SUMMARY The phylogenetic and epidemic relationships of 104 clinical isolates Clostridium difficile from three hospitals different geographical population sources in China were investigated by multilocus sequence typing. Twenty-two types (STs) identified, four which, ST117, ST118, ST119 ST129, novel. No geographically specific host population-specific lineages found there was no correlation between origin or strain genotype. ST37 the dominant type our survey but novel STs underline high...

Based on the principle of vacuum counter-pressure casting, a low gas pressure infiltration technology was developed to fabricate Ni-coated carbon fiber reinforced A357 alloy composites. The soundness and microstructure as-cast composites were investigated. results show relative density increases with increase melt temperature, while it firstly then declines as temperature increased. enhancement can eliminate incomplete defects improve uniformity distribution. insufficient leads some...

In situ MgAl2O4p/6061Al composites were prepared by a combination of ball milling, hot rolling, and ultrasonic assisted direct melt reaction (DMR) process. The results showed that submicron SiO2 could be reacted to form bimodal type sized MgAl2O4 particles with nano size in an Al–Mg alloy melt. grain refinement achieved the formed matrix alloy. With increase content from 0.0 wt% 2.0 wt%, decreased 272.3 μm 74.4 μm, morphology α-AlFeSi phases changed coherent Chinese-script relatively single...

The dimensional accuracy of shells and binders investment casting which incorporation with selective laser sintering is investigated. results show that the colloidal silica higher than ethyl silicate, variation rate produced much lower silicate shells. Moreover, possesses better performance on environmental protection production cost control. These indicate comprehensive properties are silicate. Meanwhile, average single shell silicate-colloidal alteration was almost identical it other were...

The flow behaviors of molten Al alloy in sand mould cavity with varied gating system were simulated under vacuum counter-pressure casting and the ingate velocity was predicted using a software package. At same process conditions, investigated electrode contact method. comparison between results shows that good agreement is achieved. exceeding critical large deviation are detected during filling withⅠtypes system, resulting turbulent behavior. Whereas, take on stable pattern other cavity,...

The grade-controlled filling behavior of vacuum counter-pressure casting thin wall aluminum alloy was studied by numerical simulation and experimental investigation. According to the analysis under fixed pressure structure, technology suggested. result shows that velocity controlled on grade, resulting in smoothly sequential behavior, decreasing defects castings.

During vacuum counter-pressure casting, the vacuumization is an important stage for thin-wall and complicated aluminum alloy castings. Through testing analyzing numbers of pinhole grade samples under different degree, effect degree on counter- pressure casting molten studied. The results indicate has greater in vacuumizing process. smaller is, more are, higher is. Therefore, when small, appears easily. So doesn’t choose too but castings, big either. Appropriate from 20 KPa to 40 KPa.

The solidification pressure is one of the most important factors in counter-gravity casting process. Through testing and analyzing microstructures aluminum alloy castings under different pressure, effect on secondary dendrite arm spacing grain size studied. results show that with increase decreases. When 250 KPa, thick, SDAS 37.9μm, but when increases to 450 refinement obviously, 20.7μm, which reduced by 45.3% comparing KPa. Moreover, higher, feeding force becomes more evident, broken higher...

Rapid Investment Casting can overcome the cost involved in designing and fabrication of metal tooling for wax injection process. The present investigation is aimed to determine effects CAD model placement degree size on dimension error prototype base Selective Laser Sintering. experimental results show that change law length, width height different from each other, it mainly due intersection angle between important edge forming plane. When 0° 90°, staircase effect smaller accuracy higher,...

During filling process of vacuum counter-pressure casting, the pressurizing velocity is one most important parameters, and it affects whole molten metal quality castings, must be reasonably controlled chosen. Through analyzing casting process, results show that related with absolute temperature down kettle gas, radius rising tube, initial volume kettle, height from original position to top tube gas flux. When other conditions are same during proportional flux, linear. Meanwhile, through...

The flow behaviors under different filling pressures were observed using electrode contact method. relationships of recorded time and related point location analyzed deduced in terms the tendency. behavior figures plotted at according relationship. It was found that unstable pattern takes place because cross-sectional area changes abruptly from figures. According to energy conservation mass theory, relationship velocity pressure established. Combining this critical velocity, judgment...

Through testing and analyzing Surface micromorphology of protective film elemental composition content vacuum counter-pressure filling AZ91D magnesium alloy by SF 6 mixed gas, the effect concentrations on molten was studied. The results show that have greater alloy. With increase concentrations, surface filmof becomes more continuous dense. Meanwhile, mass fraction F atom is increased, O decreased. Moreover, F/O atomic ratio increases significantly too, so MgF 2 gradually. Therefore, depends...

Through analyzing and testing the microstructure property of ZL114A aluminum alloy castings under condition alternating electromagnetic field, effects intensity field on are studied. The results showed had a great influence castings. With increase grain size was more small, 10A current intensity, finest. Whereas, with further, is big. Meanwhile, in certain rang mechanical performance been improved comprehensively, its tensile 10MPa elongation increased by 30%.

In pressurizing process of vacuum counter-pressure casting, the pressure and velocity are very important parameters. Through testing change molten aluminum alloy furnace chamber temperature with time at difference velocity, effect on counter- casting is studied. The results indicate reduces abruptly beginning process, subsequently, it elevates to initial temperature. Moreover, finished in short time. But not obvious process. At identical bigger increase pressure. Similarly, pressure, too....

Four types of Super Typhoon drip emitter with trapezoidal channel were selected out for the investigation flow field channel, and CFD (Computational Fluid Dynamics) method was applied to simulate micro-field inside channel. The simulation results showed that discharge different turbulent model is 4%-14% bigger than experimental results, average deviation κ-ω RSM 5, 4.5 respectively, but solving efficiency obviously higher model.

The SLS (Selective Laser Sintering, SLS) technology can directly manufacturing any complex structure, however, due to the limitation of engineering factor, surface quality and dimension accuracy green part are still an outstanding problem. So, experimental methods were adopted study effect orientation on machining accuracy, will significantly affects outline stair-stepping phenomenon, then accuracy. samples different orientations including 0, 20, 45, 60, 90 degree fabricated, results...

The feasibility of especial technology which complex cavity aluminum alloy castings are formed by corroding pre-burying copper pipe core is discussed researching on the size and microstructure core. results indicate basically consistent with original castings, a dimensional tolerance in permission scope about 0.01mm. Meanwhile, wall identical that without corrosion. Moreover, because equal to chilled iron, bringing cold effect, crystal grain tinier. Therefore, using form casting entirely feasible.

The solidification and defects of Al/SiC Al/C composites were investigated by directional techniques. are greatly influenced temperature gradients, rates, the size SiC particles chemical composition magnesium, but slightly volume fraction silicon. shrinkage feeding is improved hybridizing carbon fiber bundles with 3 vol% particles. A model was proposed distance derived according to preform geometry.