共查询到20条相似文献,搜索用时 46 毫秒
1.
Ultrasonic guided wave focusing by a generalized phased array is studied based on dispersion curves in a multi-layered medium. The different phase of the guided waves with different frequency is added on the excitation signal on each element of the transducer array for focusing. This can be realized by designing a proper excitation pulse based on the dispersion curves of the guided waves for each of the transducer array elements. The numerical simulation results show that the guided waves with different modes, different frequency components, and from different elements of the transducer array can all be focused at the target and focusing is achieved. 相似文献
2.
3.
4.
动态瞬时高压作用对膳食纤维酶解速度的影响 总被引:1,自引:0,他引:1
对纤维素酶对动态瞬时高压处理后膳食纤维的酶解速度进行了研究。豆渣膳食纤维(Dietary Fiber,DF)经微射流均质机的瞬时高压作用(Instantaneous High Pressure,IHP),在不同的压力以及同一压力的不同作用次数下产生不同粒径和密度,它们对应的酶解速度是不同的。纤维素酶水解膳食纤维产生纤维二糖和葡萄糖等还原糖,通过测定水解后还原糖的含量判断不同粒径和密度的膳食纤维的酶解速度。结果表明,在40~90 MPa的压力范围内随压力的增大物料粒径呈显著下降,物料密度随之增大,酶解速度增大,在90 MPa的均质压力下物料粒径达到最小,为202.4 nm;当压力继续增大时,物料因膨化作用,物料粒径呈增大趋势,但其密度开始减小,酶解速度继续增大,在140 MPa的均质压力下物料密度达到最小,为1.027 g/mL,此时酶解后还原糖含量最高,酶解速度最快。压力超过140 MPa后,由于超微颗粒间的团聚,物料的密度和粒径均增大,酶解速度减小。在90 MPa和140 MPa下对分别对物料进行多次的瞬时高压处理,发现随处理次数的增多物料粒径增大,体系密度先减小后增大,酶解速度减小。 相似文献
5.
Influences of different structures on the characteristics of H_2O-based and O_3-based La_xAl_yO films deposited by atomic layer deposition 下载免费PDF全文
H_2O-based and O_3-based La_xAl_yO nanolaminate films were deposited on Si substrates by atomic layer deposition(ALD). Structures and performances of the films were changed by different barrier layers. The effects of different structures on the electrical characteristics and physical properties of the La_xAl_yO films were studied. Chemical bonds in the La_xAl_yO films grown with different structures and different oxidants were also investigated with x-ray photoelectron spectroscopy(XPS). The preliminary testing results indicate that the La_xAl_yO films with different structures and different oxidants show different characteristics, including dielectric constant, equivalent oxide thickness(EOT), electrical properties, and stability. 相似文献
6.
CRT与LCD显示器色域特性研究 总被引:1,自引:0,他引:1
显示器的色域(Color Gamut)决定了显示器能够显示的颜色范围。由于CRT和LCD的显色原理不同,同样的RGB值在不同的显示器上将表现出不同的颜色。通过实验的方法,对不同显示器进行大量不同颜色样块的测量,研究比较LCD和CRT的显色特性和色域。结果表明:LCD的显示色域比CRT要小,并且基本上被完全包围,也就是在CRT上能表现出的图像颜色无法在LCD上表现出来;另外从颜色视觉的感知属性来看,它们所表现出来的颜色明度、彩度和色调范围也有很大的差别。 相似文献
7.
《中国物理 B》2018,(12)
As a convenient passenger transit facility between floors with different heights, escalators have been extensively used in shopping malls, metro stations, airport terminals, etc. Compared with other vertical transit facilities including stairs and elevators, escalators usually have large transit capacity. It is expected to reduce pedestrian traveling time and thus improve the quality of pedestrian's experiences especially in jamming conditions. However, it is noticed that pedestrians may present different movement patterns, e.g., queuing on each step of the escalator, walking on the left-side and meanwhile standing on the right-side of the escalator. These different patterns affect the actual escalator traffic volume and finally the passenger spatiotemporal distribution in different built environments. Thus, in the present study, a microscopic cellular automaton(CA) simulation model considering pedestrian movement behavior on escalators is built. Simulations are performed considering different pedestrian movement speeds, queuing modes, and segregation on escalators with different escalator speeds.The actual escalator capacities under different pedestrian movement patterns are investigated. It is found that walking on escalators will not always benefit escalator transit volume improvement, especially in jamming conditions. 相似文献
8.
本文采用直流磁控溅射法在三种不同的下电极(BEs)上制备了ZnO薄膜, 获得了W/ZnO/BEs存储器结构. 研究了不同的下电极材料对器件电阻开关特性的影响. 研究结果表明, 以不同下电极所制备的器件都具有单极性电阻开关特性. 在低阻态时, ZnO薄膜的导电机理为欧姆传导, 而高阻态时薄膜的导电机理为空间电荷限制电流. 不同下电极与ZnO薄膜之间的肖特基势垒高度对电阻开关过程中的操作电压有较大的影响, 并基于导电细丝模型对不同下电极上ZnO薄膜的低阻态阻值及reset电流的变化进行了解释.
关键词:
ZnO薄膜
电阻开关
下电极 相似文献
9.
V. P. Filippov D. E. Lauer Yu. A. Lauer N. I. Kargin P. G. Goloborodko I. V. Goloborodko A. M. Poliakov 《Hyperfine Interactions》2013,214(1-3):157-162
A study of the sea atmosphere influence on the corrosion products of steel constructions near Sochi at difference distances from the sea has been made. The phases and compositions of the corrosion products formed on different sides of steel construction elements were examined by using Mössbauer spectroscopy (at 298 and 78 K). The results show that phases and composition distributions in oxide films are different on different parts of the constructions. The differences depend not only on the distance from the sea, but from their relative orientation to the sea also. The phase structure of the oxide films on different positions is identified. 相似文献
10.
11.
The dependences of intermittency degree on moment-order, multiplicity and transverse momentum are discussed. The different dependences of intermittency degree on moment order at different energies are utilized to show that the dependences of intermittency degree on multiplicity are in opposite directions in low and high energy regimes. It is argued that these different trends imply that intermittency degree depends on other more basic quantity, such as transverse momentum. 相似文献
12.
13.
人工神经网络参数调整对生物光谱识别的影响 总被引:1,自引:0,他引:1
本文介绍了一种利用反向传播人工神经网络 (BP ANN)对生物可见光谱进行识别的方法。利用自组的光纤探头式光谱仪对苹果的疤痕和烂痕微区表面进行部分可见光范围 (5 0 0~ 730nm)的光谱测量 ,采用具有单隐层的BP ANN对光谱数据进行分析 ,以便对生物表面性质实现自动识别。本文着重就神经网络的输出值范围、训练方式、隐层数及不同程度的噪音信号等对神经网络识别精度的影响做了较为详尽的讨论。 相似文献
14.
基于随机激光的时域理论,利用时域有限差分法(FDTD)数值求解麦克斯韦方程组和速率方程组,利用分区域计算法,分别计算了整体和局部泵浦二维随机介质时,不同泵浦强度下,不同区域的辐射谱,得出了随机介质中模式的空间局域化分布。计算结果显示,同样条件下不同区域的辐射谱是不同的,且随着激励源泵浦强度的变化,随机激光辐射始终集中在介质中某几个固定区域,但各个区域的随机激射效率不同,在区域之间存在模式的空间范围重叠。利用该方法,可以分析介质的随机分布对随机激射的影响,理论上可以为高激射效率的伪随机介质制备提供一定指导。 相似文献
15.
基于不同色散光纤的光纤链的孤子传输研究 总被引:2,自引:2,他引:0
对不同色散光纤组成的光纤链在放大距离内的孤子传输进行了数值和实验研究,结果表明:不同的光纤组合有着不同的结果,因此在孤子传输时存在着合理地组合不同色散光纤的问题,而且即使同一根由不同色散组成的光纤链,当入纤方向了出纤方向交换时,实现孤子传输所需要的能量及孤子传输的稳定性也是不一样的。 相似文献
16.
17.
利用自组的光纤探头式光谱仪对载体肉类表面进行光谱测量,采用反向传播人工神经网络(BP-ANN)对肉类可见光谱进行识别,分析了隐层神经元、期望误差、判别输出范围等网络参数的调整对识别功能的影响.基于大量实测数据样本,优化网络结构参数选择,建立了良好的人工神经网络,对肉类光谱识别率达到97.5%. 相似文献
18.
应用红外光谱研究电场对超氧化物歧化酶二级结构的影响 总被引:1,自引:0,他引:1
超氧化物歧化酶经不同强度的电场处理,利用红外光谱法研究电场对超氧化物歧化酶二级结构的影响。结果表明,经不同电场强度处理的超氧化物歧化酶(SOD),其二级结构单元百分含量有不同程度的变化。α-螺旋和β-折叠结构单元在电场处理后,均为减少;β-转角结构单元均为增加;无规卷曲结构单元除4.0 kV·cm-1电场处理条件减少外,其余电场处理条件均为增加。电场处理具有使超氧化物歧化酶的α-螺旋、β-折叠向β-转角和无轨卷曲结构转化的作用,且不同电场条件下其转化情况不同。研究结果还表明,电场的作用使SOD活性发生改变,SOD活性变化与β-折叠含量变化相关。 相似文献
19.
针对纳秒脉冲和飞秒脉冲不同的损伤机制,分别建立了两种多脉冲激光损伤模型。脉宽小于10 ps时,损伤是由于等离子体形成造成介质发生烧蚀所致,对此建立了基于电子密度演化方程的介质击穿模型;脉宽大于100 ps时,损伤是由于热沉积造成介质发生熔融所致,对此建立了基于傅里叶热传导方程的介质热损伤模型。通过计算两种模型下激光参数和材料参数对多脉冲损伤的影响,发现由于损伤机理不同,不同参数对单脉冲损伤阈值和多脉冲损伤阈值的影响趋势不完全一致,敏感程度也不同。通过计算得到了与实验结果一致的多脉冲损伤阈值与脉冲数间关系,使定量预估多脉冲损伤阈值和元件使用寿命成为可能。 相似文献
20.
介绍了基于不同近似下的核温度的测量方法。不同测量方法给出的核温度不尽相同,这是因为它们使用的基本假设不一样。讨论了原子核系统的特殊性,这些特殊性使得核温度的提取特别困难。重点比较了动力学近似的几种温度计:使用经典Maxwell-Boltzmann 近似的,和使用量子Fermi-Dirac近似的。使用氦锂温度计对照考虑费米子属性后的斜率温度计和涨落温度计,发现考虑费米属性后提取的核温度更接近于热力学温度。仍需更多的工作,从核体系的孤立性、有限性和费米子属性等方面来研究核系统热力学温度的提取方法。Nuclear thermometers based on different approaches are reviewed. Due to the different basic assumptions of these methods, the nuclear temperatures extracted by different thermometer approaches are not consistent. Moreover,several problems which make the extraction of the nuclear temperatures even more difficult are discussed. The nuclear thermometers based on different kinetic approaches are compared. The nuclear temperatures extracted by methodsbased on quantum (Fermi-Dirac) kinetic approaches are compared to the double ratio temperatures THe; Li. Perspectives for future investigations of the thermal temperature are given. 相似文献