Observations of plasma density structures in association with the passage of traveling convection vortices and the occurrence of large plasma jets

We report important results of the first campaign specially designed to observe the formation and the initial convection of polar cap patches. The principal instrumentation used in the experiments comprised the EISCAT, the Sondrestrom, and the Super DARN network of radars. The experiment was conducted on February 18, 1996 and was complemented with additional sensors such as the Greenland chain of magnetometers and the WIND and IMP-8 satellites. Two different types of events were seen on this day, and in both events the Sondrestrom radar registered the formation and evolution of large-scale density structures. The first event consisted of the passage of traveling convection vortices (TCV). The other event occurred in association with the development of large plasma jets (LPJ) embedded in the sunward convection part of the dusk cell. TCVs were measured, principally, with the magnetometers located in Greenland, but were also confirmed by the line-of-sight velocities from the Sondrestrom and SuperDARN radars. We found that when the magnetic perturbations associated with the TCVs were larger than 100 nT, then a section of the high-latitude plasma density was eroded by a factor of 2. We suggest that the number density reduction was caused by an enhancement in the O⁺ recombination due to an elevated T_i, which was produced by the much higher frictional heating inside the vortex. The large plasma jets had a considerable (>1000 km) longitudinal extension and were 200–300 km in width. They were seen principally with the Sondrestrom, and SuperDARN radars. Enhanced ion temperature (T_i) was also observed by the Sondrestrom and EISCAT radars. These channels of high T_i were exactly collocated with the LPJs and some of them with regions of eroded plasma number density. We suggest that the LPJs bring less dense plasma from later local times. However, the recent time history of the plasma flow is important to define the depth of the density depletion. Systematic changes in the latitudinal location and in the intensity of the LPJs were observed in the 2 min time resolution data of the SuperDARN radars. The effect of the abrupt changes in the LPJs location is to create regions containing dayside plasma almost detached from the rest of the oval density. One of these density features was seen by the Sondrestrom radar at 1542 UT. The data presented here suggest that two plasma structuring mechanisms (TCVs and LPJs) can act tens of minutes apart to produce higher levels of density structures in the near noon F-region ionosphere.     

Multi-instrument probing of the polar ionosphere under steady northward IMF

Observations are presented of the polar ionosphere under steady, northward IMF. The measurements, made by six complementary experimental techniques, including radio tomography, all-sky and meridian scanning photometer optical imaging, incoherent and coherent scatter radars and satellite particle detection, reveal plasma parameters consistent with ionospheric signatures of lobe reconnection. The optical green-line footprint of the reconnection site is seen to lie in the sunward plasma convection of the lobe cells. Downstream in the region of softer precipitation the reverse energy dispersion of the incoming ions can be identified. A steep latitudinal density gradient at the equatorward edge of the precipitation identifies the general location of an adiaroic boundary, separating the open field lines of polar lobe cells from the closed field of viscous-driven cells. Enhancements in plasma density to the south of the gradient are interpreted as ionisation being reconfigured as it is thrust against the boundary by the antisunward flow of the viscous cells near noon. Each of the instruments individually provides valuable information on certain aspects of the ionosphere, but the paper demonstrates that taken together the different experiments complement each other to give a consistent and comprehensive picture of the dayside polar ionosphere.On sabbatical leave from Artic Geophysics, University Courses on Svalbard, N-9170 Longyearbyen, Norway     

A mixed continuous and discrete nonlinear constrained algorithm for optimizing ship hull structural design

A nonlinear search algorithm for optimizing constrained design of ship structures is presented. The decision variables can be continuous or discrete and the constraints can be homogeneous or inequality nonlinear functions of those variables. The algorithm does not use gradients; therefore, it can work with non-systematized functions such as tables or another class of design routine. It was tested in the structural design of a Patrol Boat and has proved to be a powerful tool decreasing the time expended in preliminary design when it is done by the conventional spiral approach.     

Application of extended state space to nonlinear ship rolling

It is well known in the field of marine hydrodynamics that the added mass, damping and wave exciting forces are functions of frequency (Newman, 1977. Marine Hydrodynamics. MIT Press, Cambridge). Although most previous studies of nonlinear ship rolling motion have assumed that these forces do not vary with frequency, in this study the frequency dependent added mass and damping coefficients are approximated in the time domain with extended state space variables. Using numerical time simulation (integration), the extended state space model is compared to the constant coefficient model with a constant frequency forcing and the results for two constant value approximations of the added mass and damping are compared to the extended state space model with a multiple component pseudo random forcing.     

合浦珠母贝人工诱导四倍体的研究

用细胞松驰素B（CB）、聚乙二醇（PEG）和静水压抑合浦珠母贝Pinctadamarlensii（D．）制第1次卵裂以及CB抑制极体形成诱导四倍体。CB抑制第1次卵裂在早期胚胎2-4细胞阶段发现四倍体,但8细胞阶段以后四倍体胚胎消失。PEG和PEG＋CB能诱导细胞融合产生四倍体,但处理组幼虫在担轮期死亡。CB抑制极体形成能诱导出较高比例的四倍体,在胚胎初期和担轮幼虫期分别占40％和30％以上。处理组幼虫进行培育,附苗后当贝苗长成4-5cm大小时通过鳃细胞染色体倍性检查,却没有发现四倍体。文中对四倍体是否能成活进行了讨论。     

Dayside ionospheric response to changes in IMF polarity: optical and plasma-flow observations

The response of the dayside ionosphere to changes in polarity of the interplanetary magnetic field was observed by two independent techniques. The signatures were seen in the 630.0 nm red-line emission, measured by a meridian scanning photometer at Ny-Ålesund on Svalbard, and also in the line-of-sight plasma velocities monitored by the Finland CUTLASS SuperDARN radar. A time difference of some 6 to 8 min occurred between the responses of the two techniques, with the flows being first to respond. In the present case study, the longer delay in the optics suggests that ion precipitation controls the auroral emission.     

三峡水库蓄水引起的地球自转扰动

本文利用较精细的三峡水库水负荷时空分布模型,模拟了该水库在蓄水阶段和蓄水后,水负荷激发的极移和地球引力位二阶球谐系数的变化。数值结果表明,蓄水过程中极移和δJ2呈现准长期变化,幅值不断增加,在蓄水阶段的2000—2009年,线性回归的极移速率为0.042mas/a,方向为73.6°W,δ2为0.025×10-12a-1,分别是全球其他88个较大型水库引起的准长期效应的8.4%和2.5%。     

大型环流演变与台风生成预报

对北半球涡位置和强度,东亚西风强度指数及南半球大气环流变化的特征与台风活动的一些观测事实进行了研究,从中得出一些用于台风生成的预报依据。     

Polar Mohr diagram method and its application in calculating the shear displacements of general shear zones with volume loss

The main problem, in determining the shear displacement of a general shear zone with volume change using the available formula, is that it is hard to know the initial angle between the planes (or lines) in the plane of shear. A planar deformation analysis of this kind of ductile shear zone is carried out with the polar Mohr diagram. If the volume change is induced by homogeneous contraction in the Z direction of the shear zone, there are sufficient conditions for constructing a polar Mohr diagram regardless of sequence of the simple shear and volume change. Therefore, the angle between a line and the shear direction before and after the deformation can be measured. Making use of these lines the shear strain and the volume change can be calculated and the shear displacement can be determined.     

船舶噪声对浅海海洋环境噪声空间相关的影响

通过对2001年亚洲海国际声学实验(ASIAEX)得到的海洋环境噪声数据进行处理,计算了噪声场空间相关系数、功率谱密度和垂直指向性,分别研究了受到远距离和近距离船舶辐射噪声影响的海洋环境噪声空间相关性.结果表明:船舶距离较远(10 km)时其辐射噪声会导致500 Hz以下的海洋环境噪声的空间相关性提高,而对500 Hz以上噪声的空间相关性没有影响;船舶距离较近(≤10 km)时,船舶辐射噪声会导致500 Hz以下的海洋环境噪声相关系数振荡变化,噪声空间相关性曲线在噪声信号声程差相差四分之一波长时出现第一个零点,对500 Hz以上的海洋环境噪声则会引起噪声能量升高,噪声的空间相关性也相对提高.基于现有理论,分别讨论了远距离船舶和近距离船舶产生的噪声场声学特性,对两种噪声场的海洋环境噪声空间相关性进行了合理的解释.