ABSTRACT
Infrared radiation (IR) characteristics are important parameters for detecting, identifying, and striking military targets in the context of systematic countermeasures. Accurate calculation of IR characteristics for aircraft is significant for the simulation of war situations and the designation of combat strategy. In this work, integrated IR characteristics of aircraft skin and exhaust plume and their interaction are investigated by considering the reflection based on a bi-directional reflectance distribution function and various influence factors such as solar irradiation, ground reflection, aerodynamic heating, and projection radiation from the background. Combined with infrared emission and reflection characteristics of the skin, omnidirectional IR intensity distributions of 3-5 µm and 8-14 µm at different Mach numbers are obtained. The exhaust plume IR characteristic for different waves and wavebands are also investigated by considering the presence or absence of base and the difference in nozzle inlet temperature. On this basis, integrated IR characteristics between the skin and exhaust plume are investigated. Results show that aircraft IR characteristics of 3-5 µm are concentrated in the exhaust plume and high-temperature skin near the exhaust plume, while the signals of 8-14 µm are concentrated in the skin. The research results are expected to supply guidance for better detection and identification of typical flight targets.
ABSTRACT
Water shortages threaten agricultural sustainability in the semi-arid areas of the Loess Plateau. Judicious mulching management can improve water conservation practices to alleviate this issue while increasing crop productivity. We investigated the effect of straw strip mulching and film mulching on soil water consumption, temperature, growth, grain yield, and economic income of soybean [Glycine max(Linn.) Merr.] from 2017 to 2018 in Qingyang on the semi-arid Loess Plateau in China using four treatments: (a) alternating ridges and furrows with ridges mulched with white polyethylene film (PMP), (b) alternating flat and bare land with only the plat mulched by white polyethylene film (PMF), (c) alternating strips mulched with maize (Zea mays L.) straw (SM), and (d) traditional land planting without mulching (CK). The mulching treatments (PMP, PMF, and SM) increased soil water consumption and soil water use efficiency. The SM, PMF, and PMP treatments had 12.3-12.5, 16.8-22.1, and 23.2-24.2 mm higher soil water consumption (0-120 cm depth) than CK, most of which occurred in the 60-120 cm soil layer. Compared with CK, PMP and PMF significantly increased soil temperature by 1.30-1.31 °C and 0.76-1.00 °C, soybean grain yield by 38.6-39.0 % and 38.8-44.2 %, and water use efficiency (WUE) by 27.7-32.8 % and 30.8-37.5 %, respectively, while SM significantly decreased soil temperature by 0.96-1.15 °C, and increased grain yield by 21.8-25.4 % and WUE by 16.9-21.9 %. PMP and PMF did not significantly change soil water consumption, WUE, or grain yield. The SM treatment increased net income by 501.3-691.7 and 1914.5-2244.9 CNY ha-1 relative to PMP and CK, respectively, but PMF and SM did not significantly differ. Therefore, the SM system could help increase grain yields and economic returns in dryland soybean production, avoiding the adverse effects of the increasingly popular plastic mulching approach.
