期刊文献+
共找到114篇文章
< 1 2 6 >
每页显示 20 50 100
On the Cosmic Evolution of the Quantum Vacuum Using Two Variable G Models and Winterberg’s Thesis
1
作者 Christopher Pilot 《Journal of High Energy Physics, Gravitation and Cosmology》 2023年第4期1134-1160,共27页
We work within a Winterberg framework where space, i.e., the vacuum, consists of a two component superfluid/super-solid made up of a vast assembly (sea) of positive and negative mass Planck particles, called planckion... We work within a Winterberg framework where space, i.e., the vacuum, consists of a two component superfluid/super-solid made up of a vast assembly (sea) of positive and negative mass Planck particles, called planckions. These material particles interact indirectly, and have very strong restoring forces keeping them a finite distance apart from each other within their respective species. Because of their mass compensating effect, the vacuum appears massless, charge-less, without pressure, net energy density or entropy. In addition, we consider two varying G models, where G, is Newton’s constant, and G<sup>-1</sup>, increases with an increase in cosmological time. We argue that there are at least two competing models for the quantum vacuum within such a framework. The first follows a strict extension of Winterberg’s model. This leads to nonsensible results, if G increases, going back in cosmological time, as the length scale inherent in such a model will not scale properly. The second model introduces a different length scale, which does scale properly, but keeps the mass of the Planck particle as, ± the Planck mass. Moreover we establish a connection between ordinary matter, dark matter, and dark energy, where all three mass densities within the Friedman equation must be interpreted as residual vacuum energies, which only surface, once aggregate matter has formed, at relatively low CMB temperatures. The symmetry of the vacuum will be shown to be broken, because of the different scaling laws, beginning with the formation of elementary particles. Much like waves on an ocean where positive and negative planckion mass densities effectively cancel each other out and form a zero vacuum energy density/zero vacuum pressure surface, these positive mass densities are very small perturbations (anomalies) about the mean. This greatly alleviates, i.e., minimizes the cosmological constant problem, a long standing problem associated with the vacuum. 展开更多
关键词 Winterberg Model Planck Particles Positive and Negative Mass Planck Particles Planckions Quantum vacuum Space as a Superfluid/Supersolid Extended Models for Space Cosmological Constant Higgs Field as a Composite Particle Higgs Boson Inherent Length Scale for the vacuum Dark energy Cosmological Scaling behavior for the Quantum vacuum Variable G Models Extended Gravity Newton’s Constant as an Order Parameter high energy behavior for the vacuum
下载PDF
Influence of temperature on the transformation and self-control of energy during sandstone damage:Experimental and theoretical research 被引量:4
2
作者 Lan Qiao Jiawang Hao +2 位作者 Zhiyi Liu Qingwen Li Naifu Deng 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2022年第4期761-777,共17页
The surrounding rock in tunnelling engineering and coal mining will sometimes be exposed to high temperature. Rock failure is the result of energy dissipation, and the study of the evolution and transformation behavio... The surrounding rock in tunnelling engineering and coal mining will sometimes be exposed to high temperature. Rock failure is the result of energy dissipation, and the study of the evolution and transformation behavior of energy is of great significance for the in-depth understanding of the deformation and failure of rock after high temperature. This study analyzed the intrinsic connection between mechanical properties and acoustic emission(AE) energy under temperature effect. Based on the energy dissipation and release theory, the distribution and transformation of energy was analyzed, and the energy selfincentive and self-inhibition(EII) model was further established. The main findings are that temperature effect affects the confidence interval trend and the value of AE energy rate, which is related to the change in mechanical properties. The ability of sandstone to store elastic strain energy after exposure to high temperature is independent of the mechanical properties. In this study, the ratio of dissipated energy to elastic energy is used to characterize the stable state of the sandstone system, which can be used as the energy indicator of rock failure precursor. During the absorption, storage, and release of energy before the peak stress, there exists self-incentive and self-inhibition of energy(control behavior). 展开更多
关键词 Exposure to high temperature Rock failure energy behavior energy indicator Self-control of energy
下载PDF
Quasi-static and low-velocity impact mechanical behaviors of entangled porous metallic wire material under different temperatures
3
作者 Yi-wan Wu Hu Cheng +3 位作者 Shang-zhou Li Yu Tang Hong-bai Bai Chun-hong Lu 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2023年第1期143-152,共10页
To improve the defense capability of military equipment under extreme conditions,impact-resistant and high-energy-consuming materials have to be developed.The damping characteristic of entangled porous metallic wire m... To improve the defense capability of military equipment under extreme conditions,impact-resistant and high-energy-consuming materials have to be developed.The damping characteristic of entangled porous metallic wire materials(EPMWM)for vibration isolation was previously investigated.In this paper,a study focusing on the impact-resistance of EPMWM with the consideration of ambient temperature is presented.The quasi-static and low-velocity impact mechanical behavior of EPMWM under different temperatures(25℃-300℃)are systematically studied.The results of the static compression test show that the damping energy dissipation of EPMWM increases with temperature while the nonlinear damping characteristics are gradually enhanced.During the impact experiments,the impact energy loss rate of EPMWM was between 65%and 85%,while the temperatures increased from 25℃to 300℃.Moreover,under the same drop impact conditions,the overall deformation of EPMWM decreases in the temperature range of 100℃-200℃.On the other hand,the impact stiffness,energy dissipation,and impact loss factor of EPMWM significantly increase with temperature.This can be attributed to an increase in temperature,which changes the thermal expansion coefficient and contact state of the internal wire helixes.Consequently,the energy dissipation mode(dry friction,air damping,and plastic deformation)of EPMWM is also altered.Therefore,the EPMWM may act as a potential candidate material for superior energy absorption applications. 展开更多
关键词 Entangled porous metallic wire material Low-velocity impact high temperature energy dissipation characteristics Mechanical behavior
下载PDF
稀土Gd对Ni-Cr-Mo合金热变形行为的影响
4
作者 杨志豪 王琳琳 +3 位作者 梁田 贾洞潇 马颖澈 王平 《特殊钢》 2024年第5期8-18,共11页
含Gd镍铬钼合金作为乏燃料贮运用中子屏蔽材料具有广阔的应用前景,却在热加工时极易发生开裂,为了优化合金热变形工艺参数,本文以Ni-Cr-Mo合金为研究对象,研究了Gd加入后引起的组织变化。在变形温度为1 000~1 200℃、应变速率为0.01~5 s... 含Gd镍铬钼合金作为乏燃料贮运用中子屏蔽材料具有广阔的应用前景,却在热加工时极易发生开裂,为了优化合金热变形工艺参数,本文以Ni-Cr-Mo合金为研究对象,研究了Gd加入后引起的组织变化。在变形温度为1 000~1 200℃、应变速率为0.01~5 s^(-1)条件下进行等温热压缩实验,计算合金相关材料常数及热变形激活能,构建热加工图并确定热加工窗口,结合微观组织进行分析,研究Gd对合金热变形行为的影响。结果表明,Ni-Cr-Mo合金中加入了1.2%的Gd,合金的变形激活能从472.15 kJ/mol降至422.9 kJ/mol,在热变形时合金的能量消耗效率更高,组织演变更充分,塑性失稳区域由高温向低温逐渐转移,并且增大了合金在1 000~1 060℃,0.01~0.32 s^(-1)低温低应变速率下安全区的面积。合金最佳热加工区间为:0.5真应变量,温度(T)为1 113~1 164℃,应变速率(ε)为0.01~0.2 s^(-1)。Gd在晶界或枝晶间以金属间化合物GdNi_(5)析出,GdNi_(5)相作为硬脆相,在热变形过程中其周围产生较大应变,导致组织中畸变能更高,从而促进周围变形晶粒发生再结晶,降低组织中的残余应变。 展开更多
关键词 中子吸收材料 真空感应熔炼 GdNi_5相 变形激活能 热加工图 动态再结晶 热变形行为
下载PDF
基于混合FTMM-SEA法的高速列车真空玻璃车窗隔声特性预测与分析
5
作者 黄蕾欣 肖新标 +1 位作者 张捷 汤晏宁 《铁道学报》 EI CAS CSCD 北大核心 2024年第4期89-96,共8页
真空玻璃在轻质高隔声方面的性能优势尤为突出,将其用于高速列车车窗是轻量化高速列车车内噪声控制的新型解决方案。将声波在真空玻璃中的传播分解为沿真空层和沿声桥结构的两条独立传播路径,分别使用有限传递矩阵法(FTMM)和统计能量分... 真空玻璃在轻质高隔声方面的性能优势尤为突出,将其用于高速列车车窗是轻量化高速列车车内噪声控制的新型解决方案。将声波在真空玻璃中的传播分解为沿真空层和沿声桥结构的两条独立传播路径,分别使用有限传递矩阵法(FTMM)和统计能量分析法(SEA)计算两条路径的声功率传递系数,建立基于混合FTMM-SEA法的真空玻璃车窗结构隔声量预测模型,并通过实测真空玻璃混响隔声量验证模型的准确性。进一步调查分析声桥结构刚度对耦合板间能量传递、真空玻璃隔声特性的影响。结果表明:减小声桥结构刚度是提高真空玻璃车窗隔声性能的一种有效的方法。与刚性声桥相比,柔性声桥具备更好的能量吸收能力与隔振特性。 展开更多
关键词 高速列车 车窗 真空玻璃 传递矩阵法 统计能量分析法
下载PDF
二硅化钼改性硅酸镱环境障涂层的高温抗氧化行为及机理
6
作者 梁锐辉 钟鑫 +4 位作者 洪督 赵芳霞 牛亚然 张振忠 郑学斌 《热喷涂技术》 2024年第1期100-108,共9页
新一代高推重比航空发动机的发展对环境障涂层(EBCs)的服役寿命和温度提出了苛刻的要求。稀土硅酸盐作为EBCs材料应用于面层,在服役过程中易产生纵向裂纹,为腐蚀性介质的侵蚀提供通道,严重影响EBCs的寿命。二硅化钼(MoSi_(2))具有优异... 新一代高推重比航空发动机的发展对环境障涂层(EBCs)的服役寿命和温度提出了苛刻的要求。稀土硅酸盐作为EBCs材料应用于面层,在服役过程中易产生纵向裂纹,为腐蚀性介质的侵蚀提供通道,严重影响EBCs的寿命。二硅化钼(MoSi_(2))具有优异的高温性能,有望改善稀土硅酸盐EBCs体系的高温性能。采用MoSi_(2)改性Yb_(2)SiO_(5)面层,通过真空等离子喷涂技术(VPS)分别制备了Yb_(2)SiO_(5)-XMoSi_(2)(X=0,5%和10%,体积分数)为面层,Yb_(2)Si_(2)O_(7)为中间层,Si为黏结层的三种环境障涂层体系。研究了涂层在1350℃长时间氧化前后显微结构演化过程。结果发现,掺杂MoSi_(2)涂层体系在高温氧化500 h后仍能保持结构完整且面层裂纹减少。原因在于,MoSi_(2)可消耗氧化剂,减缓涂层内部TGO的增长速率,反应产物Yb_(2)Si_(2)O_(7)与中间层成分一致,具有较好的化学相容性,有效改善了涂层体系的高温性能。 展开更多
关键词 环境障涂层 硅酸镱 MoSi_(2) 真空等离子喷涂 高温抗氧化行为
下载PDF
高熵合金动态力学行为研究进展
7
作者 王开心 仝永刚 +3 位作者 陈永雄 王洁 张舒研 梁秀兵 《材料工程》 EI CAS CSCD 北大核心 2024年第1期57-69,共13页
高熵合金具有高强韧、高耐磨、强耐腐蚀和抗高温氧化等优异特性,因此在能源化工、航空航天和国防等领域展现出良好的潜在应用前景。动态载荷下,高熵合金表现出更高强度、更多孪晶和绝热剪切带等异于准静态载荷下的力学行为,并且不同相... 高熵合金具有高强韧、高耐磨、强耐腐蚀和抗高温氧化等优异特性,因此在能源化工、航空航天和国防等领域展现出良好的潜在应用前景。动态载荷下,高熵合金表现出更高强度、更多孪晶和绝热剪切带等异于准静态载荷下的力学行为,并且不同相结构对高熵合金动态性能和变形机理具有显著影响。此外,动态载荷下高熵合金因表现出较好的释能特性,而在结构释能材料领域具有一定研究价值。通常动态实验稳定性较差,测试难度大;但通过本构模型与实验验证相结合的方式,可较好地预测高熵合金的动态力学性能。基于上述分析,本文综述了不同相结构高熵合金的动态力学行为、释能特性和本构模型,并对上述性能特点及其本构模型和模拟计算等方面进行了展望。最后指出高熵合金的动态力学性能可以通过调控元素种类及其配比和相结构及其浓度分布等进行改善;同时温度和应变速率等因素对高熵合金动态力学行为的影响机制需要深入研究;而模型计算在揭示其高应变速率下的变形机制和性能预测方面发挥更大作用。 展开更多
关键词 高熵合金 动态力学行为 释能特性 本构模型
下载PDF
磁悬浮透平机在高透成形纸机上的改造应用
8
作者 桑显葵 黄晖 +3 位作者 郭亚红 陈俊卿 黎坤韬 杜明 《造纸科学与技术》 2024年第4期30-32,132,共4页
磁悬浮透平机是近些年出现的新技术,在造纸行业的应用也逐渐增多,其主要技术特点是利用动态磁悬浮技术实现电机转子在悬浮状态下的高速旋转,并将转子位移的精度控制在2μm内,进而达到电机转子与定子无接触无摩擦的运行状态,实现了节能... 磁悬浮透平机是近些年出现的新技术,在造纸行业的应用也逐渐增多,其主要技术特点是利用动态磁悬浮技术实现电机转子在悬浮状态下的高速旋转,并将转子位移的精度控制在2μm内,进而达到电机转子与定子无接触无摩擦的运行状态,实现了节能、节油、节水的效果。在高透成形纸机上用一台磁悬浮透平机替换原有的五台水环真空泵,真空系统的实际运行功率均值从453kW下降到187kW,实际节能效率58.7%,同时节约用水,操作更简便,维护更简易。 展开更多
关键词 磁悬浮透平机 高透成形纸机 真空泵 节能
下载PDF
Properties of intermediate-frequency vacuum arc in sinusoidal curved contact and butt contact
9
作者 佟子昂 武建文 +1 位作者 金巍 陈均 《Plasma Science and Technology》 SCIE EI CAS CSCD 2020年第2期29-37,共9页
In this report,two new contact structures of a vacuum interrupter with a sinusoidal curved surface are proposed to improve the capability by increasing the surface area.The experimental investigation of vacuum arc at ... In this report,two new contact structures of a vacuum interrupter with a sinusoidal curved surface are proposed to improve the capability by increasing the surface area.The experimental investigation of vacuum arc at intermediate frequency(360-800 Hz)was conducted and the results were compared with a butt contact with the same contact diameter(41 mm)and the same material.By analyzing the arc behavior,arc voltage characteristics,arc energy,current interrupting capacity,ablation of the anode contact and condensation of the arc products at a 3 mm gap,the differences in their vacuum arc characteristics were determined.The correlations of their arc energy with the amplitude and the frequency of the current were also achieved.Analysis suggests that the ruled curved contact has strong application potentiality because of its low arc energy,low arc voltage noise and arc voltage peak,light ablation on the surface of the anode contact and high interrupting capacity. 展开更多
关键词 sinusoidal curved surface intermediate frequency voltage characteristics arc energy vacuum arc properties arc behavior
下载PDF
饱和红层泥岩填料动力及耗散能特性试验研究 被引量:1
10
作者 陈康 刘先峰 +3 位作者 蒋关鲁 袁胜洋 潘申鑫 余祯 《岩土工程学报》 EI CAS CSCD 北大核心 2023年第3期571-579,共9页
路基基床变形控制是保证高速铁路线路平顺性的重要前提之一,基床变形由外部荷载和路基填料动力特性决定。通过不同围压和动应力下的动三轴试验研究了饱和红层泥岩填料动力及能量耗散特性,结果表明:饱和红层泥岩填料的累积变形、应变速... 路基基床变形控制是保证高速铁路线路平顺性的重要前提之一,基床变形由外部荷载和路基填料动力特性决定。通过不同围压和动应力下的动三轴试验研究了饱和红层泥岩填料动力及能量耗散特性,结果表明:饱和红层泥岩填料的累积变形、应变速率和等效模量具有内在相关性,可通过状态边界面表征。围压变化将引起状态边界面形状和大小的改变,动应力则决定了填料动力响应在状态边界面中的位置。填料耗散能具有两阶段特征,先随振次增加而衰减随后到达稳定状态。填料的累积变形、变形速率和等效模量与耗散能大小有关,同样可通过状态边界面表征,耗散能则受动应力水平影响。当相对能量水平低于20%,填料累积变形最终能够稳定,处于动力稳定状态;当相对能量水平位于20%~60%,填料处于动力临界状态;而当相对能量水平高于60%,填料的长期稳定性无法保证,处于动力失稳状态。 展开更多
关键词 红层泥岩 高速铁路 路基填料 动力特性 耗散能
下载PDF
直流叠加高压脉冲的真空灭弧室老炼技术 被引量:1
11
作者 翟小社 彭朝政 +3 位作者 高泽熙 郑浩 刘镇玮 王建华 《高电压技术》 EI CAS CSCD 北大核心 2023年第9期3784-3791,共8页
提高真空灭弧室的老炼均匀度,并有效调控老炼电弧作用区域的能量注入方式和程度,是真空灭弧室老炼技术所要解决的两个核心问题。然而,在单一电源模式下,真空灭弧室触头间隙的击穿条件和放电能量相互制约,其老炼的时间和空间约束条件难... 提高真空灭弧室的老炼均匀度,并有效调控老炼电弧作用区域的能量注入方式和程度,是真空灭弧室老炼技术所要解决的两个核心问题。然而,在单一电源模式下,真空灭弧室触头间隙的击穿条件和放电能量相互制约,其老炼的时间和空间约束条件难以独立调节,所以难以同时满足对老炼均匀度和作用区域能量调控两方面的要求。为此提出了一种直流叠加高压脉冲的真空灭弧室双电源老炼技术方案,通过小能量的高压脉冲实现对触头间隙绝缘弱点的击穿和精确定位,引入大电流对该弱点区域进行老炼处理。与传统老炼方式的实验结果对比表明:该老炼方法可显著提升灭弧室雷电冲击耐压水平,提升幅度在40%左右,为真空灭弧室老炼技术的进一步发展提供了新的思路。 展开更多
关键词 老炼 真空灭弧室 直流叠加高压脉冲 绝缘耐压性能 双电源 均匀度 电弧能量
下载PDF
The Solution Cosmological Constant Problem
12
作者 Jaykov Foukzon Elena Men’kova Alexander Potapov 《Journal of Modern Physics》 2019年第7期729-794,共66页
The cosmological constant problem arises because the magnitude of vacuum energy density predicted by the Quantum Field Theory is about 120 orders of magnitude larger then the value implied by cosmological observations... The cosmological constant problem arises because the magnitude of vacuum energy density predicted by the Quantum Field Theory is about 120 orders of magnitude larger then the value implied by cosmological observations of accelerating cosmic expansion. We pointed out that the fractal nature of the quantum space-time with negative Hausdorff-Colombeau dimensions can resolve this tension. The canonical Quantum Field Theory is widely believed to break down at some fundamental high-energy cutoff and therefore the quantum fluctuations in the vacuum can be treated classically seriously only up to this high-energy cutoff. In this paper we argue that the Quantum Field Theory in fractal space-time with negative Hausdorff-Colombeau dimensions gives high-energy cutoff on natural way. We argue that there exists hidden physical mechanism which cancels divergences in canonical QED4, QCD4, Higher-Derivative-Quantum gravity, etc. In fact we argue that corresponding supermassive Pauli-Villars ghost fields really exist. It means that there exists the ghost-driven acceleration of the universe hidden in cosmological constant. In order to obtain the desired physical result we apply the canonical Pauli-Villars regularization up to &Lambda;*. This would fit in the observed value of the dark energy needed to explain the accelerated expansion of the universe if we choose highly symmetric masses distribution between standard matter and ghost matter below the scale &Lambda;*, i.e., The small value of the cosmological constant is explained by tiny violation of the symmetry between standard matter and ghost matter. Dark matter nature is also explained using a common origin of the dark energy and dark matter phenomena. 展开更多
关键词 COSMOLOGICAL Constant Problem QUANTUM Field theory vacuum energy Density QUANTUM Space-Time Hausdorff-Colombeau Dimension QUANTUM Fluctuations high-energy CUTOFF CANONICAL Pauli-Villars Regularization Universe
下载PDF
大采高开采高位关键层运动致灾机理研究 被引量:1
13
作者 朱卫兵 《晋控科学技术》 2023年第1期1-6,F0002,共7页
大采高工作面采场强矿压灾害与上覆高位关键层的赋存状态及破断运动密切相关。研究与实践表明:特厚煤层综放开采或特大采高综采工作面顶板高位关键层横“O-X”破断、竖“O-X”破断以及悬而未断都将显著影响采场矿压,导致工作面易出现强... 大采高工作面采场强矿压灾害与上覆高位关键层的赋存状态及破断运动密切相关。研究与实践表明:特厚煤层综放开采或特大采高综采工作面顶板高位关键层横“O-X”破断、竖“O-X”破断以及悬而未断都将显著影响采场矿压,导致工作面易出现强矿压灾害或冲击地压灾害等动力现象。结合部分工程案例,阐述了大采高开采高位关键层在不同破断形式或悬而未断条件下的致灾机制,并提出了高位关键层致灾防控技术,为西部类似大采高开采条件下的工作面安全高效开采提供借鉴。 展开更多
关键词 大采高 高位关键层 横“O-X”破断 竖“O-X”破断 矿压显现 动力灾害
下载PDF
球形Al-25W合金燃料粉末的氧化行为与能量性能 被引量:1
14
作者 胡敖博 蔡水洲 邹辉 《含能材料》 EI CAS CSCD 北大核心 2023年第8期743-752,共10页
为了获得热氧化与能量释放性能优异的新型合金燃料,采用铝热还原与超高温气雾化结合的方法,制备了球形铝钨合金燃料粉末(Al-25W),对其物相结构、氧化行为及能量性能进行了研究。结果表明,球形Al-25W合金粉末颗粒内部的亚稳态Al/W合金相... 为了获得热氧化与能量释放性能优异的新型合金燃料,采用铝热还原与超高温气雾化结合的方法,制备了球形铝钨合金燃料粉末(Al-25W),对其物相结构、氧化行为及能量性能进行了研究。结果表明,球形Al-25W合金粉末颗粒内部的亚稳态Al/W合金相均匀分布在单质Al基体中,且通过稳定化处理后亚稳态Al/W合金相转变为Al12W相,并对外释放能量。球形Al-25W合金粉末具有比单质Al粉更高的氧化放热量与氧化增重,能在1400℃空气中完全氧化,且W原子全部氧化为WO3并以气态形式挥发,残留氧化产物仅为Al2O3。球形Al-25W合金粉末的实测体积燃烧焓超过单质Al粉的理论体积燃烧焓(83000 J·cm^(-3)),可达(83132.1±608.5)J·cm^(-3),且剧烈燃烧时生成气态燃烧产物WO3。 展开更多
关键词 Al-25W合金粉末 铝热还原 超高温气雾化 Al/W合金相 氧化行为 能量性能
下载PDF
多组合混杂纤维增强UHPC断裂特性试验研究 被引量:1
15
作者 于跟社 邓宗才 王珏 《北京工业大学学报》 CAS CSCD 北大核心 2023年第5期547-557,共11页
为研究混杂纤维增强超高性能混凝土(ultra-high performance concrete,UHPC)的断裂性能,对带预制裂缝UHPC梁进行了三点弯曲断裂测试,以研究钢纤维分别与6种非金属纤维混掺对断裂性能的影响.钢纤维体积分数为1.3%,混掺合成/无机纤维体积... 为研究混杂纤维增强超高性能混凝土(ultra-high performance concrete,UHPC)的断裂性能,对带预制裂缝UHPC梁进行了三点弯曲断裂测试,以研究钢纤维分别与6种非金属纤维混掺对断裂性能的影响.钢纤维体积分数为1.3%,混掺合成/无机纤维体积分数均为0.5%.通过测得荷载-裂缝嘴张开位移(P-D)曲线,分析了起裂韧度、失稳韧度、断裂能等断裂参数,研究了切口梁弯曲强度、残余强度等.试验表明:混掺纤维UHPC的P-D曲线具有明显的二次强化特性,钢纤维与其他非金属纤维混掺具有一定的协调阻裂、控裂能力.混掺合成/无机纤维提高了切口梁裂后的变形能力;混掺直径为0.15 mm的聚烯烃纤维有利于提高断裂能;混掺直径为0.04 mm的聚乙烯醇纤维可明显提高UHPC断裂参数;混掺玻璃纤维有利于提高UHPC抗断裂能力,其长度不宜大于12 mm;聚酯纤维的直径不宜大于0.75 mm;混掺弹性模量较高的非金属纤维更有利于改善UHPC抵抗断裂的能力,混掺纤维后显著提升了UHPC的断裂能. 展开更多
关键词 混杂纤维 超高性能混凝土 断裂性能 断裂能 断裂韧度 起裂韧度
下载PDF
分级真空管道交通系统气动能耗分析
16
作者 张子为 王英学 +2 位作者 孙浩程 古理全 任文强 《空气动力学学报》 CSCD 北大核心 2023年第7期112-119,I0002,共9页
真空管道交通系统通过营造密闭低气压环境实现列车超高速节能运行。为了实现列车明线与真空管道运行的无缝连接,设计了分级真空管道交通系统,采用分隔门将管道系统分段,合理调整各管段内初始气压,列车通过管道系统过程中调整分隔门的开... 真空管道交通系统通过营造密闭低气压环境实现列车超高速节能运行。为了实现列车明线与真空管道运行的无缝连接,设计了分级真空管道交通系统,采用分隔门将管道系统分段,合理调整各管段内初始气压,列车通过管道系统过程中调整分隔门的开关使相邻段气体混合,实现列车常压与低压环境运行的合理过渡。参考理想气体功能理论,采用数值计算的方法分析管道-列车系统气动能耗,探讨分级真空管道参数对气动能耗的影响规律。结果表明:选取合理参数,系统降低的气动阻力能耗大于真空势能损失,可实现气动节能;当布置过渡管段、设计较大阻塞比、较长中间管段,系统气动节能效果较好。以气动节能效果为设计标准的分级真空管道交通系统参数设计体系,可为未来超高速运输发展,以及真空管道的设计和运营提供新的思路和参考。 展开更多
关键词 分级真空管道 超高速列车 气动阻力能耗 真空势能损失 管道参数设计
下载PDF
Hot deformation behavior of a near alpha titanium alloy with/without thermal hydrogen processing 被引量:1
17
作者 Qing WANG Dongli SUN Xiuli HAN Weigong WANG 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2010年第2期106-112,共7页
The true stress-true strain curves of Ti-6Al-2Zr-IMO-IV alloy with hydrogen were obtained by hot compression test. The microstructures of the alloy before and after thermo-compression were observed. The apparent activ... The true stress-true strain curves of Ti-6Al-2Zr-IMO-IV alloy with hydrogen were obtained by hot compression test. The microstructures of the alloy before and after thermo-compression were observed. The apparent activation energies of deformation were calculated for the alloy with and without hydrogen. The behavior and mechanism of deformation for hydrogenated Ti-6A1-2Zr-IMO-IV alloy at high temperature were analyzed. The relationship between hydrogenation time and hydrogen content at 800 ℃ can be expressed as the equation: CH(t)=1.2-1.2exp(-t/120). The true stress-true strain curves of hot compression for Ti-6Al-2Zr-IMO-IV alloy with hydrogen first move down and then move up as hydrogen content increases. Appropriate hydrogen content can reduce the peak of flow stress to minimal value. The apparent activation energies of deformation of the alloy with 0.47% hydrogen content and without hydrogen were calculated as 140 kJ·mol^-1 and 390 kJ-mol^-1, respectively, at 800 ℃ and at strain rate 8.3×10^4 s^-1. The apparent activation energy of deformation increases when the strain rate enhances from 8.3×10^-4 s^-1 to 8.3×10^-2 s^-1. 展开更多
关键词 Titanium alloy thermal hydrogen processing Compression at high temperature Hot deformation behavior Apparent activa- tion energy of deformation Microstructure
原文传递
GAP/PET/RDX基推进剂的动态冲击及点火响应行为
18
作者 范颖楠 武毅 +5 位作者 文俊杰 王昱 杨争辉 吴迎春 李海涛 侯晓 《火炸药学报》 EI CAS CSCD 北大核心 2023年第4期335-344,共10页
针对含不同粒度环三亚甲基三硝胺(RDX)的叠氮缩水甘油醚(GAP)推进剂和聚对苯二甲酸乙二醇酯(PET)推进剂,利用分离式霍普金森压杆装置开展高应变率(1000~6000s^(-1))动态冲击实验,同时结合高速摄影和数字全息光学测量技术,采用3台高速摄... 针对含不同粒度环三亚甲基三硝胺(RDX)的叠氮缩水甘油醚(GAP)推进剂和聚对苯二甲酸乙二醇酯(PET)推进剂,利用分离式霍普金森压杆装置开展高应变率(1000~6000s^(-1))动态冲击实验,同时结合高速摄影和数字全息光学测量技术,采用3台高速摄像机同步观测推进剂在撞击条件下损伤演化、点火响应和能量增长过程。结果表明,GAP基推进剂在高应变率压缩下的强度极限较PET基推进剂最大提升了一倍,弹性模量在不同应变率下均提升了一倍以上;中等粒度RDX较粗粒度RDX推进剂的强度极限最大提升了80%,弹性模量最大提升了148%;此外,GAP基推进剂较PET基推进剂、粗粒度较中粒度推进剂在高应变率压缩条件下更易点火,但中粒度推进剂的燃烧反应较粗粒度更加剧烈和完全。 展开更多
关键词 材料力学 高能推进剂 RDX粒度 GAP基推进剂 PET基推进剂 动态力学性能 低速撞击 点火响应行为
下载PDF
Sodium bismuth titanate-based perovskite ceramics with high energy storage efficiency and discharge performance 被引量:1
19
作者 Jiahui Wang Fudong Zhang +2 位作者 Zhanhui Peng Xiaolian Chao Zupei Yang 《Journal of Materiomics》 SCIE 2022年第5期1077-1085,共9页
Designing dielectric materials with the tremendous energy storage density is fundamentally important for developing pulse power capacitors.An effective approach was proposed to favorably modify the dielectric energy s... Designing dielectric materials with the tremendous energy storage density is fundamentally important for developing pulse power capacitors.An effective approach was proposed to favorably modify the dielectric energy storage properties(ESP)of Bi_(0.5)Na_(0.5)TiO_(3) ceramics using CaTiO_(3) incorporation.The dielectric breakdown strength was effectively enhanced,and simultaneously the relaxor behavior was optimized to lower the remnant polarization,which is resulted from the decreased grains size with the introduction of Ca^(2+)ion.Remarkably,at a CaTiO_(3) doping level of 0.2,a 0.8Bi_(0.5)Na_(0.5)TiO_(3)-0.2CaTiO_(3)(0.8BNT-0.2CT)ceramic obtained both high energy storage density(Wtotal)of~1.38 J/cm^(3) together with excellent efficiency(h)of~91.3%.Furthermore,an ultrafast discharge response speed(t0:9)~94 ns was achieved in 0.8BNT-0.2CT ceramic,as well as tremendous current density(C_(D)~1520 A/cm2)and power density(P_(D)~115 MW/cm^(3)).This study not only revealed the superior ESP mechanism as regards Bi_(0.5)Na_(0.5)TiO_(3) based ceramics but also provided candidate materials in pulse power capacitor devices. 展开更多
关键词 Bi_(0.5)Na_(0.5)TiO_(3)ceramics Grain size Relaxor behavior high energy storage density energy storage efficiency Ultrafast charge-discharge
原文传递
高能球磨制备纳米WC-8(Fe/Co/Ni)RE硬质合金研究 被引量:8
20
作者 陈庚 栾道成 +1 位作者 董学涛 王伟 《西华大学学报(自然科学版)》 CAS 2009年第3期65-68,共4页
用高能球磨法及真空烧结工艺制备纳米WC-8(Fe/Co/Ni)RE硬质合金。球磨时间、烧结工艺、稀土添加量对合金性能有重要影响,通过对球磨时间、烧结工艺、稀土添加量等环节的优化控制,在球磨60小时、1430℃烧结、加入Y占Co重量1%情况下,可制... 用高能球磨法及真空烧结工艺制备纳米WC-8(Fe/Co/Ni)RE硬质合金。球磨时间、烧结工艺、稀土添加量对合金性能有重要影响,通过对球磨时间、烧结工艺、稀土添加量等环节的优化控制,在球磨60小时、1430℃烧结、加入Y占Co重量1%情况下,可制备出平均粒度为700nm左右、硬度达90.7HRA的纳米WC-8(Fe/Co/Ni)RE硬质合金。 展开更多
关键词 纳米硬质合金 高能球磨 稀土 真空烧结
下载PDF
上一页 1 2 6 下一页 到第
使用帮助 返回顶部