Simultaneous Dual-frequency Research Articles

Acquisition Efficiency and Technical Repeatability of Dual-Frequency 3D Vector MR Elastography of the Liver.

MR elastography (MRE) at 60 Hz is widely used for staging liver fibrosis. MRE with lower frequencies may provide inflammation biomarkers. To establish a practical simultaneous dual-frequency liver MRE protocol at both 30 Hz and 60 Hz during a single examination and validate the occurrence of second harmonic waves at 30 Hz. Retrospective. One hundred six patients (48 females, age: 50.0 ± 13.4 years) were divided as follows: Cohort One (15 patients with chronic liver disease [CLD] and 25 healthy volunteers) with simultaneous dual-frequency MRE. Cohort Two (66 patients with CLD) with second harmonic MRE. 3-T, single- or dual-frequency MRE at 30 Hz and 60 Hz. Liver stiffness (LS) in both cohorts was evaluated with manually placed volumetric ROIs by two independent analyzers. Image quality was assessed by three independent readers on a 4-point scale (0-3: none/failed, fair, moderate, excellent) based on the depth of wave propagation with 1/3 incremental penetration. The success rate was derived from the percentage of nonzero quality scores. Measurement agreement, bias, and repeatability of LS were assessed using intraclass correlation coefficients (ICCs), Bland-Altman plots, and repeatability coefficient (RC). Mann-Whitney U tests were used to evaluate the differences in image quality between different methods. A P-value <0.05 was considered statistically significant. Success rate was 97.5% in Cohort One and 91% success rate for the second harmonic MRE in Cohort Two. The second harmonic and conventional MRE showed excellent agreement in LS (all ICCs >0.90). The quality scores for the second harmonic wave images were lower than those from the conventional MRE (Z = -4.523). Compared with conventional and second harmonic methods, simultaneous dual-frequency had better image quality, high success rate and the advantage of intrinsic co-registration, while the second harmonic method can be an alternative if custom waveform is not available. 3 TECHNICAL EFFICACY: Stage 1.

Thawing of goose meat by simultaneous dual frequency ultrasound for process efficiency: Thawing rate, quality attributes, structural characteristics

A novel method, simultaneous dual-frequency ultrasound (SDU 20 + 25, 20 + 28, 20 + 40, 20 + 50, 25 + 28, 25 + 40, 25 + 50, 28 + 40, 28 + 50 and 40 + 50 kHz) was proposed to enhance the thawing efficiency of goose meat (GM). The thawing rate, quality properties, water distribution/ migration, and structural characteristics was investigated. Compared with thawing under running water (RW), SDU considerably shortened the thawing time by 17.76–36.06%. The lowest thawing loss (13.36%) and surface hydrophobicity (67.76 μg) were observed for samples treated with SDU 28 + 50 kHz frequency mode. Furthermore, Fourier infrared spectroscopy and LF-NMR data indicated that SDU 28 + 50 kHz treated samples had a more stable secondary protein structure, the lowest free water, and the highest immobilized water, which reduced the migration of water in the GM and, eventually, thawing loss. The microstructure analysis showed that the muscle fibers in SDU 28 + 40 kHz, and 28 + 50 kHz thawed samples had minimal damage, was almost complete and dense, and the gaps between the fibers were tiny. Therefore, compared with control and the other frequency modes, SDU 28 + 50 kHz could notably shorten thawing time and conserve the quality of GM.

A Simultaneous Dual-frequency Scintillation Arc Survey of Six Bright Canonical Pulsars Using the Upgraded Giant Metrewave Radio Telescope

We use the upgraded Giant Metrewave Radio Telescope (uGMRT) to measure scintillation arc properties in six bright canonical pulsars with simultaneous dual-frequency coverage. These observations, at frequencies from 300 to 750 MHz, allowed for detailed analysis of arc evolution across frequency and epoch. We perform more robust determinations of frequency dependence for arc curvature, scintillation bandwidth, and scintillation timescale, and comparison between arc curvature and pseudo-curvature than allowed by single-frequency-band-per-epoch measurements, which we find to agree with theory and previous literature. We find a strong correlation between arc asymmetry and arc curvature, which we have replicated using simulations, and attribute to a bias in the Hough transform approach to scintillation arc analysis. Possible evidence for an approximately week-long timescale over which a given scattering screen dominates signal propagation was found by tracking visible scintillation arcs in each epoch in PSR J1136+1551. The inclusion of a 155-minute observation allowed us to resolve the scale of scintillation variations on short timescales, which we find to be directly tied to the amount of interstellar medium sampled over the observation. Some of our pulsars showed either consistent or emerging asymmetries in arc curvature, indicating instances of refraction across their lines of sight. Significant features in various pulsars, such as multiple scintillation arcs in PSR J1136+1551 and flat arclets in PSR J1509+5531, that have been found in previous works, were also detected. The simultaneous multiple-band observing capability of the upgraded GMRT shows excellent promise for future pulsar scintillation work.

A Square-Wave Stimulated DNA Analyzer Chip Featuring 120μW Power Consumption and Simultaneous Dual-Frequency Detection

DNA analyzing technologies are commonly used in prevention and treatment of various infectious diseases. A portable DNA analyzer based on impedance spectroscopy facilitates the testing, while low pow consumption is necessary to minimize the battery size. However, traditional impedance spectroscopy techniques utilize power-hungry sinusoid signal to stimulate the DNA sample. In this brief, we demonstrate a DNA analyzer chip with square-wave stimulation and detection. The spectral aliasing induced by the harmonics of square wave is avoided by a half-integer over-sampling technique. In this way, the chip eliminates the requirement of power-hungry filters in conventional works. In addition, the impedance spectroscopy corresponding to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3^{rd}$ </tex-math></inline-formula> harmonic is utilized to provide an extra stimulus frequency, enabling simultaneous DNA analysis at two frequencies. Fabricated in 65nm CMOS process, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in-vitro</i> DNA testing data of our chip matches favorably with the results of an electrochemical workstation (CHI760E). The proposed DNA analyzer chip consumes <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$120\mu \text{W}$ </tex-math></inline-formula> power, and doubles the analyzing speed by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3^{rd}$ </tex-math></inline-formula> harmonic based detection.

Effects of simultaneous dual-frequency divergent ultrasound-assisted extraction on the structure, thermal and antioxidant properties of protein from Chlorella pyrenoidosa

The aim of this study was to investigate the effects of simultaneous dual-frequency divergent ultrasound-assisted extraction (SDFUE) on the yield, structure, thermal and antioxidant activities of protein from Chlorella pyrenoidosa (CPP). Based on single factor experiments, the extraction conditions were optimized by response surface methodology (RSM). Under optimal conditions, ultrasonic power of 360 W, extraction temperature of 45 °C, 3% (w/v) alkali concentration and ultrasonic time of 20 min, the maximal extraction rate of CPP was 52.36 ± 0.31%, significantly higher than that of hot water extraction (HWE). In addition, the amino acid composition, the secondary and tertiary structure of CPP were significantly changed due to the unfolding of protein molecules and the exposure of hydrophobic groups. Moreover, the thermal property of CPP was more stable, the denaturation temperature and the heat required for denaturation were increased. Besides, the antioxidant properties of CPP (6 mg/mL) extracted by SDFUE showed that, the maximum 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was 86.96 ± 0.33%, maximum 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity was 59.07 ± 0.31%, maximum Fe2+ chelating capacity was 34.37 ± 0.43%, and the maximum 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) radical scavenging activity at pH 4.5 was 66.24 ± 0.98%, which were all improved obviously compared with that of HWE, PTIO trapping assay demonstrated that electron transfer (ET) was mainly involved in the antioxidant process of CPP. These findings revealed that ultrasound-assisted extraction not only increased the yield of CPP, but also enhanced its thermal and antioxidant properties, which was related to the changes of CPP structure. This work might break the traditional single-frequency ultrasonic extraction model and provide a reference for the utilization of ultrasonic extraction in the field of Chlorella pyrenoidosa as bioactive materials.

Application of ultrasound technology in the field of solid-state fermentation: increasing peptide yield through ultrasound-treated bacterial strain.

The increase of peptide yield contributed to reducing the usage of antibiotics in solid-state fermented feed. Ultrasound technology is used in the field of liquid-state fermentation to improve yield of fermented products but has not been utilized in the field of solid-state fermentation (SSF). The main objective of this study was to investigate the feasibility of improving peptide yield in SSF products through ultrasound-treated bacterial strain. The highest peptides content in soybean meal SSF products reached 153.28 mg g-1 , which increased by 15.05% compared with the control. This content value was acquired through treating the bacteria of Bacillus amyloliquefaciens by ultrasound before inoculating into soybean meal under the optimized mode and parameters (simultaneous dual-frequency ultrasound mode, frequency combination of 40/60 kHz, total power density of 40 W L-1 , time of 20 min, pulse-on and pulse-off times of 40 and 60 s, delayed inoculation time of 0 h). Fermenting with ultrasound-treated bacterial strain can effectively increase peptide yield, biomass and protease activity of soybean meal fermented products during the SSF prophase. After treating by ultrasound, the latent phase and logarithmic phase of the bacterial strain shortened by 1 and 3 h while the generation time reduced by 23.64%. In qualitative test of protease activity, diameter ratio (DR) value of ultrasound-treated bacterial cells enlarged by 12.0% compared with the control. Peptide yield of soybean meal SSF products can be improved through ultrasound-treated bacterial inoculum, which attributed to the promoting effect of ultrasound treatment on growth activity and protease production capability of bacterial cells. © 2021 Society of Chemical Industry.

Effects of ultrasound modification at different frequency modes on physicochemical, structural, functional, and biological properties of citrus pectin

Ultrasonic irradiation for modified pectin preparation has become a research hotspot, but the influence of ultrasonic frequency is rarely studied. Therefore, in this study, mono frequency (MFU) and simultaneous dual frequency (SDFU) ultrasounds were used to modify citrus pectin (CP), and the effects of different ultrasonic frequency modes on the physicochemical, structural, functional, and biological properties of CP were comparatively investigated. The results showed that ultrasonic irradiation at 40 kHz in the MFU mode led to a larger increment in the galacturonic acid content of CP, but greater reductions in its intrinsic viscosity, molecular weight, and degree of methoxylation than in the SDFU modes. Ultrasonic frequency had no significant influence on the main CP chain, but rather on its neutral sugar side chains. The scanning electron microscopy (SEM) results suggested that CP treated by ultrasound at 40 kHz in the MFU mode exhibited fewer aggregates or looser networks than other ultrasonic treatments. Compared with the original CP, ultrasound treatment at different frequency modes effectively enhanced the thermal stability of CP, but remarkably lowered its shear thinning fluid behavior and liquid-like property. Moreover, among ultrasonically treated CPs, the CP obtained through ultrasound at 40 kHz in MFU mode exhibited the best antioxidant activity and bile acid-binding capacity in vitro.

Influence of base material, tempered condition and hardening pattern on the residual stress profile of induction hardened gears

This paper discusses influences of the base material, pre-heat treatment and hardening pattern on the residual stresses of induction hardened gears with module 2 and 4 mm. The gears were hardened in a simultaneous dual frequency induction hardening process. After the hardening process, no peening was applied. Depending on the hardening pattern, base material and tempered condition, a wide range of residual stress profiles did occur, with the surface residual stresses reaching from compressive to tensile residual stresses at the tooth flank depending on the variant. In this paper, the main influence parameters on the residual stress profile will be identified.

Simultaneous multifrequency: A possible alternative to improve the efficacy of ultrasound treatment on cherry tomato during storage

The productiveness of ultrasound (US) is affected by its frequency, power, and time, which has been reported to be very effective during food treatment when combined with other techniques of treatments. The study was aimed to evaluate the effect of mono-frequency (MFU), simultaneous dual-frequency (SDFU), and simultaneous tri-frequency US (STFU) at treatment times of 5–25 min on microbial inactivation and nutritional quality of cherry tomato. Results revealed that within 10 min of sonication, SDFU was most effective compared with MFU toward inhibiting the spoilage microorganisms, delaying ripening as well as maintaining firmness, total phenolic, flavonoid, and antioxidant of the fruit during 21 days of storage at 4°C. Although STFU caused a higher reduction in microbial load after treatment, it, however, showed several adverse effects on the fruit during storage. Overall, SDFU treatment had great potential in preserving shelf life and nutritional value of cherry tomato during storage. Practical applications US treatment has been implemented toward improving the shelf life of fruit and vegetables. However, a high desirable result has been related to its combination with other physical or chemical methods. The remarkable inactivation of microorganisms obtained for the dual- and tri-frequency treatments under this study would contribute to the application of a nonthermal technique in the reduction of contaminants on ready-to-eat fresh products including cherry tomato. Furthermore, the positive effect of this treatment on the quality of the cherry tomato during storage indicated that this technique could be used to replace the common practice of combining US with chemical treatment in food preservation industries. Nevertheless, further exploration is needed toward determining the synergistic effect of these treatments with heat (thermosonication).

NASA's high-rate Ka-band downlink system for the NISAR mission

This paper provides a description and analyses of NASA's (National Aeronautics and Space Administration) high-rate Ka-band downlink system for the upcoming NISAR (NASA-ISRO Synthetic Aperture Radar) mission developed at the Jet Propulsion Laboratory (JPL). NISAR is a collaborative Earth-Science mission between NASA and the Indian Space Research Organisation (ISRO), which features an L-band SAR instrument and an S-band SAR instrument. The simultaneous dual-frequency radar system at peak rates will produce data at gigabit-per-second speeds, which drives the data-volume requirements. The key driving requirement for the Payload Communication Subsystem is to provide a minimum of 35 Terabits per day of radar science data to the ground. NASA's high-rate transmitter on the flight system is a software-defined radio based on the Universal Space Transponder platform, providing an offset quadrature phase shift key modulated waveform with Low-Density Parity Check encoding of the data transfer frames. Two transmitters used in a dual-polarization configuration with each transmitter providing two giga-symbols per second (Gsps) of coded data provides an aggregate rate of four Gsps. In this system, using the ISRO-provided 70-cm high-gain antenna, only 1 W of signal power is necessary on each polarization to overcome propagation losses and achieve a successful RF link. Several Near Earth Network (NEN) ground station sites (Alaska in the United States, Svalbard in Norway, and Punta Arenas in Chile) are baselined for the space-to-Earth communications link. Each ground station will also feature multiple upgrades to support NISAR's transmission starting with new Ka-band antennas, and new electronic units such as wideband downconverters and high-rate receivers. In addition, a baseband data processor called Data Acquisition Processor and Handling Network Environment (DAPHNE), newly developed by the NEN, provides data storage and connectivity to backhaul networks. With NISAR's unprecedented large volume of data (nearly 5 Petabytes over the mission duration), a cloud system enables science data processing cost reduction to the mission. The NASA downlink system described herein will be the first operational use of Gsps-class downlink rates on an Earth-Science mission.

Effect of ultrasound pretreatment with mono-frequency and simultaneous dual frequency on the mechanical properties and microstructure of whey protein emulsion gels

The effect of ultrasound pretreatment with mono-frequency ultrasound (MFU) and simultaneous dual frequency (SDFU) on rheology, texture, water holding capacity (WHC) and microstructure of whey protein emulsion gels was investigated. Also, the protein structure was displayed using circular dichroism and fluorescence spectrum. The Results showed that ultrasound could improve mechanical properties and change the microstructure of whey protein emulsion gel compared with the control. It was also found that, ultrasound could lead to decreasing in α-helix and increasing in random coil thereby exposing more tryptophan residues. As storage modulus (G'), texture hardness and WHC were negatively correlated with α-helix content, however, they had positive correlation with random coil content. Simultaneous dual frequency ultrasound exhibited the highest effect among the ultrasound pretreatments. It was indicated that the composite of oil droplet particulate aggregate network and protein aggregate network in the microstructure of emulsion gel might have resulted from enhanced molecular interactions of protein by ultrasound pretreatment. In conclusion, the dual frequency ultrasound was effective in improving the mechanical properties of whey emulsion gel when compared with the mono-frequency ultrasound.

Experimental Assessment of High Heating Rates in Induction Heating with Temperature-Sensitive Lacquers

The fast evolving temperature fields at the surface of induction-heated parts were measured by a contactless, optical method based on temperature-sensitive lacquers recorded with a high-speed imaging system. The positions of specific isotherms over time were precisely measured by image analysis. A 4340 steel cylinder and two spur gears of the same material were investigated. One spur gear was treated at high frequency, and the other one at simultaneous dual frequency. In both cases, the temperature started to rise at the root of the teeth and then expanded along the flanks. The heating rates were higher at the tips than at the roots for both treatments, with higher values for the dual-frequency treatment. The layer of transformed material was similar for both treatments, but the transformation temperature varied greatly. It was found to be 50-100 °C higher than the equilibrium values, depending on the local heating rate.

Impact of ultrasound pretreatment on hydrolysate and digestion products of grape seed protein

The effects of ultrasound pretreatment with different working modes, including mono frequency ultrasound (MFU), simultaneous dual frequency ultrasound (SDFU) and alternate dual frequency ultrasound (ADFU) using energy-gather counter flow ultrasound equipment, on the degree of hydrolysis (DH) of grape seed protein (GSP) hydrolysate and IC50 of GSP digestion products were studied. Amino acid composition analysis (AACA), ultraviolet–visible (UV) spectroscopy and atomic force microscopy (AFM) of GSP with different ultrasound pretreatments were measured. The results showed that MFU, SDFU and ADFU pretreatments improved the DH and reduced the IC50 of GSP significantly (P < .05). The MFU of 20 kHz and SDFU of 20/40 kHz showed higher ACE inhibitory activity within the MFU and SDFU groups, respectively. ADFU of 20/35 kHz produced the highest ACE inhibitory activity among the three working modes (MFU, SDFU and ADFU). AACA showed that all the working modes of the ultrasound pretreatment could increase the amount of hydrophobic amino acids and the total amino acids. The changes in UV spectra and amino acid analysis indicated the unfolding of protein structure and exposure of more hydrophobic groups by SDFU and ADFU pretreatments. AFM analysis of the GSP indicated that the microstructures were destroyed and the particle size reduced after dual-frequency ultrasound pretreatments. Therefore, energy-gather counter flow ultrasound pretreatment is an effective method to improve the DH and reducing the IC50 due to the changes of molecular conformation and effects on the microstructure by sonochemistry of GSP. In conclusion, it is necessary to select the frequency and working modes of ultrasound pretreatment for the preparation of ACE inhibitory peptide of GSP.

Simultaneous dual-frequency radio observations of S5 0716+714: A search for intraday variability with the Korean VLBI Network

This study aims to search for the existence of intraday variability (IDV) of BL Lac object S5 0716+714 at high radio frequencies for which the interstellar scintillation effect is not significant. Using the 21-meter radio telescope of the Korean VLBI Network (KVN), we present results of multi-epoch simultaneous dual-frequency radio observations. Single-dish observations of S5 0716+714 were simultaneously conducted at 21.7 GHz (K-band) and 42.4 GHz (Q-band), with a high cadence of 30-60 minute intervals.We observed four epochs between December 2009 and June 2010. Over the whole set of observation epochs, S5 0716+714 showed significant inter-month variations in flux density at both the K- and Q-bands, with modulation indices of approximately 19% for the K-band and approximately 36% for the Q-band. In all epochs, no clear intraday variability was detected at either frequency. The source shows monotonic flux density increase in epochs 1 and 3 and monotonic flux density decrease in epochs 2 and 4. In the flux density increasing phases, the flux densities at the Q-band increase more rapidly. In the decreasing phase, no significant flux density difference is seen at the two frequencies. The situation could be different close to flux density peaks that we did not witness in our observations. We find an inverted spectrum with mean spectral indices of -0.57+-0.13 in epoch 1 and -0.15+-0.11 in epoch 3. On the other hand, we find relatively steep indices of +0.24+-0.14 and +0.17+-0.18 in epochs 2 and 4, respectively. We conclude that the frequency dependence of the variability and the change of the spectral index are caused by source-intrinsic effects rather than by any extrinsic scintillation effect.

Improving the enzymolysis efficiency of potato protein by simultaneous dual-frequency energy-gathered ultrasound pretreatment: Thermodynamics and kinetics

The thermodynamics and kinetics of traditional and simultaneous dual frequency energy-gathered ultrasound (SDFU) assisted enzymolysis of potato protein were investigated to get the knowledge of the mechanisms on the SDFU’s promoting efficiency during enzymolysis. The concentration of potato protein hydrolysate and parameters of thermodynamic and kinetic during traditional and SDFU assisted enzymolysis were determined. The results showed that potato protein hydrolysate concentration of SDFU assisted enzymolysis was higher than traditional enzymolysis at the hydrolysis time of 60min (p<0.05) whereas not significantly different at 120min (p>0.05). In some cases, SDFU assisted enzymolysis took less hydrolysis time than traditional enzymolysis when the similar conversion rates of potato protein were obtained. The thermodynamic papameters including the energy of activation (Ea), enthalpy of activation (△H), entropy of activation (△S) were reduced by ultrasound pretreatment while Gibbs free energy of activation (△G) increased little (1.6%). Also, kinetic papameters including Michaelis constant (KM) and catalytic rate constant (kcat) decreased by ultrasound pretreatment. On the contrary, reaction rate constants (k) of SDFU assisted enzymolysis were higher than that of traditional enzymolysis (p<0.05). It was indicated that the efficiency of SDFU assisted enzymolysis was higher than traditional enzymolysis in a limited time. The higher efficiency of SDFU assisted enzymolysis was related with the decrease of Ea and KM by lowering the energy barrier between ground and active state and increasing affinity between substrate and enzyme.

A New Receiver Front-End for Simultaneous Dual-Frequency NMR Applications

To obtain certain information such as metabolic concentrations in neural or muscular tissues and other applications, it is necessary to design nuclear magnetic resonance (NMR) transmitters/receivers capable of operating at multiple frequencies, while maintaining a good performance at each frequencies. We have proposed a new NMR receiver front-end for simultaneous detection of proton and carbon nucleus. The system consists of two reception coils for carbon and hydrogen analysis, a multiband low-noise amplifier (LNA) for increasing the voltage level and a network for passive amplification, noise figure minimization and decreasing mutuality effect between two coils. The proposed coil set was designed, simulated and analyzed and also the signal to noise ratio (SNR) with quality factor have been calculated for it by simulation. The LNA has been designed in a 0.18[Formula: see text][Formula: see text]m CMOS technology and its gains for carbon and proton NMR signals are 45 and 48[Formula: see text]dB, respectively. The input referred noise for both signals is lower than 0.4[Formula: see text]nV/sqrt(Hz) and the power consumption is 4 mA from a single 1.8[Formula: see text]V supply.

Investigation of Heat Treatment of Gears Using a Simultaneous Dual Frequency Induction Heating Method

A heat treatment of gears (increasing hardness in the surface layers of gear teeth) significantly enhances the quality and performance of gears in terms of resistance to ware and abrasion and fatigue strength. Recently, a simultaneous dual frequency (SDF) induction heating technology has emerged as the most effective and efficient heat treatment method. It strives to achieve “uniform” temperature distributions along the outer contour of gears by applying two input currents simultaneously [1, 2]. The amplitude and frequency of both currents are regulated independently to control the hardening depth at the root and the tip of the gear teeth [3]. Obtaining the best combinations of the input frequencies and powers experimentally is very costly and time consuming. Thus, many researches have been concentrated on determining these parameters using simulation methods, but they require tremendous computational time and resources [4, 5]. In an effort to reduce computational costs in determining SDF input parameters, this paper proposes a 2D FE modeling method, and it experimentally evaluates the heat treatments of gears using a SDF induction heating system with the parameters obtained with 2D FE analysis.

PAGAN II: THE EVOLUTION OF AGN JETS ON SUB-PARSEC SCALES

We report first results from KVN and VERA Array (KaVA) VLBI observations obtained in the frame of our Plasma-physics of Active Galactic Nuclei (PAGaN) project. We observed eight selected AGN at 22 and 43 GHz in single polarization (LCP) between March 2014 and April 2015. Each source was observed for 6 to 8 hours per observing run to maximize the $uv$ coverage. We obtained a total of 15 deep high-resolution images permitting the identification of individual circular Gaussian jet components and three spectral index maps of BL Lac, 3C 111 and 3C 345 from simultaneous dual-frequency observations. The spectral index maps show trends in agreement with general expectations -- flat core and steep jets -- while the actual value of the spectral index for jets shows indications for a dependence on AGN type. We analyzed the kinematics of jet components of BL Lac and 3C 111, detecting superluminal proper motions with maximum apparent speeds of about $5c$. This constrains the lower limits of the intrinsic component velocities to $\sim0.98c$ and the upper limits of the angle between jet and line of sight to $\sim$20$\deg$. In agreement with global jet expansion, jet components show systematically larger diameters $d$ at larger core distances $r$, following the global relation $d\approx0.2r$, albeit within substantial scatter.

동시 이중주파수를 이용한 기어 열처리의 열·전자기 연성 해석

In this paper, Finite Element Analysis (FEA) for gear heat treatment using simultaneous dual frequency (SDF) induction heating is conducted. To do this, thermal-electromagnetic coupled FE model is built. A two dimensional FE model of gear and heater is introduced to reduce computation time. For more time-efficient analysis, harmonic analysis for electromagnetic model is adopted and transient analysis model, for heat transfer model. Through the coupled analysis, it can be found that the proposed FE model can solve for SDF induction heating of gear and heat treatment parameters can also be determined.

VERIFICATION OF THE ASTROMETRIC PERFORMANCE OF THE KOREAN VLBI NETWORK, USING COMPARATIVE SFPR STUDIES WITH THE VLBA AT 14/7 mm

The Korean VLBI Network (KVN) is a new mm-VLBI dedicated array with capability for simultaneous observations at multiple frequencies, up to 129 GHz. The innovative multi-channel receivers present significant benefits for astrometric measurements in the frequency domain. The aim of this work is to verify the astrometric performance of the KVN using a comparative study with the VLBA, a well established instrument. For that purpose, we carried out nearly contemporaneous observations with the KVN and the VLBA, at 14/7 mm, in April 2013. The KVN observations consisted of simultaneous dual frequency observations, while the VLBA used fast frequency switching observations. We used the Source Frequency Phase Referencing technique for the observational and analysis strategy. We find that having simultaneous observations results in a superior performance for compensation of all atmospheric terms in the observables, in addition to offering other significant benefits for astrometric analysis. We have compared the KVN astrometry measurements to those from the VLBA. We find that the structure blending effects introduce dominant systematic astrometric shifts and these need to be taken into account. We have tested multiple analytical routes to characterize the impact of the low resolution effects for extended sources in the astrometric measurements. The results from the analysis of KVN and full VLBA datasets agree within 2-$\sigma$ of the thermal error estimate. We interpret the discrepancy as arising from the different resolutions. We find that the KVN provides astrometric results with excellent agreement, within 1-$\sigma$, when compared to a VLBA configuration which has a similar resolution. Therefore this comparative study verifies the astrometric performance of KVN using SFPR at 14/7 mm, and validates the KVN as an astrometric instrument.