• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.5
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• pp.18-23
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• 2010

In this paper, we propose a computationally efficient method detecting the P300 wave for brain-machine interface. Electrophysiological researches have shown that the P300 wave's potential is decreased when human intention matches visual stimulation. Motivated by this fact, we can infer human intention for brain-machine interface by detecting the P300 wave's potential decrease. The P300 wave is recorded from EEG(electroencephalogram) electrodes attached on human brain skull after giving alphabetical stimulation. To detect the potential decrease in P300, firstly we statistically model the P300 wave's negative potential. Then we infer human intention based on maximum likelihood estimation. The proposed method was evaluated on the data recorded from three healthy human subjects. The method achieved an averaging accuracy of 98% from subject k, 90% from subject j and 79.8% from subject h.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1039-1048
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• 2008

new computational procedure for the Non-Linear Vortex Lattice Method (NLVLM) is suggested in this work. Conventional procedures suggested so far usually involves inner iteration loop to update free vortex shape and an under-relaxation based iteration loop to determine the free vortex shape. In this present work, we suggest a new formula based on quasi-steady concept to fix free vortex shape which eliminates the need for inner iteration loop. Further, the ensemble averaging of the induced velocities for a given free vortex segment evaluated at each iteration significantly improves the convergence property of the algorithm without resorting to the under-relaxation technique. Numerical experiments over several low aspect ratio wings are carried out to obtain optimal empirical parameters such as the length of the free vortex segment, the vortex core radius, and the rolled-up wake length.

• Journal of Korea Multimedia Society
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• v.10 no.3
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• pp.348-357
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• 2007

One of the major issues in recent researches on wireless sensor networks is to reduce energy consumption of sensor nodes operating with limited battery power, in order to lengthen their lifespan. Among the researches, we are interested in the schemes in which a sensor node periodically turns on and off its radio and requires information on the time when its neighbors will wake up (or turn on). Clock synchronization is essential for wakeup scheduling in such schemes. This paper proposes three methods based on the asynchronous averaging algorithm for clock synchronization in sensor nodes which periodically wake up: (1) a fast clock synchronization method during an initial network construction period, (2) a periodic clock synchronization method for saving energy consumption, and (3) a decision method for switching the operation mode of sensor nodes between the two clock synchronization methods. Through simulation, we analyze maximum clock difference and the number of messages required for clock synchronization.

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.75-82
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• 2010

A recent progress on the prediction of the thermal stability of a nanostructured exchange-coupled trilayer is reviewed. An analytical/numerical combined method is used to calculate its magnetic energy barrier and hence the thermal stability parameter. An important feature of the method is the use of an analytical equation for the total energy that contains the magnetostatic fields. Under an assumption of the single domain state, the effective values of all the magnetostatic fields can be obtained by averaging their nonuniform values over the entire magnetic volume. In an equilibrium state, however, it is not easy to calculate the magnetostatic fields at the saddle point due to the absence of suitable methods of the accessing its magnetic configuration. This difficulty is overcome with the use of equations that link the magnetostatic fields at the saddle point and critical fields. Since the critical fields can readily be obtained by micromagnetic simulation, the present method should provide accurate results for the thermal stability of a nanostructured exchange-coupled trilayer.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.5
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• pp.199-207
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• 2013

Spin images representing efficiently surface features of 3D mesh models have been used to detect facial landmark points. However, at a certain point, different normal direction can lead to quite different spin images. Moreover, since 3D points are projected to the 2D (${\alpha}-{\beta}$) space during spin image generation, surface features cannot be described clearly. In this paper, we present a method to detect 3D facial landmark using improved spin images by partitioning the search area with respect to angle. By generating sub-spin images for angular partitioned 3D spaces, more unique features describing corresponding surfaces can be obtained, and improve the performance of landmark detection. In order to generate spin images robust to inaccurate surface normal direction, we utilize on averaging surface normal with its neighboring normal vectors. The experimental results show that the proposed method increases the accuracy in landmark detection by about 34% over a conventional method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.12
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• pp.1926-1933
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• 2022

Parameterized multichannel Wiener filter (PMWF) is a linear filter that can control the trade-off between residual noise and signal distortion using the embedded parameter. To apply the PMWF to noisy inputs, accurate noise estimation is important and multichannel minima-controlled recursive averaging (MMCRA) is widely used. However, in the case of the MMCRA, the accuracy of noise estimation decreases when a directional interference is involved into the array inputs. Consequently, the performance of the PMWF is degraded. Therefore, we propose a noise power spectral density (PSD) estimation method for the PMWF in this paper. The proposed method is based on a consecutive process of eigenvalue decomposition on noisy input PSD, estimation of the target component contribution using directional information, and exponential weighting for improved estimation of the target contribution. For evaluation, four objective measures were compared with the MMCRA and we verify that the PMWF with the proposed noise estimation method can improve performance in environments where directional interfereces exist.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.12
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• pp.3242-3265
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• 2023

Ensuring reliability of a machinery system involve the prediction of remaining useful life (RUL). In most RUL prediction approaches, noise is always considered for removal. Nevertheless, noise could be properly utilized to enhance the prediction capabilities. In this paper, we proposed a novel RUL prediction approach based on noise injection and a Kalman filter ensemble of modified bagging predictors. Firstly, we proposed a new method to insert Gaussian noises into both observation and feature spaces of an original training dataset, named GN-DAFC. Secondly, we developed a modified bagging method based on Kalman filter averaging, named KBAG. Then, we developed a new ensemble method which is a Kalman filter ensemble of KBAGs, named DKBAG. Finally, we proposed a novel RUL prediction approach GN-DAFC-DKBAG in which the optimal noise-injected training dataset was determined by a GN-DAFC-based searching strategy and then inputted to a DKBAG model. Our approach is validated on the NASA C-MAPSS dataset of aero-engines. Experimental results show that our approach achieves significantly better performance than a traditional Kalman filter ensemble of single learning models (KESLM) and the original DKBAG approaches. We also found that the optimal noise-injected data could improve the prediction performance of both KESLM and DKBAG. We further compare our approach with two advanced ensemble approaches, and the results indicate that the former also has better performance than the latters. Thus, our approach of combining optimal noise injection and DKBAG provides an effective solution for RUL estimation of machinery systems.

• The Korean Journal of Cytopathology
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• v.18 no.2
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• pp.143-152
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• 2007

Sono-guided fine needle aspiration (FNA) of the thyroid is widely used, but the aspirated samples are typically not well preserved and low cellularity makes diagnosis difficult in many cases. The object of the current study is to evaluate the adequacy and diagnostic accuracy of the use of $SurePath^{TM}$ liquid-based cytology (SP-LBC) in the sonoguided fine needle aspiration of the thyroid nodule and to compare its use with that of the use of a conventional smear (CS). A total of 172 sono-guided FNAs of thyroid nodules from April to June, 2006 were prepared by the use of the split method with either SP-LBC or CS; the samples were stained with the use of hematoxylin-eosin (H&E) and Papanicolaou (Pap) stains. A cyto-histological correlation was performed in 69 (30 SP and 39 CS) cases that had been histologically confirmed. The rate of producing unsatisfactory slides by the use of the SP-LBC method (9.3%) was less than that of the use of the CS method (20.9%). The diagnostic accuracy of the SP method (93.3%) was better than that of the CS method (85.3%). The sensitivity and specificity of the SP method (94.4% and 92.3%) was better than that of the CS method (83.3% and 70%), respectively (p < 0.05). The CS of sono-guided aspirated specimens had some unavoidable limitations related to inadequate sampling such as a bloody background, low cellularity and an indication that some clinicians smeared many useless slides (averaging four to ten slides), and that most slides showed only blood that included few follicular cells. The SP method resulted in more thinly smeared slides and showed cleaner background and greater cellularity than the use of the CS method. Each follicular cell shows superior nuclear detail, and more distinct cytoplasmic features than with the use of the CS method. SP-LBC appears to be an easy, highly accurate, and reliable cytological method for employ for a diagnostic approach of thyroid disease and thyroid nodules. The SP-LBC method is a suitable alternative to the CS method to overcome diagnostic difficulties.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12C
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• pp.1225-1238
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• 2003

We present an efficient algorithm for skew correction of business card images obtained by a PDA (personal digital assistant) camera. The proposed method is composed of four parts: block adaptive binarization (BAB), stripe generation, skew angle calculation, and image rotation. In the BAB, an input image is binarized block by block so as to lessen the effect of irregular illumination and shadow over the input image. In the stripe generation, character string clusters are generated merging adjacent characters and their strings, and then only clusters useful for skew angle calculation are output as stripes. In the skew angle calculation, the direction angles of the stripes are calculated using their central moments and then the skew angle of the input image is determined averaging the direction angles. In the image rotation, the input image is rotated by the skew angle. Experimental results shows that the proposed method yields skew correction rates of about 93% for test images of several types of business cards acquired by a PDA under various surrounding conditions.

• Journal of Environmental Science International
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• v.22 no.2
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• pp.151-161
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• 2013

The assessment of personal exposure is a critical component in population-based epidemiologic studies of air pollution. This study was conducted to apply and compare the four exposure estimation methods of individual-level to air pollution concentration in a cohort including 2,283 subjects in Gwangyang, Korea. Individual-level exposure of air pollution were estimated using multiple approaches, including average across all monitors, nearest monitor, and spatial interpolation by inverse distance weighting and kriging. The mean concentrations of $PM_{10}$, $NO_2$, $SO_2$, CO, $O_3$ by four exposure estimation methods were slightly different but not significantly different from each other. Cross-validation showed that kriging was more accurate than other exposure estimation methods because kriging has probably predicted individual exposure levels equivalent to residential locations after estimating the parameters of a model according to the spatial surface of air pollution concentration. These data support that spatial interpolation methods may provide better estimates than selecting the value from the nearest monitor and averaging across values from all monitors by reflecting spatial attributes of air pollution on personal level.