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Effect of start cooling temperature on microstructure,crystallographic orientation and ductile-to-brittle transition behavior of high strength steel
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作者 LIU Wen-jian LI Hong-ying +5 位作者 KONG Yao-jie LIU Ji-wen LIU Dan GAO Qing PENG Ning-qi XIONG Xiang-jiang 《Journal of Central South University》 2025年第3期776-788,共13页
The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key ... The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key role.In this work,X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process.The quasi-polygonal ferrite(QF),granular bainite(GB),bainitic ferrite(BF)and martensite-austenite constituents were formed at the start cooling temperatures of 780℃(C1),740℃(C2)and 700℃(C3).As start cooling temperature decreased,the amount of GB decreased,the microstructure of QF and BF increased.Microstructure characteristics of the three samples,such as high-angle grain boundaries(HAGBs),MA constituents and crystallographic orientation,also varied with the start cooling temperatures.C2 sample had the lowest DBTT value(−86℃)for its highest fraction of HAGBs,highest content of<110>oriented grains and lowest content of<001>oriented grains parallel to TD.The high density of{332}<113>and low density of rotated cube{001}<110>textures also contributed to the best impact toughness of C2 sample.In addition,a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels. 展开更多
关键词 X70 steel start cooling temperature ductile-to-brittle transition martensite-austenite islands crystallographic orientation ductile-to-brittle transition temperature(dBTT) prediction model
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Advancements in energetic metal-organic frameworks, alkali and alkaline earth metal salts, and transition metal complexes: Predictive models for detonation velocity, heat, and pressure
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作者 Mohammad Hossein Keshavarz Nasser Hassanzadeh Mohammad Jafari 《Defence Technology(防务技术)》 2025年第7期96-112,共17页
Recent advancements have led to the synthesis of various new metal-containing explosives,particularly energetic metal-organic frameworks(EMOFs),which feature high-energy ligands within well-ordered crystalline structu... Recent advancements have led to the synthesis of various new metal-containing explosives,particularly energetic metal-organic frameworks(EMOFs),which feature high-energy ligands within well-ordered crystalline structures.These explosives exhibit significant advantages over traditional compounds,including higher density,greater heats of detonation,improved mechanical hardness,and excellent thermal stability.To effectively evaluate their detonation performance,it is crucial to have a reliable method for predicting detonation heat,velocity,and pressure.This study leverages experimental data and outputs from the leading commercial computer code to identify suitable decomposition pathways for different metal oxides,facilitating straightforward calculations for the detonation performance of alkali metal salts,and metal coordination compounds,along with EMOFs.The new model enhances predictive reliability for detonation velocities,aligning more closely with experimental results,as evi-denced by a root mean square error(RMSE)of 0.68 km/s compared to 1.12 km/s for existing methods.Furthermore,it accommodates a broader range of compounds,including those containing Sr,Cd,and Ag,and provides predictions for EMOFs that are more consistent with computer code outputs than previous predictive models. 展开更多
关键词 Metal-organic framework Alkali and alkaline earth metal salt transition metal complexe detonation performance decomposition pathway Predictive reliability
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Role of inclination angle on columnar-to-equiaxed transition in the eutectic Al-5Mg-2Si alloy fabricated by laser powder bed fusion 被引量:1
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作者 YANG Fei-peng WEN Tao +4 位作者 ZHANG Lei WANG Jian-ying HUANG Shi-long JI Shou-xun YANG Hai-lin 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第7期2150-2166,共17页
In this study,the effect of inclination angles relative to the building direction in the additively manufactured eutectic Al-5Mg-2Si alloy was investigated through the laser powder bed fusion(LPBF).The microstructures... In this study,the effect of inclination angles relative to the building direction in the additively manufactured eutectic Al-5Mg-2Si alloy was investigated through the laser powder bed fusion(LPBF).The microstructures and mechanical properties of the Al-5Mg-2Si alloy manufactured with different inclination angles(0°,30°,45°,60°and 90°)were reported and discussed.It is found that the“semicircular”melt pool(MP)in the load bearing face of 0°sample was eventually transformed into“stripe-like”MP in the 90°sample,accompanied by an increased fraction of melt pool boundaries(MPBs).Moreover,the microstructural analysis revealed that the columnar-to-equiaxed transition(CET)of theα-Al grains and eutectic Mg2Si was completed in the 90°sample,which were significantly refined with the average size of 10.6μm and 0.44μm,respectively.It is also found that the 90°sample exhibited good combination of strength and elongation(i.e.yield strength of 393 MPa,ultimate tensile strength of 483 MPa and elongation of 8.1%).The anisotropic mechanical properties were highly associated with the refined microstructures,thermal stress,and density of MPBs.Additionally,the CET driven by inclination angles was attributed to the variation of thermal conditions inside the local MPs. 展开更多
关键词 additive manufacturing aluminium alloys columnar-to-equiaxed transition ANISOTROPY mechanical property
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Significantly enhanced thermal stability of HMX by phase-transition lysozyme coating
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作者 Jiahui Liu Congmei Lin +3 位作者 Jianhu Zhang Chengcheng Zeng Zhijian Yang Fude Nie 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第5期60-68,共9页
A new robust bio-inspired route by using lysozyme aqueous solution for surface modification on 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)was described in this paper.HMX crystals were coated by in situ phase transitio... A new robust bio-inspired route by using lysozyme aqueous solution for surface modification on 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX)was described in this paper.HMX crystals were coated by in situ phase transition of lysozyme(PTL)molecules.The HMX decorated by PTL was characterized by SEM,XRD,FTIR and XPS,demonstrating a dense core-shell coating layer.The coverage of lysozyme on HMX crystal was calculated by the ratio of sulfur content.The surface coverage increased from 60.5% to 93.5% when the content of PTL was changed from 0.5 wt% to 2.0 wt%,indicating efficient coating.The thermal stability of HMX was investigated by in situ XRD and DSC.The thermal phase transition temperature of HMX(β to δ phase)was delayed by 42℃ with 2.0 wt% PTL coating,which prevented HMX from thermal damage and sensitivity by the effect of PTL coating.After heating at 215℃,large cracks appeared in the naked HMX crystal,while the PTL coated HMX still maintained intact,with the impact energy of HMX dropped dramatically from 5 J to 2 J.However,the impact energy of HMX with 1.0 wt% and 2.0 wt% coating content(HMX@PTL-1.0 and HMX@PTL-2.0)was unchanged(5 J).Present results potentially enable large-scale fabrication of polymorphic energetic materials with outstanding thermal stability by novel lysozyme coating. 展开更多
关键词 HMX LYSOZYME Phase transition Thermal stability Sensitivity
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Kinetics and mechanism of the low-energy β-a phase transition of the second kind in 2,4-dinitroanisole
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作者 Aleksandr V.Stankevich Nikolay A.Rasputin +3 位作者 Anisa KhRudina Gennady L.Rusinov Vera I.Filyakova Valery N.Charushin 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第10期210-224,共15页
In this work, comprehensive studies of 2,4-dinitroanisole(2,4DNAN) were carried out using powder thermorentgenography of the internal standard. The time of the complete polymorphic transition in the solid phase β→a ... In this work, comprehensive studies of 2,4-dinitroanisole(2,4DNAN) were carried out using powder thermorentgenography of the internal standard. The time of the complete polymorphic transition in the solid phase β→a in 2,4DNAN under various combinations of conditions has been determined. It has been established that, regardless of the season of manufacture of the substance, when it is stored for 8-9months, with a change in ambient temperature from minus 30℃ to plus 30℃, a complete polymorphic transition β→a occurs. When stored in conditions below minus 5℃, polymorphic transition does not occur. When stored in conditions above plus 30℃ in a closed container, polymorphic transition occurs within 3 weeks. The polymorphic transition is accompanied by a decrease in density by 1.3%-1.5% and an increase in melting temperature by 10-12℃, depending on the degree of purity of the starting substance. The activation energy of the molecular rearrangement was 68-70 k J/mol(16.5 ± 3 kcal/mol). The mechanism of polymorphic transition has been evaluated, which is presumably based on internal homodiffusion and energy transfer to the surface of the mass of powder particles and the product. The average activation energy of the polymorphic transition process was 110 ± 6.2 k J/mol(26.2 kcal/mol). In an open container, reactions proceed by a homogeneous mechanism, and in a closed container by a heterogeneous mechanism involving the gas phase. 展开更多
关键词 Energetic materials Melt-castable 2 4-dinitroanisole Polymorphic transition Kinetics Mechanism Homodiffusion SUBLIMATION
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Catalytic Effect of Transition Metal Complexes of Triaminoguanidine on the Thermolysis of Energetic NC/DEGDN Composite
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作者 Mohammed Dourari Ahmed Fouzi Tarchoun +4 位作者 Djalal Trache Amir Abdelaziz Roufaida Tiliouine Tessnim Barkat Weiqiang Pang 《火炸药学报》 EI CAS CSCD 北大核心 2024年第3期209-219,I0003,共12页
The transition metal complexes of triaminoguanidine(TAG-M,where M=Cobalt(Co)or Iron(Fe))have been prepared.The catalytic effect of these complexes on the thermolysis of energetic composite based on nitrocellulose and ... The transition metal complexes of triaminoguanidine(TAG-M,where M=Cobalt(Co)or Iron(Fe))have been prepared.The catalytic effect of these complexes on the thermolysis of energetic composite based on nitrocellulose and diethylene glycol dinitrate,has been investigated.Extensive characterization of the resulting energetic composites was carried out using scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),and differential scanning calorimetry(DSC).Isoconversional kinetic analysis was performed to determine the Arrhenius parameters associated with the thermolysis of the elaborated energetic formulations.It is found that TAG-M complexes have strong catalytic effect on the thermo-kinetic decomposition of NC/DEGDN by decreasing the apparent activation energy and significantly increased the total heat release.The models that govern the decomposition processes are also studied,and it is revealed that different reaction processes are accomplished by introduction metal complexes of triaminoguanidine.Overall,this study serves as a valuable reference for future research focused on the investigation of catalytic combustion features of solid propellants. 展开更多
关键词 triaminoguanidine transition metal complexes NITROCELLULOSE diethylene glycol dinitrate catalytic effect
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Effect of Elastic Strains on Adsorption Energies of C,H and O on Transition Metal Oxides
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作者 XIE Tian SONG Erhong 《无机材料学报》 SCIE EI CAS CSCD 北大核心 2024年第11期1292-1302,共11页
Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TM... Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TMOs)are regarded as potential substitutes for PGMs because of their stability in oxidizing environments and excellent catalytic performance.In this study,comprehensive investigation into the influence of elastic strains on the adsorption energies of carbon(C),hydrogen(H)and oxygen(O)on TMOs was conducted.Based on density functional theory(DFT)calculations,these effects in both tetragonal structures(PtO_(2),PdO_(2))and hexagonal structures(ZnO,CdO),along with their respective transition metals were systematically explored.It was identified that the optimal adsorption sites on metal oxides pinpointed the top of oxygen or the top of metal atom,while face-centered cubic(FCC)and hexagonal close-packed(HCP)holes were preferred for the transition metals.Furthermore,under the influence of elastic strains,the results demonstrated significant disparities in the adsorption energies of H and O between oxides and transition metals.Despite these differences,the effect of elastic strains on the adsorption energies of C,H and O on TMOs mirrored those on transition metals:adsorption energies increased under compressive strains,indicating weaker adsorption,and decreased under tension strains,indicating stronger adsorption.This behavior was rationalized based on the d-band model for adsorption atop a metallic atom or the p-band model for adsorption atop an oxygen atom.Consequently,elastic strains present a promising avenue for tailoring the catalytic properties of TMOs. 展开更多
关键词 density functional theory adsorption energy elastic strain engineering transition metal oxide CATALYST
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The effect of the carbon components on the performance of carbonbased transition metal electrocatalysts for the hydrogen evolution reaction
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作者 LI Guo-hua WANG Jing +6 位作者 REN Jin-tian LIU Hong-chen QIAN Jin-xiu CHENG Jia-ting ZHAO Mei-tong YANG Fan LI Yong-feng 《新型炭材料(中英文)》 SCIE EI CAS CSCD 北大核心 2024年第5期946-972,共27页
The hydrogen evolution reaction(HER)is a promising way to produce hydrogen,and the use of non-precious metals with an excellent electrochemical performance is vital for this.Carbon-based transition metal catalysts hav... The hydrogen evolution reaction(HER)is a promising way to produce hydrogen,and the use of non-precious metals with an excellent electrochemical performance is vital for this.Carbon-based transition metal catalysts have high activity and stability,which are important in reducing the cost of hydrogen production and promoting the development of the hydrogen production industry.However,there is a lack of discussion regarding the effect of carbon components on the performance of these electrocatalysts.This review of the literature discusses the choice of the carbon components in these catalysts and their impact on catalytic performance,including electronic structure control by heteroatom doping,morphology adjustment,and the influence of self-supporting materials.It not only analyzes the progress in HER,but also provides guidance for synthesizing high-performance carbon-based transition metal catalysts. 展开更多
关键词 Carbon-based transition metal catalysts Heteroatom doping Morphology adjustment Self-supporting materials Hydrogen evolution reaction
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Investigation of system parameters towards safer impact based shock-to-detonation transition in a novel laser driven flyer plate prototype
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作者 Gonca Saglam Ozkasapoglu Selis Onel 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2024年第9期103-113,共11页
Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This s... Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This study is based on developing a safer laser driven flyer plate prototype comprised of a laser initiator and a flyer plate subsystem that can be used with secondary explosives.System parameters were optimized to initiate the shock-to-detonation transition(SDT)of a secondary explosive based on the impact created by the flyer plate on the explosive surface.Rupture of the flyer was investigated at the mechanically weakened region located on the interface of these subsystems,where the product gases from the deflagration of the explosive provide the required energy.A bilayer energetic material was used,where the first layer consisted of a pyrotechnic component,zirconium potassium perchlorate(ZPP),for sustaining the ignition by the laser beam and the second layer consisted of an insensitive explosive,cyclotetramethylene-tetranitramine(HMX),for deflagration.A plexiglass interface was used to enfold the energetic material.The focal length of the laser beam from the diode was optimized to provide a homogeneous beam profile with maximum power at the surface of the ZPP.Closed bomb experiments were conducted in an internal volume of 10 cm^(3) for evaluation of performance.Dependency of the laser driven flyer plate system output on confinement,explosive density,and laser beam power were analyzed.Measurements using a high-speed camera resulted in a flyer velocity of 670±20 m/s that renders the prototype suitable as a laser detonator in applications,where controlled employment of explosives is critical. 展开更多
关键词 Laser driven flyer plate Shock to detonation transition dETONATION Secondary explosives Pyrotechnic materials CONFINEMENT
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维生素D治疗全面性发育迟缓患儿的临床疗效研究 被引量:3
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作者 牛国辉 谢加阳 +6 位作者 朱登纳 崔博 赵会玲 王明梅 冯欢欢 张萌萌 李停停 《中国全科医学》 CAS 北大核心 2025年第3期346-351,共6页
背景 除了某些有明确病因的代谢性疾病导致的全面性发育迟缓(GDD),康复治疗是GDD的主要治疗方式;维生素D通过影响神经营养因子在调节神经细胞的发育和分化方面发挥着重要的神经保护作用;但目前关于补充维生素D对GDD患儿临床疗效的研究... 背景 除了某些有明确病因的代谢性疾病导致的全面性发育迟缓(GDD),康复治疗是GDD的主要治疗方式;维生素D通过影响神经营养因子在调节神经细胞的发育和分化方面发挥着重要的神经保护作用;但目前关于补充维生素D对GDD患儿临床疗效的研究开展较少。目的 探讨补充不同剂量的维生素D对GDD患儿康复治疗的临床效果。方法 于2020年9月—2022年6月选取在郑州大学第三附属医院康复医学科首次住院就诊的120例GDD患儿为研究对象,采用随机区组化的方法将其分为常规组(38例)、400 U组(37例)和1 200 U组(35例)。常规组仅进行常规康复治疗;400 U组在常规康复治疗的基础上给予口服400 U/d维生素D;1 200 U组在常规康复训练的基础上给予口服1 200 U/d维生素D。收集3组患儿的性别、就诊年龄等基本资料;于入院时(治疗前)及第3个疗程末(治疗后)行血清25羟维生素D[25(OH)D]水平检测和Gesell发育量表评估[评估适应能力、大运动能力、精细运动能力、语言能力和社交能力5个能区的发育商(DQ)];记录发生在患儿住院期间不良事件的次数,并对上述资料进行分析比较。结果 3组患儿性别、居住地、出生季节、分娩方式、就诊年龄、出生体质量、出生胎龄、主要就诊原因比较,差异均无统计学意义(P>0.05)。治疗前,3组患儿25(OH)D水平、Gesell量表各能区DQ值比较,差异均无统计学意义(P>0.05);治疗后,1 200 U组患儿血25(OH)D水平、Gesell量表大运动能力、精细运动能力、语言能力DQ值高于常规组(P<0.05)。第1、2疗程期间,3组患儿不良事件发生率比较,差异无统计学意义(P>0.05);第3疗程期间,1 200 U组患儿不良事件发生率低于常规组及400 U组(P<0.05)。结论 补充1 200 U维生素D对GDD患儿的康复疗效有益,且能减少康复期间不良事件的发生率。 展开更多
关键词 儿童发育障碍 广泛性 全面性发育迟缓 维生素d Gesell量表 不良事件 康复治疗 神经保护
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计算机模拟手术结合3D打印技术在复杂骨折手术中的应用进展 被引量:2
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作者 杨立宇 郭文娟 +2 位作者 叶飞 张一奇 巴根 《中国医科大学学报》 北大核心 2025年第2期167-170,177,共5页
以计算机辅助设计为基础的3D打印技术能够快速制作三维立体模型,清晰显示骨折部位的解剖结构、类型和破裂程度,为了解骨折情况提供全方位的视觉化手段。该技术还能帮助医生设计个性化的植入物,选择定制的手术导向板和固定螺丝。手术医... 以计算机辅助设计为基础的3D打印技术能够快速制作三维立体模型,清晰显示骨折部位的解剖结构、类型和破裂程度,为了解骨折情况提供全方位的视觉化手段。该技术还能帮助医生设计个性化的植入物,选择定制的手术导向板和固定螺丝。手术医生通过术前模拟操作,对手术方案进行优化,提高手术的准确性和效果。本文总结了计算机模拟手术结合3D打印技术在多种骨科手术中的应用情况,并广泛阐述了3D打印技术在临床骨科领域的巨大应用潜力。 展开更多
关键词 计算机辅助设计 3d打印 复杂骨折
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维生素D水平与反复呼吸道感染患儿免疫障碍的相关性
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作者 朱瑛 南楠 +2 位作者 李婷婷 魏丽琼 黄蕾 《中国免疫学杂志》 北大核心 2025年第3期668-674,679,共8页
目的:调查甘肃省儿童维生素D水平特征,分析维生素D水平与反复呼吸道感染(RRTIs)患儿免疫障碍的相关性。方法:回顾性选取2020年1月至2021年12月期间于甘肃省6个市州妇幼保健院及三级综合医院以上儿科行维生素D检测的9790例0~6岁儿童,分... 目的:调查甘肃省儿童维生素D水平特征,分析维生素D水平与反复呼吸道感染(RRTIs)患儿免疫障碍的相关性。方法:回顾性选取2020年1月至2021年12月期间于甘肃省6个市州妇幼保健院及三级综合医院以上儿科行维生素D检测的9790例0~6岁儿童,分析其中5000例儿童维生素D特征,以5000例中出现RRTIs的90例患儿作为研究组,以80例健康儿童作为对照组。对比两组维生素D水平与免疫功能指标(IgA、IgG、IgM、补体C3、补体C4)的相关性,分析维生素D对儿童RRTIs的诊断价值。结果:分析甘肃省5000例儿童维生素D资料发现,维生素D缺乏率、不足率、充足率分别为11.58%、41.38%、47.04%,未发现维生素D过量和中毒者。儿童维生素D水平受年龄和季节的影响,3~4岁儿童维生素D缺乏较严重,冬季儿童维生素D水平最低,且维生素D水平与儿童生长发育、罹患疾病有关。研究组25(OH)D水平、免疫功能指标均低于对照组(P<0.05)。25(OH)D水平与RRTIs患儿年龄、过敏史、被动烟草暴露、易感季节有关(P<0.05)。维生素D充足患儿免疫功能指标高于维生素D不足、缺乏患儿(P<0.05)。RRTIs患儿维生素D水平与免疫功能呈正相关(P<0.05)。低出生体重、早产、偏食、每日果蔬量、户外活动时间、钙、铁、锌、25(OH)D、IgA、IgG、IgM、补体C3、补体C4均是儿童RRTIs的独立危险因素(P<0.05),维生素D对儿童RRTIs的诊断价值较高(P<0.05)。结论:甘肃省儿童维生素D水平与年龄、季节相关,在儿童RRTIs中,维生素D水平降低与患儿机体免疫障碍有关,可用于RRTIs的诊断。 展开更多
关键词 维生素d 25-羟基维生素d 儿童反复呼吸道感染 免疫球蛋白 补体
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三代测序技术在弱D表型家系调查分析中的应用
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作者 马玲 刘太香 +3 位作者 史丽莉 冯晨晨 张若洋 赵芳 《中国实验血液学杂志》 北大核心 2025年第4期1199-1202,共4页
目的:对一例表型为弱D的标本及家系成员进行分子机制研究。方法:常规血清学方法鉴定Rh表型;对先证者及家系成员RHD外显子1-10进行一代测序并检测其RHD合子型;进一步采用三代测序技术进行RHD基因单倍型分析。结果:先证者血清学表现为弱D... 目的:对一例表型为弱D的标本及家系成员进行分子机制研究。方法:常规血清学方法鉴定Rh表型;对先证者及家系成员RHD外显子1-10进行一代测序并检测其RHD合子型;进一步采用三代测序技术进行RHD基因单倍型分析。结果:先证者血清学表现为弱D,一代测序发现外显子5存在c.787G>A点突变。家系调查结果显示,先证者与其妹具有相同的血清学表型及分子机制,其父携带该基因突变,其母与其弟均正常。RHD合子型分析未检测到杂合box,提示家系成员不存在RHD基因全缺失的单倍型。三代测序结果显示,先证者与其妹分别遗传来自父亲的弱D等位基因及母亲的非功能性等位基因RHD-CE(3-9)-D。结论:三代测序技术能对RHD基因进行单倍型分析,适用于RHD/RHCE大片段基因杂交合并其他突变等复杂基因型检测。 展开更多
关键词 三代测序 d 基因型
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SiC陶瓷的3D打印成形与致密化新进展 被引量:1
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作者 殷杰 耿佳毅 +3 位作者 王康龙 陈忠明 刘学建 黄政仁 《无机材料学报》 北大核心 2025年第3期245-255,共11页
SiC陶瓷具有高强度和良好的热稳定性,在航空航天、热端部件等领域有着广泛的应用前景。随着对大尺寸和复杂形状SiC陶瓷需求的日益增长, 3D打印技术在制造周期、成本及可靠性等诸多方面明显优于传统减材、等材制造方法,越来越受到重视。3... SiC陶瓷具有高强度和良好的热稳定性,在航空航天、热端部件等领域有着广泛的应用前景。随着对大尺寸和复杂形状SiC陶瓷需求的日益增长, 3D打印技术在制造周期、成本及可靠性等诸多方面明显优于传统减材、等材制造方法,越来越受到重视。3D打印方法众多,各具特点:立体光刻(Stereolithography, SLA)技术可以实现高精度和优良的表面质量,但实际操作中往往需要设计支撑结构,再加上残余应力和低固含量等问题,极大限制了其发展;激光选区烧结(Selective laser sintering, SLS)技术具有较强的材料普适性,适用于高分子、金属和陶瓷等多种材料,可实现大尺寸快速成形,且制造成本较低,但其成形素坯表面质量较低,需进行后续加工;熔融沉积(Fused deposition modeling,FDM)技术制备的SiC陶瓷材料可借助反应烧结实现致密化,但成形素坯存在层间结合强度低、表面有较明显条纹等缺陷,并且成形速度相对较慢,不适合构建大型零件,因此在实际生产中受到限制。本文综述了近五年来3D打印SiC陶瓷的最新研究进展,讨论了成形素坯的后续高温致密化处理方法及其基本物理性能,并展望了3D打印SiC陶瓷材料的未来前景。新型3D打印技术及其与多种打印方式的融合将在陶瓷宏微观结构的精细化中发挥重要作用,或将成为未来的重要发展趋势。 展开更多
关键词 SIC陶瓷 3d打印 激光选区烧结 致密化 综述
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复杂越野场景无人履带平台3D语义占据预测方法 被引量:1
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作者 陈慧岩 司璐璐 +1 位作者 王旭睿 王文硕 《北京理工大学学报》 EI CAS 北大核心 2025年第1期1-10,共10页
为了理解和处理复杂越野场景中环境要素形状不规则、地形多变及路面属性复杂等问题,提出了一种基于多模态融合感知的3D语义占据预测方法.首先,基于图像和激光雷达融合网络获取初始3D语义标签;然后,对越野场景稀疏点云采用贝叶斯稠密化... 为了理解和处理复杂越野场景中环境要素形状不规则、地形多变及路面属性复杂等问题,提出了一种基于多模态融合感知的3D语义占据预测方法.首先,基于图像和激光雷达融合网络获取初始3D语义标签;然后,对越野场景稀疏点云采用贝叶斯稠密化算法补全3D语义占据标签;最后,生成包含复杂环境要素大小、位置和语义信息的3D语义占据栅格地图.试验结果表明,该方法能够有效地提取和表示复杂越野环境中的3D信息,为复杂越野环境下无人履带平台的路径规划提供了更加准确和丰富的先验信息. 展开更多
关键词 无人履带平台 多模态融合 3d语义占据预测
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明胶和马铃薯淀粉对大豆分离蛋白凝胶3D打印性能的影响 被引量:1
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作者 刘丽莉 段京瑶 +5 位作者 郭悦 邵贝贝 谢天怡 程伟伟 丁玥 肖枫 《食品与发酵工业》 北大核心 2025年第13期253-260,共8页
为研究不同比例明胶/马铃薯淀粉对大豆分离蛋白(soybean protein isolate,SPI)凝胶性能及3D打印性能的影响,该文以SPI、明胶和马铃薯淀粉为原料,通过热诱导的方式制备SPI复合凝胶,并对复合凝胶的水分分布、质构、流变特性、结构、微观... 为研究不同比例明胶/马铃薯淀粉对大豆分离蛋白(soybean protein isolate,SPI)凝胶性能及3D打印性能的影响,该文以SPI、明胶和马铃薯淀粉为原料,通过热诱导的方式制备SPI复合凝胶,并对复合凝胶的水分分布、质构、流变特性、结构、微观结构以及3D打印特性等进行了表征。结果表明,明胶与马铃薯淀粉比例在1∶8~6∶8(质量比,下同)范围内,随着比例增加,自由水比例降低,不易流动水比例升高,明胶与马铃薯淀粉比例为6∶8时,不易流动水比例最高,占比为2.48%。复配凝胶的硬度、内聚性和咀嚼性随着明胶与马铃薯淀粉比例的增加逐渐降低,6∶8时达到最低,质地最为柔软。随着剪切速率升高,凝胶的黏度均下降,样品的G′和G″随着明胶与马铃薯淀粉比例的增加也均呈升高趋势。傅里叶红外光谱结果显示,添加了明胶和马铃薯淀粉的样品在波长3295.44 cm-1处的—OH振动发生红移,氢键作用增强。随着明胶与马铃薯淀粉比例的增加,复配凝胶孔径逐渐减小,明胶与马铃薯淀粉比例为6∶8时,凝胶孔隙分布呈现出最高的均匀性,打印精度最好,高度打印精确度99.60%,直径打印精确度99.92%,且在1 h内未出现明显塌陷。综上所述,明胶/马铃薯淀粉比例为6∶8时,对大豆分离蛋白凝胶3D打印性能的改善最为显著,这为开发蛋白基3D打印油墨提供理论依据。 展开更多
关键词 明胶 马铃薯淀粉 大豆分离蛋白 3d打印
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基于替代分析物的LC-MS/MS检测儿童末梢血中25-羟维生素D方法建立及评价
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作者 刘菲 宋晶晶 +5 位作者 曹明鹏 祖琴琴 周曙光 张爱喜 王丽 李明 《海南医科大学学报》 北大核心 2025年第15期1163-1171,共9页
目的:建立基于同位素替代分析物的液相色谱串联质谱(LC-MS/MS)方法检测儿童末梢血中25-羟维生素D(25(OH)D)。方法:采用同位素标记物25(OH)D2-d6、25(OH)D3-d3作为替代分析物,25(OH)D3-d6作为内标,通过蛋白沉淀处理后,应用LC-MS/MS方法... 目的:建立基于同位素替代分析物的液相色谱串联质谱(LC-MS/MS)方法检测儿童末梢血中25-羟维生素D(25(OH)D)。方法:采用同位素标记物25(OH)D2-d6、25(OH)D3-d3作为替代分析物,25(OH)D3-d6作为内标,通过蛋白沉淀处理后,应用LC-MS/MS方法同时检测换算得到实际标本中25(OH)D2和25(OH)D3的含量。评价该方法的相同浓度下响应值等效性、特异性、线性、检出限(LOD)、定量限(LOQ)、准确度、精密度、基质效应、携带污染和实际样品加标回收率。结果:25(OH)D2和25(OH)D3的响应因子分别为1.46和1.04;线性相关系数均>0.995,LOD分别为0.16和0.33 ng/mL,LOQ分别为0.5和1ng/mL,替代分析物25(OH)D2-d6和25(OH)D3-d3相对回收率在96.05%~107.07%范围内,批内批间精密度均<10%,基质因子在0.882~1.121,无明显携带污染,样品可室温避光放置24 h,2~8℃下保存7 d。结论:建立了基于替代分析物的LC-MS/MS定量测定儿童末梢血中25(OH)D2和25(OH)D3的方法,该方法简单易行、结果可靠,有望成为儿童或其他采血困难人群的候选方法。 展开更多
关键词 液相色谱法 串联质谱法 25-羟维生素d 末梢血 替代分析物
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血清铁蛋白和25-羟维生素D与老年非酒精性脂肪性肝病患者颈部血管斑块及心脏代谢指数的相关性
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作者 雷蕾 胡韵 +2 位作者 张笛 黄鑫宇 彭羽 《实用医学杂志》 北大核心 2025年第1期78-83,共6页
目的探究血清铁蛋白(SF)、25-羟维生素D[25-(OH)D]与老年非酒精性脂肪性肝病(NAFLD)患者颈部血管斑块及心脏代谢指数(CMI)的相关性。方法选取医院128例老年NAFLD患者作为研究组,另选80例健康体检者资料为对照组。比较研究组和对照组及... 目的探究血清铁蛋白(SF)、25-羟维生素D[25-(OH)D]与老年非酒精性脂肪性肝病(NAFLD)患者颈部血管斑块及心脏代谢指数(CMI)的相关性。方法选取医院128例老年NAFLD患者作为研究组,另选80例健康体检者资料为对照组。比较研究组和对照组及不同病变程度患者的血清Ferritin、25-(OH)D水平。根据是否形成颈动脉血管斑块将患者分为斑块组(n=36)和非斑块组(n=92)。比较两组临床资料,SF、25-(OH)D、CMI水平,分析影响老年NAFLD患者颈部血管斑块形成的多因素及血清Ferritin、25-(OH)D水平与患者颈部血管斑块及CMI的相关性。结果研究组血清SF值显著高于对照组(P<0.05),25-(OH)D水平显著低于对照组(P<0.05);SF水平:脂肪肝组<脂肪性肝炎组<肝硬化组(P<0.05),25-(OH)D水平:脂肪肝组>脂肪性肝炎组>肝硬化组(P<0.05);斑块组BMI、合并糖尿病、高血脂、血清ALT、AST、LDL-C、SF、水平、FPG、FINS、HOMA-IR、CMI、NFS值显著高于非斑块组(P<0.05),血清25-(OH)D水平显著低于非斑块组(P<0.05);多因素logistic回归分析显示,BMI、血清LDL-C、SF水平、CMI、NFS值升高是影响老年NAFLD患者颈动脉斑块形成的危险因素(P<0.05),血清25-(OH)D水平升高为保护因素(P<0.05);相关性分析显示,SF与NAFLD患者颈动脉斑块及CMI呈显著正相关(P<0.05),血清25-(OH)D水平与NAFLD患者颈动脉斑块及CMI呈显著负相关(P<0.05)。结论血清SF、25-(OH)D与NAFLD病情进展相关,且可能影响患者颈部血管斑块形成及心脏代谢,可作为NAFLD患者血管病变的诊治观察指标。 展开更多
关键词 铁蛋白 25-羟维生素d 非酒精性脂肪性肝病 颈部血管斑块 心脏代谢指 相关性
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基于3D打印技术的软弱夹层干湿循环作用强度劣化试验研究 被引量:1
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作者 刘浩 张文 芦磊 《水文地质工程地质》 北大核心 2025年第3期125-133,共9页
软弱夹层是一类较为特殊敏感的地质体,其存在对水电工程边坡的稳定性起控制性作用。为了深入探讨库岸边坡中软弱夹层在干湿循环条件下的剪切力学特性及破坏机制,以菜籽坝抽水蓄能电站下水库坝址左岸坝肩边坡为研究对象,利用3D打印技术... 软弱夹层是一类较为特殊敏感的地质体,其存在对水电工程边坡的稳定性起控制性作用。为了深入探讨库岸边坡中软弱夹层在干湿循环条件下的剪切力学特性及破坏机制,以菜籽坝抽水蓄能电站下水库坝址左岸坝肩边坡为研究对象,利用3D打印技术制备具有真实岩石形貌特征的结构面,并计算出结构面的粗糙度系数JRC,然后开展干湿循环作用下含人工节理面的软弱夹层剪切试验。研究结果表明,经过不同次数干湿循环,抗剪强度随循环次数增加呈负指数型降低,最终会趋于一个极低的稳定值,为初始强度的5%,且抗剪强度与结构面粗糙度呈正相关。软弱夹层的剪切应力-应变曲线在破坏阶段会呈阶梯式降低,结构面粗糙度越大,残余曲线阶梯式降低次数越多,且结构面粗糙度大的试样会在更短的剪切位移到达残余强度阶段,残余强度也随干湿循环次数的增加而降低。研究成果对抽水蓄能电站岸坡的稳定性评价具有较大的参考意义。 展开更多
关键词 软弱夹层 干湿循环 3d打印 强度劣化 粗糙度 残余强度
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对美国内分泌学会2024年版维生素D指南重大修订的思考
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作者 谢忠建 《中华骨质疏松和骨矿盐疾病杂志》 北大核心 2025年第2期135-140,共6页
自从美国内分泌学会2011年发布首版维生素D指南以来,随着多项大型随机对照研究(randomized clinical trial,RCT)的结果发表,美国内分泌学会于2024年对维生素D指南进行了修订,本文介绍了新版指南的修订背景和具体修订内容,并探讨该指南... 自从美国内分泌学会2011年发布首版维生素D指南以来,随着多项大型随机对照研究(randomized clinical trial,RCT)的结果发表,美国内分泌学会于2024年对维生素D指南进行了修订,本文介绍了新版指南的修订背景和具体修订内容,并探讨该指南的推荐是否适合中国人群。本次修订幅度较大,首先废除了根据25-羟维生素D[25 hydroxyvitamin D,25(OH)D]水平所定义的维生素D“缺乏”和“不足”的分类,原因是临床研究尚未明确与特定临床结果关联的25(OH)D水平的阈值。并且,对于一般健康人群,不建议常规检测血清25(OH)D水平。对于18~74岁的健康成年人,摄入维生素D的膳食参考摄入量(600~800 IU/d)即可满足需要。而其他健康人群,如儿童、青少年、老年人、孕妇和糖尿病前期人群,则建议更高的“经验性补充”剂量。需明确的是,新版指南针对的是健康人群,而非患病人群。对于1~18岁的儿童和青少年,“经验性补充维生素D”有助于预防营养性佝偻病,并可能降低呼吸道感染风险;对于75岁及以上的老年人群,“经验性补充维生素D”有可能降低死亡风险;对于妊娠女性,“经验性补充维生素D”可能降低先兆子痫、早产和小于胎龄儿的风险及宫内死亡率;对于糖尿病前期人群,“经验性补充维生素D”可能减低从糖尿病前期进展为糖尿病的风险。鉴于各临床研究中的维生素D补充剂量差异较大,目前尚不明确最佳补充剂量,指南仅列出了临床研究中使用的剂量范围,供“经验性补充”参考。此外,指南建议50岁以上、跌倒风险较高的人群小剂量补充,而不建议过大剂量补充。 展开更多
关键词 维生素d 美国内分泌学会 指南
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