Comparative Observation of Ar,Ar-H_2 and Ar-N_2 DC Arc Plasma Jets and Their Arc Root Behaviour at Reduced Pressure

Results observed experimentally are presented, about the DC arc plasma jets and their arc-root behaviour generated at reduced gas pressure without or with an applied magnetic field. Pure argon, argon-hydrogen or argon-nitrogen mixture was used as the plasma-forming gas. A specially designed copper mirror was used for a better observation of the arc-root behaviour on the anode surface of the DC non-transferred arc plasma torch. It was found that in the cases without an applied magnetic field, the laminar plasma jets were stable and approximately axisymmetrical. The arc-root attachment on the anode surface was completely diffusive when argon was used as the plasma-forming gas, while the arc-root attachment often became constrictive when hydrogen or nitrogen was added into the argon. As an external magnetic field was applied, the arc root tended to rotate along the anode surface of the non-transferred arc plasma torch.

Characteristics of Iron Droplet Ejection Caused by Gas Bubble Bursting Under Reduced Pressure

Bursting of gas bubbles on the free surface of liquid iron produces iron droplets that are ejected into the surrounding atmosphere. The influence of the freeboard pressure on gas bubble bursting was investigated by collecting and measuring the formed droplets in water and in liquid iron systems. In water model, it was found that gas bubbles expanded markedly during the floating up when the freeboard was evacuated but the influence of the freeboard pressure on the mass of ejection is not significant when the freeboard pressure varied from 0.01 to 0.1 MPa. Besides, in steel melt, the mass of ejection was increased by 2--3 times when the pressure was reduced from atmospheric pressure to 66.5 Pa.

Improved growth rate of anodized TiO2 nanotube arrays under reduced pressure field and light illumination

The one-dimensional titanium oxide(TiO_2) nanotubes(TONT) can be rationally fabricated in the fluoridecontaining electrolyte by electrochemical anodization. The high-speed growth of TONT for elongated nanotubes is highly desirable because the undesirable chemical etching will induce ‘‘nanograss" on the top of nanotubes and restrain the continued elongation of nanotubes. Herein, the external fields were employed to accelerate the growth of TONTs and obtain the elongated TONT arrays. A growth rate up to 18 lm/h was achieved under the presence of reduced pressure(0.07 MPa) and UV light(365 nm) stimulation. The generation of longer nanotube arrays could be attributed to the applied fields, which facilitate timely gas pumping out and induce chemical equilibrium shift forward. The TONT films obtained under different parameters were subsequently employed as anodes for photoelectrochemical(PEC) water splitting. The photocurrent(at 0 V vs Ag/Ag Cl) of TONT electrode obtained under external fields represented a 50% enhancement compared with the photoanode produced by the conventional method.

Study on Reducing Injection Pressure of Low Permeability Reservoirs Characterized by High Temperature and High Salinity

In view of the problems of high injection pressure and low water injection rate in water injection wells of low permeability reservoirs featuring high temperature and high salinity,two new surfactants were synthesized,including a quaternary ammonium surfactant and a betaine amphoteric surfactant.The composite surfactant system BYJ-1 was formed by mixing two kinds of surfactants.The minimum interfacial tension between BYJ-1 solution and the crude oil could reach 1.4×10^(-3) mN/m.The temperature resistance was up to 140℃,and the salt resistance could reach up to 120 g/L.For the low permeability core fully saturated with water phase,BYJ-1 could obviously reduce the starting pressure gradient of low permeability core.While for the core with residual oil,BYJ-1 could obviously reduce the injection pressure and improve the oil recovery.Moreover,the field test showed that BYJ-1 could effectively reduce the injection pressure of the water injection well,increase the injection volume,and increase the liquid production and oil production of the corresponding production well.

Pneumatic resistance network analysis and dimension optimization of high pressure electronic pneumatic pressure reducing valve

The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the resistance and pressure of three typical pneumatic resistances are obtained.Then,the method of static characteristics analysis only considering pneumatic resistances is proposed,the resistance network from gas supply to load is built up,and the mathematical model is derived from the flow rate formulas and flow conservation equations,with the compressibility of high pressure gas and temperature drop during the expansion considered in the model.Finally,the pilot spool displacement of 1.5 mm at an output pressure of 15MPa and the enlarging operating stroke of the pilot spool are taken as optimization targets,and the optimization is carried out based on genetic algorithm and the model mentioned above.The results show that the static characteristics of the EPPRV are significantly improved.The idea of static characteristics analysis and optimization based on pneumatic resistance network is valuable for the design of pneumatic components or system.

Reducing intrathecal pressure after traumatic spinal cord injury: a potential clinical target to promote tissue survival

Spinal cord injury （SCI） is an unexpected event that is both devastating and debilitating, resulting in not just motor and sensory loss, but also autonomic dysfunction of the bladder, bowel and sexual organs. Currently, there are no treatments available to improve outcome follow- ing SCI, leaving individuals with permanent and lifelong physical disability. Worldwide it is estimated that more than 500,000 people sustain a SCI each year, with average lifetime cost of paraplegia and quadriplegia estimated at $5 million and $9.5 million respectively. We therefore urgently need effective therapies to improve quality of life following SCI, and this requires a greater understanding of how cell and axonal injury develops after the traumatic event.

A new weakly alkaline slurry for copper planarization at a reduced down pressure

This study reports a new weakly alkaline slurry for copper chemical mechanical planarization （CMP）, it can achieve a high planarization efficiency at a reduced down pressure of 1.0 psi. The slurry is studied through the polish rate, planarization, copper surface roughness and stability. The copper polishing experiment result shows that the polish rate can reach 10032 A/rain. From the multi-layers copper CMP test, a good result is obtained, that is a big step height （10870 A） that can be eliminated in just 35 s, and the copper root mean square surface roughness （sq） is very low （〈 1 rim）. Apart from this, compared with the alkaline slurry researched before, it has a good progress on stability of copper polishing rate, stable for 12 h at least. All the results presented here are relevant for further developments in the area of copper CMP.

Advance of Study on Design Methods of Hydraulic System of Radio Remote Control of Construction Machinery

The working principle of radio remote controlling of construction machinery should be that signals of the radio wave from the transmitter obtained in the receiver were controlled and then changed into electronic analog or digital signals which can be used to drive different actuators and mechanisms of the vehicle.The vehicle could be acted by following the controlling instructions sent by the operator.The best operation mode of construction machinery is suitable not only to manual operating but also to remote controlling in the same vehicle.The design methods of the hydraulic system used for the radio remote controlling of construction machinery are discussed.The design methods of hydraulic circuits for the actuators controlled by solenoid on-off type valves,hydro-electronic multi-way proportional valves,closed loop proportional servo driver or three-way proportional reducing valves are discussed in detail (with real example).The design methods of the power shift transmission of electro-hydraulic controlling,the devices of braking and the directional streering are discussed in this paper.

Lin28B Expression in Reduced Uterine Perfusion Pressure Rat Model

Objective:Preeclampsia(PE)is a serious complication of pregnancy.Placental ischemia could be an initiating event,but the molecular mechanisms underlying PE are unclear.Lin28B,a paralog of Lin28 RNA-binding protein,is predominantly expressed in human placenta,and decreased Lin28B expression may play a role in PE by reducing trophoblast invasion.The current study was intended to verify whether Lin28B plays a role in the pathogenesis of PE in rat model for reduced uterine perfusion pressure(RUPP).Methods:We used RUPP rat model.The changes in blood pressure,24-h urine protein excretion,and fetal development in RUPP rats were recorded and compared to those of normal pregnant(NP)rats.Furthermore,the expression of Lin28B mRNA and protein in placenta was determined using quantitative real-time polymerase chain reaction,Western blotting,and immunohistochemistry.Results:The blood pressure,24-h urine protein excretion,and embryo absorption rate were significantly increased in RUPP rats on the 20^(th) day of gestational period compared with the NP rats(P<0.001).However,there was no difference in the weight of placenta in RUPP versus NP rats(P>0.05).The expression levels of Lin28B mRNA and protein in the placenta of RUPP rats were also significantly decreased in comparison to NP rats(P<0.001).Conclusion:Our results show that the expression of Lin28B in the placenta of RUPP rats is different from that in NP rats,thus suggesting a role of Lin28B in the pathogenesis of preeclampsia.

Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve

In this paper, a new pressure reducing valve （PRV） with an orifice plate is proposed. The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV. A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure, outlet temperature, velocity, and superheat. A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss. The governing equations for internal flow numerical simulation are composed of the continuity, momentum, energy and k-e transport equations, based on isotropic eddy viscosity theory. Different valve plug displacement models were built to describe the double throttling process. Our analysis shows that the steam pressure drops twice and the degree of superheat increases. There are also lots of eddies which clog the flow channel and disturb the steam flow in the valve cavity after the valve plug and the outlet cavity. After modifying the structure, the numerical results show a better performance of steam flow.

Modest Exercise Reduces Blood Pressure

笔者每日的工作就是坐于电脑前,不停地操作。久坐之下,必患痼疾。果然,我的血压逐年上升。30出头的我,万分焦急。常去健身中心,不锻炼到大汗淋漓,绝不回家。后来,有朋传经:锻炼不必“劳其筋骨”,适度即可。于是,我每日步行30分钟上班,半年下来,我的血压渐趋正常。今在网上读此文,大悟!朋友,记住:Even 30 to 60 minutes of exercise per week were sufficient!文章的调查方法真科学,我国的医学界怎么就不作如此调查呢?

Fluidization behavior of graphitized glassy particles in a fluidized carbon bed cooling process for investment casting

Fluidized Carbon Bed Cooling(FCBC)is an innovative investment casting process for directional solidification of superalloy components.It takes advantage of a fluidized bed with a base of small glassy carbon beads for cooling and other low-density particles that form an insulating layer by floating to the bed surface.This so-called“Dynamic Baffle”protects the fluidized bed from the direct heat input from the high-temperature heating zone and provides the basis for an improved bed microstructure.The prerequisites for a stable casting process are stable fluidization conditions where neither collapse of the bed nor particle blow out at excessive bubble formation occur.This work aimed to investigate the fluidization behavior of spherical carbon bed material in argon and air at temperatures between 20 to 350℃.Systematic studies at reduced pressures using the FCBC prototype device were performed to understand the stable fluidization conditions at all stages of the investment casting process.The particle shape factor and size distribution characterization and the measurement of the powder’s minimum fluidization velocity and bed voidage show that this material can be fully utilized as a cooling and buoyancy medium during the FCBC process.

Dynamic modeling and simulation of a pressurized system used in flight vehicle

For a typical pressurized system with a novel dual-stage gas pressure reducing regulator,a system model is established with modular models of various typical components. The simulation study on the whole working period shows that the general trends and magnitudes of simulation curves are in agreement with experimental measured curves. As the key component in the pressurized system, the regulator is studied by a series of numerical simulations to reveal the influences of various structure parameters on its stability. Furthermore, the variable ranges which can guarantee the stability of regulator and system are obtained to provide guidance for design. The modeling and analysis approach can be applied to other systems and components.

Research on Vane End Face of Cam-Rotor Vane Servo Motor Based on Disturbing Torque

Cam-rotor vane motor(CRVM) is one of the new continuous hydraulic servo motors with the characteristics of no pulsation of instantaneous flow rate and output torque,small volume and rotating inertia.It is one of the appropriate actuators for hydraulic servo system which has good dynamic and steady-state performance requirements.The ideal output torque of CRVM is pulseless,but the actual output torque of CRVM is pulsating.This is caused by the disturbing torque of contact components,especially the friction between vane and cam-rotor.In order to get better performance of CRVM,which means more stable output torque and smaller disturbing torque,we discuss four kinds of vane end faces(VEFs).Analytic formulae of the normal contact force and the disturbing torque caused by the vane are derived from systematical force analysis.The normal contact force and the disturbing torque vary through a period under different VEF,and the reduced oil pressure is simulated in this paper.The simulation shows that the VEF with the proper round and reduced oil pressure can significantly decrease the disturbing torque and get better servo performance.The experiment results verify the correctness of the theoretical analysis and simulation.