1,200 research outputs found
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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
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Intumescent Flame Retardant Polyamide 11 Nanocomposites
Current polyamide 11 and 12 are lacking in fire retardancy and high strength/high heat
resistance characteristics for a plethora of fabricated parts that are desired and required
for performance driven applications. The introduction of selected nanoparticles such as
surface modified montmorillonite (MMT) clay or carbon nanofibers (CNFs), combined
with a conventional intumescent flame retardant (FR) additive into the polyamide
11/polyamide 12 (PA11/PA12) by melt processing conditions has resulted in the
preparation of a family of intumescent polyamide nanocomposites. These intumescent
polyamide 11 and 12 nanocomposites exhibit enhanced polymer performance
characteristics, i.e., fire retardancy, high strength and high heat resistance and are
expected to expand the market opportunities for polyamide 11 and polyamide 12 polymer
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). In the present study, a nanophase was
introduced into the polyamide 11 and combining it with a conventional intumescent FR
additive via twin screw extrusion. Arkema RILSAN® polyamide 11 molding polymer
pellets were examined with two types of nanoparticles: chemically modified
montmorillonite (MMT) organoclays, and carbon nanofibers (CNFs); and Clairant’s
Exolit® OP 1230 intumescent FR additive were used to create a family of FR
intumescent polyamide 11 nanocomposites.
Transmission electron microscopy (TEM) was used to determine the degree of
nanoparticles dispersion. Injection molded specimens were fabricated for physical,
thermal, and flammability measurements. Thermal stability of these intumescent
polyamide 11 nanocomposites was examined by TGA. Flammability properties were
obtained using the Cone Calorimeter at an external heat flux of 35 kW/m
2
and UL 94
Test Method. Heat deflection temperatures (HDT) were also measured. TEM
micrographs, physical, thermal, and flammability properties are presented. FR
intumescent polyamide 11 nanocomposites properties are compared with polyamide 11
baseline polymer. Based on flammability and mechanical material performance, selective
polymers including polyamide 11 nanocomposites and control polyamide 11 will be
cryogenically ground into fine powders for SLS RM processing. SLS specimens will be
fabricated for thermal, flammability, and mechanical properties characterization.Mechanical Engineerin
The inhomogeneous mechanical behaviour of Ascending Thoracic Aortic Aneurism (ATAA)
Surgical management of ascending thoracic aortic aneurysms (aTAAs) relies on maximum diameter,
growth rate, and presence of connective tissue disorders. The surgical decision however is often
not considering that dissection and rupture do occur in patients who do not meet criteria for surgical
repair [1,2]. In this study the authors aim to investigate the mechanical properties of aTAAs to be
implemented in computational biomechanics models for a preclinical risk evaluation. Additionally,
in some recent studies, some data about the biomechanical properties of the aTAAs have been reported
[3], but without any relation to bicuspidal or tricuspidal aTAA. The aim of this study was to
investigate aTAA mechanical properties using a biaxial system to compare the circumferential and
axial stress-strain relations for bicuspidal and tricuspidal aTAAs
Identification of a novel plasmid lineage associated with the dissemination of metallo-β-lactamase genes among pseudomonads
Acquisition of metallo-\u3b2-lactamases (MBLs) represents one of most relevant resistance mechanisms to all \u3b2-lactams, including carbapenems, ceftolozane and available \u3b2-lactamase inhibitors, in Pseudomonas spp. VIM-type enzymes are the most common acquired MBLs in Pseudomonas aeruginosa and, to a lesser extent, in other Pseudomonas species. Little is known about the acquisition dynamics of these determinants, that are usually carried on integrons embedded into chromosomal mobile genetic elements. To date, few MBL-encoding plasmids have been described in Pseudomonas spp., and their diversity and role in the dissemination of these MBLs remains largely unknown. Here we report on the genetic features of the VIM-1encoding plasmid pMOS94 from P. mosselii AM/94, the earliest known VIM-1-producing strain, and of related elements involved in dissemination of MBL. Results of plasmid DNA sequencing showed that pMOS94 had a modular organization, consisting of backbone modules associated with replication, transfer and antibiotic resistance. Plasmid pMOS94, although not typable according to the PBRT scheme, was classifiable either in MOBF11 or MPFT plasmid families. The resistance region included the class I integron In70, carrying blaVIM-1, in turn embedded in a defective Tn402-like transposon. Comparison with pMOS94-like elements led to the identification of a defined plasmid lineage circulating in different Pseudomonas spp. of clinical and environmental origin and spreading different MBL-encoding genes, including blaIMP-63, blaBIM, and blaVIM-type determinants. Genetic analysis revealed that this plasmid lineage likely shared a common ancestor and had evolved through the acquisition and recombination of different mobile elements, including the MBL-encoding transposons. Our findings provide new insights about the genetic diversity of MBL-encoding plasmids circulating among Pseudomonas spp., potentially useful for molecular epidemiology purposes, and revealed the existence and persistence of a successful plasmid lineage over a wide spatio-temporal interval, spanning over five different countries among two continents and over 20-years
Transcatheter Mitral Valve-in-Valve Dislocation: A Rescue Strategy
In the transcatheter aortic valve replacement era, transapical valve-in-valve mitral valve implantation is considered an alternative treatment for high-risk patients with degenerated mitral bioprosthesis. We report an unusual strategy to remedy the potentially fatal complication of the mitral prosthesis migration into the aortic arch. The dislocated prosthesis was successfully stabilized in the aortic arch with a bare aortic stent, ensuring adequate perfusion of epiaortic vessels. \ua9 2018 The Society of Thoracic Surgeon
A preliminary investigation of the use of inertial sensing technology for the measurement of hip rotation asymmetry in horse riders
This study investigated the use of inertial sensing technology as an indicator of asymmetry in horse riders, evidenced by discrepancies in the angle of external rotation of the hip joint. Twelve horse and rider combinations were assessed with the rider wearing the XsensTM MVN inertial motion capture suit. Asymmetry (left vs right) was revealed in mean hip external rotation of all riders, with values ranging from 1° to 27°, and 83% showed greater external rotation of the right hip. This study represents novel use of inertial sensing equipment in its application to the measurement of rider motion patterns. The technique is non-invasive, is capable of recording rider hip rotation asymmetry whilst performing a range of movements unhindered and was found to be efficient and practical, with potential to further advance the analysis of horse and rider interactions
ALICE: An Automatic Design Flow for eFPGA Redaction
Fabricating an integrated circuit is becoming unaffordable for many semiconductor design houses. Outsourcing the fabrication to a third-party foundry requires methods to protect the intellectual property of the hardware designs. Designers can rely on embedded reconfigurable devices to completely hide the real functionality of selected design portions unless the configuration string (bitstream) is provided. However, selecting such portions and creating the corresponding reconfigurable fabrics are still open problems. We propose ALICE, a design flow that addresses the EDA challenges of this problem. ALICE partitions the RTL modules between one or more reconfigurable fabrics and the rest of the circuit, automating the generation of the corresponding redacted design
In Car Audio
This chapter presents implementations of advanced in Car Audio Applications. The system is composed by three main different applications regarding the In Car listening and communication experience. Starting from a high level description of the algorithms, several implementations on different levels of hardware abstraction are presented, along with empirical results on both the design process undergone and the performance results achieved
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