Second-order Polynomial Regression Research Articles

Sentinel-MSI VNIR and SWIR Bands Sensitivity Analysis for Soil Salinity Discrimination in an Arid Landscape

Depending on the band position on the electromagnetic spectrum, optical and electronic characteristics, sensors collect the reflected energy by the Earth’s surface and the atmosphere. Currently, the availability of the new generation of medium resolution, such as the Multi-Spectral Instrument (MSI) on board the Sentinel-2 satellite, offers new opportunities for long-term high-temporal frequency for Earth’s surfaces observation and monitoring. This paper focuses on the analysis and the comparison of the visible, the near-infrared (VNIR), and the shortwave infrared (SWIR) spectral bands of the MSI for soil salinity discrimination in an arid landscape. To achieve these, a field campaign was organized, and 160 soil samples were collected with various degrees of soil salinity, including non-saline soil samples. The bidirectional reflectance factor was measured above each soil sample in a goniometric laboratory using an ASD (Analytical Spectral Devices) spectroradiometer. In the laboratory work, pHs, electrical conductivity (EC-Lab), and the major soluble cations (Na+, K+, Ca2++, and Mg2+) and anions (CO32−, HCO3−, Cl−, and SO42−) were measured using extraction from a saturated soil paste, and the sodium adsorption ratio (SAR) was calculated using a standard procedure. These parameters, in addition to the field observations, were used to interpret and investigate the spectroradiometric measurements and their relevant transformations using the continuum removed reflectance spectrum (CRRS) and the first derivative (FD). Moreover, the acquired spectra over all the soil samples were resampled and convolved in the solar-reflective spectral bands using the Canadian Modified Herman transfer radiative code (CAM5S) and the relative spectral response profiles characterizing the Sentinel-MSI band filters. The statistical analyses conducted were based on the second-order polynomial regression (p < 0.05) between the measured EC-Lab and the reflectances in the MSI convolved spectral bands. The results obtained indicate the limitation of VNIR bands and the potential of SWIR domain for soil salinity classes’ discrimination. The CRRS and the FD analyses highlighted a serious spectral-signal confusion between the salt and the soil optical properties (i.e., color and brightness) in the VNIR bands. Likewise, the results stressed the independence of the SWIR domain vis-a-vis these soil artifacts and its capability to differentiate significantly among several soil salinity classes. Moreover, the statistical fit between each MSI individual spectral band and EC-Lab corroborates this trend, which revealed that only the SWIR bands were correlated significantly (R2 of 50% and 64%, for SWIR-1 and SWIR-2, respectively), while the R2 between the VNIR bands and EC-Lab remains less than 9%. According to the convergence of these four independent analysis methods, it is concluded that the Sentinel-MSI SWIR bands are excellent candidates for an integration in soil salinity modeling and monitoring at local, regional, and global scales.

Effects of dietary biofloc on growth, digestibility, protein turnover and energy budget of sea cucumber Apostichopus japonicus (Selenka)

Bioflocs are not only rich in various bioactive compounds but also proven to be sustainable protein sources of aquafeed. A 60-day experiment was conducted to evaluate the feasibility and capacity of dietary replacement of macroalgae Sargassum thunbergii with biofloc meal as an ingredient in the diet of Apostichopus japonicus. During the experiment, the sea cucumbers of initial wet weight ∼25.18 g were fed seven diets contained graded biofloc levels of 0%, 5%, 10%, 20%, 30%, 45% and 60% (referred as group B0, B5, B10, B20, B30, B45 and B60, respectively) in a recirculating aquaculture system. Each group contained 150 sea cucumbers that were equally allocated into 3 cylinder aquaria. The results showed that dietary supplementation levels of 20% and 30% biofloc significantly enhanced specific growth rate (SGR), food conversion efficiency (FCE) and protein efficiency ratio (PER) of sea cucumber. Based on the second-order polynomial regression models of SGR and FCE, it was concluded that 27.74−30.75% were optimal dietary replacement levels of biofloc. Apparent digestibility coefficients and digestive enzyme activities all showed remarkable trends of the first increase and then decrease as dietary biofloc level increased with relatively higher values in diet B30, which might have stimulated the digestion and absorption of nutrients to maintain faster growth of sea cucumber. There were significant differences in parameters estimated by time-based turnover model of δ15 N between the experimental diets, and the sea cucumbers in diets B30 and B45 exhibited faster nitrogen turnover rates. The average formula of energy allocation was 100C = 3.8G + 65.4F + 3.3U + 27.5R in the present study. The fluctuation in energy for growth and metabolism suggested that dietary biofloc modified their energy allocation strategy by balancing the energy accumulation of growth and energy consumption of feces, excretion and respiration. In conclusion, ca. 30% replacement of S. thunbergii with biofloc powder could improve growth performance of A. japonicus, by enhancing feeding utilization and digestibility, accelerating protein turnover and optimizing energy budget of sea cucumber.

Optimizing Medium Components for the Maximum Growth of Lactobacillus plantarum JNU 2116 Using Response Surface Methodology.

This study was undertaken to find the optimum soy-peptone, glucose, yeast extract, and magnesium sulfate amounts for the maximum growth of Lactobacillus plantarum JNU 2116 and to assess the effects of these medium factors through the use of response surface methodology. A central composite design was used as the experimental design for the allocation of treatment combinations. In the analysis of the experiment, due to a significant lack of fit of the second-order polynomial regression model that was used at first, cubic terms were added to the model, and then two-way interaction terms were deleted from the model since they were found to be all statistically insignificant. A relative comparison among the four factors showed that the growth of L. plantarum JNU 2116 was affected strongly by yeast extract, moderately by glucose and peptone, and slightly by magnesium sulfate. The estimated optimum amounts of the medium factors for the growth of L. plantarum JNU 2116 are as follows: soy-peptone 0.213%, glucose 1.232%, yeast extract 1.97%, and magnesium sulfate 0.08%. These results may contribute to the production of L. plantarum L67 as a starter culture that may have potential application in yogurt and fermented meat products.

Diaphragmatic shear modulus at various submaximal inspiratory mouth pressure levels

This study assessed the shear modulus of the diaphragm at various submaximal inspiratory mouth pressure levels by ultrasound shear wave elastography. In 14 healthy male subjects, diaphragmatic shear moduli were assessed at end expiration during resting breathing and at submaximal inspiratory tasks at 15, 30, 45, 60, and 75% of the maximal inspiratory mouth pressure. The shear modulus increased along with mouth pressure, and the mouth-pressure–shear-modulus relationship fit the second-order polynomial regression equation (r2 = 0.99 ± 0.01; all subjects, r2 ≥ 0.95) better than it did the simple linear regression equation (r2 = 0.94 ± 0.05; 8/14 subjects, r2 ≥ 0.95). The second regression coefficient in the second-order polynomial equation was a negative value in 10 of 14 subjects, which indicates that the second-order polynomial regression equation opened downwards. These findings suggest that the diaphragmatic shear modulus increases along with inspiratory mouth pressure, but the rate of increase slows when the pressure reaches higher levels.

Design and fabrication of pectin-coated nanoliposomal delivery systems for a bioactive polyphenolic: Phloridzin

Nanostructured colloidal delivery systems comprising of pectin-coated nanoliposomes (pectonanoliposomes) were developed as carriers for a bioactive polyphenolic compound (phloridzin). Phloridzin-loaded nanoliposomes were fabricated using a heating-stirring-sonication method, and coated with low methoxyl pectin using an electrostatic deposition approach. Dynamic light scattering, micro-electrophoresis, atomic force microscopy, and UV–Visible spectroscopy were used to investigate the impact of system composition on the size, charge, morphology and stability as well as immobilization, adsorption and encapsulation efficiencies of the pectonanoliposomes. Response surface methodology was used to optimize the composition of the pectonanoliposomes based on particle size and charge characteristics. Linear, quadratic and interaction effects of 1,2-dioleoyl-3-trimethyl ammonium propane/lecithin, phloridzin/lecithin and pectin/liposome ratios significantly influenced the mean hydrodynamic diameter and/or surface charge of pectonanoliposomes. Second-order polynomial regression models were generated for intensity-weighted particle size and zeta potential of the designed carriers. Topographic and phase contrast images showed that pectonanoliposomes exhibited a range of different morphologies. Coating the nanoliposomes with pectin improved their immobilization and encapsulation efficiencies as well as physical storage stability. Cationic pectonanoliposomes were superior to plain systems regarding long-term stability. Our results suggest that pectonanoliposomes may be suitable delivery systems for polyphenolic nutraceuticals, such as phloridizin, in functional food and pharmaceutical applications.

Optimization of the Key Medium Components and Culture Conditions for Efficient Cultivation of G. sulfurreducens Strain PCA ATCC 51573 Using Response Surface Methodology

Microbial electrolysis cell (MEC) is a promising method for hydrogen production by microorganisms. The culture conditions were optimized for Geobacter sulfurreducens PCA ATCC 51573 using response surface methodology involving central composite design (CCD). Effects of sodium bicarbonate, sodium acetate, sodium fumarate, incubation temperature, and initial pH value of culture on cell growth of G. sulfurreducens PCA ATCC 51573 were studied. Experimental data obtained from CCD were utilized to generate a second-order polynomial regression model and to evaluate the effect of the variables studied on the optical density (OD) as the main response of bacterial growth of the strain PCA ATCC 51573. The statistical analysis showed that sodium bicarbonate, sodium acetate, and sodium fumarate had significant effect on OD value (P < 0.01). Similar results revealed sodium bicarbonate had significant interaction with sodium acetate and sodium fumarate (P < 0.05). On the other hand, quadratic term of temperature and initial pH value had a significant effect on OD value at 99% probability level (P < 0.01). Furthermore, interaction between culture temperature and initial pH value significantly affected OD value (P < 0.01). The optimum conditions suggested by the model for obtaining high OD value were 3.11 g/L NaHCO3, 4.10 g/L NaC2H3O2, 16.24 g/L Na2C4H2O4, 28.31 °C incubation temperature, and 6.80 pH value. The statistical model predicted that an OD value of 0.88 could be attained under optimum conditions. Result of verification experiment showed OD value of 0.87 was obtained which confirmed the adequacy of the model for the determining optimum conditions.

A modeling study by response surface methodology (RSM) on Th(IV) adsorption optimization using a sulfated β-cyclodextrin inclusion complex

The inclusion complex (sulfated-β-CD@NAA) of sulfated β-cyclodextrin and α-naphthylacetic acid was synthesized for adsorption of low concentrations of thorium from aqueous solutions. The structure and property of sulfated-β-CD@NAA were characterized by Fourier transform infrared spectroscopy, thermogravimetric, X-ray diffraction, proton nuclear magnetic resonance, specific surface area measurement and scanning electron microscopy. The characterization analysis confirmed the formation of new solid phase. The results indicated that α-naphthylacetic acid embedded into the cavity of sulfated β-cyclodextrin partly from the secondary face and the thermal stability of inclusion complex was significantly increased. The experiments were designed by Box–Behnken design combined with response surface methodology. The adsorption parameters of pH value, contact time, initial concentration were used as the independent variables and their effects were investigated on the Th(IV) adsorption capacity. Second-order polynomial regression models were derived and analysis of variance was utilized to judge the adequacy of the chosen models. The maximum Th(IV) adsorption capacity (12.75 mg g−1) was achieved under the following conditions: pH value 2.5, contact time 35 min, initial concentration 30 mg L−1. Prediction of models was in good agreement with experimental results. The experimental adsorption kinetic data followed a pseudo-second-order equation with the correlation of 0.9996, indicating the chemical adsorption. The obtained equilibrium isotherm data were fitted well with Langmuir model in the concentration range considered. The thermodynamic parameters (∆H0 < 0, ∆S0 < 0, ∆G0 < 0) indicated that the adsorption process was exothermic and spontaneous. Regeneration of Th(IV)-loaded sulfated-β-CD@NAA with 0.1 M HNO3 solution, and the regenerated sulfated-β-CD@NAA can be reused for adsorption of Th(IV).

Dietary histidine requirement of juvenile blunt snout bream (Megalobrama amblycephala)

A 9-week feeding trial was conducted to estimate the dietary isoleucine requirement of juvenile blunt snout bream. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded isoleucine levels ranging from 5.3 to 20.1 g kg−1 dry diet. At the end of the experiment, weight gain (WG), specific growth rate (SGR), feed efficiency ratio (FER) and protein efficiency ratio (PER) increased with increasing dietary isoleucine level up to 11.1 g kg−1 dry diet, and dietary isoleucine level above 14.2 g kg−1 dry diet declined these performances. Dietary isoleucine levels (14.2 and 17.3 g kg−1 dry diet) significantly improved whole-body protein content, but decreased whole-body lipid, plasma triglyceride and cholesterol contents. Significantly lower visceral fat index (VFI) in fish fed with 14.2 g kg−1 dietary isoleucine was observed compared to those fed with deficient or excessive isoleucine. Dietary isoleucine supplementation significantly increased plasma isoleucine concentration, while plasma valine and leucine concentrations showed a reversed trend. Dietary isoleucine levels regulated the target of rapamycin (TOR) gene expression and improved plasma superoxide dismutase (SOD) activity in juvenile blunt snout bream. Based on second-order polynomial regression model analysis of SGR and FER, the optimum dietary isoleucine requirement was estimated to be 13.8 g kg−1 dry diet (40.6 g kg−1 dietary protein) and 14.0 g kg−1 dry diet (41.2 g kg−1 dietary protein), respectively.

Single-Parameter Thin-Layer Drying Equations for Long-Grain Rice

Abstract. The use of multiple parameters in thin-layer drying equations makes it difficult to compare and quantify the impact of drying air temperature, relative humidity, and other factors on the drying characteristics of an agricultural crop. In this study, two single-parameter equations are proposed to quantify thin-layer drying characteristics of contemporary long-grain rice cultivars grown in the Mid-South U.S. Drying runs were first performed to obtain drying curves for cultivar ‘Roy J’ under 18 air conditions; several drying equations were evaluated for their fit to each drying curve. The proposed single-parameter equations (modified Page equation and infinite-series diffusion equation) described the experimental drying data very accurately; the root mean square errors in moisture ratio obtained for the modified Page and infinite-series diffusion equations varied in the ranges of 0.2 to 1.4 and 0.3 to 1.5 percentage points, respectively. The dependence of drying air temperature and relative humidity on drying parameters of the modified Page and infinite-series diffusion equations was described by second-order polynomial regression equations. The impact of harvest moisture content on the drying characteristics of rice was observed to be negligible. The validity of the developed single-parameter equations was also evaluated for five other long-grain rice cultivars; for these cultivars, the maximum errors in the moisture ratio prediction using the modified Page and infinite-series diffusion equations were 2.9 and 3.4 percentage points, respectively. This study provides thin-layer drying data for contemporary rice cultivars in the Mid-South U.S. The resulting thin-layer drying equations are expected to improve the accuracy of deep-bed drying models. While the proposed single-parameter equations were tested only for long-grain rice, the methodology presented in this research could be used to develop similar single-parameter thin-layer drying equations for short-grain and medium-grain rice, as well as other agricultural crops. As such, these equations could be readily used in quantifying the impacts of air and rice variables on drying rates. Keywords: Mathematical modeling, Rice, Thin-layer drying.

A dynamic multi-level optimal design method with embedded finite-element modeling for power transformers

This paper proposes a dynamic multi-level optimal design method for power transformer design optimization (TDO) problems. A response surface generated by second-order polynomial regression analysis is updated dynamically by adding more design points, which are selected by Shifted Hammersley Method (SHM) and calculated by finite-element method (FEM). The updating stops when the accuracy requirement is satisfied, and optimized solutions of the preliminary design are derived simultaneously. The optimal design level is modulated through changing the level of error tolerance. Based on the response surface of the preliminary design, a refined optimal design is added using multi-objective genetic algorithm (MOGA). The effectiveness of the proposed optimal design method is validated through a classic three-phase power TDO problem.

Parametric Optimization of Biohydrogen Production from Potato Waste and Scale-Up Study Using Immobilized Anaerobic Mixed Sludge

Response surface methodology (RSM) using the central composite design (CCD) approach was used in the parametric optimization of biohydrogen production from potato waste and the scale-up study was investigated using immobilized anaerobic mixed sludge. A two-level-four-factor (24)-CCD obtained via a statistical software (STATISTICA 8 release 7) was used to generate 26 fermentation experiments. The experimental results were used to generate a second-order polynomial regression equation relating the biohydrogen production to the parameters considered (potato waste concentration, pH, temperature, and fermentation time). The optimum conditions for biohydrogen production were 39.56 g/L, 7.86, 37.87 °C and 82.58 h for potato waste concentration, pH, temperature, and fermentation time, respectively with a corresponding biohydrogen yield of 68.54 mL H2/g total volatile solids (TVS). A coefficient of determination (R2) of 0.99 was obtained by solving the polynomial regression equation. The obtained optimized conditions were further validated experimentally resulting in biohydrogen yield of 79.43 mL H2/g TVS, indicating a 15.9% biohydrogen increase. Scale-up conducted at the validated optimized conditions with the immobilized bacteria generated 298.11 mL H2/g TVS with maximum fraction of 56.38%. Therefore, these results demonstrate the potential of up-scaling biohydrogen production using immobilized bacteria which could be instrumental towards its large-scale production.

Effects of dietary &lt;i&gt;Aloe vera&lt;/i&gt; crude extracts on digestive enzyme activities and muscle proximate composition of GIFT tilapia juveniles

This study investigated the effects of dietary Aloe vera powder extract on the activities of digestive enzymes and muscle composition of Oreochromis niloticus (GIFT strain) juveniles. Five dietary groups were formulated in which A. vera powder was added into a tilapia feed at 0.5%, 1.0%, 2.0%, and 4%/kg feed, and fed for eight weeks. Amylase, trypsin, and lipase activities in the liver and along the alimentary canal (stomach, midgut, and hindgut) varied significantly between dietary groups. Amylase activity was significantly enhanced in the liver of fish fed 0.5, 1, and 2% dietary A. vera , and in the stomach of those fed 1%. Total amylase activity in the gastrointestinal tract (total gut) was significantly enhanced in fish fed 0.5% and 1% compared with control and those fed 4% dietary A. vera . Trypsin activity was significantly enhanced in the stomach of fish supplemented with 0.5% dietary A. vera and in the duodenum of those supplemented with 1%, 2%, and 4% dietary A. vera when compared with the control. Lipase activity was increased in the duodenum of fish fed 1.0% dietary A. vera when compared with the control. Muscle moisture content was significantly lower in all A. vera -supplemented fish, whereas protein was lower in those fed 2% and 4% A. vera diet when compared with the control. Based on second-order polynomial regression analysis, dietary A. vera inclusion level less than or equal to 1.76%, 1.82%, 2.10%/kg feed was determined to be suitable in enhancing carbohydrate, protein and lipid digestion, respectively, in GIFT tilapia in this study. Keywords : Aquaculture, digestion enhancers, freshwater fish, medicinal herbs

Influence of processing parameters on creep and recovery behavior of FDM manufactured part using definitive screening design and ANN

PurposeThe purpose of this paper is to investigate the effect of process parameters of fused deposition modelling (FDM) 3D printing process on viscoelastic responses (creep compliance and recoverable compliance) of FDM built parts using a novel experimental design technique.Design/methodology/approachAs part of the process characterization, a recently developed class of three-level design methodology – definitive screening design (DSD) – was used in this study to fit a second-order polynomial regression model. Artificial neural network (ANN) was also used to determine the optimal process parameters to improve creep compliance and recoverable compliance. The relationship between layer thickness, air gap, raster angle, build orientation, road width, number of contours and creep performance of FDM fabricated part was thereafter established empirically. Scanning electron microscope (SEM) is used to examine and characterize the morphology of the structures for some samples.FindingsThis study found that the creep resistance of FDM-manufactured part is significantly influenced by layer thickness, air gap, raster angle and number of contours and it can be improved by optimizing the settings of the selected parameters. The relationship between FDM process parameters and creep properties was determined, with the best creep performance observed by using 0.127 mm of layer thickness, zero air gap, zero raster angle, build orientation of 17.188°, road width of 0.4572 mm and 10 contours. Finally, the result is verified by confirmation experiments. The results prove that a DSD is a very effective design in characterizing the influence of process parameters on creep properties of FDM-built part at the lowest cost.Originality/valueThe originality of this paper lies in characterizing and optimizing the effect of process parameters on creep performance of FDM manufactured part that has not been studied in all previous studies. The paper highlights, for the first time, how the application of DSD can overcome most of the limitations encountered in the conventional techniques. This study can be used as a guide to the different additive manufacturing users of various industries and the results provide a good technical database on how FDM process parameters influence the creep performance of manufactured parts.

Recovery of chromium from residue of sulfuric acid leaching of chromite

Abstract The sulfuric acid leaching process is widely considered to be a cleaner technology to prepare chromium salt from natural chromite as no Cr(VI)-bearing wastes are generated or discharged. However, some insoluble anhydrous chromium sulfate could precipitate causing a serious chromium resource loss and potential pollution problems. For the purpose of recovery of chromium from leaching residue, a Box–Behnken design (BBD) based ammonium leaching treatment is investigated and optimized. A second-order polynomial regression model that reveals the functional relationship between processing parameters and recovery time is established and verified by the analysis of variance (ANOVA). Predicted results show a good agreement with the experimental data. The main and interactive effects of the processing parameters on the recovery time are illustrated by three-dimensional (3D) response surfaces. It was found that increasing temperature (from 70 to 90 °C) and acidity (pH value from 0 to −0.5) of solution have positive effect on the leaching efficiency, and the plot of recovery time versus ammonium dosage shows a parabola-shape. On the basis of the findings in this study, an advanced sulfuric acid leaching process of chromite is proposed. Experimental results showed that hydrous and anhydrous chromium sulfate were completely recovered, and the average difference between the predicted and actual recovery times was less than 4%. All of the chromium resources can be utilized in the novel process, and no hazardous wastes or potential pollutants are discharged to the environment.

Hybrid kernel principal component regression and penalty strategy of multiple adaptive genetic algorithms for estimating optimum parameters in abrasive waterjet machining

The quality of machined surface can be improved by choosing the right values of the associated parameters through an optimization process. Recently, researchers have used nonlinear programming models, soft-computing approaches, and hybrid of them to estimate the surface roughness of abrasive waterjet (AWJ) machining. Some researchers have performed a second order polynomial regression (SOPR) as a basis in developing a nonlinear programming in AWJ machining. Nevertheless, the SOPR was developed without considering the existence of multicollinearity which can lead to inappropriate prediction. Besides, it also needs a specific nonlinear regression model in advance. It will be difficult to specify an appropriate nonlinear model of SOPR since it does not usually involve all combination variables in its model. Instead, kernel principal component regression (KPCR) will be employed to overcome the weaknesses of the SOPR. After development and model selection in the KPCR models, the best KPCR is used as an objective function in a nonlinear programming model of AWJ with a certain set of constraints. Single genetic algorithm (GA) and its variants can be conducted to solve the nonlinear programming problem. However, they can yield different decision values due to randomness of their initial population which implies that the best decision values may not converge in a certain optimum solution. Under this circumstance, multiple adaptive probabilities genetic algorithm (MAPGA) combined with a penalty method to solve the optimization problem is proposed. Hybrid of KPCR and MAPGA gives more stable solution compared to hybrid of KPCR with single genetic algorithm and original adaptive probabilities genetic algorithm. Our proposed technique also provides an optimum solution in reasonable time.

Age-Related Changes in Ocular Aberrations and the Yamagata Study (Funagata).

Human vision quality is influenced by ocular aberrations, including astigmatism and higher-order aberrations (HOAs), in combination with other optical factors. In this study, we introduce the results and perceptions of previous studies investigating these aberrations. We also introduce our results obtained as part of the Yamagata Study (Funagata), a population-based epidemiologic study. To investigate the astigmatic change with age, researchers have used the power vector analysis, allowing incorporation of the magnitude and axis of astigmatism into statistical analyses. It was found that the axes of refractive astigmatism shift from with-the-rule toward against-the-rule with aging. It was demonstrated that the change in corneal curvature causes this shift. It was further reported that HOA increase is associated with deterioration of visual function. Some authors described that HOA increases with age in adults and that aging disrupts compensation between corneal and internal aberrations. Our study confirmed these results after considering possible confounding factors. HOA decreased from childhood to early adulthood and then increased with age, as modeled by a second-order polynomial regression. It is possible that the reduction in HOA is involved in emmetropization. In addition to age, HOA is known to be influenced by several factors, including pupil diameter, accommodation, and pupil shift. Although HOA increases with aging, the increase may be compensated by decreasing the pupil diameter. Better understanding of the causes of optical alterations with aging will improve the maintenance of vision quality.

Preparation of Cu-Cr alloy powder by heat mechanical alloying and Box-Behnken design based optimization

Mechanical alloying is a promising method for preparing Cu-Cr alloy powder, while some troublesome challenges in cost and efficiency have yet to be solved. In this work, nano-scale Cu-Cr alloy powder was prepared by co-precipitation and advanced heat mechanical alloying (HMA) processes with low-cost raw materials. Results showed that the co-precipitation treatment by using ammonium hydroxide as the precipitant is an appropriate approach for manufacturing uniformly fine precursor. Box-Behnken design (BBD) was employed to investigate the combined effects of milling temperature (T), milling duration (t) and ball-to-powder mass ratio (R) on the grain size of Cu-Cr alloy powder (GS) and to optimize the HMA process for fine alloy powder production. A second-order polynomial regression model was established and was verified by the analysis of variance (ANOVA), which shows good fit of the experimental data. Three-dimensional (3D) response surfaces were plotted to elucidate the main and interactive effects of the three parameters on the grain size of Cu-Cr alloy powder, and the optimum condition for HMA process was proposed.

Discussion of “Optimization of carpet waste fibers and steel slag particles to reinforce expansive soil using response surface methodology” by M. Shahbazi, M. Rowshanzamir, S.M. Abtahi, S.M. Hejazi [Appl. Clay Sci., doi:10.1016/j.clay.2016.11.027

Shahbazi et al. (2017) adopted the response surface methodology (RSM) technique to evaluate the combined efficiency of slag treatment and fiber reinforcement in the stabilization of an expansive soil mixture. The swell percent (Sp), swelling pressure (Ps), and unconfined compressive strength (qu) were represented as a function of three independent variables (i.e. slag content, fiber content, and fiber aspect ratio) by the second-order polynomial regression model, and ANOVA analysis was adopted to allocate a contribution percentage to each component of the regression model. It was noticed that the reported fitting parameters for Sp and Ps provided ambiguous predictions, and thus were recalculated to avoid any misleading information for readers. The statistical technique proposed by the authors is limited to allocating contribution factors to regressional components rather than evaluating the net favorable impact of each independent variable on the desired dependent variable. Therefore, the partial derivative sensitivity analysis approach was proposed as a simple and practical alternative to address the aforementioned uncertainty. The new approach presented in this discussion not only provides a unique contribution factor for each independent variable but also accounts for the combined favorable contribution offered by all three independent variables.

Biomethanization of the Mixture of Cattle Manure, Pig Manure and Poultry Manure in Co-Digestion with Waste Peels of Pineapple Fruit and Content of Chicken-Gizzard - Part II: Optimization of Process Variables

Background: The indiscriminate discharge of industrial waste, agricultural-biomass waste, waste of municipal, domestic and kitchen waste has negatively impacted on the environment and human health. It is very pertinent to reduce these impacts to the barest minimum through conversion of the waste to useful products. The conversion of these wastes to generate alternative energy to fossil fuel through the technology of anaerobic fermentation is one of the viable and more fascinating options for the management of waste. Objective: To investigate the interactive effect and optimization of process parameters of temperature, total solid content and feed/inoculum ratio on the biomethanization of the mixture of cattle manure, pig manure and poultry manure in co-digestion with waste peels of pineapple fruit and content of chicken-gizzard. Method: Full-factorial central composite design of experiment (RCCD) of the response surface method (RSM) was adopted to assess the possible interactive effects of the process variables and the optimal parameters (i.e. optimization) for biogas/biomethane production in an anaerobic digester. Result: The process variables had a significant (P &lt; 0.05) positive and negative interactive effect on the biomethanization process. A second-order quadratic polynomial regression model which is statistically significant (p &lt; 0.0001) was respectively obtained for cumulative biogas yield (CBY), biomethane content (BC) and hydraulic retention time (HRT). Temperature of 55.2°C; total solid content of 6.25%; and feed/inoculums ratio of 1:2 were found to be the optimum values required to attain a predicted optimum values of 6.261 dm3/g CBY, 71.54% BC within a minimum 8 days of HRT. At this optimum process conditions, the experimental observed maximum CBY, and BC with a minimum HRT were found to be 6.217 dm3/g of slurry, 71.10% and 7 days, respectively. Conclusion: Biogas/biomethane generation through co-substrate anaerobic fermentation of animal waste with waste of fruits constitute a reasonable and applicable renewable energy alternative and this can be optimized through response surface methodology.

Estimation and Prediction of Grassland Cover in Western Mongolia Using MODIS-Derived Vegetation Indices

Spectral indices derived from satellite observations, such as the Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), are widely used for grassland monitoring and management around the globe. In this study we contrasted performance of NDVI and EVI metrics obtained from Aqua and Terra, the two satellite platforms carrying the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor, for estimating grassland cover measured at ground level on ninety-two 1 × 1 km blocks distributed from semidesert to high montane grasslands in the Sailugem Range of western Mongolia, where overgrazing and overstocking of domestic livestock are concerns for pastureland management. We also explored utility of late spring (May) vegetation indices for forecasting vegetation cover at the peak of the growing season (July). Vegetation indices developed using MODIS 1-km monthly data (MOD13A3 and MYD13A3) were strongly related to on-the-ground field estimates of the percentage of vegetation cover in July (74−85% variation explained), with second-order polynomial regressions demonstrating better fit to the data than first-order regressions, Aqua vegetation indices (VIs) explaining slightly more variance than Terra’s VIs, and NDVI performing comparably to EVI for both Aqua and Terra. Both Aqua and Terra VIs for May were highly predictive of July vegetation cover (R2 = 0.80−0.84). We conclude that monthly MODIS NDVI and EVI datasets can be useful for rangeland managers in western Mongolia to monitor and predict summer pasture conditions at the regional level, where science-based guidance on grazing policy and practices is much needed.