A model material approach to the study of fracture process zone of quasi-brittle materials

A new approach to study the fracture of quasi-brittle materials is introduced: the design and testing of model materials. By model material is understood a material with enlarged microstructure and which material parameters, such as stacking and mechanical properties of particles and cohesion force, can be fully controlled. In this paper a first example to the model materials approach is presented, consisting in 5 mm steel particles bonded in a precise stacking with an epoxy-based glue. It is shown how it is possible to correlate the different fracture mechanisms and ultimate peak load of the model material to the particle pair force and to the fracture process zone size. It is also seen how a quasi-brittle behaviour is produced in the presence of mechanisms that induced the crack to shift fracture planes, that is, in presence of energy dissipative mechanisms.     

Assimilation for Affiliation and Contrast for Control: Complementary Self-Construals.

People have knowledge about relationships (i.e., relational schemas) that is based on their experiences. Because most people have experience with complementary behavior (interaction partners behaving similarly in terms of affiliation but oppositely in terms of control), they expect complementary behavior in their relationships. Like other beliefs about relationships, expectations of complementarity affect self-construal. The authors provide evidence for complementary self-construal; people assimilate to relevant relationship partners on the affiliation dimension and contrast on the control dimension. Consistent with the proposed role of relationship knowledge in these effects, complementary self-construal was moderated by the familiarity of the target, whether people focused on their relationship with or the appearance of the target, and whether the context was relevant for the interpersonal dimension. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Single frame correction of motion artifacts in PMD-based time of flight cameras

One of the leading time of flight imaging technologies for depth sensing is based on Photonic Mixer Devices (PMD). In PMD sensors each pixel samples the correlation between emitted and received light signals. Current PMD cameras compute eight correlation samples per pixel in four sequential stages to obtain depth with invariance to signal amplitude and offset variations. With motion, PMD pixels capture different depths at each stage. As a result, correlation samples are not coherent with a single depth, producing artifacts. We propose to detect and remove motion artifacts from a single frame taken by a PMD camera. The algorithm we propose is very fast, simple and can be easily included in camera hardware. We recover depth of each pixel by exploiting consistency of the correlation samples and local neighbors of the pixel. In addition, our method obtains the motion flow of occluding contours in the image from a single frame. The system has been validated in real scenes using a commercial low-cost PMD camera and high speed dynamics. In all cases our method produces accurate results and it highly reduces motion artifacts.     

Effects of preparation conditions on the surface modification and performance of polyethersulfone ultrafiltration membranes

The impact that some membrane preparation steps had on ultrafiltration (UF) membrane characteristics and performance was studied. Polyethersulfone (PES) was employed as base polymer, while N‐methyl pyrrolidone (NMP) was used as a solvent, and polyvinylpyrrolidone (PVP) was used as a nonsolvent pore‐forming additive. The manufacturing variables studied were solvent evaporation time and membrane surface modification, using a fluorine‐based copolymer referred to as surface‐modifying macromolecule (SMM). The flat sheet membranes, prepared via phase inversion, were characterized using solute transport data, X‐ray photoelectron spectroscopy (XPS), and contact angle measurements. Membrane performance was evaluated via filtration test protocol that included a 6‐day filtration of concentrated river water. The flux reduction with time was modeled using single and dual mechanisms of fouling. The pore blockage/cake filtration model described better the behavior of the permeation rate along the experiments. Increasing the solvent evaporation time decreased the size of the pores and the permeation rate. However, it did not significantly affect the removal of the organic compounds naturally present in the river water used as feed. XPS and contact angle measurements proved that the short evaporation periods did not allow enough SMM migration to the surface to provoke a significant effect on the membrane performance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

An entropy-based persistence barcode

In persistent homology, the persistence barcode encodes pairs of simplices meaning birth and death of homology classes. Persistence barcodes depend on the ordering of the simplices (called a filter) of the given simplicial complex. In this paper, we define the notion of “minimal” barcodes in terms of entropy. Starting from a given filtration of a simplicial complex K, an algorithm for computing a “proper” filter (a total ordering of the simplices preserving the partial ordering imposed by the filtration as well as achieving a persistence barcode with small entropy) is detailed, by way of computation, and subsequent modification, of maximum matchings on subgraphs of the Hasse diagram associated to K. Examples demonstrating the utility of computing such a proper ordering on the simplices are given.     

Clinicopathologic analysis of microscopically invasive breast carcinoma

Breast biopsy or mastectomy cases having diagnoses of carcinoma in situ with "microinvasion," "minimal invasion," "focal invasion," or "suggestive of invasion" were reviewed and all histologically identified foci of invasive disease from each case were measured using an ocular micrometer. Cases in which any single focus of invasion was greater than 5 mm or the added size of separate invasive foci exceeded 10 mm were excluded, resulting in a study group of 75 patients. Invasive neoplasm was present in the initial biopsy in 69 of 75 cases (92%); however, residual invasive neoplasm was found in the subsequent lumpectomy/mastectomy from 14 of these (20%). In 59% of cases, two or more histologically separate foci of invasion were identified. Invasive foci consisted of isolated cells or cell clusters, each less than 1 mm (microfocal invasion), in 33% of cases. In 12 cases, the sum of individual invasive foci was 5 to 10 mm. Axillary lymph nodes (LN) from 5 of 69 patients (7%) contained metastatic carcinoma (four cases, one LN positive; one case, two LN positive). The cumulative sizes of all invasive foci in the LN-positive group were microfocal invasion (one case), 0.6 mm (one case), 1.1 mm, 2.5 mm, and 5.8 mm. The difference in frequency of axillary node metastasis between tumors with microfocal and measurable invasion (4.3% v 8.6%) was not statistically significant. Follow-up data were available on 55 cases (mean interval, 66.1 months). One (node-negative) patient had duct carcinoma in situ recurrence in the same breast 4 years after initial treatment. Another (with unknown node status) developed an axillary lymph node metastasis 13 months after initial treatment (96% disease-free survival). We conclude that microscopic stromal invasion in breast carcinoma, at least in the setting of significant in situ component, is often initiated from multiple foci. Patients with microscopically invasive breast carcinoma have a small but significant risk of axillary metastases, although a highly favorable survival.     

Mixed-Signal Approximate Computation: A Neural Predictor Case Study

As transistors shrink and processors trend toward low power, maintaining precise digital behavior grows more expensive. Replacing digital units with analog equivalents sometimes allows similar computation to be performed at higher speed using less power. As a case study in mixed-signal approximate computation, the authors describe an enhanced neural prediction algorithm and its efficient analog implementation.