100,767 research outputs found
An inverse energy approach to determine the flow stress of tubular materials for hydroforming applications
No full textInclusive memory. How to promote social inclusion, well-being and critical thinking skills within a museum context
No full textThe use of FEA packages in the simulation of a drawing operation with springback, in the presence of random uncertainty
No full textThe springback response on a stamped part, calculated by finite element analysis has been evaluated taking into account the uncertainty of some process conditions. In fact, in the simulation of sheet metal forming and springback, a traditional deterministic approach is not able to take into account the uncertain physical variations related to material characteristics, friction conditions, tools active surfaces status, etc.
During sheet metal forming operations many different sources of non-controllable process variations usually display their effect leading to a degree of uncertainty in the final parts’ quality. For this reason, statistical tools and methods are increasingly being used in combination with FE numerical simulation. Then, if one of the purposes of process design is to study and model robustness or reliability of a given process in aleatory conditions, a CAE study might become a feasible way to do it.
Today, the evaluation of the performances of a sheet metal stamping process, under uncertainty of the main variables, is possible using several commercial FEA packages. These software tools automatically allow the pre-emptive evaluation of the robustness of technological decisions and the process sensitivity to a random variation of uncontrollable parameters or conditions. For accurate calculations these innovative numerical approaches usually require a considerable amount of computational work both in terms of CPU time and in terms of number of CPUs. A specific experimental and numerical activity has been developed in order to better understand the technical capabilities in terms of process simulation in stochastic conditions
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Carbon nanotube-guided thermopower waves
No full textThermopower waves are a new concept for the direct conversion of chemical to electrical energy. A nanowire with large axial thermal diffusivity can accelerate a self-propagating reaction wave using a fuel coated along its length. The reaction wave drives electrical carriers in a thermopower wave, creating a high-power pulse of as much as 7 kW/kg in experiments using carbon nanotubes. We review nanomaterials designed to overcome limitations of thermoelectricity and explore the emerging scientific and practical outlook for devices using thermopower waves
Rotary draw bending of small diameter copper tubes: predicting the quality of the cross-section
No full textThe purpose of the present work is to study the correlation between the main geometrical tube parameters of the rotary draw bending process and the resulting quality of the cross-section of small hydraulic pipings. The method of choice, named free rotary draw bending, is a rotary draw bending process where no internal support from an internal mandrel or plug is
possible, because hydraulic tubes cannot be lubricated on their internal diameter. Furthermore, no axial boosting of the tube or of the pressure die is applied. Free bending is mainly used when
small-diameter tubes are involved, with high length and relatively thin wall.
A unique quality estimator QCS of the cross-section geometry of bent tubes has been developed, which is able to synthetically represent the main functional and aesthetical properties of tubes:
the maximum ovalization, the minimum hydraulic diameter, and so on. In the case of copper tubes for hydraulic applications a strongly deformed cross-section after bending means a poor
quality of the product, since it delivers an increase of head losses and of pressure drops. The deformation occurring in the cross-section of the tube has been studied through a set of FEM simulations, run with an explicit code with shell elements, and the model has been validated by comparing the experimental and numerical results of specific cases, in terms of geometry of
the cross-section in a 90 bend. The plan of simulations has been designed using the typical copper tube dimensions for hydro-thermo-sanitary applications and a few runs have been added with modified parameters with the aim of completing the plan for evaluating the sensitivity to a change either in geometrical variables (thickness t, outer diameter OD, mean bending radius RM) or in the tube material. An indicator (bending factor) is proposed, able to reliably estimate the difficulty of a bending process with respect to tendency to ovalization and collapse of the crosssection.
Some design guidelines of the bending tools are provided
Lifestyle Factors and MicroRNAs: A New Paradigm in Cancer Chemoprevention
No full textMicroRNAs (miRNAs) are characterized as small RNA molecules that modulate gene transcription in a posttranslational manner. Functionally, miRNAs play important roles in a diverse number of biological processes, including cell development, differentiation, proliferation, and apoptosis. Consequently, changes in the expression pattern of miRNAs have been associated with multiple human pathologies, including cancer. Based on these alterations, distinct miRNAs can be utilized as markers for cancer risk evaluation or used in tumour detection. Recent evidence has indicated that lifestyle factors, such as nutrition, physical activity, and glycemic control provide health benefits through regulation of miRNA expression. In this review, we provide a concise overview of miRNA regulation, biosynthesis, and their expression patterns in normal and malignant tissue. We then summarize the emerging knowledge of how lifestyle factors, including nutrients, exercise, and hypoglycemic agents modify miRNAs and are involved in cancer prevention. Finally, we conclude by providing recommendation for future investigations into novel agents that can modulate miRNAs and act as chemotherapeutic agents against cancer
Preparative and regiochemical aspects of the palladium-catalyzed carbonylative coupling of 2-hydroxyaryl iodides with ethynylarenes
No full textThe title reaction has been conveniently carried out in DMF at 60°C unakr 1 atm of CO pressure using
DBU as the base and Pd(OAc)z(DPPF)2 as the catalyst to t@ord generally muhtres offlavones 4 and atuones 5 in
varying yields, dependtng on the mbstituents in the both reactants. Factors controlling the regioselectivtty for 4 or 5
formation in thts and in sunilar, previotuly reported . coupling procedwes have been examined
Πρὸς τὴν ἐργασίαν τῶν καλῶν : Il testamento di un monaco italogreco del San Salvatore di Messina
No full textL'edizione diplomatica un atto privato greco di epoca normanna, con commento, analisi storica e testuale, è occasione per riflettere sulla tradizione linguistica e religiosa bizantina nell' Italia meridionale medievale.The diplomatic edition, a Greek private act of the Norman era, with commentary, historical and textual analysis, is an opportunity to reflect on the Byzantine linguistic and religious tradition in medieval southern Italy
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