H∞-control and filtering with initial uncertainty for time-varying systems

The H∞-control problem with a non-zero initial condition is considered. The initial conditions are assumed to be in some subspace. First, the H∞-problem with full information is considered, and necessary and sufficient conditions for the norm of an input-output operator to be less than a given number are obtained. A characterization of all admissible controllers is given. This result is then used to solve the general H∞-control problem and the filtering problem with initial uncertainty. The filtering problem on a finite horizon involves an estimate of the state at the final time. The set of al1 suboptimal filters is given both on finite and infinite horizons.     

An Expert System for Tunnel Design

In this article, we describe the development of an expert system (ES) for tunnel design and preent some applications of the system. The system has been developed by our research group consisting of 21 people closely involved with the tunnel design under the leadership of Nagoya University. The system consists of four subexpert systems (1) ES for standard tunnel design methods, (2) ES for framed structure method, (3) ES for theoretical design methods, and (4) ES for numerical analysis design method; a common part to control the overall system; and two data base systems (tunnel data base system and rock mass data base system).     

Subwavelength triangular random gratings

A subwavelength triangular diffractive element, whose local periods are not regular as an ordinary grating but has random values within a certain range, is proposed as a substitute for a common subwavelength antireflection grating. Its diffraction properties are electromagnetically analysed by the finite-difference time-domain method. Such a random grating shows some interesting properties, including suppression of higher diffraction orders. This improves the signal-to-noise ratio of a signal wave. Also, it is found possible for a random grating to retain a diffraction effciency comparable with that of a regular grating, even when some local periods violate the subwavelength condition, provided that the random local period range is properly chosen. This is another advantage of a random grating over the regular grating in the fabrication process, because upper limitation on feature sizes is partially relieved. In addition, application to general random scattering problems is discussed.     

Quadratic games and H∞-type problems for time varying systems

H^∞-type control problems with state feedback are considered for time varying systems. First, general quadratic differential games are studied and then the relationship between H^∞-problems and differential games is clarified. A necessary and sufficient condition for the existence of a stabilizing controller, such that the norm of the operator from the disturbance to the output is less than a prescribed number, is given in terms of a Riccati equation. Earlier results on time invariant systems are found to be special cases of our main results. The finite horizon problem is also studied.     

A Method for Estimating the Current–Flux Curve of a Single‐Phase Transformer for Electromagnetic Transient Simulations of Inrush Currents

When a transformer is energized, inrush currents whose magnitudes may reach tens of its nominal current occur. Since the inrush currents lead to a voltage drop, this may cause stops and malfunctions of electrical appliances. In addition, the overcurrents may cause an unnecessary operation of an overcurrent relay and affect the power quality of the distribution system. Currently, distribution system operators use current‐versus‐time curves of transformer inrush currents for the studies of such phenomena. However, the studies based on the current‐versus‐time curve give approximate results, and studies based on the current‐versus‐flux curve is required so as to obtain accurate results. Considering this point, this report proposes a method to convert a given current‐versus‐time curve to a current‐versus‐flux one for the case of single‐phase transformers. Using the current‐versus‐flux curve obtained, detailed simulations can be performed using an electromagnetic transient analysis program such as XTAP. In this report, the proposed method is validated by experimental results using a single‐phase transformer.     

Multivariable adaptive control as a natural extension of SISO adaptive control

The concepts of a potentially structural non-singularity and a structural non-singularity are introduced in this paper. Using these concepts, we derive the result that for almost all cases the plant to be controlled has a diagonal interactor by using an appropriate diagonal proper precompensator. Furthermore, both the precom-pensator and the interactor can be determined only from the structural information of T(s), the relative degrees of each element of T(s), without requiring any parametric information about T(s). Therefore, by assuming that the a priori knowledge of the plant consists of the relative degrees of each element of T(s) as well as the observability index of T(s), we can make MI MO adaptive control be quite a natural extension of SISO adaptive control.     

SENSORY AND RHEOLOGICAL PROPERTIES OF K-CARRAGEENAN GELS MIXED WITH LOCUST BEAN GUM, TARA GUM OR GUAR GUM

Mixed gels of _K-carrageenan (C) and a galactomannan gum, viz., locust bean (L), tara (T), and guar (G) in ratios of 7:3 and 1:1 (total concentration 1%), were examined for their rheological properties and by a sensory evaluation. Texture, creep and rupture were measured, and the semantic differential method (SD) was employed. _K-Carrageenan alone could not form a gel at the concentration of 0.5%, while C-L and C-T but not C-G mixtures in the ratio of 1:1 formed gels. The mixed gels of C-L were hard, very elastic and not perceived as smooth by the sensory evaluation. The values for the gels comprising T were intermediate between the C-L and C-G gels in instrumental measurements and sensory characteristics, indicating that the C-T mixture performed well as an edible gel. This difference is attributed to the synergistic effect between _K-carrageenan and the gums.     

Study on Detection of Negative Corona Discharge Generated in Rod-Plane Air Gap by Using External Electrode Method

A detective method of a negative corona discharge by means of an external electrode is presented. The relationship between an area of the external electrode and a detected voltage waveform is examined experimentally. This experimental study is carried out with the use of a rod-plane air gap. The results obtained will be applicable to problems associated with silos, ducts, and high-voltage equipment.     

计量学的电子谱:俄歇电子能谱

Electron spectroscopy is now very popular particularly in surface analysis.Many manufacturers make their sophisticated machines,in which Auger electron spectroscopy(AES)and X-ray photoelectron spectroscopy (XPS)have been widely distributed and commonly used.Although,the electron spectroscopy is not in the category of metrology,i.e.,the SI(system international).     

Adaptive control of delay system

The result of exact model matching for delay systems developed by the author is extended to the adaptive control of delay systems. Likewise, using results from the adaptive control of systems without delay, the principle of constructing adaptive systems for delay plants is also very simple and clear.