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141.
Using second-order Barker–Henderson perturbation theory we are able to derive an explicit expression for the direct correlation function of fluids with hard core potentials. Using the obtained direct correlation function, one can explicitly calculate all thermodynamic properties of simple fluids with hard core potentials. Comparisons with computer simulation data show good agreement for both thermodynamic properties and the static structure factor of the hard core double Yukawa potential.  相似文献   
142.
Ultrasonic degradation of polyvinyl alcohol (PVA) was carried out in aqueous solution at 25 degrees C. In this experiment, the effect of solution concentration on the rate of degradation was investigated. Kinetics of degradation was studied by viscometry method. The calculated rate constants indicate that degradation rate of PVA solutions decreases with increasing of solution concentration (C= g lit(-1)). The calculated rate constants correlated in terms of reverse concentration and relative viscosity of PVA solutions. This behavior in the rate of degradation was interpreted in terms of viscosity and concentration of polymer solution. With increasing solution concentration, viscosity increases and it causes a reduction in the cavitation efficiency thus, the rate of degradation will be decreased.  相似文献   
143.
144.
It is shown that there are an infinite number of radial distribution functions (RDFs), corresponding to only one direct correlation function (DCF) of the optimised random phase approximation (ORPA). This observation in the thermodynamic perturbation theory is in sharp contrast to that of integral equation theories in which they uniquely correspond. By devising a new method we will be able to introduce various perturbation theories of simple liquids all coming from one DCF. Among all, we will only present analytically seven variants of the ORPA in the thermodynamic perturbation theory of liquids. The DCF of hard-core potential for all variants is assumed to be the same as the ORPA. However, interestingly enough the resulted expressions for the Helmholtz free energies and the RDF are obtained very differently. Furthermore, the resulted thermodynamic properties come out somehow the same, whereas the structural functions of some variants are found to behave much better than the standard ORPA.  相似文献   
145.
In this paper, 2D numerical simulation of the Trombe wall performance and indoor air environment under unsteady state condition for a room located in Yazd, Iran are studied. The governing equations involve mass, momentum and energy conservation, which are discretized by the finite volume method after non-dimensionalization. The SIMPLER algorithm is used for coupling the velocity and pressure. The average absorbed solar radiation on the Trombe wall has been defined for different hours of the coldest period of the year (21 January–19 February) in Yazd. All equations have been solved together using a FORTAN code. The main aim of this research is to investigate the time duration of room heating during the non-sunny periods. The stored energy of the wall being delivered to the inside room was defined for different materials of the Trombe wall. The results show that the Trombe wall made of paraffin wax can keep the room warmer in comparison with other materials for about 9 h.  相似文献   
146.
Real-time detection and quantitation of specific amplicons have been achieved using quencher and dye-labeled oligonucleotides such as molecular beacons. The molecular beacon molecule has a fluorescent reporter dye at the 5′-end and a quencher at the 3′-end. When the closed molecular beacon is excited by irradiation, the reporter fluorescence is greatly reduced by quenching through the process of fluorescence resonance energy transfer. When the molecular beacon hybridizes to the target, the stem loop opens making the fluorophore and quencher spatially distinct, thus increasing the reporter dye fluorescence intensity. Labeling of dyes to 5′-end of oligonucleotides has been done typically using manual methods, it is possible to do manual coupling at the milligram scale. Described here is the development of a scalable process for oligonucleotide labeling, which is robust, and has been achieved for 6-carboxynaphthofluorescein by connecting it to a corresponding phosphoramidite [Theisen, P.; McCollum, C.; Upadhya, K.; Jacobson. K.; Vu, H.; Andrus, A.; Tetrahedron Lett.1992, 33, 5033-5036].  相似文献   
147.
Under investigation in this work is a (\(2+1\))-dimensional the space–time fractional coupled nonlinear Schrödinger equations, which describes the amplitudes of circularly-polarized waves in a nonlinear optical fiber. With the aid of conformable fractional derivative and the fractional wave transformation, we derive the analytical soliton solutions in the form of rational soliton, periodic soliton, hyperbolic soliton solutions by four integration method, namely, the extended trial equation method, the \(\exp (-\,\Omega (\eta ))\)-expansion method and the improved \(\tan (\phi (\eta )/2)\)-expansion method and semi-inverse variational principle method. Based on the the extended trial equation method, we derive the several types of solutions including singular, kink-singular, bright, solitary wave, compacton and elliptic function solutions. Under certain condition, the 1-soliton, bright, singular solutions are driven by semi-inverse variational principle method. Based on the analytical methods, we find that the solutions give birth to the dark solitons, the bright solitons, combine dark-singular, kink, kink-singular solutions with fractional order for nonlinear fractional partial differential equations arise in nonlinear optics.  相似文献   
148.
We report the first results from novel sub-Angstrom oscillation amplitude non-contact atomic force microscopy developed for lateral force gradient measurements. Quantitative lateral force gradients between a tungsten tip and Si(1 1 1)-(7 × 7) surface can be measured using this microscope. Simultaneous lateral force gradient and scanning tunnelling microscope images of single and multi atomic steps are obtained. In our measurement, tunnel current is used as feedback. The lateral stiffness contrast has been observed to be 2.5 N/m at single atomic step, in contrast to 13 N/m at multi atomic step on Si(1 1 1) surface. We also carried out a series of lateral stiffness-distance spectroscopy. We observed lateral stiffness-distance curves exhibit sharp increase in the stiffness as the sample is approached towards the surface. We usually observed positive stiffness and sometimes going into slightly negative region.  相似文献   
149.
We show that the splitting feature of the Einstein tensor, as the first term of the Lovelock tensor, into two parts, namely the Ricci tensor and the term proportional to the curvature scalar, with the trace relation between them is a common feature of any other homogeneous terms in the Lovelock tensor. Motivated by the principle of general invariance, we find that this property can be generalized, with the aid of a generalized trace operator which we define, for any inhomogeneous Euler–Lagrange expression that can be spanned linearly in terms of homogeneous tensors. Then, through an application of this generalized trace operator, we demonstrate that the Lovelock tensor analogizes the mathematical form of the Einstein tensor, hence, it represents a generalized Einstein tensor. Finally, we apply this technique to the scalar Gauss–Bonnet gravity as an another version of string–inspired gravity. This work was partially supported by a grant from the MSRT/Iran.  相似文献   
150.
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