Numerical Study of a Modified Time-Stepping θ-Scheme for Incompressible Flow Simulations

In [Turek (1996). Int. J. Numer. Meth. Fluids 22, 987–1011], we had performed numerical comparisons for different time stepping schemes for the incompressible Navier–Stokes equations. In this paper, we present the numerical analysis in the context of the Navier–Stokes equations for a modified time-stepping θ-scheme which has been recently proposed by Glowinski [Glowinski (2003). In: Ciarlet, P. G., and Lions, J. L. (eds.), Handbook of Numerical Analysis, Vol. IX, North-Holland, Amsterdam, pp. 3–1176]. Like the well-known classical Fractional-Step-θ-scheme which had been introduced by Glowinski [Glowinski (1985). In Murman, E. M. and Abarbanel, S. S. (eds.), Progress and Supercomputing in Computational Fluid Dynamics, Birkh?user, Boston MA; Bristeau et al. (1987). Comput. Phys. Rep. 6, 73–187], too, and which is still one of the most popular time stepping schemes, with or without operator splitting techniques, this new scheme consists of 3 substeps with nonequidistant substepping to build one macro time step. However, in contrast to the Fractional-Step-θ-scheme, the second substep can be formulated as an extrapolation step for previously computed data only, and the two remaining substeps look like a Backward Euler step so that no expensive operator evaluations for the right hand side vector with older solutions, as for instance in the Crank–Nicolson scheme, have to be performed. This modified scheme is implicit, strongly A-stable and second order accurate, too, which promises some advantageous behavior, particularly in implicit CFD simulations for the nonstationary Navier–Stokes equations. Representative numerical results, based on the software package FEATFLOW [Turek (2000). FEATFLOW Finite element software for the incompressible Navier–Stokes equations: User Manual, Release 1.2, University of Dortmund] are obtained for typical flow problems with benchmark character which provide a fair rating of the solution schemes, particularly in long time simulations.Dedicated to David Gottlieb on the occasion of his 60th anniversary     

The effects of deep zones on wetland nitrogen processing.

Twelve research wetlands were operated under varying conditions at a site west of the city of Phoenix. These were constructed as a triplicated design, with zero, one, two and three internal deep zones, all containing an inlet distribution and an outlet collection deep zone, together comprising 12.5-35% of the wetland areas. The water supply was partially nitrified effluent from a city wastewater treatment plant. Total nitrogen was reduced by about 50%, from inflow concentrations between 6 and 8 mg/L. Speciation of the inflow was approximately 25% organic nitrogen, 25% ammonium nitrogen and 50% nitrate nitrogen. Typical outflow concentrations were about 1.2 mg/L organic, 0.5 mg/L ammonium and 0.0-2.5 mg/L nitrate. Rate constants for total nitrogen were 15-20 m/year at 20 degrees C, and 20-30 m/year for nitrate, which agree well with other project reports. Temperature factors averaged 1.100 for total nitrogen, and 1.184 for nitrate. There were no differences in the internal hydraulics with deep zone numbers. Deep zone numbers in the wetlands did not affect nitrogen treatment performance. No differences with deep zone numbers were found for temperature, dissolved oxygen, pH, or nitrogen removals or rate constants. In conjunction with other reported results, there appears to be no large treatment benefit or detriment of incorporating internal deep zones in free water surface wetlands.     

Finite elements in the analysis of pressure vessels and piping-a bibliography (1976–1996)

The paper gives a bibliographical review of the finite element methods (FEMs) applied for the analysis of pressure vessel structures/components and piping from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore the aim of this review is to give the reader an encyclopaedic view of the differnt possibilities that exist today for the finite element analysis in the fields of pressure vessels and piping. The bibliography at the end of the paper contains approximately 1900 references to papers, conference proceedings and theses/dissertations on the subject that were published in 1976–1996. These are classified in the following categories: linear and non-linear, static and dynamic, stress and deflection analysis; stability problems; thermal problems; fracture mechanics problems; contact problems; fluid-structure interaction problems; manufacturing of pipes and tubes; welded pipes and pressure vessel components; development of special finite elements for pressure vessels and pipes; finite element software; and other topics. Also finite element software, general purpose and special purpose codes, used for the analysis of pressure vessels and pipes are briefly discussed and presented.     

Laser irradiation of oligosiloxane copolymer thin films functionalized with side chain bulky carbosilane moieties

Linear oligosiloxanes functionalized with bulky side chain tris(trimethylsilyl)hexyl (TTSH) substituents were transformed into cross-linked materials by UV 193 nm excimer pulsed laser ablation. The process occurred without any catalyst, by reactions of radicals formed in UV laser induced photolysis of side tris(trimethylsilyl)hexyl groups. Chemical changes were monitored by FTIR, LC/UV, GC/MS and solubility tests.     

The amphiphysin-like protein 1 (ALP1) interacts functionally with the cABL tyrosine kinase and may play a role in cytoskeletal regulation

cABL is a protooncogene, activated in a subset of human leukemias, whose protein product is a nonreceptor tyrosine kinase of unknown function. cABL has a complex structure that includes several domains and motifs found in proteins implicated in signal transduction pathways. An approach to elucidate cABL function is to identify proteins that interact directly with cABL and that may serve as regulators or effectors of its activity. To this end, a protein-interaction screen of a phage expression library was undertaken to identify proteins that interact with specific domains of cABL. An SH3-domain-containing protein has been identified that interacts with sequences in the cABL carboxyl terminus. The cDNA encoding ALP1 (amphiphysin-like protein 1) was isolated from a 16-day mouse embryo. ALP1 has high homology to BIN1, a recently cloned myc-interacting protein, and also shows significant homology to amphiphysin, a neuronal protein cloned from human and chicken. The amino terminus has homology to two yeast proteins, Rvs167 and Rvs161, which are involved in cell entry into stationary phase and cytoskeletal organization. ALP1 binds cABL in vitro and in vivo. Expression of ALP1 results in morphological transformation of NIH 3T3 fibroblasts in a cABL-dependent manner. The properties of ALP1 suggest that it may be involved in possible cytoskeletal functions of the cABL kinase. Additionally, these results provide further evidence for the importance of the cABL carboxyl terminus and its binding proteins in the regulation of cABL function.     

Optimization of ceramics bonding in the area of pressure sensor manufacturing

Ceramics joints are applied for producing products that should be made in a general shapes and dimensions for more advantageous usage. The article presents the research work related to ceramic joint quality evaluation, the thermal-structural analysis of ceramic joining and ceramic bond design and implementation. The role of ceramic material in the electronics industry and motivation for joining ceramics is described in the introduction. The requirements and methods for improving the quality of joints are summarized. Also, the results of simulations of pressure sensor cooling after removal from the oven during joining are discussed. The experimental results are evaluated by using a t-test before and after process cooling modification. Important directions for future research are summarized, with emphasis on the statistical determination of poor connection, and how the interface of modification of joint technology and process setting affects results and parameters that have been achieved.     

Phase transition in swollen gels

Summary The dynamic mechanical behaviour of 4% aqueous solutions and networks of poly (N, N-diethylacrylamide) and copolymers of diethylacrylamide with sodium methacrylate (MNa) (molar ratio x_MNA=0–0.05) swollen in water was measured in the temperature range 20–80 °C. With increasing temperature, at T_c polymer chains collapse from random coil to more compact globular conformations. While in the region of coil conformations (T > T_c) the mechanical behaviour of solutions has a liquid-like character (the loss modulus G″ is higher than the storage modulus G′ for a constant frequency ω=1 Hz), in the region of globular conformations (T > T_c) a heterogeneous physical network is built in solutions, and the mechanical behaviour has a solid-like character (G′ > G″). In networks the collapse is reflected in an increase of storage modulus G′; the magnitude of this increase decreases with ionization. The dependence of the loss modulus G″ on the temperature of solutions and networks allows us to conclude that the magnitude of losses in the collapsed state is affected rather by x_MNa (the modulus G″ increases with increasing ionization) than by the heterogeneous structure of the samples.     

The genesis of polyaniline nanotubes

Aniline has been oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. Protons are produced in the course of oxidation and the pH decreases as the reaction proceeds. The oxidation had two subsequent phases: (1) the oxidation of the neutral aniline molecules and the initially produced low-molecular weight aniline oligomers at low acidity, followed by (2) the oxidation of the anilinium cation after the acidity became higher. The two phases of oxidation gave different products, aniline oligomers with mixed ortho- and para-coupling of aniline molecules, and polyaniline nanotubes, respectively.The aniline oligomers are produced at first at low acidity, pH > 4, some of them as rod-like crystals. The molecular weight of the oligomers has been assessed by gel-permeation chromatography to be of several thousands. The 2-3 wt.% content of sulfur in deprotonated samples suggests that the oxidation products are partly sulfonated. The oxidation of ortho-coupled anilines combined with intramolecular cyclization produces phenazine units or their blocks, as indicated by FTIR spectra. A high-molecular weight polyaniline is produced at pH < 2. The protonation of the intermediate pernigraniline form of polyaniline is a prerequisite for the polymerization.The nano-sized oligomer crystallites serve as starting templates for the nucleation of PANI nanotubes. Further growth of nanotubes proceeds by the self-organization of the phenazine units or their blocks located at the ends of the PANI chains. Polyaniline nanotubes have a typical outer diameter of 100-200 nm, with a wall thickness of 50-100 nm, an inner diameter of 0-100 nm, and a length extending to several micrometres.     

Scalable Realistic Rendering with Many‐Light Methods

Recent years have seen increasing attention and significant progress in many‐light rendering, a class of methods for efficient computation of global illumination. The many‐light formulation offers a unified mathematical framework for the problem reducing the full lighting transport simulation to the calculation of the direct illumination from many virtual light sources. These methods are unrivaled in their scalability: they are able to produce plausible images in a fraction of a second but also converge to the full solution over time. In this state‐of‐the‐art report, we give an easy‐to‐follow, introductory tutorial of the many‐light theory; provide a comprehensive, unified survey of the topic with a comparison of the main algorithms; discuss limitations regarding materials and light transport phenomena and present a vision to motivate and guide future research. We will cover both the fundamental concepts as well as improvements, extensions and applications of many‐light rendering.