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Study on Melting and Recrystallization of Poly(butylene succinate) Lamellar crystals via Step Heating Differential Scanning calorimetry

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chinese Journal of Polymer Science 2017年第12期35卷 1552-1560页

作者： Zhi-yu Lv michael c.zhang Yang zhang Bao-hua Guo 徐军 Key Laboratory of Advanced Materials (Ministry of Education) Department of Chemical Engineering Tsinghua University

Differential scanning calorimetry（DSc） has been widely applied to study crystallization and melting of materials. However, for polymeric lamellar crystals, the melting thermogram during heating process usually exhibits a broad endothermic peak or even multiple endotherms, which may result from changes of metastability via recrystallization process. Sometimes, the recrystallization exotherm cannot be observed due to its overlapping with the melting endotherm. In this work, we employed a step heating procedure consisting of successive heating and temperature holding stages to measure the metastability of isothermally crystallized poly（butylene succinate）（PBS） crystals. With this approach we could gain the fraction of crystals melted at different temperature ranges and quantitatively detect the melting-recrystallization behavior. The melting-recrystallization behavior depends on the polymer chain structure and the crystallization temperature. For instance, PBS block copolymer hardly shows recrystallization behavior while PBS oligomer and high molecular weight PBS homopolymer demonstrate remarkable melting-recrystallization phenomenon. High molecular weight PBS isothermally crystallized in the low temperature range shows multiple melting-recrystallization while those isothermally crystallized at elevated temperatures do not exhibit observable recrystallization behavior. Furthermore, the melting endotherms were fitted via the melting kinetics equations. The original isothermally crystallized lamellae demonstrate quite different melting kinetics from the recrystallized lamellar crystals that melt at the highest temperature range, which is attributed to the different degrees of stabilization. Finally, the mechanism of melting-recrystallization is briefly discussed. We propose that apparent meltrecrystallization phenomenon be observed when melting of preformed lamellar crystals and recrystallization of thicker lamellae have similar free energy barrier.

关键词： DSc Step heating Poly(butylene succinate) Metastability Melting-recrystallization Melting kinetics

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A new method of calculating crown projection area and its comparative accuracy with conventional calculations for asymmetric tree crowns

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Journal of Forestry Research 2024年第4期35卷 171-188页

作者： Mingrui zhang Huiquan Bi Xingji Jin michael McLean School of Forestry Northeast Forestry UniversityHarbin 150040People’s Republic of China Forest Science NSW Department of Primary IndustriesLevel 304PSQ12 Darcy StreetParramattaNSW 2150Australia School of Ecosystem and Forest Sciences The University of MelbourneMelbourne 3010Australia

This paper introduces a new method of calculating crown projection area(cPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and *** novel method and other four existing methods of calculating cPA were compared using detailed crown radius measurements from 30 tall trees of Eucalyptus pilularis variable in crown size,shape,and *** four existing methods included the polygonal approach and three ways of calculating cPA as the area of a circle using the arithmetic,geometric and quadratic mean *** were made across a sequence of eight non-consecutive numbers(from 2 to 16)of measured crown radii for each tree over the range of crown asymmetry of the 30 trees through generalized linear models and multiple comparisons of *** sequence covered the range of the number of crown radii measured for calculating the cPA of a tree in the literature.A crown asymmetry index within the unit interval was calculated for each tree to serve as a normative *** a slight overestimation of 2.2%on average and an overall mean error size of 7.9%across the numbers of crown radii that were compared,our new method was the least biased and most *** cPA as a circle using the quadratic mean crown radius was the second best,which had an average overestimation of 4.5%and overall mean error size of 8.8%.These two methods remained by and large unbiased as crown asymmetry increased,while the other three methods showed larger bias of *** the conventional method of using the arithmetic mean crown radius to calculate cPA as a circle,bias correction factors were developed as a function of crown asymmetry index to delineate the increasing magnitude of bias associated with greater degrees of crown *** study reveals and demonstrates such relationships between the accuracy of cPA calculations and crown asymmetry and will help increase awa

关键词： crown radius measurements Interpolated crown contour Projected crown area Multiple comparisons of means

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Microscale shaping and rounding of ridge arrays and star pattern features on nickel mould via electrochemical polishing

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Advances in Manufacturing 2024年第2期12卷 207-226页

作者： Sana Zaki Nan zhang michael D.Gilchrist School of Mechanical and Materials Engineering University College DublinBelfieldDublin 4Ireland

High quality micro mould tools are critical for ensuring defect-free production of micro injection moulded *** demoulding stage of the micro injection moulding can adversely affect the surface integrity due to friction,adhesion and thermal stresses between the metallic mould and polymeric replicated *** the present work,we propose the use of precision electropolishing(EP)as a shaping and polishing process to control the draft angle and fillet radius of micro features in order to ease *** defects that occur in replicated polymer parts include cracks,burrs and distorted features.A nickel mould having multiple linear ridges and star shape patterns was designed for the present investigation to have characteristic dimensions ranging from 10μm to 150μm and with various aspect ratios to study the effect of electropolishing on modifying the shape of micro features and surface morphology.A transient 2D computational analysis has been conducted to anticipate the effect of shaping on the Ni mould after electrochemical polishing with non-uniform material removal rates,based on the distribution of current *** experimental results indicate that after shaping using EP,the draft angle of star-patterns and linear patterns can be effectively increased by approximately 3.6°,while the fillet radius increases by up to 5.0μ*** controlling the electropolishing process,the surface roughness can be maintained under 50 *** work uses a green and environmental friendly nickel sulfamate electrolyte which can be effective for shaping of nickel micro features without causing any surface deposition.

关键词： Micro feature shaping and electropolishing Micro mould tools Green electrolyte Demoulding micro patterns

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Emerging glacier forelands alter carbon dynamics on the Tibetan Plateau

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Journal of Mountain Science 2024年第9期21卷 2871-2875页

作者： GAO Tanguang zhang Yulan MEADOWS michael Edward college of Earth and Environmental Sciences Lanzhou UniversityLanzhou 730000China Key Laboratory of cryospheric Science and Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China School of Geography and Ocean Sciences Nanjing UniversityNanjing 210023China Department of Environmental&Geographical Science University of Cape TownRondebosch 7701South Africa

The critical challenge of ongoing climate warming is resulting in glacier melting globally,a process accompanied by the formation of substantial glacier *** phenomenon emerges as a pivotal area of study,especially in the Tibetan Plateau(TP),known as the Third Pole and the Asian Water *** particular,the rapid retreat of temperate glaciers in the southeastern TP has led to the formation of expansive glacier *** forelands are not merely evidence of climate shifts but are also key areas for transformative carbon ***,the newly exposed land surface actively adjusts the balance of dissolved organic carbon,especially in meltwater,and influences the release of greenhouse gases from a range of sources including glacial lakes,subglacial sediments,and supraglacial/proglacial *** processes play a crucial role in the dynamics of atmospheric carbon *** from our intensive and detailed observations over several years,this perspective not only emphasizes the importance of the underexplored impact of glacier forelands on carbon cycles but also opens a window into understanding potential future trajectories in a warming world.

关键词： Glacier climate warming carbon release Tibetan Plateau

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Spark plasma sintering of tungsten-based WTaVcr refractory high entropy alloys for nuclear fusion applications

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 146-154页

作者： Yongchul Yoo Xiang zhang Fei Wang Xin chen Xing-Zhong Li michael Nastasi Bai cui Department of Mechanical&Materials Engineering University of Nebraska-LincolnLincolnNE 68588USA Nebraska center for Materials and Nanoscience University of Nebraska-LincolnLincolnNE 68588USA Department of Nuclear Engineering Texas A&M UniversityCollege StationTX 77843USA

W-based WTaVcr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6through a combined analysis of X-ray diffraction (XRD),energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2μm. WTaVcr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro-and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°c.

关键词： refractory high entropy alloy plasma-facing material fusion reactor spark plasma sintering

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Masting promotes transformation from predation to mutualism in an oak-weevil-rodent system

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Science china(Life Sciences) 2024年第7期67卷 1514-1524页

作者： Hongmao zhang Hongyu Niu michael ASteele Liqing Peng Huimin He Aoqiang Li Xianfeng Yi Hongjun Li Zhibin zhang Institute of Evolution and Ecology School of Life SciencesCentral China Normal UniversityWuhan 430079China State Key Laboratory of Integrated Management of Pest Insects and Rodents in Agriculture Institute of ZoologyChinese Academy of SciencesBeijing 100101China Department of Biology Wilkes UniversityWilkes-Barre 18766USA School of Life Sciences Qufu Normal UniversityQufu 273165China

The significance of ecological non-monotonicity(a function whose first derivative changes signs)in shaping the structure and functions of the ecosystem has recently been recognized,but such studies involving high-order interactions are ***,we have proposed a threetrophic conceptual diagram on interactions among trees,rodents,and insects in mast and non-mast years and tested the hypothesis that oak(Quercus wutaishanica)masting could result in increased mutualism and less predation in an oak-weevil-rodent system in a warm temperate forest of *** 14-year dataset revealed that mast years coincided with a relatively low rodent abundance but a high weevil *** not only benefited seedling recruitment of oaks through increased dispersal by rodents but also a decrease in predation by rodents and weevils,as well as an increase in the overwintering survival of *** appeared to have increased weevil survival by reducing predation of infested acorns by *** results suggest that masting benefits all participants in the plant-insect-rodent system by increasing mutualism and reducing predation behavior(i.e.,a non-monotonic function).Our study highlights the significance of masting in maintaining the diversity and function of the forest ecosystem by facilitating the transformation from predation to mutualism among trophic species.

关键词： antagonism ecological non-monotonicity mutualism seed-weevil-rodent system seedling recruitment rodent overwintering survival weevil survival

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A three-dimensional feature extraction-based method for coal cleat characterization using X-ray μcT and its application to a Bowen Basin coal specimen

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第1期16卷 153-166页

作者： Yulai zhang Matthew Tsang Mark Knackstedt michael Turner Shane Latham Euan Macaulay Rhys Pitchers ARc Training centre for M3D Innovation Research School of PhysicsAustralian National UniversityCanberraACT2601Australia Department of Materials Physics Research School of PhysicsAustralian National UniversityCanberraACT2601Australia Anglo American Steelmaking coal BrisbaneQLD4000Australia ScT Operations Pty Ltd. WollongongNSW2500Australia

cleats are the dominant micro-fracture network controlling the macro-mechanical behavior of *** understanding of the spatial characteristics of cleat networks is therefore important to the coal mining *** fracture networks(DFNs)are increasingly used in engineering analyses to spatially model fractures at various *** reliability of coal DFNs largely depends on the confidence in the input cleat *** of these parameters can be made from image-based three-dimensional(3D)characterization of coal cleats using X-ray micro-computed tomography(m cT).One key step in this process,after cleat extraction,is the separation of individual cleats,without which the cleats are a connected network and statistics for different cleat sets cannot be *** this paper,a feature extraction-based image processing method is introduced to identify and separate distinct cleat groups from 3D X-ray m cT ***(filters)representing explicit cleat features of coal are built and cleat separation is successfully achieved by convolutional operations on 3D coal *** new method is applied to a coal specimen with 80 mm in diameter and 100 mm in length acquired from an Anglo American Steelmaking coal mine in the Bowen Basin,Queensland,*** is demonstrated that the new method produces reliable cleat separation capable of defining individual cleats and preserving 3D topology after ***-parallel fractures are also identified and separated,which has his-torically been challenging to delineate and rarely reported.A variety of cleat/fracture statistics is measured which not only can quantitatively characterize the cleat/fracture system but also can be used for DFN ***,variability and heterogeneity with respect to the core axis are *** heterogeneity is observed and suggests that the representative elementary volume(REV)of the cleat groups for engineering purposes may be a complex problem requ

关键词： cleat separation cleat statistics Feature extraction Discrete fracture network(DFN)modeling

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carbon coated LaFe_(0.92)Pd_(0.08)O_(3) composites for catalytic transfer hydrogenation:Balance in the ability of substrates adsorption and conversion

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Nano Research 2024年第5期17卷 3724-3732页

作者： Bowen Wang Nan zhang Ping Xiao Jian zhang Sónia A.c.carabineiro Junjiang Zhu Hubei Key Laboratory of Biomass Fibers and Eco-dyeing&Finishing College of Chemistry and Chemical EngineeringWuhan Textile UniversityWuhan 430200China college of chemistry and Materials Engineering Wenzhou UniversityWenzhou 325035China LAQV-REQUIMTE Department of ChemistryNOVA School of Science and TechnologyUniversidade NOVA de LisboaLargo da Torre2829-516 CaparicaPortugal

catalytic transfer hydrogenation(cTH)is a green and efficient pathway for selective hydrogenation of unsaturated aldehydes and ***,managing the abilities of solid catalysts to adsorb substrates and to convert them into desired products is a challenging ***,we report the synthesis of carbon coated LaFe_(0.92)Pd_(0.08)O_(3) composites(LFPO-8@c)for cTH of benzaldehyde(BzH)into benzyl alcohol(BzOH),using isopropanol(IPA)as hydrogen *** coating with carbon improves the ability to adsorb/transfer reactants from solution to active sites,and the doping of Pd2+at Fe3+site strengthens the ability of LaFeO_(3) to convert BzH into BzOH.A balanced point between them(i.e.,abilities to adsorb BzH and to convert BzH into BzOH)is obtained at LFPO-8@c,which exhibits a BzOH formation rate of 3.88 mmol·gcat^(-1)·h^(-1) at 180℃ for 3 h,which is 1.50 and 2.72 times faster than those of LFPO-8 and LaFeO_(3)@c.A reaction mechanism is proposed,in which the acidic sites(e.g.,Fe^(4+),oxygen vacancy)are used for the activation of c=O bond of BzH and O-H bond of IPA,and the basic sites(e.g.,lattice oxygen)for the activation ofα-H(O-H)bond of IPA.

关键词： LaFe_(0.92)Pd_(0.08)O_(3) porous carbon catalytic transfer hydrogenation isopropanol reaction mechanism

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Effect of various aromatic compounds with different functional groups on enzymatic hydrolysis of microcrystalline cellulose and alkaline pretreated wheat straw

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Journal of Bioresources and Bioproducts 2024年第2期9卷 211-221页

作者： Yufeng Yuan Xinyu Guo Bo Jiang Wenjuan Wu Tingwei zhang michael Sweeney Mehraj Ahmad Yongcan Jin Jiangsu co-Innovation center of Efficient Processing and Utilization of Forest Resources International Innovation Center for Forest Chemicals and MaterialsJiangsu Provincial Key Lab of Pulp and Paper Science and TechnologyNanjing Forestry UniversityNanjing 210037China School of chemistry and chemical Engineering Queen’s University BelfastBelfast BT71NNNorthern Ireland United Kingdom Department of Food Science and Engineering College of Light Industry and Food EngineeringNanjing Forestry UniversityNanjing 210037China

Low molecular aromatic compounds are detrimental to the enzymatic hydrolysis of ***,the specific role of their functional groups remains ***,a series of nine aromatic compounds as additives were tested to understand their effect on the hydrolysis yield of microcrystalline cellulose(Mcc)and alkaline pretreated wheat *** on the results,the inhibition of aldehyde groups on Mcc was greater than that of carboxyl groups,whereas for the alkaline pretreated wheat straw case,the inhibitory effect of aldehyde groups was lower than that of carboxyl *** methoxyl groups of aromatic compounds reduced the inhibitory ef-fect on enzymatic hydrolysis of both *** inhibition of aromatic compounds on Mcc hydrolysis was detected in comparison with the alkaline pretreated wheat straw,indicating that the substrate lignin can offset the inhibition to a certain *** all aromatic com-pounds,syringaldehyde with one aldehyde group and two methoxyl groups improved the glucan conversion of the alkaline pretreated wheat straw.

关键词： Aromatic compound Functional group Enzymatic hydrolysis Alkaline pretreated wheat straw Microcrystalline cellulose

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The preface: Interplay of topological and magnetic orders in the Mn-Bi-Te family

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National Science Review 2024年第2期11卷 6-7页

作者： Fu-chun zhang Hai-Zhou Lu X.c.Xie Kavli Institute for Theoretical Sciences University of Chinese Academy of Sciences Department of Physics Southern University of Science and Technology (SUSTech) International center for Quantum Materials School of Physics Peking University

The discovery and synthesis of MnBi2Te4in 2013 initially garnered little attention [1]. Yet, the revelation of its topological properties in 2019 [2–6] sparked a surge of research into the MnBiTe family. These extensive studies are primarily driven by two objectives:the realization of a high-temperature quantum anomalous Hall effect （QAHE） and the exploration of exotic phases born from the interplay of topological and magnetic orders,

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