bluuebunny/crossref_metadata_2025 huggingface dataset:
Antibiotic Resistance Decreases the Efficacy of Endodontic Filling Pastes for Root Canal Treatment in Children′s Teeth
Authors: Rivera-Albarrán Claudia Adriana , Morales-Dorantes Verónica , Ayala-Herrera José Luis , Castillo-Aguillón Mariana , Soto-Barreras Uriel , Cabeza-Cabrera Claudia Verónica , Domínguez-Pérez Rubén Abraham
Published: August 2021

The antibacterial efficacy of antimicrobial filling pastes (AFP) used in the root canal treatment of primary teeth has been widely reported. However, antibiotic resistance as an emerging global problem could impact their current efficacy. This study aimed to evaluate the efficacy of two common AFP on susceptible or resistant bacteria isolated from primary necrotic molars. Microbiological samples were obtained and cultured from the root canals of 34 children. In total, 96 colony-forming units were obtained to determine their resistance to tetracycline, rifampicin, and chloramphenicol. They were identified as S. mutans or E. faecalis using polymerase chain reaction. The antimicrobial activity of CTZ paste (chloramphenicol, tetracycline, zinc oxide, and eugenol) and Guedes-Pinto modified (GPM) paste (rifampicin, prednisolone, iodoform, and camphorated paramonochlorophenol) were tested against the identified and selected microorganisms. Larger size inhibition zones were observed in both species when the tested strains were susceptible to the antibiotics in the AFP preparation. The efficacy of AFP containing antibiotics depends on the antibiotic resistance profile of the strain. Antibiotic resistance and its effect on the AFP were shown, which calls into question the use of simplified endodontic techniques that depend on antibiotics, since in these cases these techniques could not clinically eliminate resistant bacteria from the root canal.
Obstructive Sleep Disorders in Down Syndrome’s Children with and without Lower Airway Anomalies
Authors: De Lausnay Mariska , Verhulst Stijn , Van Hoorenbeeck Kim , Boudewyns An
Published: August 2021

(1) Background: Obstructive sleep apnea (OSA) and lower airway anomalies are both highly prevalent in children with Down syndrome (DS). However, little is known on the interaction between both. We aim to investigate the co-occurrence of OSA (defined as obstructive apnea/hypopnea index (oAHI) ≥ 2/h) and lower airway anomalies in children with DS and explore their impact on OSA severity and treatment outcome. (2) Methods: Retrospective analysis of data from airway endoscopy and polysomnography (PSG) in a cohort of children with DS. (3) Results: Data on both lower airway evaluation and PSG were available for 70 patients with DS. Our study population was relatively young (mean age 3.5 years), not obese and presented with severe OSA (mean oAHI 13.1/h). Airway anomalies were found in 49/70 children (70%), most frequently laryngomalacia, tracheomalacia or a combined airway malformation. In the remaining 21 cases (30%), endoscopy was normal. A comparison between both groups showed a similar distribution of gender, age and BMI z-scores. The prevalence of OSA was not significantly higher in DS patients with airway anomalies (89.6% vs 71.4%, p = 0.078). Additionally, OSA severity or treatment choice (conservative, upper airway surgery or CPAP) were not significantly different. Follow-up data (available for 49/70 patients) showed a significant improvement of OSA in both groups. There is a not significant tendency to more patients with persistent OSA among those with lower airway anomalies (34.3% vs 7.1%, p = 0.075). (4) Conclusions: We found no significant differences in OSA severity, treatment choice or outcome between children with DS with and without lower airway anomalies. Further studies should investigate the role of DISE-directed treatment and compare the outcome of different treatment modalities in larger patient groups.
Novel Hydroxyapatite Whiskers Modified by Silver Ion and Nano Zinc Oxide Used for Bone Defect Repairment
Authors: Yan Tingting , Jiang Zhimin , Li Pan , Chen Qinghua , Zhou Jing , Cui Xiuzhen , Wang Qiang
Published: August 2021

The hydroxyapatite (HA) is widely used as bone tissue repair material. The improvement of the antibacterial performance is an aroused general interest. In the present study, the silver ion and nano-zinc oxide modified hydroxyapatite whiskers (HAw) were successfully prepared. The microstructure and the composition of the modified HAw were analyzed by Field Emission Scanning Electron Microscopy (FESEM) and X-ray diffractometer (XRD). SEM analysis showed that the length of the whiskers was 70–190 μm, and the aspect ratio was 10–60. With the increase of Ag+ content, the length and aspect ratio of the whiskers gradually decreased and incomplete spherical hydroxyapatite appeared. FEEM analysis showed that nano-zinc oxide particles on ZnO/3Ag-HAw surface are evenly distributed; the average particle size is less than 30 nm. XRD analysis showed that after sol-gel and calcination treatment, the nano-zinc oxide phase appeared in the diffraction pattern of ZnO/Ag-HAw. TEM analysis showed that the interplanar spacing of 5Ag-HAw increased slightly. The CCK-8 and cells co-culture assays were used to assess the proliferation and differentiation of MC3T3-E1 cells, respectively. The antibacterial abilities of the modified HAw against E. coli (ATCC25922) and S. aureus (ATCC6538) were investigated. The cell cytotoxicity test showed that the cytotoxicity level was 0, and there was no cytotoxicity. Cell adhesion experiments showed that ZnO/3Ag-HAw has good cell compatibility and biological activity. The modified hawthorn has a bacteriostatic rate of more than 90% and has good bacteriostatic activity.
Enhanced Electrochromic Properties of Nanostructured WO3 Film by Combination of Chemical and Physical Methods
Authors: Li Xiaoni , Li Zhijie , He Wanting , Chen Haolin , Tang Xiufeng , Chen Yeqing , Chen Yu
Published: August 2021

WO3 films are the most widely used electrochromic functional layers. It is known that WO3 films prepared by pure chemical method generally possess novel nanostructures, but the adhesion between WO3 films and substrates is weak. However, WO3 films prepared by pure physical method usually show relatively dense morphology, which limits their electrochromic properties. In order to break through these bottlenecks and further improve their electrochromic properties, this work first prepared nanostructured WO3 powder by chemical method, and then using this powder as the evaporation source, nanostructured WO3 films were fabricated by vacuum thermal evaporation method. Properties of nanostructured WO3 films were systematically compared with those of ordinary WO3 films. It turned out that the nanostructured WO3 film exhibited better cyclic stability and memory effect, and also the optical modulation rate was 14% higher than that of the ordinary WO3 film. More importantly, the nanostructured WO3 film showed better adhesion with the ITO substrates. These results demonstrate that a combination of chemical and physical methods is an effective preparation method to improve the electrochromic properties of WO3 films.
Fair and Secure Multi-Party Computation with Cheater Detection
Authors: Seo Minhye
Published: August 2021

Secure multi-party computation (SMC) is a cryptographic protocol that allows participants to compute the desired output without revealing their inputs. A variety of results related to increasing the efficiency of SMC protocol have been reported, and thus, SMC can be used in various applications. With the SMC protocol in smart grids, it becomes possible to obtain information for load balancing and various statistics, without revealing sensitive user information. To prevent malicious users from tampering with input values, SMC requires cheater detection. Several studies have been conducted on SMC with cheater detection, but none of these has been able to guarantee the fairness of the protocol. In such cases, only a malicious user can obtain a correct output prior to detection. This can be a critical problem if the result of the computation is real-time information of considerable economic value. In this paper, we propose a fair and secure multi-party computation protocol, which detects malicious parties participating in the protocol before computing the final output and prevents them from obtaining it. The security of our protocol is proven in the universal composability framework. Furthermore, we develop an enhanced version of the protocol that is more efficient when computing an average after detecting cheaters. We apply the proposed protocols to a smart grid as an application and analyze their efficiency in terms of computational cost.
Mechanical Properties of High Strength Concrete Containing Nano SiO2 Made from Rice Husk Ash in Southern Vietnam
Authors: Tran Huu-Bang , Le Van-Bach , Phan Vu To-Anh
Published: August 2021

This paper presents the experimental results of the production of Nano-SiO2 (NS) from rice husk ash (RHA) and the engineering properties of High Strength Concrete (HSC) containing various NS contents. Firstly, the mesoporous silica nanoparticles were effectively modulated from RHA using NaOH solution, and subsequently precipitated with HCl solution until the pH value reached 3. The optimum synthesis for the manufacture of SiO2 nanoparticles in the weight ratio of RHA/NaOH was 1:2.4, and the product was calcined at 550 °C for 2 h. The EDX, XRD, SEM, TEM, FT-IR, and BET techniques were used to characterize the NS products. Results revealed that the characteristics of the obtained NS were satisfactory for civil engineering materials. Secondly, the HSC was manufactured with the aforementioned NS contents. NS particles were added to HSC at various replacements of 0, 0.5, 1.0, 1.5, 2.0, and 2.5% by the mass of the binder. The water-to-binder ratio was remained at 0.3 for all mixes. The specimens were cured for 3, 7, 28, 25 days under 25 ± 2 °C and a relative humidity of 95% before testing compressive and flexural strengths. Chloride ion permeability was investigated at 28 and 56 days. Results indicated that the addition of NS dramatically enhanced compressive strength, flexural strength, chloride ion resistance, and reduced chloride ion permeability compared to control concrete. The optimal NS content was found at 1.5%, which yielded the highest strength and lowest chloride ion permeability. Next, the development of flexural and compressive strengths with an age curing of 3–28 days can be analytically described by a logarithmic equation with R2 ≥ 0.74. The ACI code was used, and the compressive strength at t-day was determined based on 28 days with R2 ≥ 0.95. The study is expected to solve the redundancy of waste RHA in southern Vietnam by making RHA a helpful additive when producing high-strength concrete and contributing meaningfully to a sustainable environment.
Study on Microstructure and Mechanical Property in Mg-Gd-Y Alloy by Secondary Extrusion Process
Authors: Liu Jianhua , Sun Jie , Chen Qingqiang , Lu Laixiao , Zhao Yanhua
Published: August 2021

Extruded Mg-Gd-Y alloy tubes were obtained by using cast ingot and extruded bar billets. Microstructure and mechanical properties were also studied with two different cooling methods: air cooling and water cooling. The result shows that by using an extruded bar as billet extruded tubes achieves higher elongation comparing to using cast ingots due to favored texture for the activation of basal slip. Using the water-cooling method, extruded tubes achieve a higher yield strength compared to the air cooling method due to their fine grain size. Using cast ingot billets and the water-cooling method, the elongation is only 6% due to large unrecrystallized grains caused by inhomogeneous deformation and unfavored texture for the activation of basal slip. Using the extruded bar billet and the water-cooling method, the tube has uniformed small grains and much more randomized texture caused by the inhibition of preferred grain growth process. The highest texture intensity is only 1.852 in this kind of tube. Both high yield strength (195.3 MPa) and high elongation (23.9%) are achieved in this tube.
Induced Smectic Phases from Supramolecular H-Bonded Complexes Based on Non-Mesomorphic Components
Authors: Alamro Fowzia S. , Ahmed Hoda A. , Naoum Magdi M. , Mostafa Ayman M. , Alserehi Asmaa A.
Published: August 2021

New non-symmetrical 1:1 supramolecular H-bonded (SMHB) interactions, Ix/II, were designed between the non-mesomorphic fatty acids (palmitic, oleic and linoleic acids) and 4-tetradecyloxyphenylazo pyridine. Mesophase behaviors of the formed complexes were examined via differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). In order to confirm the H-bond interaction formations within the prepared SMHB complexes, FT-IR spectroscopy was established whereby Fermi bands confirm these interactions. Mesomorphic investigations for all complexes indicated that, independent of the terminal alkenyl chains of the natural acids, induced dimorphic smectic phases were observed. The stability of formed mesophases was found to depend on the degree of un-saturation of the terminal alkenyl group of acid component.
Mammoth Cave: A Hotspot of Subterranean Biodiversity in the United States
Authors: Niemiller Matthew L. , Helf Kurt , Toomey Rickard S.
Published: August 2021

The Mammoth Cave System in the Interior Low Plateau karst region in central Kentucky, USA is a global hotspot of cave-limited biodiversity, particularly terrestrial species. We searched the literature, museum accessions, and database records to compile an updated list of troglobiotic and stygobiotic species for the Mammoth Cave System and compare our list with previously published checklists. Our list of cave-limited fauna totals 49 species, with 32 troglobionts and 17 stygobionts. Seven species are endemic to the Mammoth Cave System and other small caves in Mammoth Cave National Park. The Mammoth Cave System is the type locality for 33 cave-limited species. The exceptional diversity at Mammoth Cave is likely related to several factors, such as the high dispersal potential of cave fauna associated with expansive karst exposures, high surface productivity, and a long history of exploration and study. Nearly 80% of the cave-limited fauna is of conservation concern, many of which are at an elevated risk of extinction because of small ranges, few occurrences, and several potential threats.
Sunscreens’ UV Filters Risk for Coastal Marine Environment Biodiversity: A Review
Authors: Caloni Samuele , Durazzano Tiziana , Franci Giada , Marsili Letizia
Published: August 2021

Considering the rapid growth of tourism in recent years and the acknowledgement that exposure to solar UV radiation may cause skin cancer, sunscreens have been widely used by beachgoers in recent decades. UV filters contained in sunscreens, however, were recently identified as emerging pollutants in coastal waters since they accumulate in the marine environment with different adverse effects. In fact, exposure to these components was proven to be toxic to most invertebrate and vertebrate marine species. Some UV filters are linked to the production of significant amounts of reactive oxygen species (ROS), such as hydrogen peroxide, and the release of inorganic micronutrients that may alter the status of coastal habitats. Bioaccumulation and biomagnification have not yet been fully addressed. This review highlights recent progress in research and provides a comprehensive overview of the toxicological and ecotoxicological effects of the most used UV filters both on the abiotic and biotic compartments in different types of coastal areas, to gain a better understanding of the impacts on coastal biodiversity.
Uterine Fibroids and Infertility
Authors: Freytag Damaris , Günther Veronika , Maass Nicolai , Alkatout Ibrahim
Published: August 2021

Infertility is a disease of the reproductive system defined by the failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse. Uterine fibroids are the most common tumor in women, and their prevalence is high in patients with infertility. Fibroids may be the sole cause of infertility in 2–3% of women. Depending on their location in the uterus, fibroids have been implicated in recurrent pregnancy loss as well as infertility. Pregnancy and live birth rates appear to be low in women with submucosal fibroids; their resection has been shown to improve pregnancy rates. In contrast, subserosal fibroids do not affect fertility outcomes and their removal does not confer any benefit. Intramural fibroids appear to reduce fertility, but recommendations concerning their treatment remain unclear. Myomectomy should be discussed individually with the patient; other potential symptoms such as dysmenorrhea or bleeding disorders should be included in the indication for surgery.
Current Helicobacter pylori Diagnostics
Authors: Bordin Dmitry S. , Voynovan Irina N. , Andreev Dmitrii N. , Maev Igor V.
Published: August 2021

The high prevalence of Helicobacter pylori and the variety of gastroduodenal diseases caused by this pathogen necessitate the use of only accurate methods both for the primary diagnosis and for monitoring the eradication effectiveness. There is a broad spectrum of diagnostic methods available for detecting H. pylori. All methods can be classified as invasive or non-invasive. The need for upper endoscopy, different clinical circumstances, sensitivity and specificity, and accessibility defines the method chosen. This article reviews the advantages and disadvantages of the current options and novel developments in diagnostic tests for H. pylori detection. The progress in endoscopic modalities has made it possible not only to diagnose precancerous lesions and early gastric cancer but also to predict H. pylori infection in real time. The contribution of novel endoscopic evaluation technologies in the diagnosis of H. pylori such as visual endoscopy using blue laser imaging (BLI), linked color imaging (LCI), and magnifying endoscopy is discussed. Recent studies have demonstrated the capability of artificial intelligence to predict H. pylori status based on endoscopic images. Non-invasive diagnostic tests such as the urea breathing test and stool antigen test are recommended for primary diagnosis of H. pylori infection. Serology can be used for initial screening and epidemiological studies. The histology showed its value in detecting H. pylori and provided more information about the degree of gastric mucosa inflammation and precancerous lesions. Molecular methods are mainly used in detecting antibiotic resistance of H. pylori. Cultures from gastric biopsies are the gold standard and recommended for antibiotic susceptibility tests.
Effect of Polishing Systems on the Surface Roughness of Nano-Hybrid and Nano-Filling Composite Resins: A Systematic Review
Authors: Jaramillo-Cartagena Robinson , López-Galeano Eider J. , Latorre-Correa Federico , Agudelo-Suárez Andrés A.
Published: August 2021

Background: The polishing of surface roughness is an important characteristic of composite resins and is directly related to the longevity of the restoration and patient comfort. Different polishing systems utilize different protocols, as reported in the literature. This systematic review (SR) aimed to synthesize and analyze the available scientific evidence about the effect of polishing systems on the surface roughness of nano-hybrid and nano-filling composite resins. Methods: The study protocol of this SR was registered at the International Prospective Register of Systematic Reviews -PROSPERO- (CRD4201705653). A search was conducted in PubMed-Medline, Scopus, LILACS, EMBASE, for the period 2007–2020. Quality appraisal and a descriptive analysis of the papers that met the inclusion criteria were conducted. Results: 18 records were included. Seven polishing systems (PS) of one step were found, seven PS of two steps, eight PS of three steps, three PS of four steps, and four PS of five steps. Polishing protocols (PP) varied, with application times ranging from 10 s to 60 s with speeds between 10,000 and 30,000 RPM. Regarding composition, the aluminum oxide was one of the most important components used to achieve a smooth surface. Conclusions: Multistep polishing systems were the most effective (i.e., Astropol and Sof-Lex Discs).
Cluster-Delay Mean Square Consensus of Stochastic Multi-Agent Systems with Impulse Time Windows
Authors: Luo Huan , Wang Yinhe , Zhan Ruidian , Zhang Xuexi , Wen Haoxiang , Yang Senquan
Published: August 2021

This paper investigates the cluster-delay mean square consensus problem of a class of first-order nonlinear stochastic multi-agent systems with impulse time windows. Specifically, on the one hand, we have applied a discrete control mechanism (i.e., impulsive control) into the system instead of a continuous one, which has the advantages of low control cost, high convergence speed; on the other hand, we considered the existence of impulse time windows when modeling the system, that is, a single impulse appears randomly within a time window rather than an ideal fixed position. In addition, this paper also considers the influence of stochastic disturbances caused by fluctuations in the external environment. Then, based on algebraic graph theory and Lyapunov stability theory, some sufficiency conditions that the system must meet to reach the consensus state are given. Finally, we designed a simulation example to verify the feasibility of the obtained results.
Effects of Muscle Fatigue and Recovery on Complexity of Surface Electromyography of Biceps Brachii
Authors: Liao Fuyuan , Zhang Xueyan , Cao Chunmei , Hung Isabella Yu-Ju , Chen Yanni , Jan Yih-Kuen
Published: August 2021

This study aimed to investigate the degree of regularity of surface electromyography (sEMG) signals during muscle fatigue during dynamic contractions and muscle recovery after cupping therapy. To the best of our knowledge, this is the first study assessing both muscle fatigue and muscle recovery using a nonlinear method. Twelve healthy participants were recruited to perform biceps curls at 75% of the 10 repetitions maximum under four conditions: immediately and 24 h after cupping therapy (−300 mmHg pressure), as well as after sham control (no negative pressure). Cupping therapy or sham control was assigned to each participant according to a pre-determined counter-balanced order and applied to the participant’s biceps brachii for 5 min. The degree of regularity of the sEMG signal during the first, second, and last 10 repetitions (Reps) of biceps curls was quantified using a modified sample entropy (Ems) algorithm. When exercise was performed immediately or 24 h after sham control, Ems of the sEMG signal showed a significant decrease from the first to second 10 Reps; when exercise was performed immediately after cupping therapy, Ems also showed a significant decrease from the first to second 10 Reps but its relative change was significantly smaller compared to the condition of exercise immediately after sham control. When exercise was performed 24 h after cupping therapy, Ems did not show a significant decrease, while its relative change was significantly smaller compared to the condition of exercise 24 h after sham control. These results indicated that the degree of regularity of sEMG signals quantified by Ems is capable of assessing muscle fatigue and the effect of cupping therapy. Moreover, this measure seems to be more sensitive to muscle fatigue and could yield more consistent results compared to the traditional linear measures.
A Review of Hydrothermal Liquefaction of Biomass for Biofuels Production with a Special Focus on the Effect of Process Parameters, Co-Solvents, and Extraction Solvents
Authors: Mathanker Ankit , Das Snehlata , Pudasainee Deepak , Khan Monir , Kumar Amit , Gupta Rajender
Published: August 2021

Hydrothermal liquefaction is one of the common thermochemical conversion methods adapted to convert high-water content biomass feedstocks to biofuels and many other valuable industrial chemicals. The hydrothermal process is broadly classified into carbonization, liquefaction, and gasification with hydrothermal liquefaction conducted in the intermediate temperature range of 250–374 °C and pressure of 4–25 MPa. Due to the ease of adaptability, there has been considerable research into the process on using various types of biomass feedstocks. Over the years, various solvents and co-solvents have been used as mediums of conversion, to promote easy decomposition of the lignocellulosic components in biomass. The product separation process, to obtain the final products, typically involves multiple extraction and evaporation steps, which greatly depend on the type of extractive solvents and process parameters. In general, the main aim of the hydrothermal process is to produce a primary product, such as bio-oil, biochar, gases, or industrial chemicals, such as adhesives, benzene, toluene, and xylene. All of the secondary products become part of the side streams. The optimum process parameters are obtained to improve the yield and quality of the primary products. A great deal of the process depends on understanding the underlined reaction chemistry during the process. Therefore, this article reviews the major works conducted in the field of hydrothermal liquefaction in order to understand the mechanism of lignocellulosic conversion, describing the concept of a batch and a continuous process with the most recent state-of-art technologies in the field. Further, the article provides detailed insight into the effects of various process parameters, co-solvents, and extraction solvents, and their effects on the products’ yield and quality. It also provides information about possible applications of products obtained through liquefaction. Lastly, it addresses gaps in research and provides suggestions for future studies.
Short Survey of Architectures of Photovoltaic Arrays for Solar Power Generation Systems
Authors: Abramovitz Alexander , Shmilovitz Doron
Published: August 2021

Since the industrial revolution, the world’s economy has mainly relied on the consumption of fossil fuels. The burning of coal releases vast amounts of toxic COx greenhouse gasses into the atmosphere that bear an undesirable environmental impact. The ongoing offshore oil exploration activities; the infrastructure for oil extraction, production, and transportation; and the inevitable oil spills cause severe damage to the environment and huge loss of sea life, flora, and fauna. Recent awareness of the environmental issues and the worldwide climate change spurred public interest in clean and environmentally friendly “green” energy generation. Solar energy is an abundant and inexhaustible resource that can meet much of the worlds’ energy needs and, thus, has been in the focus of scientific attention for many years. Yet, converting solar energy into usable electric power is a formidable engineering and economical challenge. The recent environmental awareness triggered governments and private companies around the world to encourage further research and capital investment into the development and deployment of efficient and cost-effective solar technologies. This review reports on advances in the technological approaches that can be employed to convert sunlight to electricity. This article presents a short survey of the state-of-the-art architectures of photovoltaic arrays and a review of the concepts and strategies of their associated electronic power processors for solar energy generation. The paper aims to be of assistance to engineers and scientists who are already engaged or just joining this fascinating field, to promote the knowledge of photovoltaic energy and facilitate the proliferation of the solar power generation systems.
How Digital Twin Concept Supports Internal Transport Systems?—Literature Review
Authors: Kosacka-Olejnik Monika , Kostrzewski Mariusz , Marczewska Magdalena , Mrówczyńska Bogna , Pawlewski Paweł
Published: August 2021

In the Industry 4.0 era, the Digital Twin has become one of the most promising enabling technologies supporting material flow. Although the literature on the Digital Twin is becoming relatively well explored, including a certain number of review papers, the context of the Digital Twins application in internal transport systems has not been investigated so far. This paper thoroughly reviews the research on the Digital Twins applied in internal transport systems concerning major research trends within this research area and identification of future research directions. It provides clarification of various definitions related to the Digital Twin concept, including misconceptions such as a digital shadow, a digital model, and a digital mirror. Additionally, the relationships between terms such as material handling, material flow, and intralogistics in the context of internal transport systems coupled with the Digital Twin are explained. This paper’s contribution to the current state of the art of the Digital Twins is three-fold: (1) recognition of the most influential and high-impact journals, papers, and researchers; (2) identification of the major research trends related to the Digital Twins applications in internal transport systems, and (3) presentation of future research agendas in investigating Digital Twins applied for internal transport systems.
Cost Benefit of Implementing Advanced Monitoring and Predictive Maintenance Strategies for Offshore Wind Farms
Authors: Turnbull Alan , Carroll James
Published: August 2021

Advancements in wind turbine condition monitoring systems over the last decade have made it possible to optimise operational performance and reduce costs associated with component failure and other unplanned maintenance activities. While much research focuses on providing more automated and accurate fault diagnostics and prognostics in relation to predictive maintenance, efforts to quantify the impact of such strategies have to date been comparatively limited. Through time-based simulation of wind farm operation, this paper quantifies the cost benefits associated with predictive and condition-based maintenance strategies, taking into consideration both direct O&M costs and lost production. Predictive and condition-based strategies have been modelled by adjusting known component failure and repair rates associated with a more reactive approach to maintenance. Results indicate that up to 8% of direct O&M costs can be saved through early intervention along with up to 11% reduction in lost production, assuming 25% of major failures of the generator and gearbox can be diagnosed through advanced monitoring and repaired before major replacement is required. Condition-based approaches can offer further savings compared to predictive strategies by utilising more component life before replacement. However, if weighing up the risk between component failure and replacing a component too early, results suggest that it is more cost effective to intervene earlier if heavy lift vessels can be avoided, even if that means additional major repairs are required over the lifetime of the site.
A Combustion Regime-Based Model for Large Eddy Simulation
Authors: Giacomazzi Eugenio , Cecere Donato
Published: August 2021

The aim of this work is to propose a unified (generalized) closure of the chemical source term in the context of Large Eddy Simulation able to cover all the regimes of turbulent premixed combustion. Turbulence/combustion scale interaction is firstly analyzed: a new perspective to look at commonly accepted combustion diagrams is provided based on the evidence that actual turbulent flames can experience locally several combustion regimes although global non-dimensional numbers would locate such flames in a single specific operating point of the standard combustion diagram. The deliverable is a LES subgrid scale model for turbulent premixed flames named Localized Turbulent Scales Model (LTSM). This is founded on the estimation of the local reacting volume fraction of a computational cell that is related to the local turbulent and laminar flame speeds and to the local flame thickness.
A Simple Method for Detecting Partial Shading in PV Systems
Authors: Al Abri Waleed , Abri Rashid Al , Yousef Hassan , Al-Hinai Amer
Published: August 2021

Partial shading conditions (PSCs) can significantly reduce the output energy produced by photovoltaic (PV) systems. Moreover, when such conditions occur, conventional and advanced maximum power point tracking (MPPT) systems fail to operate the PV system at its peak because the bypassing diodes may cause the PV system to become trapped at a low power point when they are in conduction mode. The PV system can be operated at the global maximum power point (MPP) with the help of global peak searching tools. However, the frequent use of these tools will reduce the output of PV systems since they force the PV system to operate outside its power region while scanning the I-V curve in order to determine the global MPP. Thus, the global peak searching tools should be deployed only when a PSC occurs. In this paper, a simple and accurate method is proposed for detecting PSCs by means of monitoring the sign of voltage changes (positive or negative). The method predicts a PSC if the sign of successive voltage changes is the same for a certain number of successive changes. The proposed method was tested on two types of PV array configurations (series and series–parallel) with several shading patterns emulated on-site. The proposed method correctly and timely identified all emulated shading patterns. It can be used to trigger the global MPP searching techniques for improving the PV system’s output under PSCs; furthermore, it can be used to notify the PV system’s operator of the occurrence of PSCs.
Modified Model for Shallow Soil Strength Recovery Calculation during Set-Up Periods of Jetted Conductor—A Case Study of Equatorial Guinea Bay Deep-Water Drilling
Authors: Yan Wei , Kambi Said Juma , Huang Xin , Lin Hai , Liu Hailong , Deng Jingen
Published: August 2021

Jetted conductor setting depth is crucial for deep-water drilling. This paper presents an innovative method for determining the shallow soil resistance strength recovery factor based on the field data of Equatorial Guinea bay. It shows that the soil strength recovery factor of Equatorial Guinea bay is lower than that of the Gulf of Mexico. The conductor setting depth calculation referring to other place will have a high risk of wellhead sinking. According to the newly established designing charts, the conductor setting depth was recommended for the S1 well. Each preferred set-up period requires a specific setting depth. If the chosen set-up period is 2 days, the expected setting depth of a 36″ conductor should be 250 ft (76.2 m) and, similarly, 295 ft (89.9 m) for a 30″ conductor. The relationship between set-up period and surface conductor setting depth is established as well. Wellhead landed load appears to be the crucial factor for determining the conductor setting depth. The rationality of the newly developed shallow soil strength recovery model for the Equatorial Guinea deep-water block was also confirmed by the field data.
Energy Efficiency and Life Cycle Assessment with System Dynamics of Electricity Production from Rice Straw Using a Combined Gasification and Internal Combustion Engine
Authors: Reaño Resmond L. , de Padua Victor Antonio N. , Halog Anthony B.
Published: August 2021

This study assessed the environmental performance and energy efficiency of electricity generation from rice straw using a combined gasification and internal combustion engine (G/ICE). A life cycle assessment (LCA) was performed to consider the conversion to electricity of rice straw, the production of which was based on the Philippine farming practice. Rice straw is treated as a milled rice coproduct and assumes an environmental burden which is allocated by mass. The results of an impact assessment for climate change was used directly in a system dynamic model to plot the accumulated greenhouse gas emissions from the system and compare with various cases in order to perform sensitivity analyses. At a productivity of 334 kWh/t, the global warming potential (GWP) of the system is equal to 0.642 kg CO2-eq/MJ, which is 27% lower than the GWP of rice straw on-site burning. Mitigating biogenic methane emissions from flooded rice fields could reduce the GWP of the system by 34%, while zero net carbon emissions can be achieved at 2.78 kg CO2/kg of milled rice carbon sequestration. Other sources of greenhouse gas (GHG) emissions are the use of fossil fuels and production of chemicals for agricultural use. The use of agricultural machinery and transport lorries has the highest impact on eutrophication potential and human toxicity, while the application of pesticides and fertilizers has the highest impact on ecotoxicity. The biomass energy ratio (BER) and net energy ratio (NER) of the system is 0.065 and 1.64, respectively. The BER and NER can be improved at a higher engine efficiency from 22% to 50%. The use of electricity produced by the G/ICE system to supply farm and plant operations could reduce the environmental impact and efficiency of the process.
In Situ Measurement of Localized Current Distribution in H2-Br2 Redox Flow Batteries
Authors: Cantu Brenda Berenice Martinez , Fischer Peter , Zitoun David , Tübke Jens , Pinkwart Karsten
Published: August 2021

Hydrogen bromine redox flow batteries (RFB) are considered to be one of the most promising storage alternatives, as this technology offers both high energy and high-power density. In this work a printed circuit board type of segmented current collector for the measurement of locally resolved current density was developed. This analytical tool was inserted as hydrogen anode current collector in a hydrogen-bromine test cell. Charging and discharging operation was monitored under different stoichiometric flow conditions and the impact on current distribution is presented. This technique offers the possibility to prove cell limiting conditions with spatial resolution, improving our understanding and determining optimal operating conditions for a given design.
Protection Coordination Method Using Symmetrical Components in Loop Distribution System
Authors: Lee Jung-Hun , Kim Woo-Hyun , Lee Hak-Ju , Kim Jun-Oh , Chae Woo-Kyu
Published: August 2021

Power utilities worldwide commonly use the radial distribution system because of its advantages of being simple in structure and having relatively inexpensive installation costs. It has a disadvantage in that its power supply reliability is low because the load side of the fault section will suffer from an outage in the event of a fault in the system. However, recently, with ICT (Information and Communication Technologies) development, system reliability is required to be high as the outage-susceptible loads increase. In addition, the increase in the connection of distributed resources such as renewable energy and electric vehicles is making it impossible to predict the power flow and reducing line utilization. Therefore, a loop power distribution system is proposed as a measure to solve this problem. Because all buses (nodes) in a loop distribution system have two or more power supply routes, they are more reliable than the radial system. It allows them to improve line utilization by connecting lines with different load peak times. However, in the case of a fault in the loop distribution system, the fault current is supplied from both directions, making it impossible to properly isolate the fault section with the protection method of the conventional distribution system. The permissive overreach transfer trip (POTT) method using communication to compensate for the limitations of conventional protection devices, and the other method using directional distance relay, is proposed. However, these methods operate by determining the direction of the fault current but have a disadvantage. It is difficult to detect a fault due to the effects of ground faults and distributed generation (DG) occurring in other lines. Therefore, in this paper, we propose a protection coordination algorithm that uses the negative-sequence component of voltage and current that occur when an unbalanced fault occurs, rather than the determination of the directionality and use of communication. To validate this, we configured a system using PSCAD/EMTDC (Manitoba Hydro International Ltd., Winnipeg, Manitoba, Canada), a system analysis program package and verified the results depending on the type of faults with the proposed algorithm.
Complementary Optimization of Hydropower with Pumped Hydro Storage–Photovoltaic Plant for All-Day Peak Electricity Demand in Malawi
Authors: Chaima Evance , Lian Jijian , Ma Chao , Zhang Yusheng , Kavwenje Sheila
Published: August 2021

Solar energy is currently dispatched ahead of other renewable energy sources. For the first time, this study presents a concept of exploiting temporary–periodical runoff discharge in the Shire River. Pumped hydro storage–photovoltaic plant (PHS–PV) was optimized to satisfy the all-day peak electricity demand in Malawi. The effect of varying the net head on the PHS system in both the generation and pumping operation modes was investigated. The bi-objective optimization evaluated the system reliability for day-time and night-time operation together with implied costs of investment for the whole system. The optimized system generated above 53% of added power as contrasted to single-source power generation from the existing hydropower plants. The estimated optimal capacities were 182 MWp (solar PV) and 86 MW (PHS plant). These additional optimal capacities achieved a 99.8% maximum system reliability (Loss of Power Supply Probability—LPSP—of 0.2%) and Levelized Cost of Energy—LCOE—of 0.13 USD/kWh. The overall investment cost of the PHS–PV system was estimated at 671.23 USD for an LPSP of 0.20%. The net head varies from 15.5 to 17.8 m with an impact on electricity generation of the PHS–PV system. More notably, the PHS–PV production matches with daily day-time and night-time peak loads and functions as a peaking plant.
Hydrologic Restoration of the Lac des Allemands Swamp, Barataria, Louisiana
Authors: Shaffer Gary P. , Kandalepas Demetra , Stevens Nicholas , Crockett Tessera , Curole Glen
Published: August 2021

Most of the forested wetlands of coastal Louisiana are in decline, primarily due to impoundment and increased flood duration. The Lac des Allemands swamp of Barataria Basin was a prime example of prolonged inundation prior to hydrologic restoration completed in February of 2018; the swamp had been impounded for over 60 years. To characterize restoration benefits, eight paired 625 m2 permanent sites were established close to and halfway between eight 30 m × 122 m gaps cut into the spoil bank of Bayou Chevreuil. During 2018, canopy closure increased by 20%. In addition, aboveground production of wood and leaves increased over 2017 from 2018–2020. Furthermore, natural regeneration has occurred annually and many of the seedlings are now approximately 1 m tall. In conclusion, hydrologic restoration of impounded wetlands in coastal Louisiana is an extremely cost-effective landscape restoration method.
How Forest Subsidies Impact Household Income: The Case from China
Authors: Han Feng , Chen Yaru
Published: August 2021

(1) Background: It is of great significance to evaluate the impact of forestry subsidies on the income of forest farmers to improve policy and enhance efficiency. (2) Methods: Based on the static panel data of household tracking surveys from 2014 to 2018 in Sichuan, Liaoning, and Zhejiang provinces in China, the impacts of forestry subsidies on forest farmer income and impact paths were systematically verified via parameter estimation with the Fixed-Effect model. (3) Results: Forestry subsidies significantly increased forest farmer income. The impact paths could be summarized as follows: First, from the perspective of operating income, forestry subsidies effectively motivated forestry production and promoted the expenditure on forestry production, and thus increased forest farmer operating income. Second, from the perspective of wage income, forestry subsidy policies played a negative role in releasing the forest farmer labor force for off-farm employment. Third, from the perspective of transfer income as a kind of transferred governmental financial subsidy, forestry subsidies covered a large proportion of transfer income for forest farmers. (4) Conclusions: Forestry subsidies could directly increase the transfer income, effectively improve the forestry production capacity, and increase the income of forest farmers. However, forestry subsidies could also bind forest farmers to forestry production to a certain extent, which was not conducive to the liberation of the labor force.
Vibrational Spectroscopy Combined with Chemometrics as Tool for Discriminating Organic vs. Conventional Culture Systems for Red Grape Extracts
Authors: Radulescu Cristiana , Olteanu Radu Lucian , Nicolescu Cristina Mihaela , Bumbac Marius , Buruleanu Lavinia Claudia , Holban Georgeta Carmen
Published: August 2021

Food plants provide a regulated source of delivery of functional compounds, plant secondary metabolites production being also tissue specific. In grape berries, the phenolic compounds, flavonoids and non-flavonoids, are distributed in the different parts of the fruit. The aim of this study was to investigate the applicability of FTIR and Raman screening spectroscopic techniques combined with multivariate statistical tools to find patterns in red grape berry parts (skin, seeds and pulp) according to grape variety and vineyard type (organic and conventional). Spectral data were acquired and processed using the same pattern for each different berry part (skin, seeds and pulp). Multivariate analysis has allowed a separation between extracts obtained from organic and conventional vineyards for each grape variety for all grape berry parts. The innovative approach presented in this work is low-cost and feasible, being expected to have applications in studies referring to the authenticity and traceability of foods. The findings of this study are useful as well in solving a great challenge that producers are confronting, namely the consumers’ distrust of the organic origin of food products. Further analyses of the chemical composition of red grapes may enhance the capability of the method of using both vibrational spectroscopy and chemometrics for discriminating the hydroalcoholic extracts according to grape varieties.
Grape Pomace as a New Coagulant for Tofu Production: Physicochemical and Sensory Effects
Authors: Zeppa Giuseppe , Tedesco Martina , Bertolino Marta , Çilek Tatar Betül
Published: August 2021

Tofu, one of the most important products made from soymilk, is obtained through a coagulation process performed with various coagulants (acids, salts and, enzymes). In this study, innovative tofu samples were produced using the grape pomace (GP) powders of different varieties (Barbera, Chardonnay, Moscato, and Pinot Noir) with different origins (fermented and distilled) at two concentration levels (2.5% and 5% w/v) as coagulants, and comparisons with traditional tofu were made. Physicochemical characteristics, phenolic contents, radical scavenging activity levels, textural properties, and consumer acceptability were evaluated. The moisture, protein content, and pH levels of GP tofu samples were slightly lower than those of traditional tofu. Regarding textural parameters, except for hardness, all other parameters were significantly lower in GP tofu samples, with differences due to GP concentration. The colours of GP tofu varied from amber-yellow to violet according to the GP origin. The blue-violet colours were observed predominantly in tofu samples obtained with Barbera and Pinot Noir GPs, while the other GP tofu samples showed amber-yellow colours. The concentrations of polyphenols were 2–10 times higher than in traditional tofu, while the radical scavenging activity levels were 9–80 times higher. The GP tofu samples were favoured by consumers, with small differences among the GP varieties.