Institute Of Mechanics,Chinese Academy of Sciences
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Early-age mortar and concrete strength monitoring using embedded smart piezoelectric module based on wave propagation technique
No full textReal-time monitoring of cementitious material strength development in construction is of great importance for safety and stability of engineering structures. In this paper, a new method for early-age strength prediction of mortar and concrete based on classical elastic wave theory is proposed, combining embedded smart piezoelectric module (SPM) and wave propagation (WP) technique. Two Wave Modulus of Elasticity (WMoE) are derived from wave velocities as the robust indicator to monitor the curing process for mortar and concrete, respectively. Further, series experiments were conducted to determine the optimal excitation wave frequency and waveform. The optimal excitation signals could be represented by a Hanning-windowed 5-peak sine wave with the frequency bandwidth of 100 kHz to 120 kHz. And the WMoE measured by embedded SPMs was verified by surfacepatched SPMs. Finally, the early-age strength prediction models for mortar and concrete are proposed based on the WMoE and actual compressive strength of specimens. The strength prediction model can accurately evaluate the curing process as well as predict strength development of cementitious materials. These results reveal that the proposed method could offer several advantages of reliability, quantitative precision, robustness, and real-time capability for monitoring and assessing the early-age strength development of cementitious materials
On the plasticity and inheritance in shear-band-rejuvenated metallic glasses
No full textStructural rejuvenation holds promise for enhancing the plastic deformability of metallic glasses. However, whether structural rejuvenation through the introduction of shear bands unequivocally leads to enhanced plasticity remains contentious. Herein, we investigated two metallic glasses with distinct initial energy states: as- cast and well-relaxed. These glasses underwent a 50 % thickness reduction through cold rolling. Cold rolling significantly reduces the plasticity of as-cast glasses but notably enhances plasticity along the rolling direction for annealed glasses. This underscores the dependence of plasticity in processed glasses on both the initial state and shear band distribution. Additionally, it was observed that cold-rolled glasses exhibit plastic anisotropy, and re- vitrified glasses remarkably inherit this behavior. Synchrotron X-ray diffraction analysis further revealed that the transformation from face-shared to edge-shared or vertex-shared medium-range orders plays a significant role in the plastic response of glasses. Our findings suggest that regulating shear band distribution, along with appropriate re-vitrification treatment, provides a promising strategy to tailor the structure and properties of metallic glasses
MD assessment of irradiation resistance of FeMnNiCr under successive bombardment
No full textThe irradiation resistance behavior of Co-free high-entropy alloy FeMnNiCr under successive bombardment is investigated by means of molecular dynamics simulations. There are much less residual defects in FeMnNiCr referring to Ni after prolonged irradiation and large-size defect clusters are observed in FCC Ni but not FeMnNiCr. The formation and growth of dislocations in FeMnNiCr are significantly suppressed. The migration barriers of interstitials are similar to these of vacancies in FeMnNiCr, resulting in a higher efficiency of defect recombination. The defects in Co-free FeMnNiCr show similar trends with NiCoCrFeMn and NiCoCrFe during the irradiation process, suggesting its good potential in nuclear structure materials applications
Absorption spectroscopy of AlO including photodissociation
No full textPhotodissociation of AlO may be important for the aluminium chemistry in various astrophysical regions. The photodissociation cross sections and rates of AlO were investigated over the temperature range from 0 to 15000 K in this work. Firstly, the state-resolved cross sections at the wavelength of 50- 5000 nm for transitions from the ground and first excited states were calculated using ab initio potential energy curves and transition dipole moments. The temperature-dependent cross sections were then obtained by assuming a Boltzmann distribution to describe the population of the initial state. Several common radiation fields (interstellar, solar and blackbody radiation field) were selected as the radiation fields, and then the photodissociation rates in different radiation fields were obtained. The photodissociation rates in all studied radiation fields exhibit a positive correlation with increasing temperature. This finding indicates that the total photodissociation rates are sensitive to the temperature. In addition, the photodissociation rates in the solar radiation field are higher than those in the interstellar radiation fields, indicating that photodissociation rate is associated with the type of radiation field in which the molecule is exposed. The calculated photodissociation cross sections and rates of AlO are useful to investigate the chemical evolution of the aluminum element in the interstellar environment
Effects of molecular interaction and liver sinusoidal mechanical properties on leukocyte adhesions
No full textIt is interesting to find pathologically that leukocytes, especially neutrophils, tend to adhere in the liver sinusoids dominantly but not in the postsinusoidal venules. While both views of receptor-ligand interactions and physical trapping are proposed for mediating leukocyte adhesion in liver sinusoids, integrated investigations for classifying their respective contributions are poorly presented. With a combination of Monte Carlo simulation and immersed boundary method, this study explored numerically the effects of molecular interaction kinetics and sinusoidal mechanical properties on leukocyte adhesion in liver sinusoid jointly. Results showed that, within the range of biological limitations, the lumen stenosis ratio, leukocyte stiffness, Disse space stiffness and endothelium permeability regulate the comprehensive adhesion process in a descending order of significance in the presence of receptor-ligand interactions. While leukocyte adhesions could be mutually promoted with proper combinations of leukocyte stiffness, lumen stenosis, and molecular interaction, the binding affinity is insensitive under the conditions with low leukocyte stiffness in normal lumen stenosis and high leukocyte stiffness in high lumen stenosis. This work deepens the understanding of recruitment mechanism of leukocyte in liver sinusoids
重稀土晶界扩散工艺制备高矫顽力钕铁硼磁体研究进展与应用现状
No full text重稀土晶界扩散技术是目前制造高矫顽力钕铁硼磁体最重要的一种技术手段。本文简要介绍了重稀土晶界扩散的概念及用于工程化制备高性能钕铁硼磁体的应用现状，重点分析了重稀土晶界扩散技术近年来最新的代表性研究成果，提出了该技术当前亟待攻克的几个主要问题。文章对重稀土晶界扩散制备高性能钕铁硼磁材的进一步发展和工程化应用具有一定的指导意义
面向空间引力波探测的激光精密指向机构关键性能测试（特邀）
No full text针对超前指向机构的测试需求，采用外差干涉光学系统和差分波前传感技术，以实现角度和距离的高精度一体式测量，并且对系统中的四种主要噪声源进行了分析。实验结果表明在10 mHz～1 Hz的频段内，所研制的超前指向机构指向控制噪声优于10 nrad/Hz1/2；在20 mHz～1 Hz的频段内，寄生位移噪声优于10 pm/Hz1/2。验证了超前指向机构的性能指标，为推进空间引力波探测的相关技术发展提供了一定的参考依据。</p
一种提升超高速碰撞模拟计算效率和稳定性的方法
No full text本发明提供了一种提升超高速碰撞模拟计算效率和稳定性的方法，其为提高模拟效率，通过建立超高速碰撞模型、设置对称约束、刚柔转换技术及并行处理，从而显著加快求解过程；此外，为增强求解的稳定性，通过静态内存分配，确保了求解过程的稳定性，减少了不必要的波动。本发明综合运用这些策略，可以有效提升超高速碰撞的模拟效率，为超高速碰撞研究提供更高效的计算支持
一种双模式变循环涡轮火箭发动机
No full text本发明公开了一种双模式变循环涡轮火箭发动机，该发动机设有两套相互独立的燃气发生器系统：常规高压核心机系统、火箭燃气发生器系统；它们共用一套低压转子系统；所述共用的低压转子系统包括共用低压涡轮方案、以及冠生涡轮方案；当采用共用低压涡轮方案时，共用的低压涡轮在两种不同工作模式下均被两套燃气发生器各自的燃气驱动转动；当采用冠生涡轮方案时，常规高压核心机系统的主燃烧室产生的燃气流吹动低压涡轮转动，火箭燃气发生器系统的火箭燃烧室产生的燃气流吹动冠生涡轮转动；本发明共用低压涡轮方案和冠生涡轮方案，当飞行马赫数达到2.5时，从混合排气涡轮风扇模式转换到空气涡轮火箭模式，发动机稳态推力出现陡升式增大
一种辐射预冷的稀薄气体捕集装置及实现方法
No full text本发明公开了一种辐射预冷的稀薄气体捕集装置及实现方法，包括捕集进气道和制冷机构，捕集进气道为飞行器的吸气式电推进系统提供收集空气颗粒的入口；制冷机构通过降低目标区域反射的反弹粒子的速度来提高气体捕集效率，设置于捕集进气道壁面上的目标区域，用于在捕集进气道进行气体补集过程中对捕集进气道的壁面目标区域进行降温以将目标区域的壁面温度降温至目标温度；根据飞行器内的空气颗粒密度调控制冷机构的开启，且根据飞行器的飞行位置以及捕集进气道内的壁面温度动态调控制冷机构的制冷能力；本发明降低壁面反射的反弹粒子的速度，从而降低了反弹粒子反向逃逸的概率，达到提高气体捕获率的目的，实现节能和提高空气捕集效率的双功能