Effect of the particle injection position on the performance of a cyclonic gas solids classifier

This study investigates the effect of the particle injection position on particle classification performance of a cyclonic classifier. The Rankine-type vortex flow in the cyclonic classifier is divided into three characteristic regions from the wall to the center according to the tangential and axial velocity distribution. Three representative particle injection positions are selected within those regions. The particle flow and the particle residence time are investigated via the Reynolds stress and discrete phase models. The simulation result shows that particles injected in the near-wall region provide the highest separation efficiency but the lowest classification accuracy. The residence time of particles injected within the region of maximum tangential gas velocity is shorter, facilitating a rapid and efficient particle classification. The powder classification experiment result confirms the simulation result and the feasibility of this method to enhance the separation degree of particles in the vortex flow.     

Effect of processing parameters on the particle size and stabilisation of titania sols

A systematic analysis of the main parameters affecting the characteristics of titania sols for photocatalytic applications prepared from the hydrolysis of titanium i-propoxide (TIP) is presented. Stable monomodal sols were obtained at peptization temperatures between 50^∘C and 70^∘C, for water/alkoxide molar ratios ranging from 250 to 1000 and acid/alkoxide molar ratios ranging from 0.4 to 0.7. Unstable sols with bimodal distributions were obtained at higher peptization temperatures. The peptization temperature was the parameter with the greatest influence, followed by acid concentration, whereas the water/alkoxide ratio showed little influence. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to verify the primary particle size as measured by photon correlation spectroscopy (PCS). The observations are explained using the Derjaguin, Landau, Verwey and Overbeek (DLVO) theory on suspension stability.     

Effect of ball milling parameters on the particle size in nanocrystalline powders

A model describing the mechanical comminution (ball milling) of crystals to nanocrystalline powders is proposed. It is shown that a fraction of the energy deposited in the processed material is spent for the creation of microstresses ?, which slows down the comminution process.     

Light transmission by a monolayer of particles: comparison of experimental data with calculation as a single-scattering approximation

The laws of light transmission by particle monolayers are investigated. The results of measurement of coherent transmission for monolayers formed by large nonabsorbing particles are presented. The obtained results are compared to the calculation in the single-scattering approximation. Good agreement between experimental and calculated data is shown.     

A study of the mechanisms of particle buildup on single ferromagnetic wires and spheres

Particle buildup processes for paramagnetic, diamagnetic and ferromagnetic particles in HGMS are reviewed, and new data are presented. Previously published data are discussed using the local flow velocity in the vicinity of a collection wire instead of the average flow velocity.     

Microstructural evolution in two-phase solids: morphological stability of near-periodic particle arrangements

Microstructural evolution in binary alloys is studied numerically using a sharp interface model and boundary integral techniques together with a time stepping scheme. Two-dimensional matrix-inclusion type microstructures are considered with an isotropic interfacial energy density and cubically orthotropic elasticity, being distinct in the two phases. An assumption of local equilibrium is applied which provides the coupling of the diffusion and the elasticity problems via an interfacial jump condition. Special attention is paid to the verification of a phenomenon observed in an earlier work: energy considerations suggested the possibility of sustained inverse coarsening leading to equilibrium microstructures with large numbers of small particles. It is found that, while such stationary states exist, their domain of attraction is rather small; reduction of surface area is the dominant driving force in the process.     

陶瓷膜过滤微米级颗粒悬浮液操作条件的影响

测定不同操作条件下陶瓷膜过滤微米级颗粒悬浮液的渗透能量数据,并与决定膜污染柚是的ｄｐ／ｄｍ的结合进行分析,确定了操作条件对微炫有颗粒悬浮液微滤过程的影响,获得了陶瓷膜微滤微米级颗粒悬浮液过程中操作条件方法。为促进陶瓷膜在涉及微米级颗粒悬浮液分离领域中的应用尊定基础。     

工艺参数对燃烧合成硼粉的纯度和粒度的影响

以B2O3粉为原料,Mg粉为还原剂,采用燃烧合成法制备硼粉,研究了不同的工艺参数(反应物量、反应配比和压片压力)对燃烧合成制备的硼粉纯度和粒度的影响,并确定了最佳工艺参数。通过扫描电镜(SEM)和能谱对产物进行分析,结果表明,反应物量为100g时产物粒度最小,硼元素的含量最高;反应配比(摩尔比)为1时粒度最小并且硼元素的含量最高;压片压力为5MPa时粒度最小,10MPa时硼元素的含量最高。     

Calculation of the single-scattering properties of randomly oriented hexagonal ice columns: a comparison of the T-matrix and the finite-difference time-domain methods

We calculated the scattering and absorption properties of randomly oriented hexagonal ice columns using T-matrix theory, employing analytic orientation averaging, and the finite-difference time-domain method, which uses a numerical procedure to simulate random orientation. The total optical properties calculated are the extinction efficiency, absorption efficiency, single-scattering albedo, and the asymmetry parameter. The optical properties are calculated at the wavelengths of 0.66, 8.5, and 12 mum, up to a size parameter of 20 at 0.66 mum and 15 at the two other wavelengths. The phase-matrix elements P11, P12, and P22 are also calculated and compared, up to a size parameter of 20 at 0.66 mum and 15 at 12.0 mum. The scattering and absorption solutions obtained from the two independent electromagnetic methods are compared and contrasted, as well as the central processing unit time and memory load for each size parameter. It is found that the total optical properties calculated by the two methods are well within 3% of each other for all three wavelengths and size parameters. In terms of the phase-matrix elements it is found that there are some differences between the T-matrix and the finite-difference time-domain methods appearing in all three elements. Differences between the two methods for the P11 element are seen particularly at scattering angles from approximately 120 degrees to 180 degrees ; and at the scattering angle of 180 degrees , relative differences are less than 16%. At scattering angles less than 100 degrees , agreement is generally within a few percent. Similar results are also found for the P12 and P22 elements of the phase matrix. The validity of approximating randomly oriented hexagonal ice columns by randomly oriented equal surface area circular cylinders is also investigated in terms of the linear depolarization ratio.     

Effect of humidity on nanoparticle-based chemiresistors: a comparison between synthetic and real-world samples

Chemiresistors based on metal monolayer-capped nanoparticles (MCNPs) are promising candidates for fast, inexpensive, and portable tracing of (bio)chemical species in the gas phase. However, the sensitivity of such sensors to humidity is problematic, limiting their reliable and reproducible application in real-world environmental conditions. In this work, we employed a compensation method to explore the effect of humidity on a single MCNP chemiresistor as well as on an array of MCNP sensors used to analyze either synthetic or real-world samples. We show that an array of MCNP chemiresistors is able to precisely detect and estimate subtle concentrations of (mixtures of) volatile organic compounds (VOCs) under variable backgrounds of 2-83% relative humidity (RH) only after humidity compensation. Humidity effects were also tested in two clinical trials aimed at detecting prostate cancer and breast cancer through exhaled breath analysis. Analysis of the results showed improved cancer detection capabilities as a result of RH compensation, though less substantial than the impact of RH compensation on synthetic samples. This outcome is attributed to one - or a combination - of the following effects: (i) the RH variance was smaller in the breath samples than that in the synthetic samples; (ii) the VOC composition in the breath samples is less controlled than the synthetic samples; and (iii) the responses to small polar VOCs and water are not necessarily additive in breath samples. Ultimately, the results presented here could assist the development of a cost-effective, low-power method for widespread detection of VOCs in real-world applications, such as breath analysis, as well as for environmental, security, and food applications.     

Effect of ageing on different modified bituminous binders: comparison between RTFOT and radiation ageing

Standard laboratory ageing methods of bitumen only take into account the effect of thermo-oxidation during the service life of a pavement but the effect of high energy cosmic radiation on site is not simulated in these procedures. The aim of the present work is to compare the laboratory simulated short term bitumen ageing (rolling thin film oven test) with ageing produced by short exposures of bitumen samples to Ultra Violet and gamma radiation. The influence of ageing agents on the thermal properties and rheological performance of the pristine and modified bitumen binders has been evaluated in this study. The thermal behavior of various aged bitumens is characterized by both isothermal as well as non-isothermal thermogravimetric analysis. The thermoanalytic investigations on bituminous samples are carried out to evaluate the thermal stabilities and activation energies of the binders and the life time prediction of the materials is made with the help of the kinetic information. It is found that modified bituminous binders are more resistant to heat and radiation. Different rheological tests are conducted by dynamic shear rheometer to examine the effect of ageing in terms of bitumen oxidation and polymer phase degradation which has a major consequence on high temperature rutting or low temperature cracking. Type of modifier is found to be of decisive importance. Creep and recovery tests show that the structure-time dependency of pristine aged bitumen is influenced much by stress and temperature than in the case of modified aged bitumens. The study has revealed that the elastomeric modifier protects the bituminous binder more than plastic modifier or nano filler. Finally, a fair correlation has been made between standard RTFO ageing and radiation aging.     

Flow of granular materials in a bladed mixer: Effect of particle properties and process parameters on impeller torque and power consumption

The torque and power needed to drive an impeller are important quantities that can indicate flow behavior and can be used to control processes, especially mixing and granulation in the pharmaceutical industry. In this study, experiments were conducted on monodisperse spherical glass beads flowing in a cylindrical bladed mixer agitated by an impeller. The impeller torque was measured using a rotating platform and a data recording device, and the power draw for the motor driving the impeller was measured using a power meter. The effect of various impeller blade designs and material properties on the torque and power were investigated as a function of the impeller blade rotation rate. It was found that the torque exerted on a granular bed and the power consumption were a strong function of the impeller blade configuration, the position of the blades in a deep granular bed, the fill height of the glass beads, and the size and friction coefficient of the particles. It was observed that the time-averaged torque and power consumption for different particle sizes qualitatively scaled with particle diameter. A scale-up relationship for a deep granular bed was developed: the time-averaged torque and average adjusted power consumption scaled with square of the material fill height.     

Cohesive zone representations of failure between elastic or rigid solids and ductile solids

A cohesive zone model that describes tangential separation as well as normal separation along an interface is reviewed. The model is based on nonlinear traction-separation relations between the normal and tangential components of the interface tractions and relative displacements. To illustrate the application of the cohesive zone model in studies of material failure or crack growth, analyses of matrix-fibre debonding in metal matrix composites are presented, taking into account effects of residual stresses or of nonlocal plasticity for the matrix. Also studies of interface crack growth under mixed mode conditions are discussed.     

Effect of consecutive driving on accident risk: A comparison between passenger and freight train driving

This study combined driver-responsible accidents with on-board driving hours to examine the effect of consecutive driving on the accident risk of train operations. The data collected from the Taiwan Railway Administration for the period 1996–2006 was used to compute accident rates for varied accumulated driving hours for passenger and freight trains. The results showed that accident risk grew with increased consecutive driving hours for both passenger and freight trains, and doubled that of the first hour after four consecutive hours of driving. Additional accident risk was found for freight trains during the first hour due to required shunting in the marshalling yards where there are complex track layouts and semi-automatic traffic controls. Also, accident risk for train driving increased more quickly over consecutive driving hours than for automobile driving, and accumulated fatigue caused by high working pressure and monotony of the working environment are considered to be the part of the reason. To prevent human errors accidents, enhancing safety equipment, driver training programs, and establishing a sound auditing system are suggested and discussed.     

Total Lagrangian particle method for the large-deformation analyses of solids and curved shells

A high-accuracy smoothed-particle hydrodynamics (SPH) method for a large-deformation solid is developed from two aspects: improving the completeness of the approximation function and deducing the governing equation in the undeformed configuration. On the basis of Combescure’s researches and our previous studies, the SPH shell theory based on the Mindlin–Ressiner plate is detailed, which has overcome the unbridgeable drawbacks of solid modeling of thin structures and pushed forward the engineering applications of solving large-deformation and other nonlinear issues. Afterward, several treatments of SPH solid and shell are carried out, including the hourglass mode, boundary conditions and irregular structures; moreover, the corresponding validations are also conducted to reveal the feasibility and effectiveness of the proposed treatments. Finally, the accuracy of the present SPH program is verified further through two benchmarks of a curved shell.     

Ultrasonic evaluation of geometrical and surface parameters of rough defects in solids

Ultrasonic measurements from rough cracks were carried out using both broad-band and narrow-band methods. An analysis is suggested to determine parameters of the crack quantitatively such as size, shape, rms surface roughness, and distribution function of the surface roughness. Ultrasonic measurements of the parameters compare very well with the actual parameters of the defect.     

The effects of RESS parameters on the diclofenac particle size

The RESS method was used to manufacture the fine particles of diclofenac. A reduction in particle size increases the dissolution rate of the drugs in the biological fluids and enhances the bioavailability of them in body. CO2 was used as the supercritical fluid because of its mild critical temperature (31.1 °C) and pressure (7.38 MPa). In this study, effect of extraction temperature (313–333 K), extraction pressure (14–220 MPa), spraying distance (1–10 cm), nozzle length (2–15 mm) and effective nozzle diameter (450–1700 μm) were investigated.Based on the different experimental conditions, the average particle size of diclofenac was between 10.92 and 1.33 μm. The size and morphology of the micronized diclofenac particles were monitored by scanning electron microscopy (SEM). The SEM images show a successful size reduction of virgin diclofenac particles. In all the experiments, the parameters had moderate effect on the mean particle size of the diclofenac. Also, the morphology of the processed particles was change to quasi-spherical and irregular while the virgin particles of diclofenac were irregular in shape.