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Computers and Digital Techniques, IEE Proceedings -

Issue 2 • Date Mar 1994

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Displaying Results 1 - 13 of 13
  • Ultrafast pipelined arithmetic using quantum electronic devices

    Page(s): 104 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    Negative differential resistance characteristics of several new quantum electronic devices have been used to design high-speed logic gates with the latching property. These latching gates form the basis of the ultrafast pipelined adder circuit described in this paper. The latching or memory feature of these circuits, which was previously considered to be a nuisance in the design of combinational circuits, is exploited to overcome the pipeline overheads of area and time. Simulation studies show that application of pipelining techniques can provide an effective throughput of one 32-bit addition every 1.6 ns using minimal hardware View full abstract»

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  • Optimised synthesis of delay-insensitive circuits using time-sharing

    Page(s): 111 - 118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (652 KB)  

    A syntax-directed translation procedure for the synthesis of truly delay-insensitive circuits from graph theoretic specifications is presented. In the synthesised circuit, for a given specification, different synchronisation structures (e.g. joins) in the specification are enforced by distinct circuit elements (e.g. C-elements). An attempt is made to enforce different synchronisation structures in a specification with the same circuit element so that the number of circuit elements in the synthesised circuit could be reduced. The circuit element is said to be `time-shared' between the synchronisation structures in the specification. Theorems on when different synchronisation structures in a specification can time-share a circuit element are presented. An optimisation procedure based on such time-sharing is described. The optimisation procedure is illustrated with examples View full abstract»

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  • Genetic beam search for gate matrix layout

    Page(s): 123 - 128
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    The paper presents a novel implementation of the genetic algorithm in combination with beam search for gate matrix layout. This is a permutation problem, for which the traditional genetic crossover operator results in repetition of gates, and therefore the GA is not applicable without modification. However, the GA is a very efficient stochastic optimisation technique, and is easily parallelisable. To adapt it to the gate matrix layout problem, the principles of beam search have been used. The gates are ranked according to their connectivity with each other, and the ranks of the gates to be placed next to each other are picked by the GA. A beam value is used to restrict the ranks of the gates placed next to each other to a low value. This reduces the search space to be explored, and thus results in a more efficient search. The algorithm produces better results compared to a graph-theoretic approach on published netlists View full abstract»

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  • Parallel decoding of the [23, 12, 7] binary Golay code

    Page(s): 119 - 122
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    We deal with the decoding of the [23, 12, 7] binary Golay code. S.W. Wei and C.H. Wei (1990) suggested a step-by-step decoding algorithm. We present an improvement in the comparison circuit of their algorithm and construct a very high-speed parallel decoder View full abstract»

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  • Relationship between user models in HCI and AI

    Page(s): 99 - 103
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Considers the relationship between the two independent lines of research into user modelling activities in human-computer interaction (HCI) and artificial intelligence (AI). The paper begins by considering the potential use of AI user models in HCI. The user modelling research conducted in HCI and AI respectively is then discussed along with the goals of HCI and AI. Considerable differences underlie the apparent similarities of the respective research in user modelling in HCI and AI and we discuss these distinctions from the viewpoint of the roles, nature, goals and development of user models. It is argued that HCI can contribute techniques concerned with gathering and modelling user requirements to AI, and in addition a view of how the results of employing AI user models might be evaluated. On the other hand, sophisticated knowledge representation techniques can be provided by AI to the use of embedded user models in HCI View full abstract»

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  • Design of residue generators and multioperand adders modulo 3 built of multioutput threshold circuits

    Page(s): 129 - 134
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    A generator modulo 3 (mod 3) is a circuit that generates a residue mod 3 from a binary vector. It is used to build the encoding and checking circuitry for arithmetic codes with the check base A=3, i.e. residue codes mod 3 and the 3N code, and some residue number system hardware. In this paper we propose a new approach to designing high-speed and cost-effective generators mod 3 whose special case are multioperand adders mod 3. For any number of inputs n, a family of generators mod 3 can be built of multioutput threshold circuits followed by some merging network. The new generators are shown to be the least complex and the fastest circuits currently known. They also enjoy a modular and highly regular structure composed of gates with low fan-in which makes them attractive for VLSI implementation View full abstract»

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  • Representation and use of task knowledge in a user interface design environment

    Page(s): 79 - 84
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    A rapid prototyping approach to user interface design may be enhanced by integration with a theory of the users' tasks. The paper discusses various approaches to modelling user tasks including task knowledge structures (TKS) which provides a theory of the structure of task knowledge, together with a method for the identification and modelling of this knowledge. Formal specification languages may be used to provide a precise description of TKS models and to assist in their validation; the use of LOTOS for this purpose is demonstrated. The integration of task knowledge with a rapid prototyping approach to design is introduced in the context of work on the Adept project. A software demonstrator for Adept provides a graphical environment where a task model is used to derive an interface model, which may be further refined to produce an executable prototype View full abstract»

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  • Analysis and simulation of multiple-ring token networks

    Page(s): 135 - 141
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The paper presents an extended analysis for multiple token ring networks given by Yang et al (1986). The authors generalised the results in two ways: (a) for any load condition, i.e. for very lightly loaded networks to heavily loaded networks; (b) for any packet size, i.e. very small packet size (only a few bytes long) to very large packet size (several K-bytes long). The authors also obtain the optimum number of rings for various configurations to achieve minimum mean transfer time. The results show that the best ratio of number of rings to number of stations is 0.2 to 0.5, but the exact number varies nonlinearly with respect to load View full abstract»

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  • Electronic mail: case study in task-oriented restructuring of application domain

    Page(s): 65 - 71
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    Most electronic mail (e-mail) software consists of a mail delivery system and a user interface. One problem with current e-mail systems is that the user interface represents only a very thin layer on top of the delivery system. Studies have shown a wide level of diversity in the ways people work with e-mail systems and a wide range of tasks for which it is used. This work shows the need for powerful tools to facilitate the restructuring of the e-mail domain to support users. In particular, the tools must be suitable for use by a variety of users who are not computer specialists. Perspectives on electronic mail are briefly reviewed and an empirical study described which provides a basis for derivation of the higher-level concepts invoked and tasks undertaken by a range of users. The notion of a conceptual workspace is introduced as a framework for user-driven restructuring and processing of components of an application domain. An instance of the framework is described in the form of a tool for dynamic restructuring of canonical e-mail components to form higher-level task-oriented constructs identified in the empirical study. The power and generality of this approach is illustrated by the ability of the tool to support other subsequently identified electronic communication tasks, in particular, the design, administration and analysis of online questionnaires for a large-scale usability evaluation study View full abstract»

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  • Flexibility in interface development

    Page(s): 93 - 98
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    Two systems that employ intelligent user interfaces as front ends have been developed using Focus technology. The two systems, while addressing essentially the same user tasks, were built for different user populations, they had different development contexts, and produced as a result different systems. The discussion highlights the problems posed by these diverse development and user contexts and shows how the Focus project's architecture and toolkit has met these challenges. The paper looks at the organisational context of the two developments and then discusses the two systems in the context of the system architectures and interfaces View full abstract»

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  • Integrated architectures for database interface development

    Page(s): 73 - 78
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    Presents a number of approaches to the development of database interfaces, with a particular emphasis upon the development of such interfaces within the confines of the database system itself. Conventional approaches to interface development are reviewed, and weaknesses identified which stem from the decoupling of regularly interacting components. It is shown how a more integrated approach, in which databases are used to implement their own interfaces, provides significant direct benefits without precluding subsequent support for mainstream interface development architectures View full abstract»

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  • Threshold cryptosystem with multiple secret sharing policies

    Page(s): 142 - 144
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    In a group-oriented threshold cryptosystem, each group, instead of each individual member within the group, publishes a single group public key. An outsider can use this group public key to send encrypted messages to the group. However, the received encrypted messages can only be decrypted properly when the number of participating members is larger than or equal to the threshold value. All earlier solutions assume that there is only one secret sharing policy. We propose the first threshold cryptosystem with multiple secret sharing policies. In other words, a group can set up multiple secret sharing policies and a trusted key centre is responsible for selecting three publicly-known moduli, secret keys for group members, and publishing a corresponding public key for each policy during the initiation time. Moreover, there is only one single secret key kept by each group member. Whenever an outsider wants to send a message to the group, he needs to determine how the message should be revealed to the group members, and therefore selects a proper public key to encrypt messages. Once the encrypted message is received by the group, according to the specified information, a predetermined number of group members is required to decipher the cipher-text View full abstract»

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  • Constraints imposed by programme content on design, delivery and use of interactive media

    Page(s): 85 - 92
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    Systems based on digital representations of images are explored and analysed in the light of the sort of demands that interactive programmes of worthwhile complexity will place on them. By separating the processes of design from delivery, important advantages can be secured for these two quite dissimilar processes. The special advantages of analogue representations of certain types of data are highlighted and the problems of the representation of meaning are discussed in connection with the management and indexing of essential pictorial imagery. The interactive nature of programmes devised around still and moving images poses problems not usually encountered in conventional computing, and the consideration of these problems can best be carried out as an extension of human-computer interaction research View full abstract»

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