Thesis (B.A.)--Haverford College, Dept. of Psychology, 2003. / Includes bibliographical references.

Early human language technology systems were designed in a monolithic fashion. As these systems became more complex, this design became untenable. In its place, the concept of distributed processing evolved wherein the monolithic structure was decomposed into a number of functional components that could interact through a common protocol. This distributed framework was readily accepted by the research community and has been the cornerstone for the advancement in cutting edge human language technology prototype systems.The Defense Advanced Research Program Agency (DARPA) Communicator program has been highly successful in implementing this approach. The program has fueled the design and development of impressive human language technology applications. Its distributed framework has offered numerous benefits to the research community, including reduced prototype development time, sharing of components across sites, and provision of a standard evaluation platform. It has also enabled development of client-server applications with complex inter-process communication between modules. However, this latter feature, though beneficial, introduces complexities which reduce overall system robustness to failure. In addition, the ability to handle multiple users and multiple applications from a common interface is not innately supported. This thesis describes the enhancements to the original Communicator architecture that address robustness issues and provide a multiple multi-user application environment by enabling automated server startup, error detection and correction. Extensive experimentation and analysis were performed to measure improvements in robustness due to the enhancements to the DARPA architecture. A 7.2% improvement in robustness was achieved on the address querying task, which is the most complex task in the human language technology system.

Les circuits asynchrones suscitent de nombreux intérêts à bien des égards. Cependant la modélisation, l'analyse et l'optimisation des circuits asynchrones constituent des pierres d'achoppement à la diffusion de cette technologie sur un plan commercial. Ce travail vise le développement de modèles de circuits asynchrones capables de retranscrire efficacement les protocoles « poignée de main ». Sur la base de ces modèles, une technique d'analyse rapide et précise des circuits a été développée. Cette technique offre un support complet pour l'analyse de délais statistiquement variables et pour différentes structures de circuit (linéaire / non linéaire, sans / avec condition). Elle permet de réaliser des analyses statiques de timing, de consommation électrique et des effets des variabilités sur les circuits asynchrones. En sus de ces méthodes de modélisation et d'analyse, une technique d'optimisation a été développée. Cette technique d'optimisation est basée sur une réduction du nombre de registres asynchrones à un nombre minimal capable de satisfaire les contraintes de performance. L'utilisation des méthodes proposées a permis l'étude de différents protocoles asynchrones et de leurs impacts sur la vitesse, la consommation et la variabilité des procédés de fabrication. Les méthodes proposées ont été validées grâce à un jeu d'outils logiciels écrits en C + +, Java et Matlab. Ces outils se sont avérés rapides, efficaces et dotés d'une très bonne précision de calcul.

This thesis introduces a new methodology for energy estimation in asynchronous circuits. Unlike existing probabilistic methods, this is the first simulative work for energy estimation in all types of asynchronous circuits. The new simulative methodology is based on Petri net modeling. A real delay model is incorporated to capture both gate delays and interconnect delays. The switching activity at each gate is captured to measure the average dynamic energy consumed per request/acknowledge handshaking pair. The new type of Petri net is called Hierarchical Colored Asynchronous Hardware Petri net (HCAHPN). The HCAHPN is able to capture the temporal and spatial correlations of signals within a circuit, while preserving gate logic behavior and timing information. While Petri nets have been previously used for simulating combinational and sequential circuits, this is the first work that uses Petri nets for simulating asynchronous circuits. While different asynchronous design styles make various assumptions on the gate and wire delays present with the circuit, the physical implementations of these circuits always have gate and interconnect delays. Unlike previous methods, the proposed methodology is independent of the asynchronous design style used and it can be adapted for all types of asynchronous circuits that use handshaking communication.

No description available.

Wireless Sensor Networks (WSNs) have gained significant consideration these days, as opposed to wired sensor networks, by introducing multi-functional wireless nodes, which are smaller in size. The main advan-tage is that its wireless, so it costs less to install, maintain and reconfig-ure. These sensor nodes are used in various application areas. For ex-ample: residential, industrial, environmental and military application areas. However WSNs communication is prone to negative influences from the physical environment, such as physical obstacles and interfer-ence. Algorithms must be developed for handling these problems and also to investigate the channel properties. The purpose of this work is to design a testbed, which enables the communication of wireless sensor nodes, to capture the properties of the channel, which will, in the long run, enable better solutions to be designed which are, more appropriate to the errors in the channel. In this testbed, one channel, from the IEEE 802.15.4 channels spectrum, is dedicated as an emergency channel, which is used for handshaking and to handle channel/external interfer-ence or hardware failure between the communication of Transmitter (TX) and Receiver (RX) nodes. The remaining 15 channels are called data channels and are used for actual data transmission and control signals. Peer to Peer transmission of a transmitter-receiver pair is achieved with the introducing of beacons and acknowledgment (ACK) packets. The testbed also has the property of dual reception and data logging on a single PC by maeans of two RX nodes simultaneously from a single TX node. The dependency of the packet on the “Frame Length” byte(in the Frame header) during the reception is eliminated so that if the “Frame Length” byte is compromised, it will replace the programmer defined value with the “Frame Length” byte which helps to investigate the actual packets byte sent from the TX. Also, the Received Signal Strength (RSS) is calculated at the maximum sample rate of the channel. Power consumption is not considered in this testbed. The work is conducted on both the IEEE 802.15.4 physical and the application layers. Linux based TinyOS-2.x is used as an operating system for low power sensor devices. New algorithms are designed for each step in the development of the testbed. MICAz motes are used as nodes and an MIB520 programming board is used for burning the codes and for the purpose of gateways.

Humans are social by nature, and the physical distancing due to COVID has converted many of our daily interactions into virtual ones. Among the negative consequences of this, we find the lack of an element that is essential to humans' well-being, which is the physical touch. With more interactions shifting towards the digital world of the metaverse, we want to provide individuals with the means to include the physical touch in their interactions. We explore the Digital Twin technology's prospect to support in reducing the impact of this on humans. We provide a definition of the concept of Robo Twin and explain its role in mediating human interactions. Besides, we survey research works related to Digital Twin's physical representation with a focus on under-actuated Digital Twin's robotic arms. In this thesis, we first provide findings from the literature, to support researchers' decisions in the adoption and use of designs and implementations of Digital Twin's robotic arms, and to inform future research on current challenges and gaps in existing research works. Subsequently, we design and implement two right-handed under-actuated Digital Twin's robotic arms to mediate the physical interaction between two individuals by allowing them to perform a handshake while they are physically distanced. This experiment served as a proof of concept for our proposed idea of Robo Twin. The findings are very promising as our evaluation shows that the participants are highly interested in using our system to make a handshake with their loved ones when they are physically separated. With this Robo Twin Arm system, we also find a correlation between the handshake characteristics and gender and/or personality traits of the participants from the quantitative handshake data collected during the experiment. Moreover, it is a step towards the design and development of Digital Twin's under-actuated robotic arms and ways to enhance the overall user experience with such a system.

The applications of ad hoc wireless networks envisaged in this thesis are those related to issues of disaster management, rehabilitation, security and defense. The circumstances in such situations warrants the deployment of a quick ad hoc network that is simple and uses minimum resoures to get started. The communication within the network has to be reliable and it has to be simple so that it can be deployed in extremely compex topography and other climatic conditions. Since large batteries cannot be assumed to be at our disposal for the sake of communication at all the times, energy conservation by way of energy efficient schemes is a paramount issue. Ad hoc wireless networks are broadcast networks by nature. For all the communications, transmissions by the nodes are broadcast into the air. A networkwide broadcast is distinguished from this. When a node wants its data to reach all the other nodes in the network then it initiates a networkwide broadcast. There may be nodes in the network that are not directly reachable by the node that wants to do a networkwide broadcast. Networkwide broadcast is used by ad hoc wireless networks for routing protocols, updating of network status information, network organization and multicasting. Most importantly, the applications envisaged out of this thesis need all their data communication as networkwide broadcast alone. In an ad hoc wireless network, a networkwide broadcast is usually effected by the flooding mechanism, which is inherently inefficient, since all the nodes in the network have to transmit the same information. It is possible to exploit the topology of the network in such a way, that only a few of the nodes need to transmit the information to complete a networkwide broadcast. The thesis deals with a new scheme for a networkwide broadcast implemented in the media access control (MAC) layer of an ad hoc wireless network. The new scheme is developed by extending the concept of handshaking signals used in unicast, to the networkwide broadcast scenario. In the case of unicast, where there is an intended recipient, handshaking is done for reliability and happens through the RTS and CTS packets. This idea is extended to suit the networkwide broadcast scenario and the consequences are discussed in detail in the thesis. Intuitively, adding more packets for handshaking increases the number of bytes transmitted. But the results obtained are interesting, since the network transmits fewer bytes per networkwide broadcast, on an average, with the newly proposed scheme. A comparison is done with the implementation of simple flooding following the IEEE 802.11 standard. These results have been demonstrated by simulations. The average improvement is nearly 2.5 times reduction in the number of bytes transmitted per networkwide broadcast. The performance of a networkwide broadcast in an ad hoc wireless network is usually affected badly by losses due to transmssion error in the medium. In a medium with errors, persistence improves reliability. This reliability helps in bringing robustness. The advantage of the proposed scheme is that it uses the idea of persistence to ensure the networkwide broadcast reachabilityto be almost independent of transmission error rate. The MAC layer ensures that the broadcast packet reaches each and every node that is connected to the node that initiates the etworkwide broadcast. The effects of collision are also overcome. Our simulations establish that the scheme works correctly, and gives good performance.