Geometric modeling for computer aided design

NASA Technical Reports Server (NTRS)

Schwing, James L.

1993-01-01

Over the past several years, it has been the primary goal of this grant to design and implement software to be used in the conceptual design of aerospace vehicles. The work carried out under this grant was performed jointly with members of the Vehicle Analysis Branch (VAB) of NASA LaRC, Computer Sciences Corp., and Vigyan Corp. This has resulted in the development of several packages and design studies. Primary among these are the interactive geometric modeling tool, the Solid Modeling Aerospace Research Tool (smart), and the integration and execution tools provided by the Environment for Application Software Integration and Execution (EASIE). In addition, it is the purpose of the personnel of this grant to provide consultation in the areas of structural design, algorithm development, and software development and implementation, particularly in the areas of computer aided design, geometric surface representation, and parallel algorithms.

Characterization and extraction of the synaptic apposition surface for synaptic geometry analysis

PubMed Central

Morales, Juan; Rodríguez, Angel; Rodríguez, José-Rodrigo; DeFelipe, Javier; Merchán-Pérez, Angel

2013-01-01

Geometrical features of chemical synapses are relevant to their function. Two critical components of the synaptic junction are the active zone (AZ) and the postsynaptic density (PSD), as they are related to the probability of synaptic release and the number of postsynaptic receptors, respectively. Morphological studies of these structures are greatly facilitated by the use of recent electron microscopy techniques, such as combined focused ion beam milling and scanning electron microscopy (FIB/SEM), and software tools that permit reconstruction of large numbers of synapses in three dimensions. Since the AZ and the PSD are in close apposition and have a similar surface area, they can be represented by a single surface—the synaptic apposition surface (SAS). We have developed an efficient computational technique to automatically extract this surface from synaptic junctions that have previously been three-dimensionally reconstructed from actual tissue samples imaged by automated FIB/SEM. Given its relationship with the release probability and the number of postsynaptic receptors, the surface area of the SAS is a functionally relevant measure of the size of a synapse that can complement other geometrical features like the volume of the reconstructed synaptic junction, the equivalent ellipsoid size and the Feret's diameter. PMID:23847474

The two-phase flow IPTT method for measurement of nonwetting-wetting liquid interfacial areas at higher nonwetting saturations in natural porous media

PubMed Central

Zhong, Hua; Ouni, Asma El; Lin, Dan; Wang, Bingguo; Brusseau, Mark L

2017-01-01

Interfacial areas between nonwetting-wetting (NW-W) liquids in natural porous media were measured using a modified version of the interfacial partitioning tracer test (IPTT) method that employed simultaneous two-phase flow conditions, which allowed measurement at NW saturations higher than trapped residual saturation. Measurements were conducted over a range of saturations for a well-sorted quartz sand under three wetting scenarios of primary drainage (PD), secondary imbibition (SI), and secondary drainage (SD). Limited sets of experiments were also conducted for a model glass-bead medium and for a soil. The measured interfacial areas were compared to interfacial areas measured using the standard IPTT method for liquid-liquid systems, which employs residual NW saturations. In addition, the theoretical maximum interfacial areas estimated from the measured data are compared to specific solid surface areas measured with the N2/BET method and estimated based on geometrical calculations for smooth spheres. Interfacial areas increase linearly with decreasing water saturation over the range of saturations employed. The maximum interfacial areas determined for the glass beads, which have no surface roughness, are 32±4 and 36±5 cm−1 for PD and SI cycles, respectively. The values are similar to the geometric specific solid surface area (31±2 cm−1) and the N2/BET solid surface area (28±2 cm−1). The maximum interfacial areas are 274±38, 235±27, and 581±160 cm−1 for the sand for PD, SI, and SD cycles, respectively, and ~7625 cm−1 for the soil for PD and SI. The maximum interfacial areas for the sand and soil are significantly larger than the estimated smooth-sphere specific solid surface areas (107±8 cm−1 and 152±8 cm−1, respectively), but much smaller than the N2/BET solid surface area (1387±92 cm−1 and 55224 cm−1, respectively). The NW-W interfacial areas measured with the two-phase flow method compare well to values measured using the standard IPTT method. PMID:28959079

Dimensional, Geometrical, and Physical Constraints in Skull Growth.

PubMed

Weickenmeier, Johannes; Fischer, Cedric; Carter, Dennis; Kuhl, Ellen; Goriely, Alain

2017-06-16

After birth, the skull grows and remodels in close synchrony with the brain to allow for an increase in intracranial volume. Increase in skull area is provided primarily by bone accretion at the sutures. Additional remodeling, to allow for a change in curvatures, occurs by resorption on the inner surface of the bone plates and accretion on their outer surfaces. When a suture fuses too early, normal skull growth is disrupted, leading to a deformed final skull shape. The leading theory assumes that the main stimulus for skull growth is provided by mechanical stresses. Based on these ideas, we first discuss the dimensional, geometrical, and kinematic synchrony between brain, skull, and suture growth. Second, we present two mechanical models for skull growth that account for growth at the sutures and explain the various observed dysmorphologies. These models demonstrate the particular role of physical and geometrical constraints taking place in skull growth.

Dimensional, Geometrical, and Physical Constraints in Skull Growth

NASA Astrophysics Data System (ADS)

Weickenmeier, Johannes; Fischer, Cedric; Carter, Dennis; Kuhl, Ellen; Goriely, Alain

2017-06-01

After birth, the skull grows and remodels in close synchrony with the brain to allow for an increase in intracranial volume. Increase in skull area is provided primarily by bone accretion at the sutures. Additional remodeling, to allow for a change in curvatures, occurs by resorption on the inner surface of the bone plates and accretion on their outer surfaces. When a suture fuses too early, normal skull growth is disrupted, leading to a deformed final skull shape. The leading theory assumes that the main stimulus for skull growth is provided by mechanical stresses. Based on these ideas, we first discuss the dimensional, geometrical, and kinematic synchrony between brain, skull, and suture growth. Second, we present two mechanical models for skull growth that account for growth at the sutures and explain the various observed dysmorphologies. These models demonstrate the particular role of physical and geometrical constraints taking place in skull growth.

Separate processing of texture and form in the ventral stream: evidence from FMRI and visual agnosia.

PubMed

Cavina-Pratesi, C; Kentridge, R W; Heywood, C A; Milner, A D

2010-02-01

Real-life visual object recognition requires the processing of more than just geometric (shape, size, and orientation) properties. Surface properties such as color and texture are equally important, particularly for providing information about the material properties of objects. Recent neuroimaging research suggests that geometric and surface properties are dealt with separately within the lateral occipital cortex (LOC) and the collateral sulcus (CoS), respectively. Here we compared objects that differed either in aspect ratio or in surface texture only, keeping all other visual properties constant. Results on brain-intact participants confirmed that surface texture activates an area in the posterior CoS, quite distinct from the area activated by shape within LOC. We also tested 2 patients with visual object agnosia, one of whom (DF) performed well on the texture task but at chance on the shape task, whereas the other (MS) showed the converse pattern. This behavioral double dissociation was matched by a parallel neuroimaging dissociation, with activation in CoS but not LOC in patient DF and activation in LOC but not CoS in patient MS. These data provide presumptive evidence that the areas respectively activated by shape and texture play a causally necessary role in the perceptual discrimination of these features.

Influence of Laser Shock Texturing on W9 Steel Surface Friction Property

NASA Astrophysics Data System (ADS)

Fan, Yujie; Cui, Pengfei; Zhou, Jianzhong; Dai, Yibin; Guo, Erbin; Tang, Deye

2017-09-01

To improve surface friction property of high speed steel, micro-dent arrays on W9Mo3Cr4V surface were produced by laser shock processing. Friction test was conducted on smooth surface and texturing surface and effect of surface texturing density on friction property was studied. The results show that, under the same condition, friction coefficient of textured surface is lower than smooth surface with dent area density less than 6%, wear mass loss, width and depth of wear scar are smaller; Wear resistance of the surface is the best and the friction coefficient is the smallest when dent area density is 2.2%; Friction coefficient, wear mass loss, width and depth of wear scar increase correspondingly as density of dent area increases when dent area density is more than 2.2%. Abrasive wear and adhesive wear, oxidative wear appear in the wear process. Reasonable control of geometric parameters of surface texturing induced by laser shock processing is helpful to improve friction performance.

[Spatial orientation of the facies patellaris femoris].

PubMed

Hassenpflug, J; Hiss, E; Blauth, W

1987-01-01

The present article reports on the geometrical conditions of the physiological movement of the patella. The geometrical shape of 18 femoral condyles and patella sliding areas was investigated in order to describe basic data for the design of endoprostheses. Surface and direction of the facies patellaris femoris were determined by means of radiographic, mechanical and optical measurements. The curvature of the deepest patella sliding groove proves a constant correlation with the dorsal condylar curvature. In the frontal plane the lowest points of the sliding area run with a dispersion of +/- 4 degrees to the vertical line related to the transverse tangent on the dorsal condylar surface. Considering deviations of leg alignment the measures come close to an angle of about 0 degrees. So the direction of the patella sliding groove differs from the normal valgus position of the distal femur. Therefore in artificial knee replacement a lateral tilt of the patella sliding groove should not be propagated as 'physiological'.

Complex lasso: new entangled motifs in proteins

NASA Astrophysics Data System (ADS)

Niemyska, Wanda; Dabrowski-Tumanski, Pawel; Kadlof, Michal; Haglund, Ellinor; Sułkowski, Piotr; Sulkowska, Joanna I.

2016-11-01

We identify new entangled motifs in proteins that we call complex lassos. Lassos arise in proteins with disulfide bridges (or in proteins with amide linkages), when termini of a protein backbone pierce through an auxiliary surface of minimal area, spanned on a covalent loop. We find that as much as 18% of all proteins with disulfide bridges in a non-redundant subset of PDB form complex lassos, and classify them into six distinct geometric classes, one of which resembles supercoiling known from DNA. Based on biological classification of proteins we find that lassos are much more common in viruses, plants and fungi than in other kingdoms of life. We also discuss how changes in the oxidation/reduction potential may affect the function of proteins with lassos. Lassos and associated surfaces of minimal area provide new, interesting and possessing many potential applications geometric characteristics not only of proteins, but also of other biomolecules.

Modelling gas dynamics in 1D ducts with abrupt area change

NASA Astrophysics Data System (ADS)

Menina, R.; Saurel, R.; Zereg, M.; Houas, L.

2011-09-01

Most gas dynamic computations in industrial ducts are done in one dimension with cross-section-averaged Euler equations. This poses a fundamental difficulty as soon as geometrical discontinuities are present. The momentum equation contains a non-conservative term involving a surface pressure integral, responsible for momentum loss. Definition of this integral is very difficult from a mathematical standpoint as the flow may contain other discontinuities (shocks, contact discontinuities). From a physical standpoint, geometrical discontinuities induce multidimensional vortices that modify the surface pressure integral. In the present paper, an improved 1D flow model is proposed. An extra energy (or entropy) equation is added to the Euler equations expressing the energy and turbulent pressure stored in the vortices generated by the abrupt area variation. The turbulent energy created by the flow-area change interaction is determined by a specific estimate of the surface pressure integral. Model's predictions are compared with 2D-averaged results from numerical solution of the Euler equations. Comparison with shock tube experiments is also presented. The new 1D-averaged model improves the conventional cross-section-averaged Euler equations and is able to reproduce the main flow features.

Models projecting the fate of fish populations under climate change need to be based on valid physiological mechanisms.

PubMed

Lefevre, Sjannie; McKenzie, David J; Nilsson, Göran E

2017-09-01

Some recent modelling papers projecting smaller fish sizes and catches in a warmer future are based on erroneous assumptions regarding (i) the scaling of gills with body mass and (ii) the energetic cost of 'maintenance'. Assumption (i) posits that insurmountable geometric constraints prevent respiratory surface areas from growing as fast as body volume. It is argued that these constraints explain allometric scaling of energy metabolism, whereby larger fishes have relatively lower mass-specific metabolic rates. Assumption (ii) concludes that when fishes reach a certain size, basal oxygen demands will not be met, because of assumption (i). We here demonstrate unequivocally, by applying accepted physiological principles with reference to the existing literature, that these assumptions are not valid. Gills are folded surfaces, where the scaling of surface area to volume is not constrained by spherical geometry. The gill surface area can, in fact, increase linearly in proportion to gill volume and body mass. We cite the large body of evidence demonstrating that respiratory surface areas in fishes reflect metabolic needs, not vice versa, which explains the large interspecific variation in scaling of gill surface areas. Finally, we point out that future studies basing their predictions on models should incorporate factors for scaling of metabolic rate and for temperature effects on metabolism, which agree with measured values, and should account for interspecific variation in scaling and temperature effects. It is possible that some fishes will become smaller in the future, but to make reliable predictions the underlying mechanisms need to be identified and sought elsewhere than in geometric constraints on gill surface area. Furthermore, to ensure that useful information is conveyed to the public and policymakers about the possible effects of climate change, it is necessary to improve communication and congruity between fish physiologists and fisheries scientists. © 2017 John Wiley & Sons Ltd.

Impact of adhesive surface and volume of luting resin on fracture resistance of root filled teeth.

PubMed

Krastl, G; Gugger, J; Deyhle, H; Zitzmann, N U; Weiger, R; Müller, B

2011-05-01

To investigate the correlation between geometric parameters of severely compromised root filled (RCT) pre-molar teeth with irregular root canals and their fracture resistance. The null hypothesis tested was that the fracture resistance of root filled teeth is not influenced by: (i) the adhesive surface of the post-space preparation (A(PS) ), (ii) the coronal tooth surface (A(A) ), (iii) the amount of resin cement (V(C) ) and (iv) the Young's modulus of the specimens. A total of 48 noncarious human pre-molar teeth with irregular root canals were decoronated, root filled and adhesively restored with post-retained direct composite crowns. After thermomechanical loading (1,200,000×, 5-50° C), static load was applied until failure. The geometric parameters of the tooth were evaluated by microcomputed tomography (μCT) using impressions taken after post-space preparation. Linear regression analyses were performed to correlate the geometric parameters of the specimens with their fracture resistance. The amount of resin cement (V(C) ) comprised up to 88% of the entire post-space (mean 67%) and had no impact on the maximal load (P = 0.88). The latter was significantly influenced by post-space preparation (P = 0.003). Amongst the geometric parameters tested, the surface area in the root canal had the greatest impact on fracture resistance of root filled pre-molars restored with posts and composite crowns, whilst the fit of the post was less important. © 2011 International Endodontic Journal.

Pragmatic geometric model evaluation

NASA Astrophysics Data System (ADS)

Pamer, Robert

2015-04-01

Quantification of subsurface model reliability is mathematically and technically demanding as there are many different sources of uncertainty and some of the factors can be assessed merely in a subjective way. For many practical applications in industry or risk assessment (e. g. geothermal drilling) a quantitative estimation of possible geometric variations in depth unit is preferred over relative numbers because of cost calculations for different scenarios. The talk gives an overview of several factors that affect the geometry of structural subsurface models that are based upon typical geological survey organization (GSO) data like geological maps, borehole data and conceptually driven construction of subsurface elements (e. g. fault network). Within the context of the trans-European project "GeoMol" uncertainty analysis has to be very pragmatic also because of different data rights, data policies and modelling software between the project partners. In a case study a two-step evaluation methodology for geometric subsurface model uncertainty is being developed. In a first step several models of the same volume of interest have been calculated by omitting successively more and more input data types (seismic constraints, fault network, outcrop data). The positions of the various horizon surfaces are then compared. The procedure is equivalent to comparing data of various levels of detail and therefore structural complexity. This gives a measure of the structural significance of each data set in space and as a consequence areas of geometric complexity are identified. These areas are usually very data sensitive hence geometric variability in between individual data points in these areas is higher than in areas of low structural complexity. Instead of calculating a multitude of different models by varying some input data or parameters as it is done by Monte-Carlo-simulations, the aim of the second step of the evaluation procedure (which is part of the ongoing work) is to calculate basically two model variations that can be seen as geometric extremes of all available input data. This does not lead to a probability distribution for the spatial position of geometric elements but it defines zones of major (or minor resp.) geometric variations due to data uncertainty. Both model evaluations are then analyzed together to give ranges of possible model outcomes in metric units.

Geometric methods for estimating representative sidewalk widths applied to Vienna's streetscape surfaces database

NASA Astrophysics Data System (ADS)

Brezina, Tadej; Graser, Anita; Leth, Ulrich

2017-04-01

Space, and in particular public space for movement and leisure, is a valuable and scarce resource, especially in today's growing urban centres. The distribution and absolute amount of urban space—especially the provision of sufficient pedestrian areas, such as sidewalks—is considered crucial for shaping living and mobility options as well as transport choices. Ubiquitous urban data collection and today's IT capabilities offer new possibilities for providing a relation-preserving overview and for keeping track of infrastructure changes. This paper presents three novel methods for estimating representative sidewalk widths and applies them to the official Viennese streetscape surface database. The first two methods use individual pedestrian area polygons and their geometrical representations of minimum circumscribing and maximum inscribing circles to derive a representative width of these individual surfaces. The third method utilizes aggregated pedestrian areas within the buffered street axis and results in a representative width for the corresponding road axis segment. Results are displayed as city-wide means in a 500 by 500 m grid and spatial autocorrelation based on Moran's I is studied. We also compare the results between methods as well as to previous research, existing databases and guideline requirements on sidewalk widths. Finally, we discuss possible applications of these methods for monitoring and regression analysis and suggest future methodological improvements for increased accuracy.

Molecular Static Third-Order Polarizabilities of Carbon-Cage Fullerene and Their Correlation with Three Geometric Properties: Symmetry, Aromaticity, and Size

NASA Technical Reports Server (NTRS)

Moore, C. E.; Cardelino, B. H.; Frazier, D. O.; Niles, J.; Wang, X.-Q.

1998-01-01

The static third-order polarizabilities (gamma) of C60, C70, five isomers of C78 and two isomers of C84 were analyzed in terms of three properties, from a geometric point of view: symmetry, aromaticity and size. The polarizability values were based on the finite field approximation using a semiempirical Hamiltonian (AM1) and applied to molecular structures obtained from density functional theory calculations. Symmetry was characterized by the molecular group order. The selection of 6-member rings as aromatic was determined from an analysis of bond lengths. Maximum interatomic distance and surface area were the parameters considered with respect to size. Based on triple linear regression analysis, it was found that the static linear polarizability (alpha) and gamma in these molecules respond differently to geometrical properties: alpha depends almost exclusively on surface area while gamma is affected by a combination of number of aromatic rings, length and group order, in decreasing importance. In the case of alpha, valence electron contributions provide the same information as all-electron estimates. For gamma, the best correlation coefficients are obtained when all-electron estimates are used and when the dependent parameter is ln(gamma) instead of gamma.

Supercritical fluid attachment of palladium nanoparticles on aligned carbon nanotubes.

PubMed

Ye, Xiang-Rong; Lin, Yuehe; Wai, Chien M; Talbot, Jan B; Jin, Sungho

2005-06-01

Nanocomposite materials consisting of Pd nanoparticles deposited on aligned multi-walled carbon nanotubes have been fabricated through hydrogen reduction of palladium-beta-diketone precursor in supercritical carbon dioxide. The supercritical fluid processing allowed deposition of high-density Pd nanoparticles (approximately 5-10 nm) on both as-grown (unfunctionalized) and functionalized (using HNO3 oxidation) nanotubes. However, the wet processing for functionalization results in pre-agglomerated, bundle-shaped nanotubes, thus significantly reducing the effective surface area for Pd particle deposition, although the bundling provides more secure, lock-in-place positioning of nanotubes and Pd catalyst particles. The nanotube bundling is substantially mitigated by Pd nanoparticle deposition on the unfunctionalized and geometrically separated nanotubes, which provides much higher catalyst surface area. Such nanocomposite materials utilizing geometrically secured and aligned nanotubes can be useful for providing much enhanced catalytic activities to chemical and electrochemical reactions (e.g., fuel cell reactions), and eliminate the need for tedious catalyst recovery process after the reaction is completed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Huixiao; Lim, Cheolwoong; Li, Tianyi

The impact of calendering process on the geometric characteristics and electrochemical performance of LiNi1/3Mn1/3Co1/3O2 (NMC) electrode was investigated in this study. The geometric properties of NMC electrodes with different calendering conditions, such as porosity, pore size distribution, particle size distribution, specific surface area and tortuosity were calculated from the computed tomography data of the electrodes. A synchrotron transmission X-ray microscopy tomography system at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain the tomography data. The geometric and electrochemical analysis show that calendering can increase the electrochemically active area, which improves rate capability. However, more calenderingmore » will result in crushing of NMC particles, which can reduce the electrode capacity at relatively high C rates. This study shows that the optimum electrochemical performance of NMC electrode at 94:3:3 weight ratio of NMC:binder:carbon black can be achieved by calendering to 3.0 g/cm3 NMC density.« less

Biomaterial design for specific cellular interactions: Role of surface functionalization and geometric features

NASA Astrophysics Data System (ADS)

Kolhar, Poornima

The areas of drug delivery and tissue engineering have experienced extraordinary growth in recent years with the application of engineering principles and their potential to support and improve the field of medicine. The tremendous progress in nanotechnology and biotechnology has lead to this explosion of research and development in biomedical applications. Biomaterials can now be engineered at a nanoscale and their specific interactions with the biological tissues can be modulated. Various design parameters are being established and researched for design of drug-delivery carriers and scaffolds to be implanted into humans. Nanoparticles made from versatile biomaterial can deliver both small-molecule drugs and various classes of bio-macromolecules, such as proteins and oligonucleotides. Similarly in the field of tissue engineering, current approaches emphasize nanoscale control of cell behavior by mimicking the natural extracellular matrix (ECM) unlike, traditional scaffolds. Drug delivery and tissue engineering are closely connected fields and both of these applications require materials with exceptional physical, chemical, biological, and biomechanical properties to provide superior therapy. In the current study the surface functionalization and the geometric features of the biomaterials has been explored. In particular, a synthetic surface for culture of human embryonic stem cells has been developed, demonstrating the importance of surface functionalization in maintaining the pluripotency of hESCs. In the second study, the geometric features of the drug delivery carriers are investigated and the polymeric nanoneedles mediated cellular permeabilization and direct cytoplasmic delivery is reported. In the third study, the combined effect of surface functionalization and geometric modification of carriers for vascular targeting is enunciated. These studies illustrate how the biomaterials can be designed to achieve various cellular behaviors and control the interactions with cells in vivo .

Determination of the amount of physical adsorption of water vapour on platinum-iridium surfaces

NASA Astrophysics Data System (ADS)

Mizushima, S.; Ueda, K.; Ooiwa, A.; Fujii, K.

2015-08-01

This paper presents the measurement of the physical adsorption of water vapour on platinum-iridium surfaces using a vacuum mass comparator. This value is of importance for redefining the kilogram, which will be realized under vacuum in the near future. Mirror-polished artefacts, consisting of a reference artefact and a test artefact, were manufactured for this experiment. The surface area difference between the reference and test artefacts was 226.2 cm2. This surface area difference was approximately 3.2 times the geometric surface area of the prototype of the kilogram made of platinum-iridium (71.7 cm2). The measurement results indicate that the amount of physical adsorption at a relative humidity of 50% is 0.0129 μg cm{{-}2} , with a standard uncertainty of 0.0016 μg cm{{-}2} . This value is 0.03 to 0.16 times that observed in other studies.

Weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the McMurdo Dry Valleys

USGS Publications Warehouse

Gooseff, Michael N.; McKnight, Diane M.; Lyons, W. Berry; Blum, Alex E.

2002-01-01

In the McMurdo Dry Valleys, Antarctica, dilute glacial meltwater flows down well‐established streambeds to closed basin lakes during the austral summer. During the 6–12 week flow season, a hyporheic zone develops in the saturated sediment adjacent to the streams. Longer Dry Valley streams have higher concentrations of major ions than shorter streams. The longitudinal increases in Si and K suggest that primary weathering contributes to the downstream solute increase. The hypothesis that weathering reactions in the hyporheic zone control stream chemistry was tested by modeling the downstream increase in solute concentration in von Guerard Stream in Taylor Valley. The average rates of solute supplied from these sources over the 5.2 km length of the stream were 6.1 × 10−9 mol Si L−1 m−1 and 3.7 × 10−9 mol K L−1 m−1, yielding annual dissolved Si loads of 0.02–1.30 mol Si m−2 of watershed land surface. Silicate minerals in streambed sediment were analyzed to determine the representative surface area of minerals in the hyporheic zone subject to primary weathering. Two strategies were evaluated to compute sediment surface area normalized weathering rates. The first applies a best linear fit to synoptic data in order to calculate a constant downstream solute concentration gradient, dC/dx (constant weathering rate contribution, CRC method); the second uses a transient storage model to simulate dC/dx, representing both hyporheic exchange and chemical weathering (hydrologic exchange, HE method). Geometric surface area normalized dissolution rates of the silicate minerals in the stream ranged from 0.6 × 10−12 mol Si m−2 s−1 to 4.5 × 10−12 mol Si m−2 s−1 and 0.4 × 10−12 mol K m−2 s−1to 1.9 × 10−12 mol K m−2 s−1. These values are an order of magnitude lower than geometric surface area normalized weathering rates determined in laboratory studies and are an order of magnitude greater than geometric surface area normalized weathering rates determined in a warmer, wetter setting in temperate basins, despite the cold temperatures, lack of precipitation and lack of organic material. These results suggest that the continuous saturation and rapid flushing of the sediment due to hyporheic exchange facilitates weathering in Dry Valley streams.

Sastrugi Geometrical Properties and Morphometry Over Two Winter Seasons at col du Lac Blanc (french Alps, 2700 m a.s.l)

NASA Astrophysics Data System (ADS)

Naaim, Florence; Picard, Ghislain; Bellot, Hervé; Arnaud, Laurent; Vionnet, Vincent

2017-04-01

Some elements of snow surface roughness, such as ripple or sastrugi, are a direct manifestation of wind erosion and in turn modify the near-surface wind field and consequently the horizontal snow mass fluxes. This leads to a negative feedback between wind strength and surface roughness that must be taken into account in numerical models. Formation of sastrugi, which are elongated metric-scale ridges of wind-packed snow whose longitudinal axis is parallel to the prevailing wind at the time of their formation, is still not well-understood. The first step to provide new information about the formation and evolution of such features is to integrate meteorological data and accurate description of geometrical properties. But the complex and dynamic surface of sastrugi cannot be easily captured by manual measurements (Bellot et al., 2014), which furthermore must be frequent as the formation of new landforms can happen very quickly. That's why the potential of a low-cost time-lapse terrestrial laserscan RLS (Picard et al., 2016) has been investigated during the winter seasons 2015-2016 and 2016-2017 at Col du Lac Blanc in the French Alps. This experimental test site, dedicated to drifting snow studies, and subject to the formation of sastrugi is well-suited for such study : accurate meteorological data, including drifting snow fluxes, are available each 10 minutes. RLS covered a surface area of around 200 m2 for a spatial horizontal resolution of nearly 2 cm and monitored successfully surface roughness once a day during the whole winter seasons. Sastrugi geometrical parameters, such as the frontal area and average height of roughness elements has been extracted from the RLS data and the sastrugi morphometry has be examined over two winter seasons in link with snow fall, drifting snow occurence and intensity and wind speed.

Gabriel's Other Possessions

ERIC Educational Resources Information Center

Royer, Melvin

2012-01-01

Gabriel's Horn is a solid of revolution commonly featured in calculus textbooks as a counter-intuitive example of a solid having finite volume but infinite surface area. Other examples of solids with surprising geometrical finitude relationships have also appeared in the literature. This article cites several intriguing examples (some of fractal…

The Area of a Circle

ERIC Educational Resources Information Center

Greenslade, Thomas B., Jr.

2011-01-01

The geometrical shapes in Fig. 1 recently came into the Greenslade Collection. The semi-triangular pieces of wood looked like slices from a pie, each 22.5 degrees in angular width. They were tied together with a thin leather band tacked around their curved surfaces. What is this apparatus?

Radargrammetric DSM generation in mountainous areas through adaptive-window least squares matching constrained by enhanced epipolar geometry

NASA Astrophysics Data System (ADS)

Dong, Yuting; Zhang, Lu; Balz, Timo; Luo, Heng; Liao, Mingsheng

2018-03-01

Radargrammetry is a powerful tool to construct digital surface models (DSMs) especially in heavily vegetated and mountainous areas where SAR interferometry (InSAR) technology suffers from decorrelation problems. In radargrammetry, the most challenging step is to produce an accurate disparity map through massive image matching, from which terrain height information can be derived using a rigorous sensor orientation model. However, precise stereoscopic SAR (StereoSAR) image matching is a very difficult task in mountainous areas due to the presence of speckle noise and dissimilar geometric/radiometric distortions. In this article, an adaptive-window least squares matching (AW-LSM) approach with an enhanced epipolar geometric constraint is proposed to robustly identify homologous points after compensation for radiometric discrepancies and geometric distortions. The matching procedure consists of two stages. In the first stage, the right image is re-projected into the left image space to generate epipolar images using rigorous imaging geometries enhanced with elevation information extracted from the prior DEM data e.g. SRTM DEM instead of the mean height of the mapped area. Consequently, the dissimilarities in geometric distortions between the left and right images are largely reduced, and the residual disparity corresponds to the height difference between true ground surface and the prior DEM. In the second stage, massive per-pixel matching between StereoSAR epipolar images identifies the residual disparity. To ensure the reliability and accuracy of the matching results, we develop an iterative matching scheme in which the classic cross correlation matching is used to obtain initial results, followed by the least squares matching (LSM) to refine the matching results. An adaptively resizing search window strategy is adopted during the dense matching step to help find right matching points. The feasibility and effectiveness of the proposed approach is demonstrated using Stripmap and Spotlight mode TerraSAR-X stereo data pairs covering Mount Song in central China. Experimental results show that the proposed method can provide a robust and effective matching tool for radargrammetry in mountainous areas.

Analysis of geometric and electrochemical characteristics of lithium cobalt oxide electrode with different packing densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Cheolwoong; Yan, Bo; Kang, Huixiao

2016-08-06

In order to investigate geometric and electrochemical characteristics of Li ion battery electrode with different packing densities, lithium cobalt oxide (LiCoO 2) cathode electrodes were fabricated from a 94:3:3 (wt%) mixture of LiCoO 2, polymeric binder, and super-P carbon black and calendered to different densities. A synchrotron X-ray nano-computed tomography system with a spatial resolution of 58.2 nm at the Advanced Photon Source of the Argonne National Laboratory was employed to obtain three dimensional morphology data of the electrodes. The morphology data were then quantitatively analyzed to characterize their geometric properties, such as porosity, tortuosity, specific surface area, and poremore » size distribution. The geometric and electrochemical analysis reveal that high packing density electrodes have smaller average pore size and narrower pore size distribution, which improves the electrical contact between carbon-binder matrix and LiCoO 2 particles. The better contact improves the capacity and rate capability by reducing the possibility of electrically isolated LiCoO 2 particles and increasing the electrochemically active area. The results show that increase of packing density results in higher tortuosity, but electrochemically active area is more crucial to cell performance than tortuosity at up to 3.6 g/cm 3 packing density and 4 C rate.« less

Surface area-volume ratios in insects.

PubMed

Kühsel, Sara; Brückner, Adrian; Schmelzle, Sebastian; Heethoff, Michael; Blüthgen, Nico

2017-10-01

Body mass, volume and surface area are important for many aspects of the physiology and performance of species. Whereas body mass scaling received a lot of attention in the literature, surface areas of animals have not been measured explicitly in this context. We quantified surface area-volume (SA/V) ratios for the first time using 3D surface models based on a structured light scanning method for 126 species of pollinating insects from 4 orders (Diptera, Hymenoptera, Lepidoptera, and Coleoptera). Water loss of 67 species was measured gravimetrically at very dry conditions for 2 h at 15 and 30 °C to demonstrate the applicability of the new 3D surface measurements and relevance for predicting the performance of insects. Quantified SA/V ratios significantly explained the variation in water loss across species, both directly or after accounting for isometric scaling (residuals of the SA/V ∼ mass 2/3 relationship). Small insects with a proportionally larger surface area had the highest water loss rates. Surface scans of insects to quantify allometric SA/V ratios thus provide a promising method to predict physiological responses, improving the potential of body mass isometry alone that assume geometric similarity. © 2016 Institute of Zoology, Chinese Academy of Sciences.

Geometry program for aerodynamic lifting surface theory

NASA Technical Reports Server (NTRS)

Medan, R. T.

1973-01-01

A computer program that provides the geometry and boundary conditions appropriate for an analysis of a lifting, thin wing with control surfaces in linearized, subsonic, steady flow is presented. The kernel function method lifting surface theory is applied. The data which is generated by the program is stored on disk files or tapes for later use by programs which calculate an influence matrix, plot the wing planform, and evaluate the loads on the wing. In addition to processing data for subsequent use in a lifting surface analysis, the program is useful for computing area and mean geometric chords of the wing and control surfaces.

Nonequilibrium Synthesis of Highly Porous Single-Crystalline Oxide Nanostructures

DOE PAGES

Lee, Dongkyu; Gao, Xiang; Fan, Lisha; ...

2017-01-20

A novel synthesis route to the formation of vertically aligned single–crystalline oxide nanostructures is found by precisely controlling the nonequilibrium pulsed laser deposition process. Here, the columnar nanostructures with deep crevices offering a large surface area are generated owing to the diffusion limited geometric shadowing effect.

Geometric processing workflow for vertical and oblique hyperspectral frame images collected using UAV

NASA Astrophysics Data System (ADS)

Markelin, L.; Honkavaara, E.; Näsi, R.; Nurminen, K.; Hakala, T.

2014-08-01

Remote sensing based on unmanned airborne vehicles (UAVs) is a rapidly developing field of technology. UAVs enable accurate, flexible, low-cost and multiangular measurements of 3D geometric, radiometric, and temporal properties of land and vegetation using various sensors. In this paper we present a geometric processing chain for multiangular measurement system that is designed for measuring object directional reflectance characteristics in a wavelength range of 400-900 nm. The technique is based on a novel, lightweight spectral camera designed for UAV use. The multiangular measurement is conducted by collecting vertical and oblique area-format spectral images. End products of the geometric processing are image exterior orientations, 3D point clouds and digital surface models (DSM). This data is needed for the radiometric processing chain that produces reflectance image mosaics and multiangular bidirectional reflectance factor (BRF) observations. The geometric processing workflow consists of the following three steps: (1) determining approximate image orientations using Visual Structure from Motion (VisualSFM) software, (2) calculating improved orientations and sensor calibration using a method based on self-calibrating bundle block adjustment (standard photogrammetric software) (this step is optional), and finally (3) creating dense 3D point clouds and DSMs using Photogrammetric Surface Reconstruction from Imagery (SURE) software that is based on semi-global-matching algorithm and it is capable of providing a point density corresponding to the pixel size of the image. We have tested the geometric processing workflow over various targets, including test fields, agricultural fields, lakes and complex 3D structures like forests.

Surface hydrophobicity of slippery zones in the pitchers of two Nepenthes species and a hybrid

PubMed Central

Wang, Lixin; Zhou, Qiang

2016-01-01

To investigate the hydrophobicity of slippery zones, static contact angle measurement and microstructure observation of slippery surfaces from two Nepenthes species and a hybrid were conducted. Marginally different static contact angles were observed, as the smallest (133.83°) and greatest (143.63°) values were recorded for the N. alata and N. miranda respectively, and the median value (140.40°) was presented for the N. khasiana. The slippery zones under investigation exhibited rather similar surface morphologies, but different structural dimensions. These findings probably suggest that the geometrical dimensions of surface architecture exert primary effects on differences in the hydrophobicity of the slippery zone. Based on the Wenzel and Cassie-Baxter equations, models were proposed to analyze the manner in which geometrical dimensions affect the hydrophobicity of the slippery surfaces. The results of our analysis demonstrated that the different structural dimensions of lunate cells and wax platelets make the slippery zones present different real area of the rough surface and thereby generate somewhat distinguishable hydrophobicity. The results support a supplementary interpretation of surface hydrophobicity in plant leaves, and provide a theoretical foundation for developing bioinspired materials with hydrophobic properties and self-cleaning abilities. PMID:26813707

Technical note: Comparison of metal-on-metal hip simulator wear measured by gravimetric, CMM and optical profiling methods

NASA Astrophysics Data System (ADS)

Alberts, L. Russell; Martinez-Nogues, Vanesa; Baker Cook, Richard; Maul, Christian; Bills, Paul; Racasan, R.; Stolz, Martin; Wood, Robert J. K.

2018-03-01

Simulation of wear in artificial joint implants is critical for evaluating implant designs and materials. Traditional protocols employ the gravimetric method to determine the loss of material by measuring the weight of the implant components before and after various test intervals and after the completed test. However, the gravimetric method cannot identify the location, area coverage or maximum depth of the wear and it has difficulties with proportionally small weight changes in relatively heavy implants. In this study, we compare the gravimetric method with two geometric surface methods; an optical light method (RedLux) and a coordinate measuring method (CMM). We tested ten Adept hips in a simulator for 2 million cycles (MC). Gravimetric and optical methods were performed at 0.33, 0.66, 1.00, 1.33 and 2 MC. CMM measurements were done before and after the test. A high correlation was found between the gravimetric and optical methods for both heads (R 2  =  0.997) and for cups (R 2  =  0.96). Both geometric methods (optical and CMM) measured more volume loss than the gravimetric method (for the heads, p  =  0.004 (optical) and p  =  0.08 (CMM); for the cups p  =  0.01 (optical) and p  =  0.003 (CMM)). Two cups recorded negative wear at 2 MC by the gravimetric method but none did by either the optical method or by CMM. The geometric methods were prone to confounding factors such as surface deformation and the gravimetric method could be confounded by protein absorption and backside wear. Both of the geometric methods were able to show the location, area covered and depth of the wear on the bearing surfaces, and track their changes during the test run; providing significant advantages to solely using the gravimetric method.

Effects of Small Oscillations on the Effective Area

NASA Astrophysics Data System (ADS)

Cotroneo, V.; Conconi, P.; Cusumano, G.; Pareschi, G.; Spiga, D.; Tagliaferri, G.

2009-05-01

We analyze the effective area of the Simbol-X mirrors as a function of the off-axis angle for small oscillations. A reduction is expected due to: 1) geometrical effects, because some of the photons miss the secondary mirror surface; 2) reflectivity effects, caused by the variation of the coating reflectivity with the incidence angle. The former are related to the length of the two mirror surfaces, and can be reduced by making the secondary mirror longer. The second ones are energy-dependent, and strongly related to the characteristics of the reflecting coating. These effects are analyzed by means of ray-tracing simulations in order to optimize the mirror and coating design, aiming to improve the effective area stability.

3D surface reconstruction and visualization of the Drosophila wing imaginal disc at cellular resolution

NASA Astrophysics Data System (ADS)

Bai, Linge; Widmann, Thomas; Jülicher, Frank; Dahmann, Christian; Breen, David

2013-01-01

Quantifying and visualizing the shape of developing biological tissues provide information about the morphogenetic processes in multicellular organisms. The size and shape of biological tissues depend on the number, size, shape, and arrangement of the constituting cells. To better understand the mechanisms that guide tissues into their final shape, it is important to investigate the cellular arrangement within tissues. Here we present a data processing pipeline to generate 3D volumetric surface models of epithelial tissues, as well as geometric descriptions of the tissues' apical cell cross-sections. The data processing pipeline includes image acquisition, editing, processing and analysis, 2D cell mesh generation, 3D contourbased surface reconstruction, cell mesh projection, followed by geometric calculations and color-based visualization of morphological parameters. In their first utilization we have applied these procedures to construct a 3D volumetric surface model at cellular resolution of the wing imaginal disc of Drosophila melanogaster. The ultimate goal of the reported effort is to produce tools for the creation of detailed 3D geometric models of the individual cells in epithelial tissues. To date, 3D volumetric surface models of the whole wing imaginal disc have been created, and the apicolateral cell boundaries have been identified, allowing for the calculation and visualization of cell parameters, e.g. apical cross-sectional area of cells. The calculation and visualization of morphological parameters show position-dependent patterns of cell shape in the wing imaginal disc. Our procedures should offer a general data processing pipeline for the construction of 3D volumetric surface models of a wide variety of epithelial tissues.

Near-opposition martian limb-darkening: Quantification and implication for visible-near-infrared bidirectional reflectance studies.

NASA Astrophysics Data System (ADS)

de Grenier, Muriel; Pinet, Patrick C.

1995-06-01

A nearly global coverage of the martian eastern hemisphere, acquired under small phase angles and varying observational geometries conditions, has been produced from 1988 opposition by spectral (0.5-1 μm) imaging data obtained at the Pic du Midi Observatory in France. From this data set, the methodology presented here permits a systematic analysis of martian photometric behavior at a regional scale of 100-300 km in the visible and near-infrared. The quantification of limb-darkening as a function of wavelength and surface albedo gives access in martian regional properties as a function of wavelength and surface albedo and results in the production of visible and near-infrared geometric albedo maps. A linear relation between the limb darkening parameter k and geometric albedo exists in the near infrared. Based on laboratory studies, it suggests a spectral response of particulate type for the martian soil. Conversely, in the visible, the value of k parameter is 0.6 independent of albedo and is consistent with a single scattering photometric behavior in the surface layer. However, the observed change in the martian photometry from single to multiple scattering may be partially due to a large contribution of atmospheric scattering above 0.7 μm. In the absence of a multitemporal dataset analysis, it must be emphasized that the present results are a priori only pertinent to the atmospheric and surface conditions existing on Mars at the time of observation. However, this analysis may contribute to characterize some physical properties, such as surface roughness. In the near-infrared, for bright terrains, k tends to 0.8 and agrees with the presence of very fine particulate materials. Photometry of dark areas is more irregular (0.48 < k < 0.64) and might result from surface roughness heterogeneities. However, a few dark areas reveal that k anomalous values in the range 0.7-0.8 may be caused by the presence of a coating of very fine materials or duricrust. Finally, we evaluate the influence of reflectance geometrical effects on the multispectral and spectroscopic data of the martian surface.

Center for Advanced Sensors, Year One Funding (FY2005)

DTIC Science & Technology

2006-10-30

on a plane and located near a planar wall. The box is a tank-sized box and the wall can represent a building or a tree line, depending on what...antenna is needed to geometrically couple the large spot to the small detector. As in all focal plane arrays, surface area is required to route...area at the antennae plane . Current antenna implementations for focal plane arrays emphasize frequency independent and modifications of frequency

Statistical scaling of geometric characteristics in stochastically generated pore microstructures

DOE PAGES

Hyman, Jeffrey D.; Guadagnini, Alberto; Winter, C. Larrabee

2015-05-21

In this study, we analyze the statistical scaling of structural attributes of virtual porous microstructures that are stochastically generated by thresholding Gaussian random fields. Characterization of the extent at which randomly generated pore spaces can be considered as representative of a particular rock sample depends on the metrics employed to compare the virtual sample against its physical counterpart. Typically, comparisons against features and/patterns of geometric observables, e.g., porosity and specific surface area, flow-related macroscopic parameters, e.g., permeability, or autocorrelation functions are used to assess the representativeness of a virtual sample, and thereby the quality of the generation method. Here, wemore » rely on manifestations of statistical scaling of geometric observables which were recently observed in real millimeter scale rock samples [13] as additional relevant metrics by which to characterize a virtual sample. We explore the statistical scaling of two geometric observables, namely porosity (Φ) and specific surface area (SSA), of porous microstructures generated using the method of Smolarkiewicz and Winter [42] and Hyman and Winter [22]. Our results suggest that the method can produce virtual pore space samples displaying the symptoms of statistical scaling observed in real rock samples. Order q sample structure functions (statistical moments of absolute increments) of Φ and SSA scale as a power of the separation distance (lag) over a range of lags, and extended self-similarity (linear relationship between log structure functions of successive orders) appears to be an intrinsic property of the generated media. The width of the range of lags where power-law scaling is observed and the Hurst coefficient associated with the variables we consider can be controlled by the generation parameters of the method.« less

R&D 100 Awards Honor NREL Research

Science.gov Websites

National Renewable Energy Laboratory will be honored Thursday with two R&D 100 awards. The awards are sophisticated geometric shapes to provide the best surface area for condensing spent steam. Recently, geothermal the DOE's Office of Geothermal Technologies. The technology was demonstrated by the Pacific Gas and

23 CFR 470.107 - Federal-aid highway systems.

Code of Federal Regulations, 2011 CFR

2011-04-01

... permitted under the provisions of 23 U.S.C. 103(c)(4) and section 1105(e)(5)(A) of the Intermodal Surface... highest importance to the Nation, built to the uniform geometric and construction standards of 23 U.S.C. 109(h), which connect, as directly as practicable, the principal metropolitan areas, cities, and...

Multiscale geometric modeling of macromolecules I: Cartesian representation

NASA Astrophysics Data System (ADS)

Xia, Kelin; Feng, Xin; Chen, Zhan; Tong, Yiying; Wei, Guo-Wei

2014-01-01

This paper focuses on the geometric modeling and computational algorithm development of biomolecular structures from two data sources: Protein Data Bank (PDB) and Electron Microscopy Data Bank (EMDB) in the Eulerian (or Cartesian) representation. Molecular surface (MS) contains non-smooth geometric singularities, such as cusps, tips and self-intersecting facets, which often lead to computational instabilities in molecular simulations, and violate the physical principle of surface free energy minimization. Variational multiscale surface definitions are proposed based on geometric flows and solvation analysis of biomolecular systems. Our approach leads to geometric and potential driven Laplace-Beltrami flows for biomolecular surface evolution and formation. The resulting surfaces are free of geometric singularities and minimize the total free energy of the biomolecular system. High order partial differential equation (PDE)-based nonlinear filters are employed for EMDB data processing. We show the efficacy of this approach in feature-preserving noise reduction. After the construction of protein multiresolution surfaces, we explore the analysis and characterization of surface morphology by using a variety of curvature definitions. Apart from the classical Gaussian curvature and mean curvature, maximum curvature, minimum curvature, shape index, and curvedness are also applied to macromolecular surface analysis for the first time. Our curvature analysis is uniquely coupled to the analysis of electrostatic surface potential, which is a by-product of our variational multiscale solvation models. As an expository investigation, we particularly emphasize the numerical algorithms and computational protocols for practical applications of the above multiscale geometric models. Such information may otherwise be scattered over the vast literature on this topic. Based on the curvature and electrostatic analysis from our multiresolution surfaces, we introduce a new concept, the polarized curvature, for the prediction of protein binding sites.

High-Throughput 3-D Monitoring of Agricultural-Tree Plantations with Unmanned Aerial Vehicle (UAV) Technology

PubMed Central

Torres-Sánchez, Jorge; López-Granados, Francisca; Serrano, Nicolás; Arquero, Octavio; Peña, José M.

2015-01-01

The geometric features of agricultural trees such as canopy area, tree height and crown volume provide useful information about plantation status and crop production. However, these variables are mostly estimated after a time-consuming and hard field work and applying equations that treat the trees as geometric solids, which produce inconsistent results. As an alternative, this work presents an innovative procedure for computing the 3-dimensional geometric features of individual trees and tree-rows by applying two consecutive phases: 1) generation of Digital Surface Models with Unmanned Aerial Vehicle (UAV) technology and 2) use of object-based image analysis techniques. Our UAV-based procedure produced successful results both in single-tree and in tree-row plantations, reporting up to 97% accuracy on area quantification and minimal deviations compared to in-field estimations of tree heights and crown volumes. The maps generated could be used to understand the linkages between tree grown and field-related factors or to optimize crop management operations in the context of precision agriculture with relevant agro-environmental implications. PMID:26107174

High-Throughput 3-D Monitoring of Agricultural-Tree Plantations with Unmanned Aerial Vehicle (UAV) Technology.

PubMed

Torres-Sánchez, Jorge; López-Granados, Francisca; Serrano, Nicolás; Arquero, Octavio; Peña, José M

2015-01-01

The geometric features of agricultural trees such as canopy area, tree height and crown volume provide useful information about plantation status and crop production. However, these variables are mostly estimated after a time-consuming and hard field work and applying equations that treat the trees as geometric solids, which produce inconsistent results. As an alternative, this work presents an innovative procedure for computing the 3-dimensional geometric features of individual trees and tree-rows by applying two consecutive phases: 1) generation of Digital Surface Models with Unmanned Aerial Vehicle (UAV) technology and 2) use of object-based image analysis techniques. Our UAV-based procedure produced successful results both in single-tree and in tree-row plantations, reporting up to 97% accuracy on area quantification and minimal deviations compared to in-field estimations of tree heights and crown volumes. The maps generated could be used to understand the linkages between tree grown and field-related factors or to optimize crop management operations in the context of precision agriculture with relevant agro-environmental implications.

Partial molar volume of proteins studied by the three-dimensional reference interaction site model theory.

PubMed

Imai, Takashi; Kovalenko, Andriy; Hirata, Fumio

2005-04-14

The three-dimensional reference interaction site model (3D-RISM) theory is applied to the analysis of hydration effects on the partial molar volume of proteins. For the native structure of some proteins, the partial molar volume is decomposed into geometric and hydration contributions using the 3D-RISM theory combined with the geometric volume calculation. The hydration contributions are correlated with the surface properties of the protein. The thermal volume, which is the volume of voids around the protein induced by the thermal fluctuation of water molecules, is directly proportional to the accessible surface area of the protein. The interaction volume, which is the contribution of electrostatic interactions between the protein and water molecules, is apparently governed by the charged atomic groups on the protein surface. The polar atomic groups do not make any contribution to the interaction volume. The volume differences between low- and high-pressure structures of lysozyme are also analyzed by the present method.

Geometric modeling of Plateau borders using the orthographic projection method for closed cell rigid polyurethane foam thermal conductivity prediction

NASA Astrophysics Data System (ADS)

Xu, Jie; Wu, Tao; Peng, Chuang; Adegbite, Stephen

2017-09-01

The geometric Plateau border model for closed cell polyurethane foam was developed based on volume integrations of approximated 3D four-cusp hypocycloid structure. The tetrahedral structure of convex struts was orthogonally projected into 2D three-cusp deltoid with three central cylinders. The idealized single unit strut was modeled by superposition. The volume of each component was calculated by geometric analyses. The strut solid fraction f s and foam porosity coefficient δ were calculated based on representative elementary volume of Kelvin and Weaire-Phelan structures. The specific surface area Sv derived respectively from packing structures and deltoid approximation model were put into contrast against strut dimensional ratio ɛ. The characteristic foam parameters obtained from this semi-empirical model were further employed to predict foam thermal conductivity.

Geometric measures of large biomolecules: surface, volume, and pockets.

PubMed

Mach, Paul; Koehl, Patrice

2011-11-15

Geometry plays a major role in our attempts to understand the activity of large molecules. For example, surface area and volume are used to quantify the interactions between these molecules and the water surrounding them in implicit solvent models. In addition, the detection of pockets serves as a starting point for predictive studies of biomolecule-ligand interactions. The alpha shape theory provides an exact and robust method for computing these geometric measures. Several implementations of this theory are currently available. We show however that these implementations fail on very large macromolecular systems. We show that these difficulties are not theoretical; rather, they are related to the architecture of current computers that rely on the use of cache memory to speed up calculation. By rewriting the algorithms that implement the different steps of the alpha shape theory such that we enforce locality, we show that we can remediate these cache problems; the corresponding code, UnionBall has an apparent O(n) behavior over a large range of values of n (up to tens of millions), where n is the number of atoms. As an example, it takes 136 sec with UnionBall to compute the contribution of each atom to the surface area and volume of a viral capsid with more than five million atoms on a commodity PC. UnionBall includes functions for computing analytically the surface area and volume of the intersection of two, three and four spheres that are fully detailed in an appendix. UnionBall is available as an OpenSource software. Copyright © 2011 Wiley Periodicals, Inc.

Geometric Measures of Large Biomolecules: Surface, Volume and Pockets

PubMed Central

Mach, Paul; Koehl, Patrice

2011-01-01

Geometry plays a major role in our attempt to understand the activity of large molecules. For example, surface area and volume are used to quantify the interactions between these molecules and the water surrounding them in implicit solvent models. In addition, the detection of pockets serves as a starting point for predictive studies of biomolecule-ligand interactions. The alpha shape theory provides an exact and robust method for computing these geometric measures. Several implementations of this theory are currently available. We show however that these implementations fail on very large macromolecular systems. We show that these difficulties are not theoretical; rather, they are related to the architecture of current computers that rely on the use of cache memory to speed up calculation. By rewriting the algorithms that implement the different steps of the alpha shape theory such that we enforce locality, we show that we can remediate these cache problems; the corresponding code, UnionBall has an apparent (n) behavior over a large range of values of n (up to tens of millions), where n is the number of atoms. As an example, it takes 136 seconds with UnionBall to compute the contribution of each atom to the surface area and volume of a viral capsid with more than five million atoms on a commodity PC. UnionBall includes functions for computing the surface area and volume of the intersection of two, three and four spheres that are fully detailed in an appendix. UnionBall is available as an OpenSource software. PMID:21823134

Validating and improving a zero-dimensional stack voltage model of the Vanadium Redox Flow Battery

NASA Astrophysics Data System (ADS)

König, S.; Suriyah, M. R.; Leibfried, T.

2018-02-01

Simple, computationally efficient battery models can contribute significantly to the development of flow batteries. However, validation studies for these models on an industrial-scale stack level are rarely published. We first extensively present a simple stack voltage model for the Vanadium Redox Flow Battery. For modeling the concentration overpotential, we derive mass transfer coefficients from experimental results presented in the 1990s. The calculated mass transfer coefficient of the positive half-cell is 63% larger than of the negative half-cell, which is not considered in models published to date. Further, we advance the concentration overpotential model by introducing an apparent electrochemically active electrode surface which differs from the geometric electrode area. We use the apparent surface as fitting parameter for adapting the model to experimental results of a flow battery manufacturer. For adapting the model, we propose a method for determining the agreement between model and reality quantitatively. To protect the manufacturer's intellectual property, we introduce a normalization method for presenting the results. For the studied stack, the apparent electrochemically active surface of the electrode is 41% larger than its geometrical area. Hence, the current density in the diffusion layer is 29% smaller than previously reported for a zero-dimensional model.

New method for springback compensation for the stamping of sheet metal components

NASA Astrophysics Data System (ADS)

Birkert, A.; Hartmann, B.; Straub, M.

2017-09-01

The need for car body structures of higher strength and at the same time lower weight results in serious challenges for the stamping process. Especially the use of high strength steel and aluminium sheets is causing growing problems with regard to elastic springback. To produce accurate parts the stamping dies must be adjusted more or less by the amount of the springback in the opposite direction. For this purpose well-known software solutions use the Displacement Adjustment Method or algorithms which are closely based on that method. A crucial issue of this method is that the generated die surfaces deviate from those of the target geometry with regard to surface area. A new Physical Compensation Method has been developed and validated which takes geometrical nonlinearity into account and creates compensated die geometries with equal-in-area die surfaces. In contrast to the standard mathematical/geometrical approach, the adjusted geometry is generated by a physical approach, which makes use of the virtual part stiffness. Hereby the target geometry is being deformed mechanically in a virtual process based on the springback simulation results by applying virtual forces in an additional elastic simulation. By doing so better part dimensions can be obtained in less tool optimization loops.

The gravity dual of Rényi entropy.

PubMed

Dong, Xi

2016-08-12

A remarkable yet mysterious property of black holes is that their entropy is proportional to the horizon area. This area law inspired the holographic principle, which was later realized concretely in gauge-gravity duality. In this context, entanglement entropy is given by the area of a minimal surface in a dual spacetime. However, discussions of area laws have been constrained to entanglement entropy, whereas a full understanding of a quantum state requires Rényi entropies. Here we show that all Rényi entropies satisfy a similar area law in holographic theories and are given by the areas of dual cosmic branes. This geometric prescription is a one-parameter generalization of the minimal surface prescription for entanglement entropy. Applying this we provide the first holographic calculation of mutual Rényi information between two disks of arbitrary dimension. Our results provide a framework for efficiently studying Rényi entropies and understanding entanglement structures in strongly coupled systems and quantum gravity.

The gravity dual of Rényi entropy

PubMed Central

Dong, Xi

2016-01-01

A remarkable yet mysterious property of black holes is that their entropy is proportional to the horizon area. This area law inspired the holographic principle, which was later realized concretely in gauge-gravity duality. In this context, entanglement entropy is given by the area of a minimal surface in a dual spacetime. However, discussions of area laws have been constrained to entanglement entropy, whereas a full understanding of a quantum state requires Rényi entropies. Here we show that all Rényi entropies satisfy a similar area law in holographic theories and are given by the areas of dual cosmic branes. This geometric prescription is a one-parameter generalization of the minimal surface prescription for entanglement entropy. Applying this we provide the first holographic calculation of mutual Rényi information between two disks of arbitrary dimension. Our results provide a framework for efficiently studying Rényi entropies and understanding entanglement structures in strongly coupled systems and quantum gravity. PMID:27515122

Beyond-laboratory-scale prediction for channeling flows through subsurface rock fractures with heterogeneous aperture distributions revealed by laboratory evaluation

NASA Astrophysics Data System (ADS)

Ishibashi, Takuya; Watanabe, Noriaki; Hirano, Nobuo; Okamoto, Atsushi; Tsuchiya, Noriyoshi

2015-01-01

The present study evaluates aperture distributions and fluid flow characteristics for variously sized laboratory-scale granite fractures under confining stress. As a significant result of the laboratory investigation, the contact area in fracture plane was found to be virtually independent of scale. By combining this characteristic with the self-affine fractal nature of fracture surfaces, a novel method for predicting fracture aperture distributions beyond laboratory scale is developed. Validity of this method is revealed through reproduction of the results of laboratory investigation and the maximum aperture-fracture length relations, which are reported in the literature, for natural fractures. The present study finally predicts conceivable scale dependencies of fluid flows through joints (fractures without shear displacement) and faults (fractures with shear displacement). Both joint and fault aperture distributions are characterized by a scale-independent contact area, a scale-dependent geometric mean, and a scale-independent geometric standard deviation of aperture. The contact areas for joints and faults are approximately 60% and 40%. Changes in the geometric means of joint and fault apertures (µm), em, joint and em, fault, with fracture length (m), l, are approximated by em, joint = 1 × 102 l0.1 and em, fault = 1 × 103 l0.7, whereas the geometric standard deviations of both joint and fault apertures are approximately 3. Fluid flows through both joints and faults are characterized by formations of preferential flow paths (i.e., channeling flows) with scale-independent flow areas of approximately 10%, whereas the joint and fault permeabilities (m2), kjoint and kfault, are scale dependent and are approximated as kjoint = 1 × 10-12 l0.2 and kfault = 1 × 10-8 l1.1.

Teaching Materials "Surface Area of Geometric Figures," Created Using the Software Package "GeoGebra"

ERIC Educational Resources Information Center

Radovic, Slaviša

2013-01-01

Social development, the progress of technology, and changing economic forces certainly affect the development of the current educational system. One of the main problems of today's school system is how to maintain focus, concentration, and interest among students with regards to the learning that takes place during classes. An important feature of…

Effect on radioactivity concentration estimation of radon progenies with NaI(Tl) pulse height distribution from considering geometric structure around detector and infiltration of radionuclides.

PubMed

Hirouchi, J; Terasaka, Y; Hirao, S; Moriizumi, J; Yamazawa, H

2015-11-01

The surface radioactivity concentrations of the radon progenies, (214)Pb and (214)Bi, were estimated from NaI(Tl) pulse height distributions during rain. The improvement in estimation errors caused by considering geometric structures around measuring points and infiltration of radionuclides was discussed. The surface radioactivity concentrations were determined by comparing the count rates at the full-energy peak ranges between observation and calculation with the electron-photon transport code EGS5. It was shown that the concentrations can be underestimated by about 30 % unless the obstacles around the detector or infiltration of radionuclides are considered in gamma ray transfer calculations at measuring points, where there are many tall obstacles, or the ground is covered with unpaved areas. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

DMG-α--a computational geometry library for multimolecular systems.

PubMed

Szczelina, Robert; Murzyn, Krzysztof

2014-11-24

The DMG-α library grants researchers in the field of computational biology, chemistry, and biophysics access to an open-sourced, easy to use, and intuitive software for performing fine-grained geometric analysis of molecular systems. The library is capable of computing power diagrams (weighted Voronoi diagrams) in three dimensions with 3D periodic boundary conditions, computing approximate projective 2D Voronoi diagrams on arbitrarily defined surfaces, performing shape properties recognition using α-shape theory and can do exact Solvent Accessible Surface Area (SASA) computation. The software is written mainly as a template-based C++ library for greater performance, but a rich Python interface (pydmga) is provided as a convenient way to manipulate the DMG-α routines. To illustrate possible applications of the DMG-α library, we present results of sample analyses which allowed to determine nontrivial geometric properties of two Escherichia coli-specific lipids as emerging from molecular dynamics simulations of relevant model bilayers.

Feature-based characterisation of signature topography in laser powder bed fusion of metals

NASA Astrophysics Data System (ADS)

Senin, Nicola; Thompson, Adam; Leach, Richard

2018-04-01

The use of state-of-the-art areal topography measurement instrumentation allows for a high level of detail in the acquisition of topographic information at micrometric scales. The 3D geometric models of surface topography obtained from measured data create new opportunities for the investigation of manufacturing processes through characterisation of the surfaces of manufactured parts. Conventional methods for quantitative assessment of topography usually only involve the computation of texture parameters, summary indicators of topography-related characteristics that are computed over the investigated area. However, further useful information may be obtained through characterisation of signature topographic formations, as more direct indicators of manufacturing process behaviour and performance. In this work, laser powder bed fusion of metals is considered. An original algorithmic method is proposed to isolate relevant topographic formations and to quantify their dimensional and geometric properties, using areal topography data acquired by state-of-the-art areal topography measurement instrumentation.

Radiofrequency-sputtered coatings for lubrication system components and other complex surfaces

NASA Technical Reports Server (NTRS)

Spalvins, T.

1972-01-01

Irregularly shaped surfaces, such as lubrication system components (ball bearings, seals, gears, etc.), can be coated on all surfaces, including irregular shapes, when radiofrequency sputtering is used. When the specimen is properly located with respect to the sputtering target, the sputtered material covers the entire surface of the object irrespective of its geometrical configuration. An adherent, dense film is formed. The film thickness varies from 20 to 50 percent on, for example, a hearing cage or race depending on its geometry. When sputtered solid film lubricants such as molybdenum disulfide are used, a film thickness only of the order of 10 to the minus 7th power m (thousands of angstroms) is required at the contacting areas. It is only essential to determine the required film thickness at the critical areas in need of lubrication. The sections outside the areas to be lubricated fall within the thickness deviation range of 20 to 50 percent, which still constitutes a negligible change respect to tolerance requirements.

Assessing the contributions of surface waves and complex rays to far-field Mie scattering by use of the Debye series

NASA Technical Reports Server (NTRS)

Hovenac, Edward A.; Lock, James A.

1991-01-01

The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with the Debye series. Interference effects between surface waves, complex waves, and geometrical waves are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface wave-geometrical pattern is presented.

Periodic minimal surfaces

NASA Astrophysics Data System (ADS)

Mackay, Alan L.

1985-04-01

A minimal surface is one for which, like a soap film with the same pressure on each side, the mean curvature is zero and, thus, is one where the two principal curvatures are equal and opposite at every point. For every closed circuit in the surface, the area is a minimum. Schwarz1 and Neovius2 showed that elements of such surfaces could be put together to give surfaces periodic in three dimensions. These periodic minimal surfaces are geometrical invariants, as are the regular polyhedra, but the former are curved. Minimal surfaces are appropriate for the description of various structures where internal surfaces are prominent and seek to adopt a minimum area or a zero mean curvature subject to their topology; thus they merit more complete numerical characterization. There seem to be at least 18 such surfaces3, with various symmetries and topologies, related to the crystallographic space groups. Recently, glyceryl mono-oleate (GMO) was shown by Longley and McIntosh4 to take the shape of the F-surface. The structure postulated is shown here to be in good agreement with an analysis of the fundamental geometry of periodic minimal surfaces.

Method for deploying and recovering a wave energy converter

DOEpatents

Mundon, Timothy R

2017-05-23

A system for transporting a buoy and a heave plate. The system includes a buoy and a heave plate. An outer surface of the buoy has a first geometrical shape. A surface of the heave plate has a geometrical shape complementary to the first geometrical shape of the buoy. The complementary shapes of the buoy and the heave plate facilitate coupling of the heave plate to the outer surface of the buoy in a transport mode.

Modified polarized geometrical attenuation model for bidirectional reflection distribution function based on random surface microfacet theory.

PubMed

Liu, Hong; Zhu, Jingping; Wang, Kai

2015-08-24

The geometrical attenuation model given by Blinn was widely used in the geometrical optics bidirectional reflectance distribution function (BRDF) models. Blinn's geometrical attenuation model based on symmetrical V-groove assumption and ray scalar theory causes obvious inaccuracies in BRDF curves and negatives the effects of polarization. Aiming at these questions, a modified polarized geometrical attenuation model based on random surface microfacet theory is presented by combining of masking and shadowing effects and polarized effect. The p-polarized, s-polarized and unpolarized geometrical attenuation functions are given in their separate expressions and are validated with experimental data of two samples. It shows that the modified polarized geometrical attenuation function reaches better physical rationality, improves the precision of BRDF model, and widens the applications for different polarization.

Evaluation of Advanced Reactive Surface Area Estimates for Improved Prediction of Mineral Reaction Rates in Porous Media

NASA Astrophysics Data System (ADS)

Beckingham, L. E.; Mitnick, E. H.; Zhang, S.; Voltolini, M.; Yang, L.; Steefel, C. I.; Swift, A.; Cole, D. R.; Sheets, J.; Kneafsey, T. J.; Landrot, G.; Anovitz, L. M.; Mito, S.; Xue, Z.; Ajo Franklin, J. B.; DePaolo, D.

2015-12-01

CO2 sequestration in deep sedimentary formations is a promising means of reducing atmospheric CO2 emissions but the rate and extent of mineral trapping remains difficult to predict. Reactive transport models provide predictions of mineral trapping based on laboratory mineral reaction rates, which have been shown to have large discrepancies with field rates. This, in part, may be due to poor quantification of mineral reactive surface area in natural porous media. Common estimates of mineral reactive surface area are ad hoc and typically based on grain size, adjusted several orders of magnitude to account for surface roughness and reactivity. This results in orders of magnitude discrepancies in estimated surface areas that directly translate into orders of magnitude discrepancies in model predictions. Additionally, natural systems can be highly heterogeneous and contain abundant nano- and micro-porosity, which can limit connected porosity and access to mineral surfaces. In this study, mineral-specific accessible surface areas are computed for a sample from the reservoir formation at the Nagaoka pilot CO2 injection site (Japan). Accessible mineral surface areas are determined from a multi-scale image analysis including X-ray microCT, SEM QEMSCAN, XRD, SANS, and SEM-FIB. Powder and flow-through column laboratory experiments are performed and the evolution of solutes in the aqueous phase is tracked. Continuum-scale reactive transport models are used to evaluate the impact of reactive surface area on predictions of experimental reaction rates. Evaluated reactive surface areas include geometric and specific surface areas (eg. BET) in addition to their reactive-site weighted counterparts. The most accurate predictions of observed powder mineral dissolution rates were obtained through use of grain-size specific surface areas computed from a BET-based correlation. Effectively, this surface area reflects the grain-fluid contact area, or accessible surface area, in the powder dissolution experiment. In the model of the flow-through column experiment, the accessible mineral surface area, computed from the multi-scale image analysis, is evaluated in addition to the traditional surface area estimates.

Introductory Talk: Whole Frog Project

Science.gov Websites

geometric primitives (points, lines, polygons, etc.) that accurately represent the shape of the surface constant value (color). This operation effectively defines the boundary between areas of different color about 10 seconds on a 56K baud modem. The controls can be set to send compressed images of 3 different

Estimating Number of People Using Calibrated Monocular Camera Based on Geometrical Analysis of Surface Area

NASA Astrophysics Data System (ADS)

Arai, Hiroyuki; Miyagawa, Isao; Koike, Hideki; Haseyama, Miki

We propose a novel technique for estimating the number of people in a video sequence; it has the advantages of being stable even in crowded situations and needing no ground-truth data. By analyzing the geometrical relationships between image pixels and their intersection volumes in the real world quantitatively, a foreground image directly indicates the number of people. Because foreground detection is possible even in crowded situations, the proposed method can be applied in such situations. Moreover, it can estimate the number of people in an a priori manner, so it needs no ground-truth data unlike existing feature-based estimation techniques. Experiments show the validity of the proposed method.

Ducting arrangement for cooling a gas turbine structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Ching-Pang; Morrison, Jay A.

2015-07-21

A ducting arrangement (10) for a can annular gas turbine engine, including: a duct (12, 14) disposed between a combustor (16) and a first row of turbine blades and defining a hot gas path (30) therein, the duct (12, 14) having raised geometric features (54) incorporated into an outer surface (80); and a flow sleeve (72) defining a cooling flow path (84) between an inner surface (78) of the flow sleeve (72) and the duct outer surface (80). After a cooling fluid (86) traverses a relatively upstream raised geometric feature (90), the inner surface (78) of the flow sleeve (72)more » is effective to direct the cooling fluid (86) toward a landing (94) separating the relatively upstream raised geometric feature (90) from a relatively downstream raised geometric feature (94).« less

Relationships among particle number, surface area, and respirable mass concentrations in automotive engine manufacturing.

PubMed

Heitbrink, William A; Evans, Douglas E; Ku, Bon Ki; Maynard, Andrew D; Slavin, Thomas J; Peters, Thomas M

2009-01-01

This study investigated the relationships between particle number, surface area, and respirable mass concentration measured simultaneously in a foundry and an automotive engine machining and assembly center. Aerosol concentrations were measured throughout each plant with a condensation particle counter for number concentration, a diffusion charger for active surface area concentration, and an optical particle counter for respirable mass concentration. At selected locations, particle size distributions were characterized with the optical particle counter and an electrical low pressure impactor. Statistical analyses showed that active surface area concentration was correlated with ultrafine particle number concentration and weakly correlated with respirable mass concentration. Correlation between number and active surface area concentration was stronger during winter (R2 = 0.6 for both plants) than in the summer (R2 = 0.38 and 0.36 for the foundry and engine plant respectively). The stronger correlation in winter was attributed to use of direct-fire gas fired heaters that produced substantial numbers of ultrafine particles with a modal diameter between 0.007 and 0.023 mu m. These correlations support findings obtained through theoretical analysis. Such analysis predicts that active surface area increasingly underestimates geometric surface area with increasing particle size, particularly for particles larger than 100 nm. Thus, a stronger correlation between particle number concentration and active surface area concentration is expected in the presence of high concentrations of ultrafine particles. In general, active surface area concentration may be a concentration metric that is distinct from particle number concentration and respirable mass concentration. For future health effects or toxicological studies involving nano-materials or ultrafine aerosols, this finding needs to be considered, as exposure metrics may influence data interpretation.

Estimation of surface area concentration of workplace incidental nanoparticles based on number and mass concentrations

NASA Astrophysics Data System (ADS)

Park, J. Y.; Ramachandran, G.; Raynor, P. C.; Kim, S. W.

2011-10-01

Surface area was estimated by three different methods using number and/or mass concentrations obtained from either two or three instruments that are commonly used in the field. The estimated surface area concentrations were compared with reference surface area concentrations (SAREF) calculated from the particle size distributions obtained from a scanning mobility particle sizer and an optical particle counter (OPC). The first estimation method (SAPSD) used particle size distribution measured by a condensation particle counter (CPC) and an OPC. The second method (SAINV1) used an inversion routine based on PM1.0, PM2.5, and number concentrations to reconstruct assumed lognormal size distributions by minimizing the difference between measurements and calculated values. The third method (SAINV2) utilized a simpler inversion method that used PM1.0 and number concentrations to construct a lognormal size distribution with an assumed value of geometric standard deviation. All estimated surface area concentrations were calculated from the reconstructed size distributions. These methods were evaluated using particle measurements obtained in a restaurant, an aluminum die-casting factory, and a diesel engine laboratory. SAPSD was 0.7-1.8 times higher and SAINV1 and SAINV2 were 2.2-8 times higher than SAREF in the restaurant and diesel engine laboratory. In the die casting facility, all estimated surface area concentrations were lower than SAREF. However, the estimated surface area concentration using all three methods had qualitatively similar exposure trends and rankings to those using SAREF within a workplace. This study suggests that surface area concentration estimation based on particle size distribution (SAPSD) is a more accurate and convenient method to estimate surface area concentrations than estimation methods using inversion routines and may be feasible to use for classifying exposure groups and identifying exposure trends.

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCormick, F.

A method for containment and deflection of inorganic and organic aqueous surface pollutants, such as an oil slick, flotsam, debris, and jellyfish, and an apparatus for the operation of such method are described. This method comprises the generation of an air or bubble barrier which permits the passage of surface vessels and large fish, but halts the movement of floating surface pollutants by the creation of a flexible continuous band of surface turbulence. The system in one specific application is designed to protect harbor and beach areas and fishing grounds from contamination with oil from oil tankers and also actsmore » as an air wall to keep harmful jellyfish from beach areas. The system can also be employed to recover oil from sunken or leaking tankers at sea by containment and collection of the oil released within the circumference of the bubble barrier wall created in a geometric pattern about the location of the stricken vessel. (10 claims)« less

Site-to-Source Finite Fault Distance Probability Distribution in Probabilistic Seismic Hazard and the Relationship Between Minimum Distances

NASA Astrophysics Data System (ADS)

Ortega, R.; Gutierrez, E.; Carciumaru, D. D.; Huesca-Perez, E.

2017-12-01

We present a method to compute the conditional and no-conditional probability density function (PDF) of the finite fault distance distribution (FFDD). Two cases are described: lines and areas. The case of lines has a simple analytical solution while, in the case of areas, the geometrical probability of a fault based on the strike, dip, and fault segment vertices is obtained using the projection of spheres in a piecewise rectangular surface. The cumulative distribution is computed by measuring the projection of a sphere of radius r in an effective area using an algorithm that estimates the area of a circle within a rectangle. In addition, we introduce the finite fault distance metrics. This distance is the distance where the maximum stress release occurs within the fault plane and generates a peak ground motion. Later, we can apply the appropriate ground motion prediction equations (GMPE) for PSHA. The conditional probability of distance given magnitude is also presented using different scaling laws. A simple model of constant distribution of the centroid at the geometrical mean is discussed, in this model hazard is reduced at the edges because the effective size is reduced. Nowadays there is a trend of using extended source distances in PSHA, however it is not possible to separate the fault geometry from the GMPE. With this new approach, it is possible to add fault rupture models separating geometrical and propagation effects.

Identification of black hole horizons using scalar curvature invariants

NASA Astrophysics Data System (ADS)

Coley, Alan; McNutt, David

2018-01-01

We introduce the concept of a geometric horizon, which is a surface distinguished by the vanishing of certain curvature invariants which characterize its special algebraic character. We motivate its use for the detection of the event horizon of a stationary black hole by providing a set of appropriate scalar polynomial curvature invariants that vanish on this surface. We extend this result by proving that a non-expanding horizon, which generalizes a Killing horizon, coincides with the geometric horizon. Finally, we consider the imploding spherically symmetric metrics and show that the geometric horizon identifies a unique quasi-local surface corresponding to the unique spherically symmetric marginally trapped tube, implying that the spherically symmetric dynamical black holes admit a geometric horizon. Based on these results, we propose a suite of conjectures concerning the application of geometric horizons to more general dynamical black hole scenarios.

Nonthermal and geometric effects on the symmetric and anti-symmetric surface waves in a Lorentzian dusty plasma slab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Myoung-Jae; Jung, Young-Dae, E-mail: ydjung@hanyang.ac.kr; Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791

2015-02-15

The nonthermal and geometric effects on the propagation of the surface dust acoustic waves are investigated in a Lorentzian dusty plasma slab. The symmetric and anti-symmetric dispersion modes of the dust acoustic waves are obtained by the plasma dielectric function with the spectral reflection conditions the slab geometry. The variation of the nonthermal and geometric effects on the symmetric and the anti-symmetric modes of the surface plasma waves is also discussed.

Department of Defense Strategy to Support Multi-Agency Bat Conservation Initiative within the State of Utah

DTIC Science & Technology

2008-02-28

Range, and Section are entered. Datum: Geometric reference surface. Original Site Location datum is defined by user’s map datum; e.g. NAD27...Section are entered. Datum: Geometric reference surface. Original Site Location datum is defined by user’s map datum; e.g. NAD27 Conus or NAD83...Calculated and recorded automatically if the fields UTM_N and UTM_E or Township, Range, and Section are entered. 41 Datum: Geometric reference surface

Practical quality control tools for curves and surfaces

NASA Technical Reports Server (NTRS)

Small, Scott G.

1992-01-01

Curves (geometry) and surfaces created by Computer Aided Geometric Design systems in the engineering environment must satisfy two basic quality criteria: the geometric shape must have the desired engineering properties; and the objects must be parameterized in a way which does not cause computational difficulty for geometric processing and engineering analysis. Interactive techniques are described which are in use at Boeing to evaluate the quality of aircraft geometry prior to Computational Fluid Dynamic analysis, including newly developed methods for examining surface parameterization and its effects.

Geometric and electrostatic modeling using molecular rigidity functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mu, Lin; Xia, Kelin; Wei, Guowei

Geometric and electrostatic modeling is an essential component in computational biophysics and molecular biology. Commonly used geometric representations admit geometric singularities such as cusps, tips and self-intersecting facets that lead to computational instabilities in the molecular modeling. Our present work explores the use of flexibility and rigidity index (FRI), which has a proved superiority in protein B-factor prediction, for biomolecular geometric representation and associated electrostatic analysis. FRI rigidity surfaces are free of geometric singularities. We propose a rigidity based Poisson–Boltzmann equation for biomolecular electrostatic analysis. These approaches to surface and electrostatic modeling are validated by a set of 21 proteins.more » Our results are compared with those of established methods. Finally, being smooth and analytically differentiable, FRI rigidity functions offer excellent curvature analysis, which characterizes concave and convex regions on protein surfaces. Polarized curvatures constructed by using the product of minimum curvature and electrostatic potential is shown to predict potential protein–ligand binding sites.« less

Geometric and electrostatic modeling using molecular rigidity functions

DOE PAGES

Mu, Lin; Xia, Kelin; Wei, Guowei

2017-03-01

Geometric and electrostatic modeling is an essential component in computational biophysics and molecular biology. Commonly used geometric representations admit geometric singularities such as cusps, tips and self-intersecting facets that lead to computational instabilities in the molecular modeling. Our present work explores the use of flexibility and rigidity index (FRI), which has a proved superiority in protein B-factor prediction, for biomolecular geometric representation and associated electrostatic analysis. FRI rigidity surfaces are free of geometric singularities. We propose a rigidity based Poisson–Boltzmann equation for biomolecular electrostatic analysis. These approaches to surface and electrostatic modeling are validated by a set of 21 proteins.more » Our results are compared with those of established methods. Finally, being smooth and analytically differentiable, FRI rigidity functions offer excellent curvature analysis, which characterizes concave and convex regions on protein surfaces. Polarized curvatures constructed by using the product of minimum curvature and electrostatic potential is shown to predict potential protein–ligand binding sites.« less

A method for cone fitting based on certain sampling strategy in CMM metrology

NASA Astrophysics Data System (ADS)

Zhang, Li; Guo, Chaopeng

2018-04-01

A method of cone fitting in engineering is explored and implemented to overcome shortcomings of current fitting method. In the current method, the calculations of the initial geometric parameters are imprecise which cause poor accuracy in surface fitting. A geometric distance function of cone is constructed firstly, then certain sampling strategy is defined to calculate the initial geometric parameters, afterwards nonlinear least-squares method is used to fit the surface. The experiment is designed to verify accuracy of the method. The experiment data prove that the proposed method can get initial geometric parameters simply and efficiently, also fit the surface precisely, and provide a new accurate way to cone fitting in the coordinate measurement.

Algebro-geometric approach for a centrally extended Uq[sl(2|2)] R-matrix

NASA Astrophysics Data System (ADS)

Martins, M. J.

2017-04-01

In this paper we investigate the algebraic geometric nature of a solution of the Yang-Baxter equation based on the quantum deformation of the centrally extended sl (2 | 2) superalgebra proposed by Beisert and Koroteev [1]. We derive an alternative representation for the R-matrix in which the matrix elements are given in terms of rational functions depending on weights sited on a degree six surface. For generic gauge the weights geometry are governed by a genus one ruled surface while for a symmetric gauge choice the weights lie instead on a genus five curve. We have written down the polynomial identities satisfied by the R-matrix entries needed to uncover the corresponding geometric properties. For arbitrary gauge the R-matrix geometry is argued to be birational to the direct product CP1 ×CP1 × A where A is an Abelian surface. For the symmetric gauge we present evidences that the geometric content is that of a surface of general type lying on the so-called Severi line with irregularity two and geometric genus nine. We discuss potential geometric degenerations when the two free couplings are restricted to certain one-dimensional subspaces.

Oral Drug Delivery Systems Comprising Altered Geometric Configurations for Controlled Drug Delivery

PubMed Central

Moodley, Kovanya; Pillay, Viness; Choonara, Yahya E.; du Toit, Lisa C.; Ndesendo, Valence M. K.; Kumar, Pradeep; Cooppan, Shivaan; Bawa, Priya

2012-01-01

Recent pharmaceutical research has focused on controlled drug delivery having an advantage over conventional methods. Adequate controlled plasma drug levels, reduced side effects as well as improved patient compliance are some of the benefits that these systems may offer. Controlled delivery systems that can provide zero-order drug delivery have the potential for maximizing efficacy while minimizing dose frequency and toxicity. Thus, zero-order drug release is ideal in a large area of drug delivery which has therefore led to the development of various technologies with such drug release patterns. Systems such as multilayered tablets and other geometrically altered devices have been created to perform this function. One of the principles of multilayered tablets involves creating a constant surface area for release. Polymeric materials play an important role in the functioning of these systems. Technologies developed to date include among others: Geomatrix® multilayered tablets, which utilizes specific polymers that may act as barriers to control drug release; Procise®, which has a core with an aperture that can be modified to achieve various types of drug release; core-in-cup tablets, where the core matrix is coated on one surface while the circumference forms a cup around it; donut-shaped devices, which possess a centrally-placed aperture hole and Dome Matrix® as well as “release modules assemblage”, which can offer alternating drug release patterns. This review discusses the novel altered geometric system technologies that have been developed to provide controlled drug release, also focusing on polymers that have been employed in such developments. PMID:22312236

Impact of electrode geometry on an atmospheric pressure surface barrier discharge

NASA Astrophysics Data System (ADS)

Hasan, M. I.; Morabit, Y.; Dickenson, A.; Walsh, J. L.

2017-06-01

Several of the key characteristics of an atmospheric pressure surface barrier discharge (SBD) are heavily dependent on the geometrical configuration of the plasma generating electrodes. This paper reveals that increasing the surface area of an SBD device by reducing the gaps within the electrodes can have major and unforeseen consequence on the discharge properties. It is experimentally demonstrated that a critical limit exists when reducing the diameter of a circular electrode gap below 5 mm, beyond which the required breakdown voltage increases exponentially and the power deposited in the discharge is impeded. Using a numerical model, it is shown that a reduced electrode gap diameter yields a decrease in the voltage difference between the electrode and dielectric surface, thus lowering the maximum electric field. This study indicates a link between the electrode geometry and the nature of the reactive chemistry produced in the plasma, findings which have wide-reaching implications for many applications where multiple closely packed surface barrier discharges are employed to achieve uniform and large area plasma processing.

New Mathematical Model for the Surface Area of the Left Ventricle by the Truncated Prolate Spheroid

PubMed Central

Vale, Marcos de Paula; Martinez, Carlos Barreira

2017-01-01

The main aim of this study was the formula application of the superficial area of a truncated prolate spheroid (TPS) in Cartesian coordinates in obtaining a cardiac parameter that is not so much discussed in literature, related to the left ventricle (LV) surface area of the human heart, by age and sex. First we obtain a formula for the area of a TPS. Then a simple mathematical model of association of the axes measures of a TPS with the axes of the LV is built. Finally real values of the average dimensions of the humans LV are used to measure surface areas approximations of this heart chamber. As a result, the average superficial area of LV for normal patients is obtained and it is observed that the percentage differences of areas between men and women and their consecutive age groups are constant. A strong linear correlation between the obtained areas and the ventricular volumes normalized by the body areas was observed. The obtained results indicate that the superficial area of the LV, besides enabling a greater knowledge of the geometrical characteristics of the human LV, may be used as one of the normality cardiac verification criteria and be useful for medical and biological applications. PMID:28547001

SAR Polarimetry

NASA Technical Reports Server (NTRS)

vanZyl, Jakob J.

2012-01-01

Radar Scattering includes: Surface Characteristics, Geometric Properties, Dielectric Properties, Rough Surface Scattering, Geometrical Optics and Small Perturbation Method Solutions, Integral Equation Method, Magellan Image of Pancake Domes on Venus, Dickinson Impact Crater on Venus (Magellan), Lakes on Titan (Cassini Radar, Longitudinal Dunes on Titan (Cassini Radar), Rough Surface Scattering: Effect of Dielectric Constant, Vegetation Scattering, Effect of Soil Moisture. Polarimetric Radar includes: Principles of Polarimetry: Field Descriptions, Wave Polarizations: Geometrical Representations, Definition of Ellipse Orientation Angles, Scatter as Polarization Transformer, Scattering Matrix, Coordinate Systems, Scattering Matrix, Covariance Matrix, Pauli Basis and Coherency Matrix, Polarization Synthesis, Polarimeter Implementation.

Locating and defining underground goaf caused by coal mining from space-borne SAR interferometry

NASA Astrophysics Data System (ADS)

Yang, Zefa; Li, Zhiwei; Zhu, Jianjun; Yi, Huiwei; Feng, Guangcai; Hu, Jun; Wu, Lixin; Preusse, Alex; Wang, Yunjia; Papst, Markus

2018-01-01

It is crucial to locate underground goafs (i.e., mined-out areas) resulting from coal mining and define their spatial dimensions for effectively controlling the induced damages and geohazards. Traditional geophysical techniques for locating and defining underground goafs, however, are ground-based, labour-consuming and costly. This paper presents a novel space-based method for locating and defining the underground goaf caused by coal extraction using Interferometric Synthetic Aperture Radar (InSAR) techniques. As the coal mining-induced goaf is often a cuboid-shaped void and eight critical geometric parameters (i.e., length, width, height, inclined angle, azimuth angle, mining depth, and two central geodetic coordinates) are capable of locating and defining this underground space, the proposed method reduces to determine the eight geometric parameters from InSAR observations. Therefore, it first applies the Probability Integral Method (PIM), a widely used model for mining-induced deformation prediction, to construct a functional relationship between the eight geometric parameters and the InSAR-derived surface deformation. Next, the method estimates these geometric parameters from the InSAR-derived deformation observations using a hybrid simulated annealing and genetic algorithm. Finally, the proposed method was tested with both simulated and two real data sets. The results demonstrate that the estimated geometric parameters of the goafs are accurate and compatible overall, with averaged relative errors of approximately 2.1% and 8.1% being observed for the simulated and the real data experiments, respectively. Owing to the advantages of the InSAR observations, the proposed method provides a non-contact, convenient and practical method for economically locating and defining underground goafs in a large spatial area from space.

Geometric Quality Assessment of LIDAR Data Based on Swath Overlap

NASA Astrophysics Data System (ADS)

Sampath, A.; Heidemann, H. K.; Stensaas, G. L.

2016-06-01

This paper provides guidelines on quantifying the relative horizontal and vertical errors observed between conjugate features in the overlapping regions of lidar data. The quantification of these errors is important because their presence quantifies the geometric quality of the data. A data set can be said to have good geometric quality if measurements of identical features, regardless of their position or orientation, yield identical results. Good geometric quality indicates that the data are produced using sensor models that are working as they are mathematically designed, and data acquisition processes are not introducing any unforeseen distortion in the data. High geometric quality also leads to high geolocation accuracy of the data when the data acquisition process includes coupling the sensor with geopositioning systems. Current specifications (e.g. Heidemann 2014) do not provide adequate means to quantitatively measure these errors, even though they are required to be reported. Current accuracy measurement and reporting practices followed in the industry and as recommended by data specification documents also potentially underestimate the inter-swath errors, including the presence of systematic errors in lidar data. Hence they pose a risk to the user in terms of data acceptance (i.e. a higher potential for Type II error indicating risk of accepting potentially unsuitable data). For example, if the overlap area is too small or if the sampled locations are close to the center of overlap, or if the errors are sampled in flat regions when there are residual pitch errors in the data, the resultant Root Mean Square Differences (RMSD) can still be small. To avoid this, the following are suggested to be used as criteria for defining the inter-swath quality of data: a) Median Discrepancy Angle b) Mean and RMSD of Horizontal Errors using DQM measured on sloping surfaces c) RMSD for sampled locations from flat areas (defined as areas with less than 5 degrees of slope) It is suggested that 4000-5000 points are uniformly sampled in the overlapping regions of the point cloud, and depending on the surface roughness, to measure the discrepancy between swaths. Care must be taken to sample only areas of single return points only. Point-to-Plane distance based data quality measures are determined for each sample point. These measurements are used to determine the above mentioned parameters. This paper details the measurements and analysis of measurements required to determine these metrics, i.e. Discrepancy Angle, Mean and RMSD of errors in flat regions and horizontal errors obtained using measurements extracted from sloping regions (slope greater than 10 degrees). The research is a result of an ad-hoc joint working group of the US Geological Survey and the American Society for Photogrammetry and Remote Sensing (ASPRS) Airborne Lidar Committee.

Design and analysis of a curved cylindrical Fresnel lens that produces high irradiance uniformity on the solar cell.

PubMed

González, Juan C

2009-04-10

A new type of convex Fresnel lens for linear photovoltaic concentration systems is presented. The lens designed with this method reaches 100% of geometrical optical efficiency, and the ratio (Aperture area)/(Receptor area) is up to 75% of the theoretical limit. The main goal of the design is high uniformity of the radiation on the cell surface for each input angle inside the acceptance. The ratio between the maximum and the minimum irradiance on points of the solar cell is less than 2. The lens has been designed with the simultaneous multiple surfaces (SMS) method of nonimaging optics, and ray tracing techniques have been used to characterize its performance for linear symmetry systems.

Observations of Circumstellar Disks with Infrared Interferometry

NASA Technical Reports Server (NTRS)

Akeson, Rachel

2008-01-01

Star formation is arguably the area of astrophysics in which infrared interferometry has had the biggest impact. The optically thick portion of T Tauri and Herbig Ae/Be disks DO NOT extend to a few stellar radii of the stellar surface. Emission is coming from near the dust sublimation radius, but not all from a single radius. The Herbig Ae stars can be either flared or self-shadowed but very massive (early Be) stars are geometrically thin. The Herbig Ae stars can be either flared or self-shadowed but very massive (early Be) stars are geometrically thin. Observational prospects are rapidly improving: a) Higher spectral resolution will allow observations of the gas: jets, winds, accretion. b) Closure phase and imaging will help eliminate model uncertainties/dependencies.

Silica dust exposures during selected construction activities.

PubMed

Flanagan, Mary Ellen; Seixas, Noah; Majar, Maria; Camp, Janice; Morgan, Michael

2003-01-01

This study characterized exposure for dust-producing construction tasks. Eight common construction tasks were evaluated for quartz and respirable dust exposure by collecting 113 personal task period samples for cleanup; demolition with handheld tools; concrete cutting; concrete mixing; tuck-point grinding; surface grinding; sacking and patching concrete; and concrete floor sanding using both time-integrating filter samples and direct-reading respirable dust monitors. The geometric mean quartz concentration was 0.10 mg/m(3) (geometric standard deviation [GSD]=4.88) for all run time samples, with 71% exceeding the threshold limit value. Activities with the highest exposures were surface grinding, tuck-point grinding, and concrete demolition (GM[GSD] of 0.63[4.12], 0.22[1.94], and 0.10[2.60], respectively). Factors recorded each minute were task, tool, work area, respiratory protection and controls used, estimated cross draft, and whether anyone nearby was making dust. Factors important to exposure included tool used, work area configuration, controls employed, cross draft, and in some cases nearby dust. More protective respirators were employed as quartz concentration increased, although respiratory protection was found to be inadequate for 42% of exposures. Controls were employed for only 12% of samples. Exposures were reduced with three controls: box fan for surface grinding and floor sanding, and vacuum/shroud for surface grinding, with reductions of 57, 50, and 71%, respectively. Exposures were higher for sweeping compound, box fan for cleanup, ducted fan dilution, and wetted substrate. Construction masons and laborers are frequently overexposed to silica. The usual protection method, respirators, was not always adequate, and engineering control use was infrequent and often ineffective.

The use of surface layer with boron in friction pairs lubricated by engine oils

NASA Astrophysics Data System (ADS)

Szczypiński-Sala, W.; Lubas, J.

2016-09-01

The aim of the present work is to determine the influence of surface layers with boron and engine oil on the processes of friction and wear in friction pairs. The ring samples with borided surface layer cooperated under test conditions with counterparts made with CuPb30 and AlSn20 bearing alloys. During the tests, the friction pairs were lubricated with 15W/40 Lotos mineral oil and 5W/40 Lotos synthetic oil. The lubrication of friction area with Lotos mineral oil causes the reduction of the friction force, the temperature in the friction area and the wear of the bearing alloys under study, whereas the lubrication with Lotos synthetic oil reduces the changes in the geometrical structure of the cooperating friction pair elements. Lubrication of the friction area in the start-up phase of the friction pair by mineral oil causes faster stabilization of the friction conditions in the contact area than in the cause of lubrication of the friction pair by synthetic oil. The intensity of wear of the AlSn20 bearing alloy cooperating with the borided surface layer is three times smaller than the intensity of use of the CuPb30 alloy bearing.

High Density Aerial Image Matching: State-Of and Future Prospects

NASA Astrophysics Data System (ADS)

Haala, N.; Cavegn, S.

2016-06-01

Ongoing innovations in matching algorithms are continuously improving the quality of geometric surface representations generated automatically from aerial images. This development motivated the launch of the joint ISPRS/EuroSDR project "Benchmark on High Density Aerial Image Matching", which aims on the evaluation of photogrammetric 3D data capture in view of the current developments in dense multi-view stereo-image matching. Originally, the test aimed on image based DSM computation from conventional aerial image flights for different landuse and image block configurations. The second phase then put an additional focus on high quality, high resolution 3D geometric data capture in complex urban areas. This includes both the extension of the test scenario to oblique aerial image flights as well as the generation of filtered point clouds as additional output of the respective multi-view reconstruction. The paper uses the preliminary outcomes of the benchmark to demonstrate the state-of-the-art in airborne image matching with a special focus of high quality geometric data capture in urban scenarios.

Far-side geometrical enhancement in surface-enhanced Raman scattering with Ag plasmonic films

NASA Astrophysics Data System (ADS)

Perera, M. Nilusha M. N.; Gibbs, W. E. Keith; Juodkazis, Saulius; Stoddart, Paul R.

2018-01-01

Surface-enhanced Raman scattering (SERS) is a surface sensitive technique where the large increase in scattering has primarily been attributed to electromagnetic and chemical enhancements. While smaller geometrical enhancements due to thin film interference and cavity resonances have also been reported, an additional enhancement in the SERS signal, referred to as the `far-side geometrical enhancement', occurs when the SERS substrate is excited through an underlying transparent dielectric substrate. Here the far-side geometrically-enhanced SERS signal has been explored experimentally in more detail. Thermally evaporated Ag plasmonic films functionalised with thiophenol were used to study the dependence of the geometrically-enhanced SERS signal on the excitation wavelength, supporting substrate material and excitation angle of incidence. The results were interpreted using a `geometrical enhancement factor' (GEF), defined as the ratio of far-side to near-side SERS signal intensity. The experimental results confirmed that the highest GEFs of 3.2-3.5× are seen closer to the localized surface plasmon resonance peak of the Ag metallic nanostructures. Interestingly, the GEF for Ag plasmonic films deposited on glass and sapphire were the same within the measurement errors, whereas increasing angle of incidence showed a decrease in the GEF. Given this improved understanding of the far-side geometrical SERS enhancement, the potential for further signal amplification and optimisation for practical sensing applications can now be considered, especially for SERS detection modes at the farend of optical fibre probes and through process windows.

The radiation from slots in truncated dielectric-covered surfaces

NASA Technical Reports Server (NTRS)

Hwang, Y. M.; Kouyoumjian, R. G.; Pathak, P. H.

1974-01-01

A theoretical approach based on the geometrical theory of diffraction is used to study the electromagnetic radiation from a narrow slot in a dielectric-covered perfectly-conducting surface terminated at an edge. The total far-zone field is composed of a geometrical optics field and a diffracted field. The geometrical optics field is the direct radiation from the slot to the field point. The slot also generates surface waves which are incident at the termination of the dielectric cover, where singly-diffracted rays and reflected surface waves are excited. The diffraction and reflection coefficients are obtained from the canonical problem of the diffraction of a surface wave by a right-angle wedge where the dielectric-covered surface is approximated by an impedance surface. This approximation is satisfactory for a very thin cover; however, the radiation from its vertical and faces cannot be neglected in treating the thicker dielectric cover. This is taken into account by using a Kirchhoff-type approximation, which contributes a second term to the diffraction coefficient previously obtained. The contributions from the geometrical optics field, the singly-diffracted rays and all significant multiply-diffracted rays are summed to give the total radiation. Calculated and measured patterns are found to be in good agreement.

SU-E-J-205: Dose Distribution Differences Caused by System Related Geometric Distortion in MRI-Guided Radiation Treatment System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J; Yang, J; Wen, Z

2015-06-15

Purpose: MRI has superb soft tissue contrast but is also known for geometric distortions. The concerns and uncertainty about MRI’s geometric distortion have contributed to the hesitation of using only MRI for simulation in radiation therapy. There are two major categories of geometric distortion in MRI; system related and patient related. In this presentation, we studied the impact of system-related geometric distortion on dose distribution in a digital body phantom under an MR-Linac environment. Methods: Residual geometric distortion (after built-in geometric correction) was modeled based on phantom measurements of the system-related geometric distortions of a MRI scanner of a combinedmore » MR guided Radiation Therapy (MRgRT) system. A digital oval shaped phantom (40×25 cm) as well as one ellipsoid shaped tumor volume was created to simulate a simplified human body. The simulated tumor volume was positioned at several locations between the isocenter and the body surface. CT numbers in HUs that approximate soft tissue and tumor were assigned to the respective regions in the digital phantom. To study the effect of geometric distortion caused by system imperfections, an IMRT plan was optimized with the distorted image set with the B field. Dose distributions were re-calculated on the undistorted image set with the B field (as in MR-Linac). Results: The maximum discrepancies in both body contour and tumor boundary was less than 2 mm, which leads to small dose distribution change. For the target in the center, coverage was reduced from 98.8% (with distortion) to 98.2%; for the other peripheral target coverage was reduced from 98.4% to 95.9%. Conclusion: System related geometric distortions over the 40×25 area were within 2mm and the resulted dosimetric effects were minor for the two tumor locations in the phantom. Patient study will be needed for further investigation. The authors received a corporate research grant from Elekta.« less

Human body surface area: a theoretical approach.

PubMed

Wang, Jianfeng; Hihara, Eiji

2004-04-01

Knowledge of the human body surface area has important applications in medical practice, garment design, and other engineering sizing. Therefore, it is not surprising that several expressions correlating body surface area with direct measurements of body mass and length have been reported in the literature. In the present study, based on the assumption that the exterior shape of the human body is the result of convex and concave deformations from a basic cylinder, we derive a theoretical equation minimizing body surface area (BSA) at a fixed volume (V): BSA=(9pi VL)(0.5), where L is the reference length of the body. Assuming a body density value of 1,000 kg.m(-3), the equation becomes BSA=(BM.BH/35.37)(0.5), where BSA is in square meters, BM is the body mass in kilograms, and BH is the body height in meters. BSA values calculated by means of this equation fall within +/-7% of the values obtained by means of the equations available in the literature, in the range of BSA from children to adults. It is also suggested that the above equation, which is obtained by minimizing the outer body surface at a fixed volume, implies a fundamental relation set by the geometrical constraints governing the growth and the development of the human body.

Rational geometrical engineering of palladium sulfide multi-arm nanostructures as a superior bi-functional electrocatalyst.

PubMed

Nandan, R; Nanda, K K

2017-08-31

Geometrical tunability offers sharp edges and an open-armed structure accompanied with a high electrochemical active surface area to ensure the efficient and effective utilization of materials by exposing the electrochemical active sites for facile accessibility of reactant species. Herein, we report a one-step, single-pot, surfactant-free, electroless, and economic route to synthesize palladium sulfide nanostructures with different geometries at mild temperatures and their catalytic properties towards the oxygen reduction reaction (ORR) and methanol electro-oxidation (MOR). For ORR, the positive on-set, half wave potentials, smaller Tafel slope, high electrochemical active surface area, large roughness factor, and better cyclic stability of the proposed nanostructures as compared to those of the commercial state-of-the-art Pt-C/PdS catalysts suggest their superiority in an alkaline medium. In addition, high mass activity (J f ∼ 715 mA mg -1 ), in comparison with that of the commercial state-of-the-art Pt-C/PdS catalysts (J f ∼ 138/41 mA mg -1 , respectively), and high J f /J b (1.52) along with the superior operational stability of the multi-arm palladium sulfide nanostructures towards MOR advocates the bi-functional behavior of the catalyst and its potential as a promising Pt-free anode/cathode electrocatalyst in fuel cells.

Surface texture can bias tactile form perception.

PubMed

Nakatani, Masashi; Howe, Robert D; Tachi, Susumu

2011-01-01

The sense of touch is believed to provide a reliable perception of the object's properties; however, our tactile perceptions could be illusory at times. A recently reported tactile illusion shows that a raised form can be perceived as indented when it is surrounded by textured areas. This phenomenon suggests that the form perception can be influenced by the surface textures in its adjacent areas. As perception of texture and that of form have been studied independently of each other, the present study examined whether textures, in addition to the geometric edges, contribute to the tactile form perception. We examined the perception of the flat and raised contact surface (3.0 mm width) with various heights (0.1, 0.2, 0.3 mm), which had either textured or non-textured adjacent areas, under the static, passive and active touch conditions. Our results showed that texture decreased the raised perception of the surface with a small height (0.1 mm) and decreased the flat perception of the physically flat surface under the passive and active touch conditions. We discuss a possible mechanism underlying the effect of the textures on the form perception based on previous neurophysiological findings.

Percent area coverage through image analysis

NASA Astrophysics Data System (ADS)

Wong, Chung M.; Hong, Sung M.; Liu, De-Ling

2016-09-01

The notion of percent area coverage (PAC) has been used to characterize surface cleanliness levels in the spacecraft contamination control community. Due to the lack of detailed particle data, PAC has been conventionally calculated by multiplying the particle surface density in predetermined particle size bins by a set of coefficients per MIL-STD-1246C. In deriving the set of coefficients, the surface particle size distribution is assumed to follow a log-normal relation between particle density and particle size, while the cross-sectional area function is given as a combination of regular geometric shapes. For particles with irregular shapes, the cross-sectional area function cannot describe the true particle area and, therefore, may introduce error in the PAC calculation. Other errors may also be introduced by using the lognormal surface particle size distribution function that highly depends on the environmental cleanliness and cleaning process. In this paper, we present PAC measurements from silicon witness wafers that collected fallouts from a fabric material after vibration testing. PAC calculations were performed through analysis of microscope images and compare them to values derived through the MIL-STD-1246C method. Our results showed that the MIL-STD-1246C method does provide a reasonable upper bound to the PAC values determined through image analysis, in particular for PAC values below 0.1.

Differential porosimetry and permeametry for random porous media.

PubMed

Hilfer, R; Lemmer, A

2015-07-01

Accurate determination of geometrical and physical properties of natural porous materials is notoriously difficult. Continuum multiscale modeling has provided carefully calibrated realistic microstructure models of reservoir rocks with floating point accuracy. Previous measurements using synthetic microcomputed tomography (μ-CT) were based on extrapolation of resolution-dependent properties for discrete digitized approximations of the continuum microstructure. This paper reports continuum measurements of volume and specific surface with full floating point precision. It also corrects an incomplete description of rotations in earlier publications. More importantly, the methods of differential permeametry and differential porosimetry are introduced as precision tools. The continuum microstructure chosen to exemplify the methods is a homogeneous, carefully calibrated and characterized model for Fontainebleau sandstone. The sample has been publicly available since 2010 on the worldwide web as a benchmark for methodical studies of correlated random media. High-precision porosimetry gives the volume and internal surface area of the sample with floating point accuracy. Continuum results with floating point precision are compared to discrete approximations. Differential porosities and differential surface area densities allow geometrical fluctuations to be discriminated from discretization effects and numerical noise. Differential porosimetry and Fourier analysis reveal subtle periodic correlations. The findings uncover small oscillatory correlations with a period of roughly 850μm, thus implying that the sample is not strictly stationary. The correlations are attributed to the deposition algorithm that was used to ensure the grain overlap constraint. Differential permeabilities are introduced and studied. Differential porosities and permeabilities provide scale-dependent information on geometry fluctuations, thereby allowing quantitative error estimates.

A practical implementation of wave front construction for 3-D isotropic media

NASA Astrophysics Data System (ADS)

Chambers, K.; Kendall, J.-M.

2008-06-01

Wave front construction (WFC) methods are a useful tool for tracking wave fronts and are a natural extension to standard ray shooting methods. Here we describe and implement a simple WFC method that is used to interpolate wavefield properties throughout a 3-D heterogeneous medium. Our approach differs from previous 3-D WFC procedures primarily in the use of a ray interpolation scheme, based on approximating the wave front as a `locally spherical' surface and a `first arrival mode', which reduces computation times, where only first arrivals are required. Both of these features have previously been included in 2-D WFC algorithms; however, until now they have not been extended to 3-D systems. The wave front interpolation scheme allows for rays to be traced from a nearly arbitrary distribution of take-off angles, and the calculation of derivatives with respect to take-off angles is not required for wave front interpolation. However, in regions of steep velocity gradient, the locally spherical approximation is not valid, and it is necessary to backpropagate rays to a sufficiently homogenous region before interpolation of the new ray. Our WFC technique is illustrated using a realistic velocity model, based on a North Sea oil reservoir. We examine wavefield quantities such as traveltimes, ray angles, source take-off angles and geometrical spreading factors, all of which are interpolated on to a regular grid. We compare geometrical spreading factors calculated using two methods: using the ray Jacobian and by taking the ratio of a triangular area of wave front to the corresponding solid angle at the source. The results show that care must be taken when using ray Jacobians to calculate geometrical spreading factors, as the poles of the source coordinate system produce unreliable values, which can be spread over a large area, as only a few initial rays are traced in WFC. We also show that the use of the first arrival mode can reduce computation time by ~65 per cent, with the accuracy of the interpolated traveltimes, ray angles and source take-off angles largely unchanged. However, the first arrival mode does lead to inaccuracies in interpolated angles near caustic surfaces, as well as small variations in geometrical spreading factors for ray tubes that have passed through caustic surfaces.

Porous Structures in Stacked, Crumpled and Pillared Graphene-Based 3D Materials.

PubMed

Guo, Fei; Creighton, Megan; Chen, Yantao; Hurt, Robert; Külaots, Indrek

2014-01-01

Graphene, an atomically thin material with the theoretical surface area of 2600 m 2 g -1 , has great potential in the fields of catalysis, separation, and gas storage if properly assembled into functional 3D materials at large scale. In ideal non-interacting ensembles of non-porous multilayer graphene plates, the surface area can be adequately estimated using the simple geometric law ~ 2600 m 2 g -1 /N, where N is the number of graphene sheets per plate. Some processing operations, however, lead to secondary plate-plate stacking, folding, crumpling or pillaring, which give rise to more complex structures. Here we show that bulk samples of multilayer graphene plates stack in an irregular fashion that preserves the 2600/N surface area and creates regular slot-like pores with sizes that are multiples of the unit plate thickness. In contrast, graphene oxide deposits into films with massive area loss (2600 to 40 m 2 g -1 ) due to nearly perfect alignment and stacking during the drying process. Pillaring graphene oxide sheets by co-deposition of colloidal-phase particle-based spacers has the potential to partially restore the large monolayer surface. Surface areas as high as 1000 m 2 g -1 are demonstrated here through colloidal-phase deposition of graphene oxide with water-dispersible aryl-sulfonated ultrafine carbon black as a pillaring agent.

A level set method for determining critical curvatures for drainage and imbibition.

PubMed

Prodanović, Masa; Bryant, Steven L

2006-12-15

An accurate description of the mechanics of pore level displacement of immiscible fluids could significantly improve the predictions from pore network models of capillary pressure-saturation curves, interfacial areas and relative permeability in real porous media. If we assume quasi-static displacement, at constant pressure and surface tension, pore scale interfaces are modeled as constant mean curvature surfaces, which are not easy to calculate. Moreover, the extremely irregular geometry of natural porous media makes it difficult to evaluate surface curvature values and corresponding geometric configurations of two fluids. Finally, accounting for the topological changes of the interface, such as splitting or merging, is nontrivial. We apply the level set method for tracking and propagating interfaces in order to robustly handle topological changes and to obtain geometrically correct interfaces. We describe a simple but robust model for determining critical curvatures for throat drainage and pore imbibition. The model is set up for quasi-static displacements but it nevertheless captures both reversible and irreversible behavior (Haines jump, pore body imbibition). The pore scale grain boundary conditions are extracted from model porous media and from imaged geometries in real rocks. The method gives quantitative agreement with measurements and with other theories and computational approaches.

Restoring warped document images through 3D shape modeling.

PubMed

Tan, Chew Lim; Zhang, Li; Zhang, Zheng; Xia, Tao

2006-02-01

Scanning a document page from a thick bound volume often results in two kinds of distortions in the scanned image, i.e., shade along the "spine" of the book and warping in the shade area. In this paper, we propose an efficient restoration method based on the discovery of the 3D shape of a book surface from the shading information in a scanned document image. From a technical point of view, this shape from shading (SFS) problem in real-world environments is characterized by 1) a proximal and moving light source, 2) Lambertian reflection, 3) nonuniform albedo distribution, and 4) document skew. Taking all these factors into account, we first build practical models (consisting of a 3D geometric model and a 3D optical model) for the practical scanning conditions to reconstruct the 3D shape of the book surface. We next restore the scanned document image using this shape based on deshading and dewarping models. Finally, we evaluate the restoration results by comparing our estimated surface shape with the real shape as well as the OCR performance on original and restored document images. The results show that the geometric and photometric distortions are mostly removed and the OCR results are improved markedly.

Analysing surface deformation in Surabaya from sentinel-1A data using DInSAR method

NASA Astrophysics Data System (ADS)

Anjasmara, Ira Mutiara; Yusfania, Meiriska; Kurniawan, Akbar; Resmi, Awalina L. C.; Kurniawan, Roni

2017-07-01

The rapid population growth and increasing industrial space in the urban area of Surabaya have caused an excessive ground water use and load of infrastructures. This condition triggers surface deformation, especially the vertical deformation (subsidence or uplift), in Surabaya and its surroundings. The presence of dynamic processes of the Earth and geological form of Surabaya area can also fasten the rate of the surface deformation. In this research, Differential Interferometry Synthetic Aperture Radar (DInSAR) method is chosen to infer the surface deformation over Surabaya area. The DInSAR processing utilized Sentinel 1A satellite images from May 2015 to September 2016 using two-pass interferometric. Two-pass interferometric method is a method that uses two SAR imageries and Digital Elevation Model (DEM). The results from four pairs of DInSAR processing indicate the occurrence of surface deformation in the form of land subsidence and uplift based on the displacement Line of Sight (LOS) in Surabaya. The average rate of surface deformation from May 2015 to September 2016 varies from -3.52 mm/4months to +2.35 mm/4months. The subsidence mostly occurs along the coastal area. However, the result still contains errors from the processing of displacement, due to the value of coherence between the image, noise, geometric distortion of a radar signal and large baseline on image pair.

gpICA: A Novel Nonlinear ICA Algorithm Using Geometric Linearization

NASA Astrophysics Data System (ADS)

Nguyen, Thang Viet; Patra, Jagdish Chandra; Emmanuel, Sabu

2006-12-01

A new geometric approach for nonlinear independent component analysis (ICA) is presented in this paper. Nonlinear environment is modeled by the popular post nonlinear (PNL) scheme. To eliminate the nonlinearity in the observed signals, a novel linearizing method named as geometric post nonlinear ICA (gpICA) is introduced. Thereafter, a basic linear ICA is applied on these linearized signals to estimate the unknown sources. The proposed method is motivated by the fact that in a multidimensional space, a nonlinear mixture is represented by a nonlinear surface while a linear mixture is represented by a plane, a special form of the surface. Therefore, by geometrically transforming the surface representing a nonlinear mixture into a plane, the mixture can be linearized. Through simulations on different data sets, superior performance of gpICA algorithm has been shown with respect to other algorithms.

Effects of surface area and inflow on the performance of stormwater best management practices with uncertainty analysis.

PubMed

Park, Daeryong; Roesner, Larry A

2013-09-01

The performance of stormwater best management practices (BMPs) is affected by BMP geometric and hydrologic factors. The objective of this study was to investigate the effect of BMP surface area and inflow on BMP performance using the k-C* model with uncertainty analysis. Observed total suspended solids (TSS) from detention basins and retention ponds data sets in the International Stormwater BMP Database were used to build and evaluate the model. Detention basins are regarded as dry ponds because they do not always have water, whereas retention ponds have a permanent pool and are considered wet ponds. In this study, Latin hypercube sampling (LHS) was applied to consider uncertainty in both influent event mean concentration (EMC), C(in), and the areal removal constant, k. The latter was estimated from the hydraulic loading rate, q, through use of a power function relationship. Results show that effluent EMC, C(out), decreased as inflow decreased and as BMP surface area increased in both detention basins and retention ponds. However, the change in C(out), depending on inflow and BMP surface area for detention basins, differed from the change in C(out) for retention ponds. Specifically, C(in) was more dominantly associated with the performance of the k-C* model of detention basins than were BMP surface area and inflow. For retention ponds, however, results suggest that BMP surface area and inflow both influenced changes in C(out) as well as C(in). These results suggest that sensitive factors in the performance of the k-C* model are limited to C(in) for detention basins, whereas BMP surface area, inflow, and C(in) are important for retention ponds.

A study on the effect of surface topography on the actuation performance of stacked-rolled dielectric electro active polymer actuator

NASA Astrophysics Data System (ADS)

Sait, Usha; Muthuswamy, Sreekumar

2016-05-01

Dielectric electro active polymer (DEAP) is a suitable actuator material that finds wide applications in the field of robotics and medical areas. This material is highly controllable, flexible, and capable of developing large strain. The influence of geometrical behavior becomes critical when the material is used as miniaturized actuation devices in robotic applications. The present work focuses on the effect of surface topography on the performance of flat (single sheet) and stacked-rolled DEAP actuators. The non-active areas in the form of elliptical spots that affect the performance of the actuator are identified using scanning electron microscope (SEM) and energy dissipated X-ray (EDX) experiments. Performance of DEAP actuation is critically evaluated, compared, and presented with analytical and experimental results.

Animating Autonomous Pedestrians

DTIC Science & Technology

2006-01-01

walkable surface in a region may be mapped onto a horizontal plane without loss of essential geometric information. Consequently, the 3D space may be...that the walkable surface in a region may be mapped onto a horizontal plane without loss of essential geometric information, such as the distance

The Design of Case Products’ Shape Form Information Database Based on NURBS Surface

NASA Astrophysics Data System (ADS)

Liu, Xing; Liu, Guo-zhong; Xu, Nuo-qi; Zhang, Wei-she

2017-07-01

In order to improve the computer design of product shape design,applying the Non-uniform Rational B-splines(NURBS) of curves and surfaces surface to the representation of the product shape helps designers to design the product effectively.On the basis of the typical product image contour extraction and using Pro/Engineer(Pro/E) to extract the geometric feature of scanning mold,in order to structure the information data base system of value point,control point and node vector parameter information,this paper put forward a unified expression method of using NURBS curves and surfaces to describe products’ geometric shape and using matrix laboratory(MATLAB) to simulate when products have the same or similar function.A case study of electric vehicle’s front cover illustrates the access process of geometric shape information of case product in this paper.This method can not only greatly reduce the capacity of information debate,but also improve the effectiveness of computer aided geometric innovation modeling.

Surface Aesthetics and Analysis.

PubMed

Çakır, Barış; Öreroğlu, Ali Rıza; Daniel, Rollin K

2016-01-01

Surface aesthetics of an attractive nose result from certain lines, shadows, and highlights with specific proportions and breakpoints. Analysis emphasizes geometric polygons as aesthetic subunits. Evaluation of the complete nasal surface aesthetics is achieved using geometric polygons to define the existing deformity and aesthetic goals. The relationship between the dome triangles, interdomal triangle, facet polygons, and infralobular polygon are integrated to form the "diamond shape" light reflection on the nasal tip. The principles of geometric polygons allow the surgeon to analyze the deformities of the nose, define an operative plan to achieve specific goals, and select the appropriate operative technique. Copyright © 2016 Elsevier Inc. All rights reserved.

Luminous flux and illumination

NASA Astrophysics Data System (ADS)

Schröer, H.

2001-06-01

Themes of this book are luminous flux and illumination. The book begins with definitions of the notions luminous flux and solid angle. Then the luminous flux through simple geometrical areas as circle, ball, triangles and n-gons is treated. Chapter 7 deals with luminous flux through general surfaces. A comparison between photometric and radiation dimensions follow. The next chapter contains the luminous flux through simple areas in medium (gas). At last illumination and temperature are presented. The content is interesting for opticians, light technicians and all physicists and natural scientists, who have to do with radiation. There is an english and a german edition.

On Geometric Variational Models for Inpainting Surface Holes (PREPRINT)

DTIC Science & Technology

2006-01-01

email: haro@ima.umn.edu Phone: (612) 626-1501 Fax: (612) 626-7370 Affiliations: 1 Dept. de Tecnologia , University of Pompeu-Fabra, Passeig de...regions where the 3D model is incomplete. The main cause of holes are occlusions, but these can also be due to low reflectance, constraints in the...major areas where range scanners are used. With the increasing popularity of range scanners as 3D shape acquisition devices, with applications in

Volumetric Forest Change Detection Through Vhr Satellite Imagery

NASA Astrophysics Data System (ADS)

Akca, Devrim; Stylianidis, Efstratios; Smagas, Konstantinos; Hofer, Martin; Poli, Daniela; Gruen, Armin; Sanchez Martin, Victor; Altan, Orhan; Walli, Andreas; Jimeno, Elisa; Garcia, Alejandro

2016-06-01

Quick and economical ways of detecting of planimetric and volumetric changes of forest areas are in high demand. A research platform, called FORSAT (A satellite processing platform for high resolution forest assessment), was developed for the extraction of 3D geometric information from VHR (very-high resolution) imagery from satellite optical sensors and automatic change detection. This 3D forest information solution was developed during a Eurostars project. FORSAT includes two main units. The first one is dedicated to the geometric and radiometric processing of satellite optical imagery and 2D/3D information extraction. This includes: image radiometric pre-processing, image and ground point measurement, improvement of geometric sensor orientation, quasiepipolar image generation for stereo measurements, digital surface model (DSM) extraction by using a precise and robust image matching approach specially designed for VHR satellite imagery, generation of orthoimages, and 3D measurements in single images using mono-plotting and in stereo images as well as triplets. FORSAT supports most of the VHR optically imagery commonly used for civil applications: IKONOS, OrbView - 3, SPOT - 5 HRS, SPOT - 5 HRG, QuickBird, GeoEye-1, WorldView-1/2, Pléiades 1A/1B, SPOT 6/7, and sensors of similar type to be expected in the future. The second unit of FORSAT is dedicated to 3D surface comparison for change detection. It allows users to import digital elevation models (DEMs), align them using an advanced 3D surface matching approach and calculate the 3D differences and volume changes between epochs. To this end our 3D surface matching method LS3D is being used. FORSAT is a single source and flexible forest information solution with a very competitive price/quality ratio, allowing expert and non-expert remote sensing users to monitor forests in three and four dimensions from VHR optical imagery for many forest information needs. The capacity and benefits of FORSAT have been tested in six case studies located in Austria, Cyprus, Spain, Switzerland and Turkey, using optical data from different sensors and with the purpose to monitor forest with different geometric characteristics. The validation run on Cyprus dataset is reported and commented.

Solid T-spline Construction from Boundary Representations for Genus-Zero Geometry

DTIC Science & Technology

2011-11-14

Engineering, accepted, 2011. [6] M. S. Floater . Parametrization and smooth approximation of surface triangulations. Com- puter Aided Geometric Design...14(3):231 – 250, 1997. [7] M. S. Floater and K. Hormann. Surface parameterization: a tutorial and survey. Advances in Multiresolution for Geometric

Electrochemical characterization of organosilane-functionalized nanostructured ITO surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pruna, R., E-mail: rpruna@el.ub.edu; Palacio, F.; López, M.

2016-08-08

The electroactivity of nanostructured indium tin oxide (ITO) has been investigated for its further use in applications such as sensing biological compounds by the analysis of redox active molecules. ITO films were fabricated by using electron beam evaporation at different substrate temperatures and subsequently annealed for promoting their crystallization. The morphology of the deposited material was monitored by scanning electron microscopy, confirming the deposition of either thin films or nanowires, depending on the substrate temperature. Electrochemical surface characterization revealed a 45 % increase in the electroactive surface area of nanostructured ITO with respect to thin films, one third lower than themore » geometrical surface area variation determined by atomic force microscopy. ITO surfaces were functionalized with a model organic molecule known as 6-(ferrocenyl)hexanethiol. The chemical attachment was done by means of a glycidoxy compound containing a reactive epoxy group, the so-called 3-glycidoxypropyltrimethoxy-silane. ITO functionalization was useful for determining the benefits of nanostructuration on the surface coverage of active molecules. Compared to ITO thin films, an increase in the total peak height of 140 % was observed for as-deposited nanostructured electrodes, whereas the same measurement for annealed electrodes resulted in an increase of more than 400 %. These preliminary results demonstrate the ability of nanostructured ITO to increase the surface-to-volume ratio, conductivity and surface area functionalization, features that highly benefit the performance of biosensors.« less

Summary on several key techniques in 3D geological modeling.

PubMed

Mei, Gang

2014-01-01

Several key techniques in 3D geological modeling including planar mesh generation, spatial interpolation, and surface intersection are summarized in this paper. Note that these techniques are generic and widely used in various applications but play a key role in 3D geological modeling. There are two essential procedures in 3D geological modeling: the first is the simulation of geological interfaces using geometric surfaces and the second is the building of geological objects by means of various geometric computations such as the intersection of surfaces. Discrete geometric surfaces that represent geological interfaces can be generated by creating planar meshes first and then spatially interpolating; those surfaces intersect and then form volumes that represent three-dimensional geological objects such as rock bodies. In this paper, the most commonly used algorithms of the key techniques in 3D geological modeling are summarized.

The role of advanced reactive surface area characterization in improving predictions of mineral reaction rates

NASA Astrophysics Data System (ADS)

Beckingham, L. E.; Zhang, S.; Mitnick, E.; Cole, D. R.; Yang, L.; Anovitz, L. M.; Sheets, J.; Swift, A.; Kneafsey, T. J.; Landrot, G.; Mito, S.; Xue, Z.; Steefel, C. I.; DePaolo, D. J.; Ajo Franklin, J. B.

2014-12-01

Geologic sequestration of CO2 in deep sedimentary formations is a promising means of mitigating carbon emissions from coal-fired power plants but the long-term fate of injected CO2 is challenging to predict. Reactive transport models are used to gain insight over long times but rely on laboratory determined mineral reaction rates that have been difficult to extrapolate to field systems. This, in part, is due to a lack of understanding of mineral reactive surface area. Many models use an arbitrary approximation of reactive surface area, applying orders of magnitude scaling factors to measured BET or geometric surface areas. Recently, a few more sophisticated approaches have used 2D and 3D image analyses to determine mineral-specific reactive surface areas that account for the accessibility of minerals. However, the ability of these advanced surface area estimates to improve predictions of mineral reaction rates has yet to be determined. In this study, we fuse X-ray microCT, SEM QEMSCAN, XRD, SANS, and SEM-FIB analysis to determine mineral-specific accessible reactive surface areas for a core sample from the Nagaoka pilot CO2 injection site (Japan). This sample is primarily quartz, plagioclase, smectite, K-feldspar, and pyroxene. SEM imaging shows abundant smectite cement and grain coatings that decrease the fluid accessibility of other minerals. However, analysis of FIB-SEM images reveals that smectite nano-pores are well connected such that access to underlying minerals is not occluded by smectite coatings. Mineral-specific accessible surfaces are determined, accounting for the connectivity of the pore space with and without connected smectite nano-pores. The large-scale impact of variations in accessibility and dissolution rates are then determined through continuum scale modeling using grid-cell specific information on accessible surface areas. This approach will be compared with a traditional continuum scale model using mineral abundances and common surface area estimates. Ultimately, the effectiveness of advanced surface area characterization to improve mineral dissolution rates will be evaluated by comparison of model results with dissolution rates measured from a flow-through column experiment.

Chemical weathering rates of a soil chronosequence on granitic alluvium: I. Quantification of mineralogical and surface area changes and calculation of primary silicate reaction rates

USGS Publications Warehouse

White, A.F.; Blum, A.E.; Schulz, M.S.; Bullen, T.D.; Harden, J.W.; Peterson, M.L.

1996-01-01

Mineral weathering rates are determined for a series of soils ranging in age from 0.2-3000 Ky developed on alluvial terraces near Merced in the Central Valley of California. Mineralogical and elemental abundances exhibit time-dependent trends documenting the chemical evolution of granitic sand to residual kaolinite and quartz. Mineral losses with time occur in the order: hornblende > plagioclase > K-feldspar. Maximum volume decreases of >50% occur in the older soils. BET surface areas of the bulk soils increase with age, as do specific surface areas of aluminosilicate mineral fractions such as plagioclase, which increases from 0.4-1.5 m2 g-1 over 600 Ky. Quartz surface areas are lower and change less with time (0.11-0.23 m2 g-1). BET surface areas correspond to increasing external surface roughness (?? = 10-600) and relatively constant internal surface area (??? 1.3 m2 g-1). SEM observations confirm both surface pitting and development of internal porosity. A numerical model describes aluminosilicate dissolution rates as a function of changes in residual mineral abundance, grain size distributions, and mineral surface areas with time. A simple geometric treatment, assuming spherical grains and no surface roughness, predicts average dissolution rates (plagioclase, 10-17.4; K-feldspar, 10-17.8; and hornblende, 10-17.5 mol cm-1 s-1) that are constant with time and comparable to previous estimates of soil weathering. Average rates, based on BET surface area measurements and variable surface roughnesses, are much slower (plagioclase, 10-19.9; K-feldspar, 10-20.5; and hornblende 10-20.1 mol cm-2 s-1). Rates for individual soil horizons decrease by a factor of 101.5 over 3000 Ky indicating that the surface reactivities of minerals decrease as the physical surface areas increase. Rate constants based on BET estimates for the Merced soils are factors of 103-104 slower than reported experimental dissolution rates determined from freshly prepared silicates with low surface roughness (?? <10). This study demonstrates that the utility of experimental rate constants to predict weathering in soils is limited without consideration of variable surface areas and processes that control the evolution of surface reactivity with time.

Mapping Hydrophobicity on the Protein Molecular Surface at Atom-Level Resolution

PubMed Central

Nicolau Jr., Dan V.; Paszek, Ewa; Fulga, Florin; Nicolau, Dan V.

2014-01-01

A precise representation of the spatial distribution of hydrophobicity, hydrophilicity and charges on the molecular surface of proteins is critical for the understanding of the interaction with small molecules and larger systems. The representation of hydrophobicity is rarely done at atom-level, as this property is generally assigned to residues. A new methodology for the derivation of atomic hydrophobicity from any amino acid-based hydrophobicity scale was used to derive 8 sets of atomic hydrophobicities, one of which was used to generate the molecular surfaces for 35 proteins with convex structures, 5 of which, i.e., lysozyme, ribonuclease, hemoglobin, albumin and IgG, have been analyzed in more detail. Sets of the molecular surfaces of the model proteins have been constructed using spherical probes with increasingly large radii, from 1.4 to 20 Å, followed by the quantification of (i) the surface hydrophobicity; (ii) their respective molecular surface areas, i.e., total, hydrophilic and hydrophobic area; and (iii) their relative densities, i.e., divided by the total molecular area; or specific densities, i.e., divided by property-specific area. Compared with the amino acid-based formalism, the atom-level description reveals molecular surfaces which (i) present an approximately two times more hydrophilic areas; with (ii) less extended, but between 2 to 5 times more intense hydrophilic patches; and (iii) 3 to 20 times more extended hydrophobic areas. The hydrophobic areas are also approximately 2 times more hydrophobicity-intense. This, more pronounced “leopard skin”-like, design of the protein molecular surface has been confirmed by comparing the results for a restricted set of homologous proteins, i.e., hemoglobins diverging by only one residue (Trp37). These results suggest that the representation of hydrophobicity on the protein molecular surfaces at atom-level resolution, coupled with the probing of the molecular surface at different geometric resolutions, can capture processes that are otherwise obscured to the amino acid-based formalism. PMID:25462574

An analysis of the radiation from apertures in curved surfaces by the geometrical theory of diffraction. [ray technique for electromagnetic fields

NASA Technical Reports Server (NTRS)

Pathak, P. H.; Kouyoumjian, R. G.

1974-01-01

In this paper the geometrical theory of diffraction is extended to treat the radiation from apertures of slots in convex perfectly conducting surfaces. It is assumed that the tangential electric field in the aperture is known so that an equivalent infinitesimal source can be defined at each point in the aperture. Surface rays emanate from this source which is a caustic of the ray system. A launching coefficient is introduced to describe the excitation of the surface ray modes. If the field radiated from the surface is desired, the ordinary diffraction coefficients are used to determine the field of the rays shed tangentially from the surface rays. The field of the surface ray modes is not the field on the surface; hence if the mutual coupling between slots is of interest, a second coefficient related to the launching coefficient must be employed. In the region adjacent to the shadow boundary, the component of the field directly radiated from the source is represented by Fock-type functions. In the illuminated region the incident radiation from the source (this does not include the diffracted field components) is treated by geometrical optics. This extension of the geometrical theory of diffraction is applied to calculate the radiation from slots on elliptic cylinders, spheres, and spheroids.

Orienting in virtual environments: How are surface features and environmental geometry weighted in an orientation task?

PubMed

Kelly, Debbie M; Bischof, Walter F

2008-10-01

We investigated how human adults orient in enclosed virtual environments, when discrete landmark information is not available and participants have to rely on geometric and featural information on the environmental surfaces. In contrast to earlier studies, where, for women, the featural information from discrete landmarks overshadowed the encoding of the geometric information, Experiment 1 showed that when featural information is conjoined with the environmental surfaces, men and women encoded both types of information. Experiment 2 showed that, although both types of information are encoded, performance in locating a goal position is better if it is close to a geometrically or featurally distinct location. Furthermore, although features are relied upon more strongly than geometry, initial experience with an environment influences the relative weighting of featural and geometric cues. Taken together, these results show that human adults use a flexible strategy for encoding spatial information.

Automated quadrilateral surface discretization method and apparatus usable to generate mesh in a finite element analysis system

DOEpatents

Blacker, Teddy D.

1994-01-01

An automatic quadrilateral surface discretization method and apparatus is provided for automatically discretizing a geometric region without decomposing the region. The automated quadrilateral surface discretization method and apparatus automatically generates a mesh of all quadrilateral elements which is particularly useful in finite element analysis. The generated mesh of all quadrilateral elements is boundary sensitive, orientation insensitive and has few irregular nodes on the boundary. A permanent boundary of the geometric region is input and rows are iteratively layered toward the interior of the geometric region. Also, an exterior permanent boundary and an interior permanent boundary for a geometric region may be input and the rows are iteratively layered inward from the exterior boundary in a first counter clockwise direction while the rows are iteratively layered from the interior permanent boundary toward the exterior of the region in a second clockwise direction. As a result, a high quality mesh for an arbitrary geometry may be generated with a technique that is robust and fast for complex geometric regions and extreme mesh gradations.

Estimation of Vegetation Aerodynamic Roughness of Natural Regions Using Frontal Area Density Determined from Satellite Imagery

NASA Technical Reports Server (NTRS)

Jasinski, Michael F.; Crago, Richard

1994-01-01

Parameterizations of the frontal area index and canopy area index of natural or randomly distributed plants are developed, and applied to the estimation of local aerodynamic roughness using satellite imagery. The formulas are expressed in terms of the subpixel fractional vegetation cover and one non-dimensional geometric parameter that characterizes the plant's shape. Geometrically similar plants and Poisson distributed plant centers are assumed. An appropriate averaging technique to extend satellite pixel-scale estimates to larger scales is provided. ne parameterization is applied to the estimation of aerodynamic roughness using satellite imagery for a 2.3 sq km coniferous portion of the Landes Forest near Lubbon, France, during the 1986 HAPEX-Mobilhy Experiment. The canopy area index is estimated first for each pixel in the scene based on previous estimates of fractional cover obtained using Landsat Thematic Mapper imagery. Next, the results are incorporated into Raupach's (1992, 1994) analytical formulas for momentum roughness and zero-plane displacement height. The estimates compare reasonably well to reference values determined from measurements taken during the experiment and to published literature values. The approach offers the potential for estimating regionally variable, vegetation aerodynamic roughness lengths over natural regions using satellite imagery when there exists only limited knowledge of the vegetated surface.

The variants of an LOD of a 3D building model and their influence on spatial analyses

NASA Astrophysics Data System (ADS)

Biljecki, Filip; Ledoux, Hugo; Stoter, Jantien; Vosselman, George

2016-06-01

The level of detail (LOD) of a 3D city model indicates the model's grade and usability. However, there exist multiple valid variants of each LOD. As a consequence, the LOD concept is inconclusive as an instruction for the acquisition of 3D city models. For instance, the top surface of an LOD1 block model may be modelled at the eaves of a building or at its ridge height. Such variants, which we term geometric references, are often overlooked and are usually not documented in the metadata. Furthermore, the influence of a particular geometric reference on the performance of a spatial analysis is not known. In response to this research gap, we investigate a variety of LOD1 and LOD2 geometric references that are commonly employed, and perform numerical experiments to investigate their relative difference when used as input for different spatial analyses. We consider three use cases (estimation of the area of the building envelope, building volume, and shadows cast by buildings), and compute the deviations in a Monte Carlo simulation. The experiments, carried out with procedurally generated models, indicate that two 3D models representing the same building at the same LOD, but modelled according to different geometric references, may yield substantially different results when used in a spatial analysis. The outcome of our experiments also suggests that the geometric reference may have a bigger influence than the LOD, since an LOD1 with a specific geometric reference may yield a more accurate result than when using LOD2 models.

Bidirectional reflection functions from surface bump maps

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cabral, B.; Max, N.; Springmeyer, R.

1987-04-29

The Torrance-Sparrow model for calculating bidirectional reflection functions contains a geometrical attenuation factor to account for shadowing and occlusions in a hypothetical distribution of grooves on a rough surface. Using an efficient table-based method for determining the shadows and occlusions, we calculate the geometric attenuation factor for surfaces defined by a specific table of bump heights. Diffuse and glossy specular reflection of the environment can be handled in a unified manner by using an integral of the bidirectional reflection function times the environmental illumination, over the hemisphere of solid angle above a surface. We present a method of estimating themore » integral, by expanding the bidirectional reflection coefficient in spherical harmonics, and show how the coefficients in this expansion can be determined efficiently by reorganizing our geometric attenuation calculation.« less

Geometries in Soft Matter From Geometric Frustration, Liquid Droplets to Electrostatics in Solution

NASA Astrophysics Data System (ADS)

Yao, Zhenwei

This thesis explores geometric aspects of soft matter systems. The topics covered fall into three categories: (i) geometric frustrations, including the interplay of geometry and topological defects in two dimensional systems, and the frustration of a planar sheet attached to a curved surface; (ii) geometries of liquid droplets, including the curvature driven instabilities of toroidal liquid droplets and the self-propulsion of droplets on a spatially varying surface topography; (iii) the study of the electric double layer structure around charged spherical interfaces by a geometric method. In (i), we study the crystalline order on capillary bridges with varying Gaussian curvature. Energy requires the appearance of topological defects on the surface, which are natural spots for biological activity and chemical functionalization. We further study how liquid crystalline order deforms flexible structured vesicles. In particular we find faceted tetrahedral vesicle as the ground state, which may lead to the design of supra-molecular structures with tetrahedral symmetry and new classes of nano-carriers. Furthermore, by a simple paper model we explore the geometric frustration on a planar sheet when brought to a negative curvature surface in a designed elasto-capillary system. In (ii), motivated by the idea of realizing crystalline order on a stable toroidal droplet and a beautiful experiment on toroidal droplets, we study the Rayleigh instability and the shrinking instability of thin and fat toroidal droplets, where the toroidal geometry plays an essential role. In (iii), by a geometric mapping we construct an approximate analytic spherical solution to the nonlinear Poisson-Boltzmann equation, and identify the applicability regime of the solution. The derived geometric solution enables further analytical study of spherical electrostatic systems such as colloidal suspensions.

[Determination of ventricular volumes by a non-geometric method using gamma-cineangiography].

PubMed

Faivre, R; Cardot, J C; Baud, M; Verdenet, J; Berthout, P; Bidet, A C; Bassand, J P; Maurat, J P

1985-08-01

The authors suggest a new way of determining ventricular volume by a non-geometric method using gamma-cineangiography. The results obtained by this method were compared with those obtained by a geometric methods and contrast ventriculography in 94 patients. The new non-geometric method supposes that the radioactive tracer is evenly distributed in the cardiovascular system so that blood radioactivity levels can be measured. The ventricular volume is then equal to the ratio of radioactivity in the LV zone to that of 1 ml of blood. Comparison of the radionuclide and angiographic data in the first 60 patients showed systematic values--despite a satisfactory statistical correlation (r = 0.87, y = 0.30 X + 6.3). This underestimation is due to the phenomenon of attenuation related to the depth of the heart in the thoracic cage and to autoabsorption at source, the degree of which depends on the ventricular volume. An empirical method of calculation allows correction for these factors by taking into account absorption in the tissues by relating to body surface area and autoabsorption at source by correcting for the surface of isotopic ventricular projection expressed in pixels. Using the data of this empirical method, the correction formula for radionuclide ventricular volume is obtained by a multiple linear regression: corrected radionuclide volume = K X measured radionuclide volume (Formula: see text). This formula was applied in the following 34 patients. The correlation between the uncorrected and corrected radionuclide volumes and the angiographic volumes was improved (r = 0.65 vs r = 0.94) and the values were more accurate (y = 0.18 X + 26 vs y = 0.96 X + 1.5).(ABSTRACT TRUNCATED AT 250 WORDS)

Summary on Several Key Techniques in 3D Geological Modeling

PubMed Central

2014-01-01

Several key techniques in 3D geological modeling including planar mesh generation, spatial interpolation, and surface intersection are summarized in this paper. Note that these techniques are generic and widely used in various applications but play a key role in 3D geological modeling. There are two essential procedures in 3D geological modeling: the first is the simulation of geological interfaces using geometric surfaces and the second is the building of geological objects by means of various geometric computations such as the intersection of surfaces. Discrete geometric surfaces that represent geological interfaces can be generated by creating planar meshes first and then spatially interpolating; those surfaces intersect and then form volumes that represent three-dimensional geological objects such as rock bodies. In this paper, the most commonly used algorithms of the key techniques in 3D geological modeling are summarized. PMID:24772029

Reprogrammable Assembly of Molecular Motor on Solid Surfaces via Dynamic Bonds.

PubMed

Yu, Li; Sun, Jian; Wang, Qian; Guan, Yan; Zhou, Le; Zhang, Jingxuan; Zhang, Lanying; Yang, Huai

2017-06-01

Controllable assembly of molecular motors on solid surfaces is a fundamental issue for providing them to perform physical tasks. However, it can hardly be achieved by most previous methods due to their inherent limitations. Here, a general strategy is designed for the reprogrammable assembly of molecular motors on solid surfaces based on dynamic bonds. In this method, molecular motors with disulfide bonds can be remotely, reversibly, and precisely attached to solid surfaces with disulfide bonds, regardless of their chemical composition and microstructure. More importantly, it not only allows encoding geometric information referring to a pattern of molecular motors, but also enables erasing and re-encoding of geometric information via hemolytic photocleavage and recombination of disulfide bonds. Thus, solid surfaces can be regarded as "computer hardware", where molecular motors can be reformatted and reprogramed as geometric information. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fisher metric, geometric entanglement, and spin networks

NASA Astrophysics Data System (ADS)

Chirco, Goffredo; Mele, Fabio M.; Oriti, Daniele; Vitale, Patrizia

2018-02-01

Starting from recent results on the geometric formulation of quantum mechanics, we propose a new information geometric characterization of entanglement for spin network states in the context of quantum gravity. For the simple case of a single-link fixed graph (Wilson line), we detail the construction of a Riemannian Fisher metric tensor and a symplectic structure on the graph Hilbert space, showing how these encode the whole information about separability and entanglement. In particular, the Fisher metric defines an entanglement monotone which provides a notion of distance among states in the Hilbert space. In the maximally entangled gauge-invariant case, the entanglement monotone is proportional to a power of the area of the surface dual to the link thus supporting a connection between entanglement and the (simplicial) geometric properties of spin network states. We further extend such analysis to the study of nonlocal correlations between two nonadjacent regions of a generic spin network graph characterized by the bipartite unfolding of an intertwiner state. Our analysis confirms the interpretation of spin network bonds as a result of entanglement and to regard the same spin network graph as an information graph, whose connectivity encodes, both at the local and nonlocal level, the quantum correlations among its parts. This gives a further connection between entanglement and geometry.

The study of coastal ground surfaces to predict the ways of increasing efficiency of research mobile robots

NASA Astrophysics Data System (ADS)

Makarov, Vladimir; Kurkin, Andrey; Belyalov, Vladimir; Tyugin, Dmitry; Zezyulin, Denis

2017-04-01

The increase in spatial scales of studying coastal areas can be achieved by the use of mobile robotic systems (MRS) equipped with scanning equipment, video inspection system and positioning system. The project aims at increasing the capabilities for designing effective ground MRS through the use of advanced methods of forecasting characteristics of vehicle-terrain interaction in coastal zones, where hydrosphere, lithosphere, atmosphere and biosphere interact. In the period from 14 May to 18 June 2016 there was organized the expedition to Sakhalin Island for conducting full-scale testing autonomous MRS for coastal monitoring and forecasting marine natural disasters [Kurkin A.A., Zeziulin D.V., Makarov V.S., Zaitsev A.I., Belyaev A.M., Beresnev P.O., Belyakov V.V., Pelinovsky E.N., Tyugin D.Yu. Investigations of coastal areas of the Okhotsk sea using a ground mobile robot // Ecological systems and devices. 2016. No. 8. P. 11-17]. Within the framework of the expedition specific areas of terrain in the vicinity of Cape Svobodny were investigated (with the support of SRB AMR FEB RAS). Terrain areas were studied from the standpoint of possibility of the MRS movement. As a result of measuring all the necessary data on the physical-mechanical and geometric characteristics of the coastal zones, required to calculate the force factors acting on the MRS, and, accordingly, the parameters of its motion were received. The obtained data will be used for developing new statistical models of the physical-mechanical and geometrical characteristics of the coastal ground surfaces, creating methodology for assessing the efficiency and finding ways to optimize the design of the MRS.

The Geometric Phase of Stock Trading.

PubMed

Altafini, Claudio

2016-01-01

Geometric phases describe how in a continuous-time dynamical system the displacement of a variable (called phase variable) can be related to other variables (shape variables) undergoing a cyclic motion, according to an area rule. The aim of this paper is to show that geometric phases can exist also for discrete-time systems, and even when the cycles in shape space have zero area. A context in which this principle can be applied is stock trading. A zero-area cycle in shape space represents the type of trading operations normally carried out by high-frequency traders (entering and exiting a position on a fast time-scale), while the phase variable represents the cash balance of a trader. Under the assumption that trading impacts stock prices, even zero-area cyclic trading operations can induce geometric phases, i.e., profits or losses, without affecting the stock quote.

Grain boundaries at the surface of consolidated MgO nanocrystals and acid-base functionality.

PubMed

Vingurt, Dima; Fuks, David; Landau, Miron V; Vidruk, Roxana; Herskowitz, Moti

2013-09-21

The increase of the surface basicity-acidity of MgO material by factors of 1.8-3.0 due to consolidation of its nanocrystals was demonstrated by the indicator titration. It was shown that the parallel increase of surface acidity and basicity is attributed to the formation of grain boundaries (GB) after MgO aerogel densification. A simple model predicting the increase of surface acidity-basicity of MgO that correlates with the results of direct measurements was proposed. The model is based on the study of the fine atomic structure at GB surface areas in consolidated MgO nanocrystals in the framework of Density Functional Theory. It is found that the displacements of coordinatively unsaturated surface ions near the GB are significant at the distances ~3-4 atomic layers from the geometrical contact plane between nanocrystals. The detailed analysis of atomic positions inside GB demonstrated the coordination deficiency of surface atoms at the GB areas leading to the formation of stretched bonds and to creation of low coordinated surface ions due to splitting of coordination numbers of surface atoms belonging to GB areas. Density of states for electrons shows the existence of additional states in the band gap close to the bottom of the conduction band. The adsorption energy of CO2 molecules atop oxygen atoms exposed at surface GB areas is of the same order of magnitude as that reported for oxygen atoms at crystallographic edges and corners of MgO crystals. It provides additional options for bonding of molecules at the surface of nanocrystalline MgO increasing the adsorption capacity and catalytic activity.

Mesoporous-silica films, fibers, and powders by evaporation

DOEpatents

Bruinsma, Paul J.; Baskaran, Suresh; Bontha, Jagannadha R.; Liu, Jun

2008-05-06

This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s).

Mesoporous-silica films, fibers, and powders by evaporation

DOEpatents

Bruinsma, Paul J.; Baskaran, Suresh; Bontha, Jagannadha R.; Liu, Jun

1999-01-01

This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s).

Mesoporous-silica films, fibers, and powders by evaporation

DOEpatents

Bruinsma, P.J.; Baskaran, S.; Bontha, J.R.; Liu, J.

1999-07-13

This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s). 24 figs.

Electrical and fluid transport in consolidated sphere packs

NASA Astrophysics Data System (ADS)

Zhan, Xin; Schwartz, Lawrence M.; Toksöz, M. Nafi

2015-05-01

We calculate geometrical and transport properties (electrical conductivity, permeability, specific surface area, and surface conductivity) of a family of model granular porous media from an image based representation of its microstructure. The models are based on the packing described by Finney and cover a wide range of porosities. Finite difference methods are applied to solve for electrical conductivity and hydraulic permeability. Two image processing methods are used to identify the pore-grain interface and to test correlations linking permeability to electrical conductivity. A three phase conductivity model is developed to compute surface conductivity associated with the grain-pore interface. Our results compare well against empirical models over the entire porosity range studied. We conclude by examining the influence of image resolution on our calculations.

A design study for the addition of higher order parametric discrete elements to NASTRAN

NASA Technical Reports Server (NTRS)

Stanton, E. L.

1972-01-01

The addition of discrete elements to NASTRAN poses significant interface problems with the level 15.1 assembly modules and geometry modules. Potential problems in designing new modules for higher-order parametric discrete elements are reviewed in both areas. An assembly procedure is suggested that separates grid point degrees of freedom on the basis of admissibility. New geometric input data are described that facilitate the definition of surfaces in parametric space.

A geometrically controlled rigidity transition in a model for confluent 3D tissues

NASA Astrophysics Data System (ADS)

Merkel, Matthias; Manning, M. Lisa

2018-02-01

The origin of rigidity in disordered materials is an outstanding open problem in statistical physics. Previously, a class of 2D cellular models has been shown to undergo a rigidity transition controlled by a mechanical parameter that specifies cell shapes. Here, we generalize this model to 3D and find a rigidity transition that is similarly controlled by the preferred surface area S 0: the model is solid-like below a dimensionless surface area of {s}0\\equiv {S}0/{\\bar{V}}2/3≈ 5.413 with \\bar{V} being the average cell volume, and fluid-like above this value. We demonstrate that, unlike jamming in soft spheres, residual stresses are necessary to create rigidity. These stresses occur precisely when cells are unable to obtain their desired geometry, and we conjecture that there is a well-defined minimal surface area possible for disordered cellular structures. We show that the behavior of this minimal surface induces a linear scaling of the shear modulus with the control parameter at the transition point, which is different from the scaling observed in particulate matter. The existence of such a minimal surface may be relevant for biological tissues and foams, and helps explain why cell shapes are a good structural order parameter for rigidity transitions in biological tissues.

Statistical scaling of pore-scale Lagrangian velocities in natural porous media.

PubMed

Siena, M; Guadagnini, A; Riva, M; Bijeljic, B; Pereira Nunes, J P; Blunt, M J

2014-08-01

We investigate the scaling behavior of sample statistics of pore-scale Lagrangian velocities in two different rock samples, Bentheimer sandstone and Estaillades limestone. The samples are imaged using x-ray computer tomography with micron-scale resolution. The scaling analysis relies on the study of the way qth-order sample structure functions (statistical moments of order q of absolute increments) of Lagrangian velocities depend on separation distances, or lags, traveled along the mean flow direction. In the sandstone block, sample structure functions of all orders exhibit a power-law scaling within a clearly identifiable intermediate range of lags. Sample structure functions associated with the limestone block display two diverse power-law regimes, which we infer to be related to two overlapping spatially correlated structures. In both rocks and for all orders q, we observe linear relationships between logarithmic structure functions of successive orders at all lags (a phenomenon that is typically known as extended power scaling, or extended self-similarity). The scaling behavior of Lagrangian velocities is compared with the one exhibited by porosity and specific surface area, which constitute two key pore-scale geometric observables. The statistical scaling of the local velocity field reflects the behavior of these geometric observables, with the occurrence of power-law-scaling regimes within the same range of lags for sample structure functions of Lagrangian velocity, porosity, and specific surface area.

Closed geometric models in medical applications

NASA Astrophysics Data System (ADS)

Jagannathan, Lakshmipathy; Nowinski, Wieslaw L.; Raphel, Jose K.; Nguyen, Bonnie T.

1996-04-01

Conventional surface fitting methods give twisted surfaces and complicates capping closures. This is a typical character of surfaces that lack rectangular topology. We suggest an algorithm which overcomes these limitations. The analysis of the algorithm is presented with experimental results. This algorithm assumes the mass center lying inside the object. Both capping closure and twisting are results of inadequate information on the geometric proximity of the points and surfaces which are proximal in the parametric space. Geometric proximity at the contour level is handled by mapping the points along the contour onto a hyper-spherical space. The resulting angular gradation with respect to the centroid is monotonic and hence avoids the twisting problem. Inter-contour geometric proximity is achieved by partitioning the point set based on the angle it makes with the respective centroids. Avoidance of capping complications is achieved by generating closed cross curves connecting curves which are reflections about the abscissa. The method is of immense use for the generation of the deep cerebral structures and is applied to the deep structures generated from the Schaltenbrand- Wahren brain atlas.

The influence of topographic structures on night-time surface temperatures: Evaluation of a satellite thermal image of the upper Rhine plain and the surrounding highlands. [Germany and Switzerland

NASA Technical Reports Server (NTRS)

Gossmann, H. (Principal Investigator)

1980-01-01

The author has identified the following significant results. Satellite data supplied the same information as aerial IR registrations with corresponding averaging for all studies requiring a survey of the thermal pattern within an area measuring 10 km x 10 km ore more, provided that sufficiently precise control points could be established for the purpose of geometric rectification in the surroundings of the area observed. Satellite thermal data are more comprehensive than aircraft data for studies on a regional, rather than a local scale, since airborne images often obscure the basic correlation in thermal patterns because of a variety of irrelevant topographical detail. The satellite data demonstrate the dependence of surface temperature on relief more clearly than comparable airborne imagery.

Backscattering from a Gaussian distributed, perfectly conducting, rough surface

NASA Technical Reports Server (NTRS)

Brown, G. S.

1977-01-01

The problem of scattering by random surfaces possessing many scales of roughness is analyzed. The approach is applicable to bistatic scattering from dielectric surfaces, however, this specific analysis is restricted to backscattering from a perfectly conducting surface in order to more clearly illustrate the method. The surface is assumed to be Gaussian distributed so that the surface height can be split into large and small scale components, relative to the electromagnetic wavelength. A first order perturbation approach is employed wherein the scattering solution for the large scale structure is perturbed by the small scale diffraction effects. The scattering from the large scale structure is treated via geometrical optics techniques. The effect of the large scale surface structure is shown to be equivalent to a convolution in k-space of the height spectrum with the following: the shadowing function, a polarization and surface slope dependent function, and a Gaussian factor resulting from the unperturbed geometrical optics solution. This solution provides a continuous transition between the near normal incidence geometrical optics and wide angle Bragg scattering results.

Volume and surface area size distribution, water mass and model fitting of GCE/CASE/WATOX marine aerosols

NASA Astrophysics Data System (ADS)

Kim, Y.; Sievering, H.; Boatman, J.

1990-06-01

As a part of the Global Change Expedition/Coordinated Air-Sea Experiment/Western Atlantic Ocean Experiment (GCE/CASE/WATOX), size distributions of marine aerosols were measured at two altitudes of about 2750 and 150 m above sea level (asl) over the size range 0.1 ˜ 32 μm. Lognormal fitting was applied to the corrected aerosol size spectra to determine the volume and surface area size distributions of the CASE-WATOX marine aerosols. Each aerosol size distribution was fitted with three lognormal distributions representing fine-, large-, and giant-particle modes. Water volume fraction and dry particle size of each aerosol size distribution were also calculated using empirical formulas for particle size as a function of relative humidity and particle type. Because of the increased influence from anthropogenic sources in the continental United States, higher aerosol volume concentrations were observed in the fine-particle mode near-shore off the east coast; 2.11 and 3.63 μm3 cm-3 for free troposphere (FT) and marine boundary layer (MBL), compared with the open-sea Bermuda area values; 0.13 and 0.74 μm3 cm-3 for FT and MBL. The large-particle mode exhibits the least variations in volume distributions between the east coast and open-sea Bermuda area, having a volume geometric median diameter (VGMD) between 1.4 and 1.6 μm and a geometric standard deviation between 1.57 and 1.68. For the giant-particle mode, larger VGMD and volume concentrations were observed for marine aerosols nearshore off the east coast than in the open-sea Bermuda area because of higher relative humidity and higher surface wind speed conditions. Wet VGMD and aerosol water volume concentrations at 15 m asl ship level were determined by extrapolating from those obtained by analysis of the CASE-WATOX aircraft aerosol data. Abundance of aerosol water in the MBL serves as an important pathway for heterogeneous conversion of SO2 in sea salt aerosol particles.

Enhancement of surface definition and gridding in the EAGLE code

NASA Technical Reports Server (NTRS)

Thompson, Joe F.

1991-01-01

Algorithms for smoothing of curves and surfaces for the EAGLE grid generation program are presented. The method uses an existing automated technique which detects undesirable geometric characteristics by using a local fairness criterion. The geometry entity is then smoothed by repeated removal and insertion of spline knots in the vicinity of the geometric irregularity. The smoothing algorithm is formulated for use with curves in Beta spline form and tensor product B-spline surfaces.

Minimal Prospects for Radio Detection of Extensive Air Showers in the Atmosphere of Jupiter

NASA Astrophysics Data System (ADS)

Bray, J. D.; Nelles, A.

2016-07-01

One possible approach for detecting ultra-high-energy cosmic rays and neutrinos is to search for radio emission from extensive air showers created when they interact in the atmosphere of Jupiter, effectively utilizing Jupiter as a particle detector. We investigate the potential of this approach. For searches with current or planned radio telescopes we find that the effective area for detection of cosmic rays is substantial (˜3 × 107 km2), but the acceptance angle is so small that the typical geometric aperture (˜103 km2 sr) is less than that of existing terrestrial detectors, and cosmic rays also cannot be detected below an extremely high threshold energy (˜1023 eV). The geometric aperture for neutrinos is slightly larger, and greater sensitivity can be achieved with a radio detector on a Jupiter-orbiting satellite, but in neither case is this sufficient to constitute a practical detection technique. Exploitation of the large surface area of Jupiter for detecting ultra-high-energy particles remains a long-term prospect that will require a different technique, such as orbital fluorescence detection.

Damage Detection for Historical Architectures Based on Tls Intensity Data

NASA Astrophysics Data System (ADS)

Li, Q.; Cheng, X.

2018-04-01

TLS (Terrestrial Laser Scanner) has long been preferred in the cultural heritage field for 3D documentation of historical sites thanks to its ability to acquire the geometric information without any physical contact. Besides the geometric information, most TLS systems also record the intensity information, which is considered as an important measurement of the spectral property of the scanned surface. Recent studies have shown the potential of using intensity for damage detection. However, the original intensity is affected by scanning geometry such as range and incidence angle and other factors, thus making the results less accurate. Therefore, in this paper, we present a method to detect certain damage areas using the corrected intensity data. Firstly, two data-driven models have been developed to correct the range and incidence angle effect. Then the corrected intensity is used to generate 2D intensity images for classification. After the damage areas being detected, they are re-projected to the 3D point cloud for better visual representation and further investigation. The experiment results indicate the feasibility and validity of the corrected intensity for damage detection.

Comparison of the arithmetic and geometric means in estimating crown diameter and crown cross-sectional area

Treesearch

KaDonna Randolph

2010-01-01

The use of the geometric and arithmetic means for estimating tree crown diameter and crown cross-sectional area were examined for trees with crown width measurements taken at the widest point of the crown and perpendicular to the widest point of the crown. The average difference between the geometric and arithmetic mean crown diameters was less than 0.2 ft in absolute...

The Geometric Phase of Stock Trading

PubMed Central

2016-01-01

Geometric phases describe how in a continuous-time dynamical system the displacement of a variable (called phase variable) can be related to other variables (shape variables) undergoing a cyclic motion, according to an area rule. The aim of this paper is to show that geometric phases can exist also for discrete-time systems, and even when the cycles in shape space have zero area. A context in which this principle can be applied is stock trading. A zero-area cycle in shape space represents the type of trading operations normally carried out by high-frequency traders (entering and exiting a position on a fast time-scale), while the phase variable represents the cash balance of a trader. Under the assumption that trading impacts stock prices, even zero-area cyclic trading operations can induce geometric phases, i.e., profits or losses, without affecting the stock quote. PMID:27556642

Anisotropy modulations of femtosecond laser pulse induced periodic surface structures on silicon by adjusting double pulse delay.

PubMed

Han, Weina; Jiang, Lan; Li, Xiaowei; Wang, Qingsong; Li, Hao; Lu, YongFeng

2014-06-30

We demonstrate that the polarization-dependent anisotropy of the laser-induced periodic surface structure (LIPSS) on silicon can be adjusted by designing a femtosecond laser pulse train (800 nm, 50 fs, 1 kHz). By varying the pulse delay from 100 to 1600 fs within a double pulse train to reduce the deposited pulse energy, which weakens the directional surface plasmon polarition (SPP)-laser energy coupling based on the initial formed ripple structure, the polarization-dependent geometrical morphology of the LIPSS evolves from a nearly isotropic circular shape to a somewhat elongated elliptical shape. Meanwhile, the controllable anisotropy of the two-dimensional scanned-line widths with different directions is achieved based on a certain pulse delay combined with the scanning speed. This can effectively realize better control over large-area uniform LIPSS formation. As an example, we further show that the large-area LIPSS can be formed with different scanning times under different pulse delays.

Investigation of Aerosol Surface Area Estimation from Number and Mass Concentration Measurements: Particle Density Effect

PubMed Central

Ku, Bon Ki; Evans, Douglas E.

2015-01-01

For nanoparticles with nonspherical morphologies, e.g., open agglomerates or fibrous particles, it is expected that the actual density of agglomerates may be significantly different from the bulk material density. It is further expected that using the material density may upset the relationship between surface area and mass when a method for estimating aerosol surface area from number and mass concentrations (referred to as “Maynard’s estimation method”) is used. Therefore, it is necessary to quantitatively investigate how much the Maynard’s estimation method depends on particle morphology and density. In this study, aerosol surface area estimated from number and mass concentration measurements was evaluated and compared with values from two reference methods: a method proposed by Lall and Friedlander for agglomerates and a mobility based method for compact nonspherical particles using well-defined polydisperse aerosols with known particle densities. Polydisperse silver aerosol particles were generated by an aerosol generation facility. Generated aerosols had a range of morphologies, count median diameters (CMD) between 25 and 50 nm, and geometric standard deviations (GSD) between 1.5 and 1.8. The surface area estimates from number and mass concentration measurements correlated well with the two reference values when gravimetric mass was used. The aerosol surface area estimates from the Maynard’s estimation method were comparable to the reference method for all particle morphologies within the surface area ratios of 3.31 and 0.19 for assumed GSDs 1.5 and 1.8, respectively, when the bulk material density of silver was used. The difference between the Maynard’s estimation method and surface area measured by the reference method for fractal-like agglomerates decreased from 79% to 23% when the measured effective particle density was used, while the difference for nearly spherical particles decreased from 30% to 24%. The results indicate that the use of particle density of agglomerates improves the accuracy of the Maynard’s estimation method and that an effective density should be taken into account, when known, when estimating aerosol surface area of nonspherical aerosol such as open agglomerates and fibrous particles. PMID:26526560

Investigation of Aerosol Surface Area Estimation from Number and Mass Concentration Measurements: Particle Density Effect.

PubMed

Ku, Bon Ki; Evans, Douglas E

2012-04-01

For nanoparticles with nonspherical morphologies, e.g., open agglomerates or fibrous particles, it is expected that the actual density of agglomerates may be significantly different from the bulk material density. It is further expected that using the material density may upset the relationship between surface area and mass when a method for estimating aerosol surface area from number and mass concentrations (referred to as "Maynard's estimation method") is used. Therefore, it is necessary to quantitatively investigate how much the Maynard's estimation method depends on particle morphology and density. In this study, aerosol surface area estimated from number and mass concentration measurements was evaluated and compared with values from two reference methods: a method proposed by Lall and Friedlander for agglomerates and a mobility based method for compact nonspherical particles using well-defined polydisperse aerosols with known particle densities. Polydisperse silver aerosol particles were generated by an aerosol generation facility. Generated aerosols had a range of morphologies, count median diameters (CMD) between 25 and 50 nm, and geometric standard deviations (GSD) between 1.5 and 1.8. The surface area estimates from number and mass concentration measurements correlated well with the two reference values when gravimetric mass was used. The aerosol surface area estimates from the Maynard's estimation method were comparable to the reference method for all particle morphologies within the surface area ratios of 3.31 and 0.19 for assumed GSDs 1.5 and 1.8, respectively, when the bulk material density of silver was used. The difference between the Maynard's estimation method and surface area measured by the reference method for fractal-like agglomerates decreased from 79% to 23% when the measured effective particle density was used, while the difference for nearly spherical particles decreased from 30% to 24%. The results indicate that the use of particle density of agglomerates improves the accuracy of the Maynard's estimation method and that an effective density should be taken into account, when known, when estimating aerosol surface area of nonspherical aerosol such as open agglomerates and fibrous particles.

Sampling theory and automated simulations for vertical sections, applied to human brain.

PubMed

Cruz-Orive, L M; Gelšvartas, J; Roberts, N

2014-02-01

In recent years, there have been substantial developments in both magnetic resonance imaging techniques and automatic image analysis software. The purpose of this paper is to develop stereological image sampling theory (i.e. unbiased sampling rules) that can be used by image analysts for estimating geometric quantities such as surface area and volume, and to illustrate its implementation. The methods will ideally be applied automatically on segmented, properly sampled 2D images - although convenient manual application is always an option - and they are of wide applicability in many disciplines. In particular, the vertical sections design to estimate surface area is described in detail and applied to estimate the area of the pial surface and of the boundary between cortex and underlying white matter (i.e. subcortical surface area). For completeness, cortical volume and mean cortical thickness are also estimated. The aforementioned surfaces were triangulated in 3D with the aid of FreeSurfer software, which provided accurate surface area measures that served as gold standards. Furthermore, a software was developed to produce digitized trace curves of the triangulated target surfaces automatically from virtual sections. From such traces, a new method (called the 'lambda method') is presented to estimate surface area automatically. In addition, with the new software, intersections could be counted automatically between the relevant surface traces and a cycloid test grid for the classical design. This capability, together with the aforementioned gold standard, enabled us to thoroughly check the performance and the variability of the different estimators by Monte Carlo simulations for studying the human brain. In particular, new methods are offered to split the total error variance into the orientations, sectioning and cycloid components. The latter prediction was hitherto unavailable--one is proposed here and checked by way of simulations on a given set of digitized vertical sections with automatically superimposed cycloid grids of three different sizes. Concrete and detailed recommendations are given to implement the methods. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

The Backscattering Phase Function for a Sphere with a Two-Scale Relief of Rough Surface

NASA Astrophysics Data System (ADS)

Klass, E. V.

2017-12-01

The backscattering of light from spherical surfaces characterized by one and two-scale roughness reliefs has been investigated. The analysis is performed using the three-dimensional Monte-Carlo program POKS-RG (geometrical-optics approximation), which makes it possible to take into account the roughness of objects under study by introducing local geometries of different levels. The geometric module of the program is aimed at describing objects by equations of second-order surfaces. One-scale roughness is set as an ensemble of geometric figures (convex or concave halves of ellipsoids or cones). The two-scale roughness is modeled by convex halves of ellipsoids, with surface containing ellipsoidal pores. It is shown that a spherical surface with one-scale convex inhomogeneities has a flatter backscattering phase function than a surface with concave inhomogeneities (pores). For a sphere with two-scale roughness, the dependence of the backscattering intensity is found to be determined mostly by the lower-level inhomogeneities. The influence of roughness on the dependence of the backscattering from different spatial regions of spherical surface is analyzed.

A system to geometrically rectify and map airborne scanner imagery and to estimate ground area. [by computer

NASA Technical Reports Server (NTRS)

Spencer, M. M.; Wolf, J. M.; Schall, M. A.

1974-01-01

A system of computer programs were developed which performs geometric rectification and line-by-line mapping of airborne multispectral scanner data to ground coordinates and estimates ground area. The system requires aircraft attitude and positional information furnished by ancillary aircraft equipment, as well as ground control points. The geometric correction and mapping procedure locates the scan lines, or the pixels on each line, in terms of map grid coordinates. The area estimation procedure gives ground area for each pixel or for a predesignated parcel specified in map grid coordinates. The results of exercising the system with simulated data showed the uncorrected video and corrected imagery and produced area estimates accurate to better than 99.7%.

SPIDERMAN: Fast code to simulate secondary transits and phase curves

NASA Astrophysics Data System (ADS)

Louden, Tom; Kreidberg, Laura

2017-11-01

SPIDERMAN calculates exoplanet phase curves and secondary eclipses with arbitrary surface brightness distributions in two dimensions. The code uses a geometrical algorithm to solve exactly the area of sections of the disc of the planet that are occulted by the star. Approximately 1000 models can be generated per second in typical use, which makes making Markov Chain Monte Carlo analyses practicable. The code is modular and allows comparison of the effect of multiple different brightness distributions for a dataset.

Microwave-triggered laser switch

DOEpatents

Piltch, M.S.

1982-05-19

A high-repetition rate switch is described for delivering short duration, high-powered electrical pulses from a pulsed-charged dc power supply. The present invention utilizes a microwave-generating device such as a magnetron that is capable of producing high-power pulses at high-pulse repetition rates and fast-pulse risetimes for long periods with high reliability. The rail-gap electrodes provide a large surface area that reduces induction effects and minimizes electrode erosion. Additionally, breakdown is initiated in a continuous geometric fashion that also increases operating lifetime of the device.

Microwave-triggered laser switch

DOEpatents

Piltch, Martin S.

1984-01-01

A high-repetition rate switch for delivering short duration, high-power electrical pulses from a pulsed-charged dc power supply. The present invention utilizes a microwave-generating device such as a magnetron that is capable of producing high-power pulses at high-pulse repetition rates and fast-pulse risetimes for long periods with high reliability. The rail-gap electrodes provide a large surface area that reduces induction effects and minimizes electrode erosion. Additionally, breakdown is initiated in a continuous geometric fashion that also increases operating lifetime of the device.

Curved Displacement Transfer Functions for Geometric Nonlinear Large Deformation Structure Shape Predictions

NASA Technical Reports Server (NTRS)

Ko, William L.; Fleischer, Van Tran; Lung, Shun-Fat

2017-01-01

For shape predictions of structures under large geometrically nonlinear deformations, Curved Displacement Transfer Functions were formulated based on a curved displacement, traced by a material point from the undeformed position to deformed position. The embedded beam (depth-wise cross section of a structure along a surface strain-sensing line) was discretized into multiple small domains, with domain junctures matching the strain-sensing stations. Thus, the surface strain distribution could be described with a piecewise linear or a piecewise nonlinear function. The discretization approach enabled piecewise integrations of the embedded-beam curvature equations to yield the Curved Displacement Transfer Functions, expressed in terms of embedded beam geometrical parameters and surface strains. By entering the surface strain data into the Displacement Transfer Functions, deflections along each embedded beam can be calculated at multiple points for mapping the overall structural deformed shapes. Finite-element linear and nonlinear analyses of a tapered cantilever tubular beam were performed to generate linear and nonlinear surface strains and the associated deflections to be used for validation. The shape prediction accuracies were then determined by comparing the theoretical deflections with the finiteelement- generated deflections. The results show that the newly developed Curved Displacement Transfer Functions are very accurate for shape predictions of structures under large geometrically nonlinear deformations.

Quantitative detection of cartilage surfaces and ligament geometry of the wrist using an imaging cryomicrotome system.

PubMed

Dvinskikh, N A; Blankevoort, L; Foumani, M; Spaan, J A E; Streekstra, G J

2010-03-22

Biomechanical models may aid in improving diagnosis and treatment of wrist joint disorders. As input, geometrical information is required for model development. Previous studies acquired some elements of the average wrist joint geometry. However, there is a close geometric functional match between articulating surfaces and ligament geometry. Therefore, biomechanical models need to be fed with the geometric data of individual joints. This study is aimed at acquiring geometric data of cartilage surfaces and ligaments from individual wrist joints by using a cryomicrotome imaging system and the evaluation of inter- and intra-observer variability of the data. The 3D geometry of 30 cartilage surfaces and 15 ligaments in three cadaver wrists was manually detected and quantitatively reconstructed. The inter- and intra-observer variability of the cartilage surface detection was 0.14 and 0.19 mm, respectively. For the position of the radius attachment of the dorsal radiocarpal ligament (DRC), the observer variations were 0.12 and 0.65 mm, for intra-/inter-observer, respectively. For the DRC attachment on the triquetrum, the observer variations were 0.22 and 1.19 mm. Anatomic reconstruction from 3D cryomicrotome images offer a method to obtain unique geometry data of the entire wrist joint for modeling purposes. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Electric field distribution and current emission in a miniaturized geometrical diode

NASA Astrophysics Data System (ADS)

Lin, Jinpu; Wong, Patrick Y.; Yang, Penglu; Lau, Y. Y.; Tang, W.; Zhang, Peng

2017-06-01

We study the electric field distribution and current emission in a miniaturized geometrical diode. Using Schwarz-Christoffel transformation, we calculate exactly the electric field inside a finite vacuum cathode-anode (A-K) gap with a single trapezoid protrusion on one of the electrode surfaces. It is found that there is a strong field enhancement on both electrodes near the protrusion, when the ratio of the A-K gap distance to the protrusion height d /h <2. The calculations are spot checked against COMSOL simulations. We calculate the effective field enhancement factor for the field emission current, by integrating the local Fowler-Nordheim current density along the electrode surfaces. We systematically examine the electric field enhancement and the current rectification of the miniaturized geometrical diode for various geometric dimensions and applied electric fields.

On biofouling of microplastic particles of different shapes - some mathematics

NASA Astrophysics Data System (ADS)

Bagaeva, Margarita; Chubarenko, Irina

2016-04-01

Transport of microplastic particles in marine environment is difficult to quantify because their physical properties may vary with time. We made an attempt to analyse the behaviour of slightly buoyant particles (e.g., polyethylene, polypropylene), most critical process for which is their fouling: it leads to an increase in the mean particle density and its sinking. Fouling covers the surface of a relatively light particle by a denser growing film; thus, the rate of increase in the total mass is directly proportional to the surface area, and the faster the fouling process is - the sooner the mean particle density reaches the water density; the particle begins sinking, leaves the surface layer with stronger currents and can no longer be transported too far. A simplified model of biofouling in marine environment of a slightly buoyant microplastics (ρp < ρw) is applied to particles of different shapes - spheres, films and fibres. It is supposed that the thickness of biofouling cover (of density ρb > ρw) increases with time at constant rate, and thus it can be considered as time. Geometrical considerations link surface area of particles of different shapes with time rate of increase in its mass due to fouling up to the water density. Geometrical calculations demonstrate that, for the same mass of plastic material, many small particles have larger surface area than one single large particle, and this way - macroplastics will stay longer at the water surface than microplastics. For spherical particles, the time of fouling up to the water density is directly proportional to the radius of a sphere: τsink ˜ R0/ 3n, where n = R0/ R, i.e., if the particle of radius R0reaches the water density in time τsink, the particle of radius R0/3 requires only τsink/9. Spherical shape has (for the given mass m0) the minimum surface area among all other possible shapes in 3-d space. The calculations performed for the same mass m0 have shown that the ratio of surface areas of a sphere (diameter 5 mm), a film (thickness of 15-30 microns) and a fibre (diameter of 30-100 microns) is about 1 / (50- 100) / (30-110) and thus, fibres appear to have the largest surface area for the given mass, immediately followed by films. Correspondingly, time of fouling up to sinking is of the same order of magnitude for films and fibres, and almost two orders of magnitude larger for spherical particles (of the same mass m0). More generally speaking, time of fouling is linearly dependent on the characteristic length scale of a particle (radius of sphere, thickness of the film, or radius of a fibre): the smaller the scale of the particle is - the faster it is fouled up to the water density. The conclusions are important for proper physical setting of the problem of microplastics transport in marine environment and for developing of physically-based parameterisations of microplastics particles properties in numerical models. The investigations are supported by Russian Science Foundation, project number 15-17-10020.

Children's use of geometry for reorientation.

PubMed

Lee, Sang Ah; Spelke, Elizabeth S

2008-09-01

Research on navigation has shown that humans and laboratory animals recover their sense of orientation primarily by detecting geometric properties of large-scale surface layouts (e.g. room shape), but the reasons for the primacy of layout geometry have not been clarified. In four experiments, we tested whether 4-year-old children reorient by the geometry of extended wall-like surfaces because such surfaces are large and perceived as stable, because they serve as barriers to vision or to locomotion, or because they form a single, connected geometric figure. Disoriented children successfully reoriented by the shape of an arena formed by surfaces that were short enough to see and step over. In contrast, children failed to reorient by the shape of an arena defined by large and stable columns or by connected lines on the floor. We conclude that preschool children's reorientation is not guided by the functional relevance of the immediate environmental properties, but rather by a specific sensitivity to the geometric properties of the extended three-dimensional surface layout.

Tissue resistivity estimation in the presence of positional and geometrical uncertainties.

PubMed

Baysal, U; Eyüboğlu, B M

2000-08-01

Geometrical uncertainties (organ boundary variation and electrode position uncertainties) are the biggest sources of error in estimating electrical resistivity of tissues from body surface measurements. In this study, in order to decrease estimation errors, the statistically constrained minimum mean squared error estimation algorithm (MiMSEE) is constrained with a priori knowledge of the geometrical uncertainties in addition to the constraints based on geometry, resistivity range, linearization and instrumentation errors. The MiMSEE calculates an optimum inverse matrix, which maps the surface measurements to the unknown resistivity distribution. The required data are obtained from four-electrode impedance measurements, similar to injected-current electrical impedance tomography (EIT). In this study, the surface measurements are simulated by using a numerical thorax model. The data are perturbed with additive instrumentation noise. Simulated surface measurements are then used to estimate the tissue resistivities by using the proposed algorithm. The results are compared with the results of conventional least squares error estimator (LSEE). Depending on the region, the MiMSEE yields an estimation error between 0.42% and 31.3% compared with 7.12% to 2010% for the LSEE. It is shown that the MiMSEE is quite robust even in the case of geometrical uncertainties.

Photo-responsive surface topology in chiral nematic media

NASA Astrophysics Data System (ADS)

Liu, Danqing; Bastiaansen, Cees W. M.; Toonder, Jaap. M. J.; Broer, Dirk J.

2012-03-01

We report on the design and fabrication of 'smart surfaces' that exhibit dynamic changes in their surface topology in response to exposure to light. The principle is based on anisotropic geometric changes of a liquid crystal network upon a change of the molecular order parameter. The photomechanical property of the coating is induced by incorporating an azobenzene moiety into the liquid crystal network. The responsive surface topology consists of regions with two different types of molecular order: planar chiral-nematic areas and homeotropic. Under flood exposure with 365 nm light the surfaces deform from flat to one with a surface relief. The height of the relief structures is of the order of 1 um corresponding to strain difference of around 20%. Furthermore, we demonstrate surface reliefs can form either convex or concave structures upon exposure to UV light corresponding to the decrease or increase molecular order parameter, respectively, related to the isomeric state of the azobenzene crosslinker. The reversible deformation to the initial flat state occurs rapidly after removing the light source.

The effect of texture on the shaft surface on the sealing performance of radial lip seals

NASA Astrophysics Data System (ADS)

Guo, Fei; Jia, XiaoHong; Gao, Zhi; Wang, YuMing

2014-07-01

On the basis of elastohydrodynamic model, the present study numerically analyzes the effect of various microdimple texture shapes, namely, circular, square, oriented isosceles triangular, on the pumping rate and the friction torque of radial lip seals, and determines the microdimple texture shape that can produce positive pumping rate. The area ratio, depth and shape dimension of a single texture are the most important geometric parameters which influence the tribological performance. According to the selected texture shape, parameter analysis is conducted to determine the optimal combination for the above three parameters. Simultaneously, the simulated performances of radial lip seal with texture on the shaft surface are compared with those of the conventional lip seal without any texture on the shaft surface.

DCS Color near Mare Cimmerium

NASA Technical Reports Server (NTRS)

2004-01-01

[figure removed for brevity, see original site]

Released July 28, 2004 This image shows two representations of the same infra-red image covering an area near Mare Cimmerium. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations.

This area contains a mixture of basaltic materials (magenta/purple) and dust (green/blue). Faint blue areas may be due to some thin water ice clouds. The different compositional units are sometimes correlated with crater floors and other surface features, but they are often not tied to valleys, lava flows, etc... indicating that the surface materials could be mobile (dust and sand).

Image information: IR instrument. Latitude -23.7, Longitude 139.3 East (220.7 West). 100 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

In Vitro Validation of Real-Time Three-Dimensional Color Doppler Echocardiography for Direct Measurement of Proximal Isovelocity Surface Area in Mitral Regurgitation

PubMed Central

Little, Stephen H.; Igo, Stephen R.; Pirat, Bahar; McCulloch, Marti; Hartley, Craig J.; Nosé, Yukihiko; Zoghbi, William A.

2012-01-01

The 2-dimensional (2D) color Doppler (2D-CD) proximal isovelocity surface area (PISA) method assumes a hemispheric flow convergence zone to estimate transvalvular flow. Recently developed 3-dimensional (3D)-CD can directly visualize PISA shape and surface area without geometric assumptions. To validate a novel method to directly measure PISA using real-time 3D-CD echocardiography, a circulatory loop with an ultrasound imaging chamber was created to model mitral regurgitation (MR). Thirty-two different regurgitant flow conditions were tested using symmetric and asymmetric flow orifices. Three-dimensional–PISA was reconstructed from a hand-held real-time 3D-CD data set. Regurgitant volume was derived using both 2D-CD and 3D-CD PISA methods, and each was compared against a flowmeter standard. The circulatory loop achieved regurgitant volume within the clinical range of MR (11 to 84 ml). Three-dimensional–PISA geometry reflected the 2D geometry of the regurgitant orifice. Correlation between the 2D-PISA method regurgitant volume and actual regurgitant volume was significant (r2 = 0.47, p <0.001). Mean 2D-PISA regurgitant volume underestimate was 19.1 ± 25 ml (2 SDs). For the 3D-PISA method, correlation with actual regurgitant volume was significant (r2 = 0.92, p <0.001), with a mean regurgitant volume underestimate of 2.7 ± 10 ml (2 SDs). The 3D-PISA method showed less regurgitant volume underestimation for all orifice shapes and regurgitant volumes tested. In conclusion, in an in vitro model of MR, 3D-CD was used to directly measure PISA without geometric assumption. Compared with conventional 2D-PISA, regurgitant volume was more accurate when derived from 3D-PISA across symmetric and asymmetric orifices within a broad range of hemodynamic flow conditions. PMID:17493476

Highly compressible 3D periodic graphene aerogel microlattices

PubMed Central

Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A.

2015-01-01

Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young's moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications. PMID:25902277

Pore-scale spectral induced polarization (SIP) signaturesassociated with FeS biomineral transformations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slater, Lee; Ntarlagiannis, Dimitrios; Personna, Yves R.

2007-10-01

The authors measured Spectral Induced Polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate reducing bacteria (D. vulgaris) under anaerboci conditions, and (2) subsequent biomineral dissolution upon return to an aerobic state. The low-frequency (0.1-10 Hz peak) relaxations produced during biomineralization can be modeled with a Cole-Cole formulation, from which the evolution of the polarization magnitude and relaxation length scale can be estimated. They find that the modeled time constant is consistent with the polarizable elements being biomineral encrused pores. Evolution of the model parameters is consistent with FeS surface area increases and pore-size reduction duringmore » biomineral growth, and subsequent biomineral dissolution (FeS surface area decreases and pore expansion) upon return to the aerobic state. They conclude that SIP signatures are diagnostic of pore-scale geometrical changes associated with FeS biomineralization by sulfate reducing bacteria.« less

Verification of Geometric Model-Based Plant Phenotyping Methods for Studies of Xerophytic Plants.

PubMed

Drapikowski, Paweł; Kazimierczak-Grygiel, Ewa; Korecki, Dominik; Wiland-Szymańska, Justyna

2016-06-27

This paper presents the results of verification of certain non-contact measurement methods of plant scanning to estimate morphological parameters such as length, width, area, volume of leaves and/or stems on the basis of computer models. The best results in reproducing the shape of scanned objects up to 50 cm in height were obtained with the structured-light DAVID Laserscanner. The optimal triangle mesh resolution for scanned surfaces was determined with the measurement error taken into account. The research suggests that measuring morphological parameters from computer models can supplement or even replace phenotyping with classic methods. Calculating precise values of area and volume makes determination of the S/V (surface/volume) ratio for cacti and other succulents possible, whereas for classic methods the result is an approximation only. In addition, the possibility of scanning and measuring plant species which differ in morphology was investigated.

Verification of Geometric Model-Based Plant Phenotyping Methods for Studies of Xerophytic Plants

PubMed Central

Drapikowski, Paweł; Kazimierczak-Grygiel, Ewa; Korecki, Dominik; Wiland-Szymańska, Justyna

2016-01-01

This paper presents the results of verification of certain non-contact measurement methods of plant scanning to estimate morphological parameters such as length, width, area, volume of leaves and/or stems on the basis of computer models. The best results in reproducing the shape of scanned objects up to 50 cm in height were obtained with the structured-light DAVID Laserscanner. The optimal triangle mesh resolution for scanned surfaces was determined with the measurement error taken into account. The research suggests that measuring morphological parameters from computer models can supplement or even replace phenotyping with classic methods. Calculating precise values of area and volume makes determination of the S/V (surface/volume) ratio for cacti and other succulents possible, whereas for classic methods the result is an approximation only. In addition, the possibility of scanning and measuring plant species which differ in morphology was investigated. PMID:27355949

BOREAS Level-2 MAS Surface Reflectance and Temperature Images in BSQ Format

NASA Technical Reports Server (NTRS)

Hall, Forrest G. (Editor); Newcomer, Jeffrey (Editor); Lobitz, Brad; Spanner, Michael; Strub, Richard; Lobitz, Brad

2000-01-01

The BOReal Ecosystem-Atmosphere Study (BOREAS) Staff Science Aircraft Data Acquisition Program focused on providing the research teams with the remotely sensed aircraft data products they needed to compare and spatially extend point results. The MODIS Airborne Simulator (MAS) images, along with other remotely sensed data, were collected to provide spatially extensive information over the primary study areas. This information includes biophysical parameter maps such as surface reflectance and temperature. Collection of the MAS images occurred over the study areas during the 1994 field campaigns. The level-2 MAS data cover the dates of 21-Jul-1994, 24-Jul-1994, 04-Aug-1994, and 08-Aug-1994. The data are not geographically/geometrically corrected; however, files of relative X and Y coordinates for each image pixel were derived by using the C130 navigation data in a MAS scan model. The data are provided in binary image format files.

Payload/orbiter contamination control requirement study, volume 2, exhibit A

NASA Technical Reports Server (NTRS)

Bareiss, L. E.; Hooper, V. W.; Rantanen, R. O.; Ress, E. B.

1974-01-01

The computer printout data generated during the Payload/Orbiter Contamination Control Requirement Study are presented. The computer listings of the input surface data matrices, the viewfactor data matrices, and the geometric relationship data matrices for the three orbiter/spacelab configurations analyzed in this study are given. These configurations have been broken up into the geometrical surfaces and nodes necessary to define the principal critical surfaces whether they are contaminant sources, experimental surfaces, or operational surfaces. A numbering scheme was established based upon nodal numbers that relates the various spacelab surfaces to a specific surface material or function. This numbering system was developed for the spacelab configurations such that future extension to a surface mapping capability could be developed as required.

A geometrical optics polarimetric bidirectional reflectance distribution function for dielectric and metallic surfaces.

PubMed

Hyde, M W; Schmidt, J D; Havrilla, M J

2009-11-23

A polarimetric bidirectional reflectance distribution function (pBRDF), based on geometrical optics, is presented. The pBRDF incorporates a visibility (shadowing/masking) function and a Lambertian (diffuse) component which distinguishes it from other geometrical optics pBRDFs in literature. It is shown that these additions keep the pBRDF bounded (and thus a more realistic physical model) as the angle of incidence or observation approaches grazing and better able to model the behavior of light scattered from rough, reflective surfaces. In this paper, the theoretical development of the pBRDF is shown and discussed. Simulation results of a rough, perfect reflecting surface obtained using an exact, electromagnetic solution and experimental Mueller matrix results of two, rough metallic samples are presented to validate the pBRDF.

Enhancements to NURBS-Based FEA Airfoil Modeler: SABER

NASA Technical Reports Server (NTRS)

Saleeb, A. F.; Trowbridge, D. A.

2003-01-01

NURBS (Non-Uniform Rational B-Splines) have become a common way for CAD programs to fit a smooth surface to discrete geometric data. This concept has been extended to allow for the fitting of analysis data in a similar manner and "attaching" the analysis data to the geometric definition of the structure. The "attaching" of analysis data to the geometric definition allows for a more seamless sharing of data between analysis disciplines. NURBS have become a useful tool in the modeling of airfoils. The use of NURBS has allowed for the development of software that easily and consistently generates plate finite element models of the midcamber surface of a given airfoil. The resulting displacements can then be applied to the original airfoil surface and the deformed shape calculated.

Geometrical gradients in the distribution of temperature and absorbed ultraviolet radiation in ocular tissues.

PubMed

Sliney, David H

2002-01-01

The geographical variations in the incidence of age-related ocular changes such as presbyopia and cataracts and diseases such as pterygium and droplet keratopathies have led to theories pointing to sunlight, ultraviolet radiation (UVR) exposure and ambient temperature as potential etiological factors. Some epidemiological evidence also points to an association of age-related macular degeneration to sunlight exposure. The actual distribution of sunlight exposure and the determination of temperature variations of different tissues within the anterior segment of the eye are difficult to assess. Of greatest importance are the geometrical factors that influence selective UVR exposures to different segments of the lens, cornea and retina. Studies show that the temperature of the lens and cornea varies by several degrees depending upon climate, and that the incidence of nuclear cataract incidence is greater in areas of higher ambient temperature (i.e., in the tropics). Likewise, sunlight exposure to local areas of the cornea, lens and retina varies greatly in different environments. However, epidemiological studies of the influence of environmental UVR in the development of cataract, pterygium, droplet keratopathies and age-related macular degeneration have produced surprisingly inconsistent findings. The lack of consistent results is seen to be due largely to either incomplete or erroneous estimates of outdoor UV exposure dose. Geometrical factors dominate the determination of UVR exposure of the eye. The degree of lid opening limits ocular exposure to rays entering at angles near the horizon. Clouds redistribute overhead UVR to the horizon sky. Mountains, trees and building shield the eye from direct sky exposure. Most ground surfaces reflect little UVR. The result is that highest UVR exposure occurs during light overcast where the horizon is visible and ground surface reflection is high. By contrast, exposure in a high mountain valley (lower ambient temperature) with green foliage results in a much lower ocular dose. Other findings of these studies show that retinal exposure to light and UVR in daylight occurs largely in the superior retina.

Separate channels for processing form, texture, and color: evidence from FMRI adaptation and visual object agnosia.

PubMed

Cavina-Pratesi, C; Kentridge, R W; Heywood, C A; Milner, A D

2010-10-01

Previous neuroimaging research suggests that although object shape is analyzed in the lateral occipital cortex, surface properties of objects, such as color and texture, are dealt with in more medial areas, close to the collateral sulcus (CoS). The present study sought to determine whether there is a single medial region concerned with surface properties in general or whether instead there are multiple foci independently extracting different surface properties. We used stimuli varying in their shape, texture, or color, and tested healthy participants and 2 object-agnosic patients, in both a discrimination task and a functional MR adaptation paradigm. We found a double dissociation between medial and lateral occipitotemporal cortices in processing surface (texture or color) versus geometric (shape) properties, respectively. In Experiment 2, we found that the medial occipitotemporal cortex houses separate foci for color (within anterior CoS and lingual gyrus) and texture (caudally within posterior CoS). In addition, we found that areas selective for shape, texture, and color individually were quite distinct from those that respond to all of these features together (shape and texture and color). These latter areas appear to correspond to those associated with the perception of complex stimuli such as faces and places.

Comparison of microfacet BRDF model to modified Beckmann-Kirchhoff BRDF model for rough and smooth surfaces.

PubMed

Butler, Samuel D; Nauyoks, Stephen E; Marciniak, Michael A

2015-11-02

A popular class of BRDF models is the microfacet models, where geometric optics is assumed. In contrast, more complex physical optics models may more accurately predict the BRDF, but the calculation is more resource intensive. These seemingly disparate approaches are compared in detail for the rough and smooth surface approximations of the modified Beckmann-Kirchhoff BRDF model, assuming Gaussian surface statistics. An approximation relating standard Fresnel reflection with the semi-rough surface polarization term, Q, is presented for unpolarized light. For rough surfaces, the angular dependence of direction cosine space is shown to be identical to the angular dependence in the microfacet distribution function. For polished surfaces, the same comparison shows a breakdown in the microfacet models. Similarities and differences between microfacet BRDF models and the modified Beckmann-Kirchhoff model are identified. The rationale for the original Beckmann-Kirchhoff F(bk)(2) geometric term relative to both microfacet models and generalized Harvey-Shack model is presented. A modification to the geometric F(bk)(2) term in original Beckmann-Kirchhoff BRDF theory is proposed.

Effect of the nozzle tip’s geometrical shape on electrospray deposition of organic thin films

NASA Astrophysics Data System (ADS)

Ueda, Hiroyuki; Takeuchi, Keita; Kikuchi, Akihiko

2017-04-01

Electrospray deposition (ESD) is a favorable wet fabrication technique for organic thin films. We investigated the effects of the nozzle tip’s geometrical shape on the spraying properties of an organic solution used for ESD. Five types of cylindrical metal nozzles with zero (flat end) to four protrusions at the tips were prepared for depositing a solution of a small-molecule compound, tris(8-hydroxyquinolinato)aluminum (Alq3) solution. We confirmed that the diameter of the deposited droplets and their size dispersion decreased with an increase in the number of protrusions. The area occupation ratio of small droplets with a diameter smaller than 2 µm increased from 21 to 83% as the number of protrusions was increased from zero to four. The surface roughness root mean square of 60-nm-thick Alq3 films substantially improved from 32.5 to 6.8 nm with increasing number of protrusions.

Microengineering as a tool to study substratum modulation and cell behaviour.

PubMed

Keatch, R P; Armoogum, K; Schor, S L; Pridham, M S; Banks, K; Khor, T Y; Matthew, C

2002-01-01

This research is an investigation of the means by which geometrical parameters (e.g. area and shape) and various surface attributes (materials and surface finish) of microengineered structures can modulate cellular response. This is based on biological observations indicating that: (i) the response of tissue cells to injury is determined by the net signal transduction response elicited by soluble regulatory molecules (e.g. cytokines), (ii) common matrix constituents (e.g. collagen) directly affect cell behaviour by the same signal transduction mechanisms mediating cytokine bioactivity, (iii) cellular response to cytokines is modulated by the precise nature of the extracellular matrix to which the target cells are adherent, including its biochemical composition and physical structure.

Galilean satellites - Identification of water frost.

NASA Technical Reports Server (NTRS)

Pilcher, C. B.; Mccord, T. B.; Ridgway, S. T.

1972-01-01

Water frost absorptions have been detected in the infrared reflectivities of Jupiter's Galilean satellites JII (Europa) and JIII (Ganymede). We have determined the percentage of frost-covered surface area to be 50 to 100 percent for JII, 20 to 65 percent for JIII, and possibly 5 to 25 percent for JIV (Callisto). The leading side of JIII has 20 percent more frost cover than the trailing side, which explains the visible geometric albedo differences between the two sides. The reflectivity of the material underlying the frost on JII, JIII, and JIV resembles that of silicates. The surface of JI (Io) may be covered by frost particles much smaller than those on JII and JIII.

Quilt Block Symmetries

ERIC Educational Resources Information Center

Roscoe, Matt B.; Zephyrs, Joe

2016-01-01

Geometric transformations have long been topics of middle school mathematics. Generations of middle school students have learned to reflect, rotate, and translate geometric objects. Historically, though, the mathematics of "movement" might have been considered a departure from other more central middle-grades geometric content areas,…

D Surface Generation from Aerial Thermal Imagery

NASA Astrophysics Data System (ADS)

Khodaei, B.; Samadzadegan, F.; Dadras Javan, F.; Hasani, H.

2015-12-01

Aerial thermal imagery has been recently applied to quantitative analysis of several scenes. For the mapping purpose based on aerial thermal imagery, high accuracy photogrammetric process is necessary. However, due to low geometric resolution and low contrast of thermal imaging sensors, there are some challenges in precise 3D measurement of objects. In this paper the potential of thermal video in 3D surface generation is evaluated. In the pre-processing step, thermal camera is geometrically calibrated using a calibration grid based on emissivity differences between the background and the targets. Then, Digital Surface Model (DSM) generation from thermal video imagery is performed in four steps. Initially, frames are extracted from video, then tie points are generated by Scale-Invariant Feature Transform (SIFT) algorithm. Bundle adjustment is then applied and the camera position and orientation parameters are determined. Finally, multi-resolution dense image matching algorithm is used to create 3D point cloud of the scene. Potential of the proposed method is evaluated based on thermal imaging cover an industrial area. The thermal camera has 640×480 Uncooled Focal Plane Array (UFPA) sensor, equipped with a 25 mm lens which mounted in the Unmanned Aerial Vehicle (UAV). The obtained results show the comparable accuracy of 3D model generated based on thermal images with respect to DSM generated from visible images, however thermal based DSM is somehow smoother with lower level of texture. Comparing the generated DSM with the 9 measured GCPs in the area shows the Root Mean Square Error (RMSE) value is smaller than 5 decimetres in both X and Y directions and 1.6 meters for the Z direction.

Accuracy analysis of point cloud modeling for evaluating concrete specimens

NASA Astrophysics Data System (ADS)

D'Amico, Nicolas; Yu, Tzuyang

2017-04-01

Photogrammetric methods such as structure from motion (SFM) have the capability to acquire accurate information about geometric features, surface cracks, and mechanical properties of specimens and structures in civil engineering. Conventional approaches to verify the accuracy in photogrammetric models usually require the use of other optical techniques such as LiDAR. In this paper, geometric accuracy of photogrammetric modeling is investigated by studying the effects of number of photos, radius of curvature, and point cloud density (PCD) on estimated lengths, areas, volumes, and different stress states of concrete cylinders and panels. Four plain concrete cylinders and two plain mortar panels were used for the study. A commercially available mobile phone camera was used in collecting all photographs. Agisoft PhotoScan software was applied in photogrammetric modeling of all concrete specimens. From our results, it was found that the increase of number of photos does not necessarily improve the geometric accuracy of point cloud models (PCM). It was also found that the effect of radius of curvature is not significant when compared with the ones of number of photos and PCD. A PCD threshold of 15.7194 pts/cm3 is proposed to construct reliable and accurate PCM for condition assessment. At this PCD threshold, all errors for estimating lengths, areas, and volumes were less than 5%. Finally, from the study of mechanical property of a plain concrete cylinder, we have found that the increase of stress level inside the concrete cylinder can be captured by the increase of radial strain in its PCM.

A Non-Abelian Geometric Phase for Spin Systems

NASA Astrophysics Data System (ADS)

H M, Bharath; Boguslawski, Matthew; Barrios, Maryrose; Chapman, Michael

Berry's geometric phase has been used to characterize topological phase transitions. Recent works have addressed the question of whether generalizations of Berry's phase to mixed states can be used to characterize topological phase transitions. Berry's phase is essentially the geometric information stored in the overall phase of a quantum system. Here, we show that geometric information is also stored in the higher order spin moments of a quantum spin system. In particular, we show that when the spin vector of a quantum spin system with a spin 1 or higher is transported along a closed path inside the Bloch ball, the tensor of second moments picks up a geometric phase in the form of an SO(3) operator. Geometrically interpreting this phase is tantamount to defining a steradian angle for closed paths inside the Bloch ball. Typically the steradian angle is defined by projecting the path onto the surface of the Bloch ball. However, paths that pass through the center cannot be projected onto the surface. We show that the steradian angles of all paths, including those that pass through the center can be defined by projecting them onto a real projective plane, instead of a sphere. This steradian angle is equal to the geometric phase picked up by a spin system.

Numerical Modeling of Exploitation Relics and Faults Influence on Rock Mass Deformations

NASA Astrophysics Data System (ADS)

Wesołowski, Marek

2016-12-01

This article presents numerical modeling results of fault planes and exploitation relics influenced by the size and distribution of rock mass and surface area deformations. Numerical calculations were performed using the finite difference program FLAC. To assess the changes taking place in a rock mass, an anisotropic elasto-plastic ubiquitous joint model was used, into which the Coulomb-Mohr strength (plasticity) condition was implemented. The article takes as an example the actual exploitation of the longwall 225 area in the seam 502wg of the "Pokój" coal mine. Computer simulations have shown that it is possible to determine the influence of fault planes and exploitation relics on the size and distribution of rock mass and its surface deformation. The main factor causing additional deformations of the area surface are the abandoned workings in the seam 502wd. These abandoned workings are the activation factor that caused additional subsidences and also, due to the significant dip, they are a layer on which the rock mass slides down in the direction of the extracted space. These factors are not taken into account by the geometrical and integral theories.

A numerical study of electromagnetic scattering from ocean like surfaces

NASA Technical Reports Server (NTRS)

Lentz, R. R.

1972-01-01

The integral equations describing electromagnetic scattering from one dimensional conducting surfaces are formulated and numerical results are presented. The results are compared with those obtained using approximate methods such as physical optics, geometrical optics, and perturbation theory. The integral equation solutions show that the surface radius of curvature must be greater than 2.5 wavelengths for either the physical optics or geometric optics to give satisfactory results. It has also been shown that perturbation theory agrees with the exact fields as long as the root mean square surface roughness is less than one-tenth of a wavelength.

Modern Geometric Algebra: A (Very Incomplete!) Survey

ERIC Educational Resources Information Center

Suzuki, Jeff

2009-01-01

Geometric algebra is based on two simple ideas. First, the area of a rectangle is equal to the product of the lengths of its sides. Second, if a figure is broken apart into several pieces, the sum of the areas of the pieces equals the area of the original figure. Remarkably, these two ideas provide an elegant way to introduce, connect, and…

Role of geometrical cues in bone marrow-derived mesenchymal stem cell survival, growth and osteogenic differentiation.

PubMed

Gupta, Dhanak; Grant, David M; Zakir Hossain, Kazi M; Ahmed, Ifty; Sottile, Virginie

2018-02-01

Mesenchymal stem cells play a vital role in bone formation process by differentiating into osteoblasts, in a tissue that offers not a flat but a discontinuous three-dimensional (3D) topography in vivo. In order to understand how geometry may be affecting mesenchymal stem cells, this study explored the influence of 3D geometry on mesenchymal stem cell-fate by comparing cell growth, viability and osteogenic potential using monolayer (two-dimensional, 2D) with microsphere (3D) culture systems normalised to surface area. The results suggested lower cell viability and reduced cell growth in 3D. Alkaline phosphatase activity was higher in 3D; however, both collagen and mineral deposition appeared significantly lower in 3D, even after osteogenic supplementation. Also, there were signs of patchy mineralisation in 3D with or without osteogenic supplementation as early as day 7. These results suggest that the convex surfaces on microspheres and inter-particulate porosity may have led to variable cell morphology and fate within the 3D culture. This study provides deeper insights into geometrical regulation of mesenchymal stem cell responses applicable for bone tissue engineering.

Geometrical effect, optimal design and controlled fabrication of bio-inspired micro/nanotextures for superhydrophobic surfaces

NASA Astrophysics Data System (ADS)

Ma, F. M.; Li, W.; Liu, A. H.; Yu, Z. L.; Ruan, M.; Feng, W.; Chen, H. X.; Chen, Y.

2017-09-01

Superhydrophobic surfaces with high water contact angles and low contact angle hysteresis or sliding angles have received tremendous attention for both academic research and industrial applications in recent years. In general, such surfaces possess rough microtextures, particularly, show micro/nano hierarchical structures like lotus leaves. Now it has been recognized that to achieve the artificial superhydrophobic surfaces, the simple and effective strategy is to mimic such hierarchical structures. However, fabrications of such structures for these artificial surfaces involve generally expensive and complex processes. On the other hand, the relationships between structural parameters of various surface topography and wetting properties have not been fully understood yet. In order to provide guidance for the simple fabrication and particularly, to promote practical applications of superhydrophobic surfaces, the geometrical designs of optimal microtextures or patterns have been proposed. In this work, the recent developments on geometrical effect, optimal design and controlled fabrication of various superhydrophobic structures, such as unitary, anisotropic, dual-scale hierarchical, and some other surface geometries, are reviewed. The effects of surface topography and structural parameters on wetting states (composite and noncomposite) and wetting properties (contact angle, contact angle hysteresis and sliding angle) as well as adhesive forces are discussed in detail. Finally, the research prospects in this field are briefly addressed.

An analysis of Landsat-4 Thematic Mapper geometric properties

NASA Technical Reports Server (NTRS)

Walker, R. E.; Zobrist, A. L.; Bryant, N. A.; Gohkman, B.; Friedman, S. Z.; Logan, T. L.

1984-01-01

Landsat-4 Thematic Mapper data of Washington, DC, Harrisburg, PA, and Salton Sea, CA were analyzed to determine geometric integrity and conformity of the data to known earth surface geometry. Several tests were performed. Intraband correlation and interband registration were investigated. No problems were observed in the intraband analysis, and aside from indications of slight misregistration between bands of the primary versus bands of the secondary focal planes, interband registration was well within the specified tolerances. A substantial number of ground control points were found and used to check the images' conformity to the Space Oblique Mercator (SOM) projection of their respective areas. The means of the residual offsets, which included nonprocessing related measurement errors, were close to the one pixel level in the two scenes examined. The Harrisburg scene residual mean was 28.38 m (0.95 pixels) with a standard deviation of 19.82 m (0.66 pixels), while the mean and standard deviation for the Salton Sea scene were 40.46 (1.35 pixels) and 30.57 m (1.02 pixels), respectively. Overall, the data were judged to be a high geometric quality with errors close to those targeted by the TM sensor design specifications.

Digital Photogrammetry for the Geometrical Analysis of the Umbrella-Shaped Dome in Baia (naples)

NASA Astrophysics Data System (ADS)

Aliberti, L.; Alonso-Rodríguez, M. Á.

2018-05-01

This paper is focused on the use of photogrammetric measurement techniques for the valorization of architectural and archaeological heritage. The functionality of this system allows operating with unfavourable conditions and pursues the accuracy of the measurement. This case of study presents a complex situation. Currently half part of the octagonal room annexed to the Temple of Mercury in Baia is underwater. Moreover the level of water may grow due to the characteristic movement of the soil in this area. The accuracy of photogrammetric method and the high definition of the camera used for the photo captures allow the reconstruction of the interior of the dome. The particular geometry of this surface stresses the relevance of a complete documentation of the dome. The research describes the method and tools used to realize this survey in difficult conditions and then analyze the geometry of the interior of the dome. In order to develop the geometrical analysis we carried on a series of operations on the point cloud and the survey model. The study of the photogrammetric model and the construction of an ideal model based on geometrical laws generate useful material to understand this complex vault.

Non-geometric fluxes, quasi-Hopf twist deformations, and nonassociative quantum mechanics

NASA Astrophysics Data System (ADS)

Mylonas, Dionysios; Schupp, Peter; Szabo, Richard J.

2014-12-01

We analyse the symmetries underlying nonassociative deformations of geometry in non-geometric R-flux compactifications which arise via T-duality from closed strings with constant geometric fluxes. Starting from the non-abelian Lie algebra of translations and Bopp shifts in phase space, together with a suitable cochain twist, we construct the quasi-Hopf algebra of symmetries that deforms the algebra of functions and the exterior differential calculus in the phase space description of nonassociative R-space. In this setting, nonassociativity is characterised by the associator 3-cocycle which controls non-coassociativity of the quasi-Hopf algebra. We use abelian 2-cocycle twists to construct maps between the dynamical nonassociative star product and a family of associative star products parametrized by constant momentum surfaces in phase space. We define a suitable integration on these nonassociative spaces and find that the usual cyclicity of associative noncommutative deformations is replaced by weaker notions of 2-cyclicity and 3-cyclicity. Using this star product quantization on phase space together with 3-cyclicity, we formulate a consistent version of nonassociative quantum mechanics, in which we calculate the expectation values of area and volume operators, and find coarse-graining of the string background due to the R-flux.

Three-dimensional labeling program for elucidation of the geometric properties of biological particles in three-dimensional space.

PubMed

Nomura, A; Yamazaki, Y; Tsuji, T; Kawasaki, Y; Tanaka, S

1996-09-15

For all biological particles such as cells or cellular organelles, there are three-dimensional coordinates representing the centroid or center of gravity. These coordinates and other numerical parameters such as volume, fluorescence intensity, surface area, and shape are referred to in this paper as geometric properties, which may provide critical information for the clarification of in situ mechanisms of molecular and cellular functions in living organisms. We have established a method for the elucidation of these properties, designated the three-dimensional labeling program (3DLP). Algorithms of 3DLP are so simple that this method can be carried out through the use of software combinations in image analysis on a personal computer. To evaluate 3DLP, it was applied to a 32-cell-stage sea urchin embryo, double stained with FITC for cellular protein of blastomeres and propidium iodide for nuclear DNA. A stack of optical serial section images was obtained by confocal laser scanning microscopy. The method was found effective for determining geometric properties and should prove applicable to the study of many different kinds of biological particles in three-dimensional space.

Bubbles and Dust: Dissolution Rates of Unhydrated Volcanic Ash as a Function of Morphology, Composition, and Particle Size

NASA Astrophysics Data System (ADS)

Wygel, C. M.; Sahagian, D. L.

2017-12-01

Volcanic eruptions are natural hazards due to their explosive nature and widespread transportation and deposition of ash particles. After deposition and subsequent leaching in soils or water bodies, ash deposition positively (nutrients) and negatively (contaminants) impacts the health of flora and fauna, including humans. The effects of ash leachates have been difficult to replicate in field and laboratory studies due to the many complexities and differences between ash particles. Ash morphology is characteristic for each eruption, dependent upon eruption energy, and should play a critical role in determining leaching rates. Morphology reflects overall particle surface area, which is strongly influenced by the presence of surface dust. In addition, ash composition, which in part controls morphology and particle size, may also affect leaching rates. This study determines the extent to which ash morphology, surface area, composition, and particle size control ash dissolution rates. Further, it is necessary to determine whether compound vesicular ash particles permit water into their interior structures to understand if both the internal and external surface areas are available for leaching. To address this, six fresh, unhydrated ash samples from diverse volcanic environments and a large range in morphology, from Pele's spheres to vesicular compound ash, are tested in the laboratory. Ash morphology was characterized on the Scanning Electron Microscope (SEM) before and after leaching and surface area was quantified by Brunauer Emmett Teller (BET) analysis and with geometric calculations. Column Leachate Tests (CLT) were conducted to compare leaching rates over a range of basaltic to silicic ashes as a function of time and surface area, to recreate the effects of ash deposition in diverse volcanic environments. After the CLT, post-leaching water analyses were conducted by Ion Coupled Plasma-Mass Spectrometry (ICP-MS) and Ion Chromatography (IC). We find that leaching rates are correlated to characteristic surface area of ash particles.

Fifth SIAM conference on geometric design 97: Final program and abstracts. Final technical report

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1997-12-31

The meeting was divided into the following sessions: (1) CAD/CAM; (2) Curve/Surface Design; (3) Geometric Algorithms; (4) Multiresolution Methods; (5) Robotics; (6) Solid Modeling; and (7) Visualization. This report contains the abstracts of papers presented at the meeting. Proceding the conference there was a short course entitled ``Wavelets for Geometric Modeling and Computer Graphics``.

Multiscale geometric modeling of macromolecules II: Lagrangian representation

PubMed Central

Feng, Xin; Xia, Kelin; Chen, Zhan; Tong, Yiying; Wei, Guo-Wei

2013-01-01

Geometric modeling of biomolecules plays an essential role in the conceptualization of biolmolecular structure, function, dynamics and transport. Qualitatively, geometric modeling offers a basis for molecular visualization, which is crucial for the understanding of molecular structure and interactions. Quantitatively, geometric modeling bridges the gap between molecular information, such as that from X-ray, NMR and cryo-EM, and theoretical/mathematical models, such as molecular dynamics, the Poisson-Boltzmann equation and the Nernst-Planck equation. In this work, we present a family of variational multiscale geometric models for macromolecular systems. Our models are able to combine multiresolution geometric modeling with multiscale electrostatic modeling in a unified variational framework. We discuss a suite of techniques for molecular surface generation, molecular surface meshing, molecular volumetric meshing, and the estimation of Hadwiger’s functionals. Emphasis is given to the multiresolution representations of biomolecules and the associated multiscale electrostatic analyses as well as multiresolution curvature characterizations. The resulting fine resolution representations of a biomolecular system enable the detailed analysis of solvent-solute interaction, and ion channel dynamics, while our coarse resolution representations highlight the compatibility of protein-ligand bindings and possibility of protein-protein interactions. PMID:23813599

Algorithmic commonalities in the parallel environment

NASA Technical Reports Server (NTRS)

Mcanulty, Michael A.; Wainer, Michael S.

1987-01-01

The ultimate aim of this project was to analyze procedures from substantially different application areas to discover what is either common or peculiar in the process of conversion to the Massively Parallel Processor (MPP). Three areas were identified: molecular dynamic simulation, production systems (rule systems), and various graphics and vision algorithms. To date, only selected graphics procedures have been investigated. They are the most readily available, and produce the most visible results. These include simple polygon patch rendering, raycasting against a constructive solid geometric model, and stochastic or fractal based textured surface algorithms. Only the simplest of conversion strategies, mapping a major loop to the array, has been investigated so far. It is not entirely satisfactory.

Efficiency of geometric designs of flexible solar panels: mathematical simulation

NASA Astrophysics Data System (ADS)

Marciniak, Malgorzata; Hassebo, Yasser; Enriquez-Torres, Delfino; Serey-Roman, Maria Ignacia

2017-09-01

The purpose of this study is to analyze various surfaces of flexible solar panels and compare them to the traditional at panels mathematically. We evaluated the efficiency based on the integral formulas that involve flux. We performed calculations for flat panels with different positions, a cylindrical panel, conical panels with various opening angles and segments of a spherical panel. Our results indicate that the best efficiency per unit area belongs to particular segments of spherically-shaped panels. In addition, we calculated the optimal opening angle of a cone-shaped panel that maximizes the annual accumulation of the sun radiation per unit area. The considered shapes are presented below with a suggestion for connections of the cells.

Fabrication technology

NASA Astrophysics Data System (ADS)

1988-05-01

Many laboratory programs continue to need optical components of ever-increasing size and accuracy. Unfortunately, optical surfaces produced by the conventional sequence of grinding, lapping, and polishing can become prohibitively expensive. Research in the Fabrication Technology area focuses on methods of fabricating components with heretofore unrealized levels of precision. In FY87, researchers worked to determine the fundamental mechanical limits of material removal, experimented with unique material removal and deposition processes, developed servo systems for controlling the geometric position of ultraprecise machine tools, and advanced the ability to precisely measure contoured workpieces. Continued work in these areas will lead to more cost-effective processes to fabricate even higher quality optical components for advanced lasers and for visible, ultraviolet, and X-ray diagnostic systems.

The effect of photometric and geometric context on photometric and geometric lightness effects

PubMed Central

Lee, Thomas Y.; Brainard, David H.

2014-01-01

We measured the lightness of probe tabs embedded at different orientations in various contextual images presented on a computer-controlled stereo display. Two background context planes met along a horizontal roof-like ridge. Each plane was a graphic rendering of a set of achromatic surfaces with the simulated illumination for each plane controlled independently. Photometric context was varied by changing the difference in simulated illumination intensity between the two background planes. Geometric context was varied by changing the angle between them. We parsed the data into separate photometric effects and geometric effects. For fixed geometry, varying photometric context led to linear changes in both the photometric and geometric effects. Varying geometric context did not produce a statistically reliable change in either the photometric or geometric effects. PMID:24464163

The effect of photometric and geometric context on photometric and geometric lightness effects.

PubMed

Lee, Thomas Y; Brainard, David H

2014-01-24

We measured the lightness of probe tabs embedded at different orientations in various contextual images presented on a computer-controlled stereo display. Two background context planes met along a horizontal roof-like ridge. Each plane was a graphic rendering of a set of achromatic surfaces with the simulated illumination for each plane controlled independently. Photometric context was varied by changing the difference in simulated illumination intensity between the two background planes. Geometric context was varied by changing the angle between them. We parsed the data into separate photometric effects and geometric effects. For fixed geometry, varying photometric context led to linear changes in both the photometric and geometric effects. Varying geometric context did not produce a statistically reliable change in either the photometric or geometric effects.

Unpolarized emissivity with shadow and multiple reflections from random rough surfaces with the geometric optics approximation: application to Gaussian sea surfaces in the infrared band.

PubMed

Bourlier, Christophe

2006-08-20

The emissivity from a stationary random rough surface is derived by taking into account the multiple reflections and the shadowing effect. The model is applied to the ocean surface. The geometric optics approximation is assumed to be valid, which means that the rough surface is modeled as a collection of facets reflecting locally the light in the specular direction. In particular, the emissivity with zero, single, and double reflections are analytically calculated, and each contribution is studied numerically by considering a 1D sea surface observed in the near infrared band. The model is also compared with results computed from a Monte Carlo ray-tracing method.

Gliding locomotion of manta rays, killer whales and swordfish near the water surface.

PubMed

Zhan, Jie-Min; Gong, Ye-Jun; Li, Tian-Zeng

2017-03-24

The hydrodynamic performance of the locomotive near the water surface is impacted by its geometrical shape. For marine animals, their geometrical shape is naturally selective; thus, investigating gliding locomotion of marine animal under the water surface may be able to elucidate the influence of the geometrical shape. We investigate three marine animals with specific geometries: the killer whale is fusiform shaped; the manta ray is flat and broad-winged; and the swordfish is best streamlined. The numerical results are validated by the measured drag coefficients of the manta ray model in a towing tank. The friction drag of the three target models are very similar; the body shape affected form drag coefficient is order as swordfish < killer whale < manta ray; the induced wave breaking upon the body of the manta ray performs different to killer whale and swordfish. These bio-inspired observations provide a new and in-depth understanding of the shape effects on the hydrodynamic performances near the free surface.

MINIMAL PROSPECTS FOR RADIO DETECTION OF EXTENSIVE AIR SHOWERS IN THE ATMOSPHERE OF JUPITER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bray, J. D.; Nelles, A., E-mail: justin.bray@manchester.ac.uk

One possible approach for detecting ultra-high-energy cosmic rays and neutrinos is to search for radio emission from extensive air showers created when they interact in the atmosphere of Jupiter, effectively utilizing Jupiter as a particle detector. We investigate the potential of this approach. For searches with current or planned radio telescopes we find that the effective area for detection of cosmic rays is substantial (∼3 × 10{sup 7} km{sup 2}), but the acceptance angle is so small that the typical geometric aperture (∼10{sup 3} km{sup 2} sr) is less than that of existing terrestrial detectors, and cosmic rays also cannotmore » be detected below an extremely high threshold energy (∼10{sup 23} eV). The geometric aperture for neutrinos is slightly larger, and greater sensitivity can be achieved with a radio detector on a Jupiter-orbiting satellite, but in neither case is this sufficient to constitute a practical detection technique. Exploitation of the large surface area of Jupiter for detecting ultra-high-energy particles remains a long-term prospect that will require a different technique, such as orbital fluorescence detection.« less

Numerical Estimation of the Curvature of Biological Surfaces

NASA Technical Reports Server (NTRS)

Todd, P. H.

1985-01-01

Many biological systems may profitably be studied as surface phenomena. A model consisting of isotropic growth of a curved surface from a flat sheet is assumed. With such a model, the Gaussian curvature of the final surface determines whether growth rate of the surface is subharmonic or superharmonic. These properties correspond to notions of convexity and concavity, and thus to local excess growth and local deficiency of growth. In biological models where the major factors controlling surface growth are intrinsic to the surface, researchers thus gained from geometrical study information on the differential growth undergone by the surface. These ideas were applied to an analysis of the folding of the cerebral cortex, a geometrically rather complex surface growth. A numerical surface curvature technique based on an approximation to the Dupin indicatrix of the surface was developed. A metric for comparing curvature estimates is introduced, and considerable numerical testing indicated the reliability of this technique.

A new digitized reverse correction method for hypoid gears based on a one-dimensional probe

NASA Astrophysics Data System (ADS)

Li, Tianxing; Li, Jubo; Deng, Xiaozhong; Yang, Jianjun; Li, Genggeng; Ma, Wensuo

2017-12-01

In order to improve the tooth surface geometric accuracy and transmission quality of hypoid gears, a new digitized reverse correction method is proposed based on the measurement data from a one-dimensional probe. The minimization of tooth surface geometrical deviations is realized from the perspective of mathematical analysis and reverse engineering. Combining the analysis of complex tooth surface generation principles and the measurement mechanism of one-dimensional probes, the mathematical relationship between the theoretical designed tooth surface, the actual machined tooth surface and the deviation tooth surface is established, the mapping relation between machine-tool settings and tooth surface deviations is derived, and the essential connection between the accurate calculation of tooth surface deviations and the reverse correction method of machine-tool settings is revealed. Furthermore, a reverse correction model of machine-tool settings is built, a reverse correction strategy is planned, and the minimization of tooth surface deviations is achieved by means of the method of numerical iterative reverse solution. On this basis, a digitized reverse correction system for hypoid gears is developed by the organic combination of numerical control generation, accurate measurement, computer numerical processing, and digitized correction. Finally, the correctness and practicability of the digitized reverse correction method are proved through a reverse correction experiment. The experimental results show that the tooth surface geometric deviations meet the engineering requirements after two trial cuts and one correction.

GEOMETRIC, VOLUMETRIC, COLOUR AND FRICTIONAL PROPERTIES OF SELECTED SALVIA SPECIES OF TURKEY.

PubMed

Bayram, Mustafa; Altuntas, Ebubekir; Yilar, Melih

2017-01-01

Salvia seeds are promite to dietary and healthy oils because they contain essential fatty acids. Salvia seeds frequently produce mucilage on soaking, and this mucilage is used for the treatment of eye diseases in eastern countries. Salvia species studied for medicine, food and cosmetics, have the potential to be used in the various fields. In the present study, selected engineering (geometrical, volumetrical, colour and frictional) properties of 6 Salvia species seeds were determined and compared. This study was performed on selected engineering properties of seeds of 6 Salvia species ( Salvia viridis L., Salvia aethiopis L., Salvia cryptantha Montbert & Aucher ex Benthan., Salvia tomentosa Mill ., Salvia sclarea L., Salvia virgata Jacq.,) cultivated in Turkey. Plants were collected during the vegetation in 2012-2013 (May-Agust). The seeds were cleaned from foreign matter, dirt and broken seeds manually. The average length, width and thickness were found in the range of 2.61 to 3.53 mm, 1.59 to 2.92 mm and 1.14 to 2.52 mm, respectively. Salvia viridis L. specie had the lowest geometric mean diameter and surface area, whereas Salvia cryptantha L. had the least values among these 6 Salvia species for these properties. The bulk density, true density and the porosity were between 296.83 and 702.80 kg m -3 , 285.69 and 718.08 kg m -3 , 10.27 and 44.05%, respectively. The volume of unit seed and sphericity ranged between 2.56 and 13.64 mm 3 , 62.90 and 90.40%, respectively. The coefficient of friction of salvia species were largely influenced by the friction surfaces studied, and highest values were found for polywood in the Salvia crytantha L.. In the study, the static friction coefficient and the angle of repose of salvia species changed from 0.477 to 0.955, and from 14.09 to 23.57°, respectively. Determination of geometric, volumetric, colour and frictional properties of Salvia spp. seeds may increase their economic value.

Geometric and boundary element method simulations of acoustic reflections from rough, finite, or non-planar surfaces

NASA Astrophysics Data System (ADS)

Rathsam, Jonathan

This dissertation seeks to advance the current state of computer-based sound field simulations for room acoustics. The first part of the dissertation assesses the reliability of geometric sound-field simulations, which are approximate in nature. The second part of the dissertation uses the rigorous boundary element method (BEM) to learn more about reflections from finite reflectors: planar and non-planar. Acoustical designers commonly use geometric simulations to predict sound fields quickly. Geometric simulation of reflections from rough surfaces is still under refinement. The first project in this dissertation investigates the scattering coefficient, which quantifies the degree of diffuse reflection from rough surfaces. The main result is that predicted reverberation time varies inversely with scattering coefficient if the sound field is nondiffuse. Additional results include a flow chart that enables acoustical designers to gauge how sensitive predicted results are to their choice of scattering coefficient. Geometric acoustics is a high-frequency approximation to wave acoustics. At low frequencies, more pronounced wave phenomena cause deviations between real-world values and geometric predictions. Acoustical designers encounter the limits of geometric acoustics in particular when simulating the low frequency response from finite suspended reflector panels. This dissertation uses the rigorous BEM to develop an improved low-frequency radiation model for smooth, finite reflectors. The improved low frequency model is suggested in two forms for implementation in geometric models. Although BEM simulations require more computation time than geometric simulations, BEM results are highly accurate. The final section of this dissertation uses the BEM to investigate the sound field around non-planar reflectors. The author has added convex edges rounded away from the source side of finite, smooth reflectors to minimize coloration of reflections caused by interference from boundary waves. Although the coloration could not be fully eliminated, the convex edge increases the sound energy reflected into previously nonspecular zones. This excess reflected energy is marginally audible using a standard of 20 dB below direct sound energy. The convex-edged panel is recommended for use when designers want to extend reflected energy spatially beyond the specular reflection zone of a planar panel.

A computational method for sharp interface advection.

PubMed

Roenby, Johan; Bredmose, Henrik; Jasak, Hrvoje

2016-11-01

We devise a numerical method for passive advection of a surface, such as the interface between two incompressible fluids, across a computational mesh. The method is called isoAdvector, and is developed for general meshes consisting of arbitrary polyhedral cells. The algorithm is based on the volume of fluid (VOF) idea of calculating the volume of one of the fluids transported across the mesh faces during a time step. The novelty of the isoAdvector concept consists of two parts. First, we exploit an isosurface concept for modelling the interface inside cells in a geometric surface reconstruction step. Second, from the reconstructed surface, we model the motion of the face-interface intersection line for a general polygonal face to obtain the time evolution within a time step of the submerged face area. Integrating this submerged area over the time step leads to an accurate estimate for the total volume of fluid transported across the face. The method was tested on simple two-dimensional and three-dimensional interface advection problems on both structured and unstructured meshes. The results are very satisfactory in terms of volume conservation, boundedness, surface sharpness and efficiency. The isoAdvector method was implemented as an OpenFOAM ® extension and is published as open source.

Reconstruction of shapes of near symmetric and asymmetric objects

DOEpatents

Pizlo, Zygmunt; Sawada, Tadamasa; Li, Yunfeng

2013-03-26

A system processes 2D images of 2D or 3D objects, creating a model of the object that is consistent with the image and as veridical as the perception of the 2D image by humans. Vertices of the object that are hidden in the image are recovered by using planarity and symmetry constraints. The 3D shape is recovered by maximizing 3D compactness of the recovered object and minimizing its surface area. In some embodiments, these two criteria are weighted by using the geometric mean.

Competition between surface chemisorption and cage formation in Fe12O12 clusters

NASA Astrophysics Data System (ADS)

Gutsev, G. L.; Weatherford, C. A.; Jena, P.; Johnson, E.; Ramachandran, B. R.

2013-01-01

The electronic and geometrical structures of the clusters composed of 12 iron and 12 oxygen atoms are obtained using all-electron density functional theory. It is found that the states with geometrical structures corresponding to oxygen chemisorbed on the ground-state Fe12 cluster surface (Fe12O12) are close in total energy to the states whose geometrical configurations are hollow cages (FeO)12. The lowest total energy state is the ferrimagnetic triplet state of Fe12O12. A ferrimagnetic nonet state of (FeO)12 is only marginally higher in total energy. The clusters are rich in nearly degenerate isomers. Oxygen adsorption dramatically quenches the spin of Fe12 clusters.

A universal algorithm for an improved finite element mesh generation Mesh quality assessment in comparison to former automated mesh-generators and an analytic model.

PubMed

Kaminsky, Jan; Rodt, Thomas; Gharabaghi, Alireza; Forster, Jan; Brand, Gerd; Samii, Madjid

2005-06-01

The FE-modeling of complex anatomical structures is not solved satisfyingly so far. Voxel-based as opposed to contour-based algorithms allow an automated mesh generation based on the image data. Nonetheless their geometric precision is limited. We developed an automated mesh-generator that combines the advantages of voxel-based generation with improved representation of the geometry by displacement of nodes on the object-surface. Models of an artificial 3D-pipe-section and a skullbase were generated with different mesh-densities using the newly developed geometric, unsmoothed and smoothed voxel generators. Compared to the analytic calculation of the 3D-pipe-section model the normalized RMS error of the surface stress was 0.173-0.647 for the unsmoothed voxel models, 0.111-0.616 for the smoothed voxel models with small volume error and 0.126-0.273 for the geometric models. The highest element-energy error as a criterion for the mesh quality was 2.61x10(-2) N mm, 2.46x10(-2) N mm and 1.81x10(-2) N mm for unsmoothed, smoothed and geometric voxel models, respectively. The geometric model of the 3D-skullbase resulted in the lowest element-energy error and volume error. This algorithm also allowed the best representation of anatomical details. The presented geometric mesh-generator is universally applicable and allows an automated and accurate modeling by combining the advantages of the voxel-technique and of improved surface-modeling.

Estimation of reactive surface area using a combined method of laboratory analyses and digital image processing

NASA Astrophysics Data System (ADS)

Ma, Jin; Kong, Xiang-Zhao; Saar, Martin O.

2017-04-01

Fluid-rock interactions play an important role in the engineering processes such as chemical stimulation of enhanced geothermal systems and carbon capture, utilization, and storage. However, these interactions highly depend on the accessible reactive surface area of the minerals that are generally poorly constrained for natural geologic samples. In particular, quantifying surface area of each reacting mineral within whole rock samples is challenging due to the heterogeneous distribution of minerals and pore space. In this study, detailed laboratory analyses were performed on sandstone samples from deep geothermal sites in Lithuania. We measure specific surface area of whole rock samples using a gas adsorption method (so-called B.E.T.) with N2 at a temperature of 77.3K. We also quantify their porosity and pore size distribution by a Helium gas pycnometer and a Hg porosimetry, respectively. Rock compositions are determined by a combination of X-ray fluorescence (XRF) and quantitative scanning electron microscopy (SEM) - Energy-dispersive X-ray spectroscopy (EDS), which are later geometrically mapped on images of two-dimensional SEM- Backscattered electrons (BSE) with a resolution of 1.2 μm and three-dimensional micro-CT with a resolution of 10.3 μm to produce a digital mineral map for further constraining the accessibility of reactive minerals. Moreover, we attempt to link the whole rock porosity, pore size distribution, and B.E.T. specific surface area with the digital mineral maps. We anticipate these necessary analyses to provide in-depth understanding of fluid sample chemistry from later hydrothermal reactive flow-through experiments on whole rock samples at elevated pressure and temperature.

Automatic rocks detection and classification on high resolution images of planetary surfaces

NASA Astrophysics Data System (ADS)

Aboudan, A.; Pacifici, A.; Murana, A.; Cannarsa, F.; Ori, G. G.; Dell'Arciprete, I.; Allemand, P.; Grandjean, P.; Portigliotti, S.; Marcer, A.; Lorenzoni, L.

2013-12-01

High-resolution images can be used to obtain rocks location and size on planetary surfaces. In particular rock size-frequency distribution is a key parameter to evaluate the surface roughness, to investigate the geologic processes that formed the surface and to assess the hazards related with spacecraft landing. The manual search for rocks on high-resolution images (even for small areas) can be a very intensive work. An automatic or semi-automatic algorithm to identify rocks is mandatory to enable further processing as determining the rocks presence, size, height (by means of shadows) and spatial distribution over an area of interest. Accurate rocks and shadows contours localization are the key steps for rock detection. An approach to contour detection based on morphological operators and statistical thresholding is presented in this work. The identified contours are then fitted using a proper geometric model of the rocks or shadows and used to estimate salient rocks parameters (position, size, area, height). The performances of this approach have been evaluated both on images of Martian analogue area of Morocco desert and on HiRISE images. Results have been compared with ground truth obtained by means of manual rock mapping and proved the effectiveness of the algorithm. The rock abundance and rocks size-frequency distribution derived on selected HiRISE images have been compared with the results of similar analyses performed for the landing site certification of Mars landers (Viking, Pathfinder, MER, MSL) and with the available thermal data from IRTM and TES.

Temperature distribution and heat radiation of patterned surfaces at short wavelengths.

PubMed

Emig, Thorsten

2017-05-01

We analyze the equilibrium spatial distribution of surface temperatures of patterned surfaces. The surface is exposed to a constant external heat flux and has a fixed internal temperature that is coupled to the outside heat fluxes by finite heat conductivity across the surface. It is assumed that the temperatures are sufficiently high so that the thermal wavelength (a few microns at room temperature) is short compared to all geometric length scales of the surface patterns. Hence the radiosity method can be employed. A recursive multiple scattering method is developed that enables rapid convergence to equilibrium temperatures. While the temperature distributions show distinct dependence on the detailed surface shapes (cuboids and cylinder are studied), we demonstrate robust universal relations between the mean and the standard deviation of the temperature distributions and quantities that characterize overall geometric features of the surface shape.

Temperature distribution and heat radiation of patterned surfaces at short wavelengths

NASA Astrophysics Data System (ADS)

Emig, Thorsten

2017-05-01

We analyze the equilibrium spatial distribution of surface temperatures of patterned surfaces. The surface is exposed to a constant external heat flux and has a fixed internal temperature that is coupled to the outside heat fluxes by finite heat conductivity across the surface. It is assumed that the temperatures are sufficiently high so that the thermal wavelength (a few microns at room temperature) is short compared to all geometric length scales of the surface patterns. Hence the radiosity method can be employed. A recursive multiple scattering method is developed that enables rapid convergence to equilibrium temperatures. While the temperature distributions show distinct dependence on the detailed surface shapes (cuboids and cylinder are studied), we demonstrate robust universal relations between the mean and the standard deviation of the temperature distributions and quantities that characterize overall geometric features of the surface shape.

Efficient 3D geometric and Zernike moments computation from unstructured surface meshes.

PubMed

Pozo, José María; Villa-Uriol, Maria-Cruz; Frangi, Alejandro F

2011-03-01

This paper introduces and evaluates a fast exact algorithm and a series of faster approximate algorithms for the computation of 3D geometric moments from an unstructured surface mesh of triangles. Being based on the object surface reduces the computational complexity of these algorithms with respect to volumetric grid-based algorithms. In contrast, it can only be applied for the computation of geometric moments of homogeneous objects. This advantage and restriction is shared with other proposed algorithms based on the object boundary. The proposed exact algorithm reduces the computational complexity for computing geometric moments up to order N with respect to previously proposed exact algorithms, from N(9) to N(6). The approximate series algorithm appears as a power series on the rate between triangle size and object size, which can be truncated at any desired degree. The higher the number and quality of the triangles, the better the approximation. This approximate algorithm reduces the computational complexity to N(3). In addition, the paper introduces a fast algorithm for the computation of 3D Zernike moments from the computed geometric moments, with a computational complexity N(4), while the previously proposed algorithm is of order N(6). The error introduced by the proposed approximate algorithms is evaluated in different shapes and the cost-benefit ratio in terms of error, and computational time is analyzed for different moment orders.

Geometric Image Biomarker Changes of the Parotid Gland Are Associated With Late Xerostomia.

PubMed

van Dijk, Lisanne V; Brouwer, Charlotte L; van der Laan, Hans Paul; Burgerhof, Johannes G M; Langendijk, Johannes A; Steenbakkers, Roel J H M; Sijtsema, Nanna M

2017-12-01

To identify a surrogate marker for late xerostomia 12 months after radiation therapy (Xer 12m ), according to information obtained shortly after treatment. Differences in parotid gland (PG) were quantified in image biomarkers (ΔIBMs) before and 6 weeks after radiation therapy in 107 patients. By performing stepwise forward selection, ΔIBMs that were associated with Xer 12m were selected. Subsequently other variables, such as PG dose and acute xerostomia scores, were added to improve the prediction performance. All models were internally validated. Prediction of Xer 12m based on PG surface reduction (ΔPG-surface) was good (area under the receiver operating characteristic curve, 0.82). Parotid gland dose was related to ΔPG-surface (P<.001, R 2  = 0.27). The addition of acute xerostomia scores to the ΔPG-surface improved the prediction of Xer 12m significantly, and vice versa. The final model including ΔPG-surface and acute xerostomia had outstanding performance in predicting Xer 12m early after radiation therapy (area under the receiver operating characteristic curve, 0.90). Parotid gland surface reduction was associated with late xerostomia. The early posttreatment model with ΔPG-surface and acute xerostomia scores can be considered as a surrogate marker for late xerostomia. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Surface and Basal Roughness in Radar Sounding Data: Obstacle and Opportunity

NASA Astrophysics Data System (ADS)

Schroeder, D. M.; Grima, C.; Haynes, M.

2015-12-01

The surface and basal roughness of glaciers, ice sheets, and ice shelves can pose a significant obstacle to the visual interpretation and quantitative analysis of radar sounding data. Areas of high surface roughness - including grounding zones, shear margins, and crevasse fields - can produce clutter and side-lobe signals that obscure the interpretation of englacial and subglacial features. These areas can also introduce significant variation in bed echo strength profiles as a result of losses from two-way propagation through rough ice surfaces. Similarly, reflections from rough basal interfaces beneath ice sheets and ice shelves can also result in large, spatially variable losses in bed echo power. If unmitigated and uncorrected, these effects can degrade or prevent the definitive interpretation of material and geometric properties at the base of ice sheets and ice shelves using radar reflectivity and bed echo character. However, these effects also provide geophysical signatures of surface and basal interface character - including surface roughness, firn density, subglacial bedform geometry, ice shelf basal roughness, marine-ice/brine detection, and crevasse geometry - that can be observed and constrained by exploiting roughness effects in radar sounding data. We present a series of applications and approaches for characterizing and correcting surface and basal roughness effects for airborne radar sounding data collected in Antarctica. We also present challenges, insights, and opportunities for extending these techniques to the orbital radar sounding of Europa's ice shell.

Use of biomimetic hexagonal surface texture in friction against lubricated skin.

PubMed

Tsipenyuk, Alexey; Varenberg, Michael

2014-05-06

Smooth contact pads that evolved in insects, amphibians and mammals to enhance the attachment abilities of the animals' feet are often dressed with surface micropatterns of different shapes that act in the presence of a fluid secretion. One of the most striking surface patterns observed in contact pads of these animals is based on a hexagonal texture, which is recognized as a friction-oriented feature capable of suppressing both stick-slip and hydroplaning while enabling friction tuning. Here, we compare this design of natural friction surfaces to textures developed for working in similar conditions in disposable safety razors. When slid against lubricated human skin, the hexagonal surface texture is capable of generating about twice the friction of its technical competitors, which is related to it being much more effective at channelling of the lubricant fluid out of the contact zone. The draining channel shape and contact area fraction are found to be the most important geometrical parameters governing the fluid drainage rate.

Surface-engineered substrates for improved human pluripotent stem cell culture under fully defined conditions.

PubMed

Saha, Krishanu; Mei, Ying; Reisterer, Colin M; Pyzocha, Neena Kenton; Yang, Jing; Muffat, Julien; Davies, Martyn C; Alexander, Morgan R; Langer, Robert; Anderson, Daniel G; Jaenisch, Rudolf

2011-11-15

The current gold standard for the culture of human pluripotent stem cells requires the use of a feeder layer of cells. Here, we develop a spatially defined culture system based on UV/ozone radiation modification of typical cell culture plastics to define a favorable surface environment for human pluripotent stem cell culture. Chemical and geometrical optimization of the surfaces enables control of early cell aggregation from fully dissociated cells, as predicted from a numerical model of cell migration, and results in significant increases in cell growth of undifferentiated cells. These chemically defined xeno-free substrates generate more than three times the number of cells than feeder-containing substrates per surface area. Further, reprogramming and typical gene-targeting protocols can be readily performed on these engineered surfaces. These substrates provide an attractive cell culture platform for the production of clinically relevant factor-free reprogrammed cells from patient tissue samples and facilitate the definition of standardized scale-up friendly methods for disease modeling and cell therapeutic applications.

Surface Plasmons Carry the Pancharatnam-Berry Geometric Phase

NASA Astrophysics Data System (ADS)

Daniel, Salman; Saastamoinen, Kimmo; Saastamoinen, Toni; Vartiainen, Ismo; Friberg, Ari T.; Visser, Taco D.

2017-12-01

Surface plasmon polaritons (SPPs) are electromagnetic surface waves that travel along the boundary of a metal and a dielectric medium. They can be generated when freely propagating light is scattered by structural metallic features such as gratings or slits. In plasmonics, SPPs are manipulated, amplified, or routed before being converted back into light by a second scattering event. In this process, the light acquires a dynamic phase and perhaps an additional geometric phase associated with polarization changes. We examine the possibility that SPPs mediate the Pancharatnam-Berry phase, which follows from a closed path of successive in-phase polarization-state transformations on the Poincaré sphere and demonstrate that this is indeed the case. The geometric phase is shown to survive the light →SPP →light process and, moreover, its magnitude agrees with Pancharatnam's rule. Our findings are fundamental in nature and highly relevant for photonics applications.

Volumetric quantitative characterization of human patellar cartilage with topological and geometrical features on phase-contrast X-ray computed tomography.

PubMed

Nagarajan, Mahesh B; Coan, Paola; Huber, Markus B; Diemoz, Paul C; Wismüller, Axel

2015-11-01

Phase-contrast X-ray computed tomography (PCI-CT) has attracted significant interest in recent years for its ability to provide significantly improved image contrast in low absorbing materials such as soft biological tissue. In the research context of cartilage imaging, previous studies have demonstrated the ability of PCI-CT to visualize structural details of human patellar cartilage matrix and capture changes to chondrocyte organization induced by osteoarthritis. This study evaluates the use of geometrical and topological features for volumetric characterization of such chondrocyte patterns in the presence (or absence) of osteoarthritic damage. Geometrical features derived from the scaling index method (SIM) and topological features derived from Minkowski Functionals were extracted from 1392 volumes of interest (VOI) annotated on PCI-CT images of ex vivo human patellar cartilage specimens. These features were subsequently used in a machine learning task with support vector regression to classify VOIs as healthy or osteoarthritic; classification performance was evaluated using the area under the receiver operating characteristic curve (AUC). Our results show that the classification performance of SIM-derived geometrical features (AUC: 0.90 ± 0.09) is significantly better than Minkowski Functionals volume (AUC: 0.54 ± 0.02), surface (AUC: 0.72 ± 0.06), mean breadth (AUC: 0.74 ± 0.06) and Euler characteristic (AUC: 0.78 ± 0.04) (p < 10(-4)). These results suggest that such geometrical features can provide a detailed characterization of the chondrocyte organization in the cartilage matrix in an automated manner, while also enabling classification of cartilage as healthy or osteoarthritic with high accuracy. Such features could potentially serve as diagnostic imaging markers for evaluating osteoarthritis progression and its response to different therapeutic intervention strategies.

P09.43 Novel geometrical imaging biomarkers predict survival and allow for patient selection for surgery in glioblastoma patients.

PubMed Central

Pérez-Beteta, J.; Molina, D.; Martínez-González, A.; Arregui, E.; Asenjo, B.; Iglesias, L.; Martino, J.; Pérez-Romasanta, L.; Arana, E.; Pérez-García, V. M.

2017-01-01

Abstract Introduction: Glioblastoma is the most frequent and lethal malignant brain tumor in adults. Preoperative magnetic resonance imaging is routinely used for diagnosis and treatment planning. One of the gold standards in imaging are the post-contrast T1-weighted magnetic resonance images (MRIs) that are used to define the macroscopic part of the tumor. A modern mathematical model has predicted a relation between tumor’s growth speed, and so the patient outcome, with the width of contrast enhancing areas measured on the pre-surgery post-contrast 3D T1-weighted images. Other works have hypothesized the role of the tumor’s surface as a driver for growth and infiltration in cancer. Materials and Methods: A retrospective study involving 7 hospitals was organized for the validation of the model predictions. Inclusion criteria where unifocal tumors and availability of 3D T1w MRIs and clinical data (age, survival, type of treatment, etc). 219 patients were included in the study. Tumors were manually segmented and thirty quantitative geometrical 3D variables computed including volumes (total tumor, contrast enhancing and necrotic), surfaces, volume ratios, 3D maximal diameter and several measures of the contrast enhancing ‘rim’. A novel measure was defined accounting for how much the tumor surface as measured on the post-contrast T1w MRIs deviates from a sphere of the same volume. Kaplan-Meir and Cox regression methods were used to validate the relevance of the different features. Results: Patients with small contrast enhancing width (< 3.7 mm) showed a significant improvement in survival (p = 0.002, differences in median = 191 days, HR = 1.701). The tumor surface irregularity turned out to be a very powerful predictor of survival (p = 0.004, differences in median = 104 days, HR = 1.516). Both parameters were significant in multivariate analysis together with the age (p = 0.007 for surface irregularity and p = 0.009 for rim width). No other parameters including volumes, volume ratios, surfaces, maximal diameters, and other features were associated with survival neither in univariate nor in multivariate analyses. Conclusions: The width of the contrast enhancing rim and a novel surface irregularity parameter were predictors of survival in a large cohort of GBM patients. Since the study methodology was very robust (high resolution MRIs, tumor segmentation methodology) and the number of geometrically meaningful parameters large in comparison with previous studies this study may shed some light on the long debated topic of the role of geometrical measures on GBM patient’s survival. FUNDING: James S. Mc. Donnell Foundation (USA) 21st Century Science Initiative in Mathematical and Complex Systems Approaches for Brain Cancer [Collaborative award 220020450 and planning grant 220020420], MINECO/FEDER [MTM2015-71200-R], JCCM [PEII-2014-031-P].

Advanced Geometric Optics on a Programmable Pocket Calculator.

ERIC Educational Resources Information Center

Nussbaum, Allen

1979-01-01

Presents a ray-tracing procedure based on some ideas of Herzberger and the matrix approach to geometrical optics. This method, which can be implemented on a programmable pocket calculator, applies to any conic surface, including paraboloids, spheres, and planes. (Author/GA)

A comparison of stereology, structural rigidity and a novel 3D failure surface analysis method in the assessment of torsional strength and stiffness in a mouse tibia fracture model.

PubMed

Wright, David A; Nam, Diane; Whyne, Cari M

2012-08-31

In attempting to develop non-invasive image based measures for the determination of the biomechanical integrity of healing fractures, traditional μCT based measurements have been limited. This study presents the development and evaluation of a tool for assessment of fracture callus mechanical properties through determination of the geometric characteristics of the fracture callus, specifically along the surface of failure identified during destructive mechanical testing. Fractures were created in tibias of ten male mice and subjected to μCT imaging and biomechanical torsion testing. Failure surface analysis, along with previously described image based measures was calculated using the μCT image data, and correlated with mechanical strength and stiffness. Three-dimensional measures along the surface of failure, specifically the surface area and torsional rigidity of bone, were shown to be significantly correlating with mechanical strength and stiffness. It was also shown that surface area of bone along the failure surface exhibits stronger correlations with both strength and stiffness than measures of average and minimum torsional rigidity of the entire callus. Failure surfaces observed in this study were generally oriented at 45° to the long axis of the bone, and were not contained exclusively within the callus. This work represents a proof of concept study, and shows the potential utility of failure surface analysis in the assessment of fracture callus stability. Copyright © 2012 Elsevier Ltd. All rights reserved.

Use of Textured Surfaces to Mitigate Sliding Friction and Wear of Lubricated and Non-Lubricated Contacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blau, Peter Julian

If properly employed, the placement of three-dimensional feature patterns, also referred to as textures, on relatively-moving, load-bearing surfaces can be beneficial to their friction and wear characteristics. For example, geometric patterns can function as lubricant supply channels or depressions in which to trap debris. They can also alter lubricant flow in a manner that produces thicker load-bearing films locally. Considering the area occupied by solid areas and spaces, textures also change the load distribution on surfaces. At least ten different attributes of textures can be specified, and their combinations offer wide latitude in surface engineering. By employing directional machining andmore » grinding procedures, texturing has been used on bearings and seals for well over a half century, and the size scales of texturing vary widely. This report summarizes past work on the texturing of load-bearing surfaces, including past research on laser surface dimpling of ceramics done at ORNL. Textured surfaces generally show most pronounced effects when they are used in conformal or nearly conformal contacts, like that in face seals. Combining textures with other forms of surface modification and lubrication methods can offer additional benefits in surface engineering for tribology. As the literature and past work at ORNL shows, texturing does not always provide benefits. Rather, the selected pattern and arrangement of features must be matched to characteristics of the proposed application, bearing materials, and lubricants.« less

Generalized centripetal force law and quantization of motion constrained on 2D surfaces

NASA Astrophysics Data System (ADS)

Liu, Q. H.; Zhang, J.; Lian, D. K.; Hu, L. D.; Li, Z.

2017-03-01

For a particle of mass μ moves on a 2D surface f(x) = 0 embedded in 3D Euclidean space of coordinates x, there is an open and controversial problem whether the Dirac's canonical quantization scheme for the constrained motion allows for the geometric potential that has been experimentally confirmed. We note that the Dirac's scheme hypothesizes that the symmetries indicated by classical brackets among positions x and momenta p and Hamiltonian Hc remain in quantum mechanics, i.e., the following Dirac brackets [ x ,Hc ] D and [ p ,Hc ] D holds true after quantization, in addition to the fundamental ones [ x , x ] D, [ x , p ] D and [ p , p ] D. This set of hypotheses implies that the Hamiltonian operator is simultaneously determined during the quantization. The quantum mechanical relations corresponding to the classical mechanical ones p / μ =[ x ,Hc ] D directly give the geometric momenta. The time t derivative of the momenta p ˙ =[ p ,Hc ] D in classical mechanics is in fact the generalized centripetal force law for particle on the 2D surface, which in quantum mechanics permits both the geometric momenta and the geometric potential.

Geometric, Kinematic and Radiometric Aspects of Image-Based Measurements

NASA Technical Reports Server (NTRS)

Liu, Tianshu

2002-01-01

This paper discusses theoretical foundations of quantitative image-based measurements for extracting and reconstructing geometric, kinematic and dynamic properties of observed objects. New results are obtained by using a combination of methods in perspective geometry, differential geometry. radiometry, kinematics and dynamics. Specific topics include perspective projection transformation. perspective developable conical surface, perspective projection under surface constraint, perspective invariants, the point correspondence problem. motion fields of curves and surfaces. and motion equations of image intensity. The methods given in this paper arc useful for determining morphology and motion fields of deformable bodies such as elastic bodies. viscoelastic mediums and fluids.

The perception of geometrical structure from congruence

NASA Technical Reports Server (NTRS)

Lappin, Joseph S.; Wason, Thomas D.

1989-01-01

The principle function of vision is to measure the environment. As demonstrated by the coordination of motor actions with the positions and trajectories of moving objects in cluttered environments and by rapid recognition of solid objects in varying contexts from changing perspectives, vision provides real-time information about the geometrical structure and location of environmental objects and events. The geometric information provided by 2-D spatial displays is examined. It is proposed that the geometry of this information is best understood not within the traditional framework of perspective trigonometry, but in terms of the structure of qualitative relations defined by congruences among intrinsic geometric relations in images of surfaces. The basic concepts of this geometrical theory are outlined.

Treatment of geometric singularities in implicit solvent models

NASA Astrophysics Data System (ADS)

Yu, Sining; Geng, Weihua; Wei, G. W.

2007-06-01

Geometric singularities, such as cusps and self-intersecting surfaces, are major obstacles to the accuracy, convergence, and stability of the numerical solution of the Poisson-Boltzmann (PB) equation. In earlier work, an interface technique based PB solver was developed using the matched interface and boundary (MIB) method, which explicitly enforces the flux jump condition at the solvent-solute interfaces and leads to highly accurate biomolecular electrostatics in continuum electric environments. However, such a PB solver, denoted as MIBPB-I, cannot maintain the designed second order convergence whenever there are geometric singularities, such as cusps and self-intersecting surfaces. Moreover, the matrix of the MIBPB-I is not optimally symmetrical, resulting in the convergence difficulty. The present work presents a new interface method based PB solver, denoted as MIBPB-II, to address the aforementioned problems. The present MIBPB-II solver is systematical and robust in treating geometric singularities and delivers second order convergence for arbitrarily complex molecular surfaces of proteins. A new procedure is introduced to make the MIBPB-II matrix optimally symmetrical and diagonally dominant. The MIBPB-II solver is extensively validated by the molecular surfaces of few-atom systems and a set of 24 proteins. Converged electrostatic potentials and solvation free energies are obtained at a coarse grid spacing of 0.5Å and are considerably more accurate than those obtained by the PBEQ and the APBS at finer grid spacings.

Surface operators from M -strings

NASA Astrophysics Data System (ADS)

Mori, Hironori; Sugimoto, Yuji

2017-01-01

It has been found that surface operators have a significant role in Alday-Gaiotto-Tachikawa (AGT) relation. This duality is an outstanding consequence of M -theory, but it is actually encoded into the brane web for which the topological string can work. From this viewpoint, the surface defect in AGT relation is geometrically engineered as a toric brane realization. Also, there is a class of the brane configuration in M -theory called M -strings which can be translated into the language of the topological string. In this work, we propose a new M -string configuration which can realize AGT relation in the presence of the surface defect by utilizing the geometric transition in the refined topological string.

Measured body composition and geometrical data of four ``virtual family'' members for thermoregulatory modeling

NASA Astrophysics Data System (ADS)

Xu, Xiaojiang; Rioux, Timothy P.; MacLeod, Tynan; Patel, Tejash; Rome, Maxwell N.; Potter, Adam W.

2017-03-01

The purpose of this paper is to develop a database of tissue composition, distribution, volume, surface area, and skin thickness from anatomically correct human models, the virtual family. These models were based on high-resolution magnetic resonance imaging (MRI) of human volunteers, including two adults (male and female) and two children (boy and girl). In the segmented image dataset, each voxel is associated with a label which refers to a tissue type that occupies up that specific cubic millimeter of the body. The tissue volume was calculated from the number of the voxels with the same label. Volumes of 24 organs in body and volumes of 7 tissues in 10 specific body regions were calculated. Surface area was calculated from the collection of voxels that are touching the exterior air. Skin thicknesses were estimated from its volume and surface area. The differences between the calculated and original masses were about 3 % or less for tissues or organs that are important to thermoregulatory modeling, e.g., muscle, skin, and fat. This accurate database of body tissue distributions and geometry is essential for the development of human thermoregulatory models. Data derived from medical imaging provide new effective tools to enhance thermal physiology research and gain deeper insight into the mechanisms of how the human body maintains heat balance.

Geometric Model for Tracker-Target Look Angles and Line of Slight Distance

DTIC Science & Technology

2015-10-20

412TW-PA-15239 Geometric Model for Tracker -Target Look Angles and Line of Slight Distance DANIEL T. LAIRD AIR FORCE TEST CENTER EDWARDS...15 – 23 OCT 15 4. TITLE AND SUBTITLE Geometric Model for Tracker -Target Look Angles and Line of Slight Distance 5a. CONTRACT...include area code) 661-277-8615 Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39.18 GEOMETRIC MODEL FOR TRACKER -TARGET LOOK ANGLES

Vena contracta analysis by color Doppler three-dimensional transesophageal echocardiography shows geometrical differences between prolapse and pseudoprolapse in eccentric mitral regurgitation.

PubMed

Berdejo, Javier; Shiota, Maiko; Mihara, Hirotsugu; Itabashi, Yuji; Utsunomiya, Hiroto; Shiota, Takahiro

2017-05-01

Evaluation of eccentric mitral regurgitation (MR) remains extremely difficult and the role played by its etiology, functional or degenerative, is not well understood. This study aimed to demonstrate the value of three-dimensional transesophageal echocardiography (3DTEE) in the evaluation of eccentric MR identifying geometric differences in the vena contracta area between functional and degenerative etiologies. We studied 61 patients with eccentric MR (30 functional and 31 degenerative). Regurgitant orifice area was determined by the two-dimensional proximal isovelocity surface area (2DPISA) and the 3DTEE methods. The ratio between maximum and minimum lengths of the vena contracta was calculated in each patient. Effective regurgitant orifice area by the 2DPISA method was smaller than that estimated by 3DTEE (0.56±0.21 vs 0.72±0.25 cm 2 ). A better correlation between both methods was seen in degenerative mitral regurgitation (DMR; r=.83), with a mean underestimation of 8.2% by the 2DPISA method. A much worse correlation was found in functional mitral regurgitation (FMR; r=.39), where a mean underestimation by the 2DPISA method of 29.1% was observed. There was a more elongated and curved vena contracta in FMR compared to that in DMR (length ratio: 3.4±1.0 vs 2.2±0.7, P<.0001). Three-dimensional transesophageal echocardiography identifies a more elongated regurgitant orifice in eccentric FMR compared to that in eccentric DMR. This difference may explain the greater underestimation of effective regurgitant orifice area by the 2DPISA method in FMR. High-quality 3DTEE analysis of vena contracta area would be a highly recommended alternative. © 2017, Wiley Periodicals, Inc.

Highly compressible 3D periodic graphene aerogel microlattices

DOE PAGES

Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; ...

2015-04-22

Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young’s modulimore » of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Ultimately, adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.« less

Simulation of gas flow in micro-porous media with the regularized lattice Boltzmann method

DOE PAGES

Wang, Junjian; Kang, Qinjun; Wang, Yuzhu; ...

2017-06-01

One primary challenge for prediction of gas flow in the unconventional gas reservoir at the pore-scale such as shale and tight gas reservoirs is the geometric complexity of the micro-porous media. In this paper, a regularized multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is applied to analyze gas flow in 2-dimensional micro-porous medium reconstructed by quartet structure generation set (QSGS) on pore-scale. In this paper, the velocity distribution inside the porous structure is presented and analyzed, and the effects of the porosity and specific surface area on the rarefied gas flow and apparent permeability are examined and investigated. The simulation resultsmore » indicate that the gas exhibits different flow behaviours at various pressure conditions and the gas permeability is strongly related to the pressure. Finally, the increased porosity or the decreased specific surface area leads to the increase of the gas apparent permeability, and the gas flow is more sensitive to the pore morphological properties at low-pressure conditions.« less

Simulation of gas flow in micro-porous media with the regularized lattice Boltzmann method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Junjian; Kang, Qinjun; Wang, Yuzhu

One primary challenge for prediction of gas flow in the unconventional gas reservoir at the pore-scale such as shale and tight gas reservoirs is the geometric complexity of the micro-porous media. In this paper, a regularized multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is applied to analyze gas flow in 2-dimensional micro-porous medium reconstructed by quartet structure generation set (QSGS) on pore-scale. In this paper, the velocity distribution inside the porous structure is presented and analyzed, and the effects of the porosity and specific surface area on the rarefied gas flow and apparent permeability are examined and investigated. The simulation resultsmore » indicate that the gas exhibits different flow behaviours at various pressure conditions and the gas permeability is strongly related to the pressure. Finally, the increased porosity or the decreased specific surface area leads to the increase of the gas apparent permeability, and the gas flow is more sensitive to the pore morphological properties at low-pressure conditions.« less

Selective-area growth and controlled substrate coupling of transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Bersch, Brian M.; Eichfeld, Sarah M.; Lin, Yu-Chuan; Zhang, Kehao; Bhimanapati, Ganesh R.; Piasecki, Aleksander F.; Labella, Michael, III; Robinson, Joshua A.

2017-06-01

Developing a means for true bottom-up, selective-area growth of two-dimensional (2D) materials on device-ready substrates will enable synthesis in regions only where they are needed. Here, we demonstrate seed-free, site-specific nucleation of transition metal dichalcogenides (TMDs) with precise control over lateral growth by utilizing an ultra-thin polymeric surface functionalization capable of precluding nucleation and growth. This polymer functional layer (PFL) is derived from conventional photoresists and lithographic processing, and is compatible with multiple growth techniques, precursors (metal organics, solid-source) and TMDs. Additionally, we demonstrate that the substrate can play a major role in TMD transport properties. With proper TMD/substrate decoupling, top-gated field-effect transistors (FETs) fabricated with selectively-grown monolayer MoS2 channels are competitive with current reported MoS2 FETs. The work presented here demonstrates that substrate surface engineering is key to realizing precisely located and geometrically-defined 2D layers via unseeded chemical vapor deposition techniques.

Cloud cover determination in polar regions from satellite imagery

NASA Technical Reports Server (NTRS)

Barry, R. G.; Maslanik, J. A.; Key, J. R.

1987-01-01

A definition is undertaken of the spectral and spatial characteristics of clouds and surface conditions in the polar regions, and to the creation of calibrated, geometrically correct data sets suitable for quantitative analysis. Ways are explored in which this information can be applied to cloud classifications as new methods or as extensions to existing classification schemes. A methodology is developed that uses automated techniques to merge Advanced Very High Resolution Radiometer (AVHRR) and Scanning Multichannel Microwave Radiometer (SMMR) data, and to apply first-order calibration and zenith angle corrections to the AVHRR imagery. Cloud cover and surface types are manually interpreted, and manual methods are used to define relatively pure training areas to describe the textural and multispectral characteristics of clouds over several surface conditions. The effects of viewing angle and bidirectional reflectance differences are studied for several classes, and the effectiveness of some key components of existing classification schemes is tested.

3D reconstruction from multi-view VHR-satellite images in MicMac

NASA Astrophysics Data System (ADS)

Rupnik, Ewelina; Pierrot-Deseilligny, Marc; Delorme, Arthur

2018-05-01

This work addresses the generation of high quality digital surface models by fusing multiple depths maps calculated with the dense image matching method. The algorithm is adapted to very high resolution multi-view satellite images, and the main contributions of this work are in the multi-view fusion. The algorithm is insensitive to outliers, takes into account the matching quality indicators, handles non-correlated zones (e.g. occlusions), and is solved with a multi-directional dynamic programming approach. No geometric constraints (e.g. surface planarity) or auxiliary data in form of ground control points are required for its operation. Prior to the fusion procedures, the RPC geolocation parameters of all images are improved in a bundle block adjustment routine. The performance of the algorithm is evaluated on two VHR (Very High Resolution)-satellite image datasets (Pléiades, WorldView-3) revealing its good performance in reconstructing non-textured areas, repetitive patterns, and surface discontinuities.

On the Dynamical Regimes of Pattern-Accelerated Electroconvection.

PubMed

Davidson, Scott M; Wessling, Matthias; Mani, Ali

2016-03-03

Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes, and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states.

Dynamic Investigation of Triangles Inscribed in a Circle, Which Tend to an Equilateral Triangle

ERIC Educational Resources Information Center

Stupel, Moshe; Oxman, Victor; Sigler, Avi

2017-01-01

We present a geometrical investigation of the process of creating an infinite sequence of triangles inscribed in a circle, whose areas, perimeters and lengths of radii of the inscribed circles tend to a limit in a monotonous manner. First, using geometrical software, we investigate four theorems that represent interesting geometrical properties,…

Traits drive global wood decomposition rates more than climate.

PubMed

Hu, Zhenhong; Michaletz, Sean T; Johnson, Daniel J; McDowell, Nate G; Huang, Zhiqun; Zhou, Xuhui; Xu, Chonggang

2018-06-14

Wood decomposition is a major component of the global carbon cycle. Decomposition rates vary across climate gradients, which is thought to reflect the effects of temperature and moisture on the metabolic kinetics of decomposers. However, decomposition rates also vary with wood traits, which may reflect the influence of stoichiometry on decomposer metabolism as well as geometry relating the surface areas that decomposers colonize with the volumes they consume. In this paper, we combined metabolic and geometric scaling theories to formalize hypotheses regarding the drivers of wood decomposition rates, and assessed these hypotheses using a global compilation of data on climate, wood traits, and wood decomposition rates. Our results are consistent with predictions from both metabolic and geometric scaling theories. Approximately half of the global variation in decomposition rates was explained by wood traits (nitrogen content and diameter), while only a fifth was explained by climate variables (air temperature, precipitation, and relative humidity). These results indicate that global variation in wood decomposition rates is best explained by stoichiometric and geometric wood traits. Our findings suggest that inclusion of wood traits in global carbon cycle models can improve predictions of carbon fluxes from wood decomposition. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

3-D Geometric Modeling for the 21st Century.

ERIC Educational Resources Information Center

Ault, Holly K.

1999-01-01

Describes new geometric computer models used in contemporary computer-aided design (CAD) software including wire frame, surface, solid, and parametric models. Reviews their use in engineering design and discusses the impact of these new technologies on the engineering design graphics curriculum. (Author/CCM)

Geometric interpretations for resonances of plasmonic nanoparticles

NASA Astrophysics Data System (ADS)

Liu, Wei; Oulton, Rupert F.; Kivshar, Yuri S.

2015-07-01

The field of plasmonics can be roughly categorized into two branches: surface plasmon polaritons (SPPs) propagating in waveguides and localized surface plasmons (LSPs) supported by scattering particles. Investigations along these two directions usually employ different approaches, resulting in more or less a dogma that the two branches progress almost independently of each other, with few interactions. Here in this work we interpret LSPs from a Bohr model based geometric perspective relying on SPPs, thus establishing a connection between these two sub-fields. Besides the clear explanations of conventional scattering features of plasmonic nanoparticles, based on this geometric model we further demonstrate other anomalous scattering features (higher order modes supported at lower frequencies, and blueshift of the resonance with increasing particle sizes) and multiple electric resonances of the same order supported at different frequencies, which have been revealed to originate from backward SPP modes and multiple dispersion bands supported in the corresponding plasmonic waveguides, respectively. Inspired by this geometric model, it is also shown that, through solely geometric tuning, the absorption of each LSP resonance can be maximized to reach the single channel absorption limit, provided that the scattering and absorption rates are tuned to be equal.

Geometrical considerations in analyzing isotropic or anisotropic surface reflections.

PubMed

Simonot, Lionel; Obein, Gael

2007-05-10

The bidirectional reflectance distribution function (BRDF) represents the evolution of the reflectance with the directions of incidence and observation. Today BRDF measurements are increasingly applied and have become important to the study of the appearance of surfaces. The representation and the analysis of BRDF data are discussed, and the distortions caused by the traditional representation of the BRDF in a Fourier plane are pointed out and illustrated for two theoretical cases: an isotropic surface and a brushed surface. These considerations will help characterize either the specular peak width of an isotropic rough surface or the main directions of the light scattered by an anisotropic rough surface without misinterpretations. Finally, what is believed to be a new space is suggested for the representation of the BRDF, which avoids the geometrical deformations and in numerous cases is more convenient for BRDF analysis.

Geometric Continuity: A Parametrization Independent Measure of Continuity for Computer Aided Geometric Design

DTIC Science & Technology

1985-08-01

in a. typography system, the surface of a. ship hull, or the skin of a.n airplane. To define objects such as these, higher order curve a.nd surface...rate). Thus, a parametrization contains infor- mation about the geometry (the shape or image of the curve), the orientation, and the rate. Figure 2.3...2.3. Each of the curves above has the same image ; they only differ in orientation and rate. Orientation is indicated by arrowheads and rate is

Polishing mechanism of light-initiated dental composite: Geometric optics approach.

PubMed

Chiang, Yu-Chih; Lai, Eddie Hsiang-Hua; Kunzelmann, Karl-Heinz

2016-12-01

For light-initiated dental hybrid composites, reinforcing particles are much stiffer than the matrix, which makes the surface rugged after inadequate polish and favors bacterial adhesion and biofilm redevelopment. The aim of the study was to investigate the polishing mechanism via the geometric optics approach. We defined the polishing abilities of six instruments using the obtained gloss values through the geometric optics approach (micro-Tri-gloss with 20°, 60°, and 85° measurement angles). The surface texture was validated using a field emission scanning electron microscope (FE-SEM). Based on the gloss values, we sorted polishing tools into three abrasive levels, and proposed polishing sequences to test the hypothesis that similar abrasive levels would leave equivalent gloss levels on dental composites. The three proposed, tested polishing sequences included: S1, Sof-Lex XT coarse disc, Sof-Lex XT fine disc, and OccluBrush; S2, Sof-Lex XT coarse disc, Prisma Gloss polishing paste, and OccluBrush; and S3, Sof-Lex XT coarse disc, Enhance finishing cups, and OccluBrush. S1 demonstrated significantly higher surface gloss than the other procedures (p < 0.05). The surface textures (FE-SEM micrographs) correlated well with the obtained gloss values. Nominally similar abrasive abilities did not result in equivalent polish levels, indicating that the polishing tools must be evaluated and cannot be judged based on their compositions or abrasive sizes. The geometric optic approach is an efficient and nondestructive method to characterize the polished surface of dental composites. Copyright © 2015. Published by Elsevier B.V.

Effect of Coatings on the Uptake Rate and HONO Yield in Heterogeneous Reaction of Soot with NO2

NASA Astrophysics Data System (ADS)

Cruz-Quiñones, M.; Khalizov, A. F.; Zhang, R.

2009-12-01

Heterogeneous reaction of nitrogen dioxide on carbon soot aerosols has been suggested as a possible source of nighttime nitrous acid (HONO) in atmosphere boundary layer. Available laboratory data show significant variability in the measured reaction probabilities and HONO yields, making it difficult to asses the atmospheric significance of this process. Moreover, little is known of how aging of soot aerosol through internal mixing with other atmospheric trace constituents will affect the heterogeneous reactivity and HONO production. In this work, the heterogeneous reaction of NO2 on fresh and aged soot films leading to HONO formation was studied through a series of kinetic uptake experiments and HONO yield measurements. Soot samples were prepared by incomplete combustion of propane and kerosene fuels under lean and rich flame conditions. Experiments were performed in a low-pressure, fast-flow reactor coupled to a chemical ionization mass spectrometer (CIMS), using atmospheric-level NO2 concentrations. Heterogeneous uptake coefficients, γ(geom) and γ(BET), were calculated using geometric and internal BET soot surface areas, respectively. The uptake coefficient and the HONO yield depend on the type of fuel and combustion regime and are the highest for soot samples prepared using rich kerosene flame. Although, the internal surface area of soot measured by BET method is a factor of 50 to 500 larger than the geometric surface area, only the top soot layers are involved in heterogeneous reaction with NO2 as follows from the observed weak dependence of γ(geom) and decrease in γ(BET) with increasing sample mass. Heating the soot samples before exposure to NO2 increases the BET surface area, the HONO yield, and the NO2 uptake coefficient due to the removal of the organic fraction from the soot backbone that unblocks active sites and makes them accessible for physical adsorption and chemical reactions. Our results support the oxidation-reduction mechanism involving adsorptive and reactive centers on soot surface where NO2 is converted into HONO and other products. Coating the soot surface by different materials to simulate atmospheric aging has a strong impact on the reactivity of soot toward NO2. Sulfuric acid coating reduces the uptake coefficient and HONO production by physically blocking the soot active sites and initiating decomposition of HONO in the aqueous acid layer. Furthermore, the HONO yield can be reduced to zero after exposure to elevated relative humidity or partially restored when sulfuric acid is removed by heating. Coatings made of glutaric and succinic acids increase HONO yields and NO2 uptake coefficients, similarly as in the case of pre-heated soot samples. We propose that the organic acids change the top layer morphology, opening up the pores and making the internal soot surface more accessible for heterogeneous interaction with NO2. The implications of our study regarding the contribution of freshly emitted and aged soot aerosols to nighttime HONO production will be discussed.

A basis for the analysis of surface geometry of spiral bevel gears

NASA Technical Reports Server (NTRS)

Huston, R. L.; Coy, J. J.

1983-01-01

Geometrical procedures helpful in the fundamental studies of the surface geometry of spiral bevel gears are summarized. These procedures are based upon: (1) fundamental gear geometry and kinematics as exposited by Buckingham, et al; (2) formulas developed from differential geometry; and (3) geometrical concepts developed in recent papers and reports on spiral bevel gear surface geometry. Procedures which characterize the geometry so that the surface parametric equations, the principal radii of curvature, and the meshing kinematics are systematically determined are emphasized. Initially, the focus in on theoretical, logarithmic spiral bevel gears as defined by Buckingham. The gears, however, are difficult to fabricate and are sometimes considered to be too straight. Circular-cut spiral bevel gears are an alternative to this. Surface characteristics of crown circular cut gears are analyzed.

The correlation between structural properties, geometrical features, and photoactivity of freestanding TiO2 nanotubes in comparative degradation of 2,4-dichlorophenol and methylene blue

NASA Astrophysics Data System (ADS)

Vahabzadeh Pasikhani, Javad; Gilani, Neda; Ebrahimian Pirbazari, Azadeh

2018-02-01

Freestanding TiO2 nanotubes (FSNTs) with various physical dimensions were fabricated by two-step anodization process with different voltages and anodization times. The detachment method employed in this study involved voltage reduction at the end of the second step and ultrasonic chemical treatment. The results demonstrated that this detachment method is a beneficial technique to create thin open-mouthed and closed-end FSNTs (with lengths of 6-14 μm). Moreover, the influences of anodization conditions on photocatalytic activity, structural properties and geometrical features of FSNTs in comparative degradation of two non-colored (2,4-dichlorophenol) and colored (methylene blue) pollutants were investigated. Findings revealed that the quantity of the photocatalyst utilized is an effective parameter and using the optimum weight (10 mg/100 ml of 2,4-dichlorophenol) could increase the efficiency of the process up to 21%. Further, the results demonstrated that if equal optimum weights of FSNTs are chosen, decreases in voltage and anodization time significantly influence the structural properties, geometrical features, and photodegradation efficiency. The enhancement achieved in the degradation of both 2,4-dichlorophenol and methylene blue using the nanotubes with the shortest diameter (54 nm) and length (6.5 μm), which possess the lowest porosity (0.5) and also the highest surface area (0.53 m2 g-1), nanotubes’ density (19 cm2 cm-2) and wall thickness to length ratio (2). In addition, the results obtained indicated that the degradation reactions follow first-order kinetics in the degradation of the both pollutants. The apparent degradation rate constant of methylene blue was approximately 1.2 times greater than of the 2,4-dichlorophenol due to the negative charge of the nanotubes’ surface and electrostatic adsorptions.

Reversal of the asymmetry in a cylindrical coaxial capacitively coupled Ar/Cl 2 plasma

DOE PAGES

Upadhyay, Janardan; Im, Do; Popović, Svetozar; ...

2015-10-08

The reduction of the asymmetry in the plasma sheath voltages of a cylindrical coaxial capacitively coupled plasma is crucial for efficient surface modification of the inner surfaces of concave three-dimensional structures, including superconducting radio frequency cavities. One critical asymmetry effect is the negative dc self-bias, formed across the inner electrode plasma sheath due to its lower surface area compared to the outer electrode. The effect on the self-bias potential with the surface enhancement by geometric modification on the inner electrode structure is studied. The shapes of the inner electrodes are chosen as cylindrical tube, large and small pitch bellows, andmore » disc-loaded corrugated structure (DLCS). The dc self-bias measurements for all these shapes were taken at different process parameters in Ar/Cl 2 discharge. Lastly, the reversal of the negative dc self-bias potential to become positive for a DLCS inner electrode was observed and the best etch rate is achieved due to the reduction in plasma asymmetry.« less

Air formaldehyde and solvent concentrations during surface coating with acid-curing lacquers and paints in the woodworking and furniture industry.

PubMed

Thorud, Syvert; Gjolstad, Merete; Ellingsen, Dag G; Molander, Paal

2005-06-01

An investigation of contemporary exposure to formaldehyde and organic solvents has been carried out during surface coating with acid-curing lacquers and paints in the Norwegian woodworking and furniture industry over a period of 3 years. The investigation covered 27 factories of different sizes and with different types of production, and totally 557 parallel formaldehyde and solvent samples were collected. The formaldehyde concentration (geometric mean) was 0.15 ppm (range 0.01-1.48 ppm) with about 10% of the samples exceeding the Norwegian occupational exposure limit of 0.5 ppm. The solvent concentration as additive effect (geometric mean) was 0.13 (range 0.0004-5.08) and about 5% of the samples exceeded the Norwegian occupational exposure limit. The most frequently occurring solvents from acid-curing lacquers were n-butyl acetate, ethanol, ethyl acetate and 1-butanol, which were found in 88-98% of the samples. Toluene, n-butyl acetate and 1-butanol were the only solvents with maximum concentrations exceeding their respective occupational exposure limits. Curtain painting machine operators were exposed to the highest concentrations of both formaldehyde (geometric mean 0.51 ppm, range 0.08-1.48 ppm) and organic solvents (additive effect, geometric mean 1.18, range 0.02-5.08). Other painting application work tasks such as automatic and manual spray-painting, manual painting and dip painting, showed on average considerably lower concentrations of both formaldehyde (geometric means 0.07-0.16 ppm) and organic solvents (additive effect, geometric mean 0.02-0.18). Non-painting work tasks also displayed moderate concentrations of formaldehyde (geometric means 0.11-0.17 ppm) and organic solvents (additive effect, geometric mean 0.04-0.07).

Wave optics simulation of statistically rough surface scatter

NASA Astrophysics Data System (ADS)

Lanari, Ann M.; Butler, Samuel D.; Marciniak, Michael; Spencer, Mark F.

2017-09-01

The bidirectional reflectance distribution function (BRDF) describes optical scatter from surfaces by relating the incident irradiance to the exiting radiance over the entire hemisphere. Laboratory verification of BRDF models and experimentally populated BRDF databases are hampered by sparsity of monochromatic sources and ability to statistically control the surface features. Numerical methods are able to control surface features, have wavelength agility, and via Fourier methods of wave propagation, may be used to fill the knowledge gap. Monte-Carlo techniques, adapted from turbulence simulations, generate Gaussian distributed and correlated surfaces with an area of 1 cm2 , RMS surface height of 2.5 μm, and correlation length of 100 μm. The surface is centered inside a Kirchhoff absorbing boundary with an area of 16 cm2 to prevent wrap around aliasing in the far field. These surfaces are uniformly illuminated at normal incidence with a unit amplitude plane-wave varying in wavelength from 3 μm to 5 μm. The resultant scatter is propagated to a detector in the far field utilizing multi-step Fresnel Convolution and observed at angles from -2 μrad to 2 μrad. The far field scatter is compared to both a physical wave optics BRDF model (Modified Beckmann Kirchhoff) and two microfacet BRDF Models (Priest, and Cook-Torrance). Modified Beckmann Kirchhoff, which accounts for diffraction, is consistent with simulated scatter for multiple wavelengths for RMS surface heights greater than λ/2. The microfacet models, which assume geometric optics, are less consistent across wavelengths. Both model types over predict far field scatter width for RMS surface heights less than λ/2.

Noise characteristics of upper surface blown configurations. Experimental program and results

NASA Technical Reports Server (NTRS)

Brown, W. H.; Searle, N.; Blakney, D. F.; Pennock, A. P.; Gibson, J. S.

1977-01-01

An experimental data base was developed from the model upper surface blowing (USB) propulsive lift system hardware. While the emphasis was on far field noise data, a considerable amount of relevant flow field data were also obtained. The data were derived from experiments in four different facilities resulting in: (1) small scale static flow field data; (2) small scale static noise data; (3) small scale simulated forward speed noise and load data; and (4) limited larger-scale static noise flow field and load data. All of the small scale tests used the same USB flap parts. Operational and geometrical variables covered in the test program included jet velocity, nozzle shape, nozzle area, nozzle impingement angle, nozzle vertical and horizontal location, flap length, flap deflection angle, and flap radius of curvature.

Geometrically induced surface polaritons in planar nanostructured metallic cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davids, P. S.; Intravia, F; Dalvit, Diego A.

2014-01-14

We examine the modal structure and dispersion of periodically nanostructured planar metallic cavities within the scattering matrix formulation. By nanostructuring a metallic grating in a planar cavity, artificial surface excitations or spoof plasmon modes are induced with dispersion determined by the periodicity and geometric characteristics of the grating. These spoof surface plasmon modes are shown to give rise to new cavity polaritonic modes at short mirror separations that modify the density of modes in nanostructured cavities. The increased modal density of states form cavity polarirons have a large impact on the fluctuation induced electromagnetic forces and enhanced hear transfer atmore » short separations.« less

Arc Jet Screening Tests Of Phase 1 Orbiter Tile Repair Materials and Uncoated RSI High Temperature Emittance Measurements

NASA Technical Reports Server (NTRS)

DelPapa, Steven V.

2005-01-01

Arc jet tests of candidate tile repair materials and baseline Orbiter uncoated reusable surface insulation (RSI) were performed in the Johnson Space Center's (JSC) Atmospheric Reentry Materials and Structures Evaluation Facility (ARMSEF) from June 23, 2003, through August 19, 2003. These tests were performed to screen candidate tile repair materials by verifying the high temperature performance and determining the thermal stability. In addition, tests to determine the surface emissivity at high temperatures and the geometric shrinkage of bare RSI were performed. In addition, tests were performed to determine the surface emissivity at high temperatures and the geometric shrinkage of uncoated RSI.

Three-dimensional aerodynamic shape optimization of supersonic delta wings

NASA Technical Reports Server (NTRS)

Burgreen, Greg W.; Baysal, Oktay

1994-01-01

A recently developed three-dimensional aerodynamic shape optimization procedure AeSOP(sub 3D) is described. This procedure incorporates some of the most promising concepts from the area of computational aerodynamic analysis and design, specifically, discrete sensitivity analysis, a fully implicit 3D Computational Fluid Dynamics (CFD) methodology, and 3D Bezier-Bernstein surface parameterizations. The new procedure is demonstrated in the preliminary design of supersonic delta wings. Starting from a symmetric clipped delta wing geometry, a Mach 1.62 asymmetric delta wing and two Mach 1. 5 cranked delta wings were designed subject to various aerodynamic and geometric constraints.

Polychromatic Microdiffraction Analysis of Defect Self-Organization in Shock Deformed Single Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barabash, Rozaliya; Ice, Gene E; Liu, Wenjun

A spatially resolved X-ray diffraction method - with a submicron 3D resolution together with SEM and OIM analysis are applied to understand the arrangements of voids, geometrically necessary dislocations and strain gradient distributions in samples of Al (1 2 3) and Cu (0 0 1) single crystals shocked to incipient spallation fracture. We describe how geometrically necessary dislocations and the effective strain gradient alter white beam Laue patterns of the shocked materials. Several distinct structural zones are observed at different depths under the impact surface. The density of geometrically necessary dislocations (GNDs) is extremely high near the impact and backmore » surface of the shock recovered crystals. The spall region is characterized by a large density of mesoscale voids and GNDs. The spall region is separated from the impact and back surfaces by compressed regions with high total dislocation density but lower GNDs density. Self-organization of shear bands is observed in the shock recovered Cu single crystal.« less

Geometric Detection Algorithms for Cavities on Protein Surfaces in Molecular Graphics: A Survey

PubMed Central

Simões, Tiago; Lopes, Daniel; Dias, Sérgio; Fernandes, Francisco; Pereira, João; Jorge, Joaquim; Bajaj, Chandrajit; Gomes, Abel

2017-01-01

Detecting and analyzing protein cavities provides significant information about active sites for biological processes (e.g., protein-protein or protein-ligand binding) in molecular graphics and modeling. Using the three-dimensional structure of a given protein (i.e., atom types and their locations in 3D) as retrieved from a PDB (Protein Data Bank) file, it is now computationally viable to determine a description of these cavities. Such cavities correspond to pockets, clefts, invaginations, voids, tunnels, channels, and grooves on the surface of a given protein. In this work, we survey the literature on protein cavity computation and classify algorithmic approaches into three categories: evolution-based, energy-based, and geometry-based. Our survey focuses on geometric algorithms, whose taxonomy is extended to include not only sphere-, grid-, and tessellation-based methods, but also surface-based, hybrid geometric, consensus, and time-varying methods. Finally, we detail those techniques that have been customized for GPU (Graphics Processing Unit) computing. PMID:29520122

U-folds as K3 fibrations

NASA Astrophysics Data System (ADS)

Braun, Andreas P.; Fucito, Francesco; Morales, Jose Francisco

2013-10-01

We study four-dimensional flux vacua describing intrinsic non- perturbative systems of 3 and 7 branes in type IIB string theory. The solutions are described as compactifications of a G(ravity) theory on a Calabi Yau threefold which consists of a fibration of an auxiliary K3 surface over an S 2 base. In the spirit of F-theory, the complex structure of the K3 surface varying over the base codifies the details of the fluxes, the dilaton and the warp factors in type IIB string theory. We discuss in detail some simple examples of geometric and non-geometric solutions where the precise flux/geometry dictionary can be explicitly worked out. In particular, we describe non-geometric T-fold solutions exhibiting non-trivial T-duality monodromies exchanging 3- and 7-branes.

Bias Correction of MODIS AOD using DragonNET to obtain improved estimation of PM2.5

NASA Astrophysics Data System (ADS)

Gross, B.; Malakar, N. K.; Atia, A.; Moshary, F.; Ahmed, S. A.; Oo, M. M.

2014-12-01

MODIS AOD retreivals using the Dark Target algorithm is strongly affected by the underlying surface reflection properties. In particular, the operational algorithms make use of surface parameterizations trained on global datasets and therefore do not account properly for urban surface differences. This parameterization continues to show an underestimation of the surface reflection which results in a general over-biasing in AOD retrievals. Recent results using the Dragon-Network datasets as well as high resolution retrievals in the NYC area illustrate that this is even more significant at the newest C006 3 km retrievals. In the past, we used AERONET observation in the City College to obtain bias-corrected AOD, but the homogeneity assumptions using only one site for the region is clearly an issue. On the other hand, DragonNET observations provide ample opportunities to obtain better tuning the surface corrections while also providing better statistical validation. In this study we present a neural network method to obtain bias correction of the MODIS AOD using multiple factors including surface reflectivity at 2130nm, sun-view geometrical factors and land-class information. These corrected AOD's are then used together with additional WRF meteorological factors to improve estimates of PM2.5. Efforts to explore the portability to other urban areas will be discussed. In addition, annual surface ratio maps will be developed illustrating that among the land classes, the urban pixels constitute the largest deviations from the operational model.

Fullerenes and disk-fullerenes

NASA Astrophysics Data System (ADS)

Deza, M.; Dutour Sikirić, M.; Shtogrin, M. I.

2013-08-01

A geometric fullerene, or simply a fullerene, is the surface of a simple closed convex 3-dimensional polyhedron with only 5- and 6-gonal faces. Fullerenes are geometric models for chemical fullerenes, which form an important class of organic molecules. These molecules have been studied intensively in chemistry, physics, crystallography, and so on, and their study has led to the appearance of a vast literature on fullerenes in mathematical chemistry and combinatorial and applied geometry. In particular, several generalizations of the notion of a fullerene have been given, aiming at various applications. Here a new generalization of this notion is proposed: an n-disk-fullerene. It is obtained from the surface of a closed convex 3-dimensional polyhedron which has one n-gonal face and all other faces 5- and 6-gonal, by removing the n-gonal face. Only 5- and 6-disk-fullerenes correspond to geometric fullerenes. The notion of a geometric fullerene is therefore generalized from spheres to compact simply connected two-dimensional manifolds with boundary. A two-dimensional surface is said to be unshrinkable if it does not contain belts, that is, simple cycles consisting of 6-gons each of which has two neighbours adjacent at a pair of opposite edges. Shrinkability of fullerenes and n-disk-fullerenes is investigated. Bibliography: 87 titles.

Enhanced Seismic Imaging of Turbidite Deposits in Chicontepec Basin, Mexico

NASA Astrophysics Data System (ADS)

Chavez-Perez, S.; Vargas-Meleza, L.

2007-05-01

We test, as postprocessing tools, a combination of migration deconvolution and geometric attributes to attack the complex problems of reflector resolution and detection in migrated seismic volumes. Migration deconvolution has been empirically shown to be an effective approach for enhancing the illumination of migrated images, which are blurred versions of the subsurface reflectivity distribution, by decreasing imaging artifacts, improving spatial resolution, and alleviating acquisition footprint problems. We utilize migration deconvolution as a means to improve the quality and resolution of 3D prestack time migrated results from Chicontepec basin, Mexico, a very relevant portion of the producing onshore sector of Pemex, the Mexican petroleum company. Seismic data covers the Agua Fria, Coapechaca, and Tajin fields. It exhibits acquisition footprint problems, migration artifacts and a severe lack of resolution in the target area, where turbidite deposits need to be characterized between major erosional surfaces. Vertical resolution is about 35 m and the main hydrocarbon plays are turbidite beds no more than 60 m thick. We also employ geometric attributes (e.g., coherent energy and curvature), computed after migration deconvolution, to detect and map out depositional features, and help design development wells in the area. Results of this workflow show imaging enhancement and allow us to identify meandering channels and individual sand bodies, previously undistinguishable in the original seismic migrated images.

Heat transfer and material temperature conditions in the leading edge area of impingement-cooled turbine vanes

NASA Astrophysics Data System (ADS)

Berg, H. P.; Pfaff, K.; Hennecke, D. K.

The resultant effects on the cooling effectiveness at the leading edge area of an impingement-cooled turbine vane by varying certain geometrical parameters is described with reference to local internal heat transfer coefficients determined from experiment and temperature calculations. The local heat transfer on the cooling-air side is determined experimentally with the aid of the analogy between heat- and mass transfer. The impingement cooling is provided from an inserted sheet-metal containing a single row of holes. The Reynolds Number and several of the cooling geometry parameters were varied. The results demonstrate the high local resolution of the method of measurement, which allows improved analytical treatment of the leading-edge cooling configuration. These experiments also point to the necessity of not always performing model tests under idealized conditions. This becomes very clear in the case of the tests performed on an application-oriented impingement-cooling configuration like that often encountered in engine manufacture. In conclusion, as an example, temperature calculations are employed to demonstrate the effect on the cooling effectiveness of varying the distances between insert and inner surface of the leading edge. It shows how the effectiveness of the leading edge cooling can be increased by simple geometrical measures, which results in a considerable improvement in service life.

Quantifying sub-pixel urban impervious surface through fusion of optical and inSAR imagery

USGS Publications Warehouse

Yang, L.; Jiang, L.; Lin, H.; Liao, M.

2009-01-01

In this study, we explored the potential to improve urban impervious surface modeling and mapping with the synergistic use of optical and Interferometric Synthetic Aperture Radar (InSAR) imagery. We used a Classification and Regression Tree (CART)-based approach to test the feasibility and accuracy of quantifying Impervious Surface Percentage (ISP) using four spectral bands of SPOT 5 high-resolution geometric (HRG) imagery and three parameters derived from the European Remote Sensing (ERS)-2 Single Look Complex (SLC) SAR image pair. Validated by an independent ISP reference dataset derived from the 33 cm-resolution digital aerial photographs, results show that the addition of InSAR data reduced the ISP modeling error rate from 15.5% to 12.9% and increased the correlation coefficient from 0.71 to 0.77. Spatially, the improvement is especially noted in areas of vacant land and bare ground, which were incorrectly mapped as urban impervious surfaces when using the optical remote sensing data. In addition, the accuracy of ISP prediction using InSAR images alone is only marginally less than that obtained by using SPOT imagery. The finding indicates the potential of using InSAR data for frequent monitoring of urban settings located in cloud-prone areas.

A computational method for sharp interface advection

PubMed Central

Bredmose, Henrik; Jasak, Hrvoje

2016-01-01

We devise a numerical method for passive advection of a surface, such as the interface between two incompressible fluids, across a computational mesh. The method is called isoAdvector, and is developed for general meshes consisting of arbitrary polyhedral cells. The algorithm is based on the volume of fluid (VOF) idea of calculating the volume of one of the fluids transported across the mesh faces during a time step. The novelty of the isoAdvector concept consists of two parts. First, we exploit an isosurface concept for modelling the interface inside cells in a geometric surface reconstruction step. Second, from the reconstructed surface, we model the motion of the face–interface intersection line for a general polygonal face to obtain the time evolution within a time step of the submerged face area. Integrating this submerged area over the time step leads to an accurate estimate for the total volume of fluid transported across the face. The method was tested on simple two-dimensional and three-dimensional interface advection problems on both structured and unstructured meshes. The results are very satisfactory in terms of volume conservation, boundedness, surface sharpness and efficiency. The isoAdvector method was implemented as an OpenFOAM® extension and is published as open source. PMID:28018619

Effect of geometric configuration on the electrocaloric properties of nanoscale ferroelectric materials

NASA Astrophysics Data System (ADS)

Hou, Xu; Li, Huiyu; Shimada, Takahiro; Kitamura, Takayuki; Wang, Jie

2018-03-01

The electrocaloric properties of ferroelectrics are highly dependent on the domain structure in the materials. For nanoscale ferroelectric materials, the domain structure is greatly influenced by the geometric configuration of the system. Using a real-space phase field model based on the Ginzburg-Landau theory, we investigate the effect of geometric configurations on the electrocaloric properties of nanoscale ferroelectric materials. The ferroelectric hysteresis loops under different temperatures are simulated for the ferroelectric nano-metamaterials with square, honeycomb, and triangular Archimedean geometric configurations. The adiabatic temperature changes (ATCs) for three ferroelectric nano-metamaterials under different electric fields are calculated from the Maxwell relationship based on the hysteresis loops. It is found that the honeycomb specimen exhibits the largest ATC of Δ T = 4.3 °C under a field of 391.8 kV/cm among three geometric configurations, whereas the square specimen has the smallest ATC of Δ T = 2.7 °C under the same electric field. The different electrocaloric properties for three geometric configurations stem from the different domain structures. There are more free surfaces perpendicular to the electric field in the square specimen than the other two specimens, which restrict more polarizations perpendicular to the electric field, resulting in a small ATC. Due to the absence of free surfaces perpendicular to the electric field in the honeycomb specimen, the change of polarization with temperature in the direction of the electric field is more easy and thus leads to a large ATC. The present work suggests a novel approach to obtain the tunable electrocaloric properties in nanoscale ferroelectric materials by designing their geometric configurations.

Static internal performance of single-expansion-ramp nozzles with various combinations of internal geometric parameters

NASA Technical Reports Server (NTRS)

Re, R. J.; Leavitt, L. D.

1984-01-01

The effects of five geometric design parameters on the internal performance of single-expansion-ramp nozzles were investigated at nozzle pressure ratios up to 10 in the static-test facility of the Langley 16-Foot Transonic Tunnel. The geometric variables on the expansion-ramp surface of the upper flap consisted of ramp chordal angle, ramp length, and initial ramp angle. On the lower flap, the geometric variables consisted of flap angle and flap length. Both internal performance and static-pressure distributions on the centerlines of the upper and lower flaps were obtained for all 43 nozzle configurations tested.

Geometrical force constraint method for vessel and x-ray angiogram simulation.

PubMed

Song, Shuang; Yang, Jian; Fan, Jingfan; Cong, Weijian; Ai, Danni; Zhao, Yitian; Wang, Yongtian

2016-01-01

This study proposes a novel geometrical force constraint method for 3-D vasculature modeling and angiographic image simulation. For this method, space filling force, gravitational force, and topological preserving force are proposed and combined for the optimization of the topology of the vascular structure. The surface covering force and surface adhesion force are constructed to drive the growth of the vasculature on any surface. According to the combination effects of the topological and surface adhering forces, a realistic vasculature can be effectively simulated on any surface. The image projection of the generated 3-D vascular structures is simulated according to the perspective projection and energy attenuation principles of X-rays. Finally, the simulated projection vasculature is fused with a predefined angiographic mask image to generate a realistic angiogram. The proposed method is evaluated on a CT image and three generally utilized surfaces. The results fully demonstrate the effectiveness and robustness of the proposed method.

Density Functional Theory Study of Leaching Performance of Different Acids on Pyrochlore (100) Surface

NASA Astrophysics Data System (ADS)

Yang, Xiuli; Fang, Qing; Ouyang, Hui

2018-04-01

Pyrochlore leaching using hydrofluoric, sulfuric, and hydrochloric acids has been studied via experimental methods for years, but the interactions between niobium atoms on the pyrochlore surface and different acids have not been investigated. In this work, first-principles calculations based on density functional theory were used to elucidate the leaching performance of these three acids from the viewpoint of geometrical and electronic structures. The calculation results indicate that sulfate, chloride, and fluoride anions influence the geometric structure of pyrochlore (100) to different extents, decreasing in the order: sulfate, fluoride, chloride. Orbitals of O1 and O2 atoms of sulfate hybridized with those of surface niobium atom. Fluorine orbitals hybridized with those of surface niobium atoms. However, no obvious overlap exists between any orbitals of chlorine and surface niobium, revealing that chlorine does not interact chemically with surface niobium atoms.

Density Functional Theory Study of Leaching Performance of Different Acids on Pyrochlore (100) Surface

NASA Astrophysics Data System (ADS)

Yang, Xiuli; Fang, Qing; Ouyang, Hui

2018-06-01

Pyrochlore leaching using hydrofluoric, sulfuric, and hydrochloric acids has been studied via experimental methods for years, but the interactions between niobium atoms on the pyrochlore surface and different acids have not been investigated. In this work, first-principles calculations based on density functional theory were used to elucidate the leaching performance of these three acids from the viewpoint of geometrical and electronic structures. The calculation results indicate that sulfate, chloride, and fluoride anions influence the geometric structure of pyrochlore (100) to different extents, decreasing in the order: sulfate, fluoride, chloride. Orbitals of O1 and O2 atoms of sulfate hybridized with those of surface niobium atom. Fluorine orbitals hybridized with those of surface niobium atoms. However, no obvious overlap exists between any orbitals of chlorine and surface niobium, revealing that chlorine does not interact chemically with surface niobium atoms.

Geometric state space uncertainty as a new type of uncertainty addressing disparity in ';emergent properties' between real and modeled systems

NASA Astrophysics Data System (ADS)

Montero, J. T.; Lintz, H. E.; Sharp, D.

2013-12-01

Do emergent properties that result from models of complex systems match emergent properties from real systems? This question targets a type of uncertainty that we argue requires more attention in system modeling and validation efforts. We define an ';emergent property' to be an attribute or behavior of a modeled or real system that can be surprising or unpredictable and result from complex interactions among the components of a system. For example, thresholds are common across diverse systems and scales and can represent emergent system behavior that is difficult to predict. Thresholds or other types of emergent system behavior can be characterized by their geometry in state space (where state space is the space containing the set of all states of a dynamic system). One way to expedite our growing mechanistic understanding of how emergent properties emerge from complex systems is to compare the geometry of surfaces in state space between real and modeled systems. Here, we present an index (threshold strength) that can quantify a geometric attribute of a surface in state space. We operationally define threshold strength as how strongly a surface in state space resembles a step or an abrupt transition between two system states. First, we validated the index for application in greater than three dimensions of state space using simulated data. Then, we demonstrated application of the index in measuring geometric state space uncertainty between a real system and a deterministic, modeled system. In particular, we looked at geometric space uncertainty between climate behavior in 20th century and modeled climate behavior simulated by global climate models (GCMs) in the Coupled Model Intercomparison Project phase 5 (CMIP5). Surfaces from the climate models came from running the models over the same domain as the real data. We also created response surfaces from a real, climate data based on an empirical model that produces a geometric surface of predicted values in state space. We used a kernel regression method designed to capture the geometry of real data pattern without imposing shape assumptions a priori on the data; this kernel regression method is known as Non-parametric Multiplicative Regression (NPMR). We found that quantifying and comparing a geometric attribute in more than three dimensions of state space can discern whether the emergent nature of complex interactions in modeled systems matches that of real systems. Further, this method has potentially wider application in contexts where searching for abrupt change or ';action' in any hyperspace is desired.

Integration of LIDAR Data Into a Municipal GIS to Study Solar Radiation

NASA Astrophysics Data System (ADS)

Africani, P.; Bitelli, G.; Lambertini, A.; Minghetti, A.; Paselli, E.

2013-04-01

Identifying the right roofs to install solar panels inside a urban area is crucial for both private citizens and the whole local population. The aim is not easy because a lot of consideration must be made: insolation, orientation of the surface, size of the surface, shading due to topography, shading due to taller buildings next the surface, shading due to taller vegetation and other possible problems typical of urban areas like the presence of chimneys. Accuracy of data related to the analyzed surfaces is indeed fundamental, and also the detail of geometric models used to represent buildings and their roofs. The complexity that these roofs can reach is elevated. This work uses LiDAR data to obtain, with a semi-automatic technique, the full geometry of each roof part complementing the pre-existing building data in the municipal cartography. With this data is possible to evaluate the placement of solar panels on roofs of a whole city analyzing the solar potential of each building in detail. Other traditional techniques, like photogrammetry, need strong manual editing effort in order to identify slopes and insert vector on surfaces at the right height. Regarding LiDAR data, in order to perform accurate modelling, it is necessary to obtain an high density point cloud. The method proposed can also be used as a fast and linear workflow process for an area where LiDAR data are available and a municipal cartography already exist: LiDAR data can be furthermore successfully used to cross-check errors in pre-existent digital cartography that can remain otherwise hidden.

Workshop on the Integration of Finite Element Modeling with Geometric Modeling

NASA Technical Reports Server (NTRS)

Wozny, Michael J.

1987-01-01

The workshop on the Integration of Finite Element Modeling with Geometric Modeling was held on 12 May 1987. It was held to discuss the geometric modeling requirements of the finite element modeling process and to better understand the technical aspects of the integration of these two areas. The 11 papers are presented except for one for which only the abstract is given.

Locating low-frequency earthquakes using amplitude signals from seismograph stations: Examples from events at Montserrat, West Indies and from synthetic data

NASA Astrophysics Data System (ADS)

Jolly, A.; Jousset, P.; Neuberg, J.

2003-04-01

We determine locations for low-frequency earthquakes occurring prior to a collapse on June 25th, 1997 using signal amplitudes from a 7-station local seismograph network at the Soufriere Hills volcano on Montserrat, West Indies. Locations are determined by averaging the signal amplitude over the event waveform and inverting these data using an assumed amplitude decay model comprising geometrical spreading and attenuation. Resulting locations are centered beneath the active dome from 500 to 2000 m below sea level assuming body wave geometrical spreading and a quality factor of Q=22. Locations for the same events shifted systematically shallower by about 500 m assuming a surface wave geometrical spreading. Locations are consistent to results obtained using arrival time methods. The validity of the method is tested against synthetic low-frequency events constructed from a 2-D finite difference model including visco-elastic properties. Two example events are tested; one from a point source triggered in a low velocity conduit ranging between 100-1100 m below the surface, and the second triggered in a conduit located 1500-2500 m below the surface. Resulting seismograms have emergent onsets and extended codas and include the effect of conduit resonance. Employing geometrical spreading and attenuation from the finite-difference modelling, we obtain locations within the respective model conduits validating our approach.The location depths are sensitive to the assumed geometric spreading and Q model. We can distinguish between two sources separated by about 1000 meters only if we know the decay parameters.

Time scale of random sequential adsorption.

PubMed

Erban, Radek; Chapman, S Jonathan

2007-04-01

A simple multiscale approach to the diffusion-driven adsorption from a solution to a solid surface is presented. The model combines two important features of the adsorption process: (i) The kinetics of the chemical reaction between adsorbing molecules and the surface and (ii) geometrical constraints on the surface made by molecules which are already adsorbed. The process (i) is modeled in a diffusion-driven context, i.e., the conditional probability of adsorbing a molecule provided that the molecule hits the surface is related to the macroscopic surface reaction rate. The geometrical constraint (ii) is modeled using random sequential adsorption (RSA), which is the sequential addition of molecules at random positions on a surface; one attempt to attach a molecule is made per one RSA simulation time step. By coupling RSA with the diffusion of molecules in the solution above the surface the RSA simulation time step is related to the real physical time. The method is illustrated on a model of chemisorption of reactive polymers to a virus surface.

Preparation of etched tantalum semimicro capacitor stimulation electrodes.

PubMed

Robblee, L S; Kelliher, E M; Langmuir, M E; Vartanian, H; McHardy, J

1983-03-01

The ideal electrode for stimulation of the nervous system is one that will inject charge by purely capacitive processes. One approach is to exploit the type of metal-oxide combination used in electrolytic capacitors, e.g., Ta/Ta2O5. For this purpose, fine tantalum wire (0.25 mm diam) was etched electrolytically at constant current in a methanol solution of NH4Br containing 1.5 wt % H2O. Electrolytic etching produced a conical tip with a length of ca. 0.5 mm and shaft diameters ranging from 0.10 to 0.16 mm. The etched electrodes were anodized to 10 V (vs. SCE) in 0.1 vol % H3PO4. The capacitance values normalized to geometric area of etched electrodes ranged from 0.13 to 0.33 micro F mm-2. Comparison of these values to the capacitance of "smooth" tantalum anodized to 10 V (0.011 micro F mm-2) indicated that the degree of surface enhancement, or etch ratio, was 12-30. The surface roughness was confirmed by scanning electron microscopy studies which revealed an intricate array of irregularly shaped surface projections about 1-2 micrometers wide. The etched electrodes were capable of delivering 0.06-0.1 micro C of charge with 0.1 ms pulses at a pulse repetition rate of 400 Hz when operated at 50% of the anodization voltage. This quantity of charge corresponded to volumetric charge densities of 20-30 micro C mm-3 and area charge densities of 0.55-0.88 micro C mm-2. Charge storage was proportionately higher at higher fractional values of the formation voltage. Leakage currents at 5 V were ca. 2 nA. Neither long-term passive storage (1500 h) nor extended pulsing time (18 h) had a deleterious effect on electrode performance. The trend in electrical stimulation work is toward smaller electrodes. The procedures developed in this study should be particularly well-suited to the fabrication of even smaller electrodes because of the favorable electrical and geometric characteristics of the etched surface.

APPROACHES TO GEOMETRIC DATA ANALYSIS ON BIG AREA ADDITIVELY MANUFACTURED (BAAM) PARTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dreifus, Gregory D; Ally, Nadya R; Post, Brian K

The promise of additive manufacturing is that a user can design and print complex geometries that are very difficult, if not impossible, to machine. The capabilities of 3D printing are restricted by a number of factors, including properties of the build material, time constraints, and geometric design restrictions. In this paper, a thorough accounting and study of the geometric restrictions that exist in the current iteration of additive manufacturing (AM) fused deposition modeling (FDM) technologies are discussed. Offline and online methodologies for collecting data sets for qualitative analysis of large scale AM, in particular Oak Ridge National Laboratory s (ORNL)more » big area additive manufacturing (BAAM) system, are summarized. In doing so, a survey of tools for designers and software developers is provided. In particular, strategies in which geometric data can be used as training sets for smarter AM technologies in the future are explained as well.« less

Geometric modeling of space-optimal unit-cell-based tissue engineering scaffolds

NASA Astrophysics Data System (ADS)

Rajagopalan, Srinivasan; Lu, Lichun; Yaszemski, Michael J.; Robb, Richard A.

2005-04-01

Tissue engineering involves regenerating damaged or malfunctioning organs using cells, biomolecules, and synthetic or natural scaffolds. Based on their intended roles, scaffolds can be injected as space-fillers or be preformed and implanted to provide mechanical support. Preformed scaffolds are biomimetic "trellis-like" structures which, on implantation and integration, act as tissue/organ surrogates. Customized, computer controlled, and reproducible preformed scaffolds can be fabricated using Computer Aided Design (CAD) techniques and rapid prototyping devices. A curved, monolithic construct with minimal surface area constitutes an efficient substrate geometry that promotes cell attachment, migration and proliferation. However, current CAD approaches do not provide such a biomorphic construct. We address this critical issue by presenting one of the very first physical realizations of minimal surfaces towards the construction of efficient unit-cell based tissue engineering scaffolds. Mask programmability, and optimal packing density of triply periodic minimal surfaces are used to construct the optimal pore geometry. Budgeted polygonization, and progressive minimal surface refinement facilitate the machinability of these surfaces. The efficient stress distributions, as deduced from the Finite Element simulations, favor the use of these scaffolds for orthopedic applications.

Effect of agrochemical use on the drinking water quality of Agogo, a tomato growing community in Ashanti Akim, Ghana.

PubMed

Obiri-Danso, K; Adonadaga, M G; Hogarh, J N

2011-01-01

The effect of agrochemical use in agricultural activities on the drinking water quality of ground and surface water within Agogo, a prominent tomato growing area in the Ashanti region of Ghana was assessed by monitoring physicochemical parameters, trace metals and microbial quality of two water sources. Levels of contamination were greater in surface water than groundwater. Trace metal levels (mg/L) were 1.40, 0.12, 0.08 and 0.18 in surface water and 0.08, 0.10, 0.05 and 0.08 in groundwater for Fe, Pb, Zn and Cd, respectively. Lead and Cd in surface and groundwater exceeded USEPA maximum acceptable levels (MCLs) for drinking water. Bacterial indicator numbers (geometric means/100 mL) in surface water varied from 9.35 x 10⁵ to 1.57 x 10¹¹ for total coliforms, 4.15 x 10⁴ to 2.10 x 10⁷ for faecal coliforms and 2.80 x 10 to 3.25 x 10² for enterococci, but none was found in groundwater.

Integrated amplifying nanowire FET for surface and bulk sensing

NASA Astrophysics Data System (ADS)

Chui, Chi On; Shin, Kyeong-Sik

2011-10-01

For over one decade, numerous research have been performed on field-effect transistor (FET) sensors with a quasi-onedimensional (1D) nanostructure channel demonstrating highly sensitive surface and bulk sensing. The high surface and bulk sensing sensitivity respectively arises from the inherently large surface area-to-volume ratio and tiny channel volume. The generic nanowire FET sensors, however, have limitations such as impractically low output current levels especially near the limit of detection (LOD) that would require downstream remote amplification with an appreciable amount of added noise. We have recently proposed and experimentally demonstrated an innovative amplifying nanowire FET sensor structure that seamlessly integrates therein a sensing nanowire and a nanowire FET amplifier. This novel sensor structure embraces the same geometrical advantage in quasi-1D nanostructure yet it offers unprecedented closeproximity signal amplification with the lowest possible added noise. In this paper, we review the device operating principle and amplification mechanism. We also present the prototype fabrication procedures, and surface and bulk sensing experimental results showing significantly enhanced output current level difference as predicted.

Water Detection Based on Object Reflections

NASA Technical Reports Server (NTRS)

Rankin, Arturo L.; Matthies, Larry H.

2012-01-01

Water bodies are challenging terrain hazards for terrestrial unmanned ground vehicles (UGVs) for several reasons. Traversing through deep water bodies could cause costly damage to the electronics of UGVs. Additionally, a UGV that is either broken down due to water damage or becomes stuck in a water body during an autonomous operation will require rescue, potentially drawing critical resources away from the primary operation and increasing the operation cost. Thus, robust water detection is a critical perception requirement for UGV autonomous navigation. One of the properties useful for detecting still water bodies is that their surface acts as a horizontal mirror at high incidence angles. Still water bodies in wide-open areas can be detected by geometrically locating the exact pixels in the sky that are reflecting on candidate water pixels on the ground, predicting if ground pixels are water based on color similarity to the sky and local terrain features. But in cluttered areas where reflections of objects in the background dominate the appearance of the surface of still water bodies, detection based on sky reflections is of marginal value. Specifically, this software attempts to solve the problem of detecting still water bodies on cross-country terrain in cluttered areas at low cost.

Three-dimensional reconstruction of Roman coins from photometric image sets

NASA Astrophysics Data System (ADS)

MacDonald, Lindsay; Moitinho de Almeida, Vera; Hess, Mona

2017-01-01

A method is presented for increasing the spatial resolution of the three-dimensional (3-D) digital representation of coins by combining fine photometric detail derived from a set of photographic images with accurate geometric data from a 3-D laser scanner. 3-D reconstructions were made of the obverse and reverse sides of two ancient Roman denarii by processing sets of images captured under directional lighting in an illumination dome. Surface normal vectors were calculated by a "bounded regression" technique, excluding both shadow and specular components of reflection from the metallic surface. Because of the known difficulty in achieving geometric accuracy when integrating photometric normals to produce a digital elevation model, the low spatial frequencies were replaced by those derived from the point cloud produced by a 3-D laser scanner. The two datasets were scaled and registered by matching the outlines and correlating the surface gradients. The final result was a realistic rendering of the coins at a spatial resolution of 75 pixels/mm (13-μm spacing), in which the fine detail modulated the underlying geometric form of the surface relief. The method opens the way to obtain high quality 3-D representations of coins in collections to enable interactive online viewing.

Geometrical and structural properties of an Aeroelastic Research Wing (ARW-2)

NASA Technical Reports Server (NTRS)

Sandford, Maynard C.; Seidel, David A.; Eckstrom, Clinton V.; Spain, Charles V.

1989-01-01

Transonic steady and unsteady pressure tests were conducted on a large elastic wing known as the DAST ARW-2 wing. The wing has a supercritical airfoil, an aspect ratio of 10.3, a leading edge sweepback angle of 28.8 deg and is equipped with two inboard and one outboard trailing edge control surfaces. The geometrical and structural characteristics are presented of this elastic wing, using a combination of measured and calculated data, to permit future analyst to compare the experimental surface pressure data with theoretical predictions.

Voroprot: an interactive tool for the analysis and visualization of complex geometric features of protein structure.

PubMed

Olechnovic, Kliment; Margelevicius, Mindaugas; Venclovas, Ceslovas

2011-03-01

We present Voroprot, an interactive cross-platform software tool that provides a unique set of capabilities for exploring geometric features of protein structure. Voroprot allows the construction and visualization of the Apollonius diagram (also known as the additively weighted Voronoi diagram), the Apollonius graph, protein alpha shapes, interatomic contact surfaces, solvent accessible surfaces, pockets and cavities inside protein structure. Voroprot is available for Windows, Linux and Mac OS X operating systems and can be downloaded from http://www.ibt.lt/bioinformatics/voroprot/.

A lattice Boltzmann investigation of steady-state fluid distribution, capillary pressure and relative permeability of a porous medium: Effects of fluid and geometrical properties

NASA Astrophysics Data System (ADS)

Li, Zi; Galindo-Torres, Sergio; Yan, Guanxi; Scheuermann, Alexander; Li, Ling

2018-06-01

Simulations of simultaneous steady-state two-phase flow in the capillary force-dominated regime were conducted using the state-of-the-art Shan-Chen multi-component lattice Boltzmann model (SCMC-LBM) based on two-dimensional porous media. We focused on analyzing the fluid distribution (i.e., WP fluid-solid, NP fluid-solid and fluid-fluid interfacial areas) as well as the capillary pressure versus saturation curve which was affected by fluid and geometrical properties (i.e., wettability, adhesive strength, pore size distribution and specific surface area). How these properties influenced the relative permeability versus saturation relation through apparent effective permeability and threshold pressure gradient was also explored. The SCMC-LBM simulations showed that, a thin WP fluid film formed around the solid surface due to the adhesive fluid-solid interaction, resulting in discrete WP fluid distributions and reduction of the WP fluid mobility. Also, the adhesive interaction provided another source of capillary pressure in addition to capillary force, which, however, did not affect the mobility of the NP fluid. The film fluid effect could be enhanced by large adhesive strength and fine pores in heterogeneous porous media. In the steady-state infiltration, not only the NP fluid but also the WP fluid were subjected to the capillary resistance. The capillary pressure effect could be alleviated by decreased wettability, large average pore radius and improved fluid connectivity in heterogeneous porous media. The present work based on the SCMC-LBM investigations elucidated the role of film fluid as well as capillary pressure in the two-phase flow system. The findings have implications for ways to improve the macroscopic flow equation based on balance of force for the steady-state infiltration.

Exposure to 4,4'-methylene bis (2-chloroaniline) (MbOCA) in New South Wales, Australia

PubMed Central

Shankar, Kiran; Fung, Vivian; Seneviratne, Mahinda; O'Donnell, Gregory E

2017-01-01

Objectives: This study was conducted to determine the level of exposure of 4,4'-methylene bis (2-chloroaniline) (MbOCA) in New South Wales (NSW), Australia. Methods: An integrated occupational hygiene and biological monitoring program were used to assess the workers' exposure to MbOCA via inhalation, ingestion and dermal contact. This was conducted by personal air monitoring, static air monitoring and surface contamination monitoring of the work environment and biological monitoring of the workers' exposure to MbOCA at nine workplaces in NSW. Results: The air monitoring results for MbOCA gave a geometric mean (GM) of 0.06 μg/m3 and a geometric standard deviation (GSD) of 2.70 and a 95% confidence interval of 0.29 μg/m3. The surface contamination in the main work area showed the highest contamination with a GM of 74 ng/cm2 and a GSD of 17 and a 95% confidence interval of 7,751 ng/cm2. Biological monitoring showed a GM of 0.89 μmol/mol cr and a GSD of 11.9 and a 95% confidence interval of 52 μmol/mol cr. This indicated that 13% of the workers were over the SafeWork NSW Biological Occupational Exposure Limit of 15 μmol/mol cr. Conclusions: Workers' exposure through inhalation was minimal; however, evidence from biological monitoring of MbOCA suggested that the main contributing factor to exposure was skin absorption. This was attributed to poor housekeeping and inadequate personal protection. Improvements in these areas were recommended, and it was also recommended to improve the awareness of the workers to the adverse effects to their health of exposure to this carcinogen. PMID:28320979

Metasurface holograms reaching 80% efficiency.

PubMed

Zheng, Guoxing; Mühlenbernd, Holger; Kenney, Mitchell; Li, Guixin; Zentgraf, Thomas; Zhang, Shuang

2015-04-01

Surfaces covered by ultrathin plasmonic structures--so-called metasurfaces--have recently been shown to be capable of completely controlling the phase of light, representing a new paradigm for the design of innovative optical elements such as ultrathin flat lenses, directional couplers for surface plasmon polaritons and wave plate vortex beam generation. Among the various types of metasurfaces, geometric metasurfaces, which consist of an array of plasmonic nanorods with spatially varying orientations, have shown superior phase control due to the geometric nature of their phase profile. Metasurfaces have recently been used to make computer-generated holograms, but the hologram efficiency remained too low at visible wavelengths for practical purposes. Here, we report the design and realization of a geometric metasurface hologram reaching diffraction efficiencies of 80% at 825 nm and a broad bandwidth between 630 nm and 1,050 nm. The 16-level-phase computer-generated hologram demonstrated here combines the advantages of a geometric metasurface for the superior control of the phase profile and of reflectarrays for achieving high polarization conversion efficiency. Specifically, the design of the hologram integrates a ground metal plane with a geometric metasurface that enhances the conversion efficiency between the two circular polarization states, leading to high diffraction efficiency without complicating the fabrication process. Because of these advantages, our strategy could be viable for various practical holographic applications.

GEOMETRIC, VOLUMETRIC, COLOUR AND FRICTIONAL PROPERTIES OF SELECTED SALVIA SPECIES OF TURKEY

PubMed Central

Bayram, Mustafa; Altuntas, Ebubekir; Yilar, Melih

2017-01-01

Background: Salvia seeds are promite to dietary and healthy oils because they contain essential fatty acids. Salvia seeds frequently produce mucilage on soaking, and this mucilage is used for the treatment of eye diseases in eastern countries. Salvia species studied for medicine, food and cosmetics, have the potential to be used in the various fields. In the present study, selected engineering (geometrical, volumetrical, colour and frictional) properties of 6 Salvia species seeds were determined and compared. Materials and Methods: This study was performed on selected engineering properties of seeds of 6 Salvia species (Salvia viridis L., Salvia aethiopis L., Salvia cryptantha Montbert & Aucher ex Benthan., Salvia tomentosa Mill., Salvia sclarea L., Salvia virgata Jacq.,) cultivated in Turkey. Plants were collected during the vegetation in 2012-2013 (May-Agust). The seeds were cleaned from foreign matter, dirt and broken seeds manually. Results: The average length, width and thickness were found in the range of 2.61 to 3.53 mm, 1.59 to 2.92 mm and 1.14 to 2.52 mm, respectively. Salvia viridis L. specie had the lowest geometric mean diameter and surface area, whereas Salvia cryptantha L. had the least values among these 6 Salvia species for these properties. The bulk density, true density and the porosity were between 296.83 and 702.80 kg m-3, 285.69 and 718.08 kg m-3, 10.27 and 44.05%, respectively. The volume of unit seed and sphericity ranged between 2.56 and 13.64 mm3, 62.90 and 90.40%, respectively. The coefficient of friction of salvia species were largely influenced by the friction surfaces studied, and highest values were found for polywood in the Salvia crytantha L.. In the study, the static friction coefficient and the angle of repose of salvia species changed from 0.477 to 0.955, and from 14.09 to 23.57°, respectively. Conclusion: Determination of geometric, volumetric, colour and frictional properties of Salvia spp. seeds may increase their economic value. PMID:28480423

Predicting silicon pore optics

NASA Astrophysics Data System (ADS)

Vacanti, Giuseppe; Barriére, Nicolas; Bavdaz, Marcos; Chatbi, Abdelhakim; Collon, Maximilien; Dekker, Danielle; Girou, David; Günther, Ramses; van der Hoeven, Roy; Landgraf, Boris; Sforzini, Jessica; Vervest, Mark; Wille, Eric

2017-09-01

Continuing improvement of Silicon Pore Optics (SPO) calls for regular extension and validation of the tools used to model and predict their X-ray performance. In this paper we present an updated geometrical model for the SPO optics and describe how we make use of the surface metrology collected during each of the SPO manufacturing runs. The new geometrical model affords the user a finer degree of control on the mechanical details of the SPO stacks, while a standard interface has been developed to make use of any type of metrology that can return changes in the local surface normal of the reflecting surfaces. Comparisons between the predicted and actual performance of samples optics will be shown and discussed.

Two-Year-Old Children Interpret Abstract, Purely Geometric Maps

ERIC Educational Resources Information Center

Winkler-Rhoades, Nathan; Carey, Susan C.; Spelke, Elizabeth S.

2013-01-01

In two experiments, 2.5-year-old children spontaneously used geometric information from 2D maps to locate objects in a 3D surface layout, without instruction or feedback. Children related maps to their corresponding layouts even though the maps differed from the layouts in size, mobility, orientation, dimensionality, and perspective, and even when…

Geometric phase effects in ultracold chemistry

NASA Astrophysics Data System (ADS)

Hazra, Jisha; Naduvalath, Balakrishnan; Kendrick, Brian K.

2016-05-01

In molecules, the geometric phase, also known as Berry's phase, originates from the adiabatic transport of the electronic wavefunction when the nuclei follow a closed path encircling a conical intersection between two electronic potential energy surfaces. It is demonstrated that the inclusion of the geometric phase has an important effect on ultracold chemical reaction rates. The effect appears in rotationally and vibrationally resolved integral cross sections as well as cross sections summed over all product quantum states. It arises from interference between scattering amplitudes of two reaction pathways: a direct path and a looping path that encircle the conical intersection between the two lowest adiabatic electronic potential energy surfaces. Illustrative results are presented for the O+ OH --> H+ O2 reaction and for hydrogen exchange in H+ H2 and D+HD reactions. It is also qualitatively demonstrated that the geometric phase effect can be modulated by applying an external electric field allowing the possibility of quantum control of chemical reactions in the ultracold regime. This work was supported in part by NSF Grant PHY-1505557 (N.B.) and ARO MURI Grant No. W911NF-12-1-0476 (N.B.).

Electrostatics in protein–protein docking

PubMed Central

Heifetz, Alexander; Katchalski-Katzir, Ephraim; Eisenstein, Miriam

2002-01-01

A novel geometric-electrostatic docking algorithm is presented, which tests and quantifies the electrostatic complementarity of the molecular surfaces together with the shape complementarity. We represent each molecule to be docked as a grid of complex numbers, storing information regarding the shape of the molecule in the real part and information regarding the electrostatic character of the molecule in the imaginary part. The electrostatic descriptors are derived from the electrostatic potential of the molecule. Thus, the electrostatic character of the molecule is represented as patches of positive, neutral, or negative values. The potential for each molecule is calculated only once and stored as potential spheres adequate for exhaustive rotation/translation scans. The geometric-electrostatic docking algorithm is applied to 17 systems, starting form the structures of the unbound molecules. The results—in terms of the complementarity scores of the nearly correct solutions, their ranking in the lists of sorted solutions, and their statistical uniqueness—are compared with those of geometric docking, showing that the inclusion of electrostatic complementarity in docking is very important, in particular in docking of unbound structures. Based on our results, we formulate several "good electrostatic docking rules": The geometric-electrostatic docking procedure is more successful than geometric docking when the potential patches are large and when the potential extends away from the molecular surface and protrudes into the solvent. In contrast, geometric docking is recommended when the electrostatic potential around the molecules to be docked appears homogenous, that is, with a similar sign all around the molecule. PMID:11847280

Satellite and Instrument Influences on ICESat Waveforms

NASA Astrophysics Data System (ADS)

Webb, C. E.; Urban, T. J.; Neuenschwander, A. L.; Gutierrez, R.; Schutz, B. E.

2007-12-01

The White Sands Space Harbor (WSSH) has served as the principal ground calibration site throughout the Ice, Cloud and land Elevation Satellite (ICESat) mission. The Center for Space Research (CSR) at the University of Texas at Austin continues to conduct various experiments designed to validate the timing, geolocation and geometric characteristics of individual laser footprints on the surface. In addition, two airborne lidar surveys of the calibration site and surrounding area were conducted during the mission, first in 2003 and again in 2007. Chosen for its limited surface roughness and topographic flatness, this area has been targeted 3-4 times in each of the 12 ICESat mapping campaigns to date, yielding a significant altimetry data set. The derived surface elevations are compared with those from the airborne lidar surveys, as well as those obtained by the Shuttle Radar Topography Mission (SRTM). Furthermore, the Geoscience Laser Altimetry System (GLAS) onboard ICESat records a digitized waveform for each laser pulse returned from the surface. The two methods currently used to fit such signals in ICESat data processing are examined and compared for the WSSH waveforms. The first fits up to two distinct Gaussians and provides a surface elevation at the location of the maximum peak. The second fits up to six overlapping Gaussians and provides a surface elevation at the centroid of the pulse. Observed differences in the reported elevations are discussed in terms of the satellite's off-nadir targeting geometry, the laser energy, and the skewness of the returned waveforms.

Hypogeal geological survey in the "Grotta del Re Tiberio" natural cave (Apennines, Italy): a valid tool for reconstructing the structural setting

NASA Astrophysics Data System (ADS)

Ghiselli, Alice; Merazzi, Marzio; Strini, Andrea; Margutti, Roberto; Mercuriali, Michele

2011-06-01

As karst systems are natural windows to the underground, speleology, combined with geological surveys, can be useful tools for helping understand the geological evolution of karst areas. In order to enhance the reconstruction of the structural setting in a gypsum karst area (Vena del Gesso, Romagna Apennines), a detailed analysis has been carried out on hypogeal data. Structural features (faults, fractures, tectonic foliations, bedding) have been mapped in the "Grotta del Re Tiberio" cave, in the nearby gypsum quarry tunnels and open pit benches. Five fracture systems and six fault systems have been identified. The fault systems have been further analyzed through stereographic projections and geometric-kinematic evaluations in order to reconstruct the relative chronology of these structures. This analysis led to the detection of two deformation phases. The results permitted linking of the hypogeal data with the surface data both at a local and regional scale. At the local scale, fracture data collected in the underground have been compared with previous authors' surface data coming from the quarry area. The two data sets show a very good correspondence, as every underground fracture system matches with one of the surface fracture system. Moreover, in the cave, a larger number of fractures belonging to each system could be mapped. At the regional scale, the two deformation phases detected can be integrated in the structural setting of the study area, thereby enhancing the tectonic interpretation of the area ( e.g., structures belonging to a new deformation phase, not reported before, have been identified underground). The structural detailed hypogeal survey has, thus, provided very useful data, both by integrating the existing information and revealing new data not detected at the surface. In particular, some small structures ( e.g., displacement markers and short fractures) are better preserved in the hypogeal environment than on the surface where the outcropping gypsum is more exposed to dissolution and recrystallization. The hypogeal geological survey, therefore, can be considered a powerful tool for integrating the surface and log data in order to enhance the reconstruction of the deformational history and to get a three-dimensional model of the bedrock in karst areas.

Radiative transfer in shrub savanna sites in Niger: Preliminary results from HAPEX-Sahel. Part 1: Modelling surface reflectance using a geometric-optical approach

NASA Technical Reports Server (NTRS)

Franklin, Janet; Duncan, Jeff; Huete, Alfredo R.; vanLeeuwen, W. J. D.; Li, Xiaowen; Begue, Agnes

1994-01-01

To use optical remote sensing to monitor land surface-climate interactions over large areas, algorithms must be developed to relate multispectral measurements to key variables controlling the exchange of matter (water, carbon dioxide) and energy between the land surface and the atmosphere. The proportion of the ground covered by vegetation and the interception of photosynthetically active radiation (PAR) by vegetation are examples of two variables related to evapotranspiration and primary production, respectively. An areal-proportion model of the multispectral reflectance of shrub savanna, composed of scattered shrubs with a grass, forb or soil understory, predicted the reflectance of two 0.5 km(exp 2) sites as the area-weighted average of the shrub and understory or 'background' reflectances. Although the shaded crown and shaded background have darker reflectances, ignoring them in the area-weighted model is not serious when shrub cover is low and solar zenith angle is small. A submodel predicted the reflectance of the shrub crown as a function of the foliage reflectance and amount of plant material within the crown, and the background reflectance scattered or transmitted through canopy gaps (referred to as a soil-plant 'spectral interaction' term). One may be able to combine these two models to estimate both the fraction of vegetation cover and interception of PAR by green vegetation in a shrub savanna.

AFM-based tribological study of nanopatterned surfaces: the influence of contact area instabilities.

PubMed

Rota, A; Serpini, E; Gazzadi, G C; Valeri, S

2016-04-06

Although the importance of morphology on the tribological properties of surfaces has long been proved, an exhaustive understanding of nanopatterning effects is still lacking due to the difficulty in both fabricating 'really nano-' structures and detecting their tribological properties. In the present work we show how the probe-surface contact area can be a critical parameter due to its remarkable local variability, making a correct interpretation of the data very difficult in the case of extremely small nanofeatures. Regular arrays of parallel 1D straight nanoprotrusions were fabricated by means of a low-dose focused ion beam, taking advantage of the amorphization-related swelling effect. The tribological properties of the patterns were detected in the presence of air and in vacuum (dry ambient) by atomic force microscopy. We have introduced a novel procedure and data analysis to reduce the uncertainties related to contact instabilities. The real time estimation of the radius of curvature of the contacting asperity enables us to study the dependence of the tribological properties of the patterns from their geometrical characteristics. The effect of the patterns on both adhesion and the coefficient of friction strongly depends on the contact area, which is linked to the local radius of curvature of the probe. However, a detectable hydrophobic character induced on the hydrophilic native SiO2 has been observed as well. The results suggest a scenario for capillary formation on the patterns.

Grid-Sphere Electrodes for Contact with Ionospheric Plasma

NASA Technical Reports Server (NTRS)

Stone, Nobie H.; Poe, Garrett D.

2010-01-01

Grid-sphere electrodes have been proposed for use on the positively biased end of electrodynamic space tethers. A grid-sphere electrode is fabricated by embedding a wire mesh in a thin film from which a spherical balloon is formed. The grid-sphere electrode would be deployed from compact stowage by inflating the balloon in space. The thin-film material used to inflate the balloon is formulated to vaporize when exposed to the space environment. This would leave the bare metallic spherical grid electrode attached to the tether, which would present a small cross-sectional area (essentially, the geometric wire shadow area only) to incident neutral atoms and molecules. Most of the neutral particles, which produce dynamic drag when they impact a surface, would pass unimpeded through the open grid spaces. However, partly as a result of buildup of a space charge inside the grid-sphere, and partially, the result of magnetic field effects, the electrode would act almost like a solid surface with respect to the flux of electrons. The net result would be that grid-sphere electrodes would introduce minimal aerodynamic drag, yet have effective electrical-contact surface areas large enough to collect multiampere currents from the ionospheric plasma that are needed for operation of electrodynamic tethers. The vaporizable-balloon concept could also be applied to the deployment of large radio antennas in outer space.

To 3D or Not to 3D, That Is the Question: Do 3D Surface Analyses Improve the Ecomorphological Power of the Distal Femur in Placental Mammals?

PubMed Central

Gould, Francois D. H.

2014-01-01

Improvements in three-dimensional imaging technologies have renewed interest in the study of functional and ecological morphology. Quantitative approaches to shape analysis are used increasingly to study form-function relationships. These methods are computationally intensive, technically demanding, and time-consuming, which may limit sampling potential. There have been few side-by-side comparisons of the effectiveness of such approaches relative to more traditional analyses using linear measurements and ratios. Morphological variation in the distal femur of mammals has been shown to reflect differences in locomotor modes across clades. Thus I tested whether a geometric morphometric analysis of surface shape was superior to a multivariate analysis of ratios for describing ecomorphological patterns in distal femoral variation. A sample of 164 mammalian specimens from 44 genera was assembled. Each genus was assigned to one of six locomotor categories. The same hypotheses were tested using two methods. Six linear measurements of the distal femur were taken with calipers, from which four ratios were calculated. A 3D model was generated with a laser scanner, and analyzed using three dimensional geometric morphometrics. Locomotor category significantly predicted variation in distal femoral morphology in both analyses. Effect size was larger in the geometric morphometric analysis than in the analysis of ratios. Ordination reveals a similar pattern with arboreal and cursorial taxa as extremes on a continuum of morphologies in both analyses. Discriminant functions calculated from the geometric morphometric analysis were more accurate than those calculated from ratios. Both analysis of ratios and geometric morphometric surface analysis reveal similar, biologically meaningful relationships between distal femoral shape and locomotor mode. The functional signal from the morphology is slightly higher in the geometric morphometric analysis. The practical costs of conducting these sorts of analyses should be weighed against potentially slight increases in power when designing protocols for ecomorphological studies. PMID:24633081

Salinity and hydrology of closed lakes

USGS Publications Warehouse

Langbein, Walter Basil

1961-01-01

Lakes without outlets, called closed lakes, are exclusively features of the arid and semiarid zones where annual evaporation exceeds rainfall. The number of closed lakes increases with aridity, so there are relatively few perennial closed lakes, but "dry" lakes that rarely contain water are numerous.Closed lakes fluctuate in level to a much greater degree than the open lakes of the humid zone, because variations in inflow can be compensated only by changes in surface area. Since the variability of inflow increases with aridity, it is possible to derive an approximate relationship for the coefficient of variation of lake area in terms of data on rates of evaporation, lake area, lake depth, and drainage area.The salinity of closed lakes is highly variable, ranging from less than 1 percent to over 25 percent by weight of salts. Some evidence suggests that the tonnage of salts in a lake solution is substantially less than the total input of salts into the lake over the period of existence of the closed lake. This evidence suggests further that the salts in a lake solution represent a kind of long-term balance between factors of gain and loss of salts from the solution.Possible mechanisms for the loss of salts dissolved in the lake include deposition in marginal bays, entrapment in sediments, and removal by wind. Transport of salt from the lake surface in wind spray is also a contributing, but seemingly not major, factor.The hypothesis of a long-term balance between input to and losses from the lake solution is checked by deriving a formula for the equilibrium concentration and comparing the results with the salinity data. The results indicate that the reported salinities seemingly can be explained in terms of their geometric properties and hydrologic environment.The time for accumulation of salts in the lake solution the ratio between mass of salts in the solution and the annual input may also be estimated from the geometric and hydrologic factors, in the absence of data on the salt content of the lake or of the inflow.

Association between atrial fibrillation, atrial enlargement, and left ventricular geometric remodeling.

PubMed

Seko, Yuta; Kato, Takao; Haruna, Tetsuya; Izumi, Toshiaki; Miyamoto, Shoichi; Nakane, Eisaku; Inoko, Moriaki

2018-04-23

This study investigated the relationship between atrial fibrillation (AF) and left ventricular (LV) geometric patterns in a hospital-based population in Japan. We retrospectively analyzed 4444 patients who had undergone simultaneous scheduled transthoracic echocardiography (TTE) and electrocardiography during 2013. A total of 430 patients who had findings of previous myocardial infarctions (n = 419) and without the data on body surface area (n = 11) were excluded from the study. We calculated the LV mass index (LVMI) and relative wall (RWT) and categorized 4014 patients into four groups as follows: normal geometry (n = 3046); concentric remodeling (normal LVMI and high RWT, n = 437); concentric hypertrophy (high LVMI and high RWT, n = 149); and eccentric remodeling (high LVMI and normal RWT, n = 382). The mean left atrial volume indices (LAVI) were 22.5, 23.8, 33.3, and 37.0 mm/m 2 in patients with normal geometry, concentric remodeling, concentric hypertrophy, and eccentric hypertrophy, respectively. The mean LV ejection fractions (LVEF) were 62.7, 62.6, 60.8, and 53.8%, respectively, whereas the prevalence of AF was 10.4%, 10.5%, 14.8%, and 16.8% in patients with normal geometry, concentric remodeling, concentric hypertrophy, and eccentric hypertrophy, respectively. In conclusion, the prevalence of AF was increasing according to LV geometric remodeling patterns in association with LA size and LVEF.

Modelling the phase curve and occultation of WASP-43b with SPIDERMAN

NASA Astrophysics Data System (ADS)

Louden, Tom

2017-06-01

Presenting SPIDERMAN, a fast code for calculating exoplanet phase curves and secondary eclipses with arbitrary two dimensional surface brightness distributions. SPIDERMAN uses an exact geometric algorithm to calculate the area of sub-regions of the planet that are occulted by the star, with no loss in numerical precision. The speed of this calculation makes it possible to run MCMCs to marginalise effectively over the underlying parameters controlling the brightness distribution of exoplanets. The code is fully open source and available over Github. We apply the code to the phase curve of WASP-43b using an analytical surface brightness distribution, and find an excellent fit to the data. We are able to place direct constraints on the physics of heat transport in the atmosphere, such as the ratio between advective and radiative timescales at different altitudes.

Convex set and linear mixing model

NASA Technical Reports Server (NTRS)

Xu, P.; Greeley, R.

1993-01-01

A major goal of optical remote sensing is to determine surface compositions of the earth and other planetary objects. For assessment of composition, single pixels in multi-spectral images usually record a mixture of the signals from various materials within the corresponding surface area. In this report, we introduce a closed and bounded convex set as a mathematical model for linear mixing. This model has a clear geometric implication because the closed and bounded convex set is a natural generalization of a triangle in n-space. The endmembers are extreme points of the convex set. Every point in the convex closure of the endmembers is a linear mixture of those endmembers, which is exactly how linear mixing is defined. With this model, some general criteria for selecting endmembers could be described. This model can lead to a better understanding of linear mixing models.

Chemical and biological quality of surface water at the U.S. Army Atterbury Reserve Forces Training Area near Edinburgh, Indiana, September 2000 through July 2001

USGS Publications Warehouse

Risch, Martin R.

2004-01-01

A base-wide assessment of surface-water quality at the U.S. Army Atterbury Reserve Forces Training Area near Edinburgh, Indiana, examined short-term and long-term quality of surface water flowing into, across, and out of a 33,760-acre study area. The 30-day geometric-mean concentrations of fecal-indicator bacteria (Escherichia coli) in water samples from all 16 monitoring sites on streams in the study area were greater than the Indiana recreational water-quality standard. None of the bacteria concentrations in samples from four lakes exceeded the standard. Half the samples with bacteria concentrations greater than the single-sample standard contained chemical tracers potentially associated with human sewage. Increased turbidity of water samples was related statistically to increased bacteria concentration. Lead concentrations ranging from 0.5 to 2.0 micrograms per liter were detected in water samples at seven monitoring sites. Lead in one sample collected during high-streamflow conditions was greater than the calculated Indiana water-quality standard. With the exception of Escherichia coli and lead, 211 of 213 chemical constituents analyzed in water samples did not exceed Indiana water-quality standards. Out of 131 constituents analyzed in streambed-sediment and fish-tissue samples from three sites in the Common Impact Area for weapons training, the largest concentrations overall were detected for copper, lead, manganese, strontium, and zinc. Fish-community integrity, based on diversity and pollution tolerance, was rated poor at one of those three sites. Compared with State criteria, the fish-community data indicated 8 of 10 stream reaches in the study area could be categorized as "fully supporting" aquatic-life uses.

Enhancing Adhesion: Relative Merits of Different Approaches

NASA Technical Reports Server (NTRS)

Penn, L. S.; Pater, R.

1996-01-01

Adhesive performance is improved mainly by manipulation of the bimaterials interface zone, which is only a few molecules thick. There are three approaches to enhancement of interfacial adhesion at the molecular level. They are 1) changing the nonchemically bonded interactions across the interface from weak ones to strong ones, 2) making the true interfacial area much larger than the simple geometric area, and 3) inducing chemical bonding between the two materials forming the interface. Our goal this summer was to question some of the built-in assumptions contained within these approaches and to determine the most promising approach, both theoretically and practically, for enhancing adhesion in NASA structures. Our computations revealed that all three of these approaches have, in theory, the potential to enhance molecular adhesion approximately ten-fold. Experiments, however, revealed that this excellent level of enhancement is not likely to be reached in practice. Each approach was found to be severely limited by practical problems. In addition, some of the built-in assumptions associated with these approaches were found to be insufficient or inadequate. The first approach, changing the nonchemically bonded interactions from weak to strong, Is an example of one containing inadequate assumptions. The extensive literature on intermolecular interactions, based on solution studies, shows that certain functional group pairs interact much more strongly than others. It has always been assumed that these data can be reliably extended to systems where only one member of the pair is in solution and the other Is contained in a solid surface. Our experiments this summer demonstrated that solution data do not adequately predict the strength of functional group interaction at the solid-liquid interface. Furthermore, the strong solvents needed to dissolve the monomers or polymers to which the functional groups of interest are attached compete successfully with the solid surface for the functional group. As a result, functional groups in solution cannot pair with the complementary groups in the solid surface, and the expected enhancement of nonchemically bonded interactions is not realized. The second approach, increasing the true interfacial area, is an example of one containing inadequate assumptions and suffering from numerous practical problems. First, practitioners have assumed that material removal, such as bead blasting or etching, increases true surface area (and therefore interfacial area) in a meaningful way. Our geometric analysis demonstrated that removal methods increase area by a factor of two at most. To increase interfacial area by an order of magnitude or more. a thin layer of high porosity must be added to the substrate surface prior to application of the adhesive phase. Consistent with this finding, we attempted to create a thin layer of rigid, highly porous glass on the surface of our smooth glass substrate by means of sol-gel technology. We were unable to surmount a wide variety of practical problems and obtained only collapsed, nonporous layers. Thus this approach, appealing in principle, would require long term development and is not promising in the near term. The third approach, inducing chemical bonding at the interface, is an example of one having neither inadequate assumptions nor insurmountable practical problems. When silicate glass is the substrate, there are only a few chemical reactions that can be successfully conducted to create these chemical bonds, and these reactions usually involve silicon-containing reagents. We compared the silazane reagents to the silane reagents and found through experiment that the silazanes react with the glass surface much more readily, and under milder conditions, than the silanes. The functional groups attached to the glass surface by silazane reactions were not able to be removed by solvent extraction, elevated temperature exposure, or mechanical action. This clearly indicates that the formation of chemical bonds at the interface is the most effective approach for enhancing molecular adhesion.

A LiDAR based analysis of hydraulic hazard mapping

NASA Astrophysics Data System (ADS)

Cazorzi, F.; De Luca, A.; Checchinato, A.; Segna, F.; Dalla Fontana, G.

2012-04-01

Mapping hydraulic hazard is a ticklish procedure as it involves technical and socio-economic aspects. On the one hand no dangerous areas should be excluded, on the other hand it is important not to exceed, beyond the necessary, with the surface assigned to some use limitations. The availability of a high resolution topographic survey allows nowadays to face this task with innovative procedures, both in the planning (mapping) and in the map validation phases. The latter is the object of the present work. It should be stressed that the described procedure is proposed purely as a preliminary analysis based on topography only, and therefore does not intend in any way to replace more sophisticated analysis methods requiring based on hydraulic modelling. The reference elevation model is a combination of the digital terrain model and the digital building model (DTM+DBM). The option of using the standard surface model (DSM) is not viable, as the DSM represents the vegetation canopy as a solid volume. This has the consequence of unrealistically considering the vegetation as a geometric obstacle to water flow. In some cases the topographic model construction requires the identification and digitization of the principal breaklines, such as river banks, ditches and similar natural or artificial structures. The geometrical and topological procedure for the validation of the hydraulic hazard maps is made of two steps. In the first step the whole area is subdivided into fluvial segments, with length chosen as a reasonable trade-off between the need to keep the hydrographical unit as complete as possible, and the need to separate sections of the river bed with significantly different morphology. Each of these segments is made of a single elongated polygon, whose shape can be quite complex, especially for meandering river sections, where the flow direction (i.e. the potential energy gradient associated to the talweg) is often inverted. In the second step the segments are analysed one by one. Therefore, each segment was split into many reaches, so that within any of them the slope of the piezometric line can be approximated to zero. As a consequence, the hydraulic profile (open channel flow) in every reach is assumed horizontal both downslope and on the cross-section. Each reach can be seen as a polygon, delimited laterally by the hazard mapping boundaries and longitudinally by two successive cross sections, usually orthogonal to the talweg line. Simulating the progressive increase of the river stage, with a horizontal piezometric line, allow the definition of the stage-area and stage-volume relationships. Such relationships are obtained exclusively by the geometric information as provided by the high resolution elevation model. The maximum flooded area resulting from the simulation is finally compared to the potentially floodable area described by the hazard maps, to give a flooding index for every reach. Index values lower than 100% show that the mapped hazard area exceeds the maximum floodable area. Very low index values identify spots where there is a significant incongruity between the hazard map and the topography, and where a specific verification is probably needed. The procedure was successfully used for the validation of many hazard maps across Italy.

Model-based RSA of a femoral hip stem using surface and geometrical shape models.

PubMed

Kaptein, Bart L; Valstar, Edward R; Spoor, Cees W; Stoel, Berend C; Rozing, Piet M

2006-07-01

Roentgen stereophotogrammetry (RSA) is a highly accurate three-dimensional measuring technique for assessing micromotion of orthopaedic implants. A drawback is that markers have to be attached to the implant. Model-based techniques have been developed to prevent using special marked implants. We compared two model-based RSA methods with standard marker-based RSA techniques. The first model-based RSA method used surface models, and the second method used elementary geometrical shape (EGS) models. We used a commercially available stem to perform experiments with a phantom as well as reanalysis of patient RSA radiographs. The data from the phantom experiment indicated the accuracy and precision of the elementary geometrical shape model-based RSA method is equal to marker-based RSA. For model-based RSA using surface models, the accuracy is equal to the accuracy of marker-based RSA, but its precision is worse. We found no difference in accuracy and precision between the two model-based RSA techniques in clinical data. For this particular hip stem, EGS model-based RSA is a good alternative for marker-based RSA.

Performance Evaluation of Various STL File Mesh Refining Algorithms Applied for FDM-RP Process

NASA Astrophysics Data System (ADS)

Ledalla, Siva Rama Krishna; Tirupathi, Balaji; Sriram, Venkatesh

2018-06-01

Layered manufacturing machines use the stereolithography (STL) file to build parts. When a curved surface is converted from a computer aided design (CAD) file to STL, it results in a geometrical distortion and chordal error. Parts manufactured with this file, might not satisfy geometric dimensioning and tolerance requirements due to approximated geometry. Current algorithms built in CAD packages have export options to globally reduce this distortion, which leads to an increase in the file size and pre-processing time. In this work, different mesh subdivision algorithms are applied on STL file of a complex geometric features using MeshLab software. The mesh subdivision algorithms considered in this work are modified butterfly subdivision technique, loops sub division technique and general triangular midpoint sub division technique. A comparative study is made with respect to volume and the build time using the above techniques. It is found that triangular midpoint sub division algorithm is more suitable for the geometry under consideration. Only the wheel cap part is then manufactured on Stratasys MOJO FDM machine. The surface roughness of the part is measured on Talysurf surface roughness tester.

Restoring 2D content from distorted documents.

PubMed

Brown, Michael S; Sun, Mingxuan; Yang, Ruigang; Yun, Lin; Seales, W Brent

2007-11-01

This paper presents a framework to restore the 2D content printed on documents in the presence of geometric distortion and non-uniform illumination. Compared with textbased document imaging approaches that correct distortion to a level necessary to obtain sufficiently readable text or to facilitate optical character recognition (OCR), our work targets nontextual documents where the original printed content is desired. To achieve this goal, our framework acquires a 3D scan of the document's surface together with a high-resolution image. Conformal mapping is used to rectify geometric distortion by mapping the 3D surface back to a plane while minimizing angular distortion. This conformal "deskewing" assumes no parametric model of the document's surface and is suitable for arbitrary distortions. Illumination correction is performed by using the 3D shape to distinguish content gradient edges from illumination gradient edges in the high-resolution image. Integration is performed using only the content edges to obtain a reflectance image with significantly less illumination artifacts. This approach makes no assumptions about light sources and their positions. The results from the geometric and photometric correction are combined to produce the final output.

Pt Catalyst Degradation in Aqueous and Fuel Cell Environments studied via In-Operando Anomalous Small-Angle X-ray Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, James A.; Kariuki, Nancy N.; Wang, Xiaoping

2015-08-01

The evolution of Pt nanoparticle cathode electrocatalyst size distribution in a polymer electrolyte membrane fuel cell (PEMFC) was followed during accelerated stress tests using in-operando anomalous small-angle X-ray scattering (ASAXS). This evolution was compared to that observed in an aqueous electrolyte environment using stagnant electrolyte, flowing electrolyte, and flowing electrolyte at elevated temperature to reveal the different degradation trends in the PEMFC and aqueous environments and to determine the relevance of aqueous measurements to the stability of Pt nanoparticle catalyst in the fuel cell environment. The observed changes in the particle size distributions (PSDs) were analyzed to elucidate the extentmore » and mechanisms of particle growth and corresponding mass and active surface area losses in the different environments. These losses indicate a Pt nanoparticle surface area loss mechanism controlled by Pt dissolution, the particle size dependence of Pt dissolution, the loss of dissolved Pt into the membrane and electrolyte, and, to a lesser extent, the re-deposition of dissolved Pt onto larger particles. Based on the geometric surface area loss, mass loss, and mean particle size increase trends, the aqueous environment best reflecting the fuel cell environment was found to be one in which the electrolyte is flowing rather than stagnant. Pt nanoparticle surface area loss resulting from potential cycling can be inhibited by reducing the number of particles smaller than a critical particle diameter (CPD), which was found to be similar to 3.5 to similar to 4 nm, with the CPD dependent on both the cycling protocol (square wave vs triangle wave) and the catalyst environment (fuel cell, aqueous stagnant, aqueous flowing electrolyte, or elevated temperature flowing electrolyte)« less

Parameter Estimation of Fossil Oysters from High Resolution 3D Point Cloud and Image Data

NASA Astrophysics Data System (ADS)

Djuricic, Ana; Harzhauser, Mathias; Dorninger, Peter; Nothegger, Clemens; Mandic, Oleg; Székely, Balázs; Molnár, Gábor; Pfeifer, Norbert

2014-05-01

A unique fossil oyster reef was excavated at Stetten in Lower Austria, which is also the highlight of the geo-edutainment park 'Fossilienwelt Weinviertel'. It provides the rare opportunity to study the Early Miocene flora and fauna of the Central Paratethys Sea. The site presents the world's largest fossil oyster biostrome formed about 16.5 million years ago in a tropical estuary of the Korneuburg Basin. About 15,000 up to 80-cm-long shells of Crassostrea gryphoides cover a 400 m2 large area. Our project 'Smart-Geology for the World's largest fossil oyster reef' combines methods of photogrammetry, geology and paleontology to document, evaluate and quantify the shell bed. This interdisciplinary approach will be applied to test hypotheses on the genesis of the taphocenosis (e.g.: tsunami versus major storm) and to reconstruct pre- and post-event processes. Hence, we are focusing on using visualization technologies from photogrammetry in geology and paleontology in order to develop new methods for automatic and objective evaluation of 3D point clouds. These will be studied on the basis of a very dense surface reconstruction of the oyster reef. 'Smart Geology', as extension of the classic discipline, exploits massive data, automatic interpretation, and visualization. Photogrammetry provides the tools for surface acquisition and objective, automated interpretation. We also want to stress the economic aspect of using automatic shape detection in paleontology, which saves manpower and increases efficiency during the monitoring and evaluation process. Currently, there are many well known algorithms for 3D shape detection of certain objects. We are using dense 3D laser scanning data from an instrument utilizing the phase shift measuring principle, which provides accurate geometrical basis < 3 mm. However, the situation is difficult in this multiple object scenario where more than 15,000 complete or fragmentary parts of an object with random orientation are found. The goal is to investigate if the application of state-of-the-art 3D digitizing, data processing, and visualization technologies support the interpretation of this paleontological site. The obtained 3D data (approx. 1 billion points at the respective area) is analyzed with respect to their 3D structure in order to derive geometrical information. The aim of this contribution is to segment the 3D point cloud of laser scanning data into meaningful regions representing particular objects. Geometric parameters (curvature, tangent plane orientation, local minimum and maximum, etc.) are derived for every 3D point of the point cloud. A set of features is computed in each point using different kernel sizes to define neighborhoods of different size. This provides information on convexity (outer surface), concavity (inner surface) and locally flat areas, which shall be further utilized in fitting model of Crassostrea-shells. In addition, digitizing is performed manually in order to obtain a representative set of reference data for the evaluation of the obtained results. For evaluating these results the reference data (length and orientation of specimen) is then compared to the automatically derived segments of the point cloud. The study is supported by the Austrian Science Fund (FWF P 25883-N29).

Infrared Spectroscopic Imaging for Prostate Pathology Practice

DTIC Science & Technology

2011-04-01

features – geometric properties of epithelial cells/nuclei and lumens – that are quantified based on H&E stained images as well as FT-IR images of...the samples. By restricting the features used to geometric measures, we sought to mimic the pattern recognition process employed by human experts, and...relatively dark and can be modeled as small elliptical areas in the stained images. This geometrical model is often confounded as multiple nuclei can be

Dynamic Heights in the Great Lakes using OPUS Projects

NASA Astrophysics Data System (ADS)

Roman, D. R.; Li, X.

2015-12-01

The U.S. will be implementing new geometric and vertical reference frames in 2022 to replace the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88), respectively. Less emphasized is the fact that a new dynamic height datum will also be defined about the same time to replace the International Great Lakes Datum of 1985 (IGLD 85). IGLD 85 was defined concurrent with NAVD 88 and used the same geopotential values. This paper focuses on the use of an existing tool for determining geometric coordinates and a developing geopotential model as a means of determining dynamic heights. The Online Positioning User Service (OPUS) Projects (OP) is an online tool available from the National Geodetic Survey (NGS) for use in developing geometric coordinates from simultaneous observations at multiple sites during multiple occupations. With observations performed at the water level gauges throughout the Great Lakes, the geometric coordinates of the mean water level surface can be determined. NGS has also developed the xGEOID15B model from satellite, airborne and surface gravity data. Using the input geometric coordinates determined through OP, the geopotential values for the water surface at the water level stations around the Great Lakes were determined using the xGEOID15B model. Comparisons were made between water level sites for each Lake as well as to existing IGLD 85 heights. A principal advantage to this approach is the ability to generate new water level control stations using OP, while maintaining the consistency between orthometric and dynamic heights by using the same gravity field model. Such a process may provide a means for determining dynamic heights for a future Great Lakes Datum.

Evaluation of the Anisotropic Radiative Conductivity of a Low-Density Carbon Fiber Material from Realistic Microscale Imaging

NASA Technical Reports Server (NTRS)

Nouri, Nima; Panerai, Francesco; Tagavi, Kaveh A.; Mansour, Nagi N.; Martin, Alexandre

2015-01-01

The radiative heat transfer inside a low-density carbon fiber insulator is analyzed using a three-dimensional direct simulation model. A robust procedure is presented for the numerical calculation of the geometric configuration factor to compute the radiative energy exchange processes among the small discretized surface areas of the fibrous material. The methodology is applied to a polygonal mesh of a fibrous insulator obtained from three-dimensional microscale imaging of the real material. The anisotropic values of the radiative conductivity are calculated for that geometry. The results yield both directional and thermal dependence of the radiative conductivity.

Magnetization of the Ising model on the Sierpinski pastry-shell

NASA Astrophysics Data System (ADS)

Chame, Anna; Branco, N. S.

1992-02-01

Using a real-space renormalization group approach, we calculate the approximate magnetization in the Ising model on the Sierpinski Pastry-shell. We consider, as an approximation, only two regions of the fractal: the internal surfaces, or walls (sites on the border of eliminated areas), with coupling constants JS, and the bulk (all other sites), with coupling constants Jv. We obtain the mean magnetization of the two regions as a function of temperature, for different values of α= JS/ JV and different geometric parameters b and l. Curves present a step-like behavior for some values of b and l, as well as different universality classes for the bulk transition.

The O2 reduction at the IFC modified O2 fuel cell electrode

NASA Technical Reports Server (NTRS)

Fielder, William L.; Singer, Joseph; Baldwin, Richard S.; Johnson, Richard E.

1992-01-01

The International Fuel Corporation (IFC) state of the art (SOA) O2 electrode (Au-10 percent Pt electrocatalyst by weight) is currently being used in the alkaline H2-O2 fuel cell in the NASA Space Shuttle. Recently, IFC modified O2 electrode, as a possible replacement for the SOA electrode. In the present study, O2 reduction data were obtained for the modified electrode at temperatures between 23.3 and 91.7 C. BET measurements gave an electrode BET surface area of about 2070 sq. cm/sq. cm of geometric surface area. The Tafel data could be fitted to two straight line regions. The slope for the lower region, designated as the 0.04 V/decade region, was temperature dependent, and the transfer coefficient was about 1.5. The 'apparent' energy of activation for this region was about 19 kcal/mol. An O2 reduction mechanism for this 0.04 region is presented. In the upper region, designated as the 0.08 V/decade region, diffusion may be the controlling process. Tafel data are presented to illustrate the increase in performance with increasing temperature.

The effects of geometric uncertainties on computational modelling of knee biomechanics

NASA Astrophysics Data System (ADS)

Meng, Qingen; Fisher, John; Wilcox, Ruth

2017-08-01

The geometry of the articular components of the knee is an important factor in predicting joint mechanics in computational models. There are a number of uncertainties in the definition of the geometry of cartilage and meniscus, and evaluating the effects of these uncertainties is fundamental to understanding the level of reliability of the models. In this study, the sensitivity of knee mechanics to geometric uncertainties was investigated by comparing polynomial-based and image-based knee models and varying the size of meniscus. The results suggested that the geometric uncertainties in cartilage and meniscus resulting from the resolution of MRI and the accuracy of segmentation caused considerable effects on the predicted knee mechanics. Moreover, even if the mathematical geometric descriptors can be very close to the imaged-based articular surfaces, the detailed contact pressure distribution produced by the mathematical geometric descriptors was not the same as that of the image-based model. However, the trends predicted by the models based on mathematical geometric descriptors were similar to those of the imaged-based models.

A geometric modeler based on a dual-geometry representation polyhedra and rational b-splines

NASA Technical Reports Server (NTRS)

Klosterman, A. L.

1984-01-01

For speed and data base reasons, solid geometric modeling of large complex practical systems is usually approximated by a polyhedra representation. Precise parametric surface and implicit algebraic modelers are available but it is not yet practical to model the same level of system complexity with these precise modelers. In response to this contrast the GEOMOD geometric modeling system was built so that a polyhedra abstraction of the geometry would be available for interactive modeling without losing the precise definition of the geometry. Part of the reason that polyhedra modelers are effective is that all bounded surfaces can be represented in a single canonical format (i.e., sets of planar polygons). This permits a very simple and compact data structure. Nonuniform rational B-splines are currently the best representation to describe a very large class of geometry precisely with one canonical format. The specific capabilities of the modeler are described.

Geometric entropy and edge modes of the electromagnetic field

NASA Astrophysics Data System (ADS)

Donnelly, William; Wall, Aron C.

2016-11-01

We calculate the vacuum entanglement entropy of Maxwell theory in a class of curved spacetimes by Kaluza-Klein reduction of the theory onto a two-dimensional base manifold. Using two-dimensional duality, we express the geometric entropy of the electromagnetic field as the entropy of a tower of scalar fields, constant electric and magnetic fluxes, and a contact term, whose leading-order divergence was discovered by Kabat. The complete contact term takes the form of one negative scalar degree of freedom confined to the entangling surface. We show that the geometric entropy agrees with a statistical definition of entanglement entropy that includes edge modes: classical solutions determined by their boundary values on the entangling surface. This resolves a long-standing puzzle about the statistical interpretation of the contact term in the entanglement entropy. We discuss the implications of this negative term for black hole thermodynamics and the renormalization of Newton's constant.

An approach to constrained aerodynamic design with application to airfoils

NASA Technical Reports Server (NTRS)

Campbell, Richard L.

1992-01-01

An approach was developed for incorporating flow and geometric constraints into the Direct Iterative Surface Curvature (DISC) design method. In this approach, an initial target pressure distribution is developed using a set of control points. The chordwise locations and pressure levels of these points are initially estimated either from empirical relationships and observed characteristics of pressure distributions for a given class of airfoils or by fitting the points to an existing pressure distribution. These values are then automatically adjusted during the design process to satisfy the flow and geometric constraints. The flow constraints currently available are lift, wave drag, pitching moment, pressure gradient, and local pressure levels. The geometric constraint options include maximum thickness, local thickness, leading-edge radius, and a 'glove' constraint involving inner and outer bounding surfaces. This design method was also extended to include the successive constraint release (SCR) approach to constrained minimization.

Turbulent Boundary Layer Flow over Superhydrophobic Surfaces

DTIC Science & Technology

2013-05-10

DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Turbulent Boundary Layer Flow over Superhydrophobic ...modified surfaces. This study encompassed the testing of four different surfaces: 1) Teflon SLIP, 2) Aluminum SLIP, 3) Honeycomb Superhydrophobic and 4...Polydimethylsiloxane elastomer (PDMSe) Superhydrophobic . Each of these surfaces uses specific geometrical surface features to modify the original

Perceptual similarity and the neural correlates of geometrical illusions in human brain structure.

PubMed

Axelrod, Vadim; Schwarzkopf, D Samuel; Gilaie-Dotan, Sharon; Rees, Geraint

2017-01-09

Geometrical visual illusions are an intriguing phenomenon, in which subjective perception consistently misjudges the objective, physical properties of the visual stimulus. Prominent theoretical proposals have been advanced attempting to find common mechanisms across illusions. But empirically testing the similarity between illusions has been notoriously difficult because illusions have very different visual appearances. Here we overcome this difficulty by capitalizing on the variability of the illusory magnitude across participants. Fifty-nine healthy volunteers participated in the study that included measurement of individual illusion magnitude and structural MRI scanning. We tested the Muller-Lyer, Ebbinghaus, Ponzo, and vertical-horizontal geometrical illusions as well as a non-geometrical, contrast illusion. We found some degree of similarity in behavioral judgments of all tested geometrical illusions, but not between geometrical illusions and non-geometrical, contrast illusion. The highest similarity was found between Ebbinghaus and Muller-Lyer geometrical illusions. Furthermore, the magnitude of all geometrical illusions, and particularly the Ebbinghaus and Muller-Lyer illusions, correlated with local gray matter density in the parahippocampal cortex, but not in other brain areas. Our findings suggest that visuospatial integration and scene construction processes might partly mediate individual differences in geometric illusory perception. Overall, these findings contribute to a better understanding of the mechanisms behind geometrical illusions.

Images as embedding maps and minimal surfaces: Movies, color, and volumetric medical images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kimmel, R.; Malladi, R.; Sochen, N.

A general geometrical framework for image processing is presented. The authors consider intensity images as surfaces in the (x,I) space. The image is thereby a two dimensional surface in three dimensional space for gray level images. The new formulation unifies many classical schemes, algorithms, and measures via choices of parameters in a {open_quote}master{close_quotes} geometrical measure. More important, it is a simple and efficient tool for the design of natural schemes for image enhancement, segmentation, and scale space. Here the authors give the basic motivation and apply the scheme to enhance images. They present the concept of an image as amore » surface in dimensions higher than the three dimensional intuitive space. This will help them handle movies, color, and volumetric medical images.« less

Comparison of aerodynamically and model-derived roughness lengths (zo) over diverse surfaces, central Mojave Desert, California, USA

USGS Publications Warehouse

MacKinnon, D.J.; Clow, G.D.; Tigges, R.K.; Reynolds, R.L.; Chavez, P.S.

2004-01-01

The vulnerability of dryland surfaces to wind erosion depends importantly on the absence or the presence and character of surface roughness elements, such as plants, clasts, and topographic irregularities that diminish wind speed near the surface. A model for the friction velocity ratio has been developed to account for wind sheltering by many different types of co-existing roughness elements. Such conditions typify a monitored area in the central Mojave Desert, California, that experiences frequent sand movement and dust emission. Two additional models are used to convert the friction velocity ratio to the surface roughness length (zo) for momentum. To calculate roughness lengths from these models, measurements were made at 11 sites within the monitored area to characterize the surface roughness element. Measurements included (1) the number of roughness species (e.g., plants, small-scale topography, clasts), and their associated heights and widths, (2) spacing among species, and (3) vegetation porosity (a measurement of the spatial distribution of woody elements of a plant). Documented or estimated values of drag coefficients for different species were included in the modeling. At these sites, wind-speed profiles were measured during periods of neutral atmospheric stability using three 9-m towers with three or four calibrated anemometers on each. Modeled roughness lengths show a close correspondence (correlation coefficient, 0.84-0.86) to the aerodynamically determined values at the field sites. The geometric properties of the roughness elements in the model are amenable to measurement at much higher temporal and spatial resolutions using remote-sensing techniques than can be accomplished through laborious ground-based methods. A remote-sensing approach to acquire values of the modeled roughness length is particularly important for the development of linked surface/atmosphere wind-erosion models sensitive to climate variability and land-use changes in areas such as the southwestern United States, where surface roughness has large spatial and temporal variations. ?? 2004 Elsevier B.V. All rights reserved.

“Soft that molds the hard:” Geometric morphometry of lateral atlantoaxial joints focusing on the role of cartilage in changing the contour of bony articular surfaces

PubMed Central

Prasad, Prashant Kumar; Salunke, Pravin; Sahni, Daisy; Kalra, Parveen

2017-01-01

Purpose: The existing literature on lateral atlantoaxial joints is predominantly on bony facets and is unable to explain various C1-2 motions observed. Geometric morphometry of facets would help us in understanding the role of cartilages in C1-2 biomechanics/kinematics. Objective: Anthropometric measurements (bone and cartilage) of the atlantoaxial joint and to assess the role of cartilages in joint biomechanics. Materials and Methods: The authors studied 10 cadaveric atlantoaxial lateral joints with the articular cartilage in situ and after removing it, using three-dimensional laser scanner. The data were compared using geometric morphometry with emphasis on surface contours of articulating surfaces. Results: The bony inferior articular facet of atlas is concave in both sagittal and coronal plane. The bony superior articular facet of axis is convex in sagittal plane and is concave (laterally) and convex medially in the coronal plane. The bony articulating surfaces were nonconcordant. The articular cartilages of both C1 and C2 are biconvex in both planes and are thicker than the concavities of bony articulating surfaces. Conclusion: The biconvex structure of cartilage converts the surface morphology of C1-C2 bony facets from concave on concavo-convex to convex on convex. This reduces the contact point making the six degrees of freedom of motion possible and also makes the joint gyroscopic. PMID:29403249

Application of Consistency Criteria To Calculate BET Areas of Micro- And Mesoporous Metal-Organic Frameworks.

PubMed

Gómez-Gualdrón, Diego A; Moghadam, Peyman Z; Hupp, Joseph T; Farha, Omar K; Snurr, Randall Q

2016-01-13

Metal-organic frameworks (MOFs) can exhibit exceptionally high surface areas, which are experimentally estimated by applying the BET theory to measured nitrogen isotherms. The Brunauer, Emmett, and Teller (BET)-estimated nitrogen monolayer loading is thus converted to a "BET area," but the meaning of MOF BET areas remains under debate. Recent emphasis has been placed on the usage of four so-called "BET consistency criteria." Using these criteria and simulated nitrogen isotherms for perfect crystals, we calculated BET areas for graphene and 25 MOFs having different pore-size distributions. BET areas were compared with their corresponding geometrically calculated, nitrogen-accessible surface areas (NASAs). Analysis of simulation snapshots elucidated the contributions of "pore-filling" and "monolayer-formation" to the nitrogen adsorption loadings in different MOF pores, revealing the origin of inaccuracies in BET-calculated monolayer loadings, which largely explain discrepancies between BET areas and NASAs. We also find that even if all consistency criteria are satisfied, the BET calculation can significantly overestimate the true monolayer loading, especially in MOFs combining mesopores (d ≥ 20 Å) and large micropores (d = 10-20 Å), due to the overlap of pore-filling and monolayer-formation regimes of these two kinds of pores. While it is not always possible to satisfy all consistency criteria, it is critical to minimize the deviation from these criteria during BET range selection to consistently compare BET areas of different MOFs and for comparing simulated and experimental BET areas of a given MOF. To accurately assess the quality of a MOF sample, it is best to compare experimental BET areas with simulated BET areas rather than with calculated NASAs.

Solute transport by flow yields geometric shocks in shape evolution

NASA Astrophysics Data System (ADS)

Huang, Jinzi (Mac); Davies Wykes, Megan; Hajjar, George; Ristroph, Leif; Shelley, Michael

2017-11-01

Geological processes such as erosion and dissolution of surfaces often lead to striking shapes with strikingly sharp features. We present observations of such features forming in dissolution under gravity. In our experiment, a dissolving body with initially smooth surface evolves into an increasingly sharp needle shape. A mathematical model of its shape dynamics, derived from a boundary layer theory, predicts that a geometric shock forms at the tip of dissolved body, with the tip curvature becoming infinite in finite time. We further discuss the model's application to similar processes, such as flow driven erosion which can yield corners.

Emergent propagation modes of ferromagnetic swimmers in constrained geometries

NASA Astrophysics Data System (ADS)

Bryan, M. T.; Shelley, S. R.; Parish, M. J.; Petrov, P. G.; Winlove, C. P.; Gilbert, A. D.; Ogrin, F. Y.

2017-02-01

Magnetic microswimmers, composed of hard and soft ferromagnets connected by an elastic spring, are modelled under low Reynolds number conditions in the presence of geometrical boundaries. Approaching a surface, the magneto-elastic swimmer's velocity increases and its trajectory bends parallel to the surface contour. Further confinement to form a planar channel generates new propagation modes as the channel width narrows, altering the magneto-elastic swimmer's speed, orientation, and direction of travel. Our results demonstrate that constricted geometric environments, such as occuring in microfluidic channels or blood vessels, may influence the functionality of magneto-elastic microswimmers for applications such as drug delivery.

Near-Infrared Spectral Geometric Albedos of Charon and Pluto: Constraints on Charon's Surface Composition

NASA Technical Reports Server (NTRS)

Roush, Ted L.; Cruikshank, Dale P.; Pollack, James B.; Young, Eliot F.; Bartholomew, Mary J.

1996-01-01

The spectral geometric albedos of Charon and Pluto are derived at near-infrared wavelengths (1.4-2.5 jAm) from measurements obtained in 1987. Comparisons of these to theoretical calculations are used to place constraints on the identity and relative abundances of surface ices on Charon. These compari- sons suggest that widespread regions of pure CH4 ice do not occur on Charon and that if CH4 is abundant on Charon then it is large grained (-5 mm) and is likely mixed at the granular level with H20 ice, and possibly C02 ice.

Molecular induced skyhook effect for magnetic interlayer softening

NASA Astrophysics Data System (ADS)

Friedrich, Rico; Caciuc, Vasile; Atodiresei, Nicolae; Blügel, Stefan

2015-11-01

Our first-principles study demonstrates for the first time that by increasing the molecule-surface binding strength, the interlayer magnetic coupling of a ferromagnetic metal can be drastically reduced with respect to that of a clean substrate. Importantly, for a weakly chemisorbed molecule the rehybridization of metal atomic d states within the molecule-induced surface geometry (geometrical effect) plays a crucial role in obtaining interlayer magnetic softening. On the contrary, for a strongly chemisorbed molecule the interlayer magnetic coupling is further reduced due to an interplay between the geometrical effect and the hybridization of atomic d states with molecular ones.

BladeCAD: An Interactive Geometric Design Tool for Turbomachinery Blades

NASA Technical Reports Server (NTRS)

Miller, Perry L., IV; Oliver, James H.; Miller, David P.; Tweedt, Daniel L.

1996-01-01

A new metthodology for interactive design of turbomachinery blades is presented. Software implementation of the meth- ods provides a user interface that is intuitive to aero-designers while operating with standardized geometric forms. The primary contribution is that blade sections may be defined with respect to general surfaces of revolution which may be defined to represent the path of fluid flow through the turbomachine. The completed blade design is represented as a non-uniform rational B-spline (NURBS) surface and is written to a standard IGES file which is portable to most design, analysis, and manufacturing applications.

Distributed proximity sensor system having embedded light emitters and detectors

NASA Technical Reports Server (NTRS)

Lee, Sukhan (Inventor)

1990-01-01

A distributed proximity sensor system is provided with multiple photosensitive devices and light emitters embedded on the surface of a robot hand or other moving member in a geometric pattern. By distributing sensors and emitters capable of detecting distances and angles to points on the surface of an object from known points in the geometric pattern, information is obtained for achieving noncontacting shape and distance perception, i.e., for automatic determination of the object's shape, direction and distance, as well as the orientation of the object relative to the robot hand or other moving member.

Acoustic field of a wedge-shaped section of a spherical cap transducer

NASA Astrophysics Data System (ADS)

Ketterling, Jeffrey A.

2003-12-01

The acoustic pressure field at an arbitrary point in space is derived for a wedge-shaped section of a spherical cap transducer using the spatial impulse response (SIR) method. For a spherical surface centered at the origin, a wedge shape is created by taking cuts in the X-Y and X-Z planes and removing the smallest surface component. Analytic expressions are derived for the SIR based on spatial location. The expressions utilize the SIR solutions for a spherical cap transducer [Arditi et al., Ultrason. Imaging 3, 37-61 (1981)] with additional terms added to account for the reduced surface area of the wedge. Results from the numerical model are compared to experimental measurements from a wedge transducer with an 8-cm outer diameter and 9-cm geometric focus. The experimental and theoretical -3-dB beamwidths agreed to within 10%+/-5%. The SIR model for a wedge-shaped transducer is easily extended to other spherically curved transducer geometries that consist of combinations of wedge sections and spherical caps.

Acoustic field of a wedge-shaped section of a spherical cap transducer.

PubMed

Ketterling, Jeffrey A

2003-12-01

The acoustic pressure field at an arbitrary point in space is derived for a wedge-shaped section of a spherical cap transducer using the spatial impulse response (SIR) method. For a spherical surface centered at the origin, a wedge shape is created by taking cuts in the X-Y and X-Z planes and removing the smallest surface component. Analytic expressions are derived for the SIR based on spatial location. The expressions utilize the SIR solutions for a spherical cap transducer [Arditi et al., Ultrason. Imaging 3, 37-61 (1981)] with additional terms added to account for the reduced surface area of the wedge. Results from the numerical model are compared to experimental measurements from a wedge transducer with an 8-cm outer diameter and 9-cm geometric focus. The experimental and theoretical -3-dB beamwidths agreed to within 10% +/- 5%. The SIR model for a wedge-shaped transducer is easily extended to other spherically curved transducer geometries that consist of combinations of wedge sections and spherical caps.

Image processing of HCMM-satellite thermal images for superposition with other satellite imagery and topographic and thematic maps. [Upper Rhine River Valley and surrounding highlands Switzerland, Germany, and France

NASA Technical Reports Server (NTRS)

Gossmann, H.; Haberaecker, P. (Principal Investigator)

1980-01-01

The southwestern part of Central Europe between Basal and Frankfurt was used in a study to determine the accuracy with which a regionally bounded HCMM scene could be rectified with respect to a preassigned coordinate system. The scale to which excerpts from HCMM data can be sensibly enlarged and the question of how large natural structures must be in order to be identified in a satellite thermal image with the given resolution were also examined. Relief and forest and population distribution maps and a land use map derived from LANDSAT data were digitalized and adapted to a common reference system and then combined in a single multichannel data system. The control points for geometrical rectification were determined using the coordinates of the reference system. The multichannel scene was evaluated in several different manners such as the correlation of surface temperature and relief, surface temperature and land use, or surface temperature and built up areas.

Geometric and energetic considerations of surface fluctuations during ion transfer across the water-immiscible organic liquid interface

NASA Astrophysics Data System (ADS)

Karnes, John J.; Benjamin, Ilan

2016-07-01

Molecular dynamics simulations and umbrella sampling free energy calculations are used to examine the thermodynamics, energetics, and structural fluctuations that accompany the transfer of a small hydrophilic ion (Cl-) across the water/nitrobenzene interface. By examining several constrained interface structures, we isolate the energetic costs of interfacial deformation and co-transfer of hydration waters during the ion transfer. The process is monitored using both energy-based solvation coordinates and a geometric coordinate recently introduced by Morita and co-workers to describe surface fluctuations. Our simulations show that these coordinates provide a complimentary description of the water surface fluctuations during the transfer and are necessary for elucidating the mechanism of the ion transfer.

An efficient approach for computing the geometrical optics field reflected from a numerically specified surface

NASA Technical Reports Server (NTRS)

Mittra, R.; Rushdi, A.

1979-01-01

An approach for computing the geometrical optic fields reflected from a numerically specified surface is presented. The approach includes the step of deriving a specular point and begins with computing the reflected rays off the surface at the points where their coordinates, as well as the partial derivatives (or equivalently, the direction of the normal), are numerically specified. Then, a cluster of three adjacent rays are chosen to define a 'mean ray' and the divergence factor associated with this mean ray. Finally, the ampilitude, phase, and vector direction of the reflected field at a given observation point are derived by associating this point with the nearest mean ray and determining its position relative to such a ray.

Influence of the Geometric Parameter on the Regimes of Natural Convection and Thermal Surface Radiation in a Closed Parallelepiped

NASA Astrophysics Data System (ADS)

Martyushev, S. G.; Miroshnichenko, I. V.; Sheremet, M. A.

2015-11-01

We have performed a numerical analysis of the stationary regimes of thermogravitational convection and thermal surface radiation in a closed differentially heated parallelepiped. The mathematical model formulated in dimensionless natural velocity-pressure-temperature variables was realized numerically in the control volume approach. Analysis of the radiative heat exchange was carried out on the basis of the surface radiation approach with the use of the balance method in the Polyak variant. We have obtained three-dimensional temperature and velocity fields, as well as dependences for the mean Nusselt number reflecting the influence of the geometric parameter, the Rayleigh number, and the reduced emissive factor of the walls on the flow structure and the heat transfer.

Plasma effect on weld pool surface reconstruction by shape-from-polarization analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coniglio, N.; Mathieu, A., E-mail: alexandre.mathieu@u-bourgogne.fr; Aubreton, O.

2014-03-31

The polarimetric state of the thermal radiations emitted by the weld metal contains geometric information about the emitting surface. Even though the analysed thermal radiation has a wavelength corresponding to a blind spectral window of the arc plasma, the physical presence of the arc plasma itself interferes with the rays radiated by the weld pool surface before attaining the polarimeter, thus modifying the geometric information transported by the ray. In the present work, the effect of the arc plasma-surrounding zone on the polarimetric state and propagation direction of the radiated ray is analyzed. The interaction with the arc plasma zonemore » induces a drop in ray intensity and a refraction of ray optical path.« less

Integration of TerraSAR-X, RapidEye and airborne lidar for remote sensing of intertidal bedforms on the upper flats of Norderney (German Wadden Sea)

NASA Astrophysics Data System (ADS)

Adolph, Winny; Jung, Richard; Schmidt, Alena; Ehlers, Manfred; Heipke, Christian; Bartholomä, Alexander; Farke, Hubert

2017-04-01

The Wadden Sea is a large coastal transition area adjoining the southern North Sea uniting ecological key functions with an important role in coastal protection. The region is strictly protected by EU directives and national law and is a UNESCO World Heritage Site, requiring frequent quality assessments and regular monitoring. In 2014 an intertidal bedform area characterised by alternating crests and water-covered troughs on the tidal flats of the island of Norderney (German Wadden Sea sector) was chosen to test different remote sensing methods for habitat mapping: airborne lidar, satellite-based radar (TerraSAR-X) and electro-optical sensors (RapidEye). The results revealed that, although sensitive to different surface qualities, all sensors were able to image the bedforms. A digital terrain model generated from the lidar data shows crests and slopes of the bedforms with high geometric accuracy in the centimetre range, but high costs limit the operation area. TerraSAR-X data enabled identifying the positions of the bedforms reflecting the residual water in the troughs also with a high resolution of up to 1.1 m, but with larger footprints and much higher temporal availability. RapidEye data are sensitive to differences in sediment moisture employed to identify crest areas, slopes and troughs, with high spatial coverage but the lowest resolution (6.5 m). Monitoring concepts may differ in their remote sensing requirements regarding areal coverage, spatial and temporal resolution, sensitivity and geometric accuracy. Also financial budgets limit the selection of sensors. Thus, combining differing assets into an integrated concept of remote sensing contributes to solving these issues.

Die-target for dynamic powder consolidation

DOEpatents

Flinn, J.E.; Korth, G.E.

1985-06-27

A die/target is disclosed for consolidation of a powder, especially an atomized rapidly solidified metal powder, to produce monoliths by the dynamic action of a shock wave, especially a shock wave produced by the detonation of an explosive charge. The die/target comprises a rectangular metal block having a square primary surface with four rectangular mold cavities formed therein to receive the powder. The cavities are located away from the geometrical center of the primary surface and are distributed around such center while also being located away from the geometrical diagonals of the primary surface to reduce the action of reflected waves so as to avoid tensile cracking of the monoliths. The primary surface is covered by a powder retention plate which is engaged by a flyer plate to transmit the shock wave to the primary surface and the powder. Spawl plates are adhesively mounted on other surfaces of the block to act as momentum traps so as to reduce reflected waves in the block. 4 figs.

Shape-based diffeomorphic registration on hippocampal surfaces using Beltrami holomorphic flow.

PubMed

Lui, Lok Ming; Wong, Tsz Wai; Thompson, Paul; Chan, Tony; Gu, Xianfeng; Yau, Shing-Tung

2010-01-01

We develop a new algorithm to automatically register hippocampal (HP) surfaces with complete geometric matching, avoiding the need to manually label landmark features. A good registration depends on a reasonable choice of shape energy that measures the dissimilarity between surfaces. In our work, we first propose a complete shape index using the Beltrami coefficient and curvatures, which measures subtle local differences. The proposed shape energy is zero if and only if two shapes are identical up to a rigid motion. We then seek the best surface registration by minimizing the shape energy. We propose a simple representation of surface diffeomorphisms using Beltrami coefficients, which simplifies the optimization process. We then iteratively minimize the shape energy using the proposed Beltrami Holomorphic flow (BHF) method. Experimental results on 212 HP of normal and diseased (Alzheimer's disease) subjects show our proposed algorithm is effective in registering HP surfaces with complete geometric matching. The proposed shape energy can also capture local shape differences between HP for disease analysis.

Die-target for dynamic powder consolidation

DOEpatents

Flinn, John E.; Korth, Gary E.

1986-01-01

A die/target is disclosed for consolidation of a powder, especially an atomized rapidly solidified metal powder, to produce monoliths by the dynamic action of a shock wave, especially a shock wave produced by the detonation of an explosive charge. The die/target comprises a rectangular metal block having a square primary surface with four rectangular mold cavities formed therein to receive the powder. The cavities are located away from the geometrical center of the primary surface and are distributed around such center while also being located away from the geometrical diagonals of the primary surface to reduce the action of reflected waves so as to avoid tensile cracking of the monoliths. The primary surface is covered by a powder retention plate which is engaged by a flyer plate to transmit the shock wave to the primary surface and the powder. Spawl plates are adhesively mounted on other surfaces of the block to act as momentum traps so as to reduce reflected waves in the block.

Area collapse algorithm computing new curve of 2D geometric objects

NASA Astrophysics Data System (ADS)

Buczek, Michał Mateusz

2017-06-01

The processing of cartographic data demands human involvement. Up-to-date algorithms try to automate a part of this process. The goal is to obtain a digital model, or additional information about shape and topology of input geometric objects. A topological skeleton is one of the most important tools in the branch of science called shape analysis. It represents topological and geometrical characteristics of input data. Its plot depends on using algorithms such as medial axis, skeletonization, erosion, thinning, area collapse and many others. Area collapse, also known as dimension change, replaces input data with lower-dimensional geometric objects like, for example, a polygon with a polygonal chain, a line segment with a point. The goal of this paper is to introduce a new algorithm for the automatic calculation of polygonal chains representing a 2D polygon. The output is entirely contained within the area of the input polygon, and it has a linear plot without branches. The computational process is automatic and repeatable. The requirements of input data are discussed. The author analyzes results based on the method of computing ends of output polygonal chains. Additional methods to improve results are explored. The algorithm was tested on real-world cartographic data received from BDOT/GESUT databases, and on point clouds from laser scanning. An implementation for computing hatching of embankment is described.

Research on Heat Exchange Process in Aircraft Air Conditioning System

NASA Astrophysics Data System (ADS)

Chichindaev, A. V.

2017-11-01

Using of heat-exchanger-condenser in the air conditioning system of the airplane Tu-204 (Boeing, Airbus, Superjet 100, MS-21, etc.) for cooling the compressed air by the cold air with negative temperature exiting the turbine results in a number of operational problems. Mainly it’s frosting of the heat exchange surface, which is the cause of live-section channels frosting, resistance increasing and airflow in the system decreasing. The purpose of this work is to analyse the known freeze-up-fighting methods for heat-exchanger-condenser, description of the features of anti-icing protection and offering solutions to this problem. For the problem of optimizing the design of heat exchangers in this work used generalized criterion that describes the ratio of thermal resistances of cold and hot sections, which include: the ratio of the initial values of heat transfer agents flow state; heat exchange surface finning coefficients; factors which describes the ratio of operating parameters and finning area. By controlling the ratio of the thermal resistances can be obtained the desired temperature of the heat exchange surface, which would prevent freezing. The work presents the results of a numerical study of the effect of different combinations of regime and geometrical factors changes on reduction of the heat-exchanger-condenser freezing surface area, including using of variable ratio of thermal resistances.

Geometry- and Length Scale-Dependent Deformation and Recovery on Micro- and Nanopatterned Shape Memory Polymer Surfaces

PubMed Central

Lee, Wei Li; Low, Hong Yee

2016-01-01

Micro- and nanoscale surface textures, when optimally designed, present a unique approach to improve surface functionalities. Coupling surface texture with shape memory polymers may generate reversibly tuneable surface properties. A shape memory polyetherurethane is used to prepare various surface textures including 2 μm- and 200 nm-gratings, 250 nm-pillars and 200 nm-holes. The mechanical deformation via stretching and recovery of the surface texture are investigated as a function of length scales and shapes. Results show the 200 nm-grating exhibiting more deformation than 2 μm-grating. Grating imparts anisotropic and surface area-to-volume effects, causing different degree of deformation between gratings and pillars under the same applied macroscopic strain. Full distribution of stress within the film causes the holes to deform more substantially than the pillars. In the recovery study, unlike a nearly complete recovery for the gratings after 10 transformation cycles, the high contribution of surface energy impedes the recovery of holes and pillars. The surface textures are shown to perform a switchable wetting function. This study provides insights into how geometric features of shape memory surface patterns can be designed to modulate the shape programming and recovery, and how the control of reversibly deformable surface textures can be applied to transfer microdroplets. PMID:27026290

A novel rotational matrix and translation vector algorithm: geometric accuracy for augmented reality in oral and maxillofacial surgeries.

PubMed

Murugesan, Yahini Prabha; Alsadoon, Abeer; Manoranjan, Paul; Prasad, P W C

2018-06-01

Augmented reality-based surgeries have not been successfully implemented in oral and maxillofacial areas due to limitations in geometric accuracy and image registration. This paper aims to improve the accuracy and depth perception of the augmented video. The proposed system consists of a rotational matrix and translation vector algorithm to reduce the geometric error and improve the depth perception by including 2 stereo cameras and a translucent mirror in the operating room. The results on the mandible/maxilla area show that the new algorithm improves the video accuracy by 0.30-0.40 mm (in terms of overlay error) and the processing rate to 10-13 frames/s compared to 7-10 frames/s in existing systems. The depth perception increased by 90-100 mm. The proposed system concentrates on reducing the geometric error. Thus, this study provides an acceptable range of accuracy with a shorter operating time, which provides surgeons with a smooth surgical flow. Copyright © 2018 John Wiley & Sons, Ltd.

A geometric construction of the Riemann scalar curvature in Regge calculus

NASA Astrophysics Data System (ADS)

McDonald, Jonathan R.; Miller, Warner A.

2008-10-01

The Riemann scalar curvature plays a central role in Einstein's geometric theory of gravity. We describe a new geometric construction of this scalar curvature invariant at an event (vertex) in a discrete spacetime geometry. This allows one to constructively measure the scalar curvature using only clocks and photons. Given recent interest in discrete pre-geometric models of quantum gravity, we believe is it ever so important to reconstruct the curvature scalar with respect to a finite number of communicating observers. This derivation makes use of a new fundamental lattice cell built from elements inherited from both the original simplicial (Delaunay) spacetime and its circumcentric dual (Voronoi) lattice. The orthogonality properties between these two lattices yield an expression for the vertex-based scalar curvature which is strikingly similar to the corresponding hinge-based expression in Regge calculus (deficit angle per unit Voronoi dual area). In particular, we show that the scalar curvature is simply a vertex-based weighted average of deficits per weighted average of dual areas.

Foam structure :from soap froth to solid foams.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraynik, Andrew Michael

2003-01-01

The properties of solid foams depend on their structure, which usually evolves in the fluid state as gas bubbles expand to form polyhedral cells. The characteristic feature of foam structure-randomly packed cells of different sizes and shapes-is examined in this article by considering soap froth. This material can be modeled as a network of minimal surfaces that divide space into polyhedral cells. The cell-level geometry of random soap froth is calculated with Brakke's Surface Evolver software. The distribution of cell volumes ranges from monodisperse to highly polydisperse. Topological and geometric properties, such as surface area and edge length, of themore » entire foam and individual cells, are discussed. The shape of struts in solid foams is related to Plateau borders in liquid foams and calculated for different volume fractions of material. The models of soap froth are used as templates to produce finite element models of open-cell foams. Three-dimensional images of open-cell foams obtained with x-ray microtomography allow virtual reconstruction of skeletal structures that compare well with the Surface Evolver simulations of soap-froth geometry.« less

The evaluation of energy efficiency of convective heat transfer surfaces in tube bundles

NASA Astrophysics Data System (ADS)

Grigoriev, B. A.; Pronin, V. A.; Salohin, V. I.; Sidenkov, D. V.

2017-11-01

When evaluating the effectiveness of the heat exchange surfaces in the main considered characteristics such as heat flow (Q, Watt), the power required for pumps (N, Watt), and surface area of heat transfer (F, m2). The most correct comparison provides a comparison “ceteris paribus”. Carried out performance comparison “ceteris paribus” in-line and staggered configurations of bundles with a circular pipes can serve as a basis for the development of physical models of flow and heat transfer in tube bundles with tubes of other geometric shapes, considering intertubular stream with attached eddies. The effect of longitudinal and transverse steps of the pipes on the energy efficiency of different configurations would take into account by mean of physical relations between the structure of shell side flow with attached eddies and intensity of transfer processes of heat and momentum. With the aim of energy-efficient placement of tubes, such an approach opens up great opportunities for the synthesis of a plurality of tubular heat exchange surfaces, in particular, the layout of the twisted and in-line-diffuser type with a drop-shaped pipes.

Reduction and shaping of graphene-oxide by laser-printing for controlled bone tissue regeneration and bacterial killing

NASA Astrophysics Data System (ADS)

Palmieri, Valentina; Barba, Marta; Di Pietro, Lorena; Gentilini, Silvia; Chiara Braidotti, Maria; Ciancico, Carlotta; Bugli, Francesca; Ciasca, Gabriele; Larciprete, Rosanna; Lattanzi, Wanda; Sanguinetti, Maurizio; De Spirito, Marco; Conti, Claudio; Papi, Massimiliano

2018-01-01

Graphene and graphene oxide (GO) are capable of inducing stem cells differentiation into bone tissue with variable efficacy depending on reductive state of the material. Thus, modulation of osteogenic process and of bone mineral density distribution is theoretically possible by controlling the GO oxidative state. In this study, we laser-printed GO surfaces in order to obtain both a local photo-thermal GO reduction and the formation of nano-wrinkles along precise geometric pattern. Initially, after cells adhered on the surface, stem cells migrated and accumulated on the reduced and wrinkled surface. When the local density of the stem cells on the reduced stripes was high, cells started to proliferate and occupy the oxidized/flat area. The designed surfaces morphology guided stem cell orientation and the reduction accelerated differentiation. Furthermore the reduced sharp nano-wrinkles were able to enhance the GO antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), a common cause of prosthetic joints infections. This strategy can offer a revolution in present and future trends of scaffolds design for regenerative medicine.

Problems And Their Solutions When Thin-Walled Turned Parts Of High Precision With Quasi-Optical Surfaces Are Manufactured On A CNC Automatic Lathe Under Workshop Conditions

NASA Astrophysics Data System (ADS)

Jaeger, Valentin E.

1989-04-01

The geometrical accuracy and surface roughness of diamond-turned workpieces is influenced by several parameters: the properties of the machine tool, the cutting process and the environmental conditions. A thin-walled electrode made from an aluminium alloy (wall thickness: 1 mm, length: 169 mm, outer diameter: 126 mm) and intended for an electrostatic measuring instrument, serves as an example to show how quasi-optical surfaces with a surface roughness Rα < 10 nm and deviations from roundness of <= 5 μm can be achieved when some of these influence quantities are optimized. The cylindrical part of the electrode was turned by means of a rounded mirror-finish diamond tool, the width of the cutting edge being 2 mm, the rake angle -6° and the clearance angle 2°. Compliance with the tolerances of geometrical accuracy was particularly difficult. As age-hardened wrought aluminium alloys cannot be stress-relieved by annealing, or only insufficiently, the geometrical accuracy - in particular the roundness - of thin-walled, rotationally symmetric bodies decisively depends on the state of stress of the workpiece material, on the clamping fixture and on the balanced condition of this clamping fixture.

Geometric properties of commutative subalgebras of partial differential operators

NASA Astrophysics Data System (ADS)

Zheglov, A. B.; Kurke, H.

2015-05-01

We investigate further algebro-geometric properties of commutative rings of partial differential operators, continuing our research started in previous articles. In particular, we start to explore the simplest and also certain known examples of quantum algebraically completely integrable systems from the point of view of a recent generalization of Sato's theory, developed by the first author. We give a complete characterization of the spectral data for a class of 'trivial' commutative algebras and strengthen geometric properties known earlier for a class of known examples. We also define a kind of restriction map from the moduli space of coherent sheaves with fixed Hilbert polynomial on a surface to an analogous moduli space on a divisor (both the surface and the divisor are part of the spectral data). We give several explicit examples of spectral data and corresponding algebras of commuting (completed) operators, producing as a by-product interesting examples of surfaces that are not isomorphic to spectral surfaces of any (maximal) commutative ring of partial differential operators of rank one. Finally, we prove that any commutative ring of partial differential operators whose normalization is isomorphic to the ring of polynomials k \\lbrack u,t \\rbrack is a Darboux transformation of a ring of operators with constant coefficients. Bibliography: 39 titles.

Ambient occlusion effects for combined volumes and tubular geometry.

PubMed

Schott, Mathias; Martin, Tobias; Grosset, A V Pascal; Smith, Sean T; Hansen, Charles D

2013-06-01

This paper details a method for interactive direct volume rendering that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube-shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The algorithm extends the recently presented the directional occlusion shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry. Stream tube geometries are computed using an effective spline-based interpolation and approximation scheme that avoids self-intersection and maintains coherent orientation of the stream tube segments to avoid surface deforming twists. Furthermore, strategies to reduce the geometric and specular aliasing of the stream tubes are discussed.

Dynamic frequency tuning of electric and magnetic metamaterial response

DOEpatents

O'Hara, John F; Averitt, Richard; Padilla, Willie; Chen, Hou-Tong

2014-09-16

A geometrically modifiable resonator is comprised of a resonator disposed on a substrate, and a means for geometrically modifying the resonator. The geometrically modifiable resonator can achieve active optical and/or electronic control of the frequency response in metamaterials and/or frequency selective surfaces, potentially with sub-picosecond response times. Additionally, the methods taught here can be applied to discrete geometrically modifiable circuit components such as inductors and capacitors. Principally, controlled conductivity regions, using either reversible photodoping or voltage induced depletion activation, are used to modify the geometries of circuit components, thus allowing frequency tuning of resonators without otherwise affecting the bulk substrate electrical properties. The concept is valid over any frequency range in which metamaterials are designed to operate.

Ambient Occlusion Effects for Combined Volumes and Tubular Geometry

PubMed Central

Schott, Mathias; Martin, Tobias; Grosset, A.V. Pascal; Smith, Sean T.; Hansen, Charles D.

2013-01-01

This paper details a method for interactive direct volume rendering that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube-shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The algorithm extends the recently presented the directional occlusion shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry. Stream tube geometries are computed using an effective spline-based interpolation and approximation scheme that avoids self-intersection and maintains coherent orientation of the stream tube segments to avoid surface deforming twists. Furthermore, strategies to reduce the geometric and specular aliasing of the stream tubes are discussed. PMID:23559506

Geometric curvature and phase of the Rabi model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Lijun; Huai, Sainan; Guo, Liping

2015-11-15

We study the geometric curvature and phase of the Rabi model. Under the rotating-wave approximation (RWA), we apply the gauge independent Berry curvature over a surface integral to calculate the Berry phase of the eigenstates for both single and two-qubit systems, which is found to be identical with the system of spin-1/2 particle in a magnetic field. We extend the idea to define a vacuum-induced geometric curvature when the system starts from an initial state with pure vacuum bosonic field. The induced geometric phase is related to the average photon number in a period which is possible to measure inmore » the qubit–cavity system. We also calculate the geometric phase beyond the RWA and find an anomalous sudden change, which implies the breakdown of the adiabatic theorem and the Berry phases in an adiabatic cyclic evolution are ill-defined near the anti-crossing point in the spectrum.« less

Towards improved characterization of northern wetlands (or other landscapes) by remote sensing - a rapid approach to collect ground truth data

NASA Astrophysics Data System (ADS)

Gålfalk, Magnus; Karlson, Martin; Crill, Patrick; Bastviken, David

2017-04-01

The calibration and validation of remote sensing land cover products is highly dependent on accurate ground truth data, which are costly and practically challenging to collect. This study evaluates a novel and efficient alternative to field surveys and UAV imaging commonly applied for this task. The method consists of i) a light weight, water proof, remote controlled RGB-camera mounted on an extendable monopod used for acquiring wide-field images of the ground from a height of 4.5 meters, and ii) a script for semi-automatic image classification. In the post-processing, the wide-field images are corrected for optical distortion and geometrically rectified so that the spatial resolution is the same over the surface area used for classification. The script distinguishes land surface components by color, brightness and spatial variability. The method was evaluated in wetland areas located around Abisko, northern Sweden. Proportional estimates of the six main surface components in the wetlands (wet and dry Sphagnum, shrub, grass, water, rock) were derived for 200 images, equivalent to 10 × 10 m field plots. These photo plots were then used as calibration data for a regional scale satellite based classification which separates the six wetland surface components using a Sentinel-1 time series. The method presented in this study is accurate, rapid, robust and cost efficient in comparison to field surveys (time consuming) and drone mapping (which require low wind speeds and no rain, suffer from battery limited flight times, have potential GPS/compass errors far north, and in some areas are prohibited by law).

Some experiments with thin prisms

NASA Astrophysics Data System (ADS)

Fernando, P. C. B.

1980-11-01

In most attempts at modernizing the college physics curriculum one of the first branches of physics to be eliminated is geometrical optics. However, in developing countries where the curriculum must give emphasis to applied areas (if physics is to survive at all!), geometrical optics has a role to play, especially in its relationship to the professional course ''Optometry.'' The author presents a few experiments in geometrical optics with an ophthalmic opitics bias, which could be introduced into the college physics laboratory.

Hyperspectral remote sensing exploration of carbonatite - an example from Epembe, Kunene region, Namibia

NASA Astrophysics Data System (ADS)

Zimmermann, Robert; Brandmeier, Melanie; Andreani, Louis; Gloaguen, Richard

2015-04-01

Remote sensing data can provide valuable information about ore deposits and their alteration zones at surface level. High spectral and spatial resolution of the data is essential for detailed mapping of mineral abundances and related structures. Carbonatites are well known for hosting economic enrichments in REE, Ta, Nb and P (Jones et al. 2013). These make them a preferential target for exploration for those critical elements. In this study we show how combining geomorphic, textural and spectral data improves classification result. We selected a site with a well-known occurrence in northern Namibia: the Epembe dyke. For analysis LANDSAT 8, SRTM and airborne hyperspectral (HyMap) data were chosen. The overlapping data allows a multi-scale and multi-resolution approach. Results from data analysis were validated during fieldwork in 2014. Data was corrected for atmospherical and geometrical effects. Image classification, mineral mapping and tectonic geomorphology allow a refinement of the geological map by lithological mapping in a second step. Detailed mineral abundance maps were computed using spectral unmixing techniques. These techniques are well suited to map abundances of carbonate minerals, but not to discriminate the carbonatite itself from surrounding rocks with similar spectral signatures. Thus, geometric indices were calculated using tectonic geomorphology and textures. For this purpose the TecDEM-toolbox (SHAHZAD & GLOAGUEN 2011) was applied to the SRTM-data for geomorphic analysis. Textural indices (e.g. uniformity, entropy, angular second moment) were derived from HyMap and SRTM by a grey-level co-occurrence matrix (CLAUSI 2002). The carbonatite in the study area is ridge-forming and shows a narrow linear feature in the textural bands. Spectral and geometric information were combined using kohonen Self-Organizing Maps (SOM) for unsupervised clustering. The resulting class spectra were visually compared and interpreted. Classes with similar signatures were merged according to geological context. The major conclusions are: 1. Carbonate minerals can be mapped using spectral unmixing techniques. 2. Carbonatites are associated with specific geometric pattern 3. The combination of spectral and geometric information improves classification result and reduces misclassification. References Clausi, D. A. (2002): An analysis of co-occurrence texture statistics as a function of grey-level quantization. - Canadian Journal of Remote Sensing, 28 (1), 45-62 Jones, A. P., Genge, M. and Carmody, L (2013): Carbonate Melts and Carbonatites. - Reviews in Mineralogy & Geochemistry, 75, 289-322 Shahzad, F. & Gloaguen, R. (2011): TecDEM: A MATLAB based toolbox for tectonic geomorphology, Part 2: Surface dynamics and basin analysis. - Computers and Geosciences, 37 (2), 261-271

Geometrical analysis of circular-cut spiral bevel gears

NASA Technical Reports Server (NTRS)

Huston, R. L.

1983-01-01

Geometrical studies of circular cut spiral bevel gears are reported. Tooth profile changes heel to toe are studied in the transverse plane. Pressure angle changes are determined. The radiuses of curvature of the tooth surfaces generated by various cutter profiles are also determined. The consequences of cutter profile changes are explored. Crown gears are emphasized and the implications for conical gears are discussed.

The Influence of Parameters on the Generatrix of the Helicoid Form Guide of Geokhod Bar Working Body

NASA Astrophysics Data System (ADS)

Aksenov, Vladimir; Sadovets, Vladimir; Pashkov, Dmitriy

2017-11-01

Influence of geometrical parameters of generatrix of helicoid on a guide of geokhod bar working body is proved in article. The relevance of the conducted research is considered and proved. General characteristics of the geokhod are presented. Features of geokhod working body, in particular formation of irregular shape of a surface of a face and working body are formulated and also it is told that at screw movement of geokhod working body of a face, points of working body will be formed a helicoid (screw) surface of a face. For establishing of die goals and objectives of research general geometrical parameters of generatrix is marked and justified which treat length of generatrix, width of generatrix of helicoid. pitch of hehcoid and it's form. Forms of guides of geokhod bar working body based on basis parameters of geokhod and accepted general geometrical parameters of geokhod working body are received and presented. In virtue of the conducted research the dependence of a form of a guide of bar on general geometrical parameters of helicoid is defined and also basis parameters of hehcoid in influencing a form of guide of working body.

Interactive graphic editing tools in bioluminescent imaging simulation

NASA Astrophysics Data System (ADS)

Li, Hui; Tian, Jie; Luo, Jie; Wang, Ge; Cong, Wenxiang

2005-04-01

It is a challenging task to accurately describe complicated biological tissues and bioluminescent sources in bioluminescent imaging simulation. Several graphic editing tools have been developed to efficiently model each part of the bioluminescent simulation environment and to interactively correct or improve the initial models of anatomical structures or bioluminescent sources. There are two major types of graphic editing tools: non-interactive tools and interactive tools. Geometric building blocks (i.e. regular geometric graphics and superquadrics) are applied as non-interactive tools. To a certain extent, complicated anatomical structures and bioluminescent sources can be approximately modeled by combining a sufficient large number of geometric building blocks with Boolean operators. However, those models are too simple to describe the local features and fine changes in 2D/3D irregular contours. Therefore, interactive graphic editing tools have been developed to facilitate the local modifications of any initial surface model. With initial models composed of geometric building blocks, interactive spline mode is applied to conveniently perform dragging and compressing operations on 2D/3D local surface of biological tissues and bioluminescent sources inside the region/volume of interest. Several applications of the interactive graphic editing tools will be presented in this article.

A calibration method for fringe reflection technique based on the analytical phase-slope description

NASA Astrophysics Data System (ADS)

Wu, Yuxiang; Yue, Huimin; Pan, Zhipeng; Liu, Yong

2018-05-01

The fringe reflection technique (FRT) has been one of the most popular methods to measure the shape of specular surface these years. The existing system calibration methods of FRT usually contain two parts, which are camera calibration and geometric calibration. In geometric calibration, the liquid crystal display (LCD) screen position calibration is one of the most difficult steps among all the calibration procedures, and its accuracy is affected by the factors such as the imaging aberration, the plane mirror flatness, and LCD screen pixel size accuracy. In this paper, based on the deduction of FRT analytical phase-slope description, we present a novel calibration method with no requirement to calibrate the position of LCD screen. On the other hand, the system can be arbitrarily arranged, and the imaging system can either be telecentric or non-telecentric. In our experiment of measuring the 5000mm radius sphere mirror, the proposed calibration method achieves 2.5 times smaller measurement error than the geometric calibration method. In the wafer surface measuring experiment, the measurement result with the proposed calibration method is closer to the interferometer result than the geometric calibration method.

Site descriptive modeling as a part of site characterization in Sweden - Concluding the surface based investigations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersson, Johan; Winberg, Anders; Skagius, Kristina

The Swedish Nuclear Fuel and Waste Management Co., SKB, is currently finalizing its surface based site investigations for the final repository for spent nuclear fuel in the municipalities of Oestharmnar (the Forsmark area) and Oskarshamn (the Simpevar/Laxemar area). The investigation data are assessed into a Site Descriptive Model, constituting a synthesis of geology, rock mechanics, thermal properties, hydrogeology, hydro-geochemistry, transport properties and a surface system description. Site data constitute a wide range of different measurement results. These data both need to be checked for consistency and to be interpreted into a format more amenable for three-dimensional modeling. The three-dimensional modelingmore » (i.e. estimating the distribution of parameter values in space) is made in a sequence where the geometrical framework is taken from the geological models and in turn used by the rock mechanics, thermal and hydrogeological modeling. These disciplines in turn are partly interrelated, and also provide feedback to the geological modeling, especially if the geological description appears unreasonable when assessed together with the other data. Procedures for assessing the uncertainties and the confidence in the modeling have been developed during the course of the site modeling. These assessments also provide key input to the completion of the site investigation program. (authors)« less

Investigating the Origin of Bright Materials on Vesta: Synthesis, Conclusions, and Implications

NASA Technical Reports Server (NTRS)

Li, Jian-Yang; Mittlefehldt, D. W.; Pieters, C. M.; De Sanctis, M. C.; Schroder, S. E.; Hiesinger, H.; Blewett, D. T.; Russell, C. T.; Raymond, C. A.; Keller, H. U.

2012-01-01

The Dawn spacecraft started orbiting the second largest asteroid (4) Vesta in August 2011, revealing the details of its surface at an unprecedented pixel scale as small as approx.70 m in Framing Camera (FC) clear and color filter images and approx.180 m in the Visible and Infrared Spectrometer (VIR) data in its first two science orbits, the Survey Orbit and the High Altitude Mapping Orbit (HAMO) [1]. The surface of Vesta displays the greatest diversity in terms of geology and mineralogy of all asteroids studied in detail [2, 3]. While the albedo of Vesta of approx.0.38 in the visible wavelengths [4, 5] is one of the highest among all asteroids, the surface of Vesta shows the largest variation of albedos found on a single asteroid, with geometric albedos ranging at least from approx.0.10 to approx.0.67 in HAMO images [5]. There are many distinctively bright and dark areas observed on Vesta, associated with various geological features and showing remarkably different forms. Here we report our initial attempt to understand the origin of the areas that are distinctively brighter than their surroundings. The dark materials on Vesta clearly are different in origin from bright materials and are reported in a companion paper [6].

Coccolith arrangement follows Eulerian mathematics in the coccolithophore Emiliania huxleyi.

PubMed

Xu, Kai; Hutchins, David; Gao, Kunshan

2018-01-01

The globally abundant coccolithophore, Emiliania huxleyi , plays an important ecological role in oceanic carbon biogeochemistry by forming a cellular covering of plate-like CaCO 3 crystals (coccoliths) and fixing CO 2 . It is unknown how the cells arrange different-sized coccoliths to maintain full coverage, as the cell surface area of the cell changes during daily cycle. We used Euler's polyhedron formula and CaGe simulation software, validated with the geometries of coccoliths, to analyze and simulate the coccolith topology of the coccosphere and to explore the arrangement mechanisms. There were only small variations in the geometries of coccoliths, even when the cells were cultured under variable light conditions. Because of geometric limits, small coccoliths tended to interlock with fewer and larger coccoliths, and vice versa. Consequently, to sustain a full coverage on the surface of cell, each coccolith was arranged to interlock with four to six others, which in turn led to each coccosphere contains at least six coccoliths. The number of coccoliths per coccosphere must keep pace with changes on the cell surface area as a result of photosynthesis, respiration and cell division. This study is an example of natural selection following Euler's polyhedral formula, in response to the challenge of maintaining a CaCO 3 covering on coccolithophore cells as cell size changes.

Control of deviations and prediction of surface roughness from micro machining of THz waveguides using acoustic emission signals

NASA Astrophysics Data System (ADS)

Griffin, James M.; Diaz, Fernanda; Geerling, Edgar; Clasing, Matias; Ponce, Vicente; Taylor, Chris; Turner, Sam; Michael, Ernest A.; Patricio Mena, F.; Bronfman, Leonardo

2017-02-01

By using acoustic emission (AE) it is possible to control deviations and surface quality during micro milling operations. The method of micro milling is used to manufacture a submillimetre waveguide where micro machining is employed to achieve the required superior finish and geometrical tolerances. Submillimetre waveguide technology is used in deep space signal retrieval where highest detection efficiencies are needed and therefore every possible signal loss in the receiver has to be avoided and stringent tolerances achieved. With a sub-standard surface finish the signals travelling along the waveguides dissipate away faster than with perfect surfaces where the residual roughness becomes comparable with the electromagnetic skin depth. Therefore, the higher the radio frequency the more critical this becomes. The method of time-frequency analysis (STFT) is used to transfer raw AE into more meaningful salient signal features (SF). This information was then correlated against the measured geometrical deviations and, the onset of catastrophic tool wear. Such deviations can be offset from different AE signals (different deviations from subsequent tests) and feedback for a final spring cut ensuring the geometrical accuracies are met. Geometrical differences can impact on the required transfer of AE signals (change in cut off frequencies and diminished SNR at the interface) and therefore errors have to be minimised to within 1 μm. Rules based on both Classification and Regression Trees (CART) and Neural Networks (NN) were used to implement a simulation displaying how such a control regime could be used as a real time controller, be it corrective measures (via spring cuts) over several initial machining passes or, with a micron cut introducing a level plain measure for allowing setup corrective measures (similar to a spirit level).

Secondary Mathematics Education in the Soviet Union, an Individual Study Project.

DTIC Science & Technology

1982-05-14

Pythagoras and other well-known congruence theorems on angles and triangles. Concepts of set theory are developed in relation to the topics studied. Grades 6...geometry (areas, volumes, etc.). Geometric topics include: use of the ruler, protractor, and compasses in geometric constructions; Theorem of

GOSAILT: A hybrid of GOMS and SAILT with topography consideration

NASA Astrophysics Data System (ADS)

Wu, S.; Wen, J.

2017-12-01

Heterogeneous terrain significantly complicated the energy, mass and momentum exchange between the atmosphere and terrestrial ecosystem. Understanding of topographic effect on the forest reflectance is critical for biophysical parameters retrieval over rugged area. In this paper, a new hybrid bidirectional reflectance distribution function (BRDF) model of geometric optical mutual shadowing and scattering-from-arbitrarily-inclined-leaves model coupled topography (GOSAILT) for sloping forest was proposed. The effects of slope, aspect, gravity field of tree crown, multiple scattering scheme, and diffuse skylight are considered. The area proportions of scene components estimated by the GOSAILT model were compared with the geometric optical model for sloping terrains (GOST) model. The 3-D discrete anisotropic radiative transfer (DART) simulations were used to evaluate the performance of GOSAILT. The results indicate that the canopy reflectance is distorted by the slopes with a maximum variation of 78.3% in the red band and 17.3% in the NIR band on a steep 60 º slope. Compared with the DART simulations, the proposed GOSAILT model can capture anisotropic reflectance well with a determine coefficient (R2) of 0.9720 and 0.6701, root-mean-square error (RMSE) of 0.0024 and 0.0393, mean absolute percentage error of 2.4% and 4.61% for the red and near-infrared (NIR) band. The comparison results indicate the GOSAIL model can accurately reproducing the angular feature of discrete canopy over rugged terrain conditions. The GOSAILT model is promising for the land surface biophysical parameters retrieval (e.g. albedo, leaf area index) over the heterogeneous terrain.

Photonic and phononic surface and edge modes in three-dimensional phoxonic crystals

NASA Astrophysics Data System (ADS)

Ma, Tian-Xue; Wang, Yue-Sheng; Zhang, Chuanzeng

2018-04-01

We investigate the photonic and phononic surface and edge modes in finite-size three-dimensional phoxonic crystals. By appropriately terminating the phoxonic crystals, the photons and phonons can be simultaneously guided at the two-dimensional surface and/or the one-dimensional edge of the terminated crystals. The Bloch surface and edge modes show that the electromagnetic and acoustic waves are highly localized near the surface and edge, respectively. The surface and edge geometries play important roles in tailoring the dispersion relations of the surface and edge modes, and dual band gaps for the surface or edge modes can be simultaneously achieved by changing the geometrical configurations. Furthermore, as the band gaps for the bulk modes are the essential prerequisites for the realization of dual surface and edge modes, the photonic and phononic bulk-mode band gap properties of three different types of phoxonic crystals with six-connected networks are revealed. It is found that the geometrical characteristic of the crystals with six-connected networks leads to dual large bulk-mode band gaps. Compared with the conventional bulk modes, the surface and edge modes provide a new approach for the photon and phonon manipulation and show great potential for phoxonic crystal devices and optomechanics.

3D Visualization of Urban Area Using Lidar Technology and CityGML

NASA Astrophysics Data System (ADS)

Popovic, Dragana; Govedarica, Miro; Jovanovic, Dusan; Radulovic, Aleksandra; Simeunovic, Vlado

2017-12-01

3D models of urban areas have found use in modern world such as navigation, cartography, urban planning visualization, construction, tourism and even in new applications of mobile navigations. With the advancement of technology there are much better solutions for mapping earth’s surface and spatial objects. 3D city model enables exploration, analysis, management tasks and presentation of a city. Urban areas consist of terrain surfaces, buildings, vegetation and other parts of city infrastructure such as city furniture. Nowadays there are a lot of different methods for collecting, processing and publishing 3D models of area of interest. LIDAR technology is one of the most effective methods for collecting data due the large amount data that can be obtained with high density and geometrical accuracy. CityGML is open standard data model for storing alphanumeric and geometry attributes of city. There are 5 levels of display (LoD0, LoD1, LoD2, LoD3, LoD4). In this study, main aim is to represent part of urban area of Novi Sad using LIDAR technology, for data collecting, and different methods for extraction of information’s using CityGML as a standard for 3D representation. By using series of programs, it is possible to process collected data, transform it to CityGML and store it in spatial database. Final product is CityGML 3D model which can display textures and colours in order to give a better insight of the cities. This paper shows results of the first three levels of display. They consist of digital terrain model and buildings with differentiated rooftops and differentiated boundary surfaces. Complete model gives us a realistic view of 3D objects.

Syntactic Approach To Geometric Surface Shell Determination

NASA Astrophysics Data System (ADS)

DeGryse, Donald G.; Panton, Dale J.

1980-12-01

Autonomous terminal homing of a smart missile requires a stored reference scene of the target for which the missle is destined. The reference scene is produced from stereo source imagery by deriving a three-dimensional model containing cultural structures such as buildings, towers, bridges, and tanks. This model is obtained by the precise matching of cultural features from one image of the stereo pair to the other. In the past, this stereo matching process has relied heavily on local edge operators and a gray scale matching metric. The processing is performed line by line over the imagery and the amount of geometric control is minimal. As a result, the gross structure of the scene is determined but the derived three-dimensional data is noisy, oscillatory, and at times significantly inaccurate. This paper discusses new concepts that are currently being developed to stabilize this geometric reference preparation process. The new concepts involve the use of a structural syntax which will be used as a geometric constraint on automatic stereo matching. The syntax arises from the stereo configuration of the imaging platforms at the time of exposure and the knowledge of how various cultural structures are constructed. The syntax is used to parse a scene in terms of its cultural surfaces and to dictate to the matching process the allowable relative positions and orientations of surface edges in the image planes. Using the syntax, extensive searches using a gray scale matching metric are reduced.

Photometric models of disk-integrated observations of the OSIRIS-REx target Asteroid (101955) Bennu

NASA Astrophysics Data System (ADS)

Takir, Driss; Clark, Beth Ellen; Drouet d'Aubigny, Christian; Hergenrother, Carl W.; Li, Jian-Yang; Lauretta, Dante S.; Binzel, Richard P.

2015-05-01

We used ground-based photometric phase curve data of the OSIRIS-REx target Asteroid (101955) Bennu and low phase angle data from Asteroid (253) Mathilde as a proxy to fit Bennu data with Minnaert, Lommel-Seeliger, (RObotic Lunar Orbiter) ROLO, Hapke, and McEwen photometric models, which capture the global light scattering properties of the surface and subsequently allow us to calculate the geometric albedo, phase integral, spherical Bond albedo, and the average surface normal albedo for Bennu. We find that Bennu has low reflectance and geometric albedo values, such that multiple scattering is expected to be insignificant. Our photometric models relate the reflectance from Bennu's surface to viewing geometry as functions of the incidence, emission, and phase angles. Radiance Factor functions (RADFs) are used to model the disk-resolved brightness of Bennu. The Minnaert, Lommel-Seeliger, ROLO, and Hapke photometric models work equally well in fitting the best ground-based photometric phase curve data of Bennu. The McEwen model works reasonably well at phase angles from 20° to 70°. Our calculated geometric albedo values of 0.047-0.014+0.012,0.047-0.014+0.005 , and 0.048-0.022+0.012 for the Minnaert, the Lommel-Seeliger, and the ROLO models respectively are consistent with the geometric albedo of 0.045 ± 0.015 computed by Emery et al. (Emery, J.P. et al. [2014]. Icarus 234, 17-35) and Hergenrother et al. (Hergenrother, C.W. et al. [2014].

Geometric morphometrics and virtual anthropology: advances in human evolutionary studies.

PubMed

Rein, Thomas R; Harvati, Katerina

2014-01-01

Geometric morphometric methods have been increasingly used in paleoanthropology in the last two decades, lending greater power to the analysis and interpretation of the human fossil record. More recently the advent of the wide use of computed tomography and surface scanning, implemented in combination with geometric morphometrics (GM), characterizes a new approach, termed Virtual Anthropology (VA). These methodological advances have led to a number of developments in human evolutionary studies. We present some recent examples of GM and VA related research in human evolution with an emphasis on work conducted at the University of Tübingen and other German research institutions.

Geometric scalar theory of gravity beyond spherical symmetry

NASA Astrophysics Data System (ADS)

Moschella, U.; Novello, M.

2017-04-01

We construct several exact solutions for a recently proposed geometric scalar theory of gravity. We focus on a class of axisymmetric geometries and a big-bang-like geometry and discuss their Lorentzian character. The axisymmetric solutions are parametrized by an integer angular momentum l . The l =0 (spherical) case gives rise to the Schwarzschild geometry. The other solutions have naked singular surfaces. While not a priori obvious, all the solutions that we present here are globally Lorentzian. The Lorentzian signature appears to be a robust property of the disformal geometries solving the vacuum geometric scalar theory of gravity equations.

Allometric scaling of infraorbital surface topography in Homo.

PubMed

Maddux, Scott D; Franciscus, Robert G

2009-02-01

Infraorbital morphology is often included in phylogenetic and functional analyses of Homo. The inclusion of distinct infraorbital configurations, such as the "canine fossa" in Homo sapiens or the "inflated" maxilla in Neandertals, is generally based on either descriptive or qualitative assessments of this morphology, or simple linear chord and subtense measurements. However, the complex curvilinear surface of the infraorbital region has proven difficult to quantify through these traditional methods. In this study, we assess infraorbital shape and its potential allometric scaling in fossil Homo (n=18) and recent humans (n=110) with a geometric morphometric method well-suited for quantifying complex surface topographies. Our results indicate that important aspects of infraorbital shape are correlated with overall infraorbital size across Homo. Specifically, individuals with larger infraorbital areas tend to exhibit relatively flatter infraorbital surface topographies, taller and narrower infraorbital areas, sloped inferior orbital rims, anteroinferiorly oriented maxillary body facies, posteroinferiorly oriented maxillary processes of the zygomatic, and non-everted lateral nasal margins. In contrast, individuals with smaller infraorbital regions generally exhibit relatively depressed surface topographies, shorter and wider infraorbital areas, projecting inferior orbital rims, posteroinferiorly oriented maxillary body facies, anteroinferiorly oriented maxillary processes, and everted lateral nasal margins. These contrasts form a continuum and only appear dichotomized at the ends of the infraorbital size spectrum. In light of these results, we question the utility of incorporating traditionally polarized infraorbital morphologies in phylogenetic and functional analyses without due consideration of continuous infraorbital and facial size variation in Homo. We conclude that the essentially flat infraorbital surface topography of Neandertals is not unique and can be explained, in part, as a function of possessing large infraorbital regions, the ancestral condition for Homo. Furthermore, it appears likely that the diminutive infraorbital region of anatomically modern Homo sapiens is a primary derived trait, with related features such as depressed infraorbital surface topography expressed as correlated secondary characters.

A topological study of gravity free-surface waves generated by bluff bodies using the method of steepest descents

PubMed Central

2016-01-01

The standard analytical approach for studying steady gravity free-surface waves generated by a moving body often relies upon a linearization of the physical geometry, where the body is considered asymptotically small in one or several of its dimensions. In this paper, a methodology that avoids any such geometrical simplification is presented for the case of steady-state flows at low speeds. The approach is made possible through a reduction of the water-wave equations to a complex-valued integral equation that can be studied using the method of steepest descents. The main result is a theory that establishes a correspondence between different bluff-bodied free-surface flow configurations, with the topology of the Riemann surface formed by the steepest descent paths. Then, when a geometrical feature of the body is modified, a corresponding change to the Riemann surface is observed, and the resultant effects to the water waves can be derived. This visual procedure is demonstrated for the case of two-dimensional free-surface flow past a surface-piercing ship and over an angled step in a channel. PMID:27493559

Geometry effect on electrokinetic flow and ionic conductance in pH-regulated nanochannels

NASA Astrophysics Data System (ADS)

Sadeghi, Morteza; Saidi, Mohammad Hassan; Moosavi, Ali; Sadeghi, Arman

2017-12-01

Semi-analytical solutions are obtained for the electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties associated with long pH-regulated nanochannels of arbitrary but constant cross-sectional area. The effects of electric double layer overlap, multiple ionic species, and surface association/dissociation reactions are all taken into account, assuming low surface potentials. The method of analysis includes series solutions which the pertinent coefficients are obtained by applying the wall boundary conditions using either of the least-squares or point matching techniques. Although the procedure is general enough to be applied to almost any arbitrary cross section, nine nanogeometries including polygonal, trapezoidal, double-trapezoidal, rectangular, elliptical, semi-elliptical, isosceles triangular, rhombic, and isotropically etched profiles are selected for presentation. For the special case of an elliptic cross section, full analytical solutions are also obtained utilizing the Mathieu functions. We show that the geometrical configuration plays a key role in determination of the ionic conductance, surface charge density, electrical potential and velocity fields, and proton enhancement. In this respect, the net electric charge and convective ionic conductance are higher for channels of larger perimeter to area ratio, whereas the opposite is true for the average surface charge density and mean velocity; the geometry impact on the two latest ones, however, vanishes if the background salt concentration is high enough. Moreover, we demonstrate that considering a constant surface potential equal to the average charge-regulated potential provides sufficiently accurate results for smooth geometries such as an ellipse at medium-high aspect ratios but leads to significant errors for geometries having narrow corners such as a triangle.

Rayleigh's hypothesis and the geometrical optics limit.

PubMed

Elfouhaily, Tanos; Hahn, Thomas

2006-09-22

The Rayleigh hypothesis (RH) is often invoked in the theoretical and numerical treatment of rough surface scattering in order to decouple the analytical form of the scattered field. The hypothesis stipulates that the scattered field away from the surface can be extended down onto the rough surface even though it is formed by solely up-going waves. Traditionally this hypothesis is systematically used to derive the Volterra series under the small perturbation method which is equivalent to the low-frequency limit. In this Letter we demonstrate that the RH also carries the high-frequency or the geometrical optics limit, at least to first order. This finding has never been explicitly derived in the literature. Our result comforts the idea that the RH might be an exact solution under some constraints in the general case of random rough surfaces and not only in the case of small-slope deterministic periodic gratings.

Application of Stereolithographic Custom Models for Studying the Impact of Biofilms and Mineral Precipitation on Fluid Flow

PubMed Central

Stoner, D. L.; Watson, S. M.; Stedtfeld, R. D.; Meakin, P.; Griffel, L. K.; Tyler, T. L.; Pegram, L. M.; Barnes, J. M.; Deason, V. A.

2005-01-01

Here we introduce the use of transparent experimental models fabricated by stereolithography for studying the impacts of biomass accumulation, minerals precipitation, and physical configuration of flow paths on liquid flow in fracture apertures. The internal configuration of the models ranged in complexity from simple geometric shapes to those that incorporate replicated surfaces of natural fractures and computationally derived fracture surfaces. High-resolution digital time-lapse imaging was employed to qualitatively observe the migration of colloidal and soluble dyes through the flow models. In this study, a Sphingomonas sp. and Sporosarcina (Bacillus) pasteurii influenced the fluid dynamics by physically altering flow paths. Microbial colonization and calcite deposition enhanced the stagnant regions adjacent to solid boundaries. Microbial growth and calcite precipitation occurred to a greater extent in areas behind the fabricated obstacles and less in high-velocity orifices. PMID:16332867

Application of stereolithographic custom models for studying the impact of biofilms and mineral precipitation on fluid flow.

PubMed

Stoner, D L; Watson, S M; Stedtfeld, R D; Meakin, P; Griffel, L K; Tyler, T L; Pegram, L M; Barnes, J M; Deason, V A

2005-12-01

Here we introduce the use of transparent experimental models fabricated by stereolithography for studying the impacts of biomass accumulation, minerals precipitation, and physical configuration of flow paths on liquid flow in fracture apertures. The internal configuration of the models ranged in complexity from simple geometric shapes to those that incorporate replicated surfaces of natural fractures and computationally derived fracture surfaces. High-resolution digital time-lapse imaging was employed to qualitatively observe the migration of colloidal and soluble dyes through the flow models. In this study, a Sphingomonas sp. and Sporosarcina (Bacillus) pasteurii influenced the fluid dynamics by physically altering flow paths. Microbial colonization and calcite deposition enhanced the stagnant regions adjacent to solid boundaries. Microbial growth and calcite precipitation occurred to a greater extent in areas behind the fabricated obstacles and less in high-velocity orifices.

Application of Stereolithographic Custom Models for Studying the Impact of Biofilms and Mineral Precipitation on Fluid Flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. L. Stoner; S. M. Watson; R. D. Stedtfeld

Here we introduce the use of transparent experimental models fabricated by stereolithography for studying the impacts of biomass accumulation, minerals precipitation, and physical configuration of flow paths on liquid flow in fracture apertures. The internal configuration of the models ranged in complexity from simple geometric shapes to those that incorporate replicated surfaces of natural fractures and computationally derived fracture surfaces. High-resolution digital time-lapse imaging was employed to qualitatively observe the migration of colloidal and soluble dyes through the flow models. In this study, a Sphingomonas sp. and Sporosarcina (Bacillus) pasteurii influenced the fluid dynamics by physically altering flow paths. Microbialmore » colonization and calcite deposition enhanced the stagnant regions adjacent to solid boundaries. Microbial growth and calcite precipitation occurred to a greater extent in areas behind the fabricated obstacles and less in high-velocity orifices.« less

Thin sheets achieve optimal wrapping of liquids

NASA Astrophysics Data System (ADS)

Paulsen, Joseph; Démery, Vincent; Davidovitch, Benny; Santangelo, Christian; Russell, Thomas; Menon, Narayanan

2015-03-01

A liquid drop can wrap itself in a sheet using capillary forces [Py et al., PRL 98, 2007]. However, the efficiency of ``capillary origami'' at covering the surface of a drop is hampered by the mechanical cost of bending the sheet. Thinner sheets deform more readily by forming small-scale wrinkles and stress-focussing patterns, but it is unclear how coverage efficiency competes with mechanical cost as thickness is decreased, and what wrapping shapes will emerge. We place a thin (~ 100 nm) polymer film on a drop whose volume is gradually decreased so that the sheet covers an increasing fraction of its surface. The sheet exhibits a complex sequence of axisymmetric and polygonal partially- and fully- wrapped shapes. Remarkably, the progression appears independent of mechanical properties. The gross shape, which neglects small-scale features, is correctly predicted by a simple geometric approach wherein the exposed area is minimized. Thus, simply using a thin enough sheet results in maximal coverage.

Global small-scale lunar cartography

NASA Technical Reports Server (NTRS)

Lipskiy, Y. N.; Pskovskiy, Y. P.; Rodionova, Z. F.; Shevchenko, V. V.; Chikmachev, V. I.; Volchkova, L. I.

1972-01-01

The primary sources information for compiling this map were the photographs of the visible hemisphere obtained by earth-based observatories, the Luna 3 and Zond 3 pictures, and a small number of Lunar Orbiter pictures. The primary content of the complete lunar map is the surface relief and its tonal characteristics. In preparing the map, particular attention was devoted to the variety of lunar relief forms. The color spectrum of the map was selected not only for the natural coloring of the lunar surface, but also with the objective of achieving maximum expressiveness. A lunar globe to scale 1:10 million was prepared along with the preparation of the map. The scale of the globe, half that of the map, led to some selection and generalization of the relief forms. The globe permits maintaining simultaneously geometric similarity of contours, exact proportions of areas, and identical scales in all directions. The globe was prepared in both the Latin and Russian languages.

Successful Nd:Yag Laser Photocoagulation Of Arrhythmogenic Myocardium: Potential Limitations Of Current Optical Delivery Systems.

NASA Astrophysics Data System (ADS)

Svenson, Robert H.; Marroum, Marie-Claire; Frank, Frank; Selle, Jay G.; Gallagher, John J.; Bou-Saba, George; Seifert, Kathleen T.; Linder, Kathy; Tatsis, George P.

1987-04-01

Canine myocardial lesions of predictable dimensions can be achieved with Nd:YAG laser photocoagulation. These lesions are well demarcated from surrounding normal tissue and heal with homogeneous scar formation. Intraoperative Nd:YAG laser photocoagulation successfully ablated 52 of 55 ventricular tachycardias in 17 patients. Histologic examination of tissues from these arrhythmogenic areas showed differences from lesions produced on canine epicardium. Lesions from the human cases were less predictable and not well circumscribed. These differences are felt to be due to optical inhomogeneities present in diseased, scarred human myocardium, geometric irregularities of the endocardial surface, anatomical constraints on tissue-fiber distance, and the angle of incidence of the beam with the tissue. Modifications of current delivery systems may overcome some of these limitations. Ablation of ventricular tachycardia arising deeper than 4.0 to 6.0 mm. from the irradiated surface may require interstitial probes coupled to the fiberoptic.

Using the 3D active fault model to estimate the surface deformation, a study on HsinChu area, Taiwan.

NASA Astrophysics Data System (ADS)

Lin, Y. K.; Ke, M. C.; Ke, S. S.

2016-12-01

An active fault is commonly considered to be active if they have moved one or more times in the last 10,000 years and likely to have another earthquake sometime in the future. The relationship between the fault reactivation and the surface deformation after the Chi-Chi earthquake (M=7.2) in 1999 has been concerned up to now. According to the investigations of well-known disastrous earthquakes in recent years, indicated that surface deformation is controlled by the 3D fault geometric shape. Because the surface deformation may cause dangerous damage to critical infrastructures, buildings, roads, power, water and gas lines etc. Therefore it's very important to make pre-disaster risk assessment via the 3D active fault model to decrease serious economic losses, people injuries and deaths caused by large earthquake. The approaches to build up the 3D active fault model can be categorized as (1) field investigation (2) digitized profile data and (3) build the 3D modeling. In this research, we tracked the location of the fault scarp in the field first, then combined the seismic profiles (had been balanced) and historical earthquake data to build the underground fault plane model by using SKUA-GOCAD program. Finally compared the results come from trishear model (written by Richard W. Allmendinger, 2012) and PFC-3D program (Itasca) and got the calculated range of the deformation area. By analysis of the surface deformation area made from Hsin-Chu Fault, we concluded the result the damage zone is approaching 68 286m, the magnitude is 6.43, the offset is 0.6m. base on that to estimate the population casualties, building damage by the M=6.43 earthquake in Hsin-Chu area, Taiwan. In the future, in order to be applied accurately on earthquake disaster prevention, we need to consider further the groundwater effect and the soil structure interaction inducing by faulting.

Measurement of machine parts dimensions positional deviation with regard to their geometric accuracy

NASA Astrophysics Data System (ADS)

Martemyanov, D. B.; Pshenichnikova, V. V.; Penner, V. A.; Zemtsov, A. E.

2018-04-01

Real surfaces of the parts, obtained with the help of technological processes, are always characterized by deviations from a nominal (regular) form. When analyzing a nominal cylindrical surface or a prismatic component element, the interrelation between current dimensions in various sections and a surface form, as well as surfaces position, can be found.

Transformations of asymptotically AdS hyperbolic initial data and associated geometric inequalities

NASA Astrophysics Data System (ADS)

Cha, Ye Sle; Khuri, Marcus

2018-01-01

We construct transformations which take asymptotically AdS hyperbolic initial data into asymptotically flat initial data, and which preserve relevant physical quantities. This is used to derive geometric inequalities in the asymptotically AdS hyperbolic setting from counterparts in the asymptotically flat realm, whenever a geometrically motivated system of elliptic equations admits a solution. The inequalities treated here relate mass, angular momentum, charge, and horizon area. Furthermore, new mass-angular momentum inequalities in this setting are conjectured and discussed.

Infrared Spectroscopic Imaging for Prostate Pathology Practice

DTIC Science & Technology

2010-03-01

lassification a lgorithm u ses mo rphological f eatures – geometric pr operties of epithelial cells/nuclei and lumens – that are quantified based on H&E stained...images as well as FT-IR images of the samples. By restricting the features used to geometric measures, we sought to m imic t he pa ttern r...be modeled as small elliptical areas in the stained images. This geometrical model is often confounded as multiple nuclei can be so close as to ap

Numerical reproduction and explanation of road surface mirages under grazing-angle scattering.

PubMed

Lu, Jia; Zhou, Huaichun

2017-07-01

The mirror-like reflection image of the road surface under grazing-angle scattering can be easily observed in daily life. It was suggested that road surface mirages may occur due to a light-enhancing effect of the rough surface under grazing-angle scattering. The main purpose of this work is to explain the light-enhancing mechanism of rough surfaces under grazing-angle scattering. The off-specular reflection from a random rough magnesium oxide ceramic surface is analyzed by using the geometric optics approximation method. Then, the geometric optics approximation method is employed to develop a theoretical model to predict the observation effect of the grazing-angle scattering phenomenon of the road surface. The rough surface is assumed to consist of small-scale rough surface facets. The road surface mirage is reproduced from a large number of small-scale rough surface facets within the eye's resolution limit at grazing scattering angles, as the average bidirectional reflectance distribution function value at the bright location is about twice that of the surface in front of the mirage. It is suggested that the light-enhancing effect of the rough surface under grazing-angle scattering is not proper to be termed as "off-specular reflection," since it has nothing to do with the "specular" direction with respect to the incident direction.

Geometric Model of Induction Heating Process of Iron-Based Sintered Materials

NASA Astrophysics Data System (ADS)

Semagina, Yu V.; Egorova, M. A.

2018-03-01

The article studies the issue of building multivariable dependences based on the experimental data. A constructive method for solving the issue is presented in the form of equations of (n-1) – surface compartments of the extended Euclidean space E+n. The dimension of space is taken to be equal to the sum of the number of parameters and factors of the model of the system being studied. The basis for building multivariable dependencies is the generalized approach to n-space used for the surface compartments of 3D space. The surface is designed on the basis of the kinematic method, moving one geometric object along a certain trajectory. The proposed approach simplifies the process aimed at building the multifactorial empirical dependencies which describe the process being investigated.

An experimental investigation of wall-interference effects for parachutes in closed wind tunnels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Macha, J.M.; Buffington, R.J.

1989-09-01

A set of 6-ft-diameter ribbon parachutes (geometric porosities of 7%, 15%, and 30%) was tested in various subsonic wind tunnels covering a range of geometric blockages from 2% to 35%. Drag, base pressure, and inflated geometry were measured under full-open, steady-flow conditions. The result drag areas and pressure coefficients were correlated with the bluff-body blockage parameter (i.e., drag area divided by tunnel cross-sectional area) according to the blockage theory of Maskell. The data show that the Maskell theory provides a simple, accurate correction for the effective increase in dynamic pressure caused by wall constraint for both single parachutes and clusters.more » For single parachutes, the empirically derived blockage factor K{sub M} has the value of 1.85, independent of canopy porosity. Derived values of K{sub M} for two- and three-parachute clusters are 1.35 and 1.59, respectively. Based on the photometric data, there was no deformation of the inflated shape of the single parachutes up to a geometric blockage of 22%. In the case of the three-parachute cluster, decreases in both the inflated diameter and the spacing among member parachutes were observed at a geometric blockage of 35%. 11 refs., 9 figs., 3 tabs.« less

Assured crew return vehicle post landing configuration design and test

NASA Technical Reports Server (NTRS)

1992-01-01

The 1991-1992 senior Mechanical and Aerospace Engineering Design class continued work on the post landing configurations for the Assured Crew Return Vehicle (ACRV) and the Emergency Egress Couch (EEC). The ACRV will be permanently docked to Space Station Freedom fulfilling NASA's commitment of Assured Crew Return Capability in the event of an accident or illness aboard Space Station Freedom. The EEC provides medical support and a transportation surface for an incapacitated crew member. The objective of the projects was to give the ACRV Project Office data to feed into their feasibility studies. Four design teams were given the task of developing models with dynamically and geometrically scaled characteristics. Groups one and two combined efforts to design a one-fifth scale model for the Apollo Command Module derivative, an on-board flotation system, and a lift attachment point system. This model was designed to test the feasibility of a rigid flotation and stabilization system and to determine the dynamics associated with lifting the vehicle during retrieval. However, due to priorities, it was not built. Group three designed a one-fifth scale model of the Johnson Space Center (JSC) benchmark configuration, the Station Crew Return Alternative Module (SCRAM) with a lift attachment point system. This model helped to determine the flotation and lifting characteristics of the SCRAM configuration. Group four designed a full scale EEC with changeable geometric and geometric and dynamic characteristics. This model provided data on the geometric characteristics of the EEC and on the placement of the CG and moment of inertia. It also gave the helicopter rescue personnel direct input to the feasibility study. Section 1 describes in detail the design of a one-fifth scale model of the Apollo Command Module Derivative (ACMD) ACRV. The objective of the ACMD Configuration Model Team was to use geometric and dynamic constraints to design a one-fifth scale working model of the Apollo Command Module Derivative (ACMD) configuration with a Lift Attachment Point (LAP) System. This model was required to incorporate a rigidly mounted flotation system and the egress system designed the previous academic year. The LAP system was to be used to determine the dynamic effects of locating the lifting points at different locations on the vehicle. The team was then to build and test the model; however, due to priorities, this did not occur. To better simulate the ACMD after a water landing, the nose cone section was removed and the deck area exposed. The areas researched during the design process were construction, center of gravity and moment of inertia, and lift attachment points.

Undefined freeform surfaces having deterministic structure: issues of their characterization for functionality and manufacture

NASA Astrophysics Data System (ADS)

Whitehouse, David J.

2016-09-01

There is an increasing use of surfaces which have structure, an increase in the use of freeform surfaces, and most importantly an increase in the number of surfaces having both characteristics. These can be called multi-function surfaces, where more than one function is helped by the geometrical features: the structure can help one, the freeform another. Alternatively, they can be complementary to optimize a single function, but in all cases both geometries are involved. This paper examines some of the problems posed by having such disparate geometries on one surface; in particular, the methods of characterization needed to help understand the functionality and also to some extent their manufacture. This involves investigating ways of expressing how local and global geometric features of undefined freeform surfaces might influence function and how surface structure on top of or in series with the freeform affects the nature of the characterization. Some methods have been found of identifying possible strategies for tackling the characterization problem, based in part on the principles of least action and on the way that nature has solved the marriage of flexible freeform geometry and structure on surfaces.

Spatial and seasonal variation of pollution sources in proximity of the Jaranman-Saryangdo area in Korea.

PubMed

Jung, Yeoun Joong; Park, Young Cheol; Lee, Ka Jeong; Kim, Min Seon; Go, Kyeong Ri; Park, Sang Gi; Kwon, Soon Jae; Yang, Ji Hye; Mok, Jong Soo

2017-02-15

We aimed to compare the spatial and seasonal distributions of fecal coliforms (FCs) and other physiochemical factors in the drainage basin of the Jaranman-Saryangdo area. Among the pollution sources, the mean daily loads and half-circle radii of FCs were the highest in June. However, the pollutants did not reach the boundary line of the designated area due to an existing buffer zone. The value of the FC geometric mean at station 1 was highest in August during periods of heavy rainfall; however, this value was lower than the regulation limit. The highest daily loads of chemical oxygen demand (COD) and chlorophyll-a (Chl-a) in seawater were in the surface layer in August; however, dissolved oxygen (DO) in the bottom water layer was at its lowest in August. This study demonstrated that season and rainfall have significant effects on the FC, COD, DO, and Chl-a concentrations in seawater. Copyright © 2016 Elsevier Ltd. All rights reserved.

Estimation of skeletal movement of human locomotion from body surface shapes using dynamic spatial video camera (DSVC) and 4D human model.

PubMed

Saito, Toshikuni; Suzuki, Naoki; Hattori, Asaki; Suzuki, Shigeyuki; Hayashibe, Mitsuhiro; Otake, Yoshito

2006-01-01

We have been developing a DSVC (Dynamic Spatial Video Camera) system to measure and observe human locomotion quantitatively and freely. A 4D (four-dimensional) human model with detailed skeletal structure, joint, muscle, and motor functionality has been built. The purpose of our research was to estimate skeletal movements from body surface shapes using DSVC and the 4D human model. For this purpose, we constructed a body surface model of a subject and resized the standard 4D human model to match with geometrical features of the subject's body surface model. Software that integrates the DSVC system and the 4D human model, and allows dynamic skeletal state analysis from body surface movement data was also developed. We practically applied the developed system in dynamic skeletal state analysis of a lower limb in motion and were able to visualize the motion using geometrically resized standard 4D human model.

Thermophysical properties of Cu-In-Sn liquid Pb-free alloys: viscosity and surface tension

NASA Astrophysics Data System (ADS)

Dogan, Ali; Arslan, Hüseyin

2018-01-01

The viscosity of a few Cu-In-Sn liquid alloys has been investigated by a number of geometric (Muggianu, Kohler, Toop) and physical thermodynamic models (Kozlov-Romanov-Petrov, Budai-Benko-Kaptay, Schick et al.) and GSM for the cross section (z/y = 1/3) in Pb-free liquid alloy Cux-Iny-Snz at 1073 K. Moreover, the surface tensions of the same liquid alloys have been investigated by a number of geometric models and the Butler model for the cross section Cux-Iny-Snz (z/(y + z) = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) at the same temperature. The best agreement of the surface tensions was obtained in the Kohler model for xCu = 10 at % and the Butler model for xCu = 20 at % and xCu = 30 at.%, respectively. The best agreement among chosen geometric and physical models and experiment for these selected sections Cu80In15Sn5, Cu75In15Sn10, Cu55In7Sn38, Cu33In50Sn17 and Cu26In55Sn19 at 1073 K was obtained for the Budai-Benkö-Kaptay model.

Geological evaluation of Radarsat data: Plans and preliminary results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger, Z.; Irving, R.E.L.; Thompson, M.D.

1996-01-01

Radarsat, the Canadian synthetic aperture radar satellite to be launched in September 1995, is anticipated to become the prime active imaging system for geological mapping of tropical areas and other humid areas. Radarsat will provide adequate spatial resolution, stereo capabilities and relatively low incidence angles to reduce the geometric distortions of geological structures due to layover effects. As part of the Radarsat User Development Program of the Canadian Space Agency, it has been proposed to conduct an evaluation program of the terrain surface mapping capabilities of Radarsat and its application to hydrocarbon exploration, coal development, geological hazard mapping and environmentalmore » monitoring. The evaluation program will be carried out in three test sites: (1) Western Canadian Basin (a mature exploration area in Alberta with a range of geology/topography), (2) Andean Foothills (frontier tropical sedimentary basins in Columbia representing prototype active exploration areas), and (3) Philippine volcanic region (frontier tropical earthquake-prone geohazard area of Philippine wrench fault system on Luzon Island, in a typical structural setting of the sedimentary basins of southeast Asia). The paper will include the project plans, illustrate the structural setting and the relationships between surface and subsurface structures for each of the three test sites, and present a preliminary evaluation of simulated and actual Radarsat data as compared to data from ERS-1, airborne SAR, Landsat Thematic Mapper and SPOT. The preliminary application of Radarsat for exploration will be discussed.« less

Geological evaluation of Radarsat data: Plans and preliminary results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger, Z.; Irving, R.E.L.; Thompson, M.D.

1996-12-31

Radarsat, the Canadian synthetic aperture radar satellite to be launched in September 1995, is anticipated to become the prime active imaging system for geological mapping of tropical areas and other humid areas. Radarsat will provide adequate spatial resolution, stereo capabilities and relatively low incidence angles to reduce the geometric distortions of geological structures due to layover effects. As part of the Radarsat User Development Program of the Canadian Space Agency, it has been proposed to conduct an evaluation program of the terrain surface mapping capabilities of Radarsat and its application to hydrocarbon exploration, coal development, geological hazard mapping and environmentalmore » monitoring. The evaluation program will be carried out in three test sites: (1) Western Canadian Basin (a mature exploration area in Alberta with a range of geology/topography), (2) Andean Foothills (frontier tropical sedimentary basins in Columbia representing prototype active exploration areas), and (3) Philippine volcanic region (frontier tropical earthquake-prone geohazard area of Philippine wrench fault system on Luzon Island, in a typical structural setting of the sedimentary basins of southeast Asia). The paper will include the project plans, illustrate the structural setting and the relationships between surface and subsurface structures for each of the three test sites, and present a preliminary evaluation of simulated and actual Radarsat data as compared to data from ERS-1, airborne SAR, Landsat Thematic Mapper and SPOT. The preliminary application of Radarsat for exploration will be discussed.« less

A framework to analyze cerebral mean diffusivity using surface guided diffusion mapping in diffusion tensor imaging

PubMed Central

Kwon, Oh-Hun; Park, Hyunjin; Seo, Sang-Won; Na, Duk L.; Lee, Jong-Min

2015-01-01

The mean diffusivity (MD) value has been used to describe microstructural properties in Diffusion Tensor Imaging (DTI) in cortical gray matter (GM). Recently, researchers have applied a cortical surface generated from the T1-weighted volume. When the DTI data are analyzed using the cortical surface, it is important to assign an accurate MD value from the volume space to the vertex of the cortical surface, considering the anatomical correspondence between the DTI and the T1-weighted image. Previous studies usually sampled the MD value using the nearest-neighbor (NN) method or Linear method, even though there are geometric distortions in diffusion-weighted volumes. Here we introduce a Surface Guided Diffusion Mapping (SGDM) method to compensate for such geometric distortions. We compared our SGDM method with results using NN and Linear methods by investigating differences in the sampled MD value. We also projected the tissue classification results of non-diffusion-weighted volumes to the cortical midsurface. The CSF probability values provided by the SGDM method were lower than those produced by the NN and Linear methods. The MD values provided by the NN and Linear methods were significantly greater than those of the SGDM method in regions suffering from geometric distortion. These results indicate that the NN and Linear methods assigned the MD value in the CSF region to the cortical midsurface (GM region). Our results suggest that the SGDM method is an effective way to correct such mapping errors. PMID:26236180

The effects of geometric uncertainties on computational modelling of knee biomechanics

PubMed Central

Fisher, John; Wilcox, Ruth

2017-01-01

The geometry of the articular components of the knee is an important factor in predicting joint mechanics in computational models. There are a number of uncertainties in the definition of the geometry of cartilage and meniscus, and evaluating the effects of these uncertainties is fundamental to understanding the level of reliability of the models. In this study, the sensitivity of knee mechanics to geometric uncertainties was investigated by comparing polynomial-based and image-based knee models and varying the size of meniscus. The results suggested that the geometric uncertainties in cartilage and meniscus resulting from the resolution of MRI and the accuracy of segmentation caused considerable effects on the predicted knee mechanics. Moreover, even if the mathematical geometric descriptors can be very close to the imaged-based articular surfaces, the detailed contact pressure distribution produced by the mathematical geometric descriptors was not the same as that of the image-based model. However, the trends predicted by the models based on mathematical geometric descriptors were similar to those of the imaged-based models. PMID:28879008

Geometrical Calibration of the Photo-Spectral System and Digital Maps Retrieval

NASA Astrophysics Data System (ADS)

Bruchkouskaya, S.; Skachkova, A.; Katkovski, L.; Martinov, A.

2013-12-01

Imaging systems for remote sensing of the Earth are required to demonstrate high metric accuracy of the picture which can be provided through preliminary geometrical calibration of optical systems. Being defined as a result of the geometrical calibration, parameters of internal and external orientation of the cameras are needed while solving such problems of image processing, as orthotransformation, geometrical correction, geographical coordinate fixing, scale adjustment and image registration from various channels and cameras, creation of image mosaics of filmed territories, and determination of geometrical characteristics of objects in the images. The geometrical calibration also helps to eliminate image deformations arising due to manufacturing defects and errors in installation of camera elements and photo receiving matrices as well as those resulted from lens distortions. A Photo-Spectral System (PhSS), which is intended for registering reflected radiation spectra of underlying surfaces in a wavelength range from 350 nm to 1050 nm and recording images of high spatial resolution, has been developed at the A.N. Sevchenko Research Institute of Applied Physical Problems of the Belarusian State University. The PhSS has undergone flight tests over the territory of Belarus onboard the Antonov AN-2 aircraft with the aim to obtain visible range images of the underlying surface. Then we performed the geometrical calibration of the PhSS and carried out the correction of images obtained during the flight tests. Furthermore, we have plotted digital maps of the terrain using the stereo pairs of images acquired from the PhSS and evaluated the accuracy of the created maps. Having obtained the calibration parameters, we apply them for correction of the images from another identical PhSS device, which is located at the Russian Orbital Segment of the International Space Station (ROS ISS), aiming to retrieve digital maps of the terrain with higher accuracy.

Incubation pit analysis and calculation of the hydrodynamic impact pressure from the implosion of an acoustic cavitation bubble.

PubMed

Tzanakis, I; Eskin, D G; Georgoulas, A; Fytanidis, D K

2014-03-01

An experimental study to evaluate cavitation bubble dynamics is conducted. The aim is to predict the magnitude and statistical distribution of hydrodynamic impact pressure generated from the implosion of various individual acoustic cavitation bubbles near to a rigid boundary, considering geometrical features of the pitted area. A steel sample was subjected to cavitation impacts by an ultrasonic transducer with a 5mm diameter probe. The pitted surface was then examined using high-precision 3D optical interferometer techniques. Only the incubation period where surface is plastically deformed without material loss is taken into account. The exposure time was adjusted in the range of 3-60 s to avoid pit overlapping and a special procedure for pit analysis and characterisation was then followed. Moreover, a high-speed camera device was deployed to capture the implosion mechanisms of cavitation bubbles near to the surface. The geometrical characteristics of single incubation pits as well as pit clusters were studied and their deformation patterns were compared. Consequently, a reverse engineering approach was applied in order the hydrodynamic impact pressure from the implosion of an individual cavitation bubble to be determined. The characteristic parameters of the cavitation implosion process such as hydrodynamic impact pressure and liquid micro-jet impact velocity as well as the hydrodynamic severity of the cavitation impacts were quantified. It was found that the length of the hypotenuse of the orthographic projections from the center of the pit, which basically represents the deformed area of the pit, increases with the hydrodynamic impact aggressiveness in a linear rate. Majority of the hydrodynamic impacts were in the range of 0.4-1 GPa while the corresponding micro-jet velocities were found to be in the range of 200-700 m/s. Outcomes of this study, contribute to further understanding the cavitation intensity from the implosion of acoustically generated bubbles and could certainly represent a significant step towards developing more accurate cavitation models. Copyright © 2013 Elsevier B.V. All rights reserved.

Automatic detection of sweep-meshable volumes

DOEpatents

Tautges,; Timothy J. , White; David, R [Pittsburgh, PA

2006-05-23

A method of and software for automatically determining whether a mesh can be generated by sweeping for a representation of a geometric solid comprising: classifying surface mesh schemes for surfaces of the representation locally using surface vertex types; grouping mappable and submappable surfaces of the representation into chains; computing volume edge types for the representation; recursively traversing surfaces of the representation and grouping the surfaces into source, target, and linking surface lists; and checking traversal direction when traversing onto linking surfaces.

A point cloud modeling method based on geometric constraints mixing the robust least squares method

NASA Astrophysics Data System (ADS)

Yue, JIanping; Pan, Yi; Yue, Shun; Liu, Dapeng; Liu, Bin; Huang, Nan

2016-10-01

The appearance of 3D laser scanning technology has provided a new method for the acquisition of spatial 3D information. It has been widely used in the field of Surveying and Mapping Engineering with the characteristics of automatic and high precision. 3D laser scanning data processing process mainly includes the external laser data acquisition, the internal industry laser data splicing, the late 3D modeling and data integration system. For the point cloud modeling, domestic and foreign researchers have done a lot of research. Surface reconstruction technology mainly include the point shape, the triangle model, the triangle Bezier surface model, the rectangular surface model and so on, and the neural network and the Alfa shape are also used in the curved surface reconstruction. But in these methods, it is often focused on single surface fitting, automatic or manual block fitting, which ignores the model's integrity. It leads to a serious problems in the model after stitching, that is, the surfaces fitting separately is often not satisfied with the well-known geometric constraints, such as parallel, vertical, a fixed angle, or a fixed distance. However, the research on the special modeling theory such as the dimension constraint and the position constraint is not used widely. One of the traditional modeling methods adding geometric constraints is a method combing the penalty function method and the Levenberg-Marquardt algorithm (L-M algorithm), whose stability is pretty good. But in the research process, it is found that the method is greatly influenced by the initial value. In this paper, we propose an improved method of point cloud model taking into account the geometric constraint. We first apply robust least-squares to enhance the initial value's accuracy, and then use penalty function method to transform constrained optimization problems into unconstrained optimization problems, and finally solve the problems using the L-M algorithm. The experimental results show that the internal accuracy is improved, and it is shown that the improved method for point clouds modeling proposed by this paper outperforms the traditional point clouds modeling methods.

Optically transparent, scratch-resistant, diamond-like carbon coatings

DOEpatents

He, Xiao-Ming; Lee, Deok-Hyung; Nastasi, Michael A.; Walter, Kevin C.; Tuszewski, Michel G.

2003-06-03

A plasma-based method for the deposition of diamond-like carbon (DLC) coatings is described. The process uses a radio-frequency inductively coupled discharge to generate a plasma at relatively low gas pressures. The deposition process is environmentally friendly and scaleable to large areas, and components that have geometrically complicated surfaces can be processed. The method has been used to deposit adherent 100-400 nm thick DLC coatings on metals, glass, and polymers. These coatings are between three and four times harder than steel and are therefore scratch resistant, and transparent to visible light. Boron and silicon doping of the DLC coatings have produced coatings having improved optical properties and lower coating stress levels, but with slightly lower hardness.

Mechanical Engineering Department engineering research: Annual report, FY 1986

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denney, R.M.; Essary, K.L.; Genin, M.S.

1986-12-01

This report provides information on the five areas of research interest in LLNL's Mechanical Engineering Department. In Computer Code Development, a solid geometric modeling program is described. In Dynamic Systems and Control, structure control and structure dynamics are discussed. Fabrication technology involves machine cutting, interferometry, and automated optical component manufacturing. Materials engineering reports on composite material research and measurement of molten metal surface properties. In Nondestructive Evaluation, NMR, CAT, and ultrasound machines are applied to manufacturing processes. A model for underground collapse is developed. Finally, an alternative heat exchanger is investigated for use in a fusion power plant. Separate abstractsmore » were prepared for each of the 13 reports in this publication. (JDH)« less

Some physical properties of ginkgo nuts and kernels

NASA Astrophysics Data System (ADS)

Ch'ng, P. E.; Abdullah, M. H. R. O.; Mathai, E. J.; Yunus, N. A.

2013-12-01

Some data of the physical properties of ginkgo nuts at a moisture content of 45.53% (±2.07) (wet basis) and of their kernels at 60.13% (± 2.00) (wet basis) are presented in this paper. It consists of the estimation of the mean length, width, thickness, the geometric mean diameter, sphericity, aspect ratio, unit mass, surface area, volume, true density, bulk density, and porosity measures. The coefficient of static friction for nuts and kernels was determined by using plywood, glass, rubber, and galvanized steel sheet. The data are essential in the field of food engineering especially dealing with design and development of machines, and equipment for processing and handling agriculture products.

A physical optics/equivalent currents model for the RCS of trihedral corner reflectors

NASA Technical Reports Server (NTRS)

Balanis, Constantine A.; Polycarpou, Anastasis C.

1993-01-01

The scattering in the interior regions of both square and triangular trihedral corner reflectors is examined. The theoretical model presented combines geometrical and physical optics (GO and PO), used to account for reflection terms, with equivalent edge currents (EEC), used to account for first-order diffractions from the edges. First-order, second-order, and third-order reflection terms are included. Calculating the first-order reflection terms involves integrating over the entire surface of the illuminated plate. Calculating the second- and third-order reflection terms, however, is much more difficult because the illuminated area is an arbitrary polygon whose shape is dependent upon the incident angles. The method for determining the area of integration is detailed. Extensive comparisons between the high-frequency model, Finite-Difference Time-Domain (FDTD) and experimental data are used for validation of the radar cross section (RCS) of both square and triangular trihedral reflectors.

A novel algorithm using an orthotropic material model for topology optimization

NASA Astrophysics Data System (ADS)

Tong, Liyong; Luo, Quantian

2017-09-01

This article presents a novel algorithm for topology optimization using an orthotropic material model. Based on the virtual work principle, mathematical formulations for effective orthotropic material properties of an element containing two materials are derived. An algorithm is developed for structural topology optimization using four orthotropic material properties, instead of one density or area ratio, in each element as design variables. As an illustrative example, minimum compliance problems for linear and nonlinear structures are solved using the present algorithm in conjunction with the moving iso-surface threshold method. The present numerical results reveal that: (1) chequerboards and single-node connections are not present even without filtering; (2) final topologies do not contain large grey areas even using a unity penalty factor; and (3) the well-known numerical issues caused by low-density material when considering geometric nonlinearity are resolved by eliminating low-density elements in finite element analyses.

A study of the factors affecting boundary layer two-dimensionality in wind tunnels

NASA Technical Reports Server (NTRS)

Mehta, R. D.; Hoffmann, P. H.

1986-01-01

The effect of screens, honeycombs, and centrifugal blowers on the two-dimensionality of a boundary layer on the test section floors of low-speed blower tunnels is studied. Surveys of the spanwise variation in surface shear stress in three blower tunnels revealed that the main component responsible for altering the spanwise properties of the test section boundary layer was the last screen, thus confirming previous findings. It was further confirmed that a screen with varying open-area ratio, produced an unstable flow. However, contrary to popular belief, it was also found that for given incoming conditions and a screen free of imperfections, its open-area ratio alone was not enough to describe its performance. The effect of other geometric parameters such as the type of screen, honeycomb, and blower were investigated. In addition, the effect of the order of components in the settling chamber, and of wire Reynolds number were also studied.

Reconstruction and analysis of hybrid composite shells using meshless methods

NASA Astrophysics Data System (ADS)

Bernardo, G. M. S.; Loja, M. A. R.

2017-06-01

The importance of focusing on the research of viable models to predict the behaviour of structures which may possess in some cases complex geometries is an issue that is growing in different scientific areas, ranging from the civil and mechanical engineering to the architecture or biomedical devices fields. In these cases, the research effort to find an efficient approach to fit laser scanning point clouds, to the desired surface, has been increasing, leading to the possibility of modelling as-built/as-is structures and components' features. However, combining the task of surface reconstruction and the implementation of a structural analysis model is not a trivial task. Although there are works focusing those different phases in separate, there is still an effective need to find approaches able to interconnect them in an efficient way. Therefore, achieving a representative geometric model able to be subsequently submitted to a structural analysis in a similar based platform is a fundamental step to establish an effective expeditious processing workflow. With the present work, one presents an integrated methodology based on the use of meshless approaches, to reconstruct shells described by points' clouds, and to subsequently predict their static behaviour. These methods are highly appropriate on dealing with unstructured points clouds, as they do not need to have any specific spatial or geometric requirement when implemented, depending only on the distance between the points. Details on the formulation, and a set of illustrative examples focusing the reconstruction of cylindrical and double-curvature shells, and its further analysis, are presented.

Hepatitis E virus and coliphages in waters proximal to swine concentrated animal feeding operations.

PubMed

Gentry-Shields, Jennifer; Myers, Kevin; Pisanic, Nora; Heaney, Christopher; Stewart, Jill

2015-02-01

North Carolina is the second leading state in pork production in the United States, with over 10 million swine. Swine manure in NC is typically collected and stored in open-pit lagoons before the liquid waste is sprayed onto agricultural fields for disposal. Components of this waste may be able to impact surface water quality with the potential for human exposure. This study examined viruses of public health concern in creeks adjacent to swine concentrated animal feeding operation (CAFO) spray fields. Surface water samples (n=154) were collected from public access waters in proximity to swine CAFO spray fields for six months and were tested for hepatitis E virus (HEV) and coliphages. HEV was detected in one sample. Somatic coliphages were detected in 98% of samples (geometric mean 24 ± 4.1 PFU per 100 ml), and F+ coliphages were detected in 85% of samples (geometric mean 6.8 ± 5.0 PFU per 100 ml). Only 3% (21) of the F+ coliphage isolates were RNA phage, and all of the F+ RNA coliphages belonged to genogroup I. Although the pervasiveness of swine CAFOs in this area prevented a comparison with samples from un-impacted sites, the near ubiquity of coliphages, as well as the presence of HEV, suggests that current waste management practices may be associated with the dissemination of viruses of public health concern in waters proximal to CAFO spray fields. Copyright © 2014 Elsevier B.V. All rights reserved.

Geometric contribution leading to anomalous estimation of two-dimensional electron gas density in GaN based heterostructures

NASA Astrophysics Data System (ADS)

Upadhyay, Bhanu B.; Jha, Jaya; Takhar, Kuldeep; Ganguly, Swaroop; Saha, Dipankar

2018-05-01

We have observed that the estimation of two-dimensional electron gas density is dependent on the device geometry. The geometric contribution leads to the anomalous estimation of the GaN based heterostructure properties. The observed discrepancy is found to originate from the anomalous area dependent capacitance of GaN based Schottky diodes, which is an integral part of the high electron mobility transistors. The areal capacitance density is found to increase for smaller radii Schottky diodes, contrary to a constant as expected intuitively. The capacitance is found to follow a second order polynomial on the radius of all the bias voltages and frequencies considered here. In addition to the quadratic dependency corresponding to the areal component, the linear dependency indicates a peripheral component. It is further observed that the peripheral to areal contribution is inversely proportional to the radius confirming the periphery as the location of the additional capacitance. The peripheral component is found to be frequency dependent and tends to saturate to a lower value for measurements at a high frequency. In addition, the peripheral component is found to vanish when the surface is passivated by a combination of N2 and O2 plasma treatments. The cumulative surface state density per unit length of the perimeter of the Schottky diodes as obtained by the integrated response over the distance between the ohmic and Schottky contacts is found to be 2.75 × 1010 cm-1.

A Geometric Model for Specularity Prediction on Planar Surfaces with Multiple Light Sources.

PubMed

Morgand, Alexandre; Tamaazousti, Mohamed; Bartoli, Adrien

2018-05-01

Specularities are often problematic in computer vision since they impact the dynamic range of the image intensity. A natural approach would be to predict and discard them using computer graphics models. However, these models depend on parameters which are difficult to estimate (light sources, objects' material properties and camera). We present a geometric model called JOLIMAS: JOint LIght-MAterial Specularity, which predicts the shape of specularities. JOLIMAS is reconstructed from images of specularities observed on a planar surface. It implicitly includes light and material properties, which are intrinsic to specularities. This model was motivated by the observation that specularities have a conic shape on planar surfaces. The conic shape is obtained by projecting a fixed quadric on the planar surface. JOLIMAS thus predicts the specularity using a simple geometric approach with static parameters (object material and light source shape). It is adapted to indoor light sources such as light bulbs and fluorescent lamps. The prediction has been tested on synthetic and real sequences. It works in a multi-light context by reconstructing a quadric for each light source with special cases such as lights being switched on or off. We also used specularity prediction for dynamic retexturing and obtained convincing rendering results. Further results are presented as supplementary video material, which can be found on the Computer Society Digital Library at http://doi.ieeecomputersociety.org/10.1109/TVCG.2017.2677445.

Verifying the functional ability of microstructured surfaces by model-based testing

NASA Astrophysics Data System (ADS)

Hartmann, Wito; Weckenmann, Albert

2014-09-01

Micro- and nanotechnology enables the use of new product features such as improved light absorption, self-cleaning or protection, which are based, on the one hand, on the size of functional nanostructures and the other hand, on material-specific properties. With the need to reliably measure progressively smaller geometric features, coordinate and surface-measuring instruments have been refined and now allow high-resolution topography and structure measurements down to the sub-nanometre range. Nevertheless, in many cases it is not possible to make a clear statement about the functional ability of the workpiece or its topography because conventional concepts of dimensioning and tolerancing are solely geometry oriented and standardized surface parameters are not sufficient to consider interaction with non-geometric parameters, which are dominant for functions such as sliding, wetting, sealing and optical reflection. To verify the functional ability of microstructured surfaces, a method was developed based on a parameterized mathematical-physical model of the function. From this model, function-related properties can be identified and geometric parameters can be derived, which may be different for the manufacturing and verification processes. With this method it is possible to optimize the definition of the shape of the workpiece regarding the intended function by applying theoretical and experimental knowledge, as well as modelling and simulation. Advantages of this approach will be discussed and demonstrated by the example of a microstructured inking roll.

System for conversion between the boundary representation model and a constructive solid geometry model of an object

DOEpatents

Christensen, Noel C.; Emery, James D.; Smith, Maurice L.

1988-04-05

A system converts from the boundary representation of an object to the constructive solid geometry representation thereof. The system converts the boundary representation of the object into elemental atomic geometrical units or I-bodies which are in the shape of stock primitives or regularized intersections of stock primitives. These elemental atomic geometrical units are then represented in symbolic form. The symbolic representations of the elemental atomic geometrical units are then assembled heuristically to form a constructive solid geometry representation of the object usable for manufacturing thereof. Artificial intelligence is used to determine the best constructive solid geometry representation from the boundary representation of the object. Heuristic criteria are adapted to the manufacturing environment for which the device is to be utilized. The surface finish, tolerance, and other information associated with each surface of the boundary representation of the object are mapped onto the constructive solid geometry representation of the object to produce an enhanced solid geometry representation, particularly useful for computer-aided manufacture of the object.

Surface-structured bacterial cellulose with guided assembly-based biolithography (GAB).

PubMed

Bottan, Simone; Robotti, Francesco; Jayathissa, Prageeth; Hegglin, Alicia; Bahamonde, Nicolas; Heredia-Guerrero, José A; Bayer, Ilker S; Scarpellini, Alice; Merker, Hannes; Lindenblatt, Nicole; Poulikakos, Dimos; Ferrari, Aldo

2015-01-27

A powerful replica molding methodology to transfer on-demand functional topographies to the surface of bacterial cellulose nanofiber textures is presented. With this method, termed guided assembly-based biolithography (GAB), a surface-structured polydimethylsiloxane (PDMS) mold is introduced at the gas-liquid interface of an Acetobacter xylinum culture. Upon bacterial fermentation, the generated bacterial cellulose nanofibers are assembled in a three-dimensional network reproducing the geometric shape imposed by the mold. Additionally, GAB yields directional alignment of individual nanofibers and memory of the transferred geometrical features upon dehydration and rehydration of the substrates. Scanning electron and atomic force microscopy are used to establish the good fidelity of this facile and affordable method. Interaction of surface-structured bacterial cellulose substrates with human fibroblasts and keratinocytes illustrates the efficient control of cellular activities which are fundamental in skin wound healing and tissue regeneration. The deployment of surface-structured bacterial cellulose substrates in model animals as skin wound dressing or body implant further proves the high durability and low inflammatory response to the material over a period of 21 days, demonstrating beneficial effects of surface structure on skin regeneration.

The Connection Competencies of Pre-Service Mathematics Teachers about Geometric Concepts to Daily-Life

ERIC Educational Resources Information Center

Pirasa, Nimet

2016-01-01

However, geometry is the area with the most concrete possibility of mathematical topics which contains more abstract concepts, students experience difficulties while understanding. Therefore, the connection of issues with daily life to concrete the subjects and the ability of connecting geometric concepts with daily life of the teachers and…

Evolutionary Optimization of a Geometrically Refined Truss

NASA Technical Reports Server (NTRS)

Hull, P. V.; Tinker, M. L.; Dozier, G. V.

2007-01-01

Structural optimization is a field of research that has experienced noteworthy growth for many years. Researchers in this area have developed optimization tools to successfully design and model structures, typically minimizing mass while maintaining certain deflection and stress constraints. Numerous optimization studies have been performed to minimize mass, deflection, and stress on a benchmark cantilever truss problem. Predominantly traditional optimization theory is applied to this problem. The cross-sectional area of each member is optimized to minimize the aforementioned objectives. This Technical Publication (TP) presents a structural optimization technique that has been previously applied to compliant mechanism design. This technique demonstrates a method that combines topology optimization, geometric refinement, finite element analysis, and two forms of evolutionary computation: genetic algorithms and differential evolution to successfully optimize a benchmark structural optimization problem. A nontraditional solution to the benchmark problem is presented in this TP, specifically a geometrically refined topological solution. The design process begins with an alternate control mesh formulation, multilevel geometric smoothing operation, and an elastostatic structural analysis. The design process is wrapped in an evolutionary computing optimization toolset.

Electrostatic and dispersion interactions during protein adsorption on topographic nanostructures.

PubMed

Elter, Patrick; Lange, Regina; Beck, Ulrich

2011-07-19

Recently, biomaterials research has focused on developing functional implant surfaces with well-defined topographic nanostructures in order to influence protein adsorption and cellular behavior. To enhance our understanding of how proteins interact with such surfaces, we analyze the adsorption of lysozyme on an oppositely charged nanostructure using a computer simulation. We present an algorithm that combines simulated Brownian dynamics with numerical field calculation methods to predict the preferred adsorption sites for arbitrarily shaped substrates. Either proteins can be immobilized at their initial adsorption sites or surface diffusion can be considered. Interactions are analyzed on the basis of Derjaguin-Landau-Verway-Overbeek (DLVO) theory, including electrostatic and London dispersion forces, and numerical solutions are derived using the Poisson-Boltzmann and Hamaker equations. Our calculations show that for a grooved nanostructure (i.e., groove and plateau width 8 nm, height 4 nm), proteins first contact the substrate primarily near convex edges because of better geometric accessibility and increased electric field strengths. Subsequently, molecules migrate by surface diffusion into grooves and concave corners, where short-range dispersion interactions are maximized. In equilibrium, this mechanism leads to an increased surface protein concentration in the grooves, demonstrating that the total amount of protein per surface area can be increased if substrates have concave nanostructures.

Geometric Defects in Quantum Hall States

NASA Astrophysics Data System (ADS)

Gromov, Andrey

I will describe a geometric analogue of Laughlin quasiholes in fractional quantum Hall (FQH) states. These ``quasiholes'' are generated by an insertion of quantized fluxes of curvature - which can be modeled by branch points of a certain Riemann surface - and, consequently, are related to genons. Unlike quasiholes, the genons are not excitations, but extrinsic defects. Fusion of genons describes the response of an FQH state to a process that changes (effective) topology of the physical space. These defects are abelian for IQH states and non-abelian for FQH states. I will explain how to calculate an electric charge, geometric spin and adiabatic mutual statistics of the these defects. Leo Kadanoff Fellowship.

PCSYS: The optimal design integration system picture drawing system with hidden line algorithm capability for aerospace vehicle configurations

NASA Technical Reports Server (NTRS)

Hague, D. S.; Vanderburg, J. D.

1977-01-01

A vehicle geometric definition based upon quadrilateral surface elements to produce realistic pictures of an aerospace vehicle. The PCSYS programs can be used to visually check geometric data input, monitor geometric perturbations, and to visualize the complex spatial inter-relationships between the internal and external vehicle components. PCSYS has two major component programs. The between program, IMAGE, draws a complex aerospace vehicle pictorial representation based on either an approximate but rapid hidden line algorithm or without any hidden line algorithm. The second program, HIDDEN, draws a vehicle representation using an accurate but time consuming hidden line algorithm.

Resonant inelastic scattering by use of geometrical optics.

PubMed

Schulte, Jörg; Schweiger, Gustav

2003-02-01

We investigate the inelastic scattering on spherical particles that contain one concentric inclusion in the case of input and output resonances, using a geometrical optics method. The excitation of resonances is included in geometrical optics by use of the concept of tunneled rays. To get a quantitative description of optical tunneling on spherical surfaces, we derive appropriate Fresnel-type reflection and transmission coefficients for the tunneled rays. We calculate the inelastic scattering cross section in the case of input and output resonances and investigate the influence of the distribution of the active material in the particle as well as the influence of the inclusion on inelastic scattering.

Numerical procedure to determine geometric view factors for surfaces occluded by cylinders

NASA Technical Reports Server (NTRS)

Sawyer, P. L.

1978-01-01

A numerical procedure was developed to determine geometric view factors between connected infinite strips occluded by any number of infinite circular cylinders. The procedure requires a two-dimensional cross-sectional model of the configuration of interest. The two-dimensional model consists of a convex polygon enclosing any number of circles. Each side of the polygon represents one strip, and each circle represents a circular cylinder. A description and listing of a computer program based on this procedure are included in this report. The program calculates geometric view factors between individual strips and between individual strips and the collection of occluding cylinders.

Process for producing laser-formed video calibration markers.

PubMed

Franck, J B; Keller, P N; Swing, R A; Silberberg, G G

1983-08-15

A process for producing calibration markers directly on the photoconductive surface of video camera tubes has been developed. This process includes the use of a Nd:YAG laser operating at 1.06 microm with a 9.5-nsec pulse width (full width at half-maximum). The laser was constrained to operate in the TEM(00) spatial mode by intracavity aperturing. The use of this technology has produced an increase of up to 50 times the accuracy of geometric measurement. This is accomplished by a decrease in geometric distortion and an increase in geometric scaling. The process by which these laser-formed video calibrations are made will be discussed.

Simulations of direct and reflected waves trajectories for in situ GNSS-R experiments

NASA Astrophysics Data System (ADS)

Roussel, N.; Frappart, F.; Ramillien, G.; Desjardins, C.; Gegout, P.; Pérosanz, F.; Biancale, R.

2014-01-01

The detection of Global Navigation Satellite System (GNSS) signals that are reflected off the surface, together with the reception of direct GNSS signals offers a unique opportunity to monitor water level variations over land and ocean. The time delay between the reception of the direct and the reflected signal gives access to the altitude of the receiver over the reflecting surface. The field of view of the receiver is highly dependent on both the orbits of the GNSS satellites and the configuration of the study site geometries. A simulator has been developed to determine the accurate location of the reflection points on the surface by modelling the trajectories of GNSS electromagnetic waves that are reflected on the surface of the Earth. Only the geometric problem have been considered using a specular reflection assumption. The orbit of the GNSS constellations satellite (mainly GPS, GLONASS and Galileo), and the position of a fixed receiver are used as input. Three different simulation modes are proposed depending on the choice of the Earth surface (local sphere or ellipsoid) and the consideration of topography likely to cause masking effects. Atmospheric delay effects derived from adaptive mapping functions are also taken into account. This simulator was developed to determine where the GNSS-R receivers should be located to monitor efficiently a given study area. In this study, two test sites were considered. The first one at the top of the Cordouan lighthouse (45°35'11'' N; 1°10'24'' W; 65 m) and the second one in the shore of the Geneva lake (46°24'30'' N; 6°43'6'' E, with a 50 m receiver height). This site is hidden by mountains in the South (altitude up to 2000 m), and overlooking the lake in the North (altitude of 370 m). For this second test site configuration, reflections occur until 560 m from the receiver. The geometric differences between the positions of the specular reflection points obtained considering the Earth as a sphere or as an ellipsoid were found to be on average 44 cm for satellites elevation angle greater than 10° and 1 m for satellite elevation angle between 5° and 10°. The simulations highlight the importance of the DEM integration: differences with and without integrating the DEM were found to be about 3.80 m with the minimum elevation angle equal to 5° and 1.4 m with the minimum elevation angle set to 10°. The correction of the tropospheric effects on the signal leads to geometric differences about 24 m maximum for a 50 m receiver height whereas the maximum is 43 cm for a 5 m receiver height. These errors deeply increase with the receiver height. By setting it to 300 m, the geometric errors reach 103 m for satellite elevation angle lower than 10°. The tests performed with the simulator presented in this paper highlight the importance of the choice of the Earth representation and also the non-negligible effect of the troposphere on the specular reflection points positions. Various outputs (time-varying reflection point coordinates, satellites positions and ground paths, wave trajectories, Fresnel first surfaces, etc.) are provided either as text or KML files for a convenient use.

Nano-scaling law: geometric foundation of thiolated gold nanomolecules.

PubMed

Dass, Amala

2012-04-07

Thiolated gold nanomolecules show a power correlation between the number of gold atoms and the thiolate ligands with a 2/3 scaling similar to Platonic and Archimedean solids. Nanomolecule stability is influenced by a universal geometric factor that is foundational to its stability through the Euclidean surface rule, in addition to the electronic shell closing factor and staple motif requirements. This journal is © The Royal Society of Chemistry 2012

Temporal Subtraction of Digital Breast Tomosynthesis Images for Improved Mass Detection

DTIC Science & Technology

2009-11-01

imaging using two distinct methods7-15: mathematically based models defined by geometric primitives and voxelized models derived from real human...trees to complete them. We also plan to add further detail by defining the Cooper’s ligaments using geometrical NURBS surfaces. Realistic...generated model for the coronary arterial tree based on multislice CT and morphometric data," Medical Imaging 2006: Physics of Medical Imaging 6142

Effects of Corrugated Temperature Sheets on Optical Propagation along Quasi-Horizontal Paths in the Stably Stratified Atmosphere

DTIC Science & Technology

2015-12-11

diameter) are consistent with theoretical predictions based on Taylor’s frozen- turbulence hypothesis and the geometrical - optics approximation. Short...theoretical predictions based on Taylor’s frozen- turbulence hypothesis and the geometrical - optics approximation. Short-term (less than a few seconds... turbulent , quasi-horizontal interfaces, or “sheets”. Collocated in- situ and optical field measurements conducted in the atmospheric surface layer

Ideal versus real: simulated annealing of experimentally derived and geometric platinum nanoparticles

NASA Astrophysics Data System (ADS)

Ellaby, Tom; Aarons, Jolyon; Varambhia, Aakash; Jones, Lewys; Nellist, Peter; Ozkaya, Dogan; Sarwar, Misbah; Thompsett, David; Skylaris, Chris-Kriton

2018-04-01

Platinum nanoparticles find significant use as catalysts in industrial applications such as fuel cells. Research into their design has focussed heavily on nanoparticle size and shape as they greatly influence activity. Using high throughput, high precision electron microscopy, the structures of commercially available Pt catalysts have been determined, and we have used classical and quantum atomistic simulations to examine and compare them with geometric cuboctahedral and truncated octahedral structures. A simulated annealing procedure was used both to explore the potential energy surface at different temperatures, and also to assess the effect on catalytic activity that annealing would have on nanoparticles with different geometries and sizes. The differences in response to annealing between the real and geometric nanoparticles are discussed in terms of thermal stability, coordination number and the proportion of optimal binding sites on the surface of the nanoparticles. We find that annealing both experimental and geometric nanoparticles results in structures that appear similar in shape and predicted activity, using oxygen adsorption as a measure. Annealing is predicted to increase the catalytic activity in all cases except the truncated octahedra, where it has the opposite effect. As our simulations have been performed with a classical force field, we also assess its suitability to describe the potential energy of such nanoparticles by comparing with large scale density functional theory calculations.

Graded nanowell arrays: a fine plasmonic "library" with an adjustable spectral range.

PubMed

Xue, Peihong; Ye, Shunsheng; Su, Hongyang; Wang, Shuli; Nan, Jingjie; Chen, Xingchi; Ruan, Weidong; Zhang, Junhu; Cui, Zhanchen; Yang, Bai

2017-05-25

We present an effective approach for fabricating graded plasmonic arrays based on ordered micro-/nanostructures with a geometric gradient. Ag nanowell arrays with graded geometric parameters were fabricated and systematically investigated. The order of the graded plasmonic arrays is generated by colloidal lithography, while the geometric gradient is the result of inclined reactive ion etching. The surface plasmon resonance (SPR) peaks were measured at different positions, which move gradually along the Ag nanowell arrays with a geometric gradient. Such micro-/nanostructure arrays with graded and integrated SPR peaks can work as a fine plasmonic "library" (FPL), and the spectral range can be controlled using a "coarse adjustment knob" (lattice constant) and a "fine adjustment knob" (pore diameter). Additionally, the spectral resolution of the FPL is high, which benefits from the high value of the full height/full width at half-maximum and the small step size of the wavelength shift (0.5 nm). Meanwhile, the FPL could be effectively applied as a well-defined model to verify the plasmonic enhancement in surface enhanced Raman scattering. As the FPL is an integrated optical material with graded individual SPR peaks, it can not only be a theoretical model for fundamental research, but also has great potential in high-throughput screening of optical materials, multiplex sensors, etc.

Internal-Modified Dithiol DNA-Directed Au Nanoassemblies: Geometrically Controlled Self-Assembly and Quantitative Surface-Enhanced Raman Scattering Properties

NASA Astrophysics Data System (ADS)

Yan, Yuan; Shan, Hangyong; Li, Min; Chen, Shu; Liu, Jianyu; Cheng, Yanfang; Ye, Cui; Yang, Zhilin; Lai, Xuandi; Hu, Jianqiang

2015-11-01

In this work, a hierarchical DNA-directed self-assembly strategy to construct structure-controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal-modified dithiol single-strand DNA (ssDNA) (Au-B-A or A-B-Au-B-A). It is found that the dithiol-ssDNA-modified Au NPs and molecule quantity of thiol-modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au-DNA self-assembly units, geometrical structures of the Au NAs can be tailored from one-dimensional (1D) to quasi-2D and 2D. Au-B-A conjugates readily give 1D and quasi-2D Au NAs while 2D Au NAs can be formed by A-B-Au-B-A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite-difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”-number-depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique.

Treatment of charge singularities in implicit solvent models.

PubMed

Geng, Weihua; Yu, Sining; Wei, Guowei

2007-09-21

This paper presents a novel method for solving the Poisson-Boltzmann (PB) equation based on a rigorous treatment of geometric singularities of the dielectric interface and a Green's function formulation of charge singularities. Geometric singularities, such as cusps and self-intersecting surfaces, in the dielectric interfaces are bottleneck in developing highly accurate PB solvers. Based on an advanced mathematical technique, the matched interface and boundary (MIB) method, we have recently developed a PB solver by rigorously enforcing the flux continuity conditions at the solvent-molecule interface where geometric singularities may occur. The resulting PB solver, denoted as MIBPB-II, is able to deliver second order accuracy for the molecular surfaces of proteins. However, when the mesh size approaches half of the van der Waals radius, the MIBPB-II cannot maintain its accuracy because the grid points that carry the interface information overlap with those that carry distributed singular charges. In the present Green's function formalism, the charge singularities are transformed into interface flux jump conditions, which are treated on an equal footing as the geometric singularities in our MIB framework. The resulting method, denoted as MIBPB-III, is able to provide highly accurate electrostatic potentials at a mesh as coarse as 1.2 A for proteins. Consequently, at a given level of accuracy, the MIBPB-III is about three times faster than the APBS, a recent multigrid PB solver. The MIBPB-III has been extensively validated by using analytically solvable problems, molecular surfaces of polyatomic systems, and 24 proteins. It provides reliable benchmark numerical solutions for the PB equation.

Treatment of charge singularities in implicit solvent models

NASA Astrophysics Data System (ADS)

Geng, Weihua; Yu, Sining; Wei, Guowei

2007-09-01

This paper presents a novel method for solving the Poisson-Boltzmann (PB) equation based on a rigorous treatment of geometric singularities of the dielectric interface and a Green's function formulation of charge singularities. Geometric singularities, such as cusps and self-intersecting surfaces, in the dielectric interfaces are bottleneck in developing highly accurate PB solvers. Based on an advanced mathematical technique, the matched interface and boundary (MIB) method, we have recently developed a PB solver by rigorously enforcing the flux continuity conditions at the solvent-molecule interface where geometric singularities may occur. The resulting PB solver, denoted as MIBPB-II, is able to deliver second order accuracy for the molecular surfaces of proteins. However, when the mesh size approaches half of the van der Waals radius, the MIBPB-II cannot maintain its accuracy because the grid points that carry the interface information overlap with those that carry distributed singular charges. In the present Green's function formalism, the charge singularities are transformed into interface flux jump conditions, which are treated on an equal footing as the geometric singularities in our MIB framework. The resulting method, denoted as MIBPB-III, is able to provide highly accurate electrostatic potentials at a mesh as coarse as 1.2Å for proteins. Consequently, at a given level of accuracy, the MIBPB-III is about three times faster than the APBS, a recent multigrid PB solver. The MIBPB-III has been extensively validated by using analytically solvable problems, molecular surfaces of polyatomic systems, and 24 proteins. It provides reliable benchmark numerical solutions for the PB equation.

Enhancement of field effect mobility of poly(3-hexylthiophene) thin film transistors by soft-lithographical nanopatterning on the gate-dielectric surface

NASA Astrophysics Data System (ADS)

Park, Jeong-Ho; Kang, Seok-Ju; Park, Jeong-Woo; Lim, Bogyu; Kim, Dong-Yu

2007-11-01

The submicroscaled octadecyltrichlorosilane (OTS) line patterns on gate-dielectric surfaces were introduced into the fabrication of organic field effect transistors (OFETs). These spin-cast regioregular poly(3-hexylthiophene) films on soft-lithographically patterned SiO2 surfaces yielded a higher hole mobility (˜0.072cm2/Vs ) than those of unpatterned (˜0.015cm2/Vs) and untreated (˜5×10-3cm2/Vs) OFETs. The effect of mobility enhancement as a function of the patterned line pitch was investigated in structural and geometric characteristics. The resulting improved mobility is likely attributed to the formation of efficient π-π stacking as a result of guide-assisted, local self-organization-involved molecular interactions between the poly(3-hexylthiophene) polymer and the geometrical OTS patterns.

Interactive computer aided technology, evolution in the design/manufacturing process

NASA Technical Reports Server (NTRS)

English, C. H.

1975-01-01

A powerful computer-operated three dimensional graphic system and associated auxiliary computer equipment used in advanced design, production design, and manufacturing was described. This system has made these activities more productive than when using older and more conventional methods to design and build aerospace vehicles. With the use of this graphic system, designers are now able to define parts using a wide variety of geometric entities, define parts as fully surface 3-dimensional models as well as "wire-frame" models. Once geometrically defined, the designer is able to take section cuts of the surfaced model and automatically determine all of the section properties of the planar cut, lightpen detect all of the surface patches and automatically determine the volume and weight of the part. Further, his designs are defined mathematically at a degree of accuracy never before achievable.

Human eyeball model reconstruction and quantitative analysis.

PubMed

Xing, Qi; Wei, Qi

2014-01-01

Determining shape of the eyeball is important to diagnose eyeball disease like myopia. In this paper, we present an automatic approach to precisely reconstruct three dimensional geometric shape of eyeball from MR Images. The model development pipeline involved image segmentation, registration, B-Spline surface fitting and subdivision surface fitting, neither of which required manual interaction. From the high resolution resultant models, geometric characteristics of the eyeball can be accurately quantified and analyzed. In addition to the eight metrics commonly used by existing studies, we proposed two novel metrics, Gaussian Curvature Analysis and Sphere Distance Deviation, to quantify the cornea shape and the whole eyeball surface respectively. The experiment results showed that the reconstructed eyeball models accurately represent the complex morphology of the eye. The ten metrics parameterize the eyeball among different subjects, which can potentially be used for eye disease diagnosis.

Geometric Phase of a Transported Oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dittirich, W.

2004-02-25

An oscillator constrained to a plane that is transported along some surface will rotate by an angle dependent only on the path and the surface, not on the speed at which it is transported. This is thus an example of a geometric phase. We analyze this phase using the methods of parallel transport. This concept plays a key role in General Relativity, but it can also be applied in classical mechanics. The Foucault pendulum can be seen as an application of this analysis, where the surface is a sphere and the curve is a line of constant latitude. In viewmore » of some considerable confusion and erroneous treatments in the recent literature, we here present a rather simple way for visualizing the motion of the Foucault pendulum using concepts that are based on Frenet's formulae and the methods of parallel displacement.« less

Effects of fracture surface roughness and shear displacement on geometrical and hydraulic properties of three-dimensional crossed rock fracture models

NASA Astrophysics Data System (ADS)

Huang, Na; Liu, Richeng; Jiang, Yujing; Li, Bo; Yu, Liyuan

2018-03-01

While shear-flow behavior through fractured media has been so far studied at single fracture scale, a numerical analysis of the shear effect on the hydraulic response of 3D crossed fracture model is presented. The analysis was based on a series of crossed fracture models, in which the effects of fracture surface roughness and shear displacement were considered. The rough fracture surfaces were generated using the modified successive random additions (SRA) algorithm. The shear displacement was applied on one fracture, and at the same time another fracture shifted along with the upper and lower surfaces of the sheared fracture. The simulation results reveal the development and variation of preferential flow paths through the model during the shear, accompanied by the change of the flow rate ratios between two flow planes at the outlet boundary. The average contact area accounts for approximately 5-27% of the fracture planes during shear, but the actual calculated flow area is about 38-55% of the fracture planes, which is much smaller than the noncontact area. The equivalent permeability will either increase or decrease as shear displacement increases from 0 to 4 mm, depending on the aperture distribution of intersection part between two fractures. When the shear displacement continuously increases by up to 20 mm, the equivalent permeability increases sharply first, and then keeps increasing with a lower gradient. The equivalent permeability of rough fractured model is about 26-80% of that calculated from the parallel plate model, and the equivalent permeability in the direction perpendicular to shear direction is approximately 1.31-3.67 times larger than that in the direction parallel to shear direction. These results can provide a fundamental understanding of fluid flow through crossed fracture model under shear.

Geometric model from microscopic theory for nuclear absorption

NASA Technical Reports Server (NTRS)

John, Sarah; Townsend, Lawrence W.; Wilson, John W.; Tripathi, Ram K.

1993-01-01

A parameter-free geometric model for nuclear absorption is derived herein from microscopic theory. The expression for the absorption cross section in the eikonal approximation, taken in integral form, is separated into a geometric contribution that is described by an energy-dependent effective radius and two surface terms that cancel in an asymptotic series expansion. For collisions of light nuclei, an expression for the effective radius is derived from harmonic oscillator nuclear density functions. A direct extension to heavy nuclei with Woods-Saxon densities is made by identifying the equivalent half-density radius for the harmonic oscillator functions. Coulomb corrections are incorporated, and a simplified geometric form of the Bradt-Peters type is obtained. Results spanning the energy range from 1 MeV/nucleon to 1 GeV/nucleon are presented. Good agreement with experimental results is obtained.

Geometric model for nuclear absorption from microscopic theory

NASA Technical Reports Server (NTRS)

John, S.; Townsend, L. W.; Wilson, J. W.; Tripathi, R. K.

1993-01-01

A parameter-free geometric model for nuclear absorption is derived from microscopic theory. The expression for the absorption cross section in the eikonal approximation taken in integral form is separated into a geometric contribution, described by an energy-dependent effective radius, and two surface terms which are shown to cancel in an asymptotic series expansion. For collisions of light nuclei, an expression for the effective radius is derived using harmonic-oscillator nuclear density functions. A direct extension to heavy nuclei with Woods-Saxon densities is made by identifying the equivalent half density radius for the harmonic-oscillator functions. Coulomb corrections are incorporated and a simplified geometric form of the Bradt-Peters type obtained. Results spanning the energy range of 1 MeV/nucleon to 1 GeV/nucleon are presented. Good agreement with experimental results are obtained.

Complementarity of stability patches at the interfaces of protein complexes: Implication for the structural organization of energetic hot spots.

PubMed

Kuttner, Yosef Y; Engel, Stanislav

2018-02-01

A rational design of protein complexes with defined functionalities and of drugs aimed at disrupting protein-protein interactions requires fundamental understanding of the mechanisms underlying the formation of specific protein complexes. Efforts to develop efficient small-molecule or protein-based binders often exploit energetic hot spots on protein surfaces, namely, the interfacial residues that provide most of the binding free energy in the complex. The molecular basis underlying the unusually high energy contribution of the hot spots remains obscure, and its elucidation would facilitate the design of interface-targeted drugs. To study the nature of the energetic hot spots, we analyzed the backbone dynamic properties of contact surfaces in several protein complexes. We demonstrate that, in most complexes, the backbone dynamic landscapes of interacting surfaces form complementary "stability patches," in which static areas from the opposing surfaces superimpose, and that these areas are predominantly located near the geometric center of the interface. We propose that a diminished enthalpy-entropy compensation effect augments the degree to which residues positioned within the complementary stability patches contribute to complex affinity, thereby giving rise to the energetic hot spots. These findings offer new insights into the nature of energetic hot spots and the role that backbone dynamics play in facilitating intermolecular recognition. Mapping the interfacial stability patches may provide guidance for protein engineering approaches aimed at improving the stability of protein complexes and could facilitate the design of ligands that target complex interfaces. © 2017 Wiley Periodicals, Inc.

Increase of Breakthrough Pressure of Cotton Fabric by Fluoropolymer/Fluoroposs Treatment

DTIC Science & Technology

2011-11-29

obtaining superhydrophobic and superolcophobic textured surfaces. Geometrical parameters based on these textures have been developed to model predicted...contact angles with liquids of varying surfaces tensions. One way of determining the robustness of the superhydrophobic state is to study the

Influence of Geometry on the Drug Release Profiles of Stereolithographic (SLA) 3D-Printed Tablets.

PubMed

Martinez, Pamela Robles; Goyanes, Alvaro; Basit, Abdul W; Gaisford, Simon

2018-06-08

Additive manufacturing (3D printing) permits the fabrication of tablets in shapes unattainable by powder compaction, and so the effects of geometry on drug release behavior is easily assessed. Here, tablets (printlets) comprising of paracetamol dispersed in polyethylene glycol were printed using stereolithographic 3D printing. A number of geometric shapes were produced (cube, disc, pyramid, sphere and torus) with either constant surface area (SA) or constant surface area/volume ratio (SA/V). Dissolution testing showed that printlets with constant SA/V ratio released drug at the same rate, while those with constant SA released drug at different rates. A series of tori with increasing SA/V ratio (from 0.5 to 2.4) were printed, and it was found that dissolution rate increased as the SA/V ratio increased. The data show that printlets can be fabricated in multiple shapes and that dissolution performance can be maintained if the SA/V ratio is constant or that dissolution performance of printlets can be fine-tuned by varying SA/V ratio. The results suggest that 3D printing is therefore a suitable manufacturing method for personalized dosage forms.

Quaternary fluvial terraces of the Tiber Valley: geochronologic and geometric constraints on the back-arc magmatism-related uplift in central Italy.

PubMed

Marra, Fabrizio; Florindo, Fabio; Petronio, Carmelo

2017-05-31

Through a geomorphological study relying on statistically assessed classes of hilltop elevations, we reconstruct a suite of paleo-surfaces along the Tiber River Valley north of Rome that we identify as fluvial terraces formed by interplay between global sea-level fluctuations and regional upift. Using biostratigraphic constraints provided by marine through continental deposits of Santernian age, we recognize the oldest terrace in this area, corresponding to an early coastal plain of late Santernian-Emilian age. By assuming the simple chronological principle of a staircase geometry we correlate the sea-level highstands of MIS 21 through MIS 5 with the lowest eight paleo-surfaces. By plotting against time the cumulated terrace elevations and the average elevation of the Santernian coastline in the investigated area, we detect rates of uplift during the last 1.8 Ma. Two major pulses of uplift are recognized 0.86 through 0.5 Ma, and 0.25 Ma through the Present, which are interpreted as driven by the subduction process and uprising of metasomatized magma bodies on the Tyrrhenian Sea Margin of central Italy, superimposied on a smaller isostatic component of uplift.

Adhesion and migration of CHO cells on micropatterned single layer graphene

NASA Astrophysics Data System (ADS)

Keshavan, S.; Oropesa-Nuñez, R.; Diaspro, A.; Canale, C.; Dante, S.

2017-06-01

Cell patterning technology on single layer graphene (SLG) is a fairly new field that can find applications in tissue engineering and biomaterial/biosensors development. Recently, we have developed a simple and effective approach for the fabrication of patterned SLG substrates by laser micromachining, and we have successfully applied it for the obtainment of geometrically ordered neural networks. Here, we exploit the same approach to investigate the generalization of the cell response to the surface cues of the fabricated substrates and, contextually, to quantify cell adhesion on the different areas of the patterns. To attain this goal, we tested Chinese hamster ovary (CHO) cells on PDL-coated micropatterned SLG substrates and quantified the adhesion by using single cell force spectroscopy (SCFS). Our results indicate higher cell adhesion on PDL-SLG, and, consequently, an initial CHO cell accumulation on the graphene areas, confirming the neuronal behaviour observed previously; interestingly, at later time point in culture, cell migration was observed towards the adjacent SLG ablated regions, which resulted more favourable for cell proliferation. Therefore, our findings indicate that the mechanism of interaction with the surface cues offered by the micropatterned substrates is strictly cell-type dependent.

Terahertz transmission properties of an individual slit in a thin metallic plate.

PubMed

Lee, J W; Park, T H; Nordlander, Peter; Mittleman, Daniel M

2009-07-20

We report on the terahertz transmission properties through a single slit in a thin metallic film. The properties are studied by comparing the transmissions of TE- and TM-polarized electromagnetic waves over a broad spectral range from the geometrical regime to the subwavelength limit. In the geometrical regime, the remarkable terahertz transmission due to guided modes is observed even without the contribution of surface waves. Whereas in the subwavelength limit, the surface charge oscillations associated with the TM-polarized guided mode give rise to strong transmission enhancement. The nature of the mechanisms for the terahertz transmission is elucidated using theoretical simulations of the near-field distributions and electromagnetic energy flow.

Parametric design and gridding through relational geometry

NASA Technical Reports Server (NTRS)

Letcher, John S., Jr.; Shook, D. Michael

1995-01-01

Relational Geometric Synthesis (RGS) is a new logical framework for building up precise definitions of complex geometric models from points, curves, surfaces and solids. RGS achieves unprecedented design flexibility by supporting a rich variety of useful curve and surface entities. During the design process, many qualitative and quantitative relationships between elementary objects may be captured and retained in a data structure equivalent to a directed graph, such that they can be utilized for automatically updating the complete model geometry following changes in the shape or location of an underlying object. Capture of relationships enables many new possibilities for parametric variations and optimization. Examples are given of panelization applications for submarines, sailing yachts, offshore structures, and propellers.

Geometric calibration of Colour and Stereo Surface Imaging System of ESA's Trace Gas Orbiter

NASA Astrophysics Data System (ADS)

Tulyakov, Stepan; Ivanov, Anton; Thomas, Nicolas; Roloff, Victoria; Pommerol, Antoine; Cremonese, Gabriele; Weigel, Thomas; Fleuret, Francois

2018-01-01

There are many geometric calibration methods for "standard" cameras. These methods, however, cannot be used for the calibration of telescopes with large focal lengths and complex off-axis optics. Moreover, specialized calibration methods for the telescopes are scarce in literature. We describe the calibration method that we developed for the Colour and Stereo Surface Imaging System (CaSSIS) telescope, on board of the ExoMars Trace Gas Orbiter (TGO). Although our method is described in the context of CaSSIS, with camera-specific experiments, it is general and can be applied to other telescopes. We further encourage re-use of the proposed method by making our calibration code and data available on-line.

Geometric effects on surface states in topological insulator Bi2Te3 nanowire

NASA Astrophysics Data System (ADS)

Sengupta, Parijat; Kubis, Tillman; Povolotskyi, Michael; Klimeck, Gerhard

2012-02-01

Bismuth Telluride (BT) is a 3D topological insulator (TI) with surface states that have energy dispersion linear in momentum and forms a Dirac cone at low energy. In this work we investigate the surface properties of a BT nanowire and demonstrate the existence of TI states. We also show how such states vanish under certain geometric conditions. An atomistic model (sp3d5s* TB) is used to compute the energy dispersion in a BT nanowire. Penetration depth of the surface states is estimated by ratio of Fermi velocity and band-gap. BT possesses a tiny band-gap, which creates small localization of surface states and greater penetration in to the bulk. To offset this large spatial penetration, which is undesirable to avoid a direct coupling between surfaces, we expect that bigger cross-sections of BT nanowires would be needed to obtain stable TI states. Our numerical work validates this prediction. Furthermore, geometry of the nanowire is shown to influence the TI states. Using a combined analytical and numerical approach our results reveal that surface roughness impact electronic structure leading to Rashba type splits along z-direction. Cylindrical and square cross-sections are given as illustrative examples.

Influence of surface morphology on adsorption of potassium stearate molecules on diamond-like carbon substrate: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Guo, Shusen; Cao, Yongzhi; Sun, Tao; Zhang, Junjie; Gu, Le; Zhang, Chuanwei; Xu, Zhiqiang

2018-05-01

Molecular dynamics (MD) simulations were used to provide insights into the influence of nano-scale surface morphology on adsorptive behavior of Potassium stearate molecules on diamond-like carbon (DLC) substrates. Particular focus was given to explain that how the distinctive geometric properties of different surface morphologies affect the equilibrium structures and substrate-molecules interactions of monolayers, which was achieved through adsorptive analysis methods including adsorptive process, density profile, density distribution and surface potential energy. Analysis on surface potential energy demonstrated that the adsorptivity of amorphous smooth substrate is uniformly distributed over the surface, while DLC substrates with different surface morphologies appear to be more potentially corrugated, which improves the adsorptivity significantly. Because of the large distance of molecules from carbon atoms located at the square groove bottom, substrate-molecules interactions vanish significantly, and thus potassium stearate molecules cannot penetrate completely into the square groove. It can be observed that the equilibrium substrate-molecules interactions of triangle groove and semi-circle groove are much more powerful than that of square groove due to geometrically advantageous properties. These findings provided key information of optimally design of solid substrates with controllable adsorptivity.

AUTOMATIC AIR BURST DIRECTION FINDER

DOEpatents

Allard, G.A.

1952-01-31

This patent application describes an atomic explosion direction indicator comprising a geometric heat-scorchable indicating surface symmetrical about an axis, elevation and azimuth markings on the heat scorchable surface, and an indicating rod at the axis of said surface arranged to cast a shadow hereon, whereby heat from an atomic explosion will scorch a pattern on said surface indicative of the azimuth and elevation of said explosion.

Transcostal high-intensity focused ultrasound treatment using phased array with geometric correction.

PubMed

Qiao, Shan; Shen, Guofeng; Bai, Jingfeng; Chen, Yazhu

2013-08-01

In the high-intensity focused ultrasound treatment of liver tumors, ultrasound propagation is affected by the rib cage. Because of the diffraction and absorption of the bone, the sound distribution at the focal plane is altered, and more importantly, overheating on the rib surface might occur. To overcome these problems, a geometric correction method is applied to turn off the elements blocked by the ribs. The potential of steering the focus of the phased-array along the propagation direction to improve the transcostal treatment was investigated by simulations and experiments using different rib models and transducers. The ultrasound propagation through the ribs was computed by a hybrid method including the Rayleigh-Sommerfeld integral, k-space method, and angular spectrum method. A modified correction method was proposed to adjust the output of elements based on their relative area in the projected "shadow" of the ribs. The simulation results showed that an increase in the specific absorption rate gain up to 300% was obtained by varying the focal length although the optimal value varied in each situation. Therefore, acoustic simulation is required for each clinical case to determine a satisfactory treatment plan.

Exposure to ultrafine particles and black carbon in diesel-powered commuter trains

NASA Astrophysics Data System (ADS)

Jeong, Cheol-Heon; Traub, Alison; Evans, Greg J.

2017-04-01

Ultrafine particle (UFP), black carbon (BC) and lung deposited surface area (LDSA) concentrations measured during 43 trips on diesel-powered commuter trains revealed elevated exposures under some conditions. When the passenger coaches were pulled by a locomotive, the geometric mean concentrations of UFP, LDSA, and BC were 18, 10, and 6 times higher than the exposure levels when the locomotive pushed the coaches, respectively. In addition, UFP, LDSA, and BC concentrations in pull-trains were 5, 3, and 4 times higher than concentrations measured while walking on city sidewalks, respectively. Exposure to these pollutants was most elevated in the coach located closest to the locomotive: geometric means were 126,000 # cm-3 for UFP, 249 μm2 cm-3 for LDSA, and 17,800 ng m-3 of BC; these concentrations are much higher than those previously reported for other modes of public transportation. Markedly high levels of diesel exhaust are present in passenger trains powered by diesel locomotives operated in pull-mode. Thus, it is recommended that immediate steps be taken to evaluate, and where needed, mitigate exposure in diesel-powered passenger trains, both commuter and inter-city.

Radiometric Block Adjusment and Digital Radiometric Model Generation

NASA Astrophysics Data System (ADS)

Pros, A.; Colomina, I.; Navarro, J. A.; Antequera, R.; Andrinal, P.

2013-05-01

In this paper we present a radiometric block adjustment method that is related to geometric block adjustment and to the concept of a terrain Digital Radiometric Model (DRM) as a complement to the terrain digital elevation and surface models. A DRM, in our concept, is a function that for each ground point returns a reflectance value and a Bidirectional Reflectance Distribution Function (BRDF). In a similar way to the terrain geometric reconstruction procedure, given an image block of some terrain area, we split the DRM generation in two phases: radiometric block adjustment and DRM generation. In the paper we concentrate on the radiometric block adjustment step, but we also describe a preliminary DRM generator. In the block adjustment step, after a radiometric pre-calibraton step, local atmosphere radiative transfer parameters, and ground reflectances and BRDFs at the radiometric tie points are estimated. This radiometric block adjustment is based on atmospheric radiative transfer (ART) models, pre-selected BRDF models and radiometric ground control points. The proposed concept is implemented and applied in an experimental campaign, and the obtained results are presented. The DRM and orthophoto mosaics are generated showing no radiometric differences at the seam lines.

Fractal morphometry of cell complexity.

PubMed

Losa, Gabriele A

2002-01-01

Irregularity and self-similarity under scale changes are the main attributes of the morphological complexity of both normal and abnormal cells and tissues. In other words, the shape of a self-similar object does not change when the scale of measurement changes, because each part of it looks similar to the original object. However, the size and geometrical parameters of an irregular object do differ when it is examined at increasing resolution, which reveals more details. Significant progress has been made over the past three decades in understanding how irregular shapes and structures in the physical and biological sciences can be analysed. Dominant influences have been the discovery of a new practical geometry of Nature, now known as fractal geometry, and the continuous improvements in computation capabilities. Unlike conventional Euclidean geometry, which was developed to describe regular and ideal geometrical shapes which are practically unknown in nature, fractal geometry can be used to measure the fractal dimension, contour length, surface area and other dimension parameters of almost all irregular and complex biological tissues. We have used selected examples to illustrate the application of the fractal principle to measuring irregular and complex membrane ultrastructures of cells at specific functional and pathological stage.

Branching angles of pyramidal cell dendrites follow common geometrical design principles in different cortical areas.

PubMed

Bielza, Concha; Benavides-Piccione, Ruth; López-Cruz, Pedro; Larrañaga, Pedro; DeFelipe, Javier

2014-08-01

Unraveling pyramidal cell structure is crucial to understanding cortical circuit computations. Although it is well known that pyramidal cell branching structure differs in the various cortical areas, the principles that determine the geometric shapes of these cells are not fully understood. Here we analyzed and modeled with a von Mises distribution the branching angles in 3D reconstructed basal dendritic arbors of hundreds of intracellularly injected cortical pyramidal cells in seven different cortical regions of the frontal, parietal, and occipital cortex of the mouse. We found that, despite the differences in the structure of the pyramidal cells in these distinct functional and cytoarchitectonic cortical areas, there are common design principles that govern the geometry of dendritic branching angles of pyramidal cells in all cortical areas.

Branching angles of pyramidal cell dendrites follow common geometrical design principles in different cortical areas

PubMed Central

Bielza, Concha; Benavides-Piccione, Ruth; López-Cruz, Pedro; Larrañaga, Pedro; DeFelipe, Javier

2014-01-01

Unraveling pyramidal cell structure is crucial to understanding cortical circuit computations. Although it is well known that pyramidal cell branching structure differs in the various cortical areas, the principles that determine the geometric shapes of these cells are not fully understood. Here we analyzed and modeled with a von Mises distribution the branching angles in 3D reconstructed basal dendritic arbors of hundreds of intracellularly injected cortical pyramidal cells in seven different cortical regions of the frontal, parietal, and occipital cortex of the mouse. We found that, despite the differences in the structure of the pyramidal cells in these distinct functional and cytoarchitectonic cortical areas, there are common design principles that govern the geometry of dendritic branching angles of pyramidal cells in all cortical areas. PMID:25081193

Geometric correction methods for Timepix based large area detectors

NASA Astrophysics Data System (ADS)

Zemlicka, J.; Dudak, J.; Karch, J.; Krejci, F.

2017-01-01

X-ray micro radiography with the hybrid pixel detectors provides versatile tool for the object inspection in various fields of science. It has proven itself especially suitable for the samples with low intrinsic attenuation contrast (e.g. soft tissue in biology, plastics in material sciences, thin paint layers in cultural heritage, etc.). The limited size of single Medipix type detector (1.96 cm2) was recently overcome by the construction of large area detectors WidePIX assembled of Timepix chips equipped with edgeless silicon sensors. The largest already built device consists of 100 chips and provides fully sensitive area of 14.3 × 14.3 cm2 without any physical gaps between sensors. The pixel resolution of this device is 2560 × 2560 pixels (6.5 Mpix). The unique modular detector layout requires special processing of acquired data to avoid occurring image distortions. It is necessary to use several geometric compensations after standard corrections methods typical for this type of pixel detectors (i.e. flat-field, beam hardening correction). The proposed geometric compensations cover both concept features and particular detector assembly misalignment of individual chip rows of large area detectors based on Timepix assemblies. The former deals with larger border pixels in individual edgeless sensors and their behaviour while the latter grapple with shifts, tilts and steps between detector rows. The real position of all pixels is defined in Cartesian coordinate system and together with non-binary reliability mask it is used for the final image interpolation. The results of geometric corrections for test wire phantoms and paleo botanic material are presented in this article.

Retrieval of AOD and PM2.5 Concentrations over Urban Areas of Shenyang City using MODIS Data

NASA Astrophysics Data System (ADS)

Wang, Z.

2016-12-01

Atmospheric aerosols play an important part in the Earth's radiation balance as well as global climate change, aerosols also have very important impact on environment as well as human and other organisms' health, PM2.5 and other small particle aerosols, can enter bronchi directly, thus causing bronchitis, cardiovascular disease, asthma and so on.Detection of AOD by satellite and remote sensing is currently one of the hotest issues , diffierent from the traditional monitoring method, this method has much more advantanges, for emample wide area coverage, fast and convenient etc. So it is possible for people to know the regional changes of AOD real time over large area. Now, detection aerosol by RS technology has reached a high level in marine and dense vegetation land areas, but result is not ideal for urban areas, the higher surface reflectance in urban areas is a bottleneck of AOD retrieval. Focus on the high surface reflectance and low accuracy of the AOD products of urban areas, this paper propose an algorithm coupled with surface reflectance to get red band surface reflectance, based on Dens Dark Vegetation algorithm and geometrical optics model theory, to distinguish urban reflectivity from other targets. Considering the appropriate aerosol model which adapt to season and other proper parameters, this paper uses 6S model to establish look-up table, thus retrieve AOD for urban as well as other high reflectance areas. This paper take Shenyang region as pilot area, then retrieve the AOD and PM2.5 concentration of Shenyang in 2015 based on MODIS data, thus get 1km resolution distribution map, and then analyzed the results in spatial, intensity and temporal. At last, real-time monitoring data from the ground monitor station is used to verify the outcome, the results have good accuracy and the the correlation reached 0.9004 when the weather is sunny. The research shows that this algorithm has relatively higher precision and certain universality. This method has better applicability to retrieve AOD and PM2.5 concentration by remote sensing in Shenyang and Liaoning Provience, and owes guiding and reference significance, and it has a high value in terms of atmospheric environment monitoring.

Molecular dynamic heterogeneity of confined lipid films by 1H magnetization-exchange nuclear magnetic resonance

NASA Astrophysics Data System (ADS)

Buda, A.; Demco, D. E.; Jagadeesh, B.; Blümich, B.

2005-01-01

The molecular dynamic heterogeneity of monolayer to submonolayer thin lecithin films confined to submicron cylindrical pores were investigated by 1H magnetization exchange nuclear magnetic resonance. In this experiment a z-magnetization gradient was generated by a double-quantum dipolar filter. The magnetization-exchange decay and buildup curves were interpreted with the help of a theoretical model based on the approximation of a one-dimensional spin-diffusion process in a three-domain morphology. The dynamic heterogeneity of the fatty acid chains and the effects of the surface area per molecule, the diameter of the pores, and the temperature were characterized with the help of local spin-diffusion coefficients. The effect of various parameters on the molecular dynamics of the mobile region of the fatty acid chains was quantified by introducing an ad hoc Gaussian distribution function of the 1H residual dipolar couplings. For the lipid films investigated in this study, the surface induced order and the geometrical confinement affect the chain dynamics of the entire molecule. Therefore, each part of the chain independently reflects the effect of surface coverage, pore size, and temperature.

A system for saccular intracranial aneurysm analysis and virtual stent planning

NASA Astrophysics Data System (ADS)

Baloch, Sajjad; Sudarsky, Sandra; Zhu, Ying; Mohamed, Ashraf; Geiger, Berhard; Dutta, Komal; Namburu, Durga; Nias, Puthenveettil; Martucci, Gary; Redel, Thomas

2012-02-01

Recent studies have found correlation between the risk of rupture of saccular aneurysms and their morphological characteristics, such as volume, surface area, neck length, among others. For reliably exploiting these parameters in endovascular treatment planning, it is crucial that they are accurately quantified. In this paper, we present a novel framework to assist physicians in accurately assessing saccular aneurysms and efficiently planning for endovascular intervention. The approach consists of automatically segmenting the pathological vessel, followed by the construction of its surface representation. The aneurysm is then separated from the vessel surface through a graph-cut based algorithm that is driven by local geometry as well as strong prior information. The corresponding healthy vessel is subsequently reconstructed and measurements representing the patient-specific geometric parameters of pathological vessel are computed. To better support clinical decisions on stenting and device type selection, the placement of virtual stent is eventually carried out in conformity with the shape of the diseased vessel using the patient-specific measurements. We have implemented the proposed methodology as a fully functional system, and extensively tested it with phantom and real datasets.

Light cone thermodynamics

NASA Astrophysics Data System (ADS)

De Lorenzo, Tommaso; Perez, Alejandro

2018-02-01

We show that null surfaces defined by the outgoing and infalling wave fronts emanating from and arriving at a sphere in Minkowski spacetime have thermodynamical properties that are in strict formal correspondence with those of black hole horizons in curved spacetimes. Such null surfaces, made of pieces of light cones, are bifurcate conformal Killing horizons for suitable conformally stationary observers. They can be extremal and nonextremal depending on the radius of the shining sphere. Such conformal Killing horizons have a constant light cone (conformal) temperature, given by the standard expression in terms of the generalization of surface gravity for conformal Killing horizons. Exchanges of conformally invariant energy across the horizon are described by a first law where entropy changes are given by 1 /(4 ℓp2) of the changes of a geometric quantity with the meaning of horizon area in a suitable conformal frame. These conformal horizons satisfy the zeroth to the third laws of thermodynamics in an appropriate way. In the extremal case they become light cones associated with a single event; these have vanishing temperature as well as vanishing entropy.

One-Pot Soft-Template Synthesis of Nanostructured Copper-Supported Mesoporous Carbon FDU-15 Electrocatalysts for Efficient CO2 Reduction.

PubMed

Şahin, Nihat Ege; Comminges, Clément; Le Valant, Anthony; Kiener, Julien; Parmentier, Julien; Napporn, Teko W; Melinte, Georgian; Ersen, Ovidiu; Kokoh, Kouakou B

2018-03-14

Copper-supported mesoporous carbon nanocatalysts (Cu/FDU-15) were synthesized using an easy and convenient one-pot soft-template method for low-overvoltage CO 2 electroreduction. TEM imaging revealed the presence of large Cu nanoparticles (diameter 140 nm) with Cu 2 O nanoparticles (16 nm) as an additional phase. From the electron tomography observations, we found that the copper particles were placed inside and on the exterior surface of the porous FDU-15 support, providing an accessible surface for electrocatalytic reactions. CO 2 electrolyses showed that the mesostructured Cu/FDU-15-350 cathode materials were active towards CO 2 conversion to formic acid with 22 % Faradaic efficiency at a remarkably low overpotential of 290 mV, hydrogen being the only side-product. The catalyst's activity correlates to the calculated metallic surface area, as determined from a geometrical model, confirming that the mesoporous channels act as a diffusion path for the CO 2 molecule, and that the whole Cu surface is accessible to CO 2 , even if particles are entrapped in the carbon matrix. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hybrid Geometric Calibration Method for Multi-Platform Spaceborne SAR Image with Sparse Gcps

NASA Astrophysics Data System (ADS)

Lv, G.; Tang, X.; Ai, B.; Li, T.; Chen, Q.

2018-04-01

Geometric calibration is able to provide high-accuracy geometric coordinates of spaceborne SAR image through accurate geometric parameters in the Range-Doppler model by ground control points (GCPs). However, it is very difficult to obtain GCPs that covering large-scale areas, especially in the mountainous regions. In addition, the traditional calibration method is only used for single platform SAR images and can't support the hybrid geometric calibration for multi-platform images. To solve the above problems, a hybrid geometric calibration method for multi-platform spaceborne SAR images with sparse GCPs is proposed in this paper. First, we calibrate the master image that contains GCPs. Secondly, the point tracking algorithm is used to obtain the tie points (TPs) between the master and slave images. Finally, we calibrate the slave images using TPs as the GCPs. We take the Beijing-Tianjin- Hebei region as an example to study SAR image hybrid geometric calibration method using 3 TerraSAR-X images, 3 TanDEM-X images and 5 GF-3 images covering more than 235 kilometers in the north-south direction. Geometric calibration of all images is completed using only 5 GCPs. The GPS data extracted from GNSS receiver are used to assess the plane accuracy after calibration. The results after geometric calibration with sparse GCPs show that the geometric positioning accuracy is 3 m for TSX/TDX images and 7.5 m for GF-3 images.

Exploratory studies of the cruise performance of upper surface blown configurations: Program analysis and conclusions

NASA Technical Reports Server (NTRS)

Braden, J. A.; Hancock, J. P.; Hackett, J. E.; Lyman, V.

1979-01-01

The experimental data encompassing surface pressure measurements, and wake surveys at static and wind-on conditions are analyzed. Cruise performance trends reflecting nacelle geometric variations, and nozzle operating conditions are presented. Details of the modeling process are included.

Portable, space-saving medical patient support system

DOEpatents

Bzorgi,; Fariborz, [Knoxville, TN

2011-02-01

A support platform having a stowed configuration and a deployed configuration on a floor. The support platform is related to stretcher devices that are used for transporting, confining, or conducting medical procedures on medical patients in medical emergencies. The support platform typically includes a work surface that has a geometric extent. A base that typically includes a plurality of frame members is provided, and the frame members are disposed across the geometric extent of, and proximal to, the work surface in the stowed configuration. The frame members are typically disposed on the floor in the deployed configuration. There is a foldable bracing system engaged with the work surface and engaged with the base. At least a portion of the foldable bracing system is disposed substantially inside at least a portion of the plurality of frame members in the stowed configuration. Further, the foldable bracing system is configured for translocation of the work surface distal from the base in the deployed configuration.

Self-calibrating generalized phase-shifting interferometry of three phase-steps based on geometric concept of volume enclosed by a surface

NASA Astrophysics Data System (ADS)

Meneses-Fabian, Cruz

2016-12-01

This paper presents a non-iterative, fast, and simple algorithm for phase retrieval, in phase-shifting interferometry of three unknown and unequal phase-steps, based on the geometric concept of the volume enclosed by a surface. This approach can be divided in three stages; first the background is eliminated by the subtraction of two interferograms, for obtaining a secondary pattern; second, a surface is built by the product of two secondary patterns and the volume enclosed by this surface is computed; and third, the ratio between two enclosed volumes is approximated to a constant that depends on the phase-steps, with which a system of equations is established, and its solution allows the measurement of the phase-steps to be obtained. Additional advantages of this approach are its immunity to noise, and its capacity to support high spatial variations in the illumination. This approach is theoretically described and is numerically and experimentally verified.

Cross-sectional geometry of Pecos Pueblo femora and tibiae--a biomechanical investigation: II. Sex, age, side differences.

PubMed

Ruff, C B; Hayes, W C

1983-03-01

Intra-populational variation in cross-sectional geometric properties of the femur and tibia are investigated in the Pecos Pueblo skeletal sample. Sex differences in geometric parameters suggest that male lower limb bones are more adapted for A-P bending, females for M-L bending. Proposed explanations for this finding include sexual dimorphism in pelvic structure and culturally prescribed sex-related activities at Pecos. With aging, both males and females undergo endosteal resorption and cortical thinning, greater among females. Both sexes also demonstrate an increase with age in subperiosteal area and second moments of area, supporting results reported in some studies of modern population samples. Sex and site-specific remodeling of the femur and tibia with aging also occur. These localized remodeling changes appear to selectively conserve more compact cortical bone in areas of high mechanical stress. Side differences in cross-sectional geometric properties indicate that left lower limb bones are generally larger than right lower limb bones, with asymmetry greater among females. In particular, left femora and tibiae are relatively stronger in A-P bending, again more so in females.

New solutions and applications of 3D computer tomography image processing

NASA Astrophysics Data System (ADS)

Effenberger, Ira; Kroll, Julia; Verl, Alexander

2008-02-01

As nowadays the industry aims at fast and high quality product development and manufacturing processes a modern and efficient quality inspection is essential. Compared to conventional measurement technologies, industrial computer tomography (CT) is a non-destructive technology for 3D-image data acquisition which helps to overcome their disadvantages by offering the possibility to scan complex parts with all outer and inner geometric features. In this paper new and optimized methods for 3D image processing, including innovative ways of surface reconstruction and automatic geometric feature detection of complex components, are presented, especially our work of developing smart online data processing and data handling methods, with an integrated intelligent online mesh reduction. Hereby the processing of huge and high resolution data sets is guaranteed. Besides, new approaches for surface reconstruction and segmentation based on statistical methods are demonstrated. On the extracted 3D point cloud or surface triangulation automated and precise algorithms for geometric inspection are deployed. All algorithms are applied to different real data sets generated by computer tomography in order to demonstrate the capabilities of the new tools. Since CT is an emerging technology for non-destructive testing and inspection more and more industrial application fields will use and profit from this new technology.

Development of a continuous roll-to-roll processing system for mass production of plastic optical film

NASA Astrophysics Data System (ADS)

Chang, Chih-Yuan; Tsai, Meng-Hsun

2015-12-01

This paper reports a highly effective method for the mass production of large-area plastic optical films with a microlens array pattern based on a continuous roll-to-roll film extrusion and roller embossing process. In this study, a thin steel mold with a micro-circular hole array pattern is fabricated by photolithography and a wet chemical etching process. The thin steel mold was then wrapped onto a metal cylinder to form an embossing roller mold. During the roll-to-roll process operation, a thermoplastic raw material (polycarbonate grains) was put into the barrel of the plastic extruder with a flat T-die. Then, the molten polymer film was extruded and immediately pressed against the surface of the embossing roller mold. Under the proper processing conditions, the molten polymer will just partially fill the micro-circular holes of the mold and due to surface tension form a convex lens surface. A continuous plastic optical film with a microlens array pattern was obtained. Experiments are carried out to investigate the effect of plastic microlens formation on the roll-to-roll process. Finally, the geometrical and optical properties of the fabricated plastic optical film were measured and proved satisfactory. This technique shows great potential for the mass production of large-area plastic optical films with a microlens array pattern.

Porous polystyrene beads as carriers for self-emulsifying system containing loratadine.

PubMed

Patil, Pradeep; Paradkar, Anant

2006-03-01

The aim of this study was to formulate a self-emulsifying system (SES) containing a lipophilic drug, loratadine, and to explore the potential of preformed porous polystyrene beads (PPB) to act as carriers for such SES. Isotropic SES was formulated, which comprised Captex 200 (63% wt/wt), Cremophore EL (16% wt/wt), Capmul MCM (16% wt/wt), and loratadine (5% wt/wt). SES was evaluated for droplet size, drug content, and in vitro drug release. SES was loaded into preformed and characterized PPB using solvent evaporation method. SES-loaded PPB were evaluated using scanning electron microscopy (SEM) for density, specific surface area (S BET ), loading efficiency, drug content, and in vitro drug release. After SES loading, specific surface area reduced drastically, indicating filling of PPB micropores with SES. Loading efficiency was least for small size (SS) and comparable for medium size (MS) and large size (LS) PPB fractions. In vitro drug release was rapid in case of SS beads due to the presence of SES near to surface. LS fraction showed inadequate drug release owing to presence of deeper micropores that resisted outward diffusion of entrapped SES. Leaching of SES from micropores was the rate-limiting step for drug release. Geometrical features such as bead size and pore architecture of PPB were found to govern the loading efficiency and in vitro drug release from SES-loaded PPB.

Porous polystyrene beads as carriers for self-emulsifying system containing loratadine.

PubMed

Patil, Pradeep; Paradkar, Anant

2006-03-24

The aim of this study was to formulate a self-emulsifying system (SES) containing a lipophilic drug, loratadine, and to explore the potential of preformed porous polystyrene beads (PPB) to act as carriers for such SES. Isotropic SES was formulated, which comprised Captex 200 (63% wt/wt), Cremophore EL (16% wt/wt), Capmul MCM (16% wt/wt), and loratadine (5% wt/wt). SES was evaluated for droplet size, drug content, and in vitro drug release. SES was loaded into preformed and characterized PPB using solvent evaporation method. SES-loaded PPB were evaluated using scanning electron microscopy (SEM) for density, specific surface area (S(BET)), loading efficiency, drug content, and in vitro drug release. After SES loading, specific surface area reduced drastically, indicating filling of PPB micropores with SES. Loading efficiency was least for small size (SS) and comparable for medium size (MS) and large size (LS) PPB fractions. In vitro drug release was rapid in case of SS beads due to the presence of SES near to surface. LS fraction showed inadequate drug release owing to presence of deeper micropores that resisted outward diffusion of entrapped SES. Leaching of SES from micropores was the rate-limiting step for drug release. Geometrical features such as bead size and pore architecture of PPB were found to govern the loading efficiency and in vitro drug release from SES-loaded PPB.

Effect of varying internal geometry on the static performance of rectangular thrust-reverser ports

NASA Technical Reports Server (NTRS)

Re, Richard J.; Mason, Mary L.

1987-01-01

An investigation has been conducted to evaluate the effects of several geometric parameters on the internal performance of rectangular thrust-reverser ports for nonaxisymmetric nozzles. Internal geometry was varied with a test apparatus which simulated a forward-flight nozzle with a single, fully deployed reverser port. The test apparatus was designed to simulate thrust reversal (conceptually) either in the convergent section of the nozzle or in the constant-area duct just upstream of the nozzle. The main geometric parameters investigated were port angle, port corner radius, port location, and internal flow blocker angle. For all reverser port geometries, the port opening had an aspect ratio (throat width to throat height) of 6.1 and had a constant passage area from the geometric port throat to the exit. Reverser-port internal performance and thrust-vector angles computed from force-balance measurements are presented.

Normalized Implicit Radial Models for Scattered Point Cloud Data without Normal Vectors

DTIC Science & Technology

2009-03-23

points by shrinking a discrete membrane, Computer Graphics Forum, Vol. 24-4, 2005, pp. 791-808 [8] Floater , M. S., Reimers, M.: Meshless...Parameterization and Surface Reconstruction, Computer Aided Geometric Design 18, 2001, pp 77-92 [9] Floater , M. S.: Parameterization of Triangulations and...Unorganized Points, In: Tutorials on Multiresolution in Geometric Modelling, A. Iske, E. Quak and M. S. Floater (eds.), Springer , 2002, pp. 287-316 [10

Multiphase flow in geometrically simple fracture intersections

USGS Publications Warehouse

Basagaoglu, H.; Meakin, P.; Green, C.T.; Mathew, M.; ,

2006-01-01

A two-dimensional lattice Boltzmann (LB) model with fluid-fluid and solid-fluid interaction potentials was used to study gravity-driven flow in geometrically simple fracture intersections. Simulated scenarios included fluid dripping from a fracture aperture, two-phase flow through intersecting fractures and thin-film flow on smooth and undulating solid surfaces. Qualitative comparisons with recently published experimental findings indicate that for these scenarios the LB model captured the underlying physics reasonably well.

Determination of the Impact of Urbanization on Agricultural Lands using Multi-temporal Satellite Sensor Images

NASA Astrophysics Data System (ADS)

Kaya, S.; Alganci, U.; Sertel, E.; Ustundag, B.

2015-12-01

Throughout the history, agricultural activities have been performed close to urban areas. Main reason behind this phenomenon is the need of fast marketing of the agricultural production to urban residents and financial provision. Thus, using the areas nearby cities for agricultural activities brings out advantage of easy transportation of productions and fast marketing. For decades, heavy migration to cities has directly and negatively affected natural grasslands, forests and agricultural lands. This pressure has caused agricultural lands to be changed into urban areas. Dense urbanization causes increase in impervious surfaces, heat islands and many other problems in addition to destruction of agricultural lands. Considering the negative impacts of urbanization on agricultural lands and natural resources, a periodic monitoring of these changes becomes indisputably important. At this point, satellite images are known to be good data sources for land cover / use change monitoring with their fast data acquisition, large area coverages and temporal resolution properties. Classification of the satellite images provides thematic the land cover / use maps of the earth surface and changes can be determined with GIS based analysis multi-temporal maps. In this study, effects of heavy urbanization over agricultural lands in Istanbul, metropolitan city of Turkey, were investigated with use of multi-temporal Landsat TM satellite images acquired between 1984 and 2011. Images were geometrically registered to each other and classified using supervised maximum likelihood classification algorithm. Resulting thematic maps were exported to GIS environment and destructed agricultural lands by urbanization were determined using spatial analysis.

Effect of Gaussian curvature modulus on the shape of deformed hollow spherical objects.

PubMed

Quilliet, C; Farutin, A; Marmottant, P

2016-06-01

A popular description of soft membranes uses the surface curvature energy introduced by Helfrich, which includes a spontaneous curvature parameter. In this paper we show how the Helfrich formula can also be of interest for a wider class of spherical elastic surfaces, namely with shear elasticity, and likely to model other deformable hollow objects. The key point is that when a stress-free state with spherical symmetry exists before subsequent deformation, its straightforwardly determined curvature ("geometrical spontaneous curvature") differs most of the time from the Helfrich spontaneous curvature parameter that should be considered in order to have the model being correctly used. Using the geometrical curvature in a set of independent parameters unveils the role of the Gaussian curvature modulus, which appears to play on the shape of an elastic surface even though this latter is closed, contrary to what happens for surfaces without spontaneous curvature. In appendices, clues are given to apply this alternative and convenient formulation of the elastic surface model to the particular case of thin spherical shells of isotropic material (TSSIMs).

Optical and heat transfer performance of a novel non-imaging concentrator

NASA Astrophysics Data System (ADS)

Sellami, Nazmi; Meng, Xian-long; Xia, Xin-Lin; Knox, Andrew R.; Mallick, Tapas K.

2015-09-01

In this study, the Crossed Compound Parabolic Concentrator CCPC is modified to demonstrate for the first time a new generation of solar concentrators working simultaneously as an electricity generator and thermal collector. It is designed to have two complementary surfaces, one reflective and one absorptive, and is called an absorptive/reflective CCPC (AR-CCPC). Usually, the height of the CCPC is truncated with a minor sacrifice of the geometric concentration. These truncated surfaces rather than being eliminated are instead replaced with absorbent surfaces to collect heat from solar radiation. The optical, thermal and total efficiency of the AR-CCPC was simulated and compared for different geometric concentration ratios varying from 3.6x to 4x. It was found that the combined electrical and thermal efficiency of the AR-CCPC 3.6x/4x remains constant and high all day long and the overall efficiency reach up to 94%. In addition, the temperature distributions of AR-CCPC surfaces and the assembled solar cell were simulated based on those heat flux boundary conditions. It shows that the adding of thermal absorbent surface can apparently increase the wall temperature.