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61.
62.
在外界干扰和参数不确定的情况下,设计一种基于Backstepping的自适应神经滑模控制器对欠驱动船舶神经滑模航迹进行控制。采用趋近律的滑模控制,抑制常规滑模的固定切换增益系数带来的抖振现象;利用神经网络辨识对象,减少趋近律滑模控制对对象模型参数的依赖。以某实习船为例进行仿真,结果表明:在标称参数下,所设计的控制器能够有效跟踪设定的航迹并抑制常规滑模控制器的抖振现象;在外部环境扰动以及参数摄动的情况下,仍然能够实现较好的控制,表现出强鲁棒性。 相似文献
63.
网络协议电视(Internet Protocol Television,IPTV)已经成为新一代网络(Next Generation Net-work,NGN)中最具潜力的应用,主要由于其具有随时随地都能发送电视节目的特性。随着IEEE 802.16d/e的规格制订,它具有高带宽及低延迟的能力,因此适合作为发送多媒体串流的服务。此外,它也提供讯号高涵盖率、行动性支持以及非视线功能。我们可以利用IEEE 802.16d/e提供发送IPTV串流的媒介,并提出一个简单但却有效的IPTV频道切换算法以维持频道切换的时间在一个可容许的范围内。提出的算法根据热门频道及个人化频道的预载,以减少因为网络传输所造成的延迟,达到快速切换频道的目的。最后,通过实验结果证实算法的效能。 相似文献
64.
设计一种基于CS5463的双流制机车电度表。介绍了双流制电度表的技术性能、总体结构以及程序设计方法,通过对电能计量模块、中央处理模块、双路供电设备以及GPRS与RS485通信模块进行设计,实现机车交流与直流的显示、与TAX2机车监控装置通信以及远程无线抄表功能。采用型式试验、例行试验对新研制的双流制机车电度表进行测试,试验结果表明,该电度表具有制造成本低、数据处理能力强、安全保障度高、测量精度高、抗干扰能力强等优点。 相似文献
65.
针对海上浮式装置力学分析中选用不同截止频率阈值得到重构的冲击载荷对结构响应结果有较大影响的问题,采用变分模态分解(Variable Mode Decomposition, VMD)方法得到冲击载荷各本征模态函数、对应频谱的特征频率和最大加速度幅值。选取不同的截止因数,重构得到不同的冲击载荷。数值仿真结果表明:当截止因数为0.01时,重构的冲击载荷动力学响应与原始冲击载荷动力学响应基本保持一致;在保证足够的安全裕度的前提下,当截止因数选0.20时,可获得更低的截止频率。 相似文献
66.
We numerically investigate the effect of liquid cohesion on the clogging of microchannels induced by small wet particles. The computer simulation is performed by the discrete element method (DEM) with cohesive contact models in presence of pendular liquid bridges, which is embedded into the computational fluid dynamics (CFD). We find that liquid cohesion significantly promotes particle deposition and agglomerate growth. A clogging phase diagram, in the form of Weber number and Stokes number, is constructed to quantify the clogging-nonclogging transition. The competition between particle–particle and particle–fluid interactions is quantitatively discussed in terms of particle velocity and slip velocity. Strong cohesion can address a greater slip velocity or drag between particles and fluid, which depresses the resuspension of deposited particles and results in clogging. Finally, we compare our results with clogging induced by van der Waals adhesion of small dry particles and find that the competence of liquid cohesion is more prominent. 相似文献
67.
Weixin Guan Xiaochen Yang Chenyuan Dong Xiaoming Yan Wenji Zheng Yuan Xi Xuehua Ruan Yan Dai Gaohong He 《应用聚合物科学杂志》2021,138(8):49895
The packing pattern of two-dimensional (2D) sheet-like fillers in membranes is relatively random, leading to the unfavorable permeability from tortuous diffusion pathway. A new strategy that using prestructured materials with uniform channels as fillers was proposed. In this work, Ti3AlC2 is etched to prepare multilayered MXene (m-MXene), the channels aggregate as a whole unit, ensure the impossibility of ineffective packing compared with traditional individual sheets, largely facilitating the selective permeation. Then, the m-MXene/Poly (amide-6-b-ethylene oxide) (Pebax) MMMs are synthesized. SEM images demonstrate the accordion shaped structure of filler, which is the multi-channels laminates. Furthermore, the results of gas permeation test exhibit enhanced performance of m-MXene/Pebax MMMs. MMM with 0.5 wt.% m-MXene behaved best, CO2 permeability of 86.22 Barrer as well as CO2/N2 selectivity of 104.85, transcending the Robeson upper bound (2008). Having distinct enhancement for CO2 separation, the m-MXene/Pebax MMMs in this work offer prospective practical applications. 相似文献
68.
The flame retardant polypropylene containing the micro-envelope core-shell structure flame retardant, which encapsulated ammonium polyphosphate into melamine-formaldehyde resin and sodium silicate through in situ polymerization was prepared with polyamide 6, added as a carbon-forming agent. The composition of ammonium polyphosphate, encapsulated ammonium polyphosphate with melamine-formaldehyde resin and the micro-envelope core-shell structure flame retardant were characterized. The fire safety and thermal stability were investigated and showed an improvement including limiting oxygen index, thermogravimetric analysis, vertical burning tests, and microscale combustion calorimeter. The burned compounds were also studied to confirm the burning mechanism. The results showed the flame retardant performance had been greatly improved, while polyamide 6 had better char-forming effect. Besides, the water solubility of flame retardants and their influence on the mechanical properties of polypropylene were also investigated. The results on the effects of additives demonstrated a high efficiency flame retardant to polypropylene. A core-shell flame retardant that sodium silicate and melamine-formaldehyde resin-coated ammonium polyphosphate had been constructed. The effect of the built flame retardant system on the combustion performance of polypropylene was studied from the mechanism and performance. The LOI of the most flame retardant polypropylene reached 28.6%, and UL-94 reached the V-0 level. 相似文献
69.
Cleide Borsoi Betina Hansen Ruan Ezequiel Gemmer Marcos Aurélio Dahlem Júnior Edson Luiz Francisquetti Ademir José Zattera Ruth Marlene Campomanes Santana André Luis Catto 《应用聚合物科学杂志》2021,138(45):51350
This study presents the preparation of post-consumer polypropylene (r-PP) composites filled with 30 wt% yerba mate (YM) stick particles. To improve the fiber–matrix adhesion, three surface treatments were performed: alkaline treatment with sodium hydroxide (NaOH) and use of 3-aminopropyltriethoxysilane (APTS) and maleic anhydride graft polypropylene copolymer (PP-g-MA) as coupling agents. Mechanical properties including tensile, flexural, and impact resistance were determined, and chemical (Fourier transform infrared spectroscopy [FTIR]), physical (water absorption), and morphological analyses were performed. The main findings show that the treatments were efficient in improving the mechanical properties of the composites, with emphasis on the r-PP/YM30/APTS and r-PP/YM30/PP-g-MA composites, which proved to be superior in tensile, flexion and impact strength and absorption of water compared to the untreated composite. The morphological analysis showed a better interaction between the fiber and the polymeric matrix for the composites with YM/APTS and YM/PP-g-MA, which corroborates the results of tensile and flexural strength, as well as with the spectra of FTIR in which the chemical modification of the fibers is observed. However, the results show that these treatments are promising in obtaining composites with recycled matrix with better properties. 相似文献
70.