Feudalistic Platooning: Subdivide Platoons, Unite Networks, and Conquer Efficiency and Reliability

Cooperative intelligent transportation systems (C-ITSs) such as platooning rely on a robust and timely network that may not always be available in sufficient quality. Out of the box hybrid networks only partly eliminate shortcomings: mutual interference avoidance, data load balancing, and data dissemination must be sophisticated. Lacking network quality may lead to safety bottlenecks that require that the distance between the following vehicles be increased. However, increasing gaps result in efficiency loss and additionally compromise safety as the platoon is split into smaller parts by traffic: maneuvers, e.g., cut-in maneuvers bear safety risks, and consequently lower efficiency even further. However, platoons, especially if they are very long, can negatively affect the flow of traffic. This mainly applies on entry or exit lanes, on narrow lanes, or in intersection areas: automated and non-automated vehicles in traffic do affect each other and are interdependent. To account for varying network quality and enable the coexistence of non-automated and platooned traffic, we present in this paper a new concept of platooning that unites ad hoc—in form of IEEE 802.11p—and cellular communication: feudalistic platooning. Platooned vehicles are divided into smaller groups, inseparable by surrounding traffic, and are assigned roles that determine the communication flow between vehicles, other groups and platoons, and infrastructure. Critical vehicle data are redundantly sent while the ad hoc network is only used for this purpose. The remaining data are sent—relying on cellular infrastructure once it is available—directly between vehicles with or without the use of network involvement for scheduling. The presented approach was tested in simulations using Omnet++ and Simulation of Urban Mobility (SUMO)

Fission of Multiply Charged Cesium and Potassium Clusters in Helium Droplets - Approaching the Rayleigh Limit

Electron ionization of helium droplets doped with sodium, potassium or cesium results in doubly and, for cesium, triply charged cluster ions. The smallest observable doubly charged clusters are Na92+, K112+, and Cs92+; they are a factor two to three smaller than reported previously. The size of sodium and potassium dications approaches the Rayleigh limit nRay for which the fission barrier is calculated to vanish, i.e. their fissilities are close to 1. Cesium dications are even smaller than nRay, implying that their fissilities have been significantly overestimated. Triply charged cesium clusters as small as Cs193+ are observed; they are a factor 2.6 smaller than previously reported. Mechanisms that may be responsible for enhanced formation of clusters with high fissilities are discussed

Doubly Charged Coronene Clusters – Much Smaller than Previously Observed

The smallest doubly charged coronene cluster ions reported so far, Cor152+, were produced by charge exchange between bare coronene clusters and He2+ [H. A. B. Johansson et al., Phys. Rev. A 84, 043201 (2011)]. These dications are at least five times larger than the estimated Rayleigh limit, i.e., the size at which the activation barrier for charge separation vanishes. Such a large discrepancy is unheard of for doubly charged atomic or molecular clusters. Here we report the mass spectrometric observation of doubly charged coronene trimers, produced by electron ionization of helium nanodroplets doped with coronene. The observation implies that Cor32+ features a non-zero fission barrier too large to overcome under the present experimental conditions. The height of the barriers for the dimer and trimer has been estimated by means of density functional theory calculations. A sizeable barrier for the trimer has been revealed in agreement with the experimental findings

Effects of Symmetry Restriction on the Antenna Gain Optimized Using Genetic Algorithms

Automated design techniques for antennas are highly interesting regarding their ability to cut down on development time and their overall importance for communication technology. Sub-dividing a given area into individual pixels renders methods such as genetic algorithms possible, which enables an automated optimization process by evolutionary methods. While there are many examples in the literature that use this approach, most of them use the reflection coefficient as the optimization goal. Although this yields satisfying antennas for a variety of different applications, this approach generally does not achieve high directivities or antenna gains. In this work, we present the evolutionary optimization of antenna gain for pixelated antennas and the effect of symmetry restriction on the optimized topologies

Numerical Optimization of a Fully Cross-Coupled Rectifier Circuit for Wireless Passive Ultra Low Power Sensor Nodes

In the context of the Internet of Things, billions of devices—especially sensors—will be linked together in the next few years. A core component of wireless passive sensor nodes is the rectifier, which has to provide the circuit with sufficient operating voltage. In these devices, the rectifier has to be as energy efficient as possible in order to guarantee an optimal operation. Therefore, a numerical optimization scheme is proposed in this paper, which is able to find a unique optimal solution for an integrated Complementary Metal-Oxide-Semiconductor (CMOS) rectifier circuit with Self-Vth-Cancellation (SVC). An exploration of the parameter space is carried out in order to generate a meaningful target function for enhancing the rectified power for a fixed communication distance. In this paper, a mean conversion efficiency is introduced, which is a more valid target function for optimization than the Voltage Conversion Efficiency (VCE) and the commonly used Power Conversion Efficiency (PCE) and is defined as the arithmetic mean between PCE and VCE. Various trade-offs between output voltage, PCE, VCE and MCE are shown, which provide valuable information for low power rectifier designs. With the proposed method, a rectifier in a low power 55 nm process from Globalfoundries (GF55LPe) is optimized and simulated at −30 dBm input power. A mean PCE of 63.33% and a mean VCE of 63.40% is achieved

Evolutionary algorithms as a tool for shielding design

The paper deals with the shielding enclosure design using evolutionary algorithms without predetermined conditions. The designed shield consists of an array of elements that rep-resent conductive or non-conductive parts. The expected output is to design a shield with sufficient balance between shielding effectiveness and transparency in systems that need an optical line of sight. The wide frequency transparent shielding design is a complex task that researchers so far mostly solved by composite polymers. The authors use a different approach using traditional conductive material and element folding technology. Element assembly is performed by an evolutionary algorithm that decides the properties of the material used and creates the optimal structure to achieve the desired results. The paper describes the design concept for planar shielding with metaheuristics and the preliminary results. © 2022 IEEE.CZ.02.2.69/0.0/0.0/16028/0006243; Univerzita Tomáše Bati ve Zlíně: IGA/CebiaTech/2022/004, IGA/FAI/2022/00

On Subthreshold Ionization of Helium Droplets, Ejection of He+, and the Role of Anions

The mechanism of ionization of helium droplets has been investigated in numerous reports but one observation has not found a satisfactory explanation: How are He+ ions formed and ejected from undoped droplets at electron energies below the ionization threshold of the free atom? Does this path exist at all? A measurement of the ion yields of He+ and He2+ as a function of electron energy, electron emission current, and droplet size reveals that metastable He*− anions play a crucial role in the formation of free He+ at subthreshold energies. The proposed model is testable