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The character of Thurston's circle packings

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Science China Mathematics 2024年第7期67卷 1623-1640页

作者： Huabin ge Aijin lin School of Mathematics Renmin University of ChinaBeijing100872China Department of Mathematics National University of Defense TechnologyChangsha410073China

We introduce the character of Thurston's circle packings in the hyperbolic background geometry.Consequently, some quite simple criteria are obtained for the existence of hyperbolic circle packings. For example,if a closed surface X admits a circle packing with all the vertex degrees d_(i)≥7, then it admits a unique complete hyperbolic metric so that the triangulation graph of the circle packing is isotopic to a geometric decomposition of X. This criterion is sharp due to the fact that any closed hyperbolic surface admits no triangulations with all d_(i)≤6. As a corollary, we obtain a new proof of the uniformization theorem for closed surfaces with genus g≥2;moreover, any hyperbolic closed surface has a geometric decomposition. To obtain our results, we use Chow-Luo's combinatorial Ricci flow as a fundamental tool.

关键词： character circle packings combinatorial Ricci flow

Visualization of MF/Diesel RCCI Combustion Process and Soot Emission

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Journal of Thermal Science 2024年第2期33卷 779-792页

作者： HUANG Chen ni Xiao ge Dameng LI Song ZHANG Wanzhi LIU Jinping ZHANG Tingting School of Mechanical and Electronic Engineering Shandong Agricultural UniversityTaian271018China Shandong Provincial Engineering Laboratory of Agricultural Equipment Intelligence Taian271018China Taian Technician Institute Taian271000China Sinotruk Taian Wuyue Special Vehicle Co. Ltd.Taian271000China School of Mechanical Engineering Shaanxi University of TechnologyHanzhong723001China School of Mechanical Engineering Anyang Institute of TechnologyAnyang455000China

Based on the optical engine,the ignition characteristics,combustion process and soot emission characteristics of diesel under different 2-Methylfuran(MF) atmospheres were investigated by high-speed photography and in-cylinder combustion analysis technology.The results show that at the same main injection timing,the ignition time of reactivity controlled compression ignition(RCCI) combustion mode is earlier than pure diesel combustion,and the ignition point is concentrated near the nozzle.Diesel acts as a spark plug to ignite the mixture,but the flame develops slowly in the early stages and the pressure in the cylinder rises slowly.Compared with pure diesel,RCCI combustion model has smaller peak values of in-cylinder pressure and heat release rate,shorter ignition delay period,earlier combustion phase and shorter combustion duration.At main spray time at 6℃A BTDC and 12℃A BTDC,with the increase of MF premixing ratio from 0 to 0.75,the peak cylinder pressure decreased by 19.6% and 26% respectively.In addition,with the increase of the MF heat value ratio,the area of KL factor> 1.5 in the combustion chamber decreased and the space integral natural luminescence(SINL) peak value decreased by 48.37%,and the soot formation rate and yield decreased significantly.However,when the MF heat value ratio was too large(75% of the total calorific value),the ignition delay period increased,and misfire occurred at the main injection timing of 0℃A BTDC.The RCCI mode of MF/diesel dual fuel has better stability,and better control effect can be obtained at different main inj ection timing.

关键词： 2-methylfuran RCCI visualization two-color method KL factor

MOF-derived porous graphitic carbon with optimized plateau capacity and rate capability for high performance lithium-ion capacitors

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International Journal of Minerals,Metallurgy and Materials 2024年第2期31卷 395-404页

作者： ge Chu Chaohui Wang Zhewei Yang lin Qin Xin Fan College of Materials Science&Engineering Guilin University of TechnologyGuilin 541004China Institute of Energy Innovation College of Materials Science and EngineeringTaiyuan University of TechnologyTaiyuan 030024China

The development of anode materials with high rate capability and long charge-discharge plateau is the key to improve per-formance of lithium-ion capacitors(LICs).Herein,the porous graphitic carbon(PGC-1300)derived from a new triply interpenetrated co-balt metal-organic framework(Co-MOF)was prepared through the facile and robust carbonization at 1300°C and washing by HCl solu-tion.The as-prepared PGC-1300 featured an optimized graphitization degree and porous framework,which not only contributes to high plateau capacity(105.0 mAh·g^(−1)below 0.2 V at 0.05 A·g^(−1)),but also supplies more convenient pathways for ions and increases the rate capability(128.5 mAh·g^(−1)at 3.2 A·g^(−1)).According to the kinetics analyses,it can be found that diffusion regulated surface induced capa-citive process and Li-ions intercalation process are coexisted for lithium-ion storage.Additionally,LIC PGC-1300//AC constructed with pre-lithiated PGC-1300 anode and activated carbon(AC)cathode exhibited an increased energy density of 102.8 Wh·kg^(−1),a power dens-ity of 6017.1 W·kg^(−1),together with the excellent cyclic stability(91.6%retention after 10000 cycles at 1.0 A·g^(−1)).

关键词： metal-organic framework porous graphitic carbon optimized plateau capacity kinetic analysis lithium-ion capacitor

Chemoselective electrochemical seleno-cyclization of dienes to medium-sized benzo[b]azocines

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Chinese Chemical Letters 2024年第2期35卷 431-435页

作者： Zhichuan Wang Xin Wang Quanxin Li Shaofei ni Dongyang Zhao Shubin Yang ge Qiu Kai Sun College of Chemistry and Chemical Engineering Yantai UniversityYantai 264005China Department of Chemistry and Key Laboratory for Preparation and Application of Ordered Structural Materials of Guangdong Province Shantou UniversityShantou 515063China Aix Marseille Univ. CNRSCentrale MarseilleiSm2MarseilleFrance

The preparation of medium-sized benzo[b]azocines has always been challenging because of inherently unfavorable enthalpy and entropy factors.This report presents a novel approach for accessing 8-membered seleno-benzo[b]azocines via electrochemically-driven seleno-cyclization.This method enables room-temperature preparation of various structurally diverse medium-sized seleno-benzo[b]azocines.The facile deselenation of the seleno-cyclization products to generate functionalized dienes is an additional benefit of this indispensable reaction.Mechanistic insights are presented based on radical inhibition experiments and cyclic voltammetry measurements,which elucidate the radical pathway.Finally,density functional theory calculations further rationalize the rate-determining step and the unique chemoselectivity observed in this transformation.

关键词： Medium-sized n-heterocycles Electrocatalysis Radical Mechanistic insights Selenylation

Tetraphenylethene-based hole transporting material for highly efficient and stable perovskite solar cells

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Science China Chemistry 2024年第6期67卷 2009-2015页

作者： Peng Wang Pei Yuan Chenghao ge Rongjun Zhao lin Xie Yong Hua School of Materials and Energy Yunnan UniversityKunming650091China

2,2,7,7-Tetrakis-(N,N-di-p-methoxyphenylamine)-9,9-spirobifluorene(Spiro-OMeTAD)has been identified as the most widely used and effective hole transporting material(HTM)in perovskite solar cells(PSCs).However,the complicated multistep synthesis and low intrinsic hole mobility of Spiro-OMe TAD limit its commercialized application.Therefore,developing highly efficient HTMs with less synthetic steps becomes increasingly important.Moreover,understanding hot carriers transfer dynamics at the interface of perovskite layer and hole transport layer is crucial for further enhancing PSCs performance towards Shockley-Queisser limit,which still lacks full investigation to date.Herein,a new HTM based on tetraphenylethene(WP1)was successfully synthesized by a simple one-step reaction process.It was found that WP1-based HTM exhibits more matched energy level,higher hole mobility and conductivity than those of the control Spiro-OMe TAD.The femtosecond transient absorption results reveal that the transfer rate of hot holes in perovskite/WP1 sample is four times higher than that of perovskite/Spiro-OMeTAD,thereby helping enhance the device performance.Consequently,the efficiency of PSCs is enhanced to 24.04%(WP1)from 22.85%(Spiro-OMeTAD).Moreover,the un-encapsulated device prepared with WP1 exhibits better long-term stability,retaining 87%of its initial PCE value after storing for 72 days under air environment,while the reference device shows76%of its initial value.This work indicates that simple tetraphenylethene-based organic small molecule could be a very promising HTM candidate for highly efficient PSCs,and gives some significant insights for understanding intrinsic hot carriers transfer dynamics in device.

关键词： tetraphenylethene hole transporting material perovskite solar cells mobility hot carrier

Atomic-level unveiling secondary recrystallization enabled microand macroscopic polarization enhancement for piezophotocatalytic oxygen activation

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Nano Research 2024年第6期17卷 5040-5049页

作者： Kai lin Zijian Zhu Weiyi ge Tianxing Jiang Hongwei Huang Engineering Research Center of Ministry of Education for geological Carbon Storage and Low Carbon Utilization of Resources Beijing Key Laboratory of Materials Utilization of Nonmetallic Minerals and Solid WastesNational Laboratory of Mineral MaterialsSchool of Material Sciences and TechnologyChina University of Geosciences(Beijing)Beijing 100083China School of Chemistry Beihang UniversityBeijing 100191China

Piezoelectric semiconductors bear the bifunctional photocatalysis and piezocatalysis,while the absent or weak internal charge driving force severely restricts its catalytic activity.Developing polarization strategy is desirable,and particularly understanding its mechanism from a microscopic perspective remains scanty.Herein,we report a secondary recrystallization approach to achieving the simultaneous micro-and macroscopic polarization enhancement on Bi2WO6 nanosheets for boosting piezo-photocatalytic oxygen activation,and unravel the mechanism at an atom-level.The secondary recrystallization process not only results in a strengthened distortion of[WO6]octahedra with distortion index enhancement by~20%for a single octahedron,but also enables lateral crystal growth of nanosheets along the ab plane(av.50 to 180 nm),which separately allows the rise in dipole moment of unit cell(e.g.,1.63 D increase along a axis)and the stacking of the distorted[WO6]octahedron to accumulate the unit cell dipole,collectively contributing to the considerably strengthened spontaneous polarization and piezoelectricity.Besides,exposure of large-area{001}front facet enables more efficient capture and conversion of stress into piezo-potential.Therefore,the well-recrystallized Bi2WO6 nanosheets exhibit considerably promoted piezo-photocatalytic reactive oxygen species generation,given the decreased specific surface area.This work presents a feasible methodology to regulate inside-out polarization for guiding carriers transfer behavior,and may advance the solid understanding on the intrinsic mechanism.

关键词： secondary recrystallization piezo-photocatalytic oxygen activation octahedron distortion polar units stacking micro-and macroscopic polarization enhancement

Facile access to C-N bonds via unexpected side reactions of Knoevenagel condensation and their application in high-efficiency organic solar cells

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Science China Chemistry 2024年第1期67卷 323-329页

作者： Daobin Yang Shuncheng Yang Hongqian Wang lin Xie Pengyu Yan Ziyi ge Zhejiang Engineering Research Center for Energy Optoelectronic Materials and Devices Ningbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China School of Materials Science and Chemical Engineering Ningbo UniversityNingbo 315211China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

The construction of C-N bonds is of great importance in the fields of biology,medicine,chemistry and materials science.Here,the replacement of organic base from pyridine to piperidine in the Knoevenagel condensation process unexpectedly yields a series of novel organic molecules containing C-N bonds.Interestingly,the synthesis method does not require any external transition-metals catalysis,and photo-/electro-catalysis.Additionally,when the new compound 1b is added as a third component to a well-known binary system of PM6:Y6,the efficiency of the organic solar cell is significantly improved,resulting in an outstanding efficiency of 18.0%,which is one of the highest values reported to date for PM6:Y6-based ternary organic solar cells.

关键词： C-N bonds Knoevenagel condensation cross-coupling reaction third component organic solar cells

Exploring the correlation between temperature and crime:A case-crossover study of eight cities in America

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Journal of Safety Science and Resilience 2024年第1期5卷 13-36页

作者： Jinming Hu Xiaofeng Hu Xin’ge Han Yan lin Huanggang Wu Bing Shen School of Information Technology and Cyber Security People’s Public Security University of ChinaBeijing 100038China Center for Capital Social Safety People’s Public Security University of ChinaBeijing 100038China China Association for Public Safety Beijing 100084China School of Emergency Management and Safety Engineering China University of Mining and TechnologyBeijing 100083China School of International Police Studies People’s Public Security University of ChinaBeijing 100038China

Recent years have seen increasing academic interest in exploring the correlation between temperature and crime.However,it is uncertain whether similar long-term trends or seasonality(rather than causal effect)of temper-ature and crime is the major reason for the observed correlation between them.To explore whether there is still a correlation between temperature and crime when long-term trends and seasonal cycles are filtered out,we use the Kalman filter to decompose the time series of temperature and crimes,and then the fast Fourier transform is used to calculate the exact circle of their seasonality separately.Based on that,the box-plot method and linear regression are used to explore the correlation between temperature residuals and crime residuals.The results show that more than half of the crime types have similar seasonal cycles(approximately 1 year)to that of temperature.Moreover,the daily residual analyses show that temperature residuals have a positive correlation with assault and robbery residuals in all cities,whose average slopes are more than 0.1.The other four types of crimes vary greatly from case to case.The temperature residuals show a weak correlation with the residuals of some crime types.

关键词： Time series decomposition Crime Temperature Kalman filter Fast fourier transform

Lanthanum promoting bone formation by regulating osteogenesis,osteoclastogenesis and angiogenesis

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Journal of Rare Earths 2024年第3期42卷 621-628,I0007页

作者： Dandan Zou Runlian lin Yu Han Juan Jia Guoqiang Zhou Haisong Zhang Kun ge Hebei Key Laboratory of Chronic Kidney Diseases and Bone Metabolism Affiliated Hospital of Hebei UniversityBaoding071000China Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of the Ministry of Education Key Laboratory of Chemical Biology of Hebei ProvinceCollege of Chemistry and Environmental ScienceHebei UniversityBaoding071002China

With lanthanum(La) in agriculture, medicine, and the chemical industry, La shows accumulation in the body, especially in the bone, because of its similar structure to calcium. Moreover, La has a direct role in bone formation regulating osteoblasts and osteoclasts. Nevertheless, bone formation is complex under the regulation of osteogenesis, osteoclastogenesis, and angiogenesis in the bone microenvironment. It is difficult to comprehensively understand the regulation of bone homeostasis from a single kind of cell.Herein, some bone microenvironment-related cells and mouse calvaria culture models were used to study the regulatory effect of La-based compound-lanthanum nitrate(La(NO_(3))_(3)) on bone formation.La(NO_(3))_(3) has good biological safety, and the osteogenic differentiation is significantly increased under La(NO_(3))_(3) treatment for bone marrow mesenchymal stem cells(BMMSC). In contrast, the differentiation,maturation, and bone erosion ability of osteoclasts are significantly decreased. Meanwhile, the angiogenesis ability of human umbilical vein endothelial cells(HUVEC) is significantly promoted when treated with La(NO_(3))_(3). Furthermore, bone metabolism and angiogenesis are improved under La(NO_(3))_(3) treatment in the calvaria ex vivo culture model and BMMSC-HUVEC co-culture system. These results suggest that La has the beneficial effect of promoting bone metabolism and improving bone formation in the bone microenvironment.

关键词： Lanthanum Bone microenvironment Osteogenic differentiation Angiogenesis Rare earths