Fading Research Articles

A biomass-based cathode for long-life lithium-sulfur batteries

With the advantages of high conductivity and low cost, porous carbons have been considered as the most attractive host materials of sulfur cathodes in lithium-sulfur batteries (LSBs). However, LSBs always suffer short cycle life due to the “shuttle effect” of lithium polysulfide species (polysulfides), which are intermediate products during the charge/discharge processes. The weak interaction between carbon and polysulfides results in the dissolution of polysulfides from the cathodes, loss of active material of sulfur and eventually fast capacity fading. To overcome these drawbacks, we employed a biomass-derived carbon as the host material in sulfur cathodes. Results from X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen sorption reveals that this biomass-derived product is amorphous carbon and is composed of both large (>10 nm) and small (<5 nm) pores at an appropriate ratio. Using as hosts of cathodes in LSBs, the biomass-derived carbons deliver a high reversible capacity of >800 mAh/g and retain >80% of initial capacity after 200 cycles. Especially, the activated carbons exhibited an unprecedently high durability with 80% capacity retention after 400 cycles. The promising LSB performance can be ascribed to the unique porous architecture of biomass-derived carbons. The small pores in biomass-derived carbons provide more sites to anchor sulfur and polysulfides, while large pores provide channels for fast transport of ions. This is corroborated by the results from the electrochemical impedance spectroscopy (EIS), the thermogravimetric analysis (TGA) and absorption measurements.

Rationally designed heterostructure ZnS/SnS@N-doped carbon microspheres as high-performance anode for lithium-ion batteries

Metal sulfides are considered as promising anodes for lithium-ion batteries (LIBs) because of their high capacity. Among all of these metal sulfides, Tin(II) sulfide (SnS), possessing a unique 2D structure and with high lithium storage capacity, attract more attention as a promising anode for LIBs. However, serious volume change, sluggish kinetics, and low electric conductivity during the charging/discharging process, lead to poor rate capability and fast capacity fading. Herein, a ZnS/[email protected] yolk-shell microspheres ([email protected]) is synthesized through a facile hydrothermal process coupled with a PPy coating and sulfidation-in-microsphere strategy. The built-in electric field generated from ZnS/SnS heterostructure benefits the rapid transport of Li-ion and enhances the electric conductivity. Meanwhile, the N-doped carbon further improves the electronic conductivity and provides a robust support architecture, which can mitigate the volume variation of ZnS/SnS during the lithiation/delithiation process. Therefore, the ZnS/[email protected] delivers high capacity (775.5 mA h g−1 at 200 mA g−1 after 200 cycles), outstanding rate performance (395.8 mA h g−1 at 5 A g−1), and superior long-term cycling performance (571.2 mA h g−1 at 1 A g−1 after 1000 cycles).

A Network-Assisted Game-Theoretic Design to Power Control in Autoregressive Fading Channels

Several previous works have proposed game-theoretic approaches to controlling the pilot and data power levels in the uplink of both single and multi-cell multi-user multiple input multiple output (MU-MIMO) systems. Unfortunately, the vast majority of existing works design these power control schemes under the assumption that the wireless channels between the mobile terminals and the serving base station are block fading. Meanwhile, several letters have shown that modeling fast fading channels as autoregressive (AR) processes with known or estimated state transition matrices give much more accurate results than those suggested by block fading models. Thus, this letter proposes a game-theoretic approach to controlling the uplink pilot and data power levels in a MU-MIMO system, in which the wireless channels are AR processes with mobile terminal-specific state transition matrices. We find that the proposed approach outperforms a classical cellular path-loss compensating fractional power control scheme and a game-theoretic power control scheme designed for block fading channels.

Resource optimization of MIMO using neural network for 5G communication

The principal objective of this work is to optimize the resources of massive MIMO techniques by an application of a neural network algorithm in order to reduce the manufacturing cost of 5G technology within the wireless peripheries of tropical regions. For plenty of annual precipitation in the tropical regions, the radio signals of these areas get attenuated in communicating any message i.e. signal fading occurs. Various diversity techniques have been used for diminishing signal fading in these tropical areas. MIMO technique is a spatial diversity technique used to minimize signal fading. In this paper, 1 × 1 to 256 × 256 MIMO techniques have been designed with the help of MATLAB and Xilinx system generator, and an 8 × 8 MIMO has been implemented in Xilinx Kintex7 FPGA. A CMOS logic technique has been incorporated to optimize the resources of different MIMO techniques, and for this purpose a two-layer feed forward neural network algorithm has been adopted. A comparison of the theoretical values obtained from the design by using both Xilinx system generator and Simulink with the values derived from the design by using CMOS logic gates, has been displayed in this paper. For neural network optimization, three types of training algorithms have been applied.

Multifunctional Surface Construction for Long-Term Cycling Stability of Li-Rich Mn-Based Layered Oxide Cathode for Li-Ion Batteries.

Li-rich Mn-based layered oxides (LMLOs) are promising cathode material candidate for the next-generation Li-ion batteries (LIBs) of high energy density. However, the fast capacity fading and voltage decay as well as low Coulombic efficiency caused by irreversible oxygen release and phase transition during the electrochemical process hinder their practical application. To solve these problems, in the present study, a multifunctional surface construction involving a coating layer, spinel-layered heterostructure, and rich-in oxygen vacancies is successfully conducted by a facile thermal reduction of the LMLO particles with potassium borohydride (KBH4 ) as the reducing agent. The multifunctional surface structure plays synergistic effects on suppressing the interface side reaction, reducing the dissolution of transition metal, increasing electron conductivity and lithium diffusion rate. As a result, electrochemical performances of the LMLO cathode are effectively enhanced. With optimization of the addition of KBH4 , the electrode delivers a reversible capacity of 280 mAh g-1 at 0.1 C, which maintains after 100 cycles. The capacity retention with respect to the initial capacity is as high as 98% at 1 C after 400 cycles. The present work provides insights into designing a highly effective functional surface structure of LMLO cathode materials for high-performance LIBs.

Dosimetric characteristics of fabricated germanium doped optical fibres for a postal audit of therapy electron beams

The dosimetric characteristics of germanium (Ge) doped optical fibres are investigated as a potential dosimetric alternative for electron beam therapy postal audits. The dosimetric characteristics of 6 mol% Ge-doped optical fibres fabricated as cylindrical fibres (CF) and flat fibres (FF) are established in terms of signal fading, linearity of dose-response, beam energy- and dose rate dependence. Pilot electron beam therapy audit study irradiations are made with a linear accelerator located at the Royal Surrey County Hospital, applying International Atomic Energy Agency (IAEA) standard irradiation procedures for reference and non-reference conditions. Results for the CF and FF show fading of 26% and 20% respectively at 120 days post-irradiation. For a 6 MeV electron beam the dose-response is observed to be linear over the dose range 1–3 Gy, the least determination coefficient, R2, being 0.985. The results of the electron beam therapy audit are within the tolerance limit of 5% recommended by the International Commission on Radiation Units and Measurements (ICRU) Report No. 24, with a maximum deviation of 4% for FF at a 6 MeV electron beam under non-reference conditions. In conclusion, the fabricated Ge-doped optical fibres are seen to offer suitability for use as an alternative dosimeter to TLD-100 in electron beam therapy postal audit.

The effect of fast relay fading and frequency mismatch of the frequencies of the receiving and transmitting channels on the characteristics of the OFDM signal

In this paper, we consider the negative simultaneous effect of fast relay fading in the channel and mutual frequency shifts of subcarriers between the transmitting and receiving sides of the channel, causing violation of orthogonality between the signals of individual subchannels of OFDM system. Violation of orthogonality is manifested in the appearance of mutual interference signal at the receiving end of the channel in each OFDM subchannel. The paper evaluates the joint effect of fast fading and frequency shifts on the magnitude of the transient interference between subchannels and investigates in sufficient detail the manifestation of transient interference between individual subchannels caused by orthogonality violations each of the two factors cited separately. In this paper, we consider the simultaneous effect of both factors and their influence on the value of the interchannel transient interference.

Confinement and Electrocatalysis of Cerium Fluoride Nanocages to Boost the Lithium–Sulfur Batteries Performance

Lithium–sulfur batteries (LSBs) are beset by the polysulfides shuttling and the sluggish conversion kinetics, leading to fast capacity fading and inferior rate capability. A feasible solution is to confine the active species and/or electrocatalytically boost the polysulfides conversion by suitable host materials. Herein, hollow cerium fluoride nanocages (h‐CeF3) are employed as the host, which not only suppressed polysulfides shuttling via physical confinement and chemisorption, but also exhibited remarkable catalytic promotion to the polysulfide conversion, much superior to the counterparts of solid cerium fluoride nanodiscs (s‐CeF3) and hollow ceria nanospheres (h‐CeO2). Consequently, the sulfur‐filled h‐CeF3 cathode delivers an outstanding capacity of 544 mAh g−1 at 5 A g−1, demonstrating a high rate capability. With an areal sulfur loading of ≈3.5 mg cm−2, the LSB exhibits a reversible capacity of 429.5 mAh g−1 at 1 A g−1 after 200 cycles under a low electrolyte/sulfur (E/S) ratio of 10 μL mg−1. This study demonstrates the promise of the h‐CeF3 host in Li–S batteries, shedding light in developing advanced sulfur hosts of metal fluorides.

Integrating Bi@C Nanospheres in Porous Hard Carbon Frameworks for Ultrafast Sodium Storage.

Sodium-ion batteries (SIBs) have emerged as an alternative technology because of their merits in abundance and cost. Realizing their real applications, however, remains a formidable challenge. One is that among the limitations of anode materials, the alloy-type candidates tolerate fast capacity fading during cycling. Here, a 3D framework superstructure assembled with carbon nanobelt arrays decorated with a metallic bismuth (Bi) nanospheres coated carbon layer by thermolysis of Bi-based metal-organic framework nanorods is synthesized as an anode material for SIBs. Due to the unique structural superiority, the anode design promotes excellent sodium-storage performance in terms of high capacity, excellent cycling stability, and ultrahigh rate capability up to 80Ag-1 with a capacity of 308.8mAhg-1 . The unprecedented sodium-storage ability is not only attributed to the unique hybrid architecture, but also to the production of a homogeneous and thin solid electrolyte interface layer and the formation of uniform porous nanostructures during cycling in the ether-based electrolyte. Importantly, deeper understanding of the underlying cause of the performance improvement is illuminated, which is vital to provide the theoretical basis for application of SIBs.

A novel synthesis of GeO2/Ge composite as an anode material for lithium-ion batteries

Germanium (Ge) is a potential anode material in lithium-ion batteries (LIBs) due to its ultrahigh theoretical capacity (1623 mAh·g−1). However, Ge-based anodes suffer from huge volume variation during lithium insertion/extraction, leading to fast capacity fading. In this study, the GeO2/Ge composite was synthesized by facile reducing GeO2 by magnesium and utilized as an anode material for LIBs. As a result, the obtained GeO2/Ge composite exhibits significantly improved cycling stability and specific capacity compared to the pure Ge. The enhanced electrochemical performance can be derived from the impact of the GeO2 on reducing volume change during cycling.

Respiratory Viruses in Hospitalized Patients before and after SARS-CoV-2

Background: Since the emergence of COVID-19, countries have implemented combinations of non-pharmaceutical measures not only to contain the COVID-19 cases manageable for their healthcare system but also to reduce the economic burden of the disease. Among the various options, authorities have mostly adopted frequent hand disinfection and wearing surgical masks. Because these measures have long been used in medicine to prevent infections, there is reason to expect an effect not only on SARS-CoV-2 but also on other microorganisms that spread via droplet inhalation and close contact. This study investigates the epidemiology of typical respiratory viruses in Slovenian hospitalized patients before and during the ongoing SARS-CoV-2 epidemic. Methods: Molecular testing data were analyzed using a laboratory informative system for typical respiratory viruses from 2012 to 2022 in conjunction with SARS-CoV-2 testing from March 2020 onward. Results: First, we observed a significant decrease in the number of typical respiratory virus testing requirements after the SARS-CoV-2 outbreak; second, a change in the age structure of hospitalized patients, with fewer children and more working-age individuals during the 2020/21 season; third, complete disappearance of influenza A, B, RSV, and other enveloped respiratory viruses; and, fourth, unchanged epidemiology of rhinovirus. Finally, with the slow fading of all measures implemented in the 2020/21 season, respiratory viruses appear to be “back on the scene” despite the still ongoing SARS-CoV-2 epidemic in 2021/22. Conclusions: Further monitoring seems to be important in the coming seasons to shed more light on future changes in respiratory viruses’ epidemiology because restrictions are bound to be loosened.

Robust interfacial engineering construction to alleviate polysulfide shuttling in metal sulfide electrodes for achieving Fast-charge High-capacity lithium storages

Robust cathode/electrolyte interphase (CEI) layer exhibits much importance in capacity retention. However, metal sulfide electrodes with unstable CEI layers suffer from fast capacity fading and poor Coulombic efficiency caused by notorious polysulfide shuttling effect. Herein, different from nanoparticle engineering, the morphology and state of CEI interface engineering are modulated via introducing highly active lithium bisfluorosulfonylimide (LiFSI) in the ether-based electrolyte. The presence and evolution of the uniform and robust LiF-Li3N-rich CEI layer in preventing polysulfide shuttling are fully understood by electrochemical measurements, interface-sensitive sum frequency generation spectroscopy, X-ray spectroscopies and electron microscopy. With the aid of the time-of-flight secondary-ion mass spectrometry, the three-dimensional architecture of CEI is re-depicted, showing the uniform coverage and thus inhibiting the polysulfide shuttling. As a result, the so-fabricated metal sulfide electrodes with continuous CEI layer exhibit much higher rate capacity and significantly-improved Coulombic efficiency than the controlled electrode samples. Even cycled at a high-power density of 6700 W kg−1 (5 C), the FeS2 electrode remains a high initial capacity (512 mA h g−1) and long lifespan up to 1000 cycles, depicting a blue-script of constructing robust CEI on the electrode for achieving the fast-charge electrodes.

Two Low-Level Feature Distributions Based No Reference Image Quality Assessment

No reference image quality assessment (NR IQA) aims to develop quantitative measures to automatically and accurately estimate perceptual image quality without any prior information about the reference image. In this paper, we introduce two low-level feature distributions (TLLFD) based method for NR IQA. Different from the deep learning method, the proposed method characterizes image quality with the distributions of low-level features, thus it has few parameters, simple model, high efficiency, and strong robustness. First, the texture change of distorted image is extracted by the weighted histogram of generalized local binary pattern. Second, the Weibull distribution of gradient is extracted to represent the structural change of the distorted image. Furthermore, support vector regression is adopted to model the complex nonlinear relationship between feature space and quality measure. Finally, numerical tests are performed on LIVE, CISQ, MICT, and TID2008 standard databases for five different distortion categories JPEG2000 (JP2K), JPEG, White Noise (WN), Gaussian Blur (GB), and Fast Fading (FF). The experimental results indicate that TLLFD method achieves superior performance and strong generalization for image quality prediction as compared to state-of-the-art full-reference, no reference, and even deep learning IQA methods.

Additive-Assisted Hydrophobic Li+ -Solvated Structure for Stabilizing Dual Electrode Electrolyte Interphases through Suppressing LiPF6 Hydrolysis.

Lithium-metal batteries have attracted much attention due to their high energy density. However, the hydrolysis of LiPF6 leads to uncontrollable Li dendrites growth and fast capacity fading. Herein, a hydrophobic Li+ -solvated structure is designed by inducing the hexafluoroisopropyl acrylate into the electrolyte system. Due to the alkene groups and non-polar perfluorocarbon (-CF2 CF2 CF3 ) chain, a hydrophobic surface around Li-ion solvated aggregates can be obtained to protect the LiPF6 against the attack from trace H2 O. Moreover, the additive could also help to form an organic solid electrolyte interphase with rich polar C-F bonds, which can capture Li ions to restrain the dendrite growth. Therefore, the Li||Li symmetric cells show a stable cycling performance up to 500 h at a current density of 1 mA cm-2 . The Li||LiNi0.6 Co0.2 Mn0.2 O2 cells show good cycling stability, exhibiting a specific capacity of 111 mAh g-1 at 1 C with a capacity retention of 74 % after 200 cycles.

Additive‐Assisted Hydrophobic Li+‐Solvated Structure for Stabilizing Dual Electrode Electrolyte Interphases through Suppressing LiPF6Hydrolysis

AbstractLithium‐metal batteries have attracted much attention due to their high energy density. However, the hydrolysis of LiPF6leads to uncontrollable Li dendrites growth and fast capacity fading. Herein, a hydrophobic Li+‐solvated structure is designed by inducing the hexafluoroisopropyl acrylate into the electrolyte system. Due to the alkene groups and non‐polar perfluorocarbon (−CF2CF2CF3) chain, a hydrophobic surface around Li‐ion solvated aggregates can be obtained to protect the LiPF6against the attack from trace H2O. Moreover, the additive could also help to form an organic solid electrolyte interphase with rich polar C−F bonds, which can capture Li ions to restrain the dendrite growth. Therefore, the Li||Li symmetric cells show a stable cycling performance up to 500 h at a current density of 1 mA cm−2. The Li||LiNi0.6Co0.2Mn0.2O2cells show good cycling stability, exhibiting a specific capacity of 111 mAh g−1at 1 C with a capacity retention of 74 % after 200 cycles.

Generalized Receiver Designs for OFDM Systems with Alamouti Decoding in Fast Fading Channels

In the present paper, the generalized receiver designs for orthogonal frequency-division multiplex-ing (OFDM) systems that exploit the Alamouti transmit diversity technique are addressed. In Alamouti space-time coded OFDM systems, the simple Alamouti decoding at the generalized receiver relies on the assumption that the channels do not change over an Alamouti codeword period (two consecutive OFDM symbol periods). Unfortunately, when the channel is fast fading, the assumption is not met, resulting in severe performance deg-radation. In the present paper, a sequential decision feedback sequence estimation (SDFSE) scheme based on the generalized receiver with an adaptive threshold, a traditionally single-carrier equalization technique, is used to mitigate the performance degradation. A new method to set the threshold value is proposed. For small signal constellations like binary phase-shift keying (BPSK) and quadrature phase shift-keying (QPSK), the SDFSE generalized receiver with the adaptive threshold requires much lower complexity than a previous minimum me-an square error (MMSE) approach based on the generalized receiver at the cost of small performance degradati-on. Furthermore, we show that the performance difference becomes smaller when the channel estimation error is included. Adaptive effort sequence estimation (AESE) scheme based on the generalized receiver is also pro-posed to further reduce the average complexity of the SDFSE generalized receiver scheme with the adaptive threshold. The AESE generalized receiver scheme is based on the observation that a high Doppler frequency does not necessarily mean significant instantaneous channel variations. Simulations demonstrate the efficacy of the proposed SDFSE generalized receiver with the adaptive threshold and AESE generalized receiver schemes.

Constructing ultrafine Cu nanoparticles encapsulated by N-doped carbon nanosheets with fast kinetics for high-performance lithium/sodium storage

Carbon-based materials are extensively applied in Li/Na-ion batteries (LIBs/SIBs) anode material. Nevertheless, the poor rate performance, sluggish reaction kinetics, and fast capacity fading during cycling process seriously impedes large-scale commercial application. Herein, ultrafine Cu nanoparticles encapsulated within N-doped carbon nanosheets (labeled Cu/NC) with enlarged interlayer distances, increased intrinsic defects, abundant metallic Cu sites, and hierarchical porous structure were facilely and efficiently fabricated by a room-temperature grinding followed by high temperature pyrolysis. The Cu/NC as electrodes show a high capacity of 788 mAh g−1 in LIBs, and 434 mA h g−1 in SIBs at 0.2 A g−1, as well as good cycling stability with 123 mAh g−1 for LIBs and 177 mAh g−1 for SIBs at 10 A g−1 after 2000 cycles. The as-assembled sodium-ion hybrid capacitors (SIHCs) deliver a high energy/power density of 97 Wh kg−1 at 181 W kg−1, remarkable capacity retention of 95.8% after 10,000 cycles and practical applications (69 LEDs can be easily lighted). The experimental results couple with theoretical calculation indicate that the incorporating of Cu and N species can provide abundant active sites and structural defects, resulting in fast reaction kinetics for Li/Na-ion storage.

Perception of Computer Generated Images (CGI) in Nigerian made animated films: A cognitive-semiotic view

Purpose: There has been lots of positive and negative criticisms on the influences and effects of animated images on kids in Nigeria without considering the communicative potentials of such medium from our cultural perspectives. Again, many Nigerians may not have the knowledge that there are quality Nigerian local content animation. Methodology: This paper looks at the perception of computer generated imagery (CGI) in Nigerian animated films. It examines the nature of the application of CGI in popular Nigerian Animated films by analyzing the techniques used and meanings produced from The images constructed to communicate the ideas of the narratives. This paper is anchored on the framework of cognitive semiotic theory and adopts the qualitative research design to investigate the communication of meanings by use of CGI in Malika (2020), the basis for using cognitive semiotic theory in this paper is that CGI are simulated believable images that denote meanings to communicate encoded cultural ideologies to kids within and outside Nigeria. It is hoped that this study would make better appreciation of Nigerian Animated films and encourage Animators to make more. Findings: The findings in this study, is that, the use of CGI in object and character representation in Nigerian Animated films as regards reality simulates the simulacra nature of a typical African worldview and bring to life a historical antecedent. It submits that CGI boosts the visual and aural representation of the Nollywood film narratives which allow the viewer to recognize the already established meanings of the codes used in film text. Unique Contribution to Theory, Practice and Policy: It also recommends that Animation should be used for promotion and preservation of fast fading Igbo cultures

Interfacial chemistry of vinylphenol-grafted PVDF binder ensuring compatible cathode interphase for lithium batteries

Elevating operating voltage is an effective route to further promote the energy density of nickel-rich layered oxides based lithium batteries. However, high-voltage cycling generally incurs rapid capacity fade of cells due to severe decomposition of commercially available liquid electrolytes and active material degradation. Especially, reactive oxygen species including 1O2 generated under high-voltage cycling give rise to severe electrolyte decomposition and thus result in fast capacity fading of batteries. To address this issue, herein, we first develop a vinylphenol-grafted PVDF binder with 1O2-scavenging effect for nickel-rich layered oxide cathodes, which is inspired by the eliminating role of dopamine. Detailed experiment research demonstrates that the scavenging behavior of the as-developed binder can help induce compatible cathode/electrolyte interface. Resultantly, the as-developed binder endows LiNi0.6Co0.2Mn0.2O2/Li and LiNi0.8Co0.1Mn0.1O2/Li half cells with superior cycling stability, with capacity retentions of 80.53% after 200 cycles and 87.16% after 100 cycles at 0.5C under 3.0–4.5 V, respectively. This dopamine-inspired strategy with reactive oxygen-scavenging effect heralds an important paradigm for constructing compatible cathode/electrolyte interphase in various rechargeable lithium cells.

Equivalent dose estimation of calcite using isothermal thermoluminescence signals

Thermoluminescence (TL) signals of calcite can be used to potentially date geological and archaeological events back to several million years. However, several issues, such as spurious TL signals appearing at temperatures above 300 °C, have hindered its application to a wide range of samples. A single-aliquot regenerative-dose (SAR) protocol for calcite with low-temperature measurements is proposed to measure the equivalent dose (D e ). It uses the isothermal TL (ITL) signals measured at around 225-240 °C, where a D e vs. ITL temperature (D e -T) plateau can be observed. The width of the temperature range of such a plateau can be sample dependent, as it relates to the proportional contributions of the signals from corresponding TL peaks. The signal at the ITL temperature plateau range largely corresponds to the TL signals of the 280 °C TL peak. D e values obtained by the SAR-ITL protocol are in agreement with those of the multiple-aliquot additive-dose (MAA)-TL and MAA-ITL protocols. The absence of detectable anomalous fading of ITL signals at 235 °C in this and previous studies indicates that the signal is free of fading. Dose recovery tests confirm the suitability of the SAR-ITL protocol for D e estimation. The SAR-ITL protocol measured with temperatures below 300 °C avoids the effects of spurious luminescence signals induced by high-temperature heating. The dose-response curves for ITL signals at 230-235 °C have large characteristic saturation doses (D 0 ) of ∼2000-2400 Gy. The SAR-ITL protocol for calcite thus has the potential to date geological and archaeological samples spanning the entire Quaternary period. • Thermoluminescence (TL) and isothermal TL properties of calcite are investigated. • Equivalent dose plateau using isothermal TL signals is identified within ∼225-240 °C. • SAR-ITL protocol avoids the influence of spurious signals appearing at >300 °C. • Isothermal TL signals of calcite at ∼230-235 °C saturate at ∼4800 Gy.