Microscale particles

Ten Cate et al. (2004) were able to learn from their DNS about the mutual effect of microscale (particle scale) events and phenomena at the macroscale the particle collisions are brought about by the turbulence, and the particles affect the turbulence. Energy spectra confirmed that the particles generate fluid motion at length scales of the order of the particle size. This results in a strong increase in the rate of energy dissipation at these length scales and in a decrease... 

Crystallization, triggered by the addition of a miscible nonsolvent (antisolvent) to a solute-containing solvent system, can be used to produce microscale particles with narrow particle size distributions. The process is complex as it involves the coupling... 

In the formulation of a mesoscale model, the number-density function (NDF) plays a key role. For this reason, we discuss the properties of the NDF in some detail in Chapter 2. In words, the NDF is the number of particles per unit volume with a given set of values for the mesoscale variables. Since at any time instant a microscale particle will have a unique set of microscale variables, the NDF is also referred to as the one-particle NDF. In general, the one-particle NDF is nonzero only for realizable values of the mesoscale variables. In other words, the realizable mesoscale values are the ones observed in the ensemble of all particles appearing in the microscale simulation. In contrast, sets of mesoscale values that are never observed in the microscale simulations are non-realizable. Realizability constraints may occur for a variety of reasons, e.g. due to conservation of mass, momentum, energy, etc., and are intrinsic properties of the microscale model. It is also important to note that the mesoscale values are usually strongly correlated. By this we mean that the NDF for any two mesoscale variables cannot be reconstructed from knowledge of the separate NDFs for each variable. Thus, by construction, the one-particle NDF contains all of the underlying correlations between the mesoscale variables for only one particle. 

The other situation is on the microscale particles. They are particles less than 100 microns and they see largely the energy dissipation which occurs through the mechanism of viscous shear rates and shear stresses and ultimately the scale at which all energy is transformed into heat. 

H. Fudouzi, M. Kobayashi, N. Shinya Arrangement of microscale particles by electrification ... 

A partially blocked electrode is a macroscale electrode that is partially covered in electrochemicaUy inert microscale particles which block the dif-fusional path of electroactive solution-phase species to the electrode surface [14]. The inverse situation is an inert surface modified with a distribution of (usually hemispherical or spherical) electroactive nanoparticles such systems are currently finding widespread use in electroanalysis [15]. 

Nanoscale particles of a-Fe Oj have been reported to trigger different toxicological reaction pathways rather than microscale particles [6],... 

Such a velocity distribution given by Eq. 31 was verified experimentally by Yan et al. [8] in which a method is proposed to simultaneously determine the zeta potentials of the channel surface and the tracer particles in aqueous solutions. This is achieved by carrying out microscale particle image velocimetry (micro-PIV) measurements of the electrokinetic velocity distributions of tracer particles in both open- and closed-end microchannels under the same water chemistry condition. 

In the following, a method will be introduced for simultaneously determining the zeta potentials of both the microchannel surfaces and the tracer particles by using the microscale particle image velocimetry (micro-PIV) technique. 

Wereley ST, Gui L, Meinhart CD (2002) Advanced algorithms for microscale particle image velocimetry. AIAA 140 1047-1055... 

Improvements in the properties and performance of fiber-reinforced polymer matrix materials from the addition of nano- and microscale particles have been reported in the literature [8], The availabiHty of different types of nanoparticles offered the possibiHty to tailor fiber/matrix interactions at a nanoscale level. Recently, it has been proven that nanoparticles homogeneously dispersed in a polymer matrix are able to play a beneficial role on the fiber/matrix interfacial adhesion in different types of structural composites [ 11 ], as it will be shown later. Hence, regarding structural properties, nanocomposites appear particularly appropriate as means of enhancing the mechanical properties of conventional composites rather than their use as nanocomposites by themselves, except in some particular cases. 

A reduction of the required energy could be reached by the incorporation of conductive fillers such as heat conductive ceramics, carbon black and carbon nanotubes [103-105] as these materials allowed a better heat distribution between the heat source and the shape-memory devices. At the same time the incorporation of particles influenced the mechanical properties increased stiffness and recoverable strain levels could be reached by the incorporation of microscale particles [106, 107], while the usage of nanoscale particles enhanced stiffness and recoverable strain levels even more [108, 109]. When nanoscale particles are used to improve the photothermal effect and to enhance the mechanical properties, the molecular structure of the particles has to be considered. An inconsistent behavior in mechanical properties was observed by the reinforcement of polyesterurethanes with carbon nanotubes or carbon black or silicon carbide of similar size [3, 110]. While carbon black reinforced materials showed limited Ri around 25-30%, in carbon-nanotube reinforced polymers shape-recovery stresses increased and R s of almost 100% could be determined [110]. A synergism between the anisotropic carbon nanotubes and the crystallizing polyurethane switching segments was proposed as a possible... 

Reductive dechlorination of HCB can be achieved with the combination of electrokinetics with the appropriate catalysts such as nanoscale zero valent iron (NZVl). The electric field can be used as a mechanism for the delivery of NZVl into the soil [10]. Reductive dechlorination can be achieved in the soil or even upon the cathode if the contaminant reaches the cathode compartment. Other metallic catalysts such as Cu/Fe or Pd/Fe bimetal microscale particles were satisfactorily used with the same purpose. Dechlorination of hexachlorobenzene up to 98 % was achieved with Cu/Fe [27] and only 60 % with Pd/Fe [20]. 

Several techniques have been developed to measure the zeta potential, based on the principle of electrokinetics. In this entry, the conventional methods of measuring the zeta potential using the mechanisms of electrophoresis, streaming potential, and electroosmotic flow will be outlined first. Then, a novel method will be presented for simultaneously determining the zeta potentials of both the microchannel surfaces and the tracer particles by using the microscale particle image velocimetry (micro-PIV) technique. This method combines the theories of... 

Although the incorporation of microscale particles as fillers into polymers has been well explored scientifically, the decrease in size of particles to nanometers, and the simultaneous increase in interface area, results in extraordinary new material properties.In one such application, the flammability properties of polymers have been improved with the addition of nanoscale particles. These filled nanocomposites provide an attractive alternative to conventional flame retardants. At present, the most common approach to improving flammability is the use of layered silicates such as clays, as described in Chapter 3. However, there are many different shapes and types of nanoparticles. (Here, a nano scale particle is defined as having at least one dimension on the nanometer scale.) When all three dimensions are on the order of nanometers, we are dealing with true nanoparticles, such as spherical silica particles, having an aspect ratio of 1. Another type of nanoparticle has only one dimension on the nanometer scale. Such nanoscale... 

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