bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolution of plasticity prevents postinvasion extinction of a native forb
Authors: Dostál Petr
Published: August 2022

Exotic plant invaders pose a serious threat to native plants. However, despite showing inferior competitive ability and decreased performance, native species often subsist in invaded communities. The decline of native populations is hypothesized to be halted and eventually reversed if adaptive evolutionary changes can keep up with the environmental stress induced by invaders, that is, when population extinction is prevented by evolutionary rescue (ER). Nevertheless, evidence for the role of ER in postinvasion persistence of native flora remains scarce. Here, I explored the population density of a native forb,
Veronica chamaedrys
, and evaluated the changes in the shade-responsive traits of its populations distributed along the invasion chronosequence of an exotic transformer,
Heracleum mantegazzianum
, which was replicated in five areas. I found a U-shaped population trajectory that paralleled the evolution of plasticity to shade. Whereas
V. chamaedrys
genotypes from intact, more open sites exhibited a shade-tolerance strategy (pronounced leaf area/mass ratio), reduced light availability at the invaded sites selected for a shade-avoidance strategy (greater internode elongation). Field experiments subsequently confirmed that the shifts in shade-response strategies were adaptive and secured postinvasion population persistence, as indicated by further modeling. Alternative ecological mechanisms (habitat improvement or arrival of immigrants) were less likely explanations than ER for the observed population rebound, although the contribution of maternal effects cannot be dismissed. These results suggest that
V. chamaedrys
survived because of adaptive evolutionary changes operating on the same timescale as the invasion-induced stress, but the generality of ER for postinvasion persistence of native plants remains unknown.
A Pleistocene legacy structures variation in modern seagrass ecosystems
Authors: Duffy J. Emmett , Stachowicz John J. , Reynolds Pamela L. , Hovel Kevin A. , Jahnke Marlene , Sotka Erik E. , Boström Christoffer , Boyer Katharyn E. , Cusson Mathieu , Eklöf Johan , Engelen Aschwin H. , Eriksson Britas Klemens , Fodrie F. Joel , Griffin John N. , Hereu Clara M. , Hori Masakazu , Hughes A. Randall , Ivanov Mikhail V. , Jorgensen Pablo , Kruschel Claudia , Lee Kun-Seop , Lefcheck Jonathan S. , Moksnes Per-Olav , Nakaoka Masahiro , O’Connor Mary I. , O’Connor Nessa E. , Orth Robert J. , Peterson Bradley J. , Reiss Henning , Reiss Katrin , Richardson J. Paul , Rossi Francesca , Ruesink Jennifer L. , Schultz Stewart T. , Thormar Jonas , Tomas Fiona , Unsworth Richard , Voigt Erin , Whalen Matthew A. , Ziegler Shelby L. , Olsen Jeanine L.
Published: August 2022

Distribution of Earth’s biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate–trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth’s environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (
Zostera marina
), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.
Endocranial ontogeny and evolution in earlyHomo sapiens: The evidence from Herto, Ethiopia
Authors: Zollikofer Christoph P. E. , Bienvenu Thibault , Beyene Yonas , Suwa Gen , Asfaw Berhane , White Tim D. , Ponce de León Marcia S.
Published: August 2022

Fossils and artifacts from Herto, Ethiopia, include the most complete child and adult crania of earlyHomo sapiens. The endocranial cavities of the Herto individuals show that by 160,000 y ago, brain size, inferred from endocranial size, was similar to that seen in modern human populations. However, endocranial shape differed from ours. This gave rise to the hypothesis that the brain itself evolved substantially during the past ∼200,000 y, possibly in tandem with the transition from Middle to Upper Paleolithic techno-cultures. However, it remains unclear whether evolutionary changes in endocranial shape mostly reflect changes in brain morphology rather than changes related to interaction with maxillofacial morphology. To discriminate between these effects, we make use of the ontogenetic fact that brain growth nearly ceases by the time the first permanent molars fully erupt, but the face and cranial base continue to grow until adulthood. Here we use morphometric data derived from digitally restored immature and adultH. sapiensfossils from Herto, Qafzeh, and Skhul (HQS) to track endocranial development in earlyH. sapiens. Until the completion of brain growth, endocasts of HQS children were similar in shape to those of modern human children. The similarly shaped endocasts of fossil and modern children indicate that our brains did not evolve substantially over the past 200,000 y. Differences between the endocranial shapes of modern and fossilH. sapiensadults developed only with continuing facial and basicranial growth, possibly reflecting substantial differences in masticatory and/or respiratory function.
Mechanical coupling of supracellular stress amplification and tissue fluidization during exit from quiescence
Authors: Lång Emma , Pedersen Christian , Lång Anna , Blicher Pernille , Klungland Arne , Carlson Andreas , Bøe Stig Ove
Published: August 2022

Cellular quiescence is a state of reversible cell cycle arrest that is associated with tissue dormancy. Timely regulated entry into and exit from quiescence is important for processes such as tissue homeostasis, tissue repair, stem cell maintenance, developmental processes, and immunity. However, little is known about processes that control the mechanical adaption to cell behavior changes during the transition from quiescence to proliferation. Here, we show that quiescent human keratinocyte monolayers sustain an actinomyosin-based system that facilitates global cell sheet displacements upon serum-stimulated exit from quiescence. Mechanistically, exposure of quiescent cells to serum-borne mitogens leads to rapid amplification of preexisting contractile sites, leading to a burst in monolayer tension that subsequently drives large-scale displacements of otherwise motility-restricted monolayers. The stress level after quiescence exit correlates with the level of quiescence depth at the time of activation, and a critical stress magnitude must be reached to overcome the cell sheet displacement barrier. The study shows that static quiescent cell monolayers are mechanically poised for motility, and it identifies global stress amplification as a mechanism for overcoming motility restrictions in confined confluent cell monolayers.
Measuring dynamic media bias
Authors: Kim Eunji , Lelkes Yphtach , McCrain Joshua
Published: August 2022

Ideological media bias is increasingly central to the study of politics. Yet, past literature often assumes that the ideological bias of any outlet, at least in the short term, is static and exogenous to the political process. We challenge this assumption. We use longitudinal data from the Stanford Cable News Analyzer (2010 to 2021), which reports the screen time of various political actors on cable news, and quantify the partisan leaning of those actors using their past campaign donation behavior. Using one instantiation of media bias—the mean ideology of political actors on a channel, i.e., visibility bias—we examine weekly, within-day, and program-level estimates of media bias. We find that media bias is highly dynamic even in the short term and that the heightened polarization between TV channels over time was mostly driven by the prime-time shows.
Carbon mineralization with concurrent critical metal recovery from olivine
Authors: Wang Fei , Dreisinger David
Published: August 2022

Carbon dioxide utilization for enhanced metal recovery (EMR) during mineralization has been recently developed as part of CCUS (carbon capture, utilization, and storage). This paper describes fundamental studies on integrating CO
2
mineralization and concurrent selective metal extraction from natural olivine. Nearly 90% of nickel and cobalt extraction and mineral carbonation efficiency are achieved in a highly selective, single-step process. Direct aqueous mineral carbonation releases Ni
2+
and Co
2+
into aqueous solution for subsequent recovery, while Mg
2+
and Fe
2+
simultaneously convert to stable mineral carbonates for permanent CO
2
storage. This integrated process can be completed in neutral aqueous solution. Introduction of a metal-complexing ligand during mineral carbonation aids the highly selective extraction of Ni and Co over Fe and Mg. The ligand must have higher stability for Ni-/Co- complex ions compared with the Fe(II)-/Mg- complex ions and divalent metal carbonates. This single-step process with a suitable metal-complexing ligand is robust and utilizes carbonation processes under various kinetic regimes. This fundamental study provides a framework for further development and successful application of direct aqueous mineral carbonation with concurrent EMR. The enhanced metal extraction and CO
2
mineralization process may have implications for the clean energy transition, CO
2
storage and utilization, and development of new critical metal resources.
Net effect of environmental fluctuations in multiple global-change drivers across the tree of life
Authors: Cabrerizo Marco J. , Marañón Emilio
Published: August 2022

Jensen’s inequality predicts that the response of any given system to average constant conditions is different from its average response to varying ones. Environmental fluctuations in abiotic conditions are pervasive on Earth; yet until recently, most ecological research has addressed the effects of multiple environmental drivers by assuming constant conditions. One could thus expect to find significant deviations in the magnitude of their effects on ecosystems when environmental fluctuations are considered. Drawing on experimental studies published during the last 30 years reporting more than 950 response ratios (n= 5,700), we present a comprehensive analysis of the role that environmental fluctuations play across the tree of life. In contrast to the predominance of interactive effects of global-change drivers reported in the literature, our results show that their cumulative effects were additive (58%), synergistic (26%), and antagonistic (16%) when environmental fluctuations were present. However, the dominant type of interaction varied by trophic level (autotrophs: interactive; heterotrophs: additive) and phylogenetic group (additive in Animalia; additive and positive antagonism in Chromista; negative antagonism and synergism in Plantae). In addition, we identify the need to tackle how complex communities respond to fluctuating environments, widening the phylogenetic and biogeographic ranges considered, and to consider other drivers beyond warming and acidification as well as longer timescales. Environmental fluctuations must be taken into account in experimental and modeling studies as well as conservation plans to better predict the nature, magnitude, and direction of the impacts of global change on organisms and ecosystems.
Long-distance association of topological boundaries through nuclear condensates
Authors: Gamliel Amir , Meluzzi Dario , Oh Soohwan , Jiang Nan , Destici Eugin , Rosenfeld Michael G. , Nair Sreejith J.
Published: August 2022

The eukaryotic genome is partitioned into distinct topological domains separated by boundary elements. Emerging data support the concept that several well-established nuclear compartments are ribonucleoprotein condensates assembled through the physical process of phase separation. Here, based on our demonstration that chemical disruption of nuclear condensate assembly weakens the insulation properties of a specific subset (∼20%) of topologically associated domain (TAD) boundaries, we report that the disrupted boundaries are characterized by a high level of transcription and striking spatial clustering. These topological boundary regions tend to be spatially associated, even interchromosomally, segregate with nuclear speckles, and harbor a specific subset of “housekeeping” genes widely expressed in diverse cell types. These observations reveal a previously unappreciated mode of genome organization mediated by conserved boundary elements harboring highly and widely expressed transcription units and associated transcriptional condensates.
Long wavelength–emissive Ru(II) metallacycle–based photosensitizer assisting in vivo bacterial diagnosis and antibacterial treatment
Authors: Xu Yuling , Li Chonglu , Ma Xin , Tuo Wei , Tu Le , Li Xiaopeng , Sun Yan , Stang Peter J. , Sun Yao
Published: August 2022

Ruthenium (Ru) complexes are developed as latent emissive photosensitizers for cancer and pathogen photodiagnosis and therapy. Nevertheless, most existing Ru complexes are limited as photosensitizers in terms of short excitation and emission wavelengths. Herein, we present an emissive Ru(II) metallacycle (herein referred to as 1) that is excited by 808-nm laser and emits at a wavelength of ∼1,000 nm via coordination-driven self-assembly. Metallacycle 1 exhibits good optical penetration (∼7 mm) and satisfactory reactive oxygen species production properties. Furthermore, 1 shows broad-spectrum antibacterial activity (including against drug-resistantEscherichia coli) as well as low cytotoxicity to normal mammalian cells. In vivo studies reveal that 1 is employed in precise, second near-infrared biomedical window fluorescent imaging–guided, photo-triggered treatments inStaphylococcus aureus–infected mice models, with negligible side effects. This work thus broads the applications of supramolecular photosensitizers through the strategy of lengthening their wavelengths.
Perceptual resemblance and the communication of emotion in digital contexts
Authors: Sasamoto Ryoko
Published: August 2022

Online communication has created new ways to express emotions, including emoji and reaction GIFs. Emoji are often discussed as signs for meaning-making, adding emotional tone to communication. Reaction GIFs express emotions and attitudes in a playful manner. This study shows that through the lens of cognitive pragmatics, these phenomena are not distinct. Both are cases of non-verbal communication pointing to the communicator’s emotional state. Drawing on relevance-theoretic notions of theshowing-meaning continuumandperceptual resemblance, along with relevance-theoretic analyses of metaphor and irony, I argue that emoji and reaction GIFs provide clues to ostension and communicate emotions by virtue of perceptual resemblance between what they represent and the communicator’s emotional state. I will also argue that both emoji and GIFs can involve echoic use of language, enabling the communicator to convey their attitude.
Assessing climatic, travel, and methodological influences on whole‐match and worst‐case scenario locomotor demands of international men's rugby sevens match‐play
Authors: Ullersperger Eliza , Hills Samuel P. , Russell Mark , Waldron Mark , Shearer David , Lonergan Ben , Farrow Tom , Eager Robin , Kilduff Liam P.
Published: August 2022

This study assessed the influence of environmental factors, air travel, and epoch estimation method on locomotor demands of international men's rugby sevens match‐play. Eighteen men's rugby sevens players wore 10 Hz Global Positioning Systems (STATsport) during 52 international matches over nine global tournaments (418 observations). Whole‐match average speed was recorded, whilst average speed and relative high‐speed distance (>5.0 m·s−1) were quantified using FIXED and ROLL methods over 60–420 s epochs (60 s increments) to establish worst‐case scenario demands. Linear mixed models compared FIXED versus ROLL estimation methods and assessed whether temperature, humidity, travel duration, number of time‐zones crossed, and travel direction were associated with locomotor responses. Temperature and humidity were positively associated with overall and worst‐case scenario average speed (effect estimates; b: 0.18–0.54), whilst worst‐case scenario high‐speed distance at 300 s was also related to temperature (b: 0.19). Easterly air travel compromised overall and 180 and 300 s worst‐case scenario average speed (b: −8.31 to‐7.39), alongside high‐speed distance over 300 s (b: −4.54). For worst‐case scenario average speed and high‐speed distance, FIXED underestimated ROLL at all epoch lengths (∼9.9–18.4%, p≤0.001). This study indicated that international rugby sevens match‐play locomotor responses were greater as air temperature increased but reduced following eastward air travel. Underestimation of demands in FIXED vs ROLL over 60–420 s epochs was confirmed. Such climatic and travel influences warrant the adoption of strategies targeted at maximising performance and safety according to the tournament conditions. Knowing the most demanding periods of match‐play facilitates training specificity.
MSANet: efficient detection of tire defects in radiographic images
Authors: Zhao Mengmeng , Zheng Zhouzhou , Sun Yingwei , Chang Yankang , Tian Chengliang , Zhang Yan
Published: August 2022

Visual inspection has been widely studied and applied in industrial fields. Previous studies have investigated the use of established traditional machine learning and deep learning methods to perform automated defect detection for tires. However, intelligent tire defect online detection is still a challenging task due to the complex anisotropic texture background of tire radiographic images. In this paper, we propose an efficient tire defect online detection method named MSANet based on an improved lightweight YOLOv4-tiny network. A novel multi-scale self-attention feature enhancement module (MSAM) is designed to extract a feature map with rich multi-scale context information. An improved feature pyramid model, named MSAM-CBAM feature pyramid network (MC-FPN), is proposed, which utilizes MSAM and a convolutional block attention module to enhance the information representation of the feature pyramid. Ablation experiments are conducted to verify the effectiveness of the proposed modules. Comparison of experimental results with state-of-the-art methods validates the effectiveness and efficiency of the proposed method, which can achieve a mean average precision of 96.96% and an average detection time of 30.81 ms per image. The proposed method can meet the requirements of industrial online detection by virtue of its lower computational costs and has good generalization ability in other visual inspection tasks.
Bearing fault diagnosis based on partial domain adaptation adversarial network
Authors: Zhou Huafeng , Cheng Peiyuan , Shao Siyu , Zhao Yuwei , Yang Xinyu
Published: August 2022

The existing fault diagnosis algorithm based on domain adaptation solves the problem of degradation of model diagnosis performance due to different data distributions under variable working conditions and cross-machine conditions, and its excellent fault diagnosis performance relies on the assumption that the fault category space of source and target domains is the same; however, it is difficult to meet the above assumption in practical application scenarios. For this reason, focusing on the matter of imbalance within the fault category, this paper proposes a novel unsupervised partial domain adaptational fault diagnosis method—a partial domain adaptation adversarial network (PDAAN). On the one hand, it uses the source domain fault samples to expand the target domain and promotes the effective alignment of the fault feature area of the source domain and the target domain, in order for the model to effectively extract domain invariant features; on the other hand, class-level weights and weighted entropy weights are introduced into the loss function to suppress the uncertainty within the transfer process and avoid negative transfer of the model. Finally, experiments are conducted in the case of variable working conditions and cross-mechanical devices, and it is confirmed that the PDAAN model has high recognition accuracy in the case of class space asymmetry.
A novel stochastic optimization method for handling misalignments of proton and photon doses in combined treatments
Authors: Fabiano Silvia , Torelli Nathan , Papp Dávid , Unkelbach Jan
Published: August 2022

Objective. Combined proton–photon treatments, where most fractions are delivered with photons and only a few are delivered with protons, may represent a practical approach to optimally use limited proton resources. It has been shown that, when organs at risk (OARs) are located within or near the tumor, the optimal multi-modality treatment uses protons to hypofractionate parts of the target volume and photons to achieve near-uniform fractionation in dose-limiting healthy tissues, thus exploiting the fractionation effect. These plans may be sensitive to range and setup errors, especially misalignments between proton and photon doses. Thus, we developed a novel stochastic optimization method to directly incorporate these uncertainties into the biologically effective dose (BED)-based simultaneous optimization of proton and photon plans. Approach. The method considers the expected value

E

b

and standard deviation

σ

b

of the cumulative BED

b

in every voxel of a structure. For the target, a piecewise quadratic penalty function of the form

b

min

−

E

b

−
2
σ

b

+

2

is minimized, aiming for plans in which the expected BED minus two times the standard deviation exceeds the prescribed BED

b

min

.

Analogously,

E

b

+
2
σ

b

−

b

max

+

2

is considered for OARs. Main results. Using a spinal metastasis case and a liver cancer patient, it is demonstrated that the novel stochastic optimization method yields robust combined treatment plans. Tumor coverage and a good sparing of the main OARs are maintained despite range and setup errors, and especially misalignments between proton and photon doses. This is achieved without explicitly considering all combinations of proton and photon error scenarios. Significance. Concerns about range and setup errors for safe clinical implementation of optimized proton–photon radiotherapy can be addressed through an appropriate stochastic planning method.
Combined significance of spatial coincidence of high energy neutrinos from PSR B1509-58 by Super-Kamiokande and MACRO
Authors: Desai Shantanu
Published: August 2022

In their searches for astrophysical point sources of high energy neutrinos, both the Super-Kamiokande and MACRO neutrino detectors saw the largest angular excess from the same source, viz. PSR B1509-58. We estimate the probability for the observed number of events by both Super-Kamiokande and MACRO to be a chance coincidence due to atmospheric neutrino background. We find that this probability is about 0.4%, corresponding to 2.6σ significance. We also propose some additional tests to ascertain if this excess corresponds to an astrophysical signal or is only a background event.
Dielectric properties and ac conductivity of CuO and Fe2O3 doped polycarbazole nanocomposites
Authors: Raghavendra B , Sankarappa T , Malge Amarkumar , Heerasingh Mohansingh , Devidas Ashwini
Published: August 2022

This paper presents results and discussion on dielectric and ac conductivity of Polycarbazole (PCz) and its PCz/CuO and PCz/Fe2O3 nanocomposites. Samples were prepared by oxidation method using ammonium persulfate as oxidizing agent. Samples were confirmed to be crystalline. Dielectric parameters are observed to be decreased with increase of frequency and temperature. Ac electrical conductivity of pure polycarbozole was found to be more than the composites. Further, conductivity increased with loading of metal oxide nanoparticles. The conductivity of all the samples is found to vary from 10-6 (Ωm)-1 to 10-4 (Ωm)-1 with the temperature (303K- 423K) and exhibited semiconducting nature. This has been ascribed to rise in the number of charge clusters inside polymer matrix with increase of metal oxide content and which in turn adds more polarons to the conduction band and, that increase conductivity. Activation energy for conduction is determined to vary from 1.07 meV to 6.17 meV for PCz/CuO systems and 0.82 meV to 4.06 meV for PCz/Fe2O3 composites. It is for the first time that Polycarbazole and Polycarbazole metal oxide doped nanocomposites have been studied for dielectric properties and ac conductivity over wide a range of frequency and temperature and analyzed data with respect to frequency, temperature and metal oxide content.
Effect of printing parameters on the hardness of 3D printed poly-lactic acid parts using DOE approach
Authors: Maguluri Nagarjuna , Suresh Gamini , Guntur Sitaramanjaneya Reddy
Published: August 2022

Fused deposition modeling (FDM) is an extensively used method for additive manufacturing of thermoplastic materials. It is growing in a variety of engineering applications because of its ability to produce complicated structural designs with low manufacturing time. However, the mechanical characteristics of the 3D printed components are extremely dependent on the proper selection of the printing conditions. In this present work, the impact of three foremost printing parameters, including fill density, extrusion temperature, and printing speed, is examined on the hardness of poly-lactic acid (PLA) parts. Taguchi design of experiment (DOE) methodology is used to minimize the total experimental runs and evaluate the optimal printing parameters for the maximum hardness of the printed part. Analysis of S/N ratios is utilized for establishing the optimal printing parameters, and the corresponding percentage contribution of control factors is measured using ANOVA. The study results have shown that extrusion temperature profoundly influences the hardness of the 3D printed PLA specimens, while printing speeds have a much smaller impact on it.
Finite element analysis of viscoelastic media used in abrasive flow machining process
Authors: Mangesh Gharat Saurabh , Misra Aviral
Published: August 2022

The surface roughness of a part is the most important parameter in view of tribological applications and it also affects the working life of the part during application. The abrasive flow machining (AFM) process is an advanced non-conventional finishing process, used to deburr, polish, and to remove the recast layer from the surface as well as at the edges of the components. In AFM viscoelastic media is used to finish the workpiece with close dimensional tolerance and precision. The viscoelastic media used in the AFM process is laden with abrasive particles. In the present work, a finite element analysis of viscoelastic abrasive media is performed considering the AFM process. A mixture of polyborosiloxane and silicon carbide is used as viscoelastic abrasive media and the AFM process is modeled using ANSYS Polyflow. In the analysis, the flow of viscoelastic abrasive media is assumed to follow the Maxwell model of viscoelastic fluid. The simulations were performed for varying the extrusion pressure for the finishing of an internal cylindrical surface. The results of the simulations were validated with the experimental observation and found in good agreement.
Non-linear analysis of orthotropic hyperelastic plate using VAM
Authors: Burela R G , Bhadoria S K , Harusampath D
Published: August 2022

An asymptotically accurate zeroth-order constitutive relation between 2D strains and stress tensor for an orthotropic hyperelastic material is derived using the Variational Asymptotic Method (VAM). Material nonlinearity is encompassed through the hyperelastic material model while geometric nonlinearity is by allowing finite displacements and rotations. Moderate strains of order 20% are considered. The small parameters such as the ratio of thickness to characteristic dimension, and maximum allowable strain (0.2) separate strain energy density into different orders. The analysis starts with the 3D strain energy density function and is divided into the thickness analysis (1D) and mid-surface analysis (2D). The 1D analysis leads to analytical expressions for warping functions, constitutive relations, and recovery relations. The 2D analysis is based on a non-linear finite element method that takes the constitutive relation as its input and obtains 2D displacements. The recovery relation converts them to 3D field variables i.e. displacements, strains, and stresses. The theory is applied to a square clamped plate subjected to uniformly distributed pressure. The results are accurate and obtained in a computationally efficient manner.
Molecular dynamics studies of hematite surfaces with PAM, HPAM and metasilicate
Authors: Quezada Gonzalo R. , Krishna R.S , Mishra Subhabrata , Jeldres Ricardo
Published: August 2022

In the search to improve the obtaining of iron ore, different additives have been proposed to improve this activity. A deeper study is necessary to understand the affinities of different additives on iron ore and thus be able to search for or synthesize new additives according to the desired objective. In this work, the affinities of the iron mineral represented by the hematite crystal on the neutral 001 surfaces at pH ~9 are studied by molecular dynamics methods, in the presence of waters with low salinity and high salinity. The additives to be studied are a sodium metasilicate dispersant, a neutral polyacrylamide (PAM) flocculant, and 25% anionic polyacrylamide (HPAM). The study considered the calculation of the minimum distance between the surface and the additives. The results show that the affinity of the metasilicate is high with the surface. In the case of PAM polymers, their adsorption decreased as the number of salts increased. In the case of HPAM, the adsorption is greater than in PAM and improved with the addition of salts. This indicates that hematite is a surface with a high local charge density that attracts charged groups such as metasilicates and HPAM. the neutral PAM polymer is adsorbed but to a lesser extent due to its neutrality. The presence of salts indicates that there is competition for adsorption on hematite with respect to PAM, but that the salt is beneficial to HPAM due to the formation of cationic bridges. These results will help in the search for additives for the concentration or dispersion of iron ore.
Graphene as a hole transport layer for enhanced performance of P3HT: PCBM bulk heterojunction organic solar cell: a numerical simulation study
Authors: Davis Denet , Shamna M S , Nithya K S , Sudheer K S
Published: August 2022

As sustainable and green energy technologies advance, academic and industrial researchers have been more interested in organic solar cells. Organic solar cells have some key advantages, such as lightweight, flexibility and cheapness that make them an ideal choice as an alternative to other types of solar cells. Bulk heterojunction solar cells combine the advantages of easier fabrication and higher conversion efficiency, making them the best structure currently. In this work P3HT: PCBM is used as the active layer material. PDINO and PFN-Br are used as the electron transport layers in this work. Graphene, which is taken as the hole transport layer in this work, is a unique material for future applications in organic photovoltaics due to its remarkable optical properties and excellent electron/hole transport properties. Corresponding to two different electron transport layers two different device configurations are studied in the work. Bulk hetero-junction organic solar cell simulation study is done using the solar cell capacitance simulator (SCAPS1D). The thickness, electron and hole mobilities, and defect density of the active layer are varied for each device configuration, and their effect on device output performance is analysed. A comparative study of device performance between the different configurations has been done.
Structure and Properties of PBS/PBAT blends and nanocomposites
Authors: Radhakrishnan S. , Thorat S. , Desale Amolkumar , Desai Prachi , Kulkarni M.B.
Published: August 2022

The use of bio-compostable polymers such as Polybutylene Succinate (PBS), Polybutylene Adipate Co-Terephthalate (PBAT) or Polylactic acid is restricted due to the barrier properties especially the water vapor transmission rate (WVTR) which is high in these commercially available polymers. The WVTR plays an important role in preserving the freshness of fruits and vegetables and it has to be optimum. Polymer blending and incorporation of nano fillers are facile routes to formation of internal structure and morphology which gives good control of barrier properties of films. Hence, crystalline structure and morphology of PBS-PBAT blends were studied in detail with respect to composition of the blend. The effect of nanofillers (Halloysite nanotubes/HNT) incorporation as well as addition of polyethylene glycol (PEG) as plasticizer on crystallization process was also investigated. The samples were cast on a glass plate substrate from solution using membrane caster at constant speed and thickness in the range of 100 microns. The composition was varied from 0 to 40 % of PBS in PBAT matrix while addition of HNT was varied from 1 to 5%. Films were air dried in an oven at 50-55 °C for 6 hr. The crystal structure development was studied using wide angle X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and the molecular interaction examined using FTIR. XRD data indicated that PBS crystals were in monoclinic α phase but the relative intensities of the 011 and 020 reflections changed drastically in the blends. The DSC analysis revealed that there was preferential growth of PBS α phase crystals with sharp melting at 110 °C. The HNT gave distinct nucleation effect with a shift in the Tc peak as well as increase of ΔHc value. The preferential nucleation by HNT could be associated with the close lattice match for the HNT and the monoclinic phase of PBS. FTIR studies indicate that the all the contents were dispersed well and show hydrogen bonding interaction at the –OH and –COOH groups. These changes in the crystallinity and crystal phase improved the barrier properties leading to the decrease in (WVTR) with the addition of PBS to PBAT as well as incorporation of HNT in the blend. WVTR decreased from 120 g/m2/day to 55 g/m2/day which is excellent for packaging of green agriculture produce.
Fabrication of Superhydrophobic Surface on Low Carbon Steel
Authors: Satyarathi Jitendra , Kumar Vijay , Kango Saurabh , Sharma Nitin , Verma Rajeev
Published: August 2022

The purpose of the present work is to fabricate superhydrophobic surfaces on commonly used low carbon steel (AISI 1018). Laser surface texturing (LST) method is used for creating circular textures on mild steel surface having the diameter and pitch of 200 μm each. Two different materials (wax & Candle soot) are used to decrease the surface energy of the mild steel. It is observed from the results that the water contact angle of untreated surface increases from 87° to 155° after LST and lowering the surface energy by using wax, followed by candle soot.
Finite Element based Numerical Modelling of Near-Dry EDM with Glycerin-Air Dielectric Mixture
Authors: Jishnu Namboodiri V N , Pazhamannil Ribin Varghese , Govindan P
Published: August 2022

Electrical discharge machining (EDM) is an advanced, non-traditional machining process that is widely employed in sectors such as manufacturing, automotive, aerospace, and medicine. Near-dry EDM is a prospective technology that offers advantages over dry and wet EDM in terms of material removal rate (MRR), tool wear rate (TWR), and surface integrity. A 2D model of the axi-symmetric workpiece based on the Gaussian distribution of the heat flux is used to simulate the single spark in near-dry EDM. The MRR of near-dry EDM is determined at various glycerin flow rates in the glycerin-air combination. The simulation is then performed on the SS304 workpiece with different glycerin flow rates. The results are compared to EDM simulations using N2 and O2 as the dielectric medium. The average MRR of near-dry EDM with an 8 ml/min glycerin flow rate is determined to be 204% higher than that of N2 and 117% higher than that of O2 gas dielectric. When the volumetric ratio of glycerin in the glycerin-air combination increases, the MRR was also found to be increasing. The maximal MRR of near-dry EDM was found to be 129.30703 mm3/min with an 8 ml/min glycerin flow rate and a 0.18 volumetric ratio and a maximal MRR of 144.3407 mm3/min was found with a 15 ml/min glycerin flow rate and a 0.35 volumetric ratio.
Effect of Zn content on microstructure and properties of hypoeutectic and near-eutectic Al-Si alloys
Authors: Dhakar Prashant , Kumar Sandeep , Manani Sunil , Pradhan Ajaya Kumar
Published: August 2022

In this research, the microstructure and mechanical properties of permanent mould cast Al-Si (7 wt.% and 12 wt.%) alloys without and with different amounts of Zn (1 wt.%, 2 wt.% and 4 wt.%) were analysed. The Al-xSi-yZn alloys have been prepared through a stir casting process using an Al-15 wt.% Si master alloy at 800 °C. Optical microscopic analyses have revealed variation in the α-Al matrix and Si needles in the alloy with the variation in Zn content. The mechanical properties analysis has shown that the hardness, tensile strength and wear resistance of the alloys increase with the addition of Si but decrease with the addition of Zn, within the limit of the alloying additions of the present research.
Effect of Boronizing on the High Temperature Mechanical Behavior of Inconel 625
Authors: Bilgin Onur , Yapici Guney Guven
Published: August 2022

Inconel 625 is a frequently used material specifically in the exhaust and piping components of gas turbine engines, because of its good corrosion resistance even at high temperatures. In this work, the effect of boronizing on the room and high temperature tensile behavior of Inconel 625 alloy was investigated. According to the room temperature tensile test results, yield strength (YS) and ultimate tensile strength (UTS) of the samples reduced after boronizing. This strength reduction may be attributed to the softening of the material throughout the boronizing process at a high temperature of 1100°C. On the other hand, ductility of the Inconel 625 samples decreased. At elevated temperature, the yield strength of the boronized sample significantly reduced because of the possible decomposition of boron particles throughout tensile straining at elevated temperatures. Consequently, the fracture morphology observations revealed that the main fracture mechanism of both coated and uncoated conditions at high temperature was ductile fracture represented by coarse and deep dimples.
Spin dependent Electronic properties of NO-adsorbed zigzag ZnO nanoribbons: A DFT Study
Authors: Kumar Ravindra , Rakesh Ajay Kumar , Govindan Anil , Jaiswal Neeraj K.
Published: August 2022

Exploring novel nano-materials for designing the robust and efficient sensors is an area of immense potential. In the present work, we study the adsorption of NO molecules at the edges of zigzag ZnO nanoribbons (zZnONR). The adsorption of NO molecules was modelled at the edges of zZnONR in different possibilities. It is well known that pristine (H-passivated) zZnONR is a semi-conducting material. Present calculations reveal that NO-adsorption takes place via N-side and a semiconductor to metallic-transition is also witnessed in all configurations. The obtained adsorption energies are found to vary between -4.10 eV to -7.04 eV ensuring the exothermic nature of the adsorption process and energetic feasibility of the considered configurations. Interestingly, all the considered structures (with NO adsorption) prefer magnetic ground state in contrast to previously reported non-magnetic behaviour of pristine zZnONR. Furthermore, NO adsorption at both the edges makes the structure half-metallic. In contrast, rest of the two-configurations are pure metallic. Present findings indicate that zZnONR could play a vital role towards NO detection as well realizing the spintronic properties for other various other technological applications.
Electrochemical corrosion performance of eutectic Al-Si automotive alloy in 0.1 M and 0.2 M NaCl solution
Authors: Khan Akib Abdullah , Kaiser Mohammad Salim
Published: August 2022

Corrosion behavior of eutectic Al-Si automotive alloy is investigated in different strengths of 0.1 M and 0.2 M NaCl solution at room temperature. Alloy with Si as trace impurity is also considered for the comparison of the property. The study is done by electrochemical method, using potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) techniques. The alloy surfaces are characterized by both optical microscopy and scanning electron microscopy. The results indicate that Si addition improves the corrosion performance of the Al-Si automotive alloy and this improvement is more pronounced in higher corrosive environments. The corrosion rate along with current density (Icorr) of trace Si added alloy showed higher value than that of higher Si added alloy. The corrosion potential (Ecorr) and open circuit potential (OCP) of higher Si added alloy are shifted to the more noble direction. The cause behind this, the higher amount of Mg2Si precipitates in higher Si added alloys tends to form oxides like SiO2 and MgO which protects the surfaces from further corrosion. Microscopic images confirm that the polishing scratches on the surfaces of the alloys are not visible after corrosion. The SEM images also confirm that the corroded surfaces seem to have pit formations which are lower in higher Si added alloys due to formation of a protective layer of oxides. The higher corrosion performance is observed for higher Si added alloys especially in higher strength of corrosive environment.
Natural Frequency Evaluation of Low-Pressure Stage Blade of a 210 MW Steam Turbine
Authors: Rani Pooja , Agrawal Atul Kumar
Published: August 2022

Steam turbines rely heavily on the performance and reliability of their rotor blades. When a steam turbine blade fails, it can pose a risk to workers' life, need expensive repairs, and cause income losses. The failure mechanism differs from case to case and is typically quite complex. The last stage turbine blades are very long and rotate at high speed. In extreme dynamic loads, these big blades are the most susceptible to failure. So, the dynamic behaviour of the last stage steam turbine blade is of great importance and analysed by numerical simulation in this work. Mode shapes at natural frequencies of the blade at stationary condition and at different speeds of rotation are determined. A Campbell diagram is used to forecast the expected operational conditions that may result in blade resonant vibration.
Temperature Analysis of Friction Stir Welding (AA6061-T6) with Coupled Eulerian-Lagrangian Approach.
Authors: Chalurkar Chetan , Shukla Dinesh Kumar
Published: August 2022

For Friction Stir Welding (FSW), several simplified FEM models have been developed to explain key parts of thermal-mechanical phenomena. In this study, to simulate the FSW process of the AA6061-T6 aluminum alloy, a thermo-mechanical 3-D finite element model based on the Coupled Eulerian-Lagrangian (CEL) approach is used. The CEL method combines the benefits of both the Lagrangian and Eulerian approaches, allowing it to solve large-scale deformation issues. The Abaqus/CAE software is used to simulate the stages of the FSW process using the Johnson–Cook material law and the Johnson-Cook failure model. The CEL approach is used to estimate process parameters based on the model's boundary conditions of the 3-D rigid tool. Thermocouples were installed in the appropriate positions on the AA6061-T6 plate, and temperature is correlated with the simulation results. The temperature generated during the plunging, dwelling, and welding stages of the FSW of AA6061-T6 is 80% to 90% of the melting temperature being evaluated. The experimental data was obtained from the HMT made CNC (Siemens) operated VMC and the same is compared with the results obtained from the overall FEM simulation.
Analysis on the Suitability of Powder Metallurgy Technique for Making Nickel Based Superalloys
Authors: Salwan Geetika Kumari , Subbarao Rayapati , Mondal Subrata
Published: August 2022

Nickel based superalloys are of a typical class of materials with an exceptional capability of retaining strength and toughness at high temperatures. Also, they have high resistance to degradation in corrosive environments. These properties of superalloys make them ideal materials for gas turbine engines used in power generation, marine engineering and aircraft applications. Earlier, researchers studied about the suitability of cast and wrought superalloys for their applicability in gas turbines. Superalloys are developed from polycrystalline to directionally solidified alloys and finally single crystal alloys by investment casting process for making turbine blade. In this work, the powder metallurgy technique is analysed for determining its appropriateness for making nickel based superalloys in gas turbines. This technique includes powder blending, compaction and sintering with or without post heat treatment for making a product. This process can offer high performance applications, where unique microstructural and mechanical characteristics are required. Refractory material can be easily alloyed by this technique, to enhance heat bearing capabilities. In this work, the development of nickel based superalloys by powder metallurgy technique, their composition as well as the influence of various elements on mechanical properties is analysed. Major defects like prior particle boundary (PPB) precipitation, thermally induced porosity (TIP), and non-metallic inclusion have to be taken care, in order to see that the mechanical properties are not deteriorated. It is observed that alloys like IN100, Rene95, and N18, Rene 88DT, ME3 and R1000 developed by powder metallurgy technique have sufficient temperature bearing capability for 1000 hr service life at 630 MPa. Alloys like U720 Li, IN 718 plus and U 720, made by casting technique and alloys like ME3, IN 100, and U720, made by powder metallurgy technique are compared on the basis of stress and temperature bearing capability. It is found that ME3 alloy prepared by powder metallurgy technique is the efficient nickel based superalloy with maximum heat bearing capability.