Showing papers by "Yang Yang published in 2018"
TL;DR: In this article, the authors highlight recent progress on single-junction and tandem NFA solar cells and research directions to achieve even higher efficiencies of 15-20% using NFA-based organic photovoltaics are also proposed.
Abstract: Over the past three years, a particularly exciting and active area of research within the field of organic photovoltaics has been the use of non-fullerene acceptors (NFAs). Compared with fullerene acceptors, NFAs possess significant advantages including tunability of bandgaps, energy levels, planarity and crystallinity. To date, NFA solar cells have not only achieved impressive power conversion efficiencies of ~13–14%, but have also shown excellent stability compared with traditional fullerene acceptor solar cells. This Review highlights recent progress on single-junction and tandem NFA solar cells and research directions to achieve even higher efficiencies of 15–20% using NFA-based organic photovoltaics are also proposed.
1,404 citations
TL;DR: The fabrication of phase-pure formamidinium-lead tri-iodide perovskite films with excellent optoelectronic quality and stability is reported with an order of magnitude enhanced photoluminescence lifetime.
Abstract: Compositional engineering has been used to overcome difficulties in fabricating high-quality phase-pure formamidinium perovskite films together with its ambient instability. However, this comes alongside an undesirable increase in bandgap that sacrifices the device photocurrent. Here we report the fabrication of phase-pure formamidinium-lead tri-iodide perovskite films with excellent optoelectronic quality and stability. Incorporation of 1.67 mol% of 2D phenylethylammonium lead iodide into the precursor solution enables the formation of phase-pure formamidinium perovskite with an order of magnitude enhanced photoluminescence lifetime. The 2D perovskite spontaneously forms at grain boundaries to protect the formamidinium perovskite from moisture and suppress ion migration. A stabilized power conversion efficiency (PCE) of 20.64% (certified stabilized PCE of 19.77%) is achieved with a short-circuit current density exceeding 24 mA cm-2 and an open-circuit voltage of 1.130 V, corresponding to a loss-in-potential of 0.35 V, and significantly enhanced operational stability.
516 citations
TL;DR: An extremely simple and standalone solar energy converter consisting of only an as-prepared 3D cross-linked honeycomb graphene foam material without any other supporting components is demonstrated, providing a paradigm change in water purification by using a simple, point of use, reusable, and low-cost solar thermal water purifying system for a variety of environmental conditions.
Abstract: Harvesting solar energy for desalination and sewage treatment has been considered as a promising solution to produce clean water. However, state-of-the-art technologies often require optical concentrators and complicated systems with multiple components, leading to poor efficiency and high cost. Here, we demonstrate an extremely simple and standalone solar energy converter consisting of only an as-prepared 3D cross-linked honeycomb graphene foam material without any other supporting components. This simple all-in-one material can act as an ideal solar thermal converter capable of capturing and converting sunlight into heat, which in turn can distill water from various water sources into steam and produce purified water under ambient conditions and low solar flux with very high efficiency. High specific water production rate of 2.6 kg h–1 m–2 g–1 was achieved with near ∼87% under 1 sun intensity and >80% efficiency even under ambient sunlight (<1 sun). This scalable sheet-like material was used to obtain p...
475 citations
TL;DR: The stability issue of perovskite photovoltaics is discussed and a call for standardized protocols for device characterizations that could possibly match the silicon industrial standards is made.
Abstract: When translating photovoltaic technology from laboratory to commercial products, low cost, high power conversion efficiency, and high stability (long lifetime) are the three key metrics to consider in addition to other factors, such as low toxicity, low energy payback time, etc. As one of the most promising photovoltaic materials with high efficiency, today organic–inorganic metal halide perovskites draw tremendous attention from fundamental research, but their practical relevance still remains unclear owing to the notorious short device operation time. In this comment, we discuss the stability issue of perovskite photovoltaics and call for standardized protocols for device characterizations that could possibly match the silicon industrial standards.
473 citations
TL;DR: Sensing of charged and electroneutral targets (serotonin, dopamine, glucose, and sphingosine-1-phosphate) was enabled by specifically isolated aptameric stem-loop receptors, resulting in highly sensitive detection.
Abstract: Detection of analytes by means of field-effect transistors bearing ligand-specific receptors is fundamentally limited by the shielding created by the electrical double layer (the "Debye length" limitation). We detected small molecules under physiological high-ionic strength conditions by modifying printed ultrathin metal-oxide field-effect transistor arrays with deoxyribonucleotide aptamers selected to bind their targets adaptively. Target-induced conformational changes of negatively charged aptamer phosphodiester backbones in close proximity to semiconductor channels gated conductance in physiological buffers, resulting in highly sensitive detection. Sensing of charged and electroneutral targets (serotonin, dopamine, glucose, and sphingosine-1-phosphate) was enabled by specifically isolated aptameric stem-loop receptors.
472 citations
TL;DR: An efficient and reproducible method to fabricate highly uniform FAPbI3 films via the adduct approach with a stronger interaction between NMP with the FA cation than DMSO, which facilitates the formation of a stable FAI·PbI2·NMP adduct.
Abstract: The Lewis acid–base adduct approach has been widely used to form uniform perovskite films, which has provided a methodological base for the development of high-performance perovskite solar cells. However, its incompatibility with formamidinium (FA)-based perovskites has impeded further enhancement of photovoltaic performance and stability. Here, we report an efficient and reproducible method to fabricate highly uniform FAPbI3 films via the adduct approach. Replacement of the typical Lewis base dimethyl sulfoxide (DMSO) with N-methyl-2-pyrrolidone (NMP) enabled the formation of a stable intermediate adduct phase, which can be converted into a uniform and pinhole-free FAPbI3 film. Infrared and computational analyses revealed a stronger interaction between NMP with the FA cation than DMSO, which facilitates the formation of a stable FAI·PbI2·NMP adduct. On the basis of the molecular interactions with different Lewis bases, we proposed criteria for selecting the Lewis bases. Owed to the high film quality, per...
307 citations
TL;DR: Control of the roughness of the CIGS surface and the use of a heavily doped organic hole transport layer were crucial to achieve a 22.4% power conversion efficiency in a two-terminal tandem cell with hybrid perovskite/CIGS combination.
Abstract: The combination of hybrid perovskite and Cu(In,Ga)Se2 (CIGS) has the potential for realizing high-efficiency thin-film tandem solar cells because of the complementary tunable bandgaps and excellent photovoltaic properties of these materials. In tandem solar device architectures, the interconnecting layer plays a critical role in determining the overall cell performance, requiring both an effective electrical connection and high optical transparency. We used nanoscale interface engineering of the CIGS surface and a heavily doped poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) hole transport layer between the subcells that preserves open-circuit voltage and enhances both the fill factor and short-circuit current. A monolithic perovskite/CIGS tandem solar cell achieved a 22.43% efficiency, and unencapsulated devices under ambient conditions maintained 88% of their initial efficiency after 500 hours of aging under continuous 1-sun illumination.
288 citations
TL;DR: A low-cost and stable conjugated donor polymer (PTQ10) was introduced as interfacial layer in the planar n-i-p structured pero-SCs and proved to be an effective hole extraction layer due to the proper energy alignment with perovskite.
Abstract: The precise control of stoichiometric balance and ionic defects on the surface of solution-processed perovskite is critical to the performance and stability of perovskite solar cells (pero-SCs). Here, we introduce a low-cost and stable conjugated donor polymer (PTQ10) as interfacial layer in the planar n–i–p structured pero-SCs. The polymer was applied to the perovskite intermediate phase before the thermal annealing. This treatment significantly reduced the loss of surface organic cation during thermal annealing. Importantly, the kinetics of phase conversion of perovskite was influenced, and perovskite crystal showed a more preferential orientation. Moreover, the polymer proved to be an effective hole extraction layer due to the proper energy alignment with perovskite. Finally, a champion power conversion efficiency of the planar pero-SCs was achieved at 21.2% with a high fill factor of 81.6%. The devices also showed great ambient and thermal stability. This work presents a facile way of perovskite surfa...
207 citations
TL;DR: In this article, the role of grain boundaries on the optoelectronic properties and stability of perovskite solar cells is reviewed, and it is shown that grain boundaries may largely influence the Optoelectric properties of the PVSK thin film.
194 citations
TL;DR: In this paper, the authors proposed to shift the active-layer absorption spectrum to the infrared region by designing new lowbandgap donors and non-fullerene acceptors, and to reduce the invalid absorption by developing new transparent electrode materials.
187 citations
TL;DR: The present work incorporates chemically modified graphene into nanocrystal SnO2 as the electron transporting layer (ETL) for highly efficient planar perovskite solar cells with power conversion efficiency of 20.2% and improved fill factor of 82%, which could be mainly attributed to the augmented charge extraction and transport.
Abstract: Organic–inorganic hybrid lead halide perovskites have been widely investigated in optoelectronics both experimentally and theoretically. The present work incorporates chemically modified graphene into nanocrystal SnO2 as the electron transporting layer (ETL) for highly efficient planar perovskite solar cells. The modification of SnO2 with highly conductive two-dimensional naphthalene diimide-graphene can increase surface hydrophobicity and form van der Waals interaction between the surfactant and the organic–inorganic hybrid lead halide perovskite compounds. As a result, highly efficient perovskite solar cells with power conversion efficiency of 20.2% can be achieved with an improved fill factor of 82%, which could be mainly attributed to the augmented charge extraction and transport.
TL;DR: The polymeric vanadia-based SCR mechanism reported here advances the understanding of the working principle of vanadia -based catalysts and paves the way toward the development of low vanadium–loading SCR catalysts with excellent low-temperature activity.
Abstract: The structure of dispersed vanadyl species plays a crucial role in the selective catalytic reduction (SCR) of NO with NH 3 over vanadia-based catalysts. Here, we demonstrate that the polymeric vanadyl species have a markedly higher NH 3 -SCR activity than the monomeric vanadyl species. The coupling effect of the polymeric structure not only shortens the reaction pathway for the regeneration of redox sites but also substantially reduces the overall reaction barrier of the catalytic cycle. Therefore, it is the polymeric vanadyl species, rather than the monomeric vanadyl species, that determine the NH 3 -SCR activity of vanadia-based catalysts, especially under low-temperature conditions. The polymeric vanadia-based SCR mechanism reported here advances the understanding of the working principle of vanadia-based catalysts and paves the way toward the development of low vanadium–loading SCR catalysts with excellent low-temperature activity.
TL;DR: An overview of the recent progress in OSCs based on multiple-donor or multiple-acceptor components with complementary absorption spectra and the introduction of an additional component can further facilitate charge transfer and reduce charge recombination through cascade energy structure and optimized morphology is provided.
Abstract: Organic solar cells (OSCs) based on bulk heterojunction structures are promising candidates for next-generation solar cells. However, the narrow absorption bandwidth of organic semiconductors is a critical issue resulting in insufficient usage of the energy from the solar spectrum, and as a result, it hinders performance. Devices based on multiple-donor or multiple-acceptor components with complementary absorption spectra provide a solution to address this issue. OSCs based on multiple-donor or multiple-acceptor systems have achieved power conversion efficiencies over 12%. Moreover, the introduction of an additional component can further facilitate charge transfer and reduce charge recombination through cascade energy structure and optimized morphology. This progress report provides an overview of the recent progress in OSCs based on multiple-donor (polymer/polymer, polymer/dye, and polymer/small molecule) or multiple-acceptor (fullerene/fullerene, fullerene/nonfullerene, and nonfullerene/nonfullerene) components.
TL;DR: In this article, an efficient and stable perovskite CQD solar cells based on formamidinium lead triiodide (FAPbI3) CQDs realized by rational surface regulation was reported.
TL;DR: This work proposes a multistream LSTM architecture with a new smoothed score fusion technique to learn classification from different geometric feature streams and observes that the geometric relational features based on distances between joints and selected lines outperform other features and achieve the state-of-the-art performance on four datasets.
Abstract: Recent skeleton-based action recognition approaches achieve great improvement by using recurrent neural network (RNN) models. Currently, these approaches build an end-to-end network from coordinates of joints to class categories and improve accuracy by extending RNN to spatial domains. First, while such well-designed models and optimization strategies explore relations between different parts directly from joint coordinates, we provide a simple universal spatial modeling method perpendicular to the RNN model enhancement. Specifically, according to the evolution of previous work, we select a set of simple geometric features, and then seperately feed each type of features to a three-layer LSTM framework. Second, we propose a multistream LSTM architecture with a new smoothed score fusion technique to learn classification from different geometric feature streams. Furthermore, we observe that the geometric relational features based on distances between joints and selected lines outperform other features and the fusion results achieve the state-of-the-art performance on four datasets. We also show the sparsity of input gate weights in the first LSTM layer trained by geometric features and demonstrate that utilizing joint-line distances as input require less data for training.
TL;DR: A comprehensive analytical model that considers circuit, computation, offloading energy consumptions is developed for accurately evaluating the overall energy efficiency (EE) in homogeneous fog networks and a maximal energy-efficient task scheduling (MEETS) algorithm is proposed.
Abstract: A homogeneous fog network is defined as a group of peer nodes with sharable computing and storage resources, as well as spare spectrum for node-to-node/device-to-device communications and task scheduling. It promotes more intelligent applications and services in different Internet of Things (IoT) scenarios, thanks to effective collaborations among neighboring fog nodes via cognitive spectrum access techniques. In this paper, a comprehensive analytical model that considers circuit, computation, offloading energy consumptions is developed for accurately evaluating the overall energy efficiency (EE) in homogeneous fog networks. With this model, the tradeoff relationship between performance gains and energy costs in collaborative task offloading is investigated, thus enabling us to formulate the EE optimization problem for future intelligent IoT applications with practical constraints in available computing resources at helper nodes and unused spectrum in neighboring environments. Based on rigorous mathematical analysis, a maximal energy-efficient task scheduling (MEETS) algorithm is proposed to derive the optimal scheduling decision for a task node and multiple neighboring helper nodes under feasible modulation schemes and time allocations. Extensive simulation results demonstrate the tradeoff relationship between EE and task scheduling performance in homogeneous fog networks. Compared with traditional task scheduling strategies, the proposed MEETS algorithm can achieve much better EE performance under different network parameters and service conditions.
TL;DR: In this article, a group of model compounds, named DRTB-T-CX (X = 2, 4, 6, and 8), were designed to demonstrate that adjusting the length of the end alkyl chain can be used to modify the molecular orientation.
Abstract: In bulk-heterojunction organic solar cells (BHJ-OSCs), exciton dissociation and charge transport are highly sensitive to the molecular packing pattern and phase separation morphology in blend films. Efficient photovoltaic small molecules (SMs) typically possess an acceptor–donor–acceptor structure that causes intrinsic anisotropy, limiting the control over molecular packing because of the lack of an effective method for modulating molecular orientation. In this report, we design a group of model compounds, named DRTB-T-CX (X = 2, 4, 6, and 8), to demonstrate that adjusting the length of the end alkyl chain can be used to modify the molecular orientation. A top-performance power conversion efficiency (PCE) of up to 11.24% is achieved with a DRTB-T-C4/IT-4F-based device, which is the best performance reported for a state-of-the-art nonfullerene SM organic solar cell (NFSM-OSC).
TL;DR: A novel delay energy balanced tasking scheduling (DEBTS) algorithm is proposed to minimize the overall energy consumption while reducing average service delay and delay jitter and it is proved that DEBTS can achieve the theoretical tradeoff between these two performance metrics.
Abstract: Vehicular ad hoc networks, wireless sensor networks, Internet of Things, and mobile device-to-device communications can be modeled as different homogeneous fog networks, wherein similar terminals/things/devices/nodes are sharing their computation, communication, and storage resources in the neighborhood for achieving better system performance through effective collaborations. It is very desirable, but quite challenging, to simultaneously reduce service delay and energy consumption in such networks for delay-sensitive and energy-constraint applications, e.g., virtual reality and online 3-D gaming on mobile devices. In this paper, a cross-layer analytical framework is developed to formulate and study the balance between service delay and energy consumption. An effective control parameter ${V}$ is derived to characterize their tradeoff relationship during dynamic task scheduling processes in fog networks. Combining this analysis with Lyapunov optimization techniques, a novel delay energy balanced tasking scheduling (DEBTS) algorithm is proposed to minimize the overall energy consumption while reducing average service delay and delay jitter. It is proved that DEBTS can achieve the theoretical [ ${O(1/V), O(V)}$ ] tradeoff between these two performance metrics. Further, extensive simulation results show that DEBTS can offer much better delay-energy performance in task scheduling challenges. Specifically, for a typical ${V}$ value of ${4 \times 10^{4}}$ , DEBTS can save 26% and 29% more energy, and at the same time, reduce average service delay by 29% and 32%, than traditional random scheduling and least busy scheduling algorithms, respectively.
TL;DR: In this paper, the shape, chemical composition, crystal structure, optical property and surface area of Bi2MoO6/BiOBr were investigated by field emission electron microscope (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Xray photoelectron spectroscopy (XPS).
TL;DR: This new synthesis strategy successfully induces mild oxidation of the (Si2n )2n- layers in CaSi2 into neutral Si2n layers without damage of pristinesilicene structure and promotes the exfoliation of stacked silicene layers.
Abstract: Silicene, a 2D silicon allotrope with unique low-buckled structure, has attracted increasing attention in recent years due to its many superior properties. So far, epitaxial growth is one of the very limited ways to obtain high-quality silicene, which severely impedes the research and application of silicene. Therefore, large-scale synthesis of silicene is a great challenge, yet urgently desired. Herein, the first scalable preparation of free-standing high-quality silicene nanosheets via liquid oxidation and exfoliation of CaSi2 is reported. This new synthesis strategy successfully induces mild oxidation of the (Si2n )2n- layers in CaSi2 into neutral Si2n layers without damage of pristine silicene structure and promotes the exfoliation of stacked silicene layers. The obtained silicene sheets are dispersible and ultrathin ones with monolayer or few-layer thickness and exhibit excellent crystallinity. As a unique 2D layered silicon allotrope, the silicene nanosheets are further explored as new anodes for lithium-ion batteries and exhibit a nearly theoretical capacity of 721 mAh g-1 at 0.1 A g-1 and an extraordinary cycling stability with no capacity decay after 1800 cycles in contrast to previous most silicon anodes showing rapid capacity decay, thus holding great promise for energy storage and beyond.
TL;DR: Two new narrow-bandgap nonfullerene acceptors with suitable energy levels and chemical structures are designed, synthesized, and employed as the third component in the donor/acceptor binary blend, which boosts the PCE of OPV to 11.6%.
Abstract: Incorporating narrow-bandgap near-infrared absorbers as the third component in a donor/acceptor binary blend is a new strategy to improve the power conversion efficiency (PCE) of organic photovoltaics (OPV). However, there are two main restrictions: potential charge recombination in the narrow-gap material and miscompatibility between each component. The optimized design is to employ a third component (structurally similar to the donor or acceptor) with a lowest unoccupied molecular orbital (LUMO) energy level similar to the acceptor and a highest occupied molecular orbital (HOMO) energy level similar to the donor. In this design, enhanced absorption of the active layer and enhanced charge transfer can be realized without breaking the optimized morphology of the active layer. Herein, in order to realize this design, two new narrow-bandgap nonfullerene acceptors with suitable energy levels and chemical structures are designed, synthesized, and employed as the third component in the donor/acceptor binary blend, which boosts the PCE of OPV to 11.6%.
TL;DR: The C-ternary OPV is fabricated by a sequential solution process, in which the second acceptor and donor/acceptor binary blend are sequentially spin-coated, and the power conversion efficiencies are enhanced by 14-21% relative to those with the simple ternary blend.
Abstract: Recently, a new type of active layer with a ternary system has been developed to further enhance the performance of binary system organic photovoltaics (OPV). In the ternary OPV, almost all active layers are formed by simple ternary blend in solution, which eventually leads to the disordered bulk heterojunction (BHJ) structure after a spin-coating process. There are two main restrictions in this disordered BHJ structure to obtain higher performance OPV. One is the isolated second donor or acceptor domains. The other is the invalid metal-semiconductor contact. Herein, the concept and design of donor/acceptor/acceptor ternary OPV with more controlled structure (C-ternary) is reported. The C-ternary OPV is fabricated by a sequential solution process, in which the second acceptor and donor/acceptor binary blend are sequentially spin-coated. After the device optimization, the power conversion efficiencies (PCEs) of all OPV with C-ternary are enhanced by 14-21% relative to those with the simple ternary blend; the best PCEs are 10.7 and 11.0% for fullerene-based and fullerene-free solar cells, respectively. Moreover, the averaged PCE value of 10.4% for fullerene-free solar cell measured in this study is in great agreement with the certified one of 10.32% obtained from Newport Corporation.
TL;DR: In this article, the effects of top electrodes (TEs) on ferroelectric properties of Hf0.5 O2 (HZO) thin films are examined systematically and the largest 2Pr value of 38.72
Abstract: In this letter, effects of top electrodes (TEs) on ferroelectric properties of Hf0.5 Zr0.5 O2 (HZO) thin films are examined systematically. The remnant polarization (Pr) of HZO thin films increases by altering TEs with lower thermal expansions coefficient ( $\alpha $ ). The largest 2Pr value of 38.72 $\mu \text{C}$ /cm2 is observed for W TE with $\alpha = 4.5\times 10^{\mathsf {-6}}$ /K, while the 2Pr value is only $22.83~\mu \text{C}$ /cm2 for Au TE with $\alpha = 14.2\times 10^{\mathsf {-6}}$ /K. Meanwhile, coercive field (Ec) shifts along the electric field axis and the offset is found to be dependent on the difference of workfunctions (WFs) between TE and TiN bottom electrode (BE). Ec shifts toward negative/positive direction, when the WF of TE is larger/smaller (Pt, Pd, Au/W, Al, Ta) than TiN BE. This letter provides an effective way to modulate HfO2-based device performance for different requirements in actual application.
TL;DR: Liposomes are modified with a peptidomimetic that preserves bioactivity of the nanocarrier in blood circulation and attenuates IgM absorption, thereby improving the immunocompatibility of brain-targeted liposomes.
Abstract: Targeting ligands are anticipated to facilitate the precise delivery of therapeutic agents to diseased tissues; however, they may also severely affect the interaction of nanocarriers with plasma proteins. Here, we study the immunocompatibility of brain-targeted liposomes, which inversely correlates with absorbed natural IgM. Modification of long, stable positively charged peptide ligands on liposomes is inclined to absorb natural IgM, leading to rapid clearance and enhanced immunogenicity. Small peptidomimetic D8 developed by computer-aided peptide design exhibits improved immunocompatibility by attenuating natural IgM absorption. The present study highlights the effects of peptide ligands on the formed protein corona and in vivo fate of liposomes. Stable positively charged peptide ligands play double-edged roles in targeted delivery, preserving in vivo bioactivities for binding receptors and long-term unfavorable interactions with the innate immune system. The development of D8 provides insights into how to rationally design immunocompatible drug delivery systems by modulating the protein corona composition.
TL;DR: An assembled nano-complex system composed of oxygen donor, two-photon absorption (TPA) species, and photosensitizer (PS) was synthesized to address two problems in clinical practice: limited therapeutic efficiency and limited treatment depth.
Abstract: Photodynamic therapy (PDT) shows unique selectivity and irreversible destruction toward treated tissues or cells, but still has several problems in clinical practice. One is limited therapeutic efficiency, which is attributed to hypoxia in tumor sites. Another is the limited treatment depth because traditional photosensitizes are excited by short wavelength light (<700 nm). An assembled nano-complex system composed of oxygen donor, two-photon absorption (TPA) species, and photosensitizer (PS) was synthesized to address both problems. The photosensitizer is excited indirectly by two-photon laser through intraparticle FRET mechanism for improving treatment depth. The oxygen donor, hemoglobin, can supply extra oxygen into tumor location through targeting effect for enhanced PDT efficiency. The mechanism and PDT effect were verified through both in vitro and in vivo experiments. The simple system is promising to promote two-photon PDT for clinical applications.
TL;DR: In this article, conductive fabric is used to form the conducting parts of the antenna on a polydimethylsiloxane (PDMS) substrate and then the antenna and the lumped (active and passive) elements, required for electronic tuning and RF choking, are fully encapsulated with additional layers of PDMS.
Abstract: A new approach to realize robust, flexible, and electronically tunable wearable antennas is presented. Conductive fabric is used to form the conducting parts of the antenna on a polydimethylsiloxane (PDMS) substrate. Then the antenna and the lumped (active and passive) elements, required for electronic tuning and RF choking, are fully encapsulated with additional layers of PDMS. As a concept demonstration, a new frequency-reconfigurable antenna has been designed and fabricated. The details of the prototype manufacturing process are described. Two UWB human muscle equivalent phantoms were also fabricated for testing purposes. Furthermore, the antenna was subjected to several investigations on its RF performance (both in free space and on a flat phantom) and mechanical stability. The latter includes bending tests on several locations on a human-body shaped phantom and washing in a household washing machine. Good agreement between predicted and experimental results (both in free space and on the phantom) is observed, validating the proposed concept. The tests demonstrated that lumped components and other antenna parts remained intact and in working order even under extreme bending (to a bending radius of 28 mm) and after washing, thus maintaining the overall antenna performance including good frequency reconfigurability from 2.3 to 2.68 GHz. To the best of our knowledge, all these features have never been demonstrated in previously published electronically tunable antennas.
TL;DR: An extremely stable graphene electrode doped with macromolecular acid (perfluorinated polymeric sulfonic acid (PFSA)) as a p-type dopant provides not only ultra-high ambient stability for a very long time but also high chemical/thermal stability, which have been unattainable by doping with conventional small-molecules.
Abstract: Although conventional p-type doping using small molecules on graphene decreases its sheet resistance (Rsh), it increases after exposure to ambient conditions, and this problem has been considered as the biggest impediment to practical application of graphene electrodes. Here, we report an extremely stable graphene electrode doped with macromolecular acid (perfluorinated polymeric sulfonic acid (PFSA)) as a p-type dopant. The PFSA doping on graphene provides not only ultra-high ambient stability for a very long time (> 64 days) but also high chemical/thermal stability, which have been unattainable by doping with conventional small-molecules. PFSA doping also greatly increases the surface potential (~0.8 eV) of graphene, and reduces its Rsh by ~56%, which is very important for practical applications. High-efficiency phosphorescent organic light-emitting diodes are fabricated with the PFSA-doped graphene anode (~98.5 cd A-1 without out-coupling structures). This work lays a solid platform for practical application of thermally-/chemically-/air-stable graphene electrodes in various optoelectronic devices.
TL;DR: In this paper, a review of nanostructured metals, metal alloys, metal oxides, metal-free electrodes, and photoelectrodes developed in recent years are discussed in detail.
Abstract: The excessive utilization of fossil fuels accompanied by large amounts of anthropogenic CO2 emissions have led to adverse global environmental changes and a growing global energy crisis. Hence, converting CO2 into high-value chemical fuels, such as CO, CH4, HCOOH, and CH3OH, through catalysis is one of the most attractive topics in energy conversion. Among various approaches, electrochemical (EC) and photoelectrochemical (PEC) reduction are considered to be promising methods. Over the past decades, research in the area of CO2 EC and PEC reduction has been growing quickly. Herein, highly efficient nanostructured metals, metal alloys, metal oxides, metal-free electrodes, and photoelectrodes developed in recent years are discussed in detail in this review. Additionally, the strategies and mechanisms for improving the faradaic efficiency (FE), current density, and stability of catalysts are also discussed. The challenges and future perspectives for CO2 EC and PEC reduction are also discussed.
TL;DR: The enhanced prevalence and diverse genetic characteristics that occurred with mammalian-adapted and NAI-resistant mutations may have contributed to increased numbers of human infections in wave 5 of H7N9.
Abstract: H7N9 virus has caused five infection waves since it emerged in 2013. The highest number of human cases was seen in wave 5; however, the underlying reasons have not been thoroughly elucidated. In this study, the geographical distribution, phylogeny, and genetic evolution of 240 H7N9 viruses in wave 5, including 35 new isolates from patients and poultry in nine provinces, were comprehensively analyzed together with strains from first four waves. Geographical distribution analysis indicated that the newly emerging highly pathogenic (HP) and low-pathogenicity (LP) H7N9 viruses were cocirculating, causing human and poultry infections across China. Genetic analysis indicated that dynamic reassortment of the internal genes among LP-H7N9/H9N2/H6Ny and HP-H7N9, as well as of the surface genes, between the Yangtze and Pearl River Delta lineages resulted in at least 36 genotypes, with three major genotypes (G1 [A/chicken/Jiangsu/SC537/2013-like], G3 [A/Chicken/Zhongshan/ZS/2017-like], and G11 [A/Anhui/40094/2015-like]). The HP-H7N9 genotype likely evolved from G1 LP-H7N9 by the insertion of a KRTA motif at the cleavage site (CS) and then evolved into 15 genotypes with four different CS motifs, including PKG KRTA R/G, PKG KRIA R/G, PKR KRAA R/G, and PKR KRTA R/G. Approximately 46% (28/61) of HP strains belonged to G3. Importantly, neuraminidase (NA) inhibitor (NAI) resistance (R292K in NA) and mammalian adaptation (e.g., E627K and A588V in PB2) mutations were found in a few non-human-derived HP-H7N9 strains. In summary, the enhanced prevalence and diverse genetic characteristics that occurred with mammalian-adapted and NAI-resistant mutations may have contributed to increased numbers of human infections in wave 5.IMPORTANCE The highest numbers of human H7N9 infections were observed during wave 5 from October 2016 to September 2017. Our results showed that HP-H7N9 and LP-H7N9 had spread virtually throughout China and underwent dynamic reassortment with different subtypes (H7N9/H9N2 and H6Ny) and lineages (Yangtze and Pearl River Delta lineages), resulting in totals of 36 and 3 major genotypes, respectively. Notably, the NAI drug-resistant (R292K in NA) and mammalian-adapted (e.g., E627K in PB2) mutations were found in HP-H7N9 not only from human isolates but also from poultry and environmental isolates, indicating increased risks for human infections. The broad dissemination of LP- and HP-H7N9 with high levels of genetic diversity and host adaptation and drug-resistant mutations likely accounted for the sharp increases in the number of human infections during wave 5. Therefore, more strategies are needed against the further spread and damage of H7N9 in the world.
TL;DR: FA2ST and its architecture are proposed to underpin a multi-level system of fog computing services for end-to-end support of IoT applications and a use case in a vertical industry, and a performance study.
Abstract: Fog computing has emerged as a promising solution for the IoT and next generation mobile networks. As an extension to cloud computing, it enables service provisioning along the continuum from the cloud to things to reduce latency and bandwidth demands, and empower end users in their vicinity. Such a cloud-to-thing service continuum requires full technology support in infrastructure, platform, software and service levels. This article proposes FA2ST and its architecture to underpin a multi-level system of fog computing services for end-to-end support of IoT applications. It presents the concept of FA2ST and describes its architecture, main features, a use case in a vertical industry, and a performance study.