Relevant factors affecting the direction of crack propagation in complete contact problems under fretting fatigue

[EN] In fatigue problems, an accurate estimation of the propagation direction is important for life prediction. We identify the most relevant factors that affect the crack orientation during the propagation stage of fretting fatigue cracks, arising from complete contacts. Contrary to what initially expected, parameters such as normal load, cyclic bulk load, etc. do not have a noticeable influence on the orientation. However the relative Young's moduli of indenter/specimen materials, the indenter width and the surface coefficient of friction are the most influencing factors. Analyses are performed through the extended finite element method (X-FEM) and an orientation criterion for non-proportional loading proposed by the authors. Experimental fretting fatigue tests confirm the predicted trends. An explanation of this behaviour is also given.The authors gratefully acknowledge the financial support given by the Spanish Ministry of Economy and Competitiveness and the FEDER program through the projects DPI2017-89197-C2-1-R and DPI2017-89197-C2-2-R. The support of the Generalitat Valenciana, Programme PROMETEO 2016/007, is also acknowledged. The authors thank the collaboration of Mr. Francisco Gelardo RodriguezMarco, M.; Infante-Garcia, D.; Diaz-Alvarez, J.; Giner Maravilla, E. (2019). Relevant factors affecting the direction of crack propagation in complete contact problems under fretting fatigue. Tribology International. 131:343-352. https://doi.org/10.1016/j.triboint.2018.10.048S34335213

Solar Panels for Scientific Missions Using CubeSat Platforms for LEO, MEO and GTO

DHV Technology is a company specialized on the designing, manufacturing and testing of solar panels for CubeSats and Small Satellites. In this presentation is discussed about solar panels of CubeSat missions developed for Scientific missions with Space Agencies involved as CNES, ESA and NASA Goddard. DHV Technology have developed the solar panels for Angels mission developed by HEMERIA and CNES based on a 12U platform, the solar panels for GTOSat mission developed by NASA Goddard based on a 3U CubeSat and the solar panels of TRISAT-R mission developed by Maribor University and funded by ESA using a 3U CubeSat. Angels mission is a LEO mission for Earth Observation with a payload developed by Syrlinksand Thales Alenia Space to analyze the state of the oceans, GTOSat mission is a GTO mission to acquire new data about high energy particles and TRISAT-R mission is a MEO mission for in-orbit demonstration. The requirements on solar panels for LEO, MEO and GTO missions will be analyzed in this presentation and other subjects as qualification process and the quality assurance will be discussed. There are some key points that are analyzed in this presentation as the features of the solar panels for high radiation environment, the resistance torque analysis and the harness design, the electrical losses analysis and the ATOX degradation analysis

Development of a pattern recognition methodology with thermography and implementation in an experimental study of a boiler for a WHRS-ORC

Waste heat dissipated in the exhaust system in a combustion engine represents a major source of energy to be recovered and converted into useful work. A waste heat recovery system (WHRS) based on an Organic Rankine Cycle (ORC) is a promising approach, and it gained interest in the last few years in an automotive industry interested in reducing fuel consumption and exhaust emissions. Understanding the thermodynamic response of the boiler employed in an ORC plays an important role in steam cycle performance prediction and control system design. The aim of this study is, therefore, to present a methodology to study these devices by means of pattern recognition with infrared thermography. In addition, the experimental test bench and its operating conditions are described. The methodology proposed identifies the wall coordinates, traces the paths, and tracks the wall temperature along them in a way that can be exported for subsequent post-processing and analysis. As for the results, through the wall temperature paths on both sides (exhaust gas and working fluid), it was possible to quantitatively estimate the temperature evolution along the boiler and, in particular, the beginning and end of evaporation

Comparative study of the discriminating capacity of dna markers and their effectiveness in establishing genetic relationships in the genus tigridia

Tigridia Jussieu is an endemic genus to Mexico and taxonomically difficult with limited information about its genetic variability. A diversity assessment conducted using different DNA markers as an inter simple sequence repeat (ISSR) and random amplified polymorphic DNA (RAPD) markers will be helpful in the establishment of a broad- based description for improved germplasm curation and the identification of germplasm for genome mapping and breeding of these species. Thus, the objective of this study was to characterize 15 wild species of Tigridia by using RAPD and ISSR molecular markers. This study was carried out in the laboratory of Plant Molecular Biology at the Faculty of Agricultural Sciences of the Universidad Autónoma del Estado de México between August and November of 2011. In this assay, 13 RAPD primers of 10, 15 and 20 b, and five ISSR primers of the anchored type (ASSR) of 17 b were used to assess the level of genetic variation among 15 wild species of Tigridia . With both markers there were 163 amplified bands of which 150 (92.02 %) were polymorphic. The RAPD primers of 10 b generated 12 specific bands with a polymorphism of 95.12 %, for 15 b primers those values were five and 82.93 %, and for 20 b primers eight and 94.59 %, respectively. The RAPD pooled primers presented a polymorphism of 90.76 %, the genetic distance (G D ) among the species ranged from 0.16 (between T. illecebrosa and T. huajuapanensis ) to 0.57 (between T. multiflora and T. augusta ). The ISSR primers showed more polymorphism(95.45 %) than RAPD primers. With ASSR primers the highest genetic association (G D = 0.89) was observed between T. mexicana ssp. mexicana and T. durangense , whereas the least related were T. vanhouttei spp. vanhouttei and T. multiflora (G D = 0.14). This study shows that 10 base random primers and 17 base anchored primers were more efficient to detect polymorphism and genetic differentiation among Tigridia species

Loop 1 modulates the fidelity of DNA polymerase λ

Differences in the substrate specificity of mammalian family X DNA polymerases are proposed to partly depend on a loop (loop 1) upstream of the polymerase active site. To examine if this is the case in DNA polymerase λ (pol λ), here we characterize a variant of the human polymerase in which nine residues of loop 1 are replaced with four residues from the equivalent position in pol β. Crystal structures of the mutant enzyme bound to gapped DNA with and without a correct dNTP reveal that the change in loop 1 does not affect the overall structure of the protein. Consistent with these structural data, the mutant enzyme has relatively normal catalytic efficiency for correct incorporation, and it efficiently participates in non-homologous end joining of double-strand DNA breaks. However, DNA junctions recovered from end-joining reactions are more diverse than normal, and the mutant enzyme is substantially less accurate than wild-type pol λ in three different biochemical assays. Comparisons of the binary and ternary complex crystal structures of mutant and wild-type pol λ suggest that loop 1 modulates pol λ’s fidelity by controlling dNTP-induced movements of the template strand and the primer-terminal 3′-OH as the enzyme transitions from an inactive to an active conformation

From Microscopic to Macroscopic Description of Composite Thin Panels: A Roadmap for their Simulation in Time Domain

In this paper, we show a simulation strategy for composite dispersive thin-panels, starting from their microscopic characteristics and ending into a time-domain macroscopic model. In a first part, we revisit different semianalytic methods that may be used to obtain the S-parameter matrices. The validity of them is assessed with numerical simulations and experimental data. We also include some formulas that may be used to tailor the shielding effectiveness of panels in a design phase. In a second part, we present an extension to dispersive media of a subgridding hybrid implicit–explicit algorithm finite difference time domain (FDTD) devised by the authors to deal with that kind of materials. The method, here presented and applied to the FDTD method, is a robustly stable alternative to classical impedance boundary condition techniques. For this, a previous analytical procedure allowing to extract an equivalent effective media from S-parameters is presented, thus making this road map able to simulate any kind of dispersive thin layer. A numerical validation of the algorithm is finally shown by comparing with experimental data

Quantitative disentanglement of nanocrystalline phases in cement pastes by synchrotron ptychographic X-ray tomography

Mortars and concretes are ubiquitous materials with very complex hierarchical microstructures. To fully understand their main properties and to decrease their CO2 footprint, a sound description of their spatially resolved mineralogy is necessary. Developing this knowledge is very challenging as about half of the volume of hydrated cement is a nanocrystalline component, calcium silicate hydrate (C-S-H) gel. Furthermore, other poorly crystalline phases (e.g. iron siliceous hydrogarnet or silica oxide) may coexist, which are even more difficult to characterize. Traditional spatially resolved techniques such as electron microscopy involve complex sample preparation steps that often lead to artefacts (e.g. dehydration and microstructural changes). Here, synchrotron ptychographic tomography has been used to obtain spatially resolved information on three unaltered representative samples: neat Portland paste, Portland–calcite and Portland–fly-ash blend pastes with a spatial resolution below 100 nm in samples with a volume of up to 5 x 104 mm3. For the neat Portland paste, the ptychotomographic study gave densities of 2.11 and 2.52 g cm -3 and a content of 41.1 and 6.4 vol% for nanocrystalline C-S-H gel and poorly crystalline iron siliceous hydrogarnet, respectively. Furthermore, the spatially resolved volumetric mass-density information has allowed characterization of inner-product and outer-product C-S-H gels. The average density of the inner-product C-S-H is smaller than that of the outer product and its variability is larger. Full characterization of the pastes, including segmentation of the different components, is reported and the contents are compared with the results obtained by thermodynamic modelling.This work has been supported by MINECO through BIA2014-57658 and BIA2017-82391-R research grants, which are cofunded by FEDER. Instrumentation development was supported by SNF (R’EQUIP, No. 145056,‘OMNY’) and the Competence Centre for Materials Science and Technology (CCMX) of the ETH-Board, Switzerland

Electrical parameters extraction of CMOS floating-gate inverters

This work provides an accurate methodology for extracting the floating-gate gain factory, of CMOS floating-gate inverters with a clock-driven switch for accessing temporarilly to the floating-gate. With the methodology proposed in this paper, the γ factor and other parasitic capacitances coupled to the floating-gate can be easily extracted in a mismatch-free approach. This parameter plays an important role in modern analog and mixed-signal CMOS circuits, since it limits the circuit performance. Theoretical and measured values using two test cells, fabricated in a standard double poly double metal CMOS AMI-ABN process with 1.2 µm design rules, were compared. The extracted parameters can be incorporated into floating-gate PS pice macromodels for obtaining accurate electrical simulation