Intermittent chaos in nonlinear wave–wave interactions in space plasmas

There is increasing observational evidence of nonlinear wave–wave interactions in space and astrophysical plasmas. We first review a number of theoretical models of nonlinear wave–wave interactions which our group has developed in the past years. We next describe a nonlinear three-mode truncated model of Alfvén waves, involving resonant interactions of one linearly unstable mode and two linearly damped modes. We construct a bifurcation diagram for this three-wave model and investigate the phenomenon of intermittent chaos. The theoretical results presented in this paper can improve our understanding of intermittent time series frequently observed in space and astrophysical plasmas.     

热带西太平洋海温距平与Rossby波传播对1993和1994年东亚夏季风异常影响的差异

利用NCEP/NCAR再分析资料、Hadley中心海温资料与降水资料,分析了1993和1994年东亚夏季风异常的天气气候特征以及大气环流的差异.分析结果表明: 1993年东亚夏季风弱,副热带西风急流和副热带高压位置偏南,来自于孟加拉湾和南海的水汽仅输送到35°N以南地区.东亚地区出现低温凉夏天气.1994年东亚夏季风强,副热带西风急流和副热带高压位置偏北,7～8月副高持续偏强并控制日本,水汽可以输送到45°N以北的较高纬度,东亚发生破纪录的热浪干旱.对1993和1994年东亚夏季风异常物理过程差异的研究发现,副热带西风急流中静止Rossby波的传播和热带西太平洋暖池海温距平激发出来的PJ型遥相关波列作用的叠加引起1994和1993年东亚夏季风异常差异.     

An Interpretation of ISO Guidelines for the Certification of Geological Reference Materials

Recommendations for the certification of reference materials, as published by the International Organisation for Standardisation (ISO), are reviewed and proposals made as to how they can be adapted for the certification of new geological reference materials. Whilst acknowledging the important contribution made by the large number of existing matrix-matched geological reference materials, it is recommended that future characterisation programmes should follow the ISO guidelines for certification, not the least so that laboratories can readily use the resultant samples to establish the traceability of geoanalytical results.     

电磁波井间CT成象技术及其在岩土工程中的应用

简要叙述了电磁波ＣＴ成象技术的基本原理、工作方法及其在岩土工程中诸如机场跑道、隧道工程和高层建筑地基评价中的应用。通过井下激发和观测电磁波能量的衰减，利用ＣＴ技术重建了地下介质在观测平面内相对吸收系数的二维分布图象，这些图象直观准确地反映出地下介质的构造形态、地层界面、风化壳以及破碎带的分布特征，在岩土工程探测中发挥了重要作用。     

有效吸收和传递波浪能的锚泊系统的设计制作

将传统定位浮标加以改进,可以形成一种能有效吸收和传递波浪能的锚泊系统。此系统的最上端是漂浮着的海面浮标,海面浮标下端连着锚泊钢缆,锚泊钢缆下端到海底之间又依次连有张紧锤、储链和重物锚块。锚泊系统中的海面浮标随波浪同步上下起伏,从而带动与其连在一起的由张紧锤绷直的锚泊钢缆上下振动,于是海面浮标吸收波浪能并由引导缆向下传递。20 m长的储链可以保证整个装置在涨潮、退潮的极限水深情况下,仍旧可以有效地传递海表面波浪能;合适的重物锚块可以起到为整个系统定位的功能。最后给出了一个实际应用波浪能的例子。设计制作的锚泊系统可以有效吸收和传递波浪能,为波浪能的利用提供了一种行之有效的方法。     

煤岩动静力学参数关系试验研究

煤岩的动、静力学参数关系的试验研究,对研究煤岩的位移和变形特征及工程支护设计具有重要意义。将取自新河煤矿3煤的煤样加工成Φ50 mm×100 mm的圆柱体标准试件;采用500 kHz频率的纵横波换能器分别进行纵横波速度测试;在MTS815.03电液伺服试验机上进行单轴压缩试验,得到静态弹性模量和泊松比。试验结果表明:煤岩动弹性模量与横波速度相关性强于与纵波速度的相关性,煤岩介质的纵波对孔隙和裂隙发育程度的敏感程度要比横波高;煤岩试件Ed/Es比值主要集中在1.4~1.7,室内煤岩试件动、静弹性模量和动静泊松比之间存在较好的线性相关关系。     

1961—2019年青藏高原中东部夏季强降水与大尺度环流的关系

采用一元线性回归、合成分析等方法对1961—2019年青藏高原中东部71个站点夏季强降水与大尺度环流进行了分析,研究结果表明,近年来青藏高原中东部强降水呈增加趋势。在强降水高值年时,青藏高原中东部水汽辐合加强,中纬度西风和热带地区东风带向极移动加强,高层辐散流场、水汽输送以及上升运动条件,共同作用导致了强降水的产生。在强降水低值年时,青藏高原中东部大部水汽异常辐散,区域内的季风水汽输送减弱,西风带和东风带均向赤道移动减弱,高层为气旋式环流异常。通过风暴轴、波作用通量和E-P通量进一步分析发现,当北大西洋地区风暴轴偏强（偏弱）时,瞬变扰动作用加强（减弱）,使得北大西洋地区高纬度西风加速（减弱）,急流出口区的不稳定能量激发了欧洲西北部的异常反气旋（异常气旋）,并通过Rossby波列调控季风输送,导致了青藏高原中东部地区强降水的变化。     

scattering and refracting of plane strain wave by a cylindrical inclusion in fluidsaturated soils

ＳｃａｔｅｒｉｎｇａｎｄｒｅｆｒａｃｔｉｎｇｏｆｐｌａｎｅｓｔｒａｉｎｗａｖｅｂｙａｃｙｌｉｎｄｒｉｃａｌｉｎｃｌｕｓｉｏｎｉｎｆｌｕｉｄｓａｔｕｒａｔｅｄｓｏｉｌｓＹＡＹＵＡＮＨＵ（胡亚元）ＬＩＺＨＯＮＧＷＡＮＧ（王立忠）ＹＵＮＭＩＮＣＨ...     

A Modified Form of Mild-Slope Equation with Weakly Nonlinear Effect

Nonlinear effect is of importance to waves propagating from deep water to shallow water.Thenon-linearity of waves is widely discussed due to its high precision in application.But there are still someproblems in dealing with the nonlinear waves in practice.In this paper,a modified form of mild-slope equa-tion with weakly nonlinear effect is derived by use of the nonlinear dispersion relation and the steady mild-slope equation containing energy dissipation.The modified form of mild-slope equation is convenient to solvenonlinear effect of waves.The model is tested against the laboratory measurement for the case of a submergedelliptical shoal on a slope beach given by Berkhoff et al,The present numerical results are also comparedwith those obtained through linear wave theory.Better agreement is obtained as the modified mild-slope e-quation is employed.And the modified mild-slope equation can reasonably simulate the weakly nonlinear ef-fect of wave propagation from deep water to coast.     

Change of multifractal thermal characteristics in the western Philippine sea upper layer during internal wave-soliton propagation

The upper layer (above 140 m depth) temperature in the western Philippine Sea near Taiwan was sampled using a coastal monitoring buoy (CMB) with 15 attached thermistors during July 28–August 7, 2005. The data were collected every 10 min at 1, 3, 5, 10, 15, and 20 m using the CMB sensors, and every 15 sec at 15 different depths between 25 m and 140 m. Internal waves and solitons were identified from the time-depth plot of the temperature field. Without the internal waves and solitons, the power spectra, structure functions, and singular measures (representing the intermittency) of temperature field satisfy the power law with multi-scale characteristics at all depths. The internal waves do not change the basic characteristics of the multifractal structure. However, the internal solitons change the power exponent of the power spectra drastically, especially in the low wave number domain; they also break down the power law of the structure function and increase the intermittency parameter. The physical mechanisms causing these different effects need to be explored further.