The breeding system and its consequence on fruit set of Eremosparton songoricum(Litv.) Vass.,a rare shrubby legume occurring in moving or semi-fixed sand dunes of Central Asian deserts,were examined by manipulative ...The breeding system and its consequence on fruit set of Eremosparton songoricum(Litv.) Vass.,a rare shrubby legume occurring in moving or semi-fixed sand dunes of Central Asian deserts,were examined by manipulative experiments and observational studies in natural populations during the period of 2007-2009.The results showed that E.songoricum exhibits a mixed mating system.It is self-compatible,but depends strictly on pollinators to set fruits.Only two effective pollinators were detected and they triggered the specialized pollination mechanism(a 'brush type' and 'tripping mechanism').Geitonogamy becomes predominant in natural populations,because(74.5±1.3)% of visiting activity happened within or between inflorescences and(24.3±1.4)% occurred between ramets.As a result,inbreeding depression caused by geitonogamous selfing inevitably happened under natural conditions,showing 2.36 times less fruit set than was achieved by hand cross-pollination.The results explained the rarity of the species due to its breeding system,and will assist to develop suitable conservation strategies in severe desert environments.展开更多
Today, many industrial and domestic electronic appliances and equipment (devices) are exposed to power disturbances such as voltage variations of the AC mains supply which often lead to damage of the electronic device...Today, many industrial and domestic electronic appliances and equipment (devices) are exposed to power disturbances such as voltage variations of the AC mains supply which often lead to damage of the electronic devices. As these devices are quite sensitive to power disturbances, there is a need for a tripping system that can help avoid any damage to devices in use. The objective of this work is to build a system that monitors line voltage and protects appliances from unacceptable voltage variations. The system consists of a tripping mechanism that monitors the input voltage and trips according to the limits provided. An Arduino Uno microcontroller is used to determine the voltage level through a voltage divider circuit. The system’s novelty and innovation lie in its flexibility. It offers the user the ability to define different overvoltage and undervoltage threshold values depending on the specific appliances used in the household. In operation, the system displays the voltage state (overvoltage, normal voltage, overvoltage) and alerts the user by sending an SMS via a GSM modem. The system is valuable for industrial and domestic applications, especially in developing economies such as those of Sub-Saharan Africa, where overvoltage and undervoltage are acute problems.展开更多
The transformation behavior, microstructural evolution and mechanical properties were compared in a coldrolled Nb–Mo microalloyed 6.5Mn alloy after intercritical annealing(IA) and quenching and partitioning(Q & P...The transformation behavior, microstructural evolution and mechanical properties were compared in a coldrolled Nb–Mo microalloyed 6.5Mn alloy after intercritical annealing(IA) and quenching and partitioning(Q & P),respectively. The thermodynamic calculation and theoretical analysis were used to determine the optimal heat treatment parameters. The Q & P samples exhibited relatively higher strength with relatively low ductility, mainly due to the hard martensite matrix, which resulted in continuous yielding behavior upon loading, whereas the IA samples showed the significantly improved ductility, which benefited from the more sufficient transformation-induced plasticity(TRIP) effects and the softer ultrafine ferrite matrix. The dependence of yield point elongation(YPE) of IA samples on grain size demonstrated that the YPE value was in the reverse proportional relationship to the average grain size, which agreed well with theoretical analysis.展开更多
The effect of partial or full substitution of Si by Al on the microstructure and mechanical properties has been extensively studied in multi-phase transformation-induced plasticity(TRIP) steels with polygonal ferrit...The effect of partial or full substitution of Si by Al on the microstructure and mechanical properties has been extensively studied in multi-phase transformation-induced plasticity(TRIP) steels with polygonal ferrite matrix, but rarely studied in bainitic TRIP steels. The aim of the present study is to properly investigate the effect of Al and Si on bainite transformation, microstructure and mechanical properties in bainitic steels in order to provide guidelines for the alloying design as a function of process parameters for the 3 rd generation advanced high strength steels(AHSS). It is shown from the dilatometry study,microstructural investigations and tensile properties measurements that the Al addition results in an acceleration whereas Si addition leads to a retardation in bainite transformation kinetics. The addition of Al retards the decomposition of austenite into pearlite and carbides at holding temperatures higher than450℃ whereas Si retards the decomposition of austenite into carbides at temperatures lower than 450℃.Consequently, the Al-added bainitic steel has a better strength-elongation combination at bainitic holding temperatures higher than 450℃ while Si-added steel has a better strength-elongation combination at temperatures lower than 450℃. The higher yield strength of Al-added steel is mainly attributed to its finer bainitic lath. The higher tensile strength of Si-added steel is not only related to the stronger contribution of Si on work hardening during deformation, but also due to the higher volume fraction of martensite or martensite/austenite(MA) blocks in all heat treatment conditions, as well as the lower mechanical stability of retained austenite in this steel.展开更多
基金supported by the National Natural Science Foundation of China (30970547,31070472)the National Basic Research Program of China (2009CB825104)
文摘The breeding system and its consequence on fruit set of Eremosparton songoricum(Litv.) Vass.,a rare shrubby legume occurring in moving or semi-fixed sand dunes of Central Asian deserts,were examined by manipulative experiments and observational studies in natural populations during the period of 2007-2009.The results showed that E.songoricum exhibits a mixed mating system.It is self-compatible,but depends strictly on pollinators to set fruits.Only two effective pollinators were detected and they triggered the specialized pollination mechanism(a 'brush type' and 'tripping mechanism').Geitonogamy becomes predominant in natural populations,because(74.5±1.3)% of visiting activity happened within or between inflorescences and(24.3±1.4)% occurred between ramets.As a result,inbreeding depression caused by geitonogamous selfing inevitably happened under natural conditions,showing 2.36 times less fruit set than was achieved by hand cross-pollination.The results explained the rarity of the species due to its breeding system,and will assist to develop suitable conservation strategies in severe desert environments.
文摘Today, many industrial and domestic electronic appliances and equipment (devices) are exposed to power disturbances such as voltage variations of the AC mains supply which often lead to damage of the electronic devices. As these devices are quite sensitive to power disturbances, there is a need for a tripping system that can help avoid any damage to devices in use. The objective of this work is to build a system that monitors line voltage and protects appliances from unacceptable voltage variations. The system consists of a tripping mechanism that monitors the input voltage and trips according to the limits provided. An Arduino Uno microcontroller is used to determine the voltage level through a voltage divider circuit. The system’s novelty and innovation lie in its flexibility. It offers the user the ability to define different overvoltage and undervoltage threshold values depending on the specific appliances used in the household. In operation, the system displays the voltage state (overvoltage, normal voltage, overvoltage) and alerts the user by sending an SMS via a GSM modem. The system is valuable for industrial and domestic applications, especially in developing economies such as those of Sub-Saharan Africa, where overvoltage and undervoltage are acute problems.
基金financially supported by the National Natural Science Foundation of China(No.51401050)the Fundamental Research Funding for the Central Universities(No.N160204001)supported by the Australian Research Council(ARC)Laureate Fellowship(Prof.Hodgson)
文摘The transformation behavior, microstructural evolution and mechanical properties were compared in a coldrolled Nb–Mo microalloyed 6.5Mn alloy after intercritical annealing(IA) and quenching and partitioning(Q & P),respectively. The thermodynamic calculation and theoretical analysis were used to determine the optimal heat treatment parameters. The Q & P samples exhibited relatively higher strength with relatively low ductility, mainly due to the hard martensite matrix, which resulted in continuous yielding behavior upon loading, whereas the IA samples showed the significantly improved ductility, which benefited from the more sufficient transformation-induced plasticity(TRIP) effects and the softer ultrafine ferrite matrix. The dependence of yield point elongation(YPE) of IA samples on grain size demonstrated that the YPE value was in the reverse proportional relationship to the average grain size, which agreed well with theoretical analysis.
文摘The effect of partial or full substitution of Si by Al on the microstructure and mechanical properties has been extensively studied in multi-phase transformation-induced plasticity(TRIP) steels with polygonal ferrite matrix, but rarely studied in bainitic TRIP steels. The aim of the present study is to properly investigate the effect of Al and Si on bainite transformation, microstructure and mechanical properties in bainitic steels in order to provide guidelines for the alloying design as a function of process parameters for the 3 rd generation advanced high strength steels(AHSS). It is shown from the dilatometry study,microstructural investigations and tensile properties measurements that the Al addition results in an acceleration whereas Si addition leads to a retardation in bainite transformation kinetics. The addition of Al retards the decomposition of austenite into pearlite and carbides at holding temperatures higher than450℃ whereas Si retards the decomposition of austenite into carbides at temperatures lower than 450℃.Consequently, the Al-added bainitic steel has a better strength-elongation combination at bainitic holding temperatures higher than 450℃ while Si-added steel has a better strength-elongation combination at temperatures lower than 450℃. The higher yield strength of Al-added steel is mainly attributed to its finer bainitic lath. The higher tensile strength of Si-added steel is not only related to the stronger contribution of Si on work hardening during deformation, but also due to the higher volume fraction of martensite or martensite/austenite(MA) blocks in all heat treatment conditions, as well as the lower mechanical stability of retained austenite in this steel.