Analysis, design and implementation of front-end reconfigurable antenna systems (FERAS)

The increase in demand on reconfigurable systems and especially for wireless communications applications has stressed the need for smart and agile RF devices that sense and respond to the RF changes in the environment. Many different applications require frequency agility with software control ability such as in a cognitive radio environment where antenna systems have to be designed to fulfill the extendable and reconfigurable multi-service and multi-band requirements. Such applications increase spectrum efficiency as well as the power utilization in modern wireless systems. The emphasis of this dissertation revolves around the following question: Is it possible to come up with new techniques to achieve reconfigurable antenna systems with better performance?\u27 Two main branches constitute the outline of this work. The first one is based on the design of reconfigurable antennas by incorporating photoconductive switching elements in order to change the antenna electrical properties. The second branch relies on the change in the physical structure of the antenna via a rotational motion. In this work a new photoconductive switch is designed with a new light delivery technique. This switch is incorporated into new optically pumped reconfigurable antenna systems (OPRAS). The implementation of these antenna systems in applications such as cognitive radio is demonstrated and discussed. A new radio frequency (RF) technique for measuring the semiconductor carrier lifetime using optically reconfigurable transmission lines is proposed. A switching time investigation for the OPRAS is also accomplished to better cater for the cognitive radio requirements. Moreover, different reconfiguration mechanisms are addressed such as physical alteration of antenna parts via a rotational motion. This technique is supported by software to achieve a complete controlled rotatable reconfigurable cognitive radio antenna system. The inter-correlation between neural networks and cellular automata is also addressed for the design of reconfigurable and multi-band antenna systems for various applications.\u2

3D printed pneumatic soft actuators and sensors: their modeling, performance quantification, control and applications in soft robotic systems

Continued technological progress in robotic systems has led to more applications where robots and humans operate in close proximity and even physical contact in some cases. Soft robots, which are primarily made of highly compliant and deformable materials, provide inherently safe features, unlike conventional robots that are made of stiff and rigid components. These robots are ideal for interacting safely with humans and operating in highly dynamic environments. Soft robotics is a rapidly developing field exploiting biomimetic design principles, novel sensor and actuation concepts, and advanced manufacturing techniques. This work presents novel soft pneumatic actuators and sensors that are directly 3D printed in one manufacturing step without requiring postprocessing and support materials using low-cost and open-source fused deposition modeling (FDM) 3D printers that employ an off-the-shelf commercially available soft thermoplastic poly(urethane) (TPU). The performance of the soft actuators and sensors developed is optimized and predicted using finite element modeling (FEM) analytical models in some cases. A hyperelastic material model is developed for the TPU based on its experimental stress-strain data for use in FEM analysis. The novel soft vacuum bending (SOVA) and linear (LSOVA) actuators reported can be used in diverse robotic applications including locomotion robots, adaptive grippers, parallel manipulators, artificial muscles, modular robots, prosthetic hands, and prosthetic fingers. Also, the novel soft pneumatic sensing chambers (SPSC) developed can be used in diverse interactive human-machine interfaces including wearable gloves for virtual reality applications and controllers for soft adaptive grippers, soft push buttons for science, technology, engineering, and mathematics (STEM) education platforms, haptic feedback devices for rehabilitation, game controllers and throttle controllers for gaming and bending sensors for soft prosthetic hands. These SPSCs are directly 3D printed and embedded in a monolithic soft robotic finger as position and touch sensors for real-time position and force control. One of the aims of soft robotics is to design and fabricate robotic systems with a monolithic topology embedded with its actuators and sensors such that they can safely interact with their immediate physical environment. The results and conclusions of this thesis have significantly contributed to the realization of this aim

The Relationship between Substance Abuse and Suicide among Adolescents

Suicide, prominent in adolescents, presents a major public health problem. This study examined the relationship between substance abuse and suicide among adolescents after adjusting for socio-demographic, interpersonal violence, and mental health variables. Data were drawn from the Youth Risk Behavior Survey. Suicidal measures included ideation, plan, attempts, and severe attempts. Substance abuse, depression, purging, and forced sex were the major predictors. Our findings may be of value to educators, providers, and policymakers in helping to target teens contemplating suicide. To curb incidence of suicidal thoughts and behavior among teens, routine screenings for substance abuse in schools is recommended

The Relationship of Sexual Health Education and Sexual Health Risk Behavioral Outcomes among Florida Teens

We examined the relationship between sexual health education and sexual health risk behavioral outcomes among adolescents in Florida using Youth Risk Behavior Survey data from 2001 to 2013. Sexual health risk behavioral outcomes (reported condom use and alcohol and/or drug use during last intercourse) were first examined as a function of sexual health education. Multiple logistic regression analysis was then used to adjust for individual characteristics and behavioral risk factors when associating sexual health education with sexual health risk behavioral outcomes. Reported condom use was strongly associated with sexual education. However, the impact of sexual education was attenuated after adjusting for individual characteristics and behavioral risk factors. Alcohol and/or drug use during last intercourse was strongly associated with behavioral risk factors: forced sex and being sad/hopeless. Those receiving sexual education were 44% less likely to use alcohol and/or drugs. The results may be of value to policy makers in helping to profile and target teens at risk for sexually transmitted infections. These findings have important sexual health education implications and shed light on the role that individual health behaviors play in the health outcomes of adolescents

Study of impact on helicopter blade

This article presents a study of damage in structures that are similar to helicopter blade sections, subjected to an impact. These complex composite structures were impacted by a steel ball of 125 g at impact speed ranging from 30 to 130 m/s. This led to properly highlight the kinematics of the impact and to define the sequence of the damage’s mechanisms. An explicit FE model is also presented. The damage modelling of the roving is performed through a scale change. It allows a good representation of observed experimental behaviour. As the mesh density is low, it can be used for the modelling of a real structure

School Bullying and Health Risk Behavior Outcomes among Adolescents in Florida

Background: School bullying is a major social and public health threat as it presents a variety of developmental and psychological adolescent hazards that stretch into adulthood problems. Bullying victimization has been linked with a plethora of adverse health risk behavior outcomes. Purpose: To examine the association between bullying (in-person and electronic) and health risk behaviors related to school violence, mental and sexual health risks, substance abuse, and weight control practices. Methods: Data were drawn from the Florida Youth Risk Behavior Survey (YRBS). A 4-level variable was generated using the in-person and electronic bullying questions resulting in four mutually exclusive bullying categories. Logistic regression analyses, stratified by sex, examined the relationship between bullying and health risk behaviors related to violence, mental health, substance abuse, and weight-related factors after adjusting for race and grade. Results: Rates of victimization among students varied; 6.4% of students reported being bullied both in-person and electronically, 7.6% reported in-person bullying only, 4.4% reported being electronically bullied only, and 81.6% were uninvolved. Bullying was associated with almost all the health risk behavior outcomes studied with a few exceptions. Experiencing both kinds of bullying was most strongly associated with forced sexual intercourse for female adolescents as compared to suicide attempts for male adolescents. Discussion: Schools should provide safe and supportive environments and implement policies to prevent the long-term harmful effects of bullying

A 3D printed monolithic soft gripper with adjustable stiffness

Soft robotics has recently gained a significant momentum as a newly emerging field in robotics that focuses on biomimicry, compliancy and conformability with safety in near-human environments. Beside conventional fabrication methods, additive manufacturing is a primary technique to employ to fabricate soft robotic devices. We developed a monolithic soft gripper, with variable stiffness fingers, that was fabricated as a one-piece device. Negative pressure was used for the actuation of the gripper while positive pressure was used to vary the stiffness of the fingers of the gripper. Finger bending and gripping capabilities of the monolithic soft gripper were experimentally tested. Finite element simulation and experimental results demonstrate that the proposed monolithic soft gripper is fully compliant, low cost and requires an actuation pressure below -100 kPa

Analysis of Galileo E5 and E5ab code tracking

The world of global navigation satellite systems has been enhanced with several new or improved signals in space aiming to optimize accuracy, reliability, navigation solution, and interoperability between different constellations. However, such developments bring various challenges to the receivers' designers. For example, acquisition and tracking stages turn into more complex processes while handling the increasing bandwidth requires additional processing power. In this context, we study the code tracking of Galileo E5ab in a full band or of only one of its components, i.e., either E5a or E5b. More specifically, an architecture for tracking the E5 pilot channel as an AltBOC(15,10) or BPSK(10) modulation is introduced, and the performance of well-known discriminator types is analyzed using analytical derivations and simulations of linearity and stability regions, thermal noise tracking errors, multipath error envelopes and tracking thresholds. Different parameters, such as the front-end filter bandwidth, the early/late chip spacing, un-normalized and normalized discriminators, are taken into consideration. The results obtained are used to illustrate the main advantages and drawbacks of tracking the E5 signal as well as to help defining the main tracking loop parameters for an enhanced performanc

Reducing complexity and improving the reliability of frequency reconfigurable antennas

In this paper the complexity and reliability of frequency reconfigurable antennas are presented. A new approach for decreasing the complexity of reconfigurable antennas while maintaining the reliability of such structures is discussed. An example is given to prove the validity of the proposed approaches