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911.
Alexander Müller Dirk Flottmann Wolfgang Schulz Wolfram Seitz Walter H. Weber 《洁净——土壤、空气、水》2007,35(4):329-338
The development of instrumental analytics such as the LC-MS/MS has made it possible to quickly determine many component concentrations in a single chromatogram. However, the validation of such multi-methods needs new strategies for robustness and optimization. Statistical execution of analytical tests is one tool that can be utilized to meet this requirement. A Central Composite Design (CCD) was utilized for the validation of an LC-MS/MS multi-method for 84 analytes. The experimental design includes six design variables and two non-design variables (response variables). Concentration, ionization temperature, dwell time, gradient, flow (of eluent), and spraying/curtain gas (continuous design variables) were varied on five different levels; the whole design encompassed 91 runs. To investigate the robustness of a LC-MS/MS method both peak sensitivity and chromatographic separation had to be verified. Therefore, two non-design variables were necessary. The distribution of the peaks over analysis time was applied to describe the quality of the chromatographic separation. The sensitivity was described with the signal to noise ratio (S/N). The evaluation of the measured data was accomplished with the Analysis of Variance (ANOVA) and the Response Surface Methodology (RSM). Three main effects (concentration, ionization temperature, dwell time) and no significant interaction effect were found for the response variable “S/N”. The variables of concentration, ionization temperature, and dwell time had no significant effects for the response variable “S/N”. The ANOVA of the response variable chromatographic separation abandoned no significant effects as well. Therefore, robustness of the method can be guaranteed for all non significant design variables. 相似文献
912.
1975年8月河南省特大暴雨雨强极值的重新估算 总被引:1,自引:0,他引:1
通过对云中气载液态水含量以及水汽和气载液态水之间的平衡方程的讨论,建立了改进的可降水量Ia公式。按照改进的公式,重新估算了1975年8月河南省特大暴雨7日20时雨强。结果表明,分别以遂平气象站记录的8 m/s和按物象估算的12 m/s地面风速为基础的改进的板桥水库附近8月7日20时雨强估算值Iae1=75.0 mm/h和Iae1=95.8 mm/h很接近实际的雨强极值Ioe=99.7 mm/h。 相似文献
913.
914.
岩体在块系构造状态下的动力传播存在块体和块体间软弱介质的非协调变形现象,对岩体结构的动力稳定产生重要影响。目前块系岩体的非协调动力传播响应研究尚不充分,导致不能进行有效的动力响应特征识别。通过试验对块系岩体非协调动力传播过程岩块动力响应特征进行研究,分别从动力传播速度、岩块加速度振幅衰减、岩块振动位移响应、岩块振动持续时间、块体动能显现、块体振动频域响应特性等方面对比纵波传播,给出块系岩体非协调动力传播的特征分析。通过分析可知,块系介质非协调变形运动产生的动力传播现象相比于纵波传播是一种低频低速波,并伴随着岩块的大位移运动,同时岩块振动持续时间较长,蕴含着动能与势能的相互转换过程,这些现象构成了块系岩体非协调动力传播的重要特征。该研究将为识别岩体非协调动力传播特征及块系岩体的冲击预警波动特征识别提供参考。 相似文献
915.
Richard B. Larson 《Monthly notices of the Royal Astronomical Society》1998,301(2):569-581
It has frequently been suggested in the literature that the stellar IMF in galaxies was top-heavy at early times. This would be plausible physically if the IMF depended on a mass-scale such as the Jeans mass that was higher at earlier times because of the generally higher temperatures that were present then. In this paper it is suggested, on the basis of current evidence and theory, that the IMF has a universal Salpeter-like form at the upper end, but flattens below a characteristic stellar mass that may vary with time. Much of the evidence that has been attributed to a top-heavy early IMF, including the ubiquitous G-dwarf problem, the high abundance of heavy elements in clusters of galaxies, and the high rate of formation of massive stars in high-redshift galaxies, can be accounted for with such an IMF if the characteristic stellar mass was several times higher during the early stages of galaxy evolution. However, significant variations in the mass-to-light ratios of galaxies and large amounts of dark matter in stellar remnants are not as easily explained in this way, because they require more extreme and less plausible assumptions about the form and variability of the IMF. Metal-free 'population III' stars are predicted to have an IMF that consists exclusively of massive stars, and they could help to account for some of the evidence that has been attributed to a top-heavy early IMF, as well as contributing importantly to the energetics and chemical enrichment of the early Universe. 相似文献
916.
Ian A. Bonnell & Melvyn B. Davies 《Monthly notices of the Royal Astronomical Society》1998,295(3):691-698
We investigate the evolutionary effect of dynamical mass segregation in young stellar clusters. Dynamical mass segregation acts on a time-scale of order the relaxation time of a cluster. Although some degree of mass segregation occurs earlier, the position of massive stars in rich young clusters generally reflects the cluster's initial conditions. In particular, the positions of the massive stars in the Trapezium cluster in Orion cannot be due to dynamical mass segregation, but indicate that they formed in, or near, the centre of the cluster. Implications of this for cluster formation and for the formation of high-mass stars are discussed. 相似文献
917.
918.
对我国东南陆缘地区的人工地震测深、大地电磁测深、重磁测量、地热测量、地学大断面编制以及天然地震的层析成像等大量深部构造研究结果作综合分析。地热异常、地壳内存在低速层和高导层、强烈地震频繁发生等现象说明,这一地区是现代构造运动的活动区。中国东南陆缘的现今应力场主压应力方向为NWW-SEE,认为是菲律宾板块对欧亚板块的挤压,以及冲绳海槽的扩张等联合作用的结果。因此,这一地区地壳运动的驱动力是太平洋板块和菲律宾板块向欧亚板块推挤产生的。 相似文献
919.
张赤军 《大地测量与地球动力学》1998,(2)
根据推导的公式计算了由山体质量引起的梯度效应,结果与实测值甚为接近。分析了佘山重力垂直梯度偏小的原因,认为这是由于山体质量分布引起的。最后讨论了垂直梯度偏小对重力值的高度归算和大地水准面的影响。 相似文献
920.
朱春华 《广东海洋大学学报》1998,(1)
用随机区组试验方法,比较四种不同的选育群体团头鲂的后代和一个对照群体团头鲂的生长性能。结果表明:在同一环境条件下,远交群体比近交群体生长优势明显(|xi-xj|>D0.01);亲本年龄大(3足龄)的群体后代生长性能优于亲本年龄小(2足龄)的群体后代(|xi-xj|>D0.05);对照群体团头鲂与近交群体后代生长性能相当。 相似文献