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11.
In shape memory materials,that have been trained to have a two way shape memory effect(TWSM),themartensitic variants are classified into two groups,i.e.,preferentially oriented variants and self-accommodatingvariants.Applied stress may promote or constrain the transition of preferentially oriented variants and so changetransformation temperatures but has no essential effect on self-accommodating variants.According to the pointof view mentioned above,some experimental phenomena during thermocycling of a TWSM device may be ex-plained,such as the absence of synchronization between the plot of resistance change.temperature and the plotof memory strain vs.temperature. 相似文献
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本文介绍了对逆变电源进行数字PID控制的原理和方法,分析了采样周期、PID参数及不同的焊接工况对控制特性的影响。试验表明,只要恰当地选择PID(或PI)参数,不仅能实现高精度的恒流控制,而且能使系统的动态性能显著提高。 相似文献
15.
提出一种带有同心条件的双椭圆弧拟合方法。该方法利用椭圆几何定义得到的残差来衡量误差,建立关于误差的最小二乘方程,进而采用迭代方法求出描述双椭圆弧的8个参数。算法仿真实验研究了椭圆弧度、长短轴比率以及样本噪声对算法的影响,研究表明弧度越大、长短轴比率较接近1.1、样本噪声较小的时候,算法较稳定、准确。该方法也可以扩展处理多个同心椭圆弧的拟合问题。 相似文献
16.
为研究应力三维度和塑性应变对金属材料微孔聚合型损伤发展和延性断裂过程的影响,用有限元法计算16Mn钢和两种铝合金材料不同缺口根半径拉伸试样的应力、应变分布. 结果表明:缺口根半径越小,最小横截面上周向和径向应变相差越大且越不均匀,并导致最小横截面上的应力三维度与Bridgman公式预测结果不一样. 材料性质和试样几何形状对应力三维度的影响很大:缺口根半径相同的3种材料试样最小横截面的应力三维度分布形态相似,但应力三维度峰值及其所处位置有所不同;同种材料的试样缺口根半径不同,应力三维度分布形态也不同. 相似文献
17.
Tamaki Naganuma 《Nano Research》2017,10(1):199-217
Cerium oxide nanoparticles (CONPs), widely used in catalytic applications owing to their robust redox reaction, are now being considered in therapeutic applications based on their enzyme mimetic properties such as catalase and super oxide dismutase (SOD) mimetic activities. In therapeutic applications, the emerging demand for CONPs with low cytotoxicity, high cost efficiency, and high enzyme mimetic capability necessitates the exploration of alternative synthesis and effective material design. This study presents a room temperature aqueous synthesis for low-cost production of shape-selective CONPs without potentially harmful organic substances, and additionally, investigates cell viability and catalase and SOD mimetic activities. This synthesis, at room temperature, produced CONPs with particular planes: {111}/{100} nanopolyhedra, {100} nano/submicron cubes, and {111}/{100} nanorods that grew in [110] longitudinal direction. Enzymatic activity assays indicated that nanopolyhedra with a high concentration of Ce4+ ions promoted catalase mimetic activity, while nanocubes and nanorods with high Ce3+ ion concentrations enhanced SOD mimetic activity. This is the first study indicating that shape and facet configuration design of CONPs, coupled with the retention of dominant, specific Ce valence states, potentiates enzyme mimetic activities. These findings may be utilized for CONP design aimed at enhancing enzyme mimetic activities in therapeutic applications. 相似文献
18.
Liang Zhang Ting Wang Bo Yuan Bin Yu Zhichao Chen 《Advanced Engineering Materials》2023,25(11):2201823
Herein, an innovative powder-cored wire arc additive manufacturing (PC-WAAM) process is proposed to fabricate γ-TiAl thin-walled intermetallic alloy. The metallography, phase composition, and mechanical properties at different thin-wall locations are characterized. The results show that the alternatively distributed layer-like microstructure composed of α2 (Ti3Al) and γ (TiAl) phases is obtained along the building direction. The content of α2 phase exhibits the tendency of decreasing from the bottom to top region. This unique microstructure characteristic is closely related to the typical thermal cycling history during deposition. Moreover, the tensile strength and microhardness of the top region are lower than the middle and bottom region. In general, the current PC-WAAM technique shows promising capability of fabricating γ-TiAl intermetallic alloy with low cost. This work becomes a valuable reference for understanding the evolution mechanism of microstructure and paves the way for the flexible and customized additive manufacturing of γ-TiAl alloy. 相似文献
19.
D. Kraft 《Optimization methods & software》2017,32(4):790-812
We present a model for image segmentation and describe a gradient-descent method for level-set based shape optimization. It is commonly known that gradient-descent methods converge slowly due to zig–zag movement. This can also be observed for our problem, especially when sharp edges are present in the image. We interpret this in our specific context to gain a better understanding of the involved difficulties. One way to overcome slow convergence is the use of second-order methods. For our situation, they require derivatives of the potentially noisy image data and are thus undesirable. Hence, we propose a new method that can be interpreted as a self-consistent gradient flow and does not need any derivatives of the image data. It works very well in practice and leads to a far more efficient optimization algorithm. A related idea can also be used to describe the mean-curvature flow of a mean-convex surface. For this, we formulate a mean-curvature Eikonal equation, which allows a numerical propagation of the mean-curvature flow of a surface without explicit time stepping. 相似文献
20.
讨论了16QAM调制时应用不同类型和参数的滤波器对系统性能的影响.针对16QAM的特点,采用了存储波形累加求和法来代替一般的滤波成形,提高了调制速度.并利用其相位对称的特点将波形存储表压缩为原容量的1/4,有效地节约了存储空间. 相似文献