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We consider a no-wait m-machine flowshop scheduling problem which is common in different manufacturing industries such as steel, pharmaceutical, and chemical. The objective is to minimize total tardiness since it minimizes penalty costs and loss of customer goodwill. We also consider the performance measure of total completion time which is significant in environments where reducing holding cost is important. We consider both performance measures with the objective of minimizing total tardiness subject to the constraint that total completion time is bounded. Given that the problem is NP-hard, we propose an algorithm. We conduct extensive computational experiments to compare the performance of the proposed algorithm with those of three well performing benchmark algorithms in the literature. Computational results indicate that the proposed algorithm reduces the error of the best existing benchmark algorithm by 88% under the same CPU times. The results are confirmed by extensive statistical analysis. Specifically, ANOVA analysis is conducted to justify the difference between the performances of the algorithms, and a test of hypothesis is performed to justify that the proposed algorithm is significantly better than the best existing benchmark algorithm with a significance level of 0.01.

The quality of engineering education has been improved by the accreditation criteria established by credentialing agencies. As a result, the Industrial and Management Systems Engineering program at Kuwait University has been maintaining accreditation by the Engineering Accreditation Commission of the Accreditation Board for Engineering and Technology for over 15 years. Since the assessment process needs to be thorough and simple at the same time, this paper explains how the Industrial and Management Systems Engineering program at Kuwait University designed and implemented an efficient and effective process for the establishment and assessment of the new Student Outcomes required by the Engineering Accreditation Commission of the Accreditation Board for Engineering and Technology. All the seven new Student Outcomes specified by Criterion 3 of the accreditation requirements are shown to be satisfied by using four different assessment tools, two of which are direct and the other two are indirect. All the results have been statistically verified by using hypothesis testing with a significance level of 0.01. The paper presents a simple and practical assessment method which can be used by other engineering programs that are in the process of implementing the new Student Outcomes.

We address the four-machine flowshop scheduling problem with the objective of minimizing makespan with uncertain processing times The problem was addressed in the literature (RAIRO Operations Research 54, 529-553) and different algorithms were proposed. In this paper, we propose a new algorithm for the problem. The new proposed algorithm is compared with the best algorithm in the literature by using extensive computational experiments. Computational experiments indicate that the new proposed algorithm performs much better than the best algorithm in the literature in terms of error while both have the same computational time. Specifically, the new proposed algorithm reduces the error of the best existing algorithm in the literature over 40%. This result has been confirmed by using tests of hypotheses with a significance level of 0.01.

Highly pure nanosilica was synthesized through a facile hydrometallurgy-based method from silicomanganese slag as a low cost silica source. The synthesis route included short-term nitric acid dissolution at room temperature, gelation, washing, drying, and calcination steps. The experimental dissolution conditions resulted in a dissolution efficiency of 98%. The crystalline structure, chemical composition, chemical bonding, microstructure and elemental analyses, particle size distribution, and surface area of the extracted silica were then studied by appropriate characterization techniques. The characterization findings indicated that the amorphous silica particles had a microporous nature with an average particle size of ~24 nm, exhibiting a high purity of more than 99% and a high specific surface area of ~474 m2 g−1. The overall results indicated that the proposed synthesis route is a promising feasible alternative method to produce highly pure microporous nanosilica from a low cost secondary resource. The proposed method can treat 98% of the slag and uses less chemicals than conventional methods and is therefore a greener nanosilica production process. The current process also competes with the traditional process and other recently introduced processes in terms of process economy and the quality of the produced product.

The four-machine flowshop scheduling problem is investigated with the objective of minimizing total completion time. Job processing times are uncertain where only the lower and upper bounds are known. This problem is common in some manufacturing environments. Some mathematical (dominance) relations are established, and an algorithm (with ten scenarios) is proposed. The proposed algorithm converts the four-machine problem to a single machine problem for which an optimal solution is known for the deterministic problem. The difference among the scenarios is related to the weights assigned to the lower and upper bounds of processing times on the machines. The proposed algorithm is further improved by the established mathematical relations and are evaluated based on extensive computational experiments. The computational results indicate that three scenarios of the proposed algorithm perform much better than the others, and the errors of these three scenarios get better as the size of the problem increases. The results are statistically verified by constructing the confidence intervals.

We address a two-machine no-wait flowshop scheduling problem with respect to the performance measure of total completion time. Minimizing total completion time is important when inventory cost is of concern. Setup times are treated separately from processing times. Furthermore, setup times are uncertain with unknown distributions and are within some lower and upper bounds. We develop a dominance relation and propose eight algorithms to solve the problem. The proposed algorithms, which assign different weights to the processing and setup times on both machines, convert the two-machine problem into a single-machine one for which an optimal solution is known. We conduct computational experiments to evaluate the proposed algorithms. Computational experiments reveal that one of the proposed algorithms, which assigns the same weight to setup and processing times, is superior to the rest of the algorithms. The results are statistically verified by constructing confidence intervals and test of hypothesis.

This work presents green lightweight reactive powder concrete (GLRPC) as a novel lightweight composite with improved properties by incorporating modified expanded polystyrene beads (MEPS) i...

Aluminum black dross (ABD) is a solid waste of aluminum smelting process that causes serious environmental and public health problems. In addition, it imposes significant disposal costs to the aluminum industry. In this study, synthesis and characterization of mesoporous alumina (MA) from the ABD using a novel recycling procedure consisting of leaching at low temperature (85 °C) and atmospheric pressure, co-precipitation, separation through selective dissolution, re-precipitation, aging and finally calcination at 600 °C for 2 h. No hard or soft template was used during the formation of the gel. The as-synthesized MA had a specific surface area, total pore volume and average pore diameter of 123–162 m2/g, 0.37 cm3/g and 10.6 nm, respectively which were obtained by nitrogen sorption analysis. The as-synthesized MA possessed more than 98% purity. Its XRD pattern exhibited the characteristic peaks of gamma, eta, theta, and delta phase alumina. FESEM and TEM analyses revealed nanoscale morphology of the as-synthesized MA; having crystal size of ∼11 nm. The TGA analysis showed that the as-synthesized MA is thermally stable and exhibits only ∼5 wt% mass loss for heating from 30 to 800 °C. The characterization of solid residue at the end of the proposed process proved that it contains mainly silica phase which can alternatively be reused as filling agent or aggregate in concrete materials applications. It is quite clear that the process of production of MA from the ABD is feasible and practical and provides a novel mitigation to the environmental problems of the ABD.

Nano-tube array is one of the most important types of titanium dioxide-based nanostructures that attracted researchers' attention because of its superior photocatalytic properties. In this research, a thin layer of a titanium dioxide nano-tube array was first prepared by a two-step electrochemical anodizing process by using a titanium sheet. The synthesized nano-tube array was then calcined to obtain a good crystalline structure for enhanced photocatalytic properties. The length, diameter, and thickness of the nano-tubes were measured using SEM imaging technique. In order to enhance the photocatalytic properties, the synthesized nano-tube array was then doped individually with three different chemicals including silver nitrate, potassium ferricyanide and copper sulfate using the chemical bath deposition technique. The photocatalytic properties of the synthesized nano-tube array and the doped samples were evaluated and compared by photoelectrochemical water splitting. The results show that the nano-tube array doped with copper sulfate increases the rate of hydrogen production by up to three times producing as much as 21.65 mmol after 5 h.

By finding appropriate recycling approaches, the volume of wastes, corresponding disposal cost, and the pollution of environment could be diminished. Also, such promising approaches can result in the conservation of natural sources and economic benefits. Aluminum dross as a hazardous solid waste in aluminum production industries has caused serious environmental and public health challenges. Various methods have been introduced for management, utilization, and recycling of the waste. The present review describes, firstly, different types of aluminum dross, their environmental and health hazards, composition, and production process and then focuses on the direct and indirect recycling approaches and recovery strategies.

We consider the two-machine no-wait flowshop scheduling problem to minimize maximum lateness, where setup times are considered separate from processing times. Moreover, setup times are uncertain (within some intervals), where only lower and upper bounds are known. The objective is to obtain a set of dominating schedules, which contain the optimal solution. The size of dominating set can be reduced by the development of dominance relations. In this paper, we establish local and global dominance relations. Furthermore, we provide examples to illustrate how the developed dominance relations either help in finding the optimal schedule or in reducing the size of dominating set. Moreover, we establish an algorithm to find the number of developed dominance relations for given input parameters. Computational experiments indicate that the established dominance relations are helpful in reducing the size of dominating schedules.

We consider the m-machine no-wait flowshop scheduling problem with respect to two performance measures; total tardiness and makespan. Our objective is to minimize total tardiness subject to the constraint that the makespan is not larger than a given value. We develop dominance relations and propose an algorithm, called Algorithm AA, which is a combination of simulated annealing and insertion algorithm. Moreover, we adapt five existing algorithms, including three well performing algorithms known to minimize total tardiness, to our problem. We conduct extensive computational experiments to compare the performance of the proposed Algorithm AA with the existing algorithms under the same CPU times. We also evaluate the effect of the dominance relations. The computational analysis indicates that the proposed Algorithm AA performs significantly better than the existing algorithms. Specifically, the relative error of the Algorithm AA is about 60% less than that of the best algorithm among the five existing algorithms considered. All the results are statistically verified. Hence, the proposed Algorithm AA is recommended for the considered problem.

Aluminum production industry tailings are considered as hazardous solid wastes accompanied by a variety of serious disposal, environmental, and public health issues. This study is devoted to presenting a promising solution for dealing with such problems. Within the scope of the present study, synthesis of nanostructured γ-alumina from aluminum foundry tailing using a novel process was presented. The proposed process will provide a multilateral advantage to both environment and industries. Firstly, the amount of tailing and accordingly, disposal cost could be partly lessened; secondly, the environmental pollution can be reduced, and finally, if possible, green production of advanced materials from this kind of waste at a rational expense can bring about the conservation of natural sources and also gain economic benefits. Characterization of the as-synthesized products was performed using X-ray diffractometry (XRD), X-ray fluorescence (XRF), Fourier-transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDAX), and dynamic light scattering (DLS) for crystalline phase analysis, chemical composition, chemical bond recognition, morphology, elemental analysis, and particle size distribution, respectively. The chemical composition analyzed by XRF indicated that the as-synthesized alumina exhibits a purity of more than 97 wt%. The XRD pattern majorly possessed characteristic peaks related to the gamma phase of alumina. Microstructural analyses by FESEM and TEM confirmed the nano-sized morphology of the as-synthesized γ-alumina.

More than one million tons of secondary aluminum dross as a hazardous waste are produced by aluminum manufacturers per year throughout the world, which imposes high disposal costs and serious environmental problems. As secondary aluminum dross is considered as an alumina-rich inorganic waste, this study aims to propose a promising approach for clean production of activated-alumina as a widely-used adsorbent, catalyst and catalyst support. In this paper, synthesis and characterization of high crystalline activated-alumina nanopowder from secondary aluminum dross using a novel five-step leaching-based process are presented. To optimize the process, various parameters of dross particle size, leaching time, leaching temperature, acid concentration, and liquid-to-solid ratio were studied using One-Factor-At-a Time approach (OFAT). For the following optimum leaching conditions: particle sizes between 38 and 75 μm, leaching time of 120 min, leaching temperature of 85 °C, acid concentration of 5 M, and the liquid-to-solid ratio of 20 ml/g, the extraction efficiency of alumina was around 83%. The leach liquor was purified by adding 2 N NaOH resulting in sodium aluminate-rich solution. The purified liquor was treated by adding HCl to precipitate Al(OH)3, and the Al(OH)3 was then washed and calcined at 700 °C for 2 h to obtain alumina. Chemical composition, mineralogical phases, chemical bonds, morphology, and particle size distribution of the as-synthesized activated-alumina were determined using X-ray fluorescence (XRF), X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and dynamic light scattering (DLS), respectively. The as-synthesized activated-alumina exhibited 97.61% purity. Its XRD pattern showed mainly characteristic peaks of gamma phase of alumina. Morphological study by FESEM revealed that the as-synthesized alumina particles have rounded-corner shape. The crystal and average particle size values were about 18.47 and 513 nm, respectively.

In this study, secondary aluminum dross as an alumina-rich resource was valorized into the gamma-aluminum oxide ( γ -Al2O3) via a pilot-scale extraction system. The pilot-scale process was designed for a total γ -Al2O3 production of ∼ 5 kg/day. The extraction process included leaching, precipitation, hydroxide separation, aluminum hydroxide re-precipitation, drying and high-temperature dihydroxylation The obtained γ -Al2O3 was then characterized using XRD, XRF, BET, and FESEM. The XRD analysis disclosed the emergence of the gamma-crystalline phase with a crystallite size of 19.6 nm. The XRF revealed a purity of more than 99 wt%. The BET surface area, pore volume, and mean pore size were ∼ 170 m2/g, 0.45 cm 3/g, and 17.4 nm, respectively. The FESEM and TEM indicated that the as-synthesized γ -Al2O3 was in the form of agglomerates, consisting of γ -Al2O3 was then used to adsorb aqueous fluoride with two different concentrations of 10 and 20 ppm. The adsorption results revealed that the amount of fluoride adsorbed by γ -Al2O3 was 16.5 mg/g when adsorbent dosage, initial fluoride concentration, pH, and equilibrium time were 1 g/l, 20 ppm, 4, and 1 h, respectively. The maximum monolayer adsorption was obtained 35.6 mg/g by Langmuir model. Investigating the influence of the adsorbent dosage indicated that the adsorbent dosage of 4 g/l resulted in 98% fluoride removal. It was found that fluoride adsorption occurred through chemisorption, and carbonate and phosphate anions had the most interference with fluoride adsorption. The regeneration experiments showed that the regenerated γ -Al2O3 can exhibit good fluoride adsorption performance, even after 8 times regeneration.

In this work, three different foaming agents were selected and their performance on density, compressive strength, pore structure, and molecular structure of alkali-activated blast furnace slag cellular concrete have been investigated. For this purpose, pre-formed foams based on sodium lauryl sulfate, protein-based foaming agent, and hydrogen peroxide were added to the alkali-activated slag paste with determined activator composition. After curing, density and compressive strength of cellular concretes were evaluated. Also, macroscopic pore size distribution was investigated by image processing technique for studying its relation with density and compressive strength. Results showed that with increasing the amount of foam, the density and the compressive strength decreased due to increases in both the number of pores per area and the pore average size. Samples containing protein-based foam showed higher mechanical strength, which could be due to its effect on the molecular structure of hydration product resulting in a stronger bond and hence higher compressive strength.

This paper addresses a manufacturing system consisting of a single machine. The problem is to minimize the number of tardy jobs where processing times are uncertain, which are within some intervals. Minimizing the number of tardy jobs is important as on-time shipments are vital for lowering cost and increasing customers’ satisfaction for almost all manufacturing systems. The problem is addressed for such environments where the only known information is the lower and upper bounds for processing times of each job since the exact processing times may not be known until all jobs are processed. Therefore, the objective is to provide a solution that will perform well for any combination of feasible realizations of processing times. First, a dominance relation is established. Next, several versions of an algorithm, incorporating the dominance relation, are proposed. The computational analyses reveal that the error of one of the versions of the algorithm is at least 60% smaller than the errors of the other versions of the algorithm. Besides, the performance of this version is very close to the optimal solution, i.e., on average, 1.34% of the optimal solution.

Scheduling involving no-wait in process plays an important role in industries such as plastic, chemical, and pharmaceutical. Moreover, many scheduling problems in other industries, including surgery-scheduling problem, aircraft landing problem, and train scheduling problem, can also be modeled with no-wait constraint. The research interest in scheduling problems with no-wait in process began in 1970s and the interest has been increasing since then. Hall and Sriskandarajah (1996) presented an excellent review of the literature, covering about 130 papers, on scheduling problems with no-wait in process since 1970s until mid-1993. This paper is the second survey paper providing analysis and an extensive review of more than 300 papers that appeared since the mid-1993 to the beginning of 2016. This survey paper classifies scheduling problems based on shop environments as flowshop, job shop, or open shop. It further classifies the problems based on the performance measure considered along with some other factors. Throughout the survey paper, many independently investigated problems are determined, less studied problems are identified, and suggestions for future research directions are proposed.

In this research, techniques of cement paste strengthening and interfacial transition zone (ITZ) microstructure modification were simultaneously used to enhance the concrete engineering pro...

In this paper, we consider a manufacturing system with two-machine no-wait flowshop scheduling problem where setup times are uncertain. The problem with the performance measure of maximum lateness was addressed in the literature (Computational and Applied Mathematics 37, 6774-6794) where dominance relations were proposed. We establish a new dominance relation and show that the new dominance relation is, on average, about 90 \begin{document}$ \% $\end{document} more efficient than the existing ones. Moreover, since it is highly unlikely to find optimal solutions for problems of reasonable size by utilizing dominance relations and since there exist no heuristic in the literature for the problem, we propose constructive heuristics to solve real life problems. We conduct extensive computational experiments to evaluate the proposed heuristics. Computational experiments indicate that the performance of the worst proposed heuristic is at least 20 \begin{document}$ \% $\end{document} better than a benchmark solution. Furthermore, they also indicate that the best proposed heuristic is about 130 \begin{document}$ \% $\end{document} better than the worst one. The average CPU time of the heuristics is significantly less than a second.

This paper investigates the kinetics of geopolymerisation in an inorganic polymeric binder based on a natural pozzolan. The heat released by the exothermic geopolymerisation reaction process is monitored under isothermal temperature conditions, maintained in a differential scanning calorimeter using a water circulation cell. Calorimetric data are obtained isothermally at 65, 75, and 85 °C with various Na2O/Al2O3 and SiO2/Na2O molar ratios and in the presence and absence of small amounts of calcium aluminate cement (used as an efflorescence control admixture in these binder systems). The first stage of reaction, which is rapid and strongly exothermic, is shortened as the temperature increases. The total heat of reaction increases in the mixes containing calcium aluminate cement, but the apparent activation energy calculated using a pseudo-first-order reaction model is lower than without added calcium aluminate cement. At a constant overall SiO2/Na2O molar ratio, the apparent activation energy is decreased as the Na2O/Al2O3 molar ratio increases. Calcium aluminate cement, therefore, reduces the minimum energy required to initiate geopolymerisation reactions of this natural pozzolan and facilitates the progress of the reactions which lead to formation of a cementitious product.

The two-stage assembly flowshop scheduling problem has received much attention from researchers because it is applicable to many real-life environments. The objective of minimizing total tardiness is important because the fulfillment of due dates for customers must be considered when making scheduling decisions. However, the setup times were assumed to be zero in previous studies, which may not be realistic or appropriate for some scheduling environments because treating the setup times separately from the processing times increases the level of machine utilization and reduces total tardiness. In this study, we investigate the two-stage assembly flowshop scheduling problem with separate setup times to minimize the total tardiness. We propose two new algorithms and adapt four existing algorithms, which are different versions of simulated annealing, genetic, and insertion algorithms. Moreover, we formulate the problem mathematically, where we develop a dominance relation and we utilize the dominance relation in our proposed algorithms. Extensive computational experiments indicated that one of the proposed algorithms performed much better than the others on average, i.e., the error using the best algorithm was 54% to 98% less than that with the other algorithms. Computational experiments were also conducted with zero setup times in order to compare the performance of our proposed algorithms with that of the best known previously reported algorithm in the zero setup time case. When the setup times were zero, the best proposed algorithm reduced the error of the best previously reported algorithm by 48% when both algorithms were run for the same computational time. Therefore, our best proposed algorithm can be used for both zero and non-zero setup times. Hence, for the first time, the present study considers the problem with separate setup times as well as proposing much better algorithms for the zero setup time case.

One of the common methods for quick determination of compressive strength as one of the most important properties for assessment of cement quality is to apply various modeling approaches. This study is aimed at finding a model for estimating the compressive strength of phosphorus slag content cements. For this purpose, the compressive strengths of chemically activated high phosphorus slag content cement prepared from phosphorus slag (80 wt.%), Portland cement (14 wt.%) and a compound chemical activator containing sodium sulfate and anhydrite (6 wt.%) were measured at various Blaine finenesses and curing times. Based on the obtained results, a primary stochastic model in terms of curing time and Blaine fineness has been developed. Then, another different dataset was used to incorporate composition variable including weight fractions of phosphorus slag, cement, and activator in the model. This model can be effectively used to predict the compressive strength of phosphorus slag content cements at various Blaine finenesses, curing times, and compositions.

This paper focuses on the production of high-strength geopolymer binder by alkali activation of binary mix of fly ash and calcium aluminate cement (CAC). The fly ash was partially replaced ...

This study investigates the magnesium sulphate resistance of chemically activated phosphorus slag-based composite cement (CAPSCC). Enough mortar specimens were prepared from phosphorus slag (80 wt.%), type II Portland cement (14 wt.%), and compound chemical activator (6 wt.%) and were exposed to 5% magnesium sulphate solution after being cured. Mortar specimens of both type II and V Portland cements (PC2 and PC5) were also prepared and used for comparison purpose. According to the test results, after 12 months of exposure, PC2, PC5 and CAPSCC exhibited 43.5, 35.2 and 25.2% reduction in compressive strength, 0.136, 0.110, and 0.026% expansion in length, and 0.91, 2.2, and 1.78% change in weight, respectively. Complementary studies by X-ray diffractometry and scanning electron microscopy revealed that CAPSCC has a very low potential for the formation of sulphate attack products, especially ettringite. The results confirm a high magnesium sulphate resistance for CAPSCC compared to PC2 and PC5. Este trabajo aborda el estudio de la resistencia al sulfato de magnesio de un cemento compuesto con base de escoria de fósforo activada químicamente (CAPSCC). Se prepararon muestras de mortero a partir de escoria de fósforo (80% en peso), cemento Portland tipo II (14% en peso) y activador químico (6% en peso) y tras el curado, se expusieron a una solución de sulfato de magnesio al 5%. También se prepararon morteros de cementos Portland de tipo II y V (PC2 y PC5) que se usaron con fines comparativos. De acuerdo a los resultados obtenidos, después de 12 meses de exposición, PC2, PC5 y CAPSCC mostraron un 43.5, 35.2 y 25.2% de reducción en la resistencia a la compresión, 0.136, 0.110, y 0.026% de expansión en longitud, y 0.91, 2.2 y 1.78% de cambio en peso, respectivamente. Estudios complementarios por difracción de rayos X y microscopía electrónica de barrido revelaron que los cementos CAPSCC tienen un potencial muy bajo para la formación de productos de ataque de sulfato, especialmente etringita. Los resultados confirman una alta resistencia al sulfato de magnesio para CAPSCC en comparación con PC2 y PC5

In this paper, the impact of curing parameters such as precuring time, curing time, and temperature on compressive strength of mortar with phosphorous-slag cement activated with two differe...

Scheduling involving setup times/costs plays an important role in today's modern manufacturing and service environments for the delivery of reliable products on time. The setup process is not a value added factor, and hence, setup times/costs need to be explicitly considered while scheduling decisions are made in order to increase productivity, eliminate waste, improve resource utilization, and meet deadlines. However, the vast majority of existing scheduling literature, more than 90 percent, ignores this fact. The interest in scheduling problems where setup times/costs are explicitly considered began in the mid-1960s and the interest has been increasing even though not at an anticipated level. The first comprehensive review paper (Allahverdi et al., 1999) on scheduling problems with setup times/costs was in 1999 covering about 200 papers, from mid-1960s to mid-1988, while the second comprehensive review paper (Allahverdi et al., 2008) covered about 300 papers which were published from mid-1998 to mid-2006. This paper is the third comprehensive survey paper which provides an extensive review of about 500 papers that have appeared since the mid-2006 to the end of 2014, including static, dynamic, deterministic, and stochastic environments. This review paper classifies scheduling problems based on shop environments as single machine, parallel machine, flowshop, job shop, or open shop. It further classifies the problems as family and non-family as well as sequence-dependent and sequence-independent setup times/costs. Given that so many papers have been published in a relatively short period of time, different researchers have addressed the same problem independently, by even using the same methodology. Throughout the survey paper, the independently addressed problems are identified, and need for comparing these results is emphasized. Moreover, based on performance measures, shop and setup times/costs environments, the less studied problems have been identified and the need to address these problems is specified. The current survey paper, along with those of Allahverdi et al. (1999, 2008), is an up to date survey of scheduling problems involving static, dynamic, deterministic, and stochastic problems for different shop environments with setup times/costs since the first research on the topic appeared in the mid-1960s.

In this research, through compressive strength data, the order and kinetics of alkali-activation of phosphorus slag activated with two compound activators of NaOH + Na2CO3 and Na2CO3 + Ca(OH)2, has been evaluated. The kinetics and order of alkali activation is a key factor to forecasting the mechanical behavior of alkali activated cement at different curing time and temperatures without carrying out experimental tests. The apparent activation energy was obtained as 35.6 kJ.mol-1 and 60.7 kJ.mol-1 for the two activators, respectively. Investigations proved that the alkali-activation kinetics of phosphorus slag resembles chemical reactions of second order. Moreover, the order of alkali-activation of phosphorus slag does not depend on the type of activator.

The m-machine no-wait flowshop scheduling problem is addressed where setup times are treated as separate from processing times. The objective is to minimize total tardiness. Different dispatching rules have been investigated and three were found to be superior. Two heuristics, a simulated annealing (SA) and a genetic algorithm (GA), have been proposed by using the best performing dispatching rule as the initial solution for SA, and the three superior dispatching rules as part of the initial population for GA. Moreover, improved versions of SA and GA are proposed using an insertion algorithm. Extensive computational experiments reveal that the improved versions of SA and GA perform about 95% better than SA and GA. The improved version of GA outperforms the improved version of SA by about 3.5%.

The numerous ecological problems caused by the accumulation of secondary aluminum dross (SAD) as a hazardous waste generated in aluminum castings have necessitated a need for a sustainable recycling solution. This study proposes a novel and green leaching-based process for recovery of nano-alumina as a highly valuable material from SAD. The leaching phase was performed at atmospheric pressure and low temperature. To obtain optimum conditions for the recovery process, the dissolution kinetics and mechanism of SAD in hydrochloric acid were initially studied under a given liquid-to-solid ratio of 20 ml/g, various reaction temperatures and times. It was found that the dissolution of SAD in HCl was controlled by layer diffusion with an apparent activation energy of around 10.49 kJ/mol. Alumina in the form of a high purity nanostructured powder from SAD was then recovered under optimum conditions of 85 °C, acid concentration of 5 mol/l, and reaction time of 120 min by the proposed process. Characterization of nano-alumina was performed using X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDAX), and transmission electron microscopy (TEM) techniques. The results revealed that the as-produced alumina had a nano-crystalline structure, having the crystal size of 15.90 nm and consisting mainly of gamma phase. The microstructural studies disclosed the aggregations of rounded-corner shaped particles. Also, wet chemical analysis showed a purity of more than 98% for the produced alumina.

The aim of this study is to investigate the durability of geopolymer mortars based on waste-glass powder (WGP) and calcium aluminate cement (CAC) exposed to acid attack. Geopolymer specimen...