This study is dedicated to achieving efficient active noise control in a supersonic underexpanded planar jet, utilizing control parameters informed by resolvent analysis. The baseline supersonic underexpanded jet exhibits complex wave structures and substantial high-amplitude noise radiations. To perform the active control, unsteady blowing and suction are applied along the nozzle inner wall close to the exit. Employing both standard and acoustic resolvent analyses, a suitable frequency and spanwise wavenumber range for the blowing and suction is identified. Within this range, the control forcing can be significantly amplified in the near field, effectively altering the original sound-producing energetic structure while minimizing far-field amplification to prevent excessive noise. A series of large-eddy simulations are further conducted to validate the control efficiency, demonstrating an over 10 dB reduction in upstream-propagated screech noise. It is identified that the present unsteady control proves more effective than steady control at the same momentum coefficient. The controlled jet flow indicates that the shock structures become more stable, and the stronger the streamwise amplification of the forcing, the more likely it is to modify the mean flow characteristics, which is beneficial for reducing far-field noise radiation. Spectral proper orthogonal decomposition analysis of the controlled flow confirms that the control redistributes energy to higher forcing frequencies and suppresses large-scale antisymmetric and symmetric modes related to screech and its harmonics. The findings of this study highlight the potential of resolvent-guided control techniques in reducing noise in supersonic underexpanded jets and provide a detailed understanding of the inherent mechanisms for effective noise reduction through active control strategies.

Summary: Melatonin serves as an endogenous synchronizer of biological rhythms. Age-related changes are evident with a significant reduction in melatonin observed in 24-hour secretion. Melatonin exerts a significant cytoprotective action by buffering free radicals and reversing inflammation. However, few studies have explored the association between physical activity and melatonin level. In this study, we compared melatonin level and actigraphy-derived sleep and activity indicators in older adults across two levels of exercise habit (sedentary-to- light exercise and moderate -to-vigorous exercise), as well as the association of these indicators with melatonin levels. We recruited 104 participants (aged 57– 84 years) who wore a wristwatch device to monitor their activity (MotionWatch 8; CamNtech, Cambridge, UK) for 14 days. Circadian rhythms were estimated using cosinor analysis, lag 1440 mins correlation coefficient, interdaily stability, and non-parametric analysis. Saliva samples were collected every 30 mins from 18:00 pm till one hour before usual bedtime, and maximum melatonin level during this period. A 5-minute Psychomotor Vigilance Task (PVT) was used to evaluate attention. Habits of physical activities were self-reported. Melatonin level was not significantly different between participants with sedentary- to-light and moderate-to-vigorous exercise habits. Analysis showed that participants who had moderate-vigorous exercise habit were older (p = 0.04), having longer sports time (p < 0.001) and WASO (p = 0.02), more occurrence of daytime naps (intradaily variability) (p = 0.05), more fragmentated 24-h sleep-wake cycle (interdaily stability, p = 0.01), and less regular 24h rhythm (lag 1140 mins correlation, p = 0.04). They also showed shorter response time (p = 0.05), and a smaller number of lapses (p = 0.04) in PVT. Regression analysis results showed that weekly exercise time is positively associated with melatonin level. Additionally, a later start hour of M10 is associated with 5.95 pg/ml increase in melatonin level. In consistent, exercise in older adults did not promote a robust sleep- wake cycle but is related to better cognitive function and higher melatonin levels.

Timing of food intake is an emerging aspect of nutrition; however, there is a lack of research accurately assessing food timing in the context of the circadian system. The study aimed to investigate the relation between food timing relative to clock time and endogenous circadian timing with adiposity and further explore sex differences in these associations among 151 young adults aged 18–25 years. Participants wore wrist actigraphy and documented sleep and food schedules in real time for 7 consecutive days. Circadian timing was determined by dim-light melatonin onset (DLMO). The duration between last eating occasion and DLMO (last EO-DLMO) was used to calculate the circadian timing of food intake. Adiposity was assessed using bioelectrical impedance analysis. Of the 151 participants, 133 were included in the statistical analysis finally. The results demonstrated that associations of adiposity with food timing relative to circadian timing rather than clock time among young adults living in real-world settings. Sex-stratified analyses revealed that associations between last EO-DLMO and adiposity were significant in females but not males. For females, each hour increase in last EO-DLMO was associated with higher BMI by 0·51 kg/m2 (P = 0·01), higher percent body fat by 1·05 % (P = 0·007), higher fat mass by 0·99 kg (P = 0·01) and higher visceral fat area by 4·75 cm2 (P = 0·02), whereas non-significant associations were present among males. The findings highlight the importance of considering the timing of food intake relative to endogenous circadian timing instead of only as clock time.

The scaling relations mapping the turbulence statistics in compressible turbulent boundary layers (TBLs) onto their incompressible counterparts are of fundamental significance for turbulence modelling, such as the Morkovin scaling for velocity fields, while for pressure fluctuation fields, a corresponding scaling relation is currently absent. In this work, the underlying scaling relations of pressure fluctuations about Mach number ($M$) contained in their generation mechanisms are explored by analysing a series of direct numerical simulation data of compressible TBLs over a wide Mach number range $(0.5\leq M \leq 8.0)$. Based on the governing equation of pressure fluctuations, they are decomposed into components according to the properties of source terms. It is notable that the intensity of the compressible component, predominantly originating from the acoustic mode, obeys a monotonic distribution about the Mach number and wall distance; further, the intensity of the rest of the pressure components, which are mainly generated by the vorticity mode, demonstrates a uniform distribution consistent with its incompressible counterpart. Moreover, the coupling between the two components is negligibly weak. Based on the scaling relations, semiempirical models for the fluctuation intensity of both pressure and its components are constructed. Hence, a mapping relation is obtained that the profiles of pressure fluctuation intensities in compressible TBLs can be mapped onto their incompressible counterparts by removing the contribution from the acoustic mode, which can be provided by the model. The intrinsic scaling relation can provide some basic insight for pressure fluctuation modelling.

This study presents a comprehensive analysis on the extreme positive and negative events of wall shear stress and heat flux fluctuations in compressible turbulent boundary layers (TBLs) solved by direct numerical simulations. To examine the compressibility effects, we focus on the extreme events in two representative cases, i.e. a supersonic TBL of Mach number $M=2$ and a hypersonic TBL of $M=8$, by scrutinizing the coherent structures and their correlated dynamics based on conditional analysis. As characterized by the spatial distribution of wall shear stress and heat flux, the extreme events are indicated to be closely related to the structural organization of wall streaks, in addition to the occurrence of the alternating positive and negative structures (APNSs) in the hypersonic TBL. These two types of coherent structures are strikingly different, namely the nature of wall streaks and APNSs are shown to be related to the solenoidal and dilatational fluid motions, respectively. Quantitative analysis using a volumetric conditional average is performed to identify and extract the coherent structures that directly account for the extreme events. It is found that in the supersonic TBL, the essential ingredients of the conditional field are hairpin-like vortices, whose combinations can induce wall streaks, whereas in the hypersonic TBL, the essential ingredients become hairpin-like vortices as well as near-wall APNSs. To quantify the momentum and energy transport mechanisms underlying the extreme events, we proposed a novel decomposition method for extreme skin friction and heat flux, based on the integral identities of conditionally averaged governing equations. Taking advantage of this decomposition method, the dominant transport mechanisms of the hairpin-like vortices and APNSs are revealed. Specifically, the momentum and energy transports undertaken by the hairpin-like vortices are attributed to multiple comparable mechanisms, whereas those by the APNSs are convection dominated. In that, the dominant transport mechanisms in extreme events between the supersonic and hypersonic TBLs are indicated to be totally different.

Pressure fluctuations play an essential role in the transport of turbulent kinetic energy and vibrational loading. This study focuses on examining the effect of wall cooling on pressure fluctuations in compressible turbulent boundary layers by high-fidelity direct numerical simulations. Pressure fluctuations result from the vorticity mode and the acoustic mode that are both closely dependent on compressibility. To demonstrate the effects of wall cooling at various compressibility intensities, three free-stream Mach numbers are investigated, i.e. $M_\infty =0.5$, 2.0 and 8.0, with real gas effects being absent for $M_\infty =8.0$ due to a low enthalpy inflow. Overall, opposite effects of wall cooling on pressure fluctuations are found between the subsonic/supersonic cases and the hypersonic case. Specifically, the pressure fluctuations normalized by wall shear stress $p^\prime _{rms}/\tau _w$ are suppressed in the subsonic and supersonic cases, while enhanced in the hypersonic case near the wall. Importantly, travelling-wave-like alternating positive and negative structures (APNS), which greatly contribute to pressure fluctuations, are identified within the viscous sublayer and buffer layer in the hypersonic cases. Furthermore, generating mechanisms of pressure fluctuations are explored by extending the decomposition based on the fluctuating pressure equation to compressible turbulent boundary layers. Pressure fluctuations are decomposed into five components, in which rapid pressure, slow pressure and compressible pressure are dominant. The suppression of pressure fluctuations in the subsonic and supersonic cases is due to both rapid pressure and slow pressure being suppressed by wall cooling. In contrast, wall cooling strengthens compressible pressure for all Mach numbers, especially in the hypersonic case, resulting in increased wall pressure fluctuations. Compressible pressure plays a leading role in the hypersonic case, mainly due to the APNS. Essentially, the main effects of wall cooling can be interpreted by the suppression of the vorticity mode and the enhancement of the acoustic mode.

This paper examines the value-at-risk (VaR) implications of mean-variance hedging. We derive an equivalence between the VaR-based hedge and the mean-variance hedging. This method transfers the investor's subjective risk-aversion coefficient into the estimated VaR measure. As a result, we characterize the collapse probability bounds under which the VaR-based hedge could be insignificantly different from the minimum-variance hedge in the presence of estimation risk. The results indicate that the squared information ratio of futures returns is the primary factor determining the difference between the minimum-variance and VaR-based hedges.

Aiming at the problem that adaptive Monte Carlo localization (AMCL) algorithm is difficult to localize in large scenes and similar environments. This paper uses a semantic information-assisted approach to improve the AMCL algorithm. This method realizes the robust localization of the robot in the large scenes and similar environments. Firstly, the 2D grid map created by simultaneous localization and mapping using lidar can obtain highly accurate indoor environmental contour information. Secondly, the semantic object capture is achieved by using a depth camera combined with an instance segmentation algorithm. Then, the semantic grid map is created by mapping the semantic point cloud through the back-projection process of the pinhole camera. Finally, semantic grid maps are used as a priori information to assist in localization, which will be used to improve the initial particle swarm distribution in the global localization of the AMCL algorithm and thus will solve the robot localization problem in this environment. The experimental evidence shows that the semantic grid map solves the environmental information degradation problem caused by 2D lidar as well as improves the robot’s perception of the environment. In addition, this paper improves the localization robustness of the AMCL algorithm in large scenes and similar environments, resulting in an average localization success rate of about 90% or even higher, and further reduces the number of iterations. The global localization problem of robots in large scenes and similar environments is effectively solved.

This paper analyses rural migrant children's access to public schools in urban China, focusing on the implications of the recent introduction of points systems for apportioning school places. This approach, first piloted by Zhongshan city in Guangdong province from 2009, has steadily been extended nationwide. Here, we analyse the reasons for its spread and for divergence in its implementation in various urban districts. Notwithstanding rhetorical claims that points systems promote “fairness” or “equality” in the treatment of migrants, our analysis suggests that they maintain or even exacerbate the stratification of urban society, lending new legitimation to the hierarchical differentiation of entitlements. This is consistent with the aim of the 2014 “New national urbanization plan” to divert urban growth from megacities towards smaller cities. However, we argue that the use of points systems should also be seen in the context of an evolving bureaucratic-ideological project aimed at more rigorously monitoring and assessing China's entire population, invoking the logic of meritocracy for the purpose of control.

Dietary modification plays a vital role in the treatment of non-alcoholic liver diseases. We investigated the effects of the consumption of a different amount of dehulled adlay, which has hypolipidaemic and anti-inflammatory properties, on non-alcoholic fatty liver disease (NAFLD). We fed rats a high-fat-high-fructose liquid diet for 16 weeks to induce NAFLD. The rats were divided into three groups fed the NAFLD diet only (NN) or a diet containing 44·9 or 89·8 g/l of dehulled adlay (NA and NB groups, respectively). After 8 weeks, the NA and NB groups had lower C-reactive protein levels and improvement in insulin resistance. In addition, the NB group had lower liver weight and hepatic TAG and cholesterol concentrations than did the NN group. Compared with the NN group, the high-dose NB group had improved steatosis, lower hepatic TNF-α, IL-1β and IL-6 levels and lower adipose leptin levels. Our results suggest that a diet containing dehulled adlay can ameliorate NAFLD progression by decreasing of insulin resistance, steatosis and inflammation.

The dynamical stability of the cable-driven lower-limb rehabilitation training robot (CLLRTR) is a crucial question. Based on the established dynamics model of CLLRTR, the solution to the wrench closure of the under-constrained system is presented. Secondly, the stability index of CLLRTR is proposed by the Krasovski method. Finally, in order to analyze the stability distribution of CLLRTR in the workspace, the stability evaluation index in the workspace is calculated using the eigenvalue decomposition method. The stability distribution laws of CLLRTR are further verified by the experimental study. The results provide references for studying trajectory planning and anti-pendulum control of CLLRTR.

The present study aimed to investigate an interaction between energy intake, physical activity and UCP2 gene variation on weight gain and adiposity changes in Indonesian adults. This is a prospective cohort study conducted in 323 healthy adults living in the city of Yogyakarta, Indonesia. Energy intake, physical activity, body weight, BMI, percentage body fat and waist:hip ratio (WHR) were measured at baseline and after 2 years while UCP2 -866G/A gene variation was determined at baseline. We reported that after 2 years subjects had a significant increment in body weight, BMI, body fat and reduction in WHR (all P < 0·05). In all subjects, total energy intake was significantly correlated with changes in body weight (β = 0·128, P = 0·023) and body fat (β = 0·123, P = 0·030). Among subjects with the GG genotype, changes in energy intake were positively correlated with changes in body weight (β = 0·232, P = 0·016) and body fat (β = 0·201, P = 0·034). These correlations were insignificant among those with AA + GA genotypes (all P > 0·05). In summary, we show that UCP2 gene variation might influence the adiposity response towards changes in energy intake. Subjects with the GG genotype of UCP2 -866G/A gene were more responsive to energy intake, thus more prone to weight gain due to overeating.

Situated between the North China Craton to the east and the Tarim Craton to the west, the northern Alxa area in westernmost Inner Mongolia in China occupies a key location for interpreting the late-stage tectonic evolution of the southern Central Asian Orogenic Belt. New LA-ICP-MS zircon U–Pb dating results reveal 282.2 ± 3.9 Ma gabbros and 216.3 ± 3.2 Ma granites from the Yagan metamorphic core complex in northern Alxa, NW China. The gabbros are characterized by low contents of Si, Na, K, Ti and P and high contents of Mg, Ca, Al and Fe. These gabbros have arc geochemical signatures with relative enrichments in large ion lithophile elements and depletions in high field strength elements, as well as negative εNd(t) (−0.91 to −0.54) and positive εHf(t) (2.59 to 6.37) values. These features indicate that a depleted mantle magma source metasomatized by subduction fluids/melts and contaminated by crustal materials was involved in the processes of magma migration and emplacement. The granites show high-K calc-alkaline and metaluminous to weakly peraluminous affinities, similar to A-type granites. They have positive εNd(t) (1.55 to 1.99) and εHf(t) (5.03 to 7.64) values. These features suggest that the granites were derived from the mixing of mantle and crustal sources and formed in a postcollisional tectonic setting. Considering previous studies, we infer that the final closure of the Palaeo-Asian Ocean in the central part of the southern Central Asian Orogenic Belt occurred in late Permian to Early–Middle Triassic times.

The sample squared Sharpe ratio (SSR) is a critical statistic of the risk-return tradeoff. We show that sensitive upper-tail probabilities arise when the sample SSR is employed to test the mean-variance efficiency under different test statistics. Assuming the error's normality with a nonzero mean, we integrate the sample SSR and the arbitrage regression into a noncentral chi-square (χ2) test. We find that the distribution of the sample SSR based on the regression error is to the left of the F-distribution when assuming the returns' normality. Compared to two benchmarks that use the noncentral F-distribution and the central F-statistic, the χ2-statistic is more effective, competitive, significant, and locally robust when used to reject the upper-tailed mean-variance efficiency test using the usual parameters (sample size, portfolio size, and SSR).

Breakfast consumption is associated with a variety of nutritional and lifestyle-related health outcomes. The objective of the present study was to investigate how the consumption of breakfast affected blood glucose, insulin and NEFA profiles. A lower postprandial blood glucose, insulin and NEFA response is associated with a lower risk of development of metabolic diseases. In a randomised crossover non-blind design, thirteen pre-diabetic Chinese adult males (BMI 26·7 (sd 4·2) kg/m2) attended two sessions where they either consumed a high-glycaemic index breakfast or no breakfast consumption. Changes in glycaemic response over 27 h periods were measured using the Medtronic MiniMed iProTM2 continuous glucose monitoring system. Blood samples were collected using a peripheral venous catheter at fixed intervals for 3 h after the test meal and 3 h after standardised lunch consumption. Postprandial glucose, insulin and NEFA response was calculated as total AUC and incremental AUC using the trapezoidal rule that ignored the area under the baseline. It was found that breakfast consumption significantly decreased postprandial glucose, insulin and NEFA excursion response at lunch time (P = 0·001). Consumption of breakfast attenuated blood glucose profiles by minimising glycaemic excursions and reduced both insulinaemic and NEFA responses in pre-diabetic Asian males during the second meal. This simple dietary intervention may be a novel approach to help improve subsequent lunch glycaemic responses in Asians at high risk of developing diabetes.

Consumption of a high-fat diet increases fat accumulation and may further lead to inflammation and hepatic injuries. The aim of the study was to investigate the effects of Camellia oleifera seed extract (CSE) on non-alcoholic fatty liver disease (NAFLD). After a 16-week NAFLD-inducing period, rats were assigned to experimental groups fed an NAFLD diet with or without CSE. At the end of the study, we found that consuming CSE decreased the abdominal fat weight and hepatic fat accumulation and modulated circulating adipokine levels. We also found that CSE groups had lower hepatic cytochrome P450 2E1 and transforming growth factor (TGF)-β protein expressions. In addition, we found that CSE consumption may have affected the gut microbiota and reduced toll-like receptor (TLR)-4, myeloid differentiation primary response gene 88, toll/IL-1 receptor domain-containing adaptor-inducing interferon-β (TRIF) expression and proinflammatory cytokine concentrations in the liver. Our results suggest that CSE may alleviate the progression of NAFLD in rats with diet-induced steatosis through reducing fat accumulation and improving lipid metabolism and hepatic inflammation.

We investigated human understanding of different network visualizations in a large-scale online experiment. Three types of network visualizations were examined: node-link and two different sorting variants of matrix representations on a representative social network of either 20 or 50 nodes. Understanding of the network was quantified using task time and accuracy metrics on questions that were derived from an established task taxonomy. The sample size in our experiment was more than an order of magnitude larger (N = 600) than in previous research, leading to high statistical power and thus more precise estimation of detailed effects. Specifically, high statistical power allowed us to consider modern interaction capabilities as part of the evaluated visualizations, and to evaluate overall learning rates as well as ambient (implicit) learning. Findings indicate that participant understanding was best for the node-link visualization, with higher accuracy and faster task times than the two matrix visualizations. Analysis of participant learning indicated a large initial difference in task time between the node-link and matrix visualizations, with matrix performance steadily approaching that of the node-link visualization over the course of the experiment. This research is reproducible as the web-based module and results have been made available at: https://osf.io/qct84/.

Numerous efforts have been devoted to the derivation of equations describing the kinematics of finite-size spherical particles in arbitrary fluid flows. These approaches rely on asymptotic arguments to obtain a description of the particle motion in terms of a slow manifold. Here we present a novel approach that results in kinematic models with unprecedented accuracy compared with traditional methods. We apply a recently developed machine learning framework that relies on (i) an imperfect model, obtained through analytical arguments, and (ii) a long short-term memory recurrent neural network. The latter learns the mismatch between the analytical model and the exact velocity of the finite-size particle as a function of the fluid velocity that the particle has encountered along its trajectory. We show that training the model for one flow is sufficient to generate accurate predictions for any other arbitrary flow field. In particular, using as an exact model for trajectories of spherical particles, the Maxey–Riley equation, we first train the proposed machine learning framework using trajectories from a cellular flow. We are then able to accurately reproduce the trajectories of particles having the same inertial parameters for completely different fluid flows: the von Kármán vortex street as well as a two-dimensional turbulent fluid flow. For the second example we also demonstrate that the machine learned kinematic model successfully captures the spectrum of the particle velocity, as well as the extreme event statistics. The proposed scheme paves the way for machine learning kinematic models for bubbles and aerosols using high-fidelity DNS simulations and experiments.

Randomised controlled trials comparing low- v. high-fat diets on cardiometabolic risk factors in people with overweight or obesity have shown inconsistent results, which may be due to the mixed metabolic status of people with excess adiposity. The role of dietary fat manipulation in modifying cardiometabolic indicators in people with overweight or obese without metabolic disturbance is unclear. Thus, meta-analysis was conducted to compare low- v. high-fat diets on cardiometabolic indicators in people who are overweight or obese without metabolic disturbance in the present study. Databases were searched until October 2016. The pooled effects of outcomes with heterogeneity were calculated with a random-effects model, heterogeneities were analysed by subgroup and meta-regression. As a result, twenty studies with 2106 participants were included in the meta-analysis. Total cholesterol and LDL-cholesterol levels were lower following low-fat diets compared with high-fat diets: weighted mean difference (WMD) was −7·05 mg/dl (−0·18 mmol/l; 95 % CI −11·30, −2·80; P=0·001) and −4·41 mg/dl (−0·11 mmol/l; 95 % CI −7·81, −1·00; P=0·011), respectively. Conversely, significant higher level of TAG (WMD: 11·68 mg/dl (0·13 mmol/l), 95 % CI 5·90, 17·45; P<0·001) and lower level of HDL-cholesterol (WMD: −2·57 mg/dl (−0·07 mmol/l); 95 % CI −3·85, −1·28; P<0·001) were found following low-fat diets compared with high-fat diets. In conclusion, dietary fat manipulation has a significant influence on blood lipid levels in people with overweight or obesity without metabolic disturbances.