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As crucial as it is to monitor the water quality in the reservoirs, constant measurement of different water quality indices can become a serious challenge. One way to alleviate this predicament is to create accurate numerical models and yet, the modeling process itself can have various problems that need to be addressed effectively. One major problem regarding water quality modeling is the high number of parameters and the uncertainty accompanying them. Eutrophication, being a significant water quality issue in the water reservoirs, is no exception and is related to a multitude of parameters. This paper presents an uncertainty-based auto-calibrated two-dimensional water quality and hydrodynamic (CE-QUAL-W2) model which was developed to simulate the eutrophication phenomenon in the Karkheh Reservoir in Iran. Automatic calibration of the CE-QUAL-W2 model using the Sequential Uncertainty Conformity Algorithm (SUFI-2) resulted in 11, 12.8, 10, 14.7, and 37.5 percent lower root mean square error (RMSE) for dissolved oxygen, total phosphorus, NH4, NO3-NO2, and Chlorophyll-a, respectively, compared to the results obtained by the particle swarm optimization (PSO). Furthermore, 76 percent of the measured data were in a 95 percent confidence interval as a result of calibration with the SUFI-2. In addition, the SUFI-2 algorithm outperformed the PSO algorithm within just 250 function evaluations, which was 20 times fewer than what was required by the PSO. Based on the results, it seems that the SUFI-2 algorithm can help the calibration process to achieve a more accurate and reliable model while decreasing the computational burden of the modeling process. [ABSTRACT FROM AUTHOR]

A combination of experimental and analytical methods was used to study the possible occurrence of liquation during LFW of the newly developed AD730 Ni-based superalloy. LFWed joints were produced using a semi-industrial size facility and the interfaces of the joints as well as the ejected flash were examined using optical and Field Emission Gun Scanning Electron Microscopy (FEG-SEM). Physical simulation of the LFW thermal cycle, using thermomechanical simulator Gleeble™ 3800, showed that incipient melting started from 1473 K (1200 °C). The analytical model, calibrated by experiments, predicted that the highest temperature of the interface was about 1523 K (1250 °C). The constitutive equations based on lattice and pipe diffusion models were developed to quantify the self-diffusivity of the elements and control the extent of liquation by considering the effect of LFW process parameters. Analytical results show that the application of compressive stresses during LFW results in 25 times increase in the diffusion of Ni atoms at the weld interface. Therefore, no presence of re-solidified phases, i.e., occurrence of liquation, was observed in the microstructure of the weld zone or the flash in the present study. Based on the obtained results, a methodology was developed for designing the optimum pressure above which no liquation, and hence cracking, will be observable. [ABSTRACT FROM AUTHOR]

An experimental study of wear characteristics of electroless Ni-10% P coating sliding against hard AISI 52100 steel pin is investigated. Experiments are carried out at room and 550°C temperatures. Heat treatment effects on tribological behavior of this coating are studied. The wear surface and the microstructure of the coatings are analyzed using optical microscopy, scanning electron microscopy, energy dispersion analysis X-ray, and microhardness testing equipment. It is observed that the forming of continuous oxide film on contacting surfaces of pin and disk improves wear resistance and decreases friction coefficient of the Ni-10% P coating. The results indicate that the wear resistance of electroless Ni-10% P coating has improved with heat treatment at room temperature wear test, but it reverses in the wear test at 550°C. In addition, specimens without heat treatment have the highest wear resistance and the lowest friction for wear tests at elevated temperatures. [ABSTRACT FROM AUTHOR]

The Sar Cheshmeh porphyry copper deposit is located in the Central Iranian Volcanic-Sedimentary Belt (CIVSB). The hydrothermal alteration zones are well developed within and around the porphyry stock. Given the poor soil and vegetation cover in this area, we evaluated the usefulness of multispectral remote sensing data derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Enhanced Thematic Mapper Plus (ETM+) images and airborne magnetic-radiometric data for hydrothermal alteration mapping at a local scale. Principal component analysis (PCA), band ratios and the spectral angle mapper (SAM) technique were applied to the multispectral data sets to map hydrothermally altered rocks. PCA and band ratios were also applied to the airborne geophysical data. The overall results showed that the multispectral remote sensing data sets resulted in more accurate hydrothermal alteration mapping and lithological discrimination in the study area as compared with the airborne geophysical data. The radiometric data are also useful in enhancing areas with potassic alteration. [ABSTRACT FROM AUTHOR]

In this paper, a new entropy-based approach is developed for assessing the location of salinity monitoring stations in the Tehran Aquifer, Tehran, Iran. To find the optimal distance among stations, the measure of Transinformation in the Entropy Theory is used. Then a Transinformation-Distance (T-D) curve is developed and used in a multi-objective GA-based optimization model, which provides the best locations for monitoring stations. Because of the large area of the Tehran aquifer and significant spatial variations of the Electrical Conductivity (EC) of the groundwater in the study area, the C-means clustering method is used to classify the study area to some homogenous zones. The optimization model is applied to each zone to find the optimal location of monitoring stations. The results show the applicability and the efficiency of the model in assessing the groundwater monitoring systems. [ABSTRACT FROM AUTHOR]