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951.
本文介绍了基于DSP的船舶电站自动准同期装置,应用动态调整采样间隔的交流采样算法来计算交流电量并推导了最小二乘曲线拟合算法来精确预报同期点。该装置能保证在电网品质恶劣的船舶电站中使用时也具有较高的可靠性。 相似文献
952.
<正>【人物小传】他,个子不高,脸色黝黑,眼神中透露着温和与慈祥,与人谈话时甚至有些腼腆。然而,就是这位看起来普普通通的一个人,头上却顶着数不清的光环: 相似文献
953.
柔性去耦覆盖层降噪机理分析 总被引:6,自引:0,他引:6
利用Hankel变换和传递矩阵方法,推导了点激励敷设柔性层系的无限大薄板的辐射声压插入损失和辐射声功率插入损失.理论分析指出,当钢板的质量较大或者频率较高时,柔性层系对于板本身的减振效果实际上很小,辐射噪声降低的主要原因是柔性层系的隔振或隔声作用.辐射声压插入损失与通常所理解的两边都是水时覆盖层的透声系数(及相应的隔声量)没有简单的关系.数值计算表明:(1)低频段存在一个失效区,辐射噪声不降反升;(2)柔性层的损耗越大插入损失提高越多;(3)阻抗渐变的柔性层系的敷设顺序引起的插入损失不同,但均比单层结构有更好的降噪效果. 相似文献
954.
Solid oxide fuel cell (SOFC) has been identified as an effective and clean alternative choice for marine power system. This
paper emphasizes on the dynamic modeling of SOFC power system and its performance based upon marine operating circumstance.
A SOFC power system model has been provided considering thermodynamic and electrochemical reaction mechanism. Subcomponents
of lithium ion battery, power conditioning unit, stack structure and controller are integrated in the model. The dynamic response
of the system is identified according to the inertia of its subcomponent and controller. Validation of the whole system simulation
at steady state and transit period are presented, concerning the effects of thermo inertia, control strategy and seagoing
environment. The simulation results show reasonable accuracy compare with lab test. The models can be used to predict performance
of a SOFC power system and identify the system response when part of the component parameter is adjusted. 相似文献
955.
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
956.
It can be beneficial to reduce vibrations in shipboard piping, so the authors designed a new kind of piping damper with a
plunger-type accumulator. Special requirements for the piping damper included low impact displacement, low speed, as well
as an appropriate locking speed. Inside the damper, a plunger-type accumulator was installed and on the outside of the piston
rod, a tube with exposed corrugations was added. Between the piston and the cylinder, a clearance seal was added. Using mathematical
modeling, the effects of the dynamic performance of the damper’s impact displacement on vibrations were observed. Changes
to the clearance between the piston and the cylinder, the stiffness of the spring in the accumulator, the throttle valve size,
and locking speed resistance of the damper were respectively simulated and studied. Based on the results of the simulation,
dampers with optimal parameters were developed and tested with different accumulator spring stiffnesses and different throttles.
The simulation and experimental results showed that parameters such as seal clearance between piston and cylinder, accumulator
spring stiffness and throttle parameters have significant effects on the damper’s impact displacement, low speed resistance
and locking speed. 相似文献
957.
Line heating process is a very complex phenomenon as a variety of factors affects the amount of residual deformations. Numerical
thermal and mechanical analysis of line heating for prediction of residual deformation is time consuming. In the present work
dimensional analysis has been presented to obtain a new relationship between input parameters and resulting residual deformations
during line heating process. The temperature distribution and residual deformations for 6 mm, 8 mm, 10 mm and 12 mm thick
steel plates were numerically estimated and compared with experimental and published results. Extensive data generated through
a validated FE model were used to find co-relationship between the input parameters and the resulting residual deformation
by multiple regression analysis. The results obtained from the deformation equations developed in this work compared well
with those of the FE analysis with a drop in the computation time in the order of 100 (computational time required for FE
analysis is around 7 200 second to 9 000 seconds and where the time required for getting the residual deformation by developed
equations is only 60 to 90 seconds). 相似文献
958.
浅底远程海底混响(英文) 总被引:1,自引:0,他引:1
杨士莪 《船舶与海洋工程学报》2010,9(1):22-26
The method of coupled mode is introduced for investigation of bi-static distant bottom reverberation of impulsive source in
shallow water, which will not contradict with principle of reciprocity in all cases. And the method of multi-pole for directional
source is also introduced. It shows that in case of layered medium, intensity of bi-static bottom reverberation will decease
according to the cubic power of receiving time t, and the transverse spatial correlation of bottom reverberation is a little greater than longitudinal correlation for equal
separation of receivers, and both vary in form with the receiving time. 相似文献
959.
In the Pearl River Delta (PRD), there is severe competition between container ports, particularly those in Hong Kong, Shenzhen, and Guangzhou, for collecting international maritime container cargo. In addition, the second phase of the Nansha terminal in Guangzhou’s port and the first phase of the Da Chang Bay container terminal in Shenzhen opened last year. Under these circumstances, there is an increasing need to quantitatively measure the impact these infrastructure investments have on regional cargo flows. The analysis should include the effects of container terminal construction, berth deepening, and access road construction. The authors have been developing a model for international cargo simulation (MICS) which can simulate the movement of cargo. The volume of origin-destination (OD) container cargo in the East Asian region was used as an input, in order to evaluate the effects of international freight transportation policies. This paper focuses on the PRD area and, by incorporating a more detailed network, evaluates the impact of several infrastructure investment projects on freight movement. 相似文献
960.
一种基于CFD的水动力系数计算新方法(英文) 总被引:3,自引:0,他引:3
Applications of computational fluid dynamic (CFD) to the maritime industry continue to grow with the increasing development
of computers. Numerical approaches have evolved to a level of accuracy which allows them to be applied for hydrodynamic computations
in industry areas. Hydrodynamic tests, especially planar-motion-mechanism (PMM) tests are simulated by CFD software -FLUENT,
and all of the corresponding hydrodynamic coefficients are obtained, which satisfy the need of establishing the simulation
system to evaluate maneuverability of vehicles during the autonomous underwater vehicle scheme design stage. The established
simulation system performed well in tests. 相似文献