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Given the increasing necessity of simple, economical and reliable methods and instruments for performing quality tests of optical surfaces such as mirrors and lenses, in the recent years we resumed the study of the long forgotten Foucault knife-edge test from the point of view of the physical optics, ultimately achieving a closed mathematical expression that directly relates the knife-edge position along the displacement paraxial axis with the observable irradiance pattern, which later allowed us to propose a quantitative methodology for estimating the wavefronterror of an aspherical mirror with precision akin to interferometry.
In this work, we present a further improved digital image processing algorithm in which the sigmoidal cost-
function for calculating the transient slope-point of each associated intensity-illumination profile is replaced for
a simplified version of it, thus making the whole process of estimating the wavefront gradient remarkably more
stable and eficient, at the same time, the Fourier based algorithm employed for gradient integration has been
replaced as well for a regularized quadratic cost-function that allows a considerably easier introduction of the
region of interest (ROI) of the function, which solved by means of a linear gradient conjugate method largely
increases the overall accuracy and e ciency of the algorithm.
This revised approach of our methodology can be easily implemented and handled by most single-board mi-
crocontrollers in the market, hence enabling the implementation of a full-integrated automatized test apparatus,
opening a realistic path for even the proposal of a stand-alone optical mirror analyzer prototype.
Producción Científica de la Universidad Autónoma de Zacatecas UAZ
SALVADOR VENTURA GONZALEZ (2011)
We present the first measurements of transmission through the atmosphere
and thin films (SiN and Ti) at sub-millimeter and far-infrared wavelengths using
a Fourier transform spectrometer (FTS) built in the millimeter instrumentation
laboratory at the National Institute of Astrophysics, Optics and Electronics.
The principles of operation and the most important physical components of the
spectrometer are explained by splitting the instrument into four main stages: the
Martin Puplett interferometer, the bolometric detector, the readout electronics
and data acquisition system.
This thesis presents the design of software for the acquisition and subsequent
analysis of data, including control of the mechanical parts, the adequate data
storage of each experiment, frequency calibration and phase correction of the
spectrum, as well as the computation of the transmission in the different mediums
analyzed. These programs and their results are widely described in this
document. In addition, we designed a vacuum chamber to house the FTS in order
to have better control over the humidity environment in which the interferometer
is installed, as well as enabling more sensitive characterizations of different gases
as part of future spectroscopic investigations.
The results show the ability of the FTS to be an instrument that can complement
the astronomical receivers during the operation of the Large Millimeter
Telescope by providing the atmospheric transmission above the site. Furthermore,
the FTS can be used in the development of filters and materials suitable for use
in the fabrication of bolometric detectors.
Se presentan las primeras mediciones de la transmisión en la atmósfera así
como en películas delgadas (SiN y Ti) en longitudes de onda sub-milimétricas y
lejano infrarrojo mediante el uso de un espectrómetro de transformada de Fourier
(FTS, por sus siglas en inglés) construido en el laboratorio de instrumentación
milimétrica del Instituto Nacional de Astrofísica, Óptica y Electrónica.
Los principios de operación y los componentes físicos más importantes del
espectrómetro son explicados, dividiendo al instrumento en cuatro etapas principales:
el interferómetro Martin Puplett, el detector bolométrico, la electrónica de
lectura y el sistema de adquisición de datos.
El presente trabajo se basó principalmente en el diseño de rutinas para la
correcta adquisición y posterior análisis de los datos, incluyendo el control de los
elementos móviles, el adecuado almacenamiento de la información obtenida en
cada experimento, la calibración en frecuencia y la corrección en fase del espectro,
así como el cómputo de la transmisión en los diferentes medios analizados. Estos
programas y los correspondientes resultados son ampliamente descritos en este
documento. Además, se diseñó una caja de purgado con la finalidad de tener
mayor control sobre el medio donde se encuentra instalado el interferómetro, lo que
permitirá la futura caracterización de gases de distintos tipos como una aplicación
útil en investigaciones espectroscópicas.
Los resultados muestran la capacidad del FTS para ser un instrumento que
puede complementar los receptores astronómicos durante la operación del Gran
Telescopio Milimétrico en tanto que permite la caracterización atmosférica del
sitio. Además, el FTS puede ser usado en el desarrollo de filtros y materiales
susceptibles a utilizarse en la fabricación de detectores bolométricos.
"We studied the soft landing of Ni atoms on a previously damaged graphene sheet by means of molecular dynamics simulations. We found a monotonic decrease of the cluster frequency as a function of its size, but few big clusters comprise an appreciable fraction of the total number of Ni atoms. The aggregation of Ni atoms is also modeled by means of a simple phenomenological model. The results are in clear contrast with the case of hard or energetic landing of metal atoms, where there is a tendency to form mono-disperse metal clusters. This behavior is attributed to the high diffusion of unattached Ni atoms, together with vacancies acting as capture centers. The findings of this work show that a simple study of the energetics of the system is not enough in the soft landing regime, where it is unavoidable to also consider the growth process of metal clusters."
"Hydroxyapatite is a calcium phosphate in the apatite group. It has numerous applications due to its particular properties including the sorption of metallic ions. This makes it useful for the treatment of contaminated groundwater and for soil decontamination. The least expensive source of hydroxyapatite for synthesis is bovine bone, since this is a waste material. Vivianite is an iron phosphate which has received little study. Like hydroxyapatite, it has particular properties. This paper describes the method of obtaining these phosphates; calcium phosphate from bovine bone, and iron phosphate by synthesis. Also described are the methods of purifying the materials and characterization of these two phosphates by X-ray diffraction, infrared analysis, thermogravimetric and differential scanning calorimetric analysis, scanning electron microscopy, and surface area by the BET method. Physicochemical characteristics of hydroxyapatite obtained from bovine bone are described, and preliminary results are presented of an investigation into whether hydroxyapatite and iron phosphate are suitable as a permeable reactive barrier for the treatment of metallic and radionuclide contaminants."
Magnetic nanocomposites of Co-ferrite nanoparticles dispersed in silica matrix
(CoFe2O4/SiO2) have been prepared by the sol–gel technique using
tetraethylorthosilicate (TEOS) as precursor of silica, and metallic nitrates as precursors
of ferrite. Samples prepared in powder form have been dried at 100 °C for 3 h and
calcined for 2 h at temperatures between 500 and 1000 °C. Co-ferrite particles were
formed in the matrix pores and the nucleation of these particles was observed with the
increase in the calcining temperature. TEM measurements showed that the
nanoparticles had a fairly uniform morphology and an average particle size of
approximately 5 nm. The combination of different Co-ferrite concentrations and
calcining temperatures allowed to obtain samples with saturation magnetization ranging
from 0.7 to 21.8 emu/g.
This paper presents an analytical method to simultaneously determine the complex characteristic impedance and the pad parasitics of transmission lines fabricated on silicon. The method uses experimental two-port network parameters of two lines differing in length without the need of a reflect standard such as that required in TRL-like formulations. Furthermore, the losses associated with the silicon substrate are accurately considered using the experimentally determined complex propagation constant of the lines and three different configurations for the pad parasitics can be assumed. When using the extracted parameters in a model to represent transmission lines, excellent agreement between simulated and experimental data was achieved up to 50 GHz even for lines with lengths different to those used in the determination process.
We demonstrate experimentally the detection, in
a remote and noncontact manner, of human life signs using a
high-sensitivity pulsed laser vibrometer. The high surface displacement
detection sensitivity of the photo-electromotive-force
(photo-EMF) pulsed laser vibrometer, combined with its tolerance
to the presence and moderate temporal variations of optical
speckles in the light beams, allows the detection of human heartbeats,
breathing, and gross physical movement from essentially
any part of a human subject’s surface, even in the presence of
clothing, all the while without limiting the interrogation points to
specific locations like the chest and carotid areas. In contrast to
conventional Michelson interferometer-based laser vibrometers,
the photo-EMF pulsed laser vibrometer (PPLV) does not require
the use of retroreflective tapes or special electronic filtering to
retrieve vividly the biological subject’s life signs. Experimental
results demonstrating the detection of life signs from various parts
of biological subjects’ bodies, with or without the coverage of
clothing are presented. We also demonstrate the monitoring of a
human subject’s heart movements by interrogating the back of
his/her hand. Results from using PPLV to determine extremity
blood circulation at various levels of proximal occluding pressures
are also presented.
The preparation of magnetic latexes using styrene monomer was carried out via the miniemulsion polymerization technique. Magnetite
(Fe3O4), with an average size of 12 nmwas used as magnetic particles. An organic phasewas prepared dispersing the magnetite in styrene where
bis(2-ethyl, hexyl) sulphosuccinate (AOT) was used as dispersant. The dispersion was then miniemulsified in water using cethyltrimethyl
ammonium bromide (CTAB) as second emulsifier forming a stable emulsion. The miniemulsion polymerization was carried out at 60 ◦C and
was initiated with 2,2-Azobisisobutyronitrile (AIBN). The latexes obtained were characterized by X-ray diffraction (XRD), magnetometry
and transmission electron microscopy.
A planar epsilon-near-zero (ENZ) tunnel structure implemented on substrate integrated waveguide (SIW) technology is used to evaluate the complex dielectric permittivity of various materials. Design, optimization, and fabrication of the ENZ tunnel structure are explained. Simulations and measurements on various dielectric samples using the cavity perturbation technique of the proposed structure are presented. Measured values of the permittivity are in good agreement with standard values. Sensitivity analyses are performed on the ENZ structure and the conventional SIW cavity techniques. The proposed structure has very high sensitivity, which yields more accurate results when compared to other techniques, such as perturbation of conventional cavities.
"Conventional velocimetry has an intrinsic limitation because it yields 2D data, neglecting the third velocity component. For this reason, 3D-PIV has recently evolved as an area of research with success at the cost of increasing complexity in its methodology. The increased complexity and the limited optical access found in most industrial applications, meant that many of the 3D-PIV techniques, although of academic interest, cannot be used in practical industrial applications. For practical applications restricted viewing eliminates stereoscopic approaches. Lack of robustness and ease to perform an experiment make of conventional holography an unattractive option due to the fact that it involves a wet developing process, hence is very slow to yield results. However, its large depth of field and storing capacity makes it a technique that should, under the correct environment, be used. Scanning light-sheets are difficult to obtain for restricted optical access and high speeds, so they have not been tried in industrial conditions.
The required capabilities for 3D real-time measurement include the following three aspects: illumination of a volume rather than a plane, particle positioning in 3D from 2D camera information, and positioning calculation at low-magnification. Three-dimensional position and velocity information can be extracted by directly analyzing the diffraction patterns of seeding particles in imaging velocimetry using real-time CCD cameras. The Generalised Lorenz-Mie theory is shown to yield quantitative accurate models of particle position, such that it can be deduced with good accuracy from typical experimental particle images. Tunneling Velocimetry, the proposed technique to perform 3D velocity measurements, is able to provide the means to obtain particle images in a volume of interest rather than on a light sheet. Moreover, with this technique pressure and temperature measurements are feasible from the system background surface. The research reported here is concentrated in the experimental characterization of Tunneling Velocimetry and the problems involved with it. A discussion of the preliminary results is presented."