bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of ZnO Nanorods Concentration in a Micro-Structured Polymeric Composite for Nanogenerators
Authors: dos Santos Andreia , Sabino Filipe , Rovisco Ana , Barquinha Pedro , Águas Hugo , Fortunato Elvira , Martins Rodrigo , Igreja Rui
Published: January 2021

The growing use of wearable devices has been stimulating research efforts in the development of energy harvesters as more portable and practical energy sources alternatives. The field of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs), especially employing zinc oxide (ZnO) nanowires (NWs), has greatly flourished in recent years. Despite its modest piezoelectric coefficient, ZnO is very attractive due to its sustainable raw materials and the facility to obtain distinct morphologies, which increases its multifunctionality. The integration of ZnO nanostructures into polymeric matrices to overcome their fragility has already been proven to be fruitful, nevertheless, their concentration in the composite should be optimized to maximize the harvesters’ output, an aspect that has not been properly addressed. This work studies a composite with variable concentrations of ZnO nanorods (NRs), grown by microwave radiation assisted hydrothermal synthesis, and polydimethylsiloxane (PDMS). With a 25 wt % ZnO NRs concentration in a composite that was further micro-structured through laser engraving for output enhancement, a nanogenerator (NG) was fabricated with an output of 6 V at a pushing force of 2.3 N. The energy generated by the NG could be stored and later employed to power small electronic devices, ultimately illustrating its potential as an energy harvesting device.
Influence of Multi-Step Heating Methods on Properties of Al–Si Coating Boron Steel Sheet
Authors: Liang Weikang , Duan Jinchang , Wang Qianting , Dong Junhao , Liu Qiong , Lin Chen , Zhang Yisheng
Published: January 2021

In this study, the influence of the multi-step heating methods, such as two-step heating methods and three-step heating methods, on the properties of Al–Si coating boron steel sheet were evaluated by using the Gleeble-3500 thermal simulator. The evolution of microstructure and 3D surface topography of the Al–Si coating were also investigated. The results showed that the heating rates of 50 °C/s, named rapid heating, at the stage of 20–500 °C did not significantly influence the microstructure and 3D surface topography of the Al–Si coating in the two-step heating methods. The results also indicated that the volume fractions of Fe3Al2Si3 intermetallic compound, FeAl intermetallic compound and a-Fe phase in the Al–Si coating reduced by rapid heating at the stage of 700–930 °C in the three-step heating methods. The roughness of 3D surface topography of the Al–Si coating increased by rapid heating at the stage of 700–930 °C. Rapid heating at the stage of 700–930 °C had little influence on the porosity of the Al–Si coating. The results provided a theoretical basis for the popularization and application of rapid heating in the Al–Si coating boron steel sheet.
The Role of the Oxidation and Reduction Parameters on the Properties of the Reduced Graphene Oxide
Authors: Sieradzka Marta , Ślusarczyk Czesław , Biniaś Włodzimierz , Fryczkowski Ryszard
Published: January 2021

One of the methods of obtaining reduced graphene oxide (rGO) involves the oxidation of graphite to graphene oxide, which is then exfoliated and reduced. Each of these stages has a decisive influence on the properties of the produced nanoadditive, which determines its subsequent application. The process conditions which are examined during the oxidation stage are related to: The mixing time of the reactants before oxidation, sonication of the reaction mixture, and its composition. During reduction optimization, in turn, the form of the GO sample and the method of its purification, as well as the temperature at which this process took place, are examined. At each stage, the determined structural parameters of the produced materials (GO and rGO) are related to their morphology (SEM—scanning electron microscope), oxidation state (FTIR—Fourier transform infrared spectroscopy, EDS—energy-dispersive spectrometer), structure defect (Raman spectroscopy), as well as the number of layers and crystalline structure (WAXS—wide-angle X-ray scattering). The obtained results show that the shorter mixing time of the reactants determines the formation of more oxygen functional groups. On the basis of the obtained results, the process conditions that enable the production of multilayer, well-exfoliated reduced graphene oxide, with only a slightly defected structure, are established.
A Cosmetic Perspective on the Antioxidant Flavonoids from Nymphaea lotus L.
Authors: Tungmunnithum Duangjai , Kongsawadworakul Panida , Hano Christophe
Published: January 2021

Nymphaea lotus L. or water lily is a well-known traditional medicinal plant in Thailand, Indonesia, Vietnam, India, Sri Lanka, China, Nepal, Egypt and many African countries. This species has been reported as a promising flavonoid-rich raw material that can be used as an active ingredient for the development of cosmetic/cosmeceutical products. This review aims to illustrate the cosmetic potential of this species by providing botanical information, traditional uses, flavonoid accumulation, biological activities and future research challenges in the production of N. lotus extracts for cosmetic applications.
Acknowledgment to Reviewers of Cryptography in 2020
Authors:   Cryptography Editorial Office
Published: January 2021

Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that Cryptography maintains its standards for the high quality of its published papers [...]
Impact Response of Preplaced Aggregate Fibrous Concrete Hammerhead Pier Beam Designed with Topology Optimization
Authors: Salaimanimagudam Meivazhisalai Parasuraman , Murali Gunasekaran , Vardhan C. M. Vivek , Amran Mugahed , Vatin Nikolai , Fediuk Roman , Vasilev Yuriy
Published: January 2021

This research aimed to study the impact response of topology optimized hammerhead pier beam (HPB) based on the density approach. The HPB is prepared with the concept of preplaced aggregate fibrous concrete (PAFC) comprising two primary approaches; first, the coarse aggregate and fiber are prepacked into the designed formwork. Second, the gaps between the aggregate and fiber are filled with cement grout. In this work, an attempt has been made to study an impact response of HPB made with PAFC. Five HPBs were prepared and strengthened with steel fibers with two different schemes, Firstly, the HPB was reinforced with a full cross-section at 2 and 4% of steel fiber, while another set of beams were only reinforced in the tension zone with the same amount of fibers. The study parameters included compressive strength, impact strength, impact ductility index, number of main and secondary cracks, and failure pattern. It was observed that the PAFC had an increase in compressive strength up to 56.9%, compared with nonfibred concrete. A fully fibered concrete beam with 4% fiber addition was the best at taking impact, and the initial crack and failures were observed at 2725.1 J and 3009.8 J, respectively, compared with non-fibered and tension zone fibered concrete beams. Compressive local damage and transverse flexural cracks were observed, which had caused initial cracks and final failure. The HPB with a full reinforced scheme at 4% dosage exhibited higher impact strength than the normal concrete and beam reinforced only in the tension zone.
Rationale and Design of BeatNF2 Trial: A Clinical Trial to Assess the Efficacy and Safety of Bevacizumab in Patients with Neurofibromatosis Type 2 Related Vestibular Schwannoma
Authors: Fujii Masazumi , Kobayakawa Masao , Saito Kiyoshi , Inano Akihiro , Morita Akio , Hasegawa Mitsuhiro , Mukasa Akitake , Mitsuhara Takafumi , Goto Takeo , Yamaguchi Shigeru , Tamiya Takashi , Nakatomi Hirofumi , Oya Soichi , Takahashi Fumiaki , Sato Taku , Bakhit Mudathir ,   on behalf of the BeatNF2 Trial Investigators
Published: January 2021

Neurofibromatosis type 2 (NF2) causes bilateral vestibular schwannomas (VSs), leading to deafness. VS is treated by surgery or radiation, but neither treatments prevent hearing loss. Bevacizumab was found to be effective in suppressing the tumor’s growth and may help to improve hearing. We are conducting a randomized, double-blind, multicenter clinical trial to verify the efficacy and safety of bevacizumab in NF2-related VS. The primary objective is to evaluate the efficacy of bevacizumab in improving hearing in the affected ear. One of the secondary objectives is to evaluate bevacizumab’s efficacy in rechallenge treatment in relapsed cases. Sixty patients will randomly receive either bevacizumab or a placebo and will be clinically observed for 48 weeks in the initial intervention phase. In the first half (24 weeks), they will receive either 5 mg/kg of bevacizumab or a placebo drug. In the second half, all patients will receive 5 mg/kg of bevacizumab. If hearing function deteriorated in a patient who had shown improvement during the first phase, a rechallenge dose with bevacizumab would be offered.
The Perioperatively Altered Neutrophil-to-Lymphocyte Ratio Associates with Impaired DNA Damage Response in Liver Transplantation Recipients with Hepatocellular Carcinoma
Authors: Chen Kuang-Den , Hsu Chien-Ning , Wu Yi-Ju , Chu Chi-Hsiang , Huang Kuang-Tzu , Tsai Ming-Chao , Chiu King-Wah , Cheng Ben-Chung , Chiu Chien-Hua , Chen Chao-Long , Lin Chih-Che
Published: January 2021

Increasing evidence has suggested that elevated systemic inflammation with a high neutrophil-lymphocyte ratio (NLR) is associated with poor prognosis after liver transplantation (LT). The ongoing molecular events involved in poor survival remain unclear. This retrospective study evaluated LT recipients whose data was collected at Kaohsiung Chang Gung Memorial Hospital between 2005 and 2014. Clinical records of 347 patients with hepatocellular carcinoma from seven days before LT to 30 days after LT illustrated that longitudinal values of lymphocytes, RBC, and hemoglobin were persistently low in patients with peritransplant high NLR (PTH-NLR, pre-LT ≥ 4 and post-LT ≥ 5), which indicated a significantly worse survival rate in association with increased RDW-CV and pancytopenia when compared to other patients (p = 0.008). We further found that PTH-NLR patients had decreased DNA damage response (DDR) genes and detoxifying enzymes of ADH and ALDH families, and increased mitochondrial stress response genes in their liver tissues. Reduced lineage markers of liver progenitor cells were also observed in PTH-NLR patients signifying the presence of unresolved impairments after LT. Our results demonstrate the association between hematopoietic deficiencies and lack of protection against DDR with PTH-NLR in LDLT recipients with HCC and may imply abnormal hematological and organismal defects in those patients.
PET-Based Volumetric Biomarkers for Risk Stratification of Non-Small Cell Lung Cancer Patients
Authors: Pellegrino Sara , Fonti Rosa , Pulcrano Alessandro , Del Vecchio Silvana
Published: January 2021

Despite the recent advances in lung cancer biology, molecular pathology, and treatment, this malignancy remains the leading cause of cancer-related death worldwide and non-small cell lung cancer (NSCLC) is the most common form found at diagnosis. Accurate staging of the disease is a fundamental prognostic factor that correctly predicts progression-free (PFS) and overall survival (OS) of NSCLC patients. However, outcome of patients within each TNM staging group can change widely highlighting the need to identify additional prognostic biomarkers to better stratify patients on the basis of risk. 18F-FDG PET/CT plays an essential role in staging, evaluation of treatment response, and tumoral target delineation in NSCLC patients. Moreover, a number of studies showed the prognostic role of imaging parameters derived from PET images, such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG). These parameters represent three-dimensional PET-based measurements providing information on both tumor volume and metabolic activity and previous studies reported their ability to predict OS and PFS of NSCLC patients. This review will primarily focus on the studies that showed the prognostic and predictive role of MTV and TLG in NSCLC patients, addressing also their potential utility in the new era of immunotherapy of NSCLC.
Quantum Hacking on an Integrated Continuous-Variable Quantum Key Distribution System via Power Analysis
Authors: Zheng Yi , Shi Haobin , Pan Wei , Wang Quantao , Mao Jiahui
Published: January 2021

In quantum key distribution (QKD), there are some security loopholes opened by the gaps between the theoretical model and the practical system, and they may be exploited by eavesdroppers (Eve) to obtain secret key information without being detected. This is an effective quantum hacking strategy that seriously threatens the security of practical QKD systems. In this paper, we propose a new quantum hacking attack on an integrated silicon photonic continuous-variable quantum key distribution (CVQKD) system, which is known as a power analysis attack. This attack can be implemented by analyzing the power originating from the integrated electrical control circuit in state preparation with the help of machine learning, where the state preparation is assumed to be perfect in initial security proofs. Specifically, we describe a possible power model and show a complete attack based on a support vector regression (SVR) algorithm. The simulation results show that the secret key information decreases with the increase of the accuracy of the attack, especially in a situation with less excess noise. In particular, Eve does not have to intrude into the transmitter chip (Alice), and may perform a similar attack in practical chip-based discrete-variable quantum key distribution (DVQKD) systems. To resist this attack, the electrical control circuit should be improved to randomize the corresponding power. In addition, the power can be reduced by utilizing the dynamic voltage and frequency scaling (DVFS) technology.
A Time-Symmetric Formulation of Quantum Entanglement
Authors: Heaney Michael B.
Published: January 2021

I numerically simulate and compare the entanglement of two quanta using the conventional formulation of quantum mechanics and a time-symmetric formulation that has no collapse postulate. The experimental predictions of the two formulations are identical, but the entanglement predictions are significantly different. The time-symmetric formulation reveals an experimentally testable discrepancy in the original quantum analysis of the Hanbury Brown–Twiss experiment, suggests solutions to some parts of the nonlocality and measurement problems, fixes known time asymmetries in the conventional formulation, and answers Bell’s question “How do you convert an ’and’ into an ’or’?”
Using the Quantum Potential in Elementary Portfolio Management: Some Initial Ideas
Authors: Khaksar Hossein , Haven Emmanuel , Nasiri Sina , Jafari Gholamreza
Published: January 2021

Owing to the globalization of the economy, the concept of entangled markets started to form, and this occurrence has smoothed the entrance of quantum mechanics into behavioral finance. In this manuscript, we introduce quantum risk and perform an analysis on portfolio optimization by controlling the quantum potential. We apply this method to eight major indices and construct a portfolio with a minimum quantum risk. The results show quantum risk has a power law behavior with a time-scale just as a standard deviation with different exponents.
Survival of Virus Particles in Water Droplets: Hydrophobic Forces and Landauer’s Principle
Authors: Bormashenko Edward , Fedorets Alexander A. , Dombrovsky Leonid A. , Nosonovsky Michael
Published: January 2021

Many small biological objects, such as viruses, survive in a water environment and cannot remain active in dry air without condensation of water vapor. From a physical point of view, these objects belong to the mesoscale, where small thermal fluctuations with the characteristic kinetic energy of kBT (where kB is the Boltzmann’s constant and T is the absolute temperature) play a significant role. The self-assembly of viruses, including protein folding and the formation of a protein capsid and lipid bilayer membrane, is controlled by hydrophobic forces (i.e., the repulsing forces between hydrophobic particles and regions of molecules) in a water environment. Hydrophobic forces are entropic, and they are driven by a system’s tendency to attain the maximum disordered state. On the other hand, in information systems, entropic forces are responsible for erasing information, if the energy barrier between two states of a switch is on the order of kBT, which is referred to as Landauer’s principle. We treated hydrophobic interactions responsible for the self-assembly of viruses as an information-processing mechanism. We further showed a similarity of these submicron-scale processes with the self-assembly in colloidal crystals, droplet clusters, and liquid marbles.
Malicious URL Detection Based on Associative Classification
Authors: Kumi Sandra , Lim ChaeHo , Lee Sang-Gon
Published: January 2021

Cybercriminals use malicious URLs as distribution channels to propagate malware over the web. Attackers exploit vulnerabilities in browsers to install malware to have access to the victim’s computer remotely. The purpose of most malware is to gain access to a network, ex-filtrate sensitive information, and secretly monitor targeted computer systems. In this paper, a data mining approach known as classification based on association (CBA) to detect malicious URLs using URL and webpage content features is presented. The CBA algorithm uses a training dataset of URLs as historical data to discover association rules to build an accurate classifier. The experimental results show that CBA gives comparable performance against benchmark classification algorithms, achieving 95.8% accuracy with low false positive and negative rates.
Elliptic Solutions of Dynamical Lucas Sequences
Authors: Schlosser Michael J. , Yoo Meesue
Published: January 2021

We study two types of dynamical extensions of Lucas sequences and give elliptic solutions for them. The first type concerns a level-dependent (or discrete time-dependent) version involving commuting variables. We show that a nice solution for this system is given by elliptic numbers. The second type involves a non-commutative version of Lucas sequences which defines the non-commutative (or abstract) Fibonacci polynomials introduced by Johann Cigler. If the non-commuting variables are specialized to be elliptic-commuting variables the abstract Fibonacci polynomials become non-commutative elliptic Fibonacci polynomials. Some properties we derive for these include their explicit expansion in terms of normalized monomials and a non-commutative elliptic Euler–Cassini identity.
Mapping Susceptibility to Debris Flows Triggered by Tropical Storms: A Case Study of the San Vicente Volcano Area (El Salvador, CA)
Authors: Mercurio Claudio , Martinello Chiara , Rotigliano Edoardo , Argueta-Platero Abel Alexei , Reyes-Martínez Mario Ernesto , Rivera-Ayala Jacqueline Yamileth , Conoscenti Christian
Published: January 2021

In this study, an inventory of storm-triggered debris flows performed in the area of the San Vicente volcano (El Salvador, CA) was used to calibrate predictive models and prepare a landslide susceptibility map. The storm event struck the area in November 2009 as the result of the simultaneous action of low-pressure system 96E and Hurricane Ida. Multivariate Adaptive Regression Splines (MARS) was employed to model the relationships between a set of environmental variables and the locations of the debris flows. Validation of the models was performed by splitting 100 random samples of event and non-event 10 m pixels into training and test subsets. The validation results revealed an excellent (area under the receiver operating characteristic (ROC) curve (AUC) = 0.80) and stable (AUC std. dev. = 0.01) ability of MARS to predict the locations of the debris flows which occurred in the study area. However, when using the Youden’s index as probability threshold to discriminate between pixels predicted as positives and negatives, MARS exhibits a moderate ability to identify stable cells (specificity = 0.66). The final debris flow susceptibility map, which was prepared by averaging for each pixel the score of the 100 MARS repetitions, shows where future debris flows are more likely to occur, and thus may help in mitigating the risk associated with these landslides.
Battery Stress Factor Ranking for Accelerated Degradation Test Planning Using Machine Learning
Authors: Saxena Saurabh , Roman Darius , Robu Valentin , Flynn David , Pecht Michael
Published: January 2021

Lithium-ion batteries power numerous systems from consumer electronics to electric vehicles, and thus undergo qualification testing for degradation assessment prior to deployment. Qualification testing involves repeated charge–discharge operation of the batteries, which can take more than three months if subjected to 500 cycles at a C-rate of 0.5C. Accelerated degradation testing can be used to reduce extensive test time, but its application requires a careful selection of stress factors. To address this challenge, this study identifies and ranks stress factors in terms of their effects on battery degradation (capacity fade) using half-fractional design of experiments and machine learning. Two case studies are presented involving 96 lithium-ion batteries from two different manufacturers, tested under five different stress factors. Results show that neither the individual (main) effects nor the two-way interaction effects of charge C-rate and depth of discharge rank in the top three significant stress factors for the capacity fade in lithium-ion batteries, while temperature in the form of either individual or interaction effect provides the maximum acceleration.
Optimization of Powertrain in EV
Authors: Sieklucki Grzegorz
Published: January 2021

The method for preliminary powertrain design is presented in the paper. Performance of the EV is realized by motor torque–speed curve and gear ratio optimization. The typical two-zone mechanical characteristic of a PMSM traction motor is included in the optimization program. The longitudinal vehicle model is considered in the paper. Some examples try to show the calculation possibilities in application to existing vehicles: Tesla Model S and Mini Cooper SE.
Some Aspects of the Modelling of Thin-Layer Drying of Sawdust
Authors: Bryś Andrzej , Kaleta Agnieszka , Górnicki Krzysztof , Głowacki Szymon , Tulej Weronika , Bryś Joanna , Wichowski Piotr
Published: January 2021

Drying of spruce, beech, willow, and alder sawdust was examined in a laboratory type dryer. The effect of drying air temperature T (25, 60, and 80 °C) and airflow velocity v (0.01, 0.15, and 1.5 m/s) was investigated. The obtained results demonstrated that drying air temperature and airflow velocity have impacts on the drying of sawdust. The experimental dehydration data of sawdust obtained were fitted to theoretical, semi-theoretical, and empirical thin-layer models. The accuracies of the models were estimated using the correlation coefficient (R), root mean square error (RMSE), and reduced chi-square (χ2). All models except the theoretical model of a sphere described the drying characteristics of sawdust satisfactorily. The effect of T and v on the parameters (constants and coefficients) of the drying models were determined. The effect, by the proposed equations, was also described. This work combines aspects of mechanical engineering and modelling of the drying process.
Economic Evaluation of PV Installations for Self-Consumption in Industrial Parks
Authors: Pedrero Juan , Hernández Patxi , Martínez Álvaro
Published: January 2021

This paper presents an analysis of the economic performance of photovoltaic (PV) self-consumption systems at an industrial park in the Basque Country (north of Spain). The economic feasibility of the installations is largely dependent on self-consumption and compensation due to electricity injected into the grid, as well as the assumed evolution of the electricity prices. A sensitivity analysis is carried out for different installation sizes and different evolution scenarios concerning electricity prices. The potential for installations for shared self-consumption with dynamic and static distribution coefficients is also analyzed. The results show that medium sized installations are generally a cost effective way to reduce energy bills, while the economic performance of larger installations is more uncertain, and is largely dependent on the selling price for electricity injected into the grid. This case study found that the economic benefits of shared self-consumption between different companies are substantial, and are slightly more favorable when applying dynamic distribution factors.
Role of Monovalent and Divalent Ions in Low-Salinity Water Flood in Carbonate Reservoirs: An Integrated Analysis through Zeta Potentiometric and Simulation Studies
Authors: Gopani Paras H. , Singh Navpreet , Sarma Hemanta K. , Mattey Padmaja , Srivastava Vivek R.
Published: January 2021

The presence of principal ions in the water injected is essential for enhanced oil recovery by formation of water-wet state in carbonates. This study reaffirms this and presents an evaluation of the positive influence of both divalent as wells as monovalent ions on wettability alteration mechanisms during low salinity waterflooding using brines of varying ionic composition, referred to as “smart brines”. Zeta potentiometric analysis and reservoir simulation studies were conducted with diluted and smart brines that were prepared by varying the composition of principal ions. Surface charge of oil-saturated whole core samples of rock in the presence of various diluted and smart brines was estimated by zeta potential measurements. A comprehensive analysis of zeta potentiometric and reservoir simulation studies was done to establish and investigate the linkage between the recovery mechanism and the incremental recovery achieved. It is noted that zeta potential increases with the increasing level of dilution and it can be attributed to electric double-layer mechanism. On the contrary, simulation studies implied a different mechanism where an increase in effluent’s pH and Ca2+ mole fraction along with decrease in moles of minerals and saturation index implied rock dissolution was dominant mechanism. Moreover, the effect of mineral dissolution beyond the injection block is highly doubtful. This study demonstrates that an integrated approach from both zeta potentiometric and simulation studies can be used to provide insights into the underlying science of interactions at pore scale during a low salinity waterflood using smart brines. With the aid of an adequately designed upscaling procedure and protocol, the laboratory results can be further used towards developing field-scale models to obtain with realistic recovery factors with optimized brine composition and salinity.
CFD Analysis of Turbulent Flow of Power-Law Fluid in a Partially Blocked Eccentric Annulus
Authors: Singh Ravi , Ahmed Ramadan , Karami Hamidreza , Nasser Mustafa , Hussein Ibnelwaleed
Published: January 2021

This study focuses on analyzing the turbulent flow of drilling fluid in inclined wells using the Computational Fluid Dynamics (CFD) technique. The analysis is performed considering an annulus with a fixed eccentricity of 90% and varying fluid properties, diameter ratio, and bed thickness to examine velocity profile, pressure loss, and overall wall and average bed shear stresses. CFD simulation results are compared with existing data for validation. The pressure loss predicted with CFD agrees with the data. After verification, predictions are used to establish a correlation that can be applied to compute bed shear stress. The established correlation mostly displays a discrepancy of up to 10% when compared with simulation data. The correlation can be used to optimize hole cleaning and manage downhole pressure.
Environmental Vulnerability in Pre-Salt Oil and Gas Operations
Authors: Mein Tatiana Farane , Gimenes André Luiz Veiga , Dias Eduardo Mario , Rebello Pinho Dias Scoton Maria Lídia , Udaeta Miguel Edgar Morales
Published: January 2021

The objective of this work is to analyze disturbances in the environment caused by anthropic activities in the oil and gas extraction sector. Methodologically, focusing on environmental vulnerability (EV), hydrocarbons (oil and gas) are considered through a qualitative and quantitative analysis of environmental impacts, including the research of Environmental Impact Studies and procedures like EIA/RIMA (institutional Environmental Impact Reports in Brazil). This study focuses on the operation and demobilization of the offshore drilling activity and the installation and operation of the Santos Basin pre-salt oil and gas production (Stages 1, 2, and 3). The criteria addressed in the EIA/RIMAs are used, focusing on those that correlate with EV and oil and gas extraction. Impacts for long-term, permanent, partially reversible, or irreversible disturbances are filtered, totaling 53 impacts (31 effective/21 potential). We concluded that the criteria and methodologies of EIAs vary between stages. At times, the variation is so drastic that the same impact can have a completely different rating from one stage to another, despite referring to the same area. This condition makes it impossible to define a single vulnerability index for the pre-salt venture. This work does not offer a concrete resolution, but exposes the EV issue and its inconsistencies.
A Thermal-Hydraulic Model for the Stagnation of Solar Thermal Systems with Flat-Plate Collector Arrays
Authors: Eismann Ralph , Hummel Sebastian , Giovannetti Federico
Published: January 2021

Stagnation is the transient state of a solar thermal system under high solar irradiation where the useful solar gain is zero. Both flat-plate collectors with selective absorber coatings and vacuum-tube collectors exhibit stagnation temperatures far above the saturation temperature of the glycol-based heat carriers within the range of typical system pressures. Therefore, stagnation is always associated with vaporization and propagation of vapor into the pipes of the solar circuit. It is therefore essential to design the system in such a way that vapor never reaches components that cannot withstand high temperatures. In this article, a thermal-hydraulic model based on the integral form of a two-phase mixture model and a drift-flux correlation is presented. The model is applicable to solar thermal flat-plate collectors with meander-shaped absorber tubes and selective absorber coatings. Experimental data from stagnation experiments on two systems, which are identical except for the optical properties of the absorber coating, allowed comparison with simulations carried out under the same boundary conditions. The absorber of one system features a conventional highly selective coating, while the absorber of the other system features a thermochromic coating, which exhibits a significantly lower stagnation temperature. Comparison of simulation results and experimental data shows good conformity. This model is implemented into an open-source software tool called THD for the thermal-hydraulic dimensioning of solar systems. The latest version of THD, updated by the results of this article, enables planners to achieve cost-optimal design of solar thermal systems and to ensure failsafe operation by predicting the steam range under the initial and boundary conditions of worst-case scenarios.
Research on the Power Distribution Method for Hybrid Power System in the Fuel Cell Vehicle
Authors: He Yao , Miao Changchang , Wu Ji , Zheng Xinxin , Liu Xintian , Liu Xingtao , Han Feng
Published: January 2021

The power distribution strategy of hybrid power sources is an important issue for fuel cell vehicles. A good power distribution control strategy can realize the optimal control of the vehicle energy, which can save energy and improve the operating conditions of the power source. Therefore, this article proposes a power distribution strategy. First, in order to solve the problems existing in the existing fuel cell model and the lithium-ion battery model, an improved hybrid power system model with better dynamic performance was established in the Simulink. Second, in order to ensure the durability of the power system, operation constraints are added to the distribution strategy. Finally, the power allocation is regarded as a nonlinear programming optimization problem and solved by a nonlinear programming algorithm. The nonlinear programming algorithm selects the BFGS algorithm. The simulation results of other control strategies in MATLAB show that the proposed power distribution strategy greatly improves the durability of the vehicle and has good adaptability under urban conditions. This distribution method can provide support for the actual application of offline control strategies.
Optimal Management of Mobile Battery Energy Storage as a Self-Driving, Self-Powered and Movable Charging Station to Promote Electric Vehicle Adoption
Authors: Saboori Hedayat , Jadid Shahram , Savaghebi Mehdi
Published: January 2021

The high share of electric vehicles (EVs) in the transportation sector is one of the main pillars of sustainable development. Availability of a suitable charging infrastructure and an affordable electricity cost for battery charging are the main factors affecting the increased adoption of EVs. The installation location of fixed charging stations (FCSs) may not be completely compatible with the changing pattern of EV accumulation. Besides, their power withdrawal location in the network is fixed, and also, the time of receiving the power follows the EVs’ charging demand. The EV charging demand pattern conflicts with the network peak period and causes several technical challenges besides high electricity prices for charging. A mobile battery energy storage (MBES) equipped with charging piles can constitute a mobile charging station (MCS). The MCS has the potential to target the challenges mentioned above through a spatio-temporal transfer in the required energy for EV charging. Accordingly, in this paper, a new method for modeling and optimal management of mobile charging stations in power distribution networks in the presence of fixed stations is presented. The MCS is powered through its internal battery utilizing a self-powered mechanism. Besides, it employs a self-driving mechanism for lowering transportation costs. The MCS battery can receive the required energy at a different time and location regarding EVs accumulation and charging demand pattern. In other words, the mobile station will be charged at the most appropriate location and time by moving between the network buses. The stored energy will then be used to charge the EVs in the fixed stations’ vicinity at peak EV charging periods. In this way, the energy required for EV charging will be stored during off-peak periods, without stress on the network and at the lowest cost. Implementing the proposed method on a test case demonstrates its benefits for both EV owners and network operator.
A Methodology for Provision of Frequency Stability in Operation Planning of Low Inertia Power Systems
Authors: Kosmecki Michał , Rink Robert , Wakszyńska Anna , Ciavarella Roberto , Di Somma Marialaura , Papadimitriou Christina N. , Efthymiou Venizelos , Graditi Giorgio
Published: January 2021

Along with the increasing share of non-synchronous power sources, the inertia of power systems is being reduced, which can give rise to frequency containment problems should an outage of a generator or a power infeed happen. Low system inertia is eventually unavoidable, thus power system operators need to be prepared for this condition. This paper addresses the problem of low inertia in the power system from two different perspectives. At a system level, it proposes an operation planning methodology, which utilises a combination of power flow and dynamic simulation for calculation of existing inertia and, if need be, synthetic inertia (SI) to fulfil the security criterion of adequate rate of change of frequency (RoCoF). On a device level, it introduces a new concept for active power controller, which can be applied virtually to any power source with sufficient response time to create synthetic inertia. The methodology is demonstrated for a 24 h planning period, for which it proves to be effective. The performance of SI controller activated in a battery energy storage system (BESS) is positively validated using a real-time digital simulator (RTDS). Both proposals can effectively contribute to facilitating the operation of low inertia power systems.
Citizen Participation to Finance PV Power Plants Focused on Self-Consumption on Company Roofs—Findings from an Austrian Case Study
Authors: Linhart Matthias , Rodin Valerie , Moser Simon , Kollmann Andrea
Published: January 2021

Despite large amounts of available roof space, long pay-back periods for investments in photovoltaic (PV) power plants often hinder PV installations in industrial parks. Photovoltaic citizen participation initiatives (PV-CPI) are an alternative way of financing PV power plants that add non-financial benefits to these investments. This paper analyzed the feasibility of the installation of PV power plants focused on high rates of self-consumption financed by citizen participation initiatives on the roofs of five companies located in the Austrian Ennshafen industrial business park based on the net present value and the discounted pay-back period and compared it to a standard financing scheme, assuming a predetermined interest rate for participants as well as economies of scale with respect to the specific installation costs due to a joint purchase of the PV power plants. To calculate the feasibility, site-specific data and literature input have been used. The results show that despite an interest rate above the current interest rates of conservative forms of investments provided to (small-scale) investors, a payback-period of 17–23 years can be reached while the joint purchase can lead to a competitive feasibility of the PV-CPI compared to an individual purchase of PV power plants.
Application the SBAS/EGNOS Corrections in UAV Positioning
Authors: Krasuski Kamil , Wierzbicki Damian
Published: January 2021

The paper presents a new concept of determining the resultant position of a UAV (Unmanned Aerial Vehicle) based on individual SBAS (Satellite-Based Augmentation System) determinations from all available EGNOS (European Geostationary Navigation Overlay Service) satellites for the SPP (Single Point Positioning) code method. To achieve this, the authors propose a weighted mean model to integrate EGNOS data. The weighted model was based on the inverse of the square of the mean position error along the component axes of the BLh ellipsoidal frame. The calculations included navigation data from the EGNOS S123, S126, S136 satellites. In turn, the resultant UAV position model was determined using the Scilab v.6.0.0 software. Based on the proposed computational strategy, the mean values of the UAV BLh coordinates’ standard deviation were better than 0.2 m (e.g., 0.0000018° = 0.01″ in angular measurement). Additionally, the numerical solution used made it possible to increase the UAV’s position accuracy by about 29% for Latitude, 46% for Longitude and 72% for ellipsoidal height compared to the standard SPP positioning in the GPS receiver. It is also worth noting that the standard deviation of the UAV position calculated from the weighted mean model improved by about 21 ÷ 50% compared to the arithmetic mean model’s solution. It can be concluded that the proposed research method allows for a significant improvement in the accuracy of UAV positioning with the use of EGNOS augmentation systems.
Energy Performance Optimization of a House with Grid-Connected Rooftop PV Installation and Air Source Heat Pump
Authors: Stamatellos George , Zogou Olympia , Stamatelos Anastassios
Published: January 2021

The use of air source heat pump systems for space heating and cooling is a convenient retrofitting strategy for reducing building energy costs. This can be combined with the rooftop installation of photovoltaic panels, which can cover, to a significant degree—or even significantly exceed the building’s electricity needs, moving towards the zero energy building concept. Alternatively, increased capacity for rooftop photovoltaic (PV) installation may support the ongoing process of transforming the Greek power system away from the reliance on fossil fuels to potentially become one of the leaders of the energy transition in Europe by 2030. Standard building energy simulation tools allow good assessment of the Heating, Ventilation and Air Conditioning (HVAC) and PV systems’ interactions in transient operation. Further, their use enables the rational sizing and selection of the type of panels type for the rooftop PV installation to maximize the return on investment. The annual performance of a three-zone residential building in Volos, Greece, with an air-to-water heat pump HVAC system and a rooftop PV installation, are simulated in a TRNSYS environment. The simulation results are employed to assess the expected building energy performance with a high performance, inverter driven heat pump with scroll compressor and high efficiency rooftop PV panels. Further, the objective functions are developed for the optimization of the installed PV panels’ area and tilt angle, based on alternative electricity pricing and subsidies. The methodology presented can be adapted to optimize system design parameters for variable electricity tariffs and improve net metering policies.
Discounting for Energy Transition Policies—Estimation of the Social Discount Rate for Poland
Authors: Foltyn-Zarychta Monika , Buła Rafał , Pera Krystian
Published: January 2021

The transition of the energy system in Poland has a long time horizon and demands a substantial investment effort supported by proper economic evaluation. It requires a precise Social Discount Rate (SDR) estimation as discounting makes the present value of long-term effects extremely sensitive to the discount rate level. However, Polish policymakers have little information on SDR: the predominant practice applies a priori fixed 5% discount rate, while studies devoted only to Poland are quite rare. To eliminate this research gap, our paper aims at estimating SDR for Poland, applicable in energy transition policies. We derive SDR for three datasets varying in length, twofold: using market rates via Consumption Rate of Interest (CRI) and Social Opportunity Cost (SOC) of capital, and prescriptive Ramsey and Gollier approaches based on Social Welfare Function (SWF). The results indicate that the rates based on CRI and SOC deviate substantially with changing data timeframes and market conditions, while prescriptive methods show much higher time stability. Due to long-term planning horizons for energy policies, we argue for adopting, as SDR in Poland, the longest dataset’s Ramsey-based rate of 4.72% which can be reduced to 4.39% by Gollier’s precautionary term (reflecting the uncertainty over future consumption growth), which are our main findings.
On the Sizing of the DC-Link Capacitor to Increase the Power Transfer in a Series-Series Inductive Resonant Wireless Charging Station
Authors: Carloni Andrea , Baronti Federico , Di Rienzo Roberto , Roncella Roberto , Saletti Roberto
Published: January 2021

Wireless inductive-coupled power transfer is a very appealing technique for the battery recharge of autonomous devices like surveillance drones. The charger design mainly focuses on lightness and fast-charging to improve the drone mission times and reduce the no-flight gaps. The charger secondary circuit mounted on the drone generally consists of a full-bridge rectifier and a second-order filter. The filter cut-off frequency is usually chosen to make the rectifier output voltage constant and so that the battery is charged with continuous quantities. Previous works showed that an increase in power transfer is achieved, if compared to the traditional case, when the second-order filter resonant frequency is close to the double of the wireless charger excitation and the filter works in resonance. This work demonstrates that the condition of resonance is necessary but not sufficient to achieve the power increment. The bridge rectifier diodes must work in discontinuous-mode to improve the power transfer. The paper also investigates the dependence of the power transfer increase on the wireless excitation frequency. It is found the minimum frequency value below which the power transfer gain is not possible. This frequency transition point is calculated, and it is shown that the gain in power transfer is obtained for any battery when its equivalent circuit parameters are known. LTSpice simulations demonstrate that the transferred power can be incremented of around 30%, if compared to the case in which the rectifier works in continuous mode. This achievement is obtained by following the design recommendations proposed at the end of the paper, which trade off the gain in power transfer and the amplitude of the oscillating components of the wireless charger output.
Aerodynamic Analysis of a Wind-Turbine Rotor Affected by Pitch Unbalance
Authors: Castellani Francesco , Eltayesh Abdelgalil , Becchetti Matteo , Segalini Antonio
Published: January 2021

The aerodynamics of a rotor with pitch imbalance has been investigated experimentally and numerically in the present work. The comparison of mean velocity and turbulence intensity in the balanced and unbalanced cases indicated that a pitch imbalance modifies both the mean velocity and the turbulent activity; the latter is weakly increased by the imbalance. Spectral analysis indicated that the dynamics of the wake is also affected by the pitch imbalance since the tip vortices loose strength and disorganise more quickly than in the balanced case. The pitch imbalance has, however, a detrimental effect on the power coefficient and it affects the thrust coefficient as well. Only the blade affected by the imbalance shows significant modifications of the applied load, while the other blades operate with the same loading conditions.
Relating Hydro-Meteorological Variables to Water Table in an Unconfined Aquifer via Fuzzy Linear Regression
Authors: Papadopoulos Christopher , Spiliotis Mike , Gkiougkis Ioannis , Pliakas Fotios , Papadopoulos Basil
Published: January 2021

This study aims to assess the short-term response of groundwater to the main hydro-meteorological variables of drought in a coastal unconfined aquifer. For this purpose, a multiple fuzzy linear regression-based methodology is implemented in order to relate rainfall, streamflow and the potential evapotranspiration to groundwater. Fuzzy regression analysis is recommended when there is a lack of data. The uncertainty of the system is incorporated into the regression coefficients which, in this study, are considered to be fuzzy symmetrical triangular numbers. Two objective functions are used producing a fuzzy band in which all the observed data must be included. The first objective function, based on Tanaka’s model, minimizes the total width of the produced fuzzy band. The second one includes the first while additionally minimizing the distance between the central value of the fuzzy output of the model and the observed value. Validity of the model is checked through suitability measures. The present methodology is applied at the east part of the Nestos River Delta in the Prefecture of Xanthi (Greece), where the observed values of the depth of groundwater level of four wells are examined.