Effect of cross-flow on the frequency of bubble formation from a single-hole nozzle

Bubble formation from a single-hole nozzle placed vertically upward in a rotating water bath was investigated using a high-speed video camera. Air was used as the working gas. The measured values of the frequency of bubble formation, f _B, were compared with those observed in a stationary bath, f _B0. The velocity of cross-flow, ν_θ, affected the bubble formation significantly when it exceeded a critical value, ν_θc . The ratio of f _B to f _B0 was unity for ν_θ≦ν_θc , but it changed in a complex manner for ν_θ>ν_θc . In the latter case, when the air flow rate Q _g was relatively low, f _B/f _B0 became larger than unity irrespective of Q _g, and an empirical correlation of f _B/f _B0 was proposed as a function of ν_θ and the inner diameter of the nozzle, d _ni. As the gas flow rate increased, f _B/f _B0 decreased monotonically and became smaller than unity, and an empirical correlation of f _B/f _B0 was derived as a function of Q _g, ν_θ, and d _ni. These empirical correlations could approximate the measured values of f _B/f _B0 within a scatter of −15 to +20 pct.     

Decoupling properties of singular LQ regulation problem

Some properties of a limiting solution derived from a standard LQ regulator problem are discussed in the case where the input weighting matrix tends to zero, for a discrete time system. The explicit limiting solution is given in some literature. It is shown that the limiting solution is closely connected with a disturbance decoupling problem. Moreover it is pointed out that the limiting feedback gain with the help of feedforward gain constructs the decoupled system with the maximum number of blocks.     

遥操作工程机器人系统临场感技术研究——6自由度临场运动感觉反馈技术的研究进展

 研究开发出一种遥操作工程机器人系统,可以应用于诸如火灾现场的修复作业等广阔的领域．该系统由伺服控制的工程机器人、2根从远处操纵工程机器人的操纵杆、视频系统和6自由度运动模拟器组成．操作者坐于座椅上,座椅固定于运动模拟器的上方． 该系统需要解决的一个关键问题是如何使操纵者高质量地获得工作现场的临场运动感觉． 提出了一种6自由度临场运动感觉反馈方法,其信号源来自工程机器人上安装的6个加速度传感器． 该方法的有效性已为实验所证明,即应用6自由度运动模拟器不但可以高质量地模拟工程机器人单个自由度的运动：滚动、俯仰、转动以及前后、左右、上下的平移,而且可以高质量地模拟工程机器人的各种复合运动．     

飞秒激光作用下啁啾镜膜层内损伤相关动力学

光学元器件的激光损伤问题,一直以来都困扰着超强超短激光系统的进一步发展。飞秒激光领域,激光脉冲引起的光学器件损伤主要由材料的本征特性决定。光学材料内的多光子电离、雪崩电离、导带电子弛豫等一系列非线性过程,与材料的激光损伤过程密切相关。利用泵浦探测技术,采用中心波长为800 nm,重复频率1 kHz的飞秒激光脉冲,对Nb2O5/SiO2啁啾镜介质膜的内部与飞秒激光损伤相关的超快动力学进行了研究。发现强的泵浦光脉冲辐照结束后飞秒乃至几十皮秒的范围内,啁啾镜对探测光的反射率有一定程度的下降。反射率降低的主要原因是泵浦光在介质膜的Nb2O5层内激发的大量的自由电子对探测光吸收所致,且该过程对激光诱导损伤过程起主导作用。通过反射率的变化,对其介质膜内导带电子弛豫过程进行探究,测定得到其衰减寿命,分别为1.31、6.88、22.34 ps。     

Dislocation Motion in bcc Solid 3He

We have measured the shear modulus of bcc solid ³ He at 827 Hz using the high- Q torsional oscillator technique. We observed a decrease in the shear modulus from the low-temperature value G₀ to about 0.4G₀ at a molar volume of 24.80 cm ³/mole and to 0.6G₀ at 24.32 cm ³/mole near the melting point. The reduction of an effective shear modulus is explained by the dislocation theory of Granato and Lücke.     

Addressing temporal inconsistency in indirect augmented reality

Multimedia Tools and Applications - Indirect augmented reality (IAR) employs a unique approach to achieve high-quality synthesis of the real world and the virtual world, unlike traditional...