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The acidification of the marginal seawater was a more intricate process than the ocean. Although some studies have been done on seasonal acidification in the bottom water of Chinese marginal seas, research on surface water acidification has still been insufficient. We analyzed the acidification properties and controlling factors in the Bohai Sea (BS) and Yellow Sea (YS) surface water during April 2023. The observation showed that the average surface water pH of the BS, North Yellow Sea (NYS), and South Yellow Sea (SYS) were 8.09 ± 0.06, 8.13 ± 0.05, and 8.15 ± 0.05. Phytoplankton significantly impacted pH and Ω arag , while riverine inputs and biological activity played a vital role in controlling DIC and TA. The Yellow River significantly impacted the BS. The North Yellow Sea Cold Water Mass had a limited impact on acidification, while the South Yellow Sea Cold Water Mass significantly affected the SYS. Regarding seasonal fluctuations, Ω arag was significantly higher in summer than in other seasons. DIC and TA showed different patterns in both the BS and YS, with a minimal fluctuation in pH. Over the last two decades, the pH in the BS showed a slight annual decline, and the rate of change was (−1.45 ± 2.19) × 10−5 yr−1. In contrast, the NYS and SYS have slightly risen, with rates of change of (2.39 ± 1.24) × 10−5 and (1.23 ± 0.76) × 10−5 yr−1. We believed that surface water acidification in the BS and YS did not follow the expected trend of significant acidification observed in open oceanic regions. Instead, the acidification process in these marginal seas was dominated by local factors such as riverine inputs, biological activity, and cold water masses, resulting in minimal pH changes over the last two decades. [Display omitted] • River inputs and phytoplankton influenced BS and YS surface seawater acidification. • Summarizing data of past 20 years on surface water acidification in BS and YS. • The BS and YS surface water may not be acidified. [ABSTRACT FROM AUTHOR]

[Display omitted] Clinical experiences of herbal medicine (HM) have been used to treat a variety of human intractable diseases. As the treatment of diseases using HM is characterized by multi-components and multi-targets, it is difficult to determine the bio-active components, explore the molecular targets and reveal the mechanisms of action. Metabolomics is frequently used to characterize the effect of external disturbances on organisms because of its unique advantages on detecting changes in endogenous small-molecule metabolites. Its systematicity and integrity are consistent with the effective characteristics of HM. After HM intervention, metabolomics can accurately capture and describe the behavior of endogenous metabolites under the disturbance of functional compounds, which will be used to decode the bioactive ingredients of HM and expound the molecular targets. Metabolomics can provide an approach for explaining HM, addressing unclear clinical efficacy and undefined mechanisms of action. In this review, the metabolomics strategy and its applications in HM are systematically introduced, which offers valuable insights for metabolomics methods to characterizing the pharmacological effects and molecular targets of HM. [ABSTRACT FROM AUTHOR]

• Acoustical coupling for open cavity and an array of Helmholtz resonators in 3D. • Sound radiation modeling based on the coupled mode theory. • The mechanism of abatement of sound radiation from open cavity using Helmholtz resonator is investigated. • The natural frequency, location and internal resistance effect of the resonator is analyzed. • Experimental validation is conducted. This paper presents the theoretical and experimental investigations on the suppression of noise radiation from a point source inside an open cavity with three-dimensional configuration using several Helmholtz resonators (HRs). A theoretical model is established based on the modal superposition method to study the acoustical coupling between a rectangular open cavity and multiples HRs. Additionally, a baffled open cavity is considered to couple acoustically with a semi-infinite exterior field using the acoustic coupled mode theory. The theoretical model facilitates the understanding of the mechanism of the peak formation in the sound pressure level spectrum at the receiving points outside the cavity and the noise suppression mechanism by the HRs. In addition, the relationship between those sound peaks, and that of the resonances of the enclosed cavity and open cavity are investigated to have a good design of HR. The location and internal resistance of HR are optimised to obtain a desirable attenuation of noise radiation from the open cavity. Subsequently, experiments are performed to validate the proposed model and examine the feasibility of the HR in suppressing noise radiation from the open cavity. The noise reduction around the sound peak indicates that both the single and multiple sound peaks of the open cavity can be controlled successfully by adopting HRs. The practical significance of this study is to provide a new insight into sound reduction in an open acoustical system through suppressing the resonant response by resonators. [ABSTRACT FROM AUTHOR]

This paper is concerned with adaptive robust stabilization in finite time for fractional-order chaotic and hyperchaotic Electromechanical Gyrostat Systems (EGSs) with unknown parameters and uncertainties. Firstly, a fractional-order EGS mathematical model is proposed, and the existence of chaotic and hyperchaotic attractors is verified with the related Lyapunov exponents, phase portraits and Poincaré sections. Then, fractional-order adaptive laws are proposed to estimate the unknown parameters. Based on the fractional-order convergence theory in finite time, a novel discontinuous state feedback controller with the proposed fractional-order adaptive laws is designed to stabilize the fractional-order EGSs in finite time globally, and the stabilization conditions are analytically addressed. Finally, numerical simulations are employed to demonstrate the validity of the theoretical results. [ABSTRACT FROM AUTHOR]

In this paper, compact finite difference schemes for the modified anomalous fractional sub-diffusion equation and fractional diffusion-wave equation are studied. Schemes proposed previously can at most achieve temporal accuracy of order which depends on the order of fractional derivatives in the equations and is usually less than two. Based on the idea of weighted and shifted Grünwald difference operator, we establish schemes with temporal and spatial accuracy order equal to two and four respectively. [ABSTRACT FROM AUTHOR]

• Sound radiation from an unbaffled long enclosure with the ground is modeled analytically. • Preliminary experiment and convergence checks are carried out. • Numerical simulations are conducted to validate the model and examine its effectiveness in dealing with big acoustical domain. • Formation mechanisms of the radiation directivity patterns are investigated. • Potential noise control strategies for long enclosures using acoustic liners are introduced. A theoretical model is presented for the prediction of sound radiated from a semi-infinite unbaffled long enclosure with the ground. This geometrical arrangement forms an idealized representation of traffic tunnels and railway stations where noise propagates inside the long enclosures and radiates to the outside through the openings. Despite the fact that the model described here applies only to idealized situations, it contains essential elements of realistic configurations which are conducive to understanding the physics of the sound radiation phenomenon and significant for the proposal of appropriate noise control strategies. First of all, by expressing the sound field in terms of the superposition of propagating modes inside the long enclosure and adopting the Fourier transform in other regions, the intractable boundary value problem in the natural domain is reduced to a scalar modified Wiener-Hopf (W-H) equation of the second kind in the spectral domain. Then, its solution is obtained using the standard factorization and decomposition procedures, and the radiated sound field is attained through the inverse Fourier transform which involves a contour integral that can be evaluated approximately via the saddle point method. After that, the finite element method (FEM) is adopted to validate the model. Far-field directivity patterns of the radiated sound fields are presented. Finally, the properties of the sound fields both inside and outside three enclosures with different boundary conditions are analyzed, based on which, potential noise reduction methods by using acoustic liners are discussed. [ABSTRACT FROM AUTHOR]

In urban communities, parallel barriers are commonly erected for controlling environmental noise such as traffic and construction noise. However, owing to the multiple reflections between the parallel barriers, their performance may be worse than that of a single barrier. To improve the performance of parallel barriers, a small piece of flush-mounted panel backed by a slender cavity in an otherwise rigid wall of barriers is proposed. With the excitation of the incident wave from a sound source inside the parallel barriers, the flexible panel vibrates, and sound is radiated out to undergo acoustic interference with the sound field bounded by the parallel barriers. Consequently, the sound energy in this space and diffraction at the barrier top edge are reduced over a broad band in the low-frequency regime. A theoretical model for tackling the vibro-acoustic coupling between the sound field of the open cavity and the vibrating panel is established to investigate the noise reduction mechanism in the shadow zone. With optimal structural properties of the panel, an additional averaged insertion loss of approximately 5 dB can be achieved at 80–1000 Hz. The theorical results, which are experimentally validated, pave the way for the potential applications of the flexible panel devices (FPDs) for improving the noise reduction of parallel barriers. [ABSTRACT FROM AUTHOR]

• The noise radiated from an unbaffled long enclosure is predicted and controlled. • Interaction between Helmholtz resonators and the acoustical field is illustrated. • Formation and suppression mechanisms of sound pressure field are investigated. • Quasi-two-dimensional experiments are performed to validate the theoretical model. Theoretical, numerical, and experimental investigations are presented to predict and suppress the noise radiated from monopole point sources inside an unbaffled long enclosure including the ground. First, a mathematical model is established to calculate the acoustical fields. The modal superposition method is adopted to express the sound pressure inside the long enclosure, while the radiated noise is described by applying the Wiener-Hopf (W-H) technique. Subsequently, the interior and exterior acoustical fields are coupled using the continuity equations of sound pressure and particle velocity at the opening. After that, the theoretical model is validated through the finite element method. The formation mechanisms of sound peaks, lobes, the shadow, and illuminated zones are explained from the perspective of mode theory. Meanwhile, Helmholtz resonators (HRs) are proposed to control the dominant modal responses at the opening so that the radiated noise near the resonant frequencies is attenuated. Afterwards, the relationship between acoustical modes and radiation patterns is analyzed. The HR locations, optimized to reduce the radiated noise, are obtained. Besides, the influences of different noise sources on the radiated sound field are explored. Finally, a quasi-two-dimensional experiment is carried out to verify the proposed model and examine the feasibility of HRs in suppressing the noise radiated from an unbaffled long enclosure including the ground. This study facilitates the understanding of physics behind the sound radiation phenomenon and provides new insights into noise control strategies. [ABSTRACT FROM AUTHOR]