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Namal Suneth Ahmad Ijaz Saud Saad Jokinen Markku Gurtov Andrei 《Wireless Networks》2016,22(2):663-677
Wireless Networks - The static conventional network architecture is ill-suited to the growing management complexity and highly dynamic wireless network topologies. Software Defined Radio systems... 相似文献
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Femtocells are commissioned in wide range of commercial systems, such as CDMA, GSM, LTE, Wi-Fi, and WiMAX, and offer economically viable solutions to improve network scalability and indoor coverage. The ability to offer multitude of context-aware and value added services, and per-user customization have caught world-wide research interest on femtocells. In this article, we have investigated the feasibility to use femtocells as short-range mobile base stations, and discussed the demanding architectural requirements and challenges. The protocol stack on legacy femtocells must be modified to realize mobility. Mobility introduces new challenges in security and user privacy. Firstly, we analyze several candidate mobility protocols that are deployable on Mobile Femtocells (MFs). Among them, Host Identity Protocol (HIP) was chosen due to enhanced support in flexible mobility, security and end-user privacy. Secondly, we propose the indispensable modifications that enable device mobility, and the suitable transport architecture options based on direct IP links and relay chains. Finally, with the simulation results, the proposal is verified, and the architectural options are evaluated. That, in turn, proves the proposed mobility protocol has low latency in location locking with respect to another competing protocol and low resource utilization as it is depicted from mean round trip time. 相似文献
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Khagendra P. Bhandari Fadhil K. Alfadhili Ebin Bastola Suneth C. Watthage Zhaoning Song Geethika K. Liyanage Adam J. Phillips Michael J. Heben Randy J. Ellingson 《Progress in Photovoltaics: Research and Applications》2020,28(10):1024-1033
We fabricate and characterize methylammonium lead halide perovskite film as a novel back contact to CdTe thin‐film solar cells. We apply ~0.75 μm perovskite film at the interface of CdCl2‐activated and Cu‐doped CdTe surface and complete the device with Au back contact. We use Cu/Au back contact as a reference to compare results with novel back contact. Our investigation shows that incorporation of thin layer of perovskite film before the back contact metal reduces back contact barrier effect and improves fill factor (FF) and open‐circuit voltage (VOC) of the solar cells. Our low temperature JV results prove that thin‐film perovskite is a very necessary component in CdTe solar cells to reduce back contact barrier, to minimize interface or surface recombination, to improve collection efficiencies, and to increase the efficiency of solar cells. Our best device shows 7% increase in VOC to 0.875 V and ~7% increase in FF with the highest FF of 81%, and solar cell's efficiency finally increases by 10% with the use of MAPb(I1‐xBrx)3 as an interface layer. 相似文献
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Following the growth of computational fluid dynamics in engineering applications, adjoint methods for sensitivity analysis are being applied to an increasing range of industrial problems. In recent years, growth in computational power has led to widespread use of high‐fidelity, time‐resolved techniques, such as large‐eddy simulation, for applications, including bluff‐body aerodynamics, where time‐averaged equations may be less reliable. The solution of time‐dependent adjoint equations, however, becomes unstable in time as the Reynolds number increases and the flow becomes chaotic. The source of this instability has been explained by analysis of the system's Lyapunov exponents and several solutions have been proposed in the literature based on least‐squares shadowing. Currently, such techniques impose a higher computational cost compared to classical adjoint methods and may become infeasible when the number of unstable Lyapunov exponents is large. In this work, we explore a more recently proposed approach, which balances the adjoint energy source term with added artificial dissipation. The stability of this approach is investigated for a discrete adjoint solver based on the time‐dependent incompressible Navier‐Stokes equations. The accuracy of the resulting shape sensitivities is analyzed using a linear regression technique for the flow around a circular cylinder. 相似文献
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