...ELECTRIC JACQUARDS: THE FIRST HUNDRED YEARS K. Hepworth Department of Textile Industries University of Leeds Leeds LS2 9JT 1 Introduction. The recent widespread use of computers and colour monitors in the representation and development of weave structures and in the simulation of colour-and-weave effects has encouraged loom manufacturers to complete the chain of automation of fabric production by developing computer-controllable shedding mechanisms. These mostly take the form of electromagnetically actuated dobbies, although some jacquards are also available. Although activity in this field has accelerated during the past twenty years or so there is a history of over a hundred and thirty years of development of electric jacquards for weaving. It is apparent that almost as soon as the jacquard was established there was a desire to reduce the bulk and weight of the punched cards used for programming it and the expense of punching, linking and storing them. By 1833 a two-stage mechanism had been described that enabled a continuous band of paper to be substituted for the cards but punching was still needed. By the middle of the century an electrically conductive program, on which areas could be obscured by insulating paint, was being proposed in conjunction with electromagnetic methods of hook selection and at least one demonstrably operable machine resulted. By the end of the century photographically prepared programs of a similar kind were being proposed albeit with a somewhat...
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...Communication Networks Sharam Hekmat PragSoft Corporation www.pragsoft.com Contents Contents Preface 1. Introduction 1.1. Network Components 1.2. Network Types 1.3. The OSI Model 1.3.1. The Physical Layer 1.3.2. The Data Link Layer 1.3.3. The Network Layer 1.3.4. The Transport Layer 1.3.5. The Session Layer 1.3.6. The Presentation Layer 1.3.7. The Application Layer 1.4. Protocol Notations 1.4.1. Service Primitives 1.4.2. Sequence Diagrams 1.4.3. State Transition Diagrams 1.5. Standards 1.6. Further Reading 1.7. Summary 1.8. Exercises 2. The Physical Layer 2.1. Equipment 2.1.1. Equipment Types 2.1.2. Connection Types 2.2. Transmission 2.2.1. Signal Types 2.2.2. Modulation 2.2.3. Digitization 2.2.4. Synchronization 2.2.5. Transmission Media 2.3. Multiplexing 2.3.1. Space Division Multiplexing (SDM) vi Communication Networks 6 10 1 2 2 4 7 7 8 9 9 10 10 11 11 12 12 13 14 15 16 18 19 19 19 20 20 21 22 23 24 27 28 Copyright © 2005 PragSoft 2.3.2. Frequency Division Multiplexing (FDM) 2.3.3. Time Division Multiplexing (TDM) 2.3.4. Concentration 2.4. Physical Layer Standards 2.4.1. RS-232 2.4.2. CCITT X.21 2.5. Further Reading 2.6. Summary 2.7. Exercises 3. The Data Link Layer 3.1 Link Protocol Types 3.1.1. Synchronous Protocols 3.1.2. Asynchronous Protocols 3.1.3. Master-Slave Protocols 3.1.4. Peer-to-Peer Protocols 3.2. Link Protocol Functions 3.2.1. Acknowledgments 3.2.2. Timers 3.2.3. Error Checking 3.2.4. Retransmission 3.2.5. Flow Control 3.3. Sliding Window...
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