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1
Cheung, Cindy Suit. "Shielding Effectiveness of Superalloy, Aluminum, and Mumetal Shielding Tapes." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/126.
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Using MIL-HDBK-419A, MATLAB and Nomographs, Shielding Effectiveness for the Magnetic Field, Electric Field, and Plane Wave were calculated over a frequency range from 10 Hz to 1 GHz. The three shielding tapes used included superalloy, aluminum, and mumetal. Calculations for Shielding Effectiveness involve the computation of Absorption Loss, Reflection Loss, and Re-Reflection Correction Factor. From the outcome of the calculations, it was suitable to conclude that all three metals fulfill the 40 dB Shielding Effectiveness requirements for SGEMP fields for frequencies greater or equal to 1 MHz. Accordingly, all three shielding tapes provide at least 40 dB of shielding to protect certain frequencies against SGEMP Magnetic Field. However, results vary for frequencies below 1 MHz.
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Zárate, Devia Yair Daniel. "Phase shielding solitons." Tesis, Universidad de Chile, 2013. http://www.repositorio.uchile.cl/handle/2250/115388.
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Magíster en Ciencias, Mención FísicaLos solitones son el fen omeno universal m as profundamente estudiado, debido a los innumerables sistemas físicos en los cuales se observa. Estas soluciones corresponden a estados localizados y coherentes que surgen naturalmente en sistemas extendidos, siendo una de sus propiedades m as fascinantes el hecho de que pueden ser tratados como partículas macroscópicas a pesar de estar formados por numerosos componentes microscópicos. Desde su primera descripci on, realizada por J. S. Russell en 1884, el estudio de solitones se centró en sistemas conservativos por más de cien años. Sin embargo, los pioneros trabajos de Alan Turing e Ilya Prigogine demostraron que los sistemas fuera del equilibrio se auto{ organizan por medio de la generación de estructuras disipativas. Hoy en día, sabemos que es justamente este mecanismo el que permite la formación de solitones disipativos en sistemas con inyección y disipación de energía. Nuestro principal interés ha sido caracterizar de forma analítica y numérica a los solitones que emergen en sistemas forzados paramétricamente{sistemas forzados por medio de un parámetro efectivo que var a en el espacio y/o tiempo. Los sistemas forzados param etricamente pueden experimentar una resonancia paramétrica, la cual se caracteriza por una respuesta subarm onica (subm ultiplos de la frecuencia natural del sistema). Dada la complejidad que presentan los sistemas paramétricos, focalizamos nuestro estudio en la ecuación de Schrödinger no lineal disipativa forzada paramétricamente (PDNLS). Este modelo caracteriza bien la din amica de sistemas forzados param etricamente, en torno al punto de aparición de la resonancia paramétrica, en el límite de baja disipación e inyección de energía. Los solitones disipativos, presentes en PDNLS, típicamente muestran una estructura de fase uniforme. Dichas estructuras han sido ampliamente utilizadas para describir a los solitones hidrodinámicos que aparecen en el experimento de Faraday, estados localizados de la magnetización en un hilo magnético, o los clásicos solitones presentes en una cadena de péndulos con soporte verticalmente vibrado, entre otros. Por medio de simulaciones numéricas interactivas de solitones disipativos en la ecuaciónPDNLS, hemos logrado observar una interesante din amica de frentes de fase hasta ahora desconocida. Estos frentes de fase se propagan hasta alcanzar un punto de equilibrio estacionarioarbitrario. A este tipo de solitones los hemos llamado solitones escudados por la fase (phase shielding solitons), dado que la estructura nal de fase pareciera proteger al módulodel solit on. Hemos logrado caracterizar anal ticamente estas soluciones localizadas, determinando ocho posibles con guraciones. Los solitones estudiados poseen una talla característica dada por el tamaño de la estructura de fase estacionaria. Adem ás, extendimos nuestro estudio al caso bidimensional, mostrando los resultados, dos tipos de phase shilding solitons bidimensionales; axialmente simétricos y asimétricos. Los primeros pueden ser entendidos como una rotación en 2 de las soluciones simétricas encontradas en el caso unidimensional. Por su parte, las soluciones asimétricas bidimensionales presentan propiedades mucho más interesantes, ya que su estructura nal de fáse contiene todas las con guraciones halladas en el caso unidimensional. Con el n de corroborar la existencia de solitones disipativos con estructura de fase no uniforme en sistemas físicos, realizamos simulaciones numéricas de diversos sistemas paramétricos reales. Satisfactoriamente, concluimos que el fenómeno phase shielding soliton es universal, y esperamos que pueda ser prontamente observado experimentalmente.
3
Mann, Kulwinder Singh [Verfasser]. "Shielding Behaviour Analysis of Double Layered Slabs. Gamma Ray Shielding / Kulwinder Singh Mann." München : GRIN Verlag, 2018. http://d-nb.info/1165614588/34.
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Young, Jeffrey Lee. "Electromagnetic response of thin wires over an homogeneous earth." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184906.
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The electromagnetic response of infinitely long, thin wires over a flat earth is presented for two different applications: the shielding properties of an ensemble of parallel wires excited by a plane wave and the electromagnetic coupling of two perpendicular wires excited by a dipole. The shielding study begins with the formulation of the boundary value problem for N wires over a lossy half space. A suitable axial impedance operator is applied to obtain a system of equations whose unknowns are the currents flowing on each wire. Once the currents are determined, the aggregate field produced by the ensemble can be computed by summing N Fourier type integrals. For the specialized case of the infinite planar grid, Floquet's Theorem and Poisson's Summation Formula are invoked, transforming the linear system of equations into a closed form expression for the current flowing on each wire. We show that the electromagnetic response of the planar grid of finite extent and the grid of infinite extent are similar. For non-planar configurations, such as the semi-circular shell, shielding values of 60 dB are possible when the structure is of non-resonant dimensions; otherwise, the performance can degrade to 20 dB. In the case of the crossed wire configuration, the starting point is the development of the integral equations that govern the coupling between wires and the source; the unknowns are the spectral currents flowing in each wire. The equations are given in terms of generalized impedance functions for the situation where the wires are over a stratified earth. However, for the numerical work, only the case where the wires are in an unbounded, homogeneous medium is considered. Two numerical methods, with overlapping regions of validity, are applied: the method of moments and the method of multiple scatterers. By using the method of moments, we can obtain a matrix equation that will determine the spectral currents for any wire spacing. The multiple scatterer method leads to a more convenient matrix series solution and shows that the coupling strength is proportional to 1/d², where d is the wire separation, plus higher order inverse terms.
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Coker, Audra Lee. "PET/CT shielding design comparisons." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5836.
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The objective of this project was to compare two different methods of calculating
dose through lead-shielded walls in the PET/CT suite at Scott & White Hospital in
Temple, Texas. The ultimate goal was to see which of the two methods agreed with the
actual physical measurements. Minimizing shielding needed in future suite designs
would result in a possible reduction of structural as well as financial burden. Formulas
and attenuation coefficients following the basic January 2006 AAPM guidelines were
used to calculate unattenuated radiation through existing lead walls. The computer code
MCNPX was used to simulate the leaded walls of the PET/CT suite and provide another
set of results. These two sets of results were compared to doses gathered from OSL
badges placed around the suite for a period of two months. For this type of problem,
MCNPX proved to provide results that were inconsistent and unreliable. It was
concluded that the traditional computational methods are the most reliable for designing
shielding in a PET/CT suite.
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Davis, Andrew. "Radiation Shielding of Fusion Systems." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/918/.
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This thesis discusses the development, benchmarking and applications of activation dose analysis methods for fusion devices. The development and code logic of the Mesh Coupled Rigorous 2 Step (MCR2S) system is discussed. Following the development of the code, appropriate benchmarking studies were performed on the Frascati neutron generator, and revealed that the code was able to predict shutdown gamma ray doserates to within ±3% of experimentally determined values, for decay times between 3×105 and 107 seconds. The development of the Ion Cyclotron Resonance Heater (ICRH) with regards to neutronics was discussed. The ICRH went through a number of design stages and shutdown gamma ray dose rates were determined for each stage. It was determined that of all the designs analysed only one of them, the first concept design for the internally matched design did not meet the shutdown dose criteria. This was due to a flaw in the system design, brought about by a lack of consideration towards nuclear design. The ITER Light Imaging Detection and Ranging (LIDAR) system was subjected to a full shutdown nuclear analysis. It was found that the design of the LIDAR system supplied did not meet the ITER required shutdown gamma ray dose rate limit of 100 µSvhr−1, however use of the MCR2S system highlighted the components that contributed most to the shutdown gamma ray dose rate and were shown to be the mirror holder and the laser beam pipe. Future designs should include additional shielding around the beam pipe.
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Zhang, Jianan Ph D. Massachusetts Institute of Technology. "Enhancing network robustness via shielding." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93804.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 77-80).
Shielding critical links enhances network robustness and provides a new way of designing robust networks. We first consider shielding critical links to guarantee network connectivity after any failure under geographical and general failure models. We develop a mixed integer linear program (MILP) to obtain the minimum cost shielding to guarantee the connectivity of a single source-destination (SD) pair under a general failure model, and exploit geographical properties to decompose the shielding problem under a geographical failure model. We extend our MILP formulation to guarantee the connectivity of the entire network, and use Benders decomposition to significantly reduce the running time by exploiting its partial separable structure. We extend the algorithms to guarantee partial network connectivity, and observe that significantly less shielding is required, especially when the failure region is small. To mitigate the effect of random link failures on network connectivity, we consider increasing the effective min-cut of the network by shielding, where shielded links cannot be contained in effective cuts. For a single SD pair, we develop an efficient algorithm to increase the effective min-cut by one, and develop a MILP with a small number of constraints to increase the effective min-cut by an arbitrary value. Then we extend the MILP to obtain the optimal shielding to increase the effective min-cut for the entire network, which can be used to solve realistic size problems. Finally, we consider shielding critical nodes in random graphs. We demonstrate the importance of high degree nodes in random graphs constructed under the configuration model. The occupancy of higher degree nodes leads to a larger size of the giant component. Moreover, shielding a small fraction of nodes in power law random graphs guarantees the existence of a giant component if the exponent is less than three.
by Jianan Zhang.
S.M.
8
Öhrlund, Erik. "How Effective is RFID Shielding?" Thesis, Högskolan i Halmstad, Akademin för informationsteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-40107.
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Lim, Hyun. "Active shielding based on difference potentials." Thesis, University of Salford, 2011. http://usir.salford.ac.uk/26775/.
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Active control of sound is a technique for altering acoustic fields to wanted ones in aimed domains by introducing controllable active secondary sound sources called controls. This thesis describes an active shielding methodology based on difference potentials for the control of noise and preservation of sound in domains. The main feature of this methodology is its ability to automatically preserve "wanted" sound within a domain while cancelling "unwanted" noise from outside the domain. This method of preservation of the wanted sounds by active shielding control is demonstrated with various broadband and realistic sound sources such as, human voice, music, etc in multiple domains in a one dimensional enclosure. Unlike many other conventional active control methods, the proposed approach does not require the explicit characterisation of the wanted sound to be preserved. The controls are designed based on the measurements of the total field on the boundaries of the shielded domain only, which is allowed to be multiply connected, and the controls are placed on the boundaries only. The cancellation and preservation can be achieved globally over a large area of the domain. The method is tested in a variety of experimental cases. The typical attenuation of the unwanted noise is found to be about 20 dB over a large area of the shielded domain and the original wanted sound field is preserved with errors of around 1 dB and less below through a broad frequency range up to 1 kHz. This thesis reports on the results of the validation for the methodology in detail, with particular emphasis on the volumetric noise cancellation and wanted sound preservation offered by the proposed methodology, which are unique features compared to other techniques available in the literature.
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Plytus, H. R., and Г. Р. Плитус. "Special aspects of aircraft wiring shielding." Thesis, National aviation university, 2021. https://er.nau.edu.ua/handle/NAU/50501.
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1. Innovative cables and cabling solutions for next-generation Aerospace – Nexans, 2015. – 24 p.
2. Controlling the EMI effects of aircraft avionics [web resource]. - Access mode: https://cutt.ly/PxIMPTr
3. Determining When to Shield Aircraft Wiring [web resource]. - Access mode: https://cutt.ly/dxI1wKs
4. Cables Shield in Aircraft, Wilson G. Salgado, Miguel G. Molina – 15th LACCEI International Multi-Conference for Engineering, Education, and Technology: “Global Partnerships for Development and Engineering Education”, United States, 2017. – 5 p.Shielding is one of the most reliable and popular ways to avoid electromagnetic interference (EMI) exposure to wiring. This, of course, increases the reliability, but there is no need to use the shield on all wires of the aircraft, and it also has some disadvantages and extra costs. Therefore, with the aim of the correct choice of wire (shielded or not) electrical wiring interconnection system (EWIS) designers need to conduct an appropriate analysis of the transmitted data, its frequency, power, etc.
Екранування — це один з найнадійніших і найпопулярніших способів уникнути електромагнітних перешкод. Що, звичайно, підвищує надійність, але нема потреби використовувати екранування на всіх проводах повітряних суден через те, що ця процедура має деякі недоліки та додаткові витрати. Тому, з метою правильного вибору дроту (екранований чи ні) конструкторам системи з'єднань електропроводки необхідно проводити відповідний аналіз даних, що передаються по дроту, з якою частотою, потужністю тощо.
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Castro, Aguilera Abril Carolina. "Computational study of nuclear magnetic shielding constants." Doctoral thesis, Universitat de Girona, 2017. http://hdl.handle.net/10803/565597.
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Nuclear Magnetic Resonance (NMR) spectroscopy is an indispensable structural tool in the modern analytical arsenal of chemists and structural biologists. The present thesis is a computational study of the NMR shift constants in a number of chemical systems of interest, using both static and dynamic approaches via Density Functional Theory, to predict, confirm the presence of transient species, and/or explain ambiguous signals in the NMR spectra. Special attention was put on cases where there are strong interactions between the solvent and the molecule studied. In addition, this thesis addresses other methodological issues that influence the quality of the calculated NMR chemical shifts such as the level of theory, the explicit inclusion of solvent molecules, the choice of the reference molecule, as well as the relativistic effects for heavy element compoundsL’espectroscòpia de Ressonància Magnètica Nuclear (RMN) és una eina indispensable en el modern arsenal de químics analítics i biòlegs estructurals.La present tesi és un estudi computacional dels desplaçaments químics de RMN en un nombre de compostos químics d’interès, usant aproximacions estàtiques i dinàmiques mitjançant la teoria del funcional de la densitat, la qual ajudarà a predir, a confirmar i/o a complementar dades obtingudes experimentalment. S’ha donat especial atenció en casos on existeixen fortes interaccions substrat-solvent. Addicionalment, aquesta tesi aborda altres problemes metodològics que afecten la qualitat dels desplaçaments químics teòrics com el nivell de teoria, la inclusió explícita de molècules de solvent, l’elecció de la molècula de referència, així com els efectes relativistes en compostos que contenen àtoms pesats
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Rindelhardt, U., K. Noack, and A. Rogov. "Shielding and Fuel Storage Calculations for GUINEVERE." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-27990.
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Rindelhardt, U., K. Noack, and A. Rogov. "Shielding and Fuel Storage Calculations for GUINEVERE." Forschungszentrum Dresden-Rossendorf, 2008. https://hzdr.qucosa.de/id/qucosa%3A21627.
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Rafiq, Muhammad Nadeem. "Carbon Microfiber Material for Electromagnetic (Shielding) Applications." Diss., North Dakota State University, 2015. http://hdl.handle.net/10365/25293.
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Electromagnetic shielding is becoming more and more important with the
abundance of wireless devices. Therefore a need has arisen for more versatile, flexible
and low-cost solutions for shielding. For these requirements, carbon microfiber
material has been proposed for electromagnetic shielding applications. For this
purpose its shielding effectiveness has been measured and modeled in a simulation
environment. A parametric simulation was conducted for the material property
?conductivity? and the results were compared to measured ones. These simulation
results were also verified by the analytical solution for the shielding effectiveness and
the agreement between the simulated values and analytical results demonstrated that
the carbon microfiber material, though having less conductivity than the traditional
metallic shields is a good candidate for electromagnetic shielding applications. Carbon
microfiber not only provides comparable shielding effectiveness to a metallic shield but
it can be advantageous because of its light weight, corrosion resistance and flexibility.
Also, its porous nature can help with cooling of enclosed electronic circuits.COMSATS Institute of Information Technology, Pakistan
North Dakota State University (NDSU)
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Manzlak, Derrick Anthony. "Boron Carbide Filled Neutron Shielding Textile Polymers." W&M ScholarWorks, 2007. https://scholarworks.wm.edu/etd/1539626861.
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Wells, Joanne. "'Shielding behaviour' : corneal donation in the hospice setting." Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439633.
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Bhuiyan, M. A. AI-Mamun. "Modeling and Development of a Magnetic Shielding Mechanism." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28846.
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Background: Medical devices relying on biosignal acquisition are susceptible to electromagnetic interference. Current approaches are ineffective at shielding low amplitude, low frequency biosignal measurements. Objective: To develop a magnetic shielding mechanism to improve shielding effectiveness (SE) for low amplitude application. Method: A three layer shielding mechanism with the two inner layers made of cold rolled (CR) steel and an outer layer of aluminum (Al) was investigated. Modeling and simulations were performed using finite element analysis. Experiments were performed on shielding samples of CR steel and Al. Results: (1) The average SE for the three layer system was found to be S6.02 and 47.38 decibel by simulation and experiment respectively. (2) By incorporating a conductive layer of Al, performance was investigated up to 25 KHz. SE was observed to increase with the increase in interfering signal frequency. Conclusion: The proposed shielding mechanism would reduce the interference level of low amplitude, low frequency biosignal measurements.
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Lu, Yanwei. "Full-field modelling of crack tip shielding phenomena." Thesis, University of Plymouth, 2011. http://hdl.handle.net/10026.1/885.
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The application of fracture mechanics to engineering design has provided significant advances in understanding of the causes and mechanisms of failure and crack growth. Despite this, there are still some aspects that remain incompletely understood, such as the crack closure/crack shielding effect. The presence of crack closure/shielding acts to reduce . The mechanisms of crack closure/shielding are complicated, and have not been fully understood. This work focuses on the plasticity-induced crack tip shielding mechanism and presents a novel approach to characterise the elastic stress fields under the influence of the plastic enclave surrounding the crack tip. The model is successfully applied to determine the four stress parameters experimentally using full-field photoelastic stress analysis on polycarbonate CT specimens, following studies of the effect of the crack tip position and the valid data collection zone giving the best fit between the model predictions and the experimental data. The predicted values from the model demonstrate good data repeatability, and exhibit sensible trends as a function of crack length and load ratio that are interpretable in terms of physically meaningful changes to the plastic enclave. In addition, the model is proven to describe the stress field around a crack more accurately than classic Williams‟ stress solution. The model is also extended to AL 2024-T3 specimens using a full-field displacement measurement technique, digital image correlation. Using the Sobel edge detection method to identify the crack tip from the displacement fields with a rectangular shaped data collection zone employed in the current study, reasonable trends were again demonstrated in the experimental results as a function of crack length.
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Goschy, Harriet-Rosita. "Top-down shielding from distraction in visual attention." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-171000.
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The present work examines top-down shielding from distraction in visual attention; that is, under which circumstances can the intentions and goals of an observer counteract the bottom-up salience of irrelevant distractors. Several factors of influence will be considered: First, prior experience with distractors, i.e. did observers previously acquire an effective distractor shielding strategy; second, intra- vs. cross-dimensionality of distractors, i.e. are irrelevant distractors defined in the same feature dimension (e.g., shape, color) as the target or in a different feature dimension; third, time, i.e. how effective is distractor shielding early vs. later in processing; and finally, the incentive for effective distractor shielding.
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Ho, C. W. "Development of Monte Carlo methods for shielding applications." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47109.
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Colas, Dorian Frederic Marie. "A diffraction integral based turbomachinery noise shielding method." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67179.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 85-87).
A current research focus in subsonic aeronautics is the reduction of noise, emissions and fuel burn. The Silent Aircraft Initiative, NASA N+2 and N+3 projects are examples of recent efforts investigating innovative aircraft configurations to meet the future goals of air transportation. This requires novel methodologies to assess unconventional aircraft designs. This thesis is part of the N+2 program and focuses on the development of a method for the assessment of turbomachinery noise shielding in hybrid wing body aircraft. The preliminary design and assessment of novel aircraft configurations require both low computational cost and versatility of the shielding method. High fidelity methods, such as for example boundary element methods, are computationally expensive and not amenable for optimization framework integration. On the other hand, low fidelity methods, such as the barrier shielding method, are limited in their source and geometry definitions. The diffraction integral method is a simplified ray tracing method capturing edge diffracted rays. Creeping rays and reflected rays are not accounted for making the method suitable for flat geometries with sharp edges. It is based on the Maggi-Rubinowicz formulation of the Kirchoff diffraction theory for monopole source descriptions and is inherently a high frequency method. The diffraction line integral requires numerical integration and does not account for flight effects. A new method described in this thesis was developed to address these shortcomings. It is based on the Miyamoto and Wolf formulation of the boundary diffraction theory to allow the definition of source directivity inherent to turbomachinery noise. It is amenable to multipole and directional point source descriptions. Bulk flight effects are modelled with a generalized Prandtl-Glauert approach. Computational cost is dramatically decreased using uniform asymptotic theory to reduce the diffraction integral into a simple Fresnel integral. The Fresnel integral is solved via an analytical approximation such that the resulting shielding method does not require numerical integration. The method is applicable to three-dimensional aircraft configurations and comparison with an equivalent source method for sphere and disk shielding test cases show good agreement at high frequencies. Its analytical formulation offers compatibility with optimization frameworks facilitating new perspectives in aircraft design for noise reduction.
by Dorian Frederic Marie Colas.
S.M.
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Ridgeway, Robert, and Henry Newton. "An Economic Method to Increase Equipment Rack Shielding." International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606163.
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ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, CaliforniaThe ALMA Project is developing a 66 antenna radio astronomy array on a 5000 meter mountain in Chile. Radio astronomy depends on a radio frequency quiet area. The remote mountain top is ideal for such a radio astronomy array. However, RFI from equipment inside one type of antenna had a path loss of 13 dB to its feed area, when measured at 100 GHz. Carbon filled foam is being used to enhance shielding to reduce the negative effect of local radio frequency interference (RFI). This foam has been measured and verified to be effective from 1 to 100 GHz.
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Mogren, Simon. "Electromagnetic Shielding of Fine Wires for Electrophysiological Sensing." Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291457.
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Tests have been performed to determine whether electromagnetic shielding of fine wires for electrophysiological sensing is a possible way to reduce the external noise in recording of nervous signals. By shielding the wires with a layer of silver, forming a coaxial cable, a reduction of the received power on the lead of 11.8-33 dBm was shown over the 10 – 10 000 Hz range when the test wire was subject to an electromagnetic field from an injection cable. When putting the performance on the interval 50-100 Hz aside the same performance was measured to 25-33 dBm lower received power, which can be explained by 50 Hz noise from the electrical grid interfering with the measurements. However, when the shield was not grounded or grounded through a resistor worse performance was shown. The difference in received power between the unshielded and shielded configuration without grounding the shield was close to 0 dBm. Following this, the type of shielding investigated in this project has the potential to substantially shield thin wires from external interference under the condition that sufficient grounding is provided.
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Kyzymchuk, Olena, Svitlana Arabuli, Viktoriia Vlasenko, Vladimir Bajzik, Larysa Ocheretna, and Maros Tunak. "Thermophysical properties of knitted fabric for EMR shielding." Thesis, Київський національний університет технологій та дизайну, 2021. https://er.knutd.edu.ua/handle/123456789/19107.
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Rosenberg, Max. "Comparative Analysis of Electrodynamic Toroidal Radiation Shielding Configurations." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1963.
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Beyond the protective confines of Earth's atmosphere and magnetosphere, spacecraft are subject to constant bombardment by high-energy charged particles originating from our Sun in the form of Solar Particle Events (SPEs), and from outside the solar system in the form of Galactic Cosmic Rays (GCRs). The harm these particles do can be reduced or mitigated outright through radiation shielding. Because protons and other charged particles comprise most of these radiation particles, strong magnetic fields could be generated around spacecraft to deflect incoming charged radiation particles. This thesis investigates the performance of specific configurations of toroidal superconducting solenoids to generate magnetic fields that deflect incoming energetic protons via the Lorentz force. Bulk material shielding configurations using various thicknesses of liquid water are similarly investigated, as are combination shielding configurations combining the best-performing toroidal shielding configurations with a small bulk material shield surrounding the spacecraft.
The water shielding configurations tested included shields of uniform thicknesses from 1 cm to 10 cm surrounding an Apollo CSM-sized cylindrical candidate spacecraft. Water shielding was found to be very effective at reducing the SPE dose, from a 86\% reduction at 1 cm of water to a 94\% reduction at 10 cm. However water shielding was found to be minimally effective against the much higher energy Galactic Cosmic Ray protons, with no dose reduction at 1 cm and a paltry 1\% reduction at 10 cm.
The toroidal shielding geometric configurations tested consisted of either 5 or 10 primary toroidal shields surrounding the candidate spacecraft, as was the addition of smaller nested toroidal shields inside the primary toroids and of toroids on the spacecraft's endcaps. The magnetic field strengths tested were 1.7 Tesla, 8.5 Tesla, and 17 Tesla. The best geometric configurations of electrodynamic shielding consisted of 5 primary toroidal shields, 5 total nested shields placed inside the primary toroids, and 2 total shields on the spacecraft's endcaps. The second best geometric configuration consisted of 10 primary toroidal shields plus two total endcap shields. These configurations at 1.7 Tesla reduced the SPE dose by 87\% and 87\%, and reduced the GCR dose by 11\% and 10\%. At 17 Tesla, these configurations both reduced the SPE dose by 90\%, and reduced the GCR dose by 76\% and 61\%. Combining these two configurations with a 1 cm-thick shield of water improved performance against SPE protons to 95\% and 93\% at 1.7 Tesla, and a 97\% and 96\% reduction at 17 Tesla. GCR dose reductions decreased slightly.
Passive material shielding was found capable of providing substantial protection against SPE protons, but was minimally effective against GCR protons without very thick shielding. Electrodynamic shielding, at magnetic field strengths of 1.7 Tesla, was found to be similarly effective against SPE protons, and marginally more effective against GCR protons. Combining the best toroidal shielding configurations, at magnetic field strengths of 1.7 Tesla, with water shielding yielded high protection against SPE protons, but still marginal protection against GCR protons. Increasing the magnetic field strength to 17 Tesla was found to provide very high protection against SPE protons, and to significantly reduce the radiation dose from GCR protons. Of all shielding configurations tested, only those electrodynamic configurations with magnetic fields of 17 Tesla were able to reduce the GCR dose by more than half.
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Hurley, Shawn Patrick. "Liquid Crystal Displays for Pixelated Glare Shielding Eyewear." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1279550994.
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Campbell, Stuart William. "Shielding gas parameter optimisation in arc welding processes." Thesis, University of Strathclyde, 2015. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25988.
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This thesis is focussed on shielding gas optimisation in gas shielded arc welding processes, and has been conducted along two themes; deriving conditions in which the shielding gas flow rate can be safely reduced, and through the highly novel process of alternating shielding gases. The correct shielding gas flow rate is essential for providing adequate protection to the weld metal during the heating, liquid and solidification stages. Hence, there is an optimum shielding gas flow rate, but this is difficult to define and is often decided on the basis of preference or experience. A multi-disciplined, systematic study has been conducted, which has shown that there is considerable scope to reduce the shielding gas flow rate. Experimental trials have shown that the shielding gas flow rate can be reduced, in a draft-free environment, to 6 l/min, with no degradation in weld quality for the worst draft conditions measured in a typical shipyard fabrication hall, at 10 l/min. This study has resulted in shielding gas flow controllers, preset at 12 l/min, being installed in a large shipyard environment, removing the welding operatives ability to increase the shielding gas flow rate. The application of alternating shielding gases offers clear manufacturing cost reduction benefits which arise from measurable increases in productivity, improved distortion control and re-work reduction, and overall improvements to the mechanical properties of the weld. Arc pressure measurements, and the subsequent derivation of forces acting on the liquid weld metal, have indicated that flow vectors for helium are opposite in direction to that produced by argon, creating a dynamic action within the weld pool. Schlieren visualisation has shown that there is a greater degree of helium entrainment in the primary jet due to a constriction of its flow in the secondary jet, influencing the arc's behaviour and inferring more of the associated benefits.
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Armstrong, Robert. "Measurement of shielding in electrically large metallic enclosures." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/3832/.
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The measurement techniques employed to obtain the shielding effectiveness (SE) of enclosures using the current version of IEEE 299.1 only apply to enclosures of side dimension greater than 0.1m, and are also lacking in a full analysis of the field distributions within the enclosure. The work presented here uses the IEEE 299.1 draft standard as a base and investigates different methods of obtaining the SE, as well as looking at making the measurement more applicable to physically small and electrically large enclosures, and hoping to inform future versions of shielding effectiveness standards for small enclosures. The first part of this thesis investigates the use of a comb generator as a source in an enclosure under test (EUT), which provides a statistically uniform electric field inside the EUT when combined with a small mechanical stirrer. The EUT used here is an equivalent size to a 19 inch rack unit used in many equipment rigs; therefore investigations using it are of relevance to the real world. It becomes apparent that it is important to be sure that statistical field uniformity is achieved within the EUT as well as in the test chamber. The chamber at the University of York is compared with the chamber used in Ancona, Italy. Meanwhile, it is found that the presence of a direct path or unstirred component distribution in an enclosure or chamber can change the measured SE. A study of aperture dominated EUTs reveals that it is possible to obtain an indication of the SE of an enclosure using the Q−factor. This test method has the advantage that it can be applied to enclosures that have a low SE or have many apertures, as is the case in some real enclosures. Continuing the development into testing physically small enclosures that are outside the scope of IEEE 299:1997, it is shown that a physically small enclosure can be represented by an electrically equivalent larger enclosure. This is also of use when considering IEEE 299.1.
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Ko, Stephen C. "Development of Radiation Shielding Materials for Space Applications." W&M ScholarWorks, 1997. https://scholarworks.wm.edu/etd/1539626106.
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Ruekberg, Jared Allen. "STRUCTURAL MICROMETEOROID AND RADIATION SHIELDING FOR INTERPLANETARY SPACECRAFT." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1401.
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This paper focused on two significant space forces that can affect the success of a spacecraft: the radiation and micrometeoroid environments. Both are looked at in the context of the region of space between Earth and Mars. The goal was create reference environments, to provide context to results of environmental modeling, and to provide recommendations to assist in early design decisions of interplanetary spacecraft. The radiation section of this report used NASA's OLTARIS program to generate data for analysis. The area of focus was on the radiation effects for crewed missions, therefore effective dose equivalent was the metric used to compare different models of radiation and shielding. Test spheres with one, two, or three different materials layers were compared, along with modifiers such as alloys or weight vs. thickness emphasis. Results were compared to limits set by the European and Russian Space Agencies to provide context. The results hinged heavily on the intensity of the Solar Particle Events (SPEs), with testing using additional temporary radiation shielding proving to be a requirement for feasible shielding masses. Differences in shield material effectiveness were found to be negligible for thin Galactic Cosmic Rays (GCRs) and thick SPEs. Thick shields were found to perform better when the more efficient shield was on the outside of the test sphere. The micrometeoroid section used equations and programs from multiple sources to generate state vectors, flux, and finally impact models for four different case studies. Impacts v were generated with mass, velocity, and impact angle/location statistics. The mass and velocity results were run through statistical software to generate information such as mean and standard deviation with confidence intervals. Also looked at were higher mass impacts, limited to above 10-3 grams as opposed to above 10-6 for the regular case. The results of this show that very thin monolithic shields (0.1 cm-0.25 cm) could protect against the average 10-6 impact. The Ram, Nadir, and Anti-sun faces received the highest quantity of impacts and Wake received the least. When looking at the worst cases average mass and velocity for the high mass impacts significantly higher shielding was required to prevent penetration (up to 5 cm for some cases). However, the test cases had probabilities of no high mass impacts greater than 46% of the time, with shorter mission having greater chances of no high mass impacts.
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Yaslak, Halil Ibrahim. "Assessment Of Shielding Effectiveness By Using Electromagnetic Topology Method." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615609/index.pdf.
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In this thesis, determination of the shielding effectiveness of a rectangular shielding box with apertures on its walls by using electromagnetic topology (EMT) technique based on Baum-Liu-Tesche (BLT) equation is presented. The presented technique is applied to determine the field penetration into various rectangular shielding boxes with different sizes and aperture dimensions. An HP branded computer case is also analysed as a rectangular shielding box with a CD driver slot as an aperture. Results on electromagnetic field penetration through the apertures into the boxes at different frequencies are obtained by using the presented method and compared with the results obtained by using CST MICROWAVE STUDIO®software simulation.
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Banks, Julia Michelle. "Design of a ²⁵²CF-based neutron shielding test stand." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19598.
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Wong, Kok Hoong. "Use of recycled carbon fibre for electromagnetic interference shielding." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439856.
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Gibson, Nathan A. (Nathan Andrew). "Novel Resonance Self-Shielding Methods for Nuclear Reactor Analysis." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103658.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 242-246).
In the simulation of the behavior of neutrons in a nuclear reactor, there has long been a dichotomy in solution techniques. One can use Monte Carlo methods, known to be very accurate and problem agnostic but also very costly, or deterministic methods, known to be more computationally efficient but also requiring tuning to a specific application. As designers rely more and more heavily on predictive simulation, higher fidelity and more problem agnostic deterministic methods are desired. This thesis seeks to push these deterministic methods towards that goal of higher fidelity in the context of multigroup cross section generation and resonance self-shielding. This work has two primary objectives: to quantitatively assess the efficacy of current self-shielding approximations and to propose new self-shielding methods. These objectives are cast primarily in the context of mutual self-shielding, the effect of one nuclide's resonances on the neutron reaction rate with another nuclide. The first objective is accomplished through the development of a framework for the evaluation of self-shielding methods. This framework is analogous to a unit test suite in software engineering, in that specific aspects of physics modeled by a self-shielding method are isolated. The framework is used on numerous existing methods, and highlights the successes and failures of these methods on very simple problems. This objective is also accomplished via an analysis of the consequences of neglecting the angular dependence of multigroup cross sections in the solution to the multigroup neutron transport equation. The second objective is accomplished by proposing two new methods: the subgroup method with interference cross sections and ultrafine with simplified scattering. The former uses a fitting method to find the effect of interfering nuclides on the subgroup levels of a primary nuclide, allowing mutual self-shielding effects to be treated natively inside the subgroup method without increasing algorithmic complexity. The latter is a hybrid of the subgroup method and ultrafine methods, using an ultrafine energy mesh on the left hand side of the transport equation with the scatter source of the subgroup method on the right hand side. These two methods are tested in the context of the evaluation framework alongside classical methods. Although it shows promise on some simple problems, the subgroup method with interference cross sections was seen to exhibit shortcomings on problems with many nuclides. Ultrafine with simplified scattering was found to perform very well on all problems in the test suite.
by Nathan A. Gibson.
Ph. D.
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Adam, Ahmad Yahia. "Theoretical Prediction of Nuclear Magnetic Shielding Constants of Acetonitrile." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76769.
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Gauge invariant shielding constants calculations of ?H, ?C, and ??N were calculated for acetonitrile in the gas and liquid phases. Dierent basis sets as well as dierent ab initio and DFT methods were tested to select a time-ecient level of theory with reasonable accuracy. The eect of nuclear motion on the shielding constants was also explored. To investigate solvent eects on the shielding constants of acetonitrile, dierent clusters were extracted from molecular dynamics simulations. Convergence to the experimental values varied for the dierent clusters. The geometry of the central molecule in a cluster played an important factor in reaching convergence.Master of Science
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Landolt, Scott David. "An analysis of airflow patterns inside precipitation gauge shielding." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453573.
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Horner, Kate Elizabeth. "An investigation of molecular properties using magnetic shielding calculations." Thesis, University of York, 2014. http://etheses.whiterose.ac.uk/7391/.
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Isotropic shielding calculations were performed across finely spaced two- and three-dimensional grids positioned through and around a wide range of molecules. These magnetic shielding calculations were used to investigate aromaticity, antiaromaticity and a variety of chemical bonding features. This technique was found to be incredibly sensitive and able to distinguish between bonds of different order as well as bonds of the same order but in different environments. The shielding along the whole bonding region, as well as 1 Å above the bond and cross-sections through the bond, can be used to provide detailed information about the nature of the chemical bonding and the conjugation with the rest of the system. Regions of deshielding have been found around unsaturated nuclei and these areas can be used to determine relative aromaticities as well as degrees of conjugation. The same is true of shielding features found at 1 Å above the molecular plane. Unsaturated heavy atoms also display these deshielded surroundings, but they can be harder to observe. Antiaromatic systems exhibit a dumbbell shaped region of deshielding at the ring centre as well as significantly bent bonding regions which have been found to be a result, primarily, of the antiaromaticity rather than ring strain. H-bonding can also be studied with this technique and it has been found that the shielding on the atoms involved is most informative. In the case of substituted malonaldehydes, the oxygen shieldings were used to determine relative aromaticities in the pseudo rings and, therefore, H-bond strength. The sensitivity and information-rich nature of this technique has proven far superior to existing methods, such as the commonly used nucleus-independent chemical shift (NICS) technique, and therefore has great scope for future applications.
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Khatchadourian, Rafael. "Monte Carlo simulations for neutron shielding in radiotherapy bunkers." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119421.
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Photoneutrons generated in the linac head are a byproduct of the radiotherapy process and can be potentially harmful to clinical personnel. The lack of accuracy associated with analytical photoneutron shielding methods has generated much interest in the Monte-Carlo (MC) method as a more flexible and precise tool for radiotherapy bunker design. The purpose of this work was to use MC simulations to characterize photoneutron fluence, dose, and spectrum throughout various radiotherapy bunker configurations and for various room design features, such as the presence of a maze, a bulkhead, and the addition of borated polyethylene on the maze walls. Three existing rooms at the MUHC and two hypothetical doorless rooms were modelled with the MCNP5 code and using the Visual Editor GUI. The analytical spectrum of an 18 MV linac served as the point source of photoneutrons and was surrounded with a 10 cm radius tungsten sphere placed 100 cm above the isocenter. The next-event estimator variance reduction technique was used and simulations were performed with 20 million particle histories yielding un- certainties under 1%. Physical measurements were also attempted with bubble detectors and a He-3 neutron spectrometer. The latter was unsuccessful because of pulse pile-up caused by the Linac's pulsed mode of operation, whereas the former gave us qualitative information on neutron equivalent dose distribution in the maze and around the linac. Simulation results showed a marked decrease in neutron equivalent dose near the bunker entrance when maze walls are lined with BPE and when a bulk-head is added in the inner maze passage. It was found that the high thermal neutron cross-section of BPE was key in reducing the portion of thermal photoneutrons in the spectrum along the maze. The bulkhead was also useful in reducing photoneutron fluence entering the maze and hence reducing overall photoneutron dose near the entrance of the bunker. Future work will focus on validating simulations with accurate physical measurements and refining the MC code to make it more user friendly and flexible in reproducing bunker geometry.Les photoneutrons générés par le linac sont un produit secondaire de la radiothérapie et peuvent être nuisibles au personnel médical. Le manque de précision des équations analytiques pour le blindage contre les photoneutrons a accéléré le développement des méthodes Monte-Carlo (MC), qui sont considérées plus flexibles et précises pour le design des salles de radiothérapie. L'objectif de cette étude est d'utiliser les simulations MC afin de caractériser le flux, la dose, et le spectre des photoneutrons pour différentes configurations de salles de radiothérapie, telles que la présence d'un corridor, d'un bloc d'atténuation, et l'addition de borate de polyéthyléne sur les murs du corridor. Trois chambres du MUHC et deux chambres hypothétiques ont été modélisées avec le code MCNP5 et le logiciel Visual Editor. Le spectre d'énergie analytique d'un linac opérant à 18 MV a été utilisée comme source ponctuelle de photoneutrons. Ce point est entouré d'une sphére de Tungsténe de 10 cm de rayon positionnée 100 cm au dessus de l'isocentre. L'estimateur du prochain événement est la technique de réduction de variance qui a été utilisée et les simulations ont été effectuées avec 20 millions de particules résultant en des incertitudes inférieures à 1%. Des mesures physiques ont aussi été tentées à l'aide de compteurs à bulles et un spectrométre de neutrons à He-3. Ce dernier n'a pas eu de succés à cause de l'effet d'accumulation du signal pulsé. Les tests avec compteurs de bulles ont permis d'avoir une idée qualitative sur la distribution de la dose équivalente dans le corridor et autour du linac. Les résultats des simulations ont montré une diminution de la dose équivalente de neutron prés de l'entrée de la chambre quand les murs du corridor sont couverts de borate de polyéthyléne et quand un bloc d'atténuation est présent dans le passage de la chambre centrale vers le corridor. Il a été confirmé que la haute probabilité d'interaction des neutrons de basses énergies avec le borate de polyéthyléne est essentiel à la réduction de la portion de photoneutrons à basses énergies à travers le corridor. Le bloc atténuateur contribue aussi à la réduction du flux de photoneutrons entrant dans le corridor et réduit ainsi la dose totale à l'entrée de la chambre. La suite des travaux vise à mettre l'emphase sur la validation des simulations à l'aide de mesures expérimentales et sur le perfectionnement du code MC pour donner plus de flexibilité à l'utilisateur dans la reproduction des salles de radiothérapie.
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Grimaud, Lou. "Magnetic shielding topology applied to low power Hall thrusters." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2046/document.
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Les propulseurs de Hall sont l’une des techniques de propulsion fusée par plasma les plus utilisés. Ils possèdent une impulsion spécifique moyenne et un haut rapport poussé sur puissance qui les rend idéal pour une grande partie des applications commerciales et scientifiques. Une de leurs limitations principales est l’érosion des parois du propulseur par le plasma qui réduit leur durée de vie. La topologie dite “d’écrantage magnétique” est une solution proposée pour prolonger cette durée de vie. Elle est ici appliquée à un petit propulseur de Hall de 200W. Dans cette thèse les règles de mise à l’échelle pour les propulseurs de Hall de la gamme de 100 à 200W sont testées expérimentalement. Un propulseur écranté de 200W est comparé avec un propulseur standard similaire. Le comportement des ions dans ces deux moteurs est extrêmement différent. Des mesures de performance ont été réalisées avec des parois en BN-SiO2 et graphite. Le courant de décharge augmente de 25% avec le graphite dans le propulseur non-écranté. Le résultat et un rendement maximum de 38% avec le nitrure de bore mais de seulement 31% pour le graphite. Le propulseur écranté quant à lui n’atteint que 25% de rendement quel que soit le matériau.Cette baisse de performance dans les petits moteurs écrantés peut être attribuée à un mauvais rendement d’utilisation de l’ergol. Analyses des résultats expérimentaux ainsi que la conduite de simulations suggèrent que cela est dû au fait que la zone d’ionisation ne couvre pas l’ensemble du canal de décharge. Un nouveau design pour un petit propulseur de Hall écranté est proposéHall thrusters are one of the most used rocket electric propulsion technology. They combine moderate specific impulse with high thrust to power ratio which makes them ideal for a wide range of practical commercial and scientific applications. One of their limitations is the erosion of the thruster walls which reduces their lifespan.The magnetic shielding topology is a proposed solution to prolong the lifespan. It is implemented on a small200W Hall thruster.In this thesis the scaling of classical unshielded Hall thrusters down to 200 and 100W is discussed. A 200W low power magnetically shielded Hall thruster is compared with an identically sized unshielded one. The ion behavior inside the thruster is measured and significant differences are found across the discharge channel.Both thrusters are tested with classical BN-SiO2 and graphite walls. The magnetically shielded thruster is not sensitive to the material change while the discharge current increase by 25% in the unshielded one. The result is a maximum efficiency of 38% for boron nitride in the unshielded thruster but only 31% with graphite.The shielded thruster achieves a significantly lower efficiency with only 25% efficiency with both materials.Analysis of the experimental results as well as simulations of the thrusters reveal that the performance difference is mostly caused by low propellant utilization. This low propellant utilization comes from the fact that the ionization region doesn’t cover all of the discharge channel. A new magnetically shielded thruster is designed to solve this issue
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Malkowski, Susan Kate. "MAGNETIC SHIELDING STUDIES FOR THE NEUTRON ELECTRIC DIPOLE MOMENT EXPERIMENT AT THE SPALLATION NEUTRON SOURCE." UKnowledge, 2011. http://uknowledge.uky.edu/physastron_etds/1.
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The neutron Electric Dipole Moment Experiment at the Spallation Neutron Source requires an overall magnetic shielding factor of order 105 to attenuate external background magnetic fields. At present, the shielding design includes an external (room-temperature) multi-layer μ-metal magnetic shield, a cryogenic (4 Kelvin) Pb superconducting shield, and a cryogenic (4 Kelvin) ferromagnetic shield composed of Metglas ribbon. This research determined how to construct a Metglas shield using minimal material that produced axial and transverse shielding factors of ~267 and ~1500. In addition, the μ-metal and Metglas shields were modeled using finite element analysis. The FEA model includes external coils and their effect on the residual magnetic fields. This study will help with the design of the shielding.
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Gravelle, Luc B. "Shielding effectiveness of enclosures predicted via the finite element method." Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5950.
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This thesis presents the application of the numerical finite element method (FEM) in solving the electromagnetic shielding effectiveness of enclosures. The emphasis is placed on the solution of time-dependant varying fields, as for example an NEMP or a digital signal, directly in the time domain. Previous numerical prediction of shielding effectiveness on complicated structures have been analyzed with the FEM in the frequency domain whereas no study, to the author's knowledge, has been conducted in the time domain. EMP type varying fields impinging on enclosures are studied with this new CAD tool and compared to the analytical solution of a simple parallel plate shield. Following the validation of the technique for the one-dimensional case, the shielding effectiveness of a more general two dimensional structure is investigated and validated with the introduction of a second numerical technique, TLM. Included in this study are two user-friendly, general, interactive Fortran codes. One analyzes the field penetration through rectangular enclosures (with apertures) of various EMP type plane waves (TE or TM) having a certain angle of incidence on enclosures. The another analyzes the field radiation from enclosures (with apertures) due to currents in signal lines.
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Chen, Jue. "Shielding characteristics of a commercial 19-inch rack-based cabinet." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Chen_09007dcc803e6a55.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 5, 2008) Includes bibliographical references (p. 82).
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Peterson, Robert E. "Shielding requirements for an energy-recovery LINAC Free Electron Laser." Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/10671.
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Many Free Electron Lasers (FELs) utilize high current, high energy electron beams. Inevitably, a small fraction of the electrons in the beam will exist outside the core beam; these electrons are referred to as beam halo. The halo electrons will travel down an FEL's transport system with the core electrons; any portion of those halo electrons that intercept transport system components can generate radiation that is harmful to the operating personnel. The amount of shielding that is required to keep personnel safe from radiation exposure is evaluated as a function of the lost halo current. Using the modeling software FLUKA, an analysis is presented describing the amount of necessary shielding for a given shielding material.
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Ng, Leo Wai-Tsun. "Design and acoustic shielding prediction of hybrid wing-body aircraft." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/51635.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Includes bibliographical references (p. 99-101).
Recent research and developmental efforts in aircraft design have focused on the growing concerns about the environment impact of aviation and the rising costs of fuel. Under NASA's N+2 subsonics fixed-wing project, hybrid-wing-body (HWB) aircraft are investigated with the goal to meet the N+2 noise, fuel burn, and emissions requirements. As part of the N+2 program, this thesis is focused on the design and assessment of an HWB aircraft and the development of a prediction method for turbomachinery noise shielding. Based on MIT's previous experience in the Silent Aircraft Initiative, the SAX-40 aircraft concept was further developed into the N+2 HWB aircraft. The design effort resulted in two aircraft configurations: the N2A aircraft with conventional podded engines, and the N2B aircraft with a distributed propulsion system embedded in the airframe. The initial performance assessment shows that the N2A and the N2B aircraft can both meet the N+2 fuel burn goal and that the N2A aircraft is 5.7 EPNdB short of the noise goal. Also, the assessment revealed that current noise prediction methods cannot model the advanced propulsion system of the N2B aircraft, requiring the development of noise assessment tools for advanced engine-airframe configurations. NASA's Aircraft Noise Prediction Program employs the barrier shielding method to predict the airframe shielding of engine noise. However, it is an empirical formulation for straight edges and thus it is not appropriate for the planform shape of an HWB aircraft.
(cont.) At the same time, high fidelity methods such as boundary element methods and ray tracing methods are too computationally expensive if used in the early aircraft design and assessment stage. A compromise is the previously formulated diffraction integral concept based on the Maggi-Rubinowicz representation of Kirchhoff's diffraction theory. The diffraction integral method was implemented and applied to the N2A and the N2B aircraft. A noise reduction of over 20 dB in OASPL due to airframe shielding was predicted, demonstrating the shielding benefit of the HWB configuration. This shielding method is shown to be applicable to any aircraft configuration and planform geometry. The contributions of this thesis are the design of an HWB aircraft to be used as a platform for the development and evaluation of advanced analysis methods. In addition, a fast and improved-fidelity method for noise shielding prediction was developed, applicable to conventional and advanced airframe configurations such as, for example, the N2A and the N2B HWB aircraft.
by Leo Wai-Tsun Ng.
S.M.
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Di, Xiaojun. "Magnetic shielding using electrical steel panels at extremely low frequencies." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54723/.
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A new test method and finite element modelling were used to investigate how material properties of electrical steel panels affect their shielding factors. Both experiment and modelling showed an improved DC shielding factor with increasing thickness for the shields of similar magnetic properties. Enhanced shielding by the eddy currents was demonstrated by testing the same steel panel under AC and DC field conditions. Comparing to non-oriented steel panels, a decreasing shielding factor with the frequency from 50 Hz to 400 Hz was found for grain-oriented steels. This was also investigated by measuring magnetizations along rolling and transverse directions within the panels. It was found that measured shielding factors of double-layer shields with two grain-oriented steel panels could be improved significantly with orthogonally arranged rolling directions. Different shielding factors were found by placing different panel closer to the field source in the test of double-layer shields formed by one grain-oriented and one non-oriented steel panels. Although little shielding effect of aluminium panels are found at 50 Hz, adding the same aluminium panel with single electrical steel shield was dramatically improved the shielding. The magnetization of shielding sample at AC conditions has been modelled and measured. The magnetization was found very low due to the demagnetizing effect. Therefore, the permeability at very low magnetization range has a large effect on the magnetic shielding factors of the steel panels. Drilled hole as a defect in the panel and overlap of the panels have been tested with the new test method. Small hole in the panel would not cause the degradation of the overall shielding factor of the shield rooms. Overlap was proved to be an effective way to reduce the flux leakage at the joints between the panels The difference between the computed and measured shielding factors is addressed by analysing the capability of the solver used in the finite element modelling and the uncertainty of the measured B-H characteristic of the material as the input to the model.
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Girard, Guillaume. "Shielding effectiveness estimation." Thesis, 2002. http://spectrum.library.concordia.ca/1816/1/MQ72908.pdf.
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The application of SE estimation methods for small enclosures is the main subject of this thesis. Three Shielding Effectiveness estimation methods are presented; Empirical, Experimental and Numerical Simulation. SE estimates have been compared with SE measurements showing close correlations between the numerical simulation and the experimental results. It has been proved that the SE of an empty enclosure, compared with that of an enclosure containing a printed circuit board, differs due to volume change, herein Q variation. Conclusions are formulated in terms of further works to be accomplished in order to determine better measurement and simulation models for Shielding Effectiveness estimates.
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Chen, Ming-Jer, and 陳明哲. "Electromagnetic Shielding Wood Veneer Composites." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/31151076246537875147.
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碩士國立屏東科技大學
森林系
93
Abstract Student ID:M8812014 Title of thesis:Electromagnetic Shielding Wood Veneer Composites Total page:61 Name of Institute:Department of Forestry Graduate date:June, 22 2005 Degree Conferred:Master Name of student:Chen, Ming-Jer Adviser:Lin, Cheng-Jung Huang, Yaw-Fuh The contents of abstract in this thesis: The main purpose of this study was aimed at developing a method for manufacturing electromagnetic interference shielding wood veneer composites (WVC). In the study, the thin film type of electro-conductive materials (copper web, copper foil, aluminum foil and carbon fiber woven cloth) were selected for composing with sawn veneer of wood oil tree and red oak, and with rotary cut veneer of mersawa to fabricate wood veneer composites (WVC), firstly. Then, electro-conductive powder of carbon black, ferric oxide, copper powder, aluminum powder and bamboo charcoal powder prepared with different carbonization temperature of 900, 1100, 1300 and 1500℃ were applied to replace of wheat flour in the glue formulation. And, three types of veneer mentioned above were used to fabricate WVC again. Finally, the physical properties and electromagnetic interference shielding properties of WVC were evaluated, also. The results show that the MOR, MOE and impact strength of WVC which was composed with the thin sheet of electro-conductive material and mersawa rotary cut veneer or red oak sawn veneer were enhanced but the one of wood oil tree. The electromagnetic interference shielding effectiveness (insertion loss) of the WVC composed with one sheet of the thin electro-conductive material and mersawa veneer has the largest insertion loss value from 30-40 dB between the measuring frequency range of 1.5-2.7 GHz. Meanwhile, the WVC composed with two sheets of metal materials has higher electromagnetic interference shielding effectiveness (about 40-60 dB). But, the return loss of WVC mentioned above was very small. Therefore, the mechanism of electromagnetic interference shielding effectiveness of those materials was to reflect the wave back, not to absorb them. The physical properties of LVL bonded with glue which was formulated with UF and electro-conductive powder instead of wheat flour are not influenced at all as the filler dosage between the general level of 10 to 20%. As for the electromagnetic interference shielding effectiveness of this type of LVL, the insertion loss is increased with the filler dosage and larger than that of the controlled one. The return loss is decreased with the filler dosage and smaller than that of the controlled one. Key words： Insertion loss, return loss, wood veneer composites, electromagnetic interference shielding effectiveness.
48
Jalali, Mohsen. "Improving Electromagnetic Shielding with Metallic Nanoparticles." Thesis, 2013. http://spectrum.library.concordia.ca/977537/1/Jalali_PhD_F2013.pdf.
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Due to major advantages (e.g. weight saving, maintenance advantages), the airframe manufacturers use more and more Polymer Matrix Composites (PMCs) in different parts of aircraft structures. But PMCs have the substantial disadvantage of low conductivity and therefore low Electromagnetic (EM) Shielding. Electromagnetic Interference (EMI) sources are all around and inside aircraft and can potentially threaten the immunity of the aircraft. Metallic meshes have been used to overcome this deficiency. However at high frequencies (UHF, SHF), most of the metallic mesh loses the performance. Regrettably most of the present and upcoming systems onboard of aircraft are functional in the mentioned range of frequencies. Furthermore, passengers are using more and more Personal Electronic Devices (PEDs) onboard of aircraft. Interference caused by PEDs are also in the same range of frequencies. Measured susceptibility caused by PEDs is higher in composite aircraft comparing to metallic one. To develop this disadvantage of composite aircrafts, design of a new lightweight shield, particularly for aeronautic applications, is needed. Metallic nanoparticles have a great potential to be used as new EM shields for aerospace applications. The promising results of this work encourage the designers to use metallic nanoparticles as a new shield for protection of composite aircrafts.
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YI, LIU CHIA, and 劉佳益. "Shielding of Power Frequency Magnetic Field." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/65259132089781498978.
Full textAbstract:
碩士國立臺灣科技大學
電機工程系
91
This thesis is to study the magnetic-field shielding methods caused by electric power lines. The finite element based simulation package, FLUX3D, can be used to establish the simulation model and to evaluate the magnetic-field shielding effect of aluminum plates, silicon-steel plates and Amumetal. It is desired to reduce magnetic-field interferences due to three-phase currents. For the improvement-scheme of power frequency magnetic-field, we can concentrate power lines arrangement and have suitable phase arrangement. So that the magnetic-field flux density due to three-phase current can be canceled by each other. Finally, we can use appropriate metal plates to shield magnetic-field, and to reduce magnetic-field interference furthermore. We should find the better combination shielding methods of aluminum plates, silicon-steel plates and Amumetal.
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Chiang, Chih-Ming, and 蔣志明. "Metallized Plastic Pellets for EMI Shielding." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/20340837286945847042.
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