Fracture mechanics based estimation of fatigue lives of laser welded joints

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.engfailanal.2018.07.017 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/The conventional joining methods like resistance spot welding and arc welding have several challenges during joining of thin sheets of high strength steel materials. One of the main challenges is that application of these joining methods may result in a severe distortion of welded structure. Therefore, laser welding process has emerged as an alternative joining process which can help mitigate some of these challenges. Lower heat input from laser during the welding process results in a smaller size weld heat affected zone and also in lower overall distortion of the structure. The laser welding process presents an exciting opportunity in designing lighter weight structures. However, the major roadblock to application of laser welding method for large structural parts is that fatigue behavior of laser welded joints is not yet well understood. In order to study the fatigue performance of laser welded joints, detailed experimental and numerical investigations have been carried out and the results are presented in this work. The scope of experimental studies included a large set of coupons with different thicknesses and material combinations. Experimental fatigue test data has been generated for the laser welded joints produced using thin sheets of three grades of high strength steel materials (HSLA and UHSS grades) of several thicknesses (1 mm, 1.6 mm, 2 mm and 3 mm). The fatigue test data sets were obtained at R-ratios of R = 0.1, R = 0.2 and R = 0.3. Another variable introduced into experimental studies was an orientation of laser weld joint with respect to applied loading direction. After fatigue tests were completed, detailed metallurgical investigations have been carried out to understand the failure mechanism and the crack growth behavior in laser welded joints. Based on the observed experimental and numerical studies it was concluded that the strain life based fatigue analysis method which has been successfully applied to study weld toe failures for the arc weld joints is not sufficient for the evaluation of laser welded joints. This is due to the reason that laser welded joints have unique challenges due to weld root crack failures and extremely high stress concentration at the location of crack initiation in the root of laser welded joints between the plates. The fracture mechanics based method has been developed for the fatigue life assessment of laser welded joints. In order to apply this method comprehensive three-dimensional finite element studies were performed. Numerical studies show good correlation of the estimated fatigue lives obtained using proposed fracture mechanics method with the experimental data

Graaasp: a web 2.0 research platform for contextual recommendation with aggregated data

In this paper we describe Graaasp, a social software currently under development to support the creation of a real usage database of social artifacts. Our goals are twofold: First to offer a generic aggregation service and user interface to people and communities. Second, to experiment with recommendation and reputation models and algorithms in e-learning

A Social Media Platform in Higher Education

This paper reports on the successful use of Graasp, a social media platform, by university students for their collaborative work. Graasp features a number of innovations, such as administrator-free creation of collaborative spaces, context-aware recommendation and privacy management. In the context of a EU-funded project involving large test beds, we have been able to extend this platform with lightweight tools (widgets) aimed for learning and competence development and to validate its usefulness in a collaborative learning context

Classical behavior of deformed sine-Gordon models

In this work we deform the phi^4 model with distinct deformation functions, to propose a diversity of sine-Gordon-like models. We investigate the proposed models and we obtain all the topological solutions they engender. In particular, we introduce non-polynomial potentials which support some exotic two-kink solutions.Comment: 12 pages, 12 figures; version to appear in Physica

Testing timed systems modeled by stream X-machines

Stream X-machines have been used to specify real systems where complex data structures. They are a variety of extended finite state machine where a shared memory is used to represent communications between the components of systems. In this paper we introduce an extension of the Stream X-machines formalism in order to specify systems that present temporal requirements. We add time in two different ways. First, we consider that (output) actions take time to be performed. Second, our formalism allows to specify timeouts. Timeouts represent the time a system can wait for the environment to react without changing its internal state. Since timeous affect the set of available actions of the system, a relation focusing on the functional behavior of systems, that is, the actions that they can perform, must explicitly take into account the possible timeouts. In this paper we also propose a formal testing methodology allowing to systematically test a system with respect to a specification. Finally, we introduce a test derivation algorithm. Given a specification, the derived test suite is sound and complete, that is, a system under test successfully passes the test suite if and only if this system conforms to the specification

Unraveling the chemical composition, antioxidant, α-amylase and α-glucosidase inhibition of Moroccan propolis

In the present study, seven propolis samples collected from different areas of Morocco were evaluated for various potential attributes. Physicochemical parameters (moisture, pH, soluble substance, insoluble substance, ash content, conductivity, organic matter, resin, balsams, total carbohydrates, total proteins and mineral content), structural characterization by FTIR, phenolic and flavonoid composition and some biological activities (antioxidant, and -glucosidase and -amylase inhibitory activities) were determined. The analyzed physicochemical parameters showed the following values: moisture (3.35.2%), pH (4.15.5), soluble substance (66.175.4%), insoluble substance (23.833.7%), ashes (1.62.3%), conductivity (1.52.5 mS/cm), organic matter (97.7098.4%), wax (19.751.5%), resin (46.875.2%), balsam (1.53.1%), total carbohydrates (1.52.0 mg Glceq/g), and total proteins (1.76.2 g/100 g). Calcium, sodium, potassium, and magnesium were the most predominant minerals present in propolis samples. The phytochemical composition indicated the presence of phenolic acids, flavonoids and stilbens compounds described as having a high antioxidant capacity and potential -amylase (IC50 = 195.09963.79 g/mL) and -glucosidase (IC50 = 90.99876.24 g/mL) inhibitory activities. Moreover, FTIR spectra showed that the samples are structurally different between them, validating the results of the physicochemical analysis. The outcome of this study provides relevant information about Moroccan propolis composition and quality standards.This work was supported by a grant from University Sidi Mohamed Ben Abdallah for. Laboratory of Natural Substances, Pharmacology, Environment, Modeling, Health and Quality of Life (SNAMOPEQ). This research was funded by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorteoperation (NORTE-01-0145-FEDER 000004) funded by the European Regional Development Fund (FEDER) under the scope of Norte2020-Programa Operacional Regional do Norte. Zlatina Genisheva is supported by the project OH2O (POCI-01-0145- FEDER-029145) funded by FCT and FEDER under the scope of ProgramaOperacional de Competividade e Internacionalizaçao (POCI)- COMPETE 2020 and PORTUGAL 2020.info:eu-repo/semantics/publishedVersio

Topology of "white" stars in relativistic fragmentation of light nuclei

In the present paper, experimental observations of the multifragmentation processes of light relativistic nuclei carried out by means of emulsions are reviewed. Events of the type of "white" stars in which the dissociation of relativistic nuclei is not accompanied by the production of mesons and the target-nucleus fragments are considered. A distinctive feature of the charge topology in the dissociation of the Ne, Mg, Si, and S nuclei is an almost total suppression of the binary splitting of nuclei to fragments with charges higher than 2. The growth of the nuclear fragmentation degree is revealed in an increase in the multiplicity of singly and doubly charged fragments with decreasing charge of the non-excited part of the fragmenting nucleus. The processes of dissociation of stable Li, Be, B, C, N, and O isotopes to charged fragments were used to study special features of the formation of systems consisting of the lightest $\alpha$, d, and t nuclei. Clustering in form of the $^3$He nucleus can be detected in "white" stars via the dissociation of neutron-deficient Be, B, C, and N isotopes.Comment: 20 pages, 3 figures, 9 tables, conference: Conference on Physics of Fundamental Interactions, Moscow, Russia, 1-5 Mar 2004.(Author's translation

Anticancer effects of monocarbonyl analogs of curcumin: oxidative stress, nuclear translocation and modulation of AP-1 and NF-κB

Purpose: In order to elucidate anticancer effects of monocarbonyl analogs of curcumin (MACs), we have undertaken the present study to obtain information regarding drug targets by using a microarray approach, and to study the cellular localization of EF24 and the activity of two key transcription factors, AP-1 and NF-κB, involved in complex cellular responses of cell survival and death. Methods: Cytotoxic activity of various drugs was evaluated using a Neutral Red Dye assay. Cellular localization of biotinylated EF24 (active) and reduced EF24 (inactive) was determined using light and confocal microscopy. Measurement of transcription factor binding was carried out using Transfactor ELISA kits (BD Clontech, Palo Alto, CA). Gene microarray processing was performed at Expression Analysis, Inc (Durham, NC) using Affymetrix Human U133A Gene Chips.Results: In this study, we demonstrated that EF24 and UBS109 exhibit much more potent cytotoxic activity against pancreatic cancer than the current standard chemotherapeutic agent gemcitabine. EF24, rapidly localizes to the cell nucleus. The compound modulates the DNA binding activity of NF-κB and AP-1 in MDA-MB-231 human breast cancer cells and DU-145 human prostate cancer cells. Immunohistochemical studies utilizing biotinylated-EF24 and chemically-reduced EF24 show that the unsaturated compound and biotinylated EF24, but not reduced EF24, translocates to the nucleus within 30 minutes after the addition of drug. Through a gene microarray study, EF24 is shown to affect genes directly involved in cytoprotection, tumor growth, angiogenesis, metastasis and apoptosis. Conclusion: EF24 and UBS109 warrant further investigation for development of pancreatic cancer therapy. The dualistic modulations of gene expression may be a manifestation of the cell responses for survival against oxidative stress by EF24. However, the cytotoxic action of EF24 ultimately prevails to kill the cells.</p

Anticancer effects of monocarbonyl analogs of curcumin: oxidative stress, nuclear translocation and modulation of AP-1 and NF-κB

Purpose: In order to elucidate anticancer effects of monocarbonyl analogs of curcumin (MACs), we have undertaken the present study to obtain information regarding drug targets by using a microarray approach, and to study the cellular localization of EF24 and the activity of two key transcription factors, AP-1 and NF-κB, involved in complex cellular responses of cell survival and death. Methods: Cytotoxic activity of various drugs was evaluated using a Neutral Red Dye assay. Cellular localization of biotinylated EF24 (active) and reduced EF24 (inactive) was determined using light and confocal microscopy. Measurement of transcription factor binding was carried out using Transfactor ELISA kits (BD Clontech, Palo Alto, CA). Gene microarray processing was performed at Expression Analysis, Inc (Durham, NC) using Affymetrix Human U133A Gene Chips.Results: In this study, we demonstrated that EF24 and UBS109 exhibit much more potent cytotoxic activity against pancreatic cancer than the current standard chemotherapeutic agent gemcitabine. EF24, rapidly localizes to the cell nucleus. The compound modulates the DNA binding activity of NF-κB and AP-1 in MDA-MB-231 human breast cancer cells and DU-145 human prostate cancer cells. Immunohistochemical studies utilizing biotinylated-EF24 and chemically-reduced EF24 show that the unsaturated compound and biotinylated EF24, but not reduced EF24, translocates to the nucleus within 30 minutes after the addition of drug. Through a gene microarray study, EF24 is shown to affect genes directly involved in cytoprotection, tumor growth, angiogenesis, metastasis and apoptosis. Conclusion: EF24 and UBS109 warrant further investigation for development of pancreatic cancer therapy. The dualistic modulations of gene expression may be a manifestation of the cell responses for survival against oxidative stress by EF24. However, the cytotoxic action of EF24 ultimately prevails to kill the cells

Discovery of microscopic electronic inhomogeneity in the high-Tc superconductor Bi2Sr2CaCu2O8+x

The parent compounds of the copper oxide high-Tc superconductors are unusual insulators. Superconductivity arises when they are properly doped away from stoichiometry1. In Bi2Sr2CaCu2O8+x, superconductivity results from doping with excess oxygen atoms, which introduce positive charge carriers (holes) into the CuO2 planes, where superconductivity is believed to originate. The role of these oxygen dopants is not well understood, other than the fact that they provide charge carriers. However, it is not even clear how these charges distribute in the CuO2 planes. Accordingly, many models of high-Tc superconductors simply assume that the charge carriers introduced by doping distribute uniformly, leading to an electronically homogeneous system, as in ordinary metals. Here we report the observation of an electronic inhomogeneity in the high-Tc superconductor Bi2Sr2CaCu2O8+x using scanning tunnelling microscopy/spectroscopy. This inhomogeneity is manifested as spatial variations in both the local density of states spectrum and the superconducting energy gap. These variations are correlated spatially and vary on a surprisingly short length scale of ~ 14 Angs. Analysis suggests that the inhomogeneity observed is a consequence of proximity to a Mott insulator resulting in poor screening of the charge potentials associated with the oxygen ions left behind in the BiO plane after doping. Hence this experiment is a direct probe of the local nature of the superconducting state, which is not easily accessible by macroscopic measurements.Comment: 6 pages, 4 figure