In boundary zones (edges) in synthetic apertue radar (SAR) images, there is no logical (scientific) explanation for employing the kernel average for approximating the backscattering factors in ...central kernel pixels. Therefore, adaptive filters are used to decrease the speckles in these images. These filters prevent the averaging process in the edges when smoothing the images (noise reduction) in homogeneous areas, thus causing reduction of lucidity in the edges. In most existing adaptive filters, the variation coefficient (coefficient of variation) is used to detect the edges in the images. An alternative factor is introduced to detect the edges in intensity images; by employing this factor, an adaptive filter is presented. The results of evaluating this filter and comparing it with other adaptive filters illustrate that it has excellent competency in speckle reduction, and hence it protects the edges of the images during the filtering process. using various assessment measures (such as signal-to-noise ratio and mean absolute error), the obtained results provide evidence that the proposed filtering process outperforms other classical methodologies.
SPECKLE REDUCTION IN SAR IMAGES USING A BAYESIAN MULTISCALE APPROACH Zakeri, F.; Saradjian, M. R.; Sahebi, M. R.
International archives of the photogrammetry, remote sensing and spatial information sciences.,
10/2019, Letnik:
XLII-4/W18
Journal Article, Conference Proceeding
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Synthetic aperture radar (SAR) images are corrupted by speckles, which influence the interpretation of the images. Therefore, to reduce speckles and obtain reliable information from images, ...researchers studied different methods. This study proposes a Bayesian multiscale method, to reduce speckles in SAR images. First, it was shown that Laplacian probability density function can capture the characteristics of noise-free curvelet coefficients, and then, a maximum a posteriori (MAP) estimator was designed for estimating them. Comparison of the results obtained with those obtained from conventional speckle filters, such as Lee, Kuan, Frost, and Gamma filters, and also curvelet non-Bayesian despeckling, shows better achievement of the proposed algorithm. For instance, the improvement in different parameters is as follows: ‘noise mean value’ (NMV) 0.24 times, ‘noise standard deviation’ (NSD) 0.34 times, ‘mean square difference’ (MSD) 2.6 times and ‘equivalent number of looks’ (ENL) 0.61 times.
The radar signal recorded by earth observation (EO) satellites is sensitive to soil moisture and surface roughness, which both influence the onset of runoff. This paper focuses on inversion of these ...parameters using a multi-angular approach based on RADARSAT-1 data with incidence angles of 35° and 47° (in mode S3 and S7). This inversion was performed with three backscatter models: Geometrical Optics Model (GOM), Oh Model (OM), and Modified Dubois Model (MDM), which were compared to obtain the best configuration. Mean absolute errors of 1.23, 1.12, and 2.08 cm for roughness expressed in rms height and for dielectric constant, mean absolute errors of 2.46 – equal to 3.88 (m3 m−3) in volumetric soil moisture, – 4.95 – equal to 8.72 (m3 m−3) in volumetric soil moisture – and 3.31 – equal to 6.03 (m3 m−3) in volumetric soil moisture – were obtained for the MDM, GOM, and OM simulation, respectively. These results indicate that the MDM provided the most accurate data with minimum errors. Therefore, the latter inversion algorithm was applied to images, and the final results are presented in two different maps showing pixel and homogeneous zones for surface roughness and soil moisture.
•Experimental measurements of back pressure of a light duty diesel engine.•Study on the impact of substrate/cake soot mass on back pressure and regeneration.•Substrate wall is a most suitable bed for ...soot burning in high wall temperature.•Soot cake layer is an appropriate bed for soot burning in low substrate temperature.•Finding experimental costly parameters like required kinetic energy for soot burning.
In this study, the back pressure of Diesel Particulate Filter (DPF) during loading and regeneration phase is measured. Then, one dimensional approach has been implemented to model the exhaust emissions and back pressure of a DPF, focusing on the regeneration phenomenon. The simulation has been divided in three parts. In the first part, the model is validated with two types of experimental data. The first test has been done by the authors on a light duty diesel engine and the second one was conducted by Rothe et al. on a heavy duty diesel engine. In the next part, some parameters, which were costly to measure, are numerically obtained. In the last part, the effect of these parameters on exhaust emissions and back pressure during regeneration has been investigated. The results showed that the substrate/cake soot mass ratio has a strong effect on exhaust emissions, back pressure and improvement of the DPF regeneration efficiency. When this value increases from 0 to 1, the exhaust emissions (CO, CO2) increase by 94% and 95%, regeneration efficiency improves by 25% and back pressure dips to 22% respectively. It is found that the cake layer is a more efficient bed for soot burning in low substrate temperature and conversely the substrate wall is a most appropriate bed for soot burning at high temperature. Also, with an increasing in soot porosity from 0.56 to 0.96, the CO, CO2 emissions and regeneration efficiency, increase about 61%, 62% and 60% and the back pressure dips to 56% respectively.
The estimation of cultivation area and categorizing the agricultural product types is one of the prerequisites for achieving sustainable development in the agricultural studies. In this study, an ...unsupervised zoning the cultivation areas with the same cultivation pattern in Golestan province is on the agenda. Therefore, due to wide spatial range, high temporal resolution and easy access of 16-day products of the vegetation of the MODIS sensor which acquired in a year (From November 2017 to October 2018), these images are used in this research. In the proposed method, after the generating of NDVI vegetation time series as a hyper-cube and separating farmlands’ boundaries in Golestan province using the land-use map; the Sequential Maximum Angle Convex Cone (SMACC) endmember extraction algorithm and the maximum number of product variation using the statistical information of the region (Obtained from the statistics centre of Iran) are used to extract endmembers of the hyper-cube. In the following, the timing responses of the NDVI, identified as endmembers, will be refined in the second phase. In this process, identifying and eliminating noise signals (unrelated to cultivating patterns) and integrating the same cultivating patterns will be on the agenda. At the last stage of the proposed method and after refinement of the endmembers, the hyper-cube is clustered by Spectral Angle Mapper (SAM) algorithm and the mapping of regions with the same cultivation pattern is produced. In the proposed method, the zoning of agricultural land is based solely on the statistical knowledge of the variety of cultivation and the results have led to the production of interconnected spatial parts. This is consistent with the reality of the spatial occurrence of similar cultivating patterns in a geographic area. On the other hand, the visual comparison of results with large scale satellite images illustrates that there is a significant relationship between clustering results and ground truth in terms of cultivating pattern. Obviously, such products can be used as initial layers of information to produce the results of a supervised classification with the aim of applying the cultivation area of a variety of agricultural products.
The increasing concentration of greenhouse gases in the atmosphere has been identified as contributing to the increase in global mean temperature. Carbon sequestration into trees and forests is an ...effective and inexpensive method for decreasing the CO 2 level in the atmosphere. Hence, accurate measurements of biomass levels will be important to the global carbon cycle and climate change. This study used a wavelet-based forest aboveground biomass (AGB) estimation approach in a temperate deciduous forest. Two-dimensional discrete wavelet transformations was applied to ALOS AVNIR and PALSAR to obtain wavelet coefficients, which were correlated with AGB estimates using multiple linear regression analysis. Different wavelets were tested using this approach. Moreover, vegetation indices and texture parameters were calculated and correlated with AGB estimates. The results indicated that wavelet-based modeling could improve the accuracy of biomass estimation to 75% or even higher in comparison with the accuracy of 30%-40% resulting from past studies using vegetation indices and texture measures. This study demonstrates that wavelet-based biomass estimation could be a promising approach for solving the uncertainty between reflectance or backscatter values from satellite images and forest biomass and therefore provide better biomass estimations.
This work presents a thermal and flow analysis of a fin shaped microchannel heat sink (MCHS) cooled by different nanofluids (Cu and Al2O3 in water) based on “saturated porous medium” and least square ...method then results are compared with numerical procedure. The Forchheimer–Brinkman-extended Darcy equation is used to describe the fluid flow and the two-equation model with thermal dispersion is utilized for heat transfer. The effect of nanoparticle size and volume fraction, volume flow rate, inertial force parameter and channel width investigated on total thermal resistance, friction factor and Nusselt number. The effective thermal conductivity and viscosity of nanofluid are calculated by KKL correlation. Central composite design (CCD) is applied to obtain the desirability of the optimum value of the nanofluid flow characteristics. Results show that Cu–water nanofluid is more lucrative thermally versus Al2O3–water nanofluid. It is found that total thermal resistance, friction factor and Nusselt number are not sensitive to inertial effect while they change significantly due to other parameters such as nanoparticle size and volume fraction, volume flow rate and channel width. We obtained that Nusselt number enhancement has direct relationship with inertial force parameter and volume flow rate.
•Numerical study is applied for the optimization of microchannels heat sink.•KKL base nanofluids are used for the modeling.•CCD optimization is considered for obtaining the best microchannel performance.
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We performed a retrospective analysis of the European Group for Blood and Marrow Transplantation database comparing the outcomes of multiple myeloma patients who received tandem autologous followed ...by allogeneic PSCT (auto-allo) with the outcomes of patients who underwent a reduced intensity conditioning allograft (early RIC) without prior autologous transplant. From 1996 to 2013, we identified a total of 690 patients: 517 patients were planned to receive auto-allo and 173 received an early RIC allograft without prior autologous transplant. With a median follow-up of 93 months, 5-year PFS survival was significantly better in the auto-allo group, 34% compared with 22% in the early RIC group (P<0.001). OS was also significantly improved in the auto-allo group with a 5-year rate of 59% vs 42% in the early RIC group (P=0.001). The non-relapse mortality rate was lower in the auto-allo group than in the early RIC group, with 1- and 3-year rates of 8% and 13% vs 20% and 28%, respectively (P<0.001). The relapse/progression rate was similar in the two groups, with 5-year rates of 50% for auto-allo and 46% for early RIC (P=0.42). These data suggest that planned tandem autologous allograft can improve overall survival compared with upfront RIC allograft alone in patients with multiple myeloma.
Land subsidence, due to natural or anthropogenic processes, causes significant costs in both economic and structural aspects. That part of subsidence observed most is the result of human activities, ...which relates to underground exploitation. Since the gradual surface deformation is a consequence of hydrocarbon reservoirs extraction, the process of displacement monitoring is amongst the petroleum industry priorities. Nowadays, Differential SAR Interferometry, in which satellite images are utilized for elevation change detection and analysis – in a millimetre scale, has proved to be a more real-time and cost-effective technology in contrast to the traditional surveying method. In this study, surface displacements in Aghajari oil field, i.e. one of the most industrious Iranian hydrocarbon sites, are being examined using radar observations. As in a number of interferograms, the production wells inspection reveals that surface deformation signals develop likely due to extraction in a period of several months. In other words, different subsidence or uplift rates and deformation styles occur locally depending on the geological conditions and excavation rates in place.
A new glacier inventory of Iran Moussavi, M.S.; Zoej, M.J. Valadan; Vaziri, F. ...
Annals of glaciology,
2009, Letnik:
50, Številka:
53
Journal Article
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A new glacier inventory of Iran, compiled according to GLIMS guidelines through the use of photogrammetry and remote sensing supported by fieldwork, provides the first comprehensive study of its ...mountain glaciers. The glaciers are found in five main areas: two in the higher elevations of the Alborz mountain range (Damavand and Takhte–Soleiman regions), two on the Zardkuh and Oshtorankuh mountain chain in the Zagros mountain range and one in the Sabalan Mountains in northwest Iran. Several important glacier attributes, including minimum and maximum height of ice, area and maximum length and width, together with glacier extent, were successfully extracted using aerial and satellite imagery. Thereafter a comprehensive glacier database was established in a GIS environment.
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