28,068 research outputs found
Why Do We Believe in the Second Law?
Claims of exceptions to the second law of thermodynamics are generally met
with extreme skepticism that is quite reasonable given the great confidence
placed in the second law. But what specifically is the basis for that
confidence? The perspective from which we approach experimental or theoretical
results that call into question the absolute status of the second law depends
greatly on our understanding of why it must be true. For example, a belief that
there are solid theoretical arguments demonstrating that the second law must be
true leads to a very different perspective than a belief that the law is simply
a generalization of empirical observations. This paper will briefly survey and
examine some of the basic arguments on which our confidence in the second law
might be based, to help provide a well-informed perspective for evaluating the
various claims presented at this conference.Comment: 6 pages, to appear in Proc. of "First International Conference on
Quantum Limits to the Second Law," July 2002, editor D.P. Sheeha
Dynamic Multilevel Graph Visualization
We adapt multilevel, force-directed graph layout techniques to visualizing
dynamic graphs in which vertices and edges are added and removed in an online
fashion (i.e., unpredictably). We maintain multiple levels of coarseness using
a dynamic, randomized coarsening algorithm. To ensure the vertices follow
smooth trajectories, we employ dynamics simulation techniques, treating the
vertices as point particles. We simulate fine and coarse levels of the graph
simultaneously, coupling the dynamics of adjacent levels. Projection from
coarser to finer levels is adaptive, with the projection determined by an
affine transformation that evolves alongside the graph layouts. The result is a
dynamic graph visualizer that quickly and smoothly adapts to changes in a
graph.Comment: 21 page
C++ Templates as Partial Evaluation
This paper explores the relationship between C++ templates and partial
evaluation. Templates were designed to support generic programming, but
unintentionally provided the ability to perform compile-time computations and
code generation. These features are completely accidental, and as a result
their syntax is awkward. By recasting these features in terms of partial
evaluation, a much simpler syntax can be achieved. C++ may be regarded as a
two-level language in which types are first-class values. Template
instantiation resembles an offline partial evaluator. This paper describes
preliminary work toward a single mechanism based on Partial Evaluation which
unifies generic programming, compile-time computation and code generation. The
language Catat is introduced to illustrate these ideas.Comment: 13 page
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