Tailings, with their low utilisation rate and value, pose an urgent problem that needs to be solved. This study focused on foam ceramics and glass granules, which were prepared using gold tailings as the main raw materials, and the prepared microcrystalline foam ceramics were investigated. The optimum sample (S6) of foam ceramics consists of 77 wt% of gold tailings, 6 wt% of talc, 9 wt% of bentonite, 2 wt% of calcite, 0.9 wt% of foaming agent and 0.6% of water reducer. The optimum foaming temperature is 1190 °C, and the holding time is 60 min. The compressive strength and bulk density of the samples are 7.4 MPa and 396.4 kg/m3; nucleation temperature, crystallisation temperature, and crystallisation activation energy of glass particles are 700 °C ± 50 °C, 1100 °C ± 50 °C, and 1572 kJ/mol, respectively. Microanalysis results showed that the crystal phases of foam ceramics were mainly quartz, calcium silicate, and aluminium silicate, and crystallinity increases with increasing gold taili... [more]

Intake valve parameters significantly affect the performance of the piston-type expander (PTE). To improve compressed energy utilization efficiency, intake valve parameters need to be regulated according to load. In this paper, an electro-pneumatic variable valve actuation (EPVVA) system was proposed for independent control distributing valve parameters. The trajectory planning for the intake valve was proposed to obtain good mechanical properties. Then, the intake valve duration angle was optimized, and the optimum intake valve lift curves were obtained at different rotational speeds. Results show that the energy efficiency decreased with the intake valve duration angle increasing. The output power ascended sharply with increasing intake valve duration angle, but the amplitude of power growth decreased. The output power had a maximum value at a specific intake valve duration angle. The gray relation analysis (GRA) method was applied to obtain the optimum intake duration angle based on... [more]

The excessive consumption of fossil fuel, energy shortage and global warming along with environmental deterioration have increasingly become a global issue. In order to deal with the energy crisis, energy conservation has been developed and applied in vehicles and construction machineries, i.e., excavators, loaders and forklifts. Due to the shortcoming of low efficiency, high-energy consumption and bad exhaust, the energy conservation of construction machinery for pumping concrete is necessary and urgent. This paper aims to carry out a review on energy conservation of construction machinery for pumping concrete. The research methodology comprises a quantitative analysis method and literature investigation method. First, the structure and working principle of construction machinery for pumping concrete are expounded, and energy consumption ways of construction machinery for pumping concrete are analyzed. Then, research developments in the energy conservation of construction machinery fo... [more]

Poor indoor air quality (IAQ) in schools is associated with impacts on pupils’ health and learning performance. We aimed to identify the factors that affect IAQ in primary schools. The following objectives were set: (a) to develop a questionnaire to assess the prevalence of factors in primary schools, (b) to conduct content validity of the questionnaire, and (c) to assess the prevalence of factors that affect the IAQ in Slovenian primary schools. Based on the systematic literature review, we developed a new questionnaire to identify factors that affect the IAQ in primary schools and conducted its validation. The questionnaires were sent to all 454 Slovenian primary schools; the response rate was 78.19%. The results show that the most important outdoor factors were the school’s micro location and the distance from potential sources of pollution, particularly traffic. Among the indoor factors, we did not detect a pronounced dominating factor. Our study shows that the spatial location of... [more]

The rapid growth of the global population and changes in lifestyle have led to a significant increase in food waste from various industrial, agricultural, and household sources. Nearly one-third of the food produced annually is wasted, resulting in severe resource depletion. Food waste contains rich organic matter, which, if not managed properly, can pose a serious threat to the environment and human health, making the proper disposal of food waste an urgent global issue. However, various types of food waste, such as waste from fruit, vegetables, grains, and other food production and processing, contain important bioactive compounds, such as polyphenols, dietary fiber, proteins, lipids, vitamins, organic acids, and minerals, some of which are found in greater quantities in the discarded parts than in the parts accepted by the market. These bioactive compounds offer the potential to convert food waste into value-added products, and fields including nutritional foods, bioplastics, bioene... [more]

In this paper a CFD analysis of HIsarna off-gas system for post combustion of CO-H2-carbon particle mixture is presented to evaluate the effect of different sub-models and parameters on the accuracy of predictions and simulation time. The effects of different mesh type, mesh grid size, radiation models, turbulent models, kinetic mechanism, turbulence chemistry interaction models, including and excluding gas-solid reactions, number of reactive solid particles are investigated in detail. Based on the accuracy of the predictions and agreement with counterpart measured values, the best combination is selected and conclusions are derived. It was found that radiation and turbulence chemistry interaction model have a major effect on the temperature and composition profile prediction along the studied off-gas system, compared to the variations in other models. The effect of these two models becomes even more evident when the temperature and fuel content of the flue gas are high.

A modular multilevel converter (MMC) is voltage-sourced and can supply fault currents to an AC system. To clarify the fault current impact mechanism of an MMC, this paper examines the control and capacitor discharge processes of an MMC when an AC system has a three-phase short grounding fault. The theoretical analysis shows that the outer loop control of the MMCs changes the fault injection. In different control modes, the nonzero reference value of the outer MMC loop forces the converter to inject and absorb the current into the AC system when a fault occurs. The limiter of the control determines the final injecting current value of the MMC. To help the MMC adjust the AC system’s fault current, adaptive strategies are also proposed, which include an adaptive reference control, an adaptive limiter control, and an adaptive capacitor control. On the basis of the proposed strategies, the fault currents could be increased or decreased within the MMC’s capacity. The simulations verify the t... [more]

S-wave velocity (Vs) is a critical petrophysical parameter for reservoir characterization. It is desirable to predict Vs based on conventional logging data, but the logging cost is high. Therefore, a deep hybrid neural network coupling the convolutional neural network (CNN), Stacked gated recurrent unit (SGRU) is proposed to predict the Vs, where the inputs to the model are drill cutting features. In the proposed CNN-SGRU hybrid model, CNN is adopted to capture the spatial features from the input data, and SGRU is used to extract the temporal patterns of variation from both the forward and backward directions. To illustrate the prediction effect, the glutenite reservoir in the Baikouquan Formation of Mahu Sag, Junggar Basin is taken as an example. Mineral and pore information of drill cuttings, including siliciclastic content, clay content, quartz content, and void area ratio is chosen as the input data of the CNN-SGRU hybrid model. Three indices are used to quantitatively evaluate the... [more]

The rotating disk photocatalytic reactor is a kind of photocatalytic wastewater treatment technique with a high application potential, but the light energy utilization rate and photo quantum efficiency still need to be improved. Taking photogenerated electrons as the starting point, the following contents are reviewed in this work: (1) Light-harvesting excitation of photogenerated electrons. Based on the rotating disk thin solution film photocatalytic reactor, the photoanodes with light capture structures are reviewed from the macro perspective, and the research progress of light capture structure catalysts based on BiOCl is also reviewed from the micro perspective. (2) Macroscope transfer of photogenerated electrons. The research progress of photo fuel cell based on rotating disk reactors is reviewed. The system can effectively convert the chemical energy in organic pollutants into electrical energy through the macroscopic transfer of photogenerated electrons. (3) Multi-level utilizat... [more]

Microbial fuel cells (MFCs) are a promising technology that can be applied in a bifunctional process in which wastewater treatment is used for renewable electric power generation. In this study, novel transition metal-modified Keggin-type lacunar polyoxometalate salts (L-POMs) Cs5PMo11M(H2O)O39 (M = Fe, Co), were synthesized and characterized by X-ray diffraction, SEM, EDX, IR, TGA/DSC, and UV-Vis/DSR spectroscopies to be tested, for the first time, as a cathode component in wastewater-fed air chamber MFCs. Both materials were tested in the presence and absence of light to evaluate their photocatalytic behavior. The best performance in terms of electricity production was obtained for the MFC containing the Co-modified POM-based cathode, which showed a maximum power of 418.15 mW/m2 equivalent to 331 mW per cubic meter of treated wastewater, and a maximum COD removal percentage of 97% after 96 h of MFC operation. Co- and Fe-modified POMs had outstanding optical behavior with lower energy... [more]

Parenteral products appear to be sensitive to process conditions in bioprocessing steps, such as interfacial stress and shear stress. The combination of these elements is widely believed and proven to influence product stability, but the defined roles of these players in the product damage process have not yet been identified. The present work addresses a current industrial problem, by focusing on the analysis of shear stress on protein-based therapeutics flowing in tubing by means of Computational Fluid Dynamics simulations. The purpose of this article is not to pinpoint the mechanism triggering the damage of the product, but it represents the first step towards wider experimental investigations and introduces a new strategy to quantify the average shear stress. The field of scale-down approaches, used to scale the commercial process down to the laboratory level, is also explored. Since quality control is critical in the pharmaceutical realm, it is essential that the scale-down approa... [more]

The global climate crisis has led society toward cleaner energy sources. Another reason is the limited reserves of fossil energy resources. Efforts to increase the efficiency of photovoltaic modules (PVs) have gained momentum. The high temperature is the biggest factor causing a decrease in the efficiency of PVs. In this study, a commercial PV was cooled with distilled water, a multiwalled carbon nanotubes (MWCNT)/water mixture, and a graphene nanoplatelets (GNP)/water mixture. The environmental impact of electricity, total energetic efficiency, energy payback time, energy return on investment, and embodied energy of the PV/thermal (PV/T) system were compared using life cycle assessment and cumulative energy demand. The electrical efficiency of the PV/T changed between 13.5% and 14.4%. The total efficiency of PV/T changed between 39.5% and 45.7%. The energy returns on investment were 1.76, 1.80, and 1.85 for PV/T-distilled water, the PV/T-MWCNT/water mixture, and the PV/T-GNP/water mix... [more]

The rapid changes in nanotechnology over the last ten years have given scientists and engineers a lot of new things to study. The nanofluid constitutes one of the most significant advantages that has come out of all these improvements. Nanofluids, colloid suspensions of metallic and nonmetallic nanoparticles in common base fluids, are known for their astonishing ability to transfer heat. Previous research has focused on developing mathematical models and using varied geometries in nanofluids to boost heat transfer rates. However, an accurate mathematical model is another important factor that must be considered because it dramatically affects how heat flows. As a result, before using nanofluids for real-world heat transfer applications, a mathematical model should be used. This article provides a brief overview of the Tiwari and Das nanofluid models. Moreover, the effects of different geometries, nanoparticles, and their physical properties, such as viscosity, thermal conductivity, and... [more]

Thus far, the adoption of hydrogen fuel cell vehicles (HCEVs) has been hampered by the lack of hydrogen fueling infrastructure. This study aimed to determine the optimal location and prioritization of hydrogen fueling stations (HFSs) in Seoul by utilizing a multi-standard decision-making approach and optimization method. HFS candidate sites were evaluated with respect to relevant laws and regulations. Key factors such as safety, economy, convenience, and demand for HCEVs were considered. Data were obtained through a survey of experts in the fields of HCEV and fuel cells, and the Analytic Hierarchy Process method was applied to prioritize candidate sites. The optimal quantity and placement of HFSs was then obtained using optimization software, based on the acceptable travel time from intersections of popular roads in Seoul. Our findings suggest that compliance with legal safety regulations is the most important factor when constructing HFSs. Furthermore, sensitivity analysis revealed th... [more]

The present article is focused on a detailed computationalinvestigation of energy production capacity of various lightweight materials that are employed with piezoelectric vibration energy harvesters (PVEHs) subjected to various aeroelastic effects. Piezoelectric transducers are primarily employed to capture vibrational energy, which yields predictable and locally storable electrical energy. Higher energy extraction is possible under larger deflections of the structures when they are employed with PVEHs. In order to estimate the largest possible deflection of the structures, the response of them under external perturbations is estimated. An airplane wing consists of tapered planform, an advanced wind turbine blade, and the rectangular wings of an unmanned aerial vehicle (UAV) are considered for the vibrational analysis as the feasibility of achieving larger deflection is high compared with other aerodynamic surfaces. The stated elastic structures are modelled with different lightweight... [more]

Providing real-time information on the chemical properties of hydrocracking bottom oil (HBO) as the feedstock for ethylene cracker while minimizing processing time, is important to improve the real-time optimization of ethylene production. In this study, a novel approach for estimating the properties of HBO samples was developed on the basis of near-infrared (NIR) spectra. The main noise and extreme samples in the spectral data were removed by combining discrete wavelet transform with principal component analysis and Hotelling’s T2 test. Kernel partial least squares (KPLS) regression was utilized to account for the nonlinearities between NIR data and the chemical properties of HBO. Compared with the principal component regression, partial least squares regression, and artificial neural network, the KPLS model had a better performance of obtaining acceptable values of root mean square error of prediction (RMSEP) and mean absolute relative error (MARE). All RMSEP and MARE values of densi... [more]

This paper proposes a self-sustaining control model for proton-exchange membrane (PEM) electrolysis devices, aiming to maintain the temperature of their internal operating environment and, thus, improve the electrolysis efficiency and hydrogen production rate. Based on the analysis of energy−substance balance and electrochemical reaction characteristics, an electrothermal-coupling dynamic model for PEM electrolysis devices was constructed. Considering the influence of the input energy−substance and the output hydrogen and oxygen of PEM electrolysis devices on the whole dynamic equilibrium process, the required electrical energy and water molar flow rate are dynamically adjusted so that the temperature of the cathode and the anode is maintained near 338.15 K. The analytical results show that the hydrogen production rate and electrolysis efficiency are increased by 0.275 mol/min and 3.9%, respectively, by linearly stacking 100 PEM electrolysis devices to form a hydrogen production system... [more]

Monoliths are promising as catalytic structured supports due to their many operational advantages. Compared to pellets, monoliths offer low backpressure and good heat distribution, even at high flow rates. There is interest in the industry for improving temperature control in highly exothermic systems, such as the catalytic hydrogenation of CO2 for e-fuels synthesis. In this context, novel substrate shapes, such as non-homogeneous cell density monoliths, show good potential; however, to date, they have only been sparsely described. This work focuses on a dual cell density substrate and uses a computational model of a straight-channel monolith with two concentric regions to analyze its flow distribution. The central (core) and peripheral (ring) regions of the substrate differ in cell density in order to obtain a non-homogeneous cross-section. The model is validated against classical data in the literature and theoretical equations. Then, the flow fraction passing through each region of... [more]

Microwave heating has excellent potential for applications in wastewater treatment. This study proposes a highly efficient continuous liquid-phase microwave heating system to overcome the problems of low treatment capacity, low dynamic range of loads, and insufficient heating uniformity of the existing equipment. First, a quarter-wavelength impedance-matching layer improves heating efficiency, and the heating uniformity has been enhanced by horn antennas. Second, an experimental system is developed. The simulation and experimental results are consistent, with the microwave system achieving over 90% energy utilization for different thicknesses and concentrations of salt water. Finally, simulations are performed to analyze microwave efficiency and heating uniformity at different flow rates, salinities, dielectric properties, and sawtooth structures. The system can efficiently heat loads with a wide range of dielectric properties, including saline water. Generally, when the permittivity v... [more]

In this paper, the Multisphere (MS) models of three varieties of Cyperus esculentus seeds are modeled based on DEM. In addition, for comparison, other particle models based on automatic filing in EDEM software are also introduced. Then, the direct shear test, piling test, bulk density test, and rotating hub test are used to verify the feasibility of particle models of Cyperus esculentus seeds that we proposed. By comparing the simulated results and experimental results, combined with the CPU computation time, the proposed particle models achieved better simulation accuracy with fewer filing spheres. According to simulation results, some limitation was present when using one single verification test; varieties of verification tests used could improve the verification reliability, and a more appropriate particle model could be selected. Additionally, the issue of multicontact points in the MS model was studied. The Hertz Mindlin (no slip) (HM) model and Hertz Mindlin new restitution (HMN... [more]

The incorrect labeling, as well as the bioaccumulation of heavy metals in seafood, represent a recurring problem worldwide, not only for natural resources but also for the consumers’ health. Heavy metals can be accumulated through the food chain and transferred to the final human consumer. Despite its toxicology, arsenic does not have a concentration limit on food, unlike other heavy metals like cadmium, mercury, and lead. Tuna species, with a worldwide distribution and high per capita consumption, represent a well-known toxicological issue caused by heavy metals. In this context, 80 samples of canned tuna were analyzed to check if the information contained in the label was correct and complete. Genetic identification was made by sequencing a fragment of 16S rDNA from 80 samples. For the heavy metal quantification, only those samples with the complete FAO fishing area information on the label were analyzed. Only 29 out of 80 samples presented enough information on the labels for the an... [more]

This study introduces particle filtering (PF) for the tracking and fault diagnostics of complex process systems. In process systems, model equations are often nonlinear and environmental noise is non-Gaussian. We propose a method for state estimation and fault detection in a wastewater treatment system. The contributions of the paper are the following: (1) A method is suggested for sensor placement based on the state estimation performance; (2) based on the sensitivity analysis of the particle filter parameters, a tuning method is proposed; (3) a case study is presented to compare the performances of the classical PF and intelligent particle filtering (IPF) algorithms; (4) for fault diagnostics purposes, bias and impact sensor faults were examined; moreover, the efficiency of fault detection was evaluated. The results verify that particle filtering is applicable and highly efficient for tracking and fault diagnostics tasks in process systems.

A methodology for the computation of the thermal energy efficiency of modes for the heat treatment of frozen wooden prisms in an autoclave with saturated water vapor at changing operational conditions has been proposed. The methodology includes computer simulations with two own-coupled unsteady models: one to calculate the 2D temperature distribution in the cross-section of prismatic wood materials during their heat treatment, and the second to determine the heat balance of industrial autoclaves for such wood treatment. Simulations were carried out in order to determine the duration, energy consumption, and thermal efficiency of different modes, caused by changed operational conditions, for the autoclave steaming of frozen beech prisms with industrial parameters in the absence and presence of dispatcher intervention. The influence of nine combinations between the time of dispatcher intervention and the degree of reduction of the constant maximum temperature from the 130 °C of the basic... [more]

When it comes to lightweight design of automotive wheels, hybrid designs consisting of a carbon composite wheel rim and a metallic, e.g., aluminum alloy, wheel disc offer significant potential. However, the conventionally used bolted joint between the two parts is complex and requires compromises in lightweight design due to the additional mechanical elements. Within this research, an adhesive joint for a hybrid wheel is developed in order to demonstrate its performance and lightweight potential. The main challenges are the reliable resistance against high structural loads during different load cases, as well as the residual stresses in the joint due to different thermal expansion rates of the composite and aluminum material. The developed joint combines an adhesive bond with a form-fitted geometry while still enabling an assembling process of the wheel disc in rotational direction. In addition, adaptations of the fiber layup in the rim area significantly reduce the thermal residual st... [more]

The chemical industry includes a wide range of factories focused on obtaining final products as: (i) plastics; (ii) chemical fibers; (iii) rubber; (iv) perfumery and cosmetic products; and (v) cleaning products. Although the level of safety in the activities and installations of this sector is very high, the use of dangerous substances implies an increased risk of suffering an accident involving the emission of hazardous substances, as well as endangering the safety of workers. In the case of the manufacture of softeners, the presence of isopropanol (C3H8O), and dimethyl sulfate (CH3)2SO4), have been reported to be the accident cause in most of the cases. The European accident database (eMars) reported an accident in which the presence of impurities of nickel (Ni) in the hydrogenated tallow used as raw material for softener production may have increased thermal reactivity and the chances of spontaneous combustion. This paper analyzes the results obtained with the Maciejasz Index (MI) t... [more]