218 research outputs found

    Frequency shifts and relaxation rates for spin 1/2 particles moving in electromagnetic fields

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    We discuss the behaviour of the Larmor frequency shift and the longitudinal relaxation rate due to non-uniform electromagnetic fields on an assembly of spin 1/2 particles, in adiabatic and nonadiabatic regimes. We also show some general relations between the various frequency shifts and between the frequency shifts and relaxation rates. The remarkable feature of all our results is that they were obtained without any specific assumptions on the explicit form of the correlation functions of the fields. Hence, we expect that our results are valid both for diffusive and ballistic regime of motion and arbitrary cell shapes and surface scattering. These results can then be applied to a wide variety of realistic systems

    Supply Chain Analysis of Prawn in Misamis Occidental, Philippines

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    This study analyses the existing supply chains of the prawn industry in Misamis Occidental, Philippines. Specifically, the study sought to provide an overview of the situation of prawn growers and traders in the province for a better government support and to enable sustainability in the supply chain. A tracer methodology was carried out using the structured survey questionnaire among the respondents supplemented with focus group discussion (FGD) among local officials in the community. Major players were in Bonifacio, Tangub, and Ozamis. The supply chain of Bonifacio was identified as the most profitable while that of Ozamis City was found to be the most efficient chain. Prawn traders were rated high in flexibility, responsiveness, and concern on product and process quality compared to prawn growers. Traders reap also greater profitability. However, both prawn growers and traders shared similar critical logistics issues on environmental concerns. Certain inefficiencies were also identified in the study, such as poor farm-to-market road, lack or absence of market weight standards, asymmetric market information, high transaction cost, and determination of the selling price based on average body weight which may not be accurate and may prove disadvantageous to prawn growers. The following recommendations are formulated: (1) producers shall be empowered to push for standardized price determination; (2) employ more labor solely for sorting; (3) strengthen government program through agri-fishery infrastructure; (4) provide trainings and financial and technical assistance on water pollution management; (5) promote and support green-technology by integrating saline-tolerant tilapia/bangus in prawn culture; (6) organize cooperative; (7) have market-oriented framework of development; and (8) strongly rationalize fisheries ordinances with implementation of FAO 166

    Constraining short-range spin-dependent forces with polarized helium 3 at the Laue-Langevin Institute

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    We have searched for a short-range spin-dependent interaction mediated by a hypothetical light scalar boson with CP-violating couplings to the neutron using the spin relaxation of hyperpolarized 3^3He. The walls of the 3^3He cell would generate a depolarizing pseudomagnetic field.Comment: Twelfth Conference on the Intersections of Particle and Nuclear Physics (CIPANP2015), Vail Marriott Mountain Resort, Vail, Colorado, US

    Short-term changes in particulate fluxes measured by drifting sediment traps during end summer oligotrophic regime in the NW Mediterranean Sea

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    Short-term changes in the flux of particulate matter were determined in the central north western Mediterranean Sea (near DYFAMED site) using drifting sediment traps at 200 m depth in the course of the DYNAPROC 2 cruise (14 September–17 October 2004). In this period of marked water column stratification, POC fluxes varied by an order of magnitude, in the range of 0.03–0.29 mgC m<sup>−2</sup> h<sup>−1</sup> over the month and showed very rapid and high variations. Particulate carbon export represented less than 5% of integrated primary production, suggesting that phytoplankton production was essentially sustained by internal recycling of organic matter and retained within the photic zone. While PON and POP fluxes paralleled one another, the elemental ratios POC/PON and POC/POP, varied widely over short-term periods. Values of these ratios generally higher than the conventional Redfield ratio, together with the very low chlorophyll a flux recorded in the traps (mean 0.017 ÎŒg m<sup>−2</sup> h<sup>−1</sup>), and the high phaeopigment and acyl lipid hydrolysis metabolite concentrations of the settling material, indicated that the organic matter reaching 200 m depth was reworked (by grazing, fecal pellets production, degradation) and that algal sinking, dominated by nano- and picoplankton, made a small contribution to the downward flux. Over time, the relative abundance of individual lipid classes in organic matter (OM) changed from glycolipids-dominated to neutral (wax esters, triacylglycerols) and phospholipids-dominated, suggesting ecosystem maturation as well as rapid and continual exchanges between dissolved, suspended and sinking pools. Our most striking result was documenting the rapid change in fluxes of the various measured parameters. In the situation encountered here, with dominant regenerated production, a decrease of fluxes was noticed during windy periods (possibly through reduction of grazing). But fluxes increased as soon as calm conditions settle

    Continuous approximate synthesis of planar function-generators minimising the design error

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    It has been observed in the literature that as the cardinality of the prescribed discrete input-output data set increases, the corresponding four-bar linkages that minimise the Euclidean norm of the design and structural errors tend to converge to the same linkage. The important implication is that minimising the Euclidean norm, or any p-norm, of the structural error, which leads to a nonlinear least-squares problem requiring iterative solutions, can be accomplished implicitly by minimising that of the design error, which leads to a linear least-squares problem that can be solved directly. Apropos, the goal of this paper is to take the first step towards proving that as the cardinality of the data set tends towards infinity the observation is indeed true. In this paper we will integrate the synthesis equations in the range between minimum and maximum input values, thereby reposing the discrete approximate synthesis problem as a continuous one. Moreover, we will prove that a lower bound of the Euclidean norm, and indeed of any p-norm, of the design error for planar RRRR function-generating linkages exists and is attained with continuous approximate synthesis

    Re-entrant spin glass and magnetoresistance in Co_{0.2}Zn_{0.8}Fe_{1.6}Ti_{0.4}O_4 spinel oxide

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    We have investigated the static and dynamic response of magnetic clusters in Co_{0.2}Zn_{0.8}Fe_{1.6}Ti_{0.4}O_4 spinel oxide, where a sequence of magnetic phase transitions, i.e., paramagnetic (PM) to ferromagnetic at T_{C} ≀\leq 270K and ferromagnetic to canted spin glass state at T_f \leq$ 125K is observed

    Pareto Optimality and Multiobjective Trajectory Planning for a 7-DOF Redundant Manipulator

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    This paper presents a novel approach to solve multiobjective robotic trajectory planning problems. It proposes to find the Pareto optimal set, rather than a single solution usually obtained through scalarization, e.g., weighting the objective functions. Using the trajectory planning problem for a redundant manipulator as part of a captive trajectory simulation system, the general discrete dynamic programming (DDP) approximation method presented in our previous work is shown to be a promising approach to obtain a close representation of the Pareto optimal set.When compared with the set obtained by varying the weights, the results confirm that the DDP approximation method can find approximate Pareto objective vectors, where the weighting method fails, and can generally provide a closer representation of the actual Pareto optimal set

    A Method for Clustering and Cooperation in Wireless Multimedia Sensor Networks

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    Wireless multimedia sensor nodes sense areas that are uncorrelated to the areas covered by radio neighbouring sensors. Thus, node clustering for coordinating multimedia sensing and processing cannot be based on classical sensor clustering algorithms. This paper presents a clustering mechanism for Wireless Multimedia Sensor Networks (WMSNs) based on overlapped Field of View (FoV) areas. Overlapping FoVs in dense networks cause the wasting of power due to redundant area sensing. The main aim of the proposed clustering method is energy conservation and network lifetime prolongation. This objective is achieved through coordination of nodes belonging to the same cluster to perform assigned tasks in a cooperative manner avoiding redundant sensing or processing. A paradigm in this concept, a cooperative scheduling scheme for object detection, is presented based on the proposed clustering method

    A discrete dynamic programming approximation to the multiobjective deterministic finite horizon optimal control problem

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    This paper addresses the problem of finding an approximation to the minimal element set of the objective space for the class of multiobjective deterministic finite horizon optimal control problems. The objective space is assumed to be partially ordered by a pointed convex cone containing the origin. The approximation procedure consists of a two-step discretization in time and state space. Following the first-order time discretization, the dynamic programming principle is used to find the multiobjective discrete dynamic programming equation equivalent to the resulting discrete multiobjective optimal control problem. The multiobjective discrete dynamic programming equation is finally discretized in the state space. The convergence of the approximation for both discretization steps is discussed
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