Modified Splitting FDTD Methods for Two-Dimensional Maxwell’s Equations

In this paper, we develop a new method to reduce the error in the splitting finite-difference method of Maxwell’s equations. By this method two modified splitting FDTD methods (MS-FDTDI, MS-FDTDII) for the two-dimensional Maxwell equations are proposed. It is shown that the two methods are second-order accurate in time and space and unconditionally stable by Fourier methods. By energy method, it is proved that MS-FDTDI is second-order convergent. By deriving the numerical dispersion (ND) relations, we prove rigorously that MS-FDTDI has less ND errors than the ADI-FDTD method and the ND errors of ADI-FDTD are less than those of MS-FDTDII. Numerical experiments for computing ND errors and simulating a wave guide problem and a scattering problem are carried out and the efficiency of the MS-FDTDI and MS-FDTDII methods is confirmed

Improved Decentralized Fractional PD Control of Structure Vibrations

This paper presents a new strategy for the control of large displacements in structures under earthquake excitation. Firstly, an improved fractional order proportional-derivative (FOPD) controller is proposed. Secondly, a decentralized strategy is designed by adding a regulator and fault self-regulation to a standard decentralized controller. A new control architecture is obtained by combining the improved FOPD and the decentralized strategy. The parameters of the control system are tuned using an intelligent optimization algorithm. Simulation results demonstrate the performance and reliability of the proposed method.The work was supported by the National Natural Science Foundation of China (No. 11971032).info:eu-repo/semantics/publishedVersio

Design and experiments with a SLAM system for low-density canopy environments in greenhouses based on an improved Cartographer framework

To address the problem that the low-density canopy of greenhouse crops affects the robustness and accuracy of simultaneous localization and mapping (SLAM) algorithms, a greenhouse map construction method for agricultural robots based on multiline LiDAR was investigated. Based on the Cartographer framework, this paper proposes a map construction and localization method based on spatial downsampling. Taking suspended tomato plants planted in greenhouses as the research object, an adaptive filtering point cloud projection (AF-PCP) SLAM algorithm was designed. Using a wheel odometer, 16-line LiDAR point cloud data based on adaptive vertical projections were linearly interpolated to construct a map and perform high-precision pose estimation in a greenhouse with a low-density canopy environment. Experiments were carried out in canopy environments with leaf area densities (LADs) of 2.945–5.301 m2/m3. The results showed that the AF-PCP SLAM algorithm increased the average mapping area of the crop rows by 155.7% compared with that of the Cartographer algorithm. The mean error and coefficient of variation of the crop row length were 0.019 m and 0.217%, respectively, which were 77.9% and 87.5% lower than those of the Cartographer algorithm. The average maximum void length was 0.124 m, which was 72.8% lower than that of the Cartographer algorithm. The localization experiments were carried out at speeds of 0.2 m/s, 0.4 m/s, and 0.6 m/s. The average relative localization errors at these speeds were respectively 0.026 m, 0.029 m, and 0.046 m, and the standard deviation was less than 0.06 m. Compared with that of the track deduction algorithm, the average localization error was reduced by 79.9% with the proposed algorithm. The results show that our proposed framework can map and localize robots with precision even in low-density canopy environments in greenhouses, demonstrating the satisfactory capability of the proposed approach and highlighting its promising applications in the autonomous navigation of agricultural robots

The latest research progress on P53 and tumor metabolism

P53 is a key factor encoded by the TP53, and it prevents cells from becoming cancerous and has a wide range of powerful functions. p53 is found to play an important role in inducing DNA repair, apoptosis, cell cycle arrest and senescence, and the loss of these functions does not abrogate P53’s tumor suppressive activity. Metabolism is the basis of life, and metabolic abnormalities can lead to a variety of diseases, including tumors, and is one of the main drivers of cancer progression. It has recently been discovered that P53 plays a key role in regulating metabolism. P53-mediated regulation of cell metabolism is a fundamental mechanism controlling cancer occurrence and development and contributes to its tumor suppressive activity. Here, this article reviewed the relationship between P53 and glucose, fatty acid, amino acid and nucleotide metabolism, and discussed the complex mechanism and the latest research progress of P53 in the metabolic regulation in tumor development

Observation analysis of "5.22" extreme rainfall event in Guilin

An extreme heavy rainfall event struck the northern part of the Guilin urban area in the early morning of May 22, 2023, breaking local historical records for both hourly and three-hourly precipitation, resulting in severe urban waterlogging. Analysis was conducted using data from routine observation, ground-based dense automatic stations, Doppler weather radar, and ERA5 reanalysis. The results are as follows. (1) This event occurred on the edge of the subtropical high-pressure system, with the continuous strengthening of the southwest jet stream providing abundant moisture and energy for the extreme rainfall under the influence of the low-level shear line and the southward movement of the surface cold front. (2) The echoes of heavy rainfall evolved into a linear convection, which changed the direction and shape when timely met with the surface cold air. Meanwhile, the continuously developing new individual cells on its western side joined to form a "train effect," leading to extreme rainfall. The echo exhibited characteristics of low core and high efficiency. (3) The timely intrusion of weak cold air intensified convective rainfall and enhanced cold pool outflow, triggering new convection in the warm and moist region ahead of it, which favored the development and persistence of heavy rainfall. (4) During the eastward movement of individual convective cells, they merged through cloud bridges and expanded through cloud development, forming new cloud clusters and rapidly intensifying precipitation. The interaction and merging of convective cells were the main mechanisms for the prolonged and intensified heavy rainfall. (5) Various numerical models underestimated the intensity of this event, with biases in forecasting the rainfall center mainly due to deviations in the timing of forecasting the influence of surface cold air

Inhibitor selectivity between aldo–keto reductase superfamily members AKR1B10 and AKR1B1: Role of Trp112 (Trp111)

AbstractThe antineoplastic target aldo–keto reductase family member 1B10 (AKR1B10) and the critical polyol pathway enzyme aldose reductase (AKR1B1) share high structural similarity. Crystal structures reported here reveal a surprising Trp112 native conformation stabilized by a specific Gln114-centered hydrogen bond network in the AKR1B10 holoenzyme, and suggest that AKR1B1 inhibitors could retain their binding affinities toward AKR1B10 by inducing Trp112 flip to result in an “AKR1B1-like” active site in AKR1B10, while selective AKR1B10 inhibitors can take advantage of the broader active site of AKR1B10 provided by the native Trp112 side-chain orientation

Probing the Shock Breakout Signal of SN 2024ggi from the Transformation of Early Flash Spectroscopy

© 2024. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We present early-time, hour-to-day cadence spectroscopy of the nearby Type II supernova (SN II) 2024ggi, which was discovered at a phase when the SN shock had just emerged from the red supergiant (RSG) progenitor star. Over the first few days after the first light, SN 2024ggi exhibited prominent narrow emission lines formed through intense and persistent photoionization of the nearby circumstellar material (CSM). In the first 63 hr, spectral lines of He, C, N, and O revealed a rapid rise in ionization as a result of the progressive sweeping up of the CSM by the shock. The duration of the IIn-like spectra indicates a dense and relatively confined CSM distribution extending up to ∼4 × 1014 cm. Spectral modeling reveals that a CSM mass-loss rate at this region exceeding 5 × 10−3 M ⊙ yr−1 is required to reproduce low-ionization emissions, which dramatically exceeds that of an RSG. Analyzing the Hα emission shift implies the velocity of the unshocked outer CSM to be between 20 and 40 km s−1, matching the typical wind velocity of an RSG. The differences between the inner and outer layers of the CSM and an RSG progenitor highlight a complex mass-loss history before the explosion of SN 2024ggi.Peer reviewe