Joint Rate Control and Demand Balancing for Electric Vehicle Charging

Charging stations have become indispensable infrastructure to support the rapid proliferation of electric vehicles (EVs). The operational scheme of charging stations is crucial to satisfy the stability of the power grid and the quality of service (QoS) to EV users. Most existing schemes target either of the two major operations: charging rate control and demand balancing. This partial focus overlooks the coupling relation between the two operations and thus causes the degradation on the grid stability or customer QoS. A thoughtful scheme should manage both operations together. A big challenge to design such a scheme is the aggregated uncertainty caused by their coupling relation. This uncertainty accumulates from three aspects: the renewable generators co-located with charging stations, the power load of other (or non-EV) consumers, and the charging demand arriving in the future. To handle this aggregated uncertainty, we propose a stochastic optimization based operational scheme. The scheme jointly manages charging rate control and demand balancing to satisfy both the grid stability and user QoS. Further, our scheme consists of two algorithms that we design for managing the two operations respectively. An appealing feature of our algorithms is that they have robust performance guarantees in terms of the prediction errors on these three aspects. Simulation results demonstrate the efficacy of the proposed operational scheme and also validate our theoretical results

Cyber-Physical System Checkpointing and Recovery

Transitioning to more open architectures has been making Cyber-Physical Systems (CPS) vulnerable to malicious attacks that are beyond the conventional cyber attacks. This paper studies attack-resilience enhancement for a system under emerging attacks in the environment of the controller. An effective way to address this problem is to make system state estimation accurate enough for control regardless of the compromised components. This work follows this way and develops a procedure named CPS checkpointing and recovery, which leverages historical data to recover failed system states. Specially, we first propose a new concept of physical-state recovery. The essential operation is defined as rolling the system forward starting from a consistent historical system state. Second, we design a checkpointing protocol that defines how to record system states for the recovery. The protocol introduces a sliding window that accommodates attack-detection delay to improve the correctness of stored states. Third, we present a use case of CPS checkpointing and recovery that deals with compromised sensor measurements. At last, we evaluate our design through conducting simulator-based experiments and illustrating the use of our design with an unmanned vehicle case study

Energy Minimizing for Parallel Real-Time Tasks Based on Level-Packing

Abstract-While much work has addressed energy minimizing problem of real-time sequential tasks, little has been done for the parallel real-time task case. In this paper, based on level-packing, we study energy minimization problem for parallel task systems with discrete operation modes and under timing constraints. For tasks with fixed (variable) parallel degrees, we first formulate the problem as a 0-1 Integer Linear Program (0-1 ILP), and then propose a polynomial-time complexity two-step (three-step) heuristic to determine task schedule and frequency assignment (and the task parallel degree). Our simulation result shows that the heuristics consume nearly the same energy as do 0-1 ILPs

Joint Management of Energy Harvesting, Storage, and Usage for Green Wireless Sensor Networks

Recently, energy harvesting has been emerging as a promising technique to prolong the lifetime for wireless sensor nodes. Most existing efforts address the design of energy harvesting and sensor node subsystem separately or ignore some real-world constraints. In this paper, we study how to codesign the two subsystems and how to jointly manage energy harvesting, storage, and usage. We first propose a novel system architecture for energy harvesting which employs several supercapacitors to eliminate the conflicts on charging and discharging among different system components. Then, we present a method to schedule their charging and discharging, which is proved to be able to guarantee zero waste of the harvested energy if the battery is not full. Third, we propose an optimal algorithm to minimize different components’ capacity and two heuristic algorithms to maximize the system reward. We conduct extensive experiments based on real-life data traces. Results show that the proposed system architecture can harvest more energy compared to the state of the art, and the capacity optimization algorithm can choose the most suitable size for each system component

Facile Preparation of Dense Polysulfone UF Membranes with Enhanced Salt Rejection by Post-Heating

Polysulfone (PSf) membranes typically have a negligible rejection of salts due to the intrinsic larger pore size and wide pore size distribution. In this work, a facile and scalable heat treatment was proposed to increase the salt rejection. The influence of heat treatment on the structure and performance of PSf membranes was systematically investigated. The average pore size decreased from 9.94 ± 5.5 nm for pristine membranes to 1.18 ± 0.19 nm with the increase in temperature to 50 °C, while the corresponding porosity decreased from 2.07% to 0.13%. Meanwhile, the thickness of the sponge structure decreased from 20.20 to 11.5 μm as the heat treatment temperature increased to 50 °C. The MWCO of PSf decreased from 290,000 Da to 120 Da, whereas the membrane pore size decreased from 5.5 to 0.19 nm. Correspondingly, the water flux decreased from 1545 to 27.24 L·m−2·h−1, while the rejection ratio increased from 3.1% to 74.0% for Na2SO4, from 1.3% to 48.2% for MgSO4, and from 0.6% to 23.8% for NaCl. Meanwhile, mechanism analysis indicated that the water evaporation in the membranes resulted in the shrinkage of the membrane pores and decrease in the average pore size, thus improving the separation performance. In addition, the desalting performance of the heat-treated membranes for real actual industrial wastewater was improved. This provides a facile and scalable route for PSf membrane applications for enhanced desalination

Sensor placement for lifetime maximization in monitoring oil pipelines

ABSTRACT Wireless sensor networks (WSNs) have been widely deployed and it is crucial to properly control the energy consumption of the sensor nodes to achieve the maximum WSNs' operation time (i.e., lifetime) as they are normally battery powered. In this paper, for sensor nodes that are utilized to monitor oil pipelines, we study the linear sensor placement problem with the goal of maximizing their lifetime. For a simple equal-distance placement scheme, we first illustrate that the result based on the widely used ideal power model can be misleading (i.e., adding more sensor nodes can improve WSN's lifetime) when compared to that of a realistic power model derived from Tmote Sky sensors. Then, we study equal-power placement schemes and formulate the problem as a MILP (mixed integer linear programming) problem. In addition, two efficient placement heuristics are proposed. The evaluation results show that, even with the Tmote power model, the equal-power placement schemes can improve the WSN's lifetime by up to 29% with properly selected number of sensor nodes, the distance between them and the corresponding transmission power levels. Moreover, one heuristic scheme actually obtains almost the same results as that of MILP, which is optimal. The real deployment in one oil field is also discussed

miR-101-3p improves neuronal morphology and attenuates neuronal apoptosis in ischemic stroke in young mice by downregulating HDAC9

MiRNAs play a key role in ischemic stroke (IS). Although miR-101-3p can participate in multiple disease processes, its role and mechanism in IS are not clear. The aim of the present study was to observe the effect of miR-101-3p activation on IS in young mice and the role of HDAC9 in this effect