SLS Processing Studies of Nylon 11 Nanocomposites

Selective Laser Sintering (SLS) is widely used for rapid prototyping/manufacturing of nylon 11 and nylon 12 parts. This processing technique has not been explored for nylon nanocomposites. This study investigates the technicalities of processing nylon 11-clay and nylon-carbon nanofiber nanocomposites with SLS. Microstructural analyses of the SLS powders and parts were conducted under SEM. Results suggest that SLS processing is possible with the new nylon 11 nanocomposites. Yet the SLS parts built have inferior properties relative to those of injection molding, suggesting that more fine tuning for the processing is required.Mechanical Engineerin

The Cross-Cultural Invariance of the Servant Leadership Survey: A Comparative Study across Eight Countries

This paper tests and confirms the cross-cultural equivalence of the Servant Leadership Survey (SLS) in eight countries and languages: The Netherlands, Portugal, Germany, Iceland, Italy, Spain, Turkey and Finland. A composite sample consisting of 5201 respondents from eight countries that all filled out the SLS was used. A three-step approach was adopted to test configural invariance, measurement equivalence, and structural equivalence. For the full 30-item version of the SLS, configural invariance and partial measurement equivalence were confirmed. Implications of these results for the use of the SLS within cross-cultural studies are discussed

Fabrication of PEM Fuel Cell Bipolar Plates by Indirect SLS

The paper presents a new manufacturing technique involving Selective Laser Sintering (SLS) for proton exchange membrane fuel cell (PEMFC) bipolar plate fabrication. A material system for bipolar plate fabrication was identified to satisfy both the cell performance requirement and SLS operation restriction. Carbonization and liquid epoxy infiltration are subsequently performed following the completion of SLS green bipolar plate. The finished SLS bipolar plate showed impressive surface finish and mechanical strength, and a single fuel cell was assembled with two SLS end plates and membrane electrode assembly (MEA) in between. Various physical property tests were performed with positive results. Fuel cell performance (voltage vs. current density, voltage vs. time, etc.) will be assessed in the near future.Mechanical Engineerin

Relating Operating Parameters between SLS Machines which have Different Scanner Geometries and Laser Spot Sizes

As the number of SLS machines in operation increases, the opportunities to share operating parameters with other SLS operators also increases. However, if the machines are not identical down to the spot size of the laser beam, the quality of parts made on each machine can be different. The most likely differences between two SLS machines are the laser spot size and the scanning radius of the optics. The total energy flux to the powder surface is a function of the spot size and the scan speed. The algorithms defined to correct for machine differences are verified both experimentally and numerically using a one-dimensional empirical SLS model.McDonald Observator

Full-Densification of SLS Parts by Re-Melting

Among commercially available rapid prototyping processes, SLS is the most effective in terms of adaptability of various materials. However, rapid prototyped parts by the process are always porous and the physical properties of the parts are different from dense parts which is to be used in final product. This paper introduces a post process that can densify SLS processed plastic parts to almost 100%. An SLS processed polystyrene part is densified and, resultantly, a much stronger and transparent part is obtained.Mechanical Engineerin

SLS-PLAN-IT: A knowledge-based blackboard scheduling system for Spacelab life sciences missions

The primary scheduling tool in use during the Spacelab Life Science (SLS-1) planning phase was the operations research (OR) based, tabular form Experiment Scheduling System (ESS) developed by NASA Marshall. PLAN-IT is an artificial intelligence based interactive graphic timeline editor for ESS developed by JPL. The PLAN-IT software was enhanced for use in the scheduling of Spacelab experiments to support the SLS missions. The enhanced software SLS-PLAN-IT System was used to support the real-time reactive scheduling task during the SLS-1 mission. SLS-PLAN-IT is a frame-based blackboard scheduling shell which, from scheduling input, creates resource-requiring event duration objects and resource-usage duration objects. The blackboard structure is to keep track of the effects of event duration objects on the resource usage objects. Various scheduling heuristics are coded in procedural form and can be invoked any time at the user's request. The system architecture is described along with what has been learned with the SLS-PLAN-IT project

The SLS-Berlin: Validation of a German Computer-Based Screening Test to Measure Reading Proficiency in Early and Late Adulthood

Reading proficiency, i.e., successfully integrating early word-based information and utilizing this information in later processes of sentence and text comprehension, and its assessment is subject to extensive research. However, screening tests for German adults across the life span are basically non-existent. Therefore, the present article introduces a standardized computerized sentence-based screening measure for German adult readers to assess reading proficiency including norm data from 2,148 participants covering an age range from 16 to 88 years. The test was developed in accordance with the children’s version of the Salzburger LeseScreening (SLS, Wimmer and Mayringer, 2014). The SLS-Berlin has a high reliability and can easily be implemented in any research setting using German language. We present a detailed description of the test and report the distribution of SLS-Berlin scores for the norm sample as well as for two subsamples of younger (below 60 years) and older adults (60 and older). For all three samples, we conducted regression analyses to investigate the relationship between sentence characteristics and SLS-Berlin scores. In a second validation study, SLS-Berlin scores were compared with two (pseudo)word reading tests, a test measuring attention and processing speed and eye-movements recorded during expository text reading. Our results confirm the SLS-Berlin’s sensitivity to capture early word decoding and later text related comprehension processes. The test distinguished very well between skilled and less skilled readers and also within less skilled readers and is therefore a powerful and efficient screening test for German adults to assess interindividual levels of reading proficiency

Galaxy formation from dry and hydro simulations

The effects of dry and wet merging on the Scaling Laws (SLs) of elliptical galaxies (Es) are discussed. It is found that the galaxy SLs, possibly established at high redshift by the fast collapse of gas-rich and clumpy stellar distributions in preexisting dark matter halos following the cosmological SLs, are compatible with a (small) number of galaxy mergers at lower redshift.Comment: 1 page, no figures. Invited talk to Joint Discussion 01 "Dark Matter in Early-Type Galaxies". To appear in Highlights of Astronomy, Vol. 15, Proc. of the XXVIIth IAU General Assembly, Rio de Janeiro, Brazil, August 2009, eds. L.V.E. Koopmans and T. Treu, Cambridge University Pres