Concordia University

About: Concordia University is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Control theory & Population. The organization has 13565 authors who have published 31084 publications receiving 783525 citations. The organization is also known as: Sir George Williams University & Loyola College, Montreal.

Coherent states and their generalizations - A mathematical overview

Abstract: We present a survey of the theory of coherent states (CS); and some of their generalizations, with emphasis on the mathematical structure, rather than on physical applications. Starting from the standard theory of CS over Lie groups, we develop a general formalism, in which CS are associated to group representations which are square integrable over a homogeneous space. A further step allows us to dispense with the group context altogether, and thus obtain the so-called reproducing triples and continuous frames introduced in some earlier work. We discuss in detail a number of concrete examples, namely semisimple Lie groups, the relativity groups and various types of wavelets. Finally we turn to some physical applications, centering on quantum measurement and the quantization/dequantization problem, that is, the transition from the classical to the quantum level and vice versa.

Brain Tumor Type Classification via Capsule Networks

Abstract: Brain tumor is considered as one of the deadliest and most common form of cancer both in children and in adults. Consequently, determining the correct type of brain tumor in early stages is of significant importance to devise a precise treatment plan and predict patient's response to the adopted treatment. In this regard, there has been a recent surge of interest in designing Convolutional Neural Networks (CNNs) for the problem of brain tumor type classification. However, CNNs typically require large amount of training data and can not properly handle input transformations. Capsule networks (referred to as CapsNets) are brand new machine learning architectures proposed very recently to overcome these shortcomings of CNNs, and posed to revolutionize deep learning solutions. Of particular interest to this work is that Capsule networks are robust to rotation and affine transformation, and require far less training data, which is the case for processing medical image datasets including brain Magnetic Resonance Imaging (MRI) images. In this paper, we focus to achieve the following four objectives: (i) Adopt and incorporate CapsNets for the problem of brain tumor classification to design an improved architecture which maximizes the accuracy of the classification problem at hand; (ii) Investigate the over-fitting problem of CapsNets based on a real set of MRI images; (iii) Explore whether or not CapsNets are capable of providing better fit for the whole brain images or just the segmented tumor, and; (iv) Develop a visualization paradigm for the output of the CapsNet to better explain the learned features. Our results show that the proposed approach can successfully overcome CNNs for the brain tumor classification problem.

Photophysics of Cyanine Dyes: Subnanosecond Relaxation Dynamics in Monomers, Dimers, and H- and J-Aggregates in Solution

Abstract: The photophysics of three cyanine dyes (i) 1,1‘-diethyl-2,2‘-cyanine iodide (pseudoisocyanine, PIC), (ii) 3,3‘-didodecyldithia-2,2‘-carbocyanine bromide (dye 1), and (iii) 3,3‘-diethyldithia-2,2‘-carbocyanine iodide (dye 2) have been examined by picosecond-laser photolysis in aqueous and methanolic-aqueous media. At moderately high concentration, solutions of PIC in 5 M NaCl/water contain monomers, H-aggregates, and J-aggregates; dye 1 water/methanol solutions consist mostly of monomers and H-aggregates (dimers and higher n-mers); aqueous dye 2 solutions contain only monomers and dimers. Photolysis of H- and/or J-aggregates in PIC and dye 1 cyanine solutions leads to photobleaching of the respective aggregate absorption bands and subsequently decays by biphasic kinetics. Two mechanisms are discussed for the deactivation of excited aggregates. In the first, nonradiative decay of the excited singlet states results in considerable heating of the aggregates together with their surrounding solvent shells causi...

A review of research and developments of building-integrated photovoltaic/thermal (BIPV/T) systems

Abstract: The concept of building-integrated photovoltaic/thermal (BIPV/T) systems emerged in the early 1990s. It has attracted increasing attention since 2000 due to its potential to facilitate the design of net-zero energy buildings through enhanced solar energy utilisation. This article presents a comprehensive review of the BIPV/T technology, including major developments of various BIPV/T systems, experimental and numerical studies, and the impact of BIPV/T system on building performance. The BIPV/T systems reviewed here are: air-based systems, water-based systems, concentrating systems and systems involving a phase change working medium such as BIPV/T with either heat pipe or heat pump evaporator. This work provides an overview of research, development, application and status of BIPV/T systems and modules. Finally, research needs and opportunities are identified.

Photoluminescence and Transient Spectroscopy of Free Base Porphyrin Aggregates

Abstract: Solutions of free base meso-tetraphenylporphyrin (H2TPP), meso-tetra(4-carboxyphenyl)porphyrin (H2TPPC), and meso-tetra(4-pyridyl)porphyrin (H2TPyP) under various conditions generate aggregates whose absorption spectra are characterized by invariant Soret bands with bandwidths that are independent of the preparative method. One of the Soret bands is blue-shifted (H-aggregate) relative to the monomeric porphyrin band; other Soret bands are red-shifted (J-aggregates). The aggregates are characterized by different nonradiative rate constants for excited singlet-state decay and by different efficiencies of singlet−singlet annihilation at the high energies of laser excitation. The quantum yields of fluorescence vary between 10-5 and 10-2, and the corresponding fluorescence lifetimes vary in the range from 10-12 to 10-9 s; they are more than 1 order of magnitude smaller than those of the corresponding monomeric porphyrins. Lifetimes (τ) correlate with the characteristic ground-state absorption recovery times of...