Cu-Ti thin films were fabricated using a combinatorial sputtering system to realize highly sensitive surface acoustic wave (SAW) devices. The Cu-Ti sample library was grown with various chemical compositions and electrical resistivity, providing important information for selecting the most suitable materials for SAW devices. Considering that acoustic waves generated from piezoelectric materials are significantly affected by the resistivity and density of interdigital transducer (IDT) electrodes, three types of Cu-Ti thin films with different Cu contents were fabricated. The thickness of the Cu-Ti thin films used in the SAW-IDT electrode was fixed at 150 nm. As the Cu content of the Cu-Ti films was increased from 31.2 to 71.3 at%, the resistivity decreased from 10.5 to 5.8 × 10-5 ohm-cm, and the density increased from 5.5 to 7.3 g/cm3, respectively. A SAW device composed of Cu-Ti IDT electrodes resonated at exactly 143 MHz without frequency shifts, but the full width at half maximum (FWHM) values of the resonant frequency gradually increased as the Cu content increased. This means that although the increase in Cu content in the Cu-Ti thin film helps to improve the electrical properties of the IDT electrode, the increased density of the IDT electrode deteriorates the acoustic performance of SAW devices.

We explored the effect of galaxy-galaxy interaction on the FIR-radio correlation of star-forming galaxies by comparing the qFIR parameter distribution between interacting and non-interacting galaxies. Our sample galaxies were selected from the SDSS Stripe 82 region, where relatively deep optical images are available in addition to ancillary FIR and radio data. The qFIR values were 2.73±0.49 and 2.53±0.90 for interacting and non-interacting galaxies, respectively. The t-test results indicated that the difference in qFIR values between the two categories is not statistically significant. Our findings align with those of previous studies suggesting that either FIR excess or radio excess occurs only transiently during brief timescales in the merger stages, rather than persisting throughout the majority of merger events identified by features such as tidal tails or double nuclei.

GMDSS 도입 이후에도 많은 해난사고가 증가하고 있다. 선박에서 사람이 물에 빠진 경우 구조신호를 전달하는 방법은 현 재 다양한 방법으로 연구 및 개발되고 있지만, 해상이동업무용으로 지정된 주파수를 사용하는 제품의 개발은 이루어진 바 없다. 이에 따라 본 논문에서는 ITU의 최신 개정안을 통해 도입이 결정된 종별 B AMRD 기술을 적용하여 MOB 장치를 설계하고 제작해 보았 다. 또한 제작된 송신기의 성능을 확인하기 위해 수신기와 사용자 인터페이스를 제작하여 기존의 전자해도와 연동해서 사용할 수 있 음을 확인하였다. 본 논문을 통해 AIS기술을 이용하는 종별 B의 AMRD 일반조건과 기술조건을 만족하고 해상환경에서 휴대가 쉽도 록 소형화하기 위한 집적화된 소자를 선택하여 MOB 장치를 설계 및 구현해 봄으로써 AIS의 우수한 통신이 실현되고 긴급 상황에서 신속한 대응 및 안전에 핵심적인 역할을 담당할 것이라 기대한다.

This study investigates the impact of magnetic turbulence on cosmic ray (CR) electrons through Fermi-II acceleration behind merger-driven shocks in the intracluster medium and examines how the ensuing synchrotron radio emission is influenced by the decay of magnetic energy through dissipation in the postshock region. We adopt simplified models for the momentum diffusion coefficient, specifically considering transit-time-damping resonance with fast-mode waves and gyroresonance with Alfvén waves. Utilizing analytic solutions derived from diffusive shock acceleration theory, at the shock location, we introduce a CR spectrum that is either shock-injected or shock-reaccelerated. We then track its temporal evolution along the Lagrangian fluid element in the time domain. The resulting CR spectra are mapped onto a spherical shell configuration to estimate the surface brightness profile of the model radio relics. Turbulent acceleration proves to be a significant factor in delaying the aging of postshock CR electrons, while decaying magnetic fields have marginal impacts due to the dominance of inverse Compton cooling over synchrotron cooling. However, the decay of magnetic fields substantially reduces synchrotron radiation. Consequently, the spatial distribution of the postshock magnetic fields affects the volume-integrated radio spectrum and its spectral index. We demonstrate that the Mach numbers estimated from the integrated spectral index tend to be higher than the actual shock Mach numbers, highlighting the necessity for accurate modeling of postshock magnetic turbulence in interpreting observations of radio relics.

In order to attract students to the radio universe, we have constructed a three-element radio interferometer in the National Youth Space Center, Goheung, Korea. It consists of three 1.8 m off-axis parabola antennas with driving systems, sideband separation receivers operating in 12 GHz, a narrow band digitizer, and correlation software. We have used as many commercial products as possible to reduce development costs. The maximum separation of 20 m gives an angular resolution of ∼4′, and the shortest baseline of 3.8 m prevents a serious missing flux. Fringes are detected for several radio sources, including the sun and Cas A. After a rough relative calibration, we have derived visibilities for the sun, whose amplitudes are decreasing for longer baselines. We have made a solar image using the visibility amplitudes and closure phases, referring to the 17 GHz image by Nobeyama Radioheliograph. Developing a flexible real-time correlator seems most crucial if this kind of the system is to be used for more rigorous scientific studies.

Tb3+-doped CaNb2O6 (CaNb2O6:Tb3+) thin films were deposited on quartz substrates at a growth temperature of 300 °C using radio-frequency magnetron sputtering. The deposited thin films were annealed at several annealing temperatures for 20 min and characterized for their structural, morphological, and luminescent properties. The experimental results showed that the annealing temperature had a significant effect on the properties of the CaNb2O6:Tb3+ thin films. The crystalline structure of the as-grown CaNb2O6:Tb3+ thin films transformed from amorphous to crystalline after annealing at temperatures greater than or equal to 700 °C. The emission spectra of the thin films under excitation at 251 nm exhibited a dominant emission band at 546 nm arising from the 5D4 → 7F5 magnetic dipole transition of Tb3+ and three weak emission bands at 489, 586, and 620 nm, respectively. The intensity of the 5D4 → 7F5 (546 nm) magnetic dipole transition was greater than that of the 5D4 → 7F6 (489 nm) electrical dipole transition, indicating that the Tb3+ ions in the host crystal were located at sites with inversion symmetry. The average transmittance at wavelengths of 370~1,100 nm decreased from 86.8 % at 700 °C to 80.5 % at an annealing temperature of 1,000 °C, and a red shift was observed in the bandgap energy with increasing annealing temperature. These results suggest that the annealing temperature plays a crucial role in developing green light-emitting CaNb2O6:Tb3+ thin films for application in electroluminescent displays.

Since the farside of the moon is a place to avoid arti cial radio frequency interference (RFI) created byhuman civilization, it is a most suitable place for searching technosignature, which are signs of technolog-ical civilization in the universe, in the radio band. The RFI is a factor that makes the study of searchingtechnosignature quite complicated because it is di cult to distinguish between technological signals pro-duced by human and extraterrestrial civilizations. In this paper, we review why the farside of the moon isthe best place to detect technosignature and also introduce radio observatories on the farside of the moonthat have been proposed in radio astronomy. The SETI (Search for Extraterrestrial Intelligence) projecton the farside of the moon is expected to be one of the main candidates for international collaborationresearch topics on lunar surface observatory.

This study deals with improvement plans and application results to improve the safety of secondary batteries and chargers applied to Tactical Multi-band Multi-role Radio(TMMR), a new military communication equipment. Due to the nature of the portable weapon system, the terminal structure and manufacturing process of the battery and charger were improved to strengthen resistance to vibration and shock generated during movement, and the battery structure was partially changed to secure resistance to mechanical shock generated when the charger was coupled. In addition, retrospective application was completed for all secondary batteries and chargers previously delivered for TMMR, helping the Korean military to operate next-generation radios in a safer environment.