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Jorge Azorin-Lopez, Andres Fuster-Guillo, Marcelo Saval-Calvo, Higinio Mora-Mora, Juan Manuel Garcia-Chamizo
The use of visual information is a very well known input from different kinds of sensors. However, most of the perception problems are individually modeled and tackled. It is necessary to provide a general imaging model that allows us to parametrize different input systems as well as their problems and possible solutions. In this paper, we present an active vision model considering the imaging system as a whole (including camera, lighting system, object to be perceived) in order to propose solutions to automated visual systems that present problems that we perceive...
June 22, 2017: Sensors
Michael J Doughty
PURPOSE: To assess variability in endothelial cell density (ECD) estimates when polymegethism (variance in cell areas) is present. METHODS: Using noncontact specular microscope images of the corneal endothelium, 4 sets of 20 cases were selected, which included 200 cells and had coefficient of variation values of less than 30% (group 1), 31%-40% (group 2), 41%-50% (group 3), and over 50% (group 4). A stepwise analysis was undertaken, 20 cells at a time, of the ECD estimates when using different numbers of cells for the calculations...
June 13, 2017: Cornea
Hamid Gharaee, Siamak Zarei-Ghanavati, Reza Alizadeh, Mojtaba Abrishami
PURPOSE: To compare differences in the endothelial cells before and after photorefractive keratectomy (PRK) for myopia with refractive error graded mitomycin C (MMC) application. METHODS: In a prospective randomized clinical trial, forty-eight myopic patients referred to Khatam-al-Anbia Eye Hospital, Mashhad, Iran, for PRK. Patients were treated with PRK by a Bausch and Lomb Technolas 217z excimer laser (Bausch and Lomb, Rochester, NY). MMC was applied after PRK 5 s for each diopter of spherical equivalent myopic refractive error corrected...
June 13, 2017: International Ophthalmology
Fabian A Nutz, Markus Retsch
We introduce the in situ characterization of the dry sintering process of face-centred cubic colloidal crystals by two complementary techniques: thermal transport and photonic stopband characterization. Therefore, we employed time-dependent, isothermal laser flash analysis and specular reflectivity experiments close to the glass transition temperature of the colloidal crystal. Both methods yield distinctly different time constants of the film formation process. This discrepancy can be attributed to a volume- (photonic stopband) and interface-driven (thermal transport) sensitivity of the respective characterization method...
June 21, 2017: Physical Chemistry Chemical Physics: PCCP
A Blériot, E Martin, P Lebranchu, K Zimmerman, L Libeau, M Weber, B Vabres, I Orignac
The management of severe keratoconus requires corneal transplantation, for which the gold standard is deep anterior lamellar keratoplasty (DALK), preserving the healthy Descemet's membrane and endothelium. The safety and reproducibility of corneal cuts have been improved by the evolution of femtosecond lasers in refractive surgery, and femtosecond laser in DALK would seem to provide the same advantages over the manual method. In our retrospective study, we compare functional and anatomical results of femtosecond-assisted DALK versus manual trephination DALK in patients with keratoconus in stage 4 of the Krumeich classification...
June 7, 2017: Journal Français D'ophtalmologie
Toan Trung Nguyen, Sungjoon Lim
In this paper, a wide incidence angle-insensitive metamaterial absorber is proposed using eight-circular-sector (ECS). Under normal incidence, the proposed absorber shows high absorptivity at different polarizations due to its symmetric geometry. Under oblique incidence, zero-reflection conditions for transverse electric (TE) and transverse magnetic (TM) polarization are different. Nevertheless, the proposed absorber shows high absorptivity under oblique incidence of both TE and TM polarization due to ECS. The performance of the proposed absorber was demonstrated with full-wave simulation and measurements...
June 9, 2017: Scientific Reports
Susanne Goebels, Timo Eppig, Berthold Seitz, Nòra Szentmàry, Alan Cayless, Achim Langenbucher
PURPOSE: To investigate the effect of the severity of keratoconus on the corneal endothelium using specular microscopy. METHODS: Seven hundred and twelve eyes from the Homburg Keratoconus Center (HKC) database were included in this retrospective study. Corneal endothelium was evaluated using the Tomey EM-3000 specular microscope. Keratoconus-related topographic and tomographic data were obtained from Scheimpflug-based tomography (Oculus Pentacam(®) HR). Eyes were classified into stages 0 (healthy) to 4 (severe keratoconus) according to the Topographic Keratoconus Classification (TKC)...
June 9, 2017: Acta Ophthalmologica
Alexander E Minovich, Manuel Peter, Felix Bleckmann, Manuel Becker, Stefan Linden, Anatoly V Zayats
The normal mapping technique is widely used in computer graphics to visualize three-dimensional (3D) objects displayed on a flat screen. Taking advantage of optical properties of metasurfaces, which provide a highly efficient approach for manipulation of incident light wavefront, we have designed a metasurface to implement diffuse reflection and used the concept of normal mapping to control its scattering properties. As a proof of principle, we have fabricated and characterized a flat diffuse metasurface imitating lighting and shading effects of a 3D cube...
June 19, 2017: Nano Letters
Xuerui Wu, Shuanggen Jin, Junming Xia
Global Navigation Satellite Systems (GNSS) have been widely used in navigation, positioning and timing. Nowadays, the multipath errors may be re-utilized for the remote sensing of geophysical parameters (soil moisture, vegetation and snow depth), i.e., GPS-Multipath Reflectometry (GPS-MR). However, bistatic scattering properties and the relation between GPS observables and geophysical parameters are not clear, e.g., vegetation. In this paper, a new element on bistatic scattering properties of vegetation is incorporated into the traditional GPS-MR model...
June 5, 2017: Sensors
Dicle N Dövencioglu, Ohad Ben-Shahar, Pascal Barla, Katja Doerschner
Dynamic visual information facilitates three-dimensional shape recognition. It is still unclear, however, whether the motion information generated by moving specularities across a surface is congruent to that available from optic flow produced by a matte-textured shape. Whereas the latter is directly linked to the first-order properties of the shape and its motion relative to the observer, the specular flow, the image flow generated by a specular object, is less sensitive to the object's motion and is tightly related to second-order properties of the shape...
June 1, 2017: Journal of Vision
Li Sar Teoh, Siu Wan Foo, Vanessa Naseem Mansurali, Ee Ling Ang, Umi Kalthum Md Noh, Mae-Lynn Catherine Bastion
PURPOSE: To study the effects of intracameral phenylephrine 1.5% on corneal endothelial cell loss and morphological changes in patients who had uneventful phacoemulsification surgery. DESIGN: A double-blind randomized controlled trial. METHODS: This study comprised 295 patients who were randomized into the intracameral (ICM) mydriatic group or topical mydriatic group. Central corneal endothelial cell density (ECD), coefficient of variation (CV), and percentage of hexagonal cells were measured preoperatively and postoperatively at 1 week, 6 weeks, and 3 months with specular microscope...
June 1, 2017: Asia-Pacific Journal of Ophthalmology
Alfonso Rodriguez-Molares, Ali Fatemi, Lasse Lovstakken, Hans Torp
Acoustically hard objects such as bones, needles, or catheters are poorly visualized in conventional ultrasound images. These objects behave like acoustic mirrors and reflect sound in specific directions. Soft tissue and diffusive reflectors scatter sound in a broad range of directions. Conventional delayand- sum (DAS) beamforming is based on the assumption of a purely scattering domain with relatively weak reflectivity. We present an adaptive beamforming technique that takes into account the physics of specular reflection...
May 26, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Oualid Guechi, Louis Lhuillier, Naila Houmad, Christophe Goetz, Nadia Ouamara, Jean Marc Perone
OBJECTIVE: To assess objective and subjective visual outcomes achieved by patients with corneal endothelial dysfunction who have undergone surgical treatment with Descemet stripping automated endothelial keratoplasty (DSAEK). METHODS: A total of 40 eyes of 36 patients with corneal endothelial dysfunction underwent DSAEK. All were followed up for 1 year. Visual acuity (VA; logMAR), mean endothelial cell density (MCD; via noncontact specular microscopy), and topography assessment were performed at baseline (preoperatively)...
April 10, 2017: European Journal of Ophthalmology
Qamar Ul Islam, Muhammad Kamran Saeed, Mohammad Asim Mehboob
PURPOSE: To determine the age related changes in corneal morphological characteristics in normal healthy adult Pakistani population. METHODS: Four hundred and sixty-four eyes of 232 healthy volunteers with ages between 10 and 80 years of either gender were included. Corneal endothelial cell density (CED), morphology and central corneal thickness (CCT) were evaluated in each subject with non-contact specular microscope (SP-3000 P, Topcon Corporation, Japan) and average of three readings per eye was used for final analysis...
April 2017: Saudi Journal of Ophthalmology: Official Journal of the Saudi Ophthalmological Society
Peter Vangorp, Pascal Barla, Roland W Fleming
Most previous work on gloss perception has examined the strength and sharpness of specular reflections in simple bidirectional reflectance distribution functions (BRDFs) having a single specular component. However, BRDFs can be substantially more complex and it is interesting to ask how many additional perceptual dimensions there could be in the visual representation of surface reflectance qualities. To address this, we tested materials with two specular components that elicit an impression of hazy gloss. Stimuli were renderings of irregularly shaped objects under environment illumination, with either a single Ward specular BRDF component (Ward, 1992), or two such components, with the same total specular reflectance but different sharpness parameters, yielding both sharp and blurry highlights simultaneously...
May 1, 2017: Journal of Vision
Souheil Hadj Said, Mohamed Tamaazousti, Adrien Bartoli
The aim of Diminished Reality (DR) is to remove a target object in a live video stream seamlessly. In our approach, the area of the target object is replaced with new texture that blends with the rest of the image. The result is then propagated to the next frames of the video. One of the important stages of this technique is to update the target region with respect to the illumination change. This is a complex and recurrent problem when the viewpoint changes. We show that the state-of-the-art in DR fails in solving this problem, even under simple scenarios...
May 18, 2017: IEEE Transactions on Visualization and Computer Graphics
J Mendes, K J de Almeida, J L Neto, T C Ramalho, H A Duarte
B3LYP and MP2 calculations have been carried out to investigate tautomers and enantiomers of penicillamine (Pen). Their infrared (IR), ultraviolet (UV), circular dichroism (CD) and nuclear magnetic resonance (NMR) spectra were obtained at linear-response, time-dependent DFT (TD-DFT). IR, UV and NMR spectra cannot be used to identify Pen enantiomers, showing nearly equal spectral profiles. CD spectra, however, give rise to completely symmetric signals, forming a perfect specular image to each other. Distinct CD profiles were also obtained for Pen tautomers...
May 11, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Liangqi Zhang, Shiliang Yang, Zhong Zeng, Jie Chen, Lingquan Wang, Jia Wei Chew
In this study, alternative symmetry boundary implementations for the axisymmetric lattice Boltzmann (LB) method are proposed based on the nonequilibrium extrapolation and the direct extrapolation schemes. The proposed boundary schemes are directly implemented on the symmetry axis, and the postcollision distribution function and the macroscopic variables at the boundary nodes are extrapolated from the inner fluid nodes; thereby, the singularities arising at the symmetry axis (r=0) during the collision and the macroscopic variable calculations are completely avoided...
April 2017: Physical Review. E
Miguel A Pleitez, Otto Hertzberg, Alexander Bauer, Tobias Lieblein, Mathias Glasmacher, Hans Tholl, Werner Mäntele
We have recently reported infrared spectroscopy of human skin in vivo using quantum cascade laser excitation and photoacoustic or photothermal detection for non-invasive glucose measurement . Here, we analyze the IR light diffusely reflected from skin layers for spectral contributions of glucose. Excitation of human skin by an external cavity tunable quantum cascade laser in the spectral region from 1000 to 1245cm(-1), where glucose exhibits a fingerprint absorption, yields reflectance spectra with some contributions from glucose molecules...
May 1, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Reza Malehmir, Nasser Kazemi, Douglas R Schmitt
The study of the reflected acoustic waves plays an important role in our understanding of media. We provide an algorithm to propagate the ultrasonic bounded beam source and study its reflection from any horizontal and homogenous water-solid boundary. This algorithm implements a hybrid combination of the phase-advance wavefield continuation in the frequency domain and the complex analytic solution for the acoustic reflectivity. The peak amplitude of the specularly reflected beam is in agreement with the laboratory measured acoustic reflection from water-Aluminum and water-Copper alloy boundaries...
September 2017: Ultrasonics
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