• Korean journal of applied entomology
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• v.62 no.3
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• pp.161-169
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• 2023

Thrips are usually not exposed to insecticide spray due to hiding at holes, gaps, or crevices of host plants with their relatively small body sizes. This study devised a strategy to use a contact pheromone to suppress the seclusive behavior of the thrips, A contact pheromone identified as 7-methyltricosane (7TM) in the western flower thrips, Frankliniella occidentalis, was added to the diet to test the preference of the thrips. Although 7TM did not change the larval behavior, it significantly induced the avoiding behavior in male adults. In contrast, the contact pheromone was preferred by the female adults. Similar behavioral changes were also observed in another flower thrips, Frankliniella intonsa. Based on the behavioral changes induced by the contact pheromone, a mixture of 7TM and insecticide was applied to thrips infesting hot peppers in field conditions. Compared to spinetoram treatment, its mixture treatment with 7TM enhanced the control efficacy against thrips. Interestingly, 7TM treatment alone also gave slight reduction in F. intonsa density, suggesting a behavioral disruption of thrips by the contact pheromone. This study suggests a novel technology to control insect pests using contact pheromone by suppressing the seclusive behavior to avoid exposure to insecticide spray.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.751-756
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• 2014

The dynamic behavior of numerous grains interacting with each other can be easily observed. In this study, this dynamic behavior was analyzed based on the contact between numerous grains. The discrete element method was used for analyzing the dynamic behavior of each particle and the neighboring-cell algorithm was employed for detecting their contact. The Hertzian and tangential sliding friction contact models were used for calculating the contact force acting between the particles. A GPU-based parallel program was developed for conducting the computer simulation and calculating the numerous contacts. The dam break experiment was performed to verify the simulation results. The reliability of the program was verified by comparing the results of the simulation with those of the experiment.

• Tribology and Lubricants
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• v.32 no.3
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• pp.88-94
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• 2016

We conduct a series of fretting corrosion tests on tin-coated electric contact to evaluate the effects of lubricant on fretting corrosion behavior. We perform these tests with a constant contact force at 25℃ 50℃, 75°C, and 100℃. In the tests with a span amplitude of 30 μm, we could not determine the conventional behavior of the first, second, and third stages of the change in electric resistance during fretting corrosion and observed that the contact resistance continuously increases with the cycles. This behavior is due to the fact that the generation of oxides on the tin-coated contact is controlled and stabilized by the presence of lubricant. SEM observations on samples with a span amplitude of 77 μm at all testing temperatures confirm that there is less oxide debris on the fretting damaged surface. Hence, for tin-coated electric connector, the effect of lubrication on the lifetime of the electric contact increases as the fretting span decreases and testing temperature increases, compared to those for connector without lubricant. Especially, for a specimen with a span amplitude of 30 μm at 100℃, the increment in contact lifetime due to lubricant is found to be more than 20 times, compared to that without lubricant.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.328-333
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• 2002

When vehicle travelling along the track which has irregularity such as vertical profile, dynamic forces arise at the Wheel/Rail contact patch by wheel/rail interaction. In particular short wavelength irregularities on dipped joint and small stiffness of connecting rail bring about intense wheel/rail dynamic effects at higher speed. In the paper, a new model for dipped joint rail is developed to study dynamic behavior of track. A cusp behavior on dipped joint was defined by its amplitude and decay factor, which was presented by FRA track classes. The result of case study are presented, which show wheel rail contact force in each track classes, train operation speed and bending flexible rigidity ratio of fishplates which are connecting the rail.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.86-91
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• 2020

An important factor of rough road modeling is analyzing the shear behavior properties of the rough road. These properties influence the drawbar pull of the tool when interacting with the soil used in agriculture. Furthermore, shear behavior properties are important because sinkage and shear stress are generated when wheels drive on rough roads. In this study, we performed a direct shear test to investigate the shear behavior properties of soils and compare with the direct shear simulation; shear force derived by the coupled analysis of discrete element method; and multi-body dynamics. Soil contact parameters were measured in a wheel and soil contact simulation followed by comparison of the simulated and experimentally measured shear force.

• Journal of Families and Better Life
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• v.28 no.1
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• pp.13-24
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• 2010

The purpose of this study were to examine the perception and behavior for preparing their old age. In order to achieve this purpose, a survey was conducted with 723 adults from Daegu and Kyungpook. Major findings of this study are as follow: First, there were statistically significantly different perception for preparing their old age according to the personal variables such as gender, age, education, marriage status, occupation and income. Second, there were statistically significantly different perception for preparing their old age according to the elderly-related variables such as taken the elder program, interests in media for elderly, the opinion on living together with the aged, contact with aged and the opinion about contact with aged. Third, there were statistically significantly different behavior for preparing their old age according to the personal variables such as gender, age, religion, education, marriage status, occupation and income. Finally, there were statistically significantly different behavior for preparing their old age according to the elderly-related variables such as taken the elder program, interests in media for elderly, the opinion on living together with the aged and the opinion about contact with aged.

• Tribology and Lubricants
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• v.18 no.4
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• pp.255-259
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• 2002

The tribological properties of eight different liquid crystals were investigated in a concentrated point contact device and a ball-on-flat contact. For comparison, the same tests were also performed with commercial greases and the corresponding base oils. Under the fully flooded conditions studied, liquid crystals in a concentrated point contact showed lower friction than commercial greases and greater film thickness dependence on rolling speed than grease base oils or greases. Test results also showed that the film thickness and friction were little influenced by the composition of the examined liquid crystals.

• Tribology and Lubricants
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• v.23 no.6
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• pp.272-277
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• 2007

Various type of rotary unions are widely used to provide fluids between rotating parts. To prevent fluid leakage, most of the rotary unions adopt mechanical seals which is highly reliable but too expensive and complicate. In this paper, a simple lip seal system made of PTFE is adopted in designing of a compact rotary union. Using MARC, the behavior characteristics of lip seal are investigated for seal mounting process, and obtained variations of contact pressure distribution and contact width with interferences and fluid pressures. The results showed that contact width are increased with interference and pressure. The maximum contact pressure are also increased up to a certain interference and pressure, however, then decreased. The numerical methods and results can be applied in designing and performance improvement of lip seal adopted rotary union, and further extensive studies are required.

• International Journal of Railway
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• v.5 no.3
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• pp.129-134
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• 2012

Contact fatigue damages on the rail surface, such as head checks and squats are a growing problem. The fatigue cracks forming on the contact surface grow according to load and lubricating conditions and may end up breaking the rail. Rail fracture can be avoided by preventing the cracks from reaching the critical length. Therefore, the crack growth rate needs to be estimated precisely according to the conditions of the track and load to develop a maintenance plan against rail damages. Therefore, it is important to understand the mechanism of cracks initiation and growth on a rail due to repetitive rolling contact. In this study, we have investigated the crack growth behavior on the rail surface by using the twin-disc tests and the finite element analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.115-115
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• 2010

This paper introduces a measurement system that measures behavior and electrical characteristics of overhead contact line irregular sections in real-time. For verification, we developed a prototype of the real-time overhead contact line irregular section behavior measurement system and a monitoring system for field tests. The current and temperature of contact wires and messenger wires were measured real-time by applying the system at KTX a commercial line. Therefore, acquiring data is possible with the developed system and this system that measures one of the fundamental and key factors, the catenary current, should be applicable to various areas such as detecting characteristics for designing overhead contact lines, enhancing speed, and enhancing energy.