Microwave shielding of transparent and conducting single-walled carbon nanotube films

The authors measured the transport properties of single-walled carbon nanotube (SWCNT) films in the microwave frequency range from 10 MHz to 30 GHz by using the Corbino reflection technique from temperatures of 20-400 K. Based on the real and imaginary parts of the microwave conductivity, they calculated the shielding effectiveness for various film thicknesses. Shielding effectiveness of 43 dB at 10 MHz and 28 dB at 10 GHz are found for films with 90% optical transmittance, which suggests that SWCNT films are promising as a type of transparent microwave shielding material. By combining their data with those from the literature, the conductivity of SWCNT films was established in a broad frequency range from dc to visible.Comment: 4 pages, 4 figure

Mathematical Models for Natural Gas Forecasting

It is vital for natural gas Local Distribution Companies (LDCs) to forecast their customers\u27 natural gas demand accurately. A significant error on a single very cold day can cost the customers of the LDC millions of dollars. This paper looks at the financial implication of forecasting natural gas, the nature of natural gas forecasting, the factors that impact natural gas consumption, and describes a survey of mathematical techniques and practices used to model natural gas demand. Many of the techniques used in this paper currently are implemented in a software GasDayTM, which is currently used by 24 LDCs throughout the United States, forecasting about 20% of the total U.S. residential, commercial, and industrial consumption. Results of GasDay\u27sTM forecasting performance also is presented

Timescales and mechanisms of formation of amorphous silica coatings on fresh basalts at Kilauea Volcano, Hawai’i

Young basalts from Kilauea Volcano, Hawai'i, frequently feature opaque surface coatings, 1–80 μm thick, composed of amorphous silica and Fe-Ti oxides. These coatings are the product of interaction of the basaltic surface with volcanically-derived acidic fluids. Previous workers have identified these coatings in a variety of contexts on Hawai'i, but the timescales of coating development, coating growth rates, and factors controlling lateral coating heterogeneity were largely unconstrained. We sampled and analyzed young lava flows (of varying ages, from hours to ~ 40 years) along Kilauea's southwest and east rift zones to characterize variation in silica coating properties across the landscape. Coating thickness varies as a function of flow age, flow surface type, and proximity to acid sources like local fissure vents and regional plumes emitted from Kilauea Caldera and Pu'u O'o. Silica coatings that form in immediate proximity to acid sources are more chemically pure than those forming in higher pH environments, which contain significant Al and Fe. Incipient siliceous alteration was observed on basalt surfaces as young as 8 days old, but periods of a year or more are required to develop contiguous coatings with obvious opaque coloration. Inferred coating growth rates vary with environmental conditions but were typically 1-5 μm/year. Coatings form preferentially on flow surfaces with glassy outer layers, such as spatter ramparts, volcanic bombs and dense pahoehoe breakouts, due to glass strain weakening during cooling. Microtextural evidence suggests that the silica coatings form both by in situ dissolution-reprecipitation and by deposition of silica mobilized in solution. Thin films of water, acidified by contact with volcanic vapors, dissolved near-surface basalt, then precipitated amorphous silica in place, mobilizing more soluble cations. Additional silica was transported to and deposited on the surface by silica-bearing altering fluids derived from the basalt interior

Archaeological Investigations for Proposed Trail Rehabilitation within Mammoth Cave

In 2008, staff from the University of Kentucky Program for Archaeological Research (UK-PAR) and the Illinois State Museum Society (ISMS) conducted archaeological and paleontological investigations at Mammoth Cave National Park in advance of proposed rehabilitation of 40,499 linear feet of selected trail segments within Mammoth Cave. This presentation focuses on the results of archaeological investigations conducted within Mammoth Cave and is confined to discussion of the prehistoric materials. These materials were confined to the upper and lower passages of the Historic Tour, the Lantern Tour, and Gothic Avenue trail

Movements of a Polar Bear from Northern Alaska to Northern Greenland

Using satellite telemetry, we monitored the movements of an adult female polar bear (Ursus maritimus) as she traveled from the Alaskan Beaufort Sea coast to northern Greenland. She is the first polar bear known to depart the Beaufort Sea region for an extended period, and the first polar bear known to move between Alaska and Greenland. This bear traveled for four months across the polar basin and came within 2 degrees of the North Pole. During the first year following her capture, she traveled 5256 km. Evidence to suggest her use of maternity dens in northern Alaska and in northern Greenland demonstrates the potential for genetic exchange between two widely separate populations of polar bears. The long life spans of polar bears and the rarity of their long-range movements means the significance of interpopulation movement can be assessed after long-term monitoring of individuals.Key words: polar bear, Ursus maritimus, satellite telemetry, movements, Beaufort Sea, populations, Alaska, Greenland, polar basinEn utilisant la télémétrie par satellite, on a suivi les déplacements d'une ourse polaire (Ursus maritimus) alors qu'elle allait de la côte de la mer de Beaufort en Alaska au Groenland septentrional. À notre connaissance, elle est la première des ours polaires à avoir quitté la région de la mer de Beaufort pour une longue période, et la première à s'être déplacée entre l'Alaska et le Groenland. Cette ourse a traversé le bassin polaire durant quatre mois et s'est approchée à moins de 2° du pôle Nord. Au cours de la première année suivant sa capture, elle a parcouru 5256 km. Des preuves suggérant qu'elle a utilisé les tanières de mise bas dans l'Alaska septentrional et dans le Groenland septentrional démontrent le potentiel d'échanges génétiques existant entre deux populations d'ours polaires séparées par une grande distance. La longévité importante des ours polaires et la rareté des déplacements lointains signifient que les déplacements entre diverses populations ne peuvent être évalués qu'après une surveillance à long terme des individus.Mots clés: ours polaire, Ursus maritimus, télémétrie par satellite, déplacements, mer de Beaufort, populations, Alaska, Groenland, bassin polair

Frequency- and electric-field-dependent conductivity of single-walled carbon nanotube networks of varying density

We present measurements of the frequency and electric field dependent conductivity of single walled carbon nanotube(SWCNT) networks of various densities. The ac conductivity as a function of frequency is consistent with the extended pair approximation model and increases with frequency above an onset frequency $\omega_0$ which varies over seven decades with a range of film thickness from sub-monolayer to 200 nm. The nonlinear electric field-dependent DC conductivity shows strong dependence on film thickness as well. Measurement of the electric field dependence of the resistance R(E) allows for the determination of a length scale $L_{E}$ possibly characterizing the distance between tube contacts, which is found to systematically decrease with increasing film thickness. The onset frequency $\omega_0$ of ac conductivity and the length scale $L_{E}$ of SWCNT networks are found to be correlated, and a physically reasonable empirical formula relating them has been proposed. Such studies will help the understanding of transport properties and benefit the applications of this material system.Comment: 7 pages and 6 figure

Cavallo's Multiplier for in situ Generation of High Voltage

A classic electrostatic induction machine, Cavallo's multiplier, is suggested for in situ production of very high voltage in cryogenic environments. The device is suitable for generating a large electrostatic field under conditions of very small load current. Operation of the Cavallo multiplier is analyzed, with quantitative description in terms of mutual capacitances between electrodes in the system. A demonstration apparatus was constructed, and measured voltages are compared to predictions based on measured capacitances in the system. The simplicity of the Cavallo multiplier makes it amenable to electrostatic analysis using finite element software, and electrode shapes can be optimized to take advantage of a high dielectric strength medium such as liquid helium. A design study is presented for a Cavallo multiplier in a large-scale, cryogenic experiment to measure the neutron electric dipole moment.Comment: 9 pages, 10 figure

Using Video-Based Instruction To Integrate Ethics Into The Curriculum

This paper describes a video case discussion project based on the IMA’s Statement of Ethical Professional Practice that was administered in a cost accounting class to assess the extent to which students were able to identify and discuss ethical issues raised by the facts of a case scenario. The case was developed by the IMA to advance the continuing education in ethics of financial executives and management accountants. The scenario realistically portrays the kind of pressures faced by management accountants to go along with top management decisions that are driven by self-interest rather than proper accounting. We use a highly structured approach for direct assessment of student learning with pre-established rubrics. Indirect assessment of learning is approximated by a survey of students’ subjective reactions. In general, we conclude IMA’s video Success without Compromise provides an opportunity for students to apply ethics standards in a realistic setting and encourages students to become active participants in the learning experience