• Carbon letters
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• v.25
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• pp.55-59
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• 2018

Carbon chain inserted carbon nanotubes (CNTs) have been experimentally proven having undergone pronounced property change in terms of electrical conductivity compared with pure CNTs. This paper simulates the geometry of carbon chain inserted CNTs and analyzes the mechanism for conductivity change after insertion of carbon chain. The geometric simulation of Pt doped CNT was also implemented for comparison with the inserted one. The results indicate that both modification by Pt atom on the surface of CNT and addition of carbon chain in the channel of the tube are effective methods for transforming the electrical properties of the CNT, leading to the redistribution of electron and thereby causing the conductivity change in obtained configurations. All the calculations were obtained based on density functional theory method.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.573-574
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• 2006

This research deals with the wave transmission and dissipation problems for two dimensional regular waves and s vertical circular cylindersr. Using the unsteady mild slope equation, a numerical model has been developed to calculate the reflection and transmission of regular waves from a multiple-row vertical circular cylinders. In addition hydraulic model experiments have been conducted with different values of properties between the cylinders and opening ratio (distances) between the rows of the cylinders. It is found that the transmission coefficients decrease with decreasing the opening ratio and increasing the rows of vertical cylinders. Comparison between hydralic and numerical experiments results shows resonable agreement.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.263-266
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• 2003

In this paper, we propose a new progressive image transmission system including the image coding scheme that efficiently uses the relationship between the properties of a spatial image and its wavelet transform. Firstly, an original image is decomposed into several layers by the wavelet transform, and simultaneously decomposed into 2"x2" blocks. Each image is classified into two image types according to the standard deviations of its blocks. And then each block is categorized into two regions by different thresholds according to the image types, i.e., significant activity region (SAR) and insignificant activity region (IAR). Simulation results show that the proposed coding method has better performance than the EZW and SPIHT in terms of image quality and transmitted bit-rate. In addition, it can be applied to the applications requiring the progressive image transmission.nsmission.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1412-1420
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• 1994

The adhesively bonded tubular double lap joint has better torque transmission capability and reliability in bonding operation than the single lap joint. In this paper, an analytic solution for the torque transmission capabilities and stress distributions of the adhesively bonded tubular double lap joint was derived assuming the linear properties of the adhesive and adherends. From the calculation, it was found that the torque transmission capabilities of the double lap joint was more than 40% larger compared to that of the single lap joint.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.57-63
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• 2009

Magneto-Rheological(MR) fluid composes of a base fluid and ferromagnetic particles less than tens of micrometer size dispersed in the fluid. It is called as a smart material because its rheological properties are changable by a magnetic field. Its important applications are active devices such as controllable dampers and controllable clutches. The merit of those products is that their functional characteristics are controllable such that they enable active control strategies. This paper proposes an idea for machine tool applications of the MR fluid clutch as a safety device for power transmission. FEM has been used for magnetic field analyses and the results are compared with some former experiments. Some design syntheses of the MR clutches are suggested and hopefully considered that it may be an effective safety device for power transmission of machine tools.

• Applied Microscopy
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• v.45 no.2
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• pp.89-94
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• 2015

This article briefly reviews the results of recently reported research on high-temperature Pb-free solder alloys and the research trend for characterization of the interfacial reaction layer. To improve the product reliability of high-temperature Pb-free solder alloys, thorough research is necessary not only to enhance the alloy properties but also to characterize and understand the interfacial reaction occurring during and after the bonding process. Transmission electron microscopy analysis is expected to play an important role in the development of high-temperature solders by providing accurate and reliable data with a high spatial resolution and facilitating understanding of the interfacial reaction at the solder joint.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.180-183
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• 1999

It is well known that Fe3Al intermetallic compound shows an anomalous peak of the yield strength at about 50$0^{\circ}C$ and then decrease at higher temperatures The dislocation structure was examined by transmission electron microscopy and high temperatures. The dislocation structure was examined by transmission electron microscopy and high temperature mechanical properties were examined by tensile and load relaxation tests. The flow stress curves obtained from load relaxation tests were then analyzed in terms of internal variable deformation theory. it was found that the flow curves consisted of three micro-deformation mechanisms -i. e inelastic deformation mode plastic deformation mode and dislocation creep deformation mode depending on both dislocation structure and deformation temperature. The flow curves could be well described by the constitutive equations of these three micro-deformation mechanisms based on the internal variable deformation theory.

• Journal of Environmental Impact Assessment
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• v.13 no.5
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• pp.243-250
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• 2004

Recently, concerns about health risks exposed to electromagnetic fields have been brought in the safety of electric power lines. A number of governmental and international organizations have advised to avoid the magnetic field exposure to the schools and residential areas. Some epidemiologic studies showed that electromagnetic fields should not exceed the exposure limits of 2-3mG to the people living near high-voltage transmission lines. In this study, the principles, ranges and survey methods of the assessment for powerfrequency electromagnetic fields were reviewed from the relevant research papers and documents. The ranges of electromagnetic fields were determined from 50m to 100m and have been defined according to the properties of each electric power lines and a new methodology was suggested in this study. It would be necessary to develop and improve specific assessment methods for various high-voltage transmission lines projects.

• Applied Microscopy
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• v.46 no.3
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• pp.167-169
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• 2016

Solder/electroless nickel immersion gold (ENIG) joint sample which is comprised of dissimilar materials with different mechanical properties has limited the level of success in preparing thin samples for transmission electron microscopy (TEM). This short technical note reports the operation parameters for ultramicrotomy of solder joint sample and TEM analysis results. The solder joint sample was successfully sliced to 50~70 nm thick lamellae at slicing speed of 0.8~1.2 mm/s using a boat-type $45^{\circ}$ diamond knife. Ultramicrotomy can be applied as a routine sample preparation technique for TEM analysis of solder joints.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.2
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• pp.82-102
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• 2008

Packet losses tend to occur during short error bursts separated by long periods of relatively error-free transmission. There is also a significant spatial correlation in loss among the receiver nodes in a multicast session. To recover packet transmission errors at the transport layer, tree-based protocols construct a logical tree for error recovery before data transmission is started. The current tree construction scheme does not scale well because it overloads the sender node. We propose a scalable recovery tree construction scheme considering these properties. Unlike the existing tree construction schemes, our scheme distributes some tasks normally handled by the sender node to specific nodes acting as repair node distributors. It also allows receiver nodes to adaptively re-select their repair node when they experience unacceptable error recovery delay. Simulation results show that our scheme constructs the logical tree with reduced message and time overhead. Our analysis also indicates that it provides fast error recovery, since it can reduce the number of additional retransmissions from its upstream repair nodes or sender node.