Dissipation Measurements Research Articles

Comparison of the Responsivity of Solution-Suspended and Surface-Bound Poly(N-isopropylacrylamide)-Based Microgels for Sensing Applications.

In this submission, the phase transition behavior for poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAm-co-AAc) microgels and their assemblies was investigated as a function of temperature and pH using UV-vis spectroscopy (to probe light scattering behavior) and quartz crystal microbalance with dissipation (QCM-D) measurements. PNIPAm-co-AAc microgels were "painted" onto Au-coated glass substrates (for UV-vis) and the Au electrode of a QCM crystal to generate monolayers. The subsequent deposition of another Au layer on top of the pNIPAm-co-AAc microgel layer yields what is known as an etalon. UV-vis/QCM-D measurements revealed that the temperature and pH responsivities for the microgel assemblies match well with their solution behavior. UV-vis spectroscopy shows that the transmittance of the microgel monolayers decreased with increasing solution temperature at pH 3.0. At pH 6.5, the AAc groups in the microgels were deprotonated, leading to strong Coulombic repulsive forces inside the microgels that prevented their collapse and lead to minimal change in the transmitted light intensity. However, QCM-D analysis reveals more complex behavior as it is sensitive to the viscosity/viscoelasticity and thickness changes of the microgel layer, which ultimately depends on the microgel chemical composition and the interaction of the etalon's Au layer with the crystal. The maximum sensitivity to temperature is 0.8 × 10-3 °C·Hz-1, which is the most sensitive pNIPAm microgel-based QCM temperature sensor thus far reported in the literature. Finally, we exploit this new understanding to characterize the pH and ionic strength of a solution using pNIPAm-co-XAAc microgel-based etalon coated crystals. The research results and the sensing demonstration can inspire new and improved sensor designs for a variety of analytes.

Power dissipation in fractal Feynman-Sierpinski AC circuits

This paper studies the concept of power dissipation in infinite graphs and fractals associated with passive linear networks consisting of non-dissipative elements. In particular, we analyze the so-called Feynman-Sierpinski ladder, a fractal AC circuit motivated by Feynman’s infinite ladder, that exhibits power dissipation and wave propagation for some frequencies. Power dissipation in this circuit is obtained as a limit of quadratic forms, and the corresponding power dissipation measure associated with harmonic potentials is constructed. The latter measure is proved to be continuous and singular with respect to an appropriate Hausdorff measure defined on the fractal dust of nodes of the network.

Spin pumping, dissipation, and direct and alternating inverse spin Hall effects in magnetic-insulator/normal-metal bilayers

We theoretically consider the spin-wave mode- and wavelength-dependent enhancement of the Gilbert damping in magnetic insulator--normal metal bilayers due to spin pumping as well as the enhancement's relation to direct and alternating inverse spin Hall voltages in the normal metal. In the long-wavelength limit, including long-range dipole interactions, the ratio of the enhancement for transverse volume modes to that of the macrospin mode is equal to two. With an out-of-plane magnetization, this ratio decreases with both an increasing surface anisotropic energy and mode number. If the surface anisotropy induces a surface state, the enhancement can be an order of magnitude larger than for to the macrospin. With an in-plane magnetization, the induced dissipation enhancement can be understood by mapping the anisotropy parameter to the out-of-plane case with anisotropy. For shorter wavelengths, we compute the enhancement numerically and find good agreement with the analytical results in the applicable limits. We also compute the induced direct- and alternating-current inverse spin Hall voltages and relate these to the magnetic energy stored in the ferromagnet. Because the magnitude of the direct spin Hall voltage is a measure of spin dissipation, it is directly proportional to the enhancement of Gilbert damping. The alternating spin Hall voltage exhibits a similar in-plane wave-number dependence, and we demonstrate that it is greatest for surface-localized modes.

Vertical mixing and elements of mesoscale dynamics over North Carolina shelf and contiguous Gulf Stream waters

Results of microstructure measurements conducted in October–November of 2015 as a part of the Coupled Air Sea Processes and Electromagnetic Ducting Research (CASPER) project are discussed. The measurements were taken on the North Carolina shelf and across the Gulf Stream front. On the shelf, the oceanic stratification was influenced by highly variable surface salinity and along-bottom advection. Vertical mixing was mostly governed by variable winds. The vertical eddy diffusivity was estimated using the VMP-based dissipation measurements, and the diffusivity values obtained during calm periods and stormy winds were compared. Parameterization of the diffusivity for various mesoscale dynamical conditions is discussed in terms of shear instabilities and internal wave-generated turbulence based on data obtained in deep waters of the Gulf Stream and on the continental slope.

Inferring dissipation from current fluctuations

Complex physical dynamics can often be modeled as a Markov jump process between mesoscopic configurations. When jumps between mesoscopic states are mediated by thermodynamic reservoirs, the time-irreversibility of the jump process is a measure of the physical dissipation. We rederive a recently introduced inequality relating the dissipation rate to current fluctuations in jump processes. We then adapt these results to diffusion processes via a limiting procedure, reaffirming that diffusions saturate the inequality. Finally, we study the impact of spatial coarse-graining in a two-dimensional model with driven diffusion. By observing fluctuations in coarse-grained currents, it is possible to infer a lower bound on the total dissipation rate, including the dissipation associated with hidden dynamics. The tightness of this bound depends on how well the spatial coarse-graining detects dynamical events that are driven by large thermodynamic forces.

Estimating bed shear stress from remotely measured surface turbulent dissipation fields in open channel flows

AbstractSynoptic information on bed shear stress is necessary in predicting the transport of sediments and environmental contaminants in rivers and open channels. Existing methods of estimating bed shear stress typically involve measuring vertical profiles of streamwise velocity or Reynolds stress and taking advantage of the logarithmic or the constant stress region, respectively, to determine friction velocity and subsequently, bed shear stress. While effective, these methods yield local measurements of bed shear stress only. Direct measurements of bed shear stress can also be obtained through measurements with a drag plate. However, this method yields average shear stress information over the area of the plate and is impractical for large‐scale implementation in the field.Here we present a method capable of providing continuous synoptic measurements of bed shear stress over a large field‐of‐view. A series of Large‐Scale Particle Image Velocimetry (LSPIV) and Acoustic Doppler Velocimetry (ADV) measurements were made in a variety of flows generated in a wide‐open channel facility. Turbulent dissipation is calculated on the free surface from the 2‐D LSPIV results and is correlated with near‐surface ADV measurements of turbulent dissipation in the water column. The ADV results are consistent with the Nezu (1977) established relationship for the vertical variation of turbulent dissipation in the water column. Knowledge of the correlation between free‐surface and near‐surface dissipation values coupled with Nezu's (1977) relationship allow a robust and accurate estimate of friction velocity to be made and subsequently, shear stress at the bed can be estimated.

A spatially stabilized TDG based finite element framework for modeling biofilm growth with a multi-dimensional multi-species continuum biofilm model

We consider a model for biofilm growth in the continuum mechanics framework, where the growth of different components of biomass is governed by a time dependent advection---reaction equation. The recently developed time-discontinuous Galerkin (TDG) method combined with two different stabilization techniques, namely the Streamline Upwind Petrov Galerkin (SUPG) method and the finite increment calculus (FIC) method, are discussed as solution strategies for a multi-dimensional multi-species biofilm growth model. The biofilm interface in the model is described by a convective movement following a potential flow coupled to the reaction inside of the biofilm. Growth limiting substrates diffuse through a boundary layer on top of the biofilm interface. A rolling ball method is applied to obtain a boundary layer of constant height. We compare different measures of the numerical dissipation and dispersion of the simulation results in particular for those with non-trivial patterns. By using these measures, a comparative study of the TDG---SUPG and TDG---FIC schemes as well as sensitivity studies on the time step size, the spatial element size and temporal accuracy are presented.

Investigation of the Local Mechanical Properties of the SAC Solder Joint with AFM

Considering the size of the natural appearance of the micro alloy components of a SAC solder joint, AFM was used to investigate their mechanical properties in the form of their natural appearance. Contact-mode point-spectroscopy was done to determine the elastic modulus and tapping-mode point-spectroscopy was done to investigate the tip-sample power dissipation.The measured Young’s modulus values of the Cu, IML, Ag3Sn and Sn components, were 125±9 GPa, 111±20 GPa, 67±11 GPa and 57±16 GPa, respectively. The dissipation measurements were accomplished by Si and diamond probes with different spring constants. The different characteristics of the results are discussed.

Evidence of a forward energy cascade and Kolmogorov self-similarity in submesoscale ocean surface drifter observations

Using two-point velocity and position data from the near-simultaneous release of O(100) GPS-tracked surface drifters in the northern Gulf of Mexico, we examine the applicability of classical turbulent scaling laws to upper ocean velocity fields. The dataset allows direct estimates of both velocity structure functions and the temporal evolution of the distribution of particle pair separations. On 100 m-10 km spatial scales, and time scales of order 1-10 days, all metrics of the observed surface fluctuations are consistent with standard Kolmogorov turbulence theory in an energy cascade inertial-range regime. The sign of the third-order structure function is negative and proportional to the separation distance for scales ≲10 km where local, fluctuating Rossby numbers are found to be larger than 0.1. The scale-independent energy dissipation rate, or downscale spectral flux, estimated from Kolmogorov’s 4/5th law in this regime closely matches nearby microscale dissipation measurements in the near-surface. In contrast, similar statistics derived from a like-sized set of synthetic drifters advected by purely geostrophic altimetric AVISO data agree well with Kolmogorov-Kraichnan scaling for 2D turbulence in the forward enstrophy cascade range.

A one-dimensional viscoelastic and viscoplastic constitutive approach to modeling the delayed behavior of clay and organic soils

Accurate modeling of the time-dependent behavior of geomaterials is of great importance in a number of engineering structures interacting with soft, highly compressible clay layers or with organic clays and peats. In this work, a uniaxial constitutive model, based on Perzyna’s overstress theory and directly extendible to multiaxial stress conditions, is formulated and validated. The proposed constitutive approach essentially has three innovative aspects. The first concerns the implementation of two viscoplastic mechanisms within Perzyna’s theory in order to distinguish between short-term (quasi-instantaneous) and long-term plastic responses. Similarly, elastic response is simulated by combining an instantaneous and a long-term viscous deformation mechanism. The second innovative aspect concerns the use of a bespoke logarithmic law for viscous effects, which has never been used before to simulate delayed soil behavior (as far as the authors are aware). The third concerns the model’s extensive validation by simulating a number of different laboratory test results, including conventional and unconventional oedometer tests with small and large load increments/decrements and wide and narrow loading/unloading cycles, constant rates of stress and strain tests, and oedometer tests performed in a Rowe consolidation cell with measurement of pore pressure dissipation.

Determination of Interfacial Amorphicity in Functional Powders.

The nature of the surfaces of particles of pharmaceutical ingredients, food powders, and polymers is a determining factor for their performance in for example tableting, powder handling, or mixing. Changes on the surface structure of the material will impact the flow properties, dissolution rate, and tabletability of the powder blend. For crystalline materials, surface amorphization is a phenomenon which is known to impact performance. Since it is important to measure and control the level of amorphicity, several characterization techniques are available to determine the bulk amorphous content of a processed material. The possibility of characterizing the degree of amorphicity at the surface, for example by studying the mechanical properties of the particles' surface at the nanoscale, is currently only offered by atomic force microscopy (AFM). The AFM PeakForce QNM technique has been used to measure the variation in energy dissipation (eV) at the surface of the particles which sheds light on the mechanical changes occurring as a result of amorphization or recrystallization events. Two novel approaches for the characterization of amorphicity are presented here. First, since particles are heterogeneous, we present a methodology to present the results of extensive QNM analysis of multiple particles in a coherent and easily interpreted manner, by studying cumulative distributions of dissipation data with respect to a threshold value which can be used to distinguish the crystalline and amorphous states. To exemplify the approach, which is generally applicable to any material, reference materials of purely crystalline α-lactose monohydrate and completely amorphous spray dried lactose particles were compared to a partially amorphized α-lactose monohydrate sample. Dissipation data are compared to evaluations of the lactose samples with conventional AFM and SEM showing significant topographical differences. Finally, the recrystallization of the surface amorphous regions in response to humidity was followed by studying the dissipation response of a well-defined surface region over time, which confirms both that dissipation measurement is a useful measure of surface amorphicity and that significant recrystallization occurs at the surface in response to humidity.

Probing the interactions of organic molecules, nanomaterials, and microbes with solid surfaces using quartz crystal microbalances: methodology, advantages, and limitations.

Quartz crystal microbalances (QCMs) provide a new analytical opportunity and prospect to characterize many environmental processes at solid/liquid interfaces, thanks to their almost real-time measurement of physicochemical changes on their quartz sensor. This work reviews the applications of QCMs in probing the interactions of organic molecules, nanomaterials (NMs) and microbes with solid surfaces. These interfacial interactions are relevant to critical environmental processes such as biofilm formation, fate and transport of NMs, fouling in engineering systems and antifouling practices. The high sensitivity, real-time monitoring, and simultaneous frequency and dissipation measurements make QCM-D a unique technique that helps reveal the interaction mechanisms for the abovementioned processes (e.g., driving forces, affinity, kinetics, and the interplay between surface chemistry and solution chemistry). On the other hand, QCM measurement is nonselective and spatially-dependent. Thus, caution should be taken during data analysis and interpretation, and it is necessary to cross-validate the results using complementary information from other techniques for more quantitative and accurate interpretation. This review summarizes the general methodologies for collecting and analyzing raw QCM data, as well as for evaluating the associated uncertainties. It serves to help researchers gain deeper insights into the fundamentals and applications of QCMs, and provides new perspectives on future research directions.

Designing energy dissipation properties via thermal spray coatings

The coefficient of restitution is a measure of energy dissipation in a system across impact events. Often, the dissipative qualities of a pair of impacting components are neglected during the design phase. This research looks at the effect of applying a thin layer of metallic coating, using thermal spray technologies, to significantly alter the dissipative properties of a system. The dissipative properties are studied across multiple impacts in order to assess the effects of work hardening, the change in microstructure, and the change in surface topography. The results of the experiments indicate that any work hardening-like effects are likely attributable to the crushing of asperities, and the permanent changes in the dissipative properties of the system, as measured by the coefficient of restitution, are attributable to the microstructure formed by the thermal spray coating. Further, the microstructure appears to be robust across impact events of moderate energy levels, exhibiting negligible changes across multiple impact events.

Measurement of acoustic dissipation in an experimental combustor under representative conditions

The present paper is concerned with experimental estimation of acoustic dissipation under conditions representative of those in a rocket engine combustion chamber. Specifically, the influence of operating and injection conditions on acoustic dissipation is considered. Two experimental and analytical techniques are applied to measure and then compare dissipation rates of the first longitudinal and transverse acoustic modes in an experimental combustion chamber. Comparison between non-combustion and combustion tests showed that combustion chamber damping for the first transverse mode is far greater under combustion conditions. A lesser difference between non-combustion and combustion tests for the first longitudinal mode was found although the damping rates during combustion tests were still higher. A strong relationship between primary injection velocity and dissipation rate was observed, with lower injection velocities leading to decreased damping rates of the first transverse mode. Furthermore, increased film cooling injection rate decreased dissipation rate. The significant influence of representative conditions, specifically injection conditions, on dissipation rate has strong implications for both combustor design and experimental approaches aimed at quantifying dissipation in rocket combustion chambers.

Dissipation of Energy in Tissues of Berry Fruit of Selected Plants Species under Cyclic Load Conditions

Abstract Dissipation hypothesis of energy under cyclic loads conditions was used to characterize the behavior of berry fruit. The possibility of dissipation of energy as a result of plastic deformations (Dawidenkow hypothesis) or visco-elastic deformations (Voigt hypothesis) was considered. Tests of hysteresis of whole fruit squeezed among two rigid plates for various levels of load and with various speeds of deformation of samples for two directions of load application were conducted for verification of the usefulness of both hypotheses. The strength tests were preceded by the test of hysteresis, the mass and the geometry of fruit were determined additionally as well as conventional density and moisture was counted. A mutual relation of average values of the coefficients of elasticity EC was accepted as the measure of dissipation of energy as a result of changes in the angle of inclination of the curve in the springy return phase. Voigt hypothesis was confirmed as useful within the range of small speeds of deformation and lack of usefulness of the Dawidenkow hypothesis was proved.

Transfer of energy in Camassa–Holm and related models by use of nonunique characteristics

We study the propagation of energy density in finite-energy weak solutions of the Camassa–Holm and related equations. Developing the methods based on generalized nonunique characteristics, we show that the parts of energy related to positive and negative slopes are one-sided weakly continuous and of bounded variation, which allows us to define certain measures of dissipation of both parts of energy. The result is a step towards the open problem of uniqueness of dissipative solutions of the Camassa–Holm equation.

Lubrication synergy: Mixture of hyaluronan and dipalmitoylphosphatidylcholine (DPPC) vesicles

Phospholipids and hyaluronan have been implied to fulfil important roles in synovial joint lubrication. Since both components are present in synovial fluid, self-assembly structures formed by them should also be present. We demonstrate by small angle X-ray scattering that hyaluronan associates with the outer shell of dipalmitoylphophatidylcholine (DPPC) vesicles in bulk solution. Further, we follow adsorption to silica from mixed hyaluronan/DPPC vesicle solution by Quartz Crystal Microbalance with Dissipation measurements. Atomic Force Microscope imaging visualises the adsorbed layer structure consisting of non-homogeneous phospholipid bilayer with hyaluronan/DPPC aggregates on top. The presence of these aggregates generates a long-range repulsive surface force as two such surfaces are brought together. However, the aggregates are easily deformed, partly rearranged into multilayer structures and partly removed from between the surfaces under high loads. These layers offer very low friction coefficient (<0.01), high load bearing capacity (≈23MPa), and self-healing ability. Surface bound DPPC/hyaluronan aggregates provide a means for accumulation of lubricating DPPC molecules on sliding surfaces.

Real-time label-free detection and kinetic analysis of Etanercept—Protein A interactions using quartz crystal microbalance

A quartz crystal microbalance (QCM) was constructed to assess if such a biosensor has value as a complementary real-time label-free analysis platform for the biopharmaceutical industry. This was achieved through modifying QCM crystals with a low-fouling carboxymethyl-dextran layer bearing Protein A, and then injecting solutions containing Etanercept (i.e., Enbrel®) into the QCM chambers. The kinetics of Enbrel® – Protein A interactions was modeled using the Langmuir binding model and Enbrel® concentrations between 0.75–300ngmL−1. The resulting equilibrium dissociation and association constants (KD and KA) were 5.06×10−8M and 1.98×107M−1, respectively. The association and dissociation rate constants (kon and koff) decreased substantially as Enbrel® concentration, [C], increased, despite that the net binding rate, (kon[C]+koff), increased. The decrease in kon and koff was hypothesized to be a consequence of mass transport limitations. To verify this, QCM dissipation measurements were analyzed to provide insight on solution viscosity. As Enbrel® concentration increased, the net change in dissipation, ΔD, became larger. An augmentation of ΔD is associated with a higher solution viscosity, which would result in an increase in mass transport limitations. Therefore, the decrease in kon and koff for increasing Enbrel® concentration can be attributed to mass transport limitations. In conclusion, QCM is a valuable complementary real-time label-free biosensor analysis platform for the biopharmaceutical industry. Unlike the surface plasmon resonance (SPR) platform, QCM allows measuring dissipation, which can provide insight on how mass transport limitations impact interaction kinetics.

Pore Water Pressure Distribution and Dissipation During Thaw Consolidation

A novel apparatus was developed for measurement of pore water pressure distribution and dissipation during thaw consolidation. Thaw consolidation tests were conducted to verify the applicability of nonlinear stress–strain relationship in 3-D large strain thaw consolidation theory. During thawing process, the measured pore pressure at different layers of soil samples increased sharply at first; when a certain value was approached, it stepped into dissipation stage. It was proved that the calculated results have a good agreement with tested results on both pore pressure distribution and dissipation. Further analysis indicated that nonlinearity of pore pressure distribution was proportionally related to thaw consolidation ratio (R), while it was opposite for thaw consolidation degree.

Energy-harvesting potential of automobile suspension

ABSTRACTThis study is aimed quantify dissipated power in a damper of automobile suspension to predict energy harvesting potential of a passenger car more accurately. Field measurements of power dissipation in a regenerative damper are still rare. The novelty is in using the broad database of real road profiles, a 9 degrees-of-freedom full-car model with real parameters, and a tyre-enveloping contact model. Results were presented as a function of road surface type, velocity and road roughness characterised by International Roughness Index. Results were calculated for 1600 test sections of a total length about 253.5 km. Root mean square of a dissipated power was calculated from 19 to 46 W for all four suspension dampers and velocity 60 km/h and from 24 to 58 W for velocity 90 km/h. Results were compared for a full-car model with a tyre-enveloping road contact, full-car and quarter-car models with a tyre–road point contact. Mean difference among three models in calculated power was a few per cent.