To improve the demodulated signal-to-noise ratio, SNR, for colored noise environments, we present a new direct-sequence spread-spectrum receiver system, whose construction is based on the concept of Shaped M-sequence Demodulation (SMD). This receiver has the function for shaping the local dispreading-code waveform. This method can modify the frequency transfer function from a received input to the damp-integrated output according to the power spectrum of colored noise added in the transmission process. SMD performs the combined function of a whitening filter and a matched filter, which can be used to implement an optimum receiver. For the case when the additive colored-noise power spectrum is known and the transmission channel is non-band-limited, a design theory is derived that provides the maximum SNR by choosing the best dispreading-code sequence corresponding to a given signature spreading-code sequence. The noise power component produced in the receiver damp-integrated-output is anayzed by introducing the auto-correlation matrix of the additive noise. The SNR performance of systems, one using non-optimized codes and the other using optimized codes, is examined and compared for various noise models. It is verified by analysis and computer simulation that, compared to a conventional system using non-optimized codes, remarkable SNR improvements can be achieved due to the whitening effect acquired without producing inter-symbol interference. In contrast, if a transversal whitening filter is front-ended, it produces inter-frame interference, degrading the SNR performance. The band-limiting effect of the transmission channel is also analyzed, and we confirmed that the codes optimized for the non-band-limited channel can be applied to the band-limited channel with little degradation of SNR. SMD is inherently tolerant of fast-changing noise such as fading, due to its frame-by-frame operation. Considering this function as a general demodulation scheme, it may be called "Local Code Filtering."

A new type of noncausal stochastic model is proposed to represent a random image with double peak spectrum. The model based on the assumption that the double peak spectrum is expressed by a product of two spectra located at two symmetric positions in the 2D spatial frequency space. Estimation of model parameters is made by means of minimizing the "whiteness" which was proposed in authors' previous work. In a simulation for model estimation we make use of computer-generated random images with double peak spectrum. Comparing this with the estimation by a causal model, we demonstrate that the present method can better estimate not only the spectral peak location but also the spectral shape. The proposed model can be extend to an image model with multl-peak spectrum. However, Increase of parameters makes the model estimation more difficult We try a model with triple peak spectra since a real texture image usually possesses a spectral peak at the origin besides the two peaks. A result shows that the estimation of three spectral positions are good enough, but their spectral shapes are not necessarily satisfactory. It is expected that the estimation of multi-peaked spectral model can be made better by improving the process of minimizing the "whiteness."

To evaluate the radial eigenmode field distributions and the resonance wavelengths of axially symmetric pillbox resonator, a numerical method is described which is based on the FE-BPM expression in cylindrical coordinates. Under the weakly guiding approximation, we solve Fresnel equation and can get a fairly accurate result. By using effective index method, 3-D pillbox guiding structure is reduced to 2-D one which is then used for the analysis. One advantage of this method is that it is applicable for the axially symmetric optical waveguides with arbitrary index distribution. The validity of this method is checked by comparing the results of this method with those of the analytical ones. This method is applied for the evaluation of the coupling properties of a coupled structure consisting of a pillbox resonator and a curved waveguide placed outside the pillbox. This coupled structure has a good prospect to be used as optical wavelength filter. By varying the separation distance between the pillbox and the outer curved waveguide, the power transfer due to coupling is determined near the resonance wavelength 0.9 µm.

A three-dimensional analysis of Whispering-Gallery modes (W. G. modes) in a coaxial dielectric resonator is proposed and presented. The coaxial dielectric resonator is constructed from a lossy dielectric disk and ring which have diameters of several tens times as large as wavelength. Eigenvalue equations of the W. G. modes are derived rigorously from field expressions and boundary conditions. The resonant frequencies, unloaded Q values and field distributions are calculated numerically from the eigenvalue equations. These calculated results are in good agreement with experimental ones for an X band model. As a result, it is shown that a considerable quantity of modal energy can be confined in a loss-less gap between the disk and ring, and then the unloaded Q value is higher than that of a conventional dielectric disk and ring resonator.

Ultrathin GaAs, AlGaAs and GaAs/InAs wire crystals (whiskers) as thin as 20-50 nm are grown by organometallic vapor phase epitaxy (OMVPE) using Au as a growth catalyst. It is found that the whisker shape and width can be controlled by adjusting the thickness of the Au deposited on the substrate surface and the substrate temperature duing OMVPE. A new technique employing a scanning tunneling microscope (STM) for controlling the whisker growth position on the substrate surface is described. Photoluminescence spectra from the GaAs whiskers show a blue shift of the luminescene peak energy as the whisker width decreases. The amount of blue shift energy is rather small compared to that calculated by a simple square potential well model. The discrepancy is explained by the cylindrical potential well model including the surface depletion effect. Atomic composition within the portion of 1-20 nm along the AlGaAs and GaAs/InAs whiskers has been analyzed by energy dispersive X-ray analysis in combination with transmission electron microscopy. This shows the exsitence of Au at the tip of the whisker and the composition change occurs over a length of less than 5 nm at the GaAs/InAs heterojunction.

A theoretical and experimental study of a thin card-sized antenna is presented. The method of moment with a wire-grid model is used to analyze this antenna. In order to validate numerical efficiency, measurements using Wheeler method are preformed on this antenna and its wire-grid models. The experimental and theoretical results are in good agreement if the wire conductivity is well chosen. And the noise reduction of measured Wheeler efficiency using least mean square method is also examined.

The main result of this paper is an almost-everywhere hierarchy theorem for nondeterministic space that is as tight as the well-known infinitely-often hierarchy theorems for deterministic and nondeterministic space. In addition, we show that the complexity-theoretic notion of almost-everywhere complex functions is identical to the recursion-theoretic notion of bi-immune sets in the nondeterministic space domain. Finally, we investigate bi-immunity in nondeterministic and alternating time complexity classes and derive a similar hierarchy result for alternating time.

The selection method of the moment of inertia of the flywheel in a digital measurement system of torque-speed curve plotting for a kind of motor is presented. The selection standards of the moment of inertia and the map displaying the operating ranges of the measurement system are shown. The selection procedure of the moment of inertia is also shown.

A new set of self-consistent linear equations is presented for the analysis of the startup characteristics of gyrotron oscillators with an open cavity consisting of weakly irregular waveguides. Numerical results on frequency detuning and oscillation starting current for a whispering-gallery-mode gyrotron are described in which these equations were utilized. Experiments for making a check on the effectiveness of the derived equations showed that they well express the operation of gyrotrons in comparison with the linear theory using an empty cavity field as the wave field.