The collection of accurate and timely information on land use, crops, forest and vegetation are increasingly based on remote sensing spectral measurements produced by satellites. The most recent spacecrafts like the Earth Observing 1 (EO-1) produce a rich source of information being endowed with hyperspectral sensors that can provide up to 200 or more channels. In many instances such a multivariate signal has to be reduced to just one single value per pixel representing a particular characteristic of land. Linear combinations of bands are the general form of many indices. Since each individual image used to construct indices contains errors, when combined they produce a propagation of errors, a process that can distort a final output map. In this paper we measure the extent of error propagation when building linear vegetation indices. We consider three types of indices: the difference vegetation index (DVI), selected Kauth-Thomas indices (SBI, GVI and WET), and principal components, using benchmarking examples taken from the remote sensing literature. The main implication emerging from these examples is that the SBI and the first principal component are the indices more prone to error propagation. The formalization presented here allows a user to derive measures of error propagation in cases where technical characteristics of a sensor and physical characteristics of a landscape are known. These results can help a user to choose between alternative vegetation indices, and to associate a measure of reliability with such indices. 相似文献
Objective: The facial region is a commonly fractured site, but the etiology varies widely by country and geographic region. To date, there are no population-based studies of facial fractures in Taiwan.
Methods: We conducted a retrospective study of patients diagnosed with facial fracture and registered in the National Health Insurance Research Database of Taiwan between 1997 and 2011. The epidemiological characteristics of this cohort were analyzed, including the etiology, fracture site, associated injuries, and sex and age distributions.
Results: A total of 6,013 cases were identified that involved facial fractures. Most patients were male (69.8%), aged 18–29 years (35.8%), and had fractures caused by road traffic accidents (RTAs; 55.2%), particularly motorcycle accidents (31.5%). Falls increased in frequency with advancing age, reaching 23.9% among the elderly (age > 65 years). The most common sites of involvement were the malar and maxillary bones (54.0%), but nasal bone fractures were more common among those younger than 18 years.
Conclusion: Most facial injuries in Taiwan occur in young males and typically result from RTAs, particularly involving motorcycles. However, with increasing age, there is an increase in the proportion of facial injuries due to falls. 相似文献
Only with a properly designed water quality monitoring network can data be collected that can lead to accurate information
extraction. One of the main components of water quality monitoring network design is the allocation of sampling locations.
For this purpose, a design methodology, called critical sampling points (CSP), has been developed for the determination of
the critical sampling locations in small, rural watersheds with regard to total phosphorus (TP) load pollution. It considers
hydrologic, topographic, soil, vegetative, and land use factors. The objective of the monitoring network design in this methodology
is to identify the stream locations which receive the greatest TP loads from the upstream portions of a watershed. The CSP
methodology has been translated into a model, called water quality monitoring station analysis (WQMSA), which integrates a
geographic information system (GIS) for the handling of the spatial aspect of the data, a hydrologic/water quality simulation
model for TP load estimation, and fuzzy logic for improved input data representation. In addition, the methodology was purposely
designed to be useful in diverse rural watersheds, independent of geographic location. Three watershed case studies in Pennsylvania,
Amazonian Ecuador, and central Chile were examined. Each case study offered a different degree of data availability. It was
demonstrated that the developed methodology could be successfully used in all three case studies. The case studies suggest
that the CSP methodology, in form of the WQMSA model, has potential in applications world-wide. 相似文献
Summary. The odour perceptive abilities, and preferences, of three bark beetle parasitoid species; Rhopalicus tutela (Walker), Roptrocerus mirus (Walker), and Roptrocerus xylophagorum (Ratzeburg) (Hymenoptera: Pteromalidae), were investigated to isolate and identify the essential compounds involved in host
location. These parasitoids attack several economically important bark beetle species and oviposit preferentially on late
larval stages concealed under the bark of conifers. Odours were collected from Norway spruce logs (Picea abies L. Karst.) containing Ips typographus L. (Coleoptera: Scolytidae) larvae. Biologically active compounds were isolated by coupled gas chromatographic-electroantennographic
detection (GC-EAD), and identified by GC-mass spectrometry (GC-MS). Based on these analyses, four different synthetic baits
were prepared and tested in a Y-tube walking bioassay. In the complex odour samples from spruce logs, only 16 compounds were
EAD-active. The tested R. tutela and R. mirus females displayed similar trends in antennal activity to EAD-active compounds, responding mainly to oxygenated monoterpenes
that indicate damaged conifers. Consequently, the synthetic baits were exclusively prepared with oxygenated monoterpenes.
Parasitoid females (R. tutela and R. mirus) preferred spruce logs containing susceptible hosts over fresh logs, while male parasitoids (R. mirus) did not show any preference. However, when odours from fresh logs were mixed with synthetic baits (mimicking the odour composition
of logs containing susceptible hosts), these combinations attracted female parasitoids (R. tutela, R. mirus, and R. xylophagorum). All synthetic baits seemed to be equally attractive to female parasitoids.
Received 12 October 2000; accepted 18 January 2001 相似文献
Site selection is a typical strategic decision for many industries that deals with specifying the most appropriate location for a facility. In the context of sustainable development, site selection decisions need to be improved by adopting environmental, economic and social requirements. This study aims to frame sustainable location decisions by conducting a case study of siting a new cement plant in the state of Florida. As a part of the study, a wide range of technical and sustainability criteria has developed. These criteria can help decision-makers in the cement industry evaluate the selection of a location with the requirements of sustainable development. The sustainability characteristics of alternative sites in the state of Florida are evaluated based on the criteria to identify the most appropriate ones. The analytical hierarchy processand geographic information system techniques are utilized to weight the criteria and evaluate the characteristics of site candidates. 相似文献
A system combining a national soils database with a neural network was developed for prediction of source location for soil samples. The neural network was trained to predict environmental characteristics, which can be of crucial importance to investigating officers in a police operation or to environmental agencies attempting to locate the source of a pollutant. When coupled with maps of environmental conditions and a generalized opinion pool approach, the system was used to produce weighted maps of source location. The system was capable of reducing search areas of a sample source to less than 0.1% of the total area. 相似文献