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The Tibetan Plateau (TP) plays a key role in the regional environment and global climate change; however, the lack of vertical observations of atmospheric species, such as HONO and O 3 , hinders a deeper understanding of the atmospheric chemistry and atmospheric oxidation capacity (AOC) on the TP. In this study, we conducted multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements at Nam Co, the central TP, to observe the vertical profiles of aerosol, water vapor (H 2 O), NO 2 , HONO and O 3 from May to July 2019. In addition to NO 2 mainly exhibiting a Gaussian shape with the maximum value appearing at 300 =- 400 m, the other four species all showed an exponential shape and decreased with the increase in height. The maximum values of monthly averaged aerosol (0.17 km -1) and O 3 (66.71 ppb) occurred in May, H 2 O (3.68 × 10 17 molec. cm -3) and HONO (0.13 ppb) appeared in July, and NO 2 (0.39 ppb) occurred in June at the 200–400 m layer. H 2 O, HONO and O 3 all exhibited a multi-peak pattern, and aerosol appeared to have a bi-peak pattern for its averaged diurnal variations. The averaged vertical profiles of OH production rates from O 3 and HONO all exhibited an exponential shape decreasing with the increase in height, with maximum values of 2.61 and 0.49 ppb h -1 at the bottom layer, respectively. The total OH production rate contributed by HONO and O 3 on the TP was obviously larger than that in low-altitude areas. In addition, source analysis was conducted for HONO and O 3 at different height layers. The heterogeneous reaction of NO 2 on wet surfaces was a significant source of HONO. The maximum values of HONO / NO 2 appeared when H 2 O concentrations were approximately 1.0 × 10 17 molec. cm -3 and aerosol concentrations were larger than 0.15 km -1 below 1.0 km. The maximum values were usually accompanied by H 2 O concentrations of 1.0–2.0 × 10 17 molec. cm -3 and aerosol concentrations greater than 0.02 km -1 at 1.0–2.0 km. O 3 was potentially sourced from the South Asian subcontinent and Himalayas through long-range transport. Our results contribute to the new understanding of vertical distribution of atmospheric components and explain the strong AOC on the TP. [ABSTRACT FROM AUTHOR]

Due to the assumption of acceleration variation in traditional step-by-step integration methods such as Newmark, sufficiently small time steps are required to ensure numerical stability and accuracy in dynamic systems. In contrast, the state-space approach, based on piecewise interpolation of discrete load functions, does not rely on predetermined acceleration assumptions and has demonstrated high efficiency in terms of stability and accuracy. The original state-space method requires the calculation of the inverse of the structural mass in the transition matrix. However, when a lumped mass matrix is used, this computation renders the entire mass matrix singular, resulting in an invalid solution expression. To address this issue, this study proposes an improved state-space approach for the transient analysis of large-scale structural systems with local nonlinearities. In this approach, a nonlinear force corrector is introduced as an external force term applied to the linear elastic system to account for the nonlinear behavior of locally yielding components. Consequently, the original nonlinear dynamic system can be transformed into an equivalent linear elastic transient system. Furthermore, based on the lumped mass matrix, a first-order ordinary differential state-space equation for such an equivalent linear elastic transient system is derived. Simulation results from three transient system examples show that the state-space approach outperforms the Newmark method in terms of accuracy and stability for dynamic systems characterized by high frequency and low damping. The prediction results show that the state-space approach appears to be insignificantly affected by the choice of the consistent or lumped mass matrix. The numerical results show that the root-mean-square errors between the consistent and lumped matrices in the top displacement time histories of a 15-storey plane frame under various seismic intensities are all less than 1%, and in the base reaction time histories responses the discrepancies are only about 0.5%, indicating that the use of lumped mass matrices is quite reliable. When many nodes or degrees of freedom have no assigned mass, the dimensionality of the state-space equation can be significantly reduced using the lumped mass approach. Therefore, the simulation of large-scale systems can be simplified by employing the improved state-space approach with lumped mass matrices, yielding results nearly identical to those obtained using traditional methods. In conclusion, the improved state-space approach has great potential for the simulation of transient behavior in large-scale systems with local nonlinearities. [ABSTRACT FROM AUTHOR]

To passively achieve an inertial device with unidirectional force transmission similar to Bang Bang control, this study introduces a novel energy dissipation device known as the resettable‐inertia damper (RID). The ingenious motion principles of the RID, encompassing a rack‐and‐pinion, bevel gear commutation system, speed transmission, and eddy current damping, are elucidated in detail. In particular, a unidirectional rotational flywheel within the device selectively engages when the primary structure reciprocates. The physical mass of the flywheel undergoes conversion into an amplified inertia through the rack‐and‐pinion mechanism, which enables the enhancement of damping effects coupling the flywheel rotation and eddy current configuration. A coupled multibody dynamic model, combining the clutching effect, the flywheel inertia, and the rotational damping, is formulated to analyze the system with RID (RIDS). Currently, an analysis of the hysteretic behaviors of RID is carried out. To facilitate the design and evaluation of the performance of RIDS, an equivalent linearization method is proposed for RIDS. The feasibility of this simplified method is validated under harmonic excitation. Additionally, the study examines the performance of equivalent linear systems (ELSs) and RIDS under natural ground motions and stochastic stationary excitation in peak and variance responses levels, respectively. Comparison of RID with traditional inerter shows that RID can achieve a more pronounced control with less force transferred to the structure and with the potential to recover vibration energy, highlighting its unique advantages. [ABSTRACT FROM AUTHOR]

A drone delivery system, characterized by its low energy consumption, high efficiency, and extensive coverage capability, has been adopted as an effective solution to overcome the limitations of traditional ground transportation. However, due to strong interactions between urban structures and wind, the wind environment in the low-altitude airspace of urban areas poses significant safety risks for drone operations, a challenge that remains unresolved. To mitigate these risks, this study presents a methodology for precisely defining the no-fly zones (NFZs) for drone operations using computational fluid dynamics (CFD) simulations. Three hazardous indices—safe, deviation, and unsafe—are proposed to indicate the drone operation status. High-resolution CFD models of urban wind environments in a real city area are coupled with meteorological wind data to provide statistical results for the three indices. The Reynolds-averaged Navier–Stokes turbulence model is employed to simulate two wind environments, standard wind and strong wind, under 36 incoming flow directions. Considering eight flight orientations of drone operating in horizontal planes at various heights, a set of maps for the occurrence probability of the three hazardous indices is provided. These maps can be utilized to determine safe areas, identify no-fly zones corresponding to high occurrence probabilities of deviation and unsafe indices, and establish efficient flight paths for drone operations. [ABSTRACT FROM AUTHOR]