Iron-Doped Titanium Dioxide Nanomaterials: Synthesis, Characterization and Photodegradation Catalytic Behavior

Titanium dioxide (TiO2) is a very good material for various photocatalytic industrial applications because of its non-toxicity, high chemical stability, low cost and relatively good photoactivity. However, one of the most serious challenges to its applicability is its wide band gap and because of that TiO2 absorbs mainly in the UV region of the solar spectrum, which corresponds to a small portion (<10%) of the sun's energy. In this thesis, doping of TiO2 is employed as a method to improve TiO2 optical properties by decreasing the band gap and enabling the material to absorb a larger fraction of the visible spectrum. A series of iron-doped titanium dioxide nanoparticles containing various percentages of iron was prepared and their chemical, structural, optical and electrochemical properties were characterized. These results confirm that the proposed materials were successfully prepared and that they indeed have smaller band gaps. Raman imaging was also employed to map the various phases present in our samples and to identify surface functionalities on the materials and their accessibility to binding especially with dyes, such as N3 and Z907 dye, for the first time. The results shows the coexistence of phases in TiO2 as well as adsorption pattern of the dyes on the surface of the TiO2. Finally, The photodegradation of methylene blue has been studied to quantify the photocatalytic activity of all prepared iron-doped TiO2 and pure TiO2 photocatalysts under simulated sunlight. The measurements are performed at two pH values and the different mechanism observed can be explained in terms of changes in the materials potential of zero charge (PZC) and how surface charge affects the dye adsorption. Using the Langmuir-Hinshelwood model, rate constants (kobs) decreasing with an increase in the molar percentage of iron in TiO2 as well as a decrease in the materials band gap. This trend is opposite to what was expected and it could be due to a significant increase in the charge recombination rate when the band gap is reduced, meaning that less charge is available to participate in the photodegradation process

Climate Change and Eutrophication: A Short Review

Water resources are vital not only for human beings but essentially all ecosystems. Human health is at risk if clean drinking water becomes contaminated. Water is also essential for agriculture, manufacturing, energy production and other diverse uses. Therefore, a changing climate and its potential effects put more pressure on water resources. Climate change may cause increased water demand as a result of rising temperatures and evaporation while decreasing water availability. On the other hand, extreme events as a result of climate change can increase surface runoff and flooding, deteriorating water quality as well. One effect is water eutrophication, which occurs when high concentrations of nutrients, such as nitrogen and phosphorus, are present in the water. Nutrients come from different sources including agriculture, wastewater, stormwater, and fossil fuel combustion. Algal blooms can cause many problems, such as deoxygenation and water toxicity, ultimately disrupting normal ecosystem functioning. In this paper, we investigate the potential impacts of climatic factors affecting water eutrophication, how these factors are projected to change in the future, and what their projected potential impacts will be

A Muscle Model Based on Feldman's Lambda Model: 3D Finite Element Implementation

This paper presents the introduction of Feldman's muscle model in a three dimensional continuum finite element model of the human face. This model is compared to the classical Hill-type muscle modelComment: CMBBE'2013, Salt Lake City : United States (2013

Nonparametric Density Estimation Using Partially Rank-Ordered Set Samples With Application in Estimating the Distribution of Wheat Yield

We study nonparametric estimation of an unknown density function $f$ based on the ranked-based observations obtained from a partially rank-ordered set (PROS) sampling design. PROS sampling design has many applications in environmental, ecological and medical studies where the exact measurement of the variable of interest is costly but a small number of sampling units can be ordered with respect to the variable of interest by any means other than actual measurements and this can be done at low cost. PROS observations involve independent order statistics which are not identically distributed and most of the commonly used nonparametric techniques are not directly applicable to them. We first develop kernel density estimates of $f$ based on an imperfect PROS sampling procedure and study its theoretical properties. Then, we consider the problem when the underlying distribution is assumed to be symmetric and introduce some plug-in kernel density estimators of $f$. We use an EM type algorithm to estimate misplacement probabilities associated with an imperfect PROS design. Finally, we expand on various numerical illustrations of our results via several simulation studies and a case study to estimate the distribution of wheat yield using the total acreage of land which is planted in wheat as an easily obtained auxiliary information. Our results show that the PROS density estimate performs better than its SRS and RSS counterparts.Comment: 23 pages, 3 figures, 4 table

Flat Indentation of Filled and Unfilled PDMS

Recently, Polydimethylsiloxane (PDMS) has attracted much attention as a useful polymer in various fields due to its excellent properties. On the contrary poor mechanical properties are the major drawbacks of PDMS which has led to many researches to overcome this deficiency. One way to enhance the mechanical properties and broaden the applications is preparation of nanocomposite of PDMS and clay along with probing the mechanical properties. Among the mechanical characterization methods, indentation technique is known as a useful method to examine the local mechanical properties of PDMS and PDMS-clay nanocomposites. In this study, flat indentation test is carried out on bulk PDMS and PDMS-clay nanocomposites. Validity of the Sneddon’s theory proposed for flat cylindrical indenter is approved in terms of both elastic deformations under the flat tip and indentation load- displacement behavior for filled and unfilled PDMS. Moreover effect of clay and cross­ linker amount on the stress fields and indentation load-displacement curves is discussed. Stress distributions along radial distance by finite element analysis (FEA) are examined to investigate the reason of radial crack initiation during indentation test. Indentation test of thin films of PDMS and PDMS-clay filled nanocomposite adhering to the rigid substrate was also conducted. Distribution of the radial and shear stresses near the interface regime is examined by FEA to assess the validity of Dehm et al.’s model. The result showed a good agreement with Dehm’s model which was used to compute the critical interfacial shear strength leading failure in the interface of thin film and substrate

Identification of Critical Source Areas (CSAs) and Evaluation of Best Management Practices (BMPs) in Controlling Eutrophication in the Dez River Basin

Best Management Practices (BMPs) are commonly used to control pollution in the river basins. Prioritization of BMPs helps improve the efficiency and effectiveness of pollution reduction, especially in Critical Source Areas (CSAs) that produce the highest pollution loads. Recently, the Dez River in Khuzestan, Iran, has become highly eutrophic from the overuse of fertilizers and pesticides. In this basin, dry and irrigated farming produce 77.34% and 6.3% of the Total Nitrogen (TN) load, and 83.56% and 4.3% of the Total Phosphorus (TP) load, respectively. In addition, residential, pasture, and forest land uses together account for 16.36% of the TN and 12.14% of the TP load in this area. The Soil and Water Assessment Tool (SWAT) was implemented to model the Dez River basin and evaluate the applicability of several BMPs, including point source elimination, filter strips, livestock grazing, and river channel management, in reducing the entry of pollution loads to the river. Sensitivity analysis and calibration/validation of the model was performed using the SUFI-2 algorithm in the SWAT Calibration Uncertainties Program (SWAT-CUP). The CSAs were identified using individual (sediment, TN, TP) and combined indices, based on the amount of pollution produced. Among the BMPs implemented, the 10 m filter strip was most effective in reducing TN load (42.61%), and TP load (39.57%)