Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems.

Science.gov (United States)

Jo, Jae-Young; Yang, Dong-Seok; Huh, Jung-Bo; Heo, Jae-Chan; Yun, Mi-Jung; Jeong, Chang-Mo

2014-12-01

This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (Pabutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.

Effect of the refraction factor of a plastic fiber shell on the internal reflection coefficient

International Nuclear Information System (INIS)

Pkrksypkin, A.I.; Ponomarev, L.I.

1992-01-01

Results of pilot studies of the effect of refraction factor of plastic fiber shell on the coefficient of light internal reflection in the fiber are presented. It is pointed, that the shell does not absorb the light, but effects the surface layer of the fiber centre so, that dependence of the coefficient of internal reflection on refraction factor of the shell may be described using Fresnel formulae. It is shown, that coefficient of internal reflection decreases with the increase of refraction factor. Technique to determine volume length of scintillation light absorption in the fiber is suggested

Direct determination of the resonance properties of metallic conical nanoantennas

KAUST Repository

Tuccio, Salvatore; Razzari, Luca; Alabastri, Alessandro; Toma, Andrea; Liberale, Carlo; De Angelis, Francesco De; Candeloro, Patrizio; Das, Gobind; Giugni, Andrea; Di Fabrizio, Enzo M.; Proietti Zaccaria, Remo

2014-01-01

We present a simple method that is able to predict the resonant frequencies of a metallic conical nanoantenna. The alculation is based on an integral relation that takes into account the dependence of the effective refractive index of the plasmonic mode on the cone radius. Numerical simulations retrieving the near field properties of nanocones with different lengths are also performed for comparison. The fine agreement between the two approaches demonstrates the validity of our method. © 2014 Optical Society of America.

The plastic instability of clamped-clamped conical thin-walled pipe reducers

International Nuclear Information System (INIS)

Awad, Ibrahim; Saleh, Ch.A.R.; Ragab, A.R.

2016-01-01

The analytical study for plastic deformation of clamped–clamped conical reducer pipe under internal pressure does not deduce a closed form expression for the pressure at plastic instability. The presented study employs finite element analysis (FEA) to estimate the internal pressure at instability for conical reducers made of different materials and having different dimensional configurations. Forty dimensional configurations, classified as medium type, and five types of materials have been included in the analysis using ABAQUS package. A correlation expression is derived by nonlinear regression to predict the instability pressure. The proposed expression is verified for other dimensional configurations out of the above used forty models and for other materials. Experiments have been conducted by pressurizing conical clamped-clamped reducers until bursting in order to verify the finite element models. Comparison of instability pressures, strains and deflections at specific points along the conical surface shows satisfactory agreement between analysis and experiments. - Highlights: • This study offers a parametric study of the plastic instability pressure of clamped-clamped conical reducers. • A closed form analytical expression for the instability pressure is derived by using nonlinear regression. • The finite element analysis is validated by conducting bursting tests.

Effect of surface plasmon polaritons on the sensitivity of refractive index measurement using total internal reflection method

International Nuclear Information System (INIS)

Roshan Entezar, S.

2015-01-01

The phase difference between two p-polarized and s-polarized plane waves which are reflected under total internal reflection from the base of a prism with a thin metal coating is studied. Typically such a quantity can be used to measure the refractive index of a test material using the total internal reflection method. It is shown that due to the excitation of surface plasmon polaritons at the interface between the tested dielectric material and the thin metal layer, the p-polarized light experiences a large phase shift which enlarges the phase difference between the p-polarized and the s-polarized waves. As a result, the sensitivity of refractive index measurement increases and the error in determining the refractive index decreases. - Highlights: • Phase difference of totally internally reflected p and s polarized beams is studied. • Excitation of the surface wave increases the phase shift of the p-polarized light. • The sensitivity of refractive index measurement increases by using a coated prism. • The error in determining the refractive index decreases using the coated prism

The effects of internal refractive index variation in near-infrared optical tomography: a finite element modelling approach

International Nuclear Information System (INIS)

Dehghani, Hamid; Brooksby, Ben; Vishwanath, Karthik; Pogue, Brian W; Paulsen, Keith D

2003-01-01

Near-infrared (NIR) tomography is a technique used to measure light propagation through tissue and generate images of internal optical property distributions from boundary measurements. Most popular applications have concentrated on female breast imaging, neonatal and adult head imaging, as well as muscle and small animal studies. In most instances a highly scattering medium with a homogeneous refractive index is assumed throughout the imaging domain. Using these assumptions, it is possible to simplify the model to the diffusion approximation. However, biological tissue contains regions of varying optical absorption and scatter, as well as varying refractive index. In this work, we introduce an internal boundary constraint in the finite element method approach to modelling light propagation through tissue that accounts for regions of different refractive indices. We have compared the results to data from a Monte Carlo simulation and show that for a simple two-layered slab model of varying refractive index, the phase of the measured reflectance data is significantly altered by the variation in internal refractive index, whereas the amplitude data are affected only slightly

Studies of the Reflection, Refraction and Internal Reflection of Light

Science.gov (United States)

Lanchester, P. C.

2014-01-01

An inexpensive apparatus and associated experiments are described for studying the basic laws of reflection and refraction of light at an air-glass interface, and multiple internal reflections within a glass block. In order to motivate students and encourage their active participation, a novel technique is described for determining the refractive…

Dirac directional emission in anisotropic zero refractive index photonic crystals.

Science.gov (United States)

He, Xin-Tao; Zhong, Yao-Nan; Zhou, You; Zhong, Zhi-Chao; Dong, Jian-Wen

2015-08-14

A certain class of photonic crystals with conical dispersion is known to behave as isotropic zero-refractive-index medium. However, the discrete building blocks in such photonic crystals are limited to construct multidirectional devices, even for high-symmetric photonic crystals. Here, we show multidirectional emission from low-symmetric photonic crystals with semi-Dirac dispersion at the zone center. We demonstrate that such low-symmetric photonic crystal can be considered as an effective anisotropic zero-refractive-index medium, as long as there is only one propagation mode near Dirac frequency. Four kinds of Dirac multidirectional emitters are achieved with the channel numbers of five, seven, eleven, and thirteen, respectively. Spatial power combination for such kind of Dirac directional emitter is also verified even when multiple sources are randomly placed in the anisotropic zero-refractive-index photonic crystal.

Deep-water bedforms induced by refracting Internal Solitary Waves

Science.gov (United States)

Falcini, Federico; Droghei, Riccardo; Casalbore, Daniele; Martorelli, Eleonora; Mosetti, Renzo; Sannino, Gianmaria; Santoleri, Rosalia; Latino Chiocci, Francesco

2017-04-01

Subaqueous bedforms (or sand waves) are typically observed in those environments that are exposed to strong currents, characterized by a dominant unidirectional flow. However, sand-wave fields may be also observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs), induced by tides, can produce an effective, unidirectional boundary flow filed that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.

I’m Discovering Conics and Designing Buildings with Conics

Directory of Open Access Journals (Sweden)

Serkan KULOGLU

2015-01-01

Full Text Available There are three stages in this activity. At the first stage, it is provided that gifted students learn the subject of conic through discovery learning method. By this way, the formation of misconceptions that students frequently encounter in mathematics has been prevented. At the second stage, gifted students have been asked to draw the conical objects which they encounter in their daily life. Thus, it has contributed to the development of gifted students’ creativity. At the third stage, gifted students have been asked to design a buildings consisting of conics. Moreover, gifted students have been informed that the buildings which they have been asked to design, would be evaluated according to the criteria which set before. And then, the building design model has been done by gifted students.

Surface-enhanced Raman spectroscopy based on conical holed enhancing substrates

International Nuclear Information System (INIS)

Chen, Yao; Chen, Zeng-Ping; Zuo, Qi; Shi, Cai-Xia; Yu, Ru-Qin

2015-01-01

In this contribution, surface-enhanced Raman spectroscopy (SERS) based on conical holed glass substrates deposited with silver colloids was reported for the first time. It combines the advantages of both dry SERS assays based on plane films deposited with silver colloids and wet SERS assays utilizing cuvettes or capillary tubes. Compared with plane glass substrates deposited with silver colloids, the conical holed glass substrates deposited with silver colloids exhibited five-to ten-folds of increase in the rate of signal enhancement, due to the internal multiple reflections of both the excitation laser beam and the Raman scattering photons within conical holes. The application of conical holed glass substrates could also yield significantly stronger and more reproducible SERS signals than SERS assays utilizing capillary tubes to sample the mixture of silver colloids and the solution of the analyte of interest. The conical holed glass substrates in combination with the multiplicative effects model for surface-enhanced Raman spectroscopy (MEM SERS ) achieved quite sensitive and precise quantification of 6-mercaptopurine in complex plasma samples with an average relative prediction error of about 4% and a limit of detection of about 0.02 μM using a portable i-Raman 785H spectrometer. It is reasonable to expect that SERS technique based on conical holed enhancing substrates in combination with MEM SERS model can be developed and extended to other application areas such as drug detection, environmental monitoring, and clinic analysis, etc. - Highlights: • A novel conical holed SERS enhancing substrate was designed and manufactured. • The optimal conical holed glass substrates can produce stronger SERS signal. • The novel substrates can overcome the shortcomings of both dry and wet methods. • The novel substrates coupled with MEM SERS can realize quantitative SERS assays

Refractive Index Imaging of Cells with Variable-Angle Near-Total Internal Reflection (TIR) Microscopy.

Science.gov (United States)

Bohannon, Kevin P; Holz, Ronald W; Axelrod, Daniel

2017-10-01

The refractive index in the interior of single cells affects the evanescent field depth in quantitative studies using total internal reflection (TIR) fluorescence, but often that index is not well known. We here present method to measure and spatially map the absolute index of refraction in a microscopic sample, by imaging a collimated light beam reflected from the substrate/buffer/cell interference at variable angles of incidence. Above the TIR critical angle (which is a strong function of refractive index), the reflection is 100%, but in the immediate sub-critical angle zone, the reflection intensity is a very strong ascending function of incidence angle. By analyzing the angular position of that edge at each location in the field of view, the local refractive index can be estimated. In addition, by analyzing the steepness of the edge, the distance-to-substrate can be determined. We apply the technique to liquid calibration samples, silica beads, cultured Chinese hamster ovary cells, and primary culture chromaffin cells. The optical technique suffers from decremented lateral resolution, scattering, and interference artifacts. However, it still provides reasonable results for both refractive index (~1.38) and for distance-to-substrate (~150 nm) for the cells, as well as a lateral resolution to about 1 µm.

An international collaborative family-based whole genome quantitative trait linkage scan for myopic refractive error

DEFF Research Database (Denmark)

Abbott, Diana; Li, Yi-Ju; Guggenheim, Jeremy A

2012-01-01

To investigate quantitative trait loci linked to refractive error, we performed a genome-wide quantitative trait linkage analysis using single nucleotide polymorphism markers and family data from five international sites....

Straight, conic and circular fringes in single interferogram

International Nuclear Information System (INIS)

Rajkumar

2015-01-01

Interferometry is an important part of optics courses taught at the undergraduate level in universities throughout the world. It is used to explain to students the wave nature of light and is also used to measure parameters like length, refractive index, thickness of test samples and wavelength of light source, etc. The shape of interference fringes (linear, conic or circular) gives vital information about the interfering wavefronts and is used for firsthand visual inspection in optical shop testing and other applications of scientific and engineering importance. The present work describes a simple laboratory technique to generate fringes with different shapes in a single interferogram. This is achieved by using our diffraction-Lloyd mirror interferometer where two portions of the diffracted field are superimposed to generate the interference fringes. The technique is quite helpful in explaining the role of source orientation on the shape of interference fringes to students. (paper)

Understanding the Conics through Augmented Reality

Science.gov (United States)

Salinas, Patricia; Pulido, Ricardo

2017-01-01

This paper discusses the production of a digital environment to foster the learning of conics through augmented reality. The name conic refers to curves obtained by the intersection of a plane with a right circular conical surface. The environment gives students the opportunity to interact with the cone and the plane as virtual objects in real…

Optimization of the Conical Angle Design in Conical Implant-Abutment Connections: A Pilot Study Based on the Finite Element Method.

Science.gov (United States)

Yao, Kuang-Ta; Chen, Chen-Sheng; Cheng, Cheng-Kung; Fang, Hsu-Wei; Huang, Chang-Hung; Kao, Hung-Chan; Hsu, Ming-Lun

2018-02-01

Conical implant-abutment connections are popular for their excellent connection stability, which is attributable to frictional resistance in the connection. However, conical angles, the inherent design parameter of conical connections, exert opposing effects on 2 influencing factors of the connection stability: frictional resistance and abutment rigidity. This pilot study employed an optimization approach through the finite element method to obtain an optimal conical angle for the highest connection stability in an Ankylos-based conical connection system. A nonlinear 3-dimensional finite element parametric model was developed according to the geometry of the Ankylos system (conical half angle = 5.7°) by using the ANSYS 11.0 software. Optimization algorithms were conducted to obtain the optimal conical half angle and achieve the minimal value of maximum von Mises stress in the abutment, which represents the highest connection stability. The optimal conical half angle obtained was 10.1°. Compared with the original design (5.7°), the optimal design demonstrated an increased rigidity of abutment (36.4%) and implant (25.5%), a decreased microgap at the implant-abutment interface (62.3%), a decreased contact pressure (37.9%) with a more uniform stress distribution in the connection, and a decreased stress in the cortical bone (4.5%). In conclusion, the methodology of design optimization to determine the optimal conical angle of the Ankylos-based system is feasible. Because of the heterogeneity of different systems, more studies should be conducted to define the optimal conical angle in various conical connection designs.

Alternative methods for ray tracing in uniaxial media. Application to negative refraction

Science.gov (United States)

Bellver-Cebreros, Consuelo; Rodriguez-Danta, Marcelo

2007-03-01

In previous papers [C. Bellver-Cebreros, M. Rodriguez-Danta, Eikonal equation, alternative expression of Fresnel's equation and Mohr's construction in optical anisotropic media, Opt. Commun. 189 (2001) 193; C. Bellver-Cebreros, M. Rodriguez-Danta, Internal conical refraction in biaxial media and graphical plane constructions deduced from Mohr's method, Opt. Commun. 212 (2002) 199; C. Bellver-Cebreros, M. Rodriguez-Danta, Refraccion conica externa en medios biaxicos a partir de la construccion de Mohr, Opt. Pura AppliE 36 (2003) 33], the authors have developed a method based on the local properties of dielectric permittivity tensor and on Mohr's plane graphical construction in order to study the behaviour of locally plane light waves in anisotropic media. In this paper, this alternative methodology is compared with the traditional one, by emphasizing the simplicity of the former when studying ray propagation through uniaxial media (comparison is possible since, in this case, traditional construction becomes also plane). An original and simple graphical method is proposed in order to determine the direction of propagation given by the wave vector from the knowledge of the extraordinary ray direction (given by Poynting vector). Some properties of light rays in these media not described in the literature are obtained. Finally, two applications are considered: a description of optical birefringence under normal incidence and the study of negative refraction in uniaxial media.

Watching Electrons at Conical Intersections and Funnels

Science.gov (United States)

Jonas, David M.; Smith, Eric R.; Peters, William K.; Kitney, Katherine A.

2009-06-01

The electronic motion at conical intersections and funnels is probed after polarized excitation of aligned electronic wavepackets. The pulses have bandwidth sufficient to observe vibrations mainly through their effect on the electrons. Vibrational symmetry can be identified by the polarization anisotropy of vibrational quantum beats. The polarized transients show signatures of electronic wavepacket motion (due to the energy gaps) and of electron transfer between orbitals (due to the couplings) driven by the conical intersection. For a conical intersection in a four-fold symmetric symmetry silicon naphthalocyanine molecule, electronic motions on a 100 fs timescale are driven by couplings of 1 meV. In the lower symmetry free-base naphthalocyanine, the conical intersection may be missed or missing (conical funnel), and the motions are nearly as rapid, but electronic equilibration is incomplete for red-edge excitation. These experiments probe non-adiabatic electronic dynamics with near-zero nuclear momentum - the electronic motions are determined by the principal slopes of the conical intersection and the width of the vibrational wavepacket.

Determination of continuous complex refractive index dispersion of biotissue based on internal reflection

Science.gov (United States)

Deng, Zhichao; Wang, Jin; Ye, Qing; Sun, Tengqian; Zhou, Wenyuan; Mei, Jianchun; Zhang, Chunping; Tian, Jianguo

2016-01-01

The complex refractive index dispersion (CRID), which contains the information on the refractive index dispersion and extinction coefficient spectra, is an important optical parameter of biotissue. However, it is hard to perform the CRID measurement on biotissues due to their high scattering property. Continuous CRID measurement based on internal reflection (CCRIDM-IR) is introduced. By using a lab-made apparatus, internal reflectance spectra of biotissue samples at multiple incident angles were detected, from which the continuous CRIDs were calculated based on the Fresnel formula. Results showed that in 400- to 750-nm range, hemoglobin solution has complicated dispersion and extinction coefficient spectra, while other biotissues have normal dispersion properties, and their extinction coefficients do not vary much with different wavelengths. The normal dispersion can be accurately described by several coefficients of dispersion equations (Cauchy equation, Cornu equation, and Conrady equation). To our knowledge, this is the first time that the continuous CRID of scattering biotissue over a continuous spectral region is measured, and we hereby have proven that CCRIDM-IR is a good method for continuous CRID research of biotissue.

Conical : An extended module for computing a numerically satisfactory pair of solutions of the differential equation for conical functions

NARCIS (Netherlands)

T.M. Dunster (Mark); A. Gil (Amparo); J. Segura (Javier); N.M. Temme (Nico)

2017-01-01

textabstractConical functions appear in a large number of applications in physics and engineering. In this paper we describe an extension of our module Conical (Gil et al., 2012) for the computation of conical functions. Specifically, the module includes now a routine for computing the function

Zero refractive index in time-Floquet acoustic metamaterials

Science.gov (United States)

Koutserimpas, Theodoros T.; Fleury, Romain

2018-03-01

New scientific investigations of artificially structured materials and experiments have exhibited wave manipulation to the extreme. In particular, zero refractive index metamaterials have been on the front line of wave physics research for their unique wave manipulation properties and application potentials. Remarkably, in such exotic materials, time-harmonic fields have an infinite wavelength and do not exhibit any spatial variations in their phase distribution. This unique feature can be achieved by forcing a Dirac cone to the center of the Brillouin zone ( Γ point), as previously predicted and experimentally demonstrated in time-invariant metamaterials by means of accidental degeneracy between three different modes. In this article, we propose a different approach that enables true conical dispersion at Γ with twofold degeneracy and generates zero index properties. We break time-reversal symmetry and exploit a time-Floquet modulation scheme to demonstrate a time-Floquet acoustic metamaterial with zero refractive index. This behavior, predicted using stroboscopic analysis, is confirmed by full-wave finite element simulations. Our results establish the relevance of time-Floquet metamaterials as a novel reconfigurable platform for wave control.

Soft tissue modelling with conical springs.

Science.gov (United States)

Omar, Nadzeri; Zhong, Yongmin; Jazar, Reza N; Subic, Aleksandar; Smith, Julian; Shirinzadeh, Bijan

2015-01-01

This paper presents a new method for real-time modelling soft tissue deformation. It improves the traditional mass-spring model with conical springs to deal with nonlinear mechanical behaviours of soft tissues. A conical spring model is developed to predict soft tissue deformation with reference to deformation patterns. The model parameters are formulated according to tissue deformation patterns and the nonlinear behaviours of soft tissues are modelled with the stiffness variation of conical spring. Experimental results show that the proposed method can describe different tissue deformation patterns using one single equation and also exhibit the typical mechanical behaviours of soft tissues.

CONICAL EQUIPOTENTIAL SUBSTRATE FOR LIQUID METAL SOURCES

OpenAIRE

Kubby , J.; Siegel , B.

1986-01-01

Morphological changes that occur at an ion bombarded surface as a result of erosion by sputtering can be utilized for the machining of cylindrically symmetric submicron structures. Such structuring has produced tungsten field emitters of conical configuration with variable cone half angle. A conical equipotential surface with an included half angle of 49.3° would be a useful emitter substrate for experiments designed to produce an equilibrium conical interface to a conducting fluid in an appl...

Radial-firing optical fiber tip containing conical-shaped air-pocket for biomedical applications.

Science.gov (United States)

Lee, Seung Ho; Ryu, Yong-Tak; Son, Dong Hoon; Jeong, Seongmook; Kim, Youngwoong; Ju, Seongmin; Kim, Bok Hyeon; Han, Won-Taek

2015-08-10

We report a novel radial-firing optical fiber tip containing a conical-shaped air-pocket fabricated by deforming a hollow optical fiber using electric arc-discharge process. The hollow optical fiber was fusion spliced with a conventional optical fiber, simultaneously deforming into the intagliated conical-shaped region along the longitudinal fiber-axis of the fiber due to the gradual collapse of the cavity of the hollow optical fiber. Then the distal-end of the hollow optical fiber was sealed by the additional arc-discharge in order to obstruct the inflow of an external bio-substance or liquid to the inner air surface during the surgical operations, resulting in the formation of encased air-pocket in the silica glass fiber. Due to the total internal reflection of the laser beam at the conical-shaped air surface, the laser beam (λ = 632.8 nm) was deflected to the circumferential direction up to 87 degree with respect to the fiber-axis.

Using an International Medical Advisory Board to guide clinical governance in a corporate refractive surgery model.

Science.gov (United States)

Vukich, John A

2009-07-01

To describe the role played by the International Medical Advisory Board (IMAB) in clinical and corporate governance at Optical Express, a corporate provider of refractive surgery. A review of goals, objectives, and actions of the IMAB. The IMAB has contributed to study design, data analysis, and selection of instruments and procedures. Through interactions with Optical Express corporate and clinical staff, the IMAB has supported management's effort to craft a corporate culture focused on continuous improvement in the safety and visual outcomes of refractive surgery. The IMAB has fashioned significant changes in corporate policies and procedures and has had an impact on corporate culture at Optical Express.

Conical light scattering in strontium barium niobate crystals related to an intrinsic composition inhomogeneity

International Nuclear Information System (INIS)

Bastwoeste, K; Sander, U; Imlau, M

2007-01-01

Conical light scattering is uncovered in poly- and mono-domain, nominally pure and Eu-doped strontium barium niobate (SBN) crystals over a wide temperature regime. The appearance of two scattering cones, a scattering line and a corona is observed and can be explained comprehensively within the Ewald sphere concept. Photorefraction, scattering from domain boundaries or from growth striations can be excluded from explaining the origin of the scattering. It is shown that the temperature-persistent scattering process is related to a growth-induced seeding rod, i.e. a composition inhomogeneity primarily localized at the centre of the SBN sample. The rod is directed parallel to the c axis and yields a refractive-index inhomogeneity with spatial frequencies on the micro-scale

Spatiotemporal dynamics of underwater conical shock wave focusing

Czech Academy of Sciences Publication Activity Database

Hoffer, Petr; Lukeš, Petr; Akiyama, H.; Hosseini, H.

2017-01-01

Roč. 27, č. 4 (2017), s. 685-690 ISSN 0938-1287 Grant - others:Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100431203 Program:M Institutional support: RVO:61389021 Keywords : Underwater shock wave focusing * multichannel * electrohydraulic discharge * conical shock wave reflection * medical application Subject RIV: BI - Acoustics OBOR OECD: Applied mechanics Impact factor: 1.107, year: 2016 https://link.springer.com/article/10.1007/s00193-016-0703-7

Conical twist fields and null polygonal Wilson loops

Science.gov (United States)

Castro-Alvaredo, Olalla A.; Doyon, Benjamin; Fioravanti, Davide

2018-06-01

Using an extension of the concept of twist field in QFT to space-time (external) symmetries, we study conical twist fields in two-dimensional integrable QFT. These create conical singularities of arbitrary excess angle. We show that, upon appropriate identification between the excess angle and the number of sheets, they have the same conformal dimension as branch-point twist fields commonly used to represent partition functions on Riemann surfaces, and that both fields have closely related form factors. However, we show that conical twist fields are truly different from branch-point twist fields. They generate different operator product expansions (short distance expansions) and form factor expansions (large distance expansions). In fact, we verify in free field theories, by re-summing form factors, that the conical twist fields operator product expansions are correctly reproduced. We propose that conical twist fields are the correct fields in order to understand null polygonal Wilson loops/gluon scattering amplitudes of planar maximally supersymmetric Yang-Mills theory.

Bacterial colonization of the implant-abutment interface of conical connection with an internal octagon: an in vitro study using real-time PCR.

Science.gov (United States)

Baj, A; Beltramini, G A; Bolzoni, A; Cura, F; Palmieri, A; Scarano, A; Ottria, L; Giannì, A B

2017-01-01

Bacterial leakage at the implant-abutment connection of a two-piece implant system is considered the main cause of peri-implantitis. Prevention of bacterial leakage at the implant-abutment connection is mandatory for reducing inflammation process around implant neck and achieving bone stability. Micro-cavities at implant-abutment connection level can favour bacterial leakage, even in modern two-piece implant systems. The conical connection with an internal octagon (CCIO) is considered to be more stable mechanically and allows a more tight link between implant and abutment. As P. gingivalis and T. forsythia penetration might have clinical relevance, it was the purpose of this investigation to evaluate molecular leakage of these two bacteria in a new two-implant system with an internal conical implant-abutment connection with internal octagon (Shiner XT, FMD Falappa Medical Devices S.p.A. Rome, Italy). To verify the ability of the implant in protecting the internal space from the external environment, the passage of genetically modified Escherichia c oli across implant-abutment interface was evaluated. Four Shiner XT implants (FMD, Falappa Medical Devices®, Rome, Italy) were immerged in a bacterial culture for 24 h and bacteria amount was measured inside implant-abutment interface with Real-time PCR. Bacteria were detected inside all studied implants, with a median percentage of 6% for P. gingivalis and 5% for T. forsythia. Other comparable studies about the tightness of the tested implant system reported similar results. The gap size at the implant-abutment connection of CCIOs was measured by other authors discovering a gap size of 1–2μm of the AstraTech system and of 4μm for the Ankylos system. Bacterial leakage along implant-abutment connection of cylindrical and tapered implants, Shiner XT, (FMD Falappa Medical Devices S.p.A. Rome, Italy) showed better results compared to other implants. Additional studies are needed to explore the relationship in terms of

Influence of internal refractive index gradients on size measurements of spherically symmetric particles by phase Doppler anemometry.

Science.gov (United States)

Schneider, M; Hirleman, E D

1994-04-20

A model based on geometric optics for predicting the response of interferometric (phase Doppler) instruments for size measurements of particles with radially symmetric but inhomogeneous internal refractive index profiles is developed. The model and results are important for applications in which heat or mass transfer from the particles or droplets is significant, for example, in liquid-fuel combustion. To quantify the magnitude of potential bias errors introduced by the classical assumption of uniform internal properties on phase Doppler measurements, we compute calibration curves for a sequence of times during the evaporation of a decane droplet immersed in an environment of T = 2000 K and p = 10 bars. The results reveal considerable effects on the relation between phase difference and droplet diameter caused by the refractive index gradients present. The model provides an important tool to assess sizing uncertainties that can be expected when applying conventional (based on uniform properties) phase Doppler calibration curves in spray combustion and similar processes.

Path integration in conical space

International Nuclear Information System (INIS)

Inomata, Akira; Junker, Georg

2012-01-01

Quantum mechanics in conical space is studied by the path integral method. It is shown that the curvature effect gives rise to an effective potential in the radial path integral. It is further shown that the radial path integral in conical space can be reduced to a form identical with that in flat space when the discrete angular momentum of each partial wave is replaced by a specific non-integral angular momentum. The effective potential is found proportional to the squared mean curvature of the conical surface embedded in Euclidean space. The path integral calculation is compatible with the Schrödinger equation modified with the Gaussian and the mean curvature. -- Highlights: ► We study quantum mechanics on a cone by the path integral approach. ► The path integral depends only on the metric and the curvature effect is built in. ► The approach is consistent with the Schrödinger equation modified by an effective potential. ► The effective potential is found to be of the “Jensen–Koppe” and “da Costa” type.

Decomposition in conic optimization with partially separable structure

DEFF Research Database (Denmark)

Sun, Yifan; Andersen, Martin Skovgaard; Vandenberghe, Lieven

2014-01-01

Decomposition techniques for linear programming are difficult to extend to conic optimization problems with general nonpolyhedral convex cones because the conic inequalities introduce an additional nonlinear coupling between the variables. However in many applications the convex cones have...

DE 1 and Viking observations associated with electron conical distributions

Science.gov (United States)

Menietti, J. D.; Weimer, D. R.; Andre, M.; Eliasson, L.

1994-01-01

Data from the electron detectors on board the Swedish Viking satellite launched during a period of low solar activity and from the Dynamic Explorer (DE) 1 satellite launched during active solar coditions have been examined for the occurrence and location of electron conical distributions and several conclusions can be drawn. First, we note that most of the best examples of electron conics observed by the V-3 experiment onboard Viking occurred in the afternoon sector in the range of magneitc local time 14 hours less than Magnetic Local Time (MLT) less than 18 hours, at midaltitudes in the range 10,000 km less than h less than 13,500 km, with few occurring in the nightside auroral region, a region poorly sampled at altitudes greater than 5000 km. For the Viking data there is an association of electron conics with upper hybrid waves. DE 1 observations made by the high-altitude plasma instrument (HAPI) indicate that electron conics were observed in the midmorning sector and the late evening sector, and as has been reported earlier, the correlation with upper hybird waves was good. The HAPI did not sample the afternoon sector. The electon conics observed on both satellites occurred in the presence of at least a modest (several kilovolts) potential difference beneath the satellite with a maximum energy that was usually, but not always, equal to or greater than the maximum energy of the electron conics. Two independent sets of observations by DE 1 suggest two distinct production mechanisms for electron conics. Examiniation of DE 1 electric field measurements from the plasma wave instrument during the observation of electron conics show simultaneous parallel oscillations in the frequency range of 0.2 Hz less than f less than 0.5 Hz during one and perhaps two of four events examined, and upper hybrid waves were observed on all four events. In addition, recent observations of '90-deg' electron conics associated with auroral kilometric radiation source regions suggest a

Conic coconuts : the pricing of contingent capital notes using conic finance

NARCIS (Netherlands)

Madan, D.B.; Schoutens, W.

2010-01-01

In this paper we introduce a fundamental model under which we will price contingent capital notes using conic finance techniques. The model is based on more realistic balance-sheet models recognizing the fact that asset and liabilities are both risky and have been treated differently taking into

Heat transfer behaviors in round tube with conical ring inserts

International Nuclear Information System (INIS)

Promvonge, P.

2008-01-01

To increase convection heat transfer in a uniform heat flux tube by a passive method, several conical rings used as turbulators are mounted over the test tube. The effects of the conical ring turbulator inserts on the heat transfer rate and friction factor are experimentally investigated in the present work. Conical rings with three different diameter ratios of the ring to tube diameter (d/D = 0.5, 0.6, 0.7) are introduced in the tests, and for each ratio, the rings are placed with three different arrangements (converging conical ring, referred to as CR array, diverging conical ring, DR array and converging-diverging conical ring, CDR array). In the experiment, cold air at ambient condition for Reynolds numbers in a range of 6000-26,000 is passed through the uniform heat flux circular tube. It is found that the ring to tube diameter ratio and the ring arrays provide a significant effect on the thermal performance of the test tube. The experimental results demonstrate that the use of conical ring inserts leads to a higher heat transfer rate than that of the plain surface tube, and the DR array yields a better heat transfer than the others. The results are also correlated in the form of Nusselt number as a function of Reynolds number, Prandtl number and diameter ratio. An augmentation of up to 197%, 333%, and 237% in Nusselt number is obtained in the turbulent flow for the CR, DR and CDR arrays, respectively, although the effect of using the conical ring causes a substantial increase in friction factor

An internal conical mandrel technique for fracture toughness measurements on nuclear fuel cladding

Energy Technology Data Exchange (ETDEWEB)

Sainte Catherine, C.; Le Boulch, D.; Carassou, S. [CEA Saclay, DEN/DMN, Bldg 625 P, Gif-Sur-Yvette, F-91191 (France); Lemaignan, C. [CEA Grenoble, 17 rue des Martyrs, Grenoble, F-38054 (France); Ramasubramanian, N. [ECCATEC Inc., 92 Deburn Drive, Toronto, Ontario (Canada)

2006-07-01

An understanding of the limiting stress level for crack initiation and propagation in a fuel cladding material is a fundamental requirement for the development of water reactor clad materials. Conventional tests, in use to evaluate fracture properties, are of limited help, because they are adapted from ASTM standards designed for thick materials, which differ significantly from fuel cladding geometry (small diameter thin-walled tubing). The Internal Conical Mandrel (ICM) test described here is designed to simulate the effect of fuel pellet diametrical increase on a cladding with an existing axial through-wall crack. It consists in forcing a cone, having a tapered increase in diameter, inside the Zircaloy cladding with an initial axial crack. The aim of this work is to quantify the crack initiation and propagation criteria for fuel cladding material. The crack propagation is monitored by a video system for obtaining crack extension {delta}a. A finite-element (FE) simulation of the ICM test is performed in order to derive J integrals. A node release technique is applied during the FE simulation for crack propagation and the J-resistance curves (J-{delta}a) are generated. This paper presents the test methodology, the J computation validation, and results for cold-worked stress relieved Zircaloy-4 cladding at 20 deg. and 300 deg. C and also for Al 7050-T7651 aluminum alloy tubing at 20 deg. C. (authors)

Biophysical basis for the geometry of conical stromatolites.

Science.gov (United States)

Petroff, Alexander P; Sim, Min Sub; Maslov, Andrey; Krupenin, Mikhail; Rothman, Daniel H; Bosak, Tanja

2010-06-01

Stromatolites may be Earth's oldest macroscopic fossils; however, it remains controversial what, if any, biological processes are recorded in their morphology. Although the biological interpretation of many stromatolite morphologies is confounded by the influence of sedimentation, conical stromatolites form in the absence of sedimentation and are, therefore, considered to be the most robust records of biophysical processes. A qualitative similarity between conical stromatolites and some modern microbial mats suggests a photosynthetic origin for ancient stromatolites. To better understand and interpret ancient fossils, we seek a quantitative relationship between the geometry of conical stromatolites and the biophysical processes that control their growth. We note that all modern conical stromatolites and many that formed in the last 2.8 billion years display a characteristic centimeter-scale spacing between neighboring structures. To understand this prominent-but hitherto uninterpreted-organization, we consider the role of diffusion in mediating competition between stromatolites. Having confirmed this model through laboratory experiments and field observation, we find that organization of a field of stromatolites is set by a diffusive time scale over which individual structures compete for nutrients, thus linking form to physiology. The centimeter-scale spacing between modern and ancient stromatolites corresponds to a rhythmically fluctuating metabolism with a period of approximately 20 hr. The correspondence between the observed spacing and the day length provides quantitative support for the photosynthetic origin of conical stromatolites throughout geologic time.

Covered by lines and Conic connected varieties

Directory of Open Access Journals (Sweden)

Alex Massarenti

2011-12-01

Full Text Available We study some properties of an embedded variety covered by lines and give a numerical criterion ensuring the existence of a singular conic through two of its general points. We show that our criterion is sharp. Conic-connected, covered by lines, QEL, LQEL, prime Fano, defective, and dual defective varieties are closely related. We study some relations between the above mentioned classes of objects using basic results by Ein and Zak.

Performance of conical abutment (Morse Taper) connection implants: a systematic review.

Science.gov (United States)

Schmitt, Christian M; Nogueira-Filho, Getulio; Tenenbaum, Howard C; Lai, Jim Yuan; Brito, Carlos; Döring, Hendrik; Nonhoff, Jörg

2014-02-01

In this systematic review, we aimed to compare conical versus nonconical implant-abutment connection systems in terms of their in vitro and in vivo performances. An electronic search was performed using PubMed, Embase, and Medline databases with the logical operators: "dental implant" AND "dental abutment" AND ("conical" OR "taper" OR "cone"). Names of the most common conical implant-abutment connection systems were used as additional key words to detect further data. The search was limited to articles published up to November 2012. Recent publications were also searched manually in order to find any relevant studies that might have been missed using the search criteria noted above. Fifty-two studies met the inclusion criteria and were included in this systematic review. As the data and methods, as well as types of implants used was so heterogeneous, this mitigated against the performance of meta-analysis. In vitro studies indicated that conical and nonconical abutments showed sufficient resistance to maximal bending forces and fatigue loading. However, conical abutments showed superiority in terms of seal performance, microgap formation, torque maintenance, and abutment stability. In vivo studies (human and animal) indicated that conical and nonconical systems are comparable in terms of implant success and survival rates with less marginal bone loss around conical connection implants in most cases. This review indicates that implant systems using a conical implant-abutment connection, provides better results in terms of abutment fit, stability, and seal performance. These design features could lead to improvements over time versus nonconical connection systems. © 2013 Wiley Periodicals, Inc.

Design of spheromak injector using conical accelerator for large helical device

Energy Technology Data Exchange (ETDEWEB)

Miyazawa, J.; Yamada, H.; Yasui, K.; Kato, S. [National Inst. for Fusion Science, Toki, Gifu (Japan); Fukumoto, N.; Nagata, M.; Uyama, T. [Himeji Inst. of Tech., Hyogo (Japan)

1999-11-01

Optimization of CT injector for LHD has been carried out and conical electrode for adiabatic CT compression is adopted in the design. Point-model of CT acceleration in a co-axial electrode is solved to optimize the electrode geometry and the power supplies. Large acceleration efficiency of 34% is to be obtained with 3.2 m long conical accelerator and 40 kV - 42 kJ power supply. The operation scenario of a CT injector named SPICA mk. I (SPheromak Injector using Conical Accelerator) consisting of 0.8 m conical accelerator is discussed based on this design. (author)

Time resolution measurements with an improved discriminator and conical scintillators

International Nuclear Information System (INIS)

McGervey, J.D.; Vogel, J.; Sen, P.; Knox, C.

1977-01-01

A new constant fraction discriminator with improved stability and walk characteristics is described. The discriminator was used with RCA C31024 photomultiplier tubes to test scintillators of conical and cylindrical shapes. Conical scintillators of 2.54 cm base diameter, 1.0 cm top diameter, and 2.54 cm height gave a fwhm of 155 ps for 60 Co gamma rays; larger conical scintillators gave an improvement of 10-15% in fwhm over cylindrical scintillators of equal volume. (Auth.)

Conical Double Frequency Emission by Femtosecond Laser Pulses from DKDP

International Nuclear Information System (INIS)

Xi-Peng, Zhang; Hong-Bing, Jiang; Shan-Chun, Tang; Qi-Huang, Gong

2009-01-01

Conical double frequency emission is investigated by femtosecond laser pulses at a wavelength of 800 nm in a DKDP crystal. It is demonstrated that the sum frequency of incident wave and its scattering wave accounts for the conical double frequency emission. The gaps on the conical rings are observed and they are very sensitive to the propagation direction, and thus could be used to detect the small angle deviation of surface direction. (fundamental areas of phenomenology (including applications))

RECIPES FOR BUILDING THE DUAL OF CONIC OPTIMIZATION PROBLEM

Directory of Open Access Journals (Sweden)

Diah Chaerani

2010-08-01

Full Text Available Building the dual of the primal problem of Conic Optimization (CO isa very important step to make the ¯nding optimal solution. In many cases a givenproblem does not have the simple structure of CO problem (i.e., minimizing a linearfunction over an intersection between a±ne space and convex cones but there areseveral conic constraints and sometimes also equality constraints. In this paper wedeal with the question how to form the dual problem in such cases. We discuss theanswer by considering several conic constraints with or without equality constraints.The recipes for building the dual of such cases is formed in standard matrix forms,such that it can be used easily on the numerical experiment. Special attention isgiven to dual development of special classes of CO problems, i.e., conic quadraticand semide¯nite problems. In this paper, we also brie°y present some preliminariestheory on CO as an introduction to the main topic

Ultrafast X-Ray Spectroscopy of Conical Intersections

Science.gov (United States)

Neville, Simon P.; Chergui, Majed; Stolow, Albert; Schuurman, Michael S.

2018-06-01

Ongoing developments in ultrafast x-ray sources offer powerful new means of probing the complex nonadiabatically coupled structural and electronic dynamics of photoexcited molecules. These non-Born-Oppenheimer effects are governed by general electronic degeneracies termed conical intersections, which play a key role, analogous to that of a transition state, in the electronic-nuclear dynamics of excited molecules. Using high-level ab initio quantum dynamics simulations, we studied time-resolved x-ray absorption (TRXAS) and photoelectron spectroscopy (TRXPS) of the prototypical unsaturated organic chromophore, ethylene, following excitation to its S2(π π*) state. The TRXAS, in particular, is highly sensitive to all aspects of the ensuing dynamics. These x-ray spectroscopies provide a clear signature of the wave packet dynamics near conical intersections, related to charge localization effects driven by the nuclear dynamics. Given the ubiquity of charge localization in excited state dynamics, we believe that ultrafast x-ray spectroscopies offer a unique and powerful route to the direct observation of dynamics around conical intersections.

Generation of attosecond electron packets via conical surface plasmon electron acceleration

Science.gov (United States)

Greig, S. R.; Elezzabi, A. Y.

2016-01-01

We present a method for the generation of high kinetic energy attosecond electron packets via magnetostatic and aperture filtering of conical surface plasmon (SP) accelerated electrons. The conical SP waves are excited by coupling an ultrafast radially polarized laser beam to a conical silica lens coated with an Ag film. Electromagnetic and particle tracking models are employed to characterize the ultrafast electron packets. PMID:26764129

Conical wavefronts in optics and tomography

International Nuclear Information System (INIS)

Soroko, L.M.

1990-01-01

A wide range of techniques in which the information is transferred by conical (nonspherical and nonplanar) wave fronts is considered. This is the first summary of papers published in the field of mesooptics and optical tomography. After the introduction into the new branch of modern optics - mesooptics -the properties of conical wavefronts are treated in detail. Some possible applications of mesooptics in science and technology are considered. The long history of mesooptics treated in the last chapter of this review lecture goes from the early stage of our Universe, gravitational lens, first publications in the last century and up-to-date innovations in optics, mesooptics and optical tomography. 3 refs

Three-dimensional particle tracking in concave structures made by ultraviolet nanoimprint via total internal reflection fluorescence microscopy and refractive-index-matching method

Science.gov (United States)

Fujinami, Taku; Kigami, Hiroshi; Unno, Noriyuki; Taniguchi, Jun; Satake, Shin-ichi

2018-03-01

Total internal reflection fluorescence microscopy (TIRFM) is a promising method for measuring fluid flow close to a wall with nanoscale resolution in a process that is termed "multilayer nanoparticle image velocimetry" (MnPIV). TIRFM uses evanescent light that is generated on a substrate (typically a glass slide) by total internal reflection of light. Many researchers have previously studied x-y-z (3D) flows of water close to flat glass slides using MnPIV. On the other hand, a fluid flow close to a structured surface is also important. To measure flows of water near micro-patterns, we previously developed an MnPIV technique that uses a refractive-index-matching method. In previous study, the micropattern is made of a thermoplastic material with a refractive index that closely matches that of water. In this study, ultraviolet nanoimprint lithography was used for fabricating the appropriate micro-patterns because this technique can fabricate a pattern with a high resolution. As a result, we succeeded in performing MnPIV in water with a circular hole array pattern made by ultraviolet nanoimprint using a refractive-index-matching method. We believe that this technique will be helpful in elucidating fluid flows around microstructures.

Elaboration of the technology of forming a conical product of sheet metal

Directory of Open Access Journals (Sweden)

W. Matysiak

2010-01-01

Full Text Available The work presents a general knowledge about spinning draw pieces of sheets, one of multi-operational processes of spinning a sheet metal conical product without machining. The objective of the work was to elaborate both the technology of forming conical products of sheet metal and execution of technological tests as well as to determine the technological parameters for the process of spinning a conical insert. As a result of the investigations, the products with improved mechanical properties, stricter execution tolerance and low roughness have been obtained. The series of 200 prototype conical inserts for the shipbuilding industry have been made.

Black hole thermodynamics with conical defects

Energy Technology Data Exchange (ETDEWEB)

Appels, Michael [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Gregory, Ruth [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Perimeter Institute,31 Caroline Street North, Waterloo, ON, N2L 2Y5 (Canada); Kubiznák, David [Perimeter Institute,31 Caroline Street North, Waterloo, ON, N2L 2Y5 (Canada)

2017-05-22

Recently we have shown https://www.doi.org/10.1103/PhysRevLett.117.131303 how to formulate a thermodynamic first law for a single (charged) accelerated black hole in AdS space by fixing the conical deficit angles present in the spacetime. Here we show how to generalise this result, formulating thermodynamics for black holes with varying conical deficits. We derive a new potential for the varying tension defects: the thermodynamic length, both for accelerating and static black holes. We discuss possible physical processes in which the tension of a string ending on a black hole might vary, and also map out the thermodynamic phase space of accelerating black holes and explore their critical phenomena.

"Conical Hut": A Basic Form of House Types in Timor Island

Science.gov (United States)

Chen, Y. R.; Lim, Y. L.; Wang, M. H.; Chen, C. Y.

2015-08-01

Timor Island situates in the southeast end of Southeast Asia. The island accommodates many ethnic groups, which produce many diverse house types. As visiting East Timor in 2012 and Timor Island in 2014, we found the "Pair- House Type" widely spread over Timor Island. Uma Lulik (holy house), accommodating the ancestry soul, fireplace and elder's bed, and Uma Tidor (house for sleep), containing living, sleeping and working space, compose the pair-house. The research team visited 14 ethnic groups and their houses, some of which were measured and drawn into 3D models as back to Taiwan. Uma Tidors of each ethnic group are quite similar with rectangular volume and hip roof, however, one of the fourteen ethnic groups can build cylinder houses for Uma Tidor. Uma Luliks of different ethnic groups are diversified and special. One group of the Uma Luliks shows a rectangular or square volume sheltered by a hip roof. The other group of Uma Luliks presents a non-specific volume under a conical roof, that we called the "conical hut". Seven ethnic groups, Atoni, Weimua, Makassae, Mambai, Bunaq, Kemak and Bekais, have built "conical huts" for the use of Uma Lulik. People of the seven ethnic groups can construct a reasonable structural system to support the conical roof, and take good advantage of the space under the conical roof to meet their sacred needs and everyday life. "Conical Hut" may be regarded as the basic form of the house types adopted by the seven ethnic groups. It contains the basic spatial limits and the formal properties that the construction systems have to follow. Based on the concise rules of the basic form, people of each ethnic group use their talents, skills and building materials to generate variations of "conical hut", which are different in house scale, spatial layout, construction system and form. The "conical huts" contain the consistency that all the huts come from the basic form, meanwhile, they also present the diversification that each conical hut has

"Conical Hut": A Basic Form of House Types in Timor Island

Directory of Open Access Journals (Sweden)

Y. R. Chen

2015-08-01

Full Text Available Timor Island situates in the southeast end of Southeast Asia. The island accommodates many ethnic groups, which produce many diverse house types. As visiting East Timor in 2012 and Timor Island in 2014, we found the “Pair- House Type” widely spread over Timor Island. Uma Lulik (holy house, accommodating the ancestry soul, fireplace and elder’s bed, and Uma Tidor (house for sleep, containing living, sleeping and working space, compose the pair-house. The research team visited 14 ethnic groups and their houses, some of which were measured and drawn into 3D models as back to Taiwan. Uma Tidors of each ethnic group are quite similar with rectangular volume and hip roof, however, one of the fourteen ethnic groups can build cylinder houses for Uma Tidor. Uma Luliks of different ethnic groups are diversified and special. One group of the Uma Luliks shows a rectangular or square volume sheltered by a hip roof. The other group of Uma Luliks presents a non-specific volume under a conical roof, that we called the “conical hut”. Seven ethnic groups, Atoni, Weimua, Makassae, Mambai, Bunaq, Kemak and Bekais, have built “conical huts” for the use of Uma Lulik. People of the seven ethnic groups can construct a reasonable structural system to support the conical roof, and take good advantage of the space under the conical roof to meet their sacred needs and everyday life. “Conical Hut” may be regarded as the basic form of the house types adopted by the seven ethnic groups. It contains the basic spatial limits and the formal properties that the construction systems have to follow. Based on the concise rules of the basic form, people of each ethnic group use their talents, skills and building materials to generate variations of “conical hut”, which are different in house scale, spatial layout, construction system and form. The “conical huts” contain the consistency that all the huts come from the basic form, meanwhile, they also present

Black and gray Helmholtz-Kerr soliton refraction

International Nuclear Information System (INIS)

Sanchez-Curto, Julio; Chamorro-Posada, Pedro; McDonald, Graham S.

2011-01-01

Refraction of black and gray solitons at boundaries separating different defocusing Kerr media is analyzed within a Helmholtz framework. A universal nonlinear Snell's law is derived that describes gray soliton refraction, in addition to capturing the behavior of bright and black Kerr solitons at interfaces. Key regimes, defined by beam and interface characteristics, are identified, and predictions are verified by full numerical simulations. The existence of a unique total nonrefraction angle for gray solitons is reported; both internal and external refraction at a single interface is shown possible (dependent only on incidence angle). This, in turn, leads to the proposal of positive or negative lensing operations on soliton arrays at planar boundaries.

Displacement of screw-retained single crowns into implants with conical internal connections.

Science.gov (United States)

Yilmaz, Burak; Seidt, Jeremy D; McGlumphy, Edwin A; Clelland, Nancy L

2013-01-01

Internal conical implant-abutment connections without platforms may lead to axial displacement of crowns during screw tightening. This displacement may affect proximal contacts, incisal edge position, or occlusion. This study aimed to measure the displacement of screw-retained single crowns into an implant in three dimensions during screw tightening by hand or via torque driver. A stereolithic acrylic resin cast was created using computed tomography data from a patient missing the maxillary right central incisor. A 4.0- × 11-mm implant was placed in the edentulous site. Five porcelain-fused-to-metal single crowns were made using "cast-to" abutments. Crowns were tried on the stereolithic model, representing the patient, and hand tightened. The spatial relationship of crowns to the model after hand tightening was determined using three-dimensional digital image correlation (3D DIC), an optical measurement technique. The crowns were then tightened using a torque driver to 20 Ncm and the relative crown positions were again recorded. Testing was repeated three times for each crown, and displacement of the crowns was compared between the hand-tightened and torqued states. Commercial image correlation software was used to analyze the data. Mean vertical and horizontal crown displacement values were calculated after torqueing. The interproximal contacts were evaluated before and after torquing using an 8-μm aluminum foil shim. There were vertical and horizontal differences in crown positions between hand tightening and torqueing. Although these were small in magnitude, detectable displacements occurred in both apical and facial directions. After hand tightening, the 8-μm shim could be dragged without tearing. However, after torque tightening, the interproximal contacts were too tight and the 8-μm shim could not be dragged without tearing. Differences between hand tightening and torque tightening should be taken into consideration during laboratory and clinical

SAR Observation and Numerical Simulation of Internal Solitary Wave Refraction and Reconnection Behind the Dongsha Atoll

Science.gov (United States)

Jia, T.; Liang, J. J.; Li, X.-M.; Sha, J.

2018-01-01

The refraction and reconnection of internal solitary waves (ISWs) around the Dongsha Atoll (DSA) in the northern South China Sea (SCS) are investigated based on spaceborne synthetic aperture radar (SAR) observations and numerical simulations. In general, a long ISW front propagating from the deep basin of the northern SCS splits into northern and southern branches when it passes the DSA. In this study, the statistics of Envisat Advanced SAR (ASAR) images show that the northern and southern wave branches can reconnect behind the DSA, but the reconnection location varies. A previously developed nonlinear refraction model is set up to simulate the refraction and reconnection of the ISWs behind the DSA, and the model is used to evaluate the effects of ocean stratification, background currents, and incoming ISW characteristics at the DSA on the variation in reconnection locations. The results of the first realistic simulation agree with consecutive TerraSAR-X (TSX) images captured within 12 h of each other. Further sensitivity simulations show that ocean stratification, background currents, and initial wave amplitudes all affect the phase speeds of wave branches and therefore shift their reconnection locations while shapes and locations of incoming wave branches upstream of the DSA profoundly influence the subsequent propagation paths. This study clarifies the variation in reconnection locations of ISWs downstream of the DSA and reveals the important mechanisms governing the reconnection process, which can improve our understanding of the propagation of ISWs near the DSA.

''Electron Conic'' Signatures observed in the nightside auroral zone and over the polar cap

International Nuclear Information System (INIS)

Menietti, J.D.; Burch, J.L.

1985-01-01

A preliminary search of the Dynamics Explorer 1 high-altitude plasma instrument data base has yielded examples of ''electron conic'' signatures. The three example passes show an association with regions of downward electron acceleration and upward ion beams, but this is not true of all the electron conic events. The electron conic signatures are clearly discernible on energy-flux-versus-time color spectrograms as pairs of discrete vertical bands which are symmetric about a pitch angle of approximately 180 0 . One of the examples is a polar cap pass with electron conic signatures observed at invariant latitudes from 84 0 to 75 0 . The other two cases are nightside auroral zone passes in which the regions of detectable electron conics are spatially more confined, covering only about 1 0 in invariant latitude. The conic signatures have been found at energies that range from 50 eV 0 is larger than expected for a loss cone feature. If the electrons conserve the first adiabatic invariant in a dipole magnetic field, and in some cases a parallel electric field, the mirroring altitude varies between about 500 km and 8000 km, which is above the atmospheric loss region. For this reason, and in analogy with the formation of ion conics, we suggest that the conic signatures are produced by heating of the electrons perpendicular to the magnetic field

Performance Optimization of a Conical Dielectric Elastomer Actuator

Directory of Open Access Journals (Sweden)

Chongjing Cao

2018-06-01

Full Text Available Dielectric elastomer actuators (DEAs are known as ‘artificial muscles’ due to their large actuation strain, high energy density and self-sensing capability. The conical configuration has been widely adopted in DEA applications such as bio-inspired locomotion and micropumps for its good compactness, ease for fabrication and large actuation stroke. However, the conical protrusion of the DEA membrane is characterized by inhomogeneous stresses, which complicate their design. In this work, we present an analytical model-based optimization for conical DEAs with the three biasing elements: (I linear compression spring; (II biasing mass; and (III antagonistic double-cone DEA. The optimization is to find the maximum stroke and work output of a conical DEA by tuning its geometry (inner disk to outer frame radius ratio a/b and pre-stretch ratio. The results show that (a for all three cases, stroke and work output are maximum for a pre-stretch ratio of 1 × 1 for the Parker silicone elastomer, which suggests the stretch caused by out-of-plane deformation is sufficient for this specific elastomer. (b Stroke maximization is obtained for a lower a/b ratio while a larger a/b ratio is required to maximize work output, but the optimal a/b ratio is less than 0.3 in all three cases. (c The double-cone configuration has the largest stroke while single cone with a biasing mass has the highest work output.

Thermokinetics of heterogeneous droplet nucleation on conically textured substrates.

Science.gov (United States)

Singha, Sanat K; Das, Prasanta K; Maiti, Biswajit

2015-11-28

Within the framework of the classical theory of heterogeneous nucleation, a thermokinetic model is developed for line-tension-associated droplet nucleation on conical textures considering growth or shrinkage of the formed cluster due to both interfacial and peripheral monomer exchange and by considering different geometric configurations. Along with the principle of free energy extremization, Katz kinetic approach has been employed to study the effect of substrate conicity and wettability on the thermokinetics of heterogeneous water droplet nucleation. Not only the peripheral tension is found to have a considerable effect on the free energy barrier but also the substrate hydrophobicity and hydrophilicity are observed to switch over their roles between conical crest and trough for different growth rates of the droplet. Besides, the rate of nucleation increases and further promotes nucleation for negative peripheral tension as it diminishes the free energy barrier appreciably. Moreover, nucleation inhibition can be achievable for positive peripheral tension due to the enhancement of the free energy barrier. Analyzing all possible geometric configurations, the hydrophilic narrower conical cavity is found to be the most preferred nucleation site. These findings suggest a physical insight into the context of surface engineering for the promotion or the suppression of nucleation on real or engineered substrates.

Experimental conical-head abutment screws on the microbial leakage through the implant-abutment interface: an in vitro analysis using target-specific DNA probes.

Science.gov (United States)

Pita, Murillo S; do Nascimento, Cássio; Dos Santos, Carla G P; Pires, Isabela M; Pedrazzi, Vinícius

2017-07-01

The aim of this in vitro study was to identify and quantify up to 38 microbial species from human saliva penetrating through the implant-abutment interface in two different implant connections, external hexagon and tri-channel internal connection, both with conventional flat-head or experimental conical-head abutment screws. Forty-eight two-part implants with external hexagon (EH; n = 24) or tri-channel internal (TI; n = 24) connections were investigated. Abutments were attached to implants with conventional flat-head or experimental conical-head screws. After saliva incubation, Checkerboard DNA-DNA hybridization was used to identify and quantify up to 38 bacterial colonizing the internal parts of the implants. Kruskal-Wallis test followed by Bonferroni's post-tests for multiple comparisons was used for statistical analysis. Twenty-four of thirty-eight species, including putative periodontal pathogens, were found colonizing the inner surfaces of both EH and TI implants. Peptostreptococcus anaerobios (P = 0.003), Prevotella melaninogenica (P abutment screws have impacted the microbial leakage through the implant-abutment interface. Implants attached with experimental conical-head abutment screws showed lower counts of microorganisms when compared with conventional flat-head screws. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Modification of Low Refractive Index Polycarbonate for High Refractive Index Applications

Directory of Open Access Journals (Sweden)

Gunjan Suri

2009-01-01

Full Text Available Polycarbonates and polythiourethanes are the most popular materials in use today, for optical applications. Polycarbonates are of two types which fall in the category of low refractive index and medium refractive index. The present paper describes the conversion of low refractive index polycarbonates into high refractive index material by the use of a high refractive index monomer, polythiol, as an additive. Novel polycarbonates, where the properties of refractive index and Abbe number can be tailor made, have been obtained. Thermal studies and refractive index determination indicate the formation of a new polymer with improved properties and suitable for optical applications.

The influence of initial pressure on the characteristics of conical bubble sonoluminescence

Energy Technology Data Exchange (ETDEWEB)

He, Shoujie, E-mail: heshouj@hbu.edu.cn [Hebei Key Laboratory of Optic-electronic Information and Materials, College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Ha, Jing [Institute of Science, Hebei Agriculture University, Baoding 071001 (China); Duan, Pingguang [Hebei Key Laboratory of Optic-electronic Information and Materials, College of Physics Science and Technology, Hebei University, Baoding 071002 (China)

2015-12-18

Based on a conical bubble U-tube, conical bubble sonoluminescence was investigated by using pure water as the working medium. Intense cavitation luminescence can be obtained. With the decrease in initial pressure inside the bubble, the intensity and duration of light emission increased. The spectrum is mainly composed of the spectral bands of H{sub 2}O at the initial pressure of 1000 Pa. With the decrease in initial pressure, a broad continuum background spectrum that is well fitted by blackbody radiation can be detected, on which several spectral bands emitted by water molecules are superimposed. A higher temperature inside the bubble can be obtained with the decrease in initial pressure. Moreover, the intensity of the continuum background spectrum becomes more dominant compared with that of H{sub 2}O emission bands. Finally, we conclude that blackbody radiation and molecular emission contribute to luminescence of conical bubble cavitation. Moreover, the initial pressure inside the conical bubble significantly affects the emission mechanism of conical bubble sonoluminescence. - Highlights: • The spectra and light pulses of CBL are investigated in pure water. • The continuum background spectrum becomes more dominant with decrease of initial pressure. • The mechanism of CBL depends on the initial pressure of bubble. • Blackbody radiation and molecular emission contribute to luminescence of conical bubble cavitation.

A new design equation for drained stability of conical slopes in cohesive-frictional soils

Directory of Open Access Journals (Sweden)

Boonchai Ukritchon

2018-04-01

Full Text Available New plasticity solutions to the drained stability of conical slopes in homogeneous cohesive-frictional soils were investigated by axisymmetric finite element limit analysis. Three parameters were studied, i.e. excavated height ratios, slope inclination angles, and soil friction angles. The influences of these parameters on the stability factor and predicted failure mechanism of conical slopes were discussed. A new design equation developed from a nonlinear regression of the lower bound solution was proposed for drained stability analyses of a conical slope in practice. Numerical examples were given to demonstrate a practical application of the proposed equation to stability evaluations of conical slopes with both associated and non-associated flow rules. Keywords: Limit analysis, Slope stability, Conical slope, Unsupported excavation, Cohesive-frictional soils

Analysis of spatial dispersion characteristics of improved conical sprays; Kairyo kasajo funmu no kukan bunsansei no kento

Energy Technology Data Exchange (ETDEWEB)

Long, W; Murakami, A; Hama, J [Mechanical Engineering Lab., Tokyo (Japan); Obokata, T [Gunma University, Gunma (Japan)

1997-10-01

The macro-characteristics of conical and improved conical sprays were analyzed using laser sheet and high speed camera. The injection pressure was 14.7, 24.5 or 34.3 MPa and the chamber pressure was 0.098, 0.98 or 1.96 MPa, where the amount of injected fuel was 28.5 mg per cycle, and the injection frequency was 8.3 Hz. As a result, at atmospheric pressure, both of the conical spray and improved conical spray have a conical pattern, but at high chamber pressure, the sprays become three dimensional. The penetration of the improved conical spray was about 25% stronger than that of the conical spray. 10 refs., 11 figs.

Soft Computing Technique and Conventional Controller for Conical Tank Level Control

Directory of Open Access Journals (Sweden)

Sudharsana Vijayan

2016-03-01

Full Text Available In many process industries the control of liquid level is mandatory. But the control of nonlinear process is difficult. Many process industries use conical tanks because of its non linear shape contributes better drainage for solid mixtures, slurries and viscous liquids. So, control of conical tank level is a challenging task due to its non-linearity and continually varying cross-section. This is due to relationship between controlled variable level and manipulated variable flow rate, which has a square root relationship. The main objective is to execute the suitable controller for conical tank system to maintain the desired level. System identification of the non-linear process is done using black box modelling and found to be first order plus dead time (FOPDT model. In this paper it is proposed to obtain the mathematical modelling of a conical tank system and to study the system using block diagram after that soft computing technique like fuzzy and conventional controller is also used for the comparison.

Calculation of plastic deformation of a conical shell with the transformation of inner surface into outer one

Directory of Open Access Journals (Sweden)

A. I. Uvarov

2014-01-01

Full Text Available An analytical model of plastic deformation of a conical shell with the transformation of internal surface into outer one was developed with a use of the kinematic method. The shell material was assumed to be perfectly plastic. The theory of thin shells and the kinematic theorem of limit equilibrium were utilized in this work. Both geometric and physical nonlinearities were taken into account. Dependences for calculating radius of curvature of the intensive deformation zones, value of chain ring deformation and values of the deforming force as a function of axial displacement were determined. Analysis showed the possibility of using a conical shell to absorb energy with high efficiency. Obtained results could be used for calculation and selection of optimal parameters of the energy-absorbing elements in shock absorbers.

GPM GROUND VALIDATION CONICAL SCANNING MILLIMETER-WAVE IMAGING RADIOMETER (COSMIR) GCPEX V1

Data.gov (United States)

National Aeronautics and Space Administration — The GPM Ground Validation Conical Scanning Millimeter-wave Imaging Radiometer (COSMIR) GCPEx dataset used the Conical Scanning Millimeter-wave Imaging Radiometer...

Manufacture of conical springs with elastic medium technology improvement

Science.gov (United States)

Kurguzov, S. A.; Mikhailova, U. V.; Kalugina, O. B.

2018-01-01

This article considers the manufacturing technology improvement by using an elastic medium in the stamping tool forming space to improve the conical springs performance characteristics and reduce the costs of their production. Estimation technique of disk spring operational properties is developed by mathematical modeling of the compression process during the operation of a spring. A technique for optimizing the design parameters of a conical spring is developed, which ensures a minimum voltage value when operated in the edge of the spring opening.

Hole Feature on Conical Face Recognition for Turning Part Model

Science.gov (United States)

Zubair, A. F.; Abu Mansor, M. S.

2018-03-01

Computer Aided Process Planning (CAPP) is the bridge between CAD and CAM and pre-processing of the CAD data in the CAPP system is essential. For CNC turning part, conical faces of part model is inevitable to be recognised beside cylindrical and planar faces. As the sinus cosines of the cone radius structure differ according to different models, face identification in automatic feature recognition of the part model need special intention. This paper intends to focus hole on feature on conical faces that can be detected by CAD solid modeller ACIS via. SAT file. Detection algorithm of face topology were generated and compared. The study shows different faces setup for similar conical part models with different hole type features. Three types of holes were compared and different between merge faces and unmerge faces were studied.

Generation of fast multiply charged ions in conical targets

International Nuclear Information System (INIS)

Demchenko, V.V.; Chukbar, K.V.

1990-01-01

So-called conical targets, when the thermonuclear fuel is compressed and heated in a conical cavity in a heavy material (lead, gold, etc.) with the help of a spherical segment that is accelerated by a laser pulse or a beam of charged particles, are often employed in experimental studies of inertial-confinement fusion. In spite of the obvious advantages of such a scheme, one of which is a significant reduction of the required energy input compared with the complete spherical target, it also introduces additional effects into the process of cumulation of energy. In this paper the authors call attention to an effect observed in numerical calculations: the hydrodynamic heating of a small group of multiply charged heavy ions of the walls of the conical cavity up to high energies (T i approx-gt 100 keV). This effect ultimately occurs as a result of the high radiation losses of a multiply charged plasma

Performance of cylindrical-conical cyclones with different geometrical configurations

Directory of Open Access Journals (Sweden)

J.D.A.M. Santana

2001-09-01

Full Text Available The present work is a continuation of a study of the influence of geometric characteristics on the performance of reverse-flow cylindrical-conical cyclones. After studying the behavior of the pressure drop in previous work (Arnosti et al., 1998, here performance in terms of collection efficiency in the removal of particulate material is addressed. The independent variables considered in this study were inlet gas velocity (three velocities and the following dimensions of the cyclone: the cylindrical section (three heights and internal height of the gas exit duct (three heights. The tests were performed using an 3³ experimental design. Analysis of the results for overall efficiency was carried out using response surfaces and the statistical parameters were estimated from linear regression.

Change of Pressing Chamber Conicalness at Briquetting Process in Briquetting Machine Pressing Chamber

Directory of Open Access Journals (Sweden)

Peter Križan

2012-01-01

Full Text Available In this paper, we will present the impact of the conical shape of a pressing chamber, an important structural parameter. Besides the known impact of the technological parameters of pressing chambers, it is also very important to pay attention to their structural parameters. In the introduction, we present a theoretical analysis of pressing chamber conicalness. An experiment aimed at detecting this impact was performed at our institute, and it showed that increasing the conicalness of a pressing chamber improves the quality of the final briquettes. The conicalness of the pressing chamber has a significanteffect on the final briquette quality and on the construction of briquetting machines. The experimental findings presented here show the importance of this parameter in the briquetting process.

Investigation of turbulence measurements with a continuous wave, conically scanning LiDAR

DEFF Research Database (Denmark)

Wagner, Rozenn; Mikkelsen, Torben; Courtney, Michael

averaging is done in two steps: 1) the weighted averaging of the wind speed in the probe volume of the laser beam; 2) the averaging of the wind speeds occurring on the circular path described by the conically scanning lidar. Therefore the standard deviation measured by a lidar resolves only the turbulence...... of a continuous wave, conically scanning Zephir lidar. First, the wind speed standard deviation measured by such a lidar gives on average 80% of the standard deviation measured by a cup anemometer. This difference is due to the spatial averaging inherently made by a cw conically scanning lidar. The spatial...

Randomized intubation with polyurethane or conical cuffs to prevent pneumonia in ventilated patients.

Science.gov (United States)

Philippart, François; Gaudry, Stéphane; Quinquis, Laurent; Lau, Nicolas; Ouanes, Islem; Touati, Samia; Nguyen, Jean Claude; Branger, Catherine; Faibis, Frédéric; Mastouri, Maha; Forceville, Xavier; Abroug, Fekri; Ricard, Jean Damien; Grabar, Sophie; Misset, Benoît

2015-03-15

The occurrence of ventilator-associated pneumonia (VAP) is linked to the aspiration of contaminated pharyngeal secretions around the endotracheal tube. Tubes with cuffs made of polyurethane rather than polyvinyl chloride or with a conical rather than a cylindrical shape increase tracheal sealing. To test whether using polyurethane and/or conical cuffs reduces tracheal colonization and VAP in patients with acute respiratory failure. We conducted a multicenter, prospective, open-label, randomized study in four parallel groups in four intensive care units between 2010 and 2012. A cohort of 621 patients with expected ventilation longer than 2 days was included at intubation with a cuff composed of cylindrical polyvinyl chloride (n = 148), cylindrical polyurethane (n = 143), conical polyvinyl chloride (n = 150), or conical polyurethane (n = 162). We used Kaplan-Meier estimates and log-rank tests to compare times to events. After excluding 17 patients who secondarily refused participation or had met an exclusion criterion, 604 were included in the intention-to-treat analysis. Cumulative tracheal colonization greater than 10(3) cfu/ml at Day 2 was as follows (median [interquartile range]): cylindrical polyvinyl chloride, 0.66 (0.58-0.74); cylindrical polyurethane, 0.61 (0.53-0.70); conical polyvinyl chloride, 0.67 (0.60-0.76); and conical polyurethane, 0.62 (0.55-0.70) (P = 0.55). VAP developed in 77 patients (14.4%), and postextubational stridor developed in 28 patients (6.4%) (P = 0.20 and 0.28 between groups, respectively). Among patients requiring mechanical ventilation, polyurethane and/or conically shaped cuffs were not superior to conventional cuffs in preventing tracheal colonization and VAP. Clinical trial registered with clinicaltrials.gov (NCT01114022).

Atmosphere Refraction Effects in Object Locating for Optical Satellite Remote Sensing Images

Directory of Open Access Journals (Sweden)

YAN Ming

2015-09-01

Full Text Available The collinear rigorous geometric model contains the atmosphere refraction geometric error in off-nadir observation. In order to estimate and correct the atmosphere refraction geometric error, the ISO international standard atmospheric model and Owens atmosphere refractive index algorithm are applied to calculate the index of atmosphere refraction in different latitude and altitude. The paper uses the weighted mean algorithm to reduce the eight layers ISO standard atmospheric model into a simple troposphere and stratosphere two layers spherical atmosphere. And the LOS vector track geometric algorithm is used to estimate the atmosphere refraction geometric error in different observation off-nadir angle. The results show that the atmosphere refraction will introduce about 2.5 m or 9 m geometric displacement in 30 or 45 degree off-nadir angle individual. Therefore, during geo-location processing of agile platform and extra wide high spatial resolution imagery, there is need to take into account the influence of atmosphere refraction and correct the atmosphere refraction geometric error to enhance the geo-location precision without GCPs.

Effective spectral densities for system-environment dynamics at conical intersections: S{sub 2}-S{sub 1} conical intersection in pyrazine

Energy Technology Data Exchange (ETDEWEB)

Martinazzo, Rocco [Department of Physical Chemistry and Electrochemistry, University of Milan, Via Golgi 19, 20122 Milan (Italy); Hughes, Keith H. [School of Chemistry, Bangor University, Bangor, Gwynedd LL57 2UW (United Kingdom); Martelli, Fausto [Department of Physical Chemistry and Electrochemistry, University of Milan, Via Golgi 19, 20122 Milan (Italy); Departement de Chimie, Ecole Normale Superieure, 24 rue Lhomond, F-75231 Paris cedex 05 (France); Burghardt, Irene, E-mail: irene.burghardt@ens.fr [Departement de Chimie, Ecole Normale Superieure, 24 rue Lhomond, F-75231 Paris cedex 05 (France)

2010-11-25

Graphical abstract: The effect of high-dimensional environments on conical intersections can be described by hierarchies of approximate spectral densities, which translate to truncated effective-mode chains in the time domain. Abstract: A recently developed effective-mode representation is employed to characterize the influence of a multi-dimensional environment on the S{sub 2}-S{sub 1} conical intersection in pyrazine, taken as a paradigm case of high-dimensional dynamics at a conical intersection. We consider a simplified model by which four modes are strongly coupled to the electronic subsystem while a number of weakly coupled tuning modes, inducing energy gap fluctuations, are sampled from a spectral density. The latter is approximated by a series of simplified spectral densities which can be cast into a continued-fraction form, as previously demonstrated in Hughes et al. (K.H. Hughes, C.D. Christ, I. Burghardt, J. Chem. Phys. 131 (2009) 124108). In the time domain, the hierarchy of spectral densities translates to truncated effective-mode chains with a Markovian or quasi-Markovian (Rubin type) closure. A sequential deconvolution procedure is employed to generate this chain representation. The implications for the ultrafast dynamics and its representation in terms of reduced-dimensional models are discussed.

Conical diffraction as a versatile building block to implement new imaging modalities for superresolution in fluorescence microscopy

Science.gov (United States)

Fallet, Clément; Caron, Julien; Oddos, Stephane; Tinevez, Jean-Yves; Moisan, Lionel; Sirat, Gabriel Y.; Braitbart, Philippe O.; Shorte, Spencer L.

2014-08-01

We present a new technology for super-resolution fluorescence imaging, based on conical diffraction. Conical diffraction is a linear, singular phenomenon taking place when a polarized beam is diffracted through a biaxial crystal. The illumination patterns generated by conical diffraction are more compact than the classical Gaussian beam; we use them to generate a super-resolution imaging modality. Conical Diffraction Microscopy (CODIM) resolution enhancement can be achieved with any type of objective on any kind of sample preparation and standard fluorophores. Conical diffraction can be used in multiple fashion to create new and disruptive technologies for super-resolution microscopy. This paper will focus on the first one that has been implemented and give a glimpse at what the future of microscopy using conical diffraction could be.

Comparison of objective refraction in darkness to cycloplegic refraction: a pilot study.

Science.gov (United States)

Vasudevan, Balamurali; Ciuffreda, Kenneth J; Meehan, Kelly; Grk, Dejana; Cox, Misty

2016-03-01

The aim was to assess non-cycloplegic objective refraction in darkness using an open-field auto-refractor, and furthermore to compare it with distance cycloplegic subjective refraction and distance cycloplegic retinoscopy in the light, in children and young adults. Twenty-three, visually-normal, young-adults (46 eyes) ages 23 to 31 years, and five children (10 eyes) ages five to 12 years, participated in the study. The spherical component of their refraction ranged from -2.25 D to +3.75 D with a mean of +1.80 D, and a mean cylinder of -0.70 D. Three techniques were used to assess refractive error. An objective measure of the non-cycloplegic refractive state was obtained using an open-field autorefractor (WAM-5500) after five minutes in the dark to allow for dissipation of accommodative transients and relaxation of accommodation. In addition, both distance retinoscopy and subjective distance refraction were performed following cycloplegia (Cyclopentolate, 1%) using conventional clinical procedures. All measurements were obtained on the same day within a single session. The spherical component of the refraction was compared among the three techniques in both the children and adults. There was no significant difference in spherical refraction among the three techniques: non-cycloplegic objective refraction in the dark, distance cycloplegic retinoscopy and distance cycloplegic subjective refraction, in either the adults [F(2, 137) = 0.79, p = 0.45] or the children [F(2, 27) = 0.47, p = 0.62]. Mean difference in the spherical component between refraction in the dark and the cycloplegic distance retinoscopy was -0.34 D (r = 0.89) in the adults and +0.14 D (r = 0.96) in the children. The mean difference in spherical component between refraction in the dark and the cycloplegic distance subjective refraction was -0.25 D (r = 0.92) in the adults and -0.05 D (r = 0.95) in the children. Comparison of the spherical refractive component between the three techniques was not

Filling a Conical Cavity

Science.gov (United States)

Nye, Kyle; Eslam-Panah, Azar

2016-11-01

Root canal treatment involves the removal of infected tissue inside the tooth's canal system and filling the space with a dense sealing agent to prevent further infection. A good root canal treatment happens when the canals are filled homogeneously and tightly down to the root apex. Such a tooth is able to provide valuable service for an entire lifetime. However, there are some examples of poorly performed root canals where the anterior and posterior routes are not filled completely. Small packets of air can be trapped in narrow access cavities when restoring with resin composites. Such teeth can cause trouble even after many years and lead the conditions like acute bone infection or abscesses. In this study, the filling of dead-end conical cavities with various liquids is reported. The first case studies included conical cavity models with different angles and lengths to visualize the filling process. In this investigation, the rate and completeness at which a variety of liquids fill the cavity were observed to find ideal conditions for the process. Then, a 3D printed model of the scaled representation of a molar with prepared post spaces was used to simulate the root canal treatment. The results of this study can be used to gain a better understanding of the restoration for endodontically treated teeth.

Handbook on semidefinite, conic and polynomial optimization

CERN Document Server

Anjos, Miguel F

2012-01-01

This book offers the reader a snapshot of the state-of-the-art in the growing and mutually enriching areas of semidefinite optimization, conic optimization and polynomial optimization. It covers theory, algorithms, software and applications.

Controlling nanowire emission profile using conical taper

DEFF Research Database (Denmark)

Gregersen, Niels; Nielsen, Torben Roland; Mørk, Jesper

2008-01-01

The influence of a conical taper on nanowire light emission is studied. For nanowires with divergent output beams, the introduction of tapers improves the emission profile and increase the collection efficiency of the detection optics....

Refractive neutron lens

International Nuclear Information System (INIS)

Petrov, P.V.; Kolchevsky, N.N.

2013-01-01

Model of the refractive neutron lens is proposed. System of N lenses acts as one thin lens with a complex refraction index n*. The maximum number N max of individual lenses for 'thick' neutron lens is calculated. Refractive neutron lens properties (resolution, focal depth) as function of resolution factor F 0 =ρbc/μ and depth of field factor dF 0 =λF 0 =λρbc/μ are calculated. It is shown that micro resolution of the refractive neutron optics is far from the wavelength in size and its open possibilities for progress in refractive neutron optics. (authors)

Experimental study of CF4 conical theta pinch plasma expanding into vacuum

International Nuclear Information System (INIS)

Pedrow, P.D.; Nasiruddin, A.M.

1989-01-01

Langmuir probe, photodiode, and optical multichannel analyzer (OMA) measurements have been made on a pulsed CF 4 conical theta pinch plasma. A cloud of CF 4 gas was puffed into a conical theta pinch coil, converted to plasma, and propelled into the vacuum region ahead of the expanding gas cloud. At a position 67 cm away from the conical theta pinch coil, the plasma arrived in separate packets that were about 20 μs in duration. The average drift velocity of these packets corresponded to an energy of about 3 eV. The OMA measurements showed that the second packet contained neutral atomic fluorine as well as charged particles

Bio-inspired multistructured conical copper wires for highly efficient liquid manipulation.

Science.gov (United States)

Wang, Qianbin; Meng, Qingan; Chen, Ming; Liu, Huan; Jiang, Lei

2014-09-23

Animal hairs are typical structured conical fibers ubiquitous in natural system that enable the manipulation of low viscosity liquid in a well-controlled manner, which serves as the fundamental structure in Chinese brush for ink delivery in a controllable manner. Here, drawing inspiration from these structure, we developed a dynamic electrochemical method that enables fabricating the anisotropic multiscale structured conical copper wire (SCCW) with controllable conicity and surface morphology. The as-prepared SCCW exhibits a unique ability for manipulating liquid with significantly high efficiency, and over 428 times greater than its own volume of liquid could be therefore operated. We propose that the boundary condition of the dynamic liquid balance behavior on conical fibers, namely, steady holding of liquid droplet at the tip region of the SCCW, makes it an excellent fibrous medium to manipulate liquid. Moreover, we demonstrate that the titling angle of the SCCW can also affect its efficiency of liquid manipulation by virtue of its mechanical rigidity, which is hardly realized by flexible natural hairs. We envision that the bio-inspired SCCW could give inspiration in designing materials and devices to manipulate liquid in a more controllable way and with high efficiency.

Supersymmetric Conical Defects: Towards a string theoretic description of black hole formation

NARCIS (Netherlands)

Balasubramanian, V.; de Boer, J.; Keski-Vakkuri, E.; Ross, S.F.

2001-01-01

Conical defects, or point particles, in $AdS_3$ are one of the simplest non-trivial gravitating systems, and are particularly interesting because black holes can form from their collision. We embed the BPS conical defects of three dimensions into the N=4b supergravity in six dimensions, which arises

Conical Perspective Image of an Architectural Object Close to Human Perception

Science.gov (United States)

Dzwierzynska, Jolanta

2017-10-01

The aim of the study is to develop a method of computer aided constructing conical perspective of an architectural object, which is close to human perception. The conical perspective considered in the paper is a central projection onto a projection surface being a conical rotary surface or a fragment of it. Whereas, the centre of projection is a stationary point or a point moving on a circular path. The graphical mapping results of the perspective representation is realized directly on an unrolled flat projection surface. The projective relation between a range of points on a line and the perspective image of the same range of points received on a cylindrical projection surface permitted to derive formulas for drawing perspective. Next, the analytical algorithms for drawing perspective image of a straight line passing through any two points were formulated. It enabled drawing a perspective wireframe image of a given 3D object. The use of the moving view point as well as the application of the changeable base elements of perspective as the variables in the algorithms enable drawing conical perspective from different viewing positions. Due to this fact, the perspective drawing method is universal. The algorithms are formulated and tested in Mathcad Professional software, but can be implemented in AutoCAD and majority of computer graphical packages, which makes drawing a perspective image more efficient and easier. The presented conical perspective representation, and the convenient method of its mapping directly on the flat unrolled surface can find application for numerous advertisement and art presentations.

Parameter dependence of conic angle of nanofibres during electrospinning

International Nuclear Information System (INIS)

Zhou Zhengping; Wu Xiangfa; Jiang Long; Gao Xueqin; Zhao Yong; Fong Hao

2011-01-01

This paper reports the dependence of conic angle of nanofibres on the processing and material parameters during electrospinning. Solutions of polyacrylonitrile (PAN) in dimethylformamide (DMF) with varied PAN concentrations were studied as the model systems, and they were electrospun into nanofibres at different high direct current (dc) voltages, flow rates and needle diameters. The dynamic and transient shear viscosities of the PAN/DMF solutions were characterized by a parallel-plate rheometer at varied shear rates. Rheological measurements showed that the PAN/DMF solutions behaved as Newtonian fluids at relatively low to medium shear rates, while the solutions with high PAN concentrations of 18 and 20 wt% exhibited a significant shear-thinning behaviour at high shear rates, especially in the case of transient shear mode. Experimental results indicated that at the electrostatic field of ∼80 kV m -1 and needle inner diameter of 0.48 mm (22 gauge), the conic angle of the nanofibre envelope decreased from ∼160° to ∼75° with an increase in PAN concentration from 12 to 20 wt%; at the PAN concentration of 16 wt%, the conic angle increased nonlinearly from ∼40° to ∼160° with an increase in electric field from 50 to 140 kV m -1 . In addition, experimental results showed that the needle inner diameter also noticeably influenced the conic angle. This study provided the experimental evidence useful for understanding the scaling properties of electrohydrodynamic jet motion for controllable electrospinning and process modelling.

Threshold pump intensity effect on the refractive index changes in InGaN SQD: Internal constitution and size effects

Energy Technology Data Exchange (ETDEWEB)

El Ghazi, Haddou, E-mail: hadghazi@gmail.com [Special Mathematics, CPGE Rabat (Morocco); LPS, Faculty of Science, Dhar El Mehrez, BP 1796 Fes-Atlas (Morocco); A John Peter [P.G. & Research Department of Physics, Goverment Arts and Science College, Melur 625106, Madurai (India)

2015-04-01

In the present paper, internal composition and size-dependent threshold pump intensity effects on on-center impurity-related linear, third-order nonlinear and total refractive index changes are investigated in wurtzite (In,Ga)N/GaN unstrained spherical quantum dot. The calculation is performed within the framework of parabolic band and single band effective-mass approximations using a combination of Quantum Genetic Algorithm (QGA) and Hartree–Fock–Roothaan (HFR) method. According to the results obtained, (i) a significant red-shift (blue shift) is obtained as the dot size (potential barrier) increases and (ii) a threshold optical pump intensity depending strongly on the size and the internal composition is obtained which constitutes the limit between two behaviors.

Self-Propulsion Of Catalytic Conical Micro-Swimmer

Science.gov (United States)

Gallino, Giacomo; Gallaire, Francois; Lauga, Eric; Michelin, Sebastien

2017-11-01

Self-propelled artificial micro-motors have attracted much attention both as fundamental examples of active matter and for their potential biomedical applications (e.g. drug delivery, cell sorting). A popular design exploits the catalytic decomposition of a fuel (e.g. hydrogen peroxide) on the active surface of the motor to produce oxygen bubbles that propel the swimmer, effectively converting chemical energy into swimming motion. We focus here on a conical shape swimmer with chemically-active inner surfaces. Using numerical simulations of the chemical problem and viscous hydrodynamics, we analyze the formation, growth and motion of the bubbles inside the micro-motor and the resulting swimming motion. Our results shed light on the fundamental hydrodynamics of the propulsion of conical swimmers and may help to improve the efficiency of these machines. G.G. aknowledges support from the Swiss National Science Fundation.

Displacement of screw-retained splinted and nonsplinted restorations into implants with conical internal connections.

Science.gov (United States)

Yilmaz, Burak; Seidt, Jeremy D; Clelland, Nancy L

2014-01-01

Variable abutment displacement could potentially affect proximal contacts, incisal edge position, or occlusion of implant-supported prostheses. This study aimed to measure and compare displacements of splinted and nonsplinted restorations into implants featuring internal conical connections as screws were tightened by hand or by torque driver. A stereolithic resin model was printed using computed tomography data from a patient missing mandibular left first and second molars. Two 5.0 × 11-mm implants were placed in the edentulous site using a surgical guide. Two sets (splinted and nonsplinted) of gold screw-retained prostheses were made indirectly to fit the implants in the stereolithic model representing the patient. The axial position of the crowns relative to a fixed location on the model was recorded following hand tightening using the three-dimensional image correlation technique and image correlation software. A pair of high-resolution digital cameras provided a synchronized view of the model during the experiment. Relative crown positions were again recorded after tightening with a torque driver to 25 Ncm. Testing was repeated randomly three times for each set of crowns. Displacement data after torque tightening were compared using a factorial analysis of variance with JMP 9.0 software (SAS) followed by a Tukey-Kramer post hoc test (α = .05). Interproximal contacts were evaluated using an 8-μm tin foil shim after tightening by hand and torque driver. Displacements for splinted and nonsplinted restorations differed only in a buccal direction. The nonsplinted crowns displaced significantly more than splinted crowns. Discernible differences were observed for the tin foil shim when dragged through proximal contacts following hand versus torque tightening. Differences between screw tightening by hand or torque driver should be taken into consideration during laboratory and clinical adjustments to prevent esthetic and functional complications.

Nonintrusive measurement of the liquid refractive index by using properties of the cuvette wall.

Science.gov (United States)

Xu, Ming; Ren, Junpeng; Miao, Runcai; Zhang, Zongquan

2016-10-01

We present a method of nonintrusive measurement of the refractive index of a liquid in a glass cuvette, which uses some optical properties of the cuvette wall and the principle of total internal reflection. By coating a transmission-scattering paint layer on the outer surface of the cuvette, we transform an incident laser beam into a transmitted scattered light. When the transmitted scattered light reaches the interface between the container wall and the liquid inside, the light beams satisfying the condition of total internal reflection are reflected to the coating layer, automatically forming a circular dark pattern that is related to the refractive index of the liquid. Based on an analytic relation between the diameter of the circular dark pattern and the refractive index of the liquid, we devised a method of in situ nonintrusive refractive index measurement. We tested the effect of several parameters on the measuring accuracy and found that the optimal thickness of the transmission-scattering layer is in the range of 50-70 μm, and the aperture of the diaphragm should be in the range of 0.7-1.0 mm. We measured the refractive indices of ethanol, Coca Cola, and red wine, and achieved an accuracy of ±3×10-4  RIU (refractive index unit).

Crystalline lens and refractive development.

Science.gov (United States)

Iribarren, Rafael

2015-07-01

Individual refractive errors usually change along lifespan. Most children are hyperopic in early life. This hyperopia is usually lost during growth years, leading to emmetropia in adults, but myopia also develops in children during school years or during early adult life. Those subjects who remain emmetropic are prone to have hyperopic shifts in middle life. And even later, at older ages, myopic shifts are developed with nuclear cataract. The eye grows from 15 mm in premature newborns to approximately 24 mm in early adult years, but, in most cases, refractions are maintained stable in a clustered distribution. This growth in axial length would represent a refractive change of more than 40 diopters, which is compensated by changes in corneal and lens powers. The process which maintains the balance between the ocular components of refraction during growth is still under study. As the lens power cannot be measured in vivo, but can only be calculated based on the other ocular components, there have not been many studies of lens power in humans. Yet, recent studies have confirmed that the lens loses power during growth in children, and that hyperopic and myopic shifts in adulthood may be also produced by changes in the lens. These studies in children and adults give a picture of the changing power of the lens along lifespan. Other recent studies about the growth of the lens and the complexity of its internal structure give clues about how these changes in lens power are produced along life. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Poisson equation in axisymmetric domains with conical points

International Nuclear Information System (INIS)

Nkemzi, B.

2003-01-01

This paper analyzes the application of the Fourier-finite-element method (FFEM) for the resolution of the Derichlet problem for the Poisson equation -Δu-circumflex = f-circumflex in axisymmetric domains Ω-circumflex subset of R 3 with conical points on the rotation axis. The FFEM combines the approximate Fourier method with respect to one space direction with the finite element method for the approximate calculation of the Fourier coefficients of the solution. Here, the influence of the conical points on the regularity of the Fourier coefficients of the solution is analyzed and the asymptotic behaviour of the coefficients near the conical points is described by some singularity functions and treated numerically by mesh grading in the two-dimensional meridian of Ω-circumflex. It is proved that for f-circumflex in L 2 (Ω-circumflex), the rate of convergence of the combined approximations in the Sobolev space W 2 1 (Ω-circumflex) is of the order O(h + N -1 ), where h and N represent, respectively, the parameters of the finite-element- and the Fourier-approximation, with h → 0 and n → ∞. (author)

Helico-conical beams for generating optical twisters

DEFF Research Database (Denmark)

Glückstad, Jesper; Palima, Darwin; Daria, Vincent Ricardo Mancao

2010-01-01

charge is increased, the area where destructive interference at the centre increases thereby enlarging the light ring. The propagation along the optical axis follows a conical ray of light where the concentration of high intensities is maintained at the outskirts of the conical beam where constructive...... with an apodized helical phase front at the outskirts and linearly scaled towards no phase singularity at the centre of the beam. At the focal volume, we show that our beam fonms an intensity distribution that can be accurately described as an "optical twister" as it propagates along the optical axis. Unlike LG...... beams, an optical twister can have minimal changes in radius but with a scalable DAM. Furthenmore, we characterize the DAM in tenms of its capacity to introduce spiral motion on particles trapped along its orbit. We also show that our "optical twister" maintains a high concentration of photons...

Derivation of Conditions for the Normal Gain Behavior of Conical Horns

Directory of Open Access Journals (Sweden)

Chin Yeng Tan

2007-01-01

Full Text Available Monotonically increasing gain-versus-frequency pattern is in general expected to be a characteristic of aperture antennas that include the smooth-wall conical horn. While optimum gain conical horns do naturally exhibit this behavior, nonoptimum horns need to meet certain criterion: a minimum axial length for given aperture diameter, or, alternatively, a maximum aperture diameter for the given axial length. In this paper, approximate expressions are derived to determine these parameters.

RADIO REFRACTIVITY RADIO REFRACTIVITY STUDY IN AKURE ...

African Journals Online (AJOL)

eobe

Propagation of waves in a microwave link is through the troposphere which is the non-ionized lowest portion of the atmosphere [5]. The refractive index is defined as [5]. (1). Where εr is the dielectric constant of the troposphere. C is the speed of light and V is the phase velocity of the wave in the medium. The refractive index ...

Uncorrected refractive errors.

Science.gov (United States)

Naidoo, Kovin S; Jaggernath, Jyoti

2012-01-01

Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship.

Uncorrected refractive errors

Directory of Open Access Journals (Sweden)

Kovin S Naidoo

2012-01-01

Full Text Available Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC, were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR Development, Service Development and Social Entrepreneurship.

GPM GROUND VALIDATION CONICAL SCANNING MILLIMETER-WAVE IMAGING RADIOMETER (COSMIR) MC3E V1

Data.gov (United States)

National Aeronautics and Space Administration — The GPM Ground Validation Conical Scanning Millimeter-wave Imaging Radiometer (COSMIR) MC3E dataset used the Conical Scanning Millimeter-wave Imaging Radiometer...

Parsimonious refraction interferometry

KAUST Repository

Hanafy, Sherif

2016-09-06

We present parsimonious refraction interferometry where a densely populated refraction data set can be obtained from just two shot gathers. The assumptions are that the first arrivals are comprised of head waves and direct waves, and a pair of reciprocal shot gathers is recorded over the line of interest. The refraction traveltimes from these reciprocal shot gathers can be picked and decomposed into O(N2) refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. This enormous increase in the number of virtual traveltime picks and associated rays, compared to the 2N traveltimes from the two reciprocal shot gathers, allows for increased model resolution and better condition numbers in the normal equations. Also, a reciprocal survey is far less time consuming than a standard refraction survey with a dense distribution of sources.

Parsimonious refraction interferometry

KAUST Repository

Hanafy, Sherif; Schuster, Gerard T.

2016-01-01

We present parsimonious refraction interferometry where a densely populated refraction data set can be obtained from just two shot gathers. The assumptions are that the first arrivals are comprised of head waves and direct waves, and a pair of reciprocal shot gathers is recorded over the line of interest. The refraction traveltimes from these reciprocal shot gathers can be picked and decomposed into O(N2) refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. This enormous increase in the number of virtual traveltime picks and associated rays, compared to the 2N traveltimes from the two reciprocal shot gathers, allows for increased model resolution and better condition numbers in the normal equations. Also, a reciprocal survey is far less time consuming than a standard refraction survey with a dense distribution of sources.

Experiments on active precision isolation with a smart conical adapter

Science.gov (United States)

Li, H.; Li, H. Y.; Chen, Z. B.; Tzou, H. S.

2016-07-01

Based on a conical shell adaptor, an active vibration isolator for vibration control of precision payload is designed and tested in this study. Flexible piezoelectric sensors and actuators are bonded on the adaptor surface for active vibration monitoring and control. The mathematical model of a piezoelectric laminated conical shell is derived and then optimal design of the actuators is performed for the first axial vibration mode of the isolation system. A scaled conical adaptor is manufactured with four MFC actuators laminating on its outer surface. Active vibration isolation efficiency is then evaluated on a vibration shaker. The control model is built in Matlab/Simulink and programmed into the dSPACE control board. Experimental results show that, the proposed active isolator is effective in vibration suppression of payloads with the negative velocity feedback control. In contrast, the amplitude responses increase with positive feedback control. Furthermore, the amplitude responses increases when time delay is added into the control signals, and gets the maximum when the delay is close to one quarter of one cycle time.

Probabilistic structural assessment of conical grouted joint using numerical modelling

DEFF Research Database (Denmark)

Njomo-Wandji, Wilfried; Natarajan, Anand; Dimitrov, Nikolay

2018-01-01

Conical grouted joints have been proposed as a solution for the relative settlement observed between the sleeve and the pile on monopiles for wind turbines. In this paper, the influence of the design parameters such as steel wall thicknesses and conical angle on the failure modes associated...... to continual loadings are assessed based on finite element analysis. It is found that both the sleeve's and pile's wall thicknesses have a significant impact on the grouted joint health. Namely, the larger are the wall thicknesses, the more vulnerable the grout is with respect to fatigue and material...

Leidenfrost phenomenon on conical surfaces

Science.gov (United States)

Hidalgo-Caballero, S.; Escobar-Ortega, Y.; Pacheco-Vázquez, F.

2016-09-01

The Leidenfrost state is typically studied by placing droplets on flat or slightly curved surfaces. Here this phenomenon is investigated by depositing water in hot conical bowls. We found that this phase exists even for large amounts of liquid in very narrow cones without considerable effect of the confinement on the Leidenfrost transition temperature TL. At a fixed temperature, T >TL , the total evaporation time τ has a nonmonotonic dependence on the angle of confinement θ : for large volumes (˜20 ml) on flat surfaces (θ ˜0∘ ), vapor chimneys appear and accelerate the evaporation rate, their frequency diminishes as θ augments and becomes zero at a certain angle θc, at which τ reaches its maximum value; then, τ decreases again at larger angles because the vapor layer holding up the water becomes thinner due to the increase of hydrostatic pressure and because the geometry facilitates the vapor expulsion along the conical wall. For small volumes (˜1 ml), surface tension mainly determines the drop curvature and the lifetime is practically independent of θ . Different chimney regimes and oscillation patterns were observed and summarized in a phase diagram. Finally, we developed a simple model to decipher the shape adopted by the liquid volume and its evolution as a function of time, and the predictions are in good agreement with the experimental results.

Smooth structures on pseudomanifolds with isolated conical singularities

Czech Academy of Sciences Publication Activity Database

Le, Hong-Van; Somberg, P.; Vanžura, Jiří

2013-01-01

Roč. 38, č. 1 (2013), s. 33-54 ISSN 0251-4184 Institutional support: RVO:67985840 Keywords : conical pseudomanifold * symplectic form * Poisson structure Subject RIV: BA - General Mathematics http://link.springer.com/article/10.1007%2Fs40306-013-0009-0#

Analysis of the conical piezoelectric acoustic emission transducer

Czech Academy of Sciences Publication Activity Database

Červená, Olga; Hora, Petr

2008-01-01

Roč. 2, č. 1 (2008), s. 13-24 ISSN 1802-680X R&D Projects: GA ČR GA101/06/1689 Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustic emission * conical transducer * FEM Subject RIV: BI - Acoustics

Practical conic sections the geometric properties of ellipses, parabolas and hyperbolas

CERN Document Server

Downs, J W

2010-01-01

Illustrated with interesting examples from everyday life, this text shows how to create ellipses, parabolas, and hyperbolas and presents fascinating historical background on their ancient origins. The text starts with a discussion of techniques for generating the conic curves, showing how to create accurate depictions of large or small conic curves and describing their reflective properties, from light in telescopes to sound in microphones and amplifiers. It further defines the role of curves in the construction of auditoriums, antennas, lamps, and numerous other design applications. Only a ba

Production of ion beam by conical pinched electron beam diode

International Nuclear Information System (INIS)

Matsukawa, Y.; Nakagawa, Y.

1982-01-01

Some properties of the ion beam produced by pinched electron beam diode having conical shape electrodes and organic insulator anode was studied. Ion energy is about 200keV and the peak diode current is about 30 kA. At 11cm from the diode apex, not the geometrical focus point, concentrated ion beam was obtained. Its density is more than 500A/cm 2 . The mean ion current density within the radius of 1.6cm around the axis from conical diode is two or three times that from an usual pinched electron beam diode with flat parallel electrodes of same dimension and impedance under the same conditions. (author)

Variable volume combustor with a conical liner support

Science.gov (United States)

Johnson, Thomas Edward; McConnaughhay, Johnie Franklin; Keener, Chrisophter Paul; Ostebee, Heath Michael

2017-06-27

The present application provides a variable volume combustor for use with a gas turbine engine. The variable volume combustor may include a liner, a number of micro-mixer fuel nozzles positioned within the liner, and a conical liner support supporting the liner.

Iterative supervirtual refraction interferometry

KAUST Repository

Al-Hagan, Ola

2014-05-02

In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

Iterative supervirtual refraction interferometry

KAUST Repository

Al-Hagan, Ola; Hanafy, Sherif M.; Schuster, Gerard T.

2014-01-01

In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

Early structure of LPG partially premixed conically stabilized flames

KAUST Repository

Elbaz, Ayman M.

2013-01-01

This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based

Understanding refraction contrast using a comparison of absorption and refraction computed tomographic techniques

Science.gov (United States)

Wiebe, S.; Rhoades, G.; Wei, Z.; Rosenberg, A.; Belev, G.; Chapman, D.

2013-05-01

Refraction x-ray contrast is an imaging modality used primarily in a research setting at synchrotron facilities, which have a biomedical imaging research program. The most common method for exploiting refraction contrast is by using a technique called Diffraction Enhanced Imaging (DEI). The DEI apparatus allows the detection of refraction between two materials and produces a unique ''edge enhanced'' contrast appearance, very different from the traditional absorption x-ray imaging used in clinical radiology. In this paper we aim to explain the features of x-ray refraction contrast as a typical clinical radiologist would understand. Then a discussion regarding what needs to be considered in the interpretation of the refraction image takes place. Finally we present a discussion about the limitations of planar refraction imaging and the potential of DEI Computed Tomography. This is an original work that has not been submitted to any other source for publication. The authors have no commercial interests or conflicts of interest to disclose.

Energy-flux characterization of conical and space-time coupled wave packets

International Nuclear Information System (INIS)

Lotti, A.; Couairon, A.; Faccio, D.; Trapani, P. Di

2010-01-01

We introduce the concept of energy density flux as a characterization tool for the propagation of ultrashort laser pulses with spatiotemporal coupling. In contrast with calculations for the Poynting vector, those for energy density flux are derived in the local frame moving at the velocity of the envelope of the wave packet under examination and do not need knowledge of the magnetic field. We show that the energy flux defined from a paraxial propagation equation follows specific geometrical connections with the phase front of the optical wave packet, which demonstrates that the knowledge of the phase fronts amounts to the measurement of the energy flux. We perform a detailed numerical study of the energy density flux in the particular case of conical waves, with special attention paid to stationary-envelope conical waves (X or O waves). A full characterization of linear conical waves is given in terms of their energy flux. We extend the definition of this concept to the case of nonlinear propagation in Kerr media with nonlinear losses.

Wave function continuity and the diagonal Born-Oppenheimer correction at conical intersections.

Science.gov (United States)

Meek, Garrett A; Levine, Benjamin G

2016-05-14

We demonstrate that though exact in principle, the expansion of the total molecular wave function as a sum over adiabatic Born-Oppenheimer (BO) vibronic states makes inclusion of the second-derivative nonadiabatic energy term near conical intersections practically problematic. In order to construct a well-behaved molecular wave function that has density at a conical intersection, the individual BO vibronic states in the summation must be discontinuous. When the second-derivative nonadiabatic terms are added to the Hamiltonian, singularities in the diagonal BO corrections (DBOCs) of the individual BO states arise from these discontinuities. In contrast to the well-known singularities in the first-derivative couplings at conical intersections, these singularities are non-integrable, resulting in undefined DBOC matrix elements. Though these singularities suggest that the exact molecular wave function may not have density at the conical intersection point, there is no physical basis for this constraint. Instead, the singularities are artifacts of the chosen basis of discontinuous functions. We also demonstrate that continuity of the total molecular wave function does not require continuity of the individual adiabatic nuclear wave functions. We classify nonadiabatic molecular dynamics methods according to the constraints placed on wave function continuity and analyze their formal properties. Based on our analysis, it is recommended that the DBOC be neglected when employing mixed quantum-classical methods and certain approximate quantum dynamical methods in the adiabatic representation.

Bioinspired conical copper wire with gradient wettability for continuous and efficient fog collection.

Science.gov (United States)

Ju, Jie; Xiao, Kai; Yao, Xi; Bai, Hao; Jiang, Lei

2013-11-06

Inspired by the efficient fog collection on cactus spines, conical copper wires with gradient wettability are fabricated through gradient electrochemical corrosion and subsequent gradient chemical modification. These dual-gradient copper wires' fog-collection ability is demonstrated to be higher than that of conical copper wires with pure hydrophobic surfaces or pure hydrophilic surfaces, and the underlying mechanism is also analyzed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An assessment of a conical horn waveguide to represent the human eardrum

Science.gov (United States)

Fields, Taylor N.; Schnetzer, Lucia; Brister, Eileen; Yates, Charles W.; Withnell, Robert H.

2018-05-01

This study examined a model of the acoustic input impedance of the ear that includes a waveguide model of the eardrum. The eardrum was modeled as a lossless conical-horn with rigid walls. The ear canal was modeled as a one-dimensional lossy transmission line. The output impedance of the eardrum, the middle ear, and the cochlea, was modeled as a circuit analog. The model was fit to acoustic input impedance data from human ears using a nonlinear least-squares fit. The impact of a conical-horn shape for the eardrum was quantified by comparison with the eardrum modeled as a near-flat surface. The model provided a good match to the data over the frequency range examined. A conical-horn model of the human eardrum provided gain at high frequencies, most notably above 1–2 kHz, with a broader middle-ear frequency response. This finding may suggest that eardrum shape plays an important role in sound transmission to the cochlea.

On the efficiency of conical targets for laser thermonuclear fusion

International Nuclear Information System (INIS)

Borovskij, A.V.; Korobkin, V.V.

1981-01-01

Advantages and drawbacks of conical targets (CT) for laser fusion (LF) are discussed. Possibility of the laser power reduction, laser pulse lengthening and neutron yield increase are analyzed for an ideal conical target with absolutely rigid and heat-proof walls as compared to a spherical target of the same mass. A simple theory is suggested which makes it possible to take into account an effect of walls on the fusion process in the conical target with gaseous fuel and heavy shell. Energy losses due to wall deformations and heat conduction are estimated. An influence of these effects on the neutron yield is estimated. CT used in the LF experiments are found to have serious drawbacks in comparison with spherical ones. These drawbacks are connected with the effect of walls on the processes taking place in CT. Analysis of CT, for which the effect of walls is not significant, points up some definite advantages of CT as compared with spherical one. These advantages are the possibility of laser pulse lengthening and laser power reduction in comparison with the irradiation of a sphere of an equal mass. These two positive qualities are connected with the fact that CT has large linear dimensions [ru

Parsimonious Refraction Interferometry and Tomography

KAUST Repository

Hanafy, Sherif; Schuster, Gerard T.

2017-01-01

We present parsimonious refraction interferometry and tomography where a densely populated refraction data set can be obtained from two reciprocal and several infill shot gathers. The assumptions are that the refraction arrivals are head waves

Sensitivity of photonic crystal fiber grating sensors: biosensing, refractive index, strain, and temperature sensing

DEFF Research Database (Denmark)

Rindorf, Lars Henning; Bang, Ole

2008-01-01

We study the sensitivity of fiber grating sensors in the applications of strain, temperature, internal label-free biosensing, and internal refractive index sensing. New analytical expressions for the sensitivities, valid for photonic crystal fibers are rigorously derived. These are generally vali...

Spectral and spatial characteristics of third-harmonic generation in conical light beams

International Nuclear Information System (INIS)

Peet, V.E.; Shchemeljov, S.V.

2003-01-01

Generation of resonance-enhanced third harmonic in Bessel and other conical beams is analyzed from a simple picture, where the fundamental light field is decomposed into elementary configurations of crossed plain-wave sub-beams. We show that the overall harmonic output can be derived as a superposition of all partial harmonic components driven by elementary configurations of the fundamental field. Good agreement with experimental observations has been obtained in simulation of spectral and spatial characteristics of the generated third harmonic. Some peculiarities of harmonic generation in conical light fields are discussed

Crystalline lens power and refractive error.

Science.gov (United States)

Iribarren, Rafael; Morgan, Ian G; Nangia, Vinay; Jonas, Jost B

2012-02-01

To study the relationships between the refractive power of the crystalline lens, overall refractive error of the eye, and degree of nuclear cataract. All phakic participants of the population-based Central India Eye and Medical Study with an age of 50+ years were included. Calculation of the refractive lens power was based on distance noncycloplegic refractive error, corneal refractive power, anterior chamber depth, lens thickness, and axial length according to Bennett's formula. The study included 1885 subjects. Mean refractive lens power was 25.5 ± 3.0 D (range, 13.9-36.6). After adjustment for age and sex, the standardized correlation coefficients (β) of the association with the ocular refractive error were highest for crystalline lens power (β = -0.41; P lens opacity grade (β = -0.42; P lens power (β = -0.95), lower corneal refractive power (β = -0.76), higher lens thickness (β = 0.30), deeper anterior chamber (β = 0.28), and less marked nuclear lens opacity (β = -0.05). Lens thickness was significantly lower in eyes with greater nuclear opacity. Variations in refractive error in adults aged 50+ years were mostly influenced by variations in axial length and in crystalline lens refractive power, followed by variations in corneal refractive power, and, to a minor degree, by variations in lens thickness and anterior chamber depth.

Automatic fitting of conical envelopes to free-form surfaces for flank CNC machining

OpenAIRE

Bo P.; Bartoň M.; Pottmann H.

2017-01-01

We propose a new algorithm to detect patches of free-form surfaces that can be well approximated by envelopes of a rotational cone under a rigid body motion. These conical envelopes are a preferable choice from the manufacturing point of view as they are, by-definition, manufacturable by computer numerically controlled (CNC) machining using the efficient flank (peripheral) method with standard conical tools. Our geometric approach exploits multi-valued vector fields that consist of vectors in...

Preliminary study of the correlation between refractive error and corneal refractive power, corneal asphericity in myopic eye

Directory of Open Access Journals (Sweden)

Qi-Chao Han

2014-05-01

Full Text Available AIM: To investigate the correlation between myopic refractive error and relative factors, including the corneal refractive power, posterior refractive power, axial length, corneal asphericity coefficient Q value, central cornea thickness(CCTand intraocular pressure(IOP. METHODS:According to the degree of myopia measured by subjective refraction, 138 myopia patients were divided into three subgroups: mild group(-1.00D--3.00D, moderate group(-3.25D--6.00D, high group(>6.00D. The Pentacam anterior segment tomographer(Germany, Oculus Companywas used to measure the corneal refractive power, posterior refractive power, and corneal asphericity in the right eye. IOP, CCT and axial length were measured by a non-contact tonometer and A-scan ultrasonic, respectively. The data was analyzed with a Pearson correlation analysis and one-way ANOVA. RESULTS: The myopic refractive error was negatively correlated with the axial length(r=-0.682, Pr=0.009, P=0.925. The axial length was negatively correlated with corneal refractive power(r=-0.554, Pr=0.674, Pr=-0.375, P=0.01. There was no significantly correlation between the myopic refractive error and CCT, IOP(r=-0.138, P=0.141; r=-0.121, P=0.157. CONCLUSION:The corneal refractive power plays the role of emmetropization during the development of myopia. There is clinic significance for the correlation between Q value and refractive error, IOP to guide the corneal refractive surgery.

Discharge Coefficient Measurements for Flow Through Compound-Angle Conical Holes with Cross-Flow

Directory of Open Access Journals (Sweden)

M. E. Taslim

2004-01-01

Full Text Available Diffusion-shaped film holes with compound angles are currently being investigated for high temperature gas turbine airfoil film cooling. An accurate prediction of the coolant blowing rate through these film holes is essential in determining the film effectiveness. Therefore, the discharge coefficients associated with these film holes for a range of hole pressure ratios is essential in designing airfoil cooling circuits. Most of the available discharge coefficient data in open literature has been for cylindrical holes. The main objective of this experimental investigation was to measure the discharge coefficients for subsonic as well as supersonic pressure ratios through a single conical-diffusion hole. The conical hole has an exit-to-inlet area ratio of 4, a nominal flow length-to-inlet diameter ratio of 4, and an angle with respect to the exit plane (inclination angle of 0°, 30°, 45°, and 60°. Measurements were performed with and without a cross-flow. For the cases with a cross-flow, discharge coefficients were measured for each of the hole geometries and 5 angles between the projected conical hole axis and the cross-flow direction of 0°, 45°, 90°, 135°, and 180°. Results are compared with available data in open literature for cylindrical film holes as well as limited data for conical film holes.

Fabrication of hydrogel-coated single conical nanochannels exhibiting controllable ion rectification characteristics.

Science.gov (United States)

Wang, Linlin; Zhang, Huacheng; Yang, Zhe; Zhou, Jianjun; Wen, Liping; Li, Lin; Jiang, Lei

2015-03-07

Heterogeneous nanochannel materials that endow new functionalities different to the intrinsic properties of two original nanoporous materials have wide potential applications in nanofluidics, energy conversion, and biosensors. Herein, we report novel, interesting hydrogel-composited nanochannel devices with regulatable ion rectification characteristics. The heterogeneous nanochannel devices were constructed by selectively coating the tip side, base side, or both sides of a single conical nanochannel membrane with thin agar hydrogel layers. The tunable ion current rectification of the nanochannels in the three different coating states was systematically demonstrated by current-voltage (I-V) curves. The asymmetric ionic transport property of the conical nanochannel was further strengthened in the tip-coating state and weakened in the base-coating state, whereas the conical nanochannel showed nearly symmetric ionic transport in the dual-coating state. Repeated experiments presented insight into the good stability and reversibility of the three coating states of the hydrogel-nanochannel-integrated systems. This work, as an example, may provide a new strategy to further design and develop multifunctional gel-nanochannel heterogeneous smart porous nanomaterials.

Deviations of Lambert-Beer???s law affect corneal refractive parameters after refractive surgery

OpenAIRE

Jim??nez Cuesta, Jos?? Ram??n; Rodr??guez-Mar??n, Francisco; Gonz??lez Anera, Rosario; Jim??nez del Barco Jaldo, Luis Miguel

2006-01-01

We calculate whether deviations of Lambert-Beer???s law, which regulates depth ablation during corneal ablation, significantly influence corneal refractive parameters after refractive surgery and whether they influence visual performance. For this, we compute a point-to-point correction on the cornea while assuming a non-linear (including a quadratic term) fit for depth ablation. Post-surgical equations for refractive parameters using a non-linear fit show significant differences with respect...

Generalized probabilistic theories and conic extensions of polytopes

Science.gov (United States)

Fiorini, Samuel; Massar, Serge; Patra, Manas K.; Tiwary, Hans Raj

2015-01-01

Generalized probabilistic theories (GPT) provide a general framework that includes classical and quantum theories. It is described by a cone C and its dual C*. We show that whether some one-way communication complexity problems can be solved within a GPT is equivalent to the recently introduced cone factorization of the corresponding communication matrix M. We also prove an analogue of Holevo's theorem: when the cone C is contained in {{{R}}n}, the classical capacity of the channel realized by sending GPT states and measuring them is bounded by log n. Polytopes and optimising functions over polytopes arise in many areas of discrete mathematics. A conic extension of a polytope is the intersection of a cone C with an affine subspace whose projection onto the original space yields the desired polytope. Extensions of polytopes can sometimes be much simpler geometric objects than the polytope itself. The existence of a conic extension of a polytope is equivalent to that of a cone factorization of the slack matrix of the polytope, on the same cone. We show that all 0/1 polytopes whose vertices can be recognized by a polynomial size circuit, which includes as a special case the travelling salesman polytope and many other polytopes from combinatorial optimization, have small conic extension complexity when the cone is the completely positive cone. Using recent exponential lower bounds on the linear extension complexity of polytopes, this provides an exponential gap between the communication complexity of GPT based on the completely positive cone and classical communication complexity, and a conjectured exponential gap with quantum communication complexity. Our work thus relates the communication complexity of generalizations of quantum theory to questions of mainstream interest in the area of combinatorial optimization.

Generalized probabilistic theories and conic extensions of polytopes

International Nuclear Information System (INIS)

Fiorini, Samuel; Massar, Serge; Patra, Manas K; Tiwary, Hans Raj

2015-01-01

Generalized probabilistic theories (GPT) provide a general framework that includes classical and quantum theories. It is described by a cone C and its dual C*. We show that whether some one-way communication complexity problems can be solved within a GPT is equivalent to the recently introduced cone factorization of the corresponding communication matrix M. We also prove an analogue of Holevo's theorem: when the cone C is contained in R n , the classical capacity of the channel realized by sending GPT states and measuring them is bounded by logn. Polytopes and optimising functions over polytopes arise in many areas of discrete mathematics. A conic extension of a polytope is the intersection of a cone C with an affine subspace whose projection onto the original space yields the desired polytope. Extensions of polytopes can sometimes be much simpler geometric objects than the polytope itself. The existence of a conic extension of a polytope is equivalent to that of a cone factorization of the slack matrix of the polytope, on the same cone. We show that all 0/1 polytopes whose vertices can be recognized by a polynomial size circuit, which includes as a special case the travelling salesman polytope and many other polytopes from combinatorial optimization, have small conic extension complexity when the cone is the completely positive cone. Using recent exponential lower bounds on the linear extension complexity of polytopes, this provides an exponential gap between the communication complexity of GPT based on the completely positive cone and classical communication complexity, and a conjectured exponential gap with quantum communication complexity. Our work thus relates the communication complexity of generalizations of quantum theory to questions of mainstream interest in the area of combinatorial optimization. (paper)

Internal and external axial corner flows

Science.gov (United States)

Kutler, P.; Shankar, V.; Anderson, D. A.; Sorenson, R. L.

1975-01-01

The inviscid, internal, and external axial corner flows generated by two intersecting wedges traveling supersonically are obtained by use of a second-order shock-capturing, finite-difference approach. The governing equations are solved iteratively in conical coordinates to yield the complicated wave structure of the internal corner and the simple peripheral shock of the external corner. The numerical results for the internal flows compare favorably with existing experimental data.

Questionnaires for Measuring Refractive Surgery Outcomes.

Science.gov (United States)

Kandel, Himal; Khadka, Jyoti; Lundström, Mats; Goggin, Michael; Pesudovs, Konrad

2017-06-01

To identify the questionnaires used to assess refractive surgery outcomes, assess the available questionnaires in regard to their psychometric properties, validity, and reliability, and evaluate the performance of the available questionnaires in measuring refractive surgery outcomes. An extensive literature search was done on PubMed, MEDLINE, Scopus, CINAHL, Cochrane, and Web of Science databases to identify articles that described or used at least one questionnaire to assess refractive surgery outcomes. The information on content quality, validity, reliability, responsiveness, and psychometric properties was extracted and analyzed based on an extensive set of quality criteria. Eighty-one articles describing 27 questionnaires (12 refractive error-specific, including 4 refractive surgery-specific, 7 vision-but-non-refractive, and 8 generic) were included in the review. Most articles (56, 69.1%) described refractive error-specific questionnaires. The Quality of Life Impact of Refractive Correction (QIRC), the Quality of Vision (QoV), and the Near Activity Visual Questionnaire (NAVQ) were originally constructed using Rasch analysis; others were developed using the Classical Test Theory. The National Eye Institute Refractive Quality of Life questionnaire was the most frequently used questionnaire, but it does not provide a valid measurement. The QoV, QIRC, and NAVQ are the three best existing questionnaires to assess visual symptoms, quality of life, and activity limitations, respectively. This review identified three superior quality questionnaires for measuring different aspects of quality of life in refractive surgery. Clinicians and researchers should choose a questionnaire based on the concept being measured with superior psychometric properties. [J Refract Surg. 2017;33(6):416-424.]. Copyright 2017, SLACK Incorporated.

Non-linear buckling of an FGM truncated conical shell surrounded by an elastic medium

International Nuclear Information System (INIS)

Sofiyev, A.H.; Kuruoglu, N.

2013-01-01

In this paper, the non-linear buckling of the truncated conical shell made of functionally graded materials (FGMs) surrounded by an elastic medium has been studied using the large deformation theory with von Karman–Donnell-type of kinematic non-linearity. A two-parameter foundation model (Pasternak-type) is used to describe the shell–foundation interaction. The FGM properties are assumed to vary continuously through the thickness direction. The fundamental relations, the modified Donnell type non-linear stability and compatibility equations of the FGM truncated conical shell resting on the Pasternak-type elastic foundation are derived. By using the Superposition and Galerkin methods, the non-linear stability equations for the FGM truncated conical shell is solved. Finally, influences of variations of Winkler foundation stiffness and shear subgrade modulus of the foundation, compositional profiles and shell characteristics on the dimensionless critical non-linear axial load are investigated. The present results are compared with the available data for a special case. -- Highlights: • Nonlinear buckling of FGM conical shell surrounded by elastic medium is studied. • Pasternak foundation model is used to describe the shell–foundation interaction. • Nonlinear basic equations are derived. • Problem is solved by using Superposition and Galerkin methods. • Influences of various parameters on the nonlinear critical load are investigated

Influence of refraction index strength on the light propagation in dielectrics material with periodic refraction index

International Nuclear Information System (INIS)

Hidayat, Arif; Latifah, Eny; Kurniati, Diana; Wisodo, Hari

2016-01-01

This study investigated the influence of refraction index strength on the light propagation in refraction index-varied dielectric material. This dielectric material served as photonic lattice. The behavior of light propagation influenced by variation of refraction index in photonic lattice was investigated. Modes of the guiding light were determined numerically using squared-operator iteration method. It was found that the greater the strength of refraction index, the smaller the guiding modes.

Correction of refractive errors

Directory of Open Access Journals (Sweden)

Vladimir Pfeifer

2005-10-01

Full Text Available Background: Spectacles and contact lenses are the most frequently used, the safest and the cheapest way to correct refractive errors. The development of keratorefractive surgery has brought new opportunities for correction of refractive errors in patients who have the need to be less dependent of spectacles or contact lenses. Until recently, RK was the most commonly performed refractive procedure for nearsighted patients.Conclusions: The introduction of excimer laser in refractive surgery has given the new opportunities of remodelling the cornea. The laser energy can be delivered on the stromal surface like in PRK or deeper on the corneal stroma by means of lamellar surgery. In LASIK flap is created with microkeratome in LASEK with ethanol and in epi-LASIK the ultra thin flap is created mechanically.

Parsimonious Refraction Interferometry and Tomography

KAUST Repository

Hanafy, Sherif

2017-02-04

We present parsimonious refraction interferometry and tomography where a densely populated refraction data set can be obtained from two reciprocal and several infill shot gathers. The assumptions are that the refraction arrivals are head waves, and a pair of reciprocal shot gathers and several infill shot gathers are recorded over the line of interest. Refraction traveltimes from these shot gathers are picked and spawned into O(N2) virtual refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. The virtual traveltimes can be inverted to give the velocity tomogram. This enormous increase in the number of traveltime picks and associated rays, compared to the many fewer traveltimes from the reciprocal and infill shot gathers, allows for increased model resolution and a better condition number with the system of normal equations. A significant benefit is that the parsimonious survey and the associated traveltime picking is far less time consuming than that for a standard refraction survey with a dense distribution of sources.

Power of the Poincare Group: Elucidating the Hidden Symmetries in Focal Conic Domains

International Nuclear Information System (INIS)

Alexander, Gareth P.; Chen, Bryan Gin-ge; Matsumoto, Elisabetta A.; Kamien, Randall D.

2010-01-01

Focal conic domains are typically the 'smoking gun' by which smectic liquid crystalline phases are identified. The geometry of the equally spaced smectic layers is highly generic but, at the same time, difficult to work with. In this Letter we develop an approach to the study of focal sets in smectics which exploits a hidden Poincare symmetry revealed only by viewing the smectic layers as projections from one-higher dimension. We use this perspective to shed light upon several classic focal conic textures, including the concentric cyclides of Dupin, polygonal textures, and tilt-grain boundaries.

Analysis of solar water heater with parabolic dish concentrator and conical absorber

Science.gov (United States)

Rajamohan, G.; Kumar, P.; Anwar, M.; Mohanraj, T.

2017-06-01

This research focuses on developing novel technique for a solar water heating system. The novel solar system comprises a parabolic dish concentrator, conical absorber and water heater. In this system, the conical absorber tube directly absorbs solar radiation from the sun and the parabolic dish concentrator reflects the solar radiations towards the conical absorber tube from all directions, therefore both radiations would significantly improve the thermal collector efficiency. The working fluid water is stored at the bottom of the absorber tubes. The absorber tubes get heated and increases the temperature of the working fluid inside of the absorber tube and causes the working fluid to partially evaporate. The partially vaporized working fluid moves in the upward direction due to buoyancy effect and enters the heat exchanger. When fresh water passes through the heat exchanger, temperature of the vapour decreases through heat exchange. This leads to condensation of the vapour and forms liquid phase. The working fluid returns to the bottom of the collector absorber tube by gravity. Hence, this will continue as a cyclic process inside the system. The proposed investigation shows an improvement of collector efficiency, enhanced heat transfer and a quality water heating system.

Conical pitch angle distributions of very-low energy ion fluxes observed by ISEE 1

International Nuclear Information System (INIS)

Horowitz, J.L.; Baugher, C.R.; Chappell, C.R.; Shelley, E.G.; Young, D.T.

1982-01-01

Observations of low-energy ionospheric ions by the plasma composition experiment abroad ISEE 1 often show conical pitch angle distributions, that is, peak fluxes between 0 0 and 90 0 to the directions parallel or antiparallel to the magnetic field. Frequently, all three primary ionospheric ion species (H + , He + , and O + ) simultaneously exhibit conical distributions with peak fluxes at essentially the same pitch angle. A distinction is made here between unidirectional, or streaming, distributions, in which ions are traveling essentially from only one hemisphere, and symmetrical distributions, in which significant fluxes are observed traveling from both hemispheres. The orbital coverage for this survey was largely restricted to the night sector, approximately 2100--0600 LT, and moderate geomagnetic latitudes of 20 0 --40 0 . Also, lack of complete pitch angle coverage at all times may have reduced detection for conics with small cone angles. However, we may conclude that the unidirectional conical distributions observed in the northern hemisphere are always observed to be traveling from the northern hemisphere and that they exhibit the following characteristics relative to the symmetric distributions, in that they (1) are typically observed on higher L shells (that is, higher geomagnetic latitudes or larger geocentric distances or both), (2) tend to have significantly larger cone angles, and (3), are associated with higher magnetic activity levels

Optimization of SPR signals: Monitoring the physical structures and refractive indices of prisms

Science.gov (United States)

Maisarah Mukhtar, Wan; Halim, Razman Mohd; Hassan, Hazirah

2017-11-01

Surface plasmon resonance (SPR) can only be achieved if sufficient energy is provided at the boundary between metal and dielectric. An employment of prism as a light coupler by using Kretschmann configuration is one of the alternative for the production of adequate energy to be generated as surface plasmon polaritons (SPP). This work is carried out to investigate the effect of physical structure of the prism and its refractive index to the excitation of SPPs. A 50nm gold thin metal film with dielectric constant of ɛ=-12.45i+1.3 was deposited on the hypotenuse surface of the prisms. The physical structures of the prisms were varied such as triangular, conical, hemispherical and half cylindrical. These prisms were classified into two types of refractive indices (RI), namely n=1.51(type BK7) and n=1.77(type SF11). Based on SPR curve analyses, we discovered that strong SPR signals which consist of 82.98% photons were excited as SPPs can be obtained by using type-BK7 prism with physical structures of hemispherical or half cylindrical. From the view of selectivity ability as sensors, the usage of type-SF11 prisms (half cylindrical and hemispherical) able to enhance this impressive feature in which sharp SPR curves with small FWHM values were obtained. In conclusion, apart from properties of thin film materials, the physical structure of prisms and their RI values play crucial roles to obtain optimum SPR signal. High sensitivity SPR sensor can be established with the appointment of type-BK7 prisms (hemispherical or half cylindrical shape) as light couplers.

Optimization of SPR signals: Monitoring the physical structures and refractive indices of prisms

Directory of Open Access Journals (Sweden)

Mukhtar Wan Maisarah

2017-01-01

Full Text Available Surface plasmon resonance (SPR can only be achieved if sufficient energy is provided at the boundary between metal and dielectric. An employment of prism as a light coupler by using Kretschmann configuration is one of the alternative for the production of adequate energy to be generated as surface plasmon polaritons (SPP. This work is carried out to investigate the effect of physical structure of the prism and its refractive index to the excitation of SPPs. A 50nm gold thin metal film with dielectric constant of ɛ=-12.45i+1.3 was deposited on the hypotenuse surface of the prisms. The physical structures of the prisms were varied such as triangular, conical, hemispherical and half cylindrical. These prisms were classified into two types of refractive indices (RI, namely n=1.51(type BK7 and n=1.77(type SF11. Based on SPR curve analyses, we discovered that strong SPR signals which consist of 82.98% photons were excited as SPPs can be obtained by using type-BK7 prism with physical structures of hemispherical or half cylindrical. From the view of selectivity ability as sensors, the usage of type-SF11 prisms (half cylindrical and hemispherical able to enhance this impressive feature in which sharp SPR curves with small FWHM values were obtained. In conclusion, apart from properties of thin film materials, the physical structure of prisms and their RI values play crucial roles to obtain optimum SPR signal. High sensitivity SPR sensor can be established with the appointment of type-BK7 prisms (hemispherical or half cylindrical shape as light couplers.

Inversion of the conical Radon transform with vertices on a surface of revolution arising in an application of a Compton camera

International Nuclear Information System (INIS)

Moon, Sunghwan

2017-01-01

A Compton camera has been introduced for use in single photon emission computed tomography to improve the low efficiency of a conventional gamma camera. In general, a Compton camera brings about the conical Radon transform. Here we consider a conical Radon transform with the vertices on a rotation symmetric set with respect to a coordinate axis. We show that this conical Radon transform can be decomposed into two transforms: the spherical sectional transform and the weighted fan beam transform. After finding inversion formulas for these two transforms, we provide an inversion formula for the conical Radon transform. (paper)

Peripheral refraction in normal infant rhesus monkeys

Science.gov (United States)

Hung, Li-Fang; Ramamirtham, Ramkumar; Huang, Juan; Qiao-Grider, Ying; Smith, Earl L.

2008-01-01

Purpose To characterize peripheral refractions in infant monkeys. Methods Cross-sectional data for horizontal refractions were obtained from 58 normal rhesus monkeys at 3 weeks of age. Longitudinal data were obtained for both the vertical and horizontal meridians from 17 monkeys. Refractive errors were measured by retinoscopy along the pupillary axis and at eccentricities of 15, 30, and 45 degrees. Axial dimensions and corneal power were measured by ultrasonography and keratometry, respectively. Results In infant monkeys, the degree of radial astigmatism increased symmetrically with eccentricity in all meridians. There were, however, initial nasal-temporal and superior-inferior asymmetries in the spherical-equivalent refractive errors. Specifically, the refractions in the temporal and superior fields were similar to the central ametropia, but the refractions in the nasal and inferior fields were more myopic than the central ametropia and the relative nasal field myopia increased with the degree of central hyperopia. With age, the degree of radial astigmatism decreased in all meridians and the refractions became more symmetrical along both the horizontal and vertical meridians; small degrees of relative myopia were evident in all fields. Conclusions As in adult humans, refractive error varied as a function of eccentricity in infant monkeys and the pattern of peripheral refraction varied with the central refractive error. With age, emmetropization occurred for both central and peripheral refractive errors resulting in similar refractions across the central 45 degrees of the visual field, which may reflect the actions of vision-dependent, growth-control mechanisms operating over a wide area of the posterior globe. PMID:18487366

Validity of automated refraction after segmented refractive multifocal intraocular lens implantation.

Science.gov (United States)

Albarrán-Diego, César; Muñoz, Gonzalo; Rohrweck, Stephanie; García-Lázaro, Santiago; Albero, José Ricardo

2017-01-01

To evaluate the clinical utility of automated refraction (AR) and keratometry (KR) compared with subjective or manifest refraction (MR) after cataract or refractive lens exchange surgery with implantation of Lentis Mplus X (Oculentis GmbH) refractive multifocal intraocular lens (IOL). Eighty-six eyes implanted with the Lentis Mplus X multifocal IOL were included. MR was performed in all patients followed by three consecutive AR measurements using the Topcon KR-8000 autorefractor. Assessment of repeatability of consecutive AR before and after dilation with phenylephrine 10%, and comparison of the AR and KR with MR using vector analysis were performed at 3mo follow-up. Analysis showed excellent repeatability of the AR measurements. Linear regression of AR versus MR showed good correlation for sphere and spherical equivalent, whereas the correlation for astigmatism was low. The mean difference AR-MR was -1.28±0.29 diopters (D) for sphere. Astigmatism showed better correlation between KR and MR. We suggest AR sphere plus 1.25 D and the KR cylinder as the starting point for MR in eyes with a Lentis Mplus X multifocal IOL. If AR measurements are equal to MR, decentration of the IOL should be suspected.

Theory of supervirtual refraction interferometry

KAUST Repository

Bharadwaj, Pawan; Schuster, Gerard T.; Mallinson, Ian; Dai, Wei

2012-01-01

possibility of applying this method to earthquake data recorded by receivers that are inline with the refraction paths and source locations. © 2011 The Authors Geophysical Journal International © 2011 RAS.

The Expanding Bipolar Conic Shell of the Symbiotic Star AG Peg

Science.gov (United States)

Lee, Seong-Jae; Hyung, Siek

2018-06-01

Symbiotic stars are the most interesting since some systems are believed to host the most massive white dwarf, like SN Ia progenitors. Most recently, Lee and Hyung (2018, LH18) proposed a bipolar conic shell structure for the observed high expansion Hα and Hβ line profiles and other double peak lines observed in 1998 September (phase φ = 10.24): the physical conditions for the white dwarf luminosity and the ionized HII zone, responsible for double Gaussian optical lines including Balmer and Lyman line fluxes, were taken from the P-I model with gas density, nH = 109.85 cm-3 , while the column density for the scattering neutral zone was derived from the broader line components based on the result by Monte Carlo simulations. In this investigation, we examined whether the expanding shells of the bipolar conical geometry as proposed by LH18 would be able to form the other Hα and Hβ line profiles observed in other phases, φ = 11.56 and 11.98 (in 2001 August and 2002 August). We look into the kinematical property of the bipolar conic shell structure responsible for the HII and HI zones and then we discuss the secular variation of the broad line feature and the origin of the bipolar cone, i.e., part of a common envelope formed through the mass inflows from the giant star.

Conical evaporator and liquid-return wick model for vapor anode, multi-tube AMTEC cells

Science.gov (United States)

Tournier, Jean-Michel; El-Genk, Mohamed S.

2000-01-01

A detailed, 2-D thermal-hydraulic model for conical and flat evaporators and the liquid sodium return artery in PX-type AMTEC cells was developed, which predicts incipient dryout at the evaporator wick surface. Results obtained at fixed hot and cold side temperatures showed that the flat evaporator provided a slightly lower vapor pressure, but reached the capillary limit at higher temperature. The loss of performance due to partial recondensation over up to 20% of the wick surface of the deep conical evaporators was offset by the larger surface area available for evaporation, providing a slightly higher vapor pressure. Model results matched the PX-3A cell's experimental data of electrical power output, but the predicted temperature of the cell's conical evaporator was consistently ~50 K above measurements. A preliminary analysis indicated that sodium vapor leakage in the cell (through microcracks in the BASE tubes' walls or brazes) may explain the difference between predicted and measured evaporator temperatures in PX-3A. .

Wear Assessment of Conical Pick used in Coal Cutting Operation

Czech Academy of Sciences Publication Activity Database

Dewangan, S.; Chattopadhyaya, S.; Hloch, Sergej

-, 11/2014 (2014), s. 1-6 ISSN 0723-2632 Institutional support: RVO:68145535 Keywords : conical pick * wear * SEM * EDX Subject RIV: JQ - Machines ; Tools Impact factor: 2.420, year: 2014 http://link.springer.com/article/10.1007/s00603-014-0680-z

Emmetropisation and the aetiology of refractive errors

Science.gov (United States)

Flitcroft, D I

2014-01-01

The distribution of human refractive errors displays features that are not commonly seen in other biological variables. Compared with the more typical Gaussian distribution, adult refraction within a population typically has a negative skew and increased kurtosis (ie is leptokurtotic). This distribution arises from two apparently conflicting tendencies, first, the existence of a mechanism to control eye growth during infancy so as to bring refraction towards emmetropia/low hyperopia (ie emmetropisation) and second, the tendency of many human populations to develop myopia during later childhood and into adulthood. The distribution of refraction therefore changes significantly with age. Analysis of the processes involved in shaping refractive development allows for the creation of a life course model of refractive development. Monte Carlo simulations based on such a model can recreate the variation of refractive distributions seen from birth to adulthood and the impact of increasing myopia prevalence on refractive error distributions in Asia. PMID:24406411

A new approach to evaluate the response functions for conical and cylindrical collimators

International Nuclear Information System (INIS)

Gigante, G.E.

1989-01-01

A new approach to the evaluation of the conical collimator response function is shown. The basic collimator formulae are reviewed. The collimator response function has been found in a very easy way. An approximate solution has been introduced. Studying the response of a measuring system, the use of this approximation strongly reduces the complexity of the relations to be used; therefore it would provide a useful starting point for a Monte Carlo calculation. The errors introduced are less than 10%. Approximate relations that allow the evaluation of the response of conical and cylindrical collimators to plane and line sources are also given. (orig.)

STABLE CONIC-HELICAL ORBITS OF PLANETS AROUND BINARY STARS: ANALYTICAL RESULTS

Energy Technology Data Exchange (ETDEWEB)

Oks, E. [Physics Department, 206 Allison Lab., Auburn University, Auburn, AL 36849 (United States)

2015-05-10

Studies of planets in binary star systems are especially important because it was estimated that about half of binary stars are capable of supporting habitable terrestrial planets within stable orbital ranges. One-planet binary star systems (OBSS) have a limited analogy to objects studied in atomic/molecular physics: one-electron Rydberg quasimolecules (ORQ). Specifically, ORQ, consisting of two fully stripped ions of the nuclear charges Z and Z′ plus one highly excited electron, are encountered in various plasmas containing more than one kind of ion. Classical analytical studies of ORQ resulted in the discovery of classical stable electronic orbits with the shape of a helix on the surface of a cone. In the present paper we show that despite several important distinctions between OBSS and ORQ, it is possible for OBSS to have stable planetary orbits in the shape of a helix on a conical surface, whose axis of symmetry coincides with the interstellar axis; the stability is not affected by the rotation of the stars. Further, we demonstrate that the eccentricity of the stars’ orbits does not affect the stability of the helical planetary motion if the center of symmetry of the helix is relatively close to the star of the larger mass. We also show that if the center of symmetry of the conic-helical planetary orbit is relatively close to the star of the smaller mass, a sufficiently large eccentricity of stars’ orbits can switch the planetary motion to the unstable mode and the planet would escape the system. We demonstrate that such planets are transitable for the overwhelming majority of inclinations of plane of the stars’ orbits (i.e., the projections of the planet and the adjacent start on the plane of the sky coincide once in a while). This means that conic-helical planetary orbits at binary stars can be detected photometrically. We consider, as an example, Kepler-16 binary stars to provide illustrative numerical data on the possible parameters and the

BALL KINEMATICS IN FINE POLISHING BETWEEN MISALIGNED DISKS IN CONIC OPENINGS

Directory of Open Access Journals (Sweden)

K. G. Shchetnikovich

2009-01-01

Full Text Available The paper considers ball kinematics in polishing between misaligned disks rotating with equal angular velocity; one of these disks has conic openings. Analytical dependences have been obtained for calculation of an angular velocity and ball sliding speed in the conic opening. It has been revealed that at a constant contact of a ball with elastic coating of a flat disk and absence of vibrations in the technological system an instantaneous axis of ball rotation does not change its position in the moving ball. It has been ascertained that when a ball is in contact with a flat disk having elastic coating with grooves changes in the position of ball rotation instantaneous axis have a regular character and do not depend on vibrations in the technological system.

Switching Exciton Pulses Through Conical Intersections

Science.gov (United States)

Leonhardt, K.; Wüster, S.; Rost, J. M.

2014-11-01

Exciton pulses transport excitation and entanglement adiabatically through Rydberg aggregates, assemblies of highly excited light atoms, which are set into directed motion by resonant dipole-dipole interaction. Here, we demonstrate the coherent splitting of such pulses as well as the spatial segregation of electronic excitation and atomic motion. Both mechanisms exploit local nonadiabatic effects at a conical intersection, turning them from a decoherence source into an asset. The intersection provides a sensitive knob controlling the propagation direction and coherence properties of exciton pulses. The fundamental ideas discussed here have general implications for excitons on a dynamic network.

Atmospheric refraction : a history

NARCIS (Netherlands)

Lehn, WH; van der Werf, S

2005-01-01

We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of

Finite element approximation of the radiative transport equation in a medium with piece-wise constant refractive index

International Nuclear Information System (INIS)

Lehtikangas, O.; Tarvainen, T.; Kim, A.D.; Arridge, S.R.

2015-01-01

The radiative transport equation can be used as a light transport model in a medium with scattering particles, such as biological tissues. In the radiative transport equation, the refractive index is assumed to be constant within the medium. However, in biomedical media, changes in the refractive index can occur between different tissue types. In this work, light propagation in a medium with piece-wise constant refractive index is considered. Light propagation in each sub-domain with a constant refractive index is modeled using the radiative transport equation and the equations are coupled using boundary conditions describing Fresnel reflection and refraction phenomena on the interfaces between the sub-domains. The resulting coupled system of radiative transport equations is numerically solved using a finite element method. The approach is tested with simulations. The results show that this coupled system describes light propagation accurately through comparison with the Monte Carlo method. It is also shown that neglecting the internal changes of the refractive index can lead to erroneous boundary measurements of scattered light

Relationship of upflowing ion beams and conics around the dayside cusp/cleft region to the interplanetary conditions

Directory of Open Access Journals (Sweden)

W. Miyake

2002-04-01

Full Text Available The dayside cusp/cleft region is known as a major source of upflowing ionospheric ions to the magnetosphere. Since the ions are supposed to be energized by an input of energy from the dayside magnetospheric boundary region, we examined the possible influence of the interplanetary conditions on dayside ion beams and conics observed by the polar-orbiting Exos-D (Akebono satellite. We found that both the solar wind velocity and density, as well as IMF By and Bz , affect the occurrence frequency of ion conics. The energy of ion conics also depends on the solar wind velocity, IMF By and Bz . The ion beams around the local noon are not significantly controlled by the interplanetary conditions. The results reveal that ion convection, as well as the energy source, is important to understand the production of dayside ion conics while that of ion beams basically reflects the intensity of local field-aligned currents.Key words. Ionosphere (particle acceleration – magnetospheric physics (magnetopause, cusp, and boundary layers; magnetosphere ionosphere interaction

Geometrical pinning of magnetic vortices induced by a deficit angle on a surface: Anisotropic spins on a conic space background

International Nuclear Information System (INIS)

Moura-Melo, W.A.; Pereira, A.R.; Mol, L.A.S.; Pires, A.S.T.

2007-01-01

We study magnetic vortex-like excitations lying on a conic space background. Two types of them are obtained. Their energies appear to be linearly dependent on the conical aperture parameter, besides of being logarithmically divergent with the sample size. In addition, we realize a geometrical-like pinning of the vortex, say, it is energetically favorable for it to nucleate around the conical apex. We also study the problem of two vortices on the cone and obtain an interesting effect on such a geometry: excitations of the same charge, then repealing each other, may nucleate around the apex for suitable cone apertures. We also pay attention to the problem of the vortex pair and how its dissociation temperature depends upon conical geometry

Conical angles of ligands - compounds of elements of the 6(16) and 7(17) groups. Levelling effect

International Nuclear Information System (INIS)

Imyanitov, N.S.

1991-01-01

In the framework of development of a unified system of electron and steric effects of ligand conical angles of 176 compounds R 2 X and RHal, where X=O, S, Se, Te; Hal=F, Cl, Br, I; R=H, Hal (only in the case of R 2 X), Alk or Ar, were calculated. A levelling effect of large X and Hal was pointed out: in the beginning of steric series the conical angles are determined by dimensions of X and Hal and not by R ones. Similar levelled values of conical angles for previously considered ligands on the basis of N, P, As, Sb, Bi, C, Si, Ge, Sn were also calculated

Conical Magnetic Bearings Developed for Active Stall Control in Gas Turbine Engines

Science.gov (United States)

Trudell, Jeffrey J.; Kascak, Albert F.; Provenza, Andrew J.; Buccieri, Carl J.

2004-01-01

Active stall control is a current research area at the NASA Glenn Research Center that offers a great benefit in specific fuel consumption by allowing the gas turbine to operate beyond the onset of stall. Magnetic bearings are being investigated as a new method to perform active stall control. This enabling global aviation safety technology would result in improved fuel efficiency and decreased carbon dioxide emissions, as well as improve safety and reliability by eliminating oil-related delays and failures of engine components, which account for 40 percent of the commercial aircraft departure delays. Active stall control works by perturbing the flow in front of the compressor stage such that it cancels the pressure wave, which causes the compressor to go into stall. Radial magnetic bearings are able to whirl the shaft so that variations in blade tip leakage would flow upstream causing a perturbation wave that could cancel the rotating stall cell. Axial or thrust magnetic bearings cannot be used to cancel the surge mode in the compressor because they have a very low bandwidth and thus cannot modulate at a high enough frequency. Frequency response is limited because the thrust runner cannot be laminated. To improve the bandwidth of magnetic thrust bearings, researchers must use laminations to suppress the eddy currents. A conical magnetic bearing can be laminated, resulting in increased bandwidth in the axial direction. In addition, this design can produce both radial and thrust force in a single bearing, simplifying the installation. The proposed solution combines the radial and thrust bearing into one design that can be laminated--a conical magnetic bearing. The new conical magnetic bearing test rig, funded by a Glenn fiscal year 2002 Director's Discretionary Fund, was needed because none of the existing rigs has an axial degree of freedom. The rotor bearing configuration will simulate that of the main shaft on a gas turbine engine. One conical magnetic bearing

Validity of automated refraction after segmented refractive multifocal intraocular lens implantation

Directory of Open Access Journals (Sweden)

César Albarrán-Diego

2017-11-01

Full Text Available AIM: To evaluate the clinical utility of automated refraction (AR and keratometry (KR compared with subjective or manifest refraction (MR after cataract or refractive lens exchange surgery with implantation of Lentis Mplus X (Oculentis GmbH refractive multifocal intraocular lens (IOL. METHODS: Eighty-six eyes implanted with the Lentis Mplus X multifocal IOL were included. MR was performed in all patients followed by three consecutive AR measurements using the Topcon KR-8000 autorefractor. Assessment of repeatability of consecutive AR before and after dilation with phenylephrine 10%, and comparison of the AR and KR with MR using vector analysis were performed at 3mo follow-up. RESULTS: Analysis showed excellent repeatability of the AR measurements. Linear regression of AR versus MR showed good correlation for sphere and spherical equivalent, whereas the correlation for astigmatism was low. The mean difference AR-MR was -1.28±0.29 diopters (D for sphere. Astigmatism showed better correlation between KR and MR. CONCLUSION: We suggest AR sphere plus 1.25 D and the KR cylinder as the starting point for MR in eyes with a Lentis Mplus X multifocal IOL. If AR measurements are equal to MR, decentration of the IOL should be suspected.

Enhancement of strong-field multiple ionization in the vicinity of the conical intersection in 1,3-cyclohexadiene ring opening

International Nuclear Information System (INIS)

Petrovic, Vladimir S.; Kim, Jaehee; Schorb, Sebastian; White, James; Cryan, James P.; Zipp, Lucas; Glownia, J. Michael; Broege, Douglas; Miyabe, Shungo; Tao, Hongli; Martinez, Todd; Bucksbaum, Philip H.

2013-01-01

Nonradiative energy dissipation in electronically excited polyatomic molecules proceeds through conical intersections, loci of degeneracy between electronic states. We observe a marked enhancement of laser-induced double ionization in the vicinity of a conical intersection during a non-radiative transition. We measured double ionization by detecting the kinetic energy of ions released by laser-induced strong-field fragmentation during the ring-opening transition between 1,3-cyclohexadiene and 1,3,5-hexatriene. The enhancement of the double ionization correlates with the conical intersection between the HOMO and LUMO orbitals

Separation and extension of cover inequalities for second-order conic knapsack constraints with GUBs

DEFF Research Database (Denmark)

Atamtürk, Alper; Muller, Laurent Flindt; Pisinger, David

We consider the second-order conic equivalent of the classic knapsack polytope where the variables are subject to generalized upper bound constraints. We describe and compare a number of separation and extension algorithms which make use of the extra structure implied by the generalized upper bound...... constraints in order to strengthen the second-order conic equivalent of the classic cover cuts. We show that determining whether a cover can be extended with a variable is NP-hard. Computational experiments are performed comparing the proposed separation and extension algorithms. These experiments show...

The uncorrected refractive error challenge

Directory of Open Access Journals (Sweden)

Kovin Naidoo

2016-11-01

Full Text Available Refractive error affects people of all ages, socio-economic status and ethnic groups. The most recent statistics estimate that, worldwide, 32.4 million people are blind and 191 million people have vision impairment. Vision impairment has been defined based on distance visual acuity only, and uncorrected distance refractive error (mainly myopia is the single biggest cause of worldwide vision impairment. However, when we also consider near visual impairment, it is clear that even more people are affected. From research it was estimated that the number of people with vision impairment due to uncorrected distance refractive error was 107.8 million,1 and the number of people affected by uncorrected near refractive error was 517 million, giving a total of 624.8 million people.

Idealized digital models for conical reed instruments, with focus on the internal pressure waveform.

Science.gov (United States)

Kergomard, J; Guillemain, P; Silva, F; Karkar, S

2016-02-01

Two models for the generation of self-oscillations of reed conical woodwinds are presented. The models use the fewest parameters (of either the resonator or the exciter), whose influence can be quickly explored. The formulation extends iterated maps obtained for lossless cylindrical pipes without reed dynamics. It uses spherical wave variables in idealized resonators, with one parameter more than for cylinders: the missing length of the cone. The mouthpiece volume equals that of the missing part of the cone, and is implemented as either a cylindrical pipe (first model) or a lumped element (second model). Only the first model adds a length parameter for the mouthpiece and leads to the solving of an implicit equation. For the second model, any shape of nonlinear characteristic can be directly considered. The complex characteristic impedance for spherical waves requires sampling times smaller than a round trip in the resonator. The convergence of the two models is shown when the length of the cylindrical mouthpiece tends to zero. The waveform is in semi-quantitative agreement with experiment. It is concluded that the oscillations of the positive episode of the mouthpiece pressure are related to the length of the missing part, not to the reed dynamics.

Anisotropic Exchange Interaction in the Conical Magnetic Phase of Erbium

DEFF Research Database (Denmark)

Jensen, J.

1974-01-01

From a general two ion spin Hamiltonian, an expression is deduced for the energies of spin waves propagating in a hexagonal solid in which the magnetic moments are ordered in a conical or helical structure. The spin wave dispersion relation in the c direction of Er in its conical magnetic phase...... at 4.5K, which has been studied by Nicklow et al (1971) is reanalysed. In this analysis an alternative kind of anisotropic coupling between the total angular moments (Ji and Jj) on the sites i and j is introduced which is proportional to the following combination of Racah operators: O2, -2(Ji), O2, -2......(Jj), expressed with respect to a coordinate system with the z axis along the c direction. The resulting anisotropy (both the constant and the q dependent part) is reduced by an order of magnitude in comparison with that deduced by Nicklow et al (1971). The constant anisotropy is found to be equal...

Torsional Vibrations of a Conic Shaft with Opposite Tapers Carrying Arbitrary Concentrated Elements

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Jia-Jang Wu

2013-01-01

Full Text Available The purpose of this paper is to present the exact solution for free torsional vibrations of a linearly tapered circular shaft carrying a number of concentrated elements. First of all, the equation of motion for free torsional vibration of a conic shaft is transformed into a Bessel equation, and, based on which, the exact displacement function in terms of Bessel functions is obtained. Next, the equations for compatibility of deformations and equilibrium of torsional moments at each attaching point (including the shaft ends between the concentrated elements and the conic shaft with positive and negative tapers are derived. From the last equations, a characteristic equation of the form is obtained. Then, the natural frequencies of the torsional shaft are determined from the determinant equation , and, corresponding to each natural frequency, the column vector for the integration constants, , is obtained from the equation . Substitution of the last integration constants into the associated displacement functions gives the corresponding mode shape of the entire conic shaft. To confirm the reliability of the presented theory, all numerical results obtained from the exact method are compared with those obtained from the conventional finite element method (FEM and good agreement is achieved.

EDITORIAL: Sensitive structures: refractive indices in nanotechnology Sensitive structures: refractive indices in nanotechnology

Science.gov (United States)

Demming, Anna

2012-12-01

Refractive index effects using nanoscale systems are frequently applied in new imaging, sensing and even visibility cloaking technology. In this issue, researchers in Japan use simulations and experiments to describe the confinement of optical vortices in nanoscale fin structures and the sensitivity of these systems to the refractive index of the surrounding media [1]. The effects of refraction as light rays pass between different media were recorded as long ago as the first century AD, by Ptolemy [2]. Over the following centuries the phenomena inspired Ibn Sahl in 984 [3], Thomas Harriot in 1602 [4], Willebrord Snellius in 1621 [5] and Rene Descartes in 1637 [6] to independently derive the more accurate and elegant equation for refraction so familiar to us today. Recent studies of the interactions between light and matter continue to reveal a wealth of phenomena that originate in the effects of the refractive indices of materials. Nanostructures can be used to manipulate conditions that affect the refractive indices of materials, such as temperature. A E Aliev et al at the University of Texas reported a striking demonstration of temperature-dependent refractive index effects using a free-standing, highly aligned carbon nanotube aerogel sheet [7]. They used the extremely low thermal capacitance and high heat transfer ability of transparent carbon nanotube sheets to enable high-frequency modulation of the sheet temperature over an enormous temperature range. The resulting sharp, rapidly changing gradient of the refractive index in the surrounding liquid or gas makes objects seem to disappear and can be used for visibility cloaking. Light-matter interaction resonances, where light is confined at the nanoscale, can be extremely sensitive to changes in the refractive index of the surrounding media [8], even allowing single-molecule detection [9]. Plasmons, the collective oscillations of electrons in response to incident light, are a typical example. Researchers at Rice

Micro-taper as focusing or scattering optical element

Energy Technology Data Exchange (ETDEWEB)

Degtyarev, S. A., E-mail: sealek@gmail.com; Ustinov, A. V., E-mail: andr@smr.ru; Khonina, S. N., E-mail: khonina@smr.ru [Samara State Aerospace University, Moskovskoye Shosse 34, Samara, Russia, 443086 (Russian Federation); Imaging Processing Systems Institute of the Russian Academy of Science, Molodogvardeyskaya street, 151, Samara, Russia, 443001 (Russian Federation)

2016-04-13

We consider micro-taper (narrow refractive axicon) as optical element which is focusing or scattering in dependence on axicon’s cone angle. The diffraction of laser beam by micro-taper is simulated by two methods: multiply internal ray reflections using geometrical approach and Helmholtz equation solving using finite elements method. Based on ray optics we derive analytic formulas for conical angles values which provide focusing or scattering features of micro-taper. Numerical simulation by finite elements method verifies theoretical results.

Numerical Study of Motion of Falling Conical Graupel

Science.gov (United States)

Chueh, Chih-Che; Wang, Pao K.; Hashino, Tempei

2018-01-01

In the present study, the attitudes of freely-falling conical graupel with a realistic range of densities are investigated numerically by solving the transient Navier-Stokes equations and the body dynamics equations representing the 6-degrees-of-freedom motion. This framework allows us to determine the position and orientation of the graupel in response to the hydrodynamic force of the flow fields. The results show more significant horizontal movements than those cases with a fixed bulk density of ice assumed in our previous study. This is because the real graupel particles possess the density less than the bulk density of ice, which, in turn, leads to a relatively small mass and a relatively small set of moments of inertia. We demonstrate that, with the six degrees of freedom considered together, when Reynolds number is small, a typical damped oscillation occurs, whereas when Reynolds number is high, amplifying oscillation may occur which leads to more complicated and unpredictable flying attitudes such as tumbling. The drag coefficients obtained in the present study agree with the previous studies and can be approximated by that of spheres of the same Reynolds numbers. We also show that conical graupel can perform significant horizontal translations which can be on the order of 1 km in 1 h.

Interaction of a conical shock wave with a turbulent boundary layer

Science.gov (United States)

Teh, S. L.; Gai, S. L.

The paper reports an investigation on the interaction of an incident conical shock wave with a turbulent boundary layer. Although a conical shock theoretically creates a hyperbolic shock trace on the flat plate, the line joining all the experimental interaction origins takes a different form due to varying upstream influence. The existence of strong pressure gradients in the spanwise direction after the shock leads to the boundary-layer twist. A model based on the upstream influence of the shock when combined with McCabe's secondary-flow theory showed separation to occur at an external flow deflection of 11.8 deg. The oil flow measurements however show this to occur at 9.2 deg. This discrepancy is of the same order as that found by McCabe. Detailed data involving Schlieren and shadowgraph photography, surface-flow visualization, and surface-pressure measurements are presented.

Flow structures in large-angle conical diffusers measured by PIV

DEFF Research Database (Denmark)

Meyer, Knud Erik; Nielsen, L.; Nielsen, N.F.

2004-01-01

Flow in two different conical diffusers with large opening angles (30° and 18°) have been measured with stereoscopic Particle Image Velocimetry (PIV). The measurements were done in a cross section just after the exit of the diffuser. The Reynolds number was 100000 based on upstream diameter...

The spectra of conical bubble sonoluminescence in 1,2-propanediol and glycol

International Nuclear Information System (INIS)

He Shoujie; Jing Ha; Li Xuechen; Li Qing; Dong Lifang; Wang, Long

2007-01-01

A conical bubble straight tube apparatus was set up to study sonoluminescence. The spectra of conical bubble sonoluminescence for 1,2-propanediol and glycol were detected. The results show that the luminescence is intense, and the spectra consist of a broad background on which five clear sequences of Swan bands and three sequences of the B 2 Σ + → X 2 Σ + transition of CN are superimposed. A band assigned to the A 2 Δ → X 2 Π transition of CH was also measured and the vibrational and rotational structures of Swan bands could be resolved. The origin of the C* 2 and C 2 H* is discussed. Finally, the achieved molecular vibrational temperature is estimated to be about 5400 ± 350 K

Matrix analysis of the asymmetrical bending of conical shell-beams and their singular assemblies

International Nuclear Information System (INIS)

Kiedrzynski, A.; Coppens, L.

1979-01-01

As an alternative to refined finite element methodology a new method has been derived to investigate in much detail the linear static behaviour of singular assemblies of moderately thick conical shells of revolution submitted to non-axisymmetrical loads at their ends (an assembly of conical sections is said to be singular when the geometrical discontinuities are deformable, i.e. not stiffened by diaphragms). A detailed preliminary study has shown that the currently adopted simplifying assumptions in shell theories for moderate thickness lead to unconsistencies at any departure from axisymmetric loading. Therefore, FLUEGGE's general shell theory has been applied to a conical section, yielding a set of mixed first order differential equations in terms of displacements and conjuguated stress resultants well suited for a matrix formalism. The numerical integration is based on a fourth-order Runge-Kutta method and provides an 8 x 8 mixed matrix. This matrix contains complete information on the distribution of the displacements (exhibiting the warping and ovalization of the cross-section) and of the stress resultants along the meridian; also the stiffness coefficients proceed from it. (orig.)

Negative refraction angular characterization in one-dimensional photonic crystals.

Directory of Open Access Journals (Sweden)

Jesus Eduardo Lugo

2011-04-01

Full Text Available Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity developed here. We also analytically derived the negative refraction correctness condition that gives the angular region where negative refraction occurs.By using standard photonic techniques we experimentally determined the relationship between incidence and negative refraction angles and found the negative refraction range by applying the correctness condition. In order to compare both theories with experimental results an output refraction correction was utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theories in the negative refraction zone.Since both theories and the experimental observations agreed well in the negative refraction region, we can use both negative refraction theories plus the output correction to predict negative refraction angles. This can be very useful from a practical point of view for space filtering applications such as a photonic demultiplexer or for sensing applications.

Negative refraction angular characterization in one-dimensional photonic crystals.

Science.gov (United States)

Lugo, Jesus Eduardo; Doti, Rafael; Faubert, Jocelyn

2011-04-06

Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity developed here. We also analytically derived the negative refraction correctness condition that gives the angular region where negative refraction occurs. By using standard photonic techniques we experimentally determined the relationship between incidence and negative refraction angles and found the negative refraction range by applying the correctness condition. In order to compare both theories with experimental results an output refraction correction was utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theories in the negative refraction zone. Since both theories and the experimental observations agreed well in the negative refraction region, we can use both negative refraction theories plus the output correction to predict negative refraction angles. This can be very useful from a practical point of view for space filtering applications such as a photonic demultiplexer or for sensing applications.

Mixed-Integer Conic Linear Programming: Challenges and Perspectives

Science.gov (United States)

2013-10-01

The novel DCCs for MISOCO may be used in branch- and-cut algorithms when solving MISOCO problems. The experimental software CICLO was developed to...perform limited, but rigorous computational experiments. The CICLO solver utilizes continuous SOCO solvers, MOSEK, CPLES or SeDuMi, builds on the open...submitted Fall 2013. Software: 1. CICLO : Integer conic linear optimization package. Authors: J.C. Góez, T.K. Ralphs, Y. Fu, and T. Terlaky

Conical differentiability for evolution variational inequalities

Science.gov (United States)

Jarušek, Jiří; Krbec, Miroslav; Rao, Murali; Sokołowski, Jan

The conical differentiability of solutions to the parabolic variational inequality with respect to the right-hand side is proved in the paper. From one side the result is based on the Lipschitz continuity in H {1}/{2},1 (Q) of solutions to the variational inequality with respect to the right-hand side. On the other side, in view of the polyhedricity of the convex cone K={v∈ H;v |Σ c⩾0,v |Σ d=0}, we prove new results on sensitivity analysis of parabolic variational inequalities. Therefore, we have a positive answer to the question raised by Fulbert Mignot (J. Funct. Anal. 22 (1976) 25-32).

Using aircraft measurements to determine the refractive index of Saharan dust during the DODO Experiments

Directory of Open Access Journals (Sweden)

C. L. McConnell

2010-03-01

Full Text Available Much uncertainty in the value of the imaginary part of the refractive index of mineral dust contributes to uncertainty in the radiative effect of mineral dust in the atmosphere. A synthesis of optical, chemical and physical in-situ aircraft measurements from the DODO experiments during February and August 2006 are used to calculate the refractive index mineral dust encountered over West Africa. Radiative transfer modeling and measurements of broadband shortwave irradiance at a range of altitudes are used to test and validate these calculations for a specific dust event on 23 August 2006 over Mauritania. Two techniques are used to determine the refractive index: firstly a method combining measurements of scattering, absorption, size distributions and Mie code simulations, and secondly a method using composition measured on filter samples to apportion the content of internally mixed quartz, calcite and iron oxide-clay aggregates, where the iron oxide is represented by either hematite or goethite and clay by either illite or kaolinite. The imaginary part of the refractive index at 550 nm (n_i⁵⁵⁰ is found to range between 0.0001 i to 0.0046 i, and where filter samples are available, agreement between methods is found depending on mineral combination assumed. The refractive indices are also found to agree well with AERONET data where comparisons are possible. n_i⁵⁵⁰ is found to vary with dust source, which is investigated with the NAME model for each case. The relationship between both size distribution and n_i⁵⁵⁰ on the accumulation mode single scattering albedo at 550 nm (ω₀⁵⁵⁰ are examined and size distribution is found to have no correlation to ω₀⁵⁵⁰, while n_i⁵⁵⁰ shows a strong linear relationship with ω₀⁵⁵⁰. Radiative transfer modeling was performed with different

Free vibration of symmetric angle ply truncated conical shells under different boundary conditions using spline method

Energy Technology Data Exchange (ETDEWEB)

Viswanathan, K. K.; Aziz, Z. A.; Javed, Saira; Yaacob, Y. [Universiti Teknologi Malaysia, Johor Bahru (Malaysia); Pullepu, Babuji [S R M University, Chennai (India)

2015-05-15

Free vibration of symmetric angle-ply laminated truncated conical shell is analyzed to determine the effects of frequency parameter and angular frequencies under different boundary condition, ply angles, different material properties and other parameters. The governing equations of motion for truncated conical shell are obtained in terms of displacement functions. The displacement functions are approximated by cubic and quintic splines resulting into a generalized eigenvalue problem. The parametric studies have been made and discussed.

Free vibration of symmetric angle ply truncated conical shells under different boundary conditions using spline method

International Nuclear Information System (INIS)

Viswanathan, K. K.; Aziz, Z. A.; Javed, Saira; Yaacob, Y.; Pullepu, Babuji

2015-01-01

Free vibration of symmetric angle-ply laminated truncated conical shell is analyzed to determine the effects of frequency parameter and angular frequencies under different boundary condition, ply angles, different material properties and other parameters. The governing equations of motion for truncated conical shell are obtained in terms of displacement functions. The displacement functions are approximated by cubic and quintic splines resulting into a generalized eigenvalue problem. The parametric studies have been made and discussed.

Conical scan impact study. Volume 2: Small local user data processing facility. [multispectral band scanner design alternatives for earth resources data

Science.gov (United States)

Ebert, D. H.; Chase, P. E.; Dye, J.; Fahline, W. C.; Johnson, R. H.

1973-01-01

The impact of a conical scan versus a linear scan multispectral scanner (MSS) instrument on a small local-user data processing facility was studied. User data requirements were examined to determine the unique system rquirements for a low cost ground system (LCGS) compatible with the Earth Observatory Satellite (EOS) system. Candidate concepts were defined for the LCGS and preliminary designs were developed for selected concepts. The impact of a conical scan MSS versus a linear scan MSS was evaluated for the selected concepts. It was concluded that there are valid user requirements for the LCGS and, as a result of these requirements, the impact of the conical scanner is minimal, although some new hardware development for the LCGS is necessary to handle conical scan data.

Power of the Poincaré group: elucidating the hidden symmetries in focal conic domains.

Science.gov (United States)

Alexander, Gareth P; Chen, Bryan Gin-Ge; Matsumoto, Elisabetta A; Kamien, Randall D

2010-06-25

Focal conic domains are typically the "smoking gun" by which smectic liquid crystalline phases are identified. The geometry of the equally spaced smectic layers is highly generic but, at the same time, difficult to work with. In this Letter we develop an approach to the study of focal sets in smectics which exploits a hidden Poincaré symmetry revealed only by viewing the smectic layers as projections from one-higher dimension. We use this perspective to shed light upon several classic focal conic textures, including the concentric cyclides of Dupin, polygonal textures, and tilt-grain boundaries.

Dispersive O+ conics observed in the plasma-sheet boundary layer with CRRES/LOMICS during a magnetic storm

Directory of Open Access Journals (Sweden)

M. Wüest

1996-06-01

Full Text Available We present initial results from the Low-energy magnetospheric ion composition sensor (LOMICS on the Combined release and radiation effects satellite (CRRES together with electron, magnetic field, and electric field wave data. LOMICS measures all important magnetospheric ion species (H+, He++, He+, O++, O+ simultaneously in the energy range 60 eV to 45 keV, as well as their pitch-angle distributions, within the time resolution afforded by the spacecraft spin period of 30 s. During the geomagnetic storm of 9 July 1991, over a period of 42 min (0734 UT to 0816 UT the LOMICS ion mass spectrometer observed an apparent O+ conic flowing away from the southern hemisphere with a bulk velocity that decreased exponentially with time from 300 km/s to 50 km/s, while its temperature also decreased exponentially from 700 to 5 eV. At the onset of the O+ conic, intense low-frequency electromagnetic wave activity and strong pitch-angle scattering were also observed. At the time of the observations the CRRES spacecraft was inbound at L~7.5 near dusk, magnetic local time (MLT, and at a magnetic latitude of –23°. Our analysis using several CRRES instruments suggests that the spacecraft was skimming along the plasma sheet boundary layer (PSBL when the upward-flowing ion conic arrived. The conic appears to have evolved in time, both slowing and cooling, due to wave-particle interactions. We are unable to conclude whether the conic was causally associated with spatial structures of the PSBL or the central plasma sheet.

76 FR 25732 - Order of Suspension of Trading; In the Matter of Advanced Refractive Technologies, Inc., Bluebook...

Science.gov (United States)

2011-05-05

... of Advanced Refractive Technologies, Inc., Bluebook International Holding Co. (The), CBCom, Inc., Gener8xion Entertainment, Inc., Group Long Distance Inc., HiEnergy Technologies, Inc., and Holter Technologies Holding, A.G. (n/k/a International Consortium Corp.) It appears to the Securities and Exchange...

Study the Possibility for Manufacturing a Conical Pipe Thread by Expansion

Directory of Open Access Journals (Sweden)

S. A. Evsyukov

2014-01-01

Full Text Available The experience of operating oil wells showed that the weak point of tubing is a connecting thread.Currently, the pipe thread of the specified class is made using the technology of cutting. The process of cutting a thread leads to waste metal chips and cutting fibers. Therefore the idea arose to make a thread by the method of pressure shaping.The aim was to study the possibility for full filling of the threaded matrix profile.The study was conducted by means of mathematical modeling in the software complex DEFORM. The impact of technological and geometrical factors on the process of form change was in detail analyzed. Thus, a work-piece material was specified to be continuous, isotropic, homogeneous, viscous-plastic and a tool material was set as a hard one. The friction was speci-fied according to Prandtl-Siebel law with the friction factor of 0.3. The thread profile has been replaced by the annular grooves of the similar profile. The task was considered to be axisymmetric.Scientific novelty of received results consists in revealed regularities of the plastic de-formation process of the work-piece when forming a profile of the conical thread on the pipe in the process of its expansion with a conical punch.The simulation allowed us to obtain information about the stress-strain state of the work-piece and tool, about the nature of the metal flow during deformation, and about the strength parameters of the process.In particular, it was found that the work-piece metal is displaced along the pipe axis both in punch movement direction and in the opposite one. Thus, a mechanical end burr is formed. The article shows that to remove a mechanical end burr requires insertion of extra limit stop housing. The article also analyses distribution of stresses arising in the matrix at the final moment of deformation. It was proved that the highest stresses occur in the hollows of the threaded part of matrix. Thus, their absolute value does not exceed 470 MPa that

Dispersion of near-infrared laser energy through radicular dentine when using plain or conical tips.

Science.gov (United States)

Teo, Christine Yi Jia; George, Roy; Walsh, Laurence J

2018-02-01

The aim of this study was to investigate the influence of tip design on patterns of laser energy dispersion through the dentine of tooth roots when using near-infrared diode lasers. Diode laser emissions of 810 or 940 nm were used in combination with optical fiber tips with either conventional plain ends or conical ends, to irradiate tooth roots of oval or round cross-sectional shapes. The lasers were operated in continuous wave mode at 0.5 W for 5 s with the distal end of the fiber tip placed in the apical or coronal third of the root canal at preset positions. Laser light exiting through the roots and apical foramen was imaged, and the extent of lateral spread calculated. There was a significant difference in infrared light exiting the root canal apex between plain and conical fiber tips for both laser wavelengths, with more forward transmission of laser energy through the apex for plain tips. For both laser wavelengths, there were no significant differences in emission patterns when the variable of canal shape was used and all other variables were kept the same (plain vs conical tip, tip position). To ensure optimal treatment effect and to prevent the risks of inadvertent laser effects on the adjacent periapical tissues, it is important to have a good understanding of laser transmission characteristics of the root canal and root dentine. Importantly, it is also essential to understand transmission characteristics of plain and conical fibers tips.

Refractive error study in young subjects: results from a rural area in Paraguay

Directory of Open Access Journals (Sweden)

Isabel Signes-Soler

2017-03-01

Full Text Available AIM: To evaluate the distribution of refractive error in young subjects in a rural area of Paraguay in the context of an international cooperation campaign for the prevention of blindness. METHODS: A sample of 1466 young subjects (ranging from 3 to 22 years old, with a mean age of 11.21±3.63 years old, were examined to assess their distance visual acuity (VA and refractive error. The first screening examination performed by trained volunteers, included visual acuity testing, autokeratometry and non-cycloplegic autorefraction. Inclusion criteria for a second complete cycloplegic eye examination by an optometrist were VA <20/25 (0.10 logMAR or 0.8 decimal and/or corneal astigmatism ≥1.50 D. RESULTS: An uncorrected distance VA of 0 logMAR (1.0 decimal was found in 89.2% of children. VA <20/25 and/or corneal astigmatism ≥1.50 D was found in 3.9% of children (n=57, with a prevalence of hyperopia of 5.2% (0.2% of the total in this specific group. Furthermore, myopia (spherical equivalent ≤-0.5 D was found in 37.7% of the refracted children (0.5% of the total. The prevalence of refractive astigmatism (cylinder ≤-1.50 D was 15.8% (0.6% of the total. Visual impairment (VI (0.05≤VA≤0.3 was found in 12/114 (0.4% of the refracted eyes. Main causes for VI were refractive error (58%, retinal problems (17%, 2/12, albinism (17%, 2/12 and unknown (8%, 1/12. CONCLUSION: A low prevalence of refractive error has been found in this rural area of Paraguay, with higher prevalence of myopia than of hyperopia.

Observation of Biological Tissues Using Common Path Optical Coherence Tomography with Gold Coated Conical Tip Lens Fiber

International Nuclear Information System (INIS)

Taguchi, K; Sugiyama, J; Totsuka, M; Imanaka, S

2012-01-01

In this paper, we proposed a high lateral resolution common-path Fourier domain optical coherence tomography(OCT) system with the use of a chemically etched single mode fiber. In our experiments, single mode optical fiber for 1310nm was used for preparing the tapered tips. Our system used a conical microlens that was chemically etched by selective chemical etching technique using an etching solution of buffered hydrofluoric acid (BHF). From experimental results, we verified that our proposed optical coherence tomography system could operate as a common-path Fourier domain OCT system and conical tip lens fiber was very useful for a high lateral resolution common-path Fourier domain OCT system. Furthermore, we could observe a surface of paramecium bursaria and symbiotic chlorella in the paramecium bursaria using gold coated conical-tip fiber in the water.

ANALYSIS OF RIBBONING ON CONICAL YARN PACKAGE WOUND BY OPENEND SPINNING MACHINES

Directory of Open Access Journals (Sweden)

Resul FETTAHOV

2001-03-01

Full Text Available In this paper, Ribboning , one of the common faults in yarn packages, is mathematically analysed. If yarn is repeatly laid on top of or along the same path as the previously wound yarn, this duplication of yarn path on the package creates a defect known as ribboning. The number of turns of package (n per double traverse of yarn guide is calculated in two different way One is calculated the length of a coil on the package and total length of yarn in a double traverse; the other is considered transmission rate between drum and conical yarn package The result of two different approach is similar and the probable diameter of conical yarn package which ribboning is occurred is calculated and used on Schalafhorst-Autocore OE spinning machines.

Theoretical interpretation of upstreaming electrons and elevated conics on auroral field lines

International Nuclear Information System (INIS)

Ashour-Abdalla, M.; Schriver, D.

1989-01-01

Recent VIKING satellite observations in the auroral zone have shown the association of elevated ion conics (conics with a low energy cutoff above zero) with upward streaming electrons in the presence of low frequency electric field fluctuations. A self-consistent particle simulation was developed which assumed the presence of a steady state electric field on auroral zone field lines capable of accelerating ions up the magnetic field lines. Results from this study show that a low frequency ion-ion two stream instability can be excited. This low frequency instability creates a fluctuating electric field which heats the ions oblique to the magnetic field forming distributions similar to the elevated ion comics. The ion-ion waves also interact resonantly with electrons and accelerates them in the direction of the ion beam

Super-Cavitating Flow Around Two-Dimensional Conical, Spherical, Disc and Stepped Disc Cavitators

Science.gov (United States)

Sooraj, S.; Chandrasekharan, Vaishakh; Robson, Rony S.; Bhanu Prakash, S.

2017-08-01

A super-cavitating object is a high speed submerged object that is designed to initiate a cavitation bubble at the nose which extends past the aft end of the object, substantially reducing the skin friction drag that would be present if the sides of the object were in contact with the liquid in which the object is submerged. By reducing the drag force the thermal energy consumption to move faster can also be minimised. The super-cavitation behavioural changes with respect to Cavitators of various geometries have been studied by varying the inlet velocity. Two-dimensional computational fluid dynamics analysis has been carried out by applying k-ε turbulence model. The variation of drag coefficient, cavity length with respect to cavitation number and inlet velocity are analyzed. Results showed conical Cavitator with wedge angle of 30° has lesser drag coefficient and cavity length when compared to conical Cavitators with wedge angles 45° and 60°, spherical, disc and stepped disc Cavitators. Conical cavitator 60° and disc cavitator have the maximum cavity length but with higher drag coefficient. Also there is significant variation of supercavitation effect observed between inlet velocities of 32 m/s to 40 m/s.

Past and present of corneal refractive surgery

DEFF Research Database (Denmark)

Vestergaard, Anders Højslet

Surgical correction of refractive errors is becoming increasingly popular. In the 1990s, the excimer laser revolutionized the field of corneal refractive surgery with PRK and LASIK, and lately refractive lenticule extraction (ReLEx) of intracorneal tissue, using only a femtosecond laser, has become...

A web-based information system for management and analysis of patient data after refractive eye surgery.

Science.gov (United States)

Zuberbuhler, Bruno; Galloway, Peter; Reddy, Aravind; Saldana, Manuel; Gale, Richard

2007-12-01

The aim was to develop a software tool for refractive surgeons using a standard user-friendly web-based interface, providing the user with a secure environment to protect large volumes of patient data. The software application was named "Internet-based refractive analysis" (IBRA), and was programmed with the computer languages PHP, HTML and JavaScript, attached to the opensource MySQL database. IBRA facilitated internationally accepted presentation methods including the stability chart, the predictability chart and the safety chart; it was able to perform vector analysis for the course of a single patient or for group data. With the integrated nomogram calculation, treatment could be customised to reduce the postoperative refractive error. Multicenter functions permitted quality-control comparisons between different surgeons and laser units.

Human resources for refraction services in Central Nepal.

Science.gov (United States)

Kandel, Himal; Murthy, G V S; Bascaran, Covadonga

2015-07-01

Uncorrected refractive error is a public health problem globally and in Nepal. Planning of refraction services is hampered by a paucity of data. This study was conducted to determine availability and distribution of human resources for refraction, their efficiency, the type and extent of their training; the current service provision of refraction services and the unmet need in human resources for refraction in Central Nepal. This was a descriptive cross-sectional study. All refraction facilities in the Central Region were identified through an Internet search and interviews of key informants from the professional bodies and parent organisations of primary eye centres. A stratified simple random sampling technique was used to select 50 per cent of refraction facilities. The selected facilities were visited for primary data collection. Face-to-face interviews were conducted with the managers and the refractionists available in the facilities using a semi-structured questionnaire. Data was collected in 29 centres. All the managers (n=29; response rate 100 per cent) and 50 refractionists (Response rate 65.8 per cent) were interviewed. Optometrists and ophthalmic assistants were the main providers of refraction services (n=70, 92.11 per cent). They were unevenly distributed across the region, highly concentrated around urban areas. The median number of refractions per refractionist per year was 3,600 (IQR: 2,400 - 6,000). Interviewed refractionists stated that clients' knowledge, attitude and practice related factors such as lack of awareness of the need for refraction services and/or availability of existing services were the major barriers to the output of refraction services. The total number of refractions carried out in the Central Region per year was 653,176. An additional 170 refractionists would be needed to meet the unmet need of 1,323,234 refractions. The study findings demand a major effort to develop appropriately trained personnel when planning

High efficiency conical scanner for earth resources applications

Science.gov (United States)

Bates, J. C.; Dumas, H. J., Jr.

1975-01-01

A description is given of a six-arm conical scanner which was selected to provide a continuous line-of-sight scan. Two versions of the instrument are considered. The two versions differ in their weight. The weight of the heavy version is 600 lbs. A light weight design which employs beryllium and aluminum optical components weighs only 350 lbs. A multiplexer and analog-to-digital converter are to be incorporated into the design. Questions of instrument performance are also discussed.

Fully 3D refraction correction dosimetry system

International Nuclear Information System (INIS)

Manjappa, Rakesh; Makki, S Sharath; Kanhirodan, Rajan; Kumar, Rajesh; Vasu, Ram Mohan

2016-01-01

The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

Fully 3D refraction correction dosimetry system.

Science.gov (United States)

Manjappa, Rakesh; Makki, S Sharath; Kumar, Rajesh; Vasu, Ram Mohan; Kanhirodan, Rajan

2016-02-21

The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

Quasi-conical centrifugal ion trap

International Nuclear Information System (INIS)

Golikov, Yu.K.; Solov'ev, K.V.; Grigor'ev, D.V.; Flegontova, E.Yu.

1999-01-01

This paper describes a new excellent ion trap that principally differs from the classic hyperbolic one by its action. The action is based on the axisymmetric electrostatic quasi-conical field with the following potential type: F=F 0 [ln r - r 2 /2+z 2 ], where r, z are cylindrical dimensionless coordinates. The radial potential run (f=ln r-r 2 /2), in this case, is exactly presented by the approximation function f a =ar 2 +b/r 2 +c. In addition, there are some ranges of r (for example, 0.6< r<0.35), in which the concurrence accuracy value is above 0.5%. The paper presents the theory of particles dynamics in the centrifugal trap. Basic correlation for resolution ratios and sensitivity values are developed. Recommendations on the centrifugal trap design implementation, including the recording system, are given

Numerical analysis for the flow field past a two-staged conical orifice

International Nuclear Information System (INIS)

Kim, Yeon Soo; Kim, You Gon

2001-01-01

The objective of the paper was to measure the pressure drop and to investigate the recirculation region of the conical orifices used in Kwang-yang Iron and Steel Company. The flow field with water used as a working fluid was the turbulent flow for Reynolds number of 2x10 4 . The effective parameters for the pressure drop and the recirculation region were the conical orifice's inclined angle (θ) against the wall, the interval(L) between orifices, the relative angle of rotation(α) of the orifices, the shape of the orifice's hole(circle, rectangle, triangle) having the same area. It was found that the shape of the orifice's hold affected the pressure drop and the flow field a lot. But the other parameters did not make much differences to the pressure drop. The PISO algorithm with FLUENT code was employed

Adjustable internal structure for reconstructing gradient index profile of crystalline lens.

Science.gov (United States)

Bahrami, Mehdi; Goncharov, Alexander V; Pierscionek, Barbara K

2014-03-01

Employing advanced technologies in studying the crystalline lens of the eye has improved our understanding of the refractive index gradient of the lens. Reconstructing and studying such a complex structure requires models with adaptable internal geometry that can be altered to simulate geometrical and optical changes of the lens with aging. In this Letter, we introduce an optically well-defined, geometrical structure for modeling the gradient refractive index profile of the crystalline lens with the advantage of an adjustable internal structure that is not available with existing models. The refractive index profile assigned to this rotationally symmetric geometry is calculated numerically, yet it is shown that this does not limit the model. The study provides a basis for developing lens models with sophisticated external and internal structures without the need for analytical solutions to calculate refractive index profiles.

Dark refraction shift with allowance for astigmatism

Directory of Open Access Journals (Sweden)

W.D.H. Gillan

2005-12-01

Full Text Available Purpose: To show that the dark refraction shift (dark focus is a more complicated phenomenon than implied when presented as spherical. Methods: Fifty autorefractor measurements of refractive state of the right eye were obtained in light  and  dark  conditions.  Multivariate  methods were used to analyze the data and stereo-pair scat-ter plots, polar meridional profiles and other means of presenting results are used to show important characteristics of the dark refraction shift. Results: The complexity of the dark refrac-tion shift is indicated by stereo-pair scatter plots showing the amount of stigmatic and antistigmatic variation that occurs in light and dark conditions. The mean dark refraction shift is presented in a complete manner including all three components of refractive state. The greater variance and covari-ance under dark conditions is clearly shown by the term-by-term dark-light variance-covariance ratio and polar profiles  of variance and covariance.Conclusions: The  dark  refraction  shift  is  a more complicated phenomenon than implied by representations as purely spherical in nature.

Super-Virtual Refraction Interferometric Redatuming: Enhancing the Refracted Energy

KAUST Repository

Aldawood, Ali

2012-02-26

onshore seismic data processing. Refraction tomography is becoming a common way to estimate an accurate near surface velocity model. One of the problems with refraction tomography is the low signal to noise ration in far offset data. To improve, we propose using super-virtual refraction interferometry to enhance the weak energy at far offsets. We use Interferometric Green\\'s functions to redatum sources by cross-correlating two traces recorded at receiver stations, A and B, from a source at location W. The result is a redatumed trace with a virtual source at A and a receiver at B, which can also be obtained by correlating two traces recorded at A and B from different shots. Stacking them would enhance the signal-to-noise ratio of this "virtual" trace. We next augment redatuming with convolution and stacking. The trace recorded at B from a virtual source at A is convolved with the original trace recorded at A from a source at W. The result is a "super-virtual" trace at B in the far-offset from a source at W. Stacking N traces gives a vN-improvement. We applied our method to noisy synthetic and field data recorded over a complex near-surface and we could pick more traces at far offsets. It was possible to accommodate more picks resulting in a better subsurface coverage

Super-Virtual Refraction Interferometric Redatuming: Enhancing the Refracted Energy

KAUST Repository

Aldawood, Ali; Alshuhail, Abdulrahman Abdullatif Abdulrahman; Hanafy, Sherif

2012-01-01

onshore seismic data processing. Refraction tomography is becoming a common way to estimate an accurate near surface velocity model. One of the problems with refraction tomography is the low signal to noise ration in far offset data. To improve, we propose using super-virtual refraction interferometry to enhance the weak energy at far offsets. We use Interferometric Green's functions to redatum sources by cross-correlating two traces recorded at receiver stations, A and B, from a source at location W. The result is a redatumed trace with a virtual source at A and a receiver at B, which can also be obtained by correlating two traces recorded at A and B from different shots. Stacking them would enhance the signal-to-noise ratio of this "virtual" trace. We next augment redatuming with convolution and stacking. The trace recorded at B from a virtual source at A is convolved with the original trace recorded at A from a source at W. The result is a "super-virtual" trace at B in the far-offset from a source at W. Stacking N traces gives a vN-improvement. We applied our method to noisy synthetic and field data recorded over a complex near-surface and we could pick more traces at far offsets. It was possible to accommodate more picks resulting in a better subsurface coverage

Refractive regression after laser in situ keratomileusis.

Science.gov (United States)

Yan, Mabel K; Chang, John Sm; Chan, Tommy Cy

2018-04-26

Uncorrected refractive errors are a leading cause of visual impairment across the world. In today's society, laser in situ keratomileusis (LASIK) has become the most commonly performed surgical procedure to correct refractive errors. However, regression of the initially achieved refractive correction has been a widely observed phenomenon following LASIK since its inception more than two decades ago. Despite technological advances in laser refractive surgery and various proposed management strategies, post-LASIK regression is still frequently observed and has significant implications for the long-term visual performance and quality of life of patients. This review explores the mechanism of refractive regression after both myopic and hyperopic LASIK, predisposing risk factors and its clinical course. In addition, current preventative strategies and therapies are also reviewed. © 2018 Royal Australian and New Zealand College of Ophthalmologists.

Refractive Index Sensing with D-Shaped Plastic Optical Fibers for Chemical and Biochemical Applications.

Science.gov (United States)

Sequeira, Filipa; Duarte, Daniel; Bilro, Lúcia; Rudnitskaya, Alisa; Pesavento, Maria; Zeni, Luigi; Cennamo, Nunzio

2016-12-13

We report the optimization of the length of a D-shaped plastic optical fiber (POF) sensor for refractive index (RI) sensing from a numerical and experimental point of view. The sensing principle is based on total internal reflection (TIR). POFs with 1 mm in diameter were embedded in grooves, realized in planar supports with different lengths, and polished to remove the cladding and part of the core. All D-shaped POF sensors were tested using aqueous medium with different refractive indices (from 1.332 to 1.471) through intensity-based configuration. Results showed two different responses. Considering the refractive index (RI) range (1.33-1.39), the sensitivity and the resolution of the sensor were strongly dependent on the sensing region length. The highest sensitivity (resolution of 6.48 × 10 -3 refractive index units, RIU) was obtained with 6 cm sensing length. In the RI range (1.41-1.47), the length of the sensing region was not a critical aspect to obtain the best resolution. These results enable the application of this optical platform for chemical and biochemical evanescent field sensing. The sensor production procedure is very simple, fast, and low-cost.

Numerical Calculation for Whirling Motion of a Centrifugal Blood Pump with Conical Spiral Groove Bearings

Science.gov (United States)

Shigemaru, Daichi; Tsukamoto, Hiroshi

2010-06-01

Whirling motion of a pump impeller was calculated for the centrifugal blood pump with Conical Spiral Groove Bearings to get a criterion for the instability of impeller whirling motion. The motion of the centrifugal blood pump impeller was calculated based on a spring damping model, and unsteady flow in the pump was computed using the commercial CFD package ANSYS CFX. Also the whirling motion of rotating impeller was measured using two displacement sensors fixed to the blood pump casing. The numerical calculations were done for the blood pump impeller with conical spiral groove bearings, and impeller whirling motion was evaluated.

Unsteady wall pressure field of a model A-pillar conical vortex

International Nuclear Information System (INIS)

Hoarau, C.; Boree, J.; Laumonier, J.; Gervais, Y.

2008-01-01

The spatio-temporal properties of the unsteady wall pressure field of a model A-pillar conical vortex are studied in this paper by combining 2 component LDV measurements and multi-point pressure measurements using off-set microphones. The model body has sharp edges. Detailed LDV measurements are presented and discussed in the vortex region. The fluctuating velocities are the signature of both an unsteady behaviour of the organised vortical structure interacting with the wall and of finer scale turbulence carried by the unsteady flow. A spectral analysis of the fluctuating pressure under the vortex core is used to analyse the link between the temporal and spatial scales of the unsteady aerodynamics and the wall pressure field. We show that the conical vortex is a guide for the velocity perturbations and that their hydrodynamic pressure footprint is transported at the measured mean axial velocity in a local reference frame aligned with the vortex core. Two distinct peaks of coherence can then be associated with perturbations having (i) a length scale of the order of the full length of the conical structure; (ii) a length scale of the order of the width of the structure. These perturbations may correspond to a global meandering of the structure (low frequency contribution) and to large scale perturbations generated during the rolling-up of the unsteady vortex sheet. Notably, the energy containing higher frequency parts of the PSD are only weakly correlated when distant sensors are considered. The three distinct contributions extracted here have a significant impact as far as Cp' is concerned and should be transmitted in very different ways by the car structure because the frequency and length scale range is very distinct

Spheroidal and conical shapes of ferrofluid-filled capsules in magnetic fields

Science.gov (United States)

Wischnewski, Christian; Kierfeld, Jan

2018-04-01

We investigate the deformation of soft spherical elastic capsules filled with a ferrofluid in external uniform magnetic fields at fixed volume by a combination of numerical and analytical approaches. We develop a numerical iterative solution strategy based on nonlinear elastic shape equations to calculate the stretched capsule shape numerically and a coupled finite element and boundary element method to solve the corresponding magnetostatic problem and employ analytical linear response theory, approximative energy minimization, and slender-body theory. The observed deformation behavior is qualitatively similar to the deformation of ferrofluid droplets in uniform magnetic fields. Homogeneous magnetic fields elongate the capsule and a discontinuous shape transition from a spheroidal shape to a conical shape takes place at a critical field strength. We investigate how capsule elasticity modifies this hysteretic shape transition. We show that conical capsule shapes are possible but involve diverging stretch factors at the tips, which gives rise to rupture for real capsule materials. In a slender-body approximation we find that the critical susceptibility above which conical shapes occur for ferrofluid capsules is the same as for droplets. At small fields capsules remain spheroidal and we characterize the deformation of spheroidal capsules both analytically and numerically. Finally, we determine whether wrinkling of a spheroidal capsule occurs during elongation in a magnetic field and how it modifies the stretching behavior. We find the nontrivial dependence between the extent of the wrinkled region and capsule elongation. Our results can be helpful in quantitatively determining capsule or ferrofluid material properties from magnetic deformation experiments. All results also apply to elastic capsules filled with a dielectric liquid in an external uniform electric field.

Photonic bandgap narrowing in conical hollow core Bragg fibers

Energy Technology Data Exchange (ETDEWEB)

Ozturk, Fahri Emre; Yildirim, Adem; Kanik, Mehmet [UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey); Bayindir, Mehmet, E-mail: bayindir@nano.org.tr [UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara (Turkey); Department of Physics, Bilkent University, 06800 Ankara (Turkey)

2014-08-18

We report the photonic bandgap engineering of Bragg fibers by controlling the thickness profile of the fiber during the thermal drawing. Conical hollow core Bragg fibers were produced by thermal drawing under a rapidly alternating load, which was applied by introducing steep changes to the fiber drawing speed. In conventional cylindrical Bragg fibers, light is guided by omnidirectional reflections from interior dielectric mirrors with a single quarter wave stack period. In conical fibers, the diameter reduction introduced a gradient of the quarter wave stack period along the length of the fiber. Therefore, the light guided within the fiber encountered slightly smaller dielectric layer thicknesses at each reflection, resulting in a progressive blueshift of the reflectance spectrum. As the reflectance spectrum shifts, longer wavelengths of the initial bandgap cease to be omnidirectionally reflected and exit through the cladding, which narrows the photonic bandgap. A narrow transmission bandwidth is particularly desirable in hollow waveguide mid-infrared sensing schemes, where broadband light is coupled to the fiber and the analyte vapor is introduced into the hollow core to measure infrared absorption. We carried out sensing simulations using the absorption spectrum of isopropyl alcohol vapor to demonstrate the importance of narrow bandgap fibers in chemical sensing applications.

Refracting surface plasmon polaritons with nanoparticle arrays

DEFF Research Database (Denmark)

Radko, I.P.; Evlyukhin, A.B.; Boltasseva, Alexandra

2008-01-01

Refraction of surface plasmon polaritons (SPPs) by various structures formed by a 100-nm-period square lattice of gold nanoparticles on top of a gold film is studied by leakage radiation microscopy. SPP refraction by a triangular-shaped nanoparticle array indicates that the SPP effective refractive...... to design nanoparticle arrays for specific applications requiring in-plane SPP manipulation....

Measurement of the effective refractive index of a turbid colloidal suspension using light refraction

International Nuclear Information System (INIS)

Reyes-Coronado, A; Garcia-Valenzuela, A; Sanchez-Perez, C; Barrera, R G

2005-01-01

We propose and analyse a simple method to measure simultaneously the real and imaginary parts of the effective refractive index of a turbid suspension of particles. The method is based on measurements of the angle of refraction and transmittance of a laser beam that traverses a hollow glass prism filled with a colloidal suspension. We provide a comprehensive assessment of the method. It can offer high sensitivity while still being simple to interpret. We present results of experiments using an optically turbid suspension of polystyrene particles and compare them with theoretical predictions. We also report experimental evidence showing that the refractive behaviour of the diffuse component of light coming from a suspension depends on the volume fraction of the colloidal particles

Polynomial modal analysis of lamellar diffraction gratings in conical mounting.

Science.gov (United States)

Randriamihaja, Manjakavola Honore; Granet, Gérard; Edee, Kofi; Raniriharinosy, Karyl

2016-09-01

An efficient numerical modal method for modeling a lamellar grating in conical mounting is presented. Within each region of the grating, the electromagnetic field is expanded onto Legendre polynomials, which allows us to enforce in an exact manner the boundary conditions that determine the eigensolutions. Our code is successfully validated by comparison with results obtained with the analytical modal method.

Compound refractive X-ray lens

International Nuclear Information System (INIS)

Nygren, D.R.; Cahn, R.; Cederstrom, B.; Danielsson, M.; Vestlund, J.

2000-01-01

An apparatus and method are disclosed for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point

Compound refractive X-ray lens

Science.gov (United States)

Nygren, David R.; Cahn, Robert; Cederstrom, Bjorn; Danielsson, Mats; Vestlund, Jonas

2000-01-01

An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point.

Influence of Test Section Geometry on the Blast Environment in an Explosively Driven Conical Shock Tube

Science.gov (United States)

2018-03-30

ARL-TR-8335•MAR 2018 US Army Research Laboratory Influence of Test Section Geometry on theBlast Environment in an Explosively DrivenConical Shock...ARL-TR-8335•MAR 2018 US Army Research Laboratory Influence of Test Section Geometry on theBlast Environment in an Explosively DrivenConical Shock...TITLE AND SUBTITLE    5a. CONTRACT NUMBER  5b. GRANT NUMBER  5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S)    5d.  PROJECT  NUMBER  5e. TASK NUMBER  5f

On the bound states of Schrodinger operators with -interactions on conical surfaces

Czech Academy of Sciences Publication Activity Database

Lotoreichik, Vladimir; Ourmieres-Bonafos, T.

2016-01-01

Roč. 41, č. 6 (2016), s. 999-1028 ISSN 0360-5302 Institutional support: RVO:61389005 Keywords : conical and hyperconical surfaces * delta-interaction * existence of bound states * Schrodinger operator * spectral asymptotics Subject RIV: BE - Theoretical Physics Impact factor: 1.608, year: 2016

CBLIB 2014: a benchmark library for conic mixed-integer and continuous optimization

DEFF Research Database (Denmark)

Friberg, Henrik Alsing

2016-01-01

The Conic Benchmark Library is an ongoing community-driven project aiming to challenge commercial and open source solvers on mainstream cone support. In this paper, 121 mixed-integer and continuous second-order cone problem instances have been selected from 11 categories as representative...

The generalized vectorial laws of reflection and refraction

International Nuclear Information System (INIS)

Bhattacharjee, Pramode Ranjan

2005-01-01

This paper discloses two important discoveries. These are: (i) discovery of ambiguity in the well-established laws of reflection and refraction of light which have been in regular use for many years, and (ii) discovery of generalized vectorial laws of reflection and refraction of light. The existing definitions of angle of incidence, angle of reflection and angle of refraction are considered first. Each of these definitions is found to be ambiguous, not in compliance with the fundamental definition of angle in geometry. Two typical questions (one in the case of reflection and the other for refraction) have been addressed, which cannot be dealt with by using the existing laws of reflection and refraction of light. Thus, the existing laws of reflection and refraction of light seem to be ambiguous in respect of generality and their validity in a broad sense is questionable. With a view to removing the ambiguities, proper definitions of the above three angles are given first and then the statement of the generalized vectorial law of reflection (as well as that of refraction) has been offered

Fatigue induced changes in conical implant-abutment connections.

Science.gov (United States)

Blum, Kai; Wiest, Wolfram; Fella, Christian; Balles, Andreas; Dittmann, Jonas; Rack, Alexander; Maier, Dominik; Thomann, Ralf; Spies, Benedikt Christopher; Kohal, Ralf Joachim; Zabler, Simon; Nelson, Katja

2015-11-01

Based on the current lack of data and understanding of the wear behavior of dental two-piece implants, this study aims for evaluating the microgap formation and wear pattern of different implants in the course of cyclic loading. Several implant systems with different conical implant-abutment interfaces were purchased. The implants were first evaluated using synchrotron X-ray high-resolution radiography (SRX) and scanning electron microscopy (SEM). The implant-abutment assemblies were then subjected to cyclic loading at 98N and their microgap was evaluated after 100,000, 200,000 and 1 million cycles using SRX, synchrotron micro-tomography (μCT). Wear mechanisms of the implant-abutment connection (IAC) after 200,000 cycles and 1 million cycles were further characterized using SEM. All implants exhibit a microgap between the implant and abutment prior to loading. The gap size increased with cyclic loading with its changes being significantly higher within the first 200,000 cycles. Wear was seen in all implants regardless of their interface design. The wear pattern comprised adhesive wear and fretting. Wear behavior changed when a different mounting medium was used (brass vs. polymer). A micromotion of the abutment during cyclic loading can induce wear and wear particles in conical dental implant systems. This feature accompanied with the formation of a microgap at the IAC is highly relevant for the longevity of the implants. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Crystallinity, Surface Morphology, and Photoelectrochemical Effects in Conical InP and InN Nanowires Grown on Silicon.

Science.gov (United States)

Parameshwaran, Vijay; Xu, Xiaoqing; Clemens, Bruce

2016-08-24

The growth conditions of two types of indium-based III-V nanowires, InP and InN, are tailored such that instead of yielding conventional wire-type morphologies, single-crystal conical structures are formed with an enlarged diameter either near the base or near the tip. By using indium droplets as a growth catalyst, combined with an excess indium supply during growth, "ice cream cone" type structures are formed with a nanowire "cone" and an indium-based "ice cream" droplet on top for both InP and InN. Surface polycrystallinity and annihilation of the catalyst tip of the conical InP nanowires are observed when the indium supply is turned off during the growth process. This growth design technique is extended to create single-crystal InN nanowires with the same morphology. Conical InN nanowires with an enlarged base are obtained through the use of an excess combined Au-In growth catalyst. Electrochemical studies of the InP nanowires on silicon demonstrate a reduction photocurrent as a proof of photovolatic behavior and provide insight as to how the observed surface polycrystallinity and the resulting interface affect these device-level properties. Additionally, a photovoltage is induced in both types of conical InN nanowires on silicon, which is not replicated in epitaxial InN thin films.

Thermal response of an aeroassisted orbital-transfer vehicle with a conical drag brake

Science.gov (United States)

Pitts, W. C.; Murbach, M. S.

1984-01-01

As an aeroassisted orbital-transfer vehicle (AOTV) goes through an aerobraking maneuver, a significant amount of heat is generated. In this paper, the thermal response of a specific AOTV to this aerobrake heating is examined. The vehicle has a 70 deg, conical drag-brake heat shield attached to a cylindrical body which contains the payload. The heat shield is made of silica fabric. The heat-shield thickness is varied from that of a thin cloth to a 1.5-cm blanket. The fabric thickness, the radiation absorptivity of the vehicle surface materials, and radiation from the wake are all significant parameters in the thermal response to the heating produced by the braking maneuver. The maximum temperatures occur in the vicinity of the interface between the body and the conical heat shield.

Thermal Response of an Aeroassisted Orbital Transfer Vehicle with a Conical Drag Brake

Science.gov (United States)

Pitts, W. C.; Murbach, M. S.

1985-01-01

As an aeroassisted orbital transfer vehicle (AOTV) goes through an aerobraking maneuver a significant amount of heat is generated. In this paper, the thermal response of a specific AOTV to this aerobrake heating is examined. The vehicle has a 70-deg, Conical drag-brake heat shield attached to a cylindrical body which contains the payload. The heat shield is made of ceramic fabric its thickness is varied from that of a thin cloth to a 1.5-cm blanket. The fabric thickness, the radiation absorptivity of the vehicle surface materials, and radiation from the wake are all significant parameters in the thermal response to the heating produced by the braking maneuver. The maximum temperatures occur In the vicinity of the interface between the body and the conical heat shield.

General relativistic study of astrophysical jets with internal shocks

Science.gov (United States)

Vyas, Mukesh K.; Chattopadhyay, Indranil

2017-08-01

We explore the possibility of the formation of steady internal shocks in jets around black holes. We consider a fluid described by a relativistic equation of state, flowing about the axis of symmetry (θ = 0) in a Schwarzschild metric. We use two models for the jet geometry: (I) a conical geometry and (II) a geometry with non-conical cross-section. A jet with conical geometry has a smooth flow, while the jet with non-conical cross-section undergoes multiple sonic points and even standing shock. The jet shock becomes stronger, as the shock location is situated farther from the central black hole. Jets with very high energy and very low energy do not harbour shocks, but jets with intermediate energies do harbour shocks. One advantage of these shocks, as opposed to shocks mediated by external medium, is that these shocks have no effect on the jet terminal speed, but may act as possible sites for particle acceleration. Typically, a jet with specific energy 1.8c2 will achieve a terminal speed of v∞ = 0.813c for jet with any geometry, where, c is the speed of light in vacuum. But for a jet of non-conical cross-section for which the length scale of the inner torus of the accretion disc is 40rg, then, in addition, a steady shock will form at rsh ˜ 7.5rg and compression ratio of R ˜ 2.7. Moreover, electron-proton jet seems to harbour the strongest shock. We will discuss possible consequences of such a scenario.

Physics of negative refractive index materials

International Nuclear Information System (INIS)

Ramakrishna, S Anantha

2005-01-01

In the past few years, new developments in structured electromagnetic materials have given rise to negative refractive index materials which have both negative dielectric permittivity and negative magnetic permeability in some frequency ranges. The idea of a negative refractive index opens up new conceptual frontiers in photonics. One much-debated example is the concept of a perfect lens that enables imaging with sub-wavelength image resolution. Here we review the fundamental concepts and ideas of negative refractive index materials. First we present the ideas of structured materials or meta-materials that enable the design of new materials with a negative dielectric permittivity, negative magnetic permeability and negative refractive index. We discuss how a variety of resonance phenomena can be utilized to obtain these materials in various frequency ranges over the electromagnetic spectrum. The choice of the wave-vector in negative refractive index materials and the issues of dispersion, causality and energy transport are analysed. Various issues of wave propagation including nonlinear effects and surface modes in negative refractive materials (NRMs) are discussed. In the latter part of the review, we discuss the concept of a perfect lens consisting of a slab of a NRM. This perfect lens can image the far-field radiative components as well as the near-field evanescent components, and is not subject to the traditional diffraction limit. Different aspects of this lens such as the surface modes acting as the mechanism for the imaging of the evanescent waves, the limitations imposed by dissipation and dispersion in the negative refractive media, the generalization of this lens to optically complementary media and the possibility of magnification of the near-field images are discussed. Recent experimental developments verifying these ideas are briefly covered

Refractive accuracy with light-adjustable intraocular lenses.

Science.gov (United States)

Villegas, Eloy A; Alcon, Encarna; Rubio, Elena; Marín, José M; Artal, Pablo

2014-07-01

To evaluate efficacy, predictability, and stability of refractive treatments using light-adjustable intraocular lenses (IOLs). University Hospital Virgen de la Arrixaca, Murcia, Spain. Prospective nonrandomized clinical trial. Eyes with a light-adjustable IOL (LAL) were treated with spatial intensity profiles to correct refractive errors. The effective changes in refraction in the light-adjustable IOL after every treatment were estimated by subtracting those in the whole eye and the cornea, which were measured with a Hartmann-Shack sensor and a corneal topographer, respectively. The refractive changes in the whole eye and light-adjustable IOL, manifest refraction, and visual acuity were obtained after every light treatment and at the 3-, 6-, and 12-month follow-ups. The study enrolled 53 eyes (49 patients). Each tested light spatial pattern (5 spherical; 3 astigmatic) produced a different refractive change (Plight adjustments induced a maximum change in spherical power of the light-adjustable IOL of between -1.98 diopters (D) and +2.30 D and in astigmatism of up to -2.68 D with axis errors below 9 degrees. Intersubject variability (standard deviation) ranged between 0.10 D and 0.40 D. The 2 required lock-in procedures induced a small myopic shift (range +0.01 to +0.57 D) that depended on previous adjustments. Light-adjustable IOL implantation achieved accurate refractive outcomes (around emmetropia) with good uncorrected distance visual acuity, which remained stable over time. Further refinements in nomograms and in the treatment's protocol would improve the predictability of refractive and visual outcomes with these IOLs. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2014 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Refractive index contrast in porous silicon multilayers

Energy Technology Data Exchange (ETDEWEB)

Nava, R.; Mora, M.B. de la; Tagueena-Martinez, J. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Rio, J.A. del [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Centro Morelense de Innovacion y Transferencia Tecnologica, Consejo de Ciencia y Tecnologia del Estado de Morelos (Mexico)

2009-07-15

Two of the most important properties of a porous silicon multilayer for photonic applications are flat interfaces and a relative large refractive index contrast between layers in the optical wavelength range. In this work, we studied the effect of the current density and HF electrolyte concentration on the refractive index of porous silicon. With the purpose of increasing the refractive index contrast in a multilayer, the refractive index of porous silicon produced at low current was studied in detail. The current density applied to produce the low porosity layers was limited in order to keep the electrolyte flow through the multilayer structure and to avoid deformation of layer interfaces. We found that an electrolyte composed of hydrofluoric acid, ethanol and glycerin in a ratio of 3:7:1 gives a refractive index contrast around 1.3/2.8 at 600 nm. Several multilayer structures with this refractive index contrast were fabricated, such as dielectric Bragg mirrors and microcavities. Reflectance spectra of the structures show the photonic quality of porous silicon multilayers produced under these electrochemical conditions. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Development of a subjective refraction simulator

Science.gov (United States)

Perches, S.; Ares, J.; Collados, M. V.

2013-11-01

We have developed simulation software by Matlab (MathworksInc.) with a graphical interface designed for non-expert users. This simulator allows you to complete the process of subjective refraction starting from the aberrometry of the patients and analyse the influence of different factors during the exam. In addition to explain the graphical interface and its working, we show two examples about a complete process of subjective refraction with the influence of high order aberrations and without them showing the retinal image obtained in each step of the refraction process. When the Jackson Cross-Cylinder technique is made with this software, it becomes clear the difficulty of chosen between two images when high order aberrations are present. Therefore, the variability of response during the refraction can be a problem when the examiner has to reach an adequate optical prescription.

Isaac Newton and the astronomical refraction.

Science.gov (United States)

Lehn, Waldemar H

2008-12-01

In a short interval toward the end of 1694, Isaac Newton developed two mathematical models for the theory of the astronomical refraction and calculated two refraction tables, but did not publish his theory. Much effort has been expended, starting with Biot in 1836, in the attempt to identify the methods and equations that Newton used. In contrast to previous work, a closed form solution is identified for the refraction integral that reproduces the table for his first model (in which density decays linearly with elevation). The parameters of his second model, which includes the exponential variation of pressure in an isothermal atmosphere, have also been identified by reproducing his results. The implication is clear that in each case Newton had derived exactly the correct equations for the astronomical refraction; furthermore, he was the first to do so.

3D super-virtual refraction interferometry

KAUST Repository

Lu, Kai; AlTheyab, Abdullah; Schuster, Gerard T.

2014-01-01

Super-virtual refraction interferometry enhances the signal-to-noise ratio of far-offset refractions. However, when applied to 3D cases, traditional 2D SVI suffers because the stationary positions of the source-receiver pairs might be any place

Coupled-mode theory and Fano resonances in guided-mode resonant gratings: the conical diffraction mounting.

Science.gov (United States)

Bykov, Dmitry A; Doskolovich, Leonid L; Soifer, Victor A

2017-01-23

We study resonances of guided-mode resonant gratings in conical mounting. By developing 2D time-dependent coupled-mode theory we obtain simple approximations of the transmission and reflection coefficients. Being functions of the incident light's frequency and in-plane wave vector components, the obtained approximations can be considered as multi-variable generalizations of the Fano line shape. We show that the approximations are in good agreement with the rigorously calculated transmission and reflection spectra. We use the developed theory to investigate angular tolerances of the considered structures and to obtain mode excitation conditions. In particular, we obtain the cross-polarization mode excitation conditions in the case of conical mounting.

Unsteady wall pressure field of a model A-pillar conical vortex

Energy Technology Data Exchange (ETDEWEB)

Hoarau, C. [Laboratoire d' Etudes Aerodynamiques, LEA UMR CNRS/Universite de Poitiers/ENSMA 6609, Teleport 2, 1 Av. Clement Ader, BP 40109, 86961 Futuroscope Chasseneuil (France); Boree, J. [Laboratoire d' Etudes Aerodynamiques, LEA UMR CNRS/Universite de Poitiers/ENSMA 6609, Teleport 2, 1 Av. Clement Ader, BP 40109, 86961 Futuroscope Chasseneuil (France)], E-mail: jacques.boree@lea.ensma.fr; Laumonier, J.; Gervais, Y. [Laboratoire d' Etudes Aerodynamiques, LEA UMR CNRS/Universite de Poitiers/ENSMA 6609, Teleport 2, 1 Av. Clement Ader, BP 40109, 86961 Futuroscope Chasseneuil (France)

2008-06-15

The spatio-temporal properties of the unsteady wall pressure field of a model A-pillar conical vortex are studied in this paper by combining 2 component LDV measurements and multi-point pressure measurements using off-set microphones. The model body has sharp edges. Detailed LDV measurements are presented and discussed in the vortex region. The fluctuating velocities are the signature of both an unsteady behaviour of the organised vortical structure interacting with the wall and of finer scale turbulence carried by the unsteady flow. A spectral analysis of the fluctuating pressure under the vortex core is used to analyse the link between the temporal and spatial scales of the unsteady aerodynamics and the wall pressure field. We show that the conical vortex is a guide for the velocity perturbations and that their hydrodynamic pressure footprint is transported at the measured mean axial velocity in a local reference frame aligned with the vortex core. Two distinct peaks of coherence can then be associated with perturbations having (i) a length scale of the order of the full length of the conical structure; (ii) a length scale of the order of the width of the structure. These perturbations may correspond to a global meandering of the structure (low frequency contribution) and to large scale perturbations generated during the rolling-up of the unsteady vortex sheet. Notably, the energy containing higher frequency parts of the PSD are only weakly correlated when distant sensors are considered. The three distinct contributions extracted here have a significant impact as far as Cp' is concerned and should be transmitted in very different ways by the car structure because the frequency and length scale range is very distinct.

Differences between wavefront and subjective refraction for infrared light.

Science.gov (United States)

Teel, Danielle F W; Jacobs, Robert J; Copland, James; Neal, Daniel R; Thibos, Larry N

2014-10-01

To determine the accuracy of objective wavefront refractions for predicting subjective refractions for monochromatic infrared light. Objective refractions were obtained with a commercial wavefront aberrometer (COAS, Wavefront Sciences). Subjective refractions were obtained for 30 subjects with a speckle optometer validated against objective Zernike wavefront refractions on a physical model eye (Teel et al., Design and validation of an infrared Badal optometer for laser speckle, Optom Vis Sci 2008;85:834-42). Both instruments used near-infrared (NIR) radiation (835 nm for COAS, 820 nm for the speckle optometer) to avoid correction for ocular chromatic aberration. A 3-mm artificial pupil was used to reduce complications attributed to higher-order ocular aberrations. For comparison with paraxial (Seidel) and minimum root-mean-square (Zernike) wavefront refractions, objective refractions were also determined for a battery of 29 image quality metrics by computing the correcting lens that optimizes retinal image quality. Objective Zernike refractions were more myopic than subjective refractions for 29 of 30 subjects. The population mean discrepancy was -0.26 diopters (D) (SEM = 0.03 D). Paraxial (Seidel) objective refractions tended to be hyperopically biased (mean discrepancy = +0.20 D, SEM = 0.06 D). Refractions based on retinal image quality were myopically biased for 28 of 29 metrics. The mean bias across all 31 measures was -0.24 D (SEM = 0.03). Myopic bias of objective refractions was greater for eyes with brown irises compared with eyes with blue irises. Our experimental results are consistent with the hypothesis that reflected NIR light captured by the aberrometer originates from scattering sources located posterior to the entrance apertures of cone photoreceptors, near the retinal pigment epithelium. The larger myopic bias for brown eyes suggests that a greater fraction of NIR light is reflected from choroidal melanin in brown eyes compared with blue eyes.

The refractive index of relic gravitons

CERN Document Server

Giovannini, Massimo

2016-01-01

The dynamical evolution of the refractive index of the tensor modes of the geometry produces a specific class of power spectra characterized by a blue (i.e. slightly increasing) slope which is directly determined by the competition of the slow-roll parameter and of the rate of variation of the refractive index. Throughout the conventional stages of the inflationary and post-inflationary evolution, the microwave background anisotropies measurements, the pulsar timing limits and the big-bang nucleosythesis constraints set stringent bounds on the refractive index and on its rate of variation. Within the physically allowed region of the parameter space the cosmic background of relic gravitons leads to a potentially large signal for the ground based detectors (in their advanced version) and for the proposed space-borne interferometers. Conversely, the lack of direct detection of the signal will set a qualitatively new bound on the dynamical variation of the refractive index.

Intelligent Planning for Laser Refractive Surgeries

Science.gov (United States)

Wang, Wei; Yue, Yong; Elsheikh, Ahmed; Bao, Fangjun

2018-02-01

Refractive error is one of leading ophthalmic diseases for both genders all over the world. Laser refractive correction surgery, e.g., laser in-situ keratomileusis (LASIK), has been commonly used worldwide. The prediction of surgical parameters, e.g., corneal ablation depth, depends on the doctor’s experience, theoretical formula and surgery reference manual in the preoperative diagnosis. The error of prediction may present a potential surgical risk and complication. Being aware of the surgery parameters is important because these can be used to estimate a patient’s post-operative visual quality and help the surgeon plan a suitable treatment. Therefore, in this paper we discuss data mining techniques that can be utilized for the prediction of laser refractive correction surgery parameters. It can provide the surgeon with a reference for possible surgical parameters and outcomes of the patient before the laser refractive correction surgery.

Conical Stream of the Two-Sided Jets in NGC 4261 over the Range of 103–109 Schwarzschild Radii

Directory of Open Access Journals (Sweden)

Satomi Nakahara

2016-12-01

Full Text Available We report the jet width profile of of the nearby ( ∼ 30 Mpc AGN NGC 4261 for both the approaching jet and the counter jet at radial distances ranging from ∼ 10 3 – 10 9 Schwarzschild radius ( R S from the central engine. Our Very Large Array (VLA and Very Long Baseline Array (VLBA observations reveal that the jets maintain a conical structure on both sides over the range 10 3 – 10 9 R S without any structural transition (i.e., parabolic to conical like in the approaching jet in M87. Thus, NGC 4261 will provide a unique opportunity to examine the conical jet hypothesis in blazars, while it may require some additional consideration on the acceleration and collimation process in AGN jets.

A truncated conical beam model for analysis of the vibration of rat whiskers.

Science.gov (United States)

Yan, Wenyi; Kan, Qianhua; Kergrene, Kenan; Kang, Guozheng; Feng, Xi-Qiao; Rajan, Ramesh

2013-08-09

A truncated conical beam model is developed to study the vibration behaviour of a rat whisker. Translational and rotational springs are introduced to better represent the constraint conditions at the base of the whiskers in a living rat. Dimensional analysis shows that the natural frequency of a truncated conical beam with generic spring constraints at its ends is inversely proportional to the square root of the mass density. Under all the combinations of the classical free, pinned, sliding or fixed boundary conditions of a truncated conical beam, it is proved that the natural frequency can be expressed as f = α(rb/L(2))E/ρ and the frequency coefficient α only depends on the ratio of the radii at the two ends of the beam. The natural frequencies of a representative rat whisker are predicted for two typical situations: freely whisking in air and the tip touching an object. Our numerical results show that there exists a window where the natural frequencies of a rat whisker are very sensitive to the change of the rotational constraint at the base. This finding is also confirmed by the numerical results of 18 whiskers with their data available from literature. It can be concluded that the natural frequencies of a rat whisker can be adjusted within a wide range through manipulating the constraints of the follicle on the rat base by a behaving animal. Copyright © 2013 Elsevier Ltd. All rights reserved.

Peripheral refractive correction and automated perimetric profiles.

Science.gov (United States)

Wild, J M; Wood, J M; Crews, S J

1988-06-01

The effect of peripheral refractive error correction on the automated perimetric sensitivity profile was investigated on a sample of 10 clinically normal, experienced observers. Peripheral refractive error was determined at eccentricities of 0 degree, 20 degrees and 40 degrees along the temporal meridian of the right eye using the Canon Autoref R-1, an infra-red automated refractor, under the parametric conditions of the Octopus automated perimeter. Perimetric sensitivity was then undertaken at these eccentricities (stimulus sizes 0 and III) with and without the appropriate peripheral refractive correction using the Octopus 201 automated perimeter. Within the measurement limits of the experimental procedures employed, perimetric sensitivity was not influenced by peripheral refractive correction.

Design and implementation of a novel conical electrode for fast anodic bonding

International Nuclear Information System (INIS)

Yang, Chii-Rong; Chang, Long-Yin; Wu, Jim-Wei

2014-01-01

Anodic bonding is a frequently used nonintermediate wafer-bonding technique for use in MEMS. However, it has a minimum bonding time for a 4 in silicon/glass wafer that is generally limited to the order of several minutes because of the gas-trapping problem that occurs in the bonded interface when a conventional bonding electrode is used. Therefore, the purpose of this study was to develop a novel conical bonding electrode, which shortens the bonding time and solves the gas-trapping problem of the bonded interface. The 4 in silicon/glass wafers fitted with the proposed electrode exhibited a bonding ratio of 99.89% and an average bonding strength of around 15 MPa, which was attained within 15 s, at a bonding voltage of 900 V and a bonding temperature of 400 °C. A comprehensive series of experiments was performed to validate the excellent bonding performance of the proposed conical electrode. (paper)

High-Efficiency Fog Collector: Water Unidirectional Transport on Heterogeneous Rough Conical Wires.

Science.gov (United States)

Xu, Ting; Lin, Yucai; Zhang, Miaoxin; Shi, Weiwei; Zheng, Yongmei

2016-12-27

An artificial periodic roughness-gradient conical copper wire (PCCW) can be fabricated by inspiration from cactus spines and wet spider silks. PCCW can harvest fog on periodic points of the conical surface from air and transports the drops for a long distance without external force, which is attributed to dynamic as-released energy generated from drop deformation in drop coalescence, in addition to both gradients of geometric curve (inducing Laplace pressure) and periodic roughness (inducing surface energy difference). It is found that the ability of fog collection can be related to various tilt-angle wires, thus a fog collector with an array system of PCCWs is further designed to achieve a continuous process of efficient water collection. As a result, the effect of water collection on PCCWs is better than previous results. These findings are significant to develop and design materials with water collection and water transport for promising application in fogwater systems to ease the water crisis.

Quantum friction of pseudorotation in Jahn-Teller system: Passage through conical intersection

Energy Technology Data Exchange (ETDEWEB)

Pae, Kaja, E-mail: kaja.pae@gmail.com; Hizhnyakov, Vladimir [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia)

2016-08-14

A theoretical study of the relaxation of an excited impurity center with strong E × e-type Jahn-Teller effect, caused by the emission of phonons to the bulk, is presented. The dependence of the passing the system through the conical intersection of the potential surface on the momentum of the pseudorotation is figured out. An analytical description of the quantum states of the conical intersection (Slonczewski resonances) is given. It is found that for realistic vibronic interactions with phonons, the characteristic time of the energy loss is several tenths of mean periods of phonons, i.e., it is in the picosecond range. It is also found that there is a finite probability of the speeding-up of the pseudorotation of the system at the intermediate stage of relaxation. In particular, this probability increases close to the Slonczewski resonances. During the relaxation, the system may change the direction of the pseudomoment; the probability of such a change also increases near the resonances.

Refractive Index Sensing with D-Shaped Plastic Optical Fibers for Chemical and Biochemical Applications

Directory of Open Access Journals (Sweden)

Filipa Sequeira

2016-12-01

Full Text Available We report the optimization of the length of a D-shaped plastic optical fiber (POF sensor for refractive index (RI sensing from a numerical and experimental point of view. The sensing principle is based on total internal reflection (TIR. POFs with 1 mm in diameter were embedded in grooves, realized in planar supports with different lengths, and polished to remove the cladding and part of the core. All D-shaped POF sensors were tested using aqueous medium with different refractive indices (from 1.332 to 1.471 through intensity-based configuration. Results showed two different responses. Considering the refractive index (RI range (1.33–1.39, the sensitivity and the resolution of the sensor were strongly dependent on the sensing region length. The highest sensitivity (resolution of 6.48 × 10−3 refractive index units, RIU was obtained with 6 cm sensing length. In the RI range (1.41–1.47, the length of the sensing region was not a critical aspect to obtain the best resolution. These results enable the application of this optical platform for chemical and biochemical evanescent field sensing. The sensor production procedure is very simple, fast, and low-cost.

The index of Fourier integral operators on manifolds with conical singularities

International Nuclear Information System (INIS)

Nazaikinskii, Vladimir E; Sternin, B Yu; Schulze, B-W

2001-01-01

We describe homogeneous canonical transformations of the cotangent bundle of a manifold with conical singular points and compute the index of an elliptic Fourier integral operator obtained by the quantization of such a transformation. The answer involves the index of an elliptic Fourier integral operator on a smooth manifold and the residues of the conormal symbol

Reflective and refractive objects for mixed reality.

Science.gov (United States)

Knecht, Martin; Traxler, Christoph; Winklhofer, Christoph; Wimmer, Michael

2013-04-01

In this paper, we present a novel rendering method which integrates reflective or refractive objects into a differential instant radiosity (DIR) framework usable for mixed-reality (MR) applications. This kind of objects are very special from the light interaction point of view, as they reflect and refract incident rays. Therefore they may cause high-frequency lighting effects known as caustics. Using instant-radiosity (IR) methods to approximate these high-frequency lighting effects would require a large amount of virtual point lights (VPLs) and is therefore not desirable due to real-time constraints. Instead, our approach combines differential instant radiosity with three other methods. One method handles more accurate reflections compared to simple cubemaps by using impostors. Another method is able to calculate two refractions in real-time, and the third method uses small quads to create caustic effects. Our proposed method replaces parts in light paths that belong to reflective or refractive objects using these three methods and thus tightly integrates into DIR. In contrast to previous methods which introduce reflective or refractive objects into MR scenarios, our method produces caustics that also emit additional indirect light. The method runs at real-time frame rates, and the results show that reflective and refractive objects with caustics improve the overall impression for MR scenarios.

Refractive error magnitude and variability: Relation to age.

Science.gov (United States)

Irving, Elizabeth L; Machan, Carolyn M; Lam, Sharon; Hrynchak, Patricia K; Lillakas, Linda

2018-03-19

To investigate mean ocular refraction (MOR) and astigmatism, over the human age range and compare severity of refractive error to earlier studies from clinical populations having large age ranges. For this descriptive study patient age, refractive error and history of surgery affecting refraction were abstracted from the Waterloo Eye Study database (WatES). Average MOR, standard deviation of MOR and astigmatism were assessed in relation to age. Refractive distributions for developmental age groups were determined. MOR standard deviation relative to average MOR was evaluated. Data from earlier clinically based studies with similar age ranges were compared to WatES. Right eye refractive errors were available for 5933 patients with no history of surgery affecting refraction. Average MOR varied with age. Children <1 yr of age were the most hyperopic (+1.79D) and the highest magnitude of myopia was found at 27yrs (-2.86D). MOR distributions were leptokurtic, and negatively skewed. The mode varied with age group. MOR variability increased with increasing myopia. Average astigmatism increased gradually to age 60 after which it increased at a faster rate. By 85+ years it was 1.25D. J 0 power vector became increasingly negative with age. J 45 power vector values remained close to zero but variability increased at approximately 70 years. In relation to comparable earlier studies, WatES data were most myopic. Mean ocular refraction and refractive error distribution vary with age. The highest magnitude of myopia is found in young adults. Similar to prevalence, the severity of myopia also appears to have increased since 1931. Copyright © 2018 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

Reflection and refraction of light from a moving block of glass

International Nuclear Information System (INIS)

Lerche, I.

1975-01-01

For a block of glass moving with speed βc we present calculations which give the changes in the laws of reflection and refraction of light from the laws which hold when β = 0. In particular we show (i) that changes in the critical internal reflection condition, although formally of order β 2 , are obtainable by measuring the refraction angle to O(β); (ii) the reflection coefficient depends not only on the polarization plane of the incident light but also on whether the plane of incidence does, or does not, include the direction of motion of the glass block. For instance, for light incident in a plane perpendicular to the direction of motion there is no Brewster angle for either plane of polarization, while for light incident in a plane containing the direction of motion at least one (and sometimes both) plane of polarization possess a Brewster angle. We have done these calculations in order to demonstrate that the shearing of one medium relative to another can have profound effects on the reflection and refraction of light. A major point here is that even when it might appear a priori that O(β 2 ) phenomena are unobservable in the laboratory, the present calculations show that this is not always so

Enhancement of heat transfer rate with structural modification of double pipe heat exchanger by changing cylindrical form of tubes into conical form

International Nuclear Information System (INIS)

Hashemian, Mehran; Jafarmadar, Samad; Nasiri, Javid; Sadighi Dizaji, Hamed

2017-01-01

Highlights: • An improved geometry is presented by changing tubes form into conical. • Enhancement of heat transfer rate is investigated. • Frictional characteristics for novel geometry are studied. • For a proper understanding of the subject, the exact physical interpretation is added. • The effect of flow, geometry and thermodynamic parameters is considered. - Abstract: In this paper, cylindrical tubes of a double pipe heat exchanger were changed into the conical tubes as an innovative design which causes improvement of thermal performance of heat exchanger without increment of its weight. Utilization of conical tube instead of cylindrical tube can impress both thermal and frictional characteristics of heat exchanger. Hence, the effect of conical tubes on Nusselt number, friction factor and thermal performance factor are evaluated in present research which was not covered already. Moreover, the effects of hydrodynamic, thermodynamic and geometrical characteristics are analyzed. All said parameters are numerically investigated for nine different combinations of flow direction and conical tubes geometry. The results of simulations of the said configurations are presented to compare the cases from different points of view and determine the most thermally efficient case. The results reveal modified geometry makes 63% increment in Nu number and 54% increment in heat transfer rate at optimum condition.

Analytical and experimental position stability of the abutment in different dental implant systems with a conical implant?abutment connection

OpenAIRE

Semper-Hogg, Wiebke; Kraft, Silvan; Stiller, Sebastian; Mehrhof, Juergen; Nelson, Katja

2012-01-01

Objectives Position stability of the abutment should be investigated in four implant systems with a conical implant?abutment connection. Materials and methods Previously developed formulas and an established experimental setup were used to determine the position stability of the abutment in the four implant systems with a conical implant?abutment connection and different positional index designs: The theoretical rotational freedom was calculated by using the dimensions of one randomly selecte...

Parsimonious wave-equation travel-time inversion for refraction waves

KAUST Repository

Fu, Lei

2017-02-14

We present a parsimonious wave-equation travel-time inversion technique for refraction waves. A dense virtual refraction dataset can be generated from just two reciprocal shot gathers for the sources at the endpoints of the survey line, with N geophones evenly deployed along the line. These two reciprocal shots contain approximately 2N refraction travel times, which can be spawned into O(N2) refraction travel times by an interferometric transformation. Then, these virtual refraction travel times are used with a source wavelet to create N virtual refraction shot gathers, which are the input data for wave-equation travel-time inversion. Numerical results show that the parsimonious wave-equation travel-time tomogram has about the same accuracy as the tomogram computed by standard wave-equation travel-time inversion. The most significant benefit is that a reciprocal survey is far less time consuming than the standard refraction survey where a source is excited at each geophone location.

Microstructured optical fiber refractive index sensor

DEFF Research Database (Denmark)

Town, Graham E.; McCosker, Ravi; Yuan, Scott Wu

2010-01-01

We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show...

Refraction in the lower troposphere: Higher order image distortion effects due to refractive profile curvature

Science.gov (United States)

Short, Daniel J.

There are many applications that rely on the propagation of light through the atmosphere - all of which are subject to atmospheric conditions. While there are obvious processes such as scattering due to particulates like clouds and dust that affect the received intensity of the radiation, the clear atmosphere can also cause significant effects. Refraction is a clear air effect that can cause a variety of phenomena such as apparent relocation, stretching and compression of objects when viewed through the atmosphere. Recently, there has been significant interest in studying the refractive effects for low angle paths within the troposphere, and in particular, near-horizontal paths in the Earth's boundary layer, which is adjacent to the ground. Refractive effects in this case become problematic for many terrestrial optical applications. For example, the pointing of a free space optical communication or a remote sensing system can suffer wandering effects, high-resolution imagery can present distorted and/or dislocated targets, optical tracking of targets can be inaccurate, and optical geodetic surveying accuracy is also very sensitive to the effects of refraction. The work in this dissertation was inspired by data from a time-lapse camera system that collects images of distant targets over a near-horizontal path along the ground. This system was used previously to study apparent diurnal image displacement and this dissertation extends that work by exploring the higher order effects that result from curvature in the vertical refractive index profile of the atmosphere. There are surprisingly few experiments involving atmospheric refractive effects that carefully correlate field data to analytical expressions and other factors such as meteorological data. In working with the time-lapse data, which is comprised of sequences of hundreds or thousands of images collected over durations of weeks or months, it is important to develop straightforward analysis techniques that can

Born-Infeld determinantal gravity and the taming of the conical singularity in 3-dimensional spacetime

Energy Technology Data Exchange (ETDEWEB)

Ferraro, Rafael, E-mail: ferraro@iafe.uba.a [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina); Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); Fiorini, Franco, E-mail: franco@iafe.uba.a [Instituto de Astronomia y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)

2010-08-30

In the context of Born-Infeld determinantal gravity formulated in an n-dimensional spacetime with absolute parallelism, we found an exact 3-dimensional vacuum circular symmetric solution without cosmological constant consisting in a rotating spacetime with non-singular behavior. The space behaves at infinity as the conical geometry typical of 3-dimensional General Relativity without cosmological constant. However, the solution has no conical singularity because the space ends at a minimal circle that no freely falling particle can ever reach in a finite proper time. The space is curved, but no divergences happen since the curvature invariants vanish at both asymptotic limits. Remarkably, this very mechanism also forbids the existence of closed timelike curves in such a spacetime.

Born-Infeld determinantal gravity and the taming of the conical singularity in 3-dimensional spacetime

International Nuclear Information System (INIS)

Ferraro, Rafael; Fiorini, Franco

2010-01-01

In the context of Born-Infeld determinantal gravity formulated in an n-dimensional spacetime with absolute parallelism, we found an exact 3-dimensional vacuum circular symmetric solution without cosmological constant consisting in a rotating spacetime with non-singular behavior. The space behaves at infinity as the conical geometry typical of 3-dimensional General Relativity without cosmological constant. However, the solution has no conical singularity because the space ends at a minimal circle that no freely falling particle can ever reach in a finite proper time. The space is curved, but no divergences happen since the curvature invariants vanish at both asymptotic limits. Remarkably, this very mechanism also forbids the existence of closed timelike curves in such a spacetime.

The refractive index of human hemoglobin in the visible range

International Nuclear Information System (INIS)

Zhernovaya, O; Tuchin, V; Sydoruk, O; Douplik, A

2011-01-01

Because the refractive index of hemoglobin in the visible range is sensitive to the hemoglobin concentration, optical investigations of hemoglobin are important for medical diagnostics and treatment. Direct measurements of the refractive index are, however, challenging; few such measurements have previously been reported, especially in a wide wavelength range. We directly measured the refractive index of human deoxygenated and oxygenated hemoglobin for nine wavelengths between 400 and 700 nm for the hemoglobin concentrations up to 140 g l -1 . This paper analyzes the results and suggests a set of model functions to calculate the refractive index depending on the concentration. At all wavelengths, the measured values of the refractive index depended on the concentration linearly. Analyzing the slope of the lines, we determined the specific refraction increments, derived a set of model functions for the refractive index depending on the concentration, and compared our results with those available in the literature. Based on the model functions, we further calculated the refractive index at the physiological concentration within the erythrocytes of 320 g l -1 . The results can be used to calculate the refractive index in the visible range for arbitrary concentrations provided that the refractive indices depend on the concentration linearly.

Negative Refraction Angular Characterization in One-Dimensional Photonic Crystals

OpenAIRE

Lugo, Jesus Eduardo; Doti, Rafael; Faubert, Jocelyn

2011-01-01

Background Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity de...

Inverse truss design as a conic mathematical program with equilibrium constraints

Czech Academy of Sciences Publication Activity Database

Kočvara, Michal; Outrata, Jiří

2017-01-01

Roč. 10, č. 6 (2017), s. 1329-1350 ISSN 1937-1632 R&D Projects: GA ČR GA15-00735S Institutional support: RVO:67985556 Keywords : conic optimization * truss topology optimization * mathematical programs with equilibrium constraints Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics Impact factor: 0.781, year: 2016 http://library.utia.cas.cz/separaty/2017/MTR/kocvara-0477818.pdf

SU-F-T-28: Evaluation of BEBIG HDR Co-60 After-Loading System for Skin Cancer Treatment Using Conical Surface Applicator

Energy Technology Data Exchange (ETDEWEB)

Safigholi, H; Soliman, A; Song, W Y [Department of Medical Physics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON (Canada); Meigooni, A S [Department of Radiation Therapy, Comprehensive Cancer Center of Nevada, Las Vegas, NV (United States); Han, D [Departemt of Radiation Oncology, University of California San Francisco, San Francisco, CA (United States)

2016-06-15

Purpose: To evaluate the possibility of utilizing the BEBIG HDR 60Co remote after-loading system for malignant skin surface treatment using Monte Carlo (MC) simulation technique. Methods: First TG-43 parameters of BEBIG-Co-60 and Nucletron Ir-192-mHDR-V2 brachytherapy sources were simulated using MCNP6 code to benchmark the sources against the literature. Second a conical tungsten-alloy with 3-cm diameter of Planning-Target-Volume (PTV) at surface for use with a single stepping HDR source is designed. The HDR source is modeled parallel to treatment plane at the center of the conical applicator with a source surface distance (SSD) of 1.5-cm and a removable plastic end-cap with a 1-mm thickness. Third, MC calculated dose distributions from HDR Co-60 for conical surface applicator were compared with the simulated data using HDR Ir-192 source. The initial calculations were made with the same conical surface applicator (standard-applicator) dimensions as the ones used with the Ir-192 system. Fourth, the applicator wall-thickness for the Co-60 system was increased (doubled) to diminish leakage dose to levels received when using the Ir-192 system. With this geometry, percentage depth dose (PDD), and relative 2D-dose profiles in transverse/coronal planes were normalized at 3-mm prescription-depth evaluated along the central axis. Results: PDD for Ir-192 and Co-60 were similar with standard and thick-walled applicator. 2D-relative dose distribution of Co-60, inside the standard-conical-applicator, generated higher penumbra (7.6%). For thick-walled applicator, it created smaller penumbra (<4%) compared to Ir-192 source in the standard-conicalapplicator. Dose leakage outside of thick-walled applicator with Co-60 source was approximately equal (≤3%) with standard applicator using Ir-192 source. Conclusion: Skin cancer treatment with equal quality can be performed with Co-60 source and thick-walled conical applicators instead of Ir-192 with standard applicators. These conical

Experimental Determination of Refractive Index of Gas Hydrates

DEFF Research Database (Denmark)

Bylov, Martin; Rasmussen, Peter

1997-01-01

. For methane hydrate (structure I) the refractive index was found to be 1.346 and for natural gas hydrate (structure II) it was found to be 1.350. The measurements further suggest that the gas hydrate growth rate increases if the water has formed hydrates before. The induction time, on the other hand, seems......The refractive indexes of methane hydrate and natural gas hydrate have been experimentally determined. The refractive indexes were determined in an indirect manner making use of the fact that two non-absorbing materials will have the same refractive index if they cannot be distinguished visually...

The universe of conics from the ancient Greeks to 21st century developments

CERN Document Server

Glaeser, Georg; Odehnal, Boris

2016-01-01

This text presents the classical theory of conics in a modern form. It includes many novel results that are not easily accessible elsewhere. The approach combines synthetic and analytic methods to derive projective, affine and metrical properties, covering both Euclidean and non-Euclidean geometries. With more than two thousand years of history, conic sections play a fundamental role in numerous fields of mathematics and physics, with applications to mechanical engineering, architecture, astronomy, design and computer graphics. This text will be invaluable to undergraduate mathematics students, those in adjacent fields of study, and anyone with an interest in classical geometry. Augmented with more than three hundred fifty figures and photographs, this innovative text will enhance your understanding of projective geometry, linear algebra, mechanics, and differential geometry, with careful exposition and many illustrative exercises. Authors Hellmuth Stachel, born 1942, got his PhD and habilitation in geometry ...

Macroeconomic landscape of refractive surgery in the United States.

Science.gov (United States)

Corcoran, Kevin J

2015-07-01

This review examines the economic history of refractive surgery and the decline of laser-assisted in-situ keratomileusis (LASIK) in the USA, and the emergence of refractive cataract surgery as an area of growth. Since it peaked in 2007 at 1.4 million procedures per year, LASIK has declined 50% in the USA, whereas refractive cataract surgery, including presbyopia-correcting intraocular lenses (IOLs), astigmatism-correcting IOLs, and femtosecond laser-assisted cataract surgery, has grown to 350 000 procedures per year, beginning in 2003. Patients are price-sensitive and responsive to publicity (good or bad) about refractive surgery and refractive cataract surgery. LASIK's decline has been partially offset by the emergence of refractive cataract surgery. About 11% of all cataract surgery in the USA involves presbyopia-correcting IOLs, astigmatism-correcting IOLs, or a femtosecond laser. From the surgeon's perspective, there are high barriers to entry into the marketplace for refractive surgery and refractive cataract surgery due to the high capital cost of excimer and femtosecond lasers, the high skill level required to deliver spectacular results to demanding patients who pay out of pocket, and the necessity to perform a high volume of surgeries to satisfy both of these requirements. Probably, less than 7% of US cataract surgeons can readily meet all of these requirements.

Refractive Errors Affect the Vividness of Visual Mental Images

Science.gov (United States)

Palermo, Liana; Nori, Raffaella; Piccardi, Laura; Zeri, Fabrizio; Babino, Antonio; Giusberti, Fiorella; Guariglia, Cecilia

2013-01-01

The hypothesis that visual perception and mental imagery are equivalent has never been explored in individuals with vision defects not preventing the visual perception of the world, such as refractive errors. Refractive error (i.e., myopia, hyperopia or astigmatism) is a condition where the refracting system of the eye fails to focus objects sharply on the retina. As a consequence refractive errors cause blurred vision. We subdivided 84 individuals according to their spherical equivalent refraction into Emmetropes (control individuals without refractive errors) and Ametropes (individuals with refractive errors). Participants performed a vividness task and completed a questionnaire that explored their cognitive style of thinking before their vision was checked by an ophthalmologist. Although results showed that Ametropes had less vivid mental images than Emmetropes this did not affect the development of their cognitive style of thinking; in fact, Ametropes were able to use both verbal and visual strategies to acquire and retrieve information. Present data are consistent with the hypothesis of equivalence between imagery and perception. PMID:23755186

Computational imaging using lightweight diffractive-refractive optics

KAUST Repository

Peng, Yifan

2015-11-23

Diffractive optical elements (DOE) show great promise for imaging optics that are thinner and more lightweight than conventional refractive lenses while preserving their light efficiency. Unfortunately, severe spectral dispersion currently limits the use of DOEs in consumer-level lens design. In this article, we jointly design lightweight diffractive-refractive optics and post-processing algorithms to enable imaging under white light illumination. Using the Fresnel lens as a general platform, we show three phase-plate designs, including a super-thin stacked plate design, a diffractive-refractive-hybrid lens, and a phase coded-aperture lens. Combined with cross-channel deconvolution algorithm, both spherical and chromatic aberrations are corrected. Experimental results indicate that using our computational imaging approach, diffractive-refractive optics is an alternative candidate to build light efficient and thin optics for white light imaging.

Computational imaging using lightweight diffractive-refractive optics

KAUST Repository

Peng, Yifan; Fu, Qiang; Amata, Hadi; Su, Shuochen; Heide, Felix; Heidrich, Wolfgang

2015-01-01

Diffractive optical elements (DOE) show great promise for imaging optics that are thinner and more lightweight than conventional refractive lenses while preserving their light efficiency. Unfortunately, severe spectral dispersion currently limits the use of DOEs in consumer-level lens design. In this article, we jointly design lightweight diffractive-refractive optics and post-processing algorithms to enable imaging under white light illumination. Using the Fresnel lens as a general platform, we show three phase-plate designs, including a super-thin stacked plate design, a diffractive-refractive-hybrid lens, and a phase coded-aperture lens. Combined with cross-channel deconvolution algorithm, both spherical and chromatic aberrations are corrected. Experimental results indicate that using our computational imaging approach, diffractive-refractive optics is an alternative candidate to build light efficient and thin optics for white light imaging.

Free-breathing pediatric chest MRI: Performance of self-navigated golden-angle ordered conical ultrashort echo time acquisition.

Science.gov (United States)

Zucker, Evan J; Cheng, Joseph Y; Haldipur, Anshul; Carl, Michael; Vasanawala, Shreyas S

2018-01-01

To assess the feasibility and performance of conical k-space trajectory free-breathing ultrashort echo time (UTE) chest magnetic resonance imaging (MRI) versus four-dimensional (4D) flow and effects of 50% data subsampling and soft-gated motion correction. Thirty-two consecutive children who underwent both 4D flow and UTE ferumoxytol-enhanced chest MR (mean age: 5.4 years, range: 6 days to 15.7 years) in one 3T exam were recruited. From UTE k-space data, three image sets were reconstructed: 1) one with all data, 2) one using the first 50% of data, and 3) a final set with soft-gating motion correction, leveraging the signal magnitude immediately after each excitation. Two radiologists in blinded fashion independently scored image quality of anatomical landmarks on a 5-point scale. Ratings were compared using Wilcoxon rank-sum, Wilcoxon signed-ranks, and Kruskal-Wallis tests. Interobserver agreement was assessed with the intraclass correlation coefficient (ICC). For fully sampled UTE, mean scores for all structures were ≥4 (good-excellent). Full UTE surpassed 4D flow for lungs and airways (P 93% scans for all techniques (P = 0.27). Interobserver agreement was excellent for combined scores (ICC = 0.83). High-quality free-breathing conical UTE chest MR is feasible, surpassing 4D flow for lungs and airways, with equivalent PA visualization. Data subsampling only mildly degraded images, favoring lesser scan times. Soft-gating motion correction overall did not improve image quality. 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:200-209. © 2017 International Society for Magnetic Resonance in Medicine.

Hypervelocity jets from conical hollow-charges

International Nuclear Information System (INIS)

Velarde, P. M.; Martinez-Val, J. M.; Eliezer, S.; Piera, M.; Guillen, J.; Cobo, M. D.; Ogando, F.; Crisol, A.; Gonzalez, L.; Prieto, J.; Velarde, G.

1997-01-01

In this article the formation of jets by means of the implosion of conical targets is analyzed. This implosion might be induced by high intensity lasers or X rays. It is known of experiments with explosive and numeric simulations that the formation of jets depends critically on the aperture of the cone. It is found in these simulations that for a given collapsing speed an angle of the cone exists below which jet doesn't take place. This critical angle grows with the collapsing speed. The numerical simulations seem to indicate that the production of jets is related to the separation of the shock wave that takes place in the collapsing region. We will also analyze the mass and kinetic energy of the jets taken place as a function of the initial opening of the cone

WebQuest on Conic Sections as a Learning Tool for Prospective Teachers

Science.gov (United States)

Kurtulus, Aytac; Ada, Tuba

2012-01-01

WebQuests incorporate technology with educational concepts through integrating online resources with student-centred and activity-based learning. In this study, we describe and evaluate a WebQuest based on conic sections, which we have used with a group of prospective mathematics teachers. The WebQuest entitled: "Creating a Carpet Design Using…

Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK.

Science.gov (United States)

Kanellopoulos, Anastasios John

2016-01-01

To evaluate the safety, efficacy, and contralateral eye comparison of topography-guided myopic LASIK with two different refraction treatment strategies. Private clinical ophthalmology practice. A total of 100 eyes (50 patients) in consecutive cases of myopic topography-guided LASIK procedures with the same refractive platform (FS200 femtosecond and EX500 excimer lasers) were randomized for treatment as follows: one eye with the standard clinical refraction (group A) and the contralateral eye with the topographic astigmatic power and axis (topography-modified treatment refraction; group B). All cases were evaluated pre- and post-operatively for the following parameters: refractive error, best corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA), topography (Placido-disk based) and tomography (Scheimpflug-image based), wavefront analysis, pupillometry, and contrast sensitivity. Follow-up visits were conducted for at least 12 months. Mean refractive error was -5.5 D of myopia and -1.75 D of astigmatism. In group A versus group B, respectively, the average UDVA improved from 20/200 to 20/20 versus 20/16; post-operative CDVA was 20/20 and 20/13.5; 1 line of vision gained was 27.8% and 55.6%; and 2 lines of vision gained was 5.6% and 11.1%. In group A, 27.8% of eyes had over -0.50 diopters of residual refractive astigmatism, in comparison to 11.7% in group B ( P Topography-modified refraction (TMR): topographic adjustment of the amount and axis of astigmatism treated, when different from the clinical refraction, may offer superior outcomes in topography-guided myopic LASIK. These findings may change the current clinical paradigm of the optimal subjective refraction utilized in laser vision correction.

Evidence for subwavelength imaging with positive refraction

Energy Technology Data Exchange (ETDEWEB)

Ma, Yun Gui [Temasek Laboratories, National University of Singapore, Singapore 119260 (Singapore); Sahebdivan, Sahar; Tyc, Tomas; Leonhardt, Ulf [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Ong, C K, E-mail: ulf@st-andrews.ac.uk [Centre for Superconducting and Magnetic Materials, Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

2011-03-15

The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction.

Evidence for subwavelength imaging with positive refraction

International Nuclear Information System (INIS)

Ma, Yun Gui; Sahebdivan, Sahar; Tyc, Tomas; Leonhardt, Ulf; Ong, C K

2011-01-01

The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction.

Conical surface textures formed by ion bombarding 2% Be-Cu alloy

International Nuclear Information System (INIS)

Panitz, J.K.G.

1991-01-01

A homogeneous, micrometer-sized conical surface texture forms on 2% Be-Cu alloy which is bombarded with an argon beam produced by a Kaufman ion source. The dimensions of the features that form depend strongly on argon energy (from 250 to 1500 eV); argon fluence (10 19 to 10 20 ions cm -2 ); and argon flux (0.1 to 1 mA cm -2 ). The texture morphology depends less strongly on the background ambient (Mo versus graphite), earlier alloy heat treatments and the temperature during bombardment (100 o C and 450 o C). As the texture matures with increasing fluence, the number of large features increases at the expense of the number of small features. The observed relationship between texture formation and ion flux suggests that the evolution of these features is not adequately described by theories predicting that the mature conical side-wall angle is related to the angle of the maximum sputtering yield. These textured surfaces can be coated with other metals for a variety of possible applications including pulsed power Li + beam anodes; cold cathode field emission devices; optical absorbers and catalysis supports. (author)

Angle dependent focal spot size of a conical X-ray target

International Nuclear Information System (INIS)

Saeed Raza, Hamid; Jin Kim, Hyun; Nam Kim, Hyun; Oh Cho, Sung

2015-01-01

Misaligned phantoms may severely affect the focal spot calculations. A method is proposed to determine the geometry of the X-ray target and the position of the image radiograph around the X-ray target to get a relatively smaller focal spot size. Results reveal that the focal spot size is not always isotropic around the target but it decreases as the point of observation shifts radially away from the center line of the conical X-ray target. This research will help in producing high quality X-ray images in multi-directions by properly aligning the phantoms and the radiograph tallies. - Highlights: • Misaligned phantoms may severely affect the focal spot calculations. • The aim of this research is to analyze systematically the angle dependent behavior of the focal spot size around a conical shaped X-ray target. • A general purpose Monte Carlo (MCNP5) computer code is used to achieve a relatively small focal spot size. • Angular distribution of the X-ray focal spot size mainly depends on the angular orientation of the phantom and its aligned FIR tally. • This research will help in producing high quality X-ray images in multi-directions

Conical surface textures formed by ion bombarding 2% Be Cu alloy

International Nuclear Information System (INIS)

Panitz, J.K.G.

1990-01-01

A homogeneous, micrometer-sized conical surface texture forms on 2% Be-Cu alloy which is bombarded with an argon beam produced by a Kaufman ion source. The dimensions of the features that form strongly depend on: (1) argon energy (from 250 to 1500 eV), (2) fluence (10 19 to 10 20 ions/cm 2 ), and (3) flux (0.1 to 1 mA/cm 2 ). The texture morphology depends less strongly on the background ambient (Mo vs graphite), earlier alloy heat treatments and the temperature during bombardment (100 degree C and 450 degree C). As the texture matures with increasing fluence, the number of large features increases at the expense of the number of small features. The observed relationship between texture formation and ion flux suggests that the evolution of these features is not adequately described by theories predicting that the mature conical sidewall angle is related to the angle of the maximum sputtering yield. These textured surfaces can be coated with other metals for a variety of possible applications including: (1) pulsed power Li+ beam anodes, (2) cold cathode field emission devices, (3) optical absorbers and (4) catalysis supports. 18 refs., 5 figs

Seismic refraction survey of the ANS preferred site

Energy Technology Data Exchange (ETDEWEB)

Davis, R.K. (Automated Sciences Group, Inc., Oak Ridge, TN (United States)); Hopkins, R.A. (Marrich, Inc., Knoxville, TN (United States)); Doll, W.E. (Oak Ridge National Lab., TN (United States))

1992-02-01

Between September 19, 1991 and October 8, 1991 personnel from Martin Marietta Energy Systems, Inc. (Energy Systems), Automated Sciences Group, Inc., and Marrich, Inc. performed a seismic refraction survey at the Advanced Neutron Source (ANS) preferred site. The purpose of this survey was to provide estimates of top-of-rock topography, based on seismic velocities, and to delineate variations in rock and soil velocities. Forty-four seismic refraction spreads were shot to determine top-of-rock depths at 42 locations. Nine of the seismic spreads were shot with long offsets to provide 216 top-of-rock depths for 4 seismic refraction profiles. The refraction spread locations were based on the grid for the ANS Phase I drilling program. Interpretation of the seismic refraction data supports the assumption that the top-of-rock surface generally follows the local topography. The shallow top-of-rock interface interpreted from the seismic refraction data is also supported by limited drill information at the site. Some zones of anomalous data are present that could be the result of locally variable weathering, a localized variation in shale content, or depth to top-of-rock greater than the site norm.

Superfocusing modes of surface plasmon polaritons in conical geometry based on the quasi-separation of variables approach

International Nuclear Information System (INIS)

Kurihara, Kazuyoshi; Otomo, Akira; Syouji, Atsushi; Takahara, Junichi; Suzuki, Koji; Yokoyama, Shiyoshi

2007-01-01

Analytic solutions to the superfocusing modes of surface plasmon polaritons in a conical geometry are theoretically studied using an ingenious method called the quasi-separation of variables. This method can be used to look for fundamental solutions to the wave equation for a field that must satisfy boundary conditions at all points on the continuous surface of tapered geometries. The set of differential equations exclusively separated from the wave equation can be consistently solved in combination with perturbation methods. This paper presents the zeroth-order perturbation solution of conical superfocusing modes with azimuthal symmetry and graphically represents them in electric field-line patterns

On the effective refractive index of blood

Science.gov (United States)

Nahmad-Rohen, Alexander; Contreras-Tello, Humberto; Morales-Luna, Gesuri; García-Valenzuela, Augusto

2016-01-01

We calculated the real and imaginary parts of the effective refractive index {n}{eff} of blood as functions of wavelength from 400 to 800 nm; we employed van de Hulst’s theory, together with the anomalous diffraction approximation, for the calculation. We modelled blood as a mixture of plasma and erythrocytes. Our results indicate that erythrocyte orientation has a strong effect on {n}{eff}, making blood an optically anisotropic medium except when the erythrocytes are randomly oriented. In the case in which their symmetry axis is perpendicular to the wave vector, {n}{eff} equals the refractive index of plasma at certain wavelengths. Furthermore, the erythrocytes’ shape affects their contribution to {n}{eff} in an important way, implying that studies on the effective refractive index of blood should avoid approximating them as spheres or spheroids. Finally, the effective refractive index of blood predicted by van de Hulst’s theory is different from what would be obtained by averaging the refractive indices of its constituents weighted by volume; such a volume-weighted average is appropriate only for haemolysed blood. We then measured the real part of the refractive index of various blood solutions using two different experimental setups. One of the most important results of our expriment is that {n}{eff} is measurable to a good degree of precision even for undiluted blood, although not all measuring apparatuses are appropriate. The experimental data is self-consistent and in reasonable agreement with our theoretical calculations.

The light wave flow effect in a plane-parallel layer with a quasi-zero refractive index under the action of bounded light beams

International Nuclear Information System (INIS)

Gadomsky, O. N.; Shchukarev, I. A.

2016-01-01

It is shown that external optical radiation in the 450–1200 nm range can be efficiently transformed under the action of bounded light beams to a surface wave that propagates along the external and internal boundaries of a plane-parallel layer with a quasi-zero refractive index. Reflection regimes with complex and real angles of refraction in the layer are considered. The layer with a quasi-zero refractive index in this boundary problem is located on a highly reflective metal substrate; it is shown that the uniform low reflection of light is achieved in the wavelength range under study.

Light rays in gravitating, refractive media

International Nuclear Information System (INIS)

Noonan, T.W.

1982-01-01

The field-to-particle method of H. P. Robertson is applied to the general-relativistic Maxwell equations in order to obtain the general-relativistic equation of motion for a photon in a refractive medium. For the special case of an uncharged, refractive, spherically symmetric mass, the exact first-order differential equation for the light-ray path is given

Three-dimensional free vibration of functionally graded truncated conical shells subjected to thermal environment

Energy Technology Data Exchange (ETDEWEB)

Malekzadeh, P., E-mail: p_malekz@yahoo.com [Department of Mechanical Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Fiouz, A.R.; Sobhrouyan, M. [Department of Civil Engineering, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of)

2012-01-15

A three-dimensional (3D) free vibration analysis of the functionally graded (FG) truncated conical shells subjected to thermal environment is presented. The material properties are assumed to be temperature-dependent and graded in the radius direction, which can vary according to a simple power law distribution. The initial thermal stresses are obtained accurately by solving the thermoelastic equilibrium equations and by considering the two-dimensional axisymmetric temperature distribution in the shell. The differential quadrature method (DQM) as an efficient and accurate numerical tool is adopted to solve the thermal and thermo-mechanical governing equations. For this purpose, a mapping technique is employed to transform the cross section of the shell into the computational domain of DQM. The convergence behavior of the method is numerically demonstrated and comparison studies with the available solutions in the literature are performed. The effects of temperature dependence of material properties, geometrical parameters, material graded index, thermal and mechanical boundary conditions on the frequency parameters of the FG truncated conical shells are carried out. - Highlights: Black-Right-Pointing-Pointer 3D free vibration analysis of the functionally graded truncated conical shells is presented. Black-Right-Pointing-Pointer Two-dimensional axisymmetric temperature distribution in the shell is assumed. Black-Right-Pointing-Pointer The material properties are assumed to be temperature-dependent. Black-Right-Pointing-Pointer Initial thermal stresses due to thermal environment are evaluated accurately and included. Black-Right-Pointing-Pointer Representing the effects of different parameters on the non-dimensional frequencies.

A theoretical model for predicting the Peak Cutting Force of conical picks

Directory of Open Access Journals (Sweden)

Gao Kuidong

2014-01-01

Full Text Available In order to predict the PCF (Peak Cutting Force of conical pick in rock cutting process, a theoretical model is established based on elastic fracture mechanics theory. The vertical fracture model of rock cutting fragment is also established based on the maximum tensile criterion. The relation between vertical fracture angle and associated parameters (cutting parameter  and ratio B of rock compressive strength to tensile strength is obtained by numerical analysis method and polynomial regression method, and the correctness of rock vertical fracture model is verified through experiments. Linear regression coefficient between the PCF of prediction and experiments is 0.81, and significance level less than 0.05 shows that the model for predicting the PCF is correct and reliable. A comparative analysis between the PCF obtained from this model and Evans model reveals that the result of this prediction model is more reliable and accurate. The results of this work could provide some guidance for studying the rock cutting theory of conical pick and designing the cutting mechanism.

Parametric instability analysis of truncated conical shells using the Haar wavelet method

Science.gov (United States)

Dai, Qiyi; Cao, Qingjie

2018-05-01

In this paper, the Haar wavelet method is employed to analyze the parametric instability of truncated conical shells under static and time dependent periodic axial loads. The present work is based on the Love first-approximation theory for classical thin shells. The displacement field is expressed as the Haar wavelet series in the axial direction and trigonometric functions in the circumferential direction. Then the partial differential equations are reduced into a system of coupled Mathieu-type ordinary differential equations describing dynamic instability behavior of the shell. Using Bolotin's method, the first-order and second-order approximations of principal instability regions are determined. The correctness of present method is examined by comparing the results with those in the literature and very good agreement is observed. The difference between the first-order and second-order approximations of principal instability regions for tensile and compressive loads is also investigated. Finally, numerical results are presented to bring out the influences of various parameters like static load factors, boundary conditions and shell geometrical characteristics on the domains of parametric instability of conical shells.

Conical geometry for sagittal focusing as applied to X rays from synchrotrons

International Nuclear Information System (INIS)

Ice, G.E.; Sparks, C.J.

1993-06-01

The authors describe a method for simultaneously focusing and monochromatization of X rays from a fan of radiation having up to 15 mrad divergence in one dimension. This geometry is well suited to synchrotron radiation sources at magnifications of one-fifth to two and is efficient for X-ray energies between 3 and 40 keV (0.48 and 6.4 fJ). The method uses crystals bent to part of a cone for sagittal focusing and allows for the collection of a larger divergence with less mixing of the horizontal into the vertical divergence than is possible with X-ray mirrors. They describe the geometry required to achieve the highest efficiency when a conical crystal follows a flat crystal in a nondispersive two-crystal monochromator. At a magnification of one-third, the geometry is identical to a cylindrical focusing design described previously. A simple theoretical calculation is shown to agree well with ray-tracing results. Minimum aberrations are observed at magnifications near one. Applications of the conical focusing geometry to existing and future synchrotron radiation facilities are discussed

Interference of conically scattered light in surface plasmon resonance.

Science.gov (United States)

Webster, Aaron; Vollmer, Frank

2013-02-01

Surface plasmon polaritons on thin metal films are a well studied phenomena when excited using prism coupled geometries such as the Kretschmann attenuated total reflection configuration. Here we describe a novel interference pattern in the conically scattered light emanating from such a configuration when illuminated by a focused beam. We observe conditions indicating only self-interference of scattered surface plasmon polaritions without any contributions from specular reflection. The spatial evolution of this field is described in the context of Fourier optics and has applications in highly sensitive surface plasmon based biosensing.

Dirac operator on spaces with conical singularities

International Nuclear Information System (INIS)

Chou, A.W.

1982-01-01

The Dirac operator on compact spaces with conical singularities is studied via the separation of variables formula and the functional calculus of the Dirac Laplacian on the cone. A Bochner type vanishing theorem which gives topological obstructions to the existence of non-negative scalar curvature k greater than or equal to 0 in the singular case is proved. An index formula relating the index of the Dirac operator to the A-genus and Eta-invariant similar to that of Atiyah-Patodi-Singer is obtained. In an appendix, manifolds with boundary with non-negative scalar curvature k greater than or equal to 0 are studied, and several new results on constructing complete metrics with k greater than or equal to on them are obtained

REFRACTIVE ERROR STATUS IN BAYELSA STATE, NIGERIA

African Journals Online (AJOL)

LIVINGSTON

deepening poverty because of their inability to see well” . In 2002, the .... all the refractions) and other health workers. During the period .... To the best of our knowledge, there is no ... 2020 and eliminate uncorrected refractive error within the ...

Evidence for subwavelength imaging with positive refraction

OpenAIRE

Ma, Yun Gui; Sahebdivan, Sahar; Ong, C. K.; Tyc, Tomas; Leonhardt, Ulf

2011-01-01

The resolution of lenses is normally limited by the wave nature of light. Imaging with perfect resolution was believed to rely on negative refraction, but here we present experimental evidence for subwavelength imaging with positive refraction. Publisher PDF Peer reviewed

Effect of refractive error on temperament and character properties

Institute of Scientific and Technical Information of China (English)

Emine; Kalkan; Akcay; Fatih; Canan; Huseyin; Simavli; Derya; Dal; Hacer; Yalniz; Nagihan; Ugurlu; Omer; Gecici; Nurullah; Cagil

2015-01-01

AIM: To determine the effect of refractive error on temperament and character properties using Cloninger’s psychobiological model of personality.METHODS: Using the Temperament and Character Inventory(TCI), the temperament and character profiles of 41 participants with refractive errors(17 with myopia,12 with hyperopia, and 12 with myopic astigmatism) were compared to those of 30 healthy control participants.Here, temperament comprised the traits of novelty seeking, harm-avoidance, and reward dependence, while character comprised traits of self-directedness,cooperativeness, and self-transcendence.RESULTS: Participants with refractive error showed significantly lower scores on purposefulness,cooperativeness, empathy, helpfulness, and compassion(P <0.05, P <0.01, P <0.05, P <0.05, and P <0.01,respectively).CONCLUSION: Refractive error might have a negative influence on some character traits, and different types of refractive error might have different temperament and character properties. These personality traits may be implicated in the onset and/or perpetuation of refractive errors and may be a productive focus for psychotherapy.

Perfect imaging without negative refraction

OpenAIRE

Leonhardt, Ulf

2009-01-01

Perfect imaging has been believed to rely on negative refraction, but here we show that an ordinary positively-refracting optical medium may form perfect images as well. In particular, we establish a mathematical proof that Maxwell's fish eye in two-dimensional integrated optics makes a perfect instrument with a resolution not limited by the wavelength of light. We also show how to modify the fish eye such that perfect imaging devices can be made in practice. Our method of perfect focusing ma...

Conic Sections and the Discovery of a Novel Curve Using Differential Equations

Science.gov (United States)

de Alwis, Amal

2013-01-01

We began by observing a variety of properties related to the tangent and normal lines of three conic sections: a parabola, an ellipse, and a hyperbola. Some of these properties include specific relationships between the x- and y-intercepts of the tangent and normal lines. Using these properties, we were able to form several differential equations.…

Inverted-conical light guide for crosstalk reduction in tightly-packed scintillator matrix and MAPMT assembly

Energy Technology Data Exchange (ETDEWEB)

Chang, Y.-Y., E-mail: gixd@hep1.phys.ntu.edu.tw [Department of Physics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Chen, C.R. [National Space Organization (NSPO), 8F., No. 9, Prosperity 1 s Rd., Hsinchu Science Park, Hsinchu 30078, Taiwan, ROC (China); Chen, P.; Huang, J.-J. [Department of Physics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Huang, M.A. [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Department of Energy Engineering, National United University, 1, Lienda, Miaoli 36003, Taiwan, ROC (China); Liu, T.-C. [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Nam, J.W. [Department of Physics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Wang, M.-Z., E-mail: mzwang@hep1.phys.ntu.edu.tw [Department of Physics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, 1 Roosevelt Rd., Taipei 10617, Taiwan, ROC (China); Bogomolov, V. [Skobeltsyn Institute of Nuclear Physics of Lomonosov Moscow State University, Leninskie Gory 119234 (Russian Federation); Physics Department of Lomonosov Moscow State University, Leninskie Gory 119234 (Russian Federation); Brandt, S.; Budtz-Jørgensen, C. [National Space Institute, Astrophysics, Technical University of Denmark, DK-2800 Kongens, Lyngby (Denmark); and others

2015-01-21

In this paper we present the Inverted-Conical light guide designed for optical crosstalk reduction in the scintillator-MAPMT assemblies. The research was motivated by the 30% crosstalk observed in UFFO X-ray telescope, UBAT, during the preliminary calibration with MAPMTs of 64 2.88×2.88 mm{sup 2} pixels and identically gridded YSO crystal matrices. We began the study with the energy and crosstalk calibrations of the detector, then we constructed a GEANT4 simulation with the customized metallic film model as the MAPMT photocathode. The simulation reproduced more than 70% of the crosstalk and explained it as a consequence of the total reflection produced by the photocathode. The result indicated that the crosstalk mechanism could be a common case in most of the contact-assembled scintillation detectors. The concept of the Inverted-Conical light guide was to suppress the total reflection by contracting the incident angle of the scintillation. We optimized the design in the simulation and fabricated a test sample. The test sample reduced 52% crosstalk with a loss of 6% signal yield. The idea of the Inverted-Conical light guide can be adapted by scintillation detectors multi-pixel, imaging-purpose scintillation detectors such as the ultra-fast GRB observatory UFFO-UBAT, whose performances are sensitive to responding time, image resolution, and geometrical modifications.

Inverted-conical light guide for crosstalk reduction in tightly-packed scintillator matrix and MAPMT assembly

International Nuclear Information System (INIS)

Chang, Y.-Y.; Chen, C.R.; Chen, P.; Huang, J.-J.; Huang, M.A.; Liu, T.-C.; Nam, J.W.; Wang, M.-Z.; Bogomolov, V.; Brandt, S.; Budtz-Jørgensen, C.

2015-01-01

In this paper we present the Inverted-Conical light guide designed for optical crosstalk reduction in the scintillator-MAPMT assemblies. The research was motivated by the 30% crosstalk observed in UFFO X-ray telescope, UBAT, during the preliminary calibration with MAPMTs of 64 2.88×2.88 mm 2 pixels and identically gridded YSO crystal matrices. We began the study with the energy and crosstalk calibrations of the detector, then we constructed a GEANT4 simulation with the customized metallic film model as the MAPMT photocathode. The simulation reproduced more than 70% of the crosstalk and explained it as a consequence of the total reflection produced by the photocathode. The result indicated that the crosstalk mechanism could be a common case in most of the contact-assembled scintillation detectors. The concept of the Inverted-Conical light guide was to suppress the total reflection by contracting the incident angle of the scintillation. We optimized the design in the simulation and fabricated a test sample. The test sample reduced 52% crosstalk with a loss of 6% signal yield. The idea of the Inverted-Conical light guide can be adapted by scintillation detectors multi-pixel, imaging-purpose scintillation detectors such as the ultra-fast GRB observatory UFFO-UBAT, whose performances are sensitive to responding time, image resolution, and geometrical modifications

Eye laterality: a comprehensive analysis in refractive surgery candidates.

Science.gov (United States)

Linke, Stephan J; Druchkiv, Vasyl; Steinberg, Johannes; Richard, Gisbert; Katz, Toam

2013-08-01

To explore eye laterality (higher refractive error in one eye) and its association with refractive state, spherical/astigmatic anisometropia, age and sex in refractive surgery candidates. Medical records of 12 493 consecutive refractive surgery candidates were filtered. Refractive error (subjective and cycloplegic) was measured in each subject and correlated with eye laterality. Only subjects with corrected distance visual acuity (CDVA) of >20/22 in each eye were enrolled to exclude amblyopia. Associations between eye laterality and refractive state were analysed by means of t-test, chi-squared test, Spearman's correlation and multivariate logistic regression analysis, respectively. There was no statistically significant difference in spherical equivalent between right (-3.47 ± 2.76 D) and left eyes (-3.47 ± 2.76 D, p = 0.510; Pearson's r = 0.948, p laterality for anisometropia >2.5 D in myopic (-5.64 ± 2.5 D versus -4.92 ± 2.6 D; p = 0.001) and in hyperopic (4.44 ± 1.69 D versus 3.04 ± 1.79 D; p = 0.025) subjects, (II) a tendency for left eye cylindrical laterality in myopic subjects, and (III) myopic male subjects had a higher prevalence of left eye laterality. (IV) Age did not show any significant impact on laterality. Over the full refractive spectrum, this study confirmed previously described strong interocular refractive correlation but revealed a statistically significant higher rate of right eye laterality for anisometropia >2.5 D. In general, our results support the use of data from one eye only in studies of ocular refraction. © 2013 The Authors. Acta Ophthalmologica © 2013 Acta Ophthalmologica Scandinavica Foundation.

Dispersion characteristics of negative refraction sonic crystals

International Nuclear Information System (INIS)

Wu, L.-Y.; Chen, L.-W.; Wang, R.C.-C.

2008-01-01

Dispersion characteristics of negative refraction sonic crystals are investigated. The plane wave expansion method is used to calculate the equifrequency surface; the dependences of refractive direction on frequencies and incident angles for triangular lattices are shown. There exist the positive and negative refractive waves which include k.V g ≥0 and k.V g ≤0 in the second band for the triangular system. We also use the finite element method to demonstrate that the relative intensity of the transmitted acoustic waves is dependent on incident frequencies and angles. The positions of the partial band gaps obtained by the plane wave expansion method are in good agreement with those obtained by the finite element method. The sonic crystals with negative effective index are shown to have higher transmission intensities. By using the negative refraction behavior, we can design a sonic crystal plane lens to focus a sonic wave

Refractive index inhomogeneity within an aerogel block

International Nuclear Information System (INIS)

Bellunato, T.; Calvi, M.; Da Silva Costa, C.F.; Matteuzzi, C.; Musy, M.; Perego, D.L.

2006-01-01

Evaluating local inhomogeneities of the refractive index inside aerogel blocks to be used as Cherenkov radiator is important for a high energy physics experiment where angular resolution is crucial. Two approaches are described and compared. The first one is based on the bending of a laser beam induced by refractive index gradients along directions normal to the unperturbed optical path. The second method exploits the Cherenkov effect itself by shooting an ultra-relativistic collimated electron beam through different points of the aerogel surface. Local refractive index variations result in sizable differences in the Cherenkov photons distribution

Physical modelling of tsunamis generated by three-dimensional deformable granular landslides on planar and conical island slopes.

Science.gov (United States)

McFall, Brian C; Fritz, Hermann M

2016-04-01

Tsunamis generated by landslides and volcanic island collapses account for some of the most catastrophic events recorded, yet critically important field data related to the landslide motion and tsunami evolution remain lacking. Landslide-generated tsunami source and propagation scenarios are physically modelled in a three-dimensional tsunami wave basin. A unique pneumatic landslide tsunami generator was deployed to simulate landslides with varying geometry and kinematics. The landslides were generated on a planar hill slope and divergent convex conical hill slope to study lateral hill slope effects on the wave characteristics. The leading wave crest amplitude generated on a planar hill slope is larger on average than the leading wave crest generated on a convex conical hill slope, whereas the leading wave trough and second wave crest amplitudes are smaller. Between 1% and 24% of the landslide kinetic energy is transferred into the wave train. Cobble landslides transfer on average 43% more kinetic energy into the wave train than corresponding gravel landslides. Predictive equations for the offshore propagating wave amplitudes, periods, celerities and lengths generated by landslides on planar and divergent convex conical hill slopes are derived, which allow an initial rapid tsunami hazard assessment.

Cryogenic refractive index of Heraeus homosil glass

Science.gov (United States)

Miller, Kevin H.; Quijada, Manuel A.; Leviton, Douglas B.

2017-08-01

This paper reports measurements of the refractive index of Homosil (Heraeus) over the wavelength range of 0.34—3.16 μm and temperature range of 120—335 K. These measurements were performed by using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at the NASA's Goddard Space Flight Center. These measurements were in support of an integrated Structural-Thermal-Optical-Performance (STOP) model that was developed for a fieldwidened Michelson interferometer that is being built and tested for the High Spectral Resolution Lidar (HSRL) project at the NASA Langley Research Center (LaRC). The cryogenic refractive index measurements were required in order to account for the highly sensitive performance of the HSRL instrument to changes in refractive index with temperature, temperature gradients, thermal expansion, and deformation due to mounting stresses. A dense coverage of the absolute refractive index over the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dn/dT) and dispersion relation (dn/dλ) as a function of wavelength and temperature. Our measurements of Homosil will be compared with measurements of other glasses from the fused silica family studied in CHARMS as well as measurements reported elsewhere in the literature.

Plasmon-negative refraction at the heterointerface of graphene sheet arrays.

Science.gov (United States)

Huang, He; Wang, Bing; Long, Hua; Wang, Kai; Lu, Peixiang

2014-10-15

We demonstrate negative refraction of surface plasmon polaritons (SPPs) at the heterointerface of two monolayer graphene sheet arrays (MGSAs) with different periods. The refraction angle is specifically related to the period ratio of the two MGSAs. By varying the incident Bloch momentum, the SPPs might be refracted in the direction normal to the heterointerface. Moreover, both positive and negative refraction could appear simultaneously. Because of the linear diffraction relation, the incident and refracted SPP beams experience diffraction-free propagation. The heterostructures composed of the MGSAs may find great applications in deep-subwavelength spatial light modulators, optical splitters, and switches.

Graphical Derivatives and Stability Analysis for Parameterized Equilibria with Conic Constraints

Czech Academy of Sciences Publication Activity Database

Mordukhovich, B. S.; Outrata, Jiří; Ramírez, H. C.

2015-01-01

Roč. 23, č. 4 (2015), s. 687-704 ISSN 1877-0533 R&D Projects: GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985556 Keywords : Variational analysis and optimization * Parameterized equilibria * Conic constraints * Sensitivity and stability analysis * Solution maps * Graphical derivatives * Normal and tangent cones Subject RIV: BA - General Mathematics Impact factor: 0.973, year: 2015 http://library.utia.cas.cz/separaty/2015/MTR/outrata-0449259.pdf

Refractive index as materials property. Der Brechungsindex als Stoffeigenschaft

Energy Technology Data Exchange (ETDEWEB)

Zilian, U. (Ciba-Geigy AG, Basel (Switzerland))

1991-10-01

The investigation of the relationship between refractive index (n) and molecular structure of a series of gases, liquids, and solids led to the conclusion that the refractive index of a substance is an independent molecular property. Light is refracted by two types of electron pairs. a) Bonding Electron Pairs (BEP) and b) Response Electron Pairs (REP). - Paraffins exhibit only BEPs which can easily be counted. REP is a new term we introduce to quantify the effects of several nonbonding electrons. The inert gases, for example, refract solely with REPs. They can be determined, and the most important ones are herein tabulated or delineated in the text. For compounds with known formular weight (M) and density (d), the refractive index can be simply calculated using the following formula. (orig.).

Measurements of photoinduced refractive index changes in ...

Indian Academy of Sciences (India)

Abstract. We report the pump–probe measurements of nonlinear refractive index changes in photochromic bacteriorhodopsin films. The photoinduced absorption is caused by pump beam at 532 nm and the accompanying refractive index changes are studied using a probe beam at 633 nm. The proposed technique is ...

Refractive index inversion based on Mueller matrix method

Science.gov (United States)

Fan, Huaxi; Wu, Wenyuan; Huang, Yanhua; Li, Zhaozhao

2016-03-01

Based on Stokes vector and Jones vector, the correlation between Mueller matrix elements and refractive index was studied with the result simplified, and through Mueller matrix way, the expression of refractive index inversion was deduced. The Mueller matrix elements, under different incident angle, are simulated through the expression of specular reflection so as to analyze the influence of the angle of incidence and refractive index on it, which is verified through the measure of the Mueller matrix elements of polished metal surface. Research shows that, under the condition of specular reflection, the result of Mueller matrix inversion is consistent with the experiment and can be used as an index of refraction of inversion method, and it provides a new way for target detection and recognition technology.

High-latitude Conic Current Sheets in the Solar Wind

Energy Technology Data Exchange (ETDEWEB)

Khabarova, Olga V.; Obridko, Vladimir N.; Kharshiladze, Alexander F. [Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN), Moscow (Russian Federation); Malova, Helmi V. [Scobeltsyn Nuclear Physics Institute of Lomonosov Moscow State University, Moscow (Russian Federation); Kislov, Roman A.; Zelenyi, Lev M. [Space Research Centre of the Polish Academy of Sciences (CBK PAN), Warsaw (Poland); Tokumaru, Munetoshi; Fujiki, Ken’ichi [Institute for Space-Earth Environmental Research, Nagoya University (Japan); Sokół, Justyna M.; Grzedzielski, Stan [Space Research Centre of the Polish Academy of Sciences (CBK), Warsaw (Poland)

2017-02-10

We provide observational evidence for the existence of large-scale cylindrical (or conic-like) current sheets (CCSs) at high heliolatitudes. Long-lived CCSs were detected by Ulysses during its passages over the South Solar Pole in 1994 and 2007. The characteristic scale of these tornado-like structures is several times less than a typical width of coronal holes within which the CCSs are observed. CCS crossings are characterized by a dramatic decrease in the solar wind speed and plasma beta typical for predicted profiles of CCSs. Ulysses crossed the same CCS at different heliolatitudes at 2–3 au several times in 1994, as the CCS was declined from the rotation axis and corotated with the Sun. In 2007, a CCS was detected directly over the South Pole, and its structure was strongly highlighted by the interaction with comet McNaught. Restorations of solar coronal magnetic field lines reveal the occurrence of conic-like magnetic separators over the solar poles in both 1994 and 2007. Such separators exist only during solar minima. Interplanetary scintillation data analysis confirms the presence of long-lived low-speed regions surrounded by the typical polar high-speed solar wind in solar minima. Energetic particle flux enhancements up to several MeV/ nuc are observed at edges of the CCSs. We built simple MHD models of a CCS to illustrate its key features. The CCSs may be formed as a result of nonaxiality of the solar rotation axis and magnetic axis, as predicted by the Fisk–Parker hybrid heliospheric magnetic field model in the modification of Burger and coworkers.

Early structure of LPG partially premixed conically stabilized flames

KAUST Repository

Elbaz, Ayman M.

2013-01-01

This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based on the mean gas temperature and the concentration of CO, O 2, NO, and HC at the flame early region of reaction. The investigation covered the influence of the nozzle cone angle, the jet exit velocity and the jet equivalence ratio. The stability results show that the flames with cone are more stable than those without cone. For conical stabilized flames, the stability results exhibit three different sensitivity regions between the jet velocity and equivalence ratio. The inflame measurements prove that the flame stability could be attributed to the triple flame structure at the flame leading edge. The data show that the triple flame structure is influenced by cone angle, the jet velocity and the equivalence ratio. The flame is believed to be controlled by the recirculation flow inside the cone. Increasing the cone angle induced higher air entrainment to the reaction zone as depicted by a higher O 2 concentration within the flame leading edge. Increasing the jet velocity to a certain limit enhances the intensity of combustion at the flame leading edge, while excessive increase in jet velocity reduces this intensity. At a fixed jet velocity the higher the equivalence ratio, the higher the amount of fuel diffused and engulfed to the reaction zone, the more delay of the combustion completion and the higher the emission concentrations of the flame. © 2012 Elsevier Inc.

Theoretical analyses of the refractive implications of transepithelial PRK ablations.

Science.gov (United States)

Arba Mosquera, Samuel; Awwad, Shady T

2013-07-01

To analyse the refractive implications of single-step, transepithelial photorefractive keratectomy (TransPRK) ablations. A simulation for quantifying the refractive implications of TransPRK ablations has been developed. The simulation includes a simple modelling of corneal epithelial profiles, epithelial ablation profiles as well as refractive ablation profiles, and allows the analytical quantification of the refractive implications of TransPRK in terms of wasted tissue, achieved optical zone (OZ) and induced refractive error. Wasted tissue occurs whenever the actual corneal epithelial profile is thinner than the applied epithelial ablation profile, achieved OZ is reduced whenever the actual corneal epithelial profile is thicker than the applied epithelial ablation profile and additional refractive errors are induced whenever the actual difference centre-to-periphery in the corneal epithelial profile deviates from the difference in the applied epithelial ablation profile. The refractive implications of TransPRK ablations can be quantified using simple theoretical simulations. These implications can be wasted tissue (∼14 µm, if the corneal epithelial profile is thinner than the ablated one), reduced OZ (if the corneal epithelial profile is thicker than ablated one, very severe for low corrections) and additional refractive errors (∼0.66 D, if the centre-to-periphery progression of the corneal epithelial profile deviates from the progression of the ablated one). When TransPRK profiles are applied to normal, not previously treated, non-pathologic corneas, no specific refractive implications associated to the transepithelial profile can be anticipated; TransPRK would provide refractive outcomes equal to those of standard PRK. Adjustments for the planned OZ and, in the event of retreatments, for the target sphere can be easily derived.

Marginal bone levels at single tooth implants with a conical fixture design. The influence of surface macro- and microstructure.

Science.gov (United States)

Norton, M R

1998-04-01

The concept of a conical implant design to accommodate single tooth replacement, has previously been shown to result in excessive bone loss, around the machined titanium conical collar, usually down to the 1st thread. This unusually aggressive loss of bone was shown to occur within a short period of time, post loading, with greater than 3 mm of bone loss occurring within the 1st 6 months to 1 year. The influence of implant design, surface texture and microleakage have all been highlighted as a potential cause. A modification of the surface structure, both at the macroscopic and microscopic level, as well as an altered fixture-abutment interface design has resulted in the maintenance of marginal bone around a single tooth titanium implant with a similar conical design. The radiographic follow-up of 33 implants loaded for up to 4 years, has revealed, by comparison, a most favourable maintenance of marginal bone around the conical collar, with a mean marginal bone loss of 0.32 mm mesially and 0.34 mm distally for the whole group. The cumulative mean marginal bone loss mesially and distally is 0.42 mm and 0.40 mm from 1 to 2 years, 0.54 mm and 0.43 mm from 2 to 3 years, 0.51 mm and 0.24 mm from 3 to 4 years, and 0.62 mm and 0.60 mm for implants past their 4 year recall.

Influence of changes in an eye's optical system on refraction

Science.gov (United States)

Bartkowska, Janina

1998-10-01

The optical system of eye is composed of cornea, lens, anterior chamber, and vitreous body. In the standard schematic eye there are 6 refracting surfaces. The changes of the curvature radii, of the distances between them, of the refractive indices influence the ametropia, refractive power of the eye and retinal image size. The influence of these changes can be appreciated by ray tracing or by an analytical method. There are presented simplified formulae for the differentials of ametropia and refractive power of the eye with respect to the surfaces curvatures, refracting power of cornea and lens, refractive indices. The relations are valid too for bigger changes if ametropia is measured in the cornea vertex. The formulae for the differentials with respect to distances, lens translation, eye axis length are valid if ametropia is measured in the object focus of the eye.

Bi2212 HTS Tubular Bulk with Conical Shape for Current Lead

International Nuclear Information System (INIS)

Tamura, H; Mito, T; Yamada, Y; Watanabe, M; Ohkubo, J; Heller, R

2006-01-01

Current leads using HTS material have been developed for application in a large scale superconducting magnet system. Tokai University and NIFS have developed Bi2212 tubular bulk which was prepared by a diffusion process. 8 kA of maximum transport current was achieved by a tubular bulk with a cylindrical shape. The maximum current was estimated to be 2 kA at 50 K for this tubular bulk. A current lead can be designed with this bulk the warm end of the HTS part being at 50 K and the cold end at 4.2 K. Under this condition, the cross section of the cold end of the bulk can be reduced. This type of HTS bulk has a great potential for flexible design since the Bi2212 layer can be reacted on the surface of any shapes of substrate. If a conical shaped HTS bulk was made, it could be an advantage for heat leakage to the cold end. To confirm this effect, we have made two types of conical bulk. The transport current of the specimen exceeds 7 kA at 4.2 K and 4 kA of stable current flow was achieved with a warm end temperature of 50 K

Precision measurements of gas refractivity by means of a Fabry-Perot interferometer illustrated by the monitoring of radiator refractivity in the DELPHI RICH detectors

CERN Document Server

Filippas-Tassos, A; Fokitis, E; Maltezos, S; Patrinos, K

2002-01-01

With an updated, flexible, highly efficient and easily installed system we obtained accurate refractivity (n-1) values. This system is a refractometer based on a Fabry-Perot interferometer and was used to monitor the refractivity of DELPHI RICH Cherenkov radiators near the VUV region. By using a Pt-Ne spectral lamp and improved alignment and temperature control, the refractivities of C//5F//1//2 and C//4F//1 //0 have been monitored since 1996. With this light source, selected to have large coherence lengths, we can extract the refractivity at several wavelengths from one data set only. The estimated errors of the refractivity measurements are less than 1.2%, and depend on wavelength and the type of gas used. The various parameters affecting the accuracy of the refractometer are also discussed. Finally, results from special sample refractivity measurements of the liquid radiator (C//6F//1//4) in its gas phase, are presented.

Numerical method of applying shadow theory to all regions of multilayered dielectric gratings in conical mounting.

Science.gov (United States)

Wakabayashi, Hideaki; Asai, Masamitsu; Matsumoto, Keiji; Yamakita, Jiro

2016-11-01

Nakayama's shadow theory first discussed the diffraction by a perfectly conducting grating in a planar mounting. In the theory, a new formulation by use of a scattering factor was proposed. This paper focuses on the middle regions of a multilayered dielectric grating placed in conical mounting. Applying the shadow theory to the matrix eigenvalues method, we compose new transformation and improved propagation matrices of the shadow theory for conical mounting. Using these matrices and scattering factors, being the basic quantity of diffraction amplitudes, we formulate a new description of three-dimensional scattering fields which is available even for cases where the eigenvalues are degenerate in any region. Some numerical examples are given for cases where the eigenvalues are degenerate in the middle regions.

Using the combination refraction-reflection solid to design omni-directional light source used in underwater wireless optical communication

Science.gov (United States)

Rao, Jionghui; Yao, Wenming; Wen, Linqiang

2015-10-01

Underwater wireless optical communication is a communication technology which uses laser as an information carrier and transmits data through water. Underwater wireless optical communication has some good features such as broader bandwidth, high transmission rate, better security, anti—interference performance. Therefore, it is promising to be widely used in the civil and military communication domains. It is also suitable for high-speed, short-range communication between underwater mobile vehicles. This paper presents a design approach of omni-directional light source used in underwater wireless optical communication, using TRACEPRO simulation tool to help design a combination solid composed of the lens, conical reflector and parabolic reflector, and using the modulated DPSS green laser in the transmitter module to output the laser beam in small divergence angles, after expanded by the combination refraction-reflection solid, the angle turns into a space divergence angle of 2π, achieving the omni-directional light source of hemisphere space, and test in the air and underwater, the result shows that the effect is fine. This paper analyzes the experimental test in the air and water, in order to make further improvement of the uniformity of light distribution, we optimize the reflector surface parameters of combination refraction-reflection solid and test in the air and water. The result shows that omni-directional light source used in underwater wireless optical communication optimized could achieve the uniformity of light distribution of underwater space divergence angle of 2π. Omni-directional light source used in underwater wireless optical communication designed in this paper has the characteristics of small size and uniformity of light distribution, it is suitable for application between UUVs, AUVs, Swimmer Delivery Vehicles (SDVs) and other underwater vehicle fleet, it realizes point-to-multipoint communications.

Fermat's principle and the formal equivalence of local light-ray rotation and refraction at the interface between homogeneous media with a complex refractive index ratio.

Science.gov (United States)

Sundar, Bhuvanesh; Hamilton, Alasdair C; Courtial, Johannes

2009-02-01

We derive a formal description of local light-ray rotation in terms of complex refractive indices. We show that Fermat's principle holds, and we derive an extended Snell's law. The change in the angle of a light ray with respect to the normal of a refractive index interface is described by the modulus of the refractive index ratio; the rotation around the interface normal is described by the argument of the refractive index ratio.

Topography-modified refraction: adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK

OpenAIRE

Alpins, Noel

2017-01-01

Noel Alpins1,2 1NewVision Clinics, Melbourne, VIC, Australia; 2Department Ophthalmology, Melbourne University, Melbourne, VIC, Australia It is encouraging to see the results in the article by Kanellopoulos “Topography-modified refraction (TMR): adjustment of treated cylinder amount and axis to the topography versus standard clinical refraction in myopic topography-guided LASIK”,1 where the combination of refractive and corneal data in the treatment parameters pro...

Theoretical analysis of the conical premixed flame response to upstream velocity disturbances considering flame speed development effects

Directory of Open Access Journals (Sweden)

Ghazaleh Esmaeelzade

2017-03-01

Full Text Available The effect of upstream velocity perturbations on the response of a premixed flame was investigated in terms of the flame transfer function dependency on excitation frequency. In this study, the assumption of constant flame speed was extended and the effect of flame speed development was considered; i.e., the flame speed would grow with the time after ignition or with the distance from a flame-holder. In the present study, the kinematics of a conical flame was investigated by linearization of the front tracking equation of flame to uniform and convected fluctuations of the flow velocity and the response was compared with that of a V-shaped flame and the experimental data in the previous studies. The results show that the effect of flame speed development could influence a decreasing gain and increase the phase of the flame response to the uniform velocity oscillations in low and moderate frequencies. Comparing the variations in the gain of flame response upon normalized frequency, show that a conical flame has lower values than the V-flame. In other words, these flames might be less susceptible to combustion instabilities than the V-flames. Furthermore, the variations in phase of the V-flames responses, which show a quasi-linear behavior with normalized frequency, have higher values than the saturated behavior in phase of the conical flame responses. Also, considering that the flame speed development induces an increase in the gain and phase of the conical flame response to the convected velocity oscillations in certain frequencies; because the developed flame front has longer length in comparison to the flame front in constant flame speed model. Therefore, the flame length may be longer than convective wavelength and the heat release would be generated in different points of the flame; consequently the flow oscillations might exert a stronger impact on the unsteady heat release fluctuations.

Optical negative refraction by four-wave mixing in thin metallic nanostructures.

Science.gov (United States)

Palomba, Stefano; Zhang, Shuang; Park, Yongshik; Bartal, Guy; Yin, Xiaobo; Zhang, Xiang

2011-10-30

The law of refraction first derived by Snellius and later introduced as the Huygens-Fermat principle, states that the incidence and refracted angles of a light wave at the interface of two different materials are related to the ratio of the refractive indices in each medium. Whereas all natural materials have a positive refractive index and therefore exhibit refraction in the positive direction, artificially engineered negative index metamaterials have been shown capable of bending light waves negatively. Such a negative refractive index is the key to achieving a perfect lens that is capable of imaging well below the diffraction limit. However, negative index metamaterials are typically lossy, narrow band, and require complicated fabrication processes. Recently, an alternative approach to obtain negative refraction from a very thin nonlinear film has been proposed and experimentally demonstrated in the microwave region. However, such approaches use phase conjugation, which makes optical implementations difficult. Here, we report a simple but different scheme to demonstrate experimentally nonlinear negative refraction at optical frequencies using four-wave mixing in nanostructured metal films. The refractive index can be designed at will by simply tuning the wavelengths of the interacting waves, which could have potential impact on many important applications, such as superlens imaging.

[Incidence of refractive errors with corrective aids subsequent selection].

Science.gov (United States)

Benes, P; Synek, S; Petrová, S; Sokolová, Sidlová J; Forýtková, L; Holoubková, Z

2012-02-01

This study follows the occurrence of refractive errors in population and the possible selection of the appropriate type of corrective aids. Objective measurement and subsequent determination of the subjective refraction of the eye is on essential act in opotmetric practice. The file represented by 615 patients (1230 eyes) is divided according to the refractive error of myopia, hyperopia and as a control group are listed emetropic clients. The results of objective and subjective values of refraction are compared and statistically processed. The study included 615 respondents. To determine the objective refraction the autorefraktokeratometer with Placido disc was used and the values of spherical and astigmatic correction components, including the axis were recorded. These measurements were subsequently verified and tested subjectively using the trial lenses and the projection optotype to the normal investigative distance of 5 meters. After this the appropriate corrective aids were then recommended. Group I consists of 123 men and 195 women with myopia (n = 635) of clients with an average age 39 +/- 18,9 years. Objective refraction - sphere: -2,57 +/- 2,46 D, cylinder: -1,1 +/- 1,01 D, axis of: 100 degrees +/- 53,16 degrees. Subjective results are as follows--the value of sphere: -2,28 +/- 2,33 D, cylinder -0,63 +/- 0,80 D, axis of: 99,8 degrees +/- 56,64 degrees. Group II is represented hyperopic clients and consists of 67 men and 107 women (n = 348). The average age is 58,84 +/- 16,73 years. Objective refraction has values - sphere: +2,81 +/- 2,21 D, cylinder: -1,0 +/- 0,94 D; axis 95 degree +/- 45,4 degrees. Subsequent determination of subjective refraction has the following results - sphere: +2,28 +/- 2,06 D; cylinder: -0,49 +/- 0,85 D, axis of: 95,9 degrees +/- 46,4 degrees. Group III consists from emetropes whose final minimum viasual acuity was Vmin = 1,0 (5/5) or better. Overall, this control group is represented 52 males and 71 females (n = 247). The average

Acoustic metasurface for refracted wave manipulation

Science.gov (United States)

Han, Li-Xiang; Yao, Yuan-Wei; Zhang, Xin; Wu, Fu-Gen; Dong, Hua-Feng; Mu, Zhong-Fei; Li, Jing-bo

2018-02-01

Here we present a design of a transmitted acoustic metasurface based on a single row of Helmholtz resonators with varying geometric parameters. The proposed metasurface can not only steer an acoustic beam as expected from the generalized Snell's law of refraction, but also exhibits various interesting properties and potential applications such as insulation of two quasi-intersecting transmitted sound waves, ultrasonic Bessel beam generator, frequency broadening effect of anomalous refraction and focusing.

Correction for the twist and the conical defects of a sagittaly bent crystal

CERN Document Server

Ferrer, J L

1999-01-01

The symmetrical bending of the focusing crystal of a double X-ray monochromator is a difficult problem. Indeed, the slope due to the curvature is usually three orders of magnitude higher than the accepted slope error (typically, the Darwin width of the crystal). In these conditions, even a low parasitic slope error induced by the bending process may lead to quite a strong intensity decrease. When the bending moment is applied, the main parasitic distortions which may appear are typically the anticlastic curvature, the inhomogeneous sagittal curvature, the conical shape and the twist. On the D2AM beamline at the ESRF, a program called CHKC2 has been developed to correct on-line the latter two distortions: the conical shape and the twist. On this beamline the X-ray beam, which has been collimated by a grazing angle mirror, is monochromatized first by a flat silicon crystal, and then diffracted by the sagittaly curved crystal. A fluorescent screen gives an image of this diffracted beam. The CHKC2 program records...

Room-temperature growth of a carbon nanofiber on the tip of conical carbon protrusions

International Nuclear Information System (INIS)

Tanemura, Masaki; Okita, T.; Yamauchi, H.; Tanemura, S.; Morishima, R.

2004-01-01

Glassy carbon was Ar + -ion bombarded with a simultaneous Mo supply under ultrahigh vacuum conditions using a microprotrusion fabrication system that consists of a differentially pumped ion gun and a seed-material supply source. Conical protrusions were formed by sputtering with a seed supply, and carbon nanofibers (CNFs) grew on the tips even at room temperature. The length of CNFs reached up to ∼10 μm, and their diameter was almost uniform (50 nm) in the growth direction. The short CNFs aligned in the ion beam direction, whereas the long ones were non-aligned. The CNF growth on a glassy carbon surface was ascribed to the enhanced surface texturing and to the massive redeposition of C atoms onto cones, both of which are specific to the oblique ion bombardment: The former would lead to an increase in the number of possible nucleation sites for the CNF growth, and the C atoms arising from the latter process would migrate toward the conical tips, thus forming CNFs

High temperature refractive indices of GaN

Energy Technology Data Exchange (ETDEWEB)

Liu, C.; Stepanov, S.; Gott, A.; Shields, P.A.; Zhirnov, E.; Wang, W.N. [Department of Physics, University of Bath, Bath, BA2 7AY (United Kingdom); Steimetz, E.; Zettler, J.T. [LayTec, Helmholtzstr. 13-14, 10587 Berlin (Germany)

2006-06-15

Undoped GaN (u-GaN) films were grown by low pressure metalorganic vapour phase epitaxy (LP-MOVPE) on sapphire substrates. In situ optical monitoring was applied to the growth process either using a LayTec EpiR-DA TT spectroscopic reflectometer or Filmetrics F30. Refractive indices of u-GaN films at 1060 C were obtained in a spectral range from 370-900 nm. A peak at 412{+-}5 nm in refractive index spectra was observed, which most likely corresponds to the band-gap of hexagonal GaN at a temperature of 1060 C. Refractive indices below this band-gap are fitted well to the first-order Sellmeier formula. As an example of the applications of the refractive indices, the effective film thicknesses of GaN during the resumption from 3 dimensional (3D) to 2 dimensional (2D) growth have been calculated from the spectra recorded by a LayTec system using the optical constants obtained. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Bioinspired adaptive gradient refractive index distribution lens

Science.gov (United States)

Yin, Kezhen; Lai, Chuan-Yar; Wang, Jia; Ji, Shanzuo; Aldridge, James; Feng, Jingxing; Olah, Andrew; Baer, Eric; Ponting, Michael

2018-02-01

Inspired by the soft, deformable human eye lens, a synthetic polymer gradient refractive index distribution (GRIN) lens with an adaptive geometry and focal power has been demonstrated via multilayer coextrusion and thermoforming of nanolayered elastomeric polymer films. A set of 30 polymer nanolayered films comprised of two thermoplastic polyurethanes having a refractive index difference of 0.05 were coextruded via forced-assembly technique. The set of 30 nanolayered polymer films exhibited transmission near 90% with each film varying in refractive index by 0.0017. An adaptive GRIN lens was fabricated from a laminated stack of the variable refractive index films with a 0.05 spherical GRIN. This lens was subsequently deformed by mechanical ring compression of the lens. Variation in the optical properties of the deformable GRIN lens was determined, including 20% variation in focal length and reduced spherical aberration. These properties were measured and compared to simulated results by placido-cone topography and ANSYS methods. The demonstration of a solid-state, dynamic focal length, GRIN lens with improved aberration correction was discussed relative to the potential future use in implantable devices.

Experimental refractive index determination of the optic fiber's core

International Nuclear Information System (INIS)

Oezelsoy, S.

2005-01-01

In this work, the Fresnel's fundamental Law was used to be able to obtain the refractive index of the fiber optic's core. The intensity of light reflected from the boundary between two mediums was measured by the optical powermeter (Melles Griot, Universal optical powermeter). In recent technology, the light that is illuminated from the light source can be transported to the boundary region and measured with minimum loss by using the optic fibers which make the measurement more sensitively. The liquid and the optic fiber's core whose refractive indices will be measured are the two mediums and the surface of the optic fiber's core is the boundary region. By dipping the fiber optic probe to the liquids, the reflected light intensities were measured with powermeter via Silicon Detector for single mode fiber and multimode fiber respectively to obtain the refractive index of the optic fiber's core. At this work, because of the using the diode laser with 661,4 nm (FWHM) and He-Ne laser with 632,8 nm (FWHM) the refractive indices were measured at this wavelengthes with the Refractometer (Abbe 60-70, Bellingham+Stanley). If the refractive indices of two mediums are equal, the light doesn't reflect from the boundary. The graphic is drawn depend upon the refractive index of the liquids versus the back reflected light energy and from the minimum point of the curve the effective refractive index of the fiber optic's core is calculated for 661,4 nm and 780 nm

Effects of different abutment material and surgical insertion torque on the marginal adaptation of an internal conical interface: an in vitro study.

Science.gov (United States)

Farronato, Davide; Pieroni, Stefano; Mangano, Francesco Guido; Briguglio, Francesco; Re, Dino

2014-10-01

To evaluate the marginal adaptation at implant-abutment connection of an implant featuring a conical (45° taper) internal hexagonal abutment with a connection depth of 2.5mm, comparing the performance of two identical abutments of different material (titanium grade-4 and Co-Cr-alloy). Twenty implants (3.75 mm×15 mm) were connected to non-matching abutments (5.5 mm×10 mm) of two different materials (titanium grade-4: n=10; Co-Cr-alloy: n=10). The specimens were separately embedded in epoxylite resin, inside copper cylinders, and submerged without covering the most coronal portion (5 mm) of the fixture. Five specimens per group were stressed simulating a surgical 100 Ncm insertion torque, while the others had no torque simulation. All specimens were subjected to a non-axial static load (100 N) in a universal testing machine, under an angle of 30° with respect to the implant axis. Once 100 N load was reached, low shrinkage self-curing resin was injected inside the cylinders, and load was maintained until complete resin polymerization. Specimens were cut and analyzed with optical and scanning-electron-microscope (SEM) to evaluate the marginal adaptation at the implant-abutment connection. Statistical analysis was performed using one-way ANOVA (p=0.02). None of the 20 samples failed. The implant-abutment connection was able to guarantee a good optical seal; SEM analysis confirmed the absence of microgaps. Within the limits of this study (small sample size, limited time) the marginal adaptation of the implant-abutment connection was not affected by the abutment material nor by the application of surgical insertion torque. Copyright © 2014 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

THE OPTICS OF REFRACTIVE SUBSTRUCTURE

Energy Technology Data Exchange (ETDEWEB)

Johnson, Michael D.; Narayan, Ramesh, E-mail: mjohnson@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2016-08-01

Newly recognized effects of refractive scattering in the ionized interstellar medium have broad implications for very long baseline interferometry (VLBI) at extreme angular resolutions. Building upon work by Blandford and Narayan, we present a simplified, geometrical optics framework, which enables rapid, semi-analytic estimates of refractive scattering effects. We show that these estimates exactly reproduce previous results based on a more rigorous statistical formulation. We then derive new expressions for the scattering-induced fluctuations of VLBI observables such as closure phase, and we demonstrate how to calculate the fluctuations for arbitrary quantities of interest using a Monte Carlo technique.

Analytical models of optical refraction in the troposphere.

Science.gov (United States)

Nener, Brett D; Fowkes, Neville; Borredon, Laurent

2003-05-01

An extremely accurate but simple asymptotic description (with known error) is obtained for the path of a ray propagating over a curved Earth with radial variations in refractive index. The result is sufficiently simple that analytic solutions for the path can be obtained for linear and quadratic index profiles. As well as rendering the inverse problem trivial for these profiles, this formulation shows that images are uniformly magnified in the vertical direction when viewed through a quadratic refractive-index profile. Nonuniform vertical distortions occur for higher-order refractive-index profiles.

Ultraviolet light induced refractive index structures in germanosilica

DEFF Research Database (Denmark)

Svalgaard, Mikael

1997-01-01

The focus of the research presented in this ph.d. thesis is refractive index structures photoinduced in germanonsilica waveguides with ultra-violet (UV) radiation. The physical mechanisms involved in photosensitivity and applications of a wide range of UV induced refractive index structures in both...... application of a scanning near-field optical microscope to obtain high resolution images of UV induced refractive index structures and by monitoring the dynamics of UV induced index changes and luminescence. During part of my ph.d. project I have worked at the National Institute of Standards and Technolgy...

refractive errors among secondary school students in Isuikwuato

African Journals Online (AJOL)

Eyamba

STUDENTS IN ISUIKWUATO LOCAL GOVERNMENT AREA OF ... the prevalence and types of refractive errors among secondary school students ... KEYWORDS: Refractive error, Secondary School students, ametropia, .... interviews of the teachers as regards the general performance of those students with obvious visual.

Refractive Lenticule Implantation for Correction of Ametropia: Case Reports and Literature Review.

Science.gov (United States)

Lazaridis, A; Messerschmidt-Roth, A; Sekundo, W; Schulze, S

2017-01-01

The ReLEx® technique allows correction of refractive errors through the creation and extraction of refractive stromal lenticules. Contrary to excimer laser corneal refractive procedures, where the stromal tissue is photoablated, the extracted lenticules obtained with ReLEx® can be preserved. Recent studies and case reports have described autologous re-implantation and allogeneic implantation of refractive lenticules into femtosecond-laser created stromal pockets in order to reverse the refractive outcome of a myopic corneal refractive procedure, correct hyperopia, aphakia, presbyopia and treat keratoconus. The use of stromal lenticules has also been described for therapeutic purposes, with an allogenic lenticule being transplanted under a LASIK flap in order to restore corneal volume and reduce the refractive error in a case of excessive stromal tissue removal after LASIK. This review summarises the results of the latest case reports and studies that describe the implantation of cryopreserved or fresh refractive stromal lenticules and discusses the feasibility, safety and refractive outcomes of the procedure, on the basis of published literature as well as our own experience. Georg Thieme Verlag KG Stuttgart · New York.

Conical flow near singular rays. [shock generation in ideal gas

Science.gov (United States)

Zahalak, G. I.; Myers, M. K.

1974-01-01

The steady flow of an ideal gas past a conical body is investigated by the method of matched asymptotic expansions, with particular emphasis on the flow near the singular ray occurring in linearized theory. The first-order problem governing the flow in this region is formulated, leading to the equation of Kuo, and an approximate solution is obtained in the case of compressive flow behind the main front. This solution is compared with the results of previous investigations with a view to assessing the applicability of the Lighthill-Whitham theories.

Estimation of network parameters with consideration of the horizontal refraction influence

Directory of Open Access Journals (Sweden)

Ján Ježko

2007-06-01

Full Text Available The proposed paper is focused on reviewing the horizontal refraction during measurement in local geodetic networks. Based on elaborated theoretical assumptions the refraction model was arranged in a way that the questions were solved by the identity of the horizontal refraction. The necessary part of the application of the refraction model is the problem of optimizing the geodetic networks and deducting the method of the variance components, which play a major role in the precision of results. The independent acquisition of the thesis lies in the area of modeling the horizontal refraction with a stochastic approach, where the values of the refraction are gained through the measured data of the horizontal direction. In the model, it is necessary to identify the parameters according to the entire measurements and between two points. According to the attained results, I can state that the horizontal refraction was identified mainly on the measurements that were confirmed near the dam in most of the measured experiments. The experimented measurements were confirmed based on the assumptions that are in theoretical capitol, where the assumptions of the effect of the horizontal refraction are measured near the dam, river, shores, and valleys.

An investigation of the Performance of a Conical Solar Water Heater in the Kingdom of Bahrain

Science.gov (United States)

Gaaliche, Nessreen; Ayhan, Teoman; Fathallah, Raouf

2017-11-01

Domestic water heater corresponds to 25% of the house energy consumption and can play an important role to reduce energy house expenses. Solar energy offers a preferred renewable energy resource because of its economic and environmental advantages. It is considered the best alternative to reduce domestic water heater energy consumption cost. Converting solar energy into heat can be considered among the simplest used systems. Solar thermal conversion is more efficient than solar electrical direct conversion method. Solar water heater systems are particularly easy to use and to repair. The integrated conical solar collector water heater (ICSCWH) is so far the easiest among water heating systems. The ICSCWH converts directly and efficiently the solar flux into heat. In order to expand the utilization of ICSCWH systems, many design modifications have been examined and analyzed. This study provides an experimental investigation and mathematical simulation of an ICSCWH system equipped with a glass cover resulting in the increase of the maximum absorption. Integrating the cone-shaped heat collector with an aluminum spiral pipe flow system may enhance the efficiency of the proposed system. In order to maximize the solar radiation of the system, the solar water heater has been designed in a conical shape, which removes the need to change its orientation toward the sun to receive the maximum sun radiation during the day. In this system, the heating of water has been obtained using the spiral pipe flow without the use of the solar cells and mirrors in order to reduce the total cost. The storage water tank of this system is coupled with a conical solar collector. Based on the above design, the solar water heater has been fabricated and tested. In addition, an analytical modeling approach aiming to predict the flow rate within the conical integrated collector storage solar water heater (ICSSWH) and its efficiency, was developed. Modeling through a numerical simulation approach

An investigation of the Performance of a Conical Solar Water Heater in the Kingdom of Bahrain

Directory of Open Access Journals (Sweden)

Gaaliche Nessreen

2017-01-01

Full Text Available Domestic water heater corresponds to 25% of the house energy consumption and can play an important role to reduce energy house expenses. Solar energy offers a preferred renewable energy resource because of its economic and environmental advantages. It is considered the best alternative to reduce domestic water heater energy consumption cost. Converting solar energy into heat can be considered among the simplest used systems. Solar thermal conversion is more efficient than solar electrical direct conversion method. Solar water heater systems are particularly easy to use and to repair. The integrated conical solar collector water heater (ICSCWH is so far the easiest among water heating systems. The ICSCWH converts directly and efficiently the solar flux into heat. In order to expand the utilization of ICSCWH systems, many design modifications have been examined and analyzed. This study provides an experimental investigation and mathematical simulation of an ICSCWH system equipped with a glass cover resulting in the increase of the maximum absorption. Integrating the cone-shaped heat collector with an aluminum spiral pipe flow system may enhance the efficiency of the proposed system. In order to maximize the solar radiation of the system, the solar water heater has been designed in a conical shape, which removes the need to change its orientation toward the sun to receive the maximum sun radiation during the day. In this system, the heating of water has been obtained using the spiral pipe flow without the use of the solar cells and mirrors in order to reduce the total cost. The storage water tank of this system is coupled with a conical solar collector. Based on the above design, the solar water heater has been fabricated and tested. In addition, an analytical modeling approach aiming to predict the flow rate within the conical integrated collector storage solar water heater (ICSSWH and its efficiency, was developed. Modeling through a numerical

Pressure-dependent refractive indices of gases by THz time-domain spectroscopy.

Science.gov (United States)

Sang, Bark Hyeon; Jeon, Tea-In

2016-12-12

Noncontact terahertz time-domain spectroscopy was employed to measure pressure-dependent refractive indices of gases such as helium (He), argon (Ar), krypton (Kr), oxygen (O2), nitrogen (N2), methane (CH4), and carbon dioxide (CO2). The refractive indices of these gases scaled linearly with pressure, for pressures in the 55-3,750 torr range. At the highest pressure, the refractive indices ((n-1) x 106) of He and CO2 were 170 and 2,390, respectively. The refractive index of CO2 was 14.1-fold higher than that of He, owing to the stronger polarizability of CO2. Although the studied gases differed in terms of their molecular structure, their refractive indices were strongly determined by polarizability. The measured refractive indices agreed well with the theoretical calculations.

Inverted-conical light guide for crosstalk reduction in tightly-packed scintillator matrix and MAPMT assembly

DEFF Research Database (Denmark)

Chang, Y.-Y.; Chen, P.; Huang, J.-J.

2015-01-01

In this paper we present the Inverted-Conical light guide designed for optical crosstalk reduction in the scintillator-MAPMT assemblies. The research was motivated by the 30% crosstalk observed in UFFO X-ray telescope, UBAT, during the preliminary calibration with MAPMTs of 64 2.88 × 2.88 mm2...... pixels and identically gridded YSO crystal matrices. We began the study with the energy and crosstalk calibrations of the detector, then we constructed a GEANT4 simulation with the customized metallic film model as the MAPMT photocathode. The simulation reproduced more than 70% of the crosstalk...... and explained it as a consequence of the total reflection produced by the photocathode. The result indicated that the crosstalk mechanism could be a common case in most of the contact-assembled scintillation detectors. The concept of the Inverted-Conical light guide was to suppress the total reflection...

Emission performance and combustion efficiency of a conical fluidized-bed combustor firing various biomass fuels

International Nuclear Information System (INIS)

Permchart, W.; Kouprianov, V.I.

2004-01-01

This paper summarizes the results of an experimental study on combustion of three distinct biomass fuels (sawdust, rice husk and pre-dried sugar cane bagasse) in a single fluidized-bed combustor (FBC) with a conical bed using silica sand as the inert bed material. Temperature, CO, NO and O 2 concentrations along the combustor height as well as in flue (stack) gas were measured in the experimental tests. The effects of fuel properties and operating conditions (load and excess air) on these variables were investigated. Both CO and NO axial profiles were found to have a maximum whose location divides conventionally the combustor volume into formation (lower) and reduction (upper) regions for these pollutants. Based on CO emission and unburned carbon content in fly ash, the combustion efficiency of the conical FBC was quantified for the selected biomass fuels fired under different operating conditions. (Author)

Pitting and Repair of the Space Shuttle's Inconel(Registered TradeMark) Honeycomb Conical Seal Panel

Science.gov (United States)

Zimmerman, Frank R.; Gentz, Steven J.; Miller, James B.; MacKay, Rebecca A.; Bright, Mark L.

2006-01-01

During return to flight servicing of the rudder speed brake (RSB) for each Space Shuttle Orbiter, inspectors discovered numerous small pits on the surface of the #4 right hand side honeycomb panel that covers the rudder speed brake actuators. Shortly after detection of the problem, concurrent investigations were initiated to determine the extent of damage, the root cause, and to develop a repair plan, since fabrication of a replacement panel is impractical for cost, schedule, and sourcing considerations. This paper describes the approach, findings, conclusions and recommendations associated with the investigation of the conical seal pitting. It documents the cause and contributing factors of the pitting, the means used to isolate each contributor, and the supporting evidence for the primary cause of the pitting. Finally, the selection, development and verification of the repair procedure used to restore the conical seal panel is described with supporting process and metallurgical rationale for selection.

Conical square function estimates in UMD Banach spaces and applications to H?-functional calculi

NARCIS (Netherlands)

Hytönen, T.; Van Neerven, J.; Portal, P.

2008-01-01

We study conical square function estimates for Banach-valued functions and introduce a vector-valued analogue of the Coifman-Meyer-Stein tent spaces. Following recent work of Auscher-M(c)Intosh-Russ, the tent spaces in turn are used to construct a scale of vector-valued Hardy spaces associated with

Large-eddy simulation of shallow turbulent wakes behind a conical island

Science.gov (United States)

Ouro, Pablo; Wilson, Catherine A. M. E.; Evans, Paul; Angeloudis, Athanasios

2017-12-01

Large-Eddy Simulations (LESs) and experiments were employed to study the influence of water depth on the hydrodynamics in the wake of a conical island for emergent, shallow, and deeply submerged conditions. The Reynolds numbers based on the island's base diameter for these conditions range from 6500 to 8125. LES results from the two shallower conditions were validated against experimental measurements from an open channel flume and captured the characteristic flow structures around the cone, including the attached recirculation region, vortex shedding, and separated shear layers. The wake was impacted by the transition from emergent to shallow submerged flow conditions with more subtle changes in time-averaged velocity and instantaneous flow structures when the submergence increases further. Despite differences in the breakdown of the separated shear layers, vortex shedding, and the upward flow region on the leeward face (once the cone's apex is submerged), similar flow structures to cylinder flow were observed. These include an arch vortex tilted in the downstream direction and von Karman vortices in the far-wake. Spectra of velocity time series and the drag coefficient indicated that the vortex shedding was constrained by the overtopping flow layer, and thus the shedding frequency decreased as the cone's apex became submerged. Finally, the generalised flow structures in the wake of a submerged conical body are outlined.

The effectiveness of the jammer signal characteristics on conical-scan systems

Science.gov (United States)

Şahingil, Mehmet C.; Aslan, Murat Ş.

2015-05-01

Being passive systems and due to their proliferation to many regions in the world, the infrared (IR) guided missiles constitute probably the most dangerous threats for the aircraft platforms. Early generation surface-to-air and air-to-air IRguided missiles use reticle-based seekers. One of the IR countermeasure (IRCM) techniques for protecting aircraft platforms against these type of threats is to use a modulated jamming signal. Optimizing the parameters of the modulation is the most important issue for an effective protection. If the required characteristic is not satisfied, jamming may not be successful for protecting the aircraft. There are several parameters to define the jammer signal (modulation) characteristic. Optimizing them requires a good understanding of threat seekers' operating principles. In the present paper, we consider protection of a helicopter platform against conical-scan reticle based seeker systems and investigate the effect of the jammer signal modulation parameters on jamming performance via extensive batch simulations. The simulations are performed in a MATLAB-coded simulator which models reticle-based conical-scan seeker, aircraft radiation, aircraft motion and jammer system on the aircraft. The results show that if the properties of the jammer signal are similar to those of the reticle-modulated signal in the missile, the jamming can be successful. Otherwise, applied jamming may not deceive the threat seeker.

Nanofocusing refractive X-ray lenses

Energy Technology Data Exchange (ETDEWEB)

Boye, Pit

2010-02-05

This thesis is concerned with the optimization and development of the production of nanofocusing refractive X-ray lenses. These optics made of either silicon or diamond are well-suited for high resolution X-ray microscopy. The goal of this work is the design of a reproducible manufacturing process which allows the production of silicon lenses with high precision, high quality and high piece number. Furthermore a process for the production of diamond lenses is to be developed and established. In this work, the theoretical basics of X-rays and their interaction with matter are described. Especially, aspects of synchrotron radiation are emphasized. Important in X-ray microscopy are the different optics. The details, advantages and disadvantages, in particular those of refractive lenses are given. To achieve small X-ray beams well beyond the 100 nm range a small focal length is required. This is achieved in refractive lenses by moving to a compact lens design where several single lenses are stacked behind each other. The, so-called nanofocusing refractive lenses (NFLs) have a parabolic cylindrical shape with lateral structure sizes in the micrometer range. NFLs are produced by using micro-machining techniques. These micro-fabrication processes and technologies are introduced. The results of the optimization and the final fabrication process for silicon lenses are presented. Subsequently, two experiments that are exemplary for the use of NFLs, are introduced. The rst one employs a high-resolution scanning fluorescence mapping of a geological sample, and the second one is a coherent x-ray diffraction imaging (CXDI) experiment. CXDI is able to reconstruct the illuminated object from recorded coherent diffraction patterns. In a scanning mode, referred to as ptychography, this method is even able to reconstruct the illumination and the object simultaneously. Especially the reconstructed illumination and the possibility of computed propagation of the wave field along the

Nanofocusing refractive X-ray lenses

International Nuclear Information System (INIS)

Boye, Pit

2010-01-01

This thesis is concerned with the optimization and development of the production of nanofocusing refractive X-ray lenses. These optics made of either silicon or diamond are well-suited for high resolution X-ray microscopy. The goal of this work is the design of a reproducible manufacturing process which allows the production of silicon lenses with high precision, high quality and high piece number. Furthermore a process for the production of diamond lenses is to be developed and established. In this work, the theoretical basics of X-rays and their interaction with matter are described. Especially, aspects of synchrotron radiation are emphasized. Important in X-ray microscopy are the different optics. The details, advantages and disadvantages, in particular those of refractive lenses are given. To achieve small X-ray beams well beyond the 100 nm range a small focal length is required. This is achieved in refractive lenses by moving to a compact lens design where several single lenses are stacked behind each other. The, so-called nanofocusing refractive lenses (NFLs) have a parabolic cylindrical shape with lateral structure sizes in the micrometer range. NFLs are produced by using micro-machining techniques. These micro-fabrication processes and technologies are introduced. The results of the optimization and the final fabrication process for silicon lenses are presented. Subsequently, two experiments that are exemplary for the use of NFLs, are introduced. The rst one employs a high-resolution scanning fluorescence mapping of a geological sample, and the second one is a coherent x-ray diffraction imaging (CXDI) experiment. CXDI is able to reconstruct the illuminated object from recorded coherent diffraction patterns. In a scanning mode, referred to as ptychography, this method is even able to reconstruct the illumination and the object simultaneously. Especially the reconstructed illumination and the possibility of computed propagation of the wave field along the

Loads experiments study on two-story RC box and truncated conical walls

International Nuclear Information System (INIS)

Asega, H.; Iizuka, S.; Kurihara, I.; Kubo, T.

1987-01-01

The failure modes of the two specimens were the sliding shear failure. The two specimens showed almost equal deformation at the maximum shear strength. The ratio of the flexural deformation in the deformation of the truncated conical was larger than that of the box wall. The ratio of the shear deformation in the deformation of the two-story RC box wall was larger than that of the flexural deformation. (orig./HP)

Measurement of Refractive Index Using a Michelson Interferometer.

Science.gov (United States)

Fendley, J. J.

1982-01-01

Describes a novel and simple method of measuring the refractive index of transparent plates using a Michelson interferometer. Since it is necessary to use a computer program when determining the refractive index, undergraduates could be given the opportunity of writing their own programs. (Author/JN)

Nonadiabatic Eigenfunctions Can Have Amplitude, Signed Conical Nodes, or Signed Higher Order Nodes at a Conical Intersection with Circular Symmetry (Open Access Publisher’s Version)

Science.gov (United States)

2017-09-26

marked by black rings on the potential energy surfaces. In some sense, only about half of the zero point energy is available to each of the two...wheel at the bottom. The conical intersection at q1 = q2 = 0 and E = 0 is submerged below the zero-point energy of Ezp = 181 cm −1 ( black curve). The...J. Chem. Phys. 123, 044102 (2005)]. J. Chem. Phys. 2008, 128, 109902. (49) Clinton, W. L.; Rice , B. Reformulation of the Jahn-Teller Theorem. J

Perfect imaging without negative refraction

Energy Technology Data Exchange (ETDEWEB)

Leonhardt, Ulf [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom)], E-mail: ulf@st-andrews.ac.uk

2009-09-15

Perfect imaging has been believed to rely on negative refraction, but here we show that an ordinary positively refracting optical medium may form perfect images as well. In particular, we establish a mathematical proof that Maxwell's fish eye in two-dimensional (2D) integrated optics makes a perfect instrument with a resolution not limited by the wavelength of light. We also show how to modify the fish eye such that perfect imaging devices can be made in practice. Our method of perfect focusing may also find applications outside of optics, in acoustics, fluid mechanics or quantum physics, wherever waves obey the 2D Helmholtz equation.

On the optical path length in refracting media

Science.gov (United States)

Hasbun, Javier E.

2018-04-01

The path light follows as it travels through a substance depends on the substance's index of refraction. This path is commonly known as the optical path length (OPL). In geometrical optics, the laws of reflection and refraction are simple examples for understanding the path of light travel from source to detector for constant values of the traveled substances' refraction indices. In more complicated situations, the Euler equation can be quite useful and quite important in optics courses. Here, the well-known Euler differential equation (EDE) is used to obtain the OPL for several index of refraction models. For pedagogical completeness, the OPL is also obtained through a modified Monte Carlo (MC) method, versus which the various results obtained through the EDE are compared. The examples developed should be important in projects involving undergraduate as well as graduate students in an introductory optics course. A simple matlab script (program) is included that can be modified by students who wish to pursue the subject further.

Photorefractive keratectomy in refractive accommodative esotropia.

Science.gov (United States)

Bilgihan, K; Akata, F; Or, M; Hasanreisoğlu, B

1997-01-01

Photorefractive keratectomy (PRK) was performed on a 19-year-old man with hyperopic astigmatism and refractive accommodative esotropia. The patient was orthophoric while wearing spectacles, but had an esotropia of 30 prism dioptres at near and distance vision without spectacles. The best corrected visual acuity of the right eye was 20/50 and of the left eye was 20/20. The excessive accommodative convergence of the patient was eliminated by correcting the hyperopic refractive error by performing PRK, and the patient became orthophoric after the treatment.

Refractive Errors in State Junior High School Students in Bandung

Directory of Open Access Journals (Sweden)

Sabila Tasyakur Nikmah

2016-12-01

Full Text Available Background: Uncorrected refractive error is one of the avoidable causes of vision impairment in children and adults. Vision problem in children has been shown to affect their psychological and academic performance. This study aims at identifying and gaining more insights on the characteristic of the refractive errors in state junior high school students in Bandung to avoid uncorrected refractive errors. Methods: A cross-sectional study was conducted in September–November 2015 in state junior high schools in Bandung, West Java, Indonesia. Sample was selected using multistage random sampling technique. Children were examined using tumbling E examination; then students with visual acuity worse than 6/12 underwent Snellen Chart test, refractometry without pupil dilatation, correction with trial lens, then was followed by direct ophthalmoscopy. Results: From a total of 435 children who completed all the examination, 80 children (18.39% had refractive errors; consisted of 151 eyes (94.38% with myopia and 9 eyes (5.62% with astigmatism. Refractive errors were found to be more common in female children (73.7% than male children (26.3%. Among those with refractive errors, 45 children (56.3% did not use any corrective glasses before the examination. Conclusions: Routine refractive error test in vision screening examination is needed for students. It is equally important to raise more awareness toward eye disease in community.

Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy

Directory of Open Access Journals (Sweden)

Weijie Hua

2016-03-01

Full Text Available Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns. We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

Prevalence of Refractive errors among Primary School Pupils in ...

African Journals Online (AJOL)

Administrator

Effective management of blindness due to refractive errors is readily available in developed countries. 1 ... Key words: Refractive errors, Children, Prevalence, Kenya. 165 .... financial support towards the funding of this study. REFERENCES. 1.

Effect of Location of Delamination on Free Vibration of Cross-Ply Conical Shells

Directory of Open Access Journals (Sweden)

Sudip Dey

2012-01-01

Full Text Available Location of delamination is a triggering parameter for structural instability of laminated composites. In this paper, a finite element method is employed to determine the effects of location of delamination on free vibration characteristics of graphite-epoxy cross-ply composite pre-twisted shallow conical shells. The generalized dynamic equilibrium equation is derived from Lagrange's equation of motion neglecting Coriolis effect for moderate rotational speeds. The formulation is exercised by using an eight noded isoparametric plate bending element based on Mindlin's theory. Multi-point constraint algorithm is utilized to ensure the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The standard eigen value problem is solved by applying the QR iteration algorithm. Finite element codes are developed to obtain the numerical results concerning the effects of location of delamination, twist angle and rotational speed on the natural frequencies of cross-ply composite shallow conical shells. The mode shapes are also depicted for a typical laminate configuration. Numerical results obtained from parametric studies of both symmetric and anti-symmetric cross-ply laminates are the first known non-dimensional natural frequencies for the type of analyses carried out here.

Noise characteristics and flow field of an impinging jet on a conical obstacle

Energy Technology Data Exchange (ETDEWEB)

Liu, Xin; Xie, Junlong; Shu, Shuiming; Zhang, Yi, E-mail: hustxjl@163.com [School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 430074 (China)

2017-12-15

The noise characteristics and flow field of a low-speed impinging jet on a conical obstacle have been numerically simulated using the kinetic energy transport subgrid-scale model of the large-eddy simulation method. Noise measurement is carried out to validate the proposed simulation method. The effects of the impinging distance on the development, separation and diffusion of vortices on the back of the conical obstacle are investigated. The jet structure is better preserved and the vorticity value becomes larger as the impinging distance increases. Simulation results of the noise spectrums and overall sound pressure level (OASPL) agree well with the experimental data. The noise spectrums are analyzed and combined with simulation results for the flow field. When the impinging distance is small, the main acoustic sources with the broadband characteristic consist of the dipole source produced by pressure fluctuation on the surface of the obstacle, and the quadrupole source produced by vortices. As the impinging distance increases, the quadrupole source becomes the major acoustic source with low-frequency characteristics. In addition, the OASPL of the impinging jet is obtained at different impinging distances. (paper)

Negative refraction of inhomogeneous waves in lossy isotropic media

International Nuclear Information System (INIS)

Fedorov, V Yu; Nakajima, T

2014-01-01

We theoretically study negative refraction of inhomogeneous waves at the interface of lossy isotropic media. We obtain explicit (up to the sign) expressions for the parameters of a wave transmitted through the interface between two lossy media characterized by complex permittivity and permeability. We show that the criterion of negative refraction that requires negative permittivity and permeability can be used only in the case of a homogeneous incident wave at the interface between a lossless and lossy media. In a more general situation, when the incident wave is inhomogeneous, or both media are lossy, the criterion of negative refraction becomes dependent on an incidence angle. Most interestingly, we show that negative refraction can be realized in conventional lossy materials (such as metals) if their interfaces are properly oriented. (paper)

Prevalence of Refractive Error in Singaporean Chinese Children: The Strabismus, Amblyopia, and Refractive Error in Young Singaporean Children (STARS) Study

OpenAIRE

Dirani, Mohamed; Chan, Yiong-Huak; Gazzard, Gus; Hornbeak, Dana Marie; Leo, Seo-Wei; Selvaraj, Prabakaran; Zhou, Brendan; Young, Terri L.; Mitchell, Paul; Varma, Rohit; Wong, Tien Yin; Saw, Seang-Mei

2010-01-01

Using population-based data, the authors report, for the first time, the prevalence of refractive error in Singaporean Chinese children aged 6 to 72 months. In selected regions of Singapore, myopia has been shown to affect more than 80% of adults; therefore, this paper provides insights into the development of refractive error at a very young age.

Application of seismic refraction tomography for subsurface imaging ...

African Journals Online (AJOL)

Seismic refraction tomography involves the measurement of the travel times of seismic refracted raypaths in order to define an image of seismic velocity in the intervening ground. This technique was used to estimate the depth to the fresh basement, estimate thickness of the weathered basement and to determine the ...

Axial force imparted by a conical radiofrequency magneto-plasma thruster

International Nuclear Information System (INIS)

Charles, C.; Takahashi, K.; Boswell, R. W.

2012-01-01

Direct thrust measurements of a low pressure (∼0.133 Pa) conical radiofrequency (rf at 13.56 MHz) argon plasma source show a total axial force of about 5 mN for an effective rf power of 650 W and a maximum magnetic field of 0.018 T, of which a measured value of 2.5 mN is imparted by the magnetic nozzle. A simplified model of thrust including contributions from the electron pressure and from the magnetic field pressure is developed. The magnetic nozzle is modelled as a ''physical'' nozzle of increasing cross-sectional area.

Refractive power and biometric properties of the nonhuman primate isolated crystalline lens.

Science.gov (United States)

Borja, David; Manns, Fabrice; Ho, Arthur; Ziebarth, Noel M; Acosta, Ana Carolina; Arrieta-Quintera, Esdras; Augusteyn, Robert C; Parel, Jean-Marie

2010-04-01

Purpose. To characterize the age dependence of shape, refractive power, and refractive index of isolated lenses from nonhuman primates. Methods. Measurements were performed on ex vivo lenses from cynomolgus monkeys (cyno: n = 120; age, 2.7-14.3 years), rhesus monkeys (n = 61; age, 0.7-13.3 years), and hamadryas baboons (baboon: n = 16; age, 1.7-27.3 years). Lens thickness, diameter, and surface curvatures were measured with an optical comparator. Lens refractive power was measured with a custom optical system based on the Scheiner principle. The refractive contributions of the gradient, the surfaces, and the equivalent refractive index were calculated with optical ray-tracing software. The age dependence of the optical and biometric parameters was assessed. Results. Over the measured age range isolated lens thickness decreased (baboon: -0.04, cyno: -0.05, and rhesus: -0.06 mm/y) and equatorial diameter increased (logarithmically for the baboon and rhesus, and linearly for cyno: 0.07 mm/y). The isolated lens surfaces flattened and the corresponding refractive power from the surfaces decreased with age (-0.33, -0.48, and -0.68 D/y). The isolated lens equivalent refractive index decreased (only significant for the baboon, -0.001 D/y), and as a result the total isolated lens refractive power decreased with age (baboon: -1.26, cyno: -0.97, and rhesus: -1.76 D/y). Conclusions. The age-dependent trends in the optical and biometric properties, growth, and aging, of nonhuman primate lenses are similar to those of the pre-presbyopic human lens. As the lens ages, the decrease in refractive contributions from the gradient refractive index causes a rapid age-dependent decrease in maximally accommodated lens refractive power.

First-principle calculation of refractive indices of BAlN and BGaN

KAUST Repository

Alqatari, Feras; Li, Kuang-Hui; Liu, Kaikai; Li, Xiaohang

2018-01-01

The refractive indices of BAlN and BGaN ternary alloys are being investigated using first-principle calculation. The hybrid density functional theory is applied to determine the refractive indices of different alloys. A peculiar bowing effect in the static refractive indices and crossovers of different refractive index curves are found. We speculate that the explanation to these phenomena lies in the interband transitions of electrons where each band bows at a different rate from the other. An average of these bowing effects may result in the bowing of refractive indices.

First-principle calculation of refractive indices of BAlN and BGaN

KAUST Repository

Alqatari, Feras

2018-03-27

The refractive indices of BAlN and BGaN ternary alloys are being investigated using first-principle calculation. The hybrid density functional theory is applied to determine the refractive indices of different alloys. A peculiar bowing effect in the static refractive indices and crossovers of different refractive index curves are found. We speculate that the explanation to these phenomena lies in the interband transitions of electrons where each band bows at a different rate from the other. An average of these bowing effects may result in the bowing of refractive indices.

[Nature or nurture: effects of parental ametropia on children's refractive errors].

Science.gov (United States)

Landmann, A; Bechrakis, E

2013-12-01

The aim of this study was to quantify the degree of association between juvenile refraction errors and parental refraction status. Using a simple questionnaire we conducted a cross-sectional study to determine the prevalence and magnitudes of refractive errors and of parental refraction status in a sample (n=728) of 10- to 18-year-old Austrian grammar school students. Students with myopia or hyperopia were more likely to have ametropic parents and refraction was more myopic in juveniles with one or two parents being ametropic. The prevalence of myopia in children with 2 ametropic parents was 54%, decreasing to 35% in pupils with 1 and to 13% in children with no ametropic parents. The odds ratio for 1 and 2 compared with no ametropic parents was 8.3 and 3.7 for myopia and 1.3 and 1.6 for hyperopia, respectively. Furthermore, the data indicate a stronger influence of the maternal ametropia on children's refractive errors than paternal ametropia. Genetic factors play a significant role in refractive error and may be of dominant influence for school myopia under conditions of low environmental variation.

Axial Length/Corneal Radius of Curvature Ratio and Refractive ...

African Journals Online (AJOL)

2017-06-14

Jun 14, 2017 ... of individuals,[2,5-8] the relationship between CR and refractive status ... the relationship between refractive error and ocular .... AG, 07740 Jena Germany). ..... adult population in rural Myanmar: The Meiktila eye study. Clin.

Extraordinary refraction and self-collimation properties of multilayer metallic-dielectric stratified structures

Energy Technology Data Exchange (ETDEWEB)

Zhang, Liwei, E-mail: zlwhpu@hotmail.com [School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Chen, Liang [School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Zhang, Zhengren [School of Science, Chongqing Jiaotong University, Chongqing 400074 (China); Wang, Wusong [Guizhou Aerospace Institute of Measuring and Testing Technology, Guiyang 550009 (China); Zhao, Yuhuan; Song, Kechao; Kang, Chaoyang [School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China)

2015-01-15

The extraordinary refraction with negative or zero refraction angle of the layered metamaterial consisting of alternating dielectric and plasmonic layers is theoretically studied. It is shown that the electromagnetic properties can be tuned by the filling factor, the permittivity of the dielectric layer and the plasma frequency of the metallic layer. At different frequency, the layered structures possess different refraction properties with positive, zero or negative refraction angle. By choosing appropriate parameters, positive-to-zero-to-negative-to positive refraction at the desired frequency can be realized. At the frequency with flat equal frequency contour, self-collimation and slow light properties are also found. Such properties can be used in the performance of negative refraction, subwavelength imaging and information propagation.

Electro-optical study of nanoscale Al-Si-truncated conical photodetector with subwavelength aperture

Science.gov (United States)

Karelits, Matityahu; Mandelbaum, Yaakov; Chelly, Avraham; Karsenty, Avi

2017-10-01

A type of silicon photodiode has been designed and simulated to probe the optical near field and detect evanescent waves. These waves convey subwavelength resolution. This photodiode consists of a truncated conical shaped, silicon Schottky diode having a subwavelength aperture of 150 nm. Electrical and electro-optical simulations have been conducted. These results are promising toward the fabrication of a new generation of photodetector devices.

FEM simulation of a friction testing method based on combined forward conical can-backward straight can extrusion

DEFF Research Database (Denmark)

Nakamura, T; Bay, Niels

1998-01-01

A new friction testing method based on combined forward conical can-backward straight can extrusion is proposed in order to evaluate friction characteristics in severe metal forming operations. By this method the friction coefficient along the conical punch surface is determined knowing...... the friction coefficient along the die wall. The latter is determined by a combined forward and backward can extrusion of straight cans. Calibration curves determining the relationship between punch travel, can heights, and friction coefficient for the two rests are calculated based on a rigid-plastic FEM...... analysis. Experimental friction tests are carried out in a mechanical press with aluminium alloy A6061 as the workpiece material and different kinds of lubricants. They confirm that the theoretical analysis results irt reasonable values for the friction coefficient....

Rayleigh-Love model of longitudinal vibrations of conical and exponential rods: Exact solutions and numerical simulation by the method of lines

CSIR Research Space (South Africa)

Shatalov, M

2011-07-01

Full Text Available of conical surface of the rod is described by equation ( ) ( )pr x k x x kx= ? = , where px is coordinate of the pole of the cone, px x x= ? , then ( ) 2 2S x k xpi= , ( ) 4 4 2pI x k xpi= and equation (2) is rewritten as follows: ( ) ( ) ( ) ( ) ( ) 2... rod in accordance with the classi- cal theory, and 2 k c ? ?? = is the wavenumber of the conical rod which has dimension 1m? . Introducing new dimensionless variable z x?= , considering new function ( ) zV z U ? ? ? = ? ?? ? ( )W z z...

Trends in refractive surgery at an academic center: 2007-2009

Directory of Open Access Journals (Sweden)

Kuo Irene C

2011-05-01

Full Text Available Abstract Background The United States officially entered a recession in December 2007, and it officially exited the recession in December 2009, according to the National Bureau of Economic Research. Since the economy may affect not only the volume of excimer laser refractive surgery, but also the clinical characteristics of patients undergoing surgery, our goal was to compare the characteristics of patients completing excimer laser refractive surgery and the types of procedures performed in the summer quarter in 2007 and the same quarter in 2009 at an academic center. A secondary goal was to determine whether the volume of astigmatism- or presbyopia-correcting intraocular lenses (IOLs has concurrently changed because like laser refractive surgery, these "premium" IOLs involve out-of-pocket costs for patients. Methods Retrospective case series. Medical records were reviewed for all patients completing surgery at the Wilmer Laser Vision Center in the summer quarter of 2007 and the summer quarter of 2009. Outcome measures were the proportions of treated refractive errors, the proportion of photorefractive keratectomy (PRK vs. laser-assisted in-situ keratomileusis (LASIK, and the mean age of patients in each quarter. Chi-square test was used to compare the proportions of treated refractive errors and the proportions of procedures; two-tailed t-test to compare the mean age of patients; and two-tailed z-test to compare proportions of grouped refractive errors in 2007 vs. 2009; alpha = 0.05 for all tests. Refractive errors were grouped by the spherical equivalent of the manifest refraction and were considered "low myopia" for 6 diopters (D of myopia or less, "high myopia" for more than 6 D, and "hyperopia" for any hyperopia. Billing data were reviewed to obtain the volume of premium IOLs. Results Volume of laser refractive procedures decreased by at least 30%. The distribution of proportions of treated refractive errors did not change (p = 0.10. The

Trends in refractive surgery at an academic center: 2007-2009.

Science.gov (United States)

Kuo, Irene C

2011-05-14

The United States officially entered a recession in December 2007, and it officially exited the recession in December 2009, according to the National Bureau of Economic Research. Since the economy may affect not only the volume of excimer laser refractive surgery, but also the clinical characteristics of patients undergoing surgery, our goal was to compare the characteristics of patients completing excimer laser refractive surgery and the types of procedures performed in the summer quarter in 2007 and the same quarter in 2009 at an academic center. A secondary goal was to determine whether the volume of astigmatism- or presbyopia-correcting intraocular lenses (IOLs) has concurrently changed because like laser refractive surgery, these "premium" IOLs involve out-of-pocket costs for patients. Retrospective case series. Medical records were reviewed for all patients completing surgery at the Wilmer Laser Vision Center in the summer quarter of 2007 and the summer quarter of 2009. Outcome measures were the proportions of treated refractive errors, the proportion of photorefractive keratectomy (PRK) vs. laser-assisted in-situ keratomileusis (LASIK), and the mean age of patients in each quarter. Chi-square test was used to compare the proportions of treated refractive errors and the proportions of procedures; two-tailed t-test to compare the mean age of patients; and two-tailed z-test to compare proportions of grouped refractive errors in 2007 vs. 2009; alpha = 0.05 for all tests. Refractive errors were grouped by the spherical equivalent of the manifest refraction and were considered "low myopia" for 6 diopters (D) of myopia or less, "high myopia" for more than 6 D, and "hyperopia" for any hyperopia. Billing data were reviewed to obtain the volume of premium IOLs. Volume of laser refractive procedures decreased by at least 30%. The distribution of proportions of treated refractive errors did not change (p = 0.10). The proportion of high myopes, however, decreased (p = 0

Indications of Conical Emission of Charged Hadrons at the BNL Relativistic Heavy Ion Collider

Czech Academy of Sciences Publication Activity Database

Abelev, B. I.; Aggarwal, M. M.; Ahammed, Z.; Anderson, B. D.; Arkhipkin, D.; Averichev, G. S.; Balewski, J.; Barannikova, O.; Barnby, L. S.; Baudot, J.; Baumgart, S.; Beavis, D.R.; Bellwied, R.; Benedosso, F.; Betancourt, M.J.; Betts, R. R.; Bhasin, A.; Bhati, A.K.; Bichsel, H.; Bielčík, Jaroslav; Bielčíková, Jana; Biritz, B.; Bland, L.C.; Bombara, M.; Bonner, B. E.; Botje, M.; Bouchet, J.; Braidot, E.; Brandin, A. V.; Bruna, E.; Bueltmann, S.; Burton, T. P.; Bysterský, Michal; Cai, X.Z.; Caines, H.; Sanchez, M.C.D.; Catu, O.; Cebra, D.; Cendejas, R.; Cervantes, M.C.; Chajecki, Z.; Chaloupka, Petr; Chattopadhyay, S.; Chen, H.F.; Chen, J.H.; Cheng, J.; Cherney, M.; Chikanian, A.; Choi, K.E.; Christie, W.; Clarke, R.F.; Codrington, M.J.M.; Corliss, R.; Cormier, T.M.; Coserea, R. M.; Cramer, J. G.; Crawford, H. J.; Das, D.; Dash, S.; Daugherity, M.; De Silva, L.C.; Dedovich, T. G.; DePhillips, M.; Derevschikov, A.A.; de Souza, R.D.; Didenko, L.; Djawotho, P.; Dunlop, J.C.; Mazumdar, M.R.D.; Edwards, W.R.; Efimov, L.G.; Elhalhuli, E.; Elnimr, M.; Emelianov, V.; Engelage, J.; Eppley, G.; Erazmus, B.; Estienne, M.; Eun, L.; Fachini, P.; Fatemi, R.; Fedorisin, J.; Feng, A.; Filip, P.; Finch, E.; Fine, V.; Fisyak, Y.; Gagliardi, C. A.; Gaillard, L.; Ganti, M. S.; Gangaharan, D.R.; Garcia-Solis, E.J.; Geromitsos, A.; Geurts, F.; Ghazikhanian, V.; Ghosh, P.; Gorbunov, Y.N.; Gordon, A.; Grebenyuk, O.; Grosnick, D.; Grube, B.; Guertin, S.M.; Guimaraes, K.S.F.F.; Gupta, A.; Gupta, N.; Guryn, W.; Haag, B.; Hallman, T.J.; Hamed, A.; Harris, J.W.; He, W.; Heinz, M.; Heppelmann, S.; Hippolyte, B.; Hirsch, A.; Hjort, E.; Hoffman, A.M.; Hoffmann, G.W.; Hofman, D.J.; Hollis, R.S.; Huang, H.Z.; Humanic, T.J.; Igo, G.; Iordanova, A.; Jacobs, P.; Jacobs, W.W.; Jakl, Pavel; Jena, C.; Jin, F.; Jones, C.L.; Jones, P.G.; Joseph, J.; Judd, E.G.; Kabana, S.; Kajimoto, K.; Kang, K.; Kapitán, Jan; Keane, D.; Kechechyan, A.; Kettler, D.; Khodyrev, V.Yu.; Kikola, D.P.; Kiryluk, J.; Kisiel, A.; Klein, S.R.; Knospe, A.G.; Kocoloski, A.; Koetke, D.D.; Kopytine, M.; Korsch, W.; Kotchenda, L.; Kushpil, Vasilij; Kravtsov, P.; Kravtsov, V.I.; Krueger, K.; Krus, M.; Kuhn, C.; Kumar, L.; Kurnadi, P.; Lamont, M.A.C.; Landgraf, J.M.; LaPointe, S.; Lauret, J.; Lebedev, A.; Lednický, Richard; Lee, Ch.; Lee, J.H.; Leight, W.; LeVine, M.J.; Li, N.; Li, C.; Li, Y.; Lin, G.; Lindenbaum, S.J.; Lisa, M.A.; Liu, F.; Liu, J.; Liu, L.; Ljubicic, T.; Llope, W.J.; Longacre, R.S.; Love, W.A.; Lu, Y.; Ludlam, T.; Ma, G.L.; Ma, Y.G.; Mahapatra, D.P.; Majka, R.; Mall, O.I.; Mangotra, L.K.; Manweiler, R.; Margetis, S.; Markert, C.; Matis, H.S.; Matulenko, Yu.A.; McShane, T.S.; Meschanin, A.; Milner, R.; Minaev, N.G.; Mioduszewski, S.; Mischke, A.; Mitchell, J.; Mohanty, B.; Morozov, D.A.; Munhoz, M. G.; Nandi, B.K.; Nattrass, C.; Nayak, T. K.; Nelson, J.M.; Netrakanti, P.K.; Ng, M.J.; Nogach, L.V.; Nurushev, S.B.; Odyniec, G.; Ogawa, A.; Okada, H.; Okorokov, V.; Olson, D.; Pachr, M.; Page, B.S.; Pal, S.K.; Pandit, Y.; Panebratsev, Y.; Panitkin, S.Y.; Pawlak, T.; Peitzmann, T.; Perevoztchikov, V.; Perkins, C.; Peryt, W.; Phatak, S.C.; Poljak, N.; Poskanzer, A.M.; Potukuchi, B.V.K.S.; Prindle, D.; Pruneau, C.; Pruthi, N.K.; Putschke, J.; Raniwala, R.; Raniwala, S.; Ray, R.L.; Redwine, R.; Reed, R.; Ridiger, A.; Ritter, H.G.; Roberts, J.B.; Rogachevskiy, O.V.; Romero, J.L.; Rose, A.; Roy, C.; Ruan, L.; Russcher, M.J.; Sahoo, R.; Sakrejda, I.; Sakuma, T.; Salur, S.; Sandweiss, J.; Sarsour, M.; Schambach, J.; Scharenberg, R.P.; Schmitz, N.; Seger, J.; Selyuzhenkov, I.; Seyboth, P.; Shabetai, A.; Shahaliev, E.; Shao, M.; Sharma, M.; Shi, S.S.; Shi, X.H.; Sichtermann, E.P.; Simon, F.; Singaraju, R.N.; Skoby, M.J.; Smirnov, N.; Snellings, R.; Sorensen, P.; Sowinski, J.; Spinka, H.M.; Srivastava, B.; Stadnik, A.; Stanislaus, T.D.S.; Staszak, D.; Strikhanov, M.; Stringfellow, B.; Suaide, A.A.P.; Suarez, M.C.; Subba, N.L.; Šumbera, Michal; Sun, X.M.; Sun, Y.; Sun, Z.; Surrow, B.; Symons, T.J.M.; de Toledo, A. S.; Takahashi, J.; Tang, A.H.; Tang, Z.; Tarnowsky, T.; Thein, D.; Thomas, J.H.; Tian, J.; Timmins, A.R.; Timoshenko, S.; Tokarev, M. V.; Trainor, T.A.; Tram, V.N.; Trattner, A.L.; Trentalange, S.; Tribble, R. E.; Tsai, O.D.; Ulery, J.; Ullrich, T.; Underwood, D.G.; Van Buren, G.; van Leeuwen, M.; Vander Molen, A.M.; Vanfossen, J.A.; Varma, R.; Vasconcelos, G.S.M.; Vasilevski, I.M.; Vasiliev, A. N.; Videbaek, F.; Vigdor, S.E.; Viyogi, Y. P.; Vokal, S.; Voloshin, S.A.; Wada, M.; Walker, M.; Wang, F.; Wang, G.; Wang, J.S.; Wang, Q.; Wang, X.; Wang, X.L.; Wang, Y.; Webb, G.; Webb, J.C.; Westfall, G.D.; Whitten, C.; Wieman, H.; Wissink, S.W.; Witt, R.; Wu, Y.; Tlustý, David; Xie, W.; Xu, N.; Xu, Q.H.; Xu, Y.; Xu, Z.; Yang, P.; Yepes, P.; Yip, K.; Yoo, I.K.; Yue, Q.; Zawisza, M.; Zbroszczyk, H.; Zhan, W.; Zhang, S.; Zhang, W.M.; Zhang, X.P.; Zhang, Y.; Zhang, Z.; Zhao, Y.; Zhong, C.; Zhou, J.; Zoulkarneev, R.; Zoulkarneeva, Y.; Zuo, J.X.

2009-01-01

Roč. 102, č. 5 (2009), 052302/1-052302/7 ISSN 0031-9007 R&D Projects: GA ČR GA202/07/0079 Institutional research plan: CEZ:AV0Z10480505; CEZ:AV0Z10100502 Keywords : PARTICLE CORRELATIONS * QCD MATTER * CONICAL EMISSION Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 7.328, year: 2009

Refraction-contrast bone imaging using synchrotron radiation

International Nuclear Information System (INIS)

Mori, Koichi; Sekine, Norio; Sato, Hitoshi; Shikano, Naoto; Shimao, Daisuke; Shiwaku, Hideaki; Hyodo, Kazuyuki; Oka, Hiroshi

2002-01-01

The X-ray refraction-contrast imaging using synchrotron radiation with some X-ray energies is successfully performed at B120B2 of SPring-8. The refraction-contrast images of bone samples such as human dried proximal phalanx, wrist, upper cervical vertebrae and sella turcica and as mouse proximal femur using the synchrotron X-ray are always better in image contrast and resolution than those of the absorption-contrast images using the synchrotron X-ray and/or the conventional X-ray tube. There is much likeness in the image contrast and resolution of trabeculae bone in the human dried proximal phalanx between X-ray energy of 30 keV at sample-to-film distance of 1 m and those of 40, 50 keV at those of 4,5 m, respectively. High-energy refraction-contrast imaging with suitable sample-to-film distance could reduce the exposure dose in human imaging. In the refraction-contrast imaging of human wrist, upper cervcal vertebrae, sella turcica and mouse proximal femur using the synchrotron X-ray, we can obtain better image contrast and resolution to correctly extract morphological information for diagnosis corresponding to each of the clinical field than those of the absorption-contrast images. (author)

REFRACTIVE ANOMALIES OF AMBLYOPIC CHILDREN WITH AND WITHOUT STRABISMUS

Directory of Open Access Journals (Sweden)

Ljiljana Otašević

2003-04-01

Full Text Available Refractive anomalies occur when the ratio of the refraction ability and the eye length is distrurbed. Amblyopia isunderstood as dimness of vision without detectable lesions of the eye.The aim of the paper is to analyze refractive anomalies occurring in amblyopic children without of with strabismus. The cards of the children suffering from amblyopia and of five of more years of age have been singled out. The number of children obtained in that way is 243. Under special observation were bilateral and unilateral amblyopias and refractive anomalies in children both with and without strabismus. Out of 243 children there are 153 without strabismus (the majority of them reported for examination at the age of seven and 90 with strabismus (the majority of them reported at the age of five. In both the groups bilateral and unilateral amblyopia was registered so that the overall number of the observed amblyopic eyes was 369. In the children without strabismus we mostly found light amblyopia while in the froup of children with strabismus we found, in a great number, medium serious amblyopia while the presence of serious amblypia was also detected. As for refractive anomalies in both the groups of amblyopic children the most freqent were hypermetropic astigmatism and hypermetropia. Because of refractive anomalies as well as with strabismus with small angle, amblyopias are often discovered only when sharpness if vision is being checked; therefore, of great importance are regular systematic examinations of vision sharpness of younger children.

Anatase phase stability and doping concentration dependent refractivity in codoped transparent conducting TiO2 films

International Nuclear Information System (INIS)

Chen, T L; Furubayashi, Y; Hirose, Y; Hitosugi, T; Shimada, T; Hasegawa, T

2007-01-01

Nb 0.06 Sn x Ti 0.94-x O 2 (x ≤ 0.3) thin films were grown by a pulsed-laser deposition method with varying Sn concentration. Through a combinatorial technique, we find that Sn concentration can reach a maximum of about x = 0.3 while maintaining the stable anatase phase and epitaxy. A doping concentration dependence of the refractivity is revealed, in which refractivity reduction at a wavelength of λ = 500 nm is estimated to be 12.4% for Nb 0.06 Sn 0.3 Ti 0.64 O 2 thin film. Sn doping induced band-gap blue shift can be contributed to the mixing of extended Sn 5s orbitals with the conduction band of TiO 2 . Low resistivity on the order of 10 -4 Ω cm at room temperature and high internal transmittance of more than 95% in the visible light region are exhibited for Nb 0.06 Sn x Ti 0.94-x O 2 thin films (x ≤ 0.2). Optical and transport analyses demonstrate that doping Sn into Nb 0.06 Ti 0.94 O 2 can reduce the refractivity while maintaining low resistivity and high transparency

Anomalous waves propagating at very high frequency in the atmosphere and their disturbances due to changes in refractivity profiles

Directory of Open Access Journals (Sweden)

Imtiaz Alam

2018-03-01

Full Text Available Anomalous waves propagation is severely affected due to almost always present variations in refractivity under various environmental conditions at different time, location and frequency. These conditions, representing different state of the atmosphere including e.g. foggy, rainy and cloudy etc., not only degrade the quality of the signal but sometimes completely eradicate the communication link. Such severe impact on propagation cannot be ignored by the designers of communication systems. The aim of this research is to present correlation between experimental and modelled link losses for variations in refractivity values recommended by International Telecommunication Union-Recommendations (ITU-R as well as that of standard profiles. To do so, a communication setup of 50 km over the Sea operating experimentally over a period of a year at 240 MHz is analyzed for different refractivity profiles and their impact on propagation. A median value is taken for every set of 6000 values taken from the recorded data set of more than 48 million experimental link losses. This reduces the huge data set of the experimental link losses to 8000 values only. This reduced data set of experimental and modelled link losses were correlated and investigated for different evaporation duct heights throughout the year. For the considered link, the ITU-R refractivity profile was found to perform better than the standard refractivity profile. However, the new findings as observed in this research, which may be helpful for the recommendations authorities, is the existing of evaporation duct up to 10 m height. Keywords: Parabolic equation, Link loss, Refractivity, Propagation, Troposphere, Very high frequency

Refractive-Index Sensing with Ultrathin Plasmonic Nanotubes

DEFF Research Database (Denmark)

Raza, Søren; Toscano, Giuseppe; Jauho, Antti-Pekka

2013-01-01

We study the refractive-index sensing properties of plasmonic nanotubes with a dielectric core and ultrathin metal shell. The few nanometer thin metal shell is described by both the usual Drude model and the nonlocal hydrodynamic model to investigate the effects of nonlocality. We derive an analy......We study the refractive-index sensing properties of plasmonic nanotubes with a dielectric core and ultrathin metal shell. The few nanometer thin metal shell is described by both the usual Drude model and the nonlocal hydrodynamic model to investigate the effects of nonlocality. We derive...... an analytical expression for the extinction cross section and show how sensing of the refractive index of the surrounding medium and the figure of merit are affected by the shape and size of the nanotubes. Comparison with other localized surface plasmon resonance sensors reveals that the nanotube exhibits...

Miniature interferometer for refractive index measurement in microfluidic chip

Science.gov (United States)

Chen, Minghui; Geiser, Martial; Truffer, Frederic; Song, Chengli

2012-12-01

The design and development of the miniaturized interferometer for measurement of the refractive index or concentration of sub-microliter volume aqueous solution in microfludic chip is presented. It is manifested by a successful measurement of the refractive index of sugar-water solution, by utilizing a laser diode for light source and the small robust instrumentation for practical implementation. Theoretically, the measurement principle and the feasibility of the system are analyzed. Experimental device is constructed with a diode laser, lens, two optical plate and a complementary metal oxide semiconductor (CMOS). Through measuring the positional changes of the interference fringes, the refractive index change are retrieved. A refractive index change of 10-4 is inferred from the measured image data. The entire system is approximately the size of half and a deck of cards and can operate on battery power for long time.

Creating Materials with Negative Refraction Index using Topology Optimization

DEFF Research Database (Denmark)

Christiansen, Rasmus Ellebæk; Sigmund, Ole

is used for regularizationand a projection step applied to obtain clean 0/1 designs. A continuation scheme is used to avoidstagnation in the optimization. Metamaterials with negative refraction index designed using this method are presented. The angular dependence of the refraction index......We apply topology optimization along with full modeling of the electromagnetic (acoustic) field to create metamaterials with negative refraction index. We believe that our approach can be used in the design of metamaterials with specific effective permittivity and permeability e.g. by adapting....... The direction of propagation for the prescribed wave is chosen to match the angle of incidence of the incoming plane wave and its position isused to select the refraction index for the slab. We introducing a continuous design field and apply The Method of Moving Asymptotes to perform the optimization. A filter...

Anomalous waves propagating at very high frequency in the atmosphere and their disturbances due to changes in refractivity profiles

Science.gov (United States)

Alam, Imtiaz; Waqar, Asad; Aamir, Muhammad; Hassan, Shahzad; Shah, Syed Asim Ali

2018-03-01

Anomalous waves propagation is severely affected due to almost always present variations in refractivity under various environmental conditions at different time, location and frequency. These conditions, representing different state of the atmosphere including e.g. foggy, rainy and cloudy etc., not only degrade the quality of the signal but sometimes completely eradicate the communication link. Such severe impact on propagation cannot be ignored by the designers of communication systems. The aim of this research is to present correlation between experimental and modelled link losses for variations in refractivity values recommended by International Telecommunication Union-Recommendations (ITU-R) as well as that of standard profiles. To do so, a communication setup of 50 km over the Sea operating experimentally over a period of a year at 240 MHz is analyzed for different refractivity profiles and their impact on propagation. A median value is taken for every set of 6000 values taken from the recorded data set of more than 48 million experimental link losses. This reduces the huge data set of the experimental link losses to 8000 values only. This reduced data set of experimental and modelled link losses were correlated and investigated for different evaporation duct heights throughout the year. For the considered link, the ITU-R refractivity profile was found to perform better than the standard refractivity profile. However, the new findings as observed in this research, which may be helpful for the recommendations authorities, is the existing of evaporation duct up to 10 m height.

Analysis of refractive state in 708 children with ametropic amblyopia

Directory of Open Access Journals (Sweden)

Ju-Fen Huang

2016-01-01

Full Text Available AIM: To analyze the refractive state and explore the epidemiologic feature of children with ametropic amblyopia.METHODS: This study retrospectively analyzed 708 children(1 416 eyeswith amblyopia from January 2012 to December 2013 in Special Department of Strabismus and Amblyopic and Department of Pediatric Ophthalmology in our hospital, who were diagnosed as ametropic amblyopia and accepted centrally comprehensive training. The refractive state were given epidemiologic analyze.RESULTS: In the 708 cases(1 416 eyes, there were 190 eyes with hyperopia(13.42%,612 eyes with hyperopia astigmatism(43.22%,18 eyes with myopia(1.27%,134 eyes with myopia astigmatism(9.46%,462 eyes with mixed astigmatism(32.63%. The distributions of refractive state in children at different age were different, and the difference was statistically significant(PCONCLUSION: Hyperopia ametropia and mixed astigmatism are the main types of refractive errors in amblyopia children. The level of amblyopia is related to refractive state and astigmatism axial.

Conceptualization of Light Refraction

Science.gov (United States)

Sokolowski, Andrzej

2013-01-01

There have been a number of papers dealing quantitatively with light refraction. Yet the conceptualization of the phenomenon that sets the foundation for a more rigorous math analysis is minimized. The purpose of this paper is to fill that gap. (Contains 3 figures.)

Parsimonious wave-equation travel-time inversion for refraction waves

KAUST Repository

Fu, Lei; Hanafy, Sherif M.; Schuster, Gerard T.

2017-01-01

We present a parsimonious wave-equation travel-time inversion technique for refraction waves. A dense virtual refraction dataset can be generated from just two reciprocal shot gathers for the sources at the endpoints of the survey line, with N

[Use of Plusoptix as a screening method for refractive ambliopia].

Science.gov (United States)

Bogdănici, T; Tone, Silvia; Miron, Mihaela; Boboc, Mihaela; Bogdănici, Camelia

2012-01-01

Highlighting the differences in the objective refraction using the Plusoptix AO9 comparing them with the refraction performed with TOPCON KR-8900 autorefractor. Prospective study for 3 months held in the Ophthalmology Clinic in Iasi, Hospital Sf. Spiridon on a total of 39 children (21 girls and 18 boys) with mean age of 10.61 +/- 5.67 years. Clinical parameters: sex, age, objective refraction obtained with Plusoptix and with autorefractor corrected visual acuity (with different methods depending on each patient age), ortoptic examination (strabic deviation, binocular vision), the presence of symetry/asymetry while measuring with Plusoptix. The results were statistically processed by F-TEST calculating the correlation coefficient, standard deviation, significance level (using the spherical equivalent of the obtained values). Age limits of the studied cases ranged between 2-23 years. Visual acuity of children who had cooperate was between 0.2-1 with correction, achieving best values on right eye than left eye. 8 cases (20.51%) had large differences between measurements made with Plusoptix and autorefractor, half of that (4 cases) had strabismus. Three of these cases were with small hypermetropia and one with small myopia (Plusoptix shows a lower value). In 2 cases occurred higher differences (about 2-2,5D) between the 2 measurements, in patients with average hypermetropia. Plusoptix refraction was not possible at high hypermetropia or high myopia. This type of determining objective refraction using Plusoptix is a useful method of screening for discovery of refractive errors that can cause refractive amblyopia in young children and in those cases with a difficult collaboration. Because there are differences betweeti this 2 methods, for children with refractive errors are recommended further exploration to determine the appropriate optical correction. Plusoptix is a limited method because it cannot detect the exact values in those cases with high hypermetropia or high

3D super-virtual refraction interferometry

KAUST Repository

Lu, Kai

2014-08-05

Super-virtual refraction interferometry enhances the signal-to-noise ratio of far-offset refractions. However, when applied to 3D cases, traditional 2D SVI suffers because the stationary positions of the source-receiver pairs might be any place along the recording plane, not just along a receiver line. Moreover, the effect of enhancing the SNR can be limited because of the limitations in the number of survey lines, irregular line geometries, and azimuthal range of arrivals. We have developed a 3D SVI method to overcome these problems. By integrating along the source or receiver lines, the cross-correlation or the convolution result of a trace pair with the source or receiver at the stationary position can be calculated without the requirement of knowing the stationary locations. In addition, the amplitudes of the cross-correlation and convolution results are largely strengthened by integration, which is helpful to further enhance the SNR. In this paper, both synthetic and field data examples are presented, demonstrating that the super-virtual refractions generated by our method have accurate traveltimes and much improved SNR.

Fully interferometric controllable anomalous refraction efficiency using cross modulation with plasmonic metasurfaces.

Science.gov (United States)

Liu, Zhaocheng; Chen, Shuqi; Li, Jianxiong; Cheng, Hua; Li, Zhancheng; Liu, Wenwei; Yu, Ping; Xia, Ji; Tian, Jianguo

2014-12-01

We present a method of fully interferometric, controllable anomalous refraction efficiency by introducing cross-modulated incident light based on plasmonic metasurfaces. Theoretical analyses and numerical simulations indicate that the anomalous and ordinary refracted beams generated from two opposite-helicity incident beams and following the generalized Snell's law will have a superposition for certain incident angles, and the anomalous refraction efficiency can be dynamically controlled by changing the relative phase of the incident sources. As the incident wavelength nears the resonant wavelength of the plasmonic metasurfaces, two equal-amplitude incident beams with opposite helicity can be used to control the anomalous refraction efficiency. Otherwise, two unequal-amplitude incident beams with opposite helicity can be used to fully control the anomalous refraction efficiency. This Letter may offer a further step in the development of controllable anomalous refraction.

Optical bulk and surface waves with negative refraction

International Nuclear Information System (INIS)

Agranovich, V.M.; Shen, Y.R.; Baughman, R.H.; Zakhidov, A.A.

2004-01-01

In materials with negative refraction, the direction of wave propagation is opposite to the direction of the wave vector. Using an approach that characterizes the optical response of a medium totally by a generalized dielectric permittivity, ε-bar (ω,k-bar), we discuss the possibility of seeing negative refraction for optical waves in a number of nonmagnetic media. These include bulk waves in organic materials and in gyrotropic materials where additional exciton-polariton waves can have a negative group velocity. It is known that dispersion of surface waves can be engineered by tailoring a surface transition layer. We show how this effect can be used to obtain surface waves with negative refraction

Vortex breakdown in a truncated conical bioreactor

Energy Technology Data Exchange (ETDEWEB)

Balci, Adnan; Brøns, Morten [DTU Compute, Technical University of Denmark, DK-2800 Kgs. Lyngby (Denmark); Herrada, Miguel A [E.S.I, Universidad de Sevilla, Camino de los Descubrimientos s/n, E-41092 (Spain); Shtern, Vladimir N, E-mail: mobr@dtu.dk [Shtern Research and Consulting, Houston, TX 77096 (United States)

2015-12-15

This numerical study explains the eddy formation and disappearance in a slow steady axisymmetric air–water flow in a vertical truncated conical container, driven by the rotating top disk. Numerous topological metamorphoses occur as the water height, H{sub w}, and the bottom-sidewall angle, α, vary. It is found that the sidewall convergence (divergence) from the top to the bottom stimulates (suppresses) the development of vortex breakdown (VB) in both water and air. At α = 60°, the flow topology changes eighteen times as H{sub w} varies. The changes are due to (a) competing effects of AMF (the air meridional flow) and swirl, which drive meridional motions of opposite directions in water, and (b) feedback of water flow on AMF. For small H{sub w}, the AMF effect dominates. As H{sub w} increases, the swirl effect dominates and causes VB. The water flow feedback produces and modifies air eddies. The results are of fundamental interest and can be relevant for aerial bioreactors. (paper)

Vortex breakdown in a truncated conical bioreactor

International Nuclear Information System (INIS)

Balci, Adnan; Brøns, Morten; Herrada, Miguel A; Shtern, Vladimir N

2015-01-01

This numerical study explains the eddy formation and disappearance in a slow steady axisymmetric air–water flow in a vertical truncated conical container, driven by the rotating top disk. Numerous topological metamorphoses occur as the water height, H w , and the bottom-sidewall angle, α, vary. It is found that the sidewall convergence (divergence) from the top to the bottom stimulates (suppresses) the development of vortex breakdown (VB) in both water and air. At α = 60°, the flow topology changes eighteen times as H w varies. The changes are due to (a) competing effects of AMF (the air meridional flow) and swirl, which drive meridional motions of opposite directions in water, and (b) feedback of water flow on AMF. For small H w , the AMF effect dominates. As H w increases, the swirl effect dominates and causes VB. The water flow feedback produces and modifies air eddies. The results are of fundamental interest and can be relevant for aerial bioreactors. (paper)

Conically scanning lidar error in complex terrain

Directory of Open Access Journals (Sweden)

Ferhat Bingöl

2009-05-01

Full Text Available Conically scanning lidars assume the flow to be homogeneous in order to deduce the horizontal wind speed. However, in mountainous or complex terrain this assumption is not valid implying a risk that the lidar will derive an erroneous wind speed. The magnitude of this error is measured by collocating a meteorological mast and a lidar at two Greek sites, one hilly and one mountainous. The maximum error for the sites investigated is of the order of 10 %. In order to predict the error for various wind directions the flows at both sites are simulated with the linearized flow model, WAsP Engineering 2.0. The measurement data are compared with the model predictions with good results for the hilly site, but with less success at the mountainous site. This is a deficiency of the flow model, but the methods presented in this paper can be used with any flow model.

Refractive surgery trends and practice style changes in Germany over a 3-year period.

Science.gov (United States)

Schmack, Ingo; Auffarth, Gerd U; Epstein, Daniel; Holzer, Mike P

2010-03-01

To study the current practice styles and preferences of refractive surgeons in Germany. In February 2008, a seven-item questionnaire regarding the practice of refractive surgery was mailed to 282 members of the German Society of Intra-ocular Lens Implantation, Interventional, and Refractive Surgery (DGII) and the Commission of Refractive Surgery (KRC). Most questions were identical to our 2005 German refractive surgery survey. All data were analyzed in a masked fashion. The response rate was 42.2%. The majority (68%) of respondents reported that they perform refractive surgery in laser centers (exclusively or partially) followed by general hospitals (19.4%) and universities (12.6%). Although LASIK was the predominant type of refractive surgery performed (80.6%), other refractive procedures included refractive lens exchange (60.2%), photorefractive keratectomy (47.6%), phakic intraocular lens implants (45.6%), laser-assisted subepithelial keratectomy (36.9%), epithelial laser in situ keratomileusis (15.5%), intracorneal rings (5.8%), and limbal relaxing incisions (2.9%). The volume of refractive surgery procedures and the preferred type of excimer laser systems, microkeratomes, and diagnostic devices varied at different institutions. Most respondents performed either wavefront-guided custom ablation or wavefront-optimized ablation (63.1%) compared with conventional excimer laser correction (36.9%). Refractive surgery practice styles and preferences in Germany are comparable to trends in other European countries. Although LASIK is the most commonly performed refractive procedure, the numbers of various surface ablation techniques and refractive intraocular lens procedures are increasing. Copyright 2010, SLACK Incorporated.

Surgical Options for the Refractive Correction of Keratoconus: Myth or Reality

Directory of Open Access Journals (Sweden)

L. Fernández-Vega-Cueto

2017-01-01

Full Text Available Keratoconus provides a decrease of quality of life to the patients who suffer from it. The treatment used as well as the method to correct the refractive error of these patients may influence on the impact of the disease on their quality of life. The purpose of this review is to describe the evidence about the conservative surgical treatment for keratoconus aiming to therapeutic and refractive effect. The visual rehabilitation for keratoconic corneas requires addressing three concerns: halting the ectatic process, improving corneal shape, and minimizing the residual refractive error. Cross-linking can halt the disease progression, intrastromal corneal ring segments can improve the corneal shape and hence the visual quality and reduce the refractive error, PRK can correct mild-moderate refractive error, and intraocular lenses can correct from low to high refractive error associated with keratoconus. Any of these surgical options can be performed alone or combined with the other techniques depending on what the case requires. Although it could be considered that the surgical option for the refracto-therapeutic treatment of the keratoconus is a reality, controlled, randomized studies with larger cohorts and longer follow-up periods are needed to determine which refractive procedure and/or sequence are most suitable for each case.

Anterior segment surgery IOLs, lasers, and refractive keratoplasty

Energy Technology Data Exchange (ETDEWEB)

Stark, W.J.; Terry, A.C.; Maumenee, A.E.

1987-01-01

The contributors to this text combine their expertise to make this book available on intraocular lenses, refractive corneal surgery, and the use of the YAG laser. Included is information on; IOL power calculations; the use of the YAG laser; retinal damage by short wavelength light; reviews of corneal refractive surgery; possibilities for the medical prevention of cataracts; and more.

On Implementing a Homogeneous Interior-Point Algorithm for Nonsymmetric Conic Optimization

DEFF Research Database (Denmark)

Skajaa, Anders; Jørgensen, John Bagterp; Hansen, Per Christian

Based on earlier work by Nesterov, an implementation of a homogeneous infeasible-start interior-point algorithm for solving nonsymmetric conic optimization problems is presented. Starting each iteration from (the vicinity of) the central path, the method computes (nearly) primal-dual symmetric...... approximate tangent directions followed by a purely primal centering procedure to locate the next central primal-dual point. Features of the algorithm include that it makes use only of the primal barrier function, that it is able to detect infeasibilities in the problem and that no phase-I method is needed...

Shape of Multireference, Equation-of-Motion Coupled-Cluster, and Density Functional Theory Potential Energy Surfaces at a Conical Intersection.

Science.gov (United States)

Gozem, Samer; Melaccio, Federico; Valentini, Alessio; Filatov, Michael; Huix-Rotllant, Miquel; Ferré, Nicolas; Frutos, Luis Manuel; Angeli, Celestino; Krylov, Anna I; Granovsky, Alexander A; Lindh, Roland; Olivucci, Massimo

2014-08-12

We report and characterize ground-state and excited-state potential energy profiles using a variety of electronic structure methods along a loop lying on the branching plane associated with a conical intersection (CI) of a reduced retinal model, the penta-2,4-dieniminium cation (PSB3). Whereas the performance of the equation-of-motion coupled-cluster, density functional theory, and multireference methods had been tested along the excited- and ground-state paths of PSB3 in our earlier work, the ability of these methods to correctly describe the potential energy surface shape along a CI branching plane has not yet been investigated. This is the focus of the present contribution. We find, in agreement with earlier studies by others, that standard time-dependent DFT (TDDFT) does not yield the correct two-dimensional (i.e., conical) crossing along the branching plane but rather a one-dimensional (i.e., linear) crossing along the same plane. The same type of behavior is found for SS-CASPT2(IPEA=0), SS-CASPT2(IPEA=0.25), spin-projected SF-TDDFT, EOM-SF-CCSD, and, finally, for the reference MRCISD+Q method. In contrast, we found that MRCISD, CASSCF, MS-CASPT2(IPEA=0), MS-CASPT2(IPEA=0.25), XMCQDPT2, QD-NEVPT2, non-spin-projected SF-TDDFT, and SI-SA-REKS yield the expected conical crossing. To assess the effect of the different crossing topologies (i.e., linear or conical) on the PSB3 photoisomerization efficiency, we discuss the results of 100 semiclassical trajectories computed by CASSCF and SS-CASPT2(IPEA=0.25) for a PSB3 derivative. We show that for the same initial conditions, the two methods yield similar dynamics leading to isomerization quantum yields that differ by only a few percent.

Automated refraction is stable 1 week after uncomplicated cataract surgery

DEFF Research Database (Denmark)

Ostri, Christoffer; Holfort, Stig K; Fich, Marianne S

2018-01-01

PURPOSE: To compare automated refraction 1 week and 1 month after uncomplicated cataract surgery. METHODS: In this prospective cohort study, we recruited patients in a 2-month period and included consecutive patients scheduled for bilateral small-incision phacoemulsification cataract surgery....... The exclusion criteria were (i) corneal and/or retinal pathology that could lead to automated refraction miscalculation and (ii) surgery complications. Automated refraction was measured 1 week and 1 month after surgery. RESULTS: Ninety-five patients met the in- and exclusion criteria and completed follow......-up. The mean refractive shift in spherical equivalent was -0.02 dioptre (D) between 1 week and 1 month after surgery and not statistical significant (p = 0.78, paired t-test). The magnitude of refractive shift in either myopic or hyperopic direction was neither correlated to age, preoperative corneal...

Refraction in Terms of the Deviation of the Light.

Science.gov (United States)

Goldberg, Fred M.

1985-01-01

Discusses refraction in terms of the deviation of light. Points out that in physics courses where very little mathematics is used, it might be more suitable to describe refraction entirely in terms of the deviation, rather than by introducing Snell's law. (DH)

Refractive surgery or contact lenses – how and when to decide?

Directory of Open Access Journals (Sweden)

Xu K

2011-11-01

Full Text Available Kunyong Xu1, Vishal Jhanji2 1Michael G DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada; 2Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong Abstract: Correction of refractive errors can be achieved with spectacles, contact lenses, and refractive surgery. The past decade has seen a surge in the availability of alternatives for patients and surgeons in terms of both surgical and nonsurgical options for the management of refractive errors. Newer generation contact lenses provide enhanced safety and better handling, whereas modern-day refractive surgery presents a plethora of choices based on the clinical characteristics and requirements of patients. We have moved from an era of "one size fits all" to a purely customized way of treating patients with refractive errors. This review presents the background, advantages, and disadvantages of the two most commonly used options for correction of ametropia, ie, contact lenses and refractive surgery. Keywords: laser-assisted in situ keratomileusis, contact lens, patient selection, complications, outcomes

Effect of Cycloplegia on Corneal Biometrics and Refractive State.

Science.gov (United States)

Bagheri, Abbas; Feizi, Mohadeseh; Shafii, Aliakbar; Faramarzi, Amir; Tavakoli, Mehdi; Yazdani, Shahin

2018-01-01

To determine changes in refractive state and corneal parameters after cycloplegia with cyclopentolate hydrochloride 1% using a dual Scheimpflug imaging system. In this prospective cross-sectional study patients aged 10 to 40 years who were referred for optometric evaluation enrolled and underwent autorefraction and corneal imaging with the Galilei dual Scheimpflug system before and 30 minutes after twice instillation of medication. Changes in refraction and astigmatism were investigated. Corneal biometrics including anterior and posterior corneal curvatures, total corneal power and corneal pachymetry were compared before and after cycloplegia. Two hundred and twelve eyes of 106 subjects with mean age of 28 ± 5 years including 201 myopic and 11 hyperopic eyes were evaluated. Mean spherical equivalent refractive error before cycloplegia was -3.4 ± 2.6 D. A mean hyperopic shift of 0.4 ± 0.5 D occurred after cycloplegia ( P biometrics should be considered before cataract and refractive surgeries.

Evaluation of soil thermal potential under Tunisian climate using a new conic basket geothermal heat exchanger: Energy and exergy analysis

International Nuclear Information System (INIS)

Boughanmi, Hassen; Lazaar, Mariem; Farhat, Abdelhamid; Guizani, Amenallah

2017-01-01

Highlights: • Conic geothermal basket heat exchanger (CBGHE) is experimentally investigated. • Charging and discharging processes of CBGHE are evaluated. • Energy and exergy efficiencies of CBGHE are performed. • High and stable performance of surface geothermal energy in Tunisia is established. - Abstract: Geothermal heat exchangers system composed of two conic baskets serially connected is designed and realized. Both heat exchangers are made in polyethylene high-density material and have a length of 3 m each one. They will be used for greenhouse cooling and heating through a geothermal heat pump. Its conical geometry is selected to reduce the operation cost and the exploited area, compared to vertical and horizontal geothermal heat exchangers often used. It also assures the maximum of heat exchange with the soil. The aim of this study is to determine the thermal performance of one Conic Basket Geothermal Heat Exchanger (CBGHE), buried at 3 m deep, in the exploitation of the soil thermal potential, in summer. A rate of heat exchange with the soil is determined and the global heat exchange of the CBGHE is assessed. Its energy and exergy efficiencies are also evaluated using both first and second law of thermodynamic. Results show that the specific heat exchange ranges between 20 W m"−"1 and 50 W m"−"1. Maximal energetic and exergetic efficiencies of the CBGHE, equal to 62% and 37% respectively, are reached for a mass flow rate of 0.1 kg s"−"1. For this value of mass flow rate, the overall heat exchange coefficient is of 52 W m"−"2 K"−"1.

Plasmonic nanoshell functionalized etched fiber Bragg gratings for highly sensitive refractive index measurements.

Science.gov (United States)

Burgmeier, Jörg; Feizpour, Amin; Schade, Wolfgang; Reinhard, Björn M

2015-02-15

A novel fiber optical refractive index sensor based on gold nanoshells immobilized on the surface of an etched single-mode fiber including a Bragg grating is demonstrated. The nanoparticle coating induces refractive index dependent waveguide losses, because of the variation of the evanescently guided part of the light. Hence the amplitude of the Bragg reflection is highly sensitive to refractive index changes of the surrounding medium. The nanoshell functionalized fiber optical refractive index sensor works in reflectance mode, is suitable for chemical and biochemical sensing, and shows an intensity dependency of 4400% per refractive index unit in the refractive index range between 1.333 and 1.346. Furthermore, the physical length of the sensor is smaller than 3 mm with a diameter of 6 μm, and therefore offers the possibility of a localized refractive index measurement.

Refractive error in school children in Agona Swedru, Ghana

Directory of Open Access Journals (Sweden)

G. O. Ovenseri-Ogbomo

2010-12-01

Full Text Available Uncorrected refractive errors remains a public health problem among different population groups. Among schoolchildren, uncorrected refractive errors have a considerable impact on learning andacademic achievement especially in underserved and under-resourced communities. A school based cross-sectional study was carriedout to estimate the prevalence and distribution of refractive error among schoolchildren in the Agona Swedru municipality of Central Region of Ghana. 637 schoolchildren aged 11-18 years old were randomly selected for the study. Non-cycloplegic refraction was performed on each child who failed the reading test. Hyperopia was defined as spherical power of ≥ + 0.75 D, myopia as ≤ – 0.50 D and astigmatism as a cylindrical power of ≤ – 0.50 D. Of the children examined, only 13.3% had previously had an eye examination.Visual impairment (VA of 6/12 or worse in the better eye was present in 4.5% of the children examined. Of those who failed the reading test, 85.9% had refractive error. The prevalence of hyperopia, myopia and astigmatism was 5.0%, 1.7% and 6.6% respectively. The study concludes that uncorrected refractive error is a common cause of visual impairment among schoolchildren in the municipality. A low uptake of eye care is also noted in the study. The study therefore recommends that the education authority in collaboration with the District Health Directorate institute appropriate measures to ensure compulsory eye examination for schoolchildren in the Agona Swedru district. (S Afr Optom 2010 69(2 86-92

Refractive and diffractive neutron optics with reduced chromatic aberration

DEFF Research Database (Denmark)

Poulsen, Stefan Othmar; Poulsen, Henning Friis; Bentley, P.M.

2014-01-01

by the use of optics for focusing and imaging. Refractive and diffractive optical elements, e.g. compound refractive lenses and Fresnel zone plates, are attractive due to their low cost, and simple alignment. These optical elements, however, suffer from chromatic aberration, which limit their effectiveness...

Technique for forming ITO films with a controlled refractive index

Energy Technology Data Exchange (ETDEWEB)

Markov, L. K., E-mail: l.markov@mail.ioffe.ru; Smirnova, I. P.; Pavluchenko, A. S.; Kukushkin, M. V.; Zakheim, D. A.; Pavlov, S. I. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

2016-07-15

A new method for fabricating transparent conducting coatings based on indium-tin oxide (ITO) with a controlled refractive index is proposed. This method implies the successive deposition of material by electron-beam evaporation and magnetron sputtering. Sputtered coatings with different densities (and, correspondingly, different refractive indices) can be obtained by varying the ratio of the mass fractions of material deposited by different methods. As an example, films with effective refractive indices of 1.2, 1.4, and 1.7 in the wavelength range of 440–460 nm are fabricated. Two-layer ITO coatings with controlled refractive indices of the layers are also formed by the proposed method. Thus, multilayer transparent conducting coatings with desired optical parameters can be produced.

Refractive index based measurements

DEFF Research Database (Denmark)

2014-01-01

In a method for performing a refractive index based measurement of a property of a fluid such as chemical composition or temperature, a chirp in the local spatial frequency of interference fringes of an interference pattern is reduced by mathematical manipulation of the recorded light intensity...

Conical pinched electron beam diode for intense ion beam source

International Nuclear Information System (INIS)

Matsukawa, Yoshinobu; Nakagawa, Yoshiro

1982-01-01

For the purpose of improvement of the pinched electron beam diode, the production of an ion beam by a diode with electrodes in a conical shape was studied at low voltage operation (--200 kV). The ion beam is emitted from a small region of the diode apex. The mean ion beam current density near the axis at 12 cm from the diode apex is two or three times that from an usual flat parallel diode with the same dimension and impedance. The brightness and the power brightness at the otigin are 450 MA/cm 2 sr and 0.12 TW/cm 2 sr respectively. (author)

On the anodic aluminium oxide refractive index of nanoporous templates

International Nuclear Information System (INIS)

Hierro-Rodriguez, A; Rocha-Rodrigues, P; Araujo, J P; Valdés-Bango, F; Alameda, J M; Teixeira, J M; Jorge, P A S; Santos, J L; Guerreiro, A

2015-01-01

In the present study, we have determined the intrinsic refractive index of anodic aluminium oxide, which is originated by the formation of nanoporous alumina templates. Different templates have been fabricated by the conventional two-step anodization procedure in oxalic acid. Their porosities were modified by chemical wet etching allowing the tuning of their effective refractive indexes (air-filled nanopores  +  anodic aluminium oxide). By standard spectroscopic light transmission measurements, the effective refractive index for each different template was extracted in the VIS–NIR region. The determination of the intrinsic anodic aluminium oxide refractive index was performed by using the Maxwell–Garnett homogenization theory. The results are coincident for all the fabricated samples. The obtained refractive index (∼1.55) is quite lower (∼22%) than the commonly used Al 2 O 3 handbook value (∼1.75), showing that the amorphous nature of the anodic oxide structure strongly conditions its optical properties. This difference is critical for the correct design and modeling of optical plasmonic metamaterials based on anodic aluminium oxide nanoporous templates. (paper)

Refractive errors among children, adolescents and adults attending eye clinics in Mexico

Directory of Open Access Journals (Sweden)

Francisco Gomez-Salazar

2017-05-01

Full Text Available AIM: To assess the proportion of refractive errors in the Mexican population that visited primary care optometry clinics in fourteen states of Mexico. METHODS: Refractive data from 676 856 patients aged 6 to 90y were collected from optometry clinics in fourteen states of Mexico between 2014 and 2015. The refractive errors were classified by the spherical equivalent (SE, as follows: sphere+½ cylinder. Myopia (SE>-0.50 D, hyperopia (SE>+0.50 D, emmetropia (-0.50≤SE≤+0.50, and astigmatism alone (cylinder≥-0.25 D. A negative cylinder was selected as a notation. RESULTS: The proportion (95% confidence interval among all of the subjects was hyperopia 21.0% (20.9-21.0, emmetropia 40.7% (40.5-40.8, myopia 24.8% (24.7-24.9 and astigmatism alone 13.5% (13.4-13.5. Myopia was the most common refractive error and frequency seemed to increase among the young population (10 to 29 years old, however, hyperopia increased among the aging population (40 to 79 years old, and astigmatism alone showed a decreasing trend with age (6 to 90y; from 19.7% to 10.8%. There was a relationship between age and all refractive errors (approximately 60%, aged 50 and older. The proportion of any clinically important refractive error was higher in males (61.2% than in females (58.3%; P<0.0001. From fourteen states that collected information, the proportion of refractive error showed variability in different geographical areas of Mexico. CONCLUSION: Myopia is the most common refractive error in the population studied. This study provides the first data on refractive error in Mexico. Further programs and studies must be developed to address the refractive errors needs of the Mexican population.

Generalized laws of reflection and refraction from transformation optics

OpenAIRE

Xu, Yadong; Yao, Kan; Chen, Huanyang

2012-01-01

Based on transformation optics, we introduce another set of generalized laws of reflection and refraction (differs from that of [Science 334, 333 (2011)]), through which a transformation media slab is derived as a meta-surface, producing anomalous reflection and refraction for all polarizations of incident light.

Nano-imprint gold grating as refractive index sensor

International Nuclear Information System (INIS)

Kumari, Sudha; Mohapatra, Saswat; Moirangthem, Rakesh S.

2016-01-01

Large scale of fabrication of plasmonic nanostructures has been a challenging task due to time consuming process and requirement of expensive nanofabrication tools such as electron beam lithography system, focused ion beam system, and extreme UV photolithography system. Here, we present a cost-effective fabrication technique so called soft nanoimprinting to fabricate nanostructures on the larger sample area. In our fabrication process, a commercially available optical DVD disc was used as a template which was imprinted on a polymer glass substrate to prepare 1D polymer nano-grating. A homemade nanoimprinting setup was used in this fabrication process. Further, a label-free refractive index sensor was developed by utilizing the properties of surface plasmon resonance (SPR) of a gold coated 1D polymer nano-grating. Refractive index sensing was tested by exposing different solutions of glycerol-water mixture on the surface of gold nano-grating. The calculated bulk refractive index sensitivity was found to be 751nm/RIU. We believed that our proposed SPR sensor could be a promising candidate for developing low-cost refractive index sensor with high sensitivity on a large scale.

Refractive state of the Spanish Thoroughbred horse: a comparison with the Crossbred horse.

Science.gov (United States)

Rull-Cotrina, Jorge; Molleda, Jose M; Gallardo, José; Martín-Suárez, Eva

2013-01-01

To assess the refractive state of the equine eye utilizing retinoscopy. To compare the refractive state of Spanish Thoroughbred horses with the refractive state of Crossbred horses. The refractive state of 135 horses (264 eyes) was assessed utilizing streak retinoscopy. Two perpendicular meridians were examined in order to assess astigmatism at a working distance of approximately 67 cm. A group of 81 Spanish Thoroughbred horses was compared with a group of 54 Crossbred horses. Cyclopentolate ophthalmic solution was instilled in the eyes of a group of 18 horses to determine if accommodation has any influence on the assessment of the refractive state.   Mean ± SE refractive state of all horses examined was -0.17 ± 0.04 D. The mean refractive state of the Spanish Thoroughbred was -0.28 ± 0.06 D while that of the Crossbred was -0.01 ± 0.05 D. The refractive state of the Spanish Thoroughbred was found to be statistically different to that of the Crossbred. The most prevalent refractive state was emmetropia in all cases, followed by hyperopia for the Crossbred, and myopia for the Spanish Thoroughbred. Astigmatism ≥0.50 D present in both eyes from the same individual was found in 21.7% of all horses examined. Anisometropia ≥1.00 D was diagnosed in 4 out of 129 horses with both visual eyes. Cycloplegia did not statistically affect the refractive state of the evaluated eyes. The equine eye has a refractive state close to emmetropia. Myopia is higher among Spanish Thoroughbred horses than among Crossbred horses. © 2012 American College of Veterinary Ophthalmologists.

Experimental and predicted refractive index properties in ternary mixtures of associated liquids

International Nuclear Information System (INIS)

Sechenyh, Vitaliy V.; Legros, Jean-Claude; Shevtsova, Valentina

2011-01-01

Highlights: → Measurements of refractive indices of 200 different aqueous ternary mixtures have been performed for two wave lengths. → Refractive indices of the associated ternary mixtures can be modeled with a relative error of about 0.9. → Difference between experimental and calculated derivatives of refractive index with concentration is unsatisfactory large. - Abstract: Refractive indices of ternary mixtures formed by (water + ethanol + k-ethylene glycol) (when k is mono, di or tri) and (water + t-butanol + dimethyl sulfoxide) are presented over a wide range of mixture compositions. All measurements have been conducted at 298.15 K and atmospheric pressure using two light sources: one in the visible (λ = 670 nm) and the other in the infrared (λ = 925 nm) spectrum. The performance of several mixing rules that are commonly used in modeling optical constants are examined. We demonstrate that the refractive indices of the associated ternary mixtures can be modeled with a relative error of about 0.9% by using the thermodynamical properties of the pure components. The concentration derivatives of the refractive index are an important parameter, as they are required for different experimental techniques. These derivatives have been determined from the experimental data on refractive indices. However, applying mixing rules for calculation of the derivatives of the refractive indices with respect to concentrations does not provide satisfactory results in the case of ternary mixtures of associated liquids.

Optimal placement of capacitors in a radial network using conic and mixed integer linear programming

Energy Technology Data Exchange (ETDEWEB)

Jabr, R.A. [Electrical, Computer and Communication Engineering Department, Notre Dame University, P.O. Box: 72, Zouk Mikhael, Zouk Mosbeh (Lebanon)

2008-06-15

This paper considers the problem of optimally placing fixed and switched type capacitors in a radial distribution network. The aim of this problem is to minimize the costs associated with capacitor banks, peak power, and energy losses whilst satisfying a pre-specified set of physical and technical constraints. The proposed solution is obtained using a two-phase approach. In phase-I, the problem is formulated as a conic program in which all nodes are candidates for placement of capacitor banks whose sizes are considered as continuous variables. A global solution of the phase-I problem is obtained using an interior-point based conic programming solver. Phase-II seeks a practical optimal solution by considering capacitor sizes as discrete variables. The problem in this phase is formulated as a mixed integer linear program based on minimizing the L1-norm of deviations from the phase-I state variable values. The solution to the phase-II problem is obtained using a mixed integer linear programming solver. The proposed method is validated via extensive comparisons with previously published results. (author)

Empirical temperature dependence of the refractive index of semiconductors

NARCIS (Netherlands)

Herve, P.J.L.; Vandamme, L.K.J.

1995-01-01

Values of the temperature coefficient of the refractive index were obtained from the derivation of a simple relation between energy band-gap and refractive index in semiconductors. These values, (dn/dT)/n, were compared to the experimental data found in literature. Our model, with only one fitting

Prevalence of Refractive Error and Visual Impairment among Rural ...

African Journals Online (AJOL)

GB

prevalence of refractive error was 3.5% (myopia 2.6% and hyperopia 0.9%). Refractive error ... 2Department of Ophthalmology, Addis Ababa University Medical Faculty, Ethiopia. Corresponding ... the main cause of low vision and the second cause of blindness .... the visual loss. All data were entered into computers using.

Refractive aim and visual outcome after phacoemulsification: A 2 ...

African Journals Online (AJOL)

2016-03-24

Mar 24, 2016 ... was met, 21 eyes (14.3%) did not meet their refractive aim, 20 eyes (12.7%) were ... countries, where blindness is associated with considerable ... and better, the total range of refractive errors postoperatively ... required intraocular lenses (IOL), medical record efficiency, ..... problem that can be alleviated.

Refractive-index changes in lithium niobate crystals by radiation damages

International Nuclear Information System (INIS)

Zamani Meymian, Mohammad Reza

2007-01-01

For the study in this thesis 3 He 2+ ions with the energy of about 40 MeV were applied. The results of these studies show a timely very stable anisotrope refractive-index change in the range of some 10 -3 . The radiation damages caused by ions cause a decreasement of the ordinary refractive index n o and an increasement of the extra-ordinary refractive index n e . While the absolute values for Δn o and Δn e are nearly equal the birefringence of the material (n e -n o ) smaller. The generated refractive-index change is dose dependent and the curve Δn has at increasing dose a strongly nonlinear slope with a characteristic stage at the radiation dose of about 2 x 10 20 ions/m 2

Measurement of the Microwave Refractive Index of Materials Based on Parallel Plate Waveguides

Science.gov (United States)

Zhao, F.; Pei, J.; Kan, J. S.; Zhao, Q.

2017-12-01

An electrical field scanning apparatus based on a parallel plate waveguide method is constructed, which collects the amplitude and phase matrices as a function of the relative position. On the basis of such data, a method for calculating the refractive index of the measured wedge samples is proposed in this paper. The measurement and calculation results of different PTFE samples reveal that the refractive index measured by the apparatus is substantially consistent with the refractive index inferred with the permittivity of the sample. The proposed refractive index calculation method proposed in this paper is a competitive method for the characterization of the refractive index of materials with positive refractive index. Since the apparatus and method can be used to measure and calculate arbitrary direction of the microwave propagation, it is believed that both of them can be applied to the negative refractive index materials, such as metamaterials or “left-handed” materials.

Refraction-compensated motion tracking of unrestrained small animals in positron emission tomography.

Science.gov (United States)

Kyme, Andre; Meikle, Steven; Baldock, Clive; Fulton, Roger

2012-08-01

Motion-compensated radiotracer imaging of fully conscious rodents represents an important paradigm shift for preclinical investigations. In such studies, if motion tracking is performed through a transparent enclosure containing the awake animal, light refraction at the interface will introduce errors in stereo pose estimation. We have performed a thorough investigation of how this impacts the accuracy of pose estimates and the resulting motion correction, and developed an efficient method to predict and correct for refraction-based error. The refraction model underlying this study was validated using a state-of-the-art motion tracking system. Refraction-based error was shown to be dependent on tracking marker size, working distance, and interface thickness and tilt. Correcting for refraction error improved the spatial resolution and quantitative accuracy of motion-corrected positron emission tomography images. Since the methods are general, they may also be useful in other contexts where data are corrupted by refraction effects. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Beyond Reflection through an Academic Lens: Refraction and International Experiential Education

Science.gov (United States)

Pagano, Monica; Roselle, Laura

2009-01-01

Students today are becoming more interested in international opportunities for study, and are drawn to alternative programs such as international service learning and international internships. These programs, however, must be carefully designed. In this paper, the authors propose using tools that go beyond the traditional understanding of…

Model-based calculations of off-axis ratio of conic beams for a dedicated 6 MV radiosurgery unit

Energy Technology Data Exchange (ETDEWEB)

Yang, J. N.; Ding, X.; Du, W.; Pino, R. [Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030 (United States); Department of Radiation Oncology, Methodist Hospital, Houston, Texas 77030 (United States)

2010-10-15

Purpose: Because the small-radius photon beams shaped by cones in stereotactic radiosurgery (SRS) lack lateral electronic equilibrium and a detector's finite cross section, direct experimental measurement of dosimetric data for these beams can be subject to large uncertainties. As the dose calculation accuracy of a treatment planning system largely depends on how well the dosimetric data are measured during the machine's commissioning, there is a critical need for an independent method to validate measured results. Therefore, the authors studied the model-based calculation as an approach to validate measured off-axis ratios (OARs). Methods: The authors previously used a two-component analytical model to calculate central axis dose and associated dosimetric data (e.g., scatter factors and tissue-maximum ratio) in a water phantom and found excellent agreement between the calculated and the measured central axis doses for small 6 MV SRS conic beams. The model was based on that of Nizin and Mooij [''An approximation of central-axis absorbed dose in narrow photon beams,'' Med. Phys. 24, 1775-1780 (1997)] but was extended to account for apparent attenuation, spectral differences between broad and narrow beams, and the need for stricter scatter dose calculations for clinical beams. In this study, the authors applied Clarkson integration to this model to calculate OARs for conic beams. OARs were calculated for selected cones with radii from 0.2 to 1.0 cm. To allow comparisons, the authors also directly measured OARs using stereotactic diode (SFD), microchamber, and film dosimetry techniques. The calculated results were machine-specific and independent of direct measurement data for these beams. Results: For these conic beams, the calculated OARs were in excellent agreement with the data measured using an SFD. The discrepancies in radii and in 80%-20% penumbra were within 0.01 cm, respectively. Using SFD-measured OARs as the reference data, the

Prevalence of Refractive Error and Visual Impairment among Rural ...

African Journals Online (AJOL)

Refractive error was the major cause of visual impairment accounting for 54% of all causes in the study group. No child was found wearing ... So, large scale community level screening for refractive error should be conducted and integrated with regular school eye screening programs. Effective strategies need to be devised ...

Trial frame refraction versus autorefraction among new patients in a low-vision clinic.

Science.gov (United States)

DeCarlo, Dawn K; McGwin, Gerald; Searcey, Karen; Gao, Liyan; Snow, Marsha; Waterbor, John; Owsley, Cynthia

2013-01-02

To determine the relationship between refractive error as measured by autorefraction and that measured by trial frame refraction among a sample of adults with vision impairment seen in a university-based low-vision clinic and to determine if autorefraction might be a suitable replacement for trial frame refraction. A retrospective chart review of all new patients 19 years or older seen over an 18-month period was conducted and the following data collected: age, sex, primary ocular diagnosis, entering distance visual acuity, habitual correction, trial frame refraction, autorefraction, and distance visual acuity measured after trial frame refraction. Trial frame refraction and autorefraction were compared using paired t-tests, intraclass correlations, and Bland-Altman plots. Final analyses included 440 patients for whom both trial frame refraction and autorefraction data were available for the better eye. Participants were mostly female (59%) with a mean age of 68 years (SD = 20). Age-related macular degeneration was the most common etiology for vision impairment (44%). Values for autorefraction and trial frame refraction were statistically different, but highly correlated for the spherical equivalent power (r = 0.92), the cylinder power (r = 0.80) and overall blurring strength (0.89). Although the values of the cross-cylinders J(0) and J(45) were similar, they were poorly correlated (0.08 and 0.15, respectively). The range of differences in spherical equivalent power was large (-8.6 to 4.9). Autorefraction is highly correlated with trial frame refraction. Differences are sometimes substantial, making autorefraction an unsuitable substitute for trial frame refraction.

Is LASIK for Me? A Patient's Guide to Refractive Surgery

Science.gov (United States)

Is LASIK for Me? A Patient’s Guide to Refractive Surgery October 2008 Is LASIK for Me? A Patient’s Guide to Refractive Surgery Table of Contents LASIK: A COMPREHENSIVE GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 What Is ...

Comparative Performance of a Non-recessed Hole-entry Hybrid/Hydrostatic Conical Journal Bearing Compensated with Capillary and Orifice Restrictors

Directory of Open Access Journals (Sweden)

P.G. Khakse

2016-06-01

Full Text Available This research paper deals with the theoretical study of comparison of capillary and orifice compensated non-recess hole-entry hydrostatic/ hybrid conical journal bearing. Modified Reynolds equation governing the flow of lubricant in the clearance space of conical journal and bearing has been solved using FEM, Newton-Raphson method and Gauss elimination method. Spherical coordinate system has been employed to obtain the results. The results have been computed for uniform distribution of holes in the circumferential direction with the range of restrictor design parameter C ̅_s2 = 0.02 - 0.1. The numerically simulated result shows, the use of orifice restrictor is to increase bearing stiffness, threshold speed and maximum pressure compared to capillary restrictor for applied radial load.

Refractive errors in children and adolescents in Bucaramanga (Colombia).

Science.gov (United States)

Galvis, Virgilio; Tello, Alejandro; Otero, Johanna; Serrano, Andrés A; Gómez, Luz María; Castellanos, Yuly

2017-01-01

The aim of this study was to establish the frequency of refractive errors in children and adolescents aged between 8 and 17 years old, living in the metropolitan area of Bucaramanga (Colombia). This study was a secondary analysis of two descriptive cross-sectional studies that applied sociodemographic surveys and assessed visual acuity and refraction. Ametropias were classified as myopic errors, hyperopic errors, and mixed astigmatism. Eyes were considered emmetropic if none of these classifications were made. The data were collated using free software and analyzed with STATA/IC 11.2. One thousand two hundred twenty-eight individuals were included in this study. Girls showed a higher rate of ametropia than boys. Hyperopic refractive errors were present in 23.1% of the subjects, and myopic errors in 11.2%. Only 0.2% of the eyes had high myopia (≤-6.00 D). Mixed astigmatism and anisometropia were uncommon, and myopia frequency increased with age. There were statistically significant steeper keratometric readings in myopic compared to hyperopic eyes. The frequency of refractive errors that we found of 36.7% is moderate compared to the global data. The rates and parameters statistically differed by sex and age groups. Our findings are useful for establishing refractive error rate benchmarks in low-middle-income countries and as a baseline for following their variation by sociodemographic factors.

Refractive errors in children and adolescents in Bucaramanga (Colombia

Directory of Open Access Journals (Sweden)

Virgilio Galvis

Full Text Available ABSTRACT Purpose: The aim of this study was to establish the frequency of refractive errors in children and adolescents aged between 8 and 17 years old, living in the metropolitan area of Bucaramanga (Colombia. Methods: This study was a secondary analysis of two descriptive cross-sectional studies that applied sociodemographic surveys and assessed visual acuity and refraction. Ametropias were classified as myopic errors, hyperopic errors, and mixed astigmatism. Eyes were considered emmetropic if none of these classifications were made. The data were collated using free software and analyzed with STATA/IC 11.2. Results: One thousand two hundred twenty-eight individuals were included in this study. Girls showed a higher rate of ametropia than boys. Hyperopic refractive errors were present in 23.1% of the subjects, and myopic errors in 11.2%. Only 0.2% of the eyes had high myopia (≤-6.00 D. Mixed astigmatism and anisometropia were uncommon, and myopia frequency increased with age. There were statistically significant steeper keratometric readings in myopic compared to hyperopic eyes. Conclusions: The frequency of refractive errors that we found of 36.7% is moderate compared to the global data. The rates and parameters statistically differed by sex and age groups. Our findings are useful for establishing refractive error rate benchmarks in low-middle-income countries and as a baseline for following their variation by sociodemographic factors.

The Development and Numerical Analysis of the Conical Radiator Extrusion Process

Directory of Open Access Journals (Sweden)

Michalczyk J.

2017-12-01

Full Text Available The article presents a newly developed method for single-operation extrusion of conical radiators. This is the author’s radiator manufacturing method being the subject of a patent application. The proposed method enables the manufacture of radiators either with or without an inner opening and with an integral plate. Selected results of numerical computations made within Forge®3D, a finite element method (FEM-based software program, were presented during the analysis of the process. A comparative analysis of the proposed manufacturing method using the double-sided extrusion method was also made.

Imaging of Subsurface Faults using Refraction Migration with Fault Flooding

KAUST Repository

Metwally, Ahmed Mohsen Hassan

2017-05-31

We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage.

Refractive index dependence of Papilio Ulysses butterfly wings reflectance spectra

Science.gov (United States)

Isnaeni, Muslimin, Ahmad Novi; Birowosuto, Muhammad Danang

2016-02-01

We have observed and utilized butterfly wings of Papilio Ulysses for refractive index sensor. We noticed this butterfly wings have photonic crystal structure, which causes blue color appearance on the wings. The photonic crystal structure, which consists of cuticle and air void, is approximated as one dimensional photonic crystal structure. This photonic crystal structure opens potential to several optical devices application, such as refractive index sensor. We have utilized small piece of Papilio Ulysses butterfly wings to characterize refractive index of several liquid base on reflectance spectrum of butterfly wings in the presence of sample liquid. For comparison, we simulated reflectance spectrum of one dimensional photonic crystal structure having material parameter based on real structure of butterfly wings. We found that reflectance spectrum peaks shifted as refractive index of sample changes. Although there is a slight difference in reflectance spectrum peaks between measured spectrum and calculated spectrum, the trend of reflectance spectrum peaks as function of sample's refractive index is the similar. We assume that during the measurement, the air void that filled by sample liquid is expanded due to liquid pressure. This change of void shape causes non-similarity between measured spectrum and calculated spectrum.

Imaging of Subsurface Faults using Refraction Migration with Fault Flooding

KAUST Repository

Metwally, Ahmed Mohsen Hassan; Hanafy, Sherif; Guo, Bowen; Kosmicki, Maximillian Sunflower

2017-01-01

We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage.

Empirical modelling to predict the refractive index of human blood

Science.gov (United States)

Yahya, M.; Saghir, M. Z.

2016-02-01

Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient’s condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy.

Low scatter edge blackening compounds for refractive optical elements

International Nuclear Information System (INIS)

Lewis, I.T.; Telkamp, A.R.; Ledebuhr, A.G.

1989-01-01

This paper reports on low scatter edge blackening compounds for refractive optical elements. Perkin-Elmer's Applied Optics Operation recently delivered several prototype wide-field-of-view (WFOV), F/2.8, 250 mm efl, near diffraction limited, concentric lenses toLawrence Livermore National Laboratory (LLNL). In these lenses, special attention was paid to reducing stray light to allow viewing of very dim objects. Because of the very large FOV, the use of a long baffle to eliminate direct illumination of lens edges was not practical. With the existing relatively short baffle design, one-bounce stray light paths off the element edges are possible. The scattering off the inside edges thus had to be kept to an absolute minimum. While common means for blackening the edges of optical elements are easy to apply and quite cost effective for normal lens assemblies, their blackening effect is limited by the Fresnel reflection due to the index of refraction mismatch at the glass boundary. At high angles of incidence, total internal reflection (TIR) might occur ruining the effect of the blackening process. An index-match absorbing medium applied to the edges of such elements is the most effective approach for reducing the amount of undesired light reflection or scattered off these edges. The presence of such a medium provides an extended path outside the glass boundary in which an absorptive non-scattering dye can be used to eliminate light that might otherwise have propagated to the focal plane

Polymer X-ray refractive nano-lenses fabricated by additive technology.

Science.gov (United States)

Petrov, A K; Bessonov, V O; Abrashitova, K A; Kokareva, N G; Safronov, K R; Barannikov, A A; Ershov, P A; Klimova, N B; Lyatun, I I; Yunkin, V A; Polikarpov, M; Snigireva, I; Fedyanin, A A; Snigirev, A

2017-06-26

The present work demonstrates the potential applicability of additive manufacturing to X-Ray refractive nano-lenses. A compound refractive lens with a radius of 5 µm was produced by the two-photon polymerization induced lithography. It was successfully tested at the X-ray microfocus laboratory source and a focal spot of 5 μm was measured. An amorphous nature of polymer material combined with the potential of additive technologies may result in a significantly enhanced focusing performance compared to the best examples of modern X-ray compound refractive lenses.

An optomechanical model eye for ophthalmological refractive studies.

Science.gov (United States)

Arianpour, Ashkan; Tremblay, Eric J; Stamenov, Igor; Ford, Joseph E; Schanzlin, David J; Lo, Yuhwa

2013-02-01

To create an accurate, low-cost optomechanical model eye for investigation of refractive errors in clinical and basic research studies. An optomechanical fluid-filled eye model with dimensions consistent with the human eye was designed and fabricated. Optical simulations were performed on the optomechanical eye model, and the quantified resolution and refractive errors were compared with the widely used Navarro eye model using the ray-tracing software ZEMAX (Radiant Zemax, Redmond, WA). The resolution of the physical optomechanical eye model was then quantified with a complementary metal-oxide semiconductor imager using the image resolution software SFR Plus (Imatest, Boulder, CO). Refractive, manufacturing, and assembling errors were also assessed. A refractive intraocular lens (IOL) and a diffractive IOL were added to the optomechanical eye model for tests and analyses of a 1951 U.S. Air Force target chart. Resolution and aberrations of the optomechanical eye model and the Navarro eye model were qualitatively similar in ZEMAX simulations. Experimental testing found that the optomechanical eye model reproduced properties pertinent to human eyes, including resolution better than 20/20 visual acuity and a decrease in resolution as the field of view increased in size. The IOLs were also integrated into the optomechanical eye model to image objects at distances of 15, 10, and 3 feet, and they indicated a resolution of 22.8 cycles per degree at 15 feet. A life-sized optomechanical eye model with the flexibility to be patient-specific was designed and constructed. The model had the resolution of a healthy human eye and recreated normal refractive errors. This model may be useful in the evaluation of IOLs for cataract surgery. Copyright 2013, SLACK Incorporated.

Toward a general theory of conical intersections in systems of identical nuclei

Science.gov (United States)

Keating, Sean P.; Mead, C. Alden

1987-02-01

It has been shown previously that the Herzberg-Longuet-Higgins sign change produced in Born-Oppenheimer electronic wave functions when the nuclei traverse a closed path around a conical intersection has implications for the symmetry of wave functions under permutations of identical nuclei. For systems of three or four identical nuclei, there are special features present which have facilitated the detailed analysis. The present paper reports progress toward a general theory for systems of n nuclei. For n=3 or 4, the two key functions which locate conical intersections and define compensating phase factors can conveniently be defined so as to transform under permutations according to a two-dimensional irreducible representation of the permutation group. Since such representations do not exist for n>4, we have chosen to develop a formalism in terms of lab-fixed electronic basis functions, and we show how to define the two key functions in principle. The functions so defined both turn out to be totally symmetric under permutations. We show how they can be used to define compensating phase factors so that all modified electronic wave functions are either totally symmetric or totally antisymmetric under permutations. A detailed analysis is made to cyclic permutations in the neighborhood of Dnh symmetry, which can be extended by continuity arguments to more general configurations, and criteria are obtained for sign changes. There is a qualitative discussion of the treatment of more general permutations.

Analysis of turbulent conical diffuser flow using second moment closures

International Nuclear Information System (INIS)

Adane, K.K.; Tachie, M.F.; Ormiston, S.J.

2004-01-01

A commercial CFD code, CFX-TASCflow, is used to predict a turbulent conical diffuser flow. The computation was performed using a low-Reynolds number k-ω model, a low-Reynolds number k-ω based non-linear algebraic Reynolds stress model, and a second moment closure with a wall-function. The experimental data of Kassab are used to validate the numerical results. The results show that all the turbulence models reproduce the static pressure coefficient distribution reasonably well. The low Reynolds number k-ω models give better prediction of the friction velocity than the second moment closure. The models also predict the Reynolds shear stress reasonably well but fail to reproduce the correct level of the turbulent kinetic energy. (author)

The mechanical response of tetragonal zirconia polycrystal to conical indentation

International Nuclear Information System (INIS)

Asif, S.A.S.; Biswas, S.K.

1994-01-01

Blocks of 3Y-TZP were indented with conical diamond indenters. Indentation caused tetragonal to monoclinic phase transformation in a subsurface. Of the cracks generated in the subsurface, radial and lateral cracks can be accounted for by a continuum model of the indented subsurface, built using a combination of the Boussinesq and blister stress fields. Additional ring, median and cone cracks were also observed. It is hypothesized that the latter are motivated by the reduction in blister strength or residual energy brought about by the material damage caused by the phase transformation. This damage reduces the load bearing capacity of the material progressively with increasing normal load. (author). 13 refs., 5 figs., 2 tabs

Design and Manufacture of Conical Shell Structures Using Prepreg Laminates

Science.gov (United States)

Khakimova, Regina; Burau, Florian; Degenhardt, Richard; Siebert, Mark; Castro, Saullo G. P.

2016-06-01

The design and manufacture of unstiffened composite conical structures is very challenging, as the variation of the fiber orientations, lay-up and the geometry of the ply pieces have a significant influence on the thickness imperfections and ply angle deviations imprinted to the final part. This paper deals with the manufacture of laminated composite cones through the prepeg/autoclave process. The cones are designed to undergo repetitive buckling tests without accumulating permanent damage. The aim is to define a process that allows the control of fiber angle deviations and the removal of thickness imperfections generated from gaps and overlaps between ply pieces. Ultrasonic scan measurements are used to proof the effectiveness of the proposed method.

Simple atom trap in a conical hollow mirror: Numerical analysis

International Nuclear Information System (INIS)

Kim, J. A.; Lee, K. I.; Nha, H.; Noh, H. R.; Yoo, S. H.; Jhe, W

1996-01-01

We analyze the trap dynamic in a conical hollow (axicon) mirror system. Atom's trajectory is ring shaped if we move the coil (magnetic field) axis off the mirror axis and if we overlap these two axes trap cloud is ball shaped and it is consistent with experiment. We also make a simple comparison between 6-beam MOT and axicon MOT in the ball shaped case, and it shows that at low velocity limit the axicon MOT and typical 6-beam MOT have nearly same trap properties. The axicon trap may be useful as precooled atom source for many other atomic physics experiments such as cold atomic beam, atom funnel, and atom waveguide.

Automatic diagnostic system for measuring ocular refractive errors

Science.gov (United States)

Ventura, Liliane; Chiaradia, Caio; de Sousa, Sidney J. F.; de Castro, Jarbas C.

1996-05-01

Ocular refractive errors (myopia, hyperopia and astigmatism) are automatic and objectively determined by projecting a light target onto the retina using an infra-red (850 nm) diode laser. The light vergence which emerges from the eye (light scattered from the retina) is evaluated in order to determine the corresponding ametropia. The system basically consists of projecting a target (ring) onto the retina and analyzing the scattered light with a CCD camera. The light scattered by the eye is divided into six portions (3 meridians) by using a mask and a set of six prisms. The distance between the two images provided by each of the meridians, leads to the refractive error of the referred meridian. Hence, it is possible to determine the refractive error at three different meridians, which gives the exact solution for the eye's refractive error (spherical and cylindrical components and the axis of the astigmatism). The computational basis used for the image analysis is a heuristic search, which provides satisfactory calculation times for our purposes. The peculiar shape of the target, a ring, provides a wider range of measurement and also saves parts of the retina from unnecessary laser irradiation. Measurements were done in artificial and in vivo eyes (using cicloplegics) and the results were in good agreement with the retinoscopic measurements.

Wave Refraction During the May 2002 Rarefaction Event

Science.gov (United States)

Smith, C. W.; Mullan, D. J.; Ness, N. F.; Skoug, R. M.

2002-12-01

In previous work [Smith et al., 2001] we examined IMF wave refraction during the May 1999 rarefaction interval known as ``The Day The Solar Wind Disappeared.'' On that day, Alfvén speeds remained elevated over an extended region. Analysis of the recorded ACE fields and plasma data revealed depressed magnetic fluctuation levels, reduced compression in the fluctuations, and a reduced wave-like component within the region of elevated Alfvén speed, all consistent with wave refraction. The May 2002 event provides a third such period (the second identified event occured 2 weeks prior to the May 1999 period) and it again demonstrates properties which are consistent with refraction. Smith, C.~W., D.~J. Mullan, N.~F. Ness, R.~M. Skoug, and J.~Steinberg, Day the solar wind almost disappeared: Magnetic field fluctuations, wave refraction and dissipation, J. Geophys. Res., A106, 18,625--18,634, 2001. Efforts at the Bartol Research Institute were supported by CIT subcontract PC251439 under NASA grant NAG5-6912 for support of the ACE magnetic field experiment and by the NASA Delaware Space College Grant. Work at Los Alamos was performed under the auspices of the U.S. Department of Energy with financial support from the NASA ACE program.

Refractive index retrieving of polarization maintaining optical fibers

Science.gov (United States)

Ramadan, W. A.; Wahba, H. H.; Shams El-Din, M. A.; Abd El-Sadek, I. G.

2018-01-01

In this paper, the cross-section images, of two different types of polarization maintaining (PM) optical fibers, are employed to estimate the optical phase variation due to transverse optical rays passing through these optical fibers. An adaptive algorithm is proposed to recognize the different areas constituting the PM optical fibers cross-sections. These areas are scanned by a transverse beam to calculate the optical paths for given values of refractive indices. Consequently, the optical phases across the PM optical fibers could be recovered. PM optical fiber is immersed in a matching fluid and set in the object arm of Mach-Zehnder interferometer. The produced interferograms are analyzed to extract the optical phases caused by the PM optical fibers. The estimated optical phases could be optimized to be in good coincidence with experimentally extracted ones. This has been achieved through changing of the PM optical fibers refractive indices to retrieve the correct values. The correct refractive indices values are confirmed by getting the best fit between the estimated and the extracted optical phases. The presented approach is a promising one because it provides a quite direct and accurate information about refractive index, birefringence and beat length of PM optical fibers comparing with different techniques handle the same task.

Microfocussing of synchrotron X-rays using X-ray refractive lens ...

Indian Academy of Sciences (India)

2014-07-02

Jul 2, 2014 ... together. The first refractive lenses for hard X-rays were fabricated and tested by Snigirev et al [3]. ... using silicon and diamond refractive lens materials [4]. Many groups ... PMMA has lower radiation resistance com- pared to ...

Refractive and diffractive neutron optics with reduced chromatic aberration

Energy Technology Data Exchange (ETDEWEB)

Poulsen, S.O., E-mail: stefan.poulsen@northwestern.edu [NEXMAP, Department of Physics, Technical University of Denmark, Anker Engelunds Vej 1, 2800 Kgs. Lyngby (Denmark); Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208 (United States); Poulsen, H.F. [NEXMAP, Department of Physics, Technical University of Denmark, Anker Engelunds Vej 1, 2800 Kgs. Lyngby (Denmark); Bentley, P.M. [European Spallation Source ESS AB, Box 176, 221 00 Lund (Sweden)

2014-12-11

Thermal neutron beams are an indispensable tool in physics research. The spatial and the temporal resolution attainable in experiments are dependent on the flux and collimation of the neutron beam which remain relatively poor, even for modern neutron sources. These difficulties may be mitigated by the use of optics for focusing and imaging. Refractive and diffractive optical elements, e.g. compound refractive lenses and Fresnel zone plates, are attractive due to their low cost, and simple alignment. These optical elements, however, suffer from chromatic aberration, which limit their effectiveness to highly monochromatic beams. This paper presents two novel concepts for focusing and imaging non-monochromatic thermal neutron beams with well-known optical elements: (1) a fast mechanical transfocator based on a compound refractive lens, which actively varies the number of individual lenses in the beam path to focus and image a time-of-flight beam, and (2) a passive optical element consisting of a compound refractive lens, and a Fresnel zone plate, which may focus and image both continuous and pulsed neutron beams.

Refractive Index Sensor Using a Two-Hole Fiber

Energy Technology Data Exchange (ETDEWEB)

Lopez-Cortes, D; Sanchez-Mondragon, J J [Photonics and Optical Physics Laboratory, Optics Department, INAOE Apdo. Postal 51 and 216, Tonantzintla, Puebla 72000 (Mexico); Margulis, W [Department Fiber Photonics, ACREO, Electrum 236, 16440 Stockholm (Sweden); Dominguez-Cruz, R; May-Arrioja, D A, E-mail: darrioja@uat.edu.mx [Depto. de Ingenieria Electronica, UAM Reynosa Rodhe, Universidad Autonoma de Tamaulipas, Carr. Reynosa-San Fernando S/N, Reynosa, Tamaulipas 88779 (Mexico)

2011-01-01

We propose to use a twin-hole fiber to measure refractive index of liquids. The key idea is to have a single mode fiber (SMF) having two large air-holes running along the fiber length, the holes do not interact with the core. However, using wet chemical etching we can have access to the hole around the fiber, and further etching increases the holes diameter. The diameter is increased until the fiber exhibits a specific birefringence. Since the holes are open, by immersing the fiber in different liquids (n=1.33 to n=1.42) the value of the birefringence is modified and the refractive index of the liquid can be estimated from the change on the beat length. This process provides a very simple and highly sensitive mechanism for sensing refractive index in liquids, and can also be used for other applications.

[Correction of light refraction and reflection in medical transmission optical tomography].

Science.gov (United States)

Tereshchenko, S A; Potapov, D A

2002-01-01

The effects of light refraction and reflection on the quality of image reconstruction in medical transmission optical tomography of high-scattering media are considered. It has been first noted that light refraction not only distorts the geometric scheme of measurements, but may lead to the appearance of object areas that cannot be scanned. Some ways of decreasing the effect of refraction on the reconstruction of spatial distribution of the extinction coefficient are stated.

1D Photonic Crystals with a Sawtooth Refractive Index

OpenAIRE

Morozov, G. V.; Sprung, D. W. L.; Martorell, J.

2013-01-01

Exact analytical results (in terms of Bessel functions) for the bandgaps, reflectance, and transmittance of one-dimensional photonic crystals with a sawtooth refractive index profile on the period are derived for the first time. This extends a group of exactly solvable models of periodic refractive indices. The asymptotic approximations of the above exact results have been also obtained.

Index of Refraction Measurements Using a Laser Distance Meter

Science.gov (United States)

Ochoa, Romulo; Fiorillo, Richard; Ochoa, Cris

2014-01-01

We present a simple method to determine the refractive indices of transparent media using a laser distance meter. Indices of refraction have been obtained by measuring the speed of light in materials. Some speed of light techniques use time-of-flight measurements in which pulses are emitted by lasers and the time interval is measured for the pulse…

A Model of the Effect of Lens Development on Refraction in Schoolchildren.

Science.gov (United States)

He, Ji C

2017-12-01

The study provides a new theory on the mechanism underlying myopia development, and it could be useful in clinical practice to control myopia development in schoolchildren. To model the effect of the crystalline lens on refractive development in schoolchildren. The Zemax 13 was used to calculate Zernike aberrations and refractions across 50° horizontal visual fields. Optical effects of the anterior chamber depth, lens thickness, and radii of curvature of the lens surfaces on refractions were modeled. Refractive changes induced by lens development in emmetropic and myopic eyes, based on a previous longitudinal study from literature, were calculated. A lens thickness reduction with an anterior chamber depth deepening caused a hyperopic shift over the visual fields and even more at the periphery. Opposite effects were found when the lens was thinned without any change of the anterior chamber depth. While a flattening of the anterior lens surface produced hyperopic refractions overall, a posterior lens flattening caused a myopic shift at the periphery, but a hyperopic shift of the central refraction. In the myopic eye, lens development induced refractive change toward more hyperopic over the visual fields and more at the periphery. Lens thinning and lens axial movement participate in peripheral refractive development in schoolchildren, and lens development with a deeper anterior chamber depth and a flatter lens surface in the myopic eye could generate extra hyperopia over visual fields. The myopic lens development could be due to a backward movement of the lens, driven by a backward growth of the ciliary process, which might be a causative factor of myopia development.

Calculation and simulation of atmospheric refraction effects in maritime environments

Science.gov (United States)

Dion, Denis, Jr.; Gardenal, Lionel; Lahaie, P.; Forand, J. Luc

2001-01-01

Near the sea surface, atmospheric refraction and turbulence affect both IR transmission and image quality. This produces an impact on both the detection and classification/identification of targets. With the financial participation of the U.S. Office of Naval Research (ONR), Canada's Defence Research Establishment Valcartier (DREV) is developing PRIME (Propagation Resources In the Maritime Environment), a computer model aimed at describing the overall atmospheric effects on IR imagery systems in the marine surface layer. PRIME can be used as a complement to MODTRAN to compute the effective transmittance in the marine surface layer, taking into account the lens effects caused by refraction. It also provides information on image degradation caused by both refraction and turbulence. This paper reviews the refraction phenomena that take place in the surface layer and discusses their effects on target detection and identification. We then show how PRIME can benefit detection studies and image degradation simulations.

Change in refractive index of muscle tissue during laser-induced interstitial thermotherapy.

Science.gov (United States)

Chen, Na; Chen, Meimei; Liu, Shupeng; Guo, Qiang; Chen, Zhenyi; Wang, Tingyun

2014-01-01

This paper presents a long-period fiber-grating (LPG) based Michelson interferometric refractometry to monitor the change in refractive index of porcine muscle during laser-induced interstitial thermotherapy (LITT). As the wavelength of RI interferometer alters with the change in refractive index around the probe, the LPG based refractometry is combined with LITT system to measure the change in refractive index of porcine muscle when irradiated by laser. The experimental results show the denaturation of tissue alters the refractive index significantly and the LPG sensor can be applied to monitor the tissue state during the LITT.

The Refractive Index Measurement Of Silicon Dioxide Thin Film by the Coupling Prism Method

International Nuclear Information System (INIS)

Budianto, Anwar; Hariyanto, Sigit; Subarkah

1996-01-01

Refractive index of silicon dioxide thin film that doped with phosphor (SiO 2 :P) above the pure silicon dioxide substrate has been measured by light coupling prism method. The method principle is focusing the light on coupling prism base so that the light propagates into the waveguide layer while the reflected one forms a mode in the observation plane. The SiO 2 thin film as waveguide layer has a refractive index that give the thick and refractive index relation. The He-Ne laser as light source has the wavelength λ 0,6328 μm. The refractive index measurement of the thin film with the substrate refractive index n sb = 1,47 and the thin film thick d = 2μm gives n g = 1,5534 ± 0,01136. This method can distinguish the refractive index of thin film about 6% to the refractive index of substrate

Low-Coherence Reflectometry for Refractive Index Measurements of Cells in Micro-Capillaries

Science.gov (United States)

Carpignano, Francesca; Rigamonti, Giulia; Mazzini, Giuliano; Merlo, Sabina

2016-01-01

The refractive index of cells provides insights into their composition, organization and function. Moreover, a good knowledge of the cell refractive index would allow an improvement of optical cytometric and diagnostic systems. Although interferometric techniques undoubtedly represent a good solution for quantifying optical path variation, obtaining the refractive index of a population of cells non-invasively remains challenging because of the variability in the geometrical thickness of the sample. In this paper, we demonstrate the use of infrared low-coherence reflectometry for non-invasively quantifying the average refractive index of cell populations gently confined in rectangular glass micro-capillaries. A suspension of human red blood cells in plasma is tested as a reference. As a use example, we apply this technique to estimate the average refractive index of cell populations belonging to epithelial and hematological families. PMID:27727172

Refractive outcomes after multifocal intraocular lens exchange.

Science.gov (United States)

Kim, Eric J; Sajjad, Ahmar; Montes de Oca, Ildamaris; Koch, Douglas D; Wang, Li; Weikert, Mitchell P; Al-Mohtaseb, Zaina N

2017-06-01

To evaluate the refractive outcomes after multifocal intraocular lens (IOL) exchange. Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. Retrospective case series. Patients had multifocal IOL explantation followed by IOL implantation. Outcome measures included type of IOL, surgical indication, corrected distance visual acuity (CDVA), and refractive prediction error. The study comprised 29 patients (35 eyes). The types of IOLs implanted after multifocal IOL explantation included in-the-bag IOLs (74%), iris-sutured IOLs (6%), sulcus-fixated IOLs with optic capture (9%), sulcus-fixated IOLs without optic capture (9%), and anterior chamber IOLs (3%). The surgical indication for exchange included blurred vision (60%), photic phenomena (57%), photophobia (9%), loss of contrast sensitivity (3%), and multiple complaints (29%). The CDVA was 20/40 or better in 94% of eyes before the exchange and 100% of eyes after the exchange (P = .12). The mean refractive prediction error significantly decreased from 0.22 ± 0.81 diopter (D) before the exchange to -0.09 ± 0.53 D after the exchange (P exchange to 0.23 D after the exchange (P exchange can be performed safely with good visual outcomes using different types of IOLs. A lower refractive prediction error and a higher likelihood of 20/40 or better vision can be achieved with the implantation of the second IOL compared with the original multifocal IOL, regardless of the final IOL position. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Empirical modelling to predict the refractive index of human blood

International Nuclear Information System (INIS)

Yahya, M; Saghir, M Z

2016-01-01

Optical techniques used for the measurement of the optical properties of blood are of great interest in clinical diagnostics. Blood analysis is a routine procedure used in medical diagnostics to confirm a patient’s condition. Measuring the optical properties of blood is difficult due to the non-homogenous nature of the blood itself. In addition, there is a lot of variation in the refractive indices reported in the literature. These are the reasons that motivated the researchers to develop a mathematical model that can be used to predict the refractive index of human blood as a function of concentration, temperature and wavelength. The experimental measurements were conducted on mimicking phantom hemoglobin samples using the Abbemat Refractometer. The results analysis revealed a linear relationship between the refractive index and concentration as well as temperature, and a non-linear relationship between refractive index and wavelength. These results are in agreement with those found in the literature. In addition, a new formula was developed based on empirical modelling which suggests that temperature and wavelength coefficients be added to the Barer formula. The verification of this correlation confirmed its ability to determine refractive index and/or blood hematocrit values with appropriate clinical accuracy. (paper)

The Determinants of Early Refractive Error on School-Going Chinese Children

Directory of Open Access Journals (Sweden)

K. Jayaraman

2016-04-01

Full Text Available Refractive error is a common social issue in every walks of human life, and its prevalence recorded the highest among Chinese population, particularly among people living in southern China, Hong Kong, Thailand, Singapore, and Malaysia. Refractive error is the simplest disorder to treat and supposed to cost the effective health care intervention. The present study included 168 Chinese school-going children aged 10 to 12 years; they were selected from different schools of urban Malaysia. It was surprising to see that 112 (66.7% children had the early onset of refractive error; refractive error was also detected late among the primary school or secondary school students. The findings revealed that the determinants of refractive error among Chinese children were personal achievements and machine dependence. The possible reasons for the above significant factors emerged could be attributed to the inbuilt culture and traditions of Chinese parents who insist that their children should be hardworking and focus on school subjects so that their parents allow them to use luxury electronic devices.

The Power of Poincar\\'e: Elucidating the Hidden Symmetries in Focal Conic Domains

OpenAIRE

Alexander, Gareth P.; Chen, Bryan Gin-ge; Matsumoto, Elisabetta A.; Kamien, Randall D.

2010-01-01

Focal conic domains are typically the "smoking gun" by which smectic liquid crystalline phases are identified. The geometry of the equally-spaced smectic layers is highly generic but, at the same time, difficult to work with. In this Letter we develop an approach to the study of focal sets in smectics which exploits a hidden Poincar\\'e symmetry revealed only by viewing the smectic layers as projections from one-higher dimension. We use this perspective to shed light upon several classic focal...

Biomechanical evaluation of bending strength of spinal pedicle screws, including cylindrical, conical, dual core and double dual core designs using numerical simulations and mechanical tests.

Science.gov (United States)

Amaritsakul, Yongyut; Chao, Ching-Kong; Lin, Jinn

2014-09-01

Pedicle screws are used for treating several types of spinal injuries. Although several commercial versions are presently available, they are mostly either fully cylindrical or fully conical. In this study, the bending strengths of seven types of commercial pedicle screws and a newly designed double dual core screw were evaluated by finite element analyses and biomechanical tests. All the screws had an outer diameter of 7 mm, and the biomechanical test consisted of a cantilever bending test in which a vertical point load was applied using a level arm of 45 mm. The boundary and loading conditions of the biomechanical tests were applied to the model used for the finite element analyses. The results showed that only the conical screws with fixed outer diameter and the new double dual core screw could withstand 1,000,000 cycles of a 50-500 N cyclic load. The new screw, however, exhibited lower stiffness than the conical screw, indicating that it could afford patients more flexible movements. Moreover, the new screw produced a level of stability comparable to that of the conical screw, and it was also significantly stronger than the other screws. The finite element analysis further revealed that the point of maximum tensile stress in the screw model was comparable to the point at which fracture occurred during the fatigue test. Copyright © 2014 IPEM. Published by Elsevier Ltd. All rights reserved.

Negative refraction using Raman transitions and chirality

Energy Technology Data Exchange (ETDEWEB)

Sikes, D. E.; Yavuz, D. D. [Department of Physics, 1150 University Avenue, University of Wisconsin at Madison, Madison, Wisconsin 53706 (United States)

2011-11-15

We present a scheme that achieves negative refraction with low absorption in far-off resonant atomic systems. The scheme utilizes Raman resonances and does not require the simultaneous presence of an electric-dipole transition and a magnetic-dipole transition near the same wavelength. We show that two interfering Raman tran-sitions coupled to a magnetic-dipole transition can achieve a negative index of refraction with low absorption through magnetoelectric cross-coupling. We confirm the validity of the analytical results with exact numerical simulations of the density matrix. We also discuss possible experimental implementations of the scheme in rare-earth metal atomic systems.

Integrated Microfibre Device for Refractive Index and Temperature Sensing

Directory of Open Access Journals (Sweden)

Sulaiman W. Harun

2012-08-01

Full Text Available A microfibre device integrating a microfibre knot resonator in a Sagnac loop reflector is proposed for refractive index and temperature sensing. The reflective configuration of this optical structure offers the advantages of simple fabrication and ease of sensing. To achieve a balance between responsiveness and robustness, the entire microfibre structure is embedded in low index Teflon, except for the 0.5–2 mm diameter microfibre knot resonator sensing region. The proposed sensor has exhibited a linear spectral response with temperature and refractive index. A small change in free spectral range is observed when the microfibre device experiences a large refractive index change in the surrounding medium. The change is found to be in agreement with calculated results based on dispersion relationships.

Refractive index depth profile in PMMA due to proton irradiation

International Nuclear Information System (INIS)

Szilasi, S.Z.; Rajta, I.; Budai, J.; Toth, Z.; Petrik, P.; Baradacs, E.

2006-01-01

Complete text of publication follows. During Proton Beam Writing the beam damage causes chain scissioning in the polymer resist material (e.g. PMMA (Polymethyl methacrylate)), producing smaller molecular weight chains. Hydrogen implantation also takes place at the end of range. Compaction of the sample has been observed too, which means that the sample density becomes higher at the places where proton irradiation occurred. Furthermore, P-beam Writing has been successfully used to create buried channel waveguides in PMMA [1], since proton irradiation increases the refractive index. There are two ways of fabricating waveguides using P-beam Writing, one of them applies direct micromachining of the high refractive index core followed by the coating of a lower refractive index cladding layer. In this application the refractive indices of the substrate, the core and the cladding have to be known, which should be homogeneous within the whole structure. The other method allows producing buried waveguides. In this case proton beam writing is used to modify the refractive index along the ion path in the sample, where most of the ion energy is deposited near the end of range also known as the Bragg peak. For polymers 10 -3 refractive index change has been reported, which is usually sufficient for forming waveguides. Those measurements of the refractive index change have been performed by the refracted near field technique. In this work we used ellipsometry, in order to measure the optical parameters of the P-beam treated sample near the surface, and along the Bragg curve. Ellipsometry measures the change in the polarization state of light occurring during reflection. This change is related to the quality of the reflecting surface (i.e. the physical structure, layer thicknesses, optical constants, surface roughness, etc.). >From these measurements the refractive index and the extinction coefficient can be determined rather accurately, which makes ellipsometry a powerful tool

Indications for and outcomes of tertiary referrals in refractive surgery

NARCIS (Netherlands)

Patryn, Eliza K.; Vrijman, Violette; Nieuwendaal, Carla P.; van der Meulen, Ivanka J. E.; Mourits, Maarten P.; Lapid-Gortzak, Ruth

2014-01-01

To review the spectrum of disease, symptomatology, and management offered to patients referred for a second opinion after refractive surgery. A prospective cohort study was done on all patients referred from October 1, 2006, to September 30, 2011, to a tertiary eye clinic after refractive surgery of

Modeling of mouse eye and errors in ocular parameters affecting refractive state

Science.gov (United States)

Bawa, Gurinder

Rodents eye are particularly used to study refractive error state of an eye and development of refractive eye. Genetic organization of rodents is similar to that of humans, which makes them interesting candidates to be researched upon. From rodents family mice models are encouraged over rats because of availability of genetically engineered models. Despite of extensive work that has been performed on mice and rat models, still no one is able to quantify an optical model, due to variability in the reported ocular parameters. In this Dissertation, we have extracted ocular parameters and generated schematics of eye from the raw data from School of Medicine, Detroit. In order to see how the rays would travel through an eye and the defects associated with an eye; ray tracing has been performed using ocular parameters. Finally we have systematically evaluated the contribution of various ocular parameters, such as radii of curvature of ocular surfaces, thicknesses of ocular components, and refractive indices of ocular refractive media, using variational analysis and a computational model of the rodent eye. Variational analysis revealed that variation in all the ocular parameters does affect the refractive status of the eye, but depending upon the magnitude of the impact those parameters are listed as critical or non critical. Variation in the depth of the vitreous chamber, thickness of the lens, radius of the anterior surface of the cornea, radius of the anterior surface of the lens, as well as refractive indices for the lens and vitreous, appears to have the largest impact on the refractive error and thus are categorized as critical ocular parameters. The radii of the posterior surfaces of the cornea and lens have much smaller contributions to the refractive state, while the radii of the anterior and posterior surfaces of the retina have no effect on the refractive error. These data provide the framework for further refinement of the optical models of the rat and mouse

REFractions: The Representing Equivalent Fractions Game

Science.gov (United States)

Tucker, Stephen I.

2014-01-01

Stephen Tucker presents a fractions game that addresses a range of fraction concepts including equivalence and computation. The REFractions game also improves students' fluency with representing, comparing and adding fractions.

Optimal Allocation of Static Var Compensator via Mixed Integer Conic Programming

Energy Technology Data Exchange (ETDEWEB)

Zhang, Xiaohu [ORNL; Shi, Di [Global Energy Interconnection Research Institute North America (GEIRI North America), California; Wang, Zhiwei [Global Energy Interconnection Research Institute North America (GEIRI North America), California; Huang, Junhui [Global Energy Interconnection Research Institute North America (GEIRI North America), California; Wang, Xu [Global Energy Interconnection Research Institute North America (GEIRI North America), California; Liu, Guodong [ORNL; Tomsovic, Kevin [University of Tennessee, Knoxville (UTK)

2017-01-01

Shunt FACTS devices, such as, a Static Var Compensator (SVC), are capable of providing local reactive power compensation. They are widely used in the network to reduce the real power loss and improve the voltage profile. This paper proposes a planning model based on mixed integer conic programming (MICP) to optimally allocate SVCs in the transmission network considering load uncertainty. The load uncertainties are represented by a number of scenarios. Reformulation and linearization techniques are utilized to transform the original non-convex model into a convex second order cone programming (SOCP) model. Numerical case studies based on the IEEE 30-bus system demonstrate the effectiveness of the proposed planning model.

Anatase phase stability and doping concentration dependent refractivity in codoped transparent conducting TiO{sub 2} films

Energy Technology Data Exchange (ETDEWEB)

Chen, T L [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Furubayashi, Y [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Hirose, Y [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Hitosugi, T [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Shimada, T [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan); Hasegawa, T [Kanagawa Academy of Science and Technology (KAST), Kawasaki 213-0012 (Japan)

2007-10-07

Nb{sub 0.06}Sn{sub x}Ti{sub 0.94-x}O{sub 2} (x {<=} 0.3) thin films were grown by a pulsed-laser deposition method with varying Sn concentration. Through a combinatorial technique, we find that Sn concentration can reach a maximum of about x = 0.3 while maintaining the stable anatase phase and epitaxy. A doping concentration dependence of the refractivity is revealed, in which refractivity reduction at a wavelength of {lambda} = 500 nm is estimated to be 12.4% for Nb{sub 0.06}Sn{sub 0.3} Ti{sub 0.64}O{sub 2} thin film. Sn doping induced band-gap blue shift can be contributed to the mixing of extended Sn 5s orbitals with the conduction band of TiO{sub 2}. Low resistivity on the order of 10{sup -4} {omega} cm at room temperature and high internal transmittance of more than 95% in the visible light region are exhibited for Nb{sub 0.06}Sn{sub x} Ti{sub 0.94-x}O{sub 2} thin films (x {<=} 0.2). Optical and transport analyses demonstrate that doping Sn into Nb{sub 0.06} Ti{sub 0.94}O{sub 2} can reduce the refractivity while maintaining low resistivity and high transparency.

Power-controlled transition from standard to negative refraction in reorientational soft matter.

Science.gov (United States)

Piccardi, Armando; Alberucci, Alessandro; Kravets, Nina; Buchnev, Oleksandr; Assanto, Gaetano

2014-11-25

Refraction at a dielectric interface can take an anomalous character in anisotropic crystals, when light is negatively refracted with incident and refracted beams emerging on the same side of the interface normal. In soft matter subject to reorientation, such as nematic liquid crystals, the nonlinear interaction with light allows tuning of the optical properties. We demonstrate that in such material a beam of light can experience either positive or negative refraction depending on input power, as it can alter the spatial distribution of the optic axis and, in turn, the direction of the energy flow when traveling across an interface. Moreover, the nonlinear optical response yields beam self-focusing and spatial localization into a self-confined solitary wave through the formation of a graded-index waveguide, linking the refractive transition to power-driven readdressing of copolarized guided-wave signals, with a number of output ports not limited by diffraction.

Babinet's principle in double-refraction systems

Science.gov (United States)

Ropars, Guy; Le Floch, Albert

2014-06-01

Babinet's principle applied to systems with double refraction is shown to involve spatial interchanges between the ordinary and extraordinary patterns observed through two complementary screens. As in the case of metamaterials, the extraordinary beam does not follow the Snell-Descartes refraction law, the superposition principle has to be applied simultaneously at two points. Surprisingly, by contrast to the intuitive impression, in the presence of the screen with an opaque region, we observe that the emerging extraordinary photon pattern, which however has undergone a deviation, remains fixed when a natural birefringent crystal is rotated while the ordinary one rotates with the crystal. The twofold application of Babinet's principle implies intensity and polarization interchanges but also spatial and dynamic interchanges which should occur in birefringent metamaterials.

Polymer microfiber bridging Bi-tapered refractive index sensor based on evanescent field

Science.gov (United States)

Lv, Ri-Qing; Wang, Qi; Wang, Bo-Tao; Liu, Yu; Kong, Lingxin

2018-05-01

A PDMS/graphene enhanced PMMA micro optical waveguide sensor is reported in terms of fabrication method and optical characteristics. The micro optical waveguide with a diameter of 6 μm and a length of 800 μm is used as the sensing probe to realize refractive index (RI) measurement suspended in NaCl solutions with different concentrations. Experimental results show that the refractive index sensing sensitivity can reach 2027.97 nm/RIU within the refractive index ranging from 1.3333-1.3426. Research results show that PMMA/graphene micro optical waveguide doped with PDMS is an excellent high sensitive sensing technology in refractive index detection field.

The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

KAUST Repository

Elbaz, Ayman M.; Zayed, M.F.; Samy, M.; Roberts, William L.; Mansour, Mohy S.

2015-01-01

The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work

Analysis of the hologram recording on the novel chloride photo-thermo-refractive glass

Science.gov (United States)

Ivanov, S. A.; Nikonorov, N. V.; Dubrovin, V. D.; Krykova, V. A.

2017-05-01

In this research, we present new holographic material based on fluoride photo-thermo-refractive glass(PTR) - chloride PTR glass. One of the benefit of this type of PTR glass is positive refractive index change. During this work, for the first-time volume Bragg gratings were recorded in this kind of material. The first experiments revealed that such gratings are mixed i.e. possess both absorption and phase components. Complex analysis shows that both refractive index and absorption coefficient are modulated inside the grating structure. We found out that at first there is no strict dependence of the refractive index change from dosage, but as we continue the process of thermal treatment - dependence is appear. Exposure influence on the refractive index change for this glass differs from fluoride one and shows some sort of saturation after the exposure of 4-6 J/cm2 . We distinguished refractive index change and absorption coefficient change and observed both behavior with increasing thermal treatment time. We found out that the increase of thermal treatment time results in the significant refractive index change. At the same time the absorption does `not practically change. It was found that maximum modulation of refractive index is comparable with fluoride PTR glass and achieves value of 1600 ppm. The modulation of absorption is equal to induced absorption caused by silver nanoparticles and depends from reading wavelength. Our study shows that almost all absorption is modulated inside the grating.

Diagnostics of gas behind shock waves by refractive optical techniques

International Nuclear Information System (INIS)

Blaha, J.

In a brief outline of optical methods for measuring neutral gas and plasma parameters, techniques are specifically dealt with based on the interferometric measurement of the refractive index. The investigation is shown of gas density changes in a shock tube using the optical Mach-Zehnder interferometer. While in a neutral gas the refractive index is determined by gas density, in a plasma the effects of all components, ie., electrons, ions and atoms are additive. The contributions to refraction from the various components may, in view of the different character and frequencies of the components, be resolved by measurement on more than one wavelength. (J.U.)

Beyond Snel's law: Refraction of a nano-beam of light

International Nuclear Information System (INIS)

Sun Wenbo; Videen, Gorden; Lin Bing; Hu Yongxiang; Fu Qiang

2011-01-01

The refraction of a localized narrow beam is significantly different from that of a plane wave. As the beam width decreases to be in the order of the wavelength, the refraction behavior deviates noticeably from Snel's law, and when the width of a light beam is smaller than about one fifth of the wavelength of the incident light, finite-difference time-domain simulations demonstrate that refraction becomes negligible. That is, the narrow light beam retains its propagation direction even after entering another medium at an oblique angle. The result reveals novel features of nano-beams and may have applications in precise biomedical measurement or micro optical device.

Observations of Anomalous Refraction with Co-housed Telescopes

Science.gov (United States)

Taylor, Malinda S.; McGraw, J. T.; Zimmer, P. C.

2013-01-01

Anomalous refraction is described as a low frequency, large angular scale motion of the entire image plane with respect to the celestial coordinate system as observed and defined by previous astrometric catalogs. These motions of typically several tenths of an arcsecond with timescales on the order of ten minutes are ubiquitous to drift-scan ground-based astrometric measurements regardless of location or telescopes used and have been attributed to meter scale slowly evolving coherent dynamical structures in the boundary-layer below 60 meters. The localized nature of the effect and general inconsistency of the motions seen by even closely spaced telescopes in individual domes has led to the hypothesis that the dome or other type of telescope housing may be responsible. This hypothesis is tested by observing anomalous refraction using two telescopes housed in a single roll-off roof observatory building with the expected outcome that the two telescopes will see correlated anomalous refraction induced motions.

Homodyne chiral polarimetry for measuring thermo-optic refractive index variations.

Science.gov (United States)

Twu, Ruey-Ching; Wang, Jhao-Sheng

2015-10-10

Novel reflection-type homodyne chiral polarimetry is proposed for measuring the refractive index variations of a transparent plate under thermal impact. The experimental results show it is a simple and useful method for providing accurate measurements of refractive index variations. The measurement can reach a resolution of 7×10-5.

Prevalence of refractive errors among junior high school students in ...

African Journals Online (AJOL)

Among school children, uncorrected refractive errors have a considerable impact on their participation and learning in class. The aim of this study was to assess the prevalence of refractive error among students in the Ejisu-Juabeng Municipality of Ghana. A survey with multi-stage sampling was undertaken. We interviewed ...

Vertical microbial community variability of carbonate-based cones may provide insight into ancient conical stromatolite formation

Science.gov (United States)

Bradley, James; Daille, Leslie; Trivedi, Christopher; Bojanowski, Caitlin; Nunn, Heather; Stamps, Blake; Johnson, Hope; Stevenson, Bradley; Berelson, Will; Corsetti, Frank; Spear, John

2016-04-01

Stromatolite morphogenesis is poorly understood, and the process by which microbial mats become mineralized is a primary question in microbialite formation. Ancient conical stromatolites are primarily carbonate-based whereas the few modern analogues in hot springs are either non-mineralized or mineralized by silica. A team from the 2015 International GeoBiology Course investigated carbonate-rich microbial cones from near Little Hot Creek (LHC), Long Valley Caldera, California, to investigate how conical stromatolites might form in a hot spring carbonate system. The cones rise up from a layered microbial mat on the east side of a 45° C pool with very low flow that is super-saturated with respect to CaCO3. Cone structures are 8-30 mm in height, are rigid and do not deform when removed from the pool. Morphological characterization through environmental scanning electronic microscopy revealed that the cone structure is maintained by a matrix of intertwining microbial filaments around carbonate grains. This matrix gives rise to cone-filaments that are arranged vertically or horizontally, and provides further stability to the cone. Preliminary 16S rRNA gene analysis indicated variability of community composition between different vertical levels of the cone. The cone tip had comparatively greater abundance of filamentous cyanobacteria including Leptolingbya, Phormidium and Isosphaera and fewer heterotrophs (e.g. Chloroflexi) compared to the cone bottom. This supports the hypothesis that cone formation may depend on the differential abundance of the microbial community and their potential functional roles. Metagenomic analyses of the cones revealed potential genes related to chemotaxis and motility. Specifically, a genomic bin identified as a member of the genus Isosphaera contained an hmp chemotaxis operon implicated in gliding motility in the cyanobacterium Nostoc punctiforme. Isosphaera is a Planctomycete shown to have phototactic capabilities, and may play a role in

Super-virtual refraction interferometry: an engineering field data example

KAUST Repository

Hanafy, Sherif M.

2012-10-01

The theory of super-virtual refraction interferometry (SVI) was recently developed to enhance the signal-to-noise ratio (SNR) of far-offset traces in refraction surveys. This enhancement of the SNR is proportional to √N and can be as high as N if an iterative procedure is used. Here N is the number of post-critical shot positions that coincides with the receiver locations. We now demonstrate the SNR enhancement of super-virtual refraction traces for one engineering-scale synthetic data and two field seismic data sets. The field data are collected over a normal fault in Saudi Arabia. Results show that both the SNR of the super-virtual data set and the number of reliable first-arrival traveltime picks are significantly increased. © 2012 European Association of Geoscientists & Engineers.

Super-virtual refraction interferometry: an engineering field data example

KAUST Repository

Hanafy, Sherif M.; Alhagan, Ola

2012-01-01

The theory of super-virtual refraction interferometry (SVI) was recently developed to enhance the signal-to-noise ratio (SNR) of far-offset traces in refraction surveys. This enhancement of the SNR is proportional to √N and can be as high as N if an iterative procedure is used. Here N is the number of post-critical shot positions that coincides with the receiver locations. We now demonstrate the SNR enhancement of super-virtual refraction traces for one engineering-scale synthetic data and two field seismic data sets. The field data are collected over a normal fault in Saudi Arabia. Results show that both the SNR of the super-virtual data set and the number of reliable first-arrival traveltime picks are significantly increased. © 2012 European Association of Geoscientists & Engineers.

The effect of instrument alignment on peripheral refraction measurements by automated optometer.

Science.gov (United States)

Ehsaei, Asieh; Chisholm, Catharine M; Mallen, Edward A H; Pacey, Ian E

2011-07-01

Interest in peripheral refraction measurement has grown in recent years in response to the insight it may provide into myopia development. In light of the likely increase in the clinical use of open-field autorefractors for peripheral refraction measurements, the question of instrument alignment and its impact on the accuracy of refraction measurements is raised. The aim of this study was to investigate the accuracy and precision when an open-field device was moved away from alignment with the corneal reflex towards the pupil margins, and to determine the optimum alignment position for peripheral refraction measurements. Autorefractions were performed on the right eyes of 10 healthy participants using the Shin-Nippon NVision-K 5001 autorefractor. At least five measurements were taken with the subject fixating a distance target in the primary position of gaze, and then four peripheral fixation targets located along the horizontal meridian (10° and 20° eccentricities in the nasal and temporal retina). Measurements were taken at seven alignment positions across the pupil for each fixation angle. Refraction was recorded as the spherical and cylindrical power. The central objective refraction achieved under cycloplegia based on the autorefraction result for the whole sample, ranged between -5.62 D and +1.85 D for the value of sphere, with a maximum astigmatism of -1.00 D. Acceptable alignment position range varied with fixation angle but was -1.0 to +1.0 mm in width across the pupil. Peripheral refraction measurements centred on the entrance pupil were as reliable as those centred on the corneal reflex. Our data suggest that for peripheral refraction measurements, there is a range of acceptable positions and operators can be confident of the validity of results obtained if aligned half way between the pupil centre and corneal reflex. The alignment becomes more critical at greater eccentricities. Ophthalmic & Physiological Optics © 2011 The College of Optometrists.

Improvement of visual acuity by refraction in a low-vision population.

Science.gov (United States)

Sunness, Janet S; El Annan, Jaafar

2010-07-01

Refraction often may be overlooked in low-vision patients, because the main cause of vision decrease is not refractive, but rather is the result of underlying ocular disease. This retrospective study was carried out to determine how frequently and to what extent visual acuity is improved by refraction in a low-vision population. Cross-sectional study. Seven hundred thirty-nine low-vision patients seen for the first time. A database with all new low-vision patients seen from November 2005 through June 2008 recorded presenting visual acuity using an Early Treatment Diabetic Retinopathy Study chart; it also recorded the best-corrected visual acuity (BCVA) if it was 2 lines or more better than the presenting visual acuity. Retinoscopy was carried out on all patients, followed by manifest refraction. Improvement in visual acuity. Median presenting acuity was 20/80(-2) (interquartile range, 20/50-20/200). There was an improvement of 2 lines or more of visual acuity in 81 patients (11% of all patients), with 22 patients (3% of all patients) improving by 4 lines or more. There was no significant difference in age or in presenting visual acuity between the group that did not improve by refraction and the group that did improve. When stratified by diagnosis, the only 2 diagnoses with a significantly higher rate of improvement than the age-related macular degeneration group were myopic degeneration and progressive myopia (odds ratio, 4.8; 95% confidence interval [CI], 3.0-6.7) and status post-retinal detachment (odds ratio, 7.1; 95% CI, 5.2-9.0). For 5 patients (6% of those with improvement), the eye that was 1 line or more worse than the fellow eye at presentation became the eye that was 1 line or more better than the fellow eye after refraction. A significant improvement in visual acuity was attained by refraction in 11% of the new low-vision patients. Improvement was seen across diagnoses and the range of presenting visual acuity. The worse-seeing eye at presentation may

Refraction and Ocular Biometry of Preschool Children in Shanghai, China.

Science.gov (United States)

Zhang, Luoli; He, Xiangui; Qu, Xiaomei; You, Xiaofang; Wang, Bingjie; Shi, Huijing; Tan, Hui; Zou, Haidong; Zhu, Jianfeng

2018-01-01

To investigate the refraction and ocular biometry characteristics and to examine the prevalence of refractive errors in preschool children aged 3 to 6 years in Shanghai, China. A school-based cross-sectional study was conducted in Jiading and Xuhui District, Shanghai, in 2013. We randomly selected 7 kindergartens in Jiading District and 10 kindergartens in Xuhui District, with a probability proportionate to size. The children underwent comprehensive eye examinations, including cycloplegic refraction and biometric measurements. Myopia, hyperopia, astigmatism were defined as spherical equivalent (SE) ≤ -0.50 D, SE ≥ +2.00 D, and cylindrical diopters ≤ -1.00 D. The mean SE for 3- to 6-year-old children was +1.20 D (standard deviation [SD] 1.05), and the mean axial length (AL) was 22.29 mm (SD 0.73). The overall prevalence of myopia and astigmatism was 3.7% and 18.3%, respectively. No difference in prevalence of astigmatism was found across age groups. There was a statistically significant association between lower cylindrical diopters and higher spherical diopters (Spearman's correlation: -0.21, P < 0.001). Chinese children aged 3 to 6 years in the Shanghai area were mostly mildly hyperopic, with a low prevalence of myopia. Refractive astigmatism for children may be relatively stable throughout the preschool stage. Astigmatism was significantly associated with refractive error.

Intraocular lens calculation adjustment after laser refractive surgery using Scheimpflug imaging.

Science.gov (United States)

Schuster, Alexander K; Schanzlin, David J; Thomas, Karin E; Heichel, Christopher W; Purcell, Tracy L; Barker, Patrick D

2016-02-01

To test a new method of intraocular lens (IOL) calculation after corneal refractive surgery using Scheimpflug imaging (Pentacam HR) and partial coherence interferometry (PCI) (IOLMaster) that does not require historical data; that is, the Schuster/Schanzlin-Thomas-Purcell (SToP) IOL calculator. Shiley Eye Center, San Diego, California, and Walter Reed National Military Medical Center, Bethesda, Maryland, USA. Retrospective data analysis and validation study. Data were retrospectively collected from patient charts including data from Scheimpflug imaging and refractive history. Target refraction was calculated using PCI and the Holladay 1 and SRK/T formulas. Regression analysis was performed to explain the deviation of the target refraction, taking into account the following influencing factors: ratio of posterior-to-anterior corneal radius, axial length (AL), and anterior corneal radius. The regression analysis study included 61 eyes (39 patients) that had laser in situ keratomileusis (57 eyes) or photorefractive keratectomy (4 eyes) and subsequent cataract. Two factors were found that explained the deviation of the target refraction using the Holladay 1 formula; that is, the ratio of the corneal radii and the AL and the ratio of corneal radii for the SRK/T formula. A new IOL adjustment calculator was derived and validated at a second center using 14 eyes (10 patients). The error in IOL calculation for normal eyes after laser refractive treatment was related to the ratio of posterior-to-anterior corneal radius. A formula requiring Scheimpflug data and suggested IOL power only yielded an improved postoperative result for patients with previous corneal laser refractive surgery having cataract surgery. No author has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. All rights reserved.

Dependency between light intensity and refractive development under light-dark cycles.

Science.gov (United States)

Cohen, Yuval; Belkin, Michael; Yehezkel, Oren; Solomon, Arieh S; Polat, Uri

2011-01-01

The emmetropization process involves fine-tuning the refractive state by altering the refractive components toward zero refraction. In this study, we provided light-dark cycle conditions at several intensities and examined the effect of light intensity on the progression of chicks' emmetropization. Chicks under high-, medium-, and low-light intensities (10,000, 500, and 50 lux, respectively) were followed for 90 days by retinoscopy, keratometry, as well as ultrasound measurements. Emmetropization was reached from days 30-50 and from days 50-60 for the low- and medium-intensity groups, respectively. On day 90, most chicks in the low-intensity group were myopic, with a mean refraction of -2.41D (95% confidence interval (CI) -2.9 to -1.8D), whereas no chicks in the high-intensity group developed myopia, but they exhibited a stable mean hyperopia of +1.1D. The medium-intensity group had a mean refraction of +0.03D. The low-intensity group had a deeper vitreous chamber depth and a longer axial length compared with the high-intensity group, and shifted refraction to the myopic side. The low-intensity group had a flatter corneal curvature, a deeper anterior chamber, and a thinner lens compared with the high-intensity group, and shifted refraction to the hyperopic side. In all groups the corneal power was correlated with the three examined levels of log light intensity for all examined times (e.g., day 20 r = 0.6 P light-dark cycles, light intensity is an environmental factor that modulates the process of emmetropization, and the low intensity of ambient light is a risk factor for developing myopia. Copyright © 2010 Elsevier Ltd. All rights reserved.

Autorefraction versus subjective refraction in a radially asymmetric multifocal intraocular lens

NARCIS (Netherlands)

Linden, J.W.M. van der; Vrijman, V.; El-Saady, R.; Meulen, I.J. van der; Mourits, M.P.; Lapid-Gortzak, R.

2014-01-01

PURPOSE: To evaluate whether the automated refraction (AR) correlates with subjective manifest (MR) refraction in eyes implanted with radially asymmetric multifocal intraocular lens (IOLs). METHODS: This retrospective study evaluated 52 eyes (52 patients) implanted with a radially asymmetric

Nature of the Refractive Errors in Rhesus Monkeys (Macaca mulatta) with Experimentally Induced Ametropias

Science.gov (United States)

Qiao-Grider, Ying; Hung, Li-Fang; Kee, Chea-su; Ramamirtham, Ramkumar; Smith, Earl L.

2010-01-01

We analyzed the contribution of individual ocular components to vision-induced ametropias in 210 rhesus monkeys. The primary contribution to refractive-error development came from vitreous chamber depth; a minor contribution from corneal power was also detected. However, there was no systematic relationship between refractive error and anterior chamber depth or between refractive error and any crystalline lens parameter. Our results are in good agreement with previous studies in humans, suggesting that the refractive errors commonly observed in humans are created by vision-dependent mechanisms that are similar to those operating in monkeys. This concordance emphasizes the applicability of rhesus monkeys in refractive-error studies. PMID:20600237

Corrective Techniques and Future Directions for Treatment of Residual Refractive Error Following Cataract Surgery

Science.gov (United States)

Moshirfar, Majid; McCaughey, Michael V; Santiago-Caban, Luis

2015-01-01

Postoperative residual refractive error following cataract surgery is not an uncommon occurrence for a large proportion of modern-day patients. Residual refractive errors can be broadly classified into 3 main categories: myopic, hyperopic, and astigmatic. The degree to which a residual refractive error adversely affects a patient is dependent on the magnitude of the error, as well as the specific type of intraocular lens the patient possesses. There are a variety of strategies for resolving residual refractive errors that must be individualized for each specific patient scenario. In this review, the authors discuss contemporary methods for rectification of residual refractive error, along with their respective indications/contraindications, and efficacies. PMID:25663845

Anomalous refraction of light through slanted-nanoaperture arrays on metal surface

International Nuclear Information System (INIS)

Kim, Myungji; Jung, Yun Suk; Xi, Yonggang; Kim, Hong Koo

2015-01-01

We report a nanoapertured metal surface that demonstrates anomalous refraction of light for a wide range of incident angles. A nanoslit aperture is designed to serve as a tilted vertical-dipole whose radiation pattern orients to a glancing angle direction to substrate. An array of such slanted nanoslits formed in a metal film redirects an incident beam into the direction of negative refraction angle: the aperture-transmitted wave makes a far-field propagation to the tilt-oriented direction of radiation pattern. The thus-designed nanoaperture array demonstrates the −1st order diffraction (i.e., to the negative refraction-angle direction) with well-suppressed background transmission (the zero-order direct transmission and other higher-order diffractions). Engineering the radiation pattern of nanoaperture offers an approach to overcoming the limits of conventional diffractive/refractive optics and complementing metasurface-based nano-optics

Refraction in exoplanet atmospheres. Photometric signatures, implications for transmission spectroscopy, and search in Kepler data