Variability analysis of engine idle vibration

Vibration in motor vehicles is largely influenced by the engine and thus has become the focus of much automotive testing. Engine idle vibration is focused on since deviations in the vibration signature are prevalent at this operating condition. The objective of this thesis was to derive a best-practice method for the analysis of engine idle vibration. Variability of the engine vibration signatures was calculated through the implementation of multiple analysis techniques. These methods included: angle domain analysis, the fast Fourier transform, the discrete cosine transform, the moving average model, and the auto-regressive moving average model. Also included in the investigation were examinations of data normalization, detrending, and filtration. The results of the analyses were then evaluated with reference to the correlation between similar engines and the identification of outliers. It was found that the fast Fourier transform analysis technique provided the best overall results. The moving average model and the auto-regressive moving average models were also identified as methods that have great potential in vibration analysis but are limited by their computational intensity

Digital imaging technology assessment: Digital document storage project

An ongoing technical assessment and requirements definition project is examining the potential role of digital imaging technology at NASA's STI facility. The focus is on the basic components of imaging technology in today's marketplace as well as the components anticipated in the near future. Presented is a requirement specification for a prototype project, an initial examination of current image processing at the STI facility, and an initial summary of image processing projects at other sites. Operational imaging systems incorporate scanners, optical storage, high resolution monitors, processing nodes, magnetic storage, jukeboxes, specialized boards, optical character recognition gear, pixel addressable printers, communications, and complex software processes

Satellite provided customer premise services: A forecast of potential domestic demand through the year 2000. Volume 3: Appendices

Voice applications, data applications, video applications, impacted baseline forecasts, market distribution, potential CPS (customers premises services) user classes, net long haul forecasts, CPS cost analysis, overall satellite forecast, CPS satellite market, Ka-band CPS satellite forecast, nationwide traffic distribution model, and intra-urban topology are discussed

Design of a wideband, 100 W, 140 GHz gyroklystron amplifier

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 105-110).The design study of a 140 GHz, 100 W continuous wave gyroklystron amplifier is presented. The device is intended for use in Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy experiments. The gyroklystron has five cavities and operates in the TE(0,2) mode with a low power electron beam. The design was performed using MAGY, a nonlinear code for modelling gyrotron devices. The design process of the gyroklystron starting from the linear theory to the optimization of the final design in MAGY has been described in detail. Stagger tuning was employed to broadband the device. The design yields 130 W peak power, 36 dB saturated gain, and a -3 dB bandwidth of over 1 GHz (0.75%) with a 15 kV, 150 mA electron beam having a beam pitch factor of 1.5, radius of 0.64 mm and calculated perpendicular momentum spread of 4%. Preliminary designs of the Magnetron Inject Gun (MIG), the input and output couplers, and the mode converter to transform the TE(0,2) operating mode to the HE(1,1) mode for low loss transmission of the output power are also presented. The design meets the specifications for the DNP experiment.by Colin D. Joye.S.M

Advances in 3D Generation: A Survey

Generating 3D models lies at the core of computer graphics and has been the focus of decades of research. With the emergence of advanced neural representations and generative models, the field of 3D content generation is developing rapidly, enabling the creation of increasingly high-quality and diverse 3D models. The rapid growth of this field makes it difficult to stay abreast of all recent developments. In this survey, we aim to introduce the fundamental methodologies of 3D generation methods and establish a structured roadmap, encompassing 3D representation, generation methods, datasets, and corresponding applications. Specifically, we introduce the 3D representations that serve as the backbone for 3D generation. Furthermore, we provide a comprehensive overview of the rapidly growing literature on generation methods, categorized by the type of algorithmic paradigms, including feedforward generation, optimization-based generation, procedural generation, and generative novel view synthesis. Lastly, we discuss available datasets, applications, and open challenges. We hope this survey will help readers explore this exciting topic and foster further advancements in the field of 3D content generation.Comment: 33 pages, 12 figure

Proactive Mechanisms for Video-on-Demand Content Delivery

Video delivery over the Internet is the dominant source of network load all over the world. Especially VoD streaming services such as YouTube, Netflix, and Amazon Video have propelled the proliferation of VoD in many peoples' everyday life. VoD allows watching video from a large quantity of content at any time and on a multitude of devices, including smart TVs, laptops, and smartphones. Studies show that many people under the age of 32 grew up with VoD services and have never subscribed to a traditional cable TV service. This shift in video consumption behavior is continuing with an ever-growing number of users. satisfy this large demand, VoD service providers usually rely on CDN, which make VoD streaming scalable by operating a geographically distributed network of several hundreds of thousands of servers. Thereby, they deliver content from locations close to the users, which keeps traffic local and enables a fast playback start. CDN experience heavy utilization during the day and are usually reactive to the user demand, which is not optimal as it leads to expensive over-provisioning, to cope with traffic peaks, and overreacting content eviction that decreases the CDN's performance. However, to sustain future VoD streaming projections with hundreds of millions of users, new approaches are required to increase the content delivery efficiency. To this end, this thesis identifies three key research areas that have the potential to address the future demand for VoD content. Our first contribution is the design of vFetch, a privacy-preserving prefetching mechanism for mobile devices. It focuses explicitly on OTT VoD providers such as YouTube. vFetch learns the user interest towards different content channels and uses these insights to prefetch content on a user terminal. To do so, it continually monitors the user behavior and the device's mobile connectivity pattern, to allow for resource-efficient download scheduling. Thereby, vFetch illustrates how personalized prefetching can reduce the mobile data volume and alleviate mobile networks by offloading peak-hour traffic. Our second contribution focuses on proactive in-network caching. To this end, we present the design of the ProCache mechanism that divides the available cache storage concerning separate content categories. Thus, the available storage is allocated to these divisions based on their contribution to the overall cache efficiency. We propose a general work-flow that emphasizes multiple categories of a mixed content workload in addition to a work-flow tailored for music video content, the dominant traffic source on YouTube. Thereby, ProCache shows how content-awareness can contribute to efficient in-network caching. Our third contribution targets the application of multicast for VoD scenarios. Many users request popular VoD content with only small differences in their playback start time which offers a potential for multicast. Therefore, we present the design of the VoDCast mechanism that leverages this potential to multicast parts of popular VoD content. Thereby, VoDCast illustrates how ISP can collaborate with CDN to coordinate on content that should be delivered by ISP-internal multicast

NASA compendium of satellite communications programs

A comprehensive review is given of worldwide satellite communication programs that range in time from the inception of satellite communications to mid-1974. Particular emphasis is placed on program results, including experiments conducted, communications system operational performance, and technology employed. The background for understanding these results is established through brief summaries of the program organization, system configuration, and satellite and ground terminal characteristics. Major consideration is given to the communications system aspects of each program, but general spacecraft technology and other experiments conducted as part of the same program are mentioned summarily

Out of sight, out of mind : population estimates and dynamic interplay between age-related decline in hearing and cognitive functioning in late life

Age-related sensory loss and major neurocognitive impairment are two of the leading drivers of non-fatal disability burden among the oldest-old, and are often reported to co-occur. Both biological and social explanations have been given to account for links between these two functional domains. This thesis explores inter-associations between age-related hearing-loss with cognitive function. The broad substantive aims of this dissertation are: 1) to document the levels of hearing impairment, dual sensory loss, and co-morbid hearing-loss with cognitive impairment in an older adult population; 2) to identify predictors of decline in hearing acuity and its association with all-cause mortality risk; 3) to investigate longitudinal pathways between hearing thresholds, hearing aid use and processing speed. The Dynamic Analyses to Optimise Ageing (DYNOPTA) project is a collaborative inter-disciplinary project that has pooled nine Australian longitudinal studies of ageing. The DYNOPTA project constitutes an important methodological backdrop to this thesis. Data pooling is advantageous because it can enhance representativeness of a population, increased statistical power and allows for direct replication of effects. However, variability in study protocols and the need to orientate functionally equivalent measures onto a common scale can create analytic challenges. A subsidiary aim of this thesis will be to illustrate and evaluate the use of harmonised longitudinal data pooled from independently designed epidemiological surveys. This research presented in this thesis primarily draws upon data from two contributing DYNOPTA studies that began in the early 1990s and are ongoing. These two studies were selected because they collected functionally equivalent clinical measures of hearing, vision and cognition, as well as a range of comparable contextual variables including data on socio-demographics, health, noise exposure, and hearing aid use. Multistate Markov Chain models estimated transition rates and expected years lived with sensory impairment. Joint Survival-Growth Curve models demonstrated that hearing loss was associated with increased mortality risk in women but not in men. Linear Mixed Models were used to identify predictors of hearing trajectories. Bi-variate Dual Change Score models demonstrated that low levels of hearing were leading indicators of subsequent rates of decline in processing speed. Finally, hearing-aid use was shown to be associated with improved levels of processing speed after adjusting for the effects of hearing thresholds, but did not attenuate rates of decline in processing speed. Hearing loss and cognitive impairment are highly prevalent and contribute to a significant number of years lived with functional impairment in late life. Links between hearing and cognition may be due to common biological processes. Alternatively, hearing loss could limit opportunities to engage in activities that promote and maintain cognitive reserves. Reductions in cognitive resources may also mean that older adults are less well equipped to deal with sensory ageing. In the context of this thesis, the main benefits of pooling and harmonization were the capacity to derive coarse population level estimates and the fostering of inter-disciplinary collaboration. However, it was necessary to return to the use of single study data to facilitate investigations into more fine grained causal pathways between hearing and cognition