基于半球支承的静电悬浮方法

提出了一种基于半球静电支承的静电悬浮方法,该方法既可任意调节转子与电极之间的间隙,又便于观测转子的摆动情况,从而实现高精度球形转子的平衡测量.通过计算半球静电支承下球形转子与电极之间的间隙,导出了静电力与间隙的关系.在分析了半球静电支承特性的基础上,将其工作状态分为起支和支承2种状态,并设计了相应的数字控制器,保证系统可靠悬浮.试验结果表明,半球静电支承系统能稳定工作,可以满足高精度球形转子平衡测量的要求.     

Experimental investigation of supersonic flow over a hemisphere

The experimental investigation of supersonic flow over a hemisphere was conducted using Nanoparticle-based Planar Laser Scattering(NPLS) technique in a supersonic quiet wind tunnel at Ma=2.68.Ahead of the hemisphere,boundary layer separation with the formation of a three-dimensional separated flow was observed,which was resulted from the interaction between the three-dimensional bow shock wave and the boundary layer.The complex flow structures of supersonic flow over the hemisphere were visualized.Based on the time correlation of NPLS images,time-space evolutionary characteristics of supersonic flow over the hemisphere were studied,and the evolutionary characteristics of the spanwise and streamwise large scale vortex structures were obtained,which have the features of periodicity and similar geometry.     

Possible blindsight in infants lacking one cerebral hemisphere.

Patients with damage to the striate cortex have a subjectively blind region of the visual field, but may still be able to detect and localize targets within this region. But the relative roles in this 'blindsight' of subcortical neural systems, and of pathways to extra-striate visual areas, have been uncertain. Here we report results on two infants in whom one cerebral hemisphere, including both striate and extra-striate visual cortex, needed surgical removal in their first year. Single conspicuous targets in the half-field contralateral to the lesion could elicit fixations, implying detection and orienting by a subcortical system. In contrast, binocular optokinetic nystagmus (OKN), for which a subcortical pathway has often been thought adequate, showed a marked asymmetry. In normal neonates, fixation shifts and OKN have both been taken to reflect subcortical control; our results are consistent with subcortical control for fixation but not for OKN.     

地磁静日北半球电离层电子密度的反演

利用北半球IGS观测站提供的150个GPS观测资料,结合三维电离层层析方法,反演了平静日下北半球上空电离层电子密度的变化特征.结果表明:整个研究区域电子密度在不同纬度和不同高度上存在明显的日变特征,在0°经度剖面上,电子密度最大值出现在世界时13-15时,随着时间推移,峰值幅度衰减;在北纬20°附近,世界时11～ 13时电子密度出现双峰值;北纬50°～80°范围,电子密度无大的起伏;反演结果说明了电离层三维层析技术为监测电离层时空结构提供了一种强有力的实验支持.     

Left hemisphere advantage in the mouse brain for recognizing ultrasonic communication calls

In humans, sound perceived as speech is processed preferentially by the right ear and the left hemisphere of the brain. Among animals, such an advantage of one hemisphere (lateralization) in processing communication sound from other members of the species has so far been demonstrated only in macaque monkeys. I report here that in the house mouse, which has a very much less elaborate forebrain than man or macaque monkey, the ultrasonic calls that are emitted by young mice to evoke maternal caring behavior are preferentially recognized by the left hemisphere. In females with no experience of pups, which have been trained to respond to the same ultrasonic calls by conditioning, no advantage for one hemisphere is detected. The results suggest that lateralization of this function evolved early in mammals and emphasize that an innate predisposition for perceiving communication sounds is connected with a left-hemisphere advantage in processing them. This experimental system is a readily-available animal model for studying lateralized auditory brain functions.     

南半球竖直上抛落地偏差之研究

地球既有自转又有公转,所以是非惯性参考系.在自转过程中可以认为它的角速度是沿着地轴的一个恒矢量.因而只需考虑惯性离心力和科里奥利力所产生的影响.本文就是通过科里奥利力效应研究南半球竖直上抛物体的落地偏差问题,并给出一种解法及其精确解.     

北半球仲春平流层行星波活动对臭氧总量分布的影响

采用NCEP/NCAR再分析资料和TOMS臭氧总量资料,分析了1979～2003年4月份平流层行星波1波和2波的变化,及其对北半球中高纬臭氧总量分布的影响.结果表明,在通常情况下,4月份平流层中下层行星波1波强于2波,对应的位势高度场在欧亚大陆北部为一低压涡旋,而北美北部为一高压区.此时,从东北亚到北加拿大为臭氧总量的高值区,而北欧至格陵兰一带为臭氧的低值区.但在有些年份,2波比较强时,相应的位势高度场在极地为一明显的低压涡旋,此时在极地附近会出现臭氧低值区.个别年份如1997年,1波在25年中最强,2波也很强,强低涡中心比常年更靠近北极点,在与之位置相同的地方出现了25年中最明显的臭氧洞.还有一些年份,北极地区主要由高压控制,臭氧总量的高值区基本上出现在北极及其附近.     

剖析半球体偏离平衡位置的微振动

利用机械振动的基本理论以及刚体的相关知识,通过举例分析了非固定轴情况下的刚体系统偏离平衡位置的微振动,剖析错误认知的根源所在,主要问题在于讨论刚体总的机械能时,计算动能部分选择的质心是半球体的球心,而计算势能部分选择半球体的质心,标准不统一所致.利用机械能守恒定律的方法,探讨半球体做简谐振动,仅需大学物理或普通物理学中经典力学知识就可以,降低解析问题的门槛、简化了解题的步骤,避开了用到理论力学中的拉格朗日函数等知识点.通过对错误解答的剖析,有助于加深对刚体、简谐振动等相关基本知识和概念的理解.     

Correlative ionospheric disturbances in the sunlit hemisphere during the flare on July 14, 2000

Using GPS data obtained from GPS sites located on the sunlit hemisphere during the flare on July 14, 2000, the ionospheric response to the flare was analyzed. A kind of tiny correlative ionospheric fluctuations were revealed from the temporal total electron content (TEC) curves derived from GPS measurements, and the values of this kind of disturbances are about 1015 m-2. A comparative analysis of these disturbances and soft X-ray flux detected at GOES satellite during the flare is done. It is found that this kind of disturbances revealed in the temporal TEC curves did occur in a very large area of sunlit ionosphere and its behavior is mainly controlled by the characteristics of the flare's extra radiation. Because the similar fluctuations are not found in the curve of soft X-ray flux, it is concluded that the flare extra radiation in EUV band should have corresponding fluctuations and it is the fluctuations that cause the TEC disturbances. The height, where the disturbances occur, should be in the F region.     

北半球地面O3的区域分布和变化特征

利用来自GAW(Global Atmosphere Watch,全球大气监测)的、由WDCGG(World Data Centre for Greenhouse Gases,世界温室气体数据中心)收集整理和发布的、基于地基观测的北半球共15个站点的地面O3含量的逐月观测资料以及逐时观测资料,分析、对比并总结了北半球不同经纬度各区域的地面O3含量的年变化和各个季节的日变化规律.研究表明:内陆比较清洁地区的地面O3多年月平均变化曲线为单峰型,接近正弦曲线的形状,最高值出现在4月份,最低值出现在10月份;而空气污染比较严重的地区可能会发生出现推迟一个月峰值的情况,甚至出现连续多个月份浓度均较高的情况.而位于20°N～35°N的洋面以及海岸线上的站点均在夏季出现全年最低值.对于4个季节的平均日变化而言,清洁地区的日变化很小,曲线比较平直;而污染比较严重的区域则日变化明显,曲线弯曲幅度大,其中夏天的日变化差别最明显.为进一步分析地面O3含量的长期变化,我们还运用小波分析的方法,分析了各站点地面O3含量的变化周期,发现高纬度区域的地面O3表现出明显的准11年的周期,准2年周期振荡较弱.而其他纬度相对较低的区域和洋面上的站点则未看出有明显的准11年周期,表现出的是较明显的准2年周期振荡.     

利用立体角求解带电半球面球心处的场强

为了求解均匀带电半球面球心处的场强,采用立体角的方法来处理此问题,结果表明:采用立体角的方法来求解决均匀带电半球面球心处的场强与使用分割带电体直接积分方法处理此问题虽然采用的方法不同,但可以得到相同的结果,与分割带电体直接积分方法相比,使用立体角的方法来求解此问题更为简便.该方法为处理均匀带电体场强问题的求解提供了新的思路,使此类问题从新的角度得到了更为简便的解决方法,并且可以为求解均匀带电球面、球冠、柱面的场强等相关类型的问题提供可参考的研究方法.     

Early scale effect and hemisphere superiority on the visual spatial attention: From the electrophysiological evidence of ERP

The visual attention mechanism in the brain was studied among 16 young subjects through the precue-target visual search paradigm using the event-related potentials (ERPs) technique, with the attentive ranges cued with different scales of Chinese words. The results showed that the response time was shortened as the cue scale was reduced, while the amplitudes of the P1 and N1 components of the ERPs increased. These results not only provided the electrophysiological evidence supporting the spotlight theory, but also indicated that the spotlight effect occurred during the early period of the selected attention. Two kinds of separation in the P2 effect were observed. One separation was between the P1 effect and P2 effect, which meant that additional computation was needed when the spatial scale of attention was enlarged; the other was between the left and right hemisphere of the P2 effect, which indicates that the attentive processing of the cue range mainly occurred in the left hemisphere.