629 research outputs found

    User-assisted reverse modeling with evolutionary algorithms

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    This paper presents a system for user-assisted reverse modeling: from digitized point-cloud to solid models ready to be used in a CAD modeling system. Our approach consists in the following steps: segmentation, fitting, and constructive model discovery. Each of these steps are based on evolutionary algorithms. The obtained objects can then be further edited or parameterized by users and fitted to adapt their shape to different point-clouds

    Analysis of the first gigantic jet recorded over continental North America

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    [1] Two low-light cameras near Marfa, Texas, recorded a gigantic jet over northern Mexico on 13 May 2005 at approximately 0423:50 UTC. Assuming that the farthest of two candidate storm systems was its source, the bright lower channel ended in a fork at around 50–59 km height with the very dim upper branches extended to 69–80 km altitude. During the time window containing the jet, extremely low frequency magnetic field recordings show that there was no fast charge moment change larger than 50 coulomb times kilometers (C km) but there was a larger and slower charge moment change of 520 C km over 70 ms. The likely parent thunderstorm was a high-precipitation supercell cluster containing a persistent mesocyclone, with radar echo tops of at least 17 km. However, photogrammetric analysis suggests that the gigantic jet occurred over the forward flank downdraft region with echo tops of 14 km. This part of the supercell may have had an inverted-polarity charge configuration as evidenced by positive cloud-to-ground lightning flashes (+CG) dominating over negative flashes (-CG), while -CGs occurred under the downwind anvil. Four minutes before the gigantic jet, -CG activity practically ceased in this area, while +CG rates increased, culminating during the 20 s leading up to the gigantic jet with four National Lightning Detection Network–detected +CGs. A relative lull in lightning activity of both polarities was observed for up to 1.5 min after the gigantic jet. The maturing storm subsequently produced 30 sprites between 0454 and 0820 UTC, some associated with extremely large impulse charge moment change values.Peer ReviewedPostprint (published version

    Comparative analysis of forest lands cadastral appraisal estimated with regards to wood and food resources

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    Cadastral appraisal of forest fund is one of the topical challenges of modern natural resource management. The paper delivers comparison of different approaches to cadastral appraisal of forest lands. The authors suggest a uniformed model to compare objectively and choose the most effective use of parcels

    Comparative analysis of forest lands cadastral appraisal estimated with regards to wood and food resources

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    Cadastral appraisal of forest fund is one of the topical challenges of modern natural resource management. The paper delivers comparison of different approaches to cadastral appraisal of forest lands. The authors suggest a uniformed model to compare objectively and choose the most effective use of parcels

    CHANGE OF DYNAMICS OF SALES AND IMPORT OF MOTOR VEHICLES IN THE RUSSIAN MARKET UNDER THE INFLUENCE OF INSTABILITY OF THE EXTERNAL ENVIRONMENT

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    The situation with imposition of economic sanctions of the west countries West to Russia affected also on development of the Russian market of motor vehicles. In the article key parameters and the prospects of development of the Russian motor vehicles market (including its import component) in the conditions of the unstable external environment are generalized and analysed

    Investigation of initiation of gigantic jets connecting thunderclouds to the ionosphere

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    The initiation of giant electrical discharges called as "gigantic jets" connecting thunderclouds to the ionosphere is investigated by numerical simulation method in this paper. Using similarity relations, the triggering conditions of streamer formation in laboratory situations are extended to form a criterion of initiation of gigantic jets. The energy source causing a gigantic jet is considered due to the quasi-electrostatic field generated by thunderclouds. The electron dynamics from ionization threshold to streamer initiation are simulated by the Monte Carlo technique. It is found that gigantic jets are initiated at a height of ~18-24 km. This is in agreement with the observations. The method presented in this paper could be also applied to the analysis of the initiation of other discharges such as blue jets and red sprites.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

    Higher Renal Replacement Therapy Dose Delivery Influences on Drug Therapy

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    Higher doses of renal replacement therapy have profound effects on pharmacotherapy, yet little research has been conducted in this area. High-volume renal replacement therapies influence both the pharmacokinetic and the pharmacodynamic profiles of all drugs administered to these critically ill patients. Intermittent high-dose “hybrid” hemodialysis therapies remove drugs to a much different degree than standard thrice-weekly hemodialysis, yet pharmacokinetic studies have not been performed in patients receiving these therapies. High-volume continuous renal replacement therapies offer dosing challenges not seen with standard low-dose therapies. This article describes the pharmacokinetic and pharmacodynamic issues presented by high-volume renal replacement therapies. Given the importance that pharmacotherapy has on optimal patient outcomes, a better understanding of the influence that high-volume renal replacement therapy has on drugs is essential if these high volume therapies are to be used successfully in the intensive care unit.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75000/1/j.1525-1594.2003.07283.x.pd

    Comparative analysis of land management in the world

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    The article studies and compares agricultural land management performance criteria applied in different countries worldwide. It is stated that there are different definitions and classifications of agricultural lands in different countries, which implies different indicators of land use efficiency. Sometimes these indicators cannot be correlated or compared with each other. It is suggested using such criteria as arable land area and fodder yield per 1 ha as the most unified and appropriate ones

    Direct calorimetric measurements of isothermal entropy change on single crystal W-type hexaferrites at the spin reorientation transition

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    We report on the magnetic field induced isothermal entropy change, \Delta s(Ha, T), of W-type ferrite with CoZn substitution. Entropy measurements are performed by direct calorimetry. Single crystals of the composition BaCo0.62_0.62Zn1.38_1.38Fe16_16O27_27, prepared by the flux method, are measured at different fixed temperatures under an applied field perpendicular and parallel to the c axis. At 296 K one deduces a value of K1_1 = 8.7 \times 10^{4} J m3^-3 for the first anisotropy constant, which is in good agreement with the literature. The spin reorientation transition temperature is estimated to take place between 200 and 220 K

    Hybrid Function Representation with Distance Properties

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    This paper describes a novel framework allowing for a hybrid representation of heterogeneous objects. We consider the advantages and drawbacks of the conventional representations based on scalar fields of different kinds. The main result is introducing a hybrid representation called Hybrid Function Representation (HFRep) that preserves the advantages of the Function Representation (FRep) and Signed Distance Fields (SDFs) without their drawbacks. This new representation allows for obtaining a continuous smooth distance field in the Euclidean space for the FRep. We present the mathematical basics for our approach that uses the Discrete Distance Transform (DDT) and a step-function. The procedure for generation HFRep using continuous interpolation and smoothing techniques are also described. A few examples show how the approach works in practice
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