Underwater life support based on immobilized oxygen carriers

One of the primary problems that hinders humans in their efforts to explore and develop the ocean realms is the lack of a ready supply of oxygen. Practical methods have not yet been devised for using the vast amount of oxygen dissolved in ocean waters for human life support in an undersea environment. Fish and other water-breathing animals have solved this problem by utilizing hemoglobin as a molecular oxygen pump. To achieve a similar oxygen extraction capability, we have explored various methods of oxygen extraction that are based on immobilized forms of hemoglobin. Improved methods for immobilizing hemoglobin or other oxygen carrying molecules and a method for extracting the available dissolved oxygen from natural waters and other fluids are described. The techniques that have been developed allow for immobilization of oxygen carriers at high concentration in a state where they are capable of reversible oxygen binding, and also allow for regeneration of the carrier in the event of oxidation of the oxygen-binding site.     

Viscoelasticity and tack of poly(vinyl pyrrolidone)–poly(ethylene glycol) blends

The adhesive properties of blends of high molecular weight poly(vinyl pyrrolidone) (PVP) and low molecular weight poly(ethylene glycol) (PEG) were systematically investigated with a probe test and correlated with their viscoelastic properties. The material parameters that were varied were the PEG content (31–41 wt %) and the hydration rate. The 36% PEG showed the best balance of properties for a pressure‐sensitive adhesive. At low debonding rates, the debonding took place through the formation of a fibrillar structure, whereas at high debonding rates, the debonding was brittle. This transition was attributed to the breakage and reformation of hydrogen bonds between PVP units and OH groups on PEG during the large strain of the polymer chains in elongation. This transition was observed, albeit shifted in frequency, for all three compositions, and the characteristic relaxation times of the hydrogen‐bonded network were estimated. A comparison between the tack properties of the adhesives and their linear viscoelastic properties showed a very strong decoupling between the small‐strain and large‐strain properties of the adhesive, which was indicative of a pronounced deviation from rubber elasticity in the behavior of the blends. This deviation, also seen during tensile tests, was attributed to the peculiar phase behavior of the blends. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2395–2409, 2002     

Preliminary results on underwater holography

The growth of the offshore oil and gas industries has created interest in performing optical holography underwater for purposes of inspection and archiving. An investigation is proceeding to establish the influence of a disturbing medium, such as water, on holographic image quality and to determine the parameters required of an underwater holographic camera. Preliminary holograms have been produced, in the laboratory, of objects in water-filled tanks. Early indications of this work are that some of the prospective problems associated with underwater holography are likely to present constraints less severe than was first envisaged.     

Wideband acoustic absorption characteristics of rubberized coir for underwater applications

Reflection and transmission coefficients of rubberized coir pads over the frequency band 200 kHz to 4 MHz are presented in this Paper. These results are compared with those reported for neoprene, paraffin wax, rubber car mat and plastic door mat¹. The rubberized coir pads were found to possess wideband absorption characteristics. It has been experimentally found that 0.05 m thick coir pads have almost 100% absorption in the frequency range 800 kHz-3 MHz with a maximum at 2.35 MHz. We have used this material for lining the water tank for underwater acoustic studies.     

罗兰-C脉冲水下传播特性高精度预测理论算法研究

对罗兰-C脉冲水下传播特性预测模型算法进行推导研究,综合考虑了信号先沿陆海表面、再由空气入水传播时的路径损耗、相位延迟、色散效应及空气海水界面两侧场量的约束条件.分析了0~10m不同海水深度罗兰-C电场幅度与相位的变化,并与无畸变的标准场信号进行比较.结果显示:随着入水深度增加,色散效应导致脉冲前沿展宽,跟踪点相位超前.该结果去除了由参比场量近似引入的误差,精度更高.     

果蝇启发的水下传感网部署算法

在三维水下传感器网络中,恶劣的环境容易导致传感器节点失效,网络拓扑不稳定.考虑到实际水环境中存在障碍物及边界,提出一种果蝇群启发的水下传感网部署算法.该方法以网络重连通为约束条件,首先利用果蝇群的觅食行为求解节点移动位置,同时加入欧琼鸟飞行机制保持移动过程中网络拓扑的相对稳定性,最后采用障碍物局部感知移动模型进行避障.结果表明,该算法可以躲避障碍物,提高覆盖和连通,减少网络能耗.     

集成电路封装用绝缘胶漏电失效分析

在电子元器件封装领域中,塑封器件正逐步替代气密性封装器件。目前工业级塑封器件已不能满足器件的高可靠性要求,工业级塑封器件在严酷的环境应力试验中经常出现失效。研究了工业级塑封器件在可靠性筛选试验中出现失效的问题,通过X射线观察和芯片切面分析等方法,查明了造成器件失效的原因,并提出了优化改进措施。     

Mobile direct-sequence spread-spectrum underwater acoustic communication based on improved differential energy detector

A Doppler estimation method based on the structural features of spread spectrum signal was proposed,which could achieve real-time Doppler estimation for received spread spectrum signals by energy detecting the result of matching correlation calculation of adjacent received spreading symbols.In addition,this method made full use of the spread spectrum processing gain and could do Doppler estimation under low SNR condition.Improved differential energy detector was further proposed,which can effectively deal with the rapid carrier phase fluctuation interference caused by Doppler effect and time-varying multi-path interference by detecting the output energy of two correlators.Simulation verified the robustness of improved differential energy detector algorithm and the Doppler estimation method based on spread spectrum signal.At-sea data shows that improved differential energy detector combined with the proposed Doppler estimation method can achieve low bit error rate communication for direct-sequence spread spectrum underwater acoustic communication with large time-varying Doppler interference when SNR is ?10 dB.     

Detection algorithm of underwater linear target based on range-gated imaging

基于水下距离选通激光成像技术,提出了一种可用于长距离下的水下线状目标检测算法。该算法针对水下成像中低对比度、模糊和噪声等特性,首先采用对比度拉升、中值滤波、小波变换等方法对图像进行增强处理;然后利用Canny边缘检测算子提取出目标的边缘特征;最后针对边缘特征中出现的噪声边缘问题,选用了鲁棒性强的随机抽样一致性参数估计算法从边缘特征中检测出线状目标,并计算得到目标的位置和方向等相关参数。实验结果表明,该算法可以有效地检测出水下曲线状目标,弥补现有方法只能检测直线目标的不足,检测率可以达到93%,有效检测距离能达到5倍水下衰减长度。