不同水分胁迫下几种春小麦种子根形态结构的研究

实验采用快速冷冻切片法及显微摄像系统观察法对甘肃陇中地区6个品种春小麦在不同水分状况下的种子根进行了形态结构研究。结果表明,在不同程度水分胁迫下的同一品种春小麦,种子根后生木质部导管(中央大导管)直径有显著的差异,但这种变化趋势并不是简单的线性关系。随着水分胁迫的增大,不同品种春小麦种子根中央大导管的直径有不同的变化趋势。不同品种春小麦在不同程度的水分胁迫下,随着胁迫的增大,各品种中央大导管直径的变化都逐渐趋于同一区域,这一区域很可能是春小麦在形态结构上适应水分亏缺在导管直径上表现出的最佳直径范围。     

海底入射角对多波束反向散射强度的影响及其改正

综合考虑测船姿态、声线弯曲和海底地形对入射角的影响,推导了计算多波束海底入射角的实用模型。根据Lambert法则,改正海底入射角对反向散射强度的影响。实例计算结果表明,所述模型能精确地计算波束在海底的入射角,有效地改正其对反向散射强度的影响。     

Experimental study on hydrodynamic performance of SWATH vessels in calm water and in head waves

An extensive experimental investigation on four SWATH hull forms has been conducted in calm water and in regular waves at University of Naples Federico II. Calm water tests have been analyzed in the range of Froude number Fr_T from 0.1 to 0.6. For all four SWATH configurations at the speed, corresponding to Fr_T 0.32, the behaviour in regular waves has been tested. The results of heave, pitch and vertical accelerations are presented in nondimensional form as RAO. For the “most promising” SWATH #4 configuration, a set of stabilizing fins have been designed and an active stabilization system has been developed. The developed SWATH#5 has been tested in calm water on three displacements in the range of Fr_T from 0.1 to 0.65. The dynamic wetted surface has been identified and the residual resistance coefficient C_R as well as R_T/Δ are reported. Seakeeping tests have been performed in regular head sea and in head and following irregular sea at Fr_T = 0.50. The conditions for the occurrence of dynamic longitudinal instabilities have been identified. The results allows to comment the effect of slenderness of struts and SWATH’s immersed bodies on resistance and seakeeping and concerns the applicability of SWATH concept to small craft.     

船艇费用-效能分析方法研究

文中介绍了费用-效能分析的基本步骤和方法,针对船艇的特点建立了寿命周期费用的分解结构和费用模型,并编制了船艇寿命周期费用的计算程序。最后以两条船艇的费用-效能分析为例,对费用-效能分析在船艇多方案选优中的应用作了初步探讨。     

ADCP资料处理中的船速计算

船载ADCP具有走航测流的特点,弥补了传统测流仪器只有停船才能观测的不足。它可以同时观测多层海流数据,获取连续性资料。ADCP测得流速是海水相对于船体的速度,在正常观测条件下,船速远大于海水流速,因而船速计算是ADCP资料处理的关键。本文对不同的船速计算方法进行了比较,对使用参考层法计算船速的原理、特点和效果进行了论述。     

世越号起吊姿态敏感性分析与方案选择

韩国世越号打捞是世界上首次利用托底钢梁原状态整体起吊难船出水的工程。客滚难船装载的货物容易在沉没后发生移位,上层建筑长时间沉没海底后发生泥沙淤积导致难以准确估计整船的重量重心及浮力浮心的位置。利用水池模型试验和数值计算两种方法分别对大型浮吊船单臂架打捞法和双驳船抬吊打捞法进行了难船姿态受重心位置偏移的敏感性分析。水池模型试验中发现,用大型浮吊船单臂架打捞法,世越号的姿态受其重心位置偏移非常敏感,容易发生侧翻;而用双驳船抬吊打捞法,世越号的姿态受其重心位置的影响非常有限,难船和抬浮驳船都可以保持一个较好的姿态。对比水池模型试验的结果,由于难以计及托底钢梁的翘动和滑动现象,数值计算中得到的难船起吊姿态值偏小。双驳船抬吊打捞法被选为打捞世越号的施工方案,其对难船重心位置偏移不敏感的特性得到了现场实证。这个特点为世越号的成功打捞出水起到了关键作用。     

Pipe laying simulation with an active reel drive

Dynamic and quasi-static models for analysis of a pipe lay spread are presented in the paper. Depending on the type of a pipe, spooling it on a big drum (reel) may cause plastic deformations. When the pipe is reeled out at sea, again it undergoes plastic deformations. In order to model such a nonlinear behaviour, a model, which includes both elasto-plastic material characteristics and large deformations, is required. Discretisation of the pipe is performed by means of the Rigid Finite Element Method (RFEM), which allows us to study static and dynamic problems, taking into account required properties of the model. Different sea conditions are simulated and analysed. It is shown how operational conditions can limit the ability of laying operation by a dedicated vessel, due to an unstable system response. The second part of the paper presents an upgrade of a passive reel drive by application of an active drive. In the model used for control applications, the pipe is modelled by a neural network. This allows us to perform a real-time calculations. In this fast-response calculation model, nonlinear aspects of the system are taken into account. The improvements in a pipe laying vessel performance are presented by some results of numerical simulations. The conclusions are also formulated.     

Numerical simulation of water flooding into a damaged vessel’s compartment by the volume of fluid method

When a vessel is damaged, seawater floods into the damaged compartments and subsequently influences the motion of the vessel. Furthermore, the vessel’s behaviour affects the floodwater motion. In this paper, a Navier-Stokes (NS) solver with a free surface capturing technique, i.e., the volume of fluid (VOF) method, was developed to numerically simulate water flooding into a damaged vessel. To verify the developed solver, a 2-D and a 3-D dam break problems were tested. The numerical results coincide well with the experimental results and with the published numerical results. Additionally, it was used to solve the problems of linear and non-linear liquid sloshing in a hexahedral tank. The numerical results are satisfactory in comparison with the experimental results and analytical solutions. Finally, the phenomenon of water flooding into a damaged compartment of a Ro-Ro ferry was simulated numerically. The computed results are in good agreement with the experimental data.     

船载物探电子设备的接地问题及解决方案

船栽物探电子设备,是一个电气结合复杂的数据采集记录系统.各系统电子线路因船舶配电方式、工作环境的特殊性,其接地很重要,但容易被忽视.而接地处理不当,在使用时会受到噪声干扰、振荡;或造成仪器的输出榆入电路损坏,不能正常工作.更严重地甚至机壳漏电,危及人身安全.船栽物探电子设备接地问题.可分为"接地保护"和"接地故障"."接地保护"是将电气设备的金属外壳、支架和电缆的护套与大地等单位的金属船体(船壳)作永久性良好的电气连接,它分为保护接地和功能接地."接地故障"是指因设备不正确接地或由于绝缘层的破损、老化及环境恶劣引起绝缘电阻低下或者接地干扰等问题.文中从船载物探电子设备的使用特性出发.讨论在实际接地处理中出现问题的原因,分析了各种接地干扰的原理.并提出了相应的解决方案,对于船栽物探电子设备的实际安装应用有一定的指导意义.