期刊文献+
共找到221,183篇文章
< 1 2 250 >
每页显示 20 50 100
Semantic model and optimization of creative processes at mathematical knowledge formation
1
作者 Victor Egorovitch Firstov 《Natural Science》 2010年第8期915-922,共8页
The aim of this work is mathematical education through the knowledge system and mathematical modeling. A net model of formation of mathematical knowledge as a deductive theory is suggested here. Within this model the ... The aim of this work is mathematical education through the knowledge system and mathematical modeling. A net model of formation of mathematical knowledge as a deductive theory is suggested here. Within this model the formation of deductive theory is represented as the development of a certain informational space, the elements of which are structured in the form of the orientated semantic net. This net is properly metrized and characterized by a certain system of coverings. It allows injecting net optimization parameters, regulating qualitative aspects of knowledge system under consideration. To regulate the creative processes of the formation and realization of mathematical know- edge, stochastic model of formation deductive theory is suggested here in the form of branching Markovian process, which is realized in the corresponding informational space as a semantic net. According to this stochastic model we can get correct foundation of criterion of optimization creative processes that leads to “great main points” strategy (GMP-strategy) in the process of realization of the effective control in the research work in the sphere of mathematics and its applications. 展开更多
关键词 The Cybernetic Conception Optimization of CONTROL Quantitative And Qualitative Information Measures Modelling Intellectual Systems Neural Network MATHEMATICAL Education The CONTROL of Pedagogical PROCESSES CREATIVE Pedagogics Cognitive And CREATIVE PROCESSES Informal Axiomatic Thery SEMANTIC NET NET Optimization Parameters The Topology of SEMANTIC NET Metrization The System of Coverings Stochastic Model of CREATIVE PROCESSES At The Formation of MATHEMATICAL Knowledge Branching Markovian Process Great Main Points strategy (GMP-strategy) of The CREATIVE PROCESSES CONTROL Interdisciplinary Learning: Colorimetric Barycenter
下载PDF
基于多维尺度分析的个人金融产品差异性研究 被引量:13
2
作者 张方杰 高向艳 《金融论坛》 CSSCI 北大核心 2005年第6期39-42,63,共5页
本文通过问卷调查获得数据,运用多维尺度分析了国内12家主要商业银行的主打个人金融产品并对其差异性做了实证研究。文章得出如下结论:我国商业银行个人金融产品的层次差别并不十分明显,产品或服务从形式到功能上都存在着较大的同质性;... 本文通过问卷调查获得数据,运用多维尺度分析了国内12家主要商业银行的主打个人金融产品并对其差异性做了实证研究。文章得出如下结论:我国商业银行个人金融产品的层次差别并不十分明显,产品或服务从形式到功能上都存在着较大的同质性;个人金融产品主要是单一型产品,缺乏为客户提供多项业务相结合的交叉式或捆绑式服务,不能满足消费者的多元化需求;不同收入的消费人群对个人金融产品的需求不同。在此基础上,作者提出了我国商业银行应实行个人金融产品或服务的差异化战略;以核心产品为依托,实现业务向全方位拓展延伸;针对不同消费群体进行差异化的金融创新和产品推销等应对策略。 展开更多
关键词
下载PDF
Global strategy for prevention of gastric cancer
3
作者 Sergey M Kotelevets 《World Journal of Clinical Cases》 SCIE 2024年第30期6353-6357,共5页
Global prevention of gastric cancer needs to increase its level of effectiveness.The prevention strategy should include all stages of primary and secondary prevention.The necessary steps to prevent gastric cancer are ... Global prevention of gastric cancer needs to increase its level of effectiveness.The prevention strategy should include all stages of primary and secondary prevention.The necessary steps to prevent gastric cancer are the following:Maintaining a healthy lifestyle and diet,avoiding smoking and alcohol;serological screening of Helicobacter pylori infections and eradication;serological screening of atrophic gastritis in the population over 45 years of age and identification of severe atrophic gastritis with a high risk of developing gastric cancer;verification of atrophic gastritis and precancerous changes in the gastric mucosa using modern endoscopic(confocal laser endomicroscopy,narrow-spectrum imaging,and magnifying endoscopy)and morphological methods among patients with severe atrophic gastritis who were identified using serological screening;treatment of patients with atrophic gastritis during diagnosis verification;annual endoscopic and morphological monitoring of patients with atrophic gastritis during permanent treatment;annual serological monitoring of patients with atrophic gastritis who refused endoscopic and morphological monitoring;and radical treatment of patients with verified early gastric cancer.Ways to implement the algorithm for the global strategy for the prevention of gastric cancer(protocol of practical recommendations)are:State,government,and municipal programs;departmental programs of health departments;family doctors for patients who have a contract at the initiative of the doctor;family doctors for patients with a contract at the patient’s initiative;and within private healthcare system where both doctors and patients can initiate the implementation of algorithm. 展开更多
关键词 PREVENTION Gastric cancer strategy Atrophic gastritis Serological screening Precancerous changes
下载PDF
Genome-wide SNP markers provided insights into the reproductive strategy and genetic diversity of the green tide causative species Ulva prolifera in China
4
作者 Song SUN Weiwei MA +2 位作者 Nan WANG Song FENG Yan SUN 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2024年第2期533-543,共11页
Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,ar... Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China. 展开更多
关键词 green tide Ulva prolifera 2b-RAD single-nucleotide polymorphism(SNP) reproductive strategy genetic diversity
下载PDF
Dynamic plugging regulating strategy of pipeline robot based on reinforcement learning
5
作者 Xing-Yuan Miao Hong Zhao 《Petroleum Science》 SCIE EI CAS CSCD 2024年第1期597-608,共12页
Pipeline isolation plugging robot (PIPR) is an important tool in pipeline maintenance operation. During the plugging process, the violent vibration will occur by the flow field, which can cause serious damage to the p... Pipeline isolation plugging robot (PIPR) is an important tool in pipeline maintenance operation. During the plugging process, the violent vibration will occur by the flow field, which can cause serious damage to the pipeline and PIPR. In this paper, we propose a dynamic regulating strategy to reduce the plugging-induced vibration by regulating the spoiler angle and plugging velocity. Firstly, the dynamic plugging simulation and experiment are performed to study the flow field changes during dynamic plugging. And the pressure difference is proposed to evaluate the degree of flow field vibration. Secondly, the mathematical models of pressure difference with plugging states and spoiler angles are established based on the extreme learning machine (ELM) optimized by improved sparrow search algorithm (ISSA). Finally, a modified Q-learning algorithm based on simulated annealing is applied to determine the optimal strategy for the spoiler angle and plugging velocity in real time. The results show that the proposed method can reduce the plugging-induced vibration by 19.9% and 32.7% on average, compared with single-regulating methods. This study can effectively ensure the stability of the plugging process. 展开更多
关键词 Pipeline isolation plugging robot Plugging-induced vibration Dynamic regulating strategy Extreme learning machine Improved sparrow search algorithm Modified Q-learning algorithm
下载PDF
Optimizing pain management in elderly patients post-knee surgery:A novel collaborative strategy
6
作者 Abdulqadir J Nashwan 《World Journal of Clinical Cases》 SCIE 2024年第15期2475-2478,共4页
Total knee replacement,a common surgery among the elderly primarily necessitated by osteoarthritis,replaces the damaged knee joint with an artificial one.Given the aging population and the increasing prevalence of suc... Total knee replacement,a common surgery among the elderly primarily necessitated by osteoarthritis,replaces the damaged knee joint with an artificial one.Given the aging population and the increasing prevalence of such surgeries,the article highlights the critical need for effective postoperative care strategies.This editorial provides an overview of rehabilitation care for pain in elderly knee replacement patients,emphasizing the importance of a multimodal approach to postoperative recovery.Furthermore,the article advocates for a patient-centered,comprehensive rehabilitation regimen that enhances recovery and quality of life in elderly patients undergoing knee replacement surgery. 展开更多
关键词 ELDERLY Postoperative pain management Rehabilitation care Multimodal pain strategy Total knee arthroplasty Enhanced recovery after surgery
下载PDF
Significant risk factors for intensive care unit-acquired weakness:A processing strategy based on repeated machine learning 被引量:9
7
作者 Ling Wang Deng-Yan Long 《World Journal of Clinical Cases》 SCIE 2024年第7期1235-1242,共8页
BACKGROUND Intensive care unit-acquired weakness(ICU-AW)is a common complication that significantly impacts the patient's recovery process,even leading to adverse outcomes.Currently,there is a lack of effective pr... BACKGROUND Intensive care unit-acquired weakness(ICU-AW)is a common complication that significantly impacts the patient's recovery process,even leading to adverse outcomes.Currently,there is a lack of effective preventive measures.AIM To identify significant risk factors for ICU-AW through iterative machine learning techniques and offer recommendations for its prevention and treatment.METHODS Patients were categorized into ICU-AW and non-ICU-AW groups on the 14th day post-ICU admission.Relevant data from the initial 14 d of ICU stay,such as age,comorbidities,sedative dosage,vasopressor dosage,duration of mechanical ventilation,length of ICU stay,and rehabilitation therapy,were gathered.The relationships between these variables and ICU-AW were examined.Utilizing iterative machine learning techniques,a multilayer perceptron neural network model was developed,and its predictive performance for ICU-AW was assessed using the receiver operating characteristic curve.RESULTS Within the ICU-AW group,age,duration of mechanical ventilation,lorazepam dosage,adrenaline dosage,and length of ICU stay were significantly higher than in the non-ICU-AW group.Additionally,sepsis,multiple organ dysfunction syndrome,hypoalbuminemia,acute heart failure,respiratory failure,acute kidney injury,anemia,stress-related gastrointestinal bleeding,shock,hypertension,coronary artery disease,malignant tumors,and rehabilitation therapy ratios were significantly higher in the ICU-AW group,demonstrating statistical significance.The most influential factors contributing to ICU-AW were identified as the length of ICU stay(100.0%)and the duration of mechanical ventilation(54.9%).The neural network model predicted ICU-AW with an area under the curve of 0.941,sensitivity of 92.2%,and specificity of 82.7%.CONCLUSION The main factors influencing ICU-AW are the length of ICU stay and the duration of mechanical ventilation.A primary preventive strategy,when feasible,involves minimizing both ICU stay and mechanical ventilation duration. 展开更多
关键词 Intensive care unit-acquired weakness Risk factors Machine learning PREVENTION Strategies
下载PDF
In Situ Coupling Strategy for Anchoring Monodisperse Co_9S_8 Nanoparticles on S and N Dual?Doped Graphene as a Bifunctional Electrocatalyst for Rechargeable Zn–Air Battery 被引量:10
8
作者 Qi Shao Jiaqi Liu +4 位作者 Qiong Wu Qiang Li Heng?guo Wang Yanhui Li Qian Duan 《Nano-Micro Letters》 SCIE EI CAS CSCD 2019年第1期64-77,共14页
An in situ coupling strategy to prepare Co_9S_8/S and N dual?doped graphene composite(Co_9S_8/NSG) has been proposed. The key point of this strategy is the function?oriented design of organic compounds. Herein, cobalt... An in situ coupling strategy to prepare Co_9S_8/S and N dual?doped graphene composite(Co_9S_8/NSG) has been proposed. The key point of this strategy is the function?oriented design of organic compounds. Herein, cobalt porphyrin derivatives with sulfo groups are employed as not only the coupling agents to form and anchor Co_9S_8 on the graphene in situ, but also the heteroatom?doped agent to generate S and N dual?doped graphene. The tight coupling of multiple active sites endows the composite materials with fast electrochemical kinetics and excellent stability for both oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). The obtained electrocatalyst exhibits better activity parameter(ΔE = 0.82 V) and smaller Tafel slope(47.7 mV dec^(-1) for ORR and 69.2 mV dec^(-1) for OER) than commercially available Pt/C and RuO_2. Most importantly, as electrocatalyst for rechargeable Zn–air battery, Co_9S_8/NSG displays low charge–discharge voltage gap and outstanding long?term cycle stability over 138 h compared to Pt/C–RuO_2. To further broaden its application scope, a homemade all?solid?state Zn–air battery is also prepared, which displays good charge–discharge performance and cycle performance. The function?oriented design of N_4?metallomacrocycle derivatives might open new avenues to strategic construction of high?performance and long?life multifunctional electrocatalysts for wider electro?chemical energy applications. 展开更多
关键词 In situ COUPLING strategy Porphyrin derivate DOPED GRAPHENE Metal sulfide BIFUNCTIONAL ELECTROCATALYST RECHARGEABLE Znair battery
下载PDF
Extension Modeling Strategy of Intelligent Detection in D.huoshanense Photosynthesis Process 被引量:4
9
作者 Rongde Lu Can Qin Yunsheng Bao 《Intelligent Control and Automation》 2011年第2期126-132,共7页
Aiming at the limitations of the existing knowledge representations in intelligent detection, a new method of Extension-based Knowledge Representation (EKR) was proposed. The definitions, grammar rules, and storage st... Aiming at the limitations of the existing knowledge representations in intelligent detection, a new method of Extension-based Knowledge Representation (EKR) was proposed. The definitions, grammar rules, and storage structure of EKR were presented. An Extension Solving Model (ESM) based on EKR was discussed in detail, including creation of the extension constraint graph, extended inference, calculation of relevant functions and generation of extension set. A knowledge base system based on EKR and ESM was developed, which was applied in extension repository system intelligent design of detection in photosynthesis process of D.huoshanense. More reasonable results were obtained than traditional rule-based system. EKR was feasible in intelligent design to solve the problem of intelligent detection knowledge representations. 展开更多
关键词 Extension-Based KNOWLEDGE REPRESENTATION (EKR) Intelligent Detection EXTENSION Modeling strategy (EMS) PHOTOSYNTHESIS Process of D.huoshanense (PPDH)
下载PDF
对合作学习操作性策略的实验研究 被引量:5
10
作者 许峰 李健 武玉强 《中国健康心理学杂志》 2005年第3期237-240,共4页
目的探讨合作学习操作过程中一种新的教学组织模式——学习中的“合作+竞争”对学生学业成绩、合作意识、竞争精神的影响,通过改变学生学业成绩的奖励模式,使学生在公平、有序的竞争环境中增强其学业竞争力和提高学业成绩的同时,培养学... 目的探讨合作学习操作过程中一种新的教学组织模式——学习中的“合作+竞争”对学生学业成绩、合作意识、竞争精神的影响,通过改变学生学业成绩的奖励模式,使学生在公平、有序的竞争环境中增强其学业竞争力和提高学业成绩的同时,培养学生的合作意识,训练学生的合作技巧。方法选取小学四年级和六年级的学生作为实验对象,采用自行设计的学业成绩奖励模式与现有的学业成绩奖励模式作为自变量进行比较实验。结果与对照班相比,实验班中的四年级和六年级学生语文成绩都有明显提高,差异显著;数学成绩六年级学生有明显提高,差异显著,而四年级学生的成绩差异不明显。结论采用新的学业成绩奖励模式,创设“合作+竞争”的教学组织模式,可以整体性的提高学生语文科目的学业成绩,提高学生的学业竞争力;可以培养学生的合作意识,掌握必要的合作技巧,有利于提高学生的社会适应性;可以促进学生参与公平、有序的竞争。 展开更多
关键词
下载PDF
The Caching and Pricing Strategy for Information-Centric Networking with Advertisers’Participation
11
作者 Zheng Quan Yan Wenliang +4 位作者 Wu Rong Tan Xiaobin Yang Jian Yuan Liu Xu Zhenghuan 《China Communications》 SCIE CSCD 2024年第3期283-295,共13页
As users’access to the network has evolved into the acquisition of mass contents instead of IP addresses,the IP network architecture based on end-to-end communication cannot meet users’needs.Therefore,the Informatio... As users’access to the network has evolved into the acquisition of mass contents instead of IP addresses,the IP network architecture based on end-to-end communication cannot meet users’needs.Therefore,the Information-Centric Networking(ICN)came into being.From a technical point of view,ICN is a promising future network architecture.Researching and customizing a reasonable pricing mechanism plays a positive role in promoting the deployment of ICN.The current research on ICN pricing mechanism is focused on paid content.Therefore,we study an ICN pricing model for free content,which uses game theory based on Nash equilibrium to analysis.In this work,advertisers are considered,and an advertiser model is established to describe the economic interaction between advertisers and ICN entities.This solution can formulate the best pricing strategy for all ICN entities and maximize the benefits of each entity.Our extensive analysis and numerical results show that the proposed pricing framework is significantly better than existing solutions when it comes to free content. 展开更多
关键词 ADVERTISERS CACHE free content Information-Centric Networking pricing strategy
下载PDF
Making the Complicated Simple:A Minimizing Carrier Strategy on Innovative Nanopesticides
12
作者 Wenjie Shangguan Qiliang Huang +6 位作者 Huiping Chen Yingying Zheng Pengyue Zhao Chong Cao Manli Yu Yongsong Cao Lidong Cao 《Nano-Micro Letters》 SCIE EI CAS CSCD 2024年第10期31-46,共16页
The flourishing progress in nanotechnology offers boundless opportunities for agriculture,particularly in the realm of nanopesticides research and development.However,concerns have been raised regarding the human and ... The flourishing progress in nanotechnology offers boundless opportunities for agriculture,particularly in the realm of nanopesticides research and development.However,concerns have been raised regarding the human and environmental safety issues stemming from the unrestrained use of non-therapeutic nanomaterials in nanopesticides.It is also important to consider whether the current development strategy of nanopesticides based on nanocarriers can strike a balance between investment and return,and if the complex material composition genuinely improves the efficiency,safety,and circularity of nanopesticides.Herein,we introduced the concept of nanopesticides with minimizing carriers(NMC)prepared through prodrug design and molecular self-assembly emerging as practical tools to address the current limitations,and compared it with nanopesticides employing non-therapeutic nanomaterials as carriers(NNC).We further summarized the current development strategy of NMC and examined potential challenges in its preparation,performance,and production.Overall,we asserted that the development of NMC systems can serve as the innovative driving force catalyzing a green and efficient revolution in nanopesticides,offering a way out of the current predicament. 展开更多
关键词 Nanopesticides Green agrochemicals SELF-ASSEMBLY Nanomaterial safety Sustainable development strategies
下载PDF
具有改善电能质量的光伏发电并网控制器研究 被引量:8
13
作者 於锋 胡国文 《低压电器》 北大核心 2010年第22期18-21,28,共5页
基于瞬时无功理论的ip-iq电流检测方法,提出了光伏并网逆变器的2种控制方案,可实现逆变器并网发电、动态无功补偿、有源滤波的柔性结合,实现新能源发电的同时又改善了电网电能质量。最后,通过计算验证了该装置无功补偿的能力,具有实际... 基于瞬时无功理论的ip-iq电流检测方法,提出了光伏并网逆变器的2种控制方案,可实现逆变器并网发电、动态无功补偿、有源滤波的柔性结合,实现新能源发电的同时又改善了电网电能质量。最后,通过计算验证了该装置无功补偿的能力,具有实际工程应用价值。通过仿真研究表明,提出的2套并网控制策略正确,具有可行性,对智能电网的发展提供了很好的理论基础。 展开更多
关键词 Improved Electrical Energy Quality Control strategy 仿
下载PDF
Enhancing thermodynamic stability of single-crystal Ni-rich cathode material via a synergistic dual-substitution strategy
14
作者 Jixue Shen Hui Li +6 位作者 Haoyu Qi Zhan Lin Zeheng Li Chuanbo Zheng Weitong Du Hao Chen Shanqing Zhang 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2024年第1期428-436,I0010,共10页
Nickel(Ni)-rich cathode materials have become promising candidates for the next-generation electrical vehicles due to their high specific capacity.However,the poor thermodynamic stability(including cyclic performance ... Nickel(Ni)-rich cathode materials have become promising candidates for the next-generation electrical vehicles due to their high specific capacity.However,the poor thermodynamic stability(including cyclic performance and safety performance or thermal stability)will restrain their wide commercial application.Herein,a single-crystal Ni-rich Li Ni_(0.83)Co_(0.12)Mn_(0.05)O_(2) cathode material is synthesized and modified by a dual-substitution strategy in which the high-valence doping element improves the structural stability by forming strong metal–oxygen binding forces,while the low-valence doping element eliminates high Li^(+)/Ni^(2+)mixing.As a result,this synergistic dual substitution can effectively suppress H2-H3 phase transition and generation of microcracks,thereby ultimately improving the thermodynamic stability of Ni-rich cathode material.Notably,the dual-doped Ni-rich cathode delivers an extremely high capacity retention of 81%after 250 cycles(vs.Li/Li+)in coin-type half cells and 87%after 1000 cycles(vs.graphite/Li^(+))in pouch-type full cells at a high temperature of 55℃.More impressively,the dual-doped sample exhibits excellent thermal stability,which demonstrates a higher thermal runaway temperature and a lower calorific value.The synergetic effects of this dual-substitution strategy pave a new pathway for addressing the critical challenges of Ni-rich cathode at high temperatures,which will significantly advance the high-energy-density and high-safety cathodes to the subsequent commercialization. 展开更多
关键词 Ni-rich cathode Single crystalline Dual-substitution strategy High-temperature cathode Li-ion batteries
下载PDF
Ultimately Bounded Output Feedback Control for Networked Nonlinear Systems With Unreliable Communication Channel: A Buffer-Aided Strategy
15
作者 Yuhan Zhang Zidong Wang +2 位作者 Lei Zou Yun Chen Guoping Lu 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2024年第7期1566-1578,共13页
This paper concerns ultimately bounded output-feedback control problems for networked systems with unknown nonlinear dynamics. Sensor-to-observer signal transmission is facilitated over networks that has communication... This paper concerns ultimately bounded output-feedback control problems for networked systems with unknown nonlinear dynamics. Sensor-to-observer signal transmission is facilitated over networks that has communication constraints.These transmissions are carried out over an unreliable communication channel. In order to enhance the utilization rate of measurement data, a buffer-aided strategy is novelly employed to store historical measurements when communication networks are inaccessible. Using the neural network technique, a novel observer-based controller is introduced to address effects of signal transmission behaviors and unknown nonlinear dynamics.Through the application of stochastic analysis and Lyapunov stability, a joint framework is constructed for analyzing resultant system performance under the introduced controller. Subsequently, existence conditions for the desired output-feedback controller are delineated. The required parameters for the observerbased controller are then determined by resolving some specific matrix inequalities. Finally, a simulation example is showcased to confirm method efficacy. 展开更多
关键词 Buffer-aided strategy neural networks nonlinear control output-feedback control unreliable communication channel
下载PDF
Building Fe atom–cluster composite sites using a site occupation strategy to boost electrochemical oxygen reduction
16
作者 Tingyi Zhou Yi Guan +9 位作者 Changjie He Lei Zhang Xueliang Sun Zhongxin Song Qianling Zhang Chuanxin He Xiantao Jiang Zhaoyan Luo Wei Xing Xiangzhong Ren 《Carbon Energy》 SCIE EI CAS CSCD 2024年第3期276-286,共11页
The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic ... The high-temperature pyrolysis process for preparing M–N–C single-atom catalyst usually results in high heterogeneity in product structure concurrently contains multiscale metal phases from single atoms(SAs),atomic clusters to nanoparticles.Therefore,understanding the interactions among these components,especially the synergistic effects between single atomic sites and cluster sites,is crucial for improving the oxygen reduction reaction(ORR)activity of M–N–C catalysts.Accordingly,herein,we constructed a model catalyst composed of both atomically dispersed FeN4 SA sites and adjacent Fe clusters through a site occupation strategy.We found that the Fe clusters can optimize the adsorption strength of oxygen reduction intermediates on FeN4 SA sites by introducing electron-withdrawing–OH ligands and decreasing the d-band center of the Fe center.The as-developed catalyst exhibits encouraging ORR activity with halfwave potentials(E1/2)of 0.831 and 0.905 V in acidic and alkaline media,respectively.Moreover,the catalyst also represents excellent durability exceeding that of Fe–N–C SA catalyst.The practical application of Fe(Cd)–CNx catalyst is further validated by its superior activity and stability in a metalair battery device.Our work exhibits the great potential of synergistic effects between multiphase metal species for improvements of singleatom site catalysts. 展开更多
关键词 d-band center metal clusters oxygen reduction reaction single-atom catalyst site occupations strategy
下载PDF
Suppress oxygen evolution of lithium-rich manganese-based cathode materials via an integrated strategy
17
作者 Wenhua Yu Yanyan Wang +5 位作者 Aimin Wu Aikui Li Zhiwen Qiu Xufeng Dong Chuang Dong Hao Huang 《Green Energy & Environment》 SCIE EI CAS CSCD 2024年第1期138-151,共14页
Improving the reversibility of anionic redox and inhibiting irreversible oxygen evolution are the main challenges in the application of high reversible capacity Li-rich Mn-based cathode materials.A facile synchronous ... Improving the reversibility of anionic redox and inhibiting irreversible oxygen evolution are the main challenges in the application of high reversible capacity Li-rich Mn-based cathode materials.A facile synchronous lithiation strategy combining the advantages of yttrium doping and LiYO_(2) surface coating is proposed.Yttrium doping effectively suppresses the oxygen evolution during the delithiation process by increasing the energy barrier of oxygen evolution reaction through strong Y–O bond energy.LiYO_(2) nanocoating has the function of structural constraint and protection,that protecting the lattice oxygen exposed to the surface,thus avoiding irreversible oxidation.As an Li^(+) conductor,LiYO_(2) nano-coating can provide a fast Li^(+) transfer channel,which enables the sample to have excellent rate performance.The synergistic effect of Y doping and nano-LiYO_(2) coating integration suppresses the oxygen release from the surface,accelerates the diffusion of Li^(+)from electrolyte to electrode and decreases the interfacial side reactions,enabling the lithium ion batteries to obtain good electrochemical performance.The lithium-ion full cell employing the Y-1 sample(cathode)and commercial graphite(anode)exhibit an excellent specific energy density of 442.9 Wh kg^(-1) at a current density of 0.1C,with very stable safety performance,which can be used in a wide temperature range(60 to-15℃)stable operation.This result illustrates a new integration strategy for advanced cathode materials to achieve high specific energy density. 展开更多
关键词 Lithium-rich manganese-based cathodes Lithium ion batteries Oxygen redox Oxygen evolution Integrated strategy
下载PDF
A guidance strategy for rendezvous and docking to the space station in the Earth-Moon NRHO orbit
18
作者 XIE Yongchun CHEN Changqing +1 位作者 LI Xiangyu LI Zhenyu 《中国空间科学技术(中英文)》 CSCD 北大核心 2024年第4期29-39,共11页
With the development of space technology,it is possible to build a space station in Earth-Moon space as a transit for Earth-Moon round-trip and entering in the deep space.Rendezvous and docking is one of the key techn... With the development of space technology,it is possible to build a space station in Earth-Moon space as a transit for Earth-Moon round-trip and entering in the deep space.Rendezvous and docking is one of the key technologies for building an Earth-Moon space station.A guidance strategy for rendezvous and docking from the Earth orbit to the space station in the Earth-Moon NRHO orbit is proposed in this paper,which is suitable for engineering applications.Firstly,the rendezvous and docking process is divided into three sections,i.e.,the large-range orbit transfer section,far-range guidance section,and close-range approaching section.The suitable terminal of large-range orbit transfer is selected according to the eigenvalue of NRHO orbit state transition matrix.The two-impulse guidance method based on the relative motion equation in the three-body problem is adopted for the far-range guidance section.The impulse time and amplitude are solved with the optimization algorithm.The linear constant three-body relative motion equation is proposed for the close-range approaching section,and the rendezvous and docking is completed by a two-stage linear approximation.Finally,a simulation analysis is carried out,and the simulation results show that the adopted dynamics equations and the designed guidance law are effective,and the three flight phases are naturally connected to accomplish the rendezvous and docking mission from the Earth orbit to the space station on the Earth-Moon NRHO. 展开更多
关键词 Earth-Moon space station rendezvous and docking NRHO orbit relative motion guidance strategy
下载PDF
An Incentive Mechanism for Federated Learning:A Continuous Zero-Determinant Strategy Approach
19
作者 Changbing Tang Baosen Yang +3 位作者 Xiaodong Xie Guanrong Chen Mohammed A.A.Al-qaness Yang Liu 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2024年第1期88-102,共15页
As a representative emerging machine learning technique, federated learning(FL) has gained considerable popularity for its special feature of “making data available but not visible”. However, potential problems rema... As a representative emerging machine learning technique, federated learning(FL) has gained considerable popularity for its special feature of “making data available but not visible”. However, potential problems remain, including privacy breaches, imbalances in payment, and inequitable distribution.These shortcomings let devices reluctantly contribute relevant data to, or even refuse to participate in FL. Therefore, in the application of FL, an important but also challenging issue is to motivate as many participants as possible to provide high-quality data to FL. In this paper, we propose an incentive mechanism for FL based on the continuous zero-determinant(CZD) strategies from the perspective of game theory. We first model the interaction between the server and the devices during the FL process as a continuous iterative game. We then apply the CZD strategies for two players and then multiple players to optimize the social welfare of FL, for which we prove that the server can keep social welfare at a high and stable level. Subsequently, we design an incentive mechanism based on the CZD strategies to attract devices to contribute all of their high-accuracy data to FL.Finally, we perform simulations to demonstrate that our proposed CZD-based incentive mechanism can indeed generate high and stable social welfare in FL. 展开更多
关键词 Federated learning(FL) game theory incentive mechanism machine learning zero-determinant strategy
下载PDF
Reshaping Li–Mg hybrid batteries:Epitaxial electrodeposition and spatial confinement on MgMOF substrates via the lattice‐matching strategy
20
作者 Yongqin Wang Fulin Cheng +2 位作者 Jiawen Ji Chenyang Cai Yu Fu 《Carbon Energy》 SCIE EI CAS CSCD 2024年第8期248-261,共14页
The emergence of Li–Mg hybrid batteries has been receiving attention,owing to their enhanced electrochemical kinetics and reduced overpotential.Nevertheless,the persistent challenge of uneven Mg electrodeposition rem... The emergence of Li–Mg hybrid batteries has been receiving attention,owing to their enhanced electrochemical kinetics and reduced overpotential.Nevertheless,the persistent challenge of uneven Mg electrodeposition remains a significant impediment to their practical integration.Herein,we developed an ingenious approach that centered around epitaxial electrocrystallization and meticulously controlled growth of magnesium crystals on a specialized MgMOF substrate.The chosen MgMOF substrate demonstrated a robust affinity for magnesium and showed minimal lattice misfit with Mg,establishing the crucial prerequisites for successful heteroepitaxial electrocrystallization.Moreover,the incorporation of periodic electric fields and successive nanochannels within the MgMOF structure created a spatially confined environment that considerably promoted uniform magnesium nucleation at the molecular scale.Taking inspiration from the“blockchain”concept prevalent in the realm of big data,we seamlessly integrated a conductive polypyrrole framework,acting as a connecting“chain,”to interlink the“blocks”comprising the MgMOF cavities.This innovative design significantly amplified charge‐transfer efficiency,thereby increasing overall electrochemical kinetics.The resulting architecture(MgMOF@PPy@CC)served as an exceptional host for heteroepitaxial Mg electrodeposition,showcasing remarkable electrostripping/plating kinetics and excellent cycling performance.Surprisingly,a symmetrical cell incorporating the MgMOF@PPy@CC electrode demonstrated impressive stability even under ultrahigh current density conditions(10mAcm–2),maintaining operation for an extended 1200 h,surpassing previously reported benchmarks.Significantly,on coupling the MgMOF@PPy@CC anode with a Mo_(6)S_(8) cathode,the assembled battery showed an extended lifespan of 10,000 cycles at 70 C,with an outstanding capacity retention of 96.23%.This study provides a fresh perspective on the rational design of epitaxial electrocrystallization driven by metal–organic framework(MOF)substrates,paving the way toward the advancement of cuttingedge batteries. 展开更多
关键词 epitaxial electrodeposition latticematching strategy Li-Mg hybrid batteries MOF substrate spatial confinement
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部