Novel Approaches for Structural Health Monitoring

The thirty-plus years of progress in the field of structural health monitoring (SHM) have left a paramount impact on our everyday lives. Be it for the monitoring of fixed- and rotary-wing aircrafts, for the preservation of the cultural and architectural heritage, or for the predictive maintenance of long-span bridges or wind farms, SHM has shaped the framework of many engineering fields. Given the current state of quantitative and principled methodologies, it is nowadays possible to rapidly and consistently evaluate the structural safety of industrial machines, modern concrete buildings, historical masonry complexes, etc., to test their capability and to serve their intended purpose. However, old unsolved problematics as well as new challenges exist. Furthermore, unprecedented conditions, such as stricter safety requirements and ageing civil infrastructure, pose new challenges for confrontation. Therefore, this Special Issue gathers the main contributions of academics and practitioners in civil, aerospace, and mechanical engineering to provide a common ground for structural health monitoring in dealing with old and new aspects of this ever-growing research field

The Design, Fabrication, and Pressure Testing of a Low-Temperature Co-Fired Ceramic Electric Propulsion Thruster

Electric thrusters have been used for many years for orbital station-keeping and propulsion. As technology advances, smaller satellites are possible that require less thrust. The resulting miniature electric thrusters need low-weight and compact designs. This thesis specifies the design, fabrication, and testing of a thruster and its fluid delivery system designed for use with a micro-satellite weighing less than fifty kilograms. The advent of Micro-Electro-Mechanical Systems (MEMS) has sparked a new market with incredibly small scale designs. Using this technology with Low-Temperature Co-fired Ceramic (LTCC) materials has spawned the new distinction of Ceramic Micro-Electro-Mechanical Systems (C-MEMS). The thruster body is made entirely out of LTCC and it has embedded electrical connections and gas delivery channels integrated wholly within the thruster. These thrusters are tested inside a vacuum chamber system set up at Boise State University to simulate the pressure ranges seen in typical space applications. Plasma generation requires adequate gas pressures localized to the time-varying electric field inside of a vacuum. Prior testing for prototype thrusters at Boise State University proved that a single hole central gas injection point was not taking full advantage of the locations of high electric field intensity. This was the driving force to generate a computational fluid dynamics (CFD) model to simulate the pressure ranges as they applied to the areas of high electric field intensity. ANSYS Fluent was used as the modeling software to simulate the pressure ranges of the gas seen inside the thruster body. Experimental testing was done to verify the validity of the Fluent modeling. Electric field intensity was used as a driving force for the design of the gas outlets and their locations. The resulting thruster design demonstrated the successful ability to use LTCC as a substrate for a miniature thruster with fully embedded electrical components and gas channels. Experimental testing showed that a multiple hole gas injection concept created a higher localized pressure within the thruster cylinder, which increases plasma efficiency. The increase in localized pressure was as high as 49.8% larger than a single injection hole design. The experimental tests were also used as a method of validation for a CFD model that could be used in future iterations of the thruster to improve the locations of the thruster gas injection holes. Further work should be done with the external connections to the LTCC body to improve long-term durability. These results imply that LTCC is a viable medium for creating miniature thrusters for micro-satellites. The LTCC creates a hermetically sealed fluidic pathway for neutral gas to travel through, which reduces the size of the overall thruster considerably. A thruster made out of LTCC is both small in size and has excellent qualities to survive the harsh environment of space

Aeronautical Engineering: A continuing bibliography with indexes

This bibliography lists 512 reports, articles and other documents introduced into the NASA scientific and technical information system in April 1982

Aeronautical Engineering: A continuing bibliography (supplement 138)

This bibliography lists 366 reports, articles, and other documents introduced into the NASA scientific and technical information system in July 1981

Investigation into balancing of high-speed flexible shafts by compensating balancing sleeves

Engineers have been designing machines with long, flexible shafts and dealing with consequential vibration problems, caused by shaft imbalance since the beginning of the industrial revolution in the mid 1800’s. Modern machines still employ balancing techniques based on the Influence Coefficient or Modal Balancing methodologies, that were introduced in the 1930’s and 1950’s, respectively. The research presented in this thesis explores fundamental deficiencies of current trim balancing techniques and investigates novel methods of flexible attachment to provide a component of lateral compliance. Further, a new balancing methodology is established which utilizes trim balance induced bending moments to reduce shaft deflection by the application of compensating balancing sleeves. This methodology aims to create encastre simulation by closely matching the said balancing moments to the fixing moments of an equivalent, encastre mounted shaft. It is therefore significantly different to traditional methods which aim to counter-balance points of residual eccentricity by applying trim balance correction, usually at pre-set points, along a shaft. Potential benefits of this methodology are initially determined by analysis of a high-speed, simply supported, plain flexible shaft, with uniform eccentricity which shows that near elimination of the 1st lateral critical speed, (LCS) is possible, thereby allowing safe operation with much reduced LCS margins. Further study of concentrated, residual imbalances provides several new insights into the behaviour of the balancing sleeve concept: 1) a series of concentrated imbalances can be regarded simply as an equivalent level of uniform eccentricity, and balance sleeve compensation is equally applicable to a generalised unbalanced distribution consisting of any number of ii concentrated imbalances, 2) compensation depends on the sum of the applied balancing sleeve moments and can therefore be achieved using a single balancing sleeve (thereby simulating a single encastre shaft), 3) compensation of the 2nd critical speed, and to a lesser extent higher orders, is possible by use of two balancing sleeves, positioned at shaft ends, 4) the concept facilitates on-site commissioning of trim balance which requires a means of adjustment at only one end of the shaft, thereby reducing commissioning time, 5) the Reaction Ratio, RR (simply supported/ encastre) is independent of residual eccentricity, so that the implied benefits resulting from the ratio (possible reductions in the equivalent level of eccentricity) are additional to any balancing procedures undertaken prior to encastre simulation. The analysis shows that equivalent reductions of the order of 1/25th are possible. Experimental measurements from a scaled model of a typical drive coupling employed on an industrial gas turbine package, loaded asymmetrically with a concentrated point of imbalance, support this analysis and confirms the operating mechanism of balancing sleeve compensation and also it’s potential to vastly reduce shaft deflections/ reaction loads

The Public Service Media and Public Service Internet Manifesto

This book presents the collectively authored Public Service Media and Public Service Internet Manifesto and accompanying materials.The Internet and the media landscape are broken. The dominant commercial Internet platforms endanger democracy. They have created a communications landscape overwhelmed by surveillance, advertising, fake news, hate speech, conspiracy theories, and algorithmic politics. Commercial Internet platforms have harmed citizens, users, everyday life, and society. Democracy and digital democracy require Public Service Media. A democracy-enhancing Internet requires Public Service Media becoming Public Service Internet platforms – an Internet of the public, by the public, and for the public; an Internet that advances instead of threatens democracy and the public sphere. The Public Service Internet is based on Internet platforms operated by a variety of Public Service Media, taking the public service remit into the digital age. The Public Service Internet provides opportunities for public debate, participation, and the advancement of social cohesion. Accompanying the Manifesto are materials that informed its creation: Christian Fuchs’ report of the results of the Public Service Media/Internet Survey, the written version of Graham Murdock’s online talk on public service media today, and a summary of an ecomitee.com discussion of the Manifesto’s foundations

Towards the ethnography of filmic places: video-based research and found footage filmmaking in the anthropological investigation of Mexican migrant event video

This thesis offers an ethnography, with both audiovisual and written components, of the virtual places brought into being through the creation and consumption of event videos in a transnational community. It is intended as a contribution to the development of conceptual and methodological frameworks, which will allow anthropological engagements with vernacular audiovisual media that take into account their phenomenological properties as mimetically active assemblages. In San Francisco Tetlanohcan, Mexico, young parents often leave their children behind as they cross the border illegally, heading north to look for work. Event videos, made by videographers at rite of passage ceremonies and sent to the USA, are an important aspect of migrant life. This research draws on thinking in philosophy and film studies to conceptualise these videos as agents in a process of ‘filmic emplacement’ as their production and consumption bring into being imagined places and selves. The project combines methodological approaches borrowed from sensory ethnography with video editing techniques inspired by avant-garde filmmaking, in a dynamic evocation and exploration of these filmic places. Close participation in the creation and consumption of event videos combined with the movement of alternative ‘video messages’ across the border, gave the researcher a sense of these places. Shared screenings of found footage sequences materialised and refined that understanding. By co-opting the aesthetics of popular television, event videos transform that which they depict, bringing into being collectively created and experienced imagined places. This coherent and constant virtual realm allows for the creation and maintenance of kinship and fictive kinship relationships, despite separations over space and time. The video 900,000 Frames Between Us produced as part of this thesis uses the juxtaposition of ontologically diverse images and sounds to provide an audiovisual evocation of this ‘filmic home’. In addition to contributing to the anthropological understanding of San Francisco, this thesis suggests ways in which visual anthropologists might engage with and understand the mediated experiences of others

SynerCrete’18: interdisciplinary approaches for cement-based materials and structural concrete: synergizing expertise and bridging scales of space and time, vol. 2

info:eu-repo/semantics/publishedVersio

Visual Impairment and Blindness

Blindness and vision impairment affect at least 2.2 billion people worldwide with most individuals having a preventable vision impairment. The majority of people with vision impairment are older than 50 years, however, vision loss can affect people of all ages. Reduced eyesight can have major and long-lasting effects on all aspects of life, including daily personal activities, interacting with the community, school and work opportunities, and the ability to access public services. This book provides an overview of the effects of blindness and visual impairment in the context of the most common causes of blindness in older adults as well as children, including retinal disorders, cataracts, glaucoma, and macular or corneal degeneration