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Size and proportion of urban and rural middle-income group in China: A comparative analysis based on CHNS and CHIP data
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作者 WU Peng 《Ecological Economy》 2017年第3期202-212,共11页
To enlarge the middle-income group and construct the "olivary" income distribution becomes one of the important issues of the economic development and income distribution reform in China. The income distribu... To enlarge the middle-income group and construct the "olivary" income distribution becomes one of the important issues of the economic development and income distribution reform in China. The income distribution function is estimated with kernel density, and the income distribution M-curve is constructed with CHNS and CHIP data to calculate the middle-income group. Furthermore, a comparative analysis is carried out for the changing trend of the size and proportion of middle-income group. Research conclusion: it is discovered according to the income distribution M-curve that the key to the enlargement of urban middle-income group lies in the lower middle-income group, while the key to the enlargement of rural middle-income group lies in the improvement of the upper middle-income group. The range of middle-income group is expanding, but due to the small scale, low proportion, and poor stability, it has not developed the "olivary" income distribution structure yet, and income inequality tends to be deepened. 展开更多
关键词 middle-income group kernel density estimation income distribution M-curve
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Expanding the Middle-Income Group Through Education:Preliminary Evidence From China
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作者 Chen Xie Xiuxiu Yang 《ECNU Review of Education》 2025年第3期761-778,共18页
Purpose:This study explores the role of education in fostering middle-income earners in China,elucidating the development and current status of the capabilities of education in this regard.This study uses the historic... Purpose:This study explores the role of education in fostering middle-income earners in China,elucidating the development and current status of the capabilities of education in this regard.This study uses the historical changes in this demographic in the United States as a frame of reference to explore future goal-setting and implementation pathways for expanding the middle-income group through education in China.Design/Approach/Methods:This study uses data on variables such as income,educational attainment,and years since graduation from the China Family Panel Studies database to analyze the changing patterns in China's middle-income group regarding educational attainment.This study also uses data from the Panel Study of Income Dynamics to examine the historical changes in the middle-income group in the United States and compares the findings to those inChina.Findings:Results reveal the following:the changing patterns in the share of the middleincome group relative to educational attainment;the distribution of the low-,middle-,and high-income groups by educational attainment;the changing trends in the share of middleincome group by educational attainment between 2012 and 2018;and the changing trends in the share of middle-and high-income groups by educational attainment regarding the numberofyears sincegraduation.Originality/Value:Rooted in and driven by current issues facing China,this study compares education in China and the United States and offers preliminary evidence of the role of education in expanding the middle-income group. 展开更多
关键词 Educational attainment evidence-driven middle-income group
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商业银行基于Group Training技术的小样本学习应用研究
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作者 吴永飞 寿弘宇 +3 位作者 王彦博 魏文术 徐奇 张月 《金融科技时代》 2025年第3期16-22,共7页
人工智能是推动社会进步和经济发展的关键力量。商业银行已经在诸多业务领域广泛使用人工智能技术,如精准营销、智能风控、智慧运营等业务领域。然而,有些业务场景在“冷启动”阶段面临样本量不足,并且坏样本量极少的小样本学习问题,这... 人工智能是推动社会进步和经济发展的关键力量。商业银行已经在诸多业务领域广泛使用人工智能技术,如精准营销、智能风控、智慧运营等业务领域。然而,有些业务场景在“冷启动”阶段面临样本量不足,并且坏样本量极少的小样本学习问题,这导致现有的人工智能技术可能失效。基于此,文章创新提出了一种Group Training(群组训练)建模思路,可以有效解决小样本学习问题。实证结果表明,Group Training建模方案在多个金融数据集上效果均明显优于传统的建模方案,这为商业银行小样本学习提供了新的研究思路和解决方案。 展开更多
关键词 人工智能 小样本学习 group Learning group Training
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Digital psychiatry in low-and-middle-income countries:New developments and the way forward
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作者 Subho Chakrabarti 《World Journal of Psychiatry》 SCIE 2024年第3期350-361,共12页
Low-and middle-income countries(LMICs)bear the greater share of the global mental health burden but are ill-equipped to deal with it because of severe resource constraints leading to a large treatment gap.The remote p... Low-and middle-income countries(LMICs)bear the greater share of the global mental health burden but are ill-equipped to deal with it because of severe resource constraints leading to a large treatment gap.The remote provision of mental health services by digital means can effectively augment conventional services in LMICs to reduce the treatment gap.Digital psychiatry in LMICs has always lagged behind high-income countries,but there have been encouraging developments in the last decade.There is increasing research on the efficacy of digital psychiatric interventions.However,the evidence is not adequate to conclude that digital psychiatric interventions are invariably effective in LMICs.A striking development has been the rise in mobile and smartphone ownership in LMICs,which has driven the increasing use of mobile technologies to deliver mental health services.An innovative use of mobile technologies has been to optimize task-shifting,which involves delivering mental healthcare services in community settings using non-specialist health professionals.Emerging evidence from LMICs shows that it is possible to use digital tools to train non-specialist workers effectively and ensure that the psychosocial interventions they deliver are efficacious.Despite these promising developments,many barriers such as service costs,underdeveloped infrastructure,lack of trained professionals,and significant disparities in access to digital services impede the progress of digital psychiatry in LMICs.To overcome these barriers,digital psychiatric services in LMICs should address contextual factors influencing the delivery of digital services,ensure collaboration between different stakeholders,and focus on reducing the digital divide. 展开更多
关键词 Digital psychiatry Low-and middle-income countries DEVELOPMENTS Mental health
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Burnout and mental distress among community health workers in low- and middle-income countries: a scoping review of studies during the COVID-19 pandemic
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作者 Oluchi I.Ndulue Anand Chukka John A.Naslund 《Global Health Journal》 2024年第4期162-171,共10页
Community health workers(CHWs)represent the backbone of primary health systems,especially in many low-and middle-income countries(LMICs).The coronavirus disease 2019(COVID-19)pandemic stretched health sys-tems and inc... Community health workers(CHWs)represent the backbone of primary health systems,especially in many low-and middle-income countries(LMICs).The coronavirus disease 2019(COVID-19)pandemic stretched health sys-tems and increased the workload for CHWs.The objective of this scoping review was to identify the mental health symptoms experienced among CHWs in LMICs during the COVID-19 pandemic.We searched PubMed for published literature,from January 1,2020 to December 31,2022 that focused on documenting the experiences of burnout,distress,and mental health symptoms among CHWs in LMICs.The quality of included studies was assessed using the Joanna Briggs Institute Critical Appraisal Tool.Included studies were grouped into the follow-ing broad thematic categories:(1)symptoms experienced;(2)drivers of different mental health symptoms;and(3)strategies for coping with different symptoms.We identified 10 cross-sectional,qualitative,and observational studies from 11 LMICs in South and Southeast Asia,South America,and Eastern/Southern Africa that assessed the mental health burden CHWs faced during the pandemic.The studies identified disorders and symptoms such as depression,anxiety,fear,burnout,worsened stress,and fatigue.Contributing factors included increased work-load,financial constraints,and an understaffed and underequipped workplace.CHWs reported using different adaptive responses like humor,support from family and colleagues,denial,and substance use,and asked for recommended regular mental health checkups and counseling.More research and policies should be targeted to-wards promoting the mental wellbeing of CHWs to help ensure responsive and resilient health systems in LMICs in the face of future emerging public health threats. 展开更多
关键词 Community health worker BURNOUT Stress Coronavirus disease 2019(COVID-19) Low-and middle-income countries(LMICs) Mental health distress
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Exploring the current provision of pancreatic transplantations in lowand middle-income countries:Current landscape,challenges,future prospects
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作者 Hareesha Rishab Bharadwaj Joecelyn Kirani Tan +8 位作者 Syed Hasham Ali Muhammad Hamza Shah Aderinto Nicholas Khabab Abbasher Hussien Mohamed Ahmed Khansa Irfan Priyal Dalal Aashna Mehta Wireko Andrew Awuah Arkadeep Dhali 《World Journal of Gastrointestinal Pathophysiology》 2024年第6期1-10,共10页
This comprehensive review addresses the global health challenge of disparities in pancreas transplant access,particularly in low-and middle-income countries(LMICs)compared to high-income countries.Despite advancements... This comprehensive review addresses the global health challenge of disparities in pancreas transplant access,particularly in low-and middle-income countries(LMICs)compared to high-income countries.Despite advancements in surgical techniques and immunosuppression for procedures like simultaneous pancreas-kidney,pancreas-after-kidney,and pancreas-transplant alone,LMICs face significant challenges,including limited infrastructure,financial constraints,and a shortage of skilled medical professionals.Donation after brain death remains constrained by sociocultural barriers.Region-specific analyses highlight progress in Latin America,Asia,Russia,and South Africa,showcasing the regional disparities in access and outcomes.Future prospects involve minimally invasive surgeries,telemedicine for enhanced post-operative care,international collaborations with organizations like the European Union of Medical Specialists,and robust funding networks to improve organ availability.In conclusion,the review underscores the importance of multifaceted strategies to address economic,sociocultural,and infrastructural barriers,aiming to improve accessibility,quality,and effectiveness of pancreas transplantation services in LMICs. 展开更多
关键词 Pancreatic transplantation Diabetes mellitus Global health Low-and middle-income countries Transplant surgery
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Breast cancer awareness in reproductive women in the low-and middle-income countries:a scoping review
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作者 Made Satya Nugraha Gautama Saranya Pimolkatekul Nguyen Ngoc Nhat Thanh 《Frontiers of Nursing》 2024年第2期139-151,共13页
Objective:This study aimed to assess breast cancer(BC)awareness among reproductive women in low-and middle-income countries(LMICs),identify influencing factors,and propose feasible interventions or programs.Methods:We... Objective:This study aimed to assess breast cancer(BC)awareness among reproductive women in low-and middle-income countries(LMICs),identify influencing factors,and propose feasible interventions or programs.Methods:We followed a 5-step process using a modified version of Arksey and O’Malley framework methodology.A comprehensive search was conducted on the Embase,PubMed,and CINAHL electronic databases for literature published within 10 years(from 2012 to 2022).Results:Thirty-three papers published between 2012 and 2020,spanning 18 countries,were included.Of these,45.6%described a good level of knowledge,while 24.2%reported that women at reproductive ages had good awareness.Twelve influencing factors were identified in 3 categories:socio-demographic(family history,personal history,marital status,age,religion,income status,living place,and occupation),personal(self-efficacy,education,and perceived level),and external(advertisements promoting awareness).Educational programs were recommended in most(>72%)of the included studies.Conclusions:While most studies reported high levels of knowledge and awareness,some found low prevalence among certain groups.Factors affecting knowledge and awareness were classified into socio-demographic,personal,and external categories,with socio-demographic factors such as age,education,income,and marital status being the most frequently cited.The studies recommended implementing educational programs,health prevention strategies,and social interventions to increase BC knowledge and awareness. 展开更多
关键词 AWARENESS breast cancer low-and middle-income countries reproductive women scoping review
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An Improved Practical Byzantine Fault-Tolerant Algorithm Based on XGBoost Grouping for Consortium Chains
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作者 Xiaowei Wang Haiyang Zhang +5 位作者 Jiasheng Zhang Yingkai Ge Kexin Cui Zifu Peng Zhengyi Li Lihua Wang 《Computers, Materials & Continua》 SCIE EI 2025年第1期1295-1311,共17页
In response to the challenges presented by the unreliable identity of the master node,high communication overhead,and limited network support size within the Practical Byzantine Fault-Tolerant(PBFT)algorithm for conso... In response to the challenges presented by the unreliable identity of the master node,high communication overhead,and limited network support size within the Practical Byzantine Fault-Tolerant(PBFT)algorithm for consortium chains,we propose an improved PBFT algorithm based on XGBoost grouping called XG-PBFT in this paper.XG-PBFT constructs a dataset by training important parameters that affect node performance,which are used as classification indexes for nodes.The XGBoost algorithm then is employed to train the dataset,and nodes joining the system will be grouped according to the trained grouping model.Among them,the nodes with higher parameter indexes will be assigned to the consensus group to participate in the consensus,and the rest of the nodes will be assigned to the general group to receive the consensus results.In order to reduce the resource waste of the system,XG-PBFT optimizes the consensus protocol for the problem of high complexity of PBFT communication.Finally,we evaluate the performance of XG-PBFT.The experimental results show that XG-PBFT can significantly improve the performance of throughput,consensus delay and communication complexity compared to the original PBFT algorithm,and the performance enhancement is significant compared to other algorithms in the case of a larger number of nodes.The results demonstrate that the XG-PBFT algorithm is more suitable for large-scale consortium chains. 展开更多
关键词 Consortium chain PBFT groupING REPUTATION XGBoost
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Interannual succession of phytoplankton community in a canyon-shaped drinking water reservoir during the initial impoundment period:Taxonomic versus functional groups 被引量:1
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作者 Yi Hou Ya Cheng +6 位作者 Kai Li Meng Yang Kangzhe Huang Gang Ji Ruikang Xue Tinglin Huang Gang Wen 《Journal of Environmental Sciences》 2025年第5期454-468,共15页
During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure o... During the initial impoundment period of a canyon-shaped reservoir,the water body fluctuated violently regarding water level,hydrological condition,and thermal stratification.These variations may alter the structure of phytoplankton community,resulting in algal blooms and seriously threatening the ecological security of the reservoir.It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality.Therefore,a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyonshaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels.The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input,and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community,and the proportion of cyanobacteria increased significantly.The succession order of phytoplankton in the first year of the initial impoundment periodwas Chlorophyta-Bacillariophyta-Chlorophyta,or J/F/X1-P/MP/W1-A/X1/MP,respectively.And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta,or L_(M)/G/P-P/A/X1-X1/J/G.Water temperature,relativewater column stability,mixing depth,and pHwere crucial factors affecting phytoplankton community succession.This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs. 展开更多
关键词 Canyon-shaped reservoir Functional groups Initial impoundment Interannual succession Water quality
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Dynamics of a Stochastic Epidemic Model with Age-group
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作者 LAN Xiaomin CHEN Guangmin +5 位作者 ZHOU Ruiyang ZHENG Kuicheng CAI Shaojian WEI Fengying JIN Zhen MAO Xuerong 《应用数学》 北大核心 2025年第1期294-307,共14页
A stochastic epidemic model with two age groups is established in this study,in which the susceptible(S),the exposed(E),the infected(I),the hospitalized(H)and the recovered(R)are involved within the total population,t... A stochastic epidemic model with two age groups is established in this study,in which the susceptible(S),the exposed(E),the infected(I),the hospitalized(H)and the recovered(R)are involved within the total population,the aging rates between two age groups are set to be constant.The existence-and-uniqueness of global positive solution is firstly showed.Then,by constructing several appropriate Lyapunov functions and using the high-dimensional Itô’s formula,the sufficient conditions for the stochastic extinction and stochastic persistence of the exposed individuals and the infected individuals are obtained.The stochastic extinction indicator and the stochastic persistence indicator are less-valued expressions compared with the basic reproduction number.Meanwhile,the main results of this study are modified into multi-age groups.Furthermore,by using the surveillance data for Fujian Provincial Center for Disease Control and Prevention,Fuzhou COVID-19 epidemic is chosen to carry out the numerical simulations,which show that the age group of the population plays the vital role when studying infectious diseases. 展开更多
关键词 Epidemic model Age groups PERSISTENCE EXTINCTION
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On Markov and Zariski Embeddings in a Free Group
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作者 Victor Hugo Yanez Dmitri Shakhmatov 《南开大学学报(自然科学版)》 北大核心 2025年第1期18-21,共4页
Let G be a group.The family of all sets which are closed in every Hausdorf group topology of G form the family of closed sets of a T_(1) topology M_(G) on G called the Markov topology.Similarly,the family of all algeb... Let G be a group.The family of all sets which are closed in every Hausdorf group topology of G form the family of closed sets of a T_(1) topology M_(G) on G called the Markov topology.Similarly,the family of all algebraic subsets of G forms a family of closed sets for another T_(1)topology Z_(G) on G called the Zarski topology.A subgroup H of G is said to be Markov(resp.Zarski)embedded if the equality M_(G|H)=M_(H)(resp.Z_(G|H)=Z_(H))holds.I's proved that an abirary subgroup of a free group is both Zariski and Markov embedded in it. 展开更多
关键词 free group Zariski topology Markov embedding centralizer in a free group
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Application of Functional Group Migration Strategies in Photodriven Difunctionalization of Unsaturated Hydrocarbons
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作者 He Chonglong Zhou Youkang +1 位作者 Duan Xinhua Liu Le 《有机化学》 北大核心 2025年第5期1478-1508,共31页
Difunctionalization of unsaturated hydrocarbons is a pivotal synthetic strategy enabling the conversion of alkenes and alkynes into high value-added compounds.It allows for the introduction of two functional groups in... Difunctionalization of unsaturated hydrocarbons is a pivotal synthetic strategy enabling the conversion of alkenes and alkynes into high value-added compounds.It allows for the introduction of two functional groups into the unsaturated bond in a single step,facilitating the efficient construction of complex molecular architectures,which has been widely utilized in material chemistry,pharmaceutical and fine chemical synthesis.Recently,significant progress has been made via free radical-mediated difunctionalization due to the extensive application of photocatalysis.However,highly selective difunc-tionalization reactions still remain challenging.The research progress of selective difunctionalization of unsaturated hydro-carbons using a free radical addition/functional group migration strategy over the past decade is summarized,and synthetic strategies and key reaction steps are systematically elaborated. 展开更多
关键词 visible-light-driven unsaturated hydrocarbon functional group migration difunctionalization
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PBW-bases of split affineı-quantum groups
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作者 LU Ming YANG Rui-Qi 《四川大学学报(自然科学版)》 北大核心 2025年第5期1085-1094,共10页
ı-quantum groups,arising from quantum symmetric pairs,are coideal subalgebras of quantum groups.ı-quantum groups are a vast generalization of quantum groups,as quantum groups can be viewed asıquantum groups of diagona... ı-quantum groups,arising from quantum symmetric pairs,are coideal subalgebras of quantum groups.ı-quantum groups are a vast generalization of quantum groups,as quantum groups can be viewed asıquantum groups of diagonal type.Recently,the braid group symmetries and Drinfeld new presentations of quantum groups have been generalized to affineı-quantum groups.In this paper,we construct PBW type bases for splitı-quantum groups of type ADE,based on their braid group symmetries and Drinfeld new presentations.This can be viewed as anı-analogue of the PBW-basis for affine quantum groups,and it generalizes the PBW-basis ofı-quantum groups of finite type. 展开更多
关键词 Quantum group Quantum symmetric pair PBW-base
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Medical Diagnosis Based on Multi-Attribute Group Decision-Making Using Extension Fuzzy Sets,Aggregation Operators and Basic Uncertainty Information Granule
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作者 Anastasios Dounis Ioannis Palaiothodoros Anna Panagiotou 《Computer Modeling in Engineering & Sciences》 SCIE EI 2025年第1期759-811,共53页
Accurate medical diagnosis,which involves identifying diseases based on patient symptoms,is often hindered by uncertainties in data interpretation and retrieval.Advanced fuzzy set theories have emerged as effective to... Accurate medical diagnosis,which involves identifying diseases based on patient symptoms,is often hindered by uncertainties in data interpretation and retrieval.Advanced fuzzy set theories have emerged as effective tools to address these challenges.In this paper,new mathematical approaches for handling uncertainty in medical diagnosis are introduced using q-rung orthopair fuzzy sets(q-ROFS)and interval-valued q-rung orthopair fuzzy sets(IVq-ROFS).Three aggregation operators are proposed in our methodologies:the q-ROF weighted averaging(q-ROFWA),the q-ROF weighted geometric(q-ROFWG),and the q-ROF weighted neutrality averaging(qROFWNA),which enhance decision-making under uncertainty.These operators are paired with ranking methods such as the similarity measure,score function,and inverse score function to improve the accuracy of disease identification.Additionally,the impact of varying q-rung values is explored through a sensitivity analysis,extending the analysis beyond the typical maximum value of 3.The Basic Uncertain Information(BUI)method is employed to simulate expert opinions,and aggregation operators are used to combine these opinions in a group decisionmaking context.Our results provide a comprehensive comparison of methodologies,highlighting their strengths and limitations in diagnosing diseases based on uncertain patient data. 展开更多
关键词 Medical diagnosis multi-attribute group decision-making(MAGDM) q-ROFS IVq-ROFS BUI aggregation operators similarity measures inverse score function
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Synthesis and Properties of Novel A-D-A Type Molecules with Non-Fused Azacyclic End Groups
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作者 Liu Wenrui Yin Zhengchun +3 位作者 Ye Shiqi Xu Zhiwei Chen Long Wang Guanwu 《有机化学》 北大核心 2025年第4期1325-1333,共9页
Acceptor-donor-acceptor(A-D-A)type molecules,of which the novel non-fused azacyclic end-group pyrazoli-nones were modified with chlorine substitution on the phenyl ring,were synthesized.The non-fused azacyclic end-gro... Acceptor-donor-acceptor(A-D-A)type molecules,of which the novel non-fused azacyclic end-group pyrazoli-nones were modified with chlorine substitution on the phenyl ring,were synthesized.The non-fused azacyclic end-group py-razolinones have the advantages of simple synthesis steps,low cost and environmental friendliness,compared to the classical end-group dicyanomethyleneindianone.The properties of the synthesized A-D-A type molecules with non-fused azacyclic end groups were characterized by theoretical calculation,UV-vis absorption,cyclic voltammetry,X-ray diffraction and space charge limited current.It is shown that the strong UV-vis absorptions of the synthesized A-D-A type molecules are located in the wavelength range of 500~700 nm,with a moderate band gap of nearly 1.7 eV.At the same time,the influence of end-group chlorination on the properties of A-D-A type molecules was compared and explored.It is proven that this kind of A-D-A type molecule with non-fused azacyclic end groups has the potential to be applied as interfacial modified layer of the active layer in perovskite solar cell devices. 展开更多
关键词 A-D-A type molecule n-type semiconductor Non-fused end groups Medium bandgap
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Fundamental Study of Rare-earth-containing Catalytic Reduction Systems for End-group Functionalization of Telechelic Low-molecular-weight Fluoropolymers
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作者 LI Donghan NING Shurui +4 位作者 YU Lu LIAO Mingyi ZHANG Mengxia YOU Shibo FANG Qinghong 《材料导报》 北大核心 2025年第3期254-262,共9页
Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity a... Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials. 展开更多
关键词 rare-earth chloride chain-end hydroxyl group telechelic low-molecular-weight fluoropolymers sodium borohydride
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Grothendieck Groups of Finite 2-Calabi-Yau Triangulated Categories with Maximal Rigid Objects
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作者 CHANG Huimin 《数学进展》 北大核心 2025年第3期479-488,共10页
In this work,we compute the Grothendieck groups of finite 2-Calabi-Yau triangulated categories with maximal rigid objects which are not cluster tilting.These finite 2-Calabi-Yau triangulated categories are divided int... In this work,we compute the Grothendieck groups of finite 2-Calabi-Yau triangulated categories with maximal rigid objects which are not cluster tilting.These finite 2-Calabi-Yau triangulated categories are divided into,by the work of Amiot[Bull.Soc.Math.France,2007,135(3):435-474](see also[Adv.Math.,2008,217(6):2443-2484]and[J.Algebra,2016,446:426-449]),three classes:type A,type D and type E. 展开更多
关键词 finite 2-Calabi-Yau triangulated category Grothendieck group Dynkin quiver
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On σ-c-propermutable Subgroups of Finite Groups
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作者 MA Xiaojian MAO Yuemei 《数学进展》 北大核心 2025年第3期509-517,共9页
Let G be a finite group.A subgroup H of G is said to be σ-c-propermutable in G if G has a subgroup B such that G=N_(G)(H)B and for every Hall σ_(i)-subgroup B_(i) of B,there exists an element x∈B such that HB_(i)^(... Let G be a finite group.A subgroup H of G is said to be σ-c-propermutable in G if G has a subgroup B such that G=N_(G)(H)B and for every Hall σ_(i)-subgroup B_(i) of B,there exists an element x∈B such that HB_(i)^(x)=B_(i)^(x) H.In this paper,the influence of σ-c-propermutable subgroups on the structure of finite groups is investigated,and some criteria for a normal subgroup of G to be hypercyclically embedded in G are derived. 展开更多
关键词 complete Hallσ-set σ-c-propermutable subgroup supersoluble group hypercyclically embedded
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Double Grouping-Based Group Handover Scheme for Mega LEO Satellite Networks
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作者 Zhu Hongtao Wang Zhenyong +2 位作者 Li Dezhi Yang Mingchuan Guo Qing 《China Communications》 2025年第2期77-94,共18页
The rapid development of mega low earth orbit(LEO)satellite networks is expected to have a significant impact on 6G networks.Unlike terrestrial networks,due to the high-speed movement of satellites,users will frequent... The rapid development of mega low earth orbit(LEO)satellite networks is expected to have a significant impact on 6G networks.Unlike terrestrial networks,due to the high-speed movement of satellites,users will frequently hand over between satellites even if their positions remain unchanged.Furthermore,the extensive coverage characteristic of satellites leads to massive users executing handovers simultaneously.To address these challenges,we propose a novel double grouping-based group handover scheme(DGGH)specifically tailored for mega LEO satellite networks.First,we develop a user grouping strategy based on beam-limited hierarchical clustering to divide users into distinct groups.Next,we reframe the challenge of managing multiple users’simultaneous handovers as a single-objective optimization problem,solving it with a satellite grouping strategy that leverages the accuracy of greedy algorithms and the simplicity of dynamic programming.Additionally,we develop a group handover algorithm based on minimal handover waiting time to improve the satellite grouping process further.The detailed steps of the DGGH scheme’s handover procedure are meticulously outlined.Comprehensive simulations show that the proposed DGGH scheme outperforms single-user handover schemes in terms of handover signaling over-head and handover success rate. 展开更多
关键词 DGGH group handover mega LEO satellite networks satellite grouping user grouping
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COVID-19 Vaccine Distribution Patterns for Prioritized Age Group: Analysis of European Nations
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作者 Ogbonnaya Ezichi Victor Okpanachi +7 位作者 Joy Jibunoh Wuraola Awosan Prosper Tchoumo Anthony Akande Chibuzor Amaechi Jubril Sanusi Funmilayo Ogunsanwo Rofiat Adesina 《Open Journal of Epidemiology》 2025年第1期1-18,共18页
The emergence of the SARS-CoV-2 virus resulted in a health and economic crisis worldwide. Although everyone is susceptible to COVID-19, the elderly have compromised immune systems and often suffer from chronic underly... The emergence of the SARS-CoV-2 virus resulted in a health and economic crisis worldwide. Although everyone is susceptible to COVID-19, the elderly have compromised immune systems and often suffer from chronic underlying diseases, which makes them more vulnerable. This study aims to assess variation in COVID-19 vaccine distribution patterns across different age groups in European countries and to understand the extent to which European countries have prioritized vulnerable age groups (age > 70) in their vaccination programs. The study utilized open data from the European Center for Disease Prevention and Control (ECDC) and employed an observational, retrospective study design to examine the distribution of the COVID-19 vaccine among various age groups in several European countries from September 2021 to September 2023. Results reveal that vaccination rates increase with age, peaking at the 25 - 49 age group (1.34 × 10−4), after which there was a decline in vaccination rate. Analysis of variance (ANOVA) was used to investigate the equality of vaccination rates across the 29 countries in Europe, which resulted in a p-value of 70) during the study period as no country achieved the 70% coverage aimed by WHO. Continuous efforts must be made to ensure larger coverage of COVID-19 vaccination among this vulnerable population in order to protect them from severe outcomes in this region. 展开更多
关键词 SARS-CoV-2 COVID-19 Vaccines Prioritized Age group European Nations
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