• ETRI Journal
• /
• v.40 no.6
• /
• pp.693-698
• /
• 2018

This paper presents a true-time delay (TTD) using a commercial $0.13-{\mu}m$ CMOS process for wideband phased-array antennas without the beam squint. The proposed TTD consists of four wideband distributed gain amplifiers (WDGAs), a 7-bit TTD circuit, and a 6-bit digital step attenuator (DSA) circuit. The T-type attenuator with a low-pass filter and the WDGAs are implemented for a low insertion loss error between the reference and time-delay states, and has a flat gain performance. The overall gain and return losses are >7 dB and >10 dB, respectively, at 2 GHz-18 GHz. The maximum time delay of 198 ps with a 1.56-ps step and the maximum attenuation of 31.5 dB with a 0.5-dB step are achieved at 2 GHz-18 GHz. The RMS time-delay and amplitude errors are <3 ps and <1 dB, respectively, at 2 GHz-18 GHz. An output P1 dB of <-0.5 dBm is achieved at 2 GHz-18 GHz. The chip size is $3.3{\times}1.6mm^2$, including pads, and the DC power consumption is 370 mW for a 3.3-V supply voltage.

• Journal of Wind Energy
• /
• v.9 no.4
• /
• pp.24-31
• /
• 2018

Wind lidar application is increasing and its calibration method is required to use wind lidar as an alternative to the meteorological mast. A nacelle lidar calibration method is now being discussed in IEC 61400-50-3 (Wind energy generation systems - Part 50-3: Use of nacelle-mounted lidars for wind measurements), and the method is mainly based on the wind lidar beam line of sight (LOS) wind speed calibration suggested by DTU as DTU E-0020 (Calibrating Nacelle Lidars). In this paper, a LOS wind speed calibration method is introduced and a calibration example performed on Jeju island is presented. The results showed a slope of 1.011 and R2 of 0.997, which means that the LOS wind speed is highly correlated with the reference wind speed and is comparable. But LOS wind speed calibration requires a very long time due to its principle and environmental conditions, and a calibration method that can overcome this problem of uncontrollable environments needs to be developed.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.26 no.5
• /
• pp.203-209
• /
• 2022

A simplified method for earthquake response analysis of a rectangular liquid storage tank is proposed with fluid-structure interaction considered. In order to simplify the complex three-dimensional structural behavior of a rectangular liquid storage tank, it is assumed that structural deformation does not occur in the plane parallel to the direction in which the earthquake ground motion is applied but in the plane perpendicular to the direction. The structural deformation is approximated by combining the natural modes of the simple beam and the cantilever beam. The hydrodynamic pressure, the structure's mass and stiffness, and the hydrodynamic pressure's added mass are derived by applying the Rayleigh-Ritz method. The natural frequency, structural deformation, pressure, effective mode mass, and effective mode height of the rectangular liquid storage tank are obtained. The structural displacement, hydrodynamic pressure, base shear, and overturning moment are calculated. The seismic response analysis of an example rectangular liquid storage tank is performed using the proposed simplified approach, and its accuracy is verified by comparing the results with the reference solution by the finite element method. Existing seismic design codes based on the hydrodynamic pressure in rigid liquid storage tanks are observed to produce results with significant errors that cannot be ignored.

• Nuclear Engineering and Technology
• /
• v.55 no.6
• /
• pp.1994-1998
• /
• 2023

This study quantitatively evaluated the source term of a linear accelerator according to target thickness for a 6-20 MeV electron beam using MCNP6. The elements of the target were tungsten and copper, and a composite target and single target were simulated by setting different thickness parameters depending on energy. The accumulation of energy generated through interaction with the collided target was evaluated at 0.1-mm intervals, and F6 tally was used. The results indicated that less than 3% reference error was maintained according to the MCNP recommendations. At 6, 8, 10, 15, 18, and 20 MeV, the energy accumulation peaks identified for each target were 0.3 mm in tungsten, 1.3 mm in copper, 1.5 mm in copper, 0.5 mm in tungsten, 0.5 mm in tungsten, and 0.5 mm in tungsten. For 8 and 10 MeV in a single target consisting only of copper, the movement of electrons was confirmed at the end of the target, and the proportion of escaped electrons was 0.00011% and 0.00181%, respectively.

• The Journal of the Acoustical Society of Korea
• /
• v.28 no.8
• /
• pp.755-760
• /
• 2009

In this paper, we apply a reverberation suppression method using difference of singular values to improve the short-distance underwater obstacle detection probability in reverberation environment induced by a linear frequency modulation signal. The reverberation suppression method using difference of singular values suppresses LFM reverberation based on subtracting the singular values for a reference beam, assumed to contain only the reverberation, from those for the current beam of interest, assumed to contain the reverberation and target echo. For the validation, the reverberation suppression method using difference of singular values is applied to real oceanic data, which are acquired using the cross type array.

• The Journal of the Acoustical Society of Korea
• /
• v.26 no.3
• /
• pp.129-135
• /
• 2007

In this paper. we propose a prewhitening method for the km reverberation to enhance the target signal. The proposed algorithm uses the dechirping method which inversely compensates the frequency chirp rate of LFM and transforms the LFM reverberation to have stationary frequency property in each data block. Also, using the left and right adjacent beam signals as reference signals. we model frequency response of each data block by AR coefficients. From these coefficients, we implement inverse filter and prewhiten the LFM reverberation of the center beam efficiently.

• Progress in Medical Physics
• /
• v.35 no.1
• /
• pp.10-15
• /
• 2024

Purpose: This study aimed to comprehensively investigate the diverse characteristics of a novel commercial bolus, CLEANBOLUS-WHITE (CBW), to ascertain its suitability for clinical application. Methods: The evaluation of CBW encompassed both physical and biological assessments. Physical parameters such as mass density and shore hardness were measured alongside analyses of element composition. Biological evaluations included assessments for skin irritation and cytotoxicity. Dosimetric properties were examined by calculating surface dose and beam quality using a treatment planning system (TPS). Additionally, doses were measured at maximum and reference depths, and the results were compared with those obtained using a solid water phantom. The effect of air gap on dose measurement was also investigated by comparing measured doses on the RANDO phantom, under the bolus, with doses calculated from the TPS. Results: Biological evaluation confirmed that CBW is non-cytotoxic, nonirritant, and non-sensitizing. The bolus exhibited a mass density of 1.02 g/cm³ and 14 shore 00. Dosimetric evaluations revealed that using the 0.5 cm CBW resulted in less than a 1% difference compared to using the solid water phantom. Furthermore, beam quality calculations in the TPS indicated increased surface dose with the bolus. The air gap effect on dose measurement was deemed negligible, with a difference of approximately 1% between calculated and measured doses, aligning with measurement uncertainty. Conclusions: CBW demonstrates outstanding properties for clinical utilization. The dosimetric evaluation underscores a strong agreement between calculated and measured doses, validating its reliability in both planning and clinical settings.

• Tribology and Lubricants
• /
• v.28 no.4
• /
• pp.173-177
• /
• 2012

We used contact resonance force microscopy (CRFM) technique to determine the quantitative elastic properties of multiple materials integrated on the sub micrometer scale. The CRFM approach measures the frequencies of an AFM cantilever's first two flexural resonances while in contact with a material. The plain strain modulus of an unknown or test material can be obtained by comparing the resonant spectrum of the test material to that of a reference material. In this study we examined the following bumping materials for flip chip by using copper electrode as a reference material: NiP, Solder (Sn-Au-Cu alloy) and under filled epoxy. Data were analyzed by conventional beam dynamics and contact dynamics. The results showed a good agreement (~15% difference) with corresponding values determined by nanoindentaion. These results provide insight into the use of CRFM methods to attain reliable and accurate measurements of elastic properties of materials on the nanoscale.

• Progress in Medical Physics
• /
• v.6 no.2
• /
• pp.29-34
• /
• 1995

The wedge factor is defined as a ratio of the absorbed dose in a phantom at a depth of reference point on the central axis with the wedge in the place to the absorbed dose at the same point with the wedge removed. We attempted to show the wedge factors dependence on the field sizes. The wedge factors were measured at various field sizes on 6MV and 15MV x-ray of Varian Clinac 1800 and 5MV x-ray of Philips SL75/5. The single wedge factor measured for a reference field size(10cmx10cm) may not be valid for all field sizes. For the thick wedge, especially an autowedge on Philips SL75/5 for maximum field size width 30cm. the error can be significant(6.6％). Therefore, in the presence of a wedge filter in the beam, a field size dependent wedge factor may be necessary in the treatment dose calculations.

• Journal of the Korean Vacuum Society
• /
• v.11 no.4
• /
• pp.218-224
• /
• 2002

A domestic round robin test(RRT) for the quantitative analysis of minor impurities was performed by a standard procedure and standard reference material. The certified reference material(CRM)s for B-doped Si thin film and analysis specimens and the analysis specimens were prepared by an ion beam sputter deposition method. These samples were certified by inductively coupled plasma mass spectrometry(ICP-MS) with isotope dilution method which il one of the most quantitative methods in chemical analysis. By using an international standard procedure(ISO/DIS-l4237) for the quantitative analysis of B in Si by SIMS, a domestic RRT was performed for these specimens. Although only a few laboratories participated in this RRT, the average B concentration well agreed with the certified value within 2% error.