Small Facets Research Articles

Soil-Landscape Estimation and Evaluation Program (SLEEP) to predict spatial distribution of soil attributes for environmental modeling.

The spatial distribution of surface and subsurface soil attributes is an important input to environmental modeling. Soil attributes represent an important input to the Soil and Water Assessment Tool (SWAT), which influence the accuracy of the modeling outputs. An ArcGIS-based tool was developed to predict soil attributes and provide inputs to SWAT. The essential inputs are digital elevation model and field observations. Legacy soil data/maps can be used to derive observations when recent field surveys are not available. Additional layers, such as satellite images and auxiliary data, improve the prediction accuracy. The model contains a series of steps (menus) to facilitate iterative analysis. The steps are summarized in deriving many terrain attributes to characterize each pixel based on local attributes as well as the characteristics of the contributing area. The model then subdivides the entire watershed into smaller facets (subdivisions of subwatersheds) and classifies these into groups. A linear regression model to predict soil attributes from terrain attributes and auxiliary data are established for each class and implemented to predict soil attributes for each pixel within the class and then merged for the entire watershed or study area. SLEEP (Soil–Landscape Estimation and Evaluation Program) utilizes Pedo-transfer functions to provide the spatial distribution of the necessary unmapped soil data needed for SWAT prediction. An application of the tool demonstrated acceptable accuracy and better spatial distribution of soil attributes compared with two spatial interpolation techniques. The analysis indicated low sensitivity of SWAT prediction to the number of field observations when SLEEP is used to provide the soil layer. This demonstrates the potential of SLEEP to support SWAT modeling where soil data is scarce. Keywords: GIS, remote sensing, terrain analyses, watershed, SWAT, inverse distance weighted, Kriging DOI: 10.3965/j.ijabe.20150803.1270 Online first on [2015-03-17] Citation: Ziadat F M, Dhanesh Y, Shoemate D, Srinivasan R, Narasimhan B, Tech J. Soil-Landscape Estimation and Evaluation Program (SLEEP) to predict spatial distribution of soil attributes for environmental modeling. Int J Agric & Biol Eng, 2015; 8(3): 158－172.

An anatomic study of the accessory anterolateral talar facet.

A small accessory facet with articular surface morphology is occasionally seen on the talus, bordering on the lateral end of the sinus tarsi. This facet has been named the accessory anterolateral talar facet. However, few anatomical studies have addressed this facet. Here we present the precise morphology of accessory anterolateral talar facet with emphasis on anatomical correlation between the presence of this facet and the angle of the infero-lateral surface of the talus (talar infero-lateral surface - TILS angle). A total of 22 (11 male, 11 female) adult cadavers with no known pathological conditions in the talocalcaneal joints were examined during educational dissection at Nagoya City University Medical School in 2013. After exclusion of 1 joint due to the poor condition of the talus, 43 talus (22 right, 21 left) were analysed. We judged the presence of the accessory anterolateral talar facet and measured TILS angle. We performed statistical analysis on the point of laterality, gender difference and the difference in the TILS angles in tali with or without the accessory anterolateral talar facets. An accessory anterolateral talar facet was identified in 11 (26%) of the 43 specimens. Of the 21 cadavers with paired talar specimens, 5 displayed the facet bilaterally. There was no sex difference and no significant laterality, however we found that TILS angle was significantly larger in accessory anterolateral talar facet positive samples than in negative ones.

The effective equivalence of geometric irregularity and surface roughness in determining particle single-scattering properties.

This study investigates the effects of geometric irregularity and surface roughness on the single-scattering properties of randomly oriented dielectric particles. Starting from a regular crystal with smooth faces, effects of roughening are compared with effects of perturbing the regular configuration of the smooth faces. Using the same slope distribution for small roughness facets and tilted faces provides a natural way to compare the effects on the single-scattering properties. It is found that the geometric irregularity and surface roughness have similar effects on the single-scattering properties of an ensemble of randomly oriented particles. In other words, particles with irregular geometries and those with surface roughness are optically equivalent if the slope distributions are the same. Furthermore, an ensemble of particles with irregular geometries can be used as an effective approximation for simulation of the scattering properties of roughened particles, and vice versa. This approach also provides new interpretation of the observed, relatively featureless and smooth, scattering phase functions of naturally occurring particles.

How do eye size and facet lens size vary by age and sex inAcheta domesticus?

Abstract. Vision is essential to interactions with the environment and survival of many animals. House crickets, Acheta domesticus, are nocturnal insects with compound apposition eyes, and thus may have a specialized visual system selected for low-light vision. Here, an analysis of regional variation in facet diameter around the eye of a cricket was conducted. Eye surface area was estimated and facet diameter was spot-sampled across the eyes of 13 adults and 13 juveniles. Juveniles had smaller facets than adults, and there was significant variation among eye regions in facet size. Specifically, larger facets were found in the posterior eye region. Overall, facets were large given the size of this animal's eye, which is consistent with what one might expect from a nocturnal insect under selection for high sensitivity. Furthermore, juveniles had proportionally larger facets than adults, which may indicate that the insects maximize the sensitivity of their ommatidia early in development, prior to increasing ...

Observations of the Atomic Structure of Tensile and Compressive Twin Boundaries and Twin–Twin Interactions in Zirconium

The boundary structures of twins in the hexagonal close-packed metal zirconium were studied. High-resolution transmission electron microscopy was used to characterize the boundary structure of $$\{10\bar{1}2\}$$ (T1), $$\{\bar{1}\bar{1}21\}$$ (T2), and $$\{\bar{1}\bar{1}22\}$$ (C1) twins on the atomic level. Basal–prismatic (B–P) plane faceting is observed along the T1 twin boundaries, matching previous observations of T1 twins in magnesium. C1 twins are observed to form basal–pyramidal (B–Py) facets along otherwise perfect twin planes. T2 twins exhibit faceting that aligns prism planes with second-order pyramidal planes across the boundary (P–Py facets). As a function of the crystallography, T2 twins appear less likely to accommodate large deviations from perfect twin planes by P–Py faceting alone, and may rely on small dislocation-accommodated facets to achieve arbitrary boundary planes. The structure of these boundaries, specifically the modes by which faceting is permitted, has a direct impact on boundary mobility. In addition, the boundary structure of two C1 twins during a twin–twin interaction event is observed, and is compared to previous observations of tensile twin–twin interactions in magnesium.

Wear Pattern, Dental Function, and Jaw Mechanism in the Late Cretaceous Ankylosaur Hungarosaurus

Feeding in thyreophoran dinosaurs is poorly understood. Although the group existed for over 130 million years, only the Early Jurassic basal thyreophoran Scelidosaurus harrisonii and the Late Cretaceous ankylosaurid Euoplocephalus tutus have been studied from this perspective in detail. In contrast to the earlier, conservative hypothesis of a simple "orthal pulping" feeding mode with no or limited tooth-tooth contact, recent studies have demonstrated precise dental occlusion with differing jaw mechanisms in these two species. Here, we describe the first detailed study of feeding related characters in a nodosaurid ankylosaur, Hungarosaurus tormai, from the Late Cretaceous of Hungary. Dental wear patterns comprising small, apical, and low-angled facets on the maxillary and steep, extended, and bowl-like facets on the dentary teeth reveal sophisticated tooth-tooth contact in this basal nodosaurid. The presence of two different scratch generations (vertical and low-angled) on the dentary teeth unambiguously demonstrate a multiphasic powerstroke, which is further supported by the morphology of the quadrate-articular and mandibular symphyseal joints and by the architecture of the reconstructed jaw adductors. Chewing started with an initial slicing phase associated with orthal movement that was followed by a retractive powerstroke with significant occlusal contact. Because of the curved tooth rows, these movements were probably facilitated by some mediolateral translation and/or axial rotation of the mandibles to produce precise shearing along the whole tooth row. These results demonstrate that complex jaw mechanisms and dental occlusion were more widespread among thyreophorans than thought previously and that palinal movement was present in at least two ankylosaurian lineages.

Variations of Gerdy's tubercle, proposal of a morphological classification: Anatomical study and its clinical importance

Abstract Introduction: Gerdy's tubercle is described as a triangular facet in standard textbooks of human anatomy. The present study addresses the prevalence and shape of the anterolateral tubercle, which has been named as Gerdy's tubercle in adult human tibia. Examination of tibia revealed in excess of usual variations in the shape and texture of tubercle present at the anterior surface of lateral condyle of tibia. Material and Methods: The study was conducted on 103 (52 right and 51 left) of either sex dry Indian tibia bone to study the shape and texture of Gerdy's tubercle. The shape and texture of tubercle were very inconsistent and varied from a small circular smooth facet to very irregular rough facet. Results: Gerdy's tubercle was triangular & smooth in 44.6%, circular & smooth in 17.4%, vertically oval & smooth in 2.9%, transversely oval & smooth in 3.8%, irregular & rough in18.4% and triangular & rough in 6.7%. In 5.8% of tibia, it was unobtrusive. Conclusion: The different shapes of Gerdy's tubercle demonstrated in the present study may contribute to produce significant effect on surgical interventions and some shapes may be more prone to traumatic injuries on it.

Volar Plate Fixation Failure for Volar Shearing Distal Radius Fractures With Small Lunate Facet Fragments

To determine the percentage of AO B3 distal radius fractures that lose reduction after operative fixation and to see whether fracture morphology, patient factors, or fixation methods predict failure. We hypothesized that initial fracture displacement, amount of lunate facet available for fixation, plate position, and screw fixation would be significant risk factors for loss of reduction. A prospective, observational review was conducted of 51 patients (52 fractures) with AO B3 (volar shearing) distal radius fractures treated operatively between January 2007 and June 2012. We reviewed a prospective distal radius registry to determine demographic data, medical comorbidities, and physical examination findings. Radiographs were evaluated for AO classification, loss of reduction, length of volar cortex available for fixation, and adequacy of stabilization of the lunate facet fragment with a volar plate. Preoperative data were compared between patients who maintained radiographic alignment and those with loss of reduction. A multivariate logistic regression analysis was completed to determine significant predictors of loss of reduction. Volar shearing fractures with separate scaphoid and lunate facet fragments (AO B3.3), preoperative lunate subsidence distance, and length of volar cortex available for fixation were significant predictors for loss of reduction; the latter was significant in multivariate analysis. Plate position and number of screws used to stabilize the lunate facet were not statistically different between groups. Patients with AO B3.3 fractures with less than 15 mm of lunate facet available for fixation, or greater than 5 mm of initial lunate subsidence, are at risk for failure even if a volar plate is properly placed. In these cases, we recommend additional fixation to maintain reduction of the small volar lunate facet fracture fragments in the form of plate extensions, pins, wires, suture, wire forms, or mini screws. Therapeutic III.

Optimisation of Size-controllable Centroidal Voronoi Tessellation for FEM Simulation of Micro Forming Processes

Voronoi tessellation has been employed to characterise material features in Finite Element Method (FEM) simulation, however, a poor mesh quality of the voronoi tessellations causes problems in explicit dynamic simulation of forming processes. Although centroidal voronoi tessellation can partly improve the mesh quality by homogenisation of voronoi tessellations, small features, such as short edges and small facets, lead to an inferior mesh quality. Further, centroidal voronoi tessellation cannot represent all real micro structures of materials because of the almost equal tessellation shape and size. In this paper, a density function is applied to control the size and distribution of voronoi tessellations and then a Laplacian operator is employed to optimise the centroidal voronoi tessellations. After optimisation, the small features can be eliminated and the elements are quadrilateral in 2D and hexahedral in 3D cases. Moreover, the mesh quality is significantly higher than that of the mesh generated on the original voronoi or centroidal voronoi tessellation. This work is beneficial for explicit dynamic simulation of forming processes, such as micro deep drawing processes.

Cervical injuries scored according to the Subaxial Injury Classification system: An analysis of the literature

Introduction:The Subaxial Injury Classification (SLIC) system and severity score has been developed to help surgeons in the decision-making process of treatment of subaxial cervical spine injuries. A detailed description of all potential scored injures of the SLIC is lacking.Materials and Methods:We performed a systematic review in the PubMed database from 2007 to 2014 to describe the relationship between the scored injuries in the SLIC and their eventual treatment according to the system score.Results:Patients with an SLIC of 1-3 points (conservative treatment) are neurologically intact with the spinous process, laminar or small facet fractures. Patients with compression and burst fractures who are neurologically intact are also treated nonsurgically. Patients with an SLIC of 4 points may have an incomplete spinal cord injury such as a central cord syndrome, compression injuries with incomplete neurologic deficits and burst fractures with complete neurologic deficits. SLIC of 5-10 points includes distraction and rotational injuries, traumatic disc herniation in the setting of a neurological deficit and burst fractures with an incomplete neurologic deficit.Conclusion:The SLIC injury severity score can help surgeons guide fracture treatment. Knowledge of the potential scored injures and their relationships with the SLIC are of paramount importance for spine surgeons who treated subaxial cervical spine injuries.

Quantification of the Crack Fragmentation Resulting from Mode I+III Loading

The crack propagation path of a crack loaded initially in mode I+III is complex. It is formed by small facets moving away from the initial plane of the crack. Recently these facets have been retrieved in phase-field simulations and by a linear stability analysis of the phenomenon. The next step is to perform some close comparaison with experiments. In this aim, we present here a systematic method to quantify the complex geometry of the facets obtained in three point bending experiments. The post-mortem crack facies are obtained by profilometry and post-treated numerically. They are quantified by three parameters: the distance between the facets, the local and global twisting angles. They are measured as a function of the propagation distance and correlated to the local values of stress intensity factors obtained by finite element simulations.

Distal radius fractures and the volar lunate facet fragment: Kirschner wire fixation in addition to volar-locked plating.

The volar lunate facet fragment of a distal radius fracture may not be stabilized with volar-locked plating alone due to the small size and distal location of the fragment. Identification and stabilization of this small fragment is critical as unstable fixation may result in radiocarpal and radioulnar joint subluxation. The addition of spring wire fixation with volar plating can provide stable internal fixation of this critical fracture fragment. A retrospective review (2006-2011) identified nine patients with distal radius fractures with an associated volar lunate facet fragment that were treated with volar-locked plating and spring wire fixation of the volar lunate facet fragment. Radiographic indices, range of motion, grip strength, and postoperative Patient-related wrist evaluation (PRWE) scores were obtained to assess pain and function. All distal radius fractures healed, and the volar lunate facet fragment reduction was maintained. The mean follow-up was 54weeks. Mean active range of motion was 46° wrist flexion, 51° wrist extension, 80° pronation, and 68° supination. The mean grip strength was 21Kg, achieving 66% of the uninjured limb. The average PRWE score was 17. No patient required removal of hardware or had evidence of tendon irritation. The addition of spring wire fixation to volar-locked plating provided stable fixation of the volar lunate facet fragment of distal radius fractures without complication. This technique addresses a limitation of volar-locked plating to control the small volar lunate facet fragment in distal radius fractures otherwise amenable to volar plating. A retrospective case series, Level IV.

The prevalence of pulp stones in historical populations from the middle euphrates valley (Syria)

There are many reports in the literature concerning pulp stones in contemporary living populations, but there are no descriptions of cases of pulp stones and their prevalence in populations of the past. Here we present a study of pulp stones in a series of archaeologically derived samples from the Middle Euphrates Valley (Syria) obtained from two sites: Terqa and Tell Masaikh. The specimens were assigned to five periods: Early Bronze (2650-2350 BC); Middle Bronze (2200-1700 BC); late Roman (AD 200-400); Islamic (AD 600-1200); and Modern Islamic (AD 1850-1950). A total of 529 teeth representing 117 adult individuals of both sexes were examined. Pulp stones were identified by X-ray and 10 selected specimens were sectioned for histological study. Pulp stones were found in 99 of 117 individuals (85%) and in 271 of 529 (51%) teeth. Pulp stone prevalence was found to increase with age, for individuals of older age classes have more pulp stones than younger individuals. Intriguingly, the prevalence of single pulp stones was higher among older individuals (36-45, >46), while younger individuals (17-25, 26-35) more often possessed multiple stones. Individuals with moderate to highly advanced dental wear have pulp stones significantly more often than individuals whose tooth wear is limited to invisible or very small facets. Though there is no statistical significance in the prevalence of pulp stones across chronological periods, it appears that a high level of calcium in the diet is accompanied by a greater prevalence of pulp stones.

Reevaluation of the lumbosacral region of Oreopithecus bambolii

Functional interpretations of the postcranium of the late Miocene ape Oreopithecus bambolii are controversial. The claim that Oreopithecus practiced habitual terrestrial bipedalism is partly based on restored postcranial remains originally recovered from Baccinello, Tuscany (Köhler and Moyà-Solà, 1997). The lower lumbar vertebrae of BA#72 were cited as evidence that Oreopithecus exhibits features indicative of a lordotic lumbar spine, including dorsal wedging of the vertebral bodies and a caudally progressive increase in postzygapophyseal interfacet distance. Here, we demonstrate why the dorsal wedging index value obtained by Köhler and Moyà-Solà (1997) for the BA#72 last lumbar vertebra is questionable due to distortion in that region, present a more reliable way to measure postzygapophyseal interfacet distance, and include an additional metric (laminar width) with which to examine changes in the transverse dimensions of the neural arches. We also quantify the external morphology of the BA#72 proximal sacrum, which, despite well-documented links between sacral morphology and bipedal locomotion, and excellent preservation of the sacral prezygapophyses, first sacral vertebral body, and right ala, was not evaluated by Köhler and Moyà-Solà (1997). Measures of postzygapophyseal interfacet distance and laminar width on the penultimate and last lumbar vertebrae of BA#72 reveal a pattern encompassed within the range of living nonhuman hominoids and unlike that of modern humans, suggesting that Oreopithecus did not possess a lordotic lumbar spine. Results further show that the BA#72 sacrum exhibits relatively small prezygapophyseal articular facet surface areas and mediolaterally narrow alae compared with modern humans, indicating that the morphology of the Oreopithecus sacrum is incompatible with the functional demands of habitual bipedal stance and locomotion. The Oreopithecus lumbosacral region does not exhibit adaptations for habitual bipedal locomotion.

Treatment of facet cysts associated with neurogenic intermittent claudication with x-stop.

Facet degeneration often leads to the formation of synovial facet cysts. As facet cysts invade the spinal canal, they become a contributing factor to spinal stenosis. Previous studies have demonstrated successful treatment of neurogenic intermittent claudication (NIC), a major symptom of spinal stenosis, with an interspinous process device. To compare clinical outcomes of patients with and without synovial facet cysts treated with an interspinous process device. Retrospective review of prospective data of consecutive patients undergoing the X-Stop procedure at an institution. Visual Analog Scale; Oswestry Disability Index; sitting, standing, and walking tolerances; and satisfaction survey. Review of all patients from 2006 to 2010 undergoing X-Stop procedure at an institution. Imaging studies were used to identify the presence and measure the size of the facet cysts in 285 patients with a minimum of 6-month follow-up. Comparative clinical outcomes determined if X-Stop is a successful treatment option for patients with NIC in conjunction with synovial facet cysts (<3 mm, ≥3 mm). Fifty-eight of 285 patients (20.4%) were determined to have a synovial cyst as a contributing component of spinal stenosis. Twelve of 58 patients were noted to have a cyst ≥3 mm. The mean follow-up time for patients with and without a facet cyst was 21 months (6-55±12 mo) and 22 months (6-61±12 mo), respectively. The age of the patient at the time of the operation with and without facet cysts was 73 (±10 y). Patients without synovial cysts, with synovial cysts, and cysts ≥3 mm had an average change in Oswestry Disability Index of 15.6, 15.8, and 16.2, respectively. Visual Analog Scale scores were 2.3, 1.8, and 2.3, respectively. In addition, on satisfaction surveys 72.4%, 82.0%, and 77.8% were either very or somewhat satisfied, respectively. Overall complications included 4 spinous process fracture, 4 hematomas, 1 wound infection, and 1 implant migration. No statistical difference was noted in any of the outcome measures among patients with small facet cysts, large facet cysts, or without facet cysts when treated with an interspinous process device. We can thus conclude that X-Stop is an appropriate treatment consideration for NIC with or without the presence of synovial facet cysts.

Using 3‐D surface models to evaluate morphological variation in artiodactyl carpal and tarsal bones

The postcranial bones of artiodactyls are widely used in ecomorphological studies, however, there is debate about whether certain elements (such as the astragalus) vary enough in shape to be useful in such analyses. To address this issue, I am interested in two questions: 1) Are some bones more morphologically conserved than others? 2) Can surface area and angular data taken from 3‐D models provide meaningful morphological information in artiodactyls? In this study I looked at three carpal bones (lunar, unciform, and cuneiform) and one tarsal bone (astragalus) in six families of artiodactyls. My results suggest that some bones are more morphologically conserved than others, with the cuneiform and astragalus being less variable morphologically than the lunar and unciform. In addition, I have identified potentially phylogenetically informative features of the lunar and unciform, for example, ruminants have a relatively large facet for the magnum on the unciform than non‐ruminants, and bovids have a relatively larger unciform facet on the lunar than other ruminants. Other characteristics are potentially homoplastic, for example the mountain goat and bighorn sheep share a large scaphoid facet on the lunar with non‐bovids, whereas other bovids have relatively small scaphoid facets. These results suggest that some elements are more useful than others for ecomorphological research.

EFFECT OF SLAB PULLING RATE ON FRACTURE CHARACTERISTICS AND NOTCH IMPACT TOUGHNESS OF SLAB SURFACE ZONE IN Ti-Nb MICROALLOYED STEEL

The paper analyzes the marginal cut-outs from two slabs of Ti-Nb microalloyed steel. The first slab was transitional with initial pulling rate 0.5 m.min -1 and final pulling rate 0.8 m.min -1 . The second slab was cast at real pulling rate 1.03 m.min -1 . The V-notch Charpy impact test showed that at low pulling rate 0.5 m.min -1 , the values of impact toughness (KCV) were higher than those at high slab pulling rates. When the pulling rate was 0.5 m.min -1 , mixed fractures were obtained, occasionally ductile, but mostly brittle. On the other hand pulling at rates 0.8 m.min -1 and 1.03 m.min -1 resulted only in brittle fractures with low KCV. Comparison of the mean ferrite grain size d ST , showed that the most fine-grained structure was achieved at a low pulling rate 0.5 m.min -1 , and the coarsest structure at pulling rate 0.8 m.min -1 . Furthermore, it was shown that, at high slab-pulling rates 0.8 m.min -1 and 1.03 m.min -1 , a greater amount of tertiary cementite was found on the boundaries of ferritic grains, compared with the lowest rate of slab pulling 0.5 m.min -1 . At the highest rate of slab pulling 1.03 m.min -1 , in addition to tertiary cementite, presence particles were observed here and there on the boundaries of ferritic grains, mostly oval shaped. On the fracture surfaces of brittle samples transcrystalline cleavage facets (TCF) dominated. In small amounts smooth facet intercrystalline decohesion (FID) was also identified with max. 0.2% , and also ductile transcrystalline failure with dimples (DDTF), usually present only in the form of narrow dimple bridges between cleavage facets. Observation of failures using scanning electron microscope (SEM) revealed the presence of either clusters of inclusions or individual particles, and EDX analysis confirmed the presence of Al, S, O, Mn, i.e. most probably oxides of aluminum and manganese sulphides. Aluminum can come from poorly-cleaned melt contaminated by fumes from deoxidation or from mould powders. There were also complex particles based on (C, Ti, Mn, O, Al, S, Nb, Zr, Ca) observed mainly on the TCF. Moreover, the impact of heterogeneous distribution of particles on embrittlement cannot be excluded - carbides, nitrides, and complex carbonitrides based on (Ti, Nb) (C, N).

RAPID: A Radiosity Applicable to Porous IndiviDual Objects for directional reflectance over complex vegetated scenes

A novel computer graphics-based radiosity model applicable to porous individual thin objects, named RAPID, is developed for fast calculation of multiple scattering and bidirectional reflectance factor (BRF) over complex, vegetated scenes. Instead of hundreds of small leaf facets, only a small number of porous thin objects are used to construct a complex tree crown or crop canopy. With gaps inside the object, it can effectively represent a group of small leaves. Each porous object has several properties, including shape, size (R), thickness (H), leaf area index (LAI), leaf angle distribution (LAD) and leaf clumping conditions (C). These properties are used to dynamically create the small leaves at run-time; hence, only view factors between porous objects (not between hundreds of small leaves) need to be calculated and stored. As a result, the model significantly reduces the huge memory requirement and long computation time of view factors for a large, realistic vegetation scene. RAPID is able to simulate arbitrary vegetation canopies in complex landscapes and to calculate BRF within a few minutes, which makes its application possible on different satellite pixel levels. This innovative technique is evaluated by comparing with directional reflectances from other models as well as field measurements.

Time-Domain Physical Optics Method for the Analysis of Wide-Band EM Scattering from Two-Dimensional Conducting Rough Surface

Time-domain physical optics (TDPO) method is extended to investigate electromagnetic (EM) scattering from two-dimensional (2D) perfectly electrically conducting (PEC) rough surface in both time domain and frequency domain. The scheme requires relatively small amounts of computer memory and CPU time, and has advantage over the Kirchhoff Approximation (KA) method in obtaining transient response of rough surface by a program run. The 2D Gaussian randomly rough surface is generated by Monte Carlo method and then is partitioned into small triangle facets through the meshing preprocess. The accuracy of TDPO is validated by comparing the numerical results with those obtained by the KA method in both backward and specular directions. The transient response and its frequency distribution of radar cross section (RCS) from rough surface is shown, respectively. The scattering results from rough surface with different size in the specular direction are given. The influence of the root mean square height (σ) and correlation length (l) on electromagnetic scattering from PEC rough surface is discussed in detail. Finally, the comparisons of backscattering results at different incident angles are presented and analyzed.

Two-axis solar tracking accomplished through small lateral translations

High-concentration solar-power optics require precise two-axis tracking. The planar micro-optic solar concentrator uses a lenslet array over a planar waveguide with small reflective facets at the focal point of each lenslet to couple incident light into the waveguide. The concentrator can use conventional tracking, tilting the entire assembly, but the system geometry also allows tracking by small lateral translation of the lenslet relative to the waveguide. Here, we experimentally demonstrate such microtracking with the existing concentrator optics and present optimized optical designs for systems with higher efficiency and angle range.