bluuebunny/crossref_metadata_2025 huggingface dataset:
One Pot Synthesis, Surface and Magnetic Properties of Cu2O/Cu and Cu2O/CuO Nanocomposites
Authors: Al-Saeedi Sameerah I. , Al-Senani Ghadah M. , Abd-Elkader Omar H. , Deraz Nasrallah M.
Published: June 2021

A series of copper-based systems containing two different nanocomposites (Cu2O/CuO and Cu2O/Cu) was synthesized by the egg white assisted auto-combustion route. This method was distinguished by the simplicity of its steps, low cost, one-pot synthesis process at low temperature and, short time. The characterization of the as prepared nanocomposites was carried out by using X-ray diffraction (XRD), Fourier-transform infrared (FTIR), Scanning electron microscope (SEM) and transmission electron micrograph (TEM), Energy dispersive spectrometry (EDS) techniques. Surface and magnetic properties of the obtained systems were determined by using N2 adsorption/desorption isotherms at 77 K and the vibrating sample magnetometer (VSM) technique. XRD results confirmed the formation of Cu2O/CuO and Cu2O/Cu nanocomposites with different ratios of well crystalline CuO, Cu2O, and Cu phases. FTIR results of the combusted product displays the presence of both CuO and Cu2O, respectively. SEM/EDS and TEM results confirm the formation of a porous nanocomposite containing Cu, O, and C elements. The change in concentration of the oxygen vacancies at the surface or interface of both Cu2O/CuO and Cu2O/Cu nanoparticles resulted in different changes in their magnetization. Based on this study, it is possible to obtain nanocomposite-based copper with multiple valances by a simple and inexpensive route which can be suitable for the fabrication of different transition metal composites.
Effects of Curing Conditions and Supplementary Cementitious Materials on Autogenous Self-Healing of Early Age Cracks in Cement Mortar
Authors: Luo Mian , Jing Kang , Bai Jingquan , Ding Ziqi , Yang Dingyi , Huang Haoliang , Gong Yongfan
Published: June 2021

The autogenous healing potential of cement-based materials is affected by multiple factors, such as mix composition, crack width, pre-cracking age and external environmental conditions. In this study, the effects of curing conditions and supplementary cementitious materials (SCMs) on autogenous self-healing of early age cracks in cement mortar were investigated. Three curing conditions, i.e., standard curing, wet–dry cycles and incubated in water, and two SCMs, i.e., fly ash (FA) and blast furnace slag (BFS) with various contents (cement replacement ratio at 0%, 20%, and 40%) were examined. A single early age crack (pre-cracking age of 3 days) with a width of 200~300 μm was generated in cylindrical mortar specimens. Autogenous crack self-healing efficiency of mortar specimens was evaluated by performing a visual observation and a water permeability test. Moreover, microstructure analysis (XRD, SEM and TG/DTG) was utilized to characterize the healing products. The results indicated that the presence of water was essential for the autogenous self-healing of early age cracks in cement mortar. The efficiency of self-healing cracks was highest in specimens incubated in water. However, no significant self-healing occurred in specimens exposed to standard curing. For wet–dry cycles, a longer healing time was needed to obtain good self-healing compared to samples incubated in water. SCMs type and content significantly affected the autogenous self-healing ability of early age cracks. The self-healing efficiency of early age cracks decreased with increases in FA and BFS content. BFS mortars exhibited greater recovery in relation to water penetration resistance compared to the reference and FA mortars. Almost the same regain of water tightness and a lower crack-healing ratio after healing of 28 days in FA mortars were observed compared to the reference. The major healing product in the surface cracks of specimens with and without SCMs was micron-sized calcite crystals with a typical rhombohedral morphology.
Investigations of LiNb1−xTaxO3 Nanopowders Obtained with Mechanochemical Method
Authors: Vasylechko Leonid , Sydorchuk Volodymyr , Lakhnik Andrey , Suhak Yuriy , Wlodarczyk Damian , Hurskyy Stepan , Yakhnevych Uliana , Zhydachevskyy Yaroslav , Sugak Dmytro , Syvorotka Ihor I. , Solskii Ivan , Buryy Oleh , Suchocki Andrzej , Fritze Holger
Published: June 2021

Nanocrystalline compounds LiNb1−xTaxO3 of various compositions (x = 0, 0.25, 0.5, 0.75, 1) were synthesized by high-energy ball milling of the initial materials (Li2CO3, Nb2O5, Ta2O5) and subsequent high-temperature annealing of the resulting powders. Data on the phase composition of the nanopowders were obtained by X-ray diffraction methods, and the dependence of the structural parameters of LiNb1−xTaxO3 compounds on the value of x was established. As a result of the experiments, the optimal parameters of the milling and annealing runs were determined, which made it possible to obtain single-phase compounds. The Raman scattering spectra of LiNb1−xTaxO3 compounds (x = 0, 0.25, 0.5, 0.75, 1) have been investigated. Preliminary experiments have been carried out to study the temperature dependences of their electrical conductivity.
Determination of New IR and UV/VIS Spectroscopic Parameters of the C84-D2:22 Isomer for Its Quantitative Assessment, Identification and Possible Applications
Authors: Jovanović Tamara
Published: June 2021

The stable isomers of the higher fullerenes C76-D2 and C84-D2:22, as well as fullerenes C60 and C70 were isolated from carbon soot by the new and improved extraction and chromatographic methods and processes. Characterizations of the C84-D2:22 isomer in this study were performed by infrared and electronic absorption spectroscopy. All of the experimentally observed IR and UV/VIS bands were in excellent agreement with the semi-empirical, DFT and TB potential theoretical calculations for this molecule. The molar extinction coefficients and the integrated molar extinction coefficients of the observed larger number of completely separated infrared absorption maxima and shoulders of fullerene C84-D2:22, as well as of its main convoluted maxima, in different and new relevant entire integration ranges, including neighboring, and all surrounding absorption shoulders were determined and their relative intensities compared. In addition, the molar absorptivity of the electronic absorption bands of this carbon cluster was found. The new IR and UV/VIS spectroscopic parameters that are significant for the quantitative determination, identification and numerous possible applications of C84-D2:22 are obtained and their changes compared to C76-D2 observed. Isolated and characterized C84-D2:22, as well as other fullerenes from this research can be used in electronic, optical, chemical and biomedical devices, superconductors, semiconductors, batteries, catalysts, polymers, sensors, solar cells, nanophotonic lenses with better optical transmission, refraction and wettability, diagnostic and therapeutic pharmaceutical substances, such as those against diabetes, cancer, neurodegenerative disorders, free radical scavenging, radio nuclear, antibacterial and antiviral agents that can inhibit HIV 1, HSV, COVID-19, influenza, malaria and so forth.
Screening Severe Obstructive Sleep Apnea in Children with Snoring
Authors: Hsieh Hui-Shan , Kang Chung-Jan , Chuang Hai-Hua , Zhuo Ming-Ying , Lee Guo-She , Huang Yu-Shu , Chuang Li-Pang , Kuo Terry B.-J. , Yang Cheryl C.-H. , Lee Li-Ang , Li Hsueh-Yu
Published: June 2021

Efficient screening for severe obstructive sleep apnea (OSA) is important for children with snoring before time-consuming standard polysomnography. This retrospective cross-sectional study aimed to compare clinical variables, home snoring sound analysis, and home sleep pulse oximetry on their predictive performance in screening severe OSA among children who habitually snored. Study 1 included 9 (23%) girls and 30 (77%) boys (median age of 9 years). Using univariate logistic regression models, 3% oxygen desaturation index (ODI3) ≥ 6.0 events/h, adenoidal-nasopharyngeal ratio (ANR) ≥ 0.78, tonsil size = 4, and snoring sound energy of 801–1000 Hz ≥ 22.0 dB significantly predicted severe OSA in descending order of odds ratio. Multivariate analysis showed that ODI3 ≥ 6.0 events/h independently predicted severe pediatric OSA. Among several predictive models, the combination of ODI3, tonsil size, and ANR more optimally screened for severe OSA with a sensitivity of 91% and a specificity of 94%. In Study 2 (27 (27%) girls and 73 (73%) boys; median age, 7 years), this model was externally validated to predict severe OSA with an accuracy of 76%. Our results suggested that home sleep pulse oximetry, combined with ANR, can screen for severe OSA more optimally than ANR and tonsil size among children with snoring.
Cytogenetic and Biochemical Genetic Techniques for Personalized Drug Therapy in Europe
Authors: Huebner Tatjana , Scholl Catharina , Steffens Michael
Published: June 2021

For many authorized drugs, accumulating scientific evidence supports testing for predictive biomarkers to apply personalized therapy and support preventive measures regarding adverse drug reactions and treatment failure. Here, we review cytogenetic and biochemical genetic testing methods that are available to guide therapy with drugs centrally approved in the European Union (EU). We identified several methods and combinations of techniques registered in the Genetic Testing Registry (GTR), which can be used to guide therapy with drugs for which pharmacogenomic-related information is provided in the European public assessment reports. Although this registry provides information on genetic tests offered worldwide, we identified limitations regarding standard techniques applied in clinical practice and the information on test validity rarely provided in the according sections.
Parenchymal Extinction Mimicking Hepatocellular Carcinoma in a Patient with Chronic Hepatitis B-Related Liver Cirrhosis
Authors: Kang Min Kyu , Choi Joon Hyuk
Published: June 2021

Parenchymal extinction is characterized by the irreversible loss of hepatocytes and their eventual replacement by fibrous tissue, along with the alteration of the sinusoidal architecture and the obstruction of the small portal and hepatic veins. In clinical practice, radiologic modalities are not sufficient for differentiating between parenchymal extinction and hepatocellular carcinoma in patients with advanced fibrosis or cirrhosis. Herein, we present a case of parenchymal extinction mimicking hepatocellular carcinoma in a patient with chronic hepatitis B-related liver cirrhosis.
Multi-Level Stakeholder Perspectives on Determinants of Point of Care Ultrasound Implementation in a US Academic Medical Center
Authors: Maw Anna M. , Morris Megan A. , Barnard Juliana G. , Wilson Juliana , Glasgow Russell E. , Huebschmann Amy G. , Soni Nilam J. , Fleshner Michelle , Kaufman John , Ho P. Michael
Published: June 2021

There is growing interest from multiple specialties, including internal medicine, to incorporate diagnostic point of care ultrasound (POCUS) into standard clinical care. However, few internists currently use POCUS. The objective of this study was to understand the current determinants of POCUS adoption at both the health system and clinician level at a U.S. academic medical center from the perspective of multi-level stakeholders. We performed semi-structured interviews of multi-level stakeholders including hospitalists, subspecialists, and hospital leaders at an academic medical center in the U.S. Questions regarding the determinants of POCUS adoption were asked of study participants. Using the framework method, team-based analysis of interview transcripts were guided by the contextual domains of the Practical Robust Implementation and Sustainability Model (PRISM). Thirty-one stakeholders with diverse roles in POCUS adoption were interviewed. Analysis of interviews revealed three overarching themes that stakeholders considered important to adoption by clinicians and health systems: clinical impact, efficiency and cost. Subthemes included two that were deemed essential to high-fidelity implementation: the development of credentialing policies and robust quality assurance processes. These findings identify potential determinants of system and clinician level adoption that may be leveraged to achieve high-fidelity implementation of POCUS applications that result in improved patient outcomes.
Recent Advances in Salivary Scintigraphic Evaluation of Salivary Gland Function
Authors: Chen Yen-Chun , Chen Hsin-Yung , Hsu Chung-Huei
Published: June 2021

Saliva plays an important role in supporting upper gastrointestinal tract function and oral well-being. Salivary dysfunction mainly manifests with a decrease in salivary flow. Among varieties of quantitative methods, salivary scintigraphy is a relatively noninvasive, well-tolerated, reproducible, and objective approach for functional evaluation of salivary disorders, yet the lack of precise quantitative reference values and no standardized protocol limit its generalized utilization. In this article, we review the scintigraphic performance between the visual analysis and quantitative methods in predicting Sjögren’s syndrome and verify the potential aspects of the application in interpreting different disease entities and phases of functional salivary disorders.
Accuracy of New Deep Learning Model-Based Segmentation and Key-Point Multi-Detection Method for Ultrasonographic Developmental Dysplasia of the Hip (DDH) Screening
Authors: Lee Si-Wook , Ye Hee-Uk , Lee Kyung-Jae , Jang Woo-Young , Lee Jong-Ha , Hwang Seok-Min , Heo Yu-Ran
Published: June 2021

Hip joint ultrasonographic (US) imaging is the golden standard for developmental dysplasia of the hip (DDH) screening. However, the effectiveness of this technique is subject to interoperator and intraobserver variability. Thus, a multi-detection deep learning artificial intelligence (AI)-based computer-aided diagnosis (CAD) system was developed and evaluated. The deep learning model used a two-stage training process to segment the four key anatomical structures and extract their respective key points. In addition, the check angle of the ilium body balancing level was set to evaluate the system’s cognitive ability. Hence, only images with visible key anatomical points and a check angle within ±5° were used in the analysis. Of the original 921 images, 320 (34.7%) were deemed appropriate for screening by both the system and human observer. Moderate agreement (80.9%) was seen in the check angles of the appropriate group (Cohen’s κ = 0.525). Similarly, there was excellent agreement in the intraclass correlation coefficient (ICC) value between the measurers of the alpha angle (ICC = 0.764) and a good agreement in beta angle (ICC = 0.743). The developed system performed similarly to experienced medical experts; thus, it could further aid the effectiveness and speed of DDH diagnosis.
Association of Excessive Daytime Sleepiness with the Zung Self-Rated Depression Subscales in Adults with Coronary Artery Disease and Obstructive Sleep Apnea
Authors: Celik Yeliz , Yapici-Eser Hale , Balcan Baran , Peker Yüksel
Published: June 2021

Excessive daytime sleepiness (EDS) is a factor associated with both obstructive sleep apnea (OSA) and depressive symptoms. Continuous positive airway pressure (CPAP) treatment may decrease EDS in adults with OSA; however, the modulatory role of depressive symptoms on the improvement of EDS is not known. We aimed to explore the association between subscales of the Zung Self-rated Depression Scale (SDS) and Epworth Sleepiness Scale (ESS) over a 2-year period in coronary artery disease (CAD) patients with OSA. This was a post-hoc analysis of the RICCADSA cohort, in which 399 adults with CAD (155 sleepy OSA [apnea–hypopnea index ≥ 15/h] and ESS score ≥ 10, who were offered CPAP; and 244 nonsleepy OSA [ESS < 10]), randomized to CPAP [n = 122] or no-CPAP [n = 122]) were included. Three factors were extracted from the Zung SDS, based on the principal component analysis: F1, cognitive symptoms and anhedonia; F2, negative mood; and F3, appetite. In a mixed model, the ESS score decreased by 3.4 points (p < 0.001) among the sleepy OSA phenotype, which was predicted by the decline in the F2, but not in the F1 and F3 scores. The fixed effects of time were not significant in the nonsleepy OSA groups, and thus, further analyses were not applicable. Additional within-group analyses showed a significant decrease in all subscales over time both in the sleepy and nonsleepy OSA patients on CPAP whereas there was a significant increase in the nonsleepy OSA group randomized to no-CPAP. We conclude that the improvement in negative mood symptoms of depression, but not changes in cognitive symptoms and anhedonia as well as appetite, was a significant predictor of decline in the ESS scores over a 2-year period in this CAD cohort with sleepy OSA on CPAP treatment.
Subjective and Objective Quality Assessments of Display Products
Authors: Zhang Huiqing , Li Donghao , Yu Yibing , Guo Nan
Published: June 2021

In recent years, people’s daily lives have become inseparable from a variety of electronic devices, especially mobile phones, which have undoubtedly become necessity in people’s daily lives. In this paper, we are looking for a reliable way to acquire visual quality of the display product so that we can improve the user’s experience with the display product. This paper proposes two major contributions: the first one is the establishment of a new subjective assessment database (DPQAD) of display products’ screen images. Specifically, we invited 57 inexperienced observers to rate 150 screen images showing the display product. At the same time, in order to improve the reliability of screen display quality score, we combined the single stimulation method with the stimulation comparison method to evaluate the newly created display products’ screen images database effectively. The second one is the development of a new no-reference image quality assessment (IQA) metric. For a given image of the display product, first our method extracts 27 features by analyzing the contrast, sharpness, brightness, etc., and then uses the regression module to obtain the visual quality score. Comprehensive experiments show that our method can evaluate natural scene images and screen content images at the same time. Moreover, compared with ten state-of-the-art IQA methods, our method shows obvious superiority on DPQAD.
Three-Factor Kinetic Equation of Catalyst Deactivation
Authors: Gromotka Zoë , Yablonsky Gregory , Ostrovskii Nickolay , Constales Denis
Published: June 2021

The three-factor kinetic equation of catalyst deactivation was obtained in terms of apparent kinetic parameters. The three factors correspond to the main cycle with a linear, detailed mechanism regarding the catalytic intermediates, a cycle of reversible deactivation, and a stage of irreversible deactivation (aging), respectively. The rate of the main cycle is obtained for the fresh catalyst under a quasi-steady-state assumption. The phenomena of reversible and irreversible deactivation are presented as special separate factors (hierarchical separation). In this case, the reversible deactivation factor is a function of the kinetic apparent parameters of the reversible deactivation and of those of the main cycle. The irreversible deactivation factor is a function of the apparent kinetic parameters of the main cycle, of the reversible deactivation, and of the irreversible deactivation. The conditions of such separability are found. The obtained equation is applied successfully to describe the literature data on the reversible catalyst deactivation processes in the dehydration of acetaldehyde over TiO2 anatase and in crotonaldehyde hydrogenation on supported metal catalysts.
Experimental Study and Comparison of Imbalance Ensemble Classifiers with Dynamic Selection Strategy
Authors: Zhao Dongxue , Wang Xin , Mu Yashuang , Wang Lidong
Published: June 2021

Imbalance ensemble classification is one of the most essential and practical strategies for improving decision performance in data analysis. There is a growing body of literature about ensemble techniques for imbalance learning in recent years, the various extensions of imbalanced classification methods were established from different points of view. The present study is initiated in an attempt to review the state-of-the-art ensemble classification algorithms for dealing with imbalanced datasets, offering a comprehensive analysis for incorporating the dynamic selection of base classifiers in classification. By conducting 14 existing ensemble algorithms incorporating a dynamic selection on 56 datasets, the experimental results reveal that the classical algorithm with a dynamic selection strategy deliver a practical way to improve the classification performance for both a binary class and multi-class imbalanced datasets. In addition, by combining patch learning with a dynamic selection ensemble classification, a patch-ensemble classification method is designed, which utilizes the misclassified samples to train patch classifiers for increasing the diversity of base classifiers. The experiments’ results indicate that the designed method has a certain potential for the performance of multi-class imbalanced classification.
Data-Driven Analysis of Nonlinear Heterogeneous Reactions through Sparse Modeling and Bayesian Statistical Approaches
Authors: Ito Masaki , Kuwatani Tatsu , Oyanagi Ryosuke , Omori Toshiaki
Published: June 2021

Heterogeneous reactions are chemical reactions that occur at the interfaces of multiple phases, and often show a nonlinear dynamical behavior due to the effect of the time-variant surface area with complex reaction mechanisms. It is important to specify the kinetics of heterogeneous reactions in order to elucidate the microscopic elementary processes and predict the macroscopic future evolution of the system. In this study, we propose a data-driven method based on a sparse modeling algorithm and sequential Monte Carlo algorithm for simultaneously extracting substantial reaction terms and surface models from a number of candidates by using partial observation data. We introduce a sparse modeling approach with non-uniform sparsity levels in order to accurately estimate rate constants, and the sequential Monte Carlo algorithm is employed to estimate time courses of multi-dimensional hidden variables. The results estimated using the proposed method show that the rate constants of dissolution and precipitation reactions that are typical examples of surface heterogeneous reactions, necessary surface models, and reaction terms underlying observable data were successfully estimated from only observable temporal changes in the concentration of the dissolved intermediate products.
Evolution of New Approaches in Pedagogy and STEM with Inquiry-Based Learning and Post-Pandemic Scenarios
Authors: Deák Csaba , Kumar Baibhaw , Szabó István , Nagy Gábor , Szentesi Szabolcs
Published: June 2021

In the last ten years, pedagogy has been evolving rapidly in terms of teaching approaches. This study is an attempt to analyze the recently developed novel pedagogy models. STEM integration and classroom engagement are primary approaches in pedagogy in recent times. The article aims to provide educators with some analytical tools to complement the modernization of STEM pedagogy. Integration flow and skill-set balancing, along with matrix analysis, are projected to be efficient solutions for evolved pedagogy. A novel PESTLE model is framed for tackling the changes in pedagogies during pandemics and emergencies. Inquiry-based learning can foster and accelerate the cause of integrating subjects in STEM pedagogy. In addition, the article discusses the post-pandemic scenario of pedagogy in the education system as a whole.
Education and Heritage of Medieval Warfare. A Study on the Transmission of Knowledge by Informal Educators in Defensive Spaces
Authors: Español-Solana Darío , Franco-Calvo Jesús Gerardo
Published: June 2021

Historical reenactment is becoming a top-tier teaching tool in the countries of Southern Europe. In Spain specifically, this discipline is experiencing a boom as a heritage education method, particularly in informal settings. This article is the outcome of a qualitative research study of the results obtained from one hundred and fifteen educators from historical reenactment groups. The study analyses the methods used by the exponents of this discipline to teach war in the Middle Ages, specifically in three Spanish castles dating from the 11th to the 12th centuries. It has made it possible to analyse how the educational discourses are organised in relation to Medieval war within military spaces from this period, and how historical reenactment is a coadjutant in the construction of teaching/learning spaces from a heritage education perspective.
Risk and Safety Management in Physical Education: Teachers’ Perceptions
Authors: Porsanger Lise , Sandseter Ellen Beate Hansen
Published: June 2021

Bodily movement is a central component in students’ educational experiences in school-based physical education (PE) programs. PE unavoidably involves physical risk. In some respects, the risk of play, sports and adventure is portrayed as necessary and healthy for children’s development. However, concerns about students’ safety and teachers’ liability might generate risk aversion among teachers. This article explores teachers’ perceptions of risk and safety management (RSM) in PE. Designed as a mixed methods study, the data include an online survey questionnaire (n = 698) and semi-structured interviews (n = 17) among primary and lower secondary PE teachers in Norway. A majority of the survey respondents report that their students only experience minor injuries in their PE classes. The interview data coincide with these results and indicate that minor injuries are rather common. While the survey results show that teachers mostly perceive RSM to be important in PE, the interview data suggest that the teachers’ perceptions of risk are characterized by uncertainty, which restricts the teachers’ control by means of RSM. Teachers also accept risk for enhancing students’ educative experiences in PE. Consequently, this study contributes to the knowledge of the complexity of risk and teachers’ perceptions of RSM in PE.
Machine-Learning-Enabled Intrusion Detection System for Cellular Connected UAV Networks
Authors: Shrestha Rakesh , Omidkar Atefeh , Roudi Sajjad Ahmadi , Abbas Robert , Kim Shiho
Published: June 2021

The recent development and adoption of unmanned aerial vehicles (UAVs) is due to its wide variety of applications in public and private sector from parcel delivery to wildlife conservation. The integration of UAVs, 5G, and satellite technologies has prompted telecommunication networks to evolve to provide higher-quality and more stable service to remote areas. However, security concerns with UAVs are growing as UAV nodes are becoming attractive targets for cyberattacks due to enormously growing volumes and poor and weak inbuilt security. In this paper, we propose a UAV- and satellite-based 5G-network security model that can harness machine learning to effectively detect of vulnerabilities and cyberattacks. The solution is divided into two main parts: the model creation for intrusion detection using various machine learning (ML) algorithms and the implementation of ML-based model into terrestrial or satellite gateways. The system identifies various attack types using realistic CSE-CIC IDS-2018 network datasets published by Canadian Establishment for Cybersecurity (CIC). It consists of seven different types of new and contemporary attack types. This paper demonstrates that ML algorithms can be used to classify benign or malicious packets in UAV networks to enhance security. Finally, the tested ML algorithms are compared for effectiveness in terms of accuracy rate, precision, recall, F1-score, and false-negative rate. The decision tree algorithm performed well by obtaining a maximum accuracy rate of 99.99% and a minimum false negative rate of 0% in detecting various attacks as compared to all other types of ML classifiers.
A Complete Control System for a High Voltage Converter in an Electrostatic Precipitator
Authors: García Díaz Fernando Jesús , Díaz Juan , García Jorge , Pernía Alberto M. , Villegas Pedro J.
Published: June 2021

Nowadays, the emission of pollutant particles is a global problem in terms of limiting pollution in industries, as well as greenhouse gases emissions. There are different ways to filter undesired particles, such as carbon air filters, chemical washing, and so on. One of the most popular techniques is the use of electrostatic precipitators: The operation mode is based in attracting particles using electrostatic forces. In order to do that, it is necessary to use a high-voltage converter, with a relative complex control. This article deals with the design of a complete platform to control not only these kind of converters, but also those converters based on the full-bridge power topology.
Robust Model Predictive Controller Using Recurrent Neural Networks for Input–Output Linear Parameter Varying Systems
Authors: Hadian Mohsen , Ramezani Amin , Zhang Wenjun
Published: June 2021

This paper develops a model predictive controller (MPC) for constrained nonlinear MIMO systems subjected to bounded disturbances. A linear parameter varying (LPV) model assists MPC in dealing with nonlinear dynamics. In this study, the nonlinear process is represented by an LPV using past input–output information (LPV-IO). Two primary objectives of this study are to reduce online computational load compared with the existing literature of MPC with an LPV-IO model and to confirm the robustness of the controller in the presence of disturbance. For the first goal, a recurrent neural network (RNN) is employed to solve real-time optimization problems with lower online computation. Regarding robustness, a new control law is developed, which comprises a fixed control gain (K) and a free perturbation (C). The proposed method enjoys a shrunken conservatism owing to the finding of a larger possible terminal region and using free control moves. The strategy is examined in an alkylation of benzene process and displays outstanding performance in both setpoint tracking and disturbance rejection problems. Moreover, the superiority of RNN over three conventional optimization algorithms is underlined in terms of MSE, the average time for solving the optimization problem, and the value of the cost function.
Fast Computation by MLFMM-FFT with NURBS in Large Volumetric Dielectric Structures
Authors: Pons Alejandro , Somolinos Alvaro , González Ivan , Cátedra Felipe
Published: June 2021

A refinement for the computation of the rigorous part of the multi-level fast multipole method (MLFMM) of analyzing volumetric objects is presented. A scheme based on the fast Fourier technique (FFT) is proposed with the objective of reducing the computational resources required to accurately analyze large homogeneous and non-homogeneous dielectric volumes. In order to reduce the memory requirements, the storage of the near-field terms of the method of moments (MoM) matrix is performed only for the positions corresponding to a parallelepiped with the size of the level 1 block of the MLFMM, computed with the vacuum permittivity, taking advantage of the Toeplitz symmetry present in regular hexahedral meshes. The FFT avoids applying the near-field MoM matrix in the iterative solution process. The application of this approach results in huge improvements in terms of memory usage, but also a speeds up the iterative solution process because the use of three-dimensional (3D) FFTs is very efficient for computing convolutions when the number of unknowns of the problems becomes very large as happens in volumetric problems. We also propose a new approach for the numerical treatment of the transition of the dielectric permittivity between different dielectrics or between a dielectric and a free space. To validate the computation technique, the radar cross section (RCS) of several dielectric bodies is computed using the classical MLFMM approach and it is compared with the presented FFT-based-MLFMM solution. The results demonstrate that the efficient memory and computation time usage of the proposed approach.
A More Efficient Technique to Power Home Monitoring Systems Using Controlled Battery Charging
Authors: Azevedo Joaquim Amândio , Santos Filipe Edgar
Published: June 2021

Home energy monitoring has recently become a very important issue and a means to reduce energy consumption in the residential sector. Sensors and control systems are deployed at various locations in a house and an intelligent system is used to efficiently manage the consumed energy. Low power communication systems are used to provide low power consumption from a smart meter. Several of these systems are battery operated. Other systems use AC/DC adapters to supply power to sensors and communication systems. However, even using low-power technology, such as ZigBee, the power consumption of a router can be high because it must always be powered on. In this work, to evaluate power consumption, a system for monitoring energy usage and indoor air quality was developed. A technique is proposed to efficiently supply power to the components of the system. All sensor nodes are battery operated, and relays are used to control the battery charging process. In addition, an energy harvesting system based on solar energy was developed to power the proposed system.
Unbalanced Current Reduction Method of Microgrid Based on Power Conversion System Operation
Authors: Shin Hyun , Chae Sang Heon , Kim Eel-Hwan
Published: June 2021

In isolated areas such as islands with small power grids, the BESS (Battery energy storage system) can supply the standard voltage and frequency to the power system to achieve 100% of renewable sharing. In addition, the installation of additional BESS may be required in the microgrid due to technical limitations such as redundant operation and manufacturer specifications. Thus, the BESSs in a microgrid can be split into main and sub BESSs which play a role as the main source and auxiliary services, respectively. Generally, the ratio of unbalance current in microgrid system tends to be high, because of inherently unbalanced single phase load distribution. However, because the capacity of BESS is calculated under balanced conditions, the PCS (Power conversion system) of BESS may stop protecting its switching device from a single phase overcurrent in actual operation. From this perspective, this paper proposes that the sub BESSs perform dual current control to supply the unbalanced current instead of the main BESS. In the simulation result of the proposed method, the current unbalance rate of the main ESS has been reduced by about 26%. Through the proposed control scheme, it is possible to prevent an unexpected single phase overload of the main BESS in the microgrid.
Numerical Study on Energy-Saving Performance of a New Type of Phase Change Material Room
Authors: Ye Rongda , Fang Xiaoming , Zhang Zhengguo
Published: June 2021

The thermal performance of a phase change energy storage building envelope with the ventilated cavity was evaluated. CaCl2·6H2O-Mg(NO3)2·6H2O/expanded graphite (EG) was employed to combined with the building for year-round management. The energy consumption caused by the building under different influence parameters was evaluated numerically. The results indicated that CaCl2·6H2O-8wt %Mg(NO3)2·6H2O/EG should be installed on the south wall for the heating season, while CaCl2·6H2O-2wt %Mg(NO3)2·6H2O/EG should be integrated on the roof for the cooling season. When the air layer was ventilated and the south wall was coated with the solar absorbing coating, the room could save approximately 30% of energy consumption. Moreover, the energy consumption increased with an increase in the air layer thickness, and the air layers played a different role in the building envelope. The optimal value of the flow rate between air layer 2, air layer 3, and the room was 0.09 m3/s. To reduce the energy consumption, the phase change materials (PCMs) with large and small thermal conductivity should be installed in the south wall and roof, respectively. In general, the phase change energy storage building envelope with the ventilated cavity can save energy during the heating and cooling seasons.
Energy Intensity Reduction in Large-Scale Non-Residential Buildings by Dynamic Control of HVAC with Heat Pumps
Authors: Franco Alessandro , Miserocchi Lorenzo , Testi Daniele
Published: June 2021

One of the main elements for increasing energy efficiency in large-scale buildings is identified in the correct management and control of the Heating Ventilation and Air Conditioning (HVAC) systems, particularly those with Heat Pumps (HPs). The present study aimed to evaluate the perspective of energy savings achievable with the implementation of an optimal control of the HVAC with HPs. The proposed measures involve the use of a variable air volume system, demand-controlled ventilation, an energy-aware control of the heat recovery equipment, and an improved control of the heat pump and chiller supply water temperature. The analysis has been applied to an academic building located in Pisa and is carried out by means of dynamic simulation. The achieved energy saving can approach values of more than 80% if compared with actual plants based on fossil fuel technologies. A major part of this energy saving is linked to the use of heat pumps as thermal generators as well as to the implementation of an energy efficient ventilation, emphasizing the importance of such straightforward measures in reducing the energy intensity of large-scale buildings.
Towards a Framework of Operational-Risk Assessment for a Maritime Autonomous Surface Ship
Authors: Fan Cunlong , Montewka Jakub , Zhang Di
Published: June 2021

Global research interest in the domain of maritime autonomous surface ships (MASS) is dramatically increasing. With new prototypes planned to be set to the seas where various operational modes (OMs) are claimed, the issue of the safety evaluation of an MASS, and criteria for selecting the appropriate OM for given conditions remain open questions. This paper proposes a four-step risk-informed framework to assess risk in a scenario for an MASS operating at one of three OMs: manual control (MC), remote control (RC), and autonomous control (AC). To this end, the concept of risk priority numbers (RPNs), adopted from failure mode and effects analysis (FMEA), is utilized. The required parameters to defined RPNs are obtained in the course of analyzing a model MASS accident with expert knowledge. The applicability of the proposed framework is demonstrated via a model MASS case study. Results reveal that, in the same scenario, the risk of MASS varied across the analyzed OMs. On the basis of the aggregated results for each operational mode, suggestions for OM switching are put forward.
Development of the Reduced-Scale Vehicle Model for the Dynamic Characteristic Analysis of the Hyperloop
Authors: Lee Jinho , You Wonhee , Lim Jungyoul , Lee Kwan-Sup , Lim Jae-Yong
Published: June 2021

This study addresses the Hyperloop characterized by a capsule-type vehicle, superconducting electrodynamic suspension (SC-EDS) levitation, and driving in a near-vacuum tube. Because the Hyperloop is different from conventional transportation, various considerations are required in the vehicle-design stage. Particularly, pre-investigation of the vehicle dynamic characteristics is essential because of the close relationship among the vehicle design parameters, such as size, weight, and suspensions. Accordingly, a 1/10 scale Hyperloop vehicle system model, enabling the analysis of dynamic motions in the vertical and lateral directions, was developed. The reduced-scale model is composed of bogies operated by Stewart platforms, secondary suspension units, and a car body. To realize the bogie motion, an operation algorithm reflecting the external disturbance, SC-EDS levitation, and interaction between the bogie and car body, was applied to the Stewart platform. Flexible rubber springs were used in the secondary suspension unit to enable dynamic characteristic analysis of the vertical and lateral motion. Results of the verification tests were compared with simulation results to examine the fitness of the developed model. The results showed that the developed reduced-scale model could successfully represent the complete dynamic characteristics, owing to the enhanced precision of the Stewart platform and the secondary suspension allowing biaxial motions.
Temporal and Spatial Development of the EM Field in a Shielding Enclosure with Aperture after Transient Interference Caused by a Subnanosecond High-Energy EM Plane Wave Pulse
Authors: Budnarowska Magdalena , Mizeraczyk Jerzy
Published: June 2021

A proper assessment of the shielding effectiveness of an enclosure with aperture under subnanosecond transient interference requires a better understanding of the coupling and development mechanisms of the EM field induced inside the enclosure. In this paper, the results of a numerical study of the temporal and spatial development of the electromagnetic (EM) field in a shielding enclosure with aperture after transient interference caused by a subnanosecond high-energy EM plane wave pulse are presented. The interference pulse had Gaussian distribution of the electric and magnetic fields with amplitudes of 106 V/m and 2.68·103 A/m, respectively. The maximum pulse power density was 2.68 GW/m2. The novelty of this study was 2D and 3D images, which visualized the temporal and spatial build-up of electric and magnetic fields in the shielding enclosure within 90 ns after the transient interference. This is 58 times longer than the time needed by any EM wave to travel the distance between the front and rear walls of the enclosure. The presented images, showing the EM field morphology over a relatively long period of time, were crucial for understanding the EM field build-up process inside the shielding enclosure with aperture. They revealed the existence of two unknown phases of the EM field build-up in the enclosure with aperture. We call these two phases the wave phase and the interference phase. In the wave phase, the EM field is generated in the form of so-called primary and secondary wave pulses, traveling towards the enclosure rear wall. In the interference phase, the EM field has the form of temporally and spatially varying pulse-like interference (size-limited) patterns of the associated electric and magnetic fields. The EM field induced in the enclosure is long-lasting compared to the interference pulse duration. The amplitudes of the electric and magnetic fields decreased about threefold in 5 ns and 30-fold in 90 ns, thus exhibiting a severe EM hazard for much longer than the external interference duration. For a long period of time, the highest EM field amplitudes would change their locations in the enclosure, which makes it difficult to assess the shielding effectiveness on the basis of classical definitions. The existence of the long-lasting temporally and spatially varying EM field induced in the enclosure with aperture by the subnanosecond transient interference, visualized in detail in this paper, confirms that a new definition and measurement methods of shielding effectiveness under transient conditions are needed. The obtained results provide a source of data that can be useful when working on the introduction of time-domain parameters to evaluate the transient shielding effectiveness in the case of the ultrashort EM interference.
Determination of the Bucket Wheel Drive Power by Computer Modeling Based on Specific Energy Consumption and Cutting Geometry
Authors: Brînaș Ildiko , Andraș Andrei , Radu Sorin Mihai , Popescu Florin Dumitru , Andraș Iosif , Marc Bogdan Ioan , Cioclu Alexandru Robert
Published: June 2021

Starting from the general principles of material cutting, with applicability to coal and overburden excavation using bucket wheel excavators (BWEs), this paper proposes another method for calculating the drive power of the bucket wheel excavator by computer modeling. This approach required two steps. In the first step, the volume of the excavated material for one slewing movement of the boom and for a particular excavation geometry was determined, and the slewing time in the open pit coal mine was measured. In the second one, the values of the specific energy (SE) consumption for cutting were determined by laboratory tests on samples of material taken from the open pit mine. The proposed method allows for the estimation of the load of the bucket wheel drive motor by taking into account only the specific energy necessary for the cutting of the material, the excavated volume during one slewing, and the time required to excavate this volume, and not the wear coefficients of the teeth or bucket edge. This method is important for establishing the correlation between the height of the excavated slice and the slewing speed of the boom in order to optimize the drive power of the bucket wheel and thus improve energy efficiency, increase the performance of excavators, and reduce operating costs.
Using the Forestry Reclamation Approach for Reclaimed Surface Mineland in the Western Gulf: Effects on Pinus taeda Seedling Growth and Survival
Authors: Phillips Cassie , Stovall Jeremy , Williams Hans , Farrish Kenneth
Published: June 2021

While land reclamation efforts of surface mines have considerably increased soil stability since the implementation of SMCRA (Surface Mining Control and Reclamation Act), research suggests that resulting soil compaction hinders the productivity of forests post-mining. The Forestry Reclamation Approach (FRA) was developed to improve forest health in the Appalachian region through a five-step process that minimizes soil compaction and establishes a productive forest. The FRA has not yet been tested in the western Gulf Coastal Plain (GCP). The higher clay content of some GCP soils and the dearth of coarse fragments (e.g., cobbles, stones and boulders) may affect reclamation practices and the ability of these methods to create productive forests. Compaction caused by conventional reclamation methods in the GCP has not been studied in great detail. Thus, this study attempts to provide a comparison of two reclamation methods, FRA low-compaction method used in the Appalachian region with that of conventional scraper-pan (scraper) methods in the GCP. This study used the FRA with common silvicultural practices of the western Gulf. The two hectare study site was installed with a randomized complete block design with three replicates comparing conventional scraper reclamation used in the region with that of an unmined control and the FRA-style low compaction treatment. Following soil reclamation, containerized loblolly pine (Pinus taeda L.) seedlings of a western Gulf provenance were hand-planted. Soil chemical and physical parameters were assessed on each treatment to determine the effect the FRA and scraper method had on resulting tree seedling growth and survival. After three growing seasons, seedlings in the FRA plots had significantly greater tree volumes than both the scraper (p = 0.0139) and the control (p = 0.0247) treatments. The FRA plots also had a 97% survival rate, while scraper plots had a survival of 86%. The FRA plots had significantly lower soil bulk densities than scraper (p = 0.0353) and control (p < 0.0001) plots which likely influenced growth and survival trends. Soil nutrients were increasingly available on the FRA and scraper plots, likely due to mixing of the soil profile when compared to the unmined control. Leaf-level water potential and gas exchange were not correlated to growth and survival and did not differ among treatments. These results suggest reclamation practices modeled after FRA methods may benefit tree growth and survival in the Western Gulf.