9,253 research outputs found

    Pressurized bellows flat contact heat exchanger interface

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    Disclosed is an interdigitated plate-type heat exchanger interface. The interface includes a modular interconnect to thermally connect a pair or pairs of plate-type heat exchangers to a second single or multiple plate-type heat exchanger. The modular interconnect comprises a series of parallel, plate-type heat exchangers arranged in pairs to form a slot therebetween. The plate-type heat exchangers of the second heat exchanger insert into the slots of the modular interconnect. Bellows are provided between the pairs of fins of the modular interconnect so that when the bellows are pressurized, they drive the plate-type heat exchangers of the modular interconnect toward one another, thus closing upon the second heat exchanger plates. Each end of the bellows has a part thereof a thin, membrane diaphragm which readily conforms to the contours of the heat exchanger plates of the modular interconnect when the bellows is pressurized. This ensures an even distribution of pressure on the heat exchangers of the modular interconnect thus creating substantially planar contact between the two heat exchangers. The effect of the interface of the present invention is to provide a dry connection between two heat exchangers whereby the rate of heat transfer can be varied by varying the pressure within the bellows

    Low-distortion slow light using two absorption resonances

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    We consider group delay and broadening using two strongly absorbing and widely spaced resonances. We derive relations which show that very large pulse bandwidths coupled with large group delays and small broadening can be achieved. Unlike single resonance systems, the dispersive broadening dominates the absorptive broadening which leads to a dramatic increase in the possible group delay. We show that the double resonance systems are excellent candidates for realizing all-optical delay lines. We report on an experiment which achieved up to 50 pulse delays with 40% broadening.Comment: 4 pages 4 figure

    Petroleum and Natural Gas in Iowa

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    An Outlier of the So-Called Clinton Formation in Dubuque County, Iowa

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    During the summer of 1914 a considerable amount of grading was done at the forks of the road on the west side of Lora Hill, seven miles west of Dubuque. As a result of this work there was exposed along the road a band of peculiar reddish clay from one to two feet in thickness, underlain by the characteristic gray-green, plastic clay-shales of the Upper Maquoketa formation. The red clay is much less plastic than the underlying green shales, but is remarkable chiefly for the fact that it is composed largely of iron oxide and contains great numbers of small, rounded concretions or oölites. Also imbedded in this deep red clay are: a. numerous pebbles of smooth, polished chert, b. rounded fragments of indurated material similar to that of the clay, and c. rounded fragments of slightly iron stained shale

    Flight test and evaluation of Omega navigation in a general aviation aircraft. Volume 2: Appendices

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    Detailed documentation for each flight of the Omega Flight Evaluation study is presented, including flight test description sheets and actual flight data plots. Computer programs used for data processing and flight planning are explained and the data formats utilized by the Custom Interface Unit are summarized

    Nuclear magnetic octupole moment and the hyperfine structure of the 5D3/2,5/25D_{3/2,5/2} states of the Ba+^+ ion

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    The hyperfine structure of the long-lived 5D3/25D_{3/2} and 5D5/25D_{5/2} levels of Ba+^+ ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments Ω\Omega is presented. The relevant electronic matrix elements are computed in the framework of the ab initio relativistic many-body perturbation theory. Both the first- and the second-order (in the hyperfine interaction) corrections to the energy levels are analyzed. It is shown that a simultaneous measurement of the hyperfine structure of the entire 5DJ5D_J fine-structure manifold allows one to extract Ω\Omega without contamination from the second-order corrections. Measurements to the required accuracy should be possible with a single trapped barium ion using sensitive techniques already demonstrated in Ba+^+ experiments.Comment: Phys Rev A in pres

    Infrared spectroscopy of cataclysmic variables: III. Dwarf novae below the period gap and novalike variables

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    We present K-band spectra of the short-period dwarf novae YZ Cnc, LY Hya, BK Lyn, T Leo, SW UMa and WZ Sge, the novalike variables DW UMa, V1315 Aql, RW Tri, VY Scl, UU Aqr and GP Com, and a series of field dwarf stars with spectral types ranging from K2-M6. The spectra of the dwarf novae are dominated by emission lines of HI and HeI. The large velocity and equivalent widths of these lines, in conjunction with the fact that the lines are double-peaked in the highest inclination systems, indicate an accretion disc origin. In the case of YZ Cnc and T Leo, for which we obtained time-resolved data covering a complete orbital cycle, the emission lines show modulations in their equivalent widths which are most probably associated with the bright spot (the region where the gas stream collides with the accretion disc). There are no clear detections of the secondary star in any of the dwarf novae below the period gap, yielding upper limits of 10-30% for the contribution of the secondary star to the observed K-band flux. In conjunction with the K-band magnitudes of the dwarf novae, we use the derived secondary star contributions to calculate lower limits to the distances to these systems. The spectra of the novalike variables are dominated by broad, single-peaked emission lines of HI and HeI - even the eclipsing systems we observed do not show the double-peaked profiles predicted by standard accretion disc theory. With the exception of RW Tri, which exhibits NaI, CaI and 12CO absorption features consistent with a M0V secondary contributing 65% of the observed K-band flux, we find no evidence for the secondary star in any of the novalike variables. The implications of this result are discussed.Comment: 13 pages, 5 figures, to appear in MNRA

    Biomass burning and pollution aerosol over North America: Organic components and their influence on spectral optical properties and humidification response

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    Thermal analysis of aerosol size distributions provided size resolved volatility up to temperatures of 400°C during extensive flights over North America (NA) for the INTEX/ICARTT experiment in summer 2004. Biomass burning and pollution plumes identified from trace gas measurements were evaluated for their aerosol physiochemical and optical signatures. Measurements of soluble ionic mass and refractory black carbon (BC) mass, inferred from light absorption, were combined with volatility to identify organic carbon at 400°C (VolatileOC) and the residual or refractory organic carbon, RefractoryOC. This approach characterized distinct constituent mass fractions present in biomass burning and pollution plumes every 5–10 min. Biomass burning, pollution and dust aerosol could be stratified by their combined spectral scattering and absorption properties. The “nonplume” regional aerosol exhibited properties dominated by pollution characteristics near the surface and biomass burning aloft. VolatileOC included most water-soluble organic carbon. RefractoryOC dominated enhanced shortwave absorption in plumes from Alaskan and Canadian forest fires. The mass absorption efficiency of this RefractoryOC was about 0.63 m2 g−1 at 470 nm and 0.09 m2 g−1 at 530 nm. Concurrent measurements of the humidity dependence of scattering, γ, revealed the OC component to be only weakly hygroscopic resulting in a general decrease in γ with increasing OC mass fractions. Under ambient humidity conditions, the systematic relations between physiochemical properties and γ lead to a well-constrained dependency on the absorption per unit dry mass for these plume types that may be used to challenge remotely sensed and modeled optical properties
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