A study on fusion and rheological behaviors of PVC/SiO2 microcomposites and nanocomposites: The effects of SiO2 particle size

In this study, poly(vinyl chloride) (PVC) and silica (SiO₂) microcomposites and nanocomposites were prepared by melt mixing in a Haake torque rheometer. The fusion and rheological behaviors of PVC/SiO₂ composites were evaluated by means of torque data recorded during processing to investigate the influence of the SiO₂ particle size on these behaviors. It was found that the fusion time and the fusion temperature decreased with the decreasing of SiO₂ particle size, whereas the fusion torque increased with the decreasing of particle size. The PVC/Si‐25‐nm nanocomposite (PVC including the 25 nm of SiO₂) showed the highest apparent viscosity among the PVC/SiO₂ microcomposites and nanocomposites prepared in this study. Scanning electron microscopy results demonstrated that some aggregates, whose sizes about 60–90 nm, were formed when the 25 nm of SiO₂ was used as filler. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of 2% chlorhexidine gluconate cavity disinfectant on microtensile bond strength of tooth-coloured restorative materials to sound and caries-affected dentin

This study evaluated the effect of 2% chlorhexidine gluconate-based cavity disinfectant (CHX) on the microtensile bond strength (μTBS) of glass ionomer, resin-modified glass ionomer and packable resin composite to sound and caries-affected dentin. Sound and occlusal caries-affected human third molars (N?=?36, n?=?3 per group) were randomly divided into three experimental groups to receive one of the following restorative materials. (a) Glass ionomer (Ketac Molar, 3 M ESPE; GI), (b) resin-modified glass ionomer (Vitremer, 3 M ESPE; RMGI) and (c) packable resin composite (Surefil, Dentsply; PRC) with a bonding agent (Prime Bond NT, Dentsply De Trey). Caries was removed using a caries-detecting dye (Caries Detector, Kuraray Medical Ltd.) and flat dentin surfaces were achieved by finishing up to 1200-grit silicon carbide abrasive. Half of the teeth in each group received 2% CHX (Consepsis, Ultradent). Dentin surfaces were built-up with the respective materials incrementally and were sectioned with a slow-speed saw into multiple beams. The beams were subjected to μTBS test (0.5 mm/min) in a Universal Testing Machine. The data were analysed using two-way analysis of variance and Tukey’s tests. For each restorative material, μTBS results were not affected by the application of CHX (p?>?0.05) on both sound and caries-affected dentin (p?>?0.05). PRC in combination with the corresponding bonding agent showed significantly higher results (p?<?0.05) than those of GI and RMGI, on sound and caries-affected teeth, respectively. Cohesive failure in dentin was not observed in any of the groups. The use of 2% chlorhexidine-based cavity disinfectant did not impair the adhesion of the restorative materials tested to either sound or caries-affected dentin.     

Development a new mutation operator to solve the Traveling Salesman Problem by aid of Genetic Algorithms

In this study, a new mutation operator has been developed to increase Genetic Algorithm (GA) performance to find the shortest distance in the known Traveling Salesman Problem (TSP). We called this method as Greedy Sub Tour Mutation (GSTM). There exist two different greedy search methods and a component that provides a distortion in this new operator. The developed GSTM operator was tested with simple GA mutation operators in 14 different TSP examples selected from TSPLIB. The application of this GSTM operator gives much more effective results regarding to the best and average error values. The GSTM operator used with simple GAs decreases the best error values according to the other mutation operators with the ratio of between 74.24% and 88.32% and average error values between 59.42% and 79.51%.     

A Computational Investigation of the Thermohydraulics of an EGS Project

A numerical analysis of the thermohydraulics of an enhanced geothermal system project is presented. The rock structures are modelled as porous medium, based on the computationally obtained hydraulic fracturing data of other authors. The influence of the domain size, grid resolution, temporal resolution and the discretization scheme is assessed to obtain a highly accurate numerical solution under the prevailing modelling assumptions. Based on the numerical model, different production scenarios are investigated and discussed. The relative positioning of the injection and production ports is also analyzed. It is shown that there is a considerable potential for optimizing the production rate and the port configuration to obtain the most favorable results for the production temperature, investment costs and operation costs.     

Copolymerization of 2-methyl-N-1,3-thiazole-2-ylacrylamide with glycidyl methacrylate: synthesis, characterization, reactivity ratios and biological activity

The free-radical copolymerization of 2-methyl-N-1,3-thiazole-2-ylacrylamide monomer (TMA) with glycidyl methacrylate (GMA) was carried out in 1,4-dioxane at 65 ± 1 °C using azobisisobutironitril (AIBN) as an initiator. The copolymers were characterized by FTIR, ¹³C-NMR and ¹H-NMR spectroscopic methods. The copolymer compositions were determined by elemental analysis. The weight-average and number-average molecular weights of the copolymers were obtained by gel permeation chromatography (GPC). The polydispersity indices of the polymers, determined with gel permeation chromatography, suggested a strong tendency for chain termination by disproportionation. Thermal properties of the polymers were also studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The monomer reactivity ratios were calculated according to the general copolymerization equation using Kelen–Tudos and Fineman–Ross linearization methods. The reactivity ratios indicated a tendency toward for alternation. The thermal decomposition activation energies of the polymers were evaluated by Ozawa method. The antibacterial and antifungal effects of the copolymers were also investigated on various bacteria and fungi. All the products showed moderate activity against different strains of bacteria and fungi.     

Monitoring Smartphones for Anomaly Detection

In this paper we demonstrate how to monitor a smartphone running Symbian operating system and Windows Mobile in order to extract features for anomaly detection. These features are sent to a remote server because running a complex intrusion detection system on this kind of mobile device still is not feasible due to capability and hardware limitations. We give examples on how to compute relevant features and introduce the top ten applications used by mobile phone users based on a study in 2005. The usage of these applications is recorded by a monitoring client and visualized. Additionally, monitoring results of public and self-written malwares are shown. For improving monitoring client performance, Principal Component Analysis was applied which lead to a decrease of about 80% of the amount of monitored features.     

On nonlocal microfluid mechanics

The simple microfluid theory of Eringen [1] is generalized to include nonlocal effects. The balance laws, jump conditions, and constitutive equations are obtained. The nonlocal intermolecular forces, energy and entropy are accounted for by nonlocal field residuals and functional constitutive equations of space type. The second law of thermodynamics is used to obtain specific forms of these residuals, constitutive equations and restrictions to be imposed. The linear theory is developed fully for the micromorphic and micropolar nonlocal fluids. The nonlocal effects are shown to include surface tension and surface stresses. Passage is made to material gradient theories.     

A continuum theory of rigid suspensions

A continuum theory of rigid suspension is presented. The theory modifies and extends the Batchelor^1,2 theory of fiber suspensions to heat conducting thermo-viscous Newtonian solvents carrying rigid suspensions.     

Edge dislocation in nonlocal elasticity

The solution is presented for the problem of straight edge dislocation in nonlocal elasticity. The stress field and elastic energy are calculated. Classical singularities in the expressions of the stress field and stored energy are found not present in the nonlocal model. An estimate is made for the critical shear stress which will produce a single edge dislocation of one atomic distance.