Cement-based composites are one of the most popular construction materials that have been widely used since the past due to their many properties. In order to develop the current performance of these ...materials, it is of importance to investigate the changes in the engineering properties of the materials as a result of the addition of different additives to the mixture. In this context, the idea of whether cellulose derivatives, which are industrial materials with wide application areas in many sectors, can be used in construction materials has emerged. In this study, the effects of the use of cellulose derivatives Carboxymethyl cellulose (CMC) and Microcrystalline cellulose (MCC) as additives on the performance of concrete were investigated. For this purpose, cellulose additives were added to the mixture at the rates of 0.25–0.5%–0.75–1% by weight of cement and the samples were produced. Ultrasonic pulse velocity, flexural and compressive strength tests were performed to determine the engineering properties of the samples. The highest compressive and flexural strengths of 69.162 MPa and 9.592 MPa, respectively, were obtained from the sample produced using 0.5% MCC. Concrete produced using MCC showed higher values in all analyses compared to CMC samples. Furthermore, the experimental results obtained were statistically evaluated using the response surface method. Accordingly, the R2 values obtained as a result of statistical analysis of the compressive strength, flexural strength and ultrasonic sound transmission velocity test results were 0.9031, 0.9299 and 0.9785, respectively, and the suitability of the method was revealed.
Display omitted
•Experimental determination of engineering properties of concretes.•Investigation of the effect of different cellulose derivatives on the performance of concrete.•Statistical validation and prediction of experimental data using the response surface method.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Aluminum electrolysis spent cathode carbon (SCC), as typical solid hazardous waste, poses significant environmental risks. Harmless treatment of SCC and recycling of its carbon component are ...important research areas. In this study, SCC was subjected to microwave hydrothermal acid leaching to remove harmful components, followed by the production of high-quality graphite via iron-catalyzed graphitization. The effects of reaction temperature, heating time, and catalyst loading on the graphitization conversion of SCC were investigated. The catalytic graphitization process of SCC was optimized using the response surface method. The results show that when the reaction temperature is 1520 °C, the heating time is 85.24 min, and the catalyst loading is 46.15 wt%, the graphitization degree of the sample is 97.61 %. The samples prepared under the optimal conditions were characterized using XRD, Raman, SEM, and TEM. The results reveal that the catalytic graphitization process significantly influences the conversion of microcrystalline structures in SCC into graphite structures. The iron-catalyzed transformation of microcrystalline carbon was analyzed to elucidate the graphitization transformation mechanism. This study offers an effective pathway for the high-value utilization of SCC. It also serves as a technical reference for the catalytic graphitization conversion of carbon materials.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A hybrid method for short-term load forecasting, namely RF-MGF-RSM model, was established.•The paper constructed on multivariable response surface method to well solve the fluctuating problems of ...the peaks and valleys load data.•The proposed model shows stronger robustness and significantly greater forecasting accuracy for short-term loads.
Accurate load forecasting is helpful for optimizing the use of power resources. To this end, this investigation proposes a hybrid model for short-term load forecasting, namely the RF-MGF-RSM model, that hybridizes random forest (RF) model and the mean generating function (MGF) model. A time variable, a random forest forecasting value, and a forecasting value by MGF are used as the input variables to in the modeling processes. The RF-MGF-RSM model uses its primary error as the response. The forecasted values of RF and MGF are the input variables to obtain the final forecast through the response surface method. Numerical experiments prove that the hybrid model has a significantly greater forecasting accuracy for short-term load than the original model that is based on selected forecasting accuracy indicators, especially with respect to peaks and valleys in greatly fluctuating data.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The rotating mechanism is applied to a triplex-tube LHTES system.•The effect of rotation on heat transfer during solidification of PCM is studied.•Response surface method is used to optimize the ...solidification performance of LHTES.•The fluid-structure coupling functions of solidification time for each parameter are fitted.
In this paper, the rotation mechanism is applied to a triplex-tube latent heat thermal energy storage system for the first time. Numerical simulation is used to study the effect of rotation on the solidification performance of this system, and the accuracy of the numerical model is verified experimentally. Firstly, the evolution of the liquid phase, the total amount of heat energy released, and the rate of heat energy released in the solidification process of the thermal energy storage system without rotation and at different rotational speeds are compared and analyzed. It is found that the solidification time of the system at 1 rpm is reduced by 83.85 % and the heat release rate is 4.98 times higher than that at the no-rotation state. It shows that the incorporation of a rotational mechanism can effectively reduce the solidification time and increase the heat release rate of the system. Then, the internal dynamic temperature/flow rate response is used to investigate the change in the heat transfer mode of the solidification process by the addition of rotation and the improvement of the phenomenon of difficult solidification zones, which improved the internal temperature uniformity and thus the solidification behavior. By response surface method, the geometric factors of the heat storage system (fin length, fin width, fin angle) are analyzed by multiple factors. The function of the optimized target (solidification time) on each variable is fitted, and it is found that the fin length had the most significant effect on the optimized target. Finally, the effect of relevant physical parameters on the solidification process and heat release of the thermal energy storage system is investigated. To ensure low solidification time and high heat release rate, this study recommends that the temperature difference between phase change material and tube wall is higher than 25 K. This paper also proves the feasibility and superiority of copper fin/tube wall material.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Display omitted
•A nanofluid-based PVT/NPCM is numerically simulated using a transient model.•Aluminum oxide nanoparticles are dispersed into both working fluid and PCM.•Response surface method is ...applied to gain a predictive model for the system.•The system is optimized using both single and multi-objective optimization.•Adding nanoparticles to fluid is more effective than its addition into PCM.
In this study, a nanofluid-based photovoltaic thermal system integrated with nano-enhanced phase change material is numerically simulated using a transient three-dimensional model. Aluminum oxide nanoparticles are dispersed into both the heat transfer fluid, which is water, and the Rubitherm series of organic phase change material. Response surface methodology is applied to gain a predictive model for estimating the behavior of the system in terms of four different design parameters of phase change material layer thickness, heat transfer fluid mass flow rate, and the mass fraction of nanoparticles through the phase change material and working fluid. The relationships between the mentioned parameters and responses, including electrical and thermal power, exergy, and entropy generation along with their interaction impacts on system performance are obtained. Finally, employing single and multi-objective optimization, different scenarios are defined to optimize the system based on the designer’s goals. The results reveal that the dispersion of nanoparticles within the heat transfer fluid leads to a better improvement in photovoltaic thermal system performance compared to its addition to the phase change material. Based on the multi-objective optimization method to maximize electrical and thermal exergies, simultaneously, results show the best electrical and thermal exergies of the system can be achieved to 135.92 and 2.44 W/m2, respectively.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
In this study, electrochemical oxidation of combed fabric dyeing wastewater was investigated using graphite electrodes. The response surface methodology (RSM) was used to design the ...experiments via the central composite design (CCD). The planned experiments were done to track color changes and chemical oxygen demand (COD) removal. The experimental results were used to develop optimization models using RSM and the artificial neural network (ANN) and they were compared. The developed models by the two methods were in good agreement with the experimental results. The optimum conditions were found at 150 A/m2, pH 5, and 120 min. The removal efficiencies for color and COD reached 96.6% and 77.69%, respectively. The operating cost at the optimum conditions was also estimated. The energy and the cost of 1 m3 of wastewater required 34.9 kWh and 2.58 US$, respectively. The graphite electrodes can be successfully utilized for treatment of combed fabric dyeing wastewater with reasonable cost.
In this paper, a numerical study is performed to investigate the effects of nanofluid on the productivity of a stepped solar still. Moreover, a sensitivity analysis is arranged to determine the ...sensitivity of the hourly productivity to the height and length of steps. Finally, an optimization analysis is performed by using response surface method to optimize the geometry of stepped inside the still. Obtained results indicate that 22% enhancement in the hourly productivity is observed by increasing the nanoparticle concentration from 0% to 5%. Moreover, there is only 2.1% difference between the estimated results by RSM and calculated results by CFD.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•DESs highly promoted the activity of ω-transaminase (ω-TA) by 390%.•Optimal enzyme activity is achieved at 40 ℃, in 10 vol% (ChCl: Urea) and pH 8.•The mechanism is the improvement of solubility and ...proton exchange promoted by urea.•A green, economical and convenient method was explored to improve ω-TA activity.
ω-transaminase (ω-TA) shows a significant promising in the synthesis of chiral amines. However, the poor activity of ω-TA in buffer water solution limits its application in industry, so green and economic methods adopted to improve ω-TA activity still face challenges. Here, deep eutectic solvents (DES) were used as the co-solvent to improve the catalytic activity of ω-TA. The results have shown that DES (ChCl: Urea 1:1) was the most suitable co-solvent for increasing the biotransformation efficiency of the ω-TA in nine different choline chloride-based DESs. The optimal enzymatic activity was achieved at 40 ℃, in 10 vol% DES and pH 8. The specific activity of ω-TA in DES was increased by 3.9 times due to the reinforced interactions between DES and enzyme. The kinetic analysis of transaminase showed that DES enhanced affinity of ω-TA for 1-(R)-PEA and pyruvate to increase by 1.93 and 1.63 times respectively compared with the control. Molecular docking shows that urea acted as a proton donor and a receptor during the enzymatic reaction, the docking binding energy increases to 3.21 and 3.59 kcal/mol, promoting the transamination reaction. DES can significantly improve the catalytic activity of ω-TA, which has broad development prospects in the field of green and efficient synthesis of pharmaceutical and natural product intermediates.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Design of metal hydride-based hydrogen storage reactors is often performed using numerical/experimental modelling which is computationally/economically difficult. This paper investigates the ...applicability of Response Surface Methodology (RSM) coupled Local/Global Sensitivity Analysis (L/GSA) to investigate – i) the applicability of advanced RSMs in predicting the responses for storage systems efficiently, ii) the applicability of advanced RSMs to perform L/GSA to identify the sensitive input design parameters based on their effect on the Outputs of Interests (OIs), i.e., reaction fraction (i.e., C) and bed temperature (i.e., T), and iii) the dependence of importance ranking of design parameters on the employed L/GSA methodology. The study is conducted in two stages. In the first stage, the most accurate RSM was identified among fourteen traditional and advanced RSMs, i.e., radial basis, kriging, quadratic, moving least square, support vector machine etc., employing a measure of precision, i.e., Nash–Sutcliffe Efficiency (NSE). RSMs were constructed based on the values of OIs estimated using finite element simulation using COMSOL software for random realizations of inputs generated via Latin Hypercube Sampling (LHS). In the second stage, the importance ranking of design parameters was estimated for both OIs using six different L/GSAs based on the input-output relationships estimated in stage one. All the codes of RSMs and L/GSAs were written and validated in MATLAB. Finite element simulations of the random realizations were performed using COMSOL software. For the present study, NSEs of the considered RSMs were ranging between 0.6262-0.8544 and 0.4652–0.8081 for C and T respectively, indicating the importance of selection of appropriate RSM. RBF-augmented Compact-I and kriging were the most accurate RSMs with NSEs approximately 10%–20 % higher to those of frequently used polynomial RSM. Time (t) and mass of hydrogen to be stored (MH) were the most; and external temperature (Text) and porosity (E) were the least sensitive inputs corresponding to C and T, with differences of 80–90 % in the sensitivity indices respectively. The ranking prediction was highly dependent upon the employed L/GSA methodology, with Morris's screening observed to be the least accurate. The RSM methods described in this study help to design and investigate the metal hydride reactors for various applications (space heating, hydrogen storage, storage for vehicular application, metal hydride compressor) without undergoing detailed mathematical modelling of the system. The proposed methodology may significantly assist the designers to focus (or vary) on the sensitive inputs only during the physical modelling of systems to improve their performance. This sensitivity analysis is helpful to find out the most advance sensitivity analysis method which can be used to find out the most sensitivity parameter which can be varied according to their rankings to achieve the required performance of metal hydride reactor for the particular application. The advanced RSMs assist to identify these sensitive inputs quickly by reducing the mathematical efforts in the L/GSA by providing the accurate input-OIs relationships based on the limited numerical simulations. This will significantly save the resources and time of industries required in physical modelling/numerical simulations significantly, which otherwise would have been invested on investigating the non-sensitive inputs.
•Response Surface Methods (RSMs) Coupled Local/Global Sensitivity Analysis (L/GSA) proposed for hydrogen storage systems.•Performance of advanced RSMs were superior in terms of accuracy and efficiency as compared to the traditional polynomial RSMs.•Practical implementation of L/GSAs for hydrogen storage systems made feasible and efficient by coupling advanced RSMs.•Significant dependence of importance ranking of inputs on the type of L/GSAs with superior performance of Borgonovo's GSA.•Proposed methodology will save the resources/time in designing storage systems.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
