汽车路噪的分析与治理是NVH(Noise,Vibration And Harshness)工作的重要组成部分。由于路噪的产生机理复杂,建立机理模型较困难,故引入数据驱动方法对路噪进行研究。首先,对路噪影响因素进行剖析,界定出具有显著性的影响因素。在此基础...汽车路噪的分析与治理是NVH(Noise,Vibration And Harshness)工作的重要组成部分。由于路噪的产生机理复杂,建立机理模型较困难,故引入数据驱动方法对路噪进行研究。首先,对路噪影响因素进行剖析,界定出具有显著性的影响因素。在此基础上,运用长短时记忆神经网络算法(LSTM)揭示路噪与其影响因素间的复杂非线性关系,建立路噪预测模型。进而在粗糙沥青路面分别以40 km/h、60 km/h的车速工况采集悬架相关部件振动数据和驾驶员右耳畔噪声数据,以获得样本用于路噪模型的训练和检验。并采用Mixup数据增强策略合成新的样本,从而使样本量不足状况得到改善。进一步,对LSTM路噪预测模型进行检验与分析,测试结果均方误差为0.076 2,表明预测效果良好,证明所提方法的有效性。同时,将BPNN、SVR与LSTM预测方法进行比较,发现LSTM路噪预测模型精度更高,泛化能力更好,从而证明该方法的优越性。展开更多
Spacecraft orbit evasion is an effective method to ensure space safety. In the spacecraft’s orbital plane, the space non-cooperate target with autonomous approaching to the spacecraft may have a dangerous rendezvous....Spacecraft orbit evasion is an effective method to ensure space safety. In the spacecraft’s orbital plane, the space non-cooperate target with autonomous approaching to the spacecraft may have a dangerous rendezvous. To deal with this problem, an optimal maneuvering strategy based on the relative navigation observability degree is proposed with angles-only measurements. A maneuver evasion relative navigation model in the spacecraft’s orbital plane is constructed and the observability measurement criteria with process noise and measurement noise are defined based on the posterior Cramer-Rao lower bound. Further, the optimal maneuver evasion strategy in spacecraft’s orbital plane based on the observability is proposed. The strategy provides a new idea for spacecraft to evade safety threats autonomously. Compared with the spacecraft evasion problem based on the absolute navigation, more accurate evasion results can be obtained. The simulation indicates that this optimal strategy can weaken the system’s observability and reduce the state estimation accuracy of the non-cooperative target, making it impossible for the non-cooperative target to accurately approach the spacecraft.展开更多
[ Objective ] The paper was to study the effects of rapeseed straw on growth and slanghter performance of Sichuan white goose. [ Method ] Totally 400 3-day-old Sichuan white geese were randomly divided into four group...[ Objective ] The paper was to study the effects of rapeseed straw on growth and slanghter performance of Sichuan white goose. [ Method ] Totally 400 3-day-old Sichuan white geese were randomly divided into four groups ; geese in control group were fed with the fundamental diet ; geese in group 1, group 2 and group 3 were fed with the fundamental diet containing 5%, 10% and 10% rapeseed straw instead of equal amount of wheat bran, respectively. The body weight and slaughter performance of Sichuan white geese in control group, group 1 and group 2 were determined at 10 weeks of age, while those in group 3 were determined at 14 weeks of age. [ Result] There was no significant difference in gross weight, slaughter weight, eviscerated weight with giblet, head weight, sole weight, wing weight, neck weight, muscular stomach weight and intestine indexes of 10-week-old white geese between group 1 and control group, and between group 2 and con- trol group （ P 〉 0.05 ） ; the live weight slightly decreased. The growth and slaughter performance of 14-week-old Sichuan white geese were significantly higher fllan that of 10-week-old geese （P 〈0.05）, with better meat and flavor, but relatively low average daily gain （P 〈0.05 ） ; there was no significant impact on muscular stomach pH and intestinal pH （P 〉 0.05 ）. [ Conclusion] Substituting partial wheat bran with rapeseed straw can satisfy the diet requirement of Sichuan white geese, but has no significant impact on its growth and slaughter performance （ P 〉 0.05）.展开更多
基金supported by the National Key R&D Program of China (2020YFA0713502)the Special Fund Project for Guiding Local Scientific and Technological Development (2020ZYT003)+1 种基金the National Natural Science Foundation of China (U20B2055,61773021,61903086)the Natural Science Foundation of Hunan Province (2019JJ20018,2020JJ4280)。
文摘Spacecraft orbit evasion is an effective method to ensure space safety. In the spacecraft’s orbital plane, the space non-cooperate target with autonomous approaching to the spacecraft may have a dangerous rendezvous. To deal with this problem, an optimal maneuvering strategy based on the relative navigation observability degree is proposed with angles-only measurements. A maneuver evasion relative navigation model in the spacecraft’s orbital plane is constructed and the observability measurement criteria with process noise and measurement noise are defined based on the posterior Cramer-Rao lower bound. Further, the optimal maneuver evasion strategy in spacecraft’s orbital plane based on the observability is proposed. The strategy provides a new idea for spacecraft to evade safety threats autonomously. Compared with the spacecraft evasion problem based on the absolute navigation, more accurate evasion results can be obtained. The simulation indicates that this optimal strategy can weaken the system’s observability and reduce the state estimation accuracy of the non-cooperative target, making it impossible for the non-cooperative target to accurately approach the spacecraft.
基金Supported by Science and Technology Project of Sichuan Province(14010202)
文摘[ Objective ] The paper was to study the effects of rapeseed straw on growth and slanghter performance of Sichuan white goose. [ Method ] Totally 400 3-day-old Sichuan white geese were randomly divided into four groups ; geese in control group were fed with the fundamental diet ; geese in group 1, group 2 and group 3 were fed with the fundamental diet containing 5%, 10% and 10% rapeseed straw instead of equal amount of wheat bran, respectively. The body weight and slaughter performance of Sichuan white geese in control group, group 1 and group 2 were determined at 10 weeks of age, while those in group 3 were determined at 14 weeks of age. [ Result] There was no significant difference in gross weight, slaughter weight, eviscerated weight with giblet, head weight, sole weight, wing weight, neck weight, muscular stomach weight and intestine indexes of 10-week-old white geese between group 1 and control group, and between group 2 and con- trol group （ P 〉 0.05 ） ; the live weight slightly decreased. The growth and slaughter performance of 14-week-old Sichuan white geese were significantly higher fllan that of 10-week-old geese （P 〈0.05）, with better meat and flavor, but relatively low average daily gain （P 〈0.05 ） ; there was no significant impact on muscular stomach pH and intestinal pH （P 〉 0.05 ）. [ Conclusion] Substituting partial wheat bran with rapeseed straw can satisfy the diet requirement of Sichuan white geese, but has no significant impact on its growth and slaughter performance （ P 〉 0.05）.
