523 research outputs found

    Computations of Floer Homology for certain Lagrangian Tori in closed 4-manifolds

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    We compute the Lagrangian Floer cohomology groups of certain tori in closed simply connected symplectic 4-manifolds arising from Fintushel-Stern knot surgery. These manifolds are usually not symplectically aspherical. As a result of the computation we observe examples where HF(L0)HF(L1)HF(L_0)\cong HF(L_1) and L0L_0 and L1L_1 are smoothly isotopic but L0,L1L_0,L_1 are not symplectically isotopic and are distinguished by HF(L0,L1)HF(L_0,L_1).Comment: changes based on reviewer's comment

    A novel mobile communication system using Pulse Position based Chirp Spread Spectrum modulation

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    The paper presents a new mobile communication system based on Chirp Spread Spectrum (CSS) transmission. The downlink modulation scheme is extended with Pulse Position Modulation (PPM) to carry data for multiple mobile terminals simultaneously. The described novel mechanism ensures reliable and robust communication between the parties, especially for terminals moving with high speeds or at long range. Furthermore, the proposed system take care of the uplink communication as well, where Closed-Loop Power Control (CLPC) is applied to handle the near-far problem and improve the performance of the system. Based on the attributes of the proposed system the application area covers sensor networks, IoT applications and Industry 4.0 as general field of LPWAN, however, mobility of terminals also considered.Analytical investigations for downlink communication are described focusing on the instantaneous symbol-error rate and average SER in Rayleigh fading channel. The results show that the proposed Pulse Position based Chirp Spread Spectrum technique for Multiple Access (shortly PP-CSS-MA) allows higher data rates that is used for the multiple access feature. In addition, numerical results are presented as well, and they point out the benefits of the applied CLPC mechanism. Finally, considerations regarding to the implementation of the proposed communication system are described

    A novel mobile communication system using Pulse Position based Chirp Spread Spectrum modulation

    Get PDF
    The paper presents a new mobile communication system based on Chirp Spread Spectrum (CSS) transmission. The downlink modulation scheme is extended with Pulse Position Modulation (PPM) to carry data for multiple mobile terminals simultaneously. The described novel mechanism ensures reliable and robust communication between the parties, especially for terminals moving with high speeds or at long range. Furthermore, the proposed system take care of the uplink communication as well, where Closed-Loop Power Control (CLPC) is applied to handle the near-far problem and improve the performance of the system. Based on the attributes of the proposed system the application area covers sensor networks, IoT applications and Industry 4.0 as general field of LPWAN, however, mobility of terminals also considered.Analytical investigations for downlink communication are described focusing on the instantaneous symbol-error rate and average SER in Rayleigh fading channel. The results show that the proposed Pulse Position based Chirp Spread Spectrum technique for Multiple Access (shortly PP-CSS-MA) allows higher data rates that is used for the multiple access feature. In addition, numerical results are presented as well, and they point out the benefits of the applied CLPC mechanism. Finally, considerations regarding to the implementation of the proposed communication system are described

    A continuum path integral approach to the simulation of a unitary gas

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    This thesis presents an investigation by simulation of a unpolarized fermionic unitary gas system composed of two interacting fermionic species. While these species do not interact amongst themselves, they interact with each other using a pairwise zero-range delta function potential that has been tuned to unitarity i.e.the scattering length as=a_{s}=-\infty. A path integral Monte Carlo simulation of such a system is performed using an exact novel zero-range, delta function pair propagator which has been tuned to the unitary limit so that essentially all interactions amongst the interacting particles are comprised of s-wave interactions. This tuning in some sense yields the simplest imaginable interacting fermionic system which out to display features that would apply universally to interacting fermionic particles with particular interest within this field of study being in understanding the unitary BCS-BEC crossover. Numerical and ergodic challenges to sampling a divergent approximate path integral are discussed and solutions are proposed, implemented and explored. This thesis represents a step closer to this understanding by investigating this system with this novel propagator in a fixed-node path integral Monte Carlo framework and comparing to earlier work

    Optimal control inputs for fuel economy and emissions of a series hybrid electric vehicle

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    Hybrid electric vehicles offer significant fuel economy benefits, because battery and fuel can be used as complementing energy sources. This paper presents the use of dynamic programming to find the optimal blend of power sources, leading to the lowest fuel consumption and the lowest level of harmful emissions. It is found that the optimal engine behavior differs substantially to an on-line adaptive control system previously designed for the Lotus Evora 414E. When analyzing the trade-off between emission and fuel consumption, CO and HC emissions show a traditional Pareto curve, whereas NOx emissions show a near linear relationship with a high penalty. These global optimization results are not directly applicable for online control, but they can guide the design of a more efficient hybrid control system
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