• Journal of the Korean Ceramic Society
• /
• v.32 no.6
• /
• pp.748-760
• /
• 1995

Pyroelectric properties, figure of merits, and the other properties of the Pb(Zn1/3Nb2/3)O3-Pb(Fe1/2Nb1/2)O3 system, as expected to have excellent pyroelectric properties in the operating temperature range of pyroelectric type infrared sensor, were investigated. In the Pb(Zn1/3Nb2/3)O3-Pb(Fe1/2Nb1/2)O3 system, suppression of the pyrochlore phase depended on sintering condition, as like sintering temperature, holding time, sintering atmosphere. The specimen, sintered by the same composition atmosphere powder at 105$0^{\circ}C$ for 1.5h, possessed the best physical property. It was found that the piezoelectric parameters were mainly depended on the amount of spontaneous polarization and then the 0.2PZN-0.8PFN showed the best pyro- and piezoelectric properties. In terms of the experimental method, two pyroelectric-testing methods, i.e. static and dynamic methods, had a same tendency. Also the result of pyroelectric testing by the static method indicated that the diffuse phase transitiion resulted in the temperature difference of phase transition between dielectric constant and pyroelectric coefficient.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.3
• /
• pp.454-460
• /
• 2003

The modulated frequency dependence on the pyroelectric properties of LiTaO$_3$ single crystal was investigated by the dynamic method. The pyroelectric coefficient of LiTaO$_3$ single crystal was 2.1${\times}$$10^{-8}$/$\textrm{cm}^2$ㆍK. and figure of merits for the responsivity and the detectivity were 1.31${\times}$$10^{-10}$Cㆍcm/J and 1.47${\times}$$10^{-8}$C\ulcornercm/J. respectively. The voltage responsivity corresponded with the pyroelectric voltage exhibited the highest value as about 165V /W at 4Hz and then was in inverse proportion to the frequency over 20Hz. The noise equivalent power and the detectivity at 4Hz were 8.4${\times}$$10^{-9}$ W/Hz$^{1}$2/ and 2.2${\times}$$10^{7}$ cmㆍHz$^{1}$2//W, respectively. Therefore, we could found that LiTaO$_3$ single crystal shows a excellent pyroelectric properties in low frequency region for the human body detection.tection.

• Journal of the Optical Society of Korea
• /
• v.20 no.3
• /
• pp.396-400
• /
• 2016

Laser speckle patterns were used to monitor variations of thermal voltages of a cathode during a battery discharge. Discharge voltages measured with an oscilloscope were utilized as a figure of merit of thermal voltages in Zn metal. Using an optical imaging system, speckle patterns were taken for zinc metal surface over a time period of 3 minutes. Pixel sum distribution functions (PSDFs) were extracted from speckle patterns. Accumulated pixel sums quantified from PSDFs over an optimized grayscale range strongly correlated with discharge voltages. This suggested that dark matter or particles may have the capability of both absorbing and radiating thermal energies simultaneously. The black body-like properties were able to be validated by identifying coincidences with distinct features of a black body spectrum. The pixels belonging to the grayscale range were confirmed to represent dark matter of a speckle pattern. It was clear that dark matter was part of surface plasmon carriers. The proposed sensing system can be applied to monitor thermal energy variations in any material.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.178.2-178.2
• /
• 2015

In and Ga doped ZnO (IGZO) films were deposited on 5 nm thick Cu film buffered Polycarbonate (PC) substrates with RF magnetron sputtering and then the effect of Cu buffer layer on the optical and electrical properties of the films was investigated. While IGZO single layer films show the electrical resistivity of $1.2{\times}10-1{\Omega}cm$, IGZO/Cu bi-layered films show a lower resistivity of $1.6{\times}10-3{\Omega}cm$. Although the optical transmittance of the films in a visible wave length range is deteriorated by Cu buffer layer, IGZO films with 5 nm thick Cu buffer layer show the higher figure of merit of $2.6{\times}10-4{\Omega}-1$ than that of the IGZO single layer films due to the enhanced opto-electrical performance of the IGZO/Cu bi-layered films.

• Advances in aircraft and spacecraft science
• /
• v.9 no.4
• /
• pp.319-333
• /
• 2022

This work presents a numerical investigation of the aerodynamics and aero acoustics of the HVAB rotor in hover conditions. Two fully turbulent models are employed, the one-equation Spalart-Allmaras model and the two-equation k-ω SST model. Transition effects are investigated as well using the Langtry-Menter γ-Re θt transition transport model. The noise generation and propagation are being investigated using the Ffows-Williams Hawking model for far-field noise and the broadband model for near-field noise. Comparisons with other numerical solvers and with the PSP rotor test data are presented. The results are presented in terms of thrust and power coefficients, the figure of merit, surface pressure distribution, and Sound pressure level. Velocity, pressure, and vortex structures generated by the rotor are also shown in this work. In addition, this work investigates the contribution of different blade regions to the overall noise levels and emphasizes the importance of considering specific areas for future improvements.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.178.1-178.1
• /
• 2015

In and Ga doped ZnO (IGZO) thin films were prepared by radio frequency magnetron sputtering without intentional substrate heating on glass substrate and TiO2-deposited glass substrates to consider the effect of a thin TiO2 buffer layer on the optical and electrical properties of the films. The thicknesses of the TiO2 buffer layer and IGZO films were kept constant at 5 and 100 nm, respectively. Since the IGZO/TiO2 bi-layered films show the higher FOM value than that of the IGZO single layer films, it is supposed that the IGZO/TiO2 bi-layered films will likely perform better in TCO applications than IGZO single layer films.

• Journal of Powder Materials
• /
• v.20 no.5
• /
• pp.345-349
• /
• 2013

Carbon nanotube-dispersed bismuth telluride matrix (CNT/$Bi_2Te_3$) nanopowders were synthesized by chemical routes followed by a ball-milling process. The microstructures of the synthesized CNT/$Bi_2Te_3$ nanopowders showed the characteristic microstructure of CNTs dispersed among disc-shaped $Bi_2Te_3$ nanopowders with as an average size of 500 nm in-plane and a few tens of nm in thickness. The prepared nanopowders were sintered into composites with a homogeneous dispersion of CNTs in a $Bi_2Te_3$ matrix. The dimensionless figure-of-merit of the composite showed an enhanced value compared to that of pure $Bi_2Te_3$ at the room temperature due to the reduced thermal conductivity and increased electrical conductivity with the addition of CNTs.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.34S no.1
• /
• pp.72-79
• /
• 1997

Most open magnetic resonance imaging systems have used the planar gradient coils whose inductances were minimized through the magnetic energy minimization procedure in the spatial frequency domain. Though the planar gradient coils have smaller inductance than conventional gradient coils, the planar gradient coils often suffer from their poor magnetic field linearity. Scaling the spatial frequencies of the current density function designed by the magnetic energy minimization, magnetic field linearity of the planar gradient coils can be greatly improved with small sacrifice of gradient coil inductance. We have found that the figure of merit of the planar gradient coils, defined by the gradient strength divided by the linearity error and the inductance, can be improved by proposed technique.

• Nuclear Engineering and Technology
• /
• v.52 no.2
• /
• pp.360-365
• /
• 2020

A technique for the reduction of pulse pile-up effect in digital pulse-shape discrimination (PSD) of neutrons and gamma-rays with organic scintillation detectors is presented. The technique is based on an electronic reduction of the effective decay-time constant of scintillation pulses while retaining the PSD information of the pulses. The experimental results obtained with a NE213 liquid scintillation detector in a mixed radiation field of neutrons and gamma-rays are presented, demonstrating a figure of merit (FOM) of 1.20 ± 0.05 with an energy threshold of 350 keVee (electron equivalent energy) when the effective length of the pulses is reduced to 50 ns.

• Journal of the Semiconductor & Display Technology
• /
• v.16 no.2
• /
• pp.89-93
• /
• 2017

For various process pressures, aluminum doped zinc oxide(AZO) films were deposited by in-line pulsed-DC sputtering. The deposited AZO films were optically and electrically investigated and analyzed for the window layers of CIGS solar cell systems. As the pressure was increased from 9 mtorr to 15 mtorr, the thickness of AZO was decreased as a result of scattering and its sheet resistance was rapidly increased. The transmittance of AZO was slightly decreased as the pressure was increased and the calculation of figure of merit(F.O.M) was dependent on the sheet resistance. The structural characteristics of AZO thin films analyzed by X-ray diffraction(XRD) showed no significant dependency according to the pressure.