The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP)can be classified into fixed and movable types.In movable electrode structures,springs are typically used to push the ele...The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP)can be classified into fixed and movable types.In movable electrode structures,springs are typically used to push the electrodes and the propellant.The effects of spring pressure on the ignition and combustion of propellants have not yet been studied.In this paper,a universal testing machine and an electrochemical workstation were firstly utilized to investigate the compressive mechanical property and conductivity of Hydroxylamine Nitrate(HAN)-ECSP.The maximum pressure at which the propellant undergoes elastic deformation is 65 kPa.When the spring pressure increased from 5.1 kPa to 20.4 kPa,the propellant resistance decreased from 56.8 X to 36.8 X.Various observation methods were employed to study the process of electrical energy injection and the ignition and combustion characteristics under constant voltage.Appropriately increasing the spring pressure can accelerate the injection of electrical energy into the propellant,increase the electrification current,and thus reduce the initial ignition delay time of the propellant.When the spring pressure is 20.4 kPa,the squeezing speed of the propellant is too fast,making it difficult for the propellant to be adequately heated at the electrode interface,which is unfavorable for ignition.Excessive spring pressure also leads to the accumulation of a large amount of combustion residue on the electrode plate,hindering the mixing and diffusion of hot gases during the second ignition process,preventing the gaseous flame of the propellant.When the spring pressure is 5.1 kPa,improving the working voltage can enhance the repeated ignition characteristics of the propellant.展开更多
Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,th...Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,thereby reducing post-earthquake repair costs and contributing to seismic resilience.However,non-structural components,particularly those sensitive to floor acceleration,remain vulnerable,resulting in prolonged func-tional recovery times.This paper aims to address this limitation by introducing a novel structural archetype,the Self-Centering Viscous-Based Braced Frame(SC-VBBF),which integrates superelastic shape memory alloy(SMA)bars,viscous dampers(VDs),and friction springs(FSs).A streamlined analytical approach relies on the strength decoupling of VD from other components using aλfactor to design SC-VBBFs.To evaluate the effectiveness of the hybrid brace,a set of 4-,8-,and 12-story archetypes equipped with SC-PBBs and SC-VBBFs are simulated in OpenSees and analyzed under various earthquake types,including crustal,subcrustal,and subduction events.The results demonstrate the superior performance of the SC-VBBF withλ≤0.5 system compared to SC-PBBFs in mitigating floor accelerations under design-level earthquakes and improving seismic resilience.展开更多
Do you like the Spring Festival?I really like it!I can eat delicious food,wear new clothes,watch the lion dance,and join in lots of fun activities.The Spring Festival is the most important holiday in China.Do you know...Do you like the Spring Festival?I really like it!I can eat delicious food,wear new clothes,watch the lion dance,and join in lots of fun activities.The Spring Festival is the most important holiday in China.Do you know how the Spring Festival began?Let me tell you an old story about it.A long,long time ago,there was a scary monster named Nian.On the last day of the Lunar Year,when winter was ending and spring was coming,Nian would wake up from its sleep.展开更多
The cultural tradition of the Spring Festival has a long history,which is a profound embodiment of China's farming civilization and folk beliefs.The rituals and customs such as Worshipping the Kitchen God in the t...The cultural tradition of the Spring Festival has a long history,which is a profound embodiment of China's farming civilization and folk beliefs.The rituals and customs such as Worshipping the Kitchen God in the twelfth lunar month,putting up Spring Festival couplets,having family reunion dinner on Chinese New Year's Eve and temple fairs during the Spring Festival show the unique beliefs and values of the Chinese nation to bid farewell to the old and usher in the new and pray for reunion and happiness.展开更多
The Qinba Mountains are climatically and ecologically recognized as the north-south transitional zone of China.Analysis of its phenology is critical for comprehending the response of vegetation to climatic change.We r...The Qinba Mountains are climatically and ecologically recognized as the north-south transitional zone of China.Analysis of its phenology is critical for comprehending the response of vegetation to climatic change.We retrieved the start of spring phenology(SOS)of eight forest communities from the MODIS products and adopted it as an indicator for spring phenology.Trend analysis,partial correlation analysis,and GeoDetector were employed to reveal the spatio-temporal patterns and climatic drivers of SOS.The results indicated that the SOS presented an advance trend from 2001 to 2020,with a mean rate of−0.473 d yr^(−1).The SOS of most forests correlated negatively with air temperature(TEMP)and positively with precipitation(PRE),suggesting that rising TEMP and increasing PRE in spring would forward and delay SOS,respectively.The dominant factors influencing the sensitivity of SOS to climatic variables were altitude,forest type,and latitude,while the effects of slope and aspect were relatively minor.The response of SOS to climatic factors varied significantly in space and among forest communities,partly due to the influence of altitude,slope,and aspect.展开更多
基金supported by the National Natural Science Foundation of China(Nos.T222100,22205258,52302485 and 2024JJ5404).
文摘The electrode structures in ignition devices for Electrically Controlled Solid Propellants(ECSP)can be classified into fixed and movable types.In movable electrode structures,springs are typically used to push the electrodes and the propellant.The effects of spring pressure on the ignition and combustion of propellants have not yet been studied.In this paper,a universal testing machine and an electrochemical workstation were firstly utilized to investigate the compressive mechanical property and conductivity of Hydroxylamine Nitrate(HAN)-ECSP.The maximum pressure at which the propellant undergoes elastic deformation is 65 kPa.When the spring pressure increased from 5.1 kPa to 20.4 kPa,the propellant resistance decreased from 56.8 X to 36.8 X.Various observation methods were employed to study the process of electrical energy injection and the ignition and combustion characteristics under constant voltage.Appropriately increasing the spring pressure can accelerate the injection of electrical energy into the propellant,increase the electrification current,and thus reduce the initial ignition delay time of the propellant.When the spring pressure is 20.4 kPa,the squeezing speed of the propellant is too fast,making it difficult for the propellant to be adequately heated at the electrode interface,which is unfavorable for ignition.Excessive spring pressure also leads to the accumulation of a large amount of combustion residue on the electrode plate,hindering the mixing and diffusion of hot gases during the second ignition process,preventing the gaseous flame of the propellant.When the spring pressure is 5.1 kPa,improving the working voltage can enhance the repeated ignition characteristics of the propellant.
文摘Self-Centering Piston-Based Braced Frames(SC-PBBFs)are designed to curtail structural damage under severe ground motions.The self-centering mechanism in this bracing mitigates structural damage during an earthquake,thereby reducing post-earthquake repair costs and contributing to seismic resilience.However,non-structural components,particularly those sensitive to floor acceleration,remain vulnerable,resulting in prolonged func-tional recovery times.This paper aims to address this limitation by introducing a novel structural archetype,the Self-Centering Viscous-Based Braced Frame(SC-VBBF),which integrates superelastic shape memory alloy(SMA)bars,viscous dampers(VDs),and friction springs(FSs).A streamlined analytical approach relies on the strength decoupling of VD from other components using aλfactor to design SC-VBBFs.To evaluate the effectiveness of the hybrid brace,a set of 4-,8-,and 12-story archetypes equipped with SC-PBBs and SC-VBBFs are simulated in OpenSees and analyzed under various earthquake types,including crustal,subcrustal,and subduction events.The results demonstrate the superior performance of the SC-VBBF withλ≤0.5 system compared to SC-PBBFs in mitigating floor accelerations under design-level earthquakes and improving seismic resilience.
文摘Do you like the Spring Festival?I really like it!I can eat delicious food,wear new clothes,watch the lion dance,and join in lots of fun activities.The Spring Festival is the most important holiday in China.Do you know how the Spring Festival began?Let me tell you an old story about it.A long,long time ago,there was a scary monster named Nian.On the last day of the Lunar Year,when winter was ending and spring was coming,Nian would wake up from its sleep.
文摘The cultural tradition of the Spring Festival has a long history,which is a profound embodiment of China's farming civilization and folk beliefs.The rituals and customs such as Worshipping the Kitchen God in the twelfth lunar month,putting up Spring Festival couplets,having family reunion dinner on Chinese New Year's Eve and temple fairs during the Spring Festival show the unique beliefs and values of the Chinese nation to bid farewell to the old and usher in the new and pray for reunion and happiness.
基金National Key Research and Development Program of China,No.2023YFE0208100,No.2021YFC3000201Natural Science Foundation of Henan Province,No.232300420165。
文摘The Qinba Mountains are climatically and ecologically recognized as the north-south transitional zone of China.Analysis of its phenology is critical for comprehending the response of vegetation to climatic change.We retrieved the start of spring phenology(SOS)of eight forest communities from the MODIS products and adopted it as an indicator for spring phenology.Trend analysis,partial correlation analysis,and GeoDetector were employed to reveal the spatio-temporal patterns and climatic drivers of SOS.The results indicated that the SOS presented an advance trend from 2001 to 2020,with a mean rate of−0.473 d yr^(−1).The SOS of most forests correlated negatively with air temperature(TEMP)and positively with precipitation(PRE),suggesting that rising TEMP and increasing PRE in spring would forward and delay SOS,respectively.The dominant factors influencing the sensitivity of SOS to climatic variables were altitude,forest type,and latitude,while the effects of slope and aspect were relatively minor.The response of SOS to climatic factors varied significantly in space and among forest communities,partly due to the influence of altitude,slope,and aspect.
