1,648 research outputs found
Tag-Cloud Drawing: Algorithms for Cloud Visualization
Tag clouds provide an aggregate of tag-usage statistics. They are typically
sent as in-line HTML to browsers. However, display mechanisms suited for
ordinary text are not ideal for tags, because font sizes may vary widely on a
line. As well, the typical layout does not account for relationships that may
be known between tags. This paper presents models and algorithms to improve the
display of tag clouds that consist of in-line HTML, as well as algorithms that
use nested tables to achieve a more general 2-dimensional layout in which tag
relationships are considered. The first algorithms leverage prior work in
typesetting and rectangle packing, whereas the second group of algorithms
leverage prior work in Electronic Design Automation. Experiments show our
algorithms can be efficiently implemented and perform well.Comment: To appear in proceedings of Tagging and Metadata for Social
Information Organization (WWW 2007
VLSI Architecture and Design
Integrated circuit technology is rapidly approaching a state where feature sizes of one micron or less are tractable. Chip sizes are increasing slowly. These two developments result in considerably increased complexity in chip design. The physical characteristics of integrated circuit technology are also changing. The cost of communication will be dominating making new architectures and algorithms both feasible and desirable. A large
number of processors on a single chip will be possible. The cost of communication will make
designs enforcing locality superior to other types of designs.
Scaling down feature sizes results in increase of the delay that wires introduce. The delay even of metal wires will become significant. Time tends to be a local property which will make the design of globally synchronous systems more difficult. Self-timed systems will eventually become a necessity.
With the chip complexity measured in terms of logic devices increasing by more than an order of magnitude over the next few years the importance of efficient design methodologies and tools become crucial. Hierarchical and structured design are ways of dealing with the complexity of chip design. Structered design focuses on the information
flow and enforces a high degree of regularity. Both hierarchical and structured design encourage the use of cell libraries. The geometry of the cells in such libraries should be parameterized so that for instance cells can adjust there size to neighboring cells and make the proper interconnection. Cells with this quality can be used as a basis for "Silicon Compilers"
Guaranteed passive parameterized macromodeling by using Sylvester state-space realizations
A novel state-space realization for parameterized macromodeling is proposed in this paper. A judicious choice of the state-space realization is required in order to account for the assumed smoothness of the state-space matrices with respect to the design parameters. This technique is used in combination with suitable interpolation schemes to interpolate a set of state-space matrices, and hence the poles and residues indirectly, in order to build accurate parameterized macromodels. The key points of the novel state-space realizations are the choice of a proper pivot matrix and a well-conditioned solution of a Sylvester equation. Stability and passivity are guaranteed by construction over the design space of interest. Pertinent numerical examples validate the proposed Sylvester realization for parameterized macromodeling
Harnessing resilience: biased voltage overscaling for probabilistic signal processing
A central component of modern computing is the idea that computation requires
determinism. Contrary to this belief, the primary contribution of this work shows that
useful computation can be accomplished in an error-prone fashion. Focusing on low-power
computing and the increasing push toward energy conservation, the work seeks to sacrifice
accuracy in exchange for energy savings.
Probabilistic computing forms the basis for this error-prone computation by diverging from the requirement of determinism and allowing for randomness within computing.
Implemented as probabilistic CMOS (PCMOS), the approach realizes enormous energy sav-
ings in applications that require probability at an algorithmic level. Extending probabilistic
computing to applications that are inherently deterministic, the biased voltage overscaling
(BIVOS) technique presented here constrains the randomness introduced through PCMOS.
Doing so, BIVOS is able to limit the magnitude of any resulting deviations and realizes
energy savings with minimal impact to application quality.
Implemented for a ripple-carry adder, array multiplier, and finite-impulse-response (FIR)
filter; a BIVOS solution substantially reduces energy consumption and does so with im-
proved error rates compared to an energy equivalent reduced-precision solution. When
applied to H.264 video decoding, a BIVOS solution is able to achieve a 33.9% reduction in
energy consumption while maintaining a peak-signal-to-noise ratio of 35.0dB (compared to
14.3dB for a comparable reduced-precision solution).
While the work presented here focuses on a specific technology, the technique realized
through BIVOS has far broader implications. It is the departure from the conventional
mindset that useful computation requires determinism that represents the primary innovation of this work. With applicability to emerging and yet to be discovered technologies,
BIVOS has the potential to contribute to computing in a variety of fashions.PhDCommittee Chair: Anderson, David; Committee Member: Conte, Thomas; Committee Member: Ferri, Bonnie; Committee Member: Hasler, Paul; Committee Member: Mooney, Vincen
Flash ADC using 2μm CMOS P-well technology : design and test
This thesis describes the design, implementation and test for a new CMOS analog-to-digital converter IC chip. In designing the analog-to-digital converter in this thesis a radically different comparator design that is only available with CMOS logic. The design utilizes a single CMOS inverter as an ultra-high gain amplifier. This approach reduces the circuit dependence upon matching of the transistors similar to the traditional method. This new design requires less area since the comparator utilizes fewer transistors.
Flash analog-to-digital converters use 2 - 1 comparators to do a single conversion where n is the number of bits used. These comparators are traditionally made with differential transistor amplifiers in order to obtain matched characteristics. Effects of mismatch in current gains and base emitter voltage is reduced in the new design since the amplifier topology does not depend entirely upon perfectly matched transistors
Compressive Mining: Fast and Optimal Data Mining in the Compressed Domain
Real-world data typically contain repeated and periodic patterns. This
suggests that they can be effectively represented and compressed using only a
few coefficients of an appropriate basis (e.g., Fourier, Wavelets, etc.).
However, distance estimation when the data are represented using different sets
of coefficients is still a largely unexplored area. This work studies the
optimization problems related to obtaining the \emph{tightest} lower/upper
bound on Euclidean distances when each data object is potentially compressed
using a different set of orthonormal coefficients. Our technique leads to
tighter distance estimates, which translates into more accurate search,
learning and mining operations \textit{directly} in the compressed domain.
We formulate the problem of estimating lower/upper distance bounds as an
optimization problem. We establish the properties of optimal solutions, and
leverage the theoretical analysis to develop a fast algorithm to obtain an
\emph{exact} solution to the problem. The suggested solution provides the
tightest estimation of the -norm or the correlation. We show that typical
data-analysis operations, such as k-NN search or k-Means clustering, can
operate more accurately using the proposed compression and distance
reconstruction technique. We compare it with many other prevalent compression
and reconstruction techniques, including random projections and PCA-based
techniques. We highlight a surprising result, namely that when the data are
highly sparse in some basis, our technique may even outperform PCA-based
compression.
The contributions of this work are generic as our methodology is applicable
to any sequential or high-dimensional data as well as to any orthogonal data
transformation used for the underlying data compression scheme.Comment: 25 pages, 20 figures, accepted in VLD
Analog VLSI circuits for inertial sensory systems
Supervised by Rahul Sarpeshkar.Also isssued as Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references (leaves 67-68).by Maziar Tavakoli Dastjerdi
Constraint-Aware, Scalable, and Efficient Algorithms for Multi-Chip Power Module Layout Optimization
Moving towards an electrified world requires ultra high-density power converters. Electric vehicles, electrified aerospace, data centers, etc. are just a few fields among wide application areas of power electronic systems, where high-density power converters are essential. As a critical part of these power converters, power semiconductor modules and their layout optimization has been identified as a crucial step in achieving the maximum performance and density for wide bandgap technologies (i.e., GaN and SiC). New packaging technologies are also introduced to produce reliable and efficient multichip power module (MCPM) designs to push the current limits. The complexity of the emerging MCPM layouts is surpassing the capability of a manual, iterative design process to produce an optimum design with agile development requirements. An electronic design automation tool called PowerSynth has been introduced with ongoing research toward enhanced capabilities to speed up the optimized MCPM layout design process. This dissertation presents the PowerSynth progression timeline with the methodology updates and corresponding critical results compared to v1.1. The first released version (v1.1) of PowerSynth demonstrated the benefits of layout abstraction, and reduced-order modeling techniques to perform rapid optimization of the MCPM module compared to the traditional, manual, and iterative design approach. However, that version is limited by several key factors: layout representation technique, layout generation algorithms, iterative design-rule-checking (DRC), optimization algorithm candidates, etc. To address these limitations, and enhance PowerSynth’s capabilities, constraint-aware, scalable, and efficient algorithms have been developed and implemented. PowerSynth layout engine has evolved from v1.3 to v2.0 throughout the last five years to incorporate the algorithm updates and generate all 2D/2.5D/3D Manhattan layout solutions. These fundamental changes in the layout generation methodology have also called for updates in the performance modeling techniques and enabled exploring different optimization algorithms. The latest PowerSynth 2 architecture has been implemented to enable electro-thermo-mechanical and reliability optimization on 2D/2.5D/3D MCPM layouts, and set up a path toward cabinet-level optimization. PowerSynth v2.0 computer-aided design (CAD) flow has been hardware-validated through manufacturing and testing of an optimized novel 3D MCPM layout. The flow has shown significant speedup compared to the manual design flow with a comparable optimization result
Programmable latching probe microstructures for wafer testing applications
The objective of this thesis is to design a programmable wafer testing array on a single chip based on micro electromechanical systems (MEMS) and VLSI. The wafer-scale integration in this thesis is a programmable array of test probes that are used for engineering test of VLSI and ULSI silicon integrated circuits at the wafer level. This consists of two subsystems (1) the VLSI address circuits used for addressing and controlling the MEMS on the chip and (2) the latching probe MEMS microstructure array that actuates into position for testing VLSI wafers. Each of the subsystems have been designed, analyzed and simulated separately. These structures were then integrated into a demonstration 4x4 array forming a programmable probe card. A 3-micrometer critical dimension is used for both the VLSI CMOS and the MEMS physical design layouts. The fabrication technique for the MEMS microstructure is detailed. A standard 12-mask CMOS technology is used for the fabrication of the address circuits
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