11,221 research outputs found
An input adaptive, pursuit tracking model of the human opertor
Developed and evaluated is a simple model of the input adaptive behavior of the human operator (HO) in a pursuit tracking task in which the plant controlled consists of a pure gain. If it is assumed that the HO is approximately an optimal predictor using only position and velocity information, then there is a simple method of computing the values of the model parameters in terms of the autocorrelation function of the input signal. Experimental evidence indicates that the ability of the HO to use velocity information decreases with increasing signal velocity indicating that a biased estimator of the velocity weighting should be used. A suitable approximation is derived which has rapid convergence and low variance. The model thus derived is compared to actual subject transfer functions and is found to be in close agreement. In addition to tracking random processes the model can adapt to and track deterministic signals, such as sine waves, up to approximately the frequency at which human operators begin to track precognitively
Southwest Research Institute assistance to NASA in biomedical areas of the technology utilization program Cumulative quarterly report, 1 Oct. 1967 - 31 Mar. 1968
Quarterly operations summary of center for selective dissemination of biomedical information within Technology Utilization progra
A study of local and non-local spatial densities in quantum field theory
We use a one-dimensional model system to compare the predictions of two
different 'yardsticks' to compute the position of a particle from its quantum
field theoretical state. Based on the first yardstick (defined by the
Newton-Wigner position operator), the spatial density can be arbitrarily narrow
and its time-evolution is superluminal for short time intervals. Furthermore,
two spatially distant particles might be able to interact with each other
outside the light cone, which is manifested by an asymmetric spreading of the
spatial density. The second yardstick (defined by the quantum field operator)
does not permit localized states and the time evolution is subluminal.Comment: 29 pages, 3 figure
High-tip-speed, low-loading transonic fan stage. Part 3: Final report
Tests were conducted on a high-tip-speed, low-loading transonic fan stage to determine the performance and inlet flow distortion tolerance of the design. The fan was designed for high efficiency at a moderate pressure ratio by designing the hub section to operate at minimum loss when the tip operates with an oblique shock. The design objective was an efficiency of 86 percent at a pressure ratio of 1.5, a specific flow (flow per unit annulus area) of 42 lb/sec-sq. ft (205.1 kgm/sec-m sq), and a tip speed of 1600 ft/sec (488.6 m/sec). During testing, a peak efficiency of 84 percent was achieved at design speed and design specific flow. At the design speed and pressure ratio, the flow was 4 percent greater than design, efficiency was 81 percent, and a stall margin of 24 percent was obtained. The stall line was improved with hub radial distortion but was reduced when the stage was tested with tip radial and circumferential flow distortions. Blade-to-blade values of static pressures were measured over the rotor blade tips
Hightip-speed, low-loading transonic fan stage. Part 2: Data compilation
Tests were conducted on a high-tip-speed low-loading transonic fan stage to determine the performance and inlet flow distortion tolerance of the design. Test data were recorded for overall and blade element performance with both uniform and distorted inlet flows. A tabular summary of the data and a representative selection of the computer data reduction sheets are presented
Bayesian models for syndrome- and gene-specific probabilities of novel variant pathogenicity
BACKGROUND: With the advent of affordable and comprehensive sequencing technologies, access to molecular genetics for clinical diagnostics and research applications is increasing. However, variant interpretation remains challenging, and tools that close the gap between data generation and data interpretation are urgently required. Here we present a transferable approach to help address the limitations in variant annotation. METHODS: We develop a network of Bayesian logistic regression models that integrate multiple lines of evidence to evaluate the probability that a rare variant is the cause of an individual's disease. We present models for genes causing inherited cardiac conditions, though the framework is transferable to other genes and syndromes. RESULTS: Our models report a probability of pathogenicity, rather than a categorisation into pathogenic or benign, which captures the inherent uncertainty of the prediction. We find that gene- and syndrome-specific models outperform genome-wide approaches, and that the integration of multiple lines of evidence performs better than individual predictors. The models are adaptable to incorporate new lines of evidence, and results can be combined with familial segregation data in a transparent and quantitative manner to further enhance predictions. Though the probability scale is continuous, and innately interpretable, performance summaries based on thresholds are useful for comparisons. Using a threshold probability of pathogenicity of 0.9, we obtain a positive predictive value of 0.999 and sensitivity of 0.76 for the classification of variants known to cause long QT syndrome over the three most important genes, which represents sufficient accuracy to inform clinical decision-making. A web tool APPRAISE [http://www.cardiodb.org/APPRAISE] provides access to these models and predictions. CONCLUSIONS: Our Bayesian framework provides a transparent, flexible and robust framework for the analysis and interpretation of rare genetic variants. Models tailored to specific genes outperform genome-wide approaches, and can be sufficiently accurate to inform clinical decision-making
Planting and Care of Trees in South Dakota
In this circular, created by the Agriculture Extension Service at South Dakota State College, the information provided includes the topics of planting and caring for trees in South Dakota. This information is provided through the guidance of the Agriculture Department during the year 1936
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Polymer Modification with Multifunctional Additives and Unique Processing Methods
This dissertation describes the investigation of unconventional methods to enhance polymer properties either by using unique processing methods, such as solid-state deformation, or by using multifunctional additives that can simultaneously provide a number of property enhancements. The three main research areas of this dissertation are self-reinforced glassy thermosets, melt-processeable organic/inorganic thermoplastic elastomers and semi-crystalline thermoplastics with improved ductility due to a unique solid-state process treatment.
Various thermosets, including epoxies, are used in systems with fibers or other additives to improve stiffness. However such systems are difficult to process due to increased viscosity. This work investigates a new method to reinforce thermoset materials with low molecular weight (LMW) crystallizable additives. Desoxyanisoin, which is a pre-cursor to a flame-retardant molecule 4,4’-bishydroxydesoxybenzoin that is engineered to promote char, is used as a LMW organic crystallizable compound. At processing temperatures, desoxyanisoin is miscible with the matrix/epoxy thereby lowering the process viscosity. Upon cooling or reaction, desoxyanisoin phase separates and crystallizes providing unique in-situ reinforced composites. The mechanical and flammability properties of these desoxyanisoin-epoxy thermoset composites are described.
Another approach to enhancement of flammability properties is demonstrated by fabricating organic/inorganic thermoplastic elastomers (TPEs) based on isotactic polypropylene (iPP) and polydimethylsiloxane (PDMS) materials by reactive melt mixing in the presence of peroxides. These polyolefin based thermoplastic elastomers are similar to the dynamically vulcanized elastomer-thermoplastic blends of polyolefins with ethylene-propylene diene copolymer (EPDM). Herein PDMS is used as an EPDM equivalent. Furthermore, not only PDMS is dynamically cross-linked, but there are some cross-links with the amorphous iPP. Varying the content of PDMS allows for design of TPEs with a wide range of mechanical and physical properties.
Lastly, an approach to enhance the toughness and ductility of semi-crystalline polymers by deforming the material in a solid state to a strain-softening regime is described. This treatment imposes changes in the post yield behavior by process of compression and shear in the solid state at low temperature, low pressures and unconfined geometry. Crystal-structure alteration due to orientation and fragmentation of the lamellae during this treatment leads to the enhancement in non-linear ductility. The fundamental principles governing this approach are investigated
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