Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

An Energy-Efficient Current-Controlled Write and Read Scheme for Resistive RAMs (RRAMs)

Energy efficiency remains one of the main factors for improving the key performance markers of RRAMs to support IoT edge devices. This paper proposes a simple and feasible low power design scheme which can be used as a powerful tool for energy reduction in RRAM circuits. The design scheme is exclusively based on current control during write and read operations and ensures that write operations are completed without wasted energy. Self-adaptive write termination circuits are proposed to control the RRAM current during FORMING, RESET and SET operations. The termination circuits sense the programming current and stop the write pulse as soon as a preferred programming current is reached. Simulation results demonstrate that an appropriate choice of the programming currents can help obtain 4.1X improvement in FORMING, 9.1X improvement in SET and 1.12X improvement in RESET energy. Also, the possibility to have a tight control over the RESET resistance is demonstrated. READ energy optimization is also covered by leveraging on a differential sense amplifier offering a programmable current reference. Finally, an optimal trade-off between energy consumption during SET/RESET operations and an acceptable read margin is established according to the final application requirements. Computer EngineeringQuantum & Computer Engineerin

Effect of DBD plasma actuation on structures in a plane mixing layer

The influence of spanwise-uniform (linear) forcing applied by a dielectric barrier discharge (DBD) plasma actuator on the growth of a plane mixing layer and the dynamics of large-scale spanwise vortices within, are investigated experimentally. Quantitative spatio-temporal measurement of the flow field is acquired using high-speed planar particle image velocimetry. The DBD actuator is used to impart perturbations into the mixing layer to force the fundamental Kelvin-Helmholtz instability and its first sub-harmonic. Forcing the fundamental instability resulted in the inhibition of vortex pairing due to the attenuation of sub-harmonic instabilities. Correspondingly, the growth of the mixing layer is halted initially. With sub-harmonic instability forcing, two vortices interact with each other and merge together. This results in a higher growth rate compared to the unforced mixing layer at the streamwise location of this vortex interaction. Eventually, the growth rate of the forced mixing layer becomes similar to that of the unforced mixing layer. These results demonstrate the influence of the applied forcing on the growth of the turbulent mixing layer and the dynamics of the coherent vortical structures within.Aerodynamic

Effect of DBD plasma actuators on vortical structures in a turbulent mixing layer

The influence of linear (spanwise-uniform) forcing applied by a DBD plasma actuator on the growth of a turbulent mixing layer and the dynamics of large-scale spanwise vortices, are investigated experimentally. Furthermore, the freestream turbulence intensity in the low-velocity stream is maintained at a high level to examine its impact on the control-authority of the applied forcing. The influence of the applied forcing on the dynamics and interactions of the spanwise vortices in the mixing layer is apparent. However, the growth rate of the mixing layer is not affected, suggesting that the high level of freestream turbulence diminishes the control-authority of the applied forcing.Aerodynamic

Effect of porosity on Curle's dipolar sources on an aerofoil in turbulent flow

Integrating a porous material into the structure of an aerofoil constitutes a promising passive strategy for mitigating the noise from turbulence–body interactions that has been extensively explored in the past few decades. When a compact permeable body is considered in the aeroacoustic analogy derived by Curle to predict this noise source, a dipole associated with the non-zero unsteady Reynolds stresses appears on the surface in addition to the dipole linked to the pressure fluctuations. Nevertheless, the relative contribution of this source to the far-field noise radiated by a porous wing profile has not been clarified yet. The purpose of the current research work is twofold. On the one hand, it investigates the impact of porosity on the surface-pressure fluctuations of a thick aerofoil immersed in the wake of an upstream circular rod at a Mach number of 0.09. On the other hand, it quantifies the relevance of the Reynolds-stresses term on the surface as a sound-generation mechanism. The results from large-eddy simulations show that the porous treatment of the wing profile yields an attenuation of the unsteady-pressure peak, which is localised in the low-frequency range of the spectrum and is induced by the milder distortion of the incoming vortices. However, porosity is ineffective in breaking the spanwise coherence or in-phase behaviour of the surface-pressure fluctuations at the vortex-shedding frequency. The Reynolds-stresses term is found to be considerable in the stagnation region of the aerofoil, where the transpiration velocity is larger, and partly correlated with the unsteady surface pressure, suggesting constructive interference between the two terms. This results in a non-negligible contribution of this term to the far-field acoustic pressure emitted by the porous wing profile for observation angles near the stagnation streamline. The conclusions drawn in the present study eventually provide valuable insight into the design of innovative and efficient passive strategies to mitigate surface–turbulence interaction noise in industrial applications.Wind Energ

Investigation of Curle's Dipolar Sources on a Porous Airfoil Interacting with Incoming Turbulence

Integrating porous materials into the structure of an airfoil constitutes a promising passive strategy for mitigating the noise from turbulence-body interactions that has been extensively explored in the past few decades. When a compact permeable body is considered in the aeroacoustic analogy derived by Curle to predict this noise source, a dipole associated with the nonzero unsteady Reynolds stresses appears on the surface in addition to the dipole linked to the pressure fluctuations. Nevertheless, the relative contribution of this source on the far-field noise radiated by a porous wing profile has not been clarified yet. The purpose of the current research work is twofold. On the one hand, it investigates the impact of porosity on the surface-pressure fluctuations of a thick airfoil immersed in the wake of an upstream circular rod at a Mach number of 0.09. On the other hand, it quantifies the relevance of the Reynolds-stresses term on the surface as a sound-generation mechanism. Results from large-eddy simulations show that the porous treatment of the wing profile yields an attenuation of the unsteady-pressure peak, which is localized in the low-frequency range of the spectrum and is induced by the milder distortion of the incoming vortices. However, porosity is ineffective in breaking the spanwise coherence or in-phase behavior of the surface-pressure fluctuations at the vortex-shedding frequency. The Reynolds-stresses term is found to be considerable in the stagnation region of the airfoil, where the transpiration velocity is larger, and partly correlated with the unsteady surface pressure. This results in a nonnegligible contribution of this term to the far-field acoustic pressure emitted by the porous wing profile for observation angles near the stagnation streamline. The conclusions drawn in the present study eventually provide valuable insight into the design of innovative and efficient passive strategies to mitigate surface-turbulence interaction noise in industrial applications.Wind Energ

Multi-level control of resistive ram (Rram) using a write termination to achieve 4 bits/cell in high resistance state

RRAM density enhancement is essential not only to gain market share in the highly competitive emerging memory sector but also to enable future high-capacity and power-efficient brain-inspired systems, beyond the capabilities of today’s hardware. In this paper, a novel design scheme is proposed to realize reliable and uniform multi-level cell (MLC) RRAM operation without the need of any read verification. RRAM quad-level cell (QLC) capability with 4 bits/cell is demonstrated for the first time. QLC is implemented based on a strict control of the cell programming current of 1T-1R HfO2-based RRAM cells. From a design standpoint, a self-adaptive write termination circuit is proposed to control the RESET operation and provide an accurate tuning of the analog resistance value of each cell of a memory array. The different resistance levels are obtained by varying the compliance current in the RESET direction. Impact of variability on resistance margins is simulated and analyzed quantitatively at the circuit level to guarantee the robustness of the proposed MLC scheme. The minimal resistance margin reported between two consecutive states is 2.1 kΩ along with an average energy consumption and latency of 25 pJ/cell and 1.65 µs, respectively.Quantum & Computer EngineeringComputer Engineerin

The Glaciogenic Reservoir Analogue Studies Project (GRASP): An integrated approach to unravel genesis, infill and architecture of tunnel valleys reservoirs

Tunnel galleys are common features in Palaeozoic glacigenic succession in North Afrcica and Middle East and they are amongst the most challenging target for hydrocarbon exploration and developing drilling in these regions. Similarly, these buried valleys form important groundwater reservoirs in Quaternary glaciated areas and their nature and sediment composition is critical to drive a sustainable production strategy and assess their vulnerability. Seismic resolution however, often limits the understanding of channel valleys morphology, 3D geometry and internal reservoir distribution, thus increasing the risk associated with developing effectively these reservoirs. Therefore a analogue-based predictive stratigraphical and sedimentological model can help to steer drilling strategy and reduce uncertainties and associated risks. For this purpose the GRASP joint industry programme was established four years ago focusing on an integrated study of tunnel valley infill and architecture from the southern North Sea (UK and NL). The thorough examination of existing large subsurface and outcrop data set regarding the last 3 Pleistocene glaciations in NW Europe resulted in an improved understanding of tunnel valley genesis, sedimentary process and internal architecture. This learning can be used ultimately to improve our predictive capability when exploring and developing natural resources from these geological systems.Geoscience & EngineeringCivil Engineering and Geoscience

New pulsed jet using spark plasma discharge: Subsonic configuration

Active flow control is demanding for new actuation technologies as none of the actual available actuators has reached all the criterions for expecting an implementation in the coming years. Here, a new type of pulsed jet is designed and preliminary measurements of its performances in quiescent flow are conducted. Pulsed operation has been chosen because of the expected high efficiency of pulsed actuation in comparison to continuous blowing. The traditional pulsed jets being limited in term of frequency because of the use of a mechanical valve to achieve the desired pneumatic opening and closing of a jet provided by an external pressure source, the fast response of electrical discharge is exploited in the present investigation. The objective is to modulate the output of a small jet exhausting from a pressurized chamber. A spark discharge is used to affect the thermodynamic state of the gas in order to electrically achieve periodic cancellation of the chocked flow conditions at the throat upstream the jet exit. In the present study, such actuator with additional neck extension and jet diameter enlargement is investigated. The configuration results in a high-speed subsonic jet whose velocity amplitude is modified by an arc discharge with deposited energy from 18 to 780 mJ. Some characteristics of the jet are provided using optical methods such as high-speed Schlieren and PIV. In particular, it is shown that the jet flow velocity can be increased from 50 m.s-1 to 190 m.s-1.Aerodynamic

Filtration Characterization Method as Tool to Assess Membrane Bioreactor Sludge Filterability—The Delft Experience

Prevention and removal of fouling is often the most energy intensive process in Membrane Bioreactors (MBRs), responsible for 40% to 50% of the total specific energy consumed in submerged MBRs. In the past decade, methods were developed to quantify and qualify fouling, aiming to support optimization in MBR operation. Therefore, there is a need for an evaluation of the lessons learned and how to proceed. In this article, five different methods for measuring MBR activated sludge filterability and critical flux are described, commented and evaluated. Both parameters characterize the fouling potential in full-scale MBRs. The article focuses on the Delft Filtration Characterization method (DFCm) as a convenient tool to characterize sludge properties, namely on data processing, accuracy, reproducibility, reliability, and applicability, defining the boundaries of the DFCm. Significant progress was made concerning fouling measurements in particular by using straight forward approaches focusing on the applicability of the obtained results. Nevertheless, a fouling measurement method is still to be defined which is capable of being unequivocal, concerning the fouling parameters definitions; practical and simple, in terms of set-up and operation; broad and useful, in terms of obtained results. A step forward would be the standardization of the aforementioned method to assess the sludge filtration quality.Water ManagementCivil Engineering and Geoscience