Site fidelity,survival and conservation options for the threatened flapper skate (Dipturus cf. intermedia)

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Numerical Analysis of Acoustic Environment with Finite Element Method

The acoustic environment of highway tunnel is complex and has influences on the driving safety and comfort. In case of emergency, evacuation information is difficult to transfer. Finite element method is used for calculating highway tunnel acoustic modal and attenuation characteristics. The results show that acoustic mode of highway tunnel has symmetry in the horizontal pressure amplitude of symmetry regional is equal and phase is the same or opposite. The higher modal frequency, the greater sound pressure amplitude is, and the effect of tunnel length on modal frequency is smaller. Decay curves of pressure level at each point in the highway tunnel over time are nonlinear. After the source excitation, in 1.5 s, attenuation rate is faster than that of few seconds later and the attenuation time of sound pressure level 30 dB is 5.5 to 7 s.     

Acoustic emission behavior of shale under four point bending test

PXWAE Acoustic Emission System is useol to investigate the acoustic emission behavior of shale under four point bending test. In these tests, the maximum bending stress, bending strain, acoustic emission hits, acoustic emission energy and etc., are recorded. The results show that when vertical loads impose on the shale sample which has horizontal stratification planes, Kaiser effect does exist under four point bending tests. Kaiser point can be recognized directly from the stress vs. cumulative AE hits curve. But by the impact of shale’s stratifications and local failure during the tests, strain relaxation occur which makes it difficult to determine the Kaiser point only by the strain vs. acoustic emission curve. An accurate conclusion can be achieved by a comprehensive judgment combing with all test data, as well as the failure mode of rock sample. The research on acoustic emission behavior of rock in the stress state during bending tests to some extend can provide guidance to engineering practice for stability monitoring of mine roof or separation layer with acoustic emission monitoring technology.     

Uniaxial Experimental Analysis on Creep Properties of Deep Limestone

The uniaxial creep tests were carried out for deep limestone from Chongqing adoptal by the MTS815 servo controlled rock mechanical test system. Meanwhile, the DISP 2 based AE system was used to test acoustic emission (AE) signal. It is found that AE can better reflect rock microstructure such as diffusion of lattice defects, opening and close of the pore and fracture, compatible deformation among particles, the generation and connection of micro ruptures. Through different creep model parameter inversion, 〖JP2〗it is concluded that either the logarithmic function creep model or the exponential function can better reflect deep rock creep deformation behavior and the logarithmic function creep model is much better. 〖JP〗     

黄河沙坡头连续弯道环流运动与冲淤特性实测数据分析

利用声学多普勒流速剖面仪、回声测深仪等测量仪器,对黄河沙坡头段连续弯道中10个典型断面的流速、水深、河床高程等进行了实测.通过分析各断面流速等值线、平面流场和近几年河床高程的变化情况.结果表明,弯道断面流场的主流分布与河床底部泥沙冲淤分布基本相一致,满足弯道水流的一般规律:凹岸冲刷,凸岸淤积.     

牛超声心动图声学造影法研究

在兽医上首次应用３％过氧化氢溶液（双氧水）代替常规造影剂进行超声心动图声学造影法研究取得成功。经几种不同造影剂的对比试验表明：使用３％Ｈ２Ｏ２进行牛超声心动图声学造影检查，安全可靠、简单易行，可重复性好，其声像明显优于生理盐水及５％葡萄糖溶液。     

基于优化VMD组合降噪和LMD的水轮机空化声发射信号特征提取

针对水轮机空化声发射信号存在噪声,进而影响信号特征有效提取的问题,提出基于优化变分模态分解(VMD)与Birge-Massart策略组合降噪和局部均值分解( LMD)的水轮机空化声发射信号特征提取方法.针对VMD算法中惩罚因子和分解模态数对分解结果有着显著影响,提出以散布熵差异相关系数最小值为目标函数,利用哈里斯鹰优化算法(HHO)对VMD进行参数寻优.以最优参数的VMD分解信号,得到一系列本征模态函数(IMF).计算各IMF的相关系数,对相关系数小于0.1的IMF进行剔除,大于0.5的IMF进行保留,0.1到0.5的IMF采用小波BM准则进行降噪,并与保留的分量重构.对重构信号进行LMD处理,将分解得到的乘积函数(PF)分量的能量提取为信号特征.试验分析结果表明,经过优化VMD组合降噪处理和LMD处理得到PF分量的能量与空化系数之间呈负相关,验证了所提方法用于水轮机空化状态识别的可行性.     

多个内插管并联结构消声器的插入损失计算

推出具有多个内插管并联管路声学元件的声传递矩阵 ,利用声传递矩阵进行柴油机排气消声器的插入损失的计算 ,模拟计算结果与试验数据具有较好的拟合程度 .     

A system for automatic recording of fish tagged with coded acoustic transmitters

A telemetry system designed to automatically record the presence and swimming direction of fish tagged with coded acoustic transmitters is described. The present paper presents results from an extensive mapping of signal strengths and the proportion of correctly identified codes from a transmitter at various positions outside automatic listening stations (ALS). The system is evaluated on the basis of two field seasons, during which 107 Atlantic salmon, Salmo salar L., were tagged with acoustic transmitters in a fjord system in south-western Norway. By installing one ALS (two at high water discharges) in the mouth of the River Suldalslågen and two ALSs in the Hylsfjord, the presence and swimming direction of all tagged salmon entering the river and the inner part of the 750-m-wide Hylsfjord were recorded.