Une approche hybride pour la localisation et le routage avec contraintes de capacité : application aux réseaux de distribution

Download Une approche hybride pour la localisation et le routage avec contraintes de capacité : application aux réseaux de distribution PDF Online Free

Author :
Publisher :
ISBN 13 :
Total Pages : 130 pages
Book Rating : 4.:/5 (493 download)

DOWNLOAD NOW!


Book Synopsis Une approche hybride pour la localisation et le routage avec contraintes de capacité : application aux réseaux de distribution by : Lyamine Bouhafs

Download or read book Une approche hybride pour la localisation et le routage avec contraintes de capacité : application aux réseaux de distribution written by Lyamine Bouhafs and published by . This book was released on 2006 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Le travail présenté dans cette thèse s’inscrit dans le cadre de l’étude du problème de localisation-routage avec contraintes de capacité (CLRP : Capacitated Location-Routing Problem). Le CLRP consiste à déterminer les positions des dépôts et les routes des véhicules pour desservir des clients, géographiquement distribués, tout en respectant un ensemble de contraintes, telles que la capacité des dépôts et des véhicules, et en minimisant le coût global des routes et des dépôts. L’importance du CLRP se montre dans ses applications tant elles sont nombreuses. La plupart de ces applications se concentrent sur des problèmes dans le domaine de la distribution. Avant d’aborder le problème de localisation-routage (CLRP), nous avons étudié le problème des tournées de véhicules (VRP). Ce dernier constitue une des principales composantes du CLRP. Nous nous sommes particulièrement intéressés à deux variantes du VRP, à savoir le VRP avec contraintes de capacité (CVRP) et le VRP avec contraintes de fenêtres de temps (CVRPTW). Notre contribution dans l’étude du CVRP et CVRPTW consiste à proposer deux approches hybrides fondées sur les colonies de fourmis et des recherches locales. L’un est dédié au CVRP et l’autre au CVRPTW. Nous avons combiné ensuite notre algorithme de colonies de fourmis hybride, proposé pour le CVRP, avec un algorithme de recuit simulé pour résoudre le problème de localisation-routage avec contraintes de capacité (CLRP). Dans cette approche, le CLRP est divisé en deux phases : la localisation des dépôts et les tournées des véhicules. La première phase utilise le recuit simulé pour trouver une bonne localisation des dépôts. La deuxième phase, quand à elle, exploite notre algorithme de colonie de fourmis hybride pour permettre de trouver le bon routage correspondant à cette localisation. La validation des algorithmes proposés dans cette thèse et l’analyse de leurs performances sont réalisées à l’aide d’une plate-forme que nous avons développée. Les résultats expérimentaux et les tests de comparaison effectués ont montré l’efficacité de nos algorithmes.

Modèle d'auto-organisation pour les protocoles de routage dans les réseaux ad hoc de véhicules

Download Modèle d'auto-organisation pour les protocoles de routage dans les réseaux ad hoc de véhicules PDF Online Free

Author :
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (18 download)

DOWNLOAD NOW!


Book Synopsis Modèle d'auto-organisation pour les protocoles de routage dans les réseaux ad hoc de véhicules by : Lucas Rivoirard

Download or read book Modèle d'auto-organisation pour les protocoles de routage dans les réseaux ad hoc de véhicules written by Lucas Rivoirard and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Automatiser la conduite peut réduire le risque d'accidents et fluidifier le trafic en s'appuyant sur des communications entre véhicules et avec une infrastructure dédiée. Maintenir les services lorsque l'infrastructure faillit nécessite un protocole de routage adapté aux communications véhicule-à-véhicule (V2V). Cette thèse pose l'hypothèse de l'absence d'infrastructure et de service global de localisation, chaque véhicule connaissant sa seule position. Un modèle d'organisation des communications V2V, CBL, est proposé pour créer et maintenir une structure supportant les échanges proches, entre véhicules voisins, et lointains à travers le trafic. Il crée une hiérarchie où des groupes dissociés de véhicules voisins (feuilles) sont connectés via un véhicule leader (branche) à une colonne vertébrale (chaîne) formée le long de la route par interconnexion des branches. CBL requière la seule connaissance du voisinage à un saut et peut s'intégrer à tout protocole de routage. Les évaluations sur des scénarios routiers montrent que CBL exploite mieux les contraintes spatiales dues à la route, obtenant une structure plus adaptée à l'optimisation du trafic broadcast comparativement à la technique des multipoints relais dans OLSR, mais aussi face aux protocoles DSR, AODV et GRP, pour un trafic basé sur les préconisations IEEE de taille et fréquence de messages en milieu routier. Des évaluations sur des trafics d'applications coopératives telles que l'égo-localisation et la perception élargie montrent que CBL offre un service de communication à latence et taux de pertes faibles selon un compromis voulu entre fréquence de messages et performances.

Localisation et affectation

Download Localisation et affectation PDF Online Free

Author :
Publisher :
ISBN 13 :
Total Pages : 136 pages
Book Rating : 4.:/5 (8 download)

DOWNLOAD NOW!


Book Synopsis Localisation et affectation by : Jean-Mathieu Segura

Download or read book Localisation et affectation written by Jean-Mathieu Segura and published by . This book was released on 2011 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sur le réseau Internet, les usagers demandent un accès de plus en plus rapide à des contenus de plus en plus volumineux. Notamment, le service de Vidéo à la Demande (VoD) voit la taille des données échangées augmenter fortement avec l'arrivée de la haute définition et des vidéos en 3D. Les réseaux physiques des fournisseurs d’accès à Internet doivent ainsi sans cesse s'adapter à l'augmentation des demandes de téléchargements. La solution qui a pendant longtemps consisté à augmenter les débits en posant de nouveaux câbles connaît aujourd'hui ses limites. Une nouvelle approche efficace consiste à déployer des réseaux de distribution de contenus (CDN) qui peuvent être décrits comme un ensemble d'équipements, appelés caches, où les données sont dupliquées et stockées au plus proche des utilisateurs. Lors de la conception d'un CDN, plusieurs questions se posent quant au nombre, à la dimension et la localisation des caches, de manière à servir au mieux l'usager. En nous plaçant du point de vue d'un fournisseur d'accès à Internet, nous montrons que la conception d'un service de VoD s'inscrit dans la problématique de localisation et d'affectation de ressources en recherche opérationnelle. En particulier, nous nous intéressons à deux problèmes mêlant localisation et affectation: le problème du 2-p-Médian et le problème de Location-Dispatching. Nous montrons que, dans le cas où le réseau considéré est un arbre, le premier problème est polynomial. Nous formulons le second problème comme un programme linéaire en nombre entiers et nous proposons une étude polyédrale du polytope associé, ainsi que de nouvelles inégalités valides. A partir de cette étude, nous déduisons un algorithme de coupes et branchements pour résoudre le problème. Nous proposons également de nouvelles formulations entières de problèmes de localisation et d'affectation et nous comparons expérimentalement leurs efficacités. En conclusion nous tentons de répondre aux questions posées par la conception de CDN à partir des différentes approches étudiées dans ce document.

Optimisation des réseaux, routage et dimensionnement

Download Optimisation des réseaux, routage et dimensionnement PDF Online Free

Author :
Publisher :
ISBN 13 :
Total Pages : 212 pages
Book Rating : 4.:/5 (492 download)

DOWNLOAD NOW!


Book Synopsis Optimisation des réseaux, routage et dimensionnement by : Matthieu Rombaut

Download or read book Optimisation des réseaux, routage et dimensionnement written by Matthieu Rombaut and published by . This book was released on 2003 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cette étude propose une approche industrielle du problème de routage de données sur des réseaux aux capacités contraintes. Un certain nombre d'études mathématiques ont été réalisées pour définir des plans de routage, par résolution de problèmes linéaires ou en nombres entiers. On constate alors que des approximations doivent être faites pour appliquer les méthodes mathématiques aux problèmes réels. D'autre part, les routages proposés sont pour la plupart simples (mono-routage). L'utilisation des algorithmes de plus courts chemins contraint souvent les flux sur une route unique, ils ne permettent généralement pas l'utilisation de liens annexes dont la charge est faible. Nous proposons des méthodes de routage de flux sur des liens de capacités finies, le routage Mille Feuilles, et des variantes de ce routage permettant de limiter le nombre de routes. Ces méthodes sont applicables au niveau de la conception ou de l'exploitation des réseaux. Ces méthodes d'optimisation par projections successives permettent de mettre en œuvre différentes fonctions coût, elles permettent d'approcher des solutions optimales obtenues à l'aide de méthode de gradient projeté. Associée à une métrique non cumulative sur la route, elles permettent de calculer des plans de routage multi-routes, de diminuer le taux charge du lien le plus chargé sur le réseau 'augmenter la résistance du réseau aux variations de trafic et à l'apparition d'une panne simple.D'autre part, nous évaluons les performances de plusieurs méthodes de re-routage en cas de panne simple d'un lien, en fonction des méthodes de routage appliquées. L'impact des re-routages sur le réseau est évalué, la variation de la charge des liens et la variation de la longueur moyenne des routes sont bornées. Les méthodes de routages ne sont pas équivalentes et elles s'adaptent différemment aux politiques de re-routage proposées. En outre, une nouvelle politique de re-routage applicable aux plans de routage multi-routes est introduite.

Multimedia over IP and Wireless Networks

Download Multimedia over IP and Wireless Networks PDF Online Free

Author :
Publisher : Elsevier
ISBN 13 : 0080474969
Total Pages : 713 pages
Book Rating : 4.0/5 (84 download)

DOWNLOAD NOW!


Book Synopsis Multimedia over IP and Wireless Networks by : Mihaela van der Schaar

Download or read book Multimedia over IP and Wireless Networks written by Mihaela van der Schaar and published by Elsevier. This book was released on 2011-07-28 with total page 713 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multimedia over IP and Wireless Networks is an indispensable guide for professionals or researchers working in areas such as networking, communications, data compression, multimedia processing, streaming architectures, and computer graphics. Beginning with a concise overview of the fundamental principles and challenges of multimedia communication and networking, this book then branches off organically to tackle compression and networking next before moving on to systems, wireless multimedia and more advanced topics. The Compression section advises on the best means and methodology to ensure multimedia signal (images, text, audio and data) integrity for transmissions on wireless and wired systems. The Networking section addresses channel protection and performance. In the Systems section, the focus is on streaming media on demand, live broadcast and video and voice's role in real-time communication. Wireless multimedia transmission and Quality of Service issues are discussed in the Wireless Multimedia section. An Advanced Topics section concludes the book with an assortment of topics including Peer-to-Peer multimedia communication and multipath networks. Up-to-date coverage of existing standards for multimedia networking Synergistic tutorial approach reinforces knowledge gained in previous chapters Balanced treatment of audio and video with coverage of end-to-end systems

The Production and Distribution of Knowledge in the United States

Download The Production and Distribution of Knowledge in the United States PDF Online Free

Author :
Publisher : Princeton University Press
ISBN 13 : 9780691003566
Total Pages : 440 pages
Book Rating : 4.0/5 (35 download)

DOWNLOAD NOW!


Book Synopsis The Production and Distribution of Knowledge in the United States by : Fritz Machlup

Download or read book The Production and Distribution of Knowledge in the United States written by Fritz Machlup and published by Princeton University Press. This book was released on 1962 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Production and Distribution of Knowledge in the United States marked the beginning of the study of our postindustrial information society. Austrian-born economist Fritz Machlup had focused his research on the patent system, but he came to realize that patents were simply one part of a much bigger "knowledge economy." He then expanded the scope of his work to evaluate everything from stationery and typewriters to advertising to presidential addresses--anything that involved the activity of telling anyone anything. The Production and Distribution of Knowledge in the United States then revealed the new and startling shape of the U.S. economy. Machlup's cool appraisal of the data showed that the knowledge industry accounted for nearly 29 percent of the U.S. gross national product, and that 43 percent of the civilian labor force consisted of knowledge transmitters or full-time knowledge receivers. Indeed, the proportion of the labor force involved in the knowledge economy increased from 11 to 32 percent between 1900 and 1959--a monumental shift. Beyond documenting this revolution, Machlup founded the wholly new field of information economics. The transformation to a knowledge economy has resonated throughout the rest of the century, especially with the rise of the Internet. As two recent observers noted, "Information goods--from movies and music to software code and stock quotes--have supplanted industrial goods as the key drivers of world markets." Continued study of this change and its effects is testament to Fritz Machlup's pioneering work.

Big Data Analytics and Knowledge Discovery

Download Big Data Analytics and Knowledge Discovery PDF Online Free

Author :
Publisher : Springer
ISBN 13 : 9783030590642
Total Pages : 410 pages
Book Rating : 4.5/5 (96 download)

DOWNLOAD NOW!


Book Synopsis Big Data Analytics and Knowledge Discovery by : Min Song

Download or read book Big Data Analytics and Knowledge Discovery written by Min Song and published by Springer. This book was released on 2020-09-11 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: The volume LNCS 12393 constitutes the papers of the 22nd International Conference Big Data Analytics and Knowledge Discovery which will be held online in September 2020. The 15 full papers presented together with 14 short papers plus 1 position paper in this volume were carefully reviewed and selected from a total of 77 submissions. This volume offers a wide range to following subjects on theoretical and practical aspects of big data analytics and knowledge discovery as a new generation of big data repository, data pre-processing, data mining, text mining, sequences, graph mining, and parallel processing.

Building Wireless Community Networks

Download Building Wireless Community Networks PDF Online Free

Author :
Publisher : "O'Reilly Media, Inc."
ISBN 13 : 9780596005023
Total Pages : 190 pages
Book Rating : 4.0/5 (5 download)

DOWNLOAD NOW!


Book Synopsis Building Wireless Community Networks by : Rob Flickenger

Download or read book Building Wireless Community Networks written by Rob Flickenger and published by "O'Reilly Media, Inc.". This book was released on 2003 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building Wireless Community Networks is about getting people online using wireless network technology. The 802.11b standard (also known as WiFi) makes it possible to network towns, schools, neighborhoods, small business, and almost any kind of organization. All that's required is a willingness to cooperate and share resources. The first edition of this book helped thousands of people engage in community networking activities. At the time, it was impossible to predict how quickly and thoroughly WiFi would penetrate the marketplace. Today, with WiFi-enabled computers almost as common as Ethernet, it makes even more sense to take the next step and network your community using nothing but freely available radio spectrum. This book has showed many people how to make their network available, even from the park bench, how to extend high-speed Internet access into the many areas not served by DSL and cable providers, and how to build working communities and a shared though intangible network. All that's required to create an access point for high-speed Internet connection is a gateway or base station. Once that is set up, any computer with a wireless card can log onto the network and share its resources. Rob Flickenger built such a network in northern California, and continues to participate in network-building efforts. His nuts-and-bolts guide covers: Selecting the appropriate equipment Finding antenna sites, and building and installing antennas Protecting your network from inappropriate access New network monitoring tools and techniques (new) Regulations affecting wireless deployment (new) IP network administration, including DNS and IP Tunneling (new) His expertise, as well as his sense of humor and enthusiasm for the topic, makes Building Wireless Community Networks a very useful and readable book for anyone interested in wireless connectivity.

Information Rules

Download Information Rules PDF Online Free

Author :
Publisher : Harvard Business Press
ISBN 13 : 9780875848631
Total Pages : 374 pages
Book Rating : 4.8/5 (486 download)

DOWNLOAD NOW!


Book Synopsis Information Rules by : Carl Shapiro

Download or read book Information Rules written by Carl Shapiro and published by Harvard Business Press. This book was released on 1999 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: As one of the first books to distill the economics of information and networks into practical business strategies, this is a guide to the winning moves that can help business leaders--from writers, lawyers and finance professional to executives in the entertainment, publishing and hardware and software industries-- navigate successfully through the information economy.

Querying Graphs

Download Querying Graphs PDF Online Free

Author :
Publisher : Springer Nature
ISBN 13 : 3031018648
Total Pages : 166 pages
Book Rating : 4.0/5 (31 download)

DOWNLOAD NOW!


Book Synopsis Querying Graphs by : Angela Bonifati

Download or read book Querying Graphs written by Angela Bonifati and published by Springer Nature. This book was released on 2022-06-01 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Graph data modeling and querying arises in many practical application domains such as social and biological networks where the primary focus is on concepts and their relationships and the rich patterns in these complex webs of interconnectivity. In this book, we present a concise unified view on the basic challenges which arise over the complete life cycle of formulating and processing queries on graph databases. To that purpose, we present all major concepts relevant to this life cycle, formulated in terms of a common and unifying ground: the property graph data model—the pre-dominant data model adopted by modern graph database systems. We aim especially to give a coherent and in-depth perspective on current graph querying and an outlook for future developments. Our presentation is self-contained, covering the relevant topics from: graph data models, graph query languages and graph query specification, graph constraints, and graph query processing. We conclude by indicating major open research challenges towards the next generation of graph data management systems.

Wireless Hacks

Download Wireless Hacks PDF Online Free

Author :
Publisher : "O'Reilly Media, Inc."
ISBN 13 : 9780596005597
Total Pages : 310 pages
Book Rating : 4.0/5 (55 download)

DOWNLOAD NOW!


Book Synopsis Wireless Hacks by : Rob Flickenger

Download or read book Wireless Hacks written by Rob Flickenger and published by "O'Reilly Media, Inc.". This book was released on 2003 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continuing with the successful Hack Series, this title provides real-world working examples of how to make useful things happen with wireless equipment.

Ultra Wide Band Antennas

Download Ultra Wide Band Antennas PDF Online Free

Author :
Publisher : John Wiley & Sons
ISBN 13 : 1118586573
Total Pages : 217 pages
Book Rating : 4.1/5 (185 download)

DOWNLOAD NOW!


Book Synopsis Ultra Wide Band Antennas by : Xavier Begaud

Download or read book Ultra Wide Band Antennas written by Xavier Begaud and published by John Wiley & Sons. This book was released on 2013-03-04 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recognized studies.

Metaheuristics

Download Metaheuristics PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 9781402076534
Total Pages : 744 pages
Book Rating : 4.0/5 (765 download)

DOWNLOAD NOW!


Book Synopsis Metaheuristics by : Mauricio G.C. Resende

Download or read book Metaheuristics written by Mauricio G.C. Resende and published by Springer Science & Business Media. This book was released on 2003-11-30 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt: Combinatorial optimization is the process of finding the best, or optimal, so lution for problems with a discrete set of feasible solutions. Applications arise in numerous settings involving operations management and logistics, such as routing, scheduling, packing, inventory and production management, lo cation, logic, and assignment of resources. The economic impact of combi natorial optimization is profound, affecting sectors as diverse as transporta tion (airlines, trucking, rail, and shipping), forestry, manufacturing, logistics, aerospace, energy (electrical power, petroleum, and natural gas), telecommu nications, biotechnology, financial services, and agriculture. While much progress has been made in finding exact (provably optimal) so lutions to some combinatorial optimization problems, using techniques such as dynamic programming, cutting planes, and branch and cut methods, many hard combinatorial problems are still not solved exactly and require good heuristic methods. Moreover, reaching "optimal solutions" is in many cases meaningless, as in practice we are often dealing with models that are rough simplifications of reality. The aim of heuristic methods for combinatorial op timization is to quickly produce good-quality solutions, without necessarily providing any guarantee of solution quality. Metaheuristics are high level procedures that coordinate simple heuristics, such as local search, to find solu tions that are of better quality than those found by the simple heuristics alone: Modem metaheuristics include simulated annealing, genetic algorithms, tabu search, GRASP, scatter search, ant colony optimization, variable neighborhood search, and their hybrids.

Agent-based Spatial Simulation with NetLogo, Volume 2

Download Agent-based Spatial Simulation with NetLogo, Volume 2 PDF Online Free

Author :
Publisher : Elsevier
ISBN 13 : 0081010648
Total Pages : 234 pages
Book Rating : 4.0/5 (81 download)

DOWNLOAD NOW!


Book Synopsis Agent-based Spatial Simulation with NetLogo, Volume 2 by : Arnaud Banos

Download or read book Agent-based Spatial Simulation with NetLogo, Volume 2 written by Arnaud Banos and published by Elsevier. This book was released on 2016-11-26 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: Whereas Volume 1 introduced the NetLogo platform as a means of prototyping simple models, this second volume focuses on the advanced use of NetLogo to connect both data and theories, making it ideal for the majority of scientific communities. The authors focus on agent-based modeling of spatialized phenomena with a methodological and practical orientation, demonstrating how advanced agent-based spatial simulation methods and technics can be implemented. This book provides theoretical and conceptual backgrounds, as well as algorithmic and technical insights, including code and applets, so that readers can test and re-use most of its content. - Illustrates advanced concepts and methods in agent-based spatial simulation - Features practical examples developed, and commented on, in a unique platform - Provides theoretical and conceptual backgrounds, as well as algorithmic and technical insights, including code and applets, so that readers can test and re-use most of its content

Economics with Heterogeneous Interacting Agents

Download Economics with Heterogeneous Interacting Agents PDF Online Free

Author :
Publisher : Springer Science & Business Media
ISBN 13 : 3642564720
Total Pages : 340 pages
Book Rating : 4.6/5 (425 download)

DOWNLOAD NOW!


Book Synopsis Economics with Heterogeneous Interacting Agents by : Alan Kirman

Download or read book Economics with Heterogeneous Interacting Agents written by Alan Kirman and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book analyses situations in which individual agents, who might be different from each other, interact and produce behaviour on the aggregate level which does not correspond to that of the average actor. This leads to aggregate outcomes which would be impossible to explain in a more standard approach. Aggregation generates structure and, as a result, interaction and heterogeneity can be handled and we no longer have to rely on the over-simplified reduction of the behaviour of the economy to that of a "rational" individual.

MIMO

Download MIMO PDF Online Free

Author :
Publisher : Academic Press
ISBN 13 : 0123821959
Total Pages : 385 pages
Book Rating : 4.1/5 (238 download)

DOWNLOAD NOW!


Book Synopsis MIMO by : Alain Sibille

Download or read book MIMO written by Alain Sibille and published by Academic Press. This book was released on 2010-12-03 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Foreword from Arogyaswami Paulraj, Professor (Emeritus), Stanford University (USA) - The first book to show how MIMO principles can be implemented in today's mobile broadband networks and components - Explains and solves some of the practical difficulties that arise in designing and implementing MIMO systems - Both theory and implementation sections are written in the context of the most recent standards: IEEE 802.11n (WiFi); IEEE 802.16 (WIMAX); 4G networks (3GPP/3GPP2, LTE)

The Processes of Technological Innovation

Download The Processes of Technological Innovation PDF Online Free

Author :
Publisher : Free Press
ISBN 13 :
Total Pages : 328 pages
Book Rating : 4.3/5 (91 download)

DOWNLOAD NOW!


Book Synopsis The Processes of Technological Innovation by : Louis G. Tornatzky

Download or read book The Processes of Technological Innovation written by Louis G. Tornatzky and published by Free Press. This book was released on 1990 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: