Results 1 - 10 of 1822
Results 1 - 10 of 1822. Search took: 0.024 seconds
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[en] Newton’s gravitational constant G is the least known fundamental constant of nature. Since Cavendish made the first measurement of G with a torsion balance over two hundred years ago, the best results of G have been obtained by using torsion balances. However, the uncorrected anelasticity of torsion fibers makes the results questionable. We present a new method of G measurement by using a superconducting gravity gradiometer constructed with levitated test masses, which is free from the irregularities of mechanical suspension. The superconducting gravity gradiometer is rotated to generate a centrifugal acceleration that nulls the gravity field of the source mass, forming an artificial planetary system. This experiment has a potential accuracy of G better than 10 ppm. (paper)
[en] The process of reaching equilibrium concentrations in a binary liquid system with limited solubility is considered. The motion of the interface in the system in a nonequilibrium state is discussed. It is noted that mutual dissolution occurs naturally, without stirring. It is found that the time it takes to reach equilibrium concentrations under these conditions is several months. The dynamics of macroscopic processes accompanying the mutual dissolution of components is studied via dynamic light scattering. It is concluded that submicron-sized heterogeneities are observed in the lower phase within the first two hours after preparing a sample, when the lower phase is a mixture of liquids. If the lower phase is a pure liquid, such heterogeneities persist for more than two days. The lower and upper phases then remain microscopically homogeneous, though the interface continues to move for a long period of time.
[en] Electrorheological (ER) fluid is a type of smart fluid whose shear yield stress relies on the external electrical field strength. The transition of ER fluid microstructure driven by the electrical field is the reason why viscosity changes. Experimentally, the transparent electrodes are used to investigate the column size distribution where an external electric field is applied to a colloidal suspension, i.e., ER fluid is increased. The coarsening profile of ER suspensions is strongly related to electrical field strength, but it is insensitive to particle size. In addition, in a low field range the shear stress corresponding to the mean column diameter is studied and they are found to satisfy a power law. However, this dependence is invalid when the field strength surpasses a threshold value. (paper)
[en] The topic of this study is discussion aimed at developing a unified viewpoint on the problem of separation potential and separating power in the theory of separation of multicomponent molecular and isotopic mixtures. The object of study was the “generalized” separation potential for multicomponent mixtures. A critical assessment of its validity from thermodynamic viewpoint was given. The assumptions made during its derivation were analyzed.
[en] A confocal scanner for selective observation of the vertical particle tracks in the nuclear photoemulsion is described. The particle track being searched for is imaging at an angle of 45° with respect to the optical axis of the system. The confocal scanner is provided with a new optical element, an “image orthogonalizator,” by means of which the extended image of the inclined vertical particle track is rotated through an angle of 90°. The stereoscopic version of the confocal scanner is presented as well. The described systems will be used in experiments for the investigation of neutrino oscillations in the accelerator.
[en] We implement Brownian dynamics to investigate the melting processes of colloidal particles confined isotropically and interacting via a potential which can be tailored in a repulsive–attractive–respulsive fashion as the interparticle distance increases. The stable configurations of such a system is composed of a large diversity of structures, which includes quasicrystalline, triangular, square, and mixed orderings, as well as the presence of fringes and holes, which are located, respectively, at the border and interior of the clusters. Our simulations demonstrate that during the melting process particles are able to swing between different micro phases. This intermediary stage, present in a finite range of temperature, precedes the melting in all cases investigated and is different from the hexatic phase of the KTNHY framework. We also test the fringes stability and find it to be higher than the one found in compact clusters. Finally, we show that, at the high temperature regime, the system loses its angular ordering while still preserves its radial interparticle confinement, which, ultimately, causes the proliferation of small subclusters. (paper)
[en] A mathematical model is developed for macroscopic approximation and quantitative calculations of the dynamics of mixing of solid components of a binary powder mixture during its dispersion in a grinding unit. Different conditions of the process are determined, depending on the main parameters of mechanical treatment.
[en] The Haralick texture features are common in the image analysis literature, partly because of their simplicity and because their values can be interpreted. It was recently observed that the Haralick texture features are very sensitive to the size of the GLCM that was used to compute them, which led to a new formulation that is invariant to the GLCM size. However, these new features still depend on the sample size used to compute the GLCM, i.e. the size of the input image region-of-interest (ROI). The purpose of this work was to investigate the performance of density estimation methods for approximating the GLCM and subsequently the corresponding invariant features. Three density estimation methods were evaluated, namely a piece-wise constant distribution, the Parzen-windows method, and the Gaussian mixture model. The methods were evaluated on 29 different image textures and 20 invariant Haralick texture features as well as a wide range of different ROI sizes. The results indicate that there are two types of features: those that have a clear minimum error for a particular GLCM size for each ROI size, and those whose error decreases monotonically with increased GLCM size. For the first type of features, the Gaussian mixture model gave the smallest errors, and in particular for small ROI sizes (less than about ). In conclusion, the Gaussian mixture model is the preferred method for the first type of features (in particular for small ROIs). For the second type of features, simply using a large GLCM size is preferred. (paper)
[en] When an evaporating droplet of colloidal suspension dries on a solid surface with the contact line pinned, the solute particles are driven by the solvent flow toward the edge and form a ring-like deposition pattern. In this work, we take into account the contact angle hysteresis and incorporate it into the effective model of Man and Doi (2016 Phys. Rev. Lett. 116 066101) which is based on Onsager’s variational principle. We show that single-ring pattern is formed when the contact line pinning and/or friction are sufficiently strong. We demonstrate that there exists an appropriate range for contact line pinning and friction in which two rings can be formed in the deposition pattern, one at the initially pinned contact line and the other a bit closer to the center of droplet. (paper)