The following problem is considered: Given a rectilinear simple polygon P and a point q in its exterior, find the region that is reachable from q along orthogonal paths with at most k bends. For this problem we preset an efficient algorithm which runs in O(kn) time, where n is the number of vertices.

An experimental study of a strut-scattering contribution to small parabolic antenna secondary patterns is presented. The test reflector used in the measurement is the one with D (diameter)500 mm and with F (focal length)125 mm. In order to examine the strut effects on the reflector secondary patterns, all the data are measured two-dimensionally with a computer-aided antenna positioner. Two quantities, ψs (elevation angle) and φs (rotational angle varied from the plane of the source polarization), are introduced as the strut-position parameters. The results of the experiment done at f12 GHz with four struts (10 mm in diameter) show that the reflector patterns are considerably influenced by the strut. When, for example, φs0 and s30, the H-plane first sidelobe level is found to increase to about -15 dB; the value for a non-strut parabola was -20.6 dB. The cross-polar levels are also disturbed. When φs45 and s40, the cross-polar value is deteriorated to -22.5 dB; the corresponding value of a strut-free reflector was -37 dB. The loss of gain for a strut-free parabola was from 0.5 to 1.0 dB in this experiment. It is also experienced that for an one-strut parabola, on-axis cross polarization appears; the amount of which for φs45 and for s70 was about 36 dB.

This paper discusses a simplified three-dimensional (3-D) calculation method based on FEM (Finite Element Method) developed for the analysis of film heads. The calculation derived from the method allows for reproductive efficiency computation on film heads taking a 3-D configuration into consideration. As the calculation uses a two-dimensional (2-D) analysis program substituted for the full 3-D treatment, this program is, therefore, fast enough to be used interactively. The calculated results show that the head efficiency dependences of taper and yoke patterns are significant. The method is suitable for film heads with complicated geometries, because any individual length or pattern dependences can be calculated quite readily.

The so-called level-crossing problem of a random process is concerned with the properties of a sequence of time points at which the random process crosses with a fixed level. In order to intuitively understand the various properties of the level-crossing problem, we employ the ransom excursion model as a simple mode of a random process, by which the level dependence of the fluctuation of the number of the crossing points is derived for Gaussian processes having modified lowpass spectra. The comparison of the derived result with exact calculation is satisfactory. Secondly, we estimate how the magnitude of the fluctuation of the number for a narrow bandpass Gaussian process is different from that of an independent point process. Finally we obtain expressions for variance of the lengths of the level-crossing intervals and other quantities for a narrow bandpass Gaussian process and we succeed in interpreting the experimentally obtained behavior of the above variance.

This paper reports an on-line recognition method of Thai characters being composed of curves, and having many complicated and similar shapes. A character stroke is segmented into clockwise and counter clockwise arcs according as the stroke tracing is clockwise or counter clockwise, by making use of eight directional codes and directional differences of stroke tracing. Intuitively described features such as the sequence of stroke arcs, types of arc and relative positions of arcs are utilized for classifying characters. A multi-step classification method is introduced to achieve a good recognition rate. By applying the method to 69 categories (414 data) of Thai characters, a recognition rate of 100% for learning data, and a recognition rate of 96.4% for test data have been obtained.

A boundary element solution for the s-dimensional convective diffusion equation in a steady state is formulated by means of transforming its governing operator into symmetric or selfadjoint operator. The traveling material under consideration is assumed to be orthotropic. The velocity field is also assumed to be uniform or variable in spaces. Simple and two-dimensional examples (s2) are treated in numerical experiments in order to demonstrate the validity of the present formulation. A comparison with standard and upwind finite element solutions is also given. It is shown that the boundary element solution is stable and accurate with respect to the Peclet number and the ratio of orthotropy. Moreover, an example of the variable velocity field is treated using the boundary element model without internal cells. It is finally proved that the present method is an improvement over the usual boundary element method.

This letter presents a method for analyzing single server queueing models having two classes of customers. This method, based on the conservation laws, makes it possible to analyze queueing models for various types of queueing disciplines.

The linewidth enhancement factor α is analyzed for long wavelength GaInAs/InP laser. The effects of the anomalous dispersion and the free carrier plasma on α are comparable with each other. Calculated α shows strong wavelength dependence, and is about 3.55.6 at 1.551.6 µm, which is in good agreement with experiments.

A multilayered optical coupler is described which is used to couple a laser beam into a thin film waveguide. This device adopts an evanescent-field coupling technique based on a tapered-gap prism coupler. The multilayered coupler configuration without moving parts results in a mechanically stable coupling function. Experimentally, coupler insertion loss of 3 dB, including coupling imperfection loss, Fresnel reflection loss, and waveguide loss in the coupling region, was achieved in coupling an He-Ne laser beam with 0.633 µm wavelength into a 0.33 µm thick SiO2-Ta2O5 waveguide.

A heavy traffic limit theorem for the virtual waiting time of the queuing system in which several types of customers share a single server (//1) is derived. This theorem is an extension of Borovkov's heavy traffic limit theorem for the virtual waiting time of the GI/G/1 queue. Based upon this theorem, the approximate mean waiting time and mean queue length for each type of customer are formulated. Numerical examples show that the approximate formulas are useful tools for the performance evaluation of multiclass customer processing systems.

A sampling theorem valid for all band-limited distributions with most generally arranged sampling points is presented. Any bandlimited signal, whose complex frequency band has a horizontal width less than 4πb, can be reconstructed from the values of the signal and its derivatives on the sampling points in the negative time axis, as long as the average density of the points exceeds the Nyquist rate 2b.

An all-fibre sensing system having both a high handling capability and an enhanced stability has been developed by introducing a tapered fibre to laser coupling, fibre polarizers, and a threefold switching of laser injection current. Possible factors responsible for erroneous measurement are also inspected and the resultant error is estimated less than 0.01 K.

Low temperature dependences of the conductance of current constriction at the contact interface of clean metal surfaces were measured over a range from room temperature to liquid helium temperature. Singular phenomena of decreasing the conductance in decrease of temperature and hysteresis property of the conductance at low temperature were found.

Gain and loss coefficients were determined for GaInAsP/InP (λg1.5 µm) grown by OMVPE from lasing characteristics. Crystal quality of OMVPE GaInAsP/InP was found to be substantially the same as those grown be LPE. Absorption losses of the quaternary active and the binary InP layers were estimated separately.

This paper describes a digital filter realization method by simulating an LCR filter. Having the node equation of an original LCR filter the frequency variable s is transformed into a z one using the bilinear transformation. The resulting network equation can be digitally realized with the same transfer function as the original LCR filter. Using such a method, the circuit either has a large error in the transfer response near zero frequencies or causes oscillations. A technique to avoid this problem by a simple modification of the multiplier coefficients is shown. A fifth order elliptic filter is presented with illustrative comparison to classical cascade structure.

Relative-Refractive-Index-Difference (Δ) dependence of intrinsic loss of GeO2-Doped graded index silica fibers is clarified in the practical range of 1Δ2% and λ1.5 µm. It is confirmed that the decisive factor of Δ dependence is ultraviolet absorption loss, and that the Δ dependence of scattering loss is small.

This paper presents a parallel two-dimensional array matching algorithm which can report all occurrences of a given key subarray of size kk within any text array of size nn in n nk1/l steps on lk2 comparator cells, where l(1ln) is the number of matching units. Our algorithm can be regarded as a two-dimensional generalization of Mukhopadhyay's parallel string matching algorithm.

A DC-powered complementary circuit employing interferometers in investigated using simulation. It is shown that an output inductor and two kinds of damping resistors are necessary to suppress circuit oscillations. Switching speed is expected to be less than 25 ps at a current density of 5000 A/cm2 for lead-alloy devices.

A newly developed Josephson logic gate array is described. This gate array has 576 switching devices (Josephson Interferometers) and it has attained the high speed switching time of 33ps with a 2-input OR circuit. Employing and AC-powered latch circuit, the gate array has a single power supply. The total power dissipation of the gate array chip has been estimated to be 2 mW. This gate array includes all the necessary types of function blocks to accommodate any kinds of computer logics. Shift-resistor and 4-bit full-adder circuits have been successfully operated.

Numerical characteristics of mixed element solutions are studied in comparison with constant and linear elements'. It is shown that mixed elements give accurate solutions as similar to the previous investigations and also the system of equations is better-conditioned than other elements'.