bluuebunny/crossref_metadata_2025 huggingface dataset:
Combining FORGE Score and Histopathological Diagnostic Criteria of Atypical Meningioma Enables Risk Stratification of Tumor Progression
Authors: Wach Johannes , Lampmann Tim , Güresir Ági , Vatter Hartmut , Becker Albert J. , Hölzel Michael , Toma Marieta , Güresir Erdem
Published: November 2021

More than 50% of atypical meningiomas regrow within 5 years after surgery. FORGE score is a newly created tool to estimate the MIB-1 index in cranial meningiomas. In this investigation, we aimed to assess the predictive value of the FORGE score in combination with major diagnostic criteria of atypical meningioma (brain invasion, mitotic count ≥ 4) regarding recurrence in atypical meningiomas. We included patients operated on primary atypical meningiomas in our center from 2011 to 2019. The study included 71 patients (58% women, median age 63 years). ROC curves revealed a superiority of FORGE score combined with histopathological diagnostic criteria of atypical meningioma (AT-FORGE) in the prediction of tumor progression compared to FORGE score only (AUC: 0.72; 95% CI: 0.54–0.91, cut-off: ≥5/<5, sensitivity: 75%, specificity: 78%). Patients with an AT-FORGE score ≥ 5 had a shorter time to tumor progression (32.8 vs. 71.4 months, p < 0.001) in the univariable analysis. Multivariable cox regression analysis revealed significant predictive value of Simpson grade > II, presence of multiple meningiomas and AT-FORGE score ≥ 5 for tumor progression. The combination of histopathological diagnostic criteria for atypical meningioma with FORGE score might facilitate an effective identification of patients with an atypical meningioma who have an increased risk of tumor progression.
Alzheimer’s Disease-Related Metabolic Pattern in Diverse Forms of Neurodegenerative Diseases
Authors: Lau Angus , Beheshti Iman , Modirrousta Mandana , Kolesar Tiffany A. , Goertzen Andrew L. , Ko Ji Hyun
Published: November 2021

Dementia is broadly characterized by cognitive and psychological dysfunction that significantly impairs daily functioning. Dementia has many causes including Alzheimer’s disease (AD), dementia with Lewy bodies (DLB), and frontotemporal lobar degeneration (FTLD). Detection and differential diagnosis in the early stages of dementia remains challenging. Fueled by AD Neuroimaging Initiatives (ADNI) (Data used in preparation of this article were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database. As such, the investigators within ADNI contributed to the design and implementation of ADNI and/or provided data but did not participate in analysis or writing of this report.), a number of neuroimaging biomarkers for AD have been proposed, yet it remains to be seen whether these markers are also sensitive to other types of dementia. We assessed AD-related metabolic patterns in 27 patients with diverse forms of dementia (five had probable/possible AD while others had atypical cases) and 20 non-demented individuals. All participants had positron emission tomography (PET) scans on file. We used a pre-trained machine learning-based AD designation (MAD) framework to investigate the AD-related metabolic pattern among the participants under study. The MAD algorithm showed a sensitivity of 0.67 and specificity of 0.90 for distinguishing dementia patients from non-dementia participants. A total of 18/27 dementia patients and 2/20 non-dementia patients were identified as having AD-like patterns of metabolism. These results highlight that many underlying causes of dementia have similar hypometabolic pattern as AD and this similarity is an interesting avenue for future research.
Evaluation of the Determination of Dabigatran, Rivaroxaban, and Apixaban in Lupus Anticoagulant-Positive Patients
Authors: Úlehlová Jana , Piskláková Barbora , Ivanovová Eliška , Procházková Jana , Bradáčová Pavla , Kvasnička Aleš , Friedecký David , Slavík Luděk
Published: November 2021

Background: The effect of direct oral anticoagulants (DOAC) on laboratory tests dependent on the production of their targets, factor IIa and factor Xa, is a well-known problem and can cause both false positive and negative results. In particular, the situation in patients who develop lupus anticoagulant (LA) antibodies is highly complex. To evaluate the effectiveness of DOAC therapy in lupus-positive patients, 31 samples were enrolled in this retrospective study. All patient samples were spiked with three types of DOAC (dabigatran, DABI; rivaroxaban, RIVA; and apixaban, API) in a concentration that significantly influenced the screening test for LA and thus can mask the presence of LA. Subsequently, the DOAC was always unbound by the DOAC-Stop procedure. DOAC levels before and after binding were determined by functional assays, followed by liquid chromatography coupled with mass spectrometry (LC-MS) analysis. Methods: The determination of DOAC levels was performed by direct thrombin assay and determination of anti-Xa activity with specific calibration as functional tests for DABI and xabans (API and RIVA). To determine concentration levels of API, DABI, and RIVA, our in-house LC-MS method was used. Results: The results of LA-positive samples show significant differences between functional tests and the LC-MS method both before and after DOAC binding. Conclusions: The acute findings of the presence of LA-type antibodies fundamentally affects the determination of DOAC by functional tests, and in this case, it is necessary to use LC-MS analysis to determine the true value. If patients treated with DOAC develop LA of medium and higher titers, we do not recommend checking DOAC levels with functional tests.
Design and ARM-Based Implementation of Bitstream-Oriented Chaotic Encryption Scheme for H.264/AVC Video
Authors: Zhang Zirui , Chen Ping , Li Weijun , Xiong Xiaoming , Wang Qianxue , Wen Heping , Liu Songbin , Cai Shuting
Published: November 2021

In actual application scenarios of the real-time video confidential communication, encrypted videos must meet three performance indicators: security, real-time, and format compatibility. To satisfy these requirements, an improved bitstream-oriented encryption (BOE) method based chaotic encryption for H.264/AVC video is proposed. Meanwhile, an ARM-embedded remote real-time video confidential communication system is built for experimental verification in this paper. Firstly, a 4-D self-synchronous chaotic stream cipher algorithm with cosine anti-controllers (4-D SCSCA-CAC) is designed to enhance the security. The algorithm solves the security loopholes of existing self-synchronous chaotic stream cipher algorithms applied to the actual video confidential communication, which can effectively resist the combinational effect of the chosen-ciphertext attack and the divide-and-conquer attack. Secondly, syntax elements of the H.264 bitstream are analyzed in real-time. Motion vector difference (MVD) coefficients and direct-current (DC) components in Residual syntax element are extracted through the Exponential-Golomb decoding operation and entropy decoding operation based on the context-based adaptive variable length coding (CAVLC) mode, respectively. Thirdly, the DC components and MVD coefficients are encrypted by the 4-D SCSCA-CAC, and the encrypted syntax elements are re-encoded to replace the syntax elements of the original H.264 bitstream, keeping the format compatibility. Besides, hardware codecs and multi-core multi-threading technology are employed to improve the real-time performance of the hardware system. Finally, experimental results show that the proposed scheme, with the advantage of high efficiency and flexibility, can fulfill the requirement of security, real-time, and format compatibility simultaneously.
On the Operational Utility of Measures of Multichannel EEGs
Authors: Darmon David , Watanabe Tomas , Cellucci Christopher , Rapp Paul E.
Published: November 2021

Multichannel EEGs were obtained from healthy participants in the eyes-closed no-task condition and in the eyes-open condition (where the alpha component is typically abolished). EEG dynamics in the two conditions were quantified with two related binary Lempel–Ziv measures of the first principal component, and with three measures of integrated information, including the more recently proposed integrated synergy. Both integrated information and integrated synergy with model order p=1 had greater values in the eyes-closed condition. When the model order of integrated synergy was determined with the Bayesian Information Criterion, this pattern was reversed, and in line with the other measures, integrated synergy was greater in the eyes-open condition. Eyes-open versus eyes-closed separation was quantified by calculating the between-condition effect size. The Lempel–Ziv complexity of the first principal component showed greater separation than the measures of integrated information.
High-Efficient Syndrome-Based LDPC Reconciliation for Quantum Key Distribution
Authors: Mao Hao-Kun , Qiao Yu-Cheng , Li Qiong
Published: November 2021

Quantum key distribution (QKD) is a promising technique to share unconditionally secure keys between remote parties. As an essential part of a practical QKD system, reconciliation is responsible for correcting the errors due to the quantum channel noise by exchanging information through a public classical channel. In the present work, we propose a novel syndrome-based low-density parity-check (LDPC) reconciliation protocol to reduce the information leakage of reconciliation by fully utilizing the syndrome information that was previously wasted. Both theoretical analysis and simulation results show that our protocol can evidently reduce the information leakage as well as the number of communication rounds.
Dirac Spatial Search with Electric Fields
Authors: Zylberman Julien , Debbasch Fabrice
Published: November 2021

Electric Dirac quantum walks, which are a discretisation of the Dirac equation for a spinor coupled to an electric field, are revisited in order to perform spatial searches. The Coulomb electric field of a point charge is used as a non local oracle to perform a spatial search on a 2D grid of N points. As other quantum walks proposed for spatial search, these walks localise partially on the charge after a finite period of time. However, contrary to other walks, this localisation time scales as N for small values of N and tends asymptotically to a constant for larger Ns, thus offering a speed-up over conventional methods.
Influence of Environmental Parameters on the Stability of the DNA Molecule
Authors: Svidlov Alexander , Drobotenko Mikhail , Basov Alexander , Gerasimenko Eugeny , Elkina Anna , Baryshev Mikhail , Nechipurenko Yury , Dzhimak Stepan
Published: November 2021

Fluctuations in viscosity within the cell nucleus have wide limits. When a DNA molecule passes from the region of high viscosity values to the region of low values, open states, denaturation bubbles, and unweaving of DNA strands can occur. Stabilization of the molecule is provided by energy dissipation—dissipation due to interaction with the environment. Separate sections of a DNA molecule in a twisted state can experience supercoiling stress, which, among other things, is due to complex entropic effects caused by interaction with a solvent. In this work, based on the numerical solution of a mechanical mathematical model for the interferon alpha 17 gene and a fragment of the Drosophila gene, an analysis of the external environment viscosity influence on the dynamics of the DNA molecule and its stability was carried out. It has been shown that an increase in viscosity leads to a rapid stabilization of the angular vibrations of nitrogenous bases, while a decrease in viscosity changes the dynamics of DNA: the rate of change in the angular deviations of nitrogenous bases increases and the angular deformations of the DNA strands increase at each moment of time. These processes lead to DNA instability, which increases with time. Thus, the paper considers the influence of the external environment viscosity on the dissipation of the DNA nitrogenous bases’ vibrational motion energy. Additionally, the study on the basis of the described model of the molecular dynamics of physiological processes at different indicators of the rheological behavior of nucleoplasm will allow a deeper understanding of the processes of nonequilibrium physics of an active substance in a living cell to be obtained.
Inferring Users’ Social Roles with a Multi-Level Graph Neural Network Model
Authors: Zhang Chunrui , Wang Shen , Zhan Dechen , Yin Mingyong , Lou Fang
Published: November 2021

Users of social networks have a variety of social statuses and roles. For example, the users of Weibo include celebrities, government officials, and social organizations. At the same time, these users may be senior managers, middle managers, or workers in companies. Previous studies on this topic have mainly focused on using the categorical, textual and topological data of a social network to predict users’ social statuses and roles. However, this cannot fully reflect the overall characteristics of users’ social statuses and roles in a social network. In this paper, we consider what social network structures reflect users’ social statuses and roles since social networks are designed to connect people. Taking an Enron email dataset as an example, we analyzed a preprocessing mechanism used for social network datasets that can extract users’ dynamic behavior features. We further designed a novel social network representation learning algorithm in order to infer users’ social statuses and roles in social networks through the use of an attention and gate mechanism on users’ neighbors. The extensive experimental results gained from four publicly available datasets indicate that our solution achieves an average accuracy improvement of 2% compared with GraphSAGE-Mean, which is the best applicable inductive representation learning method.
Fluctuations in Extractable Work and Bounds on the Charging Power of Quantum Batteries
Authors: Wang Shang-Yung
Published: November 2021

Motivated by a recent disagreement about the claim that fluctuations in the free energy operator bound the charging power of a quantum battery, we present a critical analysis of the original derivation. The analysis shows that the above claim does not hold for both closed- and open-system dynamics. Our results indicate that the free energy operator is not a consistent quantifying operator for the work content of a charging quantum battery.
Digital Teaching Competence in Higher Education: A Systematic Review
Authors: Fernández-Batanero José María , Román-Graván Pedro , Montenegro-Rueda Marta , López-Meneses Eloy , Fernández-Cerero José
Published: November 2021

Higher education is one of the educational stages most affected by digital technologies, whose constant development has produced a favourable atmosphere for new approaches regarding the teaching–learning processes. The aim of the study was to identify the most relevant findings that specialists have analysed in terms of the digital competences of university teachers, through the analysis of the scientific production of the specialised literature in the last decade (2009–2019). A search was carried out on the Web of Science (WoS) and Scopus databases following the guidelines of the PRISMA statement (Preferred Reporting Items for Systematic reviews and Meta-Analyses). After applying the inclusion and exclusion criteria, the sample was made up of 20 articles. The main findings show the low level of digital competence among teachers and the need for training in both technological and pedagogical areas.
Using a Cooperative Educational Game to Promote Pro-Environmental Engagement in Future Teachers
Authors: Vázquez-Vílchez Mercedes , Garrido-Rosales Dalia , Pérez-Fernández Beatriz , Fernández-Oliveras Alicia
Published: November 2021

This paper explores the value of cooperative games in enhancing knowledge and generating pro-environmental engagement in students. For this, an educational board game related to global change was developed, validated, and subsequently evaluated using future primary school teachers. The board game was validated and evaluated in two phases. Phase I (validation phase): students pursuing a Master’s Degree in Secondary Education evaluated different aspects of the game, providing feedback that improved the game design and playing rules. Phase II (implementation–evaluation phase): the game was implemented using students of the Primary Education Degree, whose learning performance and engagement was assessed through a qualitative survey. These participants were considered potential users of the board game. The users’ experience was explored using a theoretical framework for pro-environmental engagement through playing the game. The findings demonstrate that the cooperative game proposed fomented a feeling of personal responsibility for the environment in the users. It also fostered cognitive, emotional, and behavioural engagement in the players. The results agree with the attributes present in the framework of engagement with respect to climate-change-related issues using gaming. Game-based learning can be used as a tool for enhancing global change knowledge and promoting pro-environmental engagement while bolstering Education for Sustainability (EfS) capacity in future primary-school teachers.
Studying Learner’s Perception of Attaining Graduate Attributes in Capstone Project Units Using Online Flipped Classroom
Authors: Memon Tayab D. , Jurin Monica , Kwan Paul , Jan Tony , Sidnal Nandini , Nafi Nazmus
Published: November 2021

This article describes an empirical study to evaluate how the flipped learning (FL) approach has impacted a learner’s perception in attaining the graduate attributes (GAs) of five capstone project units offered at Melbourne Institute of Technology in Australia, where the authors are affiliated. The subjects include one undergraduate and one postgraduate business unit, and one undergraduate and two postgraduate units in networking. Our study is distinguished from previous research in two novel aspects. First, the subject matter concerns capstone project units which are taken by students in the final year of their degree. In these units, students are expected to apply a variety of knowledge and skills that they have acquired thus far in carrying out an industry-based project of substantial complexity. The learning outcomes (LOs) require students to apply skills and knowledge that they have learned across completed units and connect them with real-world problems. Second, the FL approach has been applied wholly in an online virtual classroom setting due to the social distancing restrictions enforced by local authorities in response to the COVID-19 pandemic. Our hypothesis is that FL has positively influenced the perception of learners in their attaining the GAs. We tested this hypothesis by using data collected by an online survey administered to the student cohorts of the five chosen units at the end of Trimester 1 of 2021. The survey, which comprised 14 questions, assesses a student’s perception of achieving the LOs through developments in three dimensions, including cognitive, affective, and behavioural, acquired in a real-world client setting. Statistical analyses of the survey data reveal that the FL approach resulted in a positive perception by students of their attaining the GAs through achieving the LOs of the capstone project units, which in turn is supported by the responses to the three measured dimensions.
Fully Metallic Reflectarray for the Ku-Band Based on a 3D Architecture
Authors: Velasco Jaime , Parellada-Serrano Ignacio , Molero Carlos
Published: November 2021

This document presents the design and manufacture of a reflectarray (RA) antenna for the Ku-band that is based on a fully-metallic 3D architecture. The reflectarray unit cell is formed by a square-shaped waveguide section ending in a short circuit, which is the reflectarray back ground plane. Each cell has the ability of configuring the phase of its own reflected field by means of resonators perforated on the walls of the cell waveguide section. The resonator-based waveguide cell introduces the 3D character to the design. The geometry of the resonators and the size variation introduces the phase behavior of each cell, thus, conforming the radiation pattern of the reflectarray. This design explores the potential of phase value truncation (six states and two states) and demonstrates that proper pattern results can be obtained with this phase truncation.
Improvement of Performance Analysis of Amplitude-Comparison Monopulse Algorithm in the Presence of an Additive Noise
Authors: Ham Hyeong-Woo , Lee Joon-Ho
Published: November 2021

In this paper, it is shown how the performance of the monopulse algorithm in the presence of an additive noise can be obtained analytically. In a previous study, analytic performance analysis based on the first-order Taylor series and the second-order Taylor series was conducted. By adopting the third-order Taylor series, it is shown that the analytic performance based on the third-order Taylor series can be brought closer to the performance of the original monopulse algorithm than the analytic performance based on the first-order Taylor series and the second-order Taylor series.
Design Thinking as a Framework for the Design of a Sustainable Waste Sterilization System: The Case of Piedmont Region, Italy
Authors: Castiblanco Jimenez Ivonne Angelica , Mauro Stefano , Napoli Domenico , Marcolin Federica , Vezzetti Enrico , Rojas Torres Maria Camila , Specchia Stefania , Moos Sandro
Published: November 2021

The development of new methods for the correct disposal of waste is unavoidable for any city that aims to become eco-friendly. Waste management is no exception. In the modern era, the treatment and disposal of infectious waste should be seen as an opportunity to generate renewable energy, resource efficiency, and, above all, to improve the population’s quality of life. Northern Italy currently produces 66,600 tons/year of infectious waste, mostly treated through incineration plants. This research aims to explore a more ecological and sustainable solution, thereby contributing one more step toward achieving better cities for all. Particularly, this paper presents a conceptual design of the main sterilization chamber for infectious waste. The methodology selected was Design Thinking (DT), since it has a user-centered approach which allows for co-design and the inclusion of the target population. This study demonstrates to the possibility of obtaining feasible results based on the user’s needs through the application of DT as a framework for engineering design.
Experimental Validation of Predictive Current Control for DFIG: FPGA Implementation
Authors: Bouderbala Manale , Bossoufi Badre , Deblecker Olivier , Alami Aroussi Hala , Taoussi Mohammed , Lagrioui Ahmed , Motahhir Saad , Masud Mehedi , Alraddady Fahad A.
Published: November 2021

The purpose of this study is to design a real-time current predictive control for a wind energy conversion system (WECS) using a doubly-fed induction generator (DFIG). A wind emulator and a test bench for assessing control strategies were conceptualized. The DSPACE DS1104 board served as the foundation for the design of a wind emulation system. While power is indirectly regulated via currents, the latter is controlled directly by current predictive control. Using discrete time, the control suggests the appropriate voltages to the converter for each sample period to attain the specified set points and control the power. The field-oriented control is employed to ensure that the two components, axes d and q, are decoupled. The present predictive control was established to regulate a DFIG’s active and reactive capabilities. To begin, a thorough examination of the WECS is discussed. Following that, a comprehensive description of predictive control laws based on reference frame orientation is offered. As a result, a simulation was done using Matlab/Simulink environments to assess the performance and resilience of the proposed control model. The predictive current control was then experimentally validated on a test bench to demonstrate its efficacy. The observed results reveal an astonishing correlation between simulations and experiments.
Erratum: Hu et al. Numerical Investigation of Flow and Heat Transfer in a Rotor-Stator Cavity with Centripetal Carbon Dioxide Through-Flow. Energies 2019, 12, 2613
Authors: Hu Bo , Li Xuesong , Ren Xiaodong , Lu Jiaxing
Published: November 2021

The authors would like to make the following explanations and changes to the original paper [...]
Voltage Control of Multiphase Cage Induction Generators at a Speed Varying over a Wide Range
Authors: Drozdowski Piotr , Cholewa Dariusz
Published: November 2021

The subject of this publication is a method of controlling the DC voltage of a PWM rectifier supplied by a multiphase cage induction generator with the number of stator phases greater than three operating in a wide range of driving speeds. Voltage regulation is performed by changing the frequency and amplitude of the stator voltages with simultaneous switching of the phase sequence of these voltages. The step change of the voltage sequence is made in the designated ranges of the generator speed, which enables the stabilization of the output voltage in a wide range from the minimum speed of about 25% of the rated speed. Such sequence switching changes the number of pole pairs produced by the winding for each supply sequence. The difference compared to multi-speed induction machines is that, in the presented solution, there is only one winding, not a few, which enables good use of the machine’s magnetic core in the same dimensions as for the three-phase machine of a similar power. Steady-state characteristics and dynamic operation were obtained using laboratory measurements of a standalone nine-phase induction generator. The automatic control system maintained the output voltage at the set level, regardless of the generator load and driving power.
Analysis of the Impact of Countdown Signal Timers on Driving Behavior and Road Safety
Authors: Krukowicz Tomasz , Firląg Krzysztof , Suda Józef , Czerliński Mirosław
Published: November 2021

This article describes the safety and effectiveness issues related to signal countdown timers (SCT). These devices are used in many countries around the world. The impact of these devices on road safety and the effectiveness of traffic lights is presented. During a literature review, more than 18 aspects of device use were recognized. The research involved measurements carried out at three intersections in Płock (Poland). The initial and final period of the green signal for vehicles was analyzed. Headways, incidences of vehicles passing through after the end of the green signal, and red-light violations were examined. Additionally, a fuel consumption analysis and a case study of a road crash in Szczecin (Poland) are presented. Problems related to signal countdown timers working during traffic light failure are described. The research shows different influences of signal countdown timers at various intersections. It was observed that SCTs increase the number of red-light violations and during the red-amber signal. On the other hand, the number of entries during the amber signal with SCTs is lower. A literature review also indicated that the use of SCT causes a reduction of start-up time (positive impact) and increases vehicle speed (negative impact). The article concludes that SCTs do not always fulfill their role in improving road safety and control efficiency. Conclusions can address various stakeholders, including drivers, road authorities, and traffic engineers.
Damping Formation Mechanism and Damping Injection of Virtual Synchronous Generator Based on Generalized Hamiltonian Theory
Authors: Zeng Yun , Qian Jing , Yu Fengrong , Mei Hong , Yu Shige
Published: November 2021

Invertor as a virtual synchronous generator (VSG) to provide virtual inertia and damping can improve the stability of a microgrid, in which the damping is one of the fundamental problems in dynamics. From the view of the Hamiltonian dynamics, this paper researches the damping formation mechanism and damping injection control of VSG. First, based on the energy composition and dynamic characteristics of VSG, the differential equations system of VSG is established and is transformed into the generalized Hamiltonian system. Second, the effects of the three parameters of VSG, the damping coefficient D, active power droop coefficient, and time constant of excitation TE on damping characteristics are researched from a dynamic perspective, and simulation research is carried out with an isolated microgrid. Lastly, the control design method of Hamiltonian structure corrections used to add the damping factor and design the equivalent control inject damping to improve the stability of the isolated microgrid. Research shows that the voltage and frequency stability of the isolated microgrid can be effectively improved by selecting three key parameters of VSG and damping injection control. The innovations of this paper are 1. The Hamiltonian model of the inverter is deduced and established by taking the inverter as a virtual generator. 2. Based on the Hamiltonian model, damping characteristics of inverter in the microgrid are studied. 3. Hamiltonian structure correction method is applied to the inverter, and equivalent damping injection is designed to improve the stability of the microgrid.
Critical Conditions for the Ignition of a Gel Fuel under Different Heating Schemes
Authors: Gaidukova Olga , Strizhak Pavel
Published: November 2021

A model was developed to research the critical conditions and time characteristics of the ignition of gel fuels in the course of conductive, convective, radiant and mixed heat transfer. MATLAB was used for numerical modeling. Original MATLAB code was established pursuant to the developed mathematical model. For gel fuel ignition at initial temperatures corresponding to cryogenic storage conditions with different heating schemes, a numerical analysis of interconnected processes of heat and mass transfer in the chemical reaction conditions and exothermic and endothermic phase transitions was conducted. The model was tested by comparing the theoretical results with the experimental data. Dependencies were established between the key process characteristic (i.e., the ignition delay time) and the ambient temperature when the following parameters were varied: emissivity, heat emission coefficient, activation energy and pre-exponential factor of the fuel vapor oxidation reaction. The critical values of the main parameters of the energy source were determined. For these values, gel fuel ignition conditions were consistently realized for each heating scheme. The critical heat fluxes necessary and sufficient for the ignition of typical gel fuels were determined.
Business Models for Demand Response: Exploring the Economic Limits for Small- and Medium-Sized Prosumers
Authors: Pressmair Guntram , Amann Christof , Leutgöb Klemens
Published: November 2021

The European energy transition increasingly requires flexibility to ensure reliable operation of the electricity system, making use of demand response, a promising concept. With technological advances in the fields of big data analysis and the internet of things, small- and medium-sized prosumers could also provide flexibility services through aggregators. A lot of conceptual work has been conducted recently to formulate business models in this context, but their viability still remains unclear. In this paper, a quantitative validation is conducted of two business models that are frequently proposed in the scientific discussion. The aim of this work is to explore the economic limits of these business models and show under which conditions they can be profitable for small- and medium-sized prosumers. For this purpose, a multi-level contribution margin calculation for several scenarios, customer segments and target markets is conducted. The results show that the profitability for the participation of small loads is still very low under current market conditions. Especially for household consumers, transaction costs are too high to be covered by the revenues. Considering the quantitative results, in the future profitable business cases can only be expected for medium-sized tertiary consumers.
Possibilities of Using Inland Navigation to Improve Efficiency of Urban and Interurban Freight Transport with the Use of the River Information Services (RIS) System—Case Study
Authors: Durajczyk Piotr , Drop Natalia
Published: November 2021

Inland navigation is hardly ever used to transport cargo in cities. In most urban areas, it is performed almost exclusively via road transport, with the virtual exclusion of rail and inland transport. Research and implementation projects in several European cities have shown that employing inland navigation is a viable alternative for road transport in urban areas. The research involved a case study of transporting the same number of 40-foot containers by inland waterway and road and then comparing the results in terms of transport time, transport costs, and carbon dioxide emissions between two metropolitan areas in Poland. The article shows that River Information Services (RIS) system can contribute to improving freight transport efficiency not only on longer routes, but also in urban and inter-urban conditions. The findings were that inland shipping is much cheaper and more environmentally friendly, but transport takes much longer and is not always possible due to insufficient waterway infrastructure. The paper can be used as a road map to proceed with new approach to planning urban and inter-urban logistics, with the use of inland navigation supported by the RIS system. The study delivers evidence that the main benefits of using RIS for urban logistics are: optimization of the cargo route, improved supervision and control of cargo transport, optimization of inter-branch transport, optimization of the use of fleet, more efficient use of technical infrastructure of waterways, combination of many recipients/senders into one transport, and reduction of administrative barriers.
CO2 Recycling in the Iron and Steel Industry via Power-to-Gas and Oxy-Fuel Combustion
Authors: Perpiñán Jorge , Bailera Manuel , Romeo Luis , Peña Begoña , Eveloy Valerie
Published: November 2021

The iron and steel industry is the largest energy-consuming sector in the world. It is responsible for emitting 4–5% of the total anthropogenic CO2. As an energy-intensive industry, it is essential that the iron and steel sector accomplishes important carbon emission reduction. Carbon capture is one of the most promising alternatives to achieve this aim. Moreover, if carbon utilization via power-to-gas is integrated with carbon capture, there could be a significant increase in the interest of this alternative in the iron and steel sector. This paper presents several simulations to integrate oxy-fuel processes and power-to-gas in a steel plant, and compares gas productions (coke oven gas, blast furnace gas, and blast oxygen furnace gas), energy requirements, and carbon reduction with a base case in order to obtain the technical feasibility of the proposals. Two different power-to-gas technology implementations were selected, together with the oxy blast furnace and the top gas recycling technologies. These integrations are based on three strategies: (i) converting the blast furnace (BF) process into an oxy-fuel process, (ii) recirculating blast furnace gas (BFG) back to the BF itself, and (iii) using a methanation process to generate CH4 and also introduce it to the BF. Applying these improvements to the steel industry, we achieved reductions in CO2 emissions of up to 8%, and reductions in coal fuel consumption of 12.8%. On the basis of the results, we are able to conclude that the energy required to achieve the above emission savings could be as low as 4.9 MJ/kg CO2 for the second implementation. These values highlight the importance of carrying out future research in the implementation of carbon capture and power-to-gas in the industrial sector.
The Morphology and Differentiation of the Content of International Debate on Renewable Energy. A Bibliometric Analysis of Web of Science, Scopus, and Twitter
Authors: Sanak-Kosmowska Katarzyna , Wiktor Jan W.
Published: November 2021

This paper aims to identify a bibliometric profile, presenting the results of research and debates in social media on renewable energy sources (RES). It analyses current scientific publications (2019–2021) and tweets posted in July 2021 by international Twitter users. The subject of the study is an analysis of key words in articles, the results of research, and the content of tweets (hashtags #renewables) related to renewable energy (RE) as well as an assessment of the morphology of content and the degree of its differentiation in the analysed data resources. The conducted analysis facilitates an assessment of similarities of key words in scientific papers and the content of debates in social media—on Twitter, a global platform. In its methodological dimension, the work is based on a bibliometric analysis (articles in both bases) and the analysis of Twitter data. This methodological approach allows for identifying the main trend, profile, and bibliometric characteristics of scientific papers representing two streams of information: articles in bases and the content (hashtags) of authentic and unguided international debates on Twitter. The focus on this platform results from a great popularity of social media as a platform for social debate, expressing comments and opinions and providing an opportunity to gain understanding of social, cultural, and environmental issues related to renewable energy sources from the perspective of social media participants. The objective of the paper and the proposed methodological approach relates to a knowledge gap in the area of renewable energy, and, more specifically, climate change and sustainable development.
Unlocking the UK Continental Shelf Electrification Potential for Offshore Oil and Gas Installations: A Power Grid Architecture Perspective
Authors: Elgenedy Mohamed , Ahmed Khaled , Burt Graeme , Rogerson Graeme , Jones Greg
Published: November 2021

Most of the UK Continental Shelf (UKCS) oil and gas (OG) installations have traditionally adopted in situ power generation, which is not only inefficient but also generating about 70% of the offshore CO2 emissions. The offshore wind and energy storage technologies for deep water are developing at a fast pace, enabling great opportunities for the OG installations located in the North Sea. In this paper, a pathway for the UKCS offshore OG installations electrification is introduced. The aim is to provide different power architectures that facilitate the OG installations’ electrification, while benefiting from the existing and planned UK offshore wind power. Four hypothetical case studies (based on real data) were created, along the UKCS, where the corresponding power architectures were proposed. The selection of each architecture power component (e.g., transformers, converters and cables), as well as the transmission and distribution technology (e.g., AC or DC), is also provided and justified. Further, an overview cost estimation is carried out to predict the architecture capital cost. It is concluded that the four architectures can be mimicked not only along the UKCS but also worldwide, promoting the UKCS potential for a world-leading offshore energy hub and fostering the UK offshore wind-energy resources.
Strategies to Facilitate Photovoltaic Applications in Road Structures for Energy Harvesting
Authors: Dai Yiqing , Yin Yan , Lu Yundi
Published: November 2021

Photovoltaic (PV) facilities are sustainable and promising approaches for energy harvesting, but their applications usually require adequate spaces. Road structures account for a considerable proportion of urban and suburban areas and may be feasible for incorporation with photovoltaic facilities, and thereby have attracted research interests. One solution for such applications is to take advantage of the spare ground in road facilities without traffic load, where the solar panels are mounted as their conventional applications. Such practices have been applied in medians and slopes of roads and open spaces in interchanges. Applications in accessory buildings and facilities including noise/wind barriers, parking lots, and lightings have also been reported. More efforts in existing researches have been paid to PV applications in load-bearing pavement structures, possibly because the pavement structures cover the major area of road structures. Current strategies are encapsulating PV cells by transparent coverings to different substrates to prefabricate modular PV panels in factories for onsite installation. Test road sections with such modular solar panels have been reported, where inferior cost-effectiveness and difficulties in maintenance have been evidenced, suggesting more challenges exist than expected. In order to enhance the power output of the integrated PV facilities, experiences from building-integrated PVs may be helpful, including a selection of proper PV technologies, an optimized inclination of PV panels, and mitigating the operational temperature of PV cells. Novel integrations of amorphous silicon PV cells and glass fiber reinforced polymer profiles are proposed in this research for multi-scenario applications, and their mechanical robustness was evaluated by bending experiments.
Dimensioning Optimization of the Permanent Magnet Synchronous Generator for Direct Drive Wind Turbines
Authors: Santiago Jesús Antonio Enríquez , Danguillecourt Orlando Lastres , Duharte Guillermo Ibáñez , Díaz Jorge Evaristo Conde , Añorve Antonio Verde , Hernandez Escobedo Quetzalcoatl , Enríquez Joel Pantoja , Verea Laura , Galvez Geovanni Hernández , Portela Rafael Dorrego , Perea-Moreno Alberto-Jesus
Published: November 2021

In the present work, a methodology that allows optimizing the permanent magnet synchronous generator (PMSG) design by establishing limit values of magnet radius and length that maximize efficiency for the nominal parameters of the wind turbine is developed. The methodology consists of two fundamental models. One model calculates the generator parameters from the radius of the magnet base, and the other optimization model determines two optimum generators according to the optimization criteria of maximum efficiency and maximum efficiency with minimum weight starting from the axial length and the radius of the magnet base. For the optimization, the numerical method of the golden section was used. The model was validated from a 10 kW PMSG and the results of two optimum generators are presented according to the optimization criteria. In addition, when the obtained results are compared with the reference electric generator, an increase in efficiency of 1.15% and 0.81% and a reduction in weight of 30.79% and 39.15% of the optimized generators are obtained for maximum efficiency and minimum weight, respectively. Intermediate options between the maximum efficiency generator and the minimum weight generator allows for the selection of the optimum dimensioning for the electric generator as a function of the parameters from the wind turbine design.
Effect of Metallic Bipolar Plates Fillet Radii on Fuel Cell Performance
Authors: Hung Chien-Ju , Chen Wei-Jen , Lin Chao-An , Shiu Huan-Ruei , Chen Bin-Hao
Published: November 2021

This paper studies the effects of compression, deformation, and the contact area in the membrane electrode assembly (MEA). The electrical impedance of fuel cell stacks due to the assembly of the metallic bipolar plates is also considered. According to decades-long fuel cell (FC) assembly experience, an increase in compression force can result in adequate contact resistance, but excessive compression may cause extra contact resistance and damage to the MEA structure. The study suggests a design for improving the performance of the FC stack by proposing different fillet radii metallic bipolar plates. It is found that the appropriate fillet radius reduces contact resistance by 13% and avoids the accumulation of compression, thereby maintaining contact resistance at adequate levels. The current design proposes a simple and effective method to minimize the dimension tolerance of single fuel cell units and support sufficient compression.
Hygrothermal and Mechanical Behaviors of Fiber Mortar: Comparative Study between Palm and Hemp Fibers
Authors: Zouaoui Younes , Benmahiddine Ferhat , Yahia Ammar , Belarbi Rafik
Published: November 2021

This paper presents an experimental investigation of the hygrothermal and mechanical properties of innovative mortar mixtures reinforced with natural fibers. Fibers extracted from palm stems (PS) and hemp (HF) were evaluated at different percentages. Scanning electron microscope (SEM) observations showed that the PS fibers have rough surfaces and very complex microstructures. Prior to their incorporation into the mortar, the fibers were subjected to different treatments to reduce their hydrophilic character. The employed treatments showed good efficiency in reducing the water absorption of both PS and HF fiber types. Furthermore, the mortar mixtures incorporating these fibers exhibited low thermal conductivity and excellent moisture buffering capacity. Indeed, the moisture buffer value (MBV) of the investigated mixtures ranged between 2.7 [g/(%HR·m2)] and 3.1 [g/(%HR·m2)], hence providing them excellent moisture regulator character. As expected, the fiber mortar mixtures showed very high porosity and low compressive strength ranging between 0.6 and 0.9 MPa after 28 days of age. The low-environmental footprint materials developed in this study are intended for thermal insulation and building filling.
A Robust Algorithm for Real-Time Phasor and Frequency Estimation under Diverse System Conditions
Authors: Jafarpisheh Babak , Pal Anamitra
Published: November 2021

This paper presents a comprehensive approach for performing phasor and frequency estimation from voltage and/or current signals of the modern power system. Undesirable components, such as decaying DC, if present in the input signal, are first attenuated using a complex-gain filter. The initial estimates of phasor and frequency are obtained next using the discrete Fourier transform and an improved estimation of signal parameters via rotational invariance technique, respectively. Finally, the accuracy of phasor and frequency estimates are increased based on the identified system condition. Simulations performed to evaluate the proposed approach confirm that it can do fast and accurate estimation of phasor and frequency under diverse operating conditions, making it ideal for wide-area monitoring, protection, and control applications in power systems.