Yasuhiko Nakano

Highly efficient universal coding with classifying to subdictionaries for text compression

Describes a practical, locally adaptive data compression algorithm of the LZ78 class. According to the Lempel-Ziv incremental parsing rule, the boundary of a string is not related to the statistical history modeled by finite-state sources. The authors have already reported an algorithm classifying to subdictionaries (CSD), which uses multiple subdictionaries and conditions the current string by using the previous one to obtain a higher compression ratio for image compression. They present a practical implementation of this method for any kind of data, and show that CSD was more efficient than LZC when the UNIX facility for compression. The compression performance of CSD was about 10% better than the LZC with the practical dictionary size, an 8K-entry dictionary when the test data were used form Calgary Compression Corpus. Using hashing, the processing speed of the CSD became as fast as the LZC, though the CSD algorithm was more complicated than the LZC.<<ETX>>

Reduction of baseline fluctuation in Electrocardiogram measurement for a car driver

Baseline fluctuation in Electrocardiogram (ECG) measurement system for car drivers is analyzed. The goal of this research is to develop a system that detects changes in R-R interval fluctuation, which is related to drowsiness and stress of the driver, and alert the driver to prevent drowsy driving. This system measures ECG with a contact electrode on the steering wheel and a capacitively coupled electrode on the drivers seat. This configuration allows ECG measurement while the driver is holding the steering wheel with one hand. The major source of baseline fluctuation is the static electricity generated by body motion, especially the pedaling motions that involve contact and removal of foot on the pedal. Baseline fluctuation can be as large as hundred times of the R-wave amplitude. Analysis of equivalent circuit model and experiments have shown that the baseline fluctuation can be reduced to 0.05 V by introducing an additional electrode on the drivers floor and connect it to the electrode in the steering wheel.

Assessment and prediction of older drivers' driving performance

Traffic accidents involving older drivers have been increasing all over the world. In order to assess elder driving performance and predict the risk of traffic accidents, we analyzed data from specific license renewal tests that are obligatory for Japanese drivers aged 70 years old or older, which includes a driving simulator test and an on-road test. As a result of the analysis, we found that aging affects several test results, such as the percentage of correct answers and the reaction times in multiple judgment tasks tests. In order to be able to classify a driver as a high accident risk, we performed an outlier analysis using a one-class SVM to investigate performance characteristics, and also performed a logistics regression analysis. Using parameters strongly related to cognitive decline, we found a viable way to classify impaired drivers. Driving is a complex task requiring integration of cognition, judgment, and operation skills. Deterioration of these skills is likely to increase the risk of traffic accidents. Although our final objective was to support elderly drivers suffering such deterioration, we initially studied a measurement method to detect the area and extent of deterioration effectively.

Measurement of a Car Driver’s Pulse Interval while Driving with One Hand

R-R interval measurement system for car drivers that allows measurement while the driver is driving with one hand has been developed. This system is intended for analysis of R-R interval fluctuation which is related to drowsiness and stress. R-R interval is the interval between R-waves in electrocardiogram (ECG). Our goal is to detect changes in R-R interval fluctuation and alert the driver to prevent drowsy driving. ECG was measured with a contact electrode on the steering wheel and a capacitive coupling electrode on the driver’s seat. ECG measurement with capacitive coupling is very sensitive to body motion. Baseline fluctuation can be as large as hundred times of the R-wave. In order to utilize differential amplification to reduce the fluctuation, an additional seat electrode was placed on top of the seat electrode with a paper insulator in between the two electrodes. The outputs of the upper seat electrode and the steering wheel electrode showed similar baseline fluctuation with respect to the lower seat electrode, while R-waves appeared only in the signal from the steering wheel electrode. Baseline fluctuation was reduced by taking the difference between the two signals. The proposed measurement method was evaluated in a real car. The system was capable of measuring R-waves of a passenger who held an electrode in the hand to simulate one hand driving while driving on a highway.

New binary image compression scheme for various kinds of images

This paper presents an efficient lossless data compression scheme for various kinds of binary images as line drawings and half-tone pictures. We studied a combination of preprocessing and Lempel-Ziv universal coding. To improve the compression ratio, we modified Lempel-Ziv universal coding by dividing its dictionary into classified sub-dictionaries. We obtained improved compression ratios in computer simulation on composite images consisting of mixed test and images.

Data Compression Technology Dedicated to Distribution and Embedded Systems

In distribution and embedded systems, data compression is often used to reduce the size of flash RAM and transmission data, while a rapid decompression speed enables faster rebooting of the compressed program code. We have developed a new data compression algorithm with a high decompression speed and a good compression rate that is equivalent to zlib, the standard technology in use today. We created a LZSS-based algorithm by optimizing the parsing of data strings. LZSS is known as a high decompression speed algorithm useful for embedded systems, and optimal parsing is well known as a method for improving compression rates [1]. Previously, this combination had not been implemented because statistical code length varies during optimal parsing [1]. Our algorithm overcomes this problem by calculating the probability of the literal or the code ( distance and length ) solving the shortest path problem first. It then constructs a simple code set that enables fast decompression using those probabilities and solves the shortest path problem again. Experiments on the standard evaluation data and wireless sensor network program [2] demonstrated that we can achieve a high compression rate equivalent to zlib and a decompression speed that is twice as fast.

Verification of the Effect on “Finger Pointing and Calling” Method from Observation of Brain Activity Related Driver's Attention

We propose a driving style with “Finger Pointing and Calling (FPC)” as each driver checks safety on his own, in order to maintain alertness constantly and to reduce human error while driving. We examined the effectiveness of this safety check method by monitoring increase blood flow toward the brain. Additionally we propose “Imagined Pointing and Calling (IPC)”, which has the same effect as FPC, and can be applied in lieu of FPC. We also examined the effect by IPC in the same way. As a result, FPC and IPC increased brain activity and is likely to improve drivers alertness.

Development of adaptive noise reduction technology for in-vehicle heartbeat sensor

We proposed a noise reduction method for in-vehicle heartbeat sensor systems. The system measures the drivers heartbeat using a steering wheel electrode and a seat electrode that has dual construction. This configuration allows measurement while driving with one hand and provides two signals for noise cancellation. However, the amplitude ratio of the common mode noise varies when driving at high speeds. We multiplied a coefficient that was derived from the Root Mean Square (RMS) ratio between the two signals. This method enabled us to obtain 80% or more of the heartbeat signal while driving at high speed with one hand.

Analysis of communication data: compression network

The paper reports the effect of compressed message delivery (a compression network) on a parallel processing system such as workstation clusters. Compression network is simulated on a massively parallel processor, the Thinking Machines CM-5, using the parallel language Split-C. To examine the benefit of data compression to the system, profiles, including message pattern, number of messages, and message size, are measured by simulation. The results indicate that compression increases the network bandwidth. A theoretical compression ratio of about a half was estimated for almost all messages. Network bandwidth can be efficiently doubled using data compression.<<ETX>>

Study of binary image compression using universal coding

This paper presents a new approach to binary image compression by using universal coding for various kinds of binary images, such as line-drawings and half-tones. We studied two types of preprocessing of universal coding for binary images, and found that for various kinds of line-drawings, and half-tone (screen-dots) images, both preprocessors outperformed compared with conventional schemes.