Several Kinds Of Particles Research Articles

Bis(2-ethylhexyl) phthalate transfer from polyvinyl chloride sheet to several kinds of particles

Bis(2-ethylhexyl) phthalate (DEHP) transfer from a polyvinyl chloride (PVC) sheet to 9 kinds of particles, namely, polyethylene particles (1–10, 45–53, 90–106 μm), soda lime glass particles (1–38, 45–53, 90–106 μm), black forest soil, carbon black, and cotton linter, for the particle weights of 0.3, 1, 3, and 12 mg/cm2, were determined for 1, 3, 7, and 14 days using a passive flux sampler (PFS), as well as standard dust. Transfer amounts to small polyethylene particles (1–10 μm), black forest soil, and carbon black were large (8.5, 16, and 48 μg/mg-particle, respectively, for 0.3 mg/cm2 for 14 days) and were similar to standard house dust (35 μg/mg-particle). On the other hand, transfer amount to large polyethylene particles (0.056–0.12 μg/mg-particle), soda lime glass (0.18–0.31 μg/mg-particle), and cotton linter (0.42–0.78 μg/mg-particle) were much lower. The DEHP transfer amount to the particles was proportional to the surface area of the particles, but not associated with the organic content. The DEHP transfer amount per surface area to small polyethylene particles was larger than that of other particles, suggesting the contribution of absorption into the polyethylene particle. However, for the larger polyethylene particles with different manufacturing process that may have different crystallinity, the contribution of absorption was small. The amount of DEHP transferred to soda lime glass did not differ from 1 to 14 days, suggesting that an adsorption equilibrium was reached after 1 day. The estimated value of particle/gas partition coefficients of DEHP, Kpg, of small polyethylene, black forest soil and carbon black were much higher (3.6, 7.1, and 18 m3/mg, respectively) than those of large polyethylene and soda lime glass particles (0.028–0.11 m3/mg).

Thickening of aqueous nanoparticle suspension using DC electric field

It is challenging to thicken a well-dispersed nanoparticle suspension without changing the particle dispersion state. In our previous report, we demonstrated that several kinds of particles can be quickly settled from solutions by applying a DC electric field. Thus, we attempted to gravitationally thicken a well-dispersed aqueous nanoparticle suspension using a DC electric field instead of a flocculant. To increase the recovery ratio of nanoparticles, it is necessary to prevent particle deposition on the electrodes. Therefore, in this study, we investigated the effect of switching the direction of the DC electric field after certain intervals, and clarified the effect of the switching time on the concentration and particle size of the concentrated suspension. The concentration of an alumina nanoparticle suspension quickly increased by a factor of at least three by applying the DC electric field. In addition, the particle size measured by dynamic light scattering after the application of the DC electric field was almost the same as the nominal average particle size, suggesting that the particles in the aggregates did not overcome the potential barrier and redisperse when the field was removed. Therefore, the use of the DC electric field successfully thickened the aqueous nanoparticle suspension and the particles in the thickened suspension were well dispersed. The findings show that the proposed method has the potential to change material fabrication processes, enabling a dilute nanoparticle suspension prepared by synthesis to be easily and rapidly concentrated.

Effects of liquid property on onset velocity of circulating fluidization in liquid-solid systems: A CFD-DEM simulation

Knowledge on regime transition from conventional to circulating fluidization is important to scale-up and operation of liquid-solid fluidized systems in industrial applications. Previous experimental studies reported that the onset velocity measured by bed empty time test is pertinent to the physical properties of particle and liquid, and independent of solid inventory, bed geometry, and configuration. The effect of liquid properties is, however, not clear yet since tap water is usually used as the working fluid in laboratory test for convenience. To address this problem, a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model is applied to numerically measure the onset velocity of particles in different liquid media. The model is first validated in terms of the experimental data of bed expansion in literature. Then several kinds of particles and three kinds of liquid media of different densities and viscosities are further simulated. We find that the Reynolds number based on onset velocity and Archimedes number follows a power-law relationship. With the decrease of Archimedes number, the discrepancy of Reynolds number based on onset velocity and that on particle terminal velocity becomes highly significant. The ratio of the onset velocity to particle terminal velocity for various particles in one liquid medium is not a constant, and instead dependent on both the particle and liquid properties.

Morphology of Proeutectoid Ferrite

The morphology of grain boundary nucleated ferrite particles in iron alloys with 0.3 mass pct carbon has been classified according to the presence of facets. Several kinds of particles extend into both grains of austenite and have facets to both. It is proposed that they all belong to a continuous series of shapes. Ferrite plates can nucleate directly on the grain boundary but can also develop from edges on many kinds of particles. Feathery structures of parallel plates on both sides of a grain boundary can thus form. In sections, parallel to their main growth direction, plates have been seen to extend the whole way from the nucleation site at the grain boundary and to the growth front. This happens in the whole temperature range studied from 973 K to 673 K (700 °C to 400 °C). The plates thus grow continuously and not by subunits stopping at limited length and continuing the growth by new ones nucleating. Sometimes, the plates have ridges and in oblique sections they could be mistaken for the start of new plates. No morphological signs were observed indicating a transition between Widmanstätten ferrite and bainitic ferrite. It is proposed that there is only one kind of acicular ferrite.

Quantifying the effect of fillers on the breakage behaviour of needle-shaped particles

Understanding the relationship between the applied stress and the behaviour of packings of breakable granular particles is required in many chemical engineering applications. A pharmaceutical tablet is an example where a composite packing (a packing containing a mixture of several kinds of particles) is compacted in the process of tablet formation. In this work, the unidirectional compaction and the breakage processes in composite packings formed from a mixture of breakable needle-shaped crystals and elastic spherical filler particles were studied using a Discrete Element Method (DEM) simulation. The evolution of crystal size distribution and contacts topology with the increasing stress was computed for different relative size, volume fraction and elasticity of filler particles inside the packing. We show that crystals breakability in a packing is directly related to the number of contacts among particles and that it can be significantly influenced by an appropriate choice of added filler particles. The results can be used for the development of mathematical models that describe the pharmaceutical tablet production and other processes involving composite packings of fragile particles.

Superlight particles in special polymetric spacetime theories

A variant of polymetric generalization of general relativity is discussed regarding the possibility of neutrino propagation with a superlight speed. The examined model admits coexistence in the same space–time manifold of several kinds of particles whose motion is described by different Riemannian metrics related by transformations of special type. It is demonstrated that the existence in the examined model of particles moving with superlight speeds does not lead to unavoidable violation of causality. It is also demonstrated that the superlight particles can contribute to the dark matter.

Surface photoelectric and photodegradation activities of AgNbO 3 synthesized by solvothermal method

Silver niobate (AgNbO 3) with different morphologies is obtained by annealing the precursors prepared at different temperatures by solvothermal method at 800 °C. Scanning electron microscope images of the samples show the formation process of the morphologies. The weakest photovoltaic and the highest photocatalytic properties of the sample obtained from the precursors prepared at 190 °C are possibly caused by the synergetic effects between several kinds of particles, and between AgNbO 3 and Nb 2O 5. Both the temperature and the amount of Nb 2O 5 are crucial for the morphologies, the photoelectric and photocatalytic properties of the samples.

Gel electrolytes containing several kinds of particles used in quasi-solid-state dye-sensitized solar cells

Composite gel electrolytes containing several kinds of particles used as the quasi-solid-state electrolytes in dye-sensitized solar cells (DSSCs) were reported. Mesoporous particles (MCM-41) with unique structures composed of ordered nanochannels were served as a new kind of gelator for quasi-solid-state electrolytes. MCM-41, hydrophobic fumed silica Aerosil R972 and TiO 2 nanopatricles P25 were dispersed into gel electrolytes respectively. The solar energy-to-electricity conversion efficiency of these cells is 4.65%, 6.85% and 5.05% respectively under 30 mW·cm −2 illumination. The preparation methods and the particles sizes exert an influence on the performance of corresponding solar cells. Owing to unique pore structures and high specific BET surface area, mesoporous silica MCM-41 was expected to have the potential to afford conducting nanochannels for redox couple diffusion.

Synthesis and thermally responsive properties of novel Pluronic F87/polycaprolactone (PCL) block copolymers with short PCL blocks

AbstractPolycaprolactone (PCL) was successfully grafted to both ends of Pluronic F87 block copolymers (PEO‐PPO‐PEO) to obtain novel amphiphilic PCL‐F87‐PCL block copolymers with short PCL blocks. The block composition and structure of PCL‐F87‐PCL block copolymers were studied by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetric (DSC), and wide angle X‐ray diffraction (WXRD) techniques. Several kinds of particles consisting of small micelles and medium and large aggregates were observed by laser light scattering (LLS) measurements because of the complicated structure of these copolymers. Importantly, PCL‐F87‐PCL block copolymers exhibit temperature‐sensitive behavior similar to that found in Pluronic systems. Compared with Pluronics, the critical micellization temperature (CMT) values of PCL‐F87‐PCL block copolymers obtained from surface tension measurements are significantly lower due to the enhanced hydrophobicity of PCL segments. A fully reversible sol–gel transition was detected for the PCL‐F87‐PCL hydrogels. Preliminary results show that there is no burst release for hydrophobic model drug, 9‐(methylaminomethyl) anthracene (MAMA), from PCL‐F87‐PCL hydrogel and the initial release rate is almost constant. This indicates that PCL‐F87‐PCL hydrogels possess attractive release profiles, which are beneficial for application in controlled release systems. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4163–4172, 2006

Numerical Simulation of Sand Erosion Phenomena in a Particle Separator

Erosive actions of solid particles within a flow field are very important in a great number of engineering applications such as aircraft, ship, turbo-machinery and so on, which is referred to erosion. We have developed the numerical method to predict sand erosion phenomenon and the temporal change of the eroded surface. Performing iterative computations for the turbulent flow field, the particle trajectories, the mass removed from a wall, and the deformation of the wall, the behavior of sand erosion can be simulated numerically. In the present study, our numerical procedure is applied to the particle separator of a helicopter engine. Several kinds of particles with different diameter and combinations of wall and particle materials are selected to clear the sand erosion phenomena within the separator. Investigating the numerical results, the characteristics of particle motions, the temporal change of wall shape and the reason for the deterioration of separation efficiency are clarified.

Defect production induced by electronic excitation in iron

The contribution of high-density electronic excitation to defect production in iron has been studied. Irradiations of iron thin films with several kinds of particles in the wide energy and mass ranges are performed at ∼77 K systematically, and the electrical resistivity change is measured in situ as a function of particle fluence. For each irradiation, defect production cross-section is derived from the resistivity change rate. From the experimental data, we extract a contribution of electronic excitation to the defect production cross-section. The primary ionization rate well describes the defect production in iron induced by high-density electronic excitation.

Dissipation and reduction effects of spontaneous localization on superconducting states

The problem of quantum measurement is briefly recalled with particular reference to theories of reduction as a real physical process. The spontaneous localization models for systems containing identical particles are described and the choice of the model when several kinds of particles are present is discussed. Dissipation and reduction effects induced by spontaneous localization in superconducting systems are analyzed. It is found that dissipation effects are negligibly small; on the other hand, reduction effects are present, but their characteristic time is long, say of the order of one hour. It follows that testing reduction experimentally is far beyond present day technology.

A stochastic discrete model for neutron transport in multiplying media

Abstract In the analysis of many reactor experiments the exploitation of the information contained in the fluctuations represents a powerful approach for estimating relevant kinetic parameters together with their corlfidence intervals. In the present paper a discrete multi-energy, multi-point stochastic reactor model is proposed in which the system is fed with the neutrons coming from poissonian sources. This generalization of the usual one-velocity, one-point stochastic reactor model allows a better treatment of actual situations. In the framework of the Kolmogorov and Dmitriev theory of the branching stochastic processes with several kinds of particles, the forward differential equation for the kernel probability generating function of the state of the system at any time is obtained. This function is then related to that concerning the neutron probability distribution in space, energy and time; moreover the link between the present stochastic approach and that resulting from the transport equation in th...

A Study of Airlift for the Feeder of Solids

Some experimental and theoretical studies of airlift, which is used for a feeder of particles in the pneumatic conveyance system are described. The feeding performances are obtained experimentally using several kinds of particles, and pressure losses in airlift are analysed to estimate the power required; which are compared with experimental ones. The drag coefficients of particles in a fully developed turbulent pipe flow are determined experimentally to make an accurate calculation of the pressure losses. The feeding performance of airlift can be represented by formulae using the results of a simple discharge test of particles from a two-dimensional port. The agreement of the calculated pressure losses with experimental ones is quite good when the calculation is made using the drag coefficient of particles obtained in the test.

Calculation of the energy distributions of light nuclei accompanying the fission of 236U

The Geilikman model dealing with the emission of α-particles in the fission of 236U is modified and extended to other particles. This model treats classically the motion of the third particle in the mutual Coulomb field of the two fragments. The system of these three bodies is parametrized in terms of the initial dynamic variables, some of them are arbitrary fitted. The calculations performed for several kinds of particles indicate that the approach which gives satisfactory fit for particles with Z = 2 demands quite different parametrization for particles with Z = 1.

超薄切片法による牛痘ウイルス感染組織の電子顯微鏡的研究

In the electronmicroscopic studies of the chorioallantoic membrane of chick embryos infected with vaccinia virus, the following results were obtaind.I. In the cytoplasm of infected cells of ectodermal layer were recognized classic inclusion body (Guarnieri's body) and matrix inclusion body.2. The nuclei of the cells in which these inclusion bodies were formed, were twisted.3. The classic inclusion bodies appeared close to nuclei, were one to four microns in diameter, and in most cases one body, rarely two, were found in one cell.4. Elementary bodies could not be found within the classic inclusion bodies. This is probably due to the fact that the inclusion bodies were in their premature stage of development.5. The matrix inclusion bodies are occupied by several kinds of particles having various developmental stage as well as mature viral particles.6. As to the mature virus particles within the matrix inclusion bodies, a marked uniformity in their sizes can be seen, but their shapes vary from round to oblong and do not show a typical square as is seen in the purified preparations of vaccinia virus.7. A marked inunifomity is seen among the inmature virus particles within the matrix inclusion bodies, and their sizes are larger than those of mature ones. Their shapes vary from round to oblong.8. Unrelated to these inclusion bodies, various virus particles are scattered in the cytoplasm.9. The change of mitochondria which may be related to virus development could not be seen.