Second-order Regression Equation Research Articles

Phenolic compounds from Nerium oleander leaves: microwave assisted extraction, characterization, antiproliferative and cytotoxic activities.

A microwave-assisted extraction (MAE) method was used for the extraction of phenolic compounds from Nerium oleander leaves. The influence of variables such as ethanol concentration, microwave power, irradiation time and liquid/solid ratio on polyphenol extraction was modelled using a second-order regression equation based on response surface methodology (RSM). The optimal conditions for MAE were: extraction solvent 35% ethanol concentration, 500 W microwave power, 60 s irradiation time and a solvent/material ratio of 20 mL g-1. Under optimal MAE conditions, the recovery of TPC was 25.752 mg GAE per g dw. 19 compounds have been identified by HPLC-ESI-MS/MS analysis; the main compounds identified were chlorogenic acid, rutin and quinic acid esters, such as caffeoylquinic acids and dicaffeoylquinic acids. Additionally, the optimized extract demonstrated potential to inhibit HT29 colorectal cancer cell growth (EC50 = 2.432 μg mL-1) without presenting cytotoxicity in confluent Caco-2 cells, a model of human intestinal epithelium. These results supply new information about the phenolic composition of Nerium oleander leaves and their antiproliferative effect.

A Study of the Electrodeposition of Gold Process in Iodine Leaching Solution

This paper mainly discusses electrodeposition of gold from iodine leaching solution through single-factor testing and explores the influence of gold concentration in catholyte, mass fraction of iodine in anolyte, anolyte n(I2):n(I−), cell voltage, and electrolysis time on the percentage of gold deposition and coulombic efficiency. Moreover, a response surface methodology was adopted to study interactions among variables and influence on the percentage of gold deposition, with mass fraction of iodine in anolyte, anolyte n(I2):n(I−), and cell voltage as variable factors and percentage of gold deposition as the response value. The electrodeposition process was fitted via pseudo first-order kinetics and pseudo second-order kinetics. Finally, the free surface morphology of gold deposited on the cathode plate was observed by scanning electron microscope. Given the results, a principal effect relationship can be concluded between mass fraction of iodine in anolyte, anolyte n(I2):n(I−), cell voltage, and percentage of gold deposition, with cell voltage > anolyte n(I2):n(I−) > mass fraction of iodine in anolyte and a second-order regression equation obtained with percentage of gold deposition as the response value. The optimized process conditions were gold concentration in catholyte 20 mg/L, mass fraction of iodine in anolyte 0.59%, anolyte n(I2):n(I−) is 1:7.5, cell voltage 12.9 V, and electrolysis time 2 h. The average percentage of gold deposition of three confirmatory experiments was 96.43%, a figure very close to the predicted value of the model 97.76%, which proves that the quadratic polynomial model obtained by response surface methodology optimization is feasible and that the electrodeposition of gold process conforms to a pseudo second-order kinetic model. Au can be attached well to the cathode plate and the deposition layer is formed by granular grain accumulation.

A Comprehensive Study of the Hydroforming Process of Metallic Bellows: Investigation and Multi-objective Optimization of the Process Parameters

In this paper, for the first time, a comprehensive experimental study is performed on hydroforming process of metallic bellows. For this purpose, the effects of the main process parameters and their interactions on the characteristics of hydroformed metallic bellows are investigated using Response Surface Methodology (RSM). The selected parameters as input variables are internal pressure, die stroke and die fillet. The measured characteristics of metallic bellows are convolution height and thickness of the top point of bellows congress. A set of experiments are carried out and the convolution height and thickness of the top point of bellows congress are measured. Then a mathematical model is developed according to the second-order linear regression equations to maximize the convolution height and thickness of the top point of bellows congress. The results show that the increase in the convolution height and decrease in the thickness of the top point of bellows congress will occur by increasing the internal pressure and die stroke. Also, the convolution height and thickness of the top point of bellows congress are increased with an increase in the die fillet.

Response surface methodology approach for optimization of Cu2+ and Pb2+ removal using nanoadsorbent developed from rice husk

In this study, central composite design (CCD) a subset of response surface methodology (RSM) was employed for the evaluation of mathematical model equation and optimization of prime parameters for the removal of Cu2+ and Pb2+ from aqueous solution using rice husk nanoadsorbent (RHN). The interactive effect of three independent variables viz. pH, adsorbent dose and initial metal ion concentration on Cu2+ and Pb2+ adsorption were investigated. Relative significance of variables in removal action was depicted by analysis of variance (ANOVA). pH 6.7, adsorbent dose 0.7 g/L and initial concentration 21 mg/L for Cu2+ and pH 4, adsorbent dose 0.4 g/L and initial concentration 50 mg/L for Pb2+ were found to be influential for 82% and 76% respectively. The removal efficiency was determined by constructing second-order regression equation model using Design Expert Software. Kinetic, Isotherm and thermodynamic studies were executed to enumerate the adsorption capacity of Cu2+ and Pb2+. Langmuir adsorption capacity was found to be 13.003 mg/g and 6.101 mg/g respectively for Cu2+ and Pb2+ indicating physico-chemical adsorption. Pseudo second-order kinetic model described the adsorption process very well. Intraparticle diffusion systemically interpreted the adsorpion of Cu2+ and Pb2+ on the nanoadsorbent surface. Free energy, Enthalpy and Entropy change revealed spontaneous and endothermic nature of the adsorption process. The recyclability of nanoadsorbent RHN was also investigated upto three cycles.

Analysis and Experimental Design of Damper System and Cutting Parameters of CNC Router

. An understanding of the dynamic characteristics of a CNC machine is a vital element in the control of the machine which has a direct effect on the machining precision. The ways in which energy is dissipated, such as friction and damping, have a significant effect on the dynamic behavior and spindle vibration of a CNC machine. The paper presents kinetic analysis of the CNC machine damper system, effect of the damper and the cutting parameters such as feed rate, cutting speed, and cutting depth on the dynamic behavior and spindle vibration of a CNC machine. Experimental results have established a second-order regression equation that demonstrates the effect of three parameters such as feed rate, cutting speed, and cutting depth on the vibration amplitude of the spindle. In addition, the comparison results show that the spindle head vibration amplitude of the machine using the damper is smaller than the spindle head vibration amplitude of the machine not using the damper.

Multi-objective Optimization of Parameters in Abrasive Water Jet Machining of Carbon-Glass Fibre-Reinforced Hybrid Composites

In the present work, first an attempt has been made to prepare carbon, glass and carbon-glass fibre-reinforced polymer composites, and later, machining of these composites is done on abrasive water jet machine (AWJM) to compare and optimize the machining parameters. Actually, the carbon fibre-reinforced polymer (CFRP) composites, glass fibre-reinforced polymer (GFRP) composites and carbon-glass fibre-reinforced polymer (CGFRP) composites are prepared through vacuum bagging process by using epoxy resin as the polymer matrix. The machining experiments are conducted to analyse the effects of the predominant machining parameters, i.e. cutting speed rate, feed rate and stand-off distance on the required machining characteristics, i.e. surface roughness (Ra), kerf top width (kw) and material removal rate (MRR). The range of values of each parameter is set at three different levels, and Taguchi’s L9 orthogonal array is used to design factors so that all the interactions between the response variables and machining variables can be investigated. Based on the experimental values, second-order regression equations are fitted between each of the response parameters and the machining parameters using Minitab 18 software. The equations are then optimized by defining the three equations of Ra, kw and MRR as the three objectives of a multi-objective optimization problem (MOOP) using a multi-objective optimization algorithm called Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II). Single best compromise solutions with respect to the MOOPs of GFRP, CFRP and CGFRP composites are also determined from the Pareto optimal solutions obtained by NSGA-II. Finally, confirmation tests are conducted on specimens of GFRP, CFRP and CGFRP composites machined at their corresponding optimum parameters given by the GA. It is observed that the optimum values of Ra, kw and MRR of all the optimization problems are closer to the corresponding experimental values of confirmation tests.

Characterization of phenolic compounds from Phyllanthus emblica fruits using HPLC-ESI-TOF-MS as affected by an optimized microwave-assisted extraction

ABSTRACT A simple microwave-assisted method for extracting antioxidant phenolic compounds from emblic (Phyllanthus emblica L.) fruits was developed and optimized with response surface methodology (RSM). The influence of process conditions including microwave power, irradiation time, ethanol concentration, and solvent-to-solid ratio on the extraction of total phenolic content was analyzed by using a second-order regression equation. The optimum extraction parameters were as follows: microwave power, 480 W; irradiation time, 29 s; ethanol concentration, 66%; liquid-to-solid ratio, 25 mL/g. Under these conditions, the recovery of total phenolic content was 133.58 ± 15.61 mg gallic acid equivalent/g dry weight (DW). The extracts were also analyzed using HPLC-ESI-TOF-MS to identify eight compounds including hamamelitannin, mucic acid-1,4-lactone-3-O-gallate, ellagic acid, and isocorilagin. To our knowledge, this is the first report of hamamelitannin in emblic fruit. The extracts exhibited strong antioxidant capacities in DPPH and ABTS+ radical scavenging assays and showed an excellent inhibition of lipid peroxidation and reducing property. These findings illustrated that the optimized microwave-assisted extraction method was efficient in extracting phenolic compounds with high antioxidant activity from emblic fruits. It was suggested that emblic fruits may be a new potential source as natural antioxidant agents applied in food industry.

Optimization of cutting parameters in CNC turning of stainless steel 304 with TiAlN nano coated carbide cutting tool

In this work, turning was performed to optimize the surface finish or roughness (Ra) of stainless steel 304 with uncoated and coated carbide tools under dry conditions. The carbide tools were coated with Titanium Aluminium Nitride (TiAlN) nano coating using Physical Vapour Deposition (PVD) method. The machining parameters, viz., cutting speed, depth of cut and feed rate which show major impact on Ra are considered during turning. The experiments are designed as per Taguchi orthogonal array and machining process is done accordingly. Then second-order regression equations have been developed on the basis of experimental results for Ra in terms of machining parameters used. Regarding the effect of machining parameters, an upward trend is observed in Ra with respect to feed rate, and as cutting speed increases the Ra value increased slightly due to chatter and vibrations. The adequacy of response variable (Ra) is tested by conducting additional experiments. The predicted Ra values are found to be a close match of their corresponding experimental values of uncoated and coated tools. The corresponding average % errors are found to be within the acceptable limits. Then the surface roughness equations of uncoated and coated tools are set as the objectives of optimization problem and are solved by using Differential Evolution (DE) algorithm. Also the tool lives of uncoated and coated tools are predicted by using Taylor’s tool life equation.

Some investigations in grindability improvement of Inconel 718 under ecological grinding

This work explores the improvement in grinding characteristics of Inconel 718 (IN718) using soluble oil under minimum quantity lubrication and liquid nitrogen (LN2) environments. The coolant flow rate in minimum quantity lubrication and LN2 grinding has been regulated through indigenously developed setups. Grinding performance has been studied in terms of on-machine measured grinding forces and centre line average surface roughness ( Ra). The obtained grinding characteristics have been compared with the outcomes under dry and wet grinding. Surface integrity of ground surface, wheel morphology, and chip formation characteristics has been studied using scanning electron microscope, energy dispersive X-ray spectroscopy, and atomic force microscopy. Analysis of variance has been carried out to capture the variability in the experimental data for tangential forces and Ra. The main effect of the factors and their first-order interactions have been considered, and second-order regression equations have been developed using response surface methodology. LN2 grinding has been proved to be more efficient as it yielded lowest grinding forces, least oxidation, minimal ground surface damage and better surface integrity. The occurrence of almost circular chips in dry grinding indicates severe oxidation, whereas small C-type chips formed under minimum quantity lubrication and LN2 conditions indicate effective cooling under these environments. The energy dispersive X-ray spectroscopy analysis of the ground surfaces also supports these results through the occurrence of the highest oxidation in dry grinding. From this work, it has been concluded that LN2 and minimum quantity lubrication grinding offer a clean and effective means to improve grinding performance of IN718 compared to dry and wet grinding.

Multi-objective optimization of cutting parameters in CNC turning of stainless steel 304 with TiAlN nano coated tool

In the present day world, coated tools are used instead of uncoated tools for machining process, as they improve certain machining characteristics. Surface roughness (Ra) is one of the specified customer requirements in a machining process. It is essential to consider economy in addition to quality in any machining operations. Material removal rate (MRR), productivity and cost effectiveness are the desired requirements. The higher value of MRR reduces the machining time and finally productivity of the system increases. Thus in the present study, multi-objective optimization of Ra and MRR is considered during turning of stainless steel 304 with uncoated and TiAlN (Titanium Aluminium Nitride) nano coated carbide tools under dry conditions. The Physical Vapour Deposition (PVD) method is used for coating carbide tool insert by TiAlN nano coating. The cutting speed, feed rate and depth of cut of turning operation are considered as the variable parameters. The machining process is done as per the experiments designed under Taguchi orthogonal array. Then on the basis of experimental results for Ra and for MRR, the second-order regression equations have been developed in terms of machining parameters used. Regarding the effect of machining parameters, an upward trend is observed in Ra with respect to increasing feed rate. Also as the cutting speed increases, Ra value increased slightly due to chatter and vibrations. It is found that the feed rate and depth of cut are the dominant parameters with respect to the MRR. Then to test the adequacy of regression equations of response variables, additional experiments were conducted. The predicted Ra and MRR values of uncoated and coated tools are found to be a close match of their corresponding experimental values. After ascertaining that the average % errors are lying within acceptable limits, the Ra and MRR equations of uncoated and coated tools are set as the objectives of multi-objective optimization problems (MOOPS) and are solved by using elitist non dominated sorting genetic algorithm (NSGA II). Finally a single best compromise solution is determined from the Pareto optimal solutions obtained by NSGA II

Effect of rice husk ash and fly ash on the compressive strength of high performance concrete

The usage of industrial and agricultural wastes for building materials production plays an important role to improve the environment and economy by preserving nature materials and land resources, reducing land, water and air pollution as well as organizing and storing waste costs. This study mainly focuses on mathematical modeling dependence of the compressive strength of high performance concrete (HPC) at the ages of 3, 7 and 28 days on the amount of rice husk ash (RHA) and fly ash (FA), which are added to the concrete mixtures by using the Central composite rotatable design. The result of this study provides the second-order regression equation of objective function, the images of the surface expression and the corresponding contours of the objective function of the regression equation, as the optimal points of HPC compressive strength. These objective functions, which are the compressive strength values of HPC at the ages of 3, 7 and 28 days, depend on two input variables as: x1(amount of RHA) and x2(amount of FA). The Maple 13 program, solving the second-order regression equation, determines the optimum composition of the concrete mixture for obtaining high performance concrete and calculates the maximum value of the HPC compressive strength at the ages of 28 days. The results containMaxR28HPC= 76.716 MPa when RHA = 0.1251 and FA = 0.3119 by mass of Portland cement.

Investigation on influence of cutting parameters on spindle vibration of CNC wood milling machine

In machining operation, the cutting parameters greatly influences on the spindle vibration of a CNC wood milling machine. The paper presents the effect of the cutting parameters such as feed rate, cutting speed, and cutting depth on the vibration amplitude of the spindle when machined on CNC milling machine using Box-Hunter method of experimentation. The lowest natural frequency of this machine is 250 Hz. Experimental results have established a second-order regression equation that demonstrates the effect of three parameters such as feed rate, cutting speed, and cutting depth on the vibration amplitude of the spindle. From that base, determine the most reasonable cutting parameters when machining on CNC wood milling machines so that the spindle vibration amplitudes is minimal. In addition, The comparison results show that the spindle head vibration amplitude of the machine using the bolt joint is larger than the spindle head vibration amplitude of the machine using the weld joint.

Kinetic Studies on Petrographic Components of Coal in Batch Flotation Operation

ABSTRACTIn the present paper, an attempt was made to study the kinetic behavior of different types of maceral during flotation of a washery grade-IV type of coking coal. Three important operational variables, viz. collector dose (kg/ton), frother dose (kg/ton), and feed solid concentrations (%), were varied, and their effects on the response parameters like recoveries of ash and petrographic components, viz. vitrinite (V), liptinite (L), and inertinite (I), were evaluated. A first-order flotation kinetic equation was fitted for the batch test data for evaluating the rate of flotation (k) of coal components. Use of a three-level Box-Behnken factorial design was adopted to minimize the number of experiments and modeling of response parameters in batch coal flotation. The obtained results were evaluated with quadratic programming to develop second-order regression equations. For understanding of the influence of interactional effects, response surface methodology (RSM) approach was adopted. Taking advantages of the quadratic programming, it was observed that recovery of 100% vitrinite was obtained without collector, however, with frother dosage and feed solid concentration of 0.75kg/ton and 5%, respectively. Similarly, minimum ultimate recovery of ash and inertinite component was achieved at intermediate range of reagent dosages and pulp density (collector ≡ 0.40–0.45kg/ton, frother ≡ 0.40–0.45kg/ton, and feed solid concentration of 9–10%). The influence of these process variables of the batch coal flotation on ultimate recovery (R∞) and rate constant (k) values of maceral components are discussed critically in this paper.

Optimization of microwave-assisted extraction of zerumbone from Zingiber zerumbet L. rhizome and evaluation of antiproliferative activity of optimized extracts

BackgroundThe extraction of bioactive compounds from herbal materials requires optimization in order to recover the highest active dose. Response surface methodology was used to optimize variables affecting the microwave extraction of zerumbone from Zingiber zerumbet using the Box–Behnken design. The influence of variables, such as ethanol concentration (X1), microwave power (X2), irradiation time (X3), and liquid-to-solid ratio (X4), on the extraction of zerumbone was modeled using a second-order regression equation. The antiproliferative activity of optimized and non-optimized extracts was evaluated against the HeLa cancer cell line using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.ResultsTwo linear parameters, X1 and X4, and their quadratic parameters were highly significant at the P < 0.01 level. Two interaction parameters, X1X4 and X2X3 were significant, whereas interactions of X1X2, X1X3, X2X4 and X3X4 were insignificant (P > 0.05). The optimum microwave extraction conditions were as follows: ethanol concentration, 44%; microwave power, 518 W; irradiation time, 38.5 s; and liquid-to-solid ratio, 38 mL/g. Under these conditions, the maximum zerumbone yield was 5.88 mg/g DM, which was similar to the predicted value (5.946 mg/g DM). Optimized and non-optimized Z. zerumbet rhizome extracts exhibited significant antiproliferative activity against HeLa cancer cells, with half-maximal inhibitory concentration (IC50) values of 4.3 and 7.8 μg/mL, respectively, compared with 1.68 μg/mL for the anticancer drug cisplatin. When the extract concentration increased from 4.3 to 16.0 μg/mL, the inhibition of cancer cell growth increased from 50.0 to 79.5%.ConclusionsIn this study, the optimized microwave protocol developed for extracting zerumbone from Z. zerumbet was faster and consumed less solvent than previous methods, while improving and enhancing the antiproliferative activity.

Modeling and optimization of extrusion process parameters for the development of Nylon6–Al–Al2O3 alternative FDM filament

The present work focused the detailed investigation on the development of Nylon6–Al–Al2O3-based alternative fused deposition modeling process (FDM) feedstock filament (in lieu of commercial acrylonitrile butadiene styrene filament) by optimizing the process parameters of single-screw extruder (such as composition, mean barrel temperature, and die temperature) in terms of responses (tensile strength and diameter deviation) using response surface methodology. Initially, the suitability of alternative material as an alternative FDM filament has been verified by rheological investigations and the tensile testing (according to ASTM-638 standard). The tensile strength of feedstock filament was significantly affected by the variation of major input parameters during the processing of alternative material on single-screw extruder. A second-order regression equation for each process response (obtained by ANOVA) validates the modeling goodness of fit and selects proper forms of influentially significant process variables (main, two-way interaction, and pure quadratic terms) within 95 % of confidence interval (p value ≤0.05). A multi-objective and multi-response optimization techniques based on the use of desirability function concept have been applied for the response regression equations to simultaneously find a set of optimal input parameters, yielding the maximum tensile strength along with the minimum deviation in feedstock filament diameter. The predicted optimal results were also validated experimentally with an error <4 %. In addition to above, the dynamic mechanical analysis was performed, which indicate that the filament fabricated with optimum combination of parameters have adequate stiffness and is suitable for FDM system.

Multi-objective optimizations of multidirectional forming mold based on fractional factorial design

Taking an engine shell with branches as the research object, the response surface method and the fractional factorial design screening methods were carried out for optimization of multidirectional forming mold parameters. Selecting the flash quality of formed part and forming load act as the objective function, and the tooth surface mold parameters as design variables, establishing a second-order mathematical model. Using fractional factorial design screens effectively the design variables and their interactions. These design variables are impacted significantly factors. BOX-Behnken experimental design method optimized the design parameters (shell bottom taper α, the tooth length b, and branches mouth fillet R2), and have a second-order regression equation. Finally, an overlapping contour map of flash quality and load were drawn, which provide a wide range of values for the actual optimization design. We can predict the quality and the load under different conditions through the overlay contour map.

The Influence of Physical Properties of Sod-Podzol Soil on its Ammonifying and Nitrifying Capacity

The research was conducted by the Chair of Agricultural Chemistry and Crop Farming of the Mari State University. The model experiment helped to study the influence of temperature, moisture, and density on nitrifying and ammonifying capacity of sod-podzol midclay low-humic soil. It was found out that change of physical properties factors of sod-podzol soil influenced nitrifying and ammonifying capacity and mineral nitrogen content. Maximum content of nitrate and mineral nitrogen and the biggest nitrifying capacity were at a soil temperature of +15°C and had the following corresponding values: 74.4, 81.3, and 31.9 mg/kg. Moistening conditions optimal for developing nitrifying and ammonifying bacteria were formed at a soil moisture of 20-25% (60-75% WFC). At this moisture there were the biggest figures of nitrifying capacity (31.5-35.0 mg/kg) and maximum values of content of nitrate nitrogen (74.0-77.5 mg/kg) and mineral nitrogen (78.7-82.3 mg/kg). Soil firming had a negative effect on the microflora of soil. With soil density increase from 1.1 to 2.0 g/cm3 nitrifying capacity decreased from 21.0 mg/kg down to 10.4 mg/kg, while nitrate nitrogen content in soil decreased from 63.5 to 32.1 mg/kg. The best conditions for nitrification and ammonification in sod-podzol soil were as follows: soil temperature of +15°C, soil moisture of 20-25%, and soil density of 1.1 g/cm3. Dependence of mineral nitrogen content in soil on its temperature and moisture was curvilinear and was described by a second-order regression equation, while dependence on its density was linear and was described by a first-order regression equation.

Optimization of Operating Parameters for Flotation of Fine Coal Using a Box-Behnken Design

In this study, experiments were carried out to examine flotation characteristics of fine coal and to determine the effect of various reagents on the coal flotation and the most optimum flotation conditions. The aim of the study was to obtain low-ash content of froth products from a high-ash-containing feed. The flotation experiments were carried out in two steps. First the optimum flotation condition parameters, such as optimal particle size, frother type, conditioning time, solid-liquid ratio, depressant type, and effect of flocculants, were determined. In the second step, keeping the optimum conditions obtained from the first step constant, a Box- Behnken design was applied for modeling and optimization of some operating variables. Three independent variables are categorized as follows: collector dosage (0–2 kg/t), frother dosage (0.1–0.3 kg/t), froth collecting time (120–180 sec). The results obtained from the experiments were subjected to multiple regression analysis by using SPSSP19. A LOQO/AMPL optimization algorithm was used for the solution of the quadratic regression models. The R2 values of the second-order regression equation for ash content of clean coal and yield were calculated as 0.905 and 0.959, respectively. This showed a good relationship between observed and calculated values. Three-dimensional graphics were created to demonstrate the dependent and independent variables behaviors.

Beta-glucan rich composite flour biscuits: modelling of moisture sorption isotherms and determination of sorption heat.

Moisture adsorption isotherms of beta-glucan rich composite flour biscuits were determined at 28, 37 and 45°C. Experimental data were fitted to 12 mathematical models. A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. Statistical testing of sorption models was carried out using multiple criteria such as coefficient of determination (R (2) ), reduced chi-square (χ (2) ), mean relative percent deviation modulus (P) and plotting of residuals. BET (R (2) > 0.99; χ (2) < 0.09; P < 7.52; RMS% < 9.22) was found suitable for predicting the M e -a w relationship in the a w range of 0.10-0.53. However, in the a w range of 0.10-0.85, although Ferro-Fontan and GAB models were found to have high R (2) values (>0.99), Peleg model was found to meet the multiple statistical criteion (R (2) > 0.9996; χ (2) < 0.04; P < 3.97; RMS% < 7.09). Properties of sorbed water were also determined. BET, GAB and Caurie monolayer moisture contents ranged from 2.64 to 3.36, 1.29-2.66 and 1.88-3.38% d.b., respectively. Second-order regression equation was found to describe the relation between monolayer moisture content, M o and temperature, t (°C). The isosteric heat, calculated using Clausius-Clapeyron equation, was varied between 1.46 and 50.39kJg(-1)mol(-1) at moisture levels 1-12% (d.b.). An exponential relationship was observed between the isosteric heat of sorption and moisture content.

Development of fatigue life prediction method and effect of 10-minute mean wind speed distribution on fatigue life of small wind turbine composite blade

This study aims to develop a fatigue life prediction method and to identify the effect that a 10-minute mean wind speed distribution has on the fatigue life of a small-scale wind turbine composite blade. First, combining the von Karman isotropic turbulence model and the Weibull distribution for a 10-minute mean wind speed provided us with the 1-Hz full wind history for a specific time period. Accordingly, the fatigue stress spectra at the blade's fatigue-critical locations (FCLs) were created by applying a stress tensor, in which the interaction between flapwise and edgewise bending moments was taken into consideration. The fatigue life of a composite blade can be predicted with a reliability R = 95% by applying the P–S–N curve obtained from the constant amplitude fatigue tests and rainflow cycle counting, and cumulative damage rule to the fatigue stress spectra. To acquire the second-order regression equation, nonlinear regression analysis was performed on the fatigue lives, which were simulated by using the proposed fatigue life prediction method. In this equation, the variables were the shape parameter, K, and the scale parameter, C, of the Weibull distribution for a 10-minute mean wind speed. The effects of the Weibull parameters on fatigue life were evaluated through the sensitivity analysis of the equations.