Experimental determination of the higher electric field level inside an overmoded reverberation chamber using the generalized extreme value distribution

Reverberation chamber (RC), in which a complex electromagnetic environment is created, is of great interest as a versatile test and measurement tool, and its performance is conveniently evaluated through the field statistics. Following a previous paper in which the generalized extreme value (GEV) distribution was proposed to model the maximum field inside an RC, this work presents an experimental validation of the GEV use for the overmoded RC. The electric field is measured with a small sensor for a large number of points inside the RC, and the GEV parameters are accurately estimated. Since the maximum field distribution for this overmoded RC is found to be of reverse Weibull type, the field distribution is right bounded by a higher level that can be determined.     

Complete electric field of the infinite slot antenna

The complete electric field of an aperture, with uniform excitation, in an infinite plane is derived and studied.     

Quasi-near-zone field of a monopole antenna and the current distribution of an antenna on a finite conductive earth

A mathematical expression is derived for the quasi-near zone of a monopole antenna on a finite conductive earth. Measured data are used to show the effect of finite conductivity of earth on the current distribution of dipole antennas.     

The static electric field distribution between two semi-infinite circular cylinders: A model for the feed gap field of a dipole antenna

The static electric field distribution in the gap between two solid perfectly conducting semi-infinite cylinders is obtained in terms of a Fourier-Bessel eigenfunction series. For dipole antennas whose cylinder diameter2aand gap length2dare both much less than the operating wavelengthlambda, this field can serve as the quasistatic excitation field in the gap of the dipole. However, the Fourier-Bessel series is slowly convergent. It is transformed into a rapidly convergent series of ultrasphetical polynomials whose weighting function explicitly satisfies the Meixner edge condition. Numerical results are presented graphically for both the axial electric field on the gap surface and the associated potential distribution. Gap ratios ofd/afrom 0.01 to 10.0 are considered and it is shown that asd/a rightarrow 0the solution approaches the two-dimensional solution obtainable by conformal mapping.     

Electric current and electric field induced in the human body whenexposed to an incident electric field near the resonant frequency

The electric field and current density induced in the human body when this is exposed to electric fields near the resonant frequency, 53 MHz, are determined analytically. Since this frequency range includes an important amateur radio band of 50-60 MHz and exposure to electric fields at this frequency has been shown to be hazardous, the study has a specific motivation. A cylindrical model of the body is used to derive formulas for the total axial current and current density induced in the body subject to skin effect. Tabulations and graphical representations illuminate the results     

耳机引线对手机天线近场分布的影响

利用时域有限差分(FDTD)法分析了耳机引线对手机天线辐射近场的影响.介绍了FDTD法的计算模型,并验证了方法的可靠性.在此基础上,对不同耳机模型和耳机引线处于不同位置时手机天线的辐射场强分布进行了计算.计算结果显示,使用手机耳机可以有效减小手机天线对人脑的辐射.     

Angular phase distribution of the field of an electric dipole in a hot magnetoplasma

The angular distribution of the phase of the fields of an electric dipole with and without a sheath in a hot magnetoplasma is calculated. Like the amplitude distribution of the field, the phase distribution can also be used for estimating the electron temperature.     

The distribution of an electric field in p-n junctions of silicon edgeless detectors

Development of silicon edgeless detectors started in 2004 and was motivated by preparations for the total elastic and diffractive cross-section measurement (TOTEM) experiment at the Large Hadron Collider (LHC) at CERN. In the context of this experiment, it would be necessary to detect protons scattered at ultimately small angles with respect to the LHC proton beam, which brings about a limitation imposed on the maximum distance between the beam and the sensitive region of the detector. In order to solve this problem, a new type of silicon detector (edgeless detectors) was developed; these detectors have the structure, which controls the distribution of the current near the edge of the p-n junction. In this paper we report the results of studying the distribution of the potential and an electric field in the region of the cut edge in the silicon edgeless detectors; the models, which account for the obtained results, as well as their consistency with current-voltage characteristics of silicon edgeless detectors developed for the TOTEM experiment, are discussed.     

Potential distribution for a spheroidal cell having a conductivemembrane in an electric field

When a cell is situated in a uniform electric field, the field is modified due to the relatively low conductance of the cell membrane compared to that of the surrounding fluids. In certain cases, such as in the estimation of internal and external electrokinetic forces, one requires a means of estimating the magnitude of the electric field inside and outside the cell. Most treatments consider the case when the membrane has zero conductivity, or the case of only a spherical cell. The authors solve Laplace's equation for the electric potential distribution inside and outside a cell having a prolate spheroidal shape and having a membrane with a finite, nonzero conductivity     

FDTD analysis of field distribution in an elevator car by usingvarious antenna positions and orientations

In indoor coverage planning the lift car is considered to be one of the most difficult propagation environments. The authors have studied radiowave propagation in this environment by means of an FDTD simulation. The lift shaft and the transmitting antenna are also modelled. A short dipole antenna is placed at various orientations and positions and the influence of these factors on the electric field distribution in a lift car is examined. It is found that for practical lift car coverage planning purposes, the placement and orientation of a short dipole antenna are not of any significant importance     

Bounds on the electric field outside a radiating system

Upper and lower bounds on the (spatial) maximum electric field outside a radiating system have been obtained and studied. The results should be useful in the design of systems where microwave breakdown is an important consideration.     

Spinodal decomposition in an electric field

Spinodal decomposition in an electric field has been suggested as a mechanism initiating the phase separation hypothesized for memory switching in amorphous semi conductors. Here, it is shown that density fluctuations lead to a change in free energy which depends on the direction of the electric field and, hence, should cause preferentially oriented precipitation. In addition, the rate of reaction is influenced by the change of polarization with respect to composition, a contribution which is estimated to be the same order of magnitude as the ideal chemical and strain energy contributions.     

Simulation of radiation from an antenna mounted on a vehicle by a multilevel QR compression algorithm

We describe here a real case application of a formerly presented compression technique for the method of moments. This method is based on a QR compression of the impedance matrix off-diagonals blocks. In this letter, it is extended to the multilevel three-dimensional case, and applied to the radiation of an antenna mounted on a car model. The ability of this technique to treat antenna radiation on a large complex structure is demonstrated, as well as the improvement in memory storage and computation time when compared with the conventional method.     

Effect of rain in the near field of an antenna

The effect of rain on the field at a point irradiated by a microwave antenna is found, in contrast with previous work, to be effectively independent of the parameters of the antenna. The standard Fresnel zone criterion for the `active rain volume? has been extended to treat rain in the near field of the antenna.     

Research on indoor electromagnetic radiation field of multiple antenna system

The complexity of the indoor environment brings great challenges to predict the electromagnetic radiation field of multiple antenna systems. Based on the Finite Difference Time Domain (FDTD) algorithm, using the mobile phone shielding device as the multiple antenna systems example, the mobile phone shielding device??s indoor electromagnetic radiation field is researched by measurment method and simulation method. The effectivity of prediction method is verified by comparing the prediciton results with the measurment results. About 80% of the error can be controlled less than 4 ± dB. The quantitative research has certain guiding significance to the prediction of the multiple antenna systems radio wave propagation.     

A model study of electric field interactions between cardiacmyocytes

The transmission of excitation via electric field coupling was studied in a model comprising two myocytes abutted end-to-end and placed in an unbounded volume conductor. Each myocyte was modeled as a small cylinder of membrane (10 microns in diameter and 100 microns in length) capped at both ends. A Beeler-Reuter model modified for the Na+ current dynamics served to simulate the membrane ionic current. There was no resistive coupling between the myocytes and the intercellular junction consisted of closely apposed pre- and post-junctional membranes, separated by a uniform cleft distance. The membrane current crossing the prejunctional membrane during the action potential upstroke tends to flow out of the cleft, but it is partly prevented from doing so by the shunt resistance constituted by the cleft volume conductor. The prejunctional upstroke gives rise to a pulse of positive potential within the cleft which induces a small capacitive current across the post-junctional membrane to yield a small positive change in the intracellular potential in the post-junctional cell. The net result is an hyperpolarization of the post-junctional cleft membrane and a slight depolarization of the rest of the cell membrane since the extracellular potential outside of the cell is zero. The magnitude of this depolarization is quite small for a flat junctional membrane and it can be increased by membrane folding and interdigitation, so as to increase the junctional membrane area by a factor of 10 or more. Even then the post-junctional depolarization does not reach threshold when the extracellular potential around the post-junctional cell is effectively zero. Threshold depolarization occurs in the presence of a large decrease of post-junctional load, by increasing the junctional membrane capacitance and/or decreasing the volume of the post-junctional cell. Assuming that the normal resistive coupling between two cardiac myocytes is 1-4 M omega, our model study indicates that electric field coupling would then be about two orders of magnitude smaller. However, substantial enhancement of the efficacy of electric field transmission was observed in the case of cells with substantial junctional membrane folding.     

电力配电系统自动化发展研究

时代在进步,经济也在快速发展中。电力系统的发展也紧跟经济发展的步伐,国家对电力系统的重视度也越来越高。随着经济的发展,人们的生活水平也在不断地提高,所以对电力配电的要求也更高,在配电系统的运行方面要求更加的稳定,协调性更高。所以电力配电系统自动化是当前电力系统发展的主流趋势,自动化系统的工作方式更加的灵活,根据用户的需求而转变。     

Preliminary study on offset scan-corrected reflector antenna system

Preliminary study on offset shaped dual reflector antenna systems has been carried out to assess the feasibility for multibeam satellite applications. The two-dimensional offset shaped reflector antenna geometry is generated by first creating the nodal points according to a bifocal condition and then connecting the nodal points by smooth curves to form the profiles of the main and subreflectors. The three-dimensional geometry is created by body revolution. The offset geometry is obtained by properly tailoring the three-dimensional geometry. This offset shaped reflector antenna system has an inherent astigmatism which can be either fully or partially compensated. For applications requiring a scan range in azimuth more thanpm 5beamwidths, the offset shaped dual reflector antenna systems offer better scan performance (in terms of peak gains) than offset Cassegrain geometries at the expense of the performance of the on-axis beams. In elevation with a 16 beamwidth scan range, the shaped design provides 0.3 dB less scan loss than the Cassegrain design.     

Measurement of antenna current distribution in an anisotropic plasma

The current distribution along a cylindrical antenna immersed in a magnetized plasma has been measured. It has been observed that the standing wavelength along the antenna wire is substantially shortened to a greater degree with increasing plasma frequency under the presence of the dc magnetic field. The gyroresonance has also been observed in the current distribution.