Search

Abstract [Objective] The Northern Hengduan Mountains are rich in biodiversity. Over the last 10 years, there have been many reports of the biodiversity of the region. The team conducted a survey of plant diversity and vegetation structure in Northern Hengduan Mountains from June to August 2023. [Methods] Through field investigation and collection and photograph of plants, as well as preparing, classifying, and identifying specimens. [Results] Eight newly recorded species were reported from Chaya of Changdu in the Northern Hengduan Mountains in Xizang. They were Ephedra minuta Florin (Ephedraceae), Caragana korshinskii Kom. (Fabaceae), Rhododendron luhuoense H. P. Yang (Ericaceae), R. orthocladum var. longistylum Philipson et M. N. Philipson (Ericaceae), R. thymifolium Maxim. (Ericaceae), R. nivale Hook. f. subsp. australe Philipson et M. N. Philipson (Ericaceae), Artemisia capillaris Thunb. (Asteraceae), and Chenopodiastrum gracilispicum (H.W.Kung) Uotila (Amaranthaceae) [Conclusion] The discovery of the newly distributed plants is an important supplement for the flora of the Hengduan Mountains in Xizang. The voucher specimens are stored in the herbarium of Yibin University

The application of bio-based solvents for living radical polymerization has been a hot topic in recent year. In this article, γ-valerolactone (GVL), a bio-based solvent as green media for ARGET atom transfer radical polymerization (ATRP) of styrene (St) were investigated. We first conducted polymerization of St in γ-valerolactone using copper(ii) bromide as the catalyst, tris(2-pyridylmethyl) amine as the ligand, and only sodium ascorbate as reducing agent. The polymerization achieved moderate conversion; however, the controllability of polymerization was not very good, providing a polymer with a broad molecular weight distribution (M w/M n > 1.30). When sodium carbonate is introduced, excellent results were obtained providing high yields and low M w/M n values under very low catalyst usage (∼5 ppm). 1H NMR spectroscopy, chain extension, and MALDI–MS experiments confirmed the final polymer chains with high fidelity. The use of GVL solvent opens a new route for the easy synthesis of PS through ARGET ATRP with low catalyst usage conditions.

In the process of upper coal mining, the floor condition may be incomplete because of the lower coal goaf, and the change of the floor condition has an obvious influence on the floor failure in the upper coal mining. Based on the micro-seismic monitoring data of 15249S working face in Jiulong Mine, the activity of floor events, the ratio of roof to floor, energy and other parameters are statistically analyzed. The results show that: when the lower coal is a gob, the activity of floor events is strong and the disturbance depth is large when the upper coal is mined. With the advance of mining location and the change of underlying coal seam conditions, the frequency ratio of floor and roof events changes greatly, and its change rule is consistent with the formation of water channel. The proportion of micro-seismic events increased by 16.49% and decreased by 10.92% when the bottom floor failure depth was 0-5 m and 5-20 m respectively. In the process of overlying coal stoping approaching the underlying stoping contact roadway, the development location of large energy events extends from shallow to deep. The floor safety evaluation system is constructed by using the parameters of floor warning layer event activity, floor and roof event ratio, distance from the stoping line of the underlying coal seam and vertical energy density. The danger zone before and after the stoping position of the underlying working face is a high risk factor, which can be combined with the changes of safety evaluation parameters for early warning and strengthening hydro-geological observation.

For the problem of air-to-air missile cooperative attack on high-speed maneuvering target, a multi-missile cooperative guidance law with consistent attack time is proposed. Firstly, the geometric model of engagement between each missile and target is established in the longitudinal plane, and the relationship between the radial and normal guidance laws of line of sight and the normal acceleration of velocity is analyzed. Then, the fixed time cooperative control law is designed, and based on the line of sight dynamic equation, the robust cooperative guidance law with attack-time constraint is established by using adaptive law and integral sliding mode algorithm to ensure that multiple missiles hit the maneuvering target at the same time. Through numerical simulation, the difference of cooperative time and miss distances are 0.001 s and 0.01 m respectively. The final results verify the effectiveness and rationality of the fixed-time cooperative guidance law.