Showing papers by "Applied Science Private University published in 2004"

Anomalous Power Law Dispersions in ac Conductivity and Permittivity Shown to be Characteristics of Microstructural Electrical Networks

Abstract: The frequency dependent ac conductivity and permittivity of porous lead zirconate titanate ceramic with the pore volume filled with water are shown to match the simulated electrical response of a large network of randomly positioned resistors and capacitors. Anomalous power law dispersions in conductivity and permittivity are shown to be an electrical response characteristic of the microstructural network formed by the porous lead zirconate titanate pore structure. The anomalous power law dispersions of a wide range of materials are also suggested to be microstructural network characteristics.

Plasma devices to guide and collimate a high density of MeV electrons

Abstract: The development of ultra-intense lasers1 has facilitated new studies in laboratory astrophysics2 and high-density nuclear science3, including laser fusion4,5,6,7. Such research relies on the efficient generation of enormous numbers of high-energy charged particles. For example, laser–matter interactions at petawatt (1015 W) power levels can create pulses of MeV electrons8,9,10 with current densities as large as 1012 A cm-2. However, the divergence of these particle beams5 usually reduces the current density to a few times 106 A cm-2 at distances of the order of centimetres from the source. The invention of devices that can direct such intense, pulsed energetic beams will revolutionize their applications. Here we report high-conductivity devices consisting of transient plasmas that increase the energy density of MeV electrons generated in laser–matter interactions by more than one order of magnitude. A plasma fibre created on a hollow-cone target guides and collimates electrons in a manner akin to the control of light by an optical fibre and collimator. Such plasma devices hold promise for applications using high energy-density particles and should trigger growth in charged particle optics.

Processing and properties of porous piezoelectric materials with high hydrostatic figures of merit

Abstract: Porous piezoelectric materials are of interest for applications such as low frequency hydrophones. This is due to their high hydrostatic figures of merit and low sound velocity, which leads to reduced acoustic impedance and enhanced coupling with water or biological tissue. A wide variety of methods are available to produce porous structures such as using reticulated polymer foams or volatile additives which are burnt out during the sintering process (e.g. polymer spheres). Each processing technique and additive produces its own distinctive microstructure, particularly in terms of pore size, morphology and porosity volume fraction. The aim of this paper is to manufacture a variety of porous microstructures and relate the structures to measured hydrostatic figures of merit.

A monomeric nickel-dioxygen adduct derived from a nickel(I) complex and O2.

Abstract: The nickel(I) complex [PhTt(Ad)]Ni(CO) (PhTt(Ad), phenyltris((1-adamantylthio)methyl)borate) reacts with O(2) generating a 1:1 species identified as a side-on dioxygen adduct based on its spectroscopic properties as supported by DFT computational results and by its reactivity. The Ni EXAFS data are fit to a S(3)O(2) coordination environment with short Ni-O distances, 1.85 A. The brown complex displays a rhombic EPR signal with g values of 2.24, 2.19, 2.01. DFT and INDO/S-CI computations replicate the EXAFS and EPR features and suggest that 2 is a side-on [NiO(2)](+) complex with geometric and electronic properties that are best rationalized in terms of a highly covalent Ni(II)-superoxo description. [PhTt(Ad)]Ni(O(2)) oxidizes PPh(3) to OPPh(3), NO to NO(3)(-), and [PhTt(tBu)]Ni(CO) to the nonsymmetric [PhTt(Ad)]Ni(micro-O)(2)Ni[PhTt(tBu)] dimer.

A novel method of cold expansion which creates near-uniform compressive tangential residual stress around a fastener hole

Abstract: A recognized way of improving the fatigue resistance of a fastener hole is to introduce compressive tangential residual stress around it. This can be achieved by using a cold expansion method in which an oversized pin or ball is forced through the hole to produce a local plastic region surrounded by an elastic one. Once the pin or ball is removed allowing the elastic region to spring back it results in compressive tangential residual stress around the hole. In practise, however, it is found that such a cold expansion method creates a non-uniform residual stress distribution through the plate thickness and even tensile residual stress can be created at the entrance and exit faces. In this paper a new method of cold expansion is proposed. It uses a tapered pin with a mating tapered split sleeve and creates an almost uniform compressive residual stress around the hole as shown by FE method. Also, fatigue tests were carried out to verify that the method does significantly improve fatigue life. Finally the tangential residual stress distribution and fatigue life improvement of this new method were compared with those of a well-established cold expansion method and it was shown that the new method is more efficient in improving fatigue life.

Real wrongs in virtual communities

Abstract: Beginning with the well-known cyber-rape in LambdaMOO, I argue that it is possible to have real moral wrongs in virtual communities. I then generalize the account to show how it applies to interactions in gaming and discussion communities. My account is supported by a view of moral realism that acknowledges entities like intentions and causal properties of actions. Austin's speech act theory is used to show that real people can act in virtual communities in ways that both establish practices and moral expectations, and warrant strong identifications between themselves and their online identities. Rawls' conception of a social practice is used to analyze the nature of the wrong and the stage-setting aspect of engaging in a practice.

Bulk mixed Mo–V–Te–O catalysts for propane oxidation to acrylic acid

Abstract: The model Mo–V–Te–O catalysts containing the orthorhombic (M1) and hexagonal (M2) phases with well-defined crystal morphologies and promising for the selective oxidation of propane to oxygenates were obtained hydrothermally over a wide range of synthesis compositions (Mo 0.70–0.30 V 0.60–0.20 Te 0.15–0.05 ). The bulk (ICP), local (EDS) elemental and structural (XRD) analyses of this compositionally simple model system indicated that the M1 phase with the bulk Mo/V ratio of ∼2 was dominant in the Mo–V–Te–O catalysts. This phase has been proposed as active and selective for propane oxidation to oxygenates and ammoxidation to acrylonitrile. The model catalysts displayed high selectivity to acrylic acid in the presence of water vapor in the feed, which is believed to enhance the apparent rates of formation of oxygenates as well as maintain the catalytic surface in a partially reduced oxidation state. The selectivity to acrylic acid over these model catalysts correlated with the extent of exposure of the surface ab planes of the M1 phase proposed to contain the active and selective surface sites. Therefore, the Mo–V–Te–O catalysts represent a well-defined and highly promising model system for elucidating the surface molecular structure–activity/selectivity relationships in propane oxidation to acrylic acid over multicomponent Mo–V–Te–Nb–O catalysts.

Synthesis of alumina from high purity alum derived from coal fly ash

Abstract: High purity alum (>99.9%) has been produced by the reaction of NH4Al(SO4)2 derived from coal fly ash and ammonia in water at a controlled pH and then followed by the successive crystallization. The influence of heating source (conventional and microwave) on the decomposition of the alum and the characteristics of the resultant alumina was examined by means of XRD, TG/DTA, SEM and a laser scattering technique. The application of microwave heating for decomposition of the alum yielded finer α-Al2O3 powders with a higher specific surface area, when compared with conventional heating.

Hybrid predictive control of nonlinear systems: method and applications to chemical processes

Abstract: A hybrid control structure that unites bounded control with model predictive control (MPC) is proposed for the constrained stabilization of nonlinear systems. The structure consists of: (1) a finite-horizon model predictive controller, which can be linear or nonlinear, and with or without stability constraints, (2) a family of bounded nonlinear controllers for which the regions of constrained closed-loop stability are explicitly characterized and (3) a high-level supervisor that orchestrates switching between MPC and the bounded controllers. The central idea is to embed the implementation of MPC within the stability regions of the bounded controllers and employ these controllers as fall-back in the event that MPC is unable to achieve closed-loop stability (due, for example, to infeasibility of a given initial condition and/or horizon length, or due to computational difficulties in solving the nonlinear optimization). Switching laws, that monitor the closed-loop state evolution under MPC, are derived to orchestrate the transitions in a way that guarantees asymptotic closed-loop stability for all initial conditions within the union of the stability regions of the bounded controllers. The proposed hybrid control scheme is shown to provide a paradigm for the safe implementation of predictive control algorithms to nonlinear systems, with guaranteed stability regions. The efficacy of the proposed approach is demonstrated through applications to chemical reactor and crystallization process examples. Copyright © 2004 John Wiley & Sons, Ltd.

Dynamics of dissociative attachment of electrons to water through the {sup 2}B{sub 1} metastable state of the anion

Abstract: Calculations of cross sections for dissociative attachment to water through the $^{2}B_{1}$ resonance state are presented using the ab initio surfaces calculated previously for the energy ${E}_{R}$ and width $\ensuremath{\Gamma}$ of this resonance state as a function of nuclear geometry. The dynamics of the dissociative attachment process are treated in full dimensionality using the local complex potential model. For the ${\mathrm{H}}^{\ensuremath{-}}+\mathrm{OH}$ channel, the calculations presented here are in substantial agreement with experiment with regard to total cross section and vibrational excitation of the $\mathrm{OH}$ fragment. Cross sections for dissociative attachment to excited initial ro-vibrational states are presented and isotope effects are also examined.

Interaction of free charged particles with a chirped electromagnetic pulse.

Abstract: We study the effect of chirp on electromagnetic (EM) pulse interaction with a charged particle. Both the one-dimensional (1D) and 3D cases are considered. It is found that, in contrast to the case of a nonchirped pulse, the charged particle energy can be changed after the interaction with a 1D EM chirped pulse. Different types of chirp and pulse envelopes are considered. In the case of small chirp, an analytical expression is found for arbitrary temporal profiles of the chirp and the pulse envelope. In the 3D case, the interaction with a chirped pulse results in a polarization-dependent scattering of charged particles.

Image analysis and bending properties of model OSB panels as a function of strand distribution, shape and size

Abstract: The technique of image analysis has been used to assess the quality of model oriented strand board panels by investigating the relationships between shape and size of strands, the distribution of strands and bending properties. A batch of commercial strands was analysed by image analysis and the distribution of the shape and size of strands was quantified. The strands were categorised into five strand types as a function of size and aspect ratio. In general, strand shapes were observed to be mostly rectangular and there was also a wide variation in strand dimensions in commercial material. Bigger area strands had low aspect ratios and small strands had high aspect ratios. Half of the commercial strands were longer than 100 mm. Model OSB panels were manufactured in the laboratory by hot pressing strand mats formed from each of the five strand types. Strands were laid up by hand into the forming mat and following pressing the orientation and shape of strands was evaluated by image analysis and the panels were tested in a three point bending. Large area (type 3) strands with high aspect ratios produced model panels with optimum strand orientation and mechanical properties. Type 3 panels were also fabricated from strands dropped through a slotted forming device in order to simulate the delivery of strands to the forming line under factory conditions. As the height of strand delivery increased from 0 to 100 to 200 mm the disorientation of strands in the pressed panels progressively increased and as a result mechanical properties in bending were reduced. Image analysis is therefore a powerful tool for evaluating the distribution of commercial strand shapes and the relationship between strand geometry, strand orientation and the mechanical properties of oriented strand board.

Thermal stability of hydroxyapatite whiskers derived from the hydrolysis of α-TCP

Abstract: Figure 2 SEM micrographs of sample: (a) A, (b) B, (c) C and (d) D. Whisker shaped hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a promising candidate material for reinforcing ceramic or polymer matrices to be used in the biomedical and dental fields [1]. Various techniques for preparation of whiskerlike or fibrous HAp have been reported [2–6]. Among these, the hydrolysis of α-Ca3(PO4)2 (α-TCP) under controlled processing conditions (aqueous pH, temperature and time) is often adopted to generate a whisher shaped form of HAp [2, 3]. Several authors [7–10] have reported on the thermal stability of synthetic HAp but the results are not generally coincident. It is suggested that the reason for this that the thermal decomposition of HAp is inherently dependent on the crystallinity, stoichiometry and atmosphere conditions prevailing during the reactions

Clonal Propagation of Dalbergia sissoo Roxb. by Softwood Nodal Cuttings: Effects of Genotypes, Application of IBA and Position of Cuttings on Shoots

Abstract: Summary Softwood nodal shoot cuttings were collected from the hedge garden at New Forest campus of Forest Research Institute, Dehra Dun. The cuttings were rooted in mist chamber to investigate the effect of IBA application and position of cuttings on shoots on rooting ability in different clones of Dalbergia sissoo Roxb. As compared to the 0% (control) and 0.1%; 0.2% IBA showed maximum adventitious root formation. Overall percent rooting, percent sprouting, mean number of shoots and their length, mean number of roots and their length increased with increasing concentration of IBA. Among different positions of cuttings within the shoots, the best rooting response was recorded in the middle part followed lower and upper part. The findings exhibited significant interclonal variation regarding adventitious rooting and maximum response was observed in C42 (Gonda, Uttar Pradesh) clone. Interactive effect of clone C42 and middle position significantly increased percent sprouting while; interactive effects of middle position and 0.2% IBA treatment significantly increased percent rooting. It is concluded that the selection of genotypes with good rooting ability with respect to shoot position in hedged plants and concentration of IBA can be made to produce high quality planting stock material to start clonal forestry programme of D. sissoo.

Analysis of the cobalt content in Australian foods.

Abstract: The cobalt content of Australian foods is unknown, and as this content is, at least in part, related to the respective concentrations in the Australian soil, data collected previously in other countries may not reflect the levels in Australian produce. To compare reported food cobalt levels to that found in Australian foods, one hundred and fifty different food and beverage items from each of the major food groups were selected for analysis, based on annual sales figures in Australia. Food digests were analysed for cobalt content using a Finnigan High Resolution Inductively Coupled Plasma Mass Spectrometer. While some variation in cobalt content was seen in a small selection of foods from different States, in general terms, the cobalt content of Australian foods is similar to that seen in data from other countries.

Axial Dispersion and Wall Effects in Narrow Fixed Bed Reactors: A Comparative Study Based on RTD and NMR Measurements

Abstract: Axial dispersion and wall effects in narrow fixed beds with aspect ratios < 10 were investigated, both by classical methods and by NMR imaging. The residence time distribution (RTD) in the center and at the wall was measured, system water/ NaCI-solution as tracer, and subsequently compared with radial velocity profiles based on NMR imaging. The influence of the aspect ratio and Re p on dispersion and on the degree of non-uniformity of the velocity profile was studied. The NMR results are consistent with the RTD and also with literature data of numerical simulations. For low aspect ratios, dispersion/wall effects have a strong influence on the reactor behavior, above all, in cases where a low effluent concentration is essential, as proven by breakthrough experiments with the reaction of H 2 S with ZnO.

Gadolinia doped ceria/yttria stabilised zirconia electrolytes for solid oxide fuel cell applications

Abstract: Solid oxide fuel cells are currently constructed using a yttria stabilised zirconia electrolyte membrane. However, zirconia has a number of disadvantages associated with its use, such as the high operational temperatures required for it to exhibit acceptable levels of ionic conductivity. Alternative ceramics such as doped cerium oxide show promise as electrolytes capable of operating at reduced temperatures, but introduce additional problems such as electronic conduction and inferior mechanical properties. This paper describes the manufacture and characterisation of a number of prototype electrolytes consisting of a mixture of yttria stabilised zirconia and gadolinium doped ceria. Traditional ceramic processing techniques were used to produce the samples, which were then examined using dilatometry, impedance spectroscopy and X-ray diffraction. Results show a lowering of the ionic conductivity of zirconia with the addition of doped ceria. X-ray diffraction patterns obtained from the samples suggested that this effect could be attributed to the formation of a solid solution of ceria in zirconia.