Application of spherical nanoindentation to determine the pressure of cavitation impacts from pitting tests

This article focuses on the use of spherical nanoindentation measurements to estimate the pressure of cavitation impacts and its statistical distribution. Indeed, nanoindentation techniques are supposed to represent an effective tool in this field due to the similarities between substrate deformation under liquid impact and indentation testing. First, nanoindentation experiments were used to extract the mechanical parameters of a Nickel-Aluminum-Bronze alloy; second, pitting tests were performed at different operating pressures, and the geometrical characteristics of the pits were measured; and finally, the spectra of impact pressure and loads responsible for material erosion were obtained by coupling the findings of indentation tests with the analysis of pitting tests. Results assessed the capability of the proposed methodology to quantify the hydrodynamic aggressiveness of the cavitating flow. This procedure, which assumes the material itself as a sensor that is able to detect the impact loads, could represent an alternative solution to pressure transducers in estimating the cavitation intensit

A novel synthetic strategy for bioinspired functionally graded nanocomposites employing magnetic field gradients

In order to mimic the complex architecture of many bio-materials and synthesize composites characterized by continuously graded composition and mechanical properties, an innovative synthetic strategy making use of magnetic field gradients and based on the motion of superparamagnetic Fe3O4@SiO2 core-shell nanoparticles is adopted. It is demonstrated that by lowering the viscosity of the system through particle functionalization, and increasing the magnetic force acting on the nanoparticles upon optimization of a simple set-up composed of two permanent magnets in repulsion configuration, the magnephoretic process can be considerably accelerated. Thus, owing to the magnetic responsiveness of the Fe3O4 core and the remarkable mechanical properties of the SiO2 shell, approximately 150 mm thick polymeric films with continuous gradients in composition and characterized by considerable increments in elastic modulus (up to approximate to 70%) and hardness (up to approximate to 150%) when going from particle-depleted to particleenriched regions can be synthesized, even in times as short as 1 hour. The present methods are highly promising for a more efficient magnetic force-based synthesis of inhomogeneous soft materials whose composition is required to be locally tuned to meet the specific mechanical demands arising from non-uniform external loads

Nanoindentation of Functionally Graded Polymer Nanocomposites: Assessment of the Strengthening Parameters through Experiments and Modeling

Nanoindentation tests were carried out on the surface of polymer nanocomposites exhibiting either graded or homogeneous distributions of Fe3O4@silica core-shell nanoparticles in a photocurable polymeric matrix. The results reveal a complex interplay between graded morphology, indentation depth, and calculated modulus and hardness values, which was elucidated through numerical simulations. First, it was experimentally shown how for small (1 μm) indentations, large increases in modulus (up to +40%) and hardness (up to +93%) were obtained for graded composites with respect to their homogeneous counterparts, whereas at a larger indentation depth (20 μm), the modulus and hardness of the graded and homogeneous composites did not substantially differ from each other and from those of the pure polymer. Then, through a material point method approach, experimental nanoindentation tests were successfully simulated, confirming the importance of the indentation depth and of the associated plastic zone as key factors for a more accurate design of graded polymer nanocomposites whose mechanical properties are able to fulfill the requirements encountered during operational life

Cleavage Fracture of Brittle Semiconductors from the Nanometer to the Centimeter Scale

The objective of this paper is to present the fundamental phenomena occurring during the scribing and subsequent fracturing process usually performed when preparing surfaces of brittle semiconductors. In the first part, an overview of nano-scratching experiments of different semiconductor surfaces (InP, Si and GaAs) is given. It is shown how phase transformation can occur in Si under a diamond tip, how single dislocations can be induced in InP wafers and how higher scratching load of GaAs wafer leads to the apparition of a crack network below the surface. A nano-scratching device, inside a scanning electron microscope (SEM), has been used to observe how spalling (crack and detachment of chips) and/or ductile formation of chips may happen at the semiconductor surface. In the second part cleavage experiments are described. The breaking load of thin GaAs (100) wafers is directly related to the presence of initial sharp cracks induced by scratching. By performing finite element modelling (FEM) of samples under specific loading conditions, it is found that the depth of the median crack below the scratch determines quantitatively the onset of crack propagation. By carefully controlling the position and measuring the force during the cleavage, it is demonstrated that crack propagation through a wafer can be controlled. Besides, the influence of the loading configuration on crack propagation and on the cleaved surface quality is explained. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Global, regional, and national cancer incidence, mortality, years of life lost, years lived with disability, and disability-Adjusted life-years for 29 cancer groups, 1990 to 2017 : A systematic analysis for the global burden of disease study

Importance: Cancer and other noncommunicable diseases (NCDs) are now widely recognized as a threat to global development. The latest United Nations high-level meeting on NCDs reaffirmed this observation and also highlighted the slow progress in meeting the 2011 Political Declaration on the Prevention and Control of Noncommunicable Diseases and the third Sustainable Development Goal. Lack of situational analyses, priority setting, and budgeting have been identified as major obstacles in achieving these goals. All of these have in common that they require information on the local cancer epidemiology. The Global Burden of Disease (GBD) study is uniquely poised to provide these crucial data. Objective: To describe cancer burden for 29 cancer groups in 195 countries from 1990 through 2017 to provide data needed for cancer control planning. Evidence Review: We used the GBD study estimation methods to describe cancer incidence, mortality, years lived with disability, years of life lost, and disability-Adjusted life-years (DALYs). Results are presented at the national level as well as by Socio-demographic Index (SDI), a composite indicator of income, educational attainment, and total fertility rate. We also analyzed the influence of the epidemiological vs the demographic transition on cancer incidence. Findings: In 2017, there were 24.5 million incident cancer cases worldwide (16.8 million without nonmelanoma skin cancer [NMSC]) and 9.6 million cancer deaths. The majority of cancer DALYs came from years of life lost (97%), and only 3% came from years lived with disability. The odds of developing cancer were the lowest in the low SDI quintile (1 in 7) and the highest in the high SDI quintile (1 in 2) for both sexes. In 2017, the most common incident cancers in men were NMSC (4.3 million incident cases); tracheal, bronchus, and lung (TBL) cancer (1.5 million incident cases); and prostate cancer (1.3 million incident cases). The most common causes of cancer deaths and DALYs for men were TBL cancer (1.3 million deaths and 28.4 million DALYs), liver cancer (572000 deaths and 15.2 million DALYs), and stomach cancer (542000 deaths and 12.2 million DALYs). For women in 2017, the most common incident cancers were NMSC (3.3 million incident cases), breast cancer (1.9 million incident cases), and colorectal cancer (819000 incident cases). The leading causes of cancer deaths and DALYs for women were breast cancer (601000 deaths and 17.4 million DALYs), TBL cancer (596000 deaths and 12.6 million DALYs), and colorectal cancer (414000 deaths and 8.3 million DALYs). Conclusions and Relevance: The national epidemiological profiles of cancer burden in the GBD study show large heterogeneities, which are a reflection of different exposures to risk factors, economic settings, lifestyles, and access to care and screening. The GBD study can be used by policy makers and other stakeholders to develop and improve national and local cancer control in order to achieve the global targets and improve equity in cancer care. © 2019 American Medical Association. All rights reserved.Peer reviewe

Pitting tests and impact load measurements in an erosive cavitating flow

International audienc

Application of spherical nanoindentation to determine the pressure of cavitation impacts from pitting tests

International audienceThis article focuses on the use of spherical nanoindentation measurements to estimate the pressure of cavitation impacts and its statistical distribution. Indeed, nanoindentation techniques are supposed to represent an effective tool in this field due to the similarities between substrate deformation under liquid impact and indentation testing. First, nanoindentation experiments were used to extract the mechanical parameters of a Nickel-Aluminum-Bronze alloy; second, pitting tests were performed at different operating pressures, and the geometrical characteristics of the pits were measured; and finally, the spectra of impact pressure and loads responsible for material erosion were obtained by coupling the findings of indentation tests with the analysis of pitting tests. Results assessed the capability of the proposed methodology to quantify the hydrodynamic aggressiveness of the cavitating flow. This procedure, which assumes the material itself as a sensor that is able to detect the impact loads, could represent an alternative solution to pressure transducers in estimating the cavitation intensity

Evaluation of the hydrodynamic pressure of cavitation impacts from stress-strain analysis and geometry of individual pits

International audienceThe present paper focuses on the development of an inverse procedure able to infer the hydrodynamic pressure distribution acting on the material surface and responsible for the creation of the cavitation pit based on the stress in a cavitation pit and its geometrical features. To achieve this goal, experimental pitting and nanoindentation measurement techniques were used together with a model of pit formation based on a Gaussian distribution of the hydrodynamic impact pressure pulse. The pitting tests were performed at four different operating pressures on aluminum alloy samples and the geometrical characteristics of the pits were measured. Then the strain, stress, and load in a cavitation pit were quantified by coupling the pitting test analysis with the material information obtained via the indentation tests. Finally, a Gaussian distribution of the hydrodynamic impact pressure on the material surface has been hypothesized and the peak of this distribution as well as its width have been inferred. This procedure, allowing the evaluation of the hydrodynamic impact pressure and load responsible for the material erosion and the deduction of insightful information on the flow aggressiveness at different operating conditions, could certainly represent a significant step in developing a technique able to evaluate the cavitation intensity from pitting tests

An analytical method for the prediction of cavitation erosion

International audienc

The Mediating role of Organizational Justice in the Relationship between Transformational Leadership and Succession Planning in Higher Education (Case study: Kharazmi University)

AbstractThe aim of the present study was to investigate the mediating role of organizational justice in the relationship between transformational leadership and succession planning in higher education. The research method was descriptive correlational. The statistical population of this study included all administrators (200 people) of Kharazmi University were selected by convenience sampling method. For data collection were used the three Questionnaire of succession planning (Kim, 2006), Bass & Avolio (2004) transformational leadership, and organizational justice (Niehoff, and Moorman1993). Data analysis was done by using structural equation modeling in AMOS And Spss-22 software. The results of structural equation modeling showed that the conceptual model of research with experimental data fits very well and organizational justice plays the role of a complete mediator in the relationship between transformational leadership and succession planning. Accordingly, the variable relationship between transformational leadership and succession planning through organizational justice was confirmed in the form of path analysis. Thus, the variable of organizational justice showed a facilitating role in the relationship between leadership and transformational leadership and succession planning. Also, the leading variable of transformational leadership had a direct and positive effect on the succession planning of administrators. It can be concluded from the results of the study that organizational justice in the university has a facilitating role in the development of succession planning programs. Thus, by adopting a transformational leadership approach at the university, organizational justice will be established at the university, and eventually the process of succession planning will be upgraded and developed