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Search Results: 1 - 10 of 345841 matches for " Paul S "
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On the Definition of State Variables for an Internal State Variable Constitutive Model Describing Metal Deformation  [PDF]
Paul S. Follansbee
Materials Sciences and Applications (MSA) , 2014, DOI: 10.4236/msa.2014.58062
The quest for an internal state variable constitutive model describing metal deformation is reviewed. First, analogy is drawn between a deformation model and the Ideal Gas Law. The use of strain as a variable in deformation models is discussed, and whether strain serves as an internal state variable is considered. A simple experiment that demonstrated path dependence in copper is described. The importance of defining appropriate internal state variables for a constitutive law relates to the ability to accurately model temperature and strain-rate dependencies in deformation simulations.
Structure Evolution in Austenitic Stainless Steels—A State Variable Model Assessment  [PDF]
Paul S. Follansbee
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.66049
Abstract: Strain hardening in austenitic stainless steels is modeled according to an internal state variable constitutive model. Derivation of model constants from published stress-strain curves over a range of test temperatures and strain rates is reviewed. Model constants for this material system published previously are revised to make them more consistent with model constants in other material systems.
Some Important Characteristics of Asset Bubbles and Financial Crises  [PDF]
Paul S. L. Yip
Modern Economy (ME) , 2018, DOI: 10.4236/me.2018.97075
Abstract: This paper first discusses the major characteristics of the seeding stage, the development stage and the final stage of an asset bubble. In particular, it emphasizes the role of expectation, some major changes in economic behaviors, financial leveraging, some important vicious cycles, upward spirals and herding behavior in the eventual development of an asset bubble. Thereafter, it discusses the policy implications of such an analysis. The second half of the paper extends the discussion to some important changes in economic behaviors, financial deleveraging, vicious cycles and downward spirals that would push an early-developed financial crisis into a full-blown economic crisis. Based on the characteristics and the experience of some major financial crises in the past few decades, the paper discusses policy measures that could be adopted during the crisis period and the post-crisis recession.
Analysis of Deformation in a High Entropy Alloy Using an Internal State Variable Model  [PDF]
Aaron Stein, Paul S. Follansbee
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.86033
Abstract: Deformation in the model high entropy alloy CoCrFeMnNi is assessed using an internal state variable constitutive model. A remarkable property of these alloys is the extraordinarily high strain hardening rates they experience in the plastic region of the stress strain curve. Published stress-strain measurements over a range of temperatures are analyzed. Dislocation obstacle interactions and the observed high rate of strain hardening are characterized in terms of state variables and their evolution. A model that combines a short-range obstacle and a long-range obstacle is shown to match experimental measurements over a wide range of temperatures and grain sizes. The long-range obstacle is thought to represent interactions of dislocations with regions of incomplete mixing or partial segregation. Dynamic strain aging also is observed at higher temperatures. Comparisons with measurements in austenitic stainless steel show some common trends.
Iris pigment in ocular melanomata
Paul S
Indian Journal of Ophthalmology , 1965,
Erythrocyte sedimentation rate in uveitis - a critical analysis
Paul S
Indian Journal of Ophthalmology , 1963,
Hyperspherical Partial Wave Theory with Two-term Error Correction
S. Paul
Physics , 2008, DOI: 10.1103/PhysRevA.77.052714
Abstract: Hyperspherical Partial Wave Theory has been applied to calculate T-matrix elements and Single Differential Cross-Section (SDCS) results for electron-hydrogen ionization process within Temkin-Poet model potential. We considered three different values of step length to compute the radial part of final state wave function. Numerical outcomes show that T-matrix elements and SDCS values depend on the step length h. Here, we have presented T-matrix elements and the corresponding SDCS results for 0.0075 a.u., 0.009 a.u. and 0.01 a.u. values of h and for 27.2eV, 40.8ev and 54.4eV impact energies. With the help of the calculated data for three different step lengths, we have been able to evaluate a two-term error function depending on the step length h. Finally, two-term error corrected T-matrix elements and the corresponding SDCS values have been computed. We fitted our two-term error corrected SDCS results by a suitable curve and compared with the benchmark results of Jones et al. [Phys. Rev. A, 66, 032717 (2002)]. Our fitted curves agree very well with the calculated results of Jones et al. and two-term error corrected SDCS results somewhere agree with the benchmark results. Two-term error corrected SDCS results are significantly better than the calculated SDCS results of different step lengths.
Microstructure and Mechanical Properties of as Cast Aluminium Alloy 7075/Basalt Dispersed Metal Matrix Composites  [PDF]
S. Ezhil Vannan, S. Paul Vizhian
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2014, DOI: 10.4236/jmmce.2014.23023
Abstract: This paper aims to study the effects of short basalt fiber reinforcement on the mechanical properties of cast aluminium alloy 7075 composites containing short basalt fiber of content ranging from 2.5 to 10 percent by weight in steps of 2.5 percent and fabricated using compo-casting technique. The objective is to investigate the process feasibility and resulting material properties such as young’s modulus, ductility, hardness & compression strength. The properties obtained are compared with those of as-cast that were manufactured under the same fabrication conditions. The results of this study revealed that, as the short basalt fiber content was increased, there were significant increases in the ultimate tensile strength, hardness, compressive strength and Young’s modulus, accompanied by a reduction in its ductility. Furthermore, the microstructure & facture studies were carried out using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) in order to establish relationships between the quality of the fiber/aluminium interface bond and hence to link with mechanical properties of the composites.
A Method for Measurement of the Hypertrophic First Metatarsal Medial Eminence on Foot Radiographs—A Reliability Study with Surgical Implications  [PDF]
Paul S. Armanasco, Kathy Briffa, Nick Pang
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2014, DOI: 10.4236/jasmi.2014.41005

Background: It has been suggested that hypertrophic eminence on the medial head of the first metatarsal is a component of the patho-anatomy of hallux valgus. However, research findings in this area are inconsistent, possibly due to differences in methods in identifying and measuring the medial eminence. To date, reliability of any method of measurement has not been reported. The purpose of this study was to determine the reliability of measurement of the medial eminence on medial oblique and dorsoplantar radiographs using a previously described geometric technique. Methods: To evaluate the reliability of a method of measurement of the medial eminence of the first metatarsal duplicate standardized dorsoplantar and medial oblique radiographs were taken of one foot of 15 subjects. The feet included both rectus feet and subjects with hallux valgus. The medial eminence was measured on the digital images using Inteleviewer 2.5 (Intelerad medical systems incorporated, Montreal, Quebec) software. Observer 1 measured one randomly selected image from each subject to determine inter-observer reliability. Observer 2 measured all images to determine the overall intraobserver reliability. Reliability was calculated using intra-class correlation coefficients (ICC). Results: The mean projection of the medial eminence ranged from 0.39 to 0.44 cm in both views. The ICCs were calculated for the dorsoplantar view and the 2 medial oblique view measures between observers. They ranged from 0.76 intra-rater and 0.86 interrater in the dorsoplantar view to 0.80 intra-rater and 0.90 inter-rater in the medial oblique view indicating good reliability in all measures. The average of the 4 oblique views also showed a high level of reliability with a coefficient of 0.96. Conclusions: The medial eminence can be reliably measured in the medial oblique and dorsoplantar view using the described technique. The medial

Alzheimer's disease therapeutic research: the path forward
Paul S Aisen
Alzheimer's Research & Therapy , 2009, DOI: 10.1186/alzrt2
Abstract: Alzheimer's disease (AD) was described just over 100 years ago as an uncommon devastating dementia affecting people in middle age. In the 1970s, Dr Robert Katzman demonstrated that AD is in fact an epidemic of enormous proportions, affecting a substantial segment of the aging population [1]. This spurred basic and clinical therapeutic research activity, leading to the development of modestly effective symptomatic treatments. While efforts to improve cognitive and behavioral symptoms continue, the major focus of AD therapeutic research is now disease modification – that is, slowing the progression of the underlying neurobiology of AD [2]. Alois Alzheimer described neuronal loss with formation of plaques and tangles. Today's leading programs target the biochemical pathways leading to amyloid accumulation and neurofibrillary tangle formation, and aim to protect neuronal cells and synapses against dysfunction and destruction.Clear targets have been identified. Two enzymes, beta secretase and the gamma secretase complex, appear to be essential for cleavage of the amyloidogenic Aβ fragment from its transmembrane amyloid precursor protein (APP); inhibition of one or both is expected to reduce amyloid accumulation [3]. Genetic evidence provides strong support for these approaches: all known genetic causes of AD either increase the expression of APP or increase the generation of amyloidogenic fragments. There is also hope that inhibiting receptors that mediate Aβ trafficking [4,5] and toxicity [5,6] may modify AD neurodegeneration. Tangle-related targets, including kinase inhibitors aiming to reduce the hyperphosphorylation that characterizes the abnormal tau protein in tangles [7], have seen more limited efforts. Neurotrophic programs include direct neurosurgical delivery of nerve growth factor to the nucleus basalis [8] using a viral vector.But despite the proliferation of clinical development programs, early results have been quite disappointing. The first two anti-amyloi
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