• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1285-1296
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• 2011

Packet classification is one of the basic and important functions of the Internet routers, and it became more important along with new emerging application programs requiring real-time transmission. Since packet classification should be accomplished in line-speed on each incoming input packet for multiple header fields, it becomes one of the challenges in designing Internet routers. Various packet classification algorithms have been proposed to provide the high-speed packet classification. Hierarchical approach achieves effective packet classification performance by significantly narrowing down the search space whenever a field lookup is completed. However, hierarchical approach involves back-tracking problem. In order to solve the problem, set-pruning trie and grid-of-trie algorithms are proposed. However, the algorithm either causes excessive node duplication or heavy pre-computation. In this paper, we propose a smart set-pruning trie which reduces the number of node duplication in the set-pruning trie by the simple merging of the lower-level tries. Simulation result shows that the proposed trie has the reduced number of copied nodes by 2-8% compared with the set-pruning trie.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.3
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• pp.149-154
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• 2014

The cross-correntropy concept can be expressed with inner products of two different probability density functions constructed by Gaussian-kernel density estimation methods. Blind algorithms based on the maximization of the cross-correntropy (MCC) and a symbol set of randomly generated N samples yield superior learning performance, but have a huge computational complexity in the update process at the aim of weight adjustment based on the MCC. In this paper, a method of reducing the computational complexity of the MCC algorithm that calculates recursively the gradient of the cross-correntropy is proposed. The proposed method has only O(N) operations per iteration while the conventional MCC algorithms that calculate its gradients by a block processing method has $O(N^2)$. In the simulation results, the proposed method shows the same learning performance while reducing its heavy calculation burden significantly.

• The Korean Journal of Applied Statistics
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• v.27 no.3
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• pp.501-512
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• 2014

Modified cut-off sampling is widely used for highly skewed data. A serious drawback of modified cut-off sampling is the difficulty of adjustment of non-response in take-all stratum. Therefore, solutions of the problems of non-response in take-all stratum have been studied in various ways such as substitute of samples, imputation or re-weight method. In this paper, a new cut-off point based on minimizing MSE being used in exponential and power functions is suggested and it can be reduced the number of take-all stratum. We also investigate another cut-off point determination method with underlying distributions such as truncated log-normal and truncated gamma distributions. Finally we suggest the optimal cut-off point which has a minimum of take-all stratum size among suggested methods. Simulation studies are performed and Labor Survey data and simulated data are used for the case study.

• The Korean Journal of Applied Statistics
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• v.31 no.2
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• pp.287-301
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• 2018

It is common to encounter count data with excess zeros in various research fields such as the social sciences, natural sciences, medical science or engineering. Such count data have been explained mainly by zero-inflated Poisson model and extended models. Zero-inflated count data are also often correlated or clustered, in which random effects should be taken into account in the model. Frequentist approaches have been commonly used to fit such data. However, a Bayesian approach has advantages of prior information, avoidance of asymptotic approximations and practical estimation of the functions of parameters. We consider a Bayesian zero-inflated Poisson regression model with random effects for correlated zero-inflated count data. We conducted simulation studies to check the performance of the proposed model. We also applied the proposed model to smoking behavior data from the Regional Health Survey (2015) of the Korea Centers for disease control and prevention.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.4
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• pp.274-282
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• 2014

Time series of the dynamic response of a slender marine structure was predicted using quadratic Volterra series. The wave-structure interaction system was identified using the NARX(Nonlinear Autoregressive with Exogenous Input) technique, and the network parameters were determined through the supervised training with the prepared datasets. The dataset used for the network training was obtained by carrying out the nonlinear finite element analysis on the freely standing riser under random ocean waves of white noise. The nonlinearities involved in the analysis were both large deformation of the structure under consideration and the quadratic term of relative velocity between the water particle and structure in Morison formula. The linear and quadratic frequency response functions of the given system were extracted using the multi-tone harmonic probing method and the time series of response of the structure was predicted using the quadratic Volterra series. In order to check the applicability of the method, the response of structure under the realistic ocean wave environment with given significant wave height and modal period was predicted and compared with the nonlinear time domain simulation results. It turned out that the predicted time series of the response of structure with quadratic Volterra series successfully captures the slowly varying response with reasonably good accuracy. It is expected that the method can be used in predicting the response of the slender offshore structure exposed to the Morison type load without relying on the computationally expensive time domain analysis, especially for the screening purpose.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.864-868
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• 2008

Water transmission and distribution systems play a important role to deliver safe and clean water and are responsible for the most direct impacts of water utilities to customers. Although the performance of WDS(Water Distribution Systems) should be evaluated by a certain standards, interests has not been in WDS and developed due to invisible, hard-working and insufficient information in the evaluation process in Korea till now. The investigations and researches were carried out to develop software to assist the evaluation of WDS with respects to hydraulics, water quality and structural analysis methods. The methodologies have been developed which can be used to estimate the performance to water distribution network and software are implemented by the process. Developed systems are consisted with database, analysis techniques, simulation models, decision support systems and other tools. The concepts and functions are introduced in this paper and the performance index are discussed for accurate assessment of water distribution systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.2
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• pp.69-80
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• 2002

In this paper, signed-rank based nonparametric detectors are used for direct sequence code division multiple access pseudo-noise code acquisition systems in frequency-selective Rician fading channels. We first derive the locally optimum rank detector, and then propose the locally suboptimum rank (LSR) and k-th order modified signed-rank (MSRk) detectors using approximate score functions. We compare the serial and hybrid parallel double-dwell schemes using the LSR and MSRk detectors with those using the conventional squared-sum (SS) using the cell averaging constant false alarm rate processor and modified sign detectors. From the simulation results, it is shown that the LSR and MSRk detectors perform better than the SS detector using the cell averaging constant false alarm rate processor.

• The Journal of the Acoustical Society of Korea
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• v.30 no.6
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• pp.308-314
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• 2011

This paper presents techniques for estimating directions of multiple sound sources ranging from $0^{\circ}$ to $360^{\circ}$ using circular probability distributions having a periodic property. Phase differences containing direction information of sources can be modeled as mixtures of multiple probability distributions and source directions can be estimated by maximizing log-likelihood functions. Although the von Mises distribution is widely used for analyzing this kind of periodic data, we define a new class of circular probability distributions from Gaussian and Laplacian distributions by adopting a modulo operation to have $2{\pi}$-periodicity. Direction estimation with these circular probability distributions is done by implementing corresponding EM (Expectation-Maximization) algorithms. Simulation results in various reverberant environments confirm that Laplacian distribution provides better performance than von Mises and Gaussian distributions.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.3-8
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• 2013

In this paper, we present an energy-efficient base station operation with base station sharing in wireless cellular networks. Firstly, cost functions are modeled related with the amount of energy usage and traffic load. We use game theory and formulate an energy bill game, where the players are the service operators which are operating base stations and their strategies are the bill of their base station energy consumption and hand-over traffic load to the others service operators. We show that the global optimal performance in terms of minimizing the energy costs is achieved at the Nash equilibrium of the formulated energy bill game. Simulation results confirm that the proposed approach can reduce the energy bill of the service operator, and show the relationship between the energy cost saving and various parameters.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1713-1719
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• 2014

1FSD is a 28-residue designed protein with a ${\beta}{\beta}{\alpha}$ motif. Since this protein displays most essential features of protein structures in such a small size, this model protein can be an outstanding system for evaluating the balance in the propensity of the secondary structures and the quality of all-atom protein force fields. Particularly, this protein would be difficult to fold to its correct native structure without establishing proper balances between the secondary structure elements in all-atom energy functions. In this work, a series of the recently optimized five amber protein force fields [$ff03^*$, $f99sb^*$-ildn, ff99sb-${\phi}^{\prime}$-ildn, ff99sb-nmr1-ildn, ff99sb-${\Phi}{\Psi}$(G24, CS)-ildn] were investigated for the simulations of 1FSD using a conventional molecular dynamics (MD) and a biased-exchange meta-dynamics (BEMD) methods. Among those tested force fields, we found that ff99sb-nmr1-ildn and ff99sb-${\Phi}{\Psi}$(G24, CS)-ildn are promising in that both force fields can locate the native state of 1FSD with a high accuracy (backbone rmsd ${\leq}1.7{\AA}$) in the global free energy minimum basin with a reasonable energetics conforming to a previous circular dichroism (CD) experiment. Furthermore, both force fields led to a common set of two distinct folding pathways with a heterogeneous nature of the transition state to the folding. We anticipate that these force fields are reasonably well balanced, thereby transferable to many other protein folds.