Adaptive grid generation technique of sub-5?nm flying height air bearing slider with clearance discontinuities

An adaptive grid generation technique including three kinds of weight functions related to the maximum pressure gradient is proposed to simulate the pressure distribution of a sub-5?nm flying height air bearing slider with clearance discontinuities in the interface of the head and the disk in hard disk drives. Considering the clearance discontinuities of a slider with complex geometrical shape, we have defined a discontinuous factor to describe the mass flux crossing the discontinuous boundaries. The effect of different parameters in the weight functions on the node distribution of a typical slider is investigated. The pressure profile of a slider with sub-5?nm flying height is obtained based on the grid distribution calculated from the weight functions. The computational efficiency for simulating the pressure distributions is compared for different kinds of weight functions.     

Novel sub-100 nm surface chemical modification by optical near-field induced photocatalytic reaction

The surface modification is indispensable to facilitate new functional applications of micro/nanofluidics devices. Among many modification techniques developed so far, the photo-induced chemical modification is the most versatile method in terms of robustness, process simplicity, and feasibility of chemical functionality. In particular, the method is useful for closed spaces, such as post-bonded devices. However, the limitation by optical diffraction limit is still a challenging issue in scaling down the pattern sizes to nanoscale. Here, we demonstrated a novel surface modification on sub-100 nm scale utilizing the novel optical near-field (ONF) generated on nanostructures of photocatalyst (TiO₂). The minimum pattern size of 40 nm, which was much smaller than diffraction limit, was achieved using a visible light source (488 nm) and a conventional irradiation setup. The controllability of pattern size by light intensity, the feasibility of functionality, and the non-contact working mode have impacts on surface patterning of post-bonded micro/nanofluidics devices. It is also worthy to note that our results verified for the first time the ONF on nanostructures of non-metal materials and its ability to manipulate the chemical reaction on nanoscale.     

Replication of sub-100 nm structures using h- and s-PDMS composite stamps

Soft-UV-NIL as replication technique was used to replicate sub-100 nm structures. The aim of this work is the stamp production and the replication of structures with dimensions smaller than 100 nm in a simple manner. Composite stamps composed of two layers, a thin hard PDMS layer supported by a thick soft PDMS (s-PDMS) layer are compared to common s-PDMS stamps regarding the resolution by using a Siemens star (star burst pattern) as test structure. The master is fabricated by electron beam lithography in a 140 nm thick PMMA resist layer. The stamp is molded directly from the structured resist, without any additional anti sticking treatment. Therefore the resist thickness determines the aspect ratio, which is 1.5 at the resolution limit. The replication is done in a UV-curing cycloaliphatic epoxy material. The employed test structure provides good comparability, the resolution limit at a glance, and it integrates a smooth transition from micro- to nanostructures. Therefore it is a capable structure to characterize the UV-NIL.     

Squeeze film effects on dynamic performance of MEMS μ-mirrors-consideration of gas rarefaction and surface roughness

The squeeze film behavior of MEMS torsion mirrors is modeled, analyzed and discussed. Effects of gas rarefaction (first-order slip-flow model with non-symmetric accommodation coefficients, ACs) and surface roughness are considered simultaneously by using the average Reynolds type equation (ARTE). Based on the operating conditions with small variations in film thickness and pressure, the ARTE is linearized. A coordinate transformation, by stretching or contracting the axes by referring to the roughness flow factors, is proposed to transform the linearized ARTE into a diffusion type modal equation. The dynamic coefficients (stiffness and damping coefficients) are then derived and expressed in analytical form. The results show that the tilting frequency (or Γ₀ squeeze number), roughness parameters (γ Peklenik numbers, σ standard deviation of composite roughness) and gas rarefaction parameters (D inverse Knudsen number, ACs) are all important parameters on analyzing the dynamic performance of MEMS torsion mirrors.     

Neuro-fuzzy predictive model for surface roughness and cutting force of machined Al–20 Mg2Si–2Cu metal matrix composite using additives

Neural Computing and Applications - Today’s metal matrix composites are widely used due to their excellent properties, which are useful for high-performance applications in the automotive and...     

Do air pollution emissions and fuel consumption models for roadways include the effects of congestion in the roadway traffic flow?

Road transport emission and fuel consumption models are currently used extensively to predict levels of air pollution along roadway links and networks. This paper examines how, and to what extent, models which are currently used to predict emissions and fuel consumption from road traffic include the effects of congestion. A classification framework is presented in which a key factor, driving pattern, connects emissions to congestion. Prediction of the effects of different driving patterns in emission models is generally restricted to certain aspects of modelling, i.e. hot-running emissions of regulated pollutants. As a consequence, the effects of congestion are only partially incorporated in the predictions. The majority of emission models explicitly incorporate congestion in the modelling process, but for one important family of emission models, namely average speed models, this could not be determined directly. Re-examination of the (light-duty) driving patterns on which three average speed models (COPERT, MOBILE, EMFAC) are based, shows that it is likely that congestion is represented in these patterns. Since (hot-running) emission factors are based on these patterns, this implies that the emission factors used in these emission models also reflect different levels of congestion. Congestion is thus indirectly incorporated in these models. It is recommended, that, in order to get more accurate (local) emission predictions and to achieve correct application in particular situations, it is important to improve current average speed models by including a congestion algorithm, or alternatively, at least provide information on the level of congestion in the driving patterns on which these models are based and recommendations on what applications the models are suitable for.     

Accounting for surface–groundwater interactions and their uncertainty in river and groundwater models: A case study in the Namoi River,Australia

Surface–groundwater (SW–GW) interactions constitute a critical proportion of the surface and groundwater balance especially during dry conditions. Conjunctive management of surface and groundwater requires an explicit account of the exchange flux between surface and groundwater when modelling the two systems. This paper presents a case study in the predominantly gaining Boggabri–Narrabri reach of the Namoi River located in eastern Australia. The first component of the study uses the Upper Namoi numerical groundwater model to demonstrate the importance of incorporating SW–GW interactions into river management models. The second component demonstrates the advantages of incorporating groundwater processes in the Namoi River model.Results of the numerical groundwater modelling component highlighted the contrasting groundwater dynamics close to, and away from the Namoi River where lower declines were noted in a near-field well due to water replenishment sourced from river depletion. The contribution of pumping activities to river depletion was highlighted in the results of the uncertainty analysis, which showed that the SW–GW exchange flux is the most sensitive to pumping rate during dry conditions. The uncertainty analysis also showed that after a drought period, the 95% prediction interval becomes larger than the simulated flux, which implies an increasing probability of losing river conditions. The future prospect of a gaining Boggabri–Narrabri reach turning into losing was confirmed with a hypothetical extended drought scenario during which persistent expansion of groundwater pumping was assumed. The river modelling component showed that accounting for SW–GW interactions improved the predictions of low flows, and resulted in a more realistic calibration of the Namoi River model.Incorporating SW–GW interactions into river models allows explicit representation of groundwater processes that provides a mechanism to account for the impacts of additional aquifer stresses that may be introduced beyond the calibration period of the river model. Conventional river models that neglect the effects of such future stresses suffer from the phenomenon of non-stationarity and hence have inferior low flow predictions past the calibration period of the river model. The collective knowledge acquired from the two modelling exercises conducted in this study leads to a better understanding of SW–GW interactions in the Namoi River thus leading to improved water management especially during low flow conditions.