In this paper, the characteristics of China＇s aid to Africa under the new situation are summarized, and also the existing problems are smmnarized from the level of strategy, the level of public opinion, the level of ...In this paper, the characteristics of China＇s aid to Africa under the new situation are summarized, and also the existing problems are smmnarized from the level of strategy, the level of public opinion, the level of methods and contents, and the level of effect. Combined with the change of the current international political and economic trend, the model of China＇s aid to Afiica is innovatively concluded by tile author as Ihe model of＂Bidirectional Balance Improved Aid＂ and also its definition, main contents, and practice keys are expounded. This model provides a reference model for China＇s aid to Africa and is good for solving the problems in the aid, so that a better actual effect can be achieved.展开更多
Sampling study is an effective exploration method, but the most extreme environments of hydrothermal vents pose considerable engineering challenges for sampling hydrothermal fluids. Moreover, traditional sampler syste...Sampling study is an effective exploration method, but the most extreme environments of hydrothermal vents pose considerable engineering challenges for sampling hydrothermal fluids. Moreover, traditional sampler systems with sample valves have difficulty in maintaining samples in situ pressure. However, decompression changes have effect on microorganisms sensitive to such stresses. To address the technical difficulty of collecting samples from hydrothermal vents, a new bidirectional high pressure-resistant sample valve with balanced poppet was designed. The sample valve utilizes a soft high performance plastic ＂PEEK＂ as poppet. The poppet with inapposite dimension is prone to occur to plastic deformation or rupture for high working pressure in experiments. To address this issue, based on the fmite element model, simulated results on stress distribution of the poppet with different structure parameters and preload spring force were obtained. The static axial deformations on top of the poppet were experimented. The simulated results agree with the experimental results. The new sample valve seals well and it can withstand high working pressure.展开更多
文摘In this paper, the characteristics of China＇s aid to Africa under the new situation are summarized, and also the existing problems are smmnarized from the level of strategy, the level of public opinion, the level of methods and contents, and the level of effect. Combined with the change of the current international political and economic trend, the model of China＇s aid to Afiica is innovatively concluded by tile author as Ihe model of＂Bidirectional Balance Improved Aid＂ and also its definition, main contents, and practice keys are expounded. This model provides a reference model for China＇s aid to Africa and is good for solving the problems in the aid, so that a better actual effect can be achieved.
基金supported by National Hi-tech Research and Development Program of China (863 Program, No. 2002AA401002-05).
文摘Sampling study is an effective exploration method, but the most extreme environments of hydrothermal vents pose considerable engineering challenges for sampling hydrothermal fluids. Moreover, traditional sampler systems with sample valves have difficulty in maintaining samples in situ pressure. However, decompression changes have effect on microorganisms sensitive to such stresses. To address the technical difficulty of collecting samples from hydrothermal vents, a new bidirectional high pressure-resistant sample valve with balanced poppet was designed. The sample valve utilizes a soft high performance plastic ＂PEEK＂ as poppet. The poppet with inapposite dimension is prone to occur to plastic deformation or rupture for high working pressure in experiments. To address this issue, based on the fmite element model, simulated results on stress distribution of the poppet with different structure parameters and preload spring force were obtained. The static axial deformations on top of the poppet were experimented. The simulated results agree with the experimental results. The new sample valve seals well and it can withstand high working pressure.
