2,057 research outputs found

    An evolutionary approach to vehicle routing problem with dynamic time and precedence relationships.

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    The vehicle routing problem (VRP) deals with the allocation of vehicles to the customers that have requested products from a main depot. When the postal service, the bus system, or trucking industry plan for their everyday tasks of delivery goods or providing basic transportation needs to people, they are attempting to solve the VRP. However, this can be a daunting task because the VRP is computationally intensive. In this paper, we will address two areas of the VRP that have been relatively unexplored by previous research, yet play an important part in real-world_ applications of the VRP as well as define and create an evolutionary approach based on these ideas. The first area that we will address deals with the lack of real-world data sets when calculating the times between customers. This new implementation will allow the algorithm to calculate the actual time between customers at a given time of day, thus providing a final solution that is closer to a true optimal set of routes. The second addition to the VRP model will be contributed in the area of precedence relationships. These relationships often exist in real-world applications and are necessary in order ��o help the algorithm establish routes that are desired by the customers. The evolutionary approach provides global optimization insight to the problem

    SwarmExec: A Prolog-Based Execution Engine for a Shared-Database Language with Visualization Capabilities

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    We have implemented a Prolog execution engine for the shared-database language Swarm extended with visualization capabilities. We call this execution engine SwarmExec. SwarmExec runs on a Macintosh Iifx under Advanced A.I. Systems\u27 Prolog (AAIS) and communicates over an Ethernet connection with a Silicon Graphics Personal Iris which serves as a graphical engine and renders the visualizations. This paper describes the major design elements of SwarmExec. A basic familiarity with Swarm and its visualization extensions is assumed; the interested reader is referred to the referenced papers

    On Deriving Distributed Programs from Formal Specifications of Functional Requirements and Architectural Constraints

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    This design of distributed programs is a difficult task which can greatly benefit from the application of formal methods. Since design solutions are determined not only by functional requirements imposed by the application but also by the structure and behavior of the underlying hardware architecture, a complete formal treatment of the program derivation process becomes a significant challenge. The common approach is to state with a formal specification of the functional requirements and to derive the desired program through systematic refinements which factor in the architectural constraints informally, in an ad-hoc manner. This paper shows how one can employ a single specification method (program0wide assertions) to express both functional requirements and architectural constraints. A distributed simulation problem is used to illustrate a formal strategy for deriving a distributed program from assertions about its functionality and the constraints imposed by the choice of underlying architecture

    Metamaterials proposed as perfect magnetoelectrics

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    Magnetoelectric susceptibility of a metamaterial built from split ring resonators have been investigated both experimentally and within an equivalent circuit model. The absolute values have been shown to exceed by two orders of magnitude that of classical magnetoelectric materials. The metamaterial investigated reaches the theoretically predicted value of the magnetoelectric susceptibility which is equal to the geometric average of the electric and magnetic susceptibilities.Comment: 5 pages, 3 figure

    Metamaterials: optical activity without chirality

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    We report that the classical phenomenon of optical activity, which is traditionally associated with chirality (helicity) of organic molecules, proteins, and inorganic structures, can be observed in artificial planar media which exhibit neither 3D nor 2D chirality. We observe the effect in the microwave and optical parts of the spectrum at oblique incidence to regular arrays of nonchiral subwavelength metamolecules in the form of strong circular dichroism and birefringence indistinguishable from those of chiral three-dimensional media

    Negative index in chiral metamaterials

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    We demonstrate that planar metamaterial lacking of mirror symmetry shows asymmetric transmission of terahertz waves and bands of positive, negative and zero phase and group velocities indicating a polarization sensitive negative index and slow-light media

    Twisted split-ring-resonator photonic metamaterial with huge optical activity

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    Coupled split-ring-resonator metamaterials have previously been shown to exhibit large coupling effects, which are a prerequisite for obtaining large effective optical activity. By a suitable lateral arrangement of these building blocks, we completely eliminate linear birefringence and obtain pure optical activity and connected circular optical dichroism. Experiments at around 100-THz frequency and corresponding modeling are in good agreement. Rotation angles of about 30 degrees for 205nm sample thickness are derived.Comment: 6 pages, 4 figure

    Nonlinear Elasticity of Single Collapsed Polyelectrolytes

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    Nonlinear elastic responses of short and stiff polyelectrolytes are investigated by dynamic simulations on a single molecule level. When a polyelectrolyte condensate undergoes a mechanical unfolding, two types of force-extension curves, i.e., a force plateau and a stick-release pattern, are observed depending on the strength of the electrostatic interaction. We provide a physical interpretation of such force-extension behavior in terms of intramolecular structures of the condensates. We also describe a charge distribution of condensed counterions onto a highly stretched polyelectrolyte, which clarifies a formation of one-dimensional strongly correlated liquid at large Coulomb coupling regime where a stick-release pattern is observed. These findings may provide significant insights into the relationship between a molecular elasticity and a molecular mechanism of like-charge attractions observed in a wide range of charged biopolymer systems.Comment: 5pages, 5figure

    ПОСТАТЬ КОРОЛЯМІХАЛА КОРИБУТА ВИШНЕВЕЦЬКОГО У ЗАГАЛЬНИХ КУРСАХ З ІСТОРІЇ ПОЛЬЩІ ХІХ –ПОЧАТКУ ХХ СТ.

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    Розглянутооцінку діяльностіМіхалаВишневецького у працяхз історіїПольщіХІХ– початку ХХ ст. Виокремлено ключові епізоди часів його правління в Речі Посполитій, на яких зосереджена освновна увага польських істориків.The assessment ofMikhalVyshnevetski’s activity in theworks of Polish history of the 19th – early 20th century is considered. The key episodes of the time of his government in Polish-Lithuanian Commonwealth,towhich Polish historiansmain attention is paid, are distinguished
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