分类： 生物学 >> 植物学 提交时间： 2023-10-17 合作期刊: 《干旱区科学》
摘要： Root pullout performance of plants is an important mechanical basis for soil reinforcement by plant roots in the semi-arid areas. Studies have shown that it is affected by plant factors (species, ages, root geometry, etc.) and soil factors (soil types, soil moisture, soil bulk densities, etc.). However, the effects of loading rates on root pullout performance are not well studied. To explore the mechanical interactions under different loading rates, we conducted pullout tests on Medicago sativa L. and Hippophae rhamnoides L. roots under five loading rates, i.e., 5, 50, 100, 150, and 200 mm/min. In addition, tensile tests were conducted on the roots in diameters of 0.52.0 mm to compare the relationship between root tensile properties and root pullout properties. Results showed that two root failure modes, slippage and breakage, were observed during root pullout tests. All M. sativa roots were pulled out, while 72.2% of H. rhamnoides roots were broken. The maximum fracture diameter and fracture root length of H. rhamnoides were 1.22 mm and 7.44 cm under 100 mm/min loading rate, respectively. Root displacement values were 4.63% (0.43%) and 8.91% (0.52%) of the total root length for M. sativa and H. rhamnoides, respectively. The values of maximum pullout force were 14.6 (0.7) and 17.7 (1.8) N under 100 mm/min for M. sativa and H. rhamnoides, respectively. Values of the maximum pullout strength for M. sativa and H. rhamnoides were 38.38 (5.48) MPa under 150 mm/min and 12.47 (1.43) MPa under 100 mm/min, respectively. Root-soil friction coefficient under 100 mm/min was significantly larger than those under other loading rates for both the two species. Values of the maximum root pullout energy for M. sativa and H. rhamnoides were 87.83 (21.55) mmN under 100 mm/min and 173.53 (38.53) mmN under 200 mm/min, respectively. Root pullout force was significantly related to root diameter (P0.05). Root pullout strength was greater than root tensile strength for the two species. The results suggested that there was no need to deliberately control loading rate in root pullout tests in the semi-arid soil, and root pullout force and pullout strength could be better parameters for root reinforcement model compared with root tensile strength as root pullout force and pullout strength could more realistically reflect the working state of roots in the semi-arid soil.
分类： 天文学 >> 天文学 提交时间： 2024-05-10 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： Attitude is one of the crucial parameters for space objects and plays a vital role in collision prediction and debris removal. Analyzing light curves to determine attitude is the most commonly used method. In photometric observations, outliers may exist in the obtained light curves due to various reasons. Therefore, preprocessing is required to remove these outliers to obtain high quality light curves. Through statistical analysis, the reasons leading to outliers can be categorized into two main types: first, the brightness of the object significantly increases due to the passage of a star nearby, referred to as "stellar contamination," and second, the brightness markedly decreases due to cloudy cover, referred to as "cloudy contamination." The traditional approach of manually inspecting images for contamination is time-consuming and labor-intensive. However, we propose the utilization of machine learning methods as a substitute. Convolutional Neural Networks and SVMs are employed to identify cases of stellar contamination and cloudy contamination, achieving F1 scores of 1.00 and 0.98 on a test set, respectively. We also explore other machine learning methods such as ResNet-18 and Light Gradient Boosting Machine, then conduct comparative analyses of the results.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Ultraviolet (UV) electro-optic modulation system based on graphene-plasmonic metamaterials nanomechanical system (NEMS) with superlubricity is investigated. Due to the strong optical absorption intensity of graphene in the UV region and the combination of metamaterial structure based on surface plasmons, the modulation depth of the UV NEMS electro-optic modulator approaches as high as 8.5 times compared to the counterpart modulator in visible light region. Meanwhile, the superlubricity significantly reduces the power consumption of the UV electro-optic modulation system due to its extremely low friction coefficient. It also significantly improves the response speed of the modulator, which can reach the order of a nanosecond. The modulation voltage can be lower than 200 mV. The proposed electro-optic modulation system has a simple structure and high sensitivity, which is supposed to have important applications in UV optoelectronic devices and systems.
提交时间： 2017-05-02
Li, M [Li, Min][ 1 ]
Tan, RQ [Tan, Ruiqin][ 3 ]
Li, R [Li, Rong][ 1 ]
Song, WJ [Song, Weijie][ 2 ]
Xu, W [Xu, Wei][ 2 ]
摘要： Intermediate tin oxide [Sn3O4] crystals have been successfully synthesized through a simple one-pot hydrothermal route by employing SnCl2 center dot 2H[2]O and NaOH as raw materials. The crystmlline structure, morphology and optical properties of Sn3O4 ma
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