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671.
Some studies have shown that native Chinese speakers have different laterality in matched Stroop tasks from native English speakers. Recently, many imaging data, which show left laterality of English-matched Stroop interference, have been reported. And a few functional imaging studies have been conducted to investigate the phenomenon of the Chinese version of Stroop task. In this study, functional activity in the lateral prefrontal cortex of a group of normal Chinese boys with functional near-infrared imaging during a Stroop color-word task was measured to show different Stroop interferences in the prefrontal cortex. The results show obvious fluctuation of the cerebral blood volume in the right prefrontal cortex in all boys, which agrees with the finding of previous studies, that is, Chinese native boys have right laterality in their brain when the Chinese version of Stroop color-word task is applied.  相似文献   
672.
The morphology and organogenesis of Chinese giant salamander, Andrias davidianus, in its different developmental periods and stages are described in detail, which provides an intact criterion for distinguishing different stages of its developmental process. Based on the external morphological and internal histological features, six periods including 20 stages of organogenesis of Chinese giant salamander are established, which are cleavage period, blastula period, gastrula period, neurula period, organogenesis stage and hatching stage. Generally, the embryonic development of Chinese giant salamander is consistent with those of Eastern newt, Cynops orientalis, and Black spots frog, R. nigromaculata. However, they have some differences in the early cleavage process and the development of digestive system. The cleavage of Chinese giant salamander, A. davidianus is not a discoidal division type, which is different from other species reported. And the first three cleavages being meridional and a retardant development of its digestive system without halter and sucker existing are the evident features of the embryonic development of Chinese giant salamander.  相似文献   
673.
Some studies have shown that native Chinese speakers have different laterality in matched Stroop tasks from native English speakers.Recently,many imaging data,which show left laterality of English-matched Stroop interference,have been reported.And a few functional imaging studies have been conducted to investigate the phenomenon of the Chinese version of Stroop task.In this study,functional activity in the lateral prefrontal cortex of a group of normal Chinese boys with functional near-infrared imaging during a Stroop color-word task was measured to show different Stroop interferences in the prefrontal cortex.The results show obvious fluctuation of the cerebral blood volume in the right prefrontal cortex in all boys,which agrees with the finding of previous studies,that is,Chinese native boys have right laterality in their brain when the Chinese version of Stroop color-word task is applied.  相似文献   
674.
Local orthogonal transform for a class of acoustic waveguides   总被引:2,自引:0,他引:2  
There are some curved interfaces in acoustic waveguides. To compute wave propagation along the waveguides with some marching methods, flattening of the internal interfaces is needed. In this paper, a local orthogonal coordinate transform and an equation transform are constructed to solve the two-dimensional Helmholtz equation for the waveguides bounded by a flat top, a flat bottom and two curved internal interfaces with three layered media. The curved internal interfaces are flattened by the local orthogonal coordinate transform, and the corresponding transformed Helmholtz equation can be solved by some marching methods. This treatment can be extended in multilayered medium waveguides. The one-way reformulation based on the Dirichlet-to-Neumann (DtN) map is then used to reduce the boundary value problem to an initial value problem. Numerical implementation of the resulting operator Riccati equation uses a large range step method to discretize the range variable and a truncated local eigenfunction expansion to approximate the operators. This method is particularly useful for solving long range wave propagation problems in slowly varying waveguides with multilayered medium structure.  相似文献   
675.
Wolf spiders are predators in large quantities in the fields. How wolf spiders keep their dominant species status under long-period pesticide force? To answer this question, eight geographical populations of Pardosa pseudoannulata were used as materials to test the influence of geographical habitats on their genomic DNA polymorphism. The RAPD pattern showed polymorphic variations among and within different populations. Total 84 bands amplified by 10 random primers, of which 62 (73.81%) are polymorphic, were generated from 55 individuals of eight geographical populations. Meanwhile, Shannon’s index (Ho= 0.5177) showed a rich genetic diversity of P. pseudoannulata, and most of the genetic variation (64.24%) was found within populations. Multiple regression analysis suggested that it is the climatic variation (such as annual average temperature etc.) that results in adaptive eco-geographic differentiation, and it is the long-period pesticide force that speeds up the genetic differentiation of P. pseudoannulata which changed the genetic diversity of the population.  相似文献   
676.
Applying the wavelet theory and methods to investigate the hydrologic processes such as precipitation and runoff is a hot field. However, several aspects in research are usually ignored: the effect of admissible condition of wavelet functions and the disturbance of noises for the detection of periods, the effect of the length of a hydrologic time-series on the final result, and the choice between the anomaly and the original time series for wavelet analysis. In this paper, these issues are fully discussed. Precipitation data from Lanzhou Precipitation Station are taken for case study. The result indicates that in the wavelet analysis of hydrologic series, denoise methods should be used to eliminate the influence of noises. The MexHat wavelet function satisfies the admissible condition, which ensures that the periodic properties of hydrologic processes can be well represented by using the MexHat wavelet for decomposition. The affected range of hydro-logic series which should be discarded before analysis is given. It is also suggested that the anomaly series should be used to highlight the actual undulation of the hydrologic series.  相似文献   
677.
A new method is developed to calculate monthly CO emission data using MOZART modeled and MOPITT observed CO data in 2004. New CO emission data were obtained with budget analysis of the processes controlling CO concentration such as surface emission, transport, chemical transform and dry deposition. MOPITT data were used to constrain the model simulation. New CO emission data agree well with Horowitz’s emissions in the spatial distributions. Horowitz’s emissions are found to underes- timate CO emissions significantly in the industrial areas of Asia and North America, where high CO emissions are mainly due to the anthropogenic activities. New CO emissions can better reflect the more recent CO actual emissions than Horowitz’s.  相似文献   
678.
Zn(Ⅱ)-(NH4)2SO4-H2O体系浸出锌烟尘   总被引:2,自引:0,他引:2  
提出硫酸铵浸出法处理锌烟尘的新工艺。该工艺利用不同温度下锌在硫酸铵溶液中的溶解度的差别,先在高温下将锌浸入溶液然后降温冷却,使锌呈含F和Cl很低的复盐析出,然后回收。以株冶集团锌烟尘为试料,对浸出过程进行研究。研究结果表明:浸出温度和硫酸铵浓度显著影响锌的浸出率;最佳浸出条件是:液固比为16?1,硫酸铵浓度为4.0 mol/L,pH值为5.5,浸出温度为90℃,浸出时间为4 h,在该条件下,按渣含锌计算的浸出率达到85.16%。  相似文献   
679.
冯澎  易泰民 《北京科技大学学报》2007,29(10):1031-1032,1040
讨论了强激光场下单壁纳米管的声子增益效应. 采用含时微扰方法计算了不同温度下声子占据数随时间的变化率(声子增益系数). 计算结果表明,在强激光场下纳米管中的声子占据数随时间非线性增加,增益系数与温度和激光场强都有关系. 随着温度升高,声子增益系数迅速减小;在确定的温度情况下,激光场强越强,声子增益效应越明显,并对这个现象给出了合理的物理解释.  相似文献   
680.
固定式刚性联轴器不对中弯扭耦合振动特性   总被引:1,自引:0,他引:1  
以水轮发电机组固定式刚性联轴器平行不对中故障为研究对象,从动力学角度推导不对中机理,建立平行不对中弯扭耦合振动微分方程.基于该微分方程,理论上分析了弯振、扭振之间的相互影响;从转速、质量偏心、不对中量和阻尼系数等几方面进行弯扭耦合振动数值仿真.仿真计算表明:弯振与扭振通过固结于转子的偏心质量相互耦合;弯振主要包含工频成分,不对中越严重,工频所占比例越大.扭振包括极大的直流分量和少量倍频成分,过大的直流分量对机组安全不利.  相似文献   
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