船舶轴带发电机恒频装置RCF的传动效率研究

对德国产船舶轴带发电机液压－机械分流传动恒频装置ＲＣＦ的传动效率进行了理论和实验上的研究，提出了该传动效率的数学模型，并以江南造船厂１９８７年下水的“祥瑞”轮ＲＣＦ装置的结构参数和工况为实例，对其液压回路的效率模型进行实验验证，对传动效率进行计算机运算，得出：在主机转速变化范围内的传动效率变化规律基本符合实际情况。     

DWT-Based Robust Color Image Watermarking Scheme

A scheme of embedding an encrypted watermark into the green component of a color image is proposed. The embedding process is implemented in the discrete wavelet transformation （DWT） domain, The original binary watermark image is firstly encrypted through scrambling technique, and then spread with two orthogonal pseudo-random sequences whose mean values are equal to zero, and finally embedded into the DWT low frequency sub-band of green components, The coefficients whose energies are larger than the others are selected to hide watermark, and the hidden watermark strength is determined by the energy ratio between the selected coefficients energies and the mean energy of the subband. The experiment results demonstrate that the proposed watermarking scheme is very robust against the attacks such as additive noise, low-pass filtering, scaling, cropping image, row （or column ） deleting, and }PEG compression.     

厢式货车减阻方法的试验研究

介绍了厢式货车的减阻方法－主动控制边界层法和被动控制边界层法，主动控制边界层法利用导流滚子给边界层注入动量，以推迟边界层的分离，使尾涡区变窄，从而减少厢式货车的压差阻力，被动控制边界层法是在厢式货车厢体的迎风面上安装井字形隔栅，利用井字形隔栅的导流作用，减小厢体迎风面的压力，推迟厢体上表面前部边界层的分离，改善了气流绕流的状况，从而减少厢式货车的压差阻力，两种方法的减阻效果都非常明显。