Catálogo de publicaciones - revistas

<jats:p>Over the past two decades, a large amount of research effort has been devoted to developing algorithms that generate recommendations. The resulting research progress has established the importance of the user-item (U-I) matrix, which encodes the individual preferences of users for items in a collection, for recommender systems. The U-I matrix provides the basis for collaborative filtering (CF) techniques, the dominant framework for recommender systems. Currently, new recommendation scenarios are emerging that offer promising new information that goes beyond the U-I matrix. This information can be divided into two categories related to its source: rich side information concerning users and items, and interaction information associated with the interplay of users and items. In this survey, we summarize and analyze recommendation scenarios involving information sources and the CF algorithms that have been recently developed to address them. We provide a comprehensive introduction to a large body of research, more than 200 key references, with the aim of supporting the further development of recommender systems exploiting information beyond the U-I matrix. On the basis of this material, we identify and discuss what we see as the central challenges lying ahead for recommender system technology, both in terms of extensions of existing techniques as well as of the integration of techniques and technologies drawn from other research areas.</jats:p>

<jats:p> A brief review of the Internet history reveals the fact that the Internet evolved after the formation of primarily independent networks. Similarly, interconnected clouds, also called <jats:italic>Inter-cloud</jats:italic> , can be viewed as a natural evolution of cloud computing. Recent studies show the benefits in utilizing multiple clouds and present attempts for the realization of an Inter-cloud or federated cloud environment. However, cloud vendors have not taken into account cloud interoperability issues, and each cloud comes with its own solution and interfaces for services. This survey initially discusses all the relevant aspects motivating cloud interoperability. Furthermore, it categorizes and identifies possible cloud interoperability scenarios and architectures. The spectrum of challenges and obstacles that the Inter-cloud realization is faced with are covered, a taxonomy of them is provided, and fitting enablers that tackle each challenge are identified. All these aspects require a comprehensive review of the state of the art, including ongoing projects and studies in the area. We conclude by discussing future directions and trends toward the holistic approach in this regard. </jats:p>

<jats:p>Software-defined networking (SDN) has generated tremendous interest from both academia and industry. SDN aims at simplifying network management while enabling researchers to experiment with network protocols on deployed networks. This article is a distillation of the state of the art of SDN in the context of wireless networks. We present an overview of the major design trends and highlight key differences between them.</jats:p>

<jats:p>The recent development of telecommunication networks is producing an unprecedented wealth of information and, as a consequence, an increasing interest in analyzing such data both from telecoms and from other stakeholders' points of view. In particular, mobile phone datasets offer access to insights into urban dynamics and human activities at an unprecedented scale and level of detail, representing a huge opportunity for research and real-world applications. This article surveys the new ideas and techniques related to the use of telecommunication data for urban sensing. We outline the data that can be collected from telecommunication networks as well as their strengths and weaknesses with a particular focus on urban sensing. We survey existing filtering and processing techniques to extract insights from this data and summarize them to provide recommendations on which datasets and techniques to use for specific urban sensing applications. Finally, we discuss a number of challenges and open research areas currently being faced in this field. We strongly believe the material and recommendations presented here will become increasingly important as mobile phone network datasets are becoming more accessible to the research community.</jats:p>

<jats:p>Modeling biological systems to understand their mechanistic behavior is an important activity in molecular systems biology. Mathematical modeling typically requires deep mathematical or computing knowledge, and this limits the spread of modeling tools among biologists. Graphical modeling languages have been introduced to minimize this limit. Here, we survey the main graphical formalisms (supported by software tools) available to model biological systems with a primary focus on their usability, within the framework of modeling reaction pathways with two-dimensional (2D) (possibly nested) compartments. Considering the main characteristics of the surveyed formalisms, we synthesise a new proposal (Style) and report the results of an online survey conducted among biologists to assess usability of available graphical formalisms. We consider this proposal a guideline developed from what we learned in the survey, which can inform development of graphical formalisms to model reaction pathways in 2D space.</jats:p>

<jats:p>Recent years have witnessed phenomenal growth in the computational capabilities and applications of GPUs. However, this trend has also led to a dramatic increase in their power consumption. This article surveys research works on analyzing and improving energy efficiency of GPUs. It also provides a classification of these techniques on the basis of their main research idea. Further, it attempts to synthesize research works that compare the energy efficiency of GPUs with other computing systems (e.g., FPGAs and CPUs). The aim of this survey is to provide researchers with knowledge of the state of the art in GPU power management and motivate them to architect highly energy-efficient GPUs of tomorrow.</jats:p>

<jats:p>The Vehicle Routing Problem (VRP) is a well-known research line in the optimization research community. Its different basic variants have been widely explored in the literature. Even though it has been studied for years, the research around it is still very active. The new tendency is mainly focused on applying this study case to real-life problems. Due to this trend, the Rich VRP arises: combining multiple constraints for tackling realistic problems. Nowadays, some studies have considered specific combinations of real-life constraints to define the emerging Rich VRP scopes. This work surveys the state of the art in the field, summarizing problem combinations, constraints defined, and approaches found.</jats:p>

<jats:p>Open production communities (OPCs) provide technical features and social norms for a vast but dispersed and diverse crowd to collectively accumulate content. In OPCs, certain mechanisms, policies, and technologies are provided for voluntary users to participate in community-related activities including content generation, evaluation, qualification, and distribution and in some cases even community governance. Due to the known complexities and dynamism of online communities, designing a successful community is deemed more an art than a science. Numerous studies have investigated different aspects of certain types of OPCs. Most of these studies, however, fall short of delivering a general view or prescription due to their narrow focus on a certain type of OPCs. In contribution to theories on technology-mediated social participation (TMSP), this study synthesizes the streams of research in the particular area of OPCs and delivers a theoretical framework as a baseline for adapting findings from one specific type of community on another. This framework consists of four primary dimensions, namely, platform features, content, user, and community. The corresponding attributes of these dimensions and the existing interdependencies are discussed in detail. Furthermore, a decision diagram for selecting features and a design guideline for “decontextualizing” findings are introduced as possible applications of the framework. The framework also provides a new and reliable foundation on which future research can extend its findings and prescriptions in a systematic way.</jats:p>

<jats:p>Low-rank modeling generally refers to a class of methods that solves problems by representing variables of interest as low-rank matrices. It has achieved great success in various fields including computer vision, data mining, signal processing, and bioinformatics. Recently, much progress has been made in theories, algorithms, and applications of low-rank modeling, such as exact low-rank matrix recovery via convex programming and matrix completion applied to collaborative filtering. These advances have brought more and more attention to this topic. In this article, we review the recent advances of low-rank modeling, the state-of-the-art algorithms, and the related applications in image analysis. We first give an overview of the concept of low-rank modeling and the challenging problems in this area. Then, we summarize the models and algorithms for low-rank matrix recovery and illustrate their advantages and limitations with numerical experiments. Next, we introduce a few applications of low-rank modeling in the context of image analysis. Finally, we conclude this article with some discussions.</jats:p>

<jats:p>Key management is required for basic security services of confidentiality, integrity, and data source authentication. Wireless sensor networks (WSNs) are a challenging environment to provide such services due to the resource constraints and the increased likelihood of nodes to be captured. Various key management techniques were proposed that trade off resilience to node capture and overhead in terms of communication and memory.</jats:p> <jats:p>We identify the main factors influencing the design space of key management protocols for sensor networks and describe representative protocols that trade off the number of links established, communication overhead, and resilience to node capture. These trade-offs are due to using direct, pathbased, or multipath-based communication to establish secure links. We propose a new multipath protocol relying on an encoding scheme tailored for WSNs and analyze the effects of key pre-distribution on multipath key establishment.</jats:p> <jats:p>We provide extensive simulations to understand the trade-offs between resilience to node compromise and communication overhead under numerous network scenarios. This comparison highlights the trade-offs between these vastly different key management schemes. For the newer class of key management schemes—multipath based—we quantify experimentally the additional communication overhead required for extra paths and the improvement in resilience from using these paths.</jats:p>