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HECTOR RENE VEGA CARRILLO (2016)
The response of a scintillation neutron detector of ZnS(Ag) with 10B was calculated, using the MCNPX Monte Carlo Code. The detector consists of four panels of polymethyl methacrylate (PMMA) and five thin layers of ~0.017 cm thick 10B+ZnS(Ag) in contact with the PMMA. The response was calculated for the bare detector and with different thicknesses of High-Density Polyethylene, HDPE, moderator for 29 monoenergetic sources as well as 241AmBe and 252Cf neutrons sources. In these calculations, the reaction rate 10B(n, α)7Li and the neutron fluence in the sensitive area of the detector 10B+ZnS(Ag) was estimated. Measurements were made at the Neutron Measurements Laboratory, Universidad Politécnica de Madrid, LMN-UPM, to quantify the detections in counts per second in response to a 252Cf neutron source separated 200 cm. The MCNPX computations were compared with measurements to estimate the efficiency of ZnS(Ag) for detecting the ? that is created in the 10B(n, α)7Li reaction. After validating new models with different geometries it will be possible to improve the detector response trying to achieve a sensitivity of 2.5 cps-ng252Cf comparable with the response requirements for 3He detectors installed in the Radiation Portal Monitors, RPMs. This type of detector can be considered an alternative to the 3He detectors for detection of Special Nuclear Material, SNM.
Producción Científica de la Universidad Autónoma de Zacatecas UAZ
HECTOR RENE VEGA CARRILLO (2016)
The Radiation Portal Monitors, RPM, detection systems, include sets of gamma and neutron
detectors, for Special Nuclear Materials, SNM, and detection, installed in border areas to
combat nuclear terrorism. Usually the employed neutron detectors are 3He proportional
counters, but due to the storage of 3He, reported since 2009, they have been made different
researches to find alternative detection, seeking similarity to those already installed
equipment with 3He features. The aim of this work was the study of a scintillation detector
ZnS(Ag) mixed with highly enriched 10B, 10B+ZnS(Ag). Using Monte Carlo methods,
MCNPX code, the response of the detector for neutrons was estimated, calculated the number
of 10B(n,α)7Li reactions for 29 monoenergetic neutron sources. It has been modeled under the
same measurement conditions to validate model. The detector was manufactured by
BridgePort. The detector response was estimated and the model was validated correctly
reproducing the detector response to counts per second. With these results we conclude this
detectors 10B+ZnS(Ag) are an interesting alternative for replace the 3He detectors. Progress is
being made to improve geometry and composition looking for the optimal detector equated to
the 3He detector.
Los sistemas de detección llamados “Radiation Portal Monitors” RPMs o Monitores de
Radiación tipo Pórtico habitualmente instalados en zonas fronterizas, son un conjunto de
detectores gamma y de neutrones; el uso de detectores gamma se justifica para el control de
presencia inadvertida de fuentes radiactivas y la colocación de detectores de neutrones para
la detección de los llamados Material Nuclear Especial (SNM), como el 239Pu, utilizado para
la construcción de armas de destrucción masiva. Los detectores de neutrones empleados
habitualmente son contadores proporcionales de 3He, pero debido a la escasez de 3He,
reportada desde 2009, se han hecho diferentes investigaciones para encontrar alternativas de
detección, buscando características similares a estos equipos ya instalados. El objetivo de
este trabajo fue el estudio de un detector de centelleo de ZnS dopado con Ag con una mezcla
con 10B de alto enriquecimiento, 10B+ZnS(Ag). Mediante Métodos Monte Carlo, código
MCNPX se ha estimado la respuesta de un detector de gran dimensión calculando las reacciones de 10B(n,α)7Li en el 10B para 29 fuentes monoenergéticas de neutrones y se ha
comparado con modelos anteriores. Se ha modelado en las mismas condiciones de medición
para validar modelo. El detector fue fabricado por la empresa BridgePort Instruments LLC,
se determinó las cuentas por segundo por cada nano gramo de 252Cf a 200 cm. Con estos
resultados se concluye que los detectores de 10B+ZnS(Ag) son una interesante alternativa a
los detectores de 3He. Se avanza para mejorar en geometría y composición en busca el
detector óptimo para ser equiparable a los de 3He.
Producción Científica de la Universidad Autónoma de Zacatecas UAZ
The holographic gratings on photopolymer films are studied by three different thicknesses for samples A, B, and C. The photopolymer emulsion is prepared with potassium dichromate and nickel (II) chloride hexahydrate in polyvinyl alcohol matrix. The evolution of diffraction efficiency is evaluated during holographic recording with and without voltaje as a function of energy exposure by changing the thickness. The curves of diffraction efficiency reach a peak when the films are continuously exposed to energy for a period of time. Sample B obtains the highest diffraction efficiency ©2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3569623]
A simple automatic control for applications of optical characterization of materials using the optical Z-scan technique is presented in this paper. The emphasis is placed in the automation process. For this purpose, a communication I/O port of a PCI-MIO-16E data acquisition card (from National Instruments) was used and the graphical programming language LabVIEW.
Se presenta un control automático simple para aplicaciones de caracterización óptica de materiales usando la técnica Z-scan. En particular, se enfatiza el proceso de automatización.Para este propósito, se usó un puerto de comunicación de I/O de una tarjeta de adquisición de datos PCI-MIO-16E (de National Instruments),así como el lenguaje de programación gráfica LabVIEW.
This volume is a compilation of papers that were presented at Symposium 6B, 'Advanced Structural Materials', of the XXIV International Materials Research Congress, organized in collaboration with Materials Research Society, which was held from August 16-20, 2015 in Cancun, Quintana Roo, Mexico. The symposium was devoted to fundamental and technological applications of structural materials, and continued the tradition of providing a forum for scientists from various backgrounds with a common interest in the development and use of structural materials to come together and share their findings and expertise. The 'Advanced Structural Materials' symposium has been held for the last twenty years, with the objective of presenting overviews and recent investigations related to advanced structural metallic, ceramic, composite, and concrete materials along with their industrial applications. The topics include innovative processing, phase transformations, mechanical properties, oxidation resistance, modeling and the relationship between processing, microstructure and mechanical behavior.
Cacti are thoroughly found all across the Mexican Territory. In the mountain ranges, and sierras. The cactus known as Opuntia ficus-indica grows naturally in the State of Mexico. Cacti have been used for millennia for multiple purposes. From culinary, to art involving other materials such as calcium oxide and salt. There are about 300 different species of cacti around the globe. About 100 are found in Mexico. Extensive research has been made and often, new and innovative uses are discovered. This paper features another use for Opuntia ficus-indica: Waterproofing on building surfaces exposed to the elements (i.e. Sunlight and humidity). This paper shows the process involving six stages using Opuntia ficus-indica combined with different natural materials were experimented with, and tested by evaluating their unique performance.
Mexican cacti have captivated the scientific community due their extraordinary characteristics and benefits.This research established a new way to use this ancestral plant as a substitute for other construction materials that given their industrial and technological processes have -in several cases- skyrocketed their costs, besides of being a constant hazard for the environment. Thus, by looking back how ancestors used to solve their construction needs, it would ultimately allow us to find better ways to protect the environment. Production process is analyzed; experimented with it; and its prominent characteristics analyzed derived from Opuntia ficus-indica extract combined with other natural materials to be then used it as a waterproofing material.
ARTURO OLIVARES PEREZ (2012)
A study of the diffraction efficiency parameter, of holographic gratings recorded with thin emulsion layers of corn syrup (Karo®) photosensitized with potassium dichromate salt is presented. This was posible by the interference produced by amplitude division setup using two wavelengths at 473 nm and 530 nm respectively. The maximum diffraction efficiency for corn syrup with potassium dichromate films was on average in the order of 4.0% at first diffraction order. The energy that was applied at blue light was 10 times less than that applied at green light. Evolution in the behavior profile from the diffraction efficiency parameter is presented as a function of relaxation time necessary to obtain major performance of these gratings made with peculiar sweetener. Holograms with this material do not require developing processes, because these samples develop by themselves. After of exposition with light laser, is necessary wait to stabilize the material 96 h, to protect the film against the environmental humidity.
Persons with intellectual disability (PWID) have fewer opportunities for enrolment in school programs and post-school employment than do their peers with typical development. Evidence suggests that attitude toward PWID is a main factor in either promoting or limiting better life conditions for this population. In this paper, the goal was to determine the cognitive information integration rules underlying the expectations of 174 special education teachers and students with regard to job training for PWID. In order to accomplish this goal, four factors (Gender, Severity of disability, Type of task, and Emotional traits) were orthogonally combined to implement a cognitive algebra study design. We obtained 48 experimental conditions, with each one presented as a scenario describing a PWID in a work training situation. Participants read these scenarios and were asked to judge the probability of the success of PWID with regard to learning the skills needed to complete the required work. Patterns of response allowed us to identify low, moderate, and high viewpoints with regard to participants’ judgments of predicted success. Personal factors (Emotional traits and Severity of disability) and the Type of task factor were considered the most important in influencing the participants’ judgment. These factors seemed to be integrated in a complex systematic cognitive pattern. Implications from this type of result with regard to PWID and work training are discussed in this paper.
"We present a simple design of a field effect transistor based on graphene nanoribbons, taking advantage of the metallic and semiconductor nature of nanoribbons with different widths. Such device could be constructed by using lithography techniques. The conductance of the proposed device is obtained by using the Kubo formula, assuming a strong damping due to the substrate and imperfections of the lattice. By removing the control electrodes, the design could also be used as an electrical resistance."