bluuebunny/crossref_metadata_2025 huggingface dataset:
Obstructing Sleep Apnea in Children with Genetic Disorders—A Special Need for Early Multidisciplinary Diagnosis and Treatment
Authors: Oros Mihaela , Baranga Lucica , Plaiasu Vasilica , Cozma Sebastian R. , Neagos Adriana , Paduraru Luminita , Necula Violeta , Martu Cristian , Dima-Cozma Lucia Corina , Gheorghe Dan Cristian
Published: May 2021

Background—Children with genetic disorders have multiple anatomical and physiological conditions that predispose them to obstructive sleep apnea syndrome (OSAS). They should have priority access to polysomnography (PSG) before establishing their therapeutic protocol. We analyzed the prevalence and the severity of OSAS in a particular group of children with genetic disorders and strengthened their need for a multidisciplinary diagnosis and adapted management. Methods—The retrospective analysis included children with genetic impairments and sleep disturbances that were referred for polysomnography. We collected respiratory parameters from sleep studies: apnea–hypopnea index (AHI), SatO2 nadir, end-tidal CO2, and transcutaneous CO2. Subsequent management included non-invasive ventilation (NIV) or otorhinolaryngological (ENT) surgery of the upper airway. Results—We identified 108 patients with neuromuscular disorders or multiple congenital anomalies. OSAS was present in 87 patients (80.5%), 3 of whom received CPAP, 32 needed another form of NIV during sleep, and 15 patients were referred for ENT surgery. The post-therapeutic follow-up PSG parameters confirmed the success of the treatment. Conclusions—The upper airway obstruction diagnostics and management for children with complex genetic diseases need a multidisciplinary approach. Early detection and treatment of sleep-disordered breathing in children with genetic disorders is a priority for improving their quality of life.
Adverse Life Trajectories Are a Risk Factor for SARS-CoV-2 IgA Seropositivity
Authors: Holuka Cyrielle , Snoeck Chantal , Mériaux Sophie , Ollert Markus , Krüger Rejko , Turner Jonathan ,   the CON-VINCE Consortium
Published: May 2021

Asymptomatic individuals, called “silent spreaders” spread SARS-CoV-2 efficiently and have complicated control of the ongoing COVID-19 pandemic. As seen in previous influenza pandemics, socioeconomic and life-trajectory factors are important in disease progression and outcome. The demographics of the asymptomatic SARS-CoV-2 carriers are unknown. We used the CON-VINCE cohort of healthy, asymptomatic, and oligosymptomatic individuals that is statistically representative of the overall population of Luxembourg for age, gender, and residency to characterise this population. Gender (male), not smoking, and exposure to early-life or adult traumatic experiences increased the risk of IgA seropositivity, and the risk associated with early-life exposure was a dose-dependent metric, while some other known comorbidities of active COVID-19 do not impact it. As prior exposure to adversity is associated with negative psychobiological reactions to external stressors, we recorded psychological wellbeing during the study period. Exposure to traumatic events or concurrent autoimmune or rheumatic disease were associated with a worse evolution of anxiety and depressive symptoms throughout the lockdown period. The unique demographic profile of the “silent spreaders” highlights the role that the early-life period plays in determining our lifelong health trajectory and provides evidence that the developmental origins of health and disease is applicable to infectious diseases.
High Prevalence of Late-Onset Fabry Cardiomyopathy in a Cohort of 499 Non-Selective Patients with Left Ventricular Hypertrophy: The Asian Fabry Cardiomyopathy High-Risk Screening Study (ASIAN-FAME)
Authors: Fan Yiting , Chan Tsz-Ngai , Chow Josie T. Y. , Kam Kevin K. H. , Chi Wai-Kin , Chan Joseph Y. S. , Fung Erik , Tong Mabel M. P. , Wong Jeffery K. T. , Choi Paul C. L. , Chan David K. H. , Sheng Bun , Lee Alex Pui-Wai
Published: May 2021

Left ventricular hypertrophy (LVH) caused by cardiac variant Fabry disease (FD) is typically late-onset and may mimic LVH caused by abnormal loading conditions. We aimed to determine the prevalence of FD in a non-selective patient population of everyday practice presenting with LVH, including those with hypertension and valve disease. We measured plasma alpha-galactosidase A activity using dried blood spot tests in 499 (age = 66 ± 13 years; 336 men) Hong Kong Chinese patients with LVH defined as maximal LV septal/posterior wall thickness ≥13 mm on echocardiography. Patients with low enzyme activity underwent mutation analysis of the GLA gene. Eight (age = 53−74 years; all men) unrelated patients (1.6%) had low plasma alpha-galactosidase A activity (0.57 ± 0.27 μmol/L wb/hr) and all were confirmed to have the GLA IVS4 + 919G > A mutation. FD patients presented with heart failure (n = 5), heart block (n = 2), ventricular tachycardia (n = 1), chest pain (n = 3), and/or murmur (n = 1). Uncontrolled hypertension (n = 4) and/or severe mitral/aortic valve pathology (n = 2) were frequent. Ethnic subgroups included Teochew (n = 5), Canton (n = 2), and Wenzhou (n = 1). Endomyocardial biopsy (n = 6) revealed hypertrophic myocytes with vacuolization and dense lamellar bodies. Late-onset IVS4 + 919G > A FD is prevalent among Chinese LVH patients, and should be considered as a cause of LVH in adult patients even when hypertension and/or valve pathology are present.
Determining Whether Low Protein Intake (<1.0 g/kg) Is a Risk Factor for Malnutrition in Patients with Cirrhosis
Authors: Park Jin-Hwa , Kang Minkoo , Jun Dae-Won , Kim Mimi , Kwak Joo-Hee , Kang Bo-kyeong
Published: May 2021

Background: The prevalence of malnutrition in patients with cirrhosis is considerably high. Body mass index (BMI) is a well-known risk factor for malnutrition, but the other risk factors are unknown. We investigated the prevalence of malnutrition and its risk factors in patients with cirrhosis. Methods: In total, 361 patients with cirrhosis were enrolled. Muscle quality and quantity were retrospectively assessed using the grip strength test and bioelectrical impedance analysis. Subjective global assessment (SGA) of malnutrition and dietary intake assessments were performed by a clinical dietician. Results: The prevalence rates of sarcopenia, malnutrition assessed by SGA, and inadequate energy intake were 22.7%, 13.6%, and 27.5%, respectively. The prevalence of malnutrition evaluated using any of the assessment methods was 46.3%, and no significant difference was observed according to liver disease etiology. The prevalence of malnutrition increased with the increasing disease severity (p = 0.034) and decreasing BMI (p = 0.007). The prevalence of malnutrition was 64.4% in patients with protein intake <1.0 g/kg. Low protein intake, Child–Pugh C grade, older age, and low BMI were independent risk factors for malnutrition in multivariate analysis. Conclusions: Low protein intake (<1.0 g/kg) is an independent risk factor for malnutrition in patients with cirrhosis.
Cohesive Zone Modeling of the Elastoplastic and Failure Behavior of Polymer Nanoclay Composites
Authors: Chowdhury Uraching , Wu Xiang-Fa
Published: May 2021

Cohesive zone model (CZM) is commonly used to deal with the nonlinear zone ahead of crack tips in materials with elastoplastic deformation behavior. This model is capable of predicting the behavior of crack initiation and growth. In this paper, CZM-based finite element analysis (FEA) is performed to examine the effects of processing parameters (i.e., the clay nanoparticle volume fraction and aspect ratio) in the mechanical behaviors of a polymeric matrix reinforced with aligned clay nanoparticles. The polymeric matrix is treated as an ideal elastoplastic solid with isotropic hardening behavior, whereas the clay nanoparticles are simplified as stiff, linearly elastic platelets. Representative volume elements (RVEs) of the resulting polymer nanoclay composites (PNCs) are adopted for FEA with the clay nanoparticle distributions to follow both stack and stagger configurations, respectively. In the study, four volume fractions (Vf = 2.5%, 5%, 7.5% and 10%) and four aspect ratios (ρ = 5, 7.5, 10, and 20) of the clay nanoparticles in the PNCs are considered. Detailed computational results show that either increasing volume fraction or aspect ratio of the clay nanoparticles enhances the effective tensile strength and stiffness of the PNCs. The progressive debonding process of the clay nanoparticles in the polymeric resin was predicted, and the debonding was initiated in the linearly elastic loading range. The numerical results also show that PNCs with stagger nanoparticle configuration demonstrate slightly higher values of the engineering stress than those based on the stack nanoparticle configuration at both varying volume fractions and aspect ratios of the clay nanoparticles. In addition, CZM-based FEA predicts a slightly lower stress field around the clay particles in PNCs than that without integration of CZM. The present computational studies are applicable for processing PNCs with controllable mechanical properties, especially the control of the key processing parameters of PNCs, i.e., the volume fraction and aspect ratio of the clay nanoparticles.
It Is Hard to Read Minds without Words: Cues to Use to Achieve Empathic Accuracy
Authors: Hodges Sara D. , Kezer Murat
Published: May 2021

When faced with the task of trying to “read” a stranger’s thoughts, what cues can perceivers use? We explore two predictors of empathic accuracy (the ability to accurately infer another person’s thoughts): use of stereotypes about the target’s group, and use of the target’s own words. A sample of 326 White American undergraduate students were asked to infer the dynamic thoughts of Middle Eastern male targets, using Ickes’ (Ickes et al. 1990) empathic accuracy paradigm. We predicted use of stereotypes would reduce empathic accuracy because the stereotypes would be negative and inaccurate. However, more stereotypical inferences about the target’s thoughts actually predicted greater empathic accuracy, a pattern in line with past work on the role of stereotypes in empathic accuracy (Lewis et al. 2012), perhaps because the stereotypes of Middle Easterners (collected from a sample of 60 participants drawn from the same population) were less negative than expected. In addition, perceivers who inferred that the targets were thinking thoughts that more closely matched what the target was saying out loud were more empathically accurate. Despite the fact that words can be used intentionally to obscure what a target is thinking, they appear to be a useful cue to empathic accuracy, even in tricky contexts that cross cultural lines.
Assessment of the Offshore Wind Energy Potential in the Romanian Exclusive Economic Zone
Authors: Onea Florin , Rusu Eugen , Rusu Liliana
Published: May 2021

The European offshore wind market is continuously expanding. This means that, together with significant technological developments, new coastal environments should be considered for the implementation of the wind farms, as is the case of the Black Sea, which is targeted in the present work. From this perspective, an overview of the wind energy potential in the Romanian exclusive economic zone (EEZ) in the Black Sea is presented in this work. This is made by analyzing a total of 20 years of wind data (corresponding to the time interval 2000–2019) coming from different sources, which include ERA5 reanalysis data and satellite measurements. Furthermore, a direct comparison between these datasets was also carried out. Finally, the results of the present work indicate that the Romanian offshore areas can replicate the success reported by the onshore wind projects, of which we can mention the Fantanele-Cogealac wind farm with an operating capacity of 600 MW.
Quantitative Ship Collision Frequency Estimation Models: A Review
Authors: Čorić Mirko , Mandžuka Sadko , Gudelj Anita , Lušić Zvonimir
Published: May 2021

Ship collisions are one of the most common types of maritime accidents. Assessing the frequency and probability of ship collisions is of great importance as it provides a cost-effective and practical way to mitigate risk. In this paper, we present a review of quantitative ship collision frequency estimation models for waterway risk assessment, accompanied by a classification of the models and a description of their main modelling characteristics. Models addressing the macroscopic perspective in the estimation of ship collision frequency on waterways are reviewed in this paper with a total of 29 models. We extend the existing classification methodology and group the collected models accordingly. Special attention is given to the criteria used to detect potential ship collision candidates, as well as to causation probability and the correlation of models with real ship collision statistics. Limitations of the existing models and future improvement possibilities are discussed. The paper can be used as a guide to understanding current achievements in this field.
A Novel Profiler Driven by Tidal Energy for Long Term Oceanographic Measurements in Offshore Areas
Authors: Zang Xiaoya , Zhang Zhujun , Fan Wei
Published: May 2021

In this paper, an innovative profiler driven by tidal energy for long-term oceanographic measurements in offshore areas with abundant tidal resources is investigated. The profiler is mainly composed of an oceanographic data collection system equipped with various sensors and a cross-plate that can make an upward or downward movement under the impact of tidal currents. Theoretical research is carried out through static analysis and numerical simulation, mainly studying the hydrodynamic characteristics of the cross-plate and its dynamic response to the current velocity. The theoretical model is verified by comparison with experiments. The research results show that tidal energy can be used as a kind of energy to drive the profiler’s ascent and descent motion and to continuously measure ocean parameters without using electric energy. The theoretical model established in this study can roughly predict the position of the profiler observation platform in the vertical direction under various current velocities. Furthermore, by studying the relationship between the current velocities and the lift and drag forces of the cross-plate in the fluid, it is recognized that the current velocity is an important factor affecting the stability of the system’s motion. It is hoped that this research will contribute to the development of profilers.
A Multifaceted Approach to Advance Oil Spill Modeling and Physical Oceanographic Research at the United States Bureau of Ocean Energy Management
Authors: Li Zhen , Smith Caryn , DuFore Christopher , Zaleski Susan F. , Auad Guillermo , Johnson Walter , Ji Zhen-Gang , O’Reilly S. E.
Published: May 2021

The Environmental Studies Program (ESP) at the United States Bureau of Ocean Energy Management (BOEM) is funded by the United States Congress to support BOEM’s mission, which is to use the best available science to responsibly manage the development of the Nation’s offshore energy and mineral resources. Since its inception in 1973, the ESP has funded over $1 billion of multidisciplinary research across four main regions of the United States Outer Continental Shelf: Gulf of Mexico, Atlantic, Alaska, and Pacific. Understanding the dynamics of oil spills and their potential effects on the environment has been one of the primary goals of BOEM’s funding efforts. To this end, BOEM’s ESP continues to support research that improves oil spill modeling by advancing our understanding and the application of meteorological and oceanographic processes to improve oil spill modeling. Following the Deepwater Horizon oil spill in 2010, BOEM has invested approximately $28 million on relevant projects resulting in 73 peer-reviewed journal articles and 42 technical reports. This study describes the findings of these projects, along with the lessons learned and research information needs identified. Additionally, this paper presents a path forward for BOEM’s oil spill modeling and physical oceanographic research.
eWOM in C2C Platforms: Combining IAM and Customer Satisfaction to Examine the Impact on Purchase Intention
Authors: Bueno Salvador , Gallego M. Dolores
Published: May 2021

This study is focused on communications that come from consumer-to-consumer (C2C) ecommerce relationships. This topic is directly associated with the electronic word-of-mouth (eWOM) phenomenon. eWOM is related to the set of positive or negative opinions made by potential, actual, or former customers about a seller. The present study proposes a structural equation modeling with partial least squares (PLS-SEM) research model to analyze consumers’ opinions impact on attitude toward purchasing. This model is based on the Information Adoption Model (IAM) in combination with an ecommerce satisfaction perspective, comprising five constructs: (1) service quality, (2) ecommerce satisfaction, (3) argument quality, (4) source credibility and (5) purchase intention. The model was tested by applying the Smart Partial Least Squares (SmartPLS) software for which 116 effective data from customers of the Taobao C2C platform were used. The findings reveal that all of the defined relationships were supported, confirming the positive impact of all the proposed constructs on the purchase intention. In this respect, the findings suggest that C2C platforms should strengthen the analyzed connections to grow the business and to promote transactions. Finally, implications and limitations related to the explanatory capacity and the sample are identified.
Study of the Solid-State Synthesis of Nickel Ferrite (NiFe2O4) by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Raman Spectroscopy
Authors: Cherpin Chloé , Lister Derek , Dacquait Frédéric , Liu Lihui
Published: May 2021

Spinel ferrite compounds continue to receive a lot of attention due to their unique properties. Among the numerous synthesis routes existing, the solid-state method was applied for the production of nickel ferrite, by introducing the use of a quartz vial. A mixture of nickel oxide (NiO) and hematite (Fe2O3) was ground and vacuum-sealed in the vial and different thermal treatment programs were tested. The resulting particles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. For temperatures, below 1000 °C, the solid-state reaction is not complete as nickel oxide (NiO) and hematite (Fe2O3) are still present. The reaction time is a decisive parameter for the morphology of the particles obtained. If, for different reaction times, the particle size distribution is always between 0.3 and 1.7 µm, a longer reaction time leads to the formation of dense, interconnected clusters of particles. Optimal parameters to synthesize a pure phase of spherical nickel ferrite were sought and found to be a reaction temperature of 1000 °C for 72 h.
Metal Borohydrides beyond Groups I and II: A Review
Authors: Suárez-Alcántara Karina , Tena García Juan Rogelio
Published: May 2021

This review consists of a compilation of synthesis methods and several properties of borohydrides beyond Groups I and II, i.e., transition metals, main group, lanthanides, and actinides. The reported properties include crystal structure, decomposition temperature, ionic conductivity, photoluminescence, etc., when available. The compiled properties reflect the rich chemistry and possible borohydrides’ application in areas such as hydrogen storage, electronic devices that require an ionic conductor, catalysis, or photoluminescence. At the end of the review, two short but essential sections are included: a compilation of the decomposition temperature of all reported borohydrides versus the Pauling electronegativity of the cations, and a brief discussion of the possible reactions occurring during diborane emission, including some strategies to reduce this inconvenience, particularly for hydrogen storage purposes.
Prediction and Analysis of Ultimate Bearing Capacity of Square CFST Long Column under Eccentric Compression after Acid Rain Corrosion
Authors: Lyu Xuetao , Zhang Liqiang , Zhang Tong , Li Ben , Li Huan , Yu Yang
Published: May 2021

This paper adopts the method of steel tube wall thickness and strength reduction to simulate corrosion damage. The numerical model of the square concrete-filled steel tube long column (SCFST-LC) under eccentric compression after acid rain corrosion is established in the finite element software, ABAQUS. The reliability and accuracy of the model are verified by comparing it with published relevant experimental results. The failure mode, load-deformation curve, and ultimate compressive load were analysed. Following that, the impacts of section size, yield strength of the steel tube, axial compressive strength of concrete, steel ratio, slenderness ratio, and load eccentricity on its ultimate compressive load are comprehensively investigated. The results demonstrate that the ultimate compressive load of the SCFST-LC decreases significantly with the increase in corrosion rate. The corrosion rate increases from 10 to 40%, and the ultimate bearing capacity decreases by 37.6%. Its ultimate bearing capacity can be enhanced due to the increase in section size, material strength, and steel ratio. In contrast, the ascending slenderness ratio and load eccentricity has harmful effects on the ultimate compressive load of the specimens. Finally, a simplified formula for the axial compressive load of the SCFST-LC under eccentric compression after acid rain corrosion is proposed. The calculation accuracy is high and the deviation of the results is basically within 15%, which is in good agreement with the numerical simulation results.
Improvement of the Adhesion and Diamond Content of Electrodeposited Cu/Microdiamond Composite Coatings by a Plated Cu Interlayer
Authors: Wang Xiaoli , Chou Chau-Chang , Wu Liberty Tse-Shu , Wu Rudder , Lee Jyh-Wei , Chang Horng-Yi
Published: May 2021

Diamond-incorporated copper metal matrix layers were fabricated on brass substrates by using electrodeposition technology in this study. To improve the adhesion of the composite coatings on the brass substrate, a plated copper was applied as the interlayer between the multilayers and the substrate. The surface morphologies of the interlayer and the diamond-incorporated copper composite layers were studied by scanning electron microscopy. The effect of the copper interlayer on the incorporation and the distribution of the diamond content in the coatings was analyzed by surface roughness, electrochemical impedance spectroscopy, and cyclic voltammetry. The diamond content of the composite coating was measured by energy-dispersive X-ray. The film thickness was evaluated by the cross-sectional technique of focused ion beam microscopy. The element, composition, and crystallization direction of diamond with Cu matrix was measured by X-ray diffraction and transmission electron microscope. The adhesion of the multilayers was studied by scratch tests. The experiment results indicated that the diamond content and distribution of the coating were higher and more uniform with the Cu interlayer than that without one. The plated copper interlayer reduced the electrical double-layer impedance and enhanced the adsorption of diamond particles by the surrounding Cu ions, which promoted the diamond content in the composite coatings. The roughened surface caused by the plated Cu interlayer also improved the substrate’s mechanical interlock with the composite coating, which contributed to the strong adhesion between them.
Strength Properties of Structural Glulam Elements from Pine (Pinus sylvestris L.) Timber Reinforced in the Tensile Zone with Steel and Basalt Rods
Authors: Mirski Radosław , Kuliński Marcin , Dziurka Dorota , Thomas Marta , Antonowicz Ryszard
Published: May 2021

The study analyzed potential applicability for asymmetric reinforcement of glulam beams using materials with a higher modulus of elasticity. Reinforcement elements included smooth and ribbed steel rods as well as basalt rods. These rods were placed only in the tensile zone, assuming that they will not only impart increased rigidity but first of all will reduce the scatter of bending strength values. What is significant, tests were conducted on timber with defects, as it is most commonly used in industrial practice. Analyses showed that this provides an increase in rigidity close to the assumed level. A significant increase in strength was observed. The manufactured beams reinforced with steel and basalt rods were characterized by mean bending strength amounting to 54 and 47 N/mm2, respectively. However, no significant improvement was found in the scatter of the observed variable. Beams reinforced with steel exhibit a 20% higher strength than unreinforced beams. The lower strength of beams reinforced with basalt bars may be related to the lower modulus of elasticity of the basalt itself.
Research on the Release of Dangerous Compounds from the BTEX and PAHs Groups in Industrial Casting Conditions
Authors: Holtzer Mariusz , Dańko Rafał , Piasny Sylwester , Kubecki Michał , Drożyński Dariusz , Roczniak Agnieszka , Skrzyński Mateusz , Kmita Angelika
Published: May 2021

The assessment of the harmfulness of moulding and core sands is mainly based on investigations of compositions of gases emitted by liquid casting alloys during the mould pouring. The results of investigations of moulding sands obtained under industrial conditions are presented in this paper. A unique research stand was designed and built for this aim. It allowed us to determine emissions of gases at individual stages of casting a mass up to 50 kg. This approach enables simulation of foundry conditions. Moulding sands bound by organic binders (phenol-formaldehyde; furan), inorganic binders and green sand, were subjected to investigations. The composition of gases that evolved during the individual stages, pouring, cooling and knocking out, was tested each time, and the contents of Polycyclic Aromatic Hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylenes (BETX) were analysed. Investigations indicated that the emission of gases from sands with inorganic binders is negligible when compared with the emission of gases from sands with organic binders. The emission of gases from green sand is placed in the middle of the scale. As an example: the sand with furan resin emitted 84 mg of BTEX (in recalculation for 1 kg of sand) while from sands with inorganic binders there was a maximum of 2.2 mg (for 1 kg of sand). In the case of sands with inorganic binders, MI and MC sands indicated comparable and very low emissions of gases from the PAHs group, at the level of 0.018 mg and 0.019 mg for 1 kg of sand, respectively. The higher emission of PAHs from MG sand is the result of its different way of hardening (a binder was of an organic character) than of sands MI and MC.
Synthetic, Mesomorphic, and DFT Investigations of New Nematogenic Polar Naphthyl Benzoate Ester Derivatives
Authors: Al-Zahrani Salma A. , Ahmed Hoda A. , El-atawy Mohamed A. , Abu Al-Ola Khulood A. , Omar Alaa Z.
Published: May 2021

Four new non-symmetrical derivatives based on central naphthalene moiety, 4-((4–(alkoxy)phenyl) diazenyl)naphthalen–1–yl 4–substitutedbenzoate (In/x), were prepared, and their properties were investigated experimentally and theoretically. The synthesized materials bear two wing groups: an alkoxy chain of differing proportionate length (n = 6 and 16 carbons) and one terminal attached to a polar group, X. Their molecular structures were elucidated via elemental analyses and FT-IR and NMR spectroscopy. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were carried out to evaluate their mesomorphic properties. The results of the experimental investigations revealed that all the synthesized analogues possess only an enantiotropic nematic (N) mesophase with a high thermal stability and broad range. Density functional theory (DFT) calculations were in accordance with the experimental investigations and revealed that all prepared materials are to be linear and planar. Moreover, the rigidity of the molecule increased when an extra fused ring was inserted into the center of the structural shape, so its thermal and geometrical parameters were affected. Energy gap predictions confirmed that the I16/c derivative is more reactive than other compounds.
A New Method of Predicting the Structural and Mechanical Change of Materials during Extrusion by the Method of Multiple Plastic Deformations
Authors: Harničárová Marta , Valíček Jan , Kušnerová Milena , Palková Zuzana , Kopal Ivan , Borzan Cristina , Kadnár Milan , Paulovič Stanislav
Published: May 2021

The formulation of the Hall–Petch relationship in the early 1950s has raised immense interest in studying the influence of the grain size of solid materials on their properties. Grain refinement can be achieved through extreme deformation. In the presented study, Equal-Channel Angular Pressing (ECAP) was successfully applied to produce an ultrafine-grained microstructure in a pure commercial Cu of 99.9 wt%. Samples were processed by ECAP at 21 °C for six passes via route A. A new equation of equilibrium that allows the exact determination of the number of extrusions and other technological parameters required to achieve the desired final grain size has been developed. The presented research also deals, in a relatively detailed and comparative way, with the use of ultrasound. In this context, a very close correlation between the process functions of extrusion and the speed of longitudinal ultrasonic waves was confirmed.
A Comparison of Biomechanical Properties of Implant-Retained Overdenture Based on Precision Attachment Type
Authors: Idzior-Haufa Małgorzata , Pilarska Agnieszka A. , Hędzelek Wiesław , Boniecki Piotr , Pilarski Krzysztof , Dorocka-Bobkowska Barbara
Published: May 2021

This paper aims to compare, in vitro, the biomechanical properties of an overdenture retained by two bar-retained implants and an overdenture retained by two bar-retained implants with ball attachments. An edentulous mandible model was prepared for the study based on the FRASACO mold with two implants. In the first system, the “rider” type (PRECI-HORIX, CEKA) retention structure and the complete mandibular denture with the matrix were made. In the second system, the “rider” type retention suprastructure was also used. In the distal part, (CEKA) clips were placed symmetrically, and a complete mandibular denture, together with the matrix on the bar, and the clip patrices were made. A numerical model was developed for each system where all elements were positioned and related to geometric relations, as in reality. The FEA analysis (finite element analysis) was carried out for seven types of loads: with vertical forces of 20, 50, and 100 N and oblique forces of 20 and 50 N acting on individual teeth of the denture, namely central incisor, canine, and first molar. Displacements, stresses, and deformations within the systems were investigated. Maximum denture displacement in the first system was 0.7 mm. Maximum bar stress amounted to 27.528 MPa, and implant stress to 23.16 MPa. Maximum denture displacement in the second system was 0.6 mm. Maximum bar stress amounted to 578.6 MPa, that of clips was 136.99 MPa, and that of implants was 51.418 MPa. Clips cause smaller displacement of the overdenture when it is loaded but generate higher stress within the precision elements and implants compared to a denture retained only by a bar. Regardless of the shape of the precision element, small deformations occur that mainly affect the mucosa and the matrix.
Mechanical Characterization and Thermodynamic Analysis of Laser-Polished Landscape Design Products Using 3D Printing
Authors: Ba Yue , Wen Yu , Wu Shibin
Published: May 2021

Recent innovations in 3D printing technologies and processes have influenced how landscape products are designed, built, and developed. In landscape architecture, reduced-size models are 3D-printed to replicate full-size structures. However, high surface roughness usually occurs on the surfaces of such 3D-printed components, which requires additional post-treatment. In this work, we develop a new type of landscape design structure based on the fused deposition modeling (FDM) technique and present a laser polishing method for FDM-fabricated polylactic acid (PLA) mechanical components, whereby the surface roughness of the laser-polished surfaces is reduced from over Ra 15 µm to less than 0.25 µm. The detailed results of thermodynamics and microstructure evolution are further analyzed during laser polishing. The stability and accuracy of the results are evaluated based on the standard deviation. Additionally, the superior tensile and flexural properties are examined in the laser-polished layer, in which the ultimate tensile strength (UTS) is increased by up to 46.6% and the flexural strength is increased by up to 74.5% compared with the as-fabricated components. Finally, a real polished landscape model is simulated and optimized using a series of scales.
Hf1−xSixO2 Nanocomposite Coatings Prepared by Ion-Assisted Co-Evaporation Process for Low-Loss and High-LIDT Optics
Authors: Jiao Hongfei , Niu Xinshang , Zhang Jinlong , Ma Bin , Cheng Xinbin , Wang Zhanshan
Published: May 2021

Hf1−xSixO2 nanocomposites with different SiO2 doping ratios were synthesized using an ion-assisted co-evaporation process to achieve dense amorphous Hf1−xSixO2 coatings with low loss and a high laser-induced damage threshold (LIDT). The results showed that the Hf1−xSixO2 nanocomposites (x ≥ 0.20) exhibited excellent comprehensive performance with a wide band gap and a dense amorphous microstructure. High-temperature annealing was carried out to ensure better stoichiometry and lower absorption. Precipitation and regrowth of HfO2 grains were observed from 400 °C to 600 °C during annealing of the Hf0.80Si0.20O2 nanocomposites, resulting in excessive surface roughness. A phenomenological model was proposed to explain the phenomenon. The Hf1−xSixO2 nanocomposites (x = 0.3 and 0.4) maintained a dense amorphous structure with low absorption after annealing. Finally, a 1064-nm Hf0.70Si0.30O2/SiO2 high-performance reflector was prepared and achieved low optical loss (15.1 ppm) and a high LIDT (67 J/cm2).
Influences of Increased Pressure Foaming on the Cellular Structure and Compressive Properties of In Situ Al-4.5%Cu-xTiB2 Composite Foams with Different Particle Fraction
Authors: Niu Zhengyi , An Zhentao , Jiang Zhibao , Cao Zhuokun , Yu Yang
Published: May 2021

Metallic foams have drawn increasing attention in applications ranging from lightweight structures to energy absorption devices. Mechanical properties of metallic foams depend on both their microstructure and cellular structure. In situ Al-4.5%Cu-xTiB2 composites were used as start materials for fabrication of closed-cell foams through liquid route under atmosphere pressure and increased pressure, aiming at simultaneously strengthening the cell wall material and optimizing the cellular structure. Macro-structural features of the foams were determined by micro X-ray computed tomography (µCT); results exhibit that increasing weight ratio of in situ TiB2 particles leads to coarsened cell structure for foams made under atmosphere pressure, due to the increase in critical thickness of cell wall rupture. Significant reduction of cell size and increase in cell circularity were observed for foams fabricated under increased pressure. Quasi static compression test results indicate that yield strength of foam samples increases with increasing particle fraction and refinement of cell structure. Microstructure observation shows that the continuous network at interdendritic regions consists of in situ TiB2 particles and intermetallic compounds are responsible for the reduced ductility of cell wall materials and the reduction in energy absorption efficiency of foams with high particle fraction. The influences of cell structure on the normalized strength and specific energy absorption were also discussed, and it was found that the improvement of yield strength and energy absorption of composite foams attributes to both the reinforcement of in situ TiB2 particles and the refinement of cellular structure.
Investigation of Optimization Algorithms for Neural Network Solutions of Optimal Control Problems with Mixed Constraints
Authors: Bolodurina Irina , Zabrodina Lyubov
Published: May 2021

In this paper, we consider the problem of selecting the most efficient optimization algorithm for neural network approximation—solving optimal control problems with mixed constraints. The original optimal control problem is reduced to a finite-dimensional optimization problem by applying the necessary optimality conditions, the Lagrange multiplier method and the least squares method. Neural network approximation models are presented for the desired control functions, trajectory and conjugate factors. The selection of the optimal weight coefficients of the neural network approximation was carried out using the gravitational search algorithm and the basic particle swarm algorithm and the genetic algorithm. Computational experiments showed that evolutionary optimization algorithms required the smallest number of iterations for a given accuracy in comparison with the classical gradient optimization method; however, the multi-agent optimization methods were performed later for each operation. As a result, the genetic algorithm showed a faster convergence rate relative to the total execution time.
FMR Damping in Thin Films with Exchange Bias
Authors: Chechenin Nikolay G. , Dzhun Irina O. , Babaytsev Georgy V. , Kozin Mikhail G. , Makunin Alexey V. , Romashkina Irina L.
Published: May 2021

Ferromagnetic resonance (FMR) linewidth (LW) is a tool for studying the high frequency properties of magnetic materials for their application in high-speed devices. Here, we investigate different mechanisms which determine FMR damping in bilayer ferromagnetic/antiferromagnetic (F/AF and AF/F) exchange bias systems. Variations of FMR LW with the thickness and deposition order of the F and AF layers were studied, as well as their correlation with the exchange bias field and roughness of the sample surface. We observed much larger LW in AF/F structures compared with F/AF samples. It was found that neither the exchange bias nor surface/interface roughness in the samples could explain the difference in LW for F/AF and AF/F samples. Instead, the different underlayer microstructure influenced the grainsize, leading to different angular dispersion of magnetization and different internal stray field in F-layers, promoting a different intensity of magnon scattering and FMR damping in F/AF and AF/F samples.
Four Distances for Circular Intuitionistic Fuzzy Sets
Authors: Atanassov Krassimir , Marinov Evgeniy
Published: May 2021

In the paper, for the first time, four distances for Circular Intuitionistic Fuzzy Sets (C-IFSs) are defined. These sets are extensions of the standard IFS that are extensions of Zadeh’s fuzzy sets. As it is shown, the distances for the C-IFS are different than those for the standard IFSs. At the moment, they do not have analogues in fuzzy sets theory. Examples, comparing the proposed distances, are given and some ideas for further research are formulated.
Three-Dimensional Numerical Study of the Effect of Protective Barrier on the Dispersion of the Contaminant in a Building
Authors: Maatki Chemseddine
Published: May 2021

The finite volume method and potential-vorticity vector formalism in their three-dimensional form were used to numerically study the impact of an adiabatic and impermeable vertical barrier on the dispersion of a local aero-contaminant due to the double-diffusive Rayleigh–Benard convection inside a cubic container. Different governing parameters such as the Rayleigh number, buoyancy ratio and barrier height were analyzed for Le = 1.2 and Pr = 0.7, representing an air-contaminant mixture. The potential-vector-vorticity formalism in the three-dimensional form allowed the elimination of the pressure terms appearing in the Navier–Stokes equations. It was found that the heat and mass transfer as well as the effectiveness of the barrier in reducing contaminant dispersion are strongly influenced by the buoyancy ratio, the barrier size and the Rayleigh number. In addition, the barrier effectiveness is more than 70% for a height of half the building height.
Optimization Method to Address Psychosocial Risks through Adaptation of the Multidimensional Knapsack Problem
Authors: Eraña-Díaz Marta Lilia , Cruz-Chávez Marco Antonio , Juárez-Pérez Fredy , Enriquez-Urbano Juana , Rivera-López Rafael , Acosta-Flores Mario
Published: May 2021

This paper presents a methodological scheme to obtain the maximum benefit in occupational health by attending to psychosocial risk factors in a company. This scheme is based on selecting an optimal subset of psychosocial risk factors, considering the departments’ budget in a company as problem constraints. This methodology can be summarized in three steps: First, psychosocial risk factors in the company are identified and weighted, applying several instruments recommended by business regulations. Next, a mathematical model is built using the identified psychosocial risk factors information and the company budget for risk factors attention. This model represents the psychosocial risk optimization problem as a Multidimensional Knapsack Problem (MKP). Finally, since Multidimensional Knapsack Problem is NP-hard, one simulated annealing algorithm is applied to find a near-optimal subset of factors maximizing the psychosocial risk care level. This subset is according to the budgets assigned for each of the company’s departments. The proposed methodology is detailed using a case of study, and thirty instances of the Multidimensional Knapsack Problem are tested, and the results are interpreted under psychosocial risk problems to evaluate the simulated annealing algorithm’s performance (efficiency and efficacy) in solving these optimization problems. This evaluation shows that the proposed methodology can be used for the attention of psychosocial risk factors in real companies’ cases.
A Novel Analysis of the Smooth Curve with Constant Width Based on a Time Delay System
Authors: Fu Teng , Zhou Yusheng
Published: May 2021

In this paper, we analyze the C∞ smooth curve of constant width using the characteristic equation of a time delay system. We prove that a closed convex curve must be a circle if it is still a smooth curve of constant width after taking any number of derivatives. Finally, the simulation results are presented for analyzing the influence of derivative orders on a smooth non-circular curve of constant width.
Influence of COVID-19 Pandemic Lockdown on Patients from the Bariatric Surgery Waiting List
Authors: Walędziak Maciej , Różańska-Walędziak Anna , Bartnik Paweł , Kacperczyk-Bartnik Joanna , Janik Michał , Kowalewski Piotr , Kwiatkowski Andrzej
Published: May 2021

Background and Objectives: Social isolation and lockdown due to the COVID-19 pandemic have influenced dietary habits and physical activity of all the population, but the obese population is the most vulnerable to weight gain. Material and Methods: A group of 189 patients (166 female and 23 male) from the bariatric surgery waiting list filled in a survey about the influence of COVID-19 pandemic lockdown on their dietary habits, physical activity, and the possibility of contact with their bariatric care center. Results: The majority of patients with weight gain declared a decrease in physical activity, compared to half of the patients without weight gain (50.5% vs. 74.5%, p < 0.05). The continuation of bariatric care and the possibility of contact with a bariatric surgeon, dietician, and psychologist had each significant influence on reducing the risk of patients’ weight gain (p < 0.05). Conclusions: Maintaining physical activity and contact with bariatric care specialists are important factors in allowing to avoid weight gain in patients waiting for bariatric surgery.
Fatigue and Crack Growth under Constant- and Variable-Amplitude Loading in 9310 Steel Using “Rainflow-on-the-Fly” Methodology
Authors: Newman James C.
Published: May 2021

Fatigue of materials, like alloys, is basically fatigue-crack growth in small cracks nucleating and growing from micro-structural features, such as inclusions and voids, or at micro-machining marks, and large cracks growing to failure. Thus, the traditional fatigue-crack nucleation stage (Ni) is basically the growth in microcracks (initial flaw sizes of 1 to 30 μm growing to about 250 μm) in metal alloys. Fatigue and crack-growth tests were conducted on a 9310 steel under laboratory air and room temperature conditions. Large-crack-growth-rate data were obtained from compact, C(T), specimens over a wide range in rates from threshold to fracture for load ratios (R) of 0.1 to 0.95. New test procedures based on compression pre-cracking were used in the near-threshold regime because the current ASTM test method (load shedding) has been shown to cause load-history effects with elevated thresholds and slower rates than steady-state behavior under constant-amplitude loading. High load-ratio (R) data were used to approximate small-crack-growth-rate behavior. A crack-closure model, FASTRAN, was used to develop the baseline crack-growth-rate curve. Fatigue tests were conducted on single-edge-notch-bend, SEN(B), specimens under both constant-amplitude and a Cold-Turbistan+ spectrum loading. Under spectrum loading, the model used a “Rainflow-on-the-Fly” subroutine to account for crack-growth damage. Test results were compared to fatigue-life calculations made under constant-amplitude loading to establish the initial microstructural flaw size and predictions made under spectrum loading from the FASTRAN code using the same micro-structural, semi-circular, surface-flaw size (6-μm). Thus, the model is a unified fatigue approach, from crack nucleation (small-crack growth) and large-crack growth to failure using fracture mechanics principles. The model was validated for both fatigue and crack-growth predictions. In general, predictions agreed well with the test data.
Challenges and Potential in Increasing Lutein Content in Microalgae
Authors: Xie Yuxiao , Xiong Xiaochao , Chen Shulin
Published: May 2021

Research on enhancing lutein content in microalgae has made significant progress in recent years. However, strategies are needed to address the possible limitations of microalgae as practical lutein producers. The capacity of lutein sequestration may determine the upper limit of cellular lutein content. The preliminary estimation presented in this work suggests that the lutein sequestration capacity of the light-harvesting complex (LHC) of microalgae is most likely below 2% on the basis of dry cell weight (DCW). Due to its nature as a structural pigment, higher lutein content might interfere with the LHC in fulfilling photosynthetic functions. Storing lutein in a lipophilic environment is a mechanism for achieving high lutein content but several critical barriers must be overcome such as lutein degradation and access to lipid droplet to be stored through esterification. Understanding the mechanisms underlying lipid droplet biogenesis in chloroplasts, as well as carotenoid trafficking through chloroplast membranes and carotenoid esterification, may provide insight for new approaches to achieve high lutein contents in algae. In the meantime, building the machinery for esterification and sequestration of lutein and other hydroxyl-carotenoids in model microorganisms, such as yeast, with synthetic biology technology provides a promising option.