Records Added in May 2021
Records added in May 2021
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Showing records 101 to 125 of 160. [First] Page: 1 2 3 4 5 6 7 Last
Transient Process and Micro-mechanism of Hydrofoil Cavitation Collapse
Yuanyuan Zhao, Qiang Fu, Rongsheng Zhu, Guoyu Zhang, Chuan Wang, Xiuli Wang
May 24, 2021 (v1)
Subject: Other
Keywords: cavitation test, collapse, falling bubbles, two-dimensional hydrofoil
Cavitation will cause abnormal flow, causing a series of problems such as vibration, noise, and erosion of solid surfaces. In severe cases, it may even destroy the entire system. Cavitation is a key problem to be solved for hydraulic machinery and underwater robots, and the attack angle is one of the most important factors affecting the cavitation. In order to systematically study the impact of the attack angle on the hydrofoil cavitation, the hydrofoils of NACA 4412 with different attack angles were selected to study the collapse process and hydraulic characteristics such as pressure, velocity, vortex, and turbulent kinetic energy during cavitation. The results showed that when the cavitation number was the same, the process of cavity collapse was greatly affected by the attack angle. The length of the cavity collapse area was positively correlated with the attack angle. As the attack angle increased, the volume of the falling bubbles increased, resulting in a larger pressure peak cau... [more]
Solid-State Compounding for Recycling of Sawdust Waste into Green Packaging Composites
Rula M. Allaf, Mohammad Futian
May 24, 2021 (v1)
Subject: Materials
Keywords: compounding, cryomilling, sawdust, wood plastic composites
The present study explores solid-state cryomilling for the compounding of green composites. Herein, wood plastic composites (WPCs) composed of sawdust (SD) and poly(ε-caprolactone) (PCL) with various compositions were prepared. Two compounding techniques, namely, extrusion and cryomilling, were utilized to prepare WPC raw material pellets and powders, respectively, for comparison purposes. Flat pressing was further utilized to prepare WPC films for testing. Morphological, structural, thermal, mechanical, and surface wettability properties were investigated. Results indicate the advantages of cryomilling in producing WPCs. Scanning electron microscopy (SEM) along with optical micrographs revealed well ground SD particles and uniform distribution in the PCL matrix. Tensile strength and elongation at break of the composites declined with increasing SD content, however, the modulus of elasticity significantly increased. Water contact angles averaged less than 90°, implying partial wetting.... [more]
Non-Intrusive Monitoring Algorithm for Resident Loads with Similar Electrical Characteristic
Sheng Wu, Kwok L. Lo
May 24, 2021 (v1)
Keywords: load identification, modification of monitoring result, non-intrusive load monitoring, signal decomposition
Non-intrusive load monitoring is a vital part of an overall load management scheme. One major disadvantage of existing non-intrusive load monitoring methods is the difficulty to accurately identify loads with similar electrical characteristics. To overcome the various switching probability of loads with similar characteristics in a specific time period, a new non-intrusive load monitoring method is proposed in this paper which will modify monitoring results based on load switching probability distribution curve. Firstly, according to the addition theorem of load working currents, the complex current is decomposed into the independently working current of each load. Secondly, based on the load working current, the initial identification of load is achieved with current frequency domain components, and then the load switching times in each hour is counted due to the initial identified results. Thirdly, a back propagation (BP) neural network is trained by the counted results, the switchin... [more]
Performance Evaluation for a Sustainable Supply Chain Management System in the Automotive Industry Using Artificial Intelligence
Oana Dumitrascu, Manuel Dumitrascu, Dan Dobrotǎ
May 24, 2021 (v1)
Keywords: Artificial Intelligence, data mining, key performance indicator, neural network, performance evaluation, risk management
Increasing the sustainability of a system can be achieved by evaluating the system, identifying the issues and their root cause and solving them. Performance evaluation translates into key performance indicators (KPIs) with a high impact on increasing overall efficacy and efficiency. As the pool of KPIs has increased over time in the context of evaluating the supply chain management (SCM) system’s performance and assessing, communicating and managing its risks, a mathematical model based on neural networks has been developed. The SCM system has been structured into subsystems with the most relevant KPIs for set subsystems and their most important contributions on the increase in the overall SCM system performance and sustainability. As a result of the performed research based on the interview method, the five most relevant KPIs of each SCM subsystem and the most relevant problems are underlined. The main goal of this paper is to develop a performance evaluation model that links specifi... [more]
Au-Pd Bimetallic Nanocatalysts Incorporated into Carbon Nanotubes (CNTs) for Selective Oxidation of Alkenes and Alcohol
Hamed M. Alshammari, Abdullah S. Alshammari, Jamal R. Humaidi, Salma A. Alzahrani, Mosaed S. Alhumaimess, Obaid F. Aldosari, Hassan M. A. Hassan
May 24, 2021 (v1)
Subject: Materials
Keywords: Au-Pd nanocatalysts, carbon nanotubes, oxidation reaction
Although supported bimetallic nanoparticles (Au-Pd NPs) demonstrate outstanding efficiency, challenges appear for carbon supported small and stable bimetallic nanoparticles used in liquid-phase reactions. In this work, Au-Pd NPs were supported on two types of carbon nanotubes: CNTs decorated covalently with carboxylic acid groups (O-CNTs) and non-covalently with the conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer (P-CNTs). The Au-Pd NPs were prepared using the sol immobilization approach on the functionalized CNTs, and the effect of the utilized functionalization method on the properties of the immobilized metallic nanoparticles and the performance of the nanocomposite catalysts was investigated. The fabricated nanocomposites were characterized using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The catalytic performance of Au-Pd/O... [more]
Review of Sulfuric Acid Decomposition Processes for Sulfur-Based Thermochemical Hydrogen Production Cycles
Claudio Corgnale, Maximilian B. Gorensek, William A. Summers
May 17, 2021 (v1)
Keywords: high temperature sulfuric acid decomposition, hydrogen production, reactor concepts, sulfuric acid concentration, sulfuric acid decomposition catalysts, thermochemical processes
Thermochemical processes based on sulfur compounds are among the most developed systems to produce hydrogen through water splitting. Due to their operating conditions, sulfur cycles are suited to be coupled with either nuclear or solar plants for renewable hydrogen production. A critical review of the most promising sulfur cycles, namely the Hybrid Sulfur, the Sulfur Iodine, the Sulfur Bromine and the Sulfur Ammonia processes, is given, including the work being performed for each cycle and discussing their maturity and performance for nuclear and solar applications. Each sulfur-based process is comprised of a sulfuric acid thermal section, where sulfuric acid is concentrated and decomposed to sulfur dioxide, water and oxygen, which is then separated from the other products and extracted. A critical review of the main solutions adopted for the H2SO4 thermal section, including reactor configurations, catalytic formulations, constitutive materials and chemical process configurations, is p... [more]
Optimal Sizing and Techno-Economic Analysis of Hybrid Renewable Energy Systems—A Case Study of a Photovoltaic/Wind/Battery/Diesel System in Fanisau, Northern Nigeria
Nasser Yimen, Theodore Tchotang, Abraham Kanmogne, Idriss Abdelkhalikh Idriss, Bashir Musa, Aliyu Aliyu, Eric C. Okonkwo, Sani Isah Abba, Daniel Tata, Lucien Meva’a, Oumarou Hamandjoda, Mustafa Dagbasi
May 17, 2021 (v1)
Keywords: break-even grid extension distance, Genetic Algorithm, greenhouse gas emissions analysis, hybrid renewable energy systems, Modelling, net present value, Nigeria, replacement project, rural electrification, simple payback period, simulation and optimization, sub-Saharan Africa, Technoeconomic Analysis
Hybrid Renewable Energy Systems (HRESs) have been touted as an appropriate way for supplying electricity to remote and off-grid areas in developing countries, especially in sub-Saharan Africa (SSA), where rural electrification challenges are the most pronounced. This study proposes a two-step methodology for optimizing and analyzing a stand-alone photovoltaic/wind/battery/diesel hybrid system to meet the electricity needs of Fanisua, an off-grid and remote village of northern Nigeria. In the first step, the MATLAB environment was used to run simulations and optimize the system via the genetic algorithm. Then, techno-economic and emissions analysis was carried out in the second step to compare the proposed system to the existing traditional modes of rural electrification in sub-Saharan Africa, namely, the grid-extension and diesel generator. The break-even distance parameter was adopted in the comparison with grid-extension. Besides, the hypothetical project of replacing the diesel gene... [more]
Non-Alcoholic and Craft Beer Production and Challenges
Liana Claudia Salanță, Teodora Emilia Coldea, Maria Valentina Ignat, Carmen Rodica Pop, Maria Tofană, Elena Mudura, Andrei Borșa, Antonella Pasqualone, Haifeng Zhao
May 17, 2021 (v1)
Keywords: brewing, craft beer, dealcoholization, flavour, non-alcoholic beer
Beer is the most consumed alcoholic beverage in the world and the third most popular beverage after water and tea. Emerging health-oriented lifestyle trends, demographics, stricter legislation, religious prohibitions, and consumers’ preferences have led to a strong and steady growth of interest for non-alcoholic beers (NABs), low-alcohol beers (LABs), as well for craft beers (CBs). Conventional beer, as the worlds most consumed alcoholic beverage, recently gained more recognition also due to its potential functionality associated with the high content of phenolic antioxidants and low ethanol content. The increasing attention of consumers to health-issues linked to alcohol abuse urges breweries to expand the assortment of conventional beers through novel drinks concepts. The production of these beers employs several techniques that vary in performance, efficiency, and usability. Involved production technologies have been reviewed and evaluated in this paper in terms of efficiency and pr... [more]
Effect of Drying and Steeping Temperatures on the Phenolic Content, Antioxidant Activity, Aromatic Compounds and Sensory Properties of Cunila polyantha Benth. Infusions
Karla Araceli Silva-Ramírez, Dioselina Álvarez-Bernal, Ernesto Oregel-Zamudio, Cecilia Guízar-González, José Roberto Medina-Medrano
May 17, 2021 (v1)
Keywords: Cunila polyantha, green tea, high-performance liquid chromatography, response surface methodology, sensory evaluation, volatile organic compounds
Cunila polyantha Benth. (Lamiaceae), an aromatic plant endemic to Mexico, is used in traditional medicine as tea infusions. In this study, the effects of different drying and steeping temperatures on the phenolic content and composition, antioxidant activity, volatile composition, and sensory properties of C. polyantha infusions were determined. Commercial green tea (Camellia sinensis L. Kuntze) was used as a control. The phenolic compounds identified in the C. polyantha infusions by high-performance liquid chromatography (HPLC) include phenolic acids such as gallic acid, chlorogenic acid, caffeic acid, and p-coumaric acid, flavonoids such as epigallocatechin gallate, protocatechin, quercetin, and naringenin, as well as the phenolic aldehyde vanillin. The C. polyantha infusions showed scavenging activity of DPPH• and ABTS•+ radicals as well as relevant antioxidant capacity, which was dependent on tea preparation conditions. A total of 46 volatile organic compounds (VOCs) were detected... [more]
Mixing in Turbulent Flows: An Overview of Physics and Modelling
Jacek Pozorski, Marta Wacławczyk
May 17, 2021 (v1)
Keywords: FDF method, large eddy Simulations, Mixing, PDF method, Reynolds-averaged Navier–Stokes, scalar variables, turbulence
Turbulent flows featuring additional scalar fields, such as chemical species or temperature, are common in environmental and industrial applications. Their physics is complex because of a broad range of scales involved; hence, efficient computational approaches remain a challenge. In this paper, we present an overview of such flows (with no particular emphasis on combustion, however) and we recall the major types of micro-mixing models developed within the statistical approaches to turbulence (the probability density function approach) as well as in the large-eddy simulation context (the filtered density function). We also report on some trends in algorithm development with respect to the recent progress in computing technology.
Sequential Photodamage Driven by Chaotic Systems in NiO Thin Films and Fluorescent Human Cells
Hilario Martines-Arano, Mónica Araceli Vidales-Hurtado, Samara Palacios-Barreto, Martín Trejo-Valdez, Blanca Estela García-Pérez, Carlos Torres-Torres
May 17, 2021 (v1)
Subject: Biosystems
Keywords: human cells, laser ablation, NiO, optical Kerr effect, photodamage, semiconductor processing, thin films, two-wave mixing
A laser ablation process assisted by the feedback of a sensor with chaotic electronic modulation is reported. A synchronous bistable logic circuit was analyzed for switching optical signals in a laser-processing technique. The output of a T-type flip-flop configuration was employed in the photodamage of NiO films. Multiphotonic effects involved in the ablation threshold were evaluated by a vectorial two-wave mixing method. A photoinduced thermal phenomenon was identified as the main physical mechanism responsible for the nonlinearity of index under nanosecond irradiation at 532 nm wavelength. Comparative experiments for destroying highly transparent human cells were carried out. Potential applications for developing hierarchical functions yielding laser-induced controlled explosions with immediate applications for biomedical photothermal processes can be contemplated.
A Review of Zein as a Potential Biopolymer for Tissue Engineering and Nanotechnological Applications
Carlos Joaquín Pérez-Guzmán, Roberto Castro-Muñoz
May 17, 2021 (v1)
Subject: Biosystems
Keywords: biopolymer, nanotechnology, scaffold, tissue engineering, zein
Tissue engineering (TE) is one of the most challenging fields of research since it provides current alternative protocols and materials for the regeneration of damaged tissue. The success of TE has been mainly related to the right selection of nano-sized biocompatible materials for the development of matrixes, which can display excellent anatomical structure, functionality, mechanical properties, and histocompatibility. Today, the research community has paid particular attention to zein as a potential biomaterial for TE applications and nanotechnological approaches. Considering the properties of zein and the advances in the field, there is a need to reviewing the current state of the art of using this natural origin material for TE and nanotechnological applications. Therefore, the goal of this review paper is to elucidate the latest (over the last five years) applications and development works in the field, including TE, encapsulations of drugs, food, pesticides and bandaging for exte... [more]
Gasification Applicability of Korean Municipal Waste Derived Solid Fuel: A Comparative Study
Sang Yeop Lee, Md Tanvir Alam, Gun Ho Han, Dong Hyuk Choi, Se Won Park
May 17, 2021 (v1)
Keywords: Biomass, Coal, gasification, municipal solid waste, solid recovered fuel, Syngas
Gaining energy independence by utilizing new and renewable energy resources has become imperative for Korea. Energy recovery from Korean municipal solid waste (MSW) could be a promising option to resolve the issue, as Korean MSW is highly recyclable due to its systematic separation, collection and volume-based waste disposal system. In this study, gasification experiments were conducted on Korean municipal waste-derived solid fuel (SRF) using a fixed bed reactor by varying the equivalence ratio (ER) to assess the viability of syngas production. Experiments were also conducted on coal and biomass under similar conditions to compare the experimental results, as the gasification applicability of coal and biomass are long-established. Experimental results showed that Korean SRF could be used to recover energy in form of syngas. In particular, 50.94% cold gas efficiency and 54.66% carbon conversion ratio with a lower heating value of 12.57 MJ/Nm3 can be achieved by gasifying the SRF at 0.4... [more]
Determination of Dissolved CO2 Concentration in Culture Media: Evaluation of pH Value and Mathematical Data
Amir Izzuddin Adnan, Mei Yin Ong, Saifuddin Nomanbhay, Pau Loke Show
May 17, 2021 (v1)
Subject: Biosystems
Keywords: Carbon Dioxide, culture media, microorganism, Optimization
Carbon dioxide is the most influential gas in greenhouse gasses and its amount in the atmosphere reached 412 µmol/mol in August 2020, which increased rapidly, by 48%, from preindustrial levels. A brand-new chemical industry, namely organic chemistry and catalysis science, must be developed with carbon dioxide (CO2) as the source of carbon. Nowadays, many techniques are available for controlling and removing carbon dioxide in different chemical processes. Since the utilization of CO2 as feedstock for a chemical commodity is of relevance today, this study will focus on how to increase CO2 solubility in culture media used for growing microbes. In this work, the CO2 solubility in a different medium was investigated. Sodium hydroxide (NaOH) and monoethanolamine (MEA) were added to the culture media (3.0 g/L dipotassium phosphate (K2HPO4), 0.2 g/L magnesium chloride (MgCl2), 0.2 g/L calcium chloride (CaCl2), and 1.0 g/L sodium chloride (NaCl)) for growing microbes in order to observe the dif... [more]
Review of Artificial Intelligence Applied in Decision-Making Processes in Agricultural Public Policy
Juan M. Sánchez, Juan P. Rodríguez, Helbert E. Espitia
May 17, 2021 (v1)
Keywords: agriculture, Artificial Intelligence, decision making, policy formulation, public policy
The objective of this article is to review how Artificial Intelligence (AI) tools have helped the process of formulating agricultural public policies in the world. For this, a search process was carried out in the main scientific repositories finding different publications. The findings have shown that, first, the most commonly used AI tools are agent-based models, cellular automata, and genetic algorithms. Secondly, they have been utilized to determine land and water use, and agricultural production. In the end, the large usefulness that AI tools have in the process of formulating agricultural public policies is concluded.
A Study on the Tribological Performance of Nanolubricants
Yeoh Jun Jie Jason, Heoy Geok How, Yew Heng Teoh, Hun Guan Chuah
May 17, 2021 (v1)
Subject: Materials
Keywords: dispersion stability, lubrication mechanism, nanolubricants, nanoparticles, tribological performance
In recent years, the tribology field has expanded with the advent of nanolubrication. Nanolubricants are the name given to the dispersion of nanoparticles in a base oil, and has attracted researchers due to its potential application. In addition to being used in the tribology field, nanoparticles are also used for medical, space, and composites purposes. The addition of nanoparticles in base oils is promising because it enhances specific tribological characteristics including wear-resistance and friction, and the most important reason is that the majority of them are environmentally friendly. This paper reviews the tribological effect of various nanoparticles as lubricant additives. Parameters of nanoparticles that affect tribological performance, the technique to enhance stability, and lubrication mechanism that is currently believed to function will be delineated in detail. Moreover, this review facilitates an understanding of the role of various nanoparticles, which helps in develop... [more]
Effect of Barium Addition on Hydrolytic Enzymatic Activities in Food Waste Degradation under Anaerobic Conditions
Fuad Ale, Roberto Castro-Muñoz, Blanca Estela Barragán-Huerta, Odín Rodríguez-Nava
May 17, 2021 (v1)
Keywords: amylases, anaerobic digestion, cellulases, enzymatic hydrolysis, food waste
Enzymatic hydrolysis of complex components of residual materials, such as food waste, is a rate-limiting step that conditionates the production rate of biofuels. Research into the anaerobic degradation of cellulose and starch, which are abundant components in organic waste, could contribute to optimize biofuels production processes. In this work, a lab-scale anaerobic semi-continuous hydrolytic reactor was operated for 171 days using food waste as feedstock; the effect of Ba2+ dosage over the activity of five hydrolytic enzymes was also evaluated. No significant effects were observed on the global performance of the hydrolytic process during the steady-state of the operation of the reactor, nevertheless, it was detected that Ba2+ promoted β-amylases activity by 76%, inhibited endoglucanases and α-amylases activity by 39 and 20%, respectively, and had no effect on β-glucosidases and glucoamylases activity. The mechanisms that rule the observed enzymatic activity changes remain unknown;... [more]
Analysis of Soot Deposition Mechanisms on Nickel-Based Anodes of SOFCs in Single-Cell and Stack Environment
Konrad Motylinski, Marcin Blesznowski, Marek Skrzypkiewicz, Michal Wierzbicki, Agnieszka Zurawska, Arkadiusz Baran, Maciej Bakala, Jakub Kupecki
May 17, 2021 (v1)
Keywords: Boudouard reaction, carbon deposition, SOFC
Solid oxide fuel cells (SOFCs) can be fueled with various gases, including carbon-containing compounds. High operating temperatures, exceeding 600 °C, and the presence of a porous, nickel-based SOFC anode, might lead to the formation of solid carbon particles from fuels such as carbon monoxide and other gases with hydrocarbon-based compounds. Carbon deposition on fuel electrode surfaces can cause irreversible damage to the cell, eventually destroying the electrode. Soot formation mechanisms are strictly related to electrochemical, kinetic, and thermodynamic conditions. In the current study, the effects of carbon deposition on the lifetime and performance of SOFCs were analyzed in-operando, both in single-cell and stack conditions. It was observed that anodic gas velocity has an impact on soot formation and deposition, thus it was also studied in depth. Single-anode-supported solid oxide fuel cells were fueled with gases delivered in such a way that the initial velocities in the anodic... [more]
Prediction of the Solubility of CO2 in Imidazolium Ionic Liquids Based on Selective Ensemble Modeling Method
Luyue Xia, Shanshan Liu, Haitian Pan
May 17, 2021 (v1)
Keywords: Carbon Dioxide, fuzzy C–means, ionic liquids, Modelling, prediction, selective ensemble, solubility
Solubility data is one of the essential basic data for CO2 capture by ionic liquids. A selective ensemble modeling method, proposed to overcome the shortcomings of current methods, was developed and applied to the prediction of the solubility of CO2 in imidazolium ionic liquids. Firstly, multiple different sub−models were established based on the diversities of data, structural, and parameter design philosophy. Secondly, the fuzzy C−means algorithm was used to cluster the sub−models, and the collinearity detection method was adopted to eliminate the sub−models with high collinearity. Finally, the information entropy method integrated the sub−models into the selective ensemble model. The validation of the CO2 solubility predictions against experimental data showed that the proposed ensemble model had better performance than its previous alternative, because more effective information was extracted from different angles, and the diversity and accuracy among the sub−models were fully inte... [more]
Carbon Emission Reduction Potential in the Finnish Energy System Due to Power and Heat Sector Coupling with Different Renovation Scenarios of Housing Stock
Ilkka Jokinen, Arslan Ahmad Bashir, Janne Hirvonen, Juha Jokisalo, Risto Kosonen, Matti Lehtonen
May 17, 2021 (v1)
Subject: Energy Policy
Keywords: borehole heat exchanger, emission reduction, Optimization, power-to-heat, residential building renovation, sector coupling, wind power
In the pursuit of mitigating the effects of climate change the European Union and the government of Finland have set targets for emission reductions for the near future. This study examined the carbon emission reduction potential in the Finnish energy system with power-to-heat (P2H) coupling of the electricity and heat sectors with different housing renovation levels. The measures conducted in the energy system were conducted as follows. Wind power generation was increased in the Finnish power system with 10 increments. For each of these, the operation of hydropower was optimized to maximize the utilization of new wind generation. The excess wind generation was used to replace electricity and heat from combined heat and power production for district heating. The P2H conversion was performed by either 2000 m deep borehole heat exchangers coupled to heat pumps, with possible priming of heat, or with electrode boilers. The housing stock renovated to different levels affected both the elec... [more]
Influences of Ash-Existing Environments and Coal Structures on CO2 Gasification Characteristics of Tri-High Coal
Lang Liu, Qingrui Jiao, Jian Yang, Bowen Kong, Shan Ren, Qingcai Liu
May 17, 2021 (v1)
Keywords: ash-free coal, CO2 gasification, coal structure, tri-high coal
Two kinds of tri-high coals were selected to determine the influences of ash-existing environments and coal structures on CO2 gasification characteristics. The TGA results showed that the gasification of ash-free coal (AFC) chars was more efficient than that of corresponding raw coal (RC) chars. To uncover the reasons, the structures of RCs and AFCs, and their char samples prepared at elevated temperatures were investigated with SEM, BET, XRD, Raman and FTIR. The BET, SEM and XRD results showed that the Ash/mineral matter is associated with coal, carbon forms the main structural framework and mineral matters are found embedded in the coal structure in the low-rank tri-high coal. The Raman and FTIR results show that the ash can hinder volatile matters from exposing to the coal particles. Those results indicate that the surface of AFC chars has more free active carbon sites than raw coal chars, which are favorable for mass transfer between C and CO2, thereby improving reactivity of the A... [more]
Characterisation of Bioactive Ingredients in Extracts of Fresh and Dried Coniferous Trees for the Development of Sustainable Packaging Materials
Thomas Havelt, Jan Niklas Frase, Ralf Pude, Michaela Schmitz
May 17, 2021 (v1)
Keywords: Abies nordmanniana, Abies procera, additive, antioxidant, coniferous woods, Extraction, Picea abies, Picea pungens, stabiliser, total phenolic content, UV
Background: Coniferous woods (Abies nordmanniana (Stev.) Spach, Abies procera Rehd, Picea abies (L.) H.Karst, and Picea pungens Engelm.) could contain useful secondary metabolites to produce sustainable packaging materials, e.g., by substitution of harmful petrol-based additives in plastic packaging. This study aims to characterise the antioxidant and light-absorbing properties and ingredients of different coniferous wood extracts with regard to different plant fragments and drying conditions. Furthermore, the valorisation of used Christmas trees is evaluated. Methods: Different drying and extraction techniques were applied with the extracts being characterised by determining the total phenolic content (TPC), total antioxidant capacity (TAC), and absorbance in the ultraviolet range (UV). Gas chromatography coupled with mass spectrometry (GC-MS) and an acid−butanol assay (ABA) were used to characterise the extract constituents. Results: All the extracts show a considerably high UV absor... [more]
A Reference-Model-Based Neural Network Control Method for Multi-Input Multi-Output Temperature Control System
Yuan Liu, Song Xu, Seiji Hashimoto, Takahiro Kawaguchi
May 17, 2021 (v1)
Keywords: multi-input multi-output temperature system, neural network control, temperature uniformity, transient response
Neural networks (NNs), which have excellent ability of self-learning and parameter adjusting, has been widely applied to solve highly nonlinear control problems in industrial processes. This paper presents a reference-model-based neural network control method for multi-input multi-output (MIMO) temperature system. In order to improve the learning efficiency of the NN control, a reference model is introduced to provide the teaching signal for the NN controller. The control inputs for the MIMO system are given by the sum of the output of the conventional integral-proportional-derivative (I-PD) controller and the outputs of the neural network controller. The proposed NN control method can not only improve the transient response of the system, but can also realize temperature uniformity in MIMO temperature systems. To verify the proposed method, simulations are carried out in MATLAB/SIMULINK environment and experiments are carried out on the DSP (Digital Signal Processor)-based experimenta... [more]
Aerodynamic Performance of an Octorotor SUAV with Different Rotor Spacing in Hover
Yao Lei, Yuhui Huang, Hengda Wang
May 17, 2021 (v1)
Keywords: aerodynamic performance, Computational Fluid Dynamics, hover, octorotor SUAV, rotor spacing, vortices distribution
To study the aerodynamic performance of hovering octorotor small unmanned aerial vehicles (SUAV) with different rotor spacing, the computational fluid dynamics (CFD) method is applied to analyze the flow field of an octorotor SUAV in detail. In addition, an experimental platform is built to measure the thrust and power of the rotors with rotor spacing ratios L/D of 1.0, 1.2, 1.4, 1.6, and 1.8, sequentially. According to the theory of momentum, rotor aerodynamic performance is obtained with qualitative analysis. Further analysis with numerical simulation is presented with the flow field of the octorotor SUAV, the vorticity distribution, velocity distribution, pressure distribution, and streamline. The results show that the aerodynamic performance varies with the rotor spacing. Specifically, the aerodynamic performance is poor at L/D = 1.0, which is accompanied with strong interaction of wake and tip vortexes and interaction with each other. However, the aerodynamic efficiency is much im... [more]
Fitness Landscape Analysis and Edge Weighting-Based Optimization of Vehicle Routing Problems
László Kovács, Anita Agárdi, Tamás Bányai
May 17, 2021 (v1)
Subject: Optimization
Keywords: fitness landscape, Optimization, traveling salesman problem, vehicle routing problem
Vehicle routing problem (VRP) is a highly investigated discrete optimization problem. The first paper was published in 1959, and later, many vehicle routing problem variants appeared to simulate real logistical systems. Since vehicle routing problem is an NP-difficult task, the problem can be solved by approximation algorithms. Metaheuristics give a “good” result within an “acceptable” time. When developing a new metaheuristic algorithm, researchers usually use only their intuition and test results to verify the efficiency of the algorithm, comparing it to the efficiency of other algorithms. However, it may also be necessary to analyze the search operators of the algorithms for deeper investigation. The fitness landscape is a tool for that purpose, describing the possible states of the search space, the neighborhood operator, and the fitness function. The goal of fitness landscape analysis is to measure the complexity and efficiency of the applicable operators. The paper aims to invest... [more]
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