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In recent years, myopia among children and adolescents has become widespread, younger, and more severe in China. As the predecessor of the onset of myopia, hyperopia reserve has received increasing attention. Premature depletion of the hyperopia reserve predicts myopia's rapid and premature onset. Depleting the hyperopia reserve in children is influenced by many factors, such as pregnancy complications, pregnancy nutrition, premature birth, breastfeeding, growth velocity, outdoor activities, prolonged work and sleeping. This paper reviews the physiological changes in children's hyperopia reserve and the factors influencing children's hyperopia reserve, aiming to provide evidence for the prevention and control of myopia in children and adolescents at an early age.近年来，我国儿童青少年的近视问题呈现普遍化、低龄化、重度化趋势，近视发生前的远视储备受到越来越多的关注。远视储备过早消耗是近视快速和过早发生的预测因素，儿童远视储备消耗受很多因素影响，如妊娠并发症、孕期营养、早产、母乳喂养、生长速度、户外活动、视近作业和睡眠等。本文通过对儿童远视储备的生理变化及其影响因素进行综述，旨在为儿童青少年近视防控抓早抓小提供科学依据。.

An automatic particle imaging velocimetry (Auto-PIV) measuring technique was developed based on the external triggering and automatic control technology. Measurements of the DrivAer model wake were performed using Auto-PIV in the spanwise and vertical direction. Three-dimensional time-averaged velocity distribution was reconstructed and the spatial distribution of the large coherent structures was described. The results indicate that regions with high velocity fluctuations mainly locate at the shear layer of the upper and lower edge of the recirculation bubble. Further proper orthogonal decomposition results show that the velocity fluctuations account for a very little proportion of kinetic energy compared with the time-averaged velocity, supporting that the DrivAer model has steady aerodynamic characteristics. The smooth outlines of the DrivAer notchback model can delay the flow separation on the top and the C-pillar of the model, which inhibits the formation of the back recirculation bubble at the rear window and reduces the size of the recirculation bubble behind the baggage compartment. These promote the pressure recovery at the rear of the DrivAer notchback model, and thus reduces the pressure drag. At the rear of the model, the airflow on both sides converges towards the center due to the pressure difference, producing the streamwise vorticity by shearing the baggage compartment, then separates at the rear of the baggage compartment and generates a pair of secondary vortices. Overall, the aerodynamic behavior of the DrivAer model is robust.

The wall-normal velocity derivative of ∂u/∂y is measured in a turbulent boundary layer, down to 2 wall units from the wall, using two parallel hot-wires. The momentum-thickness- and friction-velocity-based Reynolds numbers are 1450 and 584, respectively. The experimental results indicate that ∂u/∂y may be captured with an adequate accuracy given a separation (∆y) of 2 ~ 5 Kolmogorov length scales η between the two parallel hot-wires, slightly different from that (2η ~ 4η) required for a turbulent channel flow. The surrogate $$ \overline{{\left(\Delta u/\Delta y\right)}^2} $$ for $$ \overline{{\left(\partial u/\partial y\right)}^2} $$ displays a significant departure in the buffer layer from that in the turbulent channel flow, due to a difference in the large-scale coherent structures between the two flows. The skewness and kurtosis of ∂u/∂y differ markedly from their counterparts in a turbulent channel flow, which reflects a difference in the small-scale turbulent structures of the outer region between the two flows.

In this paper, the wake modes behind a circular cylinder under streamwisely forcing oscillating motion are studied at Reynolds number Re = 360–460 which are observed by laser-induced fluorescence flow visualization technique. The forcing frequency $$f_{\mathrm{e}}$$ ranges from 0 to 6.85 $$f_{\mathrm{s}}$$ , where $$f_{\mathrm{s}}$$ is the vortex shedding frequency behind a stationary cylinder, and the forcing amplitude $$A/d = 0.2, 0.5, 1.0$$ , where d is the cylinder diameter. Both time-invariant and linearly ramping $$f_{\mathrm{e}}$$ are investigated. Following our previous modal notation, the following conclusions can be drawn: firstly, three rarely reported modes in numerical studies, C-I, C-II and S-III, are now confirmed in experiments (though with differentiable appearance in their far wake behaviour) at higher A and/or $$f_{\mathrm{e}}$$ ranges and the envelope lines of S modes and C modes, yielded from a vortex circulation model, are shown to be dependent on the peak relative velocity of the free stream to the cylinder surface. So is the occurrence of the S-II mode. Secondly, near the demarcation of A modes and S-I mode, wake mode undergoes constant transition in a stochastic manner at fixed Re, A and $$f_{\mathrm{e}}$$ . Thirdly, a typical hysteretic effect can be observed when the oscillation frequency of the cylinder ramps up and down in a linear way, and the extent of delay is dependent on the ramping rate k. Finally, mode switching during frequency ramping obeys a unidirectional order. During $$k0$$ (ramp-up), a clear and abrupt switch can be observed in the wake when A-IV or A-III switch to S-I (Type-II) modes, which are jump switches.

The intermittent distribution of localized turbulent structures is a key feature of the subcritical transitions in channel flows, which are studied in this paper with a wind channel and theoretical modeling. Entrance disturbances are introduced by small beads, and localized turbulent patches can be triggered at low Reynolds numbers (Re). High turbulence intensity represents strong ability of perturbation spread, and a maximum turbulence intensity is found for every test case as Re &ge, 950, where the turbulence fraction increases abruptly with Re. Skewness can reflect the velocity defects of localized turbulent patches and is revealed to become negative when Re is as low as about 660. It is shown that the third-order moments of the midplane streamwise velocities have minima, while the corresponding forth-order moments have maxima during the transition. These kinematic extremes and different variation scenarios of the friction coefficient during the transition are explained with an intermittent structure model, where the robust localized turbulent structure is simplified as a turbulence unit, a structure whose statistical properties are only weak functions of the Reynolds number.

This paper investigates the potential use of dielectric-barrier-discharge (DBD) plasma actuators to control the crossflow instability of the boundary layer on a 45° swept NLF-0415 airfoil at − 4 ∘ angle of attack.The disturbance evolution is resolved using nonlinear parabolized stability equations (NPSEs). Actuators are mounted near the leading edge and generate an electric wind perpendicular to the crossflow vortex axes. The spanwise distance between neighboring actuators is first set to be the fundamental wavelength of the unstable mode. This harmonic actuation reduces the disturbance energy only when the induced body force and the disturbance velocity have reverse sign. At certain different locations, the actuators can actually increase the disturbance energy. The robustness in laminar flow control is improved when two actuators per fundamental wavelength are used. This subharmonic actuation leads to reduction in the energy of the primary unstable mode independent of the actuator locations. Finally, the simulation without baseflow forcing reveals that harmonic modes play important roles in this subharmonic control.

The near wake of the polygonal cylinder with the side number N = 3 ~ ∞ is systematically studied based on particle image velocimetry (PIV) and load-cell measurements. Each cylinder is examined for two orientations, with either one leading side or leading corner. The Reynolds number Re = (1.0 ∼ 6.0) × 104 , defined by the longitudinally projected cylinder width. The dependence of the wake characteristic parameters on the cylinder orientation and N is discussed, and wake scaling analysis is conducted based on these parameters. It is found that the velocity deficit and half width of the wake scale well with the reverse flow zone length and recirculation bubble width, whilst the Strouhal number, drag and fluctuating lift coefficients scale well with the vortex formation length and wake width. The unveiled scaling relationships cast insight into the intrinsic physical connections between the aerodynamic forces and vortex formation and between the polygonal cylinder wakes of N = 3 ~ ∞, suggesting that the understanding of the time-mean wake behind individual polygonal cylinder can be unified to that of the circular cylinder wake.

The wake of polygonal cylinders with side number $N=2\sim \infty$ is systematically studied based on fluid force, hot-wire, particle image velocimetry and flow visualisation measurements. Each cylinder is examined for two orientations, with a flat surface or a corner leading and facing normally to the free stream. The Reynolds number $Re$ is $1.0\times 10^{4}\sim 1.0\times 10^{5}$, based on the longitudinally projected cylinder width. The time-averaged drag coefficient $C_{D}$ and fluctuating lift coefficient on these cylinders are documented, along with the characteristic properties including the Strouhal number $St$, flow separation point and angle $\unicode[STIX]{x1D703}_{s}$, wake width and critical Reynolds number $Re_{c}$ at which the transition from laminar to turbulent flow occurs. It is found that once $N$ exceeds 12, $Re_{c}$ depends on the difference between the inner diameter (tangent to the faces) and the outer diameter (connecting corners) of a polygon, the relationship being approximately given by the dependence of $Re_{c}$ on the height of the roughness elements for a circular cylinder. It is further found that $C_{D}$ versus $\unicode[STIX]{x1D709}$ or $St$ versus $\unicode[STIX]{x1D709}$ for all the tested cases collapse onto a single curve, where the angle $\unicode[STIX]{x1D709}$ is the corrected $\unicode[STIX]{x1D703}_{s}$ associated with the laterally widest point of the polygon and the separation point. Finally, the empirical correlation between $C_{D}$ and $St$ is discussed.

In this work, we focus on the vortex evolutions in the wake behind three non-axisymmetric rigid cylinders under high-speed, low-damping galloping in a wind tunnel. Laser displace sensor is used to measure the displacement amplitude and two branches of amplitude curves are observed—rising and falling range of galloping range. Particle Image Velocimetry is then used to investigate coherent vortex structures in the wake. It has been found that a D-section cylinder has a galloping response at the lowest free stream velocity, which also has the smallest formation length and recirculation bubble length when at static condition. The wake widths show a similar growth rate, which is independent of the galloping amplitudes.

In this study, we investigated fertilization cytology in Phascolosoma esculenta. The sperm binds to the oocyte envelope in a random position at the point of initial contact. An acrosomal reaction then occurs and the acrosomal filament penetrates the oocyte envelope. The apex of the acrosomal filament contacts with the plasma membrane of the oocyte at the point where the fertilization cone is formed. The fertilization cone then retracts, towing the acrosomal filament back and drawing the sperm into the oocyte. Subsequently, the pores on the oocyte envelope are blocked and filled with fibrin and colloid. After the oocyte is activated by sperm, the first and second meiosis processes start sequentially, followed by the release of the first and second polar bodies. After the second polar body is extruded, the haploid female nucleus rapidly reorganizes to form a female pronucleus. In comparison, the sperm nucleus begins to decondense and dilate after the first polar body is released. The male pronucleus...

Wake structures and vortex induced vibration (VIV) of a spring-supported wide-D-section cylinder were experimentally investigated using an X-wire, a novel phase-locked particle image velocimetry (PIV), and an acceleration sensor at a low speed wind tunnel. Compared with the fixed case, the 2P (two pair) vortex mode as defined by Govardhan and Williamson (2000) rather than S (single vortex) mode exists in the wake. The velocity deficit behind the cylinder is much larger than that of fixed case. The mean drag coefficient increases from 1.42 for the fixed case to 1.64 for the vibrating case. The Reynolds stress presents even distribution and small with increased distance of X / D = − 2 to X / D = − 10 . The power spectra density based on accelerator and hot wire data presents a highlight identical. It shows that after a strong interaction the cylinder vibration and the vortex shedding come to a stable state. The vortex shedding is totally locked on and controlled by the cylinder vibration.

The near wake of the polygonal cylinder with the side number N = 3~∞ is systematically studied using particle image velocimetry (PIV) at Re = 1.6 × 104. The proper orthogonal decomposition (POD) analysis is carried out to extract the large-scale coherent vortex structures and their evolution. It has been found that the vortex circulation grows to the maximum at the vortex formation length by entraining the vorticity from the separated shear layer and then undergoes a two-stage decay. The maximum circulation scales with the wake width, defined as the vertical distance between the two peaks of streamwise velocity fluctuation at vortex formation length. The vortex center trajectory indicates that the vortices move towards the centerline first and then away, with the vortex size monotonically increasing over the examined streamwise range. The vortex size at the maximum circulation also scales with the wake width. The vortex convection velocity increases gradually in the streamwise direction, and the ratio of the lateral and streamwise components of the vortex convection velocity, when scaled by wake width and vortex formation length respectively, approaches asymptotically 0.18 in the downstream, irrespective of the cylinder orientation or N.

Summary Male and female Amur sturgeon (Acipenser schrenckii) at sexual maturity (age 7 years) were identified under controlled breeding conditions, and the plasma biochemical parameters were determined at different developmental stages of the gonads. The results showed that there was significant difference of the plasma calcium (Ca2+) and lactate dehydrogenase (LDH) content between the sexually mature males and females. The LDH content in males was highest, while the Ca2+ concentration was lowest. During different gonad developmental stages (II,III,IV-A and IV-B) of the, the content in the ovaries of plasma total protein (TP), globulin (GLB), total bilirubin (TBIL), triglycerides (TRIG), Ca2+ and inorganic phosphorus (P−) initially showed an upward trend, and decreased thereafter. The values of albumin (ALB), albumin/globulin (A/G) and total cholesterol (CHOL) increased gradually from stage of II to IV-B, and showed significantly higher levels at the stage of IV-A to IV-B (P

Active control of a turbulent boundary layer has been experimentally investigated with a view to reducing the skin-friction drag and gaining some insight into the mechanism that leads to drag reduction. A spanwise-aligned array of piezo-ceramic actuators was employed to generate a transverse travelling wave along the wall surface, with a specified phase shift between adjacent actuators. Local skin-friction drag exhibits a strong dependence on control parameters, including the wavelength, amplitude and frequency of the oscillation. A maximum drag reduction of 50 % has been achieved at 17 wall units downstream of the actuators. The near-wall flow structure under control, measured using smoke–wire flow visualization, hot-wire and particle image velocimetry techniques, is compared with that without control. The data have been carefully analysed using techniques such as streak detection, power spectra and conditional averaging based on the variable-interval time-average detection. All the results point to a pronounced change in the organization of the perturbed boundary layer. It is proposed that the actuation-induced wave generates a layer of highly regularized streamwise vortices, which acts as a barrier between the large-scale coherent structures and the wall, thus interfering with the turbulence production cycle and contributing partially to the drag reduction. Associated with the generation of regularized vortices is a significant increase, in the near-wall region, of the mean energy dissipation rate, as inferred from a substantial decrease in the Taylor microscale. This increase also contributes to the drag reduction. The scaling of the drag reduction is also examined empirically, providing valuable insight into the active control of drag reduction.

The tumbling motion of freely falling plates with aspect ratio ranging from 2 to 10 is studied using both experimental measurement and simplified lifting line theory. The trajectories of plates are recorded by high-speed video camera and analysed to obtain instantaneous and average kinematic and aerodynamic parameters, including the descent angle, rotating speed, descent velocities, lift and drag coefficients, and their fluctuation spectrums. A double period rotation with period doubling is observed here for some range of aspect ratio and the double frequency is determined from a Fourier analysis. By adding a correction from the inducing effect of trailing vortices and wing-tip vortices to the corresponding two-dimensional force and torque expressions, a simplified kinematic model is obtained which successfully predicts the qualitative influence of aspect ratio on the averaged kinematics, that the descent angle and the vertical descent velocity component are decreasing functions of the aspect ratio, while the rotation speed and horizontal velocity component are increasing functions of the aspect ratio. For decreasing aspect ratio, the induced drag due to the trailing and tip vortices reduces the lift to drag ratio and thus increases the descent angle, while the dissipative torque due to translational induced drag decreases the rotation speed.

Myopia has become a major health problem on global scale due to its increasing high prevalence in the past few decades and gradual younger onset age. Accumulated epidemiological surveys have shown that decreased time of exposure to sunlight would be an inducement for the development of myopia. Increasing time spent outdoors and exposure to sunlight might be the most cost-effective and effective measure for children to prevent myopia. This paper summarizes the progress in research of the association between sunlight exposure and myopia in children and its mechanisms to provide new clues for the research on myopia prevention and control.

In this paper, we present some experimental results about the physical effects of a cylinder’s streamwise oscillation motion on a downstream one in a tandem arrangement. The upstream cylinder undergoes a controlled simple harmonic oscillation at amplitudes A/d = 0.2–0.8, where d is the cylinder diameter, and the frequency ratio of $$f_\mathrm{e}/f_\mathrm{s}$$ = 0–3.0, where $$f_\mathrm{e}$$ is the cylinder oscillation frequency and $$f_\mathrm{s}$$ is the natural frequency of vortex shedding from a single stationary cylinder. Under these conditions, the vortex shedding is locked to the controlled oscillation motion. Flow visualisation using the planar laser-induced fluorescence and qualitative measurements using hot-wire anemometry reveal three distinct flow regimes behind the downstream cylinder. For $$f_\mathrm{e}/f_\mathrm{s} > (f_\mathrm{e}/f_\mathrm{s})_\mathrm{c}$$ , where $$(f_\mathrm{e}/f_\mathrm{s})_\mathrm{c}$$ is a critical frequency ratio which depends on A/d and Reynolds number Re, a so-called SA-mode occurs. The upstream oscillating cylinder generates binary vortices symmetrically arranged about the centreline, each containing a pair of counter-rotating vortices, and the downstream cylinder sheds vortices alternately at $$0.5f_\mathrm{e}$$ . For 0.7–1.0 $$< f_\mathrm{e}/f_\mathrm{s} < (f_\mathrm{e}/f_\mathrm{s})_c$$ a complex vortex street that consists of two outer rows of vortices generated by the oscillating cylinder and two inner rows of vortices shed from the downstream stationary cylinder, which is referred to as AA-mode. For 0.3–0.6 $$< f_\mathrm{e}/f_\mathrm{s}

Recent studies have revealed that trichloroethylene (TCE) can induce occupational medicamentosa-like dermatitis (OMLD) with multi-system injuries, including liver, kidney and skin injuries, which can subsequently cause multiple organ failure later. But the mechanism of immune dysfunction leading to organ injury was rarely clarified. The present study was initiated to analyze the influence of trichloroethylene on renal injury and study the relevant mechanism in guinea pigs. Guinea pig maximization test (GPMT) was carried out. Inflammation on the guinea pigs' skin was scored. Kidney function, urine protein and ultra-structural change of kidney were determined by biochemical detection and electron microscope. Deposition of complement 3 and membrane attack complex (MAC, C5b-9) were determined by immunohistochemistry. Erythema and edema of skin impairment were observed in TCE sensitized groups, and sensitization rate was 63.16%. Through electron microscope, tubular epithelial cell mitochondrial swelling, vacuolar degeneration and atrophy of microvillus were observed in TCE sensitized groups. The parameters of urease and urinary protein elevated markedly, and a high degree of C3 and MAC deposition was found in the renal tubular epithelial cells in TCE sensitized groups. By demonstrating that TCE and its metabolites can cause the deposition of C3 and MAC in renal epithelial cells, we found that activated complement system may be the mechanism of the acceleration and the development of TCE-induced kidney disease.

In this work, the wing tip vortex structure behind a NACA 0015 airfoil with and without small flaps was studied using a Partical Image Velocimetry (PIV) system. The experiment was carried out in a low speed wind tunnel with a test section of 0.5 m × 0.5 m. The Reynolds number (Re), defined by the chord length of the wing (C), was 8.1×104. The angle of attack was fixed at 10°. The PIV measurements were made from 0 to 2C, measured from the trailing edge of the model. The dihedral angle of three flaps was −15°, 0° and 15°, respectively. Compared with the clean airfoil, the one with three flaps significantly changed the wing tip vortex structure, the vorticity and the core of the wing tip vortex. The occurrence of three flaps decreased the gradient of pressure on the two sides of the wing tip, which depressed wing tip vortex formation to some extent. Vortices shed from three flaps influence the evolution of the wingtip vortex generated by the base airfoil. The interaction of those vortices resulted in a weakening of the wing tip vortex.

Reversible addition-fragmentation chain transfer (RAFT) polymerization was adopted to synthesize starch-based conjugates that possessed controllable architecture and properties. Starch-based xanthate agent was prepared and applied as chain transfer agent to conduct the living/controlled polymerization (LCP) of vinyl acetate, which generated tailor-made conjugates of starch and well-defined poly(vinyl acetate) (SVAc). The relevant derivatives, conjugates of starch and chain length-controlled poly(vinyl alcohol) (SVA), were obtained subsequently. Various characterizations such as Fourier trans- form infrared spectra (FTIR), ultraviolet-visible spectroscopy (UV), proton nuclear magnetic resonance ( 1 H NMR), gel per- meation chromatography (GPC), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA) were performed to examine the structure of intermediates and the starch-based conjugates. Static contact angle measurements revealed that the hydrophilic character of starch-based conjugates was tunable. Well-defined SVAc was amphiphilic and it was able to self-assemble into size controllable micelles, which was verified by contact angles, transmission electron microscopy (TEM) and dynamic light scattering (DLS) tests. SVA exhibited much higher capability to form physically cross-linked hydrogel than starch did. Both the characteristic of SVAc and SVA were chain length-dependent.

With the Web 2.0 paradigm, a huge volume of Web content is generated by users at online forums, wikis, blogs, and social networks, among others. These user-contributed contents include numerous user opinions regarding products, services, or political issues. Among these user opinions, certain comparison opinions exist, reflecting customer preferences. Mining comparison opinions is useful as these types of viewpoints can bring more business values than other types of opinion data. Manufacturers can better understand relative product strengths or weaknesses, and accordingly develop better products to meet consumer requirements. Meanwhile, consumers can make purchasing decisions that are more informed by comparing the various features of similar products. In this paper, a novel Support Vector Machine-based method is proposed to automatically identify comparison opinions, extract comparison relations, and display results with the comparison relation maps by mining the volume of consumer opinions posted on the Web. The proposed method is empirically evaluated based on consumer opinions crawled from the Web. The initial experimental results show that the performance of the proposed method is promising and this research opens the door to utilizing these comparison opinions for business intelligence.

Starch is a natural polymer which possesses many unique properties and some shortcoming simultaneously. Some synthetic polymers are biodegradable and can be tailor-made easily. Therefore, by combining the individual advan- tages of starch and synthetic polymers, starch-based completely biodegradable polymers (SCBP) are potential for applica- tions in biomedical and environmental fields. Therefore it received great attention and was extensively investigated. In this paper, the structure and characteristics of starch and some synthetic degradable polymers are briefly introduced. Then, the recent progress about the preparation of SCBP via physical blending and chemical modification is reviewed and discussed. At last, some examples have been presented to elucidate that SCBP are promising materials for various applications and their development is a good solution for reducing the consumption of petroleum resources and environmental problem.