There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

An introduction to heat transfer

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Numerical Heat Transfer And Fluid Flow

統計年鑑 = Statistical yearbook

Inclusions in square billets of low-sulfur steels employed in the production of steel springs were fully extracted using an improved non-aqueous solution electrolytic method and were characterized as oxides, MnS, and TiN-MnS complex inclusions. Inclusions were analyzed using SEM for their three-dimensional morphology. The formation mechanism of the complex TiN-MnS was investigated analyzing the equilibrium precipitation conditions during cooling from the liquid through solidification and in the solid state. In this analysis, three microsegregation models were employed. It was found that titanium nitride precipitates first and then manganese sulfide. Electron backscattered diffraction is employed to explore the crystal orientation relationship between TiN and MnS in the complex inclusions, which provided additional elements to fully describe the mechanism of formation of the observed TiN-MnS complex inclusions.

Extraction, Thermodynamic Analysis, and Precipitation Mechanism of MnS-TiN Complex Inclusions in Low-Sulfur Steels

A review of the current environmental challenges of the steel industry and its value chain

A mathematical model has been developed to explain the effect of the number of nozzles on recirculation flow rate in the RH process. Experimental data from water modeling were employed to validate the mathematical model. The experimental data included the velocity fields measured with a particle image velocimetry technique and mixing time. The multiphase model volume of fluid was employed to allow a more realistic representation of the free surface in the vacuum chamber while injected argon bubbles were treated as discrete phase particles and modeled using the discrete phase model. Interfacial forces between bubbles and liquid phase were considered, including the lift force. The simulations carried out with the mathematical model involved changes in the gas flow rate from 12 to 36 L/min and a number of nozzles from 4 to 8. The results indicated a logarithmic increment in the recirculation rate as the gas flow rate increased and also corresponded with an exponential decrease in mixing time. The plume area and liquid velocities resulting from individual nozzles were computed. A maximum optimum recirculation rate was defined based on a mechanism proposed to explain the effect of gas flow rate and the number of nozzles on the recirculation rate.

Investigation on the Effect of Nozzle Number on the Recirculation Rate and Mixing Time in the RH Process Using VOF + DPM Model

The effect of slag properties (thickness and viscosity), have been evaluated in terms of mixing time, exposed surface or ladle eye and energy dissipation. A nozzle configuration defined in terms of the number of nozzles, its radial position and gas flow rate has been employed to describe the influence of the top layer on mixing phenomena. It has been found a negative effect of both slag thickness and slag viscosity on mixing time, on the other hand, the same properties are useful to decrease the exposed surface or ladle eye. An empirical approach using water modeling is suggested to evaluate the average velocity of the bulk liquid. The method was used to define the fraction of stirring energy consumed by the top layer. The result is in agreement with a previous investigation.

Effect of Slag Properties on Mixing Phenomena in Gas-stirred Ladles by Physical Modeling

This research investigates mixing phenomena in bottom gas-stirred ladles using water modeling, which incorporates hexane as the top layer. The effects of slag thickness, nozzle position, number of nozzles, and gas flow rate on mixing time have been investigated. Conditions to improve mixing time have been identified. A single nozzle located at two-thirds of the ladle radius was found to produce the shortest mixing time. Under extremely low gas flow rates, an unusual behavior was observed, where the top layer promoted a decrease in mixing time.

http://www.gotrawama.eu/Siderurgia/Effects%20of%20Top%20Layer,%20Nozzle%20Arrangement,%20and%20Gas%20Flow%20Rate%20LF%20BGI.pdf

Alberto N. Conejo

Papers

Extraction, Thermodynamic Analysis, and Precipitation Mechanism of MnS-TiN Complex Inclusions in Low-Sulfur Steels

A review of the current environmental challenges of the steel industry and its value chain

Investigation on the Effect of Nozzle Number on the Recirculation Rate and Mixing Time in the RH Process Using VOF + DPM Model

Effect of Slag Properties on Mixing Phenomena in Gas-stirred Ladles by Physical Modeling

Effects of Top Layer, Nozzle Arrangement, and Gas Flow Rate on Mixing Time in Agitated Ladles by Bottom Gas Injection