海底入射角对多波束反向散射强度的影响及其改正

综合考虑测船姿态、声线弯曲和海底地形对入射角的影响,推导了计算多波束海底入射角的实用模型。根据Lambert法则,改正海底入射角对反向散射强度的影响。实例计算结果表明,所述模型能精确地计算波束在海底的入射角,有效地改正其对反向散射强度的影响。     

Artificial neural network model for prediction of rock properties from sound level produced during drilling

In many rock engineering applications such as foundations, slopes and tunnels, the intact rock properties are not actually determined by laboratory tests, due to the requirements of high quality core samples and sophisticated test equipments. Thus, predicting the rock properties by using empirical equations has been an attractive research topic relating to rock engineering practice for many years. Soft computing techniques are now being used as alternative statistical tools. In this study, artificial neural network models were developed to predict the rock properties of the intact rock, by using sound level produced during rock drilling. A database of 832 datasets, including drill bit diameter, drill bit speed, penetration rate of the drill bit and equivalent sound level (L_eq) produced during drilling for input parameters, and uniaxial compressive strength (UCS), Schmidt rebound number (SRN), dry density (ρ), P-wave velocity (V_p), tensile strength (TS), modulus of elasticity (E) and percentage porosity (n) of intact rock for output, was established. The constructed models were checked using various prediction performance indices. Goodness of the fit measures revealed that recommended ANN model fitted the data as accurately as experimental results, indicating the usefulness of artificial neural networks in predicting rock properties.     

论基桩完整性检测技术

阐述桩的分类,产生缺陷的多重因素及完整性检测的必要性。论述一维杆件中反射波理论依据。激振及接收传感器是检测技术的关键;说明了反射波信号的频率解释和瞬态机械阻抗法的一致性并均以工程实例加以佐证。文中还论述了声波透射法检测基桩完整性的理论及依据,检测的判据,还给出了检测实例。介绍最新声CT技术及检测成果。     

地震孕育过程中的前兆地声

本文介绍了有关地声观测技术和前兆地声机制的综合研究结果,为了获得连续可靠的地声信息,研制了四路慢速磁带仪等地声极微震记录仪。经过四年连续野外观测记录证明了它的稳定性和实用性;为了解决地声源定位问题,在山东莒县及云南洱源建立了标准地声台网,进行了连续四年记录,取得了可靠的资料;为了解决地声信号处理问题,建立了全国地声数据处理中心,及相应的时间序列和地声资料处理程序库。在上述工作基础上进行了长期连续观测和全面的基础研究。通过观测,获得了可靠的前兆地声信息,特别是第一次用仪器记录到了可听前兆地声,提前时间为3—15分钟。观测研究表明前兆地声确实存在,地声可以作为地震预报的一种重要方法。     

中国黄渤海沉积物声速与物理性质研究

In order to investigate the correlation between a sound velocity and sediment bulk properties and explore the influence of frequency dependence of the sound velocity on the prediction of the sediment properties by the sound velocity,a compressional wave velocity is measured at frequencies of 25–250 k Hz on marine sediment samples collected from the Bohai Sea and the Yellow Sea in laboratory,together with the geotechnical parameters of sediments.The results indicate that the sound velocity ranges from 1.232 to 1.721 km/s for the collected sediment samples with a significant dispersion within the series measuring frequency.Poorly sorted sediments are highly dispersive nearly with a positive linear relationship.The porosity shows a better negative logarithmic correlation with the sound velocity compared with other geotechnical parameters.Generally,the sound velocity increases with the increasing of the average particle size,sand content,wet and dry bulk densities,and decreasing of the clay content,and water content.An important point should be demonstrated that the higher correlation can be obtained when the measuring frequency is low within the frequency ranges from 25 to 250 k Hz since the inhomogeneity of sediment properties has a more remarkably influence on the laboratory sound velocity measurement at the high frequency.     

圆板结构周向表面裂纹识别的振动功率流方法

从结构噪声的观点,利用振动功率流方法对圆板在集中力作用下的周向表面裂纹进行了诊断研究。周向表面裂纹模拟为转动弹簧,利用断裂力学的有关理论得到其转动刚度。在高频情况下,研究了圆板在中心受集中载荷作用下的弯曲波运动以及输入的振动功率流,分析了振动功率流与破损位置及其特征尺寸的关系,从而可进行有效的破损诊断。     

Deep CTD Casts in the Challenger Deep,Mariana Trench

On 1 December 1992, CTD (conductivity-temperature-depth profiler) casts were made at three stations in a north-south section of the Challenger Deep to examine temperature and salinity profiles. The station in the Challenger Deep was located at 11°22.78′ N and 142°34.95′ E, and the CTD cast was made down to 11197 db or 10877 m, 7 m above the bottom by reeling out titanium cable of 10980 m length. The southern station was located at 11° 14.19′ N and 142°34.79′ E, 16.1 km from the central station, where water depth is 9012 m. CTD was lowered to 7014 db or 6872 m. The northern station was located at 11°31.47′ N and 142° 35.30′ E, 15.9 km from the central station, and CTD was lowered to 8536 db or 8336 m, 10 m above the bottom. Below the thermocline, potential temperature decreased monotonously down to 7300–7500 db beyond a sill depth between 5500 m and 6000 m, or between 5597 db and 6112 db, of the trench. Potential temperature increased from 7500 db to the bottom at a constant rate of 0.9 m°C/1000 db. Salinity increased down to 6020–6320 db, and then stayed almost constant down to around 9000 db. From 9500 db to the bottom, salinity increased up to 34.703 psu at 11197 db. Potential density referred to 8000 db increased monotonously down to about 6200 db, and it was almost constant from 6500 db to 9500 db. Potential density increased from 9500 db in accordance with the salinity increase. Geostrophic flows were calculated from the CTD data at three stations. Below an adopted reference level of 3000 db, the flow was westward in the north of Challenger Deep and eastward in the south, which suggests a cyclonic circulation over the Challenger Deep. Sound speed in Challenger Deep was estimated from the CTD data, and a relation among readout depth of the sonic depth recorder, true depth, and pressure was examined.     

海洋沉积物声速与其物理-力学参数的相关性

通过对海洋沉积物声速及其物理-力学参数相关性的初步分析和研究,可以找到估算沉积物压缩波速Vp和切变波速Vs的经验式,最终为海底沉积物的性质进行声学遥测、为发展海底参数声遥感服务。本文给出了7个较为理想的回归方程。沉积物的物理参数与Vp有密切的关系;力学参数对Vs的预报有较大的作用。若增加物理参数作为修正项,其效果更佳。     

台湾省恒春西南海域声速场分析

选取联系南海与台湾海峡 及巴士海峡的主要海上交通和军事要道－我国台湾省恒春西南海域作为研究海域,依据1998年夏,冬季对本海域海洋环境补充调查的CTD资料,按《海洋调查资料处理》的声速换算经验公式,推算得到本海域的海水声速系列,结合该海域温,盐环境背景,分析其声速场特性,给出海水声速的平面,垂及断面分布,也给出了本海域海水声速跃层深度,厚度和强度等三大表征值的变化特性及其声道位置。     

海洋模态在海洋水声学中的潜在应用前景

如同音分五律、光分七色一样,海洋中错综复杂的流速、声速剖面也可以分解成为数不多的经验正交海洋模态(empiricalorthogonaloceanmode)[1～5].以此为基础,20世纪80年代初在着名物理海洋学家Munk和Wunsch的倡导下,美国在大西洋实施了海洋声层析(oceanacoustictomography)实验.声层析技术最主要的潜力在于其观测的积分性质.每秒一次的声层析观测实质上是通过高速传播的声波对长距离内的物理量取积分,因此它能够在较大的时空尺度下求得活跃的中尺度涡旋场的平均值.