• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.5
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• pp.446-452
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• 2005

As the name means, the WiBro is mobile service so that radio internet connection may be possible with high transmission speed using various terminal. Because WiBro is choosing suitable All-lP network architecture in internet service offer, structure of network is simple and the various supplementary service offer is available. This paper presented mobility model of terminal and proposed efficient way to improve existent way that transfer efficiency drops by data padding and analyze the performance by simulation.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.10a
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• pp.127-132
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• 1999

A mobile IP is proposed to support host mobility over the current Internet. One of the most important issues on the host mobility is location and routing schemes that allow mobile hosts to move effectively from one site to another. In a Mobile IP environment, frequent handoffs are likely to degrade the performance by minimizing the loss of datagrams during handoffs. The handoff scheme is using routing optimization and binding extension to improve the performance by minimizing the average transfer delay of messages and packet loss. Simulation details show the improvement of transport delays and packet loss rate.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.659-659
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• 2013

Recently, graphene has been intensively studied due to the fascinating physical, chemical and electrical properties. It shows high carrier mobility, high current density, and high thermal conductivity compare with conventional semiconductor materials even it has single atomic thickness. Especially, since graphene has fantastic electrical properties many researchers are believed that graphene will be replacing Si based technology. In order to realize it, we need to prepare the large and uniform graphene. Chemical vapor deposition (CVD) method is the most promising technique for synthesizing large and uniform graphene. Unfortunately, CVD method requires transfer process from metal catalyst. In transfer process, supporting polymer film (Such as poly (methyl methacrylate)) is widely used for protecting graphene. After transfer process, polymer layer is removed by organic solvents. However, it is impossible to remove it completely. These organic residues on graphene surface induce quality degradation of graphene since it disturbs movement of electrons. Thus, in order to get an intrinsic property of graphene completely remove of the organic residues is the most important. Here, we introduce modified wet graphene transfer method without PMMA. First of all, we grow the graphene from Cu foil using CVD method. And then, we deposited several metal films on graphene for transfer layer instead of PMMA. Finally, we fabricate graphene FET devices. Our approaches show low defect density and non-organic residues in comparison with PMMA coated graphene through Raman spectroscopy, SEM and AFM. In addition, clean graphene FET shows intrinsic electrical characteristic and high carrier mobility.

• Journal of IKEEE
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• v.27 no.3
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• pp.265-272
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• 2023

In this paper, a GPU-accelerated kernel of range Doppler algorithm (RDA) was developed for real-time image formation based on frequency modulated continuous wave (FMCW) synthetic aperture radar (SAR). A pinned memory was used to minimize the data transfer time between the host and the GPU device, and the kernel was configured to perform all RDA operations on the GPU to minimize the number of data transfers. The dataset was obtained through the FMCW drone SAR experiment, and the GPU acceleration effect was measured in an intel i7-9700K CPU, 32GB RAM, and Nvidia RTX 3090 GPU environment. Including the data transfer time between host and devices, it was measured to be accelerated up to 3.41 times compared to the CPU, and when only the acceleration effect of operation was measured without including the data transfer time, it was confirmed that it could be accelerated up to 156 times.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.5
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• pp.77-83
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• 2012

The importance of mobility management is becoming to be one of the upcomming issues to be addressed to provide the converged services and the convergence of the heterogeneous network environments. In this paper, the new user mobility management scheme which can be utilized to model the user's mobility behaviors for interworking with heterogeneous overlay convergent networks under the time-varying radio propagation environment has been proposed. Thus user mobility management scheme based on user mobility model is considered in order to optimize the dwell time of users in the overlay convergent networks. This Mobile IP user mobility management will be very useful to model the user mobility behaviors and can be used to estimate the signaling traffic and frequency spectrum demands for massive data transfer for the heterogeneous overlay convergent networks.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.87-97
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• 2015

To support the efficient mobility MIPv6v, FMIPv6, HMIPv6 and host-based mobility management protocols have been developed. AAAC (Authentication, Authorization, Accounting and Charging) system is applied in this paper analyzed the the existing IPv6 PMIPv6, FPMIPv6 network security effective and IPv6 MMP (Mobile Management Protocol) Features and performance analysis is performed. And IPv6 MMP seamless transfer performance in terms of packet loss probability, will be analyzed. That can be efficiently used as a method for the integration of QoS and mobility so that you can manage and control the resources presented QoSB usage. Results of evaluation results showed a better overall fast handover structure of mobility management techniques. PMIPv6 and FPMIPv6 in many respects the most efficient structure that can be specifically, a fast handover of the structure of the network-based mobility management scheme showed the best results.

• Journal of the Korean Graphic Arts Communication Society
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• v.22 no.1
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• pp.75-82
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• 2004

The photoluminescence and electroluminescence of poly(9-vinylcarbazole) (PVCz) containing different ratio 1.3,5-dimethly-3,5-di-tert-butyl-4,4-diphenoquinone (MBDQ), 1.3,5-diemthyl-3.5-di-tert-butyl-4,4-stylbenquinone (MBSQ) were characterized. As the contents of DQ and SQ increased, the intensity of peaks at 516 and 540nm increased in PL spectra. The results of TOF measurement were shown that the hole mobility of PVCz decreased as the ratio of DQ or SQ increased. On the other hand, the electron mobility of PVCz increased. Therefore Electron transport is more favorable than hole transport in these charge transfer complexes, due to the stronger localization of the holes. Evidence for better electron transport is the higher mobility of electrons in pure DQ or SQ compared to hole mobility in pure PVCz, and lower DQ or SQ concentration required for equivalent mobilities in the charge-transfer complexes.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.4
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• pp.161-168
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• 2001

Organic thin film transitors(TFTs) are of interest for use in broad area electronic applications. For example, in active matrix liquid crystal displays(AMLCDs), organic TFTs would allow the use of inexpensive, light-weight, flexible, and mechanically rugged plastic substrates as an alternative to the glass substrates needed for commonly used hydrogenated amorphous silicon(a-Si:H). Recently pentacene TFTs with carrier field effect, mobility as large as 2 $cm^2V^{-1}s^{-1}$ have been reported for TFTs fabricated on silicon substrates, and it is higher than that of a-Si:H. But these TFTs are fabricated on silicon wafer and $SiO_2$ was used as a gate insulator. $SiO_2$ deposition process requires a high insulator which is polyimide and photo acryl. We investigated trasfer and output characteristics of the thin film transistors having active layer of pentacene. We calculated field effect mobility and on/off ratio from transfer characteristics of pentacene thin film transistor, and measured IR absorption spectrum of polymide used as the gate dielectric layer. It was found that using the photo acryl as a gate insulator, threshold voltage decreased from -12.5 V to -7 V, field effect mobility increased from 0.012 $cm^2V^{-1}s^{-1}$ to 0.039 $cm^2V^{-1}s^{-1}$ , and on/off current ratio increased from $10^5\;to\;10^6$. It seems that TFTs using photo acryl gate insulator is apt to form channel than TFTs using polyimide gate insulator.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.355-364
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• 2010

A session transfer method, referred to as a Recipient Serving-call session control function (S-CSCF) Assured (RSA), is proposed in order to support both session mobility and consistency in IP multimedia subsystem (IMS) based next generation network (NGN). RSA session transfer simplifies a basic session transfer operation specified in [1] by using the user agent client (UAC) like characteristics of an S-CSCF. To show its efficiency, the session transfer delay and the traffic cost of RSA session transfer are investigated and compared with those of existing session transfer applications, including Assured and Consultative session transfers, by practically considering multiple session transfer failures. It is shown that RSA session transfer can further improve user experience by reducing session transfer delay as well as traffic cost than Assured and Consultative session transfers.

• Korean Journal of Materials Research
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• v.30 no.3
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• pp.142-148
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• 2020

Graphene has attracted the interest of many researchers due to various its advantages such as high mobility, high transparency, and strong mechanical strength. However, large-area graphene is grown at high temperatures of about 1,000 ℃ and must be transferred to various substrates for various applications. As a result, transferred graphene shows many defects such as wrinkles/ripples and cracks that happen during the transfer process. In this study, we address transfer-free, large-scale, and high-quality monolayer graphene. Monolayer graphene was grown at low temperatures on Ti (10nm)-buffered Si (001) and PET substrates via plasma-assisted thermal chemical vapor deposition (PATCVD). The graphene area is small at low mTorr range of operating pressure, while 4 × 4 ㎠ scale graphene is grown at high working pressures from 1.5 to 1.8 Torr. Four-inch wafer scale graphene growth is achieved at growth conditions of 1.8 Torr working pressure and 150 ℃ growth temperature. The monolayer graphene that is grown directly on the Ti-buffer layer reveals a transparency of 97.4 % at a wavelength of 550 nm, a carrier mobility of about 7,000 ㎠/V×s, and a sheet resistance of 98 W/□. Transfer-free, large-scale, high-quality monolayer graphene can be applied to flexible and stretchable electronic devices.