• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.28-37
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• 2017

Multipath TCP (MPTCP), which is a layer 4 protocol that can get the reliability and the efficiency of the transmission by using multipath transfer, was standardized by the IETF. MPTCP provides superior performance when compared to a single TCP when used in a homogeneous network with similar network characteristics. However, MPTCP degrades performance when used in heterogeneous networks with different network characteristics. In this paper, we propose 'Delay-alerted path-blocking scheduler'. It measures the delay of each path and blocks the path with a long delay to reduce the order of packets in the receive buffer. If the duplicated packet is sent to the blocked path to measure the delay and the congestion on the blocking path is reduced, the blocked path is unblocked. For performance analysis, the proposed scheduler was implemented in the Linux kernel and improved performance was obtained in the test bed. We also confirmed that the proposed scheduler reduces the degradation of MPTCP performance in real wireless networks with heterogeneous path characteristics.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.99.1-99.1
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• 2016

The materials for an electronic packaging provide diverse important functions including electrical contact to transfer signals from devices, isolation to protect from the environment and a path for heat conduction away from the devices. The packaging materials composed of metals, ceramics, polymers or combinations are crucial to the device operating properly and reliably. The demand of effective charge and heat transfer continuous to be challenge for the high-speed and high-power devices. Nanomaterials including graphene, carbon nanotube and boron nitride, have been designed for the purpose of exploiting the high thermal, electrical and mechanical properties by combining in the matrix of metal or polymer. In addition, considering the inherent electrical and surface properties of graphene, it is expected that graphene would be a good candidate for the surface layer of a template in the electroforming process. In this talk, I will present recent our on-going works in nanomaterials for microelectronic packaging: 1) porous graphene/Cu for heat dissipations, 2) carbon-metal composites for interconnects and 3) nanomaterials-epoxy composites as a thermal interface materials for electronic packaging.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.452-457
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• 2008

In this paper, the vibrations of floor systems of which buildings are under construction are studied by experimental and analysis method. The first step is to measure the operational response data and FRF at the supporting points of the utility and the second step is to calculate the dynamic load by TPA Method which provided by LMS VirtualLab System Analysis Module. The dynamics we used to identify is expressed by below equation; $$\{F_{oper}\}=[H]^{-1}\;{\cdot}\;\{{.. \atop x_{oper}}\}$$ Where, H(Transfer function between position of the force and response) and x(response) are measured by vibration test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.151-157
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• 2004

In this paper, we propose a simple control scheme, based on second order sliding modes, which guarantees a fast and precise container transfer and the swing suppression during the container movement, despite of model uncertainties and unmodeled dynamic actuators. In the actual case, the swing suppression is obtained by constraining the system motion on a suitable surface which involves both the desired path and the swing angle. Strictly speaking, the trolley velocity is modified on-line, on the actual swing angle, to obtain the suppression of the oscillations not only at the end of the transport but during transfer as well. Such controller has been tested on a laboratory-size model of the 3Dcrane, and some experimental results are reported.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1213-1218
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• 2007

The brake judder comes from non-uniformities in the tire/wheel assembly caused by mechanical effects such as a brake torque variation (BTV). A disc thickness variation (DTV) related with the kinematic behavior of the disc was investigated a main source of BTV. In this study, a dynamic model with brake corner assembly of full vehicle using MSC.ADAMS was correlated by experiment of judder phenomenon. Judder was generated and correlated systematically by judder experiment in chassis and brake dynamometer from variation in the thickness of the disc. Also it has been found a judder transfer path and variation of the braking pressure. Through analysis of transfer function and movement of subsystem caused by BTV generation, design parameters have been found. Based on the results obtained from parameter study of suspension module, the effective design process and developed model with brake corner assembly was suggested for vibration reduction of steering wheel caused by the judder phenomenon.

• Korean Journal of Geomatics
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• v.3 no.2
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• pp.123-128
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• 2004

As the applied fields of GIS are expanded to the transportation, developing internet-based applications for transportation information is getting attention increasingly. Most applications developed so far are primarily focused on guidance systems for owner-driven cars. Although some recent ones are devoted to public transportation systems, they show limitations in dealing with the following aspects: (i) people may change transportation means not only within the same type but also among different modes such as between buses and subways, and (ii) the system should take into account the time taken in transfer from one mode to the other. This study suggest the framework for developing a public transportation guidance system that generates optimized paths in the transportation network of mixed means including buses, subways and other modes. For this study, the Genetic Algorithms are used to find the best routes that take into account transfer time and other service-time constraints.

• Advanced Composite Materials
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• v.16 no.3
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• pp.207-221
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• 2007

The filling process of resin injection/compression molding (I/CM) can be divided into injection and compression phases. During the resin injection the mold is kept only partially closed and thus a gap is present between the reinforcements and the upper mold. The gap results in preferential flow path. After the gap is filled with the resin, the compression action initiates and forces the resin to penetrate into the fiber preform. In the present study, the resin flow in the gap is simplified by using the Stokes approximation, while Darcy's law is used to calculate the flow field in the fiber mats. Results show that most of the injected resins enter into the gap during the injection phase. The resin injection time is extremely short so the duration of the filling process is determined by the final closing action of the mold cavity. Compared with resin transfer molding (RTM), I/CM process can reduce the mold filling time or injection pressure significantly.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.264-270
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• 1996

In this paper, a computer automated system has been developed for measuring the focal length of camera lens using the MTF(Modurar Transfer Function) based on the signal processing around a line CCD and autocollimator. An optical Path for the focal length measurement system has been designed around thelight sourec, collimator, camera, mirror and the line CCD. The eyepiece of the collimator is replaced byline CCD, and the mirror is moved along the focal axis by a PC driven step motor. An efficient method has been designed for finding the optimum MTF value for the focal length based on the least squares approach. The developed system is fullycomputer automated: signal transmission to and from the camera, MTF evaluation based on the line CCD, step motor contorl, etc. The developed system has been applied to a practical camera manufacturing process and demonstrated its performance

• Korean Journal of Computational Design and Engineering
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• v.8 no.4
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• pp.212-221
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• 2003

In order to reduce the lead-time and cost, the technology of rapid prototyping (RP) has been widely used. A new rapid prototyping process, transfer-type variable lamination manufacturing process by using expandable polystyrene foam (VLM-ST), has been developed to reduce building time, apparatus cost and additional post-processing. At the same time, VLM Slicer, the CAD/CAM software for VLM-ST has been developed. In this study, algorithms for accuracy improvement of VLM-ST, which include offset and overrun of a cutting path and generation of a reference shape are developed. Offset algorithm improves cutting accuracy, overrun algorithm enables the VLM-ST process to make a shape of sharp edge and reference shape generation algorithm adds additional shape which makes off-line lamination easier. In addition, proposed algorithms are applied to practical CAD models for verification.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1619-1625
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• 2007

This paper deals with the heat transfer characteristics due to a fire of train standing at under-ground station. In order to analyze the fluid characteristics at under-ground station, the governing equation was assumed to be steady-state, incompressible and turbulent fluid model. The commercial Fluent ver. 6.0 was used to solve the above numerical problem. Through the numerical analysis, fluid path-line, temperature distribution and $CO_2$ density distribution are demonstrated for three kinds of cases. As a conclusion of the study, a scenario for operation of ventilation fan in a fire is proposed.