HYDRODYNAMIC BEHAVIOR OF FPSO UNDER VARIUS LOADING IN SURVIVAL STORMS IN SHALLOW WATER

The motion performance and clearance between the hull and seabed of a FPSO (Floating, Production, Storage and Offloading units) in survival storm conditions are closely related to its safety during the operation in shallow water. As an example the behavior of a 160 kDWT FPSO with single point mooring system in shallow water was investigated in this paper. Calculation for the FPSO is made based on the 3-D linear potential flow theory and time-domain numerical simulation method and corresponding model test is carried out in the wave basin at Shanghai Jiaotong University. Both the calculated and experimental results indicate that the heave, roll and pitch motions of FPSO become lazy with the increase of the draft. And the fully loaded FPSO in survival storm touched seabed few times. Therefore, it is concluded that the FPSO should be less loaded than that in the fully loaded condition when the survival storm is coming.     

考虑界面转角自由度的频域子结构法研究

采用Jetmundsen频域子结构法,针对空间刚架结构的综合进行了数值仿真,研究了界面自由度的完整性对于综合结果的影响,讨论了一种间接获取转角自由度相关频响函数信息的方法.仿真结果显示,频域子结构综合法能够有效地预报结构的动力学性能,而通过引入间接获取的转角自由度的频响信息能在一定程度上改善预报质量.     

SVPWM过调制算法的理论分析与实验应用

过调制算法能够有效提高逆变器的输出基波电压,对缩短电动机的动态响应时间、扩大稳态运行区域是十分有意义的.研究了一种基于SVPWM的过调制算法,并对过调制区的谐波成分进行了分析.最后在Matlab/Simulink仿真软件和350 kW鼠笼式异步发电机全功率变换器实验平台上进行了验证.结果表明,该过调制策略可实现在整个调...     

气液混输管线与悬链线立管系统严重段塞流数值模拟

针对气液混输管线与悬链线立管系统严重段塞流问题,采用严重段塞流形成条件一致的等效原则,发展了一种将三维管道系统等效为二维管道系统的计算流体力学(CFD)数值模拟方法.以文献中某水平/下倾管与悬链线立管组合系统为对象,结合其实验工况,数值模拟了该种管型下的严重段塞流现象,分析了其压力波动幅值及周期变化特性,数值模拟与文献所述实验结果一致,表明了该数值模拟方法的有效性.     

Simulating the variability and scale effect for slow crack growth in Hi-Nicalon SiC-based tows: A parametric study

The delayed failure time of SiC-based multifilament tows under static fatigue condition is as broadly scattered as for individual filaments, despite it is commonly used as strong scatter reduction. Moreover, the stress exponent (n) is hierarchy-dependent as revealed by a Monte-Carlo algorithm: decreasing from filament (micro) scale to tow (meso) scale. This is demonstrated to originate from the mismatch between the stress applied to the critical filament (affecting the growth kinetics), variable because of fiber misalignment in the tow, and its tow-averaged value used for endurance diagram construction. In the context of this algorithm, it is shown that n would evolve with fiber parallelism, tow stress range or the critical filament rank whereas filament strength distribution plays a secondary role. The tow structure shall therefore be considered as a major parameter for composite part design aiming long service life.     

Energy loss distribution of proton beams at normal incidence on multi-walled carbon nanotubes

The irradiation with energetic proton beams impinging normal to the axis of a multi-walled carbon nanotube (MWCNT) is studied both experimentally and theoretically, in the 2–10 keV energy range. The MWCNTs are dispersed on top of a very thin film of holey amorphous carbon (a-C) substrate. Measurements of the proton energy loss distribution are performed after MWCNT irradiation with energetic proton beams by the transmission technique. The resulting energy loss spectra in the forward direction show two well differentiated peaks, whose origin is elucidated by using a semi-classical simulation of the proton trajectory through the nanotube. We found that the experimental lower-energy loss peak mostly comes from protons travelling between the outer walls of the MWCNT, whereas the high-energy loss peak is mainly due to protons that interact with the MWCNTs just on top of the supporting a-C substrate.     

Advance in food-derived phospholipids: Sources,molecular species and structure as well as their biological activities

BackgroundPhospholipids derived from different food sources have been extensively studied and widely used in different industrial areas, including food, animal feed, medicine, and pharmaceuticals. In recent years, the utilization of phospholipids, particularly bioactive ones, has gained attention, owing to their enrichment of n-3 polyunsaturated fatty acids.Scope and approachThis article presents a detailed and up-to-date review on the sources, molecular species, and structures of food-derived phospholipids. Moreover, this review highlights the structure–activity relationship of phospholipids and provides mechanistic insights into their biological activities.Key findings and conclusionsFood-derived phospholipids have been isolated and characterized from various sources, including plant, animal, and aquatic sources. These phospholipids possess considerable differentiation in their molecular species and structure, owing to variations in the properties of the polar headgroup, the length of the fatty alkyl chain, and the degree of unsaturation. In particular, the molecular species of aquatic-source phospholipids show a substantial amount of n-3 polyunsaturated fatty acids, particularly EPA and DHA. The diversity in molecular species and structures results in different biological activities. Polar headgroups such as choline and amino groups, as well as n-3 polyunsaturated fatty acids in phospholipids, are crucial to our food system and health, especially regarding antioxidant activity, memory, improving immunity, and preventing cardiovascular disease.     

一种基于Akaike信息准则的极限学习机

为了减小传统的极限学习机网络的规模及提高网络的泛化性能,利用Akaike信息准则作为学习的最优停止准则以选择合适的隐层节点数量,同时利用修正Gram Schmidt算法自动调整网络参数,提出改进的极限学习机网络构造算法。通过与传统极限学习机在通用标杆问题上的实验结果比较表明, 该改进的极限学习机具有更精简的网络结构和更快的学习速度,同时具有良好的学习精度。     

Material selection in sandwich beam construction

A systematic procedure is presented for comparing the relative performance of sandwich beams with various combinations of materials in three-point bending. Operative failure mechanisms are identified and failure maps are constructed. The geometry of sandwich beams is optimised to minimise the mass for a required load bearing capacity in three-point bending.     

Fabrication of superhydrophobic surfaces with tunable water droplet adhesion force by a two-step method

In this paper, we present a convenient approach to prepare hierarchical structured superhydrophobic coatings with tunable adhesion force, composed of micro-size glass beads, nano-size SiO₂ particles and epoxy resin. Surfaces of two types with different roughness were fabricated, one type is only with single-scale roughness demonstrating lotus effect with low sliding angle, the other type is hierarchically micro-nano-structured roughness exhibiting petal effect with high adhesion force. The surface roughness is pivotal for controlling the wetting behavior and regulating the contact angle including the contact angle hysteresis. Varying the density of micro-size glass beads could adjust the roughness of the surface, which means the adhesion force of the prepared surface could be easily controlled based on the proposed method. Through variation of glass beads’ amount, the surface could be designed to pin the water droplet with different adhesion force when the surface turned upside down. The surface wettability, surface morphology, adhesion force of the prepared samples are investigated and mechanism of the Cassie-to-Wenzel state transition are discussed in detail. Furthermore, the convenient method provides a possibility for controlling surface morphology, composition and corresponding surface adhesion which could be applied to various substrates such as tile, wood, steel and fabric.