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In this paper partial discharges (PD) in disc-shaped cavities in polycarbonate are measured at variable frequency (0.01-100 Hz) of the applied voltage. The advantage of PD measurements at variable frequency is that more information about the insulation system may be extracted than from traditional PD measurements at a single frequency (usually 50/60 Hz). The PD activity in the cavity is seen to depend on the applied frequency. Moreover, the PD frequency dependence changes with the applied voltage amplitude, the cavity diameter, and the cavity location (insulated or electrode bounded). It is suggested that the PD frequency dependence is governed by the statistical time lag of PD and the surface charge decay in the cavity. This is the first of two papers addressing the frequency dependence of PD in a cavity. In the second paper a physical model of PD in a cavity at variable applied frequency is presented. Index Terms--Partial discharges, measurements, variable frequency, cavities, disc-shaped, electrode bounded, polycarbonate.

A technique to efficiently characterize the azimuth radiation patterns of monopole arrays based on evanescent reactive-near-field measurement in a compact anechoic box is presented. We describe a desktop-size measurement setup for determining the azimuth far-field pattern of an electronically steerable parasitic array radiator (ESPAR) at 2.5 GHz, and present a thorough statistical evaluation of the ESPAR antenna characterization technique. In addition, the sensitivity to probe position and the errors caused by possible fluctuations in the probe position are investigated. Furthermore, comparisons among patterns obtained by the proposed method, simulations and conventional far-field measurements are carried out, and a good agreement among them is obtained. We also provide a statistical evaluation of the proposed desktop-size measurement setup using forty ESPAR antennas and conclude that the proposed setup can be an inexpensive candidate to replace the conventional measuring system. Index Terms--Anechoic chamber, antenna arrays, antenna measurements, monopole arrays, probe antennas.

Two sets of synchronized phasor measurements 200 km apart have been performed during a planned outage of a double 400-kV tie-line between Eastern Denmark and Southern Sweden. The interconnection between Eastern Denmark and Southern Sweden is comprised of a double 400-kV line and a double 132-kV line. The outage of the 400-kV tie-line weakened the Eastern Danish power system and excited power oscillations in the interconnected power systems. During this event prototype, phasor measurements units gave the opportunity of real-time monitoring of positive sequence voltage and current phasors using the satellite-based global positioning system. Comparisons between real-time recordings and results from dynamic simulations with Power System Simulator for Engineering are presented. The main features from the simulation analysis are successfully verified by means of the corresponding synchronized phasor measurements. Index Terms--Power system measurements, power system monitoring, power system stability.

Maintaining dynamic security of a power system subjected to large disturbances is of utmost importance. Fast and accurate online detection of instability is essential in initiating certain emergency control measures. The techniques reported in the literature involve mainly the application of global phasor measurements and heuristic algorithms. In this paper, an accurate technique for the online detection of loss of synchronism based on voltage and current measurements in a line is presented. The technique makes use of the concept of potential energy in a line. The conditions for the system instability are derived from energy function analysis. However, no assumptions are made regarding the power-angle relationship in a line, nor are any data on the system equivalents necessary in implementing the detection scheme. Index Terms--Critical cutset, energy function, transient stability.

The development of ultrasonic techniques for imaging and measurements in molten aluminium (Al) using buffer rods operated at 10 MHz is presented. As per the results there was no ultrasonic coupling at the interface between an alumina rod and molten Al up to 1000 degrees C.

I investigate the issue of whether the various subclasses of radio-loud galaxies are intrinsically the same but have been classified differently mainly due to their being viewed from different directions. Evidence for the two key elements of this popular version of the 'unified scheme (US),' relativistic jets and nuclear tori, is updated. The case for the torus opening angle increasing with the radio luminosity of the active galactic nucleus (AGN) is freshly argued. Radio-loud AGN are particularly suited for testing the US, since their structures and polarization properties on different scales, as well as their overall radio sizes, provide useful statistical indicators of the relative orientations of their various subclasses. I summarize recent attempts to bring under a single conceptual framework the USs developed for radio-moderate [Fanaroff-Riley type I (FRI)] and radio-powerful (FRII) AGN. By focusing on FRII radio sources, I critically examine the recent claims of conflict with the US, based on the statistics of radio-size measurements for large, presumably orientation-independent, samples with essentially complete optical identifications. Possible ways of reconciling these results, and also the ones based on very-long-baseline radio interferometry polarimetric observations, with the US are pointed out. By incorporating a highly plausible temporal evolution of radio source properties into the US, I outline a scenario that allows the median linear size of quasars to approach, or even exceed, that of radio galaxies, as samples with decreasing radio luminosity are observed. Thus, even though a number of issues remain to be fully resolved, the scope of unified models continues to expand.

Byline: Chang Lin Zhang In this paper, we have discussed several critical problems of electronic measurements on acupuncture system such as the size, shape, location and stability of acu-points and acu-meridians; the violent fluctuation of the measurement data; the holographic phenomena and the statistical self-similarity of measurement data; the transmission of signal along meridian and its speed; the parallel distributions between higher-conductivity points and higher sound intensity points and the mathematical background of log-normal distribution of measurement data. A conclusion, which comes from the contradictions between these experiment results and the existing knowledge in modern anatomy, histology, neurology and biochemistry, is that there is an invisible dissipative structure of electromagnetic field which is mainly composed of an interference pattern of standing waves in the resonance cavity of human body under the condition of permanent support of energy in an open system. To some extent, the invisible structure is corresponding to the mysterious acupuncture system and closely related to many energetic medicines. The conclusion and recognition of the existence of the invisible dissipative structure of electromagnetic field inside a body offers not only a new understanding of the background of acupuncture and many other holistic medicines, but also a scientific and quantitative way to evaluate the degree of coherence, namely harmony of a body-mind system.