2,281 research outputs found
INVESTIGATING 3D RECONSTRUCTION OF NON-COLLABORATIVE SURFACES THROUGH PHOTOGRAMMETRY AND PHOTOMETRIC STEREO
Abstract. 3D digital reconstruction techniques are extensively used for quality control purposes. Among them, photogrammetry and photometric stereo methods have been for a long time used with success in several application fields. However, generating highly-detailed and reliable micro-measurements of non-collaborative surfaces is still an open issue. In these cases, photogrammetry can provide accurate low-frequency 3D information, whereas it struggles to extract reliable high-frequency details. Conversely, photometric stereo can recover a very detailed surface topography, although global surface deformation is often present. In this paper, we present the preliminary results of an ongoing project aiming to combine photogrammetry and photometric stereo in a synergetic fusion of the two techniques. Particularly, hereafter, we introduce the main concept design behind an image acquisition system we developed to capture images from different positions and under different lighting conditions as required by photogrammetry and photometric stereo techniques. We show the benefit of such a combination through some experimental tests. The experiments showed that the proposed method recovers the surface topography at the same high-resolution achievable with photometric stereo while preserving the photogrammetric accuracy. Furthermore, we exploit light directionality and multiple light sources to improve the quality of dense image matching in poorly textured surfaces
Generalized second law of thermodynamics in modified FRW cosmology with corrected entropy-area relation
Using the corrected entropy-area relation motivated by the loop quantum
gravity, we investigate the validity of the generalized second law of
thermodynamics in the framework of modified FRW cosmology. We consider a
non-flat universe filled with an interacting viscous dark energy with dark
matter and radiation. The boundary of the universe is assumed to be the
dynamical apparent horizon. We find out that the generalized second law is
always satisfied throughout the history of the universe for any spatial
curvature regardless of the dark energy model.Comment: 9 pages, accepted for publication in Europhysics Letter
Generalized second law of thermodynamics in f(T) gravity
We investigate the validity of the generalized second law (GSL) of
gravitational thermodynamics in the framework of f(T) modified teleparallel
gravity. We consider a spatially flat FRW universe containing only the
pressureless matter. The boundary of the universe is assumed to be enclosed by
the Hubble horizon. For two viable f(T) models containing
and , we first
calculate the effective equation of state and deceleration parameters. Then, we
investigate the null and strong energy conditions and conclude that a sudden
future singularity appears in both models. Furthermore, using a cosmographic
analysis we check the viability of two models. Finally, we examine the validity
of the GSL and find that for both models it is satisfied from the early times
to the present epoch. But in the future, the GSL is violated for the special
ranges of the torsion scalar T.Comment: 16 pages, 10 figures, accepted by JCAP 201
Correlation between hepatitis B G1896A precore mutations and HBeAg in chronic HBV patients
Background: Hepatitis B virus (HBV) infection is an important health concern worldwide, with critical outcomes. Hepatitis B e antigen (HBeAg) negative chronic hepatitis B is frequently caused by a mutation (G1896A) in the hepatitis B virus (HBV) precore (PC) reading frame, which creates a stop codon, causing premature termination of the HBe protein. Objectives: This study aimed to investigate the G1896A PC mutation and its effect on HBeAg detection in chronic HBV patients. Patients and Methods: In this study, 120 chronic HBV patients neither vaccinated or who had benefited from immunoglobulin therapy, were recruited. The HBV-DNA was extracted from plasma and polymerase chain reaction (PCR) was performed. Positive PCR products were subjected to automated sequencing. The HBV serological markers hepatitis B s antigen (HBsAg), HBeAg were tested. Results: One hundred out of 120 (83.3%) patients were HBeAg negative and 100% were HBsAg positive. The comparison of nucleotide sequences with the reference sequence (Accession number: AB033559) in HBeAg negative patients showed that there was a high rate of mutations in G1896A (93.18%). Conclusions: This study indicates that the rate of G1896A mutation at the PC region among HBeAg negative patients, in the Golestan province of Iran, was similar to the average rate encountered in other parts of Iran. The PC stop codon mutation was detected in 93.18% of HBeAg negative patients. Further studies with larger sample sizes are required to elucidate the exact role of these mutations in the clinical course of chronic HBV infection. © 2015, Ahvaz Jundishapur University of Medical Sciences
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