Modeling of Material Shielding Effectiveness Against Electromagnetic Pulse in Time-domain

To characterize the shielding effectiveness(SE) of materials against electromagnetic pulse(EMP) that cannot be adequately evaluated by traditional test methods,a transfer function model of SE is proposed.Using homemade broadband coaxial fixture,the SE of a metal fabric material against square-pulse and electrostatic discharge(ESD) EMP is tested in the time domain.The peak SE calculated from the test results matches well with that obtained theoretically.Based on the system identification theory,we propose the transfer function model of SE,which takes the square pulse and human body model ESD EMP data obtained in the tests as training data and takes the machine model as verification data,as well as a second-order expression of the transfer function.Using the transfer function model,the waveforms of the shield-penetrated square-pulse EMP and the ESD EMP are actually predicted.From the perspective of system identification,this accurate prediction of the shielded waveform of EMP provides a reliable way for evaluating SE of materials against EMP.

Study on Electromagnetic Shielding Effectiveness of Ni-P-La Alloy Coatings

Ni-P and Ni-P-La alloy coatings were prepared by electroplating. Electromagnetic shielding effectiveness under the different components of rare earth or the different operating conditions was tested by the network analyzer. The results show that electromagnetic shielding effectiveness of Ni-P-La alloy coating varies from 45 dB to 70 dB with the variety of the frequency from 10 MHz to 350 MHz. Corrosion of the salt fog impacts on the electromagnetic shielding effectiveness a little. A small amount of rare earth added to plating bath can not only enhance corrosion resistance of coating, but make electromagnetic shielding effectiveness increase by 1 ~ 5 dB.

Resonance suppression and electromagnetic shielding effectiveness improvement of an apertured rectangular cavity by using wall losses

The cavity-mode resonance effect could result in significant degradation of the shielding effectiveness （SE） of a shielding enclosure around its resonance frequencies. In this paper, the influence of coated wall loss on the suppression of the resonance effect is investigated. For this purpose, an equivalent circuit model is employed to analyze the SE of an apertured rectangular cavity coated with an inside layer of resistive material. The model is developed by extending Robinson＇s equivalent circuit model through incorporating the effect of the wall loss into both the propagation constant and the characteristic impedance of the waveguide. Calculation results show that the wall loss could lead to great improvement on the SE for frequencies near the resonance but almost no effect on the SE for frequencies far away from the resonance.

The Study on the Conductivity Performance and Shielding Effectiveness of Electro-magnetic Radiation of Polyethylene Film with Different Content of Carbon Black Particles

With the help of the testing apparatus made by ourselves for shielding electromagnetic radiation, the electric conductivity and shielding effectiveness of electromagnetic radiation of polyethylene film contained different content of carbon particles was systematically studied in this paper. The results indicate that the electric conductivity and shielding effectiveness of electromagnetic radiation of polyethylene /carbon film have closely relations with content of carbon black particles, which exists a critical content value as 14%～30% and its properties will have a tremendous change.

Study on Shielding Effectiveness of Fabric for Electromagnetic Wave with Different Inlaid Distances of Metal Fibres

The electremagnetic radicalization has become more serious. The shielding effectiveness of polyester fabrics with different inlaid distance of parallel metal fibres to electromagnetic wave was studied in this paper on special instrument made by ourselves. The results of test show that the fabric with different inlaid distances of metal fibres and the testing angle between electric field plane and parallel metal fibres of have obvious effect on the shielding effectiveness of electromagnetic wave.

Investigation of Electromagnetic Shielding Effectiveness of Nanostructural Carbon Black/ABS Composites

With the increasing application in electromagnetic interference shielding field of high polymer materials, there is an increasing interest in investigating of high polymer composites. The effects of carbon black fraction on volume resistivity and electromagnetic shielding effectiveness (SE) of nanostructural carbon black (CB)/Acrylonitrile Butadiene Styrene (ABS) composites were studied. The results indicated that when CB mass fraction was over 15%, the volume resistivity dropped sharply and when it rose to 35%, the volume resistivity achieved the lowest value 103 Ω?cm and the SE was about 6 dB. In addition, there are two obvious percolation effect at 15% ~ 20% and 30% ~ 35% CB respectively in the course of the volume resistivity changing.

Enhancement of the Electromagnetic Wave Shielding Effectiveness by Geometry-Controlled Carbon Coils

Carbon microcoils were deposited onto Al2O3 substrates using C2H2/H2 as source gases and SF6 as an incorporated additive gas in a thermal chemical vapor deposition system. At as-grown state, the carbon coils (d-CCs) show the diverse geometry. The geometry-controlled carbon microcoils (g-CMCs) could be obtained by manipulating the injection time of SF6 in C2H2 source gas. The d-CCs with polyurethane (PU) composite (d-CC@PU) and the g-CMCs with PU composite (g-CMC@PU) were obtained by dispersing d-CCs and g-CMCs in PU, respectively. The electromagnetic wave shielding properties of d-CC@PU and g-CMC@PU composites were investigated in the frequency range of 0.25 - 4.0 GHz. The shielding effectiveness (SE) of d-CC@PU and g-CMC@PU composites were measured and discussed according to the weight percent of d-CCs and g-CMCs in the composites with the thickness of the composites layers. On the whole frequency range in this work, the SE of g-CMC@PU composites was higher than those of d-CC@PU composites, irrespective of the weight percent of carbon coils in the composites and the layer thickness. Furthermore, we confirmed that the absorption mechanism, instead of the reflection mechanism, seemed to play the critical role to shield the EMI for not only the g-CMC@PU composites but also the d-CC@PU composites.

Frequency-time Domain Shielding Effectiveness of Materials and Their Strong Electromagnetic Field Test

To describe the shielding ability of materials accurately and comprehensively,the frequency-domain and time-domain shielding effectiveness(SE) of material is investigated.The relevance between them was analyzed based on the minimum phase method,and the time-domain SE can be derived from frequency-domain SE.The SE of an energy selective surface(ESS) made of a novel material is investigated,and the relationship between SE and radiation field intensity are analyzed.The results show that not only material,but also the intensity of radiation electric field shows influence on SE in its frequency; for some materials,the dependence of SE on radiation electric field intensity needs to be considered.Therefore,it is necessary to research on the SE of shielding material in high-intensity electromagnetic environment.

Analysis of Reflectivity and Shielding Effectiveness of Absorbing Material–Conductor Laminate for Electromagnetic Compatibility

An absorbing material–conductor laminate is widely used for electromagnetic compatibility of electronic circuits at microwave frequencies. Such a laminate when properly designed will exhibit good results in terms of electromagnetic interference and compatibility. In this paper, microwave absorbing materials like 1) Ca-NiTi hexa ferrite composites (Ca (NiTi)x Fe12-2xO19) for x = 0.4, 2) M-Type Barium ferrites (BaFe12-2xAxCoxO19 for the tetravalent A ions, Ru4+ is chosen), 3) MnZn ferrite-Rubber composites with volume fraction vf = 0.4, 4) Carbonyl-Iron particle composites with volume fraction vf = 40% and conducting materials like copper, stainless steel are considered to form the interface in the laminate. Mathematical formulations are carried out for the estimation of reflectivity and shielding effectiveness of absorbing material–conductor laminate at microwave frequencies Analysis is also carried out for various thicknesses of the microwave absorbing material and conducting material in the laminate. The reflectivity and shielding effectiveness depends not only on the type of the selected material in the laminate, but also their thickness in the laminate and frequency of operation.

Calculating magnetic shielding effectiveness for high-power dc comparator by magnetic circuit method

Magnetic shielding is very important in the design of a high-power dc comparator. This paper addressed the application of magnetic circuit method to calculate the magnetic shielding effectiveness of high-power dc comparators when an external radial magnetic field is added. The mathematical relationship between the magnetic shielding effectiveness and the parameters of the magnetic shielding body were obtained. To verify the validity of the calculation method, we developped a procedure to measure the magnetic shielding effectiveness of the magnetic body by measuring the induction voltage of the detection winding instead of the magnetic intensity at a point in the magnetic shielding body, making the manipulation much easier. The result calculated with the magnetic circuit method turns out to be closer to the measured one compared with that calculated with a conventional algorithm proposed by Ren, suggesting that the magnetic circuit method is an applicable tool for estimating the toroidal cavity magnetic shielding effectiveness of a heavy current comparator when a radial magnetic field is added.

Analysis on the Magnetic Shielding Effectiveness of DC Current Comparator

There are magnetic interference problems in the applications of DC current comparator. Analysis on the magnetic effectiveness which is applied by the external magnetic field is introduced in this paper. The effectiveness is proved by the actual results which are compared with the magnetic- circuit method and the finite element method. In addition, the reference comment is given which can be used in the practical work of DC current comparator shield design.

Correlation between Electrical Conductivity and Microwave Shielding Effectiveness of Natural Rubber Based Composites, Containing Different Hybrid Fillers Obtained by Impregnation Technology

The paper presents the synthesis and characterization of carbon black/silicone dioxide hybrid fillers obtained by an impregnation technology. The electromagnetic interference shielding effectiveness of the composites filled with carbon black/silicone dioxide hybrid fillers was measured in wide frequency range of 1 - 12 GHz. The dc and ac electrical conductivity of composites also have been investigated. The relationship between electrical (dc and ac) conductivity and shielding effectiveness was analyzed. A positive correlation was found between the absorptive shielding effectiveness and ac conductivity for composites comprising conductive carbon black/silica filler, when the filler loading is above the percolation threshold.

Shielding Effectiveness of Composites Containing Flaky Inclusions

To investigate the quantitative relationship between the electromagnetic-shielding property of composites and the distribution of inclusions, a scheme for predicting the shielding effectiveness of composites containing variously-distributed flaky inclusions is proposed. The scheme is based on equivalent parameters of homogeneous comparison materials and the plane-wave shielding theory. It leads to expli- cit formulas for the shielding effectiveness of multi-layered composites in terms of microstructural parameters that characterize the shape, distribution and orientation of the inclusions. For single layer composite that contains random and aligned flaky silver-coated carbonyl-iron particles with fractions of different volume, the predicted shielding effectiveness agrees well with the experimental data. As for composites containing aligned flaky particles,the shielding effectiveness obtained by the proposed scheme and experiment data is higher than that the random case, e.g. about 20 dB higher at 750 MHz. The proposed scheme is a straightforward method for optimizing future composite de- signs.

Time-domain dynamic constitutive model suitable for mucky soil site seismic response

Soil nonlinear behavior displays noticeable effects on the site seismic response.This study proposes a new functional expression of the skeleton curve to replace the hyperbolic skeleton curve.By integrating shear modulus and combining the dynamic skeleton curve and the damping degradation coefficient,the constitutive equation of the logarithmic dynamic skeleton can be obtained,which considers the damping effect in a soil dynamics problem.Based on the finite difference method and the multi-transmitting boundary condition,a 1D site seismic response analysis program called Soilresp1D has been developed herein and used to analyze the time-domain seismic response in three types of sites.At the same time,this study also provides numerical simulation results based on the hyperbolic constitutive model and the equivalent linear method.The results verify the rationality of the new soil dynamic constitutive model.It can analyze the mucky soil site nonlinear seismic response,reflecting the deformation characteristics and damping effect of the silty soil.The hysteresis loop area is more extensive,and the residual strain is evident.

Shielding effect and emission criterion of a screw dislocation near an interfacial blunt crack

Shielding effect and emission criterion of a screw dislocation near an interracial blunt crack are dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation located near the interracial blunt crack. The stress intensity factor on the crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of the orientation of the dislocation and the morphology of the blunt crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations can reduce the stress intensity factor of the interfacial blunt crack tip （shielding effect）. The shielding effect increases with the increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuth angle. The critical loads at infinity for dislocation emission increases with the increase of emission angle and curvature radius of blunt crack tip, and the most probable angle for screw dislocation emission is zero. The present solutions contain previous results as special cases.

The Shielding Effect of Multi-Pile Structures on Ice Force

The shielding effect of the front pile-row on the ice force acting on the back pile-row is studied by ice force model tests. In the tests, the front pile-row is designed to model jacket legs and the back pile-row to model the water resisting pipe-phalanx within the jacket. The shielding factor for ice force corresponding to different conditions are given in this paper. The research indicates that there are many factors, including the longitudinal and lateral spacing between the front and back pile-row, ice attacking angle and the ratio of pile diameter to ice thickness, that influence the shielding effect on ice force.

Design of the reflection magnet and its shielding effect analysis for the neutral beam injector of EAST

In this paper,a reflection magnet to be installed in the EAST neutral beam injection system is simulated and designed.The field intensity of reflection magnet of 42-cm maximum bending radius is about 1.539×10-1 T for 100 keV deuterium beam.The shielding cage is formed by rods.Using the ANSOFT software,the magnetic shielding effect was estimated at about 3% at the magnet pole region.

Gravitational Shielding Effect in Gauge Theory of Gravity

In 1992,E.E.Podkletnov and R.Nieminen found that under certain conditions,ceramic superconductor with composite structure reveals weak shielding properties against gravitational force.In classical Newton's theory of gravity and even in Einstein's general theory of gravity,there are no grounds of gravitational shielding effects.But in quantum gauge theory of gravity,the gravitational shielding effects can be explained in a simple and natural way.In quantum gauge theory of gravity,gravitational gauge interactions of complex scalar field can be formulated based on gauge principle.After spontaneous symmetry breaking,if the vacuum of the complex scalar field is not stable and uniform,there will be a mass term of gravitational gauge field.When gravitational gauge field propagates in this unstable vacuum of the complex scalar field,it will decays exponentially,which is the nature of gravitational shielding effects.The mechanism of gravitational shielding effects is studied in this paper,and some main properties of gravitational shielding effects are discussed.

Shielding Effect and Emission Criterion of a Screw Dislocation Near an Interfacial Crisscross Crack

Shielding effect and emission criterion of a screw dislocation near an interracial crisscross crack are dealt within this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentialsand stress fields due to a screw dislocation located near the interracial crisscross crack. The stress intensity factor onthe crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of theorientation of the dislocation and the morphology of the crisscross crack as well as the material elastic dissimilarity onthe shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations canreduce the stress intensity factor of the interracial crisscross crack tip (shielding effect). The shielding effect increases withthe increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuthangle and the distance between the dislocation and the crack tip. The critical loads at infinity for dislocation emissionincreases with the increase of emission angle and the vertical length of the crisscross crack, and the most probable anglefor screw dislocation emission is zero. The present solutions contain previous results as special cases.