• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.52.1-52.1
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• 2017

The discovery of GW150914, black hole - black hole merger via gravitational waves (GWs) opened a new window to observe the Universe. GW frequencies from heavenly bodies and early Universe are expected to span between sub-nHz up to kHz. At present, GW detectors on Earth (LIGO, Virgo, KAGRA, LIGO-India) aims frequency ranges between 10-2000 Hz. The space-borne GW detector and Pulsar Timing Array targets mHz and nHz sources. Starting in March 2017, the KKN (KASI-KISTI-NIMS) collaboration launched a pilot study of SLGT (Superconducting Low-frequency Gravitational-wave Telescope). This project is funded by NST (Korea Institute of Science and Technology). The main detection bands expected for SLGT ranges between 0.1-10Hz, which is complementary of LIGO-type detectors and LISA for multi-band GW observation. We will present an overview of the SLGT project and report the status of the NST pilot study. We will also present prospective of GW astronomy with SLGT.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.52.3-53
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• 2017

Identification of gravitational wave (GW) sources in electromagnetic (EM) wave observations is important because it enables us to understand the property of the GW-emitting sources/mechanisms much better than the GW detection. For that reason, a large number of astronomers are working on observations to identify the position and the nature of GW sources. We give a short overview of the expected EM signals from GW sources and the current EM follow-up observations that have been undertaken in Korea and the world.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.37.1-37.1
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• 2021

For the first time in Korea, we are developing technology for gravitational wave (GW) detectors as a major R&D program. Our main research target is quantum noise reduction technology which can enhance the sensitivity of a GW detector beyond its limit by classical physics. Technology of generating squeezed vacuum state of light (SQZ) can suppress quantum noise (shot noise at higher frequencies and radiation pressure noise at lower frequencies) of laser interferometer type GW detectors. Squeezing technology has recently started being used for GW detectors and becoming necessary and key components. Our ultimate goal is to participate and make contribution to international collaborations for upgrade of existing GW detectors and construction of next generation GW detectors. This presentation will summarize our results in 2020 and plan for the upcoming years. Technical details will be presented in other family talks.

• Journal of the Korean Society of Food Culture
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• v.38 no.5
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• pp.345-355
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• 2023

This study was conducted on four types of laver soup prepared using recipes from Gangwon-do (GW), Gyeongsangnam-do (GN), Jeollanam-do (JN), and the media (MD). Salinities, soluble solids, free amino acids, color values, turbidities, and pH values of soups were measured, and sensory evaluations were done. pH values were significantly higher for GW and GN recipes than the JN and MD recipes (p<0.05). The salinities of JN and MD were significantly higher than those of the other soups (p<0.05). Regarding soluble solids, JN had the highest at 2.64°Brix, whereas GW had the lowest at 0.86 °Brix (p<0.05). GW and JN had higher concentrations of valine, phenylalanine, and glutamic acid (p<0.05). JN had significantly higher redness (a) than the other soups but significantly lower lightness (L) and yellowness (b) (p<0.05). Regarding transmittance, GW had a significantly higher value (67.67%T) than the other soups. JN and MD had higher acceptability results than GW or GN in terms of flavor, mouthfeel, and overall acceptability. Sensory intensity evaluations revealed that JN and MD had higher "soy sauce aroma" and "saltiness" and a greater "broth turbidity" than the other soups. These results indicate that the physicochemical and sensory characteristics of regional laver soups differ.

• Weed & Turfgrass Science
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• v.4 no.4
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• pp.390-396
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• 2015

Water shortage is becoming a serious problem of turfgrass management on sand green. Many superintendents in golf course in Korea have interested in use of irrigation of recycled water for turfgrass water management. This study was conducted to investigate the effect of greywater as an irrigation source on the growth and quality of creeping bentgrass green. Turfgrass was irrigated with tap water (TW) and greywater (GW), under with or without compound fertilizer application (nonfertilizer + TW, N-TW; non-fertilizer + GW, N-GW; fertilizer + TW, F-TW; fertilizer + GW, F-GW). The chemical properties of the green sand soil were not changed by irrigation. Turf color index, chlorophyll index, root length, clipping yield and nutrient uptake of GW treatment were similar to TW treatment. The growth and quality of turfgrass were more likely related with the fertilizer application than irrigation source or quality. These results indicated that GW could be used as alternative irrigation source on the sand greens of golf courses.

• The KIPS Transactions:PartC
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• v.15C no.3
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• pp.205-212
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• 2008

In the environment with multiple heterogeneous wireless sensor networks with a single point of sensed data collection or a gateway (GW), relay points (RPs) may be required for the energy efficient delivery of sensed data from static or mobile sinks to the GW. The optimal placement of RPs becomes an even more difficult problem if static sinks are dynamically added or the trajectory of mobile sinks can not be known in advance. In order to resolve this problem, we propose a mechanism to deploy RPs in a grid pattern and to use the tree-based relaying network for reducing the cost of the RP and for reducing the control overhead incurred by the route setup from sinks to the GW. For the performance evaluation of our proposed mechanism, we have carried out a numerical analysis on a single route setup from a sink to the GW and, for more general performance evaluations, ns-2 based simulations have been carried out. According to the performance evaluation results, our tree-based relaying network mechanism outperforms that based on AODV in terms of the data delivery time, the network service time and the control overhead.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.53.3-54
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• 2021

We present optical follow-up observation results of three binary black hole merger (BBH) events, GW190408 181802, GW190412, and GW190503 185404, which were detected by the Advanced Ligo and Virgo gravitational wave (GW) detectors. Electromagnetic (EM) counterparts are generally not expected for BBH merger events, however, some theoretical models suggest that EM counterparts of BBH can possibly arise in special environments. To identify EM counterparts of the three BBH merger events, we observed high-credibility regions of the sky with telescopes of the Gravitational-wave EM Counterpart Korean Observatory (GECKO), including the Korea Microlensing Telescope Network (KMTNet). Our observation started as soon as 100 minutes after the GW event alert and covered roughly 29 - 63 deg2 for each event with a depth of 22.5 mag in R-band within hours of observation. No plausible EM counterparts were found for these events. Our result gives a great promise for the GECKO facilities to find EM counterparts within few hours from GW detection in future GW observation runs.

• Journal of Environmental Science International
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• v.33 no.4
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• pp.269-277
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• 2024

Scientific forensic techniques are used to verify environmental impact of groundwater pollution, surface water pollution, air pollution, noise, and vibration according to residents' complaints in connection with construction and civil engineering works. In this study, we investigated the contamination of groundwater and the lowering of the groundwater level in an area surrounding a tunnel excavation site for the Andong-Yeongdeok national road, using a forensic hydrogeological technique. We reviewed the groundwater level and water quality of well GW1 in the area surrounding the tunnel excavation site as well as tunnel construction information and then we analyzed the correlations among the obtained data. Before tunnel excavation, the water level of well GW1 was lower than the tunnel elevation. Considering the relationship between the precipitation, tunnel discharge, tunnel depth, and groundwater level of well GW1, the groundwater flowed from the tunnel to well GW1. Moreover, the tunnel discharge and groundwater levels were not related to each other. The pH of well GW1 was 8.4 before tunnel excavation. During excavation, the pH declined to 8.1-8.2 at the beginning, and increased to 8.8 at the end of the excavation. The fluorine concentration in well GW1 was 2.49 mg/L, 1.91-3.22 mg/L, and 1.7-2.67 mg/L, respectively, before, during, and after the excavation. The sulfate ion concentration was very high, over 2,000 mg/L, before and during the excavation; after the excavation, it was between 200 and 323 mg/L. Turbidity was 1.47, 10.5, and 4.51 NTU before, during, and after tunnel excavation, respectively. Therefore, the excavation of this tunnel is not related to the groundwater quality of well GW1.

• Journal of The Korean Society of Grassland and Forage Science
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• v.22 no.3
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• pp.213-220
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• 2002

The growth characteristics, forage yields and nutritive values of heading and headless types of sorghum $\times$ sudangrass(Sorghum bicolar L.) hybrids were examined to evaluate the adaptability of new cultivars at Suwon and Chunahn for two years from 2000 to 2001 in a randomized complete block design with three replications. Eleven cultivars of heading type and 4 cultivars of headless type were used in this study. The dry matter(DM) yield of AG 2501 was highest in the heading type cultivars, and PAC F8350 in the headless type cultivars, respectively. The DM yields of heading types were slightly higher than those of headless types but there were not significantly different. Early growth and regrowth characteristics of heading type was highest in AG 2501 and GW 9110G, respectively. GW 9110G and DMD were early heading types, and AG 2501 and GW 9161F were middle heading types. AG 2501 was longest and GW 9161F was shortest in plant height. Cultivars with long leaf length were appeared to be larger fur leaf width and stem diameter. Brix content was highest in DMD as 9.7%, and disease and insect resistances were not significantly different among the heading types. Early growth of headless type cultivar, PAC F8350 was slightly lower than that of Jumbo but stronger in regrowth, wider in leaf width and stem diameter, and stronger in lodging. Comparisons of growth characters between heading and headless types of cultivars were not easy in general but between them, brix contents of heading types ranging from 6.7 to 7.9% were greatly higher than those of headless types ranging from 3.6 to 3.9%. Nutritive values such as crude protein, ADF, NDF and digestibility of headless type cultivars were higher than those of heading types. In conclusion, of heading type cultivars, GW 9110G, AG 2501, DMD and GW 9161F, and of headless type cultivars, Jumbo and PAC F8350 were recommended as high yielding cultivars with good adaptability in domestic environment.

• Journal of the Institute of Convergence Signal Processing
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• v.14 no.3
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• pp.169-180
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• 2013

The modification of conditional Fuzzy C-Means (CFCM) with Gaussian weights (CFCM_GW) is accomplished for blind equalization of channels in this paper. The proposed CFCM_GW can deal with both of linear and nonlinear channels, because it searches for the optimal desired states of an unknown channel in a direct manner, which is not dependent on the type of channel structure. In the search procedure of CFCM_GW, the Bayesian likelihood fitness function, the Gaussian weighted partition matrix and the conditional constraint are exploited. Especially, in contrast to the common Euclidean distance in conventional Fuzzy C-Means(FCM), the Gaussian weighted partition matrix and the conditional constraint in the proposed CFCM_GW make it more robust to the heavy noise communication environment. The selected channel states by CFCM_GW are always close to the optimal set of a channel even when the additive white Gaussian noise (AWGN) is heavily corrupted. These given channel states are utilized as the input of the Bayesian equalizer to reconstruct transmitted symbols. The simulation studies demonstrate that the performance of the proposed method is relatively superior to those of the existing conventional FCM based approaches in terms of accuracy and speed.