58 publications from this institution
Electroencephalography (EEG) is a non-invasive and cost-effective method for studying the complexity of brain dynamics. In this study, we constructed Minimum Sp
White light scanning interference (WLSI) microscopes provide an accurate surface topography of engineered surfaces. However, the measurement accuracy is substantially reduced in surfaces with low-reflectivity regions or high roughness, like a surface affected by corrosion. An alternative technique called shape from focus (SFF) takes advantage of the surface texture to recover the 3D surface by using a focus metric through a vertical scan. In this work, we propose a technique called SFF-WLSI, which consists of recovering the 3D surface of an object by applying the Tenegrad Variance (TENV) focus metric to WLSI images. Extensive simulation results show that the proposed technique yields accurate measurements under different surface roughness and surface reflectivity, outperforming the conventional WLSI and the SFF techniques. We validated the simulation results on two real objects with a Mirau-type microscope. The first was a flat lapping specimen with Ra = 0.05 {\mu}m for which we measured an average value of Ra = 0.055 {\mu}m and standard deviation {\sigma} = 0.008 {\mu}m. The second was a metallic sphere with corrosion, which we reconstructed with WLSI versus the proposed SFF-WLSI technique, producing a better 3D reconstruction with less undefined depth values.
The integration of the Einstein-Maxwell equations for a spherically symmetric distribution of collapsing charged matter, is accomplished. Comparison with a
An exact solution of the Einstein-Maxwell theory is presented. The solution represents the metric of a radiating charged particle embedded in a de Sitter universe.
We propose a method for calculating a bandlimited diffuser with smooth spectrum in the Fresnel domain without any 2π phase ambiguities using the fractional Fourier transform. Such diffusers are necessary to avoid problems of speckles.
This paper proposes an approach to facilitate the process of individualization of patients from their medical images, without compromising the inherent confidentiality of medical data. The identification of a patient from a medical image is not often the goal of security methods applied to image records. Usually, any identification data is removed from shared records, and security features are applied to determine ownership. We propose a method for embedding a QR-code containing information that can be used to individualize a patient. This is done so that the image to be shared does not differ significantly from the original image. The QR-code is distributed in the image by changing several pixels according to a threshold value based on the average value of adjacent pixels surrounding the point of interest. The results show that the code can be embedded and later fully recovered with minimal changes in the UIQI index - less than 0.1% of different.
Watermarking is a process of embedding copyright information into an image to verify the ownership without any kind of corruption. In optical applications, the usage of diffusers is required to obtain a homogeneously distributed spectrum. However, the use of a diffuser in the input plane and the finite size of the sensor leave the recovered watermark with noise speckles. This noise affects negatively the verification process. We propose the usage of pseudo-random band-limited diffusers to place watermarks on optical images using a method based on Fourier-transform and random phase encoding algorithm. Such diffusers can help to recover a free-speckle watermark. The robustness to typical attacks is analyzed. Numerical results have shown its effectiveness.
We designed an adaptive filter based on empirical mode decomposition for the removal of fringes in an interference microscopy image. Promising results show the possibility for extended depth-of-field imaging.
No abstract is provided for this article.
Mental stress has become a prominent contemporary public health concern, exerting profound influences on both physical and mental well-being. Evaluating the psychological and physiological states under stress scenarios poses a challenging task. Detecting mental stress states is of utmost importance. In this study, we present a characterization approach to quantify the complexity of electrodermal activity during mental stress scenarios during a midterm exam to a group of university students, and use it to predict students' performance. We measure the complexity of wearable skin conductance signals using permutation entropy. The results enable discrimination of signal complexity into three groups based on exam grades: High, Mid, Low. These findings offer valuable insights for advancing the characterization of wearable signals to predict stressors in various real-world scenarios.
Tsamparlis et al. [3] have developed a systematic method for computing of the conformal algebra of 1+3 space-times. The proper CKV’s are
No abstract is provided for this article.
Air pockets in water distribution networks can cause various operational issues, as their expansion during drainage operations leads to sub-atmospheric conditions that may result in pipeline collapse depending on soil conditions and pipe stiffness. This study presents an analytical solution for calculating air pocket pressure, water column length, and water velocity during drainage operations in a pipeline with an entrapped air pocket and a closed upstream end. The existing system of three differential equations is reduced to two first-order nonlinear differential equations, enabling a rigorous analysis of the existence and uniqueness of solutions. The system is then further reduced to a single secondorder nonlinear ordinary differential equation (ODE), providing an intuitive framework for examining the physical behaviour of the hydraulic and thermodynamic variables. Furthermore, through a change of variables, the second-order ODE is transformed into a first-order linear ODE, facilitating the derivation of an analytical solution. The analytical solution is validated by comparing it with a numerical solution. Additionally, a practical application demonstrates the effectiveness of the developed tool in predicting the extreme pressure values in the air pocket during the water drainage process in a pipe, within a controlled environment.
view Abstract Citations (224) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Irradiation of Accretion Disks around Young Objects. I. Near-Infrared CO Bands Calvet, Nuria ; Patino, Alberto ; Magris, Gladis C. ; D'Alessio, Paola Abstract The effect of irradiation by the central star on the atmospheres of optically thick physically thin accretion disks around young objects are approximated, assuming radiative equilibrium. Irradiation is found to increase the temperature in the atmosphere of a viscous accretion disk relative to the case when only the viscous flux goes through it. Its effect on the near-infrared spectrum of the star-disk configuration is to decrease the strength of the absorption in the CO bands or turn them into emission, depending on the irradiation rate and on the mass accretion rate. As the stellar effect temperature increases for a given mass accretion rate, the disk surface temperature increases and the CO bands turn into emission. Observed spectra of young objects such as T Tauri stars, FU Ori subjects, and Herbig Be/Ae stars are in qualitative agreement with those predicted using the corresponding stellar parameters and disk mass accretion rates. It is inferred that the near-infrared CO bands can be used as indicators of the rate of mass accretion in the disk around young objects. Publication: The Astrophysical Journal Pub Date: October 1991 DOI: 10.1086/170618 Bibcode: 1991ApJ...380..617C Keywords: Accretion Disks; Carbon Monoxide; Near Infrared Radiation; Radiative Transfer; Stellar Atmospheres; A Stars; B Stars; Computational Astrophysics; Stellar Mass Accretion; Stellar Temperature; T Tauri Stars; Astrophysics; RADIATIVE TRANSFER; STARS: ACCRETION; STARS: PRE--MAIN-SEQUENCE full text sources ADS | data products SIMBAD (6) Related Materials (1) Part 2: 1992RMxAA..24...27C
In this work we study the use of a focus measure to improve the 3D reconstruction of low reflectivity microscopic samples using white light interference microscopy. Simulation and experimental results show the improved reconstruction.
