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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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
5
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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
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.
Testo completoAbstract (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.
11
Ooshaksaraei, P., K. Sopian, R. Zulkifli, M. A. Alghoul e Saleem H. Zaidi. "Characterization of a Bifacial Photovoltaic Panel Integrated with External Diffuse and Semimirror Type Reflectors". International Journal of Photoenergy 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/465837.
Testo completoAbstract (sommario):
Silicon wafer accounts for almost one-half the cost of a photovoltaic (PV) panel. A bifacial silicon solar cell is attractive due to its potential of enhancing power generation from the same silicon wafer in comparison with a conventional monofacial solar cell. The bifacial PV cell is able to capture solar radiation by back surface. This ability requires a suitable reflector appropriately oriented and separated from the cell’s rear surface. In order to optimize the bifacial solar cell performance with respect to an external back surface reflector, diffuse and semimirror reflectors were investigated at various angles and separations from the back surface. A simple bifacial solar panel, consisting of four monocrystalline Si solar cells, was designed and built. Reflection from the rear surface was provided by an extended semimirror and a white-painted diffuse reflector. Maximum power generation was observed at 30° with respect to ground for the semimirror reflector and 10° for diffuse reflector at an optimized reflector-panel separation of 115 mm. Output power enhancement of 20% and 15% from semimirror and diffuse reflectors, respectively, were observed. This loss from diffuse reflector is attributed to scattering of light beyond the rear surface capture cross-section of the bifacial solar panel.
12
Favretto-Cristini, Nathalie, Paul Cristini e Eric de Bazelaire. "What is a seismic reflector like?" GEOPHYSICS 74, n. 1 (gennaio 2009): T13—T23. http://dx.doi.org/10.1190/1.3033216.
Testo completoAbstract (sommario):
The spatial region that is in the vicinity of an interface and actually affects the interface response, and hence the reflected wavefield, is of particular interest for the characterization of reflectors from a seismic viewpoint. This region is represented by a volume of integration of medium properties above and below the interface whose maximum lateral extent corresponds to the lateral extent of the interface Fresnel zone, and whose maximum vertical extent is equal to a thickness we evaluate approximately for subcritical incidence angles for a plane interface as well as for curved interfaces of anticline and syncline type. The maximum vertical extent might be larger than the seismic wavelengths for subcritical incidence angles close to the critical angle and for a strong impedance contrast at the interface. Although the part of the reflector volume lying below the interface and affecting traveltime measurements actually is smaller than described in previous studies, the whole part of the reflector volume that affects the amplitude of the reflected wavefield is larger than estimates in previous studies, which considered only the spatial region below the interface. For a syncline (respectively, an anticline), it is larger (respectively, smaller) than described for a plane interface. In addition to providing more physical insights into the wave reflection process, this study might have significant implications for seismic interpretation using amplitude-variation-with-angle methodologies.
13
Diaz, Y., P. Arévalo, L. Hernández-García, L. Bassani, A. Malizia, O. González-Martín, C. Ricci et al. "Constraining X-ray reflection in the low-luminosity AGN NGC 3718 using NuSTAR and XMM–Newton". Monthly Notices of the Royal Astronomical Society 496, n. 4 (19 giugno 2020): 5399–413. http://dx.doi.org/10.1093/mnras/staa1762.
Testo completoAbstract (sommario):
ABSTRACT One distinctive feature of low-luminosity active galactic nuclei (LLAGNs) is the relatively weak reflection features they may display in the X-ray spectrum, which can result from the disappearance of the torus with decreasing accretion rates. Some material, however, must surround the active nucleus, i.e. the accretion flow itself and, possibly, a flattened-out or thinned torus. In this work, we study whether reflection is indeed absent or undetectable due to its intrinsically weak features together with the low statistics inherent to LLAGNs. Here, we focus on NGC 3718 (L/LEdd ∼ 10−5) combining observations from XMM–Newton and the deepest to date NuSTAR (0.5–79 keV) spectrum of a LLAGNs, to constrain potential reflectors, and analyse how the fitted coronal parameters depend on the reflection model. We test models representing both an accretion disc (Relxill) and a torus-like (MYTorus and Borus) neutral reflector. From a statistical point of view, reflection is not required, but its inclusion allows to place strong constraints on the geometry and physical features of the surroundings: both neutral reflectors (torus) tested should be Compton thin (NH < 1023.2cm−2) and preferentially cover a large fraction of the sky. If the reflected light instead arises from an ionized reflector, a highly ionized case is preferred. These models produce an intrinsic power-law spectral index in the range [1.81–1.87], where the torus models result in steeper slopes. The cut-off energy of the power-law emission also changes with the inclusion of reflection models, resulting in constrained values for the disc reflectors and unconstrained values for torus reflectors.
14
Schumann, Julian, Bert Schiebler e Federico Giovannetti. "Performance Evaluation of an Evacuated Tube Collector with a Low-Cost Diffuse Reflector". Energies 14, n. 24 (7 dicembre 2021): 8209. http://dx.doi.org/10.3390/en14248209.
Testo completoAbstract (sommario):
In order to increase the overall solar energy gain of evacuated tube collectors, rear-side reflectors are used. In this way, the otherwise unused incident radiation between the tubes can be reflected back to the absorber, and the performance of the collector can be improved. In this paper, the use of a low-cost, diffusely reflecting, trapezoidal roof covering made from a galvanized metal sheet is investigated and compared to a high-quality, specularly reflecting plane reflector made of aluminum. For this purpose, ray-tracing analysis and TRNSYS simulations were carried out. In the ray-tracing analysis, the experimentally determined zero-loss collector efficiency η0 as well as the incident angle modifiers for each reflector can be reproduced with an error lower than 7.5%. Thermal system simulations show that the performance of both reflectors is comparable. The use of the low-cost reflector leads to an increase in annual collector output of around 30% compared to an increase with the specular reflector of around 33%. Considering a typical domestic hot water system, both reflectors enable an increase in the solar annual yield of approx. 11%.
15
Tang, X. M., H. Glassman e D. Patterson. "Single-well acoustic imaging in anisotropic formations". GEOPHYSICS 73, n. 4 (luglio 2008): D11—D16. http://dx.doi.org/10.1190/1.2907522.
Testo completoAbstract (sommario):
The effect of formation anisotropy on single-well acoustic imaging was analyzed to provide a simple and effective correction method for the imaging application. We used analytical and synthetic modeling to analyze acoustic reflection moveout in a transversely isotropic (TI) formation for borehole configuration. Far-borehole reflections from a bed generally have small reflection angles to the bed. Thus the reflection moveout away from the borehole is controlled largely by the velocity along the TI-symmetry axis. Consequently, reflection imaging using measured velocity along the borehole can cause errors in the imaged reflector position. By correcting the anisotropy effect in the velocity, reflectors can be imaged correctly. A simple correction is to use the velocity along the TI-symmetry axis, which effectively maps the bed reflector to its correct position. Application of the correction method to synthetic and field-data examples demonstrate the anisotropy effect on reflector imaging and the effectiveness of the method.
16
Taygin, V. B., e А. V. Lopatin. "Method of achievement the high accuracy of the shape of reflectors of mirror antennas of spacecraft". Spacecrafts & Technologies 3, n. 4 (25 dicembre 2019): 200–208. http://dx.doi.org/10.26732/2618-7957-2019-4-200-208.
Testo completoAbstract (sommario):
Analysis of conditions, which are required for mirror antennas of spacecrafts destined for transmission of high-frequent radio signals, is done in this paper. These conditions are regarded to resistance and rigidity of the construction features of the material of an antenna’s reflector and its surface’s quality. It is mentioned that the requirements to the accuracy of the reflector’s shape grow together with the frequency of a radio signal. Altogether, the existing constructions of antennas and the producing technologies are not capable to obtain those requirements. The innovative method of controlling the shape of a reflector of a mirror antenna is presented in the paper. Its application gives an opportunity to produce constructions with a highly accurate surface. This method deals with the fact that the required accuracy of a reflector can be achieved via elastic deformation of its shell. Design of the regulating units for different types of reflectors is developed. We propose an algorithm of choosing the number of the regulating units and their locations. This algorithm uses the results of finite-element modal analysis of a reflector’s shell. Innovative design of axisymmetric and offset reflectors which shell’s shape can arise from controlled deformation is developed. We also suggest the design of the reflector’s shell with a timber with regulating units on it. Such design provides an opportunity to significantly decrease the number of the regulating units. Project of the reflector with a timber and console rods possessing low mass and high stiffness is developed. Method of achievement the high accuracy of a reflector, presented in the paper, can be applied to design of new space antennas operating in high-frequency interval.
17
Gong, Hao, Hao Chen, Xiao He e Xiuming Wang. "Eliminating the azimuth ambiguity in single-well imaging using 3C sonic data". GEOPHYSICS 80, n. 1 (1 gennaio 2015): A13—A17. http://dx.doi.org/10.1190/geo2014-0337.1.
Testo completoAbstract (sommario):
The shortcomings of conventional single-well sonic imaging are the inefficiency in eliminating azimuth ambiguity of the reflector outside boreholes. To resolve this problem, we proposed that 3C data of the reflection echoes be migrated simultaneously. The quantitative expressions of the received 3C data were first derived. The direct correlations between the polarity of the 3C data and the reflector azimuth were analyzed. It was revealed that the reflector positions can be fully identified by the associated echoes consisting of the transverse and axial components of wavefields. And an improved single-well imaging procedure using axial displacement component in addition to transverse components was thus developed. Numerical examples were evaluated for validation of the imaging method. According to the numerical results, the image intensity of the reflectors was effectively enhanced whereas the artificial mirrors of the reflectors were greatly weakened. It was suggested that a sonic logging tool with the 3C receivers be necessary for the image of reflectors without azimuth ambiguity.
18
Borkar, V. G., R. Ethiraj e V. M. Pandharipande. "Reflected fields from twist reflector in twist reflector scanning antenna configuration". Electronics Letters 29, n. 16 (1993): 1397. http://dx.doi.org/10.1049/el:19930936.
Testo completo
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Liang, Hong, Yi Luo, Panos G. Kelamis e Arthur B. Weglein. "Reflector spectrum for relating seismic arrivals to reflectors". GEOPHYSICS 77, n. 6 (1 novembre 2012): T239—T246. http://dx.doi.org/10.1190/geo2012-0162.1.
Testo completoAbstract (sommario):
When interpreting seismic images or suppressing multiples in seismic data, it is important to identify the reflectors from which the multiples, especially the internal multiples, originated. We evaluated a method to relate all seismic arrivals, including primaries and multiples, to their originating reflectors. We used the reflectivity forward modeling method to isolate reflectors and determine the contribution of an individual reflector to arrivals in a seismic trace. Repeating this process for all reflectors produced a reflector spectrum, which shows quantitatively the relative contribution of each reflector to all arrivals in a trace. Then we modified the reflector spectrum to relate seismic arrivals only to their shallowest reflectors. We applied the reflector spectrum and the modified reflector spectrum to a velocity model constructed from a field sonic log. We provided an indication of the minimum number of reflectors responsible for multiples and demonstrated that internal multiples originate from many reflectors distributed throughout the model, rather than from a few major ones.
20
Ha, Nguyen Thu, Trinh Van Thai, Thanh Long Cung e Hoang Si Hong. "A calculation method of the passive wireless surface acoustic wave sensor response phase". Bulletin of Electrical Engineering and Informatics 12, n. 1 (1 febbraio 2023): 86–97. http://dx.doi.org/10.11591/eei.v12i1.4068.
Testo completoAbstract (sommario):
In this research, we propose a method to calculate the phase delay angle of the reflected wave compared to the wave emitted from the interdigital transducer (IDT) of a passive wireless surface acoustic wave (SAW) sensor by combining simulation of the finite element method (FEM) and MATLAB. Based on the result, we consider the influence of the reflector position on the phase delay of the SAW sensor consisting of an IDT and three equally spaced reflectors. The distances between the IDT and the first reflector are 870 micrometers, 939.6 micrometers, and 1009.2 micrometers, and the distances between the reflector positions are 452.4 micrometers, 522 micrometers, and 591.6 micrometers. The outputs of the FEM simulation, including delay time, amplitude loss, and the length of the reflected wave are put into the model in MATLAB to determine the phase delay of the response waves. The obtained phase delay results show that as the distance between the IDT and the reflectors increases, the phase delay angle increases to 4.49 degrees, 5.39 degrees, and 5.78 degrees, respectively.
21
Mohan, Manoj Kumar Chandra, Sang Kyun Shim, June Key Lee, Nakwon Jang, Naesung Lee e Wael Z. Tawfik. "Optimized Aluminum Reflector for Enhancement of UVC Cathodoluminescence Based-AlGaN Materials with Carbon Nanotube Field Emitters". Molecules 26, n. 13 (30 giugno 2021): 4025. http://dx.doi.org/10.3390/molecules26134025.
Testo completoAbstract (sommario):
The far ultraviolet C (UVC) light sources based on carbon nanotube (CNT) field emitters as excitation sources have become promising light sources for sterilization, disinfection, and water purification. However, the low light extraction efficiency of UVC–CNT light sources still hinders the practical application of these structures. Herein, we report an optimized aluminum (Al) reflector to enhance the light extraction efficiency of UVC–CNT light sources. Optical analysis of UVC-CNT light sources covered by the Al reflectors with various thicknesses ranging from 30 to 150 nm was performed to realize the optimized reflector. The UVC-CNT light sources exhibit the highest light extraction efficiency when the Al reflector layer has an optimized thickness of 100 nm. For comparison, the cathodoluminescence (CL) spectra were recorded for UVC–CNT light sources with and without the optimized Al reflector. The measured light output power and the estimated power efficiency of the UVC–CNT light-source-tube with Al reflector were enhanced by about 27 times over the reference. This enhancement is mainly attributed to the outstanding reflection effect of the Al reflector.
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Tambunga, Gabriel James. "The Doppler Factor and Quantum Electrodynamics Basics in Laser-Driven Light Sailing". International Letters of Chemistry, Physics and Astronomy 19 (ottobre 2013): 10–14. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.19.10.
Testo completoAbstract (sommario):
Basic concepts in Quantum Electrodynamics (QED) and the doppler factor were applied to laser-driven light sailing, where this combination was not considered before. QED indicates that a reflection is an absorption and an emission of discreet energy, and the doppler factor indicates a change in velocity of a reflector would result in the reflector observing a change in wavelength from a source. Applying these concepts results in the reflectors available discrete energy states not being filled, after the reflector changes its velocity. Changes in the apparatus of the laser-driven light sail and changes in the current understanding of the transfer of momentum from light to matter for effective laser-driven light sailing are suggested.
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Tambunga, Gabriel James. "The Doppler Factor and Quantum Electrodynamics Basics in Laser-Driven Light Sailing". International Letters of Chemistry, Physics and Astronomy 19 (2 ottobre 2013): 10–14. http://dx.doi.org/10.56431/p-3ui0ua.
Testo completoAbstract (sommario):
Basic concepts in Quantum Electrodynamics (QED) and the doppler factor were applied to laser-driven light sailing, where this combination was not considered before. QED indicates that a reflection is an absorption and an emission of discreet energy, and the doppler factor indicates a change in velocity of a reflector would result in the reflector observing a change in wavelength from a source. Applying these concepts results in the reflectors available discrete energy states not being filled, after the reflector changes its velocity. Changes in the apparatus of the laser-driven light sail and changes in the current understanding of the transfer of momentum from light to matter for effective laser-driven light sailing are suggested.
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Choi, Choi, Kim, Ryu, Rim e Kim. "New Curved Reflectors for Significantly Enhanced Solar Power Generation in Four Seasons". Energies 12, n. 23 (3 dicembre 2019): 4602. http://dx.doi.org/10.3390/en12234602.
Testo completoAbstract (sommario):
A new curved-type reflector for solar power generation is proposed. By adopting the curved-type reflector between consecutive solar panel arrays, all incoming sunlight can be utilized and thus, the generated power is significantly increased. Furthermore, the proposed curved-type reflector can be generally used in four seasons regardless of the altitude or angle of the installation environment. The optimum design rule for the curved-reflector, comparing to a plane-type reflector, is completely developed in this paper. A new solar cell configuration best fit for the proposed curved-reflector is also provided. Experimental results showed that the curved-type reflector improves the spatial average solar power by 61% compared to no reflector case, which is even 11% higher than the plane-type reflector. Reflectors, especially curved-type reflectors, are found to be one of promising solutions for highly efficient solar power generation.
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Deng, H. Lydia. "Acoustic‐wave propagation in thin‐layered media with steep reflectors". GEOPHYSICS 59, n. 10 (ottobre 1994): 1593–604. http://dx.doi.org/10.1190/1.1443548.
Testo completoAbstract (sommario):
Seismic waves reflected from steep interfaces beneath layered sediments spend a significant portion of time traveling almost horizontally. Therefore, accurate imaging of steep geologic structure requires knowledge of the behavior of these horizontally propagating waves; in particular, the role of evanescence and tunneling of seismic waves propagating in thin‐layered media. For thin‐layered media, modeling of zero‐offset reflections shows frequency‐dependent amplitude and phase behavior that varies with reflector dip. Waves propagating vertically in a sequence of thin layers lose high frequencies by stratigraphic filtering. However, waves reflected from steep reflectors in a thin‐layered medium are also attenuated and dispersed by the less well‐known evanescent filtering. These two low‐pass filtering actions depend on reflector dip and bed thickness in different ways: evanescent filtering is more severe for steeper reflectors and thicker beds, while stratigraphic filtering is more severe for flat reflectors and thinner beds. Waves traveling in layered media may suffer high‐frequency loss from both these effects.
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Mohanty, S. P., S. K. Sahoo, C. S. Mishra, A. Panda e G. Palai. "Realization of 3D reflectors by using metal-air and semiconductor-air based photonic structures at three communication windows". Semiconductor Physics, Quantum Electronics and Optoelectronics 24, n. 3 (26 agosto 2021): 335–40. http://dx.doi.org/10.15407/spqeo24.03.335.
Testo completoAbstract (sommario):
This study is based on analysis of 3D photonic crystal structure (PCS) for realization of photonic reflector pertaining to suitable optical communication wavelengths of 850, 1310 and 1550 nm. The said photonic reflector application is envisaged separately by two 3D PCSs, which comprise semiconductor (germanium) and metal (iron) based circular rods respectively, arranged on a square lattice having air as the background material. The plane wave expansion (PWE) technique is employed to investigate the photonic band gap (PBG) vis-à-vis all the aforementioned wavelengths. PBG is meticulously controlled by suitably selected various structure parameters, such as lattice spacing, diameter of the circular rods and nature of their material. Simulation outcomes explored that semiconductor based PCS reflects wavelengths of 850, 1310 and 1550 nm, when selecting the diameter of the circular rods as 282, 608 and 771 nm, respectively, whereas metal based PCS reflects the aforementioned wavelengths for diameters of the circular rods close to 335, 1070 and 871 nm, respectively. Further, we assayed the variation in reflected wavelength with respect to different diameters of circular rods for both proposed structures. Thus, the proposed optical reflectors can find a wide range of applications vis-à-vis three communication windows.
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Wei, Zhou-Tuo, e Xiao-Ming Tang. "Numerical simulation of radiation, reflection, and reception of elastic waves from a borehole dipole source". GEOPHYSICS 77, n. 6 (1 novembre 2012): D253—D261. http://dx.doi.org/10.1190/geo2012-0061.1.
Testo completoAbstract (sommario):
A recent advance in single-well reflection imaging is the use of a dipole acoustic system in a borehole to radiate and receive elastic waves to and from a remote geologic reflector in formation. This dipole-acoustic imaging technology is evaluated by numerically simulating the radiation and reflection of the wavefield generated by the borehole dipole source and analyzing the receiving sensitivity of the dipole system to the incoming reflected waves. The analyses show that a borehole dipole source can radiate a compressional wave (P-wave) and two types of shear waves (i.e., SV- and SH-waves) into the formation. The SH-wave has wide radiation coverage and the best receiving sensitivity, and is most suitable for dipole-shear imaging. In an acoustically slow formation, the dipole-generated P-wave has strong receiving sensitivity and can also be used for reflection imaging. An important feature of dipole imaging is its sensitivity to reflector azimuth, which results from the directivity of the dipole source. By using a 4C data acquisition method to record the dipole-generated reflected signal, the reflector azimuth can be determined. The numerical simulation and theoretical analysis results are in good agreement, providing a solid foundation for the dipole acoustic imaging technology.
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Hirabayashi, Nobuyasu. "Reflector imaging using trial reflector and crosscorrelation: Application to fracture imaging for sonic data". GEOPHYSICS 81, n. 6 (novembre 2016): S433—S446. http://dx.doi.org/10.1190/geo2016-0046.1.
Testo completoAbstract (sommario):
I have developed two high-resolution imaging methods that do not require a priori information on the structural dip. The dip information is often necessary to image complex structures using Kirchhoff migration by selecting only the constructively interfering parts of waveforms, especially for data with limited acquisition geometry. However, such dip information is not generally available. The methods that I evaluated use a trial reflector, which is defined for each image point and source-receiver pair, to search for the true geologic reflector. The coincidence of these reflectors is judged by a coherency analysis of event signals for the trial reflector using the crosscorrelations, and the coherency is converted to a weight. The weight is combined with the stacking methods of waveform samples in migration. In the first method, a waveform sample summed at an image point for a source-receiver pair is obtained by the common-depth-point stack of array data for the trial reflector. In the second method, a waveform sample of a source-receiver pair at the traveltime of the reflected ray for the trial reflector is smeared in the Fresnel zone computed for the trial reflector. My methods were applied to image fractures for sonic data, whose frequency range is centered approximately 8 kHz, and they provide higher resolution images than those given by conventional Kirchhoff migration.
29
Lu, Chun-Hao, Jiun-Hung Lin, Han-Ming Huang, Cheng-Yang Huang e Cheng-Chi Tai. "DESIGN OF A RING-TYPE REFLECTION PULSE OXIMETER WITH A PARABOLIC REFLECTOR". Biomedical Engineering: Applications, Basis and Communications 27, n. 01 (febbraio 2015): 1550007. http://dx.doi.org/10.4015/s1016237215500076.
Testo completoAbstract (sommario):
A pulse oximeter is a noninvasive instrument used in clinical medicine to monitor arterial oxygen saturation. Fingertip-type pulse oximeters are popular, but their inconvenience for long-term monitoring in daily life means that other types of wearable pulse oximeters, such as a ring-type reflection pulse oximeter, needs to be developed. However, designing a ring-type pulse oximeter for measuring the oxygen saturation is difficult due to the complex tissue architecture of the finger base. This study used human tissue simulations to evaluate the practicability of a ring-type reflection pulse oximeter design. Moreover, given that the collection of diffusely reflected light can be enhanced by using a parabolic reflector, the efficacy of a ring-type reflection pulse oximeter with a parabolic reflector was also evaluated.
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Arabacigil, Bihter, Numan Yuksel e Atakan Avci. "The use of paraffin wax in a new solar cooker with inner and outer reflectors". Thermal Science 19, n. 5 (2015): 1663–71. http://dx.doi.org/10.2298/tsci121022031a.
Testo completoAbstract (sommario):
In this paper, the potential use and effectiveness of paraffin wax in a new solar cooker was experimentally investigated during daylight and late evening hours. For these experiments, a cooker having an inner reflecting surface was designed, constructed by filling paraffin wax and metal shavings. The side- and sub-surface temperatures of the paraffin wax in the cooker are measured in the summer months of June and July. The thermal efficiency of the cooker was tested on different conditions. The results show that the optimum angle of the outer reflector is 30?. Here, the peak temperature of the paraffin wax in the solar cooker was 83.4 ?C. The average solar radiation reflected makes a contribution of 9.26% to the temperature of paraffin wax with the outer reflector. The solar cooker with the outer reflector angle of 30? receives also reflected radiation from the inner reflectors. Besides, the heating time is decreased to approximately 1 hour. The designed solar cooker can be effectively used with 30.3% daily thermal efficiency and paraffin wax due to the amount of energy stored.
31
Bezuglyi, M. A., N. V. Bezuglaya, A. V. Ventsuryk e K. P. Vonsevych. "Angular Photometry of Biological Tissue by Ellipsoidal Reflector Method". Devices and Methods of Measurements 10, n. 2 (24 giugno 2019): 160–68. http://dx.doi.org/10.21122/2220-9506-2019-10-2-160-168.
Testo completoAbstract (sommario):
Angular measurements in optics of biological tissues are used for different applied spectroscopic task for roughness surface control, define of refractive index and for research of optical properties. Purpose of the research is investigation of the reflectance of biologic tissues by the ellipsoidal reflector method under the variable angle of the incident radiation.The research investigates functional features of improved photometry method by ellipsoidal reflectors. The photometric setup with mirror ellipsoid of revolution in reflected light was developed. Theoretical foundations of the design of an ellipsoidal reflector with a specific slot to ensure the input of laser radiation into the object area were presented. Analytical solution for calculating the angles range of incident radiation depending on the eccentricity and focal parameter of the ellipsoid are obtained. Also created the scheme of image processing at angular photometry by ellipsoidal reflector.The research represents results of experimental series for samples of muscle tissues at wavelengths 405 nm, 532 nm, 650 nm. During experiment there were received photometric images on the equipment with such parameters: laser beam incident angles range 12.5–62.5°, ellipsoidal reflector eccentricity 0.6, focal parameter 18 mm, slot width 8 mm.The nature of light scattering by muscle tissues at different wavelengths was represented by graphs for the collimated reflection area. The investigated method allows qualitative estimation of influence of internal or surface layers of biologic tissues optical properties on the light scattering under variable angles of incident radiation by the shape of zone of incident light.
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Lobanov, Ye, e G. Petchenko. "The technique of calculating the profile of a mirror reflector for discharge lamps of cylindrical shape and its testing on the example of design of an industrial lamp type ZhSP-250". Lighting engineering and power engineering 1, n. 57 (6 aprile 2020): 22–27. http://dx.doi.org/10.33042/2079-424x-2020-1-57-22-27.
Testo completoAbstract (sommario):
Current scientific trends are developments - methodological, theoretical and experimental, related to increasing the efficiency of some categories of lamps with discharge lamps. One such category is the powerful industrial spotlight class luminaires. This work is aimed at solving the urgent scientific task of finding ways to improve the design efficiency of industrial luminaires with deep and concentrated light distribution. At present, there are practically no works related to the task of calculating the geometry of the profiles of mirrored round-symmetric reflectors, which, in the presence of a light source of a fixed type and power, would provide the necessary light distribution of the luminaires. The elemental reflection method described in classical works does not determine the geometry of the reflector correctly, which provides the necessary balance in the equation that relates the light power of the lamp to the light power of the source and the reflector. The considerable time of calculation by the classical method and obtaining inaccurate decisions leads to rethinking the solution of the problem of calculating the geometry of the the reflector profile of the lamp with rigidly regulated light distribution. This task was first formulated by us in previous works. The purpose of this work is to approve the technique of solving the inverse problem of determining the geometry of a round-symmetric mirror reflector on the example of an industrial lamp type ZhKU-250 with light distribution type G-2. As the output of the calculation we used the light source and technical characteristics of the light source - DNAT-250 lamps, the required light distribution of the light fixture, the reflectance of the reflector, and the requirements for the efficiency of the designed luminaire and its gain. As a result of the performed work, it is possible to note the efficiency of the method both in terms of the accuracy of the calculations and the simple geometry of the reflector, obtained in the calculation method, which will allow to use simplified technological schemes for the serial production of such lamps. Keywords - industrial luminaires, DNaT discharge lamps, reflector LPC (Light Power Curve) required, zone LPCs of the reflector, radius vector array, luminaire gain and efficiency, elemental reflection method, reflector profile, rotary extrusion method.
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André, Julien, Dominique Attali, Quentin Mérigot e Boris Thibert. "Far-Field Reflector Problem Under Design Constraints". International Journal of Computational Geometry & Applications 25, n. 02 (giugno 2015): 143–62. http://dx.doi.org/10.1142/s0218195915500090.
Testo completoAbstract (sommario):
The far-field reflector problem is a well-known inverse problem arising in geometric optics. It consists in creating a mirror that reflects a given point light source to a prescribed target light at infinity. In this article, we study this problem under the common design constraint that the mirror is convex and is the graph of a polynomial over a given plane. We propose a method that iteratively improves the optical properties of the mirror surface while strictly fulfilling the design constraints. At each iteration, we first create an initial reflector by solving an optimal transport problem on the sphere. We then parameterize this reflector by the graph of a function over the plane. We test our algorithm with classical target lights at infinity and also show that our approach allows to create reflectors with more complex target lights.
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Titovich, Alexey, e Alex Titovich. "Macriaphone: A Stargazer’s microphone design". Journal of the Acoustical Society of America 151, n. 4 (aprile 2022): A248. http://dx.doi.org/10.1121/10.0011215.
Testo completoAbstract (sommario):
A highly directional, single channel microphone design is presented. The design utilizes a line of sight waveguide similar to a Keplerian reflector-type telescope. The key feature is that the waveguide is acoustically reflection-less thereby preventing off-axis reflected and diffracted fields from contaminating the measurement. The signal in the desired direction is amplified by a parabolic reflector, which terminates the waveguide and supports a single microphone at its focal point. The resulting directivity index is superior to that of a parabolic reflector microphone. Due to the line-of-sight cone provided by the waveguide, this device is particularly well suited for measuring distant sound, which is, why it is called the macriaphone (meaning far away sound in Greek). Theoretical background, numerical predictions, and experimental results from the prototype are presented.
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Schleicher, Jörg, Peter Hubral, German Höcht e Frank Liptow. "Seismic constant‐velocity remigration". GEOPHYSICS 62, n. 2 (marzo 1997): 589–97. http://dx.doi.org/10.1190/1.1444168.
Testo completoAbstract (sommario):
When a seismic common midpoint (CMP) stack or zero‐offset (ZO) section is depth or time migrated with different (constant) migration velocities, different reflector images of the subsurface are obtained. If the migration velocity is changed continuously, the (kinematically) migrated image of a single point on the reflector, constructed for one particular seismic ZO reflection signal, moves along a circle at depth, which we call the Thales circle. It degenerates to a vertical line for a nondipping event. For all other dips, the dislocation as a function of migration velocity depends on the reflector dip. In particular for reflectors with dips larger than 45°, the reflection point moves upward for increasing velocity. The corresponding curves in a Time‐migrated section are parabolas. These formulas will provide the seismic interpreter with a better understanding of where a reflector image might move when the velocity model is changed. Moreover, in that case, the reflector image as a whole behaves to some extent like an ensemble of body waves, which we therefore call remigration image waves. In the same way as physical waves propagate as a function of time, these image waves propagate as a function of migration velocity. Different migrated images can thus be considered as snapshots of image waves at different instants of migration velocity. By some simple plane‐wave considerations, image‐wave equations can be derived that describe the propagation of image waves as a function of the migration velocity. The Thales circles and parabolas then turn out to be the characteristics or ray trajectories for these image‐wave equations.
36
Fan, Jing Hui, Hong Li Zhao e Yi Wang. "Design, Deploy and Signal Analysis of Different Types of CR". Applied Mechanics and Materials 239-240 (dicembre 2012): 1238–41. http://dx.doi.org/10.4028/www.scientific.net/amm.239-240.1238.
Testo completoAbstract (sommario):
In Shuping area, it is difficulty to find enough nature coherent targets to use InSAR technique to monitor the landslide. In order to solve the problem, CRs(Corner Reflectors) were used to improve the effectiveness of this technology. In this article Pyramidal Corner Reflector, Asymmetric Cubic Corner Reflector, Double Direction Asymmetric Cubic Corner Reflector are designed. In order to achieve maximum reflection intensity of CR, it's attitude must be carefully adjusted to match with the SAR imaging parameters exactly. After the CRs were deployed, the strong echo signals can be retrieved from SAR images. Analyzing the SAR image peak signals to locate the CR is the premise of differential processing. Through image location and phase analysis of ASAR and RADARSAT-2, the CRs’ signals can be recognition certainly. During the data processing of ASAR and PALSAR, the CRs can be regarded as ideal coherence target points.
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Ayzenberg, Milana, Ilya Tsvankin, Arkady Aizenberg e Bjørn Ursin. "Effective reflection coefficients for curved interfaces in transversely isotropic media". GEOPHYSICS 74, n. 5 (settembre 2009): WB33—WB53. http://dx.doi.org/10.1190/1.3197862.
Testo completoAbstract (sommario):
Plane-wave reflection coefficients (PWRCs) are routinely used in amplitude-variation-with-offset analysis and for generating boundary data in Kirchhoff modeling. However, the geometrical-seismics approximation based on PWRCs becomes inadequate in describing reflected wavefields at near- and postcritical incidence angles. Also, PWRCs are derived for plane interfaces and break down in the presence of significant reflector curvature. Here, we discuss effective reflection coefficients (ERCs) designed to overcome the limitations of PWRCs for multicomponent data from heterogeneous anisotropic media. We represent the reflected wavefield in the immediate vicinity of a curved interface by a generalized plane-wave decomposition, which approximately reduces to the conventional Weyl-type integral computed for an apparent source location. The ERC then is obtainedas the ratio of the reflected and incident wavefields at each point of the interface. To conduct diffraction modeling, we combine ERCs with the tip-wave superposition method (TWSM), extended to elastic media. This methodology is implemented for curved interfaces that separate an isotropic incidence half-space and a transversely isotropic (TI) medium with the symmetry axis orthogonal to the reflector. If the interface is plane, ERCs generally are close to the exact solution, sensitive to the anisotropy parameters and source-receiver geometry. Numerical tests demonstrate that the difference between ERCs and PWRCs for typical TI models can be significant, especially at low frequencies and in the postcritical domain. For curved interfaces, ERCs provide a practical approximate tool to compute the reflected wavefield. We analyze the dependence of ERCs on reflector shape and demonstrate their advantages over PWRCs in 3D diffraction modeling of PP and PS reflection data.
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Sakai, Daisuke, Jun Nishikawa, Hiroshi Kakiuchida e Euichi Hirose. "Stack of cellular lamellae forms a silvered cortex to conceal the opaque organ in a transparent gastropod in epipelagic habitat". PeerJ 10 (28 ottobre 2022): e14284. http://dx.doi.org/10.7717/peerj.14284.
Testo completoAbstract (sommario):
Background Gelatinous zooplankton in epipelagic environments often have highly transparent bodies to avoid detection by their visual predators and prey; however, the digestive systems are often exceptionally opaque even in these organisms. In a holoplanktonic gastropod, Pterotrachea coronata, the visceral nucleus is an opaque organ located at the posterior end of its alimentary system, but this organ has a mirrored surface to conceal its internal opaque tissue. Results Our ultrastructural observation proved that the cortex of the visceral nucleus comprised a stack of thin cellular lamellae forming a Bragg reflector, and the thickness of lamellae (0.16 µm in average) and the spaces between the lamellae (0.1 µm in average) tended to become thinner toward inner lamellae. Based on the measured values, we built virtual models of the multilamellar layer comprising 50 lamellae and spaces, and the light reflection on the models was calculated using rigorous coupled wave analysis to evaluate their properties as reflectors. Our simulation supported the idea that the layer is a reflective tissue, and the thickness of the lamella/space must be chirped to reflect sunlight as white/silver light, mostly independent of the angle of incidence. Conclusions In P. coronata, the cortex of the visceral nucleus comprised multicellular lamellae that form a chirped Bragg reflector. It is distinct in structure from the intracellular Bragg structures of common iridophores. This novel Bragg reflector demonstrates the diversity and convergent evolution of reflective tissue using reflectin-like proteins in Mollusca.
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Yuan, Sichen. "Review of Root-Mean-Square Error Calculation Methods for Large Deployable Mesh Reflectors". International Journal of Aerospace Engineering 2022 (4 agosto 2022): 1–18. http://dx.doi.org/10.1155/2022/5352146.
Testo completoAbstract (sommario):
In the design of a large deployable mesh reflector, high surface accuracy is one of ultimate goals since it directly determines overall performance of the reflector. Therefore, evaluation of surface accuracy is needed in many cases of design and analysis of large deployable mesh reflectors. The surface accuracy is usually specified as root-mean-square error, which measures deviation of a mesh geometry from a desired working surface. In this paper, methods of root-mean-square error calculation for large deployable mesh reflectors are reviewed. Concept of reflector gain, which describes reflector performance, and its relationship with the root-mean-square error is presented. Approaches to prediction or estimation of root-mean-square error in preliminary design of a large deployable mesh reflector are shown. Three methods of root-mean-square error calculation for large deployable mesh reflectors, namely, the nodal deviation root-mean-square error, the best-fit surface root-mean-square error, and the direct root-mean-square error, are presented. Concept of effective region is introduced. An adjusted calculation of root-mean-square error is suggested when the concept of effective region is involved. Finally, these reviewed methods of root-mean-square error calculation are applied to surface accuracy evaluation of a two-facet mesh geometry, a center-feed mesh reflector, and an offset-feed mesh reflector for demonstration and comparison.
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Saki, Morvarid, Christine Thomas e Rafael Abreu. "Detection and modelling of strong topography of mid-mantle structures beneath the North Atlantic". Geophysical Journal International 229, n. 1 (17 novembre 2021): 219–34. http://dx.doi.org/10.1093/gji/ggab465.
Testo completoAbstract (sommario):
SUMMARY There is mounting evidence for the presence of seismic reflectors in the mantle at a depth of around 1000 km, however, the cause for these reflectors is not yet well established and published observations show a range of depth estimates for these structures. Discussion is also still ongoing whether it is one global or several different reflectors. Here, we investigate the presence of seismic reflectors beneath the North Atlantic using a large number of PP and SS underside reflections. We analyse over 2600 earthquakes with Mw ≥ 5.7 and use array seismic methods to improve the visibility of the small-amplitude reflected signals. The measured time lag between PP/SS arrivals and their corresponding precursors on robust stacks are used to estimate the depth of the reflector. Our results reveal the presence of mid-mantle structure beneath the North Atlantic in a depth range of ∼700–1300 km, consistent for both P- and S-wave observations. The reflector depth is shallower than 1000 km beneath the southern part of the investigation area and deepens seemingly abruptly towards the northern part of the North Atlantic. We find polarity variations in a region of strong depth change which we assume to be due to wave interference. Using 3-D waveform modelling, we implement models with strong topography as well as models with two overlapping reflectors and two separated reflectors and show that a large step in reflector depth over a short lateral distance, as imaged with our data set, can be resolved, while the discrimination between strong topography and two overlapping and separated reflectors, respectively, is also possible. The variations in precursor polarity can also be observed in our synthetic data in the region of strong topography confirming our assumption of wave interference for generating apparent precursor polarity and waveform changes. While the opposite polarity can be produced by the two overlapping reflectors as well, the strong topography model is preferred in this region, since we do detect only one reflected signal in our observations.
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Kostenko, Stanislav, Natalia Fedak e Olga Mayak. "SIMULATION OF THE RADIANT HEAT TRANSFER PROCESS IN THE ELEMENTS OF ROASTING EQUIPMENT". ScienceRise, n. 5 (11 novembre 2020): 80–88. http://dx.doi.org/10.21303/2313-8416.2020.001474.
Testo completoAbstract (sommario):
The object of the research is the process of radiation heat transfer, taking into account a single reflection of rays in the IR device of food production.
Investigated problem – the work is devoted to solving the problem of irregularity of radiation heat transfer during infrared roasting of food products.
Main scientific results. The inverse problem of heat transfer by radiation has been solved and a technique has been developed for determining the profiles of the ray flux reflectors for uniform irradiation of receivers of a convex section. Analytical modeling of all-round uniform irradiation of an elliptical receiver has been carried out. An experimental device with low-inertia temperature sensors for infrared roasting of semi-finished meat products has been developed, which makes it possible to use a reflector shaped according to the developed analytical technique. The verification of the created technique for determining the profiles of reflectors by means of a computer experiment using the TracePro and Mathcad software systems has been carried out.
The area of practical use of the research results: the use of an experimental device with a radiant flux reflector for roasting semi-finished meat products proves that the obtained technique for profiling reflectors of heat engineering systems is acceptable for the design of infrared equipment for food production and restaurant facilities. This technique allows simulating the profile of the radiant flux reflector depending on the shape of the receiver. Studies have shown that the use of a profiled reflector in the experimental device reduces the duration of roasting of natural portioned semi-finished beef products by 33 %.
Innovative technological product: a technique for determining the profiles of ray flux reflectors for uniform irradiation of receivers with a convex section. Device for infrared roasting of semi-finished meat products.
Scope of application of an innovative technological product. The study of an experimental device with a designed radiant flux reflector for roasting semi-finished meat products proves that the obtained technique for profiling reflectors of heat engineering systems is acceptable for the design of infrared equipment for food production and restaurant facilities. Using this approach allows to approach the solution of the problem of irregularity of irradiation of products during infrared roasting
42
Köhler, K., e M. Koenig. "Reconstruction of reflecting structures from vertical seismic profiles with a moving source". GEOPHYSICS 51, n. 10 (ottobre 1986): 1923–38. http://dx.doi.org/10.1190/1.1442049.
Testo completoAbstract (sommario):
When a vertical seismic profile (VSP) is recorded, the illuminated part of a reflector depends upon the shape and position of the reflector itself as well as on the seismic velocities and the positions of sources and receivers. A preferable arrangement for the investigation of structures of reflectors is to fix the receiver(s) at constant depth(s) in the well and move the source horizontally along a line at the Earth’s surface, usually called a “multioffset VSP” (MSP) or “walkaway VSP.” As a test of the resolution power of this survey geometry, synthetic records were generated from a subsurface model by inverse Kirchhoff migration. Three different methods were applied for the reconstruction. Wavefront construction leads to the correct shape of the reflectors, thus assuring the validity of the modeling method applied. Reflection‐point mapping delivered a near similarity to the model, but without focusing fault edges. Kirchhoff migration resulted in a detailed image of the reflectors with fault edges focused. Application of reflection‐point mapping and Kirchhoff migration to a real survey delivered results consistent with results from a survey at the Earth’s surface.
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Soni, V., A. Hadjadj, A. Chaudhuri e G. Ben-Dor. "Shock-wave reflections over double-concave cylindrical reflectors". Journal of Fluid Mechanics 813 (17 gennaio 2017): 70–84. http://dx.doi.org/10.1017/jfm.2016.825.
Testo completoAbstract (sommario):
Numerical simulations were conducted to understand the different wave configurations associated with the shock-wave reflections over double-concave cylindrical surfaces. The reflectors were generated computationally by changing different geometrical parameters, such as the radii of curvature and the initial wedge angles. The incident-shock-wave Mach number was varied such as to cover subsonic, transonic and supersonic regimes of the flows induced by the incident shock. The study revealed a number of interesting wave features starting from the early stage of the shock interaction and transition to transitioned regular reflection (TRR) over the first concave surface, followed by complex shock reflections over the second one. Two new shock bifurcations have been found over the second wedge reflector, depending on the velocity of the additional wave that appears during the TRR over the first wedge reflector. Unlike the first reflector, the transition from a single-triple-point wave configuration (STP) to a double-triple-point wave configuration (DTP) and back occurred several times on the second reflector, indicating that the flow was capable of retaining the memory of the past events over the entire process.
44
Nedlin, G. "The special features of P-S arrivals". GEOPHYSICS 51, n. 2 (febbraio 1986): 347–52. http://dx.doi.org/10.1190/1.1442093.
Testo completoAbstract (sommario):
There is no reciprocity in the arrival times for P-S reflections, i.e., arrival times are different if the locations of the shot and geophone are exchanged. For P-S reflections in CMP panels, this results in terms in the arrival times [Formula: see text] which are linear in offsets [Formula: see text] The principle of reciprocity still holds if the medium is laterally homogeneous and the reflectors are horizontal. For a laterally homogeneous‐earth model, with a nonhorizontal reflector, the analysis of [Formula: see text] curves for P-S arrivals, particularly for terms linear in x, provides new opportunities for obtaining information about local (near the reflector) velocities and velocities which have been averaged over depth. If there is a dipping reflector (or if there is a lateral variation of earth parameters) the coincident shotgeophone P-S reflection does not correspond to the normal incident angle. Therefore, for coincident locations of the shot and geophone, there exists a converted S-wave of nonzero amplitude.
45
Czikhardt, Richard, Hans van der Marel e Juraj Papco. "GECORIS: An Open-Source Toolbox for Analyzing Time Series of Corner Reflectors in InSAR Geodesy". Remote Sensing 13, n. 5 (2 marzo 2021): 926. http://dx.doi.org/10.3390/rs13050926.
Testo completoAbstract (sommario):
Artificial radar reflectors, such as corner reflectors or transponders, are commonly used for radiometric and geometric Synthetic Aperture Radar (SAR) sensor calibration, SAR interferometry (InSAR) applications over areas with few natural coherent scatterers, and InSAR datum connection and geodetic integration. Despite the current abundance of regular SAR time series, no free and open-source software (FOSS) dedicated to analyzing SAR time series of artificial radar reflectors exists. In this paper, we present a FOSS Python toolbox for efficient and automatic estimation of: (i) the clutter level of a particular site before a corner reflector installation, (ii) the Radar Cross Section (RCS) to track a corner reflector’s performance and detect outliers, for example, due to damage or debris accumulation, (iii) the Signal-to-Clutter Ratio (SCR) to predict the positioning precision and the InSAR phase variance, (iv) the InSAR displacement time series of a corner reflector network. We use the toolbox to analyze Sentinel-1 SAR time series of the network of 23 corner reflectors for InSAR monitoring of landslides in Slovakia.
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Yang, Guigeng, Aofei Tang, Yiqun Zhang, Zhenyi Yuan e Lingfei Kong. "Optimal Topology Configuration Design of Contoured-Beam Mesh Reflectors". International Journal of Antennas and Propagation 2022 (27 febbraio 2022): 1–8. http://dx.doi.org/10.1155/2022/6283486.
Testo completoAbstract (sommario):
It is significant for the practical application of space-borne mesh-shaped reflectors to reduce the structural complexity under the condition of the far-field electromagnetic (EM) performance being satisfied. To address this problem, an optimal topology configuration design method is proposed for the mesh-shaped reflectors. First, a multifrequency optimization model is established to obtain the mesh-shaped reflector. The reflector nodal deviations in the x-, y-, and z-directions are simultaneously selected as design variables to design the shape of the mesh reflector and realize the required contoured beams within the whole frequency band. Then, based on the multifrequency optimization model, an iterative design technology is proposed to obtain the optimal topology configuration of the mesh-shaped reflector. Finally, a typical example of a mesh reflector with contoured beams covering the continental United States (CONUS) is investigated to demonstrate the feasibility of the method.
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Lin, Guo Chang, Hui Feng Tan e Xiang Hong Bai. "Deformation Measurement of an Inflatable Reflector Using Digital Image Correlation". Applied Mechanics and Materials 66-68 (luglio 2011): 822–26. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.822.
Testo completoAbstract (sommario):
Inflatable antenna is a potential technique for large space deployable antenna and knowing its reflector’s deformation behavior is quite important for its accuracy improvement. A 1.5m-diameter inflatable reflector’s deformations at different internal pressures are studied using digital image correlation(DIC) in the paper. Because of the symmetry of the reflector, only two representative gores on the reflector are chosen to study. During the digital image correlation measurement, some article random dot patterns are drawn on the reflector’s surface. The 2D and 3D displacement maps of the reflector at different internal pressures are gained by DIC measurement and the cross-section of one gore of the reflector according to the internal pressure are analyzed from the measurement results.
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Robb, N. I. "Teaching reflection from a corner cube reflector". Physics Teacher 29, n. 4 (aprile 1991): 255. http://dx.doi.org/10.1119/1.2343299.
Testo completo
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Schaefer, Raymond B. "Reflectors and reflector light and sound source systems". Journal of the Acoustical Society of America 127, n. 3 (2010): 1702. http://dx.doi.org/10.1121/1.3359214.
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Larner, Ken L., e Jack K. Cohen. "Migration error in transversely isotropic media with linear velocity variation in depth". GEOPHYSICS 58, n. 10 (ottobre 1993): 1454–67. http://dx.doi.org/10.1190/1.1443360.
Testo completoAbstract (sommario):
Given the sensitivity of imaging accuracy to the velocity used in migration, migration founded (as in practice) on the erroneous assumption that a medium is isotropic can be expected to be inaccurate for steep reflectors. Here, we estimate errors in interpreted reflection time and lateral position as a function of reflector dip for transversely isotropic models in which the axis of symmetry is vertical and the medium velocity varies linearly with depth. We limit consideration to media in which ratios of the various elastic moduli are independent of depth. Tests with reflector dips up to 120 degrees on a variety of anisotropic media show errors that are tens of wavelengths for dips beyond 90 degrees when the medium (unrealistically) is homogeneous. For a given anisotropy, the errors are smaller for inhomogeneous media; the larger the velocity gradient, the smaller the errors. For gradients that are representative of the subsurface, lateral‐position errors tend to be minor for dips less than about 60 degrees, growing to two to five wavelengths as dip passes beyond 90 degrees. These errors depend on reflector depth and average velocity to the reflector only through their ratio, i.e., migrated reflection time. Migration error, which is found to be unrelated to the ratio of horizontal to vertical velocity, is such that reflections with later migrated reflection times tend to be more severely overmigrated than are those with earlier times. Over a large range of dips, migration errors that arise when anisotropy is ignored but inhomogeneity is honored tend to be considerably smaller than those encountered when inhomogeneity is ignored in migrating data from isotropic, inhomogeneous media.