<i>AIP Handbook of Modern Sensors</i>

Fraden, Jacob; Rubin, Lawrence G.

doi:10.1063/1.2808535

Cited by 38 publications

(49 citation statements)

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“…The potential hydrologic significance of falling film flow may be greatest along rougher surfaces of lower permeability media since film thicknesses can become greater, since pore water velocities in the bulk medium will be relatively low, and since the "near-zero" ½ condition encompasses a broader range. [Fraden, 1993]. The tensiometer holes were drilled completely through the rock, permitting effective purging of any accumulated air bubbles.…”

Section: Conceptual Modelmentioning

confidence: 99%

Water film flow along fracture surfaces of porous rock

Tokunaga¹,

Wan²

1997

Water Resources Research

256

186

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Abstract. This study shows that hydraulic properties of individual fracture surfaces can be meaningfully defined and measured, and that water film flow is a mechanism contributing to fast, unsaturated flow in fractures. The hydraulic conductivity of an unconfined block of Bishop Tuff was measured over a range of near-zero matric potentials, where differences between hydraulic conductivities obtained without and with wax sealing of its lateral sides allowed isolation of film flow effects. Tensiometer and flux measurements showed that surface film flow in this system was significant for matric potentials greater (more positive) than about -250 Pa. In this range the average film thickness was shown to be potential dependent and proportional to the observed enhanced hydraulic conductivity. Measured average surface film thicknesses ranged from 2 to 70 tzm, with average film velocities in the range of 2 to 40 rn d -* (about 10 3 times faster than that of the pore water under unit gradient saturated flow). Our experiments demonstrate that hydraulic properties of macroscopic surfaces of porous media are quantifiable, related to surface roughness, and potentially important in the flow of water in vadose environments. This study further shows that contrary to existing conceptual models, unsaturated flow in fractures cannot generally be predicted solely on the basis of aperture distribution information. The high velocities of these surface films suggest that film flow can be an important mechanism contributing to fast flow in unsaturated fractures and macropores, especially in media characterized by low-permeability matrix and along regions of convergent flow in partially saturated fractures.

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Section: Conceptual Modelmentioning

confidence: 99%

Water film flow along fracture surfaces of porous rock

Tokunaga¹,

Wan²

1997

Water Resources Research

256

186

View full text Add to dashboard Cite

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“…There is a residual output, V 0 ϭ 7.5 mV, during the illuminated part of the cycle which is due to the finite continuous heat flux through the film because of the difference in absolute temperature of its two sides. 8 In summary, AlN appears to have a PE voltage response comparable to values found for materials used for commercial detectors 8 and greater than that thus far reported for GaN. The crystal symmetry of both AlN and GaN, however, are quite high and so such large PE values are not expected for these compounds.…”

Section: Resultsmentioning

confidence: 64%

“…There are several immediate and potential advantages of AlN over traditional pyroelectric materials. Reactively sputtered AlN has a lower dielectric constant than current commercial PE materials 8,10 and the AlN dielectric constant is relatively temperature insensitive to at least 300°C. 11 The thermal conductivity of AlN is on the order of 100 times higher than traditional PE materials, even at 300°C.…”

mentioning

confidence: 95%

“…8 Recently Bykhovski et al 9 reported experimental observations of pyroelectric response in thin films of gallium nitride that were ϳ10 4 V/m-K. Because AlN has larger piezoelectric coefficients than GaN, it is reasonable to expect, as suggested in Ref. 2 and 7, that the pyroelectric effect might be higher in AlN.…”

mentioning

confidence: 98%

“…11 The thermal conductivity of AlN is on the order of 100 times higher than traditional PE materials, even at 300°C. 8,12 Low dielectric constant and high thermal conductivity are important for fast detector array response operation. Although a Curie temperature has not been established for the PE effect in AlN ͑it has been estimated at Ͼ300°C for GaN͒, 7 the group III-nitrides in general are high decomposition materials (Ͼ1300 K) 13 and therefore have a potential to perform at elevated temperatures.…”

mentioning

confidence: 99%

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