6,629 research outputs found
Requirements for a Research-oriented IC Design System
Computer-aided design techniques for integrated circuits grown in an incremental way, responding to various perceived needs, so that today there are a number of useful programs for logic generation, simulation at various levels, test preparation, artwork generation and
analysis (including design rule checking), and interactive graphical editing. While the design of many circuits has benefitted from these programs, when industry wants to produce a high-volume part, the design and layout are done manually, followed by digitizing and
perhaps some graphic editing before it is converted to pattern generation format, leading to the often heard statement that computer-aided design of integrated circuits doesn't work. If progress is to be made, it seems clear that the entire design process has to be thought through in basic terms, and much more attention must
be paid to the way in which computational techniques can complement the designer's abilities. Currently, it is appropriate to try to characterize the design process in abstract terms, so that implementation and technological biases don't cloud the view of a desired system. In this paper, we briefly describe the conversion of
algorithms to masks at a very general level, and then describe several projects at MIT which aim to provide contributions to an integrated design system. It is emphasized that no complete system design exists
now at MIT, and that we believe that general design considerations must constantly be tested by building (and rebuilding) the various subcomponents, the structure of which is guided by our view of the overall design process
Site investigation techniques for DNAPL source and plume zone characterisation
Establishing the location of the Source Area BioREmediation (SABRE)
research cell was a primary objective of the site characterisation
programme. This bulletin describes the development of a two-stage site
characterisation methodology that combined qualitative and
quantitative data to guide and inform an assessment of dense nonaqueous
phase liquid (DNAPL) distribution at the site.
DNAPL site characterisation has traditionally involved multiple phases of
site investigation, characterised by rigid sampling and analysis
programmes, expensive mobilisations and long decision-making
timeframes (Crumbling, 2001a) , resulting in site investigations that are
costly and long in duration. Here we follow the principles of an
innovative framework, termed Triad (Crumbling, 2001a, 2001b;
Crumbling et al., 2001, Crumbling et al. 2003), which describes a
systematic approach for the characterisation and remediation of
contaminated sites. The Triad approach to site characterisation focuses
on three main components: a) systematic planning which is
implemented with a preliminary conceptual site model from existing
data. The desired outcomes are planned and decision uncertainties are
evaluated; b) dynamic work strategies that focus on the need for
flexibility as site characterisation progresses so that new information can
guide the investigation in real-time and c) real-time measurement
technologies that are critical in making dynamic work strategies
possible.
Key to this approach is the selection of suitable measurement
technologies, of which there are two main categories (Crumbling et al.,
2003). The first category provides qualitative, dense spatial data, often
with detection limits over a preset value. These methods are generally of
lower cost, produce real-time data and are primarily used to identify site
areas that require further investigation. Examples of such "decisionquality"
methods are laser induced fluorescence (Kram et al., 2001),
membrane interface probing (McAndrews et al., 2003) and cone
penetrometer testing (Robertson, 1990), all of which produce data in
continuous vertical profiles. Because these methods are rapid, many
profiles can be generated and hence the subsurface data density is
greatly improved. These qualitative results are used to guide the
sampling strategy for the application of the second category of
technologies that generate quantitative, precise data that have low
detection limits and are analyte-specific. These methods tend to be high
cost with long turnaround times that preclude on-site decision making,
hence applying them to quantify rather than produce a conceptual
model facilitates a key cost saving. Examples include instrumental
laboratory analyses such as soil solvent extractions (Parker et al., 2004)and water analyses (USEPA, 1996). Where these two categories of
measurement technologies are used in tandem, a more complete and
accurate dataset is achieved without additional site mobilisations.
The aim of the site characterisation programme at the SABRE site was to
delineate the DNAPL source zone rapidly and identify a location for the
in situ research cell. The site characterisation objectives were to; a) test
whether semi-quantitative measurement techniques could reliably
determine geological interfaces, contaminant mass distribution and
inform the initial site conceptual model; and b) quantitatively determine
DNAPL source zone distribution, guided by the qualitative site
conceptual model
Custom Integrated Circuits
Contains report on one research project.U. S. Air Force - Office of Scientific Research (Grant AFOSR-78-3593
A Study of Charge Transport: Correlated Energetic Disorder in Organic Semiconductors, and the Fragment Hamiltonian
This dissertation details work done on two different descriptions of charge transport. The first topic is energetic disorder in organic semiconductors, and its effect on charge transport. This is motivated primarily by solar cells, which can be broadly classified as either inorganic or organic. The inorganic class of solar cells is older, and more well-developed, with the most common type being constructed from crystalline silicon. The large silicon crystals required for these cells are expensive to manufacture, which gave rise to interest in photovoltaic cells made from much less costly organic polymers. These organic materials are also less efficient than their silicon counterparts, due to a large degree of spatial and energetic disorder. In this document, the sources and structure of energetic disorder in organic semiconductors are explored, with an emphasis on spatial correlations in energetic disorder. In order for an organic photovoltaic device to function, there must be photogeneration of an exciton (a bound electron-hole pair), exciton transport, exciton dissociation, and transport of the individual charges to their respective terminals. In the case of this thesis, the main focus is exciton dissociation. The effects of correlation on exciton dissociation are examined through computer simulation, and compared to the theory and simulations of previous researchers. We conclude that energetic disorder in organic semiconductors is spatially correlated, and that this correlation improves the ability of excitons to dissociate. The second topic of this dissertation is the Fragment Hamiltonian model. This is a model currently in development as a means of describing charge transport across a range of systems. Currently there are many different systems which exhibit various charge transport behaviors, which are described by several different models. The overarching goal of the Fragment Hamiltonian model is to construct a description of charge transport which accurately describes the behavior of multiple different materials (i.e. metallic conductors or ceramic insulators) in the appropriate limits. The Fragment Hamiltonian model is explored in the context of the tight-binding model, and properties such as the conductivity of several different systems are deduced
A Sense of Duty: Retiring the Special Relationship Rule and Holding Gun Manufacturers Liable for Negligently Distributing Guns
In response to recent litigation brought against the gun industry on behalf of individuals and municipalities victimized as a result of the negligent marketing, design, and distribution of guns, the gun industry has argued that they cannot be held responsible for the victims\u27 injuries because they have no special relationship with the victims. Without a special relationship, gun manufacturers claim to have no duty whatsoever to design, market, or distribute guns in a reasonable fashion. This article examines the fallacies inherent in the gun industry\u27s special relationship argument and discusses the factual, legal and policy grounds that support holding the gun industry responsible for its role in facilitating the misuse of guns
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