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Automated pebble mosaic stylization of images

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Computational Visual Media 2019年第1期5卷 33-44页

作者： Lars Doyle Forest Anderson Ehren Choy David Mould Carleton University

Digital mosaics have usually used regular tiles, simulating historical tessellated mosaics. In this paper, we present a method for synthesizing pebble mosaics, a historical mosaic style in which the tiles are rounded pebbles. We address both the tiling problem,of distributing pebbles over the image plane so as to approximate the input image content, and the problem of geometry, creating a smooth rounded shape for each pebble. We adopt simple linear iterative clustering(SLIC)to obtain elongated tiles conforming to image content,and smooth the resulting irregular shapes into shapes resembling pebble cross-sections. Then, we create an interior and exterior contour for each pebble and solve a Laplace equation over the region between them to obtain height-field geometry. The resulting pebble set approximates the input image while representing full geometry that can be rendered and textured for a highly detailed representation of a pebble mosaic.

关键词： non-photorealistic rendering digital mosaics image stylization segmentation image processing

CONSTRUCTION OF CONTINUOUS TIME MARKOVIAN ARRIVAL PROCESSES

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Journal of Systems Science and Systems Engineering 2010年第3期19卷 351-366页

作者： Qi-Ming HE Department of Management Sciences,University of Waterloo,Waterloo,Ontario,Canada N2L 3G1 Department of Management Sciences University of Waterloo Waterloo Canada

Markovian arrival processes were introduced by Neuts in 1979 （Neuts 1979） and have been used extensively in the stochastic modeling of queueing, inventory, reliability, risk, and telecommunications systems. In this paper, we introduce a constructive approach to define continuous time Markovian arrival processes. The construction is based on Poisson processes, and is simple and intuitive. Such a construction makes it easy to interpret the parameters of Markovian arrival processes. The construction also makes it possible to establish rigorously basic equations, such as Kolmogorov differential equations, for Markovian arrival processes, using only elementary properties of exponential distributions and Poisson processes. In addition, the approach can be used to construct continuous time Markov chains with a finite number of states

关键词： Markovian arrival process Poisson process matrix-analytic methods

Improvement strategies for Ni-based alcohol steam reforming catalysts

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Journal of Energy Chemistry 2023年第11期86卷 447-479,I0010页

作者： Alex Desgagnés Ommolbanin Alizadeh Sahraei Maria C.Iliuta UniversitéLaval Département de Génie Chimique1065 Avenue de la MédecineQuébecQC G1V 0A6Canada

Steam reforming(SR)of fossil methane is already a well-known,documented and established expertise in the industrial sector as it accounts for the vast majority of global hydrogen *** a sustainable development perspective,hydrogen production by SR of biomass-derived feedstock represents a promising alternative that could help to lower the carbon footprint of the traditional *** this regard,bio-alcohols such as methanol,ethanol or glycerol are among the attractive candidates that could serve as green hydrogen carriers as they decompose at relatively low temperatures in the presence of water compared to methane,allowing for improved H_(2)***,significant challenges remain regarding the activity and stability of nickel-based catalysts,which are most widely used in alcohol SR processes due to their affordability and ability to break C–C,O–H and C–H bonds,yet are prone to rapid deactivation primarily caused by coke deposition and metal particle *** this state-of-the-art review,a portfolio of strategies to improve the performance of Ni-based catalysts used in alcohol SR processes is unfolded with the intent of pinpointing the critical issues in catalyst *** examination of the literature reveals that the efforts tackling these recurring issues can be directed at the active metal,either by tuning Ni dispersion and Ni-support interactions or by targeting synergistic effects in bimetallic systems,while others focus on the support,either by modifying acid-base character,oxygen mobility,or by embedding Ni in specific crystallographic *** review provides a very useful tool to orient future work in catalyst development.

关键词： H2 production Alcohol steam reforming Ni-based catalysts Catalyst development Sintering Coke formation

Dominance network structure across reproductive contexts in the cooperatively breeding cichlid fish Neolamprologus pulcher

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Current Zoology 2015年第1期61卷 45-54页

作者： Cody J. DEY Q.Y. Joanne TAN Constance M. O'CONNOR Adam R. REDDON J. Ryan CALDWELL Sigal BALSHINE Department of Biology McMaster University Hamilton Ontario ON L8S 4K1 Canada Department of Psychology Neuroscience and Behaviour McMaster University Hamilton Ontario L8S 4L8 Canada

While a large number of studies have described animal social networks, we have a poor understanding of how these networks vary with ecological and social conditions. For example, reproductive periods are an important life-history stage that may involve changes in dominance relationships among individuals, yet no study to date has compared social networks of do- minance interactions （i.e. dominance networks） across reproductive contexts. We first analyzed a long-term dataset on captive so- cial groups of the cooperatively breeding cichlid Neolamprologuspulcher, and found that eviction events were significantly more common around reproduction than expected by chance. Next, we compared the structure of dominance networks during early pa- rental care and non-reproductive periods, using one of the first applications of exponential random graph models in behavioral biology. Contrary to our predictions, we found that dominance networks showed few changes between early parental care and non-reproductive periods. We found no evidence that dominance interactions became more skewed towards larger individuals, became more frequent between similar-sized individuals, or became more biased towards a particular sex during parental care. However, we did find that there were relatively more dominance interactions between opposite-sex dyads in the early parental care period, which may be a by-product of increased sexual interactions during this time. This is the first study in behavioral ecology to compare social networks using exponential random graph modeling, and demonstrates a powerful analytical framework for future studies in the field [Current Zoology 61 （1）： 45-54, 2015].

关键词： Social network Aggression Submissive Hierarchy Parental care P* model

An efficient 3D cell-based discrete fracture-matrix flow model for digitally captured fracture networks

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International Journal of Coal Science & Technology 2023年第5期10卷 87-106页

作者： Lei Sun Mei Li Aly Abdelaziz Xuhai Tang Quansheng Liu Giovanni Grasselli Department of Civil and Mineral Engineering University of TorontoTorontoON M5S 1A4Canada School of Civil Engineering Wuhan UniversityWuhan 430072China

Complex hydraulic fracture networks are critical for enhancing permeability in unconventional reservoirs and mining ***,accurately simulating the fluid flow in realistic fracture networks(compared to the statistical fracture net-works)is still challenging due to the fracture complexity and computational *** work proposes a simple yet efficient numerical framework for the flow simulation in fractured porous media obtained by 3D high-resolution images,aiming at both computational accuracy and *** fractured rock with complex fracture geometries is numerically constructed with a cell-based discrete fracture-matrix model(DFM)having implicit fracture *** flow in the complex fractured porous media(including matrix flow,fracture flow,as well as exchange flow)is simulated with a pipe-based cell-centered finite volume *** performance of this model is validated against analytical/numerical *** a lab-scale true triaxial hydraulically fractured shale sample is reconstructed,and the fluid flow in this realistic fracture network is *** suggest that the proposed method achieves a good balance between computational efficiency and *** complex fracture networks control the fluid flow process,and the opened natural fractures behave as primary fuid *** and anisotropic features of fluid flow are well captured with the present model.

关键词： Fractured porous medium-Flow simulation Digital image Cell-based DFM Finite volume method

Transcriptome landscape of the early Brassica napus seed

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Journal of Integrative Plant Biology 2019年第5期61卷 639-650页

作者： Dylan J.Ziegler Deirdre Khan Jenna L.Kalichuk Michael G.Becker Mark F.Belmonte University of Manitoba

Brassica napus L.(canola) is one of the world’s most economically important oilseeds. Despite our growing knowledge of Brassica genetics, we still know little about the genes and gene regulatory networks underlying early seed development. In this work, we use laser microdissection coupled with RNA sequencing to profile gene activity of both the maternal and filial subregions of the globular seed. We find subregions of the chalazal end including the chalazal endosperm, chalazal proliferating tissue, and chalazal seed coat, have unique transcriptome profiles associated with hormone biosynthesis and polysaccharide metabolism. We confirm that the chalazal seed coat is uniquely enriched for sucrose biosynthesis and transport, and that the chalazal endosperm may function as an important regulator of the maternal region through brassinosteroid synthesis. The chalazal proliferating tissue,a poorly understood subregion, was specifically enriched in transcripts associated with megasporogenesis and trehalose biosynthesis, suggesting this ephemeral structure plays an important role in both sporophytic development and carbon nutrient balance, respectively. Finally, compartmentalization of transcription factors and their regulatory circuits has uncovered previously unknown roles for the chalazal pole in early seed development.

关键词： Brassica napus L.(canola) understood subregion

A Review on Surface?Functionalized Cellulosic Nanostructures as Biocompatible Antibacterial Materials

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Nano-Micro Letters 2020年第6期12卷 90-112页

作者： Mandana Tavakolian Seid Mahdi Jafari Theo GMvan de Ven Department of Chemical Engineering McGill UniversityMontrealQC H3A 0C5Canada Pulp and Paper Research Center McGill UniversityMontrealQC H3A 0C7Canada Quebec Centre for Advanced Materials(QCAM/CQMF) MontrealCanada Department of Food Materials and Process Design Engineering Gorgan University of Agricultural Science and Natural ResourcesGorganIran Department of Chemistry McGill UniversityMontrealQC H3A 0B8Canada

As the most abundant biopolymer on the earth,cellulose has recently gained significant attention in the development of antibacterial ***,renewability,strong mechanical properties,tunable aspect ratio,and low density offer tremendous possibilities for the use of cellulose in various *** to the high number of reactive groups(i.e.,hydroxyl groups)on the cellulose surface,it can be readily functionalized with various functional groups,such as aldehydes,carboxylic acids,and amines,leading to diverse *** addition,the ease of surface modification of cellulose expands the range of compounds which can be grafted onto its structure,such as proteins,polymers,metal nanoparticles,and *** are many studies in which cellulose nano-/microfibrils and nanocrystals are used as a support for antibacterial ***,little is known about the relationship between cellulose chemical surface modification and its antibacterial activity or *** this study,we have summarized various techniques for surface modifications of cellulose nanostructures and its derivatives along with their antibacterial and biocompatibility behavior to develop non-leaching and durable antibacterial *** the high effectiveness of surface-modified cellulosic antibacterial materials,more studies on their mechanism of action,the relationship between their properties and their effectivity,and more in vivo studies are required.

关键词： Cellulose Nanocellulose Surface modification Antibacterial activity Biocompatibility

Polarity, Continuity, and Alignment in Plant Vascular Strands

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Journal of Integrative Plant Biology 2013年第9期55卷 824-834页

作者： Megan G.Sawchuk Enrico Scarpella Department of Biological Sciences University of AlbertaEdmonton Alberta Canada T6G 2E9

Plant vascular cells are joined end to end along uninterrupted lines to connect shoot organs with roots;vascular strands are thus polar, continuous, and internally aligned. What controls the formation of vascular strands with these properties？ The “auxin canalization hypothesis”-based on positive feedback between auxin flow through a cell and the cell’s capacity for auxin transport-predicts the selection of continuous files of cells that transport auxin polarly, thus accounting for the polarity and continuity of vascular strands. By contrast, polar, continuous auxin transport-though required-is insufficient to promote internal alignment of vascular strands, implicating additional factors. The auxin canalization hypothesis was derived from the response of mature tissue to auxin application but is consistent with molecular and cellular events in embryo axis formation and shoot organ development. Objections to the hypothesis have been raised based on vascular organizations in callus tissue and shoot organs but seem unsupported by available evidence. Other objections call instead for further research; yet the inductive and orienting influence of auxin on continuous vascular differentiation remains unique.

关键词： Auxin transport callus tissue embryo axis leaf vein vascular network.

The role of sex chromosomes in mammalian germ cell differentiation： can the germ cells carrying X and Y chromosomes differentiate into fertile oocytes？

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Asian Journal of Andrology 2015年第3期17卷 360-366页

作者： Teruko Taketo Department of Surgery Research Institute of MUHC McGill University Montreal Quebec Canada Department of Biology McGill University Montreal Quebec Canada Department of Obstetrics and Gynecology McGill University Montreal Quebec Canada

The sexual differentiation of germ cells into spermatozoa or oocytes is strictly regulated by their gonadal environment, testis or ovary, which is determined by the presence or absence of the Y chromosome, respectively. Hence, in normal mammalian development, male germ cells differentiate in the presence of X and Y chromosomes, and female germ cells do so in the presence of two X chromosomes. However, gonadal sex reversal occurs in humans as well as in other mammalian species, and the resultant XX males and XY females can lead healthy lives, except for a complete or partial loss of fertility. Germ cells carrying an abnormal set of sex chromosomes are efficiently eliminated by multilayered surveillance mechanisms in the testis, and also, though more variably, in the ovary. Studying the molecular basis for sex-specific responses to a set of sex chromosomes during gametogenesis will promote our understanding of meiotic processes contributing to the evolution of sex determining mechanisms. This review discusses the fate of germ cells carrying various sex chromosomal compositions in mouse models, the limitation of which may be overcome by recent successes in the differentiation of functional germ cells from embryonic stem cells under experimental conditions.

关键词： embryonic stem cells germ cells oocyte sex chromosomes sex reversal