Laser absorption phenomena in flowing gas devices

A theoretical and experimental investigation is presented of inverse Bremsstrahlung absorption of CW CO2 laser radiation in flowing gases seeded with alkali metals. In order to motivate this development, some simple models are described of several space missions which could use laser powered rocket vehicles. Design considerations are given for a test call to be used with a welding laser, using a diamond window for admission of laser radiation at power levels in excess of 10 kW. A detailed analysis of absorption conditions in the test cell is included. The experimental apparatus and test setup are described and the results of experiments presented. Injection of alkali seedant and steady state absorption of the laser radiation were successfully demonstrated, but problems with the durability of the diamond windows at higher powers prevented operation of the test cell as an effective laser powered thruster

Quantified Uncertainty in Thermodynamic Modeling for Materials Design

Phase fractions, compositions and energies of the stable phases as a function of macroscopic composition, temperature, and pressure (X-T-P) are the principle correlations needed for the design of new materials and improvement of existing materials. They are the outcomes of thermodynamic modeling based on the CALculation of PHAse Diagrams (CALPHAD) approach. The accuracy of CALPHAD predictions vary widely in X-T-P space due to experimental error, model inadequacy and unequal data coverage. In response, researchers have developed frameworks to quantify the uncertainty of thermodynamic property model parameters and propagate it to phase diagram predictions. In previous studies, uncertainty was represented as intervals on phase boundaries (with respect to composition) or invariant reactions (with respect to temperature) and was unable to represent the uncertainty in eutectoid reactions or in the stability of phase regions. In this work, we propose a suite of tools that leverages samples from the multivariate model parameter distribution to represent uncertainty in forms that surpass previous limitations and are well suited to materials design. These representations include the distribution of phase diagrams and their features, as well as the dependence of phase stability and the distributions of phase fraction, composition activity and Gibbs energy on X-T-P location - irrespective of the total number of components. Most critically, the new methodology allows the material designer to interrogate a certain composition and temperature domain and get in return the probability of different phases to be stable, which can positively impact materials design

Effects of PTSD and MDD Comorbidity on Psychological Changes during Surf Therapy Sessions for Active Duty Service Members

Together, posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) are debilitating and commonly comorbid; however, the effects of this comorbidity on psychological outcomes during exercise programs, such as surf therapy, have not been examined. This study compared changes in depression/anxiety and positive affect during surf therapy sessions between active duty service members with comorbid PTSD and MDD and those with either disorder alone. The study applied DSM-5 criteria to baseline self-report measures to assign probable disorder status, and used a longitudinal design involving repeated measurements to assess outcomes within 6 weekly sessions. Service members completed validated self-report questionnaires using the Patient Health Questionnaire-4 and the Positive Affect Schedule before and after each session. Within surf therapy sessions, both the comorbid and single disorder groups reported significant improvements in symptoms of depression/anxiety and positive affect. However, those with comorbid PTSD and MDD experienced significantly greater reductions in depression/anxiety (beta = -1.22, p = .028) and significantly greater improvements in positive affect (beta = 3.94, p = .046) compared with the single disorder group. Surf therapy appears to have global effects on psychological symptom reduction and may be a useful adjunctive intervention for the treatment of comorbid PTSD and MDD in both clinical and community health settings

Effects of PTSD and MDD Comorbidity on Psychological Changes during Surf Therapy Sessions for Active Duty Service Members

Together, posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) are debilitating and commonly comorbid; however, the effects of this comorbidity on psychological outcomes during exercise programs, such as surf therapy, have not been examined. This study compared changes in depression/anxiety and positive affect during surf therapy sessions between active duty service members with comorbid PTSD and MDD and those with either disorder alone. The study applied DSM-5 criteria to baseline self-report measures to assign probable disorder status, and used a longitudinal design involving repeated measurements to assess outcomes within 6 weekly sessions. Service members completed validated self-report questionnaires using the Patient Health Questionnaire-4 and the Positive Affect Schedule before and after each session. Within surf therapy sessions, both the comorbid and single disorder groups reported significant improvements in symptoms of depression/anxiety and positive affect. However, those with comorbid PTSD and MDD experienced significantly greater reductions in depression/anxiety (beta = -1.22, p = .028) and significantly greater improvements in positive affect (beta = 3.94, p = .046) compared with the single disorder group. Surf therapy appears to have global effects on psychological symptom reduction and may be a useful adjunctive intervention for the treatment of comorbid PTSD and MDD in both clinical and community health settings

Development of an Hexapod BioMicroRobot with Nafion-Pt IPMC microlegs

This paper presents an artificial locomotion servo-system for an insect like hexapod BioMicroRobot (BMR). This servo-system, programmed with VHDL code, will act as a driver in a RISC architecture microcontroller to reproduce insect tripod walking. An overview of the robot control system, in accordance with the insect displacement principle, is demonstrated with timing parameters. A control algorithm of the six legs driving the robot in any direction versus Pulse Width Modulation (PWM) is reviewed. BMR microlegs are built with cylindrical Nafion-Pt Ionomeric Polymer-Metal Composite (IPMC) that have 2.5 degrees of freedom. Specific fabrication process for one leg is exposed. Dynamic behavior and microleg characteristics have been measured in deionized water using a laser vibrometer. BMR current consumption is an important parameter evaluated for each leg. Hardware test bench to acquired measurement is presented. The purpose of this design is to control a BMR for biomedical goals like implantation in human body. Experimental results on the proposed legs are conclusive for this type of bioinspired BMR