Boydbolt, a positive-latch, simple-release fastener

Fastener /Boydbolt/ has recently been designed to furnish positive lock and release characteristics that positively prevent accidental adverse functions of lock or release

Coincidence Mössbauer effect

This dissertation is concerned with the incorporation of coincidence methods into standard Mössbauer techniques and the application of the Delayed Coincidence Mössbauer Effect (DCME) to the study of certain solid state phenomena. This technique involves the accumulation of a Mössbauer spectrum which reflects the environment of the decaying nuclei during some preset time interval following the formation of the Mössbauer state. Changing the preset time permits display of the time evolution of the nuclear environment. The theoretical analysis developed in this study involves a numerical integration of the exact expression for time dependent Mössbauer absorption over the experimental window in time and is shown here to be successful in matching experimental data for single and multi-lined spectra while previous analytical techniques have been unsuccessful. In systems where no time dependent solid state effects are present we have demonstrated experimentally and fit theoretically the expected line narrowing at long delay times and have applied this effect to enhance energy resolution in absorber experiments. Studies of time dependent solid state effects reported here involve aftereffects and various relaxation processes. The aftereffects problem pertains to the formation of highly charged ions following K-capture and an Auger shower, and also the local heating of the lattice associated with the relatively energetic events in the formation of the Mössbauer state. We investigated the time dependence of the ionic charge and the local heating, reflected in the recoilless fraction, as these excited configurations relaxed to equilibrium. Previous estimates of the characteristic time for the charge state decay to equilibrium in an insulator such as CoO were about 10^-8 sec. Our experiments in MgC show that this time must be greater than 2 x 10- 6 or that high charge states are stabilized in the lattice. There are no theoretical models or predictions concerning this characteristic time or that of the local heating decay. We show in this study that the decay to equilibrium in the latter case, using a single line source and absorber, takes place with a characteristic time of less than 10^-9 sec. The DCME is also applied to the study of ionic spin and electric-field-gradient (Jahn-Teller effect) relaxations. No relaxation effects were observed in sources of Co^57 in Ti0_2 whille the parallel absorber experiment has shown such an effect. Calculations done here show that the applicability of the DCHE method to study of dynamical-Jahn-Teller effect in MgO is doubtful due to the extremely small quadrupole splitting observed

WHAT TASKS TO AUTOMATE? AN INVESTIGATION OF WHAT TASKS MAKE SENSE TO AUTOMATE FOR FUTURE AVIATION PLATFORMS

The Army is developing a new generation of aircraft called Future Vertical Lift (FVL). These aircraft will integrate new technologies that change Army Aviation’s machinery, methods, and aircrew domains. Key to this effort is the development of automation to reduce pilot cognitive workload and prevent cognitive overload. The purpose of this research was to develop an understanding of the factors that influence pilot cognitive workload and to provide insight into what tasks make sense to automate for FVL. Researchers used a mixed methods approach, relying on scholarly literature and semi-structured interviews to elicit cognitive workload data from Army rotary-wing pilots. Researchers used the data from a simple and a complex MEDEVAC flight scenario to develop an influence diagram that models pilot cognitive workload based on influencing factors and subfactors. At a high level, the data indicate that pilot task demand and environmental factors have the most influence on cognitive workload during complex missions in challenging conditions. At a low level, the data indicate that light factors, intra-flight coordination, and task complexity are most influential on cognitive workload. The results suggest that tasks impacting these factors should be considered for automation to prevent pilot cognitive overload in FVL.DEVCOM AvMCCaptain, United States ArmyMajor, United States ArmyCaptain, United States ArmyMajor, United States ArmyApproved for public release. Distribution is unlimited

Calibrating ensemble reliability whilst preserving spatial structure

Ensemble forecasts aim to improve decision-making by predicting a set of possible outcomes. Ideally, these would provide probabilities which are both sharp and reliable. In practice, the models, data assimilation and ensemble perturbation systems are all imperfect, leading to deficiencies in the predicted probabilities. This paper presents an ensemble post-processing scheme which directly targets local reliability, calibrating both climatology and ensemble dispersion in one coherent operation. It makes minimal assumptions about the underlying statistical distributions, aiming to extract as much information as possible from the original dynamic forecasts and support statistically awkward variables such as precipitation. The output is a set of ensemble members preserving the spatial, temporal and inter-variable structure from the raw forecasts, which should be beneficial to downstream applications such as hydrological models. The calibration is tested on three leading 15-d ensemble systems, and their aggregation into a simple multimodel ensemble. Results are presented for 12 h, 1° scale over Europe for a range of surface variables, including precipitation. The scheme is very effective at removing unreliability from the raw forecasts, whilst generally preserving or improving statistical resolution. In most cases, these benefits extend to the rarest events at each location within the 2-yr verification period. The reliability and resolution are generally equivalent or superior to those achieved using a Local Quantile-Quantile Transform, an established calibration method which generalises bias correction. The value of preserving spatial structure is demonstrated by the fact that 3×3 averages derived from grid-scale precipitation calibration perform almost as well as direct calibration at 3×3 scale, and much better than a similar test neglecting the spatial relationships. Some remaining issues are discussed regarding the finite size of the output ensemble, variables such as sea-level pressure which are very reliable to start with, and the best way to handle derived variables such as dewpoint depression

Multi-parameter models of innovation diffusion on complex networks

A model, applicable to a range of innovation diffusion applications with a strong peer to peer component, is developed and studied, along with methods for its investigation and analysis. A particular application is to individual households deciding whether to install an energy efficiency measure in their home. The model represents these individuals as nodes on a network, each with a variable representing their current state of adoption of the innovation. The motivation to adopt is composed of three terms, representing personal preference, an average of each individual's network neighbours' states and a system average, which is a measure of the current social trend. The adoption state of a node changes if a weighted linear combination of these factors exceeds some threshold. Numerical simulations have been carried out, computing the average uptake after a sufficient number of time-steps over many realisations at a range of model parameter values, on various network topologies, including random (Erdos-Renyi), small world (Watts-Strogatz) and (Newman's) highly clustered, community-based networks. An analytical and probabilistic approach has been developed to account for the observed behaviour, which explains the results of the numerical calculations

Ensemble prediction for nowcasting with a convection-permitting model—I: description of the system and the impact of radar-derived surface precipitation rates

A key strategy to improve the skill of quantitative predictions of precipitation, as well as hazardous weather such as severe thunderstorms and flash floods is to exploit the use of observations of convective activity (e.g. from radar). In this paper, a convection-permitting ensemble prediction system (EPS) aimed at addressing the problems of forecasting localized weather events with relatively short predictability time scale and based on a 1.5 km grid-length version of the Met Office Unified Model is presented. Particular attention is given to the impact of using predicted observations of radar-derived precipitation intensity in the ensemble transform Kalman filter (ETKF) used within the EPS. Our initial results based on the use of a 24-member ensemble of forecasts for two summer case studies show that the convective-scale EPS produces fairly reliable forecasts of temperature, horizontal winds and relative humidity at 1 h lead time, as evident from the inspection of rank histograms. On the other hand, the rank histograms seem also to show that the EPS generates too much spread for forecasts of (i) surface pressure and (ii) surface precipitation intensity. These may indicate that for (i) the value of surface pressure observation error standard deviation used to generate surface pressure rank histograms is too large and for (ii) may be the result of non-Gaussian precipitation observation errors. However, further investigations are needed to better understand these findings. Finally, the inclusion of predicted observations of precipitation from radar in the 24-member EPS considered in this paper does not seem to improve the 1-h lead time forecast skill

Bifurcation Boundary Conditions for Switching DC-DC Converters Under Constant On-Time Control

Sampled-data analysis and harmonic balance analysis are applied to analyze switching DC-DC converters under constant on-time control. Design-oriented boundary conditions for the period-doubling bifurcation and the saddle-node bifurcation are derived. The required ramp slope to avoid the bifurcations and the assigned pole locations associated with the ramp are also derived. The derived boundary conditions are more general and accurate than those recently obtained. Those recently obtained boundary conditions become special cases under the general modeling approach presented in this paper. Different analyses give different perspectives on the system dynamics and complement each other. Under the sampled-data analysis, the boundary conditions are expressed in terms of signal slopes and the ramp slope. Under the harmonic balance analysis, the boundary conditions are expressed in terms of signal harmonics. The derived boundary conditions are useful for a designer to design a converter to avoid the occurrence of the period-doubling bifurcation and the saddle-node bifurcation.Comment: Submitted to International Journal of Circuit Theory and Applications on August 10, 2011; Manuscript ID: CTA-11-016