Trends,features, and tests of common and recently introduced global optimization methods

Global optimization techniques have been used extensively due to their capability in handling complex engineering problems. In addition to a number of well known global optimization techniques, many new methods have been introduced recently for various optimal design applications. In this work, a number of representative, well known and recently introduced global optimization techniques are closely examined and compared. The historical development, special features and trends on the development of global optimization algorithms are reviewed. Special attention is devoted to the recent developments of multidisciplinary design optimization algorithms based on effective metamodelling techniques. Commonly used benchmark optimization problems are used as test examples to reveal the pros and cons of these global optimization methods. A new meta-model based global optimization search method, introduced and improved recently by the authors, is also included in the tests and comparison.     

Simple analytical model and efficiency improvement of polysilicon solar cells with porous silicon at the backside

The present study developed a simple analytical model to simulate the performance of polysilicon solar cells with porous silicon (PS) layer at the backside. It analytically solved the complete set of equations necessary for the determination of the photocurrent generated under the effect of the reflected light. It also investigated the contribution of the light absorbed by the PS layer and explored the effect that the latter’s number of double porosities and high porosity have had on photovoltaic parameters. The findings suggest that the photovoltaic parameters increase with the number of double porosities that the layer might have in a given structure. When the PS layer is formed by three-double porosity layers 20%/80% and for a 5 μm-thick film c-Si, the backside reflector gives a total improvement of about 2.65 mA/cm² in photocurrent density and 1.4% in cell efficiency. This improvement can even be of much more important for well passivated grain boundaries and back contact of solar cells.     

Effect of tubes bundle electrode on removal of cadmium from simulated wastewaters by electrodeposition

BACKGROUND: The performance of a novel pilot scale, fixed bed flow‐through cell, consisting of a cathode formed by a bundle of stainless steel tubes having two tube arrangements (920 tubes of 0.6 cm outer diameter and 360 tubes of 1.0 cm outer diameter) was investigated for the removal of cadmium in a batch re‐circulation mode. The electrochemical reaction studied was the cathodic reduction of Cd⁺² using 0.5 mol L^?1 sodium sulphate as supporting electrolyte. The parameters analyzed were initial Cd⁺² concentrations and electrolyte flow rates. RESULTS: Experimental results for the two different tube arrangements showed that the mass transfer coefficients were higher for the 0.6 cm diameter tubes than for the 1.0 cm diameter tubes. The former gave a fractional conversion of 80.4% with a current efficiency of 70.75% compared with a fractional conversion of 58.5% with a current efficiency of 45.7%, for the 1.0 cm diameter tubes, for a Cd⁺² concentration of 200 ppm and flow rate of 250 L h^?1. These results were correlated to: for 5 < Re < 28 and Sc = 649, where Sh is the Sherwood number, Re the Reynolds number and Sc the Schmidt number. CONCLUSION: Experimental results, analysis, correlations and figures of merit showed better performance of the cell for the removal of Cd⁺² with 0.6 cm diameter tubes than with 1.0 cm diameter tubes. Copyright © 2010 Society of Chemical Industry     

Synthesis of fluorescence active pyridinedicarbonitriles and studying their application in functional paper

The present study deals with synthesis of novel 6-alkoxy-2-amino-3,5-pyridinedicarbonitrile derivatives, as a safety marker. The fluorescence properties of the synthesized heterocyclic compounds were determined. The fluorescence quantum yield (?_s) of these active compounds, relative to the fluorescence quantum yield of quinine sulfate, is reached at ~ 0.83. Application of representative synthesized examples on cotton linters and/or bagasse-based paper sheets was adopted in the present study, in an attempt to obtain safety paper from non-wood fibrous pulps. The quality of the obtained safety paper was evaluated based on both fluorescence impact and strength properties. The successful application of these fluorescent active compounds in the production of functionalized paper sheets, from bagasse pulp- cotton linter blend is demonstrated.     

The effect of varying autoclaving conditions and added sodium hydroxide on amino acid content and nitrogen characteristics of feather meal

The effects upon amino acid content and nitrogen characteristics of feather meal subjected to varying lengths of processing time (30 to 70 min) moisture content (50 to 70%) and added NaOH (0.2 to 0.6%) were studied by multiple regression techniques. All test products were autoclaved at constant pressure of 345 kPa. The results obtained showed that prolonged processing periods and increased concentrations of NaOH had a substantial effect on the amino acid contents and in particular on the essential ones. There was a marked degradation of cystine, and smaller losses of lysine and methionine. Most of the amino acid contents were lower in the meals with a higher moisture content. In vitro protein digestibility and solubility in alkali and acid, were generally increased by prolonged processing conditions. It was concluded that the inverse relationship between amino acid content and nitrogen characteristics should be taken into account for feather meal evaluation. Higher values for in vitro protein digestibility and solubility were considered to be favourable unless other structural modifications to the protein affect its nutritional value.     

Multivariate Data Analysis of Fatty Acid Content in the Classification of Olive Oils Developed Through Controlled Crossbreeding

The fatty acid (FA) composition of 540 Tunisian virgin olive oil hybrids (VOO) were classified by principal component analysis (PCA). Pearson correlation between FA variables revealed an inverse association between C18:1 and C18:2; C18:1 and C16:0, while C16:0 and C16:1 were positively correlated. PCA yielded five significant PCs, which together account for 79.95% of the total variance; with PC1 contributing 36.84% of the total. Eigenvalue analysis revealed that PC1 was mainly attributed to C18:1, monounsaturated fatty acids (MUFA) and the ratios oleic/linoleic (O/L) and monounsaturated fatty acids/polyunsaturated fatty acids (MUFA/PUFA); PC2, by C16:0, saturated fatty acids (SFA) and the palmitic/linoleic ratio (P/L); PC3 by C18:2 and C22:0, PC4 by C18:0 and PC5, by C17:1. Then, PCA analysis indicated that in addition to C16:0, C18:0, C18:1, C17:1, and C22:0, MUFA, SFA and the ratios O/L, P/L and MUFA/PUFA were determined to be the main factors responsible for the olive oil hybrids discrimination.     

Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate

Decommissioning of old nuclear reactors may produce waste streams containing chlorides and carbonates, including radioactive ³⁶Cl^? and ¹⁴CO₃^2?. Their insolubilization by calcium monosulfoaluminate hydrate was investigated. Carbonates were readily depleted from the solution, giving at thermodynamic equilibrium monocarboaluminate, monocarboaluminate + calcite, or calcite only, depending on the initial ratio between the anion and calcium monosulfoaluminate hydrate. Chloride ions reacted more slowly and were precipitated as Kuzel's salt, Kuzel's and Friedel's salts, or Friedel's salt only. Rietveld refinement of X-Ray powder diffraction patterns was successfully used to quantify the phase distributions, which were compared to thermodynamic calculations. Moreover, analysing the lattice parameters of Kuzel's salt as a function of its chloride content showed the occurrence of a restricted solid solution towards the sulfate side with general formula 3CaO·Al₂O₃·xCaCl₂·(1 ? x)CaSO₄·(12 ? 2x)·H₂O (0.36 ≤ x ≤ 0.50).     

Radiological significance of beach sand used for climatotherapy from Safaga, Egypt

As a part of national survey to evaluate natural radioactivity in the environment, concentration levels of radioactivity were analysed for sand samples from Safaga, Egypt, which is an ideal area for climatotherapy of psoriasis. Gamma dose rates of three beaches in Safaga were measured. The values ranged from 195.1 to 210.7 nGy h(-1). The activity concentrations (Bq kg(-1)) of radionuclides 238U series, 232Th series and 40K in three different sand profiles (0-5, 5-10, 10-15, 15-25 and 25 - 40 cm) were measured using gamma-ray spectrometry. The annual effective doses were 259 microSv y(-1) for Minveila, 255 microSv y(-1) for Ganet Safaga and 239 microSv y(-1) for Masab El-Ghazel beaches. The dose rates, radium equivalent activities and external hazard indices were evaluated and compared with the international data. These results may contribute to the determination of absorbed dose rate reference levels in Red Sea Coast at Safaga city.     

Design of Foundations on Sensitive Champlain Clay Subjected to Cyclic Loading

Sensitive clay subjected to cyclic loading may experience gradual loss of its shear strength, which may lead to liquefaction. Foundations built on this clay would suffer extensive settlement and significant loss of bearing capacity or perhaps catastrophic failure. This paper presents an experimental investigation on sensitive (Champlain) clay obtained from the city of Rigaud, Quebec (Canada). Consolidation tests, static and cyclic undrained and drained triaxial tests were performed on representative samples of this clay. The objective of this investigation was to examine the influence of the physical and mechanical parameters, which govern the shear strength of sensitive clay subjected to cyclic loading. Based on the results of the present investigation and those available in the literature, it can be reported herein that the undrained response is the most critical for these foundations; furthermore, the preconsolidation pressure is considered as an important parameter in establishing the shear strength of sensitive clay. A design procedure is developed to determine the safe zone for the undrained and drained responses, within which a combination of the cyclic deviator stress and the number of cycles for a given soil/loading/site conditions can achieve a quasielastic resilient state without reaching failure. The proposed design procedure is applicable to all regions around the world, where sensitive clays can be found. Furthermore, this procedure can be adopted to examine the conditions of existing foundations built on sensitive clay at any time during its lifespan.