Structural study of titanium oxide films synthesized by ion beam-assisted deposition

The application of titanium dioxide (TiO(2)) films as surgical implant coatings for antibiotic attachment depends crucially on their available surface area and thus their surface morphology and crystallinity. Here, we report our fabrication of high Wenzel ratio TiO(2) films targeted to increase the film surface area using the ion beam-assisted deposition (IBAD) technique at high-deposition temperatures (approximately 610 degrees C). The modulation of the films' surface morphology was accomplished by varying the chemical identity of the concurrent ion beams bombarded on the films during the e-beam evaporation process. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to investigate the surface morphology of the as-deposited films. X-ray diffractometry (XRD) revealed that these nanocrystalline films primarily consist of anatase phase TiO(2). Wenzel ratio, the ratio of the actual surface area to the projected area, of IBAD films prepared with argon, oxygen, and nitrogen ion beams was measured to be 1.52, 1.31 and 1.49, respectively. The effect of the differences in chemical reactivity and ion size of these three type ion beams are discussed to explain the present results.     

A broadband Fourier transform microwave spectrometer based on chirped pulse excitation

Designs for a broadband chirped pulse Fourier transform microwave (CP-FTMW) spectrometer are presented. The spectrometer is capable of measuring the 7-18 GHz region of a rotational spectrum in a single data acquisition. One design uses a 4.2 Gsampless arbitrary waveform generator (AWG) to produce a 1 mus duration chirped pulse with a linear frequency sweep of 1.375 GHz. This pulse is sent through a microwave circuit to multiply the bandwidth of the pulse by a factor of 8 and upconvert it to the 7.5-18.5 GHz range. The chirped pulse is amplified by a traveling wave tube amplifier and broadcast inside the spectrometer by using a double ridge standard gain horn antenna. The broadband molecular free induction decay (FID) is received by a second horn antenna, downconverted, and digitized by a 40 Gsampless (12 GHz hardware bandwidth) digital oscilloscope. The second design uses a simplified pulse generation and FID detection scheme, employing current state-of-the-art high-speed digital electronics. In this spectrometer, a chirped pulse with 12 GHz of bandwidth is directly generated by using a 20 Gsampless AWG and upconverted in a single step with an ultrabroadband mixer. The amplified molecular emission is directly detected by using a 50 Gsampless digital oscilloscope with 18 GHz bandwidth. In both designs, fast Fourier transform of the FID produces the frequency domain rotational spectrum in the 7-18 GHz range. The performance of the CP-FTMW spectrometer is compared to a Balle-Flygare-type cavity-FTMW spectrometer. The CP-FTMW spectrometer produces an equal sensitivity spectrum with a factor of 40 reduction in measurement time and a reduction in sample consumption by a factor of 20. The CP-FTMW spectrometer also displays good intensity accuracy for both sample number density and rotational transition moment. Strategies to reduce the CP-FTMW measurement time by another factor of 90 while simultaneously reducing the sample consumption by a factor of 30 are demonstrated.     

The uncertainty of radius estimation in least-squares sphere-fitting,with an introduction to a new summation based method

This paper considers the sensitivity of three sphere-fitting algorithms to real-world measurement errors. It pays particular attention to nominally spherical surfaces, such as those typically measured by tactile and optical profilometers, addressing the limitations of sensor gauge range and angular tolerance. A recently proposed linear circle-fitting algorithm is extended to a sphere-fitting algorithm and its performance compared to two long standing sphere-fitting algorithms; namely linear and non-linear least-squares. Sources of measurement error in optical profilometers are discussed, and user defined scan parameters are optimised based on the results of a designed experiment. The performance of all three sphere-fitting algorithms are tested on a sphere superimposed with varying degrees of surface irregularities in a Monte Carlo simulation; this study shows that both linear routines display a negative skewness in their radius error distribution. Finally, a method of predicting radius uncertainty is offered that considers the surface residual that remains after sphere-fitting and relates this to the radius uncertainty of the chosen algorithm.     

Ultrasonically induced degradation of 2-methylisoborneol and geosmin

2-Methylisoborneol (MIB) and geosmin (GSM) are taste and odor compounds produced by cyanobacteria in surface waters. While the strong odors and musty flavors of MIB and GSM are generally associated with poor water quality, the removal of these semi-volatile compounds presents a significant challenge to drinking water providers. Likewise in aquaculture, accumulation of these compounds in fish meat leads to quality problems and reduces marketability. Conventional water treatments are ineffective at removing low concentration of odor compounds. We report herein ultrasonic irradiation at 640 kHz leads to rapid degradation of MIB and GSM. While radical processes generally dominate during ultrasonic-induced degradation, pyrolysis appears to be responsible for a significant fraction of the observed degradation. Several pyrolytic products from MIB and GSM have been identified and degradation pathways are elucidated. The degradation of MIB and GSM follows the first-order kinetics and the rate constants are 0.07 and 0.12 min(-1), respectively. These results suggest ultrasonic irradiation maybe applicable as an effective method for removal of taint compounds from potable water supplies and fish farms.     

Three-dimensional distinct element modelling and dynamic runout analysis of a landslide in gneissic rock, British Columbia, Canada

The McAuley Creek Landslide is a 6?million m³ gneissic rock slope failure that occurred in British Columbia (Canada) in late May–early June 2002. The geological strength index was used to characterize the quality of the overall rock mass and its reduced (damaged) quality near tectonic structures and alteration zones. Potential slope failure mechanisms were investigated using four analysis techniques including: kinematic analysis, surface wedge limit equilibrium (combination) analysis, block theory and three-dimensional distinct element models. Results from all four analyses suggested that the dominant slope failure mechanism was wedge sliding along the intersection of the gneissic foliation and a steeply dipping discontinuity set striking perpendicular to the slope. Of the 6?million m³ of material involved in the landslide, an estimated 5 million?m³ was deposited immediately below the source area against the opposite valley wall, with the remaining 1 million m³ travelling an additional 1.6?km downstream. The runout behaviour was investigated using a three-dimensional dynamic analysis code.     

Seismic damage and fragility analysis of structures with tuned mass dampers based on plastic energy

The effectiveness of using a tuned mass damper (TMD) to improve a structure's ability to dissipate earthquake input energy is investigated through the use of seismic fragility curves. The nonlinear material behaviour of the structure is captured using the force analogy method, the backbone for analytically quantifying plastic energy dissipation in the structure. Numerical analysis was performed to study the global response and local energy dissipation of a six‐storey moment‐resisting steel frame with and without a TMD installed for 100 simulated non‐stationary Gaussian earthquake ground motions. The effectiveness of the TMD, based on reduction of seismic responses and enhancement of the seismic fragility, is considered at structural performance levels for immediate occupancy and life safety as identified in FEMA 440. An ‘equivalent monotonic plastic strain’ approach—a local measure of structural damage—is used to correlate the seismic fragilities at different global performance levels based on storey drift. Results illustrate that a TMD can enhance the structure's ability to dissipate energy at low levels of earthquake shaking, while less effective during moderate to strong earthquakes, which can cause a significant period shift associated with major structural damage. This ‘de‐tuning’ effect suggests that an extremely sizable TMD is not effective in reducing damage of a structure. Published in 2010 by John Wiley & Sons, Ltd.     

Microbiology of a wetland ecosystem constructed to remediate mine drainage from a heavy metal mine

A pilot passive treatment plant (PPTP) was constructed to evaluate the potential of a composite wetland system to remediate acidic, metal-rich water draining the former Wheal Jane tin, in Cornwall, England. The treatment plant consists of three separate and controllable composite systems, each of which comprises a series of aerobic wetlands for iron oxidation and precipitation, a compost bioreactor for removing chalcophilic metals and to generate alkalinity, and rock filter ponds for removing soluble manganese and organic carbon. To understand the roles of microorganisms in remediating acid mine drainage (AMD) in constructed wetland ecosystems, populations of different groups of cultivatable acidophilic microbes in the various components of the Wheal Jane PPTP were enumerated over a 30-month period. Initially, moderately acidophilic iron-oxidising bacteria (related to Halothiobacillus neapolitanus) were found to be the major cultivatable microorganisms present in the untreated AMD, though later heterotrophic acidophiles emerged as the dominant group, on a numerical basis. Culturable microbes in the surface waters and sediments of the aerobic wetlands were similarly dominated by heterotrophic acidophiles, though both moderately and extremely acidophilic iron-oxidising bacteria were also present in significant numbers. The dominant microbial isolate in waters draining the anaerobic compost bioreactors was an iron- and sulfur-oxidising moderate acidophile that was closely related to Thiomonas intermedia. The acidophiles enumerated at the Wheal Jane PPTP accounted for 1% to 25% of the total microbial population. Phylogenetic analysis of 14 isolates from various components of the Wheal Jane PPTP showed that, whilst many of these bacteria were commonly encountered acidophiles, some of these had not been previously encountered in AMD and AMD-impacted environments.     

Prevailing wage legislation and public school construction efficiency: a stochastic frontier approach1

Stochastic frontier regression is used to examine the effect of introducing prevailing wage legislation on public school construction efficiency in British Columbia. Prior to the legislation, public school projects were from 16% to 19% smaller, in terms of square feet, than comparable private structures. However, likelihood ratio tests consistently indicate that the coefficients measuring the effect of the policy on the size differential between covered and uncovered projects are not statistically different from zero. These results suggest that construction wage requirements did not alter input utilisation in a way that significantly affected construction output. Average inefficiency for school construction in British Columbia over the period of the study is 12.1%.     

A web‐based performance assessment system for environmental protection: WePass

In response to the increasing public concern over the effects of construction waste on the environment, a performance assessment system has been designed to provide an instant, online assessment of how well a construction site performs environmentally, e.g. measuring the level of pollution generated from a construction site. Through the use of both Internet and database technologies, it is possible to collect and present data that are essential for environmental management online. To achieve this, a set of environmental performance parameters was derived through a postal questionnaire survey and interviews with experts in the field. A conceptual framework was developed, of which the key components were: template, knowledge base, output data and benchmark group. In combination, these factors provide a system that enables speedy assessment and effective management of environmental performance on construction sites, hence prompt decisions can be made and corrective actions can be taken before potential hazards turn into real disasters.