Even in an era where 8-meter class telescopes are common, small telescopes are considered very valuable research facilities since they are available for rapid follow-up or long term monitoring observations. To maximize the usefulness of small telescopes in Korea, we established the SomangNet, a network of 0.4{1.0 m class optical telescopes operated by Korean institutions, in 2020. Here, we give an overview of the project, describing the current participating telescopes, its scientic scope and operation mode, and the prospects for future activities. SomangNet currently includes 10 telescopes that are located in Australia, USA, and Chile as well as in Korea. The operation of many of these telescopes currently relies on operators, and we plan to upgrade them for remote or robotic operation. The latest SomangNet science projects include monitoring and follow-up observational studies of galaxies, supernovae, active galactic nuclei, symbiotic stars, solar system objects, neutrino/gravitational-wave sources, and exoplanets.

Processing and characterization of graphene (Gr)-reinforced aluminium alloy 7075 (AA7075) microcomposites and nanocomposites are reported in this work. Composites are fabricated by mechanical alloying process at wet conditions. The bulk composites are prepared by uniaxial die pressing to get higher densification and sintered in an inert atmosphere. Density of the nanocomposites is higher than the microcomposites due to the reduction of grain size by increased milling time. X-ray diffraction (XRD) analysis confirms graphene interaction with the AA7075 matrix lattice spaces. The effective distribution of graphene with aluminium alloy is further confirmed by the Transmission Electron Microscopy (TEM) analysis. The hardness of the composites proportionally increases with the graphene addition owing to grain refinement. Wear morphology is characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Microcomposites reveal abrasive and ploughing wear mechanism of material removal from the surface. Nanocomposites show adhesive wear with delamination and particle pull-out from the material surface.

The “Sipadan and Ligitan” dispute was settled by the ICJ (2002), but its impact on basepoint for baseline and maritime delimitation on the Ambalat remains a contentious issue until now. Since the islands are used as basepoints by Malaysia that results in controversy between Indonesia and Malaysia. This essay will investigate the current situation over Ambalat regarding two basepoints islands for maintaining Equidistance Line in Disputed Area. It will discuss why Malaysia has no right to use the straight baseline or straight archipelagic baseline to connect the basepoints of Sipadan and Ligitan at Sabah and suggest measures to maintain equidistance line in Ambalat.

We investigate two abnormal CME-Storm pairs that occurred on 2014 September 10 - 12 and 2015 March 15 - 17, respectively. The first one was a moderate geomagnetic storm (Dstmin  -75 nT) driven by the X1.6 high speed flare-associated CME (1267 km s−1) in AR 12158 (N14E02) near solar disk center. The other was a very intense geomagnetic storm (Dstmin  -223 nT) caused by a CME with moderate speed (719 km s−1) and associated with a filament eruption accompanied by a weak flare (C9.1) in AR 12297 (S17W38). Both CMEs have large direction parameters facing the Earth and southward magnetic field orientation in their solar source region. In this study, we inspect the structure of Interplanetary Flux Ropes (IFRs) at the Earth estimated by using the torus fitting technique assuming self-similar expansion. As results, we find that the moderate storm on 2014 September 12 was caused by small-scale southward magnetic fields in the sheath region ahead of the IFR. The Earth traversed the portion of the IFR where only the northward fields are observed. Meanwhile, in case of the 2015 March 17 storm, our IFR analysis revealed that the Earth passed the very portion where only the southward magnetic fields are observed throughout the passage. The resultant southward magnetic field with long- duration is the main cause of the intense storm. We suggest that 3D magnetic field geometry of an IFR at the IFR-Earth encounter is important and the strength of a geomagnetic storm is strongly affected by the relative location of the Earth with respect to the IFR structure.

We report a spatial uctuation analysis of the sky brightness in the near-infrared from observations towards the north ecliptic pole (NEP) by AKARI at 2.4 and 3.2 μm. As a follow up study of our previous work on the Monitor eld of AKARI, we used NEP deep survey data, which covered a circular area of about 0.4 square degrees, in order to extend uctuation analysis at angular scales up to 1000". After pre-processing, additional correction procedures were done to correct time varying components and instrumental effects such as MUXbleed. To remove resolved objects, we applied 2α clipping and point spread function (PSF) subtraction. We finally obtained mosaicked images which can be used for the study of various diffuse emissions in the near-infrared sky and found that there are spatial structures in the mosaicked images using a power spectrum analysis.

The recent updates of the North Ecliptic Pole deep (0.5 deg2, NEP-Deep) multi-wavelength survey covering from X-ray to radio-wave is presented. The NEP-Deep provides us with several thousands of 15 μm or 18 μm selected galaxies, which is the largest sample ever made at these wavelengths. A continuous filter coverage in the mid-infrared wavelength (7, 9, 11, 15, 18, and 24 μm) is unique and vital to diagnose the contributions from starbursts and AGNs in the galaxies out to z=2. The new goal of the project is to resolve the nature of the cosmic star formation history at the violent epoch (e.g. z=1{2), and to find a clue to understand its decline from z=1 to present universe by utilizing the unique power of the multiwavelength survey. The progress in this context is brie y mentioned.

Polarbear is a ground-based experiment located in the Atacama desert of northern Chile. The experiment is designed to measure the Cosmic Microwave Background B-mode polarization at several arcminute resolution. The CMB B-mode polarization on degree angular scales is a unique signature of primordial gravitational waves from cosmic in ation and B-mode signal on sub-degree scales is induced by the gravitational lensing from large-scale structure. Science observations began in early 2012 with an array of 1,274 polarization sensitive antenna-couple Transition Edge Sensor (TES) bolometers at 150 GHz. We published the first CMB-only measurement of the B-mode polarization on sub-degree scales induced by gravitational lensing in December 2013 followed by the first measurement of the B-mode power spectrum on those scales in March 2014. In this proceedings, we review the physics of CMB B-modes and then describe the Polarbear experiment, observations, and recent results.

The Eclipsing Binaries Minima (BIMA) Monitoring Project is a CCD-based photometric observational program initiated by Bosscha Observatory - Lembang, Indonesia in June 2012. Since December 2012 the National Astronomical Research Institute of Thailand (NARIT) has joined the BIMA Project as the main partner. This project aims to build an open-database of eclipsing binary minima and to establish the orbital period of each system and its variations. The project is conducted on the basis of multisite monitoring observations of eclipsing binaries with magnitudes less than 19 mag. Dierential photometry methods have been applied throughout the observations. Data reduction was performed using IRAF. The observations were carried out in BVRI bands using three dierent small telescopes situated in Indonesia, Thailand, and Chile. Computer programs have been developed for calculating the time of minima. To date, more than 140 eclipsing binaries have been observed. From them 71 minima have been determined. We present and discuss the O-C diagrams for some eclipsing binary systems.

We report a search for fluctuations of the sky brightness toward the North Ecliptic Pole with AKARI, at 2.4, 3.2, and 4.1 μm . The stacked images with a diameter of 10 arcminutes of the AKARI-Monitor Field show a spatial structure on the scale of a few hundred arcseconds. A power spectrum analysis shows that there is a significant excess fluctuation at angular scales larger than 100 arcseconds that cannot be explained by zodiacal light, diffuse Galactic light, shot noise of faint galaxies, or clustering of low-redshift galaxies. These findings indicate that the detected fluctuation could be attributed to the first stars of the universe, i.e., Population III stars.

The properties of SOHO/LASCO CMEs are subjected to projection effects. Their dependence on the source position is important to be studied. Our main aim is to study the dependence of CME properties on helio-longitude and latitude using the CMEs associated with type IIs observed by Wind/WAVES spacecraft (Deca-hecta metric type IIs - DH type IIs). These CMEs were identified as a separate population of geo-effective CMEs. We considered the CMEs associated with the Wind/WAVE type IIs observed during the period January 1997 - December 2005. The source locations of these CMEs were identified using their associated GOES X-ray flares and listed online. Using their locations and the cataloged properties of CMEs, we carried out a study on the dependence of CME properties on source location. We studied the above for three groups of CMEs: (i) all CMEs, (ii) halo and non-halo CMEs, and (iii) limb and non-limb CMEs. Major results from this study can be summarized as follows. (i) There is a clear dependence of speed on both the longitude and latitude; while there is an increasing trend with respect to longitude, it is opposite in the case of latitude. Our investigations show that the longitudinal dependence is caused by the projection effect and the latitudinal effect by the solar cycle effect. (ii) In the case of width, the disc centered events are observed with more width than those occurred at higher longitudes, and this result seems to be the same for latitude. (iii) The dependency of speed is confirmed on the angular distance between the sun-center and source location determined using both the longitude and latitude. (iv) There is no dependency found in the case of acceleration. (v) Among all the three groups of CMEs, the speeds of halo CMEs show more dependency on longitude. The speed of non-halo and non-limb CMEs show more dependency on latitude. The above results may be taken into account in correcting the projection effects of geo-effective CMEs.

The international cooperation project CIBER (Cosmic Infrared Background ExpeRiment) is a rocket-borne instrument, of which the scientific goal is to measure the cosmic near-infrared extra-galactic background to search for signatures of primordial galaxy formation. CIBER consists of a wide-field two-color camera, a low-resolution absolute spectrometer, and a high-resolution narrow-band imaging spectrometer. Currently, all the subsystems have been built, and the integration, testing, and calibration of the CIBER system are on process for the scheduled launch in June 2008.