Damage analysis of extrusion tools made from the austenitic hot work tool steel Böhler W750

During hot extrusion of copper alloys, extrusion tools have to withstand cyclic thermal and mechanical loads. To enhance the service life of the tools, materials with high temperature strength are designed as well as an optimised process control is performed. To characterise the tool damage evolution during service and to improve process guiding, modelling and simulation are appropriate means. The extrusion process of copper billets at three different temperatures was simulated by an FE-program to obtain the temporal boundary conditions, i.e. stress and temperature distributions at the interface billet-liner. Those boundary conditions were used to simulate the elastic–viscoplastic behaviour of the tool steel Böhler W750 in service by means of Abaqus Standard? v.6.8-3 software in conjunction with Z-Mat package. A lifetime rule was added in order to compute the lifetime consumption and the cycles to failure.     

Ultrananokristalline Diamantschichten

Ultrananocrystalline Diamond Films Innovative materials are the driving force for technological progress and with it for the international competitiveness of the industry. Recently a new area of work was opened here: nanotechnology. Hence, a matter of particular interest are self‐organized nanostructured materials. Ultra‐Nanocrystalline Diamond (UNCD) is a product of this area. The key to structuring those UNCD films is to control the ratio of the hard diamond crystals and the matrix surrounding the nanosized diamond crystals. Essential film properties can be tailored by adjusting this ratio.     

New Approach for the Application of Functional Ceramic Material in Carbon Bonded Doloma Refractories to Reduce Emissions

Doloma carbon bricks with graphite contents of approximately 2 wt% are widely used in the production of stainless steels in argon oxygen decarburisation (AOD) or in vacuum oxygen decarburisation (VOD) vessels as lining material. The application of doloma refractories is connected with metallurgical benefits such as high oxidic stability of its oxides, and the ability to bond sulphur from the hot metal. The production and application of carbon bonded refractories is linked with environmental harmful emissions in the broadest sense. Amongst the aspect of environmental friendly refractory systems this work has observed and shown the interaction of functional ceramic material TiO₂ with the organic binder system. In the centre of this work is the aspect of increased residual carbon content of the binder resin due to TiO₂ addition. The increased residual carbon content of the binder resin connected with improved mechanical, physical and thermomechanical properties due to sub‐micro scaled TiO₂ addition offers the feasibility to reduce the total carbon content without downgrading the brick properties. This aspect has not been observed yet and is of high interest with respect to reduced emissions and environmental friendly refractories. Previous works have investigated the influence of TiO₂ on other carbon bonded refractory systems such as alumina carbon and magnesia carbon. As illustrated in this work and previous work, TiO₂ is working completely different in the Doloma Carbon system from other systems.     

Psychological treatment for panic disorder with agoraphobia: A randomized controlled trial to examine the role of therapist-guided exposure in situ in CBT.

[Correction Notice: An erratum for this article was reported in Vol 79(5) of Journal of Consulting and Clinical Psychology (see record 2011-21293-002). In the article, the name of author Georg W. Alpers was misspelled as George W. Alpers. In Table 2, in the footnote, line two, the criteria should read “MI≤1.8”. The online versions of this article have been corrected.] Objective: Cognitive–behavioral therapy (CBT) is a first-line treatment for panic disorder with agoraphobia (PD/AG). Nevertheless, an understanding of its mechanisms and particularly the role of therapist-guided exposure is lacking. This study was aimed to evaluate whether therapist-guided exposure in situ is associated with more pervasive and long-lasting effects than therapist-prescribed exposure in situ. Method: A multicenter randomized controlled trial, in which 369 PD/AG patients were treated and followed up for 6 months. Patients were randomized to 2 manual-based variants of CBT (T+/T?) or a wait-list control group (WL; n = 68) and were treated twice weekly for 12 sessions. CBT variants were identical in content, structure, and length, except for implementation of exposure in situ: In the T+ variant (n = 163), therapists planned and supervised exposure in situ exercises outside the therapy room; in the T? group (n = 138), therapists planned and discussed patients' in situ exposure exercises but did not accompany them. Primary outcome measures were (a) Hamilton Anxiety Scale, (b) Clinical Global Impression, (c) number of panic attacks, and (d) agoraphobic avoidance (Mobility Inventory). Results: For T+ and T? compared with WL, all outcome measures improved significantly with large effect sizes from baseline to post (range = ?0.5 to ?2.5) and from post to follow-up (range = ?0.02 to ?1.0). T+ improved more than T? on the Clinical Global Impression and Mobility Inventory at post and follow-up and had greater reduction in panic attacks during the follow-up period. Reduction in agoraphobic avoidance accelerated after exposure was introduced. A dose–response relation was found for Time × Frequency of Exposure and reduction in agoraphobic avoidance. Conclusions: Therapist-guided exposure is more effective for agoraphobic avoidance, overall functioning, and panic attacks in the follow-up period than is CBT without therapist-guided exposure. Therapist-guided exposure promotes additional therapeutic improvement—possibly mediated by increased physical engagement in feared situations—beyond the effects of a CBT treatment in which exposure is simply instructed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Motion-compensated and gated cone beam filtered back-projection for 3-D rotational X-ray angiography

This paper presents a method to reconstruct moving objects from cone beam X-ray projections acquired during a single rotational run using a given motion vector field. The method is applicable to voxel driven cone-beam filtered back-projection reconstruction approaches. Here, a formulation based on the algorithm of Feldkamp, Davis, and Kress (FDK) is presented. The motion correction is applied during the back-projection step by shifting the voxel to be reconstructed according to the motion vector field. The method is applied to three-dimensional (3-D) rotational X-ray angiography. Projections from a beating coronary heart phantom are simulated. Motion-compensated reconstructions with varying accuracy of the applied motion field are carried out for a late diastolic heart phase and compared to the reconstruction obtained with the standard FDK-method from projections of the corresponding motion-free model in the same heart phase. Furthermore, gated reconstructions are calculated by weighting the projections according to their cardiac phase without using a motion vector field. Different gating window widths are applied, and the reconstructions are compared. Using the correct motion field with the motion-compensated reconstruction, the image quality of the standard reconstruction from the corresponding motion-free coronary model can almost be recovered. The reconstructed image quality stays acceptable if the accuracy of the motion field sampling points is better than 1 mm. The gated reconstructions with a window width of 15%-20% of the cardiac cycle lead to superior results compared to nearest neighbor gating, especially for histogram based visualization and analysis. The motion-compensated reconstructions provide sharp images of the coronaries far surpassing the image quality of gated reconstructions.     

Bayesian methods for pharmacokinetic models in dynamic contrast-enhanced magnetic resonance imaging

This paper proposes a new method for estimating kinetic parameters of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) based on adaptive Gaussian Markov random fields. Kinetic parameter estimates using neighboring voxels reduce the observed variability in local tumor regions while preserving sharp transitions between heterogeneous tissue boundaries. Asymptotic results for standard errors from likelihood-based nonlinear regression are compared with those derived from the posterior distribution using Bayesian estimation with and without neighborhood information. Application of the method to the analysis of breast tumors based on kinetic parameters has shown that the use of Bayesian analysis combined with adaptive Gaussian Markov random fields provides improved convergence behavior and more consistent morphological and functional statistics.     

Fatigue testing of implantable specimens: Effect of sample size and branching on the dynamic fatigue properties of polyisobutylene-based biomaterials

In this paper we present the first results on the effect of specimen size and branching on the fatigue properties of polyisobutylene-based thermoplastic elastomers measured by the hysteresis method. It was verified that smaller specimens were inherently stronger as expected; at the same loading rate microdumbbells induced higher strain rates so they can be considered as the “worst case” scenario. Microdumbbells, which can be implanted into small animals for in vivo studies, were used for dynamic fatigue testing of linear poly(styrene-b-isobutylene-b-styrene) triblock copolymers (L_SIBS) in comparison with long-chain branched (tree-like or dendritic) versions (D_SIBS). In dynamic stress relaxation studies, D_SIBS performed better than L_SIBS. Simulated physiological conditions had negligible effect on the dynamic properties.     

Characterization of Microemulsion Systems Formed by a Mixed 1,3-Dioxolane Ethoxylate/Octyl Glucoside Surfactant System

The phase behavior of microemulsion systems containing water (or 1.0 wt% NaCl_aq), isooctane, and the binary surfactant system consisting of n-octyl-β-d-glucopyranoside, C₈βG₁, and the acid-cleavable alkyl ethoxylate, 4-CH₃O (CH₂CH₂O)_7.2, 2-(CH₂)₁₂CH₃, 2-(CH₂)CH₃, 1,3-dioxolane, or “cyclic ketal” (“CK-2,13”), was determined. Large temperature-insensitive one, two, and three-phase microemulsion-phase regions were obtained when equal masses of the two surfactants were employed, suggesting that C₈βG₁ reduces the temperature sensitivity of CK-2,13’s ethoxylate group. Addition of C₈βG₁ to CK-2,13 greatly improves the latter’s low efficiency, evidenced by the formation of a three-phase microemulsion system for surfactant concentrations at low fractions of total surfactants for systems with equal mass ratios of water to oil and CK-2,13 to C₈βG₁. Analysis of the phase diagrams also suggests that CK-2,13 and C₈βG₁ impart hydrophobic and hydrophilic character, respectively, to the surfactant mixture, and that addition of salt further increases the hydrophilicity of C₈βG₁, presumably because of the salting-in of the latter. Analysis of small-angle neutron scattering data revealed that the mixed surfactant system formed spherical oil-in-water microemulsions, and that increasing the CK-2,13 fraction among the surfactants reduced the critical microemulsion concentration but slightly increased the nanodroplet size.