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The traditional "shielding theory" for the shielding effectiveness of enclosures is examined. It is shown that there can be significant effects which are not included within a simple barrier based theory at high frequencies. It is...
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The traditional "shielding theory" for the shielding effectiveness of enclosures is examined. It is shown that there can be significant effects which are not included within a simple barrier based theory at high frequencies. It is shown that a 1-dimensional box (using the full Maxwell's equations solution) has 1-D resonances that can significantly affect the accuracy of a barrier based shielding calculation. Treating the enclosure as a resonant cavity with perturbations on the walls is a better approach to the analysis of radiated emissions and radiated susceptibility problems at high frequencies (at and above the first resonance). This has the added advantage of having been worked out quite thoroughly for wave guides and resonant cavities.
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摘要 :
The traditional "shielding theory" for the shielding effectiveness of enclosures is examined. It is shown that there can be significant effects which are not included within a simple barrier based theory at high frequencies. It is...
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The traditional "shielding theory" for the shielding effectiveness of enclosures is examined. It is shown that there can be significant effects which are not included within a simple barrier based theory at high frequencies. It is shown that a 1-dimensional box (using the full Maxwell's equations solution) has 1-D resonances that can significantly affect the accuracy of a barrier based shielding calculation. Treating the enclosure as a resonant cavity with perturbations on the walls is a better approach to the analysis of radiated emissions and radiated susceptibility problems at high frequencies (at and above the first resonance). This has the added advantage of having been worked out quite thoroughly for wave guides and resonant cavities.
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In view of the electromagnetic information leakage of information security implication, the time-frequency characteristics of radiation signal from LCD display with a resolution of 1280×1024 through simulation is analyzed in this...
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In view of the electromagnetic information leakage of information security implication, the time-frequency characteristics of radiation signal from LCD display with a resolution of 1280×1024 through simulation is analyzed in this paper. The design and measurement of the shielding box is given. A USA military standard testing is made, which shows that the designed shielding box is less than the overall emission of radiation 35 dBμV/m and with a proper increase In protection radius, the amount of its radiation emission can be reduced to 20 dBμV/m or less, lower than the 20 dBμV/m of the ambient noise thus meeting the information security requirements.
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摘要 :
In view of the electromagnetic information leakage of information security implication, the time-frequency characteristics of radiation signal from LCD display with a resolution of 1280×1024 through simulation is analyzed in this...
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In view of the electromagnetic information leakage of information security implication, the time-frequency characteristics of radiation signal from LCD display with a resolution of 1280×1024 through simulation is analyzed in this paper. The design and measurement of the shielding box is given. A USA military standard testing is made, which shows that the designed shielding box is less than the overall emission of radiation 35 dBμV/m and with a proper increase In protection radius, the amount of its radiation emission can be reduced to 20 dBμV/m or less, lower than the 20 dBμV/m of the ambient noise thus meeting the information security requirements.
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After a first step out of this world in the late 1960's, Mankind sets new objectives for the 21st century in terms of space exploration. Its "next giant leap" will likely happen when an astronaut successfully sets foot on Mars or ...
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After a first step out of this world in the late 1960's, Mankind sets new objectives for the 21st century in terms of space exploration. Its "next giant leap" will likely happen when an astronaut successfully sets foot on Mars or on an asteroid. However, achieving such a historic milestone will require tackling several major technical issues beforehand, especially those linked to carrying humans in an interplanetary mission. Amongst these showstoppers, the need to manage the waste produced during the long duration journey and the urge to establish closed-loop water recovery architectures are at the forefront of the challenges that must be faced. More importantly, space radiation has always been considered as the major hurdle for long duration manned missions. It is therefore necessary to develop effective shielding systems and techniques to limit its harming effects on the human body to achieve a long, safe and sustained human presence in space. This paper sought to design a conceptual technology that would bring a solution to these issues simultaneously. Entirely inspired from nature, this multifunctional life support system mimics peristalsis inside a mammal intestine so as to carefully move and store the solid waste produced by a crew while efficiently extracting water from both liquid and solid waste using osmosis, ubiquitous in nature as well. The system, containing waste and water, could also use the outstanding properties of melanin nanoshells to increase the shielding against hazardous radiation. This reliable, modular and highly redundant "artificial intestine" for spacecraft is anchored in advanced concepts under recent investigation which could lead the way towards long-duration manned-spaceflight in the near future."
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The topics of this lecture will include: General ICRP parameters W, U, T Part I: Linac installation Standard layout for the radiotherapy room Primary and secondary radiation Ever green NCRP51 Area limits NCRP151 approach to calcul...
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The topics of this lecture will include: General ICRP parameters W, U, T Part I: Linac installation Standard layout for the radiotherapy room Primary and secondary radiation Ever green NCRP51 Area limits NCRP151 approach to calculations Neutron contamination of high energy units Interactions of neutrons with matter Door calculation Part II: Brachytherapy Rooms Sources and their physical characteristics Two examples: HDR and LDR shielding calculations
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The HZETRN code, which uses a deterministic approach pioneered at NASA Langley Research Center, has been developed over the past decade to evaluate the local radiation fields within sensitive materials (electronic devices and huma...
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The HZETRN code, which uses a deterministic approach pioneered at NASA Langley Research Center, has been developed over the past decade to evaluate the local radiation fields within sensitive materials (electronic devices and human tissue) on spacecraft in the space environment. The code describes the interactions of shield materials with the incident galactic cosmic rays, trapped protons, or energetic protons from solar particle events in free space and low Earth orbit. The content of incident radiations is modified by atomic and nuclear reactions with the spacecraft and radiation shield materials. High-energy heavy ions are fragmented into less massive reaction products, and reaction products are produced by direct knockout of shield constituents or from de-excitation products. An overview of the computational procedures and database which describe these interactions is given. Validation of the code with recent Monte Carlo benchmarks, and laboratory and flight measurement is also included.
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摘要 :
The HZETRN code, which uses a deterministic approach pioneered at NASA Langley Research Center, has been developed over the past decade to evaluate the local radiation fields within sensitive materials (electronic devices and huma...
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The HZETRN code, which uses a deterministic approach pioneered at NASA Langley Research Center, has been developed over the past decade to evaluate the local radiation fields within sensitive materials (electronic devices and human tissue) on spacecraft in the space environment. The code describes the interactions of shield materials with the incident galactic cosmic rays, trapped protons, or energetic protons from solar particle events in free space and low Earth orbit. The content of incident radiations is modified by atomic and nuclear reactions with the spacecraft and radiation shield materials. High-energy heavy ions are fragmented into less massive reaction products, and reaction products are produced by direct knockout of shield constituents or from de-excitation products. An overview of the computational procedures and database which describe these interactions is given. Validation of the code with recent Monte Carlo benchmarks, and laboratory and flight measurement is also included.
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A method for determining the shielding factors for gamma-ray spectrometers is described. The shielding factors are expressed by decomposing the peaked background of the spectrometer into contributions of the detector, spectrometer...
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A method for determining the shielding factors for gamma-ray spectrometers is described. The shielding factors are expressed by decomposing the peaked background of the spectrometer into contributions of the detector, spectrometer shield and ambient radiation to the spectrometer background. The dimensions of the sample and its mass-attenuation coefficient are taken into account using a simple model. For six spectrometers, with contributions to the background quantified, the shielding factors were determined for the background based on the thorium decay series and the radon daughters. For a water sample with a diameter of 9 cm and a thickness of 4 cm and the nuclides of the thorium decay series that are in the spectrometer shields, the values of the shielding factors lie in the interval 0.95-1.00. For a spectrometer exhibiting the diffusion of radon into the shielding material, the values of the shielding factors for the same sample for gamma-rays from the radon daughters lie in the interval 0.88-1.00.
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IASI (Infrared Atmospheric Sounding Interferometer) is an Earth observation instrument carried by the METOP polar platform (launch foreseen in the beginning of the second millenary) in low earth (altitude of 838 km) heliosynchrono...
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IASI (Infrared Atmospheric Sounding Interferometer) is an Earth observation instrument carried by the METOP polar platform (launch foreseen in the beginning of the second millenary) in low earth (altitude of 838 km) heliosynchronous orbit with a local time descending node of 9.00 A.M. The program is in phase B and under responsibility of CNES and ASI (Italian Space Agency). Its mission is to measure the emission spectra of atmosphere in the field 3.4 to 15.5 mm. In this range of wave length, desired performances require cooling of the detection unit around 100 K. After a trade-off, a cryogenic passive radiator has been preferred to a mechanical cooler for reliability, life duration, simplicity and absence of induced vibrations reasons. This paper describes the thermal concept of the radiator used to cool down the detectors. The detectors dissipation is 56 mW. The major problem in achieving cryogenic temperatures with passive radiator systems is to insulate thermally the system from the spacecraft and its external environment. In order to avoid direct solar input on radiative plates, a sunshield is used (cylindrical for manufacture aspect). Due to its form and its high level of specularity, the major part of albedo and earth fluxes coming on the sunshield are space rejected. Then, an earthshield is used to minimize the albedo and earth fluxes on the sunshield. Moreover, the radiative plates are in direction of Earth limb, so they can't receive direct albedo or earth fluxes. In order to reduce thermal inputs coming from the spacecraft, the cooler is a two stage cooler, each stage being thermally insulating from each other by multilayers insulation for radiative aspects and by low conductive support (glass fiber) for conductive aspects. This multistage concept reduces parasitic heat leakage to the cold stage. Each stage has its own radiative plate with high emittance to reject heat loads to space. The detectors are on the coldest stage.
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