Search

This paper proposes a rocket substage vertical landing guidance method based on the second-order Picard-Chebyshev-Newton type algorithm. Firstly, the continuous-time dynamic equation is discretized based on the natural second-order Picard iteration formulation and the Chebyshev polynomial. Secondly, the landing problem that considers terminal constraints is transformed into a nonlinear least-squares problem with respect to the terminal constraint function and solved with the Gauss-Newton method. In addition, the projection method is introduced to the iteration process of the Gauss-Newton method to realize the inequality constraints of the thrust. Finally, the closed-loop strategy for rocket substage vertical landing guidance is proposed and the numerical simulations of the rocket vertical landing stage are carried out. The simulation results demonstrate that compared with the sequential convex optimization algorithm, the proposed algorithm has higher computational efficiency.

Distinguishing humans from animals using ultra-wideband (UWB) radar is necessary in post-disaster emergency rescues to prioritize and thereby optimize the distribution of labor and material resources. However, current studies are few and have only been implemented in simple laboratory environments, such that the effectiveness of these approaches cannot be guaranteed in rescue situations. This study describes experiments under actual post-disaster emergency rescue scenarios, for which the signal-to-noise ratio of UWB radar is seriously degraded owing to multipath effects and a complicated ruin environment. Four distinguishing features are extracted from aspects of wavelet entropy, correlation coefficient, and energy to classify humans from animals. Analysis of feature effectiveness showed that each feature could identify humans from animals individually. The largest difference between humans and animals was found in a feature which combines advantages of the correlation coefficient and energy simultaneously. There was no overlap between the human and animal values for this feature among the 20 sets of radar data collected. This is the first attempt to distinguish humans from animals in an actual post-disaster trapped condition, and it yielded four features of strong classification ability. We envision this study to advance real-world applicability of UWB radar in post-disaster emergency rescue.

In order to explore the effects of different wood types with different chemical compositions and structures on the types and amounts of polycyclic aromatic hydrocarbons produced in traditional smoked meat products, the structural and pyrolysis characteristics of lignin in five kinds of wood commonly used in the production of traditional smoked and roasted meat products, pine, poplar, beech, jujube and apple wood, were investigated by infrared spectroscopy, Raman spectroscopy, thermogravimetry and thermogravimetry coupled with infrared spectroscopy. The results showed that there were differences in the contents of lignin, guaiacyl (G) and syringyl (S) in the five kinds of wood. The pyrolysis process involved three stages, mainly in the range of 200?500 ℃, but the mass loss rate, mass loss temperature, pyrolysis rate and pyrolysis temperature of lignin were different among different kinds of wood, indicating that there are significant differences in the thermal stability of lignin from different wood sources. Differences in lignin content, S/G structure content and side chain structure in smoked and roasted wood could lead to different thermal stability, and different pyrolysis characteristics could in turn affect the formation of harmful substances such as polycyclic aromatic hydrocarbons.

Due to high transport efficiency, reduced transfer time, and various other advantages, the joint operation of different rail transit systems emerges as the optimal choice for rail transit systems. This article mainly studies the line-planning problem under the line-sharing operation mode between metro and suburban railway. First, a complex multiobjective programming model is established to maximize the net profit of two operating companies and the time savings of passengers. The constraints of this model encompass passenger flow, available vehicles, line carrying capacity, station capacity, cross-line configuration, departure frequency, and variable value range. Second, the linear weighted sum method is introduced to consolidate three objective functions into a single one, while utilizing the improved artificial bee colony (IABC) algorithm to address the line-planning problem. Besides, the traditional artificial bee colony (TABC) algorithm and the simulated annealing (SA) algorithm are provided as comparison groups to solve the same numerical example problem. The results demonstrate significant reductions in travel time by adopting the line-sharing operation mode. In addition, the IABC algorithm exhibits better solution quality and higher efficiency than both the TABC and SA algorithms. The proposed method proves to be valuable in formulating and optimizing the line plan., Author(s): Li Lin (corresponding author) [1,2]; Xuelei Meng [1]; Xiaoqing Cheng [2]; Yangyang Ma [3]; Shichao Xu [1]; Zheng Han [1] 1. Introduction By the end of May 2023, 54 [...]