A scalable FETI-DP algorithm for a semi-coercive variational inequality

We develop an optimal algorithm for the numerical solution of semi-coercive variational inequalities by combining dual-primal FETI algorithms with recent results for bound and equality constrained quadratic programming problems. The discretized version of the model problem, obtained by using the FETI-DP methodology, is reduced by the duality theory of convex optimization to a quadratic programming problem with bound and equality constraints, which is solved by a new algorithm with a known rate of convergence given in terms of the spectral condition number of the quadratic problem. We present convergence bounds that guarantee the scalability of the algorithm. These results are confirmed by numerical experiments.     

Use of partial least squares within the control relevant identification for buildings

Climate changes, diminishing world supplies of non-renewable fuels, as well as economic aspects are probably the most significant driving factors of the current effort to save energy. As buildings account for about 40 % of global final energy use, efficient building climate control can significantly contribute to the saving effort. Predictive building automation can be used to operate buildings in an energy and cost effective manner with minimum retrofitting requirements. In such a predictive control approach, dynamic building models are of crucial importance for a good control performance. An algorithm which has not been used in building modeling yet, namely a combination of minimization of multi-step ahead prediction errors and partial least squares will be investigated. Subsequently, two case studies are presented: the first is an artificial model of a building constructed in Trnsys environment, while the second is a real-life case study. The proposed identification algorithm is then validated and tested.     

An analysis of the non-preemptive mixed-criticality match-up scheduling problem

Many applications have a mixed-criticality nature. They contain tasks with a different criticality, meaning that a task with a lower criticality can be skipped if a task with a higher criticality needs more time to be executed. This paper deals with a mixed-criticality scheduling problem where each task has a criticality given by a positive integer number. The exact processing time of the task is not known. Instead, we use different upper bounds of the processing time for different criticality levels of the schedule. A schedule with different criticality levels is generated off-line, but its on-line execution switches among the criticality levels depending on the actual values of the processing times. The advantage is that after the transient prolongation of a higher criticality task, the system is able to match up with the schedule on a lower criticality level. While using this model, we achieve significant schedule efficiency (assuming that the prolongation of the higher criticality task rarely occurs), and at the same time, we are able to grant a sufficient amount of time to higher criticality tasks (in such cases, some of the lower criticality tasks may be skipped). This paper shows a motivation for the non-preemptive mixed-criticality match-up scheduling problem arising from the area of the communication protocols. Using a polynomial reduction from the 3-partition problem, we prove the problem to be \(\mathcal {NP}\)-hard in the strong sense even when the release dates and deadlines are dropped and only two criticality levels are considered.     

Wavelet-based de-noising techniques in MRI

The paper deals with techniques for the enhancement of magnetic resonance (MR) images using the wavelet analysis, which is assessed from the viewpoint of choosing the mother wavelet and the thresholding technique. Three parameters are used as objective criteria of the quality of image enhancement: the signal-to-noise ratio (SNR), image contrast, and linear approximation of edge steepness. Unlike most of the standard methods, which work exclusively with image magnitude, we also examined the influence of image phase, i.e. the image is processed as a complex signal. In addition to the interpretation of results, a short summary is given that deals with the choice of the optimal mother wavelet and thresholding technique for different types of MR images.     

Calculations of the water-dimer encapsulations into C84

The water-dimer formation and its encapsulation into D₂(22)-C₈₄ and D_2d(23)-C₈₄ fullerenes is evaluated. The water-dimer populations are computed using the potential-energy change from the G3 theory and anharmonic partition functions from the MP2/AUG-cc-pVQZ approach. The encapsulation energetics is treated at the M06-2X/6-31++G** level and it is found that the water-dimer storage in C₈₄ is attractive, yielding an energy gain of more than 10 kcal mol^?1. This substantial encapsulation energy together with the computed temperature increase of the water-dimer population in the saturated steam suggests that the (H₂O)₂@C₈₄ endohedrals could be produced in a high-temperature/high-pressure approach similarly to encapsulation of rare gases in fullerenes.     

Evaluation of the relative stabilities of two non-IPR isomers of Sm@C76

Density-functional theory calculations are presented for two low-energy Sm@C₇₆ isomers with the isolated-pentagon rule (IPR) violating cages. The relative isomeric populations at high temperatures are evaluated using the calculated molecular terms and relationships to observations are discussed. It is shown that the observed Sm@C_2v(19138)-C₇₆ species can be computed as the major isomer if the encapsulate motions are treated as relatively restricted. With the restriction conjecture, the major isomer is about two times more populated than the minor Sm@C₁(17459)-C₇₆ endohedral. The study points out the importance of symmetry considerations in stability evaluations for general nanocarbons.     

Solution‐Based Processing of Optoelectronically Active Indium Selenide

Layered indium selenide (InSe) presents unique properties for high‐performance electronic and optoelectronic device applications. However, efforts to process InSe using traditional liquid phase exfoliation methods based on surfactant‐assisted aqueous dispersions or organic solvents with high boiling points compromise electronic properties due to residual surface contamination and chemical degradation. Here, these limitations are overcome by utilizing a surfactant‐free, low boiling point, deoxygenated cosolvent system. The resulting InSe flakes and thin films possess minimal processing residues and are structurally and chemically pristine. When employed in photodetectors, individual InSe nanosheets exhibit a maximum photoresponsivity of ≈5 × 10⁷ A W^?1, which is the highest value of any solution‐processed monolithic semiconductor to date. Furthermore, the surfactant‐free cosolvent system not only stabilizes InSe dispersions but is also amenable to the assembly of electronically percolating InSe flake arrays without posttreatment, which enables the realization of ultrahigh performance thin‐film photodetectors. This surfactant‐free, deoxygenated cosolvent approach can be generalized to other layered materials, thereby presenting additional opportunities for solution‐processed thin‐film electronic and optoelectronic technologies.     

Computer simulation of evolving capillary bridges in granular media

A numerical method for the simulation of spatially evolving liquid–vapour interfaces in arbitrary two dimensional granular media is presented. Solid- and liquid-phase objects are described by polynomials whose edges evolve according to surface tension forces until a prescribed equilibrium contact angle at three-phase contact points and a constant mean curvature on two-phase contact lines is achieved. The main advantage of the method is the possibility to account for topological transitions (interface coalescence or rupture) and direct calculation of the force acting on solid interfaces due to liquid bridges. The method has been validated by comparing numerical and analytical results for a single pendular liquid bridge and then demonstrated on the simulation of transition from the pendular to funicular and capillary state in a wet particle assembly.     

Improved prediction model for time-dependent deformations of concrete: Part 4—Temperature effects

This Part presents a refinement of the BP model for the effects of temperature on the basic creep and drying creep of concrete. The temperature effect on basic creep is introduced through two different activation energies, one for the effect of temperature increase on the rate of hydration, which causes a decrease of creep, and one for the effect of temperature increase on the rate of creep, which causes an increase of creep. The dichotomy of these two opposing temperature influences is an essential feature, required for good agreement with test data. The greatest error in basic creep is again caused by the prediction of the material parameters from concrete composition and strength. This error can be largely eliminated by conducting limited short-time basic creep tests at different temperatures. Comparisons with 13 different data sets from the literature show a satisfactory agreement, better than that achieved with previous models, while at the same time the scope of the present model is broader. The effect of temperature on the creep of drying specimens is rather different because heating causes a moisture loss from unsealed specimens. The paper presents prediction formulae which modify those for drying creep at room temperature on the basis of the activation energy concept and take into account the effect of heating on the moisture loss. Comparisons with the limited test data that exist show satisfactory agreement. No additional material parameters depending on concrete composition and strength are introduced for drying creep.     

Multiscale simulation of fracture of braided composites via repetitive unit cells

Two-dimensional triaxially braided composites (2DTBCs) are attractive in crashworthiness design because their fracture can dissipate a significantly larger amount of impact energy than other light-weight materials. This paper aims at predicting the fracture energy, G_f, and the effective length of the fracture process zone, c_f, of 2DTBC composites. Since the fracture parameters are best manifested in the scaling properties and are the main parameters in the size effect law, the nominal strengths of three geometrically similar notched beams of three different sizes are simulated in a 3D finite element framework. The simulations are run for three different bias tow angles: 30°, 45° and 60°. Continuum beam elements in front of the notch are replaced with repetitive unit cells (RUCs), which represent the 2DTBC’s mesostructure, and are located in the region of potential cracking. Multiscale simulations, incorporating damage mechanics, are used to predict the pre- and post-peak response from three-point bending tests. Nominal stresses are calculated from the predicted peak loads and used to fit the size effect law. The dimensionless energy release rate function g(α) is determined from the J-integral. The values of G_f and c_f are then determined using g(α) and the size effect law. With some exceptions, the results in general match well with the results of size effect experiments, and particularly the strong size effect observed in the tests.