3,999 research outputs found
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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
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Polyamide Nanocomposites for Selective Laser Sintering
Current polyamide 11 and 12 are lacking in fire retardancy and high strength/high
heat resistance characteristics for a plethora of finished parts that are desired and required
for performance driven applications. It is anticipated that nanomodification of polyamide
11 and 12 will result in enhanced polymer performance, i.e., fire retardancy, high strength
and high heat resistance for polyamide 11 and 12. It is expected that these findings will
expand the market opportunities for polyamide 11 and 12 resin manufacturers.
The objective of this research is to develop improved polyamide 11 and 12 polymers
with enhanced flame retardancy, thermal, and mechanical properties for selective laser
sintering (SLS) rapid manufacturing (RM). A nanophase was introduced into the
polyamide 11 and 12 via twin screw extrusion to provide improved material properties of
the polymer blends. Arkema RILSAN® polyamide 11 molding polymer pellets and
Degussa VESTAMID® L1670 polyamide 12 were examined with three types of
nanoparticles: chemically modified montmorillonite (MMT) organoclays, surface
modified nanosilica, and carbon nanofibers (CNFs) to create polyamide 11 and 12
nanocomposites.
Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM)
were used to determine the degree of dispersion. Injection molded test specimens were
fabricated for physical, thermal, mechanical properties, and flammability tests. Thermal
stability of these polyamide 11 and 12 nanocomposites was examined by TGA.
Mechanical properties such as tensile, flexural, and elongation at break were measured.
Flammability properties were also obtained using the Cone Calorimeter at an external
heat flux of 50 kW/m2. TEM micrographs, physical, mechanical, and flammability
properties are included in the paper. Polyamide 11 and 12 nanocomposites properties are
compared with polyamide 11 and 12 baseline polymers. Based on flammability and
mechanical material performance, selective polymers including polyamide 11
nanocomposites and control polyamide 11 were cryogenically ground into fine powders
and fabricated into SLS parts.Mechanical Engineerin
An appropriate use of iMap produces correct statistical results: a reply to McManus (2013) "iMAP and iMAP2 produce erroneous statistical maps of eye-movement differences".
McManus (2013, Perception, 42, 1075-1084) contends the validity of the statistical approach adopted in previous versions of iMap (namely, iMap and iMap2; Caldara & Miellet, 2011, Behavior Research Methods, 43, 864-878), casts doubts on earlier results obtained with the toolbox, and offers an altered version of the code. Here we dispute these claims and argue that while some of the arguments put forward are valid, McManus's conclusions are misleading, since they are based on a partial use of the toolbox. Moreover, we compared iMap with the alternative code offered by McManus and objectively demonstrate that McManus's approach is underpowered and flawed. iMap offers an appropriate and effective alternative to the commonly used regions of interest approach for statistical analyses of eye-movement data
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Innovative Selective Laser Sintering Rapid Manufacturing using Nanotechnology
The objective of this research is to develop an improved nylon 11 (polyamide 11) polymer
with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering
(SLS) rapid manufacturing (RM). A nanophase was introduced into nylon 11 via twin screw
extrusion to provide improved material properties of the polymer blends. Atofina (now known
as Arkema) RILSAN® nylon 11 injection molding polymer pellets was used with three types of
nanoparticles: chemically modified montmorillonite (MMT) organoclays, nanosilica, and carbon
nanofibers (CNF) to create nylon 11 nanocomposites. Wide angle X-ray diffraction (WAXD)
and transmission electron microscopy (TEM) were used to determine the degree of dispersion.
Fifteen nylon 11 nanocomposites and control nylon 11 were fabricated by injection molding.
Flammability properties (using a cone calorimeter with a radiant flux of 50 kW/m2
) and
mechanical properties such as tensile strength and modulus, flexural modulus, elongation at
break were determined for the nylon 11 nanocomposites and compared with the baseline nylon
11. Based on flammability and mechanical material performance, five polymers including four
nylon 11 nanocomposites and a control nylon 11 were cryogenically ground into fine powders
for SLS RM. SLS specimens were fabricated for flammability, mechanical, and thermal
properties characterization. Nylon 11-CNF nanocomposites exhibited the best overall properties
for this study.Mechanical Engineerin
A system science methodology develops a new composite highly predictable index of magnetospheric activity for the community: the whole-Earth index E(1)
For community use, a new composite whole-Earth index E(1) and its matching composite solar wind driving function S(1) are derived. A system science methodology is used based on a time-dependent magnetospheric state vector and a solar wind state vector, with canonical correlation analysis (CCA) used to reduce the two state vectors to the two time-dependent scalars E(1)(t) and S(1)(t). The whole-Earth index E(1) is based on a diversity of measures via six diverse geomagnetic indices that will be readily available in the future: SML, SMU, Ap60, SYMH, ASYM, and PCC. The CCA-derived composite index has several advantages: 1) the new “canonical” geomagnetic index E(1) will provide a more powerful description of magnetospheric activity, a description of the collective behavior of the magnetosphere–ionosphere system. 2) The new index E(1) is much more accurately predictable from upstream solar wind measurements on Earth. 3) Indications are that the new canonical geomagnetic index E(1) will be accurately predictable even when as-yet-unseen extreme solar wind conditions occur. The composite solar wind driver S(1) can also be used as a universal driver function for individual geomagnetic indices or for magnetospheric particle populations. To familiarize the use of the new index E(1), its behavior is examined in different phases of the solar cycle, in different types of solar wind plasma, during high-speed stream-driven storms, during CME sheath-driven storms, and during superstorms. It is suggested that the definition of storms are the times when E(1) >1
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Flame Retardant Intumescent Polyamide 11 Nanocomposites – Further Study
The objective of this research is to develop improved polyamide 11 and 12 polymers with
enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering
(SLS) rapid manufacturing (RM). In the present study, a nanophase was introduced into the
polyamide 11 and combine with a conventional intumescent flame retardant (FR) additive via
twin screw extrusion. Arkema Rilsan® polyamide 11 molding polymer pellets were used with
two types of nanoparticles such as: chemically modified montmorillonite (MMT) organoclays
and carbon nanofibers (CNFs). Two types of Clariant’s Exolit® OP 1311 and 1312 intumescent
FR additives were used to generate a family of FR intumescent polyamide 11 nanocomposites
with anticipated synergism.Mechanical Engineerin
Fittonia verschaffeltii Response to Artificial Light Treatments: BIOMASS, Nutrient Concentrations and Physiological Changes
The purpose of the present study was to evaluate the effects of different light treatments on biomass, nutrient concentrations and physiological parameters of Fittonia verschaffeltii (Lem) Van Houtte. The aim was to establish a methodology to evaluate the effect of photosynthetically active radiation (PAR) emitted by lamps on biomass. The light treatments used were tube luminescent Dunn (TL-D), tube luminescent Dunn + light emitting diodes (LEDs) and Tube luminescent 5 (TL-5). At the end of the experimental period, biomass, nutritional, biochemical, and physiological parameters were assessed. A clear reduction in total plant dry weight under TL-D + LEDs at the end of the experiment was recorded. With respect to nutrient concentration in the different organs assessed, there was no clear response under the different light treatments. The growth under TL-D lamps resulted in the highest concentration of total soluble sugars and starch in leaves, whereas the highest value of indole 3-acetic acid concentration was under TL-5 lamps. Plants grown under TL-D + LEDs showed the lowest values of chlorophyll a, b and a + b. The relationship proposed between integrated use of spectral energy (IUSE) and total dry weight (TDW) showed a good correlation with an R2 value of 0.86, therefore we recommend this methodology to discern the effects of the different spectral qualities on plant biomass
A Multivariate Surface-Based Analysis of the Putamen in Premature Newborns: Regional Differences within the Ventral Striatum
Many children born preterm exhibit frontal executive dysfunction, behavioral problems including attentional deficit/hyperactivity disorder and attention related learning disabilities. Anomalies in regional specificity of cortico-striato-thalamo-cortical circuits may underlie deficits in these disorders. Nonspecific volumetric deficits of striatal structures have been documented in these subjects, but little is known about surface deformation in these structures. For the first time, here we found regional surface morphological differences in the preterm neonatal ventral striatum. We performed regional group comparisons of the surface anatomy of the striatum (putamen and globus pallidus) between 17 preterm and 19 term-born neonates at term-equivalent age. We reconstructed striatal surfaces from manually segmented brain magnetic resonance images and analyzed them using our in-house conformal mapping program. All surfaces were registered to a template with a new surface fluid registration method. Vertex-based statistical comparisons between the two groups were performed via four methods: univariate and multivariate tensor-based morphometry, the commonly used medial axis distance, and a combination of the last two statistics. We found statistically significant differences in regional morphology between the two groups that are consistent across statistics, but more extensive for multivariate measures. Differences were localized to the ventral aspect of the striatum. In particular, we found abnormalities in the preterm anterior/inferior putamen, which is interconnected with the medial orbital/prefrontal cortex and the midline thalamic nuclei including the medial dorsal nucleus and pulvinar. These findings support the hypothesis that the ventral striatum is vulnerable, within the cortico-stiato-thalamo-cortical neural circuitry, which may underlie the risk for long-term development of frontal executive dysfunction, attention deficit hyperactivity disorder and attention-related learning disabilities in preterm neonates. © 2013 Shi et al
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