Prediction of Nusselt Number and Friction Factor of Water-Al2O3 Nanofluid Flow in Shell-and-Tube Heat Exchanger with Helical Baffles

Heat transfer and flow field of water-Al₂O₃ nanofluid were simulated three-dimensionally in the shell-side of shell-and-tube heat exchanger with helical baffles. The effects of Reynolds number and volume fraction on heat transfer and pressure drop were evaluated. Increasing the volume fraction and Reynolds number intensified both heat transfer and pressure drop. Reduction of the Reynolds number increased the friction factor, but no considerable change was observed in the friction factor by increasing the volume fraction at constant Reynolds number. Heat transfer of the nanofluid revealed greater dependency on the volume fraction of particles at lower Reynolds numbers. Models of Nusselt number and friction factor were obtained in the heat exchanger in terms of Reynolds number and volume fraction using neural network. The neural network predicted the output variables with great accuracy.     

Using Persulfate Oxidized Chitosan as a Novel Additives in Easy-Care Finishing for Cotton Textiles

Easy care finishing of cotton fabric using glyoxal in the presence and absence of low molecular weight chitosan, i.e., persulfate-oxidized chitosan, as a novel additive along with MgCl₂·6H₂O as an acid catalyst was studied in detail. Major factors affecting finishing reaction were studied with respect to glyoxal, oxidized chitosan, and catalyst concentrations in addition to curing time and temperature of treatment according to the pad-dry-cure method. The obtained results show the following findings: (a) increasing the glyoxal concentration from 5–50 g/l in absence of oxidized chitosan is accompanied by an increase in crease recovery angle and a decrease in tensile strength of the finished fabric, whereas that treated in the presence of oxidized chitosan shows a higher tensile strength and to some extent comparable crease recovery angle with respect to that finished in the absence of it when the concentration of glyoxal increases; (b) increasing the oxidized chitosan concentration is accompanied by decreasing crease recovery angle, whereas the tensile strength increases when glyoxal concentration increases within the range studied; (c) increasing the MgCl₂·6H₂O from 0–15 g/l is accompanied by an increase in the crease recovery angle and a decrease in tensile strength of the finished fabrics in the presence and absence of oxidized chitosan; (d) increasing the time and temperature of curing of the finished fabrics is accompanied by an increase in crease recovery angles and decreases in tensile strength; and (e) the dry wrinkle recovery angle of cotton fabric samples finished in presence of O-chitosan is decreased after washing, and the higher the washing cycle the lower the dry wrinkle recovery angle.     

Characterization and Application of Intercalated Montmorillonite with Verapamil and its Polymethyl Methacrylate Nanocomposite in Drug Delivery

This work examined two drug delivery systems: the first system studied the adsorption of Verapamil hydrochloride drug into montmorillonite clay (MMT) by intercalation process to prepare MMT-Verapamil hybrid at different intercalating time, temperatures, pH values and initial drug concentrations. The second system includes the preparation of MMT-Verapamil hybrid combined with polymethyl methacrylate via an emulsion polymerization process to produce a novel nanocomposite material to be used in drug delivery. The polymerization process was carried out using an ultrasonic technique to achieve a biologically safe drug delivery system. Best conditions for the intercalation of verapamil hydrochloride drug into the interlayer of MMT clay were found to be at 50°C and 1 hr using pH ranges of 4–6. The prepared MMT-Verapamil hybrid and the produced MMT-verapamil-MMA nanocomposite material were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and thermal gravimetric analysis (TGA). The in-vitro release profile of Verapamil in the case of a drug hybrid is faster than the release in the case of a drug nanocomposite in both gastric and intestinal fluids where, in the case of gastric fluid (pH 1.2), about 40% of the loaded drug was released from the drug hybrid in the first 4 h against only 37% in 5 h in the case of drug nanocomposite. Also in the intestinal fluid (pH 7.4), the verapamil release from drug hybrid reached 68% in 5 h against only 57% was released from drug nanocomposites in 7 h.     

Simulation of Drying Characteristics of Evaporation from a Wet Particle in a Turbulent Pulsed Opposing Jet Contactor

The motion and drying characteristics of a single particle in a novel two-dimensional pulsed opposing jet contactor (POJC) are modeled and discussed. Hot air is used as the drying medium. To simulate particle drying, the gas phase and dispersed phase conservation equations are considered in the Eulerian reference frame and the Lagrangian reference frame, respectively. The RNG turbulence model is used to determine the turbulent characteristics of the gas phase. The particle motion is described by the BBO (Basset-Boussinesq-Oseen) equation. The effects of the key parameters, such as the jet Reynolds number, amplitude of pulsation, frequency of pulsation, particle diameter, location of release of particle from one jet as well as velocity profile on residence time (RT) and particle penetration depth (PN) into the opposite jet, are examined. Results show that POJC has strong potential for particulate heat transfer as well as drying; it can improve evaporation rate relative to the corresponding steady OJC by up to 30% as a result of increased residence time in the impingement zone within the parameter ranges simulated.     

Nanocomposites of PVC/TiO2 nanorods: Surface tension and mechanical properties before and after UV exposure

In this study, nanocomposites of poly(vinyl chloride) (PVC), using the synthesized titanium dioxide (TiO₂) nanorods and commercial nanopowder of titanium dioxide (Degussa P25) were produced by melt blending. The presence of TiO₂ nanorods in PVC matrix led to an improvement in mechanical properties of PVC nanocomposites in comparison with unfilled PVC. The photocatalytic degradation behavior of PVC nanocomposites were investigated by measuring their structural change evaluations, surface tension, and mechanical properties before and after UV exposure for 500 h. It was found that mechanical and physical properties of PVC nanocomposites are not reduced significantly after UV exposure in the presence of TiO₂ nanorods in comparison with the presence of TiO₂ nanoparticles, which can be due to the amorphous structure of the synthesized nanorods. Therefore, it can be concluded that TiO₂ nanorods led to an improvement in photostability and mechanical properties of PVC nanocomposites. The interfacial adhesion between TiO₂ nanorods and PVC matrix was also investigated. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Small-scale explosivity testing

Abstract

In the area of energetic materials testing, correlation of small- and large-scale test results is a frequently sought and seldom achieved goal. We have experimented using the cartridge test to obtain a relative ranking of the explosivity of energetic materials. The cartridge test attempts to detonate a 2 gram sample of energetic material confined in a .303″ brass cartridge case with a number 8 blasting cap. Violence of an event was judged by the weight of the main body of the casing remaining attached to the base after detonation.     

Application of a New Functionalized Nanoporous Silica for Simultaneous Trace Separation and Determination of Cd(II), Cu(II), Ni(II), and Pb(II) in Food and Agricultural Products

A novel sorbent for simultaneous separation of cadmium, copper, nickel, and lead was prepared by functionalizing SBA-15 nanoporous silica with dithizone. A solid-phase extraction method using the above sorbent was developed to separate and preconcentrate trace amounts of cadmium, copper, nickel, and lead ions from food and agricultural products by flame atomic absorption spectrometry measurements. The optimum experimental conditions such as pH; flow rates; type, concentration, and volume of the eluent; breakthrough volume; and effect of coexisting ions on the separation and determination of these heavy metals were evaluated. The extraction efficiencies for the mentioned heavy metals were greater than 97 %, and the limits of detection were 0.09, 0.16, 0.21, and 0.45 μg?L^?1 for cadmium, copper, nickel, and lead, respectively. The preconcentration factor for simultaneous analysis of the four heavy metals was found to be 100 approximately. The relative standard deviations of the method were <5 % for 10 separate column experiments for the determination of 5.0 μg of cadmium, copper, nickel, and lead ions. The adsorption capacity of the dithizone-SBA-15 was 189 mg?g^?1 for cadmium, 102 mg?g^?1 for copper, 91 mg?g^?1 for nickel, and 208 mg?g^?1 for lead.     

Statistical Modeling of Strain-Hardening Exponent and Grain Size of Nb-Microalloyed Steels Using a Two-Level Factorial Design of Experiment

A factorial design of experiment (DOE) was used to statistically model the strain-hardening exponent and grain size of Nb-microalloyed steel sheets following hot rolling. The objective of the statistical model was to develop a method to simultaneously increase the strain-hardening exponent and refine the grain size of Nb-microalloyed steels by controlling three hot rolling process parameters: roughing temperature (RT), finishing temperature (FT), and coiling temperature (CT). The factorial DOE used two levels for the above temperatures and three replicates to obtain a reliable and precise estimate of the strain-hardening exponent and grain size. Analysis of variance was used to determine the most significant factors (individual parameters and their interactions) affecting the responses and develop appropriate regression equations. The regression equations predicted that optimal formability is obtained under the following conditions: RT = 1150 °C, FT = 800 °C, and CT = 700 °C. Validation of the statistical model using microstructural characterization showed that the predicted value of the grain size was close to the experimental value.     

A new robust control design based on feedback-compensator for UPFC

It has been reported that there is a strong dynamic interaction between series and shunt currents in the unified power flow controller (UPFC). In this paper, a method based on state estimator is proposed to decouple series and shunt currents of the UPFC. The suggested feedback-compensator consists of a state feedback and an estimator. The interaction terms are considered as disturbance and eliminated by state feedback based on feedback-compensator. The suggested controller has been compared with singular value decomposition (SVD)-based decoupling controller. Investigations show that although both the suggested controller and SVD show proper performance with linear model of the UPFC, the suggested controller produces fewer transients in the output. The designed controller shows proper performance of UPFC non-linear model, while in this case the SVD decoupling controller does not perform decoupling, that is, it does not follow the reference inputs. Also feedback-compensator controller maintains the proper performance despite disturbance and uncertainties in the system.     

An instance and variable selection approach in pixel-based classification for automatic white blood cells segmentation

Pattern Analysis and Applications - Instance and variable selection involve identifying a subset of instances and variables such that the learning process will use only this subset with better...