• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11A
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• pp.1237-1243
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• 2004

This paper presents and analyses the closed-form expression of the average bit error rate (BER) for an asynchronous direct-sequence code division multiple access (DS-CDMA) system with coherent binary phase shift keying (BPSK) modulation scheme using a maximal ratio combining (MRC) diversity over a Rician fading channel. In addition to the average BER, outage probability, and user capacity of system are estimated as performance measures. The results are general enough so that it includes Rayleigh fading and nonfading channel with zero and infinite Rician factor, respectively, as special cases. The effects of various channel models, processing gains, and diversity orders on the system performances are also considered for the typical multipath delay profiles characterized by Rician fading channel.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.339-341
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• 2006

Increasing interconnection of power plants in modern large electric power system has made power system dynamic studies much more complex. For effective analysis of the power system, model reduction and aggregation is required. In this paper, a new relation index is presented to identify the coherent generators in the large scale power system. In order to demonstrate the effects of this relation index, it is applied to a small scale power system of IEEE 39-bus test system and the simulation results are presented.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.5
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• pp.716-723
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• 1990

Transmission electron microscopy (TEM) and anger electron microscopy(AES) studies of GaAs/AlxGa1-xAs(x=0.58) quantum wells grown by low pressure metalorganic chemical vapor deposition(LP-MOCVD) are carried out. Isolated quantum well structure having the well width as small as 15 \ulcornerand multiquantum well structure, which consisted of 51 alternating layers with each thickness of 10\ulcorner were suscessfully grown. TEM analyses have shown that their interfaces were almost completely coherent without any structural disorder, alloy clustering and crystal defect. AES depth resolution have shown the compositional periodicity of superlattice structure.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.1
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• pp.85-95
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• 1995

The error intensity models for the ML estimation of a signal parameter have been developed in a companion paper [1]. While the methods described in [1] are applicable to any estimation problem with continuous parameters, our main application in this paper is the time delay estimation, and comparisons among the models derived in [1] (i.e. LC, LM, and ALM models)have been made. We first consider the case where only additive Gaussian noise is involved, and then the shot noise environment where coherent impulsive noise is also involved in addition to the Gaussian noise. We compare the models in terms of the probability of error, MSE(Mean Squared Error), and the computational complexity, which are the most important performance criteria in the analysis of parameter estimation. In conclusion, the ALM model turned out to be the most adequate model of all from the viewpoints of the criteria mentioned above.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.4
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• pp.336-345
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• 1996

The S.O(synchronous osillator) oscillates at its natural frequency without the externa applied signal. But if the external signal is applied, the S.O starts to track the external frequency which can be sinusoidal, pulsed or some other waveform. Thus, the output is synchronized with the wide range of tracking bandwidth to the external frequency. Specifically, the S.O also posses frequency division and multiplication capability. All of these indicate that the S.O can overcome the difficulties of syschronization in coherent digital communication systems. This papers proposed application of DS/SS communication with study on the synchronous properties of S.O.

• Journal of information and communication convergence engineering
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• v.5 no.4
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• pp.300-304
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• 2007

Wireless sensor networks represent a new and exciting communication paradigm which could have multiple applications in future wireless communication. Therefore, performance analysis of such a wireless sensor network paradigm is needed in complex wireless channel. Wireless networks could be an important means of providing ubiquitous communication in the future. In this paper, the BER performance of uniform distributed wireless sensor networks is evaluated in non-Gaussian noise channel. Using an analytical approach, the impact of Av. BER performance relating the coherent BPSK system at the end of a multi-hop route versus the spatial density of sensor nodes and impulsive noise parameters A and $\Gamma$ is evaluated.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.275-278
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• 2004

This paper focused on problems of design, construction, and maintenance caused by construction implementation processes. They were analyzed through case study of structure safety diagnosis projects. From the case study, it is expected that the introduction of Construction Management from the first stage of procurement will improve construction cost increase or burden on small design company. It strengthens coherent management from design and source contractor selection to build review of responsibility. The coherency will prevent changes in designing or infirm unreliable construction. It is desirable that expert opinions are considered when structure changes and establishment occur and that, if necessary, actions such as source selection, periodic audits, and diagnosis arc checked and fed back to maintenance.

• Journal of the Korean Institute of Telematics and Electronics
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• v.8 no.4
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• pp.17-24
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• 1971

Laser light which modulated and transmitted through one-meter water bath and one-kilometer transmission distances in atmospheric media is detected by method of direct photo-detection. Also, it is analyzed as a square law detection and the experimental apparatus are designed and constructed. Consequently, in spite that the quantitative analysis remains, the availability of coherent optical communication is understood. The average attenuation with the conditions of weather is about -25dB, and the average attenuation coefficient of water is about 0.4(m-1).

• The Korean Journal of Applied Statistics
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• v.23 no.2
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• pp.249-261
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• 2010

Long-term forecasting of seasonal time series is critical in many applications such as planning business strategies and resolving possible problems of a business company. Unlike the traditional approach that depends solely on dynamic models, Li and Hinich (2002) introduced a combination of stochastic dynamic modeling with filter bank approach for forecasting seasonal patterns using highly coherent(High-C) waveforms. We modify the filter selection and forecasting procedure on wavelet domain to be more feasible and compare the resulting predictor with one that obtained from the wavelet variance estimation method. An improvement over other seasonal pattern extraction and forecasting methods based on such as wavelet scalogram, Holt-Winters, and seasonal autoregressive integrated moving average(SARIMA) is shown in terms of the prediction error. The performance of the proposed method is illustrated by a simulation study and an application to the real stock price data.

• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.102-110
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• 1997

A two dimensional shallow-water flow around a cavity driven by a sinusoidally oscillating external flow was studied numerically with an Ekman pumping model. A container model of "T" shape was constructed in the numerical computation for comparison with the experimental observation. The material transport in the external region is in good agreement with the experimentally recorded particle trajectories. It turns out that two large coherent vortices situated in the exterior region of the cavity are responsible for clockwise and counterclockwise drift motions, in large scale, of particles. The Ekman pumping model suggested in this study was found to be satisfactory.isfactory.