We develop a hydrodynamic description of the collective modes of interacting liquids in a quasi-one-dimensional confining potential. By solving Navier-Stokes equations we determine analytically excitation spectrum of sloshing oscillations. For parabo
lic confinement, the lowest frequency eigenmode is not renormalized by interactions and is protected from decay by the Kohn theorem, which states that center of mass motion decouples from internal dynamics. We find that the combined effect of potential anharmonicity and interactions results in the depolarization shift and final lifetime of the Kohn mode. All other excited modes of sloshing oscillations thermalize with the parametrically faster rates. Our results are significant for the interpretation of recent experiments with trapped Fermi gases that observed weak violation of the Kohn theorem.
We consider the two-dimensional electron gas confined laterally to a narrow channel by a harmonic potential. As the Zeeman splitting matches the intersubband separation the nonlocal spin polarization develops a minimum as reported by Frolov et al. [N
ature (London) 458, 868 (2009)]. This phenomenon termed Ballistic Spin Resonance is due to the degeneracy between the nearest oppositely polarized subbands that is lifted by spin-orbit coupling. We showed that the resonance survives the weak and short-range interaction. The latter detunes it and as a result shifts the Zeeman splitting at which the minimum in spin polarization occurs. Here this shift is attributed to the absence of Kohn theorem for the spin sloshing collective mode. We characterized the shift due to weak interaction qualitatively by analyzing the spin sloshing mode within the Fermi liquid phenomenology.
Wireless Sensors Networks (WSNs) have a big application in heterogeneous networks. In this paper, we propose and evaluate Advanced Low-Energy Adaptive Clustering Hierarchy (Ad-LEACH) which is static clustering based heterogeneous routing protocol. Th
e complete network field is first divided into static clusters and then in each cluster separate Ad-LEACH protocol is applied. Our proposed protocol is inherited from LEACH with a cluster head selection criteria of Distributed Energy-Efficient Clustering (DEEC). This enables Ad-LEACH to cope with the heterogeneous nature of nodes. Due to small static clusters, each node reduces its broadcast message power because it only has to cover a small area. We perform simulations in MATLAB to check the efficiency of Ad-LEACH. The Simulation results show that Ad-LEACH outperforms LEACH and DEEC in energy efficiency as well as throughput.
One of the major challenges in design of Wireless Sensor Networks (WSNs) is to reduce energy consumption of sensor nodes to prolong lifetime of finite-capacity batteries. In this paper, we propose Energy-efficient Adaptive Scheme for Transmission (EA
ST) in WSNs. EAST is an IEEE 802.15.4 standard compliant. In this scheme, open-loop is used for temperature-aware link quality estimation and compensation. Whereas, closed-loop feedback process helps to divide network into three logical regions to minimize overhead of control packets. Threshold on transmitter power loss (RSSIloss) and current number of nodes (nc(t)) in each region help to adapt transmit power level (Plevel) according to link quality changes due to temperature variation. Evaluation of propose scheme is done by considering mobile sensor nodes and reference node both static and mobile. Simulation results show that propose scheme effectively adapts transmission Plevel to changing link quality with less control packets overhead and energy consumption as compared to classical approach with single region in which maximum transmitter Plevel assigned to compensate temperature variation.
