Collision efficiency of two nanoparticles with different diameters in Brownian coagulation

The collision efficiency of two nanoparticles with different diameters in the Brownian coagulation is investigated. The collision equations are solved to obtain the collision efficiency for the dioctyl phthalate nanoparticle with the diameter changing from 100 nm to 750 nm in the presence of the van der Waals force and the elastic deformation force. It is found that the collision efficiency decreases as a whole with the increase of both the particle diameter and the radius ratio of two particles. There exists an abrupt increase in the collision efficiency when the particle diameter is equal to 550 nm. Finally, a new expression is presented for the collision efficiency of two nanoparticles with different diameters.

WALL EFFECTS ON FLOWS PAST TWO TANDEM CYLINDERS OF DIFFERENT DIAMETERS

Flows past two tandem cylinders of different diameters placed centrally in a channel with fixed centre-to-centre spacing 6D and diameter ratio are simulated based on the Lattice Boltzmann Method（LBM）.In all the simulations,the diameter of the smaller cylinder is chosen as the characteristic length.The Reynolds number based on the average inflow velocity is 20-120 and studies are over the range of blockage ratio 2-8.In both Small-Big Arrangement（SBA）and Big-Small Arrangement（BSA）,the effects of the channel width and Reynolds number on the flow structures and force coefficients are studied.Results show that the flows in BSA are more regular than those in SBA for the same flow fields.In BSA with and,the force coefficients all fluctuate with constant amplitudes and a coupled frequency,the coupled frequency becomes small as the blockage ratio decreases and by an exact test we give out the relation of the blockage ratio and Strouhal number.As the blockage ratio decreases to 2,there exist pitchfork bifurcations in both SBA and BSA,and results show that the critical Reynolds numbers of pitchfork bifurcations for SBA and BSA are both between 60 and 80.In SBA with,the flow structure has a static asymmetric mode.It is found that the channel width has also an effect on the critical spacing where the flow changes from single body mode into co-shedding mode.By an accurate survey on flows past two cylinders with equal diameters placed inside a channel with the width,the relation between channel width and the critical spacing is given and results show that the critical spacing increases as the channel width increases.

Effect of self-expanding bare metal stents of different diameters on the trachea of dogs

Objective To study the effect of self-expanding bare metal stents on the trachea of dogs,and therefore to provide useful information for choice of airway stents by interventional physicians.Methods In this experiment,8beagles were randomly divided into 4 groups.Four selfexpanding metal stents of different diameters(16,18。

SPECIATION OF Cu、Pb、Zn、Cr IN DUST OF DIFFERENT ORIGINS AND DIAMETERS

Various species of Cu.Pb,Zn and Cr in dust of different origins and diameters were studied using Tessler scheme,and the partition law was revealed, The results indicated that superior form of Cu、Pb、 Zn and Cr was bound to organic master,bound to Fe-Mn oxides,bound to Fe-Mn oxides and residual.So their activity order was Zn>Pb>Cu>Cr.The exchangeable metals bound to carbonates and Fe-Mn oxides of four heary metals in small particles were superior to those in large particles,which illustrated that heavy metals in small paticles were more active and harmful.

Numerical investigation on wheel-turnout rail dynamic interaction excited by wheel diameter difference in high-speed railway

The wheel-rail relationship in turnout is more complicated than that in ordinary track. Profile wear and machining errors of the wheelset cause deviations Of the rolling radius on different wheels. Therefore, wheelsets move to the direction of smaller diameter wheels in search of a new stable state and to change the condition before entering the turnout. Thc main aim of the present work is to examine the wheel-turnout rail dynamic interaction combined with the static contact behaviour. Calculations are performed on a high-speed vehicle CRH2 and the No. 12 turnout of the passenger dedicated line. The wheel-turnout contac! geometric relationship and normal contact behaviour under wheel diameter difference are assessed by the trace principle and finite element method. A high-speed vehicle-turnout coupling dynamic model is established based on SIMPACK software to analyse the wheel-rail dynamic interaction, riding comfort, and wear. Both the wheel diameter amplitudes and distribution patterns are accounted for. The simulation shows that wheel diameter difference can greatly disturb the positions＇ variation of wheel-rail contact points and affect the normal contact behaviour on switch rails by changing the load transition position. The effect of wheel diameter diffierence on wheel-turnout rail dynamic interaction can be divided into three according to its amplitude： when the wheel diameter difference is within 0-1.5 mm, the wheel flange comes into contact with the switch rail in advance, causing a rapidly increased lateral wheel-rail force; when it is within 1.5 2.5 mm, trains are subject to instability under equivalent in-phase wheel diameter difference; when it is larger than 2.5 mm, the continuous flange-switch rail contact helps strengthen the vehicle stability, but increases the wheel-rail wear. It is recommended to control the wheel diameter difference to within 2.5 mm but limit it to 2 mm if it is distributed in-phase.

Vibration of Axle Box from Wheel Diameter Difference in Vehicle

The wheel diameter difference would worsen the dynamic performance and affect the safety of the rail vehicle.Therefore,it is necessary to detect wheel diameter difference while the train is operating.However,several existing detection methods can’t accurately detect and diagnose the wheel diameter difference under highspeed running environment.In this study,a new method of detecting wheel diameter difference was proposed for high speed rail vehicle.The wheel diameter difference would be diagnosed by the amplitude and frequency of vibration impact on the axle box.Firstly,the dynamic model with varying wheel diameters was established in SIMPACK,and LMA tread was used in high-speed rail vehicles.Then,the simulation results of rail vehicle dynamic performance were compared under different wheel diameter differences.After that,the relationship between axle box vibration and wheel diameter difference was used to demonstrate the feasibility of this detection technology.Finally,comparing and analyzing the simulation results of vibration obtained by matching treads with different wheel diameters,it shows that by increasing the wheel diameter difference,the longitudinal and lateral impacts on axle boxes increase asymmetrically,and the amplitude and the frequency become more evident.Therefore,this paper presents a technical scheme of online measuring wheel diameter difference by monitoring the vibration of the axle box.