Showing papers by "Applied Science Private University published in 2000"

Molecular Simulations of Hydrogen Storage in Carbon Nanotube Arrays

Abstract: Grand canonical ensemble Monte Carlo (GCEMC) molecular simulations of hydrogen storage at 298 and 77 K in triangular arrays of single wall carbon nanotubes (SWCNT) and in slit pores (modeling activated carbons) were performed. At 298 K the US DOE target gravimetric hydrogen storage capacity (6.5 wt %) is reached at 160 bar for optimally configured arrays of open SWCNT of wide diameter, but the equivalent volumetric capacity is ∼40% of the DOE target [695 (STP) v/v]. For slit pores at 298 K the optimal volumetric capacity is ∼20% of the target. Simulations for 77 K and 70 bar indicate that triangular arrays of open and closed SWCNT of various diameters in a wide range of configurations exceed the DOE gravimetric target. A capacity of 33 wt % is found for arrays of narrow, open, or closed SWCNT that are widely spaced. Here, adsorption occurs entirely in the interstitial space between the nanotubes. Volumetric capacities close to the DOE target are found for arrays of narrow, open or closed SWCNT with a rang...

The importance of transient states at higher coverages in catalytic reactions

Abstract: DFT-GGA periodic slab calculations were used to examine the adsorption and hydrogenation of ethylene to a surface ethyl intermediate on the Pd(111) surface. The reaction was examined for two different surface coverages, corresponding to (2×3) [low coverage] and (√3×√3)R 30° [high coverage] unit cells. For the low coverage, the di-σ adsorption of ethylene (−62 kJ/mol) is 32 kJ/mol stronger than the π-adsorption mode. The intrinsic activation barrier for hydrogenation of di-σ bonded ethylene to ethyl, for a (2×3) unit cell, was found to be +88 kJ/mol with a reaction energy of +25 kJ/mol. There appeared to be no direct pathway for hydrogenation of π-bonded ethylene to ethyl, for low surface coverages. At higher coverages, however, lateral repulsive interactions between adsorbates destabilize the di-σ adsorption of ethylene to a binding energy of −23 kJ/mol. A favorable surface geometry for the (√3×√3)R 30° coverage is achieved when ethylene is π-bound and hydrogen is bound to a neighboring bridge site. At hi...

Cold rocks, hot sands: In-situ cosmogenic applications in Australia at ANTARES

Abstract: The ANTARES AMS facility at ANSTO is conducting a comprehensive program in the application of in-situ cosmogenic radionuclides based on strong university collaborations in the earth sciences. The program targets two major objectives: (1) to determine and improve the Quaternary glacial chronology of the Southern Hemisphere in support of global climate change studies; (2) to characterise the processes of surface weathering and landscape evolution in semi-arid regions of the Australian continent. An overview of the program is presented with preliminary results from the first phase of these studies.

A Survey of Medicinal Plants and Their Traditional Uses in Iraq

Abstract: An ethnobotanical survey was carried out in different regions of Iraq following interviews with various traditional healers, who are called Attars, and various other people. Ninety-seven medicinal plants belonging to forty-three families are listed in alphabetical order giving the parts used and method of preparation according to their therapeutic use.

Integrating Ethics & Engineering: A Graduate Option in Systems Engineering, Ethics, and Technology Studies

Abstract: This paper describes an engineering graduate option in Systems Engineering designed to overcome some of the effects of specialization and compartmentalization by building a link between technical and ethical training. Students in this option produce case studies that emphasize ethical issues in the design process. The goal of the program is to turn out ethical professionals who are able to reflect on the moral implications of technology. The proposed approach uses realistic or real-hypothetical hybrid case studies as a type of vicarious mentoring, and, when supplemented with readings in ethical theory and codes, may serve as a starting point for a deeper understanding of behavioral dilemmas. The developers of this approach are a multi-disciplinary team from the Engineering School and the Darden Graduate School of Business Administration at the University of Virginia. The paper describes how the graduate option is structured and provides data on student outcomes.

Modelling of dimensional changes in irradiated nuclear graphites

Abstract: Neutron irradiation of the polygranular graphites used in reactor moderators results in an initial bulk shrinkage at low neutron fluence followed by expansion at higher neutron fluence. Recent work carried out to investigate the effects of simultaneous radiolytic oxidation on the dimensional-change behaviour of the Gilsocarbon graphites used in the UK advanced gas-cooled reactors (AGRs) has led to the development of a new dimensional change model for all irradiation-induced strains. Although in the future high-temperature graphite-moderated generating systems under development, concurrent oxidation is excluded, oxidation may still occur to a small degree. This paper presents an approach to modelling dimensional change applicable to most situations. For AGR moderator graphite, the model presented is able to reproduce semi-quantitatively the effects of irradiation and radiolytic oxidation on dimensional changes. Further work is required to refine the modelling approach to particular situations, but it is envisaged that the model can be applied to future high-temperature reactor systems.

Dissociative recombination of H3+: progress in theory

Abstract: Dissociative recombination is the main destruction process for groundstate H3+ in diffuse interstellar medium. Experiments agree on relatively large crosssections for this reaction. Timedependent t...

Impacts of Global Climate Change Scenarios on Water Supply and Demand in Jordan

Abstract: The potential impact of global climate change is one of the least addressed factors in water resources planning in developing countries The potential impacts of climate change are examined for Jordan, where a methodology is presented for improved management of water demand under the uncertainties associated with climate change A temperature/precipitation sensitivity model is constructed and combined with water demand forecasts to project deficits for the year 2020 Deficit reducing options are then evaluated in terms of social and economic viability The study concludes that only some of the deficits may be alleviated, illustrating the significance of considering climate change in planning for countries that already experience water imbalances

Uptake of Cd, Cu, Ni and Zn by the water hyacinth, Eichhornia crassipes (Mart.) solms from pulverised fuel ash (PFA) leachates and slurries.

Abstract: The main solid waste product from coal-fired power stations is pulverised fuel ash (PFA), which can be enriched in toxic elements. Disposal of PFA by dry (in landfills) or wet (by slurrying) disposal methods can release these elements into the environment. Thereafter, the contaminants can be taken up by biota such as Eichhornia crassipes, a common aquatic plant, which has the ability to accumulate elements from water. This study investigates the uptake of Cd, Cu, Ni and Zn by E. crassipes grown in leachates and slurries prepared from two different PFA samples. PFA samples were obtained from Indraprastha Power Station (IPP Stn.) in New Delhi, India and the Ratcliffe-on-Soar Power Station in the UK. E. crassipes grown in PFA leachates and slurries at 1:5 and 1:50 solid:liquid (PFA:deionised water) ratios show that the plant has a very high accumulation capacity for Cd, Cu, Ni and Zn from both leachates and slurries and the uptake of these metals is stronger in the roots than in the tops of the plant. Metal accumulation, as shown by the accumulation factor (AF) values, is higher from both leachates and slurries for plants grown in the 1:50 (PFA:DIW) ratios than in the 1:5 ratios, initial metal concentrations being higher in the 1:5 ratios than in the 1:50 ratios. Lower metal accumulation in the plants grown in slurries than in leachates is related to the high turbidity of growth medium in slurries resulting in ash particles adhering to the root surfaces thus reducing the surface area of metal absorption. Eichhornia plants are able to reduce the pH of all leachates, especially the highly alkaline Ratcliffe leachates to near neutral conditions. Accumulation of Cd and Zn by the plant is higher from the lower pH IPP leachates than the Ratcliffe leachates, indicating that these metals are more soluble and bioavailable in the acidic medium. However, accumulation of Cu and Ni is independent of the pH of the leachates, indicating that other factors, such as metal species, presence of complexing agents in the growth solutions, and effects of competing metal ions may be contributory factors towards the metal uptake and accumulation by the plant.

Inductive learning approaches to rainfall-runoff modelling.

Abstract: Trying to model the rainfall-runoff process is a complex activity as it is influenced by a number of implicit and explicit factors--for example, precipitation distribution, evaporation, transpiration, abstraction, watershed topography, and soil types. However, this kind of forecasting is particularly important as it is used to predict serious flooding, estimate erosion and identify problems associated with low flow. Inductive learning approaches (e.g. decision trees and artificial neural networks) are particularly well suited to problems of this nature as they can often interpret underlying factors (such as seasonal variations) which cannot be modelled by other techniques. In addition, these approaches can easily be trained on the explicit factors (e.g. rainfall) and the inexplicit factors (e.g. abstraction) that affect river flow. Inductive learning approaches can also be extended to account for new factors that emerge over a period of time. This paper evaluates the application of decision trees and two artificial neural network models (the multilayer perceptron and the radial basis function network) to river flow forecasting in two flood prone UK catchments using real hydrometric data. Comparisons are made between the performance of these approaches and conventional flood forecasting systems.

Use of stereo aerial photography for assessing changes in the extent and height of mangrove canopies in tropical Australia

Abstract: This paper examines the use of time-series of stereo aerial photographs for quantifying changes in the extent and height of mangrove communities. For the West Alligator River, Kakadu National Park, Australia, black and white and colour stereo aerial photographs of mangroves were acquired in 1950 and 1991 respectively. Digital ortho-images were generated for each date, and maps of mangrove extent were obtained by applying an unsupervised classification to each image. Digital elevation models (DEMs) of the mangrove canopy were derived from the stereo pairs. The comparison of mangrove extent suggested that substantial changes had occurred over the 41-year period, largely in response to saltwater intrusion. Changes in the height of mangroves were also observed but were difficult to quantify due to the poor quality of the 1950 DEM. The study concludes that time-series comparisons of aerial photographs are invaluable for assessing change in mangroves over periods of up to 4-5 decades.

Palaeochannels near West Wyalong, New South Wales: a case study in delineation and modelling using aeromagnetics

Abstract: In November 1998, the Australian Geological Survey Organisation (AGSO) and the New South Wales Department of Mineral Resources acquired high-resolution airborne magnetic and gamma-ray spectrometric data along lines spaced 50 m apart and 60 m above ground level north of West Wyalong, New South Wales. In addition, AGSO post-processed a proprietary dataset of similarly high-resolution from an area immediately to the south, between West Wyalong and Temora, along the Gilmore Fault Zone. Anomalies interpreted to be caused by palaeochannel deposits have been identified in these datasets. Modelling of the airborne magnetic data was used to define the geometry of the palaeochannel deposits. These models were constrained using data from drill holes and downhole magnetic susceptibility measurements. Mapping palaeochannel deposits is of potential significance for mineral exploration and land and water research. Historically, alluvial gold, often palaeochannel-hosted, has accounted for a large proportion of Australia's gold production. The study area is part of the historic Wyalong Goldfield and is part of the Bland Creek palaeovalley. Palaeochannel deposits may also be reservoirs of saline groundwater, and therefore are important in developing hydrogeological models for dryland salinity hazard assessment. Due to their depth of burial (often concealed beneath surficial sediments, to depths of 150 m), the palaeochannel deposits in the study area are mappable using either airborne magnetic or electromagnetic data, but not using gamma-ray spectrometry. The palaeochannel deposits contain detrital ferruginous maghaemitic pisoliths (which have extremely high magnetic susceptibility) concentrated in lenses in sand and clay. The resolution of the aeromagnetic datasets is compared with results obtained from surveys with different acquisition parameters. These tests suggest that an airborne geophysical survey flown with line spacing of less than 100 m can reveal important information

Poisoning of grain refinement of some aluminium alloys

Abstract: In this paper, the poisoning effect of Zr, Cr and Ta, present in the Al melt, on the grain refining efficiency of the commercial Al-Ti and Al-Ti-B master alloys is reviewed. The poisoning mechanism is established and three different approaches are proposed to overcome the grain refinement poisoning problem in the Al alloys containing Zr.

Zircon dating of Devonian‐Carboniferous rocks from the Bombala area, New South Wales

Abstract: Zircons from two igneous and two sedimentary units in the Bombala area of southeastern New South Wales have been examined by the sensitive high resolution ion microprobe (SHRIMP) to establish a timeframe in which to interpret these rocks. Previous studies have correlated these rocks with Late Devonian units of the south coast, solely upon the basis of stratigraphy and lithology as palaeontological evidence was absent. The two igneous units are the Hospital Porphyry and Paradise Porphyry occurring beneath the sedimentary units. Both give a Frasnian age that can be correlated with the Boyd Volcanic Complex. The sedimentary samples are from the basal and upper sections of the Rosemeath Formation, a fluvial ‘redbed’ consisting of conglomerate, coarse sandstone, and associated red siltstone and mudstone. Detrital zircons from the basal conglomeratic section at Kilbrechin indicate a dominant provenance from local Silurian granites and volcanics and a maximum depositional age that can be correlated with the Fras...

Application of radiometric temperature determination methods to semiconductor gas sensors

Abstract: A radiometric method for the determination of the operating surface temperature of very small objects to within ±5 K has been applied to commercial semiconductor gas sensors operated in a static atmosphere. The method involves the collection of the infrared (IR) emission spectrum of the sensor at regular intervals over the operating heater voltage range, followed by the fitting of ambient-corrected Planck functions to determine the temperature at each voltage. At least one independent calibrating temperature measurement (to eliminate the effects of sensor emissivity and spectrometer response) is obtained using the known melting point of an inorganic salt. The operating voltage–temperature relationships for two popular Figaro tin oxide sensors were found to be pseudo-linear and are reported as T =103 V+214±3 K for the Figaro TGS813 sensor with its base removed, T =101 V+224±5 K for the TGS813 with its base attached, and T =106 V+238±5 K for the Figaro TGS2611 sensor. (The temperature of the sensors does not rise appreciably above ambient when they are operated below 0.5 V.) These results indicate that sensor temperatures are significantly higher than most previously reported estimates, particularly those made using infrared thermometers (IRTs). A heat loss model for the sensors is discussed, and the calibration of the heater resistance–temperature relationship is achieved for the TGS2611.

A quadratic boundary element implementation in orthotropic elasticity using the real variable approach

Abstract: This paper revisits the real variable fundamental solution approach to the Boundary Integral Equation (BIE) method in two-dimensional orthotropic elasticity. The numerical implementation was carried out using quadratic isoparametric elements. The strong and weakly singular integrals were directly evaluated using Euler's transformation technique. The limiting process was done in intrinsic coordinates and no separate numerical treatment for strong and weak singular integrals was necessary. For strongly singular integrals a priori interpretation of the Cauchy principal value is not necessary. Two problems from plane stress and strain are presented to demonstrate the numerical efficiency of the approach. Excellent agreement between BEM results and exact solutions was obtained even with relatively coarse mesh discretizations

Dual-cavity Brillouin/erbium fiber laser for DWDM

Abstract: We report on the operation of a multiple wavelength dual-cavity Brillouin/erbium fiber laser (BEFL) that could output a 22 GHz comb of 2/spl times/15 channels. The all-fiber laser system consists of two erbium-doped fiber ring lasers (EDFL) that share a single mode fiber (SMF) to produce interdependent bidirectional Stokes signals. The system configuration was made such that there is a slightly higher cavity loss incurred in one the cavities and results in a small wavelength-shift in the EDFL peak gain of the cavity. Coupling of these cavities leads to a slightly broader spectrum peak from the superimposing of the two free-running EDFL spectra and this would increase the number of Stokes lines when Brillouin pump is injected into the SMF. The dual cavity BEFL system produces a stable output of 22-GHz (0.18 nm) comb of 2/spl times/15 channels at 1560 nm that can be used for dense wavelength division multiplexed (DWDM) systems.