It is reported that various radar clutter obey a Weibull distribution. To suppress such Weibull-distributed clutter, Weibull CFAR techniques are applied to data taken by an S-band radar. The results show the usefulness of Weibull CFAR.

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We describe the configuration of a system that employs the Fourier Transform Technique (FTT) to calculate an analysis signal from a time domain interference signal in real-time by using optical frequency sweeping and demonstrate that this system is capable of measuring the distance of multiple targets. Although minute vibrations of the target create a problematic Doppler effect for distance measurement using optical frequency sweeping, that problem can be reduced at the same time by averaging the values during the times of optical frequency increase and decrease. We then show that the velocity and displacement of the measured object can both be measured every 12.5 ms by measuring the velocity using the Doppler component and summing the velocities to measure the displacement. This system can be used for simultaneous measurement of distance and displacement for multiple targets.

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We have previously developed a turn-key-ready OSO (optical sampling oscilloscope) system with a jitter of 0.2 ps rms and a resolution of 1 ps. Recently, we studied the characteristics of an AANP (2-adamantylamino-5-nitropyridine) crystal, which is the newest organic crystal for achieving a high-sensitivity optical sampling head unit for the OSO system. We developed a polarization-independent sampling head with a high sum-frequency conversion efficiency over the C-L bands using the AANP crystals.
This paper reports the characteristics of the AANP crystal and the developed configuration of a polarization-independent optical sampling head unit with AANP crystals. Furthermore, we demonstrate 160 Gb/s far-end measurement using the OSO system with the developed sampling head unit.

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A method and a simple equation for determining the magnetic complex antenna factor (M-CAF) of a shielded loop antenna are presented. The investigated shielded loop antenna has two output ports of which outputs are differentially combined in time domain. The low-directivity of this loop antenna is useful for mapping magnetic fields. The proposed method is based on an equivalent circuit of the antenna system. The derived equation makes it possible to determine the M-CAF from the calculated effective length of the loop element and the measured reflection coefficient at an output port. The proposed method is confirmed by comparison between the waveform reconstruction using the M-CAF and the theoretical calculation for an electromagnetic pulse radiated from a monopole antenna on a ground plane.

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A method and configuration for generating a calculable electromagnetic pulse is proposed in which the electromagnetic pulse is radiated from a small monopole antenna placed near the edge of a semi-infinite ground plane. The monopole antenna is excited by an impulse train. The radiated electric field at a distance from the edge is calculated by the waveform of the excited impulse with the assistance of the Uniform Theory of Diffraction (UTD) to include the effect of diffraction from the edge of the ground plane. The electric field is also reconstructed by signal processing using the complex antenna factor (CAF) of a receiving wide-band antenna. The estimated systematic effects and the agreement of the calculated and reconstructed waveforms show that the generated electromagnetic pulse has a possibility to be used as a reference wave for electromagnetic pulse measurements.

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We observed sea clutter using an L-band long-range air-route surveillance radar (ARSR) having a frequency 1.3 GHz, a beamwidth 1.2°, and a pulsewidth 3.0 μs. To determine the sea clutter amplitude, we introduce the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least squares method. It is discovered that the sea clutter amplitudes obey the log-normal, Weibull, and log-Weibull distributions with the shape parameters of 0.668 to 0.989, 5.18 to 8.30, and 1.07 to 7.82, respectively, for data within the beam width of an antenna.

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We observed sea-ice clutter using a millimeter wave radar with a frequency 34.860 GHz, a beamwidth 0.25°, and a plusewidth 30 ns which is located at the city of Mombetsu in Hokkaido. To determine the sea-ice clutter amplitude, we introduce the Akaike Information Criterion (AIC). It is discovered that the sea-ice clutter amplitudes obey the log-Weibull distribution with the shape parameters of 2.36 to 2.93 in terms of the temporal and small scale range fluctuations with which a constant false alarm rate (CFAR) is concerned. We propose a new log-Weibull/CFAR system uses a modified cell-averaging LOG/CFAR system. It is found that sea-ice clutter is suppressed with the improvement of more than 40 dB.

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We observed weather clutter from rain clouds using an L-band long-range air-route surveillance radar (ARSR) having a frequency 1.3 GHz, a beamwidth 1.2°, and a pulsewidth 3.0 μs. To determine the weather clutter amplitude, we introduce the Akaike Information Criterion (AIC), which is more rigorous fit of the distribution to the data than the least squares method. It is discovered that the weather clutter amplitudes obey almost the Rayleigh distribution for entire data and the Weibull, log-Weibull, and K-distributions with the shape parameters of 1.73 to 2.43, 10.60, and 5.13 to 50.93, respectively, for data within the beam width of an antenna.

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It is reported that various radar clutter obey a Weibull distribution under certain conditions. To suppress such Weibull-distributed clutter, a new adaptive method was proposed by the present author. In this method, the parameters of the Weibull distribution and the threshold level for an adaptive Constant False Alarm Rate (CFAR) detector are determined by calculating the variance before it passes through a logarithmic amplifier. To apply this new method to practical problems observed by an X-band radar, a computer simulation are made for a finite number of samples in order to obtain the CFAR maintenance in Weibull radar clutter. Finally an improvement value of target-to-clutter ratio 30.07 dB was obtained for the detection of an aircraft embedded in ground clutter.

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Since the phase noise of an oscillator is determined by the ratio of signal power to noise power, it should technically be possible to design an ultralow-phase-noise oscillator with an extremely high output power level. When the phase noise of an oscillator is evaluated, therefore, adjustment of the output power level is needed to match the dynamic range of the measurement system. However, the target—how the phase noise is to be measured while influenced by this level adjustment—has not been elucidated.
We make clear in this report that several patterns can be expected for observed phase-noise distributions that depend on the relative magnitude of phase noise and thermal agitation noise and methods for level setting. The perspective was also obtained that phase-noise measurement of an extremely low phase noise oscillator can be made by utilizing the above.

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Measurement methods for phase noise of oscillators include one using a phase-lock loop (PLL). However, this method cannot be used for measuring extremely low phase noise since it includes the phase noise of the reference oscillator in the measured values in addition to that of the oscillator being measured. We have therefore been studying a cross-correlation method to measure extremely low phase noise.
In this report, numerical processing using a cross-correlation method is studied through computer simulations.

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In the time and frequency transfer and dissemination field, it is important to provide cost effective remote frequency calibration services with an uncertainty of around 10^-12 for end users. It is also required to develop ultra precise transfer methods with an order of 10^-15 or better uncertainty for the comparison between ultra stable frequency standards which are under developing. This study shows two methods using optical fiber networks to satisfy these demands. First, it is an economical remote calibration method using existing synchronous optical fiber communication networks. The measured frequency stability (the Allan deviation) of the transmission clock is 2×10^-13 for an averaging time of one day. The result indicates the method is promising for the simple remote frequency calibration service. Second, it is an ultra precise two-way optical fiber time and frequency transfer method using a newly proposed bi-directional optical amplifier. In this method, wavelength division multiplexing (WDM) signals are transmitted along a single optical fiber. The preliminary measured frequency stability is less than 10^-15 (τ=10⁴ s) for a 100-km-long fiber with the bi-directional amplifier. It suggests that the method has capability for improving International Atomic Time (TAI) and Coordinated Universal Time (UTC).

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The purpose of this research is to clarify characteristics of the frequency differential limen to modulated vibratory stimuli. In this study, each frequency differential limen to 15 kinds of standard stimuli is determined by psychophysical measurement. In the measurement, comparison stimuli were introduced in all four directions of the standard stimulus, and the approximation model is generated based on the measured frequency differential limen.
As a result, it was confirmed that the frequency differential limen increases with an increase in the frequency. In addition, the estimation of a frequency differential limen to an arbitrary standard stimulus in the frequency area was attempted for the approximation model.

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It has been known that human being exhibits the Fight or Flight Reaction(FFR) when they feel anxiety, strain and threat. This paper describes experiments that were conducted to arouse the fight or flight reaction. Facial skin thermograms in which the temperature fluctuation in specific regions was identified were measured, and the characteristics of the temperature fluctuations in the relevant regions were quantitatively evaluated. The results showed that, for nine of the ten subjects, the FFR was confirmed in the form of reacted areas indicating acute increases in skin temperature, primarily in facial expression muscles such as the procerus muscle and cheek muscles. Additionally, the spatio-temporal spectrum differential analysis method for facial skin thermograms was proposed, and as a result of detecting spatio-temporal skin temperature fluctuations in the facial skin thermograms accompanying manifestation of the FFR, a detection rate of 76.5% was obtained. Thus, the effectiveness of the proposed technique was confirmed.

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This study reports the estimation of different-threshold (DT) when humans recognize various modulated vibrations using their tactile sensor. The modulated vibration consists of two frequency components. A psychological or the event related potential (ERP) measurement was used to estimate DT. ERP appears in an electro-encephalogram (EEG) when a human recognizes the information emitted by an external stimulus, and this study detects P300, which is a component of ERP.
This paper proposes a single-trial analysis that uses the T-test, which deviates from the conventional method for detecting P300 called the averaged EEG method. Finally, the proposed method estimates DT. As a result, the effectiveness of the proposed method is assured by estimating DTs on five subjects.

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From a viewpoint of signal processing, some system of partial differential equations is replaced by some electric circuit. In this paper, this principle is applied to a system of plasma equations. There exists a fluid theory describing the plasma state as one of the systems of plasma equations, which consists of a system of Maxwell's equations and that of Euler's equations. A system of partial differential equations is transformed into an equivalent Kirchhoff circuit by considering all physical quantities as currents and replacing differential operators with inductances. Using technique of wave digital filters (WDF), Kirchhoff circuits are transformed into a WDF algorithm, leading to a numerical one. This numerical method is applied to an analysis of plasma wave scattering phenomena from a conductor cylinder immersed in a magnetized plasma.

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Multifunctional approach gives the properties of sensor not only multifunctional, but also a compact structure and sometimes can increase discriminative property of sensing objects. In this study, because of the advantages of multifunctional approach, based on it, a sensor for estimating direction, obliquity and torsion angle parameters which are always used to describe the movement of a widely existing structure with a conjunction between two parts, likes robot arm, human extremity and so on is proposed. In order to obtain the reconstructions of three angle parameters in a simple and precise way, a symmetrical structure with three alike sensing elements are designed. The angle parameters are converted to the length change of three iron lines move on the surface of a flexible tube. This length change is detected based on inductance principle. Measuring several measured points as a database, the reconstructions of direction, obliquity and torsion angle can be obtained. The results calculated by these reconstructions prove the feasibility of the sensor.

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It is useful method to detect targets by extracting difference in local patterns of Remote Sensing images. However, it has not been established yet. Especially, in case that the pattern has difficulty in representing mathematical description, automatic detection is difficult as well. In this case, the pattern extraction by experienced people visually is the most effective method at present. Therefore, we consider neural network as a model of human visual recognition process, and propose automatic pattern extraction method featured by neural network learning based on Infomax Learning Algorithm. We applied this method in extracting pattern of oil spills on the sea observed by SAR images, as an example, and demonstrate that target can be detected automatically. In order to save computer load in learning and detecting, process, we approximate the feature of these patterns by Gabor function and demonstrate that the target can be detected as almost same level. Hence, we demonstrate that the proposed method is effective for automatic target detection.

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This paper describes the system to measure height of persons by triangulation using stereo vision which installs two cameras on the ceiling in a stably lighted room. We propose the sphere matching method which assumes a human head as a sphere. The feature of this measurement system is as follows:
- Since a sphere template is used for head matching in the edge images of a left camera and a right camera, the proposed method is hard to be influenced of each camera's field angle.
- Since the head edge in the images is used, even when there is no feature in top of the head, the human height can be measured.
As the result of experiment by this system, average error 1.36 [cm] and maximum error 3.85 [cm] were gained, which means high precision on the height measurement. And height measurement process, including input of a pair of stereo images, was attained in approx. 0.8 [s] (Pentium III,1.0GHz). Note that this system is a simple setup consisting of stereo camera and a general-purpose personal computer with one video capture board installed.

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We report herein the constant positional control by GA of an airship-type robot propelled by pectoral fin movement.

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In three-dimensional display systems, binocular disparities must be limited within a certain fusional area, called as “Panum's fusional area". Otherwise, too larger disparity could cause double view or serious eye fatigue. However, the measurements about Panum's fusional area in the previous studies focused only on the horizontal and vertical meridian of retina. For fully measuring the Panum's fusional area in more directions, we took the measurements of the limits of Panum's fusional area, in sixteen different directions from 0 degree to 360 degrees by a step of 22.5 degrees in the fovea. It was found that the horizontal disparity limit of binocular fusional area is about 32-38.4 min of arc and the vertical limit is about 19.2-24 min of arc. The disparity limits of binocular fusional area are approximately symmetrical about horizontal meridian. However, the disparity limits are not symmetrical about vertical meridian; the nasalward disparity limits are obviously larger than temporalward disparity limits. Moreover, in the nasal side of retina, the disparity limits decrease in a monotonic fashion, and in the temporal side, however, the disparity limits have no obvious difference.

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Functionally graded materials (FGMs) that have gradient in permittivity (i.e., ε-FGMs) were fabricated from alumina/epoxy mixtures by a centrifugal method. In order to investigate the effects of filler shape on the fabrication conditions and property of FGMs, both non-spherical and spherical alumina powders with various sizes were employed as filler materials in the mixtures. Experimental results indicate that the spatial gradient in the number density and size of fillers can be intentionally regulated by changing the centrifugal conditions such as rotation velocity and operational time, as well as the shape and size of the fillers. Fillers with different shapes required different fabrication conditions such as the property of epoxy resin to be mixed, the size of the fillers, the centrifugal conditions, and so on, in order to obtain desirable profiles of filler gradient. It is concluded that due to the difference in both the viscosity of the mixture and the maximum packing fraction of fillers obtainable, the usage of the spherical fillers produces longer FGM columns with a wider range of change in permittivity between both ends and makes it easier to control the profiles of permittivity than the usage of the non-spherical fillers.

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The experiments of moisture absorption and diffusion as well as treeing were performed under artificial tropical condition which epoxy resin specimen mixed with fillers. The results highlighted that even if the moisture absorption of specimen dipped into distilled water would be faster than that of exposed to humid environment, finally each of these conditions brought the similar effect to the treeing phenomena. Although tree inception voltage decreased with introducing silica fillers, the fillers prevented the growth of the tree. Moisture accelerated the tree propagation. It suggested that moisture would weaken the electric strength of the resin, leading to the acceleration of tree propagation. In addition, it was found in the filled specimen that the interface easily splits when moisture was introduced. However, even when the specimen contained moisture, it is seen that the filler still suppresses the tree propagation.

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Experiments of rocket-triggered lightning to a conventional lightning rod and a non-conventional Semiconductor Lightning Eliminator (SLE) were conducted in summers of 1998 and 1999 in southern China. Totally 16 lightning flashes were triggered and measured successfully. The measurements included photographs, currents and electrical fields. From the 5 lightning flashes triggered in altitude in 1998, it was found that these flashes tended to strike at the 4 m high conventional lightning rod rather than the 6 m high SLE located just 5 m away from the former. From the 11 lightning flashes triggered dedicatedly to the SLE in 1999, it was fund that there were usually a phenomenon of parallel discharges between two or more SLE rods occurring during the developing stage of lightning. In addition, there were always flashovers occurred along the SLE rods struck by lightning. Current measurements on the grounding path of the SLE have been succeeded for only one case out of five struck the SLE, probably due to side-paths caused by flashovers. The peak current measured for that case was about 6.6 kilo-amperes. The results show that the SLE is neither superior to a traditional lightning rod in terms of provision of lightning attachment points and paths for the lightning current to flow into ground, nor capable to eliminate any possibility of lightning. The lightning current-limiting function of the SLE declared by the manufacturer was not confirmed by these experiments.

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