bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of digital twins to the product lifecycle management of battery packs of electric vehicles
Authors: Anandavel Suriyan , Li Wei , Garg Akhil , Gao Liang
Published: April 2021

Lithium‐ion batteries have become a core component of electric vehicles (EVs) because of their high energy density. However, several issues in lithium‐ion batteries usage, such as safety, durability, charging time, and driving range, limit the development of EVs. Meanwhile, with the emergence of Industry 4.0, the digital twins technology has received widespread attention in the manufacturing industry because it provides real‐time monitoring and intelligent management of the production process. The authors propose a framework based on digital twins, which can be used for real‐time monitoring, intelligent management, and autonomous control of battery packs. The framework covers all aspects of a battery pack's lifecycle, including design, manufacturing, operation monitoring, and second use options. Such a framework can solve some critical issues inhibiting the usage of batteries. A case study of the application of the proposed digital twins‐based framework to electric vehicle battery systems has been conducted. The results show that deploying digital twins into the battery packs of EVs will improve the safety and service life of the battery packs.
Selective kernel networks for weakly supervised relation extraction
Authors: Li Ziyang , Hu Feng , Wang Chilong , Deng Weibin , Zhang Qinghua
Published: April 2021

The purpose of relation extraction is to identify the semantic relations between entities in sentences that contain two entities. Recently, many variants of the convolution neural network (CNN) have been introduced to relation extraction for the extracting of features—the quality of the neural network model directly affects the final quality of relation extraction. However, the traditional convolution network uses a fixed convolution kernel, so it is difficult to choose the size of the convolution kernel dynamically, which results in networks with weak representation ability. To address this, a novel CNN is designed with selective kernel networks and multigranularity. In the process of feature extraction, the model can adaptively select the size of the convolution kernel, that is, give more weight to the appropriate convolution kernel. It is then combined with multigranularity convolution to obtain more abundant semantic information. Finally, a new pooling method is designed to obtain more comprehensive information and improve model performance. Experimental results indicate that this method is effective without excessively deep network layers, and it also outperforms several competitive baseline methods.
A high order statistics based multipath interference detection method
Authors: Zhan Yafeng , Zeng Guanming , Duan Chaowei
Published: April 2021

Multipath interference commonly exists in wireless communication, navigation and radar systems, which may cause severe signal fading and bit error rate (BER) performance degradation. Therefore the detection of multipath interference is urgently needed. This paper proposes a high order statistics (HOS) based multipath interference detection method, since the HOS of the received signal show distinct difference when multipath interference exists. Moreover, the generalized theoretical values of the moments and cumulants, which release the demand for prior knowledge of timing information and symbol period, are deduced in this paper. It makes the proposed HOS features based detection method robust in blind environment. Computer simulations are performed to verify the proposed method.
A high bit rate free space optics based ring topology having carrier‐less nodes
Authors: Mirza Jawad , Imtiaz Waqas A. , Aljohani Abdulah Jeza , Ghafoor Salman
Published: April 2021

A free space optics based ring topology that transmits full‐duplex data to four different nodes in the ring is proposed. The link is designed such that the four nodes do not require a local optical source to transmit the uplink data. A wavelength division multiplexed signal composed of four different wavelengths each modulated by the downlink baseband data using differential phase shift keying is transmitted towards the nodes. At each node, the downlink baseband data is extracted and the received optical pulses are remodulated by the uplink baseband data using on‐off keying modulation format. Each node has a data rate of 10 Gbps and is at a distance of 400 m from the consecutive node. The free space optical link is modelled on the basis of Gamma‐Gamma channel model under different turbulence conditions by considering the refractive index structure parameter values of , and . Bit error rate results are obtained for both the downlink and uplink channels. Finally, power budget analysis is presented to demonstrate the robustness of the link under different weather conditions.
Decentralized energy management for unbalanced networked microgrids with uncertainty
Authors: Alobaidi Abdulraheem Hassan , Khodayar Mohammad E. , Shahidehpour Mohammad
Published: April 2021

The energy management schemes in microgrids enhance the utilization of renewable energy resources and improve the reliability and resilience measures in the distribution networks. While microgrids operate autonomously, the coordination among microgrid and distribution network operators (DNOs) contributes to the improvement in the economics and reliability of serving the demand. Here, a decentralized energy management framework for the networked microgrids is proposed in which the interactions between the microgrid and DNOs are captured using the Benders decomposition technique. The proposed framework limits the information shared among these autonomous operators and facilitates decentralized energy management in the distribution networks. Furthermore, the unbalanced operation of the distribution network and microgrids, as well as the uncertainty in the operating modes of the microgrids, renewable energy resources, and demand, were addressed. Modified IEEE‐34 bus and IEEE‐123 bus distribution networks are used to validate the effectiveness of the proposed algorithm.
Integrated inventory model involving quality improvement investment and advance-cash-credit payments
Authors: Yang Chih-Te , Huang Chien-Hsiu , Ouyang Liang-Yuh
Published: April 2021

This paper investigates the effects of investment and inspection policies on an integrated production–inventory model involving defective items and upstream advance-cash-credit payment provided by the supplier. In this model, retailers offer customers a downstream credit period. Furthermore, the defective rate of the item can be improved through capital co-investment by the supplier and retailer. The objective of this study was to determine the optimal shipping quantity, order quantity, and investment alternatives for maximizing the supply chain’s joint total profit per unit time. An algorithm was developed to obtain the optimal solution for the proposed problem. Several numerical examples are used to demonstrate the proposed model and analyze the effects of parameters changes on the optimal solutions. Finally, management implications for relevant decision makers are obtained from the numerical examples.
Fuzzy reverse logistics inventory model of smart items with two warehouses of a retailer considering carbon emissions
Authors: Kumar Subhash , Sarkar Biswajit , Kumar Ashok
Published: April 2021

Running the business smoothly for protecting the environment is a significant challenge, on which industries are trying something to do at their level best. Reverse logistics play an important role in system design by reducing environmental consequences and increasing economic and social impacts. Given the recent fluctuations of the market, the production cost and ordering cost are considered triangular fuzzy numbers in this study. Customers’ demand is met at the right time, and there is no shortage of items; thus, attention can be paid to two warehouses of a retailer. The setup costs Purchasing costs and deterioration costs of this system are affected by the learning effects, which lead to a decrease in the total cost. Inflation is a significant problem in the market because manufacturing, remanufacturing, and retailers are all affected. This study proposes a reverse logistics system model so that customers can resolve their complaints about defective items and carbon emissions under two warehouses. Numerical results show that the fuzzy model is more economically beneficial than the crisp model, finds that the crisp and fuzzy model saw a difference of 0.34% in total cost. Two numerical examples illustrate this study, and a sensitivity analysis is performed using tables and graph.
Black esophagus und black duodenum – seltene Ursache einer oberen gastrointestinalen Blutung
Authors: Fleischmann Carola Christina , Gölder Stephan Karl , Messmann Helmut
Published: April 2021

Wir berichten über den fulminanten Verlauf eines black esophagus mit konsekutiver distaler Ösophagusperforation sowie eines black duodenum bei einer 73-jährigen Patientin. Die Diagnose des black esophagus erfolgt anhand des endoskopischen Bildes und ist charakterisiert durch die zirkuläre Nekrose des Ösophagus mit abruptem Übergang in regelrecht perfundierte Schleimhaut ab der Z-Linie. Der black esophagus ist eine seltene Ursache einer oberen gastrointestinalen Blutung und ist mit einer hohen Mortaliät von über 30 % verknüpft. Komplikativ können sich eine Ösophagusperforation und im langfristigen Verlauf eine Ösophagusstenose entwickeln. Eine kausale Therapie existiert nicht.
Strategie zum risikostratifizierten Einsatz von Antigen-Schnelltests: Eindämmung der SARS-CoV-2-Pandemie durch die Integration von Schnelltests in das Fall- und Kontaktpersonenmanagement
Authors: Arnold Laura , Stratil Jan
Published: April 2021

Der Einsatz von Schnelltests bietet Chancen in der Bekämpfung der SARS-CoV-2 Pandemie; jedoch müssen die Auswirkungen von falsch-positiven und falsch-negativen Testergebnissen und die Reaktion der Bevölkerung antizipiert und berücksichtigt werden, um Schaden zu vermeiden. Auch geht ein ungezielter Einsatz von Schnelltests mit hohen direkten und indirekten Kosten einher und wird bei einem ineffizienten Ressourceneinsatz begrenzte Auswirkungen auf das Pandemiegeschehen haben können. Eine risikostratifizierte Teststrategie kann bei einer direkten Verknüpfung mit dem Fall- und Kontaktpersonenmanagement des Öffentlichen Gesundheitsdienstes (ÖGD) dazu beitragen, ressourceneffizient und nachhaltig die Infektionszahlen zu senken. Die Strategie sollte eine einheitliche Kommunikationsstrategie zum Umgang mit positiven und negativen Testergebnissen, eine gezielte Ausweitung der Zugänge zu niederschwelligen Testmöglichkeiten, die Sicherstellung eines zeitnahen und kostenlosen Zugangs zu den Ergebnissen von Bestätigungstests und die Einbindung in ein übergreifendes Dokumentationssystems zur Evaluation umfassen. Im Rahmen eines risikostratifizierten Einsatzes der Schnelltests sollten alle Personen mit akuten Symptomen einer Atemwegsinfektion sowie Personengruppen mit erhöhtem Risiko für das Bestehen einer SARS-CoV-2 Infektion gezielt getestet werden um „versteckte“ Infektionsnetzwerke zu identifizieren.
Kennzahlen und ihre (Aus)Wirkungen im Arbeitsalltag des Krankenhauses – Umfrageergebnisse
Authors: Dutschkus Fabian , Lukas Christian
Published: April 2021

Finanzielle Anreize und betriebswirtschaftliche Vorgaben für leitendes ärztliches Personal in Krankenhäusern sind weit verbreitet. Die Diskussion über deren Auswirkungen hält an.

Zielsetzung Befragung von Ärztinnen und Ärzten deutscher Krankenhäuser zu finanziellen Anreizen, maßgeblichen Kennzahlen für ihre Leistungsbeurteilung und Auswirkungen betriebswirtschaftlicher Vorgaben.

Methodik Repräsentative Umfrage.

Ergebnisse Mit Abstand am häufigsten werden finanzielle Kennzahlen und Qualitätskennzahlen in Kombination als betriebswirtschaftliche Vorgaben bzw. Hinweise eingesetzt, gefolgt von ihrem kombiniertem Einsatz als Grundlage der variablen Vergütung. Ob sie als Hinweise oder Vergütungsgrundlage eingesetzt werden, ist vom Träger des Krankenhauses abhängig; in Krankenhäusern mit privatem Träger werden sie häufiger als Vergütungsgrundlage eingesetzt im Vergleich zu freigemeinnützigen oder öffentlichen Trägern. Ob und welche Kennzahlen als Vorgaben oder Grundlage variabler Vergütung eingesetzt werden, beeinflusst die Einschätzung der Auswirkungen betriebswirtschaftlicher Vorgaben im Krankenhaus.

Schlussfolgerung Kennzahlen, die den wirtschaftlichen Erfolg eines Krankenhauses abbilden, werden sehr häufig eingesetzt. Diese Tatsache und die Einschätzungen der Befragten in unserer Umfrage können als Indiz dafür interpretiert werden, dass wirtschaftliche Erwägungen einen ernstzunehmenden Einfluss auf medizinische Entscheidungen haben.
Base-Free Synthesis and Synthetic Applications of Novel 3-(Organochalcogenyl)prop-2-yn-1-yl Esters: Promising Anticancer Agents
Authors: Godoi Benhur , Gritzenco Fabiane , Kazmierczak Jean C. , Anjos Thiago , Sperança Adriane , Peixoto Maura L. B. , Godoi Marcelo , Ledebuhr Kauane N. B. , Brüning César Augusto , Zamin Lauren L.
Published: April 2021

This manuscript portrays the CuI-catalyzed Csp-chalcogen bond formation through cross-coupling reactions of propynyl esters and diorganyl dichalcogenides by using DMSO as solvent, at room temperature, under base-free and open-to-air atmosphere conditions. Generally, the reactions have proceeded very smoothly, being tolerant to a range of substituents present in both substrates, affording the novel 3-(organochalcogenyl)prop-2-yn-1-yl esters in moderate to good yields. Noteworthy, the 3-(butylselanyl)prop-2-yn-1-yl benzoate proved to be useful as synthetic precursor in palladium-catalyzed Suzuki and Sonogashira­ type cross-coupling reactions by replacing the carbon–chalcogen bond by new carbon–carbon bond. Moreover, the 3-(phenyl­selanyl)prop-2-yn-1-yl benzoate has shown promising in vitro activity against glioblastoma cancer cells.
Iridium-Catalyzed Direct C–H Allylation of Ketimines
Authors: Nishimura Takahiro , Yabe Ryota , Ebe Yusuke
Published: April 2021

Aromatic C–H allylation of N-sulfonyl ketimines with allyl alcohol or allyl phenyl ether as an allyl source is catalyzed by a cationic iridium complex. The presence of a catalytic amount of a pyridine derivative was found to be essential for the reaction. In contrast, direct C–H allylation of ketimines derived from benzophenone derivatives and p-methoxyaniline with allyl phenyl ether proceeded in the absence of pyridine derivatives.
Nickel-Catalyzed Electronically Reversed Enantioselective Hydrocarbofunctionalizations of Acrylamides
Authors: Shu Wei , Shi Lou
Published: April 2021

Asymmetric hydrocarbofunctionalization of alkenes has emerged as an efficient strategy for synthesizing optically active molecules through a carbon–carbon bond-forming process from readily available alkenes and carboelectrophiles. Here, we present a summary of our efforts to control the regio- and enantioselectivity of hydrocarbofunctionalizations of electron-deficient alkenes with a nickel catalyst and a chiral bisoxazolidine ligand. The reaction permits electron-reversed hydrocarbofunctionalizations of acrylamides with excellent enantioselectivity. This operationally simple protocol permits the asymmetric hydroalkylation, hydrobenzylation, or hydropropargylation of acrylamides. This reaction is useful for preparing a wide range of α-branched chiral amides with broad functional-group tolerance.
The Rhino-Lip-Lifting: A Novel Proposal for Midface Profileplasty Performed as a Single Surgical Procedure
Authors: Pascali Michele , Marchese Gloria , Diaspro Alberto
Published: April 2021

As facial aging occurs, aesthetic changes of the nasal tip and the senile upper lip include tip ptosis, increase in skin length, loss of vermillion height and Cupid's bow, and vertical wrinkles.

Regardless of the rejuvenation procedure, the lips are not to be considered as a single anatomical entity, instead they should be placed in a strong correlation with the nose. The aim of this study is therefore to demonstrate the effectiveness of the association of primary closed rhinoplasty together with indirect subnasal lip-lifting technique.

A total of 45 patients were enrolled in this study and underwent primary closed rhinoplasty with indirect subnasal lip-lifting. The result showed an overall average nasolabial angle width reduction of 10.9% and lip length shortening of 23.5%, as assessed 1 year after the surgical procedure. When comparing before and after photographs and using the Subjective Global Aesthetic Improvement Scale (sGAIS), the overall satisfaction was rated 4.4 on 5, as “much improved.”

The authors show that lips should not be considered as a single anatomical entity but that they indeed must be placed in a strong correlation with the nose since a droopy nasal tip is likely to be considered unattractive and is often associated with the appearance of a long nose with covered philtrum and upper lip.

Tip rotation to a normal nasolabial angle width could grant a beneficial impact on overall nose aesthetics; however, it may not fully balance the midface profile as it is the “lip position-to-incisal show” ratio that defines beauty, whereas the balance among forehead, nasal tip, upper lip, and chin is what defines the contour of harmonious profiles.

This is the first patient series to show that the combination of closed rhinoplasty and indirect lip-lifting is a highly effective, safe, and reliable procedure to address profile rejuvenation.
Endolymphatic Sac Tumor Screening and Diagnosis in von Hippel-Lindau Disease: A Consensus Statement
Authors: Mehta Gautam U. , Kim H. Jeffery , Gidley Paul W. , Daniels Anthony B. , Miller Mia E. , Lekovic Gregory P. , Butman John A. , Lonser Russell R.
Published: April 2021

Objective Endolymphatic sac tumors (ELSTs) are a frequent cause of hearing loss and other audiovestibular dysfunction in patients with von Hippel-Lindau disease (VHL). Unified screening recommendations for VHL patients have not been established. To develop consensus guidelines, the VHL Alliance formed an expert committee to define evidence-based clinical screening recommendations.

Patients and Methods Recommendations were formulated by using the Grading of Recommendations, Assessment, Development, and Evaluation framework after a comprehensive literature review.

Results Diagnosis of ELSTs in VHL requires a combination of clinical evaluation and imaging and audiometric findings. Audiovestibular signs/symptoms are often an early feature of small ELSTs, including those that are not visible on imaging. Diagnostic audiograms have the greatest sensitivity for the detection of ELST-associated sensorineural hearing loss and can help confirm clinically relevant lesions, including those that may not be radiographically evident. Magnetic resonance imaging (MRI) can be a more specific test for ELSTs in VHL particularly when supplemented with computed tomography imaging for the identification of small tumors. VHL patients between the ages 10 and 60 years carry high preponderance for ELST presentation.

Conclusion We recommend that clinical evaluation (yearly) and diagnostic audiograms (every other year) be the primary screening tools for ELSTs in VHL. We suggest that screening be performed between the ages 11 and 65 years or with the onset of audiovestibular signs/symptoms for synchronicity with other testing regimens in VHL. We recommend that baseline imaging (MRI of the internal auditory canals) can be performed between the ages of 15 and 20 years or after positive screening.
Cisternostomy in Traumatic Brain Injury for a Novel Approach to Treatment: Review of Current Status
Authors: Agrawal Manish , Mishra Keshav , Babal Rohit , Purohit Devendra
Published: April 2021

Cisternostomy (CS) is a recently introduced procedure to mitigate the cerebrospinal fluid shift edema and secondary injury in traumatic brain injury patients. There have been numerous reports describing its efficacy in various cohorts of traumatic brain injury (TBI) patients; therefore, we review the current evidences examining its utility for the same. The systematic review was done according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline including all human studies published in English language indexed with MEDLINE and Google Scholar since 2013 evaluating CS as a standalone or as an adjuvant procedure. The studies were graded according to the Oxford center for evidence-based medicine levels of evidence. Case reports were excluded from the analysis. A total of 107 articles were found by using the given search criteria. Finally, three oxford level 3 study and one level 4 study were included in the analysis. CS in combination with decompressive craniectomy was seen to confer mortality benefit and better outcome at discharge. It led to statistically significant improvement in clinical outcome at 6 months in the patients for whom it was performed as a primary procedure. CS is a promising procedure in TBI leading to survival benefit as well as better clinical outcome. But the level of evidence supporting its effectiveness is still weak owing to the methodological limitations and small sample size. A well-designed multicentric randomized controlled trial is needed to critically examine its role in TBI patients.
Steering sound beams with origami-inspired phononic structures
Authors: McConnon Aili
Published: April 2021

Combining origami phononic structures with metamaterial inclusions to steer sound beams for acoustic sensing.
Golden mean renormalization for the almost Mathieu operator and related skew products
Authors: Koch Hans
Published: April 2021

Considering SL(2,R) skew-product maps over circle rotations, we prove that a renormalization transformation associated with the golden mean α* has a nontrivial periodic orbit of length 3. We also present some numerical results, including evidence that this period 3 describes scaling properties of the Hofstadter butterfly near the top of the spectrum at α* and scaling properties of the generalized eigenfunction for this energy.
Method for controlling boundary condition effects on the measurement of acoustic properties of small samples in tubes
Authors: Dupont Thomas , Verdière Kévin , Leclaire Philippe , Panneton Raymond
Published: April 2021

As standard ASTM E2611 reveals, the normal incidence sound transmission loss measured on a small sample in an acoustic tube is not only a property of the material but also strongly dependent on boundary conditions (generally unknown) and on the way the material is mounted. This article proposes an experimental method to control the effects of the lateral boundary conditions in an acoustic tube. The main objective is to deduce the properties of a “client element” (material sample) from the measured global acoustic properties of a patchwork composed by the “client material” and a known “host support.” Three patchwork configurations have to be distinguished: patchworks with and without an impervious and rigid interface between the elements and patchworks composed by elements that cannot be identified as equivalent fluids. For each of these configurations, the use of a specific method based on the Mixing Rule Method (MRM) or on the Parallel Transfer Matrix Methods (P-TMM or dP-TMM) used in reverse way is proposed. Numerical and experimental validations are proposed in acoustic tubes on a convenient configuration: a material sample surrounded by an air ring. This configuration allows reducing the material elastic-frame behavior to leave a limp-frame behavior. The proposed methods allow removing the effect of the lateral air ring host surrounding the material. For homogeneous materials, the two methods based on MRM and dP-TMM give similar good results. For non-homogeneous materials or for materials that cannot be modeled as equivalent fluids, only the method based on dP-TMM gives good results.
PyMoDAQ: An open-source Python-based software for modular data acquisition
Authors: Weber S. J.
Published: April 2021

Thanks to the recent multiplication of scientific Python packages in the open-source software landscape, Data Acquisition frameworks (DAQ-Fs) appear as versatile replacements of custom-made or costly commercial solutions. PyMoDAQ is a DAQ-F focusing on easy-to-use graphical user interfaces allowing a simple control and automation of a large variety of experimental setups. Its development included a highly modular structure allowing any experimental data acquisition as a function of multiple varying parameters. It offers numerous additional functionalities: instrument and setup configuration, plotting, saving, logging, etc. Live visual feedback is available at all times to monitor the ongoing experiment. Flexibility of its user interfaces is the key advantage of PyMoDAQ allowing also its integration as the core of more focused applications. Its hierarchical binary format data saving mechanism includes experimental metadata highly compatible with FAIR (Findable, Accessible,Interoperable, Reusable) data. Among the presented characteristics, seven criteria have been chosen to judge the pertinence of PyMoDAQ as a versatile DAQ-F. They are also the basis for a comparison with other existing frameworks highlighting the novelty of PyMoDAQ.
Spectroscopic signature of negative electronic compressibility from the Ti core-level of titanium carbonitride MXene
Authors: Jindata Warakorn , Hantanasirisakul Kanit , Eknapakul Tanachat , Denlinger Jonathan D. , Sangphet Suppanut , Chaiyachad Sujinda , Jaisuk Chutchawan , Rasritat Aissara , Sawasdee Tanawat , Nakajima Hideki , Rattanachata Arunothai , Fongkaew Ittipon , Limpijumnong Sukit , Gogotsi Yury , Meevasana Worawat
Published: April 2021

Two-dimensional transition metal carbides, carbonitrides, and nitrides, called MXenes, exhibit high metallic conductivity, ion intercalation capability, and reversible redox activity, prompting their applications in energy storage and conversion, electromagnetic interference (EMI) shielding, and electronics, among many other fields. It has been shown that replacement of ∼50% of carbon atoms in the most popular MXene family member, titanium carbide (Ti3C2Tx), by nitrogen atoms, forming titanium carbonitride (Ti3CNTx), leads to drastically different properties. Such properties include very high negative charge in solution and extreme EMI shielding effectiveness, exceeding all known materials, even metals at comparable thicknesses. Here, by using ultraviolet photoemission spectroscopy (UPS), the electronic structures of Ti3CNTx and Ti3C2Tx are systematically investigated and compared as a function of charge carrier density. We observe that, in contrast to Ti3C2Tx, the Ti 3p core-level of Ti3CNTx exhibits a counterintuitive shift to a lower binding energy of up to ∼250 meV upon increasing the electron density, which is a spectroscopic signature of negative electronic compressibility (NEC). These experimentally measured chemical potential shifts are well captured by the density functional theory (DFT) calculation. The DFT results also further suggest that the hybridization of titanium–nitrogen bonding in Ti3CNTx helps to promote the available states of Ti atoms for receiving more electrons above the fermi level and leads to the observed NEC. Our findings explain the differences in electronic properties between the two very important and widely studied MXenes and also suggest a new strategy to apply the NEC effect of Ti3CNTx in energy and charge storage applications.
Acoustic flatbands in phononic crystal defect lattices
Authors: Ma Tian-Xue , Fan Quan-Shui , Zhang Chuanzeng , Wang Yue-Sheng
Published: April 2021

In this paper, we investigate the acoustic flatbands (FBs) in phononic crystal (PnC) defect lattices. The defects are introduced into a PnC composed of periodic rigid rods in the air background. Since the acoustic energy is highly confined inside the PnC defects, the interaction between the defects can be described by the tight-binding model. We construct the PnC defects in two bipartite lattices, namely, the stub and Lieb lattices. The acoustic FBs can be observed for both of the lattices. Moreover, the acoustic FBs are protected by the chiral symmetry. That is, the FBs can be preserved even though the hopping strengths between the neighboring defects are perturbed. The proposed PnC defect lattices provide a feasible platform for the study of acoustic FB systems and topological insulators.
Kinetic theory of effect of dust charge fluctuations on the parametric decay of lower hybrid wave instability by relativistic runaway electrons in tokamak
Authors: Sharma Jyotsna , Sharma Suresh C. , Gahlot Ajay
Published: April 2021

Dust charge fluctuation effect on the parametric decay of lower hybrid wave instability by relativistic runaway electrons is studied in a tokamak using kinetic treatment. Parametric upconversion of lower hybrid pump waves into relativistic runaway electron mode and upper sideband mode is described. A ponderomotive force is exerted on the runaway electrons by lower hybrid pump wave possessing large amplitude and upper sideband wave, which drives the runaway electron mode. The coupling of the oscillatory velocity of electrons with density perturbations produces nonlinear density perturbations on the upper sideband frequency. As a result, runaway generation is enhanced by a lower hybrid wave and the growth rate of the instability is measured as the square of the amplitude of the pump wave. Moreover, the presence of dust charge fluctuations and their number density in the tokamak have an appreciable effect on the growth rate of lower hybrid wave instabilities, which in turn affects the actual performance of the ITER due to the potential safety and operational issues.
Origami inspired phononic structure with metamaterial inclusions for tunable angular wave steering
Authors: Hathcock Megan , Popa Bogdan-Ioan , Wang K. W.
Published: April 2021

The ability to create directional sound beams is fundamental to acoustic sensing. Traditionally, acoustic beams are most commonly produced by phased arrays, which increase the cost and complexity of the systems in which they are implemented. Phononic structures have theoretically been shown to possess Dirac cones that can be manipulated to produce angular collimated beams. Dirac cones are usually encountered in phononic crystals with inclusions significantly more compressible than the surrounding media, e.g., rubber inclusions in a water medium, a characteristic not easily realized in air. In addition, there are no effective and practical means to tune phononic structures that can achieve a broad range of Dirac point manipulation, which is essential to changing the direction and focus of acoustic beams. To advance the state of the art, this research proposes a novel approach to produce steerable collimated beams in air by harnessing reconfigurable origami phononic structures with adjustable metamaterial inclusions. The proposed structure is shown to produce dramatic lattice reconfiguration and control of Dirac points in a broad range, and thus achieve collimated beams with on-demand tunable frequency and angle. These advancements provide a simple, cost-effective alternative to acoustic phased arrays, greatly expanding the potential of acoustic sensing.
Experimental evidence of a hiding zone in a density-near-zero acoustic metamaterial
Authors: Malléjac M. , Merkel A. , Sánchez-Dehesa J. , Christensen J. , Tournat V. , Romero-García V. , Groby J.-P.
Published: April 2021

This paper examines the feasibility of cloaking an obstacle using Plate-type Acoustic Metamaterials (PAMs). We present two distinct strategies to cloak this obstacle, using either the near-zero-density regime of a periodic arrangement of plates or the acoustic doping phenomenon to achieve simultaneous zero-phase propagation and impedance matching. The strong limitations induced by viscothermal and viscoelastic losses that cannot be avoided in such a system are studied. A hiding zone is reported analytically, numerically, and experimentally. In contrast to cloaking, where zero-phase propagation must be accompanied by total transmission and zero reflection, the hiding configuration requires that the scattering properties of the hiding device must not be affected by the presence of the obstacle embedded in it. Contrary to cloaking, the hiding phenomenon is achievable even with a realistic PAM possessing unavoidable losses.
3D gradient auxetic soft mechanical metamaterials fabricated by additive manufacturing
Authors: Hedayati Reza , Güven Aysun , van der Zwaag Sybrand
Published: April 2021

Materials with a negative Poisson's ratio, also known as auxetics, have attracted a lot attention as they have shown innovation potential in applications for energy damping, modern fasteners, biomedical implants, piezoelectric sensors, and soft actuators. In this study, we introduce different patterns of graded distribution of unit cells with positive and negative Poisson's ratio in tubular configurations. Seven types of patterns are programmed into the fabric of the metamaterial to create desired shape changes upon applying far-field external loads. Two of the patterns demonstrate near-zero Poisson's ratio even at axial strains as high as 44%. Other pattern distributions convert the initially cylindrical shape of the tubes to vase, barrel, hourglass, nonsymmetrical vase, and nonsymmetrical hourglass geometries. The experimental Poisson's ratio values for the linear negative-to-positive-to-negative gradient (resulting in hourglass shape) and linear positive-to-negative-to-positive gradient (resulting in barrel shape) cases are +0.53 and −0.47, respectively. The measured Poisson's ratio values at tube level are in good accordance with the analytical values of +0.5 and −0.5. Benefits of the proposed designs in applications such as action-at-a-distance actuators and wrinkle-free jointless hinges in both 3D and 2D configurations are demonstrated.
Growth kinetics and origin of residual stress of two-phase crystalline–amorphous nanostructured films
Authors: Borroto A. , Bruyère S. , Migot S. , Pierson J. F. , Mücklich F. , Horwat D.
Published: April 2021

Composition-driven amorphous-to-crystalline transition is widely observed in sputter-deposited thin films. We have recently shown that peculiar two-phase crystalline–amorphous nanostructures can be obtained for compositions in the transition zone between single-phased amorphous and crystalline films, offering a new possibility to control surface topography and related functional properties. Here, the growth kinetics of the two-phase nanostructures formed in the transition zone is explored and related to residual stress measurements. From the analysis of top-view scanning electron microscopy images, the evolution with the film thickness of relevant parameters describing the growth process was extracted, i.e., surface coverage, volume fraction, and perimeter per unit area of the crystalline regions growing in competition with the amorphous ones. We demonstrate, supported in the aforementioned parameters, that residual stress evolution in the transition zone is governed by the nucleation, growth, and interaction of the crystalline regions during the competitive growth process. Our results shed new light on the kinetics of the crystalline–amorphous competitive growth phenomenon and demonstrate the relevance of residual stress measurements for exploring the growth mechanisms of complex film microstructures.
Data-driven stability analysis and near-wake jet control for the vortex-induced vibration of a sphere
Authors: Chizfahm Amir , Jaiman Rajeev
Published: April 2021

We present a stability analysis for the vortex-induced vibration (VIV) of a sphere and a suppression control technique using a base bleed actuation. The reduced-order model (ROM) for the system is developed via the eigensystem realization algorithm (ERA), which provides a low-order representation of the unsteady flow dynamics in the neighborhood of the equilibrium steady state. A systematic ROM-based stability analysis is performed to understand the frequency lock-in mechanism and self-sustained VIV phenomenon by examining the eigenvalue trajectories for a range of reduced oscillation frequencies (Fs) at fixed Reynolds number (Re) and mass ratio (m*). Consistent with the full-order simulations, the ERA-based ROM predicts the frequency lock-in branches arising due to resonance and combined mode instabilities. The dependence of these lock-in branches is explored as a function of mass ratio. The base bleeding mechanism in the near-wake region of a sphere and its influence over the flow dynamics, the wake characteristics, and the VIV response are investigated for the freely vibrating sphere system at Re = 300. A base bleed coefficient (Cq) is defined as a ratio of near-wake jet flow rate to the freestream inflow rate to perform a parametric analysis on the hydrodynamic coefficients and the flow features. It is found that a near-wake jet with Cq=1% inhibits the synchronization of the shedding process and completely suppresses the large-amplitude oscillations for all VIV branches studied. In addition, we demonstrate the reduction of the mean drag coefficient by more than 14% in comparison to the sphere alone system. The stability analysis of the near-wake jet is performed for the sphere VIV. The resulting ROM provides an effective approach for the parameter space exploration and is able to characterize the effectiveness of the designed controller on the VIV suppression. Results from the ROM analysis are consistent with those obtained from our full-order nonlinear fluid–structure interaction simulations. The present study illustrates that VIV can be suppressed by altering the structure mode via shifting the unstable wake modes to the stable region. This finding is realized through the simulations of an active control device, wherein the presence of near-wake jet flow breaks the self-sustenance of the wake–body interaction cycle. Overall, the proposed base-bleed control is found to be effective in suppressing the vortex shedding and the VIV for a range of reduced velocities and mass ratios.
Freezing of a nanofluid droplet: From a pointy tip to flat plateau
Authors: Zhao Y. , Yang C. , Cheng P.
Published: April 2021

Understanding the dynamics during freezing of nanofluid droplets is of importance from both fundamental and practical viewpoints. It is known that a universal pointy tip is formed on the top of a frozen water droplet [Marín et al., Phys. Rev. Lett. 113(5), 054301 (2014)]. Here, we report that the formation of a pointy tip is broken down due to the presence of nanoparticles; instead, the top of a frozen nanofluid droplet exhibits a flat plateau shape and such a plateau becomes larger at higher particle concentrations. We show that the phenomenon of such shape changes in freezing nanofluid droplets is universal, independent of contact angle, droplet volume, particle size, and particle material. We propose an analytical model to attribute the plateau formation to a capillary driven compensating flow due to segregated particles moving along the freezing interface.
Formation of covalently bound C4H4+ upon electron-impact ionization of acetylene dimer
Authors: Wang Yingying , Wang Enliang , Zhou Jiaqi , Dorn Alexander , Ren Xueguang
Published: April 2021

We investigate the formation mechanisms of covalently bound C4H4+ cations from direct ionization of hydrogen bonded dimers of acetylene molecules through fragment ion and electron coincident momentum spectroscopy and quantum chemistry calculations. The measurements of momenta and energies of two outgoing electrons and one ion in triple-coincidence allow us to assign the ionization channels associated with different ionic fragments. The measured binding energy spectra show that the formation of C4H4+ can be attributed to the ionization of the outermost 1πu orbital of acetylene. The kinetic energy distributions of the ionic fragments indicate that the C4H4+ ions originate from direct ionization of acetylene dimers while ions resulting from the fragmentation of larger clusters would obtain significantly larger momenta. The formation of C4H4+ through the evaporation mechanism in larger clusters is not identified in the present experiments. The calculated potential energy curves show a potential well for the electronic ground state of (C2H2)2+, supporting that the ionization of (C2H2)2 dimers can form stable C2H2⋅C2H2+(1πu−1) cations. Further transition state analysis and ab initio molecular dynamics simulations reveal a detailed picture of the formation dynamics. After ionization of (C2H2)2, the system undergoes a significant rearrangement of the structure involving, in particular, C–C bond formation and hydrogen migrations, leading to different C44+ isomers.
A facile route toward carbon paste modification, for high-performing bi-functional hole extracting counter electrodes in C-based PSCs
Authors: Bidikoudi Maria , Stathatos Elias
Published: April 2021

An increase in the photovoltaic properties of carbon (C)-based perovskite solar cells (PSCs) of the triple mesoscopic structure has been achieved, by using a simple, solution-based method, to enhance the charge transport properties of the C electrode. In this context, a variety of Ni precursor solutions have been inserted in the typical carbon black/graphite paste. Space charge limited current measurements have revealed a higher hole mobility for the modified pastes. The power conversion efficiency of the optimized PSC, which has been prepared entirely under ambient conditions, in addition to being hole transport layer free, reaches ∼9.9%, which is higher than 9.1% for the reference C paste electrode. The results and beneficial effect of Ni incorporation have also been confirmed by electrochemical impedance spectroscopy and incident photon to current conversion efficiency measurements. Our results bring out a simple and low-cost method to improve the performance of C-based energy-related devices.
Solvation of simple ions in water at extreme conditions
Authors: Rozsa Viktor , Galli Giulia
Published: April 2021

The interaction of ions and water at high pressure and temperature plays a critical role in Earth and planetary science yet remains poorly understood. Aqueous fluids affect geochemical properties ranging from water phase stability to mineral solubility and reactivity. Here, we report first-principles molecular dynamics simulations of mono-valent ions (Li+, K+, Cl−) as well as NaCl in liquid water at temperatures and pressures relevant to the Earth’s upper mantle (11 GPa, 1000 K) and concentrations in the dilute limit (0.44–0.88 m), in the regime of ocean salinity. We find that, at extreme conditions, the average structural and vibrational properties of water are weakly affected by the presence of ions, beyond the first solvation shell, similar to what was observed at ambient conditions. We also find that the ionic conductivity of the liquid increases in the presence of ions by less than an order of magnitude and that the dielectric constant is moderately reduced by at most ∼10% at these conditions. Our findings may aid in the parameterization of deep earth water models developed to describe water–rock reactions.
Cationic and anionic cellulose nanocrystalline (CNC) hydrogels: A rheological study
Authors: Keyvani Parya , Nyamayaro Kudzanai , Mehrkhodavandi Parisa , Hatzikiriakos Savvas G.
Published: April 2021

Although the rheology of cellulose nanocrystalline (CNC) suspensions has been widely studied, less attention has been paid to the modified cellulose nanocrystals such as cationic and anionic cellulose hydrogels. In this work, the rheological behavior of cellulose nanocrystals (CNCs), anionic CNCs (pCNCs), and cationic CNCs (nCNCs), was comparatively studied. The rheological behavior demonstrated that the nCNC and pCNC form hydrogen bonding, which significantly contributes to the increase in the gel strengths in the sonicated state. The formation of such structures between individual fibers prevents flocculation due to the increased suspension stability. In addition, the extensive formation of hydrogen bonding in the case of nCNC compared to that of pCNC explains its enhanced rheological properties. The effect of pre-shear has been studied in detail for these systems by considering a combination of pre-shear and startup of steady shear in different shearing directions with certain rest/recovery time in between to eliminate strain history and thus eliminate the possible bias of pre-shearing on structure formation.
The effects of partial preheating on pressure propagation and Flow-Restart phenomena in a clogged pipeline with a weakly compressible gel
Authors: Sanyal Aniruddha , Tikariha Lomesh , Kumar Lalit
Published: April 2021

The present article aims to decipher the effect of preheating a segment of the pipe on the pressure propagation mechanisms and flow restart operation in a gelled pipeline. During the restart operation, shear-thinning thixotropic rheology governs the gel properties, where the viscosity is a function of shear strain and thermal history. A finite volume method is employed to solve the governing equations for a weakly compressible gel. Rheology of the initial gel incorporates the effect of temperature distribution from the preheating stage. Flow restart in the thixotropic gel involves three different timescales: namely, the compressive diffusion timescale (acoustic wave propagation timescale), the viscous timescale, and the gel degradation timescale. In an isothermal case, the flow restart occurs at the gel degradation timescale, whereas flow restart in the preheated gel takes place at the viscous timescale. Time evolution of nonlinear axial pressure profile and residual viscosity provides a theoretical understanding of the gel degradation process in the thermal diffusion-controlled and advection-controlled flow regimes, defined in terms of Peclet number (Pe). The results indicate that the gel degradation process is affected by thermal-induced melting in addition to shear melting. Partial preheating tends to dislodge the gel into plugs, and this is more significant at low Pe and high pristine gel strength. The local Nusselt number (Nu) at the heated portion of the wall during flow restart suggests that the wall-heat transfer is prominent when the pressure wavefront has not reached the outlet.
Curvature-induced emergence of a second critical field for domain wall dynamics in bent nanostripes
Authors: Bittencourt G. H. R. , Moreno R. , Cacilhas R. , Castillo-Sepúlveda S. , Chubykalo-Fesenko O. , Altbir D. , Carvalho-Santos V. L.
Published: April 2021

We investigate the dynamics of a transverse domain wall (DW) in a bent nanostripe under an external field and spin-polarized current. Besides the standard Walker breakdown phenomenon, we show the emergence of a second Walker-like critical field, which depends on both the curvature of the nanostripe and its cross section geometry. At this field, DW can change its phase, i.e., can be re-oriented along another direction with respect to the nanostripe face. Additionally, we show that the amplitude and frequency of the DW oscillations above the Walker breakdown field also depend on the nanostripe geometry and can be controlled by external stimuli. Our results evidence that the inclusion of local curvatures in nanostripes is an important component for applications that demand an adequate control of the DW phase by the proper choice of external stimuli.