• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2000.10a
• /
• pp.186-189
• /
• 2000

In this paper, we have designed a bandpass filter to apply the downconverter of the K-band Mu-hung-hwa satellite. To pass only the 25-30% of the bandwidth at the center frequency of 19.6GHz, we have designed a six-order interdigital bandpass filter using microstrip lines. Simulation result of optimization show that insertion loss is -0.275dB and reflection coefficient is -20.95dB at the passband frequency. measurement is determined center frequency, 19.150Hz, insertion loss, -4.1dB, input reflection coefficient. -l5dB and output reflection coefficient -l6dB.

• Electrical & Electronic Materials
• /
• v.10 no.6
• /
• pp.533-540
• /
• 1997

The microwave dielectric properties of ((P $b_{1-x}$ C $a_{x}$)Zr $O_3$ and (P $b_{0.63}$,C $a_{0.37-x}$ $M_{x}$)Zr $O_3$(M=Mg,Sr) ceramics were investigated. In (P $b_{1-x}$ C $a_{x}$)Zr $O_3$ (X=0.33~0.40) ceramics, high quality factor and small temperature coefficient of resonant frequency were obtain in (P $b_{0.63}$C $a_{0.37}$)Zr $O_3$with perovskite structure. In the case of (P $b_{0.63}$C $a_{0.37-x}$M $g_{x}$)Zr $O_3$ dielectric constant temperature coefficient of resonant frequency increased and quality factor decreased due to increase of polarization of A-O bonding. When replacing Ca ion with Sr ion with large ion radius, polarization decreased with increased of bonding length and thus dielectric constant and temperature coefficient of resonant frequency decreased.decreased.creased.

• Journal of Korea Water Resources Association
• /
• v.48 no.7
• /
• pp.523-533
• /
• 2015

In this study, the effectiveness of overflow improvement of weir was tested by conducting hydraulic experiments at the designated spot for installment of side weir under the condition of installment of hydraulic structures such as small reservoir in mainstream. The height of the reservoir was set up as a third of that of the weir, accordingly the rate of the height of the weir and the distance of the reservoir from the weir($B_h/L_b$) were 0.05, 0.025, 0.0167 each. As a result, overflows per unit width increased by 8.1%, 5.4% and 3.9% perspectively. A new discharge coefficient that adds $B_h/L_b$ as parameter to the existing discharge coefficient of trapezoidal broad crested side weir was suggested and the application of the new formula of discharge coefficient by comparing measured overflow with calculated overflow was identified.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.459-462
• /
• 2006

The diffuse attenuation coefficient for down-welling irradiance ($K_d$) is an important parameter for ocean studies including remote sensing applications. For the vast ocean, ocean color remote sensing is the only possible means to get the fine-scale measurements of $K_d$. To develop a technique of estimating $K_d$ from remotely sensed data, the following underwater optical parameters (absorption coefficient (a), attenuation coefficient (c), scattering coefficient (b), diffuse attenuation coefficient ($K_d$), etc.) have been studied. For this research we conducted the field campaign around the Yellow Sea at $8{\sim}9$ June, 2006. We obtained a set of underwater optical parameter data: down-welling irradiance ($E_d$), up-welling irradiance ($E_u$) and up-welling radiance ($L_u$) using TriOS optical sensors and a, c coefficient using Spectral Absorption and Attenuation Meter (AC-S). We then derived $K_d$ values from $E_d$ for each depth.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.7
• /
• pp.948-955
• /
• 2003

Pressure coefficient in rotating discharge hole was measured to gain insight into the influence of rotation to the discharge characteristics of rotating discharge hole. Pressure measurements were done by the telemetry system that had been developed by the authors. The telemetry system measures static pressure using piezoresistive pressure sensors. Pressure coefficients in rotating discharge hole were measured in longitudinal direction and circumferential direction with various rotating speed and 3 pressure ratios. From the results, the pressure coefficient, and therefore the discharge coefficient, is known to decrease with the increase of Ro number owing to the increase of flow approaching angle to the discharge hole inlet. However, there exists critical Ro number where the decrease rate of discharge coefficient with the increase of Ro number changes abruptly; flow separation occurs from the discharge hole exit at this critical Ro number. Critical Ro number increases with the increase of length-to-diameter ratio, but the increase is small where the length-to-diameter ratio is higher than 3. The decrease rate of discharge coefficient with the increase of Ro number depends on the pressure recovery at the discharge hole, and the rate is different from each length-to-diameter ratio; it has tendency that the short discharge hole shows higher decrease rate of discharge coefficient.

• Journal of Magnetics
• /
• v.19 no.3
• /
• pp.215-220
• /
• 2014

This study investigates the dynamic magneto-mechanical behavior of magnetization-graded ferromagnetic materials Terfenol-D/FeCuNbSiB (MF). We measure the dynamic magneto-mechanical properties as a function of the DC bias magnetic field ($H_{dc}$). Our experimental results show that these dynamic magneto-mechanical properties are strongly dependent on the DC bias magnetic field. Furthermore, the dynamic strain coefficient, electromechanical resonance frequency, Young's moduli, and mechanical quality factor of Terfenol-D/FeCuNbSiB are greater than those of Terfenol-D under a lower DC bias magnetic field. The dynamic strain coefficient increases by a factor of between one and three, under the same DC bias magnetic field. In particular, the dynamic strain coefficient of Terfenol-D/FeCuNbSiB at zero bias achieves 48.6 nm/A, which is about 3.05 times larger than that of Terfenol-D. These good performances indicate that magnetization-graded ferromagnetic materials show promise for application in magnetic sensors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.346-347
• /
• 2005

In this study, in order to develop the low temperature sintering ceramics, PZT ceramics adding $MnO_2$, $B_2O_3$ were manufactured, and their piezoelectric and dielectric properties is investigated. The results of this study were gotten such as follows. The electromechanical coupling coefficient(kp) showed good properties on the whole, showed its maximum value 28.266 in specimens sintered at 1200[$^{\circ}C$]. The mechanical quality coefficient(Qm) showed its maximum value 162.61 in specimens sintered at 1200[$^{\circ}C$] and was increased by increasing sintering temperature. The dielectric constant showed the optimum values of 538.903 at specimen sintered at $1000^{\circ}C$.

• Bulletin of the Korean Mathematical Society
• /
• v.56 no.3
• /
• pp.691-702
• /
• 2019

We characterize coefficient multipliers from certain Dirichlet type spaces to Hardy spaces and weighted Bergman spaces.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5B
• /
• pp.449-458
• /
• 2008

This study is investigating experimentally the effect of upstream Froude number, weir height, weir length, and main channel width on the discharge coefficient of rectangular sharp crested side-weirs under subcritical flow conditions in a relatively wide rectangular open channel based on the De Marchi discharge coefficient $C_M$. The effects of four main influential parameters found by dimensional analysis, $Fr_1$, $h/y_1$, L/B, and $L/y_1$ are examined by the flume tests. New estimated equations for the discharge coefficients of sharp-crested side-weir are suggested based on the experimental results. The effect of $Fr_1$ for the discharge coefficient of sharp crested side weir is decreased in wide open channel and the relative importance of other influential parameters like $h/y_1$, L/B, and $L/y_1$ are increased. Also, the experimental results are compared with the results of other studies to extend the applicability of pre-suggested formulas for sharp-crested side-weir discharge coefficient.

• Journal of Magnetics
• /
• v.16 no.3
• /
• pp.211-215
• /
• 2011

The dynamic magnetostriction characteristics of an Fe-based nanocrystalline FeCuNbSiB alloy are investigated as a function of the dc bias magnetic field. The experimental results show that the piezomagnetic coefficient of FeCuNbSiB is about 2.1 times higher than that of Terfenol-D at the low dc magnetic bias $H_{dc}$ = 46 Oe. Moreover, FeCuNbSiB has a large resonant dynamic strain coefficient at quite low Hdc due to a high mechanical quality factor, which is 3-5 times greater than that of Terfenol-D at the same low $H_{dc}$. Based on such magnetostriction characteristics, we fabricate a new type of transducer with FeCuNbSiB/PZT-8/FeCuNbSiB. Its maximum resonant magnetoelectric voltage coefficient achieves ~10 V/Oe. The ME output power reaches 331.8 ${\mu}W$ at an optimum load resistance of 7 $k{\Omega}$ under 0.4 Oe ac magnetic field, which is 50 times higher than that of the previous ultrasonic-horn-substrate composite transducer and it decreases the size by nearly 86%. The performance indicate that the FeCuNbSiB/PZT-8/FeCuNbSiB transducer is promising for application in highly efficient magnetoelectric energy conversion.