The early detection of melanoma is one of the greatest challenges in clinical practice of dermatology, and the reticular pattern is one of the most important dermoscopic structures to improve melanocytic lesion diagnosis. A texture-based approach is developed for the automatic detection of reticular patterns, whose output will assist clinical decision-making. Feature selection was based on the use of two algorithms by means of the classical graylevel co-occurrence matrix and Laws energy masks optimized on a set of 104 dermoscopy images. The AdaBoost (adaptive boosting) approach to machine learning was used within this strategy. Results suggest superiority of LEM for reticular pattern detection in dermoscopic images, achieving a sensitivity of 90.16% and a specificity of 86.67%. The use of automatic classification in dermoscopy to support clinicians is a strong tool to assist diagnosis; however, the use of automatic classification as a complementary tool in clinical routine requires algorithms with high levels of sensitivity and specificity. The results presented in this work will contribute to achieving this goal.
The frequency response of SAM-APD devices is calculated from the response of each layer using matrix algebra. Most of the results apply to devices with absorption region of InGaAs and avalanche region of InP and they assume uniform carrier ionization coefficients and velocities. The effect of the width of each layer, carrier ionization ratio and velocities on the multilayer structure frequency response has been investigated. A change of the absorption region width changes the 3-dB bandwidth at low avalanche gains whereas a change in the avalanche region width only affects the frequency response at high avalanche gains. When the ionization ratio decreases an increase of the 3-dB bandwidth is observed at high avalanche gains. The frequency response seems to be very sensitive to the carrier velocities mainly the hole velocity. In order to include the strong dependence of the ionization coefficients on the electrical field, the avalanche region was modeled piecewise uniform by breaking it into three layers. The frequency response of this structure is seen to be similar to the one obtained when uniform ionization coefficients are considered assuming they are assigned the mean value of the corresponding ionization coefficients in the three layers.
The SAIL model, a canopy reflectance model, was used to simulate narrow-band reflectance of overstory/background compositions to study the effect of the background on the estimation of the coniferous forest LAI based on remotely sensed data. We have simulated several mixed targets with a pine tree canopy and different backgrounds, including understory vegetation, soil and litter. For each type of mixed target we have modelled the reflectance for several LAI. The modeled data were used to evaluate the performance of the broad and narrow band NDVI for predicting the LAI. Results show that, for low LAI, the type of background contributes strongly to the reflectance of the mixed targets. Furthermore, the way the understory affects the mixed signal depends significantly on the vegetation species. The sensitivity of the NDVI for estimating the pine canopy LAI depends on the type of background and it was verified that mixed targets with non-vegetation backgrounds have larger sensitivity than the ones with vegetative backgrounds. The results show that the NDVI, calculated with broad or narrow bands, is not adequate to predict the LAI of open pine stands, when one does not known the type of background that is underneath the pine canopy.
a-SixGe1-x (x equals 0.70) thin films were deposited by RF- sputtering at a constant substrate temperature of 200 degree(s)C. By adding oxygen or ammonia to the sputtering atmosphere, amorphous films containing oxygen or nitrogen could be obtained. The incorporation of these elements was ascertained by IR spectroscopy which revealed the characteristic features of oxygen and nitrogen bonded to silicon. The IR spectra also showed that hydrogen incorporation has been achieved for the films prepared with ammonia. The increase of oxygen and nitrogen content shifts the peak position of the corresponding main absorption bands towards higher energies. The absorption edge and the optical gap are strongly dependent on oxygen and nitrogen incorporation. The increase of oxygen and nitrogen content increases the optical gap. The room temperature DC conductivity decreases by several orders of magnitude with oxygen and nitrogen incorporation and reflects the widening of the optical gap.
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