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Hyperelastic materials can experience a large deformation process. A constitutive relation suitable for an entire region from small, moderate, to large deformations is of great importance for practical applications such as fracture problems. Treloar's data are first investigated, and the tension curve is divided into three regimes: small-to-moderate regime, strain-hardening regime, and limiting-chain regime. Next, the modeling theory of hyperelastic materials is introduced, and the tensile behaviors of basic energy functions are analyzed for different deformation regimes. Finally, a successive procedure is suggested to establish an entire-region constitutive relation and then applied to Treloar's data. The present constitutive relation can maintain the initial shear modulus while the experimental data are satisfactorily predicted. The present procedure is simple and feasible and hence applicable to other hyperelastic materials when their entire-region constitutive relations are studied based on experimental data.

Voltage sag is a serious problem in power systems. To reduce voltage sag, it is necessary to identify and classify voltage sag sources. However, due to insufficient voltage sag data, our paper designs a CM-eCNN model through few-shot learning. Firstly, this paper introduces the CM-eCNN model and studies how to improve the extraction efficiency of the constellation model to feature map through the attention mechanism. Then, it introduces the training method of few-shot learning. Finally, our model training with few-shot learning has better performance than other models, which proves effectiveness of the model.

In this paper, based on the stability criteria described by the B–E inequality, E-inequality and T–C inequality, the region of stability is evaluated for common compressible isotropic hyper-elastic models by using the deformation modes of simple shear and volumetric change. For models with three model constants, the region of stability will be that of deformation induced by the inequalities due to the normalization conditions. For the models with four constants, for example, the region of stability will be two-folded. For the case in which the free constant is given, the region of deformation will be restricted. For the case in which the limiting deformation is given, the region of the free constant will be restricted. The current work describes how the region of deformation and/or free constant is determined when a compressible hyper-elastic model is utilized in practical engineering.

Injection molding with expandable thermoplastic microspheres (ETM) containing blowing chemicals is capable of fabricating lightweight, dimensionally stable plastic parts while using less material. This paper presents the study of microcellular injection molding of low density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) parts with various ETM contents. It was found that the molded parts exhibit relatively better surface quality than conventional foamed parts. The microcellular morphology and cell density of the fractured cross-sectional surfaces were characterized using a scanning electron microscope (SEM). As reflected by the testing results, the cell microstructure – such as cell size, cell density, and a layered structure with a foamed core sandwiched by skin layers – play an important role in the weight reduction, surface quality, and mechanical properties. A smaller cell diameter and a thicker skin layer help to improve the surface quality and tensile properties of the injection molded parts with ETM. Finally, an appropriate ETM content has a positive effect on cell microstructure and weight reduction, whereas too high a concentration of microspheres adversely affects the tensile properties and surface quality.

This study examines the morphological responses of Late Permian brachiopods to environmental changes. Quantitative analysis of body size data from Permian–Triassic brachiopods has demonstrated significant, directional changes in body size before, during and after the Late Permian mass extinction event. Brachiopod size significantly reduced before and during the extinction interval, increased for a short time in more extinction-resistant taxa in the latter stages of extinction and then dramatically reduced again across the Permian ⁄ Triassic boundary. Relative abundances of trace elements and acritarchs demonstrate that the body size reductions which happened before, during and after extinction were driven by primary productivity collapse, whereas declining oxygen levels had less effect. An episode of size increase in two of the more extinction-resistant brachiopod species is unrelated to environmental change and possibly was the result of reduced interspecific competition for resources following the extinction of competitors. Based on the results of this study, predictions can be made for the possible responses of modern benthos to present-day environmental changes.

PS/PMMA blends were prepared using a twin screw extruder and then extruded using an electromagnetic dynamic plasticating extruder equipped with a specially designed split die. During dynamic plasticating extrusion, the dynamic rheological behavior of PS/PMMA blends was investigated. The extrudates were cooled immediately and collected for morphology measurements using a scanning electron microscope (SEM). Results show that the average shear stress decreases with the introduction of vibration force field into the whole extrusion process, and reaches a minimum at the vibration amplitude of 0.15 mm and the vibration frequency of 5 Hz. At the same shear stress, the melt viscosity of the blend under dynamic plasticating extrusion is lower than that under static extrusion and decreases with vibration intensity. With increasing vibration intensity, the power-law index of the blend melt has a tendency to increase. The drop size of the dispersed phase in 25/75 PS/PMMA blend decreases at a faster rate with an increase of shear stress, compared with that in 75/25 PS/PMMA blends, correspondingly, the melt viscosity of 25/75 PS/PMMA blend has a stronger shear rate dependence. During dynamic plasticating extrusion, a negative deviation from the additivity rule is observed for the studied blend compositions.

The spreading dynamics of power-law fluids, both shear-thinning and shear-thickening fluids, that completely or partially wet solid substrate was investigated theoretically and experimentally. An evolution equation for liquid-film thickness was derived using a lubrication approximation, from which the dynamic contact angle versus the contact line moving velocity relationship was evaluated. In the capillary spreading regime, film thickness h is proportional to xi3/(n+2) (xi is the distance from the contact line), whereas in the gravitational regime, h is proportional to xi1/(n+2), relating to the rheological power exponent n. The derived model fit the experimental data well for a shear-thinning fluid (0.2% w/w xanthan solution) or a shear-thickening fluid (7.5% w/w 10 nm silica in polypropylene glycol) on a completely wetted substrate. The derived model was extended using Hoffmann's proposal for partially wetting fluids. Good agreement was also attained between model predictions and the shear-thinning fluid (1% w/w cmc solution) and shear-thickening fluid (10% w/w 15 nm silica) on partially wetted surfaces.

The diffraction patterns of submicron fluorescent particles were obtained using an air immersion objective (M = 40, NA = 0.6) under non-design optical conditions through a thick cover glass with a mismatched refractive index. The particle diffraction patterns changed with the defocus distance out of the front focal plane in the optical axis direction. A scalar diffraction model was applied to analyze the diffraction patterns for various optical conditions and to determine the defocus distance of the particle according to the measured intensity distribution of the diffraction pattern image. The results showed that the defocus distances have a submicron accuracy (0.2–0.3 µm), which can be used to determine the three-dimensional flow velocity distribution in a micro-channel and to track the three-dimensional Brownian motion of the particles for the specified defocus conditions.

A microscope objective designed for air medium has been used under non-design optical conditions to focus an exciting laser beam on sub-micron fluorescent particles with the emitted fluorescence received through a glass layer with a mismatched refractive index. The diffraction pattern with several clear interference fringes generated from the fluorescence emitted from a fluorescent particle changed with the particle's position along the optical axis. A scalar diffraction model developed by Gibson and Lanni (1991 J. Opt. Soc. Am. A 8 1601–13) was used to predict the diffraction patterns for various aberration conditions and to analyse the effects of the coherence properties of the fluorescence on the details of the diffraction pattern. The particle position along the optical axis, i.e. its defocus distance, could be determined based on the characteristic sizes of the particle's diffraction pattern to track the particle in three dimensions.

Dynamic responses of the blanket in full-scale flat-bottom type floc blanket clarifiers at the PingTsan Water Works, Taiwan Water Supply Corporation, were monitored given a step-change in coagulant (polyaluminum chloride, PACl) dosage. The blankets in the clarifiers were easily washed out using the conventional coagulation-clarification process (the single-stage process), seriously threatening drinking water quality. Consequently, the PingTsan Water Works included a pretreatment stage before the single-stage process to enhance treatment efficiency. The performance of this full-scale two-stage process for treating high-turbidity storm water was monitored on November 9 to 10, 2000. The two-stage process achieved a stable blanket and good quality clarified water that was insensitive to variation in raw water turbidity or PACl dose. Pilot tests were also conducted on October 6 to 7, 2001 to reveal performance differences between the single-stage and two-stage processes in dealing with high-turbidity water. The single-stage process yielded a blanket that was sensitive to PACl change. Not only was the produced blanket easily washed out when the PACl dose was step-decreased, it was also slow to recover when the chemical dosage was returned to its original value. The blanket yielded by the two-stage process was more robust to low coagulant dose, and recovered more easily when coagulant supply was increased. Applying the two-stage process to achieve the same effluent quality from single-stage process could significantly reduce total PACl dosage.

Free settling tests, small-angle light scattering, microtome-slicing techniques, and confocal laser scanning microscopy were performed to examine how the cationic flocculation or freezing and thawing affected the floc structure. The floc size, internal pore size, mass fractal dimensions determined from free-settling test or small angle light scattering test, aeral porosity, boundary fractal dimension and Sierpinski carpet fractal dimension of pore boundary from 2D slices, and the volume porosity, compactness, and the pores’ box-counting fractal dimension from 3D reconstructed image, were estimated and compared. Cationic flocculation would produce large flocs with internal pores of shape resembling a long “tube” with rough surface. Freezing and thawing would produce flocs with internal pores with lower aspect ratio and a smoother boundary.

In this work we investigated the use of a short time, low superheat boiling process to treat biological sludge. The treated sludge would exhibit a deteriorated filterability, and a marked increase in soluble organics content. A large portion of extracellular polymers was released from the solid phase by boiling. The microbial density levels of the total coliform bacteria and the heterotrophic bacteria were reduced after treatment. Dilution in sludge concentration could allow more organic compounds to be hydrolyzed and a greater fraction of microbes to be disinfected when compared with the undiluted samples.

Microscale boiling displays some quite unusual characteristics, such as the occurrence of so-called fictitious boiling. This article discusses some arguments on the thermodynamic and dynamic characteristics of the phase change and bubble nucleation in microchannels or microstructures. The cluster model is proposed to describe the density fluctuation in superheated liquid, and furthermore, the kinematics of a cluster are analyzed using Brownian motion. The analyses explore that the scale of microstructures has importance for the kinematics of a cluster and the boiling nucleation.

A criterion for phase change in microchannels has been proposed and developed. This criterion utilizes homogeneous nucleation and cluster theory to approximate the superheat required for phase change to occur in microchannels. The analysis performed herein indicates that while the fundamental phase-change mechanisms in micro- and macrostructures are the same, the relative importance of some aspects of these mechanisms is significantly different. In particular, because the mechanism of phase change is more strongly dependent upon molecular interaction and kinetics, the rate at which phase change occurs in microchannels ranges from milliseconds to microseconds, while for macrostructures it is of the order of seconds. This leads to a phenomenon referred to as ''flashlike evaporation'' in microchannels, something not previously observed in larger-scale channels. The good agreement between the predicted superheat and the values observed in previous experimental investigations demonstrates that this criterion c...

An optical-electronic method was developed for measurement of falling liquid film thicknesses. The method is based on the postulate that a sheet light beam passing tangentially through a vertical liquid film on a cylinder will be blocked by the falling liquid film. Hence, when the beam is much wider than the film, the output of a photodiode probe which is located on the opposite side of the cylinder from the light source will be reduced by an amount proportional to the film thickness. The shadow of the transient film shape will also appear on a screen behind the falling film. Therefore, the variation of the amplitude of the film waves can be measured from the output of the photodiode and the average film thickness can be measured from pictures of the shadow using computer aided image analysis. The average film thickness measured agrees well with commonly accepted empirical equations. The maximum relative deviation between the experimental and calculated results is 18.5% with a standard deviation of 4.34×1...

Experiments were conducted to investigate the flow characteristics of water flowing through rectangular microchannels having hydraulic diameters of 0.133-0.367 mm and H/W ratios of 0.333-1. Experimental results indicated that the laminar flow transition occurred at Reynolds numbers of 200-700. This critical Re for the laminar transition was strongly affected by the hydraulic diameter, decreasing with corresponding decreases in the microchannel. In addition, the size of the transition range was diminished and fully developed turbulent flow also occurred at much lower Re. The friction behavior of both the laminar and turbulent flow was found to depart from the classical thermqfluid correlations. lite friction factor, f, was found to be proportional to Re−1.98 rather than Re for the laminar condition, and proportional to Re−1.72i for turbulent flow. The geometric parameters, hydraulic diameter, and H/W were found to be the most important parameters and had a critical effect on the flow. Generally, increasing...

The forced-flow convection of water through rectangular microchannels having hydraulic diameters of 0.133-0.367 mm and aspect ratios of H/W = 0.333-1 was investigated experimentally. The flow friction was measured to analyze the heat transfer regimes and to explore the physical aspects of the connective heat transfer. The experimental measurements indicated that the upper bound of the laminar heat transfer regime occurred at a Reynolds number of 200-700, and fully turbulent connective heat transfer was reached at Reynolds numbers of 400-1,500. The transition Reynolds number diminished with the reduction of the microchannel dimension, and the transition range was observed to become smaller in magnitude. For the laminar heat transfer regime, the Nusselt number was found to be proportional to Re0.62while the turbulent heat transfer case exhibited a typical relationship between Nu and Re, but with a different empirical coefficient, CH,t. The geometric parameters were found to be important variables that could...

This investigation provides a theoretical description of the mechanisms that govern the rewetting of the surfaces, and presents an experimentally verified method by which the location of the rewetting front in the evaporator section of high capacity heat pipes can be determined as a function of the applied heat flux. The rewetting velocity was found to be a function of thermal properties of the liquid nd the channel, the input heat flux, the radii of the groove and the channel, and the location of the liquid front

An experimental program was conducted to investigate the rewetting characteristics of liquid flowing through multiple layers of screen mesh covering a heated vertical plate. Data obtained for acetone and R-11 were analyzed and compared with previously developed theoretical expressions for the rewetting velocity, the maximum liquid rise height, and the maximum heat flux for which rewetting could occur. The experimental results indicate that the thickness of the screen mesh layer and the liquid thermophysical properties are the most important factors affecting the rewetting behavior. As predicted by the theoretical model, small increases in the thickness of the screen layer initially caused the maximum permissible rewetting heat flux to increase. Once the layer thickness had reached a critical value, continued increases resulted in a decrease in the maximum permissible rewetting heat flux.

A series of experiments was conducted to investigate the flow boiling of R141b in hairpin tubes. A focus was addressed on visually observing flow boiling and two‐phase flow in U‐turn bends of a vertical upward hairpin tube with inner diameter of 6 mm at liquid velocities of 0.098, 0.147 and 0.196 m/s and heat fluxes in the range of 6191 W/m2 to 24763 W/m2, respectively. The bend could break up large vapor slugs in two ways, bubble tail fracture and bubble rupture, which induced significant effects on local heat and mass transfer. Under certain experimental conditions, small bubbles formed in the bend could not coalesce to be large vapor slugs but accumulate to form a unique flow pattern and greatly release thermal non‐equilibrium in the rest part of hairpin the tube.

Experimental investigations were conducted to explore the characteristics of bubble dynamics during subcooled nucleate boiling of ethanol on very thin wires (d = 0.18 mm), and an emphasis was addressed to observe bubble slipping phenomena. At small heat fluxes ((0.3∼1.6)×105 W/m2), most bubbles slipped along the heated wire instead of detaching from the wire, and moved at a uniform speed corresponding to the bubble diameter. The experimental measurements indicate that the bubble slipping velocity was closely dependent upon the applied heat flux and wire inclination (horizontal, vertical and an angle of 45° to the horizontal). Normally, bubbles slipped faster as increasing heat flux and inclination angle. For horizontal wires, a bigger bubble slipped more quickly. A special attention was paid to the effect of the buoyancy on the bubble slipping velocity.

An analytical investigation was conducted to determine the rewetting characteristics of thin, surface tension driven liquid films over heated plates as a function of the fluid properties, the film thickness, and the applied heat flux. Analytical expressions for the maximum sustainable heat flux and the rewetting velocity were developed for both flat and grooved plates and were compared with data from previous investigations. The results indicated good agreement for low film velocities; however, at high velocities the experimental data deviated significantly from the theoretical predictions. It was hypothesized that this deviation was due to the presence of liquid sputtering near the liquid front. To compensate for this liquid sputtering, the expressions for maximum sustainable heat flux and rewetting velocity were modified using an empirical correction factor developed from the data of previous thin film thickness investigations. The resulting modified expressions were found to compare very favorably with available experimental data over a large range of flow conditions and velocities.

The dynamic behavior of particles on a bubble interface contains axial and radial motions and is highly dependent upon the energy of this system. By introducing the concept of particle energy density (the average of the system energy based on particle number), four kinds of energy elements are estimated as critical elements, namely surface energy, line tension (an additive interaction at the contact line), electrostatic interaction and hydrophobic interaction (only for hydrophobic particle whose contact angle is greater than 64°). With consideration of different energy influences, the radial motion, vertical to bubble interface, and circumferential motion, parallel with bubble interface, are theoretically described and discussed.

A series of experiments was conducted to visually observe the fundamental features of the scale effect on boiling nucleation in mini/micro tubes. Boiling nucleation and/or bubble generation was observed in mini tubes of 1.5 to 2.5 mm and micro tubes of 50 to 200 μm in inner diameter. As heat flux was increased, bubbles were normally observed generating and growing inside the tubes of 2.5 mm. As tube diameter decreased from 1.5 to 0.05 mm, or in mini and micro tubes, the liquid was emitted instantaneously rather than generating bubbles and bubble growth, which is referred as liquid exploding emission in this paper. In mini tubes of Di = 1.5 mm, violent jet flows with macro bubbles were formed, and the liquid was almost totally emitted out of the tube. While in micro tubes of Di = 50–200 μm, the emission was much stronger, and only fog-like jet flow was observed consisted of extremely tiny bubbles, which indicates the mechanism of nucleation is different from that in mini tubes. It is expected that the scale effects intensely influence on not only the onset of emission, but also the strength and nature of emissions.Copyright © 2008 by ASME

Referring to regulation of ISO 9300, the discharge coefficients of 2mm, 5mm and 10mm nozzles with 2.5°, 4.0° and 6.0° diffuser angle were measured, respectively. Through comparisons among experimental results, simulation results and prediction results of empirical equations, it was clear that the discharge coefficients were the same for the nozzles with the same throat diameter and were in good agreement with the results of the empirical equations for 10mm nozzles, while that changed with different diffuser angle for other two sets of nozzles. The influence of throat diameter, surface roughness and entrance contour on discharge coefficient was analyzed one by one. The results showed the large out-of-roundness of entrance contour might be the most important reason resulted in the experimental results.

A series of experiments was conducted to understand the combustion characteristics and evaporating interface behavior of liquid fuel in capillary tubes. The flame shape, interface location of fuel front and tube outer surface temperature was visually observed and measured using CCD and IR camera, respectively. With fuel supply rate increasing, the interface location rose to tube exit and the temperature gradient of the outer tube surface increased, and consequently the evaporating interface tended to be unstable. The prediction of interfacial evaporation using available models was compared with the experimental measurements, indicating that this kind of highly non-equilibrium micro combustion with phase-change could not be described by normal mechanisms.

Membrane biofouling by microbial products adversely impacts the feasibility of adopting membrane bioreactors (MBRs) for treating wastewater. The fouling layer structure determines the pressure drop across the fouling layer. Three-dimensional distributions of nucleic acids, proteins, alpha-D-GLUCOPYRANOSE POLYSACCHARIDES, AND B-D-glucopyranose polysaccharides in the fouling layer formed on a mixed cellulose ester membrane were generated utilizing a quadruple staining protocol combined with confocal laser scanning microscopy (CLSM). For the first time, this study constructed a three-dimensional volumetric grids model representing the fouling layer structure on the basis of a series of CLSM images. Quantitative structural information about the fouling layer was extracted from the CLSM images.

Theoretical investigation is conducted to understand the bubble nucleation process in microstructures. The bubble evolution in microstructures is investigated for momentum conservation, and the evolution rate is deeply dependent on the structure. According to different dynamic characteristics in the region close to the critical radius, the nucleation process is divided into two stages. Based on the characteristics of these two stages, a nucleation kinetic equation is modified from classical theory and then is conducted to understand the special bubble nucleation process. The result concludes that the nucleation rate will be deduced if bubble evolution is restrained in microstructures.

Frost formation on flat cold surfaces was experimentally investigated, particularly the dynamic process was visually observed. During test runs, a plastic film was used to separate the cold surface from moist air, and formation of ice crystals was observed using microscope visualization technique as the film was removed and the cold surface reached to a specified temperature. In crystal growth stage of frost formation, a new phenomenon was found during ice crystal growth process. A layer of irregular crystal embryos was formed at the earlier stage, and these crystal embryos vanished when ice crystals with regular form grew up along nicks on the plate. And then, ice crystals on the plate kept growing slowly, while the area without ice crystals kept clean. This process is divided into three stages: formation of crystal embryos, mutation of ice crystals, and growth of ice crystal. Duration times of the first two stages seemed to be constant for different cases.Copyright © 2004 by ASME

The energy property in liquid near the wall was theoretically investigated to understand the effects of wall surface on inception process of nucleation or embryo bubble formation in boiling systems. Analyses indicate that the liquid near heating wall has higher pressure than in bulk region owing to existence of strong attractive forces, and this pressure could maintain a stable liquid microlayer and cause a steady energy peak near the wall. So a vapor embryo is likely to occur beyond the stable microlayer instead of exactly at the solid surface. The stable liquid layer may also be the inception structure of the ultrathin film before nucleation occurs. Fluctuations enhance the phenomenon of energy peak until the nucleation occurs, while energy peak promotes nucleation. Employing the concept of energy peak, the inception phenomena of the microlayer and the formation of embryo bubbles near solid surface were described.Copyright © 2003 by ASME

Transpiration cooling using porous triple-laminated plates was numerically investigated to understand the associated flow mechanism and heat transfer characteristics with/without crossflow. The flow structure and heat transfer behavior are very similar in the two laminate gaps, and crossflow has little influence on them. The cooling performance shows very good uniformity and high efficiency. Violent impingement and turbulent flow inside the plate contribute greatly to local heat transfer intensification. The cooling efficiency might be further improved with enhancement of film cooling effect, by enlarging the discharge holes to decrease the local jet-to-crossflow velocity ratio, or by using inclined discharge holes to increase the film attaching ability.Copyright © 2003 by ASME

Analysis T WO external artery heat pipes are currently under consideration for use as radiator elements on Space Station Freedom.* Both of these utilize a liquid and vapor channel connected by a longitudinal slot to provide axial pumping, Fig. 1. Although previous analytical and experimental investigations have demonstrated that these heat pipes will prime properly iii a zero-g environment, little is known about the effect of accelerations caused by orbital attitude adjustments or docking maneuvers. These accelerations, particularly longitudinal accelerations, could result in redistribution of the working fluid and dry out of the evaporator. This would require a reduction in the evaporator heat flux to allow rewetting. In the present work, an analytical investigation was conducted to determine what reduction in heat flux would be required and the effect of short-term longitudinal accelerations on the liquid/vapor interface. Assuming the heat pipe is properly primed and operating normally in a zero-g environment, the most damaging accelerations will be those occurring along the longitudinal axis because these are most likely to deprime the liquid channel. When the magnitude and/or duration of the acceleration is sufficient, liquid will flow out of the liquid channel through the connecting slot and accumulate in the end of the liquid and vapor channels, opposite the direction of acceleration. Because this flow may occur quite rapidly, some of the liquid may remain in the slot or adhere to the surface of the liquid and vapor channels forming a thin liquid film flowing along the length of the heat pipe. Although the flow of liquid out of the liquid channel and into the vapor channel is the most significant, the flow

A perturbation analysis of a simplified set of the Navier-Stokes equations was conducted to investigate the transport process of an evaporating and/or condensing thin liquid film. Expression of the wave growth rate was obtained by accounting for the phase transition at the interface and surface tension gradients. Effects of the surface tension gradient and phase transition on the stability were investigated by introducing two dimensionless parameters, the Marangoni number, Ma, and the phase transition number, ζ, respectively. The present investigation also provides several reasonable theoretical explanations of the fundamental characteristics of dropwise and pseudo-dropwise condensation.