Real-Space Imaging of the Tailored Plasmons in Twisted Bilayer Graphene

NASA Astrophysics Data System (ADS)

Hu, F.; Das, Suprem R.; Luan, Y.; Chung, T.-F.; Chen, Y. P.; Fei, Z.

2017-12-01

We report a systematic plasmonic study of twisted bilayer graphene (TBLG)—two graphene layers stacked with a twist angle. Through real-space nanoimaging of TBLG single crystals with a wide distribution of twist angles, we find that TBLG supports confined infrared plasmons that are sensitively dependent on the twist angle. At small twist angles, TBLG has a plasmon wavelength comparable to that of single-layer graphene. At larger twist angles, the plasmon wavelength of TBLG increases significantly with apparently lower damping. Further analysis and modeling indicate that the observed twist-angle dependence of TBLG plasmons in the Dirac linear regime is mainly due to the Fermi-velocity renormalization, a direct consequence of interlayer electronic coupling. Our work unveils the tailored plasmonic characteristics of TBLG and deepens our understanding of the intriguing nano-optical physics in novel van der Waals coupled two-dimensional materials.

Real-Space Imaging of the Tailored Plasmons in Twisted Bilayer Graphene

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

Hu, F.; Das, Suprem R.; Luan, Y.

Here, we report a systematic plasmonic study of twisted bilayer graphene (TBLG)—two graphene layers stacked with a twist angle. Through real-space nanoimaging of TBLG single crystals with a wide distribution of twist angles, we find that TBLG supports confined infrared plasmons that are sensitively dependent on the twist angle. At small twist angles, TBLG has a plasmon wavelength comparable to that of single-layer graphene. At larger twist angles, the plasmon wavelength of TBLG increases significantly with apparently lower damping. Further analysis and modeling indicate that the observed twist-angle dependence of TBLG plasmons in the Dirac linear regime is mainly duemore » to the Fermi-velocity renormalization, a direct consequence of interlayer electronic coupling. Our work unveils the tailored plasmonic characteristics of TBLG and deepens our understanding of the intriguing nano-optical physics in novel van der Waals coupled two-dimensional materials.« less

Real-Space Imaging of the Tailored Plasmons in Twisted Bilayer Graphene

DOE PAGES

Hu, F.; Das, Suprem R.; Luan, Y.; ...

2017-12-13

Here, we report a systematic plasmonic study of twisted bilayer graphene (TBLG)—two graphene layers stacked with a twist angle. Through real-space nanoimaging of TBLG single crystals with a wide distribution of twist angles, we find that TBLG supports confined infrared plasmons that are sensitively dependent on the twist angle. At small twist angles, TBLG has a plasmon wavelength comparable to that of single-layer graphene. At larger twist angles, the plasmon wavelength of TBLG increases significantly with apparently lower damping. Further analysis and modeling indicate that the observed twist-angle dependence of TBLG plasmons in the Dirac linear regime is mainly duemore » to the Fermi-velocity renormalization, a direct consequence of interlayer electronic coupling. Our work unveils the tailored plasmonic characteristics of TBLG and deepens our understanding of the intriguing nano-optical physics in novel van der Waals coupled two-dimensional materials.« less

Portable mini-chamber for temperature dependent studies using small angle and wide angle x-ray scattering

NASA Astrophysics Data System (ADS)

Dev, Arun Singh; Kumar, Dileep; Potdar, Satish; Pandit, Pallavi; Roth, Stephan V.; Gupta, Ajay

2018-04-01

The present work describes the design and performance of a vacuum compatible portable mini chamber for temperature dependent GISAXS and GIWAXS studies of thin films and multilayer structures. The water cooled body of the chamber allows sample annealing up to 900 K using ultra high vacuum compatible (UHV) pyrolytic boron nitride heater, thus making it possible to study the temperature dependent evolution of structure and morphology of two-dimensional nanostructured materials. Due to its light weight and small size, the chamber is portable and can be accommodated at synchrotron facilities worldwide. A systematic illustration of the versatility of the chamber has been demonstrated at beamline P03, PETRA-III, DESY, Hamburg, Germany. Temperature dependent grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence wide angle x-ray scattering (GIWAXS) measurements were performed on oblique angle deposited Co/Ag multilayer structure, which jointly revealed that the surface diffusion in Co columns in Co/Ag multilayer enhances by increasing temperature from RT to ˜573 K. This results in a morphology change from columnar tilted structure to densely packed morphological isotropic multilayer.

General theoretical description of angle-resolved photoemission spectroscopy of van der Waals structures

NASA Astrophysics Data System (ADS)

Amorim, B.

2018-04-01

We develop a general theory to model the angle-resolved photoemission spectroscopy (ARPES) of commensurate and incommensurate van der Waals (vdW) structures, formed by lattice mismatched and/or misaligned stacked layers of two-dimensional materials. The present theory is based on a tight-binding description of the structure and the concept of generalized umklapp processes, going beyond previous descriptions of ARPES in incommensurate vdW structures, which are based on continuous, low-energy models, being limited to structures with small lattice mismatch/misalignment. As applications of the general formalism, we study the ARPES bands and constant energy maps for two structures: twisted bilayer graphene and twisted bilayer MoS2. The present theory should be useful in correctly interpreting experimental results of ARPES of vdW structures and other systems displaying competition between different periodicities, such as two-dimensional materials weakly coupled to a substrate and materials with density wave phases.

Performance Characteristics of Plane-Wall Two-Dimensional Diffusers

NASA Technical Reports Server (NTRS)

Reid, Elliott G

1953-01-01

Experiments have been made at Stanford University to determine the performance characteristics of plane-wall, two-dimensional diffusers which were so proportioned as to insure reasonable approximation of two-dimensional flow. All of the diffusers had identical entrance cross sections and discharged directly into a large plenum chamber; the test program included wide variations of divergence angle and length. During all tests a dynamic pressure of 60 pounds per square foOt was maintained at the diffuser entrance and the boundary layer there was thin and fully turbulent. The most interesting flow characteristics observed were the occasional appearance of steady, unseparated, asymmetric flow - which was correlated with the boundary-layer coalescence - and the rapid deterioration of flow steadiness - which occurred as soon as the divergence angle for maximum static pressure recovery was exceeded. Pressure efficiency was found to be controlled almost exclusively by divergence angle, whereas static pressure recovery was markedly influenced by area ratio (or length) as well as divergence angle. Volumetric efficiency. diminished as area ratio increased, and at a greater rate with small lengths than with large ones. Large values of the static-pressure-recovery coefficient were attained only with long diffusers of large area ratio; under these conditions pressure efficiency was high and. volumetric efficiency low. Auxiliary tests with asymmetric diffusers demonstrated that longitudinal pressure gradient, rather than wall divergence angle, controlled flow separation. Others showed that the addition of even a short exit duct of uniform section augmented pressure recovery. Finally, it was found that the installation of a thin, central, longitudinal partition suppressed flow separation in short diffusers and thereby improved pressure recovery

Evidence for the presence of quasi-two-dimensional nearly incompressible fluctuations in the solar wind

NASA Technical Reports Server (NTRS)

Matthaeus, William H.; Goldstein, Melvyn L.; Roberts, D. Aaron

1990-01-01

Assuming that the slab and isotropic models of solar wind turbulence need modification (largely due to the observed anisotropy of the interplanetary fluctuations and the results of laboratory plasma experiments), this paper proposes a model of the solar wind. The solar wind is seen as a fluid which contains both classical transverse Alfvenic fluctuations and a population of quasi-transverse fluctuations. In quasi-two-dimensional turbulence, the pitch angle scattering by resonant wave-particle interactions is suppressed, and the direction of minimum variance of interplanetary fluctuations is parallel to the mean magnetic field. The assumed incompressibility is consistent with the fact that the density fluctuations are small and anticorrelated, and that the total pressure at small scales is nearly constant.

Characterization of the shape and line-edge roughness of polymer gratings with grazing incidence small-angle X-ray scattering and atomic force microscopy

DOE PAGES

Suh, Hyo Seon; Chen, Xuanxuan; Rincon-Delgadillo, Paulina A.; ...

2016-04-22

Grazing-incidence small-angle X-ray scattering (GISAXS) is increasingly used for the metrology of substrate-supported nanoscale features and nanostructured films. In the case of line gratings, where long objects are arranged with a nanoscale periodicity perpendicular to the beam, a series of characteristic spots of high-intensity (grating truncation rods, GTRs) are recorded on a two-dimensional detector. The intensity of the GTRs is modulated by the three-dimensional shape and arrangement of the lines. Previous studies aimed to extract an average cross-sectional profile of the gratings, attributing intensity loss at GTRs to sample imperfections. Such imperfections are just as important as the average shapemore » when employing soft polymer gratings which display significant line-edge roughness. Herein are reported a series of GISAXS measurements of polymer line gratings over a range of incident angles. Both an average shape and fluctuations contributing to the intensity in between the GTRs are extracted. Lastly, the results are critically compared with atomic force microscopy (AFM) measurements, and it is found that the two methods are in good agreement if appropriate corrections for scattering from the substrate (GISAXS) and contributions from the probe shape (AFM) are accounted for.« less

Three-dimensional evaluation of gettering ability for oxygen atoms at small-angle tilt boundaries in Czochralski-grown silicon crystals

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

Ohno, Yutaka, E-mail: yutakaohno@imr.tohoku.ac.jp; Inoue, Kaihei; Fujiwara, Kozo

2015-06-22

Three-dimensional distribution of oxygen atoms at small-angle tilt boundaries (SATBs) in Czochralski-grown p-type silicon ingots was investigated by atom probe tomography combined with transmission electron microscopy. Oxygen gettering along edge dislocations composing SATBs, post crystal growth, was observed. The gettering ability of SATBs would depend both on the dislocation strain and on the dislocation density. Oxygen atoms would agglomerate in the atomic sites under the tensile hydrostatic stress larger than about 2.0 GPa induced by the dislocations. It was suggested that the density of the atomic sites, depending on the tilt angle of SATBs, determined the gettering ability of SATBs.

A DYNAMIC VALGUS INDEX THAT COMBINES HIP AND KNEE ANGLES: ASSESSMENT OF UTILITY IN FEMALES WITH PATELLOFEMORAL PAIN.

PubMed

Scholtes, Sara A; Salsich, Gretchen B

2017-06-01

Two=dimensional motion analysis of lower=extremity movement typically focuses on the knee frontal plane projection angle, which considers the position of the femur and the tibia. A measure that includes the pelvis may provide a more comprehensive and accurate indicator of lower=extremity movement. Hypothesis/Purpose: The purpose of the study was to describe the utility of a two=dimensional dynamic valgus index (DVI) in females with patellofemoral pain. The hypothesis was that the DVI would be more reliable and valid than the knee frontal plane projection angle, be greater in females with patellofemoral pain during a single=limb squat than in females without patellofemoral pain, and decrease in females with patellofemoral pain following instruction. Study Design: Controlled Laboratory Study. Data were captured while participants performed single limb squats under two conditions: usual and corrected. Two=dimensional hip and knee angles and a DVI that combined the hip and knee angles were calculated. Three=dimensional sagittal, frontal, and transverse plane angles of the hip and knee and a DVI combining the frontal and transverse plane angles were calculated. The two=dimensional DVI demonstrated moderate reliability (ICC=0.74). The correlation between the two=dimensional and three=dimensional DVI's was 0.635 (p<0001). Females with patellofemoral pain demonstrated a greater two=dimensional DVI (31.14 °±13.36 °) than females without patellofemoral pain (18.30 °±14.97 °; p=0.010). Females with patellofemoral pain demonstrated a decreased DVI in the corrected (19.04 °±13.70 °) versus usual (31.14 °±13.36 °) condition (p=0.001). The DVI is a reliable and valid measure that may provide a more comprehensive assessment of lower=extremity movement patterns than the knee frontal plane projection angle in individuals with lower=extremity musculoskeletal pain problems. 2b.

Static investigation of two fluidic thrust-vectoring concepts on a two-dimensional convergent-divergent nozzle

NASA Technical Reports Server (NTRS)

Wing, David J.

1994-01-01

A static investigation was conducted in the static test facility of the Langley 16-Foot Transonic Tunnel of two thrust-vectoring concepts which utilize fluidic mechanisms for deflecting the jet of a two-dimensional convergent-divergent nozzle. One concept involved using the Coanda effect to turn a sheet of injected secondary air along a curved sidewall flap and, through entrainment, draw the primary jet in the same direction to produce yaw thrust vectoring. The other concept involved deflecting the primary jet to produce pitch thrust vectoring by injecting secondary air through a transverse slot in the divergent flap, creating an oblique shock in the divergent channel. Utilizing the Coanda effect to produce yaw thrust vectoring was largely unsuccessful. Small vector angles were produced at low primary nozzle pressure ratios, probably because the momentum of the primary jet was low. Significant pitch thrust vector angles were produced by injecting secondary flow through a slot in the divergent flap. Thrust vector angle decreased with increasing nozzle pressure ratio but moderate levels were maintained at the highest nozzle pressure ratio tested. Thrust performance generally increased at low nozzle pressure ratios and decreased near the design pressure ratio with the addition of secondary flow.

BioXTAS RAW: improvements to a free open-source program for small-angle X-ray scattering data reduction and analysis.

PubMed

Hopkins, Jesse Bennett; Gillilan, Richard E; Skou, Soren

2017-10-01

BioXTAS RAW is a graphical-user-interface-based free open-source Python program for reduction and analysis of small-angle X-ray solution scattering (SAXS) data. The software is designed for biological SAXS data and enables creation and plotting of one-dimensional scattering profiles from two-dimensional detector images, standard data operations such as averaging and subtraction and analysis of radius of gyration and molecular weight, and advanced analysis such as calculation of inverse Fourier transforms and envelopes. It also allows easy processing of inline size-exclusion chromatography coupled SAXS data and data deconvolution using the evolving factor analysis method. It provides an alternative to closed-source programs such as Primus and ScÅtter for primary data analysis. Because it can calibrate, mask and integrate images it also provides an alternative to synchrotron beamline pipelines that scientists can install on their own computers and use both at home and at the beamline.

Structural formation of huntingtin-like aggregates probed by small-angle neutron scattering

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

Stanley, Christopher B; Perevozchikova, Tatiana; Berthelier-Jung, Valerie M

2011-01-01

In several neurodegenerative disorders, including Huntington s disease (HD), aspects concerning the earliest of protein structures that form along the aggregation pathway have increasingly gained attention since these particular species are likely to be neurotoxic. We used time-resolved small-angle neutron scattering (SANS) to probe in solution these transient structures formed by peptides having the N-terminal sequence context of mutant huntingtin (Htt) exon 1. We obtained snapshots of the formed aggregates as the kinetic reaction ensued to yield quantitative information on their size and mass. At the early stage, small precursor species with an initial radius of gyration (Rg) of 16.1more » 5.9 and average mass of a dimer to trimer were monitored. Structural growth was treated as two modes with a transition from three-dimensional early aggregate formation to two-dimensional fibril growth and association. Our SANS results on the internal structure of the mature fibrils demonstrate loose packing with about 1 peptide per 4.75 -sheet repeat distance, which is shown to be quantitatively consistent with a -helix model. This research provides new insights into the structures forming along the pathway of Htt exon 1 aggregation and should assist in determining the role that precursors play in neuronal toxicity.« less

Potential for change in US diagnosis of hip dysplasia solely caused by changes in probe orientation: patterns of alpha-angle variation revealed by using three-dimensional US.

PubMed

Jaremko, Jacob L; Mabee, Myles; Swami, Vimarsha G; Jamieson, Lucy; Chow, Kelvin; Thompson, Richard B

2014-12-01

To use three-dimensional ( 3D three-dimensional ) ultrasonography (US) to quantify the alpha-angle variability due to changing probe orientation during two-dimensional ( 2D two-dimensional ) US of the infant hip and its effect on the diagnostic classification of developmental dysplasia of the hip ( DDH developmental dysplasia of the hip ). In this institutional research ethics board-approved prospective study, with parental written informed consent, 13-MHz 3D three-dimensional US was added to initial 2D two-dimensional US for 56 hips in 35 infants (mean age, 41.7 days; range, 4-112 days), 26 of whom were female (mean age, 38.7 days; range, 6-112 days) and nine of whom were male (mean age, 50.2 days; range, 4-111 days). Findings in 20 hips were normal at the initial visit and were initially inconclusive but normalized spontaneously at follow-up in 23 hips; 13 hips were treated for dysplasia. With the computer algorithm, 3D three-dimensional US data were resectioned in planes tilted in 5° increments away from a central plane, as if slowly rotating a 2D two-dimensional US probe, until resulting images no longer met Graf quality criteria. On each acceptable 2D two-dimensional image, two observers measured alpha angles, and descriptive statistics, including mean, standard deviation, and limits of agreement, were computed. Acceptable 2D two-dimensional images were produced over a range of probe orientations averaging 24° (maximum, 45°) from the central plane. Over this range, alpha-angle variation was 19° (upper limit of agreement), leading to alteration of the diagnostic category of hip dysplasia in 54% of hips scanned. Use of 3D three-dimensional US showed that alpha angles measured at routine 2D two-dimensional US of the hip can vary substantially between 2D two-dimensional scans solely because of changes in probe positioning. Not only could normal hips appear dysplastic, but dysplastic hips also could have normal alpha angles. Three-dimensional US can display the full acetabular shape, which might improve DDH developmental dysplasia of the hip assessment accuracy. © RSNA, 2014.

Unconventional superconductivity in magic-angle graphene superlattices

NASA Astrophysics Data System (ADS)

Cao, Yuan; Fatemi, Valla; Fang, Shiang; Watanabe, Kenji; Taniguchi, Takashi; Kaxiras, Efthimios; Jarillo-Herrero, Pablo

2018-04-01

The behaviour of strongly correlated materials, and in particular unconventional superconductors, has been studied extensively for decades, but is still not well understood. This lack of theoretical understanding has motivated the development of experimental techniques for studying such behaviour, such as using ultracold atom lattices to simulate quantum materials. Here we report the realization of intrinsic unconventional superconductivity—which cannot be explained by weak electron–phonon interactions—in a two-dimensional superlattice created by stacking two sheets of graphene that are twisted relative to each other by a small angle. For twist angles of about 1.1°—the first ‘magic’ angle—the electronic band structure of this ‘twisted bilayer graphene’ exhibits flat bands near zero Fermi energy, resulting in correlated insulating states at half-filling. Upon electrostatic doping of the material away from these correlated insulating states, we observe tunable zero-resistance states with a critical temperature of up to 1.7 kelvin. The temperature–carrier-density phase diagram of twisted bilayer graphene is similar to that of copper oxides (or cuprates), and includes dome-shaped regions that correspond to superconductivity. Moreover, quantum oscillations in the longitudinal resistance of the material indicate the presence of small Fermi surfaces near the correlated insulating states, in analogy with underdoped cuprates. The relatively high superconducting critical temperature of twisted bilayer graphene, given such a small Fermi surface (which corresponds to a carrier density of about 1011 per square centimetre), puts it among the superconductors with the strongest pairing strength between electrons. Twisted bilayer graphene is a precisely tunable, purely carbon-based, two-dimensional superconductor. It is therefore an ideal material for investigations of strongly correlated phenomena, which could lead to insights into the physics of high-critical-temperature superconductors and quantum spin liquids.

Grain coarsening in two-dimensional phase-field models with an orientation field

NASA Astrophysics Data System (ADS)

Korbuly, Bálint; Pusztai, Tamás; Henry, Hervé; Plapp, Mathis; Apel, Markus; Gránásy, László

2017-05-01

In the literature, contradictory results have been published regarding the form of the limiting (long-time) grain size distribution (LGSD) that characterizes the late stage grain coarsening in two-dimensional and quasi-two-dimensional polycrystalline systems. While experiments and the phase-field crystal (PFC) model (a simple dynamical density functional theory) indicate a log-normal distribution, other works including theoretical studies based on conventional phase-field simulations that rely on coarse grained fields, like the multi-phase-field (MPF) and orientation field (OF) models, yield significantly different distributions. In a recent work, we have shown that the coarse grained phase-field models (whether MPF or OF) yield very similar limiting size distributions that seem to differ from the theoretical predictions. Herein, we revisit this problem, and demonstrate in the case of OF models [R. Kobayashi, J. A. Warren, and W. C. Carter, Physica D 140, 141 (2000), 10.1016/S0167-2789(00)00023-3; H. Henry, J. Mellenthin, and M. Plapp, Phys. Rev. B 86, 054117 (2012), 10.1103/PhysRevB.86.054117] that an insufficient resolution of the small angle grain boundaries leads to a log-normal distribution close to those seen in the experiments and the molecular scale PFC simulations. Our paper indicates, furthermore, that the LGSD is critically sensitive to the details of the evaluation process, and raises the possibility that the differences among the LGSD results from different sources may originate from differences in the detection of small angle grain boundaries.

Nonlinear low-frequency electrostatic wave dynamics in a two-dimensional quantum plasma

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

Ghosh, Samiran, E-mail: sran_g@yahoo.com; Chakrabarti, Nikhil, E-mail: nikhil.chakrabarti@saha.ac.in

2016-08-15

The problem of two-dimensional arbitrary amplitude low-frequency electrostatic oscillation in a quasi-neutral quantum plasma is solved exactly by elementary means. In such quantum plasmas we have treated electrons quantum mechanically and ions classically. The exact analytical solution of the nonlinear system exhibits the formation of dark and black solitons. Numerical simulation also predicts the possible periodic solution of the nonlinear system. Nonlinear analysis reveals that the system does have a bifurcation at a critical Mach number that depends on the angle of propagation of the wave. The small-amplitude limit leads to the formation of weakly nonlinear Kadomstev–Petviashvili solitons.

An upgrade beamline for combined wide, small and ultra small-angle x-ray scattering at the ESRF

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

Van Vaerenbergh, Pierre; Léonardon, Joachim; Sztucki, Michael

2016-07-27

This contribution presents the main design features of the upgraded beamline ID02 (TRUSAXS). The beamline combines different small-angle X-ray scattering techniques in one unique instrument. The key component of this instrument is an evacuated (5×10{sup −3} mbar) stainless steel detector tube of length 34 m and diameter 2 m. Three different detectors (Rayonix MX170, Pilatus 300 K and FReLoN 4M) are housed inside a motorized wagon which travels along a rail system with very low parasitic lateral movements (± 0.3 mm). This system allows automatically changing the sample-to-detector distance from about 1 m to 31 m and selecting the desiredmore » detector. In addition, a wide angle detector (Rayonix LX170) is installed just above the entrance cone of the tube for optional wide-angle X-ray scattering measurements. The beamstop system enables monitoring of the X-ray beam intensity in addition to blocking the primary beam, and automated insertion of selected masks behind the primary beamstop. The focusing optics and collimation system permit to cover a scattering vector (q) range of 0.002 nm{sup −1} ≤ q ≤ 50 nm{sup −1} with one unique setting using 0.1 nm X-ray wavelength for moderate flux (5×10{sup 12} photons/sec). However, for higher flux (6x10{sup 13} photons/sec) or higher resolution (minimum q < 0.001 nm{sup −1}), focusing and collimation, respectively need to be varied. For a sample-to-detector distance of 31 m and 0.1 nm wavelength, two dimensional ultra small-angle X-ray scattering patterns can be recorded down to q≈0.001 nm{sup −1} with far superior quality as compared to one dimensional profiles obtained with a Bonse-Hart instrument.« less

Non-linear interaction of a detonation/vorticity wave

NASA Technical Reports Server (NTRS)

Lasseigne, D. G.; Jackson, T. L.; Hussaini, M. Y.

1991-01-01

The interaction of an oblique, overdriven detonation wave with a vorticity disturbance is investigated by a direct two-dimensional numerical simulation using a multi-domain, finite-difference solution of the compressible Euler equations. The results are compared to those of linear theory, which predict that the effect of exothermicity on the interaction is relatively small except possibly near a critical angle where linear theory no longer holds. It is found that the steady-state computational results agree with the results of linear theory. However, for cases with incident angle near the critical angle, moderate disturbance amplitudes, and/or sudden transient encounter with a disturbance, the effects of exothermicity are more pronounced than predicted by linear theory. Finally, it is found that linear theory correctly determines the critical angle.

Small-angle X-ray scattering tensor tomography: model of the three-dimensional reciprocal-space map, reconstruction algorithm and angular sampling requirements.

PubMed

Liebi, Marianne; Georgiadis, Marios; Kohlbrecher, Joachim; Holler, Mirko; Raabe, Jörg; Usov, Ivan; Menzel, Andreas; Schneider, Philipp; Bunk, Oliver; Guizar-Sicairos, Manuel

2018-01-01

Small-angle X-ray scattering tensor tomography, which allows reconstruction of the local three-dimensional reciprocal-space map within a three-dimensional sample as introduced by Liebi et al. [Nature (2015), 527, 349-352], is described in more detail with regard to the mathematical framework and the optimization algorithm. For the case of trabecular bone samples from vertebrae it is shown that the model of the three-dimensional reciprocal-space map using spherical harmonics can adequately describe the measured data. The method enables the determination of nanostructure orientation and degree of orientation as demonstrated previously in a single momentum transfer q range. This article presents a reconstruction of the complete reciprocal-space map for the case of bone over extended ranges of q. In addition, it is shown that uniform angular sampling and advanced regularization strategies help to reduce the amount of data required.

Reading angles in maps.

PubMed

Izard, Véronique; O'Donnell, Evan; Spelke, Elizabeth S

2014-01-01

Preschool children can navigate by simple geometric maps of the environment, but the nature of the geometric relations they use in map reading remains unclear. Here, children were tested specifically on their sensitivity to angle. Forty-eight children (age 47:15-53:30 months) were presented with fragments of geometric maps, in which angle sections appeared without any relevant length or distance information. Children were able to read these map fragments and compare two-dimensional to three-dimensional angles. However, this ability appeared both variable and fragile among the youngest children of the sample. These findings suggest that 4-year-old children begin to form an abstract concept of angle that applies both to two-dimensional and three-dimensional displays and that serves to interpret novel spatial symbols. © 2013 The Authors. Child Development © 2013 Society for Research in Child Development, Inc.

Three-dimensional CTOA and constraint effects during stable tearing in a thin-sheet material

NASA Technical Reports Server (NTRS)

Dawicke, D. S.; Newman, J. C., Jr.; Bigelow, C. A.

1995-01-01

A small strain theory, three-dimensional elastic-plastic finite element analysis was used to simulate fracture in thin sheet 2024-T3 aluminum alloy in the T-L orientation. Both straight and tunneled cracks were modeled. The tunneled crack front shapes as a function of applied stress were obtained from the fracture surface of tested specimens. The stable crack growth behavior was measured at the specimen surface as a function of applied stress. The fracture simulation modeled the crack tunneling and extension as a function of applied stress. The results indicated that the global constraint factor, alpha(sub g), initially dropped during stable crack growth. After peak applied stress was achieved, alpha(sub g) began to increase slightly. The effect of crack front shape on alpha(sub g) was small, but the crack front shape did greatly influence the local constraint and through-thickness crack-tip opening angle (CTOA) behavior. The surface values of CTOA for the tunneled crack front model agreed well with experimental measurements, showing the same initial decrease from high values during the initial 3mm of crack growth at the specimen's surface. At the same time, the interior CTOA values increased from low angles. After the initial stable tearing region, the CTOA was constant through the thickness. The three-dimensional analysis appears to confirm the potential of CTOA as a two-dimensional fracture criterion.

Nonimaging concentrators for photovoltaic arrays in space

NASA Technical Reports Server (NTRS)

Winston, R.; Greenman, P.; Rockey, D.

1981-01-01

Two stage concentrators are studied in order to design an optimum concentrator for photovoltaic arrays in space. The study is directed at designs with two-dimensional geometries because they are better suited to moderate concentrations of about 10 X to 50 X, and because the instantaneous flux distribution is more uniform. It is found that with an f/0.5 primary, where f is the focal length of the primary, the flux distribution is very smooth regardless of the angle of incidence of the radiation. As the focal ratio is increased, peaks in the distribution begin to appear. The nonuniformities can be reduced by introducing small, closely spaced distortions into the reflecting surfaces, and practical arrays can achieve a concentration of 10 when the acceptance half angle is 4.25 deg or 50 when the acceptance half angle is + or - 1 deg.

Magnetic guide-wire navigation in pulmonary and systemic arterial catheterization: initial experience in pigs.

PubMed

Grosse-Wortmann, Lars; Grabitz, Ralf; Seghaye, Marie-Christine

2007-04-01

Cardiovascular catheterization can be challenging whenever a stenosis or an abnormal vascular course interferes with probing the target vessel. This study addresses the feasibility of navigating a guide wire with a magnetic tip by an external magnetic field through pulmonary and systemic arteries in an experimental porcine model. We investigated six piglets using magnetic guide-wire navigation. Two pulmonary arteriograms were taken from different angles in order to reconstruct the three-dimensional vessel anatomy. A computer interface then calculated three-dimensional coordinates for the vessel in space. Using these coordinates, two external magnets were positioned to create magnetic vectors along the expected vessel course. Magnetically enabled guide wires were then navigated into the vessels using the magnetic field to orient the guide-wire tips. Aortic and renal branches were addressed in a similar fashion. Difficulty in reaching the target vessel was reflected by the number of attempts that were necessary. After 10 failed attempts, the maneuver was recorded to have failed. Thirty-five of 37 (94.6%) arteries with branches at acute angles were reached successfully using magnetic navigation. In two pigs, the left upper lobe artery could not be probed. Peripheral arteries of small diameter were easier to reach than large central arteries, requiring less attempts. Magnetic guide-wire navigation is feasible in the arteries of the lungs, the head and neck, and the kidneys. It is particularly useful in entering small arterial branches at acute angles and may facilitate interventional therapy in a variety of vascular diseases in children and adults.

Global Search of a Three-dimensional Low Solidity Circular Cascade Diffuser for Centrifugal Blowers by Meta-model Assisted Optimization

NASA Astrophysics Data System (ADS)

Sakaguchi, Daisaku; Sakue, Daiki; Tun, Min Thaw

2018-04-01

A three-dimensional blade of a low solidity circular cascade diffuser in centrifugal blowers is designed by means of a multi-point optimization technique. The optimization aims at improving static pressure coefficient at a design point and at a small flow rate condition. Moreover, a clear definition of secondary flow expressed by positive radial velocity at hub side is taken into consideration in constraints. The number of design parameters for three-dimensional blade reaches to 10 in this study, such as a radial gap, a radial chord length and mean camber angle distribution of the LSD blade with five control points, control point between hub and shroud with two design freedom. Optimization results show clear Pareto front and selected optimum design shows good improvement of pressure rise in diffuser at small flow rate conditions. It is found that three-dimensional blade has advantage to stabilize the secondary flow effect with improving pressure recovery of the low solidity circular cascade diffuser.

Numerical investigation for design and critical performance evaluation of a horizontal axis hydrokinetic turbine

NASA Astrophysics Data System (ADS)

Subhra Mukherji, Suchi; Banerjee, Arindam

2010-11-01

We will discuss findings from our numerical investigation on the hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkT) under different turbine geometries and flow conditions. Hydrokinetic turbines are a class of zero-head hydropower systems which utilizes kinetic energy of flowing water to drive a generator. However, such turbines very often suffer from low efficiency which is primarily controlled by tip-speed ratio, solidity, angle of attack and number of blades. A detailed CFD study was performed using two-dimensional and three dimensional numerical models to examine the effect of each of these parameters on the performance of small HAHkTs having power capacities <= 10 kW. The two-dimensional numerical results provide an optimum angle of attack that maximizes the lift as well as lift to drag ratio yielding maximum power output. However three-dimensional numerical studies estimate optimum turbine solidity and blade numbers that produces maximum power coefficient at a given tip speed ratio. In addition, simulations were also performed to observe the axial velocity deficit at the turbine rotor downstream for different tip-speed ratios to obtain both qualitative and quantitative details about stall delay phenomena and the energy loss suffered by the turbine under ambient flow condition.

Improved computational treatment of transonic flow about swept wings

NASA Technical Reports Server (NTRS)

Ballhaus, W. F.; Bailey, F. R.; Frick, J.

1976-01-01

Relaxation solutions to classical three-dimensional small-disturbance (CSD) theory for transonic flow about lifting swept wings are reported. For such wings, the CSD theory was found to be a poor approximation to the full potential equation in regions of the flow field that are essentially two-dimensional in a plane normal to the sweep direction. The effect of this deficiency on the capture of embedded shock waves in terms of (1) the conditions under which shock waves can exist and (2) the relations they must satisfy when they do exist is emphasized. A modified small-disturbance (MSD) equation, derived by retaining two previously neglected terms, was proposed and shown to be a consistent approximation to the full potential equation over a wider range of sweep angles. The effect of these extra terms is demonstrated by comparing CSD, MSD, and experimental wing surface pressures.

Two-dimensional wetting: the role of atomic steps on the nucleation of thin water films on BaF2(111) at ambient conditions.

PubMed

Cardellach, M; Verdaguer, A; Santiso, J; Fraxedas, J

2010-06-21

The interaction of water with freshly cleaved BaF(2)(111) surfaces at ambient conditions (room temperature and under controlled humidity) has been studied using scanning force microscopy in different operation modes. The images strongly suggest a high surface diffusion of water molecules on the surface indicated by the accumulation of water at step edges forming two-dimensional bilayered structures. Steps running along the 110 crystallographic directions show a high degree of hydrophilicity, as evidenced by small step-film contact angles, while steps running along other directions exhibiting a higher degree of kinks surprisingly behave in a quite opposite way. Our results prove that morphological defects such as steps can be crucial in improving two-dimensional monolayer wetting and stabilization of multilayer grown on surfaces that show good lattice mismatch with hexagonal ice.

The scaling and dynamics of a projectile obliquely impacting a granular medium.

PubMed

Wang, Dengming; Ye, Xiaoyan; Zheng, Xiaojing

2012-01-01

In this paper, the dynamics of a spherical projectile obliquely impacting into a two-dimensional granular bed is numerically investigated using the discrete element method. The influences of projectile's initial velocities and impacting angles are mainly considered. Numerical results show that the relationship between the final penetration depth and the initial impact velocity is very similar to that in the vertical-impact case. However, the dependence of the stopping time on the impact velocity of the projectile exhibits critical characteristics at different impact angles: the stopping time approximately increases linearly with the impact velocity for small impact angles but decreases in an exponential form for larger impact angles, which demonstrates the existence of two different regimes at low and high impact angles. When the impact angle is regarded as a parametric variable, a phenomenological force model at large impact angles is eventually proposed based on the simulation results, which can accurately describe the nature of the resistance force exerted on the projectile by the granular medium at different impact angels during the whole oblique-impact process. The degenerate model agrees well with the existing experimental results in the vertical-impact cases.

Influence of intramuscular fiber orientation on the Achilles tendon curvature using three-dimensional finite element modeling of contracting skeletal muscle.

PubMed

Kinugasa, Ryuta; Yamamura, Naoto; Sinha, Shantanu; Takagi, Shu

2016-10-03

Tendon curvature plays a key role in mechanical gain (amplifying the joint excursion relative to fiber length change) during joint motion, but the mechanism remains unresolved. A three-dimensional finite element (FE) model was used to investigate the influence of intramuscular fiber orientation upon the curvature pattern of the Achilles tendon during active muscular contraction. Two simulation models, with fiber pennation angles of θ = 25° and 47° were tested for the gastrocnemius and soleus muscles. A smaller pennation angle (25°) of the soleus muscle fibers was accompanied by a large change in curvature whereas a larger pennation angle (47°) of the soleus muscle was accompanied by small effects. These results suggest that the fiber pennation angle determines the curvature of the tendon, and the magnitude of the curvature varies along the length of the aponeurosis. Such FE modeling has the potential of determining changes in force output consequent to changes in intramuscular fiber orientation arising from resistance training or unloading, and provides mechanism for predicting the risk of Achilles tendon ruptures. Copyright © 2016 Elsevier Ltd. All rights reserved.

A study of internal drag of small-scale ducts at Mach number 4

NASA Technical Reports Server (NTRS)

Graham, L. A.; Hunton, L. W.

1972-01-01

An experimental investigation was made to examine the applicability of methods used to determine internal drag of small ducts and to study some of the problems encountered in assessing momentum losses in such ducts. Test Mach numbers ranged from 3.7 to 4.4 at angles of attack of 0 and 5 degrees and at a constant Reynolds number of 4.3 million per foot. The configurations represented small ducts used to simulate external aerodynamics of air breathing propulsion systems and consisted of wing nacelle models of ducts with circular, square, and rectangular inlets and with a two-dimensional inlet.

Kinoform optics applied to X-ray photon correlation spectroscopy.

PubMed

Sandy, A R; Narayanan, S; Sprung, M; Su, J-D; Evans-Lutterodt, K; Isakovic, A F; Stein, A

2010-05-01

Moderate-demagnification higher-order silicon kinoform focusing lenses have been fabricated to facilitate small-angle X-ray photon correlation spectroscopy (XPCS) experiments. The geometric properties of such lenses, their focusing performance and their applicability for XPCS measurements are described. It is concluded that one-dimensional vertical X-ray focusing via silicon kinoform lenses significantly increases the usable coherent flux from third-generation storage-ring light sources for small-angle XPCS experiments.

High-throughput and automated SAXS/USAXS experiment for industrial use at BL19B2 in SPring-8

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

Osaka, Keiichi, E-mail: k-osaka@spring8.or.jp; Inoue, Daisuke; Sato, Masugu

A highly automated system combining a sample transfer robot with focused SR beam has been established for small-angle and ultra small-angle X-ray scattering (SAXS/USAXS) measurement at BL19B2 for industrial use of SPring-8. High-throughput data collection system can be realized by means of X-ray beam of high photon flux density concentrated by a cylindrical mirror, and a two-dimensional pixel detector PILATUS-2M. For SAXS measurement, we can obtain high-quality data within 1 minute for one exposure using this system. The sample transfer robot has a capacity of 90 samples with a large variety of shapes. The fusion of high-throughput and robotic systemmore » has enhanced the usability of SAXS/USAXS capability for industrial application.« less

Nonplanar wing load-line and slender wing theory

NASA Technical Reports Server (NTRS)

Deyoung, J.

1977-01-01

Nonplanar load line, slender wing, elliptic wing, and infinite aspect ratio limit loading theories are developed. These are quasi two dimensional theories but satisfy wing boundary conditions at all points along the nonplanar spanwise extent of the wing. These methods are applicable for generalized configurations such as the laterally nonplanar wing, multiple nonplanar wings, or wing with multiple winglets of arbitrary shape. Two dimensional theory infers simplicity which is practical when analyzing complicated configurations. The lateral spanwise distribution of angle of attack can be that due to winglet or control surface deflection, wing twist, or induced angles due to multiwings, multiwinglets, ground, walls, jet or fuselage. In quasi two dimensional theory the induced angles due to these extra conditions are likewise determined for two dimensional flow. Equations are developed for the normal to surface induced velocity due to a nonplanar trailing vorticity distribution. Application examples are made using these methods.

The possible equilibrium shapes of static pendant drops

NASA Astrophysics Data System (ADS)

Sumesh, P. T.; Govindarajan, Rama

2010-10-01

Analytical and numerical studies are carried out on the shapes of two-dimensional and axisymmetric pendant drops hanging under gravity from a solid surface. Drop shapes with both pinned and equilibrium contact angles are obtained naturally from a single boundary condition in the analytical energy optimization procedure. The numerical procedure also yields optimum energy shapes, satisfying Young's equation without the explicit imposition of a boundary condition at the plate. It is shown analytically that a static pendant two-dimensional drop can never be longer than 3.42 times the capillary length. A related finding is that a range of existing solutions for long two-dimensional drops correspond to unphysical drop shapes. Therefore, two-dimensional drops of small volume display only one static solution. In contrast, it is known that axisymmetric drops can display multiple solutions for a given volume. We demonstrate numerically that there is no limit to the height of multiple-lobed Kelvin drops, but the total volume is finite, with the volume of successive lobes forming a convergent series. The stability of such drops is in question, though. Drops of small volume can attain large heights. A bifurcation is found within the one-parameter space of Laplacian shapes, with a range of longer drops displaying a minimum in energy in the investigated space. Axisymmetric Kelvin drops exhibit an infinite number of bifurcations.

A two-dimensional, iterative solution for the jet flap

NASA Technical Reports Server (NTRS)

Herold, A. C.

1973-01-01

A solution is presented for the jet-flapped wing in two dimensions. The main flow is assumed to be inviscid and incompressible. The flow inside the jet is considered irrotational and the upper and lower boundaries between the jet and free stream are assumed to behave as vortex sheets which allow no mixing. The solution is found to be in satisfactory agreement with two dimensional experimental results and other theoretical work for intermediate values of momentum coefficient, but the regions of agreement vary with jet exit angle. At small values of momentum coefficient, the trajectory for the jet, as computed by this method, has more penetration than that of other available data, while at high values of moment coefficient this solution results in less penetration of the jet into the main flow.

Theoretical Study of Large-Angle Bending Transport of Microparticles by 2D Acoustic Half-Bessel Beams.

PubMed

Li, Yixiang; Qiu, Chunyin; Xu, Shengjun; Ke, Manzhu; Liu, Zhengyou

2015-08-17

Conventional microparticle transports by light or sound are realized along a straight line. Recently, this limit has been overcome in optics as the growing up of the self-accelerating Airy beams, which are featured by many peculiar properties, e.g., bending propagation, diffraction-free and self-healing. However, the bending angles of Airy beams are rather small since they are only paraxial solutions of the two-dimensional (2D) Helmholtz equation. Here we propose a novel micromanipulation by using acoustic Half-Bessel beams, which are strict solutions of the 2D Helmholtz equation. Compared with that achieved by Airy beams, the bending angle of the particle trajectory attained here is much steeper (exceeding 90(o)). The large-angle bending transport of microparticles, which is robust to complex scattering environment, enables a wide range of applications from the colloidal to biological sciences.

Propagation of Circularly Polarized Light Through a Two-Dimensional Random Medium

NASA Astrophysics Data System (ADS)

Gorodnichev, E. E.

2017-12-01

The problem of small-angle multiple-scattering of circularly polarized light in a two-dimensional medium with large fiberlike inhomogeneities is studied. The attenuation lengths for elements the density matrix are calculated. It is found that with increasing the sample thickness the intensity of waves polarized along the fibers decays faster than the other density matrix elements. With further increase in the thickness, the off-diagonal element which is responsible for correlation between the cross-polarized waves dissapears. In the case of very thick samples the scattered field proves to be polarized perpendicular to the fibers. It is shown that the difference in the attenuation lengths of the density matrix elements results in a non-monotonic depth dependence of the degree of polarization.

Small-angle neutron scattering study of micropore collapse in amorphous solid water.

PubMed

Mitterdorfer, Christian; Bauer, Marion; Youngs, Tristan G A; Bowron, Daniel T; Hill, Catherine R; Fraser, Helen J; Finney, John L; Loerting, Thomas

2014-08-14

Vapor-deposited amorphous solid water (ASW) is the most abundant solid molecular material in space, where it plays a direct role in both the formation of more complex chemical species and the aggregation of icy materials in the earliest stages of planet formation. Nevertheless, some of its low temperature physics such as the collapse of the micropore network upon heating are still far from being understood. Here we characterize the nature of the micropores and their collapse using neutron scattering of gram-quantities of D2O-ASW of internal surface areas up to 230 ± 10 m(2) g(-1) prepared at 77 K. The model-free interpretation of the small-angle scattering data suggests micropores, which remain stable up to 120-140 K and then experience a sudden collapse. The exact onset temperature to pore collapse depends on the type of flow conditions employed in the preparation of ASW and, thus, the specific surface area of the initial deposit, whereas the onset of crystallization to cubic ice is unaffected by the flow conditions. Analysis of the small-angle neutron scattering signal using the Guinier-Porod model suggests that a sudden transition from three-dimensional cylindrical pores with 15 Å radius of gyration to two-dimensional lamellae is the mechanism underlying the pore collapse. The rather high temperature of about 120-140 K of micropore collapse and the 3D-to-2D type of the transition unraveled in this study have implications for our understanding of the processing and evolution of ices in various astrophysical environments.

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

Zardecki, A.

The effect of multiple scattering on the validity of the Beer-Lambert law is discussed for a wide range of particle-size parameters and optical depths. To predict the amount of received radiant power, appropriate correction terms are introduced. For particles larger than or comparable to the wavelength of radiation, the small-angle approximation is adequate; whereas for small densely packed particles, the diffusion theory is advantageously employed. These two approaches are used in the context of the problem of laser-beam propagation in a dense aerosol medium. In addition, preliminary results obtained by using a two-dimensional finite-element discrete-ordinates transport code are described. Multiple-scatteringmore » effects for laser propagation in fog, cloud, rain, and aerosol cloud are modeled.« less

Design, fabrication, and verification of a three-dimensional autocollimator.

PubMed

Yin, Yanhe; Cai, Sheng; Qiao, Yanfeng

2016-12-10

The autocollimator is an optical instrument for noncontact angle measurement with high resolution and a long detection range. It measures two-dimensional angles, i.e., pitch and yaw, but not roll. In this paper, we present a novelly structured autocollimator capable of measuring three-dimensional (3D) angles simultaneously. In this setup, two collimated beams of different wavelengths are projected onto a right-angle prism. One beam is reflected by the hypotenuse of the prism and received by an autocollimation unit for detecting pitch and yaw. The other is reflected by the two legs of the right-angle prism and received by a moiré fringe imaging unit for detecting roll. Furthermore, a prototype is designed and fabricated. Experiments are carried out to evaluate its basic performance. Calibration results show that this prototype has angular RMS errors of less than 5 arcsec in all 3Ds over a range of 1000 arcsec at a working distance of 2 m.

Methods and apparatus for laser beam scanners with different actuating mechanisms

NASA Astrophysics Data System (ADS)

Chen, Si-hai; Xiang, Si-hua; Wu, Xin; Dong, Shan; Xiao, Ding; Zheng, Xia-wei

2009-07-01

In this paper, 3 types of laser beam scanner are introduced. One is transmissive beam scanner, which is composed of convex and concave microlens arrays (MLAs). By moving the concave lens in the plane vertical to the optical axis, the incident beam can be deflected in two dimensions. Those two kinds of MLAs are fabricated by thermal reflow and replication process. A set of mechanical scanner frame is fabricated with the two MLAs assembling in it. The testing result shown that the beam deflection angles are 9.5° and 9.6°, in the 2 dimension(2D) with the scanning frequency of 2 HZ and 8 HZ, respectively. The second type of laser beam scanner is actuated by voice coil actuators (VCAs). Based on ANSOFT MAXWELL software, we have designed VCAs with small size and large force which have optimized properties. The model of VCAs is built using AutoCAD and is analyzed by Ansoft maxwell. According to the simulation results, high performance VCAs are fabricated and tested. The result is that the force of the VCAs is 6.39N/A, and the displacement is +/-2.5mm. A set up of beam scanner is fabricated and actuated by the designed VCAs. The testing result shown that the two dimensional scanning angle is 15° and 10° respectively at the frequency of 60HZ. The two dimensional scanning angle is 8.3° and 6° respectively at the frequency of 100HZ. The third type of scanner is actuated by amplified piezoelectric actuators (APAs). The scanning mirror is actuated by the piezoelectric (PZ) actuators with the scanning frequency of 700HZ, 250HZ and 87HZ respectively. The optical scanning angle is +/-0.5° at the three frequencies.

Effects of B1 inhomogeneity correction for three-dimensional variable flip angle T1 measurements in hip dGEMRIC at 3 T and 1.5 T.

PubMed

Siversson, Carl; Chan, Jenny; Tiderius, Carl-Johan; Mamisch, Tallal Charles; Jellus, Vladimir; Svensson, Jonas; Kim, Young-Jo

2012-06-01

Delayed gadolinium-enhanced MRI of cartilage is a technique for studying the development of osteoarthritis using quantitative T(1) measurements. Three-dimensional variable flip angle is a promising method for performing such measurements rapidly, by using two successive spoiled gradient echo sequences with different excitation pulse flip angles. However, the three-dimensional variable flip angle method is very sensitive to inhomogeneities in the transmitted B(1) field in vivo. In this study, a method for correcting for such inhomogeneities, using an additional B(1) mapping spin-echo sequence, was evaluated. Phantom studies concluded that three-dimensional variable flip angle with B(1) correction calculates accurate T(1) values also in areas with high B(1) deviation. Retrospective analysis of in vivo hip delayed gadolinium-enhanced MRI of cartilage data from 40 subjects showed the difference between three-dimensional variable flip angle with and without B(1) correction to be generally two to three times higher at 3 T than at 1.5 T. In conclusion, the B(1) variations should always be taken into account, both at 1.5 T and at 3 T. Copyright © 2011 Wiley-Liss, Inc.

Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

DOE PAGES

Scott, Jamieson; Tong, Katie; William, Hamilton; ...

2014-10-31

The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

Small angle neutron scattering (SANS) studies on the structural evolution of pyromellitamide self-assembled gels.

PubMed

Jamieson, Scott A; Tong, Katie W K; Hamilton, William A; He, Lilin; James, Michael; Thordarson, Pall

2014-11-25

The kinetics of aggregation of two pyromellitamide gelators, tetrabutyl- (C4) and tetrahexyl-pyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to 6 days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 h) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4, indicating one-dimensional stacking and aggregation corresponding to a multifiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggest that the C6 also forms one-dimensional stacks but that these aggregate to a thicker multifiber braided cluster that has a diameter of about 62 Å. Over a longer period of time, the radius, persistence length, and contour length all continue to increase in 6 days after cooling. These data suggest that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g., tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.

Small Angle Neutron Scattering (SANS) Studies on the Structural Evolution of Pyromellitamide Self-assembled Gels

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

Scott, Jamieson; Tong, Katie; William, Hamilton

The kinetics of aggregation of two pyromellitamide gelators; tetrabutyl- (C4) and tetrahexylpyromellitamide (C6), in deuterated cyclohexane has been investigated by small angle neutron scattering (SANS) for up to six days. The purpose of this study was to improve our understanding of how self-assembled gels are formed. Short-term (< 3 hour) time scales revealed multiple phases with the data for the tetrabutylpyromellitamide C4 indicating one dimensional stacking and aggregation corresponding to a multi-fiber braided cluster arrangement that is about 35 Å in diameter. The corresponding tetrahexylpyromellitamide C6 data suggests that the C6 also forms one-dimensional stacks but that these aggregate tomore » a thicker multi-fiber braided cluster that have a diameter of 61.8 Å. Over a longer period of time, the radius, persistence length and contour length all continue to increase in 6 days after cooling. This data suggests that structural changes in self-assembled gels occur over a period exceeding several days and that fairly subtle changes in the structure (e.g. tail-length) can influence the packing of molecules in self-assembled gels on the single-to-few fiber bundle stage.« less

A flavor symmetry model for bilarge leptonic mixing and the lepton masses

NASA Astrophysics Data System (ADS)

Ohlsson, Tommy; Seidl, Gerhart

2002-11-01

We present a model for leptonic mixing and the lepton masses based on flavor symmetries and higher-dimensional mass operators. The model predicts bilarge leptonic mixing (i.e., the mixing angles θ12 and θ23 are large and the mixing angle θ13 is small) and an inverted hierarchical neutrino mass spectrum. Furthermore, it approximately yields the experimental hierarchical mass spectrum of the charged leptons. The obtained values for the leptonic mixing parameters and the neutrino mass squared differences are all in agreement with atmospheric neutrino data, the Mikheyev-Smirnov-Wolfenstein large mixing angle solution of the solar neutrino problem, and consistent with the upper bound on the reactor mixing angle. Thus, we have a large, but not close to maximal, solar mixing angle θ12, a nearly maximal atmospheric mixing angle θ23, and a small reactor mixing angle θ13. In addition, the model predicts θ 12≃ {π}/{4}-θ 13.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors.

PubMed

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-11-19

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors

PubMed Central

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-01-01

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG. PMID:29156595

Finite Element in Angle Unit Sphere Meshing for Charged Particle Transport.

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

Ortega, Mario Ivan; Drumm, Clifton R.

Finite element in angle formulations of the charged particle transport equation require the discretization of the unit sphere. In Sceptre, a three-dimensional surface mesh of a sphere is transformed into a two-dimensional mesh. Projection of a sphere onto a two-dimensional surface is well studied with map makers spending the last few centuries attempting to create maps that preserve proportion and area. Using these techniques, various meshing schemes for the unit sphere were investigated.

Transonic Investigation of Two-Dimensional Nozzles Designed for Supersonic Cruise

NASA Technical Reports Server (NTRS)

Capone, Francis J.; Deere, Karen A.

2015-01-01

An experimental and computational investigation has been conducted to determine the off-design uninstalled drag characteristics of a two-dimensional convergent-divergent nozzle designed for a supersonic cruise civil transport. The overall objectives were to: (1) determine the effects of nozzle external flap curvature and sidewall boattail variations on boattail drag; (2) develop an experimental data base for 2D nozzles with long divergent flaps and small boattail angles and (3) provide data for correlating computational fluid dynamic predictions of nozzle boattail drag. The experimental investigation was conducted in the Langley 16-Foot Transonic Tunnel at Mach numbers from 0.80 to 1.20 at nozzle pressure ratios up to 9. Three-dimensional simulations of nozzle performance were obtained with the computational fluid dynamics code PAB3D using turbulence closure and nonlinear Reynolds stress modeling. The results of this investigation indicate that excellent correlation between experimental and predicted results was obtained for the nozzle with a moderate amount of boattail curvature. The nozzle with an external flap having a sharp shoulder (no curvature) had the lowest nozzle pressure drag. At a Mach number of 1.2, sidewall pressure drag doubled as sidewall boattail angle was increased from 4deg to 8deg. Reducing the height of the sidewall caused large decreases in both the sidewall and flap pressure drags. Summary

Characterization of low thermal conductivity PAN-based carbon fibers

NASA Technical Reports Server (NTRS)

Katzman, Howard A.; Adams, P. M.; Le, T. D.; Hemminger, Carl S.

1992-01-01

The microstructure and surface chemistry of eight low thermal conductivity (LTC) PAN-based carbon fibers were determined and compared with PAN-based fibers heat treated to higher temperatures. Based on wide-angle x ray diffraction, the LTC PAN fibers all appear to have a similar turbostratic structure with large 002 d-spacings, small crystallite sizes, and moderate preferred orientation. Limited small-angle x ray scattering (SAXS) results indicate that, with the exception of LTC fibers made by BASF, the LTC fibers do not have well developed pores. Transmission electron microscopy shows that the texture of the two LTC PAN-based fibers studied (Amoco T350/23X and /25X) consists of multiple sets of parallel, wavy, bent layers that interweave with each other forming a complex three dimensional network oriented randomly around the fiber axis. X ray photoelectron spectroscopy (XPS) analysis finds correlations between heat treated temperatures and the surface composition chemistry of the carbon fiber samples.

Asymptotic methods for internal transonic flows

NASA Technical Reports Server (NTRS)

Adamson, T. C., Jr.; Messiter, A. F.

1989-01-01

For many internal transonic flows of practical interest, some of the relevant nondimensional parameters typically are small enough that a perturbation scheme can be expected to give a useful level of numerical accuracy. A variety of steady and unsteady transonic channel and cascade flows is studied with the help of systematic perturbation methods which take advantage of this fact. Asymptotic representations are constructed for small changes in channel cross-section area, small flow deflection angles, small differences between the flow velocity and the sound speed, small amplitudes of imposed oscillations, and small reduced frequencies. Inside a channel the flow is nearly one-dimensional except in thin regions immediately downstream of a shock wave, at the channel entrance and exit, and near the channel throat. A study of two-dimensional cascade flow is extended to include a description of three-dimensional compressor-rotor flow which leads to analytical results except in thin edge regions which require numerical solution. For unsteady flow the qualitative nature of the shock-wave motion in a channel depends strongly on the orders of magnitude of the frequency and amplitude of impressed wall oscillations or fluctuations in back pressure. One example of supersonic flow is considered, for a channel with length large compared to its width, including the effect of separation bubbles and the possibility of self-sustained oscillations. The effect of viscosity on a weak shock wave in a channel is discussed.

Novel angle estimation for bistatic MIMO radar using an improved MUSIC

NASA Astrophysics Data System (ADS)

Li, Jianfeng; Zhang, Xiaofei; Chen, Han

2014-09-01

In this article, we study the problem of angle estimation for bistatic multiple-input multiple-output (MIMO) radar and propose an improved multiple signal classification (MUSIC) algorithm for joint direction of departure (DOD) and direction of arrival (DOA) estimation. The proposed algorithm obtains initial estimations of angles obtained from the signal subspace and uses the local one-dimensional peak searches to achieve the joint estimations of DOD and DOA. The angle estimation performance of the proposed algorithm is better than that of estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithm, and is almost the same as that of two-dimensional MUSIC. Furthermore, the proposed algorithm can be suitable for irregular array geometry, obtain automatically paired DOD and DOA estimations, and avoid two-dimensional peak searching. The simulation results verify the effectiveness and improvement of the algorithm.

Two-dimensional grating guided-mode resonance tunable filter.

PubMed

Kuo, Wen-Kai; Hsu, Che-Jung

2017-11-27

A two-dimensional (2D) grating guided-mode resonance (GMR) tunable filter is experimentally demonstrated using a low-cost two-step nanoimprinting technology with a one-dimensional (1D) grating polydimethylsiloxane mold. For the first nanoimprinting, we precisely control the UV LED irradiation dosage and demold the device when the UV glue is partially cured and the 1D grating mold is then rotated by three different angles, 30°, 60°, and 90°, for the second nanoimprinting to obtain 2D grating structures with different crossing angles. A high-refractive-index film ZnO is then coated on the surface of the grating structure to form the GMR filter devices. The simulation and experimental results demonstrate that the passband central wavelength of the filter can be tuned by rotating the device to change azimuth angle of the incident light. We compare these three 2D GMR filters with differential crossing angles and find that the filter device with a crossing angle of 60° exhibits the best performance. The tunable range of its central wavelength is 668-742 nm when the azimuth angle varies from 30° to 90°.

The blind student’s interpretation of two-dimensional shapes in geometry

NASA Astrophysics Data System (ADS)

Andriyani; Budayasa, I. K.; Juniati, D.

2018-01-01

The blind student’s interpretation of two-dimensional shapes represents the blind student’s mental image of two-dimensional shapes that they can’t visualize directly, which is related to illustration of the characteristics and number of edges and angles. The objective of this research is to identify the blind student’s interpretation of two-dimensional shapes. This research was an exploratory study with qualitative approach. A subject of this research is a sixth-grade student who experiencing total blind from the fifth grade of elementary school. Researchers interviewed the subject about his interpretation of two-dimensional shapes according to his thinking.The findings of this study show the uniqueness of blind students, who have been totally blind since school age, in knowing and illustrating the characteristics of edges and angles of two-dimensional shapes by utilizing visual experiences that were previously obtained before the blind. The result can inspire teachers to design further learning for development of blind student geometry concepts.

Stimulated Brillouin scattering in the field of a two-dimensionally localized pumping wave

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

Solikhov, D. K., E-mail: davlat56@mail.ru; Dvinin, S. A., E-mail: dvinin@phys.msu.ru

2016-06-15

Stimulated Brillouin scattering of electromagnetic waves in the field of a two-dimensionally localized pump wave at arbitrary scattering angles in the regime of forward scattering is analyzed. Spatial variations in the amplitudes of interacting waves are studied for different values of the pump field and different dimensions of the pump wave localization region. The intensity of scattered radiation is determined as a function of the scattering angle and the dimensions of the pump wave localization region. It is shown that the intensity increases with increasing scattering angle.

Field-induced self-assembly of iron oxide nanoparticles investigated using small-angle neutron scattering.

PubMed

Fu, Zhendong; Xiao, Yinguo; Feoktystov, Artem; Pipich, Vitaliy; Appavou, Marie-Sousai; Su, Yixi; Feng, Erxi; Jin, Wentao; Brückel, Thomas

2016-11-03

The magnetic-field-induced assembly of magnetic nanoparticles (NPs) provides a unique and flexible strategy in the design and fabrication of functional nanostructures and devices. We have investigated the field-induced self-assembly of core-shell iron oxide NPs dispersed in toluene by means of small-angle neutron scattering (SANS). The form factor of the core-shell NPs was characterized and analyzed using SANS with polarized neutrons. Large-scale aggregates of iron oxide NPs formed above 0.02 T as indicated by very-small-angle neutron scattering measurements. A three-dimensional long-range ordered superlattice of iron oxide NPs was revealed under the application of a moderate magnetic field. The crystal structure of the superlattice has been identified to be face-centred cubic.

Three-dimensional lattice Boltzmann simulations of microdroplets including contact angle hysteresis on topologically structured surfaces

DOE PAGES

Ba, Yan; Kang, Qinjun; Liu, Haihu; ...

2016-04-14

In this study, the dynamical behavior of a droplet on topologically structured surface is investigated by using a three-dimensional color-gradient lattice Boltzmann model. A wetting boundary condition is proposed to model fluid-surface interactions, which is advantageous to improve the accuracy of the simulation and suppress spurious velocities at the contact line. The model is validated by the droplet partial wetting test and reproduction of the Cassie and Wenzel states. A series of simulations are conducted to investigate the behavior of a droplet when subjected to a shear flow. It is found that in Cassie state, the droplet undergoes a transitionmore » from stationary, to slipping and finally to detachment states as the capillary number increases, while in Wenzel state, the last state changes to the breakup state. The critical capillary number, above which the droplet slipping occurs, is small for the Cassie droplet, but is significantly enhanced for the Wenzel droplet due to the increased contact angle hysteresis. In Cassie state, the receding contact angle nearly equals the prediction by the Cassie relation, and the advancing contact angle is close to 180°, leading to a small contact angle hysteresis. In Wenzel state, however, the contact angle hysteresis is extremely large (around 100°). Finally, high droplet mobility can be easily achieved for Cassie droplets, whereas in Wenzel state, extremely low droplet mobility is identified.« less

Acoustic ranging of small arms fire using a single sensor node collocated with the target.

PubMed

Lo, Kam W; Ferguson, Brian G

2015-06-01

A ballistic model-based method, which builds upon previous work by Lo and Ferguson [J. Acoust. Soc. Am. 132, 2997-3017 (2012)], is described for ranging small arms fire using a single acoustic sensor node collocated with the target, without a priori knowledge of the muzzle speed and ballistic constant of the bullet except that they belong to a known two-dimensional parameter space. The method requires measurements of the differential time of arrival and differential angle of arrival of the muzzle blast and ballistic shock wave at the sensor node. Its performance is evaluated using both simulated and real data.

The fast azimuthal integration Python library: pyFAI.

PubMed

Ashiotis, Giannis; Deschildre, Aurore; Nawaz, Zubair; Wright, Jonathan P; Karkoulis, Dimitrios; Picca, Frédéric Emmanuel; Kieffer, Jérôme

2015-04-01

pyFAI is an open-source software package designed to perform azimuthal integration and, correspondingly, two-dimensional regrouping on area-detector frames for small- and wide-angle X-ray scattering experiments. It is written in Python (with binary submodules for improved performance), a language widely accepted and used by the scientific community today, which enables users to easily incorporate the pyFAI library into their processing pipeline. This article focuses on recent work, especially the ease of calibration, its accuracy and the execution speed for integration.

Time dependent shear stress and temperature distribution over an insulated flat plate moving at hypersonic speed.

NASA Technical Reports Server (NTRS)

Rodkiewicz, C. M.; Gupta, R. N.

1971-01-01

The laminar two-dimensional flow over a stepwise accelerated flat plate moving with hypersonic speed at zero angle of attack is analysed. The governing equations in the self-similar form are linearized and solved numerically for small times. The solutions obtained are the deviations of the velocity and the temperature profiles from those of steady state. The presented results may be used to find the first order boundary layer induced pressure on the plate.

Simultaneous small-angle neutron scattering and Fourier transform infrared spectroscopic measurements on cocrystals of syndiotactic polystyrene with polyethylene glycol dimethyl ethers.

PubMed

Kaneko, Fumitoshi; Seto, Naoki; Sato, Shuma; Radulescu, Aurel; Schiavone, Maria Maddalena; Allgaier, Jürgen; Ute, Koichi

2016-10-01

Syndiotactic polystyrene (sPS) is a crystalline polymer which has a unique property; it is able to form cocrystals with a wide range of chemical compounds, in which the guest molecules are confined in the vacancies of the host sPS crystalline region. Recently, it has been found that even polyethylene glycol oligomers with a molecular weight of more than several hundreds can be introduced into the sPS crystalline region. It is quite important to know how such a long-chain molecule is stored in the host sPS lattice. To tackle this issue, a new simultaneous measurement method combing small-angle neutron scattering and Fourier transform infrared spectroscopy (SANS/FTIR), which has been recently developed by the authors, was applied to an sPS cocrystal with polyethylene glycol dimethyl ether with a molecular weight of 500 (PEGDME500). The temperature-dependent changes of the SANS profile and FTIR spectrum were followed from room temperature up to 413 K for a one-dimensionally oriented SANS/PEGDME500 cocrystal sample. The intensity of the reflections due to the stacking of crystalline lamellae showed a significant temperature dependence. The two-dimensional pattern in the high Q region of SANS also changed depending on temperature. The combined information obtained by SANS and FTIR suggested that PEGDME500 molecules are distributed in both the crystalline and amorphous regions in the low-temperature region close to room temperature, but they are predominantly included in the amorphous region in the high-temperature region. It was also suggested by the two-dimensional SANS profile that PEGDME500 molecules in the crystalline region have an elongated structure along the thickness direction of the crystalline lamellae.

Simultaneous small-angle neutron scattering and Fourier transform infrared spectroscopic measurements on cocrystals of syndiotactic polystyrene with polyethylene glycol dimethyl ethers1

PubMed Central

Kaneko, Fumitoshi; Seto, Naoki; Sato, Shuma; Radulescu, Aurel; Schiavone, Maria Maddalena; Allgaier, Jürgen; Ute, Koichi

2016-01-01

Syndiotactic polystyrene (sPS) is a crystalline polymer which has a unique property; it is able to form cocrystals with a wide range of chemical compounds, in which the guest molecules are confined in the vacancies of the host sPS crystalline region. Recently, it has been found that even polyethylene glycol oligomers with a molecular weight of more than several hundreds can be introduced into the sPS crystalline region. It is quite important to know how such a long-chain molecule is stored in the host sPS lattice. To tackle this issue, a new simultaneous measurement method combing small-angle neutron scattering and Fourier transform infrared spectroscopy (SANS/FTIR), which has been recently developed by the authors, was applied to an sPS cocrystal with polyethylene glycol dimethyl ether with a molecular weight of 500 (PEGDME500). The temperature-dependent changes of the SANS profile and FTIR spectrum were followed from room temperature up to 413 K for a one-dimensionally oriented SANS/PEGDME500 cocrystal sample. The intensity of the reflections due to the stacking of crystalline lamellae showed a significant temperature dependence. The two-dimensional pattern in the high Q region of SANS also changed depending on temperature. The combined information obtained by SANS and FTIR suggested that PEGDME500 molecules are distributed in both the crystalline and amorphous regions in the low-temperature region close to room temperature, but they are predominantly included in the amorphous region in the high-temperature region. It was also suggested by the two-dimensional SANS profile that PEGDME500 molecules in the crystalline region have an elongated structure along the thickness direction of the crystalline lamellae. PMID:27738412

Small-angle scattering from 3D Sierpinski tetrahedron generated using chaos game

NASA Astrophysics Data System (ADS)

Slyamov, Azat

2017-12-01

We approximate a three dimensional version of deterministic Sierpinski gasket (SG), also known as Sierpinski tetrahedron (ST), by using the chaos game representation (CGR). Structural properties of the fractal, generated by both deterministic and CGR algorithms are determined using small-angle scattering (SAS) technique. We calculate the corresponding monodisperse structure factor of ST, using an optimized Debye formula. We show that scattering from CGR of ST recovers basic fractal properties, such as fractal dimension, iteration number, scaling factor, overall size of the system and the number of units composing the fractal.

Scale growth of structures in the turbulent boundary layer with a rod-roughened wall

NASA Astrophysics Data System (ADS)

Lee, Jin; Kim, Jung Hoon; Lee, Jae Hwa

2016-01-01

Direct numerical simulation of a turbulent boundary layer over a rod-roughened wall is performed with a long streamwise domain to examine the streamwise-scale growth mechanism of streamwise velocity fluctuating structures in the presence of two-dimensional (2-D) surface roughness. An instantaneous analysis shows that there is a slightly larger population of long structures with a small helix angle (spanwise inclinations relative to streamwise) and a large spanwise width over the rough-wall compared to that over a smooth-wall. Further inspection of time-evolving instantaneous fields clearly exhibits that adjacent long structures combine to form a longer structure through a spanwise merging process over the rough-wall; moreover, spanwise merging for streamwise scale growth is expected to occur frequently over the rough-wall due to the large spanwise scales generated by the 2-D roughness. Finally, we examine the influence of a large width and a small helix angle of the structures over the rough-wall with regard to spatial two-point correlation. The results show that these factors can increase the streamwise coherence of the structures in a statistical sense.

Optimized resolved rate control of seven-degree-of-freedom Laboratory Telerobotic Manipulator (LTM) with application to three-dimensional graphics simulation

NASA Technical Reports Server (NTRS)

Barker, L. Keith; Mckinney, William S., Jr.

1989-01-01

The Laboratory Telerobotic Manipulator (LTM) is a seven-degree-of-freedom robot arm. Two of the arms were delivered to Langley Research Center for ground-based research to assess the use of redundant degree-of-freedom robot arms in space operations. Resolved-rate control equations for the LTM are derived. The equations are based on a scheme developed at the Oak Ridge National Laboratory for computing optimized joint angle rates in real time. The optimized joint angle rates actually represent a trade-off, as the hand moves, between small rates (least-squares solution) and those rates which work toward satisfying a specified performance criterion of joint angles. In singularities where the optimization scheme cannot be applied, alternate control equations are devised. The equations developed were evaluated using a real-time computer simulation to control a 3-D graphics model of the LTM.

Forced Oscillation Wind Tunnel Testing for FASER Flight Research Aircraft

NASA Technical Reports Server (NTRS)

Hoe, Garrison; Owens, Donald B.; Denham, Casey

2012-01-01

As unmanned air vehicles (UAVs) continue to expand their flight envelopes into areas of high angular rate and high angle of attack, modeling the complex unsteady aerodynamics for simulation in these regimes has become more difficult using traditional methods. The goal of this experiment was to improve the current six degree-of-freedom aerodynamic model of a small UAV by replacing the analytically derived damping derivatives with experimentally derived values. The UAV is named the Free-flying Aircraft for Sub-scale Experimental Research, FASER, and was tested in the NASA Langley Research Center 12- Foot Low-Speed Tunnel. The forced oscillation wind tunnel test technique was used to measure damping in the roll and yaw axes. By imparting a variety of sinusoidal motions, the effects of non-dimensional angular rate and reduced frequency were examined over a large range of angle of attack and side-slip combinations. Tests were performed at angles of attack from -5 to 40 degrees, sideslip angles of -30 to 30 degrees, oscillation amplitudes from 5 to 30 degrees, and reduced frequencies from 0.010 to 0.133. Additionally, the effect of aileron or elevator deflection on the damping coefficients was examined. Comparisons are made of two different data reduction methods used to obtain the damping derivatives. The results show that the damping derivatives are mainly a function of angle of attack and have dependence on the non-dimensional rate and reduced frequency only in the stall/post-stall regime

Two-dimensional imaging of gas temperature and concentration based on hyperspectral tomography

NASA Astrophysics Data System (ADS)

Xin, Ming-yuan; Jin, Xing; Wang, Guang-yu; Song, Junling

2016-10-01

Two-dimensional imaging of gas temperature and concentration is realized by hyperspectral tomography, which has the characteristics of using multi-wavelengths absorption spectral information, so that the imaging could be accomplished in a small number of projections and viewing angles. A temperature and concentration model is established to simulate the combustion conditions and a total number of 10 near-infrared absorption spectral information of H2O is used. An improved simulated annealing algorithm by adjusting search step is performed the main search algorithm for the tomography. By adding random errors into the absorption area information, the stability of the algorithm is tested, and the results are compared with the reconstructions provided by algebraic reconstruction technique which takes advantage of 2 spectral information contents in imaging. The results show that the two methods perform equivalent in low-level noise environment, but at high-level, hyperspectral tomography turns out to be more stable.

Fermion masses and mixing in general warped extra dimensional models

NASA Astrophysics Data System (ADS)

Frank, Mariana; Hamzaoui, Cherif; Pourtolami, Nima; Toharia, Manuel

2015-06-01

We analyze fermion masses and mixing in a general warped extra dimensional model, where all the Standard Model (SM) fields, including the Higgs, are allowed to propagate in the bulk. In this context, a slightly broken flavor symmetry imposed universally on all fermion fields, without distinction, can generate the full flavor structure of the SM, including quarks, charged leptons and neutrinos. For quarks and charged leptons, the exponential sensitivity of their wave functions to small flavor breaking effects yield hierarchical masses and mixing as it is usual in warped models with fermions in the bulk. In the neutrino sector, the exponential wave-function factors can be flavor blind and thus insensitive to the small flavor symmetry breaking effects, directly linking their masses and mixing angles to the flavor symmetric structure of the five-dimensional neutrino Yukawa couplings. The Higgs must be localized in the bulk and the model is more successful in generalized warped scenarios where the metric background solution is different than five-dimensional anti-de Sitter (AdS5 ). We study these features in two simple frameworks, flavor complimentarity and flavor democracy, which provide specific predictions and correlations between quarks and leptons, testable as more precise data in the neutrino sector becomes available.

Nanoscale modulations in (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}

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

Licurse, Mark W., E-mail: mlicurse@seas.upenn.edu; Borisevich, Albina Y., E-mail: albinab@ornl.gov; Davies, Peter K., E-mail: davies@seas.upenn.edu

2012-07-15

Complex nanoscale modulations are identified in two new A-site ordered perovskites, (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}. In (KLa)(CaW)O{sub 6}, selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) show an incommensurate nanocheckerboard modulation with {approx}9.4 Multiplication-Sign 9.4a{sub p} periodicity (a{sub p} Almost-Equal-To 4 A for the cubic perovskite aristotype). For (NaLa)(CaW)O{sub 6} a one-dimensional modulation is observed with a {approx}16(1 1 0)a{sub p} repeat; the Left-Pointing-Angle-Bracket 1 1 0 Right-Pointing-Angle-Bracket orientation of the nanostripes is different from the Left-Pointing-Angle-Bracket 1 0 0 Right-Pointing-Angle-Bracket stripes observed in other mixed A-site systems. Studies using high temperature x-ray diffraction suggest the formationmore » of the complex modulations is associated with small deviations from the ideal 1:1:1:1 stoichiometry of the (A{sup +}La{sup 3+})(CaW)O{sub 6} phases. Z-contrast images acquired on an aberration-corrected microscope provide evidence for deviations from stoichiometry with a {approx}1:15 periodic arrangement of La{sub 4/3}(CaW)O{sub 6}:(NaLa)(CaW)O{sub 6} nano-phases. - Graphical abstract: Complex nanoscale modulations are identified in two new A-site ordered perovskites, (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}. In (KLa)(CaW)O{sub 6}, selected-area electron diffraction and high-resolution transmission electron microscopy show a two-dimensional, nanocheckerboard modulation. For (NaLa)(CaW)O{sub 6} a one-dimensional modulation is observed; the Left-Pointing-Angle-Bracket 1 1 0 Right-Pointing-Angle-Bracket orientation of the nanostripes is different from the Left-Pointing-Angle-Bracket 1 0 0 Right-Pointing-Angle-Bracket stripes observed in other mixed A-site systems. Highlights: Black-Right-Pointing-Pointer Two new A-site ordered perovskites were synthesized, (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}. Black-Right-Pointing-Pointer Unusual 1D and 2D nanoscale patterns were observed. Black-Right-Pointing-Pointer Tolerance factor shown to be not enough to predict the observed morphologies. Black-Right-Pointing-Pointer High temperature x-ray diffraction data suggests a loss of stoichiometry is related to the modulations. Black-Right-Pointing-Pointer Z-contrast imaging provides direct evidence for non-stoichiometry and a new model.« less

Incidence loss for a core turbine rotor blade in a two-dimensional cascade

NASA Technical Reports Server (NTRS)

Stabe, R. G.; Kline, J. F.

1974-01-01

The effect of incidence angle on the aerodynamic performance of an uncooled core turbine rotor blade was investigated experimentally in a two-dimensional cascade. The cascade test covered a range of incidence angles from minus 15 deg to 15 deg in 5-degree increments and a range of pressure ratios corresponding to ideal exit critical velocity ratios of 0.6 to 0.95. The principal measurements were blade-surface static pressures and cross-channel surveys of exit total pressure, static pressure, and flow angle. The results of the investigation include blade-surface velocity distribution and overall performance in terms of weight flow and loss for the range of incidence angles and exit velocity ratios investigated. The measured losses are also compared with two common methods of predicting incidence loss.

Incidence loss for fan turbine rotor blade in two-dimensional cascade

NASA Technical Reports Server (NTRS)

Kline, J. F.; Moffitt, T. P.; Stabe, R. G.

1983-01-01

The effect of incidence angle on the aerodynamic performance of a fan turbine rotor blade was investigated experimentally in a two dimensional cascade. The test covered a range of incidence angles from -15 deg to 10 deg and exit ideal critical velocity ratios from 0.75 to 0.95. The principal measurements were blade-surface static pressures and cross-channel survey of exit total pressure, static pressure, and flow angle. Flow adjacent to surfaces was examined using a visualization technique. The results of the investigation include blade-surface velocity distribution and overall kinetic energy loss coefficients for the incidence angles and exit velocity ratios tested. The measured losses are compared with those from a reference core turbine rotor blade and also with two common analytical methods of predicting incidence loss.

Static internal performance of a two-dimensional convergent-divergent nozzle with thrust vectoring

NASA Technical Reports Server (NTRS)

Bare, E. Ann; Reubush, David E.

1987-01-01

A parametric investigation of the static internal performance of multifunction two-dimensional convergent-divergent nozzles has been made in the static test facility of the Langley 16-Foot Transonic Tunnel. All nozzles had a constant throat area and aspect ratio. The effects of upper and lower flap angles, divergent flap length, throat approach angle, sidewall containment, and throat geometry were determined. All nozzles were tested at a thrust vector angle that varied from 5.60 tp 23.00 deg. The nozzle pressure ratio was varied up to 10 for all configurations.

Cyclotron decay time of a two-dimensional electron gas from 0.4 to 100 K

NASA Astrophysics Data System (ADS)

Curtis, Jeremy A.; Tokumoto, Takahisa; Hatke, A. T.; Cherian, Judy G.; Reno, John L.; McGill, Stephen A.; Karaiskaj, Denis; Hilton, David J.

2016-04-01

We have studied the cyclotron decay time of a Landau-quantized two-dimensional electron gas as a function of temperature (0.4-100 K) at a fixed magnetic field (±1.25 T ) using terahertz time-domain spectroscopy in a gallium arsenide quantum well with a mobility of μd c=3.6 ×106cm2V-1s-1 and a carrier concentration of ns=2 ×1011cm-2 . We find a cyclotron decay time that is limited by superradiant decay of the cyclotron ensemble and a temperature dependence that may result from both dissipative processes as well as a decrease in ns below 1.5 K . Shubnikov-de Haas characterization determines a quantum lifetime, τq=1.1 ps , which is significantly faster than the corresponding dephasing time, τs=66.4 ps , in our cyclotron data. This is consistent with small-angle scattering as the dominant contribution in this sample, where scattering angles below θ ≤13∘ do not efficiently contribute to dephasing. Above 50 K , the cyclotron oscillations show a strong reduction in both the oscillation amplitude and lifetime that result from polar optical phonon scattering.

Yttrium oxide based three dimensional metamaterials for visible light cloaking

NASA Astrophysics Data System (ADS)

Rai, Pratyush; Kumar, Prashanth S.; Varadan, Vijay K.; Ruffin, Paul; Brantley, Christina; Edwards, Eugene

2014-04-01

Metamaterial with negative refractive index is the key phenomenon behind the concept of a cloaking device to hide an object from light in visible spectrum. Metamaterials made of two and three dimensional lattices of periodically placed electromagnetic resonant cells can achieve absorption and propagation of incident electromagnetic radiation as confined electromagnetic fields confined to a waveguide as surface plasmon polaritons, which can be used for shielding an object from in-tune electromagnetic radiation. The periodicity and dimensions of resonant cavity determine the frequency, which are very small as compared to the wavelength of incident light. Till now the phenomena have been demonstrated only for lights in near infrared spectrum. Recent advancements in fabrication techniques have made it possible to fabricate array of three dimensional nanostructures with cross-sections as small as 25 nm that are required for negative refractive index for wavelengths in visible light spectrum of 400-700 nm and for wider view angle. Two types of metamaterial designs, three dimensional concentric split ring and fishnet, are considered. Three dimensional structures consisted of metal-dielectric-metal stacks. The metal is silver and dielectric is yttrium oxide, other than conventional materials such as FR4 and Duroid. High κ dielectric and high refractive index as well as large crystal symmetry of Yttrium oxide has been investigated as encapsulating medium. Dependence of refractive index on wavelength and bandwidth of negative refractive index region are analyzed for application towards cloaking from light in visible spectrum.

Modeling and Analysis of Micro-Spacecraft Attitude Sensing with Gyrowheel.

PubMed

Liu, Xiaokun; Zhao, Hui; Yao, Yu; He, Fenghua

2016-08-19

This paper proposes two kinds of approaches of angular rate sensing for micro-spacecraft with a gyrowheel (GW), which can combine attitude sensing with attitude control into one single device to achieve a compact micro-spacecraft design. In this implementation, during the three-dimensional attitude control torques being produced, two-dimensional spacecraft angular rates can be sensed from the signals of the GW sensors, such as the currents of the torque coils, the tilt angles of the rotor, the motor rotation, etc. This paper focuses on the problems of the angular rate sensing with the GW at large tilt angles of the rotor. For this purpose, a novel real-time linearization approach based on Lyapunov's linearization theory is proposed, and a GW linearized measurement model at arbitrary tilt angles of the rotor is derived. Furthermore, by representing the two-dimensional rotor tilt angles and tilt control torques as complex quantities and separating the twice periodic terms about the motor spin speed, the linearized measurement model at smaller tilt angles of the rotor is given and simplified. According to the respective characteristics, the application schemes of the two measurement models are analyzed from the engineering perspective. Finally, the simulation results are presented to demonstrate the effectiveness of the proposed strategy.

Modeling and Analysis of Micro-Spacecraft Attitude Sensing with Gyrowheel

PubMed Central

Liu, Xiaokun; Zhao, Hui; Yao, Yu; He, Fenghua

2016-01-01

This paper proposes two kinds of approaches of angular rate sensing for micro-spacecraft with a gyrowheel (GW), which can combine attitude sensing with attitude control into one single device to achieve a compact micro-spacecraft design. In this implementation, during the three-dimensional attitude control torques being produced, two-dimensional spacecraft angular rates can be sensed from the signals of the GW sensors, such as the currents of the torque coils, the tilt angles of the rotor, the motor rotation, etc. This paper focuses on the problems of the angular rate sensing with the GW at large tilt angles of the rotor. For this purpose, a novel real-time linearization approach based on Lyapunov’s linearization theory is proposed, and a GW linearized measurement model at arbitrary tilt angles of the rotor is derived. Furthermore, by representing the two-dimensional rotor tilt angles and tilt control torques as complex quantities and separating the twice periodic terms about the motor spin speed, the linearized measurement model at smaller tilt angles of the rotor is given and simplified. According to the respective characteristics, the application schemes of the two measurement models are analyzed from the engineering perspective. Finally, the simulation results are presented to demonstrate the effectiveness of the proposed strategy. PMID:27548178

Linear Vector Quantisation and Uniform Circular Arrays based decoupled two-dimensional angle of arrival estimation

NASA Astrophysics Data System (ADS)

Ndaw, Joseph D.; Faye, Andre; Maïga, Amadou S.

2017-05-01

Artificial neural networks (ANN)-based models are efficient ways of source localisation. However very large training sets are needed to precisely estimate two-dimensional Direction of arrival (2D-DOA) with ANN models. In this paper we present a fast artificial neural network approach for 2D-DOA estimation with reduced training sets sizes. We exploit the symmetry properties of Uniform Circular Arrays (UCA) to build two different datasets for elevation and azimuth angles. Linear Vector Quantisation (LVQ) neural networks are then sequentially trained on each dataset to separately estimate elevation and azimuth angles. A multilevel training process is applied to further reduce the training sets sizes.

Quality assessment of two- and three-dimensional unstructured meshes and validation of an upwind Euler flow solver

NASA Technical Reports Server (NTRS)

Woodard, Paul R.; Yang, Henry T. Y.; Batina, John T.

1992-01-01

Quality assessment procedures are described for two-dimensional and three-dimensional unstructured meshes. The procedures include measurement of minimum angles, element aspect ratios, stretching, and element skewness. Meshes about the ONERA M6 wing and the Boeing 747 transport configuration are generated using an advancing front method grid generation package of programs. Solutions of Euler's equations for these meshes are obtained at low angle-of-attack, transonic conditions. Results for these cases, obtained as part of a validation study demonstrate the accuracy of an implicit upwind Euler solution algorithm.

Bandgap Inhomogeneity of a PbSe Quantum Dot Ensemble from Two-Dimensional Spectroscopy and Comparison to Size Inhomogeneity from Electron Microscopy

DOE PAGES

Park, Samuel D.; Baranov, Dmitry; Ryu, Jisu; ...

2017-01-03

Femtosecond two-dimensional Fourier transform spectroscopy is used to determine the static bandgap inhomogeneity of a colloidal quantum dot ensemble. The excited states of quantum dots absorb light, so their absorptive two-dimensional (2D) spectra will typically have positive and negative peaks. We show that the absorption bandgap inhomogeneity is robustly determined by the slope of the nodal line separating positive and negative peaks in the 2D spectrum around the bandgap transition; this nodal line slope is independent of excited state parameters not known from the absorption and emission spectra. The absorption bandgap inhomogeneity is compared to a size and shape distributionmore » determined by electron microscopy. The electron microscopy images are analyzed using new 2D histograms that correlate major and minor image projections to reveal elongated nanocrystals, a conclusion supported by grazing incidence small-angle X-ray scattering and high-resolution transmission electron microscopy. Lastly, the absorption bandgap inhomogeneity quantitatively agrees with the bandgap variations calculated from the size and shape distribution, placing upper bounds on any surface contributions.« less

The effect of incidence angle on the overall three-dimensional aerodynamic performance of a classical annular airfoil cascade

NASA Technical Reports Server (NTRS)

Bergsten, D. E.; Fleeter, S.

1983-01-01

To be of quantitative value to the designer and analyst, it is necessary to experimentally verify the flow modeling and the numerics inherent in calculation codes being developed to predict the three dimensional flow through turbomachine blade rows. This experimental verification requires that predicted flow fields be correlated with three dimensional data obtained in experiments which model the fundamental phenomena existing in the flow passages of modern turbomachines. The Purdue Annular Cascade Facility was designed specifically to provide these required three dimensional data. The overall three dimensional aerodynamic performance of an instrumented classical airfoil cascade was determined over a range of incidence angle values. This was accomplished utilizing a fully automated exit flow data acquisition and analysis system. The mean wake data, acquired at two downstream axial locations, were analyzed to determine the effect of incidence angle, the three dimensionality of the cascade exit flow field, and the similarity of the wake profiles. The hub, mean, and tip chordwise airfoil surface static pressure distributions determined at each incidence angle are correlated with predictions from the MERIDL and TSONIC computer codes.

Calculations of transonic boattail flow at small angle of attack

NASA Technical Reports Server (NTRS)

Nakayama, A.; Chow, W. L.

1979-01-01

A transonic flow past a boattailed afterbody under a small angle of attack was examined. It is known that the viscous effect offers significant modifications of the pressure distribution on the afterbody. Thus, the formulation for the inviscid flow was based on the consideration of a flow past a nonaxisymmetric body. The full three dimensional potential equation was solved through numerical relaxation, and quasi-axisymmetric boundary layer calculations were performed to estimate the displacement effect. It was observed again that the viscous effects were not negligible. The trend of the final results agreed well with the experimental data.

A Generalized Hydrodynamic-Impact Theory for the Loads and Motions of Deeply Immersed Prismatic Bodies

NASA Technical Reports Server (NTRS)

Markey, Melvin F.

1959-01-01

A theory is derived for determining the loads and motions of a deeply immersed prismatic body. The method makes use of a two-dimensional water-mass variation and an aspect-ratio correction for three-dimensional flow. The equations of motion are generalized by using a mean value of the aspect-ratio correction and by assuming a variation of the two-dimensional water mass for the deeply immersed body. These equations lead to impact coefficients that depend on an approach parameter which, in turn, depends upon the initial trim and flight-path angles. Comparison of experiment with theory is shown at maximum load and maximum penetration for the flat-bottom (0 deg dead-rise angle) model with bean-loading coefficients from 36.5 to 133.7 over a wide range of initial conditions. A dead-rise angle correction is applied and maximum-load data are compared with theory for the case of a model with 300 dead-rise angle and beam-loading coefficients from 208 to 530.

Crystallography and Molecular Arrangement of Polymorphic Monolayer J-Aggregates of a Cyanine Dye: Multiangle Polarized Light Fluorescence Optical Microscopy Study.

PubMed

Prokhorov, Valery V; Pozin, Sergey I; Perelygina, Olga M; Mal'tsev, Eugene I

2018-04-24

The molecular orientation in monolayer J-aggregates of 3,3-di(γ-sulfopropyl)-5,5-dichlorotiamonomethinecyanine dye has been precisely estimated using improved linear polarization measurements in the fluorescence microscope in which a multiangle set of polarization data is obtained using sample rotation. The estimated molecular orientation supplemented with the previously established crystallographic constraints based on the analysis of the well-developed two-dimensional J-aggregate shapes unambiguously indicate the staircase type of molecular arrangement for striplike J-aggregates with the staircases oriented along strips. The molecular transition dipoles are inclined at an angle of ∼25° to the strip direction, whereas the characteristic strip vertex angle ∼45° is formed by the [100] and [1-10] directions of the monoclinic unit cell. Measurements of the geometry of partially unwound tubes and their polarization properties support the model of tube formation by close-packed helical winding of flexible monolayer strips. In the tubes, the long molecular axes are oriented at a small angle in the range of 5-15° to the normal to the tube axis providing low bending energy. At a nanoscale, high-resolution atomic force microscopy imaging of J-aggregate monolayers reveals a complex quasi-one-dimensional organization.

Influence of cup-center-edge angle on micro-motion at the interface between the cup and host bone in cementless total hip arthroplasty: three-dimensional finite element analysis.

PubMed

Kaku, Nobuhiro; Tabata, Tomonori; Tsumura, Hiroshi

2015-12-01

We verified the index cup position required for bulk bone grafting instead of morcellized grafting immediately after cementless total hip arthroplasty. Three-dimensional finite element analysis was used to evaluate changes in the volume of the slippage of the cup-host bone interface as micro-motion of the cup at the acetabular bone defect site depending on the cup-center-edge (CE) angle. The conditions of bulk bone grafts were similar to those of cortical bone. Slippage increased with decreasing cup-CE angle. A bulk bone graft tightly fixed to the host bone prevented considerably larger slippage between the cup and host bone. A smaller cup-CE angle increased the impact of the bulk bone graft on slippage. When the cup-CE angle was 0° or -10°, the criterion for slippage in favorable initial fixation in all conditions was <40 μm. Even if transplanted bulk bone is used, unless good fixation is obtained between the host bone, and the cup and bone graft, it is impossible to obtain reliable fixation of the cup with a cup-CE angle <-10° and slippage exceeding 40 μm. Bulk bone grafting tightly fixed to the host bone improves initial the cup-host bone fixation, especially when the cup-CE angle is small, such as <-10°. In clinical practice, negative factors are implicated in the initial fixation of various cups, and sufficient fixation between the host bone and cup or bulk bone graft using a screw is effective when the cup-CE angle is extremely small.

A supersonic three-dimensional code for flow over blunt bodies: Program documentation and test cases

NASA Technical Reports Server (NTRS)

Chaussee, D. S.; Mcmillan, O. J.

1980-01-01

The use of a computer code for the calculation of steady, supersonic, three dimensional, inviscid flow over blunt bodies is illustrated. Input and output are given and explained for two cases: a pointed code of 20 deg half angle at 15 deg angle of attack in a free stream with M sub infinite = 7, and a cone-ogive-cylinder at 10 deg angle of attack with M sub infinite = 2.86. A source listing of the computer code is provided.

Viscous-inviscid interaction method including wake effects for three-dimensional wing-body configurations

NASA Technical Reports Server (NTRS)

Streett, C. L.

1981-01-01

A viscous-inviscid interaction method has been developed by using a three-dimensional integral boundary-layer method which produces results in good agreement with a finite-difference method in a fraction of the computer time. The integral method is stable and robust and incorporates a model for computation in a small region of streamwise separation. A locally two-dimensional wake model, accounting for thickness and curvature effects, is also included in the interaction procedure. Computation time spent in converging an interacted result is, many times, only slightly greater than that required to converge an inviscid calculation. Results are shown from the interaction method, run at experimental angle of attack, Reynolds number, and Mach number, on a wing-body test case for which viscous effects are large. Agreement with experiment is good; in particular, the present wake model improves prediction of the spanwise lift distribution and lower surface cove pressure.

Process for combining multiple passes of interferometric SAR data

DOEpatents

Bickel, Douglas L.; Yocky, David A.; Hensley, Jr., William H.

2000-11-21

Interferometric synthetic aperture radar (IFSAR) is a promising technology for a wide variety of military and civilian elevation modeling requirements. IFSAR extends traditional two dimensional SAR processing to three dimensions by utilizing the phase difference between two SAR images taken from different elevation positions to determine an angle of arrival for each pixel in the scene. This angle, together with the two-dimensional location information in the traditional SAR image, can be transformed into geographic coordinates if the position and motion parameters of the antennas are known accurately.

A novel two-dimensional dynamic anal ultrasonography technique to assess anismus comparing with three-dimensional echodefecography.

PubMed

Murad-Regadas, S M; Regadas, F S P; Barreto, R G L; Rodrigues, L V; de Souza, M H L P

2009-10-01

The aim of this prospective study was to test two-dimensional dynamic anorectal ultrasonography (2D-DAUS) in the assessment of anismus and compare it with echodefecography (ECD). Fifty consecutive female patients with outlet delay were submitted to 2D and 3D-DAUS, measuring the relaxing or contracting puborectalis muscle angle during straining. The patients were assigned to one of two groups based on ECD findings. Group I consisted of 29 patients without anismus and group II included 21 patients diagnosed with anismus. Subsequently 2D-DAUS images were checked for anismus and compared with ECD findings. Upon straining, the angle produced by the movement of the puborectalis muscle decreased in 26 out of the 29 (89.6%) patients of group I and increased 19 out of the 21 (90.4%) patients of group II. The mean angle during straining differed significantly between group I and group II. The index of agreement between the two scanning modes was 89.6% (26/29) for group I (Kappa: 0.796; CI: 95%; range: 0.51-1.0) and 90.4% (19/21) for group II (Kappa: 0.796; CI: 95%; range: 0.51-1.0). Two-dimensional dynamic anal ultrasonography can be used as an alternative method to assess patients with anismus, although the 3-D modality is more precise to evaluate the PR angle as the sphincters integrity as the whole muscle length is clearly visualized.

Theory of third-order spectroscopic methods to extract detailed molecular orientational dynamics for planar surfaces and other uniaxial systems

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

Nishida, Jun; Fayer, Michael D., E-mail: fayer@stanford.edu

Functionalized organic monolayers deposited on planar two-dimensional surfaces are important systems for studying ultrafast orientational motions and structures of interfacial molecules. Several studies have successfully observed the orientational relaxation of functionalized monolayers by fluorescence depolarization experiments and recently by polarization-resolved heterodyne detected vibrational transient grating (HDTG) experiments. In this article we provide a model-independent theory to extract orientational correlation functions unique to interfacial molecules and other uniaxial systems based on polarization-resolved resonant third-order spectroscopies, such as pump-probe spectroscopy, HDTG spectroscopy, and fluorescence depolarization experiment. It will be shown (in the small beam-crossing angle limit) that five measurements are necessary tomore » completely characterize the monolayer's motions: I{sub ∥}(t) and I{sub ⊥}(t) with the incident beams normal to the surface, I{sub ∥}(t) and I{sub ⊥}(t) with a non-zero incident angle, and a time averaged linear dichroism measurement. Once these measurements are performed, two orientational correlation functions corresponding to in-plane and out-of-plane motions are obtained. The procedure is applicable not only for monolayers on flat surfaces, but any samples with uniaxial symmetry such as uniaxial liquid crystals and aligned planar bilayers. The theory is valid regardless of the nature of the actual molecular motions on interface. We then apply the general results to wobbling-in-a-cone model, in which molecular motions are restricted to a limited range of angles. Within the context of the model, the cone angle, the tilt of the cone relative to the surface normal, and the orientational diffusion constant can be determined. The results are extended to describe analysis of experiments where the beams are not crossing in the small angle limit.« less

Projectile Motion Model

NASA Astrophysics Data System (ADS)

Cordry, Sean

2003-10-01

Textbooks almost always have a stroboscopic photograph of a ball falling alongside of one with an initial horizontal speed. These photos are great for showing how the two objects experience the same vertical acceleration; however, the photos don't usually illustrate what happens if a projectile is launched at some angle. There are a number of ways to illustrate the effects of the launch angle: shooting a ball or stream of water through hoops, for example. Those demonstrations, though, do not allow for side-by-side comparison of the effects of various launch angles. Thus, a few years ago I constructed this three-dimensional projectile model to do just that. The model is composed of two three-dimensional "stroboscopic sculptures" representing the trajectory of two projectiles.

Demonstration of a directional sonic prism in two dimensions using an air-acoustic leaky wave antenna

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

Naify, Christina J., E-mail: christina.naify@nrl.navy.mil; Rohde, Charles A.; Calvo, David C.

Analysis and experimental demonstration of a two-dimensional acoustic leaky wave antenna is presented for use in air. The antenna is comprised of a two-dimensional waveguide patterned with radiating acoustic shunts. When excited using a single acoustic source within the waveguide, the antenna acts as a sonic prism that exhibits frequency steering. This design allows for control of acoustic steering angle using only a single source transducer and a patterned aperture. Aperture design was determined using transmission line analysis and finite element methods. The designed antenna was fabricated and the steering angle measured. The performance of the measured aperture was withinmore » 9% of predicted angle magnitudes over all examined frequencies.« less

Design and fabrication of continuous-profile diffractive micro-optical elements as a beam splitter.

PubMed

Feng, Di; Yan, Yingbai; Jin, Guofan; Fan, Shoushan

2004-10-10

An optimization algorithm that combines a rigorous electromagnetic computation model with an effective iterative method is utilized to design diffractive micro-optical elements that exhibit fast convergence and better design quality. The design example is a two-dimensional 1-to-2 beam splitter that can symmetrically generate two focal lines separated by 80 microm at the observation plane with a small angle separation of +/- 16 degrees. Experimental results are presented for an element with continuous profiles fabricated into a monocrystalline silicon substrate that has a width of 160 microm and a focal length of 140 microm at a free-space wavelength of 10.6 microm.

High precise measurement of tiny angle dimensional holes for the unit-holes of the LAMOST Focal Plane Plate

NASA Astrophysics Data System (ADS)

Zhou, Zengxiang; Jin, Yi; Zhai, Chao; Xing, Xiaozheng

2008-07-01

In the LAMOST project, the unit-holes on the Focal Plane Plate are the final installation location of the optical fiber positioning system. Theirs precision will influence the observation efficiency of the LAMOST. For the unique requirements, the unit-holes on the Focal Plane Plate are composed by a series of tiny angle dimensional holes which dimensional angle are between 16' to 2.5°. According to these requirements, the measurement of the tiny angle dimensional holes for the unit-holes needs to less than 3'. And all the unit-holes point to the virtual sphere center of the Focal Plane Plate. To that end, the angle departure of the unit-holes axis is changed to the distance from the virtual sphere center of Focal Plane Plate to the unit-holes axis. That is the better way to evaluate the technical requirements of the dimensional angle errors. In the measuring process, common measuring methods do not fit for the tiny angle dimensional hole by CMM(coordinate measurement machine). An extraordinary way to solve this problem is to insert a measuring stick into a unit-hole, with a target ball on the stick. Then measure the low point of the ball center and pull out the stick for the high station of center. Finally, calculate the two points for the unit-hole axis to get the angle departure. But on the other hand, use this methods will bring extra errors for the measuring stick and the target ball. For better analysis this question, a series experiments are mentioned in this paper, which testify that the influence of the measure implement is little. With increasing the distance between the low point and the high point position in the measuring process should enhance the accuracy of dimensional angle measurement.

Aerodynamic Design of Axial-flow Compressors. Volume 2

NASA Technical Reports Server (NTRS)

1956-01-01

Available experimental two-dimensional-cascade data for conventional compressor blade sections are correlated. The two-dimensional cascade and some of the principal aerodynamic factors involved in its operation are first briefly described. Then the data are analyzed by examining the variation of cascade performance at a reference incidence angle in the region of minimum loss. Variations of reference incidence angle, total-pressure loss, and deviation angle with cascade geometry, inlet Mach number, and Reynolds number are investigated. From the analysis and the correlations of the available data, rules and relations are evolved for the prediction of the magnitude of the reference total-pressure loss and the reference deviation and incidence angles for conventional blade profiles. These relations are developed in simplified forms readily applicable to compressor design procedures.

Measurement of Galactic Logarithmic Spiral Arm Pitch Angle Using Two-dimensional Fast Fourier Transform Decomposition

NASA Astrophysics Data System (ADS)

Davis, Benjamin L.; Berrier, Joel C.; Shields, Douglas W.; Kennefick, Julia; Kennefick, Daniel; Seigar, Marc S.; Lacy, Claud H. S.; Puerari, Ivânio

2012-04-01

A logarithmic spiral is a prominent feature appearing in a majority of observed galaxies. This feature has long been associated with the traditional Hubble classification scheme, but historical quotes of pitch angle of spiral galaxies have been almost exclusively qualitative. We have developed a methodology, utilizing two-dimensional fast Fourier transformations of images of spiral galaxies, in order to isolate and measure the pitch angles of their spiral arms. Our technique provides a quantitative way to measure this morphological feature. This will allow comparison of spiral galaxy pitch angle to other galactic parameters and test spiral arm genesis theories. In this work, we detail our image processing and analysis of spiral galaxy images and discuss the robustness of our analysis techniques.

Three-dimensional representation of curved nanowires.

PubMed

Huang, Z; Dikin, D A; Ding, W; Qiao, Y; Chen, X; Fridman, Y; Ruoff, R S

2004-12-01

Nanostructures, such as nanowires, nanotubes and nanocoils, can be described in many cases as quasi one-dimensional curved objects projecting in three-dimensional space. A parallax method to construct the correct three-dimensional geometry of such one-dimensional nanostructures is presented. A series of scanning electron microscope images was acquired at different view angles, thus providing a set of image pairs that were used to generate three-dimensional representations using a matlab program. An error analysis as a function of the view angle between the two images is presented and discussed. As an example application, the importance of knowing the true three-dimensional shape of boron nanowires is demonstrated; without the nanowire's correct length and diameter, mechanical resonance data cannot provide an accurate estimate of Young's modulus.

Two-dimensional planning can result in internal rotation of the femoral component in total knee arthroplasty.

PubMed

Okamoto, Shigetoshi; Mizu-uchi, Hideki; Okazaki, Ken; Hamai, Satoshi; Tashiro, Yasutaka; Nakahara, Hiroyuki; Iwamoto, Yukihide

2016-01-01

The first purpose of this study was to compare the reproducibility of two-dimensional (2D) and three-dimensional (3D) measurements for preoperative planning of the femoral side in total knee arthroplasty (TKA). The second purpose was to evaluate the factors affecting the differences between the 2D and 3D measurements. Two-dimensional and 3D measurements for preoperative planning of the femoral side in TKA were evaluated in 75 varus knees with osteoarthritis. The femoral valgus angle, defined as the angle between the mechanical and anatomical axes of the femur, and the clinical rotation angle and surgical rotation angle, defined by the angles between the posterior condylar line and the clinical or surgical transepicondylar axes, respectively, were analysed using 2D (radiographs and axial CT slices) and 3D (3D bone models reconstructed from CT images) measurements. For all variables, 3D measurements were more reliable and reproducible than 2D measurements. The medians and ranges of the clinical rotation angle and surgical rotation angle were 6.6° (-1.7° to 12.1°) and 2.3° (-2.5° to 8.6°) in 2D, and 7.1° (2.7° to 11.4°) and 3.0° (-2.0° to 7.5°) in 3D. Varus/valgus alteration of the CT scanning direction relative to the mechanical axis affected the difference in clinical rotation angles between 2D and 3D measurements. Significantly, smaller values of the clinical rotation angle and surgical rotation angle were obtained by 2D compared to 3D measurements, which could result in internal rotation of the femoral component even if the surgeon performs the bone cutting precisely. Regarding clinical relevance, first, this study confirmed the reliability of 3D measurements. Second, it underscored the risk of internal rotation of the femoral component when using 2D measurement, even with precise bone cutting technique. These results will help surgeons avoid malpositioning of the femoral component if 2D measurements are used for preoperative planning in TKA. Prospective comparative study, Level Ш.

Spherical Ornstein-Uhlenbeck Processes

NASA Astrophysics Data System (ADS)

Wilkinson, Michael; Pumir, Alain

2011-10-01

The paper considers random motion of a point on the surface of a sphere, in the case where the angular velocity is determined by an Ornstein-Uhlenbeck process. The solution is fully characterised by only one dimensionless number, the persistence angle, which is the typical angle of rotation during the correlation time of the angular velocity. We first show that the two-dimensional case is exactly solvable. When the persistence angle is large, a series for the correlation function has the surprising property that its sum varies much more slowly than any of its individual terms. In three dimensions we obtain asymptotic forms for the correlation function, in the limits where the persistence angle is very small and very large. The latter case exhibits a complicated transient, followed by a much slower exponential decay. The decay rate is determined by the solution of a radial Schrödinger equation in which the angular momentum quantum number takes an irrational value, namely j=1/2(sqrt{17}-1). Possible applications of the model to objects tumbling in a turbulent environment are discussed.

Three-dimensional disc-satellite interaction: torques, migration, and observational signatures

NASA Astrophysics Data System (ADS)

Arzamasskiy, Lev; Zhu, Zhaohuan; Stone, James M.

2018-04-01

The interaction of a satellite with a gaseous disc results in the excitation of spiral density waves, which remove angular momentum from the orbit. In addition, if the orbit is not coplanar with the disc, three-dimensional effects will excite bending and eccentricity waves. We perform three-dimensional hydrodynamic simulations to study nonlinear disc-satellite interaction in inviscid protoplanetary discs for a variety of orbital inclinations from 0° to 180°. It is well known that three-dimensional effects are important even for zero inclination. In this work, we (1) show that for planets with small inclinations (as in the Solar system), effects such as the total torque and migration rate strongly depend on the inclination and are significantly different (about 2.5 times smaller) from the two-dimensional case, (2) give formulae for the migration rate, inclination damping, and precession rate of planets with different inclination angles in disc with different scale heights, and (3) present the observational signatures of a planet on an inclined orbit with respect to the protoplanetary disc. For misaligned planets, we find good agreement with linear theory in the limit of small inclinations, and with dynamical friction estimates for intermediate inclinations. We find that in the latter case, the dynamical friction force is not parallel to the relative planetary velocity. Overall, the derived formulae will be important for studying exoplanets with obliquity.

Deduction of two-dimensional blood flow vector by dual angle diverging waves from a cardiac sector probe

NASA Astrophysics Data System (ADS)

Maeda, Moe; Nagaoka, Ryo; Ikeda, Hayato; Yaegashi, So; Saijo, Yoshifumi

2018-07-01

Color Doppler method is widely used for noninvasive diagnosis of heart diseases. However, the method can measure one-dimensional (1D) blood flow velocity only along an ultrasonic beam. In this study, diverging waves with two different angles were irradiated from a cardiac sector probe to estimate a two-dimensional (2D) blood flow vector from each velocity measured with the angles. The feasibility of the proposed method was evaluated in experiments using flow poly(vinyl alcohol) (PVA) gel phantoms. The 2D velocity vectors obtained with the proposed method were compared with the flow vectors obtained with the particle image velocimetry (PIV) method. Root mean square errors of the axial and lateral components were 11.3 and 29.5 mm/s, respectively. The proposed method was also applied to echo data from the left ventricle of the heart. The inflow from the mitral valve in diastole and the ejection flow concentrating in the aorta in systole were visualized.

Accurate small and wide angle x-ray scattering profiles from atomic models of proteins and nucleic acids

NASA Astrophysics Data System (ADS)

Nguyen, Hung T.; Pabit, Suzette A.; Meisburger, Steve P.; Pollack, Lois; Case, David A.

2014-12-01

A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb+ and Sr2+) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein-Zernike equations, with results from the Kovalenko-Hirata closure being closest to experiment for the cases studied here.

Hard Two-Body Photodisintegration of He3

NASA Astrophysics Data System (ADS)

Pomerantz, I.; Ilieva, Y.; Gilman, R.; Higinbotham, D. W.; Piasetzky, E.; Strauch, S.; Adhikari, K. P.; Aghasyan, M.; Allada, K.; Amaryan, M. J.; Anefalos Pereira, S.; Anghinolfi, M.; Baghdasaryan, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Batourine, V.; Beck, A.; Beck, S.; Bedlinskiy, I.; Berman, B. L.; Biselli, A. S.; Boeglin, W.; Bono, J.; Bookwalter, C.; Boiarinov, S.; Briscoe, W. J.; Brooks, W. K.; Bubis, N.; Burkert, V.; Camsonne, A.; Canan, M.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Chirapatpimol, K.; Cisbani, E.; Cole, P. L.; Contalbrigo, M.; Crede, V.; Cusanno, F.; D'Angelo, A.; Daniel, A.; Dashyan, N.; de Jager, C. W.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G. E.; Doughty, D.; Dupre, R.; Dutta, C.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Fleming, J. A.; Fradi, A.; Garibaldi, F.; Geagla, O.; Gevorgyan, N.; Giovanetti, K. L.; Girod, F. X.; Glister, J.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Harrison, N.; Heddle, D.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jiang, X.; Jo, H. S.; Joo, K.; Katramatou, A. T.; Keller, D.; Khandaker, M.; Khetarpal, P.; Khrosinkova, E.; Kim, A.; Kim, W.; Klein, F. J.; Koirala, S.; Kubarovsky, A.; Kubarovsky, V.; Kuleshov, S. V.; Kvaltine, N. D.; Lee, B.; LeRose, J. J.; Lewis, S.; Lindgren, R.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Mao, Y.; Martinez, D.; Mayer, M.; McCullough, E.; McKinnon, B.; Meekins, D.; Meyer, C. A.; Michaels, R.; Mineeva, T.; Mirazita, M.; Moffit, B.; Mokeev, V.; Montgomery, R. A.; Moutarde, H.; Munevar, E.; Munoz Camacho, C.; Nadel-Turonski, P.; Nasseripour, R.; Nepali, C. S.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Park, S.; Petratos, G. G.; Phelps, E.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Qian, X.; Qiang, Y.; Ricco, G.; Rimal, D.; Ripani, M.; Ritchie, B. G.; Rodriguez, I.; Ron, G.; Rosner, G.; Rossi, P.; Sabatié, F.; Saha, A.; Saini, M. S.; Sarty, A. J.; Sawatzky, B.; Saylor, N. A.; Schott, D.; Schulte, E.; Schumacher, R. A.; Seder, E.; Seraydaryan, H.; Shneor, R.; Smith, G. D.; Sokhan, D.; Sparveris, N.; Stepanyan, S. S.; Stepanyan, S.; Stoler, P.; Subedi, R.; Sulkosky, V.; Taiuti, M.; Tang, W.; Taylor, C. E.; Tkachenko, S.; Ungaro, M.; Vernarsky, B.; Vineyard, M. F.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Wang, Y.; Watts, D. P.; Weinstein, L. B.; Weygand, D. P.; Wojtsekhowski, B.; Wood, M. H.; Yan, X.; Yao, H.; Zachariou, N.; Zhan, X.; Zhang, J.; Zhao, Z. W.; Zheng, X.; Zonta, I.

2013-06-01

We have measured cross sections for the γHe3→pd reaction at photon energies of 0.4-1.4 GeV and a center-of-mass angle of 90°. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.

Hard two-body photodisintegration of 3He.

PubMed

Pomerantz, I; Ilieva, Y; Gilman, R; Higinbotham, D W; Piasetzky, E; Strauch, S; Adhikari, K P; Aghasyan, M; Allada, K; Amaryan, M J; Anefalos Pereira, S; Anghinolfi, M; Baghdasaryan, H; Ball, J; Baltzell, N A; Battaglieri, M; Batourine, V; Beck, A; Beck, S; Bedlinskiy, I; Berman, B L; Biselli, A S; Boeglin, W; Bono, J; Bookwalter, C; Boiarinov, S; Briscoe, W J; Brooks, W K; Bubis, N; Burkert, V; Camsonne, A; Canan, M; Carman, D S; Celentano, A; Chandavar, S; Charles, G; Chirapatpimol, K; Cisbani, E; Cole, P L; Contalbrigo, M; Crede, V; Cusanno, F; D'Angelo, A; Daniel, A; Dashyan, N; de Jager, C W; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dodge, G E; Doughty, D; Dupre, R; Dutta, C; Egiyan, H; El Alaoui, A; El Fassi, L; Eugenio, P; Fedotov, G; Fegan, S; Fleming, J A; Fradi, A; Garibaldi, F; Geagla, O; Gevorgyan, N; Giovanetti, K L; Girod, F X; Glister, J; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Harrison, N; Heddle, D; Hicks, K; Ho, D; Holtrop, M; Hyde, C E; Ireland, D G; Ishkhanov, B S; Isupov, E L; Jiang, X; Jo, H S; Joo, K; Katramatou, A T; Keller, D; Khandaker, M; Khetarpal, P; Khrosinkova, E; Kim, A; Kim, W; Klein, F J; Koirala, S; Kubarovsky, A; Kubarovsky, V; Kuleshov, S V; Kvaltine, N D; Lee, B; LeRose, J J; Lewis, S; Lindgren, R; Livingston, K; Lu, H Y; MacGregor, I J D; Mao, Y; Martinez, D; Mayer, M; McCullough, E; McKinnon, B; Meekins, D; Meyer, C A; Michaels, R; Mineeva, T; Mirazita, M; Moffit, B; Mokeev, V; Montgomery, R A; Moutarde, H; Munevar, E; Munoz Camacho, C; Nadel-Turonski, P; Nasseripour, R; Nepali, C S; Niccolai, S; Niculescu, G; Niculescu, I; Osipenko, M; Ostrovidov, A I; Pappalardo, L L; Paremuzyan, R; Park, K; Park, S; Petratos, G G; Phelps, E; Pisano, S; Pogorelko, O; Pozdniakov, S; Procureur, S; Protopopescu, D; Puckett, A J R; Qian, X; Qiang, Y; Ricco, G; Rimal, D; Ripani, M; Ritchie, B G; Rodriguez, I; Ron, G; Rosner, G; Rossi, P; Sabatié, F; Saha, A; Saini, M S; Sarty, A J; Sawatzky, B; Saylor, N A; Schott, D; Schulte, E; Schumacher, R A; Seder, E; Seraydaryan, H; Shneor, R; Smith, G D; Sokhan, D; Sparveris, N; Stepanyan, S S; Stepanyan, S; Stoler, P; Subedi, R; Sulkosky, V; Taiuti, M; Tang, W; Taylor, C E; Tkachenko, S; Ungaro, M; Vernarsky, B; Vineyard, M F; Voskanyan, H; Voutier, E; Walford, N K; Wang, Y; Watts, D P; Weinstein, L B; Weygand, D P; Wojtsekhowski, B; Wood, M H; Yan, X; Yao, H; Zachariou, N; Zhan, X; Zhang, J; Zhao, Z W; Zheng, X; Zonta, I

2013-06-14

We have measured cross sections for the γ(3)He → pd reaction at photon energies of 0.4-1.4 GeV and a center-of-mass angle of 90°. We observe dimensional scaling above 0.7 GeV at this center-of-mass angle. This is the first observation of dimensional scaling in the photodisintegration of a nucleus heavier than the deuteron.

Small-angle x-ray scattering in amorphous silicon: A computational study

NASA Astrophysics Data System (ADS)

Paudel, Durga; Atta-Fynn, Raymond; Drabold, David A.; Elliott, Stephen R.; Biswas, Parthapratim

2018-05-01

We present a computational study of small-angle x-ray scattering (SAXS) in amorphous silicon (a -Si) with particular emphasis on the morphology and microstructure of voids. The relationship between the scattering intensity in SAXS and the three-dimensional structure of nanoscale inhomogeneities or voids is addressed by generating large high-quality a -Si networks with 0.1%-0.3% volume concentration of voids, as observed in experiments using SAXS and positron annihilation spectroscopy. A systematic study of the variation of the scattering intensity in the small-angle scattering region with the size, shape, number density, and the spatial distribution of the voids in the networks is presented. Our results suggest that the scattering intensity in the small-angle region is particularly sensitive to the size and the total volume fraction of the voids, but the effect of the geometry or shape of the voids is less pronounced in the intensity profiles. A comparison of the average size of the voids obtained from the simulated values of the intensity, using the Guinier approximation and Kratky plots, with that of the same from the spatial distribution of the atoms in the vicinity of void surfaces is presented.

Multidimensional High-Resolution Magic Angle Spinning and Solution-State NMR Characterization of 13C-labeled Plant Metabolites and Lignocellulose

PubMed Central

Mori, Tetsuya; Tsuboi, Yuuri; Ishida, Nobuhiro; Nishikubo, Nobuyuki; Demura, Taku; Kikuchi, Jun

2015-01-01

Lignocellulose, which includes mainly cellulose, hemicellulose, and lignin, is a potential resource for the production of chemicals and for other applications. For effective production of materials derived from biomass, it is important to characterize the metabolites and polymeric components of the biomass. Nuclear magnetic resonance (NMR) spectroscopy has been used to identify biomass components; however, the NMR spectra of metabolites and lignocellulose components are ambiguously assigned in many cases due to overlapping chemical shift peaks. Using our 13C-labeling technique in higher plants such as poplar samples, we demonstrated that overlapping peaks could be resolved by three-dimensional NMR experiments to more accurately assign chemical shifts compared with two-dimensional NMR measurements. Metabolites of the 13C-poplar were measured by high-resolution magic angle spinning NMR spectroscopy, which allows sample analysis without solvent extraction, while lignocellulose components of the 13C-poplar dissolved in dimethylsulfoxide/pyridine solvent were analyzed by solution-state NMR techniques. Using these methods, we were able to unambiguously assign chemical shifts of small and macromolecular components in 13C-poplar samples. Furthermore, using samples of less than 5 mg, we could differentiate between two kinds of genes that were overexpressed in poplar samples, which produced clearly modified plant cell wall components. PMID:26143886

Tension Strength, Failure Prediction and Damage Mechanisms in 2D Triaxial Braided Composites with Notch

NASA Technical Reports Server (NTRS)

Norman, Timothy L.; Anglin, Colin

1995-01-01

The unnotched and notched (open hole) tensile strength and failure mechanisms of two-dimensional (2D) triaxial braided composites were examined. The effect of notch size and notch position were investigated. Damage initiation and propagation in notched and unnotched coupons were also examined. Theory developed to predict the normal stress distribution near an open hole and failure for tape laminated composites was evaluated for its applicability to 2D triaxial braided textile composite materials. Four different fiber architectures were considered; braid angle, yarn and braider size, percentage of longitudinal yarns and braider angle varied. Tape laminates equivalent to textile composites were also constructed for comparison. Unnotched tape equivalents were stronger than braided textiles but exhibited greater notch sensitivity. Notched textiles and tape equivalents have roughly the same strength at large notch sizes. Two common damage mechanisms were found: braider yarn cracking and near notch longitudinal yarn splitting. Cracking was found to initiate in braider yarns in unnotched and notched coupons, and propagate in the direction of the braider yarns until failure. Damage initiation stress decreased with increasing braid angle. No significant differences in prediction of near notch strain between textile and tape equivalents could be detected for small braid angle, but the correlations were weak for textiles with large braid angle. Notch strength could not be predicted using existing anisotropic theory for braided textiles due to their insensitivity to notch.

Laser range profile of cones

NASA Astrophysics Data System (ADS)

Zhou, Wenzhen; Gong, Yanjun; Wang, Mingjun; Gong, Lei

2016-10-01

technology. Laser one-dimensional range profile can reflect the characteristics of the target shape and surface material. These techniques were motivated by applications of laser radar to target discrimination in ballistic missile defense. The radar equation of pulse laser about cone is given in this paper. This paper demonstrates the analytical model of laser one-dimensional range profile of cone based on the radar equation of the pulse laser. Simulations results of laser one-dimensional range profiles of some cones are given. Laser one-dimensional range profiles of cone, whose surface material with diffuse lambertian reflectance, is given in this paper. Laser one-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. Laser one-dimensional range profiles of different pulse width of cone is given in this paper. The influences of surface material, pulse width, attitude on the one-dimensional range are analyzed. The laser two-dimensional range profile is two-dimensional scattering imaging of pulse laser of target. The two-dimensional range profile of roughness target can provide range resolved information. An analytical model of two-dimensional laser range profile of cone is proposed. The simulations of two-dimensional laser range profiles of some cones are given. Laser two-dimensional range profiles of cone, whose surface mater with diffuse lambertian reflectance, is given in this paper. Laser two-dimensional range profiles of cone, whose surface mater with diffuse materials whose retroreflectance can be modeled closely with an exponential term that decays with increasing incidence angles, is given in this paper. The influence of pulse width, surface material on laser two-dimensional range profile is analyzed. Laser one-dimensional range profile and laser two-dimensional range profile are called as laser range profile (LRP).

Determination of facial symmetry in unilateral cleft lip and palate patients from three-dimensional data: technical report and assessment of measurement errors.

PubMed

Nkenke, Emeka; Lehner, Bernhard; Kramer, Manuel; Haeusler, Gerd; Benz, Stefanie; Schuster, Maria; Neukam, Friedrich W; Vairaktaris, Eleftherios G; Wurm, Jochen

2006-03-01

To assess measurement errors of a novel technique for the three-dimensional determination of the degree of facial symmetry in patients suffering from unilateral cleft lip and palate malformations. Technical report, reliability study. Cleft Lip and Palate Center of the University of Erlangen-Nuremberg, Erlangen, Germany. The three-dimensional facial surface data of five 10-year-old unilateral cleft lip and palate patients were subjected to the analysis. Distances, angles, surface areas, and volumes were assessed twice. Calculations were made for method error, intraclass correlation coefficient, and repeatability of the measurements of distances, angles, surface areas, and volumes. The method errors were less than 1 mm for distances and less than 1.5 degrees for angles. The intraclass correlation coefficients showed values greater than .90 for all parameters. The repeatability values were comparable for cleft and noncleft sides. The small method errors, high intraclass correlation coefficients, and comparable repeatability values for cleft and noncleft sides reveal that the new technique is appropriate for clinical use.

Multiple Acquisition InSAR Analysis: Persistent Scatterer and Small Baseline Approaches

NASA Astrophysics Data System (ADS)

Hooper, A.

2006-12-01

InSAR techniques that process data from multiple acquisitions enable us to form time series of deformation and also allow us to reduce error terms present in single interferograms. There are currently two broad categories of methods that deal with multiple images: persistent scatterer methods and small baseline methods. The persistent scatterer approach relies on identifying pixels whose scattering properties vary little with time and look angle. Pixels that are dominated by a singular scatterer best meet these criteria; therefore, images are processed at full resolution to both increase the chance of there being only one dominant scatterer present, and to reduce the contribution from other scatterers within each pixel. In images where most pixels contain multiple scatterers of similar strength, even at the highest possible resolution, the persistent scatterer approach is less optimal, as the scattering characteristics of these pixels vary substantially with look angle. In this case, an approach that interferes only pairs of images for which the difference in look angle is small makes better sense, and resolution can be sacrificed to reduce the effects of the look angle difference by band-pass filtering. This is the small baseline approach. Existing small baseline methods depend on forming a series of multilooked interferograms and unwrapping each one individually. This approach fails to take advantage of two of the benefits of processing multiple acquisitions, however, which are usually embodied in persistent scatterer methods: the ability to find and extract the phase for single-look pixels with good signal-to-noise ratio that are surrounded by noisy pixels, and the ability to unwrap more robustly in three dimensions, the third dimension being that of time. We have developed, therefore, a new small baseline method to select individual single-look pixels that behave coherently in time, so that isolated stable pixels may be found. After correction for various error terms, the phase values of the selected pixels are unwrapped using a new three-dimensional algorithm. We apply our small baseline method to an area in southern Iceland that includes Katla and Eyjafjallajökull volcanoes, and retrieve a time series of deformation that shows transient deformation due to intrusion of magma beneath Eyjafjallajökull. We also process the data using the Stanford method for persistent scatterers (StaMPS) for comparison.

Two-dimensional nuclear magnetic resonance of quadrupolar systems

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

Wang, Shuanhu

1997-09-01

This dissertation describes two-dimensional nuclear magnetic resonance theory and experiments which have been developed to study quadruples in the solid state. The technique of multiple-quantum magic-angle spinning (MQMAS) is extensively reviewed and expanded upon in this thesis. Specifically, MQMAS is first compared with another technique, dynamic-angle spinning (DAS). The similarity between the two techniques allows us to extend much of the DAS work to the MQMAS case. Application of MQMAS to a series of aluminum containing materials is then presented. The superior resolution enhancement through MQMAS is exploited to detect the five- and six-coordinated aluminum in many aluminosilicate glasses. Combiningmore » the MQMAS method with other experiments, such as HETCOR, greatly expands the possibility of the use of MQMAS to study a large range of problems and is demonstrated in Chapter 5. Finally, the technique switching-angle spinning (SAS) is applied to quadrupolar nuclei to fully characterize a quadrupolar spin system in which all of the 8 NMR parameters are accurately determined. This dissertation is meant to demonstrate that with the combination of two-dimensional NMR concepts and new advanced spinning technologies, a series of multiple-dimensional NMR techniques can be designed to allow a detailed study of quadrupolar nuclei in the solid state.« less

Quality assessment of two- and three-dimensional unstructured meshes and validation of an upwind Euler flow solver

NASA Technical Reports Server (NTRS)

Woodard, Paul R.; Batina, John T.; Yang, Henry T. Y.

1992-01-01

Quality assessment procedures are described for two-dimensional unstructured meshes. The procedures include measurement of minimum angles, element aspect ratios, stretching, and element skewness. Meshes about the ONERA M6 wing and the Boeing 747 transport configuration are generated using an advancing front method grid generation package of programs. Solutions of Euler's equations for these meshes are obtained at low angle-of-attack, transonic conditions. Results for these cases, obtained as part of a validation study demonstrate accuracy of an implicit upwind Euler solution algorithm.

Fokker-Planck simulation of runaway electron generation in disruptions with the hot-tail effect

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

Nuga, H., E-mail: nuga@p-grp.nucleng.kyoto-u.ac.jp; Fukuyama, A.; Yagi, M.

2016-06-15

To study runaway electron generation in disruptions, we have extended the three-dimensional (two-dimensional in momentum space; one-dimensional in the radial direction) Fokker-Planck code, which describes the evolution of the relativistic momentum distribution function of electrons and the induced toroidal electric field in a self-consistent manner. A particular focus is placed on the hot-tail effect in two-dimensional momentum space. The effect appears if the drop of the background plasma temperature is sufficiently rapid compared with the electron-electron slowing down time for a few times of the pre-quench thermal velocity. It contributes to not only the enhancement of the primary runaway electronmore » generation but also the broadening of the runaway electron distribution in the pitch angle direction. If the thermal energy loss during the major disruption is assumed to be isotropic, there are hot-tail electrons that have sufficiently large perpendicular momentum, and the runaway electron distribution becomes broader in the pitch angle direction. In addition, the pitch angle scattering also yields the broadening. Since the electric field is reduced due to the burst of runaway electron generation, the time required for accelerating electrons to the runaway region becomes longer. The longer acceleration period makes the pitch-angle scattering more effective.« less

Three-dimensional orientation and location-dependent varying rules of radiographic angles of the acetabular cup.

PubMed

Zhao, Jing-Xin; Su, Xiu-Yun; Zhao, Zhe; Xiao, Ruo-Xiu; Zhang, Li-Cheng; Tang, Pei-Fu

2018-02-17

The aim of this study is to demonstrate the varying rules of radiographic angles following varying three-dimensional (3D) orientations and locations of cup using an accurate mathematical model. A cone model is established to address the quantitative relationship between the opening circle of cup and its ellipse projection on radiograph. The varying rules of two-dimensional (2D) radiographic anteversion (RA) and inclination (RI) angles can be analyzed. When the centre of cup is located above X-ray source, with proper 3D RI/RA angles, 2D RA angle can be equal to its 3D counterpart, and 2D RI angle is usually greater than its 3D counterpart. Except for the original point on hip-centered anterior-posterior radiograph, there is no area on radiograph where both 2D RA and RI angles are equal to their 3D counterparts simultaneously. This study proposes an innovative model for accurately explaining how 2D RA/RI angles of cup are varying following different 3D RA/RI angles and location of cup. The analysis results provide clinicians an intuitive grasp of knowledge about 2D RA/RI angles greater or smaller than their 3D counterparts post-operatively. The established model may allow determining the effects of pelvic rotations on 2D radiographic angles of cup.

Bending wavefunctions for linear molecules

NASA Astrophysics Data System (ADS)

Hirano, Tsuneo; Nagashima, Umpei; Jensen, Per

2018-01-01

The bending motion of a linear triatomic molecule has two unique characteristics: the bending mode is doubly degenerate and only positive values of the bending angle, expressed by the bond angle supplement ρ bar , can be observed. The double degeneracy requires the wavefunction to be described as a two-dimensional oscillator. In the present work, we first review the conventional expressions based on two, symmetrically equivalent normal coordinates. Then we discuss an alternative expression for the bending wavefunction in terms of two geometrical coordinates, the bond angle supplement ρ bar (= π - τ ⩾ 0 , where τ is the bond angle) and the rotation angle χ (0 ⩽ χ < 2 π) describing rotation of the molecule around the molecular axis. In this formalism, defined for the (ρ bar , χ) polar-coordinate space with volume element ρ bar d ρ bar dχ , the one-dimensional wavefunction resulted through re-normalization for χ has zero amplitude at ρ bar = 0 , and the ro-vibrational average of the bending angle, i.e., the expectation value 〈 ρ bar 〉 , attains a non-zero, positive value for any ro-vibrational state including the vibrational ground state. This conclusion appears to cause some controversy since much conventional spectroscopic wisdom insists on 〈 ρ bar 〉 having the value zero.

Computation of transonic flow past projectiles at angle of attack

NASA Technical Reports Server (NTRS)

Reklis, R. P.; Sturek, W. B.; Bailey, F. R.

1978-01-01

Aerodynamic properties of artillery shell such as normal force and pitching moment reach peak values in a narrow transonic Mach number range. In order to compute these quantities, numerical techniques have been developed to obtain solutions to the three-dimensional transonic small disturbance equation about slender bodies at angle of attack. The computation is based on a plane relaxation technique involving Fourier transforms to partially decouple the three-dimensional difference equations. Particular care is taken to assure accurate solutions near corners found in shell designs. Computed surface pressures are compared to experimental measurements for circular arc and cone cylinder bodies which have been selected as test cases. Computed pitching moments are compared to range measurements for a typical projectile shape.

Ultra-small-angle neutron scattering with azimuthal asymmetry

DOE PAGES

Gu, X.; Mildner, D. F. R.

2016-05-16

Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding tomore » the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. Furthermore, the aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.« less

Ultra-small-angle neutron scattering with azimuthal asymmetry

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

Gu, X.; Mildner, D. F. R.

Small-angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit-smeared ultra-SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two-dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding tomore » the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double-crystal diffractometer for concatenation with the usual pinhole-geometry SANS data. Furthermore, the aspect ratio from the SANS data is used to modify the slit-smeared USANS data to produce quasi-symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.« less

Radar imaging using electromagnetic wave carrying orbital angular momentum

NASA Astrophysics Data System (ADS)

Yuan, Tiezhu; Cheng, Yongqiang; Wang, Hongqiang; Qin, Yuliang; Fan, Bo

2017-03-01

The concept of radar imaging based on orbital angular momentum (OAM) modulation, which has the ability of azimuthal resolution without relative motion, has recently been proposed. We investigate this imaging technique further in greater detail. We first analyze the principle of the technique, accounting for its resolving ability physically. The phase and intensity distributions of the OAM-carrying fields produced by phased uniform circular array antenna, which have significant effects on the imaging results, are investigated. The imaging model shows that the received signal has the form of inverse discrete Fourier transform with the use of OAM and frequency diversities. The two-dimensional Fourier transform is employed to reconstruct the target images in the case of large and small elevation angles. Due to the peculiar phase and intensity characteristics, the small elevation is more suitable for practical application than the large one. The minimum elevation angle is then obtained given the array parameters. The imaging capability is analyzed by means of the point spread function. All results are verified through numerical simulations. The proposed staring imaging technique can achieve extremely high azimuthal resolution with the use of plentiful OAM modes.

Ultrashort Channel Length Black Phosphorus Field-Effect Transistors.

PubMed

Miao, Jinshui; Zhang, Suoming; Cai, Le; Scherr, Martin; Wang, Chuan

2015-09-22

This paper reports high-performance top-gated black phosphorus (BP) field-effect transistors with channel lengths down to 20 nm fabricated using a facile angle evaporation process. By controlling the evaporation angle, the channel length of the transistors can be reproducibly controlled to be anywhere between 20 and 70 nm. The as-fabricated 20 nm top-gated BP transistors exhibit respectable on-state current (174 μA/μm) and transconductance (70 μS/μm) at a VDS of 0.1 V. Due to the use of two-dimensional BP as the channel material, the transistors exhibit relatively small short channel effects, preserving a decent on-off current ratio of 10(2) even at an extremely small channel length of 20 nm. Additionally, unlike the unencapsulated BP devices, which are known to be chemically unstable in ambient conditions, the top-gated BP transistors passivated by the Al2O3 gate dielectric layer remain stable without noticeable degradation in device performance after being stored in ambient conditions for more than 1 week. This work demonstrates the great promise of atomically thin BP for applications in ultimately scaled transistors.

Three-dimensional imaging of individual point defects using selective detection angles in annular dark field scanning transmission electron microscopy.

PubMed

Johnson, Jared M; Im, Soohyun; Windl, Wolfgang; Hwang, Jinwoo

2017-01-01

We propose a new scanning transmission electron microscopy (STEM) technique that can realize the three-dimensional (3D) characterization of vacancies, lighter and heavier dopants with high precision. Using multislice STEM imaging and diffraction simulations of β-Ga 2 O 3 and SrTiO 3 , we show that selecting a small range of low scattering angles can make the contrast of the defect-containing atomic columns substantially more depth-dependent. The origin of the depth-dependence is the de-channeling of electrons due to the existence of a point defect in the atomic column, which creates extra "ripples" at low scattering angles. The highest contrast of the point defect can be achieved when the de-channeling signal is captured using the 20-40mrad detection angle range. The effect of sample thickness, crystal orientation, local strain, probe convergence angle, and experimental uncertainty to the depth-dependent contrast of the point defect will also be discussed. The proposed technique therefore opens new possibilities for highly precise 3D structural characterization of individual point defects in functional materials. Copyright © 2016 Elsevier B.V. All rights reserved.

Atrioventricular depolarization differences identify coronary artery anomalies in Kawasaki disease.

PubMed

Cortez, Daniel; Sharma, Nandita; Jone, Pei-Ni

2017-03-01

Kawasaki disease (KD) is the leading cause of acquired heart disease in children. Signal average electrocardiogram changes in patients during the acute phase of KD with coronary artery anomalies (CAA) include depolarization changes. We set out to determine if 12-lead-derived atrioventricular depolarization differences can identify CAA in patients with KD. A blinded, retrospective case-control study of patients with KD was performed. Deep Q waves, corrected QT-intervals (QTc), spatial QRS-T angles, T-wave vector magnitudes (RMS-T), and a novel parameter for assessment of atrioventricular depolarization difference (the spatial PR angle) and a two dimensional PR angle were assessed. Comparisons between groups were performed to test for significant differences. One hundred one patients with KD were evaluated, with 68 having CAA (67.3%, mean age 3.6 ± 3.0 years, 82.6% male), and 32 without CAA (31.7%, mean age 2.7 ± 3.2 years, 70.4% male). The spatial PR angle significantly discriminated KD patients with CAA from those without, 59.7° ± 31.1° versus 41.6° ± 11.5° (p < .001). A spatial PR angle cutoff value of 56.9° gave positive/negative predictive values and odds ratios of 93.8%, 43.5%, and 11.5% (95% confidence interval (CI) 2.6-52.2). The two dimensional PR angle either below 7° or above 92° gave positive/negative predictive values and odds ratios of 100.0%, 38.8%, and 21.1% (95% CI 1.2-362.8). No other parameters significantly differentiated the groups. Atrioventricular depolarization differences, measured by the spatial or two dimensional PR angle differentiate KD patients with CAA versus those without. © 2016 Wiley Periodicals, Inc.

Pattern fidelity in nanoimprinted films using CD-SAXS

NASA Astrophysics Data System (ADS)

Jones, Ronald L.; Soles, Christopher L.; Lin, Eric K.; Hu, Walter; Reano, Ronald M.; Pang, Stella W.; Weigand, Steven J.; Keane, Denis T.; Quintana, John P.

2005-05-01

The primary measure of process quality in nanoimprint lithography (NIL) is the fidelity of pattern transfer, comparing the dimensions of the imprinted pattern to those of the mold. As a potential next generation lithography, NIL is capable of true nanofabrication, producing patterns of sub-10 nm dimensions. Routine production of nanoscale patterns will require new metrologies capable of non-destructive dimensional measurements of both the mold and the pattern with sub-nm precision. In this article, a rapid, non-destructive technique termed Critical Dimension Small Angle X-ray Scattering (CD-SAXS) is used to measure the cross sectional shape of both a pattern master, or mold, and the resulting imprinted films. CD-SAXS data are used to extract periodicity as well as pattern height, width, and sidewall angles. Films of varying materials are molded by thermal embossed NIL at temperatures both near and far from the bulk glass transition (TG). The polymer systems include a photoresist, representing a mixture of a polymer and small molecular components, and two pure homopolymers. Molding at low temperatures (T-TG < 40°C) produces small aspect ratio patterns that maintain periodicity to within a single nanometer, but feature large sidewall angles. While the pattern height does not reach that of the mold until very large imprinting temperatures (T-TG ~ 70°C), the pattern width of the mold is accurately transferred for T-TG > 30°C. In addition to obtaining basic dimensions, CD-SAXS data are used to assess the origin of loss in pattern fidelity.

Valence-band structure of organic radical p-CF3PNN investigated by angle-resolved photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Anzai, Hiroaki; Takakura, Ryosuke; Ono, Yusuke; Ishihara, Suzuna; Sato, Hitoshi; Namatame, Hirofumi; Taniguchi, Masaki; Matsui, Toshiyuki; Noguchi, Satoru; Hosokoshi, Yuko

2018-05-01

We study the electronic structure of p-trifluoromethylphenyl nitronyl nitroxide (p-CF3PNN), which forms a one-dimensional alternating antiferromagnetic chain of molecules, using angle-resolved photoemission spectroscopy. A singly occupied molecular orbital (SOMO) is observed clearly at ∼ 2 eV in the valence-band spectra. The small band gap and the overlap between the SOMO orbitals in the NO groups are associated with the antiferromagnetic interaction between neighboring spins.

Experimental and numerical study of a dual configuration for a flapping tidal current generator.

PubMed

Kim, Jihoon; Quang Le, Tuyen; Hwan Ko, Jin; Ebenezer Sitorus, Patar; Hartarto Tambunan, Indra; Kang, Taesam

2015-07-30

In this study, we conduct experimental and consecutive numerical analyses of a flapping tidal current generator with a mirror-type dual configuration with front-swing and rear-swing flappers. An experimental analysis of a small-scale prototype is conducted in a towing tank, and a numerical analysis is conducted by means of two-dimensional computational fluid dynamics simulations with an in-house code. An experimental study with a controller to determine the target arm angle shows that the resultant arm angle is dependent on the input arm angle, the frequency, and the applied load, while a high pitch is obtained simply with a high input arm angle. Through a parametric analysis conducted while varying these factors, a high applied load and a high input arm angle were found to be advantageous. Moreover, the optimal reduced frequency was found to be 0.125 in terms of the power extraction. In consecutive numerical investigations with the kinematics selected from the experiments, it was found that a rear-swing flapper contributes to the total amount of power more than a front-swing flapper with a distance of two times the chord length and with a 90° phase difference between the two. The high contribution stems from the high power generated by the rear-swing flapper, which mimics the tail fin movement of a dolphin along a flow, compared to a plunge system or a front-swing system, which mimics the tail fin movement of a dolphin against a flow. It is also due to the fact that the shed vorticities of the front-swing flapper slightly affect negatively or even positively the power performance of the rear-swing system at a given distance and phase angle.

Three-dimensional periodic supramolecular organic framework ion sponge in water and microcrystals

DOE PAGES

Tian, Jia; Zhou, Tian-You; Zhang, Shao-Chen; ...

2014-12-02

Self-assembly has emerged as a powerful approach to generating complex supramolecular architectures. Despite there being many crystalline frameworks reported in the solid state, the construction of highly soluble periodic supramolecular networks in a three-dimensional space is still a challenge. In this paper we demonstrate that the encapsulation motif, which involves the dimerization of two aromatic units within cucurbit[8]uril, can be used to direct the co-assembly of a tetratopic molecular block and cucurbit[8]uril into a periodic three-dimensional supramolecular organic framework in water. The periodicity of the supramolecular organic framework is supported by solution-phase small-angle X-ray-scattering and diffraction experiments. Upon evaporating themore » solvent, the periodicity of the framework is maintained in porous microcrystals. Lastly, as a supramolecular 'ion sponge', the framework can absorb different kinds of anionic guests, including drugs, in both water and microcrystals, and drugs absorbed in microcrystals can be released to water with selectivity.« less

Grazing-incidence small angle x-ray scattering studies of nanoscale polymer gratings

NASA Astrophysics Data System (ADS)

Doxastakis, Manolis; Suh, Hyo Seon; Chen, Xuanxuan; Rincon Delgadillo, Paulina A.; Wan, Lingshu; Williamson, Lance; Jiang, Zhang; Strzalka, Joseph; Wang, Jin; Chen, Wei; Ferrier, Nicola; Ramirez-Hernandez, Abelardo; de Pablo, Juan J.; Gronheid, Roel; Nealey, Paul

2015-03-01

Grazing-Incidence Small Angle X-ray Scattering (GISAXS) offers the ability to probe large sample areas, providing three-dimensional structural information at high detail in a thin film geometry. In this study we exploit the application of GISAXS to structures formed at one step of the LiNe (Liu-Nealey) flow using chemical patterns for directed self-assembly of block copolymer films. Experiments conducted at the Argonne National Laboratory provided scattering patterns probing film characteristics at both parallel and normal directions to the surface. We demonstrate the application of new computational methods to construct models based on scattering measured. Such analysis allows for extraction of structural characteristics at unprecedented detail.

Alphatome--Enhancing Spatial Reasoning: A Simulation in Two and Three Dimensions

ERIC Educational Resources Information Center

LeClair, Elizabeth E.

2003-01-01

Using refrigerator magnets, foam blocks, ink pads, and modeling clay, students manipulate the letters of the alphabet at multiple angles, reconstructing three-dimensional forms from two-dimensional data. This exercise increases students' spatial reasoning ability, an important component in many scientific disciplines. (Contains 5 figures.)

High frequency estimation of 2-dimensional cavity scattering

NASA Astrophysics Data System (ADS)

Dering, R. S.

1984-12-01

This thesis develops a simple ray tracing approximation for the high frequency scattering from a two-dimensional cavity. Whereas many other cavity scattering algorithms are very time consuming, this method is very swift. The analytical development of the ray tracing approach is performed in great detail, and it is shown how the radar cross section (RCS) depends on the cavity's length and width along with the radar wave's angle of incidence. This explains why the cavity's RCS oscillates as a function of incident angle. The RCS of a two dimensional cavity was measured experimentally, and these results were compared to computer calculations based on the high frequency ray tracing theory. The comparison was favorable in the sense that angular RCS minima and maxima were exactly predicted even though accuracy of the RCS magnitude decreased for incident angles far off-axis. Overall, once this method is extended to three dimensions, the technique shows promise as a fast first approximation of high frequency cavity scattering.

A Hierarchical Algorithm for Fast Debye Summation with Applications to Small Angle Scattering

PubMed Central

Gumerov, Nail A.; Berlin, Konstantin; Fushman, David; Duraiswami, Ramani

2012-01-01

Debye summation, which involves the summation of sinc functions of distances between all pair of atoms in three dimensional space, arises in computations performed in crystallography, small/wide angle X-ray scattering (SAXS/WAXS) and small angle neutron scattering (SANS). Direct evaluation of Debye summation has quadratic complexity, which results in computational bottleneck when determining crystal properties, or running structure refinement protocols that involve SAXS or SANS, even for moderately sized molecules. We present a fast approximation algorithm that efficiently computes the summation to any prescribed accuracy ε in linear time. The algorithm is similar to the fast multipole method (FMM), and is based on a hierarchical spatial decomposition of the molecule coupled with local harmonic expansions and translation of these expansions. An even more efficient implementation is possible when the scattering profile is all that is required, as in small angle scattering reconstruction (SAS) of macromolecules. We examine the relationship of the proposed algorithm to existing approximate methods for profile computations, and show that these methods may result in inaccurate profile computations, unless an error bound derived in this paper is used. Our theoretical and computational results show orders of magnitude improvement in computation complexity over existing methods, while maintaining prescribed accuracy. PMID:22707386

Localization and separation of acoustic sources by using a 2.5-dimensional circular microphone array.

PubMed

Bai, Mingsian R; Lai, Chang-Sheng; Wu, Po-Chen

2017-07-01

Circular microphone arrays (CMAs) are sufficient in many immersive audio applications because azimuthal angles of sources are considered more important than the elevation angles in those occasions. However, the fact that CMAs do not resolve the elevation angle well can be a limitation for some applications which involves three-dimensional sound images. This paper proposes a 2.5-dimensional (2.5-D) CMA comprised of a CMA and a vertical logarithmic-spacing linear array (LLA) on the top. In the localization stage, two delay-and-sum beamformers are applied to the CMA and the LLA, respectively. The direction of arrival (DOA) is estimated from the product of two array output signals. In the separation stage, Tikhonov regularization and convex optimization are employed to extract the source amplitudes on the basis of the estimated DOA. The extracted signals from two arrays are further processed by the normalized least-mean-square algorithm with the internal iteration to yield the source signal with improved quality. To validate the 2.5-D CMA experimentally, a three-dimensionally printed circular array comprised of a 24-element CMA and an eight-element LLA is constructed. Objective perceptual evaluation of speech quality test and a subjective listening test are also undertaken.

Performance Prediction of Darrieus-Type Hydroturbine with Inlet Nozzle Operated in Open Water Channels

NASA Astrophysics Data System (ADS)

Nakashima, K.; Watanabe, S.; Matsushita, D.; Tsuda, S.; Furukawa, A.

2016-11-01

Small hydropower is one of the renewable energies and is expected to be effectively used for local supply of electricity. We have developed Darrieus-type hydro-turbine systems, and among them, the Darrieus-turbine with a weir and a nozzle installed upstream of turbine is, so far, in success to obtain more output power by gathering all water into the turbine. However, there can several cases exist, in which installing the weir covering all the flow channel width is unrealistic, and in such cases, the turbine should be put alone in open channels without upstream weir. Since the output power is very small in such a utilization of small hydropower, it is important to derive more power for the cost reduction. In the present study, we parametrically investigate the preferable shape of the inlet nozzle for the Darrieus-type hydroturbine operated in an open flow channel. Experimental investigation is carried out in the open channel in our lab. Tested inlet nozzles are composed of two flat plates with the various nozzle converging angles and nozzle outlet (runner inlet) widths with the nozzle inlet width kept constant. As a result, the turbine with the nozzles having large converging angle and wide outlet width generates higher power. Two-dimensional unsteady numerical simulation is also carried out to qualitatively understand the flow mechanism leading to the better performance of turbine. Since the depth, the width and the flow rate in the real open flow channels are different from place to place and, in some cases from time to time, it is also important to predict the onsite performance of the hydroturbine from the lab experiment at planning stage. One-dimensional stream-tube model is developed for this purpose, in which the Darrieus-type hydroturbine with the inlet nozzle is considered as an actuator-disk modelled based on our experimental and numerical results.

Design and two dimensional cascade test of a jet-flap turbine stator blade with ratio of axial chord to spacing of 0.5

NASA Technical Reports Server (NTRS)

Stabe, R. G.

1971-01-01

A jet-flap blade was designed for a velocity diagram typical of the first-stage stator of a jet engine turbine and was tested in a simple two-dimensional cascade of six blades. The principal measurements were blade surface static pressure and cross-channel surveys of exit total pressure, static pressure, and flow angle. The results of the experimental investigation include blade loading, exit angle, flow, and loss data for a range of exit critical velocity ratios and three jet flow conditions.

Small animal magnetic resonance imaging: an efficient tool to assess liver volume and intrahepatic vascular anatomy.

PubMed

Melloul, Emmanuel; Raptis, Dimitri A; Boss, Andreas; Pfammater, Thomas; Tschuor, Christoph; Tian, Yinghua; Graf, Rolf; Clavien, Pierre-Alain; Lesurtel, Mickael

2014-04-01

To develop a noninvasive technique to assess liver volumetry and intrahepatic portal vein anatomy in a mouse model of liver regeneration. Fifty-two C57BL/6 male mice underwent magnetic resonance imaging (MRI) of the liver using a 4.7 T small animal MRI system after no treatment, 70% partial hepatectomy (PH), or selective portal vein embolization. The protocol consisted of the following sequences: three-dimensional-encoded spoiled gradient-echo sequence (repetition time per echo time 15 per 2.7 ms, flip angle 20°) for volumetry, and two-dimensional-encoded time-of-flight angiography sequence (repetition time per echo time 18 per 6.4 ms, flip angle 80°) for vessel visualization. Liver volume and portal vein segmentation was performed using a dedicated postprocessing software. In animals with portal vein embolization, portography served as reference standard. True liver volume was measured after sacrificing the animals. Measurements were carried out by two independent observers with subsequent analysis by the Cohen κ-test for interobserver agreement. MRI liver volumetry highly correlated with the true liver volume measurement using a conventional method in both the untreated liver and the liver remnant after 70% PH with a high interobserver correlation coefficient of 0.94 (95% confidence interval, 0.80-0.98 for untreated liver [P < 0.001] and 0.90-0.97 after 70% PH [P < 0.001]). The diagnostic accuracy of magnetic resonance angiography for the occlusion of one branch of the portal vein was 0.95 (95% confidence interval, 0.84-1). The level of agreement between the two observers for the description of intrahepatic vascular anatomy was excellent (Cohen κ value = 0.925). This protocol may be used for noninvasive liver volumetry and visualization of portal vein anatomy in mice. It will serve the dynamic study of new strategies to enhance liver regeneration in vivo. Copyright © 2014 Elsevier Inc. All rights reserved.

Quantitative 3D reconstruction of airway and pulmonary vascular trees using HRCT

NASA Astrophysics Data System (ADS)

Wood, Susan A.; Hoford, John D.; Hoffman, Eric A.; Zerhouni, Elias A.; Mitzner, Wayne A.

1993-07-01

Accurate quantitative measurements of airway and vascular dimensions are essential to evaluate function in the normal and diseased lung. In this report, a novel method is described for three-dimensional extraction and analysis of pulmonary tree structures using data from High Resolution Computed Tomography (HRCT). Serially scanned two-dimensional slices of the lower left lobe of isolated dog lungs were stacked to create a volume of data. Airway and vascular trees were three-dimensionally extracted using a three dimensional seeded region growing algorithm based on difference in CT number between wall and lumen. To obtain quantitative data, we reduced each tree to its central axis. From the central axis, branch length is measured as the distance between two successive branch points, branch angle is measured as the angle produced by two daughter branches, and cross sectional area is measured from a plane perpendicular to the central axis point. Data derived from these methods can be used to localize and quantify structural differences both during changing physiologic conditions and in pathologic lungs.

Miniature optical planar camera based on a wide-angle metasurface doublet corrected for monochromatic aberrations

PubMed Central

Arbabi, Amir; Arbabi, Ehsan; Kamali, Seyedeh Mahsa; Horie, Yu; Han, Seunghoon; Faraon, Andrei

2016-01-01

Optical metasurfaces are two-dimensional arrays of nano-scatterers that modify optical wavefronts at subwavelength spatial resolution. They are poised to revolutionize optics by enabling complex low-cost systems where multiple metasurfaces are lithographically stacked and integrated with electronics. For imaging applications, metasurface stacks can perform sophisticated image corrections and can be directly integrated with image sensors. Here we demonstrate this concept with a miniature flat camera integrating a monolithic metasurface lens doublet corrected for monochromatic aberrations, and an image sensor. The doublet lens, which acts as a fisheye photographic objective, has a small f-number of 0.9, an angle-of-view larger than 60° × 60°, and operates at 850 nm wavelength with 70% focusing efficiency. The camera exhibits nearly diffraction-limited image quality, which indicates the potential of this technology in the development of optical systems for microscopy, photography, and computer vision. PMID:27892454

Miniature optical planar camera based on a wide-angle metasurface doublet corrected for monochromatic aberrations

NASA Astrophysics Data System (ADS)

Arbabi, Amir; Arbabi, Ehsan; Kamali, Seyedeh Mahsa; Horie, Yu; Han, Seunghoon; Faraon, Andrei

2016-11-01

Optical metasurfaces are two-dimensional arrays of nano-scatterers that modify optical wavefronts at subwavelength spatial resolution. They are poised to revolutionize optics by enabling complex low-cost systems where multiple metasurfaces are lithographically stacked and integrated with electronics. For imaging applications, metasurface stacks can perform sophisticated image corrections and can be directly integrated with image sensors. Here we demonstrate this concept with a miniature flat camera integrating a monolithic metasurface lens doublet corrected for monochromatic aberrations, and an image sensor. The doublet lens, which acts as a fisheye photographic objective, has a small f-number of 0.9, an angle-of-view larger than 60° × 60°, and operates at 850 nm wavelength with 70% focusing efficiency. The camera exhibits nearly diffraction-limited image quality, which indicates the potential of this technology in the development of optical systems for microscopy, photography, and computer vision.

Three-dimensional structure of the heliosphere as inferred from observations with a Japanese Halley spacecraft

NASA Technical Reports Server (NTRS)

Saito, T.; Yumoto, K.; Hirao, K.; Aoyama, I.; Smith, E. J.

1986-01-01

A sinusoidal neutral line with a pair of giant regions appeared on the sun about one year before the launch of 'Sakigake', the first of two Japanese Comet Halley spacecraft. The Sakigake magnetometer data during the early part of the mission (February-March 1985) are well interpreted by an eastward shift of the tilting neutral sheet. The shift is further explained by an effect of a new giant region appearing at about 10 deg heliolatitude and about 50 deg Carrington longitude in August 1984. The toward polarity ratio of IMF observed by Sakigake changed from about 22 percent in February to about 62 percent in early June and then increased rapidly up to 98 percent. This ratio is interpreted as a decrease of the tilt angle of the sheet down to only about 4 deg. It is the first spacecraft observation of 'the disappearing sector structure' with such small tilt angle.

Magic tilt angle for stabilizing two-dimensional solitons by dipole-dipole interactions

NASA Astrophysics Data System (ADS)

Chen, Xing-You; Chuang, You-Lin; Lin, Chun-Yan; Wu, Chien-Ming; Li, Yongyao; Malomed, Boris A.; Lee, Ray-Kuang

2017-10-01

In the framework of the Gross-Pitaevskii equation, we study the formation and stability of effectively two-dimensional solitons in dipolar Bose-Einstein condensates (BECs), with dipole moments polarized at an arbitrary angle θ relative to the direction normal to the system's plane. Using numerical methods and the variational approximation, we demonstrate that unstable Townes solitons, created by the contact attractive interaction, may be completely stabilized (with an anisotropic shape) by the dipole-dipole interaction (DDI), in the interval θcr<θ ≤π /2 . The stability boundary θcr weakly depends on the relative strength of the DDI, remaining close to the magic angle θm=arccos(1 /√{3 }) . The results suggest that DDIs provide a generic mechanism for the creation of stable BEC solitons in higher dimensions.

A Highly Sensitive Two-Dimensional Inclinometer Based on Two Etched Chirped-Fiber-Grating Arrays †

PubMed Central

Chang, Hung-Ying; Chang, Yu-Chung; Liu, Wen-Fung

2017-01-01

We present a novel two-dimensional fiber-optic inclinometer with high sensitivity by crisscrossing two etched chirped fiber Bragg gratings (CFBG) arrays. Each array is composed of two symmetrically-arranged CFBGs. By etching away most of the claddings of the CFBGs to expose the evanescent wave, the reflection spectra are highly sensitive to the surrounding index change. When we immerse only part of the CFBG in liquid, the effective index difference induces a superposition peak in the refection spectrum. By interrogating the peak wavelengths of the CFBGs, we can deduce the tilt angle and direction simultaneously. The inclinometer has a resolution of 0.003° in tilt angle measurement and 0.00187 rad in tilt direction measurement. Due to the unique sensing mechanism, the sensor is temperature insensitive. This sensor can be useful in long term continuous monitoring of inclination or in real-time feedback control of tilt angles, especially in harsh environments with violent temperature variation. PMID:29244770

Two-dimensional time-resolved X-ray diffraction study of liquid/solid fraction and solid particle size in Fe-C binary system with an electrostatic levitator furnace

NASA Astrophysics Data System (ADS)

Yonemura, M.; Okada, J.; Watanabe, Y.; Ishikawa, T.; Nanao, S.; Shobu, T.; Toyokawa, H.

2013-03-01

Liquid state provides functions such as matter transport or a reaction field and plays an important role in manufacturing processes such as refining, forging or welding. However, experimental procedures are significantly difficult for an observation of solidification process of iron and iron-based alloys in order to identify rapid transformations subjected to fast temperature evolution. Therefore, in order to study the solidification in iron and iron-based alloys, we considered a combination of high energy X-ray diffraction measurements and an electrostatic levitation method (ESL). In order to analyze the liquid/solid fraction, the solidification of melted spherical specimens was measured at a time resolution of 0.1 seconds during rapid cooling using the two-dimensional time-resolved X-ray diffraction. Furthermore, the observation of particle sizes and phase identification was performed on a trial basis using X-ray small angle scattering with X-ray diffraction.

Review of the fundamental theories behind small angle X-ray scattering, molecular dynamics simulations, and relevant integrated application.

PubMed

Boldon, Lauren; Laliberte, Fallon; Liu, Li

2015-01-01

In this paper, the fundamental concepts and equations necessary for performing small angle X-ray scattering (SAXS) experiments, molecular dynamics (MD) simulations, and MD-SAXS analyses were reviewed. Furthermore, several key biological and non-biological applications for SAXS, MD, and MD-SAXS are presented in this review; however, this article does not cover all possible applications. SAXS is an experimental technique used for the analysis of a wide variety of biological and non-biological structures. SAXS utilizes spherical averaging to produce one- or two-dimensional intensity profiles, from which structural data may be extracted. MD simulation is a computer simulation technique that is used to model complex biological and non-biological systems at the atomic level. MD simulations apply classical Newtonian mechanics' equations of motion to perform force calculations and to predict the theoretical physical properties of the system. This review presents several applications that highlight the ability of both SAXS and MD to study protein folding and function in addition to non-biological applications, such as the study of mechanical, electrical, and structural properties of non-biological nanoparticles. Lastly, the potential benefits of combining SAXS and MD simulations for the study of both biological and non-biological systems are demonstrated through the presentation of several examples that combine the two techniques.

Magnetic small-angle neutron scattering of bulk ferromagnets.

PubMed

Michels, Andreas

2014-09-24

We summarize recent theoretical and experimental work in the field of magnetic small-angle neutron scattering (SANS) of bulk ferromagnets. The response of the magnetization to spatially inhomogeneous magnetic anisotropy and magnetostatic stray fields is computed using linearized micromagnetic theory, and the ensuing spin-misalignment SANS is deduced. Analysis of experimental magnetic-field-dependent SANS data of various nanocrystalline ferromagnets corroborates the usefulness of the approach, which provides important quantitative information on the magnetic-interaction parameters such as the exchange-stiffness constant, the mean magnetic anisotropy field, and the mean magnetostatic field due to jumps ΔM of the magnetization at internal interfaces. Besides the value of the applied magnetic field, it turns out to be the ratio of the magnetic anisotropy field Hp to ΔM, which determines the properties of the magnetic SANS cross-section of bulk ferromagnets; specifically, the angular anisotropy on a two-dimensional detector, the asymptotic power-law exponent, and the characteristic decay length of spin-misalignment fluctuations. For the two most often employed scattering geometries where the externally applied magnetic field H0 is either perpendicular or parallel to the wave vector k0 of the incoming neutron beam, we provide a compilation of the various unpolarized, half-polarized (SANSPOL), and uniaxial fully-polarized (POLARIS) SANS cross-sections of magnetic materials.

Effects of Controlled Three-Dimensional Perturbations on Boundary Layer Transition

DTIC Science & Technology

1989-03-10

49 3.3.1.3 Measured Angles .................... 61 3.3.2 Nonlinear Oblique Waves ................... .67 3.3.2.1 Higher...can be seen from the fact that there is still no well-grounded method for predicting transition point location, even for a two-dimensional airfoil ...Experiment is at F 9.2 x 10-’ and Re 6- = 1400, which is not quite the same. However, the trend with oblique angle should be quite similar. - 61

Crossflow in two-dimensional asymmetric nozzles

NASA Technical Reports Server (NTRS)

Sebacher, D. I.; Lee, L. P.

1975-01-01

An experimental investigation of the crossflow effects in three contoured, two-dimensional asymmetric nozzles is described. The data were compared with theoretical predictions of nozzle flow by using an inviscid method of characteristics solution and two-dimensional turbulent boundary-layer calculations. The effect of crossflow as a function of the nozzle maximum expansion angle was studied by use of oil-flow techniques, static wall-pressure measurements, and impact-pressure surveys at the nozzle exit. Reynolds number effects on crossflow were investigated.

Evaluation of solution stability for two-component polydisperse systems by small-angle scattering

NASA Astrophysics Data System (ADS)

Kryukova, A. E.; Konarev, P. V.; Volkov, V. V.

2017-12-01

The article is devoted to the modelling of small-angle scattering data using the program MIXTURE designed for the study of polydisperse multicomponent mixtures. In this work we present the results of solution stability studies for theoretical small-angle scattering data sets from two-component models. It was demonstrated that the addition of the noise to the data influences the stability range of the restored structural parameters. The recommendations for the optimal minimization schemes that permit to restore the volume size distributions for polydisperse systems are suggested.

Positioning and joining of organic single-crystalline wires

PubMed Central

Wu, Yuchen; Feng, Jiangang; Jiang, Xiangyu; Zhang, Zhen; Wang, Xuedong; Su, Bin; Jiang, Lei

2015-01-01

Organic single-crystal, one-dimensional materials can effectively carry charges and/or excitons due to their highly ordered molecule packing, minimized defects and eliminated grain boundaries. Controlling the alignment/position of organic single-crystal one-dimensional architectures would allow on-demand photon/electron transport, which is a prerequisite in waveguides and other optoelectronic applications. Here we report a guided physical vapour transport technique to control the growth, alignment and positioning of organic single-crystal wires with the guidance of pillar-structured substrates. Submicrometre-wide, hundreds of micrometres long, highly aligned, organic single-crystal wire arrays are generated. Furthermore, these organic single-crystal wires can be joined within controlled angles by varying the pillar geometries. Owing to the controllable growth of organic single-crystal one-dimensional architectures, we can present proof-of-principle demonstrations utilizing joined wires to allow optical waveguide through small radii of curvature (internal angles of ~90–120°). Our methodology may open a route to control the growth of organic single-crystal one-dimensional materials with potential applications in optoelectronics. PMID:25814032

SAR Processing Based On Two-Dimensional Transfer Function

NASA Technical Reports Server (NTRS)

Chang, Chi-Yung; Jin, Michael Y.; Curlander, John C.

1994-01-01

Exact transfer function, ETF, is two-dimensional transfer function that constitutes basis of improved frequency-domain-convolution algorithm for processing synthetic-aperture-radar, SAR data. ETF incorporates terms that account for Doppler effect of motion of radar relative to scanned ground area and for antenna squint angle. Algorithm based on ETF outperforms others.

Pressure-distribution measurements on a transonic low-aspect ratio wing

NASA Technical Reports Server (NTRS)

Keener, E. R.

1985-01-01

Experimental surface pressure distributions and oil flow photographs are presented for a 0.90 m semispan model of NASA/Lockheed Wing C, a generic transonic, supercritical, low aspect ratio, highly 3-dimensional configuration. This wing was tested at the design angle of attack of 5 deg over a Mach number range from 0.25 to 0.96, and a Reynolds number range from 3.4 x 1,000,000 to 10 x 1,000,000. Pressures were measured with both the tunnel floor and ceiling suction slots open for most of the tests but taped closed for some tests to simulate solid walls. A comparison is made with the measured pressures from a small model in high Reynolds number facility and with predicted pressures using two three dimesional, transonic full potential flow wing codes: design code FLO22 (nonconservative) and TWING code (conservative). At the given design condition, a small region of flow separation occurred. At a Mach number of 0.82 the flow was unseparated and the surface flow angles were less than 10 deg, indicating that the boundary layer flow was not 3-D. Evidence indicate that wings that are optimized for mild shock waves and mild pressure recovery gradients generally have small 3-D boundary layer flow at design conditions for unseparated flow.

Comparison of Dimensional Accuracy between Open-Tray and Closed-Tray Implant Impression Technique in 15° Angled Implants

PubMed Central

Balouch, F; Jalalian, E; Nikkheslat, M; Ghavamian, R; Toopchi, Sh; Jallalian, F; Jalalian, S

2013-01-01

Statement of Problem: Various impression techniques have different effects on the accuracy of final cast dimensions. Meanwhile; there are some controversies about the best technique. Purpose: This study was performed to compare two kinds of implant impression methods (open tray and closed tray) on 15 degree angled implants. Materials and Method: In this experimental study, a steel model with 8 cm in diameter and 3 cm in height were produced with 3 holes devised inside to stabilize 3 implants. The central implant was straight and the other two implants were 15° angled. The two angled implants had 5 cm distance from each other and 3.5 cm from the central implant. Dental stone, high strength (type IV) was used for the main casts. Impression trays were filled with poly ether, and then the two impression techniques (open tray and closed tray) were compared. To evaluate positions of the implants, each cast was analyzed by CMM device in 3 dimensions (x,y,z). Differences in the measurements obtained from final casts and laboratory model were analyzed using t-Test. Results: The obtained results indicated that closed tray impression technique was significantly different in dimensional accuracy when compared with open tray method. Dimensional changes were 129 ± 37μ and 143.5 ± 43.67μ in closed tray and open tray, while coefficient of variation in closed- tray and open tray were reported to be 27.2% and 30.4%, respectively. Conclusion: Closed impression technique had less dimensional changes in comparison with open tray method, so this study suggests that closed tray impression technique is more accurate. PMID:24724130

Multi-dimensional position sensor using range detectors

DOEpatents

Vann, Charles S.

2000-01-01

A small, non-contact optical sensor uses ranges and images to detect its relative position to an object in up to six degrees of freedom. The sensor has three light emitting range detectors which illuminate a target and can be used to determine distance and two tilt angles. A camera located between the three range detectors senses the three remaining degrees of freedom, two translations and one rotation. Various range detectors, with different light sources, e.g. lasers and LEDs, different collection options, and different detection schemes, e.g. diminishing return and time of flight can be used. This sensor increases the capability and flexibility of computer controlled machines, e.g. it can instruct a robot how to adjust automatically to different positions and orientations of a part.

A Method for Computing Three-Dimensional Viscous Flows over an Ogival Body at Angle of Attack

DTIC Science & Technology

1976-02-01

the ogival body problems; however, some gen- erality is still maintained by considering coordinate systems that are generated from any two ...transformation. We shall assume that the covariant derivative is the natural one derivable from the metric. This is known as the Levi - Civita connection (Ref...MV..»^^.^ R76-91202^-8 I A Method for Computing Three-Dimensional Viscoua Flows Over an Ogival Body at Angle of Attack TABLE OF CONTENTS

Nanocrystalline copper films are never flat

NASA Astrophysics Data System (ADS)

Zhang, Xiaopu; Han, Jian; Plombon, John J.; Sutton, Adrian P.; Srolovitz, David J.; Boland, John J.

2017-07-01

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy.

Reconstructing the equilibrium Boltzmann distribution from well-tempered metadynamics.

PubMed

Bonomi, M; Barducci, A; Parrinello, M

2009-08-01

Metadynamics is a widely used and successful method for reconstructing the free-energy surface of complex systems as a function of a small number of suitably chosen collective variables. This is achieved by biasing the dynamics of the system. The bias acting on the collective variables distorts the probability distribution of the other variables. Here we present a simple reweighting algorithm for recovering the unbiased probability distribution of any variable from a well-tempered metadynamics simulation. We show the efficiency of the reweighting procedure by reconstructing the distribution of the four backbone dihedral angles of alanine dipeptide from two and even one dimensional metadynamics simulation. 2009 Wiley Periodicals, Inc.

Three-dimensionality of the bulk electronic structure in WTe 2

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

Wu, Yun; Jo, Na Hyun; Mou, Daixiang

Inmore » this paper, we use temperature- and field-dependent resistivity measurements (Shubnikov–de Haas quantum oscillations) and ultrahigh-resolution, tunable, vacuum ultraviolet laser-based angle-resolved photoemission spectroscopy (ARPES) to study the three-dimensionality (3D) of the bulk electronic structure in WTe 2 , a type II Weyl semimetal. The bulk Fermi surface (FS) consists of two pairs of electron pockets and two pairs of hole pockets along the Χ–Γ–Χ direction as detected by using an incident photon energy of 6.7 eV, which is consistent with the previously reported data. However, if using an incident photon energy of 6.36 eV, another pair of tiny electron pockets is detected on both sides of the Γ point, which is in agreement with the small quantum oscillation frequency peak observed in the magnetoresistance. Therefore, the bulk, 3D FS consists of three pairs of electron pockets and two pairs of hole pockets in total. With the ability of fine tuning the incident photon energy, we demonstrate the strong three-dimensionality of the bulk electronic structure in WTe 2 . Finally, the combination of resistivity and ARPES measurements reveals the complete, and consistent, picture of the bulk electronic structure of this material.« less

Three-dimensionality of the bulk electronic structure in WTe 2

DOE PAGES

Wu, Yun; Jo, Na Hyun; Mou, Daixiang; ...

2017-05-18

Inmore » this paper, we use temperature- and field-dependent resistivity measurements (Shubnikov–de Haas quantum oscillations) and ultrahigh-resolution, tunable, vacuum ultraviolet laser-based angle-resolved photoemission spectroscopy (ARPES) to study the three-dimensionality (3D) of the bulk electronic structure in WTe 2 , a type II Weyl semimetal. The bulk Fermi surface (FS) consists of two pairs of electron pockets and two pairs of hole pockets along the Χ–Γ–Χ direction as detected by using an incident photon energy of 6.7 eV, which is consistent with the previously reported data. However, if using an incident photon energy of 6.36 eV, another pair of tiny electron pockets is detected on both sides of the Γ point, which is in agreement with the small quantum oscillation frequency peak observed in the magnetoresistance. Therefore, the bulk, 3D FS consists of three pairs of electron pockets and two pairs of hole pockets in total. With the ability of fine tuning the incident photon energy, we demonstrate the strong three-dimensionality of the bulk electronic structure in WTe 2 . Finally, the combination of resistivity and ARPES measurements reveals the complete, and consistent, picture of the bulk electronic structure of this material.« less

The bifurcations of nearly flat origami

NASA Astrophysics Data System (ADS)

Santangelo, Christian

Self-folding origami structures provide one means of fabricating complex, three-dimensional structures from a flat, two-dimensional sheet. Self-folding origami structures have been fabricated on scales ranging from macroscopic to microscopic and can have quite complicated structures with hundreds of folds arranged in complex patterns. I will describe our efforts to understand the mechanics and energetics of self-folding origami structures. Though the dimension of the configuration space of an origami structure scales with the size of the boundary and not with the number of vertices in the interior of the structure, a typical origami structure is also floppy in the sense that there are many possible ways to assign fold angles consistently. I will discuss our theoretical progress in understanding the geometry of the configuration space of origami. For random origami, the number of possible bifurcations grows surprisingly quickly even when the dimension of the configuration space is small. EFRI ODISSEI-1240441, DMR-0846582.

Two routes to expertise in mental rotation.

PubMed

Provost, Alexander; Johnson, Blake; Karayanidis, Frini; Brown, Scott D; Heathcote, Andrew

2013-01-01

The ability to imagine objects undergoing rotation (mental rotation) improves markedly with practice, but an explanation of this plasticity remains controversial. Some researchers propose that practice speeds up the rate of a general-purpose rotation algorithm. Others maintain that performance improvements arise through the adoption of a new cognitive strategy-repeated exposure leads to rapid retrieval from memory of the required response to familiar mental rotation stimuli. In two experiments we provide support for an integrated explanation of practice effects in mental rotation by combining behavioral and EEG measures in a way that provides more rigorous inference than is available from either measure alone. Before practice, participants displayed two well-established signatures of mental rotation: Both response time and EEG negativity increased linearly with rotation angle. After extensive practice with a small set of stimuli, both signatures of mental rotation had all but disappeared. In contrast, after the same amount of practice with a much larger set both signatures remained, even though performance improved markedly. Taken together, these results constitute a reversed association, which cannot arise from variation in a single cause, and so they provide compelling evidence for the existence of two routes to expertise in mental rotation. We also found novel evidence that practice with the large but not the small stimulus set increased the magnitude of an early visual evoked potential, suggesting increased rotation speed is enabled by improved efficiency in extracting three-dimensional information from two-dimensional stimuli. © 2013 Cognitive Science Society, Inc.

Aerodynamic performance of high turning core turbine vanes in a two dimensional cascade

NASA Technical Reports Server (NTRS)

Schwab, J. R.

1982-01-01

Experimental and theoretical aerodynamic performance data are presented for four uncooled high turning core turbine vanes with exit angles of 74.9, 75.0, 77.5, and 79.6 degrees in a two dimensional cascade. Data for a more conservative 67.0 degree vane are included for comparison. Correction of the experimental aftermix kinetic energy losses to a common 0.100 centimeter trailing edge thickness yields a linear trend of increased loss from 0.020 to 0.025 as the vane exit angle increases from 67.0 to 79.6 degrees. The theoretical losses show a similar trend. The experimental and theoretical vane surface velocity distributions generally agree within approximately five percent, although the suction surface theoretical velocities are generally higher than the experimental velocities as the vane exit angle increases.

Anisotropic mean-square displacements in two-dimensional colloidal crystals of tilted dipoles

NASA Astrophysics Data System (ADS)

Froltsov, V. A.; Likos, C. N.; Löwen, H.; Eisenmann, C.; Gasser, U.; Keim, P.; Maret, G.

2005-03-01

Superparamagnetic colloidal particles confined to a flat horizontal air-water interface in an external magnetic field, which is tilted relative to the interface, form anisotropic two-dimensional crystals resulting from their mutual dipole-dipole interactions. Using real-space experiments and harmonic lattice theory we explore the mean-square displacements of the particles in the directions parallel and perpendicular to the in-plane component of the external magnetic field as a function of the tilt angle. We find that the anisotropy of the mean-square displacement behaves nonmonotonically as a function of the tilt angle and does not correlate with the structural anisotropy of the crystal.

Investigation of a free-tip rotor configuration for research on spanwise life distributions and wake velocity surveys of a semi-span wing with a discontinuous twist

NASA Technical Reports Server (NTRS)

Fortin, Paul; Kumagai, Hiroyuki

1989-01-01

A wind tunnel test was conducted in the NASA Ames 7 x 10 Foot Wind Tunnel to investigate the lift distribution on a semi-span wing with a discontinuous change in spanwise twist. The semi-span wing had a tip with an adjustable pitch angle independent on the inboard section pitch angle simulating the free-tip rotor blade when its free-tip is at a deflected position. The spanwise lift distribution over the wing and the tip were measured and three component velocity surveys behind the wing were obtained with a three dimensional laser Doppler velocimeter (LV) with the wing at one angle of attack and the tip deflected at different pitch angles. A six component internal strain gage balance was also used to measure total forces and moments on the tip. The three dimensional lift was computed from the two dimensional life distributions obtained from the LV and from the strain gage balance. The results from both experimental methods are shown to be in agreement with predictions made by a steady, three dimensional panel code, VSAERO.

A small-angle x-ray scattering system with a vertical layout.

PubMed

Wang, Zhen; Chen, Xiaowei; Meng, Lingpu; Cui, Kunpeng; Wu, Lihui; Li, Liangbin

2014-12-01

A small-angle x-ray scattering (SAXS) system with a vertical layout (V-SAXS) has been designed and constructed for in situ detection on nanostructures, which is well suitable for in situ study on self-assembly of nanoparticles at liquid interface and polymer processing. A steel-tower frame on a reinforced basement is built as the supporting skeleton for scattering beam path and detector platform, ensuring the system a high working stability and a high operating accuracy. A micro-focus x-ray source combining parabolic three-dimensional multi-layer mirror and scatteringless collimation system provides a highly parallel beam, which allows us to detect the very small angle range. With a sample-to-detector distance of 7 m, the largest measurable length scale is 420 nm in real space. With a large sample zone, it is possible to install different experimental setups such as film stretching machine, which makes the system perfect to follow the microstructures evolution of materials during processing. The capability of the V-SAXS on in situ study is tested with a drying experiment of a free latex droplet, which confirms our initial design.

Cohomological rigidity of manifolds defined by 3-dimensional polytopes

NASA Astrophysics Data System (ADS)

Buchstaber, V. M.; Erokhovets, N. Yu.; Masuda, M.; Panov, T. E.; Park, S.

2017-04-01

A family of closed manifolds is said to be cohomologically rigid if a cohomology ring isomorphism implies a diffeomorphism for any two manifolds in the family. Cohomological rigidity is established here for large families of 3-dimensional and 6-dimensional manifolds defined by 3-dimensional polytopes. The class \\mathscr{P} of 3-dimensional combinatorial simple polytopes P different from tetrahedra and without facets forming 3- and 4-belts is studied. This class includes mathematical fullerenes, that is, simple 3- polytopes with only 5-gonal and 6-gonal facets. By a theorem of Pogorelov, any polytope in \\mathscr{P} admits in Lobachevsky 3-space a right-angled realisation which is unique up to isometry. Our families of smooth manifolds are associated with polytopes in the class \\mathscr{P}. The first family consists of 3-dimensional small covers of polytopes in \\mathscr{P}, or equivalently, hyperbolic 3-manifolds of Löbell type. The second family consists of 6-dimensional quasitoric manifolds over polytopes in \\mathscr{P}. Our main result is that both families are cohomologically rigid, that is, two manifolds M and M' from either family are diffeomorphic if and only if their cohomology rings are isomorphic. It is also proved that if M and M' are diffeomorphic, then their corresponding polytopes P and P' are combinatorially equivalent. These results are intertwined with classical subjects in geometry and topology such as the combinatorics of 3-polytopes, the Four Colour Theorem, aspherical manifolds, a diffeomorphism classification of 6-manifolds, and invariance of Pontryagin classes. The proofs use techniques of toric topology. Bibliography: 69 titles.

Singular-Arc Time-Optimal Trajectory of Aircraft in Two-Dimensional Wind Field

NASA Technical Reports Server (NTRS)

Nguyen, Nhan

2006-01-01

This paper presents a study of a minimum time-to-climb trajectory analysis for aircraft flying in a two-dimensional altitude dependent wind field. The time optimal control problem possesses a singular control structure when the lift coefficient is taken as a control variable. A singular arc analysis is performed to obtain an optimal control solution on the singular arc. Using a time-scale separation with the flight path angle treated as a fast state, the dimensionality of the optimal control solution is reduced by eliminating the lift coefficient control. A further singular arc analysis is used to decompose the original optimal control solution into the flight path angle solution and a trajectory solution as a function of the airspeed and altitude. The optimal control solutions for the initial and final climb segments are computed using a shooting method with known starting values on the singular arc The numerical results of the shooting method show that the optimal flight path angle on the initial and final climb segments are constant. The analytical approach provides a rapid means for analyzing a time optimal trajectory for aircraft performance.

Conventions and workflows for using Situs

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

Wriggers, Willy, E-mail: wriggers@biomachina.org

2012-04-01

Recent developments of the Situs software suite for multi-scale modeling are reviewed. Typical workflows and conventions encountered during processing of biophysical data from electron microscopy, tomography or small-angle X-ray scattering are described. Situs is a modular program package for the multi-scale modeling of atomic resolution structures and low-resolution biophysical data from electron microscopy, tomography or small-angle X-ray scattering. This article provides an overview of recent developments in the Situs package, with an emphasis on workflows and conventions that are important for practical applications. The modular design of the programs facilitates scripting in the bash shell that allows specific programs tomore » be combined in creative ways that go beyond the original intent of the developers. Several scripting-enabled functionalities, such as flexible transformations of data type, the use of symmetry constraints or the creation of two-dimensional projection images, are described. The processing of low-resolution biophysical maps in such workflows follows not only first principles but often relies on implicit conventions. Situs conventions related to map formats, resolution, correlation functions and feature detection are reviewed and summarized. The compatibility of the Situs workflow with CCP4 conventions and programs is discussed.« less

Jet oscillations caused by vorticity interactions with shock waves

NASA Technical Reports Server (NTRS)

Parthasarathy, S. P.; Harstad, K.; Massier, P. F.

1981-01-01

A linear theory is developed for the amplification of disturbances along a jet containing shock waves. The theory indicates that near grazing angles (i.e., wave angles near 90 deg) horizontal vorticity is greatly amplified after passing through the two shock waves that exist in a shock cell. The cumulative amplification and the mode that is amplified most can be obtained if the changes in shock parameters from cell to cell are known. Rapid rates of growth of disturbances are exhibited by shadowgraphs and rates of angular displacement of about 10 are observed. The linear two-dimensional theory also indicates that such rates of amplification occur, and that the behavior of a two-dimensional jet is qualitatively similar to that of a round jet.

Application of advanced shearing techniques to the calibration of autocollimators with small angle generators and investigation of error sources.

PubMed

Yandayan, T; Geckeler, R D; Aksulu, M; Akgoz, S A; Ozgur, B

2016-05-01

The application of advanced error-separating shearing techniques to the precise calibration of autocollimators with Small Angle Generators (SAGs) was carried out for the first time. The experimental realization was achieved using the High Precision Small Angle Generator (HPSAG) of TUBITAK UME under classical dimensional metrology laboratory environmental conditions. The standard uncertainty value of 5 mas (24.2 nrad) reached by classical calibration method was improved to the level of 1.38 mas (6.7 nrad). Shearing techniques, which offer a unique opportunity to separate the errors of devices without recourse to any external standard, were first adapted by Physikalisch-Technische Bundesanstalt (PTB) to the calibration of autocollimators with angle encoders. It has been demonstrated experimentally in a clean room environment using the primary angle standard of PTB (WMT 220). The application of the technique to a different type of angle measurement system extends the range of the shearing technique further and reveals other advantages. For example, the angular scales of the SAGs are based on linear measurement systems (e.g., capacitive nanosensors for the HPSAG). Therefore, SAGs show different systematic errors when compared to angle encoders. In addition to the error-separation of HPSAG and the autocollimator, detailed investigations on error sources were carried out. Apart from determination of the systematic errors of the capacitive sensor used in the HPSAG, it was also demonstrated that the shearing method enables the unique opportunity to characterize other error sources such as errors due to temperature drift in long term measurements. This proves that the shearing technique is a very powerful method for investigating angle measuring systems, for their improvement, and for specifying precautions to be taken during the measurements.

Characterization of zein assemblies by ultra-small-angle X-ray scattering

DOE PAGES

Uzun, Suzan; Ilavsky, Jan; Padua, Graciela Wild

2017-03-23

Zein, a protein of corn, has an amphiphilic molecule capable of self-assembly into distinctly different structures. In this work, ultra-small-angle X-ray scattering (USAXS) was applied to investigate the formation of self-assembled zein structures in binary solvent systems of ethanol and water. Our study included observing structural changes due to aging. Three hierarchical structures were identified in zein-solvent systems, molecular zein 2D films, believed to be formed by zein rods assembled first into one-dimensional fibers and then into two-dimensional films, and 3D spherical aggregates. Aging did not change the size or shape of primary units, but promoted their self-assembly into intermediatemore » 2D structures and shaped 3D structures into well19 defined spheres. We found that the rheological parameters, consistency index (K) and behavior index (n), storage and loss moduli (G’ and G”) were also measured. K and n, changed markedly with aging, from nearly Newtonian low consistency fresh samples to highly viscous pseudoplastic aged samples. G’ and G” increased with aging for all samples reflecting increased interactions among zein self-assembled structures. Furthermore, viscoelastic parameters indicated that zein dispersions formed gels upon aging. It was observed that USAX reported on molecular scale self-assembly processes, while rheological measurements reported on the macroscale interaction between self-assembled particles. Raman spectra suggested that α-helix to β-sheet transformations prompted zein self-assembly, which influenced the size and morphology of molecular assemblies and ultimately the rheological properties of zein dispersions.« less

β-connectin studies by small-angle x-ray scattering and single-molecule force spectroscopy by atomic force microscopy

NASA Astrophysics Data System (ADS)

Marchetti, S.; Sbrana, F.; Toscano, A.; Fratini, E.; Carlà, M.; Vassalli, M.; Tiribilli, B.; Pacini, A.; Gambi, C. M. C.

2011-05-01

The three-dimensional structure and the mechanical properties of a β-connectin fragment from human cardiac muscle, belonging to the I band, from I27 to I34, were investigated by small-angle x-ray scattering (SAXS) and single-molecule force spectroscopy (SMFS). This molecule presents an entropic elasticity behavior, associated to globular domain unfolding, that has been widely studied in the last 10 years. In addition, atomic force microscopy based SMFS experiments suggest that this molecule has an additional elastic regime, for low forces, probably associated to tertiary structure remodeling. From a structural point of view, this behavior is a mark of the fact that the eight domains in the I27-I34 fragment are not independent and they organize in solution, assuming a well-defined three-dimensional structure. This hypothesis has been confirmed by SAXS scattering, both on a diluted and a concentrated sample. Two different models were used to fit the SAXS curves: one assuming a globular shape and one corresponding to an elongated conformation, both coupled with a Coulomb repulsion potential to take into account the protein-protein interaction. Due to the predominance of the structure factor, the effective shape of the protein in solution could not be clearly disclosed. By performing SMFS by atomic force microscopy, mechanical unfolding properties were investigated. Typical sawtooth profiles were obtained and the rupture force of each unfolding domain was estimated. By fitting a wormlike chain model to each peak of the sawtooth profile, the entropic elasticity of octamer was described.

NMR structure calculation for all small molecule ligands and non-standard residues from the PDB Chemical Component Dictionary.

PubMed

Yilmaz, Emel Maden; Güntert, Peter

2015-09-01

An algorithm, CYLIB, is presented for converting molecular topology descriptions from the PDB Chemical Component Dictionary into CYANA residue library entries. The CYANA structure calculation algorithm uses torsion angle molecular dynamics for the efficient computation of three-dimensional structures from NMR-derived restraints. For this, the molecules have to be represented in torsion angle space with rotations around covalent single bonds as the only degrees of freedom. The molecule must be given a tree structure of torsion angles connecting rigid units composed of one or several atoms with fixed relative positions. Setting up CYANA residue library entries therefore involves, besides straightforward format conversion, the non-trivial step of defining a suitable tree structure of torsion angles, and to re-order the atoms in a way that is compatible with this tree structure. This can be done manually for small numbers of ligands but the process is time-consuming and error-prone. An automated method is necessary in order to handle the large number of different potential ligand molecules to be studied in drug design projects. Here, we present an algorithm for this purpose, and show that CYANA structure calculations can be performed with almost all small molecule ligands and non-standard amino acid residues in the PDB Chemical Component Dictionary.

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

Brull, S., E-mail: Stephane.Brull@math.u-bordeaux.fr; Charrier, P., E-mail: Pierre.Charrier@math.u-bordeaux.fr; Mieussens, L., E-mail: Luc.Mieussens@math.u-bordeaux.fr

It is well known that the roughness of the wall has an effect on microscale gas flows. This effect can be shown for large Knudsen numbers by using a numerical solution of the Boltzmann equation. However, when the wall is rough at a nanometric scale, it is necessary to use a very small mesh size which is much too expansive. An alternative approach is to incorporate the roughness effect in the scattering kernel of the boundary condition, such as the Maxwell-like kernel introduced by the authors in a previous paper. Here, we explain how this boundary condition can be implementedmore » in a discrete velocity approximation of the Boltzmann equation. Moreover, the influence of the roughness is shown by computing the structure scattering pattern of mono-energetic beams of the incident gas molecules. The effect of the angle of incidence of these molecules, of their mass, and of the morphology of the wall is investigated and discussed in a simplified two-dimensional configuration. The effect of the azimuthal angle of the incident beams is shown for a three-dimensional configuration. Finally, the case of non-elastic scattering is considered. All these results suggest that our approach is a promising way to incorporate enough physics of gas-surface interaction, at a reasonable computing cost, to improve kinetic simulations of micro- and nano-flows.« less

Three-dimensional architecture of the whole human soleus muscle in vivo

PubMed Central

Finni, Taija; D’Souza, Arkiev; Eguchi, Junya; Clarke, Elizabeth C.; Herbert, Robert D.

2018-01-01

Background Most data on the architecture of the human soleus muscle have been obtained from cadaveric dissection or two-dimensional ultrasound imaging. We present the first comprehensive, quantitative study on the three-dimensional anatomy of the human soleus muscle in vivo using diffusion tensor imaging (DTI) techniques. Methods We report three-dimensional fascicle lengths, pennation angles, fascicle curvatures, physiological cross-sectional areas and volumes in four compartments of the soleus at ankle joint angles of 69 ± 12° (plantarflexion, short muscle length; average ± SD across subjects) and 108 ± 7° (dorsiflexion, long muscle length) of six healthy young adults. Microdissection and three-dimensional digitisation on two cadaveric muscles corroborated the compartmentalised structure of the soleus, and confirmed the validity of DTI-based muscle fascicle reconstructions. Results The posterior compartments of the soleus comprised 80 ± 5% of the total muscle volume (356 ± 58 cm3). At the short muscle length, the average fascicle length, pennation angle and curvature was 37 ± 8 mm, 31 ± 3° and 17 ± 4 /m, respectively. We did not find differences in fascicle lengths between compartments. However, pennation angles were on average 12° larger (p < 0.01) in the posterior compartments than in the anterior compartments. For every centimetre that the muscle-tendon unit lengthened, fascicle lengths increased by 3.7 ± 0.8 mm, pennation angles decreased by −3.2 ± 0.9° and curvatures decreased by −2.7 ± 0.8 /m. Fascicles in the posterior compartments rotated almost twice as much as in the anterior compartments during passive lengthening. Discussion The homogeneity in fascicle lengths and inhomogeneity in pennation angles of the soleus may indicate a functionally different role for the anterior and posterior compartments. The data and techniques presented here demonstrate how DTI can be used to obtain detailed, quantitative measurements of the anatomy of complex skeletal muscles in living humans. PMID:29682414

The holographic display of three-dimensional medical objects through the usage of a shiftable cylindrical lens

NASA Astrophysics Data System (ADS)

Teng, Dongdong; Liu, Lilin; Zhang, Yueli; Pang, Zhiyong; Wang, Biao

2014-09-01

Through the creative usage of a shiftable cylindrical lens, a wide-view-angle holographic display system is developed for medical object display in real three-dimensional (3D) space based on a time-multiplexing method. The two-dimensional (2D) source images for all computer generated holograms (CGHs) needed by the display system are only one group of computerized tomography (CT) or magnetic resonance imaging (MRI) slices from the scanning device. Complicated 3D message reconstruction on the computer is not necessary. A pelvis is taken as the target medical object to demonstrate this method and the obtained horizontal viewing angle reaches 28°.

Heterogeneous nucleation of a droplet pinned at a chemically inhomogeneous substrate: A simulation study of the two-dimensional Ising case

NASA Astrophysics Data System (ADS)

Trobo, Marta L.; Albano, Ezequiel V.; Binder, Kurt

2018-03-01

Heterogeneous nucleation is studied by Monte Carlo simulations and phenomenological theory, using the two-dimensional lattice gas model with suitable boundary fields. A chemical inhomogeneity of length b at one boundary favors the liquid phase, while elsewhere the vapor is favored. Switching on the bulk field Hb favoring the liquid, nucleation and growth of the liquid phase starting from the region of the chemical inhomogeneity are analyzed. Three regimes occur: for small fields, HbHb*), the droplets nucleated at the chemical inhomogeneity grow to the full system size. While the relaxation time for the growth scales as τG∝Hb-1, the nucleation time τN scales as ln τN∝Hb-1. However, the prefactor in the latter relation, as evaluated for our simulations results, is not in accord with an extension of the Volmer-Turnbull theory to two-dimensions, when the theoretical contact angle θc is used.

Measurement of Galactic Logarithmic Spiral Arm Pitch Angle Using Two-Dimensional Fast Fourier Transform Decomposition

NASA Astrophysics Data System (ADS)

Davis, Benjamin L.; Berrier, J. C.; Shields, D. W.; Kennefick, J.; Kennefick, D.; Seigar, M. S.; Lacy, C. H. S.; Puerari, I.

2012-01-01

A logarithmic spiral is a prominent feature appearing in a majority of observed galaxies. This feature has long been associated with the traditional Hubble classification scheme, but historical quotes of pitch angle of spiral galaxies have been almost exclusively qualitative. We have developed a methodology, utilizing Two-Dimensional Fast Fourier Transformations of images of spiral galaxies, in order to isolate and measure the pitch angles of their spiral arms. Our technique provides a quantitative way to measure this morphological feature. This will allow the precise comparison of spiral galaxy evolution to other galactic parameters and test spiral arm genesis theories. In this work, we detail our image processing and analysis of spiral galaxy images and discuss the robustness of our analysis techniques. The authors gratefully acknowledge support for this work from NASA Grant NNX08AW03A.

Single exposure three-dimensional imaging of dusty plasma clusters.

PubMed

Hartmann, Peter; Donkó, István; Donkó, Zoltán

2013-02-01

We have worked out the details of a single camera, single exposure method to perform three-dimensional imaging of a finite particle cluster. The procedure is based on the plenoptic imaging principle and utilizes a commercial Lytro light field still camera. We demonstrate the capabilities of our technique on a single layer particle cluster in a dusty plasma, where the camera is aligned and inclined at a small angle to the particle layer. The reconstruction of the third coordinate (depth) is found to be accurate and even shadowing particles can be identified.

Multiaxis control power from thrust vectoring for a supersonic fighter aircraft model at Mach 0.20 to 2.47

NASA Technical Reports Server (NTRS)

Capone, Francis J.; Bare, E. Ann

1987-01-01

The aeropropulsive characteristics of an advanced twin-engine fighter aircraft designed for supersonic cruise have been studied in the Langley 16-Foot Tansonic Tunnel and the Lewis 10- by 10-Foot Supersonic Tunnel. The objective was to determine multiaxis control-power characteristics from thrust vectoring. A two-dimensional convergent-divergent nozzle was designed to provide yaw vector angles of 0, -10, and -20 deg combined with geometric pitch vector angles of 0 and 15 deg. Yaw thrust vectoring was provided by yaw flaps located in the nozzle sidewalls. Roll control was obtained from differential pitch vectoring. This investigation was conducted at Mach numbers from 0.20 to 2.47. Angle of attack was varied from 0 to about 19 deg, and nozzle pressure ratio was varied from about 1 (jet off) to 28, depending on Mach number. Increments in force or moment coefficient that result from pitch or yaw thrust vectoring remain essentially constant over the entire angle-of-attack range of all Mach numbers tested. There was no effect of pitch vectoring on the lateral aerodynamic forces and moments and only very small effects of yaw vectoring on the longitudinal aerodynamic forces and moments. This result indicates little cross-coupling of control forces and moments for combined pitch-yaw vectoring.

Stereo-photography of streamers in air

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

Nijdam, S.; Moerman, J. S.; Briels, T. M. P.

2008-03-10

Standard photographs of streamer discharges show a two-dimensional projection. Here, we present stereophotographic images that resolve their three-dimensional structure. We describe the stereoscopic setup and evaluation, and we present results for positive streamer discharges in air at 0.2-1 bar in a point-plane geometry with a gap distance of 14 cm and a voltage pulse of 47 kV. In this case, an approximately Gaussian distribution of branching angles of 43 deg. {+-}12 deg. is found; these angles do not significantly depend on the distance from the needle or on the gas pressure.

Convergence behavior that controls adaptive wind tunnel walls near the test section in the high angle of attack range

NASA Technical Reports Server (NTRS)

Ziemann, J.

1982-01-01

The NACA 0012 profile at Mach 0.5 was investigated in a wind tunnel with adaptive walls. It is found that adaptation of the flexible walls is possible in the high angle of attack range on both sides of maximum lift. Oil film photographs of the flow at the profile surface show three dimensional effects in the region of the corners between the profile and the sidewall. It is concluded that pure two dimensional separated flow is not possible.

Hierarchical Protein Free Energy Landscapes from Variationally Enhanced Sampling.

PubMed

Shaffer, Patrick; Valsson, Omar; Parrinello, Michele

2016-12-13

In recent work, we demonstrated that it is possible to obtain approximate representations of high-dimensional free energy surfaces with variationally enhanced sampling ( Shaffer, P.; Valsson, O.; Parrinello, M. Proc. Natl. Acad. Sci. , 2016 , 113 , 17 ). The high-dimensional spaces considered in that work were the set of backbone dihedral angles of a small peptide, Chignolin, and the high-dimensional free energy surface was approximated as the sum of many two-dimensional terms plus an additional term which represents an initial estimate. In this paper, we build on that work and demonstrate that we can calculate high-dimensional free energy surfaces of very high accuracy by incorporating additional terms. The additional terms apply to a set of collective variables which are more coarse than the base set of collective variables. In this way, it is possible to build hierarchical free energy surfaces, which are composed of terms that act on different length scales. We test the accuracy of these free energy landscapes for the proteins Chignolin and Trp-cage by constructing simple coarse-grained models and comparing results from the coarse-grained model to results from atomistic simulations. The approach described in this paper is ideally suited for problems in which the free energy surface has important features on different length scales or in which there is some natural hierarchy.

Cadaveric and three-dimensional computed tomography study of the morphology of the scapula with reference to reversed shoulder prosthesis

PubMed Central

Torrens, Carlos; Corrales, Monica; Gonzalez, Gemma; Solano, Alberto; Cáceres, Enrique

2008-01-01

Purpose The purpose of this study is to analyze the morphology of the scapula with reference to the glenoid component implantation in reversed shoulder prosthesis, in order to improve primary fixation of the component. Methods Seventy-three 3-dimensional computed tomography of the scapula and 108 scapular dry specimens were analyzed to determine the anterior and posterior length of the glenoid neck, the angle between the glenoid surface and the upper posterior column of the scapula and the angle between the major craneo-caudal glenoid axis and the base of the coracoid process and the upper posterior column. Results The anterior and posterior length of glenoid neck was classified into two groups named "short-neck" and "long-neck" with significant differences between them. The angle between the glenoid surface and the upper posterior column of the scapula was also classified into two different types: type I (mean 50°–52°) and type II (mean 62,50°–64°), with significant differences between them (p < 0,001). The angle between the major craneo-caudal glenoid axis and the base of the coracoid process averaged 18,25° while the angle with the upper posterior column of the scapula averaged 8°. Conclusion Scapular morphological variability advices for individual adjustments of glenoid component implantation in reversed total shoulder prosthesis. Three-dimensional computed tomography of the scapula constitutes an important tool when planning reversed prostheses implantation. PMID:18847487

Cadaveric and three-dimensional computed tomography study of the morphology of the scapula with reference to reversed shoulder prosthesis.

PubMed

Torrens, Carlos; Corrales, Monica; Gonzalez, Gemma; Solano, Alberto; Cáceres, Enrique

2008-10-10

The purpose of this study is to analyze the morphology of the scapula with reference to the glenoid component implantation in reversed shoulder prosthesis, in order to improve primary fixation of the component. Seventy-three 3-dimensional computed tomography of the scapula and 108 scapular dry specimens were analyzed to determine the anterior and posterior length of the glenoid neck, the angle between the glenoid surface and the upper posterior column of the scapula and the angle between the major craneo-caudal glenoid axis and the base of the coracoid process and the upper posterior column. The anterior and posterior length of glenoid neck was classified into two groups named "short-neck" and "long-neck" with significant differences between them. The angle between the glenoid surface and the upper posterior column of the scapula was also classified into two different types: type I (mean 50 degrees-52 degrees ) and type II (mean 62.50 degrees-64 degrees ), with significant differences between them (p < 0.001). The angle between the major craneo-caudal glenoid axis and the base of the coracoid process averaged 18,25 degrees while the angle with the upper posterior column of the scapula averaged 8 degrees . Scapular morphological variability advices for individual adjustments of glenoid component implantation in reversed total shoulder prosthesis. Three-dimensional computed tomography of the scapula constitutes an important tool when planning reversed prostheses implantation.

Numerical Investigation of Three-dimensional Instability of Standing Waves

NASA Astrophysics Data System (ADS)

Zhu, Qiang; Liu, Yuming; Yue, Dick K. P.

2002-11-01

We study the three-dimensional instability of finite-amplitude standing waves under the influence of gravity using the transition matrix method. For accurate calculation of the transition matrices, we apply an efficient high-order spectral element method for nonlinear wave dynamics in complex domain. We consider two types of standing waves: (a) plane standing waves; and (b) standing waves in a circular tank. For the former, in addition to the confirmation of the side-band-like instability, we find a new three-dimensional instability for arbitrary base standing waves. The dominant component of the unstable disturbance is an oblique standing wave, with an arbitrary angle relative to the base flow, whose frequency is approximately equal to that of the base standing wave. Based on direct simulations, we confirm such a three-dimensional instability and show the occurrence of the Fermi-Pasta-Ulam recurrence phenomenon during nonlinear evolution. For the latter, we find that beyond a threshold wave steepness, the standing wave with frequency Ω becomes unstable to a small three-dimensional disturbance, which contains two dominant standing-wave components with frequencies ω1 and ω_2, provided that 2Ω ω1 + ω_2. The threshold wave steepness is found to decrease/increase as the radial/azimuthal wavenumber of the base standing wave increases. We show that the instability of standing waves in rectangular and circular tanks is caused by third-order quartet resonances between base flow and disturbance.

Evolved atmospheric entry corridor with safety factor

NASA Astrophysics Data System (ADS)

Liang, Zixuan; Ren, Zhang; Li, Qingdong

2018-02-01

Atmospheric entry corridors are established in previous research based on the equilibrium glide condition which assumes the flight-path angle to be zero. To get a better understanding of the highly constrained entry flight, an evolved entry corridor that considers the exact flight-path angle is developed in this study. Firstly, the conventional corridor in the altitude vs. velocity plane is extended into a three-dimensional one in the space of altitude, velocity, and flight-path angle. The three-dimensional corridor is generated by a series of constraint boxes. Then, based on a simple mapping method, an evolved two-dimensional entry corridor with safety factor is obtained. The safety factor is defined to describe the flexibility of the flight-path angle for a state within the corridor. Finally, the evolved entry corridor is simulated for the Space Shuttle and the Common Aero Vehicle (CAV) to demonstrate the effectiveness of the corridor generation approach. Compared with the conventional corridor, the evolved corridor is much wider and provides additional information. Therefore, the evolved corridor would benefit more to the entry trajectory design and analysis.

Effects of geometrical structure on spatial distribution of thermal energy in two-dimensional triangular lattices

NASA Astrophysics Data System (ADS)

Liu, Yong-Yang; Xu, Yu-Liang; Liu, Zhong-Qiang; Li, Jing; Wang, Chun-Yang; Kong, Xiang-Mu

2018-07-01

Employing the correlation matrix technique, the spatial distribution of thermal energy in two-dimensional triangular lattices in equilibrium, interacting with linear springs, is studied. It is found that the spatial distribution of thermal energy varies with the included angle of the springs. In addition, the average thermal energy of the longer springs is lower. Springs with different included angle and length will lead to an inhomogeneous spatial distribution of thermal energy. This suggests that the spatial distribution of thermal energy is affected by the geometrical structure of the system: the more asymmetric the geometrical structure of the system is, the more inhomogeneous is the spatial distribution of thermal energy.

Development of soft x-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU

NASA Astrophysics Data System (ADS)

Ogawa, Manami; Yamamoto, Susumu; Kousa, Yuka; Nakamura, Fumitaka; Yukawa, Ryu; Fukushima, Akiko; Harasawa, Ayumi; Kondoh, Hiroshi; Tanaka, Yoshihito; Kakizaki, Akito; Matsuda, Iwao

2012-02-01

We have developed a soft x-ray time-resolved photoemission spectroscopy system using synchrotron radiation (SR) at SPring-8 BL07LSU and an ultrashort pulse laser system. Two-dimensional angle-resolved measurements were performed with a time-of-flight-type analyzer. The photoemission spectroscopy system is synchronized to light pulses of SR and laser using a time control unit. The performance of the instrument is demonstrated by mapping the band structure of a Si(111) crystal over the surface Brillouin zones and observing relaxation of the surface photo-voltage effect using the pump (laser) and probe (SR) method.

Development of soft x-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU.

PubMed

Ogawa, Manami; Yamamoto, Susumu; Kousa, Yuka; Nakamura, Fumitaka; Yukawa, Ryu; Fukushima, Akiko; Harasawa, Ayumi; Kondoh, Hiroshi; Tanaka, Yoshihito; Kakizaki, Akito; Matsuda, Iwao

2012-02-01

We have developed a soft x-ray time-resolved photoemission spectroscopy system using synchrotron radiation (SR) at SPring-8 BL07LSU and an ultrashort pulse laser system. Two-dimensional angle-resolved measurements were performed with a time-of-flight-type analyzer. The photoemission spectroscopy system is synchronized to light pulses of SR and laser using a time control unit. The performance of the instrument is demonstrated by mapping the band structure of a Si(111) crystal over the surface Brillouin zones and observing relaxation of the surface photo-voltage effect using the pump (laser) and probe (SR) method.

Review of the fundamental theories behind small angle X-ray scattering, molecular dynamics simulations, and relevant integrated application

PubMed Central

Boldon, Lauren; Laliberte, Fallon; Liu, Li

2015-01-01

In this paper, the fundamental concepts and equations necessary for performing small angle X-ray scattering (SAXS) experiments, molecular dynamics (MD) simulations, and MD-SAXS analyses were reviewed. Furthermore, several key biological and non-biological applications for SAXS, MD, and MD-SAXS are presented in this review; however, this article does not cover all possible applications. SAXS is an experimental technique used for the analysis of a wide variety of biological and non-biological structures. SAXS utilizes spherical averaging to produce one- or two-dimensional intensity profiles, from which structural data may be extracted. MD simulation is a computer simulation technique that is used to model complex biological and non-biological systems at the atomic level. MD simulations apply classical Newtonian mechanics’ equations of motion to perform force calculations and to predict the theoretical physical properties of the system. This review presents several applications that highlight the ability of both SAXS and MD to study protein folding and function in addition to non-biological applications, such as the study of mechanical, electrical, and structural properties of non-biological nanoparticles. Lastly, the potential benefits of combining SAXS and MD simulations for the study of both biological and non-biological systems are demonstrated through the presentation of several examples that combine the two techniques. PMID:25721341

Small-angle x-ray scattering study of polymer structure: Carbosilane dendrimers in hexane solution

NASA Astrophysics Data System (ADS)

Shtykova, E. V.; Feigin, L. A.; Volkov, V. V.; Malakhova, Yu. N.; Streltsov, D. R.; Buzin, A. I.; Chvalun, S. N.; Katarzhanova, E. Yu.; Ignatieva, G. M.; Muzafarov, A. M.

2016-09-01

The three-dimensional organization of monodisperse hyper-branched macromolecules of regular structure—carbosilane dendrimers of zero, third, and sixth generations—has been studied by small-angle X-ray scattering (SAXS) in solution. The use of modern methods of SAXS data interpretation, including ab initio modeling, has made it possible to determine the internal architecture of the dendrimers in dependence of the generation number and the number of cyclosiloxane end groups (forming the shell of dendritic macromolecules) and show dendrimers to be spherical. The structural results give grounds to consider carbosilane dendrimers promising objects for forming crystals with subsequent structural analysis and determining their structure with high resolution, as well as for designing new materials to be used in various dendrimer-based technological applications.

Three-dimensional Radar Imaging of a Building

DTIC Science & Technology

2012-12-01

spotlight configuration and H-V ( cross ) polarization as seen from two different aspect angles. The feature colors correspond to their brightness... cross - ranges but at different heights. This effect may create significant confusion in image interpretation and result in missed target detections...over a range of azimuth angles ( centered at  = 0°) and elevation angles ( centered at 0), creating cross -range and height resolution, while

Modified sine bar device measures small angles with high accuracy

NASA Technical Reports Server (NTRS)

Thekaekara, M.

1968-01-01

Modified sine bar device measures small angles with enough accuracy to calibrate precision optical autocollimators. The sine bar is a massive bar of steel supported by two cylindrical rods at one end and one at the other.

Comparison of two- and three-dimensional flow computations with laser anemometer measurements in a transonic compressor rotor

NASA Technical Reports Server (NTRS)

Chima, R. V.; Strazisar, A. J.

1982-01-01

Two and three dimensional inviscid solutions for the flow in a transonic axial compressor rotor at design speed are compared with probe and laser anemometers measurements at near-stall and maximum-flow operating points. Experimental details of the laser anemometer system and computational details of the two dimensional axisymmetric code and three dimensional Euler code are described. Comparisons are made between relative Mach number and flow angle contours, shock location, and shock strength. A procedure for using an efficient axisymmetric code to generate downstream pressure input for computationally expensive Euler codes is discussed. A film supplement shows the calculations of the two operating points with the time-marching Euler code.

Computer simulation of ion beam analysis of laterally inhomogeneous materials

NASA Astrophysics Data System (ADS)

Mayer, M.

2016-03-01

The program STRUCTNRA for the simulation of ion beam analysis charged particle spectra from arbitrary two-dimensional distributions of materials is described. The code is validated by comparison to experimental backscattering data from a silicon grating on tantalum at different orientations and incident angles. Simulated spectra for several types of rough thin layers and a chessboard-like arrangement of materials as example for a multi-phase agglomerate material are presented. Ambiguities between back-scattering spectra from two-dimensional and one-dimensional sample structures are discussed.

Single-slit electron diffraction with Aharonov-Bohm phase: Feynman's thought experiment with quantum point contacts.

PubMed

Khatua, Pradip; Bansal, Bhavtosh; Shahar, Dan

2014-01-10

In a "thought experiment," now a classic in physics pedagogy, Feynman visualizes Young's double-slit interference experiment with electrons in magnetic field. He shows that the addition of an Aharonov-Bohm phase is equivalent to shifting the zero-field wave interference pattern by an angle expected from the Lorentz force calculation for classical particles. We have performed this experiment with one slit, instead of two, where ballistic electrons within two-dimensional electron gas diffract through a small orifice formed by a quantum point contact (QPC). As the QPC width is comparable to the electron wavelength, the observed intensity profile is further modulated by the transverse waveguide modes present at the injector QPC. Our experiments open the way to realizing diffraction-based ideas in mesoscopic physics.

Role of Off-Line-of-Sight Propagation in Geomagnetic EMP Formation

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

Kruger, Hans W.

The author’s synchrotron radiation based 3D geomagnetic EMP code MACSYNC has been used to explore the impact on pulse rise time and air conductivity of EMP propagation paths to the observer that are located off the direct line-of-sight (LOS) between gamma source and observer. This geometry is always present because, for an isotropic source, most the gammas are emitted at an angle with respect to the LOS. Computations for a 1 kt near-surface burst observed from space yield two principal findings: 1. The rise time is generated by the combined actions of a) electron spreading along the LOS due tomore » the Compton electron emission angular distribution folded with electron multiple scattering effects, and b) radiation arrival time spreading due to length differences for different off-LOS propagation paths. The pulse rise time does not depend on the rise time of the conductivity. The conductivity rise time determines the pulse amplitude. 2. One-dimensional legacy EMP codes are inherently incapable of producing the correct pulse shape because they cannot treat the dependence of the conductivity on two dimensions, i.e. the radius from the source and the angle of the propagation path with the LOS. This divergence from one-dimensionality begins at a small fraction of a nanosecond for a sea-level burst. This effect will also be present in high-altitude bursts, however, determination of its onset time and magnitude requires high-altitude computations which have not yet been done.« less

Tunable all-angle negative refraction and photonic band gaps in two-dimensional plasma photonic crystals with square-like Archimedean lattices

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

Zhang, Hai-Feng, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn; Nanjing Artillery Academy, Nanjing 211132; Liu, Shao-Bin, E-mail: hanlor@163.com, E-mail: lsb@nuaa.edu.cn

In this paper, the tunable all-angle negative refraction and photonic band gaps (PBGs) in two types of two-dimensional (2D) plasma photonic crystals (PPCs) composed of homogeneous plasma and dielectric (GaAs) with square-like Archimedean lattices (ladybug and bathroom lattices) for TM wave are theoretically investigated based on a modified plane wave expansion method. The type-1 structure is dielectric rods immersed in the plasma background, and the complementary structure is named as type-2 PPCs. Theoretical simulations demonstrate that the both types of PPCs with square-like Archimedean lattices have some advantages in obtaining the higher cut-off frequency, the larger PBGs, more number ofmore » PBGs, and the relative bandwidths compared to the conventional square lattices as the filling factor or radius of inserted rods is same. The influences of plasma frequency and radius of inserted rod on the properties of PBGs for both types of PPCs also are discussed in detail. The calculated results show that PBGs can be manipulated by the parameters as mentioned above. The possibilities of all-angle negative refraction in such two types of PPCs at low bands also are discussed. Our calculations reveal that the all-angle negative phenomena can be observed in the first two TM bands, and the frequency range of all-angle negative refraction can be tuned by changing plasma frequency. Those properties can be used to design the optical switching and sensor.« less

Numerical simulation of the flow field and fuel sprays in an IC engine

NASA Technical Reports Server (NTRS)

Nguyen, H. L.; Schock, H. J.; Ramos, J. I.; Carpenter, M. H.; Stegeman, J. D.

1987-01-01

A two-dimensional model for axisymmetric piston-cylinder configurations is developed to study the flow field in two-stroke direct-injection Diesel engines under motored conditions. The model accounts for turbulence by a two-equation model for the turbulence kinetic energy and its rate of dissipation. A discrete droplet model is used to simulate the fuel spray, and the effects of the gas phase turbulence on the droplets is considered. It is shown that a fluctuating velocity can be added to the mean droplet velocity every time step if the step is small enough. Good agreement with experimental data is found for a range of ambient pressures in Diesel engine-type microenvironments. The effects of the intake swirl angle in the spray penetration, vaporization, and mixing in a uniflow-scavenged two-stroke Diesel engine are analyzed. It is found that the swirl increases the gas phase turbulence levels and the rates of vaporization.

Three-dimensional supersonic flow around double compression ramp with finite span

NASA Astrophysics Data System (ADS)

Lee, H. S.; Lee, J. H.; Park, G.; Park, S. H.; Byun, Y. H.

2017-01-01

Three-dimensional flows of Mach number 3 around a double-compression ramp with finite span have been investigated numerically. Shadowgraph visualisation images obtained in a supersonic wind tunnel are used for comparison. A three-dimensional Reynolds-averaged Navier-Stokes solver was used to obtain steady numerical solutions. Two-dimensional numerical results are also compared. Four different cases were studied: two different second ramp angles of 30° and 45° in configurations with and without sidewalls, respectively. Results showed that there is a leakage of mass and momentum fluxes heading outwards in the spanwise direction for three-dimensional cases without sidewalls. The leakage changed the flow characteristics of the shock-induced boundary layer and resulted in the discrepancy between the experimental data and two-dimensional numerical results. It is found that suppressing the flow leakage by attaching the sidewalls enhances the two-dimensionality of the experimental data for the double-compression ramp flow.

Transonic analysis of canted winglets

NASA Technical Reports Server (NTRS)

Rosen, B. S.

1984-01-01

A computational method developed to provide a transonic analysis for upper/lower surface wing-tip mounted winglets is described. Winglets with arbitrary planform, cant and toe angle, and airfoil section can be modeled. The embedded grid approach provides high flow field resolution and the required geometric flexibility. In particular, coupled Cartesian/cylindrical grid systems are used to model the complex geometry presented by canted upper/lower surface winglets. A new rotated difference scheme is introduced in order to maintain the stability of the small-disturbance formulation in the presence of large spanwise velocities. Wing and winglet viscous effects are modeled using a two-dimensional 'strip' boundary layer analysis. Correlations with wind tunnel and flight test data for three transport configurations are included.

Slender-Body Theory Based On Approximate Solution of the Transonic Flow Equation

NASA Technical Reports Server (NTRS)

Spreiter, John R.; Alksne, Alberta Y.

1959-01-01

Approximate solution of the nonlinear equations of the small disturbance theory of transonic flow are found for the pressure distribution on pointed slender bodies of revolution for flows with free-stream, Mach number 1, and for flows that are either purely subsonic or purely supersonic. These results are obtained by application of a method based on local linearization that was introduced recently in the analysis of similar problems in two-dimensional flows. The theory is developed for bodies of arbitrary shape, and specific results are given for cone-cylinders and for parabolic-arc bodies at zero angle of attack. All results are compared either with existing theoretical results or with experimental data.

Influence of the tilt angle of Percutaneous Aortic Prosthesis on Velocity and Shear Stress Fields

PubMed Central

Gomes, Bruno Alvares de Azevedo; Camargo, Gabriel Cordeiro; dos Santos, Jorge Roberto Lopes; Azevedo, Luis Fernando Alzuguir; Nieckele, Ângela Ourivio; Siqueira-Filho, Aristarco Gonçalves; de Oliveira, Glaucia Maria Moraes

2017-01-01

Background Due to the nature of the percutaneous prosthesis deployment process, a variation in its final position is expected. Prosthetic valve placement will define the spatial location of its effective orifice in relation to the aortic annulus. The blood flow pattern in the ascending aorta is related to the aortic remodeling process, and depends on the spatial location of the effective orifice. The hemodynamic effect of small variations in the angle of inclination of the effective orifice has not been studied in detail. Objective To implement an in vitro simulation to characterize the hydrodynamic blood flow pattern associated with small variations in the effective orifice inclination. Methods A three-dimensional aortic phantom was constructed, reproducing the anatomy of one patient submitted to percutaneous aortic valve implantation. Flow analysis was performed by use of the Particle Image Velocimetry technique. The flow pattern in the ascending aorta was characterized for six flow rate levels. In addition, six angles of inclination of the effective orifice were assessed. Results The effective orifice at the -4º and -2º angles directed the main flow towards the anterior wall of the aortic model, inducing asymmetric and high shear stress in that region. However, the effective orifice at the +3º and +5º angles mimics the physiological pattern, centralizing the main flow and promoting a symmetric distribution of shear stress. Conclusion The measurements performed suggest that small changes in the angle of inclination of the percutaneous prosthesis aid in the generation of a physiological hemodynamic pattern, and can contribute to reduce aortic remodeling. PMID:28793046

Refraction of high frequency noise in an arbitrary jet flow

NASA Technical Reports Server (NTRS)

Khavaran, Abbas; Krejsa, Eugene A.

1994-01-01

Refraction of high frequency noise by mean flow gradients in a jet is studied using the ray-tracing methods of geometrical acoustics. Both the two-dimensional (2D) and three-dimensional (3D) formulations are considered. In the former case, the mean flow is assumed parallel and the governing propagation equations are described by a system of four first order ordinary differential equations. The 3D formulation, on the other hand, accounts for the jet spreading as well as the axial flow development. In this case, a system of six first order differential equations are solved to trace a ray from its source location to an observer in the far field. For subsonic jets with a small spreading angle both methods lead to similar results outside the zone of silence. However, with increasing jet speed the two prediction models diverge to the point where the parallel flow assumption is no longer justified. The Doppler factor of supersonic jets as influenced by the refraction effects is discussed and compared with the conventional modified Doppler factor.

Two-dimensional phase separated structures of block copolymers on solids

NASA Astrophysics Data System (ADS)

Sen, Mani; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori; Ribbe, Alexander

The fundamental, yet unsolved question in block copolymer (BCP) thin films is the self-organization process of BCPs at the solid-polymer melt interface. We here focus on the self-organization processes of cylinder-forming polystyrene-block-poly (4-vinylpyridine) diblock copolymer and lamellar-forming poly (styrene-block-butadiene-block-styrene) triblock copolymer on Si substrates as model systems. In order to reveal the buried interfacial structures, the following experimental protocols were utilized: the BCP monolayer films were annealed under vacuum at T>Tg of the blocks (to equilibrate the melts); vitrification of the annealed BCP films via rapid quench to room temperature; subsequent intensive solvent leaching (to remove unadsorbed chains) with chloroform, a non-selective good solvent for the blocks. The strongly bound BCP layers were then characterized by using atomic force microscopy, scanning electron microscopy, grazing incidence small angle X-ray scattering, and X-ray reflectivity. The results showed that both blocks lie flat on the substrate, forming the two-dimensional, randomly phase-separated structure irrespective of their microdomain structures and interfacial energetics. Acknowledgement of financial support from NSF Grant (CMMI -1332499).

Two- to three-dimensional crossover in a dense electron liquid in silicon

NASA Astrophysics Data System (ADS)

Matmon, Guy; Ginossar, Eran; Villis, Byron J.; Kölker, Alex; Lim, Tingbin; Solanki, Hari; Schofield, Steven R.; Curson, Neil J.; Li, Juerong; Murdin, Ben N.; Fisher, Andrew J.; Aeppli, Gabriel

2018-04-01

Doping of silicon via phosphine exposures alternating with molecular beam epitaxy overgrowth is a path to Si:P substrates for conventional microelectronics and quantum information technologies. The technique also provides a well-controlled material for systematic studies of two-dimensional lattices with a half-filled band. We show here that for a dense (ns=2.8 ×1014 cm-2) disordered two-dimensional array of P atoms, the full field magnitude and angle-dependent magnetotransport is remarkably well described by classic weak localization theory with no corrections due to interaction. The two- to three-dimensional crossover seen upon warming can also be interpreted using scaling concepts developed for anistropic three-dimensional materials, which work remarkably except when the applied fields are nearly parallel to the conducting planes.

Analytical solutions of the two-dimensional Dirac equation for a topological channel intersection

NASA Astrophysics Data System (ADS)

Anglin, J. R.; Schulz, A.

2017-01-01

Numerical simulations in a tight-binding model have shown that an intersection of topologically protected one-dimensional chiral channels can function as a beam splitter for noninteracting fermions on a two-dimensional lattice [Qiao, Jung, and MacDonald, Nano Lett. 11, 3453 (2011), 10.1021/nl201941f; Qiao et al., Phys. Rev. Lett. 112, 206601 (2014), 10.1103/PhysRevLett.112.206601]. Here we confirm this result analytically in the corresponding continuum k .p model, by solving the associated two-dimensional Dirac equation, in the presence of a "checkerboard" potential that provides a right-angled intersection between two zero-line modes. The method by which we obtain our analytical solutions is systematic and potentially generalizable to similar problems involving intersections of one-dimensional systems.

Miniature optical planar camera based on a wide-angle metasurface doublet corrected for monochromatic aberrations

DOE PAGES

Arbabi, Amir; Arbabi, Ehsan; Kamali, Seyedeh Mahsa; ...

2016-11-28

Optical metasurfaces are two-dimensional arrays of nano-scatterers that modify optical wavefronts at subwavelength spatial resolution. They are poised to revolutionize optics by enabling complex low-cost systems where multiple metasurfaces are lithographically stacked and integrated with electronics. For imaging applications, metasurface stacks can perform sophisticated image corrections and can be directly integrated with image sensors. Here we demonstrate this concept with a miniature flat camera integrating a monolithic metasurface lens doublet corrected for monochromatic aberrations, and an image sensor. The doublet lens, which acts as a fisheye photographic objective, has a small f-number of 0.9, an angle-of-view larger than 60° ×more » 60°, and operates at 850 nm wavelength with 70% focusing efficiency. The camera exhibits nearly diffraction-limited image quality, which indicates the potential of this technology in the development of optical systems for microscopy, photography, and computer vision.« less

Accurate approximation of in-ecliptic trajectories for E-sail with constant pitch angle

NASA Astrophysics Data System (ADS)

Huo, Mingying; Mengali, Giovanni; Quarta, Alessandro A.

2018-05-01

Propellantless continuous-thrust propulsion systems, such as electric solar wind sails, may be successfully used for new space missions, especially those requiring high-energy orbit transfers. When the mass-to-thrust ratio is sufficiently large, the spacecraft trajectory is characterized by long flight times with a number of revolutions around the Sun. The corresponding mission analysis, especially when addressed within an optimal context, requires a significant amount of simulation effort. Analytical trajectories are therefore useful aids in a preliminary phase of mission design, even though exact solution are very difficult to obtain. The aim of this paper is to present an accurate, analytical, approximation of the spacecraft trajectory generated by an electric solar wind sail with a constant pitch angle, using the latest mathematical model of the thrust vector. Assuming a heliocentric circular parking orbit and a two-dimensional scenario, the simulation results show that the proposed equations are able to accurately describe the actual spacecraft trajectory for a long time interval when the propulsive acceleration magnitude is sufficiently small.

Aerodynamic Measurements of a Variable-Speed Power-Turbine Blade Section in a Transonic Turbine Cascade

NASA Technical Reports Server (NTRS)

Flegel, Ashlie B.

2014-01-01

The purpose of this thesis is to document the impact of incidence angle and Reynolds number variations on the three-dimensional flow field and midspan loss and turning of a two-dimensional section of a variable-speed power-turbine (VSPT) rotor blade. Aerodynamic measurements were obtained in a transonic linear cascade at NASA Glenn Research Center in Cleveland, Ohio. Steady-state data were obtained for 10 incidence angles ranging from +15.8deg to -51.0deg. At each angle, data were acquired at five flow conditions with the exit Reynolds number (based on axial chord) varying over an order-of-magnitude from 2.12×105 to 2.12×106. Data were obtained at the design exit Mach number of 0.72 and at a reduced exit Mach number of 0.35 as required to achieve the lowest Reynolds number. Midspan tota lpressure and exit flow angle data were acquired using a five-hole pitch/yaw probe surveyed on a plane located 7.0 percent axial-chord downstream of the blade trailing edge plane. The survey spanned three blade passages. Additionally, three-dimensional half-span flow fields were examined with additional probe survey data acquired at 26 span locations for two key incidence angles of +5.8deg and -36.7deg. Survey data near the endwall were acquired with a three-hole boundary-layer probe. The data were integrated to determine average exit total-pressure and flow angle as functions of incidence and flow conditions. The data set also includes blade static pressures measured on four spanwise planes and endwall static pressures.

Making structured metals transparency for broadband and wide-incidence-angle electromagnetic waves

NASA Astrophysics Data System (ADS)

Fan, Renhao; Peng, Ruwen; Huang, Xianrong; Wang, Mu

2014-03-01

Very recently, we have demonstrated that one-dimensional metallic gratings can become transparent and completely antireflective for extremely broadband electromagnetic (EM) waves under oblique incidence. However, the oblique-incidence geometry, is inconvenient for the technological applications. To overcome this drawback, here we instead use oblique metal gratings with optimal tilt angles to achieve normal-incidence broadband transparence for EM waves. Further we use two-dimensional periodic metallic cuboids to achieve broadband and broad-angle high transmission and antireflection. By introducing such metallic cuboids arrays into silicon solar cells, we find that high performance of light trapping in the cells can be obtained with a significant enhancement of the ultimate quantum efficiency. The structured metals, which achieve broadband and broad-angle high transmission for EM waves, may have many other potential applications, such as transparent conducting panels, white-beam polarizers, and stealth objects.

Spanwise visualization of the flow around a three-dimensional foil with leading edge protuberances

NASA Astrophysics Data System (ADS)

Stanway, M. J.; Techet, A. H.

2006-11-01

Studies of model humpback whale fins have shown that leading edge protuberances, or tubercles, can lead to delayed stall and increased lift at higher angles of attack, compared to foils with geometrically smooth leading edges. Such enhanced performance characteristics could prove highly useful in underwater vehicles such as gliders or long range AUVs (autonomous underwater vehicles). In this work, Particle Imaging Velocimetry (PIV) is performed on two static wings in a water tunnel over a range of angles of attack. These three- dimensional, finite-aspect ratio wings are modeled after a humpback whale flipper and are identical in shape, tapered from root to tip, except for the leading edge. In one of the foils the leading edge is smooth, whereas in the other, regularly spaced leading edge bumps are machined to simulate the whale’s fin tubercles. Results from these PIV tests reveal distinct cells where coherent flow structures are destroyed as a result of the leading edge perturbations. Tests are performed at Reynolds numbers Re ˜ O(10^5), based on chordlength, in a recirculating water tunnel. An inline six-axis load cell is mounted to measure the forces on the foil over a range of static pitch angles. It is hypothesized that this spanwise breakup of coherent vortical structures is responsible for the delayed angle of stall. These quantitative experiments complement exiting qualitative studies with two dimensional foils.

Stability of a flow down an incline with respect to two-dimensional and three-dimensional disturbances for Newtonian and non-Newtonian fluids.

PubMed

Allouche, M H; Millet, S; Botton, V; Henry, D; Ben Hadid, H; Rousset, F

2015-12-01

Squire's theorem, which states that the two-dimensional instabilities are more dangerous than the three-dimensional instabilities, is revisited here for a flow down an incline, making use of numerical stability analysis and Squire relationships when available. For flows down inclined planes, one of these Squire relationships involves the slopes of the inclines. This means that the Reynolds number associated with a two-dimensional wave can be shown to be smaller than that for an oblique wave, but this oblique wave being obtained for a larger slope. Physically speaking, this prevents the possibility to directly compare the thresholds at a given slope. The goal of the paper is then to reach a conclusion about the predominance or not of two-dimensional instabilities at a given slope, which is of practical interest for industrial or environmental applications. For a Newtonian fluid, it is shown that, for a given slope, oblique wave instabilities are never the dominant instabilities. Both the Squire relationships and the particular variations of the two-dimensional wave critical curve with regard to the inclination angle are involved in the proof of this result. For a generalized Newtonian fluid, a similar result can only be obtained for a reduced stability problem where some term connected to the perturbation of viscosity is neglected. For the general stability problem, however, no Squire relationships can be derived and the numerical stability results show that the thresholds for oblique waves can be smaller than the thresholds for two-dimensional waves at a given slope, particularly for large obliquity angles and strong shear-thinning behaviors. The conclusion is then completely different in that case: the dominant instability for a generalized Newtonian fluid flowing down an inclined plane with a given slope can be three dimensional.

Characteristics of angular cross correlations studied by light scattering from two-dimensional microsphere films

NASA Astrophysics Data System (ADS)

Schroer, M. A.; Gutt, C.; Grübel, G.

2014-07-01

Recently the analysis of scattering patterns by angular cross-correlation analysis (CCA) was introduced to reveal the orientational order in disordered samples with special focus to future applications on x-ray free-electron laser facilities. We apply this CCA approach to ultra-small-angle light-scattering data obtained from two-dimensional monolayers of microspheres. The films were studied in addition by optical microscopy. This combined approach allows to calculate the cross-correlations of the scattering patterns, characterized by the orientational correlation function Ψl(q), as well as to obtain the real-space structure of the monolayers. We show that CCA is sensitive to the orientational order of monolayers formed by the microspheres which are not directly visible from the scattering patterns. By mixing microspheres of different radii the sizes of ordered monolayer domains is reduced. For these samples it is shown that Ψl(q) quantitatively describes the degree of hexagonal order of the two-dimensional films. The experimental CCA results are compared with calculations based on the microscopy images. Both techniques show qualitatively similar features. Differences can be attributed to the wave-front distortion of the laser beam in the experiment. This effect is discussed by investigating the effect of different wave fronts on the cross-correlation analysis results. The so-determined characteristics of the cross-correlation analysis will be also relevant for future x-ray-based studies.

The numerical study of the rake angle of impeller blade in centrifugal compressor

NASA Astrophysics Data System (ADS)

Drozdov, A.; Galerkin, Y.

2017-08-01

Investigated impellers have blade surfaces formed by straight generatrix. Blade profiles on shroud and disc surfaces are optimized by velocity diagram control (inviscid, quasi-three dimensional calculations). The blade profiles at hub and shroud blade-to-blade surfaces must be coordinated. A designer can choose the generatrix position at a trailing edge for it. The position is defined by the rake angle that is the angle between a trailing edge generatrix and a meridional plane. Two stages with 3D impellers, vaneless diffusers and return channels were investigated. Seven candidates of impellers of these stages with rake angles in range plus-minus 30 degrees were designed and investigated by quasi-three-dimensional inviscid calculation. CFD-calculations were made for the stages with these impellers. The optimal rake angle is minus 20 degrees for the high flow rate impeller due to lesser blade surface area and favorable meridian velocity field. Zero rake angle is optimal for the medium flow rate impeller where blade surface area is not so important. The combination of inviscid and viscid calculations is the informative instrument for further studies.

Augmented reality glass-free three-dimensional display with the stereo camera

NASA Astrophysics Data System (ADS)

Pang, Bo; Sang, Xinzhu; Chen, Duo; Xing, Shujun; Yu, Xunbo; Yan, Binbin; Wang, Kuiru; Yu, Chongxiu

2017-10-01

An improved method for Augmented Reality (AR) glass-free three-dimensional (3D) display based on stereo camera used for presenting parallax contents from different angle with lenticular lens array is proposed. Compared with the previous implementation method of AR techniques based on two-dimensional (2D) panel display with only one viewpoint, the proposed method can realize glass-free 3D display of virtual objects and real scene with 32 virtual viewpoints. Accordingly, viewers can get abundant 3D stereo information from different viewing angles based on binocular parallax. Experimental results show that this improved method based on stereo camera can realize AR glass-free 3D display, and both of virtual objects and real scene have realistic and obvious stereo performance.

Wetting characteristics of 3-dimensional nanostructured fractal surfaces

NASA Astrophysics Data System (ADS)

Davis, Ethan; Liu, Ying; Jiang, Lijia; Lu, Yongfeng; Ndao, Sidy

2017-01-01

This article reports the fabrication and wetting characteristics of 3-dimensional nanostructured fractal surfaces (3DNFS). Three distinct 3DNFS surfaces, namely cubic, Romanesco broccoli, and sphereflake were fabricated using two-photon direct laser writing. Contact angle measurements were performed on the multiscale fractal surfaces to characterize their wetting properties. Average contact angles ranged from 66.8° for the smooth control surface to 0° for one of the fractal surfaces. The change in wetting behavior was attributed to modification of the interfacial surface properties due to the inclusion of 3-dimensional hierarchical fractal nanostructures. However, this behavior does not exactly obey existing surface wetting models in the literature. Potential applications for these types of surfaces in physical and biological sciences are also discussed.

Synchrotron x-ray modification of nanoparticle superlattice formation

NASA Astrophysics Data System (ADS)

Lu, Chenguang; Akey, Austin J.; Herman, Irving P.

2012-09-01

The synchrotron x-ray radiation used to perform small angle x-ray scattering (SAXS) during the formation of three-dimensional nanoparticle superlattices by drop casting nanoparticle solutions affects the structure and the local crystalline order of the resulting films. The domain size decreases due to the real-time SAXS analysis during drying and more macroscopic changes are visible to the eye.

PIV-based estimation of unsteady loads on a flat plate at high angle of attack using momentum equation approaches

NASA Astrophysics Data System (ADS)

Guissart, Amandine; Bernal, Luis; Dimitriadis, Gregorios; Terrapon, Vincent

2015-11-01

The direct measurement of loads with force balance can become challenging when the forces are small or when the body is moving. An alternative is the use of Particle Image Velocimetry (PIV) velocity fields to indirectly obtain the aerodynamic coefficients. This can be done by the use of control volume approaches which lead to the integration of velocities, and other fields deriving from them, on a contour surrounding the studied body and its supporting surface. This work exposes and discusses results obtained with two different methods: the direct use of the integral formulation of the Navier-Stokes equations and the so-called Noca's method. The latter is a reformulation of the integral Navier-Stokes equations in order to get rid of the pressure. Results obtained using the two methods are compared and the influence of different parameters is discussed. The methods are applied to PIV data obtained from water channel testing for the flow around a 16:1 plate. Two cases are considered: a static plate at high angle of attack and a large amplitude imposed pitching motion. Two-dimensional PIV velocity fields are used to compute the aerodynamic forces. Direct measurements of dynamic loads are also carried out in order to assess the quality of the indirectly calculated coefficients.

Colour-producing β-keratin nanofibres in blue penguin (Eudyptula minor) feathers

PubMed Central

D'Alba, Liliana; Saranathan, Vinodkumar; Clarke, Julia A.; Vinther, Jakob A.; Prum, Richard O.; Shawkey, Matthew D.

2011-01-01

The colours of living organisms are produced by the differential absorption of light by pigments (e.g. carotenoids, melanins) and/or by the physical interactions of light with biological nanostructures, referred to as structural colours. Only two fundamental morphologies of non-iridescent nanostructures are known in feathers, and recent work has proposed that they self-assemble by intracellular phase separation processes. Here, we report a new biophotonic nanostructure in the non-iridescent blue feather barbs of blue penguins (Eudyptula minor) composed of parallel β-keratin nanofibres organized into densely packed bundles. Synchrotron small angle X-ray scattering and two-dimensional Fourier analysis of electron micrographs of the barb nanostructure revealed short-range order in the organization of fibres at the appropriate size scale needed to produce the observed colour by coherent scattering. These two-dimensional quasi-ordered penguin nanostructures are convergent with similar arrays of parallel collagen fibres in avian and mammalian skin, but constitute a novel morphology for feathers. The identification of a new class of β-keratin nanostructures adds significantly to the known mechanisms of colour production in birds and suggests additional complexity in their self-assembly. PMID:21307042

Colour-producing [beta]-keratin nanofibres in blue penguin (Eudyptula minor) feathers

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

D; Alba, Liliana; Saranathan, Vinodkumar

2012-03-26

The colours of living organisms are produced by the differential absorption of light by pigments (e.g. carotenoids, melanins) and/or by the physical interactions of light with biological nanostructures, referred to as structural colours. Only two fundamental morphologies of non-iridescent nanostructures are known in feathers, and recent work has proposed that they self-assemble by intracellular phase separation processes. Here, we report a new biophotonic nanostructure in the non-iridescent blue feather barbs of blue penguins (Eudyptula minor) composed of parallel {beta}-keratin nanofibres organized into densely packed bundles. Synchrotron small angle X-ray scattering and two-dimensional Fourier analysis of electron micrographs of the barbmore » nanostructure revealed short-range order in the organization of fibres at the appropriate size scale needed to produce the observed colour by coherent scattering. These two-dimensional quasi-ordered penguin nanostructures are convergent with similar arrays of parallel collagen fibres in avian and mammalian skin, but constitute a novel morphology for feathers. The identification of a new class of {beta}-keratin nanostructures adds significantly to the known mechanisms of colour production in birds and suggests additional complexity in their self-assembly.« less

Structural hierarchy in molecular films of two class II hydrophobins.

PubMed

Paananen, Arja; Vuorimaa, Elina; Torkkeli, Mika; Penttilä, Merja; Kauranen, Martti; Ikkala, Olli; Lemmetyinen, Helge; Serimaa, Ritva; Linder, Markus B

2003-05-13

Hydrophobins are highly surface-active proteins that are specific to filamentous fungi. They function as coatings on various fungal structures, enable aerial growth of hyphae, and facilitate attachment to surfaces. Little is known about their structures and structure-function relationships. In this work we show highly organized surface layers of hydrophobins, representing the most detailed structural study of hydrophobin films so far. Langmuir-Blodgett films of class II hydrophobins HFBI and HFBII from Trichoderma reesei were prepared and analyzed by atomic force microscopy. The films showed highly ordered two-dimensional crystalline structures. By combining our recent results on small-angle X-ray scattering of hydrophobin solutions, we found that the unit cells in the films have dimensions similar to those of tetrameric aggregates found in solutions. Further analysis leads to a model in which the building blocks of the two-dimensional crystals are shape-persistent supramolecules consisting of four hydrophobin molecules. The results also indicate functional and structural differences between HFBI and HFBII that help to explain differences in their properties. The possibility that the highly organized surface assemblies of hydrophobins could allow a route for manufacturing functional surfaces is suggested.

A small-angle x-ray scattering system with a vertical layout

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

Wang, Zhen; Chen, Xiaowei; Meng, Lingpu

A small-angle x-ray scattering (SAXS) system with a vertical layout (V-SAXS) has been designed and constructed for in situ detection on nanostructures, which is well suitable for in situ study on self-assembly of nanoparticles at liquid interface and polymer processing. A steel-tower frame on a reinforced basement is built as the supporting skeleton for scattering beam path and detector platform, ensuring the system a high working stability and a high operating accuracy. A micro-focus x-ray source combining parabolic three-dimensional multi-layer mirror and scatteringless collimation system provides a highly parallel beam, which allows us to detect the very small angle range.more » With a sample-to-detector distance of 7 m, the largest measurable length scale is 420 nm in real space. With a large sample zone, it is possible to install different experimental setups such as film stretching machine, which makes the system perfect to follow the microstructures evolution of materials during processing. The capability of the V-SAXS on in situ study is tested with a drying experiment of a free latex droplet, which confirms our initial design.« less

Pair Interaction of Dislocations in Two-Dimensional Crystals

NASA Astrophysics Data System (ADS)

Eisenmann, C.; Gasser, U.; Keim, P.; Maret, G.; von Grünberg, H. H.

2005-10-01

The pair interaction between crystal dislocations is systematically explored by analyzing particle trajectories of two-dimensional colloidal crystals measured by video microscopy. The resulting pair energies are compared to Monte Carlo data and to predictions derived from the standard Hamiltonian of the elastic theory of dislocations. Good agreement is found with respect to the distance and temperature dependence of the interaction potential, but not regarding the angle dependence where discrete lattice effects become important. Our results on the whole confirm that the dislocation Hamiltonian allows a quantitative understanding of the formation and interaction energies of dislocations in two-dimensional crystals.

Numerical viscosity and resolution of high-order weighted essentially nonoscillatory schemes for compressible flows with high Reynolds numbers.

PubMed

Zhang, Yong-Tao; Shi, Jing; Shu, Chi-Wang; Zhou, Ye

2003-10-01

A quantitative study is carried out in this paper to investigate the size of numerical viscosities and the resolution power of high-order weighted essentially nonoscillatory (WENO) schemes for solving one- and two-dimensional Navier-Stokes equations for compressible gas dynamics with high Reynolds numbers. A one-dimensional shock tube problem, a one-dimensional example with parameters motivated by supernova and laser experiments, and a two-dimensional Rayleigh-Taylor instability problem are used as numerical test problems. For the two-dimensional Rayleigh-Taylor instability problem, or similar problems with small-scale structures, the details of the small structures are determined by the physical viscosity (therefore, the Reynolds number) in the Navier-Stokes equations. Thus, to obtain faithful resolution to these small-scale structures, the numerical viscosity inherent in the scheme must be small enough so that the physical viscosity dominates. A careful mesh refinement study is performed to capture the threshold mesh for full resolution, for specific Reynolds numbers, when WENO schemes of different orders of accuracy are used. It is demonstrated that high-order WENO schemes are more CPU time efficient to reach the same resolution, both for the one-dimensional and two-dimensional test problems.

Optical activity in chiral stacks of 2D semiconductors

NASA Astrophysics Data System (ADS)

Poshakinskiy, Alexander V.; Kazanov, Dmitrii R.; Shubina, Tatiana V.; Tarasenko, Sergey A.

2018-03-01

We show that the stacks of two-dimensional semiconductor crystals with the chiral packing exhibit optical activity and circular dichroism. We develop a microscopic theory of these phenomena in the spectral range of exciton transitions that takes into account the spin-dependent hopping of excitons between the layers in the stack and the interlayer coupling of excitons via electromagnetic field. For the stacks of realistic two-dimensional semiconductors such as transition metal dichalcogenides, we calculate the rotation and ellipticity angles of radiation transmitted through such structures. The angles are resonantly enhanced at the frequencies of both bright and dark exciton modes in the stack. We also study the photoluminescence of chiral stacks and show that it is circularly polarized.

Unsteady Thick Airfoil Aerodynamics: Experiments, Computation, and Theory

NASA Technical Reports Server (NTRS)

Strangfeld, C.; Rumsey, C. L.; Mueller-Vahl, H.; Greenblatt, D.; Nayeri, C. N.; Paschereit, C. O.

2015-01-01

An experimental, computational and theoretical investigation was carried out to study the aerodynamic loads acting on a relatively thick NACA 0018 airfoil when subjected to pitching and surging, individually and synchronously. Both pre-stall and post-stall angles of attack were considered. Experiments were carried out in a dedicated unsteady wind tunnel, with large surge amplitudes, and airfoil loads were estimated by means of unsteady surface mounted pressure measurements. Theoretical predictions were based on Theodorsen's and Isaacs' results as well as on the relatively recent generalizations of van der Wall. Both two- and three-dimensional computations were performed on structured grids employing unsteady Reynolds-averaged Navier-Stokes (URANS). For pure surging at pre-stall angles of attack, the correspondence between experiments and theory was satisfactory; this served as a validation of Isaacs theory. Discrepancies were traced to dynamic trailing-edge separation, even at low angles of attack. Excellent correspondence was found between experiments and theory for airfoil pitching as well as combined pitching and surging; the latter appears to be the first clear validation of van der Wall's theoretical results. Although qualitatively similar to experiment at low angles of attack, two-dimensional URANS computations yielded notable errors in the unsteady load effects of pitching, surging and their synchronous combination. The main reason is believed to be that the URANS equations do not resolve wake vorticity (explicitly modeled in the theory) or the resulting rolled-up un- steady flow structures because high values of eddy viscosity tend to \\smear" the wake. At post-stall angles, three-dimensional computations illustrated the importance of modeling the tunnel side walls.

Quantitative evaluation of the fetal cerebellar vermis using the median view on three-dimensional ultrasound.

PubMed

Zhao, Dan; Liu, Wei; Cai, Ailu; Li, Jingyu; Chen, Lizhu; Wang, Bing

2013-02-01

The purpose of this study was to investigate the effectiveness for quantitative evaluation of cerebellar vermis using three-dimensional (3D) ultrasound and to establish a nomogram for Chinese fetal vermis measurements during gestation. Sonographic examinations were performed in normal fetuses and in cases suspected of the diagnosis of vermian rotation. 3D median planes were obtained with both OMNIVIEW and tomographic ultrasound imaging. Measurements of the cerebellar vermis were highly correlated between two-dimensional and 3D median planes. The diameter of the cerebellar vermis follows growth approximately predicted by the quadratic regression equation. The normal vermis was almost parallel to the brain stem, with the average angle degree to be <2° in normal fetuses. The average angle degree of the 9 cases of vermian rotation was >5°. Three-dimensional median planes are obtained more easily than two-dimensional ones, and allow accurate measurements of the cerebellar vermis. The 3D approach may enable rapid assessment of fetal cerebral anatomy in standard examination. Measurements of cerebellar vermis may provide a quantitative index for prenatal diagnosis of posterior fossa malformations. © 2012 John Wiley & Sons, Ltd.

Directional interlayer spin-valley transfer in two-dimensional heterostructures

DOE PAGES

Schaibley, John R.; Rivera, Pasqual; Yu, Hongyi; ...

2016-12-14

Van der Waals heterostructures formed by two different monolayer semiconductors have emerged as a promising platform for new optoelectronic and spin/valleytronic applications. In addition to its atomically thin nature, a two-dimensional semiconductor heterostructure is distinct from its three-dimensional counterparts due to the unique coupled spin-valley physics of its constituent monolayers. In this paper, we report the direct observation that an optically generated spin-valley polarization in one monolayer can be transferred between layers of a two-dimensional MoSe 2–WSe 2 heterostructure. Using non-degenerate optical circular dichroism spectroscopy, we show that charge transfer between two monolayers conserves spin-valley polarization and is only weaklymore » dependent on the twist angle between layers. Finally, our work points to a new spin-valley pumping scheme in nanoscale devices, provides a fundamental understanding of spin-valley transfer across the two-dimensional interface, and shows the potential use of two-dimensional semiconductors as a spin-valley generator in two-dimensional spin/valleytronic devices for storing and processing information.« less

Aerodynamic and heat transfer analysis of the low aspect ratio turbine

NASA Astrophysics Data System (ADS)

Sharma, O. P.; Nguyen, P.; Ni, R. H.; Rhie, C. M.; White, J. A.

1987-06-01

The available two- and three-dimensional codes are used to estimate external heat loads and aerodynamic characteristics of a highly loaded turbine stage in order to demonstrate state-of-the-art methodologies in turbine design. By using data for a low aspect ratio turbine, it is found that a three-dimensional multistage Euler code gives good averall predictions for the turbine stage, yielding good estimates of the stage pressure ratio, mass flow, and exit gas angles. The nozzle vane loading distribution is well predicted by both the three-dimensional multistage Euler and three-dimensional Navier-Stokes codes. The vane airfoil surface Stanton number distributions, however, are underpredicted by both two- and three-dimensional boundary value analysis.

Powder agglomeration in a microgravity environment

NASA Technical Reports Server (NTRS)

Cawley, James D.

1994-01-01

This is the final report for NASA Grant NAG3-755 entitled 'Powder Agglomeration in a Microgravity Environment.' The research program included both two types of numerical models and two types of experiments. The numerical modeling included the use of Monte Carlo type simulations of agglomerate growth including hydrodynamic screening and molecular dynamics type simulations of the rearrangement of particles within an agglomerate under a gravitational field. Experiments included direct observation of the agglomeration of submicron alumina and indirect observation, using small angle light scattering, of the agglomeration of colloidal silica and aluminum monohydroxide. In the former class of experiments, the powders were constrained to move on a two-dimensional surface oriented to minimize the effect of gravity. In the latter, some experiments involved mixture of suspensions containing particles of opposite charge which resulted in agglomeration on a very short time scale relative to settling under gravity.

Analysis of Massively Separated Flows of Aircraft Using Detached Eddy Simulation

NASA Astrophysics Data System (ADS)

Morton, Scott

2002-08-01

An important class of turbulent flows of aerodynamic interest are those characterized by massive separation, e.g., the flow around an aircraft at high angle of attack. Numerical simulation is an important tool for analysis, though traditional models used in the solution of the Reynolds-averaged Navier-Stokes (RANS) equations appear unable to accurately account for the time-dependent and three-dimensional motions governing flows with massive separation. Large-eddy simulation (LES) is able to resolve these unsteady three-dimensional motions, yet is cost prohibitive for high Reynolds number wall-bounded flows due to the need to resolve the small scale motions in the boundary layer. Spalart et. al. proposed a hybrid technique, Detached-Eddy Simulation (DES), which takes advantage of the often adequate performance of RANS turbulence models in the "thin," typically attached regions of the flow. In the separated regions of the flow the technique becomes a Large Eddy Simulation, directly resolving the time-dependent and unsteady features that dominate regions of massive separation. The current work applies DES to a 70 degree sweep delta wing at 27 degrees angle of attack, a geometrically simple yet challenging flowfield that exhibits the unsteady three-dimensional massively separated phenomena of vortex breakdown. After detailed examination of this basic flowfield, the method is demonstrated on three full aircraft of interest characterized by massive separation, the F-16 at 45 degrees angle of attack, the F-15 at 65 degree angle of attack (with comparison to flight test), and the C-130 in a parachute drop condition at near stall speed with cargo doors open.

The angulation of the septal structures impacts ventricular imbalance in atrioventricular septal defects with a common atrioventricular junction.

PubMed

Ahmad, Zaheer; Lim, Zek; Roman, Kevin; Haw, Marcus; Anderson, Robert H; Vettukattil, Joseph

2016-02-01

Multiplanar re-formatting of full-volume three-dimensional echocardiography data sets offers new insights into the morphology of atrioventricular septal defects. We hypothesised that distortion of the alignment between the atrial and ventricular septums results in imbalanced venous return to the ventricles, with consequent proportional ventricular hypoplasia. A single observer evaluated 31 patients, with a mean age of 52.09 months, standard deviation of 55, and with a range from 2 to 264 months, with atrioventricular septal defects, of whom 17 were boys. Ventricular imbalance, observed in nine patients, was determined by two-dimensional assessment, and confirmed at surgical inspection in selected cases when a univentricular strategy was undertaken. Offline analysis using multiplanar re-formatting was performed. A line was drawn though the length of the ventricular septum and a second line along the plane of the atrial septum, taking the angle between these two lines as the atrioventricular septal angle. We compared the angle between 22 patients with adequately sized ventricles, and those with ventricular imbalance undergoing univentricular repair. In the 22 patients undergoing biventricular repair, the septal angle was 0 in 14 patients; the other eight patients having angles ranging from 1 to 36, with a mean angle of 7.4°, and standard deviation of 11.1°.The mean angle in the nine patients with ventricle imbalance was 28.6°, with a standard deviation of 3.04°, and with a range from 26 to 35°. Of those undergoing univentricular repair, two patients died, with angles of 26 and 30°, respectively. The atrioventricular septal angle derived via multiplanar formatting gives important information regarding the degree of ventricular hypoplasia and imbalance. When this angle is above 25°, patients are likely to have ventricular imbalance requiring univentricular repair.

Spatial reorientation experiments for NMR of solids and partially oriented liquids.

PubMed

Martin, Rachel W; Kelly, John E; Collier, Kelsey A

2015-11-01

Motional reorientation experiments are extensions of Magic Angle Spinning (MAS) where the rotor axis is changed in order to average out, reintroduce, or scale anisotropic interactions (e.g. dipolar couplings, quadrupolar interactions or chemical shift anisotropies). This review focuses on Variable Angle Spinning (VAS), Switched Angle Spinning (SAS), and Dynamic Angle Spinning (DAS), all of which involve spinning at two or more different angles sequentially, either in successive experiments or during a multidimensional experiment. In all of these experiments, anisotropic terms in the Hamiltonian are scaled by changing the orientation of the spinning sample relative to the static magnetic field. These experiments vary in experimental complexity and instrumentation requirements. In VAS, many one-dimensional spectra are collected as a function of spinning angle. In SAS, dipolar couplings and/or chemical shift anisotropies are reintroduced by switching the sample between two different angles, often 0° or 90° and the magic angle, yielding a two-dimensional isotropic-anisotropic correlation spectrum. Dynamic Angle Spinning (DAS) is a related experiment that is used to simultaneously average out the first- and second-order quadrupolar interactions, which cannot be accomplished by spinning at any unique rotor angle in physical space. Although motional reorientation experiments generally require specialized instrumentation and data analysis schemes, some are accessible with only minor modification of standard MAS probes. In this review, the mechanics of each type of experiment are described, with representative examples. Current and historical probe and coil designs are discussed from the standpoint of how each one accomplishes the particular objectives of the experiment(s) it was designed to perform. Finally, applications to inorganic materials and liquid crystals, which present very different experimental challenges, are discussed. The review concludes with perspectives on how motional reorientation experiments can be applied to current problems in chemistry, molecular biology, and materials science, given the many advances in high-field NMR magnets, fast spinning, and sample preparation realized in recent years. Copyright © 2015 Elsevier B.V. All rights reserved.

Determination of the real structure of artificial and natural opals on the basis of three-dimensional reconstructions of reciprocal space

NASA Astrophysics Data System (ADS)

Eliseev, A. A.; Gorozhankin, D. F.; Napolskii, K. S.; Petukhov, A. V.; Sapoletova, N. A.; Vasilieva, A. V.; Grigoryeva, N. A.; Mistonov, A. A.; Byelov, D. V.; Bouwman, W. G.; Kvashnina, K. O.; Chernyshov, D. Yu.; Bosak, A. A.; Grigoriev, S. V.

2009-10-01

The distribution of the scattering intensity in the reciprocal space for natural and artificial opals has been reconstructed from a set of small-angle X-ray diffraction patterns. The resulting three-dimensional intensity maps are used to analyze the defect structure of opals. The structure of artificial opals can be satisfactorily described in the Wilson probability model with the prevalence of layers in the fcc environment. The diffraction patterns observed for a natural opal confirm the presence of sufficiently long unequally occupied fcc domains.

DOA estimation of noncircular signals for coprime linear array via locally reduced-dimensional Capon

NASA Astrophysics Data System (ADS)

Zhai, Hui; Zhang, Xiaofei; Zheng, Wang

2018-05-01

We investigate the issue of direction of arrival (DOA) estimation of noncircular signals for coprime linear array (CLA). The noncircular property enhances the degree of freedom and improves angle estimation performance, but it leads to a more complex angle ambiguity problem. To eliminate ambiguity, we theoretically prove that the actual DOAs of noncircular signals can be uniquely estimated by finding the coincide results from the two decomposed subarrays based on the coprimeness. We propose a locally reduced-dimensional (RD) Capon algorithm for DOA estimation of noncircular signals for CLA. The RD processing is used in the proposed algorithm to avoid two dimensional (2D) spectral peak search, and coprimeness is employed to avoid the global spectral peak search. The proposed algorithm requires one-dimensional locally spectral peak search, and it has very low computational complexity. Furthermore, the proposed algorithm needs no prior knowledge of the number of sources. We also derive the Crámer-Rao bound of DOA estimation of noncircular signals in CLA. Numerical simulation results demonstrate the effectiveness and superiority of the algorithm.

Optical metasurfaces for high angle steering at visible wavelengths

DOE PAGES

Lin, Dianmin; Melli, Mauro; Poliakov, Evgeni; ...

2017-05-23

Metasurfaces have facilitated the replacement of conventional optical elements with ultrathin and planar photonic structures. Previous designs of metasurfaces were limited to small deflection angles and small ranges of the angle of incidence. Here, we have created two types of Si-based metasurfaces to steer visible light to a large deflection angle. These structures exhibit high diffraction efficiencies over a broad range of angles of incidence. We have demonstrated metasurfaces working both in transmission and reflection modes based on conventional thin film silicon processes that are suitable for the large-scale fabrication of high-performance devices.

Study of Effect of Impacting Direction on Abrasive Nanometric Cutting Process with Molecular Dynamics

NASA Astrophysics Data System (ADS)

Li, Junye; Meng, Wenqing; Dong, Kun; Zhang, Xinming; Zhao, Weihong

2018-01-01

Abrasive flow polishing plays an important part in modern ultra-precision machining. Ultrafine particles suspended in the medium of abrasive flow removes the material in nanoscale. In this paper, three-dimensional molecular dynamics (MD) simulations are performed to investigate the effect of impacting direction on abrasive cutting process during abrasive flow polishing. The molecular dynamics simulation software Lammps was used to simulate the cutting of single crystal copper with SiC abrasive grains at different cutting angles (0o-45o). At a constant friction coefficient, we found a direct relation between cutting angle and cutting force, which ultimately increases the number of dislocation during abrasive flow machining. Our theoretical study reveal that a small cutting angle is beneficial for improving surface quality and reducing internal defects in the workpiece. However, there is no obvious relationship between cutting angle and friction coefficient.

Study of Effect of Impacting Direction on Abrasive Nanometric Cutting Process with Molecular Dynamics.

PubMed

Li, Junye; Meng, Wenqing; Dong, Kun; Zhang, Xinming; Zhao, Weihong

2018-01-11

Abrasive flow polishing plays an important part in modern ultra-precision machining. Ultrafine particles suspended in the medium of abrasive flow removes the material in nanoscale. In this paper, three-dimensional molecular dynamics (MD) simulations are performed to investigate the effect of impacting direction on abrasive cutting process during abrasive flow polishing. The molecular dynamics simulation software Lammps was used to simulate the cutting of single crystal copper with SiC abrasive grains at different cutting angles (0 o -45 o ). At a constant friction coefficient, we found a direct relation between cutting angle and cutting force, which ultimately increases the number of dislocation during abrasive flow machining. Our theoretical study reveal that a small cutting angle is beneficial for improving surface quality and reducing internal defects in the workpiece. However, there is no obvious relationship between cutting angle and friction coefficient.

Optimal operation of turbo blowers serially connected using inlet vanes

NASA Astrophysics Data System (ADS)

Jang, Choon-Man

2011-03-01

Optimal operation of the turbo blowers having an inlet vane has been studied to understand the blowers' operating performance. To analyze three-dimensional flow field in the turbo blowers serially connected, general analysis code, CFX, is introduced in the present work. SST turbulence model is employed to estimate the eddy viscosity. Throughout the numerical analysis, it is found that the flow rates of the turbo blowers can be controlled at the vane angle between 90 (full open condition) degrees and 60 degrees effectively, because pressure loss rapidly increases below 60 degree of a vane angle. Efficiency also has almost the same values from 90 degrees to 60 degrees of a vane angle. It is noted that the distorted inlet velocity generated in the small vane angle makes performance deterioration of the turbo blowers due to the local leading edge separation and the following non-uniform blade loading.

Three dimensional reliability analyses of currently used methods for assessment of sagittal jaw discrepancy

PubMed Central

Almaqrami, Bushra-Sufyan; Alhammadi, Maged-Sultan

2018-01-01

Background The objective of this study was to analyse three dimensionally the reliability and correlation of angular and linear measurements in assessment of anteroposterior skeletal discrepancy. Material and Methods In this retrospective cross sectional study, a sample of 213 subjects were three-dimensionally analysed from cone-beam computed tomography scans. The sample was divided according to three dimensional measurement of anteroposterior relation (ANB angle) into three groups (skeletal Class I, Class II and Class III). The anterior-posterior cephalometric indicators were measured on volumetric images using Anatomage software (InVivo5.2). These measurements included three angular and seven linear measurements. Cross tabulations were performed to correlate the ANB angle with each method. Intra-class Correlation Coefficient (ICC) test was applied for the difference between the two reliability measurements. P value of < 0.05 was considered significant. Results There was a statistically significant (P<0.05) agreement between all methods used with variability in assessment of different anteroposterior relations. The highest correlation was between ANB and DSOJ (0.913), strong correlation with AB/FH, AB/SN/, MM bisector, AB/PP, Wits appraisal (0.896, 0.890, 0.878, 0.867,and 0.858, respectively), moderate with AD/SN and Beta angle (0.787 and 0.760), and weak correlation with corrected ANB angle (0.550). Conclusions Conjunctive usage of ANB angle with DSOJ, AB/FH, AB/SN/, MM bisector, AB/PP and Wits appraisal in 3D cephalometric analysis provide a more reliable and valid indicator of the skeletal anteroposterior relationship. Clinical relevance: Most of orthodontic literature depends on single method (ANB) with its drawbacks in assessment of skeletal discrepancy which is a cardinal factors for proper treatment planning, this study assessed three dimensionally the degree of correlation between all available methods to make clinical judgement more accurate based on more than one method of assessment. Key words:Anteroposterior relationships, ANB angle, Three-dimension, CBCT. PMID:29750096

Three-dimensional Model of Human Platelet Integrin αIIbβ3 in Solution Obtained by Small Angle Neutron Scattering*

PubMed Central

Nogales, Aurora; García, Carolina; Pérez, Javier; Callow, Phil; Ezquerra, Tiberio A.; González-Rodríguez, José

2010-01-01

Integrin αIIbβ3 is the major membrane protein and adhesion receptor at the surface of blood platelets, which after activation plays a key role in platelet plug formation in hemostasis and thrombosis. Small angle neutron scattering (SANS) and shape reconstruction algorithms allowed formation of a low resolution three-dimensional model of whole αIIbβ3 in Ca2+/detergent solutions. Model projections after 90° rotation along its long axis show an elongated and “arched” form (135°) not observed before and a “handgun” form. This 20-nm-long structure is well defined, despite αIIbβ3 multidomain nature and expected segmental flexibility, with the largest region at the top, followed by two narrower and smaller regions at the bottom. Docking of this SANS envelope into the high resolution structure of αIIbβ3, reconstructed from crystallographic and NMR data, shows that the solution structure is less constrained, allows tentative assignment of the disposition of the αIIb and β3 subunits and their domains within the model, and points out the structural analogies and differences of the SANS model with the crystallographic models of the recombinant ectodomains of αIIbβ3 and αVβ3 and with the cryo-electron microscopy model of whole αIIbβ3. The ectodomain is in the bent configuration at the top of the model, where αIIb and β3 occupy the concave and convex sides, respectively, at the arched projection, with their bent knees at its apex. It follows the narrower transmembrane region and the cytoplasmic domains at the bottom end. αIIbβ3 aggregated in Mn2+/detergent solutions, which impeded to get its SANS model. PMID:19897481

Structure and optical function of amorphous photonic nanostructures from avian feather barbs: a comparative small angle X-ray scattering (SAXS) analysis of 230 bird species

PubMed Central

Saranathan, Vinodkumar; Forster, Jason D.; Noh, Heeso; Liew, Seng-Fatt; Mochrie, Simon G. J.; Cao, Hui; Dufresne, Eric R.; Prum, Richard O.

2012-01-01

Non-iridescent structural colours of feathers are a diverse and an important part of the phenotype of many birds. These colours are generally produced by three-dimensional, amorphous (or quasi-ordered) spongy β-keratin and air nanostructures found in the medullary cells of feather barbs. Two main classes of three-dimensional barb nanostructures are known, characterized by a tortuous network of air channels or a close packing of spheroidal air cavities. Using synchrotron small angle X-ray scattering (SAXS) and optical spectrophotometry, we characterized the nanostructure and optical function of 297 distinctly coloured feathers from 230 species belonging to 163 genera in 51 avian families. The SAXS data provided quantitative diagnoses of the channel- and sphere-type nanostructures, and confirmed the presence of a predominant, isotropic length scale of variation in refractive index that produces strong reinforcement of a narrow band of scattered wavelengths. The SAXS structural data identified a new class of rudimentary or weakly nanostructured feathers responsible for slate-grey, and blue-grey structural colours. SAXS structural data provided good predictions of the single-scattering peak of the optical reflectance of the feathers. The SAXS structural measurements of channel- and sphere-type nanostructures are also similar to experimental scattering data from synthetic soft matter systems that self-assemble by phase separation. These results further support the hypothesis that colour-producing protein and air nanostructures in feather barbs are probably self-assembled by arrested phase separation of polymerizing β-keratin from the cytoplasm of medullary cells. Such avian amorphous photonic nanostructures with isotropic optical properties may provide biomimetic inspiration for photonic technology. PMID:22572026

An asymmetric pair of vortices adjacent to a spinning cylinder

NASA Astrophysics Data System (ADS)

Iosilevskii, G.; Seginer, A.

The two-dimensional flow field over a spinning circular cylinder is analyzed using an extension of the Foeppl method. Equilibrium equations for two asymmetric point vortices in the wake of the cylinder are solved for a case when both vortices are equidistant from the cylinder. The two Foeppl solutions for the cylinder are presented. It is observed that the spin does not affect the angle between the two vortices; however, it displaces the vortex pair in the spin direction and the sinus of the displacement angle is proportional to the spin rate.

Orthogonal vector algorithm to obtain the solar vector using the single-scattering Rayleigh model.

PubMed

Wang, Yinlong; Chu, Jinkui; Zhang, Ran; Shi, Chao

2018-02-01

Information obtained from a polarization pattern in the sky provides many animals like insects and birds with vital long-distance navigation cues. The solar vector can be derived from the polarization pattern using the single-scattering Rayleigh model. In this paper, an orthogonal vector algorithm, which utilizes the redundancy of the single-scattering Rayleigh model, is proposed. We use the intersection angles between the polarization vectors as the main criteria in our algorithm. The assumption that all polarization vectors can be considered coplanar is used to simplify the three-dimensional (3D) problem with respect to the polarization vectors in our simulation. The surface-normal vector of the plane, which is determined by the polarization vectors after translation, represents the solar vector. Unfortunately, the two-directionality of the polarization vectors makes the resulting solar vector ambiguous. One important result of this study is, however, that this apparent disadvantage has no effect on the complexity of the algorithm. Furthermore, two other universal least-squares algorithms were investigated and compared. A device was then constructed, which consists of five polarized-light sensors as well as a 3D attitude sensor. Both the simulation and experimental data indicate that the orthogonal vector algorithms, if used with a suitable threshold, perform equally well or better than the other two algorithms. Our experimental data reveal that if the intersection angles between the polarization vectors are close to 90°, the solar-vector angle deviations are small. The data also support the assumption of coplanarity. During the 51 min experiment, the mean of the measured solar-vector angle deviations was about 0.242°, as predicted by our theoretical model.

Experimental Investigation of Shock-Shock Interactions Over a 2-D Wedge at M=6

NASA Technical Reports Server (NTRS)

Jones, Michelle L.

2013-01-01

The effects of fin-leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-inch Mach 6 Air Tunnel. The fin model leading edges, which represent cylindrical leading edges or struts on hypersonic vehicles, were varied from 0.25 inches to 0.75 inches in radius. A 9deg wedge generated a planar oblique shock at 16.7deg to the flow that intersected the fin bow shock, producing a shock-shock interaction that impinged on the fin leading edge. The fin angle of attack was varied from 0deg (normal to the free-stream) to 15deg and 25deg swept forward. Global temperature data was obtained from the surface of the fused silica fins through phosphor thermography. Metal oil flow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using one-dimensional semi-infinite as well as one- and two-dimensional finite-volume methods to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for the three shock-shock interactions, respectively, between the test articles with varying leading-edge radius. The dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite one-dimensional method.

Coanda-Assisted Spray Manipulation Collar for a Commercial Plasma Spray Gun

NASA Astrophysics Data System (ADS)

Mabey, K.; Smith, B. L.; Whichard, G.; McKechnie, T.

2011-06-01

A Coanda-assisted Spray Manipulation (CSM) collar was retrofitted to a Praxair SG-100 plasma spray gun. The CSM device makes it possible to change the direction of (vector) the plasma jet and powder without moving the gun. The two-piece retrofit device replaces the standard faceplate. Two separate collars were tested: one designed for small vector angles and one for larger vector angles. It was demonstrated that the small-angle device could modify the trajectory of zirconia powder up to several degrees. Doing so could realign the plasma with the powder resulting in increased powder temperature and velocity. The large-angle device was capable of vectoring the plasma jet up to 45°. However, the powder did not vector as much. Under large-angle vectoring, the powder velocity and temperature decreased steadily with vector angle. Both devices were tested using a supersonic configuration to demonstrate that CSM is capable of vectoring supersonic plasmas.

Motivated Proteins: A web application for studying small three-dimensional protein motifs

PubMed Central

Leader, David P; Milner-White, E James

2009-01-01

Background Small loop-shaped motifs are common constituents of the three-dimensional structure of proteins. Typically they comprise between three and seven amino acid residues, and are defined by a combination of dihedral angles and hydrogen bonding partners. The most abundant of these are αβ-motifs, asx-motifs, asx-turns, β-bulges, β-bulge loops, β-turns, nests, niches, Schellmann loops, ST-motifs, ST-staples and ST-turns. We have constructed a database of such motifs from a range of high-quality protein structures and built a web application as a visual interface to this. Description The web application, Motivated Proteins, provides access to these 12 motifs (with 48 sub-categories) in a database of over 400 representative proteins. Queries can be made for specific categories or sub-categories of motif, motifs in the vicinity of ligands, motifs which include part of an enzyme active site, overlapping motifs, or motifs which include a particular amino acid sequence. Individual proteins can be specified, or, where appropriate, motifs for all proteins listed. The results of queries are presented in textual form as an (X)HTML table, and may be saved as parsable plain text or XML. Motifs can be viewed and manipulated either individually or in the context of the protein in the Jmol applet structural viewer. Cartoons of the motifs imposed on a linear representation of protein secondary structure are also provided. Summary information for the motifs is available, as are histograms of amino acid distribution, and graphs of dihedral angles at individual positions in the motifs. Conclusion Motivated Proteins is a publicly and freely accessible web application that enables protein scientists to study small three-dimensional motifs without requiring knowledge of either Structured Query Language or the underlying database schema. PMID:19210785

Quantitative determination of the lateral density and intermolecular correlation between proteins anchored on the membrane surfaces using grazing incidence small-angle X-ray scattering and grazing incidence X-ray fluorescence.

PubMed

Abuillan, Wasim; Vorobiev, Alexei; Hartel, Andreas; Jones, Nicola G; Engstler, Markus; Tanaka, Motomu

2012-11-28

As a physical model of the surface of cells coated with densely packed, non-crystalline proteins coupled to lipid anchors, we functionalized the surface of phospholipid membranes by coupling of neutravidin to biotinylated lipid anchors. After the characterization of fine structures perpendicular to the plane of membrane using specular X-ray reflectivity, the same membrane was characterized by grazing incidence small angle X-ray scattering (GISAXS). Within the framework of distorted wave Born approximation and two-dimensional Percus-Yevick function, we can analyze the form and structure factors of the non-crystalline, membrane-anchored proteins for the first time. As a new experimental technique to quantify the surface density of proteins on the membrane surface, we utilized grazing incidence X-ray fluorescence (GIXF). Here, the mean intermolecular distance between proteins from the sulfur peak intensities can be calculated by applying Abelé's matrix formalism. The characteristic correlation distance between non-crystalline neutravidin obtained by the GISAXS analysis agrees well with the intermolecular distance calculated by GIXF, suggesting a large potential of the combination of GISAXS and GIXF in probing the lateral density and correlation of non-crystalline proteins displayed on the membrane surface.

Surface layer protein characterization by small angle x-ray scattering and a fractal mean force concept: from protein structure to nanodisk assemblies.

PubMed

Horejs, Christine; Pum, Dietmar; Sleytr, Uwe B; Peterlik, Herwig; Jungbauer, Alois; Tscheliessnig, Rupert

2010-11-07

Surface layers (S-layers) are the most commonly observed cell surface structure of prokaryotic organisms. They are made up of proteins that spontaneously self-assemble into functional crystalline lattices in solution, on various solid surfaces, and interfaces. While classical experimental techniques failed to recover a complete structural model of an unmodified S-layer protein, small angle x-ray scattering (SAXS) provides an opportunity to study the structure of S-layer monomers in solution and of self-assembled two-dimensional sheets. For the protein under investigation we recently suggested an atomistic structural model by the use of molecular dynamics simulations. This structural model is now refined on the basis of SAXS data together with a fractal assembly approach. Here we show that a nondiluted critical system of proteins, which crystallize into monomolecular structures, might be analyzed by SAXS if protein-protein interactions are taken into account by relating a fractal local density distribution to a fractal local mean potential, which has to fulfill the Poisson equation. The present work demonstrates an important step into the elucidation of the structure of S-layers and offers a tool to analyze the structure of self-assembling systems in solution by means of SAXS and computer simulations.

Surface layer protein characterization by small angle x-ray scattering and a fractal mean force concept: From protein structure to nanodisk assemblies

NASA Astrophysics Data System (ADS)

Horejs, Christine; Pum, Dietmar; Sleytr, Uwe B.; Peterlik, Herwig; Jungbauer, Alois; Tscheliessnig, Rupert

2010-11-01

Surface layers (S-layers) are the most commonly observed cell surface structure of prokaryotic organisms. They are made up of proteins that spontaneously self-assemble into functional crystalline lattices in solution, on various solid surfaces, and interfaces. While classical experimental techniques failed to recover a complete structural model of an unmodified S-layer protein, small angle x-ray scattering (SAXS) provides an opportunity to study the structure of S-layer monomers in solution and of self-assembled two-dimensional sheets. For the protein under investigation we recently suggested an atomistic structural model by the use of molecular dynamics simulations. This structural model is now refined on the basis of SAXS data together with a fractal assembly approach. Here we show that a nondiluted critical system of proteins, which crystallize into monomolecular structures, might be analyzed by SAXS if protein-protein interactions are taken into account by relating a fractal local density distribution to a fractal local mean potential, which has to fulfill the Poisson equation. The present work demonstrates an important step into the elucidation of the structure of S-layers and offers a tool to analyze the structure of self-assembling systems in solution by means of SAXS and computer simulations.

Coriolis effect on dynamic stall in a vertical axis wind turbine

NASA Astrophysics Data System (ADS)

Tsai, Hsieh-Chen; Colonius, Tim

2013-11-01

The immersed boundary method is used to simulate the flow around a two-dimensional rotating NACA 0018 airfoil at moderate (sub-scale) Reynolds number in order to investigate separated flow occurring on a vertical-axis wind turbine (VAWT). The influence of dynamic stall on the forces is characterized as a function of tip-speed ratio. The influence of the Coriolis effect is also investigated by comparing the rotating airfoil to one undergoing a surging and pitching motion that produces an equivalent speed and angle-of-attack variation over the cycle. While the Coriolis force produces only small differences in the averaged forces, it plays an important role during dynamic stall. Due to the fact that the Coriolis force deflects the fluid and propagates the vortices differently, the wake-capturing phenomenon of the trailing edge vortex is observed in the flow around the rotating airfoil during a certain range of azimuthal angle. This wake-capturing of the trailing edge vortex leads to a large decrease in lift. However, because of the phase difference between each wake-capturing, there are only small differences in the average forces. The simulations are also compared to results from companion water-tunnel experiments at Caltech. This project is supported by the Gordon and Betty Moore Foundation.

Surface layer protein characterization by small angle x-ray scattering and a fractal mean force concept: From protein structure to nanodisk assemblies

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

Horejs, Christine; Pum, Dietmar; Sleytr, Uwe B.

2010-11-07

Surface layers (S-layers) are the most commonly observed cell surface structure of prokaryotic organisms. They are made up of proteins that spontaneously self-assemble into functional crystalline lattices in solution, on various solid surfaces, and interfaces. While classical experimental techniques failed to recover a complete structural model of an unmodified S-layer protein, small angle x-ray scattering (SAXS) provides an opportunity to study the structure of S-layer monomers in solution and of self-assembled two-dimensional sheets. For the protein under investigation we recently suggested an atomistic structural model by the use of molecular dynamics simulations. This structural model is now refined on themore » basis of SAXS data together with a fractal assembly approach. Here we show that a nondiluted critical system of proteins, which crystallize into monomolecular structures, might be analyzed by SAXS if protein-protein interactions are taken into account by relating a fractal local density distribution to a fractal local mean potential, which has to fulfill the Poisson equation. The present work demonstrates an important step into the elucidation of the structure of S-layers and offers a tool to analyze the structure of self-assembling systems in solution by means of SAXS and computer simulations.« less

Wedge-Shaped GaN Nanowalls: A Potential Candidate for Two-Dimensional Electronics and Spintronics

NASA Astrophysics Data System (ADS)

Deb, Swarup; Dhar, Subhabrata

Schrödingerand Poisson equations are solved self-consistently in order to obtain the potential and charge density distribution in n-type GaN nanowalls tapered along c-axis by different angles. The study shows two-dimensional (2D) quantum confinement of electrons in the central vertical plane of the wall for the entire range of tapering. Calculation of room temperature electron mobility in the 2D channel shows a steady decrease with the increase of the inclination angle of the side facets with respect to the base. However, it is interesting to note that the mobility remains to be much larger than that of bulk GaN even for the inclination angle of 65∘. The properties of high mobility and the vertical orientation of the 2DEG plane in this system can be exploited in fabricating highly conducting transparent interconnects and field effect transistors, which can lead to large scale integration of 2D devices in future.

Quantum transport in new two-dimensional heterostructures: Thin films of topological insulators, phosphorene

NASA Astrophysics Data System (ADS)

Majidi, Leyla; Zare, Moslem; Asgari, Reza

2018-06-01

The unusual features of the charge and spin transport characteristics are investigated in new two-dimensional heterostructures. Intraband specular Andreev reflection is realized in a topological insulator thin film normal/superconducting junction in the presence of a gate electric field. Perfect specular electron-hole conversion is shown for different excitation energy values in a wide experimentally available range of the electric field and also for all angles of incidence when the excitation energy has a particular value. It is further demonstrated that the transmission probabilities of the incoming electrons from different spin subbands to the monolayer phosphorene ferromagnetic/normal/ferromagnetic (F/N/F) hybrid structure have different behavior with the angle of incidence and perfect transmission occurs at defined angles of incidence to the proposed structure with different length of the N region, and different alignments of magnetization vectors. Moreover, the sign change of the spin-current density is demonstrated by tuning the chemical potential and exchange field of the F region.

Experimental studies of flow separation and stalling on two-dimensional airfoils at low speeds. Phase 2: Studies with Fowler flap extended

NASA Technical Reports Server (NTRS)

Seetharam, H. C.; Wentz, W. H., Jr.

1975-01-01

Results were given on experimental studies of flow separation and stalling on a two-dimensional GA(W)-1 17 percent thick airfoil with an extended Fowler flap. Experimental velocity profiles obtained from a five tube probe survey with optimum flap gap and overlap setting (flap at 40 deg) are shown at various stations above, below, and behind the airfoil/flap combination for various angles of attack. The typical zones of steady flow, intermittent turbulence, and large scale turbulence were obtained from a hot wire anemometer survey and are depicted graphically for an angle of attack of 12.5 deg. Local skin friction distributions were obtained and are given for various angles of attack. Computer plots of the boundary layer profiles are shown for the case of the flap at 40 deg. Static pressure contours are also given. A GA(W)-2 section model was fabricated with 30 percent Fowler flaps and with pressure tabs.

Pose determination of a blade implant in three dimensions from a single two-dimensional radiograph.

PubMed

Toti, Paolo; Barone, Antonio; Marconcini, Simone; Menchini-Fabris, Giovanni Battista; Martuscelli, Ranieri; Covani, Ugo

2018-05-01

The aim of the study was to introduce a mathematical method to estimate the correct pose of a blade by evaluating the radiographic features obtained from a single two-dimensional image. Blade-form implant bed preparation was performed using the piezosurgery device, and placement was attained with the use of magnetic mallet. The pose determination of the blade was described by means of three consecutive rotations defined by three angles of orientation (triplet φ, θ and ψ). Retrospective analysis on periapical radiographs was performed. This method was used to compare implant (axial length along the marker, i.e. the implant structure) vs angular correction factor (a trigonometric function of the triplet). The accuracy of the method was tested by generating two-dimensional radiographic simulations of the blades, which were then compared with the images of the implants as appearing on the real radiographs. Two patients had to be excluded from further evaluation because the values of the estimated pose angles showed a too-wide range to be effective for a good standardization of serial radiographs: intrapatient range from baseline to 1-year survey was > of a threshold determined by the clinicians (30°). The linear dependence between implant (CF°) and angular correction factor (CF^) was estimated by a robust linear regression, yielding the following coefficients: slope, 0.908; intercept, -0.092; and coefficient of determination, 0.924. The absolute error in accuracy was -0.29 ± 4.35, 0.23 ± 3.81 and 0.64 ± 1.18°, respectively, for the angles φ, θ and ψ. The present theoretical and experimental study established the possibility of determining, a posteriori, a unique triplet of angles (φ, θ and ψ) which described the pose of a blade upon a single two-dimensional radiograph, and of suggesting a method to detect cases in which the standardized geometric projection failed. The angular correction of the bone level yielded results very close to those obtained with an internal marker related to the implant length.

Is dynamic two-dimensional anal ultrasonography useful in the assessment of anismus? A comparison with manometry.

PubMed

Murad-Regadas, Sthela Maria; Regadas, Francisco Sérgio P; Barreto, Rosilma Gorete Lima; Rodrigues, Lusmar Veras; Fernandes, Graziela Olivia da Silva; Lima, Doryane Maria dos Reis

2010-01-01

Anismus is a prevalent functional cause of outlet delay. It is characterized by symptoms of obstructed defecation associated with paradoxical contraction of the pelvic floor muscles. To evaluate the ability of two dimensional anal ultrasonography to identify anismus patients with paradoxical contraction or normal relaxation, comparing findings with manometric measurements. Forty-nine women presenting with outlet delay and a mean validated Wexner constipation score of 13.5 were included in a prospective study. Following screening with anal manometry, the patients were assigned to one of two groups: G-I -with normal relaxation and G-II -patients with anismus. Dynamic anorectal ultrasonography was used to quantifier the movement of the puborectalis muscle and to measure changes in the angle between two converging lines drawn from the 3 o'clock and the 9 o'clock positions of the endoprobe circumference to the internal border of the puborectalis muscle. The angle decreases during straining in patients with normal relaxation, but increases in patients with anismus. The agreement between the two techniques was verified with the Kappa index. In manometry, during straining the anal canal pressure decreased by 41.3% in G-I and increased by 168.6% in G-II, indicating a diagnosis of anismus for the second group. In US, during straining, the angle produced by the movement of the puborectalis muscle decreased from 63 ± 1.31 to 58 ± 1.509 degrees (P = 0.0135) in 23 of the 30 patients in G-I, indicating normal relaxation, and increased from 66 ± 0.972 to 72 ± 0.897 degrees (P = 0.0001) in 16 of the 19 patients in G-II, indicating anismus. The index of agreement between manometry and two dimensional anal ultrasonography was moderate: 77% (23/30) for G-I and 84% (16/19) for G-II. Two-dimensional dynamic anal ultrasonography showed similar results previously suggested by anal manometry at identifying patients with normal relaxation or paradoxical contraction.

Vlasov Simulation of the Effects of Collisions on the Damping of Electron Plasma Waves

NASA Astrophysics Data System (ADS)

Banks, Jeff; Berger, Richard; Chapman, Thomas; Brunner, Stephan; Tran, T.

2015-11-01

Kinetic simulation of two dimensional plasma waves through direct discretization of the Vlasov equation may be particularly attractive for situations where minimal numerical fluctuation levels are desired, such as when measuring growth rates of plasma wave instabilities. In many cases collisional effects can be important to the evolution of plasma waves because they both set a minimum damping rate for plasma waves and can scatter particles out of resonance through pitch angle scattering. Here we present Vlasov simulations of evolving electron plasma waves (EPWs) in plasmas of varying collisionality. We consider first the effects of electron-ion pitch angle collisions on the frequency and damping, Landau and collisional, of small-amplitude EPWs for a range of collision rates. In addition, the wave phase velocities are extracted from the simulation results and compared with theory. For this study we use the Eulerian-based kinetic code LOKI that evolves the Vlasov-Poisson system in 2+2-dimensional phase space. We then discuss extensions of the collision operator to include thermalization. Discretization of these collision operators using 4th order accurate conservative finite-differencing will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and funded by the LDRD program at LLNL under project tracking code 15-ERD-038.

A NARROW SHORT-DURATION GRB JET FROM A WIDE CENTRAL ENGINE

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

Duffell, Paul C.; Quataert, Eliot; MacFadyen, Andrew I., E-mail: duffell@berkeley.edu

2015-11-01

We use two-dimensional relativistic hydrodynamic numerical calculations to show that highly collimated relativistic jets can be produced in neutron star merger models of short-duration gamma-ray bursts (GRBs) without the need for a highly directed engine or a large net magnetic flux. Even a hydrodynamic engine generating a very wide sustained outflow on small scales can, in principle, produce a highly collimated relativistic jet, facilitated by a dense surrounding medium that provides a cocoon surrounding the jet core. An oblate geometry to the surrounding gas significantly enhances the collimation process. Previous numerical simulations have shown that the merger of two neutronmore » stars produces an oblate, expanding cloud of dynamical ejecta. We show that this gas can efficiently collimate the central engine power much like the surrounding star does in long-duration GRB models. For typical short-duration GRB central engine parameters, we find jets with opening angles of an order of 10° in which a large fraction of the total outflow power of the central engine resides in highly relativistic material. These results predict large differences in the opening angles of outflows from binary neutron star mergers versus neutron star–black hole mergers.« less

Three-dimensional dynamics of scientific balloon systems in response to sudden gust loadings. [including a computer program user manual

NASA Technical Reports Server (NTRS)

Dorsey, D. R., Jr.

1975-01-01

A mathematical model was developed of the three-dimensional dynamics of a high-altitude scientific research balloon system perturbed from its equilibrium configuration by an arbitrary gust loading. The platform is modelled as a system of four coupled pendula, and the equations of motion were developed in the Lagrangian formalism assuming a small-angle approximation. Three-dimensional pendulation, torsion, and precessional motion due to Coriolis forces are considered. Aerodynamic and viscous damping effects on the pendulatory and torsional motions are included. A general model of the gust field incident upon the balloon system was developed. The digital computer simulation program is described, and a guide to its use is given.

Quadrotor trajectory tracking using PID cascade control

NASA Astrophysics Data System (ADS)

Idres, M.; Mustapha, O.; Okasha, M.

2017-12-01

Quadrotors have been applied to collect information for traffic, weather monitoring, surveillance and aerial photography. In order to accomplish their mission, quadrotors have to follow specific trajectories. This paper presents proportional-integral-derivative (PID) cascade control of a quadrotor for path tracking problem when velocity and acceleration are small. It is based on near hover controller for small attitude angles. The integral of time-weighted absolute error (ITAE) criterion is used to determine the PID gains as a function of quadrotor modeling parameters. The controller is evaluated in three-dimensional environment in Simulink. Overall, the tracking performance is found to be excellent for small velocity condition.

An advanced scanning method for space-borne hyper-spectral imaging system

NASA Astrophysics Data System (ADS)

Wang, Yue-ming; Lang, Jun-Wei; Wang, Jian-Yu; Jiang, Zi-Qing

2011-08-01

Space-borne hyper-spectral imagery is an important means for the studies and applications of earth science. High cost efficiency could be acquired by optimized system design. In this paper, an advanced scanning method is proposed, which contributes to implement both high temporal and spatial resolution imaging system. Revisit frequency and effective working time of space-borne hyper-spectral imagers could be greatly improved by adopting two-axis scanning system if spatial resolution and radiometric accuracy are not harshly demanded. In order to avoid the quality degradation caused by image rotation, an idea of two-axis rotation has been presented based on the analysis and simulation of two-dimensional scanning motion path and features. Further improvement of the imagers' detection ability under the conditions of small solar altitude angle and low surface reflectance can be realized by the Ground Motion Compensation on pitch axis. The structure and control performance are also described. An intelligent integration technology of two-dimensional scanning and image motion compensation is elaborated in this paper. With this technology, sun-synchronous hyper-spectral imagers are able to pay quick visit to hot spots, acquiring both high spatial and temporal resolution hyper-spectral images, which enables rapid response of emergencies. The result has reference value for developing operational space-borne hyper-spectral imagers.

The Interplay between Proto--Neutron Star Convection and Neutrino Transport in Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

Mezzacappa, A.; Calder, A. C.; Bruenn, S. W.; Blondin, J. M.; Guidry, M. W.; Strayer, M. R.; Umar, A. S.

1998-01-01

We couple two-dimensional hydrodynamics to realistic one-dimensional multigroup flux-limited diffusion neutrino transport to investigate proto-neutron star convection in core-collapse supernovae, and more specifically, the interplay between its development and neutrino transport. Our initial conditions, time-dependent boundary conditions, and neutrino distributions for computing neutrino heating, cooling, and deleptonization rates are obtained from one-dimensional simulations that implement multigroup flux-limited diffusion and one-dimensional hydrodynamics. The development and evolution of proto-neutron star convection are investigated for both 15 and 25 M⊙ models, representative of the two classes of stars with compact and extended iron cores, respectively. For both models, in the absence of neutrino transport, the angle-averaged radial and angular convection velocities in the initial Ledoux unstable region below the shock after bounce achieve their peak values in ~20 ms, after which they decrease as the convection in this region dissipates. The dissipation occurs as the gradients are smoothed out by convection. This initial proto-neutron star convection episode seeds additional convectively unstable regions farther out beneath the shock. The additional proto-neutron star convection is driven by successive negative entropy gradients that develop as the shock, in propagating out after core bounce, is successively strengthened and weakened by the oscillating inner core. The convection beneath the shock distorts its sphericity, but on the average the shock radius is not boosted significantly relative to its radius in our corresponding one-dimensional models. In the presence of neutrino transport, proto-neutron star convection velocities are too small relative to bulk inflow velocities to result in any significant convective transport of entropy and leptons. This is evident in our two-dimensional entropy snapshots, which in this case appear spherically symmetric. The peak angle-averaged radial and angular convection velocities are orders of magnitude smaller than they are in the corresponding ``hydrodynamics-only'' models. A simple analytical model supports our numerical results, indicating that the inclusion of neutrino transport reduces the entropy-driven (lepton-driven) convection growth rates and asymptotic velocities by a factor ~3 (50) at the neutrinosphere and a factor ~250 (1000) at ρ = 1012 g cm-3, for both our 15 and 25 M⊙ models. Moreover, when transport is included, the initial postbounce entropy gradient is smoothed out by neutrino diffusion, whereas the initial lepton gradient is maintained by electron capture and neutrino escape near the neutrinosphere. Despite the maintenance of the lepton gradient, proto-neutron star convection does not develop over the 100 ms duration typical of all our simulations, except in the instance where ``low-test'' intial conditions are used, which are generated by core-collapse and bounce simulations that neglect neutrino-electron scattering and ion-ion screening corrections to neutrino-nucleus elastic scattering. Models favoring the development of proto-neutron star convection either by starting with more favorable, albeit artificial (low-test), initial conditions or by including transport corrections that were ignored in our ``fiducial'' models were considered. Our conclusions nonetheless remained the same. Evidence of proto-neutron star convection in our two-dimensional entropy snapshots was minimal, and, as in our fiducial models, the angle-averaged convective velocities when neutrino transport was included remained orders of magnitude smaller than their counterparts in the corresponding hydrodynamics-only models.

Aerodynamic Characteristics of High Speed Trains under Cross Wind Conditions

NASA Astrophysics Data System (ADS)

Chen, W.; Wu, S. P.; Zhang, Y.

2011-09-01

Numerical simulation for the two models in cross-wind was carried out in this paper. The three-dimensional compressible Reynolds-averaged Navier-Stokes equations(RANS), combined with the standard k-ɛ turbulence model, were solved on multi-block hybrid grids by second order upwind finite volume technique. The impact of fairing on aerodynamic characteristics of the train models was analyzed. It is shown that, the flow separates on the fairing and a strong vortex is generated, the pressure on the upper middle car decreases dramatically, which leads to a large lift force. The fairing changes the basic patterns around the trains. In addition, formulas of the coefficient of aerodynamic force at small yaw angles up to 24° were expressed.

[The emotional characteristics of the sounding word].

PubMed

Videneeva, N M; Khludova, O O; Vartanov, A V

2000-01-01

The four-dimensional spherical emotional space has been obtained by multi-dimensional scaling of subjective differences between the emotional expressions in sound samples (the words "Yes" and "No" pronounced in different emotional conditions). Euclidean space axes are interpreted as the following neural mechanisms. The first two dimensions are related with the estimation of a sign of emotional condition: the dimension 1--pleasant/unpleasant, useful or not, the dimension 2--an extent of information certainty. The third and the fourth axes are associated with the incentive. The dimension 3 encodes active (anger) or passive (fear) defensive reaction, and the dimension 4 corresponds to achievement. Three angles of four-dimensional hypersphere: the one between the axes 1 and 2, the second between the axes 3 and 4, the third between these two planes determine subjectively experienced emotion characteristics such as described by Vundt emotion modality (pleasure-unpleaure), excitation-quietness-suppression, and tension-relaxation, respectively. Thus, the first and the second angles regulate the modality of ten basic emotions: five emotions determined by a situation and five emotions determined by personal activity. In case of another system of angular parameters (three angles between the axes 4 and 1, 3 and 2, and the angle between the respective planes), another system of emotion classification, which is usually described in the studies of facial expressions (Shlosberg's and Izmaĭlov's circular system) and semantics (Osgood) can be realized: emotion modality or sign (regulates 6 basic emotions), emotion activity or brightness (excitation-rest) and emotion saturation (strength of emotion expression).

Investigation of the Flow Over Simple Bodies at Mach Numbers of the Order of 20

NASA Technical Reports Server (NTRS)

Henderson, Arthur, Jr.

1960-01-01

It is shown that adequate means are available for calculating inviscid direct and induced pressures on simple axisymmetric bodies at zero angle of attack. The extent to which viscous effects can alter these predictions is indicated. It is also shown that inviscid induced pressures can significantly affect the stability of blunt, two-dimensional flat wings at low angles of attack. However, at high angles of attack, the inviscid induced pressure effects are negligible.

A development of two-dimensional birefringence distribution measurement system with a sampling rate of 1.3 MHz

NASA Astrophysics Data System (ADS)

Onuma, Takashi; Otani, Yukitoshi

2014-03-01

A two-dimensional birefringence distribution measurement system with a sampling rate of 1.3 MHz is proposed. A polarization image sensor is developed as core device of the system. It is composed of a pixelated polarizer array made from photonic crystal and a parallel read out circuit with a multi-channel analog to digital converter specialized for two-dimensional polarization detection. By applying phase shifting algorism with circularly-polarized incident light, birefringence phase difference and azimuthal angle can be measured. The performance of the system is demonstrated experimentally by measuring actual birefringence distribution and polarization device such as Babinet-Soleil compensator.

Relationship between Lateral Femoral Bowing and Varus Knee Deformity Based on Two-Dimensional Assessment of Side-to-Side Differences.

PubMed

Cho, Myung-Rae; Lee, Young Sik; Choi, Won-Kee

2018-03-01

The objective was to evaluate the relationship between side-to-side differences of lateral femoral bowing and varus knee deformity based on two-dimensional (2D) assessment in unilateral total knee arthroplasty (TKA). A total of 143 patients with varus knee osteoarthritis who underwent unilateral TKA were enrolled. We evaluated the side-to-side differences of the frontal lower limb alignment by assessing lateral femoral bowing, anatomical medial distal femoral angle, and anatomical medial proximal tibial angle (aMPTA). The average values of all anatomical indices were significantly different between the operated side and the non-operated side (p＜0.05). The side-to-side difference in hip knee ankle (HKA) angle had a statistically significant correlation with that in lateral femoral bowing (intraclass correlation coefficient, 0.259; p=0.002) and that in aMPTA. Linear regression analysis showed 0.199° of side-to-side difference in lateral femoral bowing was associated with 1° of side-to-side difference in bilateral HKA angle. The side-to-side difference in lateral femoral bowing showed a tendency to increase in proportion to varus knee deformity based on 2D assessment in unilateral TKA patients.

Generalization of the Förster resonance energy transfer theory for quantum mechanical modulation of the donor-acceptor coupling

NASA Astrophysics Data System (ADS)

Jang, Seogjoo

2007-11-01

The Förster resonance energy transfer theory is generalized for inelastic situations with quantum mechanical modulation of the donor-acceptor coupling. Under the assumption that the modulations are independent of the electronic excitation of the donor and the acceptor, a general rate expression is derived, which involves two dimensional frequency-domain convolution of the donor emission line shape, the acceptor absorption line shape, and the spectral density of the modulation of the donor-acceptor coupling. For two models of modulation, detailed rate expressions are derived. The first model is the fluctuation of the donor-acceptor distance, approximated as a quantum harmonic oscillator coupled to a bath of other quantum harmonic oscillators. The distance fluctuation results in additional terms in the rate, which in the small fluctuation limit depend on the inverse eighth power of the donor-acceptor distance. The second model is the fluctuation of the torsional angle between the two transition dipoles, which is modeled as a quantum harmonic oscillator coupled to a bath of quantum harmonic oscillators and causes sinusoidal modulation of the donor-acceptor coupling. The rate expression has new elastic and inelastic terms, depending sensitively on the value of the minimum energy torsional angle. Experimental implications of the present theory and some of the open theoretical issues are discussed.

Anisotropic scattering effect of the inclined misfit dislocation on the two-dimensional electron gas in Al(In)GaN/GaN heterostructures

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

Jin, Dong-Dong; Department of Physics, Tsinghua University, Beijing 100084; Wang, Lian-shan, E-mail: ls-wang@semi.ac.cn

In this paper, a theory is developed to study the anisotropic scattering effect of the inclined misfit dislocation on the two-dimensional electron gas in Al(In)GaN/GaN heterostructures. The inclined misfit dislocation, which differs from the well-known vertical threading dislocation, has a remarkable tilt angle from the vertical. The predicted electron mobility shows a remarkable anisotropy. It has a maximum mobility value along the direction perpendicular to the projection of the inclined dislocation line, and a minimum mobility value along the direction parallel to the projection. The degree of the anisotropic scattering effect will be even greater with the increase of themore » tilt angle.« less

Control-surface hinge-moment calculations for a high-aspect-ratio supercritical wing

NASA Technical Reports Server (NTRS)

Perry, B., III

1978-01-01

The hinge moments, at selected flight conditions, resulting from deflecting two trailing edge control surfaces (one inboard and one midspan) on a high aspect ratio, swept, fuel conservative wing with a supercritical airfoil are estimated. Hinge moment results obtained from procedures which employ a recently developed transonic analysis are given. In this procedure a three dimensional inviscid transonic aerodynamics computer program is combined with a two dimensional turbulent boundary layer program in order to obtain an interacted solution. These results indicate that trends of the estimated hinge moment as a function of deflection angle are similar to those from experimental hinge moment measurements made on wind tunnel models with swept supercritical wings tested at similar values of free stream Mach number and angle of attack.

Control-surface hinge-moment calculations for a high-aspect-ratio supercritical wing

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

Perry, B.I.

1978-09-01

The hinge moments, at selected flight conditions, resulting from deflecting two trailing edge control surfaces (one inboard and one midspan) on a high aspect ratio, swept, fuel conservative wing with a supercritical airfoil are estimated. Hinge moment results obtained from procedures which employ a recently developed transonic analysis are given. In this procedure a three dimensional inviscid transonic aerodynamics computer program is combined with a two dimensional turbulent boundary layer program in order to obtain an interacted solution. These results indicate that trends of the estimated hinge moment as a function of deflection angle are similar to those from experimentalmore » hinge moment measurements made on wind tunnel models with swept supercritical wings tested at similar values of free stream Mach number and angle of attack.« less

Reflective small angle electron scattering to characterize nanostructures on opaque substrates

NASA Astrophysics Data System (ADS)

Friedman, Lawrence H.; Wu, Wen-Li; Fu, Wei-En; Chien, Yunsan

2017-09-01

Feature sizes in integrated circuits (ICs) are often at the scale of 10 nm and are ever shrinking. ICs appearing in today's computers and hand held devices are perhaps the most prominent examples. These smaller feature sizes demand equivalent advances in fast and accurate dimensional metrology for both development and manufacturing. Techniques in use and continuing to be developed include X-ray based techniques, optical scattering, and of course the electron and scanning probe microscopy techniques. Each of these techniques has their advantages and limitations. Here, the use of small angle electron beam scattering measurements in a reflection mode (RSAES) to characterize the dimensions and the shape of nanostructures on flat and opaque substrates is demonstrated using both experimental and theoretical evidence. In RSAES, focused electrons are scattered at angles smaller than 1 ° with the assistance of electron optics typically used in transmission electron microscopy. A proof-of-concept experiment is combined with rigorous electron reflection simulations to demonstrate the efficiency and accuracy of RSAES as a method of non-destructive measurement of shapes of features less than 10 nm in size on flat and opaque substrates.

Reflective Small Angle Electron Scattering to Characterize Nanostructures on Opaque Substrates.

PubMed

Friedman, Lawrence H; Wu, Wen-Li; Fu, Wei-En; Chien, Yunsan

2017-09-01

Features sizes in integrated circuits (ICs) are often at the scale of 10 nm and are ever shrinking. ICs appearing in today's computers and hand held devices are perhaps the most prominent examples. These smaller feature sizes demand equivalent advances in fast and accurate dimensional metrology for both development and manufacturing. Techniques in use and continuing to be developed include X-ray based techniques, optical scattering and of course the electron and scanning probe microscopy techniques. Each of these techniques have their advantages and limitations. Here the use of small angle electron beam scattering measurements in a reflection mode (RSAES) to characterize the dimensions and the shape of nanostructures on flat and opaque substrates is demonstrated using both experimental and theoretical evidence. In RSAES, focused electrons are scattered at angles smaller than 1° with the assistance of electron optics typically used in transmission electron microscopy. A proof-of-concept experiment is combined with rigorous electron reflection simulations to demonstrate the efficiency and accuracy of RSAES as a method of non-destructive measurement of shapes of features less than 10 nm in size on flat and opaque substrates.

Polarization Smoothing Generalized MUSIC Algorithm with Polarization Sensitive Array for Low Angle Estimation.

PubMed

Tan, Jun; Nie, Zaiping

2018-05-12

Direction of Arrival (DOA) estimation of low-altitude targets is difficult due to the multipath coherent interference from the ground reflection image of the targets, especially for very high frequency (VHF) radars, which have antennae that are severely restricted in terms of aperture and height. The polarization smoothing generalized multiple signal classification (MUSIC) algorithm, which combines polarization smoothing and generalized MUSIC algorithm for polarization sensitive arrays (PSAs), was proposed to solve this problem in this paper. Firstly, the polarization smoothing pre-processing was exploited to eliminate the coherence between the direct and the specular signals. Secondly, we constructed the generalized MUSIC algorithm for low angle estimation. Finally, based on the geometry information of the symmetry multipath model, the proposed algorithm was introduced to convert the two-dimensional searching into one-dimensional searching, thus reducing the computational burden. Numerical results were provided to verify the effectiveness of the proposed method, showing that the proposed algorithm has significantly improved angle estimation performance in the low-angle area compared with the available methods, especially when the grazing angle is near zero.

Mixed-mode VLSI optic flow sensors for micro air vehicles

NASA Astrophysics Data System (ADS)

Barrows, Geoffrey Louis

We develop practical, compact optic flow sensors. To achieve the desired weight of 1--2 grams, mixed-mode and mixed-signal VLSI techniques are used to develop compact circuits that directly perform computations necessary to measure optic flow. We discuss several implementations, including a version fully integrated in VLSI, and several "hybrid sensors" in which the front end processing is performed with an analog chip and the back end processing is performed with a microcontroller. We extensively discuss one-dimensional optic flow sensors based on the linear competitive feature tracker (LCFT) algorithm. Hardware implementations of this algorithm are shown able to measure visual motion with contrast levels on the order of several percent. We argue that the development of one-dimensional optic flow sensors is therefore reduced to a problem of engineering. We also introduce two related two-dimensional optic flow algorithms that are amenable to implementation in VLSI. This includes the planar competitive feature tracker (PCFT) algorithm and the trajectory method. These sensors are being developed to solve small-scale navigation problems in micro air vehicles, which are autonomous aircraft whose maximum dimension is on the order of 15 cm. We obtain a proof-of-principle of small-scale navigation by mounting a prototype sensor onto a toy glider and programming the sensor to control a rudder or an elevator to affect the glider's path during flight. We demonstrate the determination of altitude by measuring optic flow in the downward direction. We also demonstrate steering to avoid a collision with a wall, when the glider is tossed towards the wall at a shallow angle, by measuring the optic flow in the direction of the glider's left and right side.

The relationship between leg preference and knee mechanics during sidestepping in collegiate female footballers.

PubMed

Brown, Scott R; Wang, Henry; Dickin, D Clark; Weiss, Kaitlyn J

2014-11-01

This study examined the relationship between leg preference and knee mechanics in females during sidestepping. Three-dimensional data were recorded on 16 female collegiate footballers during a planned 45° sidestep manoeuvre with their preferred and non-preferred kicking leg. Knee kinematics and kinetics during initial contact, weight acceptance, peak push-off, and final push-off phases of sidestepping were analysed in both legs. The preferred leg showed trivial to small increases (ES = 0.19-0.36) in knee flexion angle at initial contact, weight acceptance, and peak push-off, and small increases (ES = 0.21-0.34) in peak power production and peak knee extension velocity. The non-preferred leg showed a trivial increase (ES = 0.10) in knee abduction angle during weight acceptance; small to moderate increases (ES = 0.22-0.64) in knee internal rotation angle at weight acceptance, peak push-off, and final push-off; a small increase (ES = 0.22) in knee abductor moment; and trivial increases (ES = 0.09-0.14) in peak power absorption and peak knee flexion velocity. The results of this study show that differences do exist between the preferred and non-preferred leg in females. The findings of this study will increase the knowledge base of anterior cruciate ligament injury in females and can aid in the design of more appropriate neuromuscular, plyometric, and strength training protocols for injury prevention.

Numerical exploration of non-axisymmetric divertor closure in the small angle slot (SAS) divertor at DIII-D

DOE PAGES

Frerichs, H.; Schmitz, O.; Covele, B.; ...

2018-02-28

Numerical simulations of toroidal asymmetries in a tightly baffled small angle slot (SAS) divertor on the DIII-D tokamak show that toroidal asymmetries in divertor closure result in (non-axisymmetric) local onset of detachment within a density window of 10-15% on top of the nominal threshold separatrix density. The SAS divertor is explored at DIII-D for improving access to cold, dissipative/detached divertor conditions. The narrow width of the slot divertor coupled with a small magnetic field line-to-target angle facilitates the buildup of neutral density, thereby increasing radiative and neutrals-related (atoms and molecules) losses in the divertor. Therefore, small changes in the strikemore » point location can be expected to have a large impact on diverter conditions. The combination of misaligned slot structure and non-axisymmetric perturbations to the magnetic field configuration causes the strike point to move along the divertor target plate, possibly leaving the diverter slot at some locations. The latter extreme case essentially introduces an opening in the divertor slot from where recycling neutrals can easily escape, and thereby degrade the performance of the slot divertor. Such a strike point dislocation is approximated by a finite gap in the divertor baffle for which three dimensional edge plasma and neutral gas simulations are performed with the EMC3-EIRENE code.« less

Numerical exploration of non-axisymmetric divertor closure in the small angle slot (SAS) divertor at DIII-D

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

Frerichs, H.; Schmitz, O.; Covele, B.

Numerical simulations of toroidal asymmetries in a tightly baffled small angle slot (SAS) divertor on the DIII-D tokamak show that toroidal asymmetries in divertor closure result in (non-axisymmetric) local onset of detachment within a density window of 10-15% on top of the nominal threshold separatrix density. The SAS divertor is explored at DIII-D for improving access to cold, dissipative/detached divertor conditions. The narrow width of the slot divertor coupled with a small magnetic field line-to-target angle facilitates the buildup of neutral density, thereby increasing radiative and neutrals-related (atoms and molecules) losses in the divertor. Therefore, small changes in the strikemore » point location can be expected to have a large impact on diverter conditions. The combination of misaligned slot structure and non-axisymmetric perturbations to the magnetic field configuration causes the strike point to move along the divertor target plate, possibly leaving the diverter slot at some locations. The latter extreme case essentially introduces an opening in the divertor slot from where recycling neutrals can easily escape, and thereby degrade the performance of the slot divertor. Such a strike point dislocation is approximated by a finite gap in the divertor baffle for which three dimensional edge plasma and neutral gas simulations are performed with the EMC3-EIRENE code.« less

On the interaction of small and large eddies in two dimensional turbulent flows

NASA Technical Reports Server (NTRS)

Foias, C.; ate work.

1987-01-01

Some results concerning the interaction of small and large eddies to two dimensional turbulent flows are presented. It is shown that the amplitude of small structures decays exponentially to a small value, and from this is inferred a simplified interaction law of small and large eddies. Beside their intrinsic interest for the understanding of the physics of turbulence, these results lead to new numerical schemes to be studied in a separate work.

Computationally Efficient 2D DOA Estimation with Uniform Rectangular Array in Low-Grazing Angle.

PubMed

Shi, Junpeng; Hu, Guoping; Zhang, Xiaofei; Sun, Fenggang; Xiao, Yu

2017-02-26

In this paper, we propose a computationally efficient spatial differencing matrix set (SDMS) method for two-dimensional direction of arrival (2D DOA) estimation with uniform rectangular arrays (URAs) in a low-grazing angle (LGA) condition. By rearranging the auto-correlation and cross-correlation matrices in turn among different subarrays, the SDMS method can estimate the two parameters independently with one-dimensional (1D) subspace-based estimation techniques, where we only perform difference for auto-correlation matrices and the cross-correlation matrices are kept completely. Then, the pair-matching of two parameters is achieved by extracting the diagonal elements of URA. Thus, the proposed method can decrease the computational complexity, suppress the effect of additive noise and also have little information loss. Simulation results show that, in LGA, compared to other methods, the proposed methods can achieve performance improvement in the white or colored noise conditions.

Computationally Efficient 2D DOA Estimation with Uniform Rectangular Array in Low-Grazing Angle

PubMed Central

Shi, Junpeng; Hu, Guoping; Zhang, Xiaofei; Sun, Fenggang; Xiao, Yu

2017-01-01

In this paper, we propose a computationally efficient spatial differencing matrix set (SDMS) method for two-dimensional direction of arrival (2D DOA) estimation with uniform rectangular arrays (URAs) in a low-grazing angle (LGA) condition. By rearranging the auto-correlation and cross-correlation matrices in turn among different subarrays, the SDMS method can estimate the two parameters independently with one-dimensional (1D) subspace-based estimation techniques, where we only perform difference for auto-correlation matrices and the cross-correlation matrices are kept completely. Then, the pair-matching of two parameters is achieved by extracting the diagonal elements of URA. Thus, the proposed method can decrease the computational complexity, suppress the effect of additive noise and also have little information loss. Simulation results show that, in LGA, compared to other methods, the proposed methods can achieve performance improvement in the white or colored noise conditions. PMID:28245634

Some exact velocity profiles for granular flow in converging hoppers

NASA Astrophysics Data System (ADS)

Cox, Grant M.; Hill, James M.

2005-01-01

Gravity flow of granular materials through hoppers occurs in many industrial processes. For an ideal cohesionless granular material, which satisfies the Coulomb-Mohr yield condition, the number of known analytical solutions is limited. However, for the special case of the angle of internal friction δ equal to ninety degrees, there exist exact parametric solutions for the governing coupled ordinary differential equations for both two-dimensional wedges and three-dimensional cones, both of which involve two arbitrary constants of integration. These solutions are the only known analytical solutions of this generality. Here, we utilize the double-shearing theory of granular materials to determine the velocity field corresponding to these exact parametric solutions for the two problems of gravity flow through converging wedge and conical hoppers. An independent numerical solution for other angles of internal friction is shown to coincide with the analytical solution.

Quantitative 3D determination of self-assembled structures on nanoparticles using small angle neutron scattering.

PubMed

Luo, Zhi; Marson, Domenico; Ong, Quy K; Loiudice, Anna; Kohlbrecher, Joachim; Radulescu, Aurel; Krause-Heuer, Anwen; Darwish, Tamim; Balog, Sandor; Buonsanti, Raffaella; Svergun, Dmitri I; Posocco, Paola; Stellacci, Francesco

2018-04-09

The ligand shell (LS) determines a number of nanoparticles' properties. Nanoparticles' cores can be accurately characterized; yet the structure of the LS, when composed of mixture of molecules, can be described only qualitatively (e.g., patchy, Janus, and random). Here we show that quantitative description of the LS' morphology of monodisperse nanoparticles can be obtained using small-angle neutron scattering (SANS), measured at multiple contrasts, achieved by either ligand or solvent deuteration. Three-dimensional models of the nanoparticles' core and LS are generated using an ab initio reconstruction method. Characteristic length scales extracted from the models are compared with simulations. We also characterize the evolution of the LS upon thermal annealing, and investigate the LS morphology of mixed-ligand copper and silver nanoparticles as well as gold nanoparticles coated with ternary mixtures. Our results suggest that SANS combined with multiphase modeling is a versatile approach for the characterization of nanoparticles' LS.

A small-angle large-acceptance detection system for hadrons

NASA Astrophysics Data System (ADS)

Kalantar-Nayestanaki, N.; Bacelar, J. C. S.; Brandenburg, S.; Huisman, H.; Messchendorp, J. G.; Mul, F. A.; Schadmand, S.; van der Schaaf, K.; Schippers, J. M.; Volkerts, M.

2000-04-01

The performance of a segmented large-acceptance detector, capable of measuring particles at small forward angles, is presented. The Small-Angle Large-Acceptance Detector (SALAD), was built to handle very high rates of particles impinging on the detector. Particles down to a few MeV can be detected with it. The position of charged particles is measured by two Multi-Wire Proportional Chambers while scintillator blocks are used to measure the energy of the detected particle. A stack of thin scintillators placed behind the energy detectors allows for a hardware rejection (veto) of high-energy particles going through the scintillator blocks.

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

Ba, Yan; Kang, Qinjun; Liu, Haihu

In this study, the dynamical behavior of a droplet on topologically structured surface is investigated by using a three-dimensional color-gradient lattice Boltzmann model. A wetting boundary condition is proposed to model fluid-surface interactions, which is advantageous to improve the accuracy of the simulation and suppress spurious velocities at the contact line. The model is validated by the droplet partial wetting test and reproduction of the Cassie and Wenzel states. A series of simulations are conducted to investigate the behavior of a droplet when subjected to a shear flow. It is found that in Cassie state, the droplet undergoes a transitionmore » from stationary, to slipping and finally to detachment states as the capillary number increases, while in Wenzel state, the last state changes to the breakup state. The critical capillary number, above which the droplet slipping occurs, is small for the Cassie droplet, but is significantly enhanced for the Wenzel droplet due to the increased contact angle hysteresis. In Cassie state, the receding contact angle nearly equals the prediction by the Cassie relation, and the advancing contact angle is close to 180°, leading to a small contact angle hysteresis. In Wenzel state, however, the contact angle hysteresis is extremely large (around 100°). Finally, high droplet mobility can be easily achieved for Cassie droplets, whereas in Wenzel state, extremely low droplet mobility is identified.« less

Three-dimensional trajectory analyses of two drop sizing instruments: PMS OAP and PMS FSSP

NASA Technical Reports Server (NTRS)

Norment, Hillyer G.

1988-01-01

Flow induced distortions of water drop fluxes and speeds seen by the instruments were predicted by use of three dimensional flow and trajectory calculation methods. Sensitivities were determined for the instruments, in isolation and mounted under the wing of an airplane, to: water drop diameter (2 to 1000 microns), angle of attack and free stream air speed. For the optical array probe in isolation and on the airplane at 0 deg angle of attack, flux distortions of practical consequence are not found. At 4 deg airplane angle of attack, partial flow stagnation under the uptilted wing causes significant decreases in both flux and speed for cloud size droplets. For the forward scattering spectrometer probe in isolation, only marginally significant sensitivities to free stream air speed are found, and no sensitivity is found to angle of attack. Both speed and flux of cloud size droplets are predicted to be undermeasured by from 12 to 24 percent depending on airplane angle of attack. For the wing-mounted instruments, effects of flow about the instruments themselves are found to be equal in importance to effects of flow about the airplane. Preferred orientation (canting) angles of distorted water drops are found to be functions of drop size, angle of attack and air speed.

The Effects of Fault Bends on Rupture Propagation: A Parameter Study

NASA Astrophysics Data System (ADS)

Lozos, J. C.; Oglesby, D. D.; Duan, B.; Wesnousky, S. G.

2008-12-01

Segmented faults with stepovers are ubiquitous, and occur at a variety of scales, ranging from small stepovers on the San Jacinto Fault, to the large-scale stepover on of the San Andreas Fault between Tejon Pass and San Gorgonio Pass. Because this type of fault geometry is so prevalent, understanding how rupture propagates through such systems is important for evaluating seismic hazard at different points along these faults. In the present study, we systematically investigate how far rupture will propagate through a fault with a linked (i.e., continuous fault) stepover, based on the length of the linking fault segment and the angle that connects the linking segment to adjacent segments. We conducted dynamic models of such systems using a two-dimensional finite element code (Duan and Oglesby 2007). The fault system in our models consists of three segments: two parallel 10km-long faults linked at a specified angle by a linking segment of between 500 m and 5 km. This geometry was run both as a extensional system and a compressional system. We observed several distinct rupture behaviors, with systematic differences between compressional and extensional cases. Both shear directions rupture straight through the stepover for very shallow stepover angles. In compressional systems with steeper angles, rupture may jump ahead from the stepover segment onto the far segment; whether or not rupture on this segment reaches critical patch size and slips fully is also a function of angle and stepover length. In some compressional cases, if the angle is steep enough and the stepover short enough, rupture may jump over the step entirely and propagate down the far segment without touching the linking segment. In extensional systems, rupture jumps from the nucleating segment onto the linking segment even at shallow angles, but at steeper angles, rupture propagates through without jumping. It is easier to propagate through a wider range of angles in extensional cases. In both extensional and compressional cases, for each stepover length there exists a maximum angle through which rupture can fully propagate; this maximum angle decreases asymptotically to a minimum value as the stepover length increases. We also found that a wave associated with a stopping phase coming from the far end of the fault may restart rupture and induce full propagation after a significant delay in some cases where the initial rupture terminated.

Validation of a three-dimensional viscous analysis of axisymmetric supersonic inlet flow fields

NASA Technical Reports Server (NTRS)

Benson, T. J.; Anderson, B. H.

1983-01-01

A three-dimensional viscous marching analysis for supersonic inlets was developed. To verify this analysis several benchmark axisymmetric test configurations were studied and are compared to experimental data. Detailed two-dimensional results for shock-boundary layer interactions are presented for flows with and without boundary layer bleed. Three dimensional calculations of a cone at angle of attack and a full inlet at attack are also discussed and evaluated. Results of the calculations demonstrate the code's ability to predict complex flow fields and establish guidelines for future calculations using similar codes.

Study and Design of a Cylindrical Lens Array Antenna for Wideband Electronic Scanning.

DTIC Science & Technology

1983-12-01

n Block 30, Ii difetren from Report) Same IS. SUPPLEMENTARY NOTES RADC Project Engineer: Peter R. Franchi (RADC/EEAA) 11. KEY WORDS (COntinue on...defined by Rotman and Franchi is studied for contours, phase aberrations, amplitude distortions, and sur- face incidence angles. One form of this lens is...Rotman and Franchi (refs 1, 2, 3). The three-dimensional cylindrical lens comprises a stacked set of identical two-dimensional lenses. Each two

Three-dimensional path planning software-assisted transjugular intrahepatic portosystemic shunt: a technical modification.

PubMed

Tsauo, Jiaywei; Luo, Xuefeng; Ye, Linchao; Li, Xiao

2015-06-01

This study was designed to report our results with a modified technique of three-dimensional (3D) path planning software assisted transjugular intrahepatic portosystemic shunt (TIPS). 3D path planning software was recently developed to facilitate TIPS creation by using two carbon dioxide portograms acquired at least 20° apart to generate a 3D path for overlay needle guidance. However, one shortcoming is that puncturing along the overlay would be technically impossible if the angle of the liver access set and the angle of the 3D path are not the same. To solve this problem, a prototype 3D path planning software was fitted with a utility to calculate the angle of the 3D path. Using this, we modified the angle of the liver access set accordingly during the procedure in ten patients. Failure for technical reasons occurred in three patients (unsuccessful wedged hepatic venography in two cases, software technical failure in one case). The procedure was successful in the remaining seven patients, and only one needle pass was required to obtain portal vein access in each case. The course of puncture was comparable to the 3D path in all patients. No procedure-related complication occurred following the procedures. Adjusting the angle of the liver access set to match the angle of the 3D path determined by the software appears to be a favorable modification to the technique of 3D path planning software assisted TIPS.

The use of a selective saturation pulse to suppress t1 noise in two-dimensional 1H fast magic angle spinning solid-state NMR spectroscopy

NASA Astrophysics Data System (ADS)

Robertson, Aiden J.; Pandey, Manoj Kumar; Marsh, Andrew; Nishiyama, Yusuke; Brown, Steven P.

2015-11-01

A selective saturation pulse at fast magic angle spinning (MAS) frequencies (60+ kHz) suppresses t1 noise in the indirect dimension of two-dimensional 1H MAS NMR spectra. The method is applied to a synthetic nucleoside with an intense methyl 1H signal due to triisopropylsilyl (TIPS) protecting groups. Enhanced performance in terms of suppressing the methyl signal while minimising the loss of signal intensity of nearby resonances of interest relies on reducing spin diffusion - this is quantified by comparing two-dimensional 1H NOESY-like spin diffusion spectra recorded at 30-70 kHz MAS. For a saturation pulse centred at the methyl resonance, the effect of changing the nutation frequency at different MAS frequencies as well as the effect of changing the pulse duration is investigated. By applying a pulse of duration 30 ms and nutation frequency 725 Hz at 70 kHz MAS, a good compromise of significant suppression of the methyl resonance combined with the signal intensity of resonances greater than 5 ppm away from the methyl resonance being largely unaffected is achieved. The effectiveness of using a selective saturation pulse is demonstrated for both homonuclear 1H-1H double quantum (DQ)/single quantum (SQ) MAS and 14N-1H heteronuclear multiple quantum coherence (HMQC) two-dimensional solid-state NMR experiments.

Morphological transformations in the magnetite biomineralizing protein Mms6 in iron solutions: A small-angle x-ray scattering study

DOE PAGES

Zhang, Honghu; Liu, Xunpei; Feng, Shuren; ...

2015-02-10

In this study, magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular three-dimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence ofmore » hydroxyl/carboxyl containing residues in the C-terminal domain shuffled) exhibits subtle morphological changes in the presence of iron ions in solutions. The analysis of the SAXS data is consistent with a hierarchical core–corona micellar structure similar to that found in amphiphilic polymers. The addition of ferric and ferrous iron ions to the protein solution induces morphological changes in the micellar structure by transforming the 3D micelles into objects of reduced dimensionality of 2, with fractal-like characteristics (including Gaussian-chain-like) or, alternatively, platelet-like structures.« less

Three-dimensional turbulent-mixing-length modeling for discrete-hole coolant injection into a crossflow

NASA Technical Reports Server (NTRS)

Wang, C. R.; Papell, S. S.

1983-01-01

Three dimensional mixing length models of a flow field immediately downstream of coolant injection through a discrete circular hole at a 30 deg angle into a crossflow were derived from the measurements of turbulence intensity. To verify their effectiveness, the models were used to estimate the anisotropic turbulent effects in a simplified theoretical and numerical analysis to compute the velocity and temperature fields. With small coolant injection mass flow rate and constant surface temperature, numerical results of the local crossflow streamwise velocity component and surface heat transfer rate are consistent with the velocity measurement and the surface film cooling effectiveness distributions reported in previous studies.

Three-dimensional turbulent-mixing-length modeling for discrete-hole coolant injection into a crossflow

NASA Astrophysics Data System (ADS)

Wang, C. R.; Papell, S. S.

1983-09-01

Three dimensional mixing length models of a flow field immediately downstream of coolant injection through a discrete circular hole at a 30 deg angle into a crossflow were derived from the measurements of turbulence intensity. To verify their effectiveness, the models were used to estimate the anisotropic turbulent effects in a simplified theoretical and numerical analysis to compute the velocity and temperature fields. With small coolant injection mass flow rate and constant surface temperature, numerical results of the local crossflow streamwise velocity component and surface heat transfer rate are consistent with the velocity measurement and the surface film cooling effectiveness distributions reported in previous studies.

Second-order small-disturbance solutions for hypersonic flow over power-law bodies

NASA Technical Reports Server (NTRS)

Townsend, J. C.

1975-01-01

Similarity solutions were found which give the adiabatic flow of an ideal gas about two-dimensional and axisymmetric power-law bodies at infinite Mach number to second order in the body slenderness parameter. The flow variables were expressed as a sum of zero-order and perturbation similarity functions for which the axial variations in the flow equations separated out. The resulting similarity equations were integrated numerically. The solutions, which are universal functions, are presented in graphic and tabular form. To avoid a singularity in the calculations, the results are limited to body power-law exponents greater than about 0.85 for the two-dimensional case and 0.75 for the axisymmetric case. Because of the entropy layer induced by the nose bluntness (for power-law bodies other than cones and wedges), only the pressure function is valid at the body surface. The similarity results give excellent agreement with the exact solutions for inviscid flow over wedges and cones having half-angles up to about 20 deg. They give good agreement with experimental shock-wave shapes and surface-pressure distributions for 3/4-power axisymmetric bodies, considering that Mach number and boundary-layer displacement effects are not included in the theory.

Two-Dimensional Automatic Measurement for Nozzle Flow Distribution Using Improved Ultrasonic Sensor

PubMed Central

Zhai, Changyuan; Zhao, Chunjiang; Wang, Xiu; Wang, Ning; Zou, Wei; Li, Wei

2015-01-01

Spray deposition and distribution are affected by many factors, one of which is nozzle flow distribution. A two-dimensional automatic measurement system, which consisted of a conveying unit, a system control unit, an ultrasonic sensor, and a deposition collecting dish, was designed and developed. The system could precisely move an ultrasonic sensor above a pesticide deposition collecting dish to measure the nozzle flow distribution. A sensor sleeve with a PVC tube was designed for the ultrasonic sensor to limit its beam angle in order to measure the liquid level in the small troughs. System performance tests were conducted to verify the designed functions and measurement accuracy. A commercial spray nozzle was also used to measure its flow distribution. The test results showed that the relative error on volume measurement was less than 7.27% when the liquid volume was 2 mL in trough, while the error was less than 4.52% when the liquid volume was 4 mL or more. The developed system was also used to evaluate the flow distribution of a commercial nozzle. It was able to provide the shape and the spraying width of the flow distribution accurately. PMID:26501288

Fast generation of three-dimensional computational boundary-conforming periodic grids of C-type. [for turbine blades and propellers

NASA Technical Reports Server (NTRS)

Dulikravich, D. S.

1982-01-01

A fast computer program, GRID3C, was developed to generate multilevel three dimensional, C type, periodic, boundary conforming grids for the calculation of realistic turbomachinery and propeller flow fields. The technique is based on two analytic functions that conformally map a cascade of semi-infinite slits to a cascade of doubly infinite strips on different Riemann sheets. Up to four consecutively refined three dimensional grids are automatically generated and permanently stored on four different computer tapes. Grid nonorthogonality is introduced by a separate coordinate shearing and stretching performed in each of three coordinate directions. The grids are easily clustered closer to the blade surface, the trailing and leading edges and the hub or shroud regions by changing appropriate input parameters. Hub and duct (or outer free boundary) have different axisymmetric shapes. A vortex sheet of arbitrary thickness emanating smoothly from the blade trailing edge is generated automatically by GRID3C. Blade cross sectional shape, chord length, twist angle, sweep angle, and dihedral angle can vary in an arbitrary smooth fashion in the spanwise direction.

A Relationship Between Constraint and the Critical Crack Tip Opening Angle

NASA Technical Reports Server (NTRS)

Johnston, William M.; James, Mark A.

2009-01-01

Of the various approaches used to model and predict fracture, the Crack Tip Opening Angle (CTOA) fracture criterion has been successfully used for a wide range of two-dimensional thin-sheet and thin plate applications. As thicker structure is considered, modeling the full three-dimensional fracture process will become essential. This paper investigates relationships between the local CTOA evaluated along a three-dimensional crack front and the corresponding local constraint. Previously reported tunneling crack front shapes were measured during fracture by pausing each test and fatigue cycling the specimens to mark the crack surface. Finite element analyses were run to model the tunneling shape during fracture, with the analysis loading conditions duplicating those tests. The results show an inverse relationship between the critical fracture value and constraint which is valid both before maximum load and after maximum load.

Viewing Angle Classification of Cryo-Electron Microscopy Images Using Eigenvectors

PubMed Central

Singer, A.; Zhao, Z.; Shkolnisky, Y.; Hadani, R.

2012-01-01

The cryo-electron microscopy (cryo-EM) reconstruction problem is to find the three-dimensional structure of a macromolecule given noisy versions of its two-dimensional projection images at unknown random directions. We introduce a new algorithm for identifying noisy cryo-EM images of nearby viewing angles. This identification is an important first step in three-dimensional structure determination of macromolecules from cryo-EM, because once identified, these images can be rotationally aligned and averaged to produce “class averages” of better quality. The main advantage of our algorithm is its extreme robustness to noise. The algorithm is also very efficient in terms of running time and memory requirements, because it is based on the computation of the top few eigenvectors of a specially designed sparse Hermitian matrix. These advantages are demonstrated in numerous numerical experiments. PMID:22506089

Hydrodynamic interactions between a self-rotation rotator and passive particles

NASA Astrophysics Data System (ADS)

Ouyang, Zhenyu; Lin, Jian-Zhong; Ku, Xiaoke

2017-10-01

In this paper, we numerically investigate the hydrodynamic interaction between a self-rotation rotator and passive particles in a two-dimensional confined cavity at two typical Reynolds numbers according to the different flow features. Both the fluid-particle interaction and particle-particle interaction through fluid media are taken into consideration. The results show that from the case of a rotator and one passive particle to the case of a rotator and two passive particles, the system becomes much more complex because the relative displacement between the rotator and the passive particles and the velocity of passive particles are strongly dependent on the Reynolds number and the initial position of passive particles. For the system of two particles, the passive particle gradually departs from the rotator although its relative displacement to the rotator exhibits a periodic oscillation at the lower Reynolds number. Furthermore, the relative distance between the two particles and the rotator's rotational frequency are responsible for the oscillation amplitude and frequency of the passive particle's velocity. For the system of three particles, the passive particle's velocities exhibit a superposition of a large amplitude oscillation and a small amplitude oscillation at the lower Reynolds number, and the large amplitude oscillation will disappear at the higher Reynolds number. The change of the included angle of the two passive particles is dependent on the initial positions of the passive particles at the lower Reynolds number, whereas the included angle of the two passive particles finally approaches a fixed value at the higher Reynolds number. It is interesting that the two passive particles periodically approach and depart from each other when the included angle is not equal to π, while all the three particles (including the rotator) keep the positions in a straight line when the included angle is equal to π because the interference between two passive particles disappears. In addition, the passive particle rotates not only around the rotator but also around its own axis, and the rotation speed of the former is far greater than that of the latter.

Nanoscopic analysis of oxygen segregation at tilt boundaries in silicon ingots using atom probe tomography combined with TEM and ab initio calculations.

PubMed

Ohno, Y; Inoue, K; Fujiwara, K; Kutsukake, K; Deura, M; Yonenaga, I; Ebisawa, N; Shimizu, Y; Inoue, K; Nagai, Y; Yoshida, H; Takeda, S; Tanaka, S; Kohyama, M

2017-12-01

We have developed an analytical method to determine the segregation levels on the same tilt boundaries (TBs) at the same nanoscopic location by a joint use of atom probe tomography and scanning transmission electron microscopy, and discussed the mechanism of oxygen segregation at TBs in silicon ingots in terms of bond distortions around the TBs. The three-dimensional distribution of oxygen atoms was determined at the typical small- and large-angle TBs by atom probe tomography with a low impurity detection limit (0.01 at.% on a TB plane) simultaneously with high spatial resolution (about 0.4 nm). The three-dimensional distribution was correlated with the atomic stress around the TBs; the stress at large-angle TBs was estimated by ab initio calculations based on atomic resolution scanning transmission electron microscopy data and that at small-angle TBs were calculated with the elastic theory based on dark-field transmission electron microscopy data. Oxygen atoms would segregate at bond-centred sites under tensile stress above about 2 GPa, so as to attain a more stable bonding network by reducing the local stress. The number of oxygen atoms segregating in a unit TB area N GB (in atoms nm -2 ) was determined to be proportional to both the number of the atomic sites under tensile stress in a unit TB area n bc and the average concentration of oxygen atoms around the TB [O i ] (in at.%) with N GB ∼ 50 n bc [O i ]. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

An Assessment of Critical Dimension Small Angle X-ray Scattering Metrology for Advanced Semiconductor Manufacturing

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

Settens, Charles M.

2015-01-01

Simultaneous migration of planar transistors to FinFET architectures, the introduction of a plurality of materials to ensure suitable electrical characteristics, and the establishment of reliable multiple patterning lithography schemes to pattern sub-10 nm feature sizes imposes formidable challenges to current in-line dimensional metrologies. Because the shape of a FinFET channel cross-section immediately influences the electrical characteristics, the evaluation of 3D device structures requires measurement of parameters beyond traditional critical dimension (CD), including their sidewall angles, top corner rounding and footing, roughness, recesses and undercuts at single nanometer dimensions; thus, metrologies require sub-nm and approaching atomic level measurement uncertainty. Synchrotron criticalmore » dimension small angle X-ray scattering (CD-SAXS) has unique capabilities to non-destructively monitor the cross-section shape of surface structures with single nanometer uncertainty and can perform overlay metrology to sub-nm uncertainty. In this dissertation, we perform a systematic experimental investigation using CD-SAXS metrology on a hierarchy of semiconductor 3D device architectures including, high-aspect-ratio contact holes, H2 annealed Si fins, and a series of grating type samples at multiple points along a FinFET fabrication process increasing in structural intricacy and ending with fully fabricated FinFET. Comparative studies between CD-SAXS metrology and other relevant semiconductor dimensional metrologies, particularly CDSEM, CD-AFM and TEM are used to determine physical limits of CD-SAXS approach for advanced semiconductor samples. CD-SAXS experimental tradeoffs, advice for model-dependent analysis and thoughts on the compatibility with a semiconductor manufacturing environment are discussed.« less

What Is Carotid Artery Disease?

MedlinePlus

... Your doctor can see these pictures on a computer screen. For this test, your doctor may give ... pictures of the body from many angles. A computer combines the pictures into two- and three-dimensional ...

Thermographic Phosphor Measurements of Shock-Shock Interactions on a Swept Cylinder

NASA Technical Reports Server (NTRS)

Jones, Michelle L.; Berry, Scott A.

2013-01-01

The effects of fin leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-inch Mach 6 Air Tunnel. The fin model leading edges, which represent cylindrical leading edges or struts on hypersonic vehicles, were varied from 0.25 inches to 0.75 inches in radius. A 9deg wedge generated a planar oblique shock at 16.7deg to the flow that intersected the fin bow shock, producing a shock-shock interaction that impinged on the fin leading edge. The fin angle of attack was varied from 0deg (normal to the free-stream) to 15deg and 25deg swept forward. Global temperature data was obtained from the surface of the fused silica fins using phosphor thermography. Metal oil flow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using one-dimensional semi-infinite as well as one- and two-dimensional finite-volume methods to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for the three shock-shock interactions, respectively, between the test articles with varying leading-edge radius. The dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite onedimensional method.

A Test of Maxwell's Z Model Using Inverse Modeling

NASA Technical Reports Server (NTRS)

Anderson, J. L. B.; Schultz, P. H.; Heineck, T.

2003-01-01

In modeling impact craters a small region of energy and momentum deposition, commonly called a "point source", is often assumed. This assumption implies that an impact is the same as an explosion at some depth below the surface. Maxwell's Z Model, an empirical point-source model derived from explosion cratering, has previously been compared with numerical impact craters with vertical incidence angles, leading to two main inferences. First, the flowfield center of the Z Model must be placed below the target surface in order to replicate numerical impact craters. Second, for vertical impacts, the flow-field center cannot be stationary if the value of Z is held constant; rather, the flow-field center migrates downward as the crater grows. The work presented here evaluates the utility of the Z Model for reproducing both vertical and oblique experimental impact data obtained at the NASA Ames Vertical Gun Range (AVGR). Specifically, ejection angle data obtained through Three-Dimensional Particle Image Velocimetry (3D PIV) are used to constrain the parameters of Maxwell's Z Model, including the value of Z and the depth and position of the flow-field center via inverse modeling.

Dynamics of formation of low-angle tilt boundaries in metals and alloys at high loading rates

NASA Astrophysics Data System (ADS)

Gutkin, M. Yu.; Rzhavtsev, E. A.

2015-12-01

A computer model has been developed in which the process of formation of low-angle tilt boundaries and fragmentation of initial subgrains during shock loading of metals and alloys is clearly demonstrated by the of two-dimensional discrete dislocation-disclination dynamics method. The formation and evolution of such grains proceeds under the action of an external stress and the stress field of grain boundary disclinations distributed on the subgrain boundaries. With the D16 aluminum alloy as an example, three cases of fragmented structures formed in accordance with the initial configuration of the disclination ensemble have been considered for a dipole, quadrupole, and arbitrary octupole of wedge disclinations. It has been shown that, in all these cases, the formation of a stable fragmented structure requires a stress of ~0.5 GPa and time of 10 ns. The main results of computer simulation (the finite form of a fragmented structure, typical level of applied stress, and small fragmentation time) agree well with known experimental results on shock compression of the D16 aluminum alloy.

Liquid sprays and flow studies in the direct-injection diesel engine under motored conditions

NASA Technical Reports Server (NTRS)

Nguyen, Hung Lee; Carpenter, Mark H.; Ramos, Juan I.; Schock, Harold J.; Stegeman, James D.

1988-01-01

A two dimensional, implicit finite difference method of the control volume variety, a two equation model of turbulence, and a discrete droplet model were used to study the flow field, turbulence levels, fuel penetration, vaporization, and mixing in diesel engine environments. The model was also used to study the effects of engine speed, injection angle, spray cone angle, droplet distribution, and intake swirl angle on the flow field, spray penetration and vaporization, and turbulence in motored two-stroke diesel engines. It is shown that there are optimum conditions for injection, which depend on droplet distribution, swirl, spray cone angle, and injection angle. The optimum conditions result in good spray penetration and vaporization and in good fuel mixing. The calculation presented clearly indicates that internal combustion engine models can be used to assess, at least qualitatively, the effects of injection characteristics and engine operating conditions on the flow field and on the spray penetration and vaporization in diesel engines.

Hanging angles of two electrostatically repelling pith balls of different masses

NASA Astrophysics Data System (ADS)

Tran, Phuc G.; Mungan, Carl E.

2011-09-01

An analytic solution can be derived for the angles of two mutually repelling charged pith balls of unequal mass hanging from strings from a common point of attachment. Just as in the equal-mass case, a cubic equation is found for the square of the sine of either angle, and an approximation can be used to avoid Cardano's formula for small angles. These results extend a standard problem treated in introductory undergraduate courses in electricity and magnetism.

Influence of a depletion interaction on dynamical heterogeneity in a dense quasi-two-dimensional colloid liquid.

PubMed

Ho, Hau My; Cui, Bianxiao; Repel, Stephen; Lin, Binhua; Rice, Stuart A

2004-11-01

We report the results of digital video microscopy studies of the large particle displacements in a quasi-two-dimensional binary mixture of large (L) and small (S) colloid particles with diameter ratio sigma(L)/sigma(S)=4.65, as a function of the large and small colloid particle densities. As in the case of the one-component quasi-two-dimensional colloid system, the binary mixtures exhibit structural and dynamical heterogeneity. The distribution of large particle displacements over the time scale examined provides evidence for (at least) two different mechanisms of motion, one associated with particles in locally ordered regions and the other associated with particles in locally disordered regions. When rhoL*=Npisigma(L) (2)/4A< or =0.35, the addition of small colloid particles leads to a monotonic decrease in the large particle diffusion coefficient with increasing small particle volume fraction. When rhoL* > or =0.35 the addition of small colloid particles to a dense system of large colloid particles at first leads to an increase in the large particle diffusion coefficient, which is then followed by the expected decrease of the large particle diffusion coefficient with increasing small colloid particle volume fraction. The mode coupling theory of the ideal glass transition in three-dimensional systems makes a qualitative prediction that agrees with the initial increase in the large particle diffusion coefficient with increasing small particle density. Nevertheless, because the structural and dynamical heterogeneities of the quasi-two-dimensional colloid liquid occur within the field of equilibrium states, and the fluctuations generate locally ordered domains rather than just disordered regions of higher and lower density, it is suggested that mode coupling theory does not account for all classes of relevant fluctuations in a quasi-two-dimensional liquid. (c) 2004 American Institute of Physics.

Basilar artery angulation in association with aging and pontine lacunar infarction: a multicenter observational study.

PubMed

Jeong, Seul-Ki; Lee, Ju-Hee; Nam, Do-Hyun; Kim, Joon-Tae; Ha, Yeon Soo; Oh, Sun-Young; Park, Se-Hyoung; Lee, Sang Hyuk; Hur, Nahmkeon; Kwak, Hyo-Sung; Chung, Gyung-Ho

2015-01-01

Deep pontine lacunar infarction (DPLI) not involving the basal pial surface of the medial part of the pons, is known to be a small vessel disease in the territory of the basilar artery (BA). In the present study, we examined whether morphological features of the BA differ in individuals with an advanced age and may be associated with DPLI. This study included 338 healthy subjects and 78 patients with DPLI treated at the stroke centers of three university hospitals in Korea. Time-Of-Flight magnetic resonance angiographic images were transported to a central lab and analyzed blind to obtain the clinical data. For the quantitative analysis, the BA was projected two-dimensionally in the anteroposterior and lateral views and perceived as triangles of the vertebrobasilar junction, angulation point and BA division. The angles and triangular areas were summated into angulation indexes and used to quantify the degree of BA tortuosity. The BA showed a more acute angle at the angulation point in the elderly patients than in the healthy subjects. Compared to the healthy subjects, the DPLI patients exhibited significantly larger angles at the vertebrobasilar junction, in addition to the acute angles noted at the angulation point. A unit increase in the BA angle indexes at the vertebrobasilar junction and angulation points for DPLI was found to have an odds ratio of 1.15 (95% confidence interval, 1.05-1.26) and 0.95 (95% CI, 0.91-0.99), respectively, even after adjusting for potential confounders. The angulation point of the BA becomes more acute in elderly individuals. In this study, the vertebrobasilar junction showed a larger angle in the patients with DPLI than in the healthy controls.

Experimental investigation of vortices shed by various wing fin configurations. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Iversen, J.; Moghadam, M.

1981-01-01

Forty-six different fins, which were members of twelve plan-form families, were tested. A two dimensional Boeing single element airfoil at an angle of attack of eight degrees and a sweepback angle of thirty-two was used to simulate a portion of the wing of a generator aircraft. Various free stream velocities were used to test any individual fin at its particular angle of attack. While the fin itself was mounted on the upper surface of the generator model, the angle of attack of each fin was varied until stall was reached and/or passed. The relative fin vortex strengths were measured in two ways. First, the maximum angular velocity of a four blade rotor placed in the fin vortex center was measured with the use of a stroboscope. Second, the maximum rolling moment on a following wing model placed in the fin vortex center was measured by a force balance.

Static internal performance including thrust vectoring and reversing of two-dimensional convergent-divergent nozzles

NASA Technical Reports Server (NTRS)

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

1984-01-01

The effects of geometric design parameters on two dimensional convergent-divergent nozzles were investigated at nozzle pressure ratios up to 12 in the static test facility. Forward flight (dry and afterburning power settings), vectored-thrust (afterburning power setting), and reverse-thrust (dry power setting) nozzles were investigated. The nozzles had thrust vector angles from 0 deg to 20.26 deg, throat aspect ratios of 3.696 to 7.612, throat radii from sharp to 2.738 cm, expansion ratios from 1.089 to 1.797, and various sidewall lengths. The results indicate that unvectored two dimensional convergent-divergent nozzles have static internal performance comparable to axisymmetric nozzles with similar expansion ratios.

Development of a two-dimensional dual pendulum thrust stand for Hall thrusters.

PubMed

Nagao, N; Yokota, S; Komurasaki, K; Arakawa, Y

2007-11-01

A two-dimensional dual pendulum thrust stand was developed to measure thrust vectors [axial and horizontal (transverse) direction thrusts] of a Hall thruster. A thruster with a steering mechanism is mounted on the inner pendulum, and thrust is measured from the displacement between inner and outer pendulums, by which a thermal drift effect is canceled out. Two crossover knife-edges support each pendulum arm: one is set on the other at a right angle. They enable the pendulums to swing in two directions. Thrust calibration using a pulley and weight system showed that the measurement errors were less than 0.25 mN (1.4%) in the main thrust direction and 0.09 mN (1.4%) in its transverse direction. The thrust angle of the thrust vector was measured with the stand using the thruster. Consequently, a vector deviation from the main thrust direction of +/-2.3 degrees was measured with the error of +/-0.2 degrees under the typical operating conditions for the thruster.

Titan impacts and escape

NASA Astrophysics Data System (ADS)

Korycansky, D. G.; Zahnle, Kevin J.

2011-01-01

We report on hydrodynamic calculations of impacts of large (multi-kilometer) objects on Saturn's moon Titan. We assess escape from Titan, and evaluate the hypothesis that escaping ejecta blackened the leading hemisphere of Iapetus and peppered the surface of Hyperion. We carried out two- and three-dimensional simulations of impactors ranging in size from 4 to 100 km diameter, impact velocities between 7 and 15 km s -1, and impact angles from 0° to 75° from the vertical. We used the ZEUSMP2 hydrocode for the calculations. Simulations were made using three different geometries: three-dimensional Cartesian, two-dimensional axisymmetric spherical polar, and two-dimensional plane polar. Three-dimensional Cartesian geometry calculations were carried out over a limited domain (e.g. 240 km on a side for an impactor of size di = 10 km), and the results compared to ones with the same parameters done by Artemieva and Lunine (2005); in general the comparison was good. Being computationally less demanding, two-dimensional calculations were possible for much larger domains, covering global regions of the satellite (from 800 km below Titan's surface to the exobase altitude 1700 km above the surface). Axisymmetric spherical polar calculations were carried out for vertical impacts. Two-dimensional plane-polar geometry calculations were made for both vertical and oblique impacts. In general, calculations among all three geometries gave consistent results. Our basic result is that the amount of escaping material is less than or approximately equal to the impactor mass even for the most favorable cases. Amounts of escaping material scaled most strongly as a function of velocity, with high-velocity impacts generating the largest amount, as expected. Dependence of the relative amount of escaping mass fesc = mesc/ Mi on impactor diameter di was weak. Oblique impacts (impact angle θi > 45°) were more effective than vertical or near-vertical impacts; ratios of mesc/ Mi ˜ 1-2 were found in the simulations.

Predictor symbology in computer-generated pictorial displays

NASA Technical Reports Server (NTRS)

Grunwald, A. J.

1981-01-01

The display under investigation, is a tunnel display for the four-dimensional commercial aircraft approach-to-landing under instrument flight rules. It is investigated whether more complex predictive information such as a three-dimensional perspective vehicle symbol, predicting the future vehicle position as well as future vehicle attitude angles, contributes to a better system response, and suitable predictor laws for the predictor motions, are formulated. Methods for utilizing the predictor symbol in controlling the forward velocity of the aircraft in four-dimensional approaches, are investigated. The simulator tests show, that the complex perspective vehicle symbol yields improved damping in the lateral response as compared to a flat two-dimensional predictor cross, but yields generally larger vertical deviations. Methods of using the predictor symbol in controlling the forward velocity of the vehicle are shown to be effective. The tunnel display with superimposed perspective vehicle symbol yields very satisfactory results and pilot acceptance in the lateral control but is found to be unsatisfactory in the vertical control, as a result of too large vertical path-angle deviations.

Athermally photoreduced graphene oxides for three-dimensional holographic images

PubMed Central

Li, Xiangping; Ren, Haoran; Chen, Xi; Liu, Juan; Li, Qin; Li, Chengmingyue; Xue, Gaolei; Jia, Jia; Cao, Liangcai; Sahu, Amit; Hu, Bin; Wang, Yongtian; Jin, Guofan; Gu, Min

2015-01-01

The emerging graphene-based material, an atomic layer of aromatic carbon atoms with exceptional electronic and optical properties, has offered unprecedented prospects for developing flat two-dimensional displaying systems. Here, we show that reduced graphene oxide enabled write-once holograms for wide-angle and full-colour three-dimensional images. This is achieved through the discovery of subwavelength-scale multilevel optical index modulation of athermally reduced graphene oxides by a single femtosecond pulsed beam. This new feature allows for static three-dimensional holographic images with a wide viewing angle up to 52 degrees. In addition, the spectrally flat optical index modulation in reduced graphene oxides enables wavelength-multiplexed holograms for full-colour images. The large and polarization-insensitive phase modulation over π in reduced graphene oxide composites enables to restore vectorial wavefronts of polarization discernible images through the vectorial diffraction of a reconstruction beam. Therefore, our technique can be leveraged to achieve compact and versatile holographic components for controlling light. PMID:25901676

CH5M3D: an HTML5 program for creating 3D molecular structures.

PubMed

Earley, Clarke W

2013-11-18

While a number of programs and web-based applications are available for the interactive display of 3-dimensional molecular structures, few of these provide the ability to edit these structures. For this reason, we have developed a library written in JavaScript to allow for the simple creation of web-based applications that should run on any browser capable of rendering HTML5 web pages. While our primary interest in developing this application was for educational use, it may also prove useful to researchers who want a light-weight application for viewing and editing small molecular structures. Molecular compounds are drawn on the HTML5 Canvas element, with the JavaScript code making use of standard techniques to allow display of three-dimensional structures on a two-dimensional canvas. Information about the structure (bond lengths, bond angles, and dihedral angles) can be obtained using a mouse or other pointing device. Both atoms and bonds can be added or deleted, and rotation about bonds is allowed. Routines are provided to read structures either from the web server or from the user's computer, and creation of galleries of structures can be accomplished with only a few lines of code. Documentation and examples are provided to demonstrate how users can access all of the molecular information for creation of web pages with more advanced features. A light-weight (≈ 75 kb) JavaScript library has been made available that allows for the simple creation of web pages containing interactive 3-dimensional molecular structures. Although this library is designed to create web pages, a web server is not required. Installation on a web server is straightforward and does not require any server-side modules or special permissions. The ch5m3d.js library has been released under the GNU GPL version 3 open-source license and is available from http://sourceforge.net/projects/ch5m3d/.

CH5M3D: an HTML5 program for creating 3D molecular structures

PubMed Central

2013-01-01

Background While a number of programs and web-based applications are available for the interactive display of 3-dimensional molecular structures, few of these provide the ability to edit these structures. For this reason, we have developed a library written in JavaScript to allow for the simple creation of web-based applications that should run on any browser capable of rendering HTML5 web pages. While our primary interest in developing this application was for educational use, it may also prove useful to researchers who want a light-weight application for viewing and editing small molecular structures. Results Molecular compounds are drawn on the HTML5 Canvas element, with the JavaScript code making use of standard techniques to allow display of three-dimensional structures on a two-dimensional canvas. Information about the structure (bond lengths, bond angles, and dihedral angles) can be obtained using a mouse or other pointing device. Both atoms and bonds can be added or deleted, and rotation about bonds is allowed. Routines are provided to read structures either from the web server or from the user’s computer, and creation of galleries of structures can be accomplished with only a few lines of code. Documentation and examples are provided to demonstrate how users can access all of the molecular information for creation of web pages with more advanced features. Conclusions A light-weight (≈ 75 kb) JavaScript library has been made available that allows for the simple creation of web pages containing interactive 3-dimensional molecular structures. Although this library is designed to create web pages, a web server is not required. Installation on a web server is straightforward and does not require any server-side modules or special permissions. The ch5m3d.js library has been released under the GNU GPL version 3 open-source license and is available from http://sourceforge.net/projects/ch5m3d/. PMID:24246004

Instrumentation on Multi-Scaled Scattering of Bio-Macromolecular Solutions

PubMed Central

Chu, Benjamin; Fang, Dufei; Mao, Yimin

2015-01-01

The design, construction and initial tests on a combined laser light scattering and synchrotron X-ray scattering instrument can cover studies of length scales from atomic sizes in Angstroms to microns and dynamics from microseconds to seconds are presented. In addition to static light scattering (SLS), dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD), the light scattering instrument is being developed to carry out studies in mildly turbid solutions, in the presence of multiple scattering. Three-dimensional photon cross correlation function (3D-PCCF) measurements have been introduced to couple with synchrotron X-ray scattering to study the structure, size and dynamics of macromolecules in solution. PMID:25946340

Three-dimensional and time-ordered surface-enhanced Raman scattering hotspot matrix.

PubMed

Liu, Honglin; Yang, Zhilin; Meng, Lingyan; Sun, Yudie; Wang, Jie; Yang, Liangbao; Liu, Jinhuai; Tian, Zhongqun

2014-04-09

The "fixed" or "flexible" design of plasmonic hotspots is a frontier area of research in the field of surface-enhanced Raman scattering (SERS). Most reported SERS hotspots have been shown to exist in zero-dimensional point-like, one-dimensional linear, or two-dimensional planar geometries. Here, we demonstrate a novel three-dimensional (3D) hotspot matrix that can hold hotspots between every two adjacent particles in 3D space, simply achieved by evaporating a droplet of citrate-Ag sols on a fluorosilylated silicon wafer. In situ synchrotron-radiation small-angle X-ray scattering (SR-SAXS), combined with dark-field microscopy and in situ micro-UV, was employed to explore the evolution of the 3D geometry and plasmonic properties of Ag nanoparticles in a single droplet. In such a droplet, there is a distinct 3D geometry with minimal polydispersity of particle size and maximal uniformity of interparticle distance, significantly different from the dry state. According to theoretical simulations, the liquid adhesive force promotes a closely packed assembly of particles, and the interparticle distance is not fixed but can be balanced in a small range by the interplay of the van der Waals attraction and electrostatic repulsion experienced by a particle. The "trapping well" for immobilizing particles in 3D space can result in a large number of hotspots in a 3D geometry. Both theoretical and experimental results demonstrate that the 3D hotspots are predictable and time-ordered in the absence of any sample manipulation. Use of the matrix not only produces giant Raman enhancement at least 2 orders of magnitude larger than that of dried substrates, but also provides the structural basis for trapping molecules. Even a single molecule of resonant dye can generate a large SERS signal. With a portable Raman spectrometer, the detection capability is also greatly improved for various analytes with different natures, including pesticides and drugs. This 3D hotspot matrix overcomes the long-standing limitations of SERS for the ultrasensitive characterization of various substrates and analytes and promises to transform SERS into a practical analytical technique.

Acoustic metamaterials with broadband and wide-angle impedance matching

NASA Astrophysics Data System (ADS)

Liu, Chenkai; Luo, Jie; Lai, Yun

2018-04-01

We propose a general approach to design broadband and wide-angle impedance-matched acoustic metamaterials. Such an unusual acoustic impedance matching characteristic can be well explained by using a spatially dispersive effective medium theory. For demonstrations, we used silicone rubber, which has a huge impedance contrast with water, to design one- and two-dimensional acoustic structures which are almost perfectly impedance matched to water for a wide range of incident angles and in a broad frequency band. Our work opens up an approach to realize extraordinary acoustic impedance matching properties via metamaterial-design techniques.

Comparison of face types in Chinese women using three-dimensional computed tomography.

PubMed

Zhou, Rong-Rong; Zhao, Qi-Ming; Liu, Miao

2015-04-01

This study compared inverted triangle and square faces of 21 young Chinese Han women (18-25 years old) using three-dimensional computed tomography images retrieved from a records database. In this study, 11 patients had inverted triangle faces and 10 had square faces. The anatomic features were examined and compared. There were significant differences in lower face width, lower face height, masseter thickness, middle/lower face width ratio, and lower face width/height ratio between the two facial types (p < 0.01). Lower face width was positively correlated with masseter thickness and negatively correlated with gonial angle. Lower face height was positively correlated with gonial angle and negatively correlated with masseter thickness, and gonial angle was negatively correlated with masseter thickness. In young Chinese Han women, inverted triangle faces and square faces differ significantly in masseter thickness and lower face height. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Two-dimensional analytic weighting functions for limb scattering

NASA Astrophysics Data System (ADS)

Zawada, D. J.; Bourassa, A. E.; Degenstein, D. A.

2017-10-01

Through the inversion of limb scatter measurements it is possible to obtain vertical profiles of trace species in the atmosphere. Many of these inversion methods require what is often referred to as weighting functions, or derivatives of the radiance with respect to concentrations of trace species in the atmosphere. Several radiative transfer models have implemented analytic methods to calculate weighting functions, alleviating the computational burden of traditional numerical perturbation methods. Here we describe the implementation of analytic two-dimensional weighting functions, where derivatives are calculated relative to atmospheric constituents in a two-dimensional grid of altitude and angle along the line of sight direction, in the SASKTRAN-HR radiative transfer model. Two-dimensional weighting functions are required for two-dimensional inversions of limb scatter measurements. Examples are presented where the analytic two-dimensional weighting functions are calculated with an underlying one-dimensional atmosphere. It is shown that the analytic weighting functions are more accurate than ones calculated with a single scatter approximation, and are orders of magnitude faster than a typical perturbation method. Evidence is presented that weighting functions for stratospheric aerosols calculated under a single scatter approximation may not be suitable for use in retrieval algorithms under solar backscatter conditions.

Divergence thrust loss calculations for convergent-divergent nozzles: Extensions to the classical case

NASA Technical Reports Server (NTRS)

Berton, Jeffrey J.

1991-01-01

The analytical derivations of the non-axial thrust divergence losses for convergent-divergent nozzles are described as well as how these calculations are embodied in the Navy/NASA engine computer program. The convergent-divergent geometries considered are simple classic axisymmetric nozzles, two dimensional rectangular nozzles, and axisymmetric and two dimensional plug nozzles. A simple, traditional, inviscid mathematical approach is used to deduce the influence of the ineffectual non-axial thrust as a function of the nozzle exit divergence angle.

Endwall flows and blading design for axial flow compressors

NASA Astrophysics Data System (ADS)

Robinson, Christopher J.

Literature relevant to blading design in the endwall region is reviewed, and important three dimensional flow phenomena occurring in embedded stages of axial compressors are described. A low speed axial flow four stage compressor rig is described and bladings studied are detailed: two conventional and two with end bends. The application of a three dimensional Navier-Stokes solver to the bladings' stators, to assess the effectiveness of the code, is reported. Calculation results of exit whirl angles, losses, and surface static pressures are compared with experiment.

Tourism English Teaching Techniques Converged from Two Different Angles.

ERIC Educational Resources Information Center

Seong, Myeong-Hee

2001-01-01

Provides techniques converged from two different angles (learners and tourism English features) for effective tourism English teaching in a junior college in Korea. Used a questionnaire, needs analysis, an instrument for measuring learners' strategies for oral communication, a small-scale classroom study for learners' preferred teaching…

Light extinction method on high-pressure diesel injection

NASA Astrophysics Data System (ADS)

Su, Tzay-Fa; El-Beshbeeshy, Mahmound S.; Corradini, Michael L.; Farrell, Patrick V.

1995-09-01

A two dimensional optical diagnostic technique based on light extinction was improved and demonstrated in an investigation of diesel spray characteristics at high injection pressures. Traditional light extinction methods require the spray image to be perpendicular to the light path. In the improved light extinction scheme, a tilted spray image which has an angle with the light path is still capable of being processed. This technique utilizes high speed photography and digital image analysis to obtain qualitative and quantitative information of the spray characteristics. The injection system used was an electronically controlled common rail unit injector system with injection pressures up to 100 MPa. The nozzle of the injector was a mini-sac type with six holes on the nozzle tip. Two different injection angle nozzles, 125 degree(s) and 140 degree(s), producing an in-plane tilted spray and an out of plane tilted spray were investigated. The experiments were conducted on a constant volume spray chamber with the injector mounted tilted at an angle of 62.5 degree(s)$. Only one spray plume was viewed, and other sprays were free to inject to the chamber. The spray chamber was pressurized with argon and air under room temperature to match the combustion chamber density at the start of the injection. The experimental results show that the difference in the spray tip penetration length, spray angle, and overall average Sauter mean diameter is small between the in- plane tilted spray and the out of plane tilted spray. The results also show that in-plane tilted spray has a slightly larger axial cross- section Sauter mean diameter than the out of plane tilted spray.

Comparison of experimental and theoretical boundary-layer separation for inlets at incidence angle at low-speed conditions

NASA Technical Reports Server (NTRS)

Felderman, E. J.; Albers, J. A.

1975-01-01

Comparisons between experimental and theoretical Mach number distributions and separation locations are presented for the internal surfaces of four different subsonic inlet geometries with exit diameters of 13.97 centimeters. The free stream Mach number was held constant at 0.127, the one-dimensional throat Mach number ranged from 0.49 to 0.71, and the incidence angle ranged from 0 deg to 50 deg. Generally good agreement was found between the theoretical and experimental surface Mach number distributions as long as no flow separation existed. At high incidence angles, where separation was obvious in the experimental data, the theory predicted separation on the lip. At lower incidence angles, the theoretical results indicated diffuser separation which was not obvious from the experimental surface Mach number distributions. As incidence angle was varied from 0 deg to 50 deg, the predicted separation location shifted from the diffuser region to the inlet highlight. Relatively small total pressure losses were obtained when the predicted separation location was greater than 0.6 of the distance between the highlight and the diffuser exit.

Three-Dimensional Effects in Multi-Element High Lift Computations

NASA Technical Reports Server (NTRS)

Rumsey, Christopher L.; LeeReusch, Elizabeth M.; Watson, Ralph D.

2003-01-01

In an effort to discover the causes for disagreement between previous two-dimensional (2-D) computations and nominally 2-D experiment for flow over the three-element McDonnell Douglas 30P-30N airfoil configuration at high lift, a combined experimental/CFD investigation is described. The experiment explores several different side-wall boundary layer control venting patterns, documents venting mass flow rates, and looks at corner surface flow patterns. The experimental angle of attack at maximum lift is found to be sensitive to the side-wall venting pattern: a particular pattern increases the angle of attack at maximum lift by at least 2 deg. A significant amount of spanwise pressure variation is present at angles of attack near maximum lift. A CFD study using three-dimensional (3-D) structured-grid computations, which includes the modeling of side-wall venting, is employed to investigate 3-D effects on the flow. Side-wall suction strength is found to affect the angle at which maximum lift is predicted. Maximum lift in the CFD is shown to be limited by the growth of an off-body corner flow vortex and consequent increase in spanwise pressure variation and decrease in circulation. The 3-D computations with and without wall venting predict similar trends to experiment at low angles of attack, but either stall too early or else overpredict lift levels near maximum lift by as much as 5%. Unstructured-grid computations demonstrate that mounting brackets lower the lift levels near maximum lift conditions.

PRECISE ANGLE MONITOR BASED ON THE CONCEPT OF PENCIL-BEAM INTERFEROMETRY

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

QIAN,S.; TAKACS,P.

2000-07-30

The precise angle monitoring is a very important metrology task for research, development and industrial applications. Autocollimator is one of the most powerful and widely applied instruments for small angle monitoring, which is based on the principle of geometric optics. In this paper the authors introduce a new precise angle monitoring system, Pencil-beam Angle Monitor (PAM), base on pencil beam interferometry. Its principle of operation is a combination of physical and geometrical optics. The angle calculation method is similar to the autocollimator. However, the autocollimator creates a cross image but the precise pencil-beam angle monitoring system produces an interference fringemore » on the focal plane. The advantages of the PAM are: high angular sensitivity, long-term stability character making angle monitoring over long time periods possible, high measurement accuracy in the order of sub-microradian, simultaneous measurement ability in two perpendicular directions or on two different objects, dynamic measurement possibility, insensitive to the vibration and air turbulence, automatic display, storage and analysis by use of the computer, small beam diameter making the alignment extremely easy and longer test distance. Some test examples are presented.« less

Lyapunov spectrum of the separated flow around the NACA 0012 airfoil and its dependence on numerical discretization

NASA Astrophysics Data System (ADS)

Fernandez, P.; Wang, Q.

2017-12-01

We investigate the impact of numerical discretization on the Lyapunov spectrum of separated flow simulations. The two-dimensional chaotic flow around the NACA 0012 airfoil at a low Reynolds number and large angle of attack is considered to that end. Time, space and accuracy-order refinement studies are performed to examine each of these effects separately. Numerical results show that the time discretization has a small impact on the dynamics of the system, whereas the spatial discretization can dramatically change them. Also, the finite-time Lyapunov exponents associated to unstable modes are shown to be positively skewed, and quasi-homoclinic tangencies are observed in the attractor of the system. The implications of these results on flow physics and sensitivity analysis of chaotic flows are discussed.

Engineering correlation effects via artificially designed oxide superlattices.

PubMed

Chen, Hanghui; Millis, Andrew J; Marianetti, Chris A

2013-09-13

Ab initio calculations are used to predict that a superlattice composed of layers of LaTiO3 and LaNiO3 alternating along the [001] direction is a S=1 Mott insulator with large magnetic moments on the Ni sites, negligible moments on the Ti sites and a charge transfer gap set by the energy difference between Ni d and Ti d states, distinct from conventional Mott insulators. Correlation effects are enhanced on the Ni sites via filling the oxygen p states and reducing the Ni-O-Ni bond angle. Small hole (electron) doping of the superlattice leads to a two-dimensional single-band situation with holes (electrons) residing on the Ni d(x2-y2) (Ti d(xy)) orbital and coupled to antiferromagnetically correlated spins in the NiO2 layer.

Engineering Correlation Effects via Artificially Designed Oxide Superlattices

NASA Astrophysics Data System (ADS)

Chen, Hanghui; Millis, Andrew J.; Marianetti, Chris A.

2013-09-01

Ab initio calculations are used to predict that a superlattice composed of layers of LaTiO3 and LaNiO3 alternating along the [001] direction is a S=1 Mott insulator with large magnetic moments on the Ni sites, negligible moments on the Ti sites and a charge transfer gap set by the energy difference between Ni d and Ti d states, distinct from conventional Mott insulators. Correlation effects are enhanced on the Ni sites via filling the oxygen p states and reducing the Ni-O-Ni bond angle. Small hole (electron) doping of the superlattice leads to a two-dimensional single-band situation with holes (electrons) residing on the Ni dx2-y2 (Ti dxy) orbital and coupled to antiferromagnetically correlated spins in the NiO2 layer.

A parametric study of transonic blade-vortex interaction noise

NASA Technical Reports Server (NTRS)

Lyrintzis, A. S.

1991-01-01

Several parameters of transonic blade-vortex interactions (BVI) are being studied and some ideas for noise reduction are introduced and tested using numerical simulation. The model used is the two-dimensional high frequency transonic small disturbance equation with regions of distributed vorticity (VTRAN2 code). The far-field noise signals are obtained by using the Kirchhoff method with extends the numerical 2-D near-field aerodynamic results to the linear acoustic 3-D far-field. The BVI noise mechanisms are explained and the effects of vortex type and strength, and angle of attack are studied. Particularly, airfoil shape modifications which lead to noise reduction are investigated. The results presented are expected to be helpful for better understanding of the nature of the BVI noise and better blade design.

Ionic depletion at the crystalline Gibbs layer of PEG-capped gold nanoparticle brushes at aqueous surfaces

NASA Astrophysics Data System (ADS)

Wang, Wenjie; Zhang, Honghu; Mallapragada, Surya; Travesset, Alex; Vaknin, David

2017-12-01

In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol-capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs2SO4 ) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. By taking advantage of element specificity with the GIXFS method, we find that the cation Cs+ concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film compared with that in the bulk.

A CFD Database for Airfoils and Wings at Post-Stall Angles of Attack

NASA Technical Reports Server (NTRS)

Petrilli, Justin; Paul, Ryan; Gopalarathnam, Ashok; Frink, Neal T.

2013-01-01

This paper presents selected results from an ongoing effort to develop an aerodynamic database from Reynolds-Averaged Navier-Stokes (RANS) computational analysis of airfoils and wings at stall and post-stall angles of attack. The data obtained from this effort will be used for validation and refinement of a low-order post-stall prediction method developed at NCSU, and to fill existing gaps in high angle of attack data in the literature. Such data could have potential applications in post-stall flight dynamics, helicopter aerodynamics and wind turbine aerodynamics. An overview of the NASA TetrUSS CFD package used for the RANS computational approach is presented. Detailed results for three airfoils are presented to compare their stall and post-stall behavior. The results for finite wings at stall and post-stall conditions focus on the effects of taper-ratio and sweep angle, with particular attention to whether the sectional flows can be approximated using two-dimensional flow over a stalled airfoil. While this approximation seems reasonable for unswept wings even at post-stall conditions, significant spanwise flow on stalled swept wings preclude the use of two-dimensional data to model sectional flows on swept wings. Thus, further effort is needed in low-order aerodynamic modeling of swept wings at stalled conditions.

Emergence of a confined state in a weakly bent wire

NASA Astrophysics Data System (ADS)

Granot, Er'El

2002-06-01

In this paper we use a simple straightforward technique to investigate the emergence of a bound state in a weakly bent wire. We show that the bend behaves like an infinitely shallow potential well, and in the limit of small bending angle (φ<<1) and low energy the bend can be presented by a simple one-dimensional δ-function potential, V(x)=-(2(cb)φ2)δ(x) where cb≅2.1.

Theory of Parabolic Arcs in Interstellar Scintillation Spectra

NASA Astrophysics Data System (ADS)

Cordes, James M.; Rickett, Barney J.; Stinebring, Daniel R.; Coles, William A.

2006-01-01

Interstellar scintillation (ISS), observed as time variation in the intensity of a compact radio source, is caused by small-scale structure in the electron density of the interstellar plasma. Dynamic spectra of ISS show modulation in radio frequency and time. Here we relate the (two-dimensional) power spectrum of the dynamic spectrum-the secondary spectrum-to the scattered image of the source. Recent work has identified remarkable parabolic arcs in secondary spectra. Each point in a secondary spectrum corresponds to interference between points in the scattered image with a certain Doppler shift and a certain delay. The parabolic arc corresponds to the quadratic relation between differential Doppler shift and delay through their common dependence on scattering angle. We show that arcs will occur in all media that scatter significant power at angles larger than the rms angle. Thus, effects such as source diameter, steep spectra, and dissipation scales, which truncate high angle scattering, also truncate arcs. Arcs are equally visible in simulations of nondispersive scattering. They are enhanced by anisotropic scattering when the spatial structure is elongated perpendicular to the velocity. In weak scattering the secondary spectrum is directly mapped from the scattered image, and this mapping can be inverted. We discuss additional observed phenomena including multiple arcs and reverse arclets oriented oppositely to the main arc. These phenomena persist for many refractive scattering times, suggesting that they are due to large-scale density structures, rather than low-frequency components of Kolmogorov turbulence.

Three-dimensional displacement measurement of image point by point-diffraction interferometry

NASA Astrophysics Data System (ADS)

He, Xiao; Chen, Lingfeng; Meng, Xiaojie; Yu, Lei

2018-01-01

This paper presents a method for measuring the three-dimensional (3-D) displacement of an image point based on point-diffraction interferometry. An object Point-light-source (PLS) interferes with a fixed PLS and its interferograms are captured by an exit pupil. When the image point of the object PLS is slightly shifted to a new position, the wavefront of the image PLS changes. And its interferograms also change. Processing these figures (captured before and after the movement), the wavefront difference of the image PLS can be obtained and it contains the information of three-dimensional (3-D) displacement of the image PLS. However, the information of its three-dimensional (3-D) displacement cannot be calculated until the distance between the image PLS and the exit pupil is calibrated. Therefore, we use a plane-parallel-plate with a known refractive index and thickness to determine this distance, which is based on the Snell's law for small angle of incidence. Thus, since the distance between the exit pupil and the image PLS is a known quantity, the 3-D displacement of the image PLS can be simultaneously calculated through two interference measurements. Preliminary experimental results indicate that its relative error is below 0.3%. With the ability to accurately locate an image point (whatever it is real or virtual), a fiber point-light-source can act as the reticle by itself in optical measurement.

Global Aeroheating Measurements of Shock-Shock Interactions on a Swept Cylinder

NASA Technical Reports Server (NTRS)

Mason, Michelle L.; Berry, Scott A.

2015-01-01

The effects of fin leading-edge radius and sweep angle on peak heating rates due to shock-shock interactions were investigated in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. The cylindrical leading-edge fin models, with radii varied from 0.25 to 0.75 inches, represent wings or struts on hypersonic vehicles. A 9deg wedge generated a planar oblique shock at 16.7deg. to the flow that intersected the fin bow shock, producing a shock-shock interaction that impinged on the fin leading edge. The fin sweep angle was varied from 0deg (normal to the free-stream) to 15deg and 25deg swept forward. These cases were chosen to explore three characterized shock-shock interaction types. Global temperature data were obtained from the surface of the fused silica fins using phosphor thermography. Metal oil flow models with the same geometries as the fused silica models were used to visualize the streamline patterns for each angle of attack. High-speed zoom-schlieren videos were recorded to show the features and any temporal unsteadiness of the shock-shock interactions. The temperature data were analyzed using a one-dimensional semi-infinite method, as well as one- and two-dimensional finite-volume methods. These results were compared to determine the proper heat transfer analysis approach to minimize errors from lateral heat conduction due to the presence of strong surface temperature gradients induced by the shock interactions. The general trends in the leading-edge heat transfer behavior were similar for each explored shock-shock interaction type regardless of the leading-edge radius. However, the dimensional peak heat transfer coefficient augmentation increased with decreasing leading-edge radius. The dimensional peak heat transfer output from the two-dimensional code was about 20% higher than the value from a standard, semi-infinite one-dimensional method.

Assessment of Soft Tissue Changes by Cephalometry and Two-Dimensional Photogrammetry in Bilateral Sagittal Split Ramus Osteotomy Cases

PubMed Central

Martin, Alice

2011-01-01

ABSTRACT Objectives We aimed to compare the standard methods of cephalometry and two-dimensional photogrammetry, to evaluate the reliability and accuracy of both methods. Material and Methods Twenty-six patients (mean age 25.5, standard deviation (SD) 5.2 years) with Class II relationship and 23 patients with Class III relationship (mean age 26.4, SD 4.7 years) who had undergone bilateral sagittal split ramus osteotomy were selected, with a median follow-up of 8 months between pre- and postsurgical evaluation. Pre- and postsurgical cephalograms and lateral photograms were traced and changes were recorded. Results Pre- and postsurgical measurements of hard tissue angles and distances revealed higher correlations with cephalometrically performed soft tissue measurements of facial convexity (Class II: N-PG, r = - 0.50, P = 0.047; Class III: ANB, r = 0.73, P = 0.005; NaPg , r = 0.71, P = 0.007;) and labiomental angle (Class II: SNB, r = 0.72, P = 0.002; ANB, r = - 0.72, P = 0.002; N-B, r = - 0.68, P = 0.004; ANS-Gn, r = 0.71, P = 0.002; Class III: ANS-Gn, r = 0.65, P = 0.043) compared with two-dimensional photogrammetry. However, two-dimensional photogrammetry revealed higher correlation between lower lip length and cephalometrically assessed angular hard tissue changes (Class II: SNB, r = 0.98, P = 0.007; N-B, r = 0.89, P = 0.037; N-Pg, r = 0.90, P = 0.033; Class III: SNB, r = - 0.54, P = 0.060; NAPg, r = - 0.65, P = 0.041; N-Pg, r = 0.58, P = 0.039). Conclusions Our findings suggest that cephalometry and two-dimensional photogrammetry offer the possibility to complement one another. PMID:24421994

Calculation of three-dimensional compressible laminar and turbulent boundary layers. An implicit finite-difference procedure for solving the three-dimensional compressible laminar, transitional, and turbulent boundary-layer equations

NASA Technical Reports Server (NTRS)

Harris, J. E.

1975-01-01

An implicit finite-difference procedure is presented for solving the compressible three-dimensional boundary-layer equations. The method is second-order accurate, unconditionally stable (conditional stability for reverse cross flow), and efficient from the viewpoint of computer storage and processing time. The Reynolds stress terms are modeled by (1) a single-layer mixing length model and (2) a two-layer eddy viscosity model. These models, although simple in concept, accurately predicted the equilibrium turbulent flow for the conditions considered. Numerical results are compared with experimental wall and profile data for a cone at an angle of attack larger than the cone semiapex angle. These comparisons clearly indicate that the numerical procedure and turbulence models accurately predict the experimental data with as few as 21 nodal points in the plane normal to the wall boundary.

Investigation of two-dimensional wedge exhaust nozzles for advanced aircraft

NASA Technical Reports Server (NTRS)

Maiden, D. L.; Petit, J. E.

1975-01-01

Two-dimensional wedge nozzle performance characteristics were investigated in a series of wind-tunnel tests. An isolated single-engine/nozzle model was used to study the effects of internal expansion area ratio, aftbody cowl boattail angle, and wedge length. An integrated twin-engine/nozzle model, tested with and without empenage surfaces, included cruise, acceleration, thrust vectoring and thrust reversing nozzle operating modes. Results indicate that the thrust-minus-aftbody drag performance of the twin two-dimensional nozzle integration is significantly higher, for speeds greater than Mach 0.8, than the performance achieved with twin axisymmetric nozzle installations. Significant jet-induced lift was obtained on an aft-mounted lifting surface using a cambered wedge center body to vector thrust. The thrust reversing capabilities of reverser panels installed on the two-dimensional wedge center body were very effective for static or in-flight operation.

High-resolution three-dimensional structural microscopy by single-angle Bragg ptychography

DOE PAGES

Hruszkewycz, S. O.; Allain, M.; Holt, M. V.; ...

2016-11-21

Coherent X-ray microscopy by phase retrieval of Bragg diffraction intensities enables lattice distortions within a crystal to be imaged at nanometre-scale spatial resolutions in three dimensions. While this capability can be used to resolve structure–property relationships at the nanoscale under working conditions, strict data measurement requirements can limit the application of current approaches. Here, in this work, we introduce an efficient method of imaging three-dimensional (3D) nanoscale lattice behaviour and strain fields in crystalline materials with a methodology that we call 3D Bragg projection ptychography (3DBPP). This method enables 3D image reconstruction of a crystal volume from a series ofmore » two-dimensional X-ray Bragg coherent intensity diffraction patterns measured at a single incident beam angle. Structural information about the sample is encoded along two reciprocal-space directions normal to the Bragg diffracted exit beam, and along the third dimension in real space by the scanning beam. Finally, we present our approach with an analytical derivation, a numerical demonstration, and an experimental reconstruction of lattice distortions in a component of a nanoelectronic prototype device.« less

Solution structure of the C-terminal domain of Ole e 9, a major allergen of olive pollen

PubMed Central

Treviño, Miguel Á.; Palomares, Oscar; Castrillo, Inés; Villalba, Mayte; Rodríguez, Rosalía; Rico, Manuel; Santoro, Jorge; Bruix, Marta

2008-01-01

Ole e 9 is an olive pollen allergen belonging to group 2 of pathogenesis-related proteins. The protein is composed of two immunological independent domains: an N-terminal domain (NtD) with 1,3-β-glucanase activity, and a C-terminal domain (CtD) that binds 1,3-β-glucans. We have determined the three-dimensional structure of CtD-Ole e 9 (101 amino acids), which consists of two parallel α-helices forming an angle of ∼55°, a small antiparallel β-sheet with two short strands, and a 3–10 helix turn, all connected by long coil segments, resembling a novel type of folding among allergens. Two regions surrounded by aromatic residues (F49, Y60, F96, Y91 and Y31, H68, Y65, F78) have been localized on the protein surface, and a role for sugar binding is suggested. The epitope mapping of CtD-Ole e 9 shows that B-cell epitopes are mainly located on loops, although some of them are contained in secondary structural elements. Interestingly, the IgG and IgE epitopes are contiguous or overlapped, rather than coincident. The three-dimensional structure of CtD-Ole e 9 might help to understand the underlying mechanism of its biochemical function and to determine possible structure–allergenicity relationships. PMID:18096638

Three-Dimensional Path Planning Software-Assisted Transjugular Intrahepatic Portosystemic Shunt: A Technical Modification

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

Tsauo, Jiaywei, E-mail: 80732059@qq.com; Luo, Xuefeng, E-mail: luobo-913@126.com; Ye, Linchao, E-mail: linchao.ye@siemens.com

2015-06-15

PurposeThis study was designed to report our results with a modified technique of three-dimensional (3D) path planning software assisted transjugular intrahepatic portosystemic shunt (TIPS).Methods3D path planning software was recently developed to facilitate TIPS creation by using two carbon dioxide portograms acquired at least 20° apart to generate a 3D path for overlay needle guidance. However, one shortcoming is that puncturing along the overlay would be technically impossible if the angle of the liver access set and the angle of the 3D path are not the same. To solve this problem, a prototype 3D path planning software was fitted with a utility to calculate themore » angle of the 3D path. Using this, we modified the angle of the liver access set accordingly during the procedure in ten patients.ResultsFailure for technical reasons occurred in three patients (unsuccessful wedged hepatic venography in two cases, software technical failure in one case). The procedure was successful in the remaining seven patients, and only one needle pass was required to obtain portal vein access in each case. The course of puncture was comparable to the 3D path in all patients. No procedure-related complication occurred following the procedures.ConclusionsAdjusting the angle of the liver access set to match the angle of the 3D path determined by the software appears to be a favorable modification to the technique of 3D path planning software assisted TIPS.« less

The leaf angle distribution of natural plant populations: assessing the canopy with a novel software tool.

PubMed

Müller-Linow, Mark; Pinto-Espinosa, Francisco; Scharr, Hanno; Rascher, Uwe

2015-01-01

Three-dimensional canopies form complex architectures with temporally and spatially changing leaf orientations. Variations in canopy structure are linked to canopy function and they occur within the scope of genetic variability as well as a reaction to environmental factors like light, water and nutrient supply, and stress. An important key measure to characterize these structural properties is the leaf angle distribution, which in turn requires knowledge on the 3-dimensional single leaf surface. Despite a large number of 3-d sensors and methods only a few systems are applicable for fast and routine measurements in plants and natural canopies. A suitable approach is stereo imaging, which combines depth and color information that allows for easy segmentation of green leaf material and the extraction of plant traits, such as leaf angle distribution. We developed a software package, which provides tools for the quantification of leaf surface properties within natural canopies via 3-d reconstruction from stereo images. Our approach includes a semi-automatic selection process of single leaves and different modes of surface characterization via polygon smoothing or surface model fitting. Based on the resulting surface meshes leaf angle statistics are computed on the whole-leaf level or from local derivations. We include a case study to demonstrate the functionality of our software. 48 images of small sugar beet populations (4 varieties) have been analyzed on the base of their leaf angle distribution in order to investigate seasonal, genotypic and fertilization effects on leaf angle distributions. We could show that leaf angle distributions change during the course of the season with all varieties having a comparable development. Additionally, different varieties had different leaf angle orientation that could be separated in principle component analysis. In contrast nitrogen treatment had no effect on leaf angles. We show that a stereo imaging setup together with the appropriate image processing tools is capable of retrieving the geometric leaf surface properties of plants and canopies. Our software package provides whole-leaf statistics but also a local estimation of leaf angles, which may have great potential to better understand and quantify structural canopy traits for guided breeding and optimized crop management.

Development of the transtibial prosthesis controlled pneumatically and electrically by microcomputer system.

PubMed

Shimada, Youichi; Terayama, Yukio

2006-01-01

This report represents the development of the prototype transtibial prosthesis to assist a smooth and comfortable walking for an unilateral amputee. This prosthesis is composed of two air cylinders, solenoid valves, portable and small air tank for compressed air storage, a multiple sensor system and a microprocessor. Two air cylinders are located around the rods to act as antagonistic and agonistic muscles. The system causes flexion and extension of the foot plate jointed at the ankle with compressed air, injected -or discharged via a solenoid or electromagnetic valves. The valves or solenoids are controlled with a microprocessor (Microchip Technology Inc., PIC16F876), the microprocessor generates control signals to the interface circuits for valve opening and closing consistent with the foot position during the walking phase. The control patterns generated in the microprocessor are modified with feedback from the touch sensor, ankle joint angle sensor and the two dimensional acceleration sensor. The primary walking pattern for an individual amputee should be developed through the gait analysis with video.

Non-linear 3D evaluation of different oral implant-abutment connections.

PubMed

Streckbein, P; Streckbein, R G; Wilbrand, J F; Malik, C Y; Schaaf, H; Howaldt, H P; Flach, M

2012-12-01

Micro-gaps and osseous overload in the implant-abutment connection are the most common causes of peri-implant bone resorption and implant failure. These undesirable events can be visualized on standardized three-dimensional finite element models and by radiographic methods. The present study investigated the influence of 7 available implant systems (Ankylos, Astra, Bego, Brånemark, Camlog, Straumann, and Xive) with different implant-abutment connections on bone overload and the appearance of micro-gaps in vitro. The individual geometries of the implants were transferred to three-dimensional finite element models. In a non-linear analysis considering the pre-loading of the occlusion screw, friction between the implant and abutment, the influence of the cone angle on bone strain, and the appearance of micro-gaps were determined. Increased bone strains were correlated with small (< 15°) cone angles. Conical implant-abutment connections efficiently avoided micro-gaps but had a negative effect on peri-implant bone strain. Bone strain was reduced in implants with greater wall thickness (Ankylos) or a smaller cone angle (Bego). The results of our in silico study provide a solid basis for the reduction of peri-implant bone strain and micro-gaps in the implant-abutment connection to improve long-term stability.

A "Kane's Dynamics" Model for the Active Rack Isolation System Part Two: Nonlinear Model Development, Verification, and Simplification

NASA Technical Reports Server (NTRS)

Beech, G. S.; Hampton, R. D.; Rupert, J. K.

2004-01-01

Many microgravity space-science experiments require vibratory acceleration levels that are unachievable without active isolation. The Boeing Corporation's active rack isolation system (ARIS) employs a novel combination of magnetic actuation and mechanical linkages to address these isolation requirements on the International Space Station. Effective model-based vibration isolation requires: (1) An isolation device, (2) an adequate dynamic; i.e., mathematical, model of that isolator, and (3) a suitable, corresponding controller. This Technical Memorandum documents the validation of that high-fidelity dynamic model of ARIS. The verification of this dynamics model was achieved by utilizing two commercial off-the-shelf (COTS) software tools: Deneb's ENVISION(registered trademark), and Online Dynamics Autolev(trademark). ENVISION is a robotics software package developed for the automotive industry that employs three-dimensional computer-aided design models to facilitate both forward and inverse kinematics analyses. Autolev is a DOS-based interpreter designed, in general, to solve vector-based mathematical problems and specifically to solve dynamics problems using Kane's method. The simplification of this model was achieved using the small-angle theorem for the joint angle of the ARIS actuators. This simplification has a profound effect on the overall complexity of the closed-form solution while yielding a closed-form solution easily employed using COTS control hardware.

Quantum phases of quadrupolar Fermi gases in coupled one-dimensional systems

NASA Astrophysics Data System (ADS)

Huang, Wen-Min; Lahrz, M.; Mathey, L.

2014-01-01

Following the recent proposal to create quadrupolar gases [Bhongale et al., Phys. Rev. Lett. 110, 155301 (2013), 10.1103/PhysRevLett.110.155301], we investigate what quantum phases can be created in these systems in one dimension. We consider a geometry of two coupled one-dimensional (1D) systems, and derive the quantum phase diagram of ultracold fermionic atoms interacting via quadrupole-quadrupole interactions within a Tomonaga-Luttinger-liquid framework. We map out the phase diagram as a function of the distance between the two tubes and the angle between the direction of the tubes and the quadrupolar moments. The latter can be controlled by an external field. We show that there are two magic angles θB,1c and θB,2c between 0 and π /2, where the intratube quadrupolar interactions vanish and change signs. Adopting a pseudospin language with regard to the two 1D systems, the system undergoes a spin-gap transition and displays a zigzag density pattern, above θB,2c and below θB,1c. Between the two magic angles, we show that polarized triplet superfluidity and a planar spin-density-wave order compete with each other. The latter corresponds to a bond-order solid in higher dimensions. We demonstrate that this order can be further stabilized by applying a commensurate periodic potential along the tubes.

Distributed force probe bending model of critical dimension atomic force microscopy bias

NASA Astrophysics Data System (ADS)

Ukraintsev, Vladimir A.; Orji, Ndubuisi G.; Vorburger, Theodore V.; Dixson, Ronald G.; Fu, Joseph; Silver, Rick M.

2013-04-01

Critical dimension atomic force microscopy (CD-AFM) is a widely used reference metrology technique. To characterize modern semiconductor devices, small and flexible probes, often 15 to 20 nm in diameter, are used. Recent studies have reported uncontrolled and significant probe-to-probe bias variation during linewidth and sidewall angle measurements. To understand the source of these variations, tip-sample interactions between high aspect ratio features and small flexible probes, and their influence on measurement bias, should be carefully studied. Using theoretical and experimental procedures, one-dimensional (1-D) and two-dimensional (2-D) models of cylindrical probe bending relevant to carbon nanotube (CNT) AFM probes were developed and tested. An earlier 1-D bending model was refined, and a new 2-D distributed force (DF) model was developed. Contributions from several factors were considered, including: probe misalignment, CNT tip apex diameter variation, probe bending before snapping, and distributed van der Waals-London force. A method for extracting Hamaker probe-surface interaction energy from experimental probe-bending data was developed. Comparison of the new 2-D model with 1-D single point force (SPF) model revealed a difference of about 28% in probe bending. A simple linear relation between biases predicted by the 1-D SPF and 2-D DF models was found. The results suggest that probe bending can be on the order of several nanometers and can partially explain the observed CD-AFM probe-to-probe variation. New 2-D and three-dimensional CD-AFM data analysis software is needed to take full advantage of the new bias correction modeling capabilities.

The use of a selective saturation pulse to suppress t1 noise in two-dimensional (1)H fast magic angle spinning solid-state NMR spectroscopy.

PubMed

Robertson, Aiden J; Pandey, Manoj Kumar; Marsh, Andrew; Nishiyama, Yusuke; Brown, Steven P

2015-11-01

A selective saturation pulse at fast magic angle spinning (MAS) frequencies (60+kHz) suppresses t1 noise in the indirect dimension of two-dimensional (1)H MAS NMR spectra. The method is applied to a synthetic nucleoside with an intense methyl (1)H signal due to triisopropylsilyl (TIPS) protecting groups. Enhanced performance in terms of suppressing the methyl signal while minimising the loss of signal intensity of nearby resonances of interest relies on reducing spin diffusion--this is quantified by comparing two-dimensional (1)H NOESY-like spin diffusion spectra recorded at 30-70 kHz MAS. For a saturation pulse centred at the methyl resonance, the effect of changing the nutation frequency at different MAS frequencies as well as the effect of changing the pulse duration is investigated. By applying a pulse of duration 30 ms and nutation frequency 725 Hz at 70 kHz MAS, a good compromise of significant suppression of the methyl resonance combined with the signal intensity of resonances greater than 5 ppm away from the methyl resonance being largely unaffected is achieved. The effectiveness of using a selective saturation pulse is demonstrated for both homonuclear (1)H-(1)H double quantum (DQ)/single quantum (SQ) MAS and (14)N-(1)H heteronuclear multiple quantum coherence (HMQC) two-dimensional solid-state NMR experiments. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Measurement of circulation around wing-tip vortices and estimation of lift forces using stereo PIV

NASA Astrophysics Data System (ADS)

Asano, Shinichiro; Sato, Haru; Sakakibara, Jun

2017-11-01

Applying the flapping flight to the development of an aircraft as Mars space probe and a small aircraft called MAV (Micro Air Vehicle) is considered. This is because Reynolds number assumed as the condition of these aircrafts is low and similar to of insects and small birds flapping on the earth. However, it is difficult to measure the flow around the airfoil in flapping flight directly because of its three-dimensional and unsteady characteristics. Hence, there is an attempt to estimate the flow field and aerodynamics by measuring the wake of the airfoil using PIV, for example the lift estimation method based on a wing-tip vortex. In this study, at the angle of attack including the angle after stall, we measured the wing-tip vortex of a NACA 0015 cross-sectional and rectangular planform airfoil using stereo PIV. The circulation of the wing-tip vortex was calculated from the obtained velocity field, and the lift force was estimated based on Kutta-Joukowski theorem. Then, the validity of this estimation method was examined by comparing the estimated lift force and the force balance data at various angles of attack. The experiment results are going to be presented in the conference.

Measurement of Aerodynamic Forces for Various Mean Angles of Attack on an Airfoil Oscillating in Pitch and on Two Finite-span Wings Oscillating in Bending with Emphasis on Damping in the Stall

NASA Technical Reports Server (NTRS)

Rainey, A Gerald

1957-01-01

The oscillating air forces on a two-dimensional wing oscillating in pitch about the midchord have been measured at various mean angles of attack and at Mach numbers of 0.35 and 0.7. The magnitudes of normal-force and pitching-moment coefficients were much higher at high angles of attack than at low angles of attack for some conditions. Large regions of negative damping in pitch were found, and it was shown that the effect of increasing the Mach number 0.35 to 0.7 was to decrease the initial angle of attack at which negative damping occurred. Measurements of the aerodynamic damping of a 10-percent-thick and of a 3-percent-thick finite-span wing oscillating in the first bending mode indicate no regions of negative damping for this type of motion over the range of variables covered. The damping measured at high angles of attack was generally larger than that at low angles of attack. (author)

Displacement, distance, and shape measurements of fast-rotating rough objects by two mutually tilted interference fringe systems.

PubMed

Günther, Philipp; Kuschmierz, Robert; Pfister, Thorsten; Czarske, Jürgen W

2013-05-01

The precise distance measurement of fast-moving rough surfaces is important in several applications such as lathe monitoring. A nonincremental interferometer based on two mutually tilted interference fringe systems has been realized for this task. The distance is coded in the phase difference between the generated interference signals corresponding to the fringe systems. Large tilting angles between the interference fringe systems are necessary for a high sensitivity. However, due to the speckle effect at rough surfaces, different envelopes and phase jumps of the interference signals occur. At large tilting angles, these signals become dissimilar, resulting in a small correlation coefficient and a high measurement uncertainty. Based on a matching of illumination and receiving optics, the correlation coefficient and the phase difference estimation have been improved significantly. For axial displacement measurements of recurring rough surfaces, laterally moving with velocities of 5 m/s, an uncertainty of 110 nm has been attained. For nonrecurring surfaces, a distance measurement uncertainty of 830 nm has been achieved. Incorporating the additionally measured lateral velocity and the rotational speed, the two-dimensional shape of rotating objects results. Since the measurement uncertainty of the displacement, distance, and shape is nearly independent of the lateral surface velocity, this technique is predestined for fast-rotating objects, such as crankshafts, camshafts, vacuum pump shafts, or turning parts of lathes.

Kelvin-Mach Wake in a Two-Dimensional Fermi Sea

NASA Astrophysics Data System (ADS)

Kolomeisky, Eugene B.; Straley, Joseph P.

2018-06-01

The dispersion law for plasma oscillations in a two-dimensional electron gas in the hydrodynamic approximation interpolates between Ω ∝√{q } and Ω ∝q dependences as the wave vector q increases. As a result, downstream of a charged impurity in the presence of a uniform supersonic electric current flow, a wake pattern of induced charge density and potential is formed whose geometry is controlled by the Mach number M . For 1 √{2 }. These wakes also trail an external charge, traveling supersonically, a fixed distance away from the electron gas.

Three-dimensional morphologies of inclined equiaxed dendrites growing under forced convection by phase-field-lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Sakane, Shinji; Takaki, Tomohiro; Ohno, Munekazu; Shibuta, Yasushi; Shimokawabe, Takashi; Aoki, Takayuki

2018-02-01

Three-dimensional growth morphologies of equiaxed dendrites growing under forced convection, with their preferred growth direction inclined from the flow direction, were investigated by performing large-scale phase-field lattice Boltzmann simulations on a graphical-processing-unit supercomputer. The tip velocities of the dendrite arms with their preferred growth directions inclined toward the upstream and downstream directions increased and decreased, respectively, as a result of forced convection. In addition, the tip velocities decreased monotonically as the angle between the preferred growth direction and the upstream direction increased. Here, the degree of acceleration of the upstream tips was larger than the degree of deceleration of the downstream tips. The angles between the actual tip growth directions and the preferred growth direction of the dendrite arms exhibited a characteristic change with two local maxima and two local minima.

Recognition of 3-D symmetric objects from range images in automated assembly tasks

NASA Technical Reports Server (NTRS)

Alvertos, Nicolas; Dcunha, Ivan

1990-01-01

A new technique is presented for the three dimensional recognition of symmetric objects from range images. Beginning from the implicit representation of quadrics, a set of ten coefficients is determined for symmetric objects like spheres, cones, cylinders, ellipsoids, and parallelepipeds. Instead of using these ten coefficients trying to fit them to smooth surfaces (patches) based on the traditional way of determining curvatures, a new approach based on two dimensional geometry is used. For each symmetric object, a unique set of two dimensional curves is obtained from the various angles at which the object is intersected with a plane. Using the same ten coefficients obtained earlier and based on the discriminant method, each of these curves is classified as a parabola, circle, ellipse, or hyperbola. Each symmetric object is found to possess a unique set of these two dimensional curves whereby it can be differentiated from the others. It is shown that instead of using the three dimensional discriminant which involves evaluation of the rank of its matrix, it is sufficient to use the two dimensional discriminant which only requires three arithmetic operations.

Large enhancement of second harmonic generation from transition-metal dichalcogenide monolayer on grating near bound states in the continuum.

PubMed

Wang, Tiecheng; Zhang, Shihao

2018-01-08

Second harmonic generation from the two-layer structure where a transition-metal dichalcogenide monolayer is put on a one-dimensional grating has been studied. This grating supports bound states in the continuum which have no leakage lying within the continuum of radiation modes, we can enhance the second harmonic generation from the transition-metal dichalcogenide monolayer by more than four orders of magnitude based on the critical field enhancement near the bound states in the continuum. In order to complete this calculation, the scattering matrix theory has been extended to include the nonlinear effect and the scattering matrix of a two-dimensional material including nonlinear terms; furthermore, two methods to observe the bound states in the continuum are considered, where one is tuning the thickness of the grating and the other is changing the incident angle of the electromagnetic wave. We have also discussed various modulation of the second harmonic generation enhancement by adjusting the azimuthal angle of the transition-metal dichalcogenide monolayer.

Tracking the Magnetization Evolution in γ-Fe2O3 / Metallic Fe Core-Shell Nanoparticle Variants

NASA Astrophysics Data System (ADS)

Kons, C.; Nemati, Z.; Srikanth, H.; Phan, M.-H.; Krycka, K.; Borchers, J.; Keavney, D.; Arena, D. A.

Iron-core magnetic nanoparticles (MNPs) with oxide shells exhibit varying magnetic properties due to the different ordering temperatures of the core and shell spins, as well as the coupling across the metal/oxide interface. While spin coupling across two dimensional interfaces has been well explored, less is known about three dimensional interfaces such as those presented in the MNPs. In this work, MNPs were synthesized with a bcc Fe core and γ-Fe2O3 shell and placed in an oxygen rich environment to encourage the transition from cores shell (CS) to core void shell (CVS) to hollow (H) structures. Static magnetic measurements (MvT) and AC magnetometry were performed to explore the magnetic behavior of the various synthesized structures. To further understand the nature of the spin coupling in the MNPs, TEM and conventional magnetometry as well as variable-temperature small angle neutron scattering (SANS), x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) spectroscopy were performed. Modeling of the x-ray spectra and SANS data will enable us to develop a cohesive picture of spin coupling, freezing and frustration along the three-dimensional metal / oxide interface. Supported by Department of Energy award #DE-FG02-07ER46438; NSF Award #DMR-1508249.

Closed-form integrator for the quaternion (euler angle) kinematics equations

NASA Technical Reports Server (NTRS)

Whitmore, Stephen A. (Inventor)

2000-01-01

The invention is embodied in a method of integrating kinematics equations for updating a set of vehicle attitude angles of a vehicle using 3-dimensional angular velocities of the vehicle, which includes computing an integrating factor matrix from quantities corresponding to the 3-dimensional angular velocities, computing a total integrated angular rate from the quantities corresponding to a 3-dimensional angular velocities, computing a state transition matrix as a sum of (a) a first complementary function of the total integrated angular rate and (b) the integrating factor matrix multiplied by a second complementary function of the total integrated angular rate, and updating the set of vehicle attitude angles using the state transition matrix. Preferably, the method further includes computing a quanternion vector from the quantities corresponding to the 3-dimensional angular velocities, in which case the updating of the set of vehicle attitude angles using the state transition matrix is carried out by (a) updating the quanternion vector by multiplying the quanternion vector by the state transition matrix to produce an updated quanternion vector and (b) computing an updated set of vehicle attitude angles from the updated quanternion vector. The first and second trigonometric functions are complementary, such as a sine and a cosine. The quantities corresponding to the 3-dimensional angular velocities include respective averages of the 3-dimensional angular velocities over plural time frames. The updating of the quanternion vector preserves the norm of the vector, whereby the updated set of vehicle attitude angles are virtually error-free.

Combined particle-image velocimetry and force analysis of the three-dimensional fluid-structure interaction of a natural owl wing.

PubMed

Winzen, A; Roidl, B; Schröder, W

2016-04-01

Low-speed aerodynamics has gained increasing interest due to its relevance for the design process of small flying air vehicles. These small aircraft operate at similar aerodynamic conditions as, e.g. birds which therefore can serve as role models of how to overcome the well-known problems of low Reynolds number flight. The flight of the barn owl is characterized by a very low flight velocity in conjunction with a low noise emission and a high level of maneuverability at stable flight conditions. To investigate the complex three-dimensional flow field and the corresponding local structural deformation in combination with their influence on the resulting aerodynamic forces, time-resolved stereoscopic particle-image velocimetry and force and moment measurements are performed on a prepared natural barn owl wing. Several spanwise positions are measured via PIV in a range of angles of attack [Formula: see text] 6° and Reynolds numbers 40 000 [Formula: see text] 120 000 based on the chord length. Additionally, the resulting forces and moments are recorded for -10° ≤ α ≤ 15° at the same Reynolds numbers. Depending on the spanwise position, the angle of attack, and the Reynolds number, the flow field on the wing's pressure side is characterized by either a region of flow separation, causing large-scale vortical structures which lead to a time-dependent deflection of the flexible wing structure or wing regions showing no instantaneous deflection but a reduction of the time-averaged mean wing curvature. Based on the force measurements the three-dimensional fluid-structure interaction is assumed to considerably impact the aerodynamic forces acting on the wing leading to a strong mechanical loading of the interface between the wing and body. These time-depending loads which result from the flexibility of the wing should be taken into consideration for the design of future small flying air vehicles using flexible wing structures.

Two-dimensional unsteady lift problems in supersonic flight

NASA Technical Reports Server (NTRS)

Heaslet, Max A; Lomax, Harvard

1949-01-01

The variation of pressure distribution is calculated for a two-dimensional supersonic airfoil either experiencing a sudden angle-of-attack change or entering a sharp-edge gust. From these pressure distributions the indicial lift functions applicable to unsteady lift problems are determined for two cases. Results are presented which permit the determination of maximum increment in lift coefficient attained by an unrestrained airfoil during its flight through a gust. As an application of these results, the minimum altitude for safe flight through a specific gust is calculated for a particular supersonic wing of given strength and wing loading.

Lower-limb kinematics of single-leg squat performance in young adults.

PubMed

Horan, Sean A; Watson, Steven L; Carty, Christopher P; Sartori, Massimo; Weeks, Benjamin K

2014-01-01

To determine the kinematic parameters that characterize good and poor single-leg squat (SLS) performance. A total of 22 healthy young adults free from musculoskeletal impairment were recruited for testing. For each SLS, both two-dimensional video and three-dimensional motion analysis data were collected. Pelvis, hip, and knee angles were calculated using a reliable and validated lower-limb (LL) biomechanical model. Two-dimensional video clips of SLSs were blindly assessed in random order by eight musculoskeletal physiotherapists using a 10-point ordinal scale. To facilitate between-group comparisons, SLS performances were stratified by tertiles corresponding to poor, intermediate, and good SLS performance. Mean ratings of SLS performance assessed by physiotherapists were 8.3 (SD 0.5), 6.8 (SD 0.7), and 4.0 (SD 0.8) for good, intermediate, and poor squats, respectively. Three-dimensional analysis revealed that people whose SLS performance was assessed as poor exhibited increased hip adduction, reduced knee flexion, and increased medio-lateral displacement of the knee joint centre compared to those whose SLS performance was assessed as good (p≤0.05). Overall, poor SLS performance is characterized by inadequate knee flexion and excessive frontal plane motion of the knee and hip. Future investigations of SLS performance should consider standardizing knee flexion angle to illuminate other influential kinematic parameters.

Dynamic tailoring of surface plasmon polaritons through incident angle modulation.

PubMed

Qiu, Peizhen; Zhang, Dawei; Jing, Ming; Lu, Taiguo; Yu, Binbin; Zhan, Qiwen; Zhuang, Songlin

2018-04-16

Dynamic tailoring of the propagating surface plasmon polaritons (SPPs) through incident angle modulation is proposed and numerically demonstrated. The generation and tailoring mechanism of the SPPs are discussed. The relationship formula between the incident angle and the generated SPP wave vector direction is theoretically derived. The correctness of the formula is verified with three different approaches using finite difference time domain method. Using this formula, the generated SPP wave vector direction can be precisely modulated by changing the incident angle. The precise modulation results of two dimensional Bessel-like SPP beam and SPP bottle beam array are given. The results can deepen the understanding of the generation and modulation mechanism of the SPPs.

Scattering calculation and image reconstruction using elevation-focused beams

PubMed Central

Duncan, David P.; Astheimer, Jeffrey P.; Waag, Robert C.

2009-01-01

Pressure scattered by cylindrical and spherical objects with elevation-focused illumination and reception has been analytically calculated, and corresponding cross sections have been reconstructed with a two-dimensional algorithm. Elevation focusing was used to elucidate constraints on quantitative imaging of three-dimensional objects with two-dimensional algorithms. Focused illumination and reception are represented by angular spectra of plane waves that were efficiently computed using a Fourier interpolation method to maintain the same angles for all temporal frequencies. Reconstructions were formed using an eigenfunction method with multiple frequencies, phase compensation, and iteration. The results show that the scattered pressure reduces to a two-dimensional expression, and two-dimensional algorithms are applicable when the region of a three-dimensional object within an elevation-focused beam is approximately constant in elevation. The results also show that energy scattered out of the reception aperture by objects contained within the focused beam can result in the reconstructed values of attenuation slope being greater than true values at the boundary of the object. Reconstructed sound speed images, however, appear to be relatively unaffected by the loss in scattered energy. The broad conclusion that can be drawn from these results is that two-dimensional reconstructions require compensation to account for uncaptured three-dimensional scattering. PMID:19425653

Scattering calculation and image reconstruction using elevation-focused beams.

PubMed

Duncan, David P; Astheimer, Jeffrey P; Waag, Robert C

2009-05-01

Pressure scattered by cylindrical and spherical objects with elevation-focused illumination and reception has been analytically calculated, and corresponding cross sections have been reconstructed with a two-dimensional algorithm. Elevation focusing was used to elucidate constraints on quantitative imaging of three-dimensional objects with two-dimensional algorithms. Focused illumination and reception are represented by angular spectra of plane waves that were efficiently computed using a Fourier interpolation method to maintain the same angles for all temporal frequencies. Reconstructions were formed using an eigenfunction method with multiple frequencies, phase compensation, and iteration. The results show that the scattered pressure reduces to a two-dimensional expression, and two-dimensional algorithms are applicable when the region of a three-dimensional object within an elevation-focused beam is approximately constant in elevation. The results also show that energy scattered out of the reception aperture by objects contained within the focused beam can result in the reconstructed values of attenuation slope being greater than true values at the boundary of the object. Reconstructed sound speed images, however, appear to be relatively unaffected by the loss in scattered energy. The broad conclusion that can be drawn from these results is that two-dimensional reconstructions require compensation to account for uncaptured three-dimensional scattering.

Three dimensional thermal stresses in angle-ply composite laminates

NASA Technical Reports Server (NTRS)

Griffin, O. Hayden, Jr.

1988-01-01

The room temperature stress distributions and shapes of a family of angle ply graphite/epoxy laminates have been obtained using a three-dimensional linear finite element analysis. The sensitivity of the corners to fiber angle variations is examined, in addition to the errors introduced by assuming planes of symmetry which do not exist in angle-ply laminates. The results show that angle ply laminates with 'clustered' plies will tend to delaminate at diagonally opposite corners, and that matrix cracks in this family of laminates will be initiated in the laminate interior.

Excitations in confined helium

NASA Astrophysics Data System (ADS)

Apaja, V.; Krotscheck, E.

2003-05-01

We design models for helium in matrices such as aerogel, Vycor, or Geltech from a manifestly microscopic point of view. For that purpose, we calculate the dynamic structure function of 4He on Si substrates and between two Si walls as a function of energy, momentum transfer, and the scattering angle. The angle-averaged results are in good agreement with the neutron scattering data; the remaining differences can be attributed to the simplified model used here for the complex pore structure of the materials. A focus of the present work is the detailed identification of coexisting layer modes and bulklike excitations, and, in the case of thick films, ripplon excitations. Involving essentially two-dimensional motion of atoms, the layer modes are sensitive to the scattering angle.

High-density two-dimensional electron system induced by oxygen vacancies in ZnO

NASA Astrophysics Data System (ADS)

Rödel, T. C.; Dai, J.; Fortuna, F.; Frantzeskakis, E.; Le Fèvre, P.; Bertran, F.; Kobayashi, M.; Yukawa, R.; Mitsuhashi, T.; Kitamura, M.; Horiba, K.; Kumigashira, H.; Santander-Syro, A. F.

2018-05-01

We realize a two-dimensional electron system (2DES) in ZnO by simply depositing pure aluminum on its surface in ultrahigh vacuum and characterize its electronic structure by using angle-resolved photoemission spectroscopy. The aluminum oxidizes into alumina by creating oxygen vacancies that dope the bulk conduction band of ZnO and confine the electrons near its surface. The electron density of the 2DES is up to two orders of magnitude higher than those obtained in ZnO heterostructures. The 2DES shows two s -type subbands, that we compare with the d -like 2DESs in titanates, with clear signatures of many-body interactions that we analyze through a self-consistent extraction of the system self-energy and a modeling as a coupling of a two-dimensional Fermi liquid with a Debye distribution of phonons.

Micromachined needles and lancets with design adjustable bevel angles

NASA Astrophysics Data System (ADS)

Sparks, Douglas; Hubbard, Timothy

2004-08-01

A new method of micromachining hollow needles and two-dimensional needle arrays from single crystal silicon is described. The process involves a combination of fusion bonding, photolithography and anisotropic plasma etching. The cannula produced with this process can have design adjustable bevel angles, wall thickness and channel dimensions. A subset of processing steps can be employed to produce silicon blades and lancets with design adjustable bevel angles and shaft dimensions. Applications for this technology include painless drug infusion, blood diagnosis, glucose monitoring, cellular injection and the manufacture of microkeratomes for ocular, vascular and neural microsurgery.

Exploring bird aerodynamics using radio-controlled models.

PubMed

Hoey, Robert G

2010-12-01

A series of radio-controlled glider models was constructed by duplicating the aerodynamic shape of soaring birds (raven, turkey vulture, seagull and pelican). Controlled tests were conducted to determine the level of longitudinal and lateral-directional static stability, and to identify the characteristics that allowed flight without a vertical tail. The use of tail-tilt for controlling small bank-angle changes, as observed in soaring birds, was verified. Subsequent tests, using wing-tip ailerons, inferred that birds use a three-dimensional flow pattern around the wing tip (wing tip vortices) to control adverse yaw and to create a small amount of forward thrust in gliding flight.

Utility of three-dimensional and multiplanar reformatted computed tomography for evaluation of pediatric congenital spine abnormalities.

PubMed

Newton, Peter O; Hahn, Gregory W; Fricka, Kevin B; Wenger, Dennis R

2002-04-15

A retrospective radiographic review of 31 patients with congenital spine abnormalities who underwent conventional radiography and advanced imaging studies was conducted. To analyze the utility of three-dimensional computed tomography with multiplanar reformatted images for congenital spine anomalies, as compared with plain radiographs and axial two-dimensional computed tomography imaging. Conventional radiographic imaging for congenital spine disorders often are difficult to interpret because of the patient's small size, the complexity of the disorder, a deformity not in the plane of the radiographs, superimposed structures, and difficulty in forming a mental three-dimensional image. Multiplanar reformatted and three-dimensional computed tomographic imaging offers many potential advantages for defining congenital spine anomalies including visualization of the deformity in any plane, from any angle, with the overlying structures subtracted. The imaging studies of patients who had undergone a three-dimensional computed tomography for congenital deformities of the spine between 1992 and 1998 were reviewed (31 cases). All plain radiographs and axial two-dimensional computed tomography images performed before the three-dimensional computed tomography were reviewed and the findings documented. This was repeated for the three-dimensional reconstructions and, when available, the multiplanar reformatted images (15 cases). In each case, the utility of the advanced imaging was graded as one of the following: Grade A (substantial new information obtained), Grade B (confirmatory with improved visualization and understanding of the deformity), and Grade C (no added useful information obtained). In 17 of 31 cases, the multiplanar reformatted and three-dimensional images allowed identification of unrecognized malformations. In nine additional cases, the advanced imaging was helpful in better visualizing and understanding previously identified deformities. In five cases, no new information was gained. The standard and curved multiplanar reformatted images were best for defining the occiput-C1-C2 anatomy and the extent of segmentation defects. The curved multiplanar reformatted images were especially helpful in keeping the spine from "coming in" and "going out" of the plane of the image when there was significant spine deformity in the sagittal or coronal plane. The three-dimensional reconstructions proved valuable in defining failures of formation. Advanced computed tomography imaging (three-dimensional computed tomography and curved/standard multiplanar reformatted images) allows better definition of congenital spine anomalies. More than 50% of the cases showed additional abnormalities not appreciated on plain radiographs or axial two-dimensional computed tomography images. Curved multiplanar reformatted images allowed imaging in the coronal and sagittal planes of the entire deformity.

Diffraction mode terahertz tomography

DOEpatents

Ferguson, Bradley; Wang, Shaohong; Zhang, Xi-Cheng

2006-10-31

A method of obtaining a series of images of a three-dimensional object. The method includes the steps of transmitting pulsed terahertz (THz) radiation through the entire object from a plurality of angles, optically detecting changes in the transmitted THz radiation using pulsed laser radiation, and constructing a plurality of imaged slices of the three-dimensional object using the detected changes in the transmitted THz radiation. The THz radiation is transmitted through the object as a two-dimensional array of parallel rays. The optical detection is an array of detectors such as a CCD sensor.

Study on a two-dimensional scanning micro-mirror and its application in a MOEMS target detector.

PubMed

Zhang, Chi; You, Zheng; Huang, Hu; Li, Guanhua

2010-01-01

A two-dimensional (2D) scanning micro-mirror for target detection and measurement has been developed. This new micro-mirror is used in a MOEMS target detector to replace the conventional scanning detector. The micro-mirror is fabricated by MEMS process and actuated by a piezoelectric actuator. To achieve large deflection angles, the micro-mirror is excited in the resonance modes. It has two degrees of freedom and changes the direction of the emitted laser beam for a regional 2D scanning. For the deflection angles measurement, piezoresistors are integrated in the micro-mirror and the deflection angles of each direction can be detected independently and precisely. Based on the scanning micro-mirror and the phase-shift ranging technology, a MOEMS target detector has been developed in a size of 90 mm × 35 mm × 50 mm. The experiment shows that the target can be detected in the scanning field and the relative range and orientation can be measured by the MOEMS target detector. For the target distance up to 3 m with a field of view about 20° × 20°, the measurement resolution is about 10.2 cm in range, 0.15° in the horizontal direction and 0.22° in the vertical direction for orientation.

Study on a Two-Dimensional Scanning Micro-Mirror and Its Application in a MOEMS Target Detector

PubMed Central

Zhang, Chi; You, Zheng; Huang, Hu; Li, Guanhua

2010-01-01

A two-dimensional (2D) scanning micro-mirror for target detection and measurement has been developed. This new micro-mirror is used in a MOEMS target detector to replace the conventional scanning detector. The micro-mirror is fabricated by MEMS process and actuated by a piezoelectric actuator. To achieve large deflection angles, the micro-mirror is excited in the resonance modes. It has two degrees of freedom and changes the direction of the emitted laser beam for a regional 2D scanning. For the deflection angles measurement, piezoresistors are integrated in the micro-mirror and the deflection angles of each direction can be detected independently and precisely. Based on the scanning micro-mirror and the phase-shift ranging technology, a MOEMS target detector has been developed in a size of 90 mm × 35 mm × 50 mm. The experiment shows that the target can be detected in the scanning field and the relative range and orientation can be measured by the MOEMS target detector. For the target distance up to 3 m with a field of view about 20° × 20°, the measurement resolution is about 10.2 cm in range, 0.15° in the horizontal direction and 0.22° in the vertical direction for orientation. PMID:22163580

The accuracy of three-dimensional fused deposition modeling (FDM) compared with three-dimensional CT-Scans on the measurement of the mandibular ramus vertical length, gonion-menton length, and gonial angle

NASA Astrophysics Data System (ADS)

Savitri, I. T.; Badri, C.; Sulistyani, L. D.

2017-08-01

Presurgical treatment planning plays an important role in the reconstruction and correction of defects in the craniomaxillofacial region. The advance of solid freeform fabrication techniques has significantly improved the process of preparing a biomodel using computer-aided design and data from medical imaging. Many factors are implicated in the accuracy of the 3D model. To determine the accuracy of three-dimensional fused deposition modeling (FDM) models compared with three-dimensional CT scans in the measurement of the mandibular ramus vertical length, gonion-menton length, and gonial angle. Eight 3D models were produced from the CT scan data (DICOM file) of eight patients at the Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Indonesia, Cipto Mangunkusumo Hospital. Three measurements were done three times by two examiners. The measurements of the 3D CT scans were made using OsiriX software, while the measurements of the 3D models were made using a digital caliper and goniometry. The measurement results were then compared. There is no significant difference between the measurements of the mandibular ramus vertical length, gonion-menton length, and gonial angle using 3D CT scans and FDM 3D models. FDM 3D models are considered accurate and are acceptable for clinical applications in dental and craniomaxillofacial surgery.

Isolation and initial structural characterization of a 27 kDa protein from Zingiber officinale

NASA Astrophysics Data System (ADS)

Rasheed, Saima; Malik, Shoaib Ahmad; Falke, Sven; Arslan, Ali; Fazel, Ramin; Schlüter, Hartmut; Betzel, Christian; Choudhary, M. Iqbal

2018-03-01

Zingiber officinale Roscoe (Ginger) is a widely used traditional medicinal plant (for different ailments such as arthritis, constipation, and hypertension). This article describes the isolation and characterization of a so far unknown protein from ginger rhizomes applying ion exchange, affinity, size-exclusion chromatography, small angle X-ray scattering (SAXS), and mass spectrometry techniques. One-dimensional Coomassie-stained SDS-PAGE was performed under non-reducing conditions, showing one band corresponding to approx. 27 kDa. Dynamic light scattering (DLS) analysis of the protein solution revealed monodispersity and a monomeric state of the purified protein. Circular dichroism (CD) spectroscopy strongly indicated a β-sheet-rich protein, and disordered regions. MALDI-TOF-MS, and LC-MS/MS analysis resulted in the identification of 27.29 kDa protein, having 32.13% and 25.34% sequence coverage with Zingipain-1 and 2, respectively. The monomeric state and molecular weight were verified by small angle X-ray scattering (SAXS) studies. An elongated ab-initio model was calculated based on the scattering intensity distribution.

Resolution of ab initio shapes determined from small-angle scattering.

PubMed

Tuukkanen, Anne T; Kleywegt, Gerard J; Svergun, Dmitri I

2016-11-01

Spatial resolution is an important characteristic of structural models, and the authors of structures determined by X-ray crystallography or electron cryo-microscopy always provide the resolution upon publication and deposition. Small-angle scattering of X-rays or neutrons (SAS) has recently become a mainstream structural method providing the overall three-dimensional structures of proteins, nucleic acids and complexes in solution. However, no quantitative resolution measure is available for SAS-derived models, which significantly hampers their validation and further use. Here, a method is derived for resolution assessment for ab initio shape reconstruction from scattering data. The inherent variability of the ab initio shapes is utilized and it is demonstrated how their average Fourier shell correlation function is related to the model resolution. The method is validated against simulated data for proteins with known high-resolution structures and its efficiency is demonstrated in applications to experimental data. It is proposed that henceforth the resolution be reported in publications and depositions of ab initio SAS models.

Resolution of ab initio shapes determined from small-angle scattering

PubMed Central

Tuukkanen, Anne T.; Kleywegt, Gerard J.; Svergun, Dmitri I.

2016-01-01

Spatial resolution is an important characteristic of structural models, and the authors of structures determined by X-ray crystallography or electron cryo-microscopy always provide the resolution upon publication and deposition. Small-angle scattering of X-rays or neutrons (SAS) has recently become a mainstream structural method providing the overall three-dimensional structures of proteins, nucleic acids and complexes in solution. However, no quantitative resolution measure is available for SAS-derived models, which significantly hampers their validation and further use. Here, a method is derived for resolution assessment for ab initio shape reconstruction from scattering data. The inherent variability of the ab initio shapes is utilized and it is demonstrated how their average Fourier shell correlation function is related to the model resolution. The method is validated against simulated data for proteins with known high-resolution structures and its efficiency is demonstrated in applications to experimental data. It is proposed that henceforth the resolution be reported in publications and depositions of ab initio SAS models. PMID:27840683

Interactive graphical system for small-angle scattering analysis of polydisperse systems

NASA Astrophysics Data System (ADS)

Konarev, P. V.; Volkov, V. V.; Svergun, D. I.

2016-09-01

A program suite for one-dimensional small-angle scattering analysis of polydisperse systems and multiple data sets is presented. The main program, POLYSAS, has a menu-driven graphical user interface calling computational modules from ATSAS package to perform data treatment and analysis. The graphical menu interface allows one to process multiple (time, concentration or temperature-dependent) data sets and interactively change the parameters for the data modelling using sliders. The graphical representation of the data is done via the Winteracter-based program SASPLOT. The package is designed for the analysis of polydisperse systems and mixtures, and permits one to obtain size distributions and evaluate the volume fractions of the components using linear and non-linear fitting algorithms as well as model-independent singular value decomposition. The use of the POLYSAS package is illustrated by the recent examples of its application to study concentration-dependent oligomeric states of proteins and time kinetics of polymer micelles for anticancer drug delivery.

Polarization splitter and polarization rotator designs based on transformation optics.

PubMed

Kwon, Do-Hoon; Werner, Douglas H

2008-11-10

The transformation optics technique is employed in this paper to design two optical devices - a two-dimensional polarization splitter and a three-dimensional polarization rotator for propagating beams. The polarization splitter translates the TM- and the TE-polarized components of an incident beam in opposite directions (i.e., shifted up or shifted down). The polarization rotator rotates the polarization state of an incoming beam by an arbitrary angle. Both optical devices are reflectionless at the entry and exit interfaces. Design details and full-wave simulation results are provided.

Ultra-compact laser beam steering device using holographically formed two dimensional photonic crystal.

PubMed

Dou, Xinyuan; Chen, Xiaonan; Chen, Maggie Yihong; Wang, Alan Xiaolong; Jiang, Wei; Chen, Ray T

2010-03-01

In this paper, we report the theoretical study of polymer-based photonic crystals for laser beam steering which is based on the superprism effect as well as the experiment fabrication of the two dimensional photonic crystals for the laser beam steering. Superprism effect, the principle for beam steering, was separately studied in details through EFC (Equifrequency Contour) analysis. Polymer based photonic crystals were fabricated through double exposure holographic interference method using SU8-2007. The experiment results showed a beam steering angle of 10 degree for 30 nm wavelength variation.

Compilation of Information on the Transonic Attachment of Flows at the Leading Edges of Airfoils

NASA Technical Reports Server (NTRS)

Lindsey, Walter F; Landrum, Emma Jean

1958-01-01

Schlieren photographs have been compiled of the two-dimensional flow at transonic speeds past 37 airfoils. These airfoils have variously shaped profiles, and some are related in thickness and camber. The data for these airfoils were analyzed to provide basic information on the flow changes involved and to determine factors affecting transonic-flow attachment, which is a transition from separated to unseparated flow at the leading edges of two-dimensional airfoils at fixed angles as the subsonic Mach number is increased.

Knee rotation influences the femoral tunnel angle measurement after anterior cruciate ligament reconstruction: a 3-dimensional computed tomography model study

PubMed Central

Tang, Jing; Thorhauer, Eric; Marsh, Chelsea; Fu, Freddie H.

2013-01-01

Purpose Femoral tunnel angle (FTA) has been proposed as a metric for evaluating whether ACL reconstruction was performed anatomically. In clinic, radiographic images are typically acquired with an uncertain amount of internal/external knee rotation. The extent to which knee rotation will influence FTA measurement is unclear. Furthermore, differences in FTA measurement between the two common positions (0° and 45° knee flexion) have not been established. The purpose of this study was to investigate the influence of knee rotation on FTA measurement after ACL reconstruction. Methods Knee CT data from 16 subjects were segmented to produce 3D bone models. Central axes of tunnels were identified. The 0° and 45° flexion angles were simulated. Knee internal/external rotations were simulated in a range of ±20°. FTA was defined as the angle between the tunnel axis and femoral shaft axis, orthogonally projected into the coronal plane. Results Femoral tunnel angle was positively/negatively correlated with knee rotation angle at 0°/45° knee flexion. At 0° knee flexion, FTA for anterio-medial (AM) tunnels was significantly decreased at 20° of external knee rotation. At 45° knee flexion, more than 16° external or 19° internal rotation significantly altered FTA measurements for single-bundle tunnels; smaller rotations (±9° for AM, ±5° for PL) created significant errors in FTA measurements after double-bundle reconstruction. Conclusion Femoral tunnel angle measurements were correlated with knee rotation. Relatively small imaging malalignment introduced significant errors with knee flexed 45°. This study supports using the 0° flexion position for knee radiographs to reduce errors in FTA measurement due to knee internal/external rotation. Level of evidence Case–control study, Level III. PMID:23589127

Semi-analytical and Numerical Studies on the Flattened Brazilian Splitting Test Used for Measuring the Indirect Tensile Strength of Rocks

NASA Astrophysics Data System (ADS)

Huang, Y. G.; Wang, L. G.; Lu, Y. L.; Chen, J. R.; Zhang, J. H.

2015-09-01

Based on the two-dimensional elasticity theory, this study established a mechanical model under chordally opposing distributed compressive loads, in order to perfect the theoretical foundation of the flattened Brazilian splitting test used for measuring the indirect tensile strength of rocks. The stress superposition method was used to obtain the approximate analytic solutions of stress components inside the flattened Brazilian disk. These analytic solutions were then verified through a comparison with the numerical results of the finite element method (FEM). Based on the theoretical derivation, this research carried out a contrastive study on the effect of the flattened loading angles on the stress value and stress concentration degree inside the disk. The results showed that the stress concentration degree near the loading point and the ratio of compressive/tensile stress inside the disk dramatically decreased as the flattened loading angle increased, avoiding the crushing failure near-loading point of Brazilian disk specimens. However, only the tensile stress value and the tensile region were slightly reduced with the increase of the flattened loading angle. Furthermore, this study found that the optimal flattened loading angle was 20°-30°; flattened load angles that were too large or too small made it difficult to guarantee the central tensile splitting failure principle of the Brazilian splitting test. According to the Griffith strength failure criterion, the calculative formula of the indirect tensile strength of rocks was derived theoretically. This study obtained a theoretical indirect tensile strength that closely coincided with existing and experimental results. Finally, this paper simulated the fracture evolution process of rocks under different loading angles through the use of the finite element numerical software ANSYS. The modeling results showed that the Flattened Brazilian Splitting Test using the optimal loading angle could guarantee the tensile splitting failure initiated by a central crack.

Quantitative analysis of eyes and other optical systems in linear optics.

PubMed

Harris, William F; Evans, Tanya; van Gool, Radboud D

2017-05-01

To show that 14-dimensional spaces of augmented point P and angle Q characteristics, matrices obtained from the ray transference, are suitable for quantitative analysis although only the latter define an inner-product space and only on it can one define distances and angles. The paper examines the nature of the spaces and their relationships to other spaces including symmetric dioptric power space. The paper makes use of linear optics, a three-dimensional generalization of Gaussian optics. Symmetric 2 × 2 dioptric power matrices F define a three-dimensional inner-product space which provides a sound basis for quantitative analysis (calculation of changes, arithmetic means, etc.) of refractive errors and thin systems. For general systems the optical character is defined by the dimensionally-heterogeneous 4 × 4 symplectic matrix S, the transference, or if explicit allowance is made for heterocentricity, the 5 × 5 augmented symplectic matrix T. Ordinary quantitative analysis cannot be performed on them because matrices of neither of these types constitute vector spaces. Suitable transformations have been proposed but because the transforms are dimensionally heterogeneous the spaces are not naturally inner-product spaces. The paper obtains 14-dimensional spaces of augmented point P and angle Q characteristics. The 14-dimensional space defined by the augmented angle characteristics Q is dimensionally homogenous and an inner-product space. A 10-dimensional subspace of the space of augmented point characteristics P is also an inner-product space. The spaces are suitable for quantitative analysis of the optical character of eyes and many other systems. Distances and angles can be defined in the inner-product spaces. The optical systems may have multiple separated astigmatic and decentred refracting elements. © 2017 The Authors Ophthalmic & Physiological Optics © 2017 The College of Optometrists.

Highly cytocompatible and flexible three-dimensional graphene/polydimethylsiloxane composite for culture and electrochemical detection of L929 fibroblast cells.

PubMed

Waiwijit, Uraiwan; Maturos, Thitima; Pakapongpan, Saithip; Phokharatkul, Ditsayut; Wisitsoraat, Anurat; Tuantranont, Adisorn

2016-08-01

Recently, three-dimensional graphene interconnected network has attracted great interest as a scaffold structure for tissue engineering due to its high biocompatibility, high electrical conductivity, high specific surface area and high porosity. However, free-standing three-dimensional graphene exhibits poor flexibility and stability due to ease of disintegration during processing. In this work, three-dimensional graphene is composited with polydimethylsiloxane to improve the structural flexibility and stability by a new simple two-step process comprising dip coating of polydimethylsiloxane on chemical vapor deposited graphene/Ni foam and wet etching of nickel foam. Structural characterizations confirmed an interconnected three-dimensional multi-layer graphene structure with thin polydimethylsiloxane scaffold. The composite was employed as a substrate for culture of L929 fibroblast cells and its cytocompatibility was evaluated by cell viability (Alamar blue assay), reactive oxygen species production and vinculin immunofluorescence imaging. The result revealed that cell viability on three-dimensional graphene/polydimethylsiloxane composite increased with increasing culture time and was slightly different from a polystyrene substrate (control). Moreover, cells cultured on three-dimensional graphene/polydimethylsiloxane composite generated less ROS than the control at culture times of 3-6 h. The results of immunofluorescence staining demonstrated that fibroblast cells expressed adhesion protein (vinculin) and adhered well on three-dimensional graphene/polydimethylsiloxane surface. Good cell adhesion could be attributed to suitable surface properties of three-dimensional graphene/polydimethylsiloxane with moderate contact angle and small negative zeta potential in culture solution. The results of electrochemical study by cyclic voltammetry showed that an oxidation current signal with no apparent peak was induced by fibroblast cells and the oxidation current at an oxidation potential of +0.9 V increased linearly with increasing cell number. Therefore, the three-dimensional graphene/polydimethylsiloxane composite exhibits high cytocompatibility and can potentially be used as a conductive substrate for cell-based electrochemical sensing. © The Author(s) 2016.

Error reduction program: A progress report

NASA Technical Reports Server (NTRS)

Syed, S. A.

1984-01-01

Five finite differences schemes were evaluated for minimum numerical diffusion in an effort to identify and incorporate the best error reduction scheme into a 3D combustor performance code. Based on this evaluated, two finite volume method schemes were selected for further study. Both the quadratic upstream differencing scheme (QUDS) and the bounded skew upstream differencing scheme two (BSUDS2) were coded into a two dimensional computer code and their accuracy and stability determined by running several test cases. It was found that BSUDS2 was more stable than QUDS. It was also found that the accuracy of both schemes is dependent on the angle that the streamline make with the mesh with QUDS being more accurate at smaller angles and BSUDS2 more accurate at larger angles. The BSUDS2 scheme was selected for extension into three dimensions.

Visualization of Two Dimensional to Three Dimensional Transformations--Exploration through Technology

ERIC Educational Resources Information Center

Costa, G. B.; Gorak, M.; Melendez, B. S.

2006-01-01

A small class of functions is described that easily lend themselves to two-dimensional and three-dimensional visualizations at the basic calculus level. The intended audience is those educators involved in the instruction of elementary calculus. This note is an educational piece that begins with the question: "What happens if a function defined on…

Laser probe for measuring 2-D wave slope spectra of ocean capillary waves

NASA Technical Reports Server (NTRS)

Palm, C. S.; Anderson, R. C.; Reece, A. M.

1977-01-01

A laser-optical instrument for use in determining the two-dimensional wave-slope spectrum of ocean capillary waves is described. The instrument measures up to a 35-deg tip angle of the surface normal by measuring the position of a refracted laser beam directed vertically upward through a water surface. A telescope, a continuous two-dimensional Schottky barrier photodiode, and a pair of analog dividers render the signals independent of water height and insensitive to laser-beam intensity fluctuations. Calibration is performed entirely in the laboratory before field use. Sample records and wave-slope spectra are shown for one-dimensional wave-tank tests and for two-dimensional ocean tests. These are presented along with comparison spectra for calm and choppy water conditions. A mechanical wave follower was used to adjust the instrument position in the presence of large ocean swell and tides.

Structural consequences of metallothionein dimerization: solution structure of the isolated Cd4-alpha-domain and comparison with the holoprotein dimer.

PubMed

Ejnik, John W; Muñoz, Amalia; DeRose, Eugene; Shaw, C Frank; Petering, David H

2003-07-22

The NMR determination of the structure of Cd(7)-metallothionein was done previously using a relatively large protein concentration that favors dimer formation. The reactivity of the protein is also affected under this condition. To examine the influence of protein concentration on metallothionein conformation, the isolated Cd(4)-alpha-domain was prepared from rabbit metallothionein-2 (MT 2), and its three-dimensional structure was determined by heteronuclear, (1)H-(111)Cd, and homonuclear, (1)H-(1)H NMR, correlation experiments. The three-dimensional structure was refined using distance and angle constraints derived from these two-dimensional NMR data sets and a distance geometry/simulated annealing protocol. The backbone superposition of the alpha-domain from rabbit holoprotein Cd(7)-MT 2 and the isolated rabbit Cd(4)-alpha was measured at a RMSD of 2.0 A. Nevertheless, the conformations of the two Cd-thiolate clusters were distinctly different at two of the cadmium centers. In addition, solvent access to the sulfhydryl ligands of the isolated Cd(4)-alpha cluster was 130% larger due to this small change in cluster geometry. To probe whether these differences were an artifact of the structure calculation, the Cd(4)-alpha-domain structure in rabbit Cd(7)-MT 2 was redetermined, using the previously defined set of NOEs and the present calculation protocol. All calculations employed the same ionic radius for Cd(2+) and same cadmium-thiolate bond distance. The newly calculated structure matched the original with an RMSD of 1.24 A. It is hypothesized that differences in the two alpha-domain structures result from a perturbation of the holoprotein structure because of head-to-tail dimerization under the conditions of the NMR experiments.

Empirical Model for Predicting Rockfall Trajectory Direction

NASA Astrophysics Data System (ADS)

Asteriou, Pavlos; Tsiambaos, George

2016-03-01

A methodology for the experimental investigation of rockfall in three-dimensional space is presented in this paper, aiming to assist on-going research of the complexity of a block's response to impact during a rockfall. An extended laboratory investigation was conducted, consisting of 590 tests with cubical and spherical blocks made of an artificial material. The effects of shape, slope angle and the deviation of the post-impact trajectory are examined as a function of the pre-impact trajectory direction. Additionally, an empirical model is proposed that estimates the deviation of the post-impact trajectory as a function of the pre-impact trajectory with respect to the slope surface and the slope angle. This empirical model is validated by 192 small-scale field tests, which are also presented in this paper. Some important aspects of the three-dimensional nature of rockfall phenomena are highlighted that have been hitherto neglected. The 3D space data provided in this study are suitable for the calibration and verification of rockfall analysis software that has become increasingly popular in design practice.

An efficient user-oriented method for calculating compressible flow in an about three-dimensional inlets. [panel method

NASA Technical Reports Server (NTRS)

Hess, J. L.; Mack, D. P.; Stockman, N. O.

1979-01-01

A panel method is used to calculate incompressible flow about arbitrary three-dimensional inlets with or without centerbodies for four fundamental flow conditions: unit onset flows parallel to each of the coordinate axes plus static operation. The computing time is scarcely longer than for a single solution. A linear superposition of these solutions quite rigorously gives incompressible flow about the inlet for any angle of attack, angle of yaw, and mass flow rate. Compressibility is accounted for by applying a well-proven correction to the incompressible flow. Since the computing times for the combination and the compressibility correction are small, flows at a large number of inlet operating conditions are obtained rather cheaply. Geometric input is aided by an automatic generating program. A number of graphical output features are provided to aid the user, including surface streamline tracing and automatic generation of curves of curves of constant pressure, Mach number, and flow inclination at selected inlet cross sections. The inlet method and use of the program are described. Illustrative results are presented.

Comparison of Electron Imaging Modes for Dimensional Measurements in the Scanning Electron Microscope.

PubMed

Postek, Michael T; Vladár, András E; Villarrubia, John S; Muto, Atsushi

2016-08-01

Dimensional measurements from secondary electron (SE) images were compared with those from backscattered electron (BSE) and low-loss electron (LLE) images. With the commonly used 50% threshold criterion, the lines consistently appeared larger in the SE images. As the images were acquired simultaneously by an instrument with the capability to operate detectors for both signals at the same time, the differences cannot be explained by the assumption that contamination or drift between images affected the SE, BSE, or LLE images differently. Simulations with JMONSEL, an electron microscope simulator, indicate that the nanometer-scale differences observed on this sample can be explained by the different convolution effects of a beam with finite size on signals with different symmetry (the SE signal's characteristic peak versus the BSE or LLE signal's characteristic step). This effect is too small to explain the >100 nm discrepancies that were observed in earlier work on different samples. Additional modeling indicates that those discrepancies can be explained by the much larger sidewall angles of the earlier samples, coupled with the different response of SE versus BSE/LLE profiles to such wall angles.

Application of dot-matrix illumination of liquid crystal phase space light modulator in 3D imaging of APD array

NASA Astrophysics Data System (ADS)

Wang, Shuai; Sun, Huayan; Guo, Huichao

2018-01-01

Aiming at the problem of beam scanning in low-resolution APD array in three-dimensional imaging, a method of beam scanning with liquid crystal phase-space optical modulator is proposed to realize high-resolution imaging by low-resolution APD array. First, a liquid crystal phase spatial light modulator is used to generate a beam array and then a beam array is scanned. Since the sub-beam divergence angle in the beam array is smaller than the field angle of a single pixel in the APD array, the APD's pixels respond only to the three-dimensional information of the beam illumination position. Through the scanning of the beam array, a single pixel is used to collect the target three-dimensional information multiple times, thereby improving the resolution of the APD detector. Finally, MATLAB is used to simulate the algorithm in this paper by using two-dimensional scalar diffraction theory, which realizes the splitting and scanning with a resolution of 5 x 5. The feasibility is verified theoretically.

Investigation of normal shock inlets for highly maneuverable aircraft

NASA Technical Reports Server (NTRS)

Martin, A. W.

1977-01-01

Concepts are investigated for obtaining both low cowl drag and good inlet performance at high angles of attack. The effect of a canard on inlet performance for a kidney shaped inlet in each of two vertical locations is discussed along with a sharp lip two dimensional inlet on a canardless forebody.

Development of a two-dimensional dual pendulum thrust stand for Hall thrusters

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

Nagao, N.; Yokota, S.; Komurasaki, K.

A two-dimensional dual pendulum thrust stand was developed to measure thrust vectors (axial and horizontal (transverse) direction thrusts) of a Hall thruster. A thruster with a steering mechanism is mounted on the inner pendulum, and thrust is measured from the displacement between inner and outer pendulums, by which a thermal drift effect is canceled out. Two crossover knife-edges support each pendulum arm: one is set on the other at a right angle. They enable the pendulums to swing in two directions. Thrust calibration using a pulley and weight system showed that the measurement errors were less than 0.25 mN (1.4%)more » in the main thrust direction and 0.09 mN (1.4%) in its transverse direction. The thrust angle of the thrust vector was measured with the stand using the thruster. Consequently, a vector deviation from the main thrust direction of {+-}2.3 deg. was measured with the error of {+-}0.2 deg. under the typical operating conditions for the thruster.« less

X-ray scattering data and structural genomics

NASA Astrophysics Data System (ADS)

Doniach, Sebastian

2003-03-01

High throughput structural genomics has the ambitious goal of determining the structure of all, or a very large number of protein folds using the high-resolution techniques of protein crystallography and NMR. However, the program is facing significant bottlenecks in reaching this goal, which include problems of protein expression and crystallization. In this talk, some preliminary results on how the low-resolution technique of small-angle X-ray solution scattering (SAXS) can help ameliorate some of these bottlenecks will be presented. One of the most significant bottlenecks arises from the difficulty of crystallizing integral membrane proteins, where only a handful of structures are available compared to thousands of structures for soluble proteins. By 3-dimensional reconstruction from SAXS data, the size and shape of detergent-solubilized integral membrane proteins can be characterized. This information can then be used to classify membrane proteins which constitute some 25% of all genomes. SAXS may also be used to study the dependence of interparticle interference scattering on solvent conditions so that regions of the protein solution phase diagram which favor crystallization can be elucidated. As a further application, SAXS may be used to provide physical constraints on computational methods for protein structure prediction based on primary sequence information. This in turn can help in identifying structural homologs of a given protein, which can then give clues to its function. D. Walther, F. Cohen and S. Doniach. "Reconstruction of low resolution three-dimensional density maps from one-dimensional small angle x-ray scattering data for biomolecules." J. Appl. Cryst. 33(2):350-363 (2000). Protein structure prediction constrained by solution X-ray scattering data and structural homology identification Zheng WJ, Doniach S JOURNAL OF MOLECULAR BIOLOGY , v. 316(#1) pp. 173-187 FEB 8, 2002

Two-dimensional compressible flow in centrifugal compressors with straight blades

NASA Technical Reports Server (NTRS)

Stanitz, John D; Ellis, Gaylord O

1950-01-01

Six numerical examples are presented for steady, two-dimensional, compressible, nonviscous flow in centrifugal compressors with thin straight blades, the center lines of which generate the surface of a right circular cone when rotated about the axis of the compressor. A seventh example is presented for incompressible flow. The solutions were obtained in a region of the compressors, including the impeller tip, that was considered to be unaffected by the diffuser vanes or by the impeller-inlet configuration. Each solution applies to radial and mixed flow compressors with various cone angles but with the same angle between blades on the conic flow surface. The solution also apply to radial and mixed flow turbines with the rotation and the flow direction reversed. The effects of variations in the following parameters were investigated: (1) flow rate, (2) impeller-tip speed, (3) variation of passage height with radius, and (4) angle between blades on conic flow surface. The numerical results are presented in plots of the streamlines and constant Mach number lines. Correlation equations are developed whereby the flow conditions in any impeller with straight blades can be determined (in the region investigated by this analysis) for all operating conditions.

Theoretical and experimental study of DOA estimation using AML algorithm for an isotropic and non-isotropic 3D array

NASA Astrophysics Data System (ADS)

Asgari, Shadnaz; Ali, Andreas M.; Collier, Travis C.; Yao, Yuan; Hudson, Ralph E.; Yao, Kung; Taylor, Charles E.

2007-09-01

The focus of most direction-of-arrival (DOA) estimation problems has been based mainly on a two-dimensional (2D) scenario where we only need to estimate the azimuth angle. But in various practical situations we have to deal with a three-dimensional scenario. The importance of being able to estimate both azimuth and elevation angles with high accuracy and low complexity is of interest. We present the theoretical and the practical issues of DOA estimation using the Approximate-Maximum-Likelihood (AML) algorithm in a 3D scenario. We show that the performance of the proposed 3D AML algorithm converges to the Cramer-Rao Bound. We use the concept of an isotropic array to reduce the complexity of the proposed algorithm by advocating a decoupled 3D version. We also explore a modified version of the decoupled 3D AML algorithm which can be used for DOA estimation with non-isotropic arrays. Various numerical results are presented. We use two acoustic arrays each consisting of 8 microphones to do some field measurements. The processing of the measured data from the acoustic arrays for different azimuth and elevation angles confirms the effectiveness of the proposed methods.

Vibrational cross-angles in condensed molecules: a structural tool.

PubMed

Chen, Hailong; Zhang, Yufan; Li, Jiebo; Liu, Hongjun; Jiang, De-En; Zheng, Junrong

2013-09-05

The fluctuations of three-dimensional molecular conformations of a molecule in different environments play critical roles in many important chemical and biological processes. X-ray diffraction (XRD) techniques and nuclear magnetic resonance (NMR) methods are routinely applied to monitor the molecular conformations in condensed phases. However, some special requirements of the methods have prevented them from exploring many molecular phenomena at the current stage. Here, we introduce another method to resolve molecular conformations based on an ultrafast MIR/T-Hz multiple-dimensional vibrational spectroscopic technique. The model molecule (4'-methyl-2'-nitroacetanilide, MNA) is prepared in two of its crystalline forms and liquid samples. Two polarized ultrafast infrared pulses are then used to determine the cross-angles of vibrational transition moment directions by exciting one vibrational band and detecting the induced response on another vibrational band of the molecule. The vibrational cross-angles are then converted into molecular conformations with the aid of calculations. The molecular conformations determined by the method are supported by X-ray diffraction and molecular dynamics simulation results. The experimental results suggest that thermodynamic interactions with solvent molecules are not altering the molecular conformations of MNA in the solutions to control their ultimate conformations in the crystals.

Gas-Sensing Devices Based on Zn-Doped NiO Two-Dimensional Grainy Films with Fast Response and Recovery for Ammonia Molecule Detection

NASA Astrophysics Data System (ADS)

Wang, Jian; Wei, Xiaowei; Wangyang, Peihua

2015-12-01

Zn-doped NiO two-dimensional grainy films on glass substrates are shown to be an ammonia-sensing material with excellent comprehensive performance, which could real-time detect and monitor ammonia (NH3) in the surrounding environment. The morphology and structure analysis indicated that the as-fabricated semiconductor films were composed of particles with diameters ranging from 80 to 160 nm, and each particle was composed of small crystalline grain with a narrow size about 20 nm, which was the face-centered cubic single crystal structure. X-ray diffraction peaks shifted toward lower angle, and the size of the lattice increased compared with undoped NiO, which demonstrated that zinc ions have been successfully doped into the NiO host structure. Simultaneously, we systematically investigated the gas-sensing properties of the Zn-doped NiO sensors for NH3 detection at room temperature. The sensor based on doped NiO sensing films gave four to nine times faster response and four to six times faster recovery speeds than those of sensor with undoped NiO films, which is important for the NiO sensor practical applications. Moreover, we found that the doped NiO sensors owned outstanding selectivity toward ammonia.

Virtual Shaping of a Two-dimensional NACA 0015 Airfoil Using Synthetic Jet Actuator

NASA Technical Reports Server (NTRS)

Chen, Fang-Jenq; Beeler, George B.

2002-01-01

The Aircraft Morphing Program at NASA Langley envisions an aircraft without conventional control surfaces. Instead of moving control surfaces, the vehicle control systems may be implemented with a combination of propulsive forces, micro surface effectors, and fluidic devices dynamically operated by an intelligent flight control system to provide aircraft maneuverability over each mission segment. As a part of this program, a two-dimensional NACA 0015 airfoil model was designed to test mild maneuvering capability of synthetic jets in a subsonic wind tunnel. The objective of the experiments is to assess the applicability of using unsteady suction and blowing to alter the aerodynamic shape of an airfoil with a purpose to enhance lift and/or to reduce drag. Synthetic jet actuation at different chordwise locations, different forcing frequencies and amplitudes, under different freestream velocities are investigated. The effect of virtual shape change is indicated by a localized increase of surface pressure in the neighborhood of synthetic jet actuation. That causes a negative lift to the airfoil with an upper surface actuation. When actuation is applied near the airfoil leading edge, it appears that the stagnation line is shifted inducing an effect similar to that caused by a small angle of attack to produce an overall lift change.

Dimensional Effects on the Charge Density Waves in Ultrathin Films of TiSe 2

DOE PAGES

Chen, P.; Chan, Y. -H.; Wong, M. -H.; ...

2016-09-20

Charge density wave (CDW) formation in solids is a critical phenomenon involving the collective reorganization of the electrons and atoms in the system into a wave structure, and it is expected to be sensitive to the geometric constraint of the system at the nanoscale. Here, we study the CDW transition in TiSe 2, a quasi-two-dimensional layered material, to determine the effects of quantum confinement and changing dimensions in films ranging from a single layer to multilayers. Of key interest is the characteristic length scale for the transformation from a two-dimensional case to the three-dimensional limit. Angle-resolved photoemission (ARPES) measurements ofmore » films with thicknesses up to six layers reveal substantial variations in the energy structure of discrete quantum well states; however, the temperature-dependent band-gap renormalization converges at just three layers. The results indicate a layer-dependent mixture of two transition temperatures and a very-short-range CDW interaction within a three-dimensional framework.« less

Maximal liquid bridges between horizontal cylinders

NASA Astrophysics Data System (ADS)

Cooray, Himantha; Huppert, Herbert E.; Neufeld, Jerome A.

2016-08-01

We investigate two-dimensional liquid bridges trapped between pairs of identical horizontal cylinders. The cylinders support forces owing to surface tension and hydrostatic pressure that balance the weight of the liquid. The shape of the liquid bridge is determined by analytically solving the nonlinear Laplace-Young equation. Parameters that maximize the trapping capacity (defined as the cross-sectional area of the liquid bridge) are then determined. The results show that these parameters can be approximated with simple relationships when the radius of the cylinders is small compared with the capillary length. For such small cylinders, liquid bridges with the largest cross-sectional area occur when the centre-to-centre distance between the cylinders is approximately twice the capillary length. The maximum trapping capacity for a pair of cylinders at a given separation is linearly related to the separation when it is small compared with the capillary length. The meniscus slope angle of the largest liquid bridge produced in this regime is also a linear function of the separation. We additionally derive approximate solutions for the profile of a liquid bridge, using the linearized Laplace-Young equation. These solutions analytically verify the above-mentioned relationships obtained for the maximization of the trapping capacity.

Steady Secondary Flows Generated by Periodic Compression and Expansion of an Ideal Gas in a Pulse Tube

NASA Technical Reports Server (NTRS)

Lee, Jeffrey M.

1999-01-01

This study establishes a consistent set of differential equations for use in describing the steady secondary flows generated by periodic compression and expansion of an ideal gas in pulse tubes. Also considered is heat transfer between the gas and the tube wall of finite thickness. A small-amplitude series expansion solution in the inverse Strouhal number is proposed for the two-dimensional axisymmetric mass, momentum and energy equations. The anelastic approach applies when shock and acoustic energies are small compared with the energy needed to compress and expand the gas. An analytic solution to the ordered series is obtained in the strong temperature limit where the zeroth-order temperature is constant. The solution shows steady velocities increase linearly for small Valensi number and can be of order I for large Valensi number. A conversion of steady work flow to heat flow occurs whenever temperature, velocity or phase angle gradients are present. Steady enthalpy flow is reduced by heat transfer and is scaled by the Prandtl times Valensi numbers. Particle velocities from a smoke-wire experiment were compared with predictions for the basic and orifice pulse tube configurations. The theory accurately predicted the observed steady streaming.

Theoretical predictions of vibration-rotation-tunneling dynamics of the weakly bound trimer (H 2O) 2HCl

NASA Astrophysics Data System (ADS)

Struniewicz, Cezary; Korona, Tatiana; Moszynski, Robert; Milet, Anne

2001-08-01

In this Letter we report a theoretical study of the vibration-rotation-tunneling (VRT) states of the (H 2O) 2HCl trimer. Five degrees of freedom are considered: two angles corresponding to the torsional (flipping) motions of the free, non-hydrogen-bonded, hydrogen atoms in the complex, and three angles describing the overall rotation of the trimer in the space. A two-dimensional potential energy surface is generated ab initio by symmetry-adapted perturbation theory (SAPT). Tunneling splittings, frequencies of the intermolecular vibrations, and vibrational line strengths of spectroscopic transitions are predicted.

2-D to 3-D global/local finite element analysis of cross-ply composite laminates

NASA Technical Reports Server (NTRS)

Thompson, D. Muheim; Griffin, O. Hayden, Jr.

1990-01-01

An example of two-dimensional to three-dimensional global/local finite element analysis of a laminated composite plate with a hole is presented. The 'zoom' technique of global/local analysis is used, where displacements of the global/local interface from the two-dimensional global model are applied to the edges of the three-dimensional local model. Three different hole diameters, one, three, and six inches, are considered in order to compare the effect of hole size on the three-dimensional stress state around the hole. In addition, three different stacking sequences are analyzed for the six inch hole case in order to study the effect of stacking sequence. The existence of a 'critical' hole size, where the interlaminar stresses are maximum, is indicated. Dispersion of plies at the same angle, as opposed to clustering, is found to reduce the magnitude of some interlaminar stress components and increase others.

Ionic depletion at the crystalline Gibbs layer of PEG-capped gold nanoparticle brushes at aqueous surfaces

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

Wang, Wenjie; Zhang, Honghu; Mallapragada, Surya

In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol–capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs 2SO 4) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. In conclusion, by taking advantage of element specificity with the GIXFS method, we find that the cation Cs + concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film comparedmore » with that in the bulk.« less

Obliquely propagating low frequency electromagnetic shock waves in two dimensional quantum magnetoplasmas

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

Masood, W.

2009-04-15

Linear and nonlinear propagation characteristics of low frequency magnetoacoustic waves in quantum magnetoplasmas are studied employing the quantum magnetohydrodynamic model. In this regard, a quantum Kadomtsev-Petviashvili-Burgers (KPB) equation is derived using the small amplitude expansion method. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. Furthermore, the solution of KPB equation is presented using the tangent hyperbolic (tanh) method. The variation in the fast and slow magnetoacoustic shock profiles with the quantum Bohm potential via increasing number density, obliqueness angle {theta}, magnetic field, and the resistivity are also investigated. It is observed that themore » aforementioned plasma parameters significantly modify the propagation characteristics of nonlinear magnetoacoustic shock waves in quantum magnetoplasmas. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.« less

Nanocrystalline copper films are never flat.

PubMed

Zhang, Xiaopu; Han, Jian; Plombon, John J; Sutton, Adrian P; Srolovitz, David J; Boland, John J

2017-07-28

We used scanning tunneling microscopy to study low-angle grain boundaries at the surface of nearly planar copper nanocrystalline (111) films. The presence of grain boundaries and their emergence at the film surface create valleys composed of dissociated edge dislocations and ridges where partial dislocations have recombined. Geometric analysis and simulations indicated that valleys and ridges were created by an out-of-plane grain rotation driven by reduction of grain boundary energy. These results suggest that in general, it is impossible to form flat two-dimensional nanocrystalline films of copper and other metals exhibiting small stacking fault energies and/or large elastic anisotropy, which induce a large anisotropy in the dislocation-line energy. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Ionic depletion at the crystalline Gibbs layer of PEG-capped gold nanoparticle brushes at aqueous surfaces

DOE PAGES

Wang, Wenjie; Zhang, Honghu; Mallapragada, Surya; ...

2017-12-14

In situ surface-sensitive x-ray diffraction and grazing incidence x-ray fluorescence spectroscopy (GIXFS) methods are combined to determine the ionic distributions across the liquid/vapor interfaces of thiolated-polyethylene-glycol–capped gold nanoparticle (PEG-AuNP) solutions. Induced by the addition of salts (i.e., Cs 2SO 4) to PEG-AuNPs solutions, two-dimensional hexagonal lattices of PEG-AuNPs form spontaneously at the aqueous surfaces, as is demonstrated by x-ray reflectivity and grazing incidence small-angle x-ray scattering. In conclusion, by taking advantage of element specificity with the GIXFS method, we find that the cation Cs + concentration at the crystalline film is significantly reduced in parts of the PEG-AuNP film comparedmore » with that in the bulk.« less

A simple three dimensional wide-angle beam propagation method

NASA Astrophysics Data System (ADS)

Ma, Changbao; van Keuren, Edward

2006-05-01

The development of three dimensional (3-D) waveguide structures for chip scale planar lightwave circuits (PLCs) is hampered by the lack of effective 3-D wide-angle (WA) beam propagation methods (BPMs). We present a simple 3-D wide-angle beam propagation method (WA-BPM) using Hoekstra’s scheme along with a new 3-D wave equation splitting method. The applicability, accuracy and effectiveness of our method are demonstrated by applying it to simulations of wide-angle beam propagation and comparing them with analytical solutions.

A simple three dimensional wide-angle beam propagation method.

PubMed

Ma, Changbao; Van Keuren, Edward

2006-05-29

The development of three dimensional (3-D) waveguide structures for chip scale planar lightwave circuits (PLCs) is hampered by the lack of effective 3-D wide-angle (WA) beam propagation methods (BPMs). We present a simple 3-D wide-angle beam propagation method (WA-BPM) using Hoekstra's scheme along with a new 3-D wave equation splitting method. The applicability, accuracy and effectiveness of our method are demonstrated by applying it to simulations of wide-angle beam propagation and comparing them with analytical solutions.

Neutronographic investigations of supramolecular structures on upgraded small-angle spectrometer YuMO

NASA Astrophysics Data System (ADS)

Kuklin, A. I.; Rogachev, A. V.; Soloviov, D. V.; Ivankov, O. I.; Kovalev, Yu S.; Utrobin, P. K.; Kutuzov, S. A.; Soloviev, A. G.; Rulev, M. I.; Gordeliy, V. I.

2017-05-01

Abstract.The work is a review of neutronographic investigations of supramolecular structures on upgraded small-angle spectrometer YuMO. Here, key parameters of small-angle spectrometers are considered. It is shown that two-detector system is the basis of YuMO upgrade. It allows to widen the dynamic q-range twice. In result, the available q-range is widened and dynamic q-range and data collection rate are doubled. The detailed description of YuMO spectrometer is given.The short review of experimental researches made on the spectrometer in the polymers field, biology, material science and physical chemistry is given. The current investigations also have a methodological aspect. It is shown that upgraded spectrometer provides advanced world level of research of supramolecular structures.

Determination of three-dimensional muscle architectures: validation of the DTI-based fiber tractography method by manual digitization

PubMed Central

Schenk, P; Siebert, T; Hiepe, P; Güllmar, D; Reichenbach, J R; Wick, C; Blickhan, R; Böl, M

2013-01-01

In the last decade, diffusion tensor imaging (DTI) has been used increasingly to investigate three-dimensional (3D) muscle architectures. So far there is no study that has proved the validity of this method to determine fascicle lengths and pennation angles within a whole muscle. To verify the DTI method, fascicle lengths of m. soleus as well as their pennation angles have been measured using two different methods. First, the 3D muscle architecture was analyzed in vivo applying the DTI method with subsequent deterministic fiber tractography. In a second step, the muscle architecture of the same muscle was analyzed using a standard manual digitization system (MicroScribe MLX). Comparing both methods, we found differences for the median pennation angles (P < 0.001) but not for the median fascicle lengths (P = 0.216). Despite the statistical results, we conclude that the DTI method is appropriate to determine the global fiber orientation. The difference in median pennation angles determined with both methods is only about 1.2° (median pennation angle of MicroScribe: 9.7°; DTI: 8.5°) and probably has no practical relevance for muscle simulation studies. Determining fascicle lengths requires additional restriction and further development of the DTI method. PMID:23678961

A mathematical method for precisely calculating the radiographic angles of the cup after total hip arthroplasty.

PubMed

Zhao, Jing-Xin; Su, Xiu-Yun; Xiao, Ruo-Xiu; Zhao, Zhe; Zhang, Li-Hai; Zhang, Li-Cheng; Tang, Pei-Fu

2016-11-01

We established a mathematical method to precisely calculate the radiographic anteversion (RA) and radiographic inclination (RI) angles of the acetabular cup based on anterior-posterior (AP) pelvic radiographs after total hip arthroplasty. Using Mathematica software, a mathematical model for an oblique cone was established to simulate how AP pelvic radiographs are obtained and to address the relationship between the two-dimensional and three-dimensional geometry of the opening circle of the cup. In this model, the vertex was the X-ray beam source, and the generatrix was the ellipse in radiographs projected from the opening circle of the acetabular cup. Using this model, we established a series of mathematical formulas to reveal the differences between the true RA and RI cup angles and the measurements results achieved using traditional methods and AP pelvic radiographs and to precisely calculate the RA and RI cup angles based on post-operative AP pelvic radiographs. Statistical analysis indicated that traditional methods should be used with caution if traditional measurements methods are used to calculate the RA and RI cup angles with AP pelvic radiograph. The entire calculation process could be performed by an orthopedic surgeon with mathematical knowledge of basic matrix and vector equations. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Determination of three-dimensional muscle architectures: validation of the DTI-based fiber tractography method by manual digitization.

PubMed

Schenk, P; Siebert, T; Hiepe, P; Güllmar, D; Reichenbach, J R; Wick, C; Blickhan, R; Böl, M

2013-07-01

In the last decade, diffusion tensor imaging (DTI) has been used increasingly to investigate three-dimensional (3D) muscle architectures. So far there is no study that has proved the validity of this method to determine fascicle lengths and pennation angles within a whole muscle. To verify the DTI method, fascicle lengths of m. soleus as well as their pennation angles have been measured using two different methods. First, the 3D muscle architecture was analyzed in vivo applying the DTI method with subsequent deterministic fiber tractography. In a second step, the muscle architecture of the same muscle was analyzed using a standard manual digitization system (MicroScribe MLX). Comparing both methods, we found differences for the median pennation angles (P < 0.001) but not for the median fascicle lengths (P = 0.216). Despite the statistical results, we conclude that the DTI method is appropriate to determine the global fiber orientation. The difference in median pennation angles determined with both methods is only about 1.2° (median pennation angle of MicroScribe: 9.7°; DTI: 8.5°) and probably has no practical relevance for muscle simulation studies. Determining fascicle lengths requires additional restriction and further development of the DTI method. © 2013 Anatomical Society.

Study of Wave-Particle Interactions for Whistler Mode Waves at Oblique Angles by Utilizing the Gyroaveraging Method

NASA Astrophysics Data System (ADS)

Hsieh, Yi-Kai; Omura, Yoshiharu

2017-10-01

We investigate the properties of whistler mode wave-particle interactions at oblique wave normal angles to the background magnetic field. We find that electromagnetic energy of waves at frequencies below half the electron cyclotron frequency can flow nearly parallel to the ambient magnetic field. We thereby confirm that the gyroaveraging method, which averages the cyclotron motion to the gyrocenter and reduces the simulation from two-dimensional to one-dimensional, is valid for oblique wave-particle interaction. Multiple resonances appear for oblique propagation but not for parallel propagation. We calculate the possible range of resonances with the first-order resonance condition as a function of electron kinetic energy and equatorial pitch angle. To reveal the physical process and the efficiency of electron acceleration by multiple resonances, we assume a simple uniform wave model with constant amplitude and frequency in space and time. We perform test particle simulations with electrons starting at specific equatorial pitch angles and kinetic energies. The simulation results show that multiple resonances contribute to acceleration and pitch angle scattering of energetic electrons. Especially, we find that electrons with energies of a few hundred keV can be accelerated efficiently to a few MeV through the n = 0 Landau resonance.

A model-based approach to predict muscle synergies using optimization: application to feedback control

PubMed Central

Sharif Razavian, Reza; Mehrabi, Naser; McPhee, John

2015-01-01

This paper presents a new model-based method to define muscle synergies. Unlike the conventional factorization approach, which extracts synergies from electromyographic data, the proposed method employs a biomechanical model and formally defines the synergies as the solution of an optimal control problem. As a result, the number of required synergies is directly related to the dimensions of the operational space. The estimated synergies are posture-dependent, which correlate well with the results of standard factorization methods. Two examples are used to showcase this method: a two-dimensional forearm model, and a three-dimensional driver arm model. It has been shown here that the synergies need to be task-specific (i.e., they are defined for the specific operational spaces: the elbow angle and the steering wheel angle in the two systems). This functional definition of synergies results in a low-dimensional control space, in which every force in the operational space is accurately created by a unique combination of synergies. As such, there is no need for extra criteria (e.g., minimizing effort) in the process of motion control. This approach is motivated by the need for fast and bio-plausible feedback control of musculoskeletal systems, and can have important implications in engineering, motor control, and biomechanics. PMID:26500530

C-arm technique using distance driven method for nephrolithiasis and kidney stones detection

NASA Astrophysics Data System (ADS)

Malalla, Nuhad; Sun, Pengfei; Chen, Ying; Lipkin, Michael E.; Preminger, Glenn M.; Qin, Jun

2016-04-01

Distance driven represents a state of art method that used for reconstruction for x-ray techniques. C-arm tomography is an x-ray imaging technique that provides three dimensional information of the object by moving the C-shaped gantry around the patient. With limited view angle, C-arm system was investigated to generate volumetric data of the object with low radiation dosage and examination time. This paper is a new simulation study with two reconstruction methods based on distance driven including: simultaneous algebraic reconstruction technique (SART) and Maximum Likelihood expectation maximization (MLEM). Distance driven is an efficient method that has low computation cost and free artifacts compared with other methods such as ray driven and pixel driven methods. Projection images of spherical objects were simulated with a virtual C-arm system with a total view angle of 40 degrees. Results show the ability of limited angle C-arm technique to generate three dimensional images with distance driven reconstruction.

SNR-optimized phase-sensitive dual-acquisition turbo spin echo imaging: a fast alternative to FLAIR.

PubMed

Lee, Hyunyeol; Park, Jaeseok

2013-07-01

Phase-sensitive dual-acquisition single-slab three-dimensional turbo spin echo imaging was recently introduced, producing high-resolution isotropic cerebrospinal fluid attenuated brain images without long inversion recovery preparation. Despite the advantages, the weighted-averaging-based technique suffers from noise amplification resulting from different levels of cerebrospinal fluid signal modulations over the two acquisitions. The purpose of this work is to develop a signal-to-noise ratio-optimized version of the phase-sensitive dual-acquisition single-slab three-dimensional turbo spin echo. Variable refocusing flip angles in the first acquisition are calculated using a three-step prescribed signal evolution while those in the second acquisition are calculated using a two-step pseudo-steady state signal transition with a high flip-angle pseudo-steady state at a later portion of the echo train, balancing the levels of cerebrospinal fluid signals in both the acquisitions. Low spatial frequency signals are sampled during the high flip-angle pseudo-steady state to further suppress noise. Numerical simulations of the Bloch equations were performed to evaluate signal evolutions of brain tissues along the echo train and optimize imaging parameters. In vivo studies demonstrate that compared with conventional phase-sensitive dual-acquisition single-slab three-dimensional turbo spin echo, the proposed optimization yields 74% increase in apparent signal-to-noise ratio for gray matter and 32% decrease in imaging time. The proposed method can be a potential alternative to conventional fluid-attenuated imaging. Copyright © 2012 Wiley Periodicals, Inc.

High-density Two-Dimensional Small Polaron Gas in a Delta-Doped Mott Insulator

PubMed Central

Ouellette, Daniel G.; Moetakef, Pouya; Cain, Tyler A.; Zhang, Jack Y.; Stemmer, Susanne; Emin, David; Allen, S. James

2013-01-01

Heterointerfaces in complex oxide systems open new arenas in which to test models of strongly correlated material, explore the role of dimensionality in metal-insulator-transitions (MITs) and small polaron formation. Close to the quantum critical point Mott MITs depend on band filling controlled by random disordered substitutional doping. Delta-doped Mott insulators are potentially free of random disorder and introduce a new arena in which to explore the effect of electron correlations and dimensionality. Epitaxial films of the prototypical Mott insulator GdTiO3 are delta-doped by substituting a single (GdO)+1 plane with a monolayer of charge neutral SrO to produce a two-dimensional system with high planar doping density. Unlike metallic SrTiO3 quantum wells in GdTiO3 the single SrO delta-doped layer exhibits thermally activated DC and optical conductivity that agree in a quantitative manner with predictions of small polaron transport but with an extremely high two-dimensional density of polarons, ~7 × 1014 cm−2. PMID:24257578

Angles between orthogonal spd bond orbitals with maximum strength.

PubMed

Pauling, L

1976-05-01

An equation is derived for values of bond angles for two equivalent best spd hybrid bond orbitals with given amounts of s, p, and d character, and is applied in the discussion of structures of transargononic compounds, including the xenon and halogen fluorides. Bond orbitals with a rather small amount of d character tend to lie at angles 90 degrees and 180 degrees , and those with a larger amount, at somewhat smaller angles.

Viscous/potential flow about multi-element two-dimensional and infinite-span swept wings: Theory and experiment

NASA Technical Reports Server (NTRS)

Olson, L. E.; Dvorak, F. A.

1975-01-01

The viscous subsonic flow past two-dimensional and infinite-span swept multi-component airfoils is studied theoretically and experimentally. The computerized analysis is based on iteratively coupled boundary layer and potential flow analysis. The method, which is restricted to flows with only slight separation, gives surface pressure distribution, chordwise and spanwise boundary layer characteristics, lift, drag, and pitching moment for airfoil configurations with up to four elements. Merging confluent boundary layers are treated. Theoretical predictions are compared with an exact theoretical potential flow solution and with experimental measures made in the Ames 40- by 80-Foot Wind Tunnel for both two-dimensional and infinite-span swept wing configurations. Section lift characteristics are accurately predicted for zero and moderate sweep angles where flow separation effects are negligible.

Correlation of laser velocimeter measurements over a wing with results of two prediction techniques. [in the Langley V/STOL tunnel

NASA Technical Reports Server (NTRS)

Hoad, D. R.; Meyers, J. F.; Young, W. H., Jr.; Hepner, T. P.

1978-01-01

The flow field at the center line of an unswept wing with an aspect ratio of eight was determined using a two dimensional viscous flow prediction technique for the flow field calculation, and a three dimensional potential flow panel method to evaluate the degree of two dimensionality achieved at the wing center line. The analysis was made to provide an acceptable reference for comparison with velocity measurements obtained from a fringe type laser velocimeter optics systems operating in the backscatter mode in the Langley V/STOL tunnel. Good agreement between laser velocimeter measurements and theoretical results indicate that both methods provide a true representation of the velocity field about the wing at angles of attack of 0.6 and 4.75 deg.

Two-dimensional radiative transfer. I - Planar geometry. [in stellar atmospheres

NASA Technical Reports Server (NTRS)

Mihalas, D.; Auer, L. H.; Mihalas, B. R.

1978-01-01

Differential-equation methods for solving the transfer equation in two-dimensional planar geometries are developed. One method, which uses a Hermitian integration formula on ray segments through grid points, proves to be extremely well suited to velocity-dependent problems. An efficient elimination scheme is developed for which the computing time scales linearly with the number of angles and frequencies; problems with large velocity amplitudes can thus be treated accurately. A very accurate and efficient method for performing a formal solution is also presented. A discussion is given of several examples of periodic media and free-standing slabs, both in static cases and with velocity fields. For the free-standing slabs, two-dimensional transport effects are significant near boundaries, but no important effects were found in any of the periodic cases studied.

NON-INVASIVE DETERMINATION OF THE LOCATION AND DISTRBUTION OF FREE-PHASE DENSE NONAQUEOUS PHASE LIQUIDS (DNAPL) BY SEISMIC REFLECTION TECHNIQUES

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

Michael G. Waddell; William J. Domoracki; Jerome Eyer

2003-01-01

The Earth Sciences and Resources Institute, University of South Carolina is conducting a proof of concept study to determine the location and distribution of subsurface DNAPL carbon tetrachloride (CCl{sub 4}) contamination at the 216-Z-9 crib, 200 West area, DOE Hanford Site, Washington by use of two-dimensional high-resolution seismic reflection surveys and borehole geophysical data. The study makes use of recent advances in seismic reflection amplitude versus offset (AVO) technology to directly detect the presence of subsurface DNAPL. The techniques proposed are noninvasive means of site characterization and direct free-phase DNAPL detection. This final report covers the results of Tasks 1,more » 2, and 3. Task (1) contains site evaluation and seismic modeling studies. The site evaluation consists of identifying and collecting preexisting geological and geophysical information regarding subsurface structure and the presence and quantity of DNAPL. The seismic modeling studies were undertaken to determine the likelihood that an AVO response exists and its probable manifestation. Task (2) is the design and acquisition of 2-D seismic reflection data to image areas of probable high concentration of DNAPL. Task (3) is the processing and interpretation of the 2-D data. During the commission of these tasks four seismic reflection profiles were collected. Subsurface velocity information was obtained by vertical seismic profile surveys in three wells. The interpretation of these data is in two parts. Part one is the construction and interpretation of structural contour maps of the contact between the Hanford Fine unit and the underlying Plio/Pleistocene unit and of the contact between the Plio/Pleistocene unit and the underlying caliche layer. These two contacts were determined to be the most likely surfaces to contain the highest concentration CCl{sub 4}. Part two of the interpretation uses the results of the AVO modeling to locate any seismic amplitude anomalies that might be associated with the presence of high concentrations of CCl{sub 4}. Based on the modeling results three different methods of AVO analysis were preformed on the seismic data: enhanced amplitude stacks, offset range limited stacks, and gradient stacks. Seismic models indicate that the reflection from the contact between the Hanford Fine and the Plio/Pleistocene should exhibit amplitude variations where there are high concentrations of CCl{sub 4}. A series of different scenarios were modeled. The first scenario is the Hanford Fine pores are 100% saturated with CCl{sub 4} and the underlying Plio/Pleistocene pores are saturated with air. In this scenario the reflection coefficients are slightly negative at the small angles of incidence and become increasing more negative at the larger angles of incidence (dim-out). The second scenario is the Hanford Fine pores are saturated with air and Plio/Pleistocene pores are saturated with CCl{sub 4}. In this scenario the reflection coefficients are slightly positive at the small angles of incidence and become negative at the large angles of incidence (polarity reversal). Finally the third scenario is both the Hanford Fine and the Plio/Pleistocene pores are saturated CCl{sub 4}. In this scenario the reflection coefficients at the small angles of incidence are slightly positive, but much less than background response, and with increasing angle of incidence the reflection coefficients become slightly more positive. On the field data areas where extraction wells have high concentrations of CCl{sub 4} a corresponding dim-out and/or a polarity reversal is noted.« less

Adjoint Methods for Adjusting Three-Dimensional Atmosphere and Surface Properties to Fit Multi-Angle Multi-Pixel Polarimetric Measurements

NASA Technical Reports Server (NTRS)

Martin, William G.; Cairns, Brian; Bal, Guillaume

2014-01-01

This paper derives an efficient procedure for using the three-dimensional (3D) vector radiative transfer equation (VRTE) to adjust atmosphere and surface properties and improve their fit with multi-angle/multi-pixel radiometric and polarimetric measurements of scattered sunlight. The proposed adjoint method uses the 3D VRTE to compute the measurement misfit function and the adjoint 3D VRTE to compute its gradient with respect to all unknown parameters. In the remote sensing problems of interest, the scalar-valued misfit function quantifies agreement with data as a function of atmosphere and surface properties, and its gradient guides the search through this parameter space. Remote sensing of the atmosphere and surface in a three-dimensional region may require thousands of unknown parameters and millions of data points. Many approaches would require calls to the 3D VRTE solver in proportion to the number of unknown parameters or measurements. To avoid this issue of scale, we focus on computing the gradient of the misfit function as an alternative to the Jacobian of the measurement operator. The resulting adjoint method provides a way to adjust 3D atmosphere and surface properties with only two calls to the 3D VRTE solver for each spectral channel, regardless of the number of retrieval parameters, measurement view angles or pixels. This gives a procedure for adjusting atmosphere and surface parameters that will scale to the large problems of 3D remote sensing. For certain types of multi-angle/multi-pixel polarimetric measurements, this encourages the development of a new class of three-dimensional retrieval algorithms with more flexible parametrizations of spatial heterogeneity, less reliance on data screening procedures, and improved coverage in terms of the resolved physical processes in the Earth?s atmosphere.

Single-particle cryo-EM using alignment by classification (ABC): the structure of Lumbricus terrestris haemoglobin.

PubMed

Afanasyev, Pavel; Seer-Linnemayr, Charlotte; Ravelli, Raimond B G; Matadeen, Rishi; De Carlo, Sacha; Alewijnse, Bart; Portugal, Rodrigo V; Pannu, Navraj S; Schatz, Michael; van Heel, Marin

2017-09-01

Single-particle cryogenic electron microscopy (cryo-EM) can now yield near-atomic resolution structures of biological complexes. However, the reference-based alignment algorithms commonly used in cryo-EM suffer from reference bias, limiting their applicability (also known as the 'Einstein from random noise' problem). Low-dose cryo-EM therefore requires robust and objective approaches to reveal the structural information contained in the extremely noisy data, especially when dealing with small structures. A reference-free pipeline is presented for obtaining near-atomic resolution three-dimensional reconstructions from heterogeneous ('four-dimensional') cryo-EM data sets. The methodologies integrated in this pipeline include a posteriori camera correction, movie-based full-data-set contrast transfer function determination, movie-alignment algorithms, (Fourier-space) multivariate statistical data compression and unsupervised classification, 'random-startup' three-dimensional reconstructions, four-dimensional structural refinements and Fourier shell correlation criteria for evaluating anisotropic resolution. The procedures exclusively use information emerging from the data set itself, without external 'starting models'. Euler-angle assignments are performed by angular reconstitution rather than by the inherently slower projection-matching approaches. The comprehensive 'ABC-4D' pipeline is based on the two-dimensional reference-free 'alignment by classification' (ABC) approach, where similar images in similar orientations are grouped by unsupervised classification. Some fundamental differences between X-ray crystallography versus single-particle cryo-EM data collection and data processing are discussed. The structure of the giant haemoglobin from Lumbricus terrestris at a global resolution of ∼3.8 Å is presented as an example of the use of the ABC-4D procedure.

Refining glass structure in two dimensions

NASA Astrophysics Data System (ADS)

Sadjadi, Mahdi; Bhattarai, Bishal; Drabold, D. A.; Thorpe, M. F.; Wilson, Mark

2017-11-01

Recently determined atomistic scale structures of near-two dimensional bilayers of vitreous silica (using scanning probe and electron microscopy) allow us to refine the experimentally determined coordinates to incorporate the known local chemistry more precisely. Further refinement is achieved by using classical potentials of varying complexity: one using harmonic potentials and the second employing an electrostatic description incorporating polarization effects. These are benchmarked against density functional calculations. Our main findings are that (a) there is a symmetry plane between the two disordered layers, a nice example of an emergent phenomena, (b) the layers are slightly tilted so that the Si-O-Si angle between the two layers is not 180∘ as originally thought but rather 175 ±2∘ , and (c) while interior areas that are not completely imagined can be reliably reconstructed, surface areas are more problematic. It is shown that small crystallites that appear are just as expected statistically in a continuous random network. This provides a good example of the value that can be added to disordered structures imaged at the atomic level by implementing computer refinement.

Mechanical properties of water-assembled graphene oxide Langmuir monolayers: Guiding controlled transfer

DOE PAGES

Harrison, Katharine L.; Biedermann, Laura B.; Zavadil, Kevin R.

2015-08-24

Liquid-phase transfer of graphene oxide (GO) and reduced graphene oxide (RGO) monolayers is investigated from the perspective of the mechanical properties of these films. Monolayers are assembled in a Langmuir–Blodgett trough, and oscillatory barrier measurements are used to characterize the resulting compressive and shear moduli as a function of surface pressure. GO monolayers are shown to develop a significant shear modulus (10–25 mN/m) at relevant surface pressures while RGO monolayers do not. The existence of a shear modulus indicates that GO is acting as a two-dimensional solid driven by strong interaction between the individual GO sheets. The absence of suchmore » behavior in RGO is attributed to the decrease in oxygen moieties on the sheet basal plane, permitting RGO sheets to slide across one another with minimum energy dissipation. Knowledge of this two-dimensional solid behavior is exploited to successfully transfer large-area, continuous GO films to hydrophobic Au substrates. The key to successful transfer is the use of shallow-angle dipping designed to minimize tensile stress present during the insertion or extraction of the substrate. A shallow dip angle on hydrophobic Au does not impart a beneficial effect for RGO monolayers, as these monolayers do not behave as two-dimensional solids and do not remain coherent during the transfer process. As a result, we hypothesize that this observed correlation between monolayer mechanical properties and continuous film transfer success is more universally applicable across substrate hydrophobicities and could be exploited to control the transfer of films composed of two-dimensional materials.« less

Left ventricular mechanics in isolated mild mitral stenosis: a three dimensional speckle tracking study.

PubMed

Poyraz, Esra; Öz, Tuğba Kemaloğlu; Zeren, Gönül; Güvenç, Tolga Sinan; Dönmez, Cevdet; Can, Fatma; Güvenç, Rengin Çetin; Dayı, Şennur Ünal

2017-09-01

In a fraction of patients with mild mitral stenosis, left ventricular systolic function deteriorates despite the lack of hemodynamic load imposed by the dysfunctioning valve. Neither the predisposing factors nor the earlier changes in left ventricular contractility were understood adequately. In the present study we aimed to evaluate left ventricular mechanics using three-dimensional (3D) speckle tracking echocardiography. A total of 31 patients with mild rheumatic mitral stenosis and 27 healthy controls were enrolled to the study. All subjects included to the study underwent echocardiographic examination to collect data for two- and three-dimensional speckle-tracking based stain, twist angle and torsion measurements. Data was analyzed offline with a echocardiographic data analysis software. Patients with rheumatic mild MS had lower global longitudinal (p < 0.001) circumferential (p = 0.02) and radial (p < 0.01) strain compared to controls, despite ejection fraction was similar for both groups [(p = 0.45) for three dimensional and (p = 0.37) for two dimensional measurement]. While the twist angle was not significantly different between groups (p = 0.11), left ventricular torsion was significantly higher in mitral stenosis group (p = 0.03). All strain values had a weak but significant positive correlation with mitral valve area measured with planimetry. Subclinical left ventricular systolic dysfunction develops at an early stage in rheumatic mitral stenosis. Further work is needed to elucidate patients at risk for developing overt systolic dysfunction.

Effect of hole geometry and Electric-Discharge Machining (EDM) on airflow rates through small diameter holes in turbine blade material

NASA Technical Reports Server (NTRS)

Hippensteele, S. A.; Cochran, R. P.

1980-01-01

The effects of two design parameters, electrode diameter and hole angle, and two machine parameters, electrode current and current-on time, on air flow rates through small-diameter (0.257 to 0.462 mm) electric-discharge-machined holes were measured. The holes were machined individually in rows of 14 each through 1.6 mm thick IN-100 strips. The data showed linear increase in air flow rate with increases in electrode cross sectional area and current-on time and little change with changes in hole angle and electrode current. The average flow-rate deviation (from the mean flow rate for a given row) decreased linearly with electrode diameter and increased with hole angle. Burn time and finished hole diameter were also measured.

The Reconstruction of Three-Dimensional Morphological and Electrical Paraneters from Two-Dimensional Sections of Neurones

NASA Astrophysics Data System (ADS)

Brawn, A. D.; Wheal, H. V.

1986-07-01

A system is described which can be used to create a three-dimensional model of a neurone from the central nervous system. This model can then be used to obtain quantitative data on the physical and electrical pro, perties of the neurone. Living neurones are either raised in culture, or taken from in vitro preparations of brain tissue and optically sectioned. These two-dimensional sections are digitised, and input to a 68008-based microcomputer. The system reconstructs the three-dimensional structure of the neurone, both geanetrically and electrically. The user can a) View the structure fran any point at any angle b) "Move through" the structure along any given vector c) Nave through" the structure following a neurone process d) Fire the neurone at any point, and "watch" the action potentials propagate e) Vary the parameters of the electrical model of a process element. The system is targeted to a research programme on epilepsy, which makes frequent use of both geometric and electrical neurone modelling. Current techniques which may involve crude histology and two-dimensional drawings have considerable short camings.

Asymptotic theory of two-dimensional trailing-edge flows

NASA Technical Reports Server (NTRS)

Melnik, R. E.; Chow, R.

1975-01-01

Problems of laminar and turbulent viscous interaction near trailing edges of streamlined bodies are considered. Asymptotic expansions of the Navier-Stokes equations in the limit of large Reynolds numbers are used to describe the local solution near the trailing edge of cusped or nearly cusped airfoils at small angles of attack in compressible flow. A complicated inverse iterative procedure, involving finite-difference solutions of the triple-deck equations coupled with asymptotic solutions of the boundary values, is used to accurately solve the viscous interaction problem. Results are given for the correction to the boundary-layer solution for drag of a finite flat plate at zero angle of attack and for the viscous correction to the lift of an airfoil at incidence. A rational asymptotic theory is developed for treating turbulent interactions near trailing edges and is shown to lead to a multilayer structure of turbulent boundary layers. The flow over most of the boundary layer is described by a Lighthill model of inviscid rotational flow. The main features of the model are discussed and a sample solution for the skin friction is obtained and compared with the data of Schubauer and Klebanoff for a turbulent flow in a moderately large adverse pressure gradient.

Three-dimensional reconstruction of vessels with stenoses and aneurysms from dual biplane angiograms

NASA Astrophysics Data System (ADS)

Fessler, Jeffrey A.; Macovski, Albert

1989-05-01

Parametric model-based approaches to 3-D reconstruction of vessels overcome the inherent problem of underdeterminancy in reconstruction from limited views by incorporating a priori knowledge about the structure of vessels and about the measurement statistics. In this paper, we describe two extensions to the parametric approach. First, we consider the problem of reconstruction from a pair of bi-plane angiograms that are acquired at different projection angles. Since bi-plane angiography systems are widely available, this is a practical measurement geometry. The patient may move between acquisitions, so we have extended our model to allow for object translation between the first and second pair of projections. Second, we describe how to accurately estimate the dimensions of a aneurysm from the dual-biplane angiogram. We applied the new algorithm to four synthetic angiograms (projection angles 0°, 20°, 90°, and 110°) of a vessel with a small aneurysm and an eccentric stenosis. The angiograms were corrupted by additive noise and background structure. Except near the top and bottom of the aneurysm, the estimated cross sections of the aneurysm and stenosis agree very well with the true cross sections.

Research on self-calibration biaxial autocollimator based on ZYNQ

NASA Astrophysics Data System (ADS)

Guo, Pan; Liu, Bingguo; Liu, Guodong; Zhong, Yao; Lu, Binghui

2018-01-01

Autocollimators are mainly based on computers or the electronic devices that can be connected to the internet, and its precision, measurement range and resolution are all defective, and external displays are needed to display images in real time. What's more, there is no real-time calibration for autocollimator in the market. In this paper, we propose a biaxial autocollimator based on the ZYNQ embedded platform to solve the above problems. Firstly, the traditional optical system is improved and a light path is added for real-time calibration. Then, in order to improve measurement speed, the embedded platform based on ZYNQ that combines Linux operating system with autocollimator is designed. In this part, image acquisition, image processing, image display and the man-machine interaction interface based on Qt are achieved. Finally, the system realizes two-dimensional small angle measurement. Experimental results showed that the proposed method can improve the angle measurement accuracy. The standard deviation of the close distance (1.5m) is 0.15" in horizontal direction of image and 0.24"in vertical direction, the repeatability of measurement of the long distance (10m) is improved by 0.12 in horizontal direction of image and 0.3 in vertical direction.

Probing Nucleation and Growth Behavior of Twisted Kebabs from Shish Scaffold in Sheared Polyethylene Melts by in situ X-ray Studies

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

Keum,J.; Burger, C.; Zuo, F.

2007-01-01

By utilizing synchrotron rheo-WAXD (wide-angle X-ray diffraction) and rheo-SAXS (small-angle X-ray scattering) techniques, the nucleation and growth behavior of twisted kebabs from the shear-induced shish scaffold in entangled high-density polyethylene (HDPE) melts were investigated. The evolution of the (110) reflection intensity in WAXD at the early stages of crystallization could be described by a simplified Avrami equation, while the corresponding long period of kebabs determined by SAXS was found to decrease with time. The combined SAXS and WAXD results indicate that the kebab growth in sheared HDPE melts consists of two-dimensional geometry with thermal (sporadic) nucleation. The WAXD data clearlymore » exhibited the transformations of (110) reflection from equatorial 2-arc to off-axis 4-arc and of (200) reflection from off-axis 4-arc to meridional 2-arc, which can be explained by the rotation of crystallographic a-axis around the b-axis during twisted kebab growth. This observation is also consistent with the orientation mode changes from 'Keller/Machin II' to 'intermediate' and then to 'Keller/Machin I'.« less

Generation of Rising-tone Chorus in a Two-dimensional Mirror Field by Using the General Curvilinear PIC Code

NASA Astrophysics Data System (ADS)

Ke, Y.; Gao, X.; Lu, Q.; Wang, X.; Wang, S.

2017-12-01

Recently, the generation of rising-tone chorus has been implemented with one-dimensional (1-D) particle-in-cell (PIC) simulations in an inhomogeneous background magnetic field, where both the propagation of waves and motion of electrons are simply forced to be parallel to the background magnetic field. We have developed a two-dimensional(2-D) general curvilinear PIC simulation code, and successfully reproduced rising-tone chorus waves excited from an anisotropic electron distribution in a 2-D mirror field. Our simulation results show that whistler waves are mainly generated around the magnetic equator, and continuously gain growth during their propagation toward higher-latitude regions. The rising-tone chorus waves are formed off the magnetic equator, which propagate quasi-parallel to the background magnetic field with the finite wave normal angle. Due to the propagating effect, the wave normal angle of chorus waves is increasing during their propagation toward higher-latitude regions along an enough curved field line. The chirping rate of chorus waves are found to be larger along a field line more close to the middle field line in the mirror field.

Generation of rising-tone chorus in a two-dimensional mirror field by using the general curvilinear PIC code

NASA Astrophysics Data System (ADS)

Ke, Yangguang; Gao, Xinliang; Lu, Quanming; Wang, Xueyi; Wang, Shui

2017-08-01

Recently, the generation of rising-tone chorus has been implemented with one-dimensional (1-D) particle-in-cell (PIC) simulations in an inhomogeneous background magnetic field, where both the propagation of waves and motion of electrons are simply forced to be parallel to the background magnetic field. In this paper, we have developed a two-dimensional (2-D) general curvilinear PIC simulation code and successfully reproduced rising-tone chorus waves excited from an anisotropic electron distribution in a 2-D mirror field. Our simulation results show that whistler waves are mainly generated around the magnetic equator and continuously gain growth during their propagation toward higher-latitude regions. The rising-tone chorus waves are observed off the magnetic equator, which propagate quasi-parallel to the background magnetic field with the wave normal angle smaller than 25°. Due to the propagating effect, the wave normal angle of chorus waves is increasing during their propagation toward higher-latitude regions along an enough curved field line. The chirping rate of chorus waves is found to be larger along a field line with a smaller curvature.

Two-dimensional evolution equation of finite-amplitude internal gravity waves in a uniformly stratified fluid

PubMed

Kataoka; Tsutahara; Akuzawa

2000-02-14

We derive a fully nonlinear evolution equation that can describe the two-dimensional motion of finite-amplitude long internal waves in a uniformly stratified three-dimensional fluid of finite depth. The derived equation is the two-dimensional counterpart of the evolution equation obtained by Grimshaw and Yi [J. Fluid Mech. 229, 603 (1991)]. In the small-amplitude limit, our equation is reduced to the celebrated Kadomtsev-Petviashvili equation.

Build Angle: Does It Influence the Accuracy of 3D-Printed Dental Restorations Using Digital Light-Processing Technology?

PubMed

Osman, Reham B; Alharbi, Nawal; Wismeijer, Daniel

The aim of this study was to evaluate the effect of the build orientation/build angle on the dimensional accuracy of full-coverage dental restorations manufactured using digital light-processing technology (DLP-AM). A full dental crown was digitally designed and 3D-printed using DLP-AM. Nine build angles were used: 90, 120, 135, 150, 180, 210, 225, 240, and 270 degrees. The specimens were digitally scanned using a high-resolution optical surface scanner (IScan D104i, Imetric). Dimensional accuracy was evaluated using the digital subtraction technique. The 3D digital files of the scanned printed crowns (test model) were exported in standard tessellation language (STL) format and superimposed on the STL file of the designed crown [reference model] using Geomagic Studio 2014 (3D Systems). The root mean square estimate (RMSE) values were evaluated, and the deviation patterns on the color maps were further assessed. The build angle influenced the dimensional accuracy of 3D-printed restorations. The lowest RMSE was recorded for the 135-degree and 210-degree build angles. However, the overall deviation pattern on the color map was more favorable with the 135-degree build angle in contrast with the 210-degree build angle where the deviation was observed around the critical marginal area. Within the limitations of this study, the recommended build angle using the current DLP system was 135 degrees. Among the selected build angles, it offers the highest dimensional accuracy and the most favorable deviation pattern. It also offers a self-supporting crown geometry throughout the building process.

Self-Assembly of Hierarchical DNA Nanotube Architectures with Well-Defined Geometries.

PubMed

Jorgenson, Tyler D; Mohammed, Abdul M; Agrawal, Deepak K; Schulman, Rebecca

2017-02-28

An essential motif for the assembly of biological materials such as actin at the scale of hundreds of nanometers and beyond is a network of one-dimensional fibers with well-defined geometry. Here, we demonstrate the programmed organization of DNA filaments into micron-scale architectures where component filaments are oriented at preprogrammed angles. We assemble L-, T-, and Y-shaped DNA origami junctions that nucleate two or three micron length DNA nanotubes at high yields. The angles between the nanotubes mirror the angles between the templates on the junctions, demonstrating that nanoscale structures can control precisely how micron-scale architectures form. The ability to precisely program filament orientation could allow the assembly of complex filament architectures in two and three dimensions, including circuit structures, bundles, and extended materials.

Assessment of scoliosis by direct measurement of the curvature of the spine

NASA Astrophysics Data System (ADS)

Dougherty, Geoff; Johnson, Michael J.

2009-02-01

We present two novel metrics for assessing scoliosis, in which the geometric centers of all the affected vertebrae in an antero-posterior (A-P) radiographic image are used. This is in contradistinction to the existing methods of using selected vertebrae, and determining either their endplates or the intersections of their diagonals, to define a scoliotic angle. Our first metric delivers a scoliotic angle, comparable to the Cobb and Ferguson angles. It measures the sum of the angles between the centers of the affected vertebrae, and avoids the need for an observer to decide on the extent of component curvatures. Our second metric calculates the normalized root-mean-square curvature of the smoothest path comprising piece-wise polynomial splines fitted to the geometric centers of the vertebrae. The smoothest path is useful in modeling the spinal curvature. Our metrics were compared to existing methods using radiographs from a group of twenty subjects with spinal curvatures of varying severity. Their values were strongly correlated with those of the scoliotic angles (r = 0.850 - 0.886), indicating that they are valid surrogates for measuring the severity of scoliosis. Our direct use of positional data removes the vagaries of determining variably shaped endplates, and circumvented the significant interand intra-observer errors of the Cobb and Ferguson methods. Although we applied our metrics to two-dimensional (2- D) data in this paper, they are equally applicable to three-dimensional (3-D) data. We anticipate that they will prove to be the basis for a reliable 3-D measurement and classification system.

Automated pathologies detection in retina digital images based on complex continuous wavelet transform phase angles.

PubMed

Lahmiri, Salim; Gargour, Christian S; Gabrea, Marcel

2014-10-01

An automated diagnosis system that uses complex continuous wavelet transform (CWT) to process retina digital images and support vector machines (SVMs) for classification purposes is presented. In particular, each retina image is transformed into two one-dimensional signals by concatenating image rows and columns separately. The mathematical norm of phase angles found in each one-dimensional signal at each level of CWT decomposition are relied on to characterise the texture of normal images against abnormal images affected by exudates, drusen and microaneurysms. The leave-one-out cross-validation method was adopted to conduct experiments and the results from the SVM show that the proposed approach gives better results than those obtained by other methods based on the correct classification rate, sensitivity and specificity.

Measurement of tree canopy architecture

NASA Technical Reports Server (NTRS)

Martens, S. N.; Ustin, S. L.; Norman, J. M.

1991-01-01

The lack of accurate extensive geometric data on tree canopies has retarded development and validation of radiative transfer models. A stratified sampling method was devised to measure the three-dimensional geometry of 16 walnut trees which had received irrigation treatments of either 100 or 33 per cent of evapotranspirational (ET) demand for the previous two years. Graphic reconstructions of the three-dimensional geometry were verified by 58 independent measurements. The distributions of stem- and leaf-size classes, lengths, and angle classes were determined and used to calculate leaf area index (LAI), stem area, and biomass. Reduced irrigation trees have lower biomass of stems, leaves and fruit, lower LAI, steeper leaf angles and altered biomass allocation to large stems. These data can be used in ecological models that link canopy processes with remotely sensed measurements.

Recent advances in electron tomography: TEM and HAADF-STEM tomography for materials science and semiconductor applications.

PubMed

Kübel, Christian; Voigt, Andreas; Schoenmakers, Remco; Otten, Max; Su, David; Lee, Tan-Chen; Carlsson, Anna; Bradley, John

2005-10-01

Electron tomography is a well-established technique for three-dimensional structure determination of (almost) amorphous specimens in life sciences applications. With the recent advances in nanotechnology and the semiconductor industry, there is also an increasing need for high-resolution three-dimensional (3D) structural information in physical sciences. In this article, we evaluate the capabilities and limitations of transmission electron microscopy (TEM) and high-angle-annular-dark-field scanning transmission electron microscopy (HAADF-STEM) tomography for the 3D structural characterization of partially crystalline to highly crystalline materials. Our analysis of catalysts, a hydrogen storage material, and different semiconductor devices shows that features with a diameter as small as 1-2 nm can be resolved in three dimensions by electron tomography. For partially crystalline materials with small single crystalline domains, bright-field TEM tomography provides reliable 3D structural information. HAADF-STEM tomography is more versatile and can also be used for high-resolution 3D imaging of highly crystalline materials such as semiconductor devices.

A Full-Envelope Air Data Calibration and Three-Dimensional Wind Estimation Method Using Global Output-Error Optimization and Flight-Test Techniques

NASA Technical Reports Server (NTRS)

Taylor, Brian R.

2012-01-01

A novel, efficient air data calibration method is proposed for aircraft with limited envelopes. This method uses output-error optimization on three-dimensional inertial velocities to estimate calibration and wind parameters. Calibration parameters are based on assumed calibration models for static pressure, angle of attack, and flank angle. Estimated wind parameters are the north, east, and down components. The only assumptions needed for this method are that the inertial velocities and Euler angles are accurate, the calibration models are correct, and that the steady-state component of wind is constant throughout the maneuver. A two-minute maneuver was designed to excite the aircraft over the range of air data calibration parameters and de-correlate the angle-of-attack bias from the vertical component of wind. Simulation of the X-48B (The Boeing Company, Chicago, Illinois) aircraft was used to validate the method, ultimately using data derived from wind-tunnel testing to simulate the un-calibrated air data measurements. Results from the simulation were accurate and robust to turbulence levels comparable to those observed in flight. Future experiments are planned to evaluate the proposed air data calibration in a flight environment.

Calculation Of Correction Angles Of 3-Dimensional Vertebral Rotations Based On Bi-Plane X-Ray Photogrammetry

NASA Astrophysics Data System (ADS)

Tamaki, Tamotsu; Umezaki, Eisaku; Yamagata, Masatsune; Inoue, Shun-ichi

1984-10-01

For the therapy of diseases of spinal deformity such as scoliosis, the data of 3-dimensional and correct spinal configuration are needed. Authors developed the system of spinal configuration analysis using bi-plane X-ray photogrammetry which is strong aid for this subject. The idea of correction angle of rotation of vertebra is introduced for this system. Calculated result under this idea has the clinical meaning because the correction angle is the angle which should be corrected on the treatment such as operation or wearing the equipment. Method of 30° oblique projection which gives the apparent X-ray image and eases the measurement of the anatomically characteristic points is presented. The anatomically characteristic bony points whose images should be measured on a- or b-film are of four points. These are centers of upper and lower end plates of each vertebra the center is calculated from two points which are most distant each other on the contour of vertebral end plate ), the lower end points of root of right and left pedicles. Some clinical applications and the effectiveness of this system are presented.

Numerical simulation of three-dimensional transonic turbulent projectile aerodynamics by TVD schemes

NASA Technical Reports Server (NTRS)

Shiau, Nae-Haur; Hsu, Chen-Chi; Chyu, Wei-Jao

1989-01-01

The two-dimensional symmetric TVD scheme proposed by Yee has been extended to and investigated for three-dimensional thin-layer Navier-Stokes simulation of complex aerodynamic problems. An existing three-dimensional Navier-stokes code based on the beam and warming algorithm is modified to provide an option of using the TVD algorithm and the flow problem considered is a transonic turbulent flow past a projectile with sting at ten-degree angle of attack. Numerical experiments conducted for three flow cases, free-stream Mach numbers of 0.91, 0.96 and 1.20 show that the symmetric TVD algorithm can provide surface pressure distribution in excellent agreement with measured data; moreover, the rate of convergence to attain a steady state solution is about two times faster than the original beam and warming algorithm.

Wave scattering from a periodic dielectric surface for a general angle of incidence

NASA Technical Reports Server (NTRS)

Chuang, S. L.; Kong, J. A.

1982-01-01

Electromagnetic waves scattered from a periodic dielectric and perfectly conducting surface are studied for a general angle of incidence. It is shown that the one-dimensional corrugated surface can be solved by using two scalar functions: the components of the electric and magnetic fields along the row direction of the surface, and appropriate boundary conditions to obtain simple matrix equations. Results are compared to the case where the incident angle wave vector is perpendicular to the row direction. Numerical results demonstrate that energy conservation and reciprocity are obeyed for scattering by sinusoidal surfaces for the general case, which checks the consistency of the formalism.

Evaluation of interatomic potentials for rainbow scattering under axial channeling at KCl(0 0 1) surface by three-dimensional computer simulations based on binary collision approximation

NASA Astrophysics Data System (ADS)

Takeuchi, Wataru

2017-05-01

The rainbow angles corresponding to prominent peaks in the angular distributions of scattered projectiles with small angle, attributed to rainbow scattering (RS), under axial surface channeling conditions are strongly influenced by the interatomic potentials between projectiles and target atoms. The dependence of rainbow angles on normal energy of projectile energy to the target surface, being experimentally obtained by Specht et al. for RS of He, N, Ne and Ar atoms under <1 0 0> and <1 1 0> axial channeling conditions at a KCl(0 0 1) surface with projectile energies of 1-60 keV, was evaluated by the three-dimensional computer simulations using the ACOCT code based on the binary collision approximation with interatomic pair potentials. Good agreement between the ACOCT results using the ZBL pair potential and the individual pair potentials calculated from Hartree-Fock (HF) wave functions and the experimental ones was found for RS of He, N and Ne atoms from the atomic rows along <1 0 0> direction. For <1 1 0> direction, the ACOCT results employing the Moliere pair potential with adjustable screening length of O'Connor-Biersack (OB) formula, the ZBL pair potential and the individual HF pair potentials except for Ar → KCl using the OB pair potential are nearly in agreement with the experimental ones.

Magnetic quantum oscillations in doped antiferromagnets

NASA Astrophysics Data System (ADS)

Kabanov, V. V.

2017-10-01

Energy spectrum of electrons (holes) doped into two-dimensional (2D) antiferromagnetic (AF) semiconductors is quantized in an external magnetic field of arbitrary direction. A peculiar dependence of de Haas-van Alphen (dHvA) magneto-oscillation amplitudes on the azimuthal in-plane angle from the magnetization direction and on the polar angle from the out-of-plane direction is found. The angular dependence of the amplitude is different if the measurements are performed in the field above and below of the spin-flop field.

N-(3-Chloro-1H-indazol-5-yl)-4-meth-oxy-benzene-sulfonamide.

PubMed

Chicha, Hakima; Rakib, El Mostapha; Bouissane, Latifa; Saadi, Mohamed; El Ammari, Lahcen

2013-10-12

In the title compound, C14H12ClN3O3S, the fused five- and six-membered rings are folded slightly along the common edge, forming a dihedral angle of 3.2 (1)°. The mean plane through the indazole system makes a dihedral angle of 30.75 (7)° with the distant benzene ring. In the crystal, N-H⋯O hydrogen bonds link the mol-ecules, forming a two-dimensional network parallel to (001).

Numerical solutions of the complete Navier-Strokes equations. no. 27

NASA Technical Reports Server (NTRS)

Hassan, H. A.

1996-01-01

This report describes the development of an enstrophy model capable of predicting turbulence separation and its application to two airfoils at various angles of attack and Mach numbers. In addition, a two equation kappa-xi model with a tensor eddy viscosity was developed. Plans call for this model to be used in calculating three dimensional turbulent flows.

Anomalous spin Josephson effect

NASA Astrophysics Data System (ADS)

Wang, Mei-Juan; Wang, Jun; Hao, Lei; Liu, Jun-Feng

2016-10-01

We report a theoretical study on the spin Josephson effect arising from the exchange coupling of the two ferromagnets (Fs), which are deposited on a two-dimensional (2D) time-reversal-invariant topological insulator. An anomalous spin supercurrent Js z˜sin(α +α0) is found to flow in between the two Fs and the ground state of the system is not limited to the magnetically collinear configuration (α =n π ,n is an integer) but determined by a controllable angle α0, where α is the crossed angle between the two F magnetizations. The angle α0 is the dynamic phase of the electrons traveling in between the two Fs and can be controlled electrically by a gate voltage. This anomalous spin Josephson effect, similar to the conventional φ0 superconductor junction, originates from the definite electron chirality of the helical edge states in the 2D topological insulator. These results indicate that the magnetic coupling in a topological system is different from the usual one in conventional materials.

Development and applications of algorithms for calculating the transonic flow about harmonically oscillating wings

NASA Technical Reports Server (NTRS)

Ehlers, F. E.; Weatherill, W. H.; Yip, E. L.

1984-01-01

A finite difference method to solve the unsteady transonic flow about harmonically oscillating wings was investigated. The procedure is based on separating the velocity potential into steady and unsteady parts and linearizing the resulting unsteady differential equation for small disturbances. The differential equation for the unsteady velocity potential is linear with spatially varying coefficients and with the time variable eliminated by assuming harmonic motion. An alternating direction implicit procedure was investigated, and a pilot program was developed for both two and three dimensional wings. This program provides a relatively efficient relaxation solution without previously encountered solution instability problems. Pressure distributions for two rectangular wings are calculated. Conjugate gradient techniques were developed for the asymmetric, indefinite problem. The conjugate gradient procedure is evaluated for applications to the unsteady transonic problem. Different equations for the alternating direction procedure are derived using a coordinate transformation for swept and tapered wing planforms. Pressure distributions for swept, untaped wings of vanishing thickness are correlated with linear results for sweep angles up to 45 degrees.

An Experimental Device for Generating High Frequency Perturbations in Supersonic Wind Tunnels

NASA Technical Reports Server (NTRS)

Melcher, Kevin J.; Ibrahim, Mounir B.

1996-01-01

This paper describes the analytical study of a device that has been proposed as a mechanism for generating gust-like perturbations in supersonic wind tunnels. The device is envisioned as a means to experimentally validate dynamic models and control systems designed for high-speed inlets. The proposed gust generator is composed of two flat trapezoidal plates that modify the properties of the flow ingested by the inlet. One plate may be oscillated to generate small perturbations in the flow. The other plate is held stationary to maintain a constant angle-of-attack. Using an idealized approach, design equations and performance maps for the new device were developed from the compressible flow relations. A two-dimensional CFD code was used to confirm the correctness of these results. The idealized approach was then used to design and evaluate a new gust generator for a 3.05-meter by 3.05-meter (10-foot by 10-foot) supersonic wind tunnel.

Quantifying adsorption-induced deformation of nanoporous materials on different length scales

PubMed Central

Morak, Roland; Braxmeier, Stephan; Ludescher, Lukas; Hüsing, Nicola; Reichenauer, Gudrung

2017-01-01

A new in situ setup combining small-angle neutron scattering (SANS) and dilatometry was used to measure water-adsorption-induced deformation of a monolithic silica sample with hierarchical porosity. The sample exhibits a disordered framework consisting of macropores and struts containing two-dimensional hexagonally ordered cylindrical mesopores. The use of an H2O/D2O water mixture with zero scattering length density as an adsorptive allows a quantitative determination of the pore lattice strain from the shift of the corresponding diffraction peak. This radial strut deformation is compared with the simultaneously measured macroscopic length change of the sample with dilatometry, and differences between the two quantities are discussed on the basis of the deformation mechanisms effective at the different length scales. It is demonstrated that the SANS data also provide a facile way to quantitatively determine the adsorption isotherm of the material by evaluating the incoherent scattering contribution of H2O at large scattering vectors. PMID:29021735

Normal- and oblique-shock flow parameters in equilibrium air including attached-shock solutions for surfaces at angles of attack, sweep, and dihedral

NASA Technical Reports Server (NTRS)

Hunt, J. L.; Souders, S. W.

1975-01-01

Normal- and oblique-shock flow parameters for air in thermochemical equilibrium are tabulated as a function of shock angle for altitudes ranging from 15.24 km to 91.44 km in increments of 7.62 km at selected hypersonic speeds. Post-shock parameters tabulated include flow-deflection angle, velocity, Mach number, compressibility factor, isentropic exponent, viscosity, Reynolds number, entropy difference, and static pressure, temperature, density, and enthalpy ratios across the shock. A procedure is presented for obtaining oblique-shock flow properties in equilibrium air on surfaces at various angles of attack, sweep, and dihedral by use of the two-dimensional tabulations. Plots of the flow parameters against flow-deflection angle are presented at altitudes of 30.48, 60.96, and 91.44 km for various stream velocities.

Angles between orthogonal spd bond orbitals with maximum strength*

PubMed Central

Pauling, Linus

1976-01-01

An equation is derived for values of bond angles for two equivalent best spd hybrid bond orbitals with given amounts of s, p, and d character, and is applied in the discussion of structures of transargononic compounds, including the xenon and halogen fluorides. Bond orbitals with a rather small amount of d character tend to lie at angles 90° and 180°, and those with a larger amount, at somewhat smaller angles. PMID:16592315

Receptivity of Hypersonic Boundary Layers to Distributed Roughness and Acoustic Disturbances

NASA Technical Reports Server (NTRS)

Balakumar, P.

2013-01-01

Boundary-layer receptivity and stability of Mach 6 flows over smooth and rough seven-degree half-angle sharp-tipped cones are numerically investigated. The receptivity of the boundary layer to slow acoustic disturbances, fast acoustic disturbances, and vortical disturbances is considered. The effects of three-dimensional isolated roughness on the receptivity and stability are also simulated. The results for the smooth cone show that the instability waves are generated in the leading edge region and that the boundary layer is much more receptive to slow acoustic waves than to the fast acoustic waves. Vortical disturbances also generate unstable second modes, however the receptivity coefficients are smaller than that of the slow acoustic wave. Distributed roughness elements located near the nose region decreased the receptivity of the second mode generated by the slow acoustic wave by a small amount. Roughness elements distributed across the continuous spectrum increased the receptivity of the second mode generated by the slow and fast acoustic waves and the vorticity wave. The largest increase occurred for the vorticity wave. Roughness elements distributed across the synchronization point did not change the receptivity of the second modes generated by the acoustic waves. The receptivity of the second mode generated by the vorticity wave increased in this case, but the increase is lower than that occurred with the roughness elements located across the continuous spectrum. The simulations with an isolated roughness element showed that the second mode waves generated by the acoustic disturbances are not influenced by the small roughness element. Due to the interaction, a three-dimensional wave is generated. However, the amplitude is orders of magnitude smaller than the two-dimensional wave.

Two-way reflector based on two-dimensional sub-wavelength high-index contrast grating on SOI

NASA Astrophysics Data System (ADS)

Kaur, Harpinder; Kumar, Mukesh

2016-05-01

A two-dimensional (2D) high-index contrast grating (HCG) is proposed as a two-way reflector on Silicon-on-insulator (SOI). The proposed reflector provides high reflectivity over two (practically important) sets of angles of incidence- normal (θ = 0 °) and oblique/grazing (θ = 80 ° - 85 ° / 90 °). Analytical model of 2D HCG is presented using improved Fourier modal method. The vertical incidence is useful for application in VCSEL while oblique/grazing incidence can be utilized in high confinement (HCG mirrors based) hollow waveguides and Bragg reflectors. The proposed two-way reflector also exhibits a large reflection bandwidth (around telecom wavelength) which is an advantage for broadband photonic devices.

Analysis of a two-dimensional type 6 shock-interference pattern using a perfect-gas code and a real-gas code

NASA Technical Reports Server (NTRS)

Bertin, J. J.; Graumann, B. W.

1973-01-01

Numerical codes were developed to calculate the two dimensional flow field which results when supersonic flow encounters double wedge configurations whose angles are such that a type 4 pattern occurs. The flow field model included the shock interaction phenomena for a delta wing orbiter. Two numerical codes were developed, one which used the perfect gas relations and a second which incorporated a Mollier table to define equilibrium air properties. The two codes were used to generate theoretical surface pressure and heat transfer distributions for velocities from 3,821 feet per second to an entry condition of 25,000 feet per second.

Method and apparatus for multiple-projection, dual-energy x-ray absorptiometry scanning

NASA Technical Reports Server (NTRS)

Feldmesser, Howard S. (Inventor); Magee, Thomas C. (Inventor); Charles, Jr., Harry K. (Inventor); Beck, Thomas J. (Inventor)

2007-01-01

Methods and apparatuses for advanced, multiple-projection, dual-energy X-ray absorptiometry scanning systems include combinations of a conical collimator; a high-resolution two-dimensional detector; a portable, power-capped, variable-exposure-time power supply; an exposure-time control element; calibration monitoring; a three-dimensional anti-scatter-grid; and a gantry-gantry base assembly that permits up to seven projection angles for overlapping beams. Such systems are capable of high precision bone structure measurements that can support three dimensional bone modeling and derivations of bone strength, risk of injury, and efficacy of countermeasures among other properties.

Study of the gel films of Acetobacter Xylinum cellulose and its modified samples by {sup 1}H NMR cryoporometry and small-angle X-ray scattering

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

Babushkina, T. A.; Klimova, T. P.; Shtykova, E. V.

2010-03-15

Gel films of Acetobacter Xylinum cellulose and its modified samples have been investigated by 1H nuclear magnetic resonance (NMR) cryoporometry and small-angle X-ray scattering. The joint use of these two methods made it possible to characterize the sizes of aqueous pores in gel films and estimate the sizes of structural inhomogeneities before and after the sorption of polyvinylpyrrolidone and Se{sub 0} nanoparticles (stabilized by polyvinylpyrrolidone) into the films. According to small-angle X-ray scattering data, the sizes of inhomogeneities in a gel film change only slightly upon the sorption of polyvinylpyrrolidone and nanoparticles. The impregnated material is sorbed into water-filled cavitiesmore » that are present in the gel film. {sup 1}H NMR cryoporometry allowed us to reveal the details of changes in the sizes of small aqueous pores during modifications.« less

Non-Fermi-liquid magic angle effects in high magnetic fields

NASA Astrophysics Data System (ADS)

Lebed, A. G.

2016-07-01

We investigate a theoretical problem of electron-electron interactions in an inclined magnetic field in a quasi-one-dimensional (Q1D) conductor. We show that they result in strong non-Fermi-liquid corrections to a specific heat, provided that the direction of the magnetic field is far from the so-called Lebed's magic angles (LMAs). If magnetic field is directed close to one of the LMAs, the specific heat corrections become small and the Fermi-liquid picture restores. As a result, we predict Fermi-liquid-non-Fermi-liquid angular crossovers in the vicinities of the LMA directions of the field. We suggest to perform the corresponding experiment in the Q1D conductor (Per) 2Au (mnt) 2 under pressure in magnetic fields of the order of H ≃25 T .

Development and Operation of a High Resolution Positron Emission Tomography System to Perform Metabolic Studies on Small Animals.

NASA Astrophysics Data System (ADS)

Hogan, Matthew John

A positron emission tomography system designed to perform high resolution imaging of small volumes has been characterized. Two large area planar detectors, used to detect the annihilation gamma rays, formed a large aperture stationary positron camera. The detectors were multiwire proportional chambers coupled to high density lead stack converters. Detector efficiency was 8%. The coincidence resolving time was 500 nsec. The maximum system sensitivity was 60 cps/(mu)Ci for a solid angle of acceptance of 0.74(pi) St. The maximum useful coincidence count rate was 1500 cps and was limited by electronic dead time. Image reconstruction was done by performing a 3-dimensional deconvolution using Fourier transform methods. Noise propagation during reconstruction was minimized by choosing a 'minimum norm' reconstructed image. In the stationary detector system (with a limited angle of acceptance for coincident events) statistical uncertainty in the data limited reconstruction in the direction normal to the detector surfaces. Data from a rotated phantom showed that detector rotation will correct this problem. Resolution was 4 mm in planes parallel to the detectors and (TURN)15 mm in the normal direction. Compton scattering of gamma rays within a source distribution was investigated using both simulated and measured data. Attenuation due to scatter was as high as 60%. For small volume imaging the Compton background was identified and an approximate correction was performed. A semiquantitative blood flow measurement to bone in the leg of a cat using the ('18)F('-) ion was performed. The results were comparable to investigations using more conventional techniques. Qualitative scans using ('18)F labelled deoxy -D-glucose to assess brain glucose metabolism in a rhesus monkey were also performed.

I12: the Joint Engineering, Environment and Processing (JEEP) beamline at Diamond Light Source.

PubMed

Drakopoulos, Michael; Connolley, Thomas; Reinhard, Christina; Atwood, Robert; Magdysyuk, Oxana; Vo, Nghia; Hart, Michael; Connor, Leigh; Humphreys, Bob; Howell, George; Davies, Steve; Hill, Tim; Wilkin, Guy; Pedersen, Ulrik; Foster, Andrew; De Maio, Nicoletta; Basham, Mark; Yuan, Fajin; Wanelik, Kaz

2015-05-01

I12 is the Joint Engineering, Environmental and Processing (JEEP) beamline, constructed during Phase II of the Diamond Light Source. I12 is located on a short (5 m) straight section of the Diamond storage ring and uses a 4.2 T superconducting wiggler to provide polychromatic and monochromatic X-rays in the energy range 50-150 keV. The beam energy enables good penetration through large or dense samples, combined with a large beam size (1 mrad horizontally × 0.3 mrad vertically). The beam characteristics permit the study of materials and processes inside environmental chambers without unacceptable attenuation of the beam and without the need to use sample sizes which are atypically small for the process under study. X-ray techniques available to users are radiography, tomography, energy-dispersive diffraction, monochromatic and white-beam two-dimensional diffraction/scattering and small-angle X-ray scattering. Since commencing operations in November 2009, I12 has established a broad user community in materials science and processing, chemical processing, biomedical engineering, civil engineering, environmental science, palaeontology and physics.

I12: the Joint Engineering, Environment and Processing (JEEP) beamline at Diamond Light Source

PubMed Central

Drakopoulos, Michael; Connolley, Thomas; Reinhard, Christina; Atwood, Robert; Magdysyuk, Oxana; Vo, Nghia; Hart, Michael; Connor, Leigh; Humphreys, Bob; Howell, George; Davies, Steve; Hill, Tim; Wilkin, Guy; Pedersen, Ulrik; Foster, Andrew; De Maio, Nicoletta; Basham, Mark; Yuan, Fajin; Wanelik, Kaz

2015-01-01

I12 is the Joint Engineering, Environmental and Processing (JEEP) beamline, constructed during Phase II of the Diamond Light Source. I12 is located on a short (5 m) straight section of the Diamond storage ring and uses a 4.2 T superconducting wiggler to provide polychromatic and monochromatic X-rays in the energy range 50–150 keV. The beam energy enables good penetration through large or dense samples, combined with a large beam size (1 mrad horizontally × 0.3 mrad vertically). The beam characteristics permit the study of materials and processes inside environmental chambers without unacceptable attenuation of the beam and without the need to use sample sizes which are atypically small for the process under study. X-ray techniques available to users are radiography, tomography, energy-dispersive diffraction, monochromatic and white-beam two-dimensional diffraction/scattering and small-angle X-ray scattering. Since commencing operations in November 2009, I12 has established a broad user community in materials science and processing, chemical processing, biomedical engineering, civil engineering, environmental science, palaeontology and physics. PMID:25931103

Use of Transition Modeling to Enable the Computation of Losses for Variable-Speed Power Turbine

NASA Technical Reports Server (NTRS)

Ameri, Ali A.

2012-01-01

To investigate the penalties associated with using a variable speed power turbine (VSPT) in a rotorcraft capable of vertical takeoff and landing, various analysis tools are required. Such analysis tools must be able to model the flow accurately within the operating envelope of VSPT. For power turbines low Reynolds numbers and a wide range of the incidence angles, positive and negative, due to the variation in the shaft speed at relatively fixed corrected flows, characterize this envelope. The flow in the turbine passage is expected to be transitional and separated at high incidence. The turbulence model of Walters and Leylek was implemented in the NASA Glenn-HT code to enable a more accurate analysis of such flows. Two-dimensional heat transfer predictions of flat plate flow and two-dimensional and three-dimensional heat transfer predictions on a turbine blade were performed and reported herein. Heat transfer computations were performed because it is a good marker for transition. The final goal is to be able to compute the aerodynamic losses. Armed with the new transition model, total pressure losses for three-dimensional flow of an Energy Efficient Engine (E3) tip section cascade for a range of incidence angles were computed in anticipation of the experimental data. The results obtained form a loss bucket for the chosen blade.

Airfoil-Wake Modification with Gurney Flap at Low Reynolds Number

NASA Astrophysics Data System (ADS)

Gopalakrishnan Meena, Muralikrishnan; Taira, Kunihiko; Asai, Keisuke

2018-04-01

The complex wake modifications produced by a Gurney flap on symmetric NACA airfoils at low Reynolds number are investigated. Two-dimensional incompressible flows over NACA 0000 (flat plate), 0006, 0012 and 0018 airfoils at a Reynolds number of $Re = 1000$ are analyzed numerically to examine the flow modifications generated by the flaps for achieving lift enhancement. While high lift can be attained by the Gurney flap on airfoils at high angles of attack, highly unsteady nature of the aerodynamic forces are also observed. Analysis of the wake structures along with the lift spectra reveals four characteristic wake modes (steady, 2S, P and 2P), influencing the aerodynamic performance. The effects of the flap over wide range of angles of attack and flap heights are considered to identify the occurrence of these wake modes, and are encapsulated in a wake classification diagram. Companion three-dimensional simulations are also performed to examine the influence of three-dimensionality on the wake regimes. The spanwise instabilities that appear for higher angles of attack are found to suppress the emergence of the 2P mode. The use of the wake classification diagram as a guidance for Gurney flap selection at different operating conditions to achieve the required aerodynamic performance is discussed.

Development of a Three-Dimensional PSE Code for Compressible Flows: Stability of Three-Dimensional Compressible Boundary Layers

NASA Technical Reports Server (NTRS)

Balakumar, P.; Jeyasingham, Samarasingham

1999-01-01

A program is developed to investigate the linear stability of three-dimensional compressible boundary layer flows over bodies of revolutions. The problem is formulated as a two dimensional (2D) eigenvalue problem incorporating the meanflow variations in the normal and azimuthal directions. Normal mode solutions are sought in the whole plane rather than in a line normal to the wall as is done in the classical one dimensional (1D) stability theory. The stability characteristics of a supersonic boundary layer over a sharp cone with 50 half-angle at 2 degrees angle of attack is investigated. The 1D eigenvalue computations showed that the most amplified disturbances occur around x(sub 2) = 90 degrees and the azimuthal mode number for the most amplified disturbances range between m = -30 to -40. The frequencies of the most amplified waves are smaller in the middle region where the crossflow dominates the instability than the most amplified frequencies near the windward and leeward planes. The 2D eigenvalue computations showed that due to the variations in the azimuthal direction, the eigenmodes are clustered into isolated confined regions. For some eigenvalues, the eigenfunctions are clustered in two regions. Due to the nonparallel effect in the azimuthal direction, the eigenmodes are clustered into isolated confined regions. For some eigenvalues, the eigenfunctions are clustered in two regions. Due to the nonparallel effect in the azimuthal direction, the most amplified disturbances are shifted to 120 degrees compared to 90 degrees for the parallel theory. It is also observed that the nonparallel amplification rates are smaller than that is obtained from the parallel theory.

Periodical plasma structures controlled by external magnetic field

NASA Astrophysics Data System (ADS)

Schweigert, I. V.; Keidar, M.

2017-06-01

The characteristics of two-dimensional periodical structures in a magnetized plasma are studied using kinetic simulations. Ridges (i.e. spikes in electron and ion density) are formed and became more pronounced with an increase of magnetic field incidence angle in the plasma volume in the cylindrical chamber. These ridges are shifted relative to each other, which results in the formation of a two-dimensional double-layer structure. Depending on Larmor radius and Debye length up to 19 potential steps appear across the oblique magnetic field. The electrical current gathered into the channels is associated with the electron and ion density ridges.

Layer-by-Layer Evolution of a Two-Dimensional Electron Gas Near an Oxide Interface

NASA Astrophysics Data System (ADS)

Chang, Young Jun; Moreschini, Luca; Bostwick, Aaron; Gaines, Geoffrey A.; Kim, Yong Su; Walter, Andrew L.; Freelon, Byron; Tebano, Antonello; Horn, Karsten; Rotenberg, Eli

2013-09-01

We report the momentum-resolved measurement of a two-dimensional electron gas at the LaTiO3/SrTiO3 interface by angle-resolved photoemission spectroscopy (ARPES). Thanks to an advanced sample preparation technique, the orbital character of the conduction electrons and the electronic correlations can be accessed quantitatively as each unit cell layer is added. We find that all of these quantities change dramatically with distance from the interface. These findings open the way to analogous studies on other heterostructures, which are traditionally a forbidden field for ARPES.

The receptivity of boundary layers on blunt bodies to oscillations in the free stream

NASA Technical Reports Server (NTRS)

Grosch, C. E.

1982-01-01

It is concluded that in the region of the nose of a symmetric, two dimensional blunt body at zero angle of attack, the steady plus oscillating flow is very similar for a wide class of body shapes. This conclusion was shown to be true for elliptic cylinders with a/b 25, and for the parabolic cylinder. In all cases, the flow field in the nose region of a two dimensional blunt body is generic to that of the flow in the neighborhood of the stagnation point on a plane wall.