1,893 research outputs found
Annual Survey of Virginia Law: Property Law
Numerous court decisions affecting property law in Virginia have been announced since the last edition of this portion of the annual survey. Significant decisions of the Supreme Court of Virginia, Virginia Court of Appeals and the Court of Appeals for the Fourth Circuit are discussed in Section I of this article. Furthermore, a prolific General Assembly has passed various legislation affecting property law ranging from condominiums to zoning. Significant legislation is discussed in Section II
Lineage-Aware Temporal Windows: Supporting Set Operations in Temporal-Probabilistic Databases
In temporal-probabilistic (TP) databases, the combination of the temporal and
the probabilistic dimension adds significant overhead to the computation of set
operations. Although set queries are guaranteed to yield linearly sized output
relations, existing solutions exhibit quadratic runtime complexity. They suffer
from redundant interval comparisons and additional joins for the formation of
lineage expressions. In this paper, we formally define the semantics of set
operations in TP databases and study their properties. For their efficient
computation, we introduce the lineage-aware temporal window, a mechanism that
directly binds intervals with lineage expressions. We suggest the lineage-aware
window advancer (LAWA) for producing the windows of two TP relations in
linearithmic time, and we implement all TP set operations based on LAWA. By
exploiting the flexibility of lineage-aware temporal windows, we perform direct
filtering of irrelevant intervals and finalization of output lineage
expressions and thus guarantee that no additional computational cost or buffer
space is needed. A series of experiments over both synthetic and real-world
datasets show that (a) our approach has predictable performance, depending only
on the input size and not on the number of time intervals per fact or their
overlap, and that (b) it outperforms state-of-the-art approaches in both
temporal and probabilistic databases
The Nonlinear Debye-Onsager Relaxation Effect in Weakly Ionized Plasmas
A weakly ionized plasma under the influence of a strong electric field is
considered. Supposing a local Maxwellian distribution for the electron momenta
the plasma is described by hydrodynamic equations for the pair distribution
functions. These equations are solved and the relaxation field is calculated
for an arbitrary field strength. It is found that the relaxation effect becomes
lower with increasing strength of the electrical field.Comment: 4 pages, 1 figur
Where to restore ecological connectivity? Detecting barriers and quantifying restoration benefits
Landscape connectivity is crucial for many ecological processes, including dispersal, gene flow, demographic rescue, and movement in response to climate change. As a result, governmental and non-governmental organizations are focusing efforts to map and conserve areas that facilitate movement to maintain population connectivity and promote climate adaptation. In contrast, little focus has been placed on identifying barriers—landscape features which impede movement between ecologically important areas—where restoration could most improve connectivity. Yet knowing where barriers most strongly reduce connectivity can complement traditional analyses aimed at mapping best movement routes. We introduce a novel method to detect important barriers and provide example applications. Our method uses GIS neighborhood analyses in conjunction with effective distance analyses to detect barriers that, if removed, would significantly improve connectivity. Applicable in least-cost, circuit-theoretic, and simulation modeling frameworks, the method detects both complete (impermeable) barriers and those that impede but do not completely block movement. Barrier mapping complements corridor mapping by broadening the range of connectivity conservation alternatives available to practitioners. The method can help practitioners move beyond maintaining currently important areas to restoring and enhancing connectivity through active barrier removal. It can inform decisions on trade-offs between restoration and protection; for example, purchasing an intact corridor may be substantially more costly than restoring a barrier that blocks an alternative corridor. And it extends the concept of centrality to barriers, highlighting areas that most diminish connectivity across broad networks. Identifying which modeled barriers have the greatest impact can also help prioritize error checking of land cover data and collection of field data to improve connectivity maps. Barrier detection provides a different way to view the landscape, broadening thinking about connectivity and fragmentation while increasing conservation options
About the Algebraic Solutions of Smallest Enclosing Cylinders Problems
Given n points in Euclidean space E^d, we propose an algebraic algorithm to
compute the best fitting (d-1)-cylinder. This algorithm computes the unknown
direction of the axis of the cylinder. The location of the axis and the radius
of the cylinder are deduced analytically from this direction. Special attention
is paid to the case d=3 when n=4 and n=5. For the former, the minimal radius
enclosing cylinder is computed algebrically from constrained minimization of a
quartic form of the unknown direction of the axis. For the latter, an
analytical condition of existence of the circumscribed cylinder is given, and
the algorithm reduces to find the zeroes of an one unknown polynomial of degree
at most 6. In both cases, the other parameters of the cylinder are deduced
analytically. The minimal radius enclosing cylinder is computed analytically
for the regular tetrahedron and for a trigonal bipyramids family with a
symmetry axis of order 3.Comment: 13 pages, 0 figure; revised version submitted to publication
(previous version is a copy of the original one of 2010
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