Design and verification of a model secondary clarifier for activated sludge

A model clarifier was designed using conventional methods for the surface calculation and an alternative pathway for the determination of the height and constructed accordingly. In addition, a new approach was used to evaluate the necessary scraper speed in comparison to full-scale clarifiers. Scaling effects were taken into account. The model clarifier was first tested by tracer experiments. Conductivity measurements were used for the clarification zone, whereas the thickening zone was tested using pyrene as an organic tracer compound. Finally, the behaviour of the model clarifier was compared with a full-scale settler. The results indicated that operation of the model clarifier was representative of full-scale behaviour, except for severe overloads. Hence, the small-scale clarifier qualified as a model for small-scale studies and could be installed on large-scale plants to monitor more transparently plant performance and sludge behaviour     

Left ventricular radial tagging acquisition using gradient-recalled-echo techniques: sequence optimization

Myocardial tagging with magnetic resonance (MR) imaging offers unique possibilities for noninvasive left ventricular (LV) strain analysis. True three-dimensional strain analysis can be achieved with tags implemented in cardiac short axis and long axis images. Spin-echo (SE) techniques have been used for these studies. However, this approach is time-consuming: images at different phases of the cardiac cycle have to be obtained in successive measurements and hence the total number of measurements equals the number of time frames. Moreover, the images are often degraded by flow and motion artifacts. The purpose of this study was to optimize a faster and more robust MR tagging sequence for use on a clinical whole-body 1 T MR system with optimal persistence of the tags during the entire cardiac cycle. The tagging pulses were implemented in gradient-recalled-echo (GRE) sequences and compared to SE-based acquisitions. The effects of the use of flow-compensating gradients, the excitation angles, and the angles of the saturation pulses have been studied with MR signal simulations and in comparative measurements in volunteers. GRE acquisitions with flow-compensating gradients are robust techniques for myocardial tagging acquisitions. Use of optimized flip angles and saturation pulses can significantly improve delineation of the tag and can be used up to at least 700 ms after the R-wave. Therefore, LV tagging with GRE acquisitions using optimized MR parameters is a robust and promising technique.     

Appendicular and ureteral adenomyomas. Problem of induction of the stroma in the endometriosis foci

Among 15 chelating agents tested, sodium-2,3-dimercaptopropane 1 sulfonate (DMPS), 2,3-dimercaptopropanol (BAL), sodium-mercaptoethyliminodiacetate (MEIDA), and D-penicillamine (PA) exerted an influence on the excretion of Hg and its distribution in the organs. The excretion pattern however, is different for these compounds, and, from the practical point of view, a favourable effect is exhibited only by DMPS which enhances the urinary excretion rate and lowers the Hg-concentration in all organs.     

A versatile wavelet domain noise filtration technique for medical imaging

In this paper, we propose a robust wavelet domain method for noise filtering in medical images. The proposed method adapts itself to various types of image noise as well as to the preference of the medical expert; a single parameter can be used to balance the preservation of (expert-dependent) relevant details against the degree of noise reduction. The algorithm exploits generally valid knowledge about the correlation of significant image features across the resolution scales to perform a preliminary coefficient classification. This preliminary coefficient classification is used to empirically estimate the statistical distributions of the coefficients that represent useful image features on the one hand and mainly noise on the other. The adaptation to the spatial context in the image is achieved by using a wavelet domain indicator of the local spatial activity. The proposed method is of low complexity, both in its implementation and execution time. The results demonstrate its usefulness for noise suppression in medical ultrasound and magnetic resonance imaging. In these applications, the proposed method clearly outperforms single-resolution spatially adaptive algorithms, in terms of quantitative performance measures as well as in terms of visual quality of the images.     

A Near-Optimal Linear Crosstalk Precoder for Downstream VDSL

This letter presents a linear crosstalk precoder for very-high-speed digital subscriber lines (VDSL) that has a low run-time complexity. A lower bound on the data rate of the precoder is developed, and guarantees that the precoder achieves near-optimal performance in 99% of VDSL channels     

MIMC reliability and electrical behavior defined by a physical layer property of the dielectric

Metal–insulator–metal capacitor (MIMC) reliability and electrical properties are defined by the TDDB lifetime, breakdown voltage and leakage current. In this article, the correlation is determined between these electrical properties and the physical and chemical properties of the SiN dielectric layer. It is demonstrated how a SiN dielectrics with a high refractive index have high Si content and show an increased initial leakage current. However, contradictory to the high leakage current, these dielectrics also show high lifetimes. It is shown that SiN dielectrics with a high Si content contain high numbers of charge trapping centers. Over time, a high concentration of trapped charges is build up to such an extend that the local electric field over the dielectric is significantly decreased. This results in the observed reliability improvement of the dielectric. The final intrinsic quality and reliability of MIMC capacitors can therefore be determined by measurable physical properties of the MIMC dielectric at the time of the deposition of this layer.     

Introducing functional classification theory to land use planning by means of decision tables

This paper contributes to the conceptualisation and analysis of double-sided matching problems, taking the land use planning problem as an example. It does so by introducing functional classification theory at the knowledge level, the symbol level and the system level of a DSS. This theory explicitly expresses the methodological viewpoint of relational realism. At the knowledge level this implies defining knowledge on the basis of matching the intension and extension of concepts. At the symbol level it deals with knowledge representation and here decision tables are advanced and formally introduced. At the system level the formalism used at the symbol level is implemented to develop a relational matching DSS.     

On Stress Intensity Factors of Multiple Cracks at Small Distances in 2-D Problems

In the present work a method is proposed to predict stress intensity factors (SIFs) of strongly interacting cracks at spacings that are substantially smaller than crack lengths. The method is intended for applications where cracks are observed in stack-like/staggered arrangements as in damage patterns of some natural materials with dense lamellar microstructures. The new calculation procedure is inspired by the analytical method of Kachanov (1987) that due to its simplicity has shown to be a powerful tool for analysis of crack interactions. Although in 3-D the accuracy of Kachanov’s method remains good at quite close spacings, in 2-D problems it, however, quickly drops as the distance between cracks decreases, underestimating the effect of crack interactions, especially in ordered staggered arrangements. In this work we introduce new modeling assumptions that are suited for problems where stress fields have high gradients – a typical situation in the case of closely spaced parallel cracks. The accuracy of the method is examined on the example of two stacked cracks. The use of SIFs for estimation of material elastic compliance is also discussed.     

Homogenization of metamaterials using full-wave simulations

We present a full-wave homogenization method to determine the effective material parameters of metamaterials by considering a spherical piece of metamaterial. We use a T-matrix approach that is accelerated by a multilevel fast multipole method that is stable at low frequencies. To determine the T-matrix of one inclusion in the metamaterial a Method of Moments surface integral equation is used that is also accelerated using another multilevel fast multipole method that is stable at low frequencies. We also derive a new closed-form expression to extract the effective material parameters from the T-matrix of the spherical piece of material. Examples verify the accuracy and limitations of the method. We show results for metamaterials comprising more than 40,000 particles.