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Keywords: signal detection, empirical mode decomposition, shaft-rate electric field Abstract. In order to effectively extracting out weak ship shaft-rate electric field signal immersed in strong ocean background noise, a multi sub-band sliding detection algorithm capitalizing on Empirical Mode Decomposition (EMD) with Fourth-Order Mixed Cumulant (FOMC) Diagonal Slice is proposed. Firstly, EMD method was employed to adaptively decomposition the signal into a set of Intrinsic Mode Functions (IMFs), of which the validities were determined according to correlation coefficient criterion. Subsequently exploiting the property of higher order cumulant that Gaussian colored noise can be suppressed, sliding power spectrum detection of FOMC diagonal slice of the selected IMFs was carried out. Field data processing result illustrates that, proposed algorithm can effectively and reliably detect target signal even under very low Signal to Noise Ratio (SNR), having a promising application prospect.

A packaging polymer (PP-1) that can enhance the sensitivity of fiber Bragg grating (FBG) pressure sensor was designed and synthesized from hydroxyl terminated polypropylene oxide oligomers, toluene diisocyanate (TDI), 1,4-butandiol as chain extender, catalyzer, foam agent and foam stabilizer. The testing results show that the Young’s modulus, Poisson’s ratio of the packaging polymer are 9.0 × 10 6 N m −2 and 0.49, respectively. The static pressure sensitivity of fiber optical Bragg gratings packaged by PP-1 was discussed. The theoretical pressure sensitivity of FBG packaged with the polymer cylinder is −1.73 × 10 −3 MPa −1 , which is 896 times of that of the bare FBG (−1.93 × 10 −6 MPa −1 ). And its measured pressure sensitivity is −1.10 × 10 −3 MPa −1 , which is 558 times of that of the bare FBG.

To investigate the modeling of Shaft-Rate Electric Field, the analytic expressions of the electromagnetic fields of time-harmonic, horizontal electric dipole (HED) embedded in the sea have been derived by using image method according to uniqueness theorem of the electromagnetic field with two layer model. The distribution of electromagnetic field produced by a horizontal electric dipole embedded in seawater has been numerically calculated and analyzed by applying fast Hanker transform and fast Fourier transform. Then the case of shallow sea and harmonic electric dipole has been simulated in laboratory and the experimental results are accorded with the simulation results, thus the correctness of the solution and the derivation are validated. The electromagnetic field of a horizontal and time-harmonic dipole is put in a two-layer medium.

Noise, though considered harmful through the ages, when acting on nonlinear system can be useful under certain conditions. In this thesis, the phenomenon of stochastic resonance produced by the ship hydrodynamic pressure field signal against the background of ocean wave hydrodynamic pressure field signal is discussed. When the ship hydrodynamic pressure field signal mixed with the wave hydrodynamic pressure field signal passes the nonlinear stochastic resonator constructed on the basis of the bistable system and reciprocal of power spectrum integral, the system's output signal will show peak values at the appearance of ships, which suggests the existence of the phenomenon of stochastic resonance and the nonlinear stochastic resonator's ability to detect the ship hydrodynamic pressure field signal.

Scarcity of the spectrum resource and mobility of users make quality of service (QoS) provision a critical issue in wireless networks. This paper presents a fuzzy call admission control scheme to meet the requirement of the QoS. A performance measure is formed as a weighted linear function of new call and handoff call blocking probabilities. Simulation compares the proposed fuzzy scheme with an adaptive channel reservation scheme. Simulation results show that fuzzy scheme has a better robust performance in terms of average blocking criterion.

Scarcity of the spectrum resource and mobility of users make Quality-of-Service (QoS) provision a critical issue in wireless multimedia networks. This paper uses neural network as call admission controller to perform call admission decision. A performance measurement is formed as a weighted linear function of new call and handoff call blocking probabilities of each service class. Simulation compares the neural network with complete sharing policy. Simulation results show that neural network has a better performance in terms of average blocking criterion.