Low Dissipation Rate Research Articles

Measurement of low bit-error-rates of adiabatic quantum-flux-parametron logic using a superconductor voltage driver

Adiabatic quantum-flux-parametron (AQFP) is an energy-efficient superconductor logic. The advantage of AQFP is that the switching energy can be reduced by lowering operation frequencies or by increasing the quality factors of Josephson junctions, while keeping the energy barrier height much larger than thermal energy. In other words, both low energy dissipation and low bit error rates (BERs) can be achieved. In this paper, we report the first measurement results of the low BERs of AQFP logic. We used a superconductor voltage driver with a stack of dc superconducting-quantum-interference-devices to amplify the logic signals of AQFP gates into mV-range voltage signals for the BER measurement. Our measurement results showed 3.3 dB and 2.6 dB operation margins, in which BERs were less than 10−20, for 1 Gbps and 2 Gbps data rates, respectively. While the observed BERs were very low, the estimated switching energy for the 1-Gbps operation was only 2 zJ or 30kBT, where kB is the Boltzmann's constant and T is the temperature. Unlike conventional non-adiabatic logic, BERs are not directly associated with switching energy in AQFP.

Flame propagation across an obstacle: OH-PLIF and 2-D simulations with detailed chemistry

Flame propagation across a single obstacle inside a closed square channel is studied experimentally and numerically using a stoichiometric H2/O2 mixture at initial conditions 15 kPa and 300 K. The 50% blockage obstacle consists of a pair of fence-type obstacles mounted on the top and bottom walls of the channel. Direct optical visualization was performed using single-image measurement of the planar laser-induced fluorescence of the OH radical (OH-PLIF) and simultaneous high-speed schlieren video to study the flame topology and the flame tip velocity along the channel streamwise axis, respectively. The OH-PLIF images provide a novel level of detail and permit a thorough evaluation of the simulation accuracy. The flame tip accelerates to a peak velocity of 590 m/s just downstream of the obstacle followed by a deceleration and subsequent re-acceleration. The unburnt gas flow ahead of the flame is subsonic at all times. The flame does not show any signs of diffusive-thermal instability. Vortex–flame interactions in the recirculation zones downstream of the obstacle wrinkle the flame. The numerical simulations, based on solving the 2-D compressible reactive Navier–Stokes equations with detailed chemistry, predict the flame tip velocity accurately. However, differences in flame topology are observed, specifically, wrinkling is over-estimated. The over-prediction of flame wrinkling suggests a lower dissipation rate in the numerical simulations than in reality, which could be a consequence of neglecting the third channel dimension. Conditional means of the fuel consumption rate are similar to the consumption rates of 1-D unstretched laminar flames at all times. The increase in pressure during flame propagation causes an increase in fuel consumption rate which needs to be accounted for in simplified modeling approaches.

Theoretical model for multiple breakup of fluid particles in turbulent flow field

Generalized phenomenological model, based on the theories of probability and isotropic turbulence, is developed for multiple breakup of fluid particles in turbulent flow field. The approach uses a series of successive binary breakup events occur at a time scale comparable to the colliding eddy turnover time. It was found that the use of energy density, instead of energy, will increase the predicted binary breakup rate which is usually underestimated by the existing models in the literature. Generalization of the binary breakup model for multiple fragmentations is performed by defining a “remaining energy function” for the colliding eddy which means the contribution of original eddy to the later breakup events. For ternary breakage, the model shows a reasonably good agreement with the experimental data. The quaternary fragmentation frequency, however, is of negligible importance at lower energy dissipation rates but its contribution to breakage fraction at higher energy dissipation rates becomes considerable. The results also show that ternary and quaternary breakups have a considerable 90% contribution to the overall fragmentation, while pentenary and further fragmentations are of lower importance at low energy dissipation rates. At higher levels of energy dissipation rate, fragmentations up to six daughter particles contribute to more than 95% of the overall fragmentations. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4508–4525, 2016

Rates of Dissipation of Turbulent Kinetic Energy in a High Reynolds Number Tidal Channel

AbstractThe ability to estimate the rate of dissipation (ε) of turbulent kinetic energy at middepth in a high-speed tidal channel using broadband acoustic Doppler current profilers (ADCPs) is assessed by making comparisons to direct measurements of ε obtained using shear probes mounted on a streamlined underwater buoy. The investigation was carried out in Grand Passage, Nova Scotia, Canada, where the depth-averaged flow speed reached 2 m s−1 and the Reynolds number was 8 × 107. The speed bin–averaged dissipation rates estimated from the ADCP data agree with the shear probe data to within a factor of 2. Both the ADCP and the shear probe measurements indicate a linear dependence of ε on the cube of the flow speed during flood and much lower dissipation rates during ebb. The ebb–flood asymmetry and the small-scale intermittency in ε are also apparent in the lognormal distributions of the shear probe data. Possible sources of bias and error in the ε estimates are investigated, and the most likely causes of the discrepancy between the ADCP and shear probe estimates are the cross-channel separation of the instruments and the high degree of spatial variability that exists in the channel.

Riverine skin temperature response to subsurface processes in low wind speeds

AbstractBoth surface and subsurface processes modulate the surface thermal skin and as such the skin temperature may serve as an indicator for coastal, estuarine, and alluvial processes. Infrared (IR) imagery offers the unique tool to survey such systems, allowing not only to assess temperature variability of the thermal boundary layer, but also to derive surface flow fields through digital particle image velocimetry, optical flow techniques, or spectral methods. In this study, IR time‐series imagery taken from a boat moored in the Hudson River estuary is used to determine surface flow, turbulent kinetic energy dissipation rate, and characteristic temperature and velocity length scales. These are linked to subsurface measurements provided by in situ instruments. Under the low wind conditions and weak stratification, surface currents and dissipation rate are found to reflect subsurface mean flow (r2 = 0.89) and turbulence (r2 = 0.75). For relatively low dissipation rates, better correlations are obtained by computing dissipation rates directly from wavenumber spectra rather than when having to assume the validity of the Taylor hypothesis. Furthermore, the subsurface dissipation rate scales with the surface length scales (L) and mean flow (U) using (r2 = 0.9). The surface length scale derived from the thermal fields is found to have a strong linear relationship (r2 = 0.88) to water depth (D) with (D/L) ∼ 13. Such a relation may prove useful for remote bathymetric surveys when no waves are present.

A Method for Thermal Performance Characterization of Ultrathin Vapor Chambers Cooled by Natural Convection

Vapor chamber technologies offer an attractive approach for passive cooling in portable electronic devices. Due to the market trends in device power consumption and thickness, vapor chamber effectiveness must be compared with alternative heat spreading materials at ultrathin form factors and low heat dissipation rates. A test facility is developed to experimentally characterize performance and analyze the behavior of ultrathin vapor chambers that must reject heat to the ambient via natural convection. The evaporator-side and ambient temperatures are measured directly; the condenser-side surface temperature distribution, which has critical ergonomics implications, is measured using an infrared (IR) camera calibrated pixel-by-pixel over the field of view and operating temperature range. The high thermal resistance imposed by natural convection in the vapor chamber heat dissipation pathway requires accurate prediction of the parasitic heat losses from the test facility using a combined experimental and numerical calibration procedure. Solid metal heat spreaders of known thermal conductivity are first tested, and the temperature distribution is reproduced using a numerical model for conduction in the heat spreader and thermal insulation by iteratively adjusting the external boundary conditions. A regression expression for the heat loss is developed as a function of measured operating conditions using the numerical model. A sample vapor chamber is tested for heat inputs below 2.5 W. Performance metrics are developed to characterize heat spreader performance in terms of the effective thermal resistance and the condenser-side temperature uniformity. The study offers a rigorous approach for testing and analysis of new vapor chamber designs, with accurate characterization of their performance relative to other heat spreaders.

Application of mesotrione at different doses in an amended soil: Dissipation and effect on the soil microbial biomass and activity

The aim of this work was to estimate the dissipation of mesotrione applied at three doses (2, 10 and 50mgkg−1 dw) in an unamended agricultural soil, and this same soil amended with two organic residues (green compost (C) and sewage sludge (SS)). The effects of herbicide and organic residue on the abundance and activity of soil microbial communities were also assessed by determining soil microbial parameters such as biomass, dehydrogenase activity (DHA), and respiration. Lower dissipation rates were observed for a higher herbicide dose. The highest half-life (DT50) values were observed in the SS-amended soil for the three herbicide doses applied. Biomass values increased in the amended soils compared to the unamended one in all the cases studied, and increased over the incubation period in the SS-amended soil. DHA mean values significantly decreased in the SS-amended soil, and increased in the C-amended soil compared to the unamended ones, under all conditions. At time 0days, respiration values were significantly higher in SS-amended soils (untreated and treated with mesotrione) than in the unamended and C-amended soils. The effect of mesotrione on soil biomass, DHA and respiration was different depending on incubation time and soil amendment and herbicide dose applied. The results support the need to consider the possible non-target effects of pesticides and organic amendments simultaneously applied on soil microbial communities to prevent negative impacts on soil quality.

A cost‐effective and reliable method to predict mechanical stress in single‐use and standard pumps

The suitability of oil–water emulsions to predict shear forces in stirred bioreactors under cost‐effective and time‐saving conditions has been demonstrated several times, but no application to pumps has been described so far. In this report, the drop sizes in a model oil–water system were determined for the Levitronix PuraLev® multiuse (MU) series (PuraLev® 200MU and PuraLev® 600MU), a peristaltic pump (Masterflex® I/P Easy Load), and 4‐piston diaphragm pump (Quattroflow 1200‐SU, where SU is single‐use) using inline endoscopy. It was determined that the Sauter mean diameter could be used as a comparison criterion to estimate mechanical stress in pumps. The investigation showed that PuraLev® MU pumps are characterized by up to 59% larger Sauter mean diameters than their counterparts at comparable operational conditions. This indicates lower hydrodynamic stress in the PuraLev® MU pumps. Using computational fluid dynamics, a well‐streamlined fluid flow and low turbulent energy dissipation rates were found in the PuraLev® MU pumps, which correlated well with experimental results. A calculation model was used to predict the Sauter mean diameter by combining both experimental and computational fluid dynamics data. Good agreement with deviations below 13% was determined between model predictions and experimental data.

Development Machining of Titanium Alloys: A Review

Titanium and its alloys are hard materials, wear resistant, high strength to weight ratio. Therefore this material become very promising, especially in aerospace application. However, its application restrict when face machining processes. This material is very hard which is very difficult to manufacture by machining. Its low Youngs modulus tends to springy and creates vibration or chatter. Moreover, it has low heat dissipation rate that make the heat concentrate in the tool tip especially in the friction surface between tool and chip. Those phenomena result in very low tool life and low quality of machined surface, in term of surface roughness, surface integrity. This article describes some efforts to overcome those problems. Categorically, there are some groups of effort, i.e. varying machining parameters, modification the tool, treatment of the material, and different method of applying the coolant. It seems that using cryogenic cooling upon the tool is the most promising new technology to machine the titanium alloy.

Turbulence in Continental Stratocumulus, Part II: Eddy Dissipation Rates and Large-Eddy Coherent Structures

This study first illustrates the utility of using the Doppler spectrum width from millimetre wavelength radar to calculate the energy dissipation rate and then to use the energy dissipation rate to study turbulence structure in a continental stratocumulus cloud. It is shown that the turbulence kinetic energy dissipation rate calculated from the radar-measured Doppler spectrum width agrees well with that calculated from the Doppler velocity power spectrum. During the 16-h stratocumulus cloud event, the small-scale turbulence contributes 40 % of the total velocity variance at cloud base, 50 % at normalized cloud depth = 0.8 and 70 % at cloud top, which suggests that small-scale turbulence plays a critical role near the cloud top where the entrainment and cloud-top radiative cooling act. The 16-h mean vertical integral length scale decreases from about 160 m at cloud base to 60 m at cloud top, and this signifies that the larger scale turbulence dominates around cloud base whereas the small-scale turbulence dominates around cloud top. The energy dissipation rate, total variance and squared spectrum width exhibit diurnal variations, but unlike marine stratocumulus they are high during the day and lowest around sunset at all levels; energy dissipation rates increase at night with the intensification of the cloud-top cooling. In the normalized coordinate system, the averaged coherent structure of updrafts is characterized by low energy dissipation rates in the updraft core and higher energy dissipation rates surround the updraft core at the top and along the edges. In contrast, the energy dissipation rate is higher inside the downdraft core indicating that the downdraft core is more turbulent. The turbulence around the updraft is weaker at night and stronger during the day; the opposite is true around the downdraft. This behaviour indicates that the turbulence in the downdraft has a diurnal cycle similar to that observed in marine stratocumulus whereas the turbulence diurnal cycle in the updraft is reversed. For both updraft and downdraft, the maximum energy dissipation rate occurs at a cloud depth = 0.8 where the maximum reflectivity and air acceleration or deceleration are observed. Resolved turbulence dominates near cloud base whereas unresolved turbulence dominates near cloud top. Similar to the unresolved turbulence, the resolved turbulence described by the radial velocity variance is higher in the downdraft than in the updraft. The impact of the surface heating on the resolved turbulence in the updraft decreases with height and diminishes around the cloud top. In both updrafts and downdrafts, the resolved turbulence increases with height and reaches a maximum at cloud depth = 0.4 and then decreases to the cloud top; the resolved turbulence near cloud top, just as the unresolved turbulence, is mostly due to the cloud-top radiative cooling.

Effect of dispersed holdup on drop size distribution in oil–water dispersions: Experimental observations and population balance modeling

The drop diameter distribution (DSD) of dispersed Exxsol D80 oil-in-water in a lab scale stirred tank was predicted numerically using population balance equations (PBEs) modeling. It was assumed that the flow area was split into two zones, around the impeller with high energy dissipation rate and further away from the impeller with low energy dissipation rate. The dispersed phase chord length (CLD) distribution was experimentally measured with a focused beam reflectance method (FBRM) probe, and was then converted to the drop diameter distribution (DSD) numerically using a backward transform. Comparisons between the PBEs model results against experimental data from the current work and from previous literature showed that the PBEs predicted well the data at low dispersed phase fractions but overpredicted them at high ones. The predictions were slightly better when an increased power number was used. In addition, it was found that improved predictions could be obtained when the region of high energy dissipation rate around the impeller was enhanced.

Tidal dissipation in the early Eocene and implications for ocean mixing

AbstractThe tidally driven vertical diffusivity in the abyssal ocean during the early Eocene (55 Ma) is investigated using an established tidal model. A weak tide is predicted in the Eocene ocean, except in the Pacific. Consequently, the integrated global tidal dissipation rate is a mere 1.44TW, of which 40% dissipate in the Pacific. However, due to a stronger abyssal vertical stratification the predicted Eocene vertical diffusivities are consistently larger than at present. The results support the hypothesis that altered tidal dissipation may play a role in explaining the maintenance of past climate regimes, especially the anomalously warm temperatures in the southwest Pacific in the Eocene, and the low dissipation rates may be important for lunar evolution history.

Characterization of intermittent structures in the solar wind

AbstractThe solar wind (SW) is a suitable natural scenario to study the intermittent nature of magnetohydrodynamic (MHD) turbulence for systems with low dissipation rate. In particular, nonlinear wave-wave interactions can be characterized by the degree of phase correlation and by departures from Gaussianity of the magnetic field. In this work, we study in situ observations of magnetic field intensity from the spacecraft ACE, which is located near one astronomical unit from the Sun, in the SW near Earth. We compute the phase coherence index analyzing two sets of observations, each one consisting of approximately three months during 2008 and 2012, respectively. From these sets of data we characterize intermittent features of the magnetic field intensity corresponding to a solar maximum and a solar minimum.

Further study of grain boundary fracture in the breakage of single multiphase particles using X-ray microtomography procedures

The present work aims to verify the 3D quantitative analysis of grain boundary fracture in the breakage of single multiphase particles using X-ray microtomography. The breakage of single multiphase copper ore particles (6mm cubic particles) by slow compression was examined. From XMT reconstructed images using the Marching Cube method, interfacial areas between copper mineral grains and host rock were determined for both parent particles and progeny particles. In this way, the specific interfacial area ratio was calculated as a metric for grain boundary fracture. Preferential grain boundary fracture only occurs at low energy dissipation rates and the current results confirm initial results for 3mm cubes published previously by Garcia et al. (2009).

Kinetic Energy Dissipation and Convergence Criterion of Discontinuous Deformations Analysis (DDA) for Geotechnical Engineering

The discontinuous deformation analysis (DDA) is a numerical method for modeling discontinuous deformation behaviour of jointed rocks. In this paper, two basic problems are discussed related to kinetic energy dissipation and the convergence criterion for the DDA method when it is applied to geotechnical engineering. In view of the fact that the deformation and progressive failure can be treated as a quasi-static process with low kinetic energy dissipation rates, this paper introduces a viscous damping component to absorb discrete blocks’ kinetic energy, establishes the global equations of motion of the discrete block system that take damping effects into account, investigates the energy dissipation mechanism when solving a static or quasi-static problem, and defines the convergence criteria of displacement, kinetic energy and unbalanced force for DDA solutions when the system arrives at a stable state.

ZeROA: Zero Clock Skew Rotary Oscillatory Array

Resonant rotary clocking is a clocking technology for high frequency clock generation and distribution at a low power dissipation rate. It is commonly conceived that the multiple phases on the rings of the rotary oscillatory array (ROA) necessitate a non-zero clock skew operation. In this paper, the feasibility of zero clock skew synchronization with the rotary clocking technology implemented on the ROA is shown. Design automation experiments are performed to demonstrate that the zero clock skew operation can be achieved with minimal change in the performance of rotary clock operation. In particular, a marginal ±1.5% change in the tapping wirelength and a negligible 0.38% average skew mismatch are reported in experiments on R1-R5 and ISPD 2010 benchmark circuits.

DETERMINING COMPLETE SUSPENSION OF IMMOBILIZED ENZYMES BY ANALYSIS OF DIGITAL CAMERA IMAGES

To increase the stability of enzymes in organic solvents, they may be immobilized in a polymer matrix suspended in the solvent. It is important to know that all the immobilized enzyme particles are completely suspended in order to ensure an efficient particle-liquid mass transfer coefficient while putting as little energy into the system as necessary so that the particles are not harmed. A novel noninvasive method based on photometry and analysis of images taken with a standard digital camera is presented to estimate a mean extinction in different parts of the reactor and to finally determine the just suspending stirring speed (NJS) for complete suspension in an objective way. With this optical method, six different reactor configurations were compared based on the maximum local energy dissipation rate. Here, the 90° bladed stirrer with a flat bottom proved to be one of the best configurations for attaining complete suspension with low maximum local energy dissipation rate.

Stereoselective dissipation of epoxiconazole in grape (Vitis viniferacv. Kyoho) and soil under field conditions

Stereoselective dissipation of epoxiconazole had been studied in grape and soil during plant growing under field conditions in this paper. A sensitive and rapid chiral method was developed and validated for the determination of epoxiconazole stereoisomers in grape and soil based on liquid chromatography coupled with triple quadrupole mass spectrometry (LC–MS/MS). Phenomenex Lux Cellulose-1 column was used for enantioseparation with a mixture of acetonitrile/water (90/10, v/v) as mobile phase at flow rate of 0.3mLmin−1. Fortified recoveries in grape and soil samples ranged from 76.0% to 91.9% and relative standard deviations were less than 11.4% with fortified levels of 0.025–1.0mgkg−1. The limits of detection and quantification were 0.005mgkg−1 and 0.025mgkg−1, respectively, with linear calibration curves extending up to 5.0mgkg−1. The field experimental results showed that dissipations of epoxiconazole stereoisomers in grape followed first-order kinetics (R2>0.92) and stereoselectivity occurred in 2h after spraying. The (−)-stereoisomer with half-life of 9.3d degraded faster than (+)-stereoisomer with that of 13.2d, and resulted in relative enrichment of (+)-stereoisomer. However, the stereoisomeric dissipations in soil were triphasic (“increase–decrease–steady”) with lower dissipation rates, and also occurred with preferential degradation of (−)-stereoisomer under field condition. The results for stereoselective dissipations can be applied for food and environmental assessments of chiral pesticides.

Numerical modelling of supercritical submerged water jets in a subcritical co-flow

Among the different applications of supercritical fluids, the use of water submerged jets is common in different processes such as the production of nanoparticles or combustion applications. This paper presents a computational methodology for the modelling and simulation of subcritical and supercritical injection of water in a subcritical co-flow. In this work, we focus on numerical simulation of the process, emphasizing mixing modelling. Subcritical to supercritical submerged water jets in a subcritical co-flow are analysed and validated against experimental data with good accuracy (below 5% of absolute average deviation). The main results show that mixing zones are longer at subcritical temperatures than well above the critical point. Besides, due to the low dissipation rate found, the system is poorly micromixed and complete mixing at the molecular scale is never achieved. A methodology based on the evaluation of a macro-mixing length has been used. Using this method, the presence and location of mixing zones are better identified, showing that when pressure is well above the critical point, fluid-dynamic behaviour is more similar to subcritical conditions. Implications of these results are commented and analysed.

Quasi non-Markovian Approach to the Study of Decoherence of a Controlled-Not Quantum Gate in a Chain of Few Nuclear Spins Quantum Computer

We develop in the weak coupling approximation a quasi-non-Markovian master equation and study the phenomenon of decoherence during the operation of a controlled-not (CNOT) quantum gate in a quantum computer model formed by a linear chain of three nuclear spins system with second neighbor Ising interaction between them. We compare with the behavior of the Markovian counterpart for temperature different from zero (thermalization) and at zero temperature for low and high dissipation rates. At low dissipation there is a very small difference between Markovian and quasi no-Markovian at any temperature which is unlikely to be measured, and at high dissipation there is a difference which is likely to be measured at any temperature.