Numerical modelling and simulation in sheet metal forming

The application of numerical modelling and simulation in manufacturing technologies is looking back over about a 20–30 years history. In recent years, the role of modelling and simulation in engineering and in manufacturing industry has been continuously increasing. It is well known that during manufacturing processes simultaneous the effect of many different parameters can be observed. This is the reason why in former years, detailed analysis of manufacturing processes could have been done only by time-consuming and expensive trial-and-error methods. Due to the recent developments in the methods of modelling and simulation, as well as in computational facilities, modelling and simulation has become an everyday tool in engineering practice. Besides the aforementioned facts, the emerging role of modelling and simulation can also be explained by the growing globalisation and competition of the world market requiring shorter lead times and more cost effective solutions. In spite the enormous development of hardware and software facilities, the exclusive use of numerical modelling still seems to be very time- and cost consuming, and there is still often a high scepticism about the results among industrialists. Therefore, the purpose of this paper is to overview the present situation of numerical modelling and simulation in sheet metal forming, mainly from the viewpoint of scientific research and industrial applications

A high frequency GaAlAs travelling wave electro-optic modulator at 0.82 micrometers

Experimental GaAlAs modulators operating at 0.82 micrometers using a Mach-Zehnder interferometer configuration were designed and fabricated. Coplanar 50 ohm travelling wave microwave electrodes were used to obtain a bandwidth length product of 11.95 GHz-cm. The design, fabrication and dc performance of the GaAlAs travelling wave modulator is presented

Post-Glitch RXTE-PCA Observations of the Vela Pulsar

We report the results of analysis of observations of the Vela Pulsar by PCA on RXTE. Our data consists of two parts. The first part contains observations at 1, 4, and 9 days after the glitch in 1996 and has 27000 sec. total exposure time. The second part of observations were performed three months after this glitch and have a total exposure time of 93000 sec. We found pulsations in both sets. The observed spectrum is a power-law with no apparent change in flux or count rate. The theoretical expectations of increase in flux due to internal heating after a glitch are smaller than the uncertainty of the observations.Comment: 6 pages, 5 figures in 9 ps/eps files. Accepted for publication in A&A Main Journa

The Timing Noise of PSR 0823+26, PSR 1706-16, PSR 1749-28, PSR 2021+51 and The Anomalous Braking Indices

We have investigated the stability of the pulse frequency second derivatives ($\ddot \nu$) of PSR 0823+26, PSR 1706-16, PSR 1749-28, PSR 2021+51 which show significant quadratic trends in their pulse frequency histories in order to determine whether the observed second derivatives are secular or they arise as part of noise processes. We have used TOA data extending to more than three decades which are the longest time spans ever taken into account in pulse timing analyses. We investigated the stability of pulse frequency second derivative in the framework of low resolution noise power spectra (Deeter 1984) estimated from the residuals of pulse frequency and TOA data. We have found that the $\ddot \nu$ terms of these sources arise from the red torque noise in the fluctuations of pulse frequency derivatives which may originate from the external torques from the magnetosphere of pulsar

Feasibility of Application of Modern Methods of Construction in Iran

Various plans and policies have been adopted by the Iranian Government to address the housing shortages in Iran. Some of these policies have been successful and some have failed dramatically deteriorating the housing conditions. Technology transfer from other countries, such as the UK, may facilitate industrialisation which has been recognised as an effective way to address housing deficiencies in Iran. The Iranian and UK construction industries, however, differ in various respects which may increase the risk of failure if transferred technologies are not adapted to Iranian needs and conditions. This paper compares the current conditions of the Iranian and UK construction industries to identify the risks and opportunities if Modern Methods of Construction (MMC) were to be transferred from the UK to Iran. Several issues such as demand and supply, regulations and standards, practicality, costs, design, sustainability, and governmental policies have been studied in detail. The results reveal that MMC could potentially improve the housing conditions in Iran by addressing major issues such as skilled labour shortages, energy and materials wastes, building quality and speed of construction. The major risks are also identified as volatile economy and housing market, transportation and industry capacity. The chance of successful adoption is considerably higher for those MMC that are suitable for small projects, do not require highly skilled labour and heavy machinery, and are compatible with prevailing methods of construction in Iran

The polymerisation of oligo(ethylene glycol methyl ether) methacrylate from a multifunctional poly(ethylene imine) derived amide: a stabiliser for the synthesis and dispersion of magnetite nanoparticles

A facile synthetic route to poly(ethylene imine)-graft-poly(oligo(ethylene glycol methyl ether)) (PEI-graft-POEGMA) functionalised superparamagnetic magnetite nanoparticles is described. The polymerisation of OEGMA from a model molecular amide demonstrated the feasibility of POEGMA synthesis under mild ATRP conditions (20 °C in ethanol) albeit with low initiator efficiencies. DFT studies suggest that the amide functionality is intrinsically of lower activity than ester functional monomers and initiators for atom transfer polymerisation (ATRP) as a consequence of higher bond dissociation energies and bond dissociation free energies (BDFE). However these studies further highlighted that use of an appropriate solvent could reduce the free energy of dissociation thereby reducing the relative difference in BDFE between the ester and amide groups. A commercial branched PEI sample was functionalised by reaction with 2-bromo-2-methylpropanoyl bromide giving an amide macroinitiator suitable for the atom transfer radical polymerisation (ATRP) of oligo(ethylene glycol methyl ether) methacrylate. The resulting PEI-graft-POEGMA copolymers were characterised by SEC, FT-IR and 1H and 13C NMR spectroscopy. PEI-graft-POEGMA coated magnetite nanoparticles were synthesised by a basic aqueous co-precipitation method and were characterised by transmission electron microscopy, thermogravimetric analysis and vibrating sample magnetometry and dynamic light scattering. These copolymer coated magnetite nanoparticles were demonstrated to be effectively stabilised in an aqueous medium. Overall the particle sizes and magnetic and physical properties of the coated samples were similar to those of uncoated samples

EFFECT OF AUTOCLAVE CURE PRESSURE ON MECHANICAL PROPERTIES AND VOID CHARACTERISTICS OF COMPOSITE LAMINATES

International audienceAutoclave curing is a commonly used fabrication process for high-performance structural composite laminates used in aerospace industry. During the manufacturing, a variety of process parameters such as the temperature and the pressure in the autoclave influence the formation of voids throughout the laminate. In particular, the magnitude of autoclave pressure determines the final fiber volume fraction, overall void content, and mechanical properties, including flexural strength and modulus. In this study, a number of composite laminates made of IM7/EX-1522, a carbon fiber reinforced epoxy prepreg, are produced by autoclave curing. The influence of different pressures on flexural properties of composite laminate is examined. In addition, void volume fraction as well as shape and size distributions of voids are presented. The experimental results have shown that increasing consolidation pressure during cure alone may not increase all the mechanical properties. Flexural modulus is found to be higher at higher consolidation pressure which is attributed to the higher fiber volume fraction. Unlike the flexural modulus, the flexural strength is significantly affected by the location, size, and shape of the voids. If the magnitude of cure pressure is not chosen properly, elongated voids may form at the fiber-matrix and could lead to considerable reduction of interfacial strength of the composites

Investigation of the effect of school administrators' thoughts for change on 21st century skills

The aim of this study is to examine the effect of school administrators' tendencies towards change, working in primary schools, on 21st century skills. The research is an example of the relational screening model. In this context, the sample of the research consists of 148 school administrators working in primary schools in 5 districts of the TRNC, namely Nicosia, Girne, Famagusta, Güzelyurt and Lefke. The research was evaluated with 107 people from 148 managers, with 95% confidence level and 5% sampling error. In this study, the "Multidimensional 21st Century Skills Scale" was used with the permission of the authors to measure the 21st century skills of school administrators and their tendencies towards change. In addition, the scale named “Adaptation of the change tendencies scale for teachers” was used. As a result of the research, it was revealed that there were significant correlations between the scores obtained from the sub-dimension of resistance to change in the Managers' Tendency to Change Scale and the scores acquired from the Multidimensional 21st Century Skills Scale and the Information and Technology Literacy Skills sub-dimension in the scale. These correlations are positive, and as the scores obtained from the sub-dimension of resistance to change in the Managers' Tendency to Change Scale increase, the scores obtained from the Multidimensional 21st Century Skills Scale and from the Information and Technology Literacy Skills sub-dimension in the scale also increase

Quantitative Immunology for Physicists

The adaptive immune system is a dynamical, self-organized multiscale system that protects vertebrates from both pathogens and internal irregularities, such as tumours. For these reason it fascinates physicists, yet the multitude of different cells, molecules and sub-systems is often also petrifying. Despite this complexity, as experiments on different scales of the adaptive immune system become more quantitative, many physicists have made both theoretical and experimental contributions that help predict the behaviour of ensembles of cells and molecules that participate in an immune response. Here we review some recent contributions with an emphasis on quantitative questions and methodologies. We also provide a more general methods section that presents some of the wide array of theoretical tools used in the field.Comment: 78 page revie