将醋酸镍和葡萄糖溶于水中,与氧化石墨烯(GO)水悬浮液均匀混合,在180℃下水热处理24 h,再在Ar中700℃下炭化3 h,然后在空气中300℃下煅烧3 h得到三维Ni/NiO@C/GN。结果表明,水热处理过程中葡萄糖衍生的炭层将Ni(OH)2完全包裹,并在炭化...将醋酸镍和葡萄糖溶于水中,与氧化石墨烯(GO)水悬浮液均匀混合,在180℃下水热处理24 h,再在Ar中700℃下炭化3 h,然后在空气中300℃下煅烧3 h得到三维Ni/NiO@C/GN。结果表明,水热处理过程中葡萄糖衍生的炭层将Ni(OH)2完全包裹,并在炭化过程中转化为金属Ni,部分金属Ni在空气中煅烧中被氧化为NiO。当作为锂离子电池的负极材料时,其初始容量为711.6 mA h g^(-1),300次循环后增加到772.1 mA h g^(-1)。作为对比,没有添加GO的材料的初始容量较低,仅为584.7 mA h g^(-1),300次循环后下降到148.8 mA h g^(-1)。这些结果表明炭层可以抑制Ni/NiO纳米颗粒的团聚,有效缓解锂化过程中的体积膨胀,抑制循环过程中的电极开裂。GO的加入可形成丰富的导电网络,提高导电性。较大的比表面积可增加活性位点,有利于电解液快速浸润电极材料。这些因素显著改善了Ni/NiO@C/GN负极的电化学性能。展开更多
现实世界中存在各式各样的复杂网络,如电力网络、交通网络、社交网络,这些复杂网络和人们的生产生活息息相关。而快速、精准地识别网络中的重要节点,有助于运用有限的资源去管理、维护复杂网络。本文对网络的传播效率进行了定义,并提出...现实世界中存在各式各样的复杂网络,如电力网络、交通网络、社交网络,这些复杂网络和人们的生产生活息息相关。而快速、精准地识别网络中的重要节点,有助于运用有限的资源去管理、维护复杂网络。本文对网络的传播效率进行了定义,并提出了一种基于改进的重要节点挖掘方法GN-PR(Girvan Newman and PageRank),该方法首先通过GN算法对网络进行社区划分,在此基础上使用PageRank算法对每个社区内的节点重要性进行分析,最后结合社区的整体重要性完成重要节点的挖掘。实验结果表明,本文所提出的GN-PR算法相比较传统的重要节点挖掘方法不但性能得到了提高,而且可以有效地减少节点重叠影响力对算法性能的影响。展开更多
The reusable launch vehicle (RLV) presents a new avenue for reducing cost of space transportation. The landing mechanism, which provides landing support and impact absorption, is a vital component of the RLV at final ...The reusable launch vehicle (RLV) presents a new avenue for reducing cost of space transportation. The landing mechanism, which provides landing support and impact absorption, is a vital component of the RLV at final stage of recovery. This study proposes a novel legged deployable landing mechanism (LDLM) for RLV. The Watt-II six-bar mechanism is adopted to obtain the preferred configuration via the application of the linkage variation approach. To endow the proposed LDLM with advantages of large landing support region, lightweight, and reasonable linkage internal forces, a multi-objective optimization paradigm is developed. Furthermore, the optimal scale parameters for guiding the LDLM prototype design is obtained numerically using the non-dominated sorting genetic algorithm-II (NSGA-II) evolutionary algorithm. A fully-functional scaled RLV prototype is developed by integrating the gravity-governed deploying scheme to facilitate unfolding action to avoid full-range actuation, a dual-backup locking mechanism to enhance reliability of structure stiffening as fully deployed, and a shock absorber (SA) with multistage honeycomb to offer reliable shock absorbing performance. The experimental results demonstrate that the proposed LDLM is capable of providing rapid and smooth deployment (duration less than 1.5 s) with mild posture disturbance to the cabin (yaw and pitch fluctuations less than 6°). In addition, it provides satisfactory impact attenuation (acceleration peak less than 10g (g is the gravitational acceleration)) in the 0.2 m freefall test, which makes the proposed LDLM a potential alternative for developing future RLV archetype.展开更多
Chitosan-montmorillonite(CS-MMT) hybrid was prepared and characterized by XRD,FTIR and TG.The results showed that chitosan was intercalated into the layer structure of Na+-montmorillonite.The ability of CS-MMT hybrid ...Chitosan-montmorillonite(CS-MMT) hybrid was prepared and characterized by XRD,FTIR and TG.The results showed that chitosan was intercalated into the layer structure of Na+-montmorillonite.The ability of CS-MMT hybrid as an adsorbent for the removal of reactive orange X-GN from aqueous solution has been studied.The effects of various parameters such as initial concentration and temperature were also studied.The Langmuir and Freundlich adsorption isotherms have been used to fit the experimental data,and the former giving the higher correlation.Thermodynamic parameters of the adsorption process,ΔG°,ΔH° and ΔS° were determined to be-24.90 kJ·mol-1(at 20℃),10.58 kJ·mol-1 and 121.0 J·mol-1·K-1,respectively.The results indicated that the adsorption of reactive orange X-GN on CS-MMT hybrid was spontaneous.展开更多
文摘将醋酸镍和葡萄糖溶于水中,与氧化石墨烯(GO)水悬浮液均匀混合,在180℃下水热处理24 h,再在Ar中700℃下炭化3 h,然后在空气中300℃下煅烧3 h得到三维Ni/NiO@C/GN。结果表明,水热处理过程中葡萄糖衍生的炭层将Ni(OH)2完全包裹,并在炭化过程中转化为金属Ni,部分金属Ni在空气中煅烧中被氧化为NiO。当作为锂离子电池的负极材料时,其初始容量为711.6 mA h g^(-1),300次循环后增加到772.1 mA h g^(-1)。作为对比,没有添加GO的材料的初始容量较低,仅为584.7 mA h g^(-1),300次循环后下降到148.8 mA h g^(-1)。这些结果表明炭层可以抑制Ni/NiO纳米颗粒的团聚,有效缓解锂化过程中的体积膨胀,抑制循环过程中的电极开裂。GO的加入可形成丰富的导电网络,提高导电性。较大的比表面积可增加活性位点,有利于电解液快速浸润电极材料。这些因素显著改善了Ni/NiO@C/GN负极的电化学性能。
文摘现实世界中存在各式各样的复杂网络,如电力网络、交通网络、社交网络,这些复杂网络和人们的生产生活息息相关。而快速、精准地识别网络中的重要节点,有助于运用有限的资源去管理、维护复杂网络。本文对网络的传播效率进行了定义,并提出了一种基于改进的重要节点挖掘方法GN-PR(Girvan Newman and PageRank),该方法首先通过GN算法对网络进行社区划分,在此基础上使用PageRank算法对每个社区内的节点重要性进行分析,最后结合社区的整体重要性完成重要节点的挖掘。实验结果表明,本文所提出的GN-PR算法相比较传统的重要节点挖掘方法不但性能得到了提高,而且可以有效地减少节点重叠影响力对算法性能的影响。
文摘The reusable launch vehicle (RLV) presents a new avenue for reducing cost of space transportation. The landing mechanism, which provides landing support and impact absorption, is a vital component of the RLV at final stage of recovery. This study proposes a novel legged deployable landing mechanism (LDLM) for RLV. The Watt-II six-bar mechanism is adopted to obtain the preferred configuration via the application of the linkage variation approach. To endow the proposed LDLM with advantages of large landing support region, lightweight, and reasonable linkage internal forces, a multi-objective optimization paradigm is developed. Furthermore, the optimal scale parameters for guiding the LDLM prototype design is obtained numerically using the non-dominated sorting genetic algorithm-II (NSGA-II) evolutionary algorithm. A fully-functional scaled RLV prototype is developed by integrating the gravity-governed deploying scheme to facilitate unfolding action to avoid full-range actuation, a dual-backup locking mechanism to enhance reliability of structure stiffening as fully deployed, and a shock absorber (SA) with multistage honeycomb to offer reliable shock absorbing performance. The experimental results demonstrate that the proposed LDLM is capable of providing rapid and smooth deployment (duration less than 1.5 s) with mild posture disturbance to the cabin (yaw and pitch fluctuations less than 6°). In addition, it provides satisfactory impact attenuation (acceleration peak less than 10g (g is the gravitational acceleration)) in the 0.2 m freefall test, which makes the proposed LDLM a potential alternative for developing future RLV archetype.
基金国家自然科学基金(the National Natural Science Foundation of China under Grant No.10771092)国家重点基础研究发展规划(973)(the National Grand Fundamental Research973Program of China under Grant No.2004CB318000)
文摘Chitosan-montmorillonite(CS-MMT) hybrid was prepared and characterized by XRD,FTIR and TG.The results showed that chitosan was intercalated into the layer structure of Na+-montmorillonite.The ability of CS-MMT hybrid as an adsorbent for the removal of reactive orange X-GN from aqueous solution has been studied.The effects of various parameters such as initial concentration and temperature were also studied.The Langmuir and Freundlich adsorption isotherms have been used to fit the experimental data,and the former giving the higher correlation.Thermodynamic parameters of the adsorption process,ΔG°,ΔH° and ΔS° were determined to be-24.90 kJ·mol-1(at 20℃),10.58 kJ·mol-1 and 121.0 J·mol-1·K-1,respectively.The results indicated that the adsorption of reactive orange X-GN on CS-MMT hybrid was spontaneous.
