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ALEJANDRO, MANUEL; Rodríguez, Julio; Aponte, Milca; Guerra-Vela, Claudio, Prof., UPR-HUMACAO, Departamento de Física y Electrónica
Especroscopía mecánica ac del concreto
Hemos desarrollado un método que nos permite deducir los valores de algunas constantes elásticas de muestras de concreto a partir de los valores de las frecuencias de resonancia inducidas en las muestras. El método, llamado espectroscopía mecánica ac, consiste en forzar oscilaciones en una barra cilíndrica de concreto, con frecuencias variables, hasta conseguir ondas estacionarias. Las oscilaciones pueden ser transversales, longitudinales o rotacionales. A partir de la determinación del modo de oscilación y su frecuencia de resonancia podemos deducir los valores de los módulos de Young y de sisalladura (“shear”) así como el de la relación de Poisson. En la presentación describiremos el sistema electromecánico de laboratorio con el que hicimos las medidas y el procedimiento para fabricar las muestras.
ALICEA MUÑOZ, EMILY; Nowakowski, Leszek, Prof., UPR-MAYAGÜEZ, Department of Physics Investigations of Single Pulses from Radio Pulsars
Discovered by Jocelyn Bell in 1967 as periodic radio signals, pulsars are now thought to be highly magnetized, rapidly rotating neutron stars that form as the result of the gravitational collapse of the core of a star which explodes as a supernova. Using the 305m ARECIBO Radiotelescope at 430MHz, we have recorded thousands of single pulses from several radio pulsars, and the data has been analyzed using Fortran and Mathcad programs specifically developed for this task. The main objective of this work is to determine the number and shape of components present in each average profile, and analyze pulse phenomena such as mode switching, nulling and drifting subpulses whenever these were present. The ultimate goal of single-pulse analysis is to determine how high in the pulsar magnetosphere the emission region is located. Preliminary results are presented.
ALICEA MUÑOZ, EMILY, UPR-MAYAGÜEZ, Department of Physics; Shirley, Eric L., NIST Physics Laboratory, Optical Technology Division
Diffraction Effects in SURF Beamline 3
Diffraction is the bending of light waves that pass through an aperture. If such light is projected onto a screen, there will be a diffraction pattern of bright and dark regions. If instead of a screen there is a detector, then diffraction can cause too little or too much radiation to fall on the detector, affecting measurements. This is the situation at the Beamline 3 at NIST’s Synchrotron Ultraviolet Radiation Facility (SURF). The main objective of this work consists of modeling the radiation field from the synchrotron that enters the beamline, by means of Schwinger’s formulas for the vector and scalar potentials. The analytic results can be realized in computer programs, in order to have a
mathematical model of the radiation field. This model can then be used in Fresnel diffraction calculations that reveal the intensity of the radiation field that actually reaches the detector. We hope that, through this work, one can determine what size aperture should be used in the beamline, and where it should be placed, in order to reduce stray light and minimize or otherwise account for the diffraction effects.
ANDÚJAR, NERITZA; Merced, Juan; Ramos, Idalia, Prof., UPR-HUMACAO, Department of Physics and Electronics
Designing and Transfering Micro-Systems Patterns to Low Temperature Co-Fired Ceramics
Low Temperature Co-Fired Ceramics (LTCC) are glass-ceramic composite materials. The usual composition includes alumina, a glass frit and an organic binder. LTCC is a good material to fabricate three-dimensional micro-systems. Jet Vapor Etching (JVE) is a technique that consists of dissolving the organic binder using a jet acetone and removing the glass and ceramic grains by momentum transfer. The JVE system has a computer controlled XYZ station to the hold the LTCC sample. The movements of the station define the pattern to be transferred to the tape. Currently, to produce the desired shape on the LTCC sample the program reads the set of XYZ coordinates that define the shape. The system moves the tape to the positions define by the coordinates and fire the acetone jet. We have improved the pattern transferring method with a program that reads bitmap images and transfer them to the tape. The program is written in language C++ with an interface in Visual Basic. This improvement allows us to reproduce micro-fluidic channels on the LTCC using a Cad software. We acknowledge the support from NSF-DMR 9872689, and the help from Patricio Espinoza, Prof. Jose O. Sotero, and Prof. Rogerio Furlan.
APONTE, MILCA; Alejandro, Manuel; Rodríguez, Julio; Guerra-Vela, Claudio, Prof., UPR-HUMACAO, Departamento de Física y Electrónica
Interpretación y Análisis de Datos Experimentales de Espectroscopía Mecánica AC
La espectroscopía mecánica ac de una muestra de concreto, permite deducir valores de algunas constantes elásticas de este material. Para hacerlo se requiere el uso de un modelo matemático. Este modelo existe en la literatura y permite establecer relaciones de causa-efecto entre variables físicas para explicar el comportamiento de una barra cilíndrica de concreto sujeta a oscilaciones forzadas. Las frecuencias de resonancia de los modos oscilatorios de la barra dependen de sus constantes elásticas así como de su geometría y dimensiones. En este trabajo presentaremos este modelo y el análisis matemático que hicimos de los datos obtenidos experimentalmente para deducir los valores de estas constantes.
BENSON, ELIXIA; Müeller, Rafael, Prof., UPR-HUMACAO, Department of Physics and Electronics Position Angle Measurements of Binary Stars
We are analizing data obtained at the 31-inch NURO telescope in Flagstaff, Arizona with the objectives of measuring separation and angle of binary star systems. This measurements are important to infer the mass of stars. Of special interest is calculating the effective focal length of the NURO telescope from this data since there is a very small discrepancy between reported values of the effective focal length of the 31-inch telescope. This difference can be very important when reporting separation of close binary systems.
CERSOSIMO, D.; Vega, R.; Ortiz, S.; Ortiz, M.; Pinto, N. J., Prof., UPR-HUMACAO, Department of Physics; Lu, J.; Johnson, A. T.; MacDiarmid, A. G., University of Pennsylvania
Electronic Field Influence on the Conductivity in an Organic Electronic Polymer-Building an all Polymer Field Effect Transistor (FET)
Electronic polymers like polyaceteylene and polyaniline have been extensively studied during the past three decades since their initial discovery in 1977. Much of the focus in the last few years has been in the search of new applications that exploit the advantages (like light weight) that electronic polymers possess over conventional metals. The objective of our work is to build an all polymer field effect transistor. We present our results of the electric field effect on the conductivity of polyaniline thin films prepared in-situ on a heavily doped Si/SiO2 wafer. In the in-situ method, the polymer is deposited on the Si wafer during the polymerization process and becomes the active material connecting the source and drain terminals in a conventional FET device configuration. A constant voltage connected across the source and drain terminals results in a current flow (Isd). Upon application of a negative gate bias voltage to the heavily doped portion of the Si wafer Isd increases suggesting p-type carriers as expected. A positive gate bias voltage does not increase or decrease Isd. Voltage-Current curves for different gate bias voltages are presented and show clear behavior characteristic of field effect transistors. We present a preliminary attempt to build an all polymer FET.
CONCEPCIÓN, ARLENE; Cersósimo, Darío, UPR-HUMACAO, Department of Physics and Electronics; McDiarmid, Alan G.; Lu, Jin, University of Pennsylvania-Philadelphia, Department of Chemistry; Pinto, Nicholas, Prof. UPR-HUMACAO, Department of Physics and Electronics
Electroless Deposition of Metals on Paper Using Line Patterning
In order to fabricate and market disposable electronic devices with minimum cost it is important to be able to use cheap materials and low labor cost methods in the manufacturing process. In the present work we report on successful deposition of metals within minutes under normal atmospheric conditions on common, commercially available “Xerox” paper. Using a computer with the appropriate software we design any desired pattern and print it on the above or similar paper using a standard laser printer. The process of depositing metal on the pattern was done using our method of “Line Patterning”[1] in combination with an electroless deposition technique. The technique was originally created on the basis of conductive polymer aqueous dispersions being more readily deposited on hydrophilic surfaces, such as overhead transparencies rather than to hydrophobic surfaces, such as a toner line printed on the transparency using a standard laser printer. After deposition of the metal, the electrical resistance measured along the metal line was about six orders of magnitude smaller than the non-metallized regions. The ability to deposit metals on regular “Xerox” paper that exhibit high conductivity, good resolution and without degradation of the paper substrate gives an enormous boost to the whole idea of cheap, flexible and disposable electronics.
CRESPO PÉREZ, GILBERTO; Rivera Castillo, Neftalí S., Prof., UPR-ARECIBO, Department of Computer Sciences
Command Interface Mathematica Package for Telescope Control
We have developed a Jlink Class for communicating with the MEADE LX200 telescope through a serial port connection. This class manages the serial port connection and the messages sent to and from the telescope using Mathematica. It is the goal of this project to create a Mathematica Package and provide all the functions necessary for controlling the MEADE LX200 telescope. The package will allow the user to takes full advantage of the functionality of Mathematica and provides a useful, powerful real-time telescope’s interface toolkit.
DIAZ, WANDA; Rodríguez, Emilio; Velázquez, Rafael; Arroyo, Edwin; Pantoja, Carmen, Prof., UPR-RÍO PIEDRAS, Department of Physics
Radio Jove Project at UPR-RÍO PIEDRAS
Jupiter, the largest planet of our solar system, is an intense source of radio waves at decametric wavelengths. It is possible to detect radio emission from Jupiter (and the Sun) by building a HF shortwave radio receiver. We will present the work we have done at the UPR, Río Piedras campus, in which we have constructed a radio receiver developed by Richard S. Flagg designed to be centered at 20.1 MHz. This receiver is connected to a dipole antenna and is setup at our campus. We will discuss observations made with this system of emission from Jupiter and the Sun. Radio emission from Jupiter is synchrothron emission and some is thought to be triggered by the transit of the jovian moon Io through the planet's magnetic field. We will discuss our use of jovian storms prediction tables that are available at http://www.astro.ufl.edu/juptablesdoc.html and the coordination of observations with other observers from around the world.
DIAZ, MELISSA; Ramos, Idalia, Prof. UPR-HUMACAO, Department of Physics and Electronics
The depth of the features produced on low temperature co-fired ceramics as a function of the acetone feed rate of jet vapor etching
Low Temperature Co-Fired Ceramic (LTCC) are glass-ceramic composite materials. The ceramic component is alumina and the glass mostly silica and lead oxides. LTCC is also known as green tape because of its color and flexibility before being fired or sintered. We use a Jet Vapor Etching System (JVE) to produce features on the LTCC. In JVE a jet of acetone impinges on the LTCC sample removing the composite material and produces features of different morphologies. The morphology is a function of the temperature, pressure, nozzle shape, and distance between the jet and sample. The LTCC sample is positioned on a sample holder on a computer controlled XYZ station. By controlling the speed of the stepper motors that move sample holder we accomplished to control the feed rate of acetone on the LTCC sample. The objective of this work is to systematically study the depth of the features produced on LTCC as a function of the acetone feed rate. The features studied are produced at temperatures of 48ºC, 50ºC, and 52ºC and at a pressure of 9.7 PSI. The distance from the sample to the nozzle was kept constant at 0.066 mm. The speed of the motors varied from 20micro-m/s to150 micro-m/s. This work was support by NSF-DMR- 9872689 and PR-AMP.
GARCÍA BERRÍOS, EDGARDO, UPR-CAYEY, Department of Chemistry; Vázquez, Neslie, UPR-CAYEY, SCORE Laboratory; Otaño-Rivera, Wilfredo, Prof., UPR-CAYEY, Department of Mathematics and Physics
Use of a Sputtering System for thin film Metal Deposition
The aim of this project was to build up a sputtering system to deposit a gold thin film, and to use these thin films to form metal contacts for testing the electrical properties of different devices. Thin films are thin coatings in the micrometer size that are deposited on a suitable substrate material. The sputtering process consists of an ion bombardment impact that establishes a train of collisions in a target. It is related to momentum transfer from energetic particles to the surface atoms of the target. The first short-term goal was to build up and test the deposition system and verify the integrity of the different vacuum components. A gold target will be used to deposit several thin films to test different deposition conditions. We analyzed the films to study the optical, electrical, magnetic, chemical, mechanical, and/or thermal properties, depending on the specific applications desired.
We already build up the sputtering system, we tested it and we found a mathematic function that describe the relationship between power and thickness (y=0.0558x-0.05,x=power,y=thickness). So, when we increased the power, the sputtering rate increased and the thickness of the thin films too. In a electronic microscope we saw a growth competition between the gold molecules.
GARCÍA SERRANO, LAIZA; Ramos, Idalia, Prof., UPR-HUMACAO, Department of Physics and Electronics
Study of Features Produced on Low Temperature Co-Fired Ceramics Using Jet Vapor Etching with Micro-Fabricated Silicon Tips
A typical Low Temperature Co-Fired Ceramic (LTCC) is composed of 40% Alumina (Al2O3), 45% glass and 15% organic compounds. This material is ideal for the fabrication of Meso-Scale Structures, Multi-Layered Circuits and for MEMS (Micro Electro-Mechanical Systems) applications. LTCC thermal, physical, mechanical and economical properties overcome those found in materials commonly used for electronics such as silicon. Jet Vapor Etching (JVE) consists of removing organics in the LTCC tape by using a jet of atomized acetone. The vapor flux through the nozzle is controlled by changes in acetone pressure and the temperature. The original nozzle was made of glass, the same material of the base, with a circular shape of approximately 25micro-m of diameter. In order to control the shape and size of the nozzle we used micro-fabricated silicon tips and attached them to the glass using epoxy glue. We used tips with squared openings measuring 250 micro-m, 220 micro-m, 150 micro-m and 50 micro-m. We studied the features produced for each nozzle tip at a constant pressure, temperature, and distance between the acetone jet and the LTCC tape. We have accomplished to incorporate micro-fabricated silicon nozzle tips for etching on LTCC ceramic tapes using JVE. It is possible now to characterize the feature size as a function of the nozzle size and shape. This work is supported by NSF-CIRE DMR-9872689 and PRAMP.
GONZÁLEZ RODRÍGUEZ, ROSANA, González, Luis A.; Lind, Miguel A.; Cersósimo, Juan C., Prof., UPR-HUMACAO, Department of Physics and Electronics
TROPICAL RAIN MEASUREMENTS FOR ACTS
A tropical propagation measurement campaign using Ka-band beacon signals on the ACTS (Advanced Communications Technology Satellites) had been proposed here in. The proposal is to carry out Ka-band propagation measurements and modeling in tropical areas. The overall objective of the current experiment is to gather propagation measurement data and generate models for the provisioning of Ka-band satellite services in tropical areas. The proposed measurement campaign is carried out at a site in the southeast of Puerto Rico Island where heavy rainfall is experienced since June of 2001, and an average rain accumulation of 1800 mm was registered. The measurement system includes a hybrid receiver and ancillary weather sensors. The project is managed by professor of the Department of Physics and Electronics of the University of Puerto Rico at HUMACAO.
GONZÁLEZ RODRÍGUEZ, ROSANA; Muller, Rafael, Prof.; Cersósimo, Juan C., Prof., UPR-HUMACAO, Department of Physics and Electronics
Photometry In Delta Scutti Variable Stars
Many stars change the brightness due to macroscopic phenomena. There exist many types, according to period and spectral type. These are known as variable stars. Stellar variability is not only a macroscopic property of a star but also a tool to unlock the physics of the variability process, through time serial monitoring. Time serial measurements of photometric variations of bright stars contain insight into the physical processes of stellar pulsation, winds, and mass loss in stars of wide range of spectral type across the HR diagram.
In order to date these types of stars we are observing in broadband V, R and I photometry. Additional observations of delta scutti stars, a class of variable stars located near or on the main sequence in the region of the late A and early F stars. Delta Scutti are a kind of variables that exhibit short period and instability in their light curves. Further observations will be useful to document the behavior of these short period stars. We are doing CCD observations of delta scutti stars using the 31-inch National Undergraduate Research Observatory (NURO) telescope at Flagstaff, Arizona.
NIEVES SANTIAGO, CHRISTIAN D., UPR-ARECIBO, Department of Computer Sciences, Marganian, Paul, Prof.; Rivera-Castillo, Neftalí S., Prof., UPR-ARECIBO, Department of Physics and Chemistry
User Interface for a Robotic Telescope Java Class
We have developed a Java Class (called "Telescope") for controlling the MEADE LX200 Telescope through a serial port connection. This class manages the serial port connection, the messages sent to and from the telescope through this connection, and provide all the functions necessary for controlling the MEADE LX200. It is the goal of this project to create a User Interface for this Telescope Java Class that takes full advantage of the class's functionality and provides a useful, powerful, easy to use tool to the user.
PÉREZ ANDÚJAR, ANGÉLICA; Weiyi, Jia, Prof., UPR-MAYAGÜEZ, Department of Physics Photoluminescence of Ca1-xBixTi1-xAlxO3:Pr+3
LEDs to emit efficiently white light are an ideal solid-state light source, in which lightening industries are interested. To produce white light, one of most important approach is to combine UV or blue LEDs with phosphors, which down-convert LED emission to longer wavelength light. In order to have good color rendering, tricolor (450/520/610nm) phosphors are suggested to use for such phosphor-LEDs. In this design, the emission wavelengths of LEDs can be selected in the range from 370 to 400nm.
In this work, Pr3+ doped CaTiO3 is investigated in order to produce red phosphors which can be efficiently excited in the above UV range. Strong red emission at 612nm from 1D2 to 3H4 transition of Pr3+ has been observed. Blue emission of 3P0 to 3H4 is thermally quenched at room temperature. Excitation spectrum showed that the 4f-5d absorption transition of Pr3+ was very strong and fell in the UV range from 250 to 390nm. However, the absorption in the spectral range 370-400nm is not as strong as the peak at 340nm. Efforts have then made to shift the peak position of absorption to the longer wavelength through substituting Ca2+ with Bi3+, and also substitute Ti4+ with Al3+ for charge compensation. It was found UV excitation efficiency was greatly enhanced near 390nm, which is an emission wavelength of a commercial GaInN LED. More detailed results will be reported.
The work is supported by NASA.
RODRÍGUEZ, JULIO B.; Alejandro, Manuel; Aponte, Milca; Guerra-Vela, Claudio, Prof., UPR-HUMACAO, Departamento de Física y Electrónica
El concreto como sólido microscópicamente complejo
El concreto es un material microscópicamente complejo por ser heterogéneo y anisotrópico. En su constitución intervienen cuatro componentes: agua, arena, grava y cemento. Las proporciones relativas de estos componentes dan lugar a concretos con propiedades diferentes luego del fraguado. Como no existen modelos microscópicos para el concreto, no sabemos cómo se relacionan sus propiedades macroscópicas con sus características atómicas o moleculares. El concreto se estudia experimentalmente a traves de métodos empíricos que producen gráficas y tablas de datos, sin modelos matemáticos entre variables físicas. Esto limita la capacidad para producir tipos de concreto de forma controlada, con características específicas, para cada aplicación. En nuestro proyecto hemos desarrollado una forma sencilla, precisa, rápida, no destructiva y económica que nos permite medir algunas de las constantes elásticas del concreto. Usando esta técnica podemos crear una base de datos que nos permita asociar los valores de las constantes elásticas medidas con las diferencias en composición de las muestras.
RODRÍGUEZ, HÉCTOR; Arce, Rafael, Prof., UPR-HUMACAO, Department of Physics and Electronics
Design and prototype implementation of an inexpensive/general purpose data logger
We designed, implemented and tested a small, low-budget, generic data logger using an Atmel AVR Series microcontroller. This device is intended for use in field studies and can work with a variety of sensors. The operation of the device can be programmed via the PC serial port. In the presentation, we shall discuss the design of the data-logger as well as the challenges encountered in the implementation. A prototype of the system will be presented.
RODRÍGUEZ CORDERO, MAGDALENA, UPR-ARECIBO, Department of Biology; Pérez Santos, Noemí J.; Fontán Navarro, Ludalis Z.; Seda Miró, Jasmine; Méndez, Abel, Prof., UPR-ARECIBO, Department of Physics and Chemistry
Planetary Microbial Ecology: Stability of Liquid Water on Mars
SAN MIGUEL, LIDARIS, UPR-RÍO PIEDRAS, Natural Sciences, Department of Physics; Morales, Flavia; Guadalupe, Ana, UPR- RÍO PIEDRAS, Department of Chemistry; Resto, Oscar; Fonseca, Luis, Prof., UPR-RÍO PIEDRAS, Department of Physics
Molecular Recognition using Multilayered Porous Silicon
Porous silicon multilayered structures are prepared by electrochemical anodization of silicon wafers and controlling the porosity of each layer with the proper anodization current density. The porous silicon structure works as a Bragg diffractor and the reflected light is used as the sensing signal. In order to obtain molecular recognition capabilities, the porous are filled with silica gel and using the molecular imprinting technique.
We report about the preparation of the multilayered structures, their optical properties and the process used to synthesize the silica gel.
SANTOS IGLESIAS; ESTHER ALEXANDRA; Nowakowski, Leszek, Prof., UPR-MAYAGÜEZ, Department of Physics
Single Pulse Studies with New Arecibo Data: Pulse Profile Stability and Mode Changing
This abstract presents an analysis of single pulses from 4 radio pulsars: PSR 0611+22, PSR 1237+25, PSR 1541+09 and PSR 1133+16. Mode switching PSR 0611+22 at 430 MHz has been confirmed: it has two stable forms and switches between tem on a time scale of several hundred pulsar periods. Mode switching in this pulsar may be interpreted in terms of difference in altitudes of the emitting region in the pulsar magnetosphere, as suggested previously by other authors.
Intensity dependence of the average profiles of PSR 0611+22 and PSR 1133+16 has also been confirmed. This dependence may be interpreted as different emission heights: components are moved away from the neutron star as they decrease in intensity. This would mean then, that in the magnetosphere of these pulsars one may speak of some sort of radius to intensity mapping.
We were able to observe the mode switching phenomenon of PSR 1237+25, which changes its average profile sporadically. The pulse profile spends from 10 to some 10,000 pulsar periods in the abnormal mode and then switches back to its normal mode (Sieber 1982). In the data we were able to observe short segments of approximately 20-30 consecutive pulses and also long segments of this second mode.
VÁZQUEZ MELÉNDEZ, SAMUEL, UPR-HUMACAO, Department of Physics; Esteban, E., Prof. UPR-HUMACAO & NASA Johnson Space Center, Houston
An Estimation of the Number of Cosmic Rays Impacting a Spaceship in the Earth-Mars Travel
Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE) are a major health concern in the human travel from the Earth to Mars. This is because both of these processes contain highly energetic protons that have a large penetration power in shielding and tissue. In this work, we present a Monte Carlo program to estimate the number of hits due to solar cosmic rays impacting a spaceship in a Earth-Mars travel. We proved our algorithms are correct. In fact, in a qualitative way, they reproduce the expected results.
VÁZQUEZ MELÉNDEZ, SAMUEL, UPR-HUMACAO, Department of Physics; Forman, W. R., Murray, S. S., Jones, C., Harvard/Smithsonian Center for Astrophysics, Cambridge, MA; Hardcastle, M. J., Physics, University of Bristol, Bristol, U; Kraft, Ralph P., Prof., Harvard/Smithsonian Center for Astrophysics, Cambridge, MA
Preliminary Results from an XMM-Newton Observation of the Nearby Radio Galaxy Centaurus A
We present preliminary results from a 24ks XMM-Newton observation of the nearby radio galaxy Centaurus A. Previous X-ray observations of this source have demonstrated its complex, multi-component X-ray morphology. In this work, we will present images and spectra of X-ray emission from the radio lobes, the hot ISM, and the active nucleus taken with the EPIC instrument. We have detected a bright X-ray enhancement along the edge of the SW radio lobe, and an excess of emission above that expected from the hot ISM in the interior of the lobe. Spectral analysis indicates that this material is considerably hotter then the ISM. We model this material as a thin shell of emission surrounding the radio lobe and as the result of compression and heating of the ISM. We demonstrate that the morphology of this emission is consistent with a shell rotated to our line of sight. No such enhancement is detected around the NE radio lobe. We present radial surface brightness, temperature, and abundance profiles of the hot ISM, and compare these results with our previous Chandra observations. We find that there is a small asymmetry in the distribution of the hot ISM around the nucleus. The emission is extended along an axis approximately perpendicular to the NE-SW axis of the radio components. Finally, we present spectra from the active nucleus, which is well described by a power law model with photon index 1.79, consistent with previous ASCA observations, and a narrow Fe K alpha line at 6.4 keV.