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In the context of the growing use of hydrogen for decarbonization in combustion, understanding NO x emissions from hydrogen burners is crucial. This study focuses on the impact of partial premixing on NO x production in hydrogen flames using a coaxial injector with swirl. The goal is to expand conventional jet scaling laws to encompass additional physical phenomena. The flexible injection system employed allows the stabilization of various flame types depending on the operating conditions, and double-front flames are obtained in several configurations. Observing the limitations of known scaling laws, particularly in coaxial flows with low-velocity differences or swirl, we conduct experiments measuring NO x and flame volume. Two Large Eddy Simulations explore distinct flame configurations to deepen our understanding about coaxial jet and recirculating flames, especially in the presence of a secondary premixed front due to rich premixing. Our investigation delves into the relationship between NO production and strain rate, considering turbulent and strain-related timescales. Notably, the presence of a premixed flame front alters the velocity profile on the shear layer, and the observed relationship between strain and turbulence in jet flames does not hold for recirculating flames. Thanks to this new insight, we propose a novel formulation for NO x scaling in coaxial jets, leveraging existing literature on coaxial jet modeling. Additionally, we propose a simple model to represent the piloting strain rate for NO emission in recirculating flames. Intricate effects of both swirl and partial-premixing are then included in the derived NO x scaling laws. [Display omitted] • Nitrogen oxide (NO x) emissions are measured in many swirled hydrogen flames. • Large-eddy simulations are used to enlighten the formation mechanisms. • Scaling laws for NO x emissions are derived to work for different flame topologies. [ABSTRACT FROM AUTHOR]

• GNSS-TEC data showed ionospheric changes immediately before the 2008 M w 7.9 Wenchuan earthquake, China. • TEC trend showed positive changes in trends ∼1/2 h before the earthquake and the anomaly reached ∼5 % of the background. • These anomalies are mostly consistent with worldwide trends of past examples for ∼20 earthquakes. Ionospheric disturbances associated with large earthquakes can be observed with global navigation satellite system (GNSS) receivers on the ground as changes in total electron content (TEC). In addition to coseismic disturbances ∼10 min after earthquakes caused by acoustic-gravity waves from epicenters, there have been reports on changes immediately before very large earthquakes. We show such disturbances for the 2008 Wenchuan earthquake (M w 7.9), China, started ∼ 37 min before the main shock and reached ∼5 percent of the background value. The results of past ∼20 cases with M w 7.3 or more exhibit simple relationships that the leading times scale with fault lengths and the intensities of the anomalies relative to the backgrounds scale with fault areas. We demonstrate that the anomaly immediately before the 2008 Wenchuan earthquake fits well with these trends but with slightly longer leading time and stronger intensity. [ABSTRACT FROM AUTHOR]

For producing fine metal powders, the critical step is ligament dynamics of molten metal, while the thinning and breakup processes subjected to the interfacial heat and mass transfer are elusive. Here, we conduct high-speed visualization and infrared pyrometry on a single tin ligament that enable us to distinguish the effects of surface oxidation and cooling. On the tin ligament, a thin oxide layer grows according to the molecular diffusion of ambient oxygen, leading to the significant increase of viscosity coefficient at the interface. The capillary destabilization is then suppressed by the surface oxidation. We discover that the tin ligament thins initially following the capillary timescale, while the necking is accelerated to obey the viscous-capillary timescale as the oxide layer becomes one-tenth of the neck radius, corresponding to the Ohnesorge number of larger than unity. Simultaneously, the neck is cooled by the ambient. The accelerated thinning due to the viscous effect leads to the prompt decrease of heat capacity. We successfully formulate the rapid temperature drop at the neck based on the interfacial heat transfer coupled with the viscous-capillary necking dynamics in a consistent manner. [Display omitted] • Surface oxidation of molten tin increases viscosity and accelerates thinning. • Thinning of oxide tin ligament follows viscous-capillary timescale. • Heat transfer of tin ligament couples with interfacial mass transfer. [ABSTRACT FROM AUTHOR]

• SEC method for separation of liposomes and lipodisks. • Nanoparticle shape heterogeneity analysis by scaling law of R g vs. MW. • A semi-quantitative model to predict nanoparticle morphology. Nanoparticle-based drug delivery systems are rising technologies to access challenging therapeutic targets. Following commercial success of lipid-based nanoparticles (LBNP), accruing understandings of nanoparticle structures and critical quality attributes through advanced analytics are beneficial to future clinical development and generalization of this delivery platform. The morphological attributes of nanoparticles, such as shape, can affect uptake, cell-interaction, drug release, circulation, and flow. Gaining an understanding of these structure-activity relationships in early-stage formulation development is important because mix morphologies can affect quality and potency but often exist before process control strategies are fully implemented. In this study, we used shape heterogeneous nanoparticle mixtures, containing various populations of liposomes and lipodisks, as a model system and developed an online semi-quantitative method to characterize the nanoparticle shape heterogeneity by size exclusion chromatography (SEC) coupled with multi-angle light scattering (MALS). The liposomes and lipodisks were separated in SEC when their sizes were ∼3 fold different. When the particles of different shapes were in similar sizes, size-based separation was not always feasible. Instead, light scattering data distinguished liposomes and lipodisks by the scaling law linking radius of gyration and molecular weight of the nanoparticles, enabling morphological identification. A semi-quantitative model was built based on the exponential correlation between the scaling law exponents and the ratios of liposomes and lipodisks. The model was applied to test 6 random formulations made with different compositions and manufacturing processes, and the predicted liposome percentage for 5 formulations was within 25 % absolute difference from the percentage determined by cryogenic electron microscopy (cryo-EM). We envision this method being routinely used to characterize liposome and lipodisk shape heterogeneity during formulation screening as well as on stability studies. Potentially, the method can be converted to in-process control method and extended to other categories of nanoparticles beyond liposomes. [ABSTRACT FROM AUTHOR]

Fluid injection via a vertical well into a high-temperature formation may induce multiple longitudinal thermal fractures, which may eventually transition to two-wing fractures during fracture propagation, depending on horizontal stress ratio κ. In this study, we develop a plane strain model with radial heat conduction to investigate either two-wing fractures under highly anisotropic stresses κ h a ≫ 1 or multiple fractures under isotropic stresses κ = 1. The coupled dimensionless elasticity equation and criteria of fracture propagation (and arrest) are formulated, discretized, and solved iteratively (with two special algorithms). Two additional critical model parameters are dimensionless effective confining stress T and wellbore radius A. The multiple-fracture solution of dimensionless fracture length L , angular spacing D , and aperture consists of solutions for competitive propagation of fractures with arrests in the near-wellbore region and the subsequent stable propagation of fractures away from the wellbore. Both the multiple-fracture and two-wing-fracture solutions accurately capture the early-time transient and late-time power-law changes with dimensionless time τ , as verified numerically. The late-time fracture propagation follows scaling law L = f T , A , D τ 1 − 2 T / 2. These solutions and scaling laws can be used to well bound a general solution with 1 < κ < κ h a as demonstrated numerically for a geothermal site, for which the maximum fracture length reaches 0.45, 2.71, and 16.42 m in 1, 100 and 10,000 days of cooling, respectively. The applicability of the assumptions used in the theoretical and numerical analysis is discussed. • Solutions of two-wing thermal fractures under highly anisotropic stresses were solved. • Solutions of multiple thermal fractures under isotropic stresses were solved. • Two limiting-case solutions bound general solutions of multiple thermal fractures. [ABSTRACT FROM AUTHOR]

Our objective is to develop scaling laws for the thrust and lift coefficients of a pitching wing in a periodic freestream by extending the conventional scaling laws presented in our previous study to account for the variations in the frequency ratio. The periodic freestream is spatially uniform and temporally oscillated in the mainstream direction. We derived scaling laws by considering the added mass and circulatory forces, and experimentally validated them at frequency ratios of 1 , 2 , and 3 and phase differences of 0 − 2 π. The results showed that the proposed scaling laws agree well with the experimental data under the present conditions. Our scaling laws indicated that as the frequency ratio increases, the thrust coefficient increases and is independent of the phase difference. At a frequency ratio of 1 , the lift coefficient depends on the phase difference, whereas at frequency ratios of 2 and 3 , it is independent of the phase difference. Furthermore, using our scaling laws as a guide, we propose the method for streamwise and lateral maneuvers. • Extended scaling laws predict thrust and lift at frequency ratio of 1 , 2 and 3. • Thrust increases with frequency ratio and is independent of phase difference. • At a frequency ratio of 1 , the lift coefficient depends on the phase difference. • At frequency ratios of 2 and 3 , it is independent of the phase difference. [ABSTRACT FROM AUTHOR]

[Display omitted] • Experimentally examined the impact of varying the junction angle on droplet size. • Four flow regimes were identified: Parallel flow, Jetting, Dripping and Squeezing. • A scaling law containing the junction angle is proposed to predict droplet lengths. • Estimated the volumes of droplets, slugs, and unit cells based on 2-D snapshots. Liquid-liquid two-phase flow in T-inlet microchannels with different junction angles (θ = 30°, 60°, 90°, 120° and 150°) was investigated experimentally. Four flow regimes of the dispersed phase were identified, i.e., parallel flow, jetting, dripping and squeezing, and the distribution of flow regimes for the dispersed phase corresponding to variations in the junction angle was plotted. The consequences of varying junction angle and flow conditions in the squeezing regime on the generated droplet size were analyzed. The results indicate that low capillary number and large flow rate ratio are conducive to the formation of large-size droplets. For constant flow conditions, junction angle θ = 90° is detrimental to the formation of squeezing microdroplets. The increase in microchannel junction angle causes the droplet size to decrease until θ > 90°, where the droplet size increases with the junction angle. On the basis of experimental results, the scaling law correlation equations containing the junction angle for predicting the droplet length and droplet volume are proposed, respectively. The predicted values match well with the experimental data. The results of this work contribute to the enhancement of the monodispersity of microdroplets and the precise control over a wide range of the generated droplet size by adjusting the junction angle. [ABSTRACT FROM AUTHOR]

The rapid urbanization leading to extensive construction activities has significantly harmed the urban ecosystem. However, there remains a lack of systematic consideration regarding the interplay of energy and materials within construction projects. To bridge this gap, the present study employs emergy analysis and data envelopment analysis to comprehend the metabolic characteristics of construction projects. Specifically, 66 construction projects in China were selected for their comprehensive project-level data. The construction flows were categorized into renewable resources, local non-renewable resources, imported resources, exported products, and wastes. The results indicate that imported emergy comprises the majority of total emergy usage, with labor input being the primary contributing factor. Ecological benefit and efficiency analyses reveal that the emergy cost surpasses the emergy benefit. This inefficiency stems mainly from suboptimal utilization of imported resources and inadequate management of undesired outputs in construction projects. Furthermore, buildings in northern and central regions exhibit superior performance in total emergy use, emergy density, and emergy load ratio, whereas public and residential buildings exhibit higher environmental burdens and greater reliance on external resources. A statistically significant sublinear power-law relationship between the scale of construction projects and their metabolic rates was also identified, indicating a notable scale effect on energy and resource consumption during the building construction process. • A project-level analytical framework is built to understand the construction metabolism. • The overall metabolic performances of construction projects are measured. • The scaling law is demonstrated in Chinese construction practice. [ABSTRACT FROM AUTHOR]

• The proposed scaling strategy ensures dynamic similarity by optimizing structural parameters of rotor systems. • The distance between disk and bearing has significant influence on the first-order critical speed in optimization process. • Increasing the weighing coefficient of a certain order of critical speed effectively reduces the deviation in optimization. • The optimized GDSM rotor predicts the prototype more accurately than the SSM rotor. • Such scaling strategy practically guides the design and manufacturing of experimental rotor systems. It is difficult to perform practical experiments on working gas turbine rotors due to the factors of safety and implementability etc. Therefore, it is of great importance to design a well-scaled test rig that can accurately predict the dynamic characteristics of a prototype rotor. In this paper, a design method for scaled rotor systems considering dynamic similarity and restricted support stiffness is proposed. The structural similarity coefficients of the strictly scaled model (SSM) in a rotor system are obtained based on the similarity theory and scaling law. Key optimization parameters and ranges are determined through sensitivity analysis. By genetic algorithm, the geometrically distorted scaled model (GDSM) in rotor system with dynamic similarity is established to modify the SSM rotor. Moreover, modal experiments are carried out to verify the validity of the proposed scaling design method. Results show that the type, number and accuracy of optimized parameters are important in optimization design. The critical speed of the first three orders of the GDSM rotor are very close to ones in the prototype, and the maximum percentage deviation is 1.18%. Experimental results show that the rotor developed by the geometrically distorted scaling method is able to reflect the dynamic properties of prototype accurately despite the slightly distorted partial structural parameters. Such proposed design method can provide a highlight in the design and manufacturing of the key components of gas turbine rotors for laboratory. [ABSTRACT FROM AUTHOR]

Understanding the structure-mechanics relationships in cellular solids is essential for using the same material to achieve better mechanics. We use multiscale modeling and computation to investigate the mechanics of a series of hierarchical carbon nanoarchitectures with structural features quantitatively characterized. We find that the Young's modulus and tensile strength of the graphene network are mainly determined by its density. However, different density scaling laws of compressive strength are observed and they are related to the length, diameter, and surface roughness of the constituent struts, the buckling form of which yields different scaling laws. Therein, the graphene network with struts of a higher length-to-diameter ratio, smoother surface, and failure mode of shell buckling has a higher compressive strength for a given overall density and topology. Besides, the topology, bonding mode, and multiscale defects explain the large variance of scaling laws of different carbon materials. The work reveals the great potential of architected cellular carbons and provides insight into their future design. [Display omitted] [ABSTRACT FROM AUTHOR]

Low-saturation liquid-containing granular materials are commonly encountered in both natural and industrial settings, where interstitial liquids significantly affect the motion of particles, while particle size polydispersity plays a crucial role in determining the level of system cohesion. In this study, the collapse of wet polydisperse granular columns is numerically investigated based on the developed discrete element model, with corresponding dam-break experiments performed to validate our numerical model and methodology. The dependence of the dynamics and flow mobility on particle size distribution is primarily examined, and the underlying mechanisms are also explored by analyzing particle path lengths and average fidelity. Building upon the effective Bond number proposed using the mixing theory, a macroscopic cohesion parameter at the material scale is defined by considering the dependence of the collapse on the system size effect. The relevance of this cohesion parameter in describing different wet polydisperse granular collapses is further validated based on our designed experimental tests and DEM simulations. The approach of constructing the cohesion parameters at different scales can be extended to characterize cohesion effects in more complex wet polydisperse granular flows and describe their associated rheological behaviors. [ABSTRACT FROM AUTHOR]

• An e-exponential scaling law to relate plume radiance to flight velocity was proposed. • A power scaling law to relate plume radiance to vacuum thrust was exhibited. • A sinusoidal scaling law to relate plume radiance to detection angle was presented. • A four-parameter explicit scale law modeling approach was developed. The complexity of the rocket motor exhaust plume radiation phenomenon, along with the influence of numerous parameters and implicit propagation, makes the theoretical simulation calculations expensive. This hinders design optimization, parameter identification, and other studies. Hence, it is crucial to establish the direct correlation between thrust, velocity, altitude, detection angle, and plume radiation in engineering. The paper proposes a scaling law modeling approach for predicting plume infrared radiation from liquid oxygen (LOX)/kerosene rocket engines to solve the difficulties of quick prediction and lack of explicit models. An explicit scaling law model with four parameters is developed by utilizing the e-exponential scaling law to relate plume radiance to flight velocity, the power scaling law to relate plume radiance to vacuum thrust, and the sinusoidal scaling law to relate plume radiance to detection angle. This model employs a decoupled modeling approach for plume radiance, flight altitude, flight velocity, vacuum thrust, and detection angle. A fast prediction method for the LOX/kerosene rocket engine plume in the altitude range of 11∼61 km is achieved. The theoretical simulation test shows the relative error of the velocity-scaling law in predicting the radiance of the RD-180 template engine during the Atlas III flight trajectory is less than 20 %. The radiance of the RD-170 and RD-191 rocket engines is predicted using the thrust-scaling law based on the radiance of the RD-180 template engine exhaust plume. The radiance of the exhaust plume from the RD-170 and RD-191 rocket motors is estimated using the thrust-scaling law with an accuracy of under 15 %. Subsequently, the radiance of these two motors at detection angles between 10° and 170° is predicted using the angle-scaling with a relative error of less than 35 %. [ABSTRACT FROM AUTHOR]

• The oscillatory behavior of drops in an ambient liquid under an impact is numerically and experimentally studied using the Basilisk C and a self-designed falling drop tower facility. • The effects of dimensionless parameters on the oscillatory behavior of drops were systematically studied. • A scaling law between the maximum deformation of the drops during the oscillatory behavior and the dimensionless parameters is established, which can be well interpreted by a mass-spring-damp mode. In this work, the oscillatory behavior of drops in an ambient liquid under an impact is numerically and experimentally studied using the Basilisk C and a self-designed falling drop tower facility, respectively. The numerical results of the oscillatory drops are consistent with the experimental data. A shape parameter e is proposed to describe the oscillatory behavior of the drops. Using the energy budgets of the drops, the influence of dimensionless parameters, i.e., Reynolds number Re , Ohnesorge number Oh , Bond number Bo , and viscosity ratio η on the oscillatory amplitude and period of the shape parameter e is systematically investigated. Furthermore, a scaling law between the maximum deformation of the drops during the oscillatory behavior and the dimensionless parameters is established, which can be interpreted by a mass-spring-damp model. It is found that the established model agrees well with our numerical and experimental results without any fitting parameters when the viscosity of the ambient liquid is near or smaller than that of the drop, and the maximum deformation has a clear proportionality as O h 2 R e (1 + R e). [Display omitted] [ABSTRACT FROM AUTHOR]

Cities are constantly dynamics, but emerge the stability of urban systems as evidenced by robust urban scaling. Both properties serve as necessary perspectives for understanding the evolution of cities and the complexity of urban systems. However, the evolution trends and mechanisms behind the above relationships, particularly concerning geographic processes, remain to be explored in depth. In this study, the dynamic fluctuations within individual cities and the macro-stability of the evolution of urban systems over the past two decades are systematically demonstrated. Subsequently, associations between urban systems and individual cities are established on the basis of micro- and macro-dynamic mechanisms. The trajectory of individual cities can be divided into scaled–driven growth (SG) and urban excess growth (EG). The former is the result of scaling effects within the system, while the latter is affected by global external effects. Taking as examples urban built-up area and social productions, the evolution pathways that vary from different attributes are analyzed. The results indicate that urban built-up area is more affected by scaling effects whereas social productions is driven more by global external effects. Moreover, we examine the driving forces and mechanism of EG from the aspects of economic development level, technological and economic progress, industrial structure and regional policy through an empirical analysis. This study provides a nuanced understanding of the trends and pathways of urban land–population system from the perspective of complex urban systems and holism to deepen the understanding for general properties of cities and co-evolution for urban population size and land expansion. • Coupling the micro-dynamics of cities and macro-stability of urban systems to study the trends and pathway of urban evolution. • The trajectory of urban temporal growth of individual cities can be divided into scale-driven growth and excess growth. • Interactions within the urban land-population system approximately reappear a scale-driven evolution pathway more closely than social production. • Urban excess growth is related to the external effects of macro environment such as macro-economic environment and regional policy. [ABSTRACT FROM AUTHOR]

The small time-step due to the small size of microcapsules using the discrete element method (DEM) requires a significant number of computations when analyzing the force condition of microcapsules for mixing self-healing concrete. In this study, a speed-up method with a reduced Young's modulus is proposed to correct the particle contact force after establishing the relationship between the maximum contact force and the Young's modulus of particles in the collision process by using theoretical derivations and data fitting. The proposed method was verified using a stirred box model with the DEM and a stirred tank model with computational fluid dynamics–DEM. The effects of different particle numbers, impeller speeds, and time-step sizes on the accuracy of the proposed method were investigated. The results demonstrated the feasibility of analyzing the maximum contact force between particles using the speed-up method with a reduced Young's modulus. [Display omitted] • The relationship between maximum contact force and Young's modulus was obtained. • A speed-up method for CFD-DEM simulation of contact force was proposed. • The applicability and accuracy of the speed-up method was verified. • The computational efficiency was significantly improved due to the speed-up method. [ABSTRACT FROM AUTHOR]

We investigate diffusion processes on fractal networks at different length scales. This is achieved by the application of a box covering procedure. We find that a clearly scaling law emerges on a great variety of fractal networks. Specifically, a number of metrics for quantifying diffusion processes, such as Kemeny's constant, the expected search time and its variation, follow a power-law with the number of boxes for covering. Furthermore, we identify a power-law relation between energy and the number of boxes. Remarkably, we show that the expected time for hunting a moving target similarly presents a power law behavior on a given fractal network. Our work reveals that scaling law is a common characteristic of fractal networks beyond their structural organization. • We investigate diffusion processes on fractal networks via a box covering procedure. • We find a clearly scaling law emerges on a great variety of fractal networks. • We identify a power-law relation between energy and the number of boxes. • Our work reveals that scaling law is a common feature of fractal networks. [ABSTRACT FROM AUTHOR]

In the present study, we proposed a new type of three-dimensional (3D) graphene structures, which are orthorhombic and become tetragonal for the higher symmetry cases, by using the crystal structure prediction method and classic molecular dynamics (MD) simulations. The elastic properties have been systematically investigated, which show that the elastic constants can be expressed as functions of the graphene wall length L , i.e. the hole size. Most of the elastic constants are composed of L − 1 and L − 2 terms, where L − 1 term is the main part and the less important L − 2 term comes from the joint areas between graphene walls. Our predicted orthorhombic 3D graphene structure and the scaling laws in the elastic properties provide theoretical references for future experimental studies on the superstructures of graphene. [ABSTRACT FROM AUTHOR]

[Display omitted] • Distribution of discrete-phase flow patterns under electric fields is summarized. • Discovery of two generation mechanisms for parallel flow with high viscosity ratio. • The transformation mechanism of the flow pattern under electric field is described. • A prediction model for droplet length under electric field is derived. Although droplet microfluidics has received attention and research in the fields of chemistry and materials in recent years, research on electric field modulation of microchannel droplets is currently fragmented. In this paper, the effect of electric field and flow rate ratio on the behavior of discrete-phase flow in systems with different viscosity ratios was simulated. Subsequently, we delineated the regions of slug flow, drip flow, jet flow, and parallel flow under different parameters according to the simulation results, and investigated the mechanism of electric field manipulating the transformation of the above four flow types by combining the velocity vector diagram with the force situation. Additionally, in order to fill the gap in methods for predicting droplet length in T-junction microchannels under the presence of electric field, we present a scaling law for predicting droplet length that couples the effects of electric field, velocity, and viscosity. And it was verified that the error of the model built based on this method is less than 12 % when the flow ratio is less than 1. [ABSTRACT FROM AUTHOR]

Transient electronic systems are engineered to physically disappear after a predetermined period. Such systems hold significant promise for environmental sustainability and medical applications. The transient behavior relies on the interplay between water diffusion and the hydrolysis reaction of the device components, with the thickness of the encapsulation layer serving as a crucial parameter for controlling the lifetime of the device. The established analytical model for reactive diffusion, however, is limited to relatively thin encapsulation layers. We extend the analytical model to thick encapsulation layers in order to predict transient electronics' lifetimes for both thin and thick encapsulation layers, broadening its applicability. Furthermore, we obtain a scaling law between the dissolution time and the dissolved thickness of transient electronics for the limit of a thick encapsulation layer with no reaction. This scaling law offers a robust way for calculating the dissolution time across different device configurations. • Identify the condition in which the existing model for the thin encapsulation layer becomes invalid. • Obtained the analytical solution for the reactive-diffusion equation for transient electronics with thick encapsulation layer. • Establish the scaling law between the dissolution thickness and time. [ABSTRACT FROM AUTHOR]

The evolutionary laws of the physical and mechanical properties of shale reservoirs in the process of acid erosion have not been clarified. This paper provides the potential laws of pore size and the elastic modulus evolution of shale in the process of point-source acid erosion. The results show that the average pore size increment of the shale Δ r in the process of point-source acid erosion may be in accordance with the scaling law of two-fifth's power of the reaction time t , and the ratio of the elastic modulus E to the elastic modulus E 0 of the initial state which is E E 0 is in accordance with the scaling law of the negative third power of the ratio r r 0 . The conclusion of the study has both theoretical and practical significance for assisting the fossil energy exploitation and supply. • Fast matching method of dimensional analysis is powerful in geological discovery. • Scaling laws need to be attached great importance in energy science. • The theoretical model of acid erosion needs to be improved. [ABSTRACT FROM AUTHOR]

Space radiation in the form of Solar Energetic Protons (SEPs) and Galactic Cosmic Rays (GCR) poses a substantial risk for long-duration space exploration. Active shielding concepts, i.e. shielding a spacecraft with electric and or magnetic fields, has been a topic of interest for more than 50 years. Mass and power requirements have yet to be fulfilled to enable active shielding technology. We present results for a single electric dipole to show the utility of scale-invariance and universal scaling for advancing active shielding concepts. Scattering patterns downstream from the dipole of 2 MeV to 6 MeV electrons and protons show a semi-circular region devoid of incident particles that increases in size with increasing dipole voltage. In particular, results are presented that show how scale-invariant approaches can be leveraged to enable small-scale shields to be built and tested on the ground and then scaled up for in-space use. • Scattering from an electric dipole applied to active radiation shielding. • Shielding efficacy is developed and shown to exhibit scale-invariance. • Scaling results imply viability as method to enable ground testing of shields. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of a disk-shaped rotor rotating inside a granular medium using the discrete element method, and the torque, quantitatively characterizing the resultant of drag forces on the rotor from surrounding particles, is mainly explored. The existence of a dumbbell-shaped region induced by the rotating rotor may essentially give rise to the steady state independent of initial loading conditions, in which the pressure difference between the upper and lower surfaces of the disk disappears and the torque always tends to a stationary value. Furthermore, the rotation of the rotor induces an anisotropic structure with the formation of arches that screen the vertical pressure, leading to the occurrence of the low-pressure region above the rotor. Finally, a scaling law of the torque with the depth is proposed, in which the rotation speed of the rotor as an affecting factor is also taken into account. Unlabelled Image • The drag force experienced by a disk-shaped rotor is studied based on DEM. • The steady state is independent of the initial loading conditions. • The rotation of the rotor induces a dumbbell-shaped activated region. • The formation of arch structure screens the vertical pressure. • The scaling law of the torque with the depth and the rotation speed is proposed. [ABSTRACT FROM AUTHOR]

Turbulent flow can be generated by DC electrokinetic (EK) mechanism resulted from the electric conductivity and permittivity variation in fluids, as has been demonstrated by Varshney et al (2016), where a −1.4 slope of velocity power spectrum is observed. Here, we theoretically investigate the scaling exponents of both velocity and scalar structure functions in DC EK turbulence. The scaling exponents of the second order structure functions of velocity and scalar in the so-called electric body force (EBF) dominant subrange are 2/5 (equivalent to the −7/5 slope of velocity power spectrum) and 4/5 respectively. The theory directly explains the experimental results of Varshney et al. (2016). Based on Kármán–Howarth equation with forcing terms, the third order structure function of velocity which is the representative of energy transport process is investigated in the DC EK turbulence. Compared with the conventional hydrodynamic turbulence, the energy transport in DC EK turbulence has an additional scaling subrange and is governed by additional small length scales. • Derived 2nd order velocity and scalar structure functions of DC electrokinetic turbulence. • DC and AC electrokinetic (EK) turbulence share the same scaling exponents • Coefficient constants of the function in DC EK turbulence are larger than that in AC. • Electric body force in DC EK turbulence is stronger than that in AC. • Cascade process can be described from Karman–Howarth equation with forcing terms. [ABSTRACT FROM AUTHOR]

We use particle dynamics simulations to investigate the rheology of granular flows composed of regular octahedral particles in a rotating drum. We focus on the cascading regime and perform an extensive parametric study by varying drum size, particle size, rotation speed, and filling degree. Our simulations indicate that the passive layer undergoes quasistatic shearing and, in contrast to spherical particle flows, no sliding occurs at the drum wall due to the angular particle shape. A scaling parameter combining the Froude number, the ratio of drum to particle size, and the filling degree captures the kinematic and dynamic characteristics of the granular flow such as free surface shape, shear velocity, flow thickness, and inertial number. This scaling suggests simple linear correlations between free surface curvature, flow thickness, and inertial number. We also show that this scaling is fully consistent with the expected effects of increasing particle size. [Display omitted] • Cascading flows of polyhedral particles in a rotating drum are simulated. • Drum cascading flow can be modeled in terms of a single dimensionless parameter. • The proposed scaling implies simple linear relations between flow variables. • Particle coarsening analysis reveals dependence of flow behavior on particle size. [ABSTRACT FROM AUTHOR]

• The performance of directional changes-based trade algorithms in stock market could have been distorted. • The severity of the distortion is analyzed and discussed by comparing results from discrete data and theoretical continuous data. • The findings of this article could bring some insights for those retailing investors in the stock market. The performance of Directional Change based trading algorithms may be distorted due to omitting the difference between theoretical and actual Directional Change confirmations. The impact of the difference could be so vast so that trading algorithms are seemingly unusable. Applying theoretical confirmations instead of actual ones, we show the potential of these trading algorithms. Among 100 stocks, the number of overall-profit gains has improved from 61 to a theoretical 100, and a theoretical daily 0.1 % rate of return could be expected. The algorithm's overall return is related to the frequency of its trades. When designing a trading algorithm, the distortion should be considered. A threshold that minimizes the difference between actual and theoretical confirmations should be preferred so that the actual results could be closer to its theoretical values. [ABSTRACT FROM AUTHOR]

• A complete set of CFD model has been developed for coupling powder flow and cladding layer. • Develop a dimensionless scaling laws of generality to predict the sizes of final track. • Combine analytical method, CFD, Buckingham π theorem, experiments, and statistics to gain insightful information. • Investigate the physical cause to the general and critical trend of the scaling laws through CFD results. • Provide a systematic approach to generate processing windows. A computational framework that can be easily implemented into a two-phase flow model has been developed for DED (direction energy deposition) process. The information on the in-flight powder stream is treated by an analytical model and regarded as input to the cladding model. The cladding model utilizes Computational Fluid Dynamics (CFD) technique with the volume of fraction (VOF) method, which considers interfacial dynamics and interaction with the powder stream. Furthermore, we have applied Buckingham π theorem to develop scaling laws for the geometry of the final track. In contrast with the dimensional empirical models proposed in the previous studies, the dimensionless laws in this study can largely match the trends of measured data with noticeable variations of working conditions collected from several different studies. The dimensionless cladding width is dominated by the dimensionless laser power with a positive correlation. The increase in dimensionless laser power and powder mass flow rate usually results in a greater value of the dimensionless cladding height, but this trend could become opposite when the values of catchment and energy efficiencies are close to 100%. A threshold that dilution suddenly goes up has also been provided and validated based on the dimensionless parameters. This study provides a reliable numerical model and scaling laws with sufficient generality. The processing window has also been carried out with constraints of dilution and contact angle, bringing design guidelines to the related industries. [ABSTRACT FROM AUTHOR]

• The interface displacement has nonlinear relationships with physical conditions. • A new scaling law is proposed to predict the long-term interface displacement. • The scaling law depends on the elapsed time, vessel diameter, and competitive force. • The prediction of scaling law is in a good agreement with the experimental results. The distribution and mixing characteristics of hydrogen gas are important for assessing the hydrogen risk in nuclear power plants (NPPs) during severe accidents. To estimate such characteristics, analyzing the erosion mixing process of a stratified hydrogen layer subject to a turbulent impinging jet is necessary. In this paper, we propose a novel scaling law for the interface displacement of a stratified layer by erosion mixing as the result of a turbulent jet impingement in a long-term transient state. We show that interface displacement has nonlinear and time-dependent relationships with flow conditions such as the competitive force between the turbulent jet and stratified layer, as well as geometric parameters such as the vessel diameter. We extend the mass conservation law for the entrainment of a stratified layer over a long elapsed time by incrementally using a scaling law for the entrainment rate that is valid at a quasi-steady state. As a result, we show that the novel scaling law for the long-term interface displacement depends on the elapsed time, vessel diameter, and competitive force. The results obtained in previously reported containment flows experiments, as well as those obtained in the present study, are in good agreement with the prediction by the proposed scaling law, demonstrating that this law would be useful for predicting the behavior of the interface displacement of a stratified layer by erosion mixing under various conditions. [ABSTRACT FROM AUTHOR]

The generalized scaling law is based on the concept of two-stage scaling and allows currently available centrifuge facilities to model a large-scale prototype expanding over the spatial dimension ranging from 30 m or larger subject to earthquake motions. This paper presents the results of investigation on the applicability of the generalized scaling law to the fully nonlinear regime of soil-structure system with the induced strain level of 10% in the order of magnitude. The centrifuge model tests performed in this study under the modeling of models scheme consist of a pile model embedded in a inclined ground subject to liquefaction-induced lateral spreading. Four different centrifugal accelerations ranging from 13 g to 50 g are used whereas the actual size of the physical model is kept constant with an overall scaling factor of 1/100. The models are exposed to tapered sinusoidal input accelerations of frequency 0.59 Hz and amplitude 3.0 m/s2 in prototype scale, and the results are compared in terms of prototype by applying the generalized scaling law. As for the response of the ground during shaking, essentially identical accelerations and excess pore water pressures are recorded for all cases, while the lateral displacement shows a variation ranging from 5% to 9% in terms of shear strain due to a slight variation in experimental conditions (e.g., input peak acceleration, achieved density distribution). Practically the same responses are measured among the cases in the dissipation phase of excess pore water pressure. With regard to pile behavior, nearly identical responses for the lateral displacements and bending moments are obtained for all cases both during and after shaking. These results demonstrated that the generalized scaling law is applicable to the fully nonlinear regime of soil-structure system subject to the cumulative shear strain in the order of 10% due to cyclic mobility of sands during earthquakes. [ABSTRACT FROM AUTHOR]

The presence of a multitude of bioactive organic pollutants collectively classified as pharmaceuticals and personal care products (PPCPs) in freshwaters is of concern, considering that ecological assessments of their potential impacts on natural systems are still scarce. In this field experiment we tested whether a single pulse exposure to a mixture of 12 pharmaceuticals and personal care products, which are commonly found in European inland waters, can influence the size distributions of natural lake phytoplankton communities. Size is one of the most influential determinants of community structure and functioning, particularly in planktonic communities and food webs. Using an in-situ microcosm approach, phytoplankton communities in two lakes with different nutrient levels (mesotrophic and eutrophic) were exposed to a concentration gradient of the PPCPs mixture at five levels. We tested whether sub-lethal PPCPs doses affect the scaling of organisms' abundances with their size, and the slope of these size spectra, which describe changes in the abundances of small relative to large phytoplankton. Our results showed that a large proportion (approximately 80%) of the dataset followed a power-law distribution, thus suggesting evidence of scale invariance of abundances, as expected in steady state ecosystems. PPCPs were however found to induce significant changes in the size spectra and community structure of natural phytoplankton assemblages. The two highest treatment levels of PPCPs were associated with decreased abundance of the most dominant size class (nano-phytoplankton: 2–5 μm), leading to a flattening of the size spectra slope. These results suggest that a pulse exposure to PPCPs induce changes that potentially lead to unsteady ecosystem states and cascading effects in the aquatic food webs, by favoring larger non-edible algae at the expense of small edible species. We propose higher susceptibility due to higher surface to volume ratio in small species as the likely cause of these structural changes. Unlabelled Image • Ecological consequences of diffuse contaminants in natural systems are still scarce. • PPCPs affect the scaling of abundances relative to organisms' size in phytoplankton. • Vulnerability of smaller phytoplankton to contaminants resulted in structural changes. • Changes in the phytoplankton community composition were similarly observed. [ABSTRACT FROM AUTHOR]

A renewed interest in fault damage zones is aimed at better understanding stress perturbation around faults, earthquake ground motions and fluid flow in the upper crust. In this study, we analyse fault/fracture systems at the outcrop and map scale and define displacement - thickness (D-T) scaling of fault damage zones using scanlines, in carbonate rocks in France and Spain. We determine fault displacement and damage zone thickness perpendicular to fault planes and far from fault tips for 12 selected faults in four study sites. The data show a logarithmic decrease of fracture frequency from the fault cores. This decrease is characterized by local frequency peaks corresponding to variably-linked secondary fault segments and abandoned tips within the fault damage zone. D-T data comprised between 0 and 100 m of net fault displacement show a nearly linear scaling with very little scattering. Including two additional data for D > 100 m, the best fit corresponds better to a power law. We propose a new model based on fault segmentation and linkage to explain the linear scaling observed up to 100 m displacement, and we discuss the non-linear behaviour with respect to the role of mechanical layer thickness and the inhibition of the segmentation process down dip for large-scale faults. • Fault damage in carbonate rocks scales linearly up to 100 m of displacement. • Damage zones are formed of fault segments at all scales. • Mode I damage thickness tends to saturate for displacement larger than 100 m. • A new model is proposed based on segmentation and fault system growth processes. • Mode I and fault damage thicknesses might scale differently. [ABSTRACT FROM AUTHOR]

• The dynamic breakup potential can assist the study of ultrasound emulsification. • Power density characterizes ultrasound parameters and emulsion physical properties. • Screening of emulsification progress can be easily done using this new method. • Good prediction of droplet size with time observed. • General approach that allows widespread application in emulsification fields. The dynamics of droplet breakup during emulsification is a complicated process due to the interplay between multiple physico-chemical and hydrodynamic factors, especially in an energy-intensive ultrasound-assisted emulsification process. In this work, by mapping the physical processing parameters of ultrasound emulsification into a reduced domain that is governed by the power density and the initial average droplet diameter, a dimensionless parameter that resembles the dynamic breakup potential (η) was established via dimensional analysis. In addition to shedding important insights into the emulsification process, η further facilitates the establishment of a transient scaling relationship that is a function of the characteristic value (a) of the emulsion system. Experimental case study on a cellulose nanocrystals (CNC)-based olein-in-water emulsion system prepared via ultrasound cavitation confirmed the validity of the scaling relationship and sub-universal self-similarity was observed. Using the proposed model, good predictions of the transient of droplet size evolution were attained where the value of η, i.e. the proportionality constant, can be conveniently computed using data from a single time point. Application on other emulsion systems further suggested that the value of a possibly indicates the relative minimum size limit of a particular fluids-emulsifier system. Our approach is general, which encourages widespread adoption for emulsification related studies. [ABSTRACT FROM AUTHOR]

Optimized design of sliding-mode triboelectric nanogenerator (TENG) that is triggered by relative sliding between dielectric layers through a friction process forms one of the key focuses in this community since it may enhance the feasibility of real applications in industries. We propose here a theoretical model based on multi-parameter analysis to provide a rational optimization strategy for design of sliding mode TENG. By combining multiple parameters into dimensionless variables, the normalized output performance is expressed by virtue of two compound parameters. The scaling laws are achieved between the normalized electric output and these compound parameters, involving device dimensions (sizes, dielectric layer thickness), electrical properties of the electrode and dielectric materials, loading conditions (loading force, frequency and motor process), and the circuit conditions (open/short circuit and load resistance). The scaling laws may provide a more comprehensive and rational optimization strategy for sliding-mode TENG based on multi-parameter analysis and may help to enhance the output performance of the device as either a smart sensor or an energy harvester. A theoretical model for optimizing sliding-mode TENG based on multi-parameter analysis is established to simulate the normalized output performance of sliding-mode TENG in various working conditions. The theoretical results agree very well with experimental data. According to scaling laws between dimensionless output voltage and compound parameters, the optimal combination of all the parameters considered simultaneously could be acquired for the best output voltage, providing a more rational optimization strategy for device design. Image 1 • A theoretical approach for optimizing sliding-mode TENG based on multi-parameter analysis is proposed. • The scaling laws may help acquire the optimal combination with all the parameters considered simultaneously. • The output performance may be enhanced by tuning multiple parameters or varying single parameter with the others fixed. [ABSTRACT FROM AUTHOR]

• An adimensional model to scale LOVA events has been developed. • The model has been validated with experimental measurements in a scaled facility. • The model has been applied to the ITER vessel: long time to take countermeasures. The Loss Of Vacuum Accident is one of the hazardous events that may occur in nuclear fusion power plants which work with the magnetic confinement technology. During these accidents, the intake of air may re-suspend toxic, explosive and radioactive dust, involving a hazardous release in the external environment. Several studies have been conducted in scaled facilities, in order to investigate and understand how the phenomenon works. In the previous studies, the authors replicated these events in several different conditions by means of the scaled facility called "STARDUST-Upgrade", providing a good description of the phenomenon. A Computational Fluid Dynamic (CFD) code able to replicate these events has been developed and validated. Once a scaled experiment is realized, a specific analysis must be performed to understand if the phenomenon can be scaled and in what conditions. A result obtained in STARDUST-Upgrade, that is much different in terms of size and shape from a real TOKAMAK, must be modified by an adequate scaling law. The aim of this work is to analyse how to deduce a scaling law (for large scale flow) by a theoretical analysis based on the Buckingham π theorem. The authors will present also the experimental analysis provided to validate some features of this model. The conclusion of the work will be the use of the scaling law to obtain technical information (pressurisation time) about a LOVA inside an ITER-like reactor and further fusion power plants. [ABSTRACT FROM AUTHOR]

Abstract Determining time-dependent mechanical properties of soft materials is essential in understanding their deformation behaviors under various stimuli. This paper investigates the use of indentation creep tests to measure the viscoelastic properties of soft materials at local areas. A simple scaling law between the reduced creep function and the creep displacement of the indenter is revealed in this paper based on a theoretical analysis. We show that the scaling relation can be used to interpret indentation creep tests of viscoelastic soft solids with arbitrary surface profile provided that the contact area does not change. Both numerical and practical experiments have been performed to validate the theory and the analytical solution. In our experiments, a low-cost portable indentation system is proposed to measure the reduced creep function. Our results show that the low-cost instrument and the analytical solution to interpret the experimental data reported here represent a useful testing method to deduce the intrinsic viscoelastic properties of soft materials in a non-destructive manner. Highlights • A simple scaling law between the reduced creep function and the creep displacement of the indenter is derived and validated with finite element analysis. • A low-cost portable indentation system is presented to measure the reduced creep function. • Experiments on phantom gels demonstrate the usefulness of the method and instrument. [ABSTRACT FROM AUTHOR]

Highlights • A scaling law is developed for designing flexible piezoelectric energy harvesters. • Energy conversion efficiency depends only on two normalized system parameters. • An independent law for optimizing energy storage efficiency is indispensable. Abstract The energy conversion and storage efficiency was commonly ignored in experimental studies on nanoscale flexible piezoelectric energy harvesters (PEHs). In this study, we develop a generalized theoretical method to optimize the energy conversion and storage efficiencies of nanoscale flexible PEHs. The results are validated by comparisons with experimental measurements for various ambient excitations. A simple scaling law is established to reveal the intrinsic correlation between the efficiency of energy conversion/storage and various system parameters of the PEHs. For either the energy conversion or storage circuit, the output power density may be maximized by properly designing an intrinsic normalized parameter. Furthermore, we demonstrate that an independent optimization criterion is indispensable for standard storage circuits since including a storage module into the conversion circuit redefines the electromechanical behavior of the PEH system. The results may be used as guidelines for optimizing the energy conversion and storage efficiencies of nanoscale flexible PEHs that have promising applications in harvesting biomechanical energies. [ABSTRACT FROM AUTHOR]

Abstract This study shows that the keyhole model derived for determining the scaling laws of keyhole depths for laser welding when high power incident laser beams are used (typically in the multi-kW incident power range), can be also applied to determine the melted depths observed during the Selective Laser Melting process, where much lower incident powers of typically few hundred watts are focused on very small focal spots. The solution of the thermal analysis of this keyhole configuration is described by only three independent dimensionless parameters that are also involved for the analysis of a more general problem of heat conduction using similar input parameters. This global approach and the keyhole model describing the process of laser welding have been also validated by analyzing the melted depths generated by the Selective Laser Melting process. The dependence of the melted depths on the operating parameters of this process has been established, as well as the formation thresholds of the keyhole. [ABSTRACT FROM AUTHOR]

Abstract Triboelectric nanogenerator (TENG) is a kind of mechanical energy harvesters based on triboelectric effect. Its output performance strongly depends on the structural design, material properties, circuit status, and mechanical loading process. In this work, we develop a new theoretical method for analysing the contact-separation mode TENG devices with dimensionless formulations which are based on the V - Q - x relationship with the TENG being treated as a parallel-plate capacitor. The correctness and accuracy of the proposed method and model are verified and validated via a series of experimental results. With the proposed method, the scaling laws between the performance and structure, material properties, circuit status and mechanical loading are established, and the output performance of the devices can be predicted with all the parameters being considered simultaneously. The developed model and formulas offer good guidance for structural design and optimization strategies for TENG devices, which could lead to the fast development of high performance of TENGs through accurate numerical analysis at low cost. Graphical abstract Validation of the scaling laws for dimensionless maximum voltage of contact mode triboelectric nanogenerator (TENG). The theoretical predictions based on the proposed dimensionless formulars agree very well with the experimental measurements despite that the latter are achieved with different device structures, mechanical loadings and circuit conditions. This demonstrates that the established scaling law reveals the underlying general correlation between the physical properties of the device and its output performance, which may provide robust guidelines for optimization strategies of contact mode TENG. fx1 Highlights • An optimization method based on multi-parameter analysis is proposed for TENG. • A scaling law is established between the output performance and device parameters. • All parameters could be designed simultaneously to enhance the output performance. [ABSTRACT FROM AUTHOR]

Abstract Satellite images allow characterizing and monitoring urban slums. Yet the urban landscape as a complex geographic system is composed of hierarchical patterns and discrete objects in a spatial and temporal continuum with different scales and anisotropy which can only be estimated from image snapshots. Understanding the spatial heterogeneity of slums in terms of scale and anisotropy from discrete image pixels is nontrivial and has not been explicitly addressed by image-based studies detecting slums, where scale and direction in characterizing slum features are commonly done by trial and error. This study addresses this gap by analyzing the impact of scales and anisotropy detected in the scale space and frequency domain for the calculation of texture indices that ultimately govern the detection of slums. Employing case studies of three cities with a large portion of slum population and for which we have very high resolution satellite imagery, we identify the characteristic scales of slum and formal built-up areas. Results show that the characteristic scales correspond with the optimal grain size to obtain image texture features for detecting slums, while the directional spectral energy at the pixel level identifies characteristic directions. Thus texture indices calculated at the characteristic scale and along the characteristic directions of slum patterns improve the efficiency in feature extraction and classification of slums, where optimizing the scale has a higher impact on the detection of slums than choosing the optimal directions. This study provides a framework for scientifically selecting optimal scales and directions for slum mapping studies. The framework is recommended to be tested for more general applications in land surface characterization and classification especially by using high order texture indices. Graphic abstract Unlabelled Image Highlights • A thorough examination of the spatial heterogeneity of urban slums and formal built-up areas in terms of scaling law and anisotropy is presented. • Slum detection using texture indices is impacted by the scaling law and anisotropy of urban patterns. • Scaling law and anisotropy help to obtain the optimal characteristic scales and directions in calculating texture indices. • Characteristic scales of slums and formal built-up areas should be treated as an indicator for patterns of the entire image patch. • Characteristic directions are coupled with detection of slums yet less clear compared to characteristic scales. [ABSTRACT FROM AUTHOR]

Abstract Small arthropods are not simply scaled-down versions of their larger closest relatives, as changes in morphology and functional characters are largely governed by scaling laws. These same scaling laws set strict limits to size change toward smaller sizes. The evolution of extreme miniaturized forms involves the breaking of these constraints, by means of design innovations that allow evolutionary change to evade the limits posed by scaling laws. Here we review several cases studies in insects and other arthropods that illustrate this evolutionary path. We examine morphologies commonly recurring in miniaturized forms but not exclusive to them, morphologies exclusive to miniaturized forms and novel functional solutions supported by unconventional morphologies. We also discuss miniaturization and its evolvability taking into consideration arthropod postembryonic development and modular body organization. The modification of features commonly supposed not to change appears as a recurring pattern in arthropod miniaturization. Highlights • The properties of scaling laws set strict limits to size change toward smaller size. • Evolution of extreme miniaturized forms involves the breaking of these constraints. • Miniaturized arthropods evolved unconventional morphologies including anucleate cells. • Some unconventional morphologies are associated with novel functional solutions. • Some modifications involve body modularity throughout postembryonic development. [ABSTRACT FROM AUTHOR]

Highlights • New set of DNS for low to medium Prandtl number and Re τ = 500 , 1000 and 2000 in a Poiseuille turbulent channel flow with mixed boundary condition for the thermal flow. • DNS for Re τ = 2000 have never been published before except for PR = 0.7. • New insights are given about the turbulent budgets of the thermal fluxes, the energy of the thermal flow and its dissipation. Abstract Direct Numerical Simulations of turbulent heat transfer in a channel flow are presented for three different Reynolds numbers, namely Re τ = 500 , 1000 and 2000. Medium and low values of the molecular Prandtl number are studied, ranging from 0.71 (air), down to 0.007 (molten metals), in order to study its effect on the thermal flow. Mixed boundary conditions at both walls are used for the thermal flow. Mean value and intensities of the thermal field were obtained. Two different behaviors were observed, depending on the Prandtl and Péclet numbers. The expected logarithmic behavior of the thermal flow completely disappears for Prandtl below 0.3. This is a direct effect of the thicker viscous thermal layer generated as the Prandtl number is reduced. Von Kármán constant was computed for cases above this Prandtl, and turbulent Prandtl and Nusselt numbers were obtained for all the cases. Finally, the turbulent budgets for heat fluxes, temperature variance and its dissipation rate are presented. As a general result, there is a scaling failure near the wall in very cases studied, which is accentuated for lower Prandtl numbers. The statistics of all simulations can be downloaded from the web page of our group. [ABSTRACT FROM AUTHOR]

Highlight • The similarity conditions of a cracked beam are derived by energy approach. • Application to the cases of crack interaction and curved crack-front are discussed. • Application to the problem of structural health monitoring is discussed. Abstract Experimental studies on the problem of crack identification can be simplified and enhanced through the concept of structural similarity since the behaviors of a full-scale structure can be investigated using a reduced-scale model. The structural similarity of a rectangular cross-section beam with a through-thickness edge crack and elastically supported was investigated. The beam was subjected to concentrated forces perpendicular to its longitudinal axis and concentrated bending moments. Complete similarity conditions and scaling laws for static deflection and slope of the cracked beam were derived using the principle of conservation of energy and the strain energy release rate approach within the framework of linear elastic fracture mechanics. Accuracy of the derived complete similarity conditions and scaling laws were experimentally and numerically verified. The concept of incorporating the similarity theory to problems of structural health monitoring was explained. [ABSTRACT FROM AUTHOR]

• Scaling laws of droplet length over large ranges of flow rates are proposed. • The relation between scaling law and critical boundary is constructed. • The dynamics in jetting agree with the linear instability theory. • A bistable state mechanism is found in widening jetting. • Universal flow pattern maps are built using local dimensionless terms. The flow patterns of immiscible liquids in microscale cross junctions are experimentally studied and the influencing factors including the capillary number (3 × 10−4–6 × 10−1), flow rate ratio (0.004–60), viscosity ratio (0.04–2.8), and channel aspect ratio (1/3–1) are systematically analyzed. Evolutions of the interfacial morphologies in different flow patterns are discussed with the aid of force analysis. In the droplet group, two different breakup modes of the liquid thread are found with the symmetric mode for squeezing and the asymmetric mode for dripping, which are divided by a critical capillary number around 0.01. Two different physical models for constructing the scaling law of the droplet length are compared over large ranges of flow parameters and the universal scaling law is valid to identify the transitional boundary between squeezing and dripping regimes. In the jet group, the jet width in different channels is compared to the theoretical prediction. A detailed comparison between the experimental results in jetting and the linear instability theory is further conducted and the reason for the polydispersity of the droplet size in widening jetting is found. Finally, the flow pattern maps are built using dimensionless parameters in both the global terms and the local terms. In contrast, the local dimensionless parameters are confirmed to show a better performance in unifying the transitional boundary between two groups of flow patterns. The obtained results should be useful for the further understanding of the dynamic mechanisms of the microscale multiphase flow. [ABSTRACT FROM AUTHOR]

• New droplet formation mechanism in microfluidic cross-junctions at low Ca. • Ca dependency of droplet formation at a very low capillary number. • The leaking effect in a microfluidic channel with a rectangular cross-section. • Identification of underlying differences between cross-junctions and T-junctions. • Revision of the classical squeezing model of droplet formation. Two decades of research on droplet formation in microchannels have led to the widely accepted view that droplets form through the squeezing mechanism when interfacial forces dominate over viscous forces. The initially surprising finding that the volume of the droplets is insensitive to the relative importance of these two forces is nowadays well understood from the constrained deformation of the droplet interface during formation. In this work, we show a lower limit of the squeezing mechanism for droplets produced in microfluidic cross-junctions. Below this limit, in the leaking regime, which was recently discovered for droplets produced in T-junctions, the volume of the produced droplets strongly depends on the relative importance of interfacial and viscous forces, as captured by the capillary number. We reveal a fundamental difference in the mechanisms at play in the leaking regime between T- and cross-junctions. In cross-junctions, the droplet neck elongates substantially, and unlike the case of the T-junction, the magnitude of this elongation depends strongly on the value of the capillary number. This elongation significantly affects the final droplet volume in a low capillary number regime. Generalizing the classical squeezing law by lifting the original assumptions and incorporating both identified mechanisms of leaking through gutters and neck elongation, we derive a model for droplet formation and show that it agrees with our experiments. [ABSTRACT FROM AUTHOR]

Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) is extensively used for modeling heat transfer in gas-solid fluidized beds. However, CFD-DEM is computationally expensive, leading to a restriction regarding the number of simulated particles. Coarse-grained CFD-DEM is a technique to circumvent this constraint, allowing one to simulate larger fluidized beds. In this work, a scaling law used for coarse-graining hydrodynamics is generalized to gas-solid heat-transfer. This approach for coarse-graining heat transfer is tested using three different superficial gas velocities where the coarse-grained particle temperatures and Nusselt numbers are obtained. The particle temperature shows good correspondence with the original system for all cases and the Nusselt number is accurately predicted by the coarse-graining scaling law. • Coarse-grained CFD-DEM gas-solid heat transfer is studied. • Coarse-grained two-way heat transfer is verified. • Nusselt number for coarse-grained simulations is characterized. [ABSTRACT FROM AUTHOR]

This paper investigates the scaling of the nanoscopic elastic and tensile failure properties of calcium-silicate-hydrate (C-S-H). We report a Zhurkov-like scaling behavior for disordered C-S-H of various compositions at cryogenic temperatures, using molecular dynamics simulations. To this end, we first propose a revised molecular construction route to generate C-S-H atomic configurations with varying compositions. Then, we investigate how the tensile behavior evolves with temperature, system size, and strain rate. Our simulation results show that tensile strength, Young's modulus, fracture energy, and fracture-process zone (FPZ) length, all follow a Zhurkov-like scaling law providing a general temperature-size-time equivalence. Such scaling laws make it possible to extrapolate molecular simulation results to larger length and/or time scales. Detailed analysis shows that the typical FPZ length of C-S-H is about 150 Å, and the maximum reduction of activation energy barriers for tensile failure is 0.497 and 0.446 eV for Ca/Si of 1.7 and 1.1, respectively. [ABSTRACT FROM AUTHOR]