bluuebunny/crossref_metadata_2025 huggingface dataset:
Prognostic Value of Cardiac Troponin I in Patients with Ventricular Tachyarrhythmias
Authors: Akin Ibrahim , Behnes Michael , Müller Julian , Forner Jan , Abumayyaleh Mohammad , Mashayekhi Kambis , Akin Muharrem , Bertsch Thomas , Weidner Kathrin , Rusnak Jonas , Große Meininghaus Dirk , Kittel Maximilian , Schupp Tobias
Published: May 2022

Besides the diagnostic role in acute myocardial infarction, cardiac troponin I levels (cTNI) may be increased in various other clinical conditions, including heart failure, valvular heart disease and sepsis. However, limited data are available regarding the prognostic role of cTNI in the setting of ventricular tachyarrhythmias. Therefore, the present study sought to assess the prognostic impact of cTNI in patients with ventricular tachyarrhythmias (i.e., ventricular tachycardia (VT) and fibrillation (VF)) on admission. A large retrospective registry was used, including all consecutive patients presenting with ventricular tachyarrhythmias from 2002 to 2015. The prognostic impact of elevated cTNI levels was investigated for 30-day all-cause mortality (i.e., primary endpoint) using Kaplan–Meier, receiver operating characteristic (ROC), multivariable Cox regression analyses and propensity score matching. From a total of 1104 patients with ventricular tachyarrhythmias and available cTNI levels on admission, 46% were admitted with VT and 54% with VF. At 30 days, high cTNI was associated with the primary endpoint (40% vs. 22%; log rank p = 0.001; HR = 2.004; 95% CI 1.603–2.505; p = 0.001), which was still evident after multivariable adjustment and propensity score matching (30% vs. 18%; log rank p = 0.003; HR = 1.729; 95% CI 1.184–2.525; p = 0.005). Significant discrimination of the primary endpoint was especially evident in VT patients (area under the curve (AUC) 0.734; 95% CI 0.645–0.823; p = 0.001). In contrast, secondary endpoints, including all-cause mortality at 30 months and a composite arrhythmic endpoint, were not affected by cTNI levels. The risk of cardiac rehospitalization was lower in patients with high cTNI, which was no longer observed after propensity score matching. In conclusion, high cTNI levels were associated with increased risk of all-cause mortality at 30 days in patients presenting with ventricular tachyarrhythmias.
IR Reflectography, Pulse-Compression Thermography, MA-XRF, and Radiography: A Full-Thickness Study of a 16th-Century Panel Painting Copy of Raphael
Authors: Cavaleri Tiziana , Pelosi Claudia , Ricci Marco , Laureti Stefano , Romano Francesco Paolo , Caliri Claudia , Ventura Bernadette , De Blasi Stefania , Gargano Marco
Published: May 2022

The potential of any multi-analytical and non-invasive approach to the study of cultural heritage, both for conservation and scientific investigation purposes, is gaining increasing interest, and it was tested in this paper, focusing on the panel painting Madonna della Tenda (Musei Reali, Turin), identified as a 16th-century copy of the painting by Raffaello Sanzio. As a part of a broader diagnostic campaign carried out at the Centro Conservazione e Restauro, La Venaria Reale in Turin, Italy, the potential of the combination of X-ray radiography, pulse-compression thermography, macro X-ray fluorescence, and IR reflectography was tested to investigate the wooden support and all the preparatory phases for the realization of the painting. The results of the optical microscopy and SEM/EDS analyses on a multi-layered micro-sample were used for a precise comparison, integration, and/or confirmation of what was suggested by the non-invasive techniques. Particularly, the radiographic and thermographic techniques allowed for an in-depth study of a hole, interestingly present on the panel’s back surface, detecting the trajectory of the wood grain and confirming the presence of an old wood knot, as well as of a tau-shaped element—potentially a cracked and unfilled area of the wooden support—near the hollow. The combination of radiography, macro X-ray fluorescence, Near Infrared (NIR), and Short Wave Infrared (SWIR) reflectography allowed for an inspection of the ground layer, imprimitura, engravings, and underdrawing, not only revealing interesting technical-executive aspects of the artwork realization, but also highlighting the advantages of an integrated reading of data obtained from the different analytical techniques.
Artificial Intelligence in Marine Science and Engineering
Authors: García Márquez Fausto Pedro , Papaelias Mayorkinos , Marini Simone
Published: May 2022

This Special Issue covers research in Artificial Intelligence in Marine Science and Engineering and shows how to apply it to many different professional areas, e [...]
Economic Viability Analysis for an OTEC Power Plant at San Andrés Island
Authors: Herrera Jorge , Sierra Santiago , Hernández-Hamón Hernando , Ardila Néstor , Franco-Herrera Andrés , Ibeas Asier
Published: May 2022

This paper presents the economic feasibility analysis of a 2 MW Ocean Thermal Energy Conversion (OTEC) power plant in the open cycle. The plant can supply 6.35% of the average annual consumption of the electricity demand located at San Andrés Island (Colombia). On the one hand, the work presents the selection of the place to locate an offshore facility considering the technical viability while, on the other hand, the economic viability analysis is performed. The latter considers two scenarios: one without desalinated water production and another one with desalinated water. In this way, it is intended to first determine its construction’s technical requirements to analyse its economic performance. This approach allows us to have a general idea of the implementation costs and the benefits obtained with this type of plant, for the particular case of San Andrés, an island in the Colombian Caribbean with sustained stress on electricity production and freshwater generation. The results obtained show that the technology is viable and that the investment can be recovered in an adequate time horizon.
Back Projection Algorithm for Multi-Receiver Synthetic Aperture Sonar Based on Two Interpolators
Authors: Zhang Xuebo , Yang Peixuan
Published: May 2022

The back projection (BP) algorithm is characterized by its high performance for multi-receiver synthetic aperture sonar (SAS). For this reason, it is usually used to evaluate the imaging performance of Fourier-domain methods. However, this algorithm suffers from a large computation load, and the imaging efficiency is seriously lowered. In order to improve the imaging performance, this paper proposes focusing the multi-receiver SAS data using the BP algorithm based on two interpolators, including the linear interpolation and nearest-neighbor interpolation. The former interpolation is used to decrease the interpolation error based on adjacent sampled data; the latter estimates the data at the desired moment by assigning the data value of the nearest sample as estimated data. Then, the imaging performance of the presented method is discussed in detail based on simulations and real-data processing. With the presented method, the imaging performance can be improved without a loss of efficiency compared to nearest-neighbor interpolation without an upsampling operation. In comparison with the traditional BP algorithm, the presented method can be used to improve the imaging efficiency without any loss of performance.
An Iterative Method for Interaction of Hydro-Elastic Waves with Several Vertical Cylinders of Circular Cross-Sections
Authors: Disibuyuk Nazile B. , Yilmaz Oguz , Korobkin Alexander , Khabakhpasheva Tatyana
Published: May 2022

The problem of ice loads acting on multiple vertical cylinders of circular cross-sections frozen in an ice cover of infinite extent is studied. The loads are caused by a flexural-gravity wave propagating in the ice cover towards the rigid bottom-mounted cylinders. This is a three-dimensional linearized problem of hydroelasticity with finite water depth. The flow under the ice is potential and incompressible. The problem is solved by the vertical mode method combined with an iterative method. The velocity potential is written with respect to each cylinder and is expanded into the Fourier series. The algorithm of the problem solving is reduced to calculations of the Fourier coefficients of the velocity potential. Numerical results for the forces acting on four circular cylinders are presented for different ice thicknesses, incident wave angles and cylinder spacing. The obtained wave forces are compared with the results by others. Good agreement is reported.
A Novel Device for the In Situ Enrichment of Gold from Submarine Venting Fluids
Authors: Zeng Zhigang , Yin Xuebo , Wang Xiaoyuan , Yan Yu , Zhang Xueying
Published: May 2022

Gold and other metals (Cu, Zn, Ag, etc.) are enriched in vent fluids, approximately 3–5 orders of magnitude higher than those in seawater, and this leads to the formation of sulfide enrichment in Cu, Zn, Au, and Ag deposited on the mid-ocean ridge and island arcs, as well as in back-arc basins. We developed a device that can extract the elements such as Cu, Zn, Au, and Ag from the vent fluids before the formation of the hydrothermal plume, sulfide deposit, and metalliferous sediment at the seafloor over a long period, which is beneficial to collecting hydrothermal resources effectively and avoiding the damage of ecological environments caused by mining the polymetallic sulfide resources. The application of this device will have significance for the development and utilization of seafloor hydrothermal resources, the sustainable development and implementation of the blue economy, and the construction of the marine ecological civilization in the future.
Ectomycorrhizal Influence on the Dynamics of Sesquiterpene Release by Tricholoma vaccinum
Authors: Ezediokpu Marycolette Ndidi , Krause Katrin , Kunert Maritta , Hoffmeister Dirk , Boland Wilhelm , Kothe Erika
Published: May 2022

Tricholoma vaccinum is an ectomycorrhizal basidiomycete with high host specificity. The slow-growing fungus is able to produce twenty sesquiterpenes, including α-barbatene, sativene, isocaryophyllene, α-cuprenene, β-cedrene, ß-copaene, 4-epi-α-acoradiene, and chamigrene in axenic culture. For the three major compounds, Δ6-protoilludene, β-barbatene, and an unidentified oxygenated sesquiterpene (m/z 218.18), changed production during co-cultivation with the ectomycorrhizal partner tree, Picea abies, could be shown with distinct dynamics. During the mycorrhizal growth of T. vaccinum–P. abies, Δ6-protoilludene and the oxygenated sesquiterpene appeared at similar times, which warranted further studies of potential biosynthesis genes. In silico analyses identified a putative protoilludene synthesis gene, pie1, as being up-regulated in the mycorrhizal stage, in addition to the previously identified, co-regulated geosmin synthase, ges1. We therefore hypothesize that the sesquiterpene synthase pie1 has an important role during mycorrhization, through Δ6-protoilludene and/or its accompanied oxygenated sesquiterpene production.
Isavuconazole Treatment of Spinal Cord Invasive Aspergillosis Guided by Cerebrospinal Fluid (1,3)-β-d-Glucan Levels in a Patient with Low Interferon-Gamma and Ulcerative Colitis
Authors: O’Regan Siobhan , O’Kelly Brendan , Reidy Paul , O’Toole Aoibhlinn , Caird John , McNally Cora , McConkey Samuel , De Barra Eoghan
Published: May 2022

This case highlights the use of (1,3)-beta-d glucan to direct treatment of a cervical spinal cord Aspergillus fumigatus infection in a 22-year-old woman immunocompromised due to steroid and anti-TNF therapy in the context of ulcerative colitis and interferon gamma deficiency. A 4-year treatment course requiring neurosurgical intervention on four occasions and prolonged antifungal therapy, including isavuconazole, resulted in clinical cure with a corresponding decrease in CSF beta-d-glucan to <30 pg/mL. Serum and CSF galactomannan levels were not elevated at any point during the clinical course.
Virtual Reality Experience of Mega Sports Events: A Technology Acceptance Study
Authors: Capasa Ludovica , Zulauf Katrin , Wagner Ralf
Published: May 2022

Digitalization has advanced to become an opportunity to spectate sports during the pandemic and its restrictions for traveling to competitions. The purpose of this study is to investigate the antecedents of using virtual reality technology for spectating mega sports events. Based on a literature review, the authors created a model of behavioral intention, built on the unified theory of acceptance and use of technology and technology acceptance model to examine the curiosity and self-construal of spectators. An online survey obtained empirical evidence from 339 sports enthusiasts. The research model was fitted using the partial least squares algorithm. The results show that all the antecedents significantly affected the intention to use a VR device to spectate mega sports events, which explains a significant variance. Surprisingly, influences arising from social norm predominated over those arising from curiosity and the hedonic exploration of VR (enjoyment, and experience). The social norm strongly influences a VR device’s perceived usefulness, implying that people believe using VR will enhance their position in society and that they will thus perceive the technology as being more beneficial. The novelty of this study arises from quantifying the importance of curiosity’s relationship to VR acceptance and pinpointing the relevance of self-construal for VR acceptance.
The Role of Exercise Training in Delaying Kidney Function Decline in Non-Dialysis-Dependent Chronic Kidney Disease
Authors: Davies Mark , Sandoo Aamer , Macdonald Jamie
Published: May 2022

Chronic Kidney Disease (CKD) is a progressive condition characterised by declining eGFR and associated, particularly in advanced stages, with increased morbidity and cardiovascular mortality. Current treatment options for delaying disease progression are limited to a small number of pharmacological agents. Considering that rates of kidney function decline are greater in patients with lower levels of habitual physical activity, there is interest in the potential benefits of structured exercise training in delaying CKD progression. This discursive review summarises the current state-of-play in this field of research by critically analysing the published systematic reviews of randomised controlled trials of structured exercise training in the non-dialysis CKD population. Several issues are highlighted that hamper definite conclusions as to the therapeutic effectiveness of exercise training for this purpose. However, following an overview of the pathophysiology and risk factors for kidney function decline, several potential mechanisms explaining how exercise training may benefit CKD progression are offered. Finally, suggestions for future research in this area are made. The review concludes that there is a need for further research on the effectiveness of exercise before it can be recommended as part of routine care for the purpose of delaying CKD progression. Exercise can be recommended, however, to individual patients because of a potential benefit to kidney function, and definite benefits to other outcomes such as quality of life, with no apparent evidence of harm.
Sites of Geological Interest Assessment for Geoeducation Strategies, ESPOL University Campus, Guayaquil, Ecuador
Authors: Morante-Carballo Fernando , Merchán-Sanmartín Bethy , Cárdenas-Cruz Allen , Jaya-Montalvo Maria , Mata-Perelló Josep , Herrera-Franco Gricelda , Carrión-Mero Paúl
Published: May 2022

The development of geoeducation generates a link between people, landscapes, and their culture by recognising the geological potential around geosites and their conservation. Geosites have important scientific value and constitute a way of generating learning tools for the development of geoeducation. The city of Guayaquil, the main port of Ecuador, has a valuable geological and mining heritage, which has been affected by population growth and its invasion of protected areas, causing the displacement of animal species to the point of possible extinction. The research aims to assess geosites in the surroundings of the Gustavo Galindo campus, using the Spanish Inventory of Sites of Geological Interest (IELIG, Spanish acronym) methodology to promote geo-education in the context of sustainability. The methodological process includes (i) the inventory and initial selection of Sites of Geological Interest (SGI) based on interviews with experts and the analysis of primary data from potential sites; (ii) characterisation and semi-quantitative geosites assessment using the IELIG methodology; and (iii) qualitative assessment through SWOT analysis to formulate geotourism and geoeducation development strategies. This research emphasises the importance of promoting geological heritage in an urban area. It shows geotourism attractions represented by five SGI grouped into two types: geomorphological and petrological. In general, the SGI are in the “High” category of the degree of geological interest, ranging from 170 to 236.67. In addition, the study identified the lack of a geological culture and natural values of the university campus. It allowed the proposal of protection strategies (e.g., a geoconservation plan ensuring that the number of visitors does not exceed the maximum load capacity), geoscientific dissemination (e.g., creating games, museums, itineraries, launching geoeducational souvenirs, or developing educational content using augmented reality) and a detailed research based on evaluating sites for sustainable development.
Stewardship of Industrial Heritage Protection in Typical Western European and Chinese Regions: Values and Dilemmas
Authors: Zhang Jiazhen , Cenci Jeremy , Becue Vincent , Koutra Sesil , Liao Chenyang
Published: May 2022

Along with the increase in modern industry, original facilities and cultures have disappeared progressively, leading to the disappearance of traditional values. However, from the perspective of the stewardship of industrial heritage, preservation is vital for Western Europe, where the Industrial Revolution emerged firstly, and it has leading technology in terms of the advanced stewardship of industrial heritage protection. Meanwhile, there is a large market for industrial heritage growth in China, but its stewardship began later. Horizontal and vertical research into the stewardship of the industrial heritage of these two regions offers a review of the developed industrial regions and experiences for developing industrial regions in their future expansion. By analysing the values and dilemmas and the features of the legal, administrative, and fund guarantee systems, this paper summarizes the advanced expertise of the stewardship of industrial heritage in Western Europe and China and proposes strategies based on them.
Do We Need More Urban Green Space to Alleviate PM2.5 Pollution? A Case Study in Wuhan, China
Authors: Chen Yuanyuan , Ke Xinli , Min Min , Zhang Yue , Dai Yaqiang , Tang Lanping
Published: May 2022

Urban green space can help to reduce PM2.5 concentration by absorption and deposition processes. However, few studies have focused on the historical influence of green space on PM2.5 at a fine grid scale. Taking the central city of Wuhan as an example, this study has analyzed the spatiotemporal trend and the relationship between green space and PM2.5 in the last two decades. The results have shown that: (1) PM2.5 concentration reached a maximum value (139 μg/m3) in 2010 and decreased thereafter. Moran’s I index values of PM2.5 were in a downward trend, which indicates a sparser distribution; (2) from 2000 to 2019, the total area of green space decreased by 25.83%. The reduction in larger patches, increment in land cover diversity, and less connectivity led to fragmented spatial patterns of green space; and (3) the regression results showed that large patches of green space significantly correlated with PM2.5 concentration. The land use/cover diversity negatively correlated with the PM2.5 concentration in the ordinary linear regression. In conclusion, preserving large native natural habitats can be a supplemental measure to enlarge the air purification function of the green space. For cities in the process of PM2.5 reduction, enhancing the landscape patterns of green space provides a win-win solution to handle air pollution and raise human well-being.
Determination of Soil Hydraulic Properties from Infiltration Data Using Various Methods
Authors: Kargas George , Koka Dimitrios , Londra Paraskevi A.
Published: May 2022

In the present study, the determination of soil saturated hydraulic conductivity (Ks) and soil sorptivity (S) from one-dimensional vertical infiltration data of eight different soils were investigated using three methodologies. Specifically, the nonlinear optimization procedure with the help of the Excel Solver application using six different two-parameter infiltration equations, as described by Valiantzas, Haverkamp et al. (complete, two and three approximate expansions), Talsma and Parlange and Green and Ampt; the linearization method of cumulative infiltration data by Valiantzas and the method of Latorre et al. were used. The results showed that, in almost all cases, the relative errors in the prediction of S were smaller than those of Ks. The nonlinear optimization procedure using the Valiantzas equation gave the best prediction of S and Ks, with relative errors up to −12.49% and 13.61%, respectively. The two-term approximate expansion of Haverkamp gave the highest relative errors in both S and Ks. The various forms of the Haverkamp equation (complete and three approximate expansion), as well as the Latorre method, gave good predictions of S and Ks in fine-textured soils. In all forms of the Haverkamp equation, when parameter β was considered as an additional adjustment parameter, no improvement in the prediction of the S and Ks values was achieved, so the constant value β = 0.6 was proposed. The relative errors in the prediction of S and Ks resulting from the linearization method of the cumulative infiltration data were similar to those of the Valiantzas equation by the nonlinear optimization procedure. The accuracy in estimating the S and Ks parameters from each equation depends on its infiltration time validity and the soil type.
Growth Parameters and Mortality Rates Estimated for Seven Data-Deficient Fishes from the Azores Based on Length-Frequency Data
Authors: Santos Régis , Peixoto Ualerson Iran , Medeiros-Leal Wendell , Novoa-Pabon Ana , Pinho Mário
Published: May 2022

Given the scarcity of information suitable for stock assessments, the growth and mortality of seven exploited marine fishes in Azorean waters were estimated based on length-frequency data. The studied species were Trachurus picturatus, Sparisoma cretense, Scomber colias, Scorpaena scrofa, Serranus atricauda, Seriola spp. and Aphanopus carbo. The growth parameters L∞ (cm), k (year−1) and ϕ’ estimated through the ELEFAN_GA_boot routine were set at 55.87, 0.08 and 2.39 for T. picturatus; 55.03, 0.11 and 2.53 for S. cretense; 55.93, 0.18 and 2.76 for S. colias; 61.11, 0.11 and 2.61 for S. scrofa; 52.10, 0.12 and 2.51 for S. atricauda; 107.33, 0.12 and 3.18 for Seriola spp.; and 133.16, 0.09 and 3.19 for A. carbo; respectively. The total mortality rate estimated using the length–converted catch curve method was 0.22, 0.35, 0.58, 0.32, 0.31, 0.39 and 0.22 year−1; the natural mortality included 0.15, 0.20, 0.30, 0.20, 0.21, 0.21 and 0.16 year−1; and fishing mortality rate 0.07, 0.15, 0.28, 0.12, 0.10, 0.18 and 0.06 year−1, respectively, for the species mentioned. The relatively large sizes and slow growth with a low natural mortality rate indicate a high vulnerability to overfishing. Therefore, assessment and management initiatives are highly encouraged to ensure the sustainability of the resources.
Studies on the Microstructural Evolution and Mechanical Properties of Superalloy Inconel 718 Induced by Low Plasticity Burnishing Coupled with Turning
Authors: Hua Yang , Liu Zhanqiang , Yi Jie , Tang Aijun
Published: May 2022

Mechanical surface treatments are needed to perform on components for fatigue life enhancement by introducing beneficial compressive residual stress and material strengthening. In this study, the combined turning with low plasticity burnishing (LPB) surface modification process was performed for the sake of improving mechanical properties of Inconel 718. Firstly, the evolution of microstructure and residual stress after the LPB process were analyzed with the aid of electron backscatter diffraction (EBSD) and X-ray diffraction (XRD), respectively. Secondly, the tensile behavior of treated samples was investigated through tension tests. Finally, the micro-strengthening mechanism of Inconel 718, induced by the LPB process, was revealed. The results show that the peak compressive stress is increased by a factor of 4.2 after the LPB process. The grain refinement induced by the LPB process is attributed to the increase of average misorientation and the formation of high angle grain boundaries (HAGBs). The enhanced yield strength depends on the decreased average spacing and the increased HAGBs.
Poly(methyl methacrylate) with Oleic Acid as an Efficient Candida albicans Biofilm Repellent
Authors: Petrović Milica , Randjelović Marina , Igić Marko , Randjelović Milica , Arsić Arsenijević Valentina , Mionić Ebersold Marijana , Otašević Suzana , Milošević Irena
Published: May 2022

Poly(methyl methacrylate) (PMMA), widely used in dentistry, is unfortunately a suitable substrate for Candida (C.) albicans colonization and biofilm formation. The key step for biofilm formation is C. albicans ability to transit from yeast to hypha (filamentation). Since oleic acid (OA), a natural compound, prevents filamentation, we modified PMMA with OA aiming the antifungal PMMA_OA materials. Physico-chemical properties of the novel PMMA_OA composites obtained by incorporation of 3%, 6%, 9%, and 12% OA into PMMA were characterized by Fourier-transform infrared spectroscopy and water contact angle measurement. To test antifungal activity, PMMA_OA composites were incubated with C. albicans and the metabolic activity of both biofilm and planktonic cells was measured with a XTT test, 0 and 6 days after composites preparation. The effect of OA on C. albicans morphology was observed after 24 h and 48 h incubation in agar loaded with 0.0125% and 0.4% OA. The results show that increase of OA significantly decreased water contact angle. Metabolic activity of both biofilm and planktonic cells were significantly decreased in the both time points. Therefore, modification of PMMA with OA is a promising strategy to reduce C. albicans biofilm formation on denture.
A Modified Three-Dimensional Negative-Poisson-Ratio Metal Metamaterial Lattice Structure
Authors: Li Fangyi , Zhang Qiang , Shi Huimin , Liu Zheng
Published: May 2022

Mechanical metamaterials are of interest to researchers because of their unique mechanical properties, including a negative Poisson structure. Here, we study a three-dimensional (3D) negative-Poisson-ratio (NPR) metal metamaterial lattice structure by adding a star structure to the traditional 3D concave structure, thus designing three different angles with a modified NPR structure and control structure. We further study the mechanical properties via finite element numerical simulations and show that the stability and stiffness of the modified structures are improved relative to the control structure; the stability decreases with increasing star body angle. The star angle has the best relative energy absorption effect at 70.9°. The experimental model is made by selective laser melting (SLM) technology (3D printing), and the compression experiment verification used an MTS universal compressor. The experimental results are consistent with the changing trend in finite element simulation.
Annealing Response of Additively Manufactured High-Strength 1.2709 Maraging Steel Depending on Elevated Temperatures
Authors: Strakosova Angelina , Průša Filip , Michalcová Alena , Kratochvíl Petr , Vojtěch Dalibor
Published: May 2022

The present work describes the influence of different temperatures on mechanical properties and microstructure of additively manufactured high-strength 1.2709 maraging steel. For this purpose, samples produced by selective laser melting technology were used in their as-printed as well as their heat-treated state. Both samples were than exposed to temperatures ranging between 100 °C to 900 °C with a total dwell time of 2 h followed by water-cooling. The microhardness of the as-printed material reached its maximum (561 ± 6 HV0.1) at 500 °C, which corresponded to the microstructural changes. However, the heat-treated material retained its initial mechanical properties up to 500 °C. As the temperature increased, the microhardness of both the materials reduced, reaching their minimum at 900 °C. This phenomenon was accompanied by a change in the microstructure by forming coarse-grained martensite. This also resulted in a significant decrease in the ultimate tensile strength and an increase in the plasticity. TEM analysis confirmed the formation of Ni3Mo intermetallic phases in the as-printed material when exposed to a temperature of 500 °C. It was found that the same phase was present in the heat-treated sample and it remained stable up to a temperature of 500 °C.
Experimental Study on the Mechanical Properties, Water Absorption, and Fiber Degradation of Naturally Aged Glass Fiber and Polypropylene Fiber-Reinforced Concrete
Authors: Yuan Zhu , Jia Yanmin
Published: May 2022

The main objective of this study is to better understand the performance changes of naturally aged glass fiber-reinforced concrete (GFRC) and polypropylene fiber-reinforced concrete (PPFRC), especially the degradation of fibers, which is of great significance for evaluating the durability of structures using these two types of composite materials. The mechanical properties, water absorption, and microstructures of GFRC and PPFRC at a curing age of three years, including their compressive strength, full curves of water absorption, fiber-matrix interaction, and fiber degradation, were systematically studied, and the related properties were compared with those at the curing age of 28 days. The degradation of fibers after freeze-thaw cycles was also studied. The results revealed the following. The water/binder ratio (w/b) affects the rate of increase of the long-term compressive strength of naturally aged concrete. In general, the water absorption of fiber-reinforced concrete (FRC) at the curing age of three years was found to be significantly reduced, but with the increases of w/b and the fiber content to the maximum values, the water absorption of the specimens cured for three years was higher than that of the specimens cured for 28 days. Moreover, with the increase of the curing age, the optimal glass fiber (GF) contents for reducing the water absorption decreased from 1.35% to 0.90% (w/b = 0.30), and from 0.90% to 0.45% (w/b = 0.35), respectively. The GF surface was degraded into continuous pits with diameters of about 200 to 600 nm, and the surface of the pits was attached with spherical granular C-S-H gel products with diameters of about 30 to 44 nm. The freeze-thaw cycles were found to have no significant effect on the pits on the GF surface and the granular C-S-H gel products attached to the pits, but caused a portion of the cement matrix covering the GF to fall off. The interfacial bonding between the polypropylene fiber (PPF) and the cement matrix exhibited almost no change in the PPFRC after three years of curing as compared with that after 28 days of curing. Furthermore, the cement hydration gel on the PPF surface was not significantly damaged by 150 freeze-thaw cycles.
Comparative Study of Experimental and Modeling of Fly Ash-Based Concrete
Authors: Khan Kaffayatullah , Ahmad Ayaz , Amin Muhammad Nasir , Ahmad Waqas , Nazar Sohaib , Arab Abdullah Mohammad Abu
Published: May 2022

The application of supplementary cementitious materials (SCMs) in concrete has been reported as the sustainable approach toward the appropriate development. This research aims to compare the result of compressive strength (C-S) obtained from the experimental method and results estimated by employing the various modeling techniques for the fly-ash-based concrete. Although this study covers two aspects, an experimental approach and modeling techniques for predictions, the emphasis of this research is on the application of modeling methods. The physical and chemical properties of the cement and fly ash, water absorption and specific gravity of the aggregate used, surface area of the cement, and gradation of the aggregate were analyzed in the laboratory. The four predictive machine learning (PML) algorithms, such as decision tree (DT), multi-linear perceptron (MLP), random forest (RF), and bagging regressor (BR), were investigated to anticipate the C-S of concrete. Results reveal that the RF model was observed more exact in investigating the C-S of concrete containing fly ash (FA), as opposed to other employed PML techniques. The high R2 value (0.96) for the RF model indicates the high precision level for forecasting the required output as compared to DT, MLP, and BR model R2 results equal 0.88, 0.90, and 0.93, respectively. The statistical results and cross-validation (C-V) method also confirm the high predictive accuracy of the RF model. The highest contribution level of the cement towards the prediction was also reported in the sensitivity analysis and showed a 31.24% contribution. These PML methods can be effectively employed to anticipate the mechanical properties of concretes.
Damage Mechanisms and Anisotropy of an AA7010-T7452 Open-Die Forged Alloy: Fatigue Crack Propagation
Authors: Strohmann Tobias , Breitbarth Eric , Besel Michael , Zaunschirm Stefan , Witulski Thomas , Requena Guillermo
Published: May 2022

The process–microstructure–property relationship of high-strength 7000 series aluminum alloys during fatigue crack propagation (FCP) is highly relevant for safety during the design and service of aircraft structural components. It is scientifically evident that many metallurgical factors affect FCP properties, but partly contradictory or inconclusive results show that the quantitative description of the relationships is still a major challenge among researchers and engineers. Most research focuses on sheet or plate products and investigations lack quantitative information on the process–property relationship between open-die forged thick products and FCP. The present study contributes to this field by investigating the fatigue crack growth behavior of an open-die forged AA7010-T7452 aluminum alloy. Four different forging conditions comprising different characteristic microstructures are comparatively analyzed. The influence of grain size, grain shape, specimen orientation, crystallographic texture, and primary phase particles is investigated. Fractographic analysis reveals different active damage mechanisms during fatigue crack growth. Based on that, the microstructure features relevant to fatigue damage areidentified in each regime of crack growth.
Heat Treatments of Metastable β Titanium Alloy Ti-24Nb-4Zr-8Sn Processed by Laser Powder Bed Fusion
Authors: Hein Maxwell , Lopes Dias Nelson Filipe , Pramanik Sudipta , Stangier Dominic , Hoyer Kay-Peter , Tillmann Wolfgang , Schaper Mirko
Published: May 2022

Titanium alloys, especially β alloys, are favorable as implant materials due to their promising combination of low Young’s modulus, high strength, corrosion resistance, and biocompatibility. In particular, the low Young’s moduli reduce the risk of stress shielding and implant loosening. The processing of Ti-24Nb-4Zr-8Sn through laser powder bed fusion is presented. The specimens were heat-treated, and the microstructure was investigated using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mechanical properties were determined by hardness and tensile tests. The microstructures reveal a mainly β microstructure with α″ formation for high cooling rates and α precipitates after moderate cooling rates or aging. The as-built and α″ phase containing conditions exhibit a hardness around 225 HV5, yield strengths (YS) from 340 to 490 MPa, ultimate tensile strengths (UTS) around 706 MPa, fracture elongations around 20%, and Young’s moduli about 50 GPa. The α precipitates containing conditions reveal a hardness around 297 HV5, YS around 812 MPa, UTS from 871 to 931 MPa, fracture elongations around 12%, and Young’s moduli about 75 GPa. Ti-24Nb-4Zr-8Sn exhibits, depending on the heat treatment, promising properties regarding the material behavior and the opportunity to tailor the mechanical performance as a low modulus, high strength implant material.
Influence of Different Beam Oscillation Patterns in Electron Beam Welding of Niobium Sheets with Different Thickness
Authors: Tao Jia , Wu Jiefeng , Liu Zhihong , Ma Jianguo , Liu Zhenfei , Peng Wuqingliang
Published: May 2022

The electron beam welding of the tubes and the half-cells for our 1.3 GHz single-cell superconducting radiofrequency (SRF) cavities is complex due to the different thicknesses of the tubes and the half-cells in the iris region. However, the mechanical properties and microstructure of the iris welds in niobium SRF cavities have barely been explored in previous studies. For high-quality iris welds, welding experiments of niobium sheets of 2 mm and 2.8 mm were carried out under different oscillating conditions. The results show that welding with no oscillation or sinusoidal oscillation may not be applied in actual welding owing to the large misalignment of the bottom surface. The weld grains were not significantly refined through beam oscillation. The joints with infinity oscillation had a higher elongation than circular oscillation, which exhibited a brittle fracture in the tensile tests at 77 K. Nevertheless, the texture of the weld with infinity oscillation implies poor formability, so the feasibility of infinity oscillation in actual welding needs verification in future study.
Nanomaterials for Inner Ear Diseases: Challenges, Limitations and Opportunities
Authors: Li Liling , Luo Jia , Lin Xuexin , Tan Jingqian , Li Peng
Published: May 2022

The inner ear is located deep in the temporal bone and has a complex anatomy. It is difficult to observe and obtain pathological tissues directly. Therefore, the diagnosis and treatment of inner ear diseases have always been a major clinical problem. The onset of inner ear disease can be accompanied by symptoms such as hearing loss, dizziness and tinnitus, which seriously affect people’s lives. Nanoparticles have the characteristics of small size, high bioavailability and strong plasticity. With the development of related research on nanoparticles in inner ear diseases, nanoparticles have gradually become a research hotspot in inner ear diseases. This review briefly summarizes the research progress, opportunities and challenges of the application of nanoparticles in inner ear diseases.
Artificial Neural Network Modelling of the Effect of Vanadium Addition on the Tensile Properties and Microstructure of High-Strength Tempcore Rebars
Authors: Choi Woonam , Won Sungbin , Kim Gil-Su , Kang Namhyun
Published: May 2022

In high-strength rebar, the various microstructures obtained by the Tempcore process and the addition of V have a complex effect on the strength improvement of rebar. This study investigated the mechanism of strengthening of high-strength Tempcore rebars upon the addition of vanadium through artificial neural network (ANN) modelling. Various V contents (0.005, 0.072 and 0.14 wt.%) were investigated, and a large amount of bainite and V(C, N) were precipitated in the core of the Tempcore rebar in the high-V specimens. In addition, as the V content increased, the number of these fine precipitates (10–30 nm) increased. The precipitation strengthening proposed by the Ashby–Orowan model is a major contributing factor to the yield-strength increase (35 MPa) of the Tempcore rebar containing 0.140 wt.% V. The ANN model was developed to predict the yield and tensile strengths of Tempcore rebar after the addition of various amounts of V and self-tempering at various temperatures, and it showed high reproducibility compared to the experimental values (R-square was 93% and the average relative error was 2.6%). ANN modelling revealed that the yield strength of the Tempcore rebar increased more significantly with increasing V content (0.01–0.2 wt.%.) at relatively high self-tempering temperatures (≥530 °C). These results provide guidelines for selecting the optimal V content and process conditions for manufacturing high-strength Tempcore rebars.
Control and Dynamic Characteristics Analysis for the Double-Compound Axial Piston Pump Based on Working Conditions
Authors: Sun Zhiyuan , Zeng Qingliang , Wan Lirong , Dai Hanzheng
Published: May 2022

The periodic flow and pressure pulsation of the axial piston pump can lead to periodic vibration, noise, and even damage to various components in the hydraulic system. Therefore, the dynamic characteristics analysis of the axial piston pump in the hydraulic system is of great significance for reducing vibration and noise in the hydraulic system and improving efficiency. The double-compound axial piston pump is the key component of a high power and large flow hydraulic power system, which has a special power control mode. In this paper, the working and control principles of the double-compound axial piston pump are analyzed, the numerical model of the double-compound axial piston pump is established, and the effectiveness of the model is verified through experimental tests. The constant power control characteristics of the double-compound axial piston pump under different power settings and the variable power control characteristics under the rated load pressure are analyzed. By analyzing the dynamic characteristics of the double-compound axial piston pump, the influence of different working conditions on the dynamic characteristics is investigated. The results show that the output efficiency of the double-compound axial piston pump is higher when the output flow is larger. When the piston chamber works in the closed pre-compression pressure zone and the closed pre-release pressure zone, oil backflow occurs. The oil backflow in the piston chamber seriously intensifies the outlet flow pulsation of the double-compound axial piston pump. The flow pulsation rate is positively correlated with load pressure and power control pilot pressure, while negatively correlated with spindle speed. The paper provides a basis for the analysis and optimization of power control, flow pulsation, fluid vibration, and noise of the double-compound axial piston pump.
Coal–Rock Cutting Sound Denoising Based on Complete Ensemble Empirical Mode Decomposition with Adaptive Noise and an improved Fruit Fly Optimization Algorithm
Authors: Ren Chaofan , Xu Jing , Xu Jie , Liu Yanxin , Sun Ning
Published: May 2022

The cutting sound signal of a coal mining shearer is an important signal source for identifying the coal–rock cutting mode and load state. However, the coal–rock cutting sound signal directly collected from the industrial field always contains a large amount of background noise, which is not conducive to the subsequent feature extraction and recognition. Therefore, efficient noise elimination for the original signal is required. An intelligent processing method based on an improved complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) denoising algorithm is constructed for the cutting sound signal in this paper. CEEMDAN first decomposes the sound to generate a series of intrinsic modal functions (IMFs). Because the denoising threshold of each IMF is usually obtained by an experimental test or an empirical formula in the traditional CEEMDAN method, obtaining an optimal threshold set for each IMF is difficult. The processing effect is often restricted. To overcome this problem, the fruit fly optimization algorithm (FOA) was introduced for CEEMDAN threshold determination. Moreover, in the basic FOA, the scouting bee mutation operation and adaptive dynamic adjustment search strategy are applied to maintain the convergence speed and global search ability. The simulation result shows that the signal waveform processed by the improved CEEMDAN denoising algorithm is smoother than the other four typical eliminate noise signal algorithms. The output signal’s signal-to-noise ratio and mean square error are significantly improved. Finally, an industrial application of a shearer in a coal mining working face is performed to demonstrate the practical effect.
Towards Self-Adaptability of Instrumented Electromagnetic Energy Harvesters
Authors: Carneiro Pedro M. R. , Ferreira Jorge A. F. , Kholkin Andrei L. , Soares dos Santos Marco P.
Published: May 2022

Motion-driven electromagnetic energy harvesting is a well-suited technological solution to autonomously power a broad range of autonomous devices. Although different harvester configurations and mechanisms have been already proposed to perform effective tuning and broadband harvesting, no methodology has proven to be effective to maximize the harvester performance for unknown and time-varying patterns of mechanical power sources externally exciting the harvesters. This paper provides, for the first time, a radically new concept of energy harvester to maximize the harvested energy for time-varying excitations: the self-adaptive electromagnetic energy harvester. This research work aims to analyze the electric energy harvesting gain when self-adaptive electromagnetic harvesters, using magnetic levitation architectures, are able to autonomously adapt their architecture as variations in the excitation patterns occur. This was accomplished by identifying the optimal harvester length for different excitation patterns and load resistances. Gains related to electric current and power exceeding 100 can be achieved for small-scale harvesters. The paper also describes comprehensive case studies to verify the feasibility of the self-adaptive harvester, considering the energy demand from the adaptive mechanism, namely the sensing, processing and actuation systems. These successful results highlight the potential of this innovative methodology to design highly sophisticated energy harvesters, both for a small- and large-scale power supply.
Accurate Goertzel Algorithm: Error Analysis, Validations and Applications
Authors: Li Chuanying , Du Peibing , Li Kuan , Liu Yu , Jiang Hao , Quan Zhe
Published: May 2022

The Horner and Goertzel algorithms are frequently used in polynomial evaluation. Each of them can be less expensive than the other in special cases. In this paper, we present a new compensated algorithm to improve the accuracy of the Goertzel algorithm by using error-free transformations. We derive the forward round-off error bound for our algorithm, which implies that our algorithm yields a full precision accuracy for polynomials that are not too ill-conditioned. A dynamic error estimate in our algorithm is also presented by running round-off error analysis. Moreover, we show the cases in which our algorithms are less expensive than the compensated Horner algorithm for evaluating polynomials. Numerical experiments indicate that our algorithms run faster than the compensated Horner algorithm in those cases while producing the same accurate results, and our algorithm is absolutely stable when the condition number is smaller than 1016. An application is given to illustrate that our algorithm is more accurate than MATLAB’s fft function. The results show that the relative error of our algorithm is from 1015 to 1017, and that of the fft was from 1012 to 1015.
New Bounds for Arithmetic Mean by the Seiffert-like Means
Authors: Zhu Ling
Published: May 2022

By using the power series of the functions 1/sinnt and cost/sinnt (n=1,2,3,4,5), and the estimation of the ratio of two adjacent Bernoulli numbers, we obtained new bounds for arithmetic mean A by the weighted arithmetic means of Mtan1/3Msin2/3 and 13Mtan+23Msin,Mtanh1/3Msinh2/3 and 13Mtanh+23Msinh, where Mtan(x,y) and Msin(x,y), Mtanh(x,y) and Msinh(x,y) are the tangent mean, sine mean, hyperbolic tangent mean and hyperbolic sine mean, respectively. The upper and lower bounds obtained in this paper are compared in detail with the conclusions of the previous literature.