Mechanism Design and Testing of a Self-Deploying Structure Using Flexible Composite Tape Springs

The detailed mechanical design of a novel deployable support structure that positions and tensions a membrane optic for space imagining applications is presented. This is a complex three-dimensional deployment using freely deploying rollable composite tape spring booms that become load bearing structural members at full deployment. The deployment tests successfully demonstrate a new architecture based on rolled and freely deployed composite tape spring members that achieve simultaneous deployment without mechanical synchronization. Proper design of the flexible component mounting interface and constraint systems, which were critical in achieving a functioning unit, are described. These flexible composite components have much potential for advancing the state of the art in deployable structures, but have yet to be widely adopted. This paper demonstrates the feasibility and advantages of implementing flexible composite components, including the design details on how to integrate with required traditional mechanisms

On Mass-Spring System Implementation in Cluster-Based MANETs for Natural Disaster Applications

Communication after natural disasters is paramount.Disasters such as earthquakes, hurricanes and tsunamis leavethe affected area reachable only to wireless devices. In suchconditions, Mobile Ad-hoc Networks (MANETs) play a criticalrole. The issue of MANETs communication backbone can beaddressed by self-organized cluster-based algorithms. The vir-tual backbone will maintain an efficient communication on theMANET, adapting to the dynamic topology changes thanks toits self-organized nature. Nevertheless, they do not take intoaccount the node’s mobility. If a node moves away from itsneighboring nodes, connectivity will be lost and thus, networksegmentation will occur. Therefore, it is fundamental to maintainthe connectivity and the communication between nodes whileexploring the area. In this paper, we propose the applicationof a mass-spring system on the Energy-Efficient Self-OrganizedAlgorithm (EESOA) for Disaster Area applications. Results willshow that our proposal performs best when deployment ofMANET’s nodes is dense while maintaining a connected network.ITESO, A.C

5GNOW: Challenging the LTE Design Paradigms of Orthogonality and Synchronicity

LTE and LTE-Advanced have been optimized to deliver high bandwidth pipes to wireless users. The transport mechanisms have been tailored to maximize single cell performance by enforcing strict synchronism and orthogonality within a single cell and within a single contiguous frequency band. Various emerging trends reveal major shortcomings of those design criteria: 1) The fraction of machine-type-communications (MTC) is growing fast. Transmissions of this kind are suffering from the bulky procedures necessary to ensure strict synchronism. 2) Collaborative schemes have been introduced to boost capacity and coverage (CoMP), and wireless networks are becoming more and more heterogeneous following the non-uniform distribution of users. Tremendous efforts must be spent to collect the gains and to manage such systems under the premise of strict synchronism and orthogonality. 3) The advent of the Digital Agenda and the introduction of carrier aggregation are forcing the transmission systems to deal with fragmented spectrum. 5GNOW is an European research project supported by the European Commission within FP7 ICT Call 8. It will question the design targets of LTE and LTE-Advanced having these shortcomings in mind and the obedience to strict synchronism and orthogonality will be challenged. It will develop new PHY and MAC layer concepts being better suited to meet the upcoming needs with respect to service variety and heterogeneous transmission setups. Wireless transmission networks following the outcomes of 5GNOW will be better suited to meet the manifoldness of services, device classes and transmission setups present in envisioned future scenarios like smart cities. The integration of systems relying heavily on MTC into the communication network will be eased. The per-user experience will be more uniform and satisfying. To ensure this 5GNOW will contribute to upcoming 5G standardization.Comment: Submitted to Workshop on Mobile and Wireless Communication Systems for 2020 and beyond (at IEEE VTC 2013, Spring

Sixth Aerospace Mechanisms Symposium

Design and development of mechanisms for spacecraft components - conference

ENGINEERING VISCOELASTIC BEHAVIOR OF CARBON FIBER REINFORCED POLYMER COMPOSITES WITH NANOPARTICLES FOR CONTROLLING DEPLOYMENT OF AEROSPACE STRUCTURES

The United States Air Force is focused on reducing mass and power consumption of spacecraft to increase their capabilities for space missions. Low mass and power consumption can be achieved by using composites with low density and high stiffness and utilizing few satellite components. One way to achieve reduced mass is by eliminating attendant deployment mechanisms consuming valuable power and mass allocations on spacecraft with deployable structures. Secondary systems are typically used to assist deployable space structures to ensure 100% success. A passively deployed space structure would be of great value to the Department of Defense and the commercial marketplace. Attaining a passively deployed space structure that is reliable, predictable and controllable to tailored design applications would serve this objective. The research presented herein was experimentally focused and involved incorporation of alumina nanoparticles (ANPs) dispersed into a three-ply composite laminate tape spring structure. The FlexLam composite was designed and fabricated for this class of tape spring deployable structures. A total of 51 tape springs were structurally tested on a unique, custom-designed test fixture with methodology to analyze their stress relaxation behavior in a coiled state for lengths of time varying from 1 hour to 6 months. A finite element model (FEM) with a Fortran subroutine was built and simulations were correlated with the structural deployment testing of 26 control tape springs and 25 ANP tape springs. The FEM simulation-predicted results correlated within 5% of the experimental testing structural results. A total of 5 epoxy samples (3 neat epoxy and 2 ANP epoxy) were fabricated and cut into 29 coupons for Dynamic Mechanical Analyzation (DMA) tests and Scanning Electron Microscope with Energy Dispersive X-ray Spectroscopy (SEM/EDS) examinations were also performed on 4 test coupons (3 ANP and 1 control) to characterize the microstructure of the composites, including the ANP dispersion and agglomeration. It was shown the ANP tape spring structures were able to retain 55% more tip force and experience less stress relaxation compared to the control tape springs. Future work is recommended in optimization of the composite and further development of the FEM simulation for improving structural behavior prediction

Adaptive indoor positioning system based on locating globally deployed WiFi signal sources

Recent trends in data driven applications have encouraged expanding location awareness to indoors. Various attributes driven by location data indoors require large scale deployment that could expand beyond specific venue to a city, country or even global coverage. Social media, assets or personnel tracking, marketing or advertising are examples of applications that heavily utilise location attributes. Various solutions suggest triangulation between WiFi access points to obtain location attribution indoors imitating the GPS accurate estimation through satellites constellations. However, locating signal sources deep indoors introduces various challenges that cannot be addressed via the traditional war-driving or war-walking methods. This research sets out to address the problem of locating WiFi signal sources deep indoors in unsupervised deployment, without previous training or calibration. To achieve this, we developed a grid approach to mitigate for none line of site (NLoS) conditions by clustering signal readings into multi-hypothesis Gaussians distributions. We have also employed hypothesis testing classification to estimate signal attenuation through unknown layouts to remove dependencies on indoor maps availability. Furthermore, we introduced novel methods for locating signal sources deep indoors and presented the concept of WiFi access point (WAP) temporal profiles as an adaptive radio-map with global coverage. Nevertheless, the primary contribution of this research appears in utilisation of data streaming, creation and maintenance of self-organising networks of WAPs through an adaptive deployment of mass-spring relaxation algorithm. In addition, complementary database utilisation components such as error estimation, position estimation and expanding to 3D have been discussed. To justify the outcome of this research, we present results for testing the proposed system on large scale dataset covering various indoor environments in different parts of the world. Finally, we propose scalable indoor positioning system based on received signal strength (RSSI) measurements of WiFi access points to resolve the indoor positioning challenge. To enable the adoption of the proposed solution to global scale, we deployed a piece of software on multitude of smartphone devices to collect data occasionally without the context of venue, environment or custom hardware. To conclude, this thesis provides learning for novel adaptive crowd-sourcing system that automatically deals with tolerance of imprecise data when locating signal sources

Modeling of High Pressure Confined Inflatable Structures

Safety of transportation tunnels is a top priority among transportation agencies and public administrators and a very important aspect in the daily operation of a tunnel system. However, it is always a challenge to create and integrate protection systems in existing tunnels to prevent or at least mitigate the occurrence of hazardous events such as spread of smoke or noxious fumes, flooding, among others. Typically there two ways for preventing or mitigating the occurrence of hazardous events: one is the implementation of permanent solutions and, the second one, is the use of temporary solutions. Permanent solutions usually have relatively high sealing efficiency due to their solid and rigid sealing mechanisms such as bulkheads and floodgates. However, they can be extremely expensive and sometimes difficult to build or install due to physical, economical or operational constraints. On the other hand, temporary solutions, which can be relatively low cost and easy to install, offer a temporary countermeasure while permanent repairs are implemented. The development of flexible structures, such as inflatable plugs for temporary solutions is becoming a viable alternative for protection of transportation tunnels and other similar critical civil infrastructure.;The Resilient Tunnel System (RTS) is a passive tunnel protection system developed at West Virginia University (WVU). This system is intended to prevent or minimize the damage induced by hazardous events by creating a compartment to contain the threat. The Resilient Tunnel System implements inflatable structures at specific locations of the tunnel to seal up the tunnel and create a compartment to isolate the compromised region. WVU has conducted several validation tests on full scale inflatable structures designed to mitigate flooding in an actual rail transportation tunnel and in specially built testing facilities. However, testing at full scale either in an actual tunnel or in specially built testing facilities, is a very complex and resource demanding task. It can take several iterations to achieve desired results which cannot be accurately predicted in advance. Therefore, the development of numerical models using Finite Element Analysis becomes imperative in order to: first, reproduce experimental work done at WVU using different prototypes at different scales; and then use the calibrated models as predicting tool that can anticipate the outcome of experiments and eventually reduce its number due to the intrinsic complexity and cost.;This dissertation aims to present the results of the development of Finite Element Models of confined inflatable structures designed to withstand flooding pressures. Models of different prototypes were created and analyzed in order to reproduce experimental results. Numerical results show that the adjusted models can reproduce experimental results, ranging from deployment, full pressurization and induced failure, with a great degree of accuracy providing a reliable predicting tool for evaluation of alternative configurations and parametric studies

Stents for transcatheter aortic valve replacement

Rheumatic heart disease (RHD) is the leading cause of aortic valve disease in the world. Surgery to repair or replace the diseased valves is the only means to save a patient's life once the disease becomes symptomatic. Transcatheter aortic valve replacement (TAVR) has revolutionised the treatment of age-related degenerative aortic valve disease, but is currently not suitable for the majority of RHD sufferers due to the rapid degeneration of flexible leaflet valves in younger patients, contraindications of commercial devices to regurgitant or non-calcific aortic valve disease, and also due to resource or funding limitations. The current research project aimed to develop and test novel compressible balloon-expandable stents suitable for patients with symptomatic rheumatic aortic valve disease, and which would allow for a percutaneous polymeric valve to be manufactured, be crimped onto balloon-based devices, and be expanded into a compliant or non-calcific native aortic valve. Several stent concepts were developed and evaluated using Finite Element Analysis (FEA) and two favoured concepts were selected for more complex FEA, in which the balloon was simulated using an Ogden material model, and rigorous testing. The stent material, a nickel-cobalt-chromium alloy, was modelled as an isotropic elasto-plastic material with isotropic hardening. The novel stent designs incorporated a native leaflet-mimicking crown shape for continuous leaflet attachment and mechanisms to anchor the stented valve within compliant aortic roots. The first of the favoured designs provided tactile location during delivery and anchored using self-expanding arms on a balloon-expandable frame of the same material ("self-locating stents"). The second design anchored using arms that protruded during deployment as a consequence of plastic deformation incurred during crimping ("expanding arm stents"). Prototypes were successfully manufactured through laser cutting and electropolishing and showed good surface quality. In vitro testing included determination of crimping and expansion behaviour and measurement of mechanical properties such as resistance to migration in the anatomy. Valve performance was evaluated through in vitro haemodynamics in a pulse duplicator and durability was tested in a high-cycle fatigue tester. Simulated use testing was performed using cadaveric animal hearts. Finally, valves were also implanted into the aortic valve position of pigs (in acute termination experiments) through a transapical approach in order to verify valve deployment behaviour and function in vivo, and determine the stent's ability to anchor in the native anatomy. Stents could be crimped to diameters below 6mm and deployed using commercial balloons and proprietary non-occlusive deployment devices. FEA simulations of stent crimping and deployment matched experimental behaviour well and provide a tool to optimise stent performance. Peak Von Mises stresses during deployment (1437 MPa and 1633 MPa for self-locating and expanding arm stents, respectively) were comparable to a "zig-zag" stent simulated for control purposes (1650 MPa). Radial strength, evaluated for expanding arm stents, was lower than the Control stent (116 N vs. 347 N). This design, although predicted to be safe under fatigue loading, had a lower fatigue safety factor than the Control stent. Stents resisted migration to forces of at least 22 N, which is four times greater than physiological loading on the valves. Polymeric valves incorporating the stents were constructed and demonstrated good in vitro haemodynamic performance (Effective Orifice Areas ≥2.0cm², ΔP<9 mmHg, regurgitation <6%) and durability of over 400 million cycles. Designs functioned as intended in simulated use tests. Valves constructed using self-locating stents could be successfully deployed without rapid pacing in eight of nine pigs, and valve position was correct in seven of these. Valves of expanding arm stents remained anchored in six of eight attempted implants in pigs. This study has demonstrated proof of concept for a novel balloon-expandable stent for a polymeric transcatheter heart valve that is capable of anchoring in a compliant native aortic valve

Aeronautical engineering: A continuing bibliography, supplement 122

This bibliography lists 303 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1980