DSpace@RPI is a repository of Rensselaer Polytechnic Institute's theses and dissertations which are available in digital format, largely from 2006 to present, along with other selected resources.

Recent Submissions

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    Low-power time-to-digital converters for high-precision measurement
    (Rensselaer Polytechnic Institute, Troy, NY, 2023-12) Tong, Xing; Hella, Mona, M
    Time-to-digital converters (TDCs), which converts time delays into digital signals, have garnered significant interest for their diverse applications in fields such as high-energy nuclear physics, time-of-flight (ToF) sensors, time-domain analog-to-digital converters (TD-ADCs), and all-digital phase-locked loops (ADPLLs). The performance of a TDC is primarily measured by its resolution, range, sampling rate, and power consumption. To simultaneously achieve a fine resolution and a long range, or a high dynamic range, in an area and power efficient manner, hierarchical architectures with the potential to combine the advantages of several different approaches has been studied. This thesis investigated three different hierarchical designs implemented in technologies ranging from 350nm CMOS to 45nm SOI, each suitable for its specific applications. This work first presents a hierarchical ADC-assisted TDC with reconfigurable resolution. The reconfigurable resolution and range are achieved by adjusting reference currents in the time-to-voltage converter (TVC) and the reference voltages in the ADC. The proposed resolution-reconfigurable approach combined with a two-step hierarchical architecture can be employed in a wide range of applications with different spatial range and resolution requirements. Fabricated using a 350nm CMOS process with a core area of 0.15mm², prototype chips yielded a resolution of 39ps with a 100MHz reference clock or 78ps with a 50MHz reference clock. In both cases, the measurement rate is 384kS/s while consuming less than 6.7mW from a 3.3V supply. Secondly, a multi-channel 4-tier TDC design combining gated-ring oscillators (GRO) coarse measurement stage, time amplifier, and 2D vernier fine measurement stage designed an simulated in 90nm SOI SiPh process. A dual-counter correction scheme is proposed to address the parallel-output-misalignment (POM) error in multi-phase clock based TDCs. The finer two tiers employ time amplifiers and 2D vernier lines to measure the residual signal, achieving a sub-gate-delay resolution while keeping a high conversion rate. Post-layout extracted simulation on the proposed TDC design shows a 2ps LSB size, while consuming 5.11-mW per additional channel from a 1.2V supply when operating at the maximum sampling rate of 500MS/s. Compared to state-of-the-art TDC designs, the proposed architecture shows an improvement in quantization step, conversion time, and dynamic range. The idea of multiphase-clock-based multichannel coarse measurement is further explored in a DLL-based TDC implemented in 45nm SOI technology. Lastly, a hierarchical pipeline TDC in 45nm SOI technology, optimized for high-speed and high-precision applications, is introduced. A novel analytical model for the cross-coupled time amplifier (TA) in the pipeline TDC is formulated. Based on this model, a gain calibration scheme is proposed. To validate the time amplifier analysis, a hierarchical TDC with pipeline fine measurement is designed and fabricated in 45nm SOI technology. With look-up table correction, measurement results of the TDC demonstrate a resolution of 0.95ps, a range of 0.8ns, and a DNL/INL range of 2.14 LSB and 2.13 LSB, respectively. The device operates on 8.851mW from a 1.0V supply at a sampling rate of 120MHz, and it achieves a maximum sampling rate of at least 250MHz, highlighting its capability to simultaneously deliver high speed and fine resolution.
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    Web Science: An Interdisciplinary Approach to Understanding the Web
    (ACM, 2008-07-01) Hendler, James A.; Shadbolt, Nigel; Hall, Wendy; Berners-Lee, Tim; Weitzner, Danny
    Despite the web’s great success as a technology and the significant amount of computing infrastructure on which it is built, it remains, as an entity, surprisingly unstudied. Here, we look at some of the technical and social challenges that must be overcome to model the Web as a whole, keep it growing, and understand its continuing social impact. A systems approach, in the sense of “systems biology,” is needed if we are to be able to understand and engineer the future Web.
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    Supporting Limits on Copyright Exclusivity in a Rights Expression Language Standard
    (Samuelson Law, Technology & Public Policy Clinic (Univ. of California, Berkeley), 2002-08-13) Mulligan, Deirdre K.; Burstein, Aaron; Erickson, John S.
    Copyright law grants certain rights to purchasers and other users of copyrighted works. It is neither a legal nor a practical requirement for users to declare (or claim) these rights explicitly in order to enjoy them. While the public's legal rights cannot be altered by Digital Rights Management (DRM) systems per se, we can imagine scenarios in which DRM systems may require users to make these kinds of declarations, in order to work around inherent technical limitations. It is therefore essential that a rights expression language (REL) provide the vocabulary necessary for individuals to express, in a straightforward way, the rights that copyright law grants them to use materials. The user's claim of right would provide the essential information for a usage-rights issuing agency to give the user the technical capability to use the work in a particular way.
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    Fair Use, Drm, and Trusted Computing
    (ACM, 2003-04-01) Erickson, John S.
    The migration of trusted computing principles into end-user systems promises to increase the practical application of and market demand for digital rights management (DRM) technologies. Trusted computing platforms and the integration of DRM components into the operating system will likely make controlled, conditional access to content and services attractive for providers of copyrighted resources, and an increasingly common—if not always popular or desirable—part of the end-user experience. The ability of providers to reliably and deterministically impose rules on the end-user experience raises the question of who sets the rules dictating how users interact with digital information on their personal systems. Will the social policies and common practices that have traditionally influenced the copyright process be replaced by rules privately constructed by content owners and software providers? Will they be privately enforced by operating systems and DRM technologies? Conversely, can these emerging architectures help protect the limitations on copyright owners’ exclusive rights, preserving the flexible fair use doctrine? Here, I explore how access-control policies are evaluated, especially in the case of two rights expression languages—the eXtensible rights Markup Language (XrML; see xrml.org) and the eXtensible Access Control Markup Language (XACML; see www.xacml.org). Since the expression and interpretation of policies is but one layer of the general problem of asserting and protecting copyright with computer code, I emphasize the role of trusted systems in ensuring that computing agents interpret policies in reliable and deterministic ways. I also weigh the challenges inherent in expressing and enforcing policies that mimic social policies. Engineers often seek to simplify problems, but when the problem involves implementing legal statutes (such as copyright) with executable code, simplifications might actually do damage, especially if the solution gives either party more power to assert control than the law entitles.
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    Eliciting Survey Knowledge with Semantic Data Dictionaries
    (2024-02-28) Santos, Henrique; Pinheiro, Paulo; McGuinness, Deborah L.
    Many countries perform surveys to gather data from their population for supporting decision-making and development of public policies. Questionnaires are possibly the most used type of data acquisition instrument in surveys, although additional kinds may be employed (especially in health-related surveys). In the United States, the NHANES is a national health and nutrition examination survey conducted by the National Center for Health Statistics, designed to collect data on adults' and children's health and nutritional status. Data is organized in several tables, each containing variables to a specific theme, such as demographics, and dietary information. In addition, data dictionaries are available to (sometimes partially) document the tables' contents. While data is mostly provided by survey participants, instruments might be collecting data related to other entities (e.g. from participants' households and families, as well as laboratory results from participants' provided blood and urine samples). All this complex knowledge can often only be elicited by humans when analyzing and understanding the data dictionaries in combination with the data. The representation of this knowledge in a machine-interpretable format could facilitate further use of the data. We detail how Semantic Data Dictionaries (SDDs) have been used to elicit knowledge about surveys, using the publicly available NHANES data and data dictionaries. In SDDs, we formalize the semantics of variables, including entities, attributes, and more, using terminology from relevant ontologies, and demonstrate how they are used in an automated process to generate a rich knowledge graph that enables downstream tasks in support of survey data analysis.

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