• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.32.1-32.1
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• 2021

We present the magnetic field strengths of CTA 102 using multi-frequency data at 2.6-343.5 GHz in order to study the physical origins of radio flares. The observations at 22 and 43 GHz were conducted using the single-dish radio telescopes of the Korean VLBI Network (KVN) from December 2012 until May 2018 (MJD 56200-58400). We used multi-frequency data obtained from the Effelsberg 100-m, OVRO 40-m, Metsähovi 14-m, IRAM 30-m, SMA, ALMA, and VLBA telescopes. During the period of the observations, two major flares (R1 and R2) are seen clearly at 15 and 37 GHz during MJD 57500-57800 and MJD 58000-58300, respectively. The source shows typical variability with time-scales ranging from 20-161 days at 15 GHz. The variability Doppler factor is in the range of 11.51-31.23. The quasi-simultaneous radio data are used to investigate the synchrotron spectrum of the source, finding that the synchrotron radiation is self-absorbed. The turnover frequency and the peak flux density of the synchrotron self-absorption (SSA) spectra are in ranges of 38.06-167.86 GHz and 1.49-10.38 Jy, respectively. From the SSA spectra, magnetic field strengths are estimated to be < 10 mG. The equipartition magnetic field strengths are larger than the SSA magnetic field strengths by a factor of > 100. This indicates that the radio flares may be related to a particle energy-dominated emission region.

• The Plant Pathology Journal
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• v.29 no.4
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• pp.410-417
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• 2013

In 2011-2012, sixty nine samples were collected from alfalfa plants showing viral infection symptoms in Riyadh region. Mechanical inoculation with sap prepared from two collected samples out of twenty five possitive for Alfalfa mosaic virus (AMV) by ELISA were produced systemic mosaic on Vigna unguiculata and Nicotiana tabacum, local lesion on Chenopodium amaranticolor and C. quinoa. Vicia faba indicator plants that induce mosaic and mottle with AMV-Sagir isolate and no infection with AMV-Wadi aldawasser isolate. Approximately 700-bp was formed by RT-PCR using AMV coat protein specific primer. Samples from infected alfalfa gave positive results, while healthy plant gave negative result using dot blot hybridization assay. The nucleotide sequences of the Saudi isolates were compared with corresponding viral nucleotide sequences reported in GenBank. The obtained results showed that the AMV from Australia, Brazil, Puglia and China had the highest similarity with AMV-Sajer isolate. While, the AMV from Spain and New Zealaland had the lowest similarity with AMV-Sajer and Wadi aldawasser isolates. The data obtained in this study has been deposited in the GenBank under the accession numbers KC434083 and KC434084 for AMV-Sajer and AMV-Wadialdawasser respectively. This is the first report regarding the gnetic make up of AMV in Saudi Arabia.

• Journal of the Korean association of regional geographers
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• v.4 no.1
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• pp.1-13
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• 1998

The climatic characteristics of Korea are analyzed with the monthly variability of the temperature observed from 1961 to 1990 in 66 stations. The climate of Korea is composed of spring(April and May), summer(from June to September), autumn(October) and winter(from November to March). In the change of the variability of the temperature, it becomes the highest in winter and does the lowest in summer. In the distribution of the variability of the temperature, it shows the decreasing tendency along the transferring the southern and western coasts from the Yongso region distinctly in midsummer(August) and midwinter (December and January). The climatic regions are divided into two types : the central type and the southern one while the climatic regions of two types are subdivided into four patterns : the western coastal, the inland, the eastern coastal and the southern coastal patterns. In the distributive patterns of the climatic regions, pattern in summer is different from others, while the ones in the other seasons show similarity.

• Journal of Service Research and Studies
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• v.5 no.1
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• pp.35-43
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• 2015

Regional comparative analysis for the variability of young man's employment indexes is important to unemployment or employment policy data of central and local government. Through the result of comparative analysis, central and local government can use differentiated policies for the regions and keep the efficiency for the application of detailed policy. In this study, based on economically active population survey data which consider economically active population rate, employment population rate and unemployment rate as typical employment indexes of young man, we analyzed the variability of these indexes by metropolitan cities and province regions using coefficient of variation. Also we proposed the largest index in variability of three employment indexes, and proposed the city and province region with the largest variability for each employment index.

• Journal of Environmental Science International
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• v.19 no.9
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• pp.1083-1092
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• 2010

The spatial variability in the food chain structure of an estuary environment (Nanakita estuary, Japan) was investigated using fatty acid. Potential organic matter sources (terrestiral plants, macroalgae, benthic microalgae, dinflagellates and bacteria), sedimentary organic matters and benthic invertebrates (Nuttallia olivacea and Nereidae) were sampled in four locations with different tidal flat type. The main objective of the present study was to determine the origin of sediment and the food sources of N. olivacea and Nereidae along with small-scale spatial variability. The origin of sedimentary organic matters were mainly the fatty acid of bacteria and benthic microalgae. Especially, The organic matter of terrestrial plant origin was found the highest in station C. The diets of N. olivacea and Nereidae were found to be dominated by diatoms and terrestrial plants. Whereas, macroalgae and dinoflagellates showed little influence to benthic invertebrates. Moreover, according to principal component analysis, it is showed that benthic invertebrates in the same region are using the same food without relation with species. On the other hand, the N. olivacea and Nereidae of station D clearly contrasts with station B in terms of main food sources. From these results, it is suggested that food competition of benthic invertebrates revealed high a connection between small-scale spatial variability and food source in estuary.

• The Plant Pathology Journal
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• v.25 no.3
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• pp.236-240
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• 2009

Tylenchulus semipenetrans, citrus nematode is an important phytopathogenic nematode and responsible for serious damage on citrus. However, little information is available about genetic variability of T. semipenetrans among different populations with variation of conventional diagnostic characteristics. In this study, we compared the morphometric and genetic characteristics among different populations. The mature female of T. semipenetrans collected in this study had thicker cuticle than those in the previous studies. In comparative sequence analysis of T. semipenetrans populations obtained from Jeju in Korea, we observed genetic variations within clones generated from single individuals. To determine whether variability among copies of nuclear ribosomal DNA sequences exists in the genome of T. semipenetrans, PCR-RFLP technique from individuals of Korean isolates with MseI and MspI restriction enzymes was used to prove experimentally that all populations have intra-specific variations. Restriction enzyme digestion created several fragments on 3.0% agarose gel corresponding to several haplotypes in all populations, though some populations displayed fragment deletion. The total length of fragments was larger than before digestion, indicating sequence heterogeneity within the genome of T. semipenetrans.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.224-224
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• 2015

The East Asia monsoon is one of the most complex atmospheric phenomena caused by Land-Sea thermal contrast. It plays essential role in fulfilling the water needs of the region but also poses stern consequences in terms of flooding and droughts. This study analyzed the influence of Global Sea Surface Temperature Anomalies (SSTA) on occurrence of droughts in the East Asia monsoon region ($20^{\circ}N-50^{\circ}N$, $103^{\circ}E-149^{\circ}E$). Standardized Precipitation Index (SPI) was employed to characterize the droughts over the region using 30-year (1978-2007) gridded rainfall dataset at $0.5^{\circ}$ grid resolution. Due to high variability in intensity and spatial extent of monsoon rainfall the East Asia monsoon region was divided into the homogeneous rainfall zones using cluster analysis method. Seven zones were delineated that showed unique rainfall regimes over the region. The influence of SSTA was assessed by using lagged-correlation between global gridded SSTA ($0.2^{\circ}$ grid resolution) and SPI of each zone. Sea regions with potential influence on droughts in different zones were identified based on significant positive and negative correlation between SSTA and SPI with a lag period of 3-month. The results showed that SSTA have the potential to be used as predictor variables for prediction of droughts with a reasonable lead time. The findings of this study will assist to improve the drought prediction over the region.

• Journal of Astronomy and Space Sciences
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• v.16 no.2
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• pp.139-148
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• 1999

Bow shock formation, in case the supersonic solar wind flow is hindered by the atmosphere of Mars, is investigated. The atoms newly ionized from the extensive neutral atmosphere of Mars are loaded to the solar wind. By the conservation of momentum, the solar wind velocity is decreased. Then the supersonic flow velocity drops to the subsonic flow velocity in front of Mars at certain region, which is called the bow shock. The location of Mars subsolar bow shock is highly varying in the range of 1.3 to 2.5 Rm. Martian bow shock location is estimated by one-dimensional flux tube equations reduced from full three-dimensional MHD equations. The variability of Mars bow shock location effected by the solar wind conditions is studied. It is evident that the solar wind dynamic pressure change is able to make the Mars bow shock location variable.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.195-195
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• 2017

The patterns of occurrence of typhoons in North Pacific region are constantly changing with the increase of temperature in sea surface and the occurrence of El Nino and La Nina and changes of their development caused by global warming. In addition, alterations of flow regimes caused by large-scale hydraulic construction projects in the past few years and changes in precipitation patterns caused by climate change have imposed increased stress on hydroecology while the indiscreet utilization of water resources has a negative environmental impact on the water flows in the natural rivers and streams and hydroecological structures. The purpose of this study is to explore the impact of altered hydrologic regime on stream and riparian ecosystems that are most vulnerable to climate variability and extremes such as typhoons.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.126.1-126.1
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• 2012

The middle-latitude ionization trough, the plasma density depletion in the subauroral region, has been extensively studied since its discovery in the 1960s. Our knowledge of the variability of the trough is mostly based on the observations in the northern hemisphere. Recently, the COSMIC observations enabled the investigation of the trough in both hemispheres at all local time. However, the investigation was limited to the period of the low solar activity. In this study, we investigate the variability of the trough location and morphology with local time, solar cycle, magnetic activity, and interplanetary magnetic field. For this purpose, we analyze the DMSP F15 data acquired during 2000-2010.