Experimental Study on Wire Melting Control Ability of Twin-Body Plasma Arc

The twin-body plasma arc has the decoupling control ability of heat transfer and mass transfer,which is beneficial to shape and property control in wire arc additive manufacturing.In this paper,with the wire feeding speed as a characteristic quantity,the wire melting control ability of twin-body plasma arc was studied by adjusting the current separation ratio(under the condition of a constant total current),the wire current/main current and the position of the wire in the arc axial direction.The results showed that under the premise that the total current remains unchanged(100 A),as the current separation ratio increased,the middle and minimum melting amounts increased approximately synchronously under the effect of anode effect power,the first melting mass range remained constant;the maximum melting amount increased twice as fast as the middle melting amount under the effect of the wire feeding speed,and the second melting mass range was expanded.When the wire current increased,the anode effect power and the plasma arc power were both factors causing the increase in the wire melting amount;however,when the main current increased,the plasma arc power was the only factor causing the increase in the wire melting amount.The average wire melting increment caused by the anode effect power was approximately 2.7 times that caused by the plasma arc power.The minimum melting amount was not affected by the wire-torch distance under any current separation ratio tested.When the current separation ratio increased and reached a threshold,the middle melting amount remained constant with increasing wire-torch distance.When the current separation ratio continued to increase and reached the next threshold,the maximum melting amount remained constant with the increasing wire-torch distance.The effect of the wire-torch distance on the wire melting amount reduced with the increase in the current separation ratio.Through this study,the decoupling mechanism and ability of this innovative arc heat source is more clearly.

Study on measures for water prevention and control in Chengchao Iron Mine,China

The gush-out water in the mineral pit endangers the underground mine safety directly. It is an important task for underground mine to guarantee its safety during the flood season. The authors analyzed the status of water prevention and control in Chengchao Iron Mine,China,and put forward the necessary measures. The hydrogeological parameter controls the design of mine water prevention and affects the mineral well safety in operation. Enhance supervision and control,keeping the current facilities intact,using the existing pump house and the underground tunnel to adjust and control the amount of water and improving the hydrogeological conditions in the mine are the practical and remedial measures.

本科毕业设计过程管理的探索

对本科毕业设计在新形势下出现的一些问题作了分析,并在毕业设计过程管理中作了一些探索,采取了一些措施,以保证毕业设计质量。通过加强毕业设计工作力度,如:建立产、学、研教学基地,加强校企合作;建立一整套毕业设计质量监控管理制度;增加综合性、设计性实验;开展毕业设计先期基础训练等。使学生的创新能力、实践能力和创业精神得到了培养,提高了毕业设计质量,增加了学生的就业竞争力和适应社会的能力。

Variable optical attenuators with ability to independently control two orthogonal linearly polarized light amplitudes

New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude.Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthogonal linearly polarized light amplitudes.Experimental results demonstrate that more than 30 dB difference in slow-and fast-axis light power can be obtained by controlling an MZM input DC voltage, and over 24 dB independent power adjustment for light traveling on the slow and fast axes into a dual-polarization MZM.

Investigation of Phase Excitation Effect on Mixing Control in Coaxial Jets

Detailed unsteady numerical simulation has been carried out to investigate the mechanism of adjacent syntheticjets and the influence of different phases on the mixing of coaxial jets. The results show the combined jet, formedby coupling the vortex pairs at the orifice of two adjacent actuators, can exhibit better controlling effect. Spanwisepressure difference appears because of the existence of phase difference between the left jet and right jet, whichresults in the variation of the combined jet. When the phase difference is greater than zero, mixing enhancementof coaxial jets can be achieved, but there are maximum phase difference and optimal phase difference. On thecontrary, application of adjacent synthetic jets always leads to the mixing reduction when phase difference is lessthan zero.