Realizing rechargeable cathode-free aluminum-ion batteries via regulating solvation structure in aqueous-aprotic electrolytes

Aqueous aluminum-ion batteries(AIBs)are promising candidates for large-scale energy storage due to the abundant resource reserve,high theoretical capacity,intrinsic safety,and low cost of Al.However,the development of aqueous AIBs is constrained by the inefficient Al plating,inevitable parasitic side reactions,and the collapse of the cathode materials.Herein,we propose a novel Al^(3+)/Mn^(2+)hybrid electrolyte in a water-acetonitrile co-solvent system with a regulated solvation structure to realize cathode-free AIBs.The inclusion of acetonitrile as a co-solvent plays a crucial role in reducing the desolvation energy and suppressing side reactions.The introduction of Mn^(2+)can enable the reversible plating/stripping of Al-Mn alloy with reduced overpotentials on the anode and deposition/stripping of Al_(x)MnO_(2) on the cathodic current collector to realize cathode-free AIBs.The architected AIB delivers a high discharge capacity of 397.9 mAh g^(-1),coupled with superior rate capability and stable cycling performance.Moreover,the cathode-free AIB shows superior low-temperature performance and can operate at-20℃ for over 120 cycles.This work provides new ideas for developing high-performance and low-cost aqueous AIBs.

Federated Learning for 6G:Applications,Challenges,and Opportunities

Standard machine-learning approaches involve the centralization of training data in a data center,where centralized machine-learning algorithms can be applied for data analysis and inference.However,due to privacy restrictions and limited communication resources in wireless networks,it is often undesirable or impractical for the devices to transmit data to parameter sever.One approach to mitigate these problems is federated learning(FL),which enables the devices to train a common machine learning model without data sharing and transmission.This paper provides a comprehensive overview of FL applications for envisioned sixth generation(6G)wireless networks.In particular,the essential requirements for applying FL to wireless communications are first described.Then potential FL applications in wireless communications are detailed.The main problems and challenges associated with such applications are discussed.Finally,a comprehensive FL implementation for wireless communications is described.

Air-Stable Binary Hydrated Eutectic Electrolytes with Unique Solvation Structure for Rechargeable Aluminum-Ion Batteries

Aluminum-ion batteries(AIBs)have been highlighted as a potential alternative to lithium-ion batteries for large-scale energy storage due to the abundant reserve,light weight,low cost,and good safety of Al.However,the development of AIBs faces challenges due to the usage of AlCl_(3)-based ionic liquid electrolytes,which are expensive,corrosive,and sensitive to humidity.Here,we develop a low-cost,non-corrosive,and air-stable hydrated eutectic electrolyte composed of aluminum perchlorate nonahydrate and methylurea(MU)ligand.Through optimizing the molar ratio to achieve the unique solvation structure,the formed Al(ClO_4)_(3)·9H_(2)O/MU hydrated deep eutectic electrolyte(AMHEE)with an average coordination number of 2.4 can facilely realize stable and reversible deposition/stripping of Al.When combining with vanadium oxide nanorods positive electrode,the Al-ion full battery delivers a high discharge capacity of 320 mAh g^(-1)with good capacity retention.The unique solvation structure with a low desolvation energy of the AMHEE enables Al^(3+)insertion/extraction during charge/discharge processes,which is evidenced by in situ synchrotron radiation X-ray diffraction.This work opens a new pathway of developing low-cost,safe,environmentally friendly and high-performance electrolytes for practical and sustainable AIBs.

Efcient Algorithms for Cache-Throughput Analysis in Cellular-D2D 5G Network

In this paper,we propose a two-tiered segment-based Device-toDevice(S-D2D)caching approach to decrease the startup and playback delay experienced by Video-on-Demand(VoD)users in a cellular network.In the S-D2D caching approach cache space of each mobile device is divided into two cache-blocks.The rst cache-block reserve for caching and delivering the beginning portion of the most popular video les and the second cacheblock caches the latter portion of the requested video les‘fully or partially’depending on the users’video watching behaviour and popularity of videos.In this approach before caching,video is divided and grouped in a sequence of xed-sized fragments called segments.To control the admission to both cacheblocks and improve the system throughput,we further propose and evaluate three cache admission control algorithms.We also propose a video segment access protocol to elaborate on how to cache and share the video segments in a segmentation based D2D caching architecture.We formulate an optimisation problem and nd the optimal cache probability and beginning-segment size that maximise the cache-throughput probability of beginning-segments.To solve the non-convex cache-throughout maximisation problem,we derive an iterative algorithm,where the optimal solution is derived in each step.We used extensive simulations to evaluate the performance of our proposed S-D2D caching system.

Application of p-y approach in analyzing pile foundations in frozen ground overlying liquefiable soils

Two major earthquakes in Alaska, namely the 1964 Great Alaska Earthquake and the 2002 Denali Earthquake, occurred in winter seasons when the ground crust was frozen. None of the then-existing foundation types was able to withstand the force from the lateral spreading of frozen crust. This paper presents results from the analysis of pile foundations in frozen ground overlying lique- fiable soil utilizing the Beam-on-Nonlinear-Winlder-Foundation （BNWF） （or p-y approach）. P-multipliers were applied on tradi- tional sandy soil p-y curves to simulate soil strength degradation during liquefaction. Frozen soil p-y curves were constructed based on a model proposed in a recent study and the frozen soil mechanical properties obtained from testing of naturally frozen soils. Pile response results from the p-y approach were presented along with those from fluid-solid coupled Finite Element （FE） modeling for comparison purpose. Finally, the sensitivity of pile response to frozen soil parameters was investigated and a brief discussion is presented.

Atomically Dispersed Iron Active Sites Promoting Reversible Redox Kinetics and Suppressing Shuttle Effect in Aluminum-Sulfur Batteries

Rechargeable aluminum-sulfur(Al-S)batteries have been considered as a highly potential energy storage system owing to the high theoretical capacity,good safety,abundant natural reserves,and low cost of Al and S.However,the research progress of Al-S batteries is limited by the slow kinetics and shuttle effect of soluble polysulfides intermediates.Herein,an interconnected free-standing interlayer of iron sin-gle atoms supported on porous nitrogen-doped carbon nanofibers(FeSAs-NCF)on the separator is developed and used as both catalyst and chemical barrier for Al-S batteries.The atomically dispersed iron active sites(Fe-N_(4))are clearly identified by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption near-edge structure.The Al-S battery with the FeSAs-NCF shows an improved specific capacity of 780 mAh g^(−1)and enhanced cycle stability.As evidenced by experimental and theoretical results,the atomically dispersed iron active centers on the separator can chemically adsorb the polysulfides and accelerate reaction kinetics to inhibit the shuttle effect and promote the reversible conversion between aluminum polysulfides,thus improving the electrochemical performance of the Al-S battery.This work provides a new way that can not only promote the conversion of aluminum sulfides but also suppress the shuttle effect in Al-S batteries.

Topology Optimization of Stiffener Layout Design for Box Type Load-Bearing Component under Thermo-Mechanical Coupling

The structure optimization design under thermo-mechanical coupling is a difficult problem in the topology optimization field.An adaptive growth algorithm has become a more effective approach for structural topology optimization.This paper proposed a topology optimization method by an adaptive growth algorithm for the stiffener layout design of box type load-bearing components under thermo-mechanical coupling.Based on the stiffness diffusion theory,both the load stiffness matrix and the heat conduction stiffness matrix of the stiffener are spread at the same time to make sure the stiffener grows freely and obtain an optimal stiffener layout design.Meanwhile,the objectives of optimization are the minimization of strain energy and thermal compliance of the whole structure,and thermo-mechanical coupling is considered.Numerical studies for square shells clearly show the effectiveness of the proposed method for stiffener layout optimization under thermo-mechanical coupling.Finally,the method is applied to optimize the stiffener layout of box type load-bearing component of themachining center.The optimization results show that both the structural deformation and temperature of the load-bearing component with the growth stiffener layout,which are optimized by the adaptive growth algorithm,are less than the stiffener layout of shape‘#’stiffener layout.It provides a new solution approach for stiffener layout optimization design of box type load-bearing components under thermo-mechanical coupling.

Performance Analysis of RIS Assisted NOMA Networks over Rician Fading Channels

In this paper,we consider a downlink non-orthogonal multiple access(NOMA)network assisted by two reconfigurable intelligent surfaces(RISs)over Rician fading channels,in which each user communicates with the base station by the virtue of a RIS to enhance the reliability of the received signal.To evaluate the system performance of our proposed RIS-NOMA network,we first derive the exact and asymptotic expressions for the outage probability and ergodic rate of two users.Then,we derive the exact and asymptotic upper bound expressions for the ergodic rate of the nearby user.Based on asymptotic analytical results,the diversity orders for the outage probability and the high signal-to-noise ratio(SNR)slopes for the ergodic rate of the two users are obtained in the high SNR regime.Moreover,we derive the system throughputs of the proposed RIS-NOMA network in delay-limited and delay-tolerant transmission modes.Numerical results confirm our analysis and demonstrate that:1)The outage probability and ergodic rate of RIS-NOMA networks are superior to that of RIS-assisted orthogonalmultiple access(OMA)networks;2)The RIS-NOMA networks have ability to achieve a larger system throughput compared to RIS-OMA networks;and 3)The system performance of RIS-NOMA networks can be significantly improved as the number of reflecting elements and Rician factor increases.

Impact of brine on physical properties of saline soils

Engineering activities in the salt lake region continue to increase where fresh water resources are scarce.This paper investigates the physical properties of saline soils during mixing with brine.Fine-grained saline soils with salt content varying from 2.6%to 78.5%were collected along Qarhan-Golmud Highway(QGH)and Sebei-Qarhan Highway(SQH)on the Qinghai-Tibet Plateau to conduct laboratory physical properties tests.Liquid plastic limit tests were conducted.Results show that liquid plastic limit parameters will decrease with an increase of salt content ranging from 2.6% to 78.5%,and the relationship between them is linear.After considering the content ratio of chloride and sulfate,results show that liquid plastic limit parameters will decrease with an increase of the ratio of chloride to sulfate ranging from 0.7% to 7.0%;liquid plastic limit parameters enter a stable period at the ratio of chloride to sulfate ranging from 7.0% to 37.4%;liquid plastic limit parameters enter a decline period at the ratio of chloride to sulfate ranging from 37.4% to 77.2%.After brine and fresh water are separately mixed into saline soil,the optimal moisture content of the soil samples after the brine action is lower than the saline soil under the action of fresh water,and the maximum dry density of the soil sample is higher than that under the action of fresh water.At the same time,these changing laws show a certain correlation with the chloride ion content and the ratio of chloride to sulfate in saline soils.The results are of significance for engineering activities in salt lake regions with extensive saline soil distribution.

Discretionary Power in the Course of Granting Graduate Degree in America and Its Enlightenments

Graduate education is the key support to the national competitive and technological levels. Therefore, the system of granting graduate degree was clearly guaranteed in the national level. For example, there are Education Law and Higher Education Law in China; the people＇ s education right is protected by federal constitution in the United States, and also universities or institutes have their own charters to claim the relative rights. The system safeguards the legitimacy of degree granting, but also gives a considerable discretionary power to the granting units who can grant or cancel the degree.

6G无线空口传输技术研究进展与展望

自20世纪80年代以来,移动通信已彻底改变世界,对人们的生活产生了深远影响.在5G成功商用的今天,人们又开始思考6G会是什么样子.作为下一代移动通信系统,6G不仅在频谱效率、时延、可靠性等通信KPI指标上提出了更高的要求,其内涵也将涉及人工智能、感知等新元素,远超传统意义上移动通信的范畴.为了实现6G愿景,迫切需要业界研究与之相适应的先进无线技术方案.本文重点介绍了6G无线空口多个研究方向的技术趋势和进展,包括信道编码技术、多址和波形技术、智能超表面技术、智能MIMO(multiple input multiple output)技术等,提出并初步验证了一系列创新技术点,如便车码、格码多址等.这些创新技术的提出,对6G愿景和KPI指标的实现起到有力的支撑作用.

Weakened tanning ability is an important mechanism for evolutionary skin lightening in East Asians

The evolution of light-skin pigmentation among Eurasians is considered as an adaptation to the high-latitude environments.East Asians are ideal populations for studying skin color evolution because of the complex environment of East Asia.Here,we report a strong selection signal for the pigmentation gene phenylalanine hydroxylase(PAH)in light-skinned Han Chinese individuals.The intron mutation rs10778203 in PAH is enriched in East Asians and is significantly associated with skin color of the back of the hand in Han Chinese males(P<0.05).In vitro luciferase and transcription factor binding assays show that the ancestral allele of rs10778203 could bind to SMAD2 and has a significant enhancer activity for PAH.However,the derived T allele(the major allele in East Asians)of rs10778203 decreases the binding activity of transcription factors and enhancer activity.Meanwhile,the derived T allele of rs10778203 shows a weaker ultraviolet radiation response in A375 cells and zebrafish embryos.Furthermore,rs10778203 decreases melanin production in transgenic zebrafish embryos after ultraviolet B(UVB)treatment.Collectively,PAH is a potential pigmentation gene that regulates skin tanning ability.Natural selection has enriched the adaptive allele,resulting in weakened tanning ability in East Asians,suggesting a unique genetic mechanism for evolutionary skin lightening in East Asians.

贵州梵净山国家级自然保护区鸟兽红外相机监测

红外相机监测是了解野生动物多样性现状、动态变化和面临威胁的重要手段。本研究采用网格抽样调查法,在贵州梵净山国家级自然保护区内选取2个监测样区共40个监测位点布设红外相机,对区内兽类和鸟类物种进行监测调查。2017年4月至2018年12月间,红外相机累积监测14,808个相机工作日,共收集有效照片14,119张,独立有效物种照片3,199张。共鉴定野生动物9目22科61种,其中兽类26种,隶属于4目12科;鸟类35种,隶属于5目10科。记录到国家I级重点保护野生动物2种:黔金丝猴(Rhinopithecusbrelichi)和白颈长尾雉(Syrmaticusellioti),国家II级重点保护野生动物9种;被IUCN红色名录评估为濒危(EN)的1种、易危(VU)的5种、近危(NT)的8种。物种的相对多度指数(relative abundance index, RAI)分析结果显示,藏酋猴(Macaca thibetana, RAI=28.23)、毛冠鹿(Elaphodus cephalophus, RAI=15.46)、野猪(Sus scrofa, RAI=11.82)、小麂(Muntiacus reevesi, RAI=9.05)、黔金丝猴(RAI=7.70)为相对多度最高的5种兽类;紫啸鸫(Myophonus insularis, RAI=10.33)、红腹角雉(Tragopan temminckii, RAI=9.59)、红腹锦鸡(Chrysolophus pictus, RAI=6.96)、白颈长尾雉(RAI=3.71)、勺鸡(Pucrasia macrolopha, RAI=1.55)为相对多度最高的5种鸟类。另外,红外相机还监测到较多的家畜活动(RAI=11.14)和人为活动(RAI=12.90),保护区管理部门仍需采取相应管理措施,进一步提高周边居民的保护意识,促进保护区与社区的协调发展。

Emission characteristics and probabilistic health risk of volatile organic compounds from leather sofa

Furniture is identified as a vital volatile organic compound(VOC)emission source in the indoor environment.Leather has become the most common raw and auxiliary fabric material for upholstered furniture,particularly with extensive consumption in sofas,due to its abundant resources and efficient functions.Despite being widely traded across the world,little research has been conducted on the VOCs released by leathermaterials and their health risk assessment in the indoor environment.Accordingly,this study investigated the VOC emissions of leather with different grades and the health risk of the inhalation exposure.Based on the ultra-fast gas phase electronic nose(EN)and GC-FID/Qtof,the substantial emissions of aliphatic aldehyde ketones(Aks),particularly hexanal,appear to be the cause of off-flavor in medium and low grade(MG and LG)sofa leathers.The health risk assessment indicated that leather materials barely pose non-carcinogenic and carcinogenic effects to residents.Given the abundance of VOC sources and the accumulation of health risks in the indoor environment,more stringent specifications concerning qualitative and quantitative content should be extended to provide VOC treatment basic for the manufacturing industry and obtain better indoor air quality.

西南喀斯特地区生物文化多样性的演化与耦合:以贵州兴义坡岗自然保护区为例

本文以具有典型喀斯特环境特点的贵州兴义坡岗自然保护区为例开展实地调查和文献研究。通过层次分析法和人与自然耦合系统模型构建,从文化景观视角探讨了喀斯特地区自然与文化系统的历史演化过程中,国家生态政策制度与乡规民约等乡土保护体系对生物文化多样性的驱动作用。研究结果表明:坡岗保护区经历了管护主体和保护利用态度的转变,保存了典型的喀斯特自然生态系统,当地世居的少数民族群体在长期生存与适应过程中创造了极具特色的传统民族文化。坡岗自然保护区丰富的生物多样性与文化多样性形成一个地理重合、协同进化且相互作用的维持系统。生物文化多样性耦合体系主要存在国家政策制度类与乡规民约等乡土文化类两种驱动因素。应加强西南喀斯特地区的生物文化多样性的保护,推动该地区生物多样性与文化多样性的协同发展;除了政策与制度类驱动因子的直接作用,还需要注重村规民约以及生态传统知识等乡土文化的驱动作用,以避免保护区自然与文化保护体系的割离。

Epidemiology and genetic diversity of norovirus GII genogroups among children in Hubei,China,2017–2019

Norovirus(NoV)is an important cause of viral acute gastroenteritis(AGE).To gain insights into the epidemio-logical characteristics and genetic diversity of NoV among children in Hubei,1216 stool samples from children(≤5 years)obtained under AGE surveillance from January 2017 to December 2019 were analyzed.The results showed that NoV was responsible for 14.64%of AGE cases,with the highest detection rate in children aged 7-12 months(19.76%).Statistically significant differences were found between male and female infection rates(χ^(2)=8.108,P¼0.004).Genetic analysis of RdRp and VP1 sequences showed that NoV GII genotypes were GII.4 Sydney[P31](34.35%),GII.3[P12](25.95%),GII.2[P16](22.90%),GII.4 Sydney[P16](12.98%),GII.17[P17](2.29%),GII.6[P7]and GII.3[P16](each at 0.76%).GII.17[P17]variants were divided into the Kawasaki323-like lineage and the Kawasaki308-like lineage.A unique recombination event was detected between strains of GII.4 Sydney 2012 and GII.4 Sydney 2016.Significantly,all GII.P16 sequences associated with GII.4/GII.2 ob-tained in Hubei were correlated with novel GII.2[P16]variants that re-emerged in Germany in 2016.Antigenic site analysis of complete VP1 sequences from all GII.4 variants from Hubei identified notable variable residues of antibody epitopes.Genotyping under continuous AGE surveillance and observation of the antigenic sites of VP1 are important monitoring strategies for emerging NoV strains.

Characterization,reactivity,source apportionment,and potential source areas of ambient volatile organic compounds in a typical tropical city

Based on one-year observation,the concentration,sources,and potential source areas of volatile organic compounds(VOCs)were comprehensively analyzed to investigate the pollution characteristics of ambient VOCs in Haikou,China.The results showed that the annual average concentration of total VOCs(TVOCs)was 11.4 ppb V,and the composition was dominated by alkanes(8.2 ppb V,71.4%)and alkenes(1.3 ppb V,20.5%).The diurnal variation in the concentration of dominant VOC species showed a distinct bimodal distribution with peaks in the morning and evening.The greatest contribution to ozone formation potential(OFP)was made by alkenes(51.6%),followed by alkanes(27.2%).The concentrations of VOCs and nitrogen dioxide(NO_(2))in spring and summer were low,and it was difficult to generate high ozone(O_(3))concentrations through photochemical reactions.The significant increase in O_(3)concentrations in autumn and winter was mainly related to the transmission of pollutants from the northeast.Traffic sources(40.1%),industrial sources(19.4%),combustion sources(18.6%),solvent usage sources(15.5%)and plant sources(6.4%)were identified as major sources of VOCs through the positive matrix factorization(PMF)model.The southeastern coastal areas of China were identified as major potential source areas of VOCs through the potential source contribution function(PSCF)and concentration-weighted trajectory(CWT)models.Overall,the concentration of ambient VOCs in Haikou was strongly influenced by traffic sources and long-distance transport,and the control of VOCs emitted from vehicles should be strengthened to reduce the active species of ambient VOCs in Haikou,thereby reducing the generation of O_(3).

Wireless communications empowered by reconfigurable intelligent surfaces: Model-based vs model-free channel estimation

Reconfigurable intelligent surfaces(RISs)are lately being attractive for their great potential in future sixth generation wireless communications(6G),which is attributed to their affordable energy consumption and easy integration.However,the large numbers of low-cost reflecting elements comprising RISs impose challenges for channel acquisition in various RIS-based wireless applications,such as RIS-enhanced orthogonal frequency-division multiplexing and multi-user multipleinput multiple-output systems.In this article,we first overview the state-of-the-art RIS hardware architectures designed to assist channel estimation for RIS-empowered wireless communication systems.We also overview existing channel estimation approaches,which are categorized into model-based and model-free techniques,and discuss their advantages and limitations depending on the RIS deployment.Design challenges with RIS-empowered systems in terms of hardware and other parameter limitations are presented,together with future research directions for channel estimation in RIS-based wireless systems,such as RISs with extremely large numbers of elements,multi-hop communications with RISs,and frequency division duplexing for high mobility systems.

Deep Learning for Secure Transmission in Reconfigurable Intelligent Surface-Assisted Communications

This paper investigates the secure transmission for reconfigurable intelligent surface(RIS)-assisted wireless communication systems.In the studied model,one user connects to the access point via a RIS while an eavesdropper eavesdrops on the signal sent from the user to the access point.Therefore,it is necessary to design an appropriate RIS reflection vector to solve the eavesdropping problem.This problem is formulated as an optimization problem whose goal is to maximize the secure energy efficiency which is defined as the ratio of the secure rate to the total energy consumption of the system via jointly optimizing the RIS reflection reflector as well as the number of RIS elements,which results in a non-convex optimization problem that is intractable to solve by traditional methods.To tackle this issue,a new algorithm by leveraging the advance of the established deep learning(DL)technique is proposed so as to find the optimal RIS reflection vector and determine the optimal number of RIS reflection elements.Simulation results show that the proposed method reaches 96%of the optimal secure energy efficiency of the genie-aided algorithm.