Face-centered Composite Design Research Articles

Intensification of bio-actives extraction from pomegranate peel using pulsed ultrasound: Effect of factors, correlation, optimization and antioxidant bioactivities

Pomegranate peel (PP) is one of the interesting agri-food by-products because of its abundant bioactive phytochemicals. However, the bioactivity of valuable compounds is affected due to the extraction method used. A pulsed ultrasound-assisted extraction (PUAE) was carried out to intensify the extraction efficacy with reduced power and time. Influence of several process variables viz. peel solids/ solvent ratio, sonication power, duty cycle, and extraction time was studied using empirical quadratic models followed by multicriterial numerical optimization with respect to face-centered composite design. Power-duty cycle combination was found to be most significant (p < 0.05) for process intensification. The optimal process conditions of 2.17 g/100 mL S/S ratio at 116 W power with 80% duty cycle for 6 min resulted into 0.48 g/g yield, 177.54 mg GAE/g total phenolics content, 35.71 mg QE/g total flavonoids, 160.54 mg GAE/g antioxidant capacity, 21.65 mg cyn-3-glc/100 g anthocyanin content with 54.92 browning index in dry pomegranate peel. Significant Pearson correlation analysis was established in all responses with potent phenols and flavonoid relation with highest coefficient (r) 0.931. All response models were significantly validated with regression coefficient (R2) above 0.965. Remarkable antioxidant bioactivities were recorded for the resultant peel extract. Hence, it is strongly recommended that PUAE could be successfully applied for the intensification of the extraction process of bioactive from any peel and or plant systems with minimal process time and power consumption with a green label.

Optimising Tropical Fruit Juice Quality Using Thermosonication-Assisted Extraction via Blocked Face-Centered Composite Design

Extraction of tropical fruit juice using simple, efficient, and environmentally friendly technologies is gaining importance to produce high quality juices. Juice from pink-fleshed guava, pink-fleshed pomelo, and soursop was extracted using direct and indirect thermosonication methods by varying intensity, time, and temperature, and compared to those extracted using water bath incubation. Improvised models of juice yield, ascorbic acid, and total soluble solids responses were generated by eliminating insignificant model terms of the factors in full quadratic model using backward eliminating procedure. Main effects, 3D, or 4D plots for each response were developed based on factors that influenced the response. Results showed that the best extraction method for guava and pomelo juices were within indirect thermosonication method of 1 kW, 55 °C and 30 min, and 2.5 kW, 54 °C and 23 min, respectively. Direct thermosonication method at 10% amplitude, 55 °C for 2 to 10 min was more suitable for soursop juice. Thermosonicated extraction of tropical fruit juice can improve its juice yield, ascorbic acid content, and total soluble solids content.

Recovery of anthocyanins from sour cherry (Prunus cerasus L.) peels via microwave assisted extraction: monitoring the storage stability

Utilization of economical and environmental methods as an alternative process to recover the industrial crops and food products into high-added value compounds is of great significant. In the current study, microwave assisted extraction (MAE) was optimized by response surface methodology (RSM) in order to evaluate the waste of sour cherry as a source of phenolic compounds rich in anthocyanins. The process parameters (microwave power, irradiation time and ethanol solvent concentration) of MAE method were optimized by face centered composite design of RSM. Responses such as total phenolic componds (TPC), total anthocyanin (TA) contents and antioxidant capacity (DPPH) of extracts were measured spectrophotometrically after extractions of samples. The optimized result of MAE was 500 W of microwave power, 90 s of irradation time and 80% ethanol solvent concentration. Antioxidant capacity was tested using by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical. Chromatographic analysis (HPLC) was also used to measure the concentration of major anthocyanin (cyanidin-3-glucoside) of the samples. Maximum predicted TPC, TA and DPPH yields on optimized conditions were 44.15 mg-GAE/g-FM (mg- gallic acid equivalent per g- fresh matter), 12.47 mg-cyanidin-3-glucoside/g-FM and 69.90 (%, inhibition), respectively. A stability assay under different conditions (light, dark, ambient condition, refrigerator and deep freezer) has been also performed in order to display the stability of bioactivity profile. All of the process parameters were significant at the level of p < 0.0001.

Abstract PO-216: Design, fabrication, and evaluation of dual-loaded biodegradable nanoparticles for breast cancer treatment

Abstract Introduction: The purpose of this study was to design, fabricate and determine the cytotoxic effects of dual-loaded (paclitaxel and 17-AAG) stealth polymeric nanoparticles. HSP90 inhibitors, such as 17-AAG, sensitize lung and breast cancer cells to paclitaxel induced cytotoxicity both in vitro and in vivo. Concurrent exposure to 17-AAG and paclitaxel is required for the synergistic activity of the two drugs. Further, clinical evaluations of 17-AAG in combination with approved therapies such trastuzumab and other drugs have shown enhancement or synergistic effects. Stealth nanoparticles are capable of providing site-specific tumor targeting thereby reducing toxicity in healthy cell, improving the solubility of anticancer drugs and synchronizing the disposition of encapsulated drugs (varying biodistribution/pharmacokinetics of combination drugs through cocktail administration has been attributed to their ineffectiveness in the clinic). Further, therapeutic nanoparticles could overcome drug resistance due to P-glycoprotein efflux pump. The stealth property of nanoparticles (PEG on the surface) will prevent capture by the reticuloendothelial system (RES) and will facilitate tethering ligands (mAbs) to the surface of the nanoparticles for receptor mediated endocytosis (active targeting). Dose reduction coupled with a better quality of life during treatment would also improve patient compliance. Experimental Procedures: A central composite face-centered statistical experimental design (CCF) in three independent factors and seventeen runs was implemented for the fabrication nanoparticles by dispersion polymerization technique using biodegradable poly-ϵ-caprolactone and a pH (acid) sensitive crosslinker, followed by computer optimizations. Numerical and graphical optimizations were carried out to select the factor combination to minimize the particle size, to minimize the time (h) for maximum release of paclitaxel and 17-AAG, to maximize paclitaxel and 17-AAG loading efficiency and to maximize paclitaxel and 17-AAG encapsulation efficiency. The optimal formulation was used for nanoparticle fabrication for biological studies in SKBR3 cell line (HER-2- overexpressing human breast cancer cell line) and MCF7 cell line (human breast cancer cell line). Results and Conclusion: The dispersion polymerization method was successfully used to fabricate an optimized dual-loaded nanoparticle formulation using an acid (pH) sensitive crosslinker and a macromonomer. The cytotoxic effects of the paclitaxel treatment and that of the drug combination (free drugs or nanoparticles) observed were similar in both SKBR3 and MCF7 cell lines suggesting synergistic or potentiation effects. Also, since paclitaxel and 17-AAG in the combination were half their concentrations, when used alone, and still yielded similar cytotoxic effects, we have been able to reduce the dose of paclitaxel without lowering its therapeutic efficacy. 17AAG on its own was not as effective as paclitaxel. Citation Format: Emmanuel O. Akala. Design, fabrication, and evaluation of dual-loaded biodegradable nanoparticles for breast cancer treatment [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-216.

Investigate the effect of nano cutting fluid and cutting parameters under minimum quantity lubrication (MQL) on surface roughness in turning of DSS-2205

The Paper focused on Effect of Nano cutting fluids under minimum quantity lubrication (MQL) and parameters on surface roughness during turning of Duplex stainless steel-2205. The Nanofluids are prepared via two step processes dispersing the nano particles of Aluminium oxide (Al2O3), Copper oxide (CuO) and Silicon carbide (SiC) with the base fluid of Neat Cut oil with different volume concentration 0.3%, 0.5% and 0.7%. The experimentation were conducted based on face centered composite design(CCF) with varying % of volume concentration of nano particles, speed, feed and depth of cut. ANOVA was used to examine the influence of turning factors on roughness. The ANOVA and R-Squared value reveals the developed models were significant. The results revealed that copper oxide nano fluid are better surface roughness fallowed by silicon carbide and aluminium oxide and feed was the most significant factor followed by DOC, concentration of nano particles and cutting speed.

Optimization of ultrasound-assisted extraction of bioactive compounds from Gomphrena celosioides Mart. using response surface methodology

In this study, ultrasound-assisted extraction (UAE) was used to extract bioactive compounds from Gomphrena celosioides Mart. Central composite face design (CCF) was used to optimize the influences of extraction factors on total phenolics content (TPC), total flavonoids content (TFC), and 1,1-diphenyl-2-picrylhydrazyl free radical scavenging capacity (DPPH-RSC). The results obtained showed that all factors (solvent to solid ratio, extraction time and extraction temperature) strongly affected TPC, TFC, and DPPH-RSC. The optimal extraction conditions for TPC (3.123 mg GAE/g DW), TFC (1.736 mg QE/g DW), and DPPH-RSC (64.118%) were solvent to solid ratio of 27.3/1 (mL/g), extraction time of 40.2 min, and extraction temperature of 69 oC. In addition, under the optimal conditions, the results pointed out that the experimental values agreed with those predicted. Hence, this model has successfully optimized the extraction conditions for TPC, TFC and DPPH-RSC of Gomphrena celosioides extract.&#x0D; &#x0D; KEY WORDS: Antioxidant activity, CCF, Flavonoids, Model, Phenolic compounds, Regression equation&#x0D; &#x0D; Bull. Chem. Soc. Ethiop. 2020, 34(2), 237-248&#x0D; DOI: https://dx.doi.org/10.4314/bcse.v34i2.3

Development and evaluation of edible films based on cassava starch, whey protein, and bees wax

Films and edible coatings based on biopolymers have been developed as a packaging, which can be obtained from biodegradable materials and have properties similar to common plastics. These edible materials have many applications in the food industry, preventing mass transfer between the product and the surrounding environment. The objective of this study was to develop and evaluate the physicochemical and mechanical properties of edible films based on cassava starch (CS), whey protein (WP), and beeswax (BW). Response surface methodology has been used and the experiments were carried out based on face-centred composite design. On the other hand, three CS-based controls were formulated to evaluate the effect of the inclusion of WP and BW. The optimization of multiple responses established the optimal formulation: CS (3.17 %), WP (1.30 %), BW (0.50 %), presenting the following response variables: tensile stress (1.92 MPa), elongation (40.4 %), Young's modulus (42.1 MPa), water vapor permeability 1.79 × 10−11 (g mm/s cm2 Pa), swelling capacity (300.3 %), thickness (0.128 mm), moisture content (6.74 %), and colour: lightness (89.9), chromaticity a∗ (-1.8), chromaticity b∗ (7.7), saturation (9.9), tone (101.1°), and yellowness index (17.7). The selection and evaluation of this optimal formulation are essential because it is the material that shows the best possible mechanical and physicochemical properties using the studied components. The results, especially its good mechanical properties and low permeability to water vapour, would allow its application as a coating for fruits, vegetables, among others, effectively delaying its weight loss due to dehydration.

Automatic solvent extraction of sour cherry peels and storage stability of the products

Conversion of biomass (particularly waste of agricultural and food products) into high-added value compounds has been an attractive research field recently. Therefore, developing an alternative downstream process to recover the relevant biologically active components is of great significance. In this study, waste of sour cherry has been used as a source of phenolic compounds rich in anthocyanins. As an advanced alternative technology, automatic solvent extraction has been used to recover phenolics from sour cherry peels. The process factors (immersion time, washing time, solid mass and solvent concentration) of this novel method were optimized by face-centered composite design of response surface method. Chromatographic analysis (HPLC) was also used to measure the major anthocyanin (cyanidin-3-glucoside) of the samples. The process was optimized in order to maximize the dependent factors such as total phenolic and anthocyanin content extractions measured spectrophotometrically. Maximum predicted TPC and TA yields on optimized conditions were 119.63 mg GAE/g FM and 24.31 mg cyanidin-3-glucoside/g FM, respectively (23.79 min immersion time, 52.21 min washing time, 0.47 g solid mass, 80% solvent concentration). A stability assay under different conditions (light, dark, ambient condition, refrigerator and deep freezer) has been also performed in order to monitor the stability of bioactivity profile (total phenolic and anthocyanin contents and cyanidin-3-glucoside level). All of the independent parameters (immersion time, washing time, solid mass and solvent concentration) were significant at the level of p > 0.05. The solvent concentration was identified to be the most significant parameter on the yields obtained by automatic solvent extraction.

QbD-steered development and validation of an RP-HPLC method for quantification of ferulic acid: Rational application of chemometric tools

The present work describes the systematic development of a simple, rapid, sensitive, robust, effective and cost-effective reversed-phase high performance liquid chromatographic method for quantitative analysis of ferulic acid using analytical quality by design paradigms. Initially, apt wavelength for the analysis of ferulic acid was selected employing principal component analysis as the chemometric tool. An Ishikawa fishbone diagram was constructed to delineate various plausible variables influencing analytical target profile, viz. peak area, theoretical plate count, retention time and peak tailing as the critical analytical attributes. Risk assessment using risk estimation matrix and factor screening studies employing Taguchi design aided in demarcating two critical method parameters, viz. mobile phase ratio and flow rate affecting critical analytical attributes. Subsequently, the optimum operational conditions of the liquid chromatographic method were delineated using face-centred composite design. Multicollinearity among the chosen factors for optimization was analyzed by the magnitude of variance inflation factor optimized analytical design space, providing optimum method performance, was earmarked using numerical and graphical optimization and corroborated using Monte Carlo simulations. Validation, as per the ICH Q2(R1) guidelines, ratified the efficiency and sensitivity of the developed novel analytical method of ferulic acid in the mobile phase and the human plasma matrix. The optimal method used a mobile phase, comprising of acetonitrile: water (47:53% v/v, pH adjusted to 3.0 with glacial acetic acid), at a flow rate of 0.8 mL·min−1, at a λmax of 322 nm using a C18 column. Use of principal component analysis unearthed the suitable wavelength for analysis, while analytical quality by design approach, along with Monte Carlo simulations, facilitated the identification of influential variables in obtaining the “best plausible” validated chromatographic solution for efficient quantification of ferulic acid.

Comparison of microwave-assisted techniques for the extraction of antioxidants from Citrus paradisi Macf. biowastes.

Microwave-assisted extraction (MAE) and solvent-free microwave extraction and Soxhlet extraction were applied to Ray Ruby grapefruit leaves (Citrus paradisi Macf.) to compare extract efficiency. Face centered composite designs were constructed via response surface methodology. Effects of factors of MAE were investigated on total phenolic content (TPC) and naringin content (NC). The optimized conditions were established as 1.4 kWL-1 for microwave power density, 20.00 gL-1 for solid/solvent ratio, 218.180s for extraction time, while responses were calculated as 14.210mg of gallic acid equivalent per g of the dried leaf (mgGAE g-1DL) and 13.198mg of naringin per g of dried leaf (mgNg-1DL) for TPC and NC, respectively. SFME and classical Soxhlet methods were also conducted for comparison reasons.

A Novel Approach to Optimize Hot Melt Impregnation in Terms of Amorphization Efficiency.

In this study, an innovative methodology to optimize amorphization during the hot melt impregnation (HMI) process was proposed. The novelty of this report revolves around the use of thermal analysis in combination with design of experiments (DoEs) to reduce residual crystallinity during the HMI process. As a model formulation, a mixture of ibuprofen (IBU) and Neusilin was used. The main aim of the study was to identify the critical process parameters of HMI and determine their optimal values to assure a robust impregnation process and possibly the highest possible amorphization rate of IBU. In order to realize this, a DoE approach was proposed based on a face-centered composite design involving three factors. The IBU/Neusilin ratio, the feeding rate, and the screw speed were considered as variables, while the residual crystallinity level of IBU, determined using differential scanning calorimetry (DSC), was measured as the response. Additionally, the stability of IBU under HMI was analyzed using high-performance liquid chromatography to estimate the extent of potential degradation. In order to verify the correctness of the DoE model, tested extrudates were manufactured by HMI and the obtained extrudates were thoroughly examined using scanning electron micrography, X-ray powder diffraction, and DSC.

Adopting a circular open-field layout in designing flexible manufacturing systems

ABSTRACT A new circular open field layout composed of a vehicle-based material handling system and multiple circular loops is proposed. The suggested layout offers more flexibility for high-mix low-volume production systems compared to other layouts as it maximizes the number of equidistant machines. A novel approach that integrates experimental design with computational modelling and statistical analysis was followed to study the proposed system. Forty experimental scenarios were generated using Face Centred Composite Design (FCCD) to numerically investigate the effect of layout, production quantity, variety and complexity on minimum production cost. To determine the minimum production cost in each experiment, a linear programming (LP) optimization model was formulated with layout dependent machine distance algorithm. The model solves for the optimum location of the machines and machine cell formations that minimizes the production cost. It considers material handling costs, alternative process routing, operations sequence, lot splitting, and machine costs. Furthermore, the cost was modeled using regression analysis to provide a quick estimate without the need to run computational intensive numerical models. Results reveal the effectiveness of the proposed layout with cost savings reaching 35% compared to traditional open field layout when product variety and complexity are increased.

Optimization of microwave-assisted extraction of phenolic compounds from ginger (Zingiber officinale Rosc.) using response surface methodology

Summary Introduction: Ginger (Zingiber officinale Rosc.) is a common spice and precious herbal plant in Vietnam. It contains many bioactive compounds, especially phenolic compounds useful for human health. Hence, the extraction and application of these compounds in medical technology are necessary. Objective: The goal of this study is to determine the optimal extraction conditions with the assistance of microwave, for instance solvent/material ratio (ml/g), solvent concentration (%, v/v) and extraction time, on the extraction yield of ginger rhizome, such as total polyphenol content (TPC) and antioxidant capacity (AC). Methods: The dried sample was extracted by microwave-assisted extraction (MAE). TPC and AC of received extract were measured by the Folin-Ciocalteu method and phenanthroline assay. The optimization process used response surface methodology (RSM) (Central composite face design, CCF) with major influencing factors including solvent concentration, solvent/material ratio and extraction time. Results: The results showed that the optimal extraction conditions were the ethanol concentration of 60%, ethanol/material ratio of 48.6/1 (ml/g), extraction time of 1 minute. Conclusion: The maximum TPC and AC peaked at 27.89±1.99 mg GAE/g dry matter and 12.24±0.04 mmol Fe/g dry matter (DM) at optimal extraction conditions. Besides, some factors strongly affected the extraction yield and interacted together.

Bioprocess Optimization of L-Lysine Production by Using RSM and Artificial Neural Networks from Corynebacterium glutamicum ATCC13032

Abstract L-Lysine is one of the important amino acid required for humans and animals. It has a high commercial market. Large scale production of this amino acid is essential to meet the commercial demands. Typically, L-lysine is produced by batch fermentation. In the present study, the important process, as well as nutrient parameters such as glucose concentration (g/L), rpm, incubation temperature (°C), pH and incubation time for L-lysine production by Corynebacterium glutamicum ATCC13032, were optimized by a combined approach of response surface methodology (RSM) with artificial neural network (ANN) method. Initially, 32 runs face central composite design was employed. In the first step, the data was analyzed by the RSM and the optimum conditions for L-lysine production were determined. In the second step, the same data was used to train the neural network. A feed-forward neural network with error backpropagation was used. The best network was obtained by optimizing the no of neurons in the hidden layer. From the best network, the optimized weights and predicted responses were used to optimize the conditions of the selected parameters by genetic algorithm (GA). Overall with the combination of RSM-ANN-GA onefold of L-lysine production from Corynebacterium glutamicum ATCC 13032 was improved.

Statistical Study for Leaching of Covellite in a Chloride Media

Covellite is a secondary copper sulfide, and it is not abundant. There are few investigations on this mineral in spite of it being formed during the leaching of chalcocite or digenite; the other investigations on covellite are with the use of mineraloids, copper concentrates, and synthetic covellite. The present investigation applied the surface optimization methodology using a central composite face design to evaluate the effect of leaching time, chloride concentration, and sulfuric acid concentration on the level of copper extraction from covellite (84.3% of purity). Copper is dissolved from a sample of pure covellite without the application of temperature or pressure; the importance of its purity is that the behavior of the parameters is analyzed, isolating the impurities that affect leaching. The chloride came from NaCl, and it was effectuated in a size range from –150 to +106 μm. An ANOVA indicated that the leaching time and chloride concentration have the most significant influence, while the copper extraction was independent of sulfuric acid concentration. The experimental data were described by a highly representative quadratic model obtained by linear regression (R2 = 0.99).

Modeling and Optimizing of Microwave-Assisted Extraction of Antioxidants and Phenolics from Wormwood (Artemisia absinthium L.) Using Response Surface Methodology

In this study, modelling and optimizing microwave-assisted extraction (MAE) of antioxidants and phenolics from wormwood (Artemisia absinthium L.) was performed by using response surface methodology with face-centered composite design as factors of temperature, extraction time, solvent concentration, and solid-to-solvent ratio. The MAE process factors were optimized so that cupric reducing antioxidant capacity (CUPRAC) and total phenolic content (TPC) of the wormwood extract are maximized. All of the models calculated for the two responses (CUPRAC and TPC) were found significant (p&amp;lt;0.0001) to show the relationship between the response and independent parameters. Extraction temperature was found as the most significant operational factor in MAE. Extraction time was found is the most insignificant parameter in MAE. The data obtained by the experimental model and the predicted by the model were found to be strongly accordance. It shows the suitability of the model and its success in optimization. The CUPRAC and TPC yields were obtained as 1.22 and 1.42 mmol TR/g-dried sample under the optimum operational conditions of MAE. According to the CUPRAC and TPC values, under the same operational conditions, MAE method was found to be approximately two times more efficient than classical heat extraction. As a result, the modeled methodology can be applied to the extraction of antioxidant and phenolics from the wormwood in the natural product industry.

Optimization of ion trajectories in a dynamically harmonized Fourier-transform ion cyclotron resonance cell using a design of experiments strategy.

With the recent introduction of the dynamically harmonized Fourier-transform ion cyclotron resonance (FT-ICR) cell, the complexity of tuning has expanded drastically, and fine-tuning of the direct current voltages is required to optimize the ion cloud movement. As this adjustment must typically be performed manually, more reliable computational methods would be useful. Here we propose a computational method based on a design of experiments (DoE) strategy to overcome the limits of classical manual tuning. This DoE strategy was exemplarily applied on a 12 T FT-ICR instrument equipped with a dynamically harmonized ICR cell. The chemometric approach, based on a central composite face (CCF) design, was first applied to a reference material (sodium trifluoroacetate) allowing for the evaluation of the primary cell parameters. Eight factors related to shimming and gating were identified. The summed intensity of the signal corresponding to the even harmonics was defined as one quality criterion. The DoE response allowed for rapid and complete mapping of cell parameters resulting in an optimized parameter set. The new set of cell parameters was applied to the study of an ultra-complex sample: Tholins, an ultra-complex mixture that mimics the haze present on Titan, was chosen. We observed a substantial improvement in mass spectrometric performance. The sum of signals related to harmonics was decreased by a factor of three (from 4% for conventional tuning to 1.3%). Furthermore, the dynamic range was also increased, which in turn led to an increase in attributed peaks by 13%. This computational procedure based on an experimental design can be applied to any other mass spectrometric parameter optimization problem. This strategy will lead to a more transparent and data-driven method development.

Improvement of adhesion strength for wood-based material coating process using design of experiment methodology

The coating performance of wood-based materials is affected by different sanding conditions and coating application parameters. In particular, in the furniture industry, these processes are significant indicators for increasing the process efficiency and determining the optimum paint quantity. The purpose of this study was to improve the coating performance of medium density fiberboard using design of experiment methodology. In this study, independent variables were selected as coating amount, feed rate, belt speed and grit type, whereas the dependent variable was determined as adhesion strength. Face-centered composite design and analysis of variance were applied to determine the significant factors. Adhesion strength values of the specimens were determined by using pull-off adhesion test equipment. Sanding and coating application parameters for maximizing the adhesion strength were optimized by using response surface methodology and desirability function. Optimal processing parameters for maximizing the adhesion strength were achieved with a feed rate of 5 m/min, belt speed of 15.13 m/s, paint amount of 352.10 g/m2 and sandpaper type of SiC.

Multi-response optimization of the coagulation process of real textile wastewater using a natural coagulant

The present study is an attempt to investigate the applicability of a natural coagulant Moringa Oleifera (MO) as a potential impending alternative for the treatment of textile wastewater. Face Central Composite Design in Response Surface Methodology was used to optimize the performance of the coagulation process in terms of turbidity and colour removal efficiency. Three independent variables which are pH (2-4), coagulant dosage (4-8 ml) and settling time (10-30 min) were investigated. Quadratic models were developed for each response and their statistical fitness was evaluated using ANOVA analysis. All models were proved to be statistically adequate with R2 higher than 96%. Of the investigated variables, pH was found to have significant effect on both responses (P-value <0.001), whereas, coagulant dosage affected the colour removal efficiency significantly. Multi-response optimization was applied to optimize the process variables for both responses simultaneously using the RSM desirability function approach. Maximum turbidity reduction by more than 81% and colour removal efficiencies by more than 77% were reached at the optimum conditions of pH 2, coagulant dosage 4 mL and settling time 21 min. These results prove that MO could be used as an alternative to the conventional coagulants for real textile wastewater treatment.

Optimization of transversal flow stress and strain and weld seam microstructure analysis in butt-HDPE friction stir welded plates

The paper aims to optimize the characteristic performances of friction stir welding of high-density polyethylene in order to predict failure modes in weld nugget and interfacial zones. Three replicates of a face central composite design are employed to estimate the effects of parameters process, on the transversal flow stress and strain of the seam and to understand root causes, which may lead to structural defects such as the onset of cracks and the seam-base metal rupture. The study findings disclose that maximum responses are obtained when the tool rotation speed is set middle and both the feed rate and the plunged surface are set high. The transversal flow stress of the welded seam is found highly sensitive to the plunged surfaces and at a lesser degree to the rotation speed, whereas, the transversal flow strain of the welded seam is mostly sensitive to the rotation speed and at a lesser degree to the plunged surfaces. For the microscopic analysis, it is shown that at low rotation speed, there exist four structural layers in the transition zone between the seam and the base material giving rise to the formation of a continuous line of cracks that can initiate structure failure.