Experimental study on the cavity evolution and liquid spurt of hydrodynamic ram

In research of the characteristics of the cavity evolution, the pressure, and the liquid spurt in hydrodynamic ram, the experiment of the high-velocity fragment impacting the water-filled container had been conducted. The relationships between the above three characteristics have been researched. The evolution of the cavity can be divided into three processes according to its shape characteristics. The first liquid spurt occurred in Process Ⅱ and the rest of it occurred in Process Ⅲ. The duration of the second liquid spurt is longer than the first liquid spurt. When the impact velocity of the fragment is less than996 m/s, the velocity of the second liquid spurt is the highest. When the velocity of the fragment is greater than 996 m/s, the velocity of the first liquid spurt is the highest. The maximum velocities of the first and second liquid spurt are 111 m/s and 94 m/s respectively. The pressure fluctuated sharply in Processes Ⅰ and Ⅲ. The maximum peak pressures in the shock and the cavity oscillation phases are15.51 MPa and 7.96 MPa respectively. The time interval of the two adjacent pressure pulses increases with the increase of the fragment velocity.

Analysis on the multi-phase flow characterization in cross-measure borehole during coal hydraulic slotting

Hydraulic slotting in a gas drainage borehole is an effective method of enhancing gas drainage perfor- mance. However, it frequently occurs that a large amount of slotting products （mainly the coal slurry and gas） intensely spurt out of the borehole during the slotting, which adversely affects the slotting efficiency. Despite extensive previous investigations on the mechanism and prevention-device design of the spurt during ordinary borehole drilling, a very few studies has focused on the spurt in the s Ottlng pro ] ＂ _ cess. The slotting spurt is mainly caused by two reasons： the coal and gas outburst in the borehole and the borehole deslagging blockage. This paper focuses on the second reason, and investigates the hydraulic deslagging flow patterns in the annular space between the drill pipe and borehole wall Results show that there are six deslagging flow patterns when the drill pipe is still： pure slurry flow, pure gas flow, bubble flow, intermittent flow, layering flow and annular flow. When the drill pipe rotates, each of those six flow patterns changes due to the Taylor vortex effect. Outcomes of this study could help to better understand the slotting-spurt mechanism and provide guidance on the anti-spurt strategies through eliminating the borehole deslagging blockage.

Optimization of reverse circulation bit based on field experiment

By field experiment in Sandaozhuang W-Mo mining area in Luanchuan of Henan Province, the authors analyzed the Experimental result of reverse circulation bit on the basis of different structures and obtained the following conclusion: the design parameter of reverse circulation bit, the number, diameter and angle of the spurt hole can influence on the reverse circulation effect. The bit with inner spurt hole is better obviously than that one without inner spurt hole in reverse circulation, one or two right and the best choice of inner spurt hole is that the diameter is Φ8, the angle is 30° dip up and the suitable number is two to three.

In vivo application of poly-3-hydroxyoctanoate as peripheral nerve graft

Objective:This study aims to investigate the degree of biocompatibility and neuroregeneration of a polymer tube,poly-3-hydroxyoctanoate(PHO)in nerve gap repair.Methods:Forty Wistar Albino male rats were randomized into two groups:autologous nerve gap repair group and PHO tube repair group.In each group,a 10-mm right sciatic nerve defect was created and reconstructed accordingly.Neuroregeneration was studied by sciatic function index(SFI),electromyography,and immunohistochemical studies on Days 7,21,45 and 60 of implantation.Biocompatibility was analyzed by the capsule formation around the conduit.Biodegradation was analyzed by the molecular weight loss in vivo.Results:Electrophysiological and histomorphometric assessments demonstrated neuroregeneration in both groups over time.In the experimental group,a straight alignment of the Schwann cells parallel to the axons was detected.However,autologous nerve graft seems to have a superior neuroregeneration compared to PHO grafts.Minor biodegradation was observed in PHO conduit at the end of 60 d.Conclusions:Although neuroregeneration is detected in PHO grafts with minor degradation in 60 d,autologous nerve graft is found to be superior in axonal regeneration compared to PHO nerve tube grafts.PHO conduits were found to create minor inflammatory reaction in vivo,resulting in good soft tissue response.

Calculating the Word Spurt

幼儿学习语言的过程一直以来都是学者们感兴趣的课题,而幼儿在14个月到18个月大之间掌握语言能力的突飞猛进更是引起学者的热烈讨论。最近有人通过给词语按照从具体到抽象的不同难度标上数字,并利用计算机运算的方法探索其中的奥秘,当然其科学性还有待进一步探究。