Structured Learning of Tree Potentials in CRF for Image Segmentation

We propose a new approach to image segmentation, which exploits the advantages of both conditional random fields (CRFs) and decision trees. In the literature, the potential functions of CRFs are mostly defined as a linear combination of some pre-defined parametric models, and then methods like structured support vector machines (SSVMs) are applied to learn those linear coefficients. We instead formulate the unary and pairwise potentials as nonparametric forests---ensembles of decision trees, and learn the ensemble parameters and the trees in a unified optimization problem within the large-margin framework. In this fashion, we easily achieve nonlinear learning of potential functions on both unary and pairwise terms in CRFs. Moreover, we learn class-wise decision trees for each object that appears in the image. Due to the rich structure and flexibility of decision trees, our approach is powerful in modelling complex data likelihoods and label relationships. The resulting optimization problem is very challenging because it can have exponentially many variables and constraints. We show that this challenging optimization can be efficiently solved by combining a modified column generation and cutting-planes techniques. Experimental results on both binary (Graz-02, Weizmann horse, Oxford flower) and multi-class (MSRC-21, PASCAL VOC 2012) segmentation datasets demonstrate the power of the learned nonlinear nonparametric potentials.Comment: 10 pages. Appearing in IEEE Transactions on Neural Networks and Learning System

Diffuse gamma-ray emission around the Rosette Nebula

The Rosette Nebula is a young stellar cluster and molecular cloud complex, located at the edge of the southern shell of a middle-aged SNR Monoceros Loop (G205.5+0.5). We revisited the GeV gamma-ray emission towards the Rosette Nebula using more than 13 years of Fermi-LAT data. We tested several spatial models and found that compared to the result using the CO gas template only, the inclusion of the HII gas template can significantly improve the likelihood fit. We performed spectral analysis using the new spatial template. With both the gamma-ray observation and CO+HII gas data, we derived the cosmic ray spectrum of different components in the vicinity of the Rosette Nebula. We found the gamma-ray emissions from Rosette Nebula are substantially harder than previously reported, which may imply that Rosette Nebula is another example of a gamma-ray emitting young massive star cluster.Comment: 6 pages, 5 figures, published in MNRA

Theoretical and Experimental Investigation of Near-Field Multi-Focusing Systems

RÉSUMÉ Dans les systèmes de communication modernes, les fonctionnalités d’efficacité énergétique et d'efficacité du spectre sont mises en évidence, attirant de plus en plus l’attention dans la conception des systèmes et des appareils grâce à la demande croissante en débit de données, densité et nombre de terminaux utilisateurs. La technique multi-faisceaux est une caractéristique essentielle de la conception du réseau d'antennes pour systèmes sans fil, qui peut être utilisée pour prendre en charge plusieurs utilisateurs et plusieurs spots avec une grande efficacité. Dans ce travail de recherche, une série de méthodes de développement d’un réseau d’antennes comportant multi-faisceaux de rayonnement électromagnétique dans sa région de champ proche est proposée et présentée. Les travaux de recherche sur la mise au point multiple en champ proche couvrent le développement d’algorithmes, la conception de composants associés, la discussion sur les propriétés de focalisation et leurs méthodes d’amélioration, ainsi que le développement de fonctions d’exploitation et de scénarios d’application. Dans ce travail, un certain nombre d’algorithmes de modélisation du réseau d’antennes prenant en compte le modèle de champ proche, la compensation de phase et la stratégie d’optimisation sont développés afin non seulement d’identifier les emplacements spatiaux de multiples points focaux dans la région de champ proche, mais également de formuler le modèle de faisceau à ou autour de ces points focaux. Dans l'essentiel, les algorithmes proposés visent essentiellement à réaliser une mise en forme de motif dans la région de champ proche en mettant un accent particulier sur les aspects de conception tels que l'ajustement de la localisation spatiale des points focaux, la spécification des distributions d'amplitude et de phase et l'attribution de polarisations.La réalisation pratique est également une partie importante de ce travail qui s'intéresse au développement de réseaux d'antennes multi-focales dans la région du champ proche. Par conséquent, les composants, notamment les réseaux d’antennes et les réseaux d’alimentation correspondants, sont conçus et fabriqués pour démontrer expérimentalement les propriétés et les applications à focalisation multiple de ce travail de recherche, validant ainsi la modélisation et l’analyse théoriques. Les réseaux d'antennes multi-focales sont conçus et des travaux expérimentaux sont effectués dans les bandes de fréquences radio et ondes millimétriques avec de bonnes performances.----------ABSTRACT In modern communications systems, the features of energy efficiency and spectrum efficiency are highlighted, attracting more and more attention in the design of systems and devices thanks to the requirement of ever-increasing data rate, density and quantity of user terminals. Multi-beam technique is an essential enabling design feature of antenna array for wireless systems, which can be used in support of multiple users and multiple spots with high efficiency. In this research work, a series of methods for developing an antenna array that features multiple electromagnetic beaming focuses in its near-field region are proposed and presented. The research work on near-field multi-focus covers the development of algorithms, design of related components, discussion about the focusing properties and their improvement methods, and the expansion of operating functions and application scenarios. In this work, a number of modeling algorithms of antenna array considering near-field model, phase compensation, and optimization strategy are developed in order not only to identify the spatial locations of multiple focal points in the near-field region but also to formulate the beam pattern at or around those focal points. In essentials, the proposed algorithms aim at realizing a pattern shaping in the near-field region with particular emphasis on design aspects such as adjustment of the spatial location of focal points, specification of amplitude and phase distributions, and allocation of polarizations. The practical realization is also an important part of this work with interest in developing multi-focus arrays in the near-field region. Therefore, components including antenna arrays and related feeding networks are designed and fabricated for experimentally demonstrating the multi-focusing properties and applications in this research work, which also validate the theoretical modeling and analysis. The multi-focusing antenna arrays are designed, and experimental work is carried out in both radio-frequency and millimeter-wave bands with good performance. Different from a far-field region of antennas, the electromagnetic field in a near-field region involves reactive and radiative energy components simultaneously

Cross-Channel Integration and Customer Retention in Omnichannel Retailing: The Role of Retailer Image and Alternative Attractiveness

Cross-channel integration (CCI) is increasingly considered as an important driver of customer retention in omnichannel retailing. However, the existing findings about the relationship between CCI and customer retention are contradictory, wherein both positive and non-significant findings exist. This study aims to explore the contingency role of retailer image and alternative attractiveness for the above relationship. Specifically, both two-way and three-way interaction effects of retailer image and alternative attractiveness were tested. Our survey finding confirmed the positive relationship between CCI and customer retention. We also found that the positive relationship was negatively moderated by retailer image, while positively moderated by alternative attractiveness. This study further uncovered that alternative attractiveness can weaken the negative moderating effect of retailer image. Implications and limitations of the study are discussed

A Programmable ROADM System for SDM/WDM Networks

This paper proposed and evaluated a programmable ROADM system for MCF-based SDM/WDM networks. The proposed ROADM system employing both bypass connection and Route-and-Select wavelength switching enables adaptable virtual topology in optical networks by dynamically configuring bypass connection cores. The simulation results confirmed this ROADM system could provide acceptable performance with an around 10–20% reduction in the total cost including the number of ports and WSSs by comparing with a fully flexible SDM/WDM ROADM system, which cannot be implemented due to the required extremely high-port-count WSSs