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Reflector
Kinds of Reflector Terms modified by Reflector Selected AbstractsBeating lensing cosmic variance with galaxy tomographyMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2004Ue-Li Pen ABSTRACT We discuss the use of cross-correlations between galaxies with distance information and projected weak lensing dark matter maps to obtain a fully three-dimensional dark matter map and power spectrum. On large scales (l, 100) one expects the galaxies to be biased, but not stochastic. I show that this allows a simultaneous solution of the full three-dimensional evolving galaxy bias and the dark matter power spectrum simultaneously. Within the photometric redshift information of the Canada,France,Hawaii (CFH) lensing legacy survey, this allows a threefold reduction of statistical error, while a cross-correlation with the Canadian Large Adaptive Reflector (CLAR) or other deep spectroscopic surveys allows a tenfold improvement in dark matter power accuracy on linear scales. This makes lensing surveys more sensitive to the cosmic equation of state and the neutrino masses. [source] Color- and Reflectance-Tunable Multiple Reflectors Assembled from Three Polymer FilmsADVANCED MATERIALS, Issue 14 2010Na Young Ha Tunings of reflectance and colors of multiple photonic bandgaps are demonstrated in the whole visible region by changing the polarization state of incident light. Two tunable systems are assembled from the same three materials of an anisotropic polymeric nematic liquid crystal film and two kinds of isotropic polymer film. The only difference between the two systems is the stacking sequence. [source] Fast Inverse Reflector Design (FIRD)COMPUTER GRAPHICS FORUM, Issue 8 2009A. Mas I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism; I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling , Physically based modeling; I.3.1 [Hardware architecture]: Graphics processors Abstract This paper presents a new inverse reflector design method using a GPU-based computation of outgoing light distribution from reflectors. We propose a fast method to obtain the outgoing light distribution of a parametrized reflector, and then compare it with the desired illumination. The new method works completely in the GPU. We trace millions of rays using a hierarchical height-field representation of the reflector. Multiple reflections are taken into account. The parameters that define the reflector shape are optimized in an iterative procedure in order for the resulting light distribution to be as close as possible to the desired, user-provided one. We show that our method can calculate reflector lighting at least one order of magnitude faster than previous methods, even with millions of rays, complex geometries and light sources. [source] From the intra-desert ridges to the marine carbonate island chain: middle to late Permian (Upper Rotliegend,Lower Zechstein) of the Wolsztyn,Pogorzela high, west PolandGEOLOGICAL JOURNAL, Issue 2-3 2010Hubert Kiersnowski Abstract The tectonic Wolsztyn,Pogorzela palaeo-High (WPH) is the south-eastern termination of the Brandenburg,Wolsztyn High (western Poland), which during Late Permian times was an intra-basin ridge surrounded by Upper Rotliegend sedimentary basins within the Southern Permian Basin. The geological history and structural framework of the WPH are complex. The High belongs to the Variscan Externides, consisting at present of strongly folded, faulted and eroded Viséan to Namurian flysch deposits capped by a thick cover of Upper Carboniferous,Lower Permian volcanic rocks. This sedimentary-volcanic complex was strongly fragmented and vertically differentiated by tectonic movements and subsequently eroded, resulting in the deposition of coarse clastics surrounding uplifted tectonic blocks. During late Rotliegend time, arid climatic conditions significantly influenced occurrences of specific facies assemblages: alluvial, fluvial, aeolian and playa. Sedimentological study helped to recognize the interplay of tectonic and palaeoclimatic factors and to understand the phenomenon of aeolian sandstones interbedded with coarse deposits of alluvial cones close to fault scarps. Subsequent tectonic and possible thermal subsidence of the studied area was synchronous with inundation by the Zechstein Sea. The rapid inundation process allowed for the preservation of an almost perfectly protected Uppermost Rotliegend landscape. Based on 3D seismic data from the base Zechstein reflector, a reconstruction of Rotliegend palaeogeomorphology was carried out, which shows examples of tectonic rejuvenation of particular tectonic blocks within the WPH area before inundation by the Zechstein Sea. The inundation led to the deposition of the marine Kupferschiefer Shale followed by the Zechstein Limestone. In the deeper parts of the basin the latter is developed in thin basinal facies: in shallow parts (e.g. uplifted tectonic blocks forming in some cases islands), carbonate buildups were formed. The remarkable thickness of those buildups (bryozoan reefs) is interpreted as due to stable tectonic subsidence together with a rise of sea level. A detailed study of carbonate buildups has showed that their internal structure reflects changes in shallow marine environments and even emersion events, caused by sea-level oscillations and tectonic movements of the reef substrate. Copyright © 2010 John Wiley & Sons, Ltd. [source] P - and S -wave reflectors in D, beneath southeast AsiaGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2009Jeremy W. Chaloner SUMMARY Earthquakes from the South Pacific region recorded at the Kyrgyz Seismic Network (KNET) and the GHENGIS network (both part of the Tien Shan Continental Dynamics study) have been analysed to search for evidence of reflections from the D, region. The reflection points of this source,receiver combination are in a seismically fast area beneath Southeast Asia. Employing several array methods, we find evidence for reflections from a D, reflector in both P and S waves. The reflector depth generally agrees for both wave types. There is some evidence for a second, deeper reflector in this region; migrating the data suggests a lower-seismic reflector beneath the northeastern end of the study region. The waveforms of P and S waves imply that the upper reflector has a negative impedance contrast for P but a positive impedance contrast for S. Several possibilities are discussed for generating the observed reflector(s), with the post-perovskite phase transition in combination with a cold slab being the preferred explanation. [source] Seismic constraints on the three-dimensional geometry of low-angle intracrustal reflectors in the Southern Iberia Abyssal PlainGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2008S. M. Dean SUMMARY Several lines of evidence suggest that simple shear rifting of the continental crust, in the form of low-angle detachment faulting, occurred during the final stages of continental breakup between West Iberia and the Grand Banks. The primary evidence for such faulting is the occurrence of low-angle, high amplitude reflectors within the basement adjacent to the ocean,continent transition zone. Here we present a series of intersecting, depth migrated seismic reflection profiles that image one such reflector, the H-reflector, located on the southern edge of Galicia Bank. ,H' lies beneath several boreholes drilled during ODP Legs 149 and 173, in a region where the oceanward extent of extended continental crust steps at least 150 km westward from its location in the southern Iberia Abyssal Plain to its location off the relatively shallow Galicia Bank. In our profiles ,H' appears to define a surface that extends over a region of at least 200 km2 and that dips down ,19° to the north, towards Galicia Bank. The profiles show that a close affinity exists between ,H' and the most seaward continental crust. Based on geophysical data and ODP drilling results, we infer that the basement above ,H' is composed of continental crust deformed by extensional faults into a series of wedge-shaped blocks and thin slivers. These basement wedges have a complex 3-D geometry. ,H' rises to the basement surface on a number of the seismic profiles and appears to define locally the oceanward extent of continental fault blocks. [source] Seismic evidence for a sharp lithospheric base persisting to the lowermost mantle beneath the CaribbeanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2008Tadashi Kito SUMMARY Broad-band data from South American earthquakes recorded by Californian seismic networks are analysed using a newly developed seismic wave migration method,the slowness backazimuth weighted migration (SBWM). Using the SBWM, out-of-plane seismic P -wave reflections have been observed. The reflection locations extend throughout the Earth's lower mantle, down to the core,mantle boundary (CMB) and coincide with the edges of tomographically mapped high seismic velocities. Modelling using synthetic seismograms suggests that a narrow (10,15 km) low- or high-velocity lamella with about 2 per cent velocity contrast can reproduce the observed reflected waveforms, but other explanations may exist. Considering the reflection locations and synthetic modelling, the observed out-of-plane energy is well explained by underside reflections off a sharp reflector at the base of the subducted lithosphere. We also detect weaker reflections corresponding to the tomographically mapped top of the slab, which may arise from the boundary between the Nazca plate and the overlying former basaltic oceanic crust. The joint interpretation of the waveform modelling and geodynamic considerations indicate mass flux of the former oceanic lithosphere and basaltic crust across the 660 km discontinuity, linking processes and structure at the top and bottom of the Earth's mantle, supporting the idea of whole mantle convection. [source] Lithospheric structure of an active backarc basin: the Taupo Volcanic Zone, New ZealandGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2006Antony Harrison SUMMARY Seismic data from both explosive and earthquake sources have been used to model the crustal and upper-mantle velocity structure beneath the Taupo Volcanic Zone (TVZ), an active backarc basin in central North Island, New Zealand. Volcanic sediments with P -wave velocities of 2.0,3.5 km s,1 reach a maximum thickness of 3 km beneath the central TVZ. Underlying these sediments to 16 km depth is material with velocities of 5.0,6.5 km s,1, interpreted as quartzo-feldspathic crust. East and west of the TVZ, crust with similar velocities is found to depths of 30 and 25 km, respectively. Beneath the TVZ, material with P -wave velocities of 6.9,7.3 km s,1 is found from 16 to 30 km depth and is interpreted as heavily intruded or underplated lower crust. The base of the crust at 30 km depth under the TVZ is marked by a strong seismic reflector, interpreted as the Moho. Modelling of arrivals from deep (>40 km) earthquakes near the top of the underlying subducting Pacific Plate reveals a region with low mantle velocities of 7.4,7.8 km s,1 beneath the crust of the TVZ. This region of low mantle velocities is best explained by the presence of partially hydrated upper mantle, resulting from dehydration of hydrous minerals (e.g. serpentinite) carried down by the underlying subducting plate. Within the lower crust beneath the TVZ, a region of high (0.34) Poisson's ratio is observed, indicating the presence of at least 1 per cent partial melt. This melt probably fractionates and assimilates crustal material before some of it migrates into the upper crust, where it provides a source for the voluminous rhyolitic magmas of the TVZ. [source] The sedimentary structure of the Lomonosov Ridge between 88°N and 80°NGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2005Wilfried Jokat SUMMARY While the origin of the 1800-km-long Lomonosov Ridge (LR) in the Central Arctic Ocean is believed to be well understood, details on the bathymetry and especially on the sediment and crustal structure of this unique feature are sparse. During two expeditions in 1991 and 1998 into the Central Arctic Ocean several high quality seismic lines were collected along the margin of the ridge and in the adjacent Makarov Basin (MB). The lines collected between 87°36,N and 80°N perpendicular to and along the LR show a sediment starved continental margin with a variety of geological structures. The different features may reflect the different geological histories of certain ridge segments and/or their different subsidence histories. The sediments in the deep MB have thicknesses up to 2.2 km (3 s TWT) close to the foot of the ridge. At least in part basement reflections characteristics suggest oceanic crust. The acoustically stratified layers are flat lying, except in areas close to the ridge. Seismic units on the LR can be divided into two units based on refraction velocity data and the internal geometry of the reflections. Velocities <3.0 km s,1 are considered to represent Cenozoic sediments deposited after the ridge subsided below sea level. Velocities >4.0 km s,1 are associated with faulted sediments at deeper levels and may represent acoustic basement, which was affected by the Late Cretaceous/Early Cenozoic rift events. Along large parts of the ridge the transition of the two units is associated with an erosional unconformity. Close to the Laptev Sea such an erosional surface may not be present, because of the initial great depths of the rocks. Here, the deeper strata are affected by tectonism, which suggests some relative motion between the LR and the Laptev Shelf. Stratigraphic correlation with the Laptev Sea Shelf suggests that the ridge has not moved as a separate plate over the past 10 Myr. The seismic and regional gravity data indicate that the ridge broadens towards the Laptev Shelf. Although the deeper structure may be heavily intruded and altered, the LR appears to extend eastwards as far as 155°E, a consequence of a long-lived Late Cretaceous rift event. The seismic data across LR support the existence of iceberg scours in the central region of the ridge as far south as 81°N. However, no evidence for a large erosional events due to a more than 1000-m-thick sea ice cover is visible from the data. South of 85°N the seismic data indicate the presence of a bottom simulating reflector along all lines. [source] Recovering acoustic reflectivity using Dirichlet-to-Neumann maps and left- and right-operating adjoint propagatorsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2005M. W. P. Dillen SUMMARY Constructing an image of the Earth subsurface from acoustic wave reflections has previously been described as a recursive downward redatuming of sources and receivers. Most of the methods that have been presented involve reflectivity and propagators associated with one-way wavefield components. In this paper, we consider the reflectivity relation between two-way wavefield components, each a solution of a Helmholtz equation. To construct forward and inverse propagators, and a reflection operator, the invariant-embedding technique is followed, using Dirichlet-to-Neumann maps. Employing bilinear and sesquilinear forms, the forward- and inverse-scattering problems, respectively, are treated analogously. Through these mathematical constructs, the relationship between a causality radiation condition and symmetry, with respect to a bilinear form, is associated with the requirement of an anticausality radiation condition with respect to a sesquilinear form. Using reciprocity, sources and receivers are redatumed recursively to the reflector, employing left- and right-operating adjoint propagators. The exposition of the proposed method is formal, that is numerical applications are not derived. The key to applications lies in the explicit representation, characterization and approximation of the relevant operators (symbols) and fundamental solutions (path integrals). Existing constructive work which could be applied to the proposed method are referred to in the text. [source] Streamer tomography velocity models for the Gulf of Corinth and Gulf of Itea, GreeceGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2004Barry C. Zelt SUMMARY The Gulf of Corinth (GOC), Greece is a rapidly extending, active continental rift with a record of large, damaging earthquakes. An extensive multichannel seismic (MCS) survey of the GOC conducted in 2001 provided, in addition to the processed MCS images, the opportunity to constrain velocity structure using refracted arrivals recorded along a 6-km-long streamer. We use first-arrival traveltimes to derive tomographic P -wave velocity models for several profiles collected in the central portion of the GOC. Eight of the profiles are closely spaced, north,south lines crossing the GOC and extending into the Gulf of Itea (GOI); a ninth profile is an east,west-oriented tie line. The N,S profiles image the relatively simple velocity structure of the deep Corinth rift basin and more complicated structure of the northern margin of the currently active rift. Integration of the velocity models with migrated MCS sections shows that south of the GOI the basement, which comprises Mesozoic nappes, occurs at a velocity of 4.5 km s,1 in the velocity models, although the actual velocity at, or just below, the top of basement is probably closer to 5,5.5 km s,1. The maximum sediment thickness in the Corinth basin is 2.2 km. The basement shallows to the north into a fault-bounded terrace in the central region between the two gulfs. Sediment cover in this central region decreases in thickness from west to east. Beneath the GOI, low average velocities beneath the rift-onset reflector indicate the presence of pre-rift sediments. The pre-rift velocity structure in the GOI is complex, with significant lateral variation from west to east. The E,W line shows that high-velocity basement is shallow (,1 km depth) and flat to the west of the GOI but dips ,20° east down to ,1.5 km beneath the pre-rift sediments of the GOI. [source] A reflector at 200 km depth beneath the northwest PacificGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2001S. Rost SUMMARY We present an analysis of precursors to PP produced by underside reflections from discontinuities in the upper mantle beneath the NW Pacific. The events used for this study occur in the western Pacific Rim (New Zealand, Fiji, Tonga, Solomon, New Guinea, Philippine Islands) and are recorded at the short-period Yellowknife Array (YKA) in northern Canada. The source,receiver combination results in PP reflection points which allow us to study the upper mantle structure in a corridor from the Hawaiian Islands to the Kuril subduction zone. To detect the weak precursors in the time window between the P arrival and the PP onset and to identify them as PP underside reflections, special array techniques are used. Our analysis indicates a reflector at a depth of ,200 km beneath the northwestern Pacific. This reflector shows strong topography of some tens of kilometres on length scales of several hundred kilometres, complicating the detection of this reflector in global or regional stacks of seismograms. Different models for the impedance jump across the reflector, the thickness and the possible fine structure of the reflector are modelled using synthetic seismograms and are compared with the data. The thickness of the reflector has to be less than 7 km and the P wave impedance contrast has to be larger than 5.0,6.5 per cent to be detected by this study. This corresponds to a P -velocity jump of ,4 per cent assuming the PREM density model. [source] Hydraulic pathways in the crystalline rock of the KTBGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2000Günter Zimmermann Fracture systems and fluid pathways must be analysed in order to understand the dynamical processes in the upper crust. Various deterministic as well as stochastic fracture networks in the depth section of the Franconian Lineament (6900 to 7140 m), which appears as a brittle ductile shear zone and prominent seismic reflector, were modelled to simulate the hydraulic situation at the two boreholes of the Continental Deep Drilling Program (KTB). They led to estimations of the hydraulic permeability in crystalline rock. The geometrical parameters of the fractures, such as fracture locations and orientations, were determined from structural borehole measurements, which create an image of the borehole wall. The selection of potentially open fractures was decided according to the stress field. Only fractures with the dip direction (azimuth) of the fracture plane perpendicular to the maximum horizontal stress field were assumed to be open. The motivation for this assumption is the fact that the maximum horizontal stress is higher than the vertical stress from the formation, indicating that the state of stress is a strike-slip faulting. Therefore, the probability of open fractures due to this particular stress field at the KTB sites is enhanced. Length scales for fracture apertures and extensions were stochastically varied and calibrated by hydraulic experiments. The mean fracture aperture was estimated to be 25 ,m, assuming an exponential distribution, with corresponding permeability in the range of 10,16 m2. Similar results were also obtained for log-normal and normal distributions, with a variation of permeability of the order of a factor of 2. The influence of the fracture length on permeability of the stochastic networks was also studied. Decreasing the fracture length beyond a specific threshold of 10 m led to networks with vanishing connectivity and hence vanishing permeability. Therefore, we assume a mean fracture length exceeding the threshold of 10 m as a necessary assumption for a macroscopic hydraulically active fracture system at the KTB site. The calculated porosity due to the fracture network is of the order of 10,3 per cent, which at first sight contradicts the estimated matrix porosity of 1 to 2 per cent from borehole measurements and core measurements. It can be concluded from these results, however, that if the fluid transport is due to a macroscopic fracture system, only very low porosity is needed for hydraulic flow with permeabilities up to several 10,16 m2, and hence the contribution of matrix porosity to the hydraulic transport is of a subordinate nature. [source] Synthesis of a seismic virtual reflector,GEOPHYSICAL PROSPECTING, Issue 3 2010Flavio Poletto ABSTRACT We describe a method to process the seismic data generated by a plurality of sources and registered by an appropriate distribution of receivers, which provides new seismic signals as if in the position of the receivers (or sources) there was an ideal reflector, even if this reflector is not present there. The data provided by this method represent the signals of a virtual reflector. The proposed algorithm performs the convolution and the subsequent sum of the real traces without needing subsurface model information. The approach can be used in combination with seismic interferometry to separate wavefields and process the reflection events. The application is described with synthetic examples, including stationary phase analysis and with real data in which the virtual reflector signal can be appreciated. [source] Seismic characterization of vertical fractures described as general linear-slip interfacesGEOPHYSICAL PROSPECTING, Issue 2 2003Vladimir Grechka ABSTRACT Fluid flow in many hydrocarbon reservoirs is controlled by aligned fractures which make the medium anisotropic on the scale of seismic wavelength. Applying the linear-slip theory, we investigate seismic signatures of the effective medium produced by a single set of ,general' vertical fractures embedded in a purely isotropic host rock. The generality of our fracture model means the allowance for coupling between the normal (to the fracture plane) stress and the tangential jump in displacement (and vice versa). Despite its low (triclinic) symmetry, the medium is described by just nine independent effective parameters and possesses several distinct features which help to identify the physical model and estimate the fracture compliances and background velocities. For example, the polarization vector of the vertically propagating fast shear wave S1 and the semi-major axis of the S1 -wave normal-moveout (NMO) ellipse from a horizontal reflector always point in the direction of the fracture strike. Moreover, for the S1 -wave both the vertical velocity and the NMO velocity along the fractures are equal to the shear-wave velocity in the host rock. Analysis of seismic signatures in the limit of small fracture weaknesses allows us to select the input data needed for unambiguous fracture characterization. The fracture and background parameters can be estimated using the NMO ellipses from horizontal reflectors and vertical velocities of P-waves and two split S-waves, combined with a portion of the P-wave slowness surface reconstructed from multi-azimuth walkaway vertical seismic profiling (VSP) data. The stability of the parameter-estimation procedure is verified by performing non-linear inversion based on the exact equations. [source] Finding the strike direction of fractures using GPRGEOPHYSICAL PROSPECTING, Issue 3 2001Soon Jee Seol GPR reflection energy varies with antenna orientation relative to the strike and dip of the reflector. This directional dependence of GPR responses was investigated through numerical experiments and was used to estimate the azimuth of fractures and joints. Three antenna configurations were considered in this study: perpendicular-broadside (YY mode), parallel-broadside (XX mode) and cross-polarization (YX mode). The reflection energy in the cross-polarization mode shows a shape characteristic similar to the strike, regardless of the dip angle. Those in the other two modes show quite different amplitudes from the strike, depending on the dip angle. We have developed a strike-direction-finding scheme using data obtained from the three different modes for the same survey line. The azimuth angle of each reflector was displayed in colour on the GPR profile. This scheme was applied to a field survey at a granite quarry in southern Korea. The GPR profiles showed different images of the reflectors depending on the antenna configuration. The estimated azimuths of reflectors obtained using our scheme matched fairly well with those of known fractures and joints. [source] What is DMO coverage?GEOPHYSICAL PROSPECTING, Issue 6 2000Ralf Ferber ,Coverage' or ,fold' is defined as the multiplicity of common-midpoint (CMP) data. For CMP stacking the coverage is consistent with the number of traces sharing a common reflection point on flat subsurface reflectors. This relationship is not true for dipping reflectors. The deficiencies of CMP stacking with respect to imaging dipping events have long been overcome by the introduction of the dip-moveout (DMO) correction. However, the concept of coverage has not yet satisfactorily been updated to a ,DMO coverage' consistent with DMO stacking. A definition of constant-velocity DMO coverage will be proposed here. A subsurface reflector will be illuminated from a given source and receiver location if the time difference between the reflector zero-offset traveltime and the NMO- and DMO-corrected traveltime of the reflection event is less than half a dominant wavelength. Due to the fact that a subsurface reflector location is determined by its zero-offset traveltime, its strike and its dip, the DMO coverage also depends on these three parameters. For every surface location, the proposed DMO coverage consists of a 3D fold distribution over reflector strike, dip and zero-offset traveltime. [source] Novel mechanism for hair shine with special optical enhancement effect on blonde hairINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 2 2010S. Iwai J. Cosmet. Sci., 60, 323,336 (May/June 2009) Accepted for publication October 21, 2008. Synopsis Compared with dark or brunette hair, blonde hair has different characteristic features of appearance such as bright shine with a soft tonal color. In this report, novel optical mechanisms of the characteristic blonde hair appearance are reported. Optical analyses of goniophotometric measurements were carried out to elucidate the mechanisms of strong reflections observed in blonde hairs. As a result, reflections with much higher intensity than those from the front surface of a fiber were confirmed to play important roles in the case of blonde hair fibers, and the intensities were found to vary with the cross-sectional shape of a fiber, the ellipticity (=minor axis/major axis). From light path simulation analyses, these strong reflections were verified to result from total reflection from the back surface of a fiber. Furthermore, since each hair fiber acts as a lens and/or a reflector, intricate reflection behaviors are suggested to occur as a consequence of the combination of light condensation and total reflection. [source] Performance of laser and radar ranging devices in adverse environmental conditionsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 9 2009Julian Ryde A comparative evaluation of millimeter-wave radar and two-dimensional scanning lasers in dust and rain conditions for sensor applications in field robotics is presented. A robust and reliable method for measuring the level of suspended dust (or other obscurant media) by determining the transmission coefficient is developed and used for quantitative assessment of sensor performance. The criteria of target acquisition reliability, precision, and accuracy under varying environmental conditions are assessed via sensor operation in a controlled environment. This environment generated dust and rain of varying densities. Sensor performance is also assessed for the potential effect on digital terrain mapping and haul truck localization due to sensor-specific behaviors in these conditions (e.g., false targets, increased noise). Trials on a research electric face shovel are conducted to test observed behaviors. It is concluded that laser scanners are suitable for environments with transmissions exceeding 92%,93%/m for targets closer than 25 m. The radar remained relatively unaffected by the generated conditions of rain (50,70 mm/h) and dust (10-m visibility); however, its accuracy (0.1 m with a corner reflector and 0.3 m on a haul truck), free-space clutter, and scan rate were insufficient for locating unmodified haul trucks for this application. © 2009 Wiley Periodicals, Inc. [source] Cape Fear, Two Versions and Two Visions Separated by Thirty YearsJOURNAL OF LAW AND SOCIETY, Issue 1 2001Gerald J. Thain This essay examines the changes between 1962 and 1991 that occurred in the context within which the two very different versions of Cape Fear appeared. These two versions of the story of a threatened lawyer are emblematic of an altered perspective on law. The essay highlights the tension between art's role as a reflector of society and its values and its role shaping social views. The inference, from the different portrayals of Sam Bowden, that there has been a systematic decline in the lawyer's status and public esteem is not, however, borne out in the cinematic field. The situation has become one of moral ambiguity with the lawyer playing a more ambivalent role in society. [source] Imaging glacial sediment inclusions in 3-D using ground-penetrating radar at Kongsvegen, Svalbard,JOURNAL OF QUATERNARY SCIENCE, Issue 5 2010Tavi Murray Abstract The quiescent-phase surge-type glacier, Kongsvegen, flows confluent with the continuously fast-flowing Kronebreen in northwestern Spitsbergen. The lower regions of Kongsvegen overlie glaciomarine sediments, which have been incorporated into the ice during multiple surge events. The resulting englacial structures are exposed at the surface and on a cliff section. These structures have variously been interpreted as thrusts, formed by compression, or sediment-filled crevasses, formed by extension. We collected a grid of closely spaced ground-penetrating radar profiles in the area adjacent to the cliff section. Several structures were imaged in 3-D, including a strong subhorizontal basal reflector, which was underlain by a second, weaker subhorizontal reflector. The basal reflector was occasionally reverse faulted, suggesting compression. Clear englacial features extended upwards from it, dipping up-glacier at angles of <40° and steepening towards the glacier surface; they had complex geometries that changed rapidly cross-glacier. The structures were orientated at ,30° to ice flow, suggesting modification by lateral compression from Kronebreen. Some of these englacial structures clearly crossed the basal reflector. We conclude that the englacial features imaged are not likely to be derived from crevasse filling and were probably formed by thrusting. The results contribute to our understanding of surge initiation and termination processes, and interpretation of features in the palaeorecord. Copyright © 2009 John Wiley & Sons, Ltd. [source] Holocene sedimentation in the Skagerrak interpreted from chirp sonar and core data,JOURNAL OF QUATERNARY SCIENCE, Issue 1 2005Richard Gyllencreutz Abstract High-resolution chirp sonar profiling in the northeastern Skagerrak shows acoustically stratified sediments draping a rough-surfaced substratum. A 32 metre long sediment core retrieved from the survey area encompasses the entire Holocene and latest Pleistocene. The uppermost seismo-acoustic units in the chirp profiles represent Holocene marine sediments. The lowermost unit is interpreted as ice-proximal glacial-marine sediments rapidly deposited during the last deglaciation. The end of ice-proximal sedimentation is marked by a strong reflector, interpreted to have been formed during latest Pleistocene time as a consequence of rapid ice retreat and drastically lowered sedimentation rate. The subsequent distal glacial-marine sediments were deposited with initially high sedimentation rates caused by an isostatic rebound-associated sea-level fall. Based on correlation between the core and the chirp sonar profiles using measured sediment physical properties and AMS 14C dating, we propose a revised position for the Pleistocene/Holocene boundary in the seismo-acoustic stratigraphy of the investigated area. Copyright © 2005 John Wiley & Sons, Ltd. [source] Distribution, sediment magnetism and geochemistry of the Saksunarvatn (10 180 ± 60 cal. yr BP) tephra in marine, lake, and terrestrial sediments, northwest IcelandJOURNAL OF QUATERNARY SCIENCE, Issue 8 2002Prof. John T. Andrews Abstract In 1997, seismic surveys in the troughs off northwest and north Iceland indicated the presence of a major, regional sub-bottom reflector that can be traced over large areas of the shelf. Cores taken in 1997, and later in 1999 on the IMAGES V cruise, penetrated through the reflector. In core MD99-2269 in Húnaflóaáll, this reflector is shown to be represented by a basaltic tephra with a geochemical signature and radiocarbon age correlative with the North Atlantic-wide Saksunarvatn tephra. We trace this tephra throughout northwest Iceland in a series of marine and lake cores, as well as in terrestrial sediments; it forms a layer 1 to 25 cm thick of fine- to medium-grained basaltic volcanic shards. The base of the tephra unit is always sharp but visual inspection and other measurements (carbonate and total organic carbon weight %) indicate a more diffuse upper boundary associated with bioturbation and with sediment reworking. Off northwest Iceland the Saksunarvatn tephra has distinct sediment magnetic properties. This is evident as a dramatic reduction in magnetic susceptibility, an increase in the frequency dependant magnetic susceptibility and ,hard' magnetisation in a ,0.1T IRM backfield. Geochemical analyses from 11 sites indicate a tholeiitic basalt composition, similar to the geochemistry of a tephra found in the Greenland ice-core that dates to 10 180 ± 60 cal. yr BP, and which was correlated with the 9000 14C yr BP Saksunarvatn tephra. We present accelerator mass spectrometry 14C dates from the marine sites, which indicate that the ocean reservoir correction is close to ca. 400 yr at 9000 14C yr BP off northwest Iceland. Copyright © 2002 John Wiley & Sons, Ltd. [source] Parallel-type C+L band hybrid amplifier pumped by 1480 nm laser diodesLASER PHYSICS LETTERS, Issue 7 2008S.-K. Liaw Abstract A parallel-type, dispersion compensating C+L band erbium-doped fiber amplifier/Raman fiber amplifier is constructed by sharing a common 1480-nm pump source. The gain spectra of C+L band are flattened by optimally dividing the pump power ratio to 1:29 for EDFA and RFA, respectively. In a signal input power of ,20 dBm, the average gain is 14 dB for the C-band EDFA and 13.6 dB for the L-band RFA when a pump reflector is used to recycle the residual pump power in L-band. The noise figure value ranges from 4.6 to 6.5 dB and the polarization dependent gain is less than 0.14 dB. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Compact high-gain printed loop-antenna array integrated into a 5-GHz WLAN access pointMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2010Tzi-Chieh Hong Abstract A printed, planar loop-antenna array having a compact structure and high-gain, directional radiation properties for WLAN operation in the 5 GHz band is presented. The antenna-array design is composed of four-folded loops arranged to be of 2 × 2 configuration, printed on both sides of a 1.6-mm thick FR4 substrate, and one system printed circuit board (PCB) serving as an efficient reflector for the loops. The antenna array is set within the boundary of the PCB (size of 50 mm ×65 mm) and stacked there above by a separation distance of 5.4 mm only. That's, the design integrates the system PCB of an access point (AP) into an internal antenna solution for compact outdoor AP applications. The results show that good input matching with voltage standing wave ratio (VSWR) below 1.5 over the 5150,5825 MHz band can be achieved. Directional radiation patterns with peak gain at about 10 dBi were also obtained. Details of the antenna design are described and discussed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:2261,2267, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25487 [source] Gain factor of horn array feed offset parabolic cylindrical reflector antenna for spatial power combiningMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010Z. M. Xie Abstract A study on the horn array feeding offset parabolic cylindrical reflector antenna for spatial power combining is presented. The calculations based on the aperture integral method are agreed well with the measurements. The relationship between the gain factor and the dimensions of the antenna is analyzed. The optimal dimensions and orientation of the feeding horn as well as the optimal spread angle of the reflector are given. It is revealed that the gain factor of the antenna with an E_plane array feed is higher than that of the antenna with an H_plane array feed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1742,1747, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25348 [source] Dual-backlight unit based on a single light source integrated with a beam splitting reflectorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2009Chan-Kyu Park Abstract A dual-backlight unit incorporating a single light source integrated with a beam splitting reflector was demonstrated, providing a surface light beam for both the keypad and display section simultaneously. The reflector was realized by aligning a groove substrate with a matching cover, and a light guiding module comprising a stack of light guide panels and prism/diffuser sheets was attached to both sides of the reflector. A light emanating from the light source,placed in the middle of the substrate,undergoes a series of reflections through the reflector to reach the input of the light guiding module. Then it is transformed into a surface light beam, which is used to irradiate the keypad and display sections. As for the accomplished dual-backlight unit, the measured average luminance and the spatial luminance uniformity were respectively about 420 cd/m2 and 70% for the keypad section, and 640 cd/m2 and 80% for the display section. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1257,1260, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24297 [source] An efficient CMOS on-chip ladder reflector antenna for inter-chip communicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009Bo-Tao Jiang Abstract This article presented a new ladder reflector antenna on chip (AOC) which consisted of an active dipole and reflector array. The ladder structure was very easy to fabricate with the standard CMOS process. A ladder reflector antenna operating at the 24 GHz ISM band was designed with a standard 0.18 ,m six metal layers CMOS process. The whole antenna had a dimension of 0.025 mm × 2.84 mm. The measurement results showed that the ladder reflector antenna got a return loss of ,7.25 dB and a gain of 6.25 dBds at 24 GHz, as well as a ,5 dB impedance bandwidth of 16.2,30 GHz. The measured S12 indirectly proved the simulated radiation patterns. The data taken from the experiment indicated that the ladder reflector increased the antenna gain and effectively enhanced the energy radiating to the outside of the chip. It's very useful for the wireless interconnect for inter-chip communications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 59,63, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24000 [source] Implementation of tunable erbium doped fiber laser using a broadband fiber mirrorMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2008Shien-Kuei Liaw Abstract By using a broadband fiber mirror (BFM), a wavelength tunable erbium-doped fiber laser (TEDFL) is demonstrated composed with tunable fiber Bragg grating (TFBG). The BFM acts as a broadband reflector both for the lasing signal and pump source. At pumping power of 100 mW, stable laser output power of 21.35 dBm is obtained at a low threshold pumping power of 4.7 mW. A side mode suppression ratio (SMSR) of 57.9 dB and 16 nm wavelength scan range are demonstrated using a single TFBG. The tunable fiber laser may be a good candidate for vast applications in optical network technologies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1722,1724, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23510 [source] The experimental study of a polarization orthogonal single-longitudinal-mode distributed Bragg reflector fiber laserMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2008Luo Jian-Hua Abstract In this article, we reported a polarization orthogonal single-longitudinal-mode distributed Bragg reflector (DBR) fiber laser. The laser operated robustly in single longitudinal mode and dual polarizations with frequency difference of 976.93 MHz. This laser has simple structure as well as frequency adjustable. It can be used in a wide range of communication, sensor, and spectroscopic applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1658,1660, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23454 [source] | |||||||||||||||||||||||||||||||