In this paper, we present a pixel-level color image sensor with efficient ambient light suppression using a modulated RGB flashlight to support a recognition system. The image sensor employs bidirectional photocurrent integrators for pixel-level demodulation and ambient light suppression. It demodulates a projected flashlight with suppression of an ambient light at short intervals during an exposure period. In the imaging system using an RGB modulated flashlight, every pixel provides innate color and depth information of a target object for color-based categorization and depth-key object extraction. We have designed and fabricated a prototype chip with 6464 pixels using a 0.35 µm CMOS process. Color image reconstruction and time-of-flight range finding have been performed for the feasibility test.

As the number of mobile terminals (or users) keeps explosively increasing, the location management to track mobile terminals in cellular networks is becoming more important. However, the location management schemes presently adopted in cellular networks use static location information without considering the moving direction of a mobile terminal. This approach is insufficient in reflecting the different directional behaviors of mobile terminals. Thus, there is a need to develop a dynamic location management scheme more adaptive to the moving direction of a mobile terminal. This paper proposes a direction-based scheme (DBS) that can determine a location update and vary a paging area dynamically according to the moving direction. The direction vector was defined to represent the moving direction and to compute the distance from the cell where a location update occurs to the current cell. The offset operation of direction vectors represented the location of a mobile terminal in a paging area. This allowed the mobile terminal to determine whether a location update would be performed or not. In addition, simulations showed that DBS outperforms other location management schemes in most cases except in those with a low call-to-mobility ratio (CMR), particularly if a mobile terminal has directional behavior.

We have developed a two-dimensional flat-panel imager (FPI) utilizing conventional amorphous silicon (a-Si) thin film transistor (TFT) technology for AM-LCDs, and we have made a prototype. We can experimentally manufacture the FPI basically by utilizing conventional production lines of AM-LCDs, because the imager is based on the TFT array for AM-LCDs. The TFT performs both switching and photo-detecting functions itself. Using the FPI, we can capture monochrome images in real time, and can also achieve full-color images by introducing time-sequential driving based on a color backlight system with RGB-LEDs. The reliability of the TFT under bias and irradiation stress caused by capturing images is maintained by introducing an original driving method and processing the captured image. By making use of advantages the FPI has over conventional imaging systems, we hope that the FPI will be a useful compact imaging device for documents, pictures, fingerprints, and the like.

Software rejuvenation is a preventive and proactive solution that is particularly useful for counteracting the phenomenon of software aging. In this paper, we consider both the periodic and non-periodic software rejuvenation policies under different dependability measures. As is well known, the steady-state system availability is the probability that the software system is operating in the steady state and, at the same time, is often regarded as the mean up rate in the system operation period. We show that the mean up rate should be defined as the mean value of up rate, but not as the mean up time per mean operation time. We derive numerically the optimal software rejuvenation policies which maximize the steady-state system availability and the mean up rate, respectively, for each periodic or non-periodic model. Numerical examples show that the real mean up rate is always smaller than the system availability in the steady state and that the availability overestimates the ratio of operative time of the software system.

The enlargement of the left lobe of the liver and the shrinkage of the right lobe are helpful signs at MR imaging in diagnosis of cirrhosis of the liver. To investigate whether the volume ratio of left-to-whole (LTW) is effective to differentiate cirrhosis from a normal liver, we developed an automatic algorithm for three-dimensional (3D) segmentation and volume calculation of the liver region in multi-detector row CT scans and MR imaging. From one manually selected slice that contains a large liver area, two edge operators are applied to obtain the initial liver area, from which the mean gray value is calculated as threshold value in order to eliminate the connected organs or tissues. The final contour is re-confirmed by using thresholding technique. The liver region in the next slice is generated by referring to the result from the last slice. After continuous procedure of this segmentation on each slice, the 3D liver is reconstructed from all the extracted slices and the surface image can be displayed from different view points by using the volume rendering technique. The liver is then separated into the left and the right lobe by drawing an inter-segmental plane manually, and the volume in each part is calculated slice by slice. The degree of cirrhosis can be defined as the ratio of volume in these two lobes. Four cases including normal and cirrhotic liver with MR and CT slices are used for 3D segmentation and visualization. The volume ratio of LTW was relatively higher in cirrhosis than in the normal cases in both MR and CT cases. The average error rate on liver segmentation was within 5.6% after employing in 30 MR cases. These results demonstrate that the performance in our 3D segmentation was satisfied and the LTW ratio may be effective to differentiate cirrhosis.

We have developed a novel basic technology for terahertz (THz) imaging, which allows detection and identification of chemicals by introducing the component spatial pattern analysis. The spatial distributions of the chemicals were obtained from terahertz multispectral transillumination images, using absorption spectra previously measured with a widely tunable THz-wave parametric oscillator. We have also separated the component spatial patterns of frequency-dependent absorptions in chemicals and frequency-independent components such as plastic, paper and measurement noise in THz spectroscopic images. Further we have applied this technique to the detection and identification of illicit drugs concealed in envelopes.

In General Packet Radio Service (GPRS), combined mobility management is defined to efficiently perform both GSM and GPRS mobility management in a combined manner. In this letter, an enhanced scheme for combined mobility management based on a new mobile station (MS) state model is proposed. The steady state probabilities of the proposed MS state model are derived and the performance of the proposed scheme is analyzed. The results show that the proposed scheme outperforms the conventional scheme, especially for low mobility MSs.

Radars utilizing ultra-wide-band (UWB) pulses are attractive as an environment measurement method for various applications including household robots. Suitable filtering is essential for accurate ranging, which requires an accurate waveform estimation. This paper presents a high-resolution algorithm of estimating target location and scattered waveforms, whose accuracies are interdependent. The technique relies on iterative improvements of estimated waveforms. Description of the algorithm is followed by statistical simulation examples. The performance of the algorithm is contrasted with conventional ones and statistical bounds. Results indicate that our proposed algorithm has a remarkable performance, which is close to the theoretical limit. Next, we clarify the problem of applying HCT to multiple targets. HCT for multiple targets can not be used as an estimated waveform because of interference waves from other targets. We propose an interference suppression algorithm based on a neural network, and show an application example of the algorithm.

Due to limited radio resource, an effective paging strategy is essential for improving the utility of radio channels. This paper proposes a new paging strategy that can reduce the paging cost on radio channels by introducing the paging agent in location area (LA). When a mobile-terminated call occurs, the mobile switching center (MSC) looks up a corresponding LA paging agent to determine the exact base station (BS) of the target mobile and pages only one cell. The performance of the proposed strategy is evaluated by an analytical model, and compared with the traditional simultaneous paging strategy and a recent proposal using paging agents of BSs. The numerical results demonstrates that the proposed strategy reduces the paging cost on radio channels compared with other paging strategies.

Recent investigations using magnetic resonance imaging (MRI) of human speech organs have opened up new avenues of research. Visualization of the speech production system provides abundant information on the physiological and acoustic realization of human speech. This article summarizes the current status of MRI applications with respect to speech research as well as our own experience of discovery and re-evaluation of acoustic events emanating from the vocal tract and physiological mechanisms.

Using event-related potential (P300 and CNV), the cognitive function of elderly subjects was compared with that of young subjects. It was found that the prolonged cognitive information processing induced by aging was reflected in the P300 and N400 latency. The effects of aging were not observed in the P300 amplitude. The CNV measurements, in the range of this study, did not reflect the effects of aging. This might be because the CNV reflects a higher cognitive function as compared with P300 and the effects of aging do not appear in such a function. The data also suggested that the cognitive style must be taken into account when evaluating the deterioration of cognitive functions with aging.

This paper presents an imaging technique using the MUSIC algorithm to localize cylindrical reflectors in cross-borehole radar arrangements. Tomographic measurement, in which a transmitting and a receiving antenna are individually moved in separate boreholes, can be considered as a combination of a transmitting and a receiving array. A decorrelation technique with the transmitting array, which has been proposed for imaging point reflectors, is applied for imaging cylindrical reflectors using the MUSIC algorithm. Simulated and experimental results are shown to verify the validity of this algorithm for cylindrical targets. We analyze the evaluation error caused by the increase in the radius of the cylinder.

Making information technology (IT) more accessible to elderly users is an important objective, in particular, concerning input devices. In this study, it has been investigated how the aging factor and the letter (character) size of a keyboard affects the efficiency in data entry. In addition, computer experience by the elderly was examined relative to efficiency. The performance measures (entry speed and correctly entered number per min) were twice better in a young group of computer users than in middle-aged and elderly groups. The effect of the size of the keyboard letters on performance was observed for the middle-aged and elderly groups who had no experience using a computer. The young, middle-aged, and elderly groups with computer experience were not affected by the size of the keyboard letters.

This paper presents a technique for improving the SNR and resolution of complex bandpass ΔΣADCs which are used for wireless communication systems such as cellular phone, wireless LAN and Bluetooth. Oversampling and noise-shaping are used to achieve high accuracy of a ΔΣAD modulator. However when a multi-bit internal DAC is used inside a modulator, nonlinearities of the DAC are not noise-shaped and the SNR of the ΔΣADC degrades. For the conversion of complex intermediate frequency (IF) input signals, a complex bandpass ΔΣAD modulator can provide superior performance to a pair of real bandpass ΔΣAD modulators of the same order. This paper proposes a new noise-shaping algorithm--implemented by adding simple digital circuitry--to reduce the effects of nonlinearities in multi-bit DACs of complex bandpass ΔΣAD modulators. We have performed simulation with MATLAB to verify the effectiveness of the algorithm, and the results show that the proposed algorithm can improve the SNR of a complex bandpass ΔΣADC with nonlinear internal multi-bit DACs.

An 8-GS/s 4-bit CMOS analog-to-digital converter (ADC) chip was implemented by using a time interleaved flash architecture for very high frequency mixed signal applications with a 0.18-µm single-poly five-metal CMOS process. Eight 1-GS/s flash ADCs were time-interleaved to achieve the 8-GHz sampling rate. Eight uniformly-spaced 1 GHz clocks were generated by using a phase-locked-loop (PLL) with the peak-to-peak and rms jitters of 29.6 ps and 3.78 ps respectively. An input buffer including a preamplifier array (fifteen preamplifiers, four dummy amplifiers and averaging resistors) was shared among eight 1-GS/s flash ADCs to reduce the input capacitance and the mismatches among eight 1-GS/s flash ADCs. The adjacent output nodes of preamplifiers were connected by a resistor (resistor-averaging) to reduce the effects of the input offset voltage and the load mismatches of preamplifiers. A source follower circuit was added at the output node of a preamplifier to drive eight distributed track and hold (DTH) circuits. The Input bandwidth of ADC was measured to be 2.5 GHz. The measured SFDR values at the sampling rate of 8-GS/s were 25 dB and 22 dB for the 1.033 GHz and 2.5 GHz sinusoidal input signals respectively. The power consumption and the active input voltage range were 340 mW and 700 mV peak-to-peak, respectively, at the sampling rate of 8-GS/s and the supply voltage of 1.8 V. The active chip area was 1.32 mm2.

Digital Subtraction Angiography (DSA) is a technique used for enhancement of small details in angiogram imaging systems. In this approach, X-ray images of a subject, after injection, are subtracted from a reference X-ray image, taken from the same subject before injection. Due to the exponential absorption property of X-rays, effects of small details at different depth appear differently on X-ray images. Consequently, image subtraction cannot be employed on the original images without any adjustment or modification. Proper modification, in this case, is to use some form of logarithmic operation on images before subtraction. In medical imaging systems, the system designer has a choice to implement this logarithmic operation in the analog domain, before digitization of the video signal, or in the digital domain after analog-to-digital conversion (ADC) of the original video signal. In this paper, the difference between these two approaches is studied and upper bounds for quantization error in both cases are calculated. Based on this study, the best approach for utilization of the logarithmic function is proposed. The overall effects of these two approaches on the inherent signal noise are also addressed.

In this paper, an efficient optimization algorithm for solving the inverse problem of a two-dimensional lossless homogeneous dielectric object is investigated. A lossless homogeneous dielectric cylinder of unknown permittivity scatters the incident wave in free space and the scattered fields are recorded. Based on the boundary condition and the incident field, a set of nonlinear surface integral equation is derived. The imaging problem is reformulated into optimization problem and the steady-state genetic algorithm is employed to reconstruct the shape and the dielectric constant of the object. Numerical results show that the permittivity of the cylinders can be successfully reconstructed even when the permittivity is fairly large. The effect of random noise on imaging reconstruction is also investigated.

The software rejuvenation is a proactive fault management technique for operational software systems which age due to the error conditions that accrue with time and/or load, and is important for high assurance systems design. In this paper, fine-grained shock models are developed to determine the optimal rejuvenation policies which maximize the system availability. We introduce three kinds of rejuvenation schemes and calculate the optimal software rejuvenation schedules maximizing the system availability for respective schemes. The stochastic models with three rejuvenation policies are extentions of Bobbio et al. (1998, 2001) and represent the failure phenomenon due to the exhaustion of the software resources caused by the memory leak, the fragmentation, etc. Numerical examples are devoted to compare three control schemes quantitatively.

We have developed an ultrahigh-sensitivity "New Super-HARP" handheld camera, which has a sensitivity that is about 100 times as great as that of a CCD camera. The sensitivity of TV cameras is determined by the performance of the imaging device. We developed the world's first imaging device that achieves high sensitivity and high picture quality by using the avalanche multiplication phenomenon in an amorphous selenium photoconductive target. This "Super-HARP" pickup tube, which has already been used in TV production, has a selenium target 8-µm thick. It is about 10 times as sensitive as CCDs. We have now developed a greatly improved version of the Super-HARP tube with a target 25-µm thick. This improved version, called the New Super-HARP pickup tube, is about 10 times as sensitive as the Super-HARP pickup tube. The New Super-HARP handheld camera equipped with the new tubes has a maximum sensitivity of 11 lx at F8. This camera is a powerful tool for reporting breaking news at night and other low-light conditions, the production of scientific programs, and numerous other applications.

The objective of this study was to explore suitable spatial filters for inverse estimation of cortical potentials from the scalp electroencephalogram. The effect of incorporating noise covariance into inverse procedures was examined by computer simulations. The parametric projection filter, which allows inverse estimation with the presence of information on the noise covariance, was applied to an inhomogeneous three-concentric-sphere model under various noise conditions in order to estimate the cortical potentials from the scalp potentials. The present simulation results suggest that incorporation of information on the noise covariance allows better estimation of cortical potentials, than inverse solutions without knowledge about the noise covariance, when the correlation between the signal and noise is low. The method for determining the optimum regularization parameter, which can be applied for parametric inverse techniques, is also discussed.