基于最小二乘支持向量机的声速空间变化模型构建

建立声速空间变化模型是解决声速剖面代表性误差的有效方法。在对不同声速剖面进行标准化处理的基础上,通过声速训练样本及核函数的选取,提出并实现了一种基于最小二乘支持向量机算法的声速空间变化模型构建方法。为了检验该方法的有效性,选取实测的声速剖面数据进行验证,结果表明该方法能有效地构建声速空间变化模型,从而消除或最大限度地削弱声速剖面代表性误差。     

基于Argo浮标和EOF建立区域海水三维声速场的方法

本文提出了一种利用Argo浮标数据和经验正交函数(EOF)建立区域海水三维声速场的方法。利用局部区域内的Argo观测数据对该方法进行了验证,利用少量Argo浮标数据即可建立精度较高的三维海水声速场模型,预测区域内任意剖面的中误差在1 m/s左右。     

声速误差对圆走航水下控制点定位影响分析

针对圆走航定位声速剖面测量不准确引起水下控制点坐标解算存在偏差的问题,首先介绍了声速不确定性对测距误差的影响,并将声速测距误差分成背景声速剖面误差、随机误差、测距误差长周期项和测距误差短周期项,再通过分析坐标改正数方程得到不同声速测距误差项对控制点坐标定位的影响。最后,设计2组仿真实验对该理论进行验证,实验结果与理论推导的结论一致。     

Ab initio elasticity of FeS2 pyrite from 0 to 135 GPa

Polynomial expressions for the elastic tensor coefficients, the bulk, the shear and Young’s moduli, the speed of sound for longitudinal and transverse waves, the equation of state and the x coordinate of the sulfur atom in pyrite are reported based on ab initio calculations in the range of 0–135 GPa. Comparison with published experimental data indicates good agreement for the equation of state and for values at 0 GPa as well as reasonable agreement for first derivatives. All modeling and interpretation was performed with Materials Toolkit v.2.0 and all ab initio computations with VASP.     

公路隧道施工中的环境保护问题探讨

公路隧道施工中涉及到的环境问题包括生态环境、空气环境和声环境等方面，详细分析了公路隧道施工中对各种环境的影响，并提出了相应的环保措施。     

Determining hydraulic resistance in gravel‐bed rivers from the dynamics of their water surfaces

Traditionally, approaches to account for the effect of the boundary roughness of a gravel‐bed river have used a grain‐size index of the bed surface as a surrogate for hydraulic resistance. The use of a single grain‐size does not take into account the spatial heterogeneity in the bed surface and how this heterogeneity imparts resistance on the flow, nor the way in which this relationship changes with variables such as flow stage. A new technique to remotely quantify hydraulic resistance is proposed. It is based on measuring the dynamics of a river's water surface and relating this to the actual hydraulic resistance created by a rough sediment boundary. The water surface dynamics are measured using a new acoustic technique, grazing angle sound propagation (GRASP). This proposed method to measure hydraulic resistance is based on a greater degree of physical reasoning, and this is discussed in the letter. By measuring acoustically the temporal dynamics of turbulent water surfaces over a water‐worked gravel bed in a laboratory flume, a dependency is demonstrated between the temporal variation in the reflected acoustic pressure and measured hydraulic resistance. It is shown that the standard deviation in acoustic pressure decreases with increasing hydraulic resistance. This is shown to apply for a range of relative submergences and bed slopes that are typical of gravel‐bed rivers. This remote sensing technique is both rapid and inexpensive, and has the potential to be applied to natural river channels and to other environmental turbulent flows, such as overland flows. A whole new class of low‐cost, remote and non‐intrusive instruments could be developed as a result and used in a wide range of hydraulic and hydrological applications. Copyright © 2006 John Wiley & Sons, Ltd.     

琉球群岛附近海域声场分析

利用美国海军的GDEM(generalized digital environm ental model)数据对琉球群岛附近海域声场进行了研究,分析了该海域声速最小值分布及其对应深度的分布规律;研究了横跨和穿越宫古水道两个断面上上述声场特征的变化,结果表明杭州湾以北的沿岸约30m地形等深线内,冬、春、秋季声速最小值出现在海面,并且有较为稳定的表面声道;夏季闽浙沿岸约30m地形等深线内,声速最小值出现在海面.奄美群岛、冲绳岛东侧130km范围内有很强的海水混合,上升流很明显,导致声速最小值出现的深度在冬夏比在春秋的深400m.     

A critical review of the potential impacts of marine seismic surveys on fish & invertebrates

Marine seismic surveys produce high intensity, low-frequency impulsive sounds at regular intervals, with most sound produced between 10 and 300 Hz. Offshore seismic surveys have long been considered to be disruptive to fisheries, but there are few ecological studies that target commercially important species, particularly invertebrates. This review aims to summarise scientific studies investigating the impacts of low-frequency sound on marine fish and invertebrates, as well as to critically evaluate how such studies may apply to field populations exposed to seismic operations. We focus on marine seismic surveys due to their associated unique sound properties (i.e. acute, low-frequency, mobile source locations), as well as fish and invertebrates due to the commercial value of many species in these groups. The main challenges of seismic impact research are the translation of laboratory results to field populations over a range of sound exposure scenarios and the lack of sound exposure standardisation which hinders the identification of response thresholds. An integrated multidisciplinary approach to manipulative and in situ studies is the most effective way to establish impact thresholds in the context of realistic exposure levels, but if that is not practical the limitations of each approach must be carefully considered.     

Sound speed dispersion characteristics of three types of shallow sediments in the southern yellow sea

To accurately characterize sound speed dispersion of shallow sediments in the Southern Yellow Sea, three types of sediments, i.e., silt, clayey silt, and silty clay, were selected to measure the sound speeds at 25–250?kHz. Over the frequency range, the sound speeds vary approximately from 1,536 to 1,565?m?s^?1 in silt sediment, from 1,511 to 1,527?m?s^?1 in clayey silt sediment, and from 1,456 to 1,466?m?s^?1 in silty clay sediment. The sound speed exhibits a slow increase with frequency in a nearly linear gradient, but these three types of sediments have different sound speed dispersion characteristics. The silt sediment with relatively coarse grains has the most significant sound speed dispersion, while the sound speed dispersions of the two others are relatively weak. Comparison between the measured dispersions and the model predictions shows that the grain-shearing model can match the measured data at most of frequencies. Nevertheless, when the grain bulk modulus was assigned 3.2?×?10¹⁰?Pa according to relevant references, the Biot–Stoll model predictions were higher than the measured values at high frequencies; when it was assigned a relatively small value of 2.8?×?10¹⁰?Pa, the model predictions achieved optimal matching with the measured values.     

海洋岛附近海域春季海洋水文测量结果分析

利用2006年4月在海洋岛附近海域的CTD测量资料,系统分析了该海域温度、盐度、密度和声速的平面分布和垂直分布特征,并探讨了其形成机理。分析指出:4月份是海洋岛附近海域季节性跃层的生成期,海区会产生正跃层、逆跃层、冷中间层、暖中间层等复杂的垂直结构;中间层和底层水文要素受海流的影响较大,而表层水文要素主要受海面风场和气温的影响。