Effect of combining a DC bias current with an AC transport current on AC losses in a High Temperature Superconductor

Creating complex flux configurations by superposing a dc current or magnetic field onto the ac current in a type II superconducting tape should lead to a variety of peculiar behaviors. An example is the appearance of the Clem valley, a minimum in the ac losses as a function of the dc bias amplitude, which has been theoretically studied by LeBlanc et al., in the continuation of Clem's calculations. These situations have been investigated by applying a dc current to a silver-gold sheathed Bi-2223 tape at 77 K (critical current 29 A), in addition to the usual ac transport current. The ac losses were measured by the null calorimetric method to ensure that the total losses were being accounted for. These were recorded for different values of the ac and dc currents, leading to the observation of two different behaviors depending on the ac current. Our revelation of the Clem valley is, to our knowledge, the first experimental validation of this phenomenon in high temperature superconductors, and may provide a simple way of reducing the ac loss in industrial applications of these materials.Comment: 4 pages,4 figures - ASC 9

Seismic borehole tomography

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1988.Includes bibliographies.by Tien-when Lo.Ph.D

Experimental Determination of Elastic Anisotropy of Berea Sandstone, Chicopee Shale and Chelmsford Granite

We use the ultrasonic transmission method to measure P-, SH-, and SV-wave velocities for Chelmsford Granite, Chicopee Shale, and Berea Sandstone in different directions up to 1000 bars confining pressure. The velocity measurements indicate that these three rocks are elastically anisotropic. The stiffness constants, dynamic Young's moduli, dynamic Poisson's ratios, and dynamic bulk moduli of these three rocks were also calculated. These elastic constants, together with velocity measurements, suggest that: (1) Elastic anisotropy is due to the combined effects of pores/cracks and mineral grain orientation. (2) Elastic anisotropy decreases with increasing confining pressure. The residual anisotropy at higher confining pressure is due to mineral grain orientation

Ultrasonic laboratory tests of geophysical tomographic reconstruction

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986.Microfiche copy available in Archives and Science.Bibliography: leaves 31-35.by Tien-when Lo.M.S

Closing the knowing-applying gap in water utilities: experience from Uganda's NWSC

In recent decades, there has been a steady rise of knowledge and capacity development (KCD) interventions targeting water utilities in developing countries. However, field experiences show that very often little change occurs in what water utilities' professionals and managers do as a result of capacity development efforts. Notwithstanding that, there are also some cases of success. In this paper, the authors argue that very often the main challenge facing utilities is not the development of utility competences per se, but their actual use. Drawing on the case of Uganda's National Water and Sewerage Corporation, we identify and discuss five interrelated factors that have allowed the corporation to progressively turn its knowledge base into improved performance, by means of its change management programmes. The paper concludes that water utilities can bridge the knowing-applying gap by carefully introducing a corporate culture, and management systems and structures that motivate staff to apply their knowledge

Molecular dynamics in shape space and femtosecond vibrational spectroscopy of metal clusters

We introduce a method of molecular dynamics in shape space aimed at metal clusters. The ionic degrees of freedom are described via a dynamically deformable jellium with inertia parameters derived from an incompressible, irrotational flow. The shell correction method is used to calculate the electronic potential energy surface underlying the dynamics. Our finite temperature simulations of Ag_14 and its ions, following the negative to neutral to positive scheme, demonstrate the potential of pump and probe ultrashort laser pulses as a spectroscopy of cluster shape vibrations.Comment: Latex/Revtex, 4 pages with 3 Postscript figure

When Sherman Marched Down to the Sea

1st verse:Our camp fires shone bright on the mountain That frown\u27d on the river below,While we stood by our guns in the morning,And eagerly watch\u27d for the foe;When a horseman rode out from the darknessThat hung over mountain and tree,And shouted, Boys, up and be ready,For Sherman will march to the sea. 2nd verse:When cheer upon cheer for bold ShermanWent up from each valley and glen,And the bugles reechoed the musicThat came from the lips of the menFor we knew that the stars on our banners,More bright in their splendor would be,And the blessings from Northland would greet usWhen Sherman march\u27d down to the sea. 3rd verse:Then forward, boys; forward to battle,We march\u27d on our wearysome way,And we storm\u27d the wild hills of Resaca,God bless those who fell on that day!Then Kenesaw, dark in its glory,Frown\u27d down on the flag of the free,But the East and the West bore her standardWhen Sherman march\u27d down to the sea. 4th verse:Still onward we pressed till our bannersSwept out from Atlanta\u27s grim walls,And the blood of the patriot dampenedThe soil where the traitor\u27s flag falls;But we paused not to weep for the fallenWho slept by each river and tree,Yet we twined the a wreath of the laurel,And Sherman marched down to the sea. 5th verse:Proud, proud was our army that morningThat stood by the cypress and pine,The Sherman said, Boys, you are weary,This day fair Savannah is mine! Then sang we a song for our chieftain,That echoed o\u27er river and sea,And the stars on our banners shone brighterWhen Sherman marched down to the sea