NCTUns tool for wireless vehicular communication network researches

Several goals such as improving road safety and increasing transport efficiency are being pursued in intelligent transportation systems (ITS). Wireless vehicular communication is one technology to achieve these goals. Conducting vehicular experiments on the roads is an approach to studying the effectiveness of wireless vehicular communication. However, such an approach is costly, hard-to-control (repeat), dangerous, and infeasible when many vehicles and people are involved in the field trial. In contrast, the simulation approach does not have these problems. It is a very useful approach and complements the field trial approach. This paper presents NCTUns, an open source integrated simulation platform, for wireless vehicular communication network researches. This tool tightly integrates network and traffic simulations and provides a fast feedback loop between them. Therefore, a simulated vehicle can quickly change its driving behavior such as moving speed and direction when it receives a message from the wireless vehicular communication network. This capability is required by several novel ITS applications such as active collision avoidance systems. In this paper, we present the design, implementation, validation, and performance of this tool.     

软体机械臂水下自适应鲁棒视觉伺服

水下仿生软体机器人在水底环境勘测,水下生物观测等方面具有极高的应用价值.为进一步提升仿章鱼臂软体机器人在特殊水下环境中控制效果,提出一种自适应鲁棒视觉伺服控制方法,实现其在干扰无标定环境中的高精度镇定控制.基于水底动力学模型,设计保证动力学稳定的控制器;针对柔性材料离线标定过程繁琐、成本高,提出材料参数自适应估计算法;针对水下特殊工作条件,设计自适应鲁棒视觉伺服控制器,实现折射效应的在线补偿,并通过自适应未知环境干扰上界,避免先验环境信息的求解.所提算法在软体机器人样机中验证其镇定控制性能,为仿生软体机器人的实际应用提供理论基础.     

Interference aware resource allocation for hybrid hierarchical wireless networks

This paper addresses the problem of interference aware resource allocation for OFDMA based hybrid hierarchical wireless networks. We develop two resource allocation algorithms considering the impact of wireless interference constraints using a weighted SINR conflict graph to quantify the interference among the various nodes: (1) interference aware routing using maximum concurrent flow optimization; and (2) rate adaptive joint subcarrier and power allocation algorithm under interference and QoS constraints. We exploit spatial reuse to allocate subcarriers in the network and show that an intelligent reuse of resources can improve throughput while mitigating interference. We provide a sub-optimal heuristic to solve the rate adaptive resource allocation problem. We demonstrate that aggressive spatial reuse and fine tuned-interference modeling garner advantages in terms of throughput, end-to-end delay and power distribution.     

Ultrathin MoSSe alloy nanosheets anchored on carbon nanotubes as advanced catalysts for hydrogen evolution

The activity of transition metal dichalcogenides (TMD) toward hydrogen evolution reaction (HER) derives from the active sites at the edges, but the basal surface still remain catalytic insert. Herein, ultrathin MoSSe alloy nanosheets array on multiwalled carbon nanotubes (MWCNTs) to form a core shell structure via a simple solvothermal process. These three-dimensional (3D) MoSSe hybrids show a high activity in hydrogen evolution reaction (HER) with a small Tafel slope of 38 mV dec⁻¹ and a low overpotential of 102 mV at 10 mA cm⁻². In addition, their HER activity remains remarkably stable without significant decay after 100 h polarization. Such superior catalytic HER activity springs from the 3D hierarchical heterostructure, which is abundant of catalytic edge sites, and the alloy effect between S and Se, which will create huge defects and strain to form vacancy sites on the basal plane. This strategy may open a new avenue toward the development of nonprecious high-performance HER catalysts.     

A switching anti-windup design based on partitioning of the input space

This paper revisits the problem of enlarging the domain of attraction of a linear system with multiple inputs subject to actuator saturation by designing a switching anti-windup compensator. The closed-loop system consisting of the plant, the controller and the anti-windup compensator is first equivalently formulated as a linear system with input deadzone. We then partition the input space into several regions. In one of these regions, all inputs saturate with the time-derivative of the saturated input being zero. In each of the remaining regions, there is a unique input that does not saturate. The time derivative of the deadzone function associated with the unsaturating input is zero. By utilizing these special properties of the inputs on an existing piecewise Lyapunov function of the augmented state vector containing the deadzone function of inputs, we design a separate anti-windup gain for each region of the input space. The switching from one anti-windup gain to another is activated when the input signals leave one region for another, which can be implemented online since only the measurement of the input signals is required. Simulation results indicate that the proposed approach has the ability to obtain a significantly larger estimate of the domain of attraction than the existing approaches.     

Real-Time neural signal decoding on heterogeneous MPSocs based on VLIW ASIPs

An important research problem, at the basis of the development of embedded systems for neuroprosthetic applications, is the development of algorithms and platforms able to extract the patient’s motion intention by decoding the information encoded in neural signals. At the state of the art, no portable and reliable integrated solutions implementing such a decoding task have been identified. To this aim, in this paper, we investigate the possibility of using the MPSoC paradigm in this application domain. We perform a design space exploration that compares different custom MPSoC embedded architectures, implementing two versions of a on-line neural signal decoding algorithm, respectively targeting decoding of single and multiple acquisition channels. Each considered design points features a different application configuration, with a specific partitioning and mapping of parallel software tasks, executed on customized VLIW ASIP processing cores. Experimental results, obtained by means of FPGA-based prototyping and post-floorplanning power evaluation on a 40nm technology library, assess the performance and hardware-related costs of the considered configurations. The reported power figures demonstrate the usability of the MPSoC paradigm within the processing of bio-electrical signals and show the benefits achievable by the exploitation of the instruction-level parallelism within tasks.     

Fast multi-objective optimization of multi-parameter antenna structures based on improved MOEA/D with surrogate-assisted model

For multi-objective design of multi-parameter antenna structures, optimization efficiency and computational cost are two major concerns. In this paper, an improved multi-objective evolutionary algorithm based on decomposition (MOEA/D) is proposed to improve global optimization capability by diversity detection operation and mixed population update operation. Further, in order to reduce the computational cost, a hybrid optimization strategy integrating a dynamically updatable surrogate-assisted model into the improved MOEA/D is proposed. The numerical results of test functions show that our algorithm outperforms original MOEA/D, modified MOEA/D (M-MOEA/D), and nondominated sorting genetic algorithm II (NGSA-II) in terms of diversity. Experimental validation of Pareto-optimal planar miniaturized multiband antenna designs is also provided, showing excellent convergence and considerable computational savings compared to those previously published approaches.     

A focused review of the hydrogen storage tank embrittlement mechanism process

Hydrogen embrittlement is a widely known phenomenon in high-strength and storage materials. Hydrogen embrittlement is responsible for subcritical crack growth in material, fracture initiation, subsequent loss in mechanical properties, and catastrophic failure. Hydrogen is induced in the material during an electrochemical reaction between the hydrogen, storage materials, and high-pressure gaseous hydrogen environment. Various mechanisms which are responsible for crack development, growth, and fracture have been deliberated and reported. However, the fundamental mechanism of hydrogen embrittlement remains unclear. Several techniques such as linearly increasing stress test techniques (LIST), constant extension rate test (CERT) and slow strain rate testing (SSRT), thermal desorption spectroscopy (TDS), permeation testing (PT), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been utilized to determine the amount of hydrogen diffused and available in the hydrogen storage material. The review intends to categorize and provide a clear understanding of the degradation mechanism that occurs during hydrogen embrittlement. The improvement in mitigating the hydrogen embrittlement degradation as a function of modifying the structure and surfaces of the material is established. Prospects for addressing hydrogen embrittlement degradation through further experimental and numerical research are suggested. Lastly, this paper through recommendation endeavors to prevent hydrogen storage tank degradation and reduces high costs associated with the replacement of the component in renewable energy applications.     

Novel carbon-ceramic composite membranes with high cation exchange properties for use in microbial fuel cell and electricity generation

Actually, there are different configurations used in microbial fuel cells (MFCs) with presence or absence of an ion exchange membrane between their electrodes. Specifically, MFCs that use membranes have the objective of avoiding the diffusion of oxygen and substrate between the anodic and cathodic compartment, and to achieve a correct transfer of protons from one chamber to another. In this regard, the current study seeks to prepare and characterize new composite membranes using as precursors three types of carbonaceous materials such as bone char, coconut shell activated carbon and bituminous activated carbon and natural clay. The composite membranes of bituminous activated carbon and clay showed more promising specific conductivity (42%) than the one made with pure clay. The physicochemical properties of the membranes and their precursors were elucidated by SEM/EDX analysis, IR spectroscopy, nitrogen adsorption isotherms at 77 K and optical microscopy. Further, membranes performance was assessed using microbial fuel cells (MFCs) where the composite membranes prepared with clay-bituminous carbon reached the highest voltage values (0.95–1.02 V) in open circuits, while that reached a maximum power density of 0.699 W/m³ at a current density of 4.012 A/m³ in closed circuit. This behavior is associated with the high content of silicon and aluminum in bituminous activated carbon, which favored the proper functioning of membranes in the MFCs. Specifically, with this type of cells, energy recovery of 0.0057 kWh/m³ and 0.1322 kWh/kg chemical oxygen demand (COD) removed, which indicates an extra economic income of the order of $0.0025/kg COD. Finally, the produced power was demonstrated in prototypes to power LED and four digital clocks. This novel clay-bituminous activated carbon showed promising cost-effectiveness and sustainable energy generation, which may be suitable for wastewater treatment.