分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Wire position monitor (WPM) is designed to monitor contraction of the cold masses during the cooling-down operation in an accelerator driven system. Because of material difference, machining error, assembly error, etc., each WPM has to be calibrated. The sensing voltage and wire position are of a nonlinear relationship, which is expressed by high order polynomial. Root mean square (RMS) of the polynomial fitting error were 3.8 m and 7.4 m at x and y directions, respectively. The alignment test was carried out on the beta cryostat. Optical instruments were used to verify the WPM measuring results. The differences between WPM measuring results and optical measurements were 0.044 and 0.05 mm in x and y direction, respectively. A significant asymmetric contraction was detected, and asymmetry of material was taken as the main reason through analysis.
分类： 生物学 >> 生态学 提交时间： 2018-07-05 合作期刊: 《干旱区科学》
摘要： Soil organic carbon (SOC) and soil total nitrogen (STN) in arid regions are important components of global C and the N cycles, and their response to climate change will have important implications for both ecosystem processes and global climate feedbacks. Grassland ecosystems of Funyun County in the southern foot of the Altay Mountains are characterized by complex topography, suggesting large variability in the spatial distribution of SOC and STN. However, there has been little investigation of SOC and STN on grasslands in arid regions with a mountain-basin structure. Therefore, we investigated the characteristics of SOC and STN in different grassland types in a mountain-basin system at the southern foot of the Altai Mountains, north of the Junggar Basin in China, and explored their potential influencing factors and relationships with meteorological factors and soil properties. We found that the concentrations and storages of SOC and STN varied significantly with grassland type, and showed a decreasing trend along a decreasing elevation gradient in alpine meadow, mountain meadow, temperate typical steppe, temperate steppe desert, and temperate steppe desert. In addition, the SOC and STN concentrations decreased with depth, except in the temperate desert steppe. According to Pearson's correlation values and redundancy analysis, the mean annual precipitation, soil moisture content and soil available N concentration were significantly positively correlated with the SOC and STN concentrations. In contrast, the mean annual temperature, pH, and soil bulk density were significantly and negatively correlated with the SOC and STN concentrations. The mean annual precipitation and mean annual temperature were the primary factors related to the SOC and STN concentrations. The distributions of the SOC and STN concentrations were highly regulated by the elevation-induced differences in meteorological factors. Mean annual precipitation and mean annual temperature together explained 97.85% and 98.38% of the overall variations in the SOC and STN concentrations, respectively, at soil depth of 040 cm, with precipitation making the greatest contribution. Our results provide a basis for estimating and predicting SOC and STN concentrations in grasslands in arid regions with a mountain-basin structure.
分类： 地球科学 >> 空间物理学 提交时间： 2016-05-12
摘要： Standing sausage modes in flare loops are important for interpreting quasi-periodic pulsations(QPPs) in solar flare light curves. We propose an inversion scheme that consistently uses their periods P and damping times tau to diagnose flare loop parameters. We derive a generic dispersion relation governing linear sausage waves in pressure-less straight tubes, for which the transverse density inhomogeneity takes place in a layer of arbitrary width l and is of arbitrary form. We find that P and tau depend on the combination of [R/nu(Ai), L/R, l/R, rho(i)/rho(e)], where R is the loop radius, L is the looplength, nu(Ai) is the internal Alfven speed, and rho(i)/rho(e) is the density contrast. For all the density profiles examined, P and tau experience saturation when L/R >> 1, yielding an inversion curve in the [R/nu(Ai), l/R, rho(i)/rho(e)] space with a specific density profile when L/R is sufficiently large. When applied to a spatially unresolved QPP event, the scheme yields that R/nu(Ai) is the best constrained, whereas l/R corresponds to the other extreme. For spatially resolved QPPs, while L/R >> 1 cannot be assumed beforehand, an inversion curve remains possible due to additional geometrical constraints. When a spatially resolved QPP event involves another mode, as is the case for a recent event, the full set of [nu(Ai), l, rho(i)/rho(e)] can be inferred. We conclude that the proposed scheme provides a useful tool for magneto-seismologically exploiting QPPs.
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