Employing electron spin instead of charge to develop spintronic devices holds the merits of low-power consumption in information technologies. Meanwhile, the demand for increasing speed in ...spintronics beyond current CMOS technology has further triggered intensive researches for ultrafast control of spins even up to unprecedent terahertz regime. The femtosecond laser has been emerging as a potential technique to generate an ultrafast spin-current burst for magnetization manipulation. However, there is a great challenge to establish all-optical control and monitor of the femtosecond transient spin current. Deep insights into the physics and mechanism are extremely essential for the technique. Here, we demonstrate coherently nonthermal excitation of femtosecond spin-charge current conversion parallel to the magnetization in W/CoFeB/Pt heterostructures driven by linearly polarized femtosecond laser pulses. Through systematical investigation we observe the terahertz emission polarization depends on both the magnetization direction and structural asymmetry. We attribute this phenomenon of the terahertz generation parallel to the magnetization induced by linearly polarized femtosecond laser pulses probably to inverse spin-orbit torque effect. Our work not only is beneficial to the deep understanding of spin-charge conversion and spin transportation, but also helps develop novel on-chip terahertz opto-spintronic devices.
This paper proposes a novel adaptive interpolation filter (AIF) to reduce computational complexity and bit-rate of video coding. In the proposed AIF, the filter coefficients of B frames, which are ...predicted from those of adjacent P frames with a novel parabolic model, are unnecessary to transmit. Experimental results show that the coding complexity is reduced by 40.22% with no penalty on coding efficiency and 1.59% bit rate reduction is achieved at low bit-rate against conventional AIF.
The high current density required by Magnetic Tunneling Junction (MTJ) switching driven by Spin Transfer Torque (STT) effect leads to large power consumption and severe reliability issues therefore ...hinder the timetable for STT Magnetic Random Access Memory (STT-MRAM) to mass market. By utilizing Voltage Controlled Magnetic Anisotropy (VCMA) effect, the MTJ can be switched by voltage effect and is postulated to achieve ultra-low power (fJ). However, the VCMA coefficient measured in experiments is far too small for MTJ dimension below 100 nm. Here in this work, a novel approach for the amplification of VCMA effect which borrow ideas from negative capacitance is proposed. The feasibility of the proposal is proved by physical simulation and in-depth analysis.
To increase reliability and real time of the unmanned surface vehicle (USV), research on system design and implement of USV was completed. Introduces the hardware architecture of the control system ...and clarifies the function of all parts. The software architecture is designed based on the VxWorks real-time operating system. The USV control system adopts a three layered hierarchical architecture, includes cooperating layer, control layer and operating layer, to ensure the reliability and real time. Experiments were conducted successfully, such as heading control and simple path-following tests, to obtain useful data to be used in USV modeling and advanced control system design.
Planning of distributed energy systems is a challenging task, involving a lot of technical, economic, environmental and political factors. In this study, an optimization model based decision support ...system and the relevant software package have been developed to provide comprehensive analysis of economic, energetic and environmental issues within a distributed energy system framework. The optimization problem is formulated as a mixed integer linear programming (MILP) model where the objective is to minimize the overall cost of the distributed energy system including both investing and running costs. By using a user friendly interface, the system can be used without the necessary to have special expertise and knowledge on energy system planning and decision analysis. In addition, besides the distributed energy system planning, it can be also used for examining and visualizing impacts of local energy and environmental policies, regional development policies, and climate change within a local framework.
Cooperative localization(CL) is a crucial cycle in navigation with multiple autonomous underwater vehicles(MAUVs). Due to the terrible underwater environment, measuring and communicating each other ...are still difficult challenges for AUVs until now, which both are also essential for CL to improve the position performance. Based on the two principles below: 1 (minimizing the consumption of CL without loss of performance; 2)simplifying the communication topology, meanwhile, satisfying the communication requirements, we propose optimal decision making(ODM) for MAUVs under multiple optional measurements and communication topologies. Then, considering two common cooperative manners: homogeneous MAUVs, heterogeneous MAUVs, ODM is presented in detail to examine two tradeoffs, not only between performance and consumption, but also between group performance and single accuracy. Finally, simulation results are provided to illustrate the superiority and practicality of the proposed decision strategy.
A new distributed control system using CAN-bus for our long-range autonomous underwater vehicle named TESTBED is developed. In the well defined hierarchical architecture, this control system consists ...of a task layer with the multi-function Tele-operator, a coordination layer with the Mission Management Center, and a control layer with the Navigation and Control Center and other execution-level controllers. All the control nodes communicate with each other through the CAN bus with the proper defined message frames. The real-time control and non-realtime tasks management are assigned to different control nodes, which make the whole system more reliable, maintainable, and easy to upgrade. In the real in-water experiments, the distributed control system fulfilled the multi-waypoints tasks, and the AUV executed the preprogrammed mission completely without any fault.
The potential filed method is proposed to solve the bottom navigation problem of an underactuated autonomous underwater vehicle, including the bottom avoidance problem and the bottom following ...problem. The desired depth is treated as a stationary goal and the sea bottom is a moving obstacle in the bottom avoidance problem. And the desired altitude above the bottom is a moving goal and the maximum designed depth acts as a stationary obstacle in the bottom following problem. To improve the performance, the slope of sea bottom is added to the conventional potential forces as the relative velocity between the vehicle and the bottom, resulting in the dynamic potential field which is originally addressed for motion planning of mobile robots. A two layered hierarchical architecture is used to solve the motion control problem. The preliminary simulation results are provided to demonstrate that the proposed potential field based controller is easy for implementation with a satisfying performance.
