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Showing records 36650 to 36674 of 43292. [First] Page: 1 1463 1464 1465 1466 1467 1468 1469 1470 1471 Last
Interval-Valued Pythagorean Fuzzy Similarity Measure-Based Complex Proportional Assessment Method for Waste-to-Energy Technology Selection
Arunodaya Raj Mishra, Dragan Pamučar, Ibrahim M. Hezam, Ripon K. Chakrabortty, Pratibha Rani, Darko Božanić, Goran Ćirović
February 21, 2023 (v1)
Subject: Optimization
Keywords: complex proportional assessment, interval-valued Pythagorean fuzzy set, MCDM, municipal solid waste, waste-to-energy
This study introduces an integrated decision-making methodology to choose the best “waste-to-energy (WTE)” technology for “municipal solid waste (MSW)” treatment under the “interval-valued Pythagorean fuzzy sets (IPFSs)”. In this line, first, a new similarity measure is developed for IPFSs. To show the utility of the developed similarity measure, a comparison is presented with some extant similarity measures. Next, a weighting procedure based on the presented similarity measures is proposed to obtain the criteria weight. Second, an integrated approach called the “interval-valued Pythagorean fuzzy-complex proportional assessment (IPF-COPRAS)” is introduced using the similarity measure, linear programming model and the “complex proportional assessment (COPRAS)” method. Furthermore, a case study of WTE technologies selection for MSW treatment is taken to illustrate the applicability and usefulness of the presented IPF-COPRAS method. The comparative study is made to show the strength and s... [more]
Time-Jerk optimal Trajectory Planning of Industrial Robots Based on a Hybrid WOA-GA Algorithm
Fang Wang, Zhijun Wu, Tingting Bao
February 21, 2023 (v1)
Keywords: B-splines, industrial robots, optimal trajectory, WOA-GA
An optimal and smooth trajectory for industrial robots has a positive impact on reducing the execution time in an operation and the vibration in their joints. In this paper, a methodology for the time-optimal and jerk-continuous trajectory planning of industrial robots is proposed. The entire trajectory is interpolated in the joint space utilizing fifth-order B-splines and then optimized by a hybrid whale optimization algorithm and genetic algorithm (WOA-GA). Two objective functions, including the integral of the squared jerk along the entire trajectory and the total execution time, are minimized to obtain the optimal entire trajectory. A fifth-order B-spline interpolation technique enables the achievement of a jerk-continuous trajectory, while respecting the kinematic limits of jerk, acceleration and velocity. WOA-GA is utilized to solve the time-jerk optimal trajectory planning problem with nonlinear constraints. The proposed hybrid optimization algorithm yielded good results and ach... [more]
Hybrid ELM and MARS-Based Prediction Model for Bearing Capacity of Shallow Foundation
Manish Kumar, Vinay Kumar, Rahul Biswas, Pijush Samui, Mosbeh R. Kaloop, Majed Alzara, Ahmed M. Yosri
February 21, 2023 (v1)
Keywords: AI, ELM, EO, MARS, PSO, shallow foundation
The nature of soil varies horizontally as well as vertically, owing to the process of the formation of soil. Thus, ensuring the safe design of geotechnical structures has been a major challenge. In shallow foundations, conducting field tests is expensive and time-consuming and often conducted on significantly scaled-down models. Empirical models, too, have been found to be the least reliable in the literature. The study proposes AI-based techniques to predict the bearing capacity of a shallow foundation, simulated using the datasets obtained in experiments conducted in different laboratories in the literature. The results of the ELM-EO and ELM-PSO hybrid models are compared with that of the ELM and MARS models. The performance of the models is analyzed and compared with each other using various performance parameters. The models are graded to each other using rank analysis and the visual interpretations are provided using error matrices and REC curves. ELM-EO is concluded to be the bes... [more]
Automatic and Generic Prognosis Method Based on Data Trend Analysis and Neural Network
Youssouf Diaf, Samir Benmoussa, Mohand Djeziri
February 21, 2023 (v1)
Keywords: Machine Learning, neural network, prognostic and health management, remaining useful life, trend modeling
This paper presents a generic and unsupervised failure prognosis method which can be applied to wide scope of applications. The main contribution of the presented method is automatic relevant data identification based on signal smoothing and trendability analysis and automatic degradation model identification for health indices construction, built using a trained neural network, thus allowing for the automatic adaptation of the degradation trend model to changes in the degradation dynamic. Regarding the failure prognosis, the end of life is first predicted using a fitting model; then, the remaining useful life is predicted using a similarity algorithm. The proposed approach is validated using the turbofan engine data sets provided by NASA. The prediction results have been evaluated using accuracy metrics such as root mean square error and prognostic metrics such α−λ and relative accuracy. The obtained results show the effectiveness of the proposed method, both for the end of life and r... [more]
Recovery of Phenolic Compounds and Antioxidants from Coffee Pulp (Coffea canephora) Waste Using Ultrasound and Microwave-Assisted Extraction
Thy Minh Kieu Tran, Taiwo O. Akanbi, Timothy Kirkman, Minh H. Nguyen, Quan Van Vuong
February 21, 2023 (v1)
Keywords: bioactive compounds, Coffea canephora, coffee pulp, microwave-assisted extraction, Robusta, ultrasound-assisted extraction
Coffee pulp is a by-product generated from coffee bean production. This waste is a potential source of bioactive compounds, which can be recovered for use as an ingredient for many products. However, this by-product is typically dumped in landfills or made into compost. Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) were employed to recover bioactive compounds from coffee pulp waste. Results showed that time and instrument power significantly affected the recovery yield in both UAE and MAE. The temperature was also a significant factor in UAE. The optimal MAE conditions were a radiation time of 70 min, a power of 700 W, and a 50% (v/v) ethanol solvent to sample ratio of 100:5 (mL/g), approximately 47 mg of phenolic compounds, 36 mg of flavonoid, 8 mg of chlorogenic acid, and 6 mg of caffeine could be recovered from 1 g of the material. The optimal UAE condition were an ultrasonic time of 35 min, a temperature of 60 °C, and a power of 250 W; however, bioact... [more]
Linear Golden Section Speed Adaptive Control of Permanent Magnet Synchronous Motor Based on Model Design
Wenping Jiang, Wenchao Han, Lingyang Wang, Zhouyang Liu, Weidong Du
February 21, 2023 (v1)
Keywords: characteristic model, linear golden-section adaptive control, model-based design, permanent magnet synchronous motor
Permanent magnet synchronous motor (PMSM) is a multi-variable, strongly coupled, nonlinear complex system. It is usually difficult to establish an accurate mathematical model, and the introduction of new complex algorithms will increase the difficulty of embedded code development. In order to solve this problem, we establish the characteristic model of permanent magnet synchronous motor in this paper, and the speed control scheme of the linear golden-section adaptive control and integral compensation, which is adopted. Finally, using the model-based design (MBD) method, how to build the simulink embedded code automatic generation model is introduced in detail, and then we complete the PMSM speed control physical verification experiment. Simulation and experimental results show that compared with traditional proportional-integral-derivative (PID) control, the speed control accuracy of PMSM is improved about 3.8 times. Meanwhile, the development method based on the model design can incre... [more]
Pipeline Two-Phase Flow Pressure Drop Algorithm for Multiple Inclinations
Andrés Cepeda-Vega, Rafael Amaya-Gómez, Miguel Asuaje, Carlos Torres, Carlos Valencia, Nicolás Ratkovich
February 21, 2023 (v1)
Keywords: dimensionless numbers, flow patterns, gas–liquid two-phase flow, Generalized Additive Model, pressure gradient
A Generalized Additive Model (GAM) is proposed to predict the pressure drop in a gas−liquid two-phase flow at horizontal, vertical, and inclined pipes based on 21 different dimensionless numbers. It is fitted from 4605 points, considering a fluid pattern classification as Annular, Bubbly, Intermittent, and Segregated. The GAM non-parametric method reached high prediction capacity and allowed a great degree of interpretability (i.e., it helped to visualize and test statistical inference), considering that each predictor’s marginal effects could be described, unlike in other Machine Learning (ML) methods. The prediction capacity of the GAM model for the pressure gradient obtained an adjusted R2 and a mean relative error of 99.1% and 12.93%, respectively. This capacity is maintained even when ignoring Bubbly flow in the training sample. A regularization technique to filter some variables was used, but most of the predictors must maintain the model’s high predictive ability. For example, d... [more]
Development of Core-Shell Rh@Pt and Rh@Ir Nanoparticle Thin Film Using Atomic Layer Deposition for HER Electrocatalysis Applications
Yiming Zou, Ronn Goei, Su-Ann Ong, Amanda Jiamin ONG, Jingfeng Huang, Alfred Iing Yoong TOK
February 21, 2023 (v1)
Subject: Materials
Keywords: atomic layer deposition (ALD), HER electrocatalysis, Ir–iridium, noble metal–nanoparticle thin film core shell structure, Pt–platinum, Rh–rhodium
The efficiency of hydrogen gas generation via electrochemical water splitting has been mostly limited by the availability of electrocatalyst materials that require lower overpotentials during the redox reaction. Noble metals have been used extensively as electrocatalysts due to their high activity and low overpotentials. However, the use of single noble metal electrocatalyst is limited due to atomic aggregation caused by its inherent high surface energy, which results in poor structural stability, and, hence, poor electrocatalytic performance and long-term stability. In addition, using noble metals as electrocatalysts also causes the cost to be unnecessarily high. These limitations in noble metal electrocatalysts could be enhanced by combining two noble metals in a core-shell structure (e.g., Rh@Ir) as a thin film over a base substrate. This could significantly enhance electrocatalytic activity due to the following: (1) the modification of the electronic structure, which increases elec... [more]
Application of Deep Learning Network in Bumper Warpage Quality Improvement
Hanjui Chang, Zhiming Su, Shuzhou Lu, Guangyi Zhang
February 21, 2023 (v1)
Keywords: artificial neural network, bumper, deep learning, molding quality, prediction, recognizable performance evaluation
Based on the context of Industry 4.0 smart manufacturing and for the prediction of injection molding quality of automobile bumpers, this study proposes a deep learning network that combines artificial neural networks and recognizable performance evaluation methods to better achieve the prediction and control of product quality. A pressure sensor was used to monitor and collect real-time pressure data in the mold cavity of the bumper. The quality indicators reflecting the molding quality were selected, and the correlation between these indicators and the molding quality was evaluated using recognizable performance evaluation methods and Pearson’s correlation coefficient. The standard z-score was used to filter out the abnormal data in the experimental data, and the bumper critical length warpage was converted into different quality levels, and the bumper critical length warpage was defined as either “qualified” and “unqualified” in order to improve the prediction accuracy of the model.... [more]
Assessment of Liquid and Solid Digestates from Anaerobic Digestion of Rice Husk as Potential Biofertilizer and Nutrient Source for Microalgae Cultivation
Akinola David Olugbemide, Blaž Likozar
February 21, 2023 (v1)
Keywords: anaerobic digestion, biofertilizer, liquid digestate, microalgae cultivation, rice husk, solid digestate
The need to embrace a circular economy model for sustainable growth and development is increasing due to the rise in human population and the dwindling natural resources available to meet the demands for energy and food. In this study, anaerobic digestion of rice husk (RH) was carried out under mesophilic conditions to produce biogas and digestates. Two particle sizes (300 and 600 μm) and three dilution ratios (1:4, 1:6, and 1:8) were employed to determine the optimum conditions for biogas production. The best anaerobic digesters (300 μm/1:6 and 600 μm/1:4) in each of the categories produced a cumulative biogas of 3205 + 290 mL and 2310 + 320 mL, respectively. The digestates were separated into solid and liquid fractions and characterized to evaluate their potential as biofertilizers and nutrient sources for microalgae cultivation. The nitrogen and phosphorus contents of the solid fractions (1.00 ± 0.01 and 0.97 ± 0.04) were significantly higher (p < 0.05) than the liquid fractions... [more]
Numerical Modeling and Simulation of Blood Flow in a Rat Kidney: Coupling of the Myogenic Response and the Vascular Structure
Wei Deng, Ken-ichi Tsubota
February 21, 2023 (v1)
Keywords: biomechanics, blood flow, computer simulation, kidney, myogenic response, numerical modeling, vascular structure
A numerical simulation was carried out to investigate the blood flow behavior (i.e., flow rate and pressure) and coupling of a renal vascular network and the myogenic response to various conditions. A vascular segment and an entire kidney vascular network were modeled by assuming one single vessel as a straight pipe whose diameter was determined by Murray’s law. The myogenic response was tested on individual AA (afferent artery)−GC (glomerular capillaries)−EA (efferent artery) systems, thereby regulating blood flow throughout the vascular network. Blood flow in the vascular structure was calculated by network analysis based on Hagen−Poiseuille’s law to various boundary conditions. Simulation results demonstrated that, in the vascular segment, the inlet pressure Pinlet and the vascular structure act together on the myogenic response of each individual AA−GC−EA subsystem, such that the early-branching subsystems in the vascular network reached the well-regulated state first, with an inte... [more]
Numerical Study of the Effect of the Reynolds Number and the Turbulence Intensity on the Performance of the NACA 0018 Airfoil at the Low Reynolds Number Regime
Jan Michna, Krzysztof Rogowski
February 21, 2023 (v1)
Keywords: aerodynamic, airfoil, Computational Fluid Dynamics, drag force, lift force, NACA 0018, Reynolds-averaged Navier–Stokes, turbulent, unsteady, vertical axis wind turbine
In recent years, there has been an increased interest in the old NACA four-digit series when designing wind turbines or small aircraft. One of the airfoils frequently used for this purpose is the NACA 0018 profile. However, since 1933, for over 70 years, almost no new experimental studies of this profile have been carried out to investigate its performance in the regime of small and medium Reynolds numbers as well as for various turbulence parameters. This paper discusses the effect of the Reynolds number and the turbulence intensity on the lift and drag coefficients of the NACA 0018 airfoil under the low Reynolds number regime. The research was carried out for the range of Reynolds numbers from 50,000 to 200,000 and for the range of turbulence intensity on the airfoil from 0.01% to 0.5%. Moreover, the tests were carried out for the range of angles of attack from 0 to 10 degrees. The uncalibrated γ−Reθ transition turbulence model was used for the analysis. Our research has shown that a... [more]
Numerical Simulation Study on Flow Heat Transfer and Stress Distribution of Shell-and-Tube Superheater in Molten Salt Solar Thermal Power Station
Yong Zeng, Guangyao Cui, Wangsong Wu, Canjun Xu, Jing Huang, Jiaming Wang, Zhongqing Yang
February 21, 2023 (v1)
Keywords: heat transfer, heat–fluid–solid coupling, shell-and-tube heat exchanger, steam generation system, stress distribution
The flow heat transfer and stress distribution of the shell and tube superheater of the steam generation system in a 50 MW molten salt tank solar thermal power station are studied by numerical simulation, and the influence of the flow pattern of molten salt and water vapor in the shell-and-tube superheater on the heat transfer efficiency and stress distribution under the heat−fluid−solid coupling condition is deeply studied. When the water vapor is located on the tube side of the superheater, the molten salt is located on the shell side, and the counterflow is used in the superheater, the water vapor outlet meets the inlet temperature of the steam turbine, and the heat exchange efficiency of the superheater can reach 94.2%. The optimum inlet temperatures of molten salt and steam in the superheater are 563 and 345 °C, respectively, and the optimum flow rate of molten salt at the inlet of the superheater is 2.5 m/s. Compared with the stable condition, the heat exchange efficiency can be... [more]
How Does Long-Term Storage Influence the Physical Stability and Dissolution of Bicalutamide from Solid Dispersions and Minitablets?
Agata Antosik-Rogóż, Joanna Szafraniec-Szczęsny, Justyna Knapik-Kowalczuk, Mateusz Kurek, Karolina Gawlak, Marian Paluch, Renata Jachowicz
February 21, 2023 (v1)
Subject: Materials
Keywords: amorphous solid dispersions, bicalutamide, milling, minitablets, polyvinylpyrrolidone, stability study
The stability of amorphous drugs is among the main challenges in the development of solid dosage forms. This paper examines the effect of storage conditions (25 °C/60% RH and 40 °C/75% RH) and different packaging materials, i.e., polystyrene containers and PVC/Al blisters, on the crystallinity and dissolution characteristics of solid dispersions containing bicalutamide and polyvinylpyrrolidone. The results confirmed drug amorphization upon milling and improved dissolution resulting from the lack of a crystal lattice. These properties varied with time regarding sample composition, storage conditions, and packaging material. The most resistant to storage conditions was the 1:1 solid dispersion packed into blisters. Based on the obtained results, the 1:1 solid dispersion was formulated into minitablets, which were then tested after tableting and then packed into PVC/Al blisters and stored for six months in the same conditions as solid dispersions. We proved that efficient stabilization of... [more]
Calibration and Experimental Validation of Contact Parameters in a Discrete Element Model for Tobacco Strips
Wei Jiang, Lihua Wang, Jun Tang, Yanchao Yin, Hao Zhang, Tongpeng Jia, Jiwei Qin, Huaiyu Wang, Qike Wei
February 21, 2023 (v1)
Keywords: discrete element method, parameter calibration, redrying, stacking angle, tobacco strips, void ratio
To study the contact parameters of the tobacco strips during redrying, in this study, the funnel stacking test is used to determine the stacking angle, and the discrete element method is used to simulate the formation process of the stacking angle, to calibrate and verify the physical and contact parameters of tobacco strips. The Placket−Burman test was used to screen out the parameters that had significant effects on the stacking angle. The regression response surface model between the stacking angle and contact parameters was established by Central Composite Design using the stacking angle from physical tests as the response index. The test results show that static and rolling friction coefficients between tobacco strips have significant effects on the test results, so these two parameters must be accurately calibrated. Finally, the accuracy and validity of the calibrated tobacco strips contact parameters were verified by comparing the stacking angle and void ratio of physical and si... [more]
Effects of Wheat Bran Micronization on the Quality of Reconstituted Whole-Wheat Flour and Its Cooked Noodles
Sitong Lai, Jinlong Liu, Yanqing Zhang, Yuanmeng Wang, Guang Li, Qingliang Cui
February 21, 2023 (v1)
Keywords: micronization, noodle, particle size, wheat bran, whole wheat
The particle size of wheat bran plays an important role in the quality of reconstituted whole-wheat flour and its products. The effects of wheat bran particle size on the quality of reconstituted whole-wheat flour and its cooked noodles were analyzed; the mean particle size (D50) of wheat bran ranged from 26.05 to 46.08 μm. Results show that the decreases in D50 of wheat bran induced the changes in the quality of whole-wheat flour and its noodles. Specifically, the damaged starch content, water absorption, and the solvent retention capacity of sodium carbonate and sucrose of whole-wheat flour increased at various degrees, while pasting viscosity decreased, and the gluten index and SDS-sedimentation volume increased first and then decreased. The cooking yield, cooking loss, and break rate of fresh noodles decreased first and reached a trough at D50 of 26.05 μm, and then increased. The adhesiveness of cooked noodles increased, the score of smoothness, taste, appearance, and color increas... [more]
Depositional Environment Changes during the Cenozoic in the Northeastern Margin of the Qinghai−Tibet Plateau
Yetong Wang, Guoqiang Sun, Shuncun Zhang, Irene Cantarero, David Cruset, Vinyet Baqués, Hui Guo, Shangshang Bo, Anna Travé
February 21, 2023 (v1)
Subject: Environment
Keywords: Cenozoic climate, isotope analysis, Qaidam Basin, Qinghai–Tibet Plateau, trace elements
The uplift of the Tibetan Plateau (TP) during the late Cenozoic is thought to be one of the crucial factors controlling the Asian climate. However, the complex interaction between tectonics and climate change remains unclear. The carbon and oxygen isotopes and elementary geochemistry of rocks from the early Eocene Lulehe Formation to the Miocene Youshashan Formation in the northern margin of Qaidam Basin, shows important variations in the Rb/Sr, MgO/CaO, Sr/Cu, and V/Cr ratios, together with CMI and CIA, which are interpreted as reflecting relevant regional climate and environmental changes. Combining the above mentioned parameters, we reconstructed the evolution of the sedimentary environment in the Qaidam Basin. The climate is roughly divided into four stages: (1) warm and humid; (2) cold and dry; (3) alternations of cold and dry with warm and humid; and (4) cold and arid. At the same time, there are also minor short-term changes of dry, wet, cold, and warm in each stage. The early E... [more]
Effect of Spray Parameters on Electrical Characteristics of Printed Layer by Morphological Study
Gye Hyeon Kim, Eun Ae Shin, Je Young Jung, Jun Young Lee, Chang Kee Lee
February 21, 2023 (v1)
Keywords: electrically conductive print, spray parameter, surface morphology
Products are manufactured as printed electronics through electro-conductive ink having properties suitable for flexible substrates. As printing process conditions affect the quality of the electronic properties of the final devices, it is essential to understand how the parameters of each process affect print quality. Spray printing, one of several printing processes, suits flexible large-area substrates and continuous processes with a uniform layer for electro-conductive aqueous ink. This study adopted the spray printing process for cellulose nanofiber (CNF)/carbon nanotube (CNT) composite conductive printing. Five spray parameters (nozzle diameter, spray speed, amount of sprayed ink, distance of nozzle to substrate, and nozzle pressure) were chosen to investigate the effects between process parameters and electrical properties relating to the morphology of the printing products. This study observed the controlling morphology through parameter adjustment and confirmed how it affects t... [more]
Effect of Sparger Characteristics on Bubble-Formation Dynamics under Oscillatory Air Pattern
Ajuan Song, Sijia Zhao, Yijun Cao, Chao Li
February 21, 2023 (v1)
Keywords: bubble size, coalescence, oscillatory air pattern, sparger configuration
The size of bubbles generated from a porous sparger is at least an order of magnitude larger than the pore diameter under the steady air pattern. Recent studies have shown that the bubble size can be significantly reduced when the steady air flow is replaced by an oscillatory pattern. However, the effectiveness of oscillatory air flow on reducing bubble size under different sparger characteristics is yet to be studied. This work fundamentally investigates the response of bubble size to sparger characteristics under an oscillatory air pattern by segregating the bubble formation subprocesses into bubble detachment and consequent coalescence. The results show that bubble size significantly decreased with hydrophilic plates regardless of contact angle, owing to depressed coalescence, while no impact was observed for a hydrophobic plate. The influence of the oscillatory air pattern on decreasing bubble size was weakened as the chamber volume was increased, and above a critical volume the bu... [more]
Review of Particle Filters for Internal Combustion Engines
Rui Dong, Zhiqing Zhang, Yanshuai Ye, Huiqiong Huang, Chao Cao
February 21, 2023 (v1)
Keywords: deposition, diesel particulate filter, gasoline particulate filter, pressure drop, regeneration
Diesel engines have gradually become one of the main forces in the human transportation industry because of their high efficiency, good durability, and stable operation. However, compared with gasoline vehicles, the high emission of diesel vehicles forces manufacturers to introduce new pollutant control technologies. Although the particulate matter emissions of gasoline vehicles are lower than that of diesel vehicles, with the popularity of gasoline vehicles and the continuous rise of power, the impact of these particles on the environment cannot be ignored. Therefore, diesel particulate filters and gasoline particulate filters have been invented to collect the fine particles in the exhaust gas to protect the environment and meet increasingly stringent emission regulations. This paper summarizes the research progress on diesel particulate filters and gasoline particulate filters at present and comprehensively introduces the diesel particulate filter and gasoline particulate filter from... [more]
Non-Thermal Technologies Combined with Antimicrobial Peptides as Methods for Microbial Inactivation: A Review
Larissa Andaluz-Mejía, Daniela Ruiz-De Anda, César Ozuna
February 21, 2023 (v1)
Subject: Biosystems
Keywords: bacteriocin, chemical preservatives, high hydrostatic pressure, nisin, pulsed electric fields, ultrasound
Non-thermal technologies allow for the nutritional and sensory properties of foods to be preserved, something that consumers demand. Combining their use with antimicrobial peptides (AMPs) provides potential methods for food preservation that could have advantages over the use of chemical preservatives and thermal technologies. The aim of this review was to discuss the advances in the application of non-thermal technologies in combination with AMPs as a method for microbial inactivation. Published papers reporting studies on the combined use of power ultrasound (US), pulsed electrical fields (PEF), and high hydrostatic pressure (HHP) with AMPs were reviewed. All three technologies show a possibility of being combined with AMPs, generally demonstrating higher efficiency than the application of US, PEF, HHP, and AMPs separately. The most studied AMP used in combination with the three technologies was nisin, probably due to the fact that it is already officially regulated. However, the com... [more]
Particle Residence Time Distribution in a Concurrent Multiphase Flow Reactor: Experiments and Euler-Lagrange Simulations
Laura Unger, Juan Sebastián Gómez Bonilla, Dyrney Araújo dos Santos, Andreas Bück
February 21, 2023 (v1)
Keywords: axial flow structure, downer reactor, gas-particle flow, residence time distribution, thermal rounding
The present work focuses on investigating the residence time behavior of microparticles in a concurrent downer reactor through experiments and numerical simulations. For the numerical simulations, a three-dimensional multiphase model was developed using the Euler-Lagrange approach. The experiments were performed in a 0.8 m-long steel reactor with gravitational particle injection. The effects of different operating conditions, e.g., the sheath gas velocity on the particle residence time distribution were assessed. An increase in the sheath gas flow rate led to a decrease in the peak residence time, although the maximum residence time increased. Regarding the lowest sheath gas flow rate, the particles’ peak residence time was twice as high compared to the peak residence time within the highest flow rate. The particles’ residence time curves presented a broad distribution coinciding with the size distribution of the powder. The numerical results agreed with the experimental data; thus, th... [more]
Evaluation of Centrifugal Force, Erosion, Strain Rate, and Wall Shear in a Stairmand Cyclone
Sajed Naiemi Dizajyekan, Gholamhossein Shahgholi, Adel Rezvanivand Fanaei, Vahid Rostampour, Vali Rasooli Sharabiani, Mariusz Szymanek, Ryszard Kulig
February 21, 2023 (v1)
Keywords: centrifugal force, cyclone separator, Euler number, pressure drop, wheat conveying
In the present study, imperative parameters including centrifugal force, erosion, streamline, strain rate, and wall shear are evaluated in a cyclone separator. The flaw of the cyclone surface due to erosion is an acute problem in the industry. According to the great importance of the centrifugal force on the separation phenomenon, a comprehensive study is conducted. A computational fluid dynamics (CFD) simulation is realized by applying a Reynolds stress turbulence model (RSM), and particle−air interactions were modeled using a discrete phase model (DPM). The result shows a good agreement between the experimental data and CFD simulation on the tangential velocity and pressure drop. The maximum deviation of the validation process is 6.8%. It is found that the centrifugal force within the cyclone is increased with an enhancement in the inlet velocity. The separation efficiency indicates an increase−decrease treatment in various inlet velocities with inlet velocity up to 16 m⋅s−1 but decr... [more]
Natural Frequency Analysis of Horizontal Piping System Conveying Low Viscosity Oil−Gas−Water Slug Flow
Liedong Mi, Yunlong Zhou
February 21, 2023 (v1)
Keywords: critical gas velocity, natural frequency, slug flow, water cut
The water cut (WC) has a significant effect on the flow parameters, such as liquid holdup, liquid phase velocity, and flow regimes of the low-viscosity oil−gas−water slug flow, and it can change the vibration characteristics of piping systems. To study the effect of water cut on the vibration characteristics of piping systems conveying such internal flow, a new dynamic model is developed. Galerkin’s method is used to discretize the equation and determine the natural frequencies by solving for the eigenvalues of the equation coefficient matrix. The results show that in the range of 10−90% WC, the natural frequency increases and then decreases, and the turning point occurs near the phase inversion region (WC = 40−60%). The main reason is the highly effective viscosity in the phase inversion region, which leads to an increase in the liquid holdup. The natural frequency increases and then decreases with superficial gas velocity, and the inflection point decreases with the increase in water... [more]
Electric Drives: Complexes of Nonlinear Electromechanical Links Identified by Nonlinear Transfer Functions and Families of Frequency Characteristics
Vladimir L. Kodkin, Alexander A. Baldenkov, Maksim A. Grigoriev
February 21, 2023 (v1)
Keywords: electric drive, hyperstability, nonlinear systems
The article considers a generalized block diagram of electromechanical systems: electric drives. It is shown that all their elements have significant nonlinearities that cannot be neglected when designing systems with maximum accuracy and speed. A method for taking into account the influence of nonlinearities on the electric drive characteristics, the method of nonlinear transfer functions and families of frequency characteristics, is proposed. It is shown how these nonlinear transfer functions make it possible to form correction and control systems for electric drives in the modes of processing task signals and in the modes of parrying the load.
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