• Composites Research
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• v.32 no.5
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• pp.290-295
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• 2019

In the present study, composite insulation mat was reinforced over polyurethane foam (PUF) to improve the thermal performance and impact resistance of the PUF applied to the liquefied natural gas carrier insulation system. The composite insulation mat used Kevlar, aerogel, and cryogel composite mat that can be applied in a cryogenic environment. The thermal conductivity was measured at $20^{\circ}C$ to investigate the thermal performance, and the drop impact test was carried out under impact energy of 30 J at $20^{\circ}C$, $-163^{\circ}C$ to investigate the impact resistance. The measured thermal performance was compared with neat PUF through effective thermal conductivity theoretical value. The shock resistance was evaluated of contact force, contact time, and absorb energy. In experimental results, cryogel composite mat was the best performance in terms of thermal performance, and aerogel composite mat was the best performance in terms of impact resistance.

• Journal of Environmental Impact Assessment
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• v.18 no.2
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• pp.79-87
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• 2009

This study was performed for the application of porous concrete blocks and aquatic plants for the water purification in small urban stream. This study investigated the ability of water purification according to various environments, algae and aquatic plants. When the porous concrete was used as contact media, the average removal efficiencies of SS, BOD and COD were 85~95%, 50~60% and 65~75%, respectively. Also, when the porous concrete and aquatic plants was used the average removal efficiency of SS, BOD and COD were 90~95%, 60~70% and 70~80%, respectively. As the results, average removal efficiency of total nitrogen, at the condition of the porous concrete and aquatic plants, was about 40-50%, then, that of total phosphorus was about 60-70%.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.652-661
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• 1988

A theoretical attempt is made to analyze the dynamic contact force and response of laminated composite beams subjected to the transverse impact of steel balls. A beam finite element model based on the modified theory for laminated composites in conjunction with static contact laws is formulated for the theoretical investigation. Finally, it is shown that the present results are in good agreement with some existing solutions or wave propagation theory.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.109-117
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• 2014

This paper reports a method to modify the gear tooth profile of a wind turbine gearbox to reduce the noise caused by the impact of the gear teeth. The major causes of tooth impact are the elastic deformation of the gear teeth, shafts, and case of the gearbox under loading, and the fabrication tolerances in gear manufacturing. In this study, the tooth profile was modified considering the elastic deformation of the gear tooth and the tooth lead modification to compensate for tooth interference in the lead direction as a result of shaft deformations. The method was applied to the gearbox of a 2.5MW wind turbine, and the transmission error was characterized before and after modifying the gear teeth. For the modified gear teeth, the transmission error (67.6%) was lower by 17.8%. Additionally, the gear contact stress was reduced by 6.3%, to 22.3%.

• Journal of Welding and Joining
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• v.3 no.2
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• pp.1-9
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• 1985

In this study, the influence of carbon equivalents on friction welds of similar steels was investigated. Four types of steels with 15mm diameter tested in the wide range of carbon equivalents from 0.3 to 1.1 Main experimental results are summarized as follows : (1) Under the constant burn-off length, the friction time becomes longer with the increasing carbon equivalent, but the upset length shows no consistent tendencies. (2) Due to the recrystallization in the contact area, the maximum hardness occurs some away from the contact surface. And it increases almost linearly with the increasing carbon equivalent. (3) Even a steel with 1.1 C.E. can be friction welded to make defect-free welds. (4) With the increasing carbon equivalent, the bend angle and charpy impact value decrease very rapidly in the range from 0.3 C. E., but remain nearly unchanged for C. E. higher than 0.6. (5) Heat treatment of the base metals before welding has very little influence on the mechanical properties of welds. On the other hand, normalizing of the welds improves the bend angle and charpy impact value, but its effect becomes almost negligible, when the carbon equivalents are higher than 0.6.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.293-293
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• 2005

The differences between floating and grounded body effects in polycrystalline silicon thin-film transistors (polysilicon TFTs) are investigated by making a body contact. The floating body effects such as kink effect, subthreshold slope change, and body current characteristics are explained and modeled by impact ionization, which causes source body turn on, and activates the parasitic bipolar junction transistors (BJTs). These effects become crucial for channel lengths of 4㎛ or shorter. Our data show that making a body contact reduces kink effects significantly and identifies impact ionization mechanism in polysilicon TFTs.

• Transactions of the Society of Information Storage Systems
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• v.7 no.2
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• pp.60-64
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• 2011

Chemical mechanical planarization is one of the core processes in fabrication of semiconductors, which are increasingly used for information storage devices like solid state drives. For higher data capacity in storage devices, CMP process is required to show ultimate precision and accuracy. In this work, 2-dimensional finite element models were developed to investigate the effects of the slurry particle impact on microscratch generation and the phenomena generated at pad-particle-wafer contact interface. The results revealed that no plastic deformation and corresponding material removal could be generated by simple impact of slurry particles under real CMP conditions. From the results of finite element simulations, it could be concluded that the pad-particle mixture formed in CMP process would be one of major factors leading to microscratch generation.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.734-739
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• 2003

When a train moves on rails, wheel and rail vibrate to produce contact noise and contact force. The former results in airborne noise and the latter transmits through bogie and excites carbody to generate structure borne noise. In this paper, wheel vibration is studied by theoretical and experimental approaches. Theoretical analysis is performed by finite element method and experimental analysis is performed by impact test. Using modal analysis and model tunning, we could have good agreement between the two approaches.

• Earthquakes and Structures
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• v.17 no.1
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• pp.101-113
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• 2019

Earthquake-induced pounding is one of the major reasons for structural failure in earthquake prone cities. An accurate description of the pounding phenomenon of two buildings requires the consideration of systems with a large number of degrees of freedom including adequate contact impact formulations. In this paper, firstly, a node to surface formulation for the realization of state-of-the-art pounding models for structural beam elements is presented. Secondly, a hierarchical substructure technique is introduced, which is adapted to the structural pounding problem. The numerical accuracy and efficiency of the method, especially for the contact forces, are verified on an academic example, applying four different impact elements. Error estimations are carried out and compared with the classical modal truncation method. It is demonstrated that the hierarchical substructure method is indeed able to significantly speed up the numeric integration procedure by preserving a required level of accuracy.

• Design & Manufacturing
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• v.17 no.1
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• pp.64-69
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• 2023

This paper explores the impact of gate shape changes on the size and density of foamed cells in microcellular foam injection molding. Five different gate shapes were examined while varying the amount of nitrogen gas(N2) injected for foaming. Analysis of the results showed that while average values did not change significantly, deviation values decreased by approximately 65% for cell size and 56% for density when 3.5wt% of nitrogen gas was injected in the film gate. Further analysis was conducted to verify this phenomenon, revealing that the contact area between the gate and product had the greatest impact. Our findings indicate that to ensure uniform generation of foamed cells in microcellular foaming product design, a gate with a wide contact area should be secured.