Moderate Number Research Articles

Rebound dynamics of two droplets asymmetrically impacting single-ridge superhydrophobic surfaces

On a single-ridge superhydrophobic surface, the rebound dynamics of double droplet impacts is investigated via lattice Boltzmann method (LBM) simulations, where one droplet is on the left of macro-ridges, whereas the other droplet being on the top of macro-ridges, leading to the asymmetrical impact of double droplets. The simulation results show that under different impact conditions of various Weber numbers, that is, at low, moderate and high Weber numbers, the rebound regime of double droplet impacts always consists of the complete-coalescence-rebound (CCR), partial-coalescence-rebound (PCR) and coalescence-split-rebound (CSR) regimes. Under these three rebound regimes, the contact time of double droplet impacts is always reduced by the increased We, as the center-to-center distances in the horizontal and vertical directions, Lx and Lz, are constant. At constant Lx and We, the contact time of double droplet impacts on single-ridge superhydrophobic surfaces is increased by the increased Lz because of the earlier formation of liquid bridges at larger Lz. But under different impact conditions of various center-to-center distances in the horizontal direction, that is, at the increased Lx, the rebound regime of double droplet impacts is not always composed of the CCR, PCR and CSR regimes at low, moderate and high Weber numbers. At constant We and Lz, both coalescence strength and rebound regime are significantly affected by the increased Lx for double droplet impacts. So that the contact time of double droplet impacts on singe-ridge superhydrophobic surfaces depends on the center-to-center distance in the horizontal direction, that is, in the x- direction.

Optimization of overall sound pressure level of underexpanded impinging jets at low and moderate Mach numbers

Optimization of overall sound pressure level of underexpanded impinging jets at low and moderate Mach numbers

How trace plots help interpret meta-analysis results.

The trace plot is seldom used in meta-analysis, yet it is a very informative plot. In this article, we define and illustrate what the trace plot is, and discuss why it is important. The Bayesian version of the plot combines the posterior density of , the between-study standard deviation, and the shrunken estimates of the study effects as a function of . With a small or moderate number of studies, is not estimated with much precision, and parameter estimates and shrunken study effect estimates can vary widely depending on the correct value of . The trace plot allows visualization of the sensitivity to along with a plot that shows which values of are plausible and which are implausible. A comparable frequentist or empirical Bayes version provides similar results. The concepts are illustrated using examples in meta-analysis and meta-regression; implementation in R is facilitated in a Bayesian or frequentist framework using the bayesmeta and metafor packages, respectively.

Analysing cluster randomised controlled trials using GLMM, GEE1, GEE2, and QIF: results from four case studies

BackgroundUsing four case studies, we aim to provide practical guidance and recommendations for the analysis of cluster randomised controlled trials.MethodsFour modelling approaches (Generalized Linear Mixed Models with parameters estimated by maximum likelihood/restricted maximum likelihood; Generalized Linear Models with parameters estimated by Generalized Estimating Equations (1st order or second order) and Quadratic Inference Function, for analysing correlated individual participant level outcomes in cluster randomised controlled trials were identified after we reviewed the literature. We systematically searched the online bibliography databases of MEDLINE, EMBASE, PsycINFO (via OVID), CINAHL (via EBSCO), and SCOPUS. We identified the above-mentioned four statistical analytical approaches and applied them to four case studies of cluster randomised controlled trials with the number of clusters ranging from 10 to 100, and individual participants ranging from 748 to 9,207. Results were obtained for both continuous and binary outcomes using R and SAS statistical packages.ResultsThe intracluster correlation coefficient (ICC) estimates for the case studies were less than 0.05 and are consistent with the observed ICC values commonly reported in primary care and community-based cluster randomised controlled trials. In most cases, the four methods produced similar results. However, in a few analyses, quadratic inference function produced different results compared to the generalized linear mixed model, first-order generalized estimating equations, and second-order generalized estimating equations, especially in trials with small to moderate numbers of clusters.ConclusionThis paper demonstrates the analysis of cluster randomised controlled trials with four modelling approaches. The results obtained were similar in most cases, however, for trials with few clusters we do recommend that the quadratic inference function should be used with caution, and where possible a small sample correction should be used. The generalisability of our results is limited to studies with similar features to our case studies, for example, studies with a similar-sized ICC. It is important to conduct simulation studies to comprehensively evaluate the performance of the four modelling approaches.

Control method based on real–imaginary decomposition at the switching frequency for multiple active bridge converters

AbstractIsolated multiple port DC/DC converters, such as the Multiple Active Bridge (MAB) converter, have many recent applications, such as interconnection between grids, isolated uninterruptible power sources (UPSs) and electric vehicle chargers. MAB converter is an attractive solution from the point of view of the hardware because of its symmetry and its capability to be extended to any number of bridges with a moderate number of components. However, the main challenge of this converter is the control method in order to achieve independent control between the different ports and to minimize recirculating currents. For that reason, three‐port power converters have been already investigated, but many improvements can be done for a larger number of ports. This paper proposes to use a Fourier decomposition for the main power signals to separate their real and imaginary parts. As the signals work at the switching frequency, this decomposition is developed with analog electronics. Based on that, a general control method for regulating the power at the different ports is presented using the first harmonic component, which delivers most of the power. In this proposal, two nested control loops ensure accuracy for the DC power flow. Simulation and experimental results validate the proposal.

Thermocapillary convection in shallow liquid layers for moderate Prandtl number liquids using different cylinder configurations

In this paper, the influence of thermocapillary convection in a shallow annular pool using different cylinder configurations is numerically investigated. An axisymmetric, two-dimensional, cylindrical geometry with two concentric cylinders kept at two different temperatures constitutes the model. The main cylinder has a radius of 40 mm and the secondary cylinder has a radius of 20 mm. The effects of Prandtl numbers (Pr = 6.7, 16.1, and 25.2) and layer depths (d = 3.0 mm and 11.0 mm) on the streamlines, isotherms, velocity, and temperature profiles at various locations of the flow are investigated. Depending on the position of the secondary cylinder, three different configurations: 1) an internal cylinder 2) an external cylinder, and a 3) central cylinder is analysed. The flow is characterized by a rapid inward flow along the hot outer wall towards the colder inner wall. In deeper pool at lower Prandtl numbers, flow patterns are characterized by a single rolling cell structure. Conversely, secondary cell formations appear in shallow pool regardless of the Prandtl number. Based on the comparative analysis of various cylinder configurations, it is clear that the external cylinder generates greater velocities and temperatures along its surface. The maximum disparity in surface velocity between an external cylinder and other configurations is 7%, 12%, and 13% for Prandtl numbers of 6.7, 16.1, and 25.2 respectively. Therefore, positioning the cylinder externally promotes swifter convection and more effective mixing of the fluid.

Multiblock parallel high-order implicit residual smoothing time scheme for compressible Navier–Stokes equations

In direct and large eddy simulations, very small space steps are used close to the solid walls in order to resolve the boundary-layer structures. Due to the restrictive CFL stability criteria of explicit time-stepping schemes, the maximum allowable time step is also very small, leading to high computational costs, notably for converging flow statistics. The use of an implicit integration scheme may overcome this limitation at the price of an increased computational cost per step. Moreover, the most commonly used fully implicit schemes induce higher errors due to the necessary approximations and poor dispersion and dissipation properties. As a compromise, a fourth-order implicit residual smoothing scheme (IRS4), successfully validated for a finite volume solver in Cinnella nad Content (2016); Hoarau and Cinnella (2020), has been introduced in a multiblock high-order finite-difference solver. Several improvements are proposed to ensure better dissipation properties, a more efficient treatment of physical boundaries and an accurate and stable parallel multiblock implementation. For moderate CFL numbers, a similar accuracy as the explicit method is obtained with substantial savings in terms of computational time.

Application of Recombinant Human Bone Morphogenetic Protein-2 (RhBMP-2) in the Reconstruction of Edentulous Posterior Maxilla: Clinical Protocol, Histological Analysis, and Long-Term Implant Success and Survival Rates

Background: This study evaluated the efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2) in inducing de novo bone formation during the augmentation of the severely resorbed posterior maxilla for dental implant placement. Methods: Composite grafts consisting of rhBMP-2/absorbable collagen sponge (ACS) mixed with deproteinized bovine bone mineral (DBBM) Bio-Oss in a 1:1 ratio were used to reconstruct severely resorbed posterior maxillae in 13 patients (five men, eight women; age range: 50 to 66 years). Three patients were treated with sinus floor augmentation alone, and 10 patients with a combination of sinus floor augmentation and guided bone regeneration. A total of 71 dental implants were used in this study. The residual bone height below the maxillary sinus ranged from 0.5 to 3.0 mm. Clinical, radiological, and histomorphometric analyses were performed to assess the outcomes of bone augmentation. Results: The healing period was uneventful in all patients. The mean alveolar ridge height increased by 14 mm (range, 10–18 mm) and the mean alveolar width increased by 6 mm (range, 4–7 mm). Histopathological analysis revealed that newly formed bone was detectable throughout the implantation sites of sinus biopsies. The analysis of vascularization of the implant bed revealed large numbers of high-lumen vessels, in addition to moderate numbers of smaller blood vessels within the connective tissue. The histomorphometrical analysis of the tissue distribution showed that the amount of newly formed bone was 20.39 ± 4.95%, the amount of the remaining bone substitute was 41.85 ± 11.97%, and connective tissue was 37.76 ± 8.82%. The overall dental implant success and survival rates were 100% and remained unchanged at a follow-up period of 3 to 12 years. Conclusions: The results of this study demonstrated that a composite graft of rhBMP-2/ACS and DBBM can result in predictable reconstruction of a large bone volume of the maxilla for dental implant placement and functional loading.

Hormonal stimulation of male African catfish in order to in vivo sperm obtaining for artificial reproduction purposes

African catfish is a promising object of industrial fish farming with an urgent problem of in vivo sperm obtaining, which greatly limits the possibility of breeding this species. One of the widely used methods of obtaining sperm is hormonal stimulation of males followed by post-mortem extraction of the testes. Modern science also has surgical methods for intravital sperm collection from African catfish males with preliminary stimulation with hormonal drugs. However, the need for hormonal stimulation in Clarias gariepinus males is closely associated with the risk of developing postoperative complications, in particular in the form of hormonal shock, which can lead to the death. The article presents the results of a comparative analysis of various hormonal spawning stimulants when used in the preparatory period of intravital surgical collection of sperm products from African sharptooth catfish, including the use of a new drug for fish farming, Fertagil (gonadorelin decapeptide), in comparison with the previously used Surfagon. It has been shown that the use of Fertagil at a dose of 100 μg/kg once intramuscularly 16 hours before surgery allows you to get good quality sperm with a high concentration (115.17±3.86×106 ml–1) and a significantly higher the period of motility after activation compared with the drug Surfagon, as well as with a moderate number (65.00±1.88%) of viable sperm. After using Fertagil, the risk of developing hormonal shock in the postoperative period is reduced compared to the currently widely used drug Surfagon.

Benchmarking La‐Based Perovskites as Bifunctional Cathodes For Primary and Rechargeable Zinc−Air Batteries with Biopolymer‐Based Electrolyte

AbstractState‐of‐the‐art perovskite‐based electrocatalysts for zinc−air batteries (ZABs) may include one or more Critical Raw Materials (CRMs) like Co, Ru, and rare earth elements, for oxygen reduction/evolution reactions. Under the warnings described by the CRMs Act in Europe, future research in this field must limit the use of these elements, find more sustainable formulations, and better design/integration strategies to trade off costs, supply, and performances. In this benchmarking study, three main perovskites, i. e., LaNiO3‐δ (LNO), LaMnO3+δ (LMO), and LaMn0.5Ni0.5O3 (LMNO), are studied as quasi‐CRM‐free benchmarks and integrated with a novel gel electrolyte from a natural biopolymer in primary and secondary ZABs. By comparing literature performances based on the number of total/active site CRMs for the first time, these reference perovskites showed Zn utilizations >90 % in primary ZABs, with LMO and LMNO approaching 94 % at 2 mA/cm2, the highest result in the field. In secondary ZABs, LMO demonstrated limited cyclability (62 cycles), while LMNO had a moderate number of cycles (117 cycles) and the highest round‐trip efficiency (54.3 %), while LNO presented the lowest charge potential (2.04 V) and longer cyclability (455 cycles). This work demonstrates encouraging performance with fewer CRMs and proper integration in more sustainable ZABs, opening the way to future CRM‐free perovskites.

Prehatching development of the adrenal gland in Japanese quail (Coturnix japonica): Histological, immunohistochemical, and electron microscopic studies.

The adrenal glands play a key role in maintaining the physiological balance of birds and helping them to survive environmental changes. The objective of the present work was to give a detailed investigation of the histological, ultrastructural, and immunohistochemical findings of the adrenal gland in Japanese quail during the prehatching phase. The current study was performed on 45 healthy Japanese quail embryos at different prehatching periods. Our results showed the primordium of the quail's adrenocortical tissue appeared at 3 days of incubation as a thickening of the splanchnic mesoderm. The prospective chromaffin cells appeared at 5 days as clusters of cells migrated from the neural crest cells along the dorsal aorta toward the interrenal tissue. TH immunoreactivity was observed in the neural crest cells during their migration toward the adrenal primordium. Furthermore, these TH immunopositive cells were intermingled with the developing interrenal cell cords that developed from the coelomic epithelium. NSE immunostaining was detected within the cytoplasm of interrenal cells, chromaffin cells, and ganglion cells. Sox10 is expressed in chromaffin and ganglion cells with different staining intensities. On the 13th day of prehatching, both interrenal and chromaffin cells were β-catenin immunonegative, but on the 17th day, both cells were immunopositively. Our findings show that during prenatal life, the adrenal gland undergoes significant morphological changes. Together, the present data suggest that studying the prenatal development of the adrenal gland in birds is important for advancing our understanding of this critical organ and its functions. RESEARCH HIGHLIGHTS: The present study aimed to give a detailed study of the histological, ultrastructural, and immunohistochemical investigations of the adrenal gland in Japanese quail during the prehatching period. The interrenal primordium was observed on the third embryonic day, on the fifth ED the primordium of the chromaffin tissue appeared as row of migrating neural crest cell. At the ultrastructural level, the interrenal cells take steroid-secreting cells characters, they have varying amounts of lipid droplets and abundant mitochondria at 15th ED contained moderate number of lysosomes and mitochondria.

Digital Optimal Robust Control.

The lack of ability to determine and implement accurately quantum optimal control is a strong limitation to the development of quantum technologies. We propose a digital procedure based on a series of pulses where their amplitudes and (static) phases are designed from an optimal continuous-time protocol for given type and degree of robustness, determined from a geometric analysis. This digitalization combines the ease of implementation of composite pulses with the potential to achieve global optimality, i.e., to operate at the ultimate speed limit, even for a moderate number of control parameters. We demonstrate the protocol on IBM's quantum computers for a single qubit, obtaining a robust transfer with a series of Gaussian or square pulses in a time T=382 ns for a moderate amplitude. We find that the digital solution is practically as fast as the continuous one for square subpulses with the same peak amplitudes.

A fault-tolerant variational quantum algorithm with limited T-depth

We propose a variational quantum eigensolver (VQE) algorithm that uses a fault-tolerant (FT) gate-set, and is hence suitable for implementation on a future error-corrected quantum computer. VQE quantum circuits are typically designed for near-term, noisy quantum devices and have continuously parameterized rotation gates as the central building block. On the other hand, an FT quantum computer (FTQC) can only implement a discrete set of logical gates, such as the so-called Clifford+T gates. We show that the energy minimization of VQE can be performed with such an FT discrete gate-set, where we use the Ross–Selinger algorithm to transpile the continuous rotation gates to the error-correctable Clifford+T gate-set. We find that there is no loss of convergence when compared to the one of parameterized circuits if an adaptive accuracy of the transpilation is used in the VQE optimization. State preparation with VQE requires only a moderate number of T-gates, depending on the system size and transpilation accuracy. We demonstrate these properties on emulators for two prototypical spin models with up to 16 qubits. This is a promising result for the integration of VQE and more generally variational algorithms in the emerging FT setting, where they can form building blocks of the general quantum algorithms that will become accessible in an FTQC.

Shrinkage Methods for Estimating the Shape Parameter of the Generalized Pareto Distribution

The generalized Pareto distribution is one of the most important distributions in statistics of extremes as it has wide applications in fields such as finance, insurance, and hydrology. This study proposes two new methods for estimating the shape parameter of the generalized Pareto distribution (GPD). The proposed methods use the shrinkage principle to adapt the existing empirical Bayesian with data-based prior and the likelihood moment method to obtain two estimators. The performance of the proposed estimators is compared with the existing estimators (i.e., maximum likelihood, likelihood moment estimators, etc.) for the shape parameter of the generalized Pareto distribution in a simulation study. The results show that the proposed estimators perform better for small to moderate number of exceedances in estimating shape parameter of the light-tailed distributions and competitive when estimating heavy-tailed distributions. The proposed estimators are illustrated with practical datasets from climate and insurance studies.

Terminal organization of the corticospinal projection from the arm/hand region of the rostral primary motor cortex (M1r or old M1) to the cervical enlargement (C5-T1) in rhesus monkey.

High-resolution anterograde tracers and stereology were used to study the terminal organization of the corticospinal projection (CSP) from the rostral portion of the primary motor cortex (M1r) to spinal levels C5-T1. Most of this projection (90%) terminated contralaterally within laminae V-IX, with the densest distribution in lamina VII. Moderate bouton numbers occurred in laminae VI, VIII, and IX with few in lamina V. Within lamina VII, labeling occurred over the distal-related dorsolateral subsectors and proximal-related ventromedial subsectors. Within motoneuron lamina IX, most terminations occurred in the proximal-related dorsomedial quadrant, followed by the distal-related dorsolateral quadrant. Segmentally, the contralateral lamina VII CSP gradually declined from C5-T1 but was consistently distributed at C5-C7 in lamina IX. The ipsilateral CSP ended in axial-related lamina VIII and adjacent ventromedial region of lamina VII. These findings demonstrate the M1r CSP influences distal and proximal/axial-related spinal targets. Thus, the M1r CSP represents a transitional CSP, positioned between the caudal M1 (M1c) CSP, which is 98% contralateral and optimally organized to mediate distal upper extremity movements (Morecraft etal., 2013), and dorsolateral premotor (LPMCd) CSP being 79% contralateral and optimally organized to mediate proximal/axial movements (Morecraft etal., 2019). This distal to proximal CSP gradient corresponds to the clinical deficits accompanying caudal to rostral motor cortex injury. The lamina IX CSP is considered in the light of anatomical and neurophysiological evidence which suggests M1c gives rise to the major proportion of the cortico-motoneuronal (CM) projection, while there is a limited M1r CM projection.

Evaluating tests for cluster-randomized trials with few clusters under generalized linear mixed models with covariate adjustment: A simulation study.

Generalized linear mixed models (GLMM) are commonly used to analyze clustered data, but when the number of clusters is small to moderate, standard statistical tests may produce elevated type I error rates. Small-sample corrections have been proposed for continuous or binary outcomes without covariate adjustment. However, appropriate tests to use for count outcomes or under covariate-adjusted models remains unknown. An important setting in which this issue arises is in cluster-randomized trials (CRTs). Because many CRTs have just a few clusters (eg, clinics or health systems), covariate adjustment is particularly critical to address potential chance imbalance and/or low power (eg, adjustment following stratified randomization or for the baseline value of the outcome). We conducted simulations to evaluate GLMM-based tests of the treatment effect that account for the small (10) or moderate (20) number of clusters under a parallel-group CRT setting across scenarios of covariate adjustment (including adjustment for one or more person-level or cluster-level covariates) for both binary and count outcomes. We find that when the intraclass correlation is non-negligible ( 0.01) and the number of covariates is small ( 2), likelihood ratio tests with a between-within denominator degree of freedom have type I error rates close to the nominal level. When the number of covariates is moderate ( 5), across our simulation scenarios, the relative performance of the tests varied considerably and no method performed uniformly well. Therefore, we recommend adjusting for no more than a few covariates and using likelihood ratio tests with a between-within denominator degree of freedom.

Stokes number and coupling effects on particle interaction behavior in turbulent channel flows

The effects of Reynolds number (Reτ=180 and 300), particle Stokes number (St+=0.5, 50, and 92), and fluid–solid phase coupling level (one-way, two-way, and four-way) on particle behavior in turbulent channel flows has been investigated using direct numerical simulation and Lagrangian particle tracking. Previous studies have used all these levels of coupling, but in terms of those employing four-way coupling, no consideration is given as to how emergent phenomena due to collision dynamics within a flow affect the way in which particles impart feedback to the continuous phase. In the present work, we relate the particle–particle interaction to particle–fluid coupling, as well as in assessing its relation to the Stokes number. As the Reynolds number increases and the turbulent region narrows, fewer particles retain their velocity as they migrate to the wall-region leading to reduced streamwise velocity fluctuations and preferential concentration. It is also evident that low Stokes number particles are capable of minor wall-accumulation at Reτ=300. At this increased Reynolds number, four-way coupled simulations performed with moderate Stokes number particles (St+=50) are shown to diminish the effects of particle–fluid feedback, leading to similar fluid and particle statistics as the one-way coupled simulations. It is concluded that turbophoretic and preferential concentration effects are responsible for this phenomenon, since the increased collision rates due to larger concentrations of particles and velocity fluctuations in the wall-region correlate directly with the impact on the two-way coupling flow modifications. Analysis of the collision dynamics also indicates particles colliding with increased relative velocities and angles, which cause larger momentum transfer and directional redistribution, increasing and redirecting slip velocities. It is concluded that for midrange Stokes numbers, four-way coupling is imperative to increase simulation accuracy beyond that obtained assuming one-way coupling.

CONTROLLING CHAOS IN 3D POROUS MEDIA IN THE PRESENCE OF ORIENTATION EFFECT

The influence of orientation on the control of chaotic behaviors of the system in a porous medium is studied in this article based on the theory of dynamical systems. A three-dimensional system model is obtained using the spectral method. The results showed that chaos can be suppressed in the case of a low or moderate Prandtl number by choosing appropriate tilt angles.

GAMMA: Graph Attention Model for Multiple Agents to Solve Team Orienteering Problem With Multiple Depots.

In this work, we present an attention-based encoder-decoder model to approximately solve the team orienteering problem with multiple depots (TOPMD). The TOPMD instance is an NP-hard combinatorial optimization problem that involves multiple agents (or autonomous vehicles) and not purely Euclidean (straight line distance) graph edge weights. In addition, to avoid tedious computations on dataset creation, we provide an approach to generate synthetic data on the fly for effectively training the model. Furthermore, to evaluate our proposed model, we conduct two experimental studies on the multi-agent reconnaissance mission planning problem formulated as TOPMD. First, we characterize the model based on the training configurations to understand the scalability of the proposed approach to unseen configurations. Second, we evaluate the solution quality of the model against several baselines-heuristics, competing machine learning (ML), and exact approaches, on several reconnaissance scenarios. The experimental results indicate that training the model with a maximum number of agents, a moderate number of targets (or nodes to visit), and moderate travel length, performs well across a variety of conditions. Furthermore, the results also reveal that the proposed approach offers a more tractable and higher quality (or competitive) solution in comparison with existing attention-based models, stochastic heuristic approach, and standard mixed-integer programming solver under the given experimental conditions. Finally, the different experimental evaluations reveal that the proposed data generation approach for training the model is highly effective.

Experimental measurement of the pressure drop and heat transfer characteristics of a crossflow heat exchanger in low-density flows

NASA and other space agencies are currently planning the first human missions to Mars in the next 20 years. These missions will require much more power than current robotic missions, and so will require significant waste heat rejection capabilities to maintain steady state operations. Forced convection heat exchangers, particularly crossflow tube array compact heat exchangers, may offer significant volume- and mass-efficiency benefits over radiators for these applications. However, no experimentally validated correlations exist in the literature for the pressure drop and heat transfer characteristics of a forced-convection heat exchanger under the relevant dimensionless conditions which correspond to low (7-200) Reynolds number and moderate (0.0009-0.009) Knudsen number under axial and vortical flows. A staggered-tube crossflow heat exchanger has been constructed and its performance experimentally measured in a low-density wind tunnel. Data has been gathered in low-Reynolds, moderate-Knudsen conditions for both axial and vortical flows over a range of pressures and wall temperatures that is relevant to future Mars or high-altitude heat exchanger operation using both CO2 and air. The measured pressure drop exceeds what is predicted by correlations in the literature at very low (<75) Reynolds number while the Nusselt numbers were fairly well-predicted by existing correlations. A new correlation for pressure drop is presented for low-Reynolds, axial and vortical flow through a staggered circular tube array in crossflow.