Through molecular dynamics simulations,the mechanical behavior of nanoporous copper under impact loading was investigated with relative densities ranging from 77.91% to 98.36%,focusing on deformation ...mechanism,the scaling laws and influence of ligament sizes.Results show that the classical Gibson-Ashby′s scaling laws should be modified for prediction of both the Young′s modulus and yield stress.A proportional relationship is established between cell wall thickness and yield stress,and new modified scaling equations are built for nanoporous copper with consideration on both relative mass density and size effects of ligaments.The size effect can be explained by larger surface area/volume ratio of samples with thinner ligament size and limited dislocation source activation due to narrow space between larger numbers of voids.
We present a modeling study of photoinitiated polymerization in a thick polymer-absorbing medium using a focused UV laser. Transient profiles of the initiator concentration at various focusing ...conditions are analyzed to define the polymerization boundary. Furthermore, we demonstrate the optimal focusing conditions that yield more uniform polymerization over a larger volume than the collimated or non-optimal cases. Too much focusing with the focal length f < f* (an optimal focal length) yields a fast process; however, it provides a smaller polymerization volume at a given time than in the optimal focusing case. Finally, a scaling law is derived and shows that f* is inverse proportional to the product of the extinction coefficient and the initiator initial concentration. The scaling law provides useful guidance for the prediction of optimal conditions for photoinitiated polymerization under a focused UV laser irradiation. The focusing technique also provides a novel and unique means for obtaining uniform photo-polymerization within a limited irradiation time.
Random packings of stainless steel hollow spheres are characterised with static X-ray tomography. Compression tests were performed on the foams and size effects were investigated. Relevant parameters ...of the macroscopic mechanical behaviour are extracted and scaling law based on the foams initial density are given and used to predict the energy absorbed at densification. In situ X-ray tomography compressive test were carried out in order to analyse damage mechanisms at the mesoscale.
Three regimes: near-, middle- and far-fields of underwater explosion are proposed in this study aiming at providing an overview on the responses of submerged slender structure by pulsating bubble. In ...the near-field, the material starts to yield, thus leading to structure breakdown immediately; remarkable structural global elastic deformation occurs in the middle-field as well as substantial movement; and a structure moves as a rigid body with negligible deformation for the far-field. Equivalent dimensionless parameters are obtained by two different dimensional analysis methods, among which a dominant similarity parameter is found out. Thus, a scaling law providing us with a relation between structural global response and the dominant similarity parameter is yielded, which can be used for demarcating the three regimes quantitatively. To demonstrate, three models corresponding to typical submarine parameters are performed in the case studies. Quantitative criterion of the three regimes is presented along with the regime diagrams. The structural global response features such as the deformation and maximal acceleration/speed of different regimes are provided as well.
•Three regimes: near-, middle- and far-fields are proposed according to the degree of structural global response by an underwater explosion bubble.•A scaling law for demarcating the three regimes quantitatively is yielded.•Quantitative criterion of the three regimes is presented along with the regime diagrams for typical submarines.•Global response features of typical submarines in different regimes are provided.
This short note is intended as a “Letter to the Editor” Perspective in order that it serves as a contribution, in view of reaching the physics community caring about rare events and scaling laws and ...unexpected findings, on a domain of wide interest: sport and money. It is apparent from the data reported and discussed below that the scarcity of such data does not allow to recommend a complex elaboration of an agent based model,—at this time. In some sense, this also means that much data on sport activities is not necessarily given in terms of physics prone materials, but it could be, and would then attract much attention. Nevertheless the findings tie the data to well-known scaling laws and physics processes. It is found that a simple scaling law describes the gains of teams in recent bicycle races, like the Tour de France. An analogous case, ranking teams in Formula 1 races, is shown in an Appendix.
There are two fundamental laws of geography: scaling law and Tobler's law. Scaling law is available across all scales ranging from the smallest to the largest, and it states that there are far more ...small things than large ones in geographic space. Tobler's law is available in one scale, and it states that more or less similar things tend to be nearby or related. In this short article, I claim scaling as a design principle for cartography, but what I really wanted to convey is that scaling must become a dominant principle, if not the principle, of cartographic design. All other principles can, should, and must be subordinated to the major and dominant one.
•The dynamic rupture of the composite materials is self similar.•The avalanche phenomenon observed in the rupture of the composite materials exhibits two different velocities.•The creep phenomenon is ...characterized by two regimes in LLs rules.
We investigate the spatial distribution of mechanical stresses of composite materials densely packed with thin glass fibers and yield so low transparency that the conventional method of photoelasticity testing fails to provide good quality birefringence fringes. The failure kinetic and the scaling behavior of theses materials are also studied. The calculations are done within the framework of the fiber bundle model with the local load-sharing rule (LLS) in which the load of the failing fiber is shared between only the nearest neighbor elements. We have found that the failure properties of these materials are characterized by the avalanche phenomena with two different timescales and the number of broken fibers presents a Boltzmann distribution. The failure time tf presents a power law with the applied force and the system size. The results show also that the failure kinetic of the composite materials is self-similar. The creep rupture is also investigated. The results show that these materials are characterized by a two creep regimes characterized by the Andrade’s law with a two different exponents, and separated by a cross over time tm more consisting with the experiment results.
The ultimate goal of this multi-article series is to develop a methodology to generate continuous fields of tree height and biomass. The first paper demonstrated the need for Allometric Scaling and ...Resource Limitation (ASRL) model optimization and its ability to generate spatially continuous fields of tree heights over the continental USA at coarse (1 km) spatial resolution. The objective of this second paper is to provide an assessment of that approach at site scale, specifically at 12 FLUXNET sites where more accurate data are available. Estimates of tree heights from the Geoscience Laser Altimeter System (GLAS) waveform data are used for model optimization. Amongst the five possible GLAS metrics that are representative of tree heights, the best metric is selected based on how closely the metric resembles field-measured and Laser Vegetation Imaging Sensor tree heights. In the optimization process, three parameters of the ASRL model (area of single leaf, α; exponent for canopy radius, η; and root absorption efficiency, γ) are simultaneously adjusted to minimize the difference between model predictions and observations at the study sites (distances to valid GLAS footprints ≤ 10 km). Performance of the optimized ASRL model was evaluated through comparisons to the best GLAS metric of tree height using a two-fold cross validation approach (R2 = 0.85; RMSE = 1.81 m) and a bootstrapping approach (R2 = 0.66; RMSE = 2.60 m). The optimized model satisfactorily performed at the site scale, thus corroborating results presented in part one of this series. Future investigations will focus on generalizing these results and extending the model formulation using similar allometric concepts for the estimation of woody biomass.
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