6,352 research outputs found

    Benchmark generator for CEC 2009 competition on dynamic optimization

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    Evolutionary algorithms(EAs) have been widely applied to solve stationary optimization problems. However, many real-world applications are actually dynamic. In order to study the performance of EAs in dynamic environments, one important task is to develop proper dynamic benchmark problems. Over the years, researchers have applied a number of dynamic test problems to compare the performance of EAs in dynamic environments, e.g., the “moving peaks ” benchmark (MPB) proposed by Branke [1], the DF1 generator introduced by Morrison and De Jong [6], the singleand multi-objective dynamic test problem generator by dynamically combining different objective functions of exiting stationary multi-objective benchmark problems suggested by Jin and Sendhoff [2], Yang and Yao’s exclusive-or (XOR) operator [10, 11, 12], Kang’s dynamic traveling salesman problem (DTSP) [3] and dynamic multi knapsack problem (DKP), etc. Though a number of DOP generators exist in the literature, there is no unified approach of constructing dynamic problems across the binary space, real space and combinatorial space so far. This report uses the generalized dynamic benchmark generator (GDBG) proposed in [4], which construct dynamic environments for all the three solution spaces. Especially, in the rea

    Magnetic properties of the quasi-two-dimensional S = 1/2 Heisenberg antiferromagnet [Cu(pyz)2(HF2)]PF6

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    We report on high-field magnetization, specific-heat and electron spin resonance (ESR) studies of the quasi-two-dimensional spin-1/2 Heisenberg antiferromagnet [Cu(pyz)2(HF2)]PF6. The frequency-field diagram of ESR modes below TN = 4.38 K is described in the frame of the meanfield theory, confirming a collinear magnetic structure with an easy-plane anisotropy. The obtained results allowed us to determine the anisotropy/exchange interaction ratio, A/J = 0.003, and the upper limit for the inter/intra-plane exchange-interaction ratio, J'/J = 1/16. It is argued that despite the onset of 3D long-range magnetic ordering the magnetic properties of this material (including high-magnetic-field magnetization and non-monotonic field dependence of the Neel temperature) are strongly affected by two-dimensional spin correlations.Comment: 5 pages, 7 figure

    Lazy Abstraction-Based Controller Synthesis

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    We present lazy abstraction-based controller synthesis (ABCS) for continuous-time nonlinear dynamical systems against reach-avoid and safety specifications. State-of-the-art multi-layered ABCS pre-computes multiple finite-state abstractions of varying granularity and applies reactive synthesis to the coarsest abstraction whenever feasible, but adaptively considers finer abstractions when necessary. Lazy ABCS improves this technique by constructing abstractions on demand. Our insight is that the abstract transition relation only needs to be locally computed for a small set of frontier states at the precision currently required by the synthesis algorithm. We show that lazy ABCS can significantly outperform previous multi-layered ABCS algorithms: on standard benchmarks, lazy ABCS is more than 4 times faster

    The Role of Diffusion in ISOL Targets for the Production of radioactive Ions Beams

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    On line isotope separation techniques (ISOL) for production of ion beams of short-lived radionuclides require fast separation of nuclear reaction products from irradiated target materials followed by a transfer into an ion source. As a first step in this transport chain the release of nuclear reaction products from refractory metals has been studied systematically and will be reviewed. High-energy protons (500-1000MeV) produce a large number of radionuclides in irradiated materials via the nuclear reactions spallation, fission and fragmentation. Foils and powder of Re, W, Ta, Hf, Mo, Nb, Zr, Y, Ti and C were irradiated with protons (600-1000MeV) at the Dubna synchrocyclotron and at the CERN PS-booster to produce different nuclear reaction products. The main topic of the paper is the determination of diffusion coefficients of the nuclear reaction products in the target matrix, data evaluation and a systematic interpretation of the data. The influence of the ionic radius of the diffusing species and the lattice type of the host material used as matrix or target on the diffusion will be evaluated from these systematics. Special attention was directed to the release of group I, II and III-elements. Arrhenius plots lead to activation energies of the diffusion process

    In-medium nucleon-nucleon potentials in configuration space

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    Based on the thermodynamic Green function approach two-nucleon correlations in nuclear matter at finite temperatures are revisited. To this end, we derive phase equivalent effective rr-space potentials that include the effect of the Pauli blocking at a given temperature and density. These potentials enter into a Schr\"odinger equation that is the rr-space representation of the Galitskii-Feynman equation for two nucleons. We explore the analytical structure of the equation in the complex kk-plane by means of Jost functions. We find that despite the Mott effect the correlation with deuteron quantum numbers are manifested as antibound states, i.e., as zeros of the Jost function on the negative imaginary axis of the complex momentum space. The analysis presented here is also suited for Coulombic systems.Comment: 6 pages, 1 table, 4 figure

    Willow on yellowstone's northern range: Evidence for a trophic cascade?

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    Reintroduction of wolves (Canis lupus) to Yellowstone National Park in 1995-1996 has been argued to promote a trophic cascade by altering elk (Cervus elaphus) density, habitat-selection patterns, and behavior that, in turn, could lead to changes within the plant communities used by elk. We sampled two species of willow (Salix boothii and S. geyeriana) on the northern winter range to determine whether (1) there was quantitative evidence of increased willow growth following wolf reintroduction, (2) browsing by elk affected willow growth, and (3) any increase in growth observed was greater than that expected by climatic and hydrological factors alone, thereby indicating a trophic cascade caused by wolves. Using stem sectioning techniques to quantify historical growth patterns we found an approximately twofold increase in stem growth-ring area following wolf reintroduction for both species of willow. This increase could not be explained by climate and hydrological factors alone; the presence of wolves on the landscape was a significant predictor of stem growth above and beyond these abiotic factors. Growth-ring area was positively correlated with the previous year's ring area and negatively correlated with the percentage of twigs browsed from the stem during the winter preceding growth, indicating that elk browse impeded stem growth. Our results are consistent with the hypothesis of a behaviorally mediated trophic cascade on Yellowstone's northern winter range following wolf reintroduction. We suggest that the community-altering effects of wolf restoration are an endorsement of ecological-process management in Yellowstone National Park

    Effect of Test Sequence on Maximal Anaerobic and Aerobic Power Achievement in Adults

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    International Journal of Exercise Science 14(4): 657-665, 2021. The purpose of this study was to examine the effect of test sequence on adults’ ability to achieve maximal aerobic and anaerobic power during a single assessment visit. Forty-one adults (24 men, 17 women; 22.0 ± 1.8 years) completed two baseline visits in randomized order consisting of either a maximal oxygen consumption (V̇O2max) or Wingate anaerobic test (WAnT). The subsequent experimental visit consisted of both V̇O2max and WAnT in randomized order separated by 20 minutes of rest. Mixed-model ANOVAs compared baseline and experimental performance between and within groups. Chi Squared Goodness of Fit tests determined if test sequence significantly affected V̇O2max criteria achievement. Significant interaction effects were observed for relative V̇O2max (p = 0.005), RER (p \u3c 0.001), and exercise time (p = 0.022). Within WAnT/V̇O2max subjects, these values significantly decreased from baseline to experimental tests. No differences were found for WAnT values. During the experimental session, 50% of subjects who performed WAnt/V̇O2max and 81% of subjects who performed V̇O2max/WAnT achieved a valid V̇O2max. Chi squared analysis found the change to be significant in WAnT/V̇O2max subjects only. Therefore, performing the WAnT before V̇O2max sequence significantly reduced the percent of subjects who achieved V̇O2max criteria. These findings indicate that the sequence of V̇O2max testing before a WAnT allowed maximal results similar to expected baseline values

    Characterizing Nontarget Species Use at Bait Sites for White-Tailed Deer

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    Baiting white-tailed deer (Odocoileus virginianus) has evolved into a controversial issue of wildlife management. During August–September 2012, we established a grid of 64 cameras in the Upper Peninsula of Michigan at sites baited with corn that simulated legal bait sites for white-tailed deer to characterize presence, diversity, and frequency of species use. We detected \u3e20 species of wildlife that visited bait sites. We categorized 3,177 of 11,194 images as independent detections (i.e., species detected \u3e1 hour apart). White-tailed deer had the greatest detection rate (47%), but overall detections of nontarget species was slightly greater (53%). Most frequent nontarget species detected were northern raccoons (Procyon lotor) and American black bears (Ursus americanus). Wildlife officials should consider the potential effects of baiting on species’ ecology and the potential for disease transmission that high-use of bait sites by nontarget species present

    Medical Diagnostic Ultrasound

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    As early as 250 BCE, captains of ancient Greek ships would drop lead weights overboard to provide an estimate of water depth. They would count until those “sounders” produced an audible thud and in that way measure the propagation time of the falling weight. Even though the practice has given way to other technologies for sounding, one still hears the phrase “to sound something out.” In the 17th century, Isaac Newton became fascinated with sound propagation and was one of the first to describe relationships between the speed of sound and measurable properties of the propagation medium, such as density and pressure. Section 8 of Book 2 of the Principia, for example, is devoted to “the motion propagated through fluids” and includes the proposition that the sound speed is given by the square root of the ratio of the “elastic force” to the density of the medium
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