48,303 research outputs found

    Recent progress towards a chiral effective field theory for the NN system

    Full text link
    Since Weinberg's proposal two decades ago, chiral effective field theory in the NN sector has been developed and applied up to order O((Q/Mhi)4)O((Q/M_{hi})^4). In principle it could provide a model-independent description of nuclear force from QCD. However, in spite of its huge success, some open issues such as the renormalization group invariance and power counting, still remain to be solved. In this talk we refine the chiral effective field theory approach to the NN system based on a renormalization group analysis. Our results show that a truly model-independent description of NN system can be obtained by a new power counting which treats the subleading order corrections perturbatively.Comment: Contribution to the proceedings of the Seventh International Symposium on Chiral Symmetry in Hadrons and Nuclei, Beijing, October 2013. 4 pages, 1 figur

    Technique for extending the frequency range of digital dividers

    Get PDF
    A technique for extending the frequency range of a presettable digital divider is described. The conventional digital divider consists of several counter stages with the count of each stage compared to a preselected number. When the counts for all stages are equal to the preselected numbers, an output pulse is generated and all stages are reset. For high input frequencies, the least significant stage of the divider has to be reset in a very short time. This limits the frequency that can be handled by the conventional digital divider. This invention provides a technique in which the second least significant and higher stages are reset and the least significant stage is permitted to free-run. Hence, the time in which the reset operation can be performed is increased thereby extending the frequency range of the divider

    Estimation of Sorting Time for Arthropod Samples Collected with Tullgren Funnels

    Get PDF
    Arthropods were sorted from samples obtained with Tullgren funnels. Each sorter maintained a log of time per session and arthropods removed per session. Five individuals removed all arthropods from 12 separate samples and sorted them into previously designated class or ordinal taxa. Each sample was sorted by a single student. Students were allowed to develop their own approaches to sorting and do it as time permitted. Mean sorting rate per sample was 2.43 arthropods per minute, with a range of 1.42-5.64, while mean sorting rate for a sorting session was 3.41 specimens per minute. Specimen density was only weakly correlated with sort time. Fatigue did not appear to be a major factor in sorting rate, as indicated by the similarity of the linear and quadratic coefficients of determination for each sample

    Study of Permanent Magnet Focusing for Astronomical Camera Tubes

    Get PDF
    A design is developed of a permanent magnet assembly (PMA) useful as the magnetic focusing unit for the 35 and 70 mm (diagonal) format SEC tubes. Detailed PMA designs for both tubes are given, and all data on their magnetic configuration, size, weight, and structure of magnetic shields adequate to screen the camera tube from the earth's magnetic field are presented. A digital computer is used for the PMA design simulations, and the expected operational performance of the PMA is ascertained through the calculation of a series of photoelectron trajectories. A large volume where the magnetic field uniformity is greater than 0.5% appears obtainable, and the point spread function (PSF) and modulation transfer function(MTF) indicate nearly ideal performance. The MTF at 20 cycles per mm exceeds 90%. The weight and volume appear tractable for the large space telescope and ground based application

    Distributed MPC for coordinated energy efficiency utilization in microgrid systems

    Full text link
    To improve the renewable energy utilization of distributed microgrid systems, this paper presents an optimal distributed model predictive control strategy to coordinate energy management among microgrid systems. In particular, through information exchange among systems, each microgrid in the network, which includes renewable generation, storage systems, and some controllable loads, can maintain its own systemwide supply and demand balance. With our mechanism, the closed-loop stability of the distributed microgrid systems can be guaranteed. In addition, we provide evaluation criteria of renewable energy utilization to validate our proposed method. Simulations show that the supply demand balance in each microgrid is achieved while, at the same time, the system operation cost is reduced, which demonstrates the effectiveness and efficiency of our proposed policy.Accepted manuscrip

    Mathematical specifications of the Onboard Navigation Package (ONPAC) simulator (revision 1)

    Get PDF
    The mathematical theory of the computational algorithms employed in the onboard navigation package system is described. This system, which simulates an onboard navigation processor, was developed to aid in the design and evaluation of onboard navigation software. The mathematical formulations presented include the factorized UDU(T) form of the extended Kalman filter, the equations of motion of the user satellite, the user clock equations, the observation equations and their partial derivatives, the coodinate transformations, and the matrix decomposition algorithms
    corecore