Polystyrene Suspension Polymerization: The Effect of Polymerization Parameters on Particle Size and Distribution

Effects of polymerization parameters are studied to better understand interactions between parameters in stirred-tank polymerization reactors and to derive a regression model correlating polymer particle size and particle-size distribution with agitator speed, agitator diameter, tricalcium phosphate, dodecyl benzene sodium sulfonate concentrations, and mass cycle period. The derived equations give way to prediction of the polymerization conditions in order to obtain desired particle size and particle-size distributions which covers particle sizes between 0.3 and 5 mm. The roles of some other parameters and limiting agitation parameters are also investigated.     

A New Bootstrapped Hybrid Artificial Neural Network Approach for Time Series Forecasting

Computational Economics - In this study, a new bootstrapped hybrid artificial neural network is proposed for forecasting. This new neural network provides input significance, linearity and...     

Deep Learning for Financial Engineering

Computational Economics -     

Synthesis and characterization of poly(1,3‐thiazol‐2‐yl‐carbomoyl) methyl methacrylate: Its metal complexes and antimicrobial activity studies

Poly(1,3‐thiazol‐2‐yl‐carbomoyl) methyl methacrylate [poly(TCMMA)] is prepared in dimethyl sulfoxide using 2,2′‐azobisisobutyronitrile as an initiator at 60°C. Poly(TCMMA) is characterized by IR and ¹H‐NMR spectroscopic techniques. Cadmium(II), copper(II), and nickel(II) chelates of poly(TCMMA) were synthesized. An elemental analysis of the polychelates suggests a metal/ligand ratio of 1:2. The polychelates are further characterized by IR and magnetic susceptibility measurements. The thermal properties of the polymer and metal chelates are also discussed. The molecular weights of the poly(TCMMA) are determined by the gel permeation chromatography technique. The antimicrobial activities of the polymer and metal chelates are tested against Staphylococcus aureus COWAN I (bacteria), Escherichia coli ATCC 25922 (bacteria), Listeria monocytogenes SCOTTA (bacteria), Bacillus subtilis LMG (bacteria), Enterobacter aeroginosa CCM 2531 (bacteria), Klebsiela pneumania FMCS (bacteria), Candida albicans CCM 314 (Mayo yeast), and Saccharamyces cerevisiae UGA 102 (Mayo yeast). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3244–3251, 2003     

The Effects of Cure Temperature and Time on the Stress-Whitening Behavior of Structural Adhesives. Part II. Analysis of Fractographic Data

In this second part of the paper on the effects of cure conditions on the stress-whitening behavior of structural adhesives, fractographic data are presented and discussed. For this purpose, the size and nature of crack-tip-whitening zones obtained using single edge notched tension specimens of the model adhesive Metlbond with and without carrier cloth are studied. Scanning electron photomicrographs are utilized to investigate the effects of cure temperature and time on the crack-tip stress-whitening behavior. A brief discussion on the formation of inherent voids during the cure process is also presented since they are observed to enhance the crack-tip-whitening zones. Experimental results reveal that both the extent of voids produced during the cure process and the size of the crack-tip-whitening zones on the fracture surface increase with increasing cure temperatures. The presence of carrier cloth produces a similar effect with increases in both inherent voiding and stress-whitening sizes. The creation of stress-whitening zones are linked to stable crack propagation in those areas.     

Synthesis of some chroman derivatives and preliminary investigation on their vasodilatory activity

In this study, some N'-(chroman-4-yliden)-4-aryl-2-thiazolylhidrazide derivatives were synthesized. Their structures were elucidated by IR, NMR and microanalyses. The vasodilatory activities of the compounds obtained were examined in vitro.     

Comparative clinical and angiographic analysis of the initial efficacy and long-term follow-up of Wiktor stent implantation with conventional balloon angioplasty

This study was retrospectively designed to examine if the Wiktor stent, a balloon-expandable tantalum coil stent, provides a more favorable procedural and long-term clinical and angiographic outcome than does conventional coronary balloon angioplasty (POBA). From April 1995 to April 1996, we implanted 56 Wiktor stents in 46 lesions (LAD: 23, RCA: 16, CX: 7) in 42 patients (average age 53 +/- 10 years). Coronary lesions from the stent group were matched with similar lesions of another 42 POBA patients whose characteristics were identical to the Wiktor group. Revascularization indications in the Wiktor and POBA groups, respectively, were recent myocardial infarction (RMI) (45%, 40%), unstable (31%, 39%) and stable (24%, 21%) angina pectoris. 7% of the stents and 17% of the POBA balloons were less than 3 mm in diameter (p > 0.05). Procedural success was significantly greater in the Wiktor group than in the POBA group (100% vs. 92%, p < 0.05). Neither major cardiac event (death, CABG, acute myocardial infarction) nor (sub)acute occlusion was encountered in the Wiktor group during the hospitalization period and 1 month follow-up. There was 1 urgent CABG and 4 subacute occlusions in the POBA group. Control angiography at 8 months was performed in patients of both groups, of whom some were symptomatic at long-term follow-up or completely event free for 8 months. Angiographic restenosis (> 50% diameter stenosis) occurred in 25% of the Wiktor patients and in 43% of those in the POBA group (p < 0.05). For an 18 month clinical follow-up, 91% of the patients in the Wiktor group were asymptomatic and without ischemia in radionuclide imaging (RI), whereas 79% of the POBA patients were angina-free and 74% were without ischemia in the RI study. In conclusion, Wiktor stent implantation, with no major cardiac event or subacute occlusion, provides a more favorable procedural and long-term clinical and angiographic outcome than does conventional POBA.     

The Underlying Reasons of the Navigation Control Effect on Performance in a Virtual Reality Endoscopic Surgery Training Simulator

Navigation control skills of surgeons become very critical for surgical procedures. Strategies improving these skills are important for developing higher-quality surgical training programs. In this study, the underlying reasons of the navigation control effect on performance in a virtual reality-based navigation environment are evaluated. The participants’ performance is measured in conditions: navigation control display and paper-map display. Performance measures were collected from 45 beginners and experienced residents. The results suggest that navigation display significantly improved performance of the participants. Also, navigation was more beneficial for beginners than experienced participants. The underlying reason of the better performance in the navigation condition was due to lower number of looks to the map, which causes attention shifts between information sources. Accordingly, specific training scenarios and user interfaces can be developed to improve the navigation skills of the beginners considering some strategies to lower their number of references to the information sources.     

Characterisation of unbound aggregate materials considering physical and morphological properties

The objective of this paper is to evaluate the factors affecting resilient and permanent deformation behaviour of unbound granular materials, with a focus on the aggregate physical and morphological characteristics. To evaluate the behaviour of base course, repeated load triaxial testing is commonly used to establish the stress-dependent resilient modulus properties of unbound aggregate base and subbase materials. Although resilient modulus of aggregates is a critical input into mechanistic-empirical pavement design methods, the resilient modulus of unbound base material is often estimated from empirical correlations with index properties in the AASHTOWare Pavement ME design procedure for its simplicity. Since actual field stress conditions and resilient modulus stress states are generally quite different from those generated in the empirical test methods, use of an empirical correlation could lead to an unreliable prediction of resilient modulus and permanent deformation. In order to properly assess the stability of an unbound aggregate layer, it is necessary to establish a proper process to understand the factors affecting fundamental and performance-related properties of unbound granular materials. In this study, aggregate samples from four different sources were tested for resilient modulus and Poisson’s ratio measurements using the Precision Unbound Material Analyzer equipment. Morphological or shape properties of aggregate samples were also measured using an image analysis device. The results demonstrate that aggregate physical and morphological properties affect aggregate resilient and permanent deformation. Further, it is suggested that the resilient modulus of the aggregate should not be used as the sole indicator of rutting performance of aggregate base.