• International Journal of Industrial Entomology and Biomaterials
• /
• v.47 no.2
• /
• pp.99-114
• /
• 2023

Patanga japonica Bolívar, 1898 (Orthoptera: Acrididae) is listed as a climate-sensitive indicator species in South Korea and is called southern group of insects in that the main distributional range is southern region of South Korea and Asian continent. In South Korea, thus, the species was distributed mainly in southern region of South Korea including southward a remote Jeju Island, but recently the species has often been detected in mid to northern region of South Korea, implying northward range expansion in response to climate change. Understanding the characteristics of the changes in genetic diversity during range expansion in response to climate change could be a foundation for the understanding of future biodiversity. Thus, in this study, we attempted to understand the changing pattern of the genetic diversity of the P. japonica in newly expanded regions. For the purpose of study, we collected 125 individuals from seven localities throughout South Korea including two newly distributed regions (Pyeongtaek and Yeongwol at ~37° N). These were sequenced for a segment of mitochondrial cytochrome oxidase subunit I (COI) and analyzed for genetic diversity, haplotype frequency, and population genetic structure among populations. Interestingly, northward range expansion accompanied only haplotypes, which are most abundant in the core populations, providing a significant reduction in haplotype diversity, compared to other populations. Moreover, genetic diversity was still lower in the expanded regions, but no genetic isolation was detected. These results suggest that further longer time would take to reach to the comparable genetic diversity of preexisting populations in the expanded regions. Probably, availability of qualified habitats at the newly expanded region could be pivotal for successful northward range expansion in response to climate change.

• The Journal of the Acoustical Society of Korea
• /
• v.25 no.8
• /
• pp.395-402
• /
• 2006

When an active SONAR works in the subsurface. its detection Performance is limited by the reverberation. The winds Play a primary role in the Production of bubbles in the ocean. And the bubbles as efficient scatters contribute to the reverberant field. In this Paper the effects of wind-generated bubbles on sound propagation in the subsurface are investigated as a mid-frequency Hull-mounted SONAR works. The active signal excess is calculated at source depths 3. 5. and 10m considering bubble layer for frequencies 5. 7.5, and 10kHz. The change of the near-surface sound speed tend to increase surface reverberation levels and change the active signal excess. In the 10m/s winds. the maximum detection range reduces over 3km through the near-surface . The reason is the upper refraction due to the wind-generated bubbles.

• The Journal of the Acoustical Society of Korea
• /
• v.28 no.3
• /
• pp.174-186
• /
• 2009

When we apply a propagation model to the ocean with boundaries, we can calculate reflected wave using reflection coefficient suggested by Rayleigh assuming the boundaries are flat. But boundaries in ocean such as sea surface and sea bottom have an irregular rough surface. To calculate the reflection loss for an irregular boundary, it is needed to compute the coherent reflection coefficient based on an experimental formula or scattering theory. In this article, we derive the coherent reflection coefficients for a fluid-fluid interface using perturbation theory, Kirchhoff approximation and small-slope approximation respectively. Based on each formula, we can calculate coherent reflection coefficients for a rough sea surface or sea bottom, and then compare them to the Rayleigh reflection coefficient to analyze the reflection loss for a random rough surface. In general, the coherent reflection coefficient based on small-slope approximation has a wide valid region. Comparing it with the coherent reflection coefficients derived from the Kirchhoff approximation and perturbation theory, we discuss a valid region of them.

• The Journal of the Acoustical Society of Korea
• /
• v.43 no.3
• /
• pp.285-292
• /
• 2024

When calculating sonar detection probability, underwater acoustic uncertainty is assumed to be normal distributed with a standard deviation of 8 dB to 9 dB. However, due to the variability in experimental areas and ocean environmental conditions, predicting detection performance requires accounting for underwater acoustic uncertainty based on ocean experimental data. In this study, underwater acoustic uncertainty was determined using measured mid-frequency (2.3 kHz, 3 kHz) noise level and transmission loss data collected in the shallow water of the East Sea. After calculating the predictable probability of detection reflecting underwater acoustic uncertainty based on ocean experimental data, we compared it with the conventional detection probability results, as well as the predictable probability of detection results considering the uncertainty of the Rayleigh distribution and a negatively skewed distribution. As a result, we confirmed that differences in the detection area occur depending on each underwater acoustic uncertainty.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.6
• /
• pp.31-39
• /
• 2009

This study has found that there is a reverse phase with interdecadal variation in temporal variations of tropical cyclone (TC) genesis frequency (TCGF) between Northwest sector and Southeast sector, based on climatological mean tropical cyclone genesis location over the western North Pacific. The TCGF in the Northwest sector has been increased since the mid 1980s (1986-2005), while TCGF in the Southeast sector was higher until the early 1970s (1951-1970). The analysis of a difference between 1986-2005 and 1951-1970 showed results as follows: i) Through the analysis of vertical wind shear (VWS) and sea surface temperature (SST), less VWS and higher SST in the former (latter) period was located in the Northwest (Southeast) sector. ii) In the analysis of TC passage frequency (TCPF), TCs occurred in the Northwest sector frequently passed from east sea of the Philippines, through East China Sea, to Korea and Japan in the latter period, while TCs in the former period frequently has a lot of influences on South China Sea (SCS). In the case of TCs occurred in the Southeast sector, TCs in the west (east), based on $150^{\circ}E$ had a high passage frequency in the latter (former) period. In particular, TCs during the latter period frequently moved toward from the east sea of the Philippines to SCS and southern China. iii) This difference of TCPF between the two periods was characterized by 500 hPa anomalous pressure pattern. Particularly, anomalous cyclonic circulation strengthened over the East Asian continent caused anomalous southerlies along the East Asian coast line from the east sea of the Philippines to be predominate. These anomalous winds served as steering flows that TC can easily move toward same regions.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.7 no.1
• /
• pp.66-77
• /
• 2005

We have investigated microclimatic controls on the spatiotemporal variations of net primary production (NPP) of a rugged forested watershed using the process-based biogeochemical model (BIOME-BGC). To validate the model simulation of water and carbon cycles at the plot scale, we have conducted field survey over deciduous broadleaf forest (DBF) and evergreen needleleaf forest (ENF) since 2000. The modeled values of soil temperature, soil moisture and soil respiration showed high correlation with those from the field measurements. The modeled seasonal changes of NPP showed high correlation with air temperature but no significant correlation with water related parameters. The precipitation frequency turned out to be the best climatic factor to explain the annual variation of NPP. Furthermore, NPP of ENF was more sensitive to precipitation frequency than that of DBF. With changes in vegetation cover and topography, the spatial distribution of NPP was of great heterogeneity, which was negatively correlated with the magnitude of NPP. Despite the annual precipitation of 1,400mm, NPP at the study site was constrained by the amount of water available for the vegetation. Such a modeling result should be verified by the field measurements.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.15 no.4
• /
• pp.33-43
• /
• 2016

Public transportation card data, which is collected for purposes of the Integrated Public Transportation Fare System, provides neither transfer time nor transfer frequency occurring on the metropolitan city-rail (MCR). And because there are no transfer toll gates installed on the MCR, data on transfers between lines are estimated through means such as elicitations using survey questionnaire, or otherwise through macroscopic observations, which poses the risk of transfer time and frequencies being underestimated. For the accurate estimation thereof, an explanation of the transit path that arises between the Entry-and Exit-Gates must be provided. The purpose of this research is twofold : 1) to build a transit path model to reflect the current state of transfer movements on the basis of transportation card reader data, and 2) to deduce information on transfers occurring in the greater metropolis. To achieve these aims, the idea of Big Nodes is introduced in the model to align transportation card reader operation system characteristics with those of the MCR network. The link-label method is applied in the model as well to make certain that the MCR network runs in an effective manner. Administrative information obtained by the transportation card reader is used to derive transfer time and frequency both in the city's mid-zones, and in the Seoul-Gyeonggi-Incheon district's large-zones. Public transportation card data from a single specific day in year 2014 is employed in the building of the quantified transfer specific data. Extended usage thereof as providing comprehensive data of transfer resistance on the MCR is also examined.

• Atmosphere
• /
• v.19 no.2
• /
• pp.183-198
• /
• 2009

The purpose of this study is to summarize the tropical cyclone (TC) activity of 2008 over the western North Pacific including the verification of the official track and intensity forecast errors of these TCs. The TC activity - frequency, Normalized Typhoon Activity (NTA), and life span - was lower than 58-year (1951-2008) average. 22 tropical cyclones of tropical storm (TS) intensity or higher formed in the western North Pacific and the South China Sea in 2008. The total number is less than 58-year average frequency of 26.4. Out of 22 tropical cyclones, 11 TCs reached typhoon (TY) intensity, while the rest 11 TCs only reached severe tropical storm (STS) and tropical storm (TS) intensity - six STS and five TS storms. One typhoon KALMAEGI (0807) among them affected the Korea peninsula. However, no significant impact - casualty or property damage - was reported. On average of 22 TCs in 2008, the Korea Meteorological Administration (KMA) official track forecast error for 48 hours was 229 km. There was a big challenge for individual cyclones such as 0806 FENGSHEN and 0817 HIGOS presenting significant forecast error, with both intricate tracks and irregular moving speed. The tropical cyclone season in 2008 began in April with the formation of NEOGURI (0801). In May, four TCs formed in the western North Pacific in response to enhanced convective activity. On the other hand, the TC activity was very weak from June to August. It is found that the unusual anti-cyclonic circulation in the lower level and weak convection near the Philippines are dominant during summertime. The convection and atmospheric circulation in the western North Pacific contributed unfavorable condition for TC activity in the 2008 summertime. The 2008 TC activity has continued the below normal state since mid 1990s which is apparent the decadal variability in TC activity.

• Journal of Korean Society of Transportation
• /
• v.35 no.1
• /
• pp.11-24
• /
• 2017

Although many efforts to stop speeding or inappropriate speed, it failed to reduce the number of speeding-related crashes. Therefore, it is important to analyze the characteristics of speeding offenders and the cause of speeding at hot spots. In this study, we investigate the level of severity in speeding by the characteristics of speeding offenders using the Ordered Logistics Regression Models(OLRM). For the analysis, we use the speeding data collected by 39 traffic enforcement cameras in city of Cheongju and other related data including the speeding ticket history of drivers during the most recent 3 years, their demographic characteristics, their own vehicles, and road environment factors. The major results of this study are as follows. Firstly, commercial fleet drivers are more likely to repeat the conviction of high-range speeding with more than 30km/h over speed limits than other drivers. Secondly, mid-range speeding are observed as 21,462 frequency which is 76.7% of total speeding frequency and occurred mostly at suburban and rural area. It concludes that contributory factors affecting the severity of speeding at signalized intersection are drivers' speeding offence history, posted speed limits, time of day, gender of driver, and location of the intersection as show by the OLRM developed in this study(McFadden R-square : 0.296).

• Journal of The Korean Astronomical Society
• /
• v.49 no.5
• /
• pp.199-208
• /
• 2016

We present photometric results of the δ Sct star V1162 Ori, which is extensively monitored for a total of 49 nights from mid-December 2014 to early-March 2015. The observations are made with three KMTNet (Korea Microlensing Telescope Network) 1.6 m telescopes installed in Chile, South Africa, and Australia. Multiple frequency analysis is applied to the data and resulted in clear detection of seven frequencies without an alias problem: five known frequencies and two new ones with small amplitudes of 1.2-1.7 mmag. The amplitudes of all but one frequency are significantly different from previous results, confirming the existence of long-term amplitude changes. We examine the variations in pulsation timings of V1162 Ori for about 30 years by using the times of maximum light obtained from our data and collected from the literatures. The O − C (Observed minus Calculated) timing diagram shows a combination of a downward parabolic variation with a period decreasing rate of (1/P)dP/dt = −4.22 × 10⁻⁶ year⁻¹ and a cyclic change with a period of about 2780 days. The most probable explanation for this cyclic variation is the light-travel-time effect caused by an unknown binary companion, which has a minimum mass of 0.69 M_⊙. V1162 Ori is the first δ Sct-type pulsating star of which the observed fast period decrease can be interpreted as an evolutionary effect of a pre-main sequence star, considering its membership of the Orion OB 1c association.