91 research outputs found
Application of the ONERA model of dynamic stall
A semiempirical model to predict the unsteady loads on an airfoil that is experiencing dynamic stall, is investigated. The mathematical model is described from an engineering point of view, demonstrates the procedure for obtaining various empirical parameters, and compares the loads predicted by the model with those obtained in the experiment. It is found that the procedure is straightforward, and the final calculations are in qualitative agreement with the experimental results. Comparisons between calculations and measurements also indicate that a decrease in accuracy results when the values of both the reduced frequency and the amplitude of oscillation are large. Potential quantitative improvements in the accuracy of the calculations are discussed for accounting of both the hysteresis in the static data and the effects of stall delay in the governing equations
Electrons on a sphere in disorder potential
We investigate, both analytically and numerically, the behavior of the
electron gas on a sphere in the presence of point-like impurities. We find a
criterion when the disorder can be regarded as small one and the main effect is
the broadening of rotational multiplets. In the latter regime the statistics of
one impurity-induced band is studied numerically. The energy level spacing
distribution function follows the law P(s) ~ s exp(-a s^b) with 1<b<2. The
number variance shows various possibilities, strongly dependent on the chosen
model of disorder.Comment: 11 pages, REVTEX, 9 eps figures; references added to Sec.
Pengujian Karakteristik Unjuk Kerja Turbin Mikrohidro Di Desa Ciasmara
Experimental study of performance characteristic of micro-hydro water turbine hasbeen done in Kabitpaten Bogor. In this study performance is defined as a turbine efficiency which isrepresented by ratio between mechanical energy provided by turbine and an available potential energyofwater at a various conditions offlow. The study was limited only at several variation ofwater flowrate because the turbine installation is only equipped by conventional control system. Water level inthe basin was measured by level water meter with the precision is around 10%, while water flow ratewas measured by bridge flow meter. Mechanical energy is calculatedfrom measurement ofrotationalmoment and rotation of shaft. The moment was measured by calibrated hydraulic dynamometer andthe shaft rotation was measured by stroboscope. Based on the test results, at the full capacity (0.305mlIs flow rate and 3.17 mhead) the turbine showed agood performance with the efficiency is around59%
Record RF performance of standard 90 nm CMOS technology
We have optimized 3 key RF devices realized in standard logic 90 nm CMOS technology and report a record performance in terms of n-MOS maximum oscillation frequency f/sub max/ (280 GHz), varactor tuning range and varactor and inductor quality factor
A ferromagnet with a glass transition
We introduce a finite-connectivity ferromagnetic model with a three-spin
interaction which has a crystalline (ferromagnetic) phase as well as a glass
phase. The model is not frustrated, it has a ferromagnetic equilibrium phase at
low temperature which is not reached dynamically in a quench from the
high-temperature phase. Instead it shows a glass transition which can be
studied in detail by a one step replica-symmetry broken calculation. This spin
model exhibits the main properties of the structural glass transition at a
solvable mean-field level.Comment: 7 pages, 2 figures, uses epl.cls (included
Against quantiles: categorization of continuous variables in epidemiologic research, and its discontents
<p>Abstract</p> <p>Background</p> <p>Quantiles are a staple of epidemiologic research: in contemporary epidemiologic practice, continuous variables are typically categorized into tertiles, quartiles and quintiles as a means to illustrate the relationship between a continuous exposure and a binary outcome.</p> <p>Discussion</p> <p>In this paper we argue that this approach is highly problematic and present several potential alternatives. We also discuss the perceived drawbacks of these newer statistical methods and the possible reasons for their slow adoption by epidemiologists.</p> <p>Summary</p> <p>The use of quantiles is often inadequate for epidemiologic research with continuous variables.</p
Rotary-Wing Aeroelasticity: Current Status and Future Trends
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76177/1/AIAA-9022-592.pd
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