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基于Alpha Shapes轮廓点云识别算法的洞室表面形变区域提取方法 被引量:2
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作者 张雨婷 郑德华 李思远 《南京信息工程大学学报》 北大核心 2025年第2期181-190,共10页
针对三维激光扫描密集点云提取洞室表面变形信息的问题,本文提出一种基于改进的Alpha Shapes算法识别洞室轮廓点云和多尺度模型到模型的点云比对(Multiscale Model-to-Model Cloud Comparison,M3C2)的洞室表面变形监测方法.首先对获取... 针对三维激光扫描密集点云提取洞室表面变形信息的问题,本文提出一种基于改进的Alpha Shapes算法识别洞室轮廓点云和多尺度模型到模型的点云比对(Multiscale Model-to-Model Cloud Comparison,M3C2)的洞室表面变形监测方法.首先对获取到的两期洞室表面点云数据进行配准,采用改进的Alpha Shapes算法识别洞室表面外轮廓点云.获得的两期洞室表面外轮廓点云经精配准后,再采用M3C2算法进行各点变形值计算,最后进行距离聚类提取连续形变区域.实验结果表明:该方法能够有效剔除点云中细小沟壑处的点及受到混合像元影响的点,在洞室截面到扫描仪距离10 m的范围内,两期点云剔除率分别为14.17%及13.52%,在70 m范围内,分别为6.25%及6.42%;该方法能够准确高效地提取出2倍配准误差以上的洞室表面形变区域. 展开更多
关键词 洞室变形监测 轮廓点云识别 Alpha shapes算法 M3C2算法
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Benchmarking the composite performance of distinct shapes of ferrometallic gold nanoshells:photothermal cancer therapy 被引量:1
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作者 Sara I.Abdelsalam Essam T.Abdelwahab +2 位作者 I.M.Eldesoky Ramzy M.Abumandour M.M.Ahmed 《Acta Mechanica Sinica》 2025年第6期3-15,共13页
This article presents a detailed theoretical hybrid analysis of the magnetism and the thermal radiative heat transfer in the presence of heat generation affecting the behavior of the dispersed gold nanoparticles(AuNPs... This article presents a detailed theoretical hybrid analysis of the magnetism and the thermal radiative heat transfer in the presence of heat generation affecting the behavior of the dispersed gold nanoparticles(AuNPs)through the blood vessels of the human body.The rheology of gold-blood nanofluid is treated as magnetohydrodynamic(MHD)flow with ferromagnetic properties.The AuNPs take different shapes as bricks,cylinders,and platelets which are considered in changing the nanofluid flow behavior.Physiologically,the blood is circulated under the kinetics of the peristaltic action.The mixed properties of the slip flow,the gravity,the space porosity,the transverse ferromagnetic field,the thermal radiation,the nanoparticles shape factors,the peristaltic amplitude ratio,and the concentration of the AuNPs are interacted and analyzed for the gold-blood circulation in the inclined tube.The appropriate model for the thermal conductivity of the nanofluid is chosen to be the effective Hamilton-Crosser model.The undertaken nanofluid can be treated as incompressible non-Newtonian ferromagnetic fluid.The solutions of the partial differential governing equations of the MHD nanofluid flow are executed by the strategy of perturbation approach under the assumption of long wavelength and low Reynolds number.Graphs for the streamwise velocity distributions,temperature distributions,pressure gradients,pressure drops,and streamlines are presented under the influences of the pertinent properties.The practical implementation of this research finds application in treating cancer through a technique known as photothermal therapy(PTT).The results indicate the control role of the magnetism,the heat generation,the shape factors of the AuNPs,and its concentration on the enhancement of the thermal properties and the streamwise velocity of the nanofluid.The results reveal a marked enhancement in the temperature profiles of the nanofluid,prominently influenced by both the intensified heat source and the heightened volume fractions of the nanoparticles.Furthermore,the platelet shape is regarded as most advantageous for heat conduction owing to its highest effective thermal conductivity.AuNPs proved strong efficiency in delivering and targeting the drug to reach the affected area with tumors.These results offer valuable insights into evaluating the effectiveness of PTT in addressing diverse cancer conditions and regulating their progression. 展开更多
关键词 Peristaltic flow NANOFLUID AuNPs MAGNETISM shape factor Gravity Heat transfer Porous medium
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Study on the formation characteristics of underwater hemispherical shaped charge jet and its penetration performance into concrete 被引量:1
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作者 Chao Cao Jinxiang Wang +5 位作者 Lingquan Kong Kui Tang Yujie Xiao Yangchen Gu Ming Yang Jian Wang 《Defence Technology(防务技术)》 2025年第5期180-196,共17页
Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of sh... Shaped charge has been widely used for penetrating concrete.However,due to the obvious difference between the propagation of shock waves and explosion products in water and air,the theory governing the formation of shaped charge jets in water as well as the underwater penetration effect of concrete need to be studied.In this paper,we introduced a modified forming theory of an underwater hemispherical shaped charge,and investigated the behavior of jet formation and concrete penetration in both air and water experimentally and numerically.The results show that the modified jet forming theory predicts the jet velocity of the hemispherical liner with an error of less than 10%.The underwater jets exhibit at least 3%faster and 11%longer than those in air.Concrete shows different failure modes after penetration in air and water.The depth of penetration deepens at least 18.75%after underwater penetration,accompanied by deeper crater with 65%smaller radius.Moreover,cracks throughout the entire target are formed,whereas cracks exist only near the penetration hole in air.This comprehensive study provides guidance for optimizing the structure of shaped charge and improves the understanding of the permeability effect of concrete in water. 展开更多
关键词 shaped charge jet Underwater penetration Formation characteristic Concrete failure
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Experimental and numerical investigation of cavity characteristics in behind-armor liquid-filled containers under shaped charge jet impact 被引量:1
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作者 Shixin Ma Xiangdong Li Lanwei Zhou 《Defence Technology(防务技术)》 2025年第5期242-259,共18页
The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure ... The cavity characteristics in liquid-filled containers caused by high-velocity impacts represent an important area of research in hydrodynamic ram phenomena.The dynamic expansion of the cavity induces liquid pressure variations,potentially causing catastrophic damage to the container.Current studies mainly focus on non-deforming projectiles,such as fragments,with limited exploration of shaped charge jets.In this paper,a uniquely experimental system was designed to record cavity profiles in behind-armor liquid-filled containers subjected to shaped charge jet impacts.The impact process was then numerically reproduced using the explicit simulation program ANSYS LS-DYNA with the Structured Arbitrary Lagrangian-Eulerian(S-ALE)solver.The formation mechanism,along with the dimensional and shape evolution of the cavity was investigated.Additionally,the influence of the impact kinetic energy of the jet on the cavity characteristics was analyzed.The findings reveal that the cavity profile exhibits a conical shape,primarily driven by direct jet impact and inertial effects.The expansion rates of both cavity length and maximum radius increase with jet impact kinetic energy.When the impact kinetic energy is reduced to 28.2 kJ or below,the length-to-diameter ratio of the cavity ultimately stabilizes at approximately 7. 展开更多
关键词 Cavity characteristics shaped charge jet Behind-armor liquid-filled container Impact kinetic energy Hydrodynamic ram
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On the uniqueness of participation factors in nonlinear dynamical systems
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作者 XIA Tian-wei SUN Kai 《控制理论与应用》 北大核心 2025年第11期2147-2155,共9页
In the modal analysis and control of nonlinear dynamical systems,participation factors(PFs)of state variables with respect to a critical or selected mode serve as a pivotal tool for simplifying stability studies by fo... In the modal analysis and control of nonlinear dynamical systems,participation factors(PFs)of state variables with respect to a critical or selected mode serve as a pivotal tool for simplifying stability studies by focusing on a subset of highly influential state variables.For linear systems,PFs are uniquely determined by the mode’s composition and shape,which are defined by the system’s left and right eigenvectors,respectively.However,the uniqueness of other types of PFs has not been thoroughly addressed in literatures.This paper establishes sufficient conditions for the uniqueness of nonlinear PFs and five other PF variants,taking into account uncertain scaling factors in a mode’s shape and composition.These scaling factors arise from variations in the choice of physical units,which depend on the value ranges of real-world state variables.Understanding these sufficient conditions is essential for the correct application of PFs in practical stability analysis and control design. 展开更多
关键词 participation factor mode shape mode composition nonlinear system OSCILLATIONS
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Effect of Co Content on Microstructure and Mechanical Properties of High-Entropy High-Temperature Shape Memory Alloy
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作者 Zhao Yanchun Jin Bo +4 位作者 Feng Yuanfei Ma Huwen Yu Zhiqi Feng Li Liaw Peter K 《稀有金属材料与工程》 北大核心 2025年第1期10-16,共7页
(TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co co... (TiZrHf)_(50)Ni_(30)Cu_(20-x)Co_(x)(x=2,4,6,at%)high-entropy high-temperature shape memory alloys were fabricated by watercooled copper crucible in a magnetic levitation vacuum melting furnace,and the effects of Co content on microstructure and mechanical properties were investigated.The results indicate that the grain size of the alloy decreases with increasing the Co content.In the as-cast state,the alloy consists primarily of the B19′phase,with a trace of B2 phase.The fracture morphology is predominantly composed of the B19′phase,whereas the B2 phase is nearly absent.Increasing the Co content or reducing the sample dimensions(d)markedly enhance the compressive strength and ductility of the alloy.When d=2 mm,the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy demonstrates the optimal mechanical properties,achieving a compressive strength of 2142.39±1.8 MPa and a plasticity of 17.31±0.3%.The compressive cyclic test shows that with increasing the compressive strain,the residual strain of the(TiZrHf)_(50)Ni_(30)Cu_(14)Co_(6) alloy increases while the recovery ability declines.The superelastic recovery capability of the alloy is continuously enhanced.The superelastic recovery rate increases from 1.36%to 2.12%,the residual strain rate rises from 1.79%to 5.52%,the elastic recovery rate ascends from 3.86%to 7.36%,while the total recovery rate declines from 74.48%to 63.20%. 展开更多
关键词 high-temperature shape memory alloy high-entropy alloy MICROSTRUCTURE mechanical property
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Shape Memory Properties of Short-Glass Fiber Reinforced Epoxy Composite Programmed below Glass Transition Temperature
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作者 Kartikey Shahi Velmurugan Ramachandran +1 位作者 Ranjith Mohan Boomurugan Ramachandran 《Journal of Polymer Materials》 2025年第2期477-496,共20页
A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of sho... A Shape Memory Polymer Composite(SMPC)is developed by reinforcing an epoxy-based polymer with randomly oriented short glass fibers.Diverging from previous research,which primarily focused on the hot programming of short glass fiber-based SMPCs,this work explores the potential for programming below the glass transition temperature(Tg)for epoxy-based SMPCs.To mitigate the inherent brittleness of the SMPC during deformation,a linear polymer is incorporated,and a temperature between room temperature and Tg is chosen as the deformation temperature to study the shape memory properties.The findings demonstrate an enhancement in shape fixity and recovery stress,alongside a reduction in shape recovery,with the incorporation of short glass fibers.In addition to tensile properties,thermal properties such as thermal conductivity,specific heat capacity,and glass transition temperature are investigated for their dependence on fiber content.Microscopic properties,such as fiber-matrix adhesion and the dispersion of glass fibers,are examined through Scanning Electron Microscope imaging.The fiber length distribution and mean fiber lengths are also measured for different fiber fractions. 展开更多
关键词 shape memory polymer composite glass fiber composite shape fixity shape recovery thermomechanical cycle
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On shape coexistence and possible shape isomers of nuclei around^(172)Hg
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作者 Xin Guan Jing Guo +2 位作者 Qi-Wen Sun Bożena Nerlo-Pomorska Krzysztof Pomorski 《Nuclear Science and Techniques》 2025年第7期191-203,共13页
This study explores the phenomenon of shape coexistence in nuclei around^(172)Hg,with a focus on the isotopes^(170)Pt,^(172)Hg,and^(174)Pb,as well as the^(170)Pt to^(180)Pt isotopic chain.Utilizing a macro-microscopic... This study explores the phenomenon of shape coexistence in nuclei around^(172)Hg,with a focus on the isotopes^(170)Pt,^(172)Hg,and^(174)Pb,as well as the^(170)Pt to^(180)Pt isotopic chain.Utilizing a macro-microscopic approach that incorporates the Lublin-Strasbourg Drop model combined with a Yukawa-Folded potential and pairing corrections,we analyze the potential energy surfaces(PESs)to understand the impact of pairing interaction.For^(170)Pt,the PES exhibited a prolate ground state,with additional triaxial and oblate-shaped isomers.In^(172)Hg,the ground-state deformation transitions from triaxial to oblate with increasing pairing interaction,demonstrating its nearlyγ-unstable nature.Three shape isomers(prolate,triaxial,and oblate)were observed,with increased pairing strength leading to the disappearance of the triaxial isomer.^(174)Pb exhibited a prolate ground state that became increasingly spherical with stronger pairing.While shape isomers were present at lower pairing strengths,robust shape coexistence was not observed.For realistic pairing interaction,the ground-state shapes transitioned from prolate in^(170)Pt to a coexistence ofγ-unstable and oblate shapes in^(172)Hg,ultimately approaching spherical symmetry in^(174)Pb.A comparison between Exact and Bardeen-Cooper-Schrieffer(BCS)pairing demonstrated that BCS pairing tends to smooth out shape coexistence and reduce the depth of the shape isomer,leading to less pronounced deformation features.The PESs for even-even^(170)-180 Pt isotopes revealed significant shape evolution.^(170)Pt showed a prolate ground state,whereas^(172)Pt exhibited both triaxial and prolate shape coexistence.In^(174)Pt,the ground state was triaxial,coexisted with a prolate minimum.For^(176)Pt,aγ-unstable ground state coexists with a prolate minimum.By 178 Pt and 180Pt,a dominant prolate minimum emerged.These results highlight the role of shape coexistence andγ-instability in the evolution of nuclear structure,especially in the mid-shell region.These findings highlight the importance of pairing interactions in nuclear deformation and shape coexistence,providing insights into the structural evolution of mid-shell nuclei. 展开更多
关键词 Macro-micro-model shape coexistence shape isomers Exact and BCS pairing solutions
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Highly programmable 4D printed multi-shape gradient metamaterials and multifunctional devices
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作者 Chunli Yang Xiaozhou Xin +4 位作者 Wenjun Zhao Cheng Lin Liwu Liu Yanju Liu Jinsong Leng 《International Journal of Extreme Manufacturing》 2025年第5期416-431,共16页
Metamaterials,owing to their exceptional physical characteristics that are absent in natural materials,have emerged as a crucial constituent of intelligent devices and systems.However,there are still significant chall... Metamaterials,owing to their exceptional physical characteristics that are absent in natural materials,have emerged as a crucial constituent of intelligent devices and systems.However,there are still significant challenges that necessitate immediate attention,as they have considerably constrained the applicability of metamaterials,including fixed mechanical properties post-fabrication and restricted design freedom.Here,thermo-responsive,photo-responsive,electro-responsive,and magneto-responsive shape memory polymer nano-composites were developed,and shape memory gradient metamaterials were fabricated using multi-material 4D printing technology.The correlation mechanism between the design parameters and the mechanical properties of multi-responsive gradient metamaterials was systematically analyzed,and the highly designable and programmable configuration and mechanical properties of the gradient metamaterials were realized.More importantly,4D printed multi-responsive shape memory polymer gradient metamaterials can be programmed in situ without additional infrastructure for multi-functional mechanical functions,paving the way for the realization of multiple functions of a single structure.Based on the multi-responsive gradient metamaterials,4D printed digital pixel metamaterial intelligent information carriers were fabricated,featuring customizable encryption and decryption protocols,exceptional scalability,and reusability.Additionally,4D printed gradient metamaterial logic gate electronic devices were developed,which were anticipated to contribute to the development of smart,adaptable robotic systems that combine sensing,actuation,and decision-making capabilities. 展开更多
关键词 shape memory polymer nanocomposites 4D printing multiple shape memory effects bio-inspired metamaterials multi-functionality
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Phase Field Simulation of Fracture Behavior in Shape Memory Alloys and Shape Memory Ceramics:A Review
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作者 Junhui Hua Junyuan Xiong +2 位作者 Bo Xu Chong Wang Qingyuan Wang 《Computers, Materials & Continua》 2025年第10期65-88,共24页
Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerfu... Shape memory alloys(SMAs)and shape memory ceramics(SMCs)exhibit high recovery ability due to the martensitic transformation,which complicates the fracture mechanism of SMAs and SMCs.The phase field method,as a powerful numerical simulation tool,can efficiently resolve the microstructural evolution,multi-field coupling effects,and fracture behavior of SMAs and SMCs.This review begins by presenting the fundamental theoretical framework of the fracture phase field method as applied to SMAs and SMCs,covering key aspects such as the phase field modeling of martensitic transformation and brittle fracture.Subsequently,it systematically examines the phase field simulations of fracture behaviors in SMAs and SMCs,with particular emphasis on how crystallographic orientation,grain size,and grain boundary properties influence the crack propagation.Additionally,the interplay between martensite transformation and fracture mechanisms is analyzed to provide deeper insights into the material responses under mechanical loading.Finally,the review explores future prospects and emerging trends in phase field simulations of SMA and SMC fracture behavior,along with potential advancements in the fracture phase field method itself,including multi-physics coupling and enhanced computational efficiency for large-scale simulations. 展开更多
关键词 Phase field fracture behavior shape memory alloy shape memory ceramic
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Viticulture:History,Breeding Systems and Recent Developments
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作者 JoséLuis Rodríguez-Lorenzo Bohuslav Janoušek Emilio Cervantes 《Phyton-International Journal of Experimental Botany》 2025年第9期2649-2667,共19页
Grapevine is unique among crops because its domestication resulted not only in new morphological characteristics,but also in altered reproductive mechanisms.Viticulture involves a change from a dioecious to a hermaphr... Grapevine is unique among crops because its domestication resulted not only in new morphological characteristics,but also in altered reproductive mechanisms.Viticulture involves a change from a dioecious to a hermaphroditic mating system,which makes the reproductive system more efficient.In consequence and the fact that it is one of the oldest and most economically important cultivated plants,Vitis vinifera could be defined as an over-domesticated species.Here we review some key aspects in viticulture.The main areas of interest have remained consistent throughout history,including the origin and characterisation of cultivars,resistance to environmental con-ditions,pests and pathogens,and berry quality.Advances in genomic analysis and epigenetics shed new light on these aspects.Although the vine has a long and complex life cycle,recent haplotype sequencing techniques allow genomic characteristics related to different reproduction processes to be identified.Recent work on haplotype sequencing reveals genomic changes accompanying each reproductive type,providing improved detail about the sex-determining region(SDR).Meanwhile,the application of epigenetic analysis offers new tools for defining varietal characteristics and their responses to changing environmental conditions.However,critical issues,such as differentiating between sylvestris and feral cultivars,remain unclear.Understanding the molecular basis of morphological differences and investigating the epigenetic regulation of gene expression and genome dynamics in response to breeding and environmental factors in this species will be crucial.Seed morphology could help to resolve how to differentiate between wild and feral plants. 展开更多
关键词 EPIGENETICS evolution ferals GENOMICS HISTORY VARIETIES VITIS seed shape
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Ultra-high temperature shape memory in high-Hf content NiTiHf alloys
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作者 A.V.Shuitcev Q.Z.Li +2 位作者 M.G.Khomutov L Li Y.X.Tong 《Journal of Materials Science & Technology》 2025年第6期124-127,共4页
The active development of space industry necessitates the cre-ation of novel materials with unique properties,including shape memory alloys(SMAs).The development of ultra-high temperature SMAs(UHTSMAs)with operating t... The active development of space industry necessitates the cre-ation of novel materials with unique properties,including shape memory alloys(SMAs).The development of ultra-high temperature SMAs(UHTSMAs)with operating temperatures above 400℃is a significant challenge[1-3].It is known that reversible thermoelas-tic martensitic transformation(MT)is the basis for shape mem-ory behavior[4].Currently,there are several systems in which MT temperatures meet the above requirements,for example,RuNb[5],HfPd[6],TiPd[7]. 展开更多
关键词 shape memory alloys smas shape memory alloys ultra high temperature reversible thermoelastic martensitic transformation space industry nitihf alloys
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Geometric Morphometric Analysis of Body Shape Variation in Glossogobius giuris from Lake Mainit,Agusan del Norte,Philippines
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作者 Cresencio C.Cabuga,Jr. Ana Marie D.Empeño Jojean Marie D.Pondang 《Research in Ecology》 2025年第2期144-158,共15页
Most fish exhibit remarkable morphological diversity,which is often influenced by genetic variation and ecological pressures.Consequently,these are the outcomes of organisms’responses to their environment.Meanwhile,m... Most fish exhibit remarkable morphological diversity,which is often influenced by genetic variation and ecological pressures.Consequently,these are the outcomes of organisms’responses to their environment.Meanwhile,modern morphometrics can quantify shape variation within species of the same group.This study aims to determine the body shape variation of Glossogobius giuris from Lake Mainit,Agusan Del Norte,Philippines.60 adult,uniform-sized fish samples were collected and subjected to standardized laboratory procedures.Further,the samples were digitized for 16 homologous landmark points and loaded into Symmetry Asymmetry Geometric Data(SAGE)Software.Across the tested factors—individuals,sides,and individual x sides—result shows that shape variations among individuals were highly significant(F=2.1045,p<0.0001),along with among males(F=3.2711,p<0.0001).Females exhibited higher Fluctuating Asymmetry(FA)(F=18.99,p<0.0001)compared to males(F=7.0964,p<0.0001).It suggests morphological shape differences across the sexes,and the shape variation observed could be a response to environmental perturbations.Shape variations were associated with swimming,food hunting,and predator defense.Moreover,Principal Component Analysis(PCA)demonstrates higher scores of FA in females(81.96%)than in males(74.76%).It was noticed that females had a high fluctuating asymmetry.It might be due to various physiological and ecological pressures compared to males.The observed levels of directional and fluctuating asymmetry in males and females,respectively,may indicate sex-linked morphological and developmental processes,which are important to consider in ecological or evolutionary contexts.Thus,utilizing geometric morphometrics can depict subtle differences across the same populations. 展开更多
关键词 Caraga Region Ecology Freshwater Fish Landmarks LIMNOLOGY PHENOTYPES shape Variation
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Effect of Annealing on the Shape Memory Effect and Mechanical Properties of Laser Powder Bed Fusion NiTi Alloy
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作者 Yunting Guo Mengqi Liu +8 位作者 Chaorui Jiang Ruiyao Liu Jundong Zhang Pengwei Sha Hang Li Zhenglei Yu Zhihui Zhang Zezhou Xu Luquan Ren 《Additive Manufacturing Frontiers》 2025年第1期125-135,共11页
The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory e... The emergence of additive manufacturing technology,particularly laser powder bed fusion,has revitalized NiTi alloy production.However,challenges arise regarding its mechanical properties and diminishing shape memory effect,which hinder its widespread application.Heat treatment has been identified as a method to enhance the performance of metallic materials in the realm of additive manufacturing.This process eliminates residual stress and enhances performance through precipitation strengthening.This study conducted a comprehensive annealing investigation on NiTi alloys to explore the impact of annealing time and temperature on the phase transformation behavior and shape memory performance.The mechanism underlying the performance enhancement was analyzed using scanning electron microscopy,energy-dispersive X-ray spectroscopy,electron backscatter diffraction,and transmission electron microscopy.The findings revealed that different annealing conditions resulted in multistep phase transformation behavior,with the 500℃-5 h sample exhibiting the best mechanical properties owing to the formation of nanoscale dispersed precipitates like Ni_(4)Ti_(3).However,higher temperatures led to larger precipitates,significantly weakening the properties of the NiTi alloy.Additionally,the annealing treatment did not have a notable impact on the grain size,texture strength,or direction.This study provides valuable insights for optimizing the heat treatment process of LPBF-NiTi alloys. 展开更多
关键词 ANNEALING LPBF-NiTi shape memory effect Mechanical properties PRECIPITATES
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Egg shape in an obligate brood parasite stabilizes temperature variation during incubation
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作者 Francisco R.Magdaleno Lyndon R.Hawkins +1 位作者 Isaac Quintanilla Salinas Brian D.Peer 《Current Zoology》 2025年第4期504-510,共7页
The brood-parasitic brown-headed cowbird(Molothrus ater)has one of the shortest incubation periods of any bird.Brown-headed cowbird eggs,and those of other avian brood parasites,tend to be more spherical due to their ... The brood-parasitic brown-headed cowbird(Molothrus ater)has one of the shortest incubation periods of any bird.Brown-headed cowbird eggs,and those of other avian brood parasites,tend to be more spherical due to their greater relative width.The traditional explanation for this egg shape is that it,combined with the thicker eggshells,resists host puncture-ejection.However,very few North American hosts of the brownheaded cowbird actually engage in puncture-ejection and therefore wider eggs may instead provide greater contact with a host’s brood patch during incubation,especially in large host nests.We tested whether greater egg width increased mean temperature and reduced temperature variation in brown-headed cowbirds by inserting temperature probes into brown-headed cowbird and house sparrow(Passer domesticus)eggs and placing them into red-winged blackbird(Agelaius phoeniceus)nests.House sparrow eggs are similar in appearance and in length to cowbird eggs,but are not as wide.We found no signifcant relationship between brown-headed cowbird egg width and mean incubation temperature.However,brown-headed cowbird eggs experienced less temperature variation than house sparrow eggs,and within brown-headed cowbird eggs,more spherical eggs experienced less temperature variation when accounting for differences in width.These results suggest that brownheaded cowbirds may have short incubation periods in part because their eggs exhibit less temperature variation over the course of incubation.The brown-headed cowbird’s egg shape may contribute to its accelerated embryonic development rate relative to host eggs of similar size,which explains its ability to hatch in a variety of host nests. 展开更多
关键词 brood parasitism brown-headed cowbird DEVELOPMENT egg shape INCUBATION Molothrus ater TEMPERATURE THERMOREGULATION
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Experimental Study on the Coupling Dynamics of Metal Jet,Waves,and Bubble During Underwater Explosion of a Shaped Charge
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作者 Yu Tian A-Man Zhang +1 位作者 Liu-Yi Xu Fu-Ren Ming 《Engineering》 2025年第7期168-187,共20页
Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show ... Unlike conventional spherical charges,a shaped charge generates not only a strong shock wave and a pulsating bubble,but also a high strain rate metal jet and a ballistic wave during the underwater explosion.They show significant characteristic differences and couple each other.This paper designs and conducts experiments with shaped charges to analyze the complicated process.The effects of liner angle and weight of shaped charge on the characteristics of metal jets,waves,and bubbles are discussed.It is found that in underwater explosions,the shaped charge generates the metal jet accompanied by the ballistic wave.Then,the shock wave propagates and superimposes with the ballistic wave,and the generated bubble pulsates periodically.It is revealed that the maximum head velocity of the metal jet versus the liner angle a and length-to-diameter ratio k of the shaped charge follows the laws of 1/(α/180°)^(0.55)andλ^(0.16),respectively.The head shape and velocity of the metal jet determine the curvature and propagation speed of the initial ballistic wave,thus impacting the superposition time and region with the shock wave.Our findings also reveal that the metal jet carries away some explosion products,which hinders the bubble development,causing an inward depression of the bubble wall near the metal jet.Therefore,the maximum bubble radius and pulsation period are 5.2%and 3.9%smaller than the spherical charge with the same weight.In addition,the uneven axial energy distribution of the shaped charge leads to an oblique bubble jet formation. 展开更多
关键词 shaped charge Underwater explosion Metal jet WAVES BUBBLE Coupling dynamics
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Quantifying avian wing shapes:Evaluating indices,their relationships,and ecological correlates
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作者 Jiahui Li Canwei Xia 《Avian Research》 2025年第4期683-692,共10页
Avian wings are central to their remarkable flight ability and diverse life history strategies,including behaviors such as fighting and mating.These multifaceted functions are intricately tied to wing shape,which vari... Avian wings are central to their remarkable flight ability and diverse life history strategies,including behaviors such as fighting and mating.These multifaceted functions are intricately tied to wing shape,which varies significantly across species because of the complex interplay of evolutionary and ecological pressures.Many indices have been developed to quantify wing characteristics to facilitate the study and comparison of avian wing morphology across species.This study provides a comprehensive overview of existing quantitative methods for analyzing avian wing shapes.We then constructed a new quantification framework through the beta distribution,which can generate indices reflecting the shape of avian wings(center,dispersion,skewness,and kurtosis).Next,we used the flight feathers of 613 bird species to perform different quantitative analyses and explore the relationships between various wing shape quantification methods and life history traits,which serve as proxies for the selective forces shaping wing morphology.We find that the wing shape indices are more strongly associated with ecological variables than with morphological variables,especially for migration,habitat and territoriality.This research guides the selection of appropriate methods for wing shape analysis,contributing to a deeper understanding of avian morphology and its evolutionary drivers. 展开更多
关键词 AVIAN Beta distribution Quantification method Wing shape
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Optical transmittance and pulse shape discrimination of polystyrene/poly(methyl methacrylate)-based plastic scintillators
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作者 Yi-Yao Liang Ying-Du Liu +2 位作者 Pu-Sen Wang Jie Bao Xiao-Ping Ouyang 《Nuclear Science and Techniques》 2025年第1期94-102,共9页
Polymethyl methacrylate(PMMA)is an optically transparent thermoplastic with favorable processing conditions.In this study,a series of plastic scintillators are prepared via thermal polymerization,and the impact of PMM... Polymethyl methacrylate(PMMA)is an optically transparent thermoplastic with favorable processing conditions.In this study,a series of plastic scintillators are prepared via thermal polymerization,and the impact of PMMA content on their transparency and pulse shape discrimination(PSD)ability is investigated.The fabricated samples,comprising a polystyrene(PS)-PMMA matrix,30.0 wt%2,5-diphenyloxazole(PPO),and 0.2 wt%9,10-diphenylanthracene(DPA),exhibit high transparency with transmissivity ranging from 70.0 to 90.0%(above 415.0 nm)and demonstrate excellent n/γdiscrimination capability.Transparency increased with increasing PMMA content across the entire visible light spectrum.However,the PSD performance gradually deteriorated when the aromatic matrix was replaced with PMMA.The scintillator containing 20.0 wt%PMMA demonstrated the best stability concerning PSD properties and relative light yields. 展开更多
关键词 Neutron detection Plastic scintillation Pulse shape discrimination Polymethyl-methacrylate POLYSTYRENE
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Simulation and experimental study on the use of shaped charge jet as transient antennas for radiating electromagnetic pulses
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作者 Jiahui Guo Bin Ma +2 位作者 Zhengxiang Huang Yong Peng Xin Jia 《Defence Technology(防务技术)》 2025年第5期260-274,共15页
In this study,the potential application of shaped charge jets as transient antennas for electromagnetic signal transmission was explored and an electromagnetic pulse radiation system with a shaped charge jet as a tran... In this study,the potential application of shaped charge jets as transient antennas for electromagnetic signal transmission was explored and an electromagnetic pulse radiation system with a shaped charge jet as a transient antenna was proposed.During the research,crucial characteristics of the transient antenna formed by a shaped charge with a 30 mm diameter,such as resonant frequency,radiation pattern,and radiation efficiency,were evaluated.The typical shaped charge jet morphology was obtained based on the simulations,in which it could insight the dynamic behavior of the shaped charge jet selected.An equivalent model experiment was employed to test the radiation efficiency,and it showed that a shorting pin loading method could increase the relative bandwidth of the jet antenna to 32.8%,and the experimental results correlate with the theoretical predictions for half-wave dipole antennas reasonably well.Additionally,variations in the diameter of the shaped charge jet were found to affect the input impedance and impedance bandwidth,while the length of the jet influenced the resonant frequency of the antenna.This suggests that altering these parameters can achieve reconfigurability of the jet antenna. 展开更多
关键词 shaped charge Transient antenna Electromagnetic pulse Radiated power Reconfigurable antenna
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Topology,Size,and Shape Optimization in Civil Engineering Structures:A Review
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作者 Ahmed Manguri Hogr Hassan +1 位作者 Najmadeen Saeed Robert Jankowski 《Computer Modeling in Engineering & Sciences》 2025年第2期933-971,共39页
The optimization of civil engineering structures is critical for enhancing structural performance and material efficiency in engineering applications.Structural optimization approaches seek to determine the optimal de... The optimization of civil engineering structures is critical for enhancing structural performance and material efficiency in engineering applications.Structural optimization approaches seek to determine the optimal design,by considering material performance,cost,and structural safety.The design approaches aim to reduce the built environment’s energy use and carbon emissions.This comprehensive review examines optimization techniques,including size,shape,topology,and multi-objective approaches,by integrating these methodologies.The trends and advancements that contribute to developing more efficient,cost-effective,and reliable structural designs were identified.The review also discusses emerging technologies,such as machine learning applications with different optimization techniques.Optimization of truss,frame,tensegrity,reinforced concrete,origami,pantographic,and adaptive structures are covered and discussed.Optimization techniques are explained,including metaheuristics,genetic algorithm,particle swarm,ant-colony,harmony search algorithm,and their applications with mentioned structure types.Linear and non-linear structures,including geometric and material nonlinearity,are distinguished.The role of optimization in active structures,structural design,seismic design,form-finding,and structural control is taken into account,and the most recent techniques and advancements are mentioned. 展开更多
关键词 Structural optimization topology optimization size optimization shape optimization multi-objective optimization
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