68 research outputs found
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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
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Flammability and Thermal Properties of Polyamide 11-Alumina Nanocomposites
Neat polyamides 11 and 12 lack high strength/high heat resistance and flame retardancy.
The incorporation of selected nanoparticles is expected to enhance these properties to a
level that is desired and required for performance driven applications. This enhancement
may result in additional market opportunities for the polyamide 11 and 12 polymer
manufacturers. The objective of this study is to develop polyamide 11 polymer
nanocomposites with enhanced thermal, flammability, and mechanical performance for
selective laser sintering (SLS) rapid manufacturing. Three types of nano-alumnia (X-0
needle, X-25SR, and X-0SR) with different organic treatments were melt-compounded
into polyamide 11 in three different weight loadings of the nanoparticles (2.5%, 5%, and
7.5%). Injection molded specimens were fabricated for thermal, flammability, and
mechanical properties characterization. Although nano-alumina was uniformly dispersed
in polyamide 11 and better thermal stability of the nanomodified materials was observed,
the desired FR characteristics of the nanomodified polyamide 11 was not achieved. None
of the materials passed the desired UL 94 V0 rating.Mechanical Engineerin
Consensus document for invasive coronary physiologic assessment in Asia-Pacific countries
Background: Currently, invasive physiologic assessment such as fractional flow reserve is widely used worldwide with different adoption rates around the globe. Patient characteristics and physician preferences often differ in the Asia-Pacific (APAC) region with respect to treatment strategy, techniques, lesion complexity, access to coronary physiology and imaging devices, as well as patient management. Thus, there is a need to construct a consensus document on recommendations for use of physiology-guided percutaneous coronary intervention (PCI) in APAC populations. This document serves as an overview of recommendations describing the best practices for APAC populations to achieve more consistent and optimal clinical outcomes.
Methods and Results: A comprehensive multiple-choice questionnaire was provided to 20 interven- tional cardiologists from 10 countries in the APAC region. Clinical evidence, tips and techniques, and clinical situations for the use of physiology-guided PCI in APAC were reviewed and used to propose key recommendations. There are suggestions to continue to develop evidence for lesion and patient types that will benefit from physiology, develop directions for future research in health economics and local data, develop appropriate use criteria in different countries, and emphasize the importance of education of all stakeholders. A consensus recommendation to enhance the penetration of invasive physiology-based therapy was to adopt the 5E approach: Evidence, Education, Expand hardware, Economics and Expert consensus.
Conclusions: This consensus document and recommendations support interventional fellows and cardiologists, hospital administrators, patients, and medical device companies to build confidence and encourage wider implementation of invasive coronary physiology-guided therapy in the APAC region.
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
Development of a planar multi-body model of the human knee joint
The aim of this work is to develop a dynamic model for the biological human knee joint. The model is formulated in the framework of multibody systems methodologies, as a system of two bodies, the femur and the tibia. For the purpose of describing the formulation, the relative motion of the tibia with respect to the femur is considered. Due to their higher stiffness compared to that of the articular cartilages, the femur and tibia are considered as rigid bodies. The femur and tibia cartilages are considered to be deformable structures with specific material characteristics. The rotation and gliding motions of the tibia relative to the femur can not be modeled with any conventional kinematic joint, but rather in terms of the action of the knee ligaments and potential contact between the bones. Based on medical imaging techniques, the femur and tibia profiles in the sagittal plane are extracted and used to define the interface geometric conditions for contact. When a contact is detected, a continuous non-linear contact force law is applied which calculates the contact forces developed at the interface as a function of the relative indentation between the two bodies. The four basic cruciate and collateral ligaments present in the knee are also taken into account in the proposed knee joint model, which are modeled as non-linear elastic springs. The forces produced in the ligaments, together with the contact forces, are introduced into the system’s equations of motion as external forces. In addition, an external force is applied on the center of mass of the tibia, in order to actuate the system mimicking a normal gait motion. Finally, numerical results obtained from computational simulations are used to address the assumptions and procedures adopted in this study.Fundação para a Ciência e a Tecnologia (FCT
Leiomioma ovariano, tumor de células da granulosa e ovário policístico em cadela: uma rara associação
Efeitos da eletroacupuntura, aquapuntura e farmacopuntura em cadelas anestesiadas com isofluorano e submetidas à ovário-histerectomia
Performance evaluation of fuzzy-based decision system for pool
An important step in any machine intelligence is to automatically and reliably decide on a solution/outcome based on the inputs given. The mapping of the inputs to an output decision often follows a set of critical rules that mimic the decision that would often be decided by a human being. In this paper, the performance of a fuzzy-based decision system for playing a game of pool is presented by comparing the results involving direct hit with two known systems. The performance is also compared to the decision that would be made by the human players. The design steps for the fuzzy-based decision system are presented using the fuzzy logic approach by employing a three-input one-output fuzzy inference system based on a set of 24 rules. The results have shown that fuzzy logic is able to accurately decide on the best move, which is as good as the human players themselves. (C) 2005 Elsevier B.V. All rights reserved
Monte Carlo Studies of Metal/Phosphor Screen in Therapeutic X-Ray Imaging
In order to provide the optimal design parameters, we have investigated the characteristics of a combination of metal plate and phosphor screen, a typical X-ray sensor in electronic portal imaging system, by using Monte Carlo simulation. Detection efficiency and spatial resolution of the X-ray sensor were estimated based on the bremsstrahlung spectrum of the incident X-ray and for various thicknesses of metal plate and phosphor screen. The detection efficiency was calculated from the total absorbed energy and the spatial resolution was defined from the spatial distribution of the absorbed energy. Simulation results showed a trade-off relationship between the detection efficiency and the spatial resolution. It was also found that the detection efficiency and the spatial resolution were mainly determined by thickness of metal plate and phosphor screen, respectively. The simulation will be useful when determining the optimal thickness of phosphor screen as well as of metal plate for the sensor design of therapeutic X-ray imaging. © 1999 Elsevier Science B.V. All rights reserved
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