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Minhyung Jung,Hong Geun Kim,Dong Hyun Lee,Doo-Hyung Lee,Jaewon Kim 한국응용곤충학회 2016 한국응용곤충학회 학술대회논문집 Vol.2016 No.04
Riptortus pedestris is a major agricultural pest in Korea. To manage this pest, it is necessary to understand the complete life history of R. pedestris. However, most studies have focused on the summer period when the pest attacks crops. Therefore, we conducted laboratory and field experiment to identify overwintering behavior of adult R. pedestris. First, we conducted two laboratory experiments to examine overwintering habitat preferences and spatial distribution of R. pedestris in the habitat. Second, we conducted field survey to characterize overwintering sites of R. pedestris in diverse landscapes. In the laboratory conditions, R. pedestris almost exclusively showed overwintering behavior in the leaf litter arena (63%) among the structures tested (rocks: 3%; rotten wood: 0%). And spatial distribution of R. pedestris showed solitary behavior in leaf litters. In the field, we located 12 individuals of overwintering adults from the urban areas, whereas no individuals were found from the high-elevation mountains and agricultural landscapes. Our results suggest that R. pedestris mainly use leaf litter as an overwintering structure, with solitary behavior, and low-elevation forested areas near urban landscapes seem to be more preferred overwintering sites.
Minhyung Jung,Doo-Hyung Lee 한국응용곤충학회 2015 한국응용곤충학회 학술대회논문집 Vol.2015 No.10
Currently, the management of Riptortus pedestris (Hemiptera: Alydidae) relies mainly on insecticide application in most crop productions. However, there have been very few detailed studies concerning the potential behavioral effects of sublethal dose of insecticide. This study was conducted to address sublethal effects of five insecticides on the mobility of R. pedestris. Adult R. pedestris were individually exposed to dry residue of insecticides for 4 hours in laboratory. Tested insecticides were fenitrothion (organophosphate), etofenprox (pyrethroid), bifenthrin (pyrethroid), acetamiprid (neonicotinoid) and dinotefuran (neonicotinoid). After the exposure, vertical climbing ability and flight capacity of survived R. pedestris were evaluated and compared to water-treated control. First, the mortality of R. pedestris after the 4-h insecticide exposure was as follows: 10% for fenitrothion, 3.4% for dinotefuran, 3.4% for acetamiprid, 0% for etofenprox and 0% for bifenthrin. The vertical mobility of R. pedestris was affected differently by insecticides tested. Acetamiprid resulted in decrease (37%) in the vertical mobility, whereas dinotefuran caused increase (153%) in the ability compared to the control. There was no effect by three other insecticides on the vertical mobility. In general, tested insecticides did not affect the flight capacity of R. pedestris compared to untreated individuals. However, etofenprox resulted in increase (230%) in the flight capacity. The results of this study indicate that insecticide-treated but survived R. pedestris can show similar or even increased mobility compared to untreated individuals. This should be considered in designing insecticide application programs against of R. pedestris.
Survey of overwintering sites of R. pedestris in diverse landscapes in Korea
Minhyung Jung,Doo-Hyung Lee 한국응용곤충학회 2015 한국응용곤충학회 학술대회논문집 Vol.2015 No.04
R. pedestris is a major insect pest in agricultural production, especially on soybean and tree fruit, in Korea. Currently, the management of this pest relies mainly on insecticide application in most commodities. However, the chemical controls cause numerous environmental problems. To develop sustainable management tools, it is fundamental to understand the basic biology and ecology of R. pedestris. However, the overwintering ecology of this pest is virtually unknown. In this study, we surveyed diverse landscapes including high elevation mountains soybean fields and there neighboring forests to find and characterize the overwintering sites of R. pedestris. In the field, we sampled leaf litters from 1㎡ grids to locate overwintering R. pedestris. The samples were taken every 100m altitude in the mountain areas or every 50m distance in the flat landscapes. Overwintering R. pedestris were found from 6 samples out of 137 samples. All overwintering R. pedestris were located from forested areas adjacent to urban landscapes in Seong-Nam si, Gyeong-Gi Do. Interestingly, no overwintering R. pedestris was found from in the samples collected from high elivation mountains including Yeon-In, Song-Ni, Chi-Ak, Ga-Ya, Wol-Chul. likewise, no overwintering individual was found from soybean fields and their neighboring forested areas. With caveat that the data were collected only for 1 year, our results support that R. pedestris overwinters solitary resulting in low detection rates from the samples. Given that R. pedestris typically disperse into cultivated crops with high densities, it is important to better understand environmental factors affecting the presence or absence of overwintering R. pedestrris in diverse landscapes. The knowledge would be essential to develop sustainable monitoring and management programs for this economically important pest in Korea.
Instability of Electrically Driven Polymer Liquid Jets
Minhyung Lee,Seung Baik Kang,Joo Hyuk Park 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.3
Polymer nanofibers can be generated by a electrospinning process. The process involves electrically charged jet of polymer solutions evolving from a droplet. The jet stretches in vertical direction due to the difference between charged particle and constant current located at the collector, while the Coulomb and viscoelastic forces start to contribute to radial and azimuthal (torsional stretching. In this paper, the unstable dynamics of the liquid polymer jet is examined experimentally and theoretically. A complex viscoelastic rheological model has been adopted to analyze the behavior of a charged liquid jet. The model includes complex phenomena of stress relaxation of the liquid jet resulting from the competing force components. The experimental data of the jet paths captured by high-speed videocamera also confirm the similar behavior with the predictions.
Vortex-Induced Vibrations of a Circular Cylinder at Low Reynolds Numbers
Minhyung Lee,Sung-Yeoul Lee 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.11
The vortex-induced vibrations of a circular cylinder at low Reynolds (Re) numbers are simulated by applying a method of the two-dimensional computational fluid dynamics coupled with the structural dynamics based on the multi-physics. The fluid solver is first tested on the case of a fixed cylinder at Re≤160, and shows a good agreement with the previous highresolution numerical results. The present study then reports on the detailed findings concerning the vibrations of an elastic cylinder with two degrees of translational freedom for a number of cases in which Re is fixed at 200, a reduced damping parameter Sg=O.O1. 0.1. 1.0, 10.0 and the mass ratio M^* = I, 10.
Minhyung Jung,Po-Hyun Park,Young-Ran Joo,Lee-Hyeon Sin,Uk-Gyo Lee,Doo-Hyung Lee 한국응용곤충학회 2016 한국응용곤충학회 학술대회논문집 Vol.2016 No.04
Seasonal abundance and distribution of mosquitoes and chigger mites are important for human populations. However, factors affecting the abundance and distribution of vector species are not well - understood. Furthermore, global climate change makes it difficult to predict the population dynamics of vector species. Therefore, it is important to monitor this vector species over a long period of time. In 2015, mosquitoes were collected from three potential mosquito habitats using black light trap and BG-Sentinel trap in Gyeongi-do in April through October. Also, we collected chigger mite using sherman live traps in Cheorwon, Gangwon-do in April, September and October. From the survey, we collected a total of 11,649 mosquitoes in three potential mosquito habitats, and a total of 3,656 chigger mites from 54 wild rodents. In the samples, dominant mosquito species were Aedes vexans nipponii (Species Ratio 70%), Culex pipens pallens (SR 9.8%) in Gyeonggi area and dominant chigger mite species was Leptotrombidium pallidium (SR 59%) in Cheorwon. The results of this study can serve as provide fundamental basis to develop effective management strategy under the global climate change environment.