排序方式： 共有45条查询结果，搜索用时 15 毫秒
1.
针对船舶线性横摇系统,设计了一种基于执行依赖启发式动态规划（ADHDP）方法的在线学习最优减摇鳍控制器.在设计过程中直接使用输入输出数据获取系统状态值.利用评价网络来逼近针对船舶减摇鳍控制系统设计的性能指标函数,并通过执行网络获得最优控制律,这两个网络都是多层前馈神经网络,即反向传播（BP）神经网络.在训练过程中,这两个神经网络不仅可以使用实时测量数据,也可以减少船舶横摇模型的内部误差和不确定性干扰的影响,从而提高系统的鲁棒性.最后,仿真结果表明所提出的ADHDP控制器对于降低船舶横摇有很好的控制效果. 相似文献
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Robust control based on feedback linearization for roll stabilizing of autonomous underwater vehicle under wave disturbances 总被引：1，自引：0，他引：1
In the case of Autonomous Underwater Vehicle(AUV) navigating with low speed near water surface,a new method for design of roll motion controller is proposed in order to restrain wave disturbance effectively and improve roll stabilizing performance.Robust control is applied,which is based on uncertain nonlinear horizontal motion model of AUV and the principle of zero speed fin stabilizer.Feedback linearization approach is used to transform the complex nonlinear system into a comparatively simple linear system.For parameter uncertainty of motion model,the controller is designed with mixed-sensitivity method based on H-infinity robust control theory.Simulation results show better robustness improved by this control method for roll stabilizing of AUV navigating near water surface. 相似文献
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提出一种波纹开缝翅片管换热器,对其传热与流动特性进行三维数值模拟,选择Re范围在1 000到5 000时与平板开缝翅片的模拟相比较。结果表明,在Re小于2 752时,平板开缝比波纹开缝的换热效果好,而Re大于2 752时,波纹开缝比平板开缝换热效果更好,并且波纹开缝翅片管换热器的流动阻力小于平板开缝,因此,Re大于2 752时波纹开缝比平板开缝综合效果更好。 相似文献
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为了探明姬松茸提取物的体外抗病毒感染活性及其作用方式,进而为水产养殖鱼类高效抗淋巴囊肿病毒(lymphocystis disease virus,LCDV)感染活性物质的开发和鲆蝶类淋巴囊肿病的防治奠定基础,利用热水浸提和酒精沉淀法得到了5种姬松茸提取物组分(E1～5),并利用MTT、细胞病变程度观察等方法研究了5种组分对LCDV感染体外培养大菱鲆鳍细胞(turbot fin cells,TF细胞)的影响作用.细胞毒性实验结果显示,5种组分对体外培养TF细胞均无毒性.细胞病变程度结果表明,本文所得5种姬松茸提取物组分尤其是E5组分具有显著的抗LCDV感染TF细胞的活性.不同方式感染的实验结果进一步显示,5种姬松茸提取物组分抗LCDV感染TF细胞的作用可能主要是通过直接灭活病毒和/或阻断病毒吸附细胞来实现的. 相似文献
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仿鱼尾潜器推进系统的水动力分析 总被引：21，自引：3，他引：21
以开发适用于小型潜器的仿生操纵与推进系统为研究背景 ,对金枪鱼的月牙形尾鳍进行水动力分析。文中将金枪鱼的尾鳍处理为在做横移和摇摆的耦合运动的同时 ,以某一匀速向前运动的月牙形刚性尾翼。计算中应用了双曲面元和压力库塔条件 ,利用面元法计算分析该三维尾翼的非定常水动力性能。探讨了前进速度、横荡和摇首的幅度、频率及其相位差对推进性能的影响 相似文献
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Adaptive optimal control of an autonomous underwater vehicle in the dive plane using dorsal fins 总被引：1，自引：0，他引：1
In this paper, adaptive control of low speed bio-robotic autonomous underwater vehicles (BAUVs) in the dive plane using dorsal fins is considered. It is assumed that the model parameters are completely unknown and only the depth of the vehicle is measured for feedback. Two dorsal fins are mounted in the horizontal plane on either side of the BAUV. The normal force produced by the fins, when cambered, is used for the maneuvering. The BAUV model considered here is non-minimum phase. An indirect adaptive control system is designed for the depth control using the dorsal fins. The control system consists of a gradient based identifier for online parameter estimation, an observer for state estimation, and an optimal controller. Simulation results are presented which show that the adaptive control system accomplishes precise depth control of the BAUV using dorsal fins in spite of large uncertainties in the system parameters. 相似文献
8.
We tested the utility of chemical marking techniques in the juvenile black rockfish Sebastes schlegelii. Juveniles(30–40 mm total length) were immersed in a range of tetracycline hydrochloride(TC) solutions at concentrations ranging from 300 to 500 mg/L, and alizarin complexone(ALC) solutions at concentrations ranging from 200 to 400 mg/L in filtered sea water(salinity of 30) for 24 h, respectively. Otoliths(sagittae, asteriscus), scales, fin rays(dorsal, pectoral, ventral, anal, and caudal fin rays), and fin spines(dorsal, ventral, and anal fin spines) were sampled and used to detect fl uorescent marks after a 60-day growth experiment. With the exception of 300 mg/L TC, acceptable marks were produced in the otoliths and fin spines by all concentrations of TC and ALC. In particular, we observed clearly visible marks in the sagittae, asteriscus, and fin spines under normal light at concentrations of 200–400 mg/L, 250–400 mg/L, and 250–400 mg/L ALC, respectively. Scales and fin rays had acceptable marks at much higher concentrations(≥350 mg/L TC, ≥250 mg/L ALC for scales and ≥350 mg/L TC, ≥300 mg/L ALC for fin rays). The best mark quality(i.e., acceptable marks were observed in all sampled structures after immersion marking) were obtained following immersion in TC at between 350–500 mg/L, and ALC between 300–400 mg/L. In addition, there was no significant difference in survival and growth of TC and ALC marked fish compared to their controls up to 60 days post-marking( P 0.05). 相似文献
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Angela J. Ramsay 《新西兰海洋与淡水研究杂志》2013,47(1):77-90
The viable heterotrophic bacteria of Lake Grasmere in inland Canterbury (43° 05 S, 171° 45 E) were studied. Numbers of bacteria in water above a spring were positively correlated with rainfall in the 7 days before sampling, but bacteria in open water and from over the macrophyte Elodea canadensis were not. There was some increase in the bacterial population in the water over E. canadensis in the autumn to winter months. Numbers of bacteria in the open water ranged from 55 to 1020 cells per millilitre, and were outnumbered by algae by a factor of between 4 and 34. The bacterial population tended to increase after blooms of zooplankton, but there was little or no response to changes in phytoplankton populations. Benthic bacteria rarely increased in numbers after the deposition of organic matter. 相似文献
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Common carp (Cyprinus carpio L.) exhibits significant morphological variability in the shape and size of the caudal fin. In this study, we used 190 progeny from two F1 parents to identify and map quantitative trait loci (QTLs) that influence caudal fin length (CFL) and the ratio (RCS) between caudal fin length and standard length (SL) based on a microsatellite genetic map of common carp. A total of 15 QTLs were detected in seven different linkage groups. One significant and eight suggestive QTLs affecting CFL were identified on LG8, LG14, LG29, LG32 and LG44, which explained 8.0%–22.1% of the phenotypic variation; six suggestive QTLs affecting RCS were detected on LG8, LG32, LG46 and LG48, which explained 7.0%–15.4% of the phenotypic variation. The QTLs for caudal fin length detected in this study may serve as a starting point for identification of genes involved in caudal fin development in common carp. 相似文献