Results 1 - 10 of 40428
Results 1 - 10 of 40428. Search took: 0.076 seconds
|Sort by: date | relevance|
[en] We consider wetting phenomena in the vicinity of rough substrates. The quenched random geometry of the substrate is assumed to be a self-affine fractal with a roughness exponent of ζS. Asymptotic critical properties on approaching complete and critical wetting transitions are studied by combining the replica method with scaling and renormalization-group arguments. We find new critical behavior, controlled by a zero-temperature fixed point, when ζS exceeds the thermal roughness exponent of the emerging wetting layer. The possibility of an effective dimensional reduction due to randomness is considered. In two dimensions a number of exact results are obtained by using a many-body transfer-matrix technique
[en] Micro-pillar array is widely applied to manipulate the wettability of surfaces. Cases where liquid has infiltrated such pillar arrays completely are drawing increased attention in miniaturized systems. An equivalent surface tension model is proposed to characterize the driving force of liquid evolution in patterned micro-pillar arrays after the Young-Laplace equation and surface energy analysis are applied on both the pillar unit and bulk liquid levels. The effects of local menisci induced from the wetting of pillars are bounded and treated as 'equivalent liquid-vapor surface tension', through which the bulk liquid profile is then obtained based on the principle of minimal surface energy. The model is found to be computationally efficient and can be easily obtained through numerical methods. A typical sample case is presented to demonstrate its advantages and simplicity. The bulk profile that considers the effects of pillar array is compared with the result without pillars. The influencing effects, including apparent tilt angle, pillar spacing, and pillar shape, are addressed.
[en] Motion of a planar interface in incompressible Richtmyer-Meshkov (RM) instability with surface tension is investigated numerically by use of the boundary integral method. It is shown that an interface rolls up without regularization of the interfacial velocity when the Atwood number is relatively small. Comparison between the growth rate of the interface with and without surface tension is made, and it is shown that the growth rate without surface tension is always larger than the one with surface tension at the linear stage, that is, the linear growth rate of the RM instability with surface tension does not obey the typical growth rate of the RM instability which is proportional to time t. We also show that when the surface tension coefficient is relatively large, stable oscillatory motion of the interface is possible in the RM instability and the period of the oscillation depends on the surface tension parameter.
[en] The tidal interaction of a (rotating or nonrotating) black hole with nearby bodies produces changes in its mass, angular momentum, and surface area. Similarly, tidal forces acting on a Newtonian, viscous body do work on the body, change its angular momentum, and part of the transferred gravitational energy is dissipated into heat. The equations that describe the rate of change of the black-hole mass, angular momentum, and surface area as a result of the tidal interaction are compared with the equations that describe how the tidal forces do work, torque, and produce heat in the Newtonian body. The equations are strikingly similar, and unexpectedly, the correspondence between the Newtonian-body and black-hole results is revealed to hold in near-quantitative detail. The correspondence involves the combination k2τ of 'Love quantities' that incorporate the details of the body's internal structure; k2 is the tidal Love number, and τ is the viscosity-produced delay between the action of the tidal forces and the body's reaction. The combination k2τ is of order GM/c3 for a black hole of mass M; it does not vanish, in spite of the fact that k2 is known to vanish individually for a nonrotating black hole.
[en] In this paper, the foundations for new methodology creation which provides solving problem of surfaces structure new standards parameters huge amount conflicted with necessary actual floors quantity of surfaces structure parameters which is related to measurement complexity decreasing are considered. At the moment, there is no single assessment of the importance of a parameters. The approval of presented methodology for aerospace cluster components surfaces allows to create necessary foundation, to develop scientific estimation of surfaces texture parameters, to obtain material for investigators of chosen technological procedure. The methods necessary for further work, the creation of a fundamental reserve and development as a scientific direction for assessing the significance of microgeometry parameters are selected. (paper)
[en] Screw turns are known to be deformed as a result of the contact pliability of the nut and screw surfaces. The load distribution over the turns is investigated when fine thread is employed, when compression nuts are replaced by tension–compression and tension nuts, when the roughness of the working surfaces is increased, and when the load on the screw is increased.
[en] The Extreme Ultraviolet Lithography (EUVL) program currently is constructing an alpha-class exposure tool known as the Engineering Test Stand (ETS) that will employ 200mm wafer format masks. This report lists and explains the current specifications for the EUVL mask substrates suitable for use on the ETS. The shape and size of the mask are the same as those of a standard 200mm Si wafer. The flatness requirements are driven by the potential image placement distortion caused by the non-telecentric illumination of EUVL. The defect requirements are driven by the printable-defect size and desired yield for mask blank fabrication. Surface roughness can cause both a loss of light throughput and image speckle. The EUVL mask substrate must be made of low-thermal-expansion material because 40% of the light is absorbed by the multilayers and causes some uncorrectable thermal distortion during printing
[en] Full Text:Growth behavior of interfaces is usually described by a power-law of the growing interface width with time. This general scaling picture is an average behavior description, which may not be valid when only a finite number of interfaces is considered. In this work we study theoretically and experimentally the growth behavior of single interfaces and show that the particular growth function of the width always exhibits a non-monotonic, fluctuating behavior. This behavior results from competing mechanisms of normal growth and surface tension forces in the Quenched-noise Kardar-Parisi-Zhang (QKPZ) equation, and contains information on the growth process in this specific interface. We define a new measure of the interface width fluctuations in order to extract this information from experimental data. We analyze data of mercury droplets spreading on silver films, as well as data of water spreading on paper, in order to demonstrate the validity of our claim in a wide range of growing interfaces. The experimental results are compared to the numerical results of the QKPZ equation, for different cases of noise distributions
[en] The free layer switching properties of microstructured magnetic tunnel junctions have been investigated. The M-H loop of nonpatterned film shows ferromagnetic coupling with 10 Oe shifting associated with the interlayer roughness coupling. The MR curve of the patterned element shows stepped minor loop, less loop shifting, and larger coercive field due to shape anisotropy and stray field effects. MFM images of the element show nonuniform domain structures during reversal process
[en] The experimental investigation results on the vibration characteristics of the rods with artificial roughness in the axial flow are presented. It is shown that the roughness plays an important role in the mechanism of vibrations excitation. For the rods having artificial roughness with a relative size of 0.075+0.2 the phenomenon of dynamic instability has been revealed at the flowrates being by the order of magnitude smaller than those predicted by the Paidoussis theory. It is experimentally obtained that for the rods similar to those used as a nuclear reactor fuel element and heat exchanger tubes the critical velocities resulting in the vibration amplitude increase by the one or two order of magnitude are the values as much as 6-12 m/s. It is shown that the phenomenon revealed differs from a classic flutter by a number of attributes. (author)