• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1991.10a
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• pp.145-149
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• 1991

In this paper, an algorithm is proposed to analyze the approximating reliability of the capacity considered communication networks. In the case ofthe former methods to evaluate the source-to-termianl node reliability, it is very difficult to contract and delete the jointed terms in the simple path group. Therefore, the reliability bounds are used and compared to the exact reliability by TURBO PROLOG, the natural lanquage of artficial intelligence. In the reliability bounds, the upper bound used the valid cutset that isthe group of simple path and the lower bound used the minimal cutset by complement operation and the esact reiability is compared to this reliability bounds.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.183-186
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• 1995

A simulation method basee on upper bound method is developed in order to characterize forging characters in forging of spur gears. In this paer, utlizing a kinematically admissible velocity field and applying it to study the effect of inner diameter of holow billet. To predict the variation of inner diameter of hollow billet, neutal surface has been introduced into forging of hollow gears from hollow billes with flat punch. The neutral surface of each step is assumed as a circle and determined in order to have minimum forging energy by golden section method. According to the analysis, the magnitude of inner diameter of initial billet is vary important to reduce the relative pressure and forging load. And the variation of inner diameter of billet during spur gear forging is successfully predicted.

• Journal of Communications and Networks
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• v.4 no.2
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• pp.102-107
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• 2002

The theoretical performance of MMSE linear microdiversity combining in Rayleigh fading, additive interference channels has already been derived exactly in the literature. In the macrodiversity case the fundamental difference is that any given source may well have different average received powers at the different antennas. This makes an exact analysis more difficult and hence for the macrodiversity case we derive a bound on the mean BER and a semi-analytic upper bound on outage probabilities. Hence we provide bounds on the performance of MMSE linear microdiversity combining in Rayleigh fading with additive noise and any number of interferers with arbitrary powers.

• Proceedings of the Korea Association of Information Systems Conference
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• 2005.12a
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• pp.326-333
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• 2005

The purpose of this paper is to provide a decision support method to a rational buyer, who wants to pay the least price for the product with the highest quality and service. We suggest a minimum efficiency game model and DEA game model to valuate many vendors whose qualifies of outputs are measured by percentage. Our results gave a decision maker (buyer) the upper bound and lower bound of the true efficiency score of a decision making unit (vendor) with respect to the benchmark (target) set by the buyer. As a result, a buyer can choose the best vendor in terms of his/her preference.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.137-146
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• 1999

The SSI(Soil-Structure Interaction) analyses are being performed for the KNGR(Korean Next Generation Reactor) design because the KNGR is developed as a standard nuclear power plant concept enveloping various soil conditions. the SASSI program which adopts the flexible volume method is used for the SSI analyses. The soil curves used in the three dimensional SSI analyses of KNGR Nuclear Island(NI) structures are based on the upper bound shear modulus curve and lower bound damping degradation on SSI response the average shear modulus curve with average damping curve was used for two soil cases. This study presents the results of the variances by using different soil nonlinearity parameters based on the paametric SSI analyses. The results include the maximum member forces(shear and axial force) at the base of the NI structures and the 5% damping Floor Response Spectra (FRS) at some representative locations at the top of the NI superstructures. They are also compared together with the enveloped SSI results for eight soil cases and fixed-base analysis for rock case by using two control motions.

• Interaction and multiscale mechanics
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• v.5 no.3
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• pp.211-228
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• 2012

This paper reports the development of a generalized inverse analysis formulation for the parameter estimation of four-parameter Burger model. The analysis is carried out by formulating the problem as a mathematical programming formulation in terms of identification of the design vector, the objective function and the design constraints. Thereafter, the formulated constrained nonlinear multivariable problem is solved with the aid of fmincon: an in-built constrained optimization solver module available in MatLab. In order to gain experience, a synthetic case-study is considered wherein key issues such as the determination and setting up of variable bounds, global optimality of the solution and minimum number of data-points required for prediction of parameters is addressed. The results reveal that the developed technique is quite efficient in predicting the model parameters. The best result is obtained when the design variables are subjected to a lower bound without any upper bound. Global optimality of the solution is achieved using the developed technique. A minimum of 4-5 randomly selected data-points are required to achieve the optimal solution. The above technique has also been adopted for real-time settlement of four oil refineries with encouraging results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.3
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• pp.301-309
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• 1993

The performance of trellis coded 8-PSK systems over m-distributed fading channel is analyzed. To compensate the performance degradation due to the fading in mobile communication channels, the trellis code which can obtain the coding gain without bandwidth expansion is used. Using the Chernoff bound and generating function techniques for the trellis coded 8-PSK systems with 4-state and 8-state, the upper bound of the bit error probability is derived. The trellis code of 8-state is better than that of 4-state in the capability of error correction. The coded performance is much better under severe fading environment.

• Journal of Communications and Networks
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• v.6 no.1
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• pp.1-8
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• 2004

In this paper, we investigate the properties and performance of space-time bit-interleaved coded modulation (STBICM) systems in fast Rayleigh fading channels. We first show that ST-BICM with QPSK signaling in fast fading channels possesses the uniform distance property, which makes performance analysis tractable. We also derive the probability distribution of the squared Euclidean distance between space-time symbols assuming uniform bit-interleaving. Based on the distribution, we show that the diversity order for each codeword pair becomes maximized as the frame length becomes sufficiently long. This maximum diversity order property implies that the bit-interleaver transforms an ST-BICM system over transmit diversity channels into an equivalent coded BPSK system over independent fading channels. We analyze the performance of ST-BICM in fast fading channels by deriving an FER upper bound. The derived bound turns out very accurate, requiring only the distance spectrum of the binary channel codes of ST-BICM. Numerical results demonstrate that the bound is tight enough to render an accurate estimate of performance of ST-BICM systems.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1726-1746
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• 2022

This paper presents fracture mechanics analysis results for various cracks located at pressurized water reactor pressure vessel nozzle crotch corners taking into consideration constraint effect. Technical documents such as the ASME B&PV Code, Sec.XI were reviewed and then a fracture mechanics analysis procedure was proposed for structural integrity assessment of various nozzle crotch corner cracks under normal operation conditions considering the constraint effect. Linear elastic fracture mechanics analysis was performed by conducting finite element analysis with the proposed analysis procedure. Based on the evaluation results, elastic-plastic fracture mechanics analysis taking into account the constraint effect was performed only for the axial surface crack of the reactor pressure vessel outlet nozzle with cladding. The fracture mechanics analysis result shows that only the axial surface crack in the reactor pressure vessel outlet nozzle has the stress intensity factor exceeding the low bound of upper-shelf fracture toughness irrespectively of considering the constraint effect. It is confirmed that the J-integral for the axial crack of the outlet nozzle does not exceed the ductile crack initiation toughness. Hence, it can be ensured that the structural integrity of all the cracks is maintained during the normal operation.

• The Journal of the Acoustical Society of Korea
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• v.15 no.3E
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• pp.19-26
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• 1996

In this paper, convergence properties of the LMS, LMF, and LVCMS algorithms are investigated under the assumption of the uncorrelated Gaussian input data. By treating these algorithms as special cases of more general algorithm family, unified results on these algorithms are obtained. First the upper bound on the step size parameter is obtained. Second, an expression for misadjustment is obtained. These theoretical results confirm earlier LMS works. Further, the results explain why the LMS and LVCMS algorithms are experiencing difficulties with plant noise having heavier tailed densities. Simulation results agree with theoretical expectation closely for various plant noise statistics.