风成沙纹形成的风洞模拟研究

风成沙纹形成于沙质床面下游的沙粒蠕移,发展于沙粒跃移－风沙流的“波粒二重性”作用,消亡于气流与风沙流的正弦波共振。以细沙和极细沙为优势粒级的天然沙丘沙是风成沙纹形成的最佳粒配。沙纹移动速度ＶＲ是缓慢的,其数量级为１０－１ｃｍ·ｍｉｎ－１～１０１ｃｍ·ｍｉｎ－１,实验关系式为：ＶＲ＝１．５８×（ＶＬ－５．５）０．６７。     

毫米级高精度海水声速测量技术研究

介绍一种毫米级高精度海水声速测量技术的原理、关键技术和实验结果。     

An analytical study on the second-order resonance system of tide in an ideal partially-enclosed bay

In the numerical studies of a real tide M4 resonance system, the Xiangshan Port which is a partially-closed bay, Dong et al. [1999. Acta Oceanologica Sinica, 21 （3）： 1-6] found the interesting phenomenon that the advection plays an important role in inhibiting the growth of the amplitude of the tidal second-order resonance response （M4）. This result is contrary to the general traditional ideas for a non-resonance system. How this phenomenon is interpreted and what internal mechanism is behind the phenomenon are the main focuses of this study. The followings are examined： （1） the dynamic features of a second-order resonance system of tide; （2） the dominating factors on the second-order resonance responses; （3） the effects of both the friction and the advection on the second-order resonance responses; and （4） their roles in dominating the second-order resonance response and internal mechanisms by using the analytical methods. The respective results show that： （1） Both the bottom friction and the advection play significant roles in dominating the magnitude of the amplitude of the second-order resonance responses; （2） the effect of the friction on the second-order resonance response depends on the distribution ratio of the work-done of the system to friction force exhausted into between the damping of the first-order system and the inner excitation of the second-order system; （3） the advection plays a positive role in increasing the amplitude of the second-order non-resonance response in the second order non-resonance of tide; （4） in a second-order resonance system of tide, the effect of the advection may be either to increase or to decrease the amplitudes of the second-order resonance responses of tide, which depends on the distribution ratio mentioned above.     

地球磁层中超低频波与低能粒子的相互作用

太阳风—磁层耦合过程会产生各种等离子体波,其中超低频波的频率最低(1 mHz～1 Hz)、波长最长(与内磁层磁力线长度相当)、能量密度最大.超低频波在磁层粒子加速、物质输运和能量转化中起着重要作用.以往的研究主要关注超低频波的全球性传播和分布特征以及这些波动与磁层能量粒子(辐射带电子和环电流离子)的相互作用过程.最近几...     

悬空管线的振动特性分析

埋地管线穿河段由于河水冲刷而悬空，在水流作用下诱发涡激振动。本文在实测悬空管线固有频率的基础上，提出了其固有频率的计算方法。按本文方法所得结果和实测结果基本吻合。     

GJ 876行星系统中潜在类地行星研究

用数值积分方法模拟探讨了GJ876行星系统中存在潜在类地行星的可能性．结果表明分别产生于内外两颗巨行星的长期共振v_1和v_2可激发类地行星(其轨道半长轴分布在0．21AU≤a＜0．50AU之间)的偏心率,并使它们在极短时间内被抛射出系统．然而,从动力学角度而言,类地行星潜在存在区域可分布在0．50 AU≤a≤1．00 AU之间,其能在系统中10~5年时间尺度上稳定地存在．     

共振光猝灭法测定环境水样中痕量硒

在阿拉伯树胶(AG)存在下,0.14 mol/L硫酸介质中,硒(Ⅳ)与过量的I-反应生成I3-,加入乙酸钠后I3-与亚甲基蓝反应成离子缔合物,在波长288 nm处共振光猝灭,建立了共振光散射法测定痕量硒的方法.确定了碘化钾、亚甲基蓝、乙酸钠和增溶剂阿拉伯树胶溶液的浓度,在室温(20～30℃)下反应15 min,提高了体...     

http://www.sciencedirect.com/science/article/pii/S1674987113000091

The current lithospheric geodynamics and tectonophysics in the Baikal rift are discussed in terms of a nonlinear oscillator with dissipation.The nonlinear oscillator model is applicable to the area because stress change shows up as quasi-periodic inharmonic oscillations at rifting attractor structures （RAS）.The model is consistent with the space-time patterns of regional seismicity in which coupled large earthquakes,proximal in time but distant in space,may be a response to bifurcations in nonlinear resonance hysteresis in a system of three oscillators corresponding to the rifting attractors.The space-time distribution of coupled MLH ＞ 5.5 events has been stable for the period of instrumental seismicity,with the largest events occurring in pairs,one shortly after another,on two ends of the rift system and with couples of smaller events in the central part of the rift.The event couples appear as peaks of earthquake ‘migration＇ rate with an approximately decadal periodicity.Thus the energy accumulated at RAS is released in coupled large events by the mechanism of nonlinear oscillators with dissipation.The new knowledge,with special focus on space-time rifting attractors and bifurcations in a system of nonlinear resonance hysteresis,may be of theoretical and practical value for earthquake prediction issues.Extrapolation of the results into the nearest future indicates the probability of such a bifurcation in the region,i.e.,there is growing risk of a pending M ≈ 7 coupled event to happen within a few years.     

涡激致顶张力立管双频参量共振研究

研究了涡激力作用导致顶张力立管基于双频激励的参量共振机理。随着海洋油气开发走向深水,参量共振成为深海立管设计面临的挑战之一。立管系统一旦发生参量共振,将因应力过大或疲劳损伤而发生破坏,造成油气泄漏从而带来环境污染和重大经济损失。顶张力立管受涡激力作用产生横向运动,引起轴向张力波动,满足一定条件时,立管将发生参量共振。目前研究多以单频外激励探讨立管的马修不稳定性,而实际激励为多频叠加,因此双频外激励被提出并被应用于对立管参量稳定性的探讨。研究建立了顶张力立管非线性耦合的运动方程,并推导了多频激励马修方程,采用布勃诺夫-伽辽金法求解有阻尼马修方程,对比分析了单频和双频激励对顶张力立管参量稳定性的影响,探讨了双频激励马修方程设计深海顶张力立管参量稳定性的应用。研究表明:涡激致顶张力立管产生轴向应力波动,进而导致立管系统发生参量共振的现象值得设计人员关注;此外,实际工程设计中激励函数的选取,对被研究系统参量稳定性特性以及阻尼特性的预测具有决定性影响。     

围压对粉质粘土动力学参数影响的共振柱试验研究

土的最大动剪切模量、剪应变幅和阻尼比是对土层进行动力反应分析的重要力学参数。利用英国GDS公司生产的RCA共振柱仪,研究围压对都江堰地区粉质粘土的上述动力学参数的影响。研究表明：相同围压条件下,最大动剪切模量、剪应变幅和阻尼比随重复次数基本不变,表明该试验过程具有可重复性;最大动剪切模量、剪应变幅和阻尼比均受围压影响较大,随着围压的增大,最大动剪切模量和阻尼比均逐渐增大,而剪应变幅随着围压的增大逐渐减小。据此,建立了都江堰地区粉质粘土动力学参数随围压变化的经验公式。本研究可为土层地震动力反应分析提供参考并积累基础资料。