Corrigendum: A preliminary exploration of the regression equation for performance in amateur half-marathon runners: a perspective based on respiratory muscle function.

[This corrects the article DOI: 10.3389/fphys.2024.1340513.].

A preliminary exploration of the regression equation for performance in amateur half-marathon runners: a perspective based on respiratory muscle function.

This document presents a study on the relationship between physical characteristics, respiratory muscle capacity, and performance in amateur half-marathon runners. The aim of this study was to establish a preliminary predictive model to provide insights into training and health management for runners. Participants were recruited from the 2023 Beijing Olympic Forest Park Half-Marathon, comprising 233 individuals. Personal information including age, gender, height, weight, and other relevant factors were collected, and standardized testing methods were used to measure various parameters. Correlation analysis revealed significant associations between gender, height, weight, maximum expiratory pressure, maximal inspiratory pressure, and half-marathon performance. Several regression equations were developed to estimate the performance of amateur marathon runners, with a focus on gender, weight, maximum expiratory pressure, and height as predictive factors. The study found that respiratory muscle training can delay muscle fatigue and improve athletic performance. Evaluating the level of respiratory muscle capacity in marathon athletes is crucial for defining the potential speed limitations and achieving optimal performance. The information from this study can assist amateur runners in optimizing their training methods and maintaining their physical wellbeing.

Advances in Semiconductor Lasers Based on Parity-Time Symmetry.

Semiconductor lasers, characterized by their high efficiency, small size, low weight, rich wavelength options, and direct electrical drive, have found widespread application in many fields, including military defense, medical aesthetics, industrial processing, and aerospace. The mode characteristics of lasers directly affect their output performance, including output power, beam quality, and spectral linewidth. Therefore, semiconductor lasers with high output power and beam quality are at the forefront of international research in semiconductor laser science. The novel parity-time (PT) symmetry mode-control method provides the ability to selectively modulate longitudinal modes to improve the spectral characteristics of lasers. Recently, it has gathered much attention for transverse modulation, enabling the output of fundamental transverse modes and improving the beam quality of lasers. This study begins with the basic principles of PT symmetry and provides a detailed introduction to the technical solutions and recent developments in single-mode semiconductor lasers based on PT symmetry. We categorize the different modulation methods, analyze their structures, and highlight their performance characteristics. Finally, this paper summarizes the research progress in PT-symmetric lasers and provides prospects for future development.

The Bernoulli effect in horizontal granular flows.

The Bernoulli effect that commonly occurs in continuous fluids is simultaneously increasing a fluid's velocity and decreasing static pressure or the fluid's gravitational potential energy. Although, the Bernoulli effect has already been extensively explored, there is a lack of research on the relationship between flow velocity and pressure in a discrete medium. In the present study, this relationship in horizontal granular flows excited by vertical vibration is experimentally studied. It was found that the random motion and horizontal directed motion of the granules restrict each other so that the total pressure remains almost constant with respect to time and height. In fact, it implies that the Bernoulli effect occurs in the granular flows. It was also found that the pressure constant of the Bernoulli effect depends on the vibrating intensity and frequency, which reflects the energy transfer in the granular flows. Our results show a dynamic property of the granular flows, which is different from continuous fluids, even though it is similar to some extent.

Resonant phenomena and mechanism in vibrated granular systems.

We were motivated to perform this research by the investigation of Brownian motors in excited granular materials converting the chaotic motion of granules into the oriented motion of motors. We conducted experimental studies to explore the horizontal motion of granules in vertically vibrated annular granular systems, including mixed and pure granular systems with an asymmetrical periodic structure on the bottom. The variations of the horizontal granular flow caused by the height, vibrating parameters, and mixing ratio were described in detail. Our results revealed considerable changes in the horizontal flow of different granular systems. Most importantly, resonance was induced in the horizontal granular flow by the vertical vibration; that is, the horizontal flow reached its maximum at specific vibrating parameters. A collisional model of rigid objects was constructed to probe the flowing resonances in these granular systems and provided a qualitative agreement with the experimental results obtained. We conclude that when a flowing resonance occurs, the granular system oscillates horizontally with a natural frequency under periodic external excitation. The frequency matching between the external excitation and the horizontal oscillation is responsible for the flowing resonance. Our results could improve the current understanding of the dynamic properties of granular systems under external excitation.

Realization of an efficient electron source by ultraviolet-light-assisted field emission from a one-dimensional ZnO nanorods/n-GaN heterostructure photoconductive detector.

Field emission electron beam (EB) pumped AlGaN-based semiconductors are considered to be a potentially promising way to overcome the technical bottlenecks that restrict the development of AlGaN-based UV luminescence devices and realize efficient UV light sources. However, the required field emission electron sources based on nanomaterials are still inefficient due to their low field emission current density. Herein, a type of UV-light-assisted self-positive-feedback enhanced field emission electron source is proposed to develop a high-efficiency electron source which is promising for application in EB pumped AlGaN-based UV light sources that can also be generalized to deep UV (DUV) luminescence devices. The UV-light-assisted field emission source is composed of an n-GaN metal-semiconductor-metal (MSM) structure photodetector assembled with 1D ZnO nanorods by a self-assembled hydrothermal growth method, which simultaneously possesses attributes of the photoelectric effect and electron emission. The optical, photoelectric, and field emission properties are investigated in detail. The results show that the 1D ZnO nanorods/n-GaN heterostructure photodetector presents an obvious photoconductive effect. It has a peak spectral responsivity of 0.793 A W-1 at a bias voltage of 1.3 V, corresponding to an EQE higher than 267.8%, with an internal photoconductive gain reaching up to 2.51 × 103. As to the field emission properties, its turn-on electric field can be greatly reduced from 3.6 V µm-1 in the dark to 1.36 V µm-1 under UV illumination, and the field emission current density increases from lower than 3 mA cm-2 to as high as 8 mA cm-2 at an electric field of 4.5 V µm-1. The mechanism involved can be attributed to an increase of electron concentration in both the conduction bands and an increase of conduction band bending under UV illumination that reduces the effective potential barrier height of the ZnO nanorods. Through this research, an efficient field emission electron source with a self-enhancing effect is developed by combining the photoelectric effect with the electron emission process.

The relationship between the dislocations and microstructure in In0.82Ga0.18As/InP heterostructures.

In this work, we propose a formation mechanism to explain the relationship between the surface morphology (and microstructure) and dislocations in the In0.82Ga0.18As/InP heterostructure. The In0.82Ga0.18As epitaxial layers were grown on the InP (100) substrate at various temperatures (430 °C, 410 °C and 390 °C) using low pressure metalorganic chemical vapor deposition (LP-MOCVD). Obvious protrusions and depressions were obseved on the surface of the In0.82Ga0.18As/InP heterostructure because of the movement of dislocations from the core to the surface. The surface morphologies of the In0.82Ga0.18As/InP (100) system became uneven with increasing temperature, which was associated with the formation of dislocations. Such research investigating the dislocation of large lattice mismatch heterostructures may play an important role in the future-design of semiconductor films.

Horizontal flow and surface patterns in a vertically vibrated annular granular layer.

A set of experiments was carried out on the motion of granular materials in a vertically vibrated annular system with a sawtooth-shaped base. We observed the coexistence of granular flow and surface patterns such as periodic subharmonic waves and kink pairs. Different patterns can transit each other as control parameters vary. The flow varies with space and time, and oppositely directed flows can occur at different levels and different moments. The magnitude and direction of the flow depend on the parameters defining the system in a complex manner. The motion of the patterns relates to the granular flow in a different way from that in which the wave in an ordinary fluid relates to the moving fluid. A preliminary explanation is given to our experimental findings.

Enhanced spectral response of an AlGaN-based solar-blind ultraviolet photodetector with Al nanoparticles.

An enhanced spectral response was realized in an AlGaN-based solar-blind ultraviolet (SB-UV) detector using aluminum (Al) nanoparticles (NPs) of 20-60 nm. The peak responsivity of the detector (about 288 nm) with 60 nm Al NPs is more than two times greater than that of a detector without Al NPs under a 5-V bias, reaching 0.288 A/W. To confirm the enhancement mechanism of the Al NPs, extinction spectra were simulated using time-domain and frequency-domain finite-element methods. The calculation results show that the dipole surface plasmon resonance wavelength of the Al NPs is localized near the peak responsivity position of AlGaN-based SB-UV detectors. Thus, the improvement in the detectors can be ascribed to the localized surface plasmon resonance effect of the Al NPs. The localized electric field enhancement and related scattering effect result in the generation of more electron-hole pairs and thus a higher responsivity. In addition, the dark current of AlGaN-based SB-UV detectors does not increase after the deposition of Al nanoparticles. The results presented here is promising for applications of AlGaN-based SB-UV detectors.

Optimized performances of tetrapod-like ZnO nanostructures for a triode structure field emission planar light source.

Tetrapod-like ZnO (T-ZnO) nanostructures were synthesized by a simple vapor phase oxidation method without any catalysts or additives. We optimized the performances of T-ZnO nanostructures by adjusting the partial pressure of Zn vapour in the total pressure of the quartz chamber and obtained T-ZnO nanostructure materials of high purity, uniform morphology and size and high aspect ratio with a low turn-on electric field of 2.75 V µm(-1), a large field enhancement factor of 3410 and good field emission stability for more than 70 hour continuous emission. Besides, based on the optimized T-ZnO, we developed metal grid mask-assisted water-based electrostatic spraying technology, and fabricated a large-scale, pollution-free, hole-shaped array T-ZnO nanostructure cathode used in a triode structure field emission planar light source. The controllable performances of the triode device were intensively investigated and the results showed that the triode device uniformly illuminated with a luminous intensity as high as 8000 cd m(-2) under the conditions of 200 V grid voltage and 3300 V anode voltage. The research in this paper will benefit the development of a high performance planar light source based on T-ZnO nanostructures.

CW 50W/M2 = 10.9 diode laser source by spectral beam combining based on a transmission grating.

An external cavity structure based on the -1st transmission grating is introduced to spectral beam combining a 970 nm diode laser bar. A CW output power of 50.8 W, an electro-optical conversion efficiency of 45%, a spectral beam combining efficiency of 90.2% and a holistic M(2) value of 10.9 are achieved. This shows a way for a diode laser source with several KW power and diffraction-limited beam quality at the same time.

Short-wavelength light beam in situ monitoring growth of InGaN/GaN green LEDs by MOCVD.

In this paper, five-period InGaN/GaN multiple quantum well green light-emitting diodes (LEDs) were grown by metal organic chemical vapor deposition with 405-nm light beam in situ monitoring system. Based on the signal of 405-nm in situ monitoring system, the related information of growth rate, indium composition and interfacial quality of each InGaN/GaN QW were obtained, and thus, the growth conditions and structural parameters were optimized to grow high-quality InGaN/GaN green LED structure. Finally, a green LED with a wavelength of 509 nm was fabricated under the optimal parameters, which was also proved by ex situ characterization such as high-resolution X-ray diffraction, photoluminescence, and electroluminescence. The results demonstrated that short-wavelength in situ monitoring system was a quick and non-destroyed tool to provide the growth information on InGaN/GaN, which would accelerate the research and development of GaN-based green LEDs.

Stages in the catalyst-free InP nanowire growth on silicon (100) by metal organic chemical vapor deposition.

Catalyst-free InP nanowires were grown on Si (100) substrates by low-pressure metal organic chemical vapor deposition. The different stages of nanowire growth were investigated. The scanning electron microscopy images showed that the density of the nanowires increased as the growth continued. Catalyzing indium droplets could still be fabricated in the nanowire growing process. X-ray diffraction showed that the nanowires grown at different stages were single crystalline with <111 > growth direction. The photoluminescence studies carried out at room temperature on InP nanowires reveal that the blueshift of photoluminescence decreased as the growing time accumulates, which is related to the increase in the diameter, rather than the length. Raman spectra for nanowires at different growing stages show that the quality of the nanowire changes. The growth of InP nanowires at different growing stages is demonstrated as a dynamic process.

Improved field emission performance of carbon nanotube by introducing copper metallic particles.

To improve the field emission performance of carbon nanotubes (CNTs), a simple and low-cost method was adopted in this article. We introduced copper particles for decorating the CNTs so as to form copper particle-CNT composites. The composites were fabricated by electrophoretic deposition technique which produced copper metallic particles localized on the outer wall of CNTs and deposited them onto indium tin oxide (ITO) electrode. The results showed that the conductivity increased from 10-5 to 4 × 10-5 S while the turn-on field was reduced from 3.4 to 2.2 V/µm. Moreover, the field emission current tended to be undiminished after continuous emission for 24 h. The reasons were summarized that introducing copper metallic particles to decorate CNTs could increase the surface roughness of the CNTs which was beneficial to field emission, restrain field emission current from saturating when the applied electric field was above the critical field. In addition, it could also improve the electrical contact by increasing the contact area between CNT and ITO electrode that was beneficial to the electron transport and avoided instable electron emission caused by thermal injury of CNTs.

Aloetic-shaped SiC nanowires: synthesis and field electron emission properties.

Novel ordered aloetic-shaped SiC nanowires were synthesized on a Si (100) substrate by reacting methane with silicon dioxide using iron as a catalyst. Their structure and chemical composition were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The wires have a tapered aloetic structure with a top diameter about 50-80 nm and a length about 10 microm. The field emission properties of the aloetic nanowires were investigated. A stable emission with current density of 0.525 mA/cm2 at an applied electric field of 2.2 V/microm and a low turn-on electric fields of 1.4 V/microm were observed. The excellent field emission properties indicate that the aloetic-shaped SiC nanowires may have potential applications in flat panel displays and electron field-emitting devices.

Horizontal segregation in a vertically vibrated binary granular system.

We present numerical simulations and experiments on the horizontal transport and segregation of binary granular mixtures with different sizes and/or different densities in a vertically vibrated container with a sawtooth-shaped base. The larger particles migrate to the positive or negative end of the container, depending on the ratios of the diameters and the densities of two kinds of particles, the vibrating frequencies, and the accelerations. In particular, horizontal segregation occurred even if all the particles have the same size but different densities.

The stability of the plane free surface of water in a vertical vibrated vessel with corrugated bottom.

In this paper, an experiment was conducted to study the vibration of the shallow water in a vessel with corrugated bottom. When the bottom of the vessel is cosinoidal, the conditions of excitation of the surface waves are modified especially vastly, which has been elucidated in detail by Osipov and Garcia [V.V. Osipov, N. Garcia, Phys. Lett. A 283 (2001) 209-215]. The experiments serve to illustrate the effects under discussion and show the vivid phenomenon of localization near the band gaps. Finally we compare the results of the experiment with the theory and discover two special phenomena, which have not been revealed in theoretical computation.

Formation and transport of a sand heap in an inclined and vertically vibrated container.

We investigate experimentally the formation and the transportation of a heap formed by granular materials in an inclined and vertically vibrated container. We observe how the transport velocity of heap up the container is related to the driving acceleration, the driving frequency, and the inclination of the container. An empirical law which governs the transport velocity of the heap is presented. An analogous experiment was performed with a heap-shaped Plexiglas block. We propose that the compressive force resulted from pressure gradient in ambient gas plays a crucial role in enhancing and maintaining a heap, and the ratchet effect causes the movement of the heap.

Dynamic behaviors of supersonic granular media under vertical vibration.

We present experimental study of vibrofluidized granular materials by high speed photography. Statistical results present the averaged dynamic behaviors of granular materials in one cycle, including the variations of height, velocity and mechanical energy of the center of mass. Furthermore, time-space distribution of granular temperature which corresponds to the random kinetic energy shows that a temperature peak forms in the compression period and propagates upward with a steepened front. The Mach number in the steepened front is found to be greater than unity, indicating a shock propagating in the supersonic granular media.