共查询到19条相似文献,搜索用时 828 毫秒
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超低频磁场电缆天线的振动产生了运动感应噪声,其等效噪声场大小和天线机械性能、灵敏度有关.通过分析并作适当简化可以得到抛物线形灵敏度曲线是降低该噪声的理论最佳方案,但囿于制造工艺,可以采用梯形灵敏度曲线的替代方案. 相似文献
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对潜艇拖曳天线的综合性能试验,提出了一个可行的总体方案,并对该测控方案中实现加载控制的方法,措施进行了分析和研究。 相似文献
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桅杆类通信天线是潜艇通信天线的一种重要形式,作为潜艇通信系统的重要组成部分,是潜艇在潜望状态实现对外通信功能的关键。本文从配置、功能、性能等方面对外军常规潜艇和核潜艇桅杆类通信天线进行分析,研究提出外军潜艇桅杆类通信天线尤其是多功能通信桅杆天线的发展趋势。 相似文献
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二级深拖系统具有可控性强、母船扰动弱等优点,是重要的海洋探测平台。在实际工作中,二级拖体姿态稳定是保证探测数据准确的基本前提。本文以具有自主调节功能的二级拖体为例,对其姿态控制进行研究。首先建立了二级拖缆的“弹簧——阻尼”模型,并在此基础上建立了二级深拖系统的数学模型。其次根据该系统具有非线性、时变性等特点,设计了具有参数自修正功能的模糊自适应PID控制器,以实现在不同工况下对二级拖体的姿态进行控制。仿真结果表明,未加载控制器时,海况变化对拖体姿态有显著影响,其俯仰角和横滚角均会发生大范围波动。加载模糊自适应PID控制器后,拖体通过自主调节,能够使姿态波动控制在较小范围,从而满足工作要求,验证了拖缆数学模型的正确性和所采用的控制方法的可行性。 相似文献
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Detection of weak underwater signals is an area of general interest in marine engineering. A weak signal detection scheme
was developed; it combined nonlinear dynamical reconstruction techniques, radial basis function (RBF) neural networks and
an extended Kalman filter (EKF). In this method chaos theory was used to model background noise. Noise was predicted by phase
space reconstruction techniques and RBF neural networks in a synergistic manner. In the absence of a signal, prediction error
stayed low and became relatively large when the input contained a signal. EKF was used to improve the convergence rate of
the RBF neural network. Application of the scheme to different experimental data sets showed that the algorithm can detect
signals hidden in strong noise even when the signal-to-noise ratio (SNR) is less than −40d B. 相似文献
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极低频发射天线场地等效电阻率的计算 总被引:3,自引:0,他引:3
通过对均匀半空间有限长导线源辐射场强的理论分析,表明极低频发射天线场地等效电阻率主要由天线两端接地点的位置决定。文章对MT法测量的视电阻率数据的处理和天线等效电阻率计算方法上提出了几点看法,以供参考。 相似文献
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为了缓解交通噪声带来的干扰,设立声屏障是一种行之有效的降噪措施。现运用德国Cadna/A环境噪声模拟软件,以江苏沿江高速公路声屏障设计为例,计算了声屏障的插入损失,并将计算结果与按照《声屏障声学设计和测量规范》(HJ/T90-2004)获得的实测结果进行了比较,分析了计算结果与实测结果产生误差的原因,结果表明,在大车流、低本底噪声的情况下,Cadna/A软件可较好地应用于工程设计中。 相似文献
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《船舶与海洋工程学报》2020,(1)
Despite their high manufacturing cost and structural deficiencies especially in tip regions, highly skewed propellers are preferred in the marine industry, where underwater noise is a significant design criterion. However, hydrodynamic performances should also be considered before a decision to use these propellers is made. This study investigates the trade-off between hydrodynamic and hydroacoustic performances by comparing conventional and highly skewed Seiun Maru marine propellers for a noncavitating case.Many papers in the literature focus solely on hydroacoustic calculations for the open-water case. However, propulsive characteristics are significantly different when propeller-hull interactions take place. Changes in propulsion performance also reflect on the hydroacoustic performances of the propeller. In this study, propeller-hull interactions were considered to calculate the noise spectra.Rather than solving the full case, which is computationally demanding, an indirect approach was adopted; axial velocities from the nominal ship wake were introduced as the inlet condition of the numerical approach. A hybrid method based on the acoustic analogy was used in coupling computational fluid dynamics techniques with acoustic propagation methods, implementing the Ffowcs Williams-Hawkings(FW-H) equation. The hydrodynamic performances of both propellers were presented as a preliminary study.Propeller-hull interactions were included in calculations after observing good accordance between our results, experiments, and quasi-continuous method for the open-water case. With the use of the time-dependent flow field data of the propeller behind a nonuniform ship wake as an input, simulation results were used to solve the FW-H equation to extract acoustic pressure and sound pressure levels for several hydrophones located in the near field. Noise spectra results confirm that the highest values of the sound pressure levels are in the low-frequency range and the first harmonics calculated by the present method are in good accordance with the theoretical values. Results also show that a highly skewed propeller generates less noise even in noncavitating cases despite a small reduction in hydrodynamic efficiency. 相似文献