On a possible model of crack propagation in a solid subjected to a cyclic loading

By the use of the Griffith model, the propagation of a crack in a solid subjected to a cyclic loading is studied. It is assumed that all the energy lost per cycle in the Bauschinger process is transferred to the crack to increase its size.The paper is divided in two parts, the first dealing with materials which do not undergo work-hardening and the second with materials subjected to said phenomenon during cyclic loading. Notwithstanding the crude approximation of this model, it is shown that the main features of fatigue phenomena are accounted for.

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Zusammenfassung DurchGebrauch des Griffithschen Models, wind die Fortpflanzung eines Risses in einem zyklischbeladenenfesten Körper studiert. Es wird angenommen, dass alle in einem Zyklus verlorene Energie während des Bauschingerverfahrens zum Riss übergehen wird, um dessen Grösse zu erweiters.Das Werk umfasst zwei Teile. Der erste Teil behandelt Stoffe, die der Bearbeitungsverhärtung nichtausgesetzt siud; and der zweite Tell Stoffe, die dem Verfahren während zyklischer Belastung uaterworfen werden. Trotz dergrossen Annäherung dieses Models, wird gezeigt, dass die Hauptzüge der Zermürphassomeneerklärt werden.

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Résumé L'étude de la propagation d' une fissure dans un solide soumis à des charges cycliques a été entreprise en partant du modèle de Griffith, et d' une hypothèse selon laquelle 1' énergie dissipée au cours de chaque cycle d'hystéresis sert intégralement à accroitre la dimension de la fissure.On considère séparément le cas des materiaux qui ne subissent pas un durcissement en cours de sollicitation cyclique, et le cas des materiaux qui sont sujets à un tel durcissement.Malgré la faiblesse des hypotheses de base, due à lent caractère de grossière approximation, les résultats de l'analyse concordent qualitativement avec les caractéristiques principales du phénomène de fatigue.

     

Cable-Direct-Driven Robot (CDDR) with Passive SCARA Support: Theory and Simulation

This article presents a new planar translational cable-direct-driven robot (CDDR) with actuation redundancy and supported against loading normal to the motion plane with a passive planar two-degree-of-freedom SCARA-type (Selective Compliance Assembly Robot Arm) serial manipulator. This allows the robot to resist cable sag without being supported on the motion plane. The proposed robot architecture may assure high payload-to-weight ratio, resistance to forces normal to the plane of motion, and a potentially large workspace. Another benefit is that the passive SCARA has structure to provide end-effector moment resistance, which is not possible with many proposed translational CDDRs. Moreover, the passive robot can also serve as an independent Cartesian metrology system. This article derives the kinematics and dynamics models for the proposed hybrid serial/parallel architecture. Additionally it proposes a dynamic Cartesian controller always ensuring positive cable tensions while minimizing the sum of all the torques exerted by the actuators. Simulation examples are also presented to demonstrate the novel CDDR concept, dynamics, and controller.Category (7) – System Modelling/Simulation/Control/Computer–Aided Design/Robot Control/Teleoperation/Moving Robots     

Retrospective evaluation of lead contamination in honey from 2005 to present in northeastern Italy and future perspectives in the light of updated legislation

Lead is a naturally occurring element but largely originating from human activities. Food is the major source of exposure to lead for humans and the publication of a scientific opinion from the European Food Safety Authority on the risks to human health related to the presence of lead in foodstuffs, led European Union to establish more restrictive limits for this contaminant in food from 1 January 2016. In particular, a maximum level of 0.10 mg kg^?1 was established for honey. The retrospective evaluation of 995 honey samples analysed since 2005, revealed a progressive reduction in the concentration of lead, with a mean value of 0.045 mg kg^?1 in 2015. Total 1.5% of honeys analysed in 2015 exceeded the maximum lead level and therefore will no longer be marketable. Interested beekeepers should clarify the causes of honey contamination and adopt corrective actions to keep their honey production within the legal levels of lead.     

Classification of Pecorino cheeses using electronic nose combined with artificial neural network and comparison with GC–MS analysis of volatile compounds

An electronic nose based on an array of 6 metal oxide semiconductor sensors was used, jointly with artificial neural network (ANN) method, to classify Pecorino cheeses according to their ripening time and manufacturing techniques. For this purpose different pre-treatments of electronic nose signals have been tested. In particular, four different features extraction algorithms were compared with a principal component analysis (PCA) using to reduce the dimensionality of data set (data consisted of 900 data points per sensor). All the ANN models (with different pre-treatment data) have different capability to predict the Pecorino cheeses categories. In particular, PCA show better results (classification performance: 100%; RMSE: 0.024) in comparison with other pre-treatment systems.     

Factors Ruling the Uptake of Silica Nanoparticles by Mesenchymal Stem Cells: Agglomeration Versus Dispersions,Absence Versus Presence of Serum Proteins

The results of a systematic investigation of the role of serum proteins on the interaction of silica nanoparticles (NP) doped in their bulk with fluorescent molecules (IRIS Dots, 50 nm in size), with human mesenchymal stem cells (hMSCs) are reported. The suspension of IRIS Dots in bare Dulbecco‐modified Eagle's medium results in the formation of large agglomerates (≈1.5 μm, by dynamic light scattering), which become progressively smaller, down to ≈300 nm in size, by progressively increasing the fetal bovine serum (FBS) content of the solutions along the series 1.0%, 2.5%, 6.0%, and 10.0% v/v. Such difference in NP dispersion is maintained in the external cellular microenvironment, as observed by confocal microscopy and transmission electron microscopy. As a consequence of the limited diffusion of proteins in the inter‐NP spaces, the surface of NP agglomerates is coated by a protein corona independently of the agglomerate size/FBS concentration conditions (ζ‐potential and UV circular dichroism measurements). The protein corona appears not to be particularly relevant for the uptake of IRIS Dots by hMSCs, whereas the main role in determining the internalization rate is played by the absence/presence of serum proteins in the extracellular media.     

Database development and 3D modeling of textural variations in heterogeneous,unconsolidated aquifer media: Application to the Milan plain

The textural and hydrogeologic properties of loose deposits are closely connected to the sedimentary processes occurring in fluvial and glacio-fluvial systems. The proposed procedure combines geologic knowledge, coded well data logs stored in a hydrogeologic georeferenced database, geographic information system (GIS) and 3D calculation software to reconstruct the detailed distribution of the subsoil's hydrogeologic parameters. The calculations may apply to any subsoil part, bounded by one or more surfaces. This methodological approach may be applied to diverse investigation depths, vertical intervals detailed to varying extents, on a local or regional scale. Employing great quantities of well data logs, recorded in different ways and distributed across large areas, has enabled significant spatial sedimentologic reconstruction. Two groups of parameters were considered: textural (percentages of gravel, sand and clay) and hydrogeologic (hydraulic conductivity and porosity). In terms of sedimentology, the method reconstructs spatial heterogeneity both along cross-sections and for an entire user-defined volume to analyze the sediments’ energy functions and their distribution; deposition rates are proportional to process intensity and distribution with time. In terms of hydrogeology, detailed 3D hydrogeologic structural data provide detailed input for hydrogeologic models in groundwater resource management and planning, such as for transport models.     

ABS"Luna"ECR(R)设备:运行三年后的最新进展和使用效果

达涅利ECR(R)无头连铸连轧工艺是小型钢厂生产特殊钢和普通钢种长材产品的一项创新技术.它能够实现从钢水到完整的最终产品的不间断生产,包括在线热处理和质量检查,可显著降低现金成本.特殊钢吨钢成本可平均降低40美元(普通钢种平均降低20美元).ECR(R),实现高速铸机与轧机设备直接热连接的基础上,使其能够对来自铸机的大方坯进行不间断直接轧制,从而实现整个过程的不间断生产.     

Tissue expansion improvement: the role of epidermal growth factor

In order to achieve the most satisfactory results in tissue expansion, a cream containing human recombinant epidermal growth factor (EGF) was applied daily to the expanding skin. The capacity of EGF to stimulate tissue repair has been evaluated on expanded skin flaps, comparing surgical procedures carried out with and without EGF. The present clinical, morphological, immunohistochemical and morphometric results demonstrate that EGF used together with the tissue expander may improve skin repair after mechanical stretching. In EGF-expanded skin flaps, clinical results show a reduction in teleangectasiae and histological evidence of a more regular texture in the dermal tissue, together with a significant thickening of the epidermal malpighian layer. Without EGF some signs of immaturity, such as abundance of fibronectin, persist for longer. EGF seems to be a helpful support to improve the tissue expansion process.