Effect of filtration on rolling-element-bearing life in contaminated lubricant environment

Fatigue tests were conducted on groups of 65 millimeter-bore ball bearings under four levels of filtration with and without a contaminated MIL-L-23699 lubricant. The baseline series used noncontaminated oil with 49 micron absolute filtration. In the remaining tests contaminants of the composition found in aircraft engine filters were injected into the filter's supply line at a constant rate of 125 milligrams per bearing-hour. The test filters had absolute particle removal ratings of 3, 30, 49, and 105 microns (0.45, 10, 30, and 70 microns nominal), respectively. Bearings were tested at 15,000 rpm under 4580 newtons radial load. Bearing life and running tract condition generally improved with finer filtration. The 3 and 30 micron filter bearings in a contaminated lubricant had statistically equivalent lives, approaching those from the baseline tests. The experimental lives of 49 micron bearings were approximately half the baseline bearing's lives. Bearings tested with the 105 micron filter experienced wear failures. The degree of surface distress, weight loss, and probable failure mode were found to be dependent on filtration level, with finer filtration being clearly beneficial

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

Revisiting the Definition of a Virtual Manipulative

In 2002, Moyer, Bolyard and Spikell defined a virtual manipulative as an “an interactive, Web-based visual representation of a dynamic object that presents opportunities for constructing mathematical knowledge” (p. 373). The purpose of this chapter is to revisit, clarify and update the definition of a virtual manipulative. After clarifying what a virtual manipulative is and what it is not, we propose an updated definition for virtual manipulative: an interactive, technology-enabled visual representation of a dynamic mathematical object, including all of the programmable features that allow it to be manipulated, that presents opportunities for constructing mathematical knowledge. The chapter describes the characteristics of five of the most common virtual manipulative environments in use in education: single-representation, multi-representation, tutorial, gaming and simulation

A Review of the Literature on Mathematics and Science Teacher Quality

A large body of literature exists that examines teacher quality characteristics and the relationship of indicators of those characteristics to teacher effectiveness. This existing research literature broadly views teacher quality research without illuminating specific areas of teacher quality, such as mathematics and science. In an effort to focus the literature base for researchers and policymakers more narrowly, this review specifically examines teacher quality as it relates to mathematics and science teaching and learning. The review highlights key policy and practitioner perspectives, provides a focused synthesis on current research findings on mathematics and science teacher quality, and suggests areas of research that are limited in the literature

Code RED (remediation and enrichment days): The complex journey of a school and university partnership\u27s process to increase mathematics achievement

This study examined a focused remediation and enrichment effort among school and university faculty to affect the mathematics achievement of a group of third-grade students in a Title 1 elementary school. A total of 87 students participated in the Code RED (Remediation and Enrichment Days) Project. During the Code RED Project, student assessment data were used to identify high-need areas for mathematics instruction. The Code RED Project sessions occurred in small groups over a 10-week period. Pre-and posttest assessments, as well as state-standardized tests, were used for data gathering during the project. Pre-and posttest data indicate that students made significant gains in mathematics achievement during the Code RED Project overall, in different ability groups, and in different subgroup populations. In addition, during the Code RED Project, 100% of the third-grade class passed the end-of-grade state-standardized testing. A comparison of the pass rates for the state-standardized test for third-grade students before and during the Code RED Project indicates a significant increase in students labeled in the pass-proficient and pass-advanced categories. In addition to the students\u27 increasing their achievement results, teachers adopted new instructional practices, and preservice teachers participated in the inquiry culture of the school. Reprinted by permission of the publisher

Virtual Manipulatives Used by K-8 Teachers for Mathematics Instruction: Considering Mathematical, Cognitive, and Pedagogical Fidelity

This study examined teachers’ uses of virtual manipulatives across grades K-8 after participating in a professional development institute in which manipulatives and technology were the major resources used throughout all of the activities. Researchers analyzed 95 lesson summaries in which classroom teachers described their uses of virtual manipulatives during school mathematics instruction. The findings indicated that the content in a majority of the lessons focused on two National Council of Teachers of Mathematics (2000a) standards: Number & Operations and Geometry. Virtual geoboards, pattern blocks, base-10 blocks, and tangrams were the applets used most often by teachers. The ways teachers used the virtual manipulatives most frequently focused on investigation and skill solidification. It was common for teachers to use the virtual manipulatives alone or to use physical manipulatives first, followed by virtual manipulatives. One important finding of this study was that teachers used the virtual manipulatives during the main portion of their lessons when students were learning mathematics content. These results represent an initial exploration of teachers’ current use of virtual manipulatives in K-8 classrooms

Strategic decision quality in Flemish municipalities

Strategic planning (SP) has taken the public sector by storm because it is widely believed that SP’s approach to strategic decision-making strengthens strategic decision quality (SDQ) in public organizations. However, if or how SP relates to SDQ seems to lack empirical evidence. Drawing on survey data from 89 Flemish municipalities, we found that SP does improve SDQ if a systematic approach is taken and if top policy-makers and managers, as well as lower-level staff and external stakeholders, are involved

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

Validation of the Harvard Lyman-α in situ water vapor instrument: Implications for the mechanisms that control stratospheric water vapor

Building on previously published details of the laboratory calibrations of the Harvard Lyman-α photofragment fluorescence hygrometer (HWV) on the NASA ER-2 and WB-57 aircraft, we describe here the validation process for HWV, which includes laboratory calibrations and intercomparisons with other Harvard water vapor instruments at water vapor mixing ratios from 0 to 10 ppmv, followed by in-flight intercomparisons with the same Harvard hygrometers. The observed agreement exhibited in the laboratory and during intercomparisons helps corroborate the accuracy of HWV. In light of the validated accuracy of HWV, we present and evaluate a series of intercomparisons with satellite and balloon borne water vapor instruments made from the upper troposphere to the lower stratosphere in the tropics and midlatitudes. Whether on the NASA ER-2 or WB-57 aircraft, HWV has consistently measured about 1–1.5 ppmv higher than the balloon-borne NOAA/ESRL/GMD frost point hygrometer (CMDL), the NOAA Cryogenic Frost point Hygrometer (CFH), and the Microwave Limb Sounder (MLS) on the Aura satellite in regions of the atmosphere where water vapor is <10 ppmv. Comparisons in the tropics with the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite show large variable differences near the tropopause that converge to ~10% above 460 K, with HWV higher. Results we show from the Aqua Validation and Intercomparison Experiment (AquaVIT) at the AIDA chamber in Karlsruhe do not reflect the observed in-flight differences. We illustrate that the interpretation of the results of comparisons between modeled and measured representations of the seasonal cycle of water entering the lower tropical stratosphere is dictated by which data set is used