Cryogenic Mechanical Alloying of Poly (ether ether ketone) - Polycarbonate Composite Powders for Selective Laser Sintering

Mechanical alloying is a solid state processing technique traditionally used in the metallurgical industry to extend solubility limits in alloy systems. Mechanical alloying can also be used to blend polymer systems at ambient or cryogenic temperatures. In this work, cryogenic mechanical alloying was employed to create composite powders of Poly (ether ether ketone) (PEEK) - Polycarbonate (PC) for use in selective laser sintering applications. The microstructural development of the PEEK-PC system that occurs during laser sintering and the effects of this microstructure on mechanical properties of the laser sintered parts was investigated.Mechanical Engineerin

Factors that Determine Preschool Teacher Self-Efficacy in an Urban School District

The aim of the present study is to determine what teacher variables are predictive of preschool teacher self-efficacy in an urban school district. A total of 83 preschool teachers participated in the study. Teacher variables, such as years of teaching experience, job satisfaction, location of employment, age, and self-efficacy were included in a series of ANOVA analyses. Linear regression modeling reported years of teaching experience outside the birth-2nd grade setting (β= -.232, t(1,79) = -2.124, p\u3c .05) and job satisfaction (β = .294, t(2,78) = 2.793, p\u3c .01) were statistically significant predictors of preschool teacher self-efficacy. This study found that teachers with a greater amount of teaching experience outside of the birth-2nd setting feel less efficacious about themselves and their abilities to positively influence student achievement and outcomes in the preschool classroom. Further policy implications, such as hiring practices are discussed

Detonation Diffraction Through a Mixture Gradient

A simple one-dimensional model of a self-propagating gaseous detonation consists of a shock wave tightly coupled to a reaction zone, propagating through a combustible gas mixture as shown in Fig. 1 (Strehlow 1984). A feedback mechanism exists in that the shock wave generates the thermodynamic conditions under which the gas combusts, and the energy release from the reaction zone maintains the strength of the shock This is in contrast to a flame, or deflagrative combustion, in which thermal and species transport processes dominate. Given a particular set of initial conditions, a self-propagating detonation wave travels at a constant Chapman-Jouguet velocity (VCJ) on the order of a few thousand meters per second, with associated pressures and temperatures of tens of bar and several thousand degrees, respectively. A detonation is actually a three-dimensional shock-reaction zone complex with a dynamic wavefront composed of curved incident, mach stem, and transverse shock waves as depicted in Fig. 2 (Strehlow 1970). The transverse shocks sweep across the wavefront and the triple-point paths form a diamond-shaped cellular pattern. The cell width [Greek lambda] is a characteristic length scale of detonations, indicative of the coupling between gasdynamic and chemical processes

The gradational history of southern Ismenius Lacus

Two epochs of accelerated gradation affected the geomorphic evolution of southern Ismenius Lacus. These periods of enhanced gradational activity were likely related to periods of more clement climate induced by release of either recycled exogenic or juvenile endogenic atmospheric volatiles. Variations in the intensity and duration of gradation during the second epoch are indicated by the variability in the timing of cessation and degree of air fall deposit removal across the study area. Overall intensity of gradation decreased through successive epochs based on: (1) the decreasing diameter at which cumulative statistics from the respective surfaces cease to follow the expected production function; and (2) the decrease in size/increase in density of preserved valley networks incised into surfaces of differing age. A comparable decrease in valley density with time has been noted in the Isidis region

Reparable Harm: Assessing and Addressing Disparities Faced by Boys and Men of Color in California

The California Endowment commissioned this report to highlight the most glaring inequities in socioeconomics, health, safety, and education faced by African-American and Latino men and boys in the state. In addition to presenting the statistics on these indicators, the authors outline a framework for addressing the disparities at the individual, community, and macro levels

Properties of optically selected BL Lac candidates from the SDSS

\textbf{Context.} Deep optical surveys open the avenue for find large numbers of BL Lac objects that are hard to identify because they lack the unique properties classifying them as such. While radio or X-ray surveys typically reveal dozens of sources, recent compilations based on optical criteria alone have increased the number of BL Lac candidates considerably. However, these compilations are subject to biases and may contain a substantial number of contaminating sources. \textbf{Aims.} In this paper we extend our analysis of 182 optically selected BL Lac object candidates from the SDSS with respect to an earlier study. The main goal is to determine the number of bona fide BL Lac objects in this sample. \textbf{Methods.} We examine their variability characteristics, determine their broad-band radio-UV SEDs, and search for the presence of a host galaxy. In addition we present new optical spectra for 27 targets with improved S/N with respect to the SDSS spectra. \textbf{Results.} At least 59% of our targets have shown variability between SDSS DR2 and our observations by more than 0.1-0.27 mag de- pending on the telescope used. A host galaxy was detected in 36% of our targets. The host galaxy type and luminosities are consistent with earlier studies of BL Lac host galaxies. Simple fits to broad-band SEDS for 104 targets of our sample derived synchrotron peak frequencies between $13.5 \leq \mathrm{log}_{10}(\nu_{\mathrm{peak}}) \leq 16$ with a peak at $\mathrm{log}_{10} \sim 14.5$. Our new optical spectra do not reveal any new redshift for any of our objects. Thus the sample contains a large number of bona fide BL Lac objects and seems to contain a substantial fraction of intermediate-frequency peaked BL Lacs.Comment: Accepted for publication in A\&

Planetary impact experimentation

An understanding of impact processes in low- and microgravity environments would be advanced significantly by the construction and use of an impact facility on the Space Station. It is proposed that initial studies begin as soon as possible in ground-based impact laboratories, on the NASA KC-135 Reduced-Gravity Aircraft, and in existing drop towers. The resulting experience and information base could then be applied toward an experiment package designed for use on Shuttle orbiters to support pilot studies in orbital environments. These experiments, as well as the first efforts made on the IOC Space Station, should involve the impact of various free-floating targets; such studies would yield a substantial scientific return while providing valuable experience and engineering information for use in refining the design of the dedicated Space Station Impact Facility. The dedicated facility should be designed to support impact experimentation, including but not limited to cratering, asteroid and ring-particle dynamics, and accretional processes

Land-Use Patterns in Southwestern Skane, Sweden: A Note on a Method and Some Preliminary Results

Since 1979, the Regional Development Group at IIASA has been engaged in a case study of economic and demographic development, land-use and related problems in the region of southwestern Skane in Sweden. The case study is the third in a series of attempts made by the Regional Development Group to apply systems analytic methods to regional planning problems in regions with different economic structures, resource endowments and organizational settings. The research in the Swedish case study has been done in collaboration with the Intermunicipal Association of Southwest Skane (SSK), as a part of their ongoing work in physical and public transport planning for the metropolitan region of Malmo, and its neighboring municipalities. The research has been partly sponsored by the Swedish Council for Building Research. In the case study an integrated systems analytic package of models is used which has been developed within the Regional Development Group in cooperation with a group of Swedish researchers and planners. In that package, separate models have been developed for interregional economic and demographic problems, and for intraregional land-use problems. This paper focuses on the point of departure for the Skane analysis -- compilation of detailed information on existing land-use patterns. Because available official information was seriously incomplete, the researchers had to devise strategies for extracting data from other sources. By taking advantage of existing real estate tax information and conducting a survey of major public properties, they were able to account for nearly all land-use in the SSK region. The paper thus illustrates a creative solution to data problems that often hinder research at a subnational level