Virgilio Gonzalez

3D PRINTING OF ANISOTROPIC METAMATERIALS

Material properties in radio frequency and microwave regimes are limited due to the lack of molecular resonances at these frequencies. Metamaterials are an attractive means to realize a prescribed permittivity or permeability function, but these are often prohibitively lossy due to the use of ine-cient metallic resonators. All-dielectric metamaterials ofier excellent potential to overcome these losses, but they provide a much weaker interaction with an applied wave. Much design freedom can be realized from all-dielectric structures if their dispersion and anisotropy are cleverly engineered. This, however, leads to structures with very complex geometries that cannot be manufactured by conventional techniques. In this work, artiflcially anisotropic metamaterials are designed and then manufactured by 3D printing. The efiective material properties are measured in the lab and agree well with model predictions.

A PDA-based flexible telecommunication system for telemedicine applications

Technology has been used to deliver health care at a distance for many years. Telemedicine is a rapidly growing area and recently there are studies devoted to prehospital care of patients in emergency cases. In this work we have developed a compact, reliable, and low cost PDA-based telecommunication device for telemedicine applications to transmit audio, still images, and vital signs from a remote site to a fixed station such as a clinic or a hospital in real time. This was achieved based on a client-server architecture. A Pocket PC, a miniature camera, and a hands-free microphone were used at the client site and a desktop computer running the Windows XP operating system was used as a server. The server was located at a fixed station. The system was implemented on TCP/IP and HTTP protocol. Field tests have shown that the system can reliably transmit still images, audio, and sample vital signs from a simulated remote site to a fixed station either via a wired or wireless network in real time. The Pocket PC was used at the client site because of its compact size, low cost and processing capabilities.

Work in progress — Advising tool to improve the time for graduation and the transfer of students from a community college to engineering school

The objective of this work is to demonstrate a mechanism to improve the advising of students in a nontraditional environment. We applied two project management tools designed to help the students complete their degree plan sooner. The first tool provides a visualization map of course sequences, customized for each student, making advising adjustments that will optimize the time to obtain the degree under a constrained set of resources. The second tool collects information from multiple students through several semesters and can be used to identify bottlenecks in the curriculum. This article shows the application of the first tool in our university and in the local community college. The purpose is to optimize the time for graduation and align the students before transferring to our programs.

Developing a virtual laboratory for a communication and computer networking course

Educational institutions face financial challenges in maintaining and upgrading traditional physical laboratories. Moreover, university students have challenges in understanding the theoretical issues involved in communication and networking courses. This paper presents a new computer-aided laboratory to help the students to enhance the practical view of communication and networking systems using computer modelling and simulation and to replace a physical laboratory. The new laboratory was build using a component-based approach that integrates modelling and simulation tools, namely MATLAB, SIMULINK, VPI and OPNET. These components were integrated through the development of graphical user interface. Through this interface, the student navigates through experiments of the laboratory. The new laboratory curricula and interface were tested on students and their feedback showed that the students were satisfied. The students gave comments and suggestions for future improvements.

Architecture of a Dual-Stage Optical Label Switch Using Out-of-Band Wavelength and Code Optical Properties

A method of generating circuits in an optical network is optical multiple-protocol lambda switching (OMPlambdaS). For OMPlambdaS, the wavelength of the optical carrier is used as an out- of-band label to route data through the network without requiring periodic conversion to the electrical state. A method of adding a second dimension of optical encoding as an out-of-band label used for routing data through a label-switched network is presented. Combining wavelength and code multiplexing techniques generates an O3 circuit-switched network with a data capacity of up to 5.7 Tb/s on each point-to-point link in the network. The proposed architecture uses two stages to process and map labels for each bit transmitted through the network. The architecture and simulation results for the dual-stage optical label switch (DSOLS) are presented.

SDIm an introductory programming course with an ECE context

We report on the content of a pilot for a revised introductory programming course for ECE students titled “Software Design I, modified” (SDIm). SDIm incorporates pedagogical components from a course developed by our computer science department (CCS0) combined with an introduction to electric circuits and other ECE topics. SDIm is being developed in response to observations from several ECE faculty that many students, who attended the previously-offered courses in introductory C-programming had struggled with minor programming assignments throughout the ECE curriculum. The new course initially employs a simple interpreted programming environment based on “Python”. It uses simple small programs associated with mathematical and physical applications in order to illustrate the concepts of programming techniques combined with electric circuits. We expect that students will more quickly learn the fundamentals of and that they will effectively transfer these understandings to the study of C during the second half of the same course.

Towards an optimal placement of sensors in Wireless Sensor Networks with dynamic routing

In recent years, to ensure reliable monitoring and analysis of unknown and untested environments, practitioners have started using Wireless Sensor Networks (WSNs), i.e., collections of tiny disposable, low-power devices, equipped with programmable computing, multiple-parameter-sensing, and wireless communication capacity, able to measure ambient conditions to detect some objects located or events happening around. Hundreds to thousands of unattended sensors forming a WSN communicate with each other and with a central base-station that, in its turn, communicates with the user(s). When designing a WSN, it is critically important to place the sensors and set up routing protocols in such a way as to maintain connectivity and maximize the network lifetime. In this paper, we describe techniques that maximize the network lifetime under the constraint that connectivity is preserved.

Analysis of Phase noise of RF signals in Analog Fiber Optic Systems

Stability of phase is a critical issue in several applications, especially those that require the transmission of reference signals. A fiber optic system is considered the best medium for the transmission of reference signals due to its high bandwidth, superior stability and immunity to external interference. Even in fiber optic links, phase stability becomes an issue as the microwave frequency of operation is increased. We quantify phase noise in an analog fiber optic system and also study the effect of optical amplification on the noise. The amplifier is placed at three different positions in the link, to check for significant variations in phase noise when no other link parameters are changed. The study also examines how phase noise is affected by changing transmitter power and wavelength. Experimental results indicate fluctuations in phase noise greater than 10dB for different transmitter power outputs while wavelength changes produce very little effect on the noise. Optical amplification increases the average phase noise by 3 to 6dB depending on the location of the amplifier in the link. In addition to experimental studies, computer simulations using virtual photonics (VPI) software are performed to confirm experimental results.

Modified transfer matrix method model for a fiber Bragg grating strain sensor in polarization maintaining single mode optical fiber

Fiber-Bragg Gratings (FBG) for Structural Health Monitoring (SHM) have been studied extensively as they offer electrically passive operation, EMI immunity, high sensitivity, and multiple multiplexing schemes, as compared to conventional electricity based strain sensors. FBG sensors written in Polarization Maintaining (PM) optical fiber offer an additional dimension of strain measurement simplifying sensor implementation within a structure. This simplification however, adds complexity to the detection of the sensor’s optical response to its corresponding applied strain. We propose a modified Transfer Matrix Method model to simulate a fiber Bragg grating (FBG) in a polarization maintaining optical fiber. We study the effects of the reflected Bragg wavelength to the changes in shape of the optical fiber core waveguide and compare the results to the existing literature.

Detection and calculation of reflected spectral shifts in fiber-Bragg gratings (FBG) in polarization maintaining optical fiber

Fiber-Bragg Gratings (FBG) for Structural Health Monitoring (SHM) have been studied extensively as they offer electrically passive operation, EMI immunity, high sensitivity, and multiple multiplexing schemes, as compared to conventional electricity based strain sensors. FBG sensors written in Polarization Maintaining (PM) optical fiber offer an additional dimension of strain measurement simplifying sensor implementation within a structure. This simplification however, adds complexity to the detection of the sensor’s optical response to its corresponding applied strain. We propose a method that calculates spectral shifts caused by axial and traversal strains for PM FBG sensors. The system isolates the orthogonal propagating optical waves incident to the optical interrogators. The post-processing algorithm determines the wavelength shifts, and compares to a predetermined baseline then correlates the shift magnitudes to a respective strain. This exercise validates the method of optical detection and shift calculation of multi-axis sensors as an automated, integrated system.