• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.11
• /
• pp.924-933
• /
• 2013

In this paper, we propose a modeling of the broadcasting in the IEEE 802.11p MAC protocol for the VANET(Vehicular Ad hoc Networks). Due to the fact that the beacon message which is needed for the safety services is shared via broadcasting, the analytical modeling of the broadcasting is crucial for the optimum design of the services. Two characteristics specific to the IEEE 802.11p are reflected in the modeling; the time limited CCH interval caused by the channel switching between the CCH and SCH, and no retransmission of the broadcasted messages. In the proposal, we assumed no restriction on the moment of generation of the beacon messages. We allow the messages to be generated and broadcasted within the whole CCH interval. Simulation results prove the accuracy of the proposed modeling. Noticeable improvements are also observed in terms of the performance indices such as the successful delivery ratio, transmission delay, and the variation of the delay.

• Electrical & Electronic Materials
• /
• v.8 no.3
• /
• pp.332-339
• /
• 1995

In this paper, it was investigated the guided field intensity distribution of the channel in the silver & potassium ion-exchange glass-waveguide. The guided field intensity distribution analysis of ion-exchange glass-waveguide was based on the combination of the WKB dispersion relationship method with a Gaussian distribution function of refractive index profile and the Field Shadow method to the modeling of the channel waveguide. As the results of the channel waveguide modeling, it was represented 2-dimensional and 3-dimensional field distribution of ion-exchange glass waveguide.

• Journal of information and communication convergence engineering
• /
• v.5 no.1
• /
• pp.45-49
• /
• 2007

The analytical transport model in subthreshold regime for double gate MOSFET has been presented to analyze the short channel effects such as subthreshold swing, threshold voltage roll-off and drain induced barrier lowering. The present approach includes the quantum tunneling of carriers through the source-drain barrier. Poisson equation is used for modeling thermionic emission current, and Wentzel-Kramers-Brillouin approximations are applied for modeling quantum tunneling current. This model has been used to investigate the subthreshold operations of double gate MOSFET having the gate length of the nanometer range with ultra thin gate oxide and channel thickness under sub-20nm. Compared with results of two dimensional numerical simulations, the results in this study show good agreements with those for subthreshold swing and threshold voltage roll-off. Note the short channel effects degrade due to quantum tunneling, especially in the gate length of below 10nm, and DGMOSFETs have to be very strictly designed in the regime of below 10nm gate length since quantum tunneling becomes the main transport mechanism in the subthreshold region.

• International Journal of Contents
• /
• v.4 no.3
• /
• pp.20-28
• /
• 2008

To obtain realistic performance measures for wireless networks, one should consider changes in performance due to failure related behavior. In performability analysis, simultaneous consideration is given to both pure performance and performance with failure measures. SRN is an extension of stochastic Petri nets and provides compact modeling facilities for system analysis. In this paper, a new methodology to model and analyze performability based on stochastic reward nets (SRN) is presented. Composite performance and availability SRN models for wireless handoff schemes are developed and then these models are decomposed hierarchically. The SRN models can yield measures of interest such as blocking and dropping probabilities. These measures are expressed in terms of the expected values of reward rate functions for SRNs. Numerical results show the accuracy of the hierarchical model. The key contribution of this paper constitutes the Petri nets modeling techniques instead of complicate numerical analysis of Markov chains and easy way of performance analysis for channel allocation under SRN reward concepts.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.7 no.2
• /
• pp.88-93
• /
• 2007

In this paper, a simple and improved noise parameter model of RF MOSFETs is developed and verified. Based on the analytical model of channel thermal noise, closed form expressions for four noise parameters are developed from proposed equivalent small signal circuit. The modeling results show a excellent agreement with the measured data of $0.13{\mu}m$ CMOS devices.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.47 no.10
• /
• pp.1-6
• /
• 2010

In this paper, RF Capacitance-Voltage(C-V) curve of short-channel MOSFET has been extracted from the room temperature to $225^{\circ}C$ using a RF method based on measured S-parameter data, and its high-temperature dependent characteristics are empirically modeled. It is observed that the voltage shift according to the variation of temperature in the weak inversion region of RF C-V curves is lower than the threshold voltage shift, but it is confirmed that this phenomenon is unexplainable with a long-channel theoretical C-V equation. The new empirical equation is developed for high-temperature dependent modeling of short-channel MOSFET C-V curves. The accuracy of this equation is demonstrated by observing good agreements between the modeled and measured C-V data in the wide range of temperature. It is also confirmed that the channel capacitance decreases with increasing temperature at high gate voltage.

• Journal of Distribution Science
• /
• v.14 no.11
• /
• pp.129-138
• /
• 2016

Purpose - The ICT(information and communications technologies) development is affecting consumer behaviors on selecting channel or distribution system. This study aims to advance our knowledge about the factors influencing omni-channel behaviors. This study considers the positive brand experience as the moderating variable into the relationship between omini-channel use intention and consumer brand relation. Also, the effect of positive brand experience on consumer-brand relation is researched. Research design, data, and methodology - This study conducted an empirical test with the subject as customers who purchase goods or service through on-off cross channel simultaneously. The research model is developed from prior literatures about influencing variables on channel selection. The structure of this study is designed to identify causal relationships between the variables. 268 survey data from the questionnaire survey which is conducted to target customers who use online and offline channels, is used for empirical analysis. This study validates generality with descriptive statistics and data reliability with Cronbach's alpha value. The exploratory factor analysis is used for value purification. Then, the confirmatory factor analysis is conducted for structural equation modeling. Finally, the execute structural equation modeling is analyzed to confirm the hypotheses Results - First, the two causal influences between perceived performance risk and the propensity of omni-channel and between price consciousness and the propensity of omni-channel are verified through the empirical test. Second, the result identifies that the propensity of omni-channel is influenced on consumer-brand relationship. Third, the AMOS analysis proves that the moderating variable, positive brand experience, has significant positive impact on consumer-brand relationship. This significant relationship is highly supported by the regression analysis between brand experience and propensity of omni-channel because it results that positive brand experience has positive impact on the propensity of omni-channel. All hypotheses are verified to be true. Conclusions - Based on the empirical result, this study confirms that perceived performance risk and price consciousness are the important factors influencing propensity of omni-channel. According to the additional analysis, the moderating variable and positive brand experience plays important role between the propensity of omni-channel and consumer-brand relationship. Furthermore, positive brand experience influences more on consumer-brand relationship than non-positive brand experience.

• ETRI Journal
• /
• v.39 no.5
• /
• pp.718-728
• /
• 2017

Empirical modeling of wireless fading channels using common schemes such as autoregression and the finite state Markov chain (FSMC) is investigated. The conceptual background of both channel structures and the establishment of their mutual dependence in a confined manner are presented. The novel contribution lies in the proposal of a new approach for deriving the state transition probabilities borrowed from economic disciplines, which has not been studied so far with respect to the modeling of FSMC wireless fading channels. The proposed approach is based on equal portioning of the received signal-to-noise ratio, realized by using an alternative probability construction that was initially highlighted by Tauchen. The associated statistical procedure shows that a first-order FSMC with a limited number of channel states can satisfactorily approximate fading. The computational overheads of the proposed technique are analyzed and proven to be less demanding compared to the conventional FSMC approach based on the level crossing rate. Simulations confirm the analytical results and promising performance of the new channel model based on the Tauchen approach without extra complexity costs.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2010.05a
• /
• pp.659-663
• /
• 2010

In recent, flood inundation damages by hydraulic structure failures have increased drastically and thus a variety of countermeasures were needed to minimize such damages. A real-time flood inundation prediction technique is essential to protect and mitigate flood inundation damages. In the context of real time flood inundation modeling, this study aims to develop a grid based two-dimensional numerical method for flood inundation modeling using globally-available DEM data: SRTM with $90m{\times}90m$ spatial resolution. The newly-developed model guarantees computational efficiency in terms of geometric data processing by direct application of DEM for flood inundation modeling and also have good compatibility with various types of raster data when compared to a commercial model such as FLUMEN. The model, which employed the leap-frog algorithm to solve shallow water and continuity equations, can simulate inundating flow from channel to lowland and also returning flow from lowland to channel by comparing water levels between channel and lowland in real time. We applied the model to simulate the BaekSan levee break in the Nam river during a flood period from August 10 to 13, 2002. The simulation results had good agreements with the field-surveyed data in terms of inundated area and also showed physically-acceptable velocity vector maps with respect to inundating and returning flows.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.1
• /
• pp.17-24
• /
• 2003

A mathematical model of the hydrodynamic and heat transfer performances of two-phase flow (gas-liquid) in thin film region of micro channel is proposed. For the formulation of modeling, the flow of the vapor phase and the shear stress at the liquid-vapor interface are considered. In this work, disjoining pressure and capillary force which drive the liquid flow at the liquid-vapor interface in thin film region are adopted also. Using the model, the effects of the variations of channel height and heat flux on the flow and heat transfer characteristics are investigated. Results show that the influence of variation of vapor pressure on the liquid film flow is not negligible. The heat flux in thin-film region is the most important operation factor of micro cooler system.