10,464 research outputs found
Using Thermal Infrared Imaging to Estimate Soil Hydraulic Parameters: A Novel Approach
In this study, skin temperature measured with a thermal infrared (TIR) camera was used to estimate soil hydraulic parameters. These are the physical properties that control how soils transport and retain water, which are notoriously difficult to measure in the field due to the extreme spatial variability of their values. Laboratory experiments were set up to record surface skin temperature response in a clean soil column using a TIR camera after an artificial wetting event. An array of thermocouples, a net radiometer, heat flux sensor and weather station were used to constrain the TIR data and the energy budget during the experiment. The soil column surface was then wetted with a known amount of water over a controlled time period and the thermal response recorded at five minute intervals over the course of 18 hours. Soil hydraulic parameters were then estimated by fitting a water-energy conservation model (ECH2O) to the observed data using a Levenberg-Marquardt least squares minimization. This inversion of ECH2O was able to estimate soil air entry pressure, soil porosity, and the Brooks-Corey pore size distribution parameter with a relatively high degree of precision. The estimated parameters were compared to several sets of known values based on soil textural classification. Most of the estimates were within the range of standard published values. These results show that soil hydraulic parameter estimation based on TIR skin temperature data could prove to be a fast and useful new tool to characterize the distribution and spatial heterogeneity in soil hydraulic properties at the field scale
Using Thermal Infrared Imagery To Estimate Soil Hydraulic Parameters: A Novel Approach
In this study, skin temperature measured with a thermal infrared (TIR) camera was used to estimate soil hydraulic parameters. These physical properties that control how soils transport and retain water are notoriously difficult to measure in the field due to spatial variability. Laboratory experiments were set up to record surface skin temperature response in a clean soil column using a TIR camera after an artificial wetting event. An array of thermocouples, a net radiometer, heat flux sensor and weather station were used to constrain the TIR data and the energy budget during the experiment. The soil column surface was then wetted with a known amount of water over a controlled time period and the thermal response recorded at five minute intervals over the course of 18 hours. Soil hydraulic parameters were then estimated by fitting a water-energy conservation model (ECH2O) to the observed data using a Marqhart-Levenberg least squares minimization method. The estimated parameters obtained were then compared to several sets of known values based on soil textural classification. This inversion of ECH2O was able to estimate the Brooks-Corey λ for sand with a relatively high degree of precision; however, the inversion was unable to provide reasonable estimates of air entry pressure for sand, air entry pressure for soil, or the Brooks-Corey λ for soil. These results indicate that soil hydraulic parameter estimation based on TIR skin temperature data could potentially be a fast and useful new tool to characterize the distribution and spatial heterogeneity in some soil hydraulic parameters. However, future studies should test the method with dedicated groundwater flow models and accurately account for surface emissivity before conducting field tests
An efficient new route to dihydropyranobenzimidazole inhibitors of HCV replication.
A class of dihydropyranobenzimidazole inhibitors was recently discovered that acts against the hepatitis C virus (HCV) in a new way, binding to the IRES-IIa subdomain of the highly conserved 5' untranslated region of the viral RNA and thus preventing the ribosome from initiating translation. However, the reported synthesis of these compounds is lengthy and low-yielding, the intermediates are troublesome to purify, and the route is poorly structured for the creation of libraries. We report a streamlined route to this class of inhibitors in which yields are far higher and most intermediates are crystalline. In addition, a key variable side chain is introduced late in the synthesis, allowing analogs to be easily synthesized for optimization of antiviral activity
Deterministic quantum state transfer of atoms in a random magnetic field
We propose a method for transferring atoms to a target quantum state for a
multilevel quantum system with sequentially increasing, but otherwise unknown,
energy splitting. This is achieved with a feedback algorithm that processes
off-resonant optical measurements of state populations during adiabatic rapid
passage in real-time. Specifically, we reliably perform the transfer
for a
sample of ultracold Rb in the presence of a random external magnetic
field
Algebraic properties of generalized Rijndael-like ciphers
We provide conditions under which the set of Rijndael functions considered as
permutations of the state space and based on operations of the finite field
\GF (p^k) ( a prime number) is not closed under functional
composition. These conditions justify using a sequential multiple encryption to
strengthen the AES (Rijndael block cipher with specific block sizes) in case
AES became practically insecure. In Sparr and Wernsdorf (2008), R. Sparr and R.
Wernsdorf provided conditions under which the group generated by the
Rijndael-like round functions based on operations of the finite field \GF
(2^k) is equal to the alternating group on the state space. In this paper we
provide conditions under which the group generated by the Rijndael-like round
functions based on operations of the finite field \GF (p^k) () is
equal to the symmetric group or the alternating group on the state space.Comment: 22 pages; Prelim0
THIRD INTERNATIONAL SYMPOSIUM ON RANAVIRUSES:: ADVANCING THE UNDERSTANDING OF THE THREAT OF RANAVIRUSES TO NORTH AMERICAN HERPETOFAUNA
Members of the genus Ranavirus, one of five genera withinthe family Iridoviridae, encompass a group of large, doublestrandedDNA viruses that infect all three classes of ectothermicvertebrates: fish, amphibians, and reptiles. Ranaviruses areglobally emerging pathogens that cause considerable morbidityand mortality among diverse populations. In North America,ranavirus epizootics are regularly reported in wild and culturedfish, amphibian, and reptile populations
Elliptic Reciprocity
The paper introduces the notions of an elliptic pair, an elliptic cycle and
an elliptic list over a square free positive integer d. These concepts are
related to the notions of amicable pairs of primes and aliquot cycles that were
introduced by Silverman and Stange. Settling a matter left open by Silverman
and Stange it is shown that for d=3 there are elliptic cycles of length 6. For
d not equal to 3 the question of the existence of proper elliptic lists of
length n over d is reduced to the the theory of prime producing quadratic
polynomials. For d=163 a proper elliptic list of length 40 is exhibited. It is
shown that for each d there is an upper bound on the length of a proper
elliptic list over d. The final section of the paper contains heuristic
arguments supporting conjectured asymptotics for the number of elliptic pairs
below integer X. Finally, for d congruent to 3 modulo 8 the existence of
infinitely many anomalous prime numbers is derived from Bunyakowski's
Conjecture for quadratic polynomials.Comment: 17 pages, including one figure and two table
Role of wintertime radiation in maintaining and destroying stable layers, The
July 1993.Includes bibliographical references.Sponsored by National Science Foundation ATM-9113898.Sponsored by NOAA Cooperative Agreement A 90-RAH00077
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