An Efficient Parallel ADI Algorithm for Turbomachinery Flows

The paper describes a domain decomposition strategy which allows high efficiency parallel simulations of turbomachinery flows. The implicit ADI parallel solver is based on the scalar approximate factorisation. The Navier-Stokes (NS) and turbulence model equations are discretised by centred finite differences. The results prove that the parallel calculations with domain decomposition, in which each sub-domain explicitly communicates with the adjacent ones at the end of each implicit iteration, may suffer from a considerable deterioration of the convergence rate. A simple sub-iterative domain recoupling strategy allows recovering the convergence rate of a single processor computation. The strategy is carefully analysed and optimised in terms of inter-processor data communication rate and algorithm memory requirements. The span-wise domain decomposition is particularly suited for turbomachinery flows and is applied to a radial impeller and to an axial turbine stator and stage to prove the validity and the accuracy of the proposed approach. The results indicate that the parallel recoupled algorithm usually reach efficiencies of 0.8, with peaks over 0.9 with up to 16 processors, thereby allowing a considerable speed-up of design and verification calculations.     

Quasi-Multiplier Rules for Quasidifferentiable Extremum Problems

The purpose of the present article is to contribute to clarify the role of the Lagrange multipliers within the theory of the first order necessary optimality conditions for nonsmooth constrained optimization, when the directional derivatives of functions involved in the extremum problems are not sublinear. This task is accomplished in the particular case of quasidifferentiable problems with side constraints. In such setting, making use of the image-space approach, it is possible to establish a generalized (nonlinear) separation result by means of which a new Lagrange principle is obtained. According to this principle, which seems to fit better quasidifferentiable extremum problems than the classic one, the concept of linear multiplier is to be replaced with that of quasi-multiplier, a sublinear and continuous functional whose existence can be guaranteed under mild assumptions, even when classic multipliers fail to exist. Such as extension allows to formulate in terms of Lagrange function the known optimality necessary condition for unconstrained quasidifferentiable optimization expressed in form of quasidifferential inclusion. Along with this, other multiplier rules are established.     

胶带粘面手印显现的实验

为提高胶带粘面上汗潜手印的显出率。通过实验,对胶粘面上汗潜手印剥离和显出做了多种方法的研究,显现包括碳素墨水法、龙胆紫溶液法、"502"熏显后加染法、小颗粒悬浮液法,比较研究每种方法的显现效果及适用情况。胶粘面上手印的最佳显现方法是碳素墨水法。     

Extended Regularized Dual Averaging Methods for Stochastic Optimization

We introduce a new algorithm, extended regularized dual averaging (XRDA), for solving regularized stochastic optimization problems, which generalizes the regularized dual averaging (RDA) method. The main novelty of the method is that it allows a flexible control of the backward step size. For instance, the backward step size used in RDA grows without bound, while for XRDA the backward step size can be kept bounded. We demonstrate experimentally that additional control over the backward step size can speed up the convergence of the algorithm while preserving desired properties of the iterates, such as sparsity. Theoretically, we show that the XRDA method achieves the same convergence rate as RDA for general convex objectives.     

Piezoelectricity of ordered (ScxGa1-xN) alloys from first principles

First-principles calculations are performed to compute the e₃₃ piezoelectric coefficients of GaN, ScN and (Sc_xGa_1-xN) alloys exhibiting an alternation of hexagonal GaN, with hexagonal ScN along the c-axis. For Sc compositions larger than 50%, each atom has nearly five nearest neighbors (i.e., the ground state exhibits a phase that is five-fold coordinated). On the other hand, Sc-deficient (Sc, Ga) N alloys adopt a ground-state that is four-fold coordinated). The magnitude of e₃₃ in the Sc-deficient ideally ordered (Sc_0.25Ga_0.75N) is found to be larger than the magnitude of the corresponding e₃₃ coefficients resulting from the compositional weighted average over the hexagonal (h-ScN) and the wurtzite (w-GaN) parent compounds. On the other hand, the e₃₃ coefficients of the Sc-rich ordered (Sc_0.75Ga_0.25N) is found to be negligibly small. In addition, e₃₃ piezoelectric coefficients in ordered (Sc_0.5Ga_0.5N) exhibit quite large magnitudes, due to the nonpolar to polar transition occurs at Sc composition x = 0.5, and thus can bridge the corresponding coefficients of (Ga, In) N and ferroelectric alloys. The microscopic origins for this huge enhancement in the piezoelectric behavior in Sc-low and Sc-intermediate alloys and the role of each atom are revealed and discussed.     

An analytic method for S‐Expansion involving resonance and reduction

In this paper we describe an analytic method able to give the multiplication table(s) of the set(s) involved in an S‐expansion process (with either resonance or 0_S‐resonant‐reduction) for reaching a target Lie (super)algebra from a starting one, after having properly chosen the partitions over subspaces of the considered (super)algebras. This analytic method gives us a simple set of expressions to find the subset decomposition of the set(s) involved in the process. Then, we use the information coming from both the initial (super)algebra and the target one for reaching the multiplication table(s) of the mentioned set(s). Finally, we check associativity with an auxiliary computational algorithm, in order to understand whether the obtained set(s) can describe semigroup(s) or just abelian set(s) connecting two (super)algebras. We also give some interesting examples of application, which check and corroborate our analytic procedure and also generalize some result already presented in the literature.     

新疆紫穗槐中总黄酮的提取与含量测定

用超声波辅助乙醇溶液浸提法和索氏提取法提取新疆地方植物药材紫穗槐中黄酮化合物并进行含量测定.以芦丁为对照品,NaNO2-Al(NO3)3-NaOH体系为显色剂,利用分光光度法在510nm处测定提取物中的总黄酮的含量.校准曲线为A=11.825C-0.0139,r=0.9992.超声提取法所得总黄酮的含量以芦丁计算为2....     

A study of the evaporative deposition process: Pipes and truncated transport dynamics

We consider contact line deposition of an evaporating thin drop. Following Dupont’s proposal (unpublished), we focus on transport dynamics truncated by a maximal concentration as the single deposition mechanism. The truncated transport process, formalized as the “pipe model”, admits a characteristic shock front that has a robust functional form and depends only on local hydrodynamic properties. By applying the pipe model, we solve the density profile in different asymptotic regimes. In particular, we find that near the contact line the density profile follows a scaling law that is proportional to the square root of the concentration ratio defined as the initial solute volume concentration divided by the maximal concentration. The maximal deposit density occurs at about 2/3 of the total drying time for uniform evaporation and 1/2 for diffusion-controlled evaporation. Away from the contact line, areal density decays exponentially with the radial distance to the power of -3 for the uniform evaporation and -7 for the diffusion-controlled evaporation.     

Influence of oxygen on the ion-assisted regrowth of deposited Si layers

Summary The ion-assisted regrowth of chemical-vapour deposited Si films onto (100) Si substrates is reported. The regrowth was induced by a 600 keV Kr⁺⁺ beam at doses in the range (2·10¹⁵÷6·10¹⁵)/cm² and at a dose rate of 1·10¹²/cm²s. The target temperature was set at 450°C. During irradiations the crystal-amorphous interface velocity was measuredin situ by monitoring the reflectivity of a He-Ne laser light focused onto the sample surface. After irradiation some samples were also analysed by Rutherford backscattering in combination with the channelling effect and by transmission electron microscopy. The growth rate of deposited layers depends on the cleaning procedure performed prior to deposition,i.e on the total amount of oxygen present at the deposited layer/substrate interface. Moreover, twinned material is observed in the recrystallized layers and its concentration is strongly dependent on substrate cleaning. These phenomena are explained in terms of a decrease in the ion-assisted growth rate in the presence of high oxygen concentrations. The data are discussed and compared with those obtained during pure thermal annealing. To speed up publication, the authors of this paper has agreed to not receive the proofs for correction.