Statistics with fuzzy data in statistical quality control

Statistical quality control (SQC) is an important field where both theory of probability and theory of fuzzy sets may be used. In the paper we give a short overview of basic problems of SQC that have been solved using both these theories simultaneously. Some new results on the applications of fuzzy sets in SQC are presented in details. We also present problems which are still open, and whose solution should definitely increase the applicability of fuzzy sets in quality control.     

Analysis of Aftercavity Interaction in European ITER Gyrotrons and in the Compact Sub-THz Gyrotron FU CW-CI

Possibilities of arising of aftercavity interaction are analyzed in the ITER 170?GHz 2?MW coaxial cavity gyrotron and the 170?GHz 1?MW cylindrical cavity gyrotron, as well as in the compact 394.5?GHz low power gyrotron FU CW-CI. Also, the simulations for the gyrotron efficiency in the presence of aftercavity interaction are performed in the cold cavity approximation. Results of the analysis illustrate the subtle interplay between the geometry of the output taper and the profile of the magnetic field.     

Variations of internal friction in YBa2Cu3Ox superconductors

The internal friction (Q ^–1) spectrum of YBa₂Cu₃O_x superconducting ceramic exhibits several peaks. It has been confirmed that the high-temperature peak (around 240 K) depends on structural changes and varies during subsequent cycles of cooling and heating.Q ^–1 conductivity, X-ray spectra and the shielding effect have been measured on several samples having different superconducting properties obtained by various thermal treatments. Splitting is a characteristic feature of the high-temperature internal friction peak of the sample which exhibits good superconducting properties. In the case of the specimen exhibiting the worst properties the peaks decrease and overlap. In both cases an increase can be observed of this peak with the number of thermal cycles. After ageing at 470 K, the high-temperature peak disappears. Subsequent thermal cycles slightly recover it. Hysteresis of the Young modulus is also observed. The results are interpreted as transition of the 04 oxygen atom between two energy minima in the O4-Cu-O4 chain.     

To the Theory of Gyrotrons with Wide Emitters

Journal of Infrared, Millimeter, and Terahertz Waves - The main trends in gyrotron development are escalation of the radiated power and increasing the frequency of coherent radiation. For both...     

Design of an Optimized Resonant Cavity for a Compact Sub-Terahertz Gyrotron

Coherent sources of radiation in the sub-terahertz and the terahertz frequency range are in great demand for various spectroscopic studies (e.g. electron spin resonance spectroscopy, DNP/NMR spectroscopy etc.). The required levels of the output power as well as the needed specific spectral characteristics make the gyrotrons the most promising and high-performance devices for such applications. Recently, an initial design of a versatile second harmonic gyrotron utilizing a compact cryo-free 8 T superconducting magnet has been accomplished. In this paper we present an optimized resonator for this gyrotron. Instead of a regular (cylindrical) part as in the conventional cavities it contains an uptapered section. Such configuration offers a significant increase of the efficiency and improves the overall performance of the tube. We outline briefly the underlying theory, present and discuss the results of the numerical experiments carried out during the optimization process.     

Two efficient methods for a multifrequency solution of the Helmholtz equation

Abstact In this paper, two efficient methods for the multifrequency analysis for the Helmholtz equation are compared. The first approach is based on the direct collocation method with a subsequent approximation of the matrix by the Adaptive Cross Approximation method. Using the so-called Fourier scheme, the elements of the matrices for a series of frequencies can be computed efficiently. In the second approach an indirect Galerkin type method with piecewise linear ansatz and test functions is combined with a special source simulation technique. This combination allows a rather accurate and systematic approximation of acoustical results in major parts of the considered frequency range, leading to a significant reduction of the computer time needed to calculate complete frequency spectra. A representative example demonstrates how the two proposed approaches can be used. Both procedures turn out to be very promising steps towards a more efficient calculation of complex sound radiation problems. Communicated by: O. Steinbach     

Linked interpolation for Reissner-Mindlin plate elements: Part I—A simple quadrilateral

In most plate elements using the Reissner-Mindlin assumptions, the interpolations used for the lateral displacements (w) and the rotation (θ) involve the independent representation of each variable by its nodal values, usually with identical interpolations. To ensure a higher order of expansion for displacement w its representation is linked in the present paper with both sets of nodal variables. Conditions necessary for the use of such expansions are established here and the paper shows the development of a linear quadrilateral element (Q4BL) whose performance and robustness are good (although it possesses one singularity if only three degrees of freedom are prescribed). In Part II we apply the identical formulation to develop a triangular element (T3BL) which performs equally well and is fully robust.