Nonlinear isotropic constitutive laws: choice of the three invariants, convex potentials and constitutive inequalities

The aim of this paper is a new formulation of nonlinear isotropic constitutive laws. Our main hypothesis claims that the eigenvalues of stress and strain tensors are classified in the same order (the eigenvector associated to the highest eigenvalue of the stress tensor is also associated to the highest eigenvalue of the strain tensor, etc.). Further, we assume the existence of a differentiable convex isotropic potential. By introducing three new invariants for each tensor (called X, Y, Z for the stress tensor S and x, y, z for the strain tensor E) a constitutive law is revealed to be a simple duality between the chosen invariants: (x, y, z) and (X, Y, Z) look like Cartesian coordinates of E and S. We look at several potentials chosen as polynomials of these invariants. Finally, first and third order isotropic elasticity laws are reviewed and convexity of the potentials is discussed.     

Effect of oxide additives and particle size on stabilization of treated commercial zirconia

Commercial zirconia was milled and sedimented to separate finer and coarser particles. Then additives such as CaO and Y₂O₃ were added in proportions of 7 and 13 mol.% each. Wet mixing of these powders was done in the ball mill. These mixtures were then compacted through uniaxial compaction using 150 MPa of pressure to make pellets of 8 mm diameter and 3 mm height approximately. The compacts were sintered at 1700 °C under argon atmosphere during 1 h. Densification calculations revealed densities of more than 80% in all samples. Scanning electron microscopy (SEM) showed that closed porosity was present. X-ray diffraction (XRD) results confirmed the presence of cubic phase with quantities higher in samples of finer powder and 13 mol.% additive.     

Diagnosis Method Using ΔIDDQ Probabilistic Signatures: Theory and Results

This paper presents a diagnostic method based on differential I_DDQprobabilistic signatures, inspired by telecommunications systems. The method and its unique features are described. Then, results from an IC monitor containing controllable faults show the capability of the method to diagnose actual activated faults, despite a strong experimental current standard variation. These results validate previous simulation procedures, which are applied to quantify effects not covered by the monitor experiment, that is, the effect of the load of a bridged node and the effect of the bridge resistance value. These experimental and simulation results reveal the robustness of the proposed diagnosis method, that has identified and located every single fault considered so far.     

First-principles investigation of B2 partial disordered structure,martensitic transformation,elastic and magnetic properties of all-d-metal Ni-Mn-Ti Heusler alloys

In this work,the B2 partial disordered structure of the austenitic parent phase,martensitic transformation,elastic and magnetic properties of the Ni8 Mn4+xTi4-x(x=0,1 and 2) Heusler alloys have been systematically investigated by the first-principles calculations.The preferential atomic occupation of B2 structure is one Ti atom exchange with the nearest neighboring Mn atom from the view of lowest energy principle.This disordered exchange sites(Mn-Ti) and the excess Mn atoms occupying the Ti sites(MnTi)could reduce the nearest Mn-Mn distance,resulting in the anti ferromagnetic state in the austenitic and martensitic phases of the alloys.The total magnetic moment of the alloy decreases with the increasing Mn content;it is ascribed to the antiferromagnetic magnetic moments of the excess Mn atoms.When x=0,the alloy does not undergo martensitic transformation since the austenite has absolute phase stability.The martensitic transformation will occur during cooling process for x=1 or 2,owing to the energy difference between the austenite and the martensite could provide the driving force for the phase transformation.The elastic properties of the cubic austenitic phase for the Ni2 MnTi alloy is calculated,and the results reveal the reason why Ni-Mn-Ti alloy has excellent mechanical properties.The origin of martensitic transformation and magnetic properties was discussed based on the electronic density of states.     

《可持续发展设计指南》选载(之十一)如何选择可持续性发展水资源和室内环境技术

一、中国的缺水问题在中国的很多地区,可用水量的日益减少是当前最大的社会、经济和政治问题。以人均可用量2500m3的标准相比较,中国大陆的淡水供应只达到2000m3,属于世界     

Development of a quadruplex-real-time-PCR for screening food for genetically modified organisms

With the ever increasing number of genetically modified plants authorized worldwide, including in the European Union, high throughput detection methods need to be developed. In this paper, a quadruplex-real-time-PCR method is described which allows rapid and simultaneous screening of food for the presence of target DNA sequences from the cauliflower mosaic virus 35S promoter, the NOS terminator from Agrobacterium tumefaciens, the soya reference lectin gene and the maize reference alcool dehydrogenase gene (adh). Three of the four primers and probe combinations have already been published elsewhere, whereas primers and probe for NOS terminator-PCR were developed in-house. Validation data show sensitivities down to five copies for 35S promoter and NOS terminator PCR, even when target sequences of the competing PCRs are in large excess. Thorough adjustment of primer and probe concentrations allowed high individual PCR efficiencies with negligible physical cross-talk between the four detection channels. This method provides a basis for a rapid screening of food for the most frequently used regulatory elements present in GM crops authorized for food in the European Union. In addition it provides information about the presence of species which are possibly genetically modified.     

Characterizing short-range vs. long-range spatial correlations in dislocation distributions

Hard X-ray diffraction experiments have provided evidence of a strongly heterogeneous distribution of dislocation densities along the axis of cylindrical ice single crystals oriented for basal slip in torsion creep. The dislocation arrangements showed a complex scale-invariant character, which was analyzed by means of statistical and multifractal techniques. A trend to decreasing autocorrelation of the dislocation distribution was observed as deformation proceeds. At low strain levels, long-range spatial correlations control the distribution, but short-range correlations in relation with cross-slip progressively prevail when strain increases. This trend was reproduced by a model based on field dislocation dynamics, a theory accounting for both long-range elastic interactions and short-range interactions through transport of dislocation densities.     

Multi‐Image Based Photon Tracing for Interactive Global Illumination of Dynamic Scenes

Image space photon mapping has the advantage of simple implementation on GPU without pre‐computation of complex acceleration structures. However, existing approaches use only a single image for tracing caustic photons, so they are limited to computing only a part of the global illumination effects for very simple scenes. In this paper we fully extend the image space approach by using multiple environment maps for photon mapping computation to achieve interactive global illumination of dynamic complex scenes. The two key problems due to the introduction of multiple images are 1) selecting the images to ensure adequate scene coverage; and 2) reliably computing ray‐geometry intersections with multiple images. We present effective solutions to these problems and show that, with multiple environment maps, the image‐space photon mapping approach can achieve interactive global illumination of dynamic complex scenes. The advantages of the method are demonstrated by comparison with other existing interactive global illumination methods.