In order to solve the problems of low power transfer efficiency (PTE) and limited distance in magnetic coupling resonant wireless power transfer (MCR-WPT) technology. In this paper, based on the magnetic field control ability of metamaterials (MMs), the way to improve the performance of MCR-WPT systems is studied. First, the influence of MMs on the coupling of MCR-WPT system is theoretically analyzed by establishing an equivalent circuit model. Through a series of simulations and experiments, the relationships between the PTE and the array and placement of the MM slab are investigated. The results demonstrate that when one MM slab is placed in the middle, near the Tx coil or the Rx coil, the optimal PTE can be obtained by inserting one slab with $6 \times 6$, $1 \times 1$, and $6 \times 6$ arrays, respectively. Moreover, the systems with multilayer MM slabs are also studied. The measured PTEs on one, two, and three layers of MM slabs can increase by 20.6%, 29.3%, and 22.6%, respectively. The efficiency improvement capability of one MM slab is better than three slabs but worse than two slabs. This paper discusses the application of MMs in MCR-WPT systems, which has a certain reference significance.

The Viséan–Serpukhovian boundary is poorly defined in South China, hampering regional and global stratigraphical correlations. The foraminiferal and conodont distribution of the Baping Formation in the carbonate-slope Danlu section permits the recognition of an interval from the middle Viséan to the uppermost Serpukhovian in a continuous succession. The base of the Serpukhovian in Danlu is recognized by the first occurrences of Janischewskina delicata, Howchinia subplana and questionable ‘Millerella’ tortula. At a slightly younger level, the conodont Lochriea ziegleri is first recorded. A calibration on the first occurrence of L. ziegleri in different basins at a global scale has been revised compared to auxiliary markers within the ammonoids and foraminifers. The late occurrence of L. ziegleri in the Danlu section also supports a lack of synchronicity in the global first occurrence of this taxon. This study calls for the recognition of a new base for the Serpukhovian under a far better correlation between different zonal schemes and fossil groups.

Path-following control of wheeled mobile robots has been a crucial research topic in robotic control theory and applications. In path-following control with obstacles, the path-following control and collision avoidance goals might be conflicting, making it challenging to obtain near-optimal solutions for path-following control and obstacle avoidance with low tracking error and input energy consumption. To address this problem, we propose a potential field-based dual heuristic programming (P-DHP) algorithm with an actor–critic (AC) structure for path-following control of mobile robots with obstacle avoidance. In the proposed P-DHP, the path-following control and collision avoidance problems are decoupled into two ones to resolve the control conflict. Firstly, a neural network-based AC is constructed to approximate the near-optimal path-following control policy in a no-obstacle environment. Then, with the trained path-following control policy fixed, a potential field-based control policy structure is constructed by another AC network to generate opposite control forces as the robot moves toward the obstacle, which can guarantee the robot’s control safety and reduce the tracking error and input energy consumption in obstacle avoidance. The simulated and experimental results show that P-DHP can realize near-optimal path-following control with the satisfaction of safety constraints and outperforms state-of-the-art approaches in control performance.

Trematodes of the genus Ogmocotyle are intestinal flukes that can infect a variety of definitive hosts, resulting in significant economic losses worldwide. However, there are few studies on molecular data of these trematodes. In this study, the mitochondrial (mt) genome of Ogmocotyle ailuri isolated from red panda (Ailurus fulgens) was determined and compared with those from Pronocephalata to investigate the mt genome content, genetic distance, gene rearrangements and phylogeny. The complete mt genome of O. ailuri is a typical closed circular molecule of 14 642 base pairs, comprising 12 protein-coding genes (PCGs), 22 transfer RNA genes, 2 ribosomal RNA genes and 2 non-coding regions. All genes are transcribed in the same direction. In addition, 23 intergenic spacers and 2 locations with gene overlaps were determined. Sequence identities and sliding window analysis indicated that cox1 is the most conserved gene among 12 PCGs in O. ailuri mt genome. The sequenced mt genomes of the 48 Plagiorchiida trematodes showed 5 types of gene arrangement based on all mt genome genes, with the gene arrangement of O. ailuri being type I. Phylogenetic analysis using concatenated amino acid sequences of 12 PCGs revealed that O. ailuri was closer to Ogmocotyle sikae than to Notocotylus intestinalis. These data enhance the Ogmocotyle mt genome database and provide molecular resources for further studies of Pronocephalata taxonomy, population genetics and systematics.

In this study, the length scaling for the boundary layer separation induced by two incident shock waves is experimentally and analytically investigated. The experiments are performed in a Mach 2.73 flow. A double-wedge shock generator with two deflection angles ($\alpha _1$ and $\alpha _2$) is employed to generate two incident shock waves. Two deflection angle combinations with an identical total deflection angle are adopted: ($\alpha _1 = 7^\circ$, $\alpha _2 = 5^\circ$) and ($\alpha _1 = 5^\circ$, $\alpha _2 = 7^\circ$). For each deflection angle combination, the flow features of the dual-incident shock wave–turbulent boundary layer interactions (dual-ISWTBLIs) under five shock wave distance conditions are examined via schlieren photography, wall-pressure measurements and surface oil-flow visualisation. The experimental results show that the separation point moves downstream with increasing shock wave distance ($d$). For the dual-ISWTBLIs exhibiting a coupling separation state, the upstream interaction length ($L_{int}$) of the separation region approximately linearly decreases with increasing $d$, and the decrease rate of $L_{int}$ with $d$ increases with the second deflection angle under the condition of an identical total deflection angle. Based on control volume analysis of mass and momentum conservations, the relation between $L_{int}$ and $d$ is analytically determined to be approximately linear for the dual-ISWTBLIs with a coupling separation region, and the slope of the linear relation obtained analytically agrees well with that obtained experimentally. Furthermore, a prediction method for $L_{int}$ of the dual-ISWTBLIs with a coupling separation region is proposed, and the relative error of the predicted $L_{int}$ in comparison with the experimental result is $\sim$10 %.

The surface wave instability (SWI) of thermocapillary migration is examined by linear stability analysis for a droplet on a unidirectional heated plane. Both a Newtonian fluid and an Oldroyd-B fluid are considered. The droplet, flattened by gravity, is susceptible to two kinds of instabilities: convective instability (CI), which is independent of surface deformation; and SWI, which occurs only when the Galileo number and the surface-tension number are not too large. The wavenumber of the latter is much smaller than that of the former, while the reverse is true for the wave speed. SWI is found at different Prandtl numbers (Pr), while its mode includes streamwise and oblique waves. Energy analysis suggests that the energy of the long-wave mode comes from the shear stress induced by the surface deformation, the energy source for the mode with finite wavelength is the work done by Marangoni forces, while the energy from the basic flow is only important in some cases at small Pr. For the Oldroyd-B fluid, a small elasticity slightly changes the critical Marangoni number of SWI, while larger elasticity changes the preferred mode from SWI to CI. The instability mechanism is discussed and comparisons are made with experimental results.

Coastal eutrophication and hypoxia remain a persistent environmental crisis despite the great efforts to reduce nutrient loading and mitigate associated environmental damages. Symptoms of this crisis have appeared to spread rapidly, reaching developing countries in Asia with emergences in Southern America and Africa. The pace of changes and the underlying drivers remain not so clear. To address the gap, we review the up-to-date status and mechanisms of eutrophication and hypoxia in global coastal oceans, upon which we examine the trajectories of changes over the 40 years or longer in six model coastal systems with varying socio-economic development statuses and different levels and histories of eutrophication. Although these coastal systems share common features of eutrophication, site-specific characteristics are also substantial, depending on the regional environmental setting and level of social-economic development along with policy implementation and management. Nevertheless, ecosystem recovery generally needs greater reduction in pressures compared to that initiated degradation and becomes less feasible to achieve past norms with a longer time anthropogenic pressures on the ecosystems. While the qualitative causality between drivers and consequences is well established, quantitative attribution of these drivers to eutrophication and hypoxia remains difficult especially when we consider the social economic drivers because the changes in coastal ecosystems are subject to multiple influences and the cause–effect relationship is often non-linear. Such relationships are further complicated by climate changes that have been accelerating over the past few decades. The knowledge gaps that limit our quantitative and mechanistic understanding of the human-coastal ocean nexus are identified, which is essential for science-based policy making. Recognizing lessons from past management practices, we advocate for a better, more efficient indexing system of coastal eutrophication and an advanced regional earth system modeling framework with optimal modules of human dimensions to facilitate the development and evaluation of effective policy and restoration actions.

In recent years, the incidence of teratospermia has been increasing, and it has become a very important factor leading to male infertility. The research on the molecular mechanism of teratospermia is also progressing rapidly. This article briefly summarizes the clinical incidence of teratozoospermia, and makes a retrospective summary of related studies reported in recent years. Specifically discussing the relationship between gene status and spermatozoa, the review aims to provide the basis for the genetic diagnosis and gene therapy of teratozoospermia.

The aeroacoustic characteristics of flying vehicles with pitch-fixed rotors differ from traditional helicopters with pitch-controlled rotor blades. Accurate predictions of rotor noise are still challenging because many uncertainty factors and unsteadinesses exist. This work investigates the aeroacoustic effects of rotational speed deviation, rotation speed fluctuation, blade vibration and blade geometric asymmetry. The analysis is based on the efficient computation of rotor noise under different working conditions. The mean aerodynamic variables are computed using the blade element moment theory, while small-amplitude fluctuations are introduced to account for the unsteadiness and uncertainty factors. It is shown that periodic rotation speed fluctuations and blade vibrations can produce significant extra tones. By contrast, if the fluctuations and vibrations are random, the noise level in a wide frequency range is increased. The intriguing result reminds us of the need to revisit the rotor broadband noise sources commonly attributed to turbulent flows. The influences are observer angle dependent, and the extra noise production is more significant in the upstream and downstream directions. The asymmetric blade geometry can cause extra tonal noise at the harmonics of the blade shaft frequency. The noise features of dual rotors are also investigated. Usually, the noise is sensitive to the initial phase difference and rotation directions due to the interference effect. However, the noise features are vastly altered if there are slight differences in the rotation speeds. Although the influences of some factors on rotor noise were already known, the present study provides a more comprehensive analysis of the problem. The results also highlight the need to consider these practical factors for accurate noise prediction of multi-rotor flying vehicles.

The Yellow River originates on the Tibetan Plateau and transports vast amounts of terrestrial sediment to the ocean. However, previous studies have not reached a consensus as to when and how the Yellow River first began to flow into the sea. Here we present Sr-Nd-Pb isotope data and a high-resolution clay mineral record of a 200-m-long sediment core recovered from the modern Yellow River delta. The changes in Sr-Nd-Pb isotopic compositions and clay minerals at 0.71 Ma suggest that a larger proportion of sediment was derived from the Yellow River after this time. We propose that the Yellow River has influenced the Bohai Sea since 1.9 Ma (or even earlier), which provides important evidence for an older Yellow River than 1.2 Ma. A significant increase in discharge of Yellow River sediments since 0.71 Ma is due to continuing subsidence of the eastern China coast, the large amplitude of Quaternary sea-level changes, and increased supply of eroded loess during the last 1.0 Ma. After this time, the contribution of local rivers surrounding the Bohai Sea became negligible due to dilution by the huge amounts of Yellow River sediments. These results provide improved constraints on the evolution of the Yellow River and subsequent land-sea fluxes.

Extensive evidence has demonstrated that bilinguals non-selectively activate lexicons of both languages when reading or hearing words in one language. Here, we further investigated the electrophysiological roles of cross-linguistic orthography and phonology in the processing of L2 spoken words in unbalanced Chinese (L1)–English (L2) bilinguals in a cross-modal situation. Relative to unrelated control, the recognition of auditory L2 words showed behavioral interference effects when paired with orthographic or phonological neighbors of the correct translations of L2 words. Moreover, the lexical effects were also exhibited in the electrophysiological data, as reflected by marginally less positive late positive component (500–800 ms) amplitudes in the frontal region. Importantly, the orthographic rather than phonological translation neighbor condition elicited less negative N400 (300–500 ms) amplitudes in the parietal–occipital regions, suggesting that this orthographic translation neighbor condition facilitated the co-activation of spoken L2 words. Taken together, these findings indicate that cross-linguistic orthographic and phonological activation have different temporal dynamics with both bottom-up parallel cross-linguistic activation and the top-down inhibitory control mechanism governing the two-language lexical organization in L2 spoken word recognition.

As an internal time-keeping mechanism, circadian rhythm plays crucial role in maintaining homoeostasis when in response to nutrition change; meanwhile, branched-chain amino acids (BCAA) in skeletal muscle play an important role in preserving energy homoeostasis during fasting. Previous results from our laboratory suggested that fasting can influence peripheral circadian rhythm and BCAA metabolism in fish, but the relationship between circadian rhythm and BCAA metabolism, and whether circadian rhythm regulates BCAA metabolism to maintain physiological homoeostasis during fasting remains unclear. This study shows that the expression of fifteen core clock genes as well as KLF15 and Bcat2 is highly responsive to short-term fasting in fast muscle of Siniperca chuatsi, and the correlation coefficient between Clock and KLF15 expression is enhanced after fasting treatment. Furthermore, we demonstrate that the transcriptional expression of KLF15 is regulated by Clock, and the transcriptional expression of Bcat2 is regulated by KLF15 by using dual-luciferase reporter gene assay and Vivo-morpholinos-mediated gene knockdown technique. Therefore, fasting imposes a dynamic coordination of transcription between the circadian rhythm and BCAA metabolic pathways. The findings highlight the interaction between circadian rhythm and BCAA metabolism and suggest that fasting induces a switch in KLF15 expression through affecting the rhythmic expression of Clock, and then KLF15 promotes the transcription of Bcat2 to enhance the metabolism of BCAA, thus maintaining energy homoeostasis and providing energy for skeletal muscle as well as other tissues.

We present an experimental study of Rayleigh–Bénard convection using liquid metal alloy gallium-indium-tin as the working fluid with a Prandtl number of $Pr=0.029$. The flow state and the heat transport were measured in a Rayleigh number range of $1.2\times 10^{4} \le Ra \le 1.3\times 10^{7}$. The temperature fluctuation at the cell centre is used as a proxy for the flow state. It is found that, as $Ra$ increases from the lower end of the parameter range, the flow evolves from a convection state to an oscillation state, a chaotic state and finally a turbulent state for $Ra>10^5$. The study suggests that the large-scale circulation in the turbulent state is a residual of the cell structure near the onset of convection, which is in contrast with the case of $Pr\sim 1$, where the cell structure is transiently replaced by high order flow modes before the emergence of the large-scale circulation in the turbulent state. The evolution of the flow state is also reflected by the heat transport characterised by the Nusselt number $Nu$ and the probability density function (p.d.f.) of the temperature fluctuation at the cell centre. It is found that the effective local heat transport scaling exponent $\gamma$, i.e. $Nu\sim Ra^{\gamma }$, changes continuously from $\gamma =0.49$ at $Ra\sim 10^4$ to $\gamma =0.25$ for $Ra>10^6$. Meanwhile, the p.d.f. at the cell centre gradually evolves from a Gaussian-like shape before the transition to turbulence to an exponential-like shape in the turbulent state. For $Ra>10^6$, the flow shows self-similar behaviour, which is revealed by the universal shape of the p.d.f. of the temperature fluctuation at the cell centre and a $Nu=0.19Ra^{0.25}$ scaling for the heat transport.

In this work, we propose using an ensemble Kalman method to learn a nonlinear eddy viscosity model, represented as a tensor basis neural network, from velocity data. Data-driven turbulence models have emerged as a promising alternative to traditional models for providing closure mapping from the mean velocities to Reynolds stresses. Most data-driven models in this category need full-field Reynolds stress data for training, which not only places stringent demand on the data generation but also makes the trained model ill-conditioned and lacks robustness. This difficulty can be alleviated by incorporating the Reynolds-averaged Navier–Stokes (RANS) solver in the training process. However, this would necessitate developing adjoint solvers of the RANS model, which requires extra effort in code development and maintenance. Given this difficulty, we present an ensemble Kalman method with an adaptive step size to train a neural-network-based turbulence model by using indirect observation data. To our knowledge, this is the first such attempt in turbulence modelling. The ensemble method is first verified on the flow in a square duct, where it correctly learns the underlying turbulence models from velocity data. Then the generalizability of the learned model is evaluated on a family of separated flows over periodic hills. It is demonstrated that the turbulence model learned in one flow can predict flows in similar configurations with varying slopes.

Given a plane graph $G=(V,E)$ , a Petrie tour of G is a tour P of G that alternately turns left and right at each step. A Petrie tour partition of G is a collection ${\mathscr P}=\{P_1,\ldots,P_q\}$ of Petrie tours so that each edge of G is in exactly one tour $P_i \in {\mathscr P}$ . A Petrie tour P is called a Petrie cycle if all its vertices are distinct. A Petrie cycle partition of G is a collection ${\mathscr C}=\{C_1,\ldots,C_p\}$ of Petrie cycles so that each vertex of G is in exactly one cycle $C_i \in {\mathscr C}$ . In this paper, we study the properties of 3-regular plane graphs that have Petrie cycle partitions and 4-regular plane multi-graphs that have Petrie tour partitions. Given a 4-regular plane multi-graph $G=(V,E)$ , a 3-regularization of G is a 3-regular plane graph $G_3$ obtained from G by splitting every vertex $v\in V$ into two degree-3 vertices. G is called Petrie partitionable if it has a 3-regularization that has a Petrie cycle partition. The general version of this problem is motivated by a data compression method, tristrip, used in computer graphics. In this paper, we present a simple characterization of Petrie partitionable graphs and show that the problem of determining if G is Petrie partitionable is NP-complete.

Words’ morphemic structure and their orthographic representations vary across languages. How do bilingual experiences with structurally distinct languages influence children's morphological processes for word reading? Focusing on English literacy in monolinguals and bilinguals (N = 350, ages 5–9), we first revealed unique contributions of derivational (friend-li-est) and compound (girl-friend) morphology to early word reading. We then examined mechanisms of bilingual transfer in matched samples of Spanish–English and Chinese–English dual first language learners. Results revealed a principled cross-linguistic interaction between language group (Spanish vs. Chinese bilinguals) and type of morphological awareness. Specifically, bilinguals’ proficiency with the type of morphology that was less characteristic of their home language explained greater variance in their English literacy. These findings showcase the powerful effects of bilingualism on word reading processes in children who have similar reading proficiency but different language experiences, thereby advancing theoretical perspectives on literacy across diverse learners.