bluuebunny/crossref_metadata_2025 huggingface dataset:
Implementation and Use of Risk Evaluation and Mitigation Strategies Programs in Practice: A Scoping Review of the Literature
Authors: Tajchman Sharla , Lawler Brooke , Spence Nathan , Haque Saira , Quintana Yuri , Ateya Mohammad
Published: December 2022

Background Risk Evaluation and Mitigation Strategy (REMS) programs intend to improve medication safety but can add significant administrative burdens to providers and health systems. Various stakeholders have made efforts to use technology to improve REMS programs.

Objectives The objective of this scoping review is to describe studies evaluating workflows, automation, or electronic data exchange related to REMS programs.

Methods A literature search of PubMed, Embase, and Web of Science was performed for articles published between January 2007 and July 2021. Studies were identified using the relevant Medical Subject Headings terms and related keywords. Articles must have described a workflow change and measured the impact of the workflow change.

Results Of 299 citations initially identified, 7 were included in the final review after removing duplicates and articles not meeting predefined inclusion criteria. Included studies consisted of three manuscripts and four conference abstracts. Electronic health record interventions, such as customized order sets and clinical decision support alerts, were the most common strategy reported. Other strategies included developing a portal to verify REMS enrollment, requiring prescribers to contact the dispensing pharmacy, provider education, and restrictions based on the provider specialty. One study evaluated automated data exchange for REMS program processes in a mock environment. Although only three studies reported baseline metrics for comparison, all studies noted an improvement or benefit to the implemented workflow process changes.

Conclusion There is limited evidence describing REMS workflows, automation, and electronic data exchange. Various strategies to address REMS program requirements were reported, but no studies described the use of data exchange standards in a real-world setting despite efforts by the Food and Drug Administration and other stakeholders. Additional efforts are needed to automate REMS programs.
Internet postings and investor herd behavior: evidence from China’s open-end fund market
Authors: Zhou Shifen , Liu Xiaojun
Published: December 2022

The popularity of social media facilitates the dissemination of private information, which has significant implications for investors’ behavior and market efficiency. This paper examines the dynamic dependence between internet postings and herd behavior in China’s open-end fund market by applying the DCC-GARCH and TVP-SV-VAR models. The results show that the relationship between internet postings and herd behavior is time-varying and asymmetric. Specifically, internet postings have a negative effect on herd behavior, and the effect is more pronounced in the short term. Additionally, herd behavior will increase postings and further weaken the herding effect through the internet postings channel. Our results also show that the increase and decrease of postings have asymmetric effects on herd behavior, and the increase of postings has a greater effect on herd behavior.
Ku-band multichannel frequency comb Doppler reflectometer on the GAMMA 10/potential control and divertor simulating experiment (PDX) tandem mirror
Authors: Kohagura J. , Tokuzawa T. , Yoshikawa M. , Shima Y. , Nakanishi H. , Nakashima Y. , Sakamoto M. , Katoh H.
Published: December 2022

A Ku-band (12–18 GHz) multichannel Doppler reflectometer (DR) has been developed in the GAMMA 10/potential control and divertor simulating experiment (PDX) tandem mirror device to improve the applicability of DR measurement for simultaneous monitoring of velocity of electron density turbulence at different locations. Our previous single-channel DR circuit has been replaced by the multichannel microwave system using a nonlinear transmission line based comb generator with heterodyne technique. The multichannel DR system has been installed in the central cell of GAMMA 10/PDX. Initial results of application to GAMMA 10/PDX plasma are presented, showing Doppler frequency shifts during an additional ion cyclotron resonance frequency heating and gas-puffing experiment.
Coherent Schwartz distributions of the Heisenberg algebra and inverted oscillator
Authors: Novikova E. M.
Published: December 2022

An unusual family of generalized coherent states of the Heisenberg algebra is constructed. It consists of two families of functionals on the Schwartz space. Each of them has the key properties of ordinary coherent states: it intertwines the representations of a given algebra, has the completeness property, and minimizes the product of variances in the Heisenberg relation. However, unlike the usual coherent states that are eigenstates for the annihilation operator, the constructed distributions belong to the continuous spectrum of Hermitian generators of the Heisenberg algebra. The inner product of functionals from different families has the main properties of the overlap function of ordinary coherent states: it is continuous in parameters, satisfies the reproducing identity, and has the corresponding geometric meaning. The application of unusual coherent states of the continuous spectrum is demonstrated by an example of solving the spectral problem for an inverted oscillator.
One-dimensional bandgap modulation at continuous few-layer MoS2 steps
Authors: Chu Yu-Hsun , Chen Hou-Ju , Lee Shin-Ye , Butler Christopher John , Lu Li-Syuan , Yeh Han , Chang Wen-Hao , Lin Minn-Tsong
Published: December 2022

In pursuit of novel two-dimensional devices, lateral heterostructures based on transition metal dichalcogenides (TMDCs) have been intensively proposed and demonstrated. For instance, heterojunctions composed of TMDCs with different thicknesses function attractively in electronics and optoelectronics. Using scanning tunneling microscopy and spectroscopy, we resolved electronic structures of three types of few-layer MoS2 steps: flake edges, continuous bilayer–monolayer steps, and monolayers sitting on highly oriented pyrolytic graphite steps. Each type possesses unique bandgap features, including in-gap states and npn-like band alignment, which suggests modifiable 1D bandgaps via choices of edge conditions for the development of lateral TMDC devices.
Exciton–polaritons of hBN/WS2 heterostructure in cavity observed at room temperature
Authors: Zhao Xinchao , Cui Zhuangzhuang , Ge Anping , Lu Xinle , Guan Xueyu , Zhang Jian , Zhen Honglou , Sun Liaoxin , Wang Shaowei , Lu Wei
Published: December 2022

The layer-by-layer buildup of a two-dimensional transition metal dichalcogenide monolayer to form a stack is an important development for these materials, which performs many remarkable properties in the light–matter interaction. Herein, we find clear evidence of exciton–polaritons emerging from WS2/hBN/WS2 heterostructures embedded in a dielectric microcavity under optical pumping. A large Rabi splitting of 15 meV is observed at room temperature, which increases to 25 meV at 5 K. An all-dielectric Fabry–Pérot microcavity provides a simple but effective way to study the room temperature strong coupling between cavity photons and excitons. Our results pave the way for room-temperature polaritonic devices based on quantum-well van der Waals heterostructures.
Equilibrium and symmetries of altitudinal magnetic rotors on a circle
Authors: Cisternas J. , Navarro M. , Duarte S. , Concha A.
Published: December 2022

Macroscopic magnets can easily be manipulated and positioned so that interactions between themselves and with external fields induce interesting dynamics and equilibrium configurations. In this work, we use rotating magnets positioned in a line or at the vertices of a regular polygon. The rotation planes of the magnets can be modified at will. The rich structure of stable and unstable configurations is dictated by symmetry and the side of the polygon. We show that both symmetric solutions and their symmetry-breaking bifurcations can be explained with group theory. Our results suggest that the predicted magnetic textures should emerge at any length scale as long as the interaction is polar, and the system is endowed with the same symmetries.
Strain-engineering in two-dimensional transition metal dichalcogenide alloys
Authors: Bendavid Leah Isseroff , Zhong Yilin , Che Ziyi , Konuk Yagmur
Published: December 2022

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are attractive semiconductors for use in electronic, optoelectronic, and spintronic devices. This study examines how the electronic properties of 2D TMDs can be tuned for specific applications through a combination of alloying and applying strain. Group VIB TMDs (MoS2, MoSe2, WS2, and WSe2) are alloyed by mixing in the metal or chalcogen sublattices. Density functional theory is used to model the structures of the alloys at varying compositions and examine the electronic structure of the alloys under biaxial tensile and compressive strain. Alloying results in the continuous monotonic tuning of the direct bandgap between the limits of the pure components, with low bowing coefficients for all alloys. Applying strain results in a transition of the bandgap from direct to indirect at low values of tensile strain and higher values of compressive strain. Strain can also be used to increase or decrease the bandgap with low compressive strain or tensile strain, respectively. The shift rate, or the rate at which the bandgap changes with applied strain, changes monotonically with alloy composition. MoS2 is identified as the 2D TMD with the highest shift rate.
Quantifying chaos using Lagrangian descriptors
Authors: Hillebrand M. , Zimper S. , Ngapasare A. , Katsanikas M. , Wiggins S. , Skokos Ch.
Published: December 2022

We present and validate simple and efficient methods to estimate the chaoticity of orbits in low-dimensional conservative dynamical systems, namely, autonomous Hamiltonian systems and area-preserving symplectic maps, from computations of Lagrangian descriptors (LDs) on short time scales. Two quantities are proposed for determining the chaotic or regular nature of orbits in a system’s phase space, which are based on the values of the LDs of these orbits and of nearby ones: The difference and ratio of neighboring orbits’ LDs. Using as generic test models the prototypical two degree of freedom Hénon–Heiles system and the two-dimensional standard map, we find that these indicators are able to correctly characterize the chaotic or regular nature of orbits to better than 90% agreement with results obtained by implementing the Smaller Alignment Index (SALI) method, which is a well-established chaos detection technique. Further investigating the performance of the two introduced quantities, we discuss the effects of the total integration time and of the spacing between the used neighboring orbits on the accuracy of the methods, finding that even typical short time, coarse-grid LD computations are sufficient to provide reliable quantification of the systems’ chaotic component, using less CPU time than the SALI. In addition to quantifying chaos, the introduced indicators have the ability to reveal details about the systems’ local and global chaotic phase space structure. Our findings clearly suggest that LDs can also be used to quantify and investigate chaos in continuous and discrete low-dimensional conservative dynamical systems.
Multi-objective optimization of actuation waveform for high-precision drop-on-demand inkjet printing
Authors: Wang Hanzhi , Hasegawa Yosuke
Published: December 2022

High-precision drop-on-demand (DOD) inkjet printing has been considered as one of the promising technologies for the fabrication of advanced functional materials. For a DOD printer, high-precision dispensing techniques for achieving satellite-free smaller droplets have long been desired for patterning thin-film structures. Optimization of an actuation waveform driving a DOD inkjet printer is one of the most versatile and effective strategies to obtain high-precision droplets. Considering the complexity of physics behind the droplet dispensing mechanisms and the large degrees of freedom in the applied waveforms, conventional trial-and-error approaches are not effective for searching the optimal waveform. The present study considers the inlet velocity of a liquid chamber located upstream of a dispensing nozzle as a control variable and aims to develop an automated waveform tuning framework to optimize its waveform using a sample-efficient Bayesian optimization (BO) algorithm. First, the droplet dispensing dynamics are numerically reproduced by using an open-source OpenFOAM solver, interFoam, and the results are passed on to another code based on PyFoam. Then, the parameters characterizing the actuation waveform driving a DOD printer are determined by the BO algorithm so as to maximize a prescribed multi-objective function expressed as the sum of two factors, i.e., the size of a primary droplet and the presence of satellite droplets. The results show that the present BO algorithm can successfully find high-precision dispensing waveforms within 150 simulations. Specifically, satellite droplets can be effectively eliminated and the droplet diameter can be significantly reduced to 24.9% of the nozzle diameter by applying the optimal waveform. Moreover, the prediction using the Gaussian process regression suggests that the size of the primal droplet is highly correlated with the period of a waveform. Finally, the criterion for achieving single-droplet dispensing is proposed based on the energy budget analysis.
A characterization method for low-frequency seismic noise in LIGO
Authors: Valdes G. , Hines A. , Nelson A. , Zhang Y. , Guzman F.
Published: December 2022

We present a method to characterize the noise in ground-based gravitational-wave observatories such as the Laser Gravitational-Wave Observatory (LIGO). This method uses linear regression algorithms such as the least absolute shrinkage and selection operator to identify noise sources and analyzes the detector output vs noise witness sensors to quantify the coupling of such noise. Our method can be implemented with currently available resources at LIGO, which avoids extra coding or direct experimentation at the LIGO sites. We present two examples to validate and estimate the coupling of elevated ground motion at frequencies below 10 Hz with noise in the detector output.
Display of converse and direct magnetoelectric effect in double perovskite LaYFe2O6
Authors: Ghosh R. , Barik A. , Sahoo M. R. , Tiwary Sweta , Babu P. D. , Kaushik S. D. , Vishwakarma P. N.
Published: December 2022

This work reports the simultaneous observation of converse magnetoelectric (CME) and direct magnetoelectric (DME) effects in LaYFe2O6. The structural, magnetic, and magnetoelectric properties of LaYFe2O6, prepared by the sol-gel auto-combustion method and sintered at various temperatures, have been studied. The x-ray powder diffraction study suggests the double perovskite structure with symmetries P21nm (∼90%) and Pbnm (∼10%). The alternate ordering of La and Y ions is confirmed by the neutron powder diffraction (ND) study, which also suggests the antiferromagnetic (AFM) ordering of spins. AFM behavior is also manifested by the magnetic field-dependent magnetization (M) measurement. A higher P21nm phase content is desirable in the context of magnetoelectricity. Magnetic transition (∼700 K) is asserted in the temperature-dependent M measurement. The isothermal magnetization study shows weak ferromagnetism probably due to gradually increasing spin canting with temperature until the transition temperature. The highest CME coefficient (∼2.26 mOe cm/V) as well as DME coefficient (∼0.45 mV/cm Oe) in this material are recorded. True magnetoelectricity for temperature as high as 400 K opens up a new avenue on the playground of magnetoelectric (ME)-based applications.
Transition of catalytic recombination pathways on silica-based thermal protection materials at different temperatures using reactive molecular dynamics method
Authors: Li Qin , Yang Xiaofeng , Dong Wei , Wang Ziyi , Du Yanxia , Gui Yewei
Published: December 2022

Silica-based ceramic material is one of the most competitive options of thermal protection material. However, catalytic reaction mechanism of gaseous atoms on it is complex and confusing. To model catalytic recombination of dissociated oxygen atoms accurately in prediction of chemical non-equilibrium flow and aerodynamic heating, the reactive molecular dynamics method was adopted to simulate gas–surface interaction on the interface, and a series of post-processing methods were constructed to analyze recombination pathways of atomic oxygen on α-quartz. It was found that there are four types of adsorbates on α-quartz surface and five pathways to produce recombined oxygen molecules. Recombination pathways would change from Eley–Rideal recombination-dominated to molecule desorption-dominated with increase in temperature. Information extracted by current post-processing methods explains how and why the recombination coefficient changes with temperature. The post-processing methods can be further applied in analysis of catalytic recombination on other thermal protection materials.
Entropy-stabilized silicides: Expanding the B20 single-phase region from mono-silicide to high-entropy silicide
Authors: Kim Sang Jun , Yoon Kook Noh , Ko Won-Seok , Park Eun Soo
Published: December 2022

The formation of a single phase is an important requirement for high-entropy ceramics (HECs) because precipitation of unwanted phases generally degrades their functional properties. This paper provides a useful guideline for the single-phase formation of HECs. First, metal elements constituting HECs can be divided into two groups: elements that have a parent phase as a stable phase and elements that have a phase with the same stoichiometry as the parent phase but a different crystal structure. Second, even when the latter elements are added in an HEC, we can stabilize the parent phase if stabilizing energy by configurational entropy is larger than the difference in formation energy due to their stable phase, which can be quantitatively calculated through first-principles calculation. Interestingly, based on these guidelines, (CrMnFeCoNi)Si HE silicide with a single B20 structure was sequentially developed from mono-silicide. In particular, the HEC with maximized configurational entropy was searched in our HEC system by adding NiSi to (CrMnFeCo)Si, which is stable in B31 and B20 structures. This study offers a chance to increase the structural and compositional complexity in HECs, enabling the expansion of the single-phase region in HECs.
Dynamics of a single-phase natural circulation system under harmonic excitation
Authors: Ghosh Mazumder Arnab , Saha Ritabrata , Mondal Sirshendu , Ghosh Koushik , Mukhopadhyay Achintya , Sen Swarnendu
Published: December 2022

A natural circulation system (NCS) has a broad application in the sector of thermal engineering, for example, in nuclear reactors due to its capability in transferring heat without any support of external power or a mechanical device. NCSs, although designed for steady operation, have been found to exhibit dynamical behavior, such as periodic oscillations, depending on the input heater power. The heater power, otherwise assumed to be steady, can be fluctuating in practice. The present study focuses on the dynamics of a single-phase square NCS, which exhibits periodic dynamics and is subjected to an external harmonic perturbation (chosen as the simplest form of fluctuation) over the steady heater power. The objective of the study is to study the dynamics of NCS under external (harmonic) disturbances using the framework of forced synchronization. Toward that, a 1D transient model of a square-shaped NCS is simulated with harmonically forced input power. The transition in the nature of synchronization between mass flux oscillations and the external forcing has been characterized by varying the frequency and amplitude of external perturbation independently. We find different nonlinear effects of the harmonic forcing, such as exhibition of quasiperiodic dynamics, frequency pulling/pushing, and frequency locking or forced synchronization. The aforementioned characterization techniques open up an avenue for detailed analysis of the more complex type of fluctuating input heat in real systems.
Chemical reactivity under collective vibrational strong coupling
Authors: Wang Derek S. , Flick Johannes , Yelin Susanne F.
Published: December 2022

Recent experiments of chemical reactions in optical cavities have shown great promise to alter and steer chemical reactions, but still remain poorly understood theoretically. In particular, the origin of resonant effects between the cavity and certain vibrational modes in the collective limit is still subject to active research. In this paper, we study the unimolecular dissociation reactions of many molecules, collectively interacting with an infrared cavity mode, through their vibrational dipole moment. We find that the reaction rate can slow down by increasing the number of aligned molecules, if the cavity mode is resonant with a vibrational mode of the molecules. We also discover a simple scaling relation that scales with the collective Rabi splitting, to estimate the onset of reaction rate modification by collective vibrational strong coupling and numerically demonstrate these effects for up to 104 molecules.
Computational assessment of solute segregation at twin boundaries in magnesium: A two-factor model and solute effect on strengthening
Authors: Chen Huicong , Song Jun
Published: December 2022

This work presents a comprehensive first-principles density functional theory (DFT) study of solute segregation at {101¯1} and {101¯2} twin boundaries (TBs) in Mg. A total of 56 solute elements were investigated. For each solute element, the preferential segregation sites at two TBs were identified and the associated segregation energies were computed. A two-factor model that considers both lattice strain and electronegativity, representing the mechanical and chemical effects respectively, has been proposed to predict the solute segregation energy. The model prediction shows good agreement with the DFT calculation. It was found that the mechanical effect dominates the solute segregation energy. However, depending on the site of segregation, the chemical effect can become sizable to warrant consideration. The degree of solute segregation at TBs at different temperatures was then quantified by calculating the solute concentration at TBs at different temperatures. The effect of solutes in either strengthening or weakening the TB was also evaluated. The results provide a basis for selecting promising solutes in the development of new high-performance Mg alloys.
Fluoride ligand exchange for quantum dot light-emitting diodes with improved efficiency and stability
Authors: Lee Seung Hyuk , Kitano Keisuke , Doe Takahiro , Iwata Noboru , Izumi Makoto , Arakawa Yasuhiko , Tatsuma Tetsu
Published: December 2022

The ligands of quantum dots (QDs) not only play an important role in dispersion of the QDs in solvents and the protection of the QDs but could also block carrier injection into the QDs. Therefore, ligand engineering is important for improving performances of QD light-emitting diode (QLED) displays. In particular, exchange of an organic ligand with inorganic ones such as halides is expected to enhance efficiency and stability of QLED devices. In this study, an organic ligand on CdSe/ZnS QDs was exchanged with F− ligand in a non-polar solvent, which is suitable for device fabrication. As a result, stability of the QDs was improved, while the processability of QLED devices was maintained. Both external quantum efficiency of electroluminescence and device lifetime were improved, mainly because the thinner ligand layer improved the carrier injection efficiency.
Maxwell–Wagner polarization engineering in ferroelectric photovoltaic effect
Authors: Bai Yulong , Chen Yongquan , Zhang Lei , Wang Junyu , Chen Jieyu , Zhao Shifeng
Published: December 2022

Ferroelectric photovoltaic cells have attracted particular interest owing to their potential applications in the green energy field. But there are two drawbacks: weak polarization and wide bandgap, which make them suffer from the limitation of energy conversion efficiency. In this study, the key issue is solved in Ag2O nanoparticle-dispersed Bi5Ti3FeO15 composites. In order to clarify the mechanism, performances of the bandgap, polarization-dependent J–V curves, dielectric response, and switchable photocurrents were investigated. The Maxwell–Wagner polarization effect is confirmed by permittivity Cole–Cole plots with two or more semicircles overlapping. The spatial polarization gradient matrices can reduce the effective mass of the electron–hole pairs and further promote their separation via the Maxwell–Wagner polarization effect. The synchronous mobility of the separated carriers is enhanced. An improved ferroelectric photovoltaics is achieved in Bi5Ti3FeO15⋅3%Ag2O composites, and the key parameters are as follows: VOC ∼ −3.1 V, energy converse efficiency 9.2 × 10−4%. Furthermore, this work shows the first step toward polarization gradient composites for application in ferroelectric photovoltaic cells.
Effect of electric field induced structural ordering on photo-luminescence and piezoelectric response of praseodymium doped (Na0.41K0.09Bi0.5)TiO3 ceramics
Authors: Yadav Pinki , Sharma Ankur , Bhaumik Indranil , Singh Gurvinderjit
Published: December 2022

A correlation of the ferroelectric and photoluminescence response to the structural ordering of praseodymium doped (Na0.41K0.09Bi0.5)TiO3 has been investigated. It has been observed that the ferroelectric and photoluminescence response lacks one-to-one correlation. The ferroelectric response is generally driven by long-range polar ordering. On the contrary, photoluminescence response is concomitant to the local site symmetry around the praseodymium ion. The optimum ferroelectric response has been observed for 1.0 at. % praseodymium doped (Na0.41K0.09Bi0.5)TiO3, whereas for the sample with higher doping concentration, it diminishes gradually due to disruption of the long-range ordering. On the other hand, with the establishment of long-range ordering, no noticeable shift in the position and shape of the photoluminescence lines has been observed. However, a quenching in the photoluminescence intensity of the hypersensitive transitions (1D2 → 3H4) takes place, which has been associated with the modification in the local site symmetry. It has been argued that structural modification has an influence on the photoluminescence intensity but does not affect the energy levels of these transitions. The observed dielectric, piezoelectric, and photoluminescence response has been explained on the basis of the amphoteric nature of praseodymium in (Na0.41K0.09Bi0.5)TiO3.
Decay of secondary motion downstream bends in turbulent pipe flows
Authors: Bilde Kasper Gram , Sørensen Kim , Hærvig Jakob
Published: December 2022

Decay of secondary motion downstream 180° pipe bends is investigated using large-eddy simulations for the bend radii of 1≤rB/dh≤3.375 at a Reynolds number of Reh=10 000. The velocity and turbulence characteristics are validated against experimental data for a straight pipe section as well as against experimental and direct numerical simulations data for a 90° pipe bend. As the bend radius decreases, a larger magnitude of turbulence intensity is induced immediately downstream of the bend, and for the largest magnitude, the highest gradient of the decay turbulence intensity is observed. As a result, the recovery length needed to reestablish the velocity profile downstream of the pipe bend decreases. Turbulence is transported at a higher rate, indicating that the recovery of the velocity profile is driven by turbulence transport. Secondary motions are induced by the curvature of the pipe bend, and as the bend radius decreases, the magnitude of the secondary motion increases. The results show how the secondary motion decay in magnitude as the flow moves downstream the pipe bend. At the outlet of the bend, secondary motions are dominating at the walls and within the bulk flow. As the fluid moves further downstream, the secondary flows dominate close to the walls, and at a length of x/dh=5, a negligible difference in secondary motion is observed for the different bend radii.
Experimental study of the stable droplet formation process during micro-valve-based three-dimensional bioprinting
Authors: Chen Xinxing , O'Mahony Aidan P. , Barber Tracie
Published: December 2022

Three-dimensional (3D) bioprinting offers great potential for the fabrication of complex 3D cell-laden constructs for clinical and research applications. The droplet formation process is the important first step in droplet-based 3D bioprinting, affecting the positional accuracy and printing fidelity. In this paper, the drop ejection behavior, thresholds for stable droplet generation, and formation of satellite drops are studied, under various ink properties, printing conditions, and input cell concentrations using a micro-valve-based 3D bioprinter. Three droplet ejection behaviors are identified under different conditions: an isolated stable droplet, satellites coalescing into a single droplet, and the presence of one/multiple satellites. The droplet state is represented by a phase diagram bounded by a dimensionless Z number (the inverse of the Ohnesorge number) and a jet Weber number, Wej, to define the printability of the utilized bioprinter. The printability range is defined as 2 < Z < 15 and 10 < Wej < 25 by considering characteristics, such as stable single droplet formability and sufficient drop falling velocity. There is no fatal damage on cells within this printability range. The results show there is no strong influence of an actuation system on droplet-based bioprinting printability. As the input cell concentration increases, the bioink's density and viscosity increases, and surface tension decreases, which, in turn, causes the Z number to slightly decrease. The change in the cell concentration (from 0 to 1×107 cells/ml), within a Newtonian bioink, has negligible impact on the droplet volume, falling velocity, drop ejection behavior, breakup time, and ligament length in microvalve-based bioprinting.
The stressful way of droplets along single-fiber strands: A computational analysis
Authors: Bodziony Francisco , Wörner Martin , Marschall Holger
Published: December 2022

Droplets wetting and moving on fibers are omnipresent in both nature and industry. However, little is known on the local stresses the fiber substrates experiences and, in turn, the local forces acting on those droplets while moving on vertical fiber strands. This work is concerned with disclosing the influence of droplet volume, viscosity, and chemical substrate heterogeneity on droplet motion. For this purpose, we pursue a computational simulation campaign by means of direct numerical simulations resolving all relevant spatial and temporal scales. On the basis of local simulation data, we evaluate and analyze effective viscous dissipation rates as well as viscous and capillary forces. We also assess the validity of an assumption, which is frequently used in correlations for droplets moving on single-fiber strands—neglecting the capillary force. Our computational analysis allows to falsify/verify this assumption for different scenarios and reveals that such correlations have to be applied with care, particularly when it comes to chemical heterogeneity of the fiber substrates.
Impact of complex flow structures on the turbine blade tip region mixing
Authors: Huang Lin , Zou Zhengping , Fu Chao , Liu Yumin , Shao Fei
Published: December 2022

Mixing of the turbine blade tip leakage and mainstream flows causes considerable aerodynamic loss. Its understanding is crucial to raise a consequential improvement of the turbine performance. In the present paper, a typical high pressure turbine rotor flow is simulated by detached eddy simulation. The complex mixing in the blade tip region is assessed by the dilution index algorithm in the streamwise direction. Influences of typical parameters on mixing are consecutively identified and analyzed. Relating the influences to flow structures, the mixing mechanism is obtained. It is revealed that the normal effective diffusion coefficient is key in mixing and is correlated with the unsteady tip leakage flow stick vortices. The latter induced by the Kelvin–Helmholtz instability can significantly enhance the local mass and energy transfer and hence diffusion. As a result, mixing is strengthened. Furthermore, the tip region is knowingly divided into the juxtaposing near and far fields. The former contains the tip leakage vortex, leakage jet, mainstream flow, and two entrainment zones. Meanwhile, the latter contains the leakage jet, mainstream flow, and entrainment zone. It was found that the entrainment zone is mixed to a high-degree, whereas the leakage jet is barely mixed.
Study on the geometric characteristics effect of contact area on fracture seepage
Authors: Wei Xianfa , Ma Haichun , Qian Jiazhong , Ma Lei
Published: December 2022

Seepage in rock fractures is influenced by the geometry of the contact area. A parallel model with two circular cylindrical contact areas is studied by numerical simulation. The variation of the seepage field in the fracture model is analyzed by changing the size (radius r) and location (mutual distance s and upstream angle θ) of the two contact areas. Changing r, s, and θ is essentially changing the width and angle of the flow channel on both sides of the contact area. The contact area compresses the flow channel so that there is an obvious pressure drop around the contact area, and the reduced pressure potential energy is mainly converted into the kinetic energy of flow around the contact area and the water flow obtains a larger velocity. The resulting inertial effect controls the generation and development of the low-velocity region and eddy behind the contact area. θ is about 30°, which is the critical point of eddy current generation behind the contact area, the changing trend of −∇P and s and −∇P and sinθ. Two conceptual models are proposed that there is a quadratic function relationship between −∇P and s, and an exponential function relationship between −∇P and sinθ. The parameter N is proposed to represent the joint action of two kinds of the flow channels (the flow channel between contact area and contact area and the flow channel between contact area and lateral wall) and the relationship between −∇P and N is a quadratic function.
Morphed inception of dynamic Leidenfrost regime in colloidal dispersion droplets
Authors: V V S Vara Prasad Gudlavalleti , Yadav Mohit , Dhar Purbarun , Samanta Devranjan
Published: December 2022

Droplet impact on a heated substrate is an important area of study in spray cooling applications. On substrates significantly hotter than the saturation temperature, droplets immediately hover on its vapor cushion, exhibiting the Leidenfrost phenomenon. Here, we report the phenomena wherein addition of Al2O3 nanoparticles to water significantly increases the onset of dynamic Leidenfrost temperature (TDL) and suppresses the overall Leidenfrost regime. We experimentally revealed that the onset of TDL delays with increasing the nanoparticle concentration of the colloidal dispersions at a particular Weber number (We). But, for a constant concentration, the onset of TDL decreases with an increase in impact We. In contrast to water droplets, the colloid droplets exhibit vigorous spraying behavior due to the nanoparticulate residue deposition during the spreading and retraction stages. Further, the residue on the heated substrate changes the departure diameter of the vapor bubbles during boiling, prevents bubble coalescence and vapor layer formation, and reduces the propensity to attain dynamic Leidenfrost regime. With the aid of scaling analysis of TDL with impact We, we have explored the thermo-hydrodynamic behavior of impacting colloid droplets on a superheated substrate. Finally, we have also segregated the different boiling regimes of colloid droplets over various impact We.
A numerical investigation on the deformation of ferrofluid droplets
Authors: Zhang Shi-Ting , Niu Xiao-Dong , Li Qian-Ping , Khan Adnan , Hu Yang , Li De-Cai
Published: December 2022

In this paper, the dynamical mechanism and a general deformation law of a ferrofluid droplet suspended between the air and a liquid substrate under the action of the applied vertical uniform magnetic field are investigated by a numerical model. A generalized conservative phase-field simplified multiphase lattice Boltzmann model is adopted to solve the flow field and phase field, which has a good ability to simulate the problems of ternary fluid flows with large density ratios. Subsequently, the Maxwell equation of static magnetic field is used to solve the magnetic field using a self-correcting scheme. We used this model to numerically study the dynamic evolvement process of ferrofluid droplets placed between the air and a liquid substrate, which are exposed in a vertical uniform magnetic field. Some typical characteristics are employed to characterize the droplet shape, and it is found that the aspect ratio, the elongated velocity, and the height of the mass center of the ferrofluid droplet are related to the magnetic Bond number. Furthermore, the numerical results obtained with the model are in good agreement with the experimental results available in the literature. Finally, the quantitative power law relation between the magnetic Bond number and the aspect ratio of ferrofluid droplets is obtained by using the method of scaling law, which provides a theoretical basis for the study of the deformation mechanism and the universal laws of a ferrofluid droplet placed between the air and a liquid substrate under the action of the vertical uniform magnetic fields with different intensities.
On an origami structure of period-1 motions to homoclinic orbits in the Rössler system
Authors: Xing Siyuan , Luo Albert C. J.
Published: December 2022

In this paper, an origami structure of period-1 motions to spiral homoclinic orbits in parameter space is presented for the Rössler system. The edge folds of the origami structure are generated by the saddle-node bifurcations. For each edge, there are two layers to form the origami structure. On one layer of the origami structure, there is a pair of period-doubling bifurcations inducing periodic motions from period-1 to period-2n motions (n=1,2,…,∞). On such a layer, the unstable period-1 motion goes to the homoclinic orbits with a mapping eigenvalue approaching negative infinity. However, on the corresponding adjacent layers, no period-doubling bifurcations exist, and the unstable period-1 motion goes to the homoclinic orbit with a mapping eigenvalue approaching positive infinity. To determine the origami structure of the period-1 motions to homoclinic orbits, the implicit map of the Rössler system is developed through the discretization of the corresponding differential equations. The Poincaré mapping section can be selected arbitrarily. Before construction of the origami structure, the bifurcation diagram of periodic motions varying with one parameter is developed, and trajectories of stable periodic motions on the bifurcation diagram to homoclinic orbits are illustrated. Finally, the origami structures of period-1 motions to homoclinic orbits are developed through a few layers. This study provides the mathematical mechanisms of period-1 motions to homoclinic orbits, which help one better understand the complexity of periodic motions near the corresponding homoclinic orbit. There are two types of infinitely many homoclinic orbits in the Rössler system, and the corresponding mapping structures of the homoclinic orbits possess positive and negative infinity large eigenvalues. Such infinitely many homoclinic orbits are induced through unstable periodic motions with positive and negative eigenvalues accordingly.
Diffusion toward a nanoforest of absorbing pillars
Authors: Grebenkov Denis S. , Skvortsov Alexei T.
Published: December 2022

Spiky coatings (also known as nanoforests or Fakir-like surfaces) have found many applications in chemical physics, material sciences, and biotechnology, such as superhydrophobic materials, filtration and sensing systems, and selective protein separation, to name but a few. In this paper, we provide a systematic study of steady-state diffusion toward a periodic array of absorbing cylindrical pillars protruding from a flat base. We approximate a periodic cell of this system by a circular tube containing a single pillar, derive an exact solution of the underlying Laplace equation, and deduce a simple yet exact representation for the total flux of particles onto the pillar. The dependence of this flux on the geometric parameters of the model is thoroughly analyzed. In particular, we investigate several asymptotic regimes, such as a thin pillar limit, a disk-like pillar, and an infinitely long pillar. Our study sheds light onto the trapping efficiency of spiky coatings and reveals the roles of pillar anisotropy and diffusional screening.
Prediction of the hydrodynamic disturbance characteristics for two projectiles launched successively underwater based on the radial basis function neural network
Authors: Zhang Dehua , Wang Cong , Li Zhisheng , Wei Yingjie
Published: December 2022

When two projectiles are successively launched under different launch parameters, the motion of the first projectile affects the hydrodynamic characteristics of the second projectile. To predict and study such disturbances, a radial basis function (RBF) neural network model is established in this paper. Compared with the underwater launch of a single projectile, the hydrodynamic loads for two projectiles successively launched are more complex and severe. When the first projectile is launched, it will affect the forces and moments of subsequent projectiles, leading to launch failure. Thus, we apply a numerical simulation method that is verified through experiments to simulate two projectiles successively launched underwater. Then, we use the generated data to train the RBF neural network. The results show that vortices will form at the tail of the first projectile after launch due to viscous effects, which is the main reason for the hydrodynamic disturbance that affects the second projectile. Compared with numerical simulations and experimental methods, the RBF neural network model can more effectively predict the disturbance of the hydrodynamic characteristic variables of the first projectile to the second projectile. This disturbance can be reduced by increasing the spatial distance of the two projectiles, increasing the time interval between launches, and reducing the platform velocity. However, the launch time interval is the most sensitive factor affecting the hydrodynamic characteristics of projectiles.
Prevention of edge fracture using a nontoxic liquid metal sealant
Authors: Chan San To , Haward Simon J. , Shen Amy Q.
Published: December 2022

Edge fracture, the sudden indentation of a viscoelastic fluid's free surface, often occurs when a sufficiently strong shear is applied to the fluid, rendering rheological measurements at high shear rates difficult. We show that sealing the fluid sample's free surface with the nontoxic liquid metal Galinstan can delay fracture occurrence, extending the measurable shear rate range of a cone-and-plate fixture by a decade. The method's effectiveness is compared to the cone-partitioned plate fixture, an existing tool for mitigating the adverse effects of sample fracture. Our cheap yet effective way to prevent edge fracture will benefit the general rheological study of complex fluids.
Raman Spectroscopy-Based Techniques for 2D Layered Materials
Authors: Chacko Levna , Late Dattatray J.
Published: December 2022

It is important to identify the number of layers /thickness present in 2D materials. The techniques such as atomic force microscopy, optical contrast, and Raman spectroscopy have widely been used to determine the number of layers of 2D materials. Among all of them, Raman spectroscopy is a very much rapid, non-destructive, and direct apparatus to identify the number of layers /thickness of 2D Materials. Further, the Raman Spectroscopy is a non-destructive chemical analysis technique which provides detailed information about chemical structure, phase and polymorph, crystallinity and molecular interactions. It is based upon the interaction of light with the chemical bonds within a material. It is known that, the two-dimensional materials with remarkably electronic, optical, and mechanical properties, exhibit both high scientific interest and huge application potential. Raman spectroscopy has been proven to be a rapid, suitable and non-destructive technique to characterize the properties of wide range of 2D materials at research laboratory and mass-production scales. In this chapter, we discuss recent advances in application of Raman spectroscopy to 2D materials for probing their fundamental properties. First, we will introduce Raman characterization on different types of 2D Materials, phase transition triggered by defect, electrostatic doping and temperature, thickness-dependent interlayer and interlayer modes, and two-dimensional alloys with tunable compositions. Further, the layer dependent, temperature and pressure dependence Raman spectroscopy of wide range of 2D materials will be analyzed and discussed. The extensive capabilities of Raman spectroscopy in probing quantum phase transition will also be discussed, such as charge density wave and magnetic transition. Then, we will discuss the application of Raman spectroscopy to probe the moiré phonons, interfacial coupling and cross-dimensional electron-phonon coupling in van der Waals heterostructures. Finally, SERS in 2D materials will be discussed. The 2D materials decorated with metallic nanoparticles, the hybrid SERS substrate can provide SERS EF due to the synergic effect of EM and chemical enhancement. The 2D materials, like graphene, MoS2, WS2, WSe2 etc could offer chemically inert and biocompatible surface which is favourable in bio detection.
X-Ray-Based Techniques for 2D Materials
Authors: Shinde Pratik V. , Shinde Vitthal M. , Rout Chandra Sekhar
Published: December 2022

X-ray-based analytical techniques are the essential tool behind some of the most important scientific discoveries of the twenty-first century. The X-ray-based analysis instruments such as X-ray diffraction (XRD), X-ray fluorescence (XRF), X-ray absorption fine-structure (XAFS), and X-ray photoelectron spectroscopy (XPS) deliver rapid qualitative as well as quantitative determination of a wide variety of two-dimensional (2D) materials. By use of X-rays, these techniques provide substantial structural and compositional information on several kinds of materials including nanostructures, metals, polymers, and ceramics. These analysis techniques deliver information on structures, phases, crystallinity, elemental composition, and chemical states of 2D materials. This chapter summarizes the principle, instrumentation, and applications of these techniques for the analysis of 2D materials.