Showing papers on "Shields published in 2009"

High-Performance Slow-Wave Transmission Lines With Optimized Slot-Type Floating Shields

Abstract: A novel slow-wave transmission line with optimized slot-type floating shields in advanced CMOS technology is presented. Periodical slot-type floating shields are inserted beneath the transmission line to provide substrate shielding and to shorten the electromagnetic (EM) propagation wavelength. This is the first study that demonstrates how the wavelength, attenuation loss, and characteristic impedance can be adjusted by changing the strip length (SL), strip spacing (SS), and metal layer position of the slot-type floating shields. Wavelength shortening needs to be achieved with a tradeoff between slow-wave effect and attenuation loss. The slot-type floating shields with different SLs, SSs and metal layer positions are analyzed. It is concluded that minimum SL provides the most optimal result. A design guideline can be established to enable circuit designers to reach the most appropriate slot-type floating shields for optimal circuit performance. Transmission line test structures were fabricated by using 45-nm CMOS process technology. Both measurement and EM waves simulation were performed up to 50 GHz. Transmission lines are frequently used at a length of half- or quarter-wavelength. With a shortened wavelength, a saving in silicon area of more than 67% can be achieved by using optimized slot-type floating shields. Experimental results demonstrated a higher effective relative permittivity value, which is improved by a factor of more than 9, and a better quality factor, which is improved by a factor of more than 6, as compared to conventional transmission lines.

Shielding AC magnetic fields using commercial YBa2Cu3O7-coated conductor tapes

Abstract: High temperature superconducting materials (HTS) offer several advantages in magnetic field shielding applications. HTS materials have the potential of creating efficient shields by reducing the size and weight of the shielding systems. The main limitation until recently has been the difficulty of producing HTS tapes of large width. Recent developments in second-generation (2G) high temperature YBCO superconductors allow the production of 2G films on very large 4 cm wide substrates. Magnetic field shielding properties of coils and sheets fabricated from 4 cm wide YBa2Cu3O7-coated conductors are reported. Shielding properties of shields with multiple layers were measured at liquid nitrogen temperatures. Magnetic field amplitude inside the superconducting shields was measured using Hall probes with a phase-sensitive technique. Efficacy of the shields was characterized at varying field amplitude and frequency. Shielding of up to 95% of applied magnetic field was observed at magnetic field amplitudes of <10 mT. The frequency dependence of shielding properties depended on the geometry of the shields.

Thermal analysis of magnetic shields for induction heating

Abstract: For the design of magnetic shields for induction heating, it is useful to analyse not only the magnetic field reduction but also the temperature behaviour of the shield. The latter is heated by its electromagnetic losses and by thermal radiation from the workpiece. A coupled thermal-electromagnetic axisymmetric finite element model is used to study the temperature of a shield for an axisymmetric induction heater, highlighting the effect of the radius, length, thickness and material of the shield on its temperature and magnetic shielding factor. Also the effect of frequency and workpiece dimensions is investigated. The model is validated by measuring magnetic induction, induced currents in the shield and temperature of the shield on the experimental setup. The temperature is unacceptably high for shields close to the excitation coil, especially if the shield length is lower than the workpiece length. Although the study is carried out for one specific induction heater geometry, the paper indicates the effect of parameters such as geometry, material and frequency on shield temperature so that the results are also useful for other induction heating configurations.

On equivalent roughness of mobile bed at high shear stress

Abstract: The friction conditions at the top of a mobile bed are discussed for flows in the upper-plane-bed regime, i.e. for the flows with values of the bed Shields parameter larger than approximately 0.6. A special attention is devoted to flows of the bed Shields parameter bigger than 2. Experimental data for flows at high bed shear are collected from literature and new data are added from own measurements of flows of a 1.36-mm sand slurry in the 100-mm pipe loop of the Institute of Hydrodynamics. The database represents flows of very different solids and covers friction conditions within a broad range of Shields parameters up to the maximum value of about 23. The paper analyses the data in order to evaluate a relationship among the equivalent roughness of the top of the bed and other relevant parameters. A semi-empirical formula is proposed that relates the equivalent roughness to the bed Shields parameter, the ratio of flow velocity and particle settling velocity, and the ratio of flow hydraulic radius and particle diameter. The formula is applicable primarily to flows of combined load (contact- and suspended loads together).

Shielding structures for millimeter-wave integrated transformers

Abstract: Shielding structures intended to improve the performance of millimeter-wave transformers are presented. The loss mechanisms of the components are discussed and the losses related to the silicon substrate are shown to be the most relevant. A patterned ground shield and a floating shield are detailed and their influences in terms of inductance, quality-factors, coupling coefficients and minimum insertion loss are evaluated through measurement and electromagnetic simulations. Results indicate that quality-factors are deteriorated by the use of patterned ground shields, whereas the use of floating shields allows a slight improvement without degrading other characteristics of the transformer.

Modelling eddy currents in thin shields

Abstract: Purpose – The purpose of this paper is to present a simplified rigorous mathematical formulation of the problem of electric currents induced in thin shields with holes yielding more efficient numerical computations with respect to available methods.Design/methodology/approach – A surface integral equation satisfied by the current density was constructed, which is, subsequently, represented at any point by linear combinations of novel vector basis functions only associated with the interior nodes of the discretization mesh, such that the current continuity is everywhere insured. The existence of the holes in the shield is taken into account by associating only one surface vector function with each hole. A method of moments is then applied to compute the scalar coefficients of the vector functions employed.Findings – It was found that the induced current distribution for shields with holes having the complexity of real world structures can be determined with a satisfactory accuracy utilizing a moderate size...

Validation of a Time-Harmonic Numerical Model for Solving Magnetic Field in End Region of a Radial-Flux Machine

Abstract: We present an analysis of the magnetic field in the end region of a radial-flux rotating machine. In numerical simulations, we used three familiar boundary conditions to replace the modeling of the end shields and frame. We made measurements for comparison, and the simulation results were quite consistent with the measurements. Our analysis shows that the eddy current in the end shields and frame influences the magnetic field in the end region slightly and that the use of a homogeneous Neumann boundary condition or a standard impedance boundary condition (SIBC) to replace the end shields and frame can solve the magnetic field in the end region more accurately than a homogeneous Dirichlet boundary condition. Validation by the measurements demonstrates that 3-D current-driven time-harmonic model with suitable boundary conditions can be used to solve the magnetic field in the end region quite accurately.

High-Speed Penetration Modeling and Shape Optimization of the Projectile Penetrating into Concrete Shields #

Abstract: We generalize the existing engineering approaches to modeling of high-speed penetration of projectiles into semi-infinite concrete shields and suggest a modified semi-empirical two-stage model that...

Benchmark Experiment of Neutron Penetration through Iron and Concrete Shields for Hundreds-of-MeV Quasi-Monoenergetic Neutrons—II: Measurements of Neutron Spectrum by an Organic Liquid Scintillator

Abstract: A shielding benchmark experiment has been performed to obtain the spectra of neutrons penetrating 10- to 100-cm-thick iron shields and 25- to 200-cm-thick concrete shields and to investigate the accuracy of various calculation codes using a 137-MeV quasi-monoenergetic neutron source. The source neutrons are produced from a 1.0-cm-thick lithium target bombarded with 140-MeV protons, and the energy spectra are measured with the time-of-flight (TOF) method using a NE213 organic liquid scintillator. The neutrons emitted in the forward direction were collimated with a 150-cm-thick iron collimator with 10- X 12-cm aperture. TOF and unfolding methods are applied to obtain the energy spectra behind the shield for the peak energy region and continuous-energy region, respectively. Monte Carlo calculations with PHITS and MCNPX are compared with the measured data. The comparison shows that the calculated spectra are in good agreement with the measured spectra.

An Equivalent Surface Source Method for Computation of the Magnetic Field Reduction of Metal Shields

Abstract: A numerical method for computation of the resultant quasi-static magnetic field in the vicinity of parallel wires and metal shields is presented. The primary magnetic field source is time-harmonic currents in wires. This field is modified by conducting magnetic and/or nonmagnetic shields. The material is assumed to be linear under the applied source field. The shielding effectiveness can be estimated by a comparison between the primary and the resultant field. The reaction magnetic field is expressed by a sum of fields caused by equivalent single- and double-layer sources distributed on the shield surface. Integral equations for unknown distributions of these equivalent sources are derived from the Green's second identity implemented inside and outside the shields. These equations are coupled integral equations, and are solved by the moment method. Numerical results of the resultant (shielded) magnetic field obtained with the proposed method are compared with the results of: 1) analytically solvable problems; 2) measurements; and 3) two different numerical methods.

BENCHMARK EXPERIMENT OF NEUTRON PENETRATION THROUGH IRON AND CONCRETE SHIELDS FOR HUNDREDS-OF-MeV QUASI-MONOENERGETIC NEUTRONS-I: MEASUREMENTS OF NEUTRON SPECTRUM BY A MULTIMODERATOR SPECTROMETER

Abstract: A shielding benchmark experiment has been performed to obtain the experimental data of neutrons penetrated through iron and concrete shields by using 140-, 250-, and 350-MeV p-Li quasi-monoenergeti...

Magnetic vacuum systems and devices for use with superconducting-based computing systems

Abstract: Magnetic shields and magnetic shielding systems are described. The excessive spatial demands of known mu-metal/cryoperm and superconducting shielding systems are reduced by a new multi-piece shield construction approach. A complete magnetic shielding system for use with superconducting-based computing systems, such as superconducting quantum computing systems, is also described. This complete system may include mu-metal/cryoperm shields and superconducting shields using either compensatory magnetic fields, expulsion by temperature gradients, or a combination of the two.

Simulation of Shielding Effectiveness in Low Frequencies for Conductive Enclosure

Abstract: Electromagnetic pulses are fields of energy that they can damage electrical and electronic circuits at once. New technology of microelectronic circuits is sensitive to interference power. An intentional or inadvertent risk and unforeseen create irreparable damages, so that it is important to investigate electromagnetic interference from viewpoint: generation source, the effectiveness on¬ electronic components and safekeeping methods. One of the prevalent methods for safekeeping against these pulses is shielding. In this paper, at first, the effect of magnetic field intensity is investigated in frequency selected (0-545Hz) for various shields such as: paramagnetic materials, diamagnetic materials and ferromagnetic materials and shielding effectiveness was calculated for various low frequencies in one point in shield and shielding effectiveness changing with frequency changing for any material was obtained. In The following of paper, the effect of magnetic field intensity is investigated on shield's two apertures and six apertures with frequency changing. Then, the apertures were displaced on shield surface and were obtained shielding effectiveness changing. This apertures displacement has done for various shield materials. Finally, the effects of composite shields were investigated to shielding effectiveness. These shields have combined to two materials. We obtained interesting results from composite shields. In this paper, solution method has chosen 2DFEM and the whole of simulations have done Cosmos/M.

Metallic and oxide Zn and Ti layers on unwoven fabric as shields for electromagnetic fields

Abstract: The paper presents results of measurement of electromagnetic wave shielding effectiveness by shields based on polypropylene unwoven (PP) with metallic, or oxide layer. Thin films on PP fabric were made by means of pulsed magnetron sputtering. Deposited materials were Zn and Ti, fitted on magnetron gun of the WMK-100 Type in argon and oxygen background. Manufactured shields were characterised by good adhesion and shielding effectiveness (SE) over 35 dB in frequencies range from 10 MHz to 1.3 GHz.

Shielding of Electric Reactor Magnetic Field

Abstract: Concerning protection of the person the area of magnetic fields of industrial frequency (50 Hz) is the most large–scale and constantly operating harmful factor. In considered area, the shields from usual conducting materials are not effective. It is recommended the use of multilayer screens produced of amorphous magnetic soft alloys. The expressions are presented for the shielding efficiency calculation. The air current–limiting reactor is the source of the large magnetic field. The modeling by finite element method was performed to compare the magnetic field in the air reactor surroundings with magnetic screen and without it. The obtained results show that magnetic screen of amorphous magnetic soft materials allows to diminish the magnetic field in reactor surroundings more than 10 times. Ill. 7, bibl. 4, tabl. 1 (in English; abstracts in English, Russian and Lithuanian).

Vertical magnetic recording head and its manufacturing method

Abstract: PROBLEM TO BE SOLVED: To provide a vertical magnetic recording head capable of suppressing adjacent track erasure by making a magnetic flux flow between side shields and a trailing shield smooth. SOLUTION: In the vertical magnetic recording head provided with magnetic shields 30 surrounding a magnetic pole tip part 16A from three directions, the magnetic shields 30 are formed by forming a pair of side shields 30A integrally with the trailing shield 30B. Since joining surfaces are not generated between the side shields 30A and the trailing shield 30B, the magnetic flux flow therebetween is not impeded. Since intensity of a fringe magnetic field is reduced, adjacent track erasure is suppressed. COPYRIGHT: (C)2009,JPO&INPIT

Hysteretic ac losses in a superconductor strip between flat magnetic shields

Abstract: Hysteretic ac losses in a thin, current-carrying superconductor strip located between two flat magnetic shields of infinite permeability are calculated using Bean's model of the critical state. For the shields oriented parallel to the plane of the strip, penetration of the self-induced magnetic field is enhanced, and the current dependence of the ac loss resembles that in an isolated superconductor slab, whereas for the shields oriented perpendicular to the plane of the strip, penetration of the self-induced magnetic field is impaired, and the current dependence of the ac loss is similar to that in a superconductor strip flanked by two parallel superconducting shields. Thus, hysteretic ac losses can strongly augment or, respectively, wane when the shields approach the strip.

Development of the next generation of meteoroid and orbital debris shields

Abstract: The novel structure of metallic foams is of interest in the design of next‐generation debris shields as it introduces physical mechanisms that are advantageous to hypervelocity impact shielding (e.g. increased fragmentation/melt/vaporization, energy dissipation, etc.). Preliminary investigations have shown improved shielding capability over traditional spacecraft primary structures. In this paper, the results of a current hypervelocity impact test program on metallic open‐cell foam core sandwich panels are reported. A preliminary ballistic limit equation has been derived from the experimental results, and is presented in a form suitable for implementation in risk assessment software codes.

Design approach of the vacuum vessel and thermal shields towards assembly at the ITER-site

Abstract: Recent progress of the ITER vacuum vessel (VV) and thermal shields (TS) design is presented. As the ITER construction phase approaches, the design of the VV and TS (in particular, the vacuum vessel TS—VVTS) has been improved and developed in more detail with the focus on better performance, improved manufacturing ability and successful assembly at the ITER-site. In addition to the design progress, the main principles and operations for assembly of the VV, VVTS and other TS components at the ITER-site are described.

3D Eddy Current Field Calculation and Partial Overheat Protection Technology Research of UHV Large Transformer

Abstract: The 3D leakage magnetic field in four schemes of electric and magnetic shields of UHV transformer is analyzed with FEM.The methods to calculate eddy current and magnetic hysteresis losses are researched.The example is presented.

Magnetoresistive reader with demagnetization flux guide

Abstract: In some embodiments, a magnetic reader comprises first and second shields extending from an air bearing surface (ABS), a magnetoresistive stack is located between the first and second shields, and a flux guide is separated from the magnetoresistive stack while connecting the first and second shields. The flux guide magnetically couples the distal end of the magnetoresistive stack to the first shield.

Mechanical clock i.e. mechanical wristwatch, has magnetic shields made of alloy and comprising pot and lid that are connected with each other using spring and screw thread, where separated parts of shields are designed in plate-shape

Abstract: The clock i.e. wristwatch (1), has magnetic shields (2) made of alloy and comprising pot (10) and a lid (9) that are connected with each other using a spring and screw thread (11). The magnetic shields comprise multiple separated parts, which are designed in a plate-shape. An outer housing (5) has a transparent upper part (6), where a dial plate and an indicator are arranged under the upper part. The upper part is connected with a lower part (7) via a middle part (8). A passage opening is provided in an area of the pot.

Facility for recovery of non-defined emissions from metallurgic installation

Abstract: FIELD: metallurgy. ^ SUBSTANCE: facility consists of shelter and aspiration hood made from shields secured on beams of frame. The frame of the aspiration hood is fastened to beams of the shelter frame. Shields on the beams of the aspiration hood frame and on the beams of the shelter frame are movably connected with process gaps of 20-30 mm. The facility is equipped with straps movably attached on shields by pins attached to shields; the straps overlap the said gaps. ^ EFFECT: raised efficiency of recovery of non-defined emissions from metallurgic installation. ^ 2 cl, 6 dwg

Measurements of Coupling through Braided Shield via New Conducted Immunity Technique

Abstract: A new method for evaluating the performance of the shield and coupling through holes on braided shields is introduced. The method is based on conducted immunity test. A comparison is made between two kinds of shields, based on introduced technique. One is braided shields and the other is adhesive foil that does not contain any holes. The value of coupling through holes in braided shields is determined via a new technique.

Upgrade of the JET tangential gamma-ray spectrometer. Conceptual design

Abstract: A conceptual design for the upgrade of the JET tangential gamma-ray spectrometer (TGRS) has been carried out. The main design target for the TGRS upgrade is to maximize the signal-to background ratio at the spectrometer detector, the ratio being defined in terms of the plasma emitted gamma radiation and the gamma-ray background. A complex system of collimators and shields for both the neutron and gamma radiations define the spectrometer field of view. Two tandem collimators determine the field of view through the tokamak plasma. The entrance aperture to the penetration in the JET Torus Hall south wall is defined by a neutron shield. Two gamma-ray shields together with the existing concrete collimator determine the field of view at the bismuth germanate (BGO) gamma-ray detector. One of the gamma-ray shields (with an embedded neutron attenuator) can be remotely moved in and out of the detector line of sight thus providing flexibility in definition of the neutron and gamma-ray fields at the BGO detector. Neutron attenuators using lithium hydride (LiH) with natural isotopic composition (that meets the requirements for gamma-ray transparency) could provide the necessary attenuation factors (approximately 104 for the 2.45 MeV neutrons and 102 for the 14.1 MeV neutrons). A hot pressing technology has been proposed for the construction of the lithium hydride attenuators. The performance of a simplified geometry TGRS has been evaluated by preliminary neutron and photon transport calculations and the results show that the design parameters could be attained.

Method and Apparatus for the Purpose of Conserving Energy in the Glass Industry

Abstract: The conservation of energy in the glass industries via the use of heat shields to decrease the amount of energy lost during transportation from the forming process to the annealing process. For maximum effectiveness, the thermal shields are made of materials whose surface has an emissivity of, but not limited too, less than 0.3. They are mounted from, or adjacent to, the means of conveyance of the glass material such that their use will not prohibit the normal production of such glass product. Their installation shall include the means for quick removal or relocation in case of production upsets. The heat shields reflect the radiant energy that is emitted from the high temperature glass back onto itself, and adjacent products, in a manner such as to reduce the loss of energy from such product that may subsequently be necessary for the annealing process.

Determining the optimum placement of a Phase Change Materials (PCM) thermal shield inside frame walls using a dynamic wall simulator

Abstract: This thesis presents the results of an experimental study to determine the optimum placement and the thermal performance of a Phase Change Materials (PCMs) thermal shield incorporated into frame wall insulation systems for the purpose of reducing space cooling load energy use in residential and commercial buildings. The performance of the walls outfitted with the PCMs thermal shields was evaluated using a dynamic wall simulator. The interior of the dynamic simulator was designed to reproduce the conditions of the exterior of a conventional residential building wall and the exterior of the dynamic simulator represented the indoor conditions of a typical residential building since the dynamic simulator was located in an air conditioned research laboratory. Measurements of heat fluxes and calculation of percentages of peak heat transfer rate reductions were evaluated for 10% and 20% PCM concentration in the thermal shields along with two control walls. The main goals of using a PCM thermal shield were to reduce peak air conditioning demand, to shift the peak load, and to conserve energy. The results of this study show that the PCM thermal shields produce greater peak heat transfer rate reductions when they are placed further away from the heat source inside of the wall cavity and are less effective when temperatures are high. The 20% PCM thermal shield was more effective than 10% PCM thermal shields. For the optimal location of the thermal shield the reductions in peak heat transfer rates were in the range of 20-25% when compared with the control walls.

Study of Effective Atomic Number in Compounds Using Gamma‐Ray Interaction

Abstract: In view of low cost, hydrogenous materials such as Polyethylene and CH2 have been developed and being used currently by NASA as an effective galactic cosmic radiation shields in place of aluminum for hull design of spacecraft. Lead, steel and concrete which are currently being used as effective radiation shields for the treatment of rooms equipped with Electron accelerators are found be quite expensive. Hence, it is necessary to use alternative low cost material which serves as an effective radiation shield. In the present study, an attempt has been made to measure gamma‐ray mass attenuation coefficient, effective atomic number and absorbed dose rate of the compounds such as NH4Cl, KCl, and CdO using various gamma sources of energies 356, 511, 662, 1173, and 1332 keV. These parameters are expected to gives vital information on the selection of shielding materials.

Mathematical modeling of the heating of the metal structures of a foundry crane equipped with heat shields

Abstract: The pouring of pig iron into a basic oxygen converter is accompanied by the ejection of matter from the furnace (incandescent dust-bearing gases, flames, splashing metal, etc.) These emissions act on elements of the casting cranes: the metal structures of the crane, the lifting bogie of the main hoist, the cables, and the cross beam. The effects of high temperatures on the parts of these cranes can be mitigated by using heat shields. A mathematical model was constructed to describe the heating of the surface of the metal structures of a casting crane protected from heat by different methods. Providing the shields with a protective layer of the heat-insulating silica-based ceramic Supersil makes it possible to lower the temperature to which the metal structures of the crane are heated.