Continuous production of fine zinc oxide nanorods by hydrothermal synthesis in supercritical water

Continuous production of highly crystalline ZnO nanorods by supercritical hydrothermal synthesis was reported in this article. Zinc nitrate aqueous solution was pressurized to 30 MPa at room temperature and rapidly heated to 673 K by mixing with supercritical water and then fed into a tubular reactor. Residence time is about 10 s. Production of ZnO nanorod particles with uniform particle size distribution showed a strong ultraviolet light emission at room temperature. This article also reported in-situ surface modification of ZnO nanorods with organic reagents by the supercritical hydrothermal synthesis.     

Fine particle removal by a negatively-charged fine particle collector in silane plasma

To suppress inclusion of fine particles in amorphous silicon films, a negatively-charged fine particle (NFP) collector has been successfully installed in a silane plasma. Two modes of operation of the NFP collector biasing were examined: (i) turning on after the appearance of fine particles; and (ii) turning on from the very beginning of the plasma operation. While the former proved the effectiveness of the NFP collector in the removal of fine particles, apparently very small particles (<100 nm) removal in the latter reduced the degradation of the photo conductivity in deposited a-Si:H films by light soaking. This effect is accompanied by the increased density of SiH bonding, which can be related to the possible modification in the silicon networks in the amorphous film.     

Sorting of fine powder by gravitational classification chambers

Gravitational classification chambers (GCCs) were generally never used to classify fine powder because of its poor accuracy. However, in this study, a high quality closed-loop wind tunnel was designed and manufactured to improve this GCC drawback. A high quality closed-loop wind tunnel was designed to provide a low wall interference and low turbulence level in the test section. A wide-span feeder fed the powder smoothly as a curtain with a uniform aerodynamic interaction by the cross wind. The classification performance of GCCs has therefore been improved, and it could now classify lead–tin (Pb–Sn) powder with particle sizes smaller than 200 μm by controlling feeding rate and cross flow speed. Our experimental results show that GCCs have good classification performance from the view of the index of classification size ratio (CSR) by controlling cross flow speed and feeding rate. For GCCs the best sharpness index is about 0.4, the CSR is 1.09, and the cut size is 15.8 μm. The results demonstrate that GCCs had a fine powder classification capability and its cut-point was accurate enough for use in a classification operation. Furthermore, GCCs could be used to reduce ultra fine powder from raw powder. The volume percentage under 10 μm of raw material decreased from 7.61% to 0.64% through three repeatable classifications. This function could be considered as a good pre-process for specific classifiers (sieves or centrifugal classifiers). The product efficiency of this specific classifier could be increased by coupling it with GCCs.     

Synthesis of LiFePO4 with fine particle by co-precipitation method

LiFePO₄ is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO₄ because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe²⁺ in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO₄ is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO₄ fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property.     

Intrinsic coercive force variation with packing in fine particle assemblies

A formula is given to describe the variation of intrinsic coercive force with packing in elongated single domain (ESD) iron particle assemblies. A similar formula, which describes this variation in barium ferrite particle assemblies, is formally identical to the other one by simply changingp(packing) into1 - p(porosity). Magnetic interactions are considered, and an overall interaction field is defined that may account for intrinsic coercive force variations in the case of ESD iron particles. Experimental results on barium ferrite particle assemblies are presented that suggest the existence of a critical packing factor (p sim 0.15) separating two different, but not specified, modes of interaction.     

Selective collection of fine particles by water drops

This study was concerned with the interaction between a gaseous dispersion of fine particles travelling in the horizontal direction and discrete drops of water falling vertically through the dispersion. A simple analytical model of the particle–drop collision was developed to describe the particle recovery by the drops as a function of the water flux, covering two extremes of relative velocity between the particles and drops. The Discrete Element Method was used to validate the analytical model. Further validation of the model and insights were obtained through experimental studies. The physical process of wetting was observed to be important in influencing the tendency of particles to become engulfed by the drops of water, or to either adhere to the drops or by-pass the drops altogether. Hydrophilic particles were readily engulfed while hydrophobic particles, at best, adhered to the surface of the drop, or failed to attach. Moreover, the recovery of the hydrophilic silica particles was significantly higher than the recovery of hydrophobic coal particles, with the selectivity ratio approximately 1.5. Spherical ballotini particles were the most sensitive, with a notable increase in recovery when cleaned, and evidence of increased recovery with increasing particle size. The recovery of irregular shaped silica flour particles, however, was largely independent of the particle size. A similar result was observed for irregular coal particles, though the recoveries were all lower than relatively more hydrophilic ballotini or silica flour.     

Preparation of ZnS and CdS fine particles with different particle sizes by a spray-pyrolysis method

In the preparation of ZnS and CdS fine particles by an ultrasonic spray-pyrolysis method, the particle size was changed from submicrometre to micrometre size by changing the concentration of the metal nitrates in the starting aqueous solution containing Zn(NO3)2 or Cd(NO3)2 and SC(NH2)2. The effects of temperature profile in the reactor furnace on the properties of prepared particles were also investigated by varying the temperature profiles: constant and increasing temperature distributions. The volume mean diameter of the prepared particles was found to be approximately proportional to the one-third power of the concentration of the metal nitrates in the solution. The crystalline phase and fluorescence properties of ZnS and CdS particles did not depend on the particle size. This revised version was published online in November 2006 with corrections to the Cover Date.     

Continuous dielectrophoretic size-based particle sorting

Continuous-flow dielectrophoretic (DEP) particle separation based on size is demonstrated in a microfluidic device. Polystyrene microspheres suspended in a neutrally buoyant aqueous solution are used as model particles to study DEP induced by an array of slanted, planar, interdigitated electrodes inside of a soft-lithography microchannel. The E-field gradients from the slanted electrodes impart a net transverse force component on the particles that causes them to "ratchet" across the channel. Over the length of the device, larger particles are deflected more than smaller particles according to the balance of hydrodynamic drag and DEP forces. Consequently, a flow-focused particle suspension containing different-sized particles is fractionated as the beads flow and separate down the length of the device. The flow behavior of spherical particles is modeled, and the total transverse particle displacement in the microfluidic device predicts fourth-order size and voltage and second-order inverse flow rate dependences. The model is verified experimentally for a range of flow rates, particle sizes, and E-field strengths.     

Supervised algorithms for particle classification by a transition radiation detector

Support vector machines (SVMs) provide an interesting computational paradigm for the classification of data from high-energy physics and particle astrophysics experiments. In this study, the classification power of SVMs is compared with those from standard supervised algorithms, i.e. likelihood ratio and artificial neural networks (ANN), using test beam data from the transition radiation detector prototype of the PAMELA satellite-borne magnetic spectrometer. Concerning signal/background discrimination, SVM and ANN show the best performance. Moreover, our analysis shows that the use of SVM allows an accurate estimate of the discrimination efficiency of unseen data points: indeed, since almost the same efficiency is obtained with or without the cross-validation technique, the performance of SVM appears to be stable. On the other hand, the ANN shows a tendency to overfit the data, while this tendency is not observed using SVM. For these reasons, SVM could be used in particle astrophysics experiments where, due to the harsh experimental conditions, efficient and robust classification algorithms are needed.     

Control of microbial adhesion using fine particle technology

Microbial adhesion to an interface plays an important role in many industrial bioengineering processes. Surface physicochemical properties can be treated as an indicator of the adhesive properties of microbial cells. In this paper, the application of the aggregation/dispersion technique used in fine particle technology to biotechnology is reviewed. By way of illustration, measurements of the surface characteristics of microbes living in an anaerobic digester, analysis of microbial adhesion and aggregation/coaggregation, and their application are introduced.     

Enhancing fine particle separation by hybrid-electrostatic-turbulence coagulation: An experimental and numerical investigation

The electrostatic precipitator(ESP) has low efficiency in removing sub-micron particles. Coagulation technology, as a fine particle pretreatment technology, uses an external effect to agglomerate and grow fine particles, increase the average particle size, and make it easier to remove by subsequent dust removal equipment. However, the coagulation efficiency of a single coagulation technology is limited. Aiming at the particle charging mechanism and coagulation mechanism in the electric/turbulent composite coagulation process of fine particles, this paper uses a combination of numerical simulation and experiment to study the effects of different structural parameters, discharge parameters and flue gas parameters on corona discharge and particle charge. On this basis, the coagulation characteristics of charged particles in the turbulent flow field are studied. The results show that, when the Angle between the tip of the arista electrode is 90°, the corona discharge effect is the best. With the increase of supply voltage and temperature, the charge of particles increases. When the applied positive voltage is 29 kV and negative voltage is ?35 kV, the total coagulation coalescence efficiency of fine particles reaches the maximum. The coagulation efficiency increases with the increase of temperature, but decreases with the increase of inlet flow rate.     

Simulated annealing: An application in fine particle magnetism

Using a model of a system of interacting fine ferromagnetic particles, a computer simulation of the dynamical approach to local or global minima of the system is developed for two different schedules of the application of ac and dc magnetic fields. The process of optimization, i.e., the achievement of a global minimum, depends on the rate of reduction of the ac field and on the symmetry of the ac field cycles, The calculations carried out to illustrate these effects include remanence curves and the zero field remanence for both schedules under different conditions. The growth of the magnetization during these processes was studied, and the interaction energy was calculated to best illustrate the optimization.     

Meshfree boundary particle method applied to Helmholtz problems

This paper is concerned with the boundary particle method (BPM), a new boundary-only radial basis function collocation schemes. The method is developed based on the multiple reciprocity principle and applying either high-order nonsingular general solutions or singular fundamental solutions as the radial basis function. Like the multiple reciprocity BEM (MR-BEM), the BPM does not require any inner nodes for inhomogeneous problems and therefore is a truly boundary-only technique. On the other hand, unlike the MR-BEM, the BPM is meshfree, integration-free, symmetric, and mathematically simple technique. In particular, the method requires much less computational effort for the discretization than the MR-BEM. In this study, the accuracy and efficiency of the BPM are numerically demonstrated in some 2D inhomogeneous Helmholtz problems under complicated geometries.     

Improved cuckoo search with particle swarm optimization for classification of compressed images

The need for a general purpose Content Based Image Retrieval (CBIR) system for huge image databases has attracted information-technology researchers and institutions for CBIR techniques development. These techniques include image feature extraction, segmentation, feature mapping, representation, semantics, indexing and storage, image similarity-distance measurement and retrieval making CBIR system development a challenge. Since medical images are large in size running to megabits of data they are compressed to reduce their size for storage and transmission. This paper investigates medical image retrieval problem for compressed images. An improved image classification algorithm for CBIR is proposed. In the proposed method, RAW images are compressed using Haar wavelet. Features are extracted using Gabor filter and Sobel edge detector. The extracted features are classified using Partial Recurrent Neural Network (PRNN). Since training parameters in Neural Network are NP hard, a hybrid Particle Swarm Optimization (PSO) – Cuckoo Search algorithm (CS) is proposed to optimize the learning rate of the neural network.     

Continuous ice slurry formation by using W/O emulsion with higher water content

A W/O (water-in-oil) emulsion was made from a water–lamp oil mixture with higher water content and a small amount of an additive of amino group-modified silicone oil, and the emulsion could be changed into an ice slurry by cooling with stirring. By using a new continuous ice formation system proposed by one of the authors of this paper, the ice slurry could be formed continuously and stably in an ice formation vessel made of stainless steel. From the experimental results, the conditions were clarified for realizing continuous ice formation for 10 h without ice adhesion to the cooling wall. Moreover, in order to propagate supercooling dissolution of the emulsion effectively and to decrease viscosity in the ice slurry, voltages were applied to the emulsion and ice slurry formed, respectively, and it was clarified that the voltage impression was effective for both.