Bibliografie tematiche / Reflector

Letteratura scientifica selezionata sul tema "Reflector"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 9 marzo 2023

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Articoli di riviste sul tema "Reflector"

1

Tunalioglu, Nursu, e Cemali Altuntas. "An experimental test for detecting effective reflector height with GPS SNR data". Earth Sciences Research Journal 26, n. 1 (11 maggio 2022): 13–22. http://dx.doi.org/10.15446/esrj.v26n1.87003.

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Abstract (sommario):
This study aims to estimate effective reflector heights and height differences using the basic geometrical principle of multipath theory by controlling the signal quality for estimations. The geometry of the reflecting signal allows computing the effective reflector height, which is extracted from where the signal reflects on the ground and arrives at the GPS antenna phase center. To achieve that, an experimental case with two stations was conducted in the snow-free environment and GPS receivers were mounted on reflectors, which allowed to measure daily in-situ reflector heights and artificial decrement variations. The reflections from the roof surface were tracked with the first-Fresnel zones. To validate the estimated reflector heights in a controlled test environment, twelve different combinations within four simulated scenarios as a combination of decrement values have been implemented and accuracy analysis was performed. Here, a vertical shift procedure on reflectors was applied. Meanwhile, the vertical shift amount was tracked in each computation to determine which reflected signal could be able to use for assigning reflector height as effective. Comparisons of the estimated heights and in-situ measurements show congruency with ±1.2 cm to ±8 cm accuracy. The best overall accuracy of the model among the four scenarios is computed as ±2.2 cm. When the vertical shift decrements are considered, the RMSE values are estimated within ±2.92 cm to ±3.96 cm. Although the RMSEs of the differences show a good agreement with estimated reflector heights, it is found that some reflector height estimations are statistically insignificant.
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2

Liu, Weixu, Zhifeng Tang, Fuzai Lv, Yang Zheng, Pengfei Zhang e Xiangxian Chen. "Numerical Investigation of Locating and Identifying Pipeline Reflectors Based on Guided-Wave Circumferential Scanning and Phase Characteristics". Applied Sciences 10, n. 5 (5 marzo 2020): 1799. http://dx.doi.org/10.3390/app10051799.

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Abstract (sommario):
The methodology based on reflected guided-wave by a reflector associated with an increase or a decrease in the cross-sectional area has the challenge of determining their location and identity. This paper presents a numerical investigation of a method for locating and identifying the reflector based on guided-wave circumferential scanning and phase characteristics. To determine the axial and circumferential positions of the reflector within the pipeline, the procedures of the guided wave-based circumferential scanning were presented, including data preprocessing, median filter, image smoothing and binary processing. Through theoretical analysis, we obtained the phase relationship between the guided-wave excitation signal and reflection signals generated by a reflector, such as corrosion, crack, weld and support, which caused the change in the cross-sectional area. Consequently, an algorithm based on the phase characteristics was proposed to determine the change and type of reflector. The spatial distances were calculated between the guided wave excitation signals with different phases and the concerned reflection signals, subsequently identifying the change and type of the reflector by comparing the distance values. An identification index named the reliable index for the character of the reflector (RICR) was defined to evaluate the reliability of the predicted results. Numerical and finite element simulation validations of the proposed method were performed. It has been found that if RICR was larger than 1.05, the results predicting the reflector type were reliable. The proposed method was found to be superior relative to the conventional correlation coefficient method according to the numerical results. Finally, the simulation results demonstrated that the proposed method could be potentially applied for locating and identifying reflectors in pipelines.
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3

Bube, Kenneth P., e Robert T. Langan. "Resolution of slowness and reflectors in crosswell tomography with transmission and reflection traveltimes". GEOPHYSICS 73, n. 5 (settembre 2008): VE321—VE335. http://dx.doi.org/10.1190/1.2969777.

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Abstract (sommario):
We sometimes encounter situations in seismic imaging in which knowing the position of key reflectors between wells would be very useful. In many crosswell data sets, both transmission and reflection traveltimes for selected reflectors can be picked. We investigated the possibility that transmission-plus-reflection crosswell traveltime tomography can determine the position of these reflectors with a high level of accuracy, thereby providing an independent way of verifying (and perhaps improving) the position of these reflectors obtained from crosswell reflection imaging. We studied the effect of combining reflection traveltimes for selected reflectors with transmission traveltimes on the resolution of the interwell slowness field and depth determination of selected reflectors. We found that theoretically, the position of reflectors is determined uniquely from transmission and reflection traveltimes in a linearized continuum formulation ofcrosswell tomography. We also computed diagonal elements of the resolu-tion matrix for two crosswell geometries based on field experiments conducted in a west Texas oil field to see what effect noise has on the accuracy of our determination of reflector depths. These computational results indicate that reflector positions are indeed very well determined for these geometries, with expected errors of [Formula: see text] of the well spacing when noise in traveltimes is [Formula: see text]. Because reflector-position parameters are so well determined, including reflection traveltimes does not degrade the resolution of the slowness field as a result of introducing additional reflector-depth parameters. Actually, the resolution of the slowness field, particularly near reflectors, improves by including reflection traveltimes, in spite of the fact that we must solve for these additional depth parameters. The improvement in slowness resolution should provide velocity models that can yield more accurate reflection images.
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4

Huang, Wei, Ningye He, Renxia Ning e Zhenhai Chen. "Wideband Reflector and Analogue Electromagnetically Induced Reflection in Metamaterials". Crystals 11, n. 8 (19 agosto 2021): 985. http://dx.doi.org/10.3390/cryst11080985.

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Abstract (sommario):
Metamaterials are highly demanded for advanced applications in absorbers, sensors, and filters. However, metamaterial reflectors, especially broadband reflectors, remain challenging. In this paper, we theoretically investigate a wideband metamaterial reflector which consists of cross shaped graphene strips and a silica (SiO2) substrate. The cross shaped graphene strips are coated on the top of the structure, and the cross shape rotated 45° graphene strips are spun on the bottom of it. The calculated reflection can be tuned through length and width of the graphene strips. By comparison, not only broadband reflection but also analogue electromagnetically induced reflection (EIR) can be realized. Moreover, the structure can generate a bi-directional broadband reflection of insensitive polarization. This kind of bi-directional reflector at microwave frequencies is obtained because the top and bottom graphene strip structures are similar. We employ the electric field distribution of the designed structure to elucidate the mechanism of the analogue EIR effect. We further discuss the influence of incident angle on the analogue EIR effect. Such a bi-directional reflector can be potentially applied to a wideband reflector, antenna, and sensor.
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Kryuchkov, Igor V., Eduard O. Mozharov e Anna I. Skachkova. "Special aspects of modulation RCS measurement in Ka-band". ITM Web of Conferences 30 (2019): 11012. http://dx.doi.org/10.1051/itmconf/20193011012.

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Abstract (sommario):
Radar reflectors are used as standards for radioelectronic devices calibration, as navigation beacons for air and naval traffic control and for radar visibility increase. Controlled (parametric) reflectors change reflected signal characteristics. This leads to appearance of easily detectable additional frequency components on modulation frequency. Ka-band parametric reflector design, consisting of horn reflector and phase switch 0°/180° board, is suggested. Technique of parametric reflector modulation RCS measurement, using complex envelope of reflected signal in every phase switch state, is suggested. Measuring bench description is given. Comparative analysis of theoretical calculations and experimental results is carried out. Accuracy of modulation RCS measurement according to the said technique is obtained experimentally. Measurements accuracy constraints are detected.
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6

Parker, Andrew R., David R. Mckenzie e Maryanne C. J. Large. "Multilayer reflectors in animals using green and gold beetles as contrasting examples". Journal of Experimental Biology 201, n. 9 (1 maggio 1998): 1307–13. http://dx.doi.org/10.1242/jeb.201.9.1307.

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Abstract (sommario):
The light reflectors in the beetles Calloodes grayanus and Anoplognathus parvulus are examined. Contrasting multilayer reflectors are revealed. Calloodes grayanus appears a weak green colour, matching its background leaves, while A. parvulus is strongly metallic-gold coloured. The former reflection is diffuse, as the result of a structure causing scattering that overlies the multilayer reflector, whereas the latter reflection is strongly directional. The green colour of C. grayanus is achieved by a multilayer reflector with a fixed spatial periodicity, here termed 'regular', which is far removed from the quarterwave, or physically 'ideal', condition. The gold colour of A. parvulus is achieved by a type of reflector which involves systematically changing optical thicknesses of the component layers with depth in the structure. A layer of melanin underlies the reflector of C. grayanus to absorb the transmitted portion of light and prevent its back-reflectance, which would otherwise alter the green colour. The resultant structural reflectance from C. grayanus effectively matches green pigments, which are rare in beetles.
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7

Knapp, R. W. "Fresnel zones in the light of broadband data". GEOPHYSICS 56, n. 3 (marzo 1991): 354–59. http://dx.doi.org/10.1190/1.1443049.

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Abstract (sommario):
The investigation of zero‐offset response to circular reflectors of increasing Fresnel zone size shows that reflection response is a constant and is independent of reflector size, except when the reflector diameter is so small that the diffractions interfere with the primary reflection. The extent of this effect is dependent upon vertical resolution and the time separation of the primary reflector and the diffraction. Interference occurs for reflectors smaller in diameter than the first Fresnel zone. Migration removes this interference. For broadband data the Fresnel zone solution breaks into two parts: the primary reflector and the edge‐effects diffractor. With broadband seismic data, reflections and diffractions separate in time, except at locations near faults or very small bodies. Reflections are the seismic response to interlayer discontinuity and are independent of reflector size. Diffractions are the seismic response to lateral discontinuities and edges and depend on proximity to—and geometry of—the edge. Except in the locale of an edge, broadband reflections and diffractions are separated physically on the section and mentally by the interpreter. Furthermore, standard CMP processing attenuates diffractions, especially when CMP lateral offset is some distance from the diffractor.
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8

Le, Hien-Thanh, Lanh-Thanh Le, Ming-Jui Chen, Thanh-Hong Lam, Hsing-Yuan Liao, Guo-Feng Luo, Yung-Cheng Li e Hsiao-Yi Lee. "ECE/SAE Dual Functional SuperPin Plus Curved Reflex Reflector by Use of New Structured Corner Cubes". Applied Sciences 10, n. 2 (8 gennaio 2020): 454. http://dx.doi.org/10.3390/app10020454.

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Abstract (sommario):
We propose and demonstrate, using optical experiments, a new reflex reflector structure called SuperPin Plus. The structure is composed of special pin groups with dihedral-angle offsets in corner cubes. One of the specular features brought by this new design is that it can comply with both the US SAE (US Society of Automotive Engineers) standard and the EU ECE (Economic Commission for Europe) standard, so that manufacturing costs of reflex reflector for both European and American automobile markets can be reduced. By using genetic algorithms for optimization, the angles and the positions of the pins, which are the building elements of corner cube reflectors, serve as the parameters to tune up the performance of the SuperPin Plus curved reflex reflector. Compared with conventional ECE flat regular retro-reflectors, we found that not only can we achieve a 41% higher retro-reflection efficiency with the ECE SuperPin Plus flat reflex reflector, but that SuperPin Plus can also act as a reflex reflector within SAE standards. In addition, we demonstrate that the retro-reflection efficiency is 30.5% higher (SAE standard) and 42.7% higher (ECE standard), and that a 32% increase in working area can be achieved if double pin groups are used to construct the corner cubes instead of a single pin arrangement, in a curved SuperPin Plus reflex reflector.
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9

Lechte, Carsten, Walter Kasparek, Burkhard Plaum, Fritz Leuterer, Martin Schubert, Jörg Stober e Dietmar Wagner. "Simulation of Polarising and Reflector Gratings for High Power mm Waves". EPJ Web of Conferences 203 (2019): 04010. http://dx.doi.org/10.1051/epjconf/201920304010.

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Abstract (sommario):
High power mm waves for fusion plasma heating need to be elliptically polarised to ensure good absorption in the plasma. In some scenarios, electron cyclotron resonance heating (ECRH) at higher harmonics (X3 and O2) is used, but this has significant shine-through because of low single pass absorption. Grating reflectors at the inboard strike point form a holographic mirror that reflects the beam back into the plasma. This paper investigates the optical properties and ohmic losses of both the polariser and the reflectors with the 3D fullwave code IPF-FD3D. The reflection properties of a reflector for ASDEX Upgrade and the improved ohmic losses of a waveguide polariser were confirmed.
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10

TYGEL, MARTIN, JÖRG SCHLEICHER, LÚCIO T. SANTOS e PETER HUBRAL. "THE KIRCHHOFF–HELMHOLTZ INTEGRAL PAIR". Journal of Computational Acoustics 09, n. 04 (dicembre 2001): 1383–94. http://dx.doi.org/10.1142/s0218396x01001467.

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Abstract (sommario):
The Kirchhoff–Helmholtz integral models the reflected acoustic wavefield by an integration along the reflector over the incident field multiplied by the specular plane-wave reflection coefficient. Based on the structural relationships between the reflector and the reflection-traveltime surface, we design an asymptotic inverse Kirchhoff–Helmholtz integral. Analogously to the forward integral, the proposed inverse consists of an integration along the reflection-traveltime surface over the recorded reflected field. We show that the new inverse integral asymptotically recovers the input to the standard Kirchhoff–Helmholtz integral, that is, the reflector position and the reflection coefficients along it. A simple numerical example demonstrates the inverse relationship between the proposed and the standard Kirchhoff–Helmholtz integrals. In this way, a new technique for kinematic (positioning) and dynamic (amplitude) wavefield inversion becomes available. This is realized by means of an integral operation that is most naturally related to its counterpart Kirchhoff–Helmholtz integral.
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Tesi sul tema "Reflector"

1

Mousari, Bafrooei Seyed Pedram. "Reflector feeds for large adaptive reflector antennas". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ57513.pdf.

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2

Durnan, Gregory J. "Parasitic Feed Elements for Reflector Antennas". Thesis, Griffith University, 2005. http://hdl.handle.net/10072/368077.

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Abstract (sommario):
The use of parasitic wire dipoles are examined when placed in the proximity of a focused dipole feed in a parabolic reflector antenna. These parasitic elements are rotated around the feed dipole and a search is performed for the ideal positioning so as to yield maximum radiated power and main beam shift in order to develop a novel form of angle diversity. In addition a comparison is made between 2 element dipole feed structures and linearly and circularly polarised patch feed structures. In order to analytically model the structure, mutual coupling between feed elements is calculated taking into account a varying reflection coe±cient due to an impedance mismatch between the transmission line and driven element. An analytical treatment of the calculation of the radiated co-polar and cross-polar feed pattern is presented in addition to the projected field at the reflector surface. A comparison is made to the results presented by E.M.T Jones in the 1954 IRE Transactions of Antennas and Propagation paper entitled 'Paraboloid Reflector and Hyperboloid Lens Antennas'. A theoretical treatment of the reflected field and far field radiation pattern is then presented using the methods of Geometrical Optics, Physical Optics and Fourier analysis. The author derives analytical equations for multiple element incident feed fields and surface current equations for half wave feeds of arbitrary position and number. The fndings are confirmed using a comparison of three methods. These are; original code developed from analytical derivations, the NEC2 Method of Moments using a meshed reflector model and finally, by experimental methods. Analysis of a 30cm 0.4 F/D prime focus reflector at 3GHz using a 2 element feed yields up to 2dB gain over a single dipole feed when the element is displaced either laterally or at 60 or 120 degrees from the feed axis. The optimum offset from the driven element is in the 0.4 to 0.6¸ range. Maximum beam shift for this structure at the half power points is shown to be approximately 10 degrees. When designed as a low-cost system with undemanding polarisation requirements the structure presented provides an easily implemented or retrofitted alternative to multiple antenna diversity solutions.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Microelectronic Engineering
Full Text
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3

Shen, Bing. "Multiple reflector scanning antennas". Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40108.

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4

Wang, Yang. "Time-modulated reflector-arrays". Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/8510/.

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Abstract (sommario):
This PhD thesis introduces the time-modulated reflector-arrays which are a hybrid of conventional time-modulated array (TMA) systems and reflectarrays. The TMRAs use a similar layout of reflectarray feed by a source. Compared to conventional phased arrays, reflectarrays and time-modulated arrays, a TMRA is potentially simpler to implement in hardware as it does not need a complicated feeding network or the use of the phase shifting units. Instead of phase shifting units, TMRAs use discrete time-switching to achieve beamforming functions. The concept and operating mechanism of the TMRA is explained using a simple model based on isotropic scatterers. A more sophisticated TMRA based on an 8 element array of PIN-diode controlled bow-tie dipole elements is designed and analysed using a full-wave commercial simulator. A hardware implementation of the bowtie dipole TMRA system, including control circuitry, is also described and measured data is presented. The simulated and measured results confirm that the time-modulated reflector array system performs the required function of harmonic beam steering. Moreover, TMRAs can provide functions such as sidelobe suppression and adaptive beamforming. The thesis also provide solutions to the challenges of TMRAs such as low system efficiency and phases variances caused by feeding paths. Overall TMRAs combine the benefits of conventional TMA systems and reflectarrays. They can provide similar functions of conventional TMAs, phased arrays and reflectarrays without the need of expensive phase shifters and lossy transmission lines. This makes TMRAs a very good candidates in applications over millimetre-wavelength frequency band.
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5

Mas, Baixeras Albert. "Optimization of inverse reflector design". Doctoral thesis, Universitat de Girona, 2011. http://hdl.handle.net/10803/22705.

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Abstract (sommario):
Aquesta tesi presenta un nou mètode pel disseny invers de reflectors. Ens hem centrat en tres temes principals: l’ús de fonts de llum reals i complexes, la definició d’un algoritme ràpid pel càlcul de la il•luminació del reflector, i la definició d’un algoritme d’optimització per trobar més eficientment el reflector desitjat. Les fonts de llum estan representades per models near-field, que es comprimeixen amb un error molt petit, fins i tot per fonts de llum amb milions de raigs i objectes a il•luminar molt propers. Llavors proposem un mètode ràpid per obtenir la distribució de la il•luminació d’un reflector i la seva comparació amb la il•luminació desitjada, i que treballa completament en la GPU. Finalment, proposem un nou mètode d’optimització global que permet trobar la solució en menys passos que molts altres mètodes d’optimització clàssics, i alhora evitant mínims locals.
This thesis presents new methods for the inverse reflector design problem. We have focused on three main topics: the use of real and complex light sources, the definition of a fast lighting simulation algorithm to compute the reflector lighting, and the definition of an optimization algorithm to more efficiently find the desired reflector. The light sources are represented by near-field datasets, that are compressed with a low error, even with millions of rays and for very close objects. Then, we propose a fast method to obtain the outgoing light distribution of a reflector and the comparison with the desired one, working completely in the GPU. Finally, a new global optimization method is proposed to search the solution in less steps than most other classic optimization methods, also avoiding local minima.
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6

Stewart, Scot Howard. "Multiple feed reflector antenna analysis". Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/94472.

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Abstract (sommario):
A method of calculating the secondary pattern of a reflector illuminated by a feed array is developed. Geometrical optics is used to determine the incident field via a coordinate transformation approach. The incident field from each element is superimposed to form the total field used in finding the surface currents of the physical optics radiation integral. The technique allows each element to be arbitrarily excited, positioned and oriented. The element patterns may be different allowing mutual coupling to be included.
M.S.
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7

Fournier, Florian. "FREEFORM REFLECTOR DESIGN WITH EXTENDED SOURCES". Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3146.

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Abstract (sommario):
Reflector design stemmed from the need to shape the light emitted by candles or lamps. Over 2,000 years ago people realized that a mirror shaped as a parabola can concentrate light, and thus significantly boosts its intensity, to the point where objects can be set afire. Nowadays many applications require an accurate control of light, such as automotive headlights, streetlights, projection displays, and medical illuminators. In all cases light emitted from a light source can be shaped into a desired target distribution with a reflective surface. Design methods for systems with rotational and translational symmetry were devised in the 1930s. However, the freeform reflector shapes required to illuminate targets with no such symmetries proved to be much more challenging to design. Even when the source is assumed to be a point, the reflector shape is governed by a set of second-order partial non-linear differential equations that cannot be solved with standard numerical integration techniques. An iterative approach to solve the problem for a discrete target, known as the method of supporting ellipsoids, was recently proposed by Oliker. In this research we report several efficient implementations of the method of supporting ellipsoids, based on the point source approximation, and we propose new reflector design techniques that take into account the extent of the source. More specifically, this work has led to three major achievements. First, a thorough analysis of the method of supporting ellipsoids was performed that resulted in two alternative implementations of the algorithm, which enable a fast generation of freeform reflector shapes within the point source approximation. We tailored the algorithm in order to provide control over the parameters of interest to the designers, such as the reflector scale and geometry. Second, the shape generation algorithm was used to analyze how source flux can be mapped onto the target. We derived the condition under which a given source-target mapping can be achieved with a smooth continuous surface, referred as the integrability condition. We proposed a method to derive mappings that satisfy the integrability condition. We then use these mappings to quickly generate reflector shapes that create continuous target distributions as opposed to reflectors generated with the method of supporting ellipsoids that create discrete sets of points on the target. We also show how mappings that do not satisfy the integrability condition can be achieved by introducing step discontinuities in the reflector surface. Third, we investigated two methods to design reflectors with extended sources. The first method uses a compensation approach where the prescribed target distribution is adjusted iteratively. This method is effective for compact sources and systems with rotational or translational symmetry. The second method tiles the source images created by a reflector designed with the method of supporting ellipsoids and then blends the source images together using scattering in order to obtain a continuous target distribution. This latter method is effective for freeform reflectors and target distributions with no sharp variations. Finally, several case studies illustrate how these methods can be successfully applied to design reflectors for general illumination applications such as street lighting or luminaires. We show that the proposed design methods can ease the design of freeform reflectors and provide efficient, cost-effective solutions that avoid unnecessary energy consumption and light pollution.
Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
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8

Parkinson, Joseph R. "The analysis of microwave reflector antennas". Thesis, University of Birmingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342108.

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Sterr, U. "Radiation characteristics of corner reflector antennas". Thesis, Queen Mary, University of London, 1998. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1686.

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Abstract (sommario):
This thesis presents a study of the radiation characteristics of corner reflector antennas. The influence of the design parameters on the radiation characteristics are assessed using an analytical method and the Finite Difference Time Domain (FDTD) method. The FDTD method for corner reflector antennas which are electrically small to medium sized antennas is developed in detail. The important subject of the Absorbing Boundary Conditions (ABCs) is studied including a study of Mur ABC and Perfectly Matched Layers. It is shown that both methods reduce the reflections from the boundaries sufficient so that the far-field radiation pattern can be computed accurately. An analytical solution to compute the far-field radiation pattern for infinite comer reflector antennas is derived and used to understand the radiation mechanisms. Based on those results, the FDTD method is used to conduct a parametric study on finite sized comer reflector antennas. Experimental antennas have been built and measured in order to verify the computational predictions. Very good agreement is reported The novel idea of a variable beam-width comer reflector antenna is developed and practical designs of such an antenna are presented. The principle is to design the comer reflector antenna such that the beam-width of the antenna can be precisely modified. Data on the gain and beam-width are presented. This has been done both by computational and by an experimental model. The influence on the performance of the comer reflector antenna when substituting the solid reflector plates by rods has been investigated. The computational predictions have been verified by measurements of an experimental antenna. Very good agreement has been achieved. III[ The possibility of modifying the shape of the comer reflector antenna is investigated. It is shown that a modified comer reflector antenna with less depth produces the same far-field pattern as a standard corner reflector antenna. It is also shown that the performance of small aperture size corner reflector antennas is superior to a cylindrical parabolic reflector antenna.
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10

PEREIRA, LUIS CLAUDIO PALMA. "ASYMPTOTIC ANALYSIS OF SHAPED REFLECTOR ANTENNAS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1988. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8374@1.

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Abstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho apresenta uma nova técnica para aproximação de uma superfície refletora definida numericamente, i.e., por pontos fornecidos pelo processo de síntese da antena. As limitações inerentes às técnicas usuais são aqui eliminadas pela utilização de Pseudo-Splines Quínticas que interpolam uma distribuição arbitrária de pontos por uma superfície suave, com derivadas primeiras e segundas contínuas, assegurando uma representação única para o domínio de interesse. O procedimento é, então, aplicado ao subrefletor modelado de uma antena Cassegrain, com subseqüente cálculo do campo eletromagnético espalhado, permitindo uma análise detalhada de sua aplicabilidade. Uma teoria assintótica uniforme de difração é, também, aqui desenvolvida de modo a acomodar o espalhamento de feixes Gaussianos, descritivos, em freqüências altas, do diagrama de irradiação de alimentadores comumente empregados em sistemas refletores, por superfícies condutoras, através do rastreamento do campo eletromagnético ao longo de raios no espaço complexo. A análise do problema canônico (difração por semi-plano) estabelece as particularidades do método e a comparação com a solução rigorosa existente comprova sua acurácia, permitindo a extensão a problemas tridimensionais vetorais. A teoria Complexa da Difração, assim formulada, é, então aplicada ao cálculo do campo espalhado por diferentes geometrias de antenas refletoras, ilustrando a versatilidade do método bem como suas limitações.
In order to evaluate the electromagnetic field scattered by shaped reflector antennas, one has to fit a surface to a set of points furnished by a synthesis technique. A new method, capable of interpolating arbitrarily located data points by a smooth surface is here presented. The interpolating function, called Quintic Pseudo-Spline, has continuous first and seconde order derivatives and yields a unique representation for the entire domain. The method is tested on the shaped subreflector of a Cassegrain antenna providing a thorough investigation of its applicability. Also, an uniform asymptotic theory of diffraction is derived in order to analyse the scattering of Gaussin beams, descriptive of the high-frequency radiation pattern of feed horns commonly employed in reflector systems, by conducting surfaces with edges. The constraints inherent to usual methods of analysis are hereby avoided by tracking these beam-type fields along straight rays in a complex coordinate space. Investigation of the canonical problem of scattering of a Gaussian beam by a conducting half-plane establishes the characteristics of the complex ray diffraction process. Comparison of the results thus obtained with the rigorous solution reveals the accuracy of the proposed theory and permits its extension to the three-dimensional vector problem. The resulting Complex Theory of Diffraction is then applied to the evaluation of the scattered field for several reflector antenna geometries, illustrating the versatility of the method as well as its limitation.
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Libri sul tema "Reflector"

1

Geological Survey (U.S.), a cura di. Radar reflector detection. Reston, Va: U.S. Dept. of the Interior, U.S. Geological Survey, 1985.

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2

Harman, J. M. Earth station antenna sidelobe characteristics. [Washington, D.C.]: U.S. Dept. of Commerce, National Telecommunications and Information Administration, 1985.

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3

Scott, Craig. Modern methods of reflector antenna analysis and design. Norwood, MA: Artech House, 1990.

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4

J, Zakrajsek Robert, e United States. National Aeronautics and Space Administration., a cura di. Near-field testing of the 30-GHz TRW proof-of-concept Multibeam Antenna. [Washington, DC]: National Aeronautics and Space Administration, 1986.

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5

J, Garrett Michael, e United States. National Aeronautics and Space Administration., a cura di. Near-field antenna testing using the Hewlett Packard 8510 automated network analyzer. [Washington, DC]: National Aeronautics and Space Administration, 1991.

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6

M, Larko Jeffrey, Lagin Alan R e United States. National Aeronautics and Space Administration., a cura di. Advanced Communication Technology Satellite (ACTS) multibeam antenna technology verification experiments. [Washington, DC]: National Aeronautics and Space Administration, 1992.

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7

Scott, Craig. Modern methods of reflector antenna analysis and design. Norwood, MA: Artech House, 1990.

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8

Barger, Raymond L. A simplified approach to axisymmetric dual-reflector antenna design. [Washington, D.C.]: National Aeronautics and Space Administration, Scientific and Technical Information Division, 1988.

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9

J, Zakrajsek Robert, e United States. National Aeronautics and Space Administration., a cura di. Near-field testing of the 30-GHz TRW proof-of-concept Multibeam Antenna. [Washington, DC]: National Aeronautics and Space Administration, 1986.

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10

Harman, J. M. Earth station antenna sidelobe characteristics. [Washington, D.C.]: U.S. Dept. of Commerce, National Telecommunications and Information Administration, 1985.

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Più fonti

Capitoli di libri sul tema "Reflector"

1

Weik, Martin H. "reflector". In Computer Science and Communications Dictionary, 1449. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_15852.

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2

Rahmat-Samii, Yahya. "Reflector Antennas". In Encyclopedia of Remote Sensing, 668–81. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-0-387-36699-9_93.

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3

Gooch, Jan W. "Reflex Reflector". In Encyclopedic Dictionary of Polymers, 614. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_9867.

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4

Bird, Trevor S. "Reflector Antennas". In Handbook of Antenna Technologies, 853–922. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-4560-44-3_30.

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Bird, Trevor S. "Reflector Antennas". In Handbook of Antenna Technologies, 1–61. Singapore: Springer Singapore, 2015. http://dx.doi.org/10.1007/978-981-4560-75-7_30-1.

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Weik, Martin H. "Lambertian reflector". In Computer Science and Communications Dictionary, 868. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_9899.

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Weik, Martin H. "retrodirective reflector". In Computer Science and Communications Dictionary, 1488. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/1-4020-0613-6_16305.

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Rahmat-Samii, Yahya. "Reflector Antennas". In Antenna Handbook, 949–1072. Boston, MA: Springer US, 1988. http://dx.doi.org/10.1007/978-1-4615-6459-1_15.

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9

Moore, Patrick. "Enter the Reflector". In Eyes on the Universe, 19–25. London: Springer London, 1997. http://dx.doi.org/10.1007/978-1-4471-0627-2_4.

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Baars, Jacob W. M., e Hans J. Kärcher. "Alternative Reflector Geometries". In Radio Telescope Reflectors, 185–207. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-65148-4_7.

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Atti di convegni sul tema "Reflector"

1

Maddio, P. "Surface error correction of a mesh deployable reflector". In AIMETA 2022. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902431-107.

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Abstract (sommario):
Abstract. Large Deployable Reflector (LDR) systems are commonly used as mesh reflectors for large aperture space antennas in aerospace applications since they provide affordability while guaranteeing at the same time a high gain and a high directivity. To improve the surface accuracy several methods have been studied, most of which measure the distance between the cable-net system that forms the reflector surface and the desired paraboloid. In this paper we want to improve the reflector’s ability to convey a greater concentration of reflected rays in the direction of the feed. To deal with this issue, a numerical optimization algorithm has been proposed.
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Dressler, Max. "Structured tantalum backlight reflector design". In International Optical Design Conference. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/iodc.1998.lwb.6.

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In a spacelab experiment the shadow profile of a metallic alloy sphere of 8 mm diam. shall be imaged by means of LED illumination (640 nm) and backlight reflectors, using telecentric optics. The direction of the incident light does not meet the condition for direct reflection at the plano reflector surface; thus the reflectors must either have diffuse reflexion (model: white paper), act as diffractive elements with the correct blaze angle or consist of micro surfaces that are oriented in space to meet the condition for direct reflection.
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Schmauder, T., P. Sauer e G. Ickes. "New Reflectors and Reflector Coaters". In Society of Vacuum Coaters Annual Technical Conference. Society of Vacuum Coaters, 2014. http://dx.doi.org/10.14332/svc14.proc.1814.

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4

Sohail, S., H. Naqvi e Neal C. Gallagher. "Rigorous analysis of scattering from a strip grating twist reflector". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.wbb5.

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Periodic metallic grating structures, with periods of the order of the wavelength of the incident electromagnetic field, influence both the phase and polarization of the reflected field. A convenient decomposition of the polarization is into fast and slow polarized modes, where the magnetic or electric field component parallel to the grating direction, respectively, is zero. In the case of a corrugated surface twist reflector, Kok and Gallagher,1 derived the optimum height required for various angles of incidence in order for the reflected fast and slow polarized modes to be in phase. In practice twist reflectors are also constructed by placing wires or strip gratings on a dielectric slab of some thickness w, backed by a conducting ground plane. Recently we presented a rigorous analysis of scattering from a strip grating. We extend our solution procedure to be applicable to the analysis of scattering from a strip grating twist reflector. It is shown that completely erroneous results are obtained if an approximate procedure is used. We compare the operation of the strip grating twist reflector to the corrugated surface twist reflector and show that the two behave similarly if air is used as the dielectric for the strip grating twist reflectors.
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Ackerman, D. A., M. I. Dahbura, Y. Shani, C. H. Henry, R. C. Kistler, R. F. Kazarinov e C. Y. Kuo. "Compact hybrid resonant-optical reflector lasers with very narrow linewidths". In Integrated Photonics Research. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/ipr.1990.wd3.

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Lasers with submegahertz linewidths have importance in various applications, such as in coherent optical communications, interferometric sensors, and resonant-optical gyroscopes. For several years our laboratory has investigated a hybrid Bragg reflector laser with typical linewidths of less than 1 MHz and a narrowest linewidth of 100 kHz. The narrow line results from operating the laser at the steeply rising edge of the Bragg reflection. Understanding this mechanism led to the development1 of resonant-optical reflectors (RORs), integrated-optical elements capable of providing feedback with a reflection spectrum even sharper than previously obtained. We report hybrid ROR laser linewidths as narrow as 7.1 kHz.
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Malachias, N., I. Kakavas, S. M. Said Al Harthi e A. Said Al Saidi. "Design and Experimental Evaluation of a Novel Type Radar Reflector for use in the Marine Environment." In International Conference on Marine Engineering and Technology Oman. London: IMarEST, 2019. http://dx.doi.org/10.24868/icmet.oman.2019.033.

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The octahedral radar reflector is the one most commonly used today in marine applications, for purposes of increasing the Radar Cross Section (RCS) of small vessels at sea. The use of radar reflectors provides greater radar detection distances, therefore contributes to navigation safety. The octahedral reflector has proven to be relatively inefficient, since its RCS values do not remain fairly constant, but show significant variations resulting to changes of the angle of incidence. RCS variations in certain angles of incidence produce nulls, where the radar detection range is almost zero, thus increasing the probability of collision incidents at sea. The scope of this research is to design and evaluate more RCS efficient radar reflector types compared with the operational performance of the octahedral in X-band, thus contribute to navigation safety in the marine environment. Three new reflector models have been designed and manufactured and their RCS was compared with the octahedral reflector RCS in the Military Technological College (MTC) radar lab (in X-band). For the octahedral reflector’s and new models’ size and weight, the International Maritime Organization (IMO) Resolution MSC.164 (78) revised performance standards of radar reflectors have been considered. As a result of the measurements, the reflector model with 30 triangular trihedral elements, with side length of 13 cm, has proven to be the most efficient.
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David, Stuart R., e Claude T. Walker. "Exploring Segmented Reflector Design for Uniform Illumination". In International Optical Design Conference. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/iodc.1998.lwb.7.

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Recent advances in software and computer speeds have allowed for the reduction of prototyping and time to market for many illumination systems. This paper will address how software can significantly help the optical design in the task of designing and analyzing segmented reflectors. Segmented reflectors come in many different shapes and sizes. Therefore, the scope of this paper has been reduced to the discussion of MR16 (Metal Reflector 16/8" diameter) type reflector. MR16 reflectors have different shapes but nearly the same size (~1 ¾″ deep by ~2″ in diameter). However, the ideas and principles presented should apply to other types of segmented reflector systems.
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El Baba, Youssef, Andreas Walther e Emanuel A. P. Habets. "Reflector localization based on multiple reflection points". In 2016 24th European Signal Processing Conference (EUSIPCO). IEEE, 2016. http://dx.doi.org/10.1109/eusipco.2016.7760490.

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Lee, Jong-In, Sunjun Kim, Masaaki Fukumoto e Byungjoo Lee. "Reflector". In UIST '17: The 30th Annual ACM Symposium on User Interface Software and Technology. New York, NY, USA: ACM, 2017. http://dx.doi.org/10.1145/3126594.3126665.

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Al-Mamun, Abdullah, Jialin Liu, Tonglin Li, Quincey Koziol, Zhongyi Zhai, Junyan Qian, Haoting Shen e Dongfang Zhao. "Reflector". In PPoPP '20: 25th ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming. New York, NY, USA: ACM, 2020. http://dx.doi.org/10.1145/3332466.3374505.

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Rapporti di organizzazioni sul tema "Reflector"

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J. Nash, V. Munne e LL Stimely. Space Reflector Materials for Prometheus Application. Office of Scientific and Technical Information (OSTI), gennaio 2006. http://dx.doi.org/10.2172/883662.

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McCamy, James W., Kwaku Koram e Brian F. Kornish. Next Generation Reflector - Phase 1 Final Report. Office of Scientific and Technical Information (OSTI), maggio 2013. http://dx.doi.org/10.2172/1080364.

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RK Huang, CA Wang, MK Connors, GW Turner e M Dashiell. Hybrid Back Surface Reflector GaInAsSb Thermophotovoltaic Devices. Office of Scientific and Technical Information (OSTI), maggio 2004. http://dx.doi.org/10.2172/836454.

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Author, Not Given. Point-focus concentrator reflector assembly: Phase 1. Office of Scientific and Technical Information (OSTI), novembre 1987. http://dx.doi.org/10.2172/5691864.

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Meyer, Robert B. Development of a Liquid Crystal Smart Reflector. Fort Belvoir, VA: Defense Technical Information Center, gennaio 1996. http://dx.doi.org/10.21236/ada308782.

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Hill, David A. Out-of-band response of reflector antennas. Gaithersburg, MD: National Bureau of Standards, 1985. http://dx.doi.org/10.6028/nbs.ir.85-3021.

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Azad, Abul Kalam, Shobhita Kramadhati, Sinhara Rishi Malinda Silva, Nicholas Steven Sirica e Houtong Chen. Flat Ultrathin Metasurface Parabolic Reflector for THz Applications. Office of Scientific and Technical Information (OSTI), febbraio 2019. http://dx.doi.org/10.2172/1493535.

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J. Nash. Reflector and Shield Material Properties for Project Prometheus. Office of Scientific and Technical Information (OSTI), novembre 2005. http://dx.doi.org/10.2172/883658.

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Doerry, Armin. Beam spoiling a reflector antenna with conducting shim. Office of Scientific and Technical Information (OSTI), dicembre 2012. http://dx.doi.org/10.2172/1088051.

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Damas, J., e F. Neves. Preventing Use of Recursive Nameservers in Reflector Attacks. RFC Editor, ottobre 2008. http://dx.doi.org/10.17487/rfc5358.

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