The unsteady flow of a weakly compressible fluid in a thin porous layer. I: Two-dimensional theory

We consider the problem of determining the pressure and velocity fields for a weakly compressible fluid flowing in a two-dimensional reservoir in an inhomogeneous, anisotropic porous medium, with vertical side walls and variable upper and lower boundaries, in the presence of vertical wells injecting or extracting fluid. Numerical solution of this problem may be expensive, particularly in the case that the depth scale of the layer h is small compared to the horizontal length scale l. This is a situation which occurs frequently in the application to oil reservoir recovery. Under the assumption that epsilon=h/l<<1, we show that the pressure field varies only in the horizontal direction away from the wells (the outer region). We construct two-term asymptotic expansions in epsilon in both the inner (near the wells) and outer regions and use the asymptotic matching principle to derive analytical expressions for all significant process quantities. This approach, via the method of matched asymptotic expansions, takes advantage of the small aspect ratio of the reservoir, epsilon, at precisely the stage where full numerical computations become stiff, and also reveals the detailed structure of the dynamics of the flow, both in the neighborhood of wells and away from wells

The Role of Fur in Heat Regulation in the Guinea Pig

Author Institution: Kent State University, Kent, Ohio and University of Delaware, Newark, Delawar

Quantum process tomography of a controlled-NOT gate

We demonstrate complete characterization of a two-qubit entangling process - a linear optics controlled-NOT gate operating with coincident detection - by quantum process tomography. We use maximum-likelihood estimation to convert the experimental data into a physical process matrix. The process matrix allows accurate prediction of the operation of the gate for arbitrary input states, and calculation of gate performance measures such as the average gate fidelity, average purity and entangling capability of our gate, which are 0.90, 0.83 and 0.73, respectively.Comment: 4 pages, 2 figures. v2 contains new data corresponding to improved gate operation. Figure quality slightly reduced for arXi

Increasing compliance with low tidal volume ventilation in the ICU with two nudge-based interventions: evaluation through intervention time-series analyses

Objectives: Low tidal volume (TVe) ventilation improves outcomes for ventilated patients, and the majority of clinicians state they implement it. Unfortunately, most patients never receive low TVes. ‘Nudges’ influence decision-making with subtle cognitive mechanisms and are effective in many contexts. There have been few studies examining their impact on clinical decision-making. We investigated the impact of 2 interventions designed using principles from behavioural science on the deployment of low TVe ventilation in the intensive care unit (ICU). Setting: University Hospitals Bristol, a tertiary, mixed medical and surgical ICU with 20 beds, admitting over 1300 patients per year. Participants: Data were collected from 2144 consecutive patients receiving controlled mechanical ventilation for more than 1 hour between October 2010 and September 2014. Patients on controlled mechanical ventilation for more than 20 hours were included in the final analysis. Interventions: (1) Default ventilator settings were adjusted to comply with low TVe targets from the initiation of ventilation unless actively changed by a clinician. (2) A large dashboard was deployed displaying TVes in the format mL/kg ideal body weight (IBW) with alerts when TVes were excessive. Primary outcome measure: TVe in mL/kg IBW. Findings: TVe was significantly lower in the defaults group. In the dashboard intervention, TVe fell more quickly and by a greater amount after a TVe of 8 mL/kg IBW was breached when compared with controls. This effect improved in each subsequent year for 3 years. Conclusions: This study has demonstrated that adjustment of default ventilator settings and a dashboard with alerts for excessive TVe can significantly influence clinical decision-making. This offers a promising strategy to improve compliance with low TVe ventilation, and suggests that using insights from behavioural science has potential to improve the translation of evidence into practice

Flexible microwave system to measure the electron number density and quantify the communications impact of electric thruster plasma plumes

An advanced microwave interferometric system operating in the Ku (12–18 GHz) band has been implemented for use in very large vacuum chambers to determine the effects of electromagnetic wave propagation through a plasma plume created by a space electric propulsion thruster. This diagnostic tool is used to nonintrusively obtain the local electron number density as well as provide information necessary for understanding impact to communications and other spacecraft electromagnetic systems. The use of a nonintrusive electromagnetic measurement provides highly accurate line integrated density and avoids problems caused by intrusive measurement techniques. If the plasma is symmetrical, local plasma density can also be determined accurately using well known inversion techniques. A network analyzer acts as a transmitter and receiver while a two axis positioning system maps the amplitude and phase variation of a transmitted signal over one plane of the plasma plume. The utilization of a 6 m×9 m vacuum chamber effectively minimizes plasma boundary effects, but the longer cable path lengths have required a frequency conversion circuit to reduce power loss and phase uncertainty at high frequencies. Two studies are presented: the first is a measurement of the local electron density in the plume of a 1 kW arcjet and the second is a measurement of attenuation in the plume of a stationary plasma thruster. Both the arcjet and SPT emit a steady state conical unmagnetized plasma that is radially symmetric. The arcjet peak density is 1015–1016 m−3 along centerline and the SPT peak density is 1016–1017 m−3 along centerline. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71094/2/RSINAK-68-2-1189-1.pd

Analysis of chamber simulations of long probes in high-speed, dense plasmas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76739/1/AIAA-2001-1142-128.pd