4,985 research outputs found
Unfolding Orthogonal Polyhedra with Quadratic Refinement: The Delta-Unfolding Algorithm
We show that every orthogonal polyhedron homeomorphic to a sphere can be
unfolded without overlap while using only polynomially many (orthogonal) cuts.
By contrast, the best previous such result used exponentially many cuts. More
precisely, given an orthogonal polyhedron with n vertices, the algorithm cuts
the polyhedron only where it is met by the grid of coordinate planes passing
through the vertices, together with Theta(n^2) additional coordinate planes
between every two such grid planes.Comment: 15 pages, 10 figure
Spontaneous currents in a bosonic ring
Nonequilibrium dynamics of noninteracting bosons in a one-dimensional
ring-shaped lattice is studied by means of the Kinetic Monte Carlo method. The
system is approximated by the classical XY model (the kinetic term is
neglected) and then the simulations are performed for the planar classical
spins. We study the dynamics that follows a finite-time quench to zero
temperature. If the quench is slow enough the system can equilibrate and
finally reaches the ground state with uniform spin alignment. However, we show
that if the quench is faster than the relaxation rate, the system can get
locked in a current-carrying metastable state characterized by a nonzero
winding number. We analyze how the zero-temperature state depends on the quench
rate.Comment: 6 pages, 3 figure
Lightweight Multilingual Software Analysis
Developer preferences, language capabilities and the persistence of older
languages contribute to the trend that large software codebases are often
multilingual, that is, written in more than one computer language. While
developers can leverage monolingual software development tools to build
software components, companies are faced with the problem of managing the
resultant large, multilingual codebases to address issues with security,
efficiency, and quality metrics. The key challenge is to address the opaque
nature of the language interoperability interface: one language calling
procedures in a second (which may call a third, or even back to the first),
resulting in a potentially tangled, inefficient and insecure codebase. An
architecture is proposed for lightweight static analysis of large multilingual
codebases: the MLSA architecture. Its modular and table-oriented structure
addresses the open-ended nature of multiple languages and language
interoperability APIs. We focus here as an application on the construction of
call-graphs that capture both inter-language and intra-language calls. The
algorithms for extracting multilingual call-graphs from codebases are
presented, and several examples of multilingual software engineering analysis
are discussed. The state of the implementation and testing of MLSA is
presented, and the implications for future work are discussed.Comment: 15 page
Lightweight Call-Graph Construction for Multilingual Software Analysis
Analysis of multilingual codebases is a topic of increasing importance. In
prior work, we have proposed the MLSA (MultiLingual Software Analysis)
architecture, an approach to the lightweight analysis of multilingual
codebases, and have shown how it can be used to address the challenge of
constructing a single call graph from multilingual software with mutual calls.
This paper addresses the challenge of constructing monolingual call graphs in a
lightweight manner (consistent with the objective of MLSA) which nonetheless
yields sufficient information for resolving language interoperability calls. A
novel approach is proposed which leverages information from a
compiler-generated AST to provide the quality of call graph necessary, while
the program itself is written using an Island Grammar that parses the AST
providing the lightweight aspect necessary. Performance results are presented
for a C/C++ implementation of the approach, PAIGE (Parsing AST using Island
Grammar Call Graph Emitter) showing that despite its lightweight nature, it
outperforms Doxgen, is robust to changes in the (Clang) AST, and is not
restricted to C/C++.Comment: 10 page
Real-time dynamic articulations in the 2-D waveguide mesh vocal tract model
Time domain articulatory vocal tract modeling in one-dimensional (1-D) is well established. Previous studies into two-dimensional (2-D) simulation of wave propagation in the vocal tract have shown it to present accurate static vowel synthesis. However, little has been done to demonstrate how such a model might accommodate the dynamic tract shape changes necessary in modeling speech. Two methods of applying the area function to the 2-D digital waveguide mesh vocal tract model are presented here. First, a method based on mapping the cross-sectional area onto the number of waveguides across the mesh, termed a widthwise mapping approach is detailed. Discontinuity problems associated with the dynamic manipulation of the model are highlighted. Second, a new method is examined that uses a static-shaped rectangular mesh with the area function translated into an impedance map which is then applied to each waveguide. Two approaches for constructing such a map are demonstrated; one using a linear impedance increase to model a constriction to the tract and another using a raised cosine function. Recommendations are made towards the use of the cosine method as it allows for a wider central propagational channel. It is also shown that this impedance mapping approach allows for stable dynamic shape changes and also permits a reduction in sampling frequency leading to real-time interaction with the model
Thermal robustness of multipartite entanglement of the 1-D spin 1/2 XY model
We study the robustness of multipartite entanglement of the ground state of
the one-dimensional spin 1/2 XY model with a transverse magnetic field in the
presence of thermal excitations, by investigating a threshold temperature,
below which the thermal state is guaranteed to be entangled. We obtain the
threshold temperature based on the geometric measure of entanglement of the
ground state. The threshold temperature reflects three characteristic lines in
the phase diagram of the correlation function. Our approach reveals a region
where multipartite entanglement at zero temperature is high but is thermally
fragile, and another region where multipartite entanglement at zero temperature
is low but is thermally robust.Comment: Revised, 11 pages, 7 figure
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Low temperatures impact species distributions of jumping spiders across a desert elevational cline.
Temperature is known to influence many aspects of organisms and is frequently linked to geographical species distributions. Despite the importance of a broad understanding of an animal's thermal biology, few studies incorporate more than one metric of thermal biology. Here we examined an elevational assemblage of Habronattus jumping spiders to measure different aspects of their thermal biology including thermal limits (CTmin, CTmax), thermal preference, V̇CO2 as proxy for metabolic rate, locomotor behavior and warming tolerance. We used these data to test whether thermal biology helped explain how species were distributed across elevation. Habronattus had high CTmax values, which did not differ among species across the elevational gradient. The highest-elevation species had a lower CTmin than any other species. All species had a strong thermal preference around 37 °C. With respect to performance, one of the middle elevation species was significantly less temperature-sensitive in metabolic rate. Differences between species with respect to locomotion (jump distance) were likely driven by differences in mass, with no differences in thermal performance across elevation. We suggest that Habronattus distributions follow Brett's rule, a rule that predicts more geographical variation in cold tolerance than heat. Additionally, we suggest that physiological tolerances interact with biotic factors, particularly those related to courtship and mate choice to influence species distributions. Habronattus also had very high warming tolerance values (> 20 °C, on average). Taken together, these data suggest that Habronattus are resilient in the face of climate-change related shifts in temperature
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