Ian Cooper

Bio: Ian Cooper is an academic researcher from University of Sydney. The author has contributed to research in topics: Diffraction & Numerical integration. The author has an hindex of 7, co-authored 11 publications receiving 389 citations.

A SIR model assumption for the spread of COVID-19 in different communities

Abstract: In this paper, we study the effectiveness of the modelling approach on the pandemic due to the spreading of the novel COVID-19 disease and develop a susceptible-infected-removed (SIR) model that provides a theoretical framework to investigate its spread within a community Here, the model is based upon the well-known susceptible-infected-removed (SIR) model with the difference that a total population is not defined or kept constant per se and the number of susceptible individuals does not decline monotonically To the contrary, as we show herein, it can be increased in surge periods! In particular, we investigate the time evolution of different populations and monitor diverse significant parameters for the spread of the disease in various communities, represented by China, South Korea, India, Australia, USA, Italy and the state of Texas in the USA The SIR model can provide us with insights and predictions of the spread of the virus in communities that the recorded data alone cannot Our work shows the importance of modelling the spread of COVID-19 by the SIR model that we propose here, as it can help to assess the impact of the disease by offering valuable predictions Our analysis takes into account data from January to June, 2020, the period that contains the data before and during the implementation of strict and control measures We propose predictions on various parameters related to the spread of COVID-19 and on the number of susceptible, infected and removed populations until September 2020 By comparing the recorded data with the data from our modelling approaches, we deduce that the spread of COVID-19 can be under control in all communities considered, if proper restrictions and strong policies are implemented to control the infection rates early from the spread of the disease

Use of interactive lecture demonstrations: A ten year study

Abstract: The widely held constructivist view of learning advocates student engagement via interactivity. Within the physics education research community, several specific interactive strategies have been developed to enhance conceptual understanding. One such strategy, the Interactive Lecture Demonstration (ILD) is designed for large lecture classes and, if measured using specific conceptual surveys, is purported to provide learning gains of up to 80%. This paper reports on learning gains for two different Projects over ten years. In Project 1, the ILDs were implemented from 1999 to 2001 with students who had successfully completed senior high school physics. The learning gains for students not exposed to the ILDs were in the range 13% to 16% while those for students exposed to the ILDs was 31% to 50%. In Project 2, the ILDs were implemented from 2007 to 2009 with students who had not studied senior high school physics. Since the use of ILDs in Project 1 had produced positive results, ethical considerations dictated that all students be exposed to ILDs. The learning gains were from 28% to 42%. On the one hand it is pleasing to note that there is an increase in learning gains, yet on the other, we note that the gains are nowhere near the claimed 80%. This paper also reports on teacher experiences of using the ILDs, in Project 2.

Focusing of pseudoradial polarized beams.

Abstract: The focusing of a light beam with radial polarization has substantial advantages as the irradiance distribution in the focal plane is symmetric and there is maximum absorption at the focus. Using half wave plates cut into four quadrants with each quadrant having a linear polarization directed outwards gives a total field that approximates radial polarization, called pseudoradial polarization. The irradiance distributions in the focal region for different polarizations and beam profiles are compared. The irradiance is calculated by the numerical integration of the two-dimensional Rayleigh-Sommerfeld diffraction integral of the first kind using the 2DSC method for both circular and annular apertures.

Dynamic tracking with model-based forecasting for the spread of the COVID-19 pandemic

Abstract: In this paper, a susceptible-infected-removed (SIR) model has been used to track the evolution of the spread of COVID-19 in four countries of interest. In particular, the epidemic model, that depends on some basic characteristics, has been applied to model the evolution of the disease in Italy, India, South Korea and Iran. The economic, social and health consequences of the spread of the virus have been cataclysmic. Hence, it is imperative that mathematical models can be developed and used to compare published datasets with model predictions. The predictions estimated from the presented methodology can be used in both the qualitative and quantitative analysis of the spread. They give an insight into the spread of the virus that the published data alone cannot, by updating them and the model on a daily basis. We show that by doing so, it is possible to detect the early onset of secondary spikes in infections or the development of secondary waves. We considered data from March to August, 2020, when different communities were affected severely and demonstrate predictions depending on the model's parameters related to the spread of COVID-19 until the end of December, 2020. By comparing the published data with model results, we conclude that in this way, it may be possible to reflect better the success or failure of the adequate measures implemented by governments and authorities to mitigate and control the current pandemic.

Methods of Numerical Integration

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The Use of Research-Based Instructional Strategies in Introductory Physics: Where do Faculty Leave the Innovation-Decision Process?

Abstract: Department of Statistics, Western Michigan University, Kalamazoo, Michigan 49008, USA(Received 20 February 2012; published 31 July 2012)During the fall of 2008 aweb survey, designed to collect information about pedagogical knowledge andpractices, was completed by a representative sample of 722 physics faculty across the United States(50.3% response rate). This paper presents partial results to describe how 20 potential predictor variablescorrelate with faculty knowledge about and use of research-based instructional strategies (RBIS). Theinnovation-decision process was conceived of in terms of four stages: knowledge versus no knowledge,trial versus no trial, continuationversus discontinuation, and high versus low use. The largest losses occurat the continuation stage, with approximately 1=3 offaculty discontinuing use of all RBIS after trying oneor more of these strategies. Nine of the predictor variables were statistically significant for at least one ofthese stages when controlling for other variables. Knowledge and/or use of RBIS are significantlycorrelated with reading teaching-related journals, attending talks and workshops related to teaching,attending the physics and astronomy new faculty workshop, having an interest in using more RBIS, beingfemale, being satisfied with meeting instructional goals, and having a permanent, full-time position. Thetypes of variables that are significant at each stage vary substantially. These results suggest that commondissemination strategies are good at creating knowledge about RBIS and motivation to try a RBIS, butmore work is needed to support faculty during implementation and continued use of RBIS. Also, contraryto common assumptions, faculty age, institutional type, and percentage of job related to teaching were notfoundtobebarrierstoknowledgeoruseatanystage.Highresearchproductivityandlargeclasssizeswerenot found to be barriers to use of at least some RBIS.

Use of research-based instructional strategies in introductory physics: Where do faculty leave the innovation-decision process?

Abstract: During the fall of 2008 a web survey, designed to collect information about pedagogical knowledge and practices, was completed by a representative sample of 722 physics faculty across the United States (50.3% response rate). This paper presents partial results to describe how 20 potential predictor variables correlate with faculty knowledge about and use of research-based instructional strategies (RBIS). The innovation-decision process was conceived of in terms of four stages: knowledge versus no knowledge, trial versus no trial, continuation versus discontinuation, and high versus low use. The largest losses occur at the continuation stage, with approximately $1/3$ of faculty discontinuing use of all RBIS after trying one or more of these strategies. Nine of the predictor variables were statistically significant for at least one of these stages when controlling for other variables. Knowledge and/or use of RBIS are significantly correlated with reading teaching-related journals, attending talks and workshops related to teaching, attending the physics and astronomy new faculty workshop, having an interest in using more RBIS, being female, being satisfied with meeting instructional goals, and having a permanent, full-time position. The types of variables that are significant at each stage vary substantially. These results suggest that common dissemination strategies are good at creating knowledge about RBIS and motivation to try a RBIS, but more work is needed to support faculty during implementation and continued use of RBIS. Also, contrary to common assumptions, faculty age, institutional type, and percentage of job related to teaching were not found to be barriers to knowledge or use at any stage. High research productivity and large class sizes were not found to be barriers to use of at least some RBIS.

Effects of polarization on the de-excitation dark focal spot in STED microscopy

Abstract: The size of the dark focal spot directly determines the resolution and stability of stimulated emission depletion (STED) microscopy. This paper investigates the relationship between the size of the dark focal spot and the polarization of the input light beam. The types of fundamental polarization are discussed, their effects on the dark focal spot are compared and the optimized mode for each kind of polarization is proposed. The results of the analysis provide the theoretical basis and reference for designing a STED system.