Showing papers on "Shields published in 2016"

Radiation attenuation properties of shields containing micro and Nano WO3 in diagnostic X-ray energy range

Abstract: Background : It has recently been shown that the parcle size of materials used for radiaon shielding can affect the magnitude of radiaon aenuaon. Over the past years, applicaon of nano-structured materials in radiaon shielding has aracted aenon world-wide. The purpose of this study was to invesgate the shielding properes of the lead-free shields containing micro and nano-sized WO3 against low energy x-rays. Materials and Methods : The radiaon shields were constructed using nano and micro WO3 parcles incorporated into an EPVC polymer matrix. The aenu aon coefficients of the designed shields were evaluated for low energy x-rays (diagnosc radiology energy range). Results : The results indicate that nano-structured WO3/PVC shields have higher photon aenuaon properes comp ared to those of the micro-sized samples. Conclusion: Our experiment clearly shows that the smaller size of nano-structured WO3 parcles can guarantee a beer radiaon shielding property. However, it is too early to draw any conclusion on the possible mechanisms of enhanced aenuaon of nano-sized WO3 parcles.

Design and validation of a large-format transition edge sensor array magnetic shielding system for space application.

Abstract: The paper describes the development and the experimental validation of a cryogenic magnetic shielding system for transition edge sensor based space detector arrays. The system consists of an outer mu-metal shield and an inner superconducting niobium shield. First, a basic comparison is made between thin-walled mu-metal and superconducting shields, giving an off-axis expression for the field inside a cup-shaped superconductor as a function of the transverse external field. Starting from these preliminary analytical considerations, the design of an adequate and realistic shielding configuration for future space flight applications (either X-IFU [D. Barret et al., e-print arXiv:1308.6784 [astro-ph.IM] (2013)] or SAFARI [B. Jackson et al., IEEE Trans. Terahertz Sci. Technol. 2, 12 (2012)]) is described in more detail. The numerical design and verification tools (static and dynamic finite element method (FEM) models) are discussed together with their required input, i.e., the magnetic-field dependent permeability data. Next, the actual manufacturing of the shields is described, including a method to create a superconducting joint between the two superconducting shield elements that avoid flux penetration through the seam. The final part of the paper presents the experimental verification of the model predictions and the validation of the shield's performance. The shields were cooled through the superconducting transition temperature of niobium in zero applied magnetic field (<10 nT) or in a DC field with magnitude ∼100 μT, applied either along the system's symmetry axis or perpendicular to it. After cool-down, DC trapped flux profiles were measured along the shield axis with a flux-gate magnetometer and the attenuation of externally applied AC fields (100 μT, 0.1 Hz, both axial and transverse) was verified along this axis with superconducting quantum interference device magnetometers. The system's measured on-axis shielding factor is greater than 106, well exceeding the requirement of the envisaged missions. Following field-cooling in an axial field of 85 μT, the residual internal DC field normal to the detector plane is less than 1 μT. The trapped field patterns are compared to the predictions of the dynamic FEM model, which describes them well in the region where the internal field exceeds 6 μT.

Theoretical and experimental study of a method for the protection of spacecraft from high–speed particles

Abstract: In this paper, we perform numerical simulation and experimental determination of the limiting resistance of the spacecraft design elements used when developing anti-meteorite protection of spacecraft as well as protection against space debris. One possible way to increase the efficiency of protective shields and satisfy the requirements of the mass characteristics of the latter is the use of mesh barriers.

Shielding Effectiveness of Multiple-Shield Cables with Arbitrary Terminations via Transmission Line Analysis

Abstract: In this paper we report on a transmission-line model for calculating the shielding effectiveness of multiple-shield cables with arbitrary terminations. Since the shields are not perfect conductors and apertures in the shields permit external magnetic and electric fields to penetrate into the interior regions of the cable, we use this model to estimate the effects of the outer shield current and voltage (associated with the external excitation and boundary conditions associated with the external conductor) on the inner conductor current and voltage. It is commonly believed that increasing the number of shields of a cable will improve the shielding performance. However, this is not always the case, and a cable with multiple shields may perform similar to or in some cases worse than a cable with a single shield. We want to shed more light on these situations, which represent the main focus of this paper.

Calculation of an optimized design of magnetic shields with integrated demagnetization coils

Abstract: Magnetic shielding made from permalloy is frequently used to provide a time-stable magnetic field environment. A low magnetic field and low field gradients inside the shield can be obtained by using demagnetization coils through the walls, encircling edges of the shield. We first introduce and test the computational models to calculate magnetic properties of large size shields with thin shielding walls. We then vary the size, location and shape of the openings for the demagnetization coils at the corners of a cubic shield. It turns out that the effect on the shielding factor and the expected influence on the residual magnetic field homogeneity in the vicinity of the center of the shield is negligible. Thus, a low-cost version for the openings can be chosen and their size could be enlarged to allow for additional cables and easier handling. A construction of a shield with beveled edges and open corners turned out to substantially improve the shielding factor.

Optimization of multilayer electromagnetic shields: A genetic algorithm approach

Abstract: 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.

Simultaneous Magnetic Shielding and Magnetization Loss Measurements of YBCO Cylinders at Variable Temperatures Under Cryogenic Helium Gas Circulation

Abstract: A novel experimental setup for simultaneous measurements of magnetic shielding characteristics and magnetization ac loss measurements is described. The measurement system consists of a controllable helium circulation system that enables cooling of the samples to temperatures as low as 15 K and simultaneously allows calorimetric ac loss measurements. The simultaneous measurement of shielding characteristics and ac losses permits estimation of losses in realistic operating conditions of high-temperature superconducting magnetic shields. It is shown that if the extent of losses is high compared with the cooling efficiency, the magnetic shields could quench. The data on magnetic shielding efficacy along with the corresponding magnetization losses are presented.

Synthesis of Admissible Shields

Abstract: Shield synthesis is an approach to enforce a set of safety-critical properties of a reactive system at runtime A shield monitors the system and corrects any erroneous output values instantaneously The shield deviates from the given outputs as little as it can and recovers to hand back control to the system as soon as possible This paper takes its inspiration from a case study on mission planning for unmanned aerial vehicles (UAVs) in which k-stabilizing shields, which guarantee recovery in a finite time, could not be constructed We introduce the notion of admissible shields, which improves k-stabilizing shields in two ways: (1) whereas k-stabilizing shields take an adversarial view on the system, admissible shields take a collaborative view That is, if there is no shield that guarantees recovery within k steps regardless of system behavior, the admissible shield will attempt to work with the system to recover as soon as possible (2) Admissible shields can handle system failures during the recovery phase In our experimental results we show that for UAVs, we can generate admissible shields, even when k-stabilizing shields do not exist

Thermal Shields for Heat Loss Reduction in Siemens-Type CVD Reactors

Abstract: The use of thermal shields to reduce radiation heat loss in Siemens-type CVD reactors is analyzed, both theoretically and experimentally. The potential savings from the use of the thermal shields is first explored using a radiation heat model that takes emissivity variations with wavelength into account, which is important for materials that do not behave as grey bodies. The theoretical calculations confirm that materials with lower surface emissivity lead to higher radiation savings. Assuming that radiation heat loss is responsible for around 50% of the total power consumption, a reduction of 32.9% and 15.5% is obtained if thermal shields with constant emissivities of 0.3 and 0.7 are considered, respectively. Experiments considering different thermal shields are conducted in a laboratory CVD reactor, confirming that the real materials do not behave as grey bodies, and proving that significant energy savings in the polysilicon deposition process are obtained. Using silicon as a thermal shield leads to energy savings of between 26.5-28.5%. For wavelength-dependent emissivities, the model shows that there are significant differences in radiation heat loss, of around 25%, when compared to that of constant emissivity. The results of the model highlight the importance of having reliable data on the emissivities within the relevant range of wavelengths, and at deposition temperatures, which remains a pending issue.

Performances investigation and material selection of PMT magnetic shields for the space experiments with GRIS and PING-M instruments

Abstract: PMT performances significantly change under the influence of magnetic field. Even the relatively weak geomagnetic field, which typically value is about 0.5 gauss, has an appreciable effect. Gain variations of PMT with 76 mm photocathode diameter may reach 10-20% depending on spatial orientation. Therefore, it is necessary to apply magnetic shields for PMT response stability enhancement. The performances investigation of magnetic shields made of steel, permalloy and amorphous metallic alloy ribbon for PMT with 51 and 76 mm photocathode diameters was carried out. Based on obtained data the choice of magnetic shield was made.

Influence of the shield grounding system on choice of section

Abstract: The choice of the ground circuit of a shield that gets rid of capacity losses is becoming especially urgent to increase the transmission capacity of lines with cross-linked polyethylene insulation. Ground systems of shields of the single-phase high-voltage power cables are studied. A mathematical model to select the section of the electric conductor for single-wire power cables for a voltage of 6–500 kV is suggested which takes into account the connection circuit of the shield permits allows one to determine the capacity losses and induced voltage on the shield. The method of selection of energy-efficient grounding systems of the shield of the three-phase group is found on the basis of the mathematical model. A selection criterion is suggested determining the relative rate of return of the “open” ground system with no currents in the shields over against the “closed” system in the shields of which parasitic currents flow.

The heterogeneous anti-radiation shield for spacecraft*

Abstract: 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.

A column gas liquid exchange system

Abstract: A column gas liquid exchange system is disclosed. The system comprises rotational flow blade type gas rising holes, spraying shields, downcomer plates, collecting plates, separators and separating plates. Column plates are provided with the rotational flow blade type gas rising holes. Positions corresponding to the gas rising holes are fixed to the spraying shields through supports. A gap is provided between the bottom of each spraying shield and the corresponding column plate, thus forming a path allowing liquids on the column plates to enter the spraying shields. Side walls of the spraying shields are provided with spraying holes. The tops of the spraying shields are provided with the gas liquid separating plates. The gas liquid separators are mounted in the spraying shields. The downcomer plates and a column body form downcomer tubes. Each of the collecting plates is fixed to the back of the corresponding downcomer plate outside the corresponding downcomer tube. Two ends of each collecting plate tangent lines of which are perpendicular to the corresponding downcomer plate are fixed to the column wall, and the other end is decurved and extends into the downcomer tube of the lower column plate. The system enhances gas liquid contact, increases the gas liquid transfer efficiency, and is low in energy consumption, simple in structure and convenient to install and maintain.

It shields device alone to control eye

Abstract: The utility model provides an it shields device alone to control eye, it includes a main part support to shield the device, it corresponds the human spectacle -frame of controlling the eye respectively to be equipped with two on the main part support, every spectacle -frame is equipped with one respectively and shields the structure, and every shields the structure and all can open alone, and the spectacle -frame that corresponds does not have and shields, and the place ahead image can be seen to the human eyes that correspond, every shields the structure all can be closed alone, and the spectacle -frame that corresponds is shielded the structure and shields, and the place ahead image can't see to the human eyes that correspond The utility model discloses a shielding the device and can be used to various myopia especially among the amblyopia therapy instrument, that realizes about to eye shields convenient operation alone

Cover is shielded in thermal -insulated type insulator insulation

Abstract: The utility model discloses a cover is shielded in thermal -insulated type insulator insulation, shield the cover including the insulator, it shields the cover to shield shroud board and suspension clamp, the insulator shields the cover and sets up the shape into " U ", the insulator shields two side edges on the cover and sets up first fixed orifices, the lower part inboard that the insulator shields the cover sets up the base spread groove, the insulator shields the cover and shields cover swing joint through the base spread groove with suspension clamp, it sets up the shape into " T " to shield the shroud board, it is provided with the second fixed orifices corresponding with first fixed orifices on the shroud board to shield, suspension clamp shields cover middle part setting " U " shape metal and shields the cover, the metal shields cover surface setting " U " shape slide, the metal shields the inside fastener fixture that set up of cover, and the insulator shields cover, shields the shroud board, suspension clamp shields the cover and the metal shields the cover surface resistant high temperature resistant insulation coating that has all coated The utility model has the advantages of being simple in structure and convenient in operation, obscure effect is good, and factor of safety is big

New Material for Shields in X-Ray Diagnostic Procedures

Abstract: Shielding with the use of materials strongly absorbing X-rays is one of the oldest methods reducing patients’ exposure to radiation. This article presents the results of the research aimed at developing a material, which will reduce radiation dose more efficiently than the materials produced so far, and will not change features of the computed tomography (CT) image. The current study focuses on elastomeric composites containing bismuth, wolfram, and gadolinium as the elements strongly absorbing X-rays in the range of energies used in diagnostic radiography. The aim of the study was to evaluate the effect of the made shields on the quality of CT image and properties reducing radiation. Measurements with the use of dosimetry phantoms have proven that the impact of shields on the distribution of energy absorbed in the inside of the object is limited to the regions situated directly under the shield surface. The material containing bismuth, wolfram and gadolinium most efficiently reduced doses measured in the BODY phantom. Hence, real shield efficacy was verified by measuring dose distribution on the surface of the phantom imitating a 5-year-old child (CIRS) and comparing the dose values registered without the shield and those achieved after using the shield. On the basis of the results achieved in the study was concluded that 50% attenuation of X-ray beam emitted by the CT scanner is available using the (Bi+W+Gd shield) and the effect of reduction of X-radiation intensity is visible in the surface layer of the exposed object located directly beneath the shield.

Relativistic magnetron with cathode end shields

Abstract: FIELD: electronicsSUBSTANCE: invention relates to relativistic high-frequency electronics and can be used for generation of high-power microwave radiation Relativistic magnetron with cathode end shields has multi-resonator anode unit (1) with end covers (7), waveguide power (2) output and located on axis of holding cathode holder (4) with explosive emission cathode (3), vacuum chamber (8), cylindrical drift tube (9) and outer magnetic system (6) Cathode end shields (5) are installed on cathode holder (4) and are made of ferromagnetic material, induction saturation of which exceeds value of maximum working field induction of magnetic system (6)EFFECT: technical result is reduction of losses of current from space of interaction of device1 cl, 2 dwg

On the multishell cylindrical magnetostatic shields: Analytical and numerical approach

Abstract: In this paper one and two shells magneto static cylindrical shields are considered. Using the interface conditions at the discontinuity surfaces between the media, algebraic systems of equations have been obtained. Solution of the systems offers the value of the magneto static field inside the shields. Structures of the system's matrices were analyzed and their sparsity patterns was visualized. 3D Finite element simulations of shields with different lengths were performed and comparisons with analytical results were done. Good agreement, among the shields efficiencies for different lengths and the analytical value, were obtained.

Heat dissipation dustproof lawn lamp

Abstract: The invention discloses a heat dissipation dustproof lawn lamp. The heat dissipation dustproof lawn lamp comprises a base, a lampshade, a base plate, a heat dissipation plate, first wind shields, second wind shields, a wind shield barrel, a top cover and partition plates. The lampshade is mounted at the upper end of the base; the heat dissipation plate is disposed at the end, far away from the base, of the lampshade, and a first space is defined by the heat dissipation plate, the base and the lampshade. The base plate is disposed on the side, far away from the base, of the heat dissipation plate and located in the first space. The wind shield barrel is mounted on the side, far away from the lampshade, of the heat dissipation plate. The top cover is disposed on the side, far away from the heat dissipation plate, of the wind shield barrel. The first wind shields are mounted on the periphery of the wind shield barrel, the second wind shields are mounted on the periphery of the heat dissipation plate, and the first ends of the second wind shields are connected with the lower ends of the first wind shields. The first wind shields and the second wind shields cooperate with the wind shield barrel and the heat dissipation plate to form air channels. The multiple partition plates are disposed on the periphery of the wind shield barrel and divide the air channels into a plurality of heat dissipation channels. The upper ends of the first wind shields are provided with a plurality of air inlets. By means of the heat dissipation dustproof lawn lamp, the dustproof effect can be achieved while heat dissipation of the lawn lamp is performed.

Magnetic head comprising magneto-resistance effect element and side shields

Abstract: A magnetic head includes a magneto-resistance effect element in the form of a multilayer film, a pair of shields between which the magneto-resistance effect element is interposed in the lamination direction of the layers of the magneto-resistance effect element and each functioning as an electrode, a pair of side shields with one of said side shields on each side of the magneto-resistance effect element in the direction perpendicular to the lamination direction of the magneto-resistance effect element interposed between the pair of shields, the side shields magnetically coupled to either of the pair of shields, and an anisotropy-application layer disposed adjacent to the shield magnetically coupled to the pair of side shields. The pair of shields, the magneto-resistance effect element, and the pair of side shields are exposed on the air bearing surface facing a recording medium. The anisotropy-application layer is not exposed on the air bearing surface and is provided at a position away from the air bearing surface.

Portable cover that shields

Abstract: The utility model discloses a portable cover that shields, including setting up in the first body and the second body of wire pole both sides respectively, first body's top and the top of second body all is provided with the handle. In the assembly use, the staff can conveniently will through this handle first body with the second body is mentioned and is put to corresponding operation station department, and its operation process simple accurate has effectively reduced the degree of difficulty is put and transports in getting of portable cover that shields, has improved greatly portable cover that shields's easy -to -use nature and maneuverability.

Shield member and jet engine using the same

Abstract: The shield member (30) is disposed over a gap between platform parts (20) of adjoining turbine rotor blades (10), is formed from a ceramic-based composite material, and shields the gap between the platform parts (20).

Method for fabricating a magnetic sensor assembly

Abstract: A magnetic sensor assembly includes first and second shields each comprised of a magnetic material. The first and second shields define a physical shield-to-shield spacing. A sensor stack is disposed between the first and second shields and includes a seed layer adjacent the first shield, a cap layer adjacent the second shield, and a magnetic sensor between the seed layer and the cap layer. At least a portion of the seed layer and/or the cap layer comprises a magnetic material to provide an effective shield-to-shield spacing of the magnetic sensor assembly that is less than the physical shield-to-shield spacing.

Rolling side-drawing device for cathode shields in X-ray tubes

Abstract: The invention relates to a rolling side-drawing device for cathode shields in X-ray tubes and in particular relates to a simple and fast machining device for the cathode shields of the X-ray tubes. The rolling side-drawing device for the cathode shields in the X-ray tubes comprises a bottom die and an upper die, which are matched to form a cathode shield rolling channel; the rolling side-drawing device is characterized by further comprising a central spindle, a drawing punch and a guide pillar. The rolling side-drawing device for the cathode shields in the X-ray tubes guarantees good consistency of the cathode shield, and is simple and easy to operate; further, the effects of high drawing cost, high sample tube cost and long machining period in small batch production of cathode shield samples with specially-manufactured dies can be minimized.

Shield body and superconduction accelerator

Abstract: PROBLEM TO BE SOLVED: To provide a shield body which achieves space saving and simplification of handling and attains sufficient shield characteristics, and to provide a superconduction accelerator including the shield body.SOLUTION: A shield body 4 shields earth magnetism and radiant heat and includes: a magnetic shield part 11 formed by a magnetic material and having a plate-like shape; and a radiation shield part 15 which is deposited on at least one of interior and exterior surfaces 11a of the magnetic shield part 11 and formed by a material having heat conductivity larger than that of the magnetic material.SELECTED DRAWING: Figure 2

Pulse flux inducer

Abstract: An electromotive device comprises a rotor 1 having core windings 5 and 6 located thereon The core windings may be made from copper wire embedded in a plurality of soft iron laminations Two stators 2 and 3 have core windings 4 and 7 located thereon Force shields 8 and 9 may be provided Field windings 10 and 11are provided A pulsating DC current may be supplied to the stator and the current flow causes a magnetic field in the core windings and results in a magnetic flux entering the force shields A non pulsating DC current is supplied to the rotor Interaction of the force shields causes the rotor to turn and to continue to do so as long as the current is supplied