Statistical Simulation of Thin-Film Bearings

The information preservation (IP) method and the direct simulation Monte Carlo (DSMC) method are used to simulate the gas flows between the write/read head and the platter of the disk drive (the slider bearing problem). The results of both methods are in good agreement with numerical solution of the Reynolds equation in the cases studied. However, the DSMC method owing to the problem of large sample size demand and the difficulty in regulating boundary conditions at the inlet and outlet was able to simulate only short bearings, while IP simulates the bearing of authentic length ~1000 m ? and can provide more detailed flow information.

Reversibly strain-tunable elastomeric photonic crystals

Reversibly strain-tunable polymeric photonic crystals made of thermoplastic polyester elastomer (TPEE) were fabricated by using the self-assembled silica opals as templates. The stop band of the polymeric photonic crystal locates at the near infrared (IR) regime in its transmission spectrum, and exhibits a blue shift with the increase of the incident angle. Because of the elasticity of the TPEE, the stop band of the TPEE photonic crystal can also be reversibly tuned at ambient temperature through to and fro uniaxially or biaxially stretching and recovering by changing the lattice spacing and the symmetry of the crystal along (1 1 1) plane.

Tailoring The Mechanical Performance Of Epoxy Resin By Various Nanoparticles

Flexible organic elastomeric nanoparticles (ENP) and two kinds of rigid inorganic silica nanoparticles were dispersed respectively into a bisphenol-A epoxy resin in order to tailor and compare the performance of mechanical properties. It was found that the well-dispersed flexible ENP greatly enhanced the toughness of the epoxy with the cost of modulus and strength. Comparatively, the rigid silica nanoparticles improved Young's modulus, tensile strength and fracture toughness simultaneously. Both fumed and sol-gel-formed nanosilica particles conducted similar results in reinforcing the epoxy resin, although the latter exhibited almost perfect nanoparticle dispersion in matrix. The toughening mechanisms of nanocomposites were further discussed based on fractographic analysis.

IP Simulation of Micro Gas Flows under 3-D Head Sliders

Gas film lubrication of a three-dimensional flat read-write head slider is calculated using the information preservation (IP) method and the direct simulation Monte Carlo (DSMC) method, respectively. The pressure distributions on the head slider surface at different velocities and flying heights obtained by the two methods are in excellent agreement. IP method is also employed to deal with head slider with three-dimensional complex configuration. The pressure distribution on the head slider surface and the net lifting force obtained by the IP method also agree well with those of DSMC method. Much less (of the order about 10(2) less) computational time (the sum of the time used to reach a steady stage and the time used in sampling process) is needed by the IP method than the DSMC method and such an advantage is more remarkable as the gas velocity decreases.

High-fidelity replication of Dammann gratings using soft lithography

We report the experimental results of using the soft lithography method for replication of Dammann gratings. By using an elastomeric stamp, uniform grating structures were transferred to the LTV-curable polymer. To evaluate the quality of the replication, diffraction images and light intensity were measured. Compared with the master devices, the replicas of Dammann gratings show a slight deviation in both surface relief profile and optical performance. Experimental results demonstrated that high-fidelity replication of Dammann gratings is realized by using soft lithography with low cost and high throughput. (C) 2008 Optical Society of America.

Effect of silver nanoparticles on luminescent properties of europium complex in di-ureasil hybrid materials

Organic-inorganic hybrids containing luminescent lanthanide complex Eu(tta)(3)Phen (tta = thenoyltrifluoroaceton, phen = 1,10-phenanthroline) and silver nanoparticles have been prepared via mixing rare earth complex and nanoparticles with the precursors of di-ureasil using a sol-gel process. The obtained hybrid materials with transparent and elastomeric features were characterized by transmission electron microscope, solid-state Si-29 magic-angle spinning NMR spectra, diffuse reflectance, UV-visible absorption and photoluminescence spectroscopies. The effect of the silver nanoparticles on the luminescence properties was investigated. The experimental results showed that the luminescence intensity of the Eu(tta)(3)phen complex could be enhanced by less than ca. 9.5 nM of silver nanoparticles with the average diameter of 4 nm, and reached its maximum at the concentration of ca. 3.6 nM. Further increasing the concentration of the silver nanoparticles (> 9.5 nM) made the luminescence quenched. The enchancement and quench mechnism was discussed.

Highly oriented tunable wrinkling in polymer bilayer films confined with a soft mold induced by water vapor

The authors report the formation of highly oriented wrinkling on the surface of the bilayer [polystyrene (PS)/poly(vinyl pyrrolidone) (PVP)] confined by a polydimethylsiloxane (PDMS) mold in a water vapor environment. When PVP is subjected to water vapor, the polymer loses its mechanical rigidity and changes to a viscous state, which leads to a dramatic change in Young's modulus. This change generates the amount of strain in the bilayer to induce the wrinkling. With a shape-controlled mold, they can get the ordered wrinkles perfectly perpendicular or leaned 45 S to the channel orientation of the mold because the orientation of the resultant force changes with the process of water diffusion which drives the surface to form the wrinkling. Additionally, they can get much smaller wrinkles than the stripe spacing of PDMS mold about one order. The wrinkle period changes with the power index of about 0.5 for various values of the multiplication product of the film thicknesses of the two layers, namely, lambda similar to (h(PS)h(PVP))(1/2).

A new method for fabrication of three-dimensional polymer micropatterning - Microtransfer molding

Microtransfer molding (muTM) is a kind of soft lithography for polymer micropatterning. In muTM, a liquid prepolymer(or concentrated polymer solution) is applied to the patterned surface of an elastomeric mold and then brought into the contact with a substrate. After prepolymer is cured thermally or by UV light, the elastomeric mold is peeled away. A pattern is left on the surface of the substrate. In this study, similar to300 nm lines and three-dimensional patterns of PMMA and epoxy on planar and/or non-planar substrates are realized.

Dynamic mechanical studies of the sulfonated butyl rubber ionomers and their blends

Dynamic mechanical properties of sulfonated butyl rubber ionomers neutralized with different amine or metallic ion (zinc or barium) and their blends with polypropylene (PP), high-density polyethylene (HDPE), or styrene-butadiene-styrene (SBS) triblock copolymer were studied using viscoelastometry. The results showed that glass transition temperatures of ion pair-containing matrix and ionic domains (T-g1 and T-g2, respectively) of amine-neutralized ionomers were lower than those of ionomers neutralized with metallic ions, and the temperature range of the rubbery plateau on the storage modulus plot for amine-neutralized ionomers was narrower. The modulus of the rubbery plateau for amine-neutralized ionomers was lower than that of ionomers neutralized with zinc or barium ion. With increasing size of the amine, the temperature range for the rubbery plateau decreased, and the height of the loss peak at higher temperature increased. Dynamic mechanical properties of blends of the zinc ionomer with PP or HDPE showed that, with decreasing ionomer content, the T-m of PP or HDPE increased and T-g1 decreased, whereas T-g2 or the upper loss peak temperature changed only slightly. The T-g1 for the blend with SBS also decreased with decreasing ionomer content. The decrease of T-g1 is attributed to the enhanced compatibilization of the matrix of the ionomer-containing ion pairs with amorphous regions of PP or HDPE or the continuous phase of SBS due to the formation of thermoplastic interpenetrating polymer networks by ionic domains and crystalline or glassy domains.

滑坡和泥石流致灾条件叠合技术及风险分析-以川藏公路然乌至鲁朗段为例

As one part of national road No. 318, Sichuan-Tibet (Chengdu-Lasha) Highway is one of traffic life lines connecting Tibet municipality to the inland, which is very important to the economic development of Tibet. In addition, it is still an important national defence routeway, with extremely important strategic position on maintaining the stability and solidarity of Tibet municipality and consolidating national defence. Particular geological condition, terrain and landform condition and hydrometeorological condition induce large-scale debris flows and landslides (including landslips) and the like geological hazards frequently occur along the highway. High frequency geological hazards not only result in high casualties and a great property loss, but also block traffic at every turn, obstructing the Sichuan-Tibet highway seriously. On the basis of considerable engineering geological investigation and analysis to the relative studying achievements of predecessors, it is found that one of the dominating reason incurring landslides or debris flows again and again in a place is that abundant loose materials are accumulated in valleys and slopes along the highway. Taking landslides' and debris flows along Ranwu-Lulang section of Sichuan-Tibet highway as studying objects, the sources and cause of formation of loose accumulation materials in the studying area are analyzed in detail, the major hazard-inducing conditions, hazard, dynamic risk, prediction of susceptibility degree of landslides and debris flows, and the relations between landslides and debris flows and various hazard-inducing conditions are systematically researched in this paper. All of these will provide scientific foundation for the future highway renovating and reducing and preventing geological hazards. For the purpose of quantitatively analyzing landslide and debris flow hazards, the conception of entropy and information entropy are extended, the conception of geological hazard entropy is brought forward, and relevant mathematics model is built. Additionally, a new approach for the dynamic risk analysis of landslide and debris flow is put forward based on the dynamic characteristics of the hazard of hazard-inducings and the vulnerability of hazard-bearings. The formation of landslide and debris flow is a non-linear process, which is synthetically affected by various factors, and whose formation mechanics is extremely complex. Aiming at this question, a muli-factors classifying and overlapping technique is brought forward on the basis of engineering geomechanics meta-synthesis (EGMS) thought and approach, and relevant mathematics model is also built to predict the susceptibility degree of landslide or debris flow. The example analysis result proves the validity of this thought and approach. To studying the problem that whether the formation and space distribution of landslides and debris flows are controlled by one or several hazard-inducing conditions, the theme graphics of landslides and debris flows hazard and various hazard-inducing conditions are overlapped to determine the relationship between hazard and hazard-inducing conditions. On this basis, the semi-quantitative engineering zonation of the studying area is carried out. In addition, the overlapping analysis method of the hazard-indue ing conditions of landslides and debris flows based on "digital graphics system" is advanced to orderly organize and effectively manage the spatial and attributive data of hazard and hazard-inducing conditions theme graphics, and to realize the effectively combination of graphics, images and figures.