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Effects of Superabsorbent Polymer Addition on the Thermal Properties of Eutectic Phase Change Material
Seok-Joon Lee, Seul-Hyun Park
June 21, 2024 (v1)
Subject: Materials
Keywords: nucleating agent, phase change material, refrigerator, super absorbent polymer, supercooling, thermal properties, thickener
In this study, the influence of a super absorbent polymer (SAP) addition on the thermal properties of phase change material (PCM) was investigated. It was found that adding SAP reduced the melting temperature of PCM and improved phase separation properties. While the addition of 1.0 wt% of SAP to PCMs decreased latent heat by 3 J/g to 24.4 J/g, the addition was determined to be necessary to prevent leaks from a functional duct unit (FDU) and assure product stability. The results obtained from a series of brine refrigeration tests indicate that the supercooling temperature decreased by 0.3 °C to 1.7 °C when 1.0 wt% of SAP was added to PCM. The addition of SAP to PCM appears to promote supercooling by encouraging condensation during phase change. As a result of applying SAP-added PCM to the FDU, the isothermal operation performance was improved compared to existing refrigerators.
Critical Situations and Prevention of Accidents in Chemico-Technological Systems (Methodological Aspects)
Alexander Fedorov, Gregory Yablonsky
June 21, 2024 (v1)
Keywords: accidents, chemical plant, control systems, eliminating, emergency scale, preventing, real time, recognizing
The aim of this work is to study the causes of accidents in chemical processes, develop a methodology for accident prevention via control, and illustrat its realization by examples using a variety of strategies. The general concept of critical situations was introduced systematically covering both emergency and pre-emergency situations. In large-scale chemical plants, examples of accidents are presented. Accident causes as a result of disturbances and control faults in technological processes are analyzed. Approaches for preventing accidents are considered. The revealing of critical situations is presented as a problem of pattern recognition, and the subtasks of the recognition are analyzed. An emergency scale based on the assessment of various states of the chemico-technological process is introduced and applied for distinguishing the different levels of accident. The real obstacles in the prevention of accidents via control are shown and analyzed. Matrices of critical situations with... [more]
A Study on Defect Detection of Dissimilar Joints in Cu-STS Tubes Using Infrared Thermal Imaging of Induction Heating Brazing
Chung-Woo Lee, Suseong Woo, Jisun Kim
June 21, 2024 (v1)
Keywords: brazing, convolutional neural network, defect identification, high-frequency Induction heating, infrared thermal image
We proposed a novel detection method for identifying joint defects in the brazing process between copper tubes and stainless steel using a convolutional neural network (CNN) model. The brazing joints were created using high-frequency induction heating equipment, and infrared thermal imaging cameras were employed to capture the thermal data generated during the jointing process. The experiments involved 15.88 mm diameter copper tubes commonly used in plate heat exchangers, stainless-steel tubes, and filler metal containing 20% Ag. The thermal data were obtained with a resolution of 80 × 80 pixels per frame, resulting in 4796 normal joint data and 5437 defective joint data collected over 100 high-frequency induction-heating brazing experiments. A total of 10,233 thermal imaging data were categorized into 6548 training data, 1638 validation data, and 2047 test data for the development of the predictive model. We designed CNN models with varying hyperparameters, specifically the number of... [more]
Spatial Distribution and Migration of Heavy Metals in Dry and Windy Area Polluted by Their Production in the North China
Weimin Bao, Weifan Wan, Zhi Sun, Mei Hong, Haigang Li
June 21, 2024 (v1)
Subject: Environment
Keywords: atmospheric deposition, heavy metal distribution, heavy metal pollution, pollutant migration, surface runoff
We explored the migration and distribution of heavy metal pollution in a dry and windy area in northern China. We collected soil, atmospheric deposition, and water samples, and measured heavy metal concentrations. Cu, Zn, As, and Pb in the 0−10 cm soil layer had a fan-shaped distribution, consistent with their atmospheric deposition fluxes. This indicates that the distribution of these heavy metals was driven by strong winds. The concentration of Cd in the river increased from 0.257 mg/L upstream to 0.460 mg/L downstream, resulting in the same distribution trends as soil near the river. Surface runoff may therefore drive Cd migration. The concentration of Pb in the river exceeded the pollution threshold, resulting in accumulation in the 5−10 cm soil layer. Atmospheric deposition fluxes were consistent with the soil distribution results, and principal component analysis showed that the contribution of surface runoff was high. This suggests that the migration of Pb and Cr is driven by bo... [more]
Stochastic Modeling and Simulation of Filament Aggregation in Alzheimer’s Disease
Vaghawan Prasad Ojha, Shantia Yarahmadian, Madhav Om
June 21, 2024 (v1)
Keywords: AD, Alzheimer’s, chemical reaction, Gillespie algorithm, stochastic modeling
Alzheimer’s disease has been a serious problem for humankind, one without a promising cure for a long time now, and researchers around the world have been working to better understand this disease mathematically, biologically and computationally so that a better cure can be developed and finally humanity can get some relief from this disease. In this study, we try to understand the progression of Alzheimer’s disease by modeling the progression of amyloid-beta aggregation, leading to the formation of filaments using the stochastic method. In a noble approach, we treat the progression of filaments as a random chemical reaction process and apply the Monte Carlo simulation of the kinetics to simulate the progression of filaments of lengths up to 8. By modeling the progression of disease as a progression of filaments and treating this process as a stochastic process, we aim to understand the inherent randomness and complex spatial−temporal features and the convergence of filament propagatio... [more]
Microbiome Structure of Activated Sludge after Adaptation to Landfill Leachate Treatment in a Lab-Scale Sequencing Batch Reactor
Mihaela Kirilova, Ivaylo Yotinov, Yovana Todorova, Nora Dinova, Stilyana Lincheva, Irina Schneider, Yana Topalova
June 21, 2024 (v1)
Subject: Materials
Keywords: activated sludge adaptation, catechol dioxygenases, landfill leachate, Pseudomonas, sludge disintegration
During adaptation to waters that are rich in xenobiotics, biological systems pass through multiple stages. The first one is related to the restructuring of communities, pronounced destruction of the structure, and multiplication of active biodegradants. The purpose of the present research was to describe the microbiome restructuring that occurs during the adaptation stage in landfill leachate treatment. In a model SBR (sequencing batch reactor), a 21-day purification process of landfill leachate was simulated. Wastewater was fed in increasing concentrations. When undiluted leachate entered, the activated sludge structure disintegrated (Sludge Volume Index—4.6 mL/g). The Chemical Oxygen Demand and ammonium nitrogen concentration remained at high values in the influent (2321.11 mgO2/L and 573.20 mg/L, respectively). A significant amount of free-swimming cells was found, and the number of aerobic heterotrophs and bacteria of the genera Pseudomonas and Acinetobacter increased by up to 125... [more]
Research on AGC Nonlinear Compensation Control for Electro-Hydraulic Servo Pump Control of a Lithium Battery Pole Strip Mill
Kai Wang, Gexin Chen, Cheng Zhang, Keyi Liu, Fei Wang
June 21, 2024 (v1)
Keywords: compensation control, electro-hydraulic servo pump control, fuzzy internal model, nonlinear drive, pole rolling
Electrode roll forming involves rolling a battery electrode into a preset thickness using a hydraulic roll gap thickness automatic control system (hydraulic AGC for short). The pump-controlled AGC is a highly nonlinear servo system, which is a combination of mechanical, hydraulic and electronic control disciplines; thus, as a new technology, it still faces many challenges in the field of pole plate rolling. In this paper, electro-hydraulic servo pump-controlled AGC technology is replaced by electro-hydraulic servo valve-controlled AGC technology. With pump-controlled AGC high-precision thickness control as the research objective, the fuzzy control method is selected to deal with complex nonlinear systems based on pump-controlled AGC nonlinear stiffness characteristics and nonlinear transmission characteristics. A characteristic compensation control strategy is proposed. At the same time, considering the load fluctuation caused by the uneven thickness of the electrode plate under the in... [more]
Optimization of Smart Textiles Robotic Arm Path Planning: A Model-Free Deep Reinforcement Learning Approach with Inverse Kinematics
Di Zhao, Zhenyu Ding, Wenjie Li, Sen Zhao, Yuhong Du
June 21, 2024 (v1)
Keywords: deep reinforcement learning, inverse kinematics, Machine Learning, path planning, robotic arm
In the era of Industry 4.0, optimizing the trajectory of intelligent textile robotic arms within cluttered configuration spaces for enhanced operational safety and efficiency has emerged as a pivotal area of research. Traditional path-planning methodologies predominantly employ inverse kinematics. However, the inherent non-uniqueness of these solutions often leads to varied motion patterns in identical settings, potentially leading to convergence issues and hazardous collisions. A further complication arises from an overemphasis on the tool center point, which can cause algorithms to settle into suboptimal solutions. To address these intricacies, our study introduces an innovative path-planning optimization strategy utilizing a model-free, deep reinforcement learning framework guided by inverse kinematics experience. We developed a deep reinforcement learning algorithm for path planning, amalgamating environmental enhancement strategies with multi-information entropy-based geometric op... [more]
Experimental Assessment of a Decentralized Control Strategy for a Back-to-Back Modular Multilevel Converter Operating in Low-Frequency AC Transmission
Efrain Ibaceta, Matias Diaz, Saravanakumar Rajendran, Yeiner Arias, Roberto Cárdenas, Jose Rodriguez
June 21, 2024 (v1)
Keywords: decoupled control, LFAC, modular multilevel converter
The Modular Multilevel Converter (MMC) has been widely used in high-power applications owing to its inherent advantages, including scalability, modularity, high-power density, and fault tolerance. MMCs have recently been used in Low-Frequency Alternating Current (LFAC) transmission, particularly in the integration of offshore wind power with onshore grids. However, LFAC applications produce significant voltage oscillations in floating capacitor voltages within the MMC. Early research efforts have successfully established and validated decoupled control strategies for LFAC-based MMC systems. However, validations are usually based on simulations or small-scale prototypes equipped with limited power cells. Consequently, this paper presents a decentralized voltage control strategy based on Nearest Level Control for an MMC-based LFAC system. Experimental results obtained with a 120-cell MMC prototype are presented to validate the effectiveness and operation of the MMC in LFAC applications.
Extraction and Microencapsulation of Phytochemical Compounds from Mango Peel (Mangifera indica L.) var. “Kent” and Assessment of Bioaccessibility through In Vitro Digestion
Arantxa Roa-Tort, Ofelia Gabriela Meza-Márquez, Guillermo Osorio-Revilla, Tzayhri Gallardo-Velázquez, Oswaldo Arturo Ramos-Monroy
June 21, 2024 (v1)
Keywords: in vitro gastrointestinal digestion, Mangifera indica L., microencapsulation, phytochemical compounds, spout-fluid bed drying, spray drying
The peel from mango (Mangifera indica L.) var. “Kent” is a good source of bioactive compounds (BC). BC are sensitive to oxygen, temperature, humidity, light, and gastrointestinal digestion, which change their biological function and health benefits. This study was aimed at the extraction of the bioactive compounds present in the peel from mango var. “Kent” and their microencapsulation using spray drying (SD) and spout-fluid bed drying (SFB). The bioaccessibility of BC was also evaluated. Two consecutive extractions of 90 min at 30 °C and 80% v/v ethanol were used. The microcapsules produced via SD and SFB presented high retention and encapsulation percentages of the bioactive compounds; nevertheless, SFB showed better protection during in vitro gastrointestinal digestion. The non-encapsulated extract showed a decrease (p ≤ 0.05) of BC at the end of in vitro gastrointestinal digestion. The results show that these microcapsules might be used in the food industry as an ingredient to produ... [more]
Determining the Level of Structural and Mechanical Degradation of Steel in the Supporting Structure of Mining Excavation Machinery
Sorin Mihai Radu, Florin Vîlceanu, Mihaela Toderas, Alexandra Lihoacă, Stela Dinescu
June 21, 2024 (v1)
Keywords: austenitic grain, degradation, load-bearing structure, specimens, steels
The steels from which the components of mining machinery are constructed must be based primarily on knowledge of their behaviour under environmental conditions and of the excavation technology. Secondly, the structural changes undergone by the materials due to mechanical and thermal processing and the stresses generated by the action of excavation forces that can induce internal stresses at a level that is difficult to determine must be taken into account. Determining the level of structural and mechanical degradation involves sampling the load-bearing structure elements of the excavation and storage machinery for analysis of the mechanical and chemical properties of the component materials. The paper focuses on issues related to the structural and mechanical degradation of steel as a material for parts of mining machinery. In this paper, a methodology for evaluating the degree of structural degradation of three types of bucket wheel excavators with different operating hours (ERc 1400-... [more]
The Effect of Braid Angle on Hydraulic Hose Geometry
Filip Dýrr, Adam Bureček, Lumír Hružík, Tomáš Polášek, Marian Ledvoň, Lukáš Dvořák
June 21, 2024 (v1)
Keywords: braid angle, hose geometry, hydraulic hose, tensile force
Hydraulic hoses are part of most hydraulic systems, from industrial hydraulics with open loop hydraulic systems to mobile hydraulics with closed loop hydraulic systems. The design parameters of hydraulic hoses may influence the duty cycle dynamics of these systems. One of the factors that influence the behavior of a hydraulic hose under pressure loading is the steel braid angle with respect to the hydraulic hose axis. This work aims to determine the effect of the hydraulic hose braid angle on the change in its geometry. The next objective is to determine the forces that occur at the hose ends under pressure loading. The stresses occur when fluid pressure is applied to the inner wall of the hydraulic hose. Consequently, these stresses are transferred to the hose ends through the steel braid or spiral. The phenomenon of the neutral braid angle provides a balance between the stresses generated inside the hydraulic hose. Therefore, hydraulic hose manufacturers try to produce hydraulic hose... [more]
An Emergency Decision-Making Method for Coal Spontaneous Combustion Based on Improved Prospect Theory
Jingwei Zeng, Guoxun Jing, Qifeng Zhu
June 21, 2024 (v1)
Keywords: comprehensive prospect value, emergency response plan, entropy, grey correlation degree, risk preference, spontaneous combustion, TOPSIS
In response to the limited available information during the initial stages of coal spontaneous combustion and the influence of decision makers’ risk preferences on decision-making, this paper proposes an emergency decision-making method for coal spontaneous combustion that integrates grey correlation degree and TOPSIS with an enhanced prospect theory. Firstly, a normalized weighted evaluation matrix is established for the emergency response plan of coal spontaneous combustion, and the entropy method is utilized to determine the weights of various indexes. Then, considering the imperfect rationality of decision makers and their diverse individual risk preferences, they are categorized into three types: risk-seeking type, risk-neutral type, and risk-averse type. The corresponding risk coefficients are determined based on these different types. Positive and negative ideal solutions are taken as reference points, and matrices representing gains and losses are constructed. The grey correlat... [more]
Model and Parameter Study of Limestone Decomposition Reaction
Rongjia Zhu, Liangyu Fu, Qian Liu, Jiaqiang E, Haoyu Zhou
June 21, 2024 (v1)
Keywords: CO2 concentration, decomposition reaction rate, limestone, numerical calculation
To address the problem that there are many limestone particle decomposition reaction models and it is difficult to accurately select the appropriate one, this paper established two typical one-dimensional unsteady numerical calculation models for single-particle limestone decomposition, coupling the convective heat transfer, thermal conduction, and CO2 mass transfer processes. Two numerical calculation models were solved through the Matlab R2021a platform, and the internal temperature, CO2 concentration distribution, and decomposition reaction rate of the limestone particles during the period from the beginning of temperature rise to the end of decomposition were obtained. Compared with the experimental data, Model 1 has a better agreement with a relative error of less than 10%. The simulation results have shown that the average decomposition reaction rate is 20% higher than the average mass transfer rate. As the particle size increases from 20 mm to 80 mm, the time required for temper... [more]
Competitive Effect of Zinc and Cadmium on the Biosorption of Chromium by Orange Waste
Ana Belén Pérez-Marín, Juan Francisco Ortuño, María Isabel Aguilar, Mercedes Lloréns, Víctor Francisco Meseguer
June 21, 2024 (v1)
Subject: Biosystems
Keywords: binary system, competitive biosorption, heavy metals, isotherm models, orange waste
Batch experiments were conducted to test orange waste (OW), an agricultural solid waste byproduct from the orange juice manufacturing industry, as adsorbent for binary solutions of Cd2+-Cr3+ and Zn2+-Cr3+. Fourier transform infrared spectroscopy (FTIR) and the point of zero charge (pHpzc) were used to identify the functional groups on the OW surface involved in biosorption. The biosorption equilibrium data for both binary-metal solutions were obtained and fitted to various isotherm models. The extended Sips and the non-modified Redlich-Peterson isotherm models gave the best fit for the experimental data. According to the extended Sips model, the maximum biosorption capacity of OW was 0.573 mmol·g−1 for Cd2+, 0.453 mmol·g−1 for Zn2+, and 1.96 mmol·g−1 for Cr3+. The sorption capacity dropped to 0.061 mmol·g−1 for Cd2+ and to 0.101 mmol·g1 for Zn2+ in their binary systems with Cr3+ for the higher initial metal concentrations in the solution. However, the maximum sorption capacity of chrom... [more]
A Method for Predicting Ground Pressure in Meihuajing Coal Mine Based on Improved BP Neural Network by Immune Algorithm-Particle Swarm Optimization
Xingping Lai, Yuhang Tu, Baoxu Yan, Longquan Wu, Xiaoming Liu
June 21, 2024 (v1)
Keywords: algorithm optimization, BP, ground pressure prediction, IA-PSO-BP
Based on the background of dynamic mining pressure monitoring and pressure prediction research on the No. 232205 working face of the Meihuajing coal mine, this study systematically investigates the predictive model of mining pressure manifestation on the working face of the Meihuajing coal mine by integrating methods such as engineering investigation, theoretical analysis, and mathematical modeling. A mining pressure manifestation prediction method based on IA-PSO-BP is proposed. The IA-PSO optimization algorithm is applied to optimize the hyperparameters of the BP neural network, and the working face mining pressure prediction model based on IA-PSO-BP is established. The mean absolute error (MAE), mean square error (MSE), and coefficient of determination (R2) are selected as evaluation indicators to compare the prediction performance of the BP model, PSO-BP model, and IA-PSO-BP model. The experimental results of the model show that the convergence speed of the IA-PSO-BP model is about... [more]
Simulation Analysis of the Characteristics of Layered Cores during Pulse Decay Tests
Haobo Chen, Yongqian Liu, Pengda Cheng, Xinguang Zhu, Guofeng Han
June 21, 2024 (v1)
Keywords: layered cores, low permeability, pulse decay testing, simulation analysis
The permeability of low-permeability cores is generally measured using a pulse decay method. The core of low-permeability rocks, such as shale, often has a layered structure. The applicability of pulse decay testing for layered cores is not clear. In this study, the performance of the pulse decay method on layered cores was comprehensively investigated. Numerical simulations were conducted to investigate the influence of the interlayer permeability ratio, storativity ratio, layer thickness, interlayer location, and number of layers on the pulse decay pressure and pressure derivative curves, as well as the permeability obtained from pulse decay testing. The results revealed that the pressure curves of layered cores exhibit distinct differences from those of homogeneous cores if the upstream permeability is larger than the downstream one. The pressure derivative curve shows more inclined or horizontal straight-line segments than in the homogeneous case. The shapes of the pressure and pre... [more]
Optimization of Carbon Sequestration and Carbon Displacement in Fractured Horizontal Wells in Low Permeability Reservoirs
Xiaochen Wang, Peijun Wang, Kang Tang, Peng Dong, Can Cui, Zepeng Yang, Zhenwei Sun
June 21, 2024 (v1)
Subject: Optimization
Keywords: enhanced oil recovery, fractured horizontal well, low-permeability reservoir
The increasing use of fossil fuels has raised concerns about rising greenhouse gas emissions. Carbon capture, utilization, and storage (CCUS) is one of the most important technologies for achieving net zero carbon emissions. In oil reservoirs, fully understanding their geological characteristics, fluid characteristics, and pressure distribution and injecting CO2 in a reasonable scheme, some remaining oil can be recovered to improve oil recovery and even obtain certain economic benefits. In this paper, we investigate the effect of CCUS implementation in low-permeability reservoirs from both technical and economic aspects. First, based on the parameters of a low-permeability reservoir, a numerical simulation model of a reservoir with gas injection in a multi-stage fractured horizontal well at the top of the reservoir and oil recovery in a multi-stage fractured horizontal well at the bottom is established. Next, four cases of continuous CO2 injection, intermittent CO2 injection, CO2 injec... [more]
The Influence of a Manifold Structure on the Measurement Results of a PIV Flowmeter
Huiyu Chen, Yilong Qiu, Hui Wang, Mengjie Gao
June 21, 2024 (v1)
Keywords: flow analysis, flow measurement, Natural Gas, PIV
The application of particle image velocimetry (PIV) technology for monitoring natural gas flow is a new method of flow measurement. Since the principle of this technology was proposed, there are still some potential issues. This article investigates the influence of a manifold structure on the measurement results of a PIV flowmeter. A comparison is performed between concentric and eccentric manifold structures, using a circular straight pipe as reference, in terms of the measurement error of the PIV flowmeter and the internal flow state of the natural gas. The results demonstrate that the manifold structure significantly affects the measurement reliability of the PIV flowmeter, especially the eccentric manifold structure. Under flow conditions ranging from 100 to 600 m3/h, the maximum measurement errors caused by the concentric and eccentric manifold structures are 2.49% and 3.05%, respectively, which show a noticeable increase compared to the maximum measurement error of 2.08% observe... [more]
A Sequential Hybrid Optimization Algorithm (SHOA) to Solve the Hybrid Flow Shop Scheduling Problems to Minimize Carbon Footprint
M. Geetha, R. Chandra Guru Sekar, M. K. Marichelvam, Ömür Tosun
June 21, 2024 (v1)
Keywords: carbon footprint, firefly algorithm (FA), hybrid flow shop, pigeon-inspired optimization algorithm (PIOA), Scheduling
In today’s world, a situational awareness of sustainability is becoming increasingly important. Leaving a better world for future generations is becoming the main interest of many studies. It also puts pressure on managers to change production methods in most industries. Reducing carbon emissions in industry today is crucial to saving our planet. Theoretical research and practical industry requirements diverge, even though numerous researchers have tackled various strategies to handle carbon emission problems. Therefore, this work considers the carbon emission problem of the furniture manufacturing industry in Hosur, Tamilnadu, India. The case study company has a manufacturing system that resembles a hybrid flow shop (HFS) environment. As the HFS scheduling problems are NP-hard in nature, exact solution techniques could not be used to solve the problems. Hence, a sequential hybrid optimization algorithm (SHOA) has been developed in this paper to minimize the carbon footprint. In the SH... [more]
Characterizing Novel Acetogens for Production of C2−C6 Alcohols from Syngas
Rahul Thunuguntla, Hasan K. Atiyeh, Raymond L. Huhnke, Ralph S. Tanner
June 21, 2024 (v1)
Keywords: Butanol, Ethanol, hexanol, novel acetogens, Syngas
Utilizing syngas components CO, CO2, and H2 to produce fatty acids and alcohols offers a sustainable approach for biofuels and chemicals, reducing the global carbon footprint. The development of robust strains, especially for higher alcohol titers in C4 and C6 compounds, and the creation of cost-effective media are crucial. This study compared syngas fermentation capabilities of three novel strains (Clostridium carboxidivorans P20, C. ljungdahlii P14, and C. muellerianum P21) with existing strains (C. ragsdalei P11 and C. carboxidivorans P7) in three medium formulations. Fermentations in 250-mL bottles were conducted at 37 °C using H2:CO2:CO (30:30:40) using P11, P7, and corn steep liquor (CSL) media. Results showed that P11 and CSL media facilitated higher cell mass, alcohol titer, and gas conversion compared to the P7 medium. Strains P7, P14, and P20 formed 1.4- to 4-fold more total alcohols in the CSL medium in comparison with the P7 medium. Further, strain P21 produced more butanol... [more]
Effect of the Curvature Radius on Single-Droplet Dynamic Characteristics within a Concave-Wall Jet
Bin Gong, Aibo Jian, Jing Zhang, Guang Yang, Yifeng Liu
June 21, 2024 (v1)
Subject: Materials
Keywords: concave-wall jet, deformation mechanism, droplet, heterogeneous, interfacial energy
The centrifugal force field in a hydrocyclone was affected by the concave-wall curvature radius R0, and the mechanism underlying droplet deformation was closely related to the mass transfer efficiency. Numerical simulation and experimental data were collected to reveal the deformation characteristics and mechanism of a single droplet crossing concave-wall jet. Normalized interfacial energy γ and stretching performance were provided to investigate the droplet deformation process. The results showed that the droplet was stretched along the streamwise direction and shrank along the spanwise direction in the concave-wall jet. The droplet interfacial energy and deformation were the largest when the droplet crossed the jet boundary at t = 0.20 s. The maximum γ value increased with the increase in R0 by 57.3% to 71.4%, and the distance between the droplet and concave wall increased with R0. The Q-criterion was exported to show the increase in the vortex strength with the decrease in R0 at the... [more]
Assessment of Antioxidant and Antibacterial Potential of Phenolic Extracts from Post-Distillation Solid Residues of Oregano, Rosemary, Sage, Lemon Balm, and Spearmint
Elisavet Bouloumpasi, Magdalini Hatzikamari, Stamatia Christaki, Athina Lazaridou, Paschalina Chatzopoulou, Costas G. Biliaderis, Maria Irakli
June 21, 2024 (v1)
Subject: Biosystems
Keywords: antibacterial effect, antioxidant activity, biological activity, extracts, herbs, solid waste, valorization
Medicinal and aromatic plants (MAPs) are potential sources of natural polyphenols. Solid residues (SRs) from the essential oil (EO) industry are produced in significant volumes and may be used as natural sources of bioactive compounds. Therefore, this work was designed to examine the antioxidant and antibacterial characteristics of phenolic extracts obtained from SRs that have remained after EO distillation. SR extracts of Greek oregano, rosemary, spearmint, lemon balm, and Greek sage were assessed for their total phenolic content (TPC), antioxidant activity, and antimicrobial activity against Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes, Staphylococcus aureus, Bacillus subtilis, Bacillus licheniformis, and Bacillus cereus in the concentration range of 500-3000 mg/L. The rosemary and Greek sage extracts exhibited the strongest antibacterial activities against all the Gram-positive species, while the spearmint and oregano extracts were less effective and only had an... [more]
Simulation Experiment Design and Control Strategy Analysis in Teaching of Hydrogen-Electric Coupling System
Tao Shi, Jialin Sheng, Zhiqiang Chen, Hangyu Zhou
June 21, 2024 (v1)
Keywords: coordinated control, electrolytic hydrogen production, fuel cell, photovoltaic power generation, teaching experiment
Hydrogen energy, as a clean and green energy medium, is characterized by large capacity, extended lifespan, convenient storage, and seamless transmission. On the one hand, in the power system, hydrogen can be prepared by the electrolysis of water using the surplus power from intermittent new energy generation, such as photovoltaic and wind power, to increase the space for new energy consumption. On the other hand, it can be used to generate electricity from the chemical reaction between hydrogen and oxygen through the fuel cell and be used as a backup power source when there is a shortage of power supply. In this paper, based on the teaching practice, the conversion mechanism and coupling relationship between various forms of energy, such as photovoltaic energy, hydrogen energy, and electric energy, were deeply analyzed. Further, a hydrogen-electricity coupling digital simulation experimental system, including photovoltaic power generation, fuel cell, and electrolysis hydrogen system,... [more]
Enhancing Grid-Forming Converters Control in Hybrid AC/DC Microgrids Using Bidirectional Virtual Inertia Support
Abualkasim Bakeer, Andrii Chub, Abderahmane Abid, Sherif A. Zaid, Thamer A. H. Alghamdi, Hossam S. Salama
June 21, 2024 (v1)
Keywords: grid-forming converters, hybrid AC/DC microgrids, virtual inertia control, virtual synchronous machine
This paper presents a new grid-forming strategy for hybrid AC/DC microgrids using bidirectional virtual inertia support designed to address weak grid conditions. The stability of hybrid AC/DC microgrids heavily relies on the AC mains frequency and the DC-link voltage, and deviations in these factors can lead to undesirable outcomes such as load curtailments and power system congestions and blackouts. This paper introduces a unique approach that leverages bidirectional virtual inertia support to enhance the stability and reliability of hybrid AC/DC microgrids under weak grid conditions. The proposed strategy employs virtual inertia as a buffer to mitigate rapid changes in DC-link voltage and AC frequency, thereby enhancing system stability margins. This strategy significantly contributes to a more stable and reliable grid operation by reducing voltage and frequency fluctuations. A standard hybrid AC/DC microgrid configuration is used to implement the bidirectional virtual inertia suppor... [more]
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