黔西北土法炼锌区水土流失的特点及防治对策

作者简介: 吴桂容( 1970- ) , 女, 广西贺州人, 博士研究生, 副教授, 主要从事污染生态学研究。E - mail: hzwgr510@ 163. com。通信作者: 敖子强, 博士研究生, 主要从事环境生态和污染生态学研究。E - m ai:l aoz iq iang628@ 163. com。通过对土法炼锌区的土壤、废渣、植物、地表水和沉积物进行实地调查和采样分析,发现土法炼锌区水土流失主要是由于含有SO2和重金属的废气导致植被严重破坏、土壤裸露造成的;水土流失同时导致了重金属的迁移扩散,污染土壤中重金属可溶态比重大,而废渣中重金属可溶态比重小,主要随废渣一起流失。减少土法炼锌区水土流失的主要途径是恢复植被和利用工程措施将废渣固定。对于污染土壤来说限制因子是土壤pH值低,可溶态重金属比重大,主要对策是增加土壤的pH值,选择耐酸性和耐重金属的树种恢复植被;对于废渣来说限制因子是废渣持水保肥能力差,重金属含量高,及废渣本身的结构疏松,主要对策是保持废渣的pH值不降低,利用工程措施将废渣固定,及改变土壤的结构来恢复植被;废渣和污染土壤上的先锋植物醉鱼草(Buddleja lindleyana)可作为首选来恢复植被。贵州省科学技术基金(编号:20062014);广西重点实验室研究基金(编号:桂科能0704K002

First Sagittarius A* Event Horizon Telescope Results. VIII. Physical Interpretation of the Polarized Ring

In a companion paper, we present the first spatially resolved polarized image of Sagittarius A* on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3 mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%–28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87*, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of Sgr A* (equivalent to ≈46° ± 12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow

冬小麦旗叶光合速率对光强度和CO_2浓度的响应

通过控制光强度、CO_2浓度和温度等因素,研究华北平原冬小麦(Triticum aestivum)在抽穗期旗叶光合作用对光响应、CO_2响应以及气孔导度对光的响应。结果表明:在控制环境条件下,光合速率随光强度的增加而增大直至饱和光强度,然后随光强度的增加而降低直至出现光抑制;光合速率随CO_2浓度的增加而增加,达到饱和CO_2浓度后,光合速率几乎不变;冬小麦叶片气孔导度随光强度的增加而增加直至饱和光强度,然后随光强度的增加而降低。在气温为20和25℃、CO_2浓度相同(360μmol.mol-1)的条件下,冬小麦的最大光合速率几乎不变,但温度影响冬小麦的饱和光强度

抛光磨削工艺对齿轮振动噪声影响的试验分析

基于对比试验探究了抛光磨削工艺对齿轮振动噪声的影响。试验对象分别为抛光磨削齿轮和常规磨削齿轮各一对。试验前，对两齿轮副的齿形齿向形貌和粗糙度进行检测以得到齿面微观形貌特征；之后，对两齿轮副进行齿轮运转试验，在不同的转速下，采集振动噪声数据，利用Matlab对试验数据处理，得到频谱和噪声变化趋势；结合两齿轮副的表面形貌特征，分析探讨了抛光磨削工艺对齿轮振动噪声的影响。由频谱对比得知，抛光磨削齿轮的振动加速度明显低于常规磨削齿轮；由噪声结果对比得知，300~600 r/min时，抛光磨削齿轮比常规磨削齿轮噪声略低；700~1 000 r/min时，两齿轮副声增加均较为缓慢；1 100~1 400 r/min时，常规磨削齿轮振动噪声比抛光磨削齿轮增加的更快

氧离子与氖原子碰撞转移电离过程研究

采用位置灵敏探测和散射离子 反冲离子飞行时间测量技术,测量了氧离子与氖原子碰撞过程中转移电离截面与单电子俘获截面之比。通过比较,发现测量结果与文献结果的趋势一致,并对测量结果进行了解释

氧离子与氦、氖原子碰撞中转移电离过程的研究

采用位置灵敏探测和散射离子 反冲离子飞行时间测量技术,测量了氧离子与氖和氦原子碰撞过程中转移电离截面与单电子俘获截面之比。通过比较发现测量结果与文献结果的趋势一致,并对测量结果进行了讨论

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies