13,636 research outputs found
Gender differences in navigation dialogues with computer systems
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Gender is among the most influential of the factors underlying differences in spatial abilities, human communication and interactions with and through computers. Past research has offered important insights into gender differences in navigation and language use. Yet, given the multidimensionality of these domains, many issues remain contentious while others unexplored. Moreover, having been derived from non-interactive, and often artificial, studies, the generalisability of this research to interactive contexts of use, particularly in the practical domain of Human-Computer Interaction (HCI), may be problematic. At the same time, little is known about how gender strategies, behaviours and preferences interact with the features of technology in various domains of HCI, including collaborative systems and systems with natural language interfaces. Targeting these knowledge gaps, the thesis aims to address the central question of how gender differences emerge and operate in spatial navigation dialogues with computer systems.
To this end, an empirical study is undertaken, in which, mixed-gender and same-gender pairs communicate to complete an urban navigation task, with one of the participants being under the impression that he/she interacts with a robot. Performance and dialogue data were collected using a custom system that supported synchronous navigation and communication between the user and the robot.
Based on this empirical data, the thesis describes the key role of the interaction of gender in navigation performance and communication processes, which outweighed the effect of individual gender, moderating gender differences and reversing predicted patterns of performance and language use. This thesis has produced several contributions; theoretical, methodological and practical. From a theoretical perspective, it offers novel findings in gender differences in navigation and communication. The methodological contribution concerns the successful application of dialogue as a naturalistic, and yet experimentally sound, research paradigm to study gender and spatial language. The practical contributions include concrete design guidelines for natural language systems and implications for the development of gender-neutral interfaces in specific domains of HCI
All-to-all communication with low communication cost
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.Cataloged from PDF version of thesis.Includes bibliographical references (pages 61-64).In an all-to-all broadcast, every user wishes to broadcast its message to all the other users. This is a process that frequently appears in large-scale distributed systems such as voting and consensus protocols. In the classic solution, a user needs to receive n messages and n signatures where n is the number of users in the network. This is undesirable for large-scale distributed systems that contain millions or billions of users and can be the throughput bottleneck for some existing systems. In this thesis, we propose two protocols for the all-to-all broadcast problem. Our protocols upper bound the number of bits each user receives by [Theta](n log log2 n), which is a huge improvement from the conventional n times the signature size. Besides the all-to-all protocol, we also provide new results regarding random graphs and regular graphs. These results are used in our protocol to prove its efficiency. But they are interesting by themselves and have independent theoretic value.by Jun Wan.S.M
Small satellite optical communication receiver for simultaneous spatial tracking and data demodulation
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 71-72).Free-space optical communications in space offer many benefits over established radio frequency based communication links; in particular, high beam directivity results in efficient power usage. Such a reduced power requirement is particularly appealing to small satellites with strict size, weight and power (SWaP) requirements. In the case of free-space optical communication, precise pointing, acquisition and tracking (PAT) of the incoming beam is necessary to close the communication link. Due to the narrow beam of the laser, the critical task of accomplishing PAT becomes increasingly arduous and often requires complex systems of optical and processing hardware to account for relative movement of the terminals. Recent developments in body pointing mechanisms have allowed small satellites to point with greater precision. In this thesis, an approach to a low-complexity PAT system that utilizes a single quad-cell photodetector as an optical spatial sensor is presented in the context of a system which exploits the body pointing capabilities of the spacecraft to perform tracking maneuvers, eschewing the need for additional dedicated optical hardware. The design and validation of this approach is presented, and preliminary results regarding the implementation of this system are discussed. In particular, we examine the implementation of the system on NASA's TeraByte InfraRed Delivery (TBIRD) demonstration.National Aeronautics and Space Administrationunder Air Force Contract No. FA8702-15-D-0001by Jessica S. Chang.M. Eng.M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc
An automatic grader for embedded systems education
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 65-66).In this thesis, we introduce MicroGrader, an automated grader for embedded systems projects. The grader runs on a laptop or desktop computer, while the embedded system being evaluated runs on a microcontroller. By implementing a custom communication protocol between the grader and the embedded system, we enable the grader to inject test inputs and observe the resulting outputs. We describe a data structure for defining the technical requirements of an assignment. This data structure is meant to be simple to use, but highly expressive to allow for a wide range of possible assignments. We also outline the implementation of the MicroGrader system and the underlying communication protocol. We discuss the constraints that this implementation imposes on instructors. Finally, we describe a method of automatically constructing tests using a staff-built reference solution for a generic assignment.by Daniel L. Mendelsohn.M. Eng
Construction of a support tool for the design of the activity structures based computer system architectures
No full textThis thesis was submitted for the degree of Doctor of Philosophy and was awarded by Brunel University.This thesis is a reapproachment of diverse design concepts, brought to bear upon the computer system
engineering problem of identification and control of highly constrained multiprocessing (HCM)
computer machines. It contributes to the area of meta/general systems methodology, and brings
a new insight into the design formalisms, and results afforded by bringing together various design
concepts that can be used for the construction of highly constrained computer system architectures.
A unique point of view is taken by assuming the process of identification and control of HCM
computer systems to be the process generated by the Activity Structures Methodology (ASM).
The research in ASM has emerged from the Neuroscience research, aiming at providing the
techniques for combining the diverse knowledge sources that capture the 'deep knowledge' of this
application field in an effective formal and computer representable form. To apply the ASM design
guidelines in the realm of the distributed computer system design, we provide new design definitions
for the identification and control of such machines in terms of realisations. These realisation definitions
characterise the various classes of the identification and control problem. The classes covered
consist of:
1. the identification of the designer activities,
2. the identification and control of the machine's distributed structures of behaviour,
3. the identification and control of the conversational environment activities (i.e. the randomised/
adaptive activities and interactions of both the user and the machine environments),
4. the identification and control of the substrata needed for the realisation of the machine, and
5. the identification of the admissible design data, both user-oriented and machineoriented,
that can force the conversational environment to act in a self-regulating
manner.
All extent results are considered in this context, allowing the development of both necessary
conditions for machine identification in terms of their distributed behaviours as well as the substrata
structures of the unknown machine and sufficient conditions in terms of experiments on the unknown
machine to achieve the self-regulation behaviour.
We provide a detailed description of the design and implementation of the support software tool
which can be used for aiding the process of constructing effective, HCM computer systems, based
on various classes of identification and control. The design data of a highly constrained system, the
NUKE, are used to verify the tool logic as well as the various identification and control procedures.
Possible extensions as well as future work implied by the results are considered.Government of Ira
Cyber-attack detection and resilient state estimation in power systems
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, May, 2020Cataloged from the official PDF of thesis.Includes bibliographical references (pages 99-108).Many critical infrastructures, such as transportation and electric energy networks, and health care, are now becoming highly integrated with information and communication technology, in order to be more efficient and reliable. These cyber-physical systems (CPS) now face an increasing threat of cyber-attacks. Intelligent attackers can leverage their knowledge of the system, disruption, and disclosure resources to critically damage the system while remaining undiscovered. In this dissertation, we develop a defense strategy, with the ability to uncover malicious and intelligent attacks and enable resilient operation of cyber-physical systems. Specifically, we apply this defense strategy to power systems, described by linear frequency dynamics around the nominal operating point. Our methodology is based on the notion of data aggregation as a tool for extracting internal information about the system that may be unknown to the attacker. As the first step to resilience and security, we propose several methods for active attack detection in cyber-physical systems. In one approach we design a clustering-based moving-target active detection algorithm and evaluate it against stealthy attacks on the 5-bus and 24-bus power grids. Next, we consider an approach based on Interaction Variables (IntVar), as another intuitive way to extract internal information in power grids. We evaluate the eectiveness of this approach on Automatic Generation Control (AGC), a vital control mechanism in today's power grid. After an attack has been detected, mitigation procedures must be put in place to allow continued reliable operation or graceful degradation of the power grid. To that end, we develop a resilient state estimation algorithm, that provides the system operator with situational awareness in the presence of wide-spread coordinated cyber-attacks when many system measurements may become unavailable.by Ana Jevtić.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc
Automatic software upgrades for distributed systems
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 156-164).Upgrading the software of long-lived, highly-available distributed systems is difficult. It is not possible to upgrade all the nodes in a system at once, since some nodes may be unavailable and halting the system for an upgrade is unacceptable. Instead, upgrades may happen gradually, and there may be long periods of time when different nodes are running different software versions and need to communicate using incompatible protocols. We present a methodology and infrastructure that address these challenges and make it possible to upgrade distributed systems automatically while limiting service disruption. Our methodology defines how to enable nodes to interoperate across versions, how to preserve the state of a system across upgrades, and how to schedule an upgrade so as to limit service disrup- tion. The approach is modular: defining an upgrade requires understanding only the new software and the version it replaces. The upgrade infrastructure is a generic platform for distributing and installing software while enabling nodes to interoperate across versions. The infrastructure requires no access to the system source code and is transparent: node software is unaware that different versions even exist. We have implemented a prototype of the infrastructure called Upstart that intercepts socket communication using a dynamically-linked C++ library. Experiments show that Upstart has low overhead and works well for both local-area-and Internet systems.by Sameer Ajmani.Ph.D
Time-based circuits for communication systems in advanced CMOS technology
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 145-151).As device size scales down, there have been challenges to design conventional analog circuits, such as low voltage headroom and the low intrinsic gain of a device. Although ever-decreasing device channel length in CMOS technology has mainly negative effects on analog circuits, it increases device speed and reduces the power consumption of digital circuits. As a result, time-based signal processing has been attracting attention because time-based circuits take advantage of high speed and low power devices to deal with analog information in the time domain. In this thesis, we focus on a ring oscillator as a core time-based circuit for communication systems. Ring oscillators are employed in analog-to-time conversion or time-to-digital conversion. In this work, we present A/D converters and an RF modulator based on ring oscillators in deep sub-micron CMOS processes. We introduce a VCO-based [sigma][delta] A/D converter utilizing a voltage-controlled ring oscillator (ring VCO) as a continuous-time integrator. We propose to replace conventional integrators designed with analog circuits in a [sigma][delta] modulator with a ring VCO and a phase detector, thereby implementing an A/D converter without traditional analog circuits. We also propose a single-slope A/D converter using time-to-digital conversion. By combining a few analog circuits and a ring oscillator based Time-to-Digital Converter (TDC), we achieve highly digital A/D conversion. Finally, we demonstrate a VCO-based RF modulator. The proposed RF modulator generates an RF signal by simply switching transistors. As opposed to an RFDAC approach, the proposed RF modulator is not limited by quantization noise because it employs multiphase PWM signals. A VCO-based OP amp is also introduced as an alternative method of designing an OP amp in deep sub-micron CMOS. The proposed VCO-based OP amp is utilized to generate the multiphase PWM signals in the RF modulator. This thesis also presents the fundamental limitations of a ring oscillator as a timebased circuit. Although the idea of time-based signal processing employing a ring oscillator has its own limitations such as non-linear tuning characteristics and phase noise, the basic idea is worth investigating to solve the serious problems of analog circuits for future CMOS technology.by Min Park.Ph.D
Distinguishing codes from noise : fundamental limits and applications to sparse communication
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 99-100).This thesis investigates the problem of distinguishing codes from noise. We develop a slotted channel model where in each time slot, the channel input is either a codeword or a noise sequence. In this model, successful communication requires both correctly detecting the presence of a codeword and decoding it to the correct message. While the decoding problem has been extensively studied, the problem of distinguishing codes from noise is relatively new, and we ask the following question regarding the "distinguishability" of a channel code: given a noisy channel and a code with a certain rate, what are the fundamental limits of distinguishing this code from noise at the output of the channel? The problem of distinguishing codes from noise involves both detection and decoding. In our analysis, we first extend the classical channel coding problem to incorporate the requirement of detection, which admits both miss and false alarm errors. Then we investigate the fundamental limits of code distinguishing in terms of the error exponents of miss and false alarm error probabilities. In a scenario that miss probability is required to vanish asymptotically but not necessarily exponentially, we characterize the maximum false alarm error exponent at each rate, and show that an i.i.d. codebook with typicality decoding is sufficient to achieve the maximum exponent. In another scenario that requires certain miss error exponent, we show that for DMC channels, the i.i.d. codebook is suboptimal and the constant composition codebook achieves the best known performance. For AWGN channels, we develop a clustered spherical codebook that achieves the best known performance in all operating regimes. This code distinguishability problem is strongly motivated by the synchronization problem in sparse communication, a new communication paradigm where transmissions take place intermittently and each transmission consists of a small amount of data. Our results show that, in sparse communication, the traditional approach of conducting synchronization and coding separately is suboptimal, and our approach of designing codes for joint synchronization and information transmission achieves better performance, especially at high rates. Therefore, for systems with sparse transmissions such as sensor networks, it is beneficial to adopt the joint sync-coding architecture instead of the traditional separate sync-coding architecture.by Da Wang.S.M
Communication-efficient hierarchical federated learning for IoT heterogeneous systems with imbalanced data
No full textFederated Learning (FL) is a distributed learning methodology that allows multiple nodes to cooperatively train a deep learning model, without the need to share their local data. It is a promising solution for telemonitoring systems that demand intensive data collection, for detection, classification, and prediction of future events, from different locations while maintaining a strict privacy constraint. Due to privacy concerns and critical communication bottlenecks, it can become impractical to send the FL updated models to a centralized server. Thus, this paper studies the potential of hierarchical FL in Internet of Things (IoT) heterogeneous systems. In particular, we propose an optimized solution for user assignment and resource allocation over hierarchical FL architecture for IoT heterogeneous systems. This work focuses on a generic class of machine learning models that are trained using gradient-descent-based schemes while considering the practical constraints of non-uniformly distributed data across different users. We evaluate the proposed system using two real-world datasets, and we show that it outperforms state-of-the-art FL solutions. Specifically, our numerical results highlight the effectiveness of our approach and its ability to provide 4–6% increase in the classification accuracy, with respect to hierarchical FL schemes that consider distance-based user assignment. Furthermore, the proposed approach could significantly accelerate FL training and reduce communication overhead by providing 75–85% reduction in the communication rounds between edge nodes and the centralized server, for the same model accuracy.Other InformationPublished in: Future Generation Computer SystemsLicense: http://creativecommons.org/licenses/by/4.0/See article on publisher's website: https://dx.doi.org/10.1016/j.future.2021.10.016</p
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