Atmospheric correction of high spatial resolution (10–30 m pixel sizes) satellite imagery for use in large-area land-cover monitoring is difficult due to the lack of aerosol optical depth (AOD) estimates made coincident with image acquisition. We present a methodology to determine the upper and lower bounds of AOD estimates that allow the subsequent calculation of a biophysical variable of interest to a pre-determined precision. Knowledge of that range can be used to identify an appropriate method for estimating AOD. We applied the methodology to Landsat 5 Thematic Mapper data in Queensland (QLD) and New South Wales (NSW), Australia, and determined that AOD must be estimated within approximately 0.05 of actual AOD for retrieval of foliage projective cover (FPC) to a precision of 10%. That knowledge was then used to determine the relative merit of using a fixed constant, Aerosol Robotic Network (AERONET) climatology, or dense dark vegetation (DDV) method for estimating AOD in QLD and NSW. It was found that using a fixed AOD of 0.05 allows estimates of FPC within 10% of their true value when the true value of AOD is less than 0.1. Such AOD values account for approximately 90% of all inland observations and 65% of coastal observations as determined by analysis of data obtained from AERONET. Using an AERONET climatology to estimate AOD was found to increase the likelihood of accurate FPC retrieval in coastal locations to 83%, although it should be noted that AERONET data are very sparse. DDV has potential in eastern and central areas for retrieving AOD observations with greater precision than fixed values or climatologies. However, more work is needed to understand the temporal variation of vegetation reflectance before the DDV method can be used operationally. 相似文献
Systems and cybernetic methodology have traditionally drawn upon the concepts of analogy and metaphor. These are, however, contentious on both philosophical and practical grounds. The work we present in this paper mostly aims to overcome the philosophical difficulties by uncovering the basic principles of analogic modeling and by showing how these can complement inductive and deductive reasoning. Analogy and metaphor are then shown to be complementary and can be considered to be on one spectrum, from creative metaphor to the more formal approach of analogy. Contention on practical grounds is allayed as the role of analogy and metaphor in systems and cybernetic methodology is outlined. 相似文献
In this study, we developed and tested a causal model to predict innovative work behaviour (IWB) integrating the literatures on psychological contract, job design and organizational justice. Two hundred and four employees from Irish manufacturing organizations participated in the study, and we collected data using a survey questionnaire. The psychological contract variable of perceived obligation to innovate, job autonomy and pay showed direct effects on IWB. In addition, pay and job autonomy also had indirect effects on IWB through the mediating variable of psychological contract – perceived obligation to innovate. The organizational process of meritocracy, equity perceptions and procedural justice perceptions influenced IWB through the mediating variables of psychological contract, although none of these variables influenced IWB directly. Overall, the results indicated good support for the integrative model and provided support for the crucial role played by psychological contract in influencing IWB. Implications are discussed. 相似文献
Wireless Networks - This study has investigated the mitigations necessary for successful compatibility between International Mobile Telecommunications (IMT) services and Fixed Satellite Service... 相似文献
We show that the fundamental legal structure of a well-written financial contract follows a state-transition logic that can be formalized mathematically as a finite-state machine (specifically, a deterministic finite automaton or DFA). The automaton defines the states that a financial relationship can be in, such as “default,” “delinquency,” “performing,” etc., and it defines an “alphabet” of events that can trigger state transitions, such as “payment arrives,” “due date passes,” etc. The core of a contract describes the rules by which different sequences of events trigger particular sequences of state transitions in the relationship between the counterparties. By conceptualizing and representing the legal structure of a contract in this way, we expose it to a range of powerful tools and results from the theory of computation. These allow, for example, automated reasoning to determine whether a contract is internally coherent and whether it is complete relative to a particular event alphabet. We illustrate the process by representing a simple loan agreement as an automaton.
We describe a novel phase-sensing and control system, based on phase-contrast imaging, operating within a linear external cavity laser consisting of 18 GaAlAs edge-emitting gain stripes. The system is used to achieve single-spatial-mode operation and diffraction-limited output from the linear cavity, which uses diffractive coupling at a Talbot plane to achieve coherent operation. 相似文献
We evaluated the TaqMan Salmonella amplification/detection kit from PE Applied Biosystems, which uses a polymerase chain reaction (PCR) assay for rapid detection of Salmonella in food samples. This system uses the 5' nuclease activity of Taq DNA polymerase, which digests an internal fluorogenic probe to monitor the amplification of the target gene. The system's sensitivity and specificity were evaluated using 42 serotypes of 68 Salmonella strains isolated from fecal samples from patients in Tokyo, Japan, and 39 non-Salmonella strains in 22 genera. There were no false-negative or false-positive results. This PCR assay can detect 3 CFU per PCR tube of Salmonella in pure culture (120 CFU/ml of TSB culture). PCR signals were attenuated with artificially contaminated shrimp, but a similar detection limit was obtained. TaqMan's performance was tested with 100 meat and chicken samples purchased from stores in Tokyo. Overall, two of the DNA extraction protocols (the Chelex and EnviroAmp methods) worked equally well, with some exceptions. Of the 100 samples analyzed, 10 were positive for Salmonella with both conventional culture methods and the kit and 89 were negative with both. One sample was negative by the culture method but positive by the kit assay. These results indicate that TaqMan is a reliable and rapid method for Salmonella analysis in the food industry. With this system, food samples can be analyzed for Salmonella in less than 20 h. 相似文献
The gain saturation behavior of an L-band erbium-doped fiber amplifier is investigated. Experimental results show that amplifiers configured to operate in the L-band exhibit decidedly different saturation behavior compared to what is observed in C-band amplifiers. It is shown that the gain can vary by as much as 2.3 dB. Results suggest that the unique saturation behavior observed in the L-band is due, in part, to backward traveling amplified spontaneous emission power 相似文献