Multilayer Shield Research Articles

Crossover Frequency and Transmission-Line Matrix Formalism of Electromagnetic Shielding Properties of Laminated Conductive Sheets

This paper proposes an approach to calculate the crossover frequency of each layer in the multilayered shield and subsequently that of structure constructed by n layers. This important frequency provides a useful approximation for field penetration in a conductor. It is used in a wide variety of calculations. It is in this context that a simplification of the transmission-line matrix formalism for laminated conductive sheets is done using this frequency. Two ranges of frequency are considered: lower and higher than the crossover frequency. Simples formulas and easy to use of the reflection loss, the internal reflection, the absorption loss and the electromagnetic shielding effectiveness of laminated shield are obtained. Analysis is carried out for the study of two shields: i) single shield of carbon nanotube polymer composites (CNTs), ii) multilayered shield constructed with Nickel–carbon nanotube polymer composites–Aluminum (Ni–CNTs–Al).

Numerical Modeling and Material Characterization for Multilayer Magnetically Shielded Room Design

In this paper, a method for the assessment of magnetic properties of ferromagnetic materials at low magnetic field values is presented. The knowledge of these properties is crucial for the design of magnetically shielded rooms that must be effective against low-frequency external magnetic field disturbances on the order of 0.1– $1~\mu \mathrm {T}$ . The considered shielding structure is composed by a number of layers made of different high-permeability ferromagnetic sheets as grain-oriented electric steel and nickel–iron soft magnetic alloy. The ferromagnetic materials in this region follow the Rayleigh law that is a quadratic law between magnetic flux density and the applied field. Two material-dependent parameters of this law are obtained by a characterization of the material behaviour performed on a scaled prototype of a magnetically shielded room. The procedure is validated on a multilayer shield structure.

High-precision terahertz frequency modulated continuous wave imaging method using continuous wavelet transform

Inspired by the extensive application of terahertz (THz) imaging technologies in the field of aerospace, we exploit a THz frequency modulated continuous-wave imaging method with continuous wavelet transform (CWT) algorithm to detect a multilayer heat shield made of special materials. This method uses the frequency modulation continuous-wave system to catch the reflected THz signal and then process the image data by the CWT with different basis functions. By calculating the sizes of the defects area in the final images and then comparing the results with real samples, a practical high-precision THz imaging method is demonstrated. Our method can be an effective tool for the THz nondestructive testing of composites, drugs, and some cultural heritages.

Measurements of the Reactor Antineutrino with Solid State Scintillation Detector

Measurements of reactor antineutrino play an important role in the efforts at the frontier of the modern physics. The DANSS collaboration presents preliminary results of a one year run with a cubic meter solid state detector placed below 3.1 GW industrial light water reactor. The experiment is sensitive to sterile neutrino in the most interesting region of mixing parameter space. 2500 scintillation strips of the sensitive volume of the detector have multilayer passive shielding of copper, lead and borated polyethylene and active muon veto. Detector position below the reactor gives an advantage of overburden about 50 m of water equivalent providing factor of six in cosmic muon suppression and eliminating fast neutrons.The detector is placed on a vertically movable platform which allows to change the distance to the reactor core center in the range 10.7-12.7 m within a few minutes. The strips are read out individually by SiPMs and in groups of 50 by PMTs. 5000 inverse beta-decay events per day are collected in the fiducial volume, which is 78% of the whole detector, at the position closest to the reactor. Overburden, active veto and good segmentation of the detector result in an excellent signal to background ratio. The talk is dedicated to the data analysis and preliminary results. The experiment status is also presented.

Major Tom to Ground Control: How Lipoproteins Communicate Extracytoplasmic Stress to the Decision Center of the Cell.

The envelope of bacteria is a complex multilayered shield that ensures multiple essential functions, including protecting the cell from external assaults. Hence, bacterial cells have evolved intricate mechanisms called envelope stress response systems (ESRS) to monitor all kinds of perturbations affecting the integrity of their envelope and to mount an appropriate response to contain or repair the damage. In the model bacterium Escherichia coli, several ESRS are built around a two-component system, in which envelope stress triggers a phosphotransfer between a sensor protein in the inner membrane of the envelope and a response regulator in the cytoplasm. In this review, we focus on two major ESRS in E. coli, the Rcs and Cpx pathways, in which additional proteins not directly involved in the phosphotransfer modulate signal transduction. Both the Rcs and Cpx systems can be turned on by a lipoprotein anchored in the outer membrane, RcsF and NlpE, respectively, providing a molecular connection between the most exterior layer of the envelope and the ground control center in the cytoplasm. Here, we review how these two lipoproteins, which share a striking set of features while being distinct in several aspects, act as sentinels at the front line of the bacterium by sensing and transducing stress to the downstream components of the Rcs and Cpx systems.

Multilayer magnetic shielding: an innovative overlapping structure

The study deals with magnetic shields for distribution systems mainly devoted to medium voltage/low voltage sub-station. In the category of passive system, a new multilayer shielding plate is presented. The main purpose of the proposed solution is the reduction of the gap between the ferromagnetic sheets by a proper overlapping in order to reduce the local leakage fluxes. Plates characterised by different conductive and ferromagnetic thicknesses have been realised and tested. The effect of the welding of the conductive part is finally analysed.

Shielding of a magnetic pulse by the multilayer film shield with alternating magnetic and nonmagnetic layers

The edge problem of the penetration of the magnetic field pulse with millisecond and microsecond front duration inside a multilayer circular cylindrical shield has been solved by the analytical methods. The mathematical model of the shielding problem is based on the use of the Laplace equation and nonclassical two-sided boundary conditions that connect magnetic fields on both sides of the thin-wall shield. A structure of the magnetic pulse inside the shield and shielding efficiency has been studied numerically depending on the layering structure of the shield at fixed thickness of the shield.

Computational Design of Metal–Fabric Orbital Debris Shielding

Hybrid particle–finite element methods, developed specifically to simulate hypervelocity impact physics, may be used to compliment experimental and analytical research on micrometeoroid and orbital debris shielding. Recent research has applied a hybrid particle–finite element method to model the hypervelocity impact response of an enhanced metal–fabric orbital debris shield developed for the Soyuz Orbital Module, composed of both thermal insulation and orbital debris protection layers. The numerical model was employed to simulate impact effects in a high-velocity impact regime outside the capabilities of current light-gas guns. The simulation results suggest that momentum scaling may be applied to estimate the ballistic limit performance of multilayer composite shields, for spherical projectiles over an impact velocity range important in low Earth orbit applications but not accessible to experiments.

Optimum Design of ThinWideband Multilayer Electromagnetic Shield Using Evolutionary Algorithms

This paper describes the method of optimum design of multilayer perforated electromagnetic shield using Evolutionary algorithms, namely Particle Swarm Optimization Algorithm (PSO) and Genetic Algorithm (GA). Different parameters which are inherently conflicting in nature corresponds to the multilayer structure of the electromagnetic shields have been considered. The goal is to minimize the overall mass of the shield with respect to its shielding effectiveness and cost. Three different models are considered and synthesized using evolutionary algorithms. Numerical optimal results for each model using different algorithms are presented and compared with each other to establish the effectiveness of the proposed method of designing.

Enhancement of the shielding effectiveness of multilayer materials by gradient thickness in the stacked layers

Nowadays, with the proliferation of commercial scientific, electrical devices and equipments in high frequencies, the electromagnetic interference (EMI) becomes an important problem because this EMI can disturb the function of electronic circuits. Metals are particularly suitable as shielding materials against (EMI) due to their high electrical conductivity, however, there are few drawbacks to use metals as shielding materials. The weight of the ‘heavy’ metal can be an issue in the case of full metal shielding especially in applications where mass should be as low as possible. Conducting polymers have received much attention because of its unique high electrical conductivity ease of preparation and low cost. polyaniline–polyurethane (Pani/PU) Composites are required in many engineering applications, especially electromagnetic compatibility. The purpose of this study is to enhance the shielding of electronic circuit by using multilayer structure. We propose a new multilayer structure shield with a gradual increase thickness in each layer stacked in that shield, this structure is based on two Kapton dielectric layer sandwiched between three conductive layers of Pani8.8/PU for better protection against electromagnetic waves. The simulation results prove that the proposed five-layered material exhibits very good electromagnetic interference shielding efficiency compared to the previously developed Pani8.8/PU monolayer and three-layered in the frequency range (0.8–1.8 GHz) and is a potential candidate for several EMI shielding applications.

Multi-parameter optimization of a (3He-252Cf-3He) neutron backscattering sensor for landmine detection

Experimental measurements were carried out to optimize the performance of a (3He-252Cf-3He) assembly for plastic anti-personnel landmine detection in dry soils. This is done by employing a 252Cf source producing 0.7 × 104 n.s−1 and a pair of two identical 3He detectors. The Signal-to-background ratio due to the responses of the two 3He detectors is monitored and analyzed as a function of detector-detector distance, stand-off distance, mine depth and source position while scanning the mine. The laboratory measurements were followed by Monte Carlo simulations to explore the capabilities of the laboratory measurements in the presence of 252Cf sources producing 104n.s−1 and 106n.s−1. The optimal 252Cf source was selected and employed in further Monte Carlo simulations to study the impact of a multi-layer shield on the performance of the (3He-252Cf-3He) assembly.

Detector of the reactor AntiNeutrino based on Solid-state plastic Scintillator (DANSS). Status and first results.

A detector of the reactor antineutrino based on a cubic meter of plastic scintillator is installed below 3.1 GW industrial reactor. The detector is placed on a movable platform which allows to change the distance to the reactor core center in the range 10.7-12.7 m. 2500 scintillator strips are read out individually by SiPMs and in groups of 50 by PMTs. In addition to the overburden by the reactor (50 m w.e.) the detector has multilayer passive shielding and active muon veto.Inverse beta-decay count rate of about 5000 events per day in the fiducial volume (78% of the detector) with about 5% of cosmic background has been reached. DANSS is sensitive to sterile neutrino in the most interesting region of mixing parameter space.The article covers the detector status and performance, as well as the first results.

The GeMSE facility for low-background γ-ray spectrometry

We describe a new high-purity germanium (HPGe) detector setup for low-background γ-ray spectrometry. The GeMSE facility (Germanium Material and meteorite Screening Experiment) is dedicated to material screening for rare event searches in astroparticle physics as well as to the characterization of meteorites. It is installed in a medium depth (∼620 m.w.e.) underground laboratory in Switzerland in a multi-layer shielding and is equipped with an active muon veto. We have reached a very competitive integral background rate of (246±2) counts/day (100–2700 keV) and measured a sensitivity of ∼0.5–0.6 mBq/kg for long-lived isotopes from the 238U/232Th chains in a ∼1 kg sample screened for ∼27 days. An extrapolation to higher sample masses and measurement times suggests a maximum sensitivity in the O(50) μ Bq/kg range. We describe the data analysis based on Bayesian statistics, background simulations, the efficiency calibration and first sample measurements.

Novel multilayer arrangement of conductive layers traps the electromagnetic interferences by multiple internal reflections at high frequency in the far field

The use of the wireless cellular phone is increasing dramatically, and this use can disturb the electronic circuits function with an electromagnetic interference (EMI). Metals are particularly suitable as shielding material against (EMI) due to their high electrical conductivity, but there are a few drawbacks to the use of metal as a shielding material. The weight of the ‘heavy’ metal can be classified as an issue in the case of full metal shielding, especially in the applications where mass should be as low as possible. The purpose behind this study is to ameliorate the shielding of electronic circuit by using multilayer structure. We propose a new multilayer structure shield based on an alumina dielectric layer (Al2O3) sandwiched between two conductive layers of Titanium for better protection against electromagnetic waves. The simulation results prove that the proposed multilayer structure displays more effectiveness of electromagnetic shielding, and a better performance in high frequencies than the Ti monolayer structure, which is achieved due to the impedance mismatch of our structure. Moreover, this multilayer structure has a lighter weight, lower cost, and more efficient shielding than the monolayer structure.

New results on ballistic performance of multi-layered metal shields: Review

This survey includes, mainly, investigations that were published during recent years and a few earlier studies that were not included in the review by the same authors published in 2012. The survey covers analytical, numerical and experimental studies in which the effect of layering, spacing and change of the order of the plates on the protective performance of metallic shields against high-speed impact is investigated, and also studies that suggested analytical methods for optimization of multilayered shields.

The heterogeneous anti-radiation shield for spacecraft*

The paper deals with modeling of elemental composition and properties of heterogeneous layers in multilayered shields to protect spacecraft onboard equipment from radiation emitted by the natural Earth’s radiation belt. This radiation causes malfunctioning of semiconductor elements in electronic equipment and may result in a failure of the spacecraft as a whole. We consider four different shield designs and compare them to the most conventional radiation-protective material for spacecraft - aluminum. Out of light and heavy chemical elements we chose the materials with high reaction cross sections and low density. The mass attenuation coefficient of boron- containing compounds is 20% higher than that of aluminum. Heterogeneous shields consist of three layers: a glass cloth, borated material, and nickel. With a protective shield containing heavy metal the output bremsstrahlung can be reduced. The amount of gamma rays that succeed to penetrate the shield is 4 times less compared to aluminum. The shields under study have the thicknesses of 5.95 and 6.2 mm. A comparative analysis of homogeneous and multilayered protective coatings of the same chemical composition has been performed. A heterogeneous protective shield has been found to be advantageous in weight and shielding properties over its homogeneous counterparts and aluminum. The dose characteristics and transmittance were calculated by the Monte Carlo method. The results of our study lead us to conclude that a three-layer boron carbide shield provides the most effective protection from radiation. This shield ensures twice as low absorbed dose and 4 times less the number of penetrated gamma-ray photons compared to its aluminum analogue. Moreover, a heterogeneous shield will have a weight 10% lighter than aluminum, with the same attenuation coefficient of the electron flux. Such heterogeneous shields can be used to protect spacecraft launched to geostationary orbit. Furthermore, a protective boron-containing and nickel coating can be deposited onto a finished housing frame of space equipment.

Optimization of multilayer electromagnetic shields: A genetic algorithm approach

Composites filled with carbon nanoplatelets designed as multi‐layer electromagnetic shields are considered because of their interesting electromagnetic characteristics, such as high electrical conductivity and excellent microwave absorption and shielding behaviour. Layers disposal, their composition and electrical parameters, number and thicknesses are optimized through a real‐coded genetic algorithm to achieve the minimization of the transmitted waves and minimization of reflection loss of the absorbing composites as coating on metal surface. Numerical design of wide frequency band radar absorbing multi‐layer composite structures and highly shielding structures are presented and compared with experimental results.

Модификация фенолоформальдегидных смол для производства конструкционных древесных плит

Модификация фенолоформальдегидных смол для производства конструкционных древесных плит

ON ACQUISITION OF ELECTRICAL ACTIVITY OF RATS CEREBRAL CORTEX

We constructed a portable system for acquisition of the electrical activity of a brain. We succeeded in acquiring the electroencephalogram and nociceptive evoked potentials in the somatosensory S 1 HL and the anterior cingulate Cg cortexes in the right hemisphere in rats. The key features of the system consist of the following: high sensitivity; absence of any filters; high-resolution measurement; this results in the near absense of data loss while acquiring the real time brain electric activity. The problem to get rid of the intense electromagnetic pollution was solved by making use of a multilayer shielding of the analogue part of the system and by using an autonomous direct current source to feed the whole system. This system is portable and works with a notebook computer. The solutions we have utilised while setting up this system are pioneering and allow us to deal with a wide range of problems of electrophysiology.

Влияние мелких фракций на свойства древесных плит без связующего

Влияние мелких фракций на свойства древесных плит без связующего