Search Results (3,122)

This study investigated the potential of low-grade gold deposits in modern mining, particularly in the context of declining high-grade resources. The primary method for processing these ores was gravity separation with the Knelson concentrator. A GRG test (gravity recoverable gold test) was conducted on two gold-bearing samples: a polymetallic Cu-Zn-Au ore from Zlaté Hory–Západ (Czech Republic) containing refractory gold and an ore with free gold from Kašperské Hory (Czech Republic). The study evaluated the effectiveness of the GRG test for gold recovery from these ores. The results showed that the Kašperské Hory sample predominantly contained relatively large gold grains, with recovery rates dropping significantly upon finer comminution. In the sample from the Zlaté Hory–Západ deposit, the greatest GRG release occurred in the first and last test stages, suggesting that larger sulfide grains with bound gold passed predominantly in the first stage, while fine gold with residual sulfides passed in the third. Both samples achieved high overall GRG recovery rates, with 64.2% for Kašperské Hory and more than 66% for Zlaté Hory–Západ, demonstrating the efficacy of centrifugal concentrators for both ores. Full article

Objectives: Small extracellular vesicles (sEVs) are nanosized vesicles with biological activities that exist in milk, playing functional roles in immunity, gut balance, and the nervous system. Currently, little is known about the impact of processing on milk sEVs. Methods: In this study, sEVs were collected from raw goat milk (g-sEV), pasteurized goat milk (pg-sEV), and goat milk powder (p-sEV) using a sucrose cushion centrifugation combined with qEV chromatography. Then, the sEVs were identified and compared using NTA, Western blot, and TEM. After extracting RNA and the total proteome from sEVs derived from different samples, the RNA was subjected to high-throughput sequencing, and peptide fragments were analyzed using mass spectrometry. Finally, GO and KEGG pathway analyses were performed on the results. Results: The characterization results revealed a decrease in diameter as the level of processing increased. High-throughput sequencing results showed that all three types of small extracellular vesicles were found to be rich in miRNA, and no significant differences were observed in the most abundant sEV species. Comparing with g-sEV, there were 3938 and 4645 differentially expressed miRNAs in pg-sEV and p-sEV, respectively, with the majority of them (3837 and 3635) being downregulated. These differentially expressed miRNAs were found to affect biological processes or signaling pathways such as neurodevelopment, embryonic development, and transcription. Proteomic analysis showed that there were 339 differentially expressed proteins between g-sEV and pg-sEV, with 209 proteins being downregulated. Additionally, there were 425 differentially expressed proteins between g-sEV and p-sEV, with 293 proteins being downregulated. However, no significant differences were observed in the most abundant protein species among the three types of sEVs. Enrichment analysis indicated that the differentially expressed proteins were associated with inflammation, immunity, and other related processes. Conclusions: These results indicate that extracellular vesicles have a protective effect on their cargo, while processing steps can have an impact on the size and quantity of the sEVs. Furthermore, processing can also lead to the loss of immune-related miRNA and proteins in sEVs. Full article

Background: Advanced platelet-rich fibrin (A-PRF) is produced by centrifuging the patient’s blood in vacuum tubes for 14 min at 1500 rpm. The most important component of A-PRF is the platelets, which release growth factors from their ⍺-granules during the clotting process. This process is believed to be the main source of growth factors. The aim of this paper was to systematically review the literature and to summarize the role of A-PRF in oral and maxillo-facial surgery. Materials and Methods: A systematic review was carried out, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (PROSPERO: CRD42024584161). Results: Thirty-eight articles published before 11 November 2024 were included in the systematic review. The largest study group consisted of 102 patients, and the smallest study group consisted of 10 patients. A-PRF was most often analyzed compared to leukocyte-PRF (L-PRF) or blood cloth. A-PRF was correlated with lower postoperative pain. Also, A-PRF was highlighted to have a positive effect on grafting material integration. A-PRF protected areas after free gingival graft very well, promoted more efficient epithelialization of donor sites and enhanced wound healing. Conclusions: Due to its biological properties, A-PRF could be considered a reliable addition to the surgical protocols, both alone and as an additive to bio-materials, with the advantages of healing improvement, pain relief, soft tissue management and bone preservation, as well as graft integration. However, to determine the long-term clinical implications and recommendations for clinical practice, more well-designed randomized clinical trials are needed in each application, especially those with larger patient cohorts, as well as additional blinding of personnel and long follow-up periods. Full article

Flywheels have been largely used in rotating machine engines to save inertial energy and to limit speed fluctuations. A stress distribution problem is created due to the centrifugal forces that are formed when the flywheel is spinning around, which leads to different levels of pressure and decompression inside its structure. Lack of balance leads to high energy losses through various mechanisms, which deteriorate both the flywheel’s expectancy and their ability to rotate at high speeds. Deviation in the design of flywheels from their optimum performance can cause instability issues and even a catastrophic failure during operation. This paper aims to analytically examine the stress distribution of radial and tangential directions along the flywheel structure within a linear elastic range. The eigenvalues and eigenvectors, which are representative of free vibrational features, were extracted by applying finite element analysis (FEA). Natural frequencies and their corresponding vibrating mode shapes and mass participation factors were identified. Furthermore, Kirchhoff–Love plate theory was employed to model the transverse vibration of the system. A general solution for the radial component of the equation of flywheel motion was derived with the help of the Bessel function. The results show certain modes of vibration identified as particularly influential in specific directions. Advanced time-frequency analysis techniques, including but not limited to continuous wavelet transform (CWT) and Hilbert–Huang transform (HHT), were applied to extract transverse vibration features of the flywheel system. It was also found that using CWT, low-frequency vibrations contribute to the majority of the energy in the extracted signal spectrum, while HHT exposes the high-frequency components of vibration that may cause significant structural damage if not addressed in time. Full article

Global energy consumption has continued to increase in recent years with economic development. Fossil energy sources are now being replaced with renewable energy, and hydrogen is one of such alternatives. Pumps are used for storage, transportation, and distribution. One such pump is the liquefied hydrogen centrifugal pump. In this study, optimisation design of a liquefied hydrogen centrifugal pump was performed using the response surface method, which is the optimisation method of the DesignXplorer provided by ANSYS, based on the flow analysis results of the impeller of the centrifugal pump. The design variables used in the optimisation process are the outlet width b₂, % of the blade thickness Su₂, leading edge inclination angle α, hub inclination angle δ, wrap angle θ, and outlet blade angle β₂. The optimisation analysis results obtained confirmed that all the selected design variables are semi-galactic and are sensitive to pump efficiency and head. It was confirmed that the efficiency of the centrifugal pump achieved using liquefied hydrogen as the working fluid is approximately 82.4%, which is significantly higher than that achieved by a centrifugal pump using water as the working fluid under the same operating conditions. Full article

Biomass harvesting represents one of the main bottlenecks in microalgae large-scale production. Solid–liquid separation of the biomass accounts for 30% of the total production costs, which can be reduced by the use of flocculants as a pre-concentration step in the downstream process. The natural polymer chitosan and the two chemical flocculants FeCl₃ and AlCl₃ were tested on freshwater Chlorella sorokiniana and two marine algae, Dunaliella tertiolecta and Tetraselmis striata. A preliminary screening at the laboratory scale was performed to detect the most suitable doses of flocculants. On the basis of these results, selected doses were tested on the pilot scale, using the flocculants for a pre-concentration step and the centrifugation as a second step to confirm the effectiveness of flocculants in a realistic operational environment. The biomass recoveries (R_pilot, %) of 100 L cultures were as follows: (1) for T. striata, R_pilot = 94.6% for 0.08 g/L AlCl₃, 88.4% for 0.1 g/L FeCl₃, and 68.3% for 0.04 g/L chitosan; (2) for D. tertiolecta, R_pilot = 81.7% for 0.1 g/L AlCl₃, 87.9% for 0.2 g/L FeCl₃, and 81.6% for 0.1 g/L chitosan; and (3) for C. sorokiniana, R_pilot = 89.6% for 0.1 g/L AlCl₃, 98.6% for 0.2 g/L FeCl₃, and 68.3% for 0.1 g/L chitosan. Flocculation reduced the harvesting costs by 85.9 ± 4.5% using chemical flocculants. Excesses of aluminum and iron in the biomass could be solved by decreasing the pH in the biomass combined with washing. This is the first study, to the best of our knowledge, that investigates the pilot-scale flocculation of three native Canarian microalgal strains. A pilot-scale pre-concentration step before centrifugation can improve the yield and reduce costs in the microalgae harvesting process. Full article

Non-centrifugal cane sugar (NCS) is prepared by evaporating sugarcane syrup to form a solidified, dehydrated brown sugar with a distinct flavor. This study investigated the effect of final evaporation temperatures (120–140 °C) on the volatile components, retronasal aroma profile, and sensory characteristics of NCS. Solid-phase microextraction–gas chromatography–mass spectrometry showed that the concentration of most volatiles, including pyrazines, furans, and furanones, in the NCS significantly increased as the evaporation temperature increased (p < 0.05). The evaporation temperature affected the aroma release from NCS, as shown in proton transfer reaction time-of-flight-mass spectrometry, with the intensity of volatile compounds detected from panelists’ noses or mouths significantly increasing after consuming NCS obtained at higher temperatures. Moreover, the intensity of aroma release in the mouth was greater than that in the nose; the most prevalent released substance, m/z 87.10, which could be derived from dihydro-2(3H)-furanone and 2,3-butanedione, rapidly decreased over seven breath cycles compared to other ions, suggesting its importance as a top-note aroma substance in NCS. In addition, the perceived roasted aroma and bitterness of the NCS obtained at higher temperatures were intensified. These findings underscore the importance of modifying the evaporation temperature on the volatile component composition, aroma release, and sensory characteristics of NCS. Full article

This study investigates the performance of a centrifugal radial turbine within an Organic Rankine Cycle (ORC) system, focusing on operation beyond the design point due to variable waste heat sources. With the goal of integrating the turbine into optimal ORC operating conditions, its performance was analyzed using R245fa as the working fluid over three stages with varying numbers of blades. A detailed computational analysis was performed using Ansys CFX software (Version 2020 R2) with the k-ω SST turbulence model using thermodynamic data from the NIST Refprop database. The results showed significant discrepancies when operating beyond the design point. At an inlet pressure of 780 kPa, the turbine internal power was calculated to be 120 kW—double the manufacturer’s maximum of 60 kW—and the mass flow rate exceeded 6 kg/s compared to the design value of 2.72 kg/s. These results highlight the challenges of adapting the turbine to fluctuating waste heat conditions, as factors such as tip clearance, blade geometry, and high outlet pressure have a significant impact on efficiency and system performance. Full article

Double suction pumps are widely used in the Yellow River in the China water intake pump stations, which face serious sediment wear. A prediction model for gap erosion in gas-liquid solid three-phase flow was constructed. A gas core factor has been added to the gap erosion model to achieve accurate prediction of particle impact velocity and impact angle caused by cavitation air core deformation. The influence mechanism of cavitation flow and sand-laden suction vortex on the sediment erosion. Usually, double suction pumps are one type. This study aims to explore the effects of the symmetrical and asymmetrical installation of double suction pump impellers on the wear and energy dissipation of pumps under sediment conditions in three-stage centrifugal pumps. The research results indicate that under symmetrical installation, the wear of the impeller caused by sediment impact is significantly intensified with a maximum velocity of 27 m/s. In contrast, asymmetric installation significantly improves sediment wear, with a maximum velocity of 24.3 m/s. By optimizing the staggered angle on both sides of the impeller, it was found that when the staggered angle was set to 10.85°, the performance of the pump under sediment conditions reached its optimal level, with a minimal erosion rate of 0.000008 kg·m⁻²·s⁻¹. These results provide an important basis for the design and optimization of three-stage centrifugal pumps in sediment transport and have significant theoretical significance and engineering application value. Full article

The design and technological scheme of a small-sized forage harvester with a capture width of 1.35 m equipped with a device oriented along the length of the stems was developed in this study. As a result of theoretical studies, the process of the movement of mass into the chamber of the mowing rotor due to centrifugal forces was revealed. The speed of mass movement and the average size of crushed particles with the mowing rotor were determined. The oriented feeding process of stems in the chamber of the chopping rotor is mathematically described in this paper. An analytical expression is obtained for determining the average size of crushed particles by the forage harvester, that is, a mathematical model of the processes of mowing, oriented feeding, and the chopping of stem fodder by the forage harvester. Laboratory and field tests of a forage harvester equipped with a device oriented along the length of the stems were conducted. The combine harvester’s productivity was 6.14 t/h when mowing alfalfa. Special experiments were conducted to determine the average size of crushed particles after the mowing rotor. The average size of crushed particles with the mowing rotor was 147.4 mm, while the theoretical value was 144 mm. The difference between these values was only 2.31%. A special experiment was conducted on the combine without an orienting device to compare the quality indicators. The mass fractions of crushed particles of up to 50 mm in length when the combine was operating with and without an orienting device were 79.3 and 46.7, respectively. Accordingly, the average length of crushed particles was 33.79 mm and that without an orienting device was 77.07 mm. The theoretical value of the average length of crushed particles was 34.9 mm (i.e., the difference between the theoretical and actual value of the average size of the crushed particles was only 3.25%). All this proves that when the combine harvester was operated with an orienting device, there was a significant increase in the quality indicators of the chopped feed, and the reliability of the theoretical studies and the resulting mathematical model were determined. Full article

This comprehensive review explores data-driven methodologies that facilitate the prognostics and health management (PHM) of centrifugal pumps (CPs) while utilizing both vibration and non-vibration sensor data. This review investigates common fault types in CPs, while placing a specific emphasis on artificial intelligence (AI) approaches, including machine learning (ML) and deep learning (DL) techniques, for fault diagnosis and prognosis. A key innovation of this review is its in-depth analysis of cutting-edge methods, such as adaptive thresholding, hybrid models, and advanced neural network architectures, aimed at accurately predicting the remaining useful life (RUL) of CPs under varying operational conditions. This review also addresses the limitations and challenges of the current AI-driven methodologies, offering insights into potential solutions. By synthesizing these methodologies and presenting practical applications through case studies, this review provides a forward-looking perspective to empower industry professionals and researchers with effective strategies to ensure the reliability and efficiency of centrifugal pumps. These findings could contribute to optimizing industrial processes and advancing health management strategies for critical components. Full article

Significant in various industrial applications, centrifugal pumps (CPs) play an important role in ensuring operational efficiency, yet they are susceptible to faults that can disrupt production and increase maintenance costs. This study proposes a robust hybrid model for accurate fault detection and classification in CPs, integrating Wavelet Coherence Analysis (WCA) with deep learning architectures VGG16 and ResNet50. WCA is initially applied to vibration signals, creating time–frequency representations that capture both temporal and frequency information, essential for identifying subtle fault characteristics. These enhanced signals are processed by VGG16 and ResNet50, each contributing unique and complementary features that enhance feature representation. The hybrid approach fuses the extracted features, resulting in a more discriminative feature set that optimizes class separation. The proposed model achieved a test accuracy of 96.39%, demonstrating minimal class overlap in t-SNE plots and a precise confusion matrix. When compared to the ResNet50-based and VGG16-based models from previous studies, which reached 91.57% and 92.77% accuracy, respectively, the hybrid model displayed better classification performance, particularly in distinguishing closely related fault classes. High F1-scores across all fault categories further validate its effectiveness. This work underscores the value of combining multiple CNN architectures with advanced signal processing for reliable fault diagnosis, improving accuracy in real-world CP applications. Full article

Since late 2021, outbreaks of highly pathogenic avian influenza virus have caused a record number of mortalities in wild birds, domestic poultry, and mammals in North America. Wetlands are plausible environmental reservoirs of avian influenza virus; however, the transmission and persistence of the virus in the aquatic environment are poorly understood. To explore environmental contamination with the avian influenza virus, a large-volume concentration method for detecting infectious avian influenza virus in waterbodies was developed. A variety of filtering, elution, and concentration methods were explored, in addition to testing filtering speeds using artificially amended 20 L water matrices (deionized water with sterile dust, autoclaved wetland water, and wetland water). The optimal protocol was dead-end ultrafiltration coupled with salt solution elution and centrifugation concentration. Using this method, infectious virus was recovered at 1 × 10⁻¹ 50% egg infectious dose per milliliter (EID₅₀/mL), whereas viral RNA was detected inconsistently down to 1 × 10⁰ EID₅₀/mL. This method will aid in furthering our understanding of the avian influenza virus in the environment and may be applicable to the environmental detection of other enveloped viruses. Full article

Extreme marine environmental cyclic loading significantly affects the serviceability of monopiles applied for the foundation of offshore wind turbines (OWTs). Existing research has primarily used p-y methods or total stress-based models to investigate the behavior of monopile–marine clay systems, overlooking the pore pressure development in subsea clay. Studies on the effective stress-based behavior of clay under various lateral cyclic loading conditions are limited. This paper presents an effective stress-based 3D finite element numerical method developed to predict key behaviors of pile–clay systems, including permanent pile rotation under cyclic loading, pile bending moment, and the evolution of pore pressure in subsea clay. The model is verified by contrasting the simulations results to centrifuge experimental results. Cyclic lateral loading is divided into average cyclic load and amplitude of cyclic load to investigate their impacts on the pile–clay system response. The research findings offer insights for the design of large-diameter monopiles under complex cyclic loading conditions. Full article

The nozzle is a crucial component in unmanned aerial vehicle (UAV) sprayers. The centrifugal nozzle offers unique advantages; however, there is a scarcity of published research regarding the structural parameters, spraying parameters, and practical applications specifically for UAV spraying. Furthermore, there is a need for UAV-specific nozzles that demonstrate high efficiency and excellent atomization performance. In this present study, a multi-disc centrifugal nozzle (MCN) capable of controlling droplet size was designed and optimized. The droplet size spectra with different atomizing discs were tested, and indoor and field tests were conducted to investigate the atomization and spray deposition characteristics of the MCN. It was found that the MCN with six atomizing discs with a curved groove, a disc angle of 120°, and a disc diameter of 77 mm demonstrated better atomizing performance. The volume median diameter was 96–153 μm, and the relative span was 1.0–1.3. Compared with the conventional hydraulic nozzle, this nozzle increased the effective spray swath width from 2.5–3.0 m to 4.0–5.0 m and promoted the average deposition rate by 132.4% at a flying height of 1.0 m and a flying speed of 3.0 m/s, which tends to raise the operation efficiency by four to five times. This study can provide a reference for the design and optimization of centrifugal nozzles for a UAV sprayer and the selection of operating parameters in aerial spraying operations. Full article