Flexible Transparent Electrochemical Energy Conversion and Storage: From Electrode Structures to Integrated Applications

The rapid progress of flexible electronics tremendously stimulates the urgent demands for the matching power supply systems. Flexible transparent electrochemical energy conversion and storage devices (FT–EECSDs), with endurable mechanical flexibility, outstanding optical transmittance, excellent electrochemical performance, and additional intelligent functions, are considered as preferable energy supplies for future self-powered flexible electronic systems. A comprehensive review of the reasonable design of flexible transparent electrode and recent progress on the FT–EECSDs is presented herein. The manufacturing techniques of generally classified three types of flexible transparent electrodes are systematically summarized. Emphasis is given to the recent developments in the transparent solid-state electrolyte, flexible transparent energy conversion, and storage devices. The standard evaluation methods and reasonable evaluation parameters to evaluate the flexibility and transparency of FT–EECSDs are highlighted. Additionally, the typical integrated applications of FT–EECSDs are also described. Finally, the current challenges and a future perspective on the research and development direction are further outlined.

Influence of vegetation parameters on runoff and sediment characteristics in patterned Artemisia capillaris plots

Vegetation patterns are important in the regulation of earth surface hydrological processes in arid and semi-arid areas. Laboratory-simulated rainfall experiments were used at the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Yangling, northwestern China, to quantify the effects of Artemisia capillaris patterns on runoff and soil loss. The quantitative relationships between runoff/sediment yield and vegetation parameters were also thoroughly analyzed using the path analysis method for identifying the reduction mechanism of vegetation on soil erosion. A simulated rainfall intensity of 90 mm/h was applied on a control plot without vegetation （Co） and on the other three different vegetation distribution patterns： a checkerboard pattern （CP）, a banded pattern perpendicular to the slope direction （BP）, and a single long strip parallel to the slope direction （LP）. Each patterned plot received two sets of experiments, i.e. intact plants and roots only, respectively. All treatments had three replicates. The results showed that all the three other different patterns （CP, BP and LP） of A. capillaris could effectively reduce the runoff and sediment yield. Compared with Co, the other three intact plant plots had a 12%-25% less runoff and 58%-92% less sediment. Roots contributed more to sediment reduction （46%-70%）, whereas shoots contributed more to runoff reduction （57%-81%）. BP and CP exhibited preferable controlling effects on soil erosion compared with LP. Path analysis indicated that root length density and plant number were key parameters influencing runoff rate, while root surface area density and root weight density were central indicators affecting sediment rate. The results indicated that an appropriate increase of sowing density has practical significance in conserving soil and water.

Emerging miniaturized energy storage devices for microsystem applications:from design to integration

The rapid progress of micro/nanoelectronic systems and miniaturized portable devices has tremendously increased the urgent demands for miniaturized and integrated power supplies.Miniaturized energy storage devices(MESDs),with their excellent properties and additional intelligent functions,are considered to be the preferable energy supplies for uninterrupted powering of microsystems.In this review,we aim to provide a comprehensive overview of the background,fundamentals,device configurations,manufacturing processes,and typical applications of MESDs,including their recent advances.Particular attention is paid to advanced device configurations,such as two-dimensional(2D)stacked,2D planar interdigital,2D arbitrary-shaped,three-dimensional planar,and wire-shaped structures,and their corresponding manufacturing strategies,such as printing,scribing,and masking techniques.Additionally,recent developments in MESDs,including microbatteries and microsupercapacitors,as well as microhybrid metal ion capacitors,are systematically summarized.A series of on-chip microsystems,created by integrating functional MESDs,are also highlighted.Finally,the remaining challenges and future research scope on MESDs are discussed.

Hierarchically Micro/Nanostructured Current Collectors Induced by Ultrafast Femtosecond Laser Strategy for High-Performance Lithium-ion Batteries

Commercial Cu and Al current collectors for lithium-ion batteries(LIBs)possess high electrical conductivity,suitable chemical and electrochemical stability.However,the relatively flat surface of traditional current collectors causes weak bonding strength and poor electrochemical contact between current collectors and electrode materials,resulting in potential detachment of active materials and rapid capacity degradation during extended cycling.Here,we report an ultrafast femtosecond laser strategy to manufacture hierarchical micro/nanostructures on commercial Al and Cu foils as current collectors for high-performance LIBs.The hierarchically micro/nanostructured current collectors(HMNCCs)with high surface area and roughness offer strong adhesion to active materials,fast electronic delivery of entire electrodes,significantly improving reversible capacities and cyclic stability of HMNCCs based LIBs.Consequently,LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)(NCM523)cathode with Al HMNCC generated a high reversible capacity after 200 cycles(25%higher than that of cathode with Al CC).Besides,graphite anode with Cu HMNCC also maintained prominent reversible capacity even after 600 cycles.Moreover,the full cell assembled by graphite anode with Cu HMNCC and NCM523 cathode with Al HMNCC achieved high reversible capacity and remarkable cycling stability under industrial-grade mass loading.This study provides promising candidate for achieving high-performance LIBs current collectors.

Highly active Fe_(7)S_(8) encapsulated in N-doped hollow carbon nanofibers for high-rate sodium-ion batteries

Nanostructured iron sulfides are regarded as a potential anode material for sodium-ion batteries in virtue of the rich natural abundance and remarkable theoretical capacity.However,poor rate performance and inferior cycling stability caused by sluggish kinetics and volume swelling represent two main obstacles at present. The previous research mainly focuses on nanostructure design and/or hybridizing with conductive materials.Further boosting the property by adjusting Fe/S atomic ratio in iron sulfides is rarely reported.In this work,Fe_7 S_8 and FeS_2 encapsulated in N-doped hollow carbon fibers(NHCFs/Fe_7 S_8 and NHCFs/FeS_2) are constructed by a combined chemical bath deposition and subsequent sulfidation treatment.The well-designed NHCFs/Fe_(7) S_(8) electrode displays a remarkable capacity of 517 mAh g^(-1) at 2 A g^(-1)after 1000 cycles and a superb rate capability with a capability of 444 mAh g^(-1) even at 20 A g^(-1) in etherbased electrolyte.Additionally,the rate capability of NHCFs/Fe_(7) S_(8) is superior to that of the contrast NHCFs/FeS_(2) electrode and also much better than the values of the most previously reported iron sulfide-based anodes.The in-depth mechanism explanation is explained by further experimental analysis and theoretical calculation,revealing Fe_(7) S_(8) displays improved intrinsic electronic conductivity and faster Na^(+) diffusion coefficient as well as higher reaction reversibility.

面向情绪识别的脑电特征研究综述

情绪是人对外界事物产生的心理和生理反应.准确地识别情绪在人机交互研究中占据着重要位置,其成果可应用在医学、教育、心理、军事等方向.由于脑电信号具有客观,不易伪装等特点,其在情绪识别领域的应用广受关注.从脑电信号中提取与情绪关联大、区分能力强的特征,有助于后续的分类器更有效地识别不同情绪状态.本文调研了目前常用于情绪识别研究领域的脑电信号特征,从时域、频域、时频域和空间域4个方面介绍其定义、计算方法,以及与情绪的联系,在SEED, DREAMER和CAS-THU 3个公开的脑电–情绪数据集上,使用SLDA算法评估和比较了各类脑电特征区分不同效价的能力.本文也对目前存在的问题和未来的研究方向进行了讨论和展望,可以为研究人员系统性地了解面向情绪识别的脑电特征研究现状以及开展后续研究提供思路.

Review of small aspheric glass lens molding technologies

Aspheric lens can eliminate spherical aberra- tions, coma, astigmatism, field distortions, and other adverse factors. This type of lens can also reduce the loss of light energy and obtain high-quality images and optical characteristics. The demand for aspheric lens has increased in recent years because of its advantageous use in the electronics industry, particularly for compact, portable devices and high-performance products. As an advanced manufacturing technology, the glass lens molding process has been recognized as a low-cost and high-efficiency manufacturing technology for machining small-diameter aspheric lens for industrial production. However, the residual stress and profile deviation of the glass lens are greatly affected by various key technologies for glass lens molding, including glass and mold-die material forming, mold-die machining, and lens molding. These key technical factors, which affect the quality of the glass lens molding process, are systematically discussed and reviewed to solve the existing technical bottlenecks and problems, as well as to predict the potential applicability of glass lens molding in the future.

Effects of patchy distributed Artemisia capillaris on overland flow hydrodynamic characteristics

Laboratory-simulated rainfall experiments were conducted to quantify the effects of patchy distributed Artemisia capillaris on overland flow hydrodynamics.Rainfall intensities of 60,90,120,and 150 mm h-1 were applied on a bare plot (CK) and four different patched patterns:a checkerboard pattern (CP),a banded pattern perpendicular to slope direction (BP),a single long strip parallel to slope direction (LP),and a pattern with small patches distributed like the letter'X'(XP).Each patterned plot underwent two sets of experiments,intact plant and root (the above-ground parts were removed),respectively.Results showed that flow velocity increased with rainfall intensity,and the lower slope velocity was higher than the upper slope.The removal of grass shoots significantly increased flow velocity.The contributions of grass shoots and roots to the reductions in flow velocity under different rainfall intensities were different.The shoots made greater contribution of 53-97% at 60 and 90 mm h-1,and the roots contributed more (51-81%) at 120 and 150 mm h-1.Mean flow depth increased with rainfall intensity and it declined after the aboveground parts were cleared.Reynold numbers (Re) in this study were 25-80,indicating a laminar flow in the study.Froude numbers (Fr) were ≥ 1 for CK and < 1 for patterned treatments.Fr of the lower slope was higher than the upper ones.Darcy-weisbach (f) and Manning (n) friction coefficient ranked in the order of CK < LP < BP/CP/XP with values of grass sections being higher than the bare sections and upper slope higher than the lower slope,and both decreased after removing the grass shoots.BP,CP,and XP performed more effectively than LP in retarding flow velocity and increasing hydraulic roughness.

Tailoring polysulfide trapping and kinetics by engineering hollow carbon bubble nanoreactors for high-energy Li-S pouch cells

Despite great progress of lithium-sulfur(Li-S)battery performance at the laboratory-level,both key parameters and challenges at cell scales to achieve practical high energy density require high-sulfur-loading cathodes and lean electrolytes.Herein,a novel carbon foam integrated by hollow carbon bubble nanoreactors with ultrahigh pore volume of 6.9 cm3·g−1 is meticulously designed for ultrahigh sulfur content up to 96 wt.%.Tailoring polysulfide trapping and ion/electron transport kinetics during the charge-discharge process can be achieved by adjusting the wall thickness of hollow carbon bubbles.And a further in-depth understanding of electrochemical reaction mechanism for the cathode is impelled by the in-situ Raman spectroscopy.As a result,the as-prepared cathode delivers high specific capacitances of 1,269 and 695 mAh·g−1 at 0.1 and 5 C,respectively.Furthermore,Li-S pouch cells with high areal sulfur loading of 6.9 mg·cm−2 yield exceptional practical energy density of 382 Wh·kg−1 under lean electrolyte of 3.5µL·mg−1,which demonstrates the great potential for realistic high-energy Li-S batteries.

Osiers-sprout-like heteroatom-doped carbon nanofibers as ultrastable anodes for lithium/sodium ion storage

We report an in situ carbothermic reduction process to prepare osiers-sprout-like heteroatom-doped carbon nanofibers. The dosage of copper salts and a unique annealing process have a crucial effect on the development of this unique carbon structure. A systematic analysis is performed to elucidate the possible mechanism of synthesis of the carbon nanofibers decorated with carbon bubbles. As anodes for rechargeable lithium/sodium ion batteries, the heteroatom-doped nanofibers exhibit high reversible capacities and satisfactory long-term cycling stabilities. The osiers-sprout-like heteroatom-doped carbon nanofiber electrodes deliver an ultrastable cycling performance with reversible capacities of 480 and 160 mAh·g^-1 for lithium-ion and sodium-ion batteries after 900 cycles at a current density of 800 mA·g^-1, respectively.

Control of Chronic Hepatitis B in China:Perspective of Diagnosis and Treatment

In the last three decades,China has made extraordinary effort and achieved great progress in the control of hepatitis B.Thanks to the adoption of universal administering of HBV vaccinations for newborns since 1992,the prevalence of hepatitis B surface antigen(HBsAg)in the population born after 1992 decreased significantly resulting in a decline in the general population from 9.75%to about 6%(1).

Numerical and experimental research of the characteristics of concentration solar cells

The development of automatic tracking solar concentrator photovoltaic systems is currently attracting growing interest.High concentration photovoltaic systems(HCPVs)combining triple-junction InGaP/lnGaAs/Ge solar cells with a concentrator provide high conversion efficiencies.The mathematical model for triple-junction solar cells,having a higher efficiency and superior temperature characteristics,was established based on the one-diode equivalent circuit cell model.A paraboloidal concentrator with a secondary optic system and a concentration ratio in the range of 100X–150X along with a sun tracking system was developed in this study.The GaInP/GalnAs/Ge triple-junction solar cell,produced by AZUR SPACE Solar Power,was also used in this study.The solar cells produced by Shanghai Solar Youth Energy(SY)and Shenzhen Yinshengsheng Technology Co.Ltd.(YXS)were used as comparison samples in a further comparative study at different concentration ratios(200X–1000X).A detailed analysis on the factors that influence the electrical output characteristics of the InGaP/lnGaAs/Ge solar cell was conducted with a dish-style concentrating photovoltaic system.The results show that the short-circuit current(Isc)and the open-circuit voltage(Voc)of multi-junction solar cells increases with the increasing concentration ratio,while the cell efficiency(ηc)of the solar cells increases first and then decreases with increasing concentration ratio.With increasing solar cell temperature,Isc increases,while Voc andηc decrease.A comparison of the experimental and simulation results indicate that the maximum root mean square error is less than 10%,which provides a certain theoretical basis for the study of the characteristics of triple-junction solar cell that can be applied in the analysis and discussion regarding the influence of the relevant parameters on the performance of high concentration photovoltaic systems.