Ocean wave energy converters(WECs) are obtaining more and more attentions in the world. So far, many types of converters have been invented. Oscillating body systems are a major class of WECs, which typically have one...Ocean wave energy converters(WECs) are obtaining more and more attentions in the world. So far, many types of converters have been invented. Oscillating body systems are a major class of WECs, which typically have one degree of freedom(DOF), and the power absorption efficiency is not quite satisfactory. In this paper, a 3-DOF WEC is proposed and a simplified frequency-domain dynamic model of the WEC depending on the linear potential theory is conducted. The performances of three geometries of the oscillating body including the cone, the cylinder and the hemisphere have been compared, and the results show that the hemisphere is more suitable for the 3-DOF WEC.Subsequently, the relationship among the parameters of the hemisphere is established based on the equal natural frequencies of the heave and pitch(or roll) motions, and the results show that lowering the center of gravity leads to the better power absorption in the pitch(or roll) motion. In the end, the power matrixes of different sizes of the hemispheres under different irregular waves are obtained, which can give a size design reference for engineers.展开更多
为解决民航机坪覆盖面积大、设备分布分散以及资源受限导致的消息投递率低、传输时延长以及网络开销大的问题,提出一种机坪感知网络机会控制方法(MPCS)。利用机坪节点接触特性,融合节点多维属性构建节点转发能力模型筛选候选转发节点,...为解决民航机坪覆盖面积大、设备分布分散以及资源受限导致的消息投递率低、传输时延长以及网络开销大的问题,提出一种机坪感知网络机会控制方法(MPCS)。利用机坪节点接触特性,融合节点多维属性构建节点转发能力模型筛选候选转发节点,提高目标跟踪准确度;依据节点分布确定可转发节点数,即消息副本转发数,解决多副本传输开销大问题;结合余弦相似度进一步确定候选转发节点并转发消息,扩大消息传播范围,提高消息投递率。在ONE仿真模拟器的验证结果表明,与传统Epidemic、Prophet和Spray and Wait相比,MPCS策略的消息平均投递率达到80%,消息平均时延低至235 s,表现了相对较好的网络性能。展开更多
Feeding rhythm of common carp was investigated from 4℃ to 34℃. The results indicated that there was a diel feeding rhythm for both adult （630-850 g） and youth （61-91 g） at all tested temperatures. There were two...Feeding rhythm of common carp was investigated from 4℃ to 34℃. The results indicated that there was a diel feeding rhythm for both adult （630-850 g） and youth （61-91 g） at all tested temperatures. There were two main activity peaks at 8：00-11：00 a.m. and 19：00-23：00 p.m., during which feeding quantities were 10.68%-32.53% and 16.25%-33.41% of the daily intake, respectively. When water temperature dropped to below 10℃, the feeding peak concentrated at 8：00-11：00 a.m. and 19：00 p.m. to 4：00 a.m. At 6℃, though both adult and youth would still feed, the feeding quantities were only 0.01% and 0.35% of body mass. Daily feeding rate of adult and youth reached 1.21% and 2.63% at 14℃, respectively. Both adult and youth carps reached the maximum daily feeding rate at 28℃, being 2.84% and 12.06% of body mass, respectively. The daily feeding rate of adult and youth reduced suddenly after at 34℃, and the daily feeding rate was only 0.74% and 9.45% of body mass, respectively. There was significant difference in daily feeding rate at different water temperatures （P〈0.05）.展开更多
基金financially supported by China Postdoctoral Science Foundation(Grant No.2017M611554)the National Natural Science Foundation of China(Grant No.51335007)
文摘Ocean wave energy converters(WECs) are obtaining more and more attentions in the world. So far, many types of converters have been invented. Oscillating body systems are a major class of WECs, which typically have one degree of freedom(DOF), and the power absorption efficiency is not quite satisfactory. In this paper, a 3-DOF WEC is proposed and a simplified frequency-domain dynamic model of the WEC depending on the linear potential theory is conducted. The performances of three geometries of the oscillating body including the cone, the cylinder and the hemisphere have been compared, and the results show that the hemisphere is more suitable for the 3-DOF WEC.Subsequently, the relationship among the parameters of the hemisphere is established based on the equal natural frequencies of the heave and pitch(or roll) motions, and the results show that lowering the center of gravity leads to the better power absorption in the pitch(or roll) motion. In the end, the power matrixes of different sizes of the hemispheres under different irregular waves are obtained, which can give a size design reference for engineers.
文摘为解决民航机坪覆盖面积大、设备分布分散以及资源受限导致的消息投递率低、传输时延长以及网络开销大的问题,提出一种机坪感知网络机会控制方法(MPCS)。利用机坪节点接触特性,融合节点多维属性构建节点转发能力模型筛选候选转发节点,提高目标跟踪准确度;依据节点分布确定可转发节点数,即消息副本转发数,解决多副本传输开销大问题;结合余弦相似度进一步确定候选转发节点并转发消息,扩大消息传播范围,提高消息投递率。在ONE仿真模拟器的验证结果表明,与传统Epidemic、Prophet和Spray and Wait相比,MPCS策略的消息平均投递率达到80%,消息平均时延低至235 s,表现了相对较好的网络性能。
文摘Feeding rhythm of common carp was investigated from 4℃ to 34℃. The results indicated that there was a diel feeding rhythm for both adult （630-850 g） and youth （61-91 g） at all tested temperatures. There were two main activity peaks at 8：00-11：00 a.m. and 19：00-23：00 p.m., during which feeding quantities were 10.68%-32.53% and 16.25%-33.41% of the daily intake, respectively. When water temperature dropped to below 10℃, the feeding peak concentrated at 8：00-11：00 a.m. and 19：00 p.m. to 4：00 a.m. At 6℃, though both adult and youth would still feed, the feeding quantities were only 0.01% and 0.35% of body mass. Daily feeding rate of adult and youth reached 1.21% and 2.63% at 14℃, respectively. Both adult and youth carps reached the maximum daily feeding rate at 28℃, being 2.84% and 12.06% of body mass, respectively. The daily feeding rate of adult and youth reduced suddenly after at 34℃, and the daily feeding rate was only 0.74% and 9.45% of body mass, respectively. There was significant difference in daily feeding rate at different water temperatures （P〈0.05）.
