Electric ignition energy evaluation and the energy distribution structure of energy released in electrostatic discharge process

Ignition energy is one of tbe important parameters of flammable materials, and evaluating ignition energy precisely is essential to the safety of process industry and combustion science and technology. By using electric spark discharge test system, a series of electric spark discharge experiments were conducted with the capacitor-stored energy in the range of 10 J, 100 J, and 1000 J, respectively. The evaluation method for energy consumed by electric spark, wire, and switch during capacitor discharge process has been studied respectively. The resistance of wire, switch, and plasma between electrodes has been evaluated by different methods and an optimized evaluation method has been obtained. The electric energy consumed by wire, electric switch, and electric spark-induced plasma between electrodes were obtained and the energy structure of capacitor-released energy was analyzed. The dynamic process and the characteristic parameters （the maximum power, duration of discharge process） of electric spark discharge process have been analyzed. Experimental results showed that, electric spark-consumed energy only accounts for 8%-14% of the capacitor-released energy. With the increase of capacitor-released energy, the duration of discharge process becomes longer, and the energy of plasma accounts for more in the capacitor-released energy. The power of electric spark varies with time as a damped sinusoids function and the period and the maximum value increase with the capacitor-released energy.

Research on model testing of a new ultrasonic multi-wav detecting method

The traditional crack exploring method with echo （reflected wave） in metals is called the ＂single-wave detecting method＂ that uses a probe of single weight. This method is not able to detect directly the size and shape of the crack and the result can only be obtained by relative comparison, that is to compare the echo amplitudes of the unknown quantity （crack） with the known quantity （regular artificial crack） to determine the equivalent size and shape of a certain crack.

Direct Preparation of the Nanocrystalline MnZn Ferrites by Using Oxalate as Precipitant

Oxalate was generally used as a precipitant for synthesis of MnZn ferrites during the co-precipitation process. However, the MnZn ferrite couldn’t be directly obtained and a calcination process was needed. In this research, we reported a direct preparation of the MnZn ferrite nanoparticles by using co-precipitation method, together with refluxing process. XRD measurements proved that crystallite size of the obtained samples increased with an increase in pH value of the co-precipitation solution, and that the crystallite size of about 25 nm was obtained for the sample at a pH of 13. This sample showed the maximum Ms of 58.6 emu/g, which was about one times larger than that of 12 (pH value). Calcination to the obtained samples result in an enlargement in their crystal size and an improvement in their magnetic properties with an increase in temperatures. The samples calcinated in CO2 + H2 atmosphere presented good stability, and the maximum Ms value of 188.2 emu/g was obtained for the 1100。C-heated sample. Unfortunately, precipitation of some Fe2O3 at 800。C suggested poor stability of the nanocrystalline MnZn ferrite in N2 atmosphere.

Synthesis and Crystal Structure of the First Hybrid Manganese Phosphate with 1-D Framework of Dinuclear Structure

A novel hybrid manganese phosphate, [（bipy）Mn（H2PO4）2] （bipy = 2,2＇-bipyridine） 1, was synthesized, and its structure is characteristic of i-D framework involving a dinuclear structure made up of edge-sharing Mn（Ⅱ） octahedra. 1 crystallizes in the monoclinic system, space group C2/c with a = 12.230（2）, b = 17.800（4）, c = 13.530（3） A°, β = 105.00（3）°, V= 2845.0（10） A°^3, Z = 8. Dc = 1.892 g/cm^3, F（000） = 1640, Mr = 405.10,μ（MoKα） = 1.198 mm^-1, R = 0.0306 and wR = 0.0657 for 2093 observed reflections （I 〉 2σ（I））.

Adaptive DirectShow Framework for Layered MPEG-4 Video Multicast

An extensible framework was proposed to implement the hierarchical and adaptive control and feedback mechanism of layered MPEG-4 video multicast transmission in DirectShow architecture. In our framework, layers of MPEG-4 video and FEC data are wrapped dynamically in RTP packets to pass through the heterogeneous network effectively. An adaptive control center is designed to control the actions of the related components dynamically according to varying resources availability on local host and network. This effective and adaptive framework can be used to instruct the implementation of applications based on layered MPEG-4 video multicast transmission and other designs of multimedia application frameworks.

Experimental and LES investigation of flame propagation in a hydrogen/air mixture in a combustion vessel

This work presents an experimental and numerical investigation of premixed flame propagation in a hydrogen/air mixture in a closed combustion vessel.In the experiment,high-speed schlieren video photography and pressure sensor are used to examine the flame dynamics and pressure transient.In the numerical study,a large eddy simulation(LES)based on a RNG sub-grid approach and a LES combustion model is applied to reproduce experimental observations.The effects of four physical phenomena on the burning velocity are considered in the combustion model,and the impact of grid type on the combustion dynamics is examined in the LES calculations.The flame experiences four stages both in experiment and LES calculations with structured and unstructured grids,i.e.,spherical flame,finger-shaped flame,flame with its skirt in contact with the sidewalls,and tulip-shaped flame.The flame speed and pressure in the vessel develop with periodical oscillations in both the experiment and LES simulations due to the interaction of flame front with pressure wave.The numerical simulations compare well with the detailed experimental measurements,especially in term of the flame shape and position,pressure build-up,and periodical oscillation behaviors.The LES combustion model is successfully validated against the bench-scale experiment.It is put into evidence that mesh type has an impact to a certain extent on the numerical combustion dynamics,and the LES calculation on structured grid canpredict the flame dynamics and pressure rise more accurately than that on unstructured grid with the same mesh resolution.The flame shape is more asymmetrical in the LES on an unstructured grid than that on a structured grid,and both the flame speed and the pressure rise at the later flame stage are underestimated in the LES on the unstructured grid.