A comparison of the value of viscosity for several water models using Poiseuille flow in a nano-channel.

The viscosity-temperature relation is determined for the water models SPC/E, TIP4P, TIP4P/Ew, and TIP4P/2005 by considering Poiseuille flow inside a nano-channel using molecular dynamics. The viscosity is determined by fitting the resulting velocity profile (away from the walls) to the continuum solution for a Newtonian fluid and then compared to experimental values. The results show that the TIP4P/2005 model gives the best prediction of the viscosity for the complete range of temperatures for liquid water, and thus it is the preferred water model of these considered here for simulations where the magnitude of viscosity is crucial. On the other hand, with the TIP4P model, the viscosity is severely underpredicted, and overall the model performed worst, whereas the SPC/E and TIP4P/Ew models perform moderately.

Jetting behaviour of polymer solutions in drop-on-demand inkjet printing

The jetting of dilute polymer solutions in drop-on-demand printing is investigated. A quantitative model is presented which predicts three different regimes of behaviour depending upon the jet Weissenberg number Wi and extensibility of the polymer molecules. In regime I (Wi < ½) the polymer chains are relaxed and the fluid behaves in a Newtonian manner. In regime II (½ < Wi < L) where L is the extensibility of the polymer chain the fluid is viscoelastic, but the polymer do not reach their extensibility limit. In regime III (Wi > L) the chains remain fully extended in the thinning ligament. The maximum polymer concentration at which a jet of a certain speed can be formed scales with molecular weight to the power of (1-3ν), (1-6ν) and -2ν in the three regimes respectively, where ν is the solvent quality coefficient. Experimental data obtained with solutions of mono-disperse polystyrene in diethyl phthalate with molecular weights between 24 - 488 kDa, previous numerical simulations of this system, and previously published data for this and another linear polymer in a variety of “good” solvents, all show good agreement with the scaling predictions of the model.

Influence of fluid viscosity on the response of buried structures in earthquakes

The use of high viscous pore fluid has been widely established to match the rate of excess pore pressure generation and subsequent dissipation in dynamic centrifuge tests. The appropriate viscosity is linked to the geometric and gravity scaling factors which corresponds to the use of pore fluid of 'N' cSt in a 'N'g centrifuge test. The use of either water (1 cSt) or pore fluid lower than 'N' cSt can influence the behaviour of soil liquefaction in a centrifuge test. In this paper, the floatation of a tunnel following soil liquefaction is investigated using pore fluids with two different viscosities. The results show that the uplift displacement of the tunnel is significantly affected by the pore fluid viscosity. © 2010 Taylor & Francis Group, London.

Closing the gap: Improved bounds on optimal POMDP solutions

POMDP algorithms have made significant progress in recent years by allowing practitioners to find good solutions to increasingly large problems. Most approaches (including point-based and policy iteration techniques) operate by refining a lower bound of the optimal value function. Several approaches (e.g., HSVI2, SARSOP, grid-based approaches and online forward search) also refine an upper bound. However, approximating the optimal value function by an upper bound is computationally expensive and therefore tightness is often sacrificed to improve efficiency (e.g., sawtooth approximation). In this paper, we describe a new approach to efficiently compute tighter bounds by i) conducting a prioritized breadth first search over the reachable beliefs, ii) propagating upper bound improvements with an augmented POMDP and iii) using exact linear programming (instead of the sawtooth approximation) for upper bound interpolation. As a result, we can represent the bounds more compactly and significantly reduce the gap between upper and lower bounds on several benchmark problems. Copyright © 2011, Association for the Advancement of Artificial Intelligence. All rights reserved.

Compact three-dimensional silicon termination solutions for high voltage SOI SuperJunction

This paper demonstrates and discusses novel "three dimensional" silicon based junction isolation/termination solutions suitable for high density ultra-low-resistance Lateral Super-Junction structures. The proposed designs are both compact and effective in safely distributing the electrostatic potential away from the active device area. The designs are based on the utilization of existing layers in the device fabrication line, hence resulting in no extra complexity or cost increase. The study/demonstration is done through extensive experimental measurements and numerical simulations. © 2012 IEEE.

Global solutions

As manufacturing enterprises become increasingly globalised, the supply chain is becoming more fragmented, with multiple players engaged in key aspects of the value chain. This has seen the emergence of suppliers offering specialised operations (research, design, production, service) which are capable of serving widely dispersed markets. It is generally assumed that managing these increasingly complex international supply chains requires sophisticated management techniques. Many companies have installed advanced planning systems for just this reason - systems that require skilled staff to implement the complex processes involved.

Dynamic programming solutions for decentralized state-feedback LQG problems with communication delays

This paper presents explicit solutions for a class of decentralized LQG problems in which players communicate their states with delays. A method for decomposing the Bellman equation into a hierarchy of independent subproblems is introduced. Using this decomposition, all of the gains for the optimal controller are computed from the solution of a single algebraic Riccati equation. © 2012 AACC American Automatic Control Council).

Laminar and turbulent radial jets

In this paper the radial free jet which is produced by a continuous discharge of fluid from the space between two identical, parallel, circular, concentric discs into an infinite region of stagnant fluid of the same density and viscosity is investigated. Both laminar and turbulent jets are considered with analytical solutions being obtained near to the origin of the jet and at large distances along the jet. These asymptotic solutions are matched using a computational technique, and the numerical predictions show very good agreement with all the available experimental data.

Graphics processing unit cooling solutions: Acoustic characteristics

The change in acoustic characteristics in personal computers to console gaming and home entertainment systems with the change in the Graphics Processing Unit (GPU), is presented. The tests are carried out using identical configurations of the software and system hardware. The prime components of the hardware used in the project are central processing unit, motherboard, hard disc drive, memory, power supply, optical drive, and additional cooling system. The results from the measurements taken for each GPU tested are analyzed and compared. The test results are obtained using a photo tachometer and reflective tape adhered to one particular fan blade. The test shows that loudness is a psychoacoustic metric developed by Zwicker and Fastal that aims to quantify how loud a sound is perceived as compared to a standard sound. The acoustic experiment reveals that the inherent noise generation mechanism increases with the increase of the complexity of the cooling solution.