Water leakage problems at the Tangab Dam Reservoir (SW Iran), case study of the complexities of dams on karst

Bulletin of Engineering Geology and the Environment - The Tangab Dam was constructed at a unique geological structure, within a karst valley at the deepest point of a saddle-shaped feature which...     

Antioxidants and antiradicals in almond hull and shell (Amygdalus communis L.) as a function of genotype

To compare the antioxidant and antiradical activity of Amygdalus communis L. hulls and shells phenolic extracts in different genotypes, 18 A. communis L. genotypes were selected from those in Qooshchi, Qalgachi, Qovarchin Qale, Najaf Abad, Jamal Abad, Kahriz, Sfahlan of West and East Azerbayjan provinces of Iran in 2007. The fruits of these almonds were collected, their hulls and shells dried, ground and then methanolic extracts prepared from these hulls and shells. Total phenolic content was determined using the Folin–Ciocalteu (F–C) method. The extracts’ reducing power and scavenging capacity for radical nitrite, hydrogen peroxide and superoxide were evaluated. Significant differences were found in phenolic content of hulls and shells among various genotypes, radical scavenging capacity percentage varied significantly among genotypes and their hulls and shells. S₃-7 genotype with the highest phenolic content and antioxidant activity in its hulls represents a valuable genotype for procuring antioxidant phenolic compounds.     

Silicon nano-crystalline structures fabricated by a sequential plasma hydrogenation and annealing technique

Silicon nano-crystalline structures have been prepared from amorphous silicon films on silicon substrates using direct-current plasma hydrogenation and annealing at temperatures about 450 °C. Plasma power densities about 5.5 W/cm² were found to be suitable for the creation of nano-porous layers. The nano-porous structures produced visible luminescence at room temperature as confirmed by photoluminescence spectroscopy. The effects of plasma power and annealing temperature on the grain size and luminescence properties of these layers have been investigated by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and photoluminescence. Lowering the temperature during the hydrogenation step led to an increase in the diameter of the grains. In addition, lowering the plasma power density caused the distribution of the porous surface structures to become less widely distributed and the formation of more packed structures resulted.     

Nanofluids thermal conductivity prediction applying a novel hybrid data-driven model validated using Monte Carlo-based sensitivity analysis

Accurate estimation of the thermal conductivity of nanofluids plays a key role in industrial heat transfer applications. Currently available experimental and empirical relationships can be used to estimate thermal conductivity. However, since the environmental conditions and properties of the nanofluids constituents are not considered these models cannot provide the expected accuracy and reliability for researchers. In this research, a robust hybrid artificial intelligence model was developed to accurately predict wide variety of relative thermal conductivity of nanofluids. In the new approach, the improved simulated annealing (ISA) was used to optimize the parameters of the least-squares support vector machine (LSSVM-ISA). The predictive model was developed using a data bank, consist of 1800 experimental data points for nanofluids from 32 references. The volume fraction, average size and thermal conductivity of nanoparticles, temperature and thermal conductivity of base fluid were selected as influent parameters and relative thermal conductivity was chosen as the output variable. In addition, the obtained results from the LSSVM-ISA were compared with the results of the radial basis function neural network (RBF-NN), K-nearest neighbors (KNN), and various existing experimental correlations models. The statistical analysis shows that the performance of the proposed hybrid predictor model for testing stage (R = 0.993, RMSE = 0.0207) is more reliable and efficient than those of the RBF-NN (R = 0.970, RMSE = 0.0416 W/m K), KNN (R = 0.931, RMSE = 0.068 W/m K) and all of the existing empirical correlations for estimating thermal conductivity of wide variety types of nanofluids. Finally, robustness and convergence analysis were conducted to evaluate the model reliability. A comprehensive sensitivity analysis using Monte Carlo simulation was carried out to identify the most significant variables of the developed models affecting the thermal conductivity predictions of nanofluids.

     

The importance of almond (Prunus amygdalus L.) and its by-products

Almond fruit consists of three or correctly four portions: kernel or meat, middle shell, outer green shell cover or almond hull and a thin leathery layer known as brown skin of meat or seedcoat. The nutritional importance of almond fruit is related to its kernel. Other parts of fruit such as shells and hulls were used as livestock feed and burned as fuel. In the past decades, different phenolic compounds were characterised and identified in almond seed extract and its skin, shell and hull as almond by-products. In addition, polyphenols are abundant micronutrients in the human diet, and evidence for their role in the prevention of degenerative diseases such as cancer and cardiovascular diseases is emerging. The health effects of polyphenols depend on the amount consumed and on their bioavailability. In this contribution, various phenolic compounds present in almond and its by-products, their antioxidant properties and potential use as natural dietary antioxidant, as well as their other beneficial compounds and applications are reviewed.     

Stability of blueberry (Cornus mas – Yulyush) anthocyanin pigment under pH and co-pigment treatments

In this study, the effects of different pH values and co-pigments, including tannic, caffeic, benzoic, and coumaric acids, in various concentrations on anthocyanin co-pigment complexes (ratio 1:1) were investigated. The anthocyanin was extracted from a round sweet variety of blueberry and subjected to the highest co-pigment concentration (960 mg/l) at different pH values. The results showed that caffeic acid produced the highest stability of anthocyanin compared to the other co-pigments. In addition, benzoic acid had the lowest hyperchromic and bathochromic changes. A positive correlation was found between the co-pigment concentrations and the stability of anthocyanin as well as hyperchromic and bathochromic changes. The results also demonstrated that higher pH values resulted in further destruction of anthocyanin. Furthermore, the absorption rate of anthocyanin in the anthocyanin–co-pigment complex within lower pH values was more compared with the higher ones. The strongest hyperchromic and bathochromic effects for all organic acids were observed in pH values 1 and 4, respectively. It can be concluded that among the tested co-pigments, caffeic acid was the best co-pigment, while benzoic acid was the weakest, which was not suitable for anthocyanin in the round sweet variety of blueberry.     

DEM simulations of stiff and soft materials with crushable particles: an application of expanded perlite as a soft granular material

The mechanical behavior of granular materials is largely affected by particle breakage. Physical and mechanical properties of granular materials, such as grain size distribution, deviatoric and volumetric behavior, compressibility and mobilized friction angle are affected by particle crushing. This paper focuses on the evolution of the above mentioned characteristics using the Discrete Element Method (DEM). Behaviors of stiff and soft materials are studied using well established crushing criteria. Results from simulations indicate that stiff materials, have a typical fractal distribution of particle size, which is dominant when confining pressure increases. The fractal characteristic parameter of grain size effect is discussed. Evolution of shear stresses and volumetric strains during shearing are also predicted and analyzed. Expanded perlite, selected as a soft material, is investigated in terms of shear and volumetric behavior. For perlite, triaxial compression tests and corresponding DEM simulations are also performed. Results show good agreement between experiments and simulations and support the fact that the DEM can be considered as a useful tool to predict the behavior of crushable granular materials.     

Antiradical activity of different parts of Walnut (Juglans regia L.) fruit as a function of genotype

The objective of this work was to analyse phenolic compounds and antiradical capacity of different parts of walnut fruit among six genotypes of Juglans regia L. Therefore, total phenolic and flavonoid content were determined and methanolic extracts of walnut genotypes were considered by the reducing power, DPPH (2,2-diphenyl-1-picrylhydrazyl), superoxide anion and nitric oxide radical scavenging. Significant differences were found in phenolic content and radical scavenging capacity of different parts of fruits and among various genotypes. High correlation coefficient (R² = 0.81) was observed between phenol content and radical scavenging activity, but this was not always true (R² = 0.01). These results demonstrated that walnut genotypes have different phenolic compounds and phenolic compounds have different radical scavenging power. The differences of phenolic compounds were confirmed by using high performance liquid chromatography (HPLC).     

The Preparation of Nanocrystalline Silicon by Plasma-Enhanced Hydrogenation for the Fabrication of Light-Emitting Diodes

The fabrication of nanocrystalline silicon light-emitting diodes is reported using a novel plasma-enhanced hydrogenation method. The fabrication process consisted of the deposition of amorphous silicon on a silicon substrate, a hydrogen plasma treatment, and subsequent annealing, and the deposition of TiO₂, indium-tin oxide, and metal contact layers. The entire process was performed at temperatures below 400 degC and is compatible with standard silicon fabrication technologies. The current-voltage (I-V) characteristics of the device showed a rectifying diode behavior where electrons tunneled through the thin TiO₂ layer and recombined with the holes injected from the P-type silicon substrate leading to photon generation. The structure of the nanocrystalline silicon films was investigated by scanning electron and transmission electron microscopies, and the spectral distribution of the emitted light was measured by a cathodoluminescence     

Multiresolution image motion detection and displacement estimation

A motion vision system is developed in which a moving object can be detected and image displacement can be estimated based on human visual characteristics and use of a multiresolution image. The system consists of four parts: (1) Temporal gradient, logic AND, and dynamic thresholding operations are used to obtain the primary mask. (2) A region growing algorithm is applied. (3) A hierarchical object detection algorithm is used to identify image patterns. (4) Displacement of the image is estimated by breaking each frame of the motion sequence into local regions (edges). A search is undertaken to discover how the image pattern within a given region appears displaced. This search takes the form of motion channels, the output of which are used to obtain the estimation of displacement. A correlative measure is proposed to match the patterns.