2,004 research outputs found

    Influence of Different Material Models on the Result of Numerical High Speed Cutting Simulations

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    Extreme conditions for the workpiece and the tool can occur in high speed cutting processes. Temperatures above 1000 °C at very high strains over 3 and strain rates near 105 1/s are not unusual. In the first part of this paper an overview about the well known and new developed testing methods for these extreme conditions is given. For numerical simulations it is necessary to formulate closed material models which include strain, strain rate, and the temperature. In the second part some well known material models are presented and compared. Furthermore, advantages and disadvantages are named. The flow stress behaviour of two types of steel (1.1191, 1.2311) as a function of strain rate and temperature is presented. A Johnson-Cook and a Zerilli-Armstrong model is used for the comparative numerical simulations of an orthogonal cutting process. To indicate the process of chip segmentation, a damage model is often used. The influence of various damage models with different damage parameters and failure modes is shown. The calculated cutting forces and the shape of the chips are compared with results determined at a quickstop cutting device with integrated force measurement. Additionally, the calculated chip formation is compared with the measured shape by means of highspeed photography. The temperatures, forces, and chip shape for both used models are presented and the influence of different material models are evaluated and named

    Reaction of Cr+, Mn+, Fe+, Co+, and Ni+ with O2 and N2O. Examination of the translational energy dependence of the cross sections of endothermic reactions

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    Journal ArticleReactions of Cr+, Mn+, Fe+, Co+, and Ni+ with 02 and N20 to yield metal oxide ions are examined using an ion beam apparatus. Reaction cross sections a as a function of ion translational energy E are reported. With one exception, Fe+ + N20, the cross sections exhibit an energy threshold E0

    Reaction of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O. Examination of the translational energy dependence of the cross sections of endothermic reactions

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    Reactions of Cr + , Mn + , Fe + , Co + , and Ni + with O2 and N2O to yield metal oxide ions are examined using an ion beam apparatus. Reaction cross sections sigma as a function of ion translational energy E are reported. With one exception, Fe + +N2O, the cross sections exhibit an energy threshold Eo. Several models are used to interpret the excitation functions for the O2 reactions and it is concluded that the classical line-of-centers form sigma alpha (1–Eo/E) is most useful. Bond energies derived in this manner are D°(CrO + ) = 3.45±0.1 eV, D°(MnO + ) = 2.48±0.1 eV, D°(FeO + ) = 3.01±0.1 eV, D°(CoO + ) = 2.76±0.1 eV, and D°(NiO + ) = 1.95±0.1 eV. Since these bond energies are all greater than D°(N2–O) = 1.7 eV, the observation of energy thresholds for the reactions with N2O are surprising. These results are explained in terms of a qualitative view of the electronic potential energy surfaces involved

    Quality Improvement of a Post-Concussion Recovery Protocol

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    OBJECTIVE To determine the effectiveness of a post-concussion recovery protocol in an adolescent athletic population

    An AI-Assisted Design Method for Topology Optimization Without Pre-Optimized Training Data

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    Topology optimization is widely used by engineers during the initial product development process to get a first possible geometry design. The state-of-the-art is the iterative calculation, which requires both time and computational power. Some newly developed methods use artificial intelligence to accelerate the topology optimization. These require conventionally pre-optimized data and therefore are dependent on the quality and number of available data. This paper proposes an AI-assisted design method for topology optimization, which does not require pre-optimized data. The designs are provided by an artificial neural network, the predictor, on the basis of boundary conditions and degree of filling (the volume percentage filled by material) as input data. In the training phase, geometries generated on the basis of random input data are evaluated with respect to given criteria. The results of those evaluations flow into an objective function which is minimized by adapting the predictor's parameters. After the training is completed, the presented AI-assisted design procedure supplies geometries which are similar to the ones generated by conventional topology optimizers, but requires a small fraction of the computational effort required by those algorithms. We anticipate our paper to be a starting point for AI-based methods that requires data, that is hard to compute or not available

    Baby\u27s Prayer

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    https://digitalcommons.library.umaine.edu/mmb-vp/4438/thumbnail.jp

    10/10/1947 Letter from Auburn Mayor Rosaire Halle

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    Letter from Rosaire L. Halle, Mayor of Auburn, Maine, to Louis-Philippe Gagné.https://digitalcommons.usm.maine.edu/fac-lpg-1947-10-12/1007/thumbnail.jp

    Linguistics

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    Contains research objectives and summary of research on one research project.National Institute of Mental Health (Grant 3 P01 MH13390-08S1)National Institutes of Health (Grant 5 TOl HD00111-10)National Institute of Mental Health (Grant HD 05168-01, 02, 03)M.I.T. Sloan Fund for Basic ResearchGrant Foundatio

    Community Livelihood and Agricultural Techniques in Peri-Urban Farming in Cameroon

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    Agriculture is the bedrock of Cameroon’s economy as it contributes significantly to food, income and employment. However, the country’s agriculture is confronted by a myriad of challenges which include inter-alia issues of land tenure, inadequate finance, weak market information system and use of simple technology. The unprecedented growth in Cameroon’s urban population has given rise to peri-urban agriculture. Using survey data of 150 randomly sampled farmers, we assess the socio-economic contributions of peri-urban farming to livelihoods and the constraints faced by farmers in study area, at the periphery of Buea in the South West Region of Cameroon. The study identified some of the agricultural techniques being practiced to include slash and burn, shifting cultivation, crop rotation, farming without ridges, monoculture, and livestock farming. The commonest crops and livestock are tubers, grains, horticultural products, oil palm, poultry, goats and pigs. We found that peri-urban agriculture contributes significantly to household food security and nutrition, income, and employment of farmers. These findings have important policy implications for urban food security and nutrition, and sustainable development. Keywords: Cameroon, Peri-urban farming, Agricultural techniques, Community livelihood

    Board 270: Engineering Faculty Members’ Experience of Professional Shame: Summary of Insights from Year Two

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    In this paper, we present an overview of an NSF CAREER project, in which we seek to advance academic well-being by understanding how engineering faculty experience and reproduce experiences of professional shame. We present an overview of our data collection of non-standardized interviews with engineering faculty (n = 21) and how we are using interpretative phenomenological analysis to examine select individual cases (n = 12). We report our preliminary insights that 1) participants experienced complex and manifold socially constructed expectations that form the basis of their professional shame experiences and 2) participants’ experiences of professional shame varied according to how central their roles as faculty were to their identities. We describe our immediate next steps to integrate the processes of two qualitative studies so that we can generate insight into how engineering faculty link their experiences to their departmental cultures and ultimately train departments to build cultures where faculty and students are able to live well with the experience of professional shame
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