Aggregate Production Research Articles

Conjugated oligo (phenylene vinylene) covalently linked porphyrin for sonodynamic therapy

AbstractSonodynamic therapy (SDT) is garnering considerable attention as a promising treatment for deep‐seated tumors because of its strong tissue penetration ability, non‐invasiveness, and controllability. However, the SDT efficiency of traditional sonosensitizers including porphyrins and their derivatives are limited due to their poor water dissolubility, high aggregation, and low reactive oxygen species (ROS) production efficiency. Consequently, it is crucial to develop novel sonosensitizers with high yields of ROS, outstanding water solubility, and good biocompatibility. Herein, we constructed a new platform for SDT based on unimolecular porphyrin derivatives OPV‐C3‐TPP. The probe OPV‐C3‐TPP was synthesized by covalently linking conjugated oligomers (OPV) with 5, 10, 15, 20‐tetra (4‐aminophenyl) porphyrin (TAPP). The introduction of OPV greatly improves the water solubility of the porphyrins and reduces the self‐aggregation of the porphyrins. In addition, OPV‐C3‐TPP has good intramolecular energy transfer efficiency, thus enhancing the yield of ROS. The experimental results show that OPV‐C3‐TPP exhibits excellent ROS generation capacity under ultrasound (US) irradiation, which leads to apoptosis and necrosis of tumor cells. In vivo tumor growth is also significantly inhibited in the OPV‐C3‐TPP + US group, exhibiting better SDT effects than TAPP. Therefore, the unimolecular OPV‐C3‐TPP can be used as a potential sonosensitizer, providing a promising SDT for deep‐tissue tumors.

Forecast Of Rainfed Agricultural Production In The State Of Pernambuco, Brazil

This research assesses rainfed agricultural production in the state of Pernambuco, which has 137 of its 185 municipalities officially characterized as being part of the semi-arid climate regime. The study classified rainfall periods in Pernambuco between 1944 and 2022 and investigated rainfall instability and its impact on aggregate productivity, aggregate harvested area and production value per hectare of bean, cassava and maize crops. The Auto-Regressive Integrated Moving Average model with Exogenous Variable Inputs (ARIMAX) was used, considering rainfall as an exogenous variable. The results showed that rainfall has a direct effect on the variables investigated, especially the harvested area. It was proven that in periods classified as normal and rainy, productivity, harvested area and production value per hectare showed higher results than those observed in the dry periods of, as was the assumption of the research. The study also confirmed that the models developed were parsimonious and capable of predicting the variables investigated. The results showed that productivities, harvested areas and production values per hectare for beans, cassava and corn experienced greater instability during periods of drought. The research also shows that the aggregated production values per hectare for the three crops are very low. In dry years, they are even lower than the minimum wage. This result confirms that the rural areas of Pernambuco where these crops are mostly grown are very poor

On the Cementitious Mixtures Reinforced with Waste Polyethylene Terephthalate.

The last decade was dominated by a serious problem that now affects all the planet's natural ecosystems: the increasing growth of plastics and microplastics that are difficult to dispose of. One strategy to mitigate this problem is to close the life cycle of one of them-polyethylene terephthalate (PET)-by reusing it within the most common building materials, such as mortars and concretes. The reuse of PET waste as aggregates also allows us to limit the CO2 emissions released during the production of natural aggregates. This paper analyzes the outcomes of many studies carried out on the characteristics of cementitious mixtures reinforced with waste PET material. Many researchers have demonstrated how PET used as reinforcement of mortars and concretes can produce an increase in the mechanical strengths of the corresponding cementitious mixtures without PET. The tensile strength of this resin is higher than that of concrete; so, by combining the two materials it is possible to obtain a mixture with an overall higher tensile strength, resulting in increased flexural strength and reduced cracking. Using an effective size of PET fibers, it is possible to achieve an increase in the ductility and toughness of the cementitious mixture. Several studies reveal that PET reinforcement reduces the density with a consequent decrease in weight and structural loads, while the workability increases using spherical and smoother PET aggregates.

Pricing in spatial classification system in non-symmetric market demand based on the calculations of double interval grey numbers

PurposeThe contemporary landscape of supply chains necessitates a comprehensive integration of multiple components encompassing production, distribution and customer engagement. The pursuit of supply chain harmony underscores the significance of pricing strategies within the framework of dual-channel distribution, particularly when confronted with the dynamics of asymmetric demand performance.Design/methodology/approachThis paper delves into a nuanced decision-making challenge anchored in a dual-channel distribution context featuring a retailer and two distinct products. Notably, the retailer’s decision-making process employs the computational framework of dual grey numbers, a robust tool for handling uncertainty.FindingsThis study revolves around applying game theory to manufacturers. Each manufacturer presents its aggregated price proposition to the retailer. Subsequently, the retailer identifies the optimal pricing configuration among the manufacturers' aggregate prices while adhering to constraints such as spatial classification and inventory costs. This article’s contribution extends to delineating the retailer’s capacity to discern the influence of product market potential and the aggregate product cost on the overall demand.Originality/valueThe model’s innovation lies in its harmonious fusion of spatial classification, pricing strategies and inventory control. Notably, this novel integration provides a platform for unraveling the intricate interplay between non-symmetric market potential, production costs and cross-sensitivity. The investigation is underscored by the utilization of the double interval grey numbers, a powerful computational approach that accommodates the inherent uncertainty pervasive in the domain. This study fills a gap in the existing literature by offering an integrated framework unifying spatial allocation, pricing decisions and inventory optimization.

Enhancing Regional Wind Power Forecasting through Advanced Machine-Learning and Feature-Selection Techniques

In this study, an in-depth analysis is presented on forecasting aggregated wind power production at the regional level, using advanced Machine-Learning (ML) techniques and feature-selection methods. The main problem consists of selecting the wind speed measuring points within a large region, as the wind plant locations are assumed to be unknown. For this purpose, the main cities (province capitals) are considered as possible features and four feature-selection methods are explored: Pearson correlation, Spearman correlation, mutual information, and Chi-squared test with Fisher score. The results demonstrate that proper feature selection significantly improves prediction performance, particularly when dealing with high-dimensional data and regional forecasting challenges. Additionally, the performance of five prominent machine-learning models is analyzed: Long Short-Term Memory (LSTM) networks, Artificial Neural Networks (ANNs), Support Vector Machines (SVMs), Convolutional Neural Networks (CNNs), and Extreme-Learning Machines (ELMs). Through rigorous testing, LSTM is identified as the most effective model for the case study in northern Italy. This study offers valuable insights into optimizing wind power forecasting models and underscores the importance of feature selection in achieving reliable and accurate predictions.

The Effect of the Ratio of Fly Ash to Alkaline Activator and the Molarity of NaOH on the Mechanical Properties of Fly Ash-Based Aggregates

The global demand for aggregates has escalated, leading to a decline in the availability of quality natural aggregates. In response, the cold bond pelletization (CBP) process emerged in the early 2000s as a novel approach to artificial aggregate production, utilizing dry powdered fly ash. This method involves agglomerating fly ash particles at room temperature in an inclined rotating pan to form pellets. However, the abstract lacks clarity in elucidating the significance of this approach. Our study investigates the mechanical properties of aggregates produced through the CBP method via experimental laboratory methods, focusing on variations in the ratio of fly ash to alkaline activator (FA/AA) and the molarity of Sodium Hydroxide (NaOH). Notably, we found that an effective molarity of 15 resulted in the lowest Aggregate Impact Value (AIV) percentage, indicating improved mechanical properties. Furthermore, we observed fluctuations in AIV values across different FA/AA ratios and NaOH molarities, suggesting nuanced effects on aggregate quality. Our findings underscore the importance of optimizing parameters in the CBP process for enhanced aggregate performance.

Improving truck service performance in transporting rock aggregate using Genetic Ant Colony Algorithm

Inter-island shipment requests for rock aggregate products are served through the terminal for their own needs (TFON). The high demand for rock aggregate products causes many ships to queue up to be loaded. However, this condition is not comparable to the availability of dump trucks used to serve loading and unloading activities. This study aims to improve the performance of dump truck service in transporting rock aggregate so that the number of dump truck vehicles and optimal loading and unloading service times from the stockpile to ship at TFON are obtained. The research location was carried out at active rock mining companies in the Central Sulawesi region. The data collection method is carried out using field surveys (observations) using a time recording device by recording the process of transporting rock aggregates from the stockpile location to the ship in TFON and collecting secondary data on the demand for rock aggregates to be transported. The analysis method uses the hybrid Genetic Ant Colony Algorithm (ACO-GA) method namely a combination method between the Ant Colony Optimization algorithm and the Genetic Algorithm which aims to maximize the optimal number of trucks used in the transportation process and minimize the time in the loading and unloading process. The results showed that there had been an increase in service performance of the dump truck used in transporting rock aggregate with the longest distance of 2.3 km with a total of 5 dump trucks. The number of dump trucks of 5 units was selected because it falls within the fitness value criteria which is closest to the optimum value or equal to the value of the resources owned. Meanwhile, the optimal loading and unloading process time is in the range of 1.81–3.34 working days

Presidential Address: Metallurgical slags: A drive to circularity and search for new research agenda

Poor phase separation and fine dissemination of the desired components within congruous slag phases are key challenges limiting the recoverability of values from slags by conventional beneficiation methods. Slag microstructure conditioning is a pragmatic approach to increasing the value-in-use of discard slags, especially when integrated with the broader smelter infrastructure. Although not yet tested on oxide slag systems, this paper explores the potential application of magnetohydrodynamic principles to the crystallization behaviour of bulk slags. Integrating the slag microstructure conditioning infrastructure to the existing smelter infrastructure is key to unlocking the economic value of slags because it is most economic to condition the properties of molten slag directly after tapping. A new business model that integrates smelting units to transversal economic activities, such as cement production and suppliers of construction aggregates, can significantly increase the circularity of metallurgical slags.

Limited Firm Insurance and Aggregate Implications

This paper studies the impacts of financial shocks on firm insurance, firm dynamics, and macroeconomic implications. A key departure from the literature is that firms provide wage insurance contracts to risk-averse workers in a long-term relationship. Such contracts endogenously impose a form of inflexible debt liability to firms, and make firms with limited financial net worth more vulnerable to shocks than others. In our model, firms have heterogenous productivity and financial net worth, and also firms face financial frictions. Search and matching in the labor market endogenously determines the value of wage contract, and thus the level of liability to the firm. We have three new findings: (1) The wage dynamics of the quantitative model are consistent with those in empirical studies, with significant insurance against firm-level idiosyncratic shocks, and also a weak comovement between aggregate wage and GDP when there are aggregate shocks. (2) Firms with limited financial resources are hit by financial shocks significantly more than others, with larger negative impacts on dividends, credit borrowing, firm value, and firm entry; the endogenous wage insurance also becomes more limited, and there are more separations. These impacts on both firms and workers are different from—and cannot be accounted for by—standard models with a representative firm or worker. (3) Quantitative exercises for the Great Recession in the United States suggest that aggregate productivity shocks and financial shocks play different roles; without financial shocks, we cannot account for the dynamics of financial variables, including the reduced credit borrowing, spikes in credit spreads, and large drops in dividend payments. Lastly, we provide microlevel empirical supports for our model implications. This paper was accepted by Lukas Schmid, finance. Funding: Y. Wang acknowledges the financial support from the National Natural Science Foundation of China [Grant 72150003] and the grant from Shenzhen Municipal Government [Grant 1210614103]. Supplemental Material: The data files are available at https://doi.org/10.1287/mnsc.2023.01627 .

The Basic Properties of Lightweight Artificial Aggregates Made with Recycled Concrete Fines

The production of lightweight aggregate based on waste is an important step towards sustainable and ecological construction. It contributes to reducing the negative impact of the construction sector on the environment by reducing the consumption of natural raw materials and reducing waste of various origins, including rubble concrete. The physical and mechanical properties, including grain shape index, water absorption, bulk density, resistance to crushing, frost resistance, leachability of heavy metals, and porosity of lightweight artificial aggregate made from rubble concrete waste (KRC) were presented in the paper. The obtained test results prove that the proposed artificial aggregate has similar water absorption and bulk density and even better frost and crushing resistance than artificial aggregates available on the market. Due to its properties, it can be used for lightweight concrete, gardening, or as a separating layer in home sewage treatment plants.

Comparison of Curing Conditions on Physical Properties, Mechanical Strength Development, and Pore Structures of Phosphogypsum-Based Cold-Bonded Aggregates.

This study compared the physical properties and mechanical strength development of PCBAs with water, sealed, standard, and open ambient air curing over 28 days to find a suitable curing method for the production of phosphogypsum-based cold-bonded aggregates. The types and relative amounts of hydration products, microstructural morphology and pore structure parameters were characterized utilizing XRD, TGA, FTIR, SEM and nitrogen adsorption methods. According to the results, water curing leads to rapid increases in single aggregate strength, reaching 5.26 MPa at 7 d. The standard curing condition improved the 28 d mechanical strength of the aggregates by 19.3% over others by promoting the generation of hydration products and the transformation of the C-S-H gel to a higher degree of polymerization and by optimizing the pore structure. Further, PCBAs achieved an excellent solidification of phosphorus impurities under all four curing conditions. This work provides significant guidance for selecting an optimized PCBA curing method for industrial production.

Motherhood and the allocation of talent

ABSTRACT In this paper we show that motherhood triggers changes in the allocation of talent in the labour market beyond the well-known effects on gender gaps in employment and earnings. Based on an event study approach around the birth of the first child and retrospective panel data for 28 European countries and Israel, we assess the labour market responses to motherhood across ‘talent’ groups–i.e. groups with different educational attainment, Math performance at age 10, and personality traits associated to entrepreneurial ability. We show that even the most talented women–both in absolute terms and relative to their husbands–leave the labour market or uptake part-time jobs after the birth of the first child. We also find that motherhood induces a negative selection of female talents into self-employment. Overall, our results suggest relevant changes in the allocation of talent associated to gender differences in non-market responsibilities that can have sizable impacts on aggregate market productivity.

Valorisation of Aggregate-Washing Sludges in Innovative Applications in Construction.

The valorisation of sludges from aggregate production into construction materials is required for full circularity in mining waste management. This study explores valorisation pathways, relevant regulatory frameworks, and End-of-Waste (EoW) criteria for specific settings in Spain and Norway. The explored valorisation routes involved the production of filler, supplementary cementitious materials (SCMs), and lightweight aggregates (LWAs) for the production of cement-based products, and precursors for 3D printed construction material. The sludge from Norway revealed a non-polluted stream and a stream contaminated with organic phases and clays. Sludge-based filler proved suitable in concrete production with contents of up to 40% of total binder, providing adequate consistency and cohesion. However, clays in the sludge increased the demand for water and superplasticizer. Clay contents were still insufficient for the applications as SCMs, as the calcined sludge demonstrated limited reactivity. The application to produce LWAs was promising, but further microstructure optimization is still required. The clay content was also relevant for the sludge from the site in Spain, as it provided 3D printing mixes with good plasticity. The dosage optimization still required the addition of enzymes, limestone, and natural fibres to improve cohesion, workability, and resistance to the cracking of the 3D printing mix.

Recycling phosphogypsum to produce artificial lightweight aggregates via stirring and pelleting all-in-one technique: Technical assessment and performance optimization

Currently, production of artificial lightweight aggregates (ALAs) is becoming one of the most promising approaches for solid wastes recycling via pelletization technique. In this study, an innovative stirring and pelleting all-in-one technique (S-pelleting) was employed to prepare the ALAs by using phosphogypsum (PG). The effects of different pelleting techniques on properties of the ALAs were investigated. Furthermore, the NaHCO3, Al2(SO4)3+CaCO3 (Al-Ca) and foamed particles (FP) were introduced as foaming agents to optimize the performance of the ALAs. The specific strength was used as the main assessment index for performance of the aggregates. The results indicated that the specific strength of the aggregates was improved to 10.96 MPa⋅cm3/g by S-pelleting, which was 60.7 % and 35.6 % higher than that of one-step pelleting or double-step pelleting technique. Compared to NaHCO3, the Al-Ca was more conducive to the specific strength development of the aggregates, and the FP addition could further improve the specific strength of the ALAs. When the concentration of Al-Ca was 7% and the mass fraction of FP was 10%, the ALAs with high specific strength of 9.6 MPa⋅cm3/g were obtained in this study. Moreover, the mineral composition, microstructure and pore structure of the ALAs were analyzed and the results reveled that the Al-Ca could promote to form more ettringite and reduce the proportion of harmful pores in the aggregates, which was responsible for the improvement in specific strength. The FP acted as a lightweight skeleton supported inside the aggregates and the well bonded ITZ between FP and the matrix could further improve the specific strength of the ALAs. Finally, the durability and environmental impact of the ALAs were evaluated acceptable. Overall, this study not only provided a green approach for PG recycling, but also presented a new technical scheme for more efficient production of ALAs.

A novel use of incineration bottom ash for H2 aeration in the production of artificial lightweight aggregates

Cold bonding is an energy-efficient method for producing artificial aggregate (AA). However, the relatively high density of AA restricts its use in lightweight concrete products. This study aims to fully upcycle aluminum (Al) content in municipal solid waste incineration bottom ash (IBA) for H2 aeration in the production of lightweight artificial aggregate through alkali activation. To achieve this, the glass particles (GP) in IBA were ground into powder and used as the precursor for NaOH, while the remaining IBA (RIBA), rich in Al, served as the foaming agent. The results showed that RIBA particles (<300 μm) can be used to produce lightweight AA with a loose bulk density ranging from 780 to 840 kg/m3, comparable to sintered fly ash aggregates, and a wide pore size distribution ranging from 0.02 mm to over 1 mm. The inclusion of finer RIBA particles (<75 μm) enhanced the homogeneity of the pore structure, resulting in aggregate strengths of 0.4–0.6 MPa. Moreover, increasing the GP content in IBA up to 40% further boosted the aggregate strength to 1.1 MPa by refining the pore structure and promoting more (C)-N-A-S-H gels with Q4 structures. To ensure sufficient geopolymerization reactions and achieve high strength in the AAs, the alkali concentration should be kept above 3 mol/L. The proposed strategy for lightweight AA production reduced the global warming potential by about 20% compared to the conventional sintered method, offering a more environmentally friendly approach.

The Elasticity of Aggregate Output with Respect to Capital and Labor

It is often assumed that the elasticity of GDP with respect to capital is one-third, but this assumes zero markups and an aggregate production function. I estimate the elasticity allowing markups to vary by industry and with a rich input-output structure. Assumptions about capital costs provide bounds on elasticity. In the United States from 1948–1995, the capital elasticity ranged from 0.19–0.32 and shifted to 0. 24–0.37 by 1996–2018. Excluding housing or decapitalizing intellectual property lowers bounds to as low as 0. 11–0.26. Based on these elasticities, common estimates of total factor productivity growth represent a lower bound. (JEL E13, E22, E23, E25, N12)

Indonesian SDGS Problems: Technical Inefficiency Due to Economic Crime and Income Inequality

Objective: The study objective is investigating the technical inefficiency resulted from economic crime and its association with income inequality, with the study aims are modeling a stochastic frontier aggregate production function, measuring inefficiency, and mapping the economic inefficiency due to economic crime with income inequality association. Theoretical Framework: The main concepts are Crime Economics, Stochastic Frontier Analysis, and Aggregate Production Function. Method: The methodology comprises a stochastic frontier aggregate production function modelling to calculate technical inefficiency due to economic crime and mapping technical inefficiency due to economic crime with income inequality association. The data is Indonesian provincial data from 2016 to 2019 provided by Indonesian Statistics. Results and Discussion: The modelling reveals that aggregate production stochastic frontier is established and technical inefficiency due to economic crime is calculated. The mapping shows that some provinces experience positive association between technical inefficiency due to economic crime with income inequality. Research Implications: This study implies the importance of concerning theoritically and practically to technical inefficiency due to economic crime and its association with income inequality. These implication can encompass economic, social, and security sectors. Originality/Value: This study contributes to the literature by modeling the stochastic frontier aggregate production function that accommodates economic crime, measuring technical inefficiency due to economic crime, and mapping the technical inefficiency due to the economic crime with income inequality association. The relevance and value of this research are evidenced by SDGs components such as decent work and economic growth, reduced inequalities, and peace, justice, and strong institutions.

Feasibility study of utilizing Autoclaved Aerated Concrete (AAC) waste for the production of cold bonded lightweight artificial aggregate using high volume fly ash (HVFA) binders

Autoclaved Aerated Concrete (AAC) is a popular construction material used for partitions and insulation in buildings. At the end of its service life, AAC (Autoclaved Aerated Concrete) will be demolished and subsequently disposed of in landfills, thereby creating depository problem. Therefore, the study of reutilization and recycling of AAC waste is imperative. Artificial aggregate production can be an alternative to the reutilization of AAC waste. This paper assesses the feasibility of using Autoclaved Aerated Concrete Powder (AACP) waste as a raw material for the production of artificial aggregate and investigate its physico-mechanical properties. The investigation incorporates the comparison of cement-based binder with high-volume fly ash (HVFA) binder with different replacement levels of cement. The study uses image analysis based on photographic, optical microscopic, and scanning electron microscopy (SEM) images, to describe the porosity of the aggregate. The results show that the AACP aggregates with both cement and HVFA binders meets the current industry requirement for density and cylinder crushing strength as lightweight artificial aggregate. The appropriate binder content lies between 30 % and 40 %. The best cement to fly ash ratio in HVFA binder is determined to be of 1:1 with 50 % replacement of cement with fly ash. Image analysis showed that the porosity largely affected the properties of the AACP aggregate such as density and water absorption. However, further investigation into the reducing high-water absorption of AACP aggregates is necessary to improve their overall quality.

Productivity Growth and Workers’ Job Transitions: Evidence from Censal Microdata

Abstract We use administrative data for Chile to provide novel insights on the relationship between job transitions and productivity differentials and quantify how different groups contribute to aggregate reallocation. While on average workers move to more productive firms, almost half of transitions are ‘down the productivity ladder.’ Reallocation gains are mostly explained by a narrow subset of transitions: young, high-skilled workers generate the lion’s share of aggregate productivity gains. Workers with high turnover contribute proportionally the least. Therefore, while job reallocation yields a net benefit it hides massive and heterogeneous gross flows, with many appearing to add little to aggregate efficiency.

Capital misallocation and economic development in a dynamic open economy

Some countries, such as Canada, Italy, and Mexico, have experienced a higher growth rate of capital per worker but a lower growth rate for GDP per worker compared to the United States. This paper explains these two facts through the lens of a dynamic multisector open economy model where capital flows across countries. In the model, firms face sector-specific distortions on capital and intermediate inputs that influence the actual rate of return on capital and the aggregate total factor productivity (TFP). We calibrate the model to Mexico for the period 2000-2014 and show that changes in sectoral distortions and productivities reduced the actual rate of return on capital, triggering capital accumulation and a reduction in TFP. The results show that aggregate output decreased by 7.3% and aggregate capital increased by 10.6%. From 33 sectors (out of 48) that suffered productivity losses, approximately 50% accumulated more capital. Furthermore, the capital-intensive sectors explain 82% of the capital-output ratio increase.