bluuebunny/crossref_metadata_2025 huggingface dataset:
Free Flap Reconstruction of the Lower Lip: A Systematic Review and Meta-Analysis
Authors: Murray-Douglass Alexander , Romeo Pascalino , Fox Carly
Published: July 2024

Background Large defects of the lower lip often require free tissue coverage. Fasciocutaneous free flaps have been traditionally used, but innervated muscular free flaps may fundamentally address orbicularis oris deficiency and improve dynamic competence. This review aimed to determine if innervated muscular free flaps provided benefit over fasciocutaneous free flaps for reconstruction of defects of more than 50% of the lower lip. Outcomes of interest included functional oral outcomes including oral competence, aesthetic outcomes, and patient-reported outcome measures.

Methods Five databases (PubMed, Embase, Web of Science, CINAHL, and CENTRAL) were searched for variations of “lip” and “free flap.” Two authors screened articles and included primary research of free flap reconstruction of more than 50% of the lower lip from any etiology in living humans with an English full-text available. Composite bony flaps were excluded. Oral competence and aesthetic satisfaction, reconstruction details, and complications were extracted. Proportional meta-analyses were used to synthesize results for fasciocutaneous free flaps, which were compared with those for muscular free flaps.

Results Fifty-nine articles describing 242 patients were included. Muscular free flaps reported significantly higher proportional oral competence than fasciocutaneous free flaps (98 vs. 83%, p = 0.01). Aesthetic outcomes (98 vs. 97%, p = 0.22) and complications (17 vs. 18%, p = 0.79) were equivalent between fasciocutaneous and muscular free flaps.

Conclusion Muscular free flaps may address the fundamental orbicularis oris defect that causes oral incompetence and seem to provide better functional results. Aesthetic outcomes and complications seem to be equivalent.
Trifecta of Tumors: Simultaneous Detection of Three Primary Malignancies by Different Radiotracers of Nuclear Medicine
Authors: Kar Siven , Gupta Harshita , Shaikh Nusrat , Lele Vikram
Published: July 2024

Malignancies are increasing worldwide with changing lifestyle, pollution, increasing life expectancy, and diagnostic advancements. However, multiple primary malignancies (MPMs) detected simultaneously are very rare. Here, we present a rare case of three primary malignancies (sigmoid colon, prostate, and thyroid) detected simultaneously in a 77-year-old male patient, who initially presented with bleeding per rectum and was then found to have a large pedunculated mass in the sigmoid colon on colonoscopy, which further turned out to be adenocarcinoma. On further imaging and investigations, two new separate malignancies (prostate and thyroid) were found by two different positron emission tomography radiotracers: prostate-specific membrane antigen (PSMA) and fluorodeoxyglucose (FDG). Hence, nuclear medicine modalities can play an important role in detecting MPMs using the vast array of radiotracers available now and perhaps reduce the need for multiple biopsies.
Malaysian youth’s propensity towards ambidextrous learning: an in-depth analysis of behavioural insights dimensions
Authors: Shaari Roziana , Haron Mohamad Zhurad , Abdul Wahab Shah Rollah , Abu Samah Irza Hanie , Yusof Junaidah
Published: July 2024

The aim of this experimental study was to compare the results before and after an intervention that included ambidextrous training to accelerate the enrolment of adolescents in technical, vocational, and educational training (TVET). In particular, the effects of an ambidextrous learning-based training programme on increasing the intention to enter TVET were examined. The independent variables constructed in this study include self-efficacy and TVET knowledge, while the dependent variable is TVET intention. The sample consisted of 480 16-year-old students from government schools in four Malaysian regions selected by cluster sampling. The study used a randomised experimental design with a no-treatment control group. The intervention included training developed as part of Behavioural Insights. Methods of analysis included descriptive and bivariate analysis of mean differences and structural equation modelling to describe the predictive model. The results showed significant differences between the actual and the control groups in terms of post-test results across all factors, including TVET intention, TVET knowledge, and self-efficacy. The structural equation modelling test found that TVET knowledge emerged as the strongest predictor of TVET intention, surpassing self-efficacy. As knowledge about TVET is the most important factor influencing a person’s intention to choose TVET, these initiatives should provide clear and comprehensive explanations of the concepts of TVET, the different TVET clusters available, and the potential career opportunities within these sectors.
Effects of anti-corruption campaigns on cesarean section rate: evidence from China
Authors: Sun Jessica Ya , Huang Jingwei , Chen Renjing , Qin Ni , Kong Dongmin
Published: July 2024

The excessive utilization of cesarean section (CS) has become a global concern, given the potential short-term and long-term detrimental effects for mothers and infants. Worldwide, the rate of CS continues to rise, but efforts to curtail unnecessary CS procedures have yielded limited success. By combining data from three resources, this study aims to estimate the effects of anti-corruption campaigns under the Xi administration on CS rates. We focus on Shanxi Province, a major coal-producing province in north-central China, with notoriety for the collusion between local politicians and business elites. Using the data from the China Corruption Investigation Dataset and data from publicly listed firms between 2013 and 2016, we found that anti-corruption campaigns significantly changed the social environment as firms’ business entertainment spending experienced substantial reductions. Using discharge records from 137 public hospitals, we adopted an instrumental variable (IV) approach and found that the anti-corruption campaigns led to significant reductions in unnecessary CS rates. The reductions are bigger among patients with second or later deliveries. We also find that the anti-corruption campaigns changed behaviors of attending and resident physicians. Our results provide insights into strategies to reduce corrupt practices within the healthcare sector and implementing interventions to minimize the occurrence of CS among healthy women and newborns.
Appraising protein conformational changes by resampling time-resolved serial x-ray crystallography data
Authors: Vallejos Adams , Katona Gergely , Neutze Richard
Published: July 2024

With the development of serial crystallography at both x-ray free electron laser and synchrotron radiation sources, time-resolved x-ray crystallography is increasingly being applied to study conformational changes in macromolecules. A successful time-resolved serial crystallography study requires the growth of microcrystals, a mechanism for synchronized and homogeneous excitation of the reaction of interest within microcrystals, and tools for structural interpretation. Here, we utilize time-resolved serial femtosecond crystallography data collected from microcrystals of bacteriorhodopsin to compare results from partial occupancy structural refinement and refinement against extrapolated data. We illustrate the domain wherein the amplitude of refined conformational changes is inversely proportional to the activated state occupancy. We illustrate how resampling strategies allow coordinate uncertainty to be estimated and demonstrate that these two approaches to structural refinement agree within coordinate errors. We illustrate how singular value decomposition of a set of difference Fourier electron density maps calculated from resampled data can minimize phase bias in these maps, and we quantify residual densities for transient water molecules by analyzing difference Fourier and Polder omit maps from resampled data. We suggest that these tools may assist others in judging the confidence with which observed electron density differences may be interpreted as functionally important conformational changes.
A gyrokinetic simulation model for 2D equilibrium potential in the scrape-off layer of a field-reversed configuration
Authors: Wang W. H. , Wei X. S. , Lin Z. , Lau C. , Dettrick S. , Tajima T.
Published: July 2024

The equilibrium potential structure in the scrape-off layer (SOL) of the field-reversed configuration (FRC) can be affected by the penetration of edge biasing applied at the divertor ends. The primary focus of the paper is to establish a formulation that accurately captures both parallel and radial variations of the two-dimensional (2D) potential in SOL. The formulation mainly describes a quasi-neutral plasma with a logical sheath boundary. A full-f gyrokinetic ion model and a massless electron model are implemented in the GTC-X code to solve for the self-consistent equilibrium potential, given fixed radial potential profiles at the boundaries. The first essential point of this 2D model lies in its ability to couple radial and parallel dynamics stemming from resistive currents and drag force on ions. The model successfully recovers the fluid force balance and continuity equations. These collisional effects on 2D potential mainly appear through the density profile changes, modifying the potential through electron pressure gradient. This means an accurate prescription of electron density and temperature profiles is important in predicting the potential structure in the FRC SOL. The Debye sheath potential and the potential profiles applied at the boundaries can be additional factors contributing to the 2D variations in SOL. This comprehensive full-f scheme holds promise for future investigations into turbulent transport in the presence of the self-consistent 2D potential together with the non-Maxwellian distributions and open boundary conditions in the FRC SOL.
Investigating the mechanism of flow of transonic compact crossover tandem diffuser
Authors: Zhang Cheng , Zhang Hongxin , Huang Guoping , Li Manling , Yang Yuxuan , Long Yongqiang
Published: July 2024

Dealing with high transonic airflow at the outlet of a mixed-flow impeller is a challenging issue in research on the design of efficient and compact diffusers. A low aspect ratio and an adverse pressure gradient in the passage of the diffuser can lead to flow separation on the hub side of the bend and the suction side of the aft blade. Tandem blading can be used to attain flow control through an appropriate relative circumferential tandem position (λ). However, a comprehensive understanding of flow in a compact crossover tandem diffuser (CTD) requires further investigation. This study provides a detailed analysis of the mechanism of flow in a compact crossover baseline tandem diffuser (CBTD) as well as the influence of different values of λ on the structure of flow of the CTD. The findings show that the CBTD can suppress secondary flow separation on the hub side of the bend by reasonably distributing the radial load. We also found that a value of λ of 75% can delay the point of separation on the suction side of the aft blade over a wide range of spans, where this inhibits the corner separation vortex and improves the structure of flow and performance of the diffuser. We also preliminarily explore the impacts of excitation of full-span jet intensities with different values of λ on the corner separation vortex on the suction side of the aft blade and offer guidance for the design of a compact and efficient CTD.
An updated technique to obtain explosive kinetics data on microsecond timescales
Authors: Tasker Douglas G. , Skrabacz Daniel A. , Campbell Maria C. , Spielvogel Kyle D. , Morinec Allen G. , McLaughlin Aidan B. , Houlton Robert , Tucker Robert , Moore Jeremiah D. , Cawkwell M. J. , Manner Virginia W.
Published: July 2024

There are few techniques available for chemists to obtain time-to-explosion data with known temperature inputs at the early stages of the design and synthesis of new explosives. In the 1960s, a technique was developed to rapidly heat milligram-quantities of confined explosives to ∼1000 K on microsecond timescales. Wenograd [Trans. Faraday Soc. 57, 1612 (1961)] loaded explosives inside stainless steel hypodermic needles, connected them to a fireset and rapidly discharged a capacitor through the steel. He obtained the temperature by measuring the needle resistance in a Wheatstone bridge arrangement and the time to explosion from a needle rupture. However, owing to the narrow-gauge needles used in the original research, the experiment was only possible with melt-castable explosives; it was never replicated, and modern diagnostics are now available with advances beyond the 1960s. Here, we report the development of the High Explosives Initiation Time (HEIT) test, which utilizes a 250 J pulsed power system to heat the needles. This work extends the Wenograd approach by using optical diagnostics, computational modeling, and advanced techniques to measure needle resistance and needle rupture. Preliminary rate information for pentaerythritol tetranitrate (PETN) will be presented.
L-PBF processing and characterization of a Ti35Nb30Zr29Mo3Ta3 multiprincipal element alloy for medical implants
Authors: Arjmand Farzin , Mourgout Adrien , Chali Alima , Djemai Madjid , Langueh Credson-Yannick , Monasson Olivier , Peroni Elisa , Boissiere Michel , Ammar-Merah Souad , Dirras Guy
Published: July 2024

This Letter reports on the processing, mechanical properties, electrochemical performance, and toxicity behavior of a multiprincipal element Ti35Nb30Zr29Mo3Ta3 alloy. The recovered centimeter-sized cubes or parallelepipeds were polished before analysis. It was found that the homogeneity and yield stress of the alloys get increased when higher volumetric energy densities are applied during processing. The synthesized alloys also exhibited a Young modulus closer to those of bones than those usually reported on the conventional orthopedic metals (60–80 GPa for this alloy against 110 and 4–30 GPa for the Ti-6Al-4V and bone, respectively). The electrochemical corrosion assays performed at 25 and 37 °C, in sodium chloride (NaCl, 0.1 M), deoxygenated high glucose Dulbecco's Modified Eagle Medium (DMEM), and deoxygenated DMEM implemented with fetal bovine serum showed corrosion potentials (Ecorr) ranged in the order NaCl(25 °C) ≈ DMEM + PBS(37 °C) > DMEM(37 °C) and impedances much larger in the DMEM and DMEM + PBS media than in NaCl. Finally, pre-osteoblasts cells cultured in the medium conditioned by the alloy did not evidence cytotoxicity effect, because no effects on the cell proliferation and morphology were observed. These data suggest the biocompatibility of this alloy, indicating no acute toxicity, which is a prerequisite for the integration of an alloy as a bioimplant.
Acceleration of particle-in-cell simulations using sparse grid algorithms. I. Application to dual frequency capacitive discharges
Authors: Garrigues L. , Chung-To-Sang M. , Fubiani G. , Guillet C. , Deluzet F. , Narski J.
Published: July 2024

The use of sparse particle-in-cell (PIC) algorithms to accelerate the standard explicit PIC scheme has recently been successfully applied in the context of single-frequency capacitively coupled plasma discharges [Garrigues et al., J. Appl. Phys. 129, 153303 (2021)]. We have extended the sparse PIC scheme to model dual-frequency capacitive discharges. Comparisons between standard and sparse PIC algorithms show that the plasma properties as well as the electron and ion distribution functions can be retrieved with a maximum error of 2%. This work opens the interest of using the sparse PIC algorithm to perform 2D and 3D simulations under real operating conditions of capacitively coupled plasma discharges.
Diffusion-driven instabilities in the BT-GN oscillatory carbonylation reaction network
Authors: Maćešić Stevan , Novakovic Katarina
Published: July 2024

This study explores the role of diffusion in creating instabilities in the Bruk Temkin-Gorodsky Novakovic (BT-GN) oscillatory carbonylation reaction network. Stoichiometric network analysis and numerical methods revealed the presence of two destabilizing feedback cycles responsible for these instabilities. Analysis of a spatially uniform system showed that the saddle-node bifurcation can be simulated within the reaction network. The introduction of diffusion results in two types of instabilities: one occurs when a spatially uniform system is already unstable, leading to a reaction–diffusion front; and another involves diffusion-driven instabilities where introducing diffusion destabilizes a stable spatially uniform system. Slower PdI2 diffusion plays a key role in inducing these instabilities. Equations describing conditions for the emergence of the instabilities in both cases were derived.
Emergent order in adaptively rewired networks
Authors: Sinha Sudeshna
Published: July 2024

We explore adaptive link change strategies that can lead a system to network configurations that yield ordered dynamical states. We propose two adaptive strategies based on feedback from the global synchronization error. In the first strategy, the connectivity matrix changes if the instantaneous synchronization error is larger than a prescribed threshold. In the second strategy, the probability of a link changing at any instant of time is proportional to the magnitude of the instantaneous synchronization error. We demonstrate that both these strategies are capable of guiding networks to chaos suppression within a prescribed tolerance, in two prototypical systems of coupled chaotic maps. So, the adaptation works effectively as an efficient search in the vast space of connectivities for a configuration that serves to yield a targeted pattern. The mean synchronization error shows the presence of a sharply defined transition to very low values after a critical coupling strength, in all cases. For the first strategy, the total time during which a network undergoes link adaptation also exhibits a distinct transition to a small value under increasing coupling strength. Analogously, for the second strategy, the mean fraction of links that change in the network over time, after transience, drops to nearly zero, after a critical coupling strength, implying that the network reaches a static link configuration that yields the desired dynamics. These ideas can then potentially help us to devise control methods for extended interactive systems, as well as suggest natural mechanisms capable of regularizing complex networks.
In-plane distribution of huge local permittivity of KTa1−xNbxO3 estimated from local phase transition temperatures and spatially averaged permittivity
Authors: Sakamoto Takashi , Imai Tadayuki , Sasaura Masahiro , Yagi Shogo , Fujiura Kazuo , Cho Yasuo
Published: July 2024

Potassium tantalate niobate (KTa1−xNbxO3, KTN) single crystals have a very large relative permittivity εr (>104) just above the paraelectric to ferroelectric phase transition temperature (TC). The quadratic electro-optic coefficient and the electro-strictive coefficient are also very large because of their proportionality to εr2. However, the local relative permittivity can easily vary spatially due to the incongruently melting nature of KTN. In this study, we quantitatively estimated the in-plane distribution of the huge local relative permittivity of KTN. First, we measured the spatial distribution of TC using scanning nonlinear dielectric microscopy, then deposited the electrodes and measured the temperature dependence of the spatially averaged permittivity using an LCR meter. Following that, we evaluated the spatial distribution of the huge local permittivity from the combination of the spatial distribution of TC and the spatially averaged permittivity. Finally, we measured the deflection angle of light to confirm the validity of the εr estimation procedure. The maximum error for the estimated permittivity was estimated to be around 3.3%.
Comprehensive study of hydraulic fracturing in shale oil reservoirs comprising shale–sandstone transitions
Authors: Suo Yu , Li Zi-Hao , Fu Xiao-Fei , Zhang Cheng-Chen , Jia Zhen-Jia , Peng Dong-Zhe , He Wen-Yuan , Pan Zhe-Jun
Published: July 2024

Hydraulic fracturing technology is a crucial technique for effectively developing shale oil reservoirs. In field fracturing treatment operations, these reservoirs are often consisting of a combination of various rock types that making them complex. Therefore, this study specially focuses on the sandstone–shale layers in the G zone of the Daqingzi Well G Area in the southern part of the Songliao Basin. It aims to provide essential parameter support for subsequent theoretical and numerical research through laboratory mechanical experiments. Using the finite discrete element method, we have established four different numerical models for the hydraulic fracturing of shale oil with varying geological conditions, (including transition zones). The study reveals that when the vertical stress difference is 6 MPa, the crack height increases, and the offset distance decreases. At 8 and 10 MPa, crack propagation exhibits a “forking” phenomenon. A decrease in rock cohesion leads to increased offset distances in the transition zone, along with an increase in crack height. For type a and b transition zones, it is recommended to use a fracturing fluid with a viscosity of approximately 10 mPa s and a flow rate of 12 m3/min for fracturing. For type c transition zones, it is advisable to select fracturing fluid with a viscosity in the range of 10–30 mPa s and use a flow rate of 12 m3/min for fracturing. For the type d transition zones in the fracturing reservoir, it is recommended to use fracturing fluid with a viscosity of around 10 mPa s and a flow rate of 15 m3/min for optimal field fracturing operations.
Surrogate-based multi-objective design optimization of tree-shaped fins with uniform branch end distribution for latent heat thermal energy storage
Authors: Kim Hansol , Seo Joseph , Hassan Yassin A.
Published: July 2024

The enhancement of latent heat thermal energy storage (LHTES) systems through fin geometry optimization remains a critical challenge for leveraging the full potential of renewable energy sources. This study focuses on optimizing the geometries of tree-shaped fins to enhance power and energy densities in LHTES systems. The goal is to find branch designs with high energy and power density through a novel surrogate model-based optimization strategy that explores a broad design space. The surrogate models applied, including linear regression, principal component analysis-based linear regression, artificial neural networks, and random forest, are evaluated for their predictive performance. The random forest model demonstrates superior accuracy in predicting targets. The optimization process results in a Pareto-optimal design with a volume fraction of 33.9%. This optimal design substantially enhances the system's power density by 61.6% compared to conventional plate fins at an equivalent energy density. This optimized design improves energy and power density, achieving a uniform end-to-branch distribution, which is a pivotal factor for consistent temperature distribution and improved thermal efficiency. By integrating surrogate-based optimization with broad ranges of the tree-shaped fin design, this research has significantly improved the operational efficiency of LHTES systems. This research promises more effective thermal management and provides a methodological framework for design innovation in thermal energy storage.
Insight into the electrolyte concentration impact on single hydrogen bubble evolution dynamics at a microelectrode during electrochemical water splitting
Authors: Guo Chenyu , Lu Xinlong , Zhu Yizhou , Ma Lijing , Jing Dengwei
Published: July 2024

Bubbles generated during electrochemical water splitting could adhere to the electrode surface and therefore impede the reaction. Thus, understanding and manipulating the evolution dynamics of bubbles is crucial for enhancing electrolysis efficiency. In this study, we investigated the evolution mechanism and forces acting on individual hydrogen bubble on Pt microelectrode surface by employing different H2SO4 electrolyte concentrations (0.2–1.0 M) under various applied voltages [−2 to −6 V vs saturated calomel electrode (SCE)]. We focused on bubble detachment diameter, average current, and bubble lifetime and subsequently established relational equations over these variables. At −6 V vs SCE, the growth coefficient has a maximum value of 14.42 × 10−4 m/s0.333 when the concentration of electrolyte is around 0.6 M. Gas production at 0.6 M increased by 63.4% compared to 0.2 M and by 11.2% compared to 1.0 M. Therefore, choosing the appropriate electrolyte concentration can maximize gas production and bubble detachment efficiency. Additionally, a force balance model incorporating the Marangoni force for single bubbles on the microelectrode surface was established across varying concentrations of H2SO4 electrolyte. At −4 V vs SCE, the solutal Marangoni force starts to dominate when electrolyte concentrations above 0.4 M. The results demonstrate the critical role of the solutal Marangoni force beyond a certain value of electrolyte concentration.
Dynamical analysis of a periodically forced chaotic chemical oscillator
Authors: Ramírez-Ávila Gonzalo Marcelo , Kapitaniak Tomasz , Gonze Didier
Published: July 2024

We present a comprehensive dynamical analysis of a chaotic chemical model referred to as the autocatalator, when subject to a periodic administration of one substrate. Our investigation encompasses the dynamical characterization of both unforced and forced systems utilizing isospikes and largest Lyapunov exponents-based parameter planes, bifurcation diagrams, and analysis of complex oscillations. Additionally, we present a phase diagram showing the effect of the period and amplitude of the forcing signal on the system’s behavior. Furthermore, we show how the landscapes of parameter planes are altered in response to forcing application. This analysis contributes to a deeper understanding of the intricate dynamics induced by the periodic forcing of a chaotic system.
Water entry of a sphere moving along a circular path at a constant speed
Authors: Suh I. D. , Go S. C. , Rhee S. H.
Published: July 2024

When a marine propeller rotates in partially submerged conditions, air is entrained from above the undisturbed free-surface, which is called the reference surface, and the ventilated air surrounds the propeller blades, causing thrust loss and excessive vibration, all of which seriously damage the durability of the propeller shaft system of a ship. In the present study, the entry of a propeller blade is simplified by the water entry problem of a sphere moving along a circular path at a constant speed. A high-speed camera was employed to capture the rapidly changing flow structures in detail. Above the reference surface, we focused on the free-surface disturbances, including splash and dome formation. Beneath the reference surface, the development and collapse of ventilated cavities, followed by the line-vortex cavity and cavity undulation, were observed. The ventilated cavity of the present study appears to be more elongated than those of the free-falling sphere's water entry experiments. Two parallel vortical structures appeared after the cavity pinch-off, and bubbles were entrained into these structures to form the line-vortex cavity. The sphere's drag was directly measured via the torque meter attached to the sphere's rotating axis. The relation between the measured drag and the flow around the sphere was identified.
Aerodynamic force characteristics and flow field mechanism of multiple square cylinders in a tandem arrangement
Authors: Jiang Huimin , Yang Qun , Liu Xiaobing , Chen Anjie , Zhang Dewang
Published: July 2024

Wind tunnel tests and large eddy simulations were employed to obtain the aerodynamic coefficients and flow fields of two and three tandem square cylinders across various spacing ratios. The spacing ratio L/D, defined as the ratio of the center-to-center spacing between adjacent square cylinders to their width, ranges from 1.2 to 8. By analyzing these results, the aerodynamic force characteristics and their generation mechanism of the three tandem square cylinders at a high Reynolds number (Re = 3.2 × 104) were revealed. By comparing the results of the two and three tandem square cylinders, the effect of adding a third square cylinder behind the two tandem square cylinders on its aerodynamic characteristics was clarified. The results show that unlike the two tandem square cylinders, the three tandem square cylinders exhibit two critical spacing ratios, (L/D)cr1 = 2.5–3 and (L/D)cr2 = 3.5–4, respectively. Based on these two critical spacing ratios, the flow around the three tandem square cylinders is identified as single blunt body, reattachment, and co-shedding regimes. In the single blunt body and reattachment regimes, the addition of a third square cylinder behind significantly alters the flow around the two tandem square cylinders, leading to reduced mean drag coefficients, fluctuating lift coefficients, and Strouhal numbers, along with an increased critical spacing ratio. In the co-shedding regime, this addition has little effect on the flow.
Experimental investigation on the impact of fuel injection schemes on the fuel/air mixing characteristics in alternating wedge struts
Authors: Wu Pinxin , Song Wenyan , Wang Yuhang , Li Jie
Published: July 2024

To enhance the performance of scramjet engines, it is essential to understand the fuel/air mixing characteristics downstream of alternating wedge struts and the dynamics of streamwise vortices. Two optical measurement techniques, Mie scattering and acetone-particle laser-induced fluorescence, were employed to study the impact of fuel injection location and different injection gases on the fuel/air mixing characteristics downstream of alternating wedge struts at total temperature of 300 K and total pressure of 800 kPa. The results indicated that the particle laser-induced fluorescence measurements provided superior results compared to Mie scattering, due to the more uniform distribution and better following characteristics of acetone molecules as seeding particles. Different fuel injection locations resulted in varying fuel distributions and plume morphologies downstream. The plume sizes obtained from the three types of fuel orifices were generally consistent, but the mixing effect of the orifices on the first strut was better, whose injection locations being at the trailing edge intersections, with a larger plume area and more uniform fuel distribution. The fuel/air mixing process downstream of the alternating wedge struts was primarily dominated by streamwise vortices. Despite certain differences in the physical properties of nitrogen and hydrogen molecules, the measurement results showed that the plume morphologies obtained with both gases were quite similar. Additionally, a streamwise vortex model was developed to predict the dynamics of streamwise vortices and the evolution of fuel plume morphology, and it was compared with experimental results.
Nanogap resistive switch mechanism study and performance degradation analysis
Authors: Yu Dacheng , Tian Zhongzheng , Ren Liming , Fu Yunyi
Published: July 2024

The nanogap resistive switch holds potential as a candidate for nonvolatile memory, although its durability needs enhancement. This study delves into the operational mechanisms through detailed morphological examination during continuous operation of nanogap resistive switches. By developing a finite element model of nanogaps, we reveal the mechanisms behind the formation of electrode surface hillocks and filaments during continuous switching. Our findings suggest that “set” operations include processes such as field evaporation, electric field-induced diffusion, and field-assisted migration within the gap. Conversely, “reset” operations, driven by Joule heating and electromigration, lead to filament breakage and the creation of a fine gap. This research elucidates device degradation issues, such as periodic fluctuations in set threshold voltage (Vset) and the presence of non-steep set curves, providing both theoretical and experimental insights to improve future device performance.
Flame dynamics and oscillation characteristics based on statistical analysis in a combustor with prefilming and non-prefilming atomization
Authors: Wang Zhikai , Gong Ka , Liu Yibo , Chen Sheng , Lei Qingchun , Fan Wei
Published: July 2024

Suppressing thermoacoustic oscillations in low-emission combustors during their operation poses a major challenge. In this study, we report dynamic flame tests on combustors with prefilming (S1) and non-prefilming (S2) airblast atomizers. We used the image fast Fourier transform, proper orthogonal decomposition, dynamic mode decomposition, and continuous wavelet transform to obtain the spatial distribution of pulsations and spectral characteristics of the flames. The results reveal that the flames of S1 and S2 were significantly different. The combustor of S1 had a dome-attached flame confined to the primary combustion zone, while S2 had a lifted flame that filled the entire combustor. As the rate of airflow at the inlet increased, the flame of S1 exhibited oscillatory combustion, while the flame of S2 remained stable under all tested conditions, which was consistent with observations of its dynamic images. No characteristic peak was observed in the spectra of S2 under all operating conditions, and under rates of inlet airflow of 40 and 60 g/s for S1. However, pulsations in the chemiluminescence signals of the flame had a primary frequency of 116.4 Hz and secondary harmonic at 232.4 Hz at 80 g/s for S1. At 100 g/s, the S1 flame exhibited a primary frequency of 142.9 Hz, secondary harmonic at 285.4 Hz, and tertiary harmonic at 428.3 Hz. Minor adjustments to the geometry of the airblast atomizer can thus significantly alter the mode of spray–wall interactions and impact flame dynamics. Consequently, this study proposes a new control technique for instability suppression.
Shock response of two epoxy resins at up to 330 GPa pressure
Authors: Mochalova Valentina , Utkin Alexander , Nikolaev Dmitry , Savinykh Andrey , Garkushin Gennady , Kapasharov Artur , Malkov Georgiy
Published: July 2024

Experimental studies of the shock wave properties of two epoxy resins with the same composition but different curing temperatures (160 and 200 °C) at up to 330 GPa pressure have been carried out. Laser interferometry was used to record particle velocity profiles at up to 73 GPa pressure while measuring the shock wave velocity. The release sound velocity was experimentally determined in the 3–73 GPa pressure range. Cumulative explosive shock wave generators were used to study the shock Hugoniot of epoxy resins at pressures above 100 GPa. It was shown that the shock compressibility data of both samples are approximated by a single shock Hugoniot within the experimental error. A kink on Hugoniot recorded close to 25 GPa pressure indicates a chemical decomposition in epoxy resin. Above this kink, a change in the shock wave front structure was recorded. Hugoniots of epoxy resin and unidirectional carbon/epoxy composite were compared at up to 370 GPa pressure.
Effects of dynamic wetting and liquid–solid slip on self-propelled nanodrops in tapered nanochannels
Authors: Zhang Yixin , Zhao Chengxi
Published: July 2024

Drops inside tapered microchannels exhibit self-propelled behavior, driven by the capillary pressure gradient within the drops. This driven force may be balanced by the viscous drag and the contact line drag to determine the drop displacement, in analogy to the way to predict capillary imbibition. However, how the drops move exactly with time at the nanoscale is unclear. This study employs molecular dynamics simulations to explore the dynamics of nanodrops within tapered channels with hydrophobic and hydrophilic coatings. The simulations reveal that in a hydrophobic tapered channel, drops migrate toward the wider side of the channel but may halt midway as the driving pressure approaches zero during their movements. Conversely, in hydrophilic tapered channels, drops move unlimitedly toward the channel's tip. Incorporating considerations for dynamic contact angles based on the molecular kinetic theory and liquid–solid slip, a theoretical model is derived that accurately predicts the drop displacement observed in molecular simulations without free parameters. In our simulations of drop motion in hydrophilic tapered channels, the drop displacement x is found linear with time x ∼t, as the viscous drag is dominant and the slip length is small. However, the theory further predicts that drop displacement may behave as x2 ∼t when slip length is large. Conversely, under dominant contact line drag, the theory predicts x3 ∼t for drop motion in tapered nanoslits. These findings underscore the critical influence of dynamic wetting and liquid–solid slip in precisely predicting drop motions on solid surfaces at the nanoscale.
Observation of acoustic meron textures
Authors: Zhou Nong , Chen Wan-Na , Sun Wen-Jun , Sheng Zong-Qiang , Wu Hong-Wei
Published: July 2024

Merons, as a member of quasiparticle family characterized by half-integer of the skyrmion topological charge with nontrivial topological textures, are of great interest in various branches of physics. Here, we report the first experimental observation of a meron texture configuration in acoustic waves. A squared metastructure is designed to support the spoof acoustic surface wave, forming meron lattice patterns in the acoustic velocity field vectors. The experimental results indicate that the meron textures can be moved and shaped by tuning the phase and amplitude differences between the excited sound sources, respectively. To demonstrate the topologically protected character of meron against structure defects, we further measure the acoustic pressure and velocity field distributions on a defective surface. The acoustic meron texture not only provides potential applications toward topologically robust ways to manipulate vectorial characteristics of the acoustic waves but also instills confidence for exploring other members of the quasiparticle family, such as the acoustic hopfion in acoustic waves.
Scaling laws for optimal power-law fluid flow within converging–diverging dendritic networks of tubes and rectangular channels
Authors: Garg Ashish
Published: July 2024

Flows in dendritic–fractal networks have garnered extensive research attention, but most studies assume a constant tube or channel cross section. In many applications, the cross section of the tube or channel changes as the flow progresses through it, such as the blood flow through the arterial system, which is a prime example of a deformable or non-uniform tree-like network. Heating, ventilation, and air conditioning ductwork also exemplify a tree-like network with varying cross sections. This research investigates power-law fluid flows in the converging–diverging tubes and rectangular channels, prevalent in engineered microfluidic devices, many industrial processes, and heat transfer applications. Power-law fluid flows through linear, parabolic, hyperbolic, hyperbolic cosine, and sinusoidal converging–diverging dendritic networks of tubes and rectangular channels are studied. The flow is assumed to be steady, incompressible, two-dimensional planar, and axisymmetric laminar flow without considering network losses. A theoretical model has been derived to evaluate the flow conductance under network volume and surface-area constraints. The flow conductance is highly sensitive to network geometry. The effective conductance of all networks increases with increasing daughter-to-parent radius ratio before eventually declining. The maximum conductance occurs when a specific radius or channel-height daughter–parent ratio β* is achieved. This value depends on the constraint and vessel geometry, such as tubes or rectangular channels. The optimal flow conditions for maximum conductance in a constrained tube volume network, βmax*=βmin*=N−1/3, while for a constrained tube's surface-area network, βmax*=βmin*=N−(n+1)/(3n+2). This scaling applies to all converging–diverging tube network profiles. Here, βmax*, βmin* are the radius ratios of the daughter–parent pair at the maximum divergent or minimum convergent part of the vessel. N represents the number of branches splitting at each junction, and n is the power-law index of the fluid. Furthermore, the optimal flow scaling for the height ratio in the rectangular channel, βmax*=βmin*=N−1/2α−1/2 for constrained channel volume and βmax*=βmin*=N−1/2α−n/(2n+2) for constrained surface area for all converging–diverging channel networks, respectively, where α is the channel-width ratio between parent and daughter branches. Additionally, at optimal conditions in both the channels and tube network, pressure drops are equally partitioned across each branching level. The results in this work are validated with experiments and existing theories for limiting conditions. This research expands existing design principles for efficient flow systems, previously in the literature developed for uniform vessels, to encompass non-uniform converging–diverging vessels. Additionally, it provides a valuable framework for studying non-Newtonian flows within complex, non-uniform tree-like networks.
Deep reinforcement learning-based active flow control of an elliptical cylinder: Transitioning from an elliptical cylinder to a circular cylinder and a flat plate
Authors: Jia Wang , Xu Hang
Published: July 2024

We study the adaptability of deep reinforcement learning (DRL)-based active flow control (AFC) technology for bluff body flows with complex geometries. It is extended from a cylinder with an aspect ratio Ar = 1 to a flat elliptical cylinder with Ar = 2, slender elliptical cylinders with Ar less than 1, and a flat plate with Ar = 0. We utilize the Proximal Policy Optimization (PPO) algorithm to precisely control the mass flow rates of synthetic jets located on the upper and lower surfaces of a cylinder to achieve reduction in drag, minimization of lift, and suppression of vortex shedding. Our research findings indicate that, for elliptical cylinders with Ar between 1.75 and 0.75, the reduction in drag coefficient ranges from 0.9% to 15.7%, and the reduction in lift coefficient ranges from 95.2% to 99.7%. The DRL-based control strategy not only significantly reduces lift and drag, but also completely suppresses vortex shedding while using less than 1% of external excitation energy, demonstrating its efficiency and energy-saving capabilities. Additionally, for Ar from 0.5 to 0, the reduction in drag coefficient ranges from 26.9% to 43.6%, and the reduction in lift coefficient from 50.2% to 68.0%. This reflects the control strategy's significant reduction in both drag and lift coefficients, while also alleviating vortex shedding. The interaction and nonlinear development of vortices in the wake of elliptical cylinders lead to complex flow instability, and DRL-based AFC technology shows adaptability and potential in addressing flow control problems for this type of bluff body flow.
A parametric approach to flow loss with incidence and tip clearance variables for a compressor linear cascade
Authors: Kan Xiaoxu , Lei Haodong , Gao Limin , Wu Wanyang , Zhong Jingjun
Published: July 2024

A study was conducted using theoretical and numerical calculations to analyze the flow losses of a compressor linear cascade called SMU37-RL02. Its main goal is to determine the parametric expressions for vortex structure weight loss at the 103% axial chord position on the quasi-S3 section of the cascade. A flow loss distribution band delineation extraction method is proposed to improve data acquisition efficiency. The method expands the database by single-parameter variable expressions, and the simulated annealing algorithm solves the full-condition optimized tip clearance range for the cascade. The results show that the dominant flow loss weight of the vortex structures is transferred from the passage vortex to the tip leakage vortex following the increased tip clearance. Making the tip clearance Ct = 0.19%H as the optimization objective has the most stable and best performance at the full incoming flow conditions compared to the cascade with an equidistant tip clearance. The maximum loss reduction is 13.16% relative to the original cascade loss at the i = +1.9° incoming flow condition. The optimal cascade achieves relatively stable optimization over the full range of incoming flow conditions.
Dynamical behavior of liquid-filled rotors with axial motion
Authors: Wang Guangding , Bao Rui , Chen Liqing , Yuan Huiqun
Published: July 2024

In the present study, the dynamical behavior of liquid-filled rotors with axial motion is investigated. Based on the differential equations of motion for ideal fluids, the fluid forces exerted on the rotor are obtained. Then, the Euler–Bernoulli beam theory is utilized to establish the governing equations of motion for the rotor system. By applying Hamilton's principle, the governing equation and the corresponding boundary conditions are derived. Furthermore, in order to solve the eigenvalue problem of the system, the extended Galerkin method is applied to discrete equations of motion for the rotor system. As a result, the system stability, divergence, and flutter instability are defined. Moreover, a comparative study is presented to verify the accuracy of the proposed model. Finally, the effects of liquid parameters on the dynamic characteristics of the rotor system are investigated in detail. The results show that for liquid-filled rotors with axial motion, the stability of the system depends on the liquid parameters, axial velocity, and spinning velocity.
A triple emulsion droplet in a uniform flow
Authors: Favelukis Moshe
Published: July 2024

The fluid mechanics problem of a triple emulsion droplet in a uniform creeping flow is theoretically studied. The triple emulsion, submerged in an external fluid 1, is composed of an inner spherical drop (fluid 4), covered by a spherical shell (fluid 3), which is subsequently covered by another spherical shell (fluid 2). In the absence of a body force, eight parameters are governed: the Capillary number (Ca), three viscosity ratios (λ21, λ32, λ43), two radii ratios (K, k), and two-surface tension ratios (M, m). If all surfaces remain spherical and concentric, five parameters (λ21, λ32, λ43, K, k) are sufficient. Expressions for the stream functions and the drag forces were obtained to calculate the terminal velocity of the triple emulsion falling or rising in a stagnant fluid under the influence of gravity. With gravity, four additional parameters are needed: the ratio of the buoyancy force to the external viscous force (B), and three density ratios (γ21, γ31, γ41). To remain concentric, all surfaces must have the same velocity (magnitude and direction). This results in two restricted parameters, but even then, not every combination of parameters leads to a physical solution. Our findings suggest that the terminal velocity of a triple emulsion is equal to or lower than that of a double emulsion, which is subsequently equal to or lower than that of a single drop. Similar to single and double emulsion droplets, no deformation takes place in a concentric spherical triple emulsion subjected to a gravitational field under creeping flow conditions.
Searching for the maximal packing fraction of hard disks confined by a circular cavity through replica exchange/event-chain Monte Carlo
Authors: Basurto Eduardo , Gurin Peter , Specht Eckard , Odriozola Gerardo
Published: July 2024

We utilized a blend of replica exchange and event-chain Monte Carlo techniques to generate candidate configurations, aiming for a maximal packing fraction of hard disks within a circular enclosure. Our investigation encompassed systems comprising N particles, with N ranging from 300 to 720. Through our analysis, we identified 108 novel maximal packings, with some surpassing existing configurations by over 0.001 in packing fraction. As such, Monte Carlo methods demonstrate their efficacy in tackling optimization challenges of this nature.