Recent technology on the precise measurement of time and frequency makes it rather easy to detect the relativistic effects. It is, therefore, indispensable to take these effects into account when we conduct such precise measurement. Though the fully understanding of the theory of relativity is not so easy, the effects that appeared in the precise time and frequency measurements is rather restricted and not so difficult to handle with. In this article, we will show the outline of the relativity and try an intimate illustration on most popular four relativistic effects; second Doppler effect, gravitational red shift, Sagnac effect and Shapiro delay.

抄録全体を表示

The advancement of the communication technology in recent years demands the technology of the high frequency and low phase noise of oscillator required for mobile telecommunications. In general, there are two important things for improving the phase noise characteristics of the oscillator. One is a design that the phase noise in the amplifier is suppressed to low. The other is a design having loaded Q as greatly as possible.
In this paper we shall discuss a configuration of oscillator circuit to obtain an extremely low phase noise and an oscillator operating at a non-reactive frequency of SAW resonator.

抄録全体を表示

This paper describes an analysis of the close to carrier phase-noise characteristics of the narrow-band Colpitts oscillators. The open-loop impedance, that is, series of the SC-cut resonator and the oscillator active circuit, is calculated using a linear circuit model with a non-linear transistor model. It is shown that the loaded Q can be improved by introducing the resonator filter in the oscillation circuit. Based on the Leeson's model, the near carrier phase-noise is estimated using the calculated Q values. The results corresponded well with the previous experiments. It is also shown that the phase-noise can be exceedingly improved, that is, under -148 dBc/Hz at 10Hz offset, by using resonator filter with high Q.

抄録全体を表示

International time comparison network has been performed by GPS common view to calculate TAI/UTC at BIPM. Recently, since IGS provides precise ephemerides and clock offsets for the GPS satellites, we can calculate time difference between two stations via GPS Time instead of a common GPS satellite. This method is called all in view as contrasted with common view. We compared time transfer precision between all in view and common view with UTC(NPL) and UTC(TL). The results show that all in view better than common view about 1.8 times.

抄録全体を表示

We have proposed a new piezoelectric oscillator circuit suitable for use in frequency range between 100 MHz and 1.24GHz. The proposed oscillator is composed of a colpitts oscillator and a two-stage common-emitter amplifier. The amplifier picks up the signal from the emitter of the oscillator transistor and feeds back the amplified signal to the base of the oscillator transistor with adequate phase shift. Simulation has shown that sufficiently large negative resistance can be obtained compared to the usual colpitts oscillator at 311MHz, 622MHz, 933MHz and 1.24GHz.

抄録全体を表示

The “Temperature Compensated Crystal Oscillator (TCXO)" is widely used as a stable frequency source of mobile communication equipment. Demand for low-power operation of TCXOs stimulates the development of fully integrated CMOS analog TCXOs. A TCXO is composed of a voltage controlled crystal oscillator and a temperature characteristics compensation circuit. We have proposed a new CMOS temperature characteristics compensation circuit for TCXO. The proposed circuit is composed of a new temperature sensor and a new compensation function generator. The performance of the proposed sensor and compensation function generator are estimated by simulation. And the total performance of TCXO is estimated. The compensated frequency deviation is within ± 0.5ppm.

抄録全体を表示

One of the JJY stations, placed on Mt. Otakadoya, has been operational since 10 June 1999 with a frequency of 40kHz. A set of time codes modulates the amplitude of LF radiowave by the amplitude shift keying (ASK) so that the time of the radio-controlled clock can be adjusted automatically. The time-codes of JJY signal are sent at a very low rate of 1 bps using pulse width modulation. The authors measured the delay-times of the three kinds of the decoded time-code: 0.2s, 0.5s, and 0.8s. The PPS (pulse per second) signal from the time transfer GPS receiver with accuracy of 1×10^-6 and a rubidium frequency standard with a stability of 5×10^-11/month were used for the time standard and the delay measurement counter respectively.
The delay-times measured for three kinds of time-code sent from the 40 kHz JJY station at a distance about 233 km are 65 ms for pulse-width of 0.2 s, 83 ms for pulse-width of 0.5 s, and 105 ms for pulse-width of 0.8 s. As the propagation delay of standard wave for the distance of 233 km is 0.7 ms, the delay-times obtained are mainly from the crystal filter in the 40 kHz receiver.

抄録全体を表示

The Quasi-Zenith satellites System (QZSS) is developed as an integrated satellite service system of communication, broadcasting and positioning for mobile users in specified regions of Japan from high elevation angle. Purposes of the satellite positioning system using Quasi-Zenith satellite (QZS) are to complement and augment the GPS. The national institutes concerned have been developing the positioning system using QZS since 2003 and will carry out experiments and researches in three years after the launch.
In this system, National Institute of Information and Communications Technology (NICT) is mainly in charge of timing system for the satellite positioning system using QZS, such as onboard hydrogen maser atomic clock and precise time management system of the QZSS. We started to develop the engineering model of the time management system for the QZSS. The time management system for the QZSS will be used to compare time differences between QZS and earth station as well as to compare between three onboard atomic clocks. This paper introduces time management of satellite positioning system using the QZSS.

抄録全体を表示

GPS is widely used to obtain not only the position information but also the time information. Specially, it is used to synchronize the time between separate stations in the measurement system or the communications system. However, in these systems, the output circuit of the 1PPS signal in the GPS receiver has not been optimized. In this paper, we examine the error sources of the time measurement by GPS and show the time measurement accuracy is about 10 ns, and the improvement of the precision of 1PPS signal is most important to realize high accurate 1PPS signal. We propose the precise 1PPS generating method by the analog circuit whose output precision is sufficiently higher than the time measurement accuracy by GPS. We evaluated the time measurement accuracy and the accuracy of 1PPS signal in the relative time synchronization by 24 hours test, and succeeded to realize a few ns precision and several ns accuracy of 1PPS signal in the relative time synchronization using our precise 1PPS generating method.

抄録全体を表示

We suggest a gigabit ethernet (GbE) based time transfer technique. In this technique, timing signals used for clock error measurements are inserted into inter-frame gaps and transmitted. We developed the GbE based time transfer system and evaluated the phase stability and precision.

抄録全体を表示

Two Way Satellite Time and Frequency Transfer (TWSTFT) enables us to perform time transfer precisely, for atmospheric and geometric delays between the earth station and the satellite are almost canceled because of the path reciprocity. However, the delays in the uplink path and the downlink path of the earth station cannot cancel due to the different signal paths. The delay difference makes the absolute value of the time difference unknown, while the fluctuation in the delay difference degrades the stability of the time transfer.
We have developed a delay-difference calibration system using a multi-channel TWSTFT modem. Because the signals for the calibration are processed with the received time-transfer signals from other stations, not only a short-term variation but also a secular change in the delay difference can be measured. It is found that the diurnal variation of the delay difference becomes a few hundred pico-second even if the low noise amplifier works in the temperature-controlled box. As for the time transfer result between two hydrogen masers, its stability was improved by the correction of the delay difference. We confirmed the calibration system was important to improve the precision of TWSTFT.

抄録全体を表示

The Japan Standard Time (JST) is calculated from the ensemble of the cesium atomic clocks at NICT Koganei headquarters. JST had a problem that the frequency of the timescale greatly changed by exiting of a clock from the ensemble. We found that the improper presuming method of the clock rate was the cause of this problem. We changed the presuming method so as to reflect the current performance of clocks, and the frequency change at the clock exiting was improved. We also confirmed the relation between the rate of exiting clock and frequency change of the time scale theoretically. It helps us to estimate the influence of the clock exiting.

抄録全体を表示

Engineering Test Satellite VIII (ETS-VIII) is planning to be launched in 2005 for fundamental studies on satellite positioning technologies and is the one first to be installed a highly precise cesium clock in Japan. To measure the clock offset between the satellite and the TCE Earth station, Time Comparison Equipment (TCE) has been developed in the NICT. The TCE will be used to measure both code and carrier phases and this system will improve two way time and frequency transfer. This equipment makes it possible to compare two clocks with high precision. Moreover, TCE and TCE Earth stations have abilities to remove the delay caused by terrestrial ionosphere and that between the receivers and transmitters.
We estimated measurement precision in code and carrier phases. Furthermore, from the examinations using TCE-EM (Engineering Model), we confirmed that TCE is able to measure the phases of clock with precision of sub-nanoseconds by code phase observation and of a few picoseconds by carrier phase observation.

抄録全体を表示

Recently, the demand of high speed network in home is increasing, and PLC is expected as one of the solutions. We can see related researches on the high speed PLC system using a frequency band 2 MHz to 30 MHz. In this paper, we propose a wavelet based OFDM as a suitable method for realizing the high speed PLC system. The proposed wavelet OFDM method is composed of the M-band transmultiplexer which consists of the perfect reconstruction cosine-modulated filter bank. And the attenuation of the first side-lobe is above 35dB, which is a characteristic of the proposed method. As a result, we show that the proposed method has the inter-carrier interference characteristic which is superior to FFT-OFDM, and it also provides the flexible notch filter function which can reduce the influence on other communication systems existing in the communication band which the PLC uses. Finally, we describe that the simulation results about the BER characteristic of the proposed method in AWGN were almost the same as the theory, and that transmission rates which were measured by using prototype modems in a field test house in U.S. were above 35Mbps.

抄録全体を表示

An acousto-optic laser deflector was used to image the intensity distribution of a continuous wave laser in the order of μs. Undeflected light was blocked while the deflected light was directed to a CCD camera, which allowed imaging of the incident laser intensity distribution in the order of μs. Experiments using a test pattern showed that there was no distortion in the deflected image. The resolution limit, estimated from diffractive effects, was about 0.2 mrad. Using this method of high-speed imaging, density variations accompanying laser-induced breakdown in air were visualized by shadowgraphy and interferometry.

抄録全体を表示

This paper proposes an algorithm for synthesizing music suitable for emotions in moving pictures. Our goal is to support multi-media content creation; web page design, animation films and so on. Here we adopt a human dance as a moving picture to examine the availability of our method. Because we think the dance image has high affinity with music. This algorithm is composed of three modules. The first is the module for computing emotions from an input dance image, the second is for computing emotions from music in the database and the last is for selecting music suitable for input dance via an interface of emotion.

抄録全体を表示

This paper presents a new model based on Neural Network(NN) for estimating distribution of materials concentration in polluted water lake. A spectral radiance reflectance method has been employed to estimate the materials concentration below the water surface. Lake Kasumigaura, Japan, has been selected as a target area in our research observation, and the lake was polluted by rich chlorophyll-a (chl.a) concentration and suspended solid (SS). The essence of our research is to scrutinize a set of wavelength effective to the estimation using NN model and employing Genetic Algorithm (GA). The obtained results show that proposed method is applicable to use in a remote-sensing image method. The results demonstrate that our NN model is capable to provide a pragmatic approach to accommodate existing and future demands for defining the quality of water and environmental monitoring.

抄録全体を表示

In this paper, we propose an individual discernment method using the speech sound and movement feature of the lip in speech. To compute the similarity obtained from the input data and registration data in the sound and image data, respectively, the proposed method uses DP matching processing. The method takes not only his or her registration data but also other registration data into consideration; it is able to decrease a non-registrant's number of incorrect receipts without increasing a registrant's number of incorrect rejections.
A case study was carried out on condition that the range of weight coefficient for the sound and image data was 0 to 1.0 at every 0.1. When ten subjects (person a to person j) were registrants, the proposed method is possible to distinguish them perfectly from others. Also 99.3% cased has rightly estimated in case of all subjects were divided into registrants and non-registrants. The experimental results indicate that the proposed method is useful.

抄録全体を表示

Hopfield model is a representative associative memory. It was improved to Bidirectional Associative Memory(BAM) by Kosko and Multidirectional Associative Memory(MAM) by Hagiwara. They have two layers or multilayers. Since they have symmetric connections between layers, they ensure to converge. MAM can deal with multiples of many patterns, such as (x₁, x₂,…), where x_m is the pattern on layer-m.
Noest, Hirose and Nemoto proposed complex-valued Hopfield model. Lee proposed complex-valued Bidirectional Associative Memory. Zemel proved the rotation invariance of complex-valued Hopfield model. It means that the rotated pattern also stored.
In this paper, the complex-valued Multidirectional Associative Memory is proposed. The rotation invariance is also proved. Moreover it is shown by computer simulation that the differences of angles of given patterns are automatically reduced.
At first we define complex-valued Multidirectional Associative Memory. Then we define the energy function of network. By using energy function, we prove that the network ensures to converge.
Next, we define the learning law and show the characteristic of recall process. The characteristic means that the differences of angles of given patterns are automatically reduced. Especially we prove the following theorem. In case that only a multiple of patterns is stored, if patterns with different angles are given to each layer, the differences are automatically reduced.
Finally, we invest that the differences of angles influence the noise robustness. It reduce the noise robustness, because input to each layer become small. We show that by computer simulations.

抄録全体を表示

A mobile agent is a one of important platform for applications for coming ubiquitous world. Many different kinds of mobile agent platforms have been developed. However, agents from one agent platform are generally not able to migrate into another agent platform. As a solution to this problem, we propose an interoperability concept using an Incarnation agent. The concept realizes logical mobility within different kinds of agent platforms. The Incarnation agent extracts an agent's procedures and status, compiling them into agent platform independent format and then re-compiling them to target agent platform format, thus enabling the process to continue. The Incarnation agent also has autonomy for interoperability. It manages complex migration for interoperability, so agent's procedure can be described in simple mobile model. Moreover, the Incarnation Agent modifies agent's procedures as applicable to facilities of target agent platform. This paper also reports an interoperability middle-ware and its examination. The middle-ware is a foundation of realizing the Incarnation Agent, and the response time and network traffic overheads by the interoperability middle-ware has been measured.

抄録全体を表示

In this paper, we propose a new idle time shortening method for Job-shop scheduling problems (JSPs). We insert its method into a genetic algorithm (GA). The purpose of JSP is to find a schedule with the minimum makespan. We suppose that it is effective to reduce idle time of a machine in order to improve the makespan. The left shift is a famous algorithm in existing algorithms for shortening idle time. The left shift can not arrange the work to idle time. For that reason, some idle times are not shortened by the left shift. We propose two kinds of algorithms which shorten such idle time. Next, we combine these algorithms and the reversal of a schedule. We apply GA with its algorithm to benchmark problems and we show its effectiveness.

抄録全体を表示

The purpose of this paper is to present the supporting system developed for the persons of diverse characteristics of color vision, who try to create color design works. Here, the authors focus attention on the field of two-color-combination design, as the object of support. The supporting system provides advices, which correspond to the requirement for affective expression of a color design work, in the form of concrete examples of two-color combination. The system also provides the information about the color difference between the color sensed by dichromats and that by trichromats; it makes possible to recognize the extent of color sensation over people, including the designers and the appreciators. The effect of the system is confirmed by the experiment of two-color-combination design done with non-trichromatic designers and trichromatic appreciators.

抄録全体を表示

The electric power distribution system drawing represents a structure of power system by combining lines which shows electric wire and cable, and symbols which shows equipment, customer, etc.
When displaying wide area on the Geographic information system, the scale on a display will be very small. In this case, a symbol becomes too small to be checked by our eyes. Also, problem of overlapping will occur for the lines nearby.
Therefore we have proposed an algorithm to regulate size of symbol and arrangement of lines, to ensure the visibility. In displaying a large area on a small scale on the Geographic information system. In this paper, we will describe about method and validity of this algorithm.

抄録全体を表示

Recently, virtual simulation which is a realtime simulation with 3-Dimensional computer graphics is now noticed, to apply it to the examination of various process in production systems. However, traditional ways of virtual simulation do not make the most of advantage of VR (Virtual Reality) technology, those only use VR as visualization tool of the result of the simulation, but use not enough the convenient for realizing the space instinctively.
We have studied the method and mechanism of merging VR technology and simulator, and this paper realizes the virtual simulation system for production systems which can exploit the advantage of VR effectively. This method can be applied to not only virtual production but also wide field of production systems such as factory maintainance and so on, and is a pioneer in the field of advanced virtual simulation.

抄録全体を表示

The purpose of this study is to apply the fuzzy theory to an Optimal Routing Problem for Sightseeing (ORPS) in which we consider time varying travel time and location value. In the conventional ORPS, the travel time or the location value has been treated as a crisp number. However, it is better that these values are expressed by ambiguous value like “about 10 minutes" rather than by crisp number. In this paper we propose a Fuzzy ORPS (FORPS) considering time-varying and ambiguity. FORPS is defined on a complete graph in which location value is associated with a node weight while travel time depends on an edge weight. The aim of the problem is to construct a path with maximal total value under the condition that a time constraint has to be satisfied. In order to confirm that a candidate solution satisfies the time constraint, we introduce an agreement index which is proposed by Kaufmann and Gupta. The value of the agreement index is regarded as the degree of satisfying the time constraint. Moreover, the location value and the travel time are calculated by introducing the expectation value. Finally, comparing the result of ORPS and FORPS which are obtained by the numerical example, we discuss the characteristic of results obtained by FORPS.

抄録全体を表示

Wrong:Graduate School of Medicine and Faulty of Medicine, the University of Tokyou
Right:Graduate School of Medicine and Faulty of Medicine, the University of Tokyo

抄録全体を表示

文献(3)

抄録全体を表示