Comparison of satellite images with different spatial resolutions to estimate stand structural diversity in urban forests

The structural diversity in urban forests is highly important to protect biodiversity. In particular, fruit trees and bush species, cavity-bearing trees and coarse, woody debris provide habitats for animals to feed, nest and hide. Improper silvicultural practices, intensive recreational use and illegal harvesting lead to a decline in the structural diversity in forests within larger metropolitan cities. It is important to monitor the structural diversity at definite time intervals using effective technologies with a view to instituting the necessary conservation measures. The use of satellite images seems to be appropriate to this end. Here we aimed to identify the associations between the textural features derived from the satellite images with different spatial resolutions and the structural diversity indices in urban forest stands (Shannon-Wiener index, complexity index, dominance index and density of wildlife trees). RapidEye images with a spatial resolution of 5 m × 5 m, ASTER images with a spatial resolution of 15 m × 15 m and Landsat-8 ETM satellite images with a spatial resolution of 30 m × 30 m were used in this study. The first-order (standard deviation of gray levels) and second order (GLCM entropy, GLCM contrast and GLCM correlation) textural features were calculated from the satellite images. When associations between textural features in the images and the structural diversity indices were assessed using the Pearson correlation coefficient, very high associations were found between the image textural features and the diversity indices. The highest association was found between the standard deviation of gray levels (SDGLRAP) derived from RVIRAP of RapidEye image and the Shannon-Wiener index (H h) calculated on the basis of tree height (R 2 = 0.64). The findings revealed that RapidEye satellite images with a spatial resolution of 5 m × 5 m are most suitable for estimating the structural diversity in urban forests.

Calculation of skid resistance from texture measurements

There is a wide range of routine skid resistance measurement devices on the market. All of them are measuring the friction force between a rubber wheel and the wetted road surface. Common to all of them is that they are relatively complex and costly because generally a truck carrying a large water tank is needed to wet the surface with a defined water layer. Because of the limited amount of water they can carry they are limited in range. Besides that the measurement is depending on factors like water film thickness, temperature, measurement speed, rubber aging, rubber wear and even road evenness and curviness. All of these factors will affect the skid resistance and are difficult to control. We present a concept of contactless skid resistance measurement which is based on optical texture measurement and consists of two components： measurement of the pavement texture by means of an optical measufin~ system and calculation of the skid resistance based on the measured texture by means of a rubber friction model. The basic assumptions underlying the theoretical approach and the model itself based on the theory of Persson are presented. The concept is applied to a laboratory device called Wehner/Schulze （W/S） machine to prove the theoretical approach. The results are very promising. A strong indication could be provided that skid resistance could be measured without contact in the future.

Research on Online Texture Measurements in Metal Rolling Field

In rolled strip material,the orientation of the crystallites,known as texture,is influenced by various kinds of thermo-mechanical processes,such as casting,plastic deformation,annealing and phase transformation. The modern industry production requires stable product performance,real-time monitoring and full controlling of the quality.The online texture measurement in metal rolling can be used to real-time monitor the whole process, and then feedback control to the production process can be implied to adjust the process parameters to ensure the stability of the products.The principles,advantages and disadvantages of related detection methods(2D X-ray diffraction,neutron diffraction,laser-ultrasonics and electromagnetic acoustic transducers(EMAT)) and the possibility of online measurement are discussed.Finally,2D X-ray diffraction and laser-ultrasonics are employed on online texture measurement,and the schemes of online texture measurement are proposed.