Decline in Youth Participation in Canada in the 1990s: Structural or Cyclical?

Of the three major age groups, youth (aged 15-24), experienced the largest fall in labour force participation and accounted for the lion’s share of the aggregate decline. Consequently, an understanding of the factors behind this development is essential to an overall understanding of the fall in labour force participation in the 1990s in Canada. In the fifth and final article in the symposium, Richard Archambault and Louis Grignon examine the causes of this large fall in youth labour force participation in Canada in the 1990s. They disaggregate the youth participation rate into three components: the student participation rate, the non-student participation rate, and the school enrolment rate. The aggregate youth rate is the sum of the student and non-student rates weighted by their respective shares of the population (the enrolment rate for students). Such an approach makes it possible to take account of behavioural differences between students and non-students and to treat the enrolment rate as a phenomenon to be explained rather than a determinant of the participation rate. All three variables are modelled as a function of a cyclical variable and a number of structural variables - the real wage, the relative minimum wage, employment insurance, social assistance, and a time trend. The results show the importance of economic conditions and the modest effect of public policy programs on the decision to participate in the labour market and go to school. Based on the equations estimated for the 1976-96 period, a dynamic simulation was conducted over the 1990-96 period to account for the impact of the variables on the student and non-student participation rates and enrolment rate. According to the equations estimated for the 15-24 age group, the cyclical variable accounts for about one half of the decline in the youth participation rate between 1990 and 1996, two thirds of the decline in the student participation rate, and about one third of the fall in both the non-student participation rate and rise in the enrolment rate. The remaining decline in the two participation rates and rise in the enrolment rate are not to any significant degree explained by the four structural variables, but rather are either captured by the time trend or not explained at all. Given these results, the authors conclude that we have a poor understanding of the non-cyclical forces that account for up to one half of the decline in youth labour force participation in the 1990s.Canada, Labour Force Participation, Labor Force Participation, Participation Rate, Labour Force Participation Rate, Labor Force Participation Rate, Age Structure, Age, Youth, Teenage, Young Adult, Student, Enrolment Rate, Enrolment, Enrollment Rate, Enrollment

Discriminative neural network for hero selection in professional Heroes of the Storm and DOTA 2

Multiplayer online battle arena games (MOBAs) are one of the most popular types of online games. Annual tournaments draw large online viewership and reward the winning teams with large monetary prizes. Character selection prior to the start of the game (draft) plays a major role in the way the game is played and can give a large advantage to either team. Hence, professional teams try to maximize their winning chances by selecting the optimal team composition to counter their opponents. However, drafting is a complex process that requires deep game knowledge and preparation, which makes it stressful and error-prone. In this paper, we present an automatic drafter system based on the suggestions of a discriminative neural network and evaluate how it performs on the MOBAs Heroes of the Storm and DOTA 2. We propose a method to appropriately exploit very heterogeneous datasets that aggregates data from various versions of the games. Drafter testing on professional games shows that the actual selected hero was present in the top 3 determined by our drafting tool 30.4% of the time for HotS and 17.6% for DOTA 2. The performance obtained by this method exceed all previously reported results

Accurate Dose Measurements Using Cherenkov Polarization Imaging

Purpose: Cherenkov radiation carries the potential of direct in-water dose measurements, but its precision is currently limited by a strong anisotropy. Taking advantage of polarization imaging, this work proposes a new approach for high accuracy Cherenkov dose measurements. Methods: Cherenkov produced in a 15x15x20 cm^3 water tank is imaged with a cooled CCD camera from four polarizer transmission axes [0{\deg}, 45{\deg}, 90{\deg}, 135{\deg}]. The water tank is positioned at the isocenter of a 5x5 cm^2, 6 MV photon beam. Using Malus' law, the polarized portion of the signal is extracted. Corrections are applied to the polarized signal following azimuthal and polar Cherenkov angular distributions extracted from Monte Carlo simulations. Percent depth dose and beam profiles are measured and compared with the prediction from a treatment planning system (TPS). Results: Corrected polarized signals on the central axis reduced deviations at depth from 20% to 0.8\pm1%. For the profile measurement, differences between the corrected polarized signal and the TPS calculations are 1\pm3% and 8\pm3% on the central axis and penumbra regions respectively. 29\pm1% of the Cherenkov signal was found to be polarized. Conclusions: This work proposes a novel polarization imaging approach enabling high precision water-based Cherenkov dose measurements. The method allows correction of the Cherenkov anisotropy within 3% on the beam central axis and in depth

An EPID-based method to determine mechanical deformations in a linear accelerator

Purpose: Medical linear accelerators (linac) are delivering increasingly complex treatments using modern techniques in radiation therapy. Complete and precise mechanical QA of the linac is therefore necessary to ensure that there is no unexpected deviation from the gantry's planned course. However, state-of-the-art EPID-based mechanical QA procedures often neglect some degrees of freedom (DOF) like the in-plane rotations of the gantry and imager or the source movements inside the gantry head. Therefore, the purpose of this work is to characterize a 14 DOF method for the mechanical QA of linacs. This method seeks to measure every mechanical deformation in a linac, including source movements, in addition to relevant clinical parameters like mechanical and radiation isocenters. Methods: A widely available commercial phantom and a custom-made accessory inserted in the linac's interface mount are imaged using the electronic portal imaging device (EPID) at multiple gantry angles. Then, simulated images are generated using the nominal geometry of the linac and digitized models of the phantoms. The nominal geometry used to generate these images can be modified using 14 DOF (3 rigid rotations and 3 translations for the imager and the gantry, and 2 in-plane translations of the source) and any change will modify the simulated image. The set of mechanical deformations that minimizes the differences between the simulated and measured image is found using a genetic algorithm coupled with a gradient-descent optimizer. Phantom mispositioning and gantry angular offset were subsequently calculated and extracted from the results. Simulations of the performances of the method for different levels of noise in the phantom models were performed to calculate the absolute uncertainty of the measured mechanical deformations. The measured source positions and the center of collimation were used to define the beam central axis and calculate the radiation isocenter position and radius. Results: After the simultaneous optimization of the 14 DOF, the average distance between the center of the measured and simulated ball bearings on the imager was 0.086 mm. Over the course of a full counter-clockwise gantry rotation, all mechanical deformations were measured, showing sub-millimeter translations and rotations smaller than 1° along every axis. The average absolute uncertainty of the 14 DOF (1 SD) was 0.15 mm or degree. Phantom positioning errors were determined with more than 0.1 mm precision. Errors introduced in the experimental setup like phantom positioning errors, source movements or gantry angular offsets were all successfully detected by our QA method. The mechanical deformations measured are shown to be reproducible over the course of a few weeks and are not sensitive to the experimental setup. Conclusion: This work presents of new method for an accurate mechanical QA of the linacs. It features a 14 DOF model of the mechanical deformations that is both more complete and precise than other available methods. It has demonstrated sub-millimeter accuracy through simulation and experimentation. Introduced errors were successfully detected with high precision

A discrete interaction numerical model for coagulation and fragmentation of marine detritic particulate matter (Coagfrag v.1)

A simplified model, representing the dynamics of marine organic particles in a given size range experiencing coagulation and fragmentation reactions, is developed. The framework is based on a discrete size spectrum on which reactions act to exchange properties between different particle sizes. The reactions are prescribed according to triplet interactions. Coagulation combines two particle sizes to yield a third one, while fragmentation breaks a given particle size into two (i.e. the inverse of the coagulation reaction). The complete set of reactions is given by all the permutations of two particle sizes associated with a third one. Since, by design, some reactions yield particle sizes that are outside the resolved size range of the spectrum, a closure is developed to take into account this unresolved range and satisfy global constraints such as mass conservation. In order to minimize the number of tracers required to apply this model to an ocean general circulation model, focus is placed on the robustness of the model to the particle size resolution. Thus, numerical experiments were designed to study the dependence of the results on (i) the number of particle size bins used to discretize a given size range (i.e. the resolution) and (ii) the type of discretization (i.e. linear vs. nonlinear). The results demonstrate that in a linearly size-discretized configuration, the model is independent of the resolution. However, important biases are observed in a nonlinear discretization. A first attempt to mitigate the effect of nonlinearity of the size spectrum is then presented and shows significant improvement in reducing the observed biases.Fil: Gremion, Gwenaëlle. Institut des Sciences de la Mer de Rimouski; CanadáFil: Nadeau, Louis Philippe. Institut des Sciences de la Mer de Rimouski; CanadáFil: Dufresne, Christiane. Institut des Sciences de la Mer de Rimouski; CanadáFil: Schloss, Irene Ruth. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego. Instituto de Ciencias Polares, Recursos Naturales y Ambiente; ArgentinaFil: Archambault, Philippe. Laval University; CanadáFil: Dumont, Dany. Institut des Sciences de la Mer de Rimouski; Canad

Non-negative Matrix Factorization using Partial Prior Knowledge for Radiation Dosimetry

Hyperspectral unmixing aims at decomposing a given signal into its spectral signatures and its associated fractional abundances. To improve the accuracy of this decomposition, algorithms have included different assumptions depending on the application. The goal of this study is to develop a new unmixing algorithm that can be applied for the calibration of multi-point scintillation dosimeters used in the field of radiation therapy. This new algorithm is based on a non-negative matrix factorization. It incorporates a partial prior knowledge on both the abundances and the endmembers of a given signal. It is shown herein that, following a precise calibration routine, it is possible to use partial prior information about the fractional abundances, as well as on the endmembers, in order to perform a simplified yet precise calibration of these dosimeters. Validation and characterization of this algorithm is made using both simulations and experiments. The experimental validation shows an improvement in accuracy compared to previous algorithms with a mean spectral angle distance (SAD) on the estimated endmembers of 0.0766, leading to an average error of $(0.25 \pm 0.73)$ % on dose measurements.Comment: 11 pages, 6 figure