bluuebunny/crossref_metadata_2025 huggingface dataset:
The Roles of Chromatin Accessibility in Regulating the Candida albicans White-Opaque Phenotypic Switch
Authors: Qasim Mohammad N. , Valle Arevalo Ashley , Nobile Clarissa J. , Hernday Aaron D.
Published: January 2021

Candida albicans, a diploid polymorphic fungus, has evolved a unique heritable epigenetic program that enables reversible phenotypic switching between two cell types, referred to as “white” and “opaque”. These cell types are established and maintained by distinct transcriptional programs that lead to differences in metabolic preferences, mating competencies, cellular morphologies, responses to environmental signals, interactions with the host innate immune system, and expression of approximately 20% of genes in the genome. Transcription factors (defined as sequence specific DNA-binding proteins) that regulate the establishment and heritable maintenance of the white and opaque cell types have been a primary focus of investigation in the field; however, other factors that impact chromatin accessibility, such as histone modifying enzymes, chromatin remodelers, and histone chaperone complexes, also modulate the dynamics of the white-opaque switch and have been much less studied to date. Overall, the white-opaque switch represents an attractive and relatively “simple” model system for understanding the logic and regulatory mechanisms by which heritable cell fate decisions are determined in higher eukaryotes. Here we review recent discoveries on the roles of chromatin accessibility in regulating the C. albicans white-opaque phenotypic switch.
Genetic Manipulation of the Brassicaceae Smut Fungus Thecaphora thlaspeos
Authors: Plücker Lesley , Bösch Kristin , Geißl Lea , Hoffmann Philipp , Göhre Vera
Published: January 2021

Investigation of plant–microbe interactions greatly benefit from genetically tractable partners to address, molecularly, the virulence and defense mechanisms. The smut fungus Ustilago maydis is a model pathogen in that sense: efficient homologous recombination and a small genome allow targeted modification. On the host side, maize is limiting with regard to rapid genetic alterations. By contrast, the model plant Arabidopsis thaliana is an excellent model with a vast amount of information and techniques as well as genetic resources. Here, we present a transformation protocol for the Brassicaceae smut fungus Thecaphora thlaspeos. Using the well-established methodology of protoplast transformation, we generated the first reporter strains expressing fluorescent proteins to follow mating. As a proof-of-principle for homologous recombination, we deleted the pheromone receptor pra1. As expected, this mutant cannot mate. Further analysis will contribute to our understanding of the role of mating for infection biology in this novel model fungus. From now on, the genetic manipulation of T. thlaspeos, which is able to colonize the model plant A. thaliana, provides us with a pathosystem in which both partners are genetically amenable to study smut infection biology.
Intellectual Capital and Bank Risk in Vietnam—A Quantile Regression Approach
Authors: Nguyen Dat T. , Le Tu D. Q. , Ho Tin H.
Published: January 2021

This study empirically presents evidence of nonlinearity and heterogeneity relation between intellectual capital and risk-taking for the Vietnamese banking system. We used quantile regression methods on a data set of 30 Vietnamese banks from 2007 to 2019. The results showed that bank insolvency was positively affected by its value-added intellectual coefficient (VAIC) at the upper quantiles (i.e., 80th and 90th), while the opposite was true for credit risk (i.e., 10th and 20th quantiles). When observing the VAIC’s components, risk-taking behaviors were also significantly affected by HCE (Human Capital Efficiency), CEE (Capital Employed Efficiency) and SCE (Structural Capital Efficiency) at the 90th quantile of instability distribution and the 10th quantile of credit risk distribution. Furthermore, the results also emphasized that there was an inverse U-shaped association between intellectual capital and bank risk-taking. Therefore, this study provides important implications for policymakers, regulators, bank managers and academics that encourage increasing investment in knowledge assets to minimize bank risks in the long run.
Posture as a Non-Invasive Indicator of Arousal in American Toads (Anaxyrus americanus)
Authors: Woody Sarah M. , Santymire Rachel M. , Cronin Katherine A.
Published: January 2021

Animal welfare has become a priority for modern zoos and aquariums. However, amphibians have not yet been the focus of much welfare research, perhaps in part because they do not tend to display many quantifiable active behaviors. This study focused on nine zoo-housed American toads (Anaxyrus americanus), a species that displays long periods of sedentary behavior, to explore whether more subtle cues could serve as welfare indicators. A novel American toad posture index was developed that characterized toad posture based on the angle of their forelimbs, visibility of ventral regions, and body weight distribution. As an indicator of arousal, approximate breathing rates were assessed based on the rate of expansion of the toads’ throats. Subsequent analyses revealed that lower body postures were associated with slower rates of throat expansion and raised postures with faster rates of throat expansion, suggesting that posture may be a promising way to quickly and non-invasively assess toad arousal. This work lays important groundwork for assessing welfare of an understudied species, and we are optimistic that, with additional validation, these approaches can be applied in future amphibian welfare research.
The Legal Element of Fixing the Boundary for Indonesian Complete Cadastre
Authors: Martono Dwi Budi , Aditya Trias , Subaryono Subaryono , Nugroho Prijono
Published: January 2021

In 2017, the Indonesian government implemented the systematic land registration (PTSL) process, projected to be finished by 2025. However, this process faces some challenges in the spatial and legal data collection process, resulting in the Indonesian cadastral system still being incomplete. For instance, during the three years of its implementation, out of about 135 million parcels, only 49.5% have been registered. Therefore, the level of completeness needs to be improved. This research aims to assess the compliance of the fixed boundary process’ legal elements, such as the parties that locate the boundary, agreement between the adjoining landowners, and boundary markers. This is a piece of qualitative research in which the data were obtained through interviews from questionnaire surveys to land administration policymakers. Subsequently, the research carried out regulation assessments to develop a country-context cadastre typology of the current cadastral mapping activities. Data were obtained from the results of the PTSL campaign in the Madiun regency. The result showed that the high percentage (i.e., 96.61%) of legal elements regarding the boundary agreement in a rural area could be used as a potential enabler towards achieving completion of the Indonesian cadastre.
Is There Urban Landscape in Metropolitan Areas? An Unobvious Answer Based on Corine Land Cover Analyses
Authors: Myga-Piątek Urszula , Żemła-Siesicka Anna , Pukowiec-Kurda Katarzyna , Sobala Michał , Nita Jerzy
Published: January 2021

The recent increase in urban areas has stimulated landscape urbanization. One of the ways to study this process is an analysis based on the structure of land cover. The aim of this paper is to assess the intensity of the urban landscape on the basis of the CORINE in the seven largest metropolitan areas in Poland and in the Ruhr Metropolis in Germany. To this end, an urban landscape intensity indicator (ULII) was used based on Corine Land Cover at three levels of detail: the metropolitan area, municipalities and hexagons. There are similarities in landscape structure in areas with similar origin (industrial function) and spatial organization (mono- and polycentric agglomerations). The landscape of the Upper Silesia-Zagłębie Metropolis differs from the landscape of other metropolitan areas in Poland and simultaneously shows similarities to the landscape of the Ruhr Metropolis. The results of the ULII also revealed a dependency: the dominance of rural and transitional landscapes in a majority of the study areas. Urban landscapes occur only in the central zones of the metropolitan areas. This proves that determining the range of a metropolitan area in terms of landscape factors is different from doing it with formal or legal ones.
Influence of the Changes in Land-Use and Land Cover on Temperature over Northern and North-Eastern India
Authors: Nayak Sridhara , Maity Suman , Singh Kuvar S. , Nayak Hara Prasad , Dutta Soma
Published: January 2021

This study explores the influence of land-use and land cover (LULC) changes on the temperature over North India (NI) and North-Eastern India (NEI) during 1981–2006 by subtracting the reanalysis temperature from the observed temperature (observation minus reanalysis (OMR) method). The normalized difference vegetation index (NDVI) data of the AVHRR satellite for the period 1981–2006 were analyzed to understand the type of LULC changes during this period and their linkage with the temperature change over the two regions. The results from OMR indicated that the LULC change over NI during 1981–2006 resulted a warming of 0.03 °C, and that of NEI during this period resulted a cooling of 1.5 °C. The results from LULC changes during the said period indicated an increase of dry land/snow cover and agriculture/fallow land by ~0.1% of total area and a decrease of shrubs/small vegetation and dense forest over NI by about 0.1–0.2%. Over NEI, the areas under agricultural/fallow land, open forest and dense forest showed an increase by about 0.8–2.4% during this period, and the areas under dry/snow cover and shrubs/small vegetation indicated a decrease by ~0.7–3.6%. The comparison between the OMR analysis and LULC changes indicated that the warming over NI during 1981–2006 is due to the expansion of the dry land and the decline of dense forest. On the other hand, the cooling over NEI during the period is attributed to the decline of non-vegetated/small vegetated lands and the expansion of agricultural land/forest covers in that period. This study has an overall implication towards the modeling studies for the impact assessment of LULC changes in the present as well as future climate.
Functional Coupling Degree and Human Activity Intensity of Production–Living–Ecological Space in Underdeveloped Regions in China: Case Study of Guizhou Province
Authors: Zhang Xuesong , Xu Zijin
Published: January 2021

(1) Background: Clarify the coordinated development level of production, living, and ecological spaces in the underdeveloped areas of China and their relationship with the intensity of human activity. Explore and address the problems that are likely to be faced when developing these areas and improve the quality of China’s new urbanization development. Promote the coordinated and sustainable development of the economy, society and ecology in underdeveloped areas. Guizhou Province is located in southwest China; the landform is broken and complex. Its economic development level is low. It is one of the representatives of underdeveloped areas in China. Therefore, Guizhou Province of China was selected as the study area. (2) Methods: This paper constructs the evaluation index system of the production–living–ecological space (PLES) functional system in China’s underdeveloped areas, and uses the coupling coordination degree model to measure the development coordination level of the study area. The human activity intensity model was used to calculate the human activity intensity in the study area. Response index is introduced to analyze the relationship between the spatial function coupling coordination degree and the intensity of human activities. (3) Results: Before 2015, the level of functional coupling coordination degree of production–living–ecological space (PLES) in the study area fluctuated, and after 2015, it showed a stable and coordinated development trend. The intensity of human activity continues to increase, and the interaction between human activity and local production–living–ecological space (PLES) function coupling coordination is intense. (4) Conclusions: human activity is a significant factor affecting regional, coordinated and sustainable development. In less developed areas, the impact of human activity is more obvious. Human activity, in combination with the theory of the human–land relationship and the moderate intensity of human activity, are important ways to improve the coordinated and sustainable development of underdeveloped regions.
Hedgerows and Enclosures in Rural Areas: Traditional vs. Modern Land Use in Mediterranean Mountains
Authors: Álvarez Fernando Allende , Gómez-Mediavilla Gillian , López-Estébanez Nieves , Holgado Pedro Molina , Barajas Judith Ares
Published: January 2021

The present paper highlights the importance of hedgerows and enclosures in the mountains of Central Spain. Now, these landscapes have suffered profound variations in terms of agroforestry practices, especially in the Mediterranean mountains where the characteristic multifunctional has largely been lost. The article analyzes land uses changes, dynamics, and their morphological features between the first half of the 20th Century (1956) and the second decade of the present time (2019). The paper was divided into three sections. First, the identification of land uses using orthophotograph and aerial photograph; after that the info was checked with fieldwork. Eleven categories were identified according to the dominant use and land use changes and size of land parcels were taken into consideration. Second, the configuration and the information collected through the type and intensity of change in land uses made it possible to recognise and quantify their distribution and trend between these two dates. Also, the kernel density algorithm available in the Arcgis 10.5 software was used to obtain density and changes in land parcels. Finally, an overview is given of the main role that this agroforestry plays due to the social, ecological, and economic benefits that they provide for allowing sustainable development.
The Return of Wooded Landscapes in Wales: An Exploration of Possible Post-Brexit Futures
Authors: Manzoor Syed Amir , Griffiths Geoffrey , Christian Rose David , Lukac Martin
Published: January 2021

Changes in agricultural policy may have a rapid impact, even on landscapes which have taken millennia to form. Here we explore the potential impact of the UK leaving the EU as a catalyst for profound changes in the pastoral landscapes of Wales. Impending change of the trading regime governing agricultural produce, concurrent with public pressure to use agricultural subsidies for environmental goals, may lead to unforeseen consequences for the Welsh natural environment. We employ a combination of change demand modelling and a ‘story and simulation approach’ to project the effect of five hypothetical plausible scenarios on land use and land use change in Wales by 2030. We show that the most extreme trade scenario would result in a significant expansion of broadleaf woodland across much of Wales. By contrast, the ‘green futures’ scenario introduced to supersede the Common Agricultural Policy, results in significant expansion of woodland but not at the level seen with the more extreme trade scenarios.
Portuguese as Heritage Language in Germany—A Linguistic Perspective
Authors: Rinke Esther , Flores Cristina
Published: January 2021

This article provides a comprehensive overview of the contribution of linguistic research on Portuguese as a heritage language in Germany to the general understanding of heritage language development. From 1955 to 1973, nearly 166,000 Portuguese migrants found work in Germany as so-called ‘guest workers’ (Gastarbeiter). Because the aim of many Portuguese migrant families was to return to Portugal, their children met relatively good conditions for the acquisition of their heritage language. Nonetheless, second-generation heritage speakers (HSs) show some linguistic particularities in comparison to monolingual Portuguese speakers in Portugal. Based on the results of previous research, we show that the following factors shape the linguistic knowledge of this group of bilinguals: (1) Restricted exposure to the heritage language may cause a delay in the development of certain linguistic structures, (2) deviations from the standard norm may be related to the lack of formal education and the primacy of the colloquial register and (3) heritage bilinguals may accelerate ongoing diachronic development. We argue that apparent effects of influence from the environmental language can often have alternative explanations.
Shear Stress and RBC-NOS Serine1177 Phosphorylation in Humans: A Dose Response
Authors: Horobin Jarod T. , Sabapathy Surendran , Kuck Lennart , Simmonds Michael J.
Published: January 2021

Red blood cells (RBC) express a nitric oxide synthase isoform (RBC-NOS) that appears dependent on shear stress for Serine1177 phosphorylation. Whether this protein is equally activated by varied shears in the physiological range is less described. Here, we explored RBC-NOS Serine1177 phosphorylation in response to shear stress levels reflective of in vivo conditions. Whole blood samples were exposed to specific magnitudes of shear stress (0.5, 1.5, 4.5, 13.5 Pa) for discrete exposure times (1, 10, 30 min). Thereafter, RBC-NOS Serine1177 phosphorylation was measured utilising immunofluorescence labelling. Shear stress exposure at 0.5, 1.5, and 13.5 Pa significantly increased RBC-NOS Serine1177 phosphorylation following 1 min (p < 0.0001); exposure to 4.5 Pa had no effect after 1 min. RBC-NOS Serine1177 phosphorylation was significantly increased following 10 min at each magnitude of shear stress (0.5, 1.5, 13.5 Pa, p < 0.0001; 4.5 Pa, p = 0.0042). Shear stress exposure for 30 min significantly increased RBC-NOS Serine1177 phosphorylation at 0.5 Pa and 13.5 Pa (p < 0.0001). We found that RBC-NOS phosphorylation via shear stress is non-linear and differs for a given magnitude and duration of exposure. This study provides a new understanding of the discrete relation between RBC-NOS and shear stress.
Tribological Properties of Al2O3 Nanoparticles as Lithium Grease Additives
Authors: Nabhan Ahmed , Rashed Ahmed , Ghazaly Nouby M. , Abdo Jamil , Haneef M. Danish
Published: January 2021

The tribological properties of Lithium grease specimens with different concentrations of Al2O3 nanoparticles were investigated using a pin on disc apparatus under different sliding speeds and normal loads. Results showed that Al2O3 nanoparticles enhanced the tribological properties of lithium grease and reduced the COF and wear scar width by approximately 57.9% and 47.5% respectively.
Corrosion Behavior of Reinforcing Steel Undergoing Stray Current and Anodic Polarization
Authors: Chen Zhipei , Koleva Dessi
Published: January 2021

Different concrete structures (viaducts, bridges, or tunnels) in the neighborhoods of railways may be subject to the stray current leaking from the rails. In these cases, the reinforcing rebars embedded in concrete act as conductors, “pick up” the stray current, and can corrode. For simulating the stray current-induced corrosion of metals, most researchers just supplied anodic polarization on samples. However, stray current induces both cathodic polarization and anodic polarization. This work experimentally justifies the different effects of stray current and anodic polarization on reinforcing steel embedded in mortar. A comparison between stray current and anodic polarization effects on the corrosion behavior of embedded steel is performed for both fresh (24 hour-cured) and hardened matrix (28 day-cured) in chloride-free (Cl-free) and chloride-containing (Cl-containing) environments. It is found that in all studied conditions, anodic polarization leads to a significantly different electrochemical performance of the steel rebar compared to the stray current. Hence, anodic polarization cannot reflect all the effects of stray current, and therefore, it has limited significance for simulating stray current. It is also clarified that the curing regimes and starting time of the stray current play significant roles in the formation of a corrosion product layer on the steel surface.
Superparamagnetic Iron Oxide Particles (VSOPs) Show Genotoxic Effects but No Functional Impact on Human Adipose Tissue-Derived Stromal Cells (ASCs)
Authors: Radeloff Katrin , Ramos Tirado Mario , Haddad Daniel , Breuer Kathrin , Müller Jana , Hochmuth Sabine , Hackenberg Stephan , Scherzad Agmal , Kleinsasser Norbert , Radeloff Andreas
Published: January 2021

Adipose tissue-derived stromal cells (ASCs) represent a capable source for cell-based therapeutic approaches. For monitoring a cell-based application in vivo, magnetic resonance imaging (MRI) of cells labeled with iron oxide particles is a common method. It is the aim of the present study to analyze potential DNA damage, cytotoxicity and impairment of functional properties of human (h)ASCs after labeling with citrate-coated very small superparamagnetic iron oxide particles (VSOPs). Cytotoxic as well as genotoxic effects of the labeling procedure were measured in labeled and unlabeled hASCs using the MTT assay, comet assay and chromosomal aberration test. Trilineage differentiation was performed to evaluate an impairment of the differentiation potential due to the particles. Proliferation as well as migration capability were analyzed after the labeling procedure. Furthermore, the labeling of the hASCs was confirmed by Prussian blue staining, transmission electron microscopy (TEM) and high-resolution MRI. Below the concentration of 0.6 mM, which was used for the procedure, no evidence of genotoxic effects was found. At 0.6 mM, 1 mM as well as 1.5 mM, an increase in the number of chromosomal aberrations was determined. Cytotoxic effects were not observed at any concentration. Proliferation, migration capability and differentiation potential were also not affected by the procedure. Labeling with VSOPs is a useful labeling method for hASCs that does not affect their proliferation, migration and differentiation potential. Despite the absence of cytotoxicity, however, indications of genotoxic effects have been demonstrated.
Utilization of the Validated Windshield Material Model in Simulation of Tram to Pedestrian Collision
Authors: Špirk Stanislav , Špička Jan , Vychytil Jan , Křížek Michal , Stehlík Adam
Published: January 2021

The rail industry has been significantly affected by the passive safety technology in the last few years. The tram front-end design must fulfill the new requirements for pedestrian passive safety performance in the near future. The requirements are connected with a newly prepared technical guide “Tramway front end design” prepared by Technical Agency for ropeways and Guided Transport Systems. This paper describes research connected with new tram front-end design safe for pedestrians. The brief description of collision scenario and used human-body model “Virthuman” is provided. The numerical simulations (from field of passive safety) are supported by experiments. The interesting part is the numerical model of the tram windshield experimentally validated here. The results of simulations are discussed at the end of paper.
How Do Parameters of Implant Primary Stability Correspond with CT-Evaluated Bone Quality in the Posterior Maxilla? A Correlation Analysis
Authors: Kim Ji-Hyun , Lim Young-Jun , Kim Bongju , Lee Jungwon
Published: January 2021

The aim of the present study was to evaluate correlations between bone density and implant primary stability, considering various determinants such as age, gender, and geometry of implants (design, diameter). Bone density of edentulous posterior maxillae was assessed by computed tomography (CT)-derived Hounsfield units, and implant primary stability values were measured with insertion torque and resonance frequency analysis (RFA). A total of 60 implants in 30 partially edentulous patients were evaluated in the posterior maxilla with two different types of dental implants. The bone density evaluated by CT-derived Hounsfield units showed a significant correlation with primary stability parameters. The bone quality was more influenced by gender rather than age, and the type of implant was insignificant when determining primary stability. Such results imply that primary stability parameters can be used for objective assessment of bone quality, allowing surgical modifications especially in sites suspected of poor bone quality.
Prospect of Metal Ceramic (Titanium-Wollastonite) Composite as Permanent Bone Implants: A Narrative Review
Authors: Shanmuganantha Lohashenpahan , Baharudin Azmi , Sulong Abu Bakar , Shamsudin Roslinda , Ng Min Hwei
Published: January 2021

This literature review discusses the influence of titanium ceramic composites as a biomaterial towards the fabrication of implants for orthopedic applications. The concept of applying metal-ceramic composites enable many novel combinations in the design and fabrication of complex materials which enhances functionality to improve cell and tissue matrix interactions particularly in the formation of bone. Specific focus is placed on its plethora of materials selected from the metals and ceramic group and identifying the optimal combination that matches them. The prospect of wollastonite as the ceramic counterpart is also highlighted. In this review, we have highlighted the different fabrication methods for such metal-ceramic materials as well as the role that these hybrids play in an in vitro and in vivo environment. Its economic potential as a bone implant material is also discussed.
Electrochemically Produced Copolymers of Pyrrole and Its Derivatives: A Plentitude of Material Properties Using “Simple” Heterocyclic Co-Monomers
Authors: Jarosz Tomasz , Ledwon Przemyslaw
Published: January 2021

Polypyrrole is a classical, well-known conjugated polymer that is produced from a simple heterocyclic system. Numerous pyrrole derivatives exhibit biological activity, and the repeat unit is a common building block present in the chemical structure of many polymeric materials, finding wide application, primarily in optoelectronics and sensing. In this work, we focus on the variety of copolymers and their material properties that can be produced electrochemically, even though all these systems are obtained from mixtures of the “simple” pyrrole monomer and its derivatives with different conjugated and non-conjugated species.
A Non-Isokinetic Approach for Modeling Solid-State Transformations: Application to Crystallization of a Fe-B Amorphous Alloy
Authors: Ma Yazhu , Zhang Yubing , Liu Feng
Published: January 2021

Solid-state phase transformations like crystallization of amorphous alloys can be described by an analytical model incorporating a nucleation index a. However, this model cannot be used to examine isochronal transformations with abrupt changing of enthalpy differences performed with differential scanning calorimetry. Based on the model, a non-isokinetic approach is proposed and applied to analyze the isochronal crystallization kinetics of Fe85B15 amorphous alloy. The approach enabled us to obtain the kinetic parameters and activation energies for nucleation and growth.
Significant Enhancement of Piezoelectric Response in AlN by Yb Addition
Authors: Hirata Kenji , Mori Yuto , Yamada Hiroshi , Uehara Masato , Anggraini Sri Ayu , Akiyama Morito
Published: January 2021

This study employs first-principles calculations to investigate how introducing Yb into aluminum nitride (AlN) leads to a large enhancement in the material’s piezoelectric response (d33). The maximum d33 is calculated to be over 100 pC/N, which is 20 times higher than that of AlN. One reason for such a significant improvement in d33 is the elastic-softening effect, which is indicated by a decrease in the elastic constant, C33. The strain sensitivity (du/dε) of the internal parameter, u, is also an important factor for improving the piezoelectric stress constant, e33. On the basis of mixing enthalpy calculations, YbxAl1−xN is predicted to be more stable as a wurtzite phase than as a rock salt phase at composition up to x ≈ 0.7. These results suggest that Yb can be doped into AlN at high concentrations. It was also observed that the dielectric constant, ε33, generally increases with increasing Yb concentrations. However, the electromechanical coupling coefficient, k332, only increases up to x = 0.778, which is likely because of the relatively lower values of ε33 within this range.
Studies of Fracture Toughness in Concretes Containing Fly Ash and Silica Fume in the First 28 Days of Curing
Authors: Golewski Grzegorz Ludwik , Gil Damian Marek
Published: January 2021

This paper presents the results of the fracture toughness of concretes containing two mineral additives. During the tests, the method of loading the specimens according to Mode I fracture was used. The research included an evaluation of mechanical parameters of concrete containing noncondensed silica fume (SF) in an amount of 10% and siliceous fly ash (FA) in the following amounts: 0%, 10% and 20%. The experiments were carried out on mature specimens, i.e., after 28 days of curing and specimens at an early age, i.e., after 3 and 7 days of curing. In the course of experiments, the effect of adding SF to the value of the critical stress intensity factor—KIcS in FA concretes in different periods of curing were evaluated. In addition, the basic strength parameters of concrete composites, i.e., compressive strength—fcm and splitting tensile strength—fctm, were measured. A novelty in the presented research is the evaluation of the fracture toughness of concretes with two mineral additives, assessed at an early age. During the tests, the structures of all composites and the nature of macroscopic crack propagation were also assessed. A modern and useful digital image correlation (DIC) technique was used to assess macroscopic cracks. Based on the conducted research, it was found the application of SF to FA concretes contributes to a significant increase in the fracture toughness of these materials at an early age. Moreover, on the basis of the obtained test results, it was found that the values of the critical stress intensity factor of analyzed concretes were convergent qualitatively with their strength parameters. It also has been demonstrated that in the first 28 days of concrete curing, the preferred solution is to replace cement with SF in the amount of 10% or to use a cement binder substitution with a combination of additives in proportions 10% SF + 10% FA. On the other hand, the composition of mineral additives in proportions 10% SF + 20% FA has a negative effect on the fracture mechanics parameters of concretes at an early age. Based on the analysis of the results of microstructural tests and the evaluation of the propagation of macroscopic cracks, it was established that along with the substitution of the cement binder with the combination of mineral additives, the composition of the cement matrix in these composites changes, which implies a different, i.e., quasi-plastic, behavior in the process of damage and destruction of the material.
On the Size Effect of Additives in Amorphous Shape Memory Polymers
Authors: Zirdehi Elias , Dumlu Hakan , Eggeler Gunther , Varnik Fathollah
Published: January 2021

Small additive molecules often enhance structural relaxation in polymers. We explore this effect in a thermoplastic shape memory polymer via molecular dynamics simulations. The additive-to-monomer size ratio is shown to play a key role here. While the effect of additive-concentration on the rate of shape recovery is found to be monotonic in the investigated range, a non-monotonic dependence on the size-ratio emerges at temperatures close to the glass transition. This work thus identifies the additives’ size to be a qualitatively novel parameter for controlling the recovery process in polymer-based shape memory materials.
Reduction of Influence of the High-Frequency Noise on the Results of Surface Topography Measurements
Authors: Podulka Przemysław
Published: January 2021

The influence of errors in the processes of detection and then reduction of surface topography measurement noise is of great importance; many research papers are concerned with the definition of this type of measurement error. This paper presents the influence of high-frequency measurement noise, defined for various types of surface textures, e.g., two-process plateau-honed, turned, ground, or isotropic. Procedures for the processing of raw measured data as a detection of the high-frequency errors from the results of surface topography measurements were proposed and verified (compared) according to the commonly used (available in the commercial software of the measuring equipment) algorithms. It was assumed that commonly used noise-separation algorithms did not always provide consistent results for two process textures with the valley-extraction analysis; as a result, some free-of-dimple (part of the analyzed detail where dimples do not exist) areas were not carefully considered. Moreover, the influence of measured data processing errors on surface topography parameter calculation was not comprehensively studied with high-frequency measurement noise assessments. It was assumed that the application of the Wavelet Noise Extraction Procedure (WNEP) might be exceedingly valuable when the reduction of a disparate range of measured frequencies (measurement noise) was carefully considered.
Interfacial Reactions and Mechanical Properties of Sn–58Bi Solder Joints with Ag Nanoparticles Prepared Using Ultra-Fast Laser Bonding
Authors: Jeong Gyuwon , Yu Dong-Yurl , Baek Seongju , Bang Junghwan , Lee Tae-Ik , Jung Seung-Boo , Kim JungSoo , Ko Yong-Ho
Published: January 2021

The effects of Ag nanoparticle (Ag NP) addition on interfacial reaction and mechanical properties of Sn–58Bi solder joints using ultra-fast laser soldering were investigated. Laser-assisted low-temperature bonding was used to solder Sn–58Bi based pastes, with different Ag NP contents, onto organic surface preservative-finished Cu pads of printed circuit boards. The solder joints after laser bonding were examined to determine the effects of Ag NPs on interfacial reactions and intermetallic compounds (IMCs) and high-temperature storage tests performed to investigate its effects on the long-term reliabilities of solder joints. Their mechanical properties were also assessed using shear tests. Although the bonding time of the laser process was shorter than that of a conventional reflow process, Cu–Sn IMCs, such as Cu6Sn5 and Cu3Sn, were well formed at the interface of the solder joint. The addition of Ag NPs also improved the mechanical properties of the solder joints by reducing brittle fracture and suppressing IMC growth. However, excessive addition of Ag NPs degraded the mechanical properties due to coarsened Ag3Sn IMCs. Thus, this research predicts that the laser bonding process can be applied to low-temperature bonding to reduce thermal damage and improve the mechanical properties of Sn–58Bi solders, whose microstructure and related mechanical properties can be improved by adding optimal amounts of Ag NPs.
Material Origins of the Accelerated Operational Wear of RD-33 Engine Blades
Authors: Kozakiewicz Adam , Jóźwiak Stanisław , Jóźwiak Przemysław , Kachel Stanisław
Published: January 2021

The structural and strength analysis of the materials used to construct an important engine element such as the turbine is of great significance, at both the design stage and during tests and training relating to emergency situations. This paper presents the results of a study on the chemical composition, morphology, and phased structure of the metallic construction material used to produce the blades of the high- and low-pressure turbines of the RD-33 jet engine, which is the propulsion unit of the MiG-29 aircraft. On the basis of an analysis of the chemical composition and phased structure, the data obtained from tests of the blade material allowed the grade of the alloy used to construct the tested elements of the jet engine turbine to be determined. The structural stability of the material was found to be lower in comparison with the engine operating conditions, which was shown by a clear decrease in the resistance properties of the blade material. The results obtained may be used as a basis for analyzing the life span of an object or a selection of material replacements, which may enable the production of the analyzed engine element.
A Decoupled 6-DOF Compliant Parallel Mechanism with Optimized Dynamic Characteristics Using Cellular Structure
Authors: Pham Minh Tuan , Yeo Song Huat , Teo Tat Joo , Wang Pan , Nai Mui Ling Sharon
Published: January 2021

This paper presents a novel six degrees-of-freedom (DOF) compliant parallel mechanism (CPM) with decoupled output motions, large workspace of ≥6 mm for translations and ≥12° for rotations, optimized stiffness, and dynamic properties. The working range and the motion decoupling capability of the six-DOF CPM are experimentally verified, and the mechanical properties are shown to be predictable. The proposed CPM is synthesized by applying the beam-based structural optimization method together with the criteria for achieving motion decoupling capability. In order to improve the dynamic behaviors for the CPM, cellular structure is used to design its end effector. The obtained results show that the dynamic performance of the CPM with cellular end effector is significantly enhanced with the increase of 33% of the first resonance frequency as compared to the initial design. Performances of the three-dimensional (3D)-printed prototype are experimentally evaluated in terms of mechanical characteristics and decoupled motions. The obtained results show that the actual stiffness and dynamic properties agree with the predictions with the highest deviation of ~10.5%. The motion decoupling capability of the CPM is also demonstrated since almost input energy (>99.5%) generates the desired output motions while the energy causes parasitic motions is only minor (<0.5%).
Working Speed Analysis of the Gear-Driven Dibbling Mechanism of a 2.6 kW Walking-Type Automatic Pepper Transplanter
Authors: Iqbal Md Zafar , Islam Md Nafiul , Chowdhury Milon , Islam Sumaiya , Park Tusan , Kim Yong-Joo , Chung Sun-Ok
Published: January 2021

The development of an automatic walking-type pepper transplanter could be effective in improving the mechanization rate in pepper cultivation, where the dibbling mechanism plays a vital role and determines planting performance and efficiency. The objective of this research was to determine a suitable working speed for a gear-driven dibbling mechanism appropriate for a pepper transplanter, while considering agronomic transplanting requirements. The proposed dibbling mechanism consisted of two dibbling hoppers that simultaneously collected free-falling seedlings from the supply mechanism and dibbled them into soil. To enable the smooth collection and plantation of pepper seedlings, analysis was carried out via a mathematical working trajectory model of the dibbling mechanism, virtual prototype simulation, and validation tests, using a physical prototype. In the mathematical model analysis and simulation, a 300 mm/s forward speed of the transplanter and a 60 rpm rotational speed of the dibbling mechanism were preferable in terms of seedling uprightness and low mulch film damage. During the field test, transplanting was conducted at a 40 mm planting depth, using different forward speed levels. Seedlings were freely supplied to the hopper from a distance of 80 mm, and the success rate for deposition was 96.79%. A forward speed of 300 mm/s with transplanting speed of 120 seedlings/min was preferable in terms of achieving a high degree of seedling uprightness (90 ± 3.26), a low rate of misplanting (8.19%), a low damage area on mulch film (2341.95 ± 2.89 mm2), high uniformity of planting depth (39.74 ± 0.48 mm), and low power consumption (40.91 ± 0.97 W).
Position and Singularity Analysis of a Class of Planar Parallel Manipulators with a Reconfigurable End-Effector
Authors: Marchi Tommaso , Mottola Giovanni , Porta Josep M. , Thomas Federico , Carricato Marco
Published: January 2021

Parallel robots with configurable platforms are a class of robots in which the end-effector has an inner mobility, so that its overall shape can be reconfigured: in most cases, the end-effector is thus a closed-loop kinematic chain composed of rigid links. These robots have a greater flexibility in their motion and control with respect to rigid-platform parallel architectures, but their kinematics is more challenging to analyze. In our work, we consider n-RRR planar configurable robots, in which the end-effector is a chain composed of n links and revolute joints, and is controlled by n rotary actuators located on the base of the mechanism. In particular, we study the geometrical design of such robots and their direct and inverse kinematics for n=4, n=5 and n=6; we employ the bilateration method, which can simplify the kinematic analysis and allows us to generalize the approach and the results obtained for the 3-RRR mechanism to n-RRR robots (with n>3). Then, we study the singularity configurations of these robot architectures. Finally, we present the results from experimental tests that have been performed on a 5–RRR robot prototype.
A Novel Computational Method to Identify/Analyze Hysteresis Loops of Hard Magnetic Materials
Authors: D’Aloia Alessandro Giuseppe , Francesco Antonio Di , Santis Valerio De
Published: January 2021

In this study, a novel computational method capable of reproducing hysteresis loops of hard magnetic materials is proposed. It is conceptually based on the classical Preisach model but has a completely different approach in the modeling of the hysteron effect. Indeed, the change in magnetization caused by a single hysteron is compared here to the change in velocity of two disk-shaped solids elastically colliding with each other rather than the effect of ideal geometrical entities giving rise to so-called Barkhausen jumps. This allowed us to obtain a simple differential formulation for the global magnetization equation with a significant improvement in terms of computational performance. A sensitivity analysis on the parameters of the proposed method has indeed shown the capability to model a large class of hysteresis loops. Moreover, the proposed method permits modeling of the temperature effect on magnetization of neodymium magnets, which is a key point for the design of electrical machines. Therefore, application of the proposed method to the hysteresis loop of a real NdFeB magnet has been proven to be very accurate and efficient for a large temperature range.
Fuzzy Stability Results of Generalized Quartic Functional Equations
Authors: Kim Sang Og , Tamilvanan Kandhasamy
Published: January 2021

In the present paper, we introduce a new type of quartic functional equation and examine the Hyers–Ulam stability in fuzzy normed spaces by employing the direct method and fixed point techniques. We provide some applications in which the stability of this quartic functional equation can be controlled by sums and products of powers of norms. In particular, we show that if the control function is the fuzzy norm of the product of powers of norms, the quartic functional equation is hyperstable.
Polynomial Representations of High-Dimensional Observations of Random Processes
Authors: Loskot Pavel
Published: January 2021

The paper investigates the problem of performing a correlation analysis when the number of observations is large. In such a case, it is often necessary to combine random observations to achieve dimensionality reduction of the problem. A novel class of statistical measures is obtained by approximating the Taylor expansion of a general multivariate scalar symmetric function by a univariate polynomial in the variable given as a simple sum of the original random variables. The mean value of the polynomial is then a weighted sum of statistical central sum-moments with the weights being application dependent. Computing the sum-moments is computationally efficient and amenable to mathematical analysis, provided that the distribution of the sum of random variables can be obtained. Among several auxiliary results also obtained, the first order sum-moments corresponding to sample means are used to reduce the numerical complexity of linear regression by partitioning the data into disjoint subsets. Illustrative examples provided assume the first and the second order Markov processes.
Approximation of CDF of Non-Central Chi-Square Distribution by Mean-Value Theorems for Integrals
Authors: Baricz Árpád , Jankov Maširević Dragana , Pogány Tibor
Published: January 2021

The cumulative distribution function of the non-central chi-square distribution χn′2(λ) of n degrees of freedom possesses an integral representation. Here we rewrite this integral in terms of a lower incomplete gamma function applying two of the second mean-value theorems for definite integrals, which are of Bonnet type and Okamura’s variant of the du Bois–Reymond theorem. Related results are exposed concerning the small argument cases in cumulative distribution function (CDF) and their asymptotic behavior near the origin.
Limiting Genotype Frequencies of Y-Linked Genes with a Mutant Allele in a Two-Sex Population
Authors: González Miguel , Gutiérrez Cristina , Martínez Rodrigo
Published: January 2021

A two-type two-sex branching process is considered to model the evolution of the number of carriers of an allele and its mutations of a Y-linked gene. The limiting growth rates of the different types of couples and males (depending on the allele, mutated or not, that they carry on) on the set of coexistence of both alleles and on the fixation set of the mutant allele are obtained. In addition, the limiting genotype of the Y-linked gene and the limiting sex frequencies on those sets are established. Finally, the main results have been illustrated with simulated studies contextualized in problems of population genetics.
Estimation for Varying Coefficient Models with Hierarchical Structure
Authors: Li Feng , Li Yajie , Feng Sanying
Published: January 2021

The varying coefficient (VC) model is a generalization of ordinary linear model, which can not only retain strong interpretability but also has the flexibility of the nonparametric model. In this paper, we investigate a VC model with hierarchical structure. A unified variable selection method for VC model is proposed, which can simultaneously select the nonzero effects and estimate the unknown coefficient functions. Meanwhile, the selected model enforces the hierarchical structure, that is, interaction terms can be selected into the model only if the corresponding main effects are in the model. The kernel method is employed to estimate the varying coefficient functions, and a combined overlapped group Lasso regularization is introduced to implement variable selection to keep the hierarchical structure. It is proved that the proposed penalty estimators have oracle properties, that is, the coefficients are estimated as well as if the true model were known in advance. Simulation studies and a real data analysis are carried out to examine the performance of the proposed method in finite sample case.