The VHF broadband radio interferometry operated from 25 MHz to 250 MHz has been developed for observing lightning discharge progression. The lightning images are derived by sensing the electromagnetic-waves which are radiated during the discharges. The perpendicular baseline geometry provides the angular locations (azimuth and elevation) of lightning radiation sources. The lightning observations have been conducted in the Hokuriku District in 1999. The station consisted of three broadband antennas and an electric field antenna as well as a GPS receiver. The system was able to reconstruct lightning discharge channels in two-spatial dimensions and in time sequence. As one of the observation results, an upward negative cloud-to-ground lightning flash will be presented.

In order to maintain the diversity of structures in the population and prevent premature convergence, I have developed a new genetic algorithm called DCGA. In the experiments on many standard benchmark problems, DCGA showed good performances, whereas with harder problems, in some cases, the phenomena were observed that the search was stagnated at a local optimum despite that the diversity of the population is maintained. In this paper, I propose methods for escaping such phenomena and improving the performance by reinitializing the population, that is, a method called each-structure-based reinitializing method with a deterministic structure diverging procedure as a method for producing new structures and an adaptive improvement probability bound as a search termination criterion. The results of experiments demonstrate that DCGA becomes robust in harder problems by employing these proposed methods.

Telepresentations will be popular in the future of ubiquitous digital media. To realize a telepresentation easily over the Internet, we design a communication protocol to control a remote material (digital media) used in a telepresentation. We describe our proposed protocol; RMOP (Remote Material Operation Protocol) in this paper. This protocol specifies commands for material operations such as synchronization of slides, drawing, and pointing. Since this protocol just specifies the common formats through IP networks independent of special functions of presentation tools, it can be applied to various presentation tools. To design the protocol, we consider the trade-off between reliability of IP multicast and practical availability in the actual Internet. We adopt the reliable multicast mechanism to improve reliability but not to lose practicality in the protocol. Also, we describe an implementation of our prototype system using RMOP for a telepresentation. Then we show some evaluations such as the protocol overhead and comparisons with the other existing systems. Last, we show a case study of a telepresentation over the Internet using our system.

This paper presents methods for estimating the ocean wavelength in satellite altimetry and discusses the possibility of detecting the ocean wavelength. Numerical analyses show that there exists a relation between the significant wavelength and the pulse-to-pulse correlation coefficient. Presented methods are based on processing the data of existing satellite altimeters. Accordingly, we will be able to propose a method for measuring the wavelength without a large change in existing altimetry system.

This study is intended to realize an in-situ gas sensor based upon the principle of millimeter/submillimeter wave spectroscopy. In-situ gas sensor will be attractive because of gas selectivity, multiple parametric measurement such as gas temperature, pressure and density, and of the in-situ measurement capability. One of the major technical problem to be solved is to develop an instrument accurate enough to discern the spectrum change due to the variation of parameters such as temperature. In this paper a proposed gas absorption measurement system is investigated, which schematically consists of Fabry-Perot type gas cell for effective long path length, and vector signal processing to reject leak signal coupled between resonator input and output ports so as to achieve precise absorption measurement. Also included is an parametric study of oxygen absorption characteristics, which is served as the predicted value in the evaluation of the instrument. The experiment at 60 GHz and 120 GHz bands using oxygen demonstrates the effectiveness of the current system configuration.

The scatterometer is a real aperture radar capable to perform a set of normalized radar cross section measurements under different azimuth angles for each resolution cell. The main field of application of a wind scatterometer regards the sea surface wind field determination. As a matter of fact, once such measurements have been performed it is possible to determine the sea surface wind field by means of an inversion procedure. In this paper we present a novel inversion scheme which is an evolution of the procedure nowday used by the Italian Space Agency (ASI) under the Italian Processing and Archiving Facility (I-PAF). A full comparative study shows that the novel inversion scheme better behaves whenever light wind regimes are in question.

This work provides a generalization of structural logic optimization methods to general boolean networks. This generalization is based on a functional description of the nodes in the network. Therefore, this approach is no longer restricted to networks that consist of simple gates. Within this framework, we present necessary and sufficient conditions to identify all the possible functional expansions of a node that allow to eliminate a wire elsewhere in the network. These conditions are also given for the case of multiple variable expansion, providing an incremental mechanism to perform functional transformations involving any number of variables that can be applied in a very efficient manner. On the other hand, we will show in this paper that relevant simplifications can be obtained when this framework is applied to the particular case of AND-OR-NOT networks, resulting in important savings in the computational effort. When compared to previous approaches, the experimental results show an important reduction in the number of computations required.

The capacity of quantum channel with product input states was formulated by the quantum coding theorem. However, whether entangled input states can enhance the quantum channel is still open. It turns out that this problem is reduced to a special case of the more general problem whether the capacity of product quantum channel exhibits additivity. In the present study, we apply one of the quantum Arimoto-Blahut type algorithms to the latter problem. The results suggest that the additivity of product quantum channel capacity always holds and that entangled input states cannot enhance the quantum channel capacity.

Recently, Kasahara and Murakami proposed new product-sum public-key cryptosystems using the Chinese remainder theorem as the trapdoor. We proposed 'Yaezakura' as the high-density product-sum PKC applying the method using the reduced bases. In this paper, we propose another high-density scheme with the Chinese remainder theorem trapdoor using the message extension. We also show that the proposed scheme is invulnerable to the low-density attack. In the proposed scheme, the sender can freely select the positions of the dummy messages.

In this paper, we shall construct mathematical theory based on the concept of set-valued mappings, suitable for available operation of network systems extraordinarily complicated and diversified on large scales. Fundamental conditions for availability of system behaviors of such network systems are clarified in a form of fixed point theorem for system of set-valued mappings.

The efficiency-fractional bandwidth product (EB), which is expressed as a ratio of the radiation resistance to the absolute value of the input reactance of an antenna, is used as a performance criterion for small dielectric loaded monopole antennas (DLMAs). The dependence of the EB on the permittivity of the dielectric loading (i.e., the electrical volume) is experimentally and numerically investigated for the first time in antenna research. As a result, it is found that the EBs of the some DLMAs are enhanced over a bare monopole antenna and an EB characteristic curve has a maximum point. This result suggests the presence of the optimum electrical volume for the dielectric loading in order to obtain the best EB performance. A general reason for the existence of the peak value is also explained using a mathematical deduction. Finally the system EB, which is an efficiency-fractional bandwidth product of the DLMA with a practical matching circuit, is defined and its dependence on the relative permittivity is illustrated. Consequently, the existence of the peak value is also confirmed for the system EBs. In addition, it is demonstrated that the enhancement of the system EB is mainly due to the enhancement in the efficiency of the antenna system.

A flexible noise generation algorithm using DCT is proposed. The proposed method outperforms the conventional methods when a noise model requires complicated PSD (Power Spectral Density) specifications. Also, it is shown that the proposed system can be used for the test of VDSL (Very high-speed Digital Subscriber Line).

A remote auscultation support system was developed that compresses and records in real time the patient's breath sound and heart sound, obtained using a stethoscope, and sends this data to an attending doctor at a hospital via network. For real-time recording of the breath sound and heart sound, special-purpose, high-quality sound coding technology was developed and incorporated in the system. This sound coding technology enables the amount of data to be reduced to about 1/18 with virtually no deterioration of the properties of the auscultation sound, high-speed transmission of this data using network, and remote diagnosis of the auscultation sound by a medical specialist. The auscultation locations of each patient, together with the doctor, stethoscoper, and patient database are input into the system in advance at the hospital. At the patient's home or sanatorium, the auscultation sound is recorded according to a human body display that shows auscultation locations, and then sent to the hospital. To ensure patient confidentiality when the auscultation data is transmitted via network, the system scrambles the auscultation data and allows only the attending doctor to play and diagnose the auscultation sound. These features not only support an understanding of the condition of patients being treated at home, but they also enable the construction of an auscultation database for electronic charts that allows auscultation results to be shared within the hospital. When this remote auscultation support system was manufactured and its performance was assessed, virtually the same waveform was obtained for the recorded and played breath sound as for the original breath sound. Results showed that even at a sampling frequency of 11 kHz, remote diagnosis by a medical specialist was in fact possible. Furthermore, if auscultation data of 10 seconds per location for 10 locations is sent, the amount of data sent is only about 120 Kbytes. Since this amount of data converts to only about 25 pages of electronic mail text, even via the existing mobile network the auscultation sounds of many patients can be sent efficiently.

Fingerprint recognition is a well-researched problem, and there are several highly accurate systems commercially available. However, this biometric technology still suffers from problems with the handling of bad quality prints. Recent research has begun to tackle the problems of poor quality data. This paper takes a new approach to one problem besetting fingerprints--that of distortion. Previous attempts have been made to ensure that acquired prints are not distorted, but the novel approach presented here corrects distortions in fingerprints that have already been acquired. This correction is a completely automatic and unsupervised operation. The distortion modelling and correction are explained, and results are presented demonstrating significant improvements in matching accuracy through the application of the technique.

This letter shows the results of a series of link level simulations conducted to evaluate the performances of spatial and temporal equalizers (S/T-equalizers) using field measurement data. The configuration of the spatial and temporal equalizer discussed in this letter can be expressed as a cascade of an adaptive array antenna and maximum likelihood sequence estimator (MLSE): each of the adaptive array antenna elements has a fractionally spaced tapped delay line (FTDL), and the MLSE has taps covering a portion of channel delay profile. Bit error rate (BER) performances of the S/T-equalizers are presented, and performance sensitivity to symbol timing offset is investigated.

Providing results of a series of link-level simulations for a class of spatial and temporal equalizer (S/T-equalizer) is the primary objective of this letter, which is supplemental to this letter's companion article. The S/T-equalizers discussed in this letter have a configuration that can be expressed as the cascaded connection of adaptive array antenna and maximum likelihood sequence estimator (MLSE): each of the adaptive array antenna elements has a fractionally spaced tapped delay line (FTDL), and the MLSE has taps covering a portion of the channel delay profile. Both the desired and interference signals suffer from severe inter-symbol interference (ISI). A major difference of this article from its companion letter is that account is taken of the presence of co-channel interference (CCI). Bit error rate (BER) performance of the S/T-equalizer is presented as a result of the link-level simulations that use field measurement data.

Precise and quick multi-beam forming including null control will be one of the key technologies for the future satellite communication systems utilizing SDMA (Space Division Multiple Access) and DOA (Direction of Arrival) estimation. In order to realize the precise multi-beam forming, calibration procedure is indispensable since there are several unavoidable factors that degrade the multi-beam patterns of the array. Particularly amplitude and phase imbalance between RF circuits needs to be calibrated frequently and quickly when the array system exists in changeable environment since the imbalance easily occurs due to thermal characteristics of each RF circuit. This paper proposes a simple and high-speed remote calibration scheme compensating for amplitude and phase imbalance among RF circuits of a transmitting adaptive array antenna onboard satellite. This calibration is conducted at a remote station such as a gateway station on the ground in the satellite communication system, by utilizing the received signal including the temporally multiplexed orthogonal codes transmitted from the array antenna onboard satellite. Since the calibration factors for all the antenna elements can be simultaneously obtained by the parallel digital signal processing, calibration time can be drastically reduced. The accuracy of this calibration is estimated by simulation. Simulation results show that the amplitude imbalance among RF circuits can be suppressed within the range from -0.5 dB to +0.25 dB for the initial imbalance ranging from -2 dB to +3.5 dB, phase imbalance can be suppressed within the range of -3 deg. to +3 deg. for the initial imbalance ranging from -120 or +180 deg. by this method. The amplitude and phase deviations among the elements can be suppressed within 0.36 dB and 2.5 degrees, respectively, in 80% of probability. Simulation results also show that this calibration method is valid under the relatively bad carrier-to-noise conditions such as -10 dB at the receiver. Good improvement of the multi-beam patterns by this calibration is shown under the low carrier-to-noise ratio condition.

A method for estimating complex permittivity of a material using a rectangular waveguide with a flange is presented by the finite difference time domain (FDTD) method. An advantage of the present method is that it is not necessary to vary the material structure in order to insert it into the waveguide. Therefore estimation errors related to the dimensions of the material are almost negligible. In this case, fluoridated rubber is chosen as the low-loss material. The comparison of the complex permittivity of the material determined by the present method with FDTD and the conventional waveguide method at 10 GHz is performed. It was confirmed that the present method is effective for estimating the complex permittivity under the condition that the length of the flange is about 50 mm (1.7λ) square.

Efficient query processing in multi-dimensional indexing structures is an important issue for multimedia data applications. In this paper, we propose incremental k-nearest neighbor query (k-NNQ) and range query algorithms for R-tree based structures. The novel aspect of these algorithms is that they make use of the notion of VP filtering, a concept borrowed from the MVP-tree. The filtering notion allows for delaying of computational overhead until absolutely necessary. By so doing, we attain considerable performance benefits while paying insignificant overhead during the construction of the index structure. We implemented our algorithms and carried out experiments to demonstrate the capability and usefulness of our method. Results show that improvements range from 8% to 23% in response time for the experimental environment that we considered.

A tight bound on the bit error probability for turbo codes is derived by refining the Sphere bound by means of the reduced value of the coefficients which apply Verdu theorem. This approach is simpler than other upper bound techniques and extends the reliable region of Eb/N0 for which the bound yields meaningful results.