Results 11 - 20 of 157872
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[en] The authors consider the problem of particle transport including scattering in renewal statistical media. The general description of this problem leads to an infinite hierarchy of equations. A new closure scheme is developed to obtain a more tractable set of equations. Numerical results in planar geometry are given which compare the predictions of this new closure with exact benchmark results as well as with a previous model available in the literature. The development of the new closure and the comparisons the authors make underline the importance of having a physical basis in the elaboration of closure schemes for the hierarchy of equations describing the transport of particle with collisions in stochastic mixtures
[en] In this paper, we report a new method for size-based capturing of suspended particles by a specially designed micro fluidic structure named 'vernier walls'. A number of particles in suspension can be captured based on their sizes by a series of gaps between the closest walls, one standing on the ceiling and the other on the bottom of a wide microfluidic channel. The dimensions of the gaps narrow stepwise along the flow direction with a fixed step size per gap, which can be determined according to the required capturing resolution. Particles are captured based on their sizes in a line along each of the gaps with their corresponding dimensions. A part of the wide channel works as a bypass area, where the gap is constant to avoid clogging, letting the excess number of particles go through the channel. To realize the proposed structure, a new device assembly method has also been developed adopting planar gear-shaped structures surrounding the microfluidic channel solely for the fine and easy alignment of the narrowing gaps. The performance of the present method was evaluated using a device designed and fabricated for size-based capturing with a 5 µm resolution, and it was demonstrated that three kinds of particles with diameters from 10 to 26 µm were successfully captured by size. Additionally, we confirmed that the capturing rate was no less than 20% under the experimental condition. The present method can be used as a basic tool for handling particles with certain ranges of sizes.
[en] The magnetically induced yield stress in a sample of suspension of magnetic particles is associated with formation of a field-oriented structure, the strength of which depends on the degree of particles magnetization. This factor is largely defined by the actual magnetic field strength in the sample. At the same time it is common practice to present and analyze magnetorheological characteristics as a function of the applied magnetic field. Uncertainty of an influence function in magnetorheology hampers interpretation of data obtained with different measurement configurations. It was shown in this paper that rheological response of magnetorheological fluid to the applied magnetic field is defined by the sample's actual (internal) magnetic field intensity, which, in turn, depends on sample geometry and field orientation all other factors being equal. Utilization of the sample's actual field as an influence function in magnetorheology allows proper interpretation of data obtained with different measuring system configurations. Optimization of the actual internal field is a promising approach in designing of energy efficient magnetorheological devices.
[en] Colloidal dispersions are commonly encountered in everyday life and represent an important class of complex fluid. Of particular significance for many commercial products and industrial processes is the ability to control and manipulate the macroscopic flow response of a dispersion by tuning the microscopic interactions between the constituents. An important step towards attaining this goal is the development of robust theoretical methods for predicting from first-principles the rheology and nonequilibrium microstructure of well defined model systems subject to external flow. In this review we give an overview of some promising theoretical approaches and the phenomena they seek to describe, focusing, for simplicity, on systems for which the colloidal particles interact via strongly repulsive, spherically symmetric interactions. In presenting the various theories, we will consider first low volume fraction systems, for which a number of exact results may be derived, before moving on to consider the intermediate and high volume fraction states which present both the most interesting physics and the most demanding technical challenges. In the high volume fraction regime particular emphasis will be given to the rheology of dynamically arrested states. (topical review)
[en] Mathematical structural invariants and quantum theoretical descriptors have been used extensively in quantitative structure-activity relationships (QSARs) for the estimation of pharmaceutical activities, biological properties, physicochemical properties, and the toxicities of chemicals. Recently our research team has explored the relative importance of various levels of chemodescriptors, i.e., topostructural, topochemical, geometrical, and quantum theoretical descriptors, in property estimation. This study examines the contribution of chemodescriptors ranging from topostructural to quantum theoretic calculations up to the Gaussian STO-3G level in the prediction of the toxicity of a set of twenty halocarbons. We also report the results of experimental cell-level toxicity studies on these twenty halocarbons to validate our models
[en] In order to increase a write frequency in hard disk drive, suspension designers have introduced that the improvement of the write driver and read/write head. Another choice is the selection of the location of the driver IC chip. This paper is about the change of the resonant frequency of the chip-on-suspension both by moving the location and varying the mass. During operation the IC chip generates heat which causes the thermal deformation. Also the effect on variation of the head loading force resulted from the thermal stress and thermal deformation is investigated. The simulation is performed by using Ansys program which can analyze both the temperature distribution and the thermal-stress analysis
[en] Spray drying is a unit operation very common in many industrial processes. For each particular application, the resulting granulated material must possess determined properties that depend on the conditions in which the spray drying processing has been carried out, and whose dependence must be known in order to optimize the quality of the material obtained. The large number of variables that influence on the processes of matter and energy transfer and on the formation of granular material has required a detailed analysis of the drying process. Over the years there have been many studies on the spray drying processing of all kind of materials and the influence of process variables on the drying kinetics of the granulated material properties obtained. This article lists the most important works published for both the spray drying processing and the drying of individual droplets, as well as studies aimed at modeling the drying kinetics of drops. (Author)