The shortest path from some vertex v to some other vertex w in edge weighted graph G(V, E, W) is the path from v to w with the minimum distance. Shortest path problem is defined to be the problem of finding the shortest path in G(V, E, W). In this paper a different version of shortest path problem is considered. The length of a path is defined to be the number of edges in the path here. The problem considered in this paper is the average length of the shortest paths in G(V, E, W) with non-negative edge distances. It is proved that the upper bound of the average length of a shortest path in G(V, E, W) is O(log N) when G(V, E, W) is a complete graph with N vertices and the distances associated to the edges in G are identically distributed on [0, 1] mutually independent random variables. A concept called shortest path spanning tree that is used in proving the upper bound is also given. Combining with an appropiate data structure, the upper bound proved in this paper implies that there is a shortest path enquiry system with response time O(log N) at the cost of O(N2) space requirement.
Introducing temperature-dependent terms into the propagation constant and its derivatives, and extinction coefficient of a core material of optical fiber, the equation of pulse propagation in a multimode fiber is derived, allowing us to evaluate the temperature dependence of a pulse waveform such as the peak-intensity, the pulse duration or width and the pulse delay-time at the peak as a function of ambient temperature. Using the weighting function for higher order modes in the above equation, the theoretically calculated waveforms are compared with the mode-locked He-Ne 3.39 µm laser pulses propagated through As-S fiber over the range from room temperature to 220, being in good agreement each other.
High speed optical system to measure the shape and the cross section of the three dimensional object was developed; this system consists mainly of a He-Ne laser, a polygon mirror, a PSD, a turn-table for rotation of the object, and a personal computer.
Hideaki SONE Masao NAKAI Tasuku TAKAGI
A method for automatic detection of a critical point in voltage waveform in breaking contact arc has been developed. The point and a transition term from metallic to gaseous phase were detected by searching a peak in voltage fluctuation. Each phase differed in feature of corresponding waveform such as the gradient and the fluctuation.
This letter investigates the convergence property of first-available-task approach which is an asynchronous version of global-timestep Iterated Timing Analysis (ITA). This asynchronous iteration is proven to converge under the same condition as that for the convergence of the global-timestep ITA.
A 0.1 to 18 GHz hybrid distributed amplifier using GaAs HEMTs with 0.3 micron gate length and 200 micron gate width has been realized. This amplifier exhibits 9.00.5 dB of gain and less than 5.4 dB of noise figure. This letter describes the design approach which maximizes the gain-bandwidth product of the hybrid distributed amplifier, adding several FETs.
Ken-ichi HAYASHI Shigeki AISAWA Yoshio IDA Kazuo ARAI
Spectral properties of an unlocked semiconductor laser under an external light injection are numerically analyzed and experimentally observed. It is found that the unlocked spectrum consists of a shifted carrier and a number of harmonics and that their distributions are varied by the detuning.
Yoshinori NAMIHIRA Yukio HORIUCHI Hiroharu WAKABAYASHI
Polarization fluctuation in optical fiber submarine cable coupling under periodic variable tensile force with 4-7 tons are presented. It is found that the polarization fluctuation of the optical fiber submarine cable coupling linearly changes with periodic variable tension.
Photovoltaic properties of a Pb2CrO5 ceramic disk with a pair of planar electrodes are described. Open circuit photovoltage of the devices with Au or Ag electrodes is shown as functions of the light intensity and the wavelength, which is related with a metal-semiconductor contact.
Kazunori UCHIDA Takeaki NODA Toshiaki MATSUNAGA
This letter is concerned with the investigation of electromagnetic wave scattering by an infinite patch grating. The analytical method used here is based on the spectral domain method combined with the sampling theorem. Numerical results are given for transmitted and reflected powers when frequency or polarization angle is changed.
Hirokazu NAKAYAMA Wakao SASAKI Tatehisa OHTA
This letter reports the 4.3 ns (230 MHz) optoelectronic switching utilizing the mode-hopping phenomenon in a semiconductor laser. The speed is not limited by the phenomenon itself but the driving capabilities. Some influences of a.c. modulation on mode-hopping are also measured.
Hiroki MATSUMOTO Kenzo WATANABE
Switched-capacitor frequency-to-voltage and voltage-to-frequency converters integrable onto a small chip area are developed. Their conversion sensitivity is insensitive to non-ideal circuit elements. Therefore, both the converters allow the accurate conversion over the wide dynamic range.
Hafez M. EL-ZAYYAT Haldun GÜRMEN
Character analysis technique is very simple and of basic importance in defining expressions of physical quantities where scalar and/or vector characters are to be determined. This article discusses briefly the application of recently established character analysis approach to few examples of electromagnetic equations existing in well-known textbooks. Furthermore it is shown that dotting a physical vector quantity by a non-physical operator such as a normal unit vector, does not change the character of the physical quantity. This dotting only gives the magnitude of the physical quantity in the direction of the unit vector. This component is still a physical vector quantity.
Mikio ASAKURA Yoshio MATSUDA Katsuhiro TSUKAMOTO Kazuyasu FUJISHIMA Tsutomu YOSHIHARA
This letter reports a charge collection experiment of alpha-particle-induced carriers in the cell arrays of the 1 Mb DRAM. It is indicated that this experiment is effective to estimate the soft error rate of VLSI memories with various kinds of structures.
Design of ferrule hole diameters in a ferrule-type single mode fiber connector has been investigated to achieve a low-loss multi-fiber connection. Based on the theory of the connection loss statistics, connection losses for various designs of ferrule hole diameters are evaluated and discussed.
Tomohiro NAKAMORI Taiji TSURUOKA Takashi KANAMORI Susumu SHIBATA
Change in film properties, especially resistivity and the thermal dependence of resistance, that are due to differences in the thickness and the temperature of heat treatment of Ta-Si-C films developed as high resistivity materials were investigated. From these results, the mechanism of film thermal changes was discussed. Further, the effect of film thickness on the performance of Ta-Si-C thin film thermal printing heads was also investigated. The results show that; (1) a ln ρT-1/2 relationship between resistivity and temperature in Ta-Si-C thin films holds good over a wide temperature range from 293 to 873 K, (2) resistivity is dependent of film thickness when film thickness is less than 2000 (greater resistivity in thinner films), (3) the thermal dependence of resistance is dependent on film thickness when film thickness is less than 3000 (greater thermal dependence in thinner films), (4) resistivity is increased and thermal dependence of resistance is decreased by heat treatment below 400 , and that (5) excellent performance is achieved when Ta-Si-C thin films greater than 3000 in thickness are used as the thermal printing head resistor film.
A wavetheoretical method has been proposed to analyze the phase shifted DFB lasers with reflective ends. Mathieu's functions whose parameters are complex numbers are used to express the waves in periodic laseractive regions. Numerical examples show fundamental characters of phase shifted DFB lasers and effects of reflective ends.
Tadashi NAGASAWA Kenzo WATANABE
An active circuit for detecting a small capacitance change accurately with a minimum number of components is presented for interfacing a capacitive sensor with a digital system. No component trimming is required and the sensitivity to circuit constants is minimum. Thus, it meets all the requirements for the on-chip interface.
ZHAO Qingfu Masayuki KAWAMATA Tatsuo HIGUCHI
This paper proposes a statistical expression of the output error variance due to coefficient quantization in separable denominator M-D digital filters. Using this expression, this paper shows that minimization of overall quantization errors can be performed by minimizing the roundoff noise.