Statistical properties of visibility graph of energy dissipation rates in three-dimensional fully developed turbulence

We study the statistical properties of complex networks constructed from time series of energy dissipation rates in three-dimensional fully developed turbulence using the visibility algorithm. The degree distribution is found to have a power-law tail with the tail exponent α=3.0. The exponential relation between the number of the boxes N_B and the box size l_B based on the edge-covering box-counting method illustrates that the network is not self-similar, which is also confirmed by the hub-hub attraction according to the visibility algorithm. In addition, it is found that the skeleton of the visibility network exhibits excellent allometric scaling with the scaling exponent η=1.163±0.005.     

Art gallery problem with guards whose range of vision is 180

It is shown that in any polygonal art gallery of n sides it is possible to place n/3 point guards whose range of vision is 180° so that every interior point of the gallery can be seen by at least one of them. The guards can be stationed at any point of the art gallery. This settles an open problem posed by J. Urrutia.     

流速传感器定比例跟踪技术

本文根据作者所研制的流速传感器跟踪控制器川,阐述在水工、河工模型试验中,使流速仪的流速传感器自动按规定的比例跟踪水位变化的一种技术,该技术使流速仪始终能测到一定比例水深处的流速.     

玻璃微、纳米管及其在电分析化学中的应用

本文简单介绍了玻璃微、纳米管的发展历史及其制备进展。对其在分析化学中的应用进展,特别对其在液/液界面电化学和电分析化学研究中的应用进行了较详尽地评述和展望。     

轻质油料电导率仪检定方法研究

叙述轻质油料电导率仪的检定原理及检定方法。采用高阻结合标准物质的方法解决了轻质油料电导率仪无法检定的问题。     

用指针式晶体管毫伏表测非正弦周期电压有效值

指针式晶体管毫伏表可用于测量直流分量为零的非正弦周期信号电压的有效值.提出了改进其功能的设想.     

Computing a flattest, undercut-free parting line for a convex polyhedron, with application to mold design

A parting line for a polyhedron is a closed curve on its surface, which identifies the two halves of the polyhedron for which mold-boxes must be made. A parting line is undercut-free if the two halves that it generates do not contain facets that obstruct the de-molding of the polyhedron. Computing an undercut-free parting line that is as “flat” as possible is an important problem in mold design. In this paper, algorithms are presented to compute such a parting line for a convex polyhedron, based on different flatness criteria.     

Measurement of very small liquid flows

A measuring principle for the flow rate of liquid follows consists in the determination of the volume change of a liquid in a tank in relation to unit of time. The development and the realization of three measurement systems based on this principle are presented in this paper. The devices can measure liquid flows below 0.2 L/h. One flow meter uses an air bubble in the form of a stopper as tracer. A special design keeps the bubble in the measuring tube; it does not have to be replaced. Another flow meter measures the volume changes by determining the pressure at the bottom of a vertical tube. To achieve a continuous operation, a differential design with two corresponding tubes was realized. The third flow meter measures the mass of a drop at the end of a horizontal silicone tube working as a bending beam. The liquid flows through the tube and is forced to form drops at its end. Owing to their design, each of the three devices has distinctive characteristics. A theory of measurement systems that facilitates synthesis and analysis of measuring devices serves as the basis for the development of the flow meters.