Top Layer Research Articles

Analyses of an Ultra-Wideband Absorber from UV-B to Middle-IR Utilizing a Square Nanopillar and a Square Hollow Embedded in a Square Cavity of the Top Layer of Multilayer Metamaterials

Analyses of an Ultra-Wideband Absorber from UV-B to Middle-IR Utilizing a Square Nanopillar and a Square Hollow Embedded in a Square Cavity of the Top Layer of Multilayer Metamaterials

The Surface Deterioration of Prefabricated Zirconia Crowns on Exposure to Acidulated Phosphate Fluoride Gel: An In Vitro Study.

Introduction Zirconia is a widely used restorative material in dentistry due to its superior aesthetic and mechanical properties. The oral cavity is a complex ecosystem with various components, which affect the teeth, as well as artificial restorative materials. Various personal and professional interventions carried out can severely affect the properties of restorative materials, thus altering the longevity of the prosthesis; 1.23% acidulated phosphate fluoride (APF) gel is one such professionally applied topical fluoride agent used to prevent caries. The interaction of this APF gel with highly aesthetic restorative material such as zirconia crowns is unknown. Objective The objective of this study is the evaluation of the surface deterioration of prefabricated zirconia crowns on exposure to deionised water and 1.23% acidulated phosphate fluoride (APF) gel with field emission scanning electron microscope (FE-SEM) and mass loss analysis. Material and method Sixty prefabricated paediatric zirconia crowns were taken, 10 samples were immersed in deionised water, 40 samples were immersed in 1.23% APF gel and 10 samples were used ascontrol. Surface morphology and mass loss analysis were carried out at time intervals of four minutes, 24 hours, 48 hours and 72 hours using FE-SEM and digital weighing machine. Results No visual change was observed in the samples immersed in deionised water at the time interval of 72 hours. There was a marked visual change in samples immersed in 1.23% APF gel at the time interval of four minutes to 72 hours; this change involved a loss of gloss to the appearance of chalkiness. FE-SEM analysis for the control group and samples immersed in deionised water showed a smooth, continuous, undisrupted top layer, while samples immersed in 1.23% APF gel showed changes ranging from surface etching, to pinhole porosities, to crack formation and disruption of the surface depending upon the exposure time. Conclusions On the immersion of zirconia crowns in an aqueous acidic medium of 1.23% APF gel, the crowns showed flaws, imperfectionsand uneven superficial layers. It has been observed that surface grains are disrupted and micropores have been formed. This degraded superficial surface when undergoes cyclic mechanical loading can accelerate the ageing phenomenon of zirconia. Mechanical forces along with a dynamic electrochemical environment can degrade the material properties of zirconia.

Effect of Nitrogen Fertilizer on Capsaicinoids and Related Metabolic Substances of Dried Chili Pepper Fruit

Reducing fertilizer pollution is an important direction for modern ecological agriculture. Commonly, excessive nitrogen is applied to pepper. Capsaicin is one of the most important economic qualities of spicy peppers, but the effect of nitrogen on capsaicin is still inconsistent. This study aims to elucidate the impact of nitrogen fertilizer on capsaicin accumulation and to provide guidance on fertilizer application on highly spicy chili peppers. The experiment was conducted with five nitrogen fertilizer concentrations: N1 (urea 750 kg ha−1), N2 (urea 562.5 kg ha−1), N3 (urea 375 kg ha−1), N4 (urea 187.5 kg ha−1), and N0 (no nitrogen fertilizer). Nitrogen treatment was applied to two varieties with different spiciness levels from the seedling stage. The fruits in different layers of pepper plants were sampled on the 20th, 35th, and 50th day after anthesis, and the fruits’ size, content of capsaicin, capsaicin precursors, capsaicin competitors, as well as capsaicin-related enzyme activities and gene expression level were analyzed. The results indicate that, when applying N2 and N3, both chili pepper varieties exhibited higher fruit length, diameter, weight, and yield values. There were increased contents of total phenol, flavonoids, and tannins in both fruit varieties with N2 application. Moreover, the placenta weights of the bottom, middle, and top layers of the fruits on the 35th day were improved by 40.14%, 26.80%, and 55.91% for ‘Honglong 23’ and 55.10%, 37.04%, and 75.56% for ‘Hongxi’ compared with N0. At the same time, under N2 treatment, the phenylalanine ammonia-lyase (PAL) enzyme activity of capsaicin synthase significantly increased. In contrast, the capsaicin-degrading enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO) decreased notably. The expression levels of capsaicin-synthetic genes such as phenylalanine cleavage enzyme gene (PAL), acyltransferase gene (AT3), 4-Coumaroyl coenzyme A ligase gene (4CL), cinnamate 4-hydroxylase gene (C4H), caffeoyl coenzyme A-3-oxo-methyltransferase gene (COMT), paminotransferase gene (PAMT), and hydroxycinnamyltransferase gene (HCT) were up-regulated in N2 fruits, which led to a significant increase in capsaicin content compared with the other four nitrogen amounts. A further reduction in nitrogen application to N3 and N4 resulted in a decrease in the precursor substance’s total phenol content and PAL activity and an increase in the competitive substance’s flavonoid, lignin, POD, and PPO enzyme activities. At the same time, the expression levels of capsaicinoid synthetic genes were downregulated in the N3 and N4 treatments, leading to a low content of total capsaicinoids. The capsaicinoid content showed a trend of 35th day > 50th day > 20th day for both varieties. Additionally, the contents of total capsaicinoids, total phenols, flavonoids, and lignins, as well as PAL enzyme activity, and the expression levels of PAL, AT3, 4CL, C4H, COMT, PAMT, and HCT exhibited characteristics of bottom layers > middle layers > top layers. The activities of POD and PPO gradually increased from the bottom to the top layers. The N2 (562.5 kg ha−1) treatment resulted in increases in placenta mass, maximum capsaicinoid precursor substance of total phenol content, and synthase enzyme activity, as well as decreases in capsaicinoid competing substances and degradative enzyme activity, so there were more substances available for capsaicin synthesis. Combined with the higher fruit weight and capsaicinoid content in the N2 treatment, N2 was considered a suitable nitrogen fertilizer dosage for highly spicy chili pepper cultivation.

Thermo-micromechanical finite element modelling of tyre–pavement interaction under UAE environmental conditions

ABSTRACT This work presents a finite element model of the thermo-mechanical behaviour of tyre–pavement interaction, focusing on the effects of temperature variations in the UAE on skid resistance under various tyre operating conditions. The pavement is modelled as multiple layers to account for the stiffness contribution of each layer. The top asphalt layer is modelled at a microscale level to consider its various constituents such as air voids, aggregates and binder. Moreover, the model accounts for the viscoelastic properties of tyre and pavement, considering their dependence on time and temperature. The finite element simulations of a rolling tyre over the pavement have been carried out under different tyre operating conditions and various temperature cases reflecting the winter, spring, and summer seasons in the UAE. The simulation results show that the maximum level of skid resistance occurs during the winter season and thereafter drops by a significant amount during the summer. This research provides good insights about the seasonal variation of skid resistance in the UAE, which enhances road safety.

Efficient and stable perovskite mini-module via high-quality homogeneous perovskite crystallization and improved interconnect

The efficiency and stability of perovskite module devices are mainly limited by the quality of scalable perovskite films and sub-cells’ lateral contact. Here, firstly, we report constant low temperature substrate to regulate the growth of perovskite intermediate films to slow down the crystallization for obtaining high-quality homogeneous perovskite films in large scale size, which avoid the effect of the ambient temperature on the film quality. Secondly, a scribing step named P1.5 was added before the top function layers deposition, the diffusion barrier layer can be formed “naturally” at the interconnection interface without introducing any additional materials, which well alleviates the diffusion degradation process. As a result, our inverted perovskite devices exhibit a very small efficiency loss with area expansion comparable to other photovoltaic devices (for example, Cadmium Telluride), the perovskite module (aperture area 14.61 cm2) shows a certified quasi-steady-state power conversion efficiency of 22.73%, and the module maintaining over 90% of its initial efficiency after 1000 hours of continuous operation under illumination.

Development of anex vivo patient-derived tumor model (PDTM) to assess the tumor microenvironment in renal cell carcinoma (RCC)

Abstract Background With the rise of immune checkpoint inhibitors (ICIs) as the primary treatment option for metastatic RCC, investigating the role of T cells within the tumor microenvironment (TME) is a critical component of understanding both treatment response and resistance. Prior efforts, including single-cell transcriptomic approaches, have provided an important landscape of T cell transcriptional phenotypes. However, these immuno-profiling efforts require validation through functional interrogation of the TME to facilitate the development of novel immunomodulatory therapies. Thus, we established a patient derived tumor model (PDTM) system to directly assess the effect of inhibitory immune interactions on T cell function and anti-tumor activity in the RCC TME. In this initial proof-of-concept study, we evaluated T cell activation in the RCC TME using the PDTM system. Methods Fresh tumor samples were obtained from surgical resections of RCC at Yale-New Haven Hospital. The tumor was minced to ~1-3 mm³ pieces and suspended in an air-liquid interface system, consisting of tumor fragments embedded in a collagen matrix on an insert with a semi-permeable membrane, exposed to culture media. The tumor fragment and matrix suspension were carefully pipetted onto the Millicell insert, which served as the top layer. The PDTM setup includes an inner dish containing the bottom gel layer and the tissue-containing top layer. To complete the assembly, 1.5 ml of DMEM media with or without an anti-CD3 monoclonal antibody (aCD3mAb) and 500 nM of anti-PD-1 monoclonal antibody (aPD1mAb) was added to the outer dish surrounding the insert. Results We successfully optimized PDTM experimental workflows for culture, dissociation, and analysis using immunohistochemistry (IHC), flow cytometry (FCM), and enzyme-linked immunosorbent assays (ELISA). Hematoxylin and eosin (H&E) staining and IHC showed that the TME cellular architecture and immune cell composition was broadly preserved during the three day experimental period. Using FCM to analyze the dissociated tumor samples, we identified well-preserved CA9+ tumor cells, CD4+ and CD8+ T cell populations, CD4+CD25+ regulatory T cells, CD56+ natural killer cells, CD20+ B cells, and CD14+CD11b+ myeloid subsets including monocytes and CD163-/+macrophages. Among the T cells, we detected PD1+, LAG3+, TIM3+, and TIGIT+ cells. For dose-response analysis of aCD3mAb, we observed that stimulation with 0.025 ng/mL aCD3mAb for T cells from healthy donor peripheral blood mononuclear cells (PBMCs) yielded significant but non-saturating levels of interferon gamma (IFN-γ) production as quantified by ELISA. We tested the effect of the anti-PD-1 antibody on PDTM under the low-dose of aCD3mAb, and importantly, found that treatment of the PDTM with aPD1mAb resulted in more activated CD8 T cells and higher IFN-γ production than the control samples. Conclusions Through optimization of assays evaluating T cell cytokine production, we were able to assess multiple axes of T-cell function in the RCC TME. This study revealed that our PDTM system preserves the RCC TME for functional interrogation. Furthermore, our system for assessing T cell phenotype and cytokine production successfully demonstrated the activity of PD-1 blockade ex vivo. Taken together, this novel ex vivo PDTM system has extensive applications in the study of RCC, including assessing the impact of ICIs on T cell function. DOD CDMRP Funding: yes

Investigating the influence of chromium layer thickness on thermal stability, adhesion and agglomeration of Cr/Ag/Cr sandwich layers in microelectromechanical systems (MEMS)

This study explores the influence of chromium layer thickness on the thermal stability and agglomeration of Cr/Ag/Cr sandwich layers used in MEMS applications. Achieving uniform and consistent deposition of thin films is crucial for optimal device performance. Magnetron sputtering, a technique offering precise control over film properties, is commonly employed for depositing thin films in MEMS. Silver is a popular choice due to its desirable properties, but it tends to agglomerate at high temperatures. The researchers investigated the effect of chromium layer thickness on thermal stability and agglomeration. They deposited chromium layers of varying thicknesses onto silicon substrates, followed by a silver layer and another chromium layer to create a sandwich structure. Annealing was performed at different temperatures to assess thermal stability and prevent silver agglomeration. Thermal stability was evaluated by measuring electrical resistance using a four-point probe method, and surface topography was analyzed using a non-contact atomic force microscope. The goal was to identify the optimal chromium layer thickness to minimize agglomeration and maximize thermal stability. The results showed that a sandwich structure with a 5 nm top chromium layer (Si/Cr (5 nm)/Ag (100 nm)/Cr (5-10-15-20 nm)) exhibited decreased adhesion force with increasing annealing temperatures. The use of a chromium sandwich layer significantly reduced surface roughness, as indicated by reductions in Ra and RMS values. A 15 nm thick chromium layer above and below the silver layer provided the best thermal stability and prevented silver agglomeration, resulting in the highest degree of adhesion. This thickness also yielded optimal surface parameters for the chromium sandwich layers at the annealing temperatures. In conclusion, the study demonstrates that the thickness of the chromium layer influences thermal stability, agglomeration, and surface parameters in MEMS applications and enables better control over thin film deposition.

On Low-Velocity Impact Response and Compression after Impact of Hybrid Woven Composite Laminates

This paper aims to study the low-velocity impact (LVI) response and compression after impact (CAI) performance of carbon/aramid hybrid woven composite laminates employed in marine structures subjected to different energy impacts. The study includes a detailed analysis of the typical LVI responses of hybrid woven composite laminates subjected to the impact with three different energies, as well as a comparative analysis of cracks and internal delamination damage within impact craters. Additionally, the influence of different impact energies on the residual compressive strength of hybrid woven composite laminate is investigated through CAI tests and a comparative analysis of internal delamination damage is also conducted. The results indicate that as the impact energy increases, the impact load and CAI strength show a decreasing trend, while impact displacement and impact dent show an increasing trend. The low-velocity impact tests revealed a range of failure modes observed in the hybrid woven composite laminates. Depending on the specific combination of fiber materials and their orientations, the laminates exhibited different failure mechanisms. Buckling failures were observed in the uppermost composite layers of laminates with intermediate modulus systems. In contrast, laminates with higher modulus systems showed early damage in the form of delamination within the top surface layers.

Anomalous diffusion of hydrocarbon vapor through an aqueous foam bubble structure

Hydrocarbons are known as “anti-foamers” because they cause bubble rupture, coalescence, and reduce foaming. We show that the dynamics of bubble structure allows hydrocarbon vapors permeate rapidly when an aqueous foam is placed on a hydrocarbon pool. Two distinct foam layers are formed. Vapor accumulates in an expanding bottom layer at the foam-pool interface where bubbles grow rapidly, rupture, and coalesce. Simultaneously, vapor diffuses through a top layer having small bubble structure, which changes slowly due to Ostwald-ripening. Very little vapor accumulates in the top layer, which has a constant thickness equal to the initial foam thickness. Surprisingly, both accumulation in the bottom layer and diffusion through top layer occur at constant rates, which are independent of time and initial foam thickness. The vapor diffusion rate in the top layer should have decreased, inversely proportional to the initial foam thickness, based on classical diffusion theory; only the fluorosurfactant containing foam (RefAFFF) placed on gasoline follows the classical theory where the bottom foam layer is absent. Therefore, we propose a theory to show a linear increase in diffusion time with initial foam thickness using an effective diffusion-coefficient. Experiments show that this variation could be because of increased liquid drainage, drying, and bubble coarsening, which are not considered explicitly in the theory. We also describe a theory for the expanding bottom layer to show that most vapor formed at the pool surface accumulates for very volatile hydrocarbons. The vapor diffusion controls foam ignition. We show that the measured foam ignition time also increases linearly with initial foam thickness, qualitatively consistent with the predicted diffusion time. By employing different hydrocarbons, we show that the measured foam ignition times decrease inversely proportion to square root of hydrocarbon vapor concentration for a given surfactant. This could be because a surfactant exhibits different degrees of oleophobicity towards different hydrocarbons that can reduce vapor adsorption, solubility, and diffusion at a bubble surface. Different surfactants also exhibit different degrees of oleophobicity towards a given hydrocarbon (n-pentane) and increase ignition times by a factor of six: RefAFFF having the longest ignition time, followed by siloxane-polyoxyethylene formulation, and its individual surfactant components.

In-situ aircraft observations of aerosol and cloud microphysical characteristics of mixed-phase clouds over the North China Plain

Aerosol-cloud interactions play a vital role in climate change. This study leverages observations from the King-350 aircraft over the North China Plain on November 29, 2019, to examine aerosol and cloud microphysical characteristics of mixed-phase clouds. Through detailed vertical and spectral distributions, we investigate aerosol, cloud droplet, and ice crystal distributions in seeded clouds (SC) and natural precipitating clouds (NPC) within the same cloud system. From the vertical profile, SC and NPC have similar vertical distributions of aerosol and cloud droplets, with over 95 % of aerosols concentrated below 1600 m near the ground. Cloud droplets are more evenly distributed within the two clouds, cloud droplet number concentrations (Nc) in SC were three orders of magnitude higher than in NPC. Ice water content (IWC) and ice crystal number concentration (Ni) show distinct layer preferences—accumulating predominantly in SC's top layer and NPC's middle layer. From spectral distribution, a smaller proportion of cloud droplets (40–50 μm in diameter, the same hereafter) in SC compared to NPC. Rimed ice crystals and globular graupel (1325–1550 μm in diameter) were in SC, while plate and irregular ice crystals (300–450 μm) were in NPC with an order of magnitude higher than in SC. These microphysical differences highlight the complexity of cloud seeding efficacy, which varies based on cloud conditions and microphysical properties. In the first seeding, Ni increased by 1–2 orders of magnitude (125–300 μm) in the high Nc (Nc > 1.11 × 105 L−1) region. Seeding in low Nc (Nc < 1.11 × 105 L−1) regions was hard to be effective, especially in low Nc and low liquid water content (LWC) (LWC < 0.122 g/m3) regions. In the second seeding, ice crystals (125–250 μm) produced by the first seeding enhance the seeding efficiency. The responded regions were more sensitive to subsequent seeding, resulting in stronger reactions or longer duration.

Investigation of microstructure, tribological, and corrosion behaviors of TiN@AISI 316 CN processed by rf plasma

In order to enhance the tribological and corrosion properties of AISI 316 substrate, rf plasma carbonitriding was involved to form a carbonitrided layer on AISI 316 base substrate. The deposition of TiN top layer was executed engaging titanium nitride target in argon plasma atmosphere. All the deposition working parameters were reserved to be constant excepting the deposition period that was altered from 4 to 20 min. The effect of TiN top layer thickness on the structure, tribological and electrochemical characteristics of TiN@AISI 316 CN duplex treatment was explored. It was demonstrated, that the duplex coating enhanced the hardness (max: 1740 HV0.025 for TiN (1325nm)@AISI 316 CN sample) and improved the wear and corrosion resistance. Besides, the coefficient of friction is reduced to 0.12–0.2 for TiN@AISI 316 CN duplex treated samples compared with untreated AISI 316 which recorded a value of 0.47.

Impedance dynamics in tandem solar cells based on c-Si with upper layers of CsPbBr3 (CsPbI3) perovskite nanocrystals

The application of an additional nanoparticle layer is a common practice for enhancing the optical and electrical properties of third-generation solar cells. In this study, we present the results of impedance spectroscopy (IS) for modified solar cells using Nyquist and Bode diagrams. The structure investigated consists of a conventional double junction based on crystalline silicon (c-Si) coated with thin films of inorganic perovskite nanocrystals (NC) of lead halides CsPbI3 and CsPbBr3. The latter are characterized by a significant phonon disorder, which leads to unique electron-phonon interactions and dielectric responses. The IS results indicate that, under the same conditions, the measured Nyquist plots align well with the simulated ones. An equivalent circuit model is proposed, featuring ohmic resistance, recombination resistance, and geometric capacitance. These elements arise due to charge accumulation, charge transfer resistance, and/or additional interfacial electronic states. The study finds that the introduction of a CsPbI3 layer enhances the photoresponse under bias conditions, but this photoresponse leads to a decrease in DC conductivity. In contrast, the addition of a CsPbBr3 layer obstructs the photoresponse under bias while slightly improving the photoresponse in the absence of an applied voltage. The results obtained contribute to the improvement of tandem solar cell characteristics featuring top layers of perovskite nanocrystals.

A substrate-integrated waveguide-based wideband circularly polarized slot antenna using the parasitic square patch array

In this paper, a planar low-profile wideband circularly polarized substrate-integrated waveguide (SIW) based antenna is investigated. The antenna comprises two substrates stacked over each other. The top layer of the antenna is loaded with a 4 × 4 array of parasitic square patches stacked over a spiral slot loaded in the SIW cavity. The spiral slot is utilized for the generation of narrow band circular polarization and to enhance the CP bandwidth, the parasitic patch array is excited through the electromagnetic coupling mechanism without any air gap between them. The antenna is fabricated and tested to validate the simulated results. A wide relative impedance bandwidth of 33% (8.25–11.55 GHz) and the axial ratio bandwidth of 8.55–9.70 GHz (12.60%) is exhibited. The broadside radiation characteristics are achieved with peak gain of 8.05dBic at 9 GHz. The overall size of the antenna structure is 0.8λ0 × 0.8λ0. The proposed antenna is suitable for various satellite applications.

A new CsPbI2Br/CuZnSnSSe/Si tandem solar cell with higher than 32 % efficiency

To avoid Shockley-Queisser limit in single p-n junctions, tandem solar cells were proposed. A new tandem cell is simulated here using the 1-dimensional SCAPS. The new cell combines two reported single solar cells together, aiming at achieving high performance by optimizing various layer characteristics. The bottom sub-cell is Mo/Si(p)/CZTSSe(p)/CdS(n)/ZnO(i)/ZnO(Al), where ZnO is an electrodeposited transparent-conductor oxide, with high UV transmittance, ZnO(i) is intrinsic layer, CZTSSe/Si is bi-absorber layer of p-CuZnSnSSe and p-Si, Mo is back contact. The optimized sub-cell exhibits a high fill factor of 85.18 % with overall efficiency 20 %. Based on literature, a perovskite CsPbI2Br layer is included in the top sub-cell Cu2O(HTL)/CsPbI2Br)/TiO2(ETL), where Cu2O is a hole-transport layer and TiO2 is electron-transport layer. The top sub-cell layers have been carefully selected for best alignment. Matching and optimizing various parameters in the two sub-cells is a simulation challenge. Therefore, layers in the two sub-cells have been studied separately, keeping in mind the proper combinations between various layers. With optimized layer thicknesses and band gaps, together with proper alignment of band edges, the proposed tandem solar cell exhibits high characteristics of 80 % fill factor and higher than 32 % overall efficiency.

Synergism in the electrocatalytic properties of cobalt phthalocyanine-carbon nanotube-polymeric electrospun nanofibers immobilized on a gold electrode for the detection of lead(II) ions

Core-shelled electrospun nanofibers (ENFs) comprising of a polyvinyl acetate (PVA) shell encapsulating a composite of polyaniline (PANI), tetra-4-(3-oxyflavonephthalocyaninato)cobalt(II) (CoPc-flav), carboxylic acid functionalized multiwalled carbon nanotubes (f-MWCNTs) and an annealed conductive top layer of Nafion (Nf) were used to fabricated a chemically modified gold electrode (Au|ENFs-1-Nf) via the adsorption method. The electrocatalytic sensing capabilities of the Au|ENFs-1-Nf electrode towards Pb(II) ions were evaluated. In comparison to the bare gold electrode and other chemically modified electrodes (CMEs), the Au|ENFs-1-Nf electrode was less prone to fouling showing more stable analyte signal and less compromised background electrolyte currents. The Au|ENFs-1-Nf electrode could detect the Pb(II) cations in a reproducible manner ranging from 8 to 125 μM where limits of detection and quantification of 0.51 and 1.55 μM were obtained, respectively. The analytical performance of the aforementioned CME rendered a comparable percentage recovery (103 %) with that of Inductively coupled plasma-optical emission spectroscopy (ICP-OES) (115 %).

Enhancing the tribological performance of polyimide composite coatings with amino-functionalized MXene nanofillers

At the nanoscale, the surface properties of nanomaterials are of utmost importance. Amino-functionalized MXene (AMXene) was prepared by grafting 3-aminopropyltriethoxysilane (APTES) upon the top layer of Ti3C2Tx. AMXene is introduced into the polyimide (PI) matrix coatings. The findings indicate that the dispersion of AMXene in PI is further substantially enhanced based on the principle of “similar compatibility”, which is attributable to the creation of more hydrogen bonds between AMXene and highly polar PI matrix molecular chains. The addition of AMXene lowered the factor of friction by 34.1 % and the rate of abrasion by 84.8 % compared to unadulterated PI. In addition, the PI/AMXene composites exhibit significant reinforcement properties at different loads and speeds.

Reactive Solid Polymer Layer: From a Single Fluoropolymer to Divergent Fluorinated Interface

AbstractControlling the structure and chemistry of solid electrolyte interphase (SEI) underpins the stability of electrolyte‐electrode interface, and is crucial for advancing rechargeable lithium metal batteries (LMBs). Here, we utilized photo‐controlled copolymerization to achieve the on‐demand synthesis of fluorosulfonyl fluoropolymers as unprecedented artificial SEI layers on Li metal anodes. This work not only enables instant formation of a hybrid polymer‐inorganic interphase that consists of a polymer‐enriched top layer and a LiF‐fortified bottom layer, originating from a single polymeric component, but also imparts various desirable physical properties (e.g., good mechanical strength and flexibility, high ion conductivity, low overpotential) to SEI via a single‐to‐divergent strategy. Model reactions and structural characterizations supported the formation of a divergent fluorinated interphase, which furnished prolonged stabilization of Li deposition, high coulombic efficiency and improved cycling behavior in electrochemical experiments. This work highlights the great potential of exploring reactive polymers as versatile coatings to stabilize Li metal anodes, providing a promising avenue to solve electrode‐electrolyte interfacial problems for LMBs.

Distributed Neurodynamics-Based Backstepping Optimal Control for Robust Constrained Consensus of Underactuated Underwater Vehicles Fleet.

Robust constrained formation tracking control of underactuated underwater vehicles (UUVs) fleet in 3-D space is a challenging but practical problem. To address this problem, this article develops a novel consensus-based optimal coordination protocol and a robust controller, which adopts a hierarchical architecture. On the top layer, the spherical coordinate transform is introduced to tackle the nonholonomic constraint, and then a distributed optimal motion coordination strategy is developed. As a result, the optimal formation tracking of UUVs fleet can be achieved, and the constraints are fulfilled. To realize the generated optimal commands better and, meanwhile, deal with the underactuation, at the lower-level control loop a neurodynamics-based robust backstepping controller is designed, and in particular, the issue of "explosion of terms" appearing in conventional backstepping-based controllers is avoided and control activities are improved. The stability of the overall UUVs formation system is established to ensure that all the states of the UUVs are uniformly ultimately bounded in the presence of unknown disturbances. Finally, extensive simulation comparisons are made to illustrate the superiority and effectiveness of the derived optimal formation tracking protocol.

Evaluation of the impacts of turbidity on Gilgel-Gibe I reservoir storage, Omo-Gibe River Basin, Ethiopia

Quantity and quality of the water held in the reservoir fluctuates due to turbidity alterations. The influence of turbidity on the amount of the water held in a reservoir was described explicitly in this research. This study aimed to evaluate turbidity's impact on the Gilgel-Gibe I reservoir water. The samples were obtained by longitudinally stratifying the reservoir water throughout its course. Ten burrowed pools wrapped in transparent white plastic were used to retain water, for detection of the association between turbidity and surface water temperature, and to demonstrate the vertical variation in water temperature. The pan evaporation rate was measured using two Class A pans placed in the field to indicate the disparity in the amount of water evaporated from reservoir owing to reservoir turbidity variation. SPSS and MS Excel spreadsheet softwares were used to analyze the data. According to the results of this study, turbidity and water temperature have a significant direct relationship that is positive at 9:00 and 13:00 and negative at 17:00 observation hours. From the top layer of pool water to the bottom layer, the water temperature decreased vertically. Intensity of the light rays absorbed and scattered alters with turbidity variation and significant amounts of light rays was absorbed and scattered in the most turbid water. The reported water temperature differences between the top and bottom layers at 13:00 observation hour were 9.78 °C and 1.53 °C, for the most and least turbid pool water, respectively. Turbidity directly affects reservoir water by increasing both the water temperature and evaporation rates. Among all turbid-water samples, substantial quantity of water evaporated from the most turbid-water. For the most and least turbid water samples, the volume difference of the evaporated water from the reservoir was approximately 65.812 m3. According to these findings, if the reservoir water turbidity increases, the amount of water held in the reservoir significantly reduced due to substantial water loss.

Design of a Ka‐band low‐cost microstrip line phase shifter and a sum‐difference beam antenna based on liquid crystal technology

AbstractThis letter presents a Ka‐band low‐cost microstrip line phase shifter based on liquid crystal (LC) technology. Furthermore, a sum‐difference beamforming antenna array based on the LC phase shifter is designed. The phase shifter is composed of two coaxial connectors, a metal base, an intermediate dielectric layer, a gradient metal sheet and a top glass layer. The simulated results show that a nearly 360° phase shift coverage can be achieved with the effective permittivity of LC varying from 2.5 to 3.5. The sum‐difference beam antenna array is composed of a circulator, a sum‐difference network, a one‐to‐eight power‐division network, eight liquid crystal phase shifters, and a serious fed antenna array. The simulation results show that the antenna array can achieve sum‐difference beam scanning range of ±30°. A prototype of LC phase shifter is fabricated and tested. The results show that the designed LC phase shifter can achieve a 360° phase coverage by applying a direct current (DC) voltage ranging from 0 to 12 V. Compared to traditional phase shifters, the proposed design offers a simple structure at a lower cost. When applied in the design of a sum‐difference beam antenna array, it can reduce the producing cost and enable integrated design.