Transparent 2-Element 5G MIMO Antenna for Sub-6 GHz Applications

A dual-port transparent multiple-input multiple-output (MIMO) antenna resonating at sub-6 GHz 5G band is proposed by using patch/ground material as transparent conductive oxide (AgHT-8) and a transparent Plexiglas substrate. Two identical circular-shaped radiating elements fed by using a microstrip feedline are designed using the finite element method (FEM) based high-frequency structure simulator (HFSS) software. The effect of the isolation mechanism is discussed using two cases. In case 1, the two horizontally positioned elements are oriented in a similar direction with a separate ground plane, whereas in case 2, the elements are vertically placed facing opposite to each other with an allied ground. In both cases, the transparent antennas span over a −10 dB band of 4.65 to 4.97 GHz (300 MHz) with isolation greater than 15 dB among two elements. The diversity parameters are also analyzed for both the cases covering the correlation coefficient (ECC), mean effective gain (MEG), diversity gain (DG), and channel capacity loss (CCL). The average gain and efficiency above 1 dBi and 45%, respectively with satisfactory MIMO diversity performance, makes the transparent MIMO antenna an appropriate choice for smart IoT devices working in the sub-6 GHz 5G band by mitigating the co-site location and visual clutter issues.

Inhibition of vacuum sublimation artefacts for (Scanning) Transmission Electron Microscopy ((S)TEM) of sulphur samples via encapsulation

Lithium-sulfur battery is one of promising candidates for next-generation energy storage device due to the sulfur cathode material with low cost and nontoxicity, and super high theoretical energy density (nearly 2600Wh kg−1) and specific energy (2567Wh kg−1). Sulphur, however, poses a few interesting challenges before it can gain widespread utilisation. The biggest issue is known as the polysulphide shuttling effect which contributes to rapid capacity loss after cycling. Accurate characterisation of sulphur cathodic materials becomes critical to our understanding polysulphide shuttling effect in the quest of finding mitigating solutions. Electron microscopy is playing a crucial role in battery research in determining structure–property–function relations. However, sulphur undergoes sublimation at a point above the typical pressures found in the column of a transmission electron microscope (TEM) at room temperature. This makes the imaging and characterisation of any sort of nanostructured sulphur samples challenging, as the material will be modified or even disappear rapidly as soon as it is inserted into the TEM vacuum. As a result, materials characterised by such methods are prone to deviation from normal conditions to a great extent. To prevent this, a novel method of encapsulating sulphur particles between silicon nitride (SiNx) membranes is demonstrated in this work.

The Role of Silicon in Silicon-Graphite Composite Electrodes Regarding Specific Capacity, Cycle Stability, and Expansion

One promising way of compensating for the repeated volume expansion and contraction of silicon as an anode active material in lithium ion batteries (LIBs) is to embed silicon within a graphite matrix. Silicon-graphite (SiG) composites combine the advantageous properties of graphite, i.e., large electrical conductivity and high structural stability, with the advantageous properties of silicon, i.e., high theoretical capacity. Graphite has a much lower volume expansion upon lithiation (≈ 10%) than pure silicon (≈ 300%) and provides a mechanically stable matrix. Herein, we present an investigation into the electrochemical performance and thickness change behavior of porous SiG anode compositions with silicon contents ranging from 0 wt% to 20 wt%. The electrode composites were studied using two methods: in situ dilatometry for the thickness change investigation and conventional coin cells for the assessment of electrochemical performance. The measurements show that the initial thickness change of SiG electrodes increased significantly with the silicon content, but it leveled off during cycling for all compositions. There appears to be a correlation between silicon content and capacity loss, but no clear correlation between thickness change and capacity loss rate was found.

Titanium Hydride Nanoplates Enable 5 wt% of Reversible Hydrogen Storage by Sodium Alanate below 80°C

Sodium alanate (NaAlH4) with 5.6 wt% of hydrogen capacity suffers seriously from the sluggish kinetics for reversible hydrogen storage. Ti-based dopants such as TiCl4, TiCl3, TiF3, and TiO2 are prominent in enhancing the dehydrogenation kinetics and hence reducing the operation temperature. The tradeoff, however, is a considerable decrease of the reversible hydrogen capacity, which largely lowers the practical value of NaAlH4. Here, we successfully synthesized a new Ti-dopant, i.e., TiH2 as nanoplates with ~50 nm in lateral size and ~15 nm in thickness by an ultrasound-driven metathesis reaction between TiCl4 and LiH in THF with graphene as supports (denoted as NP-TiH2@G). Doping of 7 wt% NP-TiH2@G enables a full dehydrogenation of NaAlH4 at 80°C and rehydrogenation at 30°C under 100 atm H2 with a reversible hydrogen capacity of 5 wt%, superior to all literature results reported so far. This indicates that nanostructured TiH2 is much more effective than Ti-dopants in improving the hydrogen storage performance of NaAlH4. Our finding not only pushes the practical application of NaAlH4 forward greatly but also opens up new opportunities to tailor the kinetics with the minimal capacity loss.

Exogenous Salicylic and Ascorbic Acids Delay Peel Enzymatic Browning and Improve Quality of Dried Figs Under Low-Temperature Storage

Dried figs undergo undesirable changes during storage, particularly browning reactions. An approach to this issue is using, separately, antioxidants such as ascorbic acid and salicylic acid as anti-enzymatic browning agents. The aforementioned chemical agents were tested at the concentrations 0.1, 0.2, and 0.3% during 6 weeks-storage at 4 °C, for dried figs sealed within polyethylene terephthalate bags. For both agents, the results demonstrated that a concentration of 0.3% lowered the browning index compared to the control by 55 and 54%, respectively. Compared to other concentrations, the same concentration suppressed polyphenol oxidase to 75 and 80%, respectively. A significant impact (p < 0.05), for both treatments, particularly at 0.3%, was obtained on dried figs quality by lowering the total phenols loss and antioxidant capacity loss during the storage period. The results of vibrational spectroscopy were able to confirm the same pattern of the polyphenols compared to those examined by UV-Visible spectrophotometry, revealing thus a decreasing absorbance. A similar tendency was revealed using integrated intensity around the phenols vibration within the region of 1175–940 cm-1, as the concentrations of anti-browning agents increased. Thus, pre-storage ascorbic and salicylic acids treatments at 0.3% on dried figs could be appropriate to delay enzymatic browning and quality loss and, therefore to extend their shelf-life.

A Segmented Cell Measuring Technique for Current Distribution Measurements in Batteries, Exemplified by the Operando Investigation of a Zn-Air Battery

A transimpedance amplifier circuit as well as an instrumental amplifier circuit were used to measure current densities of a zinc-air battery with an integrated segmented current collector foil. Error calculation showed that the transimpedance amplifier is superior to the used instrumental amplifier, but both methods provide valuable and consistent results. They both showed comparable results with operando insight into the current distribution of the battery. The knowledge about those distributions is essential to avoid fast degradation of battery materials and irreversible capacity loss due to heterogeneous dissolution of the anode during discharge. In this work we showed that oxygen starvation as well as gas flow rate leads to large current gradients. It was also demonstrated that heterogeneous current distributions on cathode side induces also a heterogenous dissolution behavior on the anode, resulting in irreversible capacity loss.

Influence of the Calendar Aging on the Cycle Aging of LiNiMnCoO2 Lithium-Ion Batteries

An experimental and theoretical study of lithium nickel manganese cobalt oxide (NMC) cells with a long rest time under different storage temperatures is carried out. We show that the long-term storage of a cell decisively influences its cycle life, and this influence is more pronounced at the late stage of the battery cycle life. Experimental outcomes demonstrate that the cycle life drops as the storage span lengthens, and the storage under relatively low temperature helps to reduce the cycle fading. Based on the experimental data, we identify the point on the fading trajectory to separate the early-medium stage and the late stage for the cycle aging. By extending the previously proposed semi-empirical model to incorporate the two-stage fading into a single formulation, the cycling capacity loss of the stored NMC cells is predicted. An incremental capacity analysis is further performed to assess the cycle fading of the cells under various storage conditions.

Bioactivity of Essential Oils for Mitigation of Listeria monocytogenes Isolated from Fresh Retail Chicken Meat

Listeria monocytogenes is one of the most severe foodborne pathogens found in several habitats. Therefore, this study aims to investigate the antilisterial activity of different essential oils (EOs) against multidrug-resistant (MDR) L. monocytogenes strains isolated from fresh chicken meat. Our results showed that the prevalence of L. monocytogenes in the examined samples was 48%. Seventy-eight isolates were identified as L. monocytogenes. Out of these, 64.1% were categorized as MDR and were categorized in 18 patterns with 50 MDR isolates. One isolate was selected randomly from each pattern to investigate their biofilm-forming ability, resistance, and virulence genes incidence. Out of 18 MDR isolates, 88.9% showed biofilm-forming ability. Moreover, the most prevalent resistance genes were ermB (72%), aadA (67%), penA (61%), and floR genes (61%). However, the most prevalent virulence genes were inlA (94.4%), prfA (88.9%), plcB (83.3%), and actaA (83.3%). The antilisterial activity of EOs showed that cinnamon bark oil (CBO) was the most effective antilisterial agent. CBO activity could be attributed to the bioactivity of cinnamaldehyde which effects cell viability by increasing the bacterial cell electrical conductivity, ion leakage, and salt tolerance capacity loss. Therefore, CBO could be an effective alternative natural agent for food safety applications.

Determining the Electrical Capacity of Lithium BEV and PHEV Battery in Situ

The work deals with the quality of batteries in electric vehicles manufactured today’s and the determination of warranty conditions and guarantees for built-in lithium batteries. However, the design, testing, prototyping and creation of new vehicles is not without errors, as the experience of some manufacturers, including the more inexperienced Mercedes, shows now. On a tested sample of the Mercedes E350e PHEV, a capacity loss of more than 30% from the original nominal value was measured after 18 months of vehicle operation, well above the manufacturer's expectations and declarations.