• The Journal of the Acoustical Society of Korea
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• v.21 no.1E
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• pp.18-24
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• 2002

This paper discusses the development of an acoustic vector channel simulator for the performance analysis of an acoustic digital communication system. The channel simulator consists of transmission module, acoustic channel model, receiver, beamformer, and adaptive equalizer. The source signal (QPSK) is generated by the specified parameters. The transmitted signal generates multipath signals which have a different delay, amplitude and doppler frequency. The paper presents in details the approach to the performance analysis of an acoustic digital communication system according to the antenna structure and the various baseband signal processing techniques.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.923-926
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• 2001

In this paper, we investigate a new approach pilot-symbol-aided channel estimation for orthogonal frequency division multi-plexing (OFDM) systems. Until now, lots of channel estimation methods are proposed. The pilot symbol assisted modulation (PSAM) has good performance. But, our proposed Algorithm has more good performance than the conventional PSAM system. Our algorithm is that channel estimation performance using the less inserted pilot-symbols systems is almost same to the two times inserted pilot-symbols system. The proposed method is highly robust to fast Rayleigh fading channel. Simulation results are presented to demonstrate the performance of our proposed algorithm.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.3
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• pp.237-244
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• 2013

A continuous, explicit drain-current equation for short-channel double-gate (DG) MOSFETs has been derived based on the explicit surface potential equation. The model is physically derived from Poisson's equation in each region of operation and adopted in the unified regional approach. The proposed model has been verified with numerical solutions, physically scalable with channel length and gate/oxide materials as well as oxide/channel thicknesses.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1777-1782
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• 2003

This paper presents the design, fabrication, and testing of the capillary-induced pressure drop valve, thermocapillary pumping of liquid droplet in hydrophilic channels and the splitting of droplet. The capillaryinduced pressure drop is derived with thermodynamic approach considering three-dimensional meniscus shape which is essential for calculating pressure drop in the diverging shape channel when the aspect ratio is close to one. The micro channel is fabricated via MEMS processes, which consists of the liquid stop valve to retard the liquid droplet, thermocapillary pumping region and the bifurcation region. Also the micro heaters are fabricated to drive the droplet by thermocapillary. The theoretical approaches agree well with the experimental data. The functionality of capillary valve is confirmed to be valid when the aspect ratio is smaller than one. To overcome the difficulty in splitting of the droplet due to the pressure drop in the general Y-shape channel, the protrusion shape is employed for easy splitting in the bifurcation channel.

• ETRI Journal
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• v.28 no.5
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• pp.688-691
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• 2006

This letter addresses the superimposed pilot aided multiuser channel estimation for the uplinks of multi-input multi-output orthogonal frequency-division multiplexing systems. To mitigate the embedded-data effects on the performance of channel estimation, a novel combining algorithm is proposed. Optimal pilot symbols are developed with respect to the least square channel estimate's mean square error. The averaged sum-capacity lower bound is derived and simulated. Simulation results show that on a low signal-to-noise ratio regime, our proposed scheme achieves better performance and higher capacity than the conventional pilot aided approach.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1451-1454
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• 2002

In recent years, there are growing concerns about land mobile satellite (LMS) communication systems and mobile stratospheric communication systems (SCS) for the purpose of service upgrade of personal and mobile communications in near future. It is important to possess accurate channel model for prediction of the above system performance. Thus, in this paper, we evaluate the bit error rates of a coded BPSK system based on realistic channel model which can be applied to stratospheric communication systems. The channel data was made by fitting the parameters of probability distribution model to measured data. This approach was proposed by Corraza〔1〕and modified by You〔2〕. And also the effects of channel codings on the system performance are analyzed. As results, we can get the performance curve characteristics on realistic Rician log-normal fading channels with various communication environments.

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

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.867-873
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• 2008

Cyclic delay diversity (CDD) is considered as a simple approach to exploit the frequency diversity in OFDM system. In this paper, we apply CDD to the conventional STBC/SFBC/STFBC-OFDM transmit diversity schemes for Rayleigh fading channels. We compare the performances of STBC/SFBC/STFBC with and without CDD schemes. Simulation results show that the combination of block coding with CDD works well when using the ITU-R M. 1225 channel for both Pedestrian A (Ped A) channel with the mobility of 3 km/h, and Vehicular A (Veh A) channel with the mobility of 120km/h. For a BER of $10^{-3}$, compared to the conventional block coding schemes, a gain of 2dB, 4dB, and 5dB is obtained under the Ped A channel environment by STBC-OFDM, SFBC-OFDM and STFBC-OFDM with CDD, respectively Under the Veh A channel. gains by the combined schemes are 6dB, 2dB, and 4dB, respectivcly.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 1993.07a
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• pp.122-123
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• 1993

Bangkok Bar Channel is a unique approach channel to Bangkok(on Toi)Harbor that is the representative river port constructed along the river mouth of Chao Praya River. Various facilities are scattered along the both sides of the river between the river mouth and the bridge located about 50km upward. The construction of the channel began in 1951 and was completed in 1954. (omitted)

• Management & Information Systems Review
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• v.33 no.2
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• pp.281-299
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• 2014

This study using a transaction cost approach perspective, this paper presents a model for understanding shopper's buying behavior. Finally, based on the results of these studies, this paper suggests practical implications to companies establishing their management strategy of the channels. In order to achieve the research purpose, it derived hypotheses from the literature studies and conducted questionnaire survey for the buyer who actually purchased by distribution channels. In this paper, 876 of the samples has been used in practice and with those samples it analyzes its empirical testing through reliability verification, validation, factor analysis, correlation analysis and covariance structure analysis.