• Horticultural Science & Technology
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• v.35 no.4
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• pp.510-522
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• 2017

To better understand the morphological variation for Perilla crop in different areas of China, we studied the morphological variation in 87 accessions (84 cultivated var. frutescens and three cultivated var. crispa) from high latitude (Northeast China) and middle latitude (North and Northwest China) areas of China by examining seven quantitative and 10 qualitative characters. Analysis of the morphological variation determined that there was significant morphological differences in five quantitative traits between cultivated var. frutescens and cultivated var. crispa, including effective number of branches (QN2), number of internodes (QN3), number of branches (QN4), length of the largest inflorescence (QN5), and days from germination to flowering (QN7). However, two quantitative traits-plant height and number of florets of the largest inflorescence-did not show any significant differences between cultivated var. frutescens and cultivated var. crispa. In addition, significant differences for six quantitative traits were found between the accessions of cultivated var. frutescens originating from high and middle latitude areas in China, which included QN2, QN3, QN5, number of florets of the largest inflorescence (QN6), and QN7. Principal components analysis (PCA) identified five quantitative characters [plant height (QN1), QN2, QN3, QN4, QN7] and six qualitative characters [fragrance of plant (QL1), color of reverse side of leaf (QL3), degree of pubescence (QL5), color of flower (QL6), shape of leaf (QL7), and hardness of seed (QL10)] that contributed to the positive direction on the first axis. The other quantitative and qualitative characters contributed to the negative direction on the first axis. Most accessions of cultivated var. frutescens and cultivated var. crispa were clearly separated by the first axis. In addition, most accessions of cultivated var. frutescens are from high latitude and middle latitude areas that were clearly separated by the first axis, except for several accessions. The findings from this study will provide useful information towards understanding the morphological variation of Perilla crop according to geographical distribution in high and middle latitude regions of China.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.26.3-27
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• 2011

Formation of a steep plasma density gradient in the middle-latitude ionosphere during geomagnetic storms and the latitudinal migration of its location depending on the storm phase are suggested to be associated with the ionospheric signature of the plasmapause. We test this idea by using the satellite and ground observation data during the 11 April 2001 storm. The locations of the steep plasma density gradient identified by TOPEX/Poseidon (2001 LT) and DMSP (1800 and 2130 LT) satellites coincide with the ionospheric footprints of the plasmapause identified by the IMAGE satellite. This observation may support the dependence of the middle-latitude plasma density gradient location on the plasmapause motion, but does not explain why the steep density gradient whose morphology is largely different from the morphology of the middle-latitude ionization trough during quiet period is formed in association with the plasmapause. The ionospheric disturbances in the total electron content (TEC) maps shows that the steep TEC gradient is formed at the boundary of the positive ionospheric storm in low-middle latitudes and the negative ionospheric storm in middle-high latitudes. We interpret that the thermospheric neutral composition disturbance in the dayside is confined within the middle-high latitude ionospheric convection zone. The neutral composition latitudes and, therefore, the locations of the steep plasma density gradient coincide with the footprints of the plasmapause. The TEC maps show that the appearance of the steep plasma density gradient in the pre-midnight sector during the recovery phase is related to the co-rotation of the gradient that is created during the main phase.

• Journal of Astronomy and Space Sciences
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• v.32 no.1
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• pp.33-38
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• 2015

Forbush Decreases (FD) are transient, sudden reductions of cosmic ray (CR) intensity lasting a few days, to a week. Such events are observed globally using ground neutron monitors (NMs). Most studies of FD events indicate that an FD event is observed simultaneously at NM stations located all over the Earth. However, using statistical analysis, previous researchers verified that while FD events could occur simultaneously, in some cases, FD events could occur non-simultaneously. Previous studies confirmed the statistical reality of non-simultaneous FD events and the mechanism by which they occur, using data from high-latitude and middle-latitude NM stations. In this study, we used long-term data (1971-2006) from middle-latitude NM stations (Irkutsk, Climax, and Jungfraujoch) to enhance statistical reliability. According to the results from this analysis, the variation of cosmic ray intensity during the main phase, is larger (statistically significant) for simultaneous FD events, than for non-simultaneous ones. Moreover, the distribution of main-phase-onset time shows differences that are statistically significant. While the onset times for the simultaneous FDs are distributed evenly over 24-hour intervals (day and night), those of non-simultaneous FDs are mostly distributed over 12-hour intervals, in daytime. Thus, the existence of the two kinds of FD events, according to differences in their statistical properties, were verified based on data from middle-latitude NM stations.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.319-327
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• 2010

We examine the ionospheric F2-layer electron density variation by solar activity in middle latitude by using foF2 observed at the Kokubunji ionosonde station in Japan for the period from 1997 to 2008. The semi-annual variation of foF2 shows obviously in high solar activity (2000-2002) than low solar activity (2006-2008). It seems that variation of geomagnetic activity by solar activity influences on the semi-annual variation of the ionospheric F2-layer electron density. According to the Lomb-Scargle periodogram analysis of foF2 and Ap index, interplanetary magnetic field (IMF) Bs (IMF Bz <0) component, solar wind speed, solar wind number density and flow pressure which influence the geomagnetic activity, we examine how the geomagnetic activity affects the ionospheric F2-layer electron density variation. We find that the semi-annual variation of daily foF2, Ap index and IMF Bs appear clearly during the high solar activity. It suggests that the semi-annual variation of geomagnetic activity, caused by Russell-McPherron effect, contributes greatly to the ionospheric F2-layer semi-annual electron density variation, except dynamical effects in the thermosphere.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.4
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• pp.413-422
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• 2005

The ozone concentration measured by HALOE (Ver 19) from Oct. 1991 to Dec. 2003 is used for analyzing the variation of ozone concentration. The HALOE loaded in UARS is observing several gases in the atmosphere, from 10km to 80km. Fourier analysis of these data in the middle latitude northern hemisphere is reported in this paper. To detect any possible long term trends, the fourier transformed time series was back transformed after removing signals with time periods of less than 6 months. Although the results clearly show the strong annual cycle, it is difficult to show any long term trends from the fourier series. We also compared the ozone volume mixing ratio's from HALOE with that from the ground-based radiometry to evaluate the accuracy of microwave observation at Sookmyung Women's University.

• Journal of Astronomy and Space Sciences
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• v.38 no.2
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• pp.135-143
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• 2021

We report, for the first time, the afternoon (i.e., from noon to sunset time) observations of the northern mid-latitude E-region field-aligned irregularities (FAIs) made by the very high frequency (VHF) coherent backscatter radar operated continuously since 29 December 2009 at Daejeon (36.18°N, 127.14°E, 26.7°N dip latitude) in South Korea. We present the statistical characteristics of the mid-latitude afternoon E-region FAIs based on the continuous radar observations. Echo signal-to-noise ratio (SNR) of the afternoon E-region FAIs is found to be as high as 35 dB, mostly occurring around 100-135 km altitudes. Most spectral widths of the afternoon echoes are close to zero, indicating that the irregularities during the afternoon time are not related to turbulent plasma motions. The occurrence of afternoon E-regional FAI is observed with significant seasonal variation, with a maximum in summer and a minimum in winter. Furthermore, to investigate the afternoon E-region FAIs-Sporadic E (E_s) relationship, the FAIs have also been compared with E_s parameters based on observations made from an ionosonde located at Icheon (37.14°N, 127.54°E, 27.7°N dip latitude), which is 100 km north of Daejeon. The virtual height of E_s (h'E_s) is mainly in the height range of 105 km to 110 km, which is 5 km to 10 km greater than the bottom of the FAI. There is no relationship between the FAI SNR and the highest frequencies (f_tE_s) (or blanket frequencies (f_bE_s)). SNR of FAIs, however, is found to be related well with (f_tE_s-f_bE_s).

• Ocean and Polar Research
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• v.39 no.3
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• pp.181-194
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• 2017

The long-term linear trend of global sea-to-air dimethyl sulfide (DMS) flux was analyzed over a 16-year time span (2000~2015), based on satellite observation data. The emission rates of DMS (i.e. DMS flux) in the global ocean were estimated from sea surface DMS concentrations, which were constructed with chlorophyll a (Chl-a) concentrations and mixed layer depths (MLD), and transfer velocity from sea to air, which was parameterized with sea surface wind (SSW) and sea surface temperature (SST). In general, the DMS flux in the global ocean exhibited a gradual decreasing pattern from 2000 (a total of 12.1 Tg/yr) to 2015 (10.7 Tg/yr). For the latitude band ($10^{\circ}$ interval between $0^{\circ}$ and $60^{\circ}$), the DMS flux at the low latitude of the Northern (NH) and Southern hemisphere (SH) was significantly higher than that at the middle latitude. The seasonal mean DMS flux was highest in winter followed by in summer in both hemispheres. From the long-term analysis with the Mann-Kendall (MK) statistical test, a clear downward trend of DMS flux was predicted to be broad over the global ocean during the study period (NH: $-0.001{\sim}-0.036{\mu}mol/m^2/day\;per\;year$, SH: $-0.011{\sim}-0.051{\mu}mol/m^2/day\;per\;year$). These trend values were statistically significant (p < 0.05) for most of the latitude bands. The magnitude of the downward trend of DMS flux at the low latitude in the NH was somewhat higher than that at the middle latitude during most seasons, and vice versa for the SH. The spatio-temporal characteristics of DMS flux and its long-term trend were likely to be primarily affected not only by the SSW (high positive correlation of r = 0.687) but also in part by the SST (r = 0.685).

• Journal of Navigation and Port Research
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• v.44 no.2
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• pp.136-143
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• 2020

Maritime autonomous surface ships (MASS) has been developed over the years. But, there are many unresolved problems. To overcome these problems, this study proposes connected ship navigation system. The system comprises a slave ship and a master ship that leads the slave ship. To implement this system, communication network, route planning algorithms, and controllers are designed. The communication network is built using the transmission control protocol/Internet protocol (TCP/IP) socket communication method to exchange data between ships. The route planning algorithms calculate the course and distance of the slave ship using the middle latitude sailing method. Nomoto model is used as the mathematical model of the slave ship maneuvering motion. Then, the autoregressive with exogenous variables (ARX) model is used to estimate the parameters of Nomoto model. Based on the above model, the automatic steering controller is designed using a proportional-derivative (PD) control. Also, the speed controller is designed for the slave ship to maintain constant distance from the master ship. Sea experiments are conducted to verify the proposed system with two remodeled boats.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.2
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• pp.54-60
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• 1978

This study was conducted to find gene source for high germination ability of rice varieties at low temperature. At low temperature of 1$0^{\circ}C$, percent germination of most varieties orginating from middle and high latitude was high, but some varieties were low. Percent germination of some varieties orginating form low latitude was high.

• 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.