Effects of Ultra-Clean and centrifugal filtration on rolling-element bearing life

Fatigue tests were conducted on groups of 65-millimeter bore diameter deep-groove ball bearings in a MIL-L-23699 lubricant under two levels of filtration. In one test series, the oil cleanliness was maintained at an exceptionally high level (better than a class "000" per NAS 1638) with a 3 micron absolute barrier filter. These tests were intended to determine the "upper limit" in bearing life under the strictest possible lubricant cleanliness conditions. In the tests using a centrifugal oil filter, contaminants of the type found in aircraft engine filters were injected into the filters' supply line at 125 milligrams per bearing-hour. "Ultra-clean" lubrication produced bearing fatigue lives that were approximately twice that obtained in previous tests with contaminated oil using 3 micron absolute filtration and approximately three times that obtained with 49 micron filtration. It was also observed that the centrifugal oil filter had approximately the same effectiveness as a 30 micron absolute filter in preventing bearing surface damage

Tools for cognition: Student free access to manipulative materials in controlversus autonomy-oriented middle grades teachers’ classrooms

This study investigated how middle grades students provided with free access to manipulative materials use these mathematical tools in classrooms where their teachers are identified as Control-Oriented and Autonomy-Oriented. Also of interest in this investigation was how Control-Oriented and Autonomy-Oriented teachers administered the free access treatment in their classrooms. A Pre -- Post -1 Post -2 design was used with two treatments. During Treatment 1, teachers used the manipulatives for mathematics instruction using the strategies learned in the summer professional development workshop. During Treatment 2, teachers provided students with free access to the manipulative materials. Results indicated teachers\u27 control orientations--control versus autonomy--were significantly different. The study also reveals that when students are allowed some measure of control in the selection and use of manipulative materials given the time to overcome their initial apprehension, they will spontaneously and selectively use these materials effectively as appropriate mathematical tools to mediate learning. Contains 20 references

Learning Mathematics with Technology: The Influence of Virtual Manipulatives on Different Achievement Groups

This study examined the influence of virtual manipulatives on different achievement groups during a teaching experiment in four fifth-grade classrooms. During a two-week unit focusing on two rational number concepts (fraction equivalence and fraction addition with unlike denominators) one low achieving, two average achieving, and one high achieving group participated in two instructional treatments (three groups used virtual manipulatives and one group used physical manipulatives). Data sources included pre- and post-tests of students’ mathematical content knowledge and videotapes of classroom sessions. Results of paired samples t-tests examining the three groups using virtual manipulatives indicated a statistically significant overall gain following the treatment. Follow-up paired samples individual t-tests on the low, average, and high achieving groups indicated a statistically significant gain for students in the low achieving group, but only numerical gains for students in the average and high achieving groups. There were no significant differences between the average achieving student groups in the virtual manipulatives and physical manipulatives treatments. Qualitative data gathered during the study indicated that the different achievement groups experienced the virtual manipulatives in different ways, with the high achieving group recognizing patterns quickly and transitioning to the use of symbols, while the average and low achieving groups relied heavily on pictorial representations as they methodically worked stepby- step through processes and procedures with mathematical symbols

Reducing Fretting Corrosion at the Femoral Neck to Taper Junction in Total Hip Arthroplasty

Fretting corrosion due to micromotion between the femoral head and neck of hip implants is a growing concern of surgeons and patients. Debris from corrosion can lead to severe adverse effects for patients of total hip arthroplasty and reduce the lifespan of the product. Previous studies conducted by Zimmer Biomet show a connection between higher impaction force and reduced fretting corrosion and debris. This design project explored this issue and developed a training device using a current technology, a dynamic force sensor, and data analysis software for surgeons to obtain muscle memory of a 4kN strike on the head impactor, which will improve performance in the operating room and reduce the occurrence of fretting corrosion

The radial electric field as a measure for field penetration of resonant magnetic perturbations

In this paper we introduce a new indirect method for identifying the radial extent of the stochastic layer due to applying resonant magnetic perturbations (RMPs) in H-mode plasmas by measuring the spin-up of the plasma near the separatrix. This spin-up is a predicted consequence of enhanced electron loss, due to magnetic stochastization (Kaveeva et al 2008 Nucl. Fusion 48 075003). We find that in DIII-D H-mode plasmas with n = 3 RMPs applied for edge localized mode suppression, the stochastic layer is limited to the outer 5% region in normalized magnetic flux, Psi(N). This is in contrast to vacuum modelling predictions where this layer can penetrate up to 20% in Psi(N). Theoretical predictions of a stochastic radial electric field, Er component exceed the experimental measurements by about a factor 3 close to the separatrix, suggesting that the outer region of the plasma is weakly stochastic. Linear response calculations with M3D-C1, a resistive two-fluid model, show that in this outer 5% region, plasma response often reduces the resonant magnetic field components by 67% or more in comparison with vacuum calculations. These results for DIII-D are in reasonable agreement with results from the MAST tokamak, where the magnetic field perturbation from vacuum field calculations needed to be reduced by 75% for agreement with experimental measurements of the x-point lobe structure

Stability and electronic structure of the complex K2_2PtCl6_6 structure-type hydrides

The stability and bonding of the ternary complex K$_2$PtCl$_6$ structure hydrides is discussed using first principles density functional calculations. The cohesion is dominated by ionic contributions, but ligand field effects are important, and are responsible for the 18-electron rule. Similarities to oxides are discussed in terms of the electronic structure. However, phonon calculations for Sr$_2$RuH$_6$ also show differences, particularly in the polarizability of the RuH$_6$ octahedra. Nevertheless, the yet to be made compounds Pb$_2$RuH$_6$ and Be$_2$FeH$_6$ are possible ferroelectrics. The electronic structure and magnetic properties of the decomposition product, FeBe$_2$ are reported. Implications of the results for H storage are discussed

Assessing Driver Fitness to Participate in FHWA Field Experimentation at Night

A Driving Fitness Form was developed to ensure that drivers areready to participate in field driving experiments at night. The form was tested in afield experiment conducted in Delta, Pennsylvania, during August 2004. The fieldexperiment was part of a cooperative research program conducted by the FederalHighway Administration and the Pennsylvania Department of Transportation.Sixteen research participants drove a curvy stretch of rural two-lane highway eachnight for 8 nights with different pavement markings and markers on the roadway.Partly due to the Driving Fitness Form, the experiment was completedsuccessfully by all participants without any incidents or crashes. The DrivingFitness Form performed well, and summary data were collected on the sample of16 drivers