A new ac electrospray mechanism by Maxwell-Wagner polarization and capillary resonance

We report a new high-frequency (>10 kHz) ac electrospray that is capable of generating micron-sized electroneutral drops. Unlike its dc counterpart, the drops are not ejected continuously from a sharp Taylor cone but intermittently from a resonating meniscus at the orifice. We attribute the resonant frequency to the capillary-inertia vibration time of the meniscus and the drop ejection to the Maxwell-Wagner electric stress at the drop tip, which is observed to reverse its direction across a crossover frequency. Above this frequency, the oppositely directed Maxwell-Wagner force causes the liquid to recede up the microneedle as an apparent electrowetting effect.     

Resource Inputs and Performance Outputs in Social Security Offices

This paper describes a model of a Social Security office developed by the Operational Research Service of the DHSS. The model, based mainly on queueing theory, relates staffing levels, workloads, and productivity to performance measures based on customer delays. The paper describes the hypothesis underlying the model, the data requirements, technical details, and model calibration. Illustrative outputs of the model are presented and some uses of the model are briefly described.     

Flow and field induced instabilities in a smectic C liquid crystal

This paper discusses the possibility of flow induced instabilities occurring in smectic C liquid crystals by examining appropriate solutions of a recently proposed continuum theory for such materials. These preliminary calculations suggest that results rather similar to those obtained for nematics some twenty years ago are equally likely in smectics.Paper originally intended for publication in Vol. 31/5, Special Issue dedicated to Gianfranco Capriz, but omitted due to an unfortunate misunderstanding.     

Ellipsometrical determination of barrier thicknesses of metal-insulator-metal tunnel junctions

The thickness of the tunneling barrier of AlAl_xO_yAl and AlAl_xO_yPb junctions was determined using an automated ellipsometer. It is shown that the tunneling resistance depends exponentially on the barrier thickness. A practical consequence is that any wanted tunneling resistance can be realized within the accuracy of half an order of magnitude.     

Exhaustive checking of sparse algebras

We checked the 107-dimensional alternative algebra constructed by E. Kleinfeld (On centers of alternative algebras, Comm. Algebra8(3) 1980, 289–297) and verified that it was alternative. To straightforwardly check the alternative law for the basis elements proved to be too time consuming for the computer. We developed a new algorithm which is much faster for sparse multiplication tables and which requires much less memory. Instead of testing the identities for all possible choices of basis elements, our algorithm is based on “factoring” the basis elements in all possible ways. The factorization algorithm took 5 minutes of C.P.U. time; it is estimated direct substitution with no consideration for sparseness would take 600 hours. Even when the substitution technique was improved to account for sparseness it is estimated it would take 12 hours of C.P.U. time. Substitution also requires 100 times as much memory space as factorization.