Automatic Determination of Number of Homogenous Regions in SAR Images Utilizing Splitting and Merging Based on a Reversible Jump MCMC Algorithm

This paper presents an algorithm dealing with initial segmentation of speckled Synthetic Aperture Radar (SAR) intensity images in order to automatically determine the number of homogeneous regions. Taking this problem into account, segmentation procedure utilizing splitting and merging is designed, iteratively. The proposed approach is based upon Bayesian inference, a maximum likelihood gamma distribution parameter estimator, and a Reversible Jump Markov Chain Monte Carlo (RJMCMC) algorithm. By using of image splitting operation, SAR image is partitioned into finite regions iteratively, until all individual regions are coherent. Then each region is assigned a unique label to indicate the class to which the homogeneous region belongs. The intensities of pixels in each coherent region are assumed to satisfy identical and independent gamma distribution. Then an RJMCMC scheme is designed to simulate the posterior distribution in order to estimate the number of components and delineate an initial segmentation. Thus, the main purpose of this research is to define the number of homogeneous regions rather than a perfect segmentation, i.e. model outputs can be served for unsupervised segmentation methodologies as prior information. The results obtained from Radarsat-1/2 of SAR intensity images show that the proposed algorithm is both capable and reliable in defining the accurate number of homogeneous regions in a wide variety of SAR intensity images, comprising a high level of speckle noise.     

Closure to ＂Discussion on ＇Optimum placement and characteristics of velocity-dependent dampers under seismic excitation＇ by SA Mousavi and AK Ghorbani-Tanha＂ by Izuru Takewaki

The authors would like to thank the discusser for his considerations and comments. The discusser believes that some of the derived formulations need to be referred to his previously published works and also some related studies have not been cited.     

Suspended load estimation using L1-fuzzy regression,L2-fuzzy regression and MARS-fuzzy regression models

ABSTRACT

The problem of estimation of suspended load carried by a river is an important topic for many water resources projects. Conventional estimation methods are based on the assumption of exact observations. In practice, however, a major source of natural uncertainty is due to imprecise measurements and/or imprecise relationships between variables. In this paper, using the Multivariate Adaptive Regression Splines (MARS) technique, a novel fuzzy regression model for imprecise response and crisp explanatory variables is presented. The investigated fuzzy regression model is applied to forecast suspended load by discharge based on two real-world datasets. The accuracy of the proposed method is compared with two well-known parametric fuzzy regression models, namely, the fuzzy least-absolutes model and the fuzzy least-squares model. The comparison results reveal that the MARS-fuzzy regression model performs better than the other models in suspended load estimation for the particular datasets. This comparison is done based on four goodness-of-fit criteria: the criterion based on similarity measure, the criterion based on absolute errors and the two objective functions of the fuzzy least-absolutes model and the fuzzy least-squares model. The proposed model is general and can be used for modelling natural phenomena whose available observations are reported as imprecise rather than crisp.

Editor D. Koutsoyiannis; Associate editor H. Aksoy     

The distribution of Spearman’s rho trend statistic for persistent hydrologic data

Abstract

Spearman’s rho, a distribution-free statistic, has been suggested in the literature for testing the significance of trend in time series data. Although the use of the test based on Spearman’s rho (also known as the Daniels test) is less widespread than that based on Kendall’s tau (the Mann-Kendall test), the two tests have been shown in the literature to be equivalent for time series with independent observations. The distribution of the Mann-Kendall trend statistic for persistent data has been previously addressed in the literature. In this paper, the distribution of Spearman’s rho as a trend test statistic for persistent data is studied. Following the same procedures used for Kendall’s tau in earlier work, an exact expression for the variance of Spearman’s rho for persistent data with multivariate Gaussian dependence is derived, and a method for calculating the exact full distribution of rho for small sample sizes is also outlined. Approximations for moderate and large sample sizes are also discussed. A case study of testing the significance of trends in a group of world river flow station data using both Kendall’s tau and Spearman’s rho is presented. Both the theoretical results and those of the case study confirm the equivalence of trend testing based on Spearman’s rho and Kendall’s tau for persistent hydrologic data.

Editor Z. W. Kundzewicz; Associate editor S. Grimaldi     

Removal of the Alphazurine FG Dye from Simulated Solution by Electrocoagulation

The removal of Alphazurine FG (AF) dye from water by an electrocoagulation process has been studied. The effect of some operational parameters, such as anode material, current density, initial dye concentration, pH of solution, conductivity, and inter‐electrode distance, on the removal efficiency was investigated. Iron and aluminum were used as anodes in the electrocoagulation cell. It was found that the efficiency of the iron anode was better than that of the aluminum anode for AF removal. The factors that affected the removal efficiency were the current density and the initial dye concentration. The removal efficiency increased from about 35% at 25 A m^–2 to about 97% at 100 A m^–2, during 4 min of electrocoagulation. The results exhibited pseudo‐first‐order kinetics for AF removal by electrocoagulation. In addition, a mathematical model was successfully established for predicting the removal efficiency. A comparison between the model results and experimental data gave a high correlation coefficient (R² = 0.9925), which indicates that the model is able to predict the removal efficiency of AF.     

Spatial distribution and biodiversity of macrofauna in the southeast of the Caspian Sea, Gorgan Bay in relation to environmental conditions

Spatial distribution and biodiversity of macrofauna in the Gorgan Bay, southeast of the Caspian Sea, were studied at fifteen stations in June 2010. Also, depth, temperature, salinity, dissolved oxygen, total organic matter content and sediment particle size were measured in each station. A total 3,356 individuals belonged to eight families and ten species were identified. Polychaeta were numerically dominated groups and Streblospio gynobranchiata, was constant and dominant species with 60.28% of total individuals but Bivalvia with four species had highest species number, though the density of them were low. The maximum density (4,500 ind/m²) was obtained at station 1 while the minimum (411 ind/m²) was observed at station 6. There was not significant correlation between the density of macrofauna with all environmental conditions. In total, six feeding group were considered but surface deposit feeder and deposit feeder were dominant in all stations. The maximum mean species number, diversity, richness, and evenness were obtained, 6.33, 1.46, 1.38 and 0.87, respectively. Based on the M-AMBI and the AMBI classification it seems that bentic environment in Gorgan Bay was not bad but the results of Shannon-Wiener, Margalef and Simpson indices the results were vice versa. In general, the values of the mentioned indices decreased from the western to the eastern part of the bay. Furthermore, the nonmetric multidimensional scaling (nMDS) showed that the structure of the macrofaunal assemblages was divides to six groups.     

伊朗锡斯坦地区沙漠灾害区划(英文)

Desertification process as a great problem affects most of the countries in the world.This process has a high rate in arid and semiarid areas.Today,human societies are encountering the desertification phenomenon as a serious problem which causes various irreparable damages to economic and social sectors.In order to assess desertification results in production of different regional models for their application in another region the indices should be re-investigated and adjusted to local conditions.Several models have been developed for desertification evaluation.The present study,attempts to assess quantitatively the desertification process has in an area located at Sistan plain of Iran(Niatak region as a case study) by using Modified MEDALUS method.The obtained results indicated that of the whole studied region(comprising 4819.6 acres),2651.56 acres(55%) are located in medium desertification intensity class,1269.48 acres(26.34%) are positioned in severe desertification intensity class,and 898.54 acres(18.64%) are placed in vary severe desertification intensity class.     

Development and experimental evaluation of a passive gap damper device to prevent pounding in base‐isolated structures

Studies have shown the effectiveness of providing supplemental energy dissipation in base‐isolated structures to reduce displacements at the isolation level. A previous analytical study demonstrated the benefits of providing this energy dissipation at a specified gap larger than the design displacement. The gap before engagement allows the base isolation system to meet performance criteria in varying levels of ground excitation. Use of this ‘gap damper’ device eliminates undesirable effects often exhibited with large amounts of supplemental damping at lower intensity motions. Using results from an analytical study, the primary purpose of this research was to develop devices for practical implementation. Development of the devices demanded simplicity, feasibility, economy, and reliability to be an effective option in building design and construction. Multiple designs were proposed, and a final design was chosen based on selection criteria and finite element analyses. The device was designed and tested in Auburn University's Structural Research Lab. Experimental results were compared with theoretical models to verify behavior and make necessary adjustments for a shake table experiment. The design parameters were selected to accommodate re‐use of the device for the shake table test. Copyright © 2015 John Wiley & Sons, Ltd.