Abstract： Previous efforts to define these terms are reviewed and their deficiencies noted. New quantitative measures of size and shape are proposed, based upon measurements made possible by image analysis techniques. These may be applied to both single particle and to assemblages of particles. Laboratory test results are presented to demonstrate the application of one of the new measures. Suggestions are made for further research.
Keywords：Quantitative measuresParticle shapeParticle size
Abstract：Morphological parameters of coarse aggregates, including the angularity index (AI), flat and elongated ratio, flatness ratio, and sphericity, strongly affect the performance of asphalt concrete. A device must be developed to efficiently and accurately measure these parameters. Herein, a charge-coupled device camera and a linear profile scanner are combined to evaluate the parameters. The AI is calculated using three methods. The results show that the fitted-ellipse method provides superior results among the three AI measurement methods. Moreover, the use of a linear profile scanner improves the AI measurement accuracy. Therefore, the proposed combination has high measurement efficiency and is suitable for batch inspections.
Keywords：Charge-coupled device cameraLinear profile scannerAngularityFlatness ratioSphericity
American Geophysical Union, Canada
Applications are invited for a postdoctoral position at Trent University to carry out research on enhanced rock weathering (ERW) and CO2 mineralization for carbon dioxide removal. The successful applicant will conduct laboratory experiments to study mineral-water-gas interactions and/or microbially mediated processes as it relates to accelerating ERW and CO2 mineralization using mine wastes. Opportunities to conduct fieldwork and experiments at operating mines will also be possible. The postdoctoral researcher will become part of a dynamic research network with opportunities for inter-laboratory collaboration. The position will be based in the Environmental Geochemistry Laboratory (powergeolab.com) with Prof. Ian Power, Canada Research Chair Tier 2 in Environmental Geoscience, in the Trent School of the Environment.
The successful applicant will have experience and skills in one or more of the following fields: aqueous geochemistry, geomicrobiology, soil geochemistry, carbonate sedimentology, and mine site remediation, as well as an outstanding publication record. The candidate will have a Ph.D. or equivalent degree in Earth sciences or a closely allied field. They will be independent, creative thinkers, and team players who can work across fields and with industry partners. Fluent English is required for the position and a full driver’s licence is beneficial. The candidates must be technically capable in the laboratory and have experience doing fieldwork.
Terms of appointment
The initial appointment will be for a period of 1 year, with the possibility of renewal based on performance and funding availability. Salary is dependent on experience of the candidate. Healthcare benefits are provided as part of the terms of employment.
Commitment to diversity
Trent University is actively committed to creating a diverse and inclusive campus community and encourages applications from all qualified candidates. Trent University offers accommodation for applicants with disabilities in its recruitment processes. If you require accommodation during the recruitment process or require an accessible version of a document/publication, please contact Powergeolab@gmail.com.
How to apply
Review of applications will begin on August 28th, 2020 until the position is filled. The successful candidate will be expected to commence work by January 2021 or thereabouts. Applications should consist of (1) a short cover letter outlining how the candidate fulfills the requirements of the position, (2) a full CV, (3) a 1–2 page letter of research interests that aligns Dr. Power’s research program, and (4) contact information for no less than 3 referees. Applications should be sent as a single PDF to Powergeolab@gmail.com. Queries about this opportunity should be sent to the same email address.
Abstract: A method of measuring the sphericity, shape factor, and convexity of coarse aggregate for concrete using digital image processing (DIP) is developed. Unlike other DIP methods, this method is capable of estimating the thickness and volume of the particles, and can thus be used to measure shape parameters dependent on thickness and to evaluate weighted mean values of the shape parameters of the individual particles in an aggregate sample. A total of 46 rock aggregate samples obtained from five different sources derived from three different types of rock have been analyzed by the method and the shape parameters so measured are correlated to the traditional measure of angularity with the hope of identifying shape parameters that may be used as direct measures of angularity. Several shape parameters are found to have good correlation with the traditional measure of angularity but among them, only the convexity ratio and fullness ratio may be used as measures of angularity. Lastly, it is advocated that the traditional measure of angularity in terms of packing density should be abandoned; packing density by itself is an important indicator of aggregate performance but is not a good measure of angularity.
Keywords: AggregateCoarse aggregate for concreteDigital image processingPacking densityParticle shape analysis