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

Atomic Spectra Database

The formation of cone-jets in charged liquids with electrical conductivities larger than 10−4 S/m is reviewed for steady supported menisci and transient Coulomb fissions in charged drops. Taylor's hydrostatic model does not apply strictly, but it forms the basis for subsequent developments. The jet structure is critically dependent on the model used for charge transport, which has been based mostly on a constant conductivity assumption. Saville's (1997) more general model predicts the formation of rarefaction fronts with wide space charge–dominated regions near the liquid surface, which apparently do arise in polar liquids near the minimum flow rate. Known approximate scaling laws for the jet break down at electrical conductivities of about 1 S/m due to ion evaporation from the meniscus. In molten salts and liquid metals a regime of purely ionic emissions exists without drop or jet formation.

The Fluid Dynamics of Taylor Cones

Cubesats: Cost-effective science and technology platforms for emerging and developing nations

Patterning of controllable surface wettability has attracted wide scientific attention due to its importance in both fundamental research and practical applications. In particular, it is crucial to form clear image areas and non-image areas in printing techniques based on wetting and dewetting. This review summarizes the recent research on and applications of patterning of controllable surface wettability for printing techniques, with a focus on the design and fabrication of the precise surface wettability patterning by enhancing the contrast of hydrophilicity and hydrophobicity, such as superhydrophilicity and superhydrophobicity. The selected topics mainly include patterned surface wettability for lithographic printing with different plate-making techniques, patterned surface wettability for microcontact printing with a patterned wetting stamp and special wettability mediated patterning microtransfer printing, patterned surface wettability for inkjet printing with controllable surface wettability of the substrate and printing head to ink, and patterned surface wettability by a combination of different printing techniques. A personal perspective on the future development and remaining challenges of this research is also briefly discussed.

Patterning of controllable surface wettability for printing techniques

Ionic liquid ion sources: characterization of externally wetted emitters.

Ionic liquid ion sources: suppression of electrochemical reactions using voltage alternation

The identity and the energy distributions of positive and negative ions electrostatically extracted from the liquid phase in an ionic liquid ion source (ILIS) are analysed with a time-of-flight mass spectrometer and a multi-grid retarding potential analyzer. Accurate energy measurements using ionic liquids in an externally wetted configuration are reported for the first time. Droplet-free beams are produced using the ionic liquid 1-ethyl-3-methylimidazolium bis(triflouromethylsulfonyl)amide (EMI-Im) in which the solvated ions (EMI-Im)nEMI+ and (EMI-Im)nIm− with n = 0,1,2 are observed. The small ion source size and the energy distribution widths and deficits of a few electronvolts are quite similar to those of liquid metal ion sources, confirming that ILIS can be used in applications requiring highly focusable beams, e.g. sub-micron ion lithography. Measurements also suggest that solvated ions with n ≥ 1 exhibit post-extraction fragmentation into lighter species at a rate increasing with their original degree of solvation. About 10% of the total beam current is carried away by metastable species that break up almost immediately after extraction while inside the emitter accelerating region.

https://iopscience.iop.org/article/10.1088/0022-3727/39/1/020/pdf

Energy properties of an EMI-Im ionic liquid ion source

indicating that the thrust density can be increased with emitter miniaturization and clustering. A two-dimensional emitter array is constructed from three linear arrays and experiments show that the device produces an average current of around 1 �A per emitter at the highest voltages. Direct thrust measurements using a torsional balance show that the test fixture produces between 0.05 to 0:1 � N of thrust per emitter, as anticipated by theoretical estimates.

Electrospray Propulsion Based on Emitters Microfabricated in Porous Metals

The characterization of a miniaturized ionic liquid electrospray thruster for nanosatellite applications is presented. The thruster investigated features an emitter array of 480 emitter tips per sq...

/pdf/emission-characteristics-of-passively-fed-electrospray-1rlxn4iwg1.pdf

Paulo C. Lozano

Papers

Ionic liquid ion sources: characterization of externally wetted emitters.

Ionic liquid ion sources: suppression of electrochemical reactions using voltage alternation

Energy properties of an EMI-Im ionic liquid ion source

Electrospray Propulsion Based on Emitters Microfabricated in Porous Metals

Emission Characteristics of Passively Fed Electrospray Microthrusters with Propellant Reservoirs