• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.74.2-75
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• 2021

We demonstrate that a deep learning classifier that only uses to gravitational wave (GW) detectors auxiliary channel data can distinguish various types of non-Gaussian noise transients (glitches) with significant accuracy, i.e., ≳ 80%. The classifier is implemented using the multi-scale neural networks (MSNN) with PyTorch. The glitches appearing in the GW strain data have been one of the main obstacles that degrade the sensitivity of the gravitational detectors, consequently hindering the detection and parameterization of the GW signals. Numerous efforts have been devoted to tracking down their origins and to mitigating them. However, there remain many glitches of which origins are not unveiled. We apply the MSNN classifier to the auxiliary channel data corresponding to publicly available GravitySpy glitch samples of LIGO O1 run without using GW strain data. Investigation of the auxiliary channel data of the segments that coincide to the glitches in the GW strain channel is particularly useful for finding the noise sources, because they record physical and environmental conditions and the status of each part of the detector. By only using the auxiliary channel data, this classifier can provide us with the independent view on the data quality and potentially gives us hints to the origins of the glitches, when using the explainable AI technique such as Layer-wise Relevance Propagation or GradCAM.

• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1819-1827
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• 2021

Land-use/cover change caused by rapid urbanization in South Korea is one of the concerns in flood risk management because groundwater recharge by precipitation hardly occurs due to an increase in impermeable surfaces in urban areas. This study investigated the hydrologic effects of land-use/cover on groundwater recharge in the Yeonje-gu district of Busan, South Korea. A statistical time series analysis was conducted with temporal variations of precipitation and groundwater level to estimate lag-time based on correlation coefficients calculated from auto-correlation function (ACF), cross-correlation function (CCF), and moving average (MA) at five sites. Landform and land-use/cover within 250 m radius of the monitoring wells(GW01, GW02, GW03, GW04, and GW05) at five sites were identified by land cover and digital map using Arc-GIS software. Long lag-times (CCF: 42-71 days and MA: 148-161 days) were calculated at the sites covered by mainly impermeable surfaces(GW01, GW03, and GW05) while short lag-times(CCF: 4 days and MA: 67 days) were calculated at GW04 consisting of mainly permeable surfaces. The results suggest that lag-time would be one of the good indicators to evaluate the effects of land-use/cover on estimating groundwater recharge. The results of this study also provide guidance on the application of statistical time series analysis to environmentally important issues on creating an urban green space for natural groundwater recharge from precipitation in the city and developing a management plan for hydrological disaster prevention.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1090_1091
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• 2009

In 2008, the global photovoltaic(PV) market reached 5.6GW and the cumulative PV power installed totalled almost 15GW compared to 9GW in 2007. Due to a favourable feed-in-tariff, Korea emerged in 2008 as the 4th largest PV market worldwide. PV power installation rose 495.5 percent to 268MW in 2008 compare to 45MW in 2007. And PV manufacturer will increase the capacity of production facilities by 910MW in 2009. If the 500MW cap is removed, the growth of the korea market will reach up to 1GW by 2013.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.31.3-31.3
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• 2016

Exploring a universe with gravitational waves (GWs) was only theoretical expectation for long time. In September 2015, the Laser Interferometer GW Observatory (LIGO) first detected GWs emitted from the collision of two stellar-mass black holes in cosmological distance (1.3 billion light years) on Earth. This confirms the existence of black-hole binary mergers, and further, opens a new field of GW astronomy. We begin our discussion with a list of important GW sources that can be detectable on Earth by large-scale laser interferometers such as LIGO. Focusing on compact objects such as neutron stars and black holes, we then discuss possible research in the context of GW astronomy. By coordinating with existing observatories, searching for electromagnetic waves or particles from astronomical objects, around the world, multi-messenger astronomy for the universe's most cataclysmic phenomena (e.g. gamma-ray bursts) will be available in the near future.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.58.1-58.1
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• 2019

Gravitational-wave (GW) sources for the next decades would be in majority binaries consisting of neutron stars and/or black holes reside in the extragalactic environment. For example, GW170817 was the first extragalactic neutron star - neutron star binary found by GW observations and it was proved the power of multi-messenger astronomy (MMA) including the KMTNet observations. With the ever increased sensitivity, the $3^{rd}$ observation run (O3) led by the advanced LIGO and advanced Virgo this year aims to search for more 'standard' populations as well as 'exotic' ones expected by stellar evolution. I will present highlights of on-going efforts by researchers in Korea and those in abroad for estimating physical parameters of a source. Mass, spin, distance, and location are prerequisite information to constrain theoretical understanding of the source formation and evolution. Furthermore, these information are to be shared with the international community for follow-up multi-messenger observations. I will present the observational accuracy expected for the future GW observations and discuss their implications. If time allows, I will make a few remarks on prospects of O3 with KAGRA collaborations, which many domestic researchers are closely involved in.

• Research in Plant Disease
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• v.22 no.2
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• pp.65-71
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• 2016

Cymbidium mosaic virus (CymMV) is a major virus infecting orchid plants and causing economic loss. In this study, the incidence of viral infection in Calanthe spp. at the Korean Institute of Calanthe was investigated using reverse transcription polymerase chain reaction. The CymMV infection rate was 42%, and the two viruses Odontoglossum ringspot virus and Cucumber mosaic virus had frequencies of 8% and 2%, respectively. Additionally, we characterized an isolate of CymMV, CymMV-GW, using biological tests and examined the nucleotide sequence properties of its complete genome. CymMV-GW induced chlorotic ringspots and chlorotic spot symptoms in inoculated leaves of Chenopodium amaranticolor and Nicotiana benthamiana, respectively. In this study, we have for the first complete genome sequence of CymMV-GW in Korea. The CymMV-GW genome was 6,225 nucleotides in length, excluding the poly-(A) tail, and showed whole-genome nucleotide and amino acid sequence identities of 97.7% and 100%, respectively, with the NJ-1 isolate of CymMV. Here, we report the complete genome sequence of the CymMV-GW isolate and viral infection rates for Calanthe spp. in Korea.

• The Journal of the Korean Society for Microbiology
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• v.18 no.1
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• pp.53-58
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• 1983

Enterotoxigenic E. coli is one of causative agents of the infantile diarrhea and traveler's diarrhea. A modified infant mouse assay(IMA) was developed for the detection of heat stable enterotoxin (ST) of E. coli isolated from diarrheal and control infants and assay system was established with using enterotoxin producing reference strains. The supernatant of the 24 hour-shaking culture of E. coli in Casamino Acid Yeast Extract Salt Broth(CYES-2) was ingested orally into the 2-4 day old ICR mice. After the mice were kept at $25^{\circ}C$ for 4 hours, they were sacrificed and the gut weight body weight ratio(GW/BW) was taken as the index of fluid accumulation induced by heat stable enterotoxin of E. coli. The results obtained were as follows; 1. The GW/BW responses of IMA tested with enterotoxin reference strains of E. coli(E. coli O148H28:$ST^+LT^+$, E. coli $O78H^-:ST^+LT^+$, E. coli O15H11:$ST^-LT^+$, E. coli O1H7:$ST^-LT^-$) appeared ta be ST dose-dependent, and not LT-dependent. From the dose-response curve, $25{\mu}l$ of culture supernatant was determined as test amount of the IMA. 2. Frequency distribution of IMA result from 643 strain of E. coli showed normal distribution at low GW/BW ratio and dispersed pattern at high GW/BW ratio. The GW/BW ratios of $0.056{\pm}0.004(mean{\pm}SD)$ of normal distribution which distributed from 0.044 to 0.068(P<0.01) was considered as ST negative. Thus the GW/BW ratio above 0.069 could be regarded as ST positive.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.31.3-31.3
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• 2018

On August 17th 2017, for the first time in the history, the gravitational wave (GW) detectors recorded signals coming from the merger of two neutron stars. This event was named as GW170817, and more interestingly, gamma-ray emission was detected 2 seconds after the gravitational wave signal, and 11 hours later, telescopes in Chile identified that the GW signal came from the NGC 4993 galaxy at the distance of about 40 Mpc. This is again the first time that electromagnetic (EM) signals are detected for a GW source. The follow-up observations by astronomers all around the world, including our group in Korea, successfully identified the optical emission as the kilonova, the elusive optical/NIR counterpart that has been proposed to originate from a neutron star merger. This whole event started the new era of astronomy, so-called the "multi-messenger astronomy", where the combined information from GW and EM radiation reveals an unprecedented view of the universe. In this talk, I summarize this exciting event, and describe the efforts by Korean astronomers that have led to important discoveries about the kilonova and the host galaxy properties, and finally provide the future prospects.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.76.1-76.1
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• 2019

After the first identification of electromagnetic counterpart of gravitational wave source (GW170817), era of multi-messenger astronomy has begun. For specifying coordinate, magnitude, and host galaxy information, optical follow-up observation of GW source becomes important. The O3 run of LIGO / VIRGO started after April 2019. We present searching strategy of GW optical counterpart using the KMTNet. By performing tiling observation of high probability area in GW localization map, we expect to observe early light-curve of GW optical counterpart. We will also present observation result for three gravitational wave events of binary black hole mergers. After identification of optical counterpart, we will study collision mechanism, progenitor, and characteristics of host galaxy using observation data of GW source.

• PNF and Movement
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• v.22 no.1
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• pp.129-137
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• 2024

Purpose: The aim of this study was to investigate and compare the risk factors focusing on the neck and lower back between general workers (GW) and mild intellectual disability workers (MIDW) in the automobile manufacturing industry. Methods: A total of 32 participants were required for this study design to achieve 80% power, 0.9 effect size, and an alpha level of 0.05. Each group consisted of 16 subjects, including GW and MIDW. Pain levels in the neck and lower back were measured for all participants using the visual analog scale (VAS). A dual digital inclinometer was used to measure the range of motion (ROM) in the neck and lower back three times, and the average was used for analysis. The independent t-test was used to compare between the wo groups. Cohen's d effect analysis was employed to determine the effect size. The significant level was set at 0.05. Results: In the MIDW, neck pain was significantly higher, and left cervical flexion was significantly decreased compared with the GW. There was no significant difference in lower back pain between the MIDW and GW. However, both lumbar flexion and extension, as well as lateral flexion, were significantly reduced in the MIDW compared with the GW. Conclusion: This study reveals that MIDW working in the automobile manufacturing industry have a greater risk of neck pain, limitation in left cervical flexion, and overall restriction in the ROM of the lower back compared with GW.