On the non-linear vibration of circular plates of variable thickness elastically restrained along the edges

Berger's technique of neglecting the second strain invariant in the middle plane of the plate is used in an investigation of the effect of non-linearity on the frequency of a vibrating circular plate of variable thickness which is elastically restrained along its circumference. A simple polynomial expression for the deflection function and a Galerkin method are used in the analysis.     

Tricetin 4′-<Emphasis Type="Italic">O-α</Emphasis>-L-rhamnopyranoside: A new flavonoid from the aerial parts of <Emphasis Type="Italic">Erica arborea</Emphasis>

Reversed-phase preparative HPLC purification of the methanol (MeOH) extract of the aerial parts of Erica arborea resulted in the isolation of a new flavonoid glycoside, tricetin 4′-O-α-L-rhamnopyranoside, together with the known flavonoid, isorhamnetin 3-O-α-L-rhamnopyranoside. The structures of these compounds were determined by spectroscopic means. The antioxidant properties of these compounds were assessed by the DPPH assay. Published in Khimiya Prirodnykh Soedinenii, No. 2, pp. 138–140, March–April, 2008.     

Fabrication and Mechanical Performance of Non-Crimp Unidirectional Jute-Yarn Preform-Based Composites

This work developed novel jute-yarn, non-crimp, unidirectional (UD) preforms and their composites, with three different types of warp jute yarns of varying linear densities and twists in the dry UD preforms, in order to present a possible solution to the detrimental effects of higher yarn twists and crimp at the warp–weft yarn interlacements of traditional, woven, preform-based composites on their mechanical properties. In the developed UD preforms, warp jute yarns were placed in parallel by using a wooden picture-frame pin board, with the minimal number of glass weft yarns to avoid crimp at the warp–weft yarns interlacements, which can significantly enhance the load-bearing ability of UD composites compared to traditional, woven, preform composites. It was found that an optimal combination of jute warp yarn linear densities and twists in the UD preforms is important to achieve the best possible mechanical properties of newly developed UD composites, because it encourages a proper polymer-matrix impregnation on jute fibres, leading to excellent fibre–matrix interface bonding. Composites made from the 25 lb/spindle jute warp yarn linear density (UD25) exhibited higher tensile and flexural properties than other UD composites (UD20, UD30). All the UD composites showed a much better performance compared to the traditional woven preform composites (W20), which were obviously related to the higher crimp and yarn interlacements, less load-carrying capacity, and poor fiber–matrix interfaces of W20 composites. UD25 composites exhibited a significant enhancement in tensile modulus by ~232% and strength by ~146%; flexural modulus by 138.5% and strength by 145% compared to W20 composites. This reveals that newly developed, non-crimp, UD preform composites can effectively replace the traditional woven composites in lightweight, load-bearing, complex-shaped composite applications, and hence, this warrants further investigations of the developed composites, especially on long-term and dynamic-loading mechanical characterizations.     

Memetic algorithms for solving job-shop scheduling problems

The job-shop scheduling problem is well known for its complexity as an NP-hard problem. We have considered JSSPs with an objective of minimizing makespan while satisfying a number of hard constraints. In this paper, we developed a memetic algorithm (MA) for solving JSSPs. Three priority rules were designed, namely partial re-ordering, gap reduction and restricted swapping, and used as local search techniques in our MA. We have solved 40 benchmark problems and compared the results obtained with a number of established algorithms in the literature. The experimental results show that MA, as compared to GA, not only improves the quality of solutions but also reduces the overall computational time.     

Biomimetic growth of gallic acid–ZnO hybrid assemblies and their applications

In this study, we probed the biomimetic formation of gallic acid (GA)–ZnO nanoparticle hybrids. It was found that the morphologies formed were dependent upon pH values, resulting in GA–ZnO hybrids of varying shapes such as micro or nanoplates or fibers. The formed supramolecular GA–ZnO hybrids were found to be luminescent as indicated by confocal microscopy and were utilized for the photocatalytic degradation of the organic dye methylene blue. We also explored the bactericidal effects of the hybrids on Staphylococcus aureus (S. aureus) as well as Escherichia Coli (E. Coli). Thus, we have developed a new class of shape-controlled nanohybrid assemblies via mild, green synthetic methods that may be utilized for photocatalytic degradation for environmental remediation as well as for antibacterial applications.     

An assessment of models for predicting refrigerant characteristics in adiabatic and non-adiabatic capillary tubes

Small vapor compression refrigeration systems incorporate a non-adiabatic capillary tube called a capillary tube-suction line heat exchanger (SLHX) in order to improve performance. The thermodynamic properties of the refrigerant in the capillary tube and suction pipe are influenced by associated phenomena. This study compares various relevant models. Based on the comparison recommended correlations were selected and the simulation results show that the friction factor model has the most dominant.     

Synthesis, Structure, and Conformational Dynamics of Bridgehead-Substituted Nitrosamines. Di-1-adamantylnitrosamine and Di-1-norbornylnitrosamine

The synthesis of two bridgehead-substituted nitrosamines, di-1-adamantylnitrosamine (1) and di-1-norbornylnitrosamine (2), is described, and their solid state crystal structures are reported. Large bridgehead substituents increase the NNO angle of the nitrosamine (compared to that found for dimethylnitrosamine) without deconjugating the NNO pi system significantly. This structural change correlates with a red-shifted optical absorption, a diminished N,N rotational barrier, and a greater ease of oxidation of these hindered nitrosamines than is observed for dimethylnitrosamine. The electronic basis of these structure/function correlations is examined. It is concluded that 1 is more strained than N-nitroso-2,2,6,6-tetramethylpiperidine (3) which is more strained than 2 and that a raised (in energy) NO n orbital is primarily responsible for the extreme properties of the former.     

X=Y-ZH systems as potential 1,3-dipoles. Part 61: Metal exchanged zeolites, silver(I) oxide, Ni(II) and Cu(I) complexes as catalysts for 1,3-dipolar cycloaddition reactions of imines generating proline derivatives

A range of regio- and stereo-selective 1,3-dipolar reactions of imines of α-amino esters, generating polysubstituted prolines, catalysed by silver(I) exchanged zeolites or silver(I) supported on titania, both in combination with DBU, are described. The use of a catalytic amount of silver(I) oxide, Ni(II) complexes and cuprous iodide as catalysts for the cycloaddition reactions are also disclosed.     

Simultaneous Determination of Hydroquinone and Catechol at an Activated Glassy Carbon Electrode

A selective and very simple electrochemical method, based on anodization of a glassy carbon electrode (GCE), was developed for the simultaneous detection of hydroquinone (HQ) and catechol (CT). It was found that the activated GCE showed an excellent catalytic behavior and enhanced reversibility towards the oxidation of both HQ and CT. The redox responses from the mixture of HQ and CT were easily resolved at an activated GCE. The detection limits for HQ and CT were calculated to be 0.16 and 0.11 μM, respectively. The activated GCE was successfully examined for real sample analysis with tap water and it showed a stable and reliable recovery data.     

Syntheses of new poly (arylene vinylene) analogues: Poly (4,7-benzofuran vinylene) and poly (4,7-benzothiophene vinylene)

The reaction of bis(4,7-tetrahydrothiopheniomethyl) benzofuran dibromide with aqueous tetramethylammonium hydroxide leads to a water-soluble polyelectrolyte which can be film cast and thermolytically eliminated to give poly(4,7-benzofuran vinylene) (PBFV). Subjection of bis(4,7-tetrahydrothiopheniomethyl) benzothiophene dibromide to the same reaction sequence gives poly(4,7-benzothiophene vinylene) (PBTV). UV-VIS studies show that PBFV has a band gap of 2.76 eV, while PBTV has a band gap of 2.92 eV. These polymers are members of a new class of conjugated poly (arylene vinylene)s, in which heterocyclic pseudoaromatic rings are fused onto a poly(1,4-phenylene vinylene) backbone. © 1994 John Wiley & Sons, Inc.