A multigrid solver for modeling complex interseismic stress fields

We develop a multigrid, multiple time stepping scheme to reduce computational efforts for calculating complex stress interactions in a strike-slip 2D planar fault for the simulation of seismicity. The key elements of the multilevel solver are separation of length scale, grid-coarsening, and hierarchy. In this study the complex stress interactions are split into two parts: the first with a small contribution is computed on a coarse level, and the rest for strong interactions is on a fine level. This partition leads to a significant reduction of the number of computations. The reduction of complexity is even enhanced by combining the multigrid with multiple time stepping. Computational efficiency is enhanced by a factor of 10 while retaining a reasonable accuracy, compared to the original full matrix-vortex multiplication. The accuracy of solution and computational efficiency depend on a given cut-off radius that splits multiplications into the two parts. The multigrid scheme is constructed in such a way that it conserves stress in the entire half-space.     

Validation of plant part measurements using a 3D reconstruction method suitable for high-throughput seedling phenotyping

In plant phenotyping, there is a demand for high-throughput, non-destructive systems that can accurately analyse various plant traits by measuring features such as plant volume, leaf area, and stem length. Existing vision-based systems either focus on speed using 2D imaging, which is consequently inaccurate, or on accuracy using time-consuming 3D methods. In this paper, we present a computer-vision system for seedling phenotyping that combines best of both approaches by utilizing a fast three-dimensional (3D) reconstruction method. We developed image processing methods for the identification and segmentation of plant organs (stem and leaf) from the 3D plant model. Various measurements of plant features such as plant volume, leaf area, and stem length are estimated based on these plant segments. We evaluate the accuracy of our system by comparing the measurements of our methods with ground truth measurements obtained destructively by hand. The results indicate that the proposed system is very promising.     

Analysis of a variational multiscale method for Large–Eddy simulation and its application to homogeneous isotropic turbulence

In this paper a variational multiscale method based on local projection and grad–div stabilization for Large–Eddy simulation for the incompressible Navier–Stokes problem is considered. An a priori error estimate is given for a case with rather general nonlinear (piecewise constant) coefficients of the subgrid models for the unresolved scales of velocity and pressure. Then the design of the subgrid scale models is specified for the case of homogeneous isotropic turbulence and studied for the standard benchmark problem of decaying homogeneous isotropic turbulence.     

In vivo interactive visualization of four-dimensional blood flow patterns

In this paper we give an overview over a series of experiments to visualize and measure flow fields in the human vascular system with respect to their diagnostic capabilities. The experiments utilize a selection of GPU-based sparse and dense flow visualization algorithms to show the diagnostic opportunities for volumetric cardiovascular phase contrast magnetic resonance imaging data sets. Besides classical hardware accelerated particle and line-based approaches, an extensible tublet-based visualization, a four-dimensional volumetric line integral convolution and a new two-dimensional cutting plane tool for three-dimensional velocity data sets have been implemented. To evaluate the results, several hearts of human subjects have been investigated and a flow phantom was built to artificially simulate distinctive flow features. Our results demonstrate that we are able to provide an interactive tool for cardiovascular diagnostics with complementary hardware accelerated visualizations. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.

Modeling culture in intelligent virtual agents

This work addresses the challenge of creating virtual agents that are able to portray culturally appropriate behavior when interacting with other agents or humans. Because culture influences how people perceive their social reality it is important to have agent models that explicitly consider social elements, such as existing relational factors. We addressed this necessity by integrating culture into a novel model for simulating human social behavior. With this model, we operationalized a particular dimension of culture—individualism versus collectivism—within the context of an interactive narrative scenario that is part of an agent-based tool for intercultural training. Using this scenario we conducted a cross-cultural study in which participants from a collectivistic country (Portugal) were compared with participants from an individualistic country (the Netherlands) in the way they perceived and interacted with agents whose behavior was either individualistic or collectivistic, according to the configuration of the proposed model. In the obtained results, Portuguese subjects rated the collectivistic agents more positively than the Dutch but both countries had a similarly positive opinion about the individualistic agents. This experiment sheds new light on how people from different countries differ when assessing the social appropriateness of virtual agents, while also raising new research questions on this matter.     

Test Time Minimization for Hybrid BIST of Core-Based Systems

This paper presents a solution to the test time minimization problem for core-based systems. We assume a hybrid BIST approach, where a test set is assembled, for each core, from pseudorandom test patterns that are generated online, and deterministic test patterns that are generated off-line and stored in the system. In this paper we propose an iterative algorithm to find the optimal combination of pseudorandom and deterministic test sets of the whole system, consisting of multiple cores, under given memory constraints, so that the total test time is minimized. Our approach employs a fast estimation methodology in order to avoid exhaustive search and to speed-up the calculation process. Experimental results have shown the efficiency of the algorithm to find near optimal solutions.     

Effect of pH on the affinity of phospholipids for cholesterol

The ability of multilamellar vesicles of phosphatidylcholine and phosphatidylethanolamine in aqueous phase to prevent access to cholesterol by a nonpolar solvent was examined. Phosphatidylethanolamine vesicles retained less sterol than phosphatidylcholine vesicles. In mixed vesicles, cholesterol was retained in proportion to the amount of phosphatidylcholine. To alter the charge and hydration of head groups, pH was adjusted from 1.2 to 12.5. Above pH 8, both phosphatidylethanolamine and phosphatidylcholine retained sterol in a 1∶1 molar ratio of phospholipid to cholesterol, regardless of acyl side chain composition. Between pH 2.0 and pH 8.0, sterol retention varied with type of head group and side chain. Lipids with 16-carbon saturated side chains retained more sterol than 18-carbon unsaturated or 12-carbon saturated side chains. Between pH 1.1 and 2.0, none of the phosphatidylethanolamines retained sterol, but long chain phosphatidylcholines, saturated or unsaturated, retained sterol in a 1∶1 molar ratio of phospholipid to sterol. Short chain phosphatidylethanolamines and phosphatidylcholines retained 0 to 20% at the low- to mid-pH range. Size of multilamellar vesicles, measured by Doppler effect light scattering analysis, had no bearing on sterol retention. Sonication of vesicles, which increases surface curvature, increases the retention of sterol. Fluorescence polarization indicated that cholesterol does not interact with DPPC or DLPC side chains. The observations can be interpreted in terms of space requirements of head groups, including charge repulsion and hydration. Other factors, such as monovalent cation replacement by protons, juxtaposition of charged groups on vesicle surfaces and length and unsaturation of acyl side chains affect the affinity of phospholipids for cholesterol.     

污泥作为污水厂内碳源的水解特性及工艺选择

随着各地污水厂出水水质对氮、磷要求的日益提高,强化脱氮除磷成为必然要求,但是我国多数污水厂由于多种原因导致进水碳源不足,尤其是进水SCOD、VFAs的匮乏,直接影响了生物脱氮除磷的效率,甚至不得已采用人工投加外碳源脱氮或者化学除磷方式以满足严格的出水氮、磷要求,但这无疑大大提高了污水厂的产泥率及运行成本.充分挖掘污水厂的“内碳源”,利用污泥水解产生VFAs,不仅能有效提高除磷脱氮效率,而且可以降低污水厂的污泥产量,是可持续的资源化技术.比较了初沉污泥和活性污泥的水解特性差异,介绍了污泥水解工艺的常用构型及参数选择,以及国内外一些成功的实施案例.