On the intertranslatability of non‐monotonic logics

This paper concentrates on comparing the expressive powers of five non‐monotonic logics that have appeared in the literature. For this purpose, the concept of a polynomial, faithful and modular (PFM) translation function is adopted from earlier work by Gottlob, but a weaker notion of faithfulness is proposed. The existence of a PFM translation function from one non‐monotonic logic to another is interpreted to indicate that the latter logic is capable of expressing everything that the former logic does. Several translation functions are presented in the paper and shown to be PFM. Moreover, it is shown that PFM translation functions are impossible in certain cases, which indicates that the expressive powers of the logics involved differ strictly. The comparisons made in terms of PFM translation functions give rise to an exact classification of non‐monotonic logics, which is then named as the expressive power hierarchy (EPH) of non‐monotonic logics. Three syntactically restricted variants of default logic are also analyzed, and EPH is refined accordingly. Most importantly, the classes of EPH indicate some astonishing relationships in light of earlier results on the expressive power of non‐monotonic logics presented by Gottlob as well as Bonatti and Eiter: Moore’s autoepistemic logic and prerequisite‐free default logic are of equal expressive power and less expressive than Reiter’s default logic and Marek and Truszczyński’s strong autoepistemic logic. This revised version was published online in June 2006 with corrections to the Cover Date.     

Feature‐selection ability of the decision‐tree algorithm and the impact of feature‐selection/extraction on decision‐tree results based on hyperspectral data

The decision‐tree (DT) algorithm is a very popular and efficient data‐mining technique. It is non‐parametric and computationally fast. Besides forming interpretable classification rules, it can select features on its own. In this article, the feature‐selection ability of DT and the impacts of feature‐selection/extraction on DT with different training sample sizes were studied by using AVIRIS hyperspcetral data. DT was compared with three other feature‐selection methods; the results indicated that DT was an unstable feature selector, and the number of features selected by DT was strongly related to the sample size. Trees derived with and without feature‐selection/extraction were compared. It was demonstrated that the impacts of feature selection on DT were shown mainly as a significant increase in the number of tree nodes (14.13–23.81%) and moderate increase in tree accuracy (3.5–4.8%). Feature extraction, like Non‐parametric Weighted Feature Extraction (NWFE) and Decision Boundary Feature Extraction (DBFE), could enhance tree accuracy more obviously (4.78–6.15%) and meanwhile a decrease in the number of tree nodes (6.89–16.81%). When the training sample size was small, feature‐selection/extraction could increase the accuracy more dramatically (6.90–15.66%) without increasing tree nodes.     

A two‐step method for estimating the extent of burnt areas with the use of coarse‐resolution data

The extent of the burnt area for five fires that took place in Greece in July 1998 was estimated with the use of Advanced Very High Resolution Radiometer (AVHRR) data by employing existing methods that use spectral indices for burnt‐pixel detection and relationships between single‐channel reflectance and the fraction of the pixel that has been burnt. The results of these methods were compared with field validation data. The burnt‐pixel detection methods resulted in large omission and commission errors and tended to provide an overestimation of the total burnt area extent while the sub‐pixel methods tended to identify areas as partially burnt, when in fact they were not, thus providing errors of commission. A two‐step method that combines burnt‐pixel identification methods with sub‐pixel techniques was employed in order to overcome the limitations associated with the use of the methods individually. This combined technique provided improved estimations of burnt‐area extent when compared with any of the methods employed individually.     

The making of the Xian terra‐cotta soldiers

Abstract

This paper describes the making of a short film on the Xian terra‐cotta soldiers using our integrated HU‐MANOID software. The method of creating and animating the soldiers’ faces is first presented. Then, we show how our approach, based on metaballs and spline surfaces, was used for designing and deforming soldiers’ bodies. For the animation of the bodies, we describe the motion control methods. Clothes for the soldiers are then described as well as horses and decor design. For the rendering, we explained our strategy using parallel machines. Finally, problems of integration are addressed.     

Detecting the onset of snow‐melt using SSM/I data and the self‐organizing map

In this paper, we present an algorithm to estimate the onset of seasonal snow‐melt using space‐borne microwave radiometer data. We have earlier developed a simple model called a Channel Difference Algorithm (CDA) to estimate the beginning of the snow‐melt. The new algorithm, the SOM Detection Algorithm (SDA), is based on the use of an artificial neural network system a called Self‐Organizing Map (SOM). The purpose of this research is to develop a robust and simple algorithm feasible for operative use. The algorithm is tested using SSM/I data with hydrological predictions as reference data. The reference data covers two winters, 1997 and 1998, and is for the boreal forest zone in Finland. The results are promising. The SDA is able to estimate the beginning of the final snow‐melt well, especially if the snow water equivalent exhibits large values. Using low‐pass filtering for the SDA estimated time series, the estimation can be improved.     

Corn‐yield estimation through assimilation of remotely sensed data into the CSM‐CERES‐Maize model

One of the applications of crop simulation models is to estimate crop yield during the current growing season. Several studies have tried to integrate crop simulation models with remotely sensed data through data‐assimilation methods. This approach has the advantage of allowing reinitialization of model parameters with remotely sensed observations to improve model performance. In this study, the Cropping System Model‐CERES‐Maize was integrated with the Moderate Resolution Imaging Spectroradiometer (MODIS) leaf area index (LAI) products for estimating corn yield in the state of Indiana, USA. This procedure, inversion of crop simulation model, facilitates several different user input modes and outputs a series of agronomic and biophysical parameters, including crop yield. The estimated corn yield in 2000 compared reasonably well with the US Department of Agriculture National Agricultural Statistics Service statistics for most counties. Using the seasonal LAI in the optimization procedure produced the best results compared with only the green‐up LAIs or the highest LAI values. Planting, emergence and maturation dates, and N fertilizer application rates were also estimated at a regional level. Further studies will include investigating model uncertainties and using other MODIS products, such as the enhanced vegetation index.     

Building‐based damage detection due to earthquake using the watershed segmentation of the post‐event aerial images

This paper presents an approach for detecting the damaged buildings due to earthquake using the watershed segmentation of the post‐event aerial images. The approach utilizes the relationship between the buildings and their cast shadows. It is based on an idea that if a building is damaged, it will not produce shadows. The cast shadows of the buildings are detected through an immersion‐based watershed segmentation. The boundaries of the buildings are available and stored in a GIS as vector polygons. The vector‐building boundaries are used to match the shadow casting edges of the buildings with their corresponding shadows and to perform assessments on a building‐specific manner. For each building, a final decision on the damage condition is taken, based on the assessments carried out for that building only. The approach was implemented in Golcuk, one of the urban areas most strongly hit by the 1999 Izmit, Turkey earthquake. To implement the approach, a system called the Building‐Based Earthquake Damage Assessment System was developed in MATLAB. Of the 284 buildings processed and analysed, 229 were correctly labelled as damaged and undamaged, providing an overall accuracy of 80.63%.     

Satellite‐based assessment of the dynamics of new lakes in southern Egypt

Lakes in arid landscapes are indicators of environmental change and important sources of water for human use. In regions without in situ hydrologic measurements, remote sensing may provide the only means to monitor long‐term changes in water storage. We used a synergistic combination of multiple satellite remote‐sensing methods to provide the first comprehensive assessment of the dynamics of a newly formed chain of large lakes in the hyper‐arid Toshka Depression of southern Egypt. A total of 145 MODIS and AVHRR satellite images were used to monitor changes in lake surface area, which increased to a maximum of 1740 km² before declining to 900 km². Two methods were tested for satellite‐based measurement of lake levels and volumes, one based on analysis of a digital elevation model and one using data from the ICESat GLAS laser altimeter. This study shows the power of satellite remote sensing for long‐term monitoring of regional‐scale hydrologic transformations.     

Modelling the population density of China at the pixel level based on DMSP/OLS non‐radiance‐calibrated night‐time light images

The spatial distribution of population density is crucial for analysing the relationships among economic growth, environmental protection and resource use. In this study we simulated China's population density in 1998 at 1 km×1 km resolution by integrating DMSP/OLS non‐radiance‐calibrated night‐time images, SPOT/VGT 10‐day maximum NDVI composite, population census data and vector county boundaries. Population density, both inside and outside of light patches, was estimated for four types of counties, which were classified according to their light characteristics. The model for estimating population density inside the light patches was developed based on a significant correlation between light intensity and population, while the model for estimating population density outside of light patches was constructed by combining Coulomb's law with electric field superposition principle. Our method was simpler and less expensive than existing methods for spatializing population density. The results were consistent with other estimates but exhibited more spatial heterogeneity and richer information.     

A comparison of the wind magnitudes obtained from the microwave radiometer onboard IRS‐P4 satellite and the ERS‐2 scatterometer

Wind speeds obtained from the Multifrequency Scanning Microwave Radiometer (MSMR) are evaluated with those obtained from the European Remote Sensing Satellite (ERS‐2) scatterometer over the global oceans over the period 15 June 1999 to 23 August 1999. A detailed statistical analysis has been carried out to assess the accuracy of the MSMR wind magnitudes. The analysis consists of an examination of the mean bias and Root Mean Square (rms) differences between the two gridded fields for different regions. The biases and the rms errors are different for different regions, being less over the tropical oceans and more over the polar regions. The biases range from about 3?m?s^?1 in the tropics to over 6?m?s^?1 in high latitudes, with the global average of 4.2?m?s^?1. These biases are different for different wind speed ranges, being highest for the low wind speed range (0–4?m?s^?1). The global standard deviation (SD) is found to be 2.2?m?s^?1. The MSMR overestimated wind magnitude.     

Multi‐year circumpolar assessment of the area burnt in boreal ecosystems using SPOT‐VEGETATION

The Russian Academy of Sciences' Space Research Institute has developed a new burnt area mapping method and a five‐year database to estimate biomass burning in the Earth's entire boreal region. The mapping method involved SPOT‐VEGETATION time‐series data analysis to detect inter‐annual vegetation changes combined with MODIS hot‐spot data to distinguish fire‐related changes from other types of disturbances. The burnt area database actually covers the boreal biome for the period 2000–2004 with 1 km spatial resolution and 10‐day time frequency, while an automatic data processing chain allows this database to be updated continuously. The accuracy assessment involved comparison with Landsat‐ETM+ derived burnt area estimates for Northern Eurasia and ground data for Canada. This Letter describes the satellite sensor data processing method and the results of the accuracy assessment of the burnt area database and provides burnt area statistics for the boreal region countries.     

ASTER‐based study of the night‐time urban heat island effect in Metro Manila

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) was used to derive land surface temperatures to quantify the night‐time urban heat island (UHI) effect in Metro Manila. Temperature differences between Metro Manila and its adjacent rural towns were compared to determine heat island intensity and analyse spatial variation of surface temperature. Transects were drawn across from the rural to the urban region to characterize the UHI profile and the Normalized Difference Vegetation Index (NDVI) was used to examine the relationship between amount of vegetation and temperature. The thermal images revealed the highest UHI intensity to be 2.96°C with the presence of a heat island existing in the central part of the city. The transects described the cross‐sectional heat island profile characterized by gradients of ‘cliffs’, ‘plateaus’ and a ‘peak’ occurring in the city centre. The study also showed an inverse relationship between NDVI and temperature, which suggests that increasing the amount of plants in cities can reduce the UHI effect.     

A view‐dependent method for the multi‐resolution representation of terrains with roads embedded

Generating multi‐resolution terrain models dynamically is necessary for rapid visualization because of the huge volume of data and the limited memory of computers. However, it is difficult to generate dynamic multi‐resolution terrain models with the roads embedded. This paper proposes a new method for generating these models. In contrast to previous approaches, our method divides the integrated terrains into multiple levels with a ‘?’ shape, and dynamically generates multi‐resolution terrain models with the roads embedded. Moreover, our method efficiently overcomes thin, long‐shaped triangles in multi‐resolution terrain models. On the other hand, the number of triangles in adjacent frames is efficiently updated during walking/flying through visualization. The experimental results demonstrate that the proposed method acquires better performance in terms of accuracy for the multi‐resolution representation of terrains with the roads embedded.     

Super‐resolution mapping of the waterline from remotely sensed data

Methods for mapping the waterline at a subpixel scale from a soft image classification of remotely sensed data are evaluated. Unlike approaches based on hard classification, these methods allow the waterline to run through rather than between image pixels and so have the potential to derive accurate and realistic representations of the waterline from imagery with relatively large pixels. The most accurate predictions of waterline location were made from a geostatistical approach applied to the output of a soft classification (RMSE = 2.25 m) which satisfied the standards for mapping at 1 : 5000 scale from imagery with a 20 m spatial resolution.     

First algorithm for chlorophyll‐a retrieval from MODIS‐Terra imagery of Sun‐induced fluorescence in the Southern Ocean

The measurements of in situ samplers, the ENEA Light Detection and Ranging (Lidar) Fluorosensor (ELF) and Moderate Resolution Imaging Spectroradiometer on‐board the Terra satellite (MODIS‐Terra), carried out in the Southern Ocean during the Austral summer 2002–2003, were used to provide the first algorithm for chlorophyll‐a (Chl‐a) retrieval from MODIS‐Terra imagery of Sun‐induced fluorescence in the Southern Ocean. The results of the algorithm indicate that the standard MODIS‐Terra algorithm underestimated Chl‐a. The discrepancy (20%) is below the expected error of MODIS (35%).     

Side‐scan sonographs of steep slopes in the Wushieh Reservoir

Operators tow side‐scan sonar transducers at the optimum height from the bottom to produce better quality side‐scan sonographs. This can be done only if the bottom is moderately flat. Sonographs with maximum tonal intensity are easily produced on steep slopes e.g. valley banks. Strong signatures are recorded over all ranges due to the poor geometry of sonographs produced without acoustic shadows. In order to create clear scanned images of a steep slope using a side‐scan sonar, rotation of the towed fish or tilting the transducer face to the dipping slope surface is suggested. Cases conducted on the shore of the Wushieh Reservoir, Taiwan, in which the bank slopes varied from 10° to 45° are discussed in this work. In general, the angle of the scanned slope determines the degree of towed fish rotation angle. The rotation angle is set at a smaller angle than the slope, giving stronger returns from the lower slope. In contrast, if the rotation angle is set at a larger angle a null return outside the insonified area in the lower slope is produced. A sub‐aqueous landslide was observed in the side‐scan sonographs using this strategy. This study also gives results that affirm the value of a side‐scan sonar as a powerful tool for underwater inspection.     

Evaluating the performance of the space‐borne SAR sensor systems for oil spill detection and sea monitoring over the south‐eastern Mediterranean Sea

Synthetic Aperture Radar (SAR) images have been extensively used for the detection of oil spills in the marine environment as they are independent of local weather conditions, cloudiness and sun illumination. The objective of the study was to provide the users with specific knowledge on SAR image availability over a target area and assess the monitoring capability (visibility of an area) with respect to the requirements for oil‐spill detection and marine environment protection over the south‐eastern part of the Mediterranean Sea. For this purpose, a web GIS tool has been implemented, enabling the users to submit their queries and receive answers in the form of reports and statistics, concerning the current image acquisition capability over the area of interest. It also provides the user with graphic representations of the sensors' swath coverages over the same geographic location. The system has been tested over the Hellenic Seas and the resulting figures denoting the temporal resolution in the observation are analysed and discussed. The analysis shows that the operation of the Envisat satellite, in conjunction with ERS‐2 and Radarsat satellites, has significantly improved the monitoring capability. As shown, the increase in the number of observations over a target location can reach theoretically a level of 130%. In conclusion, the study provides the user with an assessment of the remaining technological gaps and unmet user needs in the domain of marine environment protection.     

Fractal analysis of the structure and dynamics of a satellite‐detected urban heat island

In this Letter, three fractal models—surface, profile and pixel models are developed to analyse the structure and dynamics of an urban heat island (UHI). These three models were tested using data from Shanghai taken in 1990, 1995 and 1998. The surface model is capable of capturing the fractal dimension of the entire study area. The profile model can be used to analyse the structural characteristics of the UHI along certain directions and is capable of revealing changes in the texture characteristics of UHI. The pixel model can describe the changes in thermal characteristics surrounding each pixel in a particular locale and is suitable for analysing the micro‐structure of the UHI.     

An analysis of the business characteristics of adopters and non‐adopters of World Wide Web technology

The World Wide Web has received considerable media attention in recent times. Little is known concerning the technology’s appeal for commercial applications, and the topic deserves investigation. This study aims to analyze the differences between adopter and non‐adopter businesses according to their organizational characteristics. Six characteristics consistently associated with the adoption of technology, business size, age, industry, use of an IT support unit and IT budget, and degree of technology experience, are selected from the literature. A sample of 245 adopter businesses is gathered using on‐line directories and “keyword” searches of the World Wide Web. A sample of 245 non‐adopter businesses is obtained from the state business telephone directory. The study finds a number of interesting associations. No significant relationship is found between business size and World Wide Web adoption. Adopters tend to be younger yet more experienced with technology than non‐adopters. Businesses that made use of IT budgets and IT support units also tended to be adopters, however adoption did not rely on the existence of these two factors. The study raises a number of additional findings that are of interest but are not directly related to this work. These findings merit further research. This revised version was published online in July 2006 with corrections to the Cover Date.