In-situ Transmission Electron Microscopy of Crystal Growth under MOVPE Conditions

The presented work introduces in-situ (scanning) transmission electron microscopy ((S)TEM) using a closed gas cell and heating TEM holder as a new experimental approach to investigate crystal growth on an atomic scale under metal-organic vapor phase epitaxy (MOVPE) comparable conditions. This bridges the gap from in-situ investigations performed in environmental TEMs (ETEMs) comparable to molecular beam epitaxy (MBE) towards the industrially relevant MOVPE processes. The setup enables the safe handling of toxic and pyrophoric gases, such as metal-organic precursors utilized in the growth of semiconductor materials. A proof of concept is given by thermal decomposition studies of the precursor molecules tertiary butyl phosphine (TBP) and trimethyl gallium (TMGa) and comparing these findings to those obtained in industrial reactor designs. Moreover, live observations of the growth of GaP nanowires in zinc blende structure by gold-catalyzed vapor-liquid-solid (VLS) growth using TBP and TMGa were performed, demonstrating the versatile capabilities of the technique and setup. Thereby, its dynamic was investigated, revealing unique insights into the growth process. Thermal precursor decomposition was analyzed by mass spectrometry utilizing an inline quadrupole mass spectrometer. The unimolecular and bimolecular reaction pathways and the respective decomposition temperatures of TBP and TMGa were revealed through methodical data analysis. These conclusions are compatible with results obtained in conventional reactor designs, and the setup has been shown to be an appropriate model for an MOVPE reactor on a micrometer scale. In-situ STEM observations of gold-catalyzed VLS growth of GaP nanowires using TBP and TMGa were performed under MOVPE-comparable conditions. In order to handle vast amounts of image data gathered during the STEM video recordings in a reasonable time, an automated MATLAB-based data evaluation was created. Important geometric properties of the nanowires, such as diameter, areas of the phase boundaries, as well as growth rate, are determined and synchronized with the experimental parameters, such as growth and imaging conditions. It was shown that the utilized growth conditions lead to diameter-independent growth kinetics. The precursor partial pressure and the ratio of the vapor-liquid and liquid-solid interfaces solely determined growth rates. A transition from group V to group III limited growth occurs that aligns with the growth kinetics observed in MOVPE. The confirmation of this transition at V/III ratios also observed in MOVPE, represents an essential difference to other in-situ studies performed in ETEMs under high vacuum conditions more comparable to MBE and highlights the importance of a setup capable of operating at MOVPE conditions. The dependence of the growth rate on the surface ratio has not been reported in the literature so far. Revealing this dependency was enabled through live monitoring of the growth process and the availability of many different wire geometries simultaneously under the same conditions. In dealing with nanowire growth rates, the introduced normalized growth rate as a fraction of growth velocity and surface ratio should be considered in the diffusion-limited regime. In addition, nanowire kink formation could be observed as it was happening. In agreement with the in-situ observations, post-growth investigations by scanning precession electron diffraction measurements confirmed that the formation of kinks could be related to twin formation. A substrate preparation method was developed to improve further the in-situ VLS growth observation that facilitates epitaxial growth in zone axis imaging conditions. The method is based on mechanical abrading the substrate, conserving a nanometer-thin gold layer deposited on its crystalline surface, and FIB transfer onto a microelectromechanical system chip. With the advantages of this technique, investigations with a predetermined zone axis orientation of growing nanowires become possible, opening the door to live imaging of crystal growth at atomic resolution. While the experimental proof is still pending, the advantages of this technique promise more profound insights into growth kinetics by examining, for example, the nucleation of crystalline layers or the formation of crystal defects. Thereby lays the foundation for crystal growth observations under MOVPE-comparable conditions in a TEM. Besides successfully demonstrating functionality and delivering new insights into the VLS growth process, this method promises a wide variety of possible avenues of investigation. Overall, the groundwork on closed gas cell in-situ TEM laid in this work is expected to lead to many new insights into the VLS growth process and deepen the understanding of the MOVPE process in general

Choreographing the extended agent : performance graphics for dance theater

Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.Includes bibliographical references (v. 2, leaves 448-458).The marriage of dance and interactive image has been a persistent dream over the past decades, but reality has fallen far short of potential for both technical and conceptual reasons. This thesis proposes a new approach to the problem and lays out the theoretical, technical and aesthetic framework for the innovative art form of digitally augmented human movement. I will use as example works a series of installations, digital projections and compositions each of which contains a choreographic component - either through collaboration with a choreographer directly or by the creation of artworks that automatically organize and understand purely virtual movement. These works lead up to two unprecedented collaborations with two of the greatest choreographers working today; new pieces that combine dance and interactive projected light using real-time motion capture live on stage. The existing field of"dance technology" is one with many problems. This is a domain with many practitioners, few techniques and almost no theory; a field that is generating "experimental" productions with every passing week, has literally hundreds of citable pieces and no canonical works; a field that is oddly disconnected from modern dance's history, pulled between the practical realities of the body and those of computer art, and has no influence on the prevailing digital art paradigms that it consumes.(cont.) This thesis will seek to address each of these problems: by providing techniques and a basis for "practical theory"; by building artworks with resources and people that have never previously been brought together, in theaters and in front of audiences previously inaccessible to the field; and by proving through demonstration that a profitable and important dialogue between digital art and the pioneers of modern dance can in fact occur. The methodological perspective of this thesis is that of biologically inspired, agent-based artificial intelligence, taken to a high degree of technical depth. The representations, algorithms and techniques behind such agent architectures are extended and pushed into new territory for both interactive art and artificial intelligence. In particular, this thesis ill focus on the control structures and the rendering of the extended agents' bodies, the tools for creating complex agent-based artworks in intense collaborative situations, and the creation of agent structures that can span live image and interactive sound production. Each of these parts becomes an element of what it means to "choreograph" an extended agent for live performance.Marc Downie.Ph.D

Biomechanical study of rigid ankle-foot orthoses in the treatment of stroke patients

Error on title page, date of award is 2021.Rigid Ankle-Foot Orthoses (AFOs) are commonly prescribed for stroke patients who exhibit equinovarus deformity as an orthotic intervention. The main purpose of prescribing a rigid AFO is to provide appropriate control of unwanted ankle and foot motions in any plane. To achieve the optimal effects of the AFO, appropriate stiffness and alignment optimisation (tuning) should be considered. The AFO provides moments (referred to as the orthotic moments) to control ankle motion. Orthotic moments are different from the moments generated by ground reaction forces, the later are known as total ankle moments. Reviewing the literature showed limited research in this area. The aims of this study are to investigate the biomechanical effects of using rigid AFO (before and after tuning) and to investigate the orthotic moment during walking in stroke patients. Gait data were collected from six stroke participants (2 females, 4 males) and six healthy participants (3 females, 3 males) using a Motekforce Link dual belt instrumented treadmill and a Vicon 3-dimensional motion analysis system. Each participant was fitted with a custom made rigid AFO instrumented using four strain gauges. Walking at a self-selected speed was investigated while wearing: (1) Standard shoes only (2) Rigid AFO with standard shoes (3) Rigid Tuned-AFO with standard shoes. Lower limb temporal-spatial, kinetic and kinematic parameters, and electromyographic activity (Delsys TrignoTM) of the knee muscles were compared among the test conditions. The orthotic moments were also quantified using the strain gauges data combined with gait analysis. Repeated measures ANOVA and Friedman’s ANOVA were used for statistical analysis. The rigid AFO showed immediate improvement in the temporal-spatial parameters and the kinematics and the kinetics of post stroke gait. Greater improvement in knee kinematics and kinetics was achieved when tuning the rigid AFO. The rigid AFO (before and after tuning) increased quadriceps muscle activity and reduced hamstring muscle activity compared to walking with standard shoes only. Tuning a rigid AFO further increased quadriceps muscle activity and reduced hamstring muscle activity compared to AFO before tuning. Strain gauges data combined with gait analysis can be used in evaluating the orthotic moment around the ankle in sagittal and frontal planes. Tuning a rigid AFO had no clear changes in the orthotic moment, and it did not alter the anatomical moments at the ankle joint in sagittal and at the subtalar joint in frontal plane.Rigid Ankle-Foot Orthoses (AFOs) are commonly prescribed for stroke patients who exhibit equinovarus deformity as an orthotic intervention. The main purpose of prescribing a rigid AFO is to provide appropriate control of unwanted ankle and foot motions in any plane. To achieve the optimal effects of the AFO, appropriate stiffness and alignment optimisation (tuning) should be considered. The AFO provides moments (referred to as the orthotic moments) to control ankle motion. Orthotic moments are different from the moments generated by ground reaction forces, the later are known as total ankle moments. Reviewing the literature showed limited research in this area. The aims of this study are to investigate the biomechanical effects of using rigid AFO (before and after tuning) and to investigate the orthotic moment during walking in stroke patients. Gait data were collected from six stroke participants (2 females, 4 males) and six healthy participants (3 females, 3 males) using a Motekforce Link dual belt instrumented treadmill and a Vicon 3-dimensional motion analysis system. Each participant was fitted with a custom made rigid AFO instrumented using four strain gauges. Walking at a self-selected speed was investigated while wearing: (1) Standard shoes only (2) Rigid AFO with standard shoes (3) Rigid Tuned-AFO with standard shoes. Lower limb temporal-spatial, kinetic and kinematic parameters, and electromyographic activity (Delsys TrignoTM) of the knee muscles were compared among the test conditions. The orthotic moments were also quantified using the strain gauges data combined with gait analysis. Repeated measures ANOVA and Friedman’s ANOVA were used for statistical analysis. The rigid AFO showed immediate improvement in the temporal-spatial parameters and the kinematics and the kinetics of post stroke gait. Greater improvement in knee kinematics and kinetics was achieved when tuning the rigid AFO. The rigid AFO (before and after tuning) increased quadriceps muscle activity and reduced hamstring muscle activity compared to walking with standard shoes only. Tuning a rigid AFO further increased quadriceps muscle activity and reduced hamstring muscle activity compared to AFO before tuning. Strain gauges data combined with gait analysis can be used in evaluating the orthotic moment around the ankle in sagittal and frontal planes. Tuning a rigid AFO had no clear changes in the orthotic moment, and it did not alter the anatomical moments at the ankle joint in sagittal and at the subtalar joint in frontal plane

Emotion and Stress Recognition Related Sensors and Machine Learning Technologies

This book includes impactful chapters which present scientific concepts, frameworks, architectures and ideas on sensing technologies and machine learning techniques. These are relevant in tackling the following challenges: (i) the field readiness and use of intrusive sensor systems and devices for capturing biosignals, including EEG sensor systems, ECG sensor systems and electrodermal activity sensor systems; (ii) the quality assessment and management of sensor data; (iii) data preprocessing, noise filtering and calibration concepts for biosignals; (iv) the field readiness and use of nonintrusive sensor technologies, including visual sensors, acoustic sensors, vibration sensors and piezoelectric sensors; (v) emotion recognition using mobile phones and smartwatches; (vi) body area sensor networks for emotion and stress studies; (vii) the use of experimental datasets in emotion recognition, including dataset generation principles and concepts, quality insurance and emotion elicitation material and concepts; (viii) machine learning techniques for robust emotion recognition, including graphical models, neural network methods, deep learning methods, statistical learning and multivariate empirical mode decomposition; (ix) subject-independent emotion and stress recognition concepts and systems, including facial expression-based systems, speech-based systems, EEG-based systems, ECG-based systems, electrodermal activity-based systems, multimodal recognition systems and sensor fusion concepts and (x) emotion and stress estimation and forecasting from a nonlinear dynamical system perspective

Full Proceedings, 2018

Full conference proceedings for the 2018 International Building Physics Association Conference hosted at Syracuse University

12th Man in Space Symposium: The Future of Humans in Space. Abstract Volume

The National Aeronautics and Space Administration (NASA) is pleased to host the 12th IAA Man in Space Symposium. A truly international forum, this symposium brings together scientists, engineers, and managers interested in all aspects of human space flight to share the most recent research results and space agency planning related to the future of humans in space. As we look out at the universe from our own uniquely human perspective, we see a world that we affect at the same time that it affects us. Our tomorrows are highlighted by the possibilities generated by our knowledge, our drive, and our dreams. This symposium will examine our future in space from the springboard of our achievements

Technology 2002: the Third National Technology Transfer Conference and Exposition, Volume 1

The proceedings from the conference are presented. The topics covered include the following: computer technology, advanced manufacturing, materials science, biotechnology, and electronics

Measurement of Elements in the Stratosphere

Balloon-borne winch system; stratospheric free radicals; stratospheric sounding; copper vapor lasers; ozone measurement; NO2 analysis; chlorine chemistry; trace elements; and ClO observations are discussed