• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9C
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• pp.907-912
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• 2005

An efficient method for calculation of observation probability in CDHMM(Continous Density Hidden Markov Model) is proposed in this paper. the proposed algorithm, called FCOP(Fast Computation of Observation Probability), approximate obsewation probabilities in CDHMM by eliminating insignificant PDFs(Probability Density Functions) and reduces the computational load. When applied to a speech recognition system, the proposed FCOP algorithm can reduce the instruction cycles by $20\%-30\%$ and can also increase the recognition speed about $30\%$ while minimizing the loss in its recognition rate. When implemented on a practical cellular phone, the FCOP algorithm can increase its recognition speed about $30\%$ while suffering $0.2\%$ loss in recognition rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.387-397
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• 1992

The spatial domain design of 2-dimensional separable denominator digital filters(SDDF) based on the reduced dimensional decomposition can be realized when the given 2-D impulse response specifications are decomposed into a pair of 1-D specifications via singular value decompositions(SVD). Because of use of the balaned approximation and equivalent transform as 1-D design algorithm, 2-D design algorithm retains the advantage that is numerically stable and can minimize quantization errors. In this paper in order to analyze and reduce these errors, minimum comfficient quantization realization is directly derived from impulse response specification. And using the equivalent trans form relation between mininum coefficient quantization error and minimum roundoff error realizations, we optimally realize a SDDF. This algorithm is analyzed by the simulation, which shows that it is superior to direct or balanced realization in quantization errors.

• The Journal of the Acoustical Society of Korea
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• v.11 no.2
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• pp.5-14
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• 1992

In the fields of astronomy, communication, X-ray crystallography, and engineering, it is a very important and useful fact that the original signal can be reconstructed from a partial information, only spectral magnitude or phase, of the signal. In this paper, we proposed a modified iterative algorithm to solve the Magnitude Retrieval Problem (MRP) for 1-D, 2-D signals. In oder to accelerate the convergence rate, the unit constant initial function which is used in the references is replaced by the exponential initial function for the modified adaptive iterative method. As a result, MRP with 1-D signal and low-pass detail image is significantly enhanced from an iterative convergence rate and a computer storage memory points of view.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.123-128
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• 2011

In this paper, we design the CA-CFAR processor using a root-square approximation approach and a fixed-point operation to improve hardware complexity and reduce computational effort. We also propose CA-CFAR processor with multi-window, which is capable of concurrent parallel processing. The proposed architecture is synthesized and implemented into the FPGA and the performance is compared with the conventional processor designed by root-square libarary licensed by FPGA corporation.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.469-473
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• 2003

Milling 가공시 공구와 피삭재의 접합명에서는 절삭가공의 잔유물인 burr가 생성되고, 이러한 Burr는 작업효율과 정밀도를 감소시키며 추처리과정 (Deburring)을 야기시키는 원인이 된다. 그러므로 정밀도와 작업효율을 극대화하기 위해서는 이러한 Burr의 생성원리를 파악함과 동시에 Exit Burr의 여부에 대한 판별을 하여 최적의 가공조건을 맞추어 주어야 하는데, 이러한 경우에 지금까지는 점, 선 및 원으로 피삭재의 형상을 재현하여 공구의 경로와의 Exit 각을 통해 결과를 예측하는 연구를 해왔었다. 본 논문에서 추구하고자 하는 핵심은 이러한 피삭재의 형상을 재현하기 위해 지금까지 사용해왔던 요소를 보다 다양화시키는 방안을 제시하여 프로그램의 적용 범위를 넓히려는 것이다. 예컨대 이제까지 실제 가공에서 사용되고 있는 임의형상에 대한 표현 방식 중에서 대다수 CAD 프로그램에서 곡선 및 곡면을 표현하는 경우, B-Spline Curve의 알고리즘은 패삭재의 불규칙적인 곡면을 가장 근사하게 표현하는 최적의 해결책으로 쓰여지고 있다. 그러므로 이러한 알고리즘을 통해 프로그램의 적용예를 넓히는 것은 보다 다양한 조건에서의 Burr생성에 대한 예측을 가능케 해주는 것이다. 본 논문에서는 앞에서 언급한 바와 같이 B-Spline Curve 알고리즘을 개발하고, 프로그램에 적용하는 일련의 과정을 통해 보다 다양한 형상의 피삭재에서 단일 혹은 복합경로의 공구가 지나갈 경우에 생길 수 있는 Burr를 얼마나 효율적으로 판별할 수 있는지를 소개하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.4
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• pp.19-27
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• 2002

We proposed an auto-tuning method of learning rate for performance improvement of backpropagation algorithm. Proposed method is used a fuzzy logic system for automatic tuning of learning rate. Instead of choosing a fixed learning rate, the fuzzy logic system is used to dynamically adjust learning rate. The inputs of fuzzy logic system are ${\Delta}$ and $\bar{{\Delta}}$, and the output is the learning rate. In order to verify the effectiveness of the proposed method, we performed simulations on a N-parity problem, function approximation, and Arabic numerals classification. The results show that the proposed method has considerably improved the performance compared to the backpropagation, the backpropagation with momentum, and the Jacobs' delta-bar-delta.

• The Korean Journal of Applied Statistics
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• v.23 no.2
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• pp.305-315
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• 2010

In this paper, a frequentistic approach to impute the values of R, G, B-components in random missing pixels of color image is provided. Under assumption that the given image is a realization of Gaussian Markov random field, its model is designed such that each neighbor pixel values for a given pixel follows (independently) the normal distribution with covariance matrix scaled by an evaluates of the similarity between two pixel values, so that the imputation is not to be affected by the neighbors with different color. An approximate EM-based algorithm maximizing the underlying likelihood is implemented to estimate the parameters and to impute the missing pixel values. Some experiments are presented to show its effectiveness through performance comparison with a popular interpolation method.

• Journal of Korea Multimedia Society
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• v.16 no.4
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• pp.472-482
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• 2013

This paper proposes a wireless LAN topology configuration method for enhancing indoor location-awareness and improving network performance simultaneously. We first develop four objective functions that yield objective goals significant to the optimal design of a wireless LAN topology in terms of location-awareness accuracy and network performance factors. Then, we develop metaheuristic algorithms such as simulated annealing, tabu search, and genetic algorithm that examine the proposed objective functions and generate a near-optimal solution for a given objective function. Finally, four objective functions and metaheuristic algorithms developed in this paper are exploited to evaluate and measure the performance of the proposed wireless LAN topology configuration method.

• Journal of the Korea Computer Industry Society
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• v.3 no.2
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• pp.185-190
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• 2002

As the TSP(Traveling Salesman Problem) belongs to the class of NP-complete problems, various techniques are required for finding optimum or near optimum solution to the TSP. This paper designs a distributed genetic algorithm in order to reduce the execution time and obtain more near optimal using multi-slave model for the TSP. Especially, distributed genetic algorithms with multiple populations are difficult to configure because they are controlled by many parameters that affect their efficiency and accuracy. Among other things, one must decide the number and the size of the populations (demes), the rate of migration, the frequency of migrations, and the destination of the migrants. In this paper, I develop random dynamic migration rate that controls the size and the frequency of migrations. In addition to this, I design new migration policy that selects the destination of the migrants among the slaves

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.66-74
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• 1994

Gradient projection (GP) technique is applied for solving the optical routing problem (ORP) in high speed packet switched networks. The ORP minimizing average network packet loss probability is non-convex due to packet losses at intermediate switching nodes and its routing solution cannot be directly sought by the GP algorithm. Thus the non-convex ORP is transformed into a convex problem called the reduced-ORP (R-ORP) for which the GP algorithm can be used to obtain a routing solution. Through simulations, the routing solution of the R-ORP is shown to be a good approximation to that of the original ORP. Theoretical upper bound of difference between two (ORP and R-ORP) routing solutions is also derived.