Prediction of cooling curves during solidification of Al 6061–SiCp based metal matrix composites using finite element analysis

In recent years, aluminium based cast composites have gained popularity in all the emerging fields of technology owing to their superior high stiffness and strength. The properties of cast composites are dictated largely by the solidification phenomenon, which needs to be well understood by foundry technologists. Information on the solidification studies of cast composites is scarce. However, the theoretical prediction of the solidification behaviour of cast composites by the use of commercially available finite element analysis (FEA) software has not yet been reported. The theoretical prediction can definitely yield good lot of information as regards the cooling rates of the cast composites saving enormous time in experimentation. In light of the above, the present investigation is aimed at the prediction of cooling curves of Al 6061–SiC_p composites using finite element analysis. L-shaped composite castings were prepared using stir cast technique. The temperature of the composite during solidification was measured by K-type thermocouple, from which the cooling curves were constructed. Experiments were carried out over a range of particle weight percentage of 2–6 wt% in steps of 2 wt%. Comparison of the cooling curves of Al 6061–SiC_p composite with the un-reinforced alloy reveals significant decrease in cooling rate with the addition of SiC particles. A two-dimensional transient heat transfer model was used in commercial finite element analysis software to predict the cooling curves of composite castings. The predicted cooling curves are compared with results obtained from experiments and found to be in good agreement.     

Comparison of the pervaporation separation of a water–acetonitrile mixture with zeolite‐filled sodium alginate and poly(vinyl alcohol)–polyaniline semi‐interpenetrating polymer network membranes

The pervaporation (PV) separation performance of ZSM‐5‐ and Na‐Y‐type zeolite‐filled sodium alginate (NaAlg) membranes were compared with those of pure NaAlg and semi‐interpenetrating polymer network (semi‐IPN) membranes of poly(vinyl alcohol) (PVA) with polyaniline (PANI) for the dehydration of acetonitrile. The PV separation characteristics of the zeolite‐filled membranes showed a dependence on the nature of the zeolites. The variation of the acidity function of the ZSM‐5 zeolite had an influence on the flux and selectivity of the membranes when compared to unfilled membranes. The crosslinked membranes were characterized by differential scanning calorimetry, X‐ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Increasing the PANI content of the semi‐IPN network increased the separation selectivity. Among the NaAlg membranes, the plain NaAlg membrane showed the highest selectivity of 414 at 30 mass % water in the feed mixture, whereas the Na‐Y‐ and ZSM‐5 (40)‐filled NaAlg membranes exhibited much lower values of selectivity, that is, 7.3 and 4.3, respectively for 30 mass % water in the feed. When the flux and selectivity data of ZSM‐5 (250)‐filled NaAlg membranes were compared with that of Na‐Y‐ or ZSM‐5 (40)‐filled NaAlg membranes, a noticeable increase in the selectivity for the ZSM‐5 (250)‐filled NaAlg membrane was observed, but a somewhat comparable flux was observed compared to the plain NaAlg membrane. For the first time, PANI was polymerized with PVA to yield a semi‐IPN. The total flux and water flux increased systematically, whereas the selectivity decreased greatly from 251.87 to 5.95 with increasing amounts of water in the feed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1968–1978, 2005     

Acrylamide‐grafted‐acacia gum polymer matrix tablets as erosion‐controlled drug delivery systems

Acrylamide was grafted onto acacia gum in different ratios (1 : 1, 1 : 3, and 1 : 5). The graft copolymers formed were characterized by FTIR, rheological measurements, and differential thermal analysis. Tablets were prepared from these polymers loaded with two antihypertensive drugs, viz., diltiazem hydrochloride and nifedipine. The in vitro release experiments were carried out in simulated gastric and intestinal conditions. The graft copolymer prepared in the ratio 1 : 5 of acacia gum : acrylamide matrix was found to be a suitable matrix to investigate the controlled release of diltiazem hydrochloride and nifedipine. The drug release continued up to 6 and 14 h, respectively, for diltiazem hydrochloride and nifedipine. The release mechanism was investigated by using the mathematical equations proposed by Higuchi, Hixson‐Crowell, and Kopcha. Based on the release kinetics data, a correlation was attempted between the erosion‐controlled release and the dissolution‐controlled release. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2245–2253, 2004     

Spectral and electrochemical investigation of octanitro substituted metal phthalocyanines

A simple and convenient method has been developed for the synthesis of 1,3,8,10,15,17,22,24-octanitrophthalocyanine derivatives MPcON's [M = Fe(III)Cl, Zn(II), Co(II), Cu(II) and Ni(II)]. The compounds were prepared from 3,5-dinitrophthalic acid in the presence of ammonium chloride, urea and catalytic quantity of ammonium molybdate in nitrobenzene solvent; the complexes were characterized by elemental analysis, electronic and IR spectra and powder XRD. The electrochemical redox properties of the complexes were studied using glassy carbon and platinum electrodes in non-aqueous media employing tetra butyl ammonium perchlorate as supporting electrolyte.     

Peanut improvement: production of fertile hybrids and backcross progeny between Arachis hypogaea and A. kretschmeri

There are only a few reports of successful crosses between cultivated peanut (Arachis hypogaea L., section Arachis) and wild species from sections other than section Arachis. Many of the wild Arachis species harbor important traits necessary for the improvement of peanut. For example, Arachis kretschmeri Krapov., W.C. Gregory & C.E. Simpson (section Procumbentes) can grow under water-logged conditions and has been identified as one of the few wild species of Arachis with resistance to late leaf spot (LLS) and peanut rosette disease. Peanut rosette, caused by a combination of viruses, is an economically important disease only in Africa, while LLS, caused by Cercosporidium personatum, is an important fungal disease in Asia and the Americas as well as Africa. Interspecific hybrids between A. hypogaea and A. kretschmeri were produced by applying growth regulators to pollinated pistils and hybrid plants were obtained by germinating embryos in vitro. A total of seven hybrids were produced and confirmed by Simple Sequence Repeat (SSR) analysis. All hybrids were fertile, although initially slow growing. F₁ hybrids were backcrossed to A. hypogaea and all plants in the F₁BC₁ generation were single-seeded with a prominent beak, characteristic of A. kretschmeri, but many of the F₁BC₂ pods were double-seeded resembling A. hypogaea. F₁BC₂ plants were moderately resistant to LLS. When a large number of seeds are obtained, the progeny will be screened for resistance to both LLS and rosette disease. Thus crosses with species outside the section Arachis may not only confer disease resistance but will also broaden the genetic base of cultivated peanut.     

Alginate-coated alginate-polyethyleneimine beads for prolonged release of furosemide in simulated intestinal fluid

Furosemide-loaded calcium alginate (ALG), calcium alginate-polyethyleneimine (ALG-PEI) and alginate-coated ALG-PEI (ALG-PEI-ALG) beads were prepared by ionotropic/polyelectrolyte complexation method to achieve controlled release of the drug. Effects of several formulation factors on the characteristics of the beads were investigated. Although variation in formulation factors did not influence the drug-loading efficiency (DLE) of ALG beads, rapid release of the drug in simulated intestinal fluid (SIF) could not be prevented. PEI treatment of ALG beads, however, prolonged the drug release considerably. Ionic interaction, as appeared from FTIR studies, between alginate and PEI led to the formation of polyelectrolyte complex membrane, the thickness of which was dependent on the conditions of PEI treatment as demonstrated by scanning electron microscopy (SEM). The membrane acted as a physical barrier to drug release from ALG-PEI beads. Alginate coating of ALG-PEI beads further prolonged the release of the drug by increasing membrane thickness and reducing swelling of the beads possibly by blocking the surface pores. Differential scanning calorimetry (DSC) study indicated that drug was not degraded by PEI treatment. The release data from ALG-PEI beads showed a good fit in power law expression, whereas the release data from ALG-PEI-ALG beads were found to fit in modified power law expression, and the mechanism of drug release changed from super case II transport to nearly Fickian transport, depending on the degree of gelation and formation of polyelectrolyte complex membrane.     

Free vibration of symmetrically laminated plates using a higher-order theory with finite element technique

A C⁰ finite element formulation of the higher-order theory is used to determine the natural frequencies of isotropic, orthotropic and layered anisotropic composite and sandwich plates. The material properties that are typical of high modulus fibre reinforced composites are used to show the parametric effects of plate aspect ratio, length-to-thickness ratio, degree of orthotropy, number of layers and lamination angle/scheme. The present theory is based on a higher-order displacement model and the three-dimensional Hooke's laws for plate material. The theory represents a more realistic quadratic variation of the transverse shearing strains and linear variation of the transverse normal strains through the plate thickness. A special mass matrix diagonalization scheme is adopted which conserves the total mass of the element and includes the effects due to rotary inertia terms. The results presented should be useful in obtaining better correlation between theory and experiment, and to numerical analysts in verifying their results.     

Hydrogen fueled spark ignition engine with electronically controlled manifold injection: An experimental study

In this work, a single cylinder conventional spark ignition engine was converted to operate with hydrogen using the timed manifold fuel injection technique. A solenoid operated gas injector was used to inject hydrogen into the inlet manifold at the specified time. A dedicated electronic circuit developed for this work was used to control the injection timing and duration. The spark timing was set to minimum advance for best torque (MBT). The engine was operated at the wide-open throttle condition. For comparison of results, the same engine was also run on gasoline.The performance and emission characteristics with hydrogen and gasoline are compared. From the results, it is found that there is a reduction of about 20% in the peak power output of the engine when operating with hydrogen. The brake thermal efficiency with hydrogen is about 2% greater than that of gasoline. A lean limit equivalence ratio of about 0.3 could be attained with hydrogen as compared to 0.83 with gasoline. CO, CO₂ and HC emissions were negligible with hydrogen operation. However, for hydrogen operation, NO_x emission was four times higher than that of gasoline at full load power. The best ignition timing for hydrogen was much retarded when compared to gasoline. The effect of hydrogen injection pressure was also studied and no specific changes were observed. The effect of operating speed was also studied.     

Hyperbranched poly(glycerol esteramide): A biocompatible drug carrier from glycerol feedstock and dicarboxylic acid

Polymer carrier with biodegradable, biocompatible as well as solubility enhancing properties are highly looked upon in the pharmaceutical industry to improve the drug delivery systems. A series of hyperbranched poly(glycerol esteramide) (HPGEA) with M_w of 5000–12,000 Da, degree of branching of 57%–62%, and hydroxyl values of 200–280 mg KOH/g sample were synthesized through polycondensation of N,N-bis(2-hydroxyethyl)stearamide (diethanolamide) and poly(glycerol ester) (PGE). The HPGEAs were characterized by ATR-FTIR, GPC, ¹H and ¹³C-NMR, and DSC. The enthalpy of fusion of HPGEAs (43–84 J g⁻¹) were lower than the commercial polymers (193–391 J g⁻¹), indicating its potential as drug carrier for solid dispersion (SD). HPGEA-based SDs showed substantial enhancement in solubility and release rate than pure drug, commercial polymer-based SDs, as well as commercial formulation. The safety of HPGEAs and HPGEA-based SDs were proven through MTT assay with IC₅₀ of 2400–9800 and 1200–3500 μg ml⁻¹, respectively.     

Optimisation of operations sequence in CAPP using an ant colony algorithm

Computer-aided process planning (CAPP) forms an important interface between Computer-aided design (CAD) and Computer-aided manufacturing (CAM). It is concerned with determining the sequence of individual manufacturing operations required to produce a product as per technical specifications given in the part drawing. Any sequence of manufacturing operations that is generated in a process plan cannot be the best possible sequence every time in a changing production environment. As the complexity of the product increases, the number of feasible sequences increases exponentially, and there is a need to choose the best among them. This paper presents an application of a newly developed metaheuristic called the ant colony algorithm as a global search technique for the quick identification of the optimal operations sequence by considering various feasibility constrains. A couple of case studies are taken from the literature to comparing the results obtained by the proposed method.