Study of Deposition Methods for Silicon Powder

Silicon powder tends to agglomerate at normal atmospheric conditions and is, hence, difficult to aerosolize. Several methods of aerosolizing silicon powder and finally depositing it on various substrates were investigated. This paper presents the investigated methods of aerosolization. The electrostatic spray coating used in dry paint application was found to be the most suitable. The general merits of this method and its use for silicon powder deposition to form films are discussed

Constant amplitude and post-overload fatigue crack growth behavior in PM aluminum alloy AA 8009

A recently developed, rapidly solidified, powder metallurgy, dispersion strengthened aluminum alloy, AA 8009, was fatigue tested at room temperature in lab air. Constant amplitude/constant delta kappa and single spike overload conditions were examined. High fatigue crack growth rates and low crack closure levels compared to typical ingot metallurgy aluminum alloys were observed. It was proposed that minimal crack roughness, crack path deflection, and limited slip reversibility, resulting from ultra-fine microstructure, were responsible for the relatively poor da/dN-delta kappa performance of AA 8009 as compared to that of typical IM aluminum alloys

Low-Cost Flow Visualization for a Supersonic Ejector

Shadowgraph techniques were applied to the cold flow ejector facility at the Propulsion Research Center at the University of Alabama in Huntsville. The setup for the experiments was relatively simple and was accomplished at very little cost. Series of shadowgraph images were taken of both dual nozzle and single nozzle strut based ejectors operating over a range of chamber pressures. The density gradient patterns in the shadowgraphs were compared to pressure data measured along the top and side walls of the mixing duct. The shadowgraph images showed the presence of barrel shocks emanating from the nozzles which at low pressures terminated in Mach disks and at higher pressures extended beyond the barrel shape and reflected off the walls of the duct. Based on pressure data from previous testing, reflected shocks were expected on the walls of the duct. The shadowgraph images confirmed the locations of these reflected shocks on the top wall of the duct. The shadowgraph images also showed the structure change which correlated to a change in pitch of the ejector noise, and corresponded to a change in trend of the duct wall pressure ratio distributions. The images produced from the setup provided insight into the complex flow behavior inside the ejector duct. In addition, the techniques were a valuable tool as an educational device for students

Tall Fescue for Trouble Spots

Livestock don\u27t like this new grass too well. It won\u27t take the place of our popular pasture plants. But there\u27s a specialized use for tall fescue on many Iowa farms

Emerald Crownvetch - a pasture legume

Used up to now primarily for erosion control on steep high-way banks, Emerald Crownvetch has stood up under sustained grazing and shows promise as a pasture legume on soils not well suited for birdsfoot trefoil

Controllability and Design of Unmanned Multirotor Aircraft Robust to Rotor Failure

A new design method for multi-rotor aircraft with distributed electric propulsion is presented to ensure a property of robustness against rotor failure from the control perspective. Based on the concept of null controllability, a quality measure is derived to evaluate and quantify the performance of a given design with the consideration of rotor failure. An optimization problem whose cost function is based on the quality measure is formulated and its optimal solution identifies a set of optimal design parameters that maximizes an aircraft’s ability to control its attitude and hence its position. The effectiveness of the proposed design procedure is validated through the results of experimentation with the Autonomous Flying Ambulance model being developed at Caltech’s Center for Autonomous Systems and Technologies

The relationship between chiropractor required and current level of business knowledge

Background: Chiropractors frequently practice within health care systems requiring the business acumen of an entrepreneur. However, some chiropractors do not know the relationship between the level of business knowledge required for practice success and their current level of business knowledge. The purpose of this quantitative study was to examine the relationship between chiropractors’ perceived level of business knowledge required and their perceived level of current business knowledge. Methods: Two hundred and seventy-four participants completed an online survey (Health Care Training and Education Needs Survey) which included eight key business items. Participants rated the level of perceived business knowledge required (Part I) and their current perceived level of knowledge (Part II) for the same eight items. Data was collected from November 27, 2013 to December 18, 2013. Data were analyzed using Spearman’s ranked correlation to determine the statistically significant relationships for the perceived level of knowledge required and the perceived current level of knowledge for each of the paired eight items from Parts I and II of the survey. Wilcoxon Signed Ranks Tests were performed to determine the statistical difference between the paired items. Results: The results of Spearman’s correlation testing indicated a statistically significant (p < 0.01) positive correlation for the perceived level of knowledge required and perceived current level of knowledge for six variables: (a) organizational behavior, (b) strategic management, (c) marketing, (d) legal and ethical, (e) managerial decisions, and (f) operations. Wilcoxon Signed Ranks testing indicated a significant difference for three paired items: strategic management; marketing and; legal and ethical. The results suggest that relationships exist for the majority of business items (6 of 8) however a statistically difference was demonstrated in only three of the paired business items. Conclusion: The implications of this study for social change include the potential to improve chiropractors’ business knowledge and skills, enable practice success, enhance health services delivery and positively influence the profession as a viable career.https://doi.org/10.1186/s12998-017-0134-

Inclusive jet cross section in pˉp{\bar p p} collisions at s=1.8\sqrt{s}=1.8 TeV

The inclusive jet differential cross section has been measured for jet transverse energies, $E_T$, from 15 to 440 GeV, in the pseudorapidity region 0.1$\leq | \eta| \leq$0.7. The results are based on 19.5 pb$^{-1}$ of data collected by the CDF collaboration at the Fermilab Tevatron collider. The data are compared with QCD predictions for various sets of parton distribution functions. The cross section for jets with $E_T>200$ GeV is significantly higher than current predictions based on O($\alpha_s^3$) perturbative QCD calculations. Various possible explanations for the high-$E_T$ excess are discussed.Comment: 8 pages with 2 eps uu-encoded figures Submitted to Physical Review Letter