.367-379
• /
• 2020

In recent railway projects where the railway connects between cities, newly planned tunnels are often located close to, or beneath an existing tunnel. Many claims and petitions have voiced public concern about the vibration and noise resulting from the situation. Vibrations and noises are engineering issues as well as environmental problems, and have become more important as people have become more concerned with their the quality of life. However, it is unlikely that the effects of vibration in situations where trains simultaneously pass a multileveled tunnel crossing have been appropriately considered in the phase of planning and design. This study investigates the superposition characteristic of ground-born vibrations from a multileveled tunnel crossing. The results from model tests and numerical analysis show that the ground-born vibration can be amplified by a maximum of about 30% compared to that resulting from the existing single tunnel. Numerical parametric study has also shown that the vibration amplification effect increases as the ground stiffness, the tunnel depth, and the distance between tunnels decrease.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.05a
• /
• pp.139-142
• /
• 2009

Rapid developments in the field of electronic communication have given people's daily life much more convenience and abundance. However, making precise electrical and electronic devices and control systems lighter, smaller, and faster have caused lots of problems such as interference of external electric source, malfunction brought by electric fast transient(EFT), and influence on human body. In this research, the EMC filter in the high powered breaker was designed and fabricated as a countermeasure. The filter attenuated noise more than 30 ~ 75 dB in the range of 10 MHz ~ 1.5 GHz. And, when the EFT of 4 kV in the level 4 of IEC 61000-4-4 was induced, it was soon suppressed to 600 V.

• Geomechanics and Engineering
• /
• v.11 no.6
• /
• pp.821-845
• /
• 2016

Extensive researches on distribution of earthquake induced damages in different regions have shown that geological and geotechnical conditions of the local soils significantly influence behavior of alluvial areas under seismic loading. In this article, the site of Babol city which is formed up of saturated fine alluvial soils is considered as a case study. In order to reduce the uncertainties associated with earthquake resistant design of structures in this area (Babol city), the required design parameters have been evaluated with consideration of site's dynamic effects. The utilized methodology combines experimental ground ambient noise analysis, expressed in terms of horizontal to vertical (H/V) spectral ratio, with numerical one-dimensional response analysis of soil columns using DEEPSOIL software. The H/V spectral analysis was performed at 60 points, experimentally, for the region in order to estimate both the fundamental period and its corresponding amplification for the ground vibration. The investigation resulted in amplification ratios that were greater than one in all areas. A good agreement between the proposed ranges of natural periods and alluvial amplification ratios obtained through the analytical model and the experimental microtremor studies verifies the analytical model to provide a good engineering reflection of the subterraneous alluviums.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.05a
• /
• pp.383-386
• /
• 2009

Todays, many young people suffer from noise-induced hearing loss by using wearable hearing devices, such as Bluetooth headset. This paper present hearing loss reduction algorithms considering individual hearing characteristics and threshold of feeling for Bluetooth headset. Experimental results using CSR Bluetooth headset example design board(DEV-PC-1645) show that individuals may be able to perceive without the inconvenience at the less sound intensity and the more sensitive frequency bands. As a result, we may prevent hearing loss to reduce excessive sound energy in each frequency bands.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.68 no.3
• /
• pp.430-438
• /
• 2019

For a pump or a compressor motor, a high periodic load torque variation is induced by the mechanical works, and it causes system vibration and noise. To minimize these problems, load torque compensation method, injecting periodic torque current, could be utilized. However, with the sensorless control method, which is usually utilized in the pump and compressor for low cost, the periodic torque current degrades the accuracy of the rotor position estimation owing to the inductance variation. This paper analyzes the rotor position and speed estimation error of sensorless control method with constant motor parameters under period loading. Assuming the constant speed by the accurate load torque compensation, the speed error equation is derived in frequency domain with inductance depending on the stator current. Further, it is also shown that the rotor position error could be minimized by compensating the inductance variation. The simulation and experimental results verify that the derived speed error model and the validity of the inductance compensation method.

• ETRI Journal
• /
• v.46 no.2
• /
• pp.323-332
• /
• 2024

Receiver and transmitter monolithic microwave integrated circuit (MMIC) multifunction chips (MFCs) for active phased-array antennas for Ka-band satellite communication (SATCOM) terminals have been designed and fabricated using a 0.15-㎛ GaAs pseudomorphic high-electron mobility transistor (pHEMT) process. The MFCs consist of four-channel radio frequency (RF) paths and a 4:1 combiner. Each channel provides several functions such as signal amplification, 6-bit phase shifting, and 5-bit attenuation with a 44-bit serial-to-parallel converter (SPC). RF pads are implemented on the bottom side of the chip to remove the parasitic inductance induced by wire bonding. The area of the fabricated chips is 5.2 mm × 4.2 mm. The receiver chip exhibits a gain of 18 dB and a noise figure of 2.0 dB over a frequency range from 17 GHz to 21 GHz with a low direct current (DC) power of 0.36 W. The transmitter chip provides a gain of 20 dB and a 1-dB gain compression point (P1dB) of 18.4 dBm over a frequency range from 28 GHz to 31 GHz with a low DC power of 0.85 W. The P1dB can be increased to 20.6 dBm at a higher bias of +4.5 V.