Transactions of Japanese Society for Medical and Biological Engineering, 2012
This paper proposes the use of electrode grid for Japanese vowel recognition based on surface ele... more This paper proposes the use of electrode grid for Japanese vowel recognition based on surface electromyography (sEMG). Previous studies have indicated the potential effectiveness of sEMG-based speech recognition, not only for healthy people, but also for dysarthric patients. In these studies, however, disc electrodes or parallel bar electrodes were used and located empirically, although there exist relatively small muscles in proximity to each other in the face or neck region. In order to avoid missing out information about speech, we examined the effectiveness of using an electrode grid, which consists of densely-spaced multielectrodes. In our experiments, we measured sEMG signals from the submental region with the electrode grid during the production of 5 vowel sounds. Continuous hidden Markov models were applied to the sEMG signals for vowel recognition. We compared the recognition accuracies between the two methods : One was based on signals from all channels and the other was b...
Transactions of the Institute of Systems, Control and Information Engineers, 2011
The paper proposes a rear-end collision warning system for drivers, where the collision risk is a... more The paper proposes a rear-end collision warning system for drivers, where the collision risk is adaptively set from driving signals. The system employs the inverse of the time-to-collision with a constant relative acceleration as the risk and the one-class support vector machine as the anomaly detector. The system also utilizes brake sequences for outliers detection. When a brake sequence has a low likelihood with respect to trained hidden Markov models, the driving data during the sequence are removed from the training dataset. This data selection is confirmed to increase the robustness of the system by computer simulations.
SICE Journal of Control, Measurement, and System Integration, 2015
This paper proposes a very simple user-state recognizer for mobile applications. The proposed met... more This paper proposes a very simple user-state recognizer for mobile applications. The proposed method copes with the limitation in available electric power by using only a single three-axis accelerometer which is equipped with almost any mobile phone. In order to keep a high accuracy in recognition with a low computational complexity, the authors employ the wavelet transform and the singular value decomposition as feature extraction, and a multi-layer perceptron as a classifier. In the experiment, the algorithm could classify user contexts into walking, running, standing still and being in a moving train with an accuracy of over 90%.
Motile cells transduce environmental chemical signals into mechanical forces to achieve properly ... more Motile cells transduce environmental chemical signals into mechanical forces to achieve properly controlled migration. This signal-force transduction is thought to require regulated mechanical coupling between actin filaments (F-actins), which undergo retrograde flow at the cellular leading edge, and cell adhesions via linker "clutch" molecules. However, the molecular machinery mediating this regulatory coupling remains unclear. Here we show that the F-actin binding molecule cortactin directly interacts with a clutch molecule, shootin1, in axonal growth cones, thereby mediating the linkage between F-actin retrograde flow and cell adhesions through L1-CAM. Shootin1-cortactin interaction was enhanced by shootin1 phosphorylation by Pak1, which is activated by the axonal chemoattractant netrin-1. We provide evidence that shootin1-cortactin interaction participates in netrin-1-induced F-actin adhesion coupling and in the promotion of traction forces for axon outgrowth. Under ce...
Highlights d Actin waves are confirmed to translocate actin and associated proteins along axons d... more Highlights d Actin waves are confirmed to translocate actin and associated proteins along axons d F-actins in the wave are anchored to the plasma membrane and underlying substrate d Wave migration is driven by directional assembly and disassembly of membrane-anchored F-actins d Protein delivery by waves promotes axonal protrusion during neuronal polarization
SICE Journal of Control, Measurement, and System Integration, 2012
For monophonic music instrument identification, various feature extraction and selection methods ... more For monophonic music instrument identification, various feature extraction and selection methods have been proposed. One of the issues toward instrument identification is that the same spectrum is not always observed even in the same instrument due to the difference of the recording condition. Therefore, it is important to find non-redundant instrument-specific features that maintain information essential for high-quality instrument identification to apply them to various instrumental music analyses. For such a dimensionality reduction method, the authors propose the utilization of linear projection methods: local Fisher discriminant analysis (LFDA) and LFDA combined with principal component analysis (PCA). After experimentally clarifying that raw power spectra are actually good for instrument classification, the authors reduced the feature dimensionality by LFDA or by PCA followed by LFDA (PCA-LFDA). The reduced features achieved reasonably high identification performance that was comparable or higher than those by the power spectra and those achieved by other existing studies. These results demonstrated that our LFDA and PCA-LFDA can successfully extract low-dimensional instrument features that maintain the characteristic information of the instruments.
The human brain has important abilities for manipulating phonemes, the basic building blocks of s... more The human brain has important abilities for manipulating phonemes, the basic building blocks of speech; these abilities represent phonological processing. Previous studies have shown change in the activation levels of broad cortical areas such as the premotor cortex, the inferior frontal gyrus, and the superior temporal gyrus during phonological processing. However, whether these areas actually convey signals to representations related to individual phonemes remains unclear. This study focused on single vowels and investigated cortical areas important for representing single vowels using electrocorticography (ECoG) during covert articulation. To identify such cortical areas, we used a neural decoding approach in which machine learning models identify vowels. A decoding model was trained on the ECoG signals from individual electrodes placed on the subjects' cortices. We then statistically evaluated whether each decoding model showed accurate identification of vowels, and we found...
A large body of evidence supports that visual attention - the cognitive process of selectively co... more A large body of evidence supports that visual attention - the cognitive process of selectively concentrating on a salient or task-relevant subset of visual information - often works on object-based representation. Recent studies have postulated two possible accounts for the object-specific attentional advantage: attentional spreading and attentional prioritization, each of which modulates a bottom-up signal for sensory processing and a top-down signal for attentional allocation, respectively. It is still unclear which account can explain the object-specific attentional advantage. To address this issue, we examined the influence of object-specific advantage on two types of visual search: parallel search, invoked when a bottom-up signal is fully available at a target location, and serial search, invoked when a bottom-up signal is not enough to guide target selection and a top-down control for shifting of focused attention is required. Our results revealed that the object-specific adva...
2013 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2013
Prediction of driving behaviors is an important problem in developing a next-generation driving s... more Prediction of driving behaviors is an important problem in developing a next-generation driving support system. In order to take diverse driving situations into account, it is necessary to model multiple driving operation time series data. In this study we modeled multiple driving operation time series with four modeling methods including beta process autoregressive hidden Markov model (BP-AR-HMM), which we used in our previous study. We quantitatively compared the modeling methods with respect to prediction accuracies, and concluded that BP-AR-HMM excelled the other modeling methods in modeling multiple driving operation time series and predicting unknown driving operations. The result suggests that BP-AR-HMM estimated behaviors of a driver and transition probabilities between the behaviors more successfully than the other methods, because BP-AR-HMM can deal with commonalities and differences among multiple time series, but the others cannot. Therefore BP-AR-HMM may help us to predict driver behaviors in real environment and to develop the next-generation driving support system.
2013 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2013
Artists have a specific evaluation of abstract paintings while art novices do that with difficult... more Artists have a specific evaluation of abstract paintings while art novices do that with difficulty. This difference is shown in eye fixation patterns, although the cause is not clear. To explain the difference in fixation patterns, we used one of the saliency maps of paintings which predict fixations well without prior knowledge such as a meaningful target. If artists had a deep knowledge of art, they attend less to the salient features than novices in observing abstract paintings. On the other hand, the fixation patterns possibly vary in visual tasks. Therefore we examined the effect of salient features in two tasks: free viewing and preference judgment. To evaluate this quantitatively, the correlation coefficient (CC) between fixation distribution and a saliency map was used. The CCs were compared between artists and novices for each task. We found that the CCs of artists were lower than those of novices in the free viewing task, but not in the preference judgment task. This implies that the artist's knowledge of observation paintings was appeared only in free viewing.
When viewing a painting, artists perceive more information from the painting on the basis of thei... more When viewing a painting, artists perceive more information from the painting on the basis of their experience and knowledge than art novices do. This difference can be reflected in eye scan paths during viewing of paintings. Distributions of scan paths of artists are different from those of novices even when the paintings contain no figurative object (i.e. abstract paintings). There are two possible explanations for this difference of scan paths. One is that artists have high sensitivity to high-level features such as textures and composition of colors and therefore their fixations are more driven by such features compared with novices. The other is that fixations of artists are more attracted by salient features than those of novices and the fixations are driven by low-level features. To test these, we measured eye fixations of artists and novices during the free viewing of various abstract paintings and compared the distribution of their fixations for each painting with a topological attentional map that quantifies the conspicuity of low-level features in the painting (i.e. saliency map). We found that the fixation distribution of artists was more distinguishable from the saliency map than that of novices. This difference indicates that fixations of artists are less driven by low-level features than those of novices. Our result suggests that artists may extract visual information from paintings based on high-level features. This ability of artists may be associated with artists' deep aesthetic appreciation of paintings.
2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2014
From optimal supply decisions to anticipatory control systems, wind-based energy applications rel... more From optimal supply decisions to anticipatory control systems, wind-based energy applications rely heavily upon accurate, local, short-term forecasts of future wind speed. Recent studies have shown continuous ranked probability score (CRPS) minimizing models with Gaussian assumptions to be effective for well-researched sites where those assumptions are appropriate. We consider the more general case where Gaussianity is not assumed and access to historical data may be constrained. Deriving a CRPS expression for a minimum Extreme Value distribution, we use it to propose a site-adaptive Weibull-based CRPS-minimizing model, which is tested and shown to perform better than both deterministic and probabilistic reference models on a ground-based array of weather observation sites in northern Japan.
2013 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2013
In this paper, we propose an interactive evolutionary programming based recommendation system for... more In this paper, we propose an interactive evolutionary programming based recommendation system for online shopping that estimates the human preference based on eye movement analysis. Given a set of images of different clothes, the eye movement patterns of the human subjects while looking at the clothes they like differ from clothes they do not like. Therefore, in the proposed system, human preference is measured from the way the human subjects look at the images of different clothes. In other words, the human preference can be measured by using the fixation count and the fixation length using an eye tracking system. Based on the level of human preference, the evolutionary programming suggests new clothes that close the human preference by operations such as selection and mutation. The proposed recommendation is tested with several human subjects and the experimental results are demonstrated. I.
e203 trial. We recorded the intrinsic signal from the retina for 2 s before the stimulus, then fo... more e203 trial. We recorded the intrinsic signal from the retina for 2 s before the stimulus, then for 4 s during the stimulus and finally 20 s after the stimulus in each trial, and repeated them for 10 times (Okawa et al., 2007. Invest. Ophthalmol. Vis. Sci.). To improve signal to noise ratio, 10 consecutive images were averaged in each trial, then the images of 10 trials were averaged. Subtracting pre-stimulus images from post-stimulus images, two-dimensional topography of retinal reflectance change was constructed. Single electrode stimulation evoked the reflectance changes in localized area near the stimulating electrode at the current of 0.3-1.0 mA. Simultaneous stimulation with two electrodes evoked the reflectance changes in two separated retinal areas, which were correspondent to those of single electrode stimulation. It indicated that two-point discrimination was able to achieve by STS in the retina. Research fund: Strategic Research Program for Brain Sciences.
The generalization properties of support vector machines (SVMs) are examined. From a geometrical ... more The generalization properties of support vector machines (SVMs) are examined. From a geometrical point of view, the estimated parameter of an SVM is the one nearest the origin in the convex hull formed with given examples. Since introducing soft margins is equivalent to reducing the convex hull of the examples, an SVM with soft margins has a different learning curve from the original. In this paper we derive the asymptotic average generalization error of SVMs with soft margins in simple cases, that is, only when the dimension of inputs is one, and quantitatively show that soft margins increase the generalization error.
IEEE Transactions on Wireless Communications, 2008
We propose generic relay and subcarrier allocation schemes for Multi-Carrier (MC) system with Amp... more We propose generic relay and subcarrier allocation schemes for Multi-Carrier (MC) system with Amplify-and-Forward (AF) relays. The outage probability bounds are derived analytically for each scheme. Simulation results show that these bounds are very tight and better than the bounds obtained straightforwardly from the analysis in the Single-Carrier (SC) case. This is because in our analysis we reckon with the increased degree of freedom brought by the parallel channels. One of the proposed schemes, the Average Best Relay Selection scheme, is best suited for practical implementation since it approaches the best performance while minimizing the required amount of signaling.
This paper presents a numerically stable fast Newton-type adaptive filter algorithm. Two problems... more This paper presents a numerically stable fast Newton-type adaptive filter algorithm. Two problems are dealt with in the paper. First, we derive the proposed algorithm from an order-recursive least squares algorithm. The result of the proposed algorithm is equivalent to that of the fast Newton transversal filter (FNTF) algorithm. However, the derivation process is different. Instead of extending a covariance matrix of the input based on the min-max and the max-min criteria, the derivation shown in this paper is to solve an optimum extension problem of the gain vector based on the information of the th-order forward or backward predictor. The derivation provides an intuitive explanation of the FNTF algorithm, which may be easier to understand. Second, we present stability analysis of the proposed algorithm using a linear time-variant state-space method. We show that the proposed algorithm has a well-analyzable stability structure, which is indicated by a transition matrix. The eigenvalues of the ensemble average of the transition matrix are proved all to be asymptotically less than unity. This results in a much-improved numerical performance of the proposed algorithm compared with the combination of the stabilized fast recursive least squares (SFRLS) and the FNTF algorithms. Computer simulations implemented by using a finite-precision arithmetic have confirmed the validity of our analysis.
Transactions of Japanese Society for Medical and Biological Engineering, 2012
This paper proposes the use of electrode grid for Japanese vowel recognition based on surface ele... more This paper proposes the use of electrode grid for Japanese vowel recognition based on surface electromyography (sEMG). Previous studies have indicated the potential effectiveness of sEMG-based speech recognition, not only for healthy people, but also for dysarthric patients. In these studies, however, disc electrodes or parallel bar electrodes were used and located empirically, although there exist relatively small muscles in proximity to each other in the face or neck region. In order to avoid missing out information about speech, we examined the effectiveness of using an electrode grid, which consists of densely-spaced multielectrodes. In our experiments, we measured sEMG signals from the submental region with the electrode grid during the production of 5 vowel sounds. Continuous hidden Markov models were applied to the sEMG signals for vowel recognition. We compared the recognition accuracies between the two methods : One was based on signals from all channels and the other was b...
Transactions of the Institute of Systems, Control and Information Engineers, 2011
The paper proposes a rear-end collision warning system for drivers, where the collision risk is a... more The paper proposes a rear-end collision warning system for drivers, where the collision risk is adaptively set from driving signals. The system employs the inverse of the time-to-collision with a constant relative acceleration as the risk and the one-class support vector machine as the anomaly detector. The system also utilizes brake sequences for outliers detection. When a brake sequence has a low likelihood with respect to trained hidden Markov models, the driving data during the sequence are removed from the training dataset. This data selection is confirmed to increase the robustness of the system by computer simulations.
SICE Journal of Control, Measurement, and System Integration, 2015
This paper proposes a very simple user-state recognizer for mobile applications. The proposed met... more This paper proposes a very simple user-state recognizer for mobile applications. The proposed method copes with the limitation in available electric power by using only a single three-axis accelerometer which is equipped with almost any mobile phone. In order to keep a high accuracy in recognition with a low computational complexity, the authors employ the wavelet transform and the singular value decomposition as feature extraction, and a multi-layer perceptron as a classifier. In the experiment, the algorithm could classify user contexts into walking, running, standing still and being in a moving train with an accuracy of over 90%.
Motile cells transduce environmental chemical signals into mechanical forces to achieve properly ... more Motile cells transduce environmental chemical signals into mechanical forces to achieve properly controlled migration. This signal-force transduction is thought to require regulated mechanical coupling between actin filaments (F-actins), which undergo retrograde flow at the cellular leading edge, and cell adhesions via linker "clutch" molecules. However, the molecular machinery mediating this regulatory coupling remains unclear. Here we show that the F-actin binding molecule cortactin directly interacts with a clutch molecule, shootin1, in axonal growth cones, thereby mediating the linkage between F-actin retrograde flow and cell adhesions through L1-CAM. Shootin1-cortactin interaction was enhanced by shootin1 phosphorylation by Pak1, which is activated by the axonal chemoattractant netrin-1. We provide evidence that shootin1-cortactin interaction participates in netrin-1-induced F-actin adhesion coupling and in the promotion of traction forces for axon outgrowth. Under ce...
Highlights d Actin waves are confirmed to translocate actin and associated proteins along axons d... more Highlights d Actin waves are confirmed to translocate actin and associated proteins along axons d F-actins in the wave are anchored to the plasma membrane and underlying substrate d Wave migration is driven by directional assembly and disassembly of membrane-anchored F-actins d Protein delivery by waves promotes axonal protrusion during neuronal polarization
SICE Journal of Control, Measurement, and System Integration, 2012
For monophonic music instrument identification, various feature extraction and selection methods ... more For monophonic music instrument identification, various feature extraction and selection methods have been proposed. One of the issues toward instrument identification is that the same spectrum is not always observed even in the same instrument due to the difference of the recording condition. Therefore, it is important to find non-redundant instrument-specific features that maintain information essential for high-quality instrument identification to apply them to various instrumental music analyses. For such a dimensionality reduction method, the authors propose the utilization of linear projection methods: local Fisher discriminant analysis (LFDA) and LFDA combined with principal component analysis (PCA). After experimentally clarifying that raw power spectra are actually good for instrument classification, the authors reduced the feature dimensionality by LFDA or by PCA followed by LFDA (PCA-LFDA). The reduced features achieved reasonably high identification performance that was comparable or higher than those by the power spectra and those achieved by other existing studies. These results demonstrated that our LFDA and PCA-LFDA can successfully extract low-dimensional instrument features that maintain the characteristic information of the instruments.
The human brain has important abilities for manipulating phonemes, the basic building blocks of s... more The human brain has important abilities for manipulating phonemes, the basic building blocks of speech; these abilities represent phonological processing. Previous studies have shown change in the activation levels of broad cortical areas such as the premotor cortex, the inferior frontal gyrus, and the superior temporal gyrus during phonological processing. However, whether these areas actually convey signals to representations related to individual phonemes remains unclear. This study focused on single vowels and investigated cortical areas important for representing single vowels using electrocorticography (ECoG) during covert articulation. To identify such cortical areas, we used a neural decoding approach in which machine learning models identify vowels. A decoding model was trained on the ECoG signals from individual electrodes placed on the subjects' cortices. We then statistically evaluated whether each decoding model showed accurate identification of vowels, and we found...
A large body of evidence supports that visual attention - the cognitive process of selectively co... more A large body of evidence supports that visual attention - the cognitive process of selectively concentrating on a salient or task-relevant subset of visual information - often works on object-based representation. Recent studies have postulated two possible accounts for the object-specific attentional advantage: attentional spreading and attentional prioritization, each of which modulates a bottom-up signal for sensory processing and a top-down signal for attentional allocation, respectively. It is still unclear which account can explain the object-specific attentional advantage. To address this issue, we examined the influence of object-specific advantage on two types of visual search: parallel search, invoked when a bottom-up signal is fully available at a target location, and serial search, invoked when a bottom-up signal is not enough to guide target selection and a top-down control for shifting of focused attention is required. Our results revealed that the object-specific adva...
2013 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2013
Prediction of driving behaviors is an important problem in developing a next-generation driving s... more Prediction of driving behaviors is an important problem in developing a next-generation driving support system. In order to take diverse driving situations into account, it is necessary to model multiple driving operation time series data. In this study we modeled multiple driving operation time series with four modeling methods including beta process autoregressive hidden Markov model (BP-AR-HMM), which we used in our previous study. We quantitatively compared the modeling methods with respect to prediction accuracies, and concluded that BP-AR-HMM excelled the other modeling methods in modeling multiple driving operation time series and predicting unknown driving operations. The result suggests that BP-AR-HMM estimated behaviors of a driver and transition probabilities between the behaviors more successfully than the other methods, because BP-AR-HMM can deal with commonalities and differences among multiple time series, but the others cannot. Therefore BP-AR-HMM may help us to predict driver behaviors in real environment and to develop the next-generation driving support system.
2013 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2013
Artists have a specific evaluation of abstract paintings while art novices do that with difficult... more Artists have a specific evaluation of abstract paintings while art novices do that with difficulty. This difference is shown in eye fixation patterns, although the cause is not clear. To explain the difference in fixation patterns, we used one of the saliency maps of paintings which predict fixations well without prior knowledge such as a meaningful target. If artists had a deep knowledge of art, they attend less to the salient features than novices in observing abstract paintings. On the other hand, the fixation patterns possibly vary in visual tasks. Therefore we examined the effect of salient features in two tasks: free viewing and preference judgment. To evaluate this quantitatively, the correlation coefficient (CC) between fixation distribution and a saliency map was used. The CCs were compared between artists and novices for each task. We found that the CCs of artists were lower than those of novices in the free viewing task, but not in the preference judgment task. This implies that the artist's knowledge of observation paintings was appeared only in free viewing.
When viewing a painting, artists perceive more information from the painting on the basis of thei... more When viewing a painting, artists perceive more information from the painting on the basis of their experience and knowledge than art novices do. This difference can be reflected in eye scan paths during viewing of paintings. Distributions of scan paths of artists are different from those of novices even when the paintings contain no figurative object (i.e. abstract paintings). There are two possible explanations for this difference of scan paths. One is that artists have high sensitivity to high-level features such as textures and composition of colors and therefore their fixations are more driven by such features compared with novices. The other is that fixations of artists are more attracted by salient features than those of novices and the fixations are driven by low-level features. To test these, we measured eye fixations of artists and novices during the free viewing of various abstract paintings and compared the distribution of their fixations for each painting with a topological attentional map that quantifies the conspicuity of low-level features in the painting (i.e. saliency map). We found that the fixation distribution of artists was more distinguishable from the saliency map than that of novices. This difference indicates that fixations of artists are less driven by low-level features than those of novices. Our result suggests that artists may extract visual information from paintings based on high-level features. This ability of artists may be associated with artists' deep aesthetic appreciation of paintings.
2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2014
From optimal supply decisions to anticipatory control systems, wind-based energy applications rel... more From optimal supply decisions to anticipatory control systems, wind-based energy applications rely heavily upon accurate, local, short-term forecasts of future wind speed. Recent studies have shown continuous ranked probability score (CRPS) minimizing models with Gaussian assumptions to be effective for well-researched sites where those assumptions are appropriate. We consider the more general case where Gaussianity is not assumed and access to historical data may be constrained. Deriving a CRPS expression for a minimum Extreme Value distribution, we use it to propose a site-adaptive Weibull-based CRPS-minimizing model, which is tested and shown to perform better than both deterministic and probabilistic reference models on a ground-based array of weather observation sites in northern Japan.
2013 Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, 2013
In this paper, we propose an interactive evolutionary programming based recommendation system for... more In this paper, we propose an interactive evolutionary programming based recommendation system for online shopping that estimates the human preference based on eye movement analysis. Given a set of images of different clothes, the eye movement patterns of the human subjects while looking at the clothes they like differ from clothes they do not like. Therefore, in the proposed system, human preference is measured from the way the human subjects look at the images of different clothes. In other words, the human preference can be measured by using the fixation count and the fixation length using an eye tracking system. Based on the level of human preference, the evolutionary programming suggests new clothes that close the human preference by operations such as selection and mutation. The proposed recommendation is tested with several human subjects and the experimental results are demonstrated. I.
e203 trial. We recorded the intrinsic signal from the retina for 2 s before the stimulus, then fo... more e203 trial. We recorded the intrinsic signal from the retina for 2 s before the stimulus, then for 4 s during the stimulus and finally 20 s after the stimulus in each trial, and repeated them for 10 times (Okawa et al., 2007. Invest. Ophthalmol. Vis. Sci.). To improve signal to noise ratio, 10 consecutive images were averaged in each trial, then the images of 10 trials were averaged. Subtracting pre-stimulus images from post-stimulus images, two-dimensional topography of retinal reflectance change was constructed. Single electrode stimulation evoked the reflectance changes in localized area near the stimulating electrode at the current of 0.3-1.0 mA. Simultaneous stimulation with two electrodes evoked the reflectance changes in two separated retinal areas, which were correspondent to those of single electrode stimulation. It indicated that two-point discrimination was able to achieve by STS in the retina. Research fund: Strategic Research Program for Brain Sciences.
The generalization properties of support vector machines (SVMs) are examined. From a geometrical ... more The generalization properties of support vector machines (SVMs) are examined. From a geometrical point of view, the estimated parameter of an SVM is the one nearest the origin in the convex hull formed with given examples. Since introducing soft margins is equivalent to reducing the convex hull of the examples, an SVM with soft margins has a different learning curve from the original. In this paper we derive the asymptotic average generalization error of SVMs with soft margins in simple cases, that is, only when the dimension of inputs is one, and quantitatively show that soft margins increase the generalization error.
IEEE Transactions on Wireless Communications, 2008
We propose generic relay and subcarrier allocation schemes for Multi-Carrier (MC) system with Amp... more We propose generic relay and subcarrier allocation schemes for Multi-Carrier (MC) system with Amplify-and-Forward (AF) relays. The outage probability bounds are derived analytically for each scheme. Simulation results show that these bounds are very tight and better than the bounds obtained straightforwardly from the analysis in the Single-Carrier (SC) case. This is because in our analysis we reckon with the increased degree of freedom brought by the parallel channels. One of the proposed schemes, the Average Best Relay Selection scheme, is best suited for practical implementation since it approaches the best performance while minimizing the required amount of signaling.
This paper presents a numerically stable fast Newton-type adaptive filter algorithm. Two problems... more This paper presents a numerically stable fast Newton-type adaptive filter algorithm. Two problems are dealt with in the paper. First, we derive the proposed algorithm from an order-recursive least squares algorithm. The result of the proposed algorithm is equivalent to that of the fast Newton transversal filter (FNTF) algorithm. However, the derivation process is different. Instead of extending a covariance matrix of the input based on the min-max and the max-min criteria, the derivation shown in this paper is to solve an optimum extension problem of the gain vector based on the information of the th-order forward or backward predictor. The derivation provides an intuitive explanation of the FNTF algorithm, which may be easier to understand. Second, we present stability analysis of the proposed algorithm using a linear time-variant state-space method. We show that the proposed algorithm has a well-analyzable stability structure, which is indicated by a transition matrix. The eigenvalues of the ensemble average of the transition matrix are proved all to be asymptotically less than unity. This results in a much-improved numerical performance of the proposed algorithm compared with the combination of the stabilized fast recursive least squares (SFRLS) and the FNTF algorithms. Computer simulations implemented by using a finite-precision arithmetic have confirmed the validity of our analysis.
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Papers by Kazushi Ikeda