62,112 research outputs found

    Chrysler improved numerical differencing analyzer for third generation computers CINDA-3G

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    New and versatile method has been developed to supplement or replace use of original CINDA thermal analyzer program in order to take advantage of improved systems software and machine speeds of third generation computers. CINDA-3G program options offer variety of methods for solution of thermal analog models presented in network format

    Using statutory guidance and codes of practice to build on whistleblowing legislation: the Irish experience

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    In our opinion, the use of Guidance regarding whistleblower protection represents best international practice with regard to protected disclosures. It is devised on the premise that a one-size-fits-all approach is not appropriate given the different nature and scope of public sector bodies. In the authors’ opinion, the Irish experience demonstrates how statutory guidance and Codes of Practice can be valuable methods of explaining how the law is intended to operate as well as encouraging best practice which goes beyond the minimum statutory floor of rights

    Man-machine interface and control of the shuttle digital flight system

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    The space shuttle main engine (SSME) presented new requirements in the design of controls for large pump fed liquid rocket engine systems. These requirements were the need for built in full mission support capability, and complexity and flexibility of function not previously needed in this type of application. An engine mounted programmable digital control system was developed to meet these requirements. The engine system and controller and their function are described. Design challenges encountered during the course of development included accommodation for a very severe engine environment, the implementation of redundancy and redundancy management to provide fail operational/fail safe capability, removal of heat from the package, and significant constraints on computer memory size and processing time. The flexibility offered by programmable control reshaped the approach to engine design and development and set the pattern for future controls development in these types of applications

    Ion-ion dynamic structure factor, acoustic modes and equation of state of two-temperature warm dense aluminum

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    The ion-ion dynamical structure factor and the equation of state of warm dense aluminum in a two-temperature quasi-equilibrium state, with the electron temperature higher than the ion temperature, are investigated using molecular-dynamics simulations based on ion-ion pair potentials constructed from a neutral pseudoatom model. Such pair potentials based on density functional theory are parameter-free and depend directly on the electron temperature and indirectly on the ion temperature, enabling efficient computation of two-temperature properties. Comparison with ab initio simulations and with other average-atom calculations for equilibrium aluminum shows good agreement, justifying a study of quasi-equilibrium situations. Analyzing the van Hove function, we find that ion-ion correlations vanish in a time significantly smaller than the electron-ion relaxation time so that dynamical properties have a physical meaning for the quasi-equilibrium state. A significant increase in the speed of sound is predicted from the modification of the dispersion relation of the ion acoustic mode as the electron temperature is increased. The two-temperature equation of state including the free energy, internal energy and pressure is also presented

    Isochoric, isobaric and ultrafast conductivities of aluminum, lithium and carbon in the warm dense matter (WDM) regime

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    We study the conductivities σ\sigma of (i) the equilibrium isochoric state (σis\sigma_{\rm is}), (ii) the equilibrium isobaric state (σib\sigma_{\rm ib}), and also the (iii) non-equilibrium ultrafast matter (UFM) state (σuf\sigma_{\rm uf}) with the ion temperature TiT_i less than the the electron temperature TeT_e. Aluminum, lithium and carbon are considered, being increasingly complex warm dense matter (WDM) systems, with carbon having transient covalent bonds. First-principles calculations, i.e., neutral-pseudoatom (NPA) calculations and density-functional theory (DFT) with molecular-dynamics (MD) simulations, are compared where possible with experimental data to characterize σic,σib\sigma_{\rm ic}, \sigma_{\rm ib} and σuf\sigma_{\rm uf}. The NPA σib\sigma_{\rm ib} are closest to the available experimental data when compared to results from DFT+MD, where simulations of about 64-125 atoms are typically used. The published conductivities for Li are reviewed and the value at a temperature of 4.5 eV is examined using supporting X-ray Thomson scattering calculations. A physical picture of the variations of σ\sigma with temperature and density applicable to these materials is given. The insensitivity of σ\sigma to TeT_e below 10 eV for carbon, compared to Al and Li, is clarified.Comment: 10 figure
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