Spin Decay in a Quantum Dot Coupled to a Quantum Point Contact

We consider a mechanism of spin decay for an electron spin in a quantum dot due to coupling to a nearby quantum point contact (QPC) with and without an applied bias voltage. The coupling of spin to charge is induced by the spin-orbit interaction in the presence of a magnetic field. We perform a microscopic calculation of the effective Hamiltonian coupling constants to obtain the QPC-induced spin relaxation and decoherence rates in a realistic system. This rate is shown to be proportional to the shot noise of the QPC in the regime of large bias voltage and scales as $a^{-6}$ where $a$ is the distance between the quantum dot and the QPC. We find that, for some specific orientations of the setup with respect to the crystallographic axes, the QPC-induced spin relaxation and decoherence rates vanish, while the charge sensitivity of the QPC is not changed. This result can be used in experiments to minimize QPC-induced spin decay in read-out schemes.Comment: 10 pages, 2 figures, 2 table

Secure smart contract-enabled control of battery energy storage systems against cyber-attacks

Battery Energy Storage Systems (BESSs) are an integral part of a sustainable and resilient smart grid. The security of such critical cyber-physical infrastructure is considered as a major priority for both industry and academia. In this paper, we propose a new distributed smart-contract based control approach of BESSs to enable collaborative and secure operations among them. We present a comprehensive discussion on how control strategies can be implemented as smart contracts and deployed on a distributed network of BESSs nodes in order to operate these storage systems according to secure consensus. To verify the effectiveness of the proposed method, we analyze the vulnerabilities of BESSs when controlled according to traditional schemes vs. smart-contract enabled control. Simulation results show that if individual BESSs achieve a certain maximum threshold of exploitability, then the network of distributed BESSs is more robust to cyber-attacks in smart contract-defined control. - 2019 Faculty of Engineering, Alexandria UniversityThe publication of this article was funded by the Qatar National Library.Scopu

Movement analysis to indicate discomfort in vehicle seats

Long distance travel is associated with discomfort and fatigue. It is a significant challenge to design a seat that remains comfortable for the occupant over the several hours required for many long-distance journeys. When designing seats, an indication of the perception of comfort/discomfort can be useful either for research and development purposes or potentially for automated systems to take actions that might mitigate discomfort. This paper considered a system that uses measurements of body movement in a seat to provide an objective measure of perceptions of discomfort. The system uses cameras and image processing to recognize when a seat occupant makes a movement in the seat which could be associated with relief of discomfort. The system was validated using a laboratory driving simulator. 10 participants volunteered to complete a study in which they drove for 90 minutes and gave subjective ratings of discomfort every 10 minutes, whilst also being observed using the camera system. It was shown that using a simple algorithm an association could be made between the movements of the driver and subjective ratings of discomfort. However, there remain challenges to improve reliability, optimize movement detection thresholds, and to make it more robust to naturalistic driving scenarios

Development of a three-phase interleaved converter based on SEPIC DC-DC converter operating in discontinuous conduction mode for ultra-fast electric vehicle charging stations

One of the main challenges that impact transportation systems electrification is their batteries' charging process. This work presents the development of a three-phase ultra-fast Electric Vehicle (EV) charger based on the SEPIC converter. Since SEPIC operating in Discontinuous Conduction Mode (DCM) is usually recommended for low-power applications, this work proposes a scheme for its employment in high-power EV chargers. This is achieved through three single-phase modules of interleaved SEPIC converters. The presented scheme ensures reducing the stresses on the semiconductor devices since the power is divided over the interleaved modules. The design addresses DCM operation in terms of both capacitor voltage and inductor current (DCVM and DICM, respectively). This paper examines the analysis of the proposed converter and the small-signal modelling. Also, the converter efficiency is assessed. A Constant Current (CC) charging approach is deployed for charging the EV battery. The validation of the designs is explored through simulation results using MATLAB/Simulink platform. A 4 kW experimental prototype for the interleaved SEPIC DC-DC converter is built to verify the claimed contributions with 92% efficiency.Qatar Foundation; Qatar National Research FundScopu

Structure, DFT Calculations, and Magnetic Characterization of Coordination Polymers of Bridged Dicyanamido-Metal(II) Complexes

Three coordination polymers of metal(II)-dicyanamido (dca) complexes with 4-methoxypyridine-N-oxide (4-MOP-NO); namely, catena-[Co(µ1,5-dca)2(4-MOP-NO)2] (1), catena-[Mn(µ1,5-dca)2(4-MOP-NO)2] (2), catena-[Cd(µ1,5-dca)2(4-MOP-NO)2] (3), and the mononuclear [Cu(κ1dca)2(4-MOP-NO)2] (4), were synthesized in this research. The complexes were analyzed by single crystal X-ray diffraction as well as spectroscopic methods (UV/vis, IR). The polymeric 1-D chains in complexes 1-3 were achieved by the doubly µ1,5-bridging dca ligands and the O-donor atoms of two axial 4-MOP-NO molecules in trans configuration around the distorted M(II) octahedral. On the other hand, the two "trans-axial" pyridine-N-oxide molecules in complexes 2 and 3 display opposite orientation (s-trans). The DFT (density functional theory) computational studies on the complexes 1-3 were consistent with the experimentally observed crystal structures. Compounds 1 and 2 display weak antiferromagnetic coupling between metal ions (J = −10.8 for 1 and −0.35 for 2)

Coordination Dynamics meets Active Inference and Artificial Intelligence (CD + AI2):A multi-pronged approach to understanding the dynamics of brain and the emergence of conscious agency

How do humans discover their ability to act on the world? By tethering a baby’s foot to a mobile (Fig. 1a) and measuring the motion of both in 3D, we explore how babies begin to make sense of their coordinative relationship with the world and realize their ability to make things happen (N= 16; mean age = 100.33 days). Machine and deep learning classification architectures (e.g., CapsNet) indicate that functionally connecting infants to a mobile via a tether influences the baby movement most where it matters, namely at the point of infant∼world connection (Table 1). Using dynamics as a guide, we have developed tools to identify the moment an infant switches from spontaneous to intentional action (Fig. 1b). Preliminary coordination dynamics analysis and active inference generative modeling indicate that moments of stillness hold important epistemic value for young infants discovering their ability to change the world around them (Fig. 1c). Finally, a model of slow~fast brain coordination dynamics based on a 3D extension of the Jirsa-Kelso Excitator successfully simulated the evolution of tethered foot activity as infants transition from spontaneous to ordered action. By tuning a small number of parameters, this model captures patterns of emergent goal-directed action (Fig. 1d). Meshing concepts, methods and tools of Active Inference, Artificial Intelligence and Coordination Dynamics at multiple levels of description, the CD + AI2 program of research aims to identify key control parameters that shift the infant system from spontaneous to intentional behavior. The potent combination of mathematical modeling and quantitative analysis along with empirical study allow us to express the emergence of agency in quantifiable, lawful terms